Dictionary of Biomedical Sciences

Peter J.Gosling

London and New York First published 2002 by Taylor & Francis 11 New Fetter Lane, London EC4P 4EE

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This edition published in the Taylor & Francis e-Library, 2002.

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ISBN 0-203-77758-1 (Adobe eReader Format) ISBN 0-415-23723-8 (pbk) ISBN 0-415-24138-3 (hbk) Preface

Why write a dictionary of biomedical science? After all, several medical and science dictionaries have been published in the last few years. To answer that question it is first necessary to consider what is meant by ‘biomedical science’. Biomedical science involves and relates biological, medical and physical science. Biomedical scientists must be familiar with a great number of technical terms, many of which are from disciplines other than their own speciality, including anatomy, audiology, biochemistry, biology, chemistry, computing science, cytology, genetics, haematology, histology, mathematics, medicine, microbiology, molecular biology, microscopy, mycology, parasitology, pharmacology, physics, physiology, radiology, statistics, virology, and so on. So the answer to the initial question is that the dictionaries published to date do not provide the mix of terminology within a single volume that is required of biomedical scientists and none have had the aims of the present dictionary. The aim of the present dictionary is to define not just terms from one field of biomedical science but as many as possible of those terms from related disciplines that pop out of the page whenever one reads anything on biomedical science. In fact, were it not that the title is awkward this volume would have been called “A Dictionary for Biomedical Scientists”. Although the dictionary contains no extended essays, and it is not intended to be a dictionary of medical laboratory scientific techniques, formulae and methods, I have, however, tried to give enough material on each term to allow the reader to grasp both its meaning and its significance. By its very nature therefore it was not my intention nor could the dictionary hope to comprehensively cover all the terms used in all disciplines of biomedical science. The expert in any of the disciplines touched upon in compiling this dictionary will undoubtedly find omissions. Those seeking such comprehensive coverage of terms of any particular discipline would do better to consult a volume more specifically targeted to their needs. However it was my intention that the Dictionary of Biomedical Sciences should provide the breadth of knowledge to make it both an informative and useful volume for students and experts alike.

Acknowledgements

I must acknowledge the constant encouragement and support that my family, Betty and Jim Martin, and Paul and Kathy Gosling, have freely provided, without which this work would not have been accomplished.

Notes on use

The order of headings is based on the alphabetical sequence of letters in the term, ignoring spaces, hyphens, accents, and numerals. (Thus A-band is to be found between ABA and aberration). No headings are inverted, for example, there is an entry under gamma radiation, and not under radiation, gamma. Headings defined appear in bold type and cross-references appear in SMALL CAPITALS. Plurals formed by the addition of ‘s’ have not usually been regarded, but abnormal formations may be given. The term ‘abbreviations’ includes contracted and shortened forms of words and phrases, and acronyms and initials. I have followed the common practice of omitting the full point after each initial in abbreviations but have used them when a word has been truncated. (Thus AAM has no full points but chemo. does). Throughout the dictionary I have supplied American spellings to words where they differ from those in current use in the United Kingdom.

A (1,2 physics) An abbreviation for 1 A-alpha fibre (histology) An alternative ‘A’mplitude. 2 An abbreviation for term for ALPHA MOTOR NEURON. (USA: ‘A’mpere. A-alpha fiber).

Aa (chemistry) An abbreviation of AAM (society) An abbreviation of ‘A’bsolute ‘a’lcohol. ‘A’merican ‘A’ssociation for ‘M’icrobiology.

AA (society) An abbreviation for AAPCC (society) An abbreviation of ‘A’lcoholics ‘A’nonymous. ‘American ‘A’ssociation of ‘P’oison ‘C’ontrol ‘C’enters. AAA (1 chemistry; 2 society) 1 Amino- acid lysine. 2 An abbreviation of AAPS (society) An abbreviation of ‘A’merican ‘A’ssociation of ‘A’natomists. ‘A’merican ‘A’ssociation for the ‘P’romotion of ‘S’cience. AAAN (education) An abbreviation of ‘A’merican ‘A’cademy of ‘A’pplied AAS (1,2, education; 3 physics) An ‘N’utrition. abbreviation of 1 ‘A’ustralian ‘A’cademy of ‘S’cience. 2 An abbreviation of AAAS (society) An abbreviation of ‘A’ssociate in ‘A’pplied ‘S’cience. 3 An ‘A’merican ‘A’ssociation for the abbreviation of ‘A’tomic ‘A’bsorption ‘A’dvancement of ‘S’cience. ‘S’pectrometry.

AAB (society) An abbreviation ‘A’ssociation AASH (physiology/biochemistry) An of ‘A’pplied ‘B’iologists. of abbreviation of ‘A’drenal ‘A’ndrogen- ‘S’timulating ‘H’ormone. AABB (society) An abbreviation of ‘A’merican ‘A’ssociation of ‘B’lood AAVS (society) An abbreviation of ‘B’anks. ‘A’merican ‘A’nti-‘V’ivisection ‘S’ociety.

AACC (society) An abbreviation of a/b (pathogenicity and epidemiology) ‘A’merican ‘A’ssociation of ‘C’linical An abbreviation of ‘a’ir‘b’orne. Also termed ‘C’hemists. abn.

AACT (education) An abbreviation of AB (1 medical; 2 haematology) 1 An ‘A’merican ‘A’cademy of ‘C’linical ‘T’oxicology. abbreviation of ‘A’sthmatic ‘B’ronchitis. 2 A human BLOOD type of the ABO GROUP. AAFS (education) An abbreviation of ‘A’merican ‘A’academy of ‘F’orensic ABA (biochemistry) An abbreviation of ‘S’ciences. ‘A’drenergic ‘B’locking ‘A’gent.

1 A-BAND ABN

A-band (histology) One of the alternating ANALYSIS. PRECIPITATION of CHOLE- bands of extrafusal MUSCLE FIBRE (USA: STEROL esters after an initial extraction muscle fiber), seen through a MICROSCOPE separates esterified from free CHOLE- as a dark band, which corresponds to STEROL, permitting measurement of only the thick MYOSIN filaments. the free FRACTION.

ABC (physiology/biochemistry) An abbre- aberration (1 physics; 2 genetics) 1 viation of ‘A’TP-‘B’inding ‘C’assette. The production of an IMAGE with coloured (USA: colored) fringes that occurs because ABD (governing body) An abbreviation the FOCAL LENGTH of a LENS is different of ‘A’merican ‘B’oard of ‘D’ermatology. for different colours of LIGHT (CHROMATIC ABERRATION), so that the LENS focuses abd (radiology) An abbreviation of different colours in different planes; ‘a’verage ‘b’ody ‘d’ose. or the production of an IMAGE that is not sharp when a beam of LIGHT falls abdom. (anatomy) An abbreviation of on the edges as well as on the centre ‘abdom’en or ‘abdom’inal. (USA: center) of a LENS (SPERICAL ABERRATION). 2 Change in the number abdomen (abdom.) (anatomy) The part or the structure of chromosomes in a of the trunk between the THORAX and CELL. the PELVIS. It is separated above from the THORAX by a muscular partition See also MUTATION. called the DIAPHRAGM, and below by the PELVIC floor. The structures which ABFT (governing body) An abbreviation make up the abdominal wall are SKIN, of ‘A’merican ‘B’oard of ‘F’orensic fat of varying thickness, MUSCLE, another ‘T’oxicology. layer of fat, and the thin, slippery MEMBRANE abiogenesis (biology) Theory of the called the PERITONEUM which lines the ORIGIN of life which states that living abdominal cavity. The PERITONEUM, which organisms gradually formed from non- is rather like wet cellophane, covers ill living material. the internal organs in the abdominal cavity. The abdomen contains the STOMACH, See also SPONTANEOUS GENERATION. and most of the organs of the digestive system i.e. the small and LARGE INTESTINE abiotic (biology) Nonliving; in biomedical with the APPENDIX and CAECUM, and science used primarily for the nonliving the LIVER and PANCREAS, Other abdominal parts of ecosystems, or of the organs include the kidneys, the ADRENAL ENVIRONMENT in general. GLANDS, the SPLEEN, and some large and important BLOOD VESSELS including ablation (medical) Surgical removal the AORTA and the INFERIOR VENA of an ORGAN or part of an ORGAN. CAVA. The PROSTATE GLAND in the male and the UTERUS, ovaries and ABMT (governing body) An abbreviation FALLOPIAN TUBES in the female are in of ‘A’merican ‘B’oard of ‘M’edical the PELVIS below the abdominal cavity. ‘T’oxicology.

Abell-Kendall Method (biochemistry) A abn (pathogenicity) An abbreviation chemical method of CHOLESTEROL of ‘a’ir‘b’or‘n’e. Also termed a/b.

2 ABNORMAL ABSCESS abnormal (general terminology) abbreviation of ‘A’ndrogen-‘B’inding Departing from normality. The term is ‘P’rotein. usually used for departures from normality in an undesirable direction rather than ABR (governing body) An abbreviation in a desirable one. of ‘A’merican ‘B’oard of ‘R’adiology.

ABO (1 governing body; 2 haematology) abrasion (medical) The AREA from 1 An abbreviation of ‘A’merican ‘B’oard which the surface layer of the SKIN of ‘O’phthalmology/‘O’pticianry/‘O’rtho- has been rubbed. dontics/‘O’tolaryngology; 2 A CLAS- SIFICATION of human BLOOD. See abs. (general terminology) An abbreviation ABO BLOOD GROUPS. of ‘abs’olute/‘abs’orbent/‘abs’tract. abs. vise, (physics) An abbreviation of ABO blood groups (haematology) A ‘abs’olute ‘visc’osity. system of classifying BLOOD GROUPS. BLOOD is classified in various ways. abscess (medical/microbiology) Painful The most common classifications are swollen localised AREA where pus forms. by the agglutinogens in red BLOOD An abscess forms in the tissues as the corpuscles (factors A and B) and by result of irritation, usually because of the RHESUS FACTOR. BLOOD can BACTERIAL INFECTION. Increased therefore have either FACTOR (Group BLOOD flow leads to EFFUSION of FLUID A and Group B) or both factors (Group into the TISSUE spaces and the collection AB) or neither (Group O) and each of of a great number of WHITE BLOOD these groups can be Rhesus negative CELLS. The AREA of INFECTION becomes or POSITIVE. It is medically important, cut off from the healthy TISSUE and in because in a BLOOD transfusion the time the dead WHITE BLOOD CELLS, DONOR’S ABO BLOOD GROUP must BACTERIA and exuded FLUID form pus. be compatible with the RECIPIENT’S The earliest outward sign of abscess or rejection will occur. formation on the surface of the body is a painful and tender AREA of redness. abortion (medical) The expulsion of As the abscess becomes localised and the FOETUS (USA: fetus) from the UTERUS pus forms, so the AREA of redness before the end of PREGNANCY, especially becomes more sharply defined, and its during the first twenty-eight weeks of centre (USA: center) begins to soften. PREGNANCY when it is not likely to Usually the pus tracks to the AREA of survive birth. A natural abortion is often least resistance, which in the case of termed a MISCARRIAGE. a surface abscess or boil is the surface of the body. If left, the abscess will abortus fever (medical/bacteriology) eventually burst and DISCHARGE, but BRUCELLOSIS. often much pain and illness can be avoided if it is lanced or incised as soon as it ABP (1 governing body; 2 haematology, has localised and pus has formed. While 3 biochemistry) 1 An abbreviation of abscesses on the surface of the body ‘A’merican ‘B’oard of ‘P’athology/ are caused by INFECTION entering through ‘P’ediatrics/‘P’edodontics/‘P’eridontology/ a small cut or through the tiny lubricating ‘P’rosthodontics. 2 An abbreviation of GLANDS of the SKIN or HAIR follicles, ‘A’rterial ‘B’lood ‘P’ressure. 3 An internal abscesses can be caused by

3 ABSCISSA ABSORPTANCE theentry of a foreign body as in the absolute threshold (physiology) The case of knife or bullet WOUNDS, or, in lowest INTENSITY of a STIMULUS at the lungs, by the accidental inhalation which it can be detected, it is usually of food or a TOOTH. Other internal measured by determining the INTENSITY abscesses are caused by the spread at which the STIMULUS is detected on of local infections, as in a burst APPENDIX 50 per cent of presentations. which causes a PELVIC abscess, or the spread of INFECTION from the MIDDLE absolute unit (physics) UNIT defined EAR to the BRAIN. The GROWTH of in terms of units of fundamental quantities ANAEROBIC BACTERIA is often favoured such as length, time, MASS and by the ENVIRONMENT inside an abscess ELECTRIC CHARGE or CURRENT. and they are frequently the underlying cause of the INFECTION. absolute value (mathematics) Numerical value of a REAL NUMBER irrespective abscissa (mathematics) The horizontal of whether it is POSITIVE or negative. CO-ORDINATE of a GRAPH, conventionally Also termed: modulus (or mod) x, where called the X-AXIS. See CARTESIAN CO- x is the number. ORDINATES. absolute zero (physics) Lowest absgiute value (mathematics) A number TEMPERATURE theoretically possible, or value expressed regardless of its sign. at which a substance has no HEAT ENERGY whatever. It corresponds to absol. (gerneral terminology) abbreviation -273.15 C, or zero on the KELVIN scale. of ‘absol’ute. An absolute alcohol (chemistry) ETHANOL absorbance (chemistry) A measure of (ETHYL ALCOHOL) that contains no the amount of LIGHT absorbed by a more than 1 per cent WATER. SOLUTION. The difference between the amount of incident LIGHT and transmitted absolute configuration (chemistry) LIGHT expressed mathematically is referred Arrangement of groups about an to as the ABSORBANCE of the SOLUTION. asymmetric ATOM. See CONFIGURATION. absorbance rate (chemistry) Rate at absolute humidity (physics) Amount of which a LIQUID is absorbed by a SOLID. WATER VAPOUR in a given VOLUME of AIR, also called VAPOUR CONCENTRATION. See also ABSORPTION.

See also RELATIVE HUMIDITY. absorbed dose (biochemistry) The amount of a chemical that enters the absolute temperature (physics) body of an exposed organism. Fundamental TEMPERATURE SCALE used in theoretical physics and chemistry. absorptance (a) (physics) Ability of It is expressed in either KELVIN or a medium to absorb RADIATION. It is degrees Rankine (corresponding the ratio of the total RADIATION absorbed respectively to the Celsius and Fahrenheit by a medium to the total RADIATION scales). On both these scales, zero is arriving at its surface. Also termed: taken as ABSOLUTE ZERO. Also termed ABSORPTIVITY. thermodynamic TEMPERATURE.

4 ABSORPTION ACCESS TIME absorption (1 physics; 2 biochemistry; ac. (general terminology) An abbreviation 3 medical) 1 ACTION of taking a LIQUID of ‘ac’tivity. into a SOLID. 2 The uptake of WATER or dissolved chemicals by CELLS or Acad. sci. (education) An abbreviation organisms. 3 Taking substances into of ‘Acad’emy of ‘sci’ence. the body, such as proteins or fats which have been digested from food and are acanthosis (medical/histology) Thickening taken into the bloodstream from the of the inner layer of CELLS of the STOMACH and intestines. EPIDERMIS by ABNORMAL increase in the number of CELLS. absorption factor (biochemistry) That FRACTION of a chemical coming into acaricide (parasitololgy) PESTICIDE contact with an organism that is absorbed which kills mites. via the SKIN, respiratory system or GASTROINTESTINAL tract and enters acarus (parasitololgy) A GENUS of the body of the organism. mites which often live as PARASITES on the external surface of larger animals. absorption spectrum (physics) The They cause various SKIN diseases such proportion of incident LIGHT of each as itch and mange. WAVELENGTH absorbed when passed through a selectively absorbing medium. acceleration (1 genetics; 2 physics) 1 The appearance of a structure in absorptivity (physics) See ABSORPTANCE. EMBRYOGENESIS earlier than in ancestral forms. The opposite is retardation. 2 A abstr. (general terminology) An abbreviation rate of change of velocity; its SI UNITS of ‘abst’ract. are ms-2 (metres per second per second). abt (general terminology) An abbreviation accelerator (1 chemistry; 2 biology; of ‘ab’ou‘t’. 3 physics) 1 An alternative term for CATALYST. 2 A substance that increases ABT (governing body) An abbreviation the effectiveness of an ENZYME. 3 of ‘A’merican ‘B’oard of ‘T’oxicology. Machine that increases the KINETIC ENERGY of an OBJECT or PARTICLE, AC (1 physics; 2 computing; 3 e.g. a PARTICLE accelerator. employment) 1 An abbreviation of ‘A’lternating ‘C’urrent. 2 An abbreviation acceptable daily intake (ADI) (toxicology/ of ‘A’nalogue ‘C’omputer. 3 An pharmacology) The ESTIMATED amount abbreviation of ‘A’nalytical ‘C’hemist. of a substance that can be ingested daily during life without causing ac (1 advisory body; 2 physics) 1 An appreciable adverse effects. It is abbreviation of ‘a’dvisory ‘c’ommittee. expressed in mg/kg body-WEIGHT/day. 2 An abbreviation of ‘a’lternating ‘c’urrent. access time (computing) PERIOD of Ac (chemistry) CHEMICAL SYMBOL time required for reading out of, or writing for ACTINIUM. into, a COMPUTER’S MEMORY.

5 ACCIDENTAL HOST ACETAMINOPHEN accidental host (parasitology) An ‘A’ngiotensin ‘C’onverting ‘E’nzyme. 2 ANIMAL HOST to a PARASITE which An abbreviation of ‘A’dvisory ‘C’entre is not the usual HOST SPECIES for for ‘E’ducation. 3 An abbreviation of that PARASITE. ‘A’lcohol-‘C’hloroform-‘E’ther. acclimatization (biology) Way in which acellular (biology) Not made up of CELLS; an organism adapts to a different or in particular, describing an organism changing ENVIRONMENT (e.g. the thin that is not divided into separate CELLS. AIR at higher altitudes). acentric chromosome (genetics) A accolé (microbiology) Early ring form CHROMOSOME with no CENTROMERE. of Plasmodium falciparum found at margin This may be merely a large part of a of red CELL. CHROMOSOME that has broken off from accommodation (physiology) The process another one. Acentrics tend to get lost by which the LENS of the EYE brings because they cannot be manoeuvred during images to a sharp FOCUS on the RETINA. the NORMAL CELL-DIVISION process. The LENS of the EYE is made of elastic TISSUE so that its shape can be altered acet. (chemistry) An abbreviation of by contraction of the CILIARY MUSCLE ‘acet’one. which surrounds it. When the MUSCLE contracts the LENS becomes more CONVEX, acetal (chemistry) CH3CH(OC2H 5) 2 and as it relaxes the LENS becomes Colourless (USA: colorless) VOLATILE less CONVEX. LIQUID ORGANIC COMPOUND. Also termed: 1,1- diethoxyethane. accreditation (quality standards)

Certification of the expertise of individuals acetaldehyde (biochemistry) CH3CHO and establishments WORKING in Colourless (USA: colorless) LIQUID biomedical sciences. Accreditation is ORGANIC COMPOUND with a pungent performed by several organisations who odour (USA: odor); a simple ALDEHYDE establish standards and accredit on made by the OXIDATION of ETHANOL the basis of education, experience, (ETHYL ALCOHOL). Produced physiologically and accomplishments. in significant quantities in individuals taking isulfiram who have also ingested ETHANOL. accumulator (1 computing; 2 physics) Also termed: acetic ALDEHYDE; ETHANAL. 1 The part of the CENTRAL PROCESSOR that executes logical or arithmetic operations. acetaldol (chemistry) An alternative 2 An alternative term for a SECONDARY term for ALDOL. CELL, or STORAGE BATTERY. acetamide (chemistry) CH CONH Colour- accuracy (quality standards) See QUALITY 3 2 less (USA: colorless) DELIQUESCENT CONTROL. CRYSTALLINE ORGANIC COMPOUND, ACDP (advisory committee) An with a ‘mousy’ odour (USA: odor). Also abbreviation of ‘A’dvisory ‘C’ommittee termed: ethanamide. on ‘D’angerous ‘P’athogens. acetaminophen (pharmacology) The stan- ACE (1 biochemistry; 2 education; 3 dard name in the USA for paracetamol. chemistry) An abbreviation of 1

6 ACETATE ACETYLCHOLINE acetate (1,2 chemistry) 1 SALT of acetonuria (biochemistry) The presence ACETICACID (ETHANOIC ACID) in which of ACETONE in the URINE, which gives the terminal HYDROGEN ATOM is it a sweet CHARACTERISTIC SMELL. substituted by a METAL ATOM; e.g.

COPPER acetate Cu(CH3COO)2. 2 ESTER acetophenone (chemistry) C6H5COCH3 of ACETIC ACID in which the terminal Colourless LIQUID ORGANIC COMPOUND, HYDROGEN ATOM is substituted by with a sweet pungent odour (USA: odor). a RADICAL, e.g. ETHYL ACETATE Also termed: phenyl methyl KETONE.

CH3COOC2H5. Also termed: ETHANOATE.

acetyl chloride (chemistry) CH3COCI acetazolamide (physiology/pharmacology) Colourless (USA: colorless), highly A carbonic anhydrase inhibitor that has refractive LIQUID ORGANIC COMPOUND, wide-ranging actions in the body. It with a strong odour (USA: odor). Also reduces the formation of aqueous humour termed: ETHANOYL CHLORIDE. in the eye, acts as a DIURETIC, and has use in treatment of glaucoma and acetylcholinesterase stain (histology) OEDEMA (USA: edema) respectively. Histochemical enzymatic staining It has also been used as an ANTI- technique. EPILEPTIC DRUG, in treatment of premenstrual syndrome, and in the acetylcholine (ACH) (biochemistry) White prevention of motion sickness. HYGROSCOPIC CRYSTALLINE ORGANIC COMPOUND. The CHOLINE ESTER of acetic acid (chemistry) CH3COOH ACETIC ACID which is synthesised from Colourless (USA: colorless) LIQUID CHOLINE and acetyl CoA by the CARBOXYLIC ACID, with a pungent mitochondrial ENZYME CHOLINE odour. (USA: odor) and acidic properties. acetyltransferase. ACh is released in It is the acid in vinegar. Also termed: vertebrates as the NEUROTRANSMITTER ETHANOIC ACID. for cholinergic neurons in the CENTRAL NERVOUS SYSTEM, in addition to several acetone (biochemistry) CH3COCH3 other PERIPHERAL locations, including Colourless (USA: colorless), VOLATILE NEUROMUSCULAR JUNCTIONS; LIQUID ORGANIC COMPOUND, formed preganglionic neurons in both divisions during the DEGRADATION of fats as of the AUTONOMIC NERVOUS SYSTEM; well as a widely manufactured SOLVENT. parasympathetic postganglionic neurons; It is a simple KETONE. May be found and a few sympathetic postganglionic in the URINE, primarily in severe cases neurons. CHOLINE, but not ACh, is of DIABETES, sometimes in CHRONIC absorbed into NERVE terminals by a wasting diseases such as CANCER, and specific, high-AFFINITY, SODIUM- and after prolonged vomiting. It has a ENERGY-dependent process. This high- CHARACTERISTIC SMELL which can AFFINITY uptake process is specific to often he detected in the breath of patients cholinergic NERVE terminals, is tightly in diabetic coma. Also termed: 2-propanone. coupled to ACh SYNTHESIS, is the rate- LIMITING STEP for ACh levels. Cholinergic acetonitrile (chemistry) CH3CN Colourless receptors (cholinoceptors), that mediate LIQUID ORGANIC COMPOUND, with the effects of ACh, are generally classified a pleasant odour (USA: odor). Also as nicotinic or muscarinic, based on termed: METHYL CYANIDE. their binding preferences for NICOTINE

7 ACETYLCHOLINE ACETYT-HYDROLASE ACHROMATIC LENS and muscarine, respectively. Receptors pour l‘A’dvancement des ‘S’ciences. can be blocked by such agents as d- [French-Canadian, meaning ‘Assossication tubocurarine, decamethonium, ATROPINE for the Advancement of Science’.] and scopolamine. ACh is hydrolysed to CHOLINE and ACETATE by acetyl- ACH (biochemistry) An abbreviation cholinesterase. of ‘A’CETYL‘CH’OLINE. acetylcholine acetyt-hydrolase (biochem- ACHE (biochemistry) An abbreviation istry) See ACETYLCHOLINESTERASE. of ‘A’CETYL‘CH’OLIN‘E’STERASE. acetylcholinesterase (ACHE) Achilles tendon (anatomy) The TENDON, (biochemistry) An ENZYME that which runs from the great muscles of hydrolyses the NEUROTRANSMITTER the calf to the calcancum, the BONE ACETYLCHOLINE (ACh) to CHOLINE which forms the heel, and draws the foot and ACETATE, thereby terminating the downwards about the hinge of the ankle. ACTION of ACh. It is found extensively throughout the NERVOUS SYSTEM, achlorhydria (biochemistry) A condition as well as in many non-nervous tissues. where the GASTRIC JUICES do not contain HYDROCHLORIC ACID. It is acetyl Co-A (pharmacology) An abbreviation found in 4 to 5 per cent of NORMAL of ACETYL ‘CO’ENZYME A. people in whom it produces no ill effects, acetyl coenzyme A (acetyl Co-A) but it is a common symptom of those (physiology/biochemistry) A derivative with STOMACH CANCER or PERNICIOUS of pantothenic acid acetyl coenzyme A ANAEMIA (USA: pernicious anemia). is an intermediate in many key metabolic processes, particularly in the transfer achondroplasia (medical/genetics) A of the products of glycolysis to the KREB’S genetic disease caused by a DOMINANT CYCLE and in FATTY ACID METABOLISM. ALLELE. Easily recognisable at birth, the features of the disease are very short limbs and a large HEAD but usually acetylene (chemistry) C2H2 Colourless (USA: colorless) organic GAS with an a small nose. Adults grow to a height ETHER-like odour (USA: odor) (when of 4 feet (1.2 m) or less. Achondroplastics pure), used as a fuel and in organic are perfectly healthy and have NORMAL SYNTHESIS. It is the simplest alkyne intelligence, fertility and so on. About (OLEFIN). Also termed: ETHYNE. one baby in 50,000 is born with achondroplasia. Some 80 per cent of acetylide (chemistry) Type of carbide them have NORMAL parents, which means resulting from the INTERACTION of that the achondroplasia GENE must arise ACETYLENE and a SOLUTION of a heavy by a new MUTATION in these cases, METAL SALT. Most acetylides are unstable which appears to occur more often when and explosive. Also termed: ethynide. the father is over the age of 30. acetylsalicyllic acid (biochemistry) achromatic lens (optics) COMBINATION See ASPIRIN. of two or more lenses that has a FOCAL LENGTH that is the same for two or ACFAS (education) An abbreviation of more different wavelengths of LIGHT. ‘A’ssociation ‘C’anadienne ‘F’ranncaise

8 A CHROMOSOMES ACID PHOSPHATASE STAIN

Thisarrangement largely overcomes ORGANIC COMPOUNDS, GENERAL CHROMATIC ABERRATION. FORMULA RCOCI (where R is an alkyl RADICAL), much used in organic SYNTHESIS. A chromosomes (genetics) The NORMAL chromosomes in a EUKARYOTE. Occasion- acid-fast (microbiology/histology) ally extra chromosomes occur, which CHARACTERISTIC of certain BACTERIA, are known as B chromosomes. such as mycobacteria, which involves resistance to decolourisation (USA: acid (chemistry) Member of a CLASS of decolorization) by acids when stained chemical compounds whose AQUEOUS by an ANILINE dye, such as carbol fuchsin. SOLUTIONS contain HYDROGEN IONS. SOLUTIONS of acids have a PH of less acidic oxide (chemistry) OXIDE of a than 7. STRONG ACIDS dissociate completely NON-METAL, usually an ANHYDRIDE, (into ions) in SOLUTION; WEAK ACIDS that reacts with WATER to form an only partly dissociate. An acid neutralizes ACID; e.g. SULPHUR DIOXIDE (USA: a BASE to form a SALT, and reacts with SULFUR DIOXIDE), SO2, reacts to form most metals to liberate HYDROGEN GAS. SULPHUROUS ACID (USA: SULFUROUS

ACID), H2SO3. acidaemia (biochemistry/haematology) Abnormally high BLOOD acidity (low See also BASIC OXIDE. PH). (USA: acidemia). acidosis (biochemistry/haematology) See also ACIDOSIS. A condition in which the pH of the BLOOD is acidic beyond the NORMAL acid anhydride (chemistry) Member range (7.35 to 7.45). Acidosis may result of a GROUP of ORGANIC COMPOUNDS, from the generation of excess ACID GENERAL FORMULA RCOOCOR# and the resultant disturbance of the (where R and R# are alkyl radicals), ACID/BASE BALANCE, as occurs in that can be regarded as a CARBOXYLIC DIABETES and renal disease; or from ACID from which a MOLECULE of WATER failure to expire CARBON DIOXIDE, has been removed. which may occur in pneumonia, emphysema and congestive HEART failure. acid/base balance (bichemistry/ haematology) The ratio of acidic to BASIC acid phosphatase (biochemistry) A lysosomal ions in a SOLUTION. In vivo the acid/ ACID hydrolase that hydrolyses phosphoric BASE BALANCE is controlled physiologically, ACID esters. It is important in the and disturbances can have profound effects. ABSORPTION and METABOLISM of CARBON DIOXIDE is transported in the carbohydrates, nucleotides and phospholipids. BLOOD primarily as BICARBONATE ions SERUM levels of acid phosphatase become

(HCO3-), the BICARBONATE ION being elevated in patients with METASTATIC formed in the RED BLOOD CELL by carbonic prostatic CARCINOMA, BENIGN prostatic anhydrase. BICARBONATE is important HYPERTROPHY, prostatitis, Paget’s disease in maintaining BLOOD pH at 7.4. Disturbances and metastases to BONE and LIVER from in acid/BASE BALANCE affect BLOOD breast CARCINOMA. pH, giving rise to ACIDOSIS or ALKALOSIS. acid phosphatase stain (histology) acid chloride (chemistry) Member of a Histochemical enzymatic staining GROUP of VOLATILE pungent-smelling technique.

9 ACID PICRO MALLORY STAIN ACOUSTIC PRESSURE acid picro mallory stain (histology) ACMT (education) An abbreviation of A histological staining technique that ‘A’merican ‘C’ollege of ‘M’edical may be used to make CONNECTIVE ‘T’echnologists. TISSUE visible under the MICROSCOPE. acne vulgaris (medical) A CHRONIC acid salt (chemistry) SALT formed when SKIN disease affecting the SEBACEOUS not all the replaceable HYDROGEN GLANDS of the face, shoulders, back atoms of an ACID are substituted by or chest. It occurs most often in people a METAL or its equivalent; e.g. SODIUM between the ages of 14 and 20. The HYDROGENCARBONATE medical name for a blackhead is comedo; comedones are found not only in the (BICARBONATE), NaHCO3, diammonium acne of puberty but also as a result of hydrogenphosphate, (NH4)-2HPO4. exposure of the SKIN to oil and grease. acid value (AV) (chemistry) Measure of the amount of free FATTY ACID present aconitase (biochemistry) The ENZYME in fat or oil, indicated by the number that reversibly interconverts CITRIC of milligrams of POTASSIUM HYDROXIDE ACID, cis-aconitic ACID and isoCITRIC required to neutralize the FATTY ACIDS ACID in the CITRIC ACID (KREBS) in 1g of the substance being tested. CYCLE by DEHYDRATION and HYDRATION reactions. acini (histology) GROUP of small sacs ACOP (quality standards) An abbreviation or cavities lined with secreting CELLS of ‘A’pproved ‘C’ode ‘O’f ‘P’ractice. in a GLAND. [Greek, meaning ‘bunch of grapes’.] Sing; ‘acinus’. ACOS (advisory committee) An abbreviation of ‘A’dvisory ‘C’ommittee acipimox (pharmacology) A drug ‘O’n ‘S’afety. administered orally in cases of hyperlipidaemia (USA: hyperlipidemia), acoustic (physics) Pertaining to sound to reduce or change the proportions waves. of various LIPIDS in the bloodstream. It acts, similar to nicotinic acid, by inhibiting acoustic nerve tumour (medical/ synthesis of LIPIDS in the LIVER. histology) A FIBROUS TISSUE TUMOUR which forms on the ACOUSTIC NERVE, ack. (literature terminology) An abbreviation one of the CRANIAL NERVES which of ‘acknowledge. Also termed ackt. connects the BRAIN with the EAR. As it grows it presses upon the BRAIN ackt (literature terminology) See ack. STEM and on the other CRANIALNERVES which originate there causing giddiness, ACM (advisory committee) An abbrevia- double vision, deafness, weakness of tion of ‘A’dvisory ‘C’ommittee on one side of the face, and various other ‘M’utagenesis. signs that points to its presence. (USA: acoustic nerve tumor). ACME (computing) An abbreviation of ‘A’dvanced ‘C’omputer for ‘ME’dical acoustic pressure (audiology) The research. VARIATION in the PRESSURE of a medium as a sound is conducted through it. The human EAR is sensitive to sound

10 ACOUSTIC RADIATIONS ACRYLAMIDE

PRESSURE variations of as little as at 530 nm when intercalated into 0.0001 dyne per square centimetre (USA: doublestranded DNA, or at 640 nm when dyne per square centimeter) and to about ionically bound to single-stranded DNA. a million-fold range of pressures. It produces MUTATIONS, some involving reading frame shifts, although its acoustic radiations (audiology) The carcinogenicity is uncertain. pathways running from the MEDIAL geniculate bodies to the AUDITORY acriflavine (chemistry/pharmacology) Orange CORTEX, which transmit information CRYSTALLINE ORGANIC COMPOUND about sounds. used as an ANTISEPTIC. Also termed: 2,8-diaminoACRIDINE methochloride. acoustics (physics) The scientific study of the physical properties of sound. acroanaesthesia (medical) Loss of sensation in one or more of the bodily ACP (society) An abbreviation of extremities. (USA: acroanesthesia). ‘A’ssociation of ‘C’linical ‘P’athologists. acrocentric chromosome (genetics) A CHROMOSOME whose CENTROMERE acquired characteristics (microbiology/ is towards one end. biology) Physical or behavioural (USA: behavioral) characteristics that are acrolein (chemistry) CH2=CHCHO acquired during INTERACTION of an Colourless (USA: colorless) LIQUID organism and its ENVIRONMENT during ORGANIC COMPOUND, with a pungent its lifetime (e.g. scars following WOUNDS), odour (USA: odor). Also termed: 2-propenal. and which cannot be genetically transferred to any offspring. acromegaly (medical/biochemistry) A condition produced by over-SECRETION See also LAMARCKISM. of the PITUITARY GROWTH HORMONE, commonly as the result of a TUMOUR acquired immune deficiency syndrome (USA: tumor) of the PITUITARY GLAND. (AIDS) (medical/virology) VIRUS disease GIGANTISM occurs in cases were more commonly known by its abbreviation ACROMEGALY occurs early in life, before AIDS. A disease caused by the HIV the bones have stopped growing. TREATMENT (human immunodeficiency) VIRUS, is directed toward restoring the LEVEL transmitted through the exchange of of GROWTH HORMONE to NORMAL and body fluids such as BLOOD or SEMEN. preventing further GROWTH of the PITUITARY TUMOUR (USA: pituitary tumor), and may acridine (chemistry) A mutagenic be achieved by RADIOTHERAPY, surgery COMPOUND occurring in coal tar that or the use of the drug bromocriptine. has been used in the manufacture of dyes and intermediates. Derivatives are acrosome (biology) Cap-like structure used as antiseptics e.g. acriflavin, and at the tip of ANIMAL SPERM CELLS. antimalarial drugs. ACRIDINE is a strong It contains ENZYMES that dissolve irritant to MUCOUS MEMBRANES and the MEMBRANE of the OVUM during SKIN, and it causes sneezing on inhalation. FERTILIZATION. acridine orange (chemistry) A dye used acrylamide (chemistry) A substance used to stain NUCLEIC ACIDS. It fluoresces in the preparation of clear GEL for use

11 ACRYLAMIDE GEL ELECTROPHORESIS ACTION POTENTIAL in ACRYLAMIDE GEL ELECTROPHORESIS. MYOSIN in skeletal MUSCLE. It exists in Humans exposed to ACRYLAMIDE two forms: G-ACTIN, which is globular, MONOMER, but not its polymers, are and its POLYMER, F-ACTIN, which is fibrous. vulnerable to neurotoxic injury. Although ACUTE high doses can result in an actinic radiation (physics/chemistry) encephalopathy that is apparently reversible, ELECTROMAGNETIC RADIATION repeated smaller doses are cumulative (particularly ULTRAVIOLET RADIATION) and result in a distal sensorimotor axonopathy. that can cause a CHEMICAL REACTION. acrylamide gel electrophoresis (chemis- actinide (chemistry) Member of a SERIES try) A technique using an ACRYLAMIDE of elements in GROUP IIIB of the GEL for the electrophorectic separation PERIODIC TABLE, of ATOMIC NUMBERS of proteins and RNA according to their 90 to 103 (ACTINIUM, at. no. 89, is MOLECULAR WEIGHT. The MONOMER sometimes also included). All ACTINIDES can be cast in the form of sheets or are RADIOACTIVE. Also termed: actinoid. cylinders by polymerisation in situ to give a clear GEL. actinium (chemistry) Ac RADIOACTIVE ELEMENT in GROUP IIIB of the acrylic resin (chemistry/OPTICS) TRANS- PERIODIC TABLE (usually regarded PARENT thermoplastic formed by the as one of the ACTINIDES); it has several POLYMERIZATION of ESTER or AMIDE isotopes, with half-lives of up to 21.7 derivatives of acrylic ACID. The resins years. It results from the DECAY of are used to make artificial fibres (USA: URANIUM-235. At. no. 89; r.a.m. 227 fibers) and for optical purposes, such (most STABLE ISOTOPE). as making lenses (e.g. Acrilan, PERSPEX). actinomycetes (microbiology) GROUP of mostly saprophytic BACTERIA that acrylonitrile (chemistry) CH2=CHCN Colourless (USA: colorless) LIQUID are characterized by branching NITRILE used in manufacture of ACRYLIC MULTICELLULAR filaments (hyphae). RESINS. Also termed: vinyl cyanide, propenonitrile. actinomycin D (microbiology) A CYTO- TOXIC ANTIBIOTIC produced by ACS (society) An abbreviation of Streptomyces parvullus. ACTINOMYCIN ‘A’merican ‘C’hemical ‘S’ociety. D inhibits DNA-dependent RNA SYNTHESIS and DNA SYNTHESIS. In ACT (1 advisory committee; 2, 3 humans, it produces BONE MARROW education) 1 Abbreviation of ‘A’dvisory suppression, GASTROINTESTINAL ‘C’ouncil on ‘T’echnology. 2 Abbreviation toxicity and the possibility of anaphalaxis. of ‘A’ssociate of the ‘C’ollege of ‘T’echnology. 3 An abbreviation of action (physics) An alternative term ‘A’merican ‘C’ollege of ‘T’oxicology. for FORCE.

ACTH (biochemistry) An abbreviation action current (physiology) See ACTION of ‘A’dreno‘C’ortico‘T’rophic‘H’ormone. POTENTIAL. (USA: Adrenocorticotropic HORMONE). action potential (physiology) The change actin (histology) A PROTEIN whose in POTENTIAL across the MEMBRANE INTERACTION with MYOSIN forms ACTO- of a MUSCLE or NERVE CELL that generates

12 ACTIVATED CHARCOAL ACUTE an IMPULSE along its length. Also termed GLUTAMIC ACID and aspartic ACID, and ACTION CURRENT. for some ENZYMES a COENZYME or cofactor.

See also ALL-OR-NONE RESPONSE. active site (biochemistry) Part of an ENZYME MOLECULE to which its activated charcoal (chemistry) CHARCOAL SUBSTRATE is bound during CATALYSIS. that, after PYROLYSIS during manufacture, has been subjected to steam or AIR at active transport (biochemistry/ high TEMPERATURE, which makes it physiology) The various ENERGY- an effective absorber of substances. requiring processes that permit the movement of chemicals/ions across activation energy (chemistry) Amount biological membranes. All ACTIVE of ENERGY required to initiate the breaking TRANSPORT systems require metabolic and re-formation of CHEMICAL BONDS, ENERGY; can be inhibited by chemicals and thus to start a CHEMICAL REACTION. that affect ENERGY METABOLISM; are selective in terms of the molecules active immunity (immunology) An transported; are saturable; and can IMMUNITY to a disease that has been transport chemicals against a acquired through previous exposure CONCENTRATION GRADIENT. Contrast to it. Contrast passive IMMUNITY. DIFFUSION. See also IMMUNE SYSTEM. actomyosin (physiology) Substance formed active mass (chemistry) CONCENTRATION from the association of ACTIN and MYOSIN of a substance that is involved in a in skeletal MUSCLE, upon which the CHEMICAL REACTION. contraction mechanism is based. active site (biochemistry) Part of an acupuncture (medical) A method of ENZYME that firstly specifically binds TREATMENT used in Chinese medicine the SUBSTRATE(S) and secondly for the TREATMENT of pain, to produce catalyses PRODUCT formation. The anaesthesia (USA: anesthesia), or to ACTIVE SITE consists of two or more treat various general illnesses. It consists often overlapping regions that recognize of puncturing the surface of the body and bind the SUBSTRATE(S) and then with needles at traditionally established catalyse the ensuing reactions. The sites. The needles may be rotated, initial binding of the SUBSTRATE involves vibrated or electrically stimulated. There the formation of non-COVALENT BONDS is evidence to suggest that pain can (e.g. HYDROGEN BONDS, IONIC be relieved by ACUPUNCTURE, and BONDS, HYDROPHOBIC INTERAC- an explanation sought in Western terms TIONS) with chemical groups at the is that needling has been shown to ACTIVE SITE. During CATALYSIS, increase BLOOD levels of naturally COVALENT BONDS may be formed, occurring substances called endorphins, and then broken, as part of the REACTION which are known to be concerned in mechanism. The chemical groups involved the relief of pain. in CATALYSIS include the chemically reactive sidechains of the AMINO ACIDS acute (1 medical; 2 mathematics) 1 HISTIDINE, LYSINE, ARGININE, SERINE, Any process which has a sudden onset THREONINE, TYROSINE, CYSTEINE, and has a relatively brief duration.

13 ACUTE ABDOMEN ADDICTION

Contrast CHRONIC. 2 Describing an ad hoc. (General terminology) Unprinci- angle of less than 90 degrees. pled, particularly of explanations constructed post hoc. to explain DATA. acute abdomen (medical) The condition in which the patient is suffering from ADA (1 chemistry; 2 society) 1 An ACUTE severe pain in the ABDOMEN. abbreviation of ‘A’cetone-‘D’icarboxylic This is typical in such cases as appendicitis, ‘A’cid. 2 An abbreviation of ‘A’merican/ perforated ulcers, and ACUTE INFLAM- ‘A’ustralian ‘D’ental ‘A’ssociation. MATION of the GALL-BLADDER. adaptation (1,2 biology; 3 physiology) acute brain disorder (medical) Any 1 CHARACTERISTIC of an organism organic BRAIN disorder that is temporary, which improves that organism’s chance and from which the patient makes a of survival in its ENVIRONMENT. 2 Change full recovery. in the BEHAVIOUR (USA: behavior) of an organism in RESPONSE to environmental acute tolerance (pharmacology) Develop- conditions. 3 Change in the sensitivity ment of TOLERANCE to a drug after of a sensory mechanism after it has only one or a few doses. Contrast been exposed to a particular continuous CHRONIC TOLERANCE. STIMULUS. This allows the mechanism to adjust the sensitivity scale according acyclic (chemistry) Not CYCLIC; to the LEVEL of the STIMULUS; e.g. describing a chemical COMPOUND that the process by which the EYE is able does not contain a ring of atoms in its to adjust to varying intensities of LIGHT. molecular structure. adaptive radiation (biology) Mechanism of EVOLUTION in which a single ancestor acyclovir (pharmacology/microbiology) gives rise to a number of SPECIES A SYNTHETIC antiviral drug. It acts as that coexist but occupy different an inhibitor of DNA SYNTHESIS, and is ECOLOGICAL NICHES. Also termed: active against the VIRUS of HERPES divergent EVOLUTION. simplex (HSV), but less so against the VIRUS of HERPES ZOSTER (HVZ). adaptive value (genetics) The amount ACYCLOVIR is phosphorylated by HERPES- of increase or decrease in reproductive specific thymidine kinases, resulting in fitness that a given GENOTYPE or MUTATION the formation of acyclo-GTP, that inhibits confers, relative to other GENOTYPES viral DNA polymerase 10 to 30 times and in a particular ENVIRONMENT. more efficiently than it does cellular DNA polymerase. Acyclo-GTP is incorporated ADCC (histology/immunology) An into viral DNA causing TERMINATION abbreviation of ‘A’ntibody-‘D’ependent of strand SYNTHESIS. See HERPES. ‘C’ellular ‘C’ytotoxicity. acyl group (chemistry) Part of an ORGANIC adder (computing) Part of a COMPUTER COMPOUND that has the FORMULA that adds digital signals (addend, augend RCO; where R is a HYDROCARBON and a carry DIGIT) to produce the

GROUP, (e.g. acetyl GROUP CH3CO-). sum and a carry DIGIT.

addiction (medical/biochemistry) DEPEND- ENCE on the use of a drug such as

14 ADDISON’S DISEASE ADENOIDS

ALCOHOL, HEROIN, or cocaine. The habits large MOLECULE such as DNA or PROTEIN. of drug takers may be such as to LEAD The term may cover both the chemical to grave deterioration in their general and the portion of the MACROMOLECULE physical as well as mental health. with which it is combined.

Addison’s disease (medical/biochemistry) adenine (molecular biology) One of the A degenerative illness caused by deficiency four nitrogenous bases which form the of adrenocortical HORMONE. It is CORE of both DNA and RNA. It pairs characterised by weakness, vomiting, with THYMINE (T) in DNA, and URACIL anorexia, HYPERTENSION, IRRITABILITY, (U) in RNA. Also termed: 6-aminopurine. and other symptoms. The HORMONE deficiency is caused by destruction of See also REPLICATION. the suprarenal GLANDS due to AUTO- IMMUNE DISEASE, TUBERCULOSIS adenitis (medical) INFLAMMATION of or TUMOURS (USA: tumors) leading a GLAND. Usually applied to to loss of the HORMONES which are INFLAMMATION of the lymphatic GLANDS. essential to life. The disease is rare in childhood or old age. adenocarcinoma (histology) A MALIGNANT tumor arising from EPITHELIUM and addition reaction (chemistry) CHEMICAL comprising MALIGNANT CELLS CHARAC- REACTION in which one substance TERISTIC of the TISSUE from which it combines with another to form a third, arises. Due to profound degeneration without any other substance being of MORPHOLOGY accompanying produced. The term is most commonly MALIGNANT TRANSFORMATION in the used in ORGANIC CHEMISTRY; e.g. CANCER CELLS, the TISSUE of ORIGIN for the REACTION between HYDROGEN of a disseminated ADENOCARCINOMA BROMIDE (HBr) and ETHYLENE often cannot be determined. (ETHENE, CH2=CH2) to form ETHYL

BROMIDE (bromoethane, C2H 5Br). adenofibroma (histology) A TUMOUR (USA: tumor) composed of CONNECTIVE See also SUBSTITUTION REACTION. TISSUE with glandular elements. additive effect (biochemistry) The adenohypophysis (biochemistry) The combined effect of two or more chemicals, ANTERIOR portion of the HYPOPHYSIS this being equal to the sum of the (PITUITARY), which secretes a VARIETY individual effects. of tropic HORMONES in RESPONSE to additive variance (genetics) The COMPO- the releasing factors (releasing HORMONES) NENT of GENETIC VARIANCE that is secreted by the HYPOTHALAMUS. due to the ADDITIVE EFFECT of two or HORMONES of the ADENOHYPOPHYSIS more genes on the trait in question, i.e. are adrenocorticotrophic HORMONE (ACTH), excluding any dominance or INTERACTION. FOLLICLE-STIMULATING HORMONE (FSH), LUTEINIZING HORMONE (LH), address (1,2 computing) 1 identity of a PROLACTIN, somatotrophin (GROWTH location’s position in a MEMORY or store. HORMONE), and THYROID-STIMULATING 2 specification of an OPERAND’S location. HORMONE (TSH). adduct (biochemistry) A chemical moiety adenoids (anatomy) Pair of LYMPH that has become covalently bound to a GLANDS, more prominent in children

15 ADENOMA ADH than in adults, present at the back of adenosine monophosphate (AMP) the nose, which may become enlarged (biochemistry) A NUCLEOTIDE that as the result of CHRONIC INFECTION is part of the ATP ENERGY CYCLE and obstruct the free passage of AIR. that supplies ENERGY to drive reactions INFECTION and enlargement of the that require input of FREE ENERGY, ADENOIDS is associated with CHRONIC such as MUSCLE contraction. FREE tonsillitis and recurrent colds. ENERGY is liberated when ATP is hydrolysed to AMP and pyrophosphate. adenoma (histology) A TUMOUR (USA: The AMP can be recycled to ADP via tumor), usually BENIGN, arising from adenylate KINASE and oxidative EPITHELIUM and containing CELLS PHOSPHORYLATION. CHARACTERISTIC of the TISSUE from which it arises. The term is most often adenosine triphosphatase (atpase) stain applied to TUMOURS (USA: tumors) of (histology) ENZYME histochemical staining GLANDS or of mucosal EPITHELIUM technique. (e.g. the lining of the mouth, bronchial tree, intestines, etc.). adenosine triphosphate (ATP) (biochemistry) A chemical COMPOUND found in adenomyoma (histology) A BENIGN all living CELLS, essential in the production TUMOUR (USA: tumor) made up of of PROTEIN and a source of cellular GLANDS and MUSCLE. ENERGY. It carries the chemical ENERGY obtained from the oxygenation of food. adenomyosis (histology) Ectopic When it is converted to ADENOSINE endometrium in the MUSCLE. DIPHOSPHATE and then ADENOSINE adenopathy (medical) Disease of a GLAND. MONOPHOSPHATE, the REACTION releases ENERGY that is used in the adenosine (biochemistry) COMPOUND CELL’S METABOLISM, to energise consisting of the BASE ADENINE linked GROWTH, muscular contraction, or the to the SUGAR RIBOSE. Its phosphates SODIUM PUMP, etc. are important ENERGY carriers in biochemical processes. adenosis (medical) Any disease or disorder of the GLANDS. adenosine deaminase (ADA) (biochemistry/immunology) An ENZYME involved adenovirus (virology) One of a GROUP in the IMMUNE SYSTEM. Lack of it is of VIRUSES first isolated from human one of the causes of severe combined adenoid TISSUE, that contain DNA and immune deficiency. are found in a number of animals, including human beings. They cause infections adenosine diphosphate (ADP) (biochemis- of the respiratory tract, (e.g. LARYNGITIS try) The PRECURSOR of ADENOSINE and some kinds of pneumonia), conjunctival TRIPHOSPHATE, formed by the addition infections and may induce cancerous of an extra PHOSPHATE GROUP. ENERGY TUMOURS (USA: tumors). is released when it is formed from ADENOSINE TRIPHOSPHATE (ATP). It ADH (biochemistry) An abbreviation is converted back to ATP during of ‘A’nti‘D’iuretic ‘H’ormone. RESPIRATION. See also VASOPRESSIN.

16 ADHESION ADVISORY COMMITTEE ON DANGEROUS PATHOGENS adhesion (physics) Attraction between NORADRENALINE (USA: norepinephrine); different substances (at the atomic or and the outer CORTEX, which secretes molecular LEVEL); e.g. between WATER certain STEROID HORMONES. Also particles and GLASS, creating a MENISCUS. termed: suprarenal GLAND.

See also COHESION. adrenaline (biochemistry) HORMONE secreted by the MEDULLA of the ADRENAL ADI (pharmacology) An abbreviation GLAND and at some NERVE endings of ‘A’cceptable ‘D’aily ‘I’ntake. of the SYMPATHETIC NERVOUS SYSTEM. It is produced when the body prepares adiabatic process (physics) Process for violent physical ACTION. Its effects that occurs without interchange of HEAT include increased HEARTBEAT, raised with the surroundings. levels of SUGAR (GLUCOSE) in the BLOOD and improved MUSCLE ACTION. adipose tissue (histology) TISSUE that Also termed: adrenalin. (USA: epinephrine). contains CELLS specialized for the STORAGE of fat. It gives INSULATION adrenergic drugs (biochemistry) Sub- and acts as an ENERGY reserve. stances, such as AMPHETAMINE, that increase activity at ADRENERGIC adiposis (histology) An ABNORMAL synapses. accumulation of fatty TISSUE in the body. adrenergic (biochemistry) Releasing or stimulated by ADRENALINE (USA: ADMA (pharmacology) An abbreviation epinephrine) or NORADRENALINE (USA: of ‘A’merican ‘D’rug ‘M’anufacturers’ norepinephrine). The term is applied ‘A’ssociation. to the SYMPATHETIC NERVOUS SYSTEM. admittance (Y) (physics) Property that adrenocorticotrophic hormone (ACTH) allows the flow of ELECTRIC CURRENT (biochemistry) PROTEIN released by the across a POTENTIAL DIFFERENCE; ANTERIOR PITUITARY. It controls SECRETION the RECIPROCAL of IMPEDANCE. from the CORTEX of the ADRENAL GLAND. Also termed: CORTICOTROPHIN. ADP (biochemistry) An abbreviation of ‘A’denosine ‘D’i‘P’hosphate. adsorbent (physics) Substance on which ADSORPTION takes place. ADR (biochemistry/toxicology) An abbreviation of ‘A’dverse ‘D’rug ‘R’eaction. adsorption (physics) Accumulation of molecules or atoms of a substance adrenal cortex (anatomy) Outer part (usually a GAS) on the surface of another of the ADRENAL GLAND. substance (a SOLID or a LIQUID). adrenal gland (anatomy/biochemistry) Advisory Committee on Dangerous ENDOCRINE GLAND that occurs in Pathogens (ACDP) (advisory committee) vertebrates (in mammals there are two A UK Government committee which advises GLANDS, located on the kidneys). Each the Health and Safety Commission, the GLAND has two sections: the central Health and Safety Executive and Health MEDULLA, which secretes the HORMONES and Agriculture Ministers, as required, ADRENALINE (USA: epinephrine) and on all aspects of hazards and risks to

17 ADVISORY COMMITTEE ON MUTAGENESIS AFFINITY workers and others from exposure to aerosol transmission (microbiology) pathogens. The ACDP was SET up in Person-to-person transmission of disease 1981 following a second outbreak of agents via AEROSOLised droplets. Many LABORATORY-acquired smallpox and respiratory diseases are transmitted was the successor to the Dangerous in this way. Pathogens Advisory GROUP. aerotolerant (microbiology) Ability of Advisory Committee on Mutagenesis an ANAEROBIC MICRO-ORGANISM (ACM) (advisory committee) Canadian to grow in AIR, albeit usually poorly, expert committee to advise the Canadian especially after ANAEROBIC ISOLATION. government on the evaluation and regulation of chemical mutagens. aesthesiometer (physiology/physics) A device for measuring SKIN sensitivity, -aemia (haematology) Suffix pertaining usually by determining the two-point to the BLOOD. (USA: -emia). THRESHOLD. aerobic (microbiology) Pertaining to an aetiology (1, 2 epidemiology) 1 The organism that requires free OXYGEN, or cause or causes of a disease. 2 Study to the uptake of OXYGEN by an organism. of the causes of a disease. (USA: etiology). AEROBIC CELLS or organisms require OXYGEN and depend upon the pathways See also EPIDEMIOLOGY. of AEROBIC RESPIRATION i.e. GLYCOLYSIS to PYRUVATE, TRICARBOXYLIC ACID AFAS (society) An abbreviation of CYCLE and ELECTRON TRANSPORT ‘A’ssociation ‘F’rançaise pour system, for their ENERGY generation. I’‘A’vancement des ‘S’ciences. [French, See AEROBIC RESPIRATION. meaning ‘Association for the Advancement aerobic respiration (biochemistry) of the Sciences’.] Process by which CELLS obtain ENERGY from the OXIDATION of fuel molecules AFD (physics) An abbreviation of by MOLECULAR OXYGEN with the ‘A’ccelerated ‘F’reeze ‘D’ried. formation of CARBON DIOXIDE and WATER. This process yields more ENERGY afferent (anatomy) Leading towards than ANAEROBIC RESPIRATION. (e.g. towards an ORGAN of the body); the term is particularly used of various See also GLYCOLYSIS; KREBS CYCLE. NERVES and BLOOD VESSELS. aerogenic (microbiology) GAS producing. See also EFFERENT. Contrast ANAEROGENIC. affinity (1 chemistry; 2 biology) 1 The aerosol (1, 2 physics) 1 SUSPENSION tendency of some substances to combine of particles of a LIQUID or SOLID in a chemically with others e.g. the likelihood GAS; a type of COLLOID. Haze and cloud of a SUBSTRATE binding to an ENZYME, are the commonest atmospheric AEROSOLS, a LIGAND binding to a RECEPTOR, or with fall speeds much less than 10 mm/ an ANTIBODY combining site with a single sec. 2 Device used to produce such a antigenic DETERMINANT. 2 A similarity SUSPENSION. of structure or form between different SPECIES of plants or animals.

18 AFFINITY LABELLING AGGR. affinity labelling (chemistry) A procedure afterdischarge (physics) Electrical activity for identifying or quantifying receptors in a neuron continuing for a brief time by covalently binding a high AFFINITY after the STIMULUS has stopped. LIGAND to the RECEPTOR. Binding can be achieved by either using a LIGAND AFTM (society) An abbreviation of possessing a chemical GROUPING capable ‘A’merican ‘F’oundation of ‘T’ropical of covalently binding to the RECEPTOR ‘M’edicine. directly, or by allowing a cross-linking REAGENT to covalently bind to both ag. feb. (medical) An abbreviation of the LIGAND and the RECEPTOR. ‘ag’grediente feb’re. [Latin, meaning ‘when the FEVER increases’.] aflatoxin (mycology) One of a FAMILY of mycotoxins, including CARCINOGENS AGA (society) An abbreviation of and HEPATOTOXICANTS, produced by ‘A’merican ‘G’enetic ‘A’ssociation. the mould (USA: mold) Aspergillus flavus and related FUNGI. AFLATOXINS are agar (microbiology) Complex POLY- found as contaminants in both human SACCHARIDE obtained from seaweed, foodstuffs and ANIMAL feed, particularly especially that of the GENUS Gelidium. in corn and peanuts. The extent of It resists the digestive ACTION of AFLATOXIN contamination is a FUNCTION BACTERIA, and is therefore used by of environmental conditions at the time BACTERIOLOGISTS to make a medium of harvest and STORAGE conditions. on which cultures can be grown. It is Although generally a LIVER commonly combined with broth or BLOOD CARCINOGEN, there are SPECIES for this purpose. Also termed: AGAR- differences. CARCINOGENESIS is believed AGAR. to be initiated when this potent ELECTROPHILE reacts with DNA, and ageing (physiology) The phenomenon HEPATOTOXICITY when it reacts with of progressive failure of self-repair of proteins to cause either fatty LIVER an organism. or LIVER necrosis. agglutination (physiology) Clumping AFNOR (quality standards) An or sticking together, e.g. of RED BLOOD abbreviation of ‘A’ssociation ‘F’rançaisede CELLS from incompatible BLOOD ‘Nor’malisation, French Standards GROUPS, or of BACTERIA. Association. AGGLUTINATION is commonly used as an END POINT in immunological tests. AFP (biochemistry) An abbreviation of ‘a’lpha‘f’eto‘p’rotein. agglutinin (immunology) ANTIBODY that causes AGGLUTINATION. The term african swine fever (virology) A DNA commonly refers to such an ANTIBODY VIRUS with icosahedral SYMMETRY, in a person’s BLOOD PLASMA that enveloped, within the VIRUS FAMILY reacts with the RED BLOOD CELLS Iridoviridae. of another person’s BLOOD. after birth (medical) PLACENTA and aggr. (general terminology) An membranes expelled in the third stage abbreviation of ‘aggr’egate. of LABOUR (USA: LABOR).

19 AGIT. AIST agit. (general terminology) Abbreviation ahr (EPIDEMIOLOGY/risk ANALYSIS) of ‘agit’atum. [Latin, meaning ‘shaken’.] An abbreviation of ‘a’cceptable ‘h’azard ‘r’ate. aglm (general terminology) An abbreviation of ‘ag’g‘l’o‘m’erate. AIBS (society) An abbreviation of ‘A’merican ‘I’nstitute of ‘B’iological agonist (physiology/pharmacology) ‘S’ciences. Substances or drugs which possess intrinsic activity. The responses to AID (1 medical/microbiology; 2 medical) AGONISTS may be prevented or reduced 1 An abbreviation of ‘A’cute ‘I’nfectious by ANTAGONISTS. See ANTAGONIST. ‘D’isease. 2 An abbreviation of ‘A’rtificial ‘I’nsemination by ‘D’onor. agranulocytosis (haematology) BLOOD disorder in which there is a deficiency AIDS (medical/virology) An abbreviation of granulocytes. It may be accompanied of ‘A’cquired ‘I’mmune ‘D’eficiency by mouth ulcers and a sore THROAT, ‘S’yndrome. and a much reduced resistance to INFECTION. It has been found to be Aids-related complex (ARC) (medical/ associated with the toxic side effects virology) The medical condition of a on the BONE MARROW of various drugs, debilitated HIV-POSITIVE person not but the commonest are those used in diagnosed with AIDS. the chemotherapeutic TREATMENT of CANCER. Monitoring patients at risk See also AIDS. by conducting regular BLOOD counts enables the offending drug to be withdrawn AIP (society) An abbreviation of ‘A’merican immediately if there is any suspicion ‘I’nstitute of ‘P’hysics. that the white CELL count has dropped. The condition is sometimes fatal due air (chemistry) MIXTURE of gases that to the impaired IMMUNE SYSTEM. forms the EARTH’S ATMOSPHERE. Its composition varies slightly from place agv (chemistry) An abbreviation of ‘a’niline to place—particularly with regard to the ‘g’entian ‘v’iolet. amounts of CARBON DIOXIDE and WATER VAPOUR it contains—but the AVERAGE agw (measurement) An abbreviation composition of dry AIR is (percentages of ‘a’ctual ‘g’ross ‘w’eight. by VOLUME): NITROGEN 78. 1 per cent; OXYGEN 20.9 per cent; agon 0.9 per AHF (1 chemistry; 2 haematology; 3 cent; other gases 0.1 per cent. microbiology) 1 An abbreviation of ‘A’nhydrous ‘H’ydro‘F’luoric acid. 2 ‘A’nti- AIS (education) An abbreviation of ‘H’aemophilic (USA: antihemophilic) ‘A’ssociate of the ‘I’nstitute of ‘F’actor. 3 An abbreviation of ‘A’rgentine ‘S’tatisticians. ‘H’aemorrhagic ‘F’ever (USA: Argentine hemorrhagic fever). AIST (education) An abbreviation of ‘A’ssociate of the ‘I’nstitute of ‘S’cience AHG (physiology/biochemistry) An and ‘T’echnology. abbreviation of ‘A’nti‘H’aemophilic ‘G’lobulin (USA: antihemophilic globulin).

20 AIT ALBUMINURIA

AIT (society) An abbreviation of ‘A’merican pigmentation in the SKIN, HAIR, eyes, ‘I’nstitute of ‘T’echnology. etc. It is commonly caused by a RECESSIVE ALLELE; the corresponding AIWM (society) An abbreviation of NORMAL ALLELE codes for the ENZYME ‘A’merican ‘I’nstitute of ‘W’eights and tyrosinase which is one step in the ‘M’easures. production of MELANIN, the PIGMENT that usually gives these tissues their AIWMA (education) An abbreviation COLOUR (USA: color). Albino humans of ‘A’ssociate Member of the ‘I’nstitute are healthy but they must avoid bright of ‘W’eights and ‘M’easures sunlight which damages their SKIN ‘A’dministration. and eyes. ak (medical) An abbreviation of ‘a’bove albumen (biochemistry) White of an EGG. ‘k’nee. albumin (biochemistry/haematology) A akinesia (medical) Loss of muscular GROUP of proteins characterised by their responsiveness, arrest of motion. HEAT COAGULATION characteristics and SOLUBILITY in DILUTE SALT solutions. AI (chemistry) The CHEMICAL SYMBOL Although found in most tissues and SPECIES, for ELEMENT 13, aluminum. they are best known from mammalian BLOOD. SERUM ALBUMINS together form -al (chemistry) Suffix usually denoting the most abundant CLASS of BLOOD that an ORGANIC COMPOUND is an proteins, and are mainly responsible for ALDEHYDE. keeping the OSMOTIC PRESSURE CONSTANT in the circulation, and facilitates al. (chemistry) An abbreviation of ‘al’cohol. the transport of fats, HORMONES, haptens and drugs. ALBUMINS vary in their Ala (physiology/biochemistry) An composition, but all contain CARBON, abbreviation of ‘Ala’nine. HYDROGEN, NITROGEN, OXYGEN and SULPHUR (USA: sulfur). ALBUMINS are ALAC (society/quality standards) An colloidal and do not pass through parchment abbreviation of ‘A’merican association membranes or the membranes of NORMAL for ACCREDITATION of ‘L’aboratory living CELLS; they are coagulated by ‘A’nimal ‘C’are. HEAT, following which they become INSOLUBLE in WATER until treated with ALAD (biochemistry/haematology) An CAUSTIC ALKALIS (USA: caustic alkalies) abbreviation of ‘A’mino‘L’evulinic ‘A’cid or MINERAL ACIDS; they are precipitated ‘D’ehydratase. See FREE ERYTHROCYTE by various chemicals such as ALCOHOL, PROTOPORPHYRIN. tannin, NITRIC ACID and mercury perchloride. alanine (Ala) (biochemistry) CH3C(NH2)- COOH AMINO ACID commonly found albuminuria (biochemistry) A condition in proteins. Also termed: 2- where ALBUMIN is found in the URINE, aminoPROPANOIC ACID. which it is not normally present in as it does not pass through the KIDNEY CELLS albinism (genetics) A genetically deter- unless they are damaged e.g. by NEPHRITIS mined condition in which there is no or INFLAMMATION of the KIDNEYS. It

21 ALBUMOSE ALDOL is usually a sign of KIDNEY disease, alcoholics anonymous (AA) (society) but also sometimes of HEART failure. An international organisation, started in the US in 1935, for helping people to albumose (biochemistry) An INTERMEDIATE stop drinking and for rehabilitating them. PRODUCT in the DIGESTION of PROTEIN. alcoholism (medical) ADDICTION to alcian blue stain (histology) Histological ALCOHOL. A condition in which there staining technique for ACID mucins. is CHRONIC or periodic drinking of a compulsive nature. alcian blue/PAS stain (histology) Histological staining technique for ACID aldehyde (chemistry) Member of a large and NEUTRAL mucins. CLASS of ORGANIC COMPOUNDS that have the GENERAL FORMULA RCHO, alcian blue/safranine stain (histology) where R is an ALKYL GROUP or ARYL Histological staining technique for different GROUP. ALDEHYDES may be made types of mast cell. by the controlled OXIDATION of ALCOHOLS. Their systematic names alcohol (1,2 chemistry) 1 Member of a end with the suffix -al (e.g. the systematic large CLASS of ORGANIC COMPOUNDS name of ACETALDEHYDE, CH CHO, that contain one or more hydroxyl (-OH) 3 is ETHANAL). All are REDUCING AGENTS, groups. A PRIMARY ALCOHOL has the and undergo addition, CONDENSATION GENERAL FORMULA R—CH OH, where 2 and polymerisation reactions. When R is an ALKYL GROUP (or H in the case oxidised, they form CARBOXYLIC ACIDS. of METHANOL). A secondary ALCOHOL has the FORMULA RR’CHOH, and a tertiary aldehyde dehydrogenase (biochemistry) ALCOHOL has the FORMULA RR’R” OH. An ENZYME that catalyses the formation ALCOHOLS with two -OH groups are of acids from ALIPHATIC and aromatic diols. ALCOHOLS react with acids to ALDEHYDES. form esters. 2 The term ALCOHOL is often used to refer specifically to ETHANOL. aldehyde fuchsin stain (histology) Histological staining technique for alcohol dehydrogenase (biochemistry) pancreatic islet CELLS. An ENZYME that catalyses the conversion of ALCOHOLS to ALDEHYDES or aldehyde oxidase (biochemistry) A KETONES. The ENZYME is found in the FLAVOPROTEIN, also containing SOLUBLE FRACTION of LIVER, KIDNEY molybdenum, that is found in the SOLUBLE and LUNG, and is the most important FRACTION of LIVER CELLS. Its primary ENZYME involved in the METABOLISM role appears to be the OXIDATION of of foreign ALCOHOLS. It is a DIMER, ENDOGENOUS ALDEHYDES. the subunits of which can occur in several forms, thus giving rise to a large number aldimine (biochemistry) See SCHIFF’S of variants of the ENZYME. BASE.

alcohol withdrawal (medical) An ACUTE aldol (chemistry) CH3CHOHCH2CHO Vis- mental disorder caused by withdrawal cous LIQUID ORGANIC COMPOUND. It is from ALCOHOL, and marked by tremor, an ALDEHYDE, 3 CONDENSATION PRODUCT nausea, sweating, anxiety, IRRITABILITY, of acetaldehyde (ETHANAL). Also termed: and depressed mood. ACETALDOL; beta-hydroxy-butyraldehyde.

22 ALDOL REACTION ALIPHATIC COMPOUND aldol reaction (chemistry) CONDENSATION used to determine people’s sensitivity REACTION between two ALDEHYDE to pain. or two KETONE molecules that produces a MOLECULE containing an ALDEHYDE alginic acid (chemistry) (C6H 8O 6) n (-CHO) GROUP and an ALCOHOL (- Yellowish-white organic SOLID, a OH) GROUP, hence ald-ol REACTION. POLYMER of mannuronic ACID in the PYRANOSE ring form, that occurs in aldose (chemistry) Type of SUGAR brown seaweeds. Even very DILUTE whose molecules contain an ALDEHYDE solutions of the ACID are extremely (-CHO) GROUP and one or more viscous, and because of this property ALCOHOL (-OH) groups. it has many industrial applications. aldosterone (biochemistry) A HORMONE ALGOL (computing) Acronym for the secreted by the CORTEX of the ADRENAL early high-level COMPUTER programming GLAND. Its FUNCTION is to control language ‘ALGO’rithmic ‘L’anguage, the SALT BALANCE of the body, promoting used for manipulating mathematical by its ACTION on the KIDNEY the retention and scientific DATA. of SODIUM ions and WATER and the EXCRETION of POTASSIUM ions. algorithm (computing) Operation or SET of operations that are required aldosterone antagonists (pharmacology) to effect a particular calculation or to DIURETICS such as POTASSIUM manipulate DATA in a certain way, usually canrenoate that act by blocking the to solve a specific problem. The term action of the normal minerlocorticoid is commonly used in the context of HORMONE aldosterone. They are useful COMPUTER programming. in treating OEDEMA (USA: EDEMA) associated with aldosteronism, LIVER alicyclic compound (chemistry) Member failure and certain HEART conditions. of a CLASS of organic chemicals that aleppo boil (medical/microbiology) A possess properties of both ALIPHATIC common name for cutaneous LEISH- COMPOUNDS and CYCLIC compounds. MANIASIS. alimentary canal (anatomy) Tube in algae (biology) Simple plants, which the body of animals along which food may be UNICELLULAR or passes, and in which the food is subjected MULTICELLULAR (e.g. some seaweeds). to physical and chemical DIGESTION ALGAe contain a VARIETY of photosynthetic and is absorbed. Also termed: digestive pigments, and are present in many habitats; tract; enteric canal; GUT. most are aquatic. aliphatic compound (chemistry) An algebra (mathematics) Branch of ORGANIC COMPOUND (HYDROCARBON) mathematics that deals with the general whose molecules contain a main chain properties of numbers by means of of CARBON atoms, as opposed to ring abstract symbols. structures. The chain of CARBON atoms may be straight or branched, and the algesimeter (physiology/physics) An componds saturated or UNSATURATED. instrument, containing a calibrated needle, The CLASS includes ALKANES, ALKENEs and alkynes and their derivatives.

23 ALIZARIN ALKAPTONURIA

alizarin (chemistry) C6H4(CO)2C6H2(OH)2 JAUNDICE, Paget’s disease or BONE Orange-red CRYSTALLINE ORGANIC CARCINOMA. COMPOUND important in the manufacture of dyes. Also termed: 1,2-dihydroxy- alkaline phosphatase stain (histology) anthraquinone. Immunohistochemical staining technique. alizarin red stain (histology) Histological alkaloid (pharmacology) One of a GROUP staining technique for CALCIUM deposits. of NITROGEN-containing ORGANIC COMPOUNDS found in plants, many of alk. (chemistry) An abbreviation of which have pharmacological effects on ‘alk’aline. the NERVOUS SYSTEM and form the basis of many drugs. Common ALKALOIDS alkali (chemistry) A chemical are ATROPINE from the belladonna plant, COMPOUND, usually oxides, hydroxides, cocaine from coca leaves, CAFFEINE or carbonates and bicarbonates of metals. from tea and coffee, MORPHINE, CODEINE Alkalis (USA: alkalies) that combine and other drugs from the OPIUM in the with ACID in WATER to form SALTS, poppy, NICOTINE from tobacco, QUININE hence neutralising the ACID. [pl. ALKALIS and QUINIDINE from Peruvian bark, (USA: alkalies)] See PH. STRYCHNINE from nux vomica seeds. Most ALKALOIDS are CRYSTALLINE alkali metal (chemistry) One of the solids with a very bitter TASTE; they elements in GROUP IA of the PERIODIC are sparingly SOLUBLE in WATER, but TABLE. They are LITHIUM, SODIUM, usually SOLUBLE in organic solvents POTASSIUM, RUBIDIUM, CAESIUM such as ETHANOL, ETHER and (USA: cesium) and FRANCIUM, which TRICHLOROMETHANE. The majority are are all soft silvery metals that react very toxic both by inhalation and ingestion. vigorously with WATER and occur naturally only as their compounds. alkalosis (biochemistry/haematology) A condition in which the PH of the alkaline (chemistry) Having a PH between BLOOD is ALKALINE beyond the 7 and 14. NORMAL range, usually above 7.8, due to a disturbance in the ACID/BASE alkaline congo red stain (histology) BALANCE. Contrast ACIDOSIS. Histological TISSUE staining technique for amyloid. alkane (chemistry) Member of a GROUP of saturated ALIPHATIC COMPOUNDS alkaline earth (chemistry) One of the that have the GENERAL FORMULA metallic elements in GROUP IIA of C nH 2n+ 2; e.g. methane (CH4), ETHANE the PERIODIC TABLE. They are (C2H 6), etc. Also termed: paraffin. BERYLLIUM, MAGNESIUM, CALCIUM, STRONTIUM, BARIUM and RADIUM. alkaptonuria (medical) A genetic disease in which a defective enzyme leads to alkaline phosphatase (biochemistry) the accumulation of a coloured (USA: An ENZYME that hydrolyses PHOSPHATE colored) polymer molecule. This binds monoesters. It has an ALKALINE PH to the collagen of cartilage, making it optimum. An elevation of its activity brittle and easily worn away. The result in the SERUM usually indicates obstructive is a form of osteoarthritis.

24 ALKENE ALLELIC EXCLUSION alkene (chemistry) Member of a GROUP birds, it grows to surround the EMBRYO of UNSATURATED ALIPHATIC COMPOUNDS in the shell; in mammals it becomes that have CARBON-to-CARBON DOUBLE incorporated into the PLACENTA.

BONDS and the GENERAL FORMULA CnH2n; e.g. ETHENE (ETHYLENE, C2H4), PROPENE allele (genetics) One of a pair of genes

(propylene, C3H6), etc. Also termed: OLEFIN. situated at the same location on HOMOLOGOUS CHROMOSOMES that alkoxyalkane (chemistry) An alternative controls a specific inherited trait. If term for an ETHER. the two ALLELES are identical, the individual is a HOMOZYGOTE, in respect alkyl group (chemistry) GROUP formed of that LOCUS, and if they are different, by removing a HYDROGEN ATOM from the individual is a HETEROZYGOTE. an ALIPHATIC COMPOUND, e.g. methane Each GENE may have a very large

(CH4) and ETHANE (C2H6) form methyl number of alternative ALLELES, since

(CH3-) and ETHYL (C2H5-) groups, respectively. an ALLELE need only differ from the It is a HYDROCARBON RADICAL. original form by one BASE-pair out of thousands. Also termed ‘ALLELOMORPH’. alkyl halide (chemistry) An ORGANIC See MUTATION. COMPOUND of GENERAL FORMULA RX, where R is an ALKYL GROUP allele-specific oligonucleotides (ASO) and X is a HALOGEN. Also termed: (chemistry) SYNTHETIC DNA probes used HALOGENOALKANE. to detect single BASE MUTATIONS. These probes, usually about 18 BASE-PAIRS alkylating agents (biochemistry) Chemicals long but sometimes as long as 80 BASE- that can add ALKYL GROUPS to DNA, PAIRS, can be used to detect the presence a REACTION that can result either in or absence of the sequence in question mispairing of bases or in CHROMOSOME (perhaps a disease-producing MUTANT) breaks. Thus ALKYLATING AGENTS such in a SAMPLE of natural DNA: when a as N-dimethyinitrosamine are frequently quantity of the NUCLEOTIDE is added CARCINOGENS and/or mutagens. to the natural SAMPLE, it will bind if it can find its exact complementary sequence, alkylation (chemistry) CHEMICAL but not otherwise, being accurate to a REACTION that introduces an ALKYL single BASE. In a case such as sickle- GROUP into an ORGANIC COMPOUND CELL ANAEMIA (USA: sickle-cell anemia), (by either addition or substitution). where the exact sequence of the MUTATION site is known, an ALLELE-specific alkyllaryl sulphide See THIOETHER. oligonucleotide is an efficient way of detecting the presence of the MUTATION, ALL (medical/haematology) An abbreviation and is used in prenatal diagnosis. of ‘A’cute ‘L’ymphocytic ‘L’eukaemia (USA: Acute Lymphocytic Leukemia). allelic exclusion (immunology) An assembly of functional IMMUNOGLOBULIN heavy allantois (biology) Membranous sac or LIGHT chain genes on only one of that develops in the embryos of reptiles, the two HOMOLOGOUS CHROMOSOMES birds and mammals. It is involved in for each chain. This arrangement ensures the STORAGE of waste and the provision that a given B CELL makes only one of food and OXYGEN. In reptiles and unique functional ANTIBODY after DNA

25 ALLELIC SERIES ALLOY rearrangement. The ALLELES encoding allometry (genetics) Differential GROWTH the IMMUNOGLOBULIN genes on the of one part of the body compared to ‘unused’ CHROMOSOME are excluded another or to the body as a whole. from the rearrangement process by an unknown mechanism. allophene (genetics) An organism that has received a transplant of foreign CELLS, allelic series (genetics) The SET of such as in a patient who receives a ALLELES available for a given LOCUS. BONE-MARROW transplant to replace their own defective MARROW TISSUE. allelomorph (genetics) See ALLELE. The transplanted CELLS have their own GENOTYPE different from the HOST’S, allergen (immunology) Any substance and they make their own GENE PRODUCTS. that is capable of eliciting an ALLERGIC RESPONSE. Allergens are usually allopurinol (pharmacology/biochemistry) proteins, and include foods, ANIMAL A drug used to reduce the formation of DANDER, POLLEN from flowers, trees URIC ACID in the TREATMENT of GOUT. and weeds, and so on. all-or-none response (physiology) The See also ALLERGY, ALLERGIC RESPONSE. RESPONSE of excitable TISSUE (e.g. some NERVE CELLS) that occurs in allergenicity (immunology) The full only at or above a certain LEVEL POTENTIAL of a COMPOUND to provoke of STIMULUS, the THRESHOLD, but an ALLERGIC RESPONSE. not at all below that LEVEL. allergic response (immunology) A See also ACTION POTENTIAL. physiological response occurring when an ANTIGEN makes contact with mast allosterism (biochemistry) The modulation cells of the IMMUNE SYSTEM. This contact or regulation of the activity of a PROTEIN triggers the release of histamine, which through reversible changes in the physical induces local inflammation and produces CONFORMATION of the PROTEIN. symptoms of asthma, hay fever or the swelling of insect bites. See ALLERGY. allotrope (chemistry) One of the forms of an ELEMENT that exhibits ALLOTROPY. allergic shellfish poisoning (immunology) Allergic REACTION that can result in allotropy (chemistry) Existence of certain individuals after the ingestion different structural forms of an ELEMENT. of shellfish that contain powerful sensitising e.g. graphite and diamond are agents. Such poisoning is rarely fatal. ALLOTROPES of CARBON. allergy (immunology) ABNORMAL alloy (chemistry) Metallic substance that sensitivity of the body to a substance is made up of two or more elements (known as an ALLERGEN). Contact (usually metals); e.g. brass (COPPER with the ALLERGEN causes symptoms and ZINC), bronze (COPPER and TIN), such as SKIN rashes, watery eyes, solder (LEAD and TIN) and steel (IRON and sneezing. Hay FEVER is a widespread and CARBON). ALLERGY to the POLLEN of certain plants.

26 ALLOZYME ALTEPLASE allozyme (biochemistry/genetics) One of of STARCH to form a MIXTURE of dextrins, the variant forms of an ENZYME coded tri-and di-saccharides, and GLUCOSE. Levels for by ALLELES at a given LOCUS. of this ENZYME can rise during renal failure and fall following hepatobilary toxicity. allyl group (chemistry) CH2=CHCH2- UNSATURATED HYDROCARBON RADICAL alpha-fetoprotein (AFP) (biochemistry) found in compounds such as allylbromide. PROTEIN found in high concentrations in foetal (USA: fetal) SERUM. Transfers to alpha decay (radiology) RADIOACTIVE AMNIOTIC FLUID and maternal BLOOD DISINTEGRATION of a substance with in increased amounts when there is a the emission of ALPHA PARTICLES. DEFECT in the developing NERVOUS SYSTEM of the growing FOETUS (USA: alpha level (statistics) The probability fetus) such as spina bifida or anencephaly. that the outcome of a statistical test Samples of the AMNIOTIC FLUID can be will reject a HYPOTHESIS when it is taken by the process of AMNIOCENTESIS in fact true. Compare significance LEVEL. early in the second three months of PREGNANCY in cases where it is thought alpha motor neuron (histology) A large to be advisable, and ANALYSIS carried motor neuron that innervates out. High levels may indicate a foetal (USA: EXTRAFUSAL FIBRES (USA: fibers) fetal) abnormality such as spina bifida. thus causing skeletal muscles to contract. Alphafetoprotein is also found in increased quantities in the BLOOD of adult patients alpha particles (radiology) Heavy particles suffering from certain MALIGNANT tumours composed of two protons and two neutrons (USA: tumors). of IONIZING RADIATION produced by some modes of RADIOACTIVE DECAY alphanumeric (computing) Describing e.g. DECAY of PLUTONIUM, with little characters or their codes that represent penetrative POWER, but damaging when letters of the alphabet or NUMERALS, in contact with living TISSUE such as particularly in COMPUTER applications. occurs following inhalation or ingestion. They have little penetrative POWER. alprazolam (pharmacology) A benzodiazepine drug, which is used as an alpha radiation (radiology) IONIZING ANXIOLYTIC drug, administered orally, RADIATION consisting of a stream of in the short-term treatment of anxiety. ALPHA PARTICLES. ALS (medical) An abbreviation of alpha ray (radiology) An alternative ‘A’myotrophic ‘L’ateral ‘S’clerosis. term for ALPHA RADIATION. ALT (biochemistry) An abbreviation alpha rhythm (physiology) Pattern of of ‘AL’anine amino‘T’ransferase. electrical activity in the BRAIN (as recorded by an ELECTROENCEPHALOGRAPH) alteplase (pharmacology) A tissue-type that is CHARACTERISTIC of a person plasminogen activator which is used who is awake, but relaxed and inactive. therapeuticlly as a fibrinolytic drug, as when administered by injection or alpha-amylase (biochemistry) An ENZYME infusion, it has the property of breaking that hydrolyses 1,4-GLUCOSIDE linkages up blood clots.

27 ALTERNATE ANGLE ALUMINIUM CHLORIDE alternate angle (mathematics) In geometry, human DNA. The copies exist in slightly one of a pair of angles on opposite varying forms, and it is the COMBINATION sides of a line (TRANSVERSAL) that of these variants that gives the individuality cuts two other lines; the angles are between analysed in GENETIC FINGERPRINTING. the other lines and the TRANSVERSAL. The Alu sequence got its name from If the two other lines are parallel, the that of the restriction endonuelease, ALTERNATE ANGLES are equal. See Alu I, by which it was isolated.

also CORRESPONDING ANGLE. alum (1,2 chemistry) 1 AI2(SO4)3.K2SO4.-

24H2O ALUMINIUM POTASSIUM alternating current (a.c.) (physics) SULPHATE (USA: aluminium potassium ELECTRIC CURRENT that reverses its sulfate), a white CRYSTALLINE substance direction of flow in periodic cycles (measured (that occurs naturally as kalinite) used in hertz). Mains ELECTRICITY in Britain in leather-making and as a mordant alternates at a rate of 50 cycles per in dyeing. 2 Any of a GROUP of salts second; its FREQUENCY is 50 Hz. with an ANALOGOUS composition to ALUM (i.e. a double SULPHATE of a alternative medicine (medical) The TRIVALENT and MONOVALENT METAL term applied to systems of TREATMENT with 24 molecules of WATER OF which cannot be accepted by orthodox CRYSTALLIZATION). medical practitioners because they cannot be ratified by accepted scientific methods. alum. (chemistry) An abbreviation of ‘ALUM’inium. alternative splicing (genetics) The production of multiple MESSENGER RNAs alumina (chemistry) An alternative term from a single TRANSCRIPTION UNIT. for ALUMINIUM OXIDE. alternator (physics) Generator that aluminate (chemistry) Type of SALT produces ALTERNATING CURRENT (a.c.) formed when ALUMINIUM OXIDE or by rotating coils in a MAGNETIC FIELD. HYDROXIDE dissolves in a strong ALKALI. altruism (biology) Category of ANIMAL aluminium AI (chemistry) Silvery-white BEHAVIOUR (USA: behavior), especially metallic ELEMENT in GROUP IIIA of common among social insects, in which the PERIODIC TABLE. It occurs (as older individuals tend to sacrifice themselves, ALUMINO-SILICATES) in many rocks losing their lives if necessary, in ORDER and clays and in bauxite, its principal that offspring and younger individuals ore, from which it is extracted by may survive or otherwise benefit. ELECTROLYSIS. It is a LIGHT METAL, protected against corrosion by a surface Alu family (genetics) A SET of highly FILM of OXIDE. Its ALLOYS are used repetitive DNA elements dispersed in the aerospace industry and in throughout the human GENOME; each lightweight structures. At. no. 13; r.a.m. member is about 300 BASE-pairs in 26.9815. length, and is repeated 300,000 times, the copies being scattered around the aluminium chloride (chemistry) AICI3 chromosomes. The Alu sequence copies White or yellowish DELIQUESCENT SOLID, make up some 3 per cent of the total covalently bonded when ANHYDROUS,

28 ALUMINIUM HYDROXIDE AMALGAM which fumes in moist AIR. It is used as that kills and engulfs MICRO-ORGANISMS a CATALYST in the cracking of petroleum as well as secreting antimicrobial substances. HYDROCARBONS. The ALVEOLAR MACROPHAGE may also secrete ENZYMES involved in the LYSIS aluminium hydroxide (pharmacology) of LUNG TISSUE. An antacid which is relatively insoluble in water and has a long duration of action See also PHAGOCYTOSIS. when retained in the STOMACH. It can also be used to treat hyperphoshataemia alveolus (1,2 anatomy) 1 MINUTE sac (USA: hyperphoshatemia). in the VERTEBRATE LUNG. There are vast numbers of alveoli, and most of aluminium oxide (chemistry) AI2O3 White the exchange of gases between AIR CRYSTALLINE AMPHOTERIC COMPOUND, and BLOOD takes place within them. the principal source of ALUMINIUM, which See also RESPIRATION. 2 In zoology occurs as the mineral corundum and in the term is also used for any small bauxite. A thin surface FILM of ALUMINIUM indent or sac in the surface of an ORGAN. OXIDE gives ALUMINIUM and its ALLOYS their corrosion-resistant properties. Such Alzheimer’s disease (medical) films can be created by ANODIZING. Progressive neurodegenerative disease, Also termed: ALUMINA. usually of people in their fifties and beyond, producing severe intellectual, aluminium sulphate (chemistry) AI2(SO4)3 sensory, and motor deterioration, and White CRYSTALLINE COMPOUND, used ultimately death. CHARACTERISTIC as a flocculating agent in WATER neuropathological features in the BRAIN TREATMENT and sewage works, as a include amyloid plaques (PROTEIN mordant in dyeing, as a size in paper- deposits) and neurofibrillary tangles. making and as a foaming agent in fire The disease is named after the Bavarian extinguishers. (USA: ALUMINIUM SULFATE). physician, Alois Alzheimer (1864–1915). aluminosilicate (chemistry) Common AM (physics) An abbreviation of chemical COMPOUND in minerals and ‘a’mplitude ‘m’odulation. rocks (e.g. clays, mica) consisting of ALUMINA and silica with WATER and Am (1 chemistry; 2 physics) 1 CHEMICAL various bases; such compounds are also SYMBOL for AMERICIUM. 2 An formed in GLASS and various ceramics. abbreviation of ‘am’meter. alveolar clearance (physiology) Particles AMA (1 general terminology; 2, 3 that reach the alveoli are cleared by two governing body) 1 An abbreviation of principal routes: 1 by PHAGO-CYTOSIS ‘A’gainst ‘M’edical ‘A’dvice. 2 An and removal either via the mucociliary abbreviation of ‘A’ustralian ‘M’edical process or via the LYMPHATIC SYSTEM; ‘A’ssociation. 3 An abbreviation of 2 by dissolution of the particles, with the ‘A’merican ‘M’edical ‘A’ssociation. dissolved material passing either to the BLOOD stream or the LYMPHATIC SYSTEM. amalgam (chemistry) MIXTURE of MERCURY with one or more other metals, alveolar macrophage (haematology/ used for dental fillings. immunology) A CELL-type in the LUNG

29 AMANTADINE HYDROCHLORIDE AMINASE amantadine hydrochloride (pharmacology) American Standard Code for A drug administered orally to treat Information Interchange (ASCII) PARKINSON’S disease. It also has antiviral (computing) A standard format for activity and has been used to prevent representing characters in differing infection with specific influenzae viruses COMPUTER programs. and in the treatment of HERPES VARICELLA ZOSTER VIRUS (HVZ). americium Am (chemistry) RADIOACTIVE ELEMENT in GROUP IIIB of the PERIODIC AMBAC (education) An abbreviation TABLE (one of the ACTINIDES). It has of ‘A’ssociate ‘M’ember of the ‘B’ritish several isotopes, with half-lives of up ‘A’ssociation of ‘C’hemists. to 7,650 years. It is used as a source of alpha-particles. At. no. 95; r.a.m. amber codon (genetics) One of the 243 (most STABLE ISOTOPE). three NONSENSE CODONS in DNA that code for ‘stop’ and therefore signal amethocaine hydrochloride (pharmacol- the TERMINATION of the PROTEIN ogy) A local anaesthetic drug administered being synthesised. Amber is UAG. See by topical application, to treat localised PROTEIN SYNTHESIS. pain and irritation and in ophthalmic treatments. ambient (physics) Environmental or surrounding conditions e.g. AMBIENT amide (chemistry) Member of a GROUP TEMPERATURE. of organic chemical compounds in which one or more of the HYDROGEN atoms amenorrhoea (medical) Absence or of AMMONIA (NH3) have been replaced stoppage of the menstrual flow. May by an ACYL GROUP (-RCO). In primary be primary, i.e. never menstruated, amides one, in secondary amides two or secondary i.e. after previous and in tertiary amides three of the MENSTRUATION. The commonest cause hydrogens have been so replaced. Also of amenorrhoea is PREGNANCY. See termed: alkanamides. MENSTRUATION. (USA: amenorrhea). amiloride hydrochloride (pharmacology) American Academy of Clinical A weak DIURETIC drug that is administered Toxicology (AACT) (education) An orally and has the property of retaining organisation of professionals active the body’s POTASSIUM. It is therefore in clinical toxicology or teaching and/ frequently used in combination with or research related to clinical toxicology. other DIURETICS, such as the THIAZIDES that are prone to cause a loss of American Academy of Forensic POTASSIUM from the body. It has use Sciences (AAFS) (society) A society in treatment of OEDEMA (USA: EDEMA), to encourage the study of all aspects ascites in LIVER cirrhosis, as an of forensic science. ANTIHYPERTENSIVE and in treatment of congestive HEART FAILURE. American Association for the Advance- ment of Science (society) A US profes- aminase (biochemistry) One of a GROUP sional society whose members are from of ENZYMES that can catalyse the all branches of science, medicine and HYDROLYSIS of amines. engineering.

30 AMINATION AMMETER amination (chemistry) Transfer of an aminoisovaleric acid (chemistry) An

AMINO GROUP (-NH2) to a COMPOUND. alternative term for VALINE. amine (chemistry) Member of a GROUP aminophylline (pharmacology) A broncho- of organic chemical substances in which dilator drug that can be administered one or more of the HYDROGEN atoms orally or by injection and used as an of AMMONIA (NH3) have been replaced acute ANTI-ASTHMATIC or a bronchitis by a HYDROCARBON GROUP. In primary treatment for severe attacks. amines one, in secondary amines two and in tertiary amines three hydrogens aminoplastic resin (chemistry) have been so replaced. SYNTHETIC RESIN derived from the REACTION of UREA, THIOUREA or amino acid (biochemistry) The building melamine with an ALDEHYDE, particularly blocks of proteins, AMINO ACIDS are FORMALDEHYDE (METHANAL). ORGANIC COMPOUNDS that contain an acidic CARBOXYL GROUP (-COOH) and aminotoluene (chemistry) An alternative a BASIC AMINO GROUP (-NH ). Twenty 2 term for TOLUIDINE. AMINO ACIDS are commonly found in proteins in animals, and about 100 more amiodarone hydrochloride (pharmacol- that are rare and found only in plants. ogy) An anti-arrhymic drug which may Those that can be synthesized by a particular be administered orally or by injection organism are known as ‘non-essential’; to treat certain severe irregularities ‘essential’ AMINO ACIDS must be obtained of the HEARTBEAT, although it has from the ENVIRONMENT, usually from many sideeffects and is potentially toxic. food. The ESSENTIAL AMINO ACIDS for humans are: ISOLEUCINE, LEUCINE, amitriptyline hydrochloride (pharmacol- LYSINE, methionme, PHENYLALANINE, ogy) An ANTIDEPRESSANT drug of THREONINE, TRYPTOPHAN and VALINE. the tricyclic group. It may be administered amino group (biochemistry) Chemical orally or by injection and has marked GROUP with the GENERAL FORMULA sedative properties, which may be of -NRR’, where R and R’ may be benefit to agitated or violent patients, HYDROGEN atoms or organic radicals; but has pronounced ANTICHOLINERGIC sideeffects. the commonest form is -NH2. Compounds containing AMINO GROUPS include amines and AMINO ACIDS. AML (medical/haematology) An abbreviation of ‘A’cute ‘M’yelocytic ‘L’eukaemia (USA: aminobenzene (chemistry) An alternative ACUTE Myelocytic Leukemia). term for ANILINE. AMM (1,2 society) 1 An abbreviation aminobutyric acid transaminase (bio- of ‘A’ssociation of ‘M’edical chemistry) An ENZYME found in ‘M’icrobiologists. 2 An abbreviation of mitochondria that is responsible for the ‘A’ssociation ‘M’édicale ‘M’ondiale [French, DEGRADATION of GABA by transferring meaning ‘World Medical Association’.] its AMINO GROUP to alpha-ketoglutaric ACID, which is an INTERMEDIATE in ammeter (physics) An instrument for the KREBS CYCLE, yielding succinic measuring ELECTRIC CURRENT, usually semialdehyde and GLUTAMIC ACID. calibrated in AMPERES. The common

31 AMML AMNION moving-coil AMMETER is a type of dry batteries, as a flux in soldering galvanometer. and as a mordant in dyeing.

AMML (medical/haematology) An ammonium hydroxide (chemistry) abbreviation of ‘A’cute ‘M’yelo‘M’onocytic NH4OH ALKALI made by dissolving ‘L’eukaemia (USA: ACUTE Myelomonocytic AMMONIA in WATER, giving a SOLUTION Leukemia). that probably contains hydrates of AMMONIA. It is used for making soaps ammonia (chemistry) (NH3) A colourless and fertilizers. 880 AMMONIA is a (USA: colorless) GAS with a pungent saturated AQUEOUS SOLUTION of odour (USA: odor), detectable by humans AMMONIA (DENSITY 0.88 g cm-3). Also down to concentrations of 53 ppm. Inhalation termed: AMMONIA SOLUTION. of the VAPOUR arising from a SOLUTION of AMMONIA, while uncomfortable, is not ammonium ion (chemistry) The ION dangerous, but inhalation of the GAS NH4+, which behaves like a METAL ION. can cause oedema (USA: edema) of the lungs and bronchitis but this is rarely ammonium nitrate (chemistry) NH4NO3 serious. It is formed naturally by the Colourless (USA: colorless) CRYSTALLINE BACTERIAL DECOMPOSITION of proteins, COMPOUND, used as a fertilizer and purines and UREA; made in the in explosives. LABORATORY by the ACTION of ALKALIS (USA: alkalies) on ammonium salts; or ammonium phosphate (chemistry) synthesized commercially by FIXATION (NH4) 3PO4 Colourless (USA: colorless) OF NITROGEN. LIQUID AMMONIA is used CRYSTALLINE COMPOUND, used as as a REFRIGERANT. The GAS is the a fertilizer (when it adds both NITROGEN starting material for making NITRIC ACID and PHOSPHORUS to the soil). and NITRATES. ammonium sulphate (chemistry) ammonia solution (chemistry) An (NH4) 2SO4 White CRYSTALLINE alternative term for AMMONIUM COMPOUND, much used as a fertilizer. HYDROXIDE. (USA: AMMONIUM sulfate). ammonium carbonate (chemistry) amnesia (medical) Loss of MEMORY,

(NH4)2CO3 Unstable white CRYSTALLINE a symptom occurring in a number of COMPOUND which decomposes BRAIN disorders such as early spontaneously to produce AMMONIA, used ALZHEIMER’S DISEASE or increased in smelling salts. The substance known PRESSURE from a TUMOUR (USA: tumor). in industry as AMMONIUM CARBONATE is usually a double SALT consisting of amniocentesis (histology) Test in which ammonium HYDROGENCARBONATE a SAMPLE of AMNIOTIC FLUID is taken (BICARBONATE) and ammonium from the AMNION surrounding a FOETUS aminomethanoate (carbamate). Also termed: (USA: fetus). The CELLS that this contains sal volatile. are examined for FOETAL (USA: fetal) ABNORMALITIES. ammonium chloride (chemistry) NH4CI Colourless (USA: colorless) or white amnion (histology) Innermost MEMBRANE CRYSTALLINE COMPOUND, used in that envelops an EMBRYO or FOETUS

32 AMNIOTIC FLUID AMU

(USA: fetus) (in mammals, reptiles and at a point due to a given CURRENT birds) and encloses the FLUID-filled in terms of the CURRENT elements amniotic cavity. and their positions relative to the point. Also termed: Laplace LAW. amniotic fluid (anatomy) LIQUID that occurs in the AMNION surrounding a amphetamine (pharmacology) Drug that FOETUS (USA: fetus). stimulates the CENTRAL NERVOUS SYSTEM. It was once much used for amoeba (biology) Single-celled organism, the TREATMENT of depression and to a protozoan, that moves and feeds by lessen appetite, but is now seldom prescribed the projection of pseudopodia. (USA: because of its addictive properties. ameba). amphoteric (chemistry) Describing a amoebiasis (medical/microbiology) An chemical COMPOUND with both BASIC INFECTION caused by AMOEBA (USA: and acidic properties e.g. ALUMINIUM ameba), which can result in amoebic OXIDE, AI2O3, dissolves in acids (behaving dysentery (USA: amebic dysentery). like a BASE) to form ALUMINIUM salts (USA: amebiasis). and dissolves in ALKALIS (USA: alkalies) (acting like an acid) to form acuminates. amoebocyte (cytology) CELL that demonstrates amoeboid movement. Such amplifier (1 physics; 2 microbiology) CELLS may be present in body fluids, 1 A device that can magnify a physical such as the BLOOD of invertebrates. quantity, such as electrical CURRENT or mechanical FORCE. An electronic See also AMOEBA. AMPLIFIER increases the AMPLITUDE of the input signal, to produce a GAIN. AMOL (medical/haematology) An 2 A HOST that epidemiologically serves abbreviation of ‘A’cute ‘MO’nocytic the FUNCTION of increasing the size ‘L’eukaemia (USA: ACUTE Monocytic of the PATHOGEN population. Leukemia). amplitude (physics) A term used in amorphous (biology) Without clear shape defining a LIGHT WAVE. The distance or structure. between the peak and trough. The higher the AMPLITUDE, the more intense the amp (measurement) An abbreviation LIGHT and the more ENERGY produced of ‘amp’ere/‘amp’erage. at that WAVELENGTH.

AMP (biochemistry) An abbreviation amputation (medical) The removal of of ‘a’denosine ‘m’ono‘p’hosphate. part of the body, usually a limb. ampere (A) (measurement) SI UNIT AMT (1,2 education) 1 An abbreviation of ELECTRIC CURRENT. It was named of ‘A’cademy of ‘M’edicine, ‘T’oronto; after the French physicist André Marie 2 An abbreviation of ‘A’ssociate in Ampère (1775–1836). ‘M’edical ‘T’echnology.

Ampère’s law (physics) Relationship AMU (physics) An abbreviation of ‘a’tomic that gives the MAGNETIC INDUCTION ‘m’ass ‘u’nit.

33 AMV ANALOG COMPUTER

AMV (society) An abbreviation of ‘A’sso- CONCENTRATION is below NORMAL. ciation ‘M’ondiale ‘V’itirinaire. [French, Causes may include BLOOD loss, increased meaning ‘World Veterinary Association’.] intravascular destruction of BLOOD CELLS or decreased production of BLOOD CELLS. amyl group (chemistry) C H11- MONO- 5 (USA: anemia) VALENT ALKYL GROUP. Also termed: PENTYL GROUP. anaerobe (microbiology) Organism that respires anaerobically. See ANAEROBIC amyl nitrite (chemistry) C5H11ONO Pale brown VOLATILE LIQUID ORGANIC RESPIRATION. COMPOUND, often used in medicine to DILATE the BLOOD VESSELS of anaerobic (microbiology) Living in the patients with some forms of HEART absence of free OXYGEN. disease (e.g. ANGINA). anaerobic respiration (biology) Process amylase (biochemistry) Member of a by which organisms obtain ENERGY from GROUP of ENZYMES that digest STARCH the breakdown of food molecules in the or GLYCOGEN to DEXTRIN, MALTOSE absence of OXYGEN (e.g. FERMENTATION). and GLUCOSE. AMYLASES are found This process yields less ENERGY than in the salivary GLANDS and the AEROBIC RESPIRATION. PANCREAS, and MICRO-ORGANISMS. Also termed: DIASTASE. anaerogenic (microbiology) Non-GAS- producing. Contrast AEROGENIC. amylose (chemistry) POLYSACCHARIDE, a POLYMER of GLUCOSE, that occurs anaesthetic (pharmacology) Drug that in STARCH. induces overall insensibility (general amylum (chemistry) An alternative term ANAESTHETIC [USA: general anesthetic]) for STARCH. or loss of sensitivity in one AREA (local ANAESTHETIC [USA: local anesthetic]). anabolic steroid (biochemistry/pharma- (USA: anesthetic). cology) COMPOUND that is concerned with ANABOLISM. Commonly used analeptic (pharmacology) Any stimulant ANABOLIC STEROIDS are SYNTHETIC drug such as CAFFEINE and male SEX HORMONES (ANDROGENS) AMPHETAMINE, excluding the specific which promote PROTEIN SYNTHESIS antidepressant drugs. (hence their use by some athletes wishing to build up MUSCLE). analgesia (medical) The relief of pain in the conscious patient. See also STEROID. anabolism (physiology) PHASE of METABO- analgesic (pharmacology) Drug that LISM that is concerned with the building relieves pain without causing loss of up (or BIOSYNTHESIS) of molecules. consciousness.

See also CATABOLISM. analog computer (computing) COMPUTER that represents numerical values by anaemia (medical/haematology) General continuously VARIABLE physical quantities term for any disorder in which the BLOOD (e.g. VOLTAGE, CURRENT). Contrast HAEMOGLOBIN (USA: hemoglobin) DIGITAL COMPUTER.

34 ANALOGIDIGITAL CONVERTER ANDROGEN analogidigital converter (computing) within the TISSUE and with respect A device that converts the output of an to adjacent TISSUE. ANALOG COMPUTER into digital signals for a DIGITAL COMPUTER. anastomosis (1 histology; 2 medical) 1 Natural VESSEL that connects two analogous (biology) Describing features BLOOD VESSELS. 2 Artificially made that have similar functions which have connection between two body tubes developed completely independently. (e.g. in the GUT).

See HOMOLOGOUS. anat. (anatomy) An abbreviation of ‘Anat’omy/‘Anat’omical. analysis See CHROMATOGRAPHY; QUALITATIVE ANALYSIS; QUANTITATIVE anatomy (anatomy) The study of the ANALYSIS; VOLUMETRIC ANALYSIS. structural forms of the body and its parts. analysis of variance (ANOVA) (statistics) A statistical procedure for testing And gate (computing) COMPUTER hypotheses about population means LOGIC ELEMENT that combines two in which the overall VARIABILITY in binary input signals to produce one samples of DATA is split into additive output signal according to particular components associated with the rules. Also termed: AND ELEMENT. INDEPENDENT VARIABLES. androblastoma (histology/biochemistry) analytic reagent (AR) (chemistry) Grade ANDROGEN secreting TUMOUR (USA: of chemical. tumor) of the OVARY. analytical geometry (mathematics) An androgen (physiology/pharmacology) alternative term for CO-ORDINATE Term used to describe the predominantly geometry. male (steroid) sex HORMONES, which stimulate the development of male sex anaphase (cytology/genetics) Stage characteristics. In men, they are produced in MITOSIS and moiosis (CELL DIVISION) primarily by the testes and the main in which chromosomes migrate to opposite form is called TESTOSTERONE. However, poles of the CELL by means of the ANDROGENS are produced in both men spindle. and women by the adrenal glands and in women small quantities are also secreted anaphylaxis (medical/immunology) A by the ovaries. An excessive amount sudden severe REACTION (an ALLERGY) in women causes masculinization. Forms to a drug or venom, requiring urgent of the natural HORMONES and a number medical TREATMENT. Also termed: of synthetic ANDROGENS including anaphylactic shock. TESTOSTERONE and mesterolone, are used therapeutically to correct hormonal anaplasia (histology) A CHARAC- deficiency, and can also be used as TERISTIC of tumor TISSUE in which ANTICANCER treatments for cancers there is loss of differentiation of CELLS linked to sex HORMONES, e.g. breast and of their orientation to one another cancer in women.

35 ANDROGEN INSENSITIVITY SYNDROME ANGSTROM androgen insensitivity syndrome applied to the disease causing the pain, (genetics) A condition occurring in some e.g. VINCENT’S ANGINA and ANGINA chromosomal males in which the TESTES pectoris. The former named after the develop, but because the organs are physician and BACTERIOLOGIST, J.H. insensitive to TESTOSTERONE, most Vincent (1862–1950). of the bodily characteristics are female, including the external genitalia. Such angiogenesis (medical/haematology) people are usually brought up as females The formation of new BLOOD VESSELS. and tend to behave as females. angiogram (radiography) X-RAY picture androgenisation (medical) The TRANSFOR- produced following the injection of an MATION of any bodily structure or part X-RAY OPAQUE dye into an ARTERY. of the BRAIN into those typical of a male rather than of a female. angioma (histology/haematology) A BENIGN (non-MALIGNANT) TUMOUR androsterone (biochemistry) A breakdown (USA: tumor) consisting of BLOOD PRODUCT OF TESTOSTERONE, which VESSELS (HAEMANGIOMA; USA: acts as an ANDROGEN. hemANGIOMA) or LYMPH vessels (lymphANGIOMA). These tumours may -ane (chemistry) Suffix usually denoting occur in any part of the body where that an ORGANIC COMPOUND is an these types of vessels are found. ALKANE or CYCLOALKANE; e.g. methane, cyclohexane. angiotensin converting enzyme (ACE) anergy (immunology) Absence of (physiology/biochemistry) An enzyme REACTION to antigens or ALLERGENS. that converts angiotensin I to the potent VASOPRESSOR form, angiotensin II. anes. (biochemistry) An abbreviation angle of incidence (physics) Angle that of ‘anes’thetic. a RAY or any other straight line makes with the NORMAL to a surface at which aneuploidy (genetics) The condition in it arrives. which the number of CHROMOSOMES in a CELL is not an exact multiple of angle of reflection (physics) Angle the HAPLOID number. The loss of one made by a RAY with the NORMAL to or more chromosomes, or the presence a surface from which it is reflected at of extra chromosomes can bring about the point of REFLECTION. the condition. One form of ANEUPLOIDY is TRISOMY, in which there are three angle of refraction (physics) Angle copies of a CHROMOSOME: a well- made by a RAY refracted at a surface known example is DOWN’S SYNDROME, separating two media with the NORMAL also called TRISOMY 21, in which there to the surface at the point of are three copies of CHROMOSOME 21. REFRACTION. aneurin (biochemistry) An term for See also LAWS OF REFRACTION OF LIGHT.

THIAMINE (VITAMIN B1). angstrom (A) (measurement) UNIT of angina (medical) Spasmodic, choking WAVELENGTH for ELECTROMAGNETIC or suffocating pain. The word is now RADIATION, including VISIBLE LIGHT

36 ANHYD. ANKYLOSIS and X-RAYS, equal to 10-10 m, or 0.1 anisocytosis (haematology) The condition nm. It was named after the Swedish in which there is excessive VARIATION physicist Anders Ångstrom (1814–74). in size between individual ERYTHROCYTES. anhyd. (chemistry) An abbreviation of anisogamy (genetics) The production ‘anhyd’rous. Also termed anhydr. of two unequal-sized types of gametes in a SPECIES. It is the system used by anhydride (chemistry) Chemical COM- all higher eukaryotes, including humans, POUND formed by removing WATER from in which the OVUM is much larger than another COMPOUND (usually an acid); the SPERM. Contrast ISOGAMY. e.g. an ACID ANHYDRIDE or ACIDIC OXIDE. anisotropic (physics) Describing a substance that has different properties anhydrite (chemistry) Naturally occurring with respect to velocity of LIGHT CALCIUM SULPHATE (USA: CALCIUM transmission, CONDUCTIVITY of HEAT sulfate), used to make fertilizers. and ELECTRICITY, and compressibility in different directions of its MATRIX. See also GYPSUM. ankylosing spondylitis (medical) A human anhydrous (chemistry) Describing a disease probably caused by a VIRUS substance that is devoid of moisture, but with an ELEMENT of genetic susceptibility. or lacking WATER OF CRYSTALLIZATION. The symptoms are the fusing together of the vertebrae of the SPINE, starting aniline (chemistry) C H NH Colourless 6 5 2 from the lowest, but even though there (USA: colorless) oily LIQUID ORGANIC may be almost no movement in the back, COMPOUND, one of the BASIC chemicals the patient is usually well enough to LEAD (feedstock) used in the manufacture of a NORMAL life. Men are affected four dyes, pharmaceuticals and plastics. Also times more often than women, and there termed: AMINOBENZENE; PHENYLamine. is often more than one case in a FAMILY. The FACTOR that makes someone liable animal (biology) Member of a large to develop ANKYLOSING SPONDYLITIS KINGDOM of organisms that feed seems to be linked with a GENE in the heterotrophically on other organisms hla complex, part of the IMMUNE SYSTEM: or organic MATTER. Animals are usually almost all cases of the condition are in capable of movement and react quickly people with HLA type B27, though this to stimuli (because they have SENSE type occurs in only 3 or 4 per cent in the ORGANS and a NERVOUS SYSTEM). population. The HLA genes may be directly ANIMAL CELLS have limited GROWTH, involved in the disease, in causing an no chlorophyll, and are surrounded attack on the body’s own tissues, or they by a CELL MEMBRANE. may only be genetic markers linked very closely to the real genetic factor. See animal starch (chemistry) An alternative GENETIC CODE. term for GLYCOGEN. ankylosis (medical) Fixation or near- anion (physics) A negatively charged fixation of a JOINT normally freely PARTICLE, which in an ELECTRIC FIELD movable, brought about by disease, will migrate toward the POSITIVE POLE. injury or surgical operation. Common See ANODE. causes of ANKYLOSIS are TUBERCULOSIS,

37 ANNEALING ANTAGONIST rheumatoid ARTHRITIS or septic ANOVA (statistics) An abbreviation of ARTHRITIS, in which conditions the bones ‘AN’alysis ‘O’f ‘VA’riance. become bound together by scar TISSUE. JOINT deformities caused by fractures anoxaemia (haematology) Less than can also result in ANKYLOSIS, and fixation the NORMAL amount of OXYGEN in of a JOINT may follow if it is kept immobilised the BLOOD. (USA: anoxemia). See ANOXIA. for a long time. anoxia (medical) Condition where body annealing (biochemistry/molecular tissues receive inadequate amounts of biology) The reassociation of complemen- OXYGEN. ANOXIA may result from low tary strands of DNA after they have atmospheric OXYGEN PRESSURE, been denatured, usually by melting ANAEMIA (USA: anemia), INTERFERENCE at a high TEMPERATURE. The annealed with BLOOD flow or the inability of tissues strands can either be original to utilize OXYGEN normally. complementary strands or they can be any two strands that have enough ANP (physiology/biochemistry) An BASE-pairs matching for reassociation abbreviation of ‘A’trial ‘N’atriuretic to occur. This HYBRIDIZATION of DNA ‘P’eptide. is one technique used in GENETIC ENGINEERING. ANNEALING can also ANS (anatomy) An abbreviation for occur between a strand of DNA and ‘A’utonomic ‘N’ervous ‘S’ystem. a strand of RNA. See denaturation. ANSL (quality standards) An abbreviation anode (physics) An ELECTRODE that of ‘A’ustralian ‘N’ational ‘S’tandards is positively charged relative to another ‘L’aboratory. with a CURRENT flowing between the two; it attracts anions. Contrast CATHODE. antacid (pharmacology) Substance used medicinally to combat excess STOMACH See also ELECTROLYSIS. ACID (e.g. various compounds of anodizing (chemistry) Process of coating MAGNESIUM). a METAL (e.g. ALUMINIUM) with a thin layer of OXIDE by ELECTROLYSIS. antagonist (pharmacology) Substances that have no pharmacological actions anon. (literary terminology) An abbreviation in their own right, but that have profound of ‘anon’ymous, used with capital as actions because they actually physically attribution of unknown authorship occupy receptors, thus blocking, those that normally allow natural mediators, anorexia nervosa (medical) Pathological or sometimes synthetic drugs, to have and CHRONIC FASTING, occurring most an effect. Many widely used drugs in frequently in adolescent girls; it is usually medicine are ATAGONISTS, used to prevent accompanied by AMENORRHOEA (USA: the actions of mediators within the body, amenorrhea), sickness, weakness, severe thereby ‘switching off’ systems that are WEIGHT loss, and psychological distur- not functioning correctly, such as in the bance. disease states caused by excessive amounts of NEUROTRANSMITTERS and anosmia (medical) Complete loss of HORMONES. Examples of ANTAGONISTS the sense of SMELL. include BETA-BLOCKERS, that prevent

38 ANTERIOR ANTICOAGULANT the action of adrenaline and pectoris originating from the heart due NORADRENALINE by blocking the receptors to insufficient blood supply to the heart called BETAADRENOCEPTORS, and muscle. ANTIHISTAMINES that inhibit the effects in the body of the local HORMONE histamine anti-arrhythmic drugs (pharmacology) by blocking receptors called H1 receptors. Drugs that strengthen and regularise a HEARTBEAT that is unsteady or not See also AGONIST. showing its usual pattern of activity. anterior (biology) Near the HEAD of anti-asthmatic drugs (pharmacology) an ANIMAL. Drugs used to relieve the symptoms of bronchial asthma or prevent recurrent See also POSTERIOR. attacks.

anthracene (chemistry) C14H10 White antibiotic (pharmacology) Member of SOLID AROMATIC COMPOUND whose a GROUP of chemical substances that molecules consist of three BENZENE are byproducts of METABOLISM in certain RINGS fused in line. MICRO-ORGANISMS. Antibiotics cause the destruction of other MICRO- anthraquinone (chemistry) C6H4(CO)2C6H4 ORGANISMS, and are used as drugs Yellow CRYSTALLINE ORGANIC to kill BACTERIA. COMPOUND important in the manufacture of dyes. antibody (immunology) Highly specific MOLECULE produced by the IMMUNE anthrax (medical/microbiology) SYSTEM in RESPONSE to the presence BACTERIAL disease that affects many of an ANTIGEN, which it neutralizes. animals, including human beings, and which is frequently fatal. The disease- See also acquired IMMUNITY. causing BACTERIUM can form spores, and remain dormant in the soil or on anticancer agents (pharmacology) Drugs stored ANIMAL hides for many years. used to treat cancer, most of which are cytotoxic i.e. they act by interfering anthropoid (biology) Man-like. Members with CELL replication or production, of the suborder Anthropoidea, which so preventing the growth of new cancerous consists of monkeys, apes and man. TISSUE. They are usually administered in combination in a series of treatments anthropology (biology) Study of the known collectively as CHEMOTHERAPY. human RACE. Physical anthropology is concerned with human EVOLUTION, anticholinergic drugs (pharmacology) social anthropology with BEHAVIOUR Drugs used to inhibit the action, release (USA: behavior). or production of the NEUROTRANSMITTER ACETYLCHOLINE. anti-androgens (pharmacology) Drugs that inhibit the actions of ANDROGENS. anticoagulant (pharmacology/haematology) An agent that prevents BLOOD from clotting. anti-angina drugs (pharmacology) Drugs Anticoagulants are used to prevent the that relieve the intense pain of angina formation of clots in the veins after operation

39 ANTICODON ANTIMONY and, in cases where it is known that of toxicity in a manner not clearly related clotting has occurred, to prevent further to the mechanism of ACTION. extension of the clot. WARFARIN which can be given orally and HEPARIN which antiemetics (pharmacology) Drugs that requires INTRAVENOUS infusion are suppress vomiting. The chief examples of therapeutic anticoagulants. ANTIEMETICS are the phenothiazines, such as chlorpromazine, perphenazine, anticodon (genetics) The three adjacent prochlorperazine or promethazine. nucleotides in a transfer-RNA MOLECULE that are complementary to, and BASE anti-epileptic drugs (pharmacology) PAIR with, the three complementary Drugs used to prevent the occurrence nucleotides of a codon in a messenger- of epileptic seizures. RNA MOLECULE. See PROTEIN SYNTHESIS; GENETIC CODE. antigen (immunology) A substance that elicits an IMMUNE RESPONSE. Usually anticonvulsant drugs (pharmacology) a PROTEIN MOLECULE that the body’s Drugs used to prevent the onset of IMMUNE SYSTEM recognizes as ‘foreign’, epileptic seizures or to reduce their but they may be other macromolecules severity should they occur. (e.g. BACTERIA, transplanted TISSUE). antidepressants (pharmacology) Drugs See also ANTIBODY. used to control the psychiatric illness of depression. The three classes of drugs antihistamine (pharmacology) Chemical that are most commonly used are the substance that inhibits the ACTION of selective SEROTONIN re-uptake inhibitors HISTAMINE by blocking its site of ACTION. (SSRIs), tricyclic antidepressants, and It may be used to treat an ALLERGY. the monoamine OXIDASE inhibitors (MAOIs). antihypertensive (pharmacology) A antidiuretic hormone (ADH) (biochemis- drug used to treat raised BLOOD try) HORMONE secreted from the PRESSURE (HYPERTENSION). POSTERIOR PITUITARY and synthesized in the HYPOTHALAMUS. In mammals anti-inflammatory drugs (pharmacology) it stimulates the reABSORPTION of Drugs used to reduce the body’s WATER in the KIDNEY, and thus INFLAMMATORY RESPONSE to for diminishes the VOLUME of URINE instance injury, infection or presence produced. of foreign proteins.

See also VASOPRESSIN. antilogarithm (mathematics) Number that is represented by a LOGARITHM. antidote (pharmacology) A COMPOUND that is administered in ORDER to counteract antimony Sb (chemistry) Blue-white the effect of a POISON. ANTIDOTES semimetallic ELEMENT in GROUP VA may be specific, exerting their effect of the PERIODIC TABLE. It is used to through a mechanism related to the impart hardness to LEAD-TIN ALLOYS mechanism of ACTION of the TOXICANT, and as a DONOR impurity in semiconductors. or non-specific, counteracting the symptoms Its compounds, used as pigments, are poisonous. At. no. 51; r.a.m. 121.75.

40 ANTINAUSEANT DRUGS ANZIC antinauseant drugs (pharmacology) to treat or prevent a disease or to Drugs used to prevent or minimise combat ANIMAL venom (e.g. snakebite). the sensation of nausea and to reduce any subsequent vomiting. antispasmodic drugs (pharmacology) Drugs used to relieve spasm in smooth antineopastics (pharmacology) See muscle such as those in the respiratory ANTICANCER agents. tract or intestinal wall. antioxidant (biochemistry) Chemicals antisympathetic drugs (pharmacology) that hinder OXIDATION, frequently serving Drugs that act at some site within the as FREE RADICAL scavengers e.g. SYMPATHETIC NERVOUS SYSTEM to VITAMINS C and E. Most antioxidants reduce its overall effect. are ORGANIC COMPOUNDS. Natural antithyroid drugs (pharmacology) Drugs ones are found in vegetable oils and used in the treatment of over-activity in some fruits. of the THYROID gland. antiparallel (genetics) The orientation antitoxin (immunology) Type of of DNA strands in a duplex. One strand ANTIBODY against a TOXOID produced runs 5’ to 3’ in one direction whereas in the body by a disease organism or the complementary strand runs 5’ to by VACCINATION. 3’ in the opposite direction. By virtue of the POLARITY of DNA, the two strands antrum (1,2 anatomy) 1 Cavity in a are therefore ANTIPARALLEL. BONE (e.g. a SINUS). 2 Part of the STOMACH next to the pyloris. antiparticle (physics) SUBATOMIC PARTICLE that corresponds to another anus (anatomy) POSTERIOR opening PARTICLE of equal MASS but opposite of the ALIMENTARY CANAL, through ELECTRIC CHARGE (e.g. a POSITRON which the undigested residue of is the ANTIPARTICLE of the ELECTRON). DIGESTION is passed. antirheumatic drugs (pharmacology) Drugs anx (literary term) An abbreviation of used to relieve the pain and inflammation ‘an’ne‘x’. of rheumatism and arthritis, and sometimes other musculoskeletal disorders. anxiolytic drugs (pharmacology) Agents which alleviate anxiety without inducing antisense RNA (genetics) An RNA sedation. The most widely used anxiolytic transcript having the POLARITY drugs are the benzodiazepines, such complementary to that of normally as DIAZEPAM and chlordiazepoxide. transcribed RNA. ANZAAS (education) An abbreviation of ‘A’ustralian and ‘N’ew ‘Z’ealand antiseptic (pharmacology) Substance ‘A’ssociation for the ‘A’dvancement of that prevents sepsis by killing BACTERIA ‘S’cience. or preventing their GROWTH. Also termed: germicide. ANZIC (education) An abbreviation of ‘A’ssociate of the ‘N’ew ‘Z’ealand ‘I’nstitute antiserum (immunology) BLOOD SERUM of ‘C’hemists. containing antibodies, used in vaccines

41 AORTA APPARENT DEPTH aorta (anatomy) Principal ARTERY that APML (medical/haematology) An ab- takes oxygenated BLOOD from the HEART breviation of ‘A’cute ‘P’ro‘M’yelocytic to all parts of the body other than the ‘L’eukaemia (USA: ACUTE Promyelocytic lungs. Leukemia). a.-part. (radiology) An abbreviation apnoea (medical) Cessation of of ‘a’lpha-‘part’icle. BREATHING for short periods of time. (USA: apnea). apatite (chemistry) Mineral that consists mainly of CALCIUM PHOSPHATE, used apoenzyme (biochemistry) PROTEIN as a source of PHOSPHORUS and for part of an ENZYME that consists of making fertilizers. a PROTEIN and a non-PROTEIN portion.

APC (physiology/biochemistry) An apomorphine hydrochloride (pharmacol- abbreviation of ‘A’ctivated ‘P’rotein ‘C’. ogy) An anti-PARKINSON’S drug that has similar actions to bromocriptine. aperture (optics) Effective DIAMETER It is chemically related to morphine, of a LENS or LENS system. Its though it is not an ANALGESIC and RECIPROCAL is the f-number. has been used as an emetic. apex (physics) Point on a SOLID or apoprotein (biochemistry) PROTEIN part plane figure that is farthest from its of any complex or CONJUGATED PROTEIN. BASE. e.g. the pointed top of a pyramid. apoptosis (physiology) The process Apgar score (medical) A method of of programmed CELL death. assessing the condition of a newborn infant by assigning 0 to 2 points to apothecary ounce (measurement) UNIT the quality of HEART rate, RESPIRATION, of WEIGHT, 1/12 of a pound (apothecary). COLOUR (USA: color), tone and REFLEX 1 oz ap.=1.0971 oz (AVOIRDUPOIS)= activity at one and five minutes of 31.103481 grams. Also termed: ounce, life. The method is named after the troy. physician Virginia Apgar (1909–74). APP (biochemistry) An abbreviation APH (1 medical; 2 biochemistry) 1 An of ‘A’myloid ‘P’recusor ‘P’rotein. abbreviation of ‘A’nte‘P’artum ‘H’aemor- rhage (USA: antepartum hemorrhage), app. (1, 2, 3, 4, general terminology) bleeding during PREGNANCY or LABOUR 1 An abbreviation of ‘app’aratus (also (USA: labor). 2 An abbreviation of termed appar.; apparat.). 2 An abbreviation ‘A’nterior ‘P’ituitary ‘H’ormone. of ‘app’arent. 3 ‘app’lied (also termed appl.). 4 ‘app’roximate (also termed approx.). APHA (society) An abbreviation of ‘A’merican ‘P’ublic ‘H’ealth ‘A’ssocia- apparat. (general terminology) See app. tion. apparent depth (physics) Perceived apical growth (biology) An alternative depth of a LIQUID, which is different term for primary GROWTH. from its actual depth because of the REFRACTION OF LIGHT.

42 APPD ARBD appd. (general terminology) An abbrevia- AQL (quality standards) An abbreviation tion of ‘app’rove‘d’. of ‘A’cceptable ‘Q’uality ‘L’evel. appendix (anatomy) Vestigial outgrowth aqua fortis (chemistry) Obsolete term of the caecum in some mammals. In for concentrated NITRIC ACID. human beings its full name is VERMIFORM APPENDIX. aqua regia (chemistry) MIXTURE of one part concentrated NITRIC ACID to appl. (1, 2 general terminology) 1 An three parts concentrated HYDROCHLORIC abbreviation of ‘appl’icable. 2 An ACID, so called because it dissolves abbreviation of ‘appl’ied. the ‘noble’ metals GOLD and PLATINUM. applications program (computing) aqueous (chemistry) Dissolved in WATER, COMPUTER PROGRAM written by the or chiefly consisting of WATER. user for a specific purpose, e.g. RECORD- keeping or stock control. aqueous humour (anatomy) The LIQUID between the LENS and CORNEA of the approx. (general terminology) See app. EYE. apps (literary terminology) An abbreviation aqueous solution (chemistry) SOLUTION of ‘app’endice‘s’. in which the SOLVENT is WATER. appx (literary terminology) An abbreviation Ar (chemistry) The CHEMICAL SYMBOL of ‘app’endi‘x’. for ARGON.

aprotinin (pharmacology) An inhibitor arabinose (chemistry) C5H10O5 CRYS- of proteolytic ENZYMES and has TALLINE PENTOSE SUGAR derived from antifibrinolytic activity, because it prevents plant POLYSACCHARIDES (such as gums). thrombosis by an action on the blood clot formation system. arachnoid layer (anatomy) The middle of the three layers of TISSUE that enclose APST (society) An abbreviation of the CENTRAL NERVOUS SYSTEM. Named ‘A’ssociation of ‘P’rofessional ‘S’cientists after its resemblance to a spider’s web. and ‘T’echnologists. See MENINGES.

APTT (haematology) An abbreviation arachnoid membrane (histology) One of ‘A’ctivated ‘P’artial ‘T’hromboplastin of the three thin membranes that cover ‘T’ime. the BRAIN, the other two being the pia mater and the dura mater. APUD cells (physiology/biochemistry) An abbreviation of ‘A’mine ‘P’recursor aragonite (chemistry) Fairly unstable ‘U’ptake and ‘D’ecarboxylation CELLS. mineral form of CALCIUM CARBONATE

(CaCO3). aq. (chemistry) An abbreviation of ‘aq’ueous/‘aq’ua. [Latin, meaning ARBD (medical) An abbreviation of ‘WATER’.] ‘A’lcohol-‘R’elated ‘B’irth ‘D’efects.

43 ARBORIZATION ARITHMETIC PROGRESSION arborization (anatomy) The branching Arg. (biochemistry) An abbreviation of NERVE CELLS. of ‘Arg’inine.

Arboviruses (microbiology) A GROUP arginine (chemistry) C6H14N4O2 Colourless of VIRUSES transmitted by arthropods. (USA: colorless) CRYSTALLINE Examples include the causative agents ESSENTIAL AMINO ACID of the alpha- of dengue, sandfly FEVER, St Louis ketoglutaric ACID FAMILY. encephalitis, western equine encephalitis and YELLOW FEVER. The GENOME argon Ar (chemistry) An INERT GAS is single-stranded RNA. ELEMENT in GROUP O of the PERIODIC TABLE (the RARE GASes). It makes up ARC (medical/virology) An abbreviation 0.93 per cent of AIR (by VOLUME), of ‘A’IDS-‘R’elated ‘C’omplex. from which it is extracted. It is used to provide an INERT ATMOSPHERE in electric Archimedes’ principle (physics) When lamps and DISCHARGE tubes, and for a body is immersed in a FLUID it has welding reactive metals (such as an apparent loss in WEIGHT equal to ALUMINIUM). At. no. 18; r.a.m. 39.948. the WEIGHT of the FLUID it displaces. It was named after the ancient Greek ARIC (education) An abbreviation of mathematician Archimedes (c.287–212BC). ‘A’ssociate of the ‘R’oyal ‘I’nstitute of ‘C’hemistry. arc (mathematics) Part of a curve. The length of an ARC of a circle, RADIUS arithmetic mean (statistics) A measure r, that subtends an angle of ? degrees of central tendency, obtained by dividing at the centre (USA: center) is given the sum of a SET of numbers by the by 27pr?/360 (equal to r? if the angle number in the SET. Contrast GEOMETRIC is in radians). MEAN; MEDIAN; MODE.

ARDS (physiology/biochemistry) An arithmetic mean average (statistics) abbreviation of ‘A’dult ‘R’espiratory of a collection of numbers obtained ‘D’istress ‘S’yndrome. by dividing the sum of the numbers by the quantity of numbers. area (mathematics) Measure of the size of a surface. arithmetic progression (mathematics) Sequence of numbers for which there areola (1,2 anatomy) 1 Part of the IRIS is a CONSTANT COMMON DIFFERENCE, of the EYE, bordering the pupil. 2 Dark d, such that the difference between any SKIN on the breast surrounding a nipple. two successive terms is equal to d. e.g. for the ARITHMETIC PROGRESSION areolar tissue (histology) CONNECTIVE 2, 9, 16, 23, 30, the COMMON TISSUE made up of CELLS separated DIFFERENCE is 7. If the nth term of by bundles of FIBRES (USA: fibers) the SERIES is given by [a+(n-1)d], the embedded in MUCIN. sum of n terms is n[2a+(n-1)d]/2.

ARF (medical) An abbreviation of ‘A’cute See also GEOMETRIC PROGRESSION. ‘R’enal ‘F’ailure.

44 ARITHMETIC SERIES ARTIFICIAL INSEMINATION arithmetic series (mathematics) SERIES as several ALLOTROPES. It is extracted whose terms form an ARITHMETIC from SULPHIDE (USA: sulfide) ores (e.g. PROGRESSION. arsenopyrite) and is used in ALLOYS, as a DONOR impurity in semiconductors arithmetic unit (computing) Part of a and in insecticides and drugs; its compounds COMPUTER’S CENTRAL PROCESSOR are very poisonous. The substance known that performs arithmetical operations as WHITE ARSENIC is ARSENIC(III)

(addition, subtraction, multiplication, OXIDE (arsenious OXIDE), As4O6. At. DIVISION). no. 33; r.a.m. 74.9216. aromatase (biochemistry) The name given arsenide (chemistry) COMPOUND formed to an ENZYME catalysing the aromatization from ARSENIC and another METAL; e.g. of the A-ring of the STEROID NUCLEUS IRON(III) [FERRIC] ARSENIDE, FeAs2. during the conversion of ANDROGENS to oestrogens (USA, estrogens). arsenious acid (chemistry) H3AsO3 Tribasic ACID from which arsenates aromatic compound (chemistry) Member are derived; an AQUEOUS SOLUTION of a large CLASS of organic chemicals of ARSENIC(III) OXIDE (arsenious OXIDE, that exhibit AROMATICITY, the simplest WHITE ARSENIC), As4O6. Also termed: of which is BENZENE. ARSENIC(III) ACID; arsenous ACID. aromaticity (chemistry) Presence in an arsenite (chemistry) SALT or ESTER organic chemical of five or more CARBON of ARSENIOUS ACID (H3AsO3). Also atoms joined in a ring that exhibits termed: ARSENATE(III). DELOCALIZATION of electrons, as in

BENZENE and its compounds. All the arsine (chemistry) H3As Colourless (USA: CARBON-CARBON bonds are equivalent. colorless) highly poisonous GAS with an unpleasant odour (USA: odor). Organic array (computing) An ordered pattern derivatives, in which ALKYL GROUPS of symbol strings having one or more replace one or more HYDROGEN atoms, dimensions. are also called ARSINES. Also termed: ARSENIC(III) HYDRIDE. arrhythmia (medical) Irregular HEART beat. arteriole (anatomy) Small ARTERY. arsenate (chemistry) SALT or ESTER of ARSENIC ACID (H3AsO4). Also termed: artery (anatomy) BLOOD VESSEL that arsenates). carries oxygenated BLOOD from the HEART to other tissues. An exception arsenic acid (chemistry) H3AsO4 Tribasic is the PULMONARY ARTERY, which carries ACID from which ARSENATES are derived. deoxygenated BLOOD to the lungs. an AQUEOUS SOLUTION of ARSENIC(V)

OXIDE, As2O5. Also termed: ORTHOARSENIC arthritis (medical) INFLAMMATION of ACID; ARSENIC(V) ACID. the joints and the surrounding tissues. arsenic As (chemistry) SILVER-grey artificial insemination (1, 2 medical) semimetallic ELEMENT in GROUP VA 1 Artificial IMPLANTATION of SPERM- of the PERIODIC TABLE which exists containing SEMEN into the female

45 ARTIFICIAL INTELLIGENCE ASEXUAL REPRODUCTION

CERVIX. 2 Transfer of a fertilized OVUM ASc.W (society) An abbreviation of from the reproductive tract of one female ‘A’ssociation of ‘Sc’ientific ‘W’orkers. to that of a HOST mother. ASCII (computing) An abbreviation of artificial intelligence (AI) (computing) ‘A’merican ‘S’tandard ‘C’ode for The study of how to make computers ‘I’nformation ‘I’nterchange. perform intelligently. ascites (medical) ABNORMAL accumulation artificial radioactivity (radiology) of FLUID from the BLOOD in the peritoneal RADIOACTIVITY in a substance that cavity, occurring in HEART, LIVER and is not normally RADIOACTIVE. It is KIDNEY FAILURE. created by bombarding the substance with IONIZING RADIATION. Also termed: ascitic fluid (medical) Serous FLUID INDUCED RADIOACTIVITY. in peritoneal cavity.

ARV (virology) An abbreviation of ‘A’IDS- Ascomycetes (mycology) important ‘R’elated ‘V’irus. CLASS of FUNGI in which the SPORE- producing body is an ASCUS. It includes aryl group (chemistry) RADICAL that morels, truffles, the fungal part of most is derived from a COMPOUND exhibiting lichens, and many yeasts. Also termed: AROMATICITY by the removal of one ASCOMYCOTINA.

HYDROGEN ATOM. e.g. phenyl, C6H 5 derived from BENZENE. Ascomycotina (mycology) An alternative term for ASCOMYCETES. arylation (chemistry) The chemical addition of an ARYL GROUP to another ascorbic acid (VITAMIN C) (biochemistry)

MOLECULE. C6H8O6 A white CRYSTALLINE, WATER- SOLUBLE VITAMIN that has seven known As (chemistry) The CHEMICAL SYMBOL biochemical roles including acting as for ELEMENT 33, ARSENIC. cofactor in TYROSINE METABOLISM. ASCORBIC ACID is necessary for, asap (general terminology) An abbreviation amongst other things, formation of BONE, of ‘a’s ‘s’oon ‘a’s ‘p’ossible. and CARTILAGE. Lack of the VITAMIN leads to scurvy in humans. The principal asb (chemistry) An abbreviation of sources of ASCORBIC ACID in the ‘asb’estos. diet are fruits and vegetables.

ASB (society) An abbreviation of ascus (mycology) CELL in FUNGI in ‘A’merican ‘S’ociety of ‘B’acteriologists. which HAPLOID spores are formed. See ASCOMYCETES. asbestos (chemistry) Fibrous VARIETY of a number of rock-forming silicate aseptic (microbiology) Referring to being minerals that are HEAT-resistant and free from PATHOGENIC MICRO- chemically INERT. ORGANISMS (particularly BACTERIA).

ASc. (education) An abbreviation of asexual reproduction (biology) REPRO- ‘A’ssociate in ‘Sc’ience. DUCTION that does not involve gametes

46 ASGBI ASSOCIATIVE or FERTILIZATION. There is a single asphyxia (medical) Suffocation. It can parent, and all offspring are genetically be brought about by obstruction to identical. This commonly occurs in the AIR-passages, by lack of OXYGEN prokaryotes, and also FUNGI, PROTOZOA in the AIR, or by gases which interfere and some plants. BACTERIA normally with the use of OXYGEN by the body, reproduce asexually, but are also capable such as CARBON MONOXIDE. of a form of SEXUAL REPRODUCTION known as CONJUGATION. See CLONE. aspiration (medical) The removal of fluids by suction. See also VEGETATIVE PROPAGATION. aspirator (physics) Apparatus that ASGBI (society) An abbreviation of produces suction in ORDER to draw a ‘A’natomical ‘S’ociety of ‘G’reat ‘B’ritain GAS or LIQUID from a VESSEL or cavity. and ‘I’reland.

aspirin (pharmacology) CH3COO.C6H4- Asherman’s syndrome (medical) COOH Drug that is commonly used AMENORRHOEA (USA: amenorrhea) as an ANALGESIC, antipyretic (to reduce due to ADHESIONS in the uterine cavity. FEVER) and anti-inflammatory. Also termed: acetylsalicyllic acid. Asn (biochemistry) An abbreviation of ‘As’paragi‘n’e. assimilation (biochemistry) Process of turning food into body substances ASN (statistics) An abbreviation of after it has been digested (e.g. in animals ‘A’verage ‘S’ample ‘N’umber. excess GLUCOSE is turned into GLYCOGEN or fat, AMINO ACIDS are Asp. (biochemistry) An abbreviation made into proteins). of ‘Asp’artic acid. Assoc.Sc. (education) An abbreviation aspartame (chemistry) Artificial sweetener of ‘Assoc’iate in ‘Sc’ience. Also termed (a dipeptide) that is 200 times as sweet Assoc.Sci. as ordinary SUGAR (SUCROSE), but does not have the bitter aftertaste association (general term) A connection. CHARACTERISTIC of SACCHARIN. Association of the British Pharmaceutical ASPCA (society) An abbreviation of Industry (ABPI) (association) A UK trade ‘A’merican ‘S’ociety for ‘P’revention association that aims to ensure that medicinal of ‘C’ruelty to ‘A’nimals. and related products are of the highest quality and are readily available for the Aspergillosis (medical/mycology) TREATMENT of human and ANIMAL INFECTION of the lungs with Aspergillus disease. SPECIES, a type of FUNGUS. associative (mathematics) Describing ASPET (society) An abbreviation of a two-stage mathematical operation of ‘A’merican ‘S’ociety for ‘P’harmacology the type a * (b * c) whose result does and ‘E’xperimental ‘T’herapeutics. not depend on the ORDER in which the operation is carried out; e.g. the multiplication 5×(6×7) gives the same result as (5×6)×7,

47 AST ATHEROSELEROSIS and thus multiplication is associative. astroglia (histology) See ASTROCYTE. DIVISION, however, is not; e.g. 40÷(20÷4) does not equal (40÷20)÷4. asymptomatic (medical) Not showing any signs or symptoms of disease whether See also COMMUTATIVE. disease is present or not.

AST (biochemistry) An abbreviation asymptote (mathematics) In geometry of ‘AS’partate amino‘T’ransferase. and CO-ORDINATE geometry, a line that a curve approaches closer and astatine At (chemistry) RADIOACTIVE closer but never reaches. ELEMENT in GROUP VIIA of the asystole (medical) Absence of PERIODIC TABLE (the halogens). It HEARTBEAT. has several isotopes, of half-lives of 6 2×10- sec to 8 hr. Because of their at. no. (physics) An abbreviation of short half-lives, they are available in ‘at’omic number. only MINUTE quantities. At. no. 85; r.a.m. 210 (most STABLE ISOTOPE). at. wt. (physics) An abbreviation of ‘at’omic ‘w’eigh‘t’. aster phase (genetics) An alternative term for METAPHASE. ataxia (medical) Inability to control motor coordination caused by damage astigmatism (1 medical; 2 optics) 1 The to the CENTRAL NERVOUS SYSTEM, refractive error PRODUCT by a CORNEA e.g. by drugs, disease, or lesions. that is more CONVEX in some directions than others, so that lines or edges in ATG (haematology) An abbreviation different orientations cannot simultaneously of ‘A’nti‘T’hymocyte ‘G’lobulin. be brought into FOCUS on the RETINA. 2 Failure of an optical system, such as atheroma (medical/haematology) The a LENS or a mirror, to FOCUS the IMAGE thickening of the wall or the FATTY of a point as a single point. DEGENERATION occurring in the walls of the larger arteries in atherosclerosis. ASTM (society) An abbreviation of Scar TISSUE which limits BLOOD circulation ‘A’merican ‘S’ociety for ‘T’esting and and predisposes to THROMBOSIS. ‘M’aterials. atheroselerosis (medical/haematology) An accumulation of LIPID deposits within astrocyte (histology) One of the many or beneath the surfaces of BLOOD VESSELS types of non-NEURONE CELL found that partially occludes the LUMEN of the within the NERVOUS SYSTEM, the name VESSEL and roughens its interior surface. being derived from the star-like appearance. This reduces BLOOD flow to tissues, Astrocytes support the FUNCTION of increases the chance of PLATELET neurones. Also termed astroglia. aggregation and BLOOD COAGULATION by increasing the turbulence within the astrocytosis (medical/histology) An increase BLOOD, and increases the chances of in numbers and size of ASTROCYTES OCCLUSION by trapping a circulating as a result of traumatic BRAIN damage BLOOD clot. If CALCIUM becomes deposited or in neurodegenerative disease. in the atherosclerotic plaques, then arterioscle-

48 ATLAS ATOMIC WEIGHT rosis (‘hardening of the arteries’) results. (electrically NEUTRAL); HYDROGEN Certain diets may contribute to atherosclerosis, is exceptional in having merely one as may CHROMIUM deficiency or excess PROTON in its NUCLEUS. The number COPPER. of electrons is equal to the number of protons, and this is the ATOMIC NUMBER. atlas (anatomy) The first (CERVICAL) The chemical BEHAVIOUR (USA: behavior) VERTEBRA, which joins the SKULL of an ATOM is determined by how many to the SPINE and articulates with the electrons it has, and how they are AXIS, allowing nodding movements of transferred to, or shared with, other the HEAD. atoms to form CHEMICAL BONDS.

Atm. (physiology/physics) An abbreviation See also RELATIVE ATOMIC MASS; of ‘Atm’osphere. ISOTOPE; MOLECULE; SUBATOMIC PARTICLE; VALENCE. atmosphere (1 physics; 2 measurement) 1 AIR or gases surrounding the EARTH atomic mass (chemistry) An alternative or other heavenly body. The EARTH’S term for ATOMIC WEIGHT. ATMOSPHERE extends outwards several thousand kilometres, becoming See also RELATIVE ATOMIC MASS. increasingly rarefied until it merges gradually into space. See AIR. 2 (atm.) atomic mass unit (AMU) (chemistry) UNIT of PRESSURE, equal to 101,325 Arbitrary UNIT that is used to express pascals (equivalent to 760 mm Hg). the MASS of individual atoms. The standard is a MASS equal to 1/12 of the MASS atmospheric pressure (physics) FORCE of a CARBON ATOM (the CARBON-12 exerted on the surface of the EARTH ISOTOPE). A MASS expressed on this (and any other planetary body), and standard is called a RELATIVE ATOMIC on the organisms that live there, by MASS (r.a.m.), symbol Ar. ATOMIC MASS the WEIGHT of the ATMOSPHERE. Its UNIT is also termed dalton. standard value at sea-LEVEL is 1.01325×105 Nm2, and it decreases atomic number (at. no.) (chemistry) with altitude, but is subject to local Number equal to the number of protons and temporary VARIATION. It is measured in the NUCLEUS of an ATOM of a with a BAROMETER. particular ELEMENT, symbol Z. Also termed: PROTON NUMBER. ATN (medical) An abbreviation of ‘A’cute ‘T’ubular ‘N’ecrosis. atomic orbital (chemistry) WAVE FUNCTION that characterizes the BEHAVIOUR (USA: atom (chemistry) Fundamental PARTICLE behavior) of an ELECTRON when orbiting that is the BASIC UNIT of MATTER. the NUCLEUS of an ATOM. It can be An ATOM consists of a positively charged visualized as the region in space occupied NUCLEUS surrounded by negatively by the ELECTRON. charged electrons restricted to orbitals of a given ENERGY LEVEL. Most of atomic weight (at. wt.) (chemistry) Relative the MASS of an ATOM is in the NUCLEUS, MASS of an ATOM given in terms of which is composed principally of protons ATOMIC MASS UNITS. See RELATIVE (positively charged) and neutrons ATOMIC MASS.

49 ATOMICITY AUTISM atomicity (chemistry) Number of atoms Au (chemistry) The symbol for the in one MOLECULE of an ELEMENT; ELEMENT GOLD. [From the Latin, ‘aurum’.] e.g. ARGON has an ATOMICITY of 1, NITROGEN 2, OZONE 3. AUC (statistics) An abbreviation of ‘A’rea ‘U’nder ‘C’urve. ATP (biochemistry) An abbreviation of ‘A’denosine ‘T’ri‘P’hosphate. audiology (audiology) The scientific study of hearing. ATPD (physics) An abbreviation of ‘A’mbient ‘T’emperature and ‘P’ressure, auditory canal (anatomy) Tube that ‘D’ry. leads from the OUTER EAR to the EAR DRUM (tympanum). ATPS (physics) An abbreviation of ‘A’mbient ‘T’emperature and ‘P’ressure, auditory nerve (histology) NERVE that ‘S’aturated with water vapour (USA: carries impulses concerned with hearing vapor). from the INNER EAR to the BRAIN. atrium (anatomy) One of the thin-walled auditory (medical) Relating to the EAR upper chambers of the HEART. Also or hearing. termed: AURICLE. Auger effect (chemistry) Radiationless atrophy (medical) A wasting away, or ejection of an ELECTRON from an ION. decrease in the size and FUNCTION It is named after the French physicist of a CELL, TISSUE, or ORGAN. Pierre Auger (1899–1993). Also termed: AUTOIONIZATION. atropine (1 toxicology; 2 pharmacology) 1 White CRYSTALLINE poisonous AUL (haematology) An abbreviation ALKALOID that occurs in deadly of ‘A’cute ‘U’ndifferentiated ‘L’eukaemia nightshade. Also termed: belladonna. (USA: ACUTE Undifferentiated Leukemia). 2 A muscarinic ANTAGONIST. This powerful ANTICHOLINERGIC drug is auranofin (pharmacology) A disease able to depress certain functions of modifying ANTIRHEUMATIC and ANTI- the autonomic nervous system and is INFLAMMATORY drug containing gold. therefore a useful ANTISPASMODIC It is administered orally to treat severe drug. It can also be used to cause a progressive rheumatoid arthritis. long-lasting dilation of the pupil of the eye for ophthalmic procedures. auric (chemistry) TRIVALENT GOLD. Also termed: GOLD(III); GOLD(3+). attenuated (microbiology) Weakened, reduced in VIRULENCE (e.g. live auricle (anatomy) An alternative term poliovirus VACCINE). for ATRIUM. attenuation (physics) Loss of strength aurous (chemistry) MONOVALENT GOLD. of a physical quantity (e.g. a radio signal Also termed: GOLD(I); GOLD(1+). or an ELECTRIC CURRENT) caused by ABSORPTION or scattering. autism (medical) BRAIN disorder that develops in infancy and which is

50 AUTOCATALYSIS AVERAGE characterized by extreme learning parasympathetic and SYMPATHETIC difficulties and a lack of responsiveness NERVOUS SYSTEMS. to other people. auto-oxidation (chemistry) OXIDATION autocatalysis (chemistry) Catalytic caused by the unaided ATMOSPHERE. REACTION that is started by the products of a REACTION that was itself catalytic. autopsy (medical) The examination See CATALYST. of a body after death, so that physicians can arrive at a true diagnosis of the autoclave (laboratory equipment) Airtight cause of death. container that heats and sometimes agitates its contents under high-PRESSURE steam. autoradiography (radiology) Technique Autoclaves are usually used for for photographing a specimen by injecting STERILIZATION or industrial processing. it with RADIOACTIVE material so that it produces its own IMAGE on a autogamy (biology) Uniting of gametes photographic FILM or plate. produced by the same CELL. Also termed: self-FERTILIZATION. autosome (genetics) AnY CHROMOSOME other than one of the SEX CHROMOSOMES. auto-immune diseases (medical/ immunology) A wide range of conditions autotroph (biology) Organism that lives e.g. rheumatoid arthritis, ulcerative colitis, using AUTOTROPHISM. and so on, in which destructive inflammation of various body tissues autotrophism (biology) In BACTERIA is caused by antibodies produced because and green plants, the ability to build the body has ceased to regard the up food materials from simple substances, affected part as ‘self’. e.g. by PHOTOSYNTHESIS. autoionization (chemistry) Spontaneous See also HETEROTROPHISM. IONIZATION of excited atoms, molecules or fragments of an ION. Also termed: AV (chemistry) An abbreviation of ‘A’cid pre-IONIZATION. ‘V’alue.

See also AUGER EFFECT. avalanche diode (physics) An alternative term for ZENER DIODE. autolysis (biochemistry) Breakdown of the contents of an ANIMAL or plant A-V difference (physiology/biochemistry) CELL by the ACTION of ENZYMES An abbreviation of ‘A’rterio‘V’enous produced within that CELL. concentration ‘difference’ of any given substance. autonomic nervous system (ANS) (physiology) In vertebrates, the part average (statistics) Number that is of the NERVOUS SYSTEM that is not representative of a collection of numbers; under voluntary control and carries e.g. an ARITHMETIC MEAN, GEOMETRIC NERVE IMPULSES to the SMOOTH MEAN, MODE or MEDIAN. MUSCLES, GLANDS, HEART and other organs. It is subdivided into the

51 AVG AZO DYE

Avg (statistics) An abbreviation of A/W (measurement) An abbreviation ‘av’era‘g’e. of ‘A’ctual ‘W’eight.

AV node (physiology/biochemistry) An axiom (philosophy) Principle that is abbreviation of ‘A‘trioV’entricular ‘node’. taken as true, without needing PROOF.

See also HYPOTHESIS; LAW; THEOREM. Avogadro constant (L or NA) (chemistry) Number of particles (atoms or molecules) axis (1 mathematics; 2 biology; 3 anatomy) in a mole of a substance. It has a 1A line of significant reference for a GRAPH value of 6.02253×1023. It was named or figure; e.g. x- and y-axes in CARTESIAN after the Italian scientist Amedeo Avogadro CO-ORDINATES. 2 Central line of (1776–1856). Also termed: AVOGADRO’S SYMMETRY of an organism. 3 The second NUMBER. (CERVICAL) VERTEBRA, which articulates with the ATLAS and allows the HEAD to Avogadro’s law (chemistry) Under the turn from side to side. same conditions of PRESSURE and TEMPERATURE, equal volumes of all axon (histology) Long, thread-like gases contain equal numbers of outgrowth of a NERVE CELL (NEURONE), molecules. Also termed: Avogadro’s the main FUNCTION of which is to HYPOTHESIS. carry impulses away from the CELL.

Avogadro’s number (chemistry) An azathioprine (pharmacology) A powerful alternative term for AVOGADRO CONSTANT. cytotoxic and immunosuppressant drug that may be administered orally or by avoirdupois (measurements) System injection. It is used to reduce tissue of weights based on a pound (symbol rejection in transplant recipients as Ib), equivalent to 2.205kg, and subdivided well as to treat patients with several into 16 ounces, or 7,000 grains. In autoimmune diseases, myasthenia gravis, science and medicine it has been almost rheumatoid arthritis and ulcerative colitis. entirely replaced by SI UNITS. See AVOIRDUPOIS OUNCE. azeotrope (chemistry) MIXTURE of two liquids that boil at the same avoirdupois ounce (measurement) UNIT TEMPERATURE. of WEIGHT, 1/16 of a pound. 1 oz= 28.349527 grams. See AVOIRDUPOIS. azide (chemistry) One of the ACYL GROUP of compounds, or salts, derived

AVP (physiology/biochemistry) An from hydrazoic ACID (N3H). Most azides abbreviation of ‘A’rginine ‘V’aso‘P’ressin. are unstable, and heavy METAL azides are explosive. AVS (society) An abbreviation of ‘A’nti- ‘V’ivisection ‘S’ociety. azo compound (chemistry) ORGANIC COMPOUND of GENERAL FORMULA AV valves (physiology) An abbreviation R-N=N-R’, in which R and R’ are usually of ‘A’trioV’entricular ‘valves’ of HEART. aromatic groups. aw (chemistry) An abbreviation of azo dye (chemistry) Member of a CLASS ‘a’tomic ‘w’eight. of dyes that are derived from compounds

52 AZOMETHINE AZT containing an AMINO GROUP and have an -N=N- LINKAGE in their molecules. They are intensely coloured (USA: colored) (usually red, brown or yellow) and account for a large proportion of the SYNTHETIC dyes produced. Azo DYES can be made as ACID, BASIC, direct or mordant dyes. Their use as food colourants (USA: colorants) has been questioned because of their possible effects on sensitive people, particularly children. azomethine (biochemistry) See SCHIFF’S BASE.

AZT (pharmacology) An abbreviation of ‘AZ’ido‘T’hymidine.

53 B

B (1 chemistry; 2 haematology) 1 The Ba (chemistry) The CHEMICAL SYMBOL CHEMICAL SYMBOL for ELEMENT 5, BORON. for ELEMENT 56, BARIUM. 2 A BLOOD type. See ABO BLOOD GROUPS. BA Sc. (education) An abbreviation B App. Sc. (education) An abbreviation of ‘B’achelor of ‘A’pplied ‘Sc’ience. of ‘B’achelor of ‘App’lied ‘Sc’ience. BAAS (education) An abbreviation of B cell (immunology/haematology) An ‘B’ritish ‘A’ssociation for the ‘A’dvance- abbreviation of ‘b’eta CELL. ment of ‘S’cience.

B Hy. (education) An abbreviation of BAC (1 biochemistry; 2 society) 1 An ‘B’achelor of ‘Hy’giene/Public Health. abbreviation of ‘B’lood ‘A’lcohol ‘C’oncentration. 2 An abbreviation of B Med Biol. (education) An abbreviation ‘B’ritish ‘A’ssociation of ‘C’hemists. of ‘B’achelor of ‘Med’ical ‘Biol’ogy.

B Med Sc. (education) An abbreviation Bacillus (bacteriology) The name of ‘B’achelor of ‘Med’ical ‘Sc’ience. originally used in bacteriology to MEAN any ROD-shaped as opposed to a round B Sc. App. (education) An abbreviation MICRO-ORGANISM. It is now properly of ‘B’achelor of ‘App’lied ‘Sc’ience. used to denote only one GENUS of SPORE-producing BACTERIA, one b. pt (physics) An abbreviation of member of which is BACILLUS anthracis ‘b’oiling ‘p’oin‘t’. the causative organism of ANTHRAX.

B. Sc. (education) Bachelor of Science; Bacille Calmette-Guérin (BCG) (immunol- -(LA) Bachelor of Science (LABORATORY ogy) A VACCINE used against TUBERCU- Assistant);—(Med.) Bachelor of Science LOSIS. It was named after two French in Medicine;—(Med. Lab. Tech.) Bachelor BACTERIOLOGISTS, Albert Calmette (1863– of Science in Medical LABORATORY 1933) and Camille Guérin (1872–1961). Technology;—(Med. Sci.) Bachelor of Science in Medical Sciences;—(M.L.S.) Bachelor bacillus cereus (bacteriology) a gram- of Science in Medical LABORATORY POSITIVE, an AEROBIC BACILLUS that Science;—(Nutr.) Bachelor of Science in produces toxins that cause foodpoison- Nutrition;—(Pharm.) Bachelor of Science ing. They include a THERMOLABILE TOXIN in Pharmacy;—(R.T.) Bachelor of Science causing DIARRHOEA (USA: diarrhea) in Radiologic Technology; -(Vet.) Bachelor and a thermostable TOXIN causing EMESIS. of Science in Veterinary Science,—(Vet.Sc. & A.1A.) Bachelor of Science in Veterinary back emf (physics) ELECTROMOTIVE FORCE Science and ANIMAL Husbandry. produced in a CIRCUIT that opposes the

54 BACKBONE BACTERIOLOGIST main flow of CURRENT; e.g. in an almost any ENVIRONMENT. Some can ELECTROLYTIC CELL because of even use inorganic elements such as POLARIZATION or in an ELECTRIC MOTOR SULPHUR (USA: sulfur).The activities because of ELECTROMAGNETIC INDUCTION. of some BACTERIA are of great significance to man, e.g. FIXATION OF NITROGEN backbone (anatomy) An alternative in certain plants, as agents of DECAY, term for VERTEBRAL COLUMN. and their medical importance as disease- causing agents (pathogens). Much genetical background radiation (radiology) research is done on BACTERIA because, RADIATION from natural sources, including being prokaryotes, they have simple genetic outer space (cosmic RADIATION) and machinery. Sing. ‘BACTERIUM’. See RADIOACTIVE substances on the EARTH ESCHERICHIA COLI. (e.g. in igneous rocks such as granite). bacterial (bacteriology) Refering to backing store (computing) COMPUTER BACTERIA or caused by BACTERIA. store that is larger than the main (immediate access) MEMORY, but with bacterial endocarditis (medical/ a longer ACCESS TIME. bacteriology) BACTERIAL INFECTION of the endocardium. baclofen (pharmacology) A skeletal muscle relaxant drug that is administered orally bacterial strain (bacteriology) A distinct to relax muscles that are in spasm, particularly VARIETY of BACTERIA. when caused by injury or by a disease of the CENTRAL NERVOUS SYSTEM. bactericidal (bacteriology) The ACTION of a substance which destroys BACTERIA. bact. (bacteriology) An abbreviation of ‘bact’eria/‘bact’erial/‘bact’eriology. bactericide (bacteriology) A substance which kills BACTERIA. bacteraemia (bacteriology) The condition See also BACTERIOSTATIC. of having BACTERIA in the bloodstream. (USA: bacteremia). bacteriocins (bacteriology) PROTEIN ANTIBIOTIC-like substances produced bacteria (bacteriology) A large GROUP by some BACTERIA, which are lethal to of single-celled microscopic organisms. other strains of BACTERIA, generally They can occur either free-living in AIR, those closely related to the producer WATER, soil, etc; or they may be parasitic organism. upon a HOST plant or ANIMAL. Only a minority cause any disease, and more bacteriological (bacteriology) Pertaining are actually useful to their hosts, e.g. to bacteriology. in breaking down food as part of the digestive process. The three BASIC shapes bacteriological warfare (bacteriology) are BACILLUS (ROD), spirillum (spiral) War where one side tries to kill or and COCCUS (spherical), but some affect the people of the enemy side BACTERIA may link up to form chains by infecting them with BACTERIA. or clumps. Multiplication is fast, usually by FISSION. Between them, the various bacteriologist (bacteriology) A scientist SPECIES can utilize almost any type who specialises in the study of BACTERIA. of organic MOLECULE as food and inhabit

55 BACTERIOLOGY BAR bacteriology (microbiology) The scientific baker’s dermatitis (medical/immunology) study of BACTERIA, their effects on Irratation of the SKIN caused by handling organisms, including humans, and their YEAST. Also termed baker’s itch. uses in agriculture and industry (e.g. in biotechnology). baker’s itch (medical/immunology) See BAKER’S DERMATITIS. bacteriolysin (bacteriology) A PROTEIN, usually an IMMUNOGLOBULIN, which baking soda (chemistry) An alternative destroys BACTERIAL CELLS. term for SODIUM HYDROGENCARBONATE (SODIUM BICARBONATE). bacteriolysis (bacteriology) The destruction of BACTERIAL CELLS. balance (1 physics; 2 physiology) 1 Apparatus for weighing things accurately; bacteriolytic (bacteriology) A substance types include a beam BALANCE, spring which can destroy BACTERIA. BALANCE, torsion BALANCE and substitution BALANCE. 2 Sense supplied bacteriophage (bacteriology) VIRUS by organs within the SEMICIRCULAR that infects BACTERIA. When inside a CANALS of the INNER EAR. CELL it replicates using its HOST’S ENZYMES; the release of new VIRUSES balanitis (medical) INFLAMMATION may disintegrate the CELL. Bacteriophages of the glans of the PENIS. have been used extensively in research on genes. Also termed: PHAGE. balanoposthitis (medical) INFLAMMATION of the foreskin and the end of the PENIS. bacteriostatic (bacteriology) Substance that inhibits the GROWTH of BACTERIA Balmer series (physics) Visible atomic without killing them. SPECTRUM of HYDROGEN, consisting of a unique SERIES of ENERGY emission See also BACTERICIDE. levels which appears as lines of red, blue and blue-violet LIGHT. It is the key bacterium (bacteriology) The singular to the discrete ENERGY LEVELS of electrons. form of BACTERIA. See BACTERIA. bals. (microscopy) An abbreviation of bacteriuria (bacteriology) Presence ‘bals’am. of BACTERIA in URINE. balsam (microscopy) Vegetable RESIN BAFM (society) An abbreviation of combined with oil, e.g. Canada balsam, ‘B’ritish ‘A’ssociation of ‘F’orensic used in preparing slides for microscopy, ‘M’edicine. which comes from the balsam fir of North America. Baker’s cyst (medical/histology) Swelling filled with SYNOVIAL FLUID, at the bar (measurement) UNIT of PRESSURE back of the knee, caused by weakness defined as 105 newtons per square of the JOINT MEMBRANE. Named after METRE; equal to approximately one the physician, W.M.Baker (1838–96). ATMOSPHERE.

56 BAR CHART BASE bar chart (statistics) GRAPH that has barometer (physics) Instrument for vertical or horizontal bars whose lengths measuring ATMOSPHERIC PRESSURE, are proportional to the quantities they much used in meteorology. represent. Barr body (genetics) Condensed X- See also PIE CHART. CHROMOSOME, seen in female CELLS of mammals, due to one or other of bar code (general terminology) Information the two X-CHROMOSOMES in each about a PRODUCT coded as a SERIES CELL being inactivated. of thick and thin parallel lines printed on it (or on a LABEL attached to it), which BAS (education) An abbreviation of can be scanned and ‘read’ by a machine. ‘B’achelor of ‘A’pplied ‘S’cience.

See also CHARACTER recognition. basal ganglion (anatomy) Region of GREY MATTER within the WHITE MATTER barbiturate (pharmacology) SEDATIVE that forms the inner part of the CEREBRAL and hypnotic drug derived from HEMISPHERES of the BRAIN. BARBITURIC ACID. basal metabolic rate (BMR) (physiology) barbituric acid (pharmacology) C4H4N2O3 Minimum amount of ENERGY on which DIBASIC ORGANIC ACID that gives the body can survive, measured by rise to BARBITURATE drugs. OXYGEN consumption and expressed in kilojoules per UNIT body surface. barium Ba (chemistry) SILVER-white metallic ELEMENT in GROUP IIA of basal nucleus (anatomy) Also known the PERIODIC TABLE (the ALKALINE as basal ganglia, a body of GREY EARTHS), obtained mainly from the MATTER (NERVE TISSUE) located deep mineral barytes (BARIUM SULPHATE within the CEREBRAL HEMISPHERES [USA: barium sulfate]). Its SOLUBLE of the BRAIN, and concerned with compounds are poisonous, and used movement. in fireworks; its INSOLUBLE compounds are used in pigments and medicine. base (1 chemistry; 2, 3, 4 mathematics; At. no. 56; r.a.m. 137.34. molecular biology) 1 A member of a CLASS of chemical compounds whose barium sulphate (chemistry) BaSO4 AQUEOUS SOLUTIONS contain OH- ions. White CRYSTALLINE INSOLUBLE A BASE neutralizes an ACID to form a powder, used as a PIGMENT and as SALT. See also ALKALI. 2 The horizontal the basis of ‘BARIUM meal’ to show line upon which a geometric figure stands. up structures in X-RAY diagnosis (because 3 The starting number for a numerical it is OPAQUE to X-RAYS). It occurs or logarithmic system; e.g. binary as the mineral barytes (also called NUMERALS have the BASE 2, COMMON barite). (USA: barium sulfate). LOGARITHMS are to the BASE 10.4 Number on which an EXPONENT operates; barograph (physics) Type of BAROMETER e.g. in 52, 5 is the BASE (and 2 the that produces a chart recording changes EXPONENT). 5 One of the nucleotides in ATMOSPHERIC PRESIURE over a of DNA or RNA (i.e. ADENINE, CYTOSINE, PERIOD of time. GUANINE, THYMINE or URACIL).

57 BASE METALS BEER’S LAW base metals (chemistry) Metals that corrode, BC (education) An abbreviation of oxidize or tarnish on exposure to AIR, ‘B’achelor of ‘C’hemistry. moisture or HEAT; e.g. COPPER, IRON, LEAD. BCG (immunology) An abbreviation of ‘B’ACILLUS ‘C’ALMETTE-‘G’UERIN base pair (Bp) (molecular biology) Used (VACCINE). as a UNIT of length to describe a sequence of DNA. BCMA (governing body) An abbreviation of ‘B’ritish ‘C’olumbia ‘M’edical base pairing (molecular biology) Specific ‘A’ssociation. pairing between complementary BDA (society) An abbreviation of ‘B’ritish nueleotides in double-stranded DNA ‘D’ental/‘D’iabetic ‘A’ssociation (now or RNA by hydrogen bonding; e.g. in Diabetes UK). DNA GUANINE pairs with CYTOSINE, and ADENINE pairs with THYMINE. BDH (chemistry) An abbreviation of ‘B’ritish ‘D’rug ‘H’ouses. See also PURINE; PYRIMIDINE. BDNF (physiology/biochemistry) An basic (chemistry) Having a tendency to abbreviation of ‘B’rain-‘D’erived release HYDROXIDE (OH-) ions. See BASE. ‘N’eurotrophic ‘F’actor. basic oxide (chemistry) Metallic OXIDE Be (chemistry) CHEMICAL SYMBOL that reacts with an ACID to form a for BERYLLIUM. SALT and WATER. Beckmann thermometer (physics) See also ACIDIC OXIDE. MERCURY THERMOMETER used for accurately measuring very small changes basic salt (chemistry) SALT that contains or differences in TEMPERATURE. The HYDROXIDE (OH-) ions; e.g. BASIC scale usually covers only 6 or 7 degrees.

LEAD CARBONATE, 2PbCO3.Pb(OH)2. It was named after the German chemist Ernst Beckmann (1853–1923). battery (physics) Device for producing ELECTRICITY (DIRECT CURRENT) by becquerel (Bq) (measurement) SI UNIT chemical ACTION; Also termed: CELL. of RADIOACTIVITY, equal to the number See DANIELL CELL; DRY CELL; PRIMARY of atoms of a RADIOACTIVE substance CELL; SECONDARYCELL. that disintegrate in one second. It was named after the French physicist Antoine See also SOLAR CELL. Henri BECQUEREL (1852–1908). 1 Bq=2.7× 10-11 curies (the former UNIT BBA (medical) An abbreviation of ‘B’orn of RADIOACTIVITY). ‘B’efore ‘A’rrival. Beer’s law (physics) Concerned with BBC (chemistry) An abbreviation of the ABSORPTION of LIGHT by ‘B’romo-‘B’enzyl ‘C’yanide. substances, it states that the FRACTION of incident LIGHT absorbed by a BBT (physiology) An abbreviation of SOLUTION at a given WAVELENGTH ‘B’asal ‘B’ody ‘T’emperature. is related to the thickness of the absorbing

58 BEET SUGAR BERKELIUM

layer and the CONCENTRATION of benzene (chemistry) C6H6 Colourless the absorbing substance. Also termed: (USA: colorless) inflammable LIQUID Beer Lambert LAW. HYDROCARBON, simplest of the AROMATIC COMPOUNDS. It is used as a SOLVENT beet sugar (chemistry) An alternative and in the manufacture of plastics. term for SUCROSE.

benzene-1,3-diol (chemistry) C6H4(OH)2 behaviour (medical) Way of acting. An alternative term for RESORCINOL. (USA: behavior). benzene ring (chemistry) CYCLIC (closed- behavioural scientist (medical) A person chain) arrangement of six CARBON atoms, who specialises in the study of as in a MOLECULE of BENZENE. BEHAVIOUR. (USA: behavioral scientist). Molecules containing one or more BENZENE RINGS DISPLAY aromatic bel (B) (measurement) UNIT representing CHARACTER. See AROATICITY. the ratio of two amounts of POWER, e.g. of sound or an electronic signal, benzocaine (pharmacology) A local equal to 10 decibels. It was named after anaesthetic drug administered by topical the American inventor Alexander Graham application for the relief of pain in the Bell (1847–1922). skin surface or MUCOUS MEMBRANES.

Benedict’s test (biochemistry) Food test benzodiazepine (pharmacology) Member used to detect the presence of a REDUCING of a GROUP of drugs used as ANTIDE- SUGAR by the addition of a SOLUTION PRESSANTS and anticonvulsants. containing SODIUM CARBONATE, SODIUM citrate, POTASSIUM THIOCYANATE, benzoic acid (chemistry) C6H5COOH White COPPER SULPHATE (USA: copper sulfate) CRYSTALLINE ORGANIC COMPOUND, and POTASSIUM FERROCYANIDE. A change used as a food preservative because it in COLOUR (USA: color) from blue to inhibits the GROWTH of yeasts and moulds red or yellow on boiling indicates a POSITIVE (USA: molds). result. It was named after the American chemist S.Benedict (1884–1936). benzole (chemistry) An alternative term for BENZENE. See also FEHLING’S TEST. benzpyrene (chemistry) CYCLIC benign (medical/histology) Describing ORGANIC COMPOUND, found in coal- a TUMOUR (USA: tumor) that does tar and tobacco smoke, which has strong not spread or destroy the TISSUE where CARCINOGENIC properties. it is located; not MALIGNANT; not recurrent; favourable for recovery. benzpyrrole (chemistry) An alternative term for INDOLE. See also MALIGNANT. BER (physiology) An abbreviation of benzaldehyde (chemistry) C6H 5CHO ‘B’asic ‘E’lectric ‘R’hythm. Colourless (USA: colorless) aromatic ALDEHYDE, with a SMELL of almonds, berkelium Bk (chemistry) RADIOACTIVE used as a flavouring, in perfumes and ELEMENT in GROUP IIIB of the PERIODIC as an INTERMEDIATE in making dyes. TABLE (one of the ACTINIDES). It has

59 BERNOULLI’S THEOREM BICARBONATE several isotopes, with half-lives of up associated with SKIN conditions such to 1,400 years, made by alpha-particle as eczema and psoriasisis. bombardment of AMERICIUM-241. At. no. 97; r.a.m. 247 (most STABLE ISOTOPE). beta particle (radiology) High-velocity ELECTRON emitted by a RADIOACTIVE Bernoulli’s theorem (physics) At any NUCLEUS undergoing BETA DECAY. point in a tube through which a LIQUID is flowing the sum of the POTENTIAL, beta radiation (radiology) RADIATION, kinetic and PRESSURE energies is consisting of BETA PARTICLES CONSTANT. Also termed: Bernoulli’s principle. (electrons), due to BETA DECAY. It was named after the Swiss mathematician and physicist Daniel Bernoulli (1700–82). beta ray (radiology) Stream of BETA PARTICLES. beryllium Be (chemistry) SILVER-grey metallic ELEMENT in GROUP IIA of bethanechol chloride (pharmacology) the PERIODIC TABLE (the ALKALINE A parasympathomimetic drug EARTHS). It is used for windows in X- administered orally to stimulate motility RAY TUBES and as a moderator in in the INTESTINES and to treat urinary nuclear reactors. At. no. 4; r.a.m. 9.0122. retention. beta-adrenoceptors (physiology/ bezafibrate (pharmacology) A LIPID- pharmacology) Receptor sites at which lowering drug administered orally to NORADRENALINE and other HORMONES reduce levels, or change the proportions act to cause muscle to contract or relax. of various LIPIDS in the bloodstream of patients with hyperLIPIDaemia (USA: beta-blocker (pharmacology) Drugs hyperLIPIDemia). that block beta-adrenergic receptors, used to treat HYPERTENSION (HIGH betz cells (cytology) The large pyramidal BLOOD PRESSURE). cells of the motor cortex of the brain. Named after the Ukrainian anatomist beta decay (radiology) DISINTEGRATION Vladimir Betz (1834–94). of an unstable RADIOACTIVE NUCLEUS that involves the emission of a BETA BFO (physics) An abbreviation of ‘B’eat- PARTICLE. It occurs when a NEUTRON ‘F’requency ‘O’scillator. emits an ELECTRON and is itself converted to a PROTON, resulting in an increase BGP (physiology/biochemistry) An of one PROTON in the NUCLEUS concerned abbreviation of ‘B’one ‘G’la ‘P’rotein. and a corresponding decrease of one NEUTRON. This leads to the formation bibl. (literary terminology) An abbreviation of a different ELEMENT (e.g. BETA DECAY of ‘bibl’iographer/bibliographical/ of CARBON-14 produces NITROGEN). bibliography. Also termed bibliog. betamethasone (pharmacology) A bicarb. (chemistry) An abbreviation corticosteroid that has ANTI- of ‘bicarb’onate of SODA. INFLAMMATORY properties. It is used in the treatment of many kinds of bicarbonate (chemistry) An alternative inflammation, particularly inflammation term for HYDROGENCARBONATE.

60 BICEPS BINDING ENERGY biceps (anatomy) Two-headed MUSCLE biliary (anatomy) To do with BILE or in the arm or thigh. the GALL BLADDER. bichromate (chemistry) An alternative bilirubin (biochemistry) Major PIGMENT term for DICHROMATE. in BILE, formed in the LIVER by the breakdown of HAEMOGLOBIN (USA: biconcave (optics) Describing a LENS hemoglobin). Its accumulation causes that is CONCAVE on both surfaces. the symptom JAUNDICE. biconvex (optics) Describing a LENS billion (measurement) Number now generally that is CONVEX on both surfaces. accepted as being equivalent to 1,000 million (109). Formerly in Britain a BILLION bilateral symmetry (physiology) Type was regarded as a million million (1012). of SYMMETRY in which a shape is symmetrical about a single AXIS or binary code (mathematics) An alternative plane (each half being a mirror IMAGE term for BINARY NOTATION. of the other). E.g. most vertebrates are bilaterally symmetrical. binary compound (chemistry) Chemical that consists of two elements. See also RADIAL SYMMETRY. binary fission (physiology) Method bile (biochemistry) ALKALINE MIXTURE of REPRODUCTION employed by many of substances produced by the LIVER single-celled organisms, in which the and stored in the GALL BLADDER, so-called mother CELL divides in half which passes it to the DUODENUM, (by MITOSIS), forming two identical, where it emulsifies fats (preparing them but independent, DAUGHTER CELLS. for DIGESTION) and neutralizes ACID. It is a type of ASEXUAL REPRODUCTION. Its (yellowish) COLOUR (USA: color) is due to BILE pigments (e.g. BILIRUBIN). binary notation (mathematics) Number system to the BASE 2, involving only bile duct (anatomy) A tube that carries two digits, 0 and 1. Instead of the units, BILE from the GALL BLADDER to the tens, hundreds, etc; of the DECIMAL DUODENUM. SYSTEM, units, twos, fours, eights, etc; are used. Thus, eg; 8 is given as 1000 bilharzia (parasitology) Disease that affects and 9 as 1001. BINARY NOTATION is human beings and domestic ANIMALS important in ELECTRONICS and computers in some subtropical regions, which results because the 0 and 1 can be represented from an INFESTATION by one of the parasitic by a CIRCUIT being ‘on’ or ‘off. Also BLOOD FLUKES belonging to the GENUS termed: BINARY CODE; BINARY SYSTEM. Schistosoma. The larvae of the FLUKES develop inside freshwater snails and become binary system (mathematics) An free-swimming organisms which can attach alternative term for BINARY NOTATION. themselves to a wading mammal, penetrating the SKIN and entering the bloodstream. binding energy (physics) ENERGY Also termed: SCHISTOSOMIASIS. required to cause a NUCLEUS to decompose into its constituent NEUTRONS and PROTONS.

61 BINOMIAL BIOPSY binomial (mathematics) POLYNOMIAL concerned aware of measurements from that has two variables, e.g. (x+2y) 2. instruments monitoring that process. binomial nomenclature (biology) System biogenesis (biology) Theory that living by which organisms are identified by two organisms may originate only from other Latin names. The first is the name of the living organisms, as opposed to the GENUS (GENERIC name), the second theory of SPONTANEOUS GENERATION. is the name of the SPECIES (specific name), e.g. HOMO SAPIENS. Also termed: See also ABIOGENESIS. LINNAEAN SYSTEM (after the Swedish biologist Carolus Linnaeus, 1707–78). biological clock (biology) Hypothetical mechanism in plants and animals that See also CLASSIFICATION. controls periodic changes in internal binomial theorem (mathematics) functions and BEHAVIOUR (USA: behavior) FORMULA for calculating the POWER independently of ENVIRONMENT, e.g. of a BINOMIAL without complicated diurnal rhythms and hibernation patterns. multiplication. biology (biology) Study of living bioassay (biochemistry) Method for organisms. quantitatively determining the CON- CENTRATION of a substance by its bioluminescence (physiology) Emission effect on living organisms, e.g. its effect of VISIBLE LIGHT by living organisms, on the GROWTH of BACTERIA. e.g. certain BACTERIA, FUNGI, fish and insects. The LIGHT is produced biochemistry (biochemistry) Study of by ENZYME reactions in which chemical the chemistry of living organisms. ENERGY is converted to LIGHT. biodegradation (biology) Breakdown biomass (biology) Total MASS of living or DECAY of substances by the ACTION MATTER in a given ENVIRONMENT of living organisms, especially saprophytic or food chain LEVEL. BACTERIA and FUNGI. Through BIODEGRADATION, organic MATTER biometry (biology) Application of is recycled. mathematical and statistical methods bioenergetics (physiology) Study of to the study of living organisms. the transfer and utilization of ENERGY in living systems. bionic (bioengineering) Describing an artificial device or system that has See also ATP. the properties of a living one. bioengineering (biology) Application biophysics (biology) Use of ideas and of engineering science and technology methods of physics in the study of to living systems. living organisms and processes. biofeedback (physiology) Method of biopsy (histology) Small SAMPLE of controlling a bodily process (e.g. CELLS or TISSUE removed from a living HEARTBEAT) that is not normally subject subject for LABORATORY examination to voluntary control by making the person (usually as an aid to diagnosis).

62 BIORHYTHM BLASTULA biorhythm (physiology) One of the bit (computing) An abbreviation of ‘bi’nary CYCLIC pattern of ‘highs’ and ‘lows’ digi’t’; either 1 or 0, the only two digits which some people believe govern each in BINARY NOTATION. Amount of information person’s emotional, physical and that is required to express choice between intellectual BEHAVIOUR (USA: behavior). two possibilities. The term is commonly Most scientists are sceptical because applied to a single DIGIT of BINARY the idea is based on the individual’s NOTATION in a COMPUTER. subjective perceptions of these qualities. See also BYTE. biosynthesis (biology) Formation of the major molecular components of CELLS, biuret test (biochemistry) Test used to e.g. proteins, from simple components. detect peptides and proteins in SOLUTION

by TREATMENT of biuret (NH2CONHCONH2) biotechnology (biotechnology) Utilization with COPPER SULPHATE (USA: copper of living organisms for the production sulfate) and ALKALI to give a purple of useful substances or processes, e.g. COLOUR (USA: color). in FERMENTATION and milk production. bivalent (chemistry) Having a VALENCE biotin (biochemistry) COENZYME that of two. Also termed: DIVALENT. is involved in the transfer of CARBONYL GROUPS in bioCHEMICAL REACTIONS, bkgd (general terminology) An abbrevia- such as the METABOLISM of fats; one tion of ‘b’ac‘kg’roun‘d’. of the B VITAMINS. bladder (anatomy) A membranous sac bisacodyl (pharmacology) A stimulant containing GAS or FLUID, e.g. the GALL laxative administered orally or topically BLADDER and urinary BLADDER. as suppositories to promote defecation and relieve constipation. It can be used See also VESICLE. to evacuate the colon prior to rectal examination or surgery. blastocyst (biology) A stage in the EMBRYOGENESIS of mammals, prior bismuth Bi (chemistry) Silvery-white metallic to IMPLANTATION. It is the first stage ELEMENT in GROUP VA of the PERIODIC at which there is any differentiation TABLE. It is used as a LIQUID METAL among the ball of CELLS. The COOLANT in nuclear reactors and as a BLASTOCYST consists of an outer layer COMPONENT of low-MELTING POINT of protective CELLS (the trophectoderm) LEAD ALLOYS. Its SOLUBLE compounds surrounding a FLUID filled cavity are poisonous; its INSOLUBLE ones are containing the inner CELL MASS that used in medicine. At. no. 83. r.a.m. 208.9806. goes on to develop as the EMBRYO. The human BLASTOCYST is about 0.15 bisulphate (chemistry) An alternative mm in DIAMETER. term for HYDROGENSULPHATE (USA: hydrogensulfate). (USA: bisulfate). blastula (histology) Hollow sphere composed of a single layer of CELLS bisulphite (chemistry) An alternative produced by CLEAVAGE of a fertilized term for HYDROGENSULPHITE (USA: OVUM in animals. hydrogensulfite). (USA: bisulfite).

63 BLEACH BLOOD VESSEL bleach (chemistry) Substance used for blood group (haematology) See ABO removing COLOUR (USA: color) from, BLOOD GROUPS. e.g. cloth, paper and straw. A common BLEACH is a SOLUTION of SODIUM blood plasma (haematology) FLUID part CHLORATE(I) (SODIUM HYPOCHLORITE), of BLOOD in which BLOOD CELLS are NaCIO, although HYDROGEN PEROXIDE, suspended. It contains PLASMA SULPHUR DIOXIDE (USA: sulfur dioxide), PROTEINS, UREA, sugars and salts. CHLORINE, OXYGEN and even sunlight are also used as bleaches. All are blood poisoning (medical/microbiology) OXIDIZING AGENTS. An alternative term for SEPTICAEMIA (USA: septicemia). bleaching powder (chemistry) White powder containing CALCIUM CHLORATE(I) blood pressure (physiology) PRESSURE

(CALCIUM HYPOCHLORITE), Ca(OCI)2, of BLOOD flowing in the arteries. It made by the ACTION of CHLORINE on varies between the higher value of CALCIUM HYDROXIDE (slaked LIME). the systolic PRESSURE (when the When treated with DILUTE ACID it generates HEART’S ventricles are contracting and CHLORINE, which acts as a BLEACH. forcing BLOOD out of the HEART) and the lower value of the diastolic PRESSURE blind spot (biology) AREA on the RETINA (when the HEART is filling with BLOOD). of the VERTEBRATE EYE which, because It is affected by exercise, emotion and it is at the point of entry of the OPTIC various drugs. NERVE, is without LIGHT sensitive CELLS and is thus blind. blood serum (haematology) FLUID part of BLOOD from which all BLOOD CELLS blood (haematology) FLUID in the bodies and FIBRIN have been removed. It of animals that circulates and transports may contain antibodies, and such serums OXYGEN and nutrients to CELLS, and are used as vaccines. carries waste products from them to the organs of EXCRETION. It also blood sugar (biochemistry) The ENERGY- transports HORMONES and the products generating SUGAR GLUCOSE, whose of DIGESTION. Essential for maintaining LEVEL in the BLOOD is controlled by uniform TEMPERATURE in warmblooded the HORMONE INSULIN. animals, BLOOD is made up mainly of ERYTHROCYTES, LEUCOCYTES, blood vascular system (anatomy) platelets, WATER and proteins. System consisting of the HEART, arteries, See also HAEMOCYANIN; HAEMOGLOBIN. veins and capillaries. The HEART acts as a central muscular PUMP which blood cells (haematology) See propels oxygenated BLOOD from the ERYTHROCYTES; leueocytes. lungs along arteries to the tissues; deoxygenated BLOOD is carried along blood clotting (pharmacology) See veins back to the HEART and lungs. HAEMOSTASIS. blood vessel (anatomy) An ARTERY, VEIN, blood count (haematology) A count or CAPILLARY. Many BLOOD VESSELS of the number of red and WHITE BLOOD have muscular walls, whose contraction CELLS and platelets. and relaxation aids BLOOD flow.

64 BLUE VITRIOL BORAX blue vitriol (chemistry) An alternative BOILS is called a carbuncle. Recurrent term for the HYDRATED form of COPPER(II) BOILS may be associated with DIABETES SULPHATE (USA: copper (II) sulfate). MELLITUS. blue-green alga (microbiology) An bond (chemistry) Link between two atoms alternative term for a member of the in a MOLECULE. See CO-ORDINATE CYANOPHYTA. BOND; COVALENT BOND; IONIC BOND.

BLWA (society) An abbreviation of ‘B’ritish bond energy (chemistry) ENERGY ‘L’aboratory ‘W’are ‘A’ssociation. involved in BOND formation.

BM (medical) An abbreviation of ‘B’owel bond length (chemistry) Distance ‘M’ovement. between the nuclei of two atoms that are chemically bonded. BMA (governing body) An abbreviation of ‘B’ritish ‘M’edical ‘A’ssociation. bone (anatomy) The skeletal substance of vertebrates. It consists of CELLS BMJ (literary terminology) An abbreviation called osteocytes distributed in a MATRIX of ‘B’ritish ‘M’edical ‘J’ournal. of COLLAGEN fibres (USA: collagen fibers) impregnated with a complex BMR (physiology) An abbreviation of SALT (BONE SALT), mainly CALCIUM ‘B’asal ‘M’etabolic ‘R’ate. PHOSPHATE, for hardness. CELLS are connected by fine channels that permeate BMS (society) An abbreviation of ‘B’ritish the MATRIX. Larger channels contain ‘M’ycological ‘S’ociety. BLOOD VESSELS and NERVES. Some bones are hollow and contain BONE BNP (physiology/biochemistry) An MARROW. There are about 206 bones abbreviation of ‘B’rain ‘N’atriuretic ‘P’eptide. in an adult human SKELETON. body-centred cube (crystallography) bone marrow (haematology) The soft Crystal structure that is CUBIC, with haematopoietic (USA: hematopoietic) an ATOM at the centre of each cube. TISSUE that has STEM CELLS capable Each ATOM is surrounded by eight of differentiating into ERYTHROCYTES, others. (USA: body-centered cube). LEUCOCYTES (USA: leukocytes) or platelets (THROMBOCYTES). boiling point (b.p.) (physics) TEMPERATURE at which a LIQUID boils freely turning boracic acid (chemistry) An alternative into a VAPOUR; its VAPOUR PRESSURE term for BORIC ACID. then equals the external PRESSURE.

borax (chemistry) Na2B4O7. 10H2O A boils (medical/microbiology) Staphylo- white AMORPHOUS COMPOUND, coccal infections of the HAIR follicles SOLUBLE in WATER, which occurs naturally of the SKIN. A painful red nodule appears as TINCAL. It is used in the manufacture which grows bigger and then breaks of enamels and HEAT-resistant GLASS. down in the middle for pus to appear. Also termed: DISODIUM TETRABORATE; In a few days it usually discharges and SODIUM BORATE. heals. An interconnecting collection of

65 BORIC ACID BRANCHED CHAIN

boric acid (chemistry) H3BO3 White V is inversely proportional to its CRYSTALLINE COMPOUND, SOLUBLE PRESSURE p; i.e. p V=a CONSTANT. in WATER, which occurs naturally in It was named after the Irish chemist volcanic regions of Italy. It has ANTISEPTIC Robert Boyle (1627–91). properties. Also termed: BORACIC ACID. bp (genetics) An abbreviation of ‘b’ase- Bornholm disease (medical/virology) ‘p’air. An INFECTION caused by the Coxsakie VIRUS B, which usually lasts about a brain (anatomy) Principal collection week. There may be FEVER with a of NERVE CELLS that form the headache and sometimes a sore THROAT, ANTERIOR part of the CENTRAL and it may occur in EPIDEMIC form. It NERVOUS SYSTEM, consisting (in gets its name from being first described mammals) of a moist pinkish-grey MASS as occurring on the Danish island Bornholm. protected by the bones of the CRANIUM (SKULL). It receives, mostly via SPINAL boron B (chemistry) AMORPHOUS, NON- NERVES from the SPINAL CORD but metallic ELEMENT in GROUP IIIA of also via CRANIAL NERVES from organs the PERIODIC TABLE. Because of its in the HEAD, sensory information through high NEUTRON ABSORPTION it is used AFFERENTS carrying the output of for control rods in nuclear reactors. SENSE ORGANS and it sends out Important compounds include BORAX instructions along efferents (e.g. motor and BORIC ACID. At. no. 5; r.a.m. 10.81. NERVES) to the EFFECTOR organs (e.g. muscles). It is also the centre borosilicate glass (chemistry) HEAT- (USA: center) of intellect and MEMORY resistant GLASS of low thermal expansion, (so that BEHAVIOUR (USA: behavior) made by adding BORON OXIDE (B2O 3) can be based on past experience), to GLASS during manufacture. and is responsible for the coordination of the whole body. botulism (toxicology/bacteriology) A severe form of FOOD POISONING. An often fatal See also CEREBELLUM; CEREBRUM; disorder caused by eating food contaminated CORTEX. with a TOXIN produced by the BACTERIUM Clostridium botulinum (which is destroyed brain stem (anatomy) Part of the BRAIN by adequate cooking). Botulinus TOXIN at the end of the SPINAL CORD, is one of the most potent poisons known. consisting of the midbrain, MEDULLA OBLONGATA and pons. bowel (anatomy) An alternative term for INTESTINE. brainwave (physiology) Pattern of electrical activity in the BRAIN as revealed by Bowman’s capsule (anatomy) Dense an ELECTROENCEPHALOGRAPH. Alpha ball of CAPILLARY BLOOD VESSELS waves correspond to wakefulness with that cover the closed end of every NEPHRON eyes closed, beta waves to wakefulness in the KIDNEY. From it leads the uriniferous with eyes open and delta waves to deep tubule. It was named after the British sleep. physician William Bowman (1816–92). branched chain (chemistry) Side GROUP(S) Boyle’s law (physics) At CONSTANT attached to the main chain in the MOLECULE TEMPERATURE the VOLUME of a GAS of an ORGANIC COMPOUND.

66 BREASTBONE BROWN RING TEST breastbone (anatomy) An alternative for making black-and-white photographic term for STERNUM. prints and enlargements. breathing (physiology) An alternative bromine Br (chemistry) Dark red LIQUID term for RESPIRATION, but often non-metallic ELEMENT in GROUP VIIA restricted to the physical actions of of the PERIODIC TABLE (the halogens), inhalation and exhalation. extracted from sea-WATER. It has a pungent SMELL. Its compounds are used in bretylium tosylate (pharmacology) An PHOTOGRAPHY and as anti-knock additives ANTISYMPATHETIC class of drug that to petrol. At. no. 35; r.a.m. 79.904. administered by injection, is an ADRENERGIC neurone blocker, preventing bromocriptine (pharmacology) An ergot the release of NORADRENALINE from alkaloid drug that is administered orally sympathetic nerves. It can be used in in patients primarily to treat Parkinsonism, ANTI-ARRHYTHMIC treatment of abnormal but not the parkinsonian symptoms HEART rhythms in resuscitation. caused by certain drug therapies. It acts by stimulating the DOPAMINE BRI (education) An abbreviation of receptors in the BRAIN. It additionally ‘B’iological/‘B’rain ‘R’esearch ‘I’nstitute. inhibits prolactin secretion by the pituitary gland and may be used for a variety Bright’s disease (medical) ACUTE of conditions including delayed puberty NEPHRITIS. Named after the physician, caused by hormonal insufficiency; to Richard Bright (1789–1858). relieve certain menstrual disorders and to reduce or halt lactation in galactorrhoea. brine (chemistry) Concentrated SOLUTION of COMMON SALT (SODIUM CHLORIDE). bronchiole (anatomy) Terminal AIR- conducting tube (1mm in DIAMETER) British thermal unit (BTU) (measurement) of mammalian lungs, arising from Amount of HEAT required to raise the secondary subdivision of a BRONCHUS TEMPERATURE of 1 pound of WATER and terminating in alveoli. through 1°F. 1 BTU=1,055 joules. bronchus (anatomy) One of the two Broca’s area (anatomy) Speech centre AIR-carrying divisions of the TRACHEA (USA: center) of the BRAIN. It was (windpipe) into the lungs. The bronchi named after the French surgeon Paul become inflamed in the disorder bronchitis. Broca (1824–80). brown ring test (chemistry) LABORATORY brom. (chemistry) An abbreviation of test for NITRATES in SOLUTION. An ‘brom’ide. acidic SOLUTION of IRON (II) SULPHATE (USA: iron(II) sulfate) (FERROUS bromide (chemistry) BINARY COMPOUND SULPHATE [USA: ferrous sulfate]) is added containing BROMINE; a SALT of to the suspected NITRATE SOLUTION HYDROBROMIC ACID. in a test-tube, and concentrated SULPHURIC ACID (USA: sulfuric acid) carefully poured bromide paper (photography) LIGHT- down the inside of the tube. A brown sensitive paper coated with an EMULSION ring at the junction of the liquids indicates containing SILVER BROMIDE, used the presence of a NITRATE.

67 BROWNIAN MOVEMENT BUFFER

Brownian movement (physics) Random BSP (society) Abbreviation of ‘B’achelor motion of particles of a SOLID suspended of ‘S’cience in ‘P’harmacy. in a LIQUID or GAS, caused by collisions with molecules of the suspending medium. BSRA (society) Abbreviation of ‘B’ritish It was named after the British botanist ‘S’ociety for ‘R’esearch on ‘A’geing. Robert Brown (1773–1858). Also termed: Brownian motion. BTPS (physics) An abbreviation of ‘B’ody ‘T’emperature and ‘P’ressure, ‘S’aturated brucellosis (medical/bacteriology) An with water vapour (USA: vapor). infectious disease, caused by bacteria of the genus Brucella, and contracted BTX (1 chemistry; 2 toxicology) 1 An by eating infected meat and dairy products abbreviation of ‘b’enzene, ‘t’oluene and or by contact with the secretions of ‘x’ylene. 2 An abbreviation of sheep, goats or cows. Named after ‘B’atracho‘T’o‘X’in. the British pathologist Sir David Bruce (1855–1931). bty (physics) An abbreviation of ‘b’at‘t’er‘y’.

BS (1 education; 2 society; 3 quality bubo (medical) The swelling of a lymphatic standards) 1 An abbreviation of ‘B’achelor GLAND or GROUP of GLANDS, of ‘S’cience/‘S’urgery. 2 An abbreviation particularly in the groin or the armpit. of ‘B’iochemical/ ‘B’iometric/‘B’iological ‘S’ociety. 3 An abbreviation of ‘B’ritish buccal (anatomy) Pertaining to the ‘S’tandard. cheek and mouth.

BSAVA (society) An abbreviation of buccal cavity (anatomy) Mouth cavity ‘B’ritish ‘S’mall ‘A’nimals ‘V’eterinary in front of the opening of the PHARYNX, ‘A’ssociation. where in mammals food is usually chewed and subjected to the initial stages of BSc (education) An abbreviation of DIGESTION. ‘B’achelor of ‘Sc’ience. budding (biology) Method of ASEXUAL bsc (general terminology) An abbreviation REPRODUCTION employed by yeasts of ‘b’a‘s’i‘c’. and simple ANIMAL organisms.

BSCC (society) An abbreviation of ‘B’ritish budesonide (pharmacology) A cortico- ‘S’ociety for ‘C’linical ‘C’ytology. steroid drug with ant-inflammatory, ant- allergic and ANTI-ASTHMATIC properties. BSCP (quality standards) Abbreviation It may be administered by inhalation of ‘B’ritish ‘S’tandard ‘C’ode of ‘P’ractice. to prevent attacks of asthma and rhinitis and topically to treat severe inflammatory BSI (quality standards) An abbreviation skin disorders such as psoriasis and of ‘B’ritish ‘S’tandards ‘I’nstitution. eczema.

BSIRA (society) An abbreviation of buffer (1 chemistry; 2 computing) 1 A ‘B’ritish ‘S’cientific ‘I’nstrument ‘R’esearch SOLUTION that resists changes in PH ‘A’ssociation. on DILUTION or on the addition of

68 BUFFY COAT BUTANOL

ACID or ALKALI. 2 A temporary store West Africa. It appears to be triggered for DATA in transit between the CENTRAL by a VIRUS INFECTION and is one of PROCESSOR and an OUTPUT DEVICE. the commonest cancers found in people with AIDS. Named after the surgeon, buffy coat (haematology) Layer of WHITE Denis Parsons Burkitt (1911–93). BLOOD CELLS and platelets above RED BLOOD CELL MASS when BLOOD Bursa (anatomy) A closed sac lined is sedimented. with SYNOVIAL MEMBRANE containing FLUID placed where there may be friction bug (1 parasitology; 2 computing) 1 between structures such as tendons BLOOD-sucking insect of the ORDER and bones so that they can move easily Hemiptera. 2 Error in a COMPUTER over each other. Sometimes they become PROGRAM or a fault in HARDWARE. inflamed, as the result of either injury or INFECTION, a condition called bursitis. bumetanide (pharmacology) A powerful DIURETIC drug which can be Bursa of fabricius (immunology) administered orally or by injection and Lymphoid ORGAN which processes B- is used to treat OEDEMA (USA: edema), LYMPHOCYTES. particularly pulmonary OEDEMA. It is one of the class of LOOP DIURETICS. bus (computing) A pathway connecting the components of a COMPUTER, usually BUN (biochemistry/haematology) An shared by several components. abbreviation of ‘B’lood ‘U’rea ‘N’itrogen. bushel (measurement) UNIT for Bunsen burner (laboratory equipment) measuring dry goods by VOLUME, equal GAS burner that efficiently mixes AIR to 4 pecks and equivalent to 8 gallons with the fuel GAS, commonly used for or 36.369 LITRES (in Britain) or 35.238 heating in laboratories. It was named LITRES (United States). after the German chemist Robert Bunsen (1811–99). buspirone hydrochloride (pharmacology) An antiolytic drug which is used for bupivacaine hydrochloride (pharmacology) short-term treatment of anxiety. It is A local anaesthetic drug administered administered orally and acts by stimulating by injection that has a long duration of SEROTONIN receptors in the BRAIN. action. It is an amide and chemically related to lignocaine hydrochloride. butane (chemistry) C4H 10 Gaseous ALKANE, used as a portable supply burette (laboratory equipment) A long of fuel. vertical graduated GLASS tube with a tap, used for the addition of controlled butanedioic acid (chemistry) An and measurable volumes of liquids (e.g. alternative term for SUCCINIC ACID. in making titrations in VOLUMETRIC

ANALYSIS). butanol (chemistry) C4H9OH Colourless (USA: colorless) LIQUID ALCOHOL that Burkitts lymphoma (medical/histology) exists in four isomeric forms. Also termed: A TUMOUR (USA: tumor) of the LYMPH BUTYL ALCOHOL. GLANDS, common in some parts of

69 BUTYL ALCOHOL BYTE butyl alcohol (chemistry) An alternative term for BUTANOL.

BV (haematolgy) An abbreviation of ‘B’lood ‘V’olume.

BVA (society) An abbreviation of ‘B’ritish ‘V’eterinary ‘A’ssociation. bw (1 microbiology; 2 medical) An abbreviation of ‘b’iological ‘w’arfare. 2 An abbreviation of ‘b’irth‘w’eight. bwd (general terminology) An abbreviation of ‘b’ack‘w’ar‘d’. by-product (biotechnology) Incidental or secondary PRODUCT of manufacture. byte (computing) A number of binary digits that FUNCTION as a UNIT, e.g. in the store of a COMPUTER. The term is sometimes limited to a UNIT consisting of eight binary digits.

70 C

C (1 chemistry; 2 measurement) 1 Its compounds are used as yellow or CHEMICAL SYMBOL for CARBON. 2 red pigments. At. no. 48; r.a.m. 112.40. An abbreviation of ‘C’elsius. cADPR (physiology/biochemistry) An

C H20 (physiology) A water ‘C’learance. abbreviation of ‘c’yclic ‘A’denosine symbol for Free ‘D’is‘P’hosphate ‘R’ibose.

CA (1 medical; 2, 3 biochemistry) An caecum (anatomy) Pouch or pocket, abbreviation for 1 ‘C’hronological ‘A’ge. such as one at the junction of the 2 An abbreviation for ‘ca’techolamine. small and LARGE INTESTINES from 3 An abbreviation of ‘C’ellulose ‘A’cetate. which hangs the APPENDIX.

Ca (chemistry) The CHEMICAL SYMBOL caesium Cs (chemistry) Soft reactive metallic for CALCIUM. ELEMENT in GROUP IA of the PERIODIC TABLE (the ALKALI METALS), 3 major ca. (1 physics; 2 Literature terminology) FISSION PRODUCT of URANIUM. It is used 1 An abbreviation of ‘ca’thode. 2 An in PHOTOELECTRIC CELLS. The ISOTOPE abbreviation of ‘c’irc‘a’. [Latin, meaning CAESIUM-137 is used in RADIOTHERAPY. about]. At. no. 55; r.a.m. 132.9055. (USA: cesium) cabergoline (pharmacology) An caesium clock (physics) Atomic clock antiparkinsonism drug that is adminis- used in the si UNIT definition of the tered orally with similar properties to second. (USA: cesium clock). BROMOCRIPTINE. CAF (medical) An abbreviation of ‘C’ardiac CAD (medical) An abbreviation of ‘A’ssessment ‘F’actor. ‘C’oronary ‘A’rtery ‘D’isease. caffeine (pharmacology) White ALKALOID cad (medical) An abbreviation of ‘cad’aver. with a bitter TASTE, obtained from coffee Also termed cadav. beans, tea leaves, kola nuts, or by chemical SYNTHESIS. It is a diuretic and a stimulant CADE (computing) An abbreviation of to the CENTRAL NERVOUS SYSTEM. ‘C’omputer ‘A’ssisted ‘D’ata ‘E’valua- tion. cal (measurement) An abbreviation of ‘cal’orie (small). cadmium Cd (chemistry) Silvery-white metallic ELEMENT in GROUP IIB of Cal (measurement) An abbreviation the PERIODIC TABLE. It is used in control of ‘Cal’orie. rods for nuclear reactors and as a corrosion- resistant electroplating on steel articles. calamine (chemistry) ZINC ore whose main constituent is ZINC OXIDE.

71 CALCIFEROL CALEANCUS

calciferol (biochemistry) Fat-SOLUBLE calcium hydroxide (chemistry) Ca(OH)2 VITAMIN formed in the SKIN by the White CRYSTALLINE powder which gives ACTION of sunlight, which controls an ALKALINE AQUEOUS SOLUTION levels of CALCIUM in the BLOOD. Also known as limewater, used as a test termed: VITAMIN D. for CARBON DIOXIDE (which turns it cloudy). Also termed: CALCIUM calcification (histology) Depositing of HYDRATE; HYDRATED LIME; CAUSTIC CALCIUM salts in body TISSUE, a LIME; slaked LIME. NORMAL process in the formation of bones and TEETH but ABNORMAL in calcium oxide (chemistry) CaO White the formation of calculi (‘stones’). CRYSTALLINE powder made commercially by roasting limestone (CALCIUM See also CARTILAGE. CARBONATE). It is used to make CALCIUM HYDROXIDE. Also termed: LIME, QUICKLIME. calcitonin (biochemistry) HORMONE secreted in vertebrates that controls calcium phosphate (chemistry) Ca3(PO4)2 the release of CALCIUM from BONE. White CRYSTALLINE SOLID which makes In mammals it is secreted by the THYROID up the mineral COMPONENT of bones GLAND. Also termed: thyrocalcitonin. and TEETH, and occurs as the mineral APATITE. It is produced commercially as calcium Ca (chemistry) SILVER-white BONE ash and BASIC slag. Treated with metallic ELEMENT in GROUP IIA of the SULPHURICACID (USA: sulfuric acid) it PERIODIC TABLE (the ALKALINE EARTH). forms the fertilizer known as superphosphate. The fifth most abundant ELEMENT on the EARTH, it occurs mainly in CALCIUM calcium sulphate (chemistry) CaSO4 CARBONATE minerals; it also occurs in White CRYSTALLINE COMPOUND which bones and TEETH. At. no. 20; r.a.m. occurs as the minerals ANHYDRITE and 40.08. (as the DIHYDRATE) GYPSUM, used to make PLASTER OF PARIS. It is the calcium carbonate (chemistry) CaCO3 cause of permanent HARDNESS OF White powder or colourless (USA: WATER. It is used in making ceramics, colorless) crystals, the main constituent paint, paper and SULPHURIC ACID (USA: of CHALK, limestone and marble. sulfuric acid), and is the substance in blackboard CHALK. (USA: calcium sulfate). calcium chloride (chemistry) CaCI2 White CRYSTALLINE COMPOUND, which forms calculus (1 mathematics; 2 medical/ several hydrates, used to control dust, biochemistry) AREA of mathematics as a de-icing agent and as a REFRIGERANT. that deals with INTEGRATION and The ANHYDROUS SALT is DELIQUESCENT differentiation. 2 Hard accretion (a ‘stone’) and is employed as a DESICCANT. of CALCIUM salts and other compounds that forms in the kidneys and urinary calcium hydrogencarbonate (chemistry) tract, GALL BLADDER, BILE DUCTS CaHCO3 White CRYSTALLINE COMPOUND, or salivary GLANDS. STABLE only in SOLUTION and the cause of temporary HARDNESS OF WATER. caleancus (anatomy) Heel-bone; the Also termed: CALCIUM BICARBONATE. major BONE of the foot. Also termed: calcaneum.

72 CALIBRATION CANDELA calibration (1, 2 measurements) 1 food (when it is sometimes spelled with Measuring scale on a scientific instrument a small c). Also termed: KILOCALORIE; or apparatus. 2 Method of putting a large CALORIE. scale on a scientific instrument, usually by checking it against fixed quantities See also CALORIE. or standards. calorific value (physics) Quantity of californium Cf (chemistry) RADIOACTIVE HEAT liberated on the complete ELEMENT in GROUP IIIB of the PERIODIC COMBUSTION of a UNIT WEIGHT or TABLE (one of the ACTINIDES), produced UNIT VOLUME of fuel. by alpha-PARTICLE bombardment of CURIUM-242; it has several isotopes, calorimeter (physics/chemistry) Apparatus with half-lives of up to 800 years. At. for measuring HEAT quantities generated no. 98; r.a.m. 251 (most STABLE ISOTOPE). in or evolved by materials in processes such as CHEMICAL REACTIONS, changes calliper (1 equipment; 2 medical) 1 of state and SALVATION. The technique Measuring instrument that resembles a is known as calorimetry. large pair of geometrical dividers; there are internal and external versions. 2 METAL CAM (physiology/biochemistry) An brace that supports an injured or paralysed abbreviation of ‘C’ell ‘A’dhesion ‘M’olecule. leg, keeping the leg rigid and helping to support the WEIGHT of the body. CaMKII (physiology/biochemistry) Abbreviation of ‘Ca’ 2+/cal‘M’odulin- calomel (chemistry) An alternative term dependent ‘K’inase II. for MERCURY(I) CHLORIDE. cAMP (biochemistry) An abbreviation calomel half-cell (physics) An of ‘c’yclic ‘A’denosine ‘M’ono‘P’hosphate. eLECTRODE consisting of MERCURY, MERCURY(I) CHLORIDE and POTASSIUM camphor (chemistry) Naturally-occurring CHLORIDE SOLUTION, employed as ORGANIC COMPOUND with a penetrating a reference ELECTRODE because it aromatic odour (USA: odor). Also termed: has a known CONSTANT POTENTIAL. gum CAMPHOR; 2-camphanone. Also termed: CALOMEL ELECTRODE; CALOMEL reference ELECTRODE. cancer (medical/histology) Disorder that results when body CELLS undergo calorie (measurement) Amount of HEAT unrestrained DIVISION, because of a required to raise the TEMPERATURE of breakdown in the NORMAL control of I g of WATER by 1°C at one ATMOSPHERE cellular processes, to form a MALIGNANT PRESSURE; equal to 4.184 joules. TUMOUR (USA: malignant tumor). CANCER may spread by METASTASIS, See also CALORIE. when TUMOUR CELLS (USA: tumor cells) leave their original position and Calorie (measurement) Amount of HEAT invade other tissues. required to raise the TEMPERATURE of I kg of WATER by 1°C at one ATMOSPHERE candela (cd) (measurement) SI UNIT PRESSURE; equal to 4.184 kilojoules. of LUMINOUS INTENSITY. It is used as an UNIT of ENERGY of

73 C AND G CARBAMAZEPINE

C and G (education) An abbreviation causes low-DENSITY liquids to flow along of ‘C’ity and ‘G’uilds. narrow (CAPILLARY) tubes or soak into porous materials. Also termed: CAPILLARY candle power (cp) (measurement) LUMI- ACTION. NOUS INTENSITY expressed in candelas (formerly in INTERNATIONAL CANDLES). capillary (1 physics; 2 anatomy) 1 Any narrow tube, in which CAPILLARITY cane-sugar (chemistry) An alternative can occur. 2 Finest VESSEL of the BLOOD term for SUCROSE. VASCULAR SYSTEM in vertebrates. Large numbers of capillaries are present in canine tooth (anatomy) Pointed TOOTH tissues. Their walls are composed of a in most mammals, adapted for stabbing single layer of CELLS through which and tearing food. There are two canines exchange of substances, e.g. OXYGEN, in each JAW. Also termed: EYE-TOOTH. occurs between the tissues and BLOOD.

Cannizzaro reaction (chemistry) The caprylic acid (chemistry) An alternative formation of an ALCOHOL and an ACID term for OCTANOIC ACID. SALT by the REACTION between certain ALDEHYDES and strong ALKALIS (USA: capsule (1 bacteriology; 2 anatomy) alkalies). The REACTION was named 1 In certain BACTERIA, a gelatinous after the Italian chemist Stanislao EXTRACELLULAR ENVELOPE, which Cannizzaro (1826–1910). in some cases confers protective properties on the CELL. 2 Sheath of canonical form (chemistry) See MESOMER- MEMBRANE that surrounds an ORGAN ISM. or AREA of TISSUE; e.g. the synovial CAPSULE that surrounds the moving cap. (general terminology) An abbreviation parts of joints. of ‘cap’acity. captopril (pharmacology) A powerful capacitance (physics) Ratio of the ACE inhibitor which is administered orally CHARGE on one of the conductors of and used as an ANTIHYPERTENSIVE a CAPACITOR (there being an equal and in HEART FAILURE treatment. and an opposite CHARGE on the other CONDUCTOR) to the POTENTIAL carbachol (pharmacology) A parasympa- DIFFERENCE between them. The SI thomimetic drug which is administered UNIT of CAPACITANCE is the farad. orally, by injection, or through eye drops in the treatment of glaucoma to lower capacitor (physics) Device that can store pressure in the eyeball, and which is CHARGE and introduces CAPACITANCE also used to treat urinary retention. into an electrical CIRCUIT. Also termed: CONDENSER; ELECTRICAL CONDENSER. carbamazepine (pharmacology) An ANTICONVULSANT and ANTI-EPILEPTIC capacity (general terminology) The drug with is administered orally or by amount necessary to fill a container suppositories. It is used to prevent most or VESSEL. forms of epilepsy, to relieve the pain of trieminal neuralgia, in the management capillarity (physics) A phenomenon of manic-depressive illnesses and in resulting from SURFACE TENSION that the treatment of diabetes insipidus.

74 CARBAMIDE CARBONATE carbamide (chemistry) An alternative ALLOTROPES (including diamond and term for UREA. graphite). It occurs in all living things and its compounds are the basis of ORGANIC carbanion (chemistry) Transient CHEMISTRY. It is the principal ELEMENT negatively charged organic ION that in coal and petroleum. Its nonORGANIC has one more ELECTRON than the COMPOUNDS include the oxides CARBON corresponding FREE RADICAL. MONOXIDE (CO) and CARBON DIOXIDE

(CO2), carbides and carbonates. CARBON carbene (chemistry) Organic RADICAL is used for making electrodes, brushes that contains DIVALENT CARBON. for ELECTRIC MOTORS, CARBON fibres (USA: carbon fibers) and in steel. Diamonds carbimazole (pharmacology) A drug that are used as gemstones and industrially acts as an indirect HORMONE ANTAGONIST, as abrasives. Its ISOTOPE CARBON- by inhibiting the production of the THYROID 14 is the basis of radiocarbon dating. HORMONES by the THYROID gland. It See BETA DECAY. At. no. 6; r.a.m. 12.001. is thus administered orally in cases of thyrotoxicosis to reduce the excess of carbon dioxide CO2 (chemistry) Colourless THYROID HORMONES in the blood. (USA: colorless) GAS formed by the COMBUSTION of CARBON and its carbocyclic (chemistry) Describing a ORGANIC COMPOUNDS, by the ACTION CYCLIC ORGANIC COMPOUND of acids on carbonates, and as a PRODUCT consisting of aromatic rings containing of FERMENTATION and RESPIRATION. only CARBON and HYDROGEN atoms. It is a raw material of PHOTOSYNTHESIS. Also termed: HOMOCYCLIC. It is used in fire extinguishers, in fizzy (carbonated) drinks, as a COOLANT in nuclear reactors and, as SOLID CARBON carbohydrate (chemistry) COMPOUND DIOXIDE (DRY ICE), as a REFRIGERANT. of CARBON; HYDROGEN and OXYGEN The accumulation of CARBON DIOXIDE that contains a SACCHAROSE GROUP in the ATMOSPHERE creates the or its first REACTION PRODUCT, and greenhouse effect. in which the ratio of HYDROGEN to OXYGEN is 2:1 (the same as in WATER). CELLULOSE, carbon disulphide (chemistry) CS STARCH and all sugars are common 2 LIQUID chemical, used as a SOLVENT carbohydrates. Digestible carbohydrates for oils, fats and rubber and in paint- in the diet are a good source of ENERGY. removers. (USA: carbon disulfide). carbolic acid (chemistry) An alternative carbon monoxide (chemistry) CO Colourless term for PHENOL. (USA: colorless) odourless (USA: odorless) poisonous GAS produced by the incomplete carbon black (chemistry) Finely divided COMBUSTION of CARBON or its form of CARBON obtained by the compounds. It is used in the chemical incomplete COMBUSTION or thermal industry as a REDUCING AGENT. DECOMPOSITION of natural GAS or petroleum oil. carbon tetrachloride (chemistry) An alternative term for TETRACHLOROMETHANE. carbon C (chemistry) Non-metallic ELEMENT in GROUP IVA of the PERIODIC carbonate (chemistry) SALT of CARBONIC 2- TABLE which exists as several ACID (H2CO3), containing the ION CO3 .

75 CARBONATION CARDIAC GLYCOSIDES

Carbonates commonly occur as minerals childbirth, which is caused by tonal loss (e.g. CALCIUM CARBONATE) and are in the muscles of the uterus. It is an readily decomposed by acids to produce analogue of prostaglandin which is a CARBON DIOXIDE. local HORMONE naturally involved in controlling the muscles of the uterus. See also HYDROGENCARBONATE. carboxyl group (chemistry) The organic carbonation (chemistry) Addition of CARBON GROUP -COOH, CHARACTERISTIC of DIOXIDE under PRESSURE to a LIQUID. CARBOXYLIC ACIDS. Also termed: carboxy GROUP, OXATYL GROUP. carbonic acid (chemistry) H2CO3 ACID formed by the COMBINATION of CARBON carboxylic acid (chemistry) ORGANIC ACID DIOXIDE and WATER. Its salts are that contains the CARBOXYL GROUP, - carbonates. COOH (e.g. acetic (ethanoic) ACID, CH3COOH). carbonic anhydrase inhibitors (pharma- carbylamine (chemistry) An alternative cology) Drugs that have enzyme-inhibitor term for ISOCYANIDE. actions against the enzyme carbonic anhydrase, which is distributed widely carcinogen (toxicology) A substance throughout the body and that has a capable of inducing a CANCER. Most fundamental role in controlling the acid- CARCINOGENS are also mutagens, and base balance (pH). Some are used as this is thought to be their principal mode weak DIURETICS such as acetazolamide, of action. which is useful in reducing fluid in the anterior of the eye in treatment of carcinogenesis (medical) The causation glaucoma. of cancer. carbonium ion (chemistry) Positively carcinogenic (toxicology) Causing cancer charged fragment that arises from the or capable of causing cancer. HETEROLYTIC FISSION of a COVALENT BOND involving CARBON. carcinoma (medical/histology) CANCER in epithelial TISSUE. carbonyl chloride (chemistry) An alternative term for PHOSGENE. card punch (computing) Machine for punching coded sets of holes in punched carbonyl compound (chemistry) Chemical cards, to be fed through a CARD READER containing the RADICAL CO (CARBONYL for inputting DATA into a COMPUTER. GROUP), formed when CARBON MONOXIDE combines with a METAL card reader (computing) COMPUTER INPUT

(e.g. NICKEL carbonyl, Ni(CO)4). DEVICE that reads DATA off punched cards. carbonyl group (chemistry) The GROUP cardiac (anatomy) Relating to the HEART. =CO. See CARBONYL COMPOUND. cardiac glycosides (pharmacology) A carboprost (pharmacology) A drug which class of drugs derived from the leaf of may be administered by injection to treat the Digitalis foxgloves, which includes haemorrhage (USA: hemorrhage) following DIGOXIN and DIGITOXIN. These drugs

76 CARDIAC MUSCLE CARTILAGE increase the force of contraction of the carotid artery (anatomy) Either of two HEART and so have been used for their main arteries that carry BLOOD from cardiac stimulant actions to increase the HEART to the HEAD. the force in treatment of congestive HEART FAILURE. carotid body (physiology) RECEPTOR located between the internal and external cardiac muscle (anatomy) Specialized carotid arteries. It is sensitive to changes STRIATED MUSCLE, found only in the in the CARBON DIOXIDE and OXYGEN HEART, that continually contracts rhythmically content of the BLOOD, and sends impulses and automatically (i.e. it is myogenic). to the respiratory and BLOOD-vascular centres (USA: centers) in the BRAIN See also CARDIAC MUSCLE. to adjust these levels if necessary. cardinal number (mathematics) Number carpal (anatomy) BONE in the foot of elements in a SET (e.g. all sets with and wrist of tetrapods. There are 10– 5 elements have the CARDINAL NUMBER 12 carpals in most animals; in human 5); in everyday terms, an ordinary counting beings there are eight. number. carpus (anatomy) The wrist, consisting See also ORDINAL NUMBER. of eight bones in human beings. cardiogram (physiology) An alternative carrier (1 EPIDEMIOLOGY; 2 medical) term for an ELECTROCARDIOGRAM. 1 Somebody who carries pathogens (e.g. BACTERIA, VIRUSES) and can cardiovascular system (anatomy) HEART pass them on to others, although not and the NETWORK of BLOOD VESSELS necessarily themselves having symptoms that circulate BLOOD around the body. of the disease. 2 VECTOR (in medicine).

Caro’s acid (chemistry) An alternative See also COENZYME. term for peroxomonosulphuric(VI) ACID

(USA: peroxomonosulfuric acid), H2SO5 Cartesian co-ordinates (mathematics) (perSULPHURIC ACID [USA: persulfuric System for locating a point, P, by specifying acid]). its distance from axes at rightangles, which intersect at a point, O, called carotene (biochemistry) PIGMENT that the ORIGIN. For a point on a plane, belongs to the carotenoids, a PRECURSOR the distance from the horizontal or X- of RETINOL (VITAMIN A). AXIS is called the ORDINATE of P; the distance from the Y-AXIS is called carotenoid (biology/chemistry) Member the ABSCISSA. The point’s CARTESIAN of a GROUP of pigments found in e.g. CO-ORDINATES are (x, y). They were carrots, which can absorb LIGHT during named after the French mathematician PHOTOSYNTHESIS. They also aid in Rene Descartes (1596–1650). the protection of prokaryotes from damage by LIGHT. cartilage (anatomy) In animals that have a bony SKELETON, pre-BONE TISSUE See also CAROTENE. occurring in young animals that becomes

77 CARVEDILOL CAUSTIC LIME hard through CALCIFICATION. It also occurs and HORMONES (e.g. ADRENALINE in some parts of the SKELETON of adults, [USA: epinephrine]). where it is structural (e.g. forming EAR flaps and the LARYNX) or provides a cathode (physics) Negatively-charged cushioning or lubricating effect during ELECTRODE in an ELECTROLYTIC movement (e.g. intervertebral discs, CELL or BATTERY. CARTILAGE at the ends of bones in joints). In some animals, e.g. sharks, rays and cathode rays (physics) Stream of related fish (Chondrichthyes), the whole electrons produced by the CATHODE SKELETON is composed of CARTILAGE (negative ELECTRODE) of an evacuated even in the adult. Also termed: gristle. DISCHARGE tube (such as a CATHODE- RAY TUBE). carvedilol (pharmacology) A BETA- BLOCKER drug which can be administered cathode-ray oscilloscope (CRO) orally as an ANTIHYPERTENSIVE. (physics) Apparatus based on a CATHODE-RAY TUBE which provides casein (biochemistry) PROTEIN that a visible IMAGE of one or more rapidly occurs in milk which serves to store varying electrical signals. AMINO ACIDS as nutrients for the young of mammals. cathode-ray tube (physics) VACUUM tube that allows the direct observation CAT (radiology) An abbreviation of of the BEHAVIOUR (USA: behavior) of ‘C’omputerised ‘A’xial ‘T’omography. CATHODE RAYS. It is used as the picture tube in television receivers, radar displays, catabolism (biochemistry) The part of visual DISPLAY units (VDUs) of computers METABOLISM concerned with the and in CATHODE-RAY OSCILLOSCOPES. breakdown of complex ORGANIC COMPOUNDS into simple molecules for cation (chemistry) Positively charged the release of ENERGY in living organisms. ION, which travels towards the CATHODE during ELECTROLYSIS. See also ANABOLISM. cauda equina (anatomy) Sheaf of NERVE catalysis (chemistry) The ACTION of roots that arise from the lower end of a CATALYST. the SPINAL CORD and serve the lower parts of the body. catalyst (chemistry) Substance that increases the rate of a CHEMICAL caudal vertebra (anatomy) One of the REACTION without itself undergoing any SET of vertebrae nearest to the BASE permanent chemical change. Some reactions of the SPINAL COLUMN. take place so slowly without a CATALYST that they are rendered virtually impossible. caustic (chemistry) Describing ALKALINE substances that are corrosive towards See also ENZYME. organic MATTER. catecholamine (biochemistry) Member caustic lime (chemistry) An alternative of a GROUP of amines that include term for CALCIUM HYDROXIDE. NEUROTRANSMITTERS (e.g. DOPAMINE)

78 CAUSTIC POTASH CDR caustic potash (chemistry) An alternative cckw (general terminology) An term for POTASSIUM HYDROXIDE. abbreviation of ‘c’ounter‘c’loc‘k’‘w’ise. Also termed ccw. caustic soda (chemistry) An alternative term for SODIUM HYDROXIDE. c cm (measurement) An abbreviation of ‘c’ubic ‘c’enti‘m’etre (USA: CUBIC CBC (haematology) An abbreviation centimeter). Also termed cc or millilitre of ‘C’omplete ‘B’lood and differential (USA: milliliter). ‘C’ount. CCRU (education) An abbreviation of CBF (physiology) An abbreviation of ‘C’ommon ‘C’old ‘R’esearch ‘U’nit. ‘C’erebral ‘B’lood ‘F’low. cc sec (measurement) An abbreviation CBG (physiology/biochemistry) An of ‘c’ubic ‘c’entimetres per ‘sec’ond abbreviation of ‘C’orticosteroid-‘B’inding (USA: CUBIC centimeters per second). ‘G’lobulin. CCU (medical) An abbreviation of C Biol. (education) An abbreviation ‘C’oronary ‘C’are ‘U’nit. of ‘C’hartered ‘Biol’ogist. CD (1 haematology; 2 medical) 1 An CBR (statistics) An abbreviation of ‘C’rude abbreviation of ‘C’luster ‘D’ifferentiating ‘B’irth ‘R’ate. type antigens. 2 An abbreviation of ‘C’aesarean ‘D’elivery. CBS (society) An abbreviation of ‘C’anadian ‘B’iochemical ‘S’ociety. Cd (chemistry) CHEMICAL SYMBOL for CADMIUM. CBW (general terminology) chemical and biological warfare. cd (measurement) An abbreviation of ‘c’an‘d’ela. cc (measurement) See c cm. CD4 (immunology) A CELL surface CCD (physics) An abbreviation of ‘c’harge- PROTEIN, usually on helper T- ‘c’oupled ‘d’evice. LYMPHOCYTES, that recognizes foreign antigens on ANTIGEN-presenting CELLS. CCE (chemistry) An abbreviation of ‘C’arbon-‘C’hloroform ‘E’xtract. CDC (governing body) An abbreviation of ‘C’enters for ‘D’isease ‘C’ontrol and CCF (medical) An abbreviation of ‘C’hronic Prevention. ‘C’ardiac ‘F’ailure. CDNA (genetics) An abbreviation of cc hr (measurement) An abbreviation ‘C’omplementary ‘D’eoxyribo‘N’ucleic of ‘c’ubic ‘c’entimetres per ‘h’ou‘r’(USA: ‘A’cid. CUBIC centimeters per hour). CDR (statistics) An abbreviation of CCK-PZ (physiology/biochemistry) An ‘C’rude ‘D’eath ‘R’ate. abbreviation of ‘C’hole‘C’ysto‘K’inin- ‘P’ancreo‘Z’ymin.

79 CE CENTRE OF CURVATURE

CE (1 chemistry; 2 statistics) An cellulose (biology) Major POLYSACCHARIDE abbreviation of ‘C’arbon ‘E’quivalent. of plants found in CELL walls and in some 2 An abbreviation of ‘C’onstant ‘E’rror. ALGAe and FUNGI. It is composed of GLUCOSE units aligned in long parallel Ce (chemistry) CHEMICAL SYMBOL chains, and gives CELL walls their strength for CERIUM. and rigidity. cell (biology) Fundamental UNIT of living Celsius scale (measurement) TEMPERATURE organisms. It consists of a MEMBRANE SCALE on which the FREEZING POINT bound compartment, often microscopic of WATER is 0°C and the BOILING POINT in size, containing PROTOPLASM. Although is 100°C. It is the same as the formerly a CELL is not independent of its used CENTIGRADE SCALE, and a ENVIRONMENT, all bioCHEMICAL DEGREE Celsius is equal to a UNIT on REACTIONS of METABOLISM necessary the KELVIN scale. To convert a Celsius for life (within a favourable ECOLOGICAL TEMPERATURE to KELVIN add 273.15 NICHE) are located either within the (and omit the DEGREE sign). To convert PROTOPLASM, within or associated with a Celsius TEMPERATURE to a Fahrenheit the CELL MEMBRANE, or within the one, multiply by 9/5 and add 32. It was local ENVIRONMENT surrounding the named after the Swedish astronomer CELL (which may be modified by secretory Anders Celsius (1701–44). substances). In all CELLS the NUCLEUS contains NUCLEIC ACIDS (e.g. DNA) cent. (measurement) An abbreviation essential for the SYNTHESIS of new of ‘cent’igrade. proteins. CELLS may be highly specialized for their particular FUNCTION and grouped centigrade scale (measurement) Former into tissues, e.g. MUSCLE CELLS. name for the CELSIUS SCALE. cell body (cytology) Part of a NERVE central nervous system (CNS) (anatomy) CELL that contains the CELL NUCLEUS The CONCENTRATION of nervous and other CELL components from which TISSUE responsible for co-ordination an AXON extends. of the body. In vertebrates it is highly cell differentiation (cytology) Way in developed to form the BRAIN and SPINAL which previously undifferentiated CELLS CORD. The CNS processes information change structurally and take on from the SENSE ORGANS and effects specialized roles during GROWTH and a RESPONSE, e.g. MUSCLE movement. development (e.g. becoming LIVER CELLS or BONE CELLS). central processor (computing) HEART of a DIGITAL COMPUTER which controls cell division (cytology) Splitting of CELLS and coordinates all the other activities in two by DIVISION of the NUCLEUS of the machine, and performs logical (MITOSIS) and DIVISION of the CYTOPLASM processes on DATA loaded into it after duplication of the CELL contents. according to PROGRAM instructions it holds. See also MEIOSIS. centre of curvature (optics) Geometric cell membrane (cytology) See PLASMA centre of a spherical mirror. (USA: center MEMBRANE. of curvature).

80 CENTRE OF MASS CERVICAL VERTEBRA centre of mass (physics) Point at which cerebral hemisphere (anatomy) Paired the whole MASS of an OBJECT may expansions of the ANTERIOR end of be considered to be concentrated. Also the FOREBRAIN. The FOREBRAIN is termed: centre of gravity (USA: center enormously enlarged by these expansions. of gravity). (USA: center of mass). cerebrospinal fluid (CSF) (anatomy) centrifugal force (physics) Outward FORCE LIQUID that fills the cavities of the on any OBJECT moving in a circular path. BRAIN, which are continuous with each other and the central canal of the SPINAL See also CENTRIPETAL FORCE. CORD. The FLUID nourishes and removes secretions from the tissues of the centrifuge (laboratory equipment) Instru- CENTRAL NERVOUS SYSTEM (CNS). ment used for the separation of substances by SEDIMENTATION through rotation cerebrum (anatomy) Part of FOREBRAIN at high speeds, e.g. the separation of which expands to form the CEREBRAL components of CELLS. SEDIMENTATION HEMISPHERES. varies according to the size of the COMPONENT. Cerenkov counter (radiology) Method of measuring RADIOACTIVITY by utilizing centriole (cytology) Cylindrical body the effect of CERENKOV RADIATION. present in the MICROTUBULE organizing centre (USA: center) of most ANIMAL Cerenkov radiation (radiology) LIGHT CELLS. During MITOSIS it forms the emitted when charged particles pass poles of the spindle. through a TRANSPARENT medium at a velocity which is greater than that centripetal force (physics) FORCE, directed of LIGHT in the medium. It was named towards the centre (USA: center), that after the Soviet physicist Pavel Cerenkov causes a body to move in a circular (1904–90). path. For an OBJECT of MASS m moving with a speed v in a curve of RADIUS OF cerium Ce (chemistry) Steel-grey metallic CURVATURE r, it is equal to mv2/r. ELEMENT in GROUP IIIB of the PERIODIC TABLE (one of the LANTHANIDES). It centromere (genetics) Region on a is used in lighter flints, catalytic converters CHROMOSOME that attaches to the for car exhausts and GAS mantles. At. spindle during CELL DIVISION. no. 58; r.a.m.140.12. cerebellum (anatomy) Front part of cerumen (biochemistry) WAX that forms hindbrain. It is important in BALANCE in the EAR. and muscular co-ordination. cervical (anatomy) Relating to the neck cerebral cortex (anatomy) Outer region or to the CERVIX of the womb. of the CEREBRAL HEMISPHERES of the BRAIN that contains densely packed cervical vertebra (anatomy) VERTEBRA NERVE CELLS which are interconnected in the neck region of the SPINAL COLUMN, in a complex manner. concerned with movements of the HEAD.

81 CERVIX CHARCOAL cervix (anatomy) Neck, usually referring CGRP (physiology/biochemistry) An to the neck of the UTERUS (womb) at abbreviation of ‘C’alcitonin ‘G’ene- the inner end of the VAGINA. ‘R’elated ‘P’eptide.

Cf (measurement) An abbreviation of cgs (measurement) An abbreviation ‘c’ubic ‘f’eet. of ‘c’entimetre ‘g’ram ‘s’econd. (USA: centimeter gram second). CF (medical) An abbreviation of ‘C’ystic ‘F’ibrosis. Ch D (education) An abbreviation of ‘D’octor of ‘Ch’emistry. CFBS (society) An abbreviation of ‘C’anadian ‘F’ederation of ‘B’iological Chagas disease (medical/microbiology) ‘S’ciences. South American trypanosomiasis, a disease spread by the cone-nosed or assassin CFC (chemistry) An abbreviation of reduviid bug. The organism is Trypanosma ‘c’hloro‘f’luoro‘c’arbon. cruzi and the disease is a major cause of heart damage and heart failure in CFF (physiology) An abbreviation of endemic areas. Named after the Brazilian ‘C’ritical ‘F’usion ‘F’requency. physician Carlos Chagas (1879–1934).

CFU (microbiology) An abbreviation chain of infection (epidemiology) A SERIES of ‘C’olony ‘F’orming ‘U’nit. of infections that are directly or immediately connected to a particular source. c ft (measurement) An abbreviation of ‘c’ubic ‘f’ee‘t’/‘f’oo‘t’. chain reaction (physics/chemistry) Nuclear or CHEMICAL REACTION in which the CFTR (physiology/biochemistry) An products ensure that the REACTION abbreviation of ‘C’ystic ‘F’ibrosis continues (e.g. COMBUSTION). ‘T’ransmembrane conductance ‘R’egula- tor. chalk (chemistry) Mineral form of

CALCIUM CARBONATE (CaCO3), a soft cg (measurement) An abbreviation of white limestone derived from the skeletons ‘c’enti‘g’ram. Also termed cgm. of microscopic marine animals.

CGI (education) An abbreviation of character (genetics) VARIATION caused ‘C’ity and ‘G’uilds ‘I’nstitute. by a GENE; an inherited trait. cgm (measurement) See eg. characteristic (mathematics) INTEGER part of a LOGARITHM; e.g. the cGMP (physiology/biochemistry) An LOGARITHM (to the BASE 10) of 200 abbreviation of ‘c’yclic 3’,5’-‘G’uanosine is 2.3010, in which 2 is the ‘M’ono‘P’hosphate. CHARACTERISTIC.

CGP (physiology/biochemistry) An charcoal (chemistry) Form of CARBON abbreviation of ‘C’horionic ‘G’rowth made from incomplete burning of ANIMAL HORMONE-‘P’rolactin. or vegetable MATTER.

82 CHARGE CHEMICAL SYMBOL charge (physics) See ELECTRIC to form a different substance or sub- CHARGE; ELECTRON CHARGE. stances. charge-coupled device (CCD) (physics) chemical equation (chemistry) Way Semiconductor device used in television of expressing a CHEMICAL REACTION cameras, video cameras and astronomical by placing the formulas of the reactants telescopes to produce an electronic to the left and those of the products signal from an optical IMAGE. to the right, with an equality sign or directional arrow in between. The number charge/mass ratio (physics) Fundamental of atoms of any particular ELEMENT physical CONSTANT, the ratio of an are the same on each side of the equation ELECTRON’S CHARGE to its MASS (when the REACTION is in EQUILIBRIUM). 11 1 E.g. the CHEMICAL EQUATION for the e/me, equal to 1.758796×10 C kg- (coulombs per KILOGRAM). COMBINATION of HYDROGEN and OXYGEN to form WATER is written as: ® Charles’s law (physics) At a given 2H2+O2 2H2O PRESSURE, the VOLUME of an ideal GAS is directly proportional to its chemical equilibrium (chemistry) The ABSOLUTE TEMPERATURE. It was balanced state of a CHEMICAL REACTION, named after the French physicist Jacques when the CONCENTRATION of reactants Charles (1746–1823). and products remain CONSTANT.

See also EQUILIBRIUM CONSTANT. See also KINETIC THEORY. chemical formula (chemistry) Method chelate (chemistry) Chemical COMPOUND of representing the chemical composition in which a central METAL ION forms of a single substance that uses the part of one or more organic rings of CHEMICAL SYMBOLS of the atoms, atoms. The formation of these compounds and indicates the numbers of those is useful in many contexts, e.g. medicine, atoms, in a MOLECULE of the substance in which chelating agents are administered e.g. the CHEMICAL FORMULAe of WATER, to counteract poisoning by certain heavy CALCIUM CARBONATE and ETHANE metals. They can also act to BUFFER are H2O, CaCO3 and C2H 6. the CONCENTRATION of METAL ions (e.g. IRON and CALCIUM) in natural chemical potential (chemistry) Measure biological systems. of the tendency of a CHEMICAL REACTION to take place. chemical bond (chemistry) LINKAGE between atoms or ions within a chemical reaction (chemistry) Process MOLECULE. A CHEMICAL REACTION in which one or more substances react and the input or output of ENERGY to form a different substance or substances. are involved in the formation or destruction of a CHEMICAL BOND. chemical symbol (chemistry) Letter or letters that represent the name of a chemical See also COVALENT BOND. IONIC BOND. ELEMENT, or one ATOM of it in a CHEMICAL FORMULA, e.g. the symbols of CARBON, chemical combination (chemistry) Union and CHLORINE are C, and CI. The symbol of two or more chemical substances may be based on the ELEMENT’S Latin,

83 CHEMILUMINESCENCE CHLORINATION not English, name; e.g. Au for GOLD different tissues arising e.g. from (aurum), Fe for IRON (ferrum). MUTATION or mixing of CELL types of different organisms. It can be achieved chemiluminescence (chemistry/biochem- by incorporating DONOR CELLS at istry) LUMINESCENCE that results from an early stage of embryonic development a CHEMICAL REACTION (e.g. the OXIDATION of the RECIPIENT. of PHOSPHORUS in AIR). In living organisms it is termed BIOLUMINESCENCE. Chinese restaurant syndrome (medical) Headache, nausea, a tight or burning chemistry (chemistry) The study of sensation in the face, head and chest elements and their compounds, particu- and sometimes dizziness and diarrhoea larly how they behave in CHEMICAL (USA: diarrhea) coming on one or two REACTIONS. hours after a meal containing a large amount of MONOSODIUM GLUTAMATE. chemo. (medical) An abbreviation of ‘CHEMO’THERAPY. chirality (chemistry) Property of a MOLECULE that has a CARBON ATOM chemoreceptor (physiology) CELL that attached to four different atoms or groups, fires a NERVE IMPULSE in RESPONSE and which can therefore exist as a pair to stimulation by a specific type of chemical of OPTICALLY ACTIVE stercoisomers substance; e.g. the TASTE BUDS on (whose molecules are mirror images of the TONGUE and OLFACTORY bulbs each other). Commonly called ‘handedness’, in the nose contain chemoreceptors that CHIRALITY is significant in the biological provide the SENSES of TASTE and SMELL. activity of molecules, in some of which the righthanded version is active and chemotaxis (biology) RESPONSE of the left-handed version is not, or vice organisms to chemical stimuli; e.g. the versa (e.g. many pheromones). movement of BACTERIA towards nutrients. chitin (biochemistry) POLYSACCHARIDE chemotherapy (pharmacology) TREATMENT found in the exoskeleton of arthropods, of a disorder with drugs that are giving it hard waxy properties. designed to destroy pathogens or cancerous TISSUE. chloral (chemistry) An alternative term for TRICHLOROETHANAL. chiasma (1 genetics; 2 anatomy) 1 Point along the CHROMATID of a chloral hydrate (chemistry) An alternative HOMOLOGOUS CHROMOSOME at which term for TRICHLOROETHANEDIOL. connections occur during crossing-over or exchange of genetic material in chlorate (chemistry) SALT of chloric

MEIOSIS. 2 Crossing-over point of the ACID (HCIO3). OPTIC NERVES in the BRAIN. chloride (chemistry) BINARY COMPOUND chile saltpetre (chemistry) Old name containing CHLORINE; a SALT of for impure SODIUM NITRATE. HYDROCHLORIC ACID (HCI). chimaera (genetics) Genetic MOSAIC chlorination (1 chemistry; 2 microbiology) or organism composed of genetically 1 REACTION between CHLORINE and

84 CHLORINE CHORIONIC GONADOTROPHIN an ORGANIC COMPOUND to form the chlorpropamide (pharmacology) A drug corresponding chlorinated COMPOUND; of the sulphonylurea type which can e.g. the CHLORINATION of BENZENE be administered orally in diabetic treatment produces chlorobenzene, C6H 5CI. 2 of non-insulin-dependent diabetes. TREATMENT of a substance with CHLORINE; e.g. to disinfect it. chlortalidone (pharmacology) A DIURETIC related to the THIAZIDES which can chlorine CI (chemistry) Gaseous be administered orally to treat hypertension, nonmetallic ELEMENT in GROUP VIIA OEDEMA (USA: edema) and diabetes of the PERIODIC TABLE (the HALOGENS), insipidus. obtained by the ELECTROLYSIS of SODIUM CHLORIDE (COMMON SALT). cholesterol (biochemistry) STEROL It is a green-yellow poisonous GAS found in ANIMAL tissues, a LIPID-like with an irritating SMELL, used as a substance that occurs in BLOOD disinfectant and BLEACH and to make PLASMA, CELL MEMBRANES and CHLORINE containing organic chemicals. NERVES, and may form gallstones. At. no. 17; r.a.m. 35.453. High levels of CHOLESTEROL in the BLOOD are connected to the onset of chlorofluorocarbon (chemistry) FLUORO- ATHEROSELEROSIS, in which fatty CARBON that has CHLORINE atoms materials are deposited in patches on in place of some of the FLUORINE ARTERY walls and can restrict BLOOD atoms. Chlorofluorocarbons and flow. Many steroids are derived from fluorocarbons have similar properties, CHOLESTEROL. and are used as AEROSOL propellants and refrigerants. choline (biochemistry) HOC2H4N(CH3)3OH ORGANIC COMPOUND that is a chloroform (chemistry) An alternative constituent of the NEUROTRANSMITTER term for TRICHLOROMETHANE. ACETYLCHOLINE and some fats. It is one of the B VITAMINS. chloroquine (pharmacology) An antimalarial drug which can be adminis- chondriosome (cytology) An alternative tered orally, by injection or infusion to term for MITOCHONDRION. prevent and treat contraction of malaria. chlordiazepoxide (pharmacology) A chlorothiazide (pharmacology) A benzodiazepine drug which can be DIURETIC drug of the THIAZIDE class, administered orally as an ANXIOLYTIC. which can be administered orally as an ANTIHYPERTENSIVE and in the treatment chorion (biology) The MEMBRANE that of OEDEMA (USA: edema) and congestive surrounds an implanted BLASTOCYST HEART FAILURE. and the EMBRYO and FOETUS (USA: fetus) that develop from it. chlorpromazine hydrochloride (pharmacology) An antipsychotic drug which chorionic gonadotrophin (biochemistry) can be administered orally, by injection HORMONE produced by the PLACENTA or topically as suppositories in the during PREGNANCY. Its presence in treatment of schizophrenia and other the URINE is the basis of many kinds psychoses. It can also be used as an of PREGNANCY testing. anxolytic, ANTINAUSEANT and ANTIEMETIC.

85 CHORIONIC VILLUS SAMPLING CILIARY BODY chorionic villus sampling (biochemistry) have COLOUR (USA: color) (e.g. the Testing during early PREGNANCY of -N=N-GROUP in an AZO DYE). small samples of TISSUE taken from the CHORION for the presence of FOETAL chromosome map (genetics) Diagram (USA: fetal) ABNORMALITIES. showing the positions of various genes on appropriate chromosomes. See also AMNIOCENTESIS. chromosome (genetics) Structure within choroid (histology) Layer of pigmented the NUCLEUS of a CELL that contains CELLS, rich in BLOOD VESSELS, between PROTEIN and the genetic DNA. the RETINA and SCLEROTIC of the EYE. Chromosomes occur in pairs in DIPLOID CELLS (ordinary body CELLS); HAPLOID chromatic aberration (physics/genetics) CELLS (gametes or SEX CELLS) have See ABERRATION. only one CHROMOSOME in their nuclei. The number of chromosomes varies chromatid (genetics) One of two thread- in different SPECIES. During CELL like parts of a CHROMOSOME, visible DIVISION, each CHROMOSOME doubles during PROPHASE of MEIOSIS or MITOSIS, and the two duplicates separate into when the CHROMOSOME has duplicated. the two new DAUGHTER CELLS. Chromatids are separated during ANAPHASE. chronic (medical) Describing a condition chromatin (biochemistry) BASIC or disorder that is long-standing, and PROTEIN that is associated with often difficult to treat. Compare ACUTE. EUKARYOTIC chromosomes, visible during certain stages of CELL duplication. chronic obstructive pulmonary disease (COPD) (medical) A progressive chromatography (chemistry) Method irreversible condition characterised by of separating a MIXTURE by carrying airway obstruction, the most common it in SOLUTION or in a GAS stream cause of which is smoking. through an absorbent. The separated substances may be extracted by ELUTION. chyle (biochemistry) Milky FLUID resulting from the ABSORPTION of fats in the chromium Cr (chemistry) SILVER-grey LACTEALS of the SMALL INTESTINE; metallic ELEMENT in GROUP VIB of it is removed by the LYMPHATIC SYSTEM. the PERIODIC TABLE (a TRANSITION ELEMENT), obtained mainly from its chyme (physiology) Partly digested food ore chromite. It is electroplated onto that passes from the STOMACH into other metals (particularly steel) to provide the DUODENUM and SMALL INTESTINE. a corrosion-resistant decorative finish, and ALLOYed with NICKEL and IRON Ci (measurement) An abbreviation of to make stainless steels; its compounds ‘C’ur‘i’e. are used in pigments and dyes. At. no. 24; r.a.m. 51.996. ciliary body (histology) Ring of TISSUE that surrounds the LENS of the EYE. It chromophore (chemistry) A chemical generates the AQUEOUS HUMOUR and GROUPING that causes compounds to contains CILIARY MUSCLES, which are used in ACCOMMODATION.

86 CILIARY MUSCLE CITRIC ACID ciliary muscle (histology) MUSCLE that circuit (physics) An electrical term controls the LENS of the EYE and thus for the path that an ELECTRIC CURRENT achieves ACCOMMODATION. flows along. cilium (cytology) Small HAIR-like structure circuit breaker (physics) Safety device that moves rhythmically on the surface in an electric CIRCUIT that interrupts the of a CELL or the whole EPITHELIUM. CURRENT flow in the event of a fault. Cilia usually cover the surface of a CELL and cause movement in the FLUID See also FUSE. surrounding it. They are used for locomotion by some single-celled aquatic organisms. circulatory system (physiology) In animals, transport system that maintains a CONSTANT See also FLAGELLUM. flow of TISSUE FLUID in sealed vessels to all parts of body e.g. in the BLOOD cimetidine (pharmacology) A histamine2- VASCULAR SYSTEM, OXYGEN and food ANTAGONIST which can be administered materials dissolved in BLOOD diffuse orally, by injection or infusion as an into each CELL; waste products, including ulcer-healing drug. CARBON DIOXIDE, diffuse out of the CELLS and into the BLOOD. cinnarizine (pharmacology) An ANTI- HISTAMINE drug which can be See also LYMPHATIC SYSTEM. administered orally as an ANTINAUSEANT and ANTIEMETIC, that also has vasodilator circum. (measurement) An abbreviation properties. of ‘circum’ference. ciprofibrate (pharmacology) A LIPID- circumference (measurement) Boundary lowering drug which can be administered of a circle, equal in length to p times orally in hyperlipidaemia (USA: the DIAMETER (or 2p times the RADIUS). hyperlipidemia) to reduce the levels, or change the proportions, of various cisapride (pharmacology) A motility LIPIDS in the bloodstream. stimulant which can be administered orally to release the NEUROTRANSMITTER circ. (physics) An abbreviation of acetylcholine from the nerves of the ‘circ’uit. STOMACH and INTESTINE to treat conditions such as oesophageal reflux. circadian rhythm (physiology) Cyclical VARIATION in the physiological, metabolic cistron (molecular biology) Functional or behavioural (USA: behavioral) aspects UNIT of a DNA chain that controls of an organism over a PERIOD of about PROTEIN manufacture. 24 hours; e.g. sleep patterns. It may arise from inside an organism or be a cit. (literary terminology) An abbreviation RESPONSE to a regular CYCLE of some of ‘cit’ed. external VARIATION in the ENVIRONMENT.

Also termed: diurnal rhythm. citric acid (chemistry) C6H8O7 Hydroxy- triCARBOXYLIC ACID, present in the See also BIOLOGICAL CLOCK. juices of fruits and made by fermenting residues from SUGAR refining. It is important

87 CITRIC ACID CYCLE CLOBAZAM in the KREBS CYCLE, and is much used CLASSIFICATION schemes for animals as a flavouring and in medicines. or for plants. citric acid cycle (biochemistry) alternative See also BINOMIAL NOMENCLATURE. term for KREBS CYCLE. clathrate (chemistry) Chemical structure C-J disease (medical) An abbreviation in which one ATOM or MOLECULE is of ‘C’reutzfeldt-‘J’acob disease. Also ‘encaged’ by a structure of other termed CJD. molecules, and not held by CHEMICAL BONDS. CK (biochemistry) An abbreviation of ‘C’reatine ‘K’inase. See also CHELATE.

CI (chemistry) CHEMICAL SYMBOL clavicle (anatomy) In vertebrates, the for CHLORINE. ANTERIOR BONE of the VENTRAL side of the shoulder girdle. Also termed: Claisen condensation (chemistry) A COLLARBONE. CHEMICAL REACTION in which two molecules combine to give a COMPOUND containing cleavage (1 biology; 2 chemistry; 3 a KETONE GROUP and an ESTER GROUP. biochemistry) 1 A SERIES of mitotic It was named after the German chemist divisions of a fertilized OVUM. 2 The Ludwig Claisen (1851–1930). splitting of a crystal structure along a certain plane parallel to a POTENTIAL class (biology) In biological CLASSIFI- crystal face. 3 The splitting of CHEMICAL CATION, one of the groups into which BONDS (e.g. PROTEASE ENZYMES a PHYLUM is divided, and which is itself cleave PEPTIDE BONDS from proteins divided into orders; e.g. Mammalia to release AMINO ACID residues). (mammals), Aves (birds). clinical thermometer (medical) Type of classical physics (physics) Physics (MERCURY) THERMOMETER used for prior to the introduction of QUANTUM taking body TEMPERATURE. It measures THEORY and a knowledge of RELATIVITY. only a small range of temperatures. classification (biology) The placing of CLIP (physiology/biochemistry) An living organisms into a SERIES of groups abbreviation of ‘C’orticotropin-‘L’ike according to similarities in structure, ‘I’ntermediate-lobe ‘P’olypeptide. physiology, biochemistry, and other characteristics. The smallest GROUP clitoris (anatomy) MASS of erectile is the SPECIES. Similar SPECIES are TISSUE in female mammals, the placed in a GENUS, similar GENERA equivalent of the PENIS in males, situated are grouped into families, families into in front of the opening of the VAGINA. orders, orders into classes, classes into phyla (or divisions in plants), and phyla CLL (haematology) An abbreviation of into kingdoms. Modern CLASSIFICATION ‘C’hronic ‘L’ymphocytic ‘L’eukaemia. (USA: is usually intended to reflect degrees CHRONIC Lymphocytic Leukemia). of evolutionary relationship, although not all experts agree on single clobazam (pharmacology) A benzodiazepine drug which can be administered

88 CLOFIBRATE COAGULATION orally as an ANXIOLYTIC in the treatment Clozapine can cause potentially serious of anxiety. side-effects including agranulocytosis and neutropenia. clofibrate (pharmacology) A LIPID-lowering drug which can be administered orally in Cm (chemistry) CHEMICAL SYMBOL hyperlipidaemia (USA: hyperlipidemia) to for CURIUM. reduce the levels, or change the proportions, of various LIPIDS in the bloodstream. cm (measurement) An abbreviation of ‘c’enti‘m’etre (USA: centimeter). clomiphene citrate (pharmacology) A sex HORMONE anAGONIST which prevents CMA (1 education; 2 society) 1 An the action of OESTROGENs thus increasing abbreviation of ‘C’ertified ‘M’edical secretion of gonadotrophins and causing ‘A’ssistant. 2 An abbreviation of ‘C’hemical ovulation. It can be administered orally ‘M’anufacturers ‘A’ssociation. as a fertility treatment in women whose condition is linked to the persistent presence CML (medical/haematology) An of OESTROGENs and a consequent failure abbreviation of ‘C’hronic ‘M’yelocytic to ovulate. ‘L’eukaemia. (USA: CHRONIC Myelocytic Leukemia). clonazepam (pharmacology) A benzodiazepine drug which can be administered cmpd (chemistry) An abbreviation of orally, by injection or infusion, as an ‘c’o‘mp’oun‘d’. ANTICONVULSANT and ANTI-EPILEPTIC in the treatment of epilepsy. CMRO2 (physiology/biochemistry) An abbreviation of ‘C’erebral ‘M’etabolic clone (genetics) One of many descen- ‘R’ate for ‘O’xygen. dants produced by ASEXUAL REPRODUCTION. Members of a CLONE CMV (virology) An abbreviation of have identical genetic constitution. ‘C’yto‘M’egalo‘V’irus. clonidine hydrochloride (pharmacology) CNS (medical) An abbreviation of ‘C’entral An ANTISYMPATHETIC class of drug ‘N’ervous ‘S’ystem. that decreases the release of NORADRENALINE from sympathetic CNTF (physiology) An abbreviation of nerves. It can be administered orally ‘C’iliary ‘N’euro‘T’rophic ‘F’actor. or by injection in ANTIHYPERTENSIVE treatment and antimigraine treatment. co. (anatomy) An abbreviation of ‘co’lon. clotting factor (haematology) PROTEIN- Co (chemistry) CHEMICAL SYMBOL like structure, e.g. THROMBIN and for COBALT. FIBRINOGEN, that induces BLOOD COAGULATION when a BLOOD VESSEL CoA (physiology/biochemistry) An is broken. abbreviation of ‘Co’enzyme ‘A’. clozapine (pharmacology) An antipsy- coagulation (1 haematology; 2 biochem- chotic drug which can be administered istry; 3 chemistry) 1 The process by orally in the treatment of schizophrenia. which bleeding is arrested. THROMBIN

89 COBALT COHERENT UNITS is produced in the absence of antithrombin NERVE to the BRAIN, where they are from the COMBINATION of prothrombin interpreted as sounds. and CALCIUM ions. This interacts with SOLUBLE FIBRINOGEN to PRECIPITATE Cockeroft-Walton generator (physics) it as the INSOLUBLE BLOOD PROTEIN High-VOLTAGE DIRECT CURRENT FIBRIN, which forms a mesh of fine generator used for accelerating nuclear threads over the WOUND. BLOOD CELLS particles to high speeds. It was named become trapped in the mesh and form after the British scientist John Cockcroft a clot. 2 Irreversible setting of (1897–1967) and the Irish physicist PROTOPLASM on exposure to HEAT Ernest Walton (1903–95). or POISON. 3 PRECIPITATION of colloids, e.g. proteins, from solutions. codeine (pharmacology) Pain-killing drug (a NARCOTIC ANALGESIC), the cobalt Co (chemistry) SILVER-white methyl DERIVATIVE of MORPHINE. magnetic metallic ELEMENT in GROUP VIII of the PERIODIC TABLE, used in coefficient (1 mathematics; 2 physics) ALLOYS to make cutting tools and 1 In an ALGEBRAic expression, the magnets. The RADIOACTIVE ISOTOPE numerical FACTOR by which the VARIABLE Co-60 is used in RADIOTHERAPY. At. is multiplied; e.g. in 5xy, the COEFFICIENT no. 27; r.a.m. 58.9332. of xy is 5. 2 Number or parameter that measures some specified property of COBOL (computing) An acronym of a given substance; e.g. COEFFICIENT ‘CO’mmon ‘B’usiness ‘O’riented of friction, COEFFICIENT of VISCOSITY. ‘L’anguage, a COMPUTER programming language designed for commercial use. coefficient of variation (statistics) A measurement of the amount of VARIATION cocaine (pharmacology) A central within a population. It equals the STANDARD nervous system stimulant that rapidly DEVIATION expressed as a PERCENTAGE causes dependence. It may be used of the value of the MEAN. therapeutically as a topically applied local anaesthetic. coenzyme (biochemistry) ORGANIC COMPOUND essential to catalytic coccus (bacteriology) Spherical-shaped activities of ENZYMES without being BACTERIUM. Cocci may join together utilized in the REACTION. Coenzymes to form clumps (staphylococci) or chains usually act as carriers of INTERMEDIATE (streptococci). products, e.g. ATP. coccyx (anatomy) Bony structure in COHb (physiology/biochemistry) An primates and amphibians, formed by abbreviation of ‘C’arbonmon’O‘xy’- FUSION of tail vertebrae; e.g. in human H’aemoglo‘b’in (USA: carbon oxyhemo- beings it consists of three to five vestigial globin). vertebrae at the BASE of the SPINE. coherent units (measurement) System cochlea (anatomy) Spirally coiled part of units in which the desired units are of the INNER EAR in mammals. It translates obtained by multiplying or dividing BASE sound-induced vibrations into NERVE units, with no numerical CONSTANT IMPULSES that travel along the AUDITORY involved.

90 COHESION COLUMBIUM

See also SI UNITS. colony (bacteriology) BACTERIAL GROWTH on a SOLID medium that cohesion (physics) Attraction between forms a visible MASS. similar particles (atoms or molecules of the same substance); e.g. between colorimeter (physics/chemistry) Instru- WATER molecules to create SURFACE ment for measuring the COLOUR (USA: TENSION. color) INTENSITY of a medium such as a coloured SOLUTION (which can See also ADHESION. be related to CONCENTRATION and therefore provide a method of colestipol hydrochloride (pharmacology) QUANTITATIVE ANALYSIS). The technique A resin that binds bile acids and lowers is termed colorimetry. LDL-cholesterol that is used as a LIPID- colostrum (biology) Yellowish milky lowering drug which can be administered FLUID secreted from the mammalian orally in hyperlipidaemia (USA: breast immediately before and after hyperlipidemia) to reduce the levels, or childbirth. It contains more antibodies change the proportions, of various LIPIDS and leucocytes (and less fat and in the bloodstream. carbohydrates) than true milk, which follows within a few days. colestyramine (pharmacology) A resin that binds bile acids in the gut that, similarly colour blindness (medical) Inability to to COLESTIPOL HYDROCHLORIDE, is distinguish between certain colours. It used as a LIPID-lowering drug which can is a CONGENITAL abnormality that affects be administered orally in hyperlipidaemia 6 per cent of human males and 1 per (USA: hyperlipidemia) to reduce the levels, cent of females. The most common DEFECT or change the proportions, of various is red-green COLOUR BLINDNESS, which LIPIDS in the bloodstream. results in observation of both colours in grey, blue or yellow, depending on collagen (biochemistry) Fibrous PROTEIN the amount of yellow and blue present CONNECTIVE TISSUE that binds together in the LIGHT. (USA: color blindness) bones, ligaments, CARTILAGE, muscles and SKIN. colour (physics) Visual sensation or perception that results from the ADSORPTION collarbone (anatomy) An alternative of LIGHT ENERGY of a particular term for the CLAVICLE. WAVELENGTH by the cones of the RETINA of the EYE. There are two or more types colloid (physics) Form of MATTER that of CONE, each of which are sensitive to consists of small particles, about 10-4 to different wavelengths of LIGHT. The BRAIN 10-6 mm across, dispersed in a medium combines NERVE IMPULSES from these such as AIR or WATER. Common colloids cones to produce the perception of COLOUR. include AEROSOLS (e.g. fog, mist) and The COLOUR of an OBJECT thus depends gels (e.g. GELATIN, rubber). A non-colloidal on the WAVELENGTH of LIGHT it reflects substance is termed a CRYSTALLOID. (other wavelengths being absorbed) or transmits. (USA: color) colon (anatomy) LARGE INTESTINE, in which the main FUNCTION is the ABSORPTION columbium (chemistry) Former name of of WATER from FAECES (USA: FECES). NIOBIUM.

91 COMBINATION COMPOSITE combination (mathematics) Any selection COMMUTATIVE. Subtraction is not; e.g. of a given number of objects from a 7–2 is not the same as 2–7. SET, irrespective of their ORDER. The number of combinations of r objects See also ASSOCIATIVE. that can be obtained from a SET of n objects (usually writtennCr) is n![r!(n— competition (biology) The struggle within r)!]. (The symbol ! stands for FACTORIAL.) a community between organisms of the same or different SPECIES for survival. combustion (chemistry) Burning; the rapid OXIDATION of a substance See also NATURAL SELECTION. accompanied by HEAT, LIGHT and flame. Usually the OXIDIZING AGENT is compiler (computing) COMPUTER PROGRAM OXYGEN (often from AIR). that converts a source language into MACHINE CODE (readable by the COMPUTER). commensalism (biology) Close relationship between two organisms from which complementary deoxyribonucleic acid one benefits and the other neither benefits (CDNA) (genetics) Single-stranded DNA nor suffers. complementary to an RNA; it is synthesized in vitro by using the RNA See also, PARASITISM; SYMBIOSIS. as a template for the ACTION of reverse transcriptase. common denominator (mathematics) Same DENOMINATOR assigned to fractions complex compound (chemistry) An (formerly with different ones) so that alternative term for a CO-ORDINATION they can be added or subtracted; e.g. to COMPOUND. subtract 1/3 from 1/2 the fractions are first assigned the COMMON DENOMINATOR complex ion (chemistry) CATION bonded of 6, becoming 2/6 and 3/6, and subtracted by means of a CO-ORDINATE BOND. to give 1/6; using the same method they can be added (to give 5/6). complex number (mathematics) Number written in the form x+iy, where x and common difference (mathematics) y are REAL NUMBERS and i is the Difference between any two consecutive SQUARE ROOT of -1 (i.e. i2=-1). terms of an ARITHMETIC PROGRESSION. component (1 mathematics; 2 chemistry) common logarithm (mathematics) 1 The resolved part of a VECTOR quantity LOGARITHM to the BASE 10. in a particular direction, usually one of a pair at right-angles. 2 One of the common salt (chemistry) An alternative substances in a system. term for SODIUM CHLORIDE. composite (physics) Material composed commutative (mathematics) A term of two or more other materials that give describing a mathematical operation of a COMBINATION with better properties the type a*b whose result does not depend than any of the components individually; on the order in which the operation is e.g. glass fibre (USA: glass fiber) or carried out. E.g. the addition 7+2 has carbon fibre (USA: carbon fiber) reinforced the same result as 2+7, so addition is plastic RESIN.

92 COMPOUND CONDUCTION BAND compound (chemistry) Substance that or kg per LITRE of SOLVENT or per consists of two or more elements LITRE of SOLUTION, moles per LITRE chemically united in definite proportions of SOLUTION (MOLARITY), moles per by WEIGHT. Also termed: chemical kg of SOLVENT (molality), or in terms COMPOUND. of normality. See NORMAL.

Compton effect (physics) REDUCTION See also SOLUBILITY. in the ENERGY of a PHOTON as a result of its INTERACTION with a FREE condensation (1 physics; 2 chemistry) ELECTRON. Some of the PHOTON’S 1 Change of a GAS or VAPOUR into ENERGY is transferred to the ELECTRON. a LIQUID or SOLID by cooling. 2 It was named after the American physicist CONDENSATION REACTION. Arthur Compton (1892–1962). condensation pump (laboratory Compton wavelength (physics) WAVE- equipment) An alternative term for LENGTH associated with a SUBATOMIC DIFFUSION PUMP. PARTICLE, dependent on its MASS. For an ELECTRON it is 2.42621×10-12 condensation reaction (chemistry) A m; for a PROTON 1.321398×10-15 m. CHEMICAL REACTION in which two or more small molecules combine to computer (computing) Electronic device form a larger one, often with the elimination that can accept DATA, apply a SERIES of a simpler substance, usually WATER. of logical operations to it (obeying a PROGRAM), and supply the results condenser (1 chemistry; 2 physics; 3 of these operations. See ANALOG optics) 1 An apparatus for changing COMPUTER; DIGITAL COMPUTER. a VAPOUR into a LIQUID (by cooling it and causing CONDENSATION). 2 computerized axial tomography (CAT) An alternative term for a CAPACITOR. scan (radiology) A technique for 3 A LENS or mirror that concentrates producing X-RAY pictures of cross- a LIGHT source. sectional ‘slices’ through the BRAIN and other parts of the body. conditioned reflex (physiology) ANIMAL’S RESPONSE to a NEUTRAL COMT (physiology/biochemistry) An STIMULUS that learning has associated abbreviation of ‘C’atechol-‘O’-‘M’ethyl’- with a particular effect; e.g. a rat may T’ransferase. learn (be conditioned) to press a lever when hungry because it associates concave (optics) Describing a surface this ACTION with receiving food. that curves inwards (as opposed to one that is CONVEX). conductance (physics) Ability to convey ENERGY as HEAT or ELECTRICITY. concentration (chemistry) Strength of Electrical CONDUCTANCE, measured MIXTURE or SOLUTION. Concentrations in siemens, is the RECIPROCAL of can be expressed in very many ways; resistance. Also termed: CONDUCTIVITY. e.g. parts per million (for traces of a substance), PERCENTAGE (i.e. parts per conduction band (physics) ENERGY hundred by WEIGHT or VOLUME), gm range in a semiconductor within which

93 CONDUCTOR CONVECTION electrons can be made to flow by an conjunctiva (histology) Layer of protective applied ELECTRIC FIELD. MUCUS-secreting EPIDERMIS that covers the CORNEA on the eyeball and is conductor (1,2 physics) 1 Material that continuous with the inner lining of the allows HEAT to flow through it by conduction. eyelids of vertebrates. 2 Material that allows ELECTRICITY to flow through it; a CONDUCTOR has connective tissue (histology) Strong a low resistance. TISSUE that binds organs and tissues together. It consists of a GLYCOPROTEIN cone (cytology) LIGHT-sensitive NERVE MATRIX containing COLLAGEN in which CELL present in the RETINA of the EYE CELLS, fibres (USA: fibers) and vessels of most vertebrates; it can detect COLOUR are embedded. The most widespread (USA: color). CONNECTIVE TISSUE is arcolar TISSUE.

See also ROD. conservation of energy (physics) LAW that states that in all processes occurring configuration (1 physics; 2 chemistry) in an isolated system the ENERGY of 1 The arrangement of electrons about the system remains CONSTANT. the NUCLEUS of an ATOM. Also termed: ELECTRON CONFIGURATION. 2 The See also THERMODYNAMICS, LAWS OF. arrangement in space of the atoms in a MOLECULE. conservation of mass (physics) Principle which states that the products of a conformation (chemistry) Particular purely CHEMICAL REACTION have the shape of a MOLECULE that arises same total MASS as the reactants. through the NORMAL rotation of its atoms or groups about SINGLE BONDS. constant (measurement) Quantity that remains the same in all circumstances; congenital (medical) Dating from birth e.g. in the expression 2y=5x 2, the or before birth. CONGENITAL conditions numbers 2 and 5 are constants (and may be caused by environmental factors x and y are variables). or be inherited. continuous wave (physics) ELECTRO conjugated (chemistry) Describing an MAGNETIC WAVE of CONSTANT ORGANIC COMPOUND that has alternate AMPLITUDE. single and double or TRIPLE BONDS.) e.g. buta-1, 3-diene, H2C=CH-CH=CH2. contractile vacuole (biology) Membranous sac within a single-celled organism (e.g. conjugation (biology) Form of REPRO- AMOEBA (USA: ameba) and other DUCTION that involves the permanent protozoans) which fills with WATER and or temporary union of two isogametes, suddenly contracts, expelling its contents e.g. in certain green ALGAe. In PROTOZOA, from the CELL. It carries out OSMO- two individuals partly FUSE, exchanging REGULATION and EXCRETION. nuclear materials. When separated, each CELL divides further to give uninucleate convection (physics) Transport of HEAT spores which eventually develop into by the movement of the heated substance full adults. (usually a FLUID such as AIR or WATER).

94 CONVERGING LENS CORNEA converging lens (optics) LENS capable of DIHYDRATE. It is used in fireworks to bringing LIGHT to a FOCUS; a CONVEX LENS. give a green flame and to remove SULPHUR (USA: sulfur) in the refining of petroleum. convex (optics) Describing a surface Also termed: CUPRIC CHLORIDE. that is rounded outwards (as opposed to one that is CONCAVE). copper(II) (chemistry) An alternative term for CUPRIC. coolant (physics) LIQUID or GAS that removes HEAT by CONVECTION. copper(II) carbonate (chemistry) CuCO3 Green CRYSTALLINE COMPOUND which co-ordinate bond (chemistry) Type of occurs (as the BASIC SALT) in the minerals COVALENT BOND that is formed by the azurite and malachite. It is also a donation of a lone pair of electrons from COMPONENT of verdigris, which forms one ATOM to another. Also termed: DATIVE on COPPER and its ALLOYS exposed BOND. to the ATMOSPHERE. co-ordination compound (chemistry) copper(II) oxide (chemistry) CuO INSOLUBLE Chemical COMPOUND that has CO- black SOLID, used as a PIGMENT. Also ORDINATE BONDS. Also termed: termed: CUPRIC OXIDE; COPPER OXIDE. complex; COMPLEX COMPOUND.

copper(II) sulphate (chemistry) CuSO co-ordination number (chemistry) Number 4 of nearest neighbours of an ATOM or White HYGROSCOPIC COMPOUND, an ION in a chemical COMPOUND. which forms a blue CRYSTALLINE PENTAHYDRATE, CuSO4.5H2O, used COPD (medical) Abbreviation of ‘C’hronic as a wood preservative, FUNGICIDE, ‘O’bstructive ‘P’ulmonary ‘D’isease. dyestuff and in electroplating. Also termed: CUPRIC SULPHATE (USA: cupric sulfate); copper Cu (chemistry) Reddish metallic BLUE VITRIOL. (USA: copper(II) sulfate). ELEMENT in GROUP IB of the PERIODIC

TABLE (a TRANSITION ELEMENT) which copper(I) oxide (chemistry) Cu2O occurs as the free METAL (native) and INSOLUBLE red powder, used in rectifiers in various ores, chief of which is and as a PIGMENT. Also termed: CUPROUS chalcopyrite. The METAL is a good OXIDE; COPPER OXIDE; CUPRITE; red CONDUCTOR of ELECTRICITY and is COPPER OXIDE. used for making wire, pipes and coins. Its chief ALLOYS are brass and bronze. core (1 physics; 2 computing) 1 Magnetic Its compounds are used as pesticides material at the centre (USA: center) of and pigments. COPPER is an important a SOLENOID or within the windings of TRACE ELEMENT in many plants and a transformer. 2 ELEMENT in a COMPUTER animals. At. no. 29; r.a.m. 63.546. MEMORY consisting of a piece of magnetic material that can retain a permanent copper(I) (chemistry) An alternative POSITIVE or negative ELECTRIC CHARGE term for CUPROUS. until a CURRENT passes through it (when the CHARGE changes POLARITY). copper(II) chloride (chemistry) CuCI2 Brown covalently bonded COMPOUND, cornea (histology) TRANSPARENT which forms a green CRYSTALLINE CONNECTIVE TISSUE at the front surface

95 CORNIFICATION COUPLING of the EYE of vertebrates, overlying corticosteroid (biochemistry) HORMONE the IRIS. Togther with the LENS, it focuses secreted by the ADRENAL CORTEX, incoming LIGHT onto the RETINA. which controls SODIUM and WATER METABOLISM as well as GLYCOGEN cornification (histology) An alternative formation. term for KERATINIZATION. corticotrophin (biochemistry) An alternative coronary vessels (anatomy) Arteries term for ADRENOCORTICOTROPHIC and veins that carry the BLOOD supplying HORMONE (ACTH). the HEART MUSCLE in vertebrates. cortisol (pharmacology) See HYDRO- coronene (chemistry) Aromatic ORGANIC CORTISONE. COMPOUND which consists of six (or seven) BENZENE RINGS fused to form cortisone (biochemistry/pharmacology) a circle. HORMONE isolated from the ADRENAL CORTEX, used in the TREATMENT of corpus callosum (histology) Thick bundle rheumatoid ARTHRITIS and other of NERVE FIBRES (USA: nerve fibers) inflammatory conditions. Also termed: in the middle of the BRAIN that connects 17-hydroxy- 11-dehydrocorticosterone. the two CEREBRAL HEMISPHERES. costal (anatomy) Concerning the ribs. corpus luteum (histology/biochemistry) Yellow body formed in the OVARY of coulomb (C) (measurement) SI UNIT female mammals which produces the of ELECTRIC CHARGE, defined as HORMONE PROGESTERONE. It develops the quantity of ELECTRICITY transported from the Graaflan FOLLICLE after by a CURRENT of 1 AMPERE in 1 OVULATION. If FERTILIZATION does not second. It was named after the French occur, the CORPUS LUTEUM degenerates. physicist Charles Coulomb (1736–1806). corresponding angle (mathematics) In counter (1 physics; 2 computing) 1 geometry, one of a pair of angles on the An electronic apparatus for detecting same side of a line (TRANSVERSAL) and counting particles, usually by making that cuts two other lines; the angles are them generate pulses of ELECTRIC between the TRANSVERSAL and the other CURRENT; the actual counting CIRCUIT lines. If the two other lines are parallel, is a sealer. 2 Any device that accumulates the corresponding angles are equal. totals (e.g. of repeated PROGRAM loops or cards passing through a punched See also ALTERNATE ANGLE. CARD READER). corrosive sublimate (chemistry) An couple (physics) A pair of equal and alternative term for MERCURY(II) CHLORIDE. parallel forces acting in opposite directions upon an OBJECT. This produces a turning cortex (anatomy) Outer layer of a effect (torque) equal to one of the structure, e.g. the outer layer of CELLS forces times the distance between them. of the ADRENAL GLAND or BRAIN. coupling (physics) Connection between See also MEDULLA. two oscillating systems.

96 COVALENT BOND CREUTZFELDT-JACOB DISEASE covalent bond (chemistry) CHEMICAL cps (measurement) An abbreviation BOND that results from the sharing of of ‘c’ycles ‘p’er ‘s’econd. a pair of electrons between two atoms. CR (physiology) An abbreviation of See also CO-ORDINATE BOND; IONIC BOND. ‘C’onditioned ‘R’eflex. covalent compound (chemistry) Chemical Cr. (physiology/biochemistry) An COMPOUND in which the atoms are abbreviation of ‘Cr’eatinine. covalently bonded. cranial (anatomy) Relating to the covalent radius (chemistry) Effective CRANIUM and BRAIN. RADIUS of an ATOM involved in a COVALENT BOND. cranial nerve (histology) One of the 10 to 12 pairs of NERVES connected Cowper’s gland (anatomy) One of a directly with a VERTEBRATE’S BRAIN pair of small GLANDS located below and supplying the SENSE ORGANS, the PROSTATE GLAND and connected muscles of the HEAD and neck and to the URETHRA which produces FLUID abdominal organs. Together with the for SEMEN. It was named after the British SPINAL NERVES they make up the anatomist William Cowper (1666–1709). PERIPHERAL NERVOUS SYSTEM.

Coxsackie virus (virology) Member cranium (anatomy) Part of the SKULL of a GROUP of VIRUSES that cause that encloses and protects the BRAIN, inflammatory diseases in human beings. consisting of eight fused bones in human It was named after the city in New beings. York state where it was first found. cream of tartar (chemistry) An alternative CP (medical) An abbreviation of ‘C’erebral term for POTASSIUM hydrogentartrate. ‘P’alsy.

creatine (biochemistry) NH2C(NH)N(CH3)-

CPD (1 education; 2 haematology) An CH2COOH White CRYSTALLINE AMINO abbreviation of ‘C’ontinuing ‘P’rofessional ACID present in MUSCLE, where it plays ‘D’evelopment. 2 An abbreviation of an important role in MUSCLE contraction. ‘ C ’ itrate-‘ P ’ hosphate-‘ D ’ extrose It is broken down to CREATININE. anticoagulant.

creatinine (biochemistry) C4H 7N 3O cpd (chemistry) An abbreviation of HETEROCYCLIC CRYSTALLINE SOLID ‘c’om‘p’oun‘d’. formed by the breakdown of CREATINE and excreted in URINE. C peptide (physiology/biochemistry) An abbreviation of ‘C’onnecting ‘peptide’. Creutzfeldt-Jacob disease (medical) A rapidly progressive transmissible CPR (physiology/medical) An abbrevia- disease of the nervous system associated tion of ‘C’ardio‘P’ulmonary ‘R’esuscita- with an abnormal protein called a prion, tion. which causes death within a few months of onset. Named after the German psychiatrist Hans Gerhard Creutzfeldt

97 CRH CS

(1885–1964) and the German neurologist CRT (physics) An abbreviation for Alfons Maria Jakob (1884–1931). ‘C’antode ‘R’ay ‘T’ube.

CRH (physiology/biochemistry) An cryogenics (physics) Branch of physics abbreviation of ‘C’orticotropin-‘R’eleasing that involves low temperatures and their ‘H’ormone. effects. critical angle (optics) The smallest Crypto. (parasitology) An abbreviation ANGLE OF INCIDENCE at which total of ‘Cryto’sporidium. internal REFLECTION occurs. cryst. (chemistry) An abbreviation of critical pressure (physics) Pressure ‘cryst’al/‘cryst’alline. necessary to condense a substance at its CRITICAL TEMPERATURE. crystal lattice (crystallography) Regular arrangement of atoms or ions in a critical state (physics) Conditions of crystal. TEMPERATURE and PRESSURE at which the LIQUID and GAS phases become crystalline (crystallography) Having the one PHASE, i.e. they have the same DENSITY. form of crystals, as opposed to being AMORPHOUS. critical temperature (1, 2 physics) 1 TEMPERATURE above which a GAS crystallization (crystallography) Process cannot be liquefied (no MATTER how in which crystals form from a molten high the PRESSURE). 2 TEMPERATURE MASS or SOLUTION. at which a magnetic material loses its MAGNETISM. Also termed: Curie point. crystallog. (chemistry) An abbreviation of ‘crystallog’raphy. critical volume (physics) VOLUME of one UNIT of MASS of a substance at its CRITICAL crystallography (chemistry) Study of PRESSURE and CRITICAL TEMPERATURE. crystals.

CRO (equipment) An abbreviation of crystalloid (physics) Substance that ‘c’athode-‘r’ay ‘o’scilloscope. is not a COLLOID and can therefore pass through a SEMIPERMEABLE cross linkage (chemistry) Cross-linking MEMBRANE. between chains within a POLYMER. crystd (chemistry) An abbreviation of crossing over (genetics) Exchange ‘cryst’allise‘d’. of material between HOMOLOGOUS CHROMOSOMES during MEIOSIS (CELL crystn (chemistry) An abbreviation of DIVISION). It is the mechanism that ‘cryst’allisatio’n’. alters the pattern of genes in the chromosomes of offspring, giving the CS (physiology/biochemistry) An genetic VARIATION associated with abbreviation of ‘C’onditioned ‘S’timulus. SEXUAL REPRODUCTION. Cs (chemistry) CHEMICAL SYMBOL for CrP (physiology/biochemistry) An CAESIUM (USA: cesium). abbreviation of ‘Cr’eatinine ‘P’hosphate.

98 CSA CV

CSA (1 quality standards; 2 Immunology) cu. (measurement) An abbreviation of 1 An abbreviation of ‘C’anadian ‘cu’bic. ‘S’tandards ‘A’ssociation. 2 An abbreviation of ‘C’olony ‘S’timulating ‘A’ctivity. cu. ft (measurement) An abbreviation of ‘cu’bic ‘f’ee‘t’/‘f’oo‘t’. CSF (1 anatomy; 2 physiology) 1 An abbreviation of ‘C’erebro‘S’pinal ‘F’luid; cu. in. (measurement) An abbreviation 2 An abbreviation of ‘C’olony- of ‘cu’bic ‘in’ch. ‘S’timulating ‘F’actor. cubic (cu.) (measurement) Of three CSLT (society) An abbreviation of dimensions. ‘C’anadian ‘S’ociety of ‘L’aboratory ‘T’echnologists. cupric (chemistry) BIVALENT COPPER. Also termed: COPPER(II). CSM (medical) An abbreviation of ‘C’erebro‘S’pinal ‘M’eningitis. cuprite (chemistry) Mineral form of COPPER(I) OXIDE. CSO (education) An abbreviation of ‘C’hief ‘S’cientific ‘O’fficer. cuprous (chemistry) MONOVALENT COPPER. Also termed: COPPER(I). CST (education) An abbreviation of ‘C’ollege of ‘S’cience and ‘T’echnology. curie (Ci) (measurement) Measure of RADIOACTIVITY. 1 Ci=3.700×1010

C19 steroids (physiology/biochemistry) disintegrations per second. It was named A symbol for steroids containing 19 after the Polish-born French scientist carbon atoms. Marie Curie (1867–1934). It has been replaced in SI UNITS by the BECQUEREL.

C21 steroids (physiology/biochemistry) A symbol for steroids containing 21 curium Cm (chemistry) RADIOACTIVE carbon atoms. ELEMENT in GROUP IIIA of the PERIODIC TABLE (one of the ACTINIDES), made CT (radiology) An abbreviation for by the alpha-PARTICLE bombardment ‘C’omputerized ‘T’omography. of PLUTONIUM-239. It has several isotopes, with half-lives up to 1.7×107 years. At. CTA (society) An abbreviation of no. 96; r.a.m. 247 (most STABLE ISOTOPE). ‘C’anadian ‘T’uberculosis ‘A’ssociation. cusp (1 mathematics; 2 anatomy) 1 In C terminal (physiology/biochemistry) CO-ORDINATE geometry, point on a curve A term signifying an end to peptide where it crosses itself, the two branches or PROTEIN having a free -COOH group. being on opposite sides of a common tangent. 2 The pointed part of a TOOTH. CTP (physiology/biochemistry) Abbrevia- tion of ‘Cytidine ‘T’ri‘P’hosphate. CV (1 measurement; 2 medical; 3 physiology) 1 Abbreviation of ‘C’alorific Cu (chemistry) CHEMICAL SYMBOL for ‘V’alue. 2 An abbreviation of COPPER. [The symbol is derived from ‘C’ardio‘V’ascular. 3 An abbreviation of Latin, ‘cuprum’.] ‘C’losing ‘V’olume.

99 CVA CYPROTERONE ACETATE

CVA (medical) An abbreviation of cyclic (chemistry) Describing the ‘C’erebro-‘V’ascular ‘A’ccident. MOLECULE of any (usually organic) COMPOUND whose atoms form a ring. CVR (physiology) An abbreviation of BENZENE and the cycIOALKANES are ‘C’erebral ‘V’ascular ‘R’esistance. simple CYCLIC compounds. cw (general terminology) An abbreviation See also ACYCLIC COMPOUND; of ‘c’lock‘w’ise. ALICYCLIC COMPOUNDS; CARBOCYCLIC; HETEROCYCLIC.) CY (chemistry) An abbreviation of ‘CY’anide. cyclicAMP (physiology/biochemistry) An abbreviation of ‘cyclic’ ‘A’denosine 3’,5’- cy (general terminology) An abbreviation ‘M’ono‘P’hosphate. of ‘c’apacit‘y’. cyclizine (pharmacology) An ANTIHIS- TAMINE drug which can be administered cyanide (chemistry) COMPOUND orally or by injection as an ANTINAUSEANT. containing the CYANIDE ION (CN-); a SALT of HYDROCYANIC ACID (HCN). cycloalkane (chemistry) Saturated CYCLIC All cyanides are highly poisonous. HYDROCARBON whose MOLECULE has a ring of CARBON atoms, GENERAL cyanobacteria (microbiology) An FORMULA CnH2n; e.g. cyclohexane, C6H12. alternative term for the CYANOPHYTA. cyclophosphamide (pharmacology) A cyanoferrate (chemistry) See FERRI- cytotoxic drug that acts by interfering CYANIDE; FERROCYANIDE. with DNA and so preventing CELL replication. It is used as an ANTICANCER cyanogen (chemistry) NCCN Colourless AGENT and also has uses as an immuno- (USA: colorless) highly poisonous GAS suppressant. made by the ACTION of acids on cyanides. cyclosporin (pharmacology) An immuno- Cyanophyta (microbiology) DIVISION suppressant drug that can be adminis- of single-celled, photosynthetic, tered orally or by INTRAVENOUS infusion PROKARYOTIC organisms. Cyanophytes to limit tissue rejection during and sometimes join together in colonies, following organ transplant surgery. and are most commonly found in WATER. Also termed: BLUE-GREEN ALGAE; cyclopenthiazide (pharmacology) A CYANOBACTERIA; Cyanophyceae. DIURETIC of the THIAZIDE class which can be administered orally as a cycle (physics) One of a repeating SERIES hypertensive, and in the treatment of of similar changes, e.g. in a WAVE OEDEMA (USA: edema). motion or vibration. One CYCLE is equal to the PERIOD of the motion; the number cyproterone acetate (pharmacology) of cycles per UNIT time is its FREQUENCY. A sex HORMONE anAGONIST that A FREQUENCY of 1 CYCLE per second=1 reduces the effects of ANDROGENS hertz. that is administered as an ANTICANCER treatment for cancer of the prostate gland.

100 CYSTEINE CYTOSOL

cysteine (biochemistry) HSCH2CH(NH2)- cytochrome oxidase stain (histology) COOH AMINO ACID found in proteins. ENZYME histochemical staining technique. cystic fibrosis (medical/genetics) A cytochrome P450 (biochemistry) See hereditary disease in which a thick P450. MUCUS is produced that obstructs intestinal GLANDS, PANCREAS and cytogenetics (genetics) The scientific bronchi. Severe respiratory infections study of the number, BEHAVIOUR (USA: are a common complication. The GENE behavior) and MORPHOLOGY of chromo- responsible was known by the early somes as a means of understanding 1980s to be situated on CHROMOSOME the genetics of an organism. 7, and was found, isolated and cloned in 1989. It differs from the equivalent cytokines (immunology) Substances, NORMAL GENE in having a deletion usually peptides or proteins, that act of three BASE-pairs (i.e. one codon) as GROWTH factors, i.e. affect the so that one AMINO ACID is missing GROWTH, DIVISION or differentiation from the GENE PRODUCT. The fact of CELLS. Examples include INTERFERON that the GENE has been identified means and PLATELET derived GROWTH FACTOR. that in most cases carriers of the GENE can now be identified, and prenatal cytology (medical) The study of living diagnosis carried out. CELLS, their ORIGIN, structure, FUNCTION and PATHOLOGY. cystine (biochemistry) (SCH2CH(NH2)-

COOH)2 Dimeric form of the AMINO cytomegalovirus (CMV) (virology) One ACID CYSTEINE, found in KERATIN. of a GROUP of highly HOST-specific HERPES VIRUSES that affect humans cystinuria (biochemistry) The abnormal and other animals. They generally produce presence in the urine of the amino mild flu-like symptoms but infections acid cystine, usually as a result of an can be more severe and in the inherited kidney tubule defect that allows immunosuppressed it may cause some amino acids to pass into the pneumonia. urine from the blood. cytoplasm (cytology) PROTOPLASM cytochrome (biochemistry) RESPIRATORY of a CELL other than that of the NUCLEUS. PIGMENT found in organisms that use AEROBIC RESPIRATION. cytosine (biochemistry) Colourless (USA: colorless) CRYSTALLINE COMPOUND, cytochrome b (biochemistry) A micro- derived from PYRIMIDINE. It is a major somal CYTOCHROME involved in such constituent of DNA and RNA. Also termed: metabolic activities as FATTY ACID 4-amino-2(H)-pyrimidinone. desaturation. cytosol (histology/cytology) A watery cytochrome c (biochemistry) A respira- material remaining when all the organelles tory chain enzyme having the same and membranes have been removed prosthetic group as haemoglobin (USA: from an homogenate of CELLS by hemoglobin). centrifugation.

101 CYTOTOXIC CZI cytotoxic (1 toxicology; 2 pharmacology) 1 Poisonous to CELLS. 2 Describing a drug that destroys or prevents the replication of CELLS, used in CHEMOTHERAPY to treat CANCER.

CZI (physiology/biochemistry) An abbreviation of ‘C’rystalline ‘Z’inc ‘I’nsulin.

102 D

D (1 chemistry; 2 biochemistry) 1 dalton (measurement) An alternative CHEMICAL SYMBOL for DEUTERIUM. term for ATOMIC MASS UNIT. 2 Symbol for aspartic acid. Dalton’s atomic theory (physics) Theory d (1 measurement; 2 physics; 3 medical; that states that MATTER consists of tiny 4 general terminology) 1 An abbreviation particles (atoms), and that all the atoms of prefix ‘d’eci, 10-1. 2 An abbreviation of a particular ELEMENT are exactly alike, of ‘d’euteron. 3 An abbreviation of ‘d’ied. but different from the atoms of other 4 An abbreviation of ‘d’ay. elements in BEHAVIOUR (USA: behavior) and MASS. The theory also states that D- (biochemistry) A symbol for the chemical ACTION takes place as a result geometric isomer Of L- form of chemical of attraction between atoms, but it fails compound. to account satisfactorily for the VOLUME relationships that exist between combining Da (chemistry) CHEMICAL SYMBOL gases. It was proposed by the British for davyum. scientist John Dalton (1766–1844). da (measurement) Prefix m eaning 10, Dalton’s law of partial pressures used with units of measurement. Also (physics) In a MIXTURE of gases, the termed deca. PRESSURE exerted by one of the COMPONENT gases is the same as dB (measurement) An abbreviation of if it alone occupied the total VOLUME. ‘d’eci‘B’el.

DBP (physiology/biochemistry) An damping (physics) REDUCTION in the abbreviation of ‘Vitamin ‘D’-‘B’inding AMPLITUDE of a waveform or oscillation. ‘P’rotein. danazol (pharmacology) A HORMONE dc (physics) An abbreviation of ‘d’irect ANTAGONIST which acts as an antioestro- ‘c’urrent. gen and antiprogesterone drug, that has weak ANDROGEN activity. It can dacryo (medical) Prefix denoting tears be administered orally to inhibit the release or the lacrimal system. of pituitary HORMONES, gonadotrophins, to treat a variety of conditions including DAG (biochemistry) An abbreviation endometriosis and menstrual disorders. of ‘D’i‘A’cyl‘G’lycerol. dander (immunology) Small scales of dag (measurement) An abbreviation ANIMAL SKIN, HAIR or feathers. DANDER of ‘d’ek‘ag’ram (10 grams). Also termed commonly cause allergic effects, espe- decagram. cially asthma.

103 DANIELL CELL DC

Daniell cell (physics) ELECTROLYTIC data base (1,2 computing) 1 Organized CELL that consists of a ZINC HALF- collection of DATA that is held on a CELL and a COPPER HALF-CELL, usually COMPUTER, where it is regularly updated arranged as a ZINC CATHODE and a and can easily be accessed (often by COPPER ANODE dipping into an many users). Also termed: DATA BANK. ELECTROLYTE of DILUTE SULPHURIC 2 APPLICATIONS PROGRAM that controls ACID (USA: sulfuric acid). and makes use of a DATA BASE.

DAP&E (education) An abbreviation data base management system (DBMS) of ‘D’iploma in ‘A’pplied ‘P’arasitology (computing) COMPUTER SOFTWARE and ‘E’ntomology. designed to establish and maintain a DATA BASE. Daphnia magna (toxicology) A standard INVERTEBRATE used for aquatic toxicology data processing (DP) (computing) The tests. The common name is ‘water flea’. process of inputting, storing, and manipulating large amounts of information, DApp.Sc. (education) An abbreviation using a COMPUTER. of ‘D’octor of ‘App’lied ‘Sc’ience. data transmission (computing) Transfer daraf (measurement) UNIT of the of DATA between outstations and a elastance of an electrical COMPONENT. central COMPUTER or between different It is the RECIPROCAL of CAPACITANCE COMPUTER systems. (the word is farad backwards). dative bond (chemistry) An alternative darwin (measurement/genetics) A UNIT term for a CO-ORDINATE BOND. of evolutionary change. A darwin is equal to a change, increase or decrease, daughter cell (cytology) One of the in any one CHARACTER by a FACTOR two CELLS produced when a CELL of 2.7 per million years. As this is a divides, e.g. as a result of MITOSIS. very fast rate of change, most evolutionary change is expressed in millidarwins. daughter nucleus (cytology) One of the two nuclei produced when the Darwinism (biology) Theory of EVOLUTION NUCLEUS of a CELL divides. which states that living organisms arise in their different forms by gradual change db (measurement) An abbreviation of over many generations, and that this ‘d’eci‘b’el. Also termed dB. process is governed by NATURAL SELECTION. It was proposed by the British dB (measurement) See db. naturalist Charles Darwin (1809–82). dbl (general terminology) An abbreviation data (statistics) Collection of information, of ‘d’ou‘bl’e. often referring to results of a statistical study or to information supplied to, DBMS (computing) An abbreviation of processed by or provided by a ‘D’ata ‘B’ase ‘M’anagement ‘S’ystem. COMPUTER. The plural of ‘datum’. DC (physics) An abbreviation of ‘D’irect data bank (computing) An alternative ‘C’urrent. Also termed: d.c. term for a DATA BASE.

104 D & C DECAY

D & C (medical) An abbreviation of DEAS (biochemistry) An abbreviation ‘D’ilatation ‘and’ ‘C’urettage. of ‘D’ehydro‘E’pi‘A’ndrosterone ‘S’ulphate (USA: Dehydroepiandrosterone sulfate). DCI. Sc. (education) An abbreviation of ‘D’octor of ‘Cl’inical ‘Sc’ience. debug (computing) To remove a fault in a COMPUTER PROGRAM; hence, dcm (measurement) An abbreviation by analogy, to correct any form of fault. of ‘d’e‘c’a‘m’etre (USA: decameter). Debye-Hückel theory (physics) Theory DCP (education) An abbreviation of that explains variations from the ideal ‘D’iploma of ‘C’linical ‘P’athology. BEHAVIOUR (USA: behavior) of electrolytes in terms of interionic attraction, DCPath. (education) An abbreviation and assumes that electrolytes in of ‘D’iploma of the ‘C’ollege of SOLUTION are completely dissociated ‘Path’ologists. into charged ions. It was named after the Dutch physicists Peter Debye (1884– DCSO (governing body) An abbreviation 1966) and Erich Hückel (1896–1980). of ‘D’eputy ‘C’hief ‘S’cientific ‘O’fficer. dec. (1 medical; 2 measurement) 1 DCTD (education) An abbreviation of An abbreviation of ‘dec’eased. 2 An ‘D’iploma in ‘C’hest and ‘T’uberculous abbreviation of ‘dec’imetre (USA: ‘D’iseases. decimeter). deca (measurement) Prefix meaning 10 times, used with units of DDAVP (biochemistry) An abbreviation measurement. Also termed da; deka. of 1- ‘D’eamino- 8- ‘D’- ‘A’rginine ‘V’aso- ‘P’ression. decalcification (1 biochemistry; 2 histology) 1 Loss of CALCIUM and DDR (education) An abbreviation of other MINERAL SALTS from the normally ‘D’iploma in ‘D’iagnostic ‘R’adiology. mineralized tissues, BONE and TEETH. 2 A histological LABORATORY technique. DEA (biochemistry) An abbreviation of ‘D’ehydro‘E’pi‘A’ndrosterone. decant (chemistry) Carefully pour away the LIQUID above a PRECIPITATE, dead (medical) Deceased. once it has settled. deaminase (biochemistry) ENZYME that decay (1 biology; 2 radiology) 1 Natural catalyses the removal of an AMINO GROUP breakdown of an organic substance;

(-NH2) from an organic MOLECULE. DECOMPOSITION. 2 Breakdown, through RADIOACTIVITY, of a deamination (biochemistry) Enzymatic RADIOACTIVE substance. The rate removal of an AMINO GROUP (-NH2) of such DECAY is typically an from a COMPOUND. The process is EXPONENTIAL FUNCTION. important in the breakdown of AMINO ACIDS in the LIVER and KIDNEY. See also HALF-LIFE. AMMONIA formed by DEAMINATION is converted to UREA and excreted.

105 DECEASED DEHYDRATING AGENT deceased (dec.) (medical) Pertaining defect (chemistry/crystallography) An to a person who has died. irregularity in the ordered arrangement of atoms, ions or electrons in a crystal. deci (measurement) Prefix meaning one- tenth, used with units of measurements. deficiency disease (medical/biochemistry) Disorder brought about by the lack of decibel (db or dB) (measurement) UNIT a certain food substance in the diet, used for comparing POWER levels (on e.g. a VITAMIN, mineral or AMINO ACID. a LOGARITHMIC SCALE); one-tenth of a BEL. It is commonly used in comparisons definite integral (mathematics) INTEGRAL of sound INTENSITY. that has exact limits.

See also BEL. deg. (measurement) An abbreviation of ‘deg’ree. decigram (dg) (measurement) One-tenth of a gram. deglutition (physiology) Another term for swallowing. decim. (measurement) An abbreviation of ‘decim’etre (USA: decimeter). degradation (1 chemistry; 2 physics) decimal system (mathematics) Number 1 The conversion of a MOLECULE into system that uses the BASE 10; i.e. it simpler components. 2 The irreversible uses the digits 1 to 9 and 0. loss of ENERGY available to do WORK.

See also BINARY NOTATION. degree (1, 2 measurement) 1 UNIT of difference in TEMPERATURE used in decimetre (dm; decim.) (measurement) TEMPERATURE SCALES. 2 UNIT derived One-tenth of a METRE (USA: meter). by dividing a circle into 360 segments, (USA: decimeter). used to measure angles and describe direction. It is subdivided into minutes decomposer (microbiology) Saprophytic and seconds (of ARC). Both types of organism that breaks down organic degrees have the symbol °. materials into simple molecules, e.g. FUNGI. degree of freedom (physics) One of several VARIABLE factors, e.g. TEM- decomposition (1 chemistry; 2 microbiol- PERATURE, PRESSURE and ogy) 1 Breaking down of a chemical CONCENTRATION, that must be made COMPOUND into its COMPONENT parts CONSTANT for the condition of a system (elements or simpler substances), often at EQUILIBRIUM to be defined. brought about by HEAT, LIGHT or ELECTROLYSIS. See also DOUBLE dehalogenation (biochemistry) The DECOMPOSITION. 2 Rotting of a dead process of removal of HALOGEN organism, often brought about by substituents from organic chemicals. BACTERIA or FUNGI. dehydrating agent (chemistry) An decubitus ulcers (medical) Bedsores, alternative term for a DESICCANT. ulcers caused by unduly sustained SKIN PRESSURE.

106 DEHYDRATION DENTAL FORMULA dehydration (1 chemistry; 2 medical) 1 of biological activity and a decrease in Elimination of WATER from a substance SOLUBILITY. or organism. 2 Lack of WATER in the body. dendrite (1 biology; 2 crystallography) dehydrogenase (biochemistry) An ENZYME 1 An elongated process from a NERVE that activates OXIDATION-REDUCTION CELL that projects it towards another REACTIONS by the removal of a pair of NERVE CELL. Also termed: DENDRON. HYDROGEN atoms from a MOLECULE. 2 A branching crystal, such as occurs in some rocks and minerals. deionization (chemistry) A method of purifying or otherwise altering the composition dendron (1 biology; 2 crystallography) of a SOLUTION using ION EXCHANGE. An alternative term for DENDRITE. deka (measurement) Prefix meaning 10, denitrification (microbiology) Process used with units of measurement. Also that occurs in organisms, e.g. BACTERIA termed da; deca. in soil, which breaks down NITRATES and nitrites, with the liberation of NITROGEN. deliquescence (chemistry) The gradual change undergone by certain substances denominator (mathematics) The lower that absorb WATER from the ATMOSPHERE number of a FRACTION (the upper number to become first damp and then AQUEOUS of the NUMERATOR); e.g. in the fractions SOLUTIONS. 2/3, 7/12 and 83/100, the denominators are 3, 12 and 100. deliquescent (chemistry) Describing a substance that exhibits DELIQUESCENCE. See also COMMON DENOMINATOR. delocalization (chemistry) Phenomenon dens. (physics) An abbreviation of that occurs in certain molecules, e.g. ‘dens’ity. BENZENE. Some of the electrons involved in bonding the atoms are not restricted density (1 physics; 2 statistics) 1 MASS to one particular BOND, but are free to of a UNIT VOLUME of a substance. move between two or more bonds. The For an OBJECT of MASS m and VOLUME electrical CONDUCTIVITY of metals is V, the DENSITY d is m/V. It is commonly due to the presence of delocalized electrons. expressed in units such as g cm3 (although the SI UNIT is kg m-3). 2 Number of See also AROMATICITY. items in a defined surface AREA (e.g. population DENSITY, CHARGE delta ray (physics) ELECTRON that is DENSITY). ejected from an ATOM when it is struck by a high-ENERGY PARTICLE. DEnt. (education) An abbreviation of ‘D’octor of ‘Ent’omology. demise (medical) Death. dent. (medical) An abbreviation of denature (chemistry) To unfold the structure ‘dent’al. of the POLYPEPTIDE chain of a PROTEIN by exposing it to TEMPERATURE or dental formula (anatomy) Notation that extremes of PH. This results in the loss shows the number of each kind of TOOTH

107 DENTINE DESICCATOR possessed by a mammal. The number of depolarization (physics/chemistry) TEETH in one side of the JAW is given, Removal or prevention of electrical with the number in the upper JAW before POLARITY or POLARIZATION. that in the lower JAW, and in the ORDER incisors, canines, premolars, molars; e.g. depression of freezing point (physics) the human FORMULA is 2/2 1/1 2/2 3/3. REDUCTION of the FREEZING POINT of a LIQUID when a SOLID is dissolved dentine (histology) Layer that occurs in it. At CONSTANT PRESSURE and under the ENAMEL of TEETH. It is similar for DILUTE solutions of a non-VOLATILE to BONE, but harder, and is perforated SOLVENT, the depression of the by thin extensions from TOOTH-forming FREEZING POINT is directly CELLS. proportional to the CONCENTRATION of the solutes. deoxyribonucleic acid (DNA) (molecular biology) NUCLEIC ACID that is usually derivative (1 chemistry; 2 mathematics) referred to by its abbreviation. The 1 A COMPOUND, usually organic, obtained long thread-like MOLECULE consists from another COMPOUND. 2 A COEFFICIENT of a double HELIX of polynucleotides representing the rate of change of one held together by HYDROGEN BONDS. quantity. DNA is found chiefly in chromosomes, and is the material that carries the dermal (medical) Pertaining to the SKIN. hereditary information of all living organisms (although most, but not all, dermatitis (medical) INFLAMMATION VIRUSES have only RIBONUCLEIC ACID, of the SKIN. RNA). dermis (histology) Layer of SKIN that deoxyribonucleotides (molecular is the innermost of the two main layers. biology) Compounds that are the It is composed of CONNECTIVE TISSUE FUNDAMENTAL UNITS of DNA. Each and contains BLOOD, LYMPH vessels, nuelcotide contains a nitrogenous BASE, sensory NERVES, HAIR follicles, SWEAT a PENTOSE SUGAR and phosphoric GLANDS and some MUSCLE CELLS. ACID. The four bases CHARACTERISTIC of DEOXYRIBONUCLEOTIDES are See also EPIDERMIS. ADENINE, GUANINE, CYTOSINE and THYMINE. DES (pharmacology) An abbreviation See also DEOXYRIBONUCLEIC ACID. of ‘D’i‘E’thyl‘S’tilbestrol. deoxyribose (biochemistry) The SUGAR desiccant (chemistry) Substance that that forms part of the structure of DNA. absorbs WATER and can therefore be used as a drying agent or to prevent dependence (1 medical; 2 statistics) DELIQUESCENCE (e.g. ANHYDROUS 1 A condition that is said to exist when CALCIUM CHLORIDE, SILICA GEL), equivalent or increasing doses of a often used in a DESICCATOR. Also drug are necessary to avoid termed: DEHYDRATING AGENT. WITHDRAWALSYMPTOMS. 2 Changes in one VARIABLE occurring systematically desiccator (laboratory equipment) Appa- with changes in another. ratus used for drying substances or preventing

108 DESK TOP PUBLISHING DEXTROROTATORY

DELIQUESCENCE, e.g. a closed GLASS deuterium D2 (chemistry) One of the VESSEL containing a DESICCANT. three isotopes of HYDROGEN, having one NEUTRON and one PROTON in desk top publishing (DTP) (computing) its NUCLEUS. R.a.m. 2.0141. Also termed: Technique that uses a microcomputer heavy HYDROGEN. linked to a WORD PROCESSOR, with access to various type founts and See also TRITIUM. justification programs, and a LASER

PRINTER to produce multiple copies deuterium oxide (chemistry) D2O of a document that rivals conventional Chemical name of heavy WATER. printing in quality. The addition of a SCANNER allows the introduction of deuteron (chemistry) Positively charged graphics or illustra-tions. PARTICLE that is composed of one NEUTRON and one PROTON; it is the desorption (1, 2 chemistry) 1 Reverse NUCLEUS of a DEUTERIUM ATOM. process to ADSORPTION. 2 Removal of an adsorbate from an ADSORBENT deviation (mathematics) The amount in CHROMATOGRAPHY. by which one value in a SET of values differs from the ARITHMETIC MEAN. detergent (chemistry) SURFACTANT that is used as a cleaning agent. Detergents See also STANDARD DEVIATION. are particularly useful for cleaning because they lower SURFACE TENSION and emulsify devitrification (optics) Loss of transpar- FATS AND OILS (allowing them to go ency, e.g. in GLASS, caused by into SOLUTION with WATER without forming CRYSTALLIZATION. a scum with any of the substances that cause HARDNESS OF WATER). Soaps dexamethasone (pharmacology) A act in a similar way, but form an INSOLUBLE corticosteroid and ANTI-INFLAMMATORY scum in hard WATER. drug that, administered orally, topically or by injection, can be used for a variety determinant (1 immunology; 2 biology; of purposes including the suppression 3 mathematics) 1 Region or regions of of allergic and inflammatory conditions. an ANTIGEN MOLECULE required for its recognition (binding) by a PARTICLE dextrin (chemistry) POLYSACCHARIDE or ANTIBODY. The selective nature of of INTERMEDIATE chain length produced this molecular INTERACTION confers from the ACTION of AMYLASES on STARCH. specificity on the immune REACTION of the ANTIBODY-producer. 2 FACTOR dextromoethorphan hydrobromide (phar- that transmits inherited characteristics, macology) A drug that is used to suppress e.g. a GENE. 3 Quantity obtained by coughing which is used in a variety of adding products of elements of a square linctuses and syrups. MATRIX according to certain rules. dextronic acid (chemistry) An alternative deuterated compound (chemistry) Sub- term for gluconic ACID. stance in which ordinary HYDROGEN has been replaced by DEUTERIUM. dextrorotatory (chemistry) Describing an OPTICALLY ACTIVE COMPOUND that

109 DEXTROSE DIAMORPHINE HYDROCHLORIDE causes the plane of POLARIZED LIGHT impaired sensitivity to the actions of to rotate in a clockwise direction. It is insulin. indicated by the prefix (+)- or d-. diag. (1 medical; 2, 3 general terminology) dextrose (chemistry) An alternative term 1 An abbreviation of ‘diag’nose. 2 An for GLUCOSE. abbreviation of ‘diag’onal. 3 An abbreviation of ‘diag’ram. df (statistics) An abbreviation for ‘d’egrees of ‘f’reedom. diakinesis (cytology) PHASE of CELL DIVISION that occurs at the final stage DFP (biochemistry) An abbreviation of PROPHASE of the first DIVISION of ‘D’iisopropyl ‘F’luoro‘P’hosphate. in MEIOSIS. During this PHASE the chromosomes become short and thick, dg (measurement) An abbreviation of forming more chiasmata, the nucleoli ‘d’eci‘g’ram. and NUCLEAR MEMBRANE disappear, and the spindle appears for the process DHEW (governing body) An abbreviation of DIVISION, of ‘D’epartment of ‘H’ealth, ‘E’ducation and ‘W’elfare. Dial. (chemistry/pharmacology) An abbreviation of ‘dial’lyl-BARBITURIC ACID. DHHS (governing body) An abbreviation of ‘D’epartment of ‘H’ealth and ‘H’uman dialysed iron (chemistry) Colloidal ‘S’ervices. SOLUTION of IRON(III) HYDROXIDE,

Fe(OH)3. It is a red LIQUID, used in medicine. DHP (education) An abbreviation of ‘D’iplome en ‘H’ygiene ‘P’ublique. dialysis (biochemistry) Separation of [French, meaning ‘Diploma in Public colloids from crystalloids using selective Health’.] DIFFUSION through a SEMIPERMEABLE MEMBRANE. It is the process by which DHS (education) An abbreviation of globular proteins can be separated ‘D’octor of ‘H’ealth ‘S’ciences. from low-MOLECULAR WEIGHT solutes, as in filtering (‘purifying’) BLOOD in DHT (biochemistry) An abbreviation an artificial KIDNEY machine: the of ‘D’i‘H’ydro‘T’estosterone. MEMBRANE retains PROTEIN molecules and allows small SOLUTE molecules diabetes (medical/biochemistry) See and WATER to pass through. DIABETES MELLITUS. diam. (measurement) An abbreviation diabetes mellitus (medical/biochemistry) of ‘diam’eter. Also termed dia. A disease in which the supply of insulin is insufficient for the body’s needs. diameter (dia. or diam.) (measurement) Type 1 diabetes results from destruction The length of a line segment intersecting of the insulin-producing cells in the the circle’s centre (USA: center) between pancreas by an auto-immune process two points on the circle. probably triggered by a virus infection. Type 2 diabetes is due to a relative diamorphine hydrochloride (pharmacol- insufficiency of INSULIN along with ogy) The chemical name of heroin

110 DIAPH. DICARBOXYLIC ACID hydrochloride which, administered orally orally, through suppositories or by or by injection, is a powerful, additive injection, as an ANXIOLYTIC, hypnotic, narcotic ANALGESIC. ANTICONVULSANT, sedative, skeletal muscle relaxant and ANTI-EPILEPTIC. It is diaph. (anatomy) An abbreviation of used in a variety of treatments including ‘diaph’ragm. the treatment of anxiety and epilepsy. diaphragm (1 anatomy; 2 medical) 1 diazo compound (chemistry) ORGANIC A sheet of MUSCLE present in mammals, COMPOUND that contains two adjacent located below the lungs attached to NITROGEN atoms, but only one attached the body wall at the sides and separating to a CARBON ATOM. Formed by the THORAX from the ABDOMEN. During DIAZOTIZATION, DIAZO COMPOUNDS are RESPIRATION it forms an important very important in SYNTHESIS, being the part of the mechanism for filling and starting point of various dyes and drugs. expelling AIR from the lungs. 2 A birth- control device fitted over the entrance diazonium compound (chemistry) An to the UTERUS to prevent the entry ORGANIC COMPOUND of the type RN2+X, of SPERM. Also termed: Dutch cap. where R is an ARYL GROUP. The compounds are colourless (USA: colorless) solids, extremely diarrhoea (medical) The result of too SOLUBLE in WATER, used for making AZO rapid a transit of the BOWEL contents DYES. Many of them (particularly the NITRATES) so that there is insufficient time for are explosive in the SOLID state. reabsorption of water from the FAECES (USA: FECES). Consequently, the stools diazotization (chemistry) Formation of are loose, liquid and are passed more a DIAZO COMPOUND by the INTERACTION frequently than normal. (USA: diarrhea). of SODIUM NITRITE, an inORGANIC ACID, and a primary aromatic AMINE at diastase (biochemistry) An alternative low temperatures. term for AMYLASE. dibasic (chemistry) Describing an ACID diastole (physiology) PHASE of the that contains two replaceable HYDROGEN HEARTBEAT in which the HEART atoms in its molecules, e.g. CARBONIC undergoes relaxation and refills with ACID, H2CO3, SULPHURIC ACID (USA:

BLOOD from the veins. The term also sulfuric acid), H2SO4. A DIBASIC ACID applies to a CONTRACTILE VACUOLE can form two types of salts: a NORMAL in a CELL when it refills with FLUID. SALT, in which both HYDROGEN atoms are replaced by a METAL or its equivalent

See also SYSTOLE. (e.g. SODIUM CARBONATE, Na2CO3), and an acidic SALT, in which only one diatomic (chemistry) Describing a HYDROGEN ATOM is replaced, e.g. SODIUM MOLECULE that is composed of two HYDROGENSULPHATE (USA: sodium identical atoms, e.g. O2, H2 and CI2. hydrogen sulfate) (BISULPHATE[USA:

bisulfate]), NaHSO4. See also ATOMICITY. dicarboxylic acid (chemistry) ORGANIC diazepam (pharmacology) A benzodiaze- ACID that contains two CARBOXYL GROUPS. pine drug which can be administered

111 DICHROISM DIFFUSION PUMP dichroism (chemistry) Property of some change, slopes of curves, maximum substances that makes them transmit and minimum values, etc. some colours (USA: colors) and reflect others, or which DISPLAY certain colours differentiation (mathematics) Method when viewed from one angle and different used in CALCULUS to determine the colours when viewed from another. DERIVATIVE f’ of a FUNCTION f. If f’ (x)= Axn, f’(x)=nAxn-1. dichromate (chemistry) SALT containing 2- the DICHROMATE(VI) ION (Cr2O7 ), an diffraction (physics) Bending of the OXIDIZING AGENT; e.g. POTASSIUM path of a beam (e.g. of LIGHT or electrons)

DICHROMATE, K2Cr2O7. Also termed: at the edge of an OBJECT. BICHROMATE. diffraction grating (optics) Optical device diclofenac sodium (pharmacology) A that is used for producing spectra. It non-steroidal ANTI-INFLAMMATORY drug consists of a sheet of GLASS or plastic (NSAID) which, administered orally, marked with closely spaced parallel lines topically as suppositories or by injection, (as many as 10,000 per centimetre). The is used as a non-narcotic ANALGESIC spectra are produced by a COMBINATION and ANTIRHEUMATIC to treat pain and of DIFFRACTION and INTERFERENCE. inflammation in rheumatic disease and other musculoskeletal conditions. diffusion (chemistry) The process by which a gas or a substance in solution dielectric constant (physics) An expands, because of the motion of its alternative term for RELATIVE PERMITTIVITY. particles, to fill all of the available volume. Contrast ACTIVE TRANSPORT. dielectric (physics) Nonconductor of ELECTRICITY in which an ELECTRIC FIELD diffusion of gases (chemistry) Phenome- persists in the presence of an inducing non by which gases mix together, reducing FIELD (but opposes it). A DIELECTRIC any CONCENTRATION GRADIENT to is the insulating material in a CAPACITOR. zero. e.g. in GAS EXCHANGE between plant leaves and AIR. dielectric strength (physics) Property of an INSULATOR that enables it to withstand See also ACTIVE TRANSPORT. electric STRESS without breaking down. diffusion of light (physics) Spreading dielectrophoresis (physics) Movement or SCATTERING OF LIGHT. of electrically polarized particles in a VARIABLE ELECTRIC FIELD. diffusion of solutions (chemistry) Free movement of molecules or ions of a 1,1-diethoxyethane (chemistry) An dissolved substance through a SOLVENT, alternative term for acetal. resulting in complete mixing. differential calculus (mathematics) See also OSMOSIS. Branch of mathematics that deals with continuously varying quantities. It uses diffusion pump (laboratory equipment) differentiation for calculating rates of Apparatus used to produce a high VACUUM. The PUMP employs MERCURY or oil at

112 DIFLUNISAL DILATE low VAPOUR PRESSURE which carries digital/analog converter (computing) along in its flow molecules of a GAS from Device that converts digital signals into a low PRESSURE established by a backing continuously VARIABLE electrical signals PUMP. Also termed: CONDENSATION PUMP; for use by an ANALOG COMPUTER. VACUUM PUMP. digitoxin (pharmacology) A cardiac diflunisal (pharmacology) A non-steroidal glycoside derived from the leaf of the ANTI-INFLAMMATORY drug (NSAID) which, Digitalis foxglove, which administered administered orally, is used as a non- orally acts as a cardiac stimulant narcotic ANALGESIC and ANTIRHEUMATIC increasing the force of contraction of to treat pain and inflammation in rheumatic the HEART in congestive HEART disease and other musculoskeletal FAILURE, and as an ANTI-ARRHYTHMIC. conditions. digoxin (pharmacology) A cardiac di-form (chemistry) Term indicating that glycoside, similar to DIGITOXIN, derived a MIXTURE contains the DEXTROROTATORY from the leaf of the Digitalis foxglove, and the LAEVOROTATORY forms of an which administered orally or by injection OPTICALLY ACTIVE COMPOUND in equal acts as a cardiac stimulant increasing molecular proportions. the force of contraction of the HEART in congestive HEART FAILURE, and digestion (physiology) Breakdown of as an ANTI-ARRHYTHMIC. complex substances in food by ENZYMES dihydrate (chemistry) Chemical (a in the ALIMENTARY CANAL to produce HYDRATE) whose molecules have two simpler SOLUBLE compounds, which pass associated molecules of WATER OF into the body by ABSORPTION and CRYSTALLIZATION; e.g. SODIUM ASSIMILATION. Ultimately carbohydrates DICHROMATE, Na Cr O .2H O. (e.g. STARCH, SUGAR) are broken down 2 2 7 2 to GLUCOSE, proteins to AMINO ACIDS, 2,3-dihydroxybutanedioic acid (chemis- and fats to FATTY ACIDS and GLYCEROL. try) An alternative term for TARTARIC ACID. digit (1 mathematics/computing; 2 Dihydroxyphenylalanine (dopa) (pharma- anatomy) 1 A single NUMERAL; an cology) AMINO ACID DERIVATIVE that INTEGER under 10.2 A finger or toe. is a PRECURSOR in the SYNTHESIS of DOPAMINE and has laevorotation digital computer (computing) COMPUTER (L-DOPA). Found particularly in the that operates on DATA supplied and ADRENAL GLAND and in some types stored in digital or number form. of beans, it is used in the TREATMENT of PARKINSON’S DISEASE. digital display (equipment) DISPLAY that shows readings of a measuring machine, dihydroxypurine (chemistry) An alterna- clock, etc. by displaying NUMERALS. tive term for XANTHINE. digitalis (pharmacology) Potent ALKALOID dihydroxysuccinic acid (chemistry) that is extracted from plants of the An alternative term for TARTARIC ACID. GENUS DIGITALIS (foxgloves). It is used in medicine as a HEART stimulant. dilate (physiology) To widen; to produce DILATION.

113 DILATION DIOXAN dilation (physiology) The widening or dimethylbenzene (chemistry) An expansion of an ORGAN, opening, passage alternative term for XYLENE. or VESSEL. An alternative term: dilatation.

dinitrogen oxide N2O (chemistry/medical) diltiazem hydrochloride (pharmacology) Colourless (USA: colorless) GAS made A calcium-channel blocker drug used by heating AMMONIUM NITRATE and as an orally administered ANTI-ANGINA used as an ANAESTHETIC (USA: anesthetic). drug in the prevention of attacks and Also termed: NITROGEN OXIDE; NITROUS as an ANTIHYPERTENSIVE treatment. OXIDE; dental GAS; laughing GAS. diluent (chemistry) SOLVENT used to dinoprostone (pharmacology) The reduce the strength of a SOLUTION. prostaglandin E2, which administered orally, topically as pessaries or by injection dilute (1,2 chemistry) 1 To reduce the causes contractions in the muscular strength of a SOLUTION by adding WATER walls of the uterus. It can be used to or other SOLVENT. 2 Describing a induce labour or to assist in termination SOLUTION in which the amount of SOLUTE of PREGNANCY. is small compared to that of the SOLVENT. diode (1, 2 physics) 1 ELECTRON dilution (chemistry) Process that involves TUBE (VALVE) containing two electrodes, the lowering of CONCENTRATION. an ANODE and a CATHODE. 2 RECTIFIER made up of a semiconducting dim. (general terminology) An abbrevia- crystal with two terminals. tion of ‘dim’ension. diol (chemistry) ORGANIC COMPOUND dimenhydrinate (pharmacology) An containing two HYDROXYL GROUPS and

ANTIHISTAMINE drug which can be having the GENERAL FORMULA CnH2n(OH)2. administered orally as an ANTINAUSEANT Diols are thick liquids or CRYSTALLINE in the treatment of nausea, motion sickness solids, and some have a sweet TASTE. etc. ETHANE-1,2-DIOL (ETHYLENE GLYCOL) is the simplest DIOL, widely used as a dimension (mathematics) POWER to SOLVENT and as an antifreeze agent. which a fundamental UNIT is raised Also termed: dihydric ALCOHOL; GLYCOL. in a derived UNIT; e.g. ACCELERATION has the dimensions [LT-2], i.e.+1 for dioptre (measurement) UNIT that is length and–2 for time, equivalent to used to express the POWER of a LENS. length divided by the square of time. It is the RECIPROCAL of the FOCAL LENGTH of the LENS in metres. The dimensional analysis (mathematics) POWER of a convergent LENS with a Prediction of the relationship of quantities. FOCAL LENGTH of one METRE is said If an equation is correct the dimensions to be+1 dioptre. The POWER of a divergent of the quantities on each side must LENS is given a negative value. be identical. It is an important way of checking the VALIDITY of an equation. dioxan (chemistry) (CH2)2O2 Colourless (USA: colorless) LIQUID CYCLIC ETHER. dimer (chemistry) Chemical formed from It is INERT to many reagents and frequently two similar MONOMER molecules. used in mixtures with WATER to increase

114 DIOXIN DISAB. the SOLUBILITY of ORGANIC COMPOUNDS of chromatids begin to separate from such as ALKYL HALIDES. Also termed: the TETRAD formed by the association 1,4-DIOXAN. of HOMOLOGOUS CHROMOSOMES. Chiasmata can be seen at this stage. dioxin (chemistry) C12H 4CI4O2 BY- PRODUCT of organic SYNTHESIS (e.g. dipole (physics) Pair of equal and opposite of the disinfectant trichlorophenol) which ELECTRIC CHARGES at a (short) distance can cause allergic SKIN reactions. Also from each other. Some asymmetric termed: 2,3,7,8-tetrachlorodibenzo-p- molecules act as dipoles. DIOXIN. dipole moment (physics) PRODUCT dip. (education) An abbreviation of of one CHARGE of a DIPOLE and the ‘dip’loma. distance between the charges.

Dip. Pharm (education) An abbreviation dipso. (medical) An abbreviation of of ‘Dip’loma in ‘Pharm’acy. ‘dipso’maniac.

Dip.App.Sc. (education) An abbreviation dipyridamole (pharmacology) An anti- of ‘Dip’loma of ‘App’lied ‘Sc’ience. thrombotic drug administered orally or by injection that prevents blood- Dip.Bac. (education) An abbreviation clot formation, but does not have the of ‘Dip’loma in ‘Bac’teriology. usual action of an ANTICOAGULANT. It acts by preventing platelets sticking Dip.BMS (education) An abbreviation together or to surgically inserted objects of ‘Dip’loma in ‘B’asic ‘M’edical ‘S’ciences. such as tubes or valves. diphenhydramine hydrochloride (pharma- dir. (governing body) An abbreviation cology) An ANTIHISTAMINE drug which of ‘dir’ector. can be administered orally for the symptomatic relief of allergic symptoms direct current (d.c.) (physics) ELECTRIC and as a sedative for relief of occassional CURRENT that always flows in the same insomnia. direction (as opposed to ALTERNATING CURRENT). Also termed: DC. diphenoxylate hydrochloride (pharmacology) An opiod anti-diarrhoeal (USA: anti- direct dye (chemistry) Dye that does diarrheal) drug used to treat chronic not require a mordant. DIARRHOEA (USA: diarrhea). director (dir.) (governing body) The diploid (genetics) In a CELL or organism, HEAD of a department or institution. describing the existence of chromosomes in HOMOLOGOUS pairs, i.e. twice the dis. (medical) An abbreviation of HAPLOID number (2n). Apart from gametes, ‘dis’CHARGE. Also termed disch. it is CHARACTERISTIC of all ANIMAL CELLS. disab. (medical) An abbreviation of ‘disab’ility. Also termed disabl. diplotene (genetics) In MEIOSIS, the stage in late PROPHASE when the pairs

115 DISACCHARIDE DISSOCIATION disaccharide (chemistry) One of the CLASS dislocation (crystallography) Imperfection of common sugars, including LACTOSE in a CRYSTAL LATTICE. and SUCROSE, that can be broken down by HYDROLYSIS, under the ACTION of disodium oxide (chemistry) An alternative ENZYMES, to yield two monosaccharides. term for SODIUM monoxide. disch. (medical) See dis. disodium tetraborate (chemistry) An alternative term for BORAX. discharge (1,2 physics) 1 High-VOLTAGE ‘spark’ (CURRENT flow) between points disp. (pharmacology) An abbreviation of large POTENTIAL difference (e.g. of ‘disp’ensary. lightning); 2 Removal of the CHARGE between the plates of a CAPACITOR dispensary (pharmacology) A department by allowing CURRENT to flow out of it; of a hospital or clinic supplying drugs 3 Removal of ENERGY from an and other medical supplies on demand. ELECTROLYTIC CELL (BATTERY or ACCUMULATOR) by allowing CURRENT dispersion (physics) Splitting of an to flow out of it. 4. In ELECTROCHEMISTRY, ELECTROMAGNETIC RADIATION (e.g. the process by which ions are converted VISIBLE LIGHT) into its COMPONENT to NEUTRAL atoms at an ELECTRODE wavelengths when it passes through a during ELECTROLYSIS (by GAIN or loss medium (because different wavelengths of electrons). undergo different degrees of DIFFRACTION or REFRACTION). discriminant (mathematics) Quantity b2–4ac, derived from the coefficients displacement (mathematics) Position of a QUADRATIC EQUATION of GENERAL of one point relative to another, including FORMULA ax2+bx+c=0. both the distance between the two points and the direction of the first disintegration (radiology) Break-up of point from the second point. an atomic NUCLEUS either through bombardment by SUBATOMIC PARTICLES displacement reaction (chemistry) An or through RADIOACTIVE DECAY. alternative term for SUBSTITUTION REACTION. disintegration constant (radiology) Probability of a RADIOACTIVE DECAY display (equipment) Short name for of an atomic NUCLEUS per UNIT time. a LIQUID-CRYSTAL DISPLAY (LCD) Also termed: DECAY CONSTANT; or a visual DISPLAY UNIT (VDU). TRANSFORMATION CONSTANT. dissociation constant (chemistry) EQUILIB- disk (computing) Magnetic disc used RIUM CONSTANT of a DISSOCIATION to RECORD DATA in computers. REACTION, and therefore a measure of the AFFINITY of atoms or molecules See also FLOPPY DISK, HARD DISK. in a COMPOUND. diskette (computing) An alternative dissociation (chemistry) The temporary term for a FLOPPY DISK. reversible chemical DECOMPOSITION of a substance into its COMPONENT atoms

116 DISTILLATE DIVISION

or molecules, which often take the form dithionous acid (chemistry) H2S 2O 4 of ions, e.g. it occurs when most ionic Strong but unstable ACID that is found compounds dissolve in WATER. only in SOLUTION. distillate (chemistry) Condensed LIQUID diuresis (pharmacology) An unusually obtained by DISTILLATION. or abnormally large output of URINE. distillation (chemistry) Method for diuretics (pharmacology) Drugs used to purification or separation of liquids by reduce fluid in the body by increasing heating to the BOILING POINT, condensing the excretion of water and mineral salts the VAPOUR, and collecting the DISTILLATE. by the KIDNEY, so increasing URINE Formerly, the method was used to produce production. DIURETICS are divided into DISTILLED WATER for chemical experiments a number of distinct classes in relation and processes that required WATER to to their specific actions and uses: OSMOTIC be much purer than that in the mains DIURETICS, LOOP DIURETICS, WATER supply. In this application POTASSIUM-SPARING DIURETICS, DISTILLATION has been largely superseded CARBONIC ANHYDRASE INHIBITORS, by ION EXCHANGE. ALDOSTERONE ANTAGONISTS and THIAZIDE and THIAZIDE-LIKE DIURETICS. distilled water (chemistry) See DISTILLATION. diurnal (physiology/pharmacology) Pertaining to a day, in the sense of distortion (physics) Change from the occurring every 24 hours. ideal shape of an OBJECT or IMAGE, or in the form of a WAVE pattern (e.g. divalent (chemistry) Capable of combining an electrical signal). with two atoms of HYDROGEN or their equivalent. Also termed: BIVALENT. disulphuric acid (chemistry) An alternative term for oleum. (USA: disulfuric acid). diverging lens (optics) LENS that spreads out a beam of LIGHT passing through DIT (biochemistry) An abbreviation of it, often a CONCAVE LENS. ‘D’i‘I’odo‘T’yrosine. dividend (mathematics) Number to be dithionate (chemistry) SALT derived divided by another one (the DIVISOR). from DITHIONIC ACID (H2S 2O 6). Also The result of the DIVISION is the QUOTIENT. termed: hyposulphate (USA: hyposulfate). division (1,2 biology; 3 mathematics) dithionic acid (chemistry) H2S2O6 STRONG 1 In biological CLASSIFICATION, one ACID that decomposes slowly in of the major groups into which the plant concentrated solutions and when heated. KINGDOM is divided. The members of Also termed: HYPOSULPHURIC ACID the GROUP, although often quite different (USA: hyposulfuric acid). in form and structure, share certain common features, e.g. bryophytes include the dithionite (chemistry) Name that is given mosses and liverworts. Divisions are to any of the salts of DITHIONOUS ACID, divided into classes, often with an all of which are strong REDUCING AGENTS. INTERMEDIATE subdivision. The equivalent of a DIVISION in the ANIMAL KINGDOM

117 DIVISOR DOBUTAMINE HYDROCHLORIDE is a PHYLUM. 2 In biology, the formation DMS (1 computing; 2 education; 3 of a pair of DAUGHTER CELLS from a chemistry) 1 An abbreviation of ‘D’ata parent CELL. See CELL DIVISION. 3 ‘M’anagement ‘S’ystem. 2 An abbreviation In mathematics, the inverse of multiplication, of ‘D’octor of ‘M’edical ‘S’cience. 3 An in which a DIVIDEND is divided by a abbreviation of ‘D’ocumentation of DIVISOR to give a QUOTIENT. ‘M’olecular ‘S’pectroscopy. divisor (mathematics) Number that is DMSO (chemistry) An abbreviation of divided into another one (the DIVIDEND). ‘D’i‘M’ETHYL ‘S’ulph‘O’xide (USA: The result of the DIVISION is the QUOTIENT. dimethyl sulfoxide).

D-lines (physics) Pair of CHARACTERISTIC DMT (biochemistry) An abbreviation lines in the yellow region of the SPECTRUM of N,N-‘D’i‘M’ethyl‘T’ryptamine. of SODIUM, used as standards in SPECTROSCOPY. DNA (molecular biology) An abbreviation of ‘D’eoxyribo‘N’ucleic ‘A’cid. dm (measurement) An abbreviation of ‘d’eci‘m’etre (USA: decimeter). DNA hybridization (molecular biology) Technique in which DNA from one DMed. (education) An abbreviation of SPECIES is induced to undergo base ‘D’octor of ‘Med’icine. pairing with DNA or RNA from another SPECIES to produce a HYBRID DNA dmg. (general terminology) An abbrevia- (a process known as ANNEALING). tion of ‘d’a‘m’a‘g’e. D/N ratio (physiology/biochemistry) An DMLT (education) An abbreviation of abbreviation of ‘D’extrose to ‘N’itrogen ‘D’iploma in ‘M’edical ‘L’aboratory ‘ratio’ in the URINE. ‘T’echnology.

D2O (biochemistry) Symbol for Deuterium DMPB (education) An abbreviation of oxide (heavy water). ‘D’iploma in ‘M’edical ‘P’athology and ‘B’acteriology. DOA (1 medical; 2 chemistry) 1 An abbreviation of ‘D’ead ‘O’n ‘A’rrival. DMR (education) An abbreviation of 2 An abbreviation of ‘D’issolved ‘O’xygen ‘D’iploma in ‘M’edical ‘R’adiology; ‘A’nalyser. ‘D’iploma in ‘M’edical ‘R’adiodiagnostics. dob (statistics) An abbreviation of ‘d’ate DMR(T) (education) An abbreviation ‘o’f ‘b’irth. of ‘D’iploma in ‘M’edical ‘R’adio ‘T’herapy. dobutamine hydrochloride (pharmacol- DMRD (education) An abbreviation of ogy) A cardiac stimulant drug with ‘D’iploma in ‘M’edical ‘R’adio‘D’iagnosis. sympathomimetic and beta-receptor stimulant properties which administered DMRE (education) An abbreviation of by infusion increases the HEART’S ‘D’iploma in ‘M’edical ‘R’adiology and force of contraction and can be used ‘E’lectrology. to treat various serious HEART disorders.

118 DOCA DOSIMETER

DOCA (biochemistry) An abbreviation dopamine (biochemistry) PRECURSOR of ‘D’es‘O’xy‘C’orticosterone ‘A’cetate. in the SYNTHESIS of ADRENALINE (USA: epinephrine) and NORADRENALINE dod (1 statistics; 2 medical) 1 An (USA: norepinephrine) in animals. It is abbreviation of ‘d’ate ‘o’f ‘d’eath. 2 found in highest CONCENTRATION in An abbreviation of ‘d’ied ‘o’f ‘d’isease. the corpus striatum of the BRAIN, where it functions as a NEUROTRANSMITTER. dodecanoic acid (chemistry) An Low levels are associated with Parkinson’s alternative term for LAURIC ACID. disease in human beings.

dodecylbenzene (chemistry) C6H5(CH2)11- DOPEG (biochemistry) An abbreviation

CH3 HYDROCARBON of the BENZENE of 3,4-‘D’ihydr‘O’xy‘P’h‘E’nyl‘G’lycol. FAMILY, important in the manufacture of detergents. DOPET (biochemistry) An abbreviation of 3,4-‘D’ihydr‘O’xy‘P’henyl ‘ET’hanol. DOM (biochemistry) Abbreviation of 2,5-D’imeth‘O’xy-4-‘M’ethyl-amphetamine. dormancy (physiology) PERIOD of minimal metabolic activity of an organism or DOMA (biochemistry) An abbreviation reproductive body. It is a means of of 3,4-‘D’ihydr‘O’xy‘M’andelic ‘A’cid. surviving a PERIOD of adverse environmental conditions, e.g. cold or dominant (genetics) In a HETEROZYGOUS drought. Examples of some dormant organism, describing the GENE that structures are spores, cysts and prevents the expression of a RECESSIVE perennating organs of plants. ALLELE in a pair of HOMOLOGOUS Environmental factors such as day length CHROMOSOMES. Thus the PHENOTYPE and TEMPERATURE control both the of an organism with a COMBINATION onset and ending of DORMANCY. of DOMINANT and RECESSIVE genes DORMANCY may also be prompted and is similar to that with two DOMINANT terminated by the ACTION of HORMONES, ALLELES. e.g. abscinic ACID and gibberellins, respectively. donor (1 medical; 2 chemistry; 3 physics) 1 Person or ANIMAL that donates BLOOD, dorsal (anatomy) Describing the upper TISSUE or organs for use by another surface of an organism. In vertebrates person or ANIMAL. 2 ATOM that donates this is the surface nearest to the both electrons to form a CO-ORDINATE BACKBONE. In plants a DORSAL surface BOND. 3 An ELEMENT that donates electrons is considered to be one facing away to form an n-type semiconductor; e.g. from the main stem or ROOT. ANTIMONY or ARSENIC may be DONOR elements for GERMANIUM or SILICON. DOS (computing) An abbreviation of ‘D’isk ‘O’perating ‘S’ystem. Dopa (biochemistry) An abbreviation of ‘D’IHYDR‘O’XY‘P’HENYL‘A’LANINE. dosimeter (radiology) Instrument that measures the dose of RADIATION DOPAC (biochemistry) An abbreviation received by an individual or an AREA. of 3,4-‘D’ihydr‘O’xy‘P’henylacetic ‘AC’id.

119 DOUBLE BOND DS double bond (chemistry) COVALENT DPH (education) An abbreviation of BOND that is formed by sharing two ‘D’epartment/‘D’iploma/‘D’octor of pairs of electrons between two atoms. ‘P’ublic ‘H’ealth. double decomposition (chemistry) RE- DPhil. (education) An abbreviation of ACTION between two dissolved ionic ‘D’octor of ‘Phil’osophy. substances (usually salts) in which the reactants ‘change partners’ to form a DPL (biochemistry) An abbreviation of new SOLUBLE SALT and an INSOLUBLE ‘D’i‘P’almitoyl ‘L’ecithin. one, which is precipitated e.g. solutions of SODIUM CHLORIDE (NaCI) and SILVER DPN (biochemistry) An abbreviation of

NITRATE (AgNO3) react to form a SOLUTION ‘D’i‘P’hosphopyridine ‘N’ucleotide. of SODIUM NITRATE (NaNO3) and a PRECIPITATE of SILVER CHLORIDE (AgCI). DPPC (biochemistry) An abbreviation of ‘D’i‘P’almitoyl‘P’hosphatidyl‘C’holine. double recessive (genetics) HOMOZYGOTE condition in which two RECESSIVE ALLELES DPT (immunology) An abbreviation of of a particular GENE are at the same ‘D’iphtheria, ‘P’ertussis, ‘T’etanus (VAC- LOCUS on a pair of HOMOLOGOUS CINE). CHROMOSOMES, so that the RECESSIVE form of the GENE is expressed in the DR (education) An abbreviation of PHENOTYPE. ‘D’iploma in ‘R’adiology. double refraction (crystallography) Dr (education) An abbreviation of Phenomenon shown by certain crystals ‘D’octo‘r’. (e.g. calcite) that split an incident RAY of LIGHT into two refracted rays (termed ordinary Dr Med. (education) An abbreviation and extraordinary rays) polarized at right- of ‘D’octo’r’ of ‘Med’icine. angles to each other. Also termed: birefringence. Dr PH (education) An abbreviation of Down’s syndrome (medical/genetics) ‘D’octor of ‘P’ublic ‘H’ealth. ABNORMAL chromosomal condition caused by the presence of an extra autosomal DRCPath (education) An abbreviation of CHROMOSOME 21. It is characterized ‘D’iploma of the ‘R’oyal ‘C’ollege of by ABNORMAL physical development ‘Path’ologists. and mental retardation. Also termed: MONGOLISM; TRISOMY 21. dry cell (physics) ELECTROLYTIC CELL containing no free LIQUID ELECTROLYTE. DP (computing) An abbreviation of ‘D’ata A moist paste of AMMONIUM CHLORIDE

‘P’rocessing. (NH4CI) often acts as the ELECTROLYTE. DRY CELLS are used in batteries for DPath. (education) An abbreviation of torches, portable radios, etc. ‘D’iploma in ‘Path’ology. dry ice (chemistry) SOLID CARBON DIOXIDE. DPG (biochemistry) An abbreviation of 2/3-‘D’i‘P’hospho‘G’lycerate. DS (education) An abbreviation of ‘D’octor of ‘S’cience. Also termed DSc.

120 DSC. DYSPROSIUM

DSc. (education) See ds. duodecimal system (mathematics) Number system that uses the BASE DSc.-(PH) (education) An abbreviation 12, which requires two additional numbers of ‘D’octor of ‘Sc’ience—(‘P’ublic ‘H’ealth). in addition to 1 to 9 (to represent ten and eleven), usually called A and B. DSc.-(Tech.) (education) An abbreviation of ‘D’octor of ‘Sc’ience-(‘Tech’nical). duodenum (anatomy) First SECTION of the SMALL INTESTINE which is DTCD (education) An abbreviation of mainly secretory in FUNCTION, producing ‘D’iploma in ‘T’uberculosis and ‘C’hest digestive ENZYMES. It also receives ‘D’iseases. pancreatic juice from the PANCREAS and BILE from the GALL BLADDER. DTCH (education) An abbreviation of ‘D’iploma in ‘T’ropical ‘C’hild ‘H’ealth. dv (medical) An abbreviation of ‘d’ouble ‘v’ision. DTD (education) An abbreviation of ‘D’iploma in ‘T’uberculosis/‘T’uberculous DXR (radiology) An abbreviation of ‘D’iseases. ‘D’eep ‘X’-‘R’ay.

DTech. (education) An abbreviation Dy (chemistry) The CHEMICAL SYMBOL of ‘D’octor of ‘Tech’nology. for DYSPROSIUM.

DTH (education) An abbreviation of dynamic isomerism (chemistry) An ‘D’iploma in ‘T’ropical ‘H’ygiene. alternative term for TAUTOMERISM.

DTM (education) An abbreviation of dyne (measurement) FORCE that gives an ‘D’iploma in ‘T’ropical ‘M’edicine. OBJECT of MASS 1 gram an ACCELERATION of 1 cm s-2. The SI UNIT of FORCE is the DTM&H (education) An abbreviation NEWTON, equal to 105 dynes. of ‘D’iploma in ‘T’ropical ‘M’edicine and ‘H’ygiene. dysprosium Dy (chemistry) Silvery metallic ELEMENT in GROUP IIIB of the PERIODIC DTP (computing) An abbreviation of TABLE (one of the LANTHANIDES), ‘D’esk ‘T’op ‘P’ublishing. used to make magnets and nuclear REACTOR control rods. At. no. 66; r.a.m. DTPH (education) An abbreviation of 162.50. ‘D’iploma in ‘T’ropical ‘P’ublic ‘H’ealth.

DTR (education) An abbreviation of ‘D’iploma in ‘T’herapeutic ‘R’adiology.

DT’s (medical) An abbreviation of ‘D’elirium ‘T’remens. ductless gland (anatomy) An alternative term for ENDOCRINE GLAND

121 E

E (biochemistry) A symbol for glutamic have only one EAR OSSICLE, the columella acid. auris.

E1 (biochemistry) A symbol for estrone. earth (physics) In electric circuits, a connection to a piece of METAL that is E2 (biochemistry) A symbol for estradiol. in turn linked to the EARTH. It has the effect of preventing any earthed apparatus e (1 mathematics; 2 physics) 1 from retaining an ELECTRIC CHARGE. Fundamental mathematical CONSTANT and the BASE of natural (Napierian) EB virus (virology) See EBV. logarithms. It is an IRRATIONAL NUMBER, the limiting value of the SERIES (1+I/ EBV (virology) An abbreviation of n)n as n tends to INFINITY, approximately ‘E’pstein-‘B’arr ‘V’irus. Also termed EB equal to 2.71828. It is the CONSTANT VIRUS. in an EXPONENTIAL FUNCTION or SERIES. 2 An abbreviation of ‘electron. ec (literary terminology) An abbreviation of ‘e’xempli ‘c’ausa. [Latin, meaning, EACA (biochemistry) An abbreviation ‘for example’.] of ‘E’psilon-‘A’mino‘C’aproic ‘A’cid. E cells (physiology) A symbol for ear (anatomy) One of a pair of hearing expiratory neurons. and BALANCE sensory organs situated on each side of the HEAD of vertebrates. ECF (histology) An abbreviation of In mammals it consists of three parts: ‘E’xtra‘C’ellular ‘F’luid. the outer, middle and INNER EAR. ECG (physiology) An abbreviation of ear drum (anatomy) MEMBRANE at the ‘E’lectro‘C’ardio‘G’ram. inner end of the AUDITORY CANAL of the OUTER EAR which transmits sound eCG (biochemistry) An abbreviation vibrations to the EAR OSSICLES of the of ‘e’quine ‘C’horionic ‘G’onadotrophin MIDDLE EAR. Also termed: tympanum. (USA: equine Chorionic Gonadotropin). ear ossicle (anatomy) Small BONE found echovirus (virology) Any of a subgroup in the MIDDLE EAR of vertebrates. In of human enteroviruses associated with mammals there are three, which transmit neurological disorders. There are 34 sound waves from the EAR DRUM to serovars, each designated by an Arabic the hearing sensory CELLS in the COCHLEA NUMERAL; ECHOVIRUS 1, ECHOVIRUS of the INNER EAR. The three mammalian 2, etc. [From ‘e’nteric ‘c’ytopathic ‘o’rphan OSSICLES are the mailcus, INCUS and ‘VIRUS’.] stapes. Amphibians, reptiles and birds

122 ECOG EFFECTOR

ECoG (physiology) An abbreviation of ED (pharmacology) An abbreviation ‘E’lectro‘Co’rtico‘G’ram. of ‘E’ffective ‘D’ose. ecological niche (biology) Position that Ed. in Ch. (literary terminology) An a particular SPECIES occupies within abbreviation of ‘Ed’itor in ‘Ch’ief. an ECOSYSTEM. The term both describes the FUNCTION of a SPECIES in terms eddy current (physics) ELECTRIC of interactions with other SPECIES, e.g. CURRENT within a CONDUCTOR caused feeding BEHAVIOUR (USA: behavior), by ELECTROMAGNETIC INDUCTION. and defines the physical boundaries of Such currents result in losses of ENERGY the ENVIRONMENT occupied by the in electrical machines (e.g. a transformer, SPECIES, e.g. bats are said to occupy in which they are overcome by laminating an airborne NICHE. the CORE), but are utilized in INDUCTION HEATING and some braking ecology (biology) Study of INTERACTION systems. of organisms between themselves and with their physical ENVIRONMENT. Edison accumulator (physics) An alternative term for NICKEL-IRON ACCUMULATOR. ecosystem (biology) Natural UNIT that contains living and non-living components EDRF (physiology) An abbreviation (e.g. a community and its ENVIRONMENT) of ‘E’ndothelium-‘D’erived ‘R’elaxing interacting and exchanging materials, ‘F’actor. and generally balanced as a STABLE system; e.g. grassland or rainforest. EDTA (biochemistry/pharmacology) An abbreviation of ‘E’thylene‘D’iamine- ECT (medical) An abbreviation of ‘e’lectro- ‘T’etracetic ‘A’cid. It is a white ‘c’onvulsant ‘t’herapy. CRYSTALLINE ORGANIC COMPOUND, used generally as its SODIUM SALT ectoderm (histology) Outermost GERM as an analytical REAGENT and LAYER of the EMBRYO of a metazoan ANTIDOTE for heavy-METAL poisoning, which develops into tissues of the when it forms chelates. EPIDERMIS, e.g. SKIN, HAIR, SENSE ORGANS. Also termed: EPIBLAST. EEG (physiology) An abbreviation of ‘E’lectro‘E’ncephalo‘G’ram. ectoparasite (parasitology) PARASITE that lives on the outside of its HOST; e.g. flea. EET (biochemistry) An abbreviation of ‘E’poxy‘E’icosa‘T’etraenoic acid. ectoplasm (cytology) Non-granulated jelly-like outer layer of CYTOPLASM effective resistance (physics) Total that is located below the PLASMA ALTERNATING CURRENT resistance MEMBRANE. It is CHARACTERISTIC of a CONDUCTOR of ELECTRICITY. of most amoeboid ANIMAL CELLS, in which at its boundary with PLASMASOL effector (physiology) TISSUE or ORGAN it aids cytoplasmic streaming, and thus that responds to a nervous STIMULUS movement; e.g. in amoeboid PROTOZOA (e.g. ENDOCRINE GLAND, MUSCLE). and LEUCOCYTES.

123 EFFERENT ELECTRIC CONSTANT efferent (anatomy) Leading away from, ego (medical) Psychological term for as applied to vessels, fibres (USA: fibers) the aspect of personality concerned with and ducts leading from organs. rationality and common sense.

See also AFFERENT. See also id. effervescence (chemistry) EVOLUTION EHF (physics) An abbreviation of bubbles of a GAS from a LIQUID. of ‘E’xtremely ‘H’igh ‘F’requency. efflorescence (chemistry) Property of Einstein equation (physics) Equation certain CRYSTALLINE salts that lose deduced from Einstein’s special theory WATER OF CRYSTALLIZATION on of RELATIVITY: E=me2, where E is exposure to AIR and become powdery; ENERGY, m is MASS and c is the e.g. SODIUM CARBONATE decahydrate velocity of LIGHT. It is named after

(WASHING SODA), Na2CO3. 10H2O. It the German-born American physicist is the opposite of DELIQUESCENCE. Albert Einstein (1879–1955). effort (physics) In a simple machine einsteinium Es (chemistry) RADIOACTIVE (e.g. lever, pulley) the FORCE that is metallic ELEMENT in GROUP IIIB of applied to move a load. The ratio of the PERIODIC TABLE (one of the the load to the EFFORT is the mechanical LANTHANIDES). It has several isotopes, advantage (FORCE RATIO). with half-lives of up to 2 years. At. no. 99; r.a.m. 254 (most STABLE ISOTOPE). effusion (physics) Passage of gases under PRESSURE through small holes. EJP (physiology) An abbreviation of ‘E’xcitatory ‘J’unction ‘P’otential. e.g. (literary terminology) An abbreviation of ‘e’xempli ‘g’ratia. [Latin, meaning, elastic Van Gieson stain (histology) ‘for example’.] A histological technique that may be used for staining elastic and EGA (computing) An abbreviation of CONNECTIVE TISSUE. ‘E’nhanced ‘G’raphics ‘A’dapter. electrical conductivity (measurement) EGF (histology) An abbreviation of Measure of the ability of a substance to ‘E’pidermal ‘G’rowth ‘F’actor. conduct ELECTRICITY, the RECIPROCAL of resistivity. It is measured in ohms-1 m-1. egg membrane (histology) Thin protective MEMBRANE that surrounds the fertilized See also CONDUCTANCE. OVUM of animals. It is secreted by the OOCYTE and the FOLLICLE CELLS. electric charge (physics) Excess or deficiency of electrons in an OBJECT, See also CHORION. giving rise to an overall POSITIVE or negative ELECTRIC CHARGE respectively. egg (cytology) See OVUM. electric constant (physics) An alternative term for the absolute permittivity of free space.

124 ELECTRIC CURRENT ELECTRODIALYSIS

See also RELATIVE PERMITTIVITY. caused by static or dynamic ELECTRIC CHARGES. electric current (physics) Flow of electrons through a CONDUCTOR in the same electrocardiogram (ECG) (physiology) direction, usually because there is a RECORD of the electrical activity of the POTENTIAL DIFFERENCE across it. HEART produced by an electrocardiograph machine. Also termed: CARDIOGRAM. electric displacement (physics) ELECTRICCHARGE per UNIT AREA, electrocardiograph (physiology) Machine in coulombs persquare METRE (C m- that uses electrodes taped to the body 2). Also termed: ELECTRIC FLUX DENSITY. to produce electrocardiograms. electric field (physics) Region surrounding electrochemical series (chemistry) an ELECTRIC CHARGE in which a charged List of metals arranged in ORDER of PARTICLE is subjected to a FORCE. their ELECTRODE POTENTIALS. A METAL will displace from their salts electric flux (physics) Lines of FORCE metals lower down in the SERIES. Also that make up an ELECTRIC FIELD. termed: ELECTROMOTIVE SERIES. electric motor (physics) Device that electrochemistry (chemistry) Branch converts electrical ENERGY into mechani- of science that is concerned with the cal ENERGY. A Simple ELECTRIC MOTOR study of electrical chemical ENERGY, consists of a CURRENT-carrying coil such as the effects of ELECTRIC that rotates in the MAGNETIC FIELD CURRENT on chemicals (particularly between the poles of a permanent MAGNET. electrolytes) and the generation of ELECTRICITY by chemical ACTION electric polarization (physics) Difference (as in an ELECTROLYTIC CELL). between the DISPLACEMENT of CHARGE and the ELECTRIC FIELD strength in electrode (1,2 chemistry) 1 Conducting a DIELECTRIC. plate (ANODE or CATHODE) that collects or emits electrons from an ELECTROLYTE electrical condenser (physics) An during ELECTROLYSIS. 2 Conducting plate alternative term for CAPACITOR. in an ELECTROLYTIC CELL (BATTERY), DISCHARGE tube or VACUUM tube. electrical line of force (physics) Line radiating from an ELECTRIC FIELD. electrode potential (chemistry) POTENTIAL developed by a substance in EQUILIBRIUM electrical relay (physics) Electromagnetic with a SOLUTION of its ions. switching device that brings about changes in an independent CIRCUIT. electrodeposition (chemistry) Deposition of a substance from an ELECTROLYTE electrical resistance (physics) Property on to an ELECTRODE, as in electroplating. of an electrical CONDUCTOR that makes it oppose the flow of CURRENT through electrodialysis (chemistry) Removal of it. It is measured in ohms. salts from a SOLUTION (often a COLLOID) by placing the SOLUTION between two electricity (physics) Branch of science SEMIPERMEABLE MEMBRANES, outside that is concerned with all phenomena which are electrodes in pure SOLVENT.

125 ELECTRODYNAMICS ELECTROMAGNETIC SPECTRUM electrodynamics (physics) Study of or the molten state into electrically charged moving ELECTRIC CHARGES, especially ions. in electric or MAGNETIC FIELDS, which has important applications in the design electrolytic rectifier (physics) RECTIFIER of generators and motors. that consists of two electrodes and an ELECTROLYTE in which the CURRENT electroencephalogram (EEG) (physiology) flows in one direction only. RECORD of the electrical activity of the BRAIN produced by an ELECTROEN- electrolytic separation (chemistry) A CEPHALOGRAPH machine. method of separating metals from a SOLUTION by varying the applied electroencephalograph (physiology) Machine POTENTIAL according to the ELECTRODE that uses electrodes taped to the SKULL POTENTIALS of the metals. to produce electroencephalograms. electromagnet (physics) A temporary MAGNET consisting of a CURRENT- electrokinetic potential (physics) An carrying coil of wire WOUND on a alternative term for ZETA POTENTIAL. ferromagnetic core. It is the basis of many items of electrical equipment, e.g. electrokinetics (physics) Branch of electric bells, solenoids and lifting magnets. science concerned with the study of ELECTRIC CHARGES in motion. electromagnetic induction (physics) The ELECTROMOTIVE FORCE (emf) electrolysis (chemistry) Conduction produced in a CONDUCTOR when it is of ELECTRICITY between two electrodes, moved in a MAGNETIC FIELD. It is the through a SOLUTION of a substance WORKING principle of an electrical (or a substance in its molten state) generator (e.g. dynamo). It can give containing ions and accompanied by rise to a BACK EMF and EDDY CURRENTS. chemical changes at the electrodes. electromagnetic interaction (physics) electrolyte (chemistry) Substance that INTERACTION between electrically in its molten state or in SOLUTION charged ELEMENTARY PARTICLES. can conduct an ELECTRIC CURRENT. electromagnetic radiation (physics) electrolytic capacitor (physics) The ENERGY that results from moving ELECTROLYTIC CELL in which a thin ELECTRIC CHARGES and travels in FILM of nonconducting substance has association with electric and MAGNETIC been deposited on one of the electrodes FIELDS, e.g. radio waves, HEAT rays, by an ELECTRIC CURRENT. LIGHT and X-RAYS, which form part of the ELECTROMAGNETIC SPECTRUM. electrolytic cell (physics) Apparatus that consists of electrodes immersed electromagnetic spectrum (physics) in an ELECTROLYTE. The range of frequencies over which ELECTROMAGNETIC RADIATION is electrolytic dissociation (chemistry) The propagated. In ORDER of increasing partial or complete reversible DECOM- FREQUENCY (decreasing WAVELENGTH) POSITION of a substance in SOLUTION it consists of radio waves, microwaves, INFRA-RED RADIATION, VISIBLE LIGHT,

126 ELECTROMAGNETIC WAVE ELECTRON MULTIPLIER

ULTRAVIOLET RADIATION, X-RAYS and FORMATION of a PROTON into a NEUTRON gamma-rays. in the NUCLEUS of an ATOM (accompanied by the emission of X-RAYS) through the electromagnetic wave (physics) WAVE capture of an ORBITAL ELECTRON, so formed by electric and MAGNETIC FIELDS, converting the ELEMENT into another with i.e. of ELECTROMAGNETIC RADIATION. an ATOMIC NUMBER one less. Such waves do not require a medium in which to propagate, and will travel in a VACUUM. electron charge (e) (measurement) Fundamental physical CONSTANT, equal electromagnetism (physics) COMBINATION to 1.602102×10-19 coulombs. of an ELECTRIC FIELD and a MAGNETIC FIELD, their INTERACTION with stationary electron configuration (physics) See or moving ELECTRIC CHARGES, and CONFIGURATION. their study and application. It therefore applies to LIGHT and other forms of electron density (physics) DENSITY ELECTROMAGNETIC RADIATION, as well of ELECTRIC CHARGE. as to devices such as electromagnets, ELECTRIC MOTORS and generators. electron diffraction (physics) Method of determining the arrangement of the electromotive force (emf) (physics) atoms in a SOLID, and hence its crystal POTENTIAL DIFFERENCE of a source structure, by the DIFFRACTION of a of ELECTRIC CURRENT, such as an beam of electrons. ELECTROLYTIC CELL (BATTERY) or generator. Often it can be measured only electron donor (chemistry) An alternative at EQUILIBRIUM (when there is no CURRENT term for REDUCING AGENT. flow). An alternative term: VOLTAGE. electron gun (physics) ELECTRODE electromotive series (chemistry) An assembly for producing a narrow beam alternative term for ELECTROCHEMICAL of electrons, as used, e.g. in CATHODE- SERIES. RAY TUBES. electron (physics) A fundamental negatively- electron lens (physics) Arrangement of charged SUBATOMIC PARTICLE (RADIUS electrodes or of permanent magnets or 2.81777×10-15 m; rest MASS 9.10908×10- electromagnets used to FOCUS or divert 31 kg; CHARGE 1.602102× 10-19 coulombs). beams of electrons in the same way as an Every NEUTRAL ATOM has as many optical LENS modifies a beam of LIGHT, orbiting electrons as there are protons as in, e.g. an ELECTRON MICROSCOPE. in its NUCLEUS. A flow of electrons constitutes an ELECTRIC CURRENT. electron microscope (microscopy) An instrument that uses a beam of electrons electron affinity (physics) ENERGY from an ELECTRON GUN to produce liberated when an ELECTRON is acquired magnified images of extremely small by a NEUTRAL ATOM. objects, beyond the range of an optical MICROSCOPE. electron capture (1,2 physics) 1 Formation of a negative ION through the capture of an electron multiplier (physics) An ELECTRON by a substance. 2 TRANS- alternative term for PHOTOMULTIPLIER.

127 ELECTRON OCTET ELECTROPHORESIS electron octet (chemistry) See OCTET. insufficient electrons to form two- ELECTRON COVALENT BONDS between electron optics (physics) Study of the all the adjacent atoms (e.g. boranes). control of FREE ELECTRONS by curved electric and MAGNET fields, particularly electronegativity (chemistry) POWER the use of such fields to FOCUS and of an ATOM in a MOLECULE to attract deflect beams of electrons. electrons. For elements arranged in the PERIODIC TABLE, it increases up electron probe microanalysts (EPM) a GROUP and across a PERIOD. (physics) QUANTITATIVE ANALYSIS of small amounts of substances by electronics (physics) Branch of science FOCUSING a beam of electrons on to concerned with the study of ELECTRICITY a point on the surface of the SAMPLE in a VACUUM, in gases and in semiconductors. so that CHARACTERISTIC X-RAY intensifies are produced. electron-spin resonance (ESR) (physics) Branch of MICROWAVE SPECTRO-SCOPY electron radius (r e) (measurement) in which RADIATION of measurable A fundamental physical CONSTANT, FREQUENCY and WAVELENGTH is used which is equal to 2.81777×10-15 m. to supply ENERGY to protons.

electron rest mass (me) (measurement) electrophile (chemistry) An ELECTRON- Fundamental physical CONSTANT, equal deficient ION or MOLECULE that attacks to 9.10908×10-31 kg. molecules of high ELECTRON DENSITY. electron transport (physiology) Process See also NUCLEOPHILE. found mainly in AEROBIC RESPIRATION and PHOTOSYNTHESIS that provides electrophilic addition (chemistry) A a source of ENERGY in the form of CHEMICAL REACTION that involves ATP. HYDROGEN atoms are used in the addition of a MOLECULE to an this system and taken up by a HYDROGEN UNSATURATED ORGANIC COMPOUND CARRIER, e.g. fad; the electrons of across a double or TRIPLE BOND. the HYDROGEN pass along a chain of carriers which are in turn reduced and electrophilic reagent (chemistry) oxidized. This is coupled to the formation REAGENT that attacks molecules of of ATP. The HYDROGEN atoms together high ELECTRON DENSITY. with OXYGEN eventually form WATER. electrophilic substitution (chemistry) electron tube (physics) An alternative A REACTION that involves the substitution term for a VALVE. of an ATOM or GROUP of atoms in an ORGANIC COMPOUND. An ELECTROPHILE electron volt (eV) (measurement) General is the attacking SUBSTITUENT. UNIT of ENERGY equal to WORK done on an ELECTRON when it passes through electrophoresis (physics) Movement of POTENTIAL GRADIENT of 1 VOLT. charged COLLOID particles in a SOLUTION placed in an ELECTRIC FIELD. electron-deficient compound (chemistry) A COMPOUND in which there are

128 ELECTROPHORUS EMBRYOL. electrophorus (physics) A device for elementary particle (physics) SUBATOMIC producing charges by electrostatic PARTICLE not known to be made up of INDUCTION; an electrostatic generator. simpler particles. electropositive (physics) Tending to elevation of boiling point (physics) form POSITIVE ions; having a deficiency Rise in the BOILING POINT of a LIQUID of electrons. caused by dissolving a substance in the LIQUID. electrostatic field (physics) ELECTRIC FIELD associated with stationary ELF (physics) An abbreviation of ELECTRIC CHARGES. ‘E’xtremely ‘L’ow ‘F’requency. electrostatic units (ESU) (measurement) eluate (chemistry) SOLUTION obtained System of electrical units based on from ELUTION. the FORCE exerted between two ELECTRIC CHARGES. eluent (chemistry) SOLVENT used for ELUTION, the mobile PHASE. electrostatics (physics) The branch of ELECTRICITY concerned with the elution (chemistry) Removal of an study of electrical charges at rest. adsorbed substance by washing the ADSORBENT with a SOLVENT (ELUENT). electrostriction (physics) Change in The technique is used in some forms the dimensions of a DIELECTRIC that of CHROMATOGRAPHY. is caused by the reorientation of molecules when an ELECTRIC FIELD is applied. EM (microscopy) An abbreviation of ‘E’lectron ‘M’icroscope. electrovalent bond (chemistry) An alternative term for IONIC BOND. em (physics) An abbreviation of ‘e’lectro‘m’agnetic. electrovalent crystal (crystallography) Crystal in which the ions are linked e-mail (computing) An abbreviation by a BOND resulting from electrostatic of ‘e’lectronic ‘mail’. attraction between their charges. Also termed: IONIC CRYSTAL. EMBO (society) An abbreviation of ‘E’uropean ‘M’olecular ‘B’iology element (1 chemistry; 2 mathematics; ‘O’rganisation. 3 physics) 1 Substance consisting of similar atoms of the same ATOMIC embryo (biology) Organism formed after NUMBER. It cannot be decomposed CLEAVAGE of the ZYGOTE before birth. by chemical ACTION to a simpler A maturing EMBRYO is often termed substance. Also termed: chemical a FOETUS (USA: fetus). ELEMENT. See also ISOTOPE; PERIODIC TABLE. 2 In mathematics, one of the embryogenesis (medical) The develop- members of a SET. 3 In physics, one ment of the EMBRYO. of several lenses in a COMPOUND LENS, or one of several components embryol. (medical) An abbreviation in an electrical CIRCUIT. of ‘embryol’ogy.

129 EMBRYOLOGY ENDOCRINE GLAND embryology (biology) Study of embryos, EMTD (toxicology) An abbreviation of their formation and development. ‘E’stimated ‘M’aximum ‘T’olerated ‘D’ose.

EMC virus (virology) An abbreviation emulsion (chemistry) Colloidal SUSPENSION of ‘E’ncephalo‘M’yo‘C’arditis ‘VIRUS’. of one LIQUID dispersed in another. emer. (general terminology) An abbrevia- enamel (histology) White protective tion of ‘emer’gency. calcified outer coating of the crown of the TOOTH of a VERTEBRATE. It emergency room (ER) (medical) The is produced by epidermal CELLS, the part of a hospital that provides immediate ameloblasts, and it consists almost care. entirely of CALCIUM salts bound together by KERATIN fibres (USA: keratin fibers). emesis (medical) The act of vomiting. enatiomer (chemistry) MOLECULE that emetics (medical) Drugs which cause is a mirror IMAGE of another, and which vomiting. cannot be superimposed on it. Both molecules are OPTICALLY ACTIVE, emf (physics) An abbreviation of but differ in the direction in which they ‘e’lectro‘m’otive ‘f’orce. rotate the plane of POLARIZED LIGHT.

EMG (physiology) An abbreviation of encephalin (biochemistry) One of two ‘E’lectro‘M’yo‘G’ram. peptides which are natural ANALGESICS, produced in the BRAIN and released emission spectrum (physics) SPECTRUM after injury. The encephalins have obtained when the LIGHT from a luminous properties similar to MORPHINE. Also source undergoes DISPERSION and termed: ENDORPHIN; enkephalin. is observed directly. end point (chemistry) Point at which EMK (physics) An abbreviation of ‘E’lektro- a CHEMICAL REACTION is complete, ‘M’otorische ‘K’raft. [German, meaning such as the end of a TITRATION. ‘ELECTROMOTIVE FORCE’.] See also VOLUMETRIC ANALYSIS. empirical formula (chemistry) CHEMICAL FORMULA that shows the simplest ratio endemic (EPIDEMIOLOGY) Describing between atoms of a MOLECULE e.g. a disease that continually occurs among GLUCOSE, MOLECULAR FORMULA people or animals in a particular region.

C 6H 12O 6, and acetic (ethanoic) ACID,

C2H4O2, both have the same EMPIRICAL See also EPIDEMIC; PANDEMIC.

FORMULA, CH2O. endocrine gland (anatomy) Ductless See also MOLECULAR FORMULA; ORGAN or discrete GROUP of CELLS STRUCTURAL FORMULA. that synthesize HORMONES and secrete them directly into the bloodstream. Such EMSA (society) An abbreviation of GLANDS include the PITUITARY, pineal, ‘E’lectron ‘M’icroscope ‘S’ociety of THYROID, PARATHYROID and ADRENAL ‘A’merica. GLANDS, the GONADS and PLACENTA

130 ENDOCRINOLOGY ENERGY LEVEL

(in mammals), ISLETS OF LANGERHANS endorphin (biochemistry) One of a (in the PANCREAS) and parts of the GROUP of peptides that are produced ALIMENTARY CANAL. Their FUNCTION by the PITUITARY GLAND and which is parallel to the NERVOUS SYSTEM, act as painkillers in the body. that of regulation of responses in animals. Also termed: DUCTLESS GLAND. endoscope (optics) A tubular optical device, perhaps using FIBRE OPTICS endocrinology (histology/biochemistry) (USA: fiber optics), that is inserted into Study of structure and FUNCTION of a natural orifice or a surgical incision to ENDOCRINE GLANDS and the roles study organs and tissues inside the body. of their HORMONES as the chemical messengers of the body. endospore (1, 2 biology) 1 Innermost layer of the wall of a SPORE. 2 Tough endogenous (biology) Produced or ASEXUAL SPORE that is formed by some originating within an organism. BACTERIA to resist adverse conditions. endolymph (anatomy) FLUID that fills endothelium (histology) TISSUE formed the cavity of the middle, inner and the from a single layer of CELLS found SEMICIRCULAR CANALS of the EAR. lining spaces and tubes within the body, e.g. lining the HEART in vertebrates. endoparasite (parasitology) PARASITE that lives inside the body of its HOST, e.g. See also EPITHELIUM. FLUKE, MALARIA PARASITE, TAPEWORM. endothermic (chemistry) Describing endoplasm (cytology) Central portion a process in which HEAT is taken in; of CYTOPLASM, surrounded by the e.g. in many CHEMICAL REACTIONS. ECTOPLASM and containing organelles. Also termed: PLASMASOL. See also EXOTHERMIC. endoplasmic reticulum (ER) (cytology) energy (physics) CAPACITY for doing Structure that occurs in most EUKARYOTIC WORK, measured in joules. ENERGY CELLS in the form of a flattened takes various forms: e.g. KINETIC MEMBRANE-bound sac of CELL ENERGY, POTENTIAL ENERGY, electrical organelles, continuous with the outer ENERGY, chemical ENERGY, HEAT, LIGHT NUCLEAR MEMBRANE. When covered and sound. All forms of ENERGY can with ribosomes it is termed rough ER, be regarded as being aspects of kinetic in their absence smooth ER. Its main or POTENTIAL ENERGY; e.g. HEAT FUNCTION is the SYNTHESIS of proteins ENERGY in a substance is the KINETIC and their transport within or to the outside ENERGY of that substance’s molecules. of the CELL. In LIVER CELLS ER is involved in detoxification processes and energy level (physics) The ENERGY in LIPID and CHOLESTEROL of electrons in an ATOM is not continuously METABOLISM. In association with the VARIABLE, but has a discrete SET of GOLGI APPARATUS, ER is involved in values, i.e. ENERGY LEVELS. At any LYSOSOME production. instant the ENERGY of a given ELECTRON can correspond to only one of these levels.

131 ENFLURANE EPIDIDYMIS enflurane (pharmacology) An inhalant WATER supply and presence of other general anaesthetic drug, which is similar (competing) organisms. to halothane. It is often used along with nitrous oxide-oxygen mixtures for enzyme (biochemistry) PROTEIN that the induction and maintenance of acts as a CATALYST for the CHEMICAL anaesthesia during major surgery. REACTIONS that occur in living systems. Without such a CATALYST most of the enol (chemistry) ORGANIC COMPOUND reactions of METABOLISM would not that contains the GROUP C=CH(OH); occur under the conditions that prevail. the ALCOHOLic form of a KETONE. Most ENZYMES are specific to a particular SUBSTRATE (and therefore a particular enrichment (microbiology) ISOLATION REACTION) and act by activating the of a particular type of organism by SUBSTRATE and binding to it. enhancing its GROWTH over other organisms in a mixed population. EP (physiology/biochemistry) An abbreviation of ‘E’ndogenous ‘P’yrogen. ENT (medical) An abbreviation of ‘E’ar, ‘N’ose and ‘T’hroat. EPI (biochemistry/pharmacology) An abbreviation for ‘EPI’nephrine. (UK: Ent. (parasitology) An abbreviation of ADRENALINE). ‘Ent’omology. epiblast (biology) An alternative term enthalpy (H) (physics) Amount of HEAT for ECTODERM. ENERGY a substance possesses, measurable in terms of the HEAT change epidemic (epidemiology) Describing that accompanies a CHEMICAL a disease that, for a limited time, affects REACTION carried out at CONSTANT many people or animals in a particular PRESSURE. In any system, H=U+pV, region. where U is the INTERNAL ENERGY, p the PRESSURE and V the VOLUME. See also ENDEMIC; PANDEMIC. entropy (S) (physics) In THERMODYNAMICS, epidemiology (epidemiology) Study of quantity that is a measure of a system’s diseases as they affect the population, disorder, or the unavailability of its ENERGY including their INCIDENCE and prevention. to do WORK. In a REVERSIBLE PROCESS the change in ENTROPY is equal to the epidermis (histology) Layer of CELLS amount of ENERGY adsorbed divided at the surface of a plant or ANIMAL. In by the ABSOLUTE TEMPERATURE at plants and some invertebrates, it forms which it is taken up. a single protective layer, often overlaid by a cuticle which is IMPERMEABLE to envelope (mathematics) Curve that WATER. In vertebrates, it forms the SKIN touches every one of a whole FAMILY and is composed of several layers of of curves. CELLS, the outermost becoming keratinized. See KERATINIZATION. environment (biology) All the conditions in which an organism lives, including epididymis (anatomy) Long coiled tube the amount of LIGHT, TEMPERATURE, in the TESTES of some vertebrates through

132 EPIGLOTTIS EQUIVALENT FRACTION which SPERM from the seminiferous EPP (physiology) An abbreviation of tubules pass, before going into the VAS ‘e’nd ‘p’late ‘p’otential. DEFERENS and to the exterior.

Epsom salt (pharmacology) MgSO4.7H2O epiglottis (anatomy) VALVE-like flap White CRYSTALLINE SALT, used in of CARTILAGE in mammals that closes mineral waters, as a laxative. Also termed: the opening into the LARYNX, the epsomite; MAGNESIUM SULPHATE (USA: GLOTTIS, during swallowing. magnesium sulfate). epinephrine (biochemistry) An alternative EPSP (physiology) An abbreviation for term for ADRENALINE. ‘e’xcitatory ‘p’ost‘s’ynaptic ‘p’otential. epiphysis (1, 2 anatomy) 1 Growing eq (chemistry) An abbreviation of end of a BONE, at which CARTILAGE ‘eq’uivalent(s). is converted to SOLID BONE. 2 An alternative term for PINEAL GLAND. equation of state (physics) Any FORMULA that connects the VOLUME, PRESSURE epithelium (histology) ANIMAL lining and TEMPERATURE of a given system, TISSUE of varying complexity, whose e.g. van der Waals’ equation. main FUNCTION is protective. It may be specialized for lining a particular ORGAN. equilibrium (1, 2 physics) 1 An OBJECT e.g. SQUAMOUS EPITHELIUM lines is in EQUILIBRIUM when the forces capillaries and is PERMEABLE to molecules acting on it are such that there is no in SOLUTION, glandular EPITHELIUM tendency for the OBJECT to move. 2 contains CELLS that are secretory. State in which no change occurs in a system if no change occurs in the epithermal neutron (physics) NEUTRON surrounding ENVIRONMENT (e.g. that has ENERGY of between 10-2 and CHEMICAL EQUILIBRIUM). 102 ELECTRON volts (eV); a NEUTRON having ENERGY greater than that equilibrium constant (Kc) (chemistry) associated with thermal agitation. CONCENTRATION of the products of a CHEMICAL REACTION divided by epoxide (chemistry) ORGANIC COMPOUND the CONCENTRATION of the reactants, whose molecules include a three-membered in accordance with the CHEMICAL OXYGEN ring (a CYCLIC ETHER). EQUATION, at a given TEMPERATURE. epoxy resin (chemistry) SYNTHETIC equimolecular mixture (chemistry) A polymeric thermosetting RESIN with MIXTURE of substances in equal EPOXIDE groups (e.g. polyethers). Such molecular proportions. resins are used in surface coatings and as adhesives and electrical insulators. equivalence point (chemistry) Theoretical Also termed: EPOXIDE RESIN. END POINT of a TITRATION.

EPP (haematology) An abbreviation See also VOLUMETRIC ANALYSIS. of ‘E’rythrocyte ‘P’roto‘P’orphyrin. equivalent fraction (mathematics) One of two or more fractions that represent

133 EQUIVALENT WEIGHT ESR the same number; e.g. the fractions See also LEUCOCYTE. 2/3, 4/6, 14/21 and 40/60 are equivalent. Es (chemistry) The CHEMICAL SYMBOL equivalent weight (chemistry) Number for EINSTEINIUM. of parts by MASS of an ELEMENT that can combine with or displace one ES (society) An abbreviation of part by MASS of HYDROGEN. ‘E’ntomological ‘S’ociety.

Er (chemistry) The CHEMICAL SYMBOL ESA (society) An abbreviation of for ERBIUM. ‘E’cological/‘E’ntomological/‘S’ociety of ‘A’merica. ER (medical) An abbreviation of ‘E’mergency ‘R’oom. ESB (medical) An abbreviation of ‘E’lectrical ‘S’timulation of the ‘B’rain. erbium Er (chemistry) Metallic ELEMENT in GROUP IIIB of the PERIODIC TABLE ESC (society) An abbreviation of (one of the LANTHANIDES), used in ‘E’ntomological ‘S’ociety of ‘C’anada. making lasers for medical applications. Its pink OXIDE is used as a PIGMENT Escherichia coli (bacteriology) A member in ceramics. At. no. 68; r.a.m. 167.26. of the bacterial family Enterobacteriacae. A gram negative non-motile rod and ERG (physiology) An abbreviation of a natural inhabitant of the intestinal ‘E’lectro‘R’etino‘G’ram. tract in man; usually non-pathogenic, but pathogenic strains frequently cause erg (measurement) ENERGY transferred urinary tract infections, enteritis, when a FORCE of 1 dyne moves through peritonitis, cystitis, and wound infections. 1 cm, equivalent to 10-7 joules. ESH (society) An abbreviation of ergosterol (biochemistry) White CRYSTAL- ‘E’uropean ‘S’ociety of ‘H’aematology. LINE STEROL. It occurs in ANIMAL fat and in some MICRO-ORGANISMS. esl (statistics) An abbreviation of In animals it is converted to VITAMIN ‘e’xpected ‘s’ignificance ‘l’evel.

D 2 by ULTRAVIOLET RADIATION. esn (general terminology) An abbreviation erogenous (biology) Originating outside of ‘es’se‘n’tial. Also termed esntl. an organism, ORGAN or CELL. The term may refer to such things as substances ESNZ (society) An abbreviation of (e.g. nutrients) or stimuli (e.g. LIGHT). ‘E’ntomological ‘S’ociety of ‘N’ew ‘Z’ealand. ERPF (physiology) An abbreviation of ‘E’ffective ‘R’enal ‘P’lasma ‘F’low. esp. (general terminology) An abbreviation of ‘esp’ecially. erythrocyte (haematology) RED BLOOD CELL. It contains HAEMOGLOBIN (USA: ESR (1 haematology; 2 physics) 1 An hemaglobin) and carries OXYGEN around abbreviation of ‘E’rythrocyte ‘S’edimen- the body. In mammals, ERYTHROCYTES tation ‘R’ate. 2 An abbreviation of have no nuclei. ‘E’lectron ‘S’pin ‘R’esonance.

134 ESRA ETHER

ESRA (governing body) An abbreviation etc. (literary terminology) An abbreviation of ‘E’uropean ‘S’ociety of ‘R’egulatory of ‘et’ ‘c’etera. [Latin, meaning, ‘and so ‘A’ffairs. forth’.] essential amino acid (biochemistry) ethanal (chemistry) An alternative term Any AMINO ACID that cannot be for ACETALDEHYDE. manufactured in some vertebrates, including human beings. These acids must therefore ethanal trimer (chemistry) An alternative be obtained from the diet. They are as term for PARALDEHYDE, follows: ARGININE, HISTIDINE, ISOLEUCINE, LEUCINE, LYSINE, ethane (chemistry) C2H6 Gaseous ALKANE METHIONINE, PHENYLALANINE, which occurs with methane in natural THREONINE, TRYPTOPHAN and VALINE. GAS. essential fatty acid (biochemistry) Any ethanedioic acid (chemistry) An FATTY ACID that is required in the diet alternative term for ACID. of mammals because it cannot be synthesized. ethanoate (chemistry) An alternative They include linoLEIC ACID and y-linolenic term for ACETATE. ACID, obtained from plant sources. ethanoic acid (chemistry) An alternative essential oil (chemistry) VOLATILE term for acetic ACID. oil with a pleasant odour (USA: odor), obtained from various plants. Such oils ethanol (chemistry) C H OH Colourless are widely used in perfumery. 2 5 (USA: colorless) LIQUID ALCOHOL. It est. (general termino’ogy) An abbreviation is the active constituent of ALCOHOLic of ‘est’imated. drinks (in which it is produced by FERMENTATION); it is also used as a ester (chemistry) COMPOUND formed fuel and in the preparation of esters, when the HYDROGEN ATOM of the ethers and other ORGANIC COMPOUNDS. hydroxy GROUP in an OXYGEN- Also termed: ETHYL ALCOHOL; ALCOHOL. containing ACID is replaced by an ALKYL GROUP. Most important esters are derived ethanoyl chloride (chemistry) An from CARBOXYLIC ACIDS. alternative term for ACETYL CHLORIDE. esterification (chemistry) Formation ethene (chemistry) CH2=CH2 Colourless of an ESTER, generally by REACTION (USA: colorless) GAS with a sweetish between an ACID and an ALCOHOL. SMELL, important in chemical SYNTHESIS. Also termed: ETHYLENE. estimated (est.) (general terminology) An approximation. ether (chemistry) Member of a GROUP of ORGANIC COMPOUNDS that have estn (general terminology) An abbrevia- the GENERAL FORMULA ROR’, where tion of ‘est’imatio‘n’. R and R’ are ALKYL GROUPS. The commonest, diethyl OXIDE (diethyl ETHER, et al. (literary terminology) An abbrevia- or simply ETHER), (C2H5)O2, is a useful tion of ‘et’ ‘al’ii. [Latin, meaning, ‘and VOLATILE SOLVENT formerly used as others’.] an ANAESTHETIC (USA: anesthetic).

135 ETHOLOGY EUSTACHIAN TUBE ethology (biology) Scientific study of EUA (medical) An abbreviation of ANIMAL BEHAVIOUR (USA: behavior) ‘E’xamination ‘U’nder ‘A’naesthetic (USA: in the wild. examination under anesthetic).

ethyl (chemistry) C2H 5- Common eubacteria (bacteriology) The largest ALKYLGROUP derived from ETHANE. GROUP of BACTERIA, containing the most commonly encountered forms that ethyl acetate (chemistry) An alternative inhabit soil and WATER. The GROUP term for ETHYL ETHANOATE. contains gram POSITIVE BACTERIA and green photosynthetic BACTERIA. ethyl alcohol (chemistry) An alternative term for ETHANOL. eugenics (biology) Theory and practice of improving the human RACE through ethyl carbamate (chemistry) An alterna- genetic principles. This can range from tive term URETHANE. the generally discredited idea of selective breeding programmes to counselling ethyl ethanoate (chemistry) CH3COOC2H5 of parents who may be carriers of harmful Colourless (USA: colorless) LIQUID genes. ESTER with a fruity SMELL, produced by the REACTION between ETHANOL eukaryote (cytology) CELL with a certain (ETHYL ALCOHOL) and ethanoic (acetic) LEVEL of complexity. Eukaryotes have ACID, used as a SOLVENT and in a NUCLEUS separated from the medicine. Also termed: ETHYL ACETATE. CYTOPLASM by a NUCLEAR MEMBRANE. Genetic material is carried on chromosomes ethylbenzene (chemistry) An alternative consisting of DNA associated with term for styrene. PROTEIN. The CELL contains MEMBRANE- bounded organelles, e.g. mitochrondria ethylene (chemistry) An alternative and chloroplasts. All organisms are term for ETHENE. EUKARYOTIC except for BACTERIA and cyanophytes, which are prokaryotes. Also ethylene dibromide (chemistry) An termed: eucaryote. alternative term for dibromoethane. eukaryotic (cytology) Describing or ethylene glycol (chemistry) An alternative relating to a EUKARYOTE. term for ethanediol. europium Eu (chemistry) Silvery-white ethylene tetrachloride (chemistry) An metallic ELEMENT in GROUP IIIB of alternative term for TETRACHLOROETHENE. the PERIODIC TABLE (one of the LANTHANIDES), used in nuclear REACTOR ethyne (chemistry) An alternative term control rods. At. no. 63; r.a.m. 151.96. for ACETYLENE. Eustachian tube (anatomy) Channel ETP (physiology) An abbreviation of that connects the MIDDLE EAR with ‘E’lectron ‘T’ransport ‘P’article. the PHARYNX at the back of the THROAT in mammals and some other vertebrates. Eu (chemistry) The CHEMICAL SYMBOL It ensures that the AIR PRESSURE on for EUROPIUM. each side of the EAR DRUM is equal.

136 EUTECTIC MIXTURE EXPONENT

It is named after the Italian anatomist than the GROUND STATE, resulting Bartolomeo Eustachio (1520–74). (USA: from EXCITATION. eustachian tube). See also ENERGY LEVEL. eutectic mixture (chemistry) MIXTURE of substances in such proportions that exclusion principle (physics) An no other MIXTURE of the same substances alternative term for the Pauli EXCLUSION has a lower FREEZING POINT. PRINCIPLE. eV (measurement) An abbreviation of excretion (physiology) Removal of waste ‘e’lectron ‘V’olt. products of METABOLISM, carried out by elimination from the body or STORAGE evaporation (physics) Process by which in INSOLUBLE form. Products of PROTEIN a LIQUID changes to its VAPOUR. It METABOLISM are the main substances can occur (slowly) at a TEMPERATURE liberated. The chief organs of EXCRETION below the BOILING POINT, but is faster in vertebrates are the kidneys. if the LIQUID is heated and fastest when the LIQUID is boiling. exocrine gland (anatomy) GLAND that discharges secretions into ducts, e.g. even-odd nucleus (chemistry) Atomic salivary GLANDS. NUCLEUS with an even number of protons and an odd number of neutrons. See also ENDOCRINE GLAND. evolution (biology) Successive altering exogamy (biology) Outbreeding as distinct of SPECIES through time. Evolutionary from INBREEDING. See INBREEDING. theory states that the ORIGIN of all SPECIES is through EVOLUTION, and exothermic (chemistry) Describing a thus they are related by descent. process in which HEAT is evolved. exp. (1–7 general terminology) An abbreviation See also DARWINISM; NATURAL of 1 ‘exp’eriment. 2 ‘exp’ires. 3 ‘exp’onential. SELECTION. 4 ‘exp’eriment 5 ‘exp’erimental. 6 ex. (literary terminology) An abbreviation ‘exp’iration. 7 ‘exp’ire. of ‘ex’ample. Also termed e.g. expansion of gas (physics) Increase exch. (chemistry) An abbreviation of in VOLUME of an ideal GAS is at the ‘exch’ange. rate of 1/273 of its VOLUME at 0°C for each DEGREE rise in TEMPERATURE. excitation (physics) Addition of ENERGY See CHARLES’S LAW. to a system, such as an ATOM or NUCLEUS, causing it to transfer from its GROUND See also KINETIC THEORY. STATE to one of higher ENERGY. exponent (mathematics) Number that excitation energy (physics) ENERGY indicates the POWER to which a quantity required for EXCITATION. (the BASE) is to be raised, usually written as a superior number or symbol after excited state (physics) ENERGY state the quantity, e.g. in 23, 2X, the exponents of an ATOM or MOLECULE that is higher are 3 and x.

137 EXPONENTIAL GROWTH EYE TOOTH exponential growth (microbiology) The GROWTH that occurs, e.g. in cultures of MICRO-ORGANISMS, in which a population of CELLS increases in numbers logarithmically. exponential series (mathematics) A mathematical SERIES of functions of x that converges to ex. extracellular (histology) External to a CELL; in a MULTICELLULAR organism, EXTRACELLULAR TISSUE may still be within the organism.

See also INTRACELLULAR. extrafusal fibres (histology) The large contractile fibres (USA: fibers) contained in MUSCLE; their movement causes MUSCLE contraction. They consist of longitudinally arranged filaments of two kinds: MYOSIN and ACTIN. (USA: extrafusal fibers). extrapolation (statistics) Estimation of a value outside the range of those already known, usually by graphical methods. eye (anatomy) ORGAN for detecting LIGHT. eye tooth (anatomy) An alternative term for CANINE TOOTH.

138 F

F (1 measurement; 2 general terminolgy; that involves CARRIER molecules in 3 chemistry; 4 biochemistry) An the MEMBRANE, which eases the abbreviation of 1 ‘F’ahrenheit. Also transport of a specific substance but termed Fahr. 2 ‘F’emale. 3 The CHEMICAL does not involve the use of ENERGY; SYMBOL for FLUORINE. 4 A symbol e.g. the uptake of GLUCOSE by for phenylalanine. ERYTHROCYTES (RED BLOOD CELLS). The transport system can become

F 1 (genetics) The offspring of any two saturated with the transported substance, parents. Compare F2. in contrast to simple DIFFUSION.

F 2 (genetics) The offspring of two F, FACR (education) An abbreviation of parents (i.e. the third generation). ‘F’ellow of the ‘A’merican ‘C’ollege of

Compare F1. ‘R’adiology. f (microscopy) An abbreviation of ‘f’ocal facs. (general terminology) An abbreviation length. of ‘facs’imile. Also termed fs, and facsim. fa (chemistry) An abbreviation of ‘fatty facsim. (general terminology) See facs. ‘a’cid/‘f’olic ‘a’cid. factor (1 general; 2, 3 statistics; 4 FAAAS (society) An abbreviation of mathematics) 1 Anything having a causal ‘F’ellow of the ‘A’merican ‘A’ssociation influence on something, usually where for the ‘A’dvancement of ‘S’cience. there are several different causal influences. 2 A discrete VARIABLE used to classify FACA (education) An abbreviation of DATA (e.g. an INDEPENDENT VARIABLE) ‘F’ellow of the ‘A’merican ‘C’ollege of Compare LEVEL. 3 Any of the ‘A’llergists. INTERVENING VARIABLES discovered through FACTOR ANALYSIS that accounts face-centred cube (crystallography) Crystal for a significant proportion of the VARIANCE structure that is CUBIC with an ATOM of the DATA. 4 A number that divides or ION at the centre of each of the six into another number without remainder. faces of the cube in addition to the eight at its corners. (USA: face-centered cube). factor analysis (statistics) A GENERIC term for techniques whose OBJECTIVE FACG (education) An abbreviation of is to discover whether the correlations ‘F’ellow of the ‘A’merican ‘C’ollege of or covariances between a SET of observed ‘G’astroenterology. variables can be accounted for in terms of their relationships to a small number facilitated diffusion (biochemistry) of unobservable or INTERVENING MODE of transport through a MEMBRANE VARIABLES i.e. the factors. Essentially

139 FACTOR AXES FAJANS’ RULES

FACTOR ANALYSIS postulates a LINEAR (LEVEL) of each INDEPENDENT relation between the observed variables VARIABLE (FACTOR) is combined with and the underlying factors, which may each value (LEVEL) of every other be ESTIMATED by a VARIETY of methods. INDEPENDENT VARIABLE (FACTOR); At its simplest, FACTOR ANALYSIS is e.g. if there are two factors (A and B) a method for DATA REDUCTION, reducing each with two levels (1 and 2) the a large number of intercorrelated variables following combinations would be used: to a smaller number of INTERVENING A1B1, A1B2, A2BI, A2B2. VARIABLES which account for as much of the VARIANCE as possible. factorial validity (statistics) The extent to which scores on different tests factor axes (statistics) In FACTOR purporting to measure the same thing ANALYSIS the axes representing the are correlated. relations of the factors to one another; they may be orthogonal or oblique. facultative anaerobe (microbiology) MICRO-ORGANISM that grows under factor (mathematics) One of the numbers either ANAEROBIC or AEROBIC conditions. that will divide exactly into another given number (e.g. 2 and 3 are factors FAD (biochemistry) An abbreviation of 6), or which is one of the polynomials of ‘F’lavin ‘A’denine ‘D’inucleotide. that will divide exactly into another POLYNOMIAL (e.g. (x+2) and (x-5) are faeces (medical) The waste products factors of x 2 -3x-10). from the intestines, a third of which consists of dead or living BACTERIA. The remainder factor loading (statistics) In FACTOR being made up of food which has not ANALYSIS the correlation between a been digested, mostly CELLULOSE and test item and a FACTOR, i.e. the extent FIBRE (USA: fiber), dead CELLS from to which the score on an item is the lining of the INTESTINE, WATER, determined by a FACTOR. MUCUS, and the whole coloured (USA: colored) by BILE pigments. (USA: feces). factor matrix (statistics) A table showing the FACTOR LOADING of each test Fahr. (measurement) An abbreviation item with each FACTOR. of ‘fahr’enheit. factor VIII concentrate (medical/ Fahrenheit (F) (measurement) A UNIT haematology) A concentrated preparation of DEGREE of TEMPERATURE. The of FACTOR VIII that is used in the FREEZING POINT of WATER is 32° F; TREATMENT of those with HAEMOPHILIA the BOILING POINT of WATER is 212° A (USA: hemophilia A). F under standard atmospheric PRESSURE. Named after the German physicist Gabriel factorial (mathematics) PRODUCT of Daniel Fahrenheit (1686–1736). all the whole numbers from a given whole number n down to 1, written as FAIC (education) An abbreviation of n!; e.g. the FACTORIAL of 6 (written ‘F’ellow of the ‘A’merican ‘I’nstitute 6!) is 6×5× 4×3×2×1=720. of ‘C’hemists. factorial design (statistics) An Fajans’ rules (chemistry) SET of rules experimental design in which each value that state when IONIC BONDS are

140 FALLOPIAN TUBE FARADAY’S LAWS OF ELECTROMAGNETIC INDUCTION likely in a chemical COMPOUND (as FAPT (education) An abbreviation of opposed to COVALENT BONDS). They ‘F’ellow of the ‘A’ssociation of were named after the Polish chemist ‘P’hotographic ‘T’echnicians. Kasimir Fajans (1887–1975). farad (F) (measurement) SI UNIT of Fallopian tube (anatomy) Tube that electrical CAPACITANCE, defined as in female mammals conducts ova (eggs) the CAPACITANCE that, when charged from an OVARY to the UTERUS (womb) by a POTENTIAL DIFFERENCE of 1 by ciliary ACTION. FERTILIZATION can VOLT, carries a CHARGE of 1 coulomb. occur when SPERM meet eggs in the It was named after the British scientist tube. It was named after the Italian Michael Faraday (1791–1867). anatomist Gabriel Fallopius (1523–62). Also termed: OVIDUCT. (USA: fallopian faraday (F) (measurement) UNIT of tube). ELECTRIC CHARGE, equal to the quantity of CHARGE that during ELECTROLYSIS false negative (general terminology) liberates one gram EQUIVALENT WEIGHT Failure of a test to demonstrate the of an ELEMENT. It has the value disease or condition when present. 9.6487×104 coulombs per gram-equivalent. Contrast FALSE POSITIVE. See also FARAD; FARADAY CONSTANT. false positive (general terminology) A POSITIVE test result caused by a Faraday constant (F) (physics) Funda- disease or condition other than the mental physical CONSTANT, the disease for which the test is designed, ELECTRIC CHARGE carried by one or in the absence of disease altogether. mole of singly-charged ions or electrons, equal to 9.6487×104 coulombs per mole. false pregnancy (medical) An alternative It is the PRODUCT of the AVOGADRO term for PSEUDOPREGNANCY. CONSTANT and the ELECTRON CHARGE. family (biology) In biological CLASSIFI- Faraday effect (physics) Rotation of CATION, one of the groups into which the plane of vibration of a beam of an ORDER is divided, and which is itself POLARIZED LIGHT passing through divided into GENERA. See TAXONOMY. a substance such as GLASS, in the direction of an applied MAGNETIC FIELD. FAMS (education) An abbreviation of ‘F’ellow of the ‘I’ndian ‘A’cademy of Faraday’s laws of electrolysis (1, 2 ‘M’edical ‘S’ciences. chemistry) 1 The amount of chemical DECOMPOSITION that takes place during FANZAAS (education) An abbreviation ELECTROLYSIS is proportional to the of ‘F’ellow of ‘A’ustralian and ‘N’ew ELECTRIC CURRENT passed. 2 The ‘Z’ealand ‘A’ssociation for ‘A’dvancement amounts of substances liberated during of ‘S’cience. ELECTROLYSIS are proportional to their chemical EQUIVALENT WEIGHTS. FAPHA (education) An abbreviation of ‘F’ellow of the ‘A’merican ‘P’ublic Faraday’s laws of electromagnetic induction ‘H’ealth ‘A’ssociation. (1, 2 physics) 1 An induced ELECTRO- MOTIVE FORCE is established in an

141 FARINA FAUCES electric CIRCUIT whenever the MAGNETIC FASEB (society) An abbreviation of FIELD linking that CIRCUIT changes. ‘F’ederation of ‘A’merican ‘S’ocieties 2 The magnitude of the induced for ‘E’xperimental ‘B’iology. ELECTROMOTIVE FORCE in any CIRCUIT is proportional to the rate of change of fasting (general terminology) A length the MAGNETIC FLUX linking the CIRCUIT. of time without food and WATER. BASE levels are often obtained after the patient farina (1,2 biology) 1 STARCH or flour. has fasted where the intake of food 2 An alternative term for POLLEN. may influence the LEVEL of the FACTOR under investigation, as is the case for farmer’s lung (medical/mycology/immu- instance with BLOOD GLUCOSE levels. nology) A type of extrinsic allergic alveolitis sometimes called HYPERSENSITIVITY fat embolism (medical) Following serious pneumonitis. It is caused by the inhalation BONE injuries fat globules may be of dust from mouldy (USA: moldy) hay released into the bloodstream and cause or straw containing spores of the an embolism. organisms Micropolyspora faeni and Thermoactinomyces vulgaris, which infect fate map (genetics) A map of the CELLS the hay when it is damp and warm, or tissues in the fertilized EGG or early and are released when it has dried EMBRYO that shows where they will end out. These, in those sensitive, sets up in the adult organism. The DATA can up an allergic REACTION in the lungs, be collected by staining specific CELLS causing symptoms which include a in the EMBRYO with a non-diffusible FEVER, dry cough and shortness of dye; artificial chimaeras can also be used. breath. The disease may become CHRONIC with continued exposure and fats and oils (biochemistry) Naturally result in FIBROSIS of the LUNG. occurring esters (of GLYCEROL and FATTY ACIDS) that are used as ENERGY-STORAGE FAS (1 medical/biochemistry; 2 society) compounds. They are HYDROCARBONS 1 An abbreviation of ‘F’oetal ‘A’lcohol and members of a larger CLASS of naturally ‘S’yndrome. (USA: Fetal ALCOHOL occurring compounds called LIPIDS. SYNDROME). 2 An abbreviation of ‘F’ederation of ‘A’merican ‘S’cientists. fatty acid (chemistry) A monobasic CARBOXYLIC ACID, an essential fascia (histology) FIBROUS TISSUE constituent of FATS AND OILS. The organised to form sheets which lie simplest FATTY ACIDS are formic just under the SKIN (superficial FASCIA), (methanoic) ACID, HCOOH, and acetic and round muscles (deep FASCIA). (ethanoic) ACID, CH3COOH. The superficial FASCIA contains fat and the NERVES and BLOOD VESSELS fatty degeneration (histology) Disease running to the SKIN. The deep FASCIA of TISSUE caused by poisoning or lack forms dense fibrous sheaths for the of OXYGEN, in which droplets of fat muscles and compartments in which form within CELLS. groups of muscles lie together. fauces (anatomy) The opening between fascicle (histology) A slender bundle the mouth and the THROAT, bounded of NERVE FIBRES (USA: nerve fibers). above by the SOFT PALATE, below Also termed fasciculus. by the TONGUE, and on each side by

142 FBP FEHLING’S TEST the tonsils. The two folds of MUCOUS feedback (cybernetics) The influencing MEMBRANE containing MUSCLE fibres of the BEHAVIOUR (USA: behavior) of (USA: muscle fibers) before and behind a system by signals received about the the tonsils are called the pillars of effects of its output. In negative FEEDBACK the FAUCES. (the most common kind) the activity of the system is reduced by FEEDBACK FBP (physics) An abbreviation of ‘F’inal (a thermostat turns off the boiler when ‘B’oiling ‘P’oint. the external TEMPERATURE has risen enough). Most drives involve negative FCAP (education) An abbreviation of FEEDBACK. In POSITIVE feed-back the ‘F’ellow of the ‘C’ollege of ‘A’merican signals fed back increase the activity of ‘P’athologists. the system, producing a runaway process.

FCRA (education) An abbreviation of feedback inhibition (genetics) End- ‘F’ellow of the ‘C’ollege of ‘R’adiologists PRODUCT INHIBITION. A GENETIC of ‘A’ustralasia. ENGINEERING control system in which the PRODUCT, e.g. an ENZYME, inhibits FCS (education) An abbreviation of further production of itself. ‘F’ellow of the ‘C’hemical ‘S’ociety. feedback loop (cybernetics) The channel FCST (governing body) An abbreviation through which the output of a system of ‘F’ederal ‘C’ouncil for ‘S’cience and is fed back to it. See FEEDBACK. ‘T’echnology. feeder cells (immunology) CELLS whose FD (microscopy) An abbreviation of FUNCTION is to maintain the GROWTH ‘F’ocal ‘D’istance. of other CELLS, usually by secreting GROWTH factors. FDA (governing body) An abbreviation of ‘F’ood and ‘D’rug ‘A’dministration. Fehling’s solution (biochemistry) Test REAGENT consisting of two parts: a F distribution (statistics) The theoretical SOLUTION of COPPER(II) SULPHATE distribution of the F RATIO. It is the distribution (USA: copper(II) sulfate), and a SOLUTION of the ratio of the variances of two of POTASSIUM SODIUM TARTRATE and independent samples drawn from NORMAL SODIUM HYDROXIDE. When the two populations. It is used when testing the solutions are mixed, an ALKALINE HYPOTHESIS that the samples yielding SOLUTION of a SOLUBLE COPPER(II) the F RATIO have been drawn from the complex is formed. In the presence of an same population. It plays a part in numerous ALDEHYDE or REDUCING SUGAR, a tests including ANALYSIS OF VARIANCE pink-red PRECIPITATE of COPPER(I) OXIDE and those used in regression ANALYSIS. forms. It was named after the German chemist Hermann Fehling (1812–85). FDP (physiology/biochemistry) An abbreviation of ‘F’ibrinogen ‘D’egradation See also FEHLING’S TEST. ‘P’roducts. Fehling’s test (biochemistry) Test for Fe (chemistry) The CHEMICAL SYMBOL an ALDEHYDE GROUP or REDUCING for IRON. Derived from Latin, ‘ferrum’. SUGAR, indicated by the formation of

143 FEL FERTILIZATION

COPPER(I) OXIDE as a pink-red FEHLING’S ferrite (chemistry) Non-conducting ceramic SOLUTION. PRECIPITATE with material that exhibits FERRIMAGNETISM;

GENERAL FORMULA MFe2O 4, where FEL (toxicology) An abbreviation of M is a DIVALENT METAL of the ‘F’rank ‘E’ffect ‘L’evel. TRANSITION ELEMENTS. Ferrites are used to make powerful magnets in radars FELASA (society) An abbreviation of and other high-FREQUENCY electronic ‘F’ederation of ‘E’uropean ‘L’aboratory apparatus, such as COMPUTER memories. ‘A’nimal ‘S’cience ‘A’ssociation.

ferrocene (chemistry) C10H10Fe Orange felon (medical/microbiology) An INFECTION ORGAOMETALLIC COMPOUND, whose and ABSCESS of the pulp of the finger. molecules consist of an IRON ATOM ‘sandwiched’ between two molecules fem. (general terminology) An abbreviation of cyclopentadiene. Also termed: dicyclo- of ‘fem’ale/‘fem’inine. pentadienyliron. femur (anatomy) The thigh BONE. 4- ferrocyanide (chemistry) [Fe(CN)6] Very fermentation (chemistry/microbiology) STABLE COMPLEX ION of IRON(II). ENERGY-producing breakdown of Also termed: hexacyanoferrate(II). ORGANIC COMPOUNDS by MICRO- ORGANISMS (in the absence of OXYGEN); ferromagnetism (physics) Property of e.g. the breakdown of SUGAR by yeasts certain substances that in a magnetizing into ETHANOL, CARBON DIOXIDE and FIELD have INDUCED MAGNETISM, which ORGANIC ACIDS. FERMENTATION is persists when the FIELD is removed and a type of ANAEROBIC RESPIRATION. they become permanent magnets. Examples include IRON, COBALT and their ALLOYS. fermium Fm (chemistry) RADIOACTIVE ELEMENT in GROUP IIIB of the PERIODIC ferrous (chemistry) BIVALENT IRON. TABLE (one of the ACTINIDES). It has Also termed: IRON(II). several isotopes, with half-lives of up to 95 days. At. no. 100; r.a.m. (most fertility drug (pharmacology) A drug STABLE ISOTOPE) 257. given to a female to stimulate the OVARY to produce ripe eggs. A COMPOUND ferric (chemistry) TRIVALENT IRON. that stimulates the body’s own production Also termed: IRON(III). of the FOLLICLE-STIMULATING HORMONE (FSH) is used for this in the course of 3- ferricyanide (chemistry) [Fe(CN)6] Very TREATMENT for infertility, when it is STABLE COMPLEX ION of IRON(III). A often responsible for the woman becoming SOLUTION of the POTASSIUM SALT gives pregnant with more than one baby. a deep blue PRECIPITATE (Prussian blue) in the presence of IRON(II) (FERROUS) fertilization (biology) FUSION of ions. Also termed: hexacyanoferrate(III). specialized SEX CELLS or gametes which are HAPLOID to form a single CELL, a ferrimagnetism (physics) Property of DIPLOID ZYGOTE. It occurs in SEXUAL certain compounds in which the magnetic REPRODUCTION; e.g. in vertebrates moments of neighbouring ions align the OVUM (female GAMETE) is fertilized in anti-parallel fashion. by the SPERM (male GAMETE).

144 FES FIBRINOGEN

FES (education) An abbreviation of FIBMS (education) An abbreviation of ‘F’ellow of the ‘E’ntomological ‘S’ociety. ‘F’ellow of the ‘I’nstitute of ‘B’io‘-M’edical ‘S’ciences. Feulgen reaction for DNA (histology) Histological staining technique for fibre (anatomy) Any long thread-like NUCLEIC ACIDS. Feulgen REAGENT structure in the body. (USA: fiber). which contains fuchsin and SULPHURIC ACID (USA: sulfuric acid) is named fibre optics (optics) Branch of OPTICS after the German physiologist and chemist, that uses bundles of pure GLASS fibres R.Feulgen (1884–1955). (USA: glass fibers) within straight or curved ‘pipes’ or cables, along which LIGHT travels FEV (physiology) An abbreviation of as it is internally reflected. A modulated ‘F’orced ‘E’xpiratory ‘V’olume—in first LIGHT signal in such a cable can carry second of forced expiration after maximum much more DATA (e.g. COMPUTER DATA, inspiration. telephone signals, television channels) than a wire of similar dimensions. FIBRE- fever (physiology) A condition in which OPTIC cables are also used for making the body TEMPERATURE is above endoscopes. Also termed: OPTICAL FIBRES NORMAL, i.e. 37°C. Body TEMPERATURE (USA: optical fibers). is controlled by a centre (USA: center) in the BRAIN which maintains a BALANCE fibrescope (medical) An ENDOSCOPE between HEAT production and its loss using GLASS or plastic fibres (USA: from the surface of the body. INFECTION fibers) to carry images and LIGHT, by BACTERIA or VIRUSES, excite the which means that the instrument is MACROPHAGE CELLS of the reticulo- flexible and more readily introduced endothelial system to produce pyrogens, into the body cavity that is being examined substances which make the TEMPERATURE than the older endoscopes which were rise. A great number of conditions can rigid. (USA: fiberscope). produce FEVER, and when the cause of the FEVER is not known it is referred fibrillation (medical) MUSCLE fibres to as pyrexia of unknown (PUO). (USA: muscle fibers) normally contract in an orderly and co-ordinated fashion. FFA (biochemistry) An abbreviation In FIBRILLATION, the fibres contract of unesterified ‘F’ree ‘F’atty ‘A’cid. independently and spontaneously.

FGF (physiology) An abbreviation of fibrin (haematology) A PROTEIN ‘F’ibroblast ‘G’rowth ‘F’actor. substance which forms the framework of BLOOD clots. It is precipitated from FHR (medical) An abbreviation of ‘F’oetal the BLOOD by the ACTION of the ENZYME ‘H’eart ‘R’ate. (USA: Fetal HEART Rate). THROMBIN or FIBRINOGEN, which creates a BLOOD clot in a WOUND fi (general terminology) An abbreviation where BLOOD is exposed to AIR. of ‘f’or ‘i’nstance. fibrinogen (haematology) SOLUBLE FIBiol (education) An abbreviation of PLASMA PROTEIN found in BLOOD ‘F’ellow of the ‘I’nstitute of ‘Biol’ogy. which, after triggering of chemical factors (e.g. caused by a WOUND), is converted

145 FIBRO-ADENOMA FILAMENT to FIBRIN as part of the BLOOD-clotting fibrous tissue (histology) Scar TISSUE. mechanism. A simple, strong structural or repair TISSUE comprising of two proteins, fibro-adenoma (histology) A BENIGN COLLAGEN and elastin, laid down by TUMOUR (USA: tumor) which is commonly CELLS called fibroblasts. found in the breast, consisting of glandular and FIBROUS TISSUE. fibula (anatomy) Leg BONE, located below the knee and outside the TIBIA (shin BONE) fibroblast (cytology) Long flat CELL in the hind-limb of a tetrapod VERTEBRATE. found in CONNECTIVE TISSUE which secretes PROTEIN; e.g. COLLAGEN FIC (education) An abbreviation of ‘F’ellow and elastic fibres (USA: elastic fibers). of the ‘I’nstitute of ‘C’hemistry. fibrocystic disease (medical) See fiche (general terminology) An CYSTIC FIBROSIS. abbreviation of micro‘fiche’. fibroid (histology) A common BENIGN field (1 physics; 2 optics; 3 computing) TUMOUR (USA: benign tumor) consisting 1 In physics, region in which one OBJECT of MUSCLE and FIBROUS TISSUE exerts a FORCE on another OBJECT; enclosed within a CAPSULE found in e.g. ELECTRIC FIELD, GRAVITATIONal the UTERUS, usually in women over FIELD, MAGNETIC FIELD. 2 In OPTICS, thirty years of age. There is often more AREA that is visible through an optical than one, and symptoms may include instrument. 3 In computing, specific part pain, heavy menstrual PERIODS, and of a RECORD, or a GROUP of characters the size of the TUMOUR (USA: tumor) that make up one piece of information. may interfere with the BLADDER and cause difficulty in passing URINE. field-emission microscope (microscopy) MICROSCOPE used for the observation fibroma (histology) A BENIGN TUMOUR of the positions of atoms in a surface. (USA: benign tumor) composed of FIBROUS TISSUE, usually small and fig. (literary terminology) An abbreviation unimportant. of ‘fig’ure. fibrosarcoma (histology) A MALIGNANT figure (fig.) (literary terminology) TUMOUR (USA: malignant tumor) of Referring to a chart or table within a FIBROUS TISSUE which grows relatively text. slowly, often in muscles near the surface of the body. It invades neighbouring FIH (education) An abbreviation of ‘F’ellow tissues but is slow to spread to other of the ‘I’nstitute of ‘H’ygiene. parts; if it does so, it may metastasise to the lungs. filament (1 physics; 2, 3 biology) 1 In electrical apparatus, a fine wire of fibrosis (histology) Formation of high resistance which is heated by FIBROUS TISSUE or scar TISSUE usually passing an ELECTRIC CURRENT directly in repair or replacement of cellular through it. Filaments are used in electric elements destroyed by injury, INFECTION fires and incandescent lamps, and as or deficient BLOOD supply. heaters in thermionic valves. 2 HYPHA

146 FILARIASIS FISSURE of a FUNGUS. 3 String of CELLS that porous medium, e.g. FILTER paper or make up certain ALGAE. GLASS WOOL, through which only the LIQUID passes. filariasis (medical/parasitology) Infestation with Filaria, a genus of parasitic thread- fine chemical (chemistry) Chemical like worms, found mainly in the tropics produced in pure form and in small and subtropics. The adults of Filaria quantities. bancrofti and Filaria malayi live in lymphatics, connective tissues or mesentery, fine structure (physics) Splitting of where they may cause obstruction, but certain lines in a line SPECTRUM into the embryos migrate to the blood stream. a number of further discrete lines, which Completion of the life cycle is dependent are observable only when high resolution upon passage through a mosquito. is employed. film (1 physics; 2 PHOTOGRAPHY) 1 Flnst. P (education) An abbreviation Thin layer of one substance on the of ‘F’ellow of the ‘Inst’itute of ‘P’hysics. surface of another substance, e.g. oil floating on WATER. Thin films can firing (physiology) The initiation of a sometimes diffract LIGHT and produce NERVE IMPULSE. rainbow colours (USA: colors). See DIFFRACTION. 2 Plastic strip carrying Fisher’s exact probability test (statistics) a LIGHT-sensitive EMULSION that is A test of independence in two-by-two used in PHOTOGRAPHY. contingency tables giving exact probability levels for all SAMPLE sizes. filter (1 physics; 2 OPTICS) 1 Porous material through which a LIQUID is Fisher’s z-test (statistics) A test to passed to remove suspended MATTER. determine the significance of a correlation 2 In OPTICS, LIGHT-absorbing semi- COEFFICIENT employing FISHER’S TRANSPARENT material that passes Z-TRANSFORMATION. only certain wavelengths (colours [USA: colors]). 3. In ELECTRONICS, device Fisher’s z-transformation (statistics) A that passes only certain a.c. frequencies. TRANSFORMATION of the PRODUCT-moment correlation which yields an approximately filter pump (laboratory equipment) Simple NORMAL DISTRIBUTION. It is useful in VACUUM PUMP in which a jet of WATER constructing tests of the significance draws AIR molecules from the system. of correlations and their differences. It can produce only low pressures and is commonly used to increase the speed fission (1 physics; 2 biology) Splitting. of FILTRATION by drawing through the 1 In atomic physics, DISINTEGRATION FILTRATE. of an ATOM into two parts, usually with the release of ENERGY and one or more filtrate (chemistry) LIQUID obtained neutrons. 2 In biology, DIVISION of a after FILTRATION. CELL or single-celled organism into two. See MEIOSIS; MITOSIS. filtration (chemistry) Method of separating a suspended SOLID from a LIQUID fissure (anatomy) A groove in a surface, by passing the MIXTURE through a particularly a comparatively large groove

147 FISTULA FLOCCULATION in the surface of the CORTEX. The term in most MOTILE gametes and UNICELLULAR sulcus is used of smaller grooves in plants or animals (e.g. PROTOZOA), in the CORTEX, but in practice the terms which they occur singly or in small clusters. are often interchangeable. In some MULTICELLULAR organisms (e.g. sponges and hydra) they are used for fistula (medical) An opening either circulation of WATER containing food and into the interior of the body or in an respiratory gases. internal ORGAN, such as can be produced by a WOUND, or by surgery (e.g. a See also CILIUM. tube implanted through the wall of the STOMACH). The term is used both for flame test (chemistry) QUALITATIVE the opening in the TISSUE and for chemical test in which an ELEMENT any tube that is passed through it. in a substance is identified by the CHARACTERISTIC COLOUR (USA: color) fixation of nitrogen (biology) Part of it imparts to a BUNSEN BURNER flame. the NITROGEN CYCLE that involves flash point (chemistry) Lowest TEM- the conversion and eventual incorporation PERATURE at which a substance or a of atmospheric NITROGEN into MIXTURE gives off sufficient VAPOUR compounds that contain NITROGEN. to produce a flash on the application of NITROGEN FIXATION in nature is carried a flame. out by nitrifying soil BACTERIA or BLUE- GREEN ALGAe (CYANOPHYTA) in the flavin adenine dinucleotide (FAD) sea. Soil BACTERIA may exist symbiotically (chemistry) CO-ENZYME that functions in the ROOT nodules of leguminous in the OXIDATION-REDUCTION REactions plants or they may be free-living. Small of ENZYMES, e.g. the oxidative amounts of NITROGEN are also fixed, DEGRADATION of PYRUVATE, FATTY as NITRIC OXIDE, by the ACTION of ACIDS and AMINO ACIDS, and in lightning. See SYMBIOSIS. ELECTRON TRANSPORT. Also termed: flavine. fixed point (physics) Standard TEM- PERATURE chosen to define a flavonoid (chemistry) Aromatic, OXYGEN- TEMPERATURE SCALE or at which containing HETEROCYCLIC ORGANIC properties are measured, e.g. the ICE COMPOUND. Many natural pigments POINT (0°C) and the steam point (100°C). are flavonoids. Also termed: fixed TEMPERATURE. flavoprotein (chemistry) Member of a fl.rt (general terminology) An abbreviation GROUP of CONJUGATED proteins in of ‘fl’ow ‘r’a‘t’e. which the PROSTHETIC GROUP constitutes a DERIVATIVE of RIBOFLAVIN (e.g. FAD flagellate (microbiology) Single-celled or FMN). FLAVOPROTEIN dehydrogenases protozoan ANIMAL that moves by beating (ENZYMES) are involved in the ELECTRON flagella. See FLAGELLUM. TRANSPORT chain of AEROBIC RESPIRATION. flagellum (microbiology) Long HAIR-like ORGANELLE whose beating movement flocculation (chemistry) COAGULATION causes locomotion or the movement of of a finely divided PRECIPITATE into FLUID over a CELL. Flagella are present larger particles.

148 FLOPPY DISK FLUORINE floppy disk (computing) Flexible, portable lungs and the BLOOD. Some such as MAGNETIC DISK that provides DATA and Chlonorchis sinensis, the LIVER FLUKE, PROGRAM STORAGE for microcomputers. parasitises humans and causes disease. The DISK may be enclosed in a flexible or a rigid casing. Also termed: DISKETTE. fluor. (1 physics; 2 chemistry) 1 An abbreviation of ‘fluor’escent. 2 An See also HARD DISK. abbreviation of ‘fluor’ide.

fluid (physics) Form of MATTER that fluorescein (chemistry) C20H12O5 A dark can flow; thus both gases and liquids orange-red dye which dissolves in ALKALIS are fluids. Fluids can offer no permanent (USA: alkalies) to give a solution with resistance to changes of shape. a green FLUORESCENCE. It is used Resistance to flow is manifest as as a chemical marker and for dyeing VISCOSITY. textiles. Also termed: resorcinolphthalein. fluid balance (physiology) On AVERAGE fluorescence (chemistry) Emission of the loss of FLUID through URINE, between RADIATION (generally VISIBLE LIGHT) 1200 ml and 1500 ml a day, and from after ABSORPTION of RADIATION of another perspiration and in the breath, up to 1000 WAVELENGTH (usually ULTRAVIOLET ml, requires to be balanced by the intake RADIATION or near-ULTRAVIOLET of about two or three LITRES of FLUID RADIATION) or electrons; it ceases when a day. Additional loss through vomiting the stimulating source is removed. or DIARRHOEA (USA: diarrhea), which also results in a loss of essential electrolyes, See also LUMINESCENCE; PHOSPHORE- requires additional intake of FLUID and SCENCE. electrolyes. See DEHYDRATION. fluorescent lamp (laboratory equipment) fluid ounce (measurement) Measure MERCURY-VAPOUR DISCHARGE LAMP of the VOLUME of liquids. 1 fl oz=28.41 that uses phosphors to produce LIGHT cm3. by FLUORESCENCE. fluid retention (medical) A condition fluoridation (chemistry) Addition of in which URINE DISCHARGE from the inorganic fluorides to drinking WATER urinary tract is drastically reduced. to combat dental DECAY. The most common cause is impaired KIDNEY FUNCTION. FLUID RETENTION fluoride (chemistry) COMPOUND can have important consequences on containing FLUORINE; SALT of both WATER and ELECTROLYTE HYDROFLUORIC ACID (HF). BALANCE and is treated symptomatically during maintenance THERAPY. fluorination (chemistry) Replacement of atoms, usually HYDROGEN, in an fluidity (physics) Property of flowing ORGANIC COMPOUND by FLUORINE. easily; the opposite of VISCOSITY. fluorine F (chemistry) Gaseous nonmetal- flukes (TREMATODES) (parasitology) lic ELEMENT in GROUP VIIA of the A large GROUP of parasitic flatworms PERIODIC TABLE (the HALOGENS). A which can infest the intestines, LIVER, pale green-yellow poisonous GAS, it is

149 FLUORITE FOCUSING highly reactive and the most electronegative LENS it is the FOCAL LENGTH divided ELEMENT, occurring in FLUORIDE minerals by the DIAMETER of the APERTURE. such as FLUORSPAR. It is used, as The smaller the f-number, the larger the gaseous URANIUM(VI) FLUORIDE the APERTURE. In the usual sequence

(UF6), in the separation by DIFFUSION f22, f11, f8, f5.6, f4 etc., each APERTURE of URANIUM isotopes and in making has twice the AREA, and therefore fluorocarbons. Inorganic fluorides are admits twice the amount of LIGHT as added to WATER supplies to combat the preceding one in the series. TOOTH DECAY. At. no. 9; r.a.m. 18.9984. FNZ1C (education) An abbreviation fluorite (chemistry) An alternative term of ‘F’ellow of the ‘N’ew ‘Z’ealand ‘I’nstitute for FLUORSPAR. of ‘C’hemistry. fluorocarbon (chemistry) Very STABLE foam (physics) See FROTH. ORGANIC COMPOUND in which some or all of the HYDROGEN atoms have focal distance (FD) (microscopy) been replaced by FLUORINE. Distance from the OPTICAL CENTRE Fluorocarbons are used as solvents, (USA: center) of a LENS to the point AEROSOL propellants and refrigerants. where LIGHT rays from a distant OBJECT Their use is being limited because converge. Also known as FOCAL LENGTH. they have been implicated in damage to the OZONE layer of the ATMOSPHERE. focal length (optics) Distance from the centre (USA: center) of a LENS See also FREON. or curved mirror to its FOCUS. Also termed: FOCAL DISTANCE. fluoroscope (radiology) FLUORESCENT screen that allows direct observation of focal plane (microscopy) A plane perpendicular X-RAY images, often connected to a camera. to the OPTICAL AXIS of a LENS and It is used in medicine (RADIOGRAPHY) passing through the FOCAL POINT. and industrial X-RAY applications. focal point (microscopy) The point fluorspar (chemistry) CaF Naturally 2 on the OPTICAL AXIS of a LENS at occurring CALCIUM FLUORIDE, used which parallel rays converge. as a flux in GLASS and as a COMPONENT of certain cements. Also termed: FLUORITE. focus (1,2 microscopy) 1 The point or Fm (chemistry) The CHEMICAL SYMBOL plane at which LIGHT rays, or other for FERMIUM. electromagnetic rays, converge after passing through an optical system. An IMAGE on FMN (biochemistry) An abbreviation this plane is said to be ‘in FOCUS’ and of ‘F’lavin ‘M’ono‘N’ucleotide. will have the minimum amount of blur. 2 An alternative term for FOCAL LENGTH. fn. (literary terminology) An abbreviation of ‘f’oot‘n’ote. focusing (microsopy) Adjusting a LENS or optical system so that LIGHT rays f-number (photography) Method of from points at a given distance converge denoting the DIAMETER of a LENS to form an IMAGE in a particular plane. APERTURE in a camera. For a simple

150 FOETAL ABNORMALITIES FOOD POISONING foetal abnormalities (toxicology) The HORMONES that are secreted by the results of teratogenic effects on the ANTERIOR LOBE of the PITUITARY GLAND FOETUS (USA: fetus). These differ from in vertebrates. It stimulates the GROWTH those that occur on exposure of the and maturation of OVARIAN FOLLICLES EMBRYO. Characteristically they are and the GROWTH only of oocytes, which GROWTH retardation and functional are matured under the ACTION of deficits rather than anatomical birth LUTEINIZING HORMONE. In males FSH defects. (USA: fetal abnormalities). stimulates SPERM formation in the TESTES. foetal stage (medical) The stage of follicular phase (physiology) The PHASE prenatal existence that follows the of the OESTROUS CYCLE (USA: estrous embryonic stage; it lasts from about cycle) in which the OVUM matures in women, the eighth week after conception until roughly the first 14 days of the CYCLE. birth. (USA: fetal stage). fomites (EPIDEMIOLOGY) Articles that foetus (biology) The unborn mammalian have been in contact with an infected EMBRYO from the time that it has the person such as clothes, bedding, toys, recognisable features of its final form books, etc; that might be capable of i.e. from the end of the second month becoming contaminated and of spreading after conception, (pl. foetuses). (USA: the INFECTION. fetus, pl. fetuses). See EMBRYOGENESIS. folic acid (haematology/biochemistry) Fontana stain (histology) Histological A WATER SOLUBLE VITAMIN of the B staining technique for MELANIN. complex which acts as a COENZYME in various processes involing the METABOLISM fontanelle (anatomy) The hole covered of purines and pyrimidines and which is by a MEMBRANE in the infant’s SKULL essential for the formation of NORMAL where the bones are not yet fully closed. RED BLOOD CELLS. Insufficient FOLIC ACID in the diet, available in green leafy Food and Drug Administration (FDA) vegetables and YEAST, or impaired (governing body) A US government ABSORPTION because of intestinal disease agency within the Department of Health leads to deficiency of this VITAMIN. and Human Services that monitors the Deficiency may result in a REDUCTION purity and safety of food, cosmetics, of RED BLOOD CELLS and those that and drugs; truth in packaging and labelling are present may be larger than they information; and sanitary practices in should be, a state called megaloblastic restaurants and other food-handling ANAEMIA (USA: megaloblastic anemia). establishments. Deficiency of FOLIC ACID may also be caused by CHRONIC ALCOHOLISM and food poisoning (medical/microbiology/ as the result of taking certain drugs toxicology) Food poisoning can be due such as phenytoin. to toxic chemicals contaminating the food, to eating poisonous plants or, in most follicle (histology) A very small secreting cases, to BACTERIAL INFECTION. The GLAND, or cyst. commonest organisms are Campylobacter jejuni. Salmonella sp., Staphylococcus follicle stimulating hormone (FSH) aureus, and Clostridium perfringens and (biochemistry) Member of a GROUP of very rarely Clostridium botulinum.

151 FOOT FORTIN BAROMETER

Occasionally Bacillus cereus is the cause. forebrain (anatomy) Largest and topmost See DIARRHOEA. portion of the VERTEBRATE BRAIN that comprises the CEREBRAL HEMISPHERES foot (measurement) UNIT of length and the BASAL NUCLEUS. in the IMPERIAL SYSTEM, corresponding to 12 inches or 1/3 of a YARD, and forensic medicine (medical) That part equal to 30.48 centimetres. of medicine concerned with the LAW. foot-pound (measurement) WORK done formal saline (histology) A 10 per when a MASS of 1 pound is lifted 1 cent SOLUTION of FORMAL SALINE foot against the FORCE of gravity, is used as a fixative preparation. equivalent to 1.3558 joules. Also termed: foot-pound-FORCE. formaldehyde (chemistry) HCHO Colour- less (USA: colorless) pungent organic footprinting (molecular biology) Techni- GAS, an ALDEHYDE, which is readily que for finding DNA sequences that SOLUBLE in WATER. It is used as a have a PROTEIN bound to them which disinfectant and in the manufacture of protects them from being cut by plastics. Also termed: METHANAL. endonucleases. Two samples of the whole DNA MOLECULE are prepared, formalin (histology) A 40 per cent one with the PROTEIN and one without. SOLUTION of the GAS FORMALDEHYDE, Both are digested with a restriction used for fixing and preserving tissues, endonuclease and the resulting fragments and in DILUTION as an ANTISEPTIC. are run on an electrophoretic GEL. When the two gels are compared, the formic acid (chemistry) HCOOH Simplest bands that have resisted cutting by CARBOXYLIC ACID, made commercially the ENZYME, because of being protected by the catalytic COMBINATION of CARBON by the PROTEIN, will be distinguishable MONOXIDE and SUPERHEATED STEAM. because they do not match the bands It occurs naturally in the stings of certain on the other GEL. In this way, DNA insects such as ants, bees and wasps. sequences that bind proteins, such Also termed: METHANOIC ACID. as regulatory sequences, promoters, formula (1 mathematics; 2 chemistry) and so on, can be identified. 1 Mathematical expression that shows for. (1 general terminology; 2 medical) the relationship between various 1 An abbreviation of ‘for’eign. 2 An quantities; e.g. the FORMULA for the p 2 abbreviation of ‘for’ensic. AREA of a circle of RADIUS r is A= r . 2 Chemical composition of a substance force (physics) Influence that can make indicated by the symbols of each a stationary OBJECT move, or a moving ELEMENT present in it and subscripts OBJECT change speed or direction, i.e. that show the number of each type of that changes the OBJECT’S momentum. ATOM involved; e.g. the FORMULA for

It is equal to MASS multiplied by WATER is H2O, that for POTASSIUM

ACCELERATION. The SI UNIT of FORCE DICHROMATE is K2Cr2O 7.2H2O. Also is the NEWTON. termed: CHEMICAL FORMULA. force ratio (physics) An alternative Fortin barometer (physics) MERCURY term for mechanical advantage. BAROMETER, used for the accurate

152 FORTRAN FRACTIONATING COLUMN measurement of ATMOSPHERIC PRES- FPAS (education) An abbreviation of SURE. It was named after the French ‘F’ellow of the ‘P’akistan ‘A’cademy physicist Jean Fortin (1750–1831). of ‘S’ciences.

FORTRAN (computing) An abbreviation FPharmS (education) An abbreviation of ‘FOR’mula ‘TRAN’slation. A COMPUTER of ‘F’ellow of the ‘Pharm’aceutical ‘S’ociety programming language designed for of Great Britain. mathematical and scientific use. Fr (chemistry) The CHEMICAL SYMBOL forward mutation (genetics) A change for FRANCIUM. from the NORMAL, or wild-type, version of an ALLELE to a MUTANT form. The FRACI (education) An abbreviation of vast majority of MUTATIONS are of ‘F’ellow of the ‘R’oyal ‘A’ustralian this type. Contrast back MUTATION. ‘C’hemical ‘I’nstitute. fossa (anatomy) A depressed or hollow fraction (mathematics) Part of a whole, AREA. represented mathematically by a pair of numbers. The upper NUMERATOR Fouchet stain (histology) Histological is written above the lower DENOMINATOR staining technique for BILE pigments. and separated from it by a horizontal or diagonal line; e.g. 1/2, 3/4, 7/10. Fourier analysis (mathematics) Mathe- Fractions of a hundred may be given matical method of expressing a complex as percentages; e.g. 65/100=65 per FUNCTION that represents a WAVE cent (sometimes written 65%). In decimal as a SERIES of simpler SINE WAVES. fractions, the denominators are powers It was named after the French of 10 (10, 100, 1,000, etc.), usually mathematical physicist Jean Fourier written using a decimal point and place (1768–1830). values as for whole numbers, for instance 27/1,000=0.027. fovea (histology) Part of the RETINA of the EYE that has a CONCENTRATION See also COMMON DENOMINATOR. of cones (but no rods), which comes into play when ACUTE vision is required. fractional crystallization (chemistry) Also termed: YELLOW SPOT. Separation of mixtures of substances by the repeated CRYSTALLIZATION foxglove (pharmacology) A plant, DIGI- of a SOLUTION, each time at a lower TALIS purpurea in the FAMILY Scro- TEMPERATURE. phulariaceae, that contains the cardioa- ctive agent DIGITALIS. fractional distillation (chemistry) Separa- tion of a number of liquids with different See also DIGITALIS. BOILING POINTS by DISTILLATION and collecting separately the liquids fp (1 general terminology; 2, 3 physics; that come off at different temperatures. 4 literary terminology) 1 Abbreviation Also termed: FRACTIONATION. of ‘f’lame‘p’roof. 2 Abbreviation of ‘f’lash‘- p’oint. 3 An Abbreviation of ‘f’reezing‘- fractionating column (chemistry) Long p’oint. 4 Abbreviation of ‘f’rontis‘p’iece. vertical tube containing bubble-caps,

153 FRACTIONATION FREE ERYTHROCYTE PROTOPORPHYRIN sieve plates, or various irregular packing F ratio (statistics) The ratio of the variances materials, used for industrial FRACTIO- of two independent samples from NORMAL NAL DISTILLATION. populations. It is used in ANALYSIS OF VARIANCE. See F DISTRIBUTION. fractionation (chemistry) An alternative term for FRACTIONAL DISTILLATION. FRCPath. (education) An abbreviation of ‘F’ellow of the ‘R’oyal ‘C’ollege of fragile x syndrome (genetics) A genetic ‘Path’ologists. disorder causing mental retardation in males. It is the result of a MUTATION FRCR (education) An abbreviation of in the region at the very end of the ‘F’ellow of the ‘R’oyal ‘C’ollege of X CHROMOSOME, which is particularly ‘R’adiologists. liable to lose pieces—hence the name free electron (physics) An eLECTRON ‘fragile X’. Some female carriers are free to move from one ATOM or also slightly affected. MOLECULE to another under the influence of an ELECTRIC FIELD. The movement fragilitas ossium (medical/genetics) of free electrons enables a CONDUCTOR A rare inherited disease in which the to carry an ELECTRIC CURRENT. bones are abnormally fragile. Also termed osteogenesis imperfecta. free energy (physics) Measure of the ability of a system to perform WORK. framboesia (bacteriology) See YAWS. free erythrocyte protoporphyrin (FEP) frameshift mutation (genetics) A (haematology) An indirect measure of MUTATION in which one or more BASE- LEAD levels in BLOOD. Protoporphyrin pairs are inserted into or deleted from is formed in the MITOCHONDRION during a GENE, so that the reading frame of the differentiation of the ERYTHROCYTE every codon after that point is shifted in the BONE MARROW. The conversion along. For example, if the original code to haem (USA: heme) requires the was UCU-CAA-AGG-UUA, and the INSERTION of IRON into the proto- MUTATION put an extra U at the beginning, porphyrin ring. There is an exponential the message would be read as UUC- increase in INHIBITION of porphobilinogen UCA-AAG and so on. synthase (aminolevulinic ACID dehydratase, ALAD) as BLOOD levels francium Fr (chemistry) RADIOACTIVE of LEAD increases. The result is a metallic ELEMENT in GROUP IA of decreased production of porphobilinogen the PERIODIC TABLE (the ALKALI (protoporphyrin PRECURSOR) and METALS), made by PROTON inhibition of ferrochelatase, which causes bombardment of THORIUM. It has several accumulation of inactive HAEMOGLOBIN isotopes with half-lives of up to 22 (USA: hemaglobin) molecules which min. At. no. 87; r.a.m. 223 (most STABLE contain ZINC protoporphyrin (ZPP) instead ISOTOPE). of haem (USA: heme). The FEP ANALYSIS, based on the FLUORESCENCE of ZPP, frank effect level (FEL) (toxicology) is technically much simpler than the A LEVEL of exposure to a chemical measurement of LEAD in BLOOD. or MIXTURE that provides an ACUTE, unequivocal deleterious effect. See also LEAD.

154 FREE RADICAL FRIPHH free radical (chemistry) INTERMEDIATE freq. (general terminology) An abbrevia- and highly reactive MOLECULE that tion of ‘freq’uency. has an unpaired ELECTRON and so easily forms a CHEMICAL BOND. frequency (freq.) (1 physics; 2 statistics) 1 Rate of recurrence of WAVE, i.e. freeze drying (chemistry) Method of drying number of cycles, oscillations or vibrations HEAT-sensitive substances such as BLOOD in UNIT time, usually one second. The PLASMA or food by FREEZING them FREQUENCY of a WAVE is inversely below 0°C and then removing the frozen proportional to the WAVELENGTH. The WATER by volatilization in a VACUUM. SI UNIT of FREQUENCY is the hertz (which corresponds to 1 CYCLE per freezing (physics) Solidification of a second). 2 The number of times a given LIQUID that occurs when it is cooled phenomenon occurs. sufficiently (to below its FREEZING POINT). frequency curve (statistics) A curve freezing mixture (chemistry) MIXTURE in which the FREQUENCY of occurrence of two substances that absorbs HEAT of each of a SET of consecutive values, and can be used to produce a or of values grouped in intervals, is TEMPERATURE below 0°C. plotted on the vertical AXIS and the values on the horizontal AXIS. See also EUTECTIC MIXTURE. frequency distribution (statistics) The freezing point (physics) TEMPERATURE FREQUENCY with which the members at which a LIQUID solidifies. Also termed: of a SAMPLE or of a population take solidification point. one of a SET of consecutive values, or values grouped in intervals, or with FREnt.S (education) An abbreviation which they are distributed among different of ‘F’ellow of the ‘R’oyal ‘Ent’omological categories. ‘S’ociety. FRES (education) An abbreviation of free energy (physics) Measure of the ‘F’ellow of the ‘R’oyal ‘E’ntomological ability of a system to perform WORK. ‘S’ociety of London. free erythrocyte protoporphyrin (FEP) FRIC (education) An abbreviation of (haematology) An indirect measure of ‘F’ellow of the ‘R’oyal ‘I’nstitute of LEAD levels in BLOOD. Protoporphyrin ‘C’hemistry. is formed in the MITOCHONDRION during the differentiation of the Friedman test (statistics) A non- ERYTHROCYTE in the BONE MARROW. parametric test applicable to DATA in The conversion to haem (USA: heme) which there are more than two MATCHED requires the INSERTION of SAMPLES. It is based on ranking the scores within each SAMPLE. Compare freon (chemistry) Trade name for certain Wilcoxon test. fluorocarbons and chlorofluorocarbons derived from methane and ETHANE. FRIPHH (education) An abbreviation They are used as refrigerants. of ‘F’ellow of the ‘R’oyal ‘I’nstitute of ‘P’ublic ‘H’ealth and ‘H’ygiene.

155 FRMS FUNGI

FRMS (education) An abbreviation of F test (statistics) A statistical test based ‘F’ellow of the ‘R’oyal ‘M’icroscopical on the F RATIO and F DISTRIBUTION. ‘S’ociety. It is used in anova and in testing whether two variances are equal. frontal (anatomy) Towards the front of the body or of an ORGAN. fulminant (medical) Severe. froth (physics) Collection of fairly STABLE fumigation (microbiology/parasitology) small bubbles in a LIQUID produced The process of burning or volatilising by shaking, aeration or addition of a substances in ORDER to produce vapours foaming agent, e.g a DETERGENT. which destroy infective organisms and Also termed: foam. vermin. It is now rarely employed. frozen section (histology) A process function (1 general terminology; 2 in which a BIOPSY is taken, frozen mathematics; 3 computing) 1 The natural and cut into sections for the pathologist use to which anything can be put, its to examine under the MICROSCOPE role or purpose. 2 Mathematical and provide a rapid answer as to whether expression that involves one or more a TISSUE is MALIGNANT or not. variables. 3 Any operation performed by a PROGRAM, a use similar to the FRS (education) An abbreviation ‘F’ellow term’s mathematical meaning. of the ‘R’oyal ‘S’ociety. of functional group (chemistry) ATOM FRSSI (education) An abbreviation of or GROUP of atoms that cause a chemical ‘F’ellow of the ‘R’oyal ‘S’tatistical ‘S’ociety COMPOUND to behave in a particular of ‘I’reland. way; e.g. the FUNCTIONAL GROUP in ALCOHOLS is the -OH (hydroxyl) GROUP. FRSSS (education) An abbreviation of ‘F’ellow of the ‘R’oyal ‘S’tatistical fundamental units (measurements) ‘S’ociety of ‘S’cotland. Units of length, MASS and time that form the basis of most systems of units. FRSTM & H (education) An abbreviation See SI UNITS. of ‘F’ellow of the ‘R’oyal ‘S’ociety of ‘T’ropical ‘M’edicine and ‘H’ygiene. fungi (mycology) One of the five kingdoms of living things, containing a number fructose (chemistry) C6H12O6 Fruit SUGAR, of GENERA that are medically important a MONOSACCHARIDE CARBOHYDRATE such as Candida SPECIES and Aspergillus (HEXOSE) found in sweet fruits and SPECIES, and others of economical honey. Also termed: LAEVULOSE. importance such as the YEAST Saccharomyces. Much genetic research fs (general terminology) See FACS. has been done on other FUNGI, including the moulds (USA: molds) Aspergillus FSH (biochemistry) An abbreviation and Neurospora. Although they are plants, of ‘F’ollicle-‘S’timulating ‘H’ormone. FUNGI are unable to photosynthesize (i.e. utilize ENERGY from sunlight to FSH-RH (physiology/biochemistry) Ab- synthesize ORGANIC COMPOUNDS), breviation of ‘FSH’-‘R’eleasing ‘H’ormone so they have to obtain their food by

156 FUNGICIDES FUSION GENE living off other plants or animals, alive the CIRCUIT, that heats and melts or dead. FUNGI can reproduce either (thereby breaking the CIRCUIT) when by CELL DIVISION (equal or unequal, the CURRENT exceeds a certain value. the latter including either BUDDING or the production of spores) or by SEXUAL fusiform (microbiology) Spindle shaped, REPRODUCTION, in which case they as in the ANAEROBE Fusobacterium have alternation of generations, with nucleatum. HAPLOID and DIPLOID forms. fusiform cell (cytology) A type of stellate See also CLASSIFICATION. CELL in the CORTEX that has two short vertical projections which divide fungicides (pharmacology/mycology) into many long processes running upwards Substance that kills FUNGI. A diverse or downwards from the CELL BODY. GROUP of chemicals drawn from several different classes, produced for the control fusiform layer (histology/cytology) The of PATHOGENIC FUNGI, primarily those innermost layer of NERVE CELLS in affecting food and ornamental plants, the CEREBRAL CORTEX, containing although a few drugs are available to mostly FUSIFORM CELLS. treat fungal diseases of humans and animals. fusion (1 cytology; 2 physics) 1 The intimate mixing of CELLS to produce fungus (mycology) Mainly terrestrial plant- a HYBRID CELL. 2 Act of melting or like organism, different from other plants joining together. because of its lack of chlorophyll. Most FUNGI are saprophytic or parasitic organisms fusion gene (genetics) A GENE resulting e.g. moulds (USA: molds) whose walls from the accidental mixing of parts of consists of CHITIN, although a few produce two different genes. This may happen CELLULOSE as well. They are classified as the result of a small deletion occurring as the plant DIVISION (PHYLUM) Mycota, between two genes, leaving their ends although some authorities put them in joined up. FUSION GENES can also a KINGDOM of their own. be made in vitro using RECOMBINANT DNA technology. furanose (chemistry) Any of a GROUP of MONOSACCHARIDE sugars (pentoses) whose molecules have a five-membered HETEROCYCLIC ring of four CARBON atoms and one OXYGEN ATOM.

See also PYRANOSE. furuncle (medical) A boil. fuse (physics) Device used for protecting against an excess ELECTRIC CURRENT passing through a CIRCUIT. It consists of a piece of METAL, connected into

157 G

G (1 measurement; 2 computing; 3 put on a GALACTOSE-free (i.e. nonmilk) physics; 4 biochemistry) 1 An abbreviation diet, in which case there are no ill effects. of ‘G’iga-. 2 An abbreviation of ‘G’igabyte. This diet can be relaxed after the age 3 An abbreviation of ‘G’ravitational of five. The genetic cause is an autosomal CONSTANT. 4 A symbol for glycine. RECESSIVE, and about 1 in 50,000 babies is affected. HETEROZYGOTES g (measurement) An abbreviation of (i.e. carriers) among the siblings of an ‘g’ram. Also termed gm. affected child can be identified by biochemical tests. (USA: galactosemic). Ga (chemistry) The CHEMICAL SYMBOL for GALLIUM. galactose (chemistry) C6H12O6 MONO- SACCHARIDE SUGAR that occurs in GABA (biochemistry) An abbreviation milk and in certain gums and seaweeds for ‘G’amma-‘A’mino‘B’utyric ‘A’cid. as the POLYSACCHARIDE galactan.

GABA-T (biochemistry) An abbreviation gall (biochemistry) An alternative term of ‘GABA’ ‘T’ransaminase. for BILE.

GAD (biochemistry) An abbreviation gall bladder (anatomy) STORAGE of ‘G’lut‘A’mate ‘D’ecarboxylase. ORGAN in some vertebrates that, stimulated by HORMONES, releases gadolinium Gd (chemistry) Silvery- BILE (along the BILE DUCT) to the white metallic ELEMENT in GROUP DUODENUM during DIGESTION. IIIB of the PERIODIC TABLE (one of the LANTHANIDES), which becomes gallium Ga (chemistry) Blue-grey metallic strongly magnetic at low temperatures. ELEMENT in GROUP IIIa of the At. no. 64; r.a.m. 157.25. PERIODIC TABLE, used in low-MELTING POINT ALLOYS and thermometers. At. gain (physics) The DEGREE to which no. 31; r.a.m. 69.72. a signal is amplified (POSITIVE GAIN) or reduced (negative GAIN) when it gallon (measurement) UNIT of LIQUID passes through a system or from one and dry CAPACITY, equal to four quarts system to another. or eight pints. One Imperial gallon is the VOLUME occupied by ten pounds galactosaemic (biochemistry) A geneti- of DISTILLED WATER. One Imperial cally determined disease in which the gallon= 4.54609 LITRES. One US gallon=5/ LIVER degenerates from early infancy 6 Imperial gallons, or 3.7854 LITRES. owing to the inability to metabolize the SUGAR GALACTOSE; there is also serious gallstone (biochemistry) Accretion, mental deterioration. If the condition is usually of CHOLESTEROL or CALCIUM diagnosed at birth, the baby can be salts, that occurs in the GALL BLADDER

158 GALLYAS TECHNIQUE GAS or its ducts. Also termed: BILIARY produced, e.g. during the DECAY of CALCULUS. certain RADIO-ISOTOPES. It is used to sterilize food, to make industrial gallyas technique (histology) A staining radiographs and in medicine (RADIO- technique that may be used to show THERAPY). neurofibrillary changes in CNS. gamma rays (radiology) High-ENERGY GALT (histology) An abbreviation of photons that make up GAMMA RADIATION. ‘G’ut ‘A’ssociated ‘L’ymphoid ‘T’issue. gamma-aminobutyric acid (GABA) galvanic (physics) Pertaining to DIRECT (biochemistry) An AMINO ACID that CURRENT, as opposed to ALTERNATING is an inhibitory NEUROTRANSMITTER; CURRENT. it is found in the CORTEX, basal ganglia, and elsewhere in the CENTRAL galvanic cell (physics) An alternative NERVOUS SYSTEM. term for a VOLTAIC CELL. ganglion (1,2, medical) 1 A collection galvanic skin response (GSR) (physiol- of NERVE CELLS in the course of a ogy) A decrease in the ELECTRICAL NERVE or a NETWORK of NERVE RESISTANCE of the SKIN, occurring FIBRES (USA: nerve fibers) outside in a state of arousal, whether pleasant the CENTRAL NERVOUS SYSTEM. or unpleasant; it is produced by activity of the SWEAT GLANDS. The resistance Compare NUCLEUS. 2 A cystic swelling change is often measured in ORDER found in relation to a TENDON. to detect arousal. ganglion cell (cytology) A CELL with galvanometer (physics) Device that a large roughly spherical body. They detects or measures small ELECTRIC are found, e.g. as the third-ORDER CURRENTS passing through it. retinal CELLS (whose axons enter the OPTIC NERVE) and as the first-ORDER gamete (cytology) Specialized SEX CELL AUDITORY CELLS, as well as in other (e.g. an OVUM or a SPERM), which is sensory systems. usually HAPLOID (containing half the NORMAL number of chromo-somes). gangrene (medical/microbiology) Death Gametes are customarily produced by of a part or TISSUE due to failure of a male and a female, and they combine BLOOD supply, disease, or injury. at FERTILIZATION to form a ZYGOTE that develops into a new organism (with gap junction (physiology) A SYNAPSE the NORMAL, DIPLOID, CHROMOSOME at which the gap between the presynaptic number). Also termed: GERM CELL. and postsynaptic CELLS is only about 2 nm wide and is bridged by channels See also PARTHENOGENESIS. of membranous particles. Ions and other small molecules can pass through it from gamma globulin (immunology) An one CELL to the other. GAP JUNCTIONS alternative term for IMMUNOGLOBULIN. are the basis of the electrical SYNAPSE. gamma radiation (radiology) Penetrating gas (chemistry) Form (PHASE) of form of ELECTROMAGNETIC RADIATION MATTER in which the atoms and of shorter WAVELENGTH than X-RAYS, molecules move randomly with high

159 GAS CHROMATOGRAPHY GASTROINTESTINAL speeds, occupy all the space available, place directly between CELLS and the and are comparatively far apart; a ENVIRONMENT. VAPOUR. A LIQUID heated above its BOILING POINT changes into a GAS. gas laws (physics) Relationships between PRESSURE, VOLUME and TEMPERA- gas chromatography (biochemistry) TURE of a GAS. The COMBINATION A method of analysing mixtures of of Boyle’s, CHARLES’S and Gay-Lussac’s substances. The SAMPLE is volatilized laws is the GAS EQUATION. and then introduced into a column containing the stationary PHASE (a gas thermometer (physics) THERMO- SOLID or a non-VOLATILE LIQUID on METER based on the VARIATION in an INERT support), and an INERT PRESSURE or VOLUME of a GAS. Also CARRIER GAS (e.g. ARGON) is passed termed: CONSTANT-VOLUME GAS through the column. Components of THERMOMETER. the MIXTURE are removed from the gas-liquid chromatography (physics/ column by the CARRIER GAS at different chemistry) (GLC) Type of GAS CHRO- rates. A detector measures the electrical MATOGRAPHY in which the column CONDUCTIVITY of the GAS leaving contains a non-VOLATILE LIQUID on the column, which is recorded on a an INERT support. chart as a SERIES of peaks corresponding to each of the components. The chart gastric (medical) Pertaining to the is calibrated by passing samples of STOMACH or DIGESTION. known composition through the machine. gastric juice (biochemistry) FLUID gas constant (R or R ) (physics) A 0 secreted by GLANDS in the STOMACH CONSTANT in the GAS EQUATION, wall during DIGESTION; it contains -1 -1 value 8.31434 j mol K . Also termed: two principal ENZYMES, PEPSIN and universal molar gas constant. RENNIN, and HYDROCHLORIC ACID. gas equation (physics) For n moles gastric lavage (medical) The washing of a GAS, pV=nRT, where p=PRESSURE, of the STOMACH usually with SALINE V =VOLUME, n=number of moles, R= solutions via a lavage tube. It is used the GAS CONSTANT and T ABSOLUTE as a rapid method to remove STOMACH TEMPERATURE. contents in poisoning cases, particularly in cases in which EMESIS is not gas exchange (physiology) Part of recommended. RESPIRATION in which organisms exchange gases (CARBON DIOXIDE gastric ulcer (medical) See PEPTIC ULCER. and OXYGEN) with their ENVIRONMENT: AIR for terrestrial plants and animals, gastritis (medical) INFLAMMATION of WATER for aquatic ones. It may involve the STOMACH. the use of lungs (mammals, birds, adult amphibians and reptiles), gills (larval gastrointestinal (anatomy) Pertaining to amphibians, fish and other aquatic the digestive tract. In humans, this consists animals), spiracles (insects and other of the BUCCAL CAVITY, OESOPHAGUS terrestrial arthropods) or stomata (green (USA: esophagus), STOMACH, SMALL plants). In other organisms (e.g. aquatic INTESTINE (DUODENUM, JEJUNUM and plants, FUNGI) GAS EXCHANGE takes ILEUM), LARGE INTESTINE (COLON and

160 GASTROSCOPE GENE

RECTUM), with various associated GLANDS measurements. It was named after the and accessory structures. German physicist Hans Geiger (1882– 1945). Also termed: Geiger-Müller COUNTER. gastroscope (medical) An ENDOSCOPE for viewing the interior of the STOMACH. See also COUNTER. No ANAESTHETIC (USA: anesthetic) is needed for the examination, which Geiger-Nuttal law (physics) Empirical is perhaps uncomfortable but safe. LAW for calculating the distance that an ALPHA PARTICLE can travel once it gastrostomy (medical) An operation is emitted from a RADIOACTIVE substance. on the STOMACH in which an opening is made between the STOMACH and gel filtration chromatography (biochemis- the overlying abdominal wall, used in try) See CHROMATOGRAPHY, GEL cases in which the OESOPHAGUS (USA: FILTRATION. esophagus) is blocked or the patient is unable to swallow. A self-retaining catheter gel filtration (chemistry) A type of or tube is introduced into the opening CHROMATOGRAPHY in which compounds through which the patient is fed. are separated according to their molecular size. Molecules of the components of gate (computing) An electronic CIRCUIT a MIXTURE penetrate the surface of (switch) that produces a single output an INERT porous material in proportion signal from two or more input signals. to their size. Also termed: gel permeation. Also termed: LOGIC ELEMENT. gel. (chemistry) An abbreviation of Gay-Lussac’s law of volume (physics) ‘GEL’ATIN. When gases react their volumes are in a simple ratio to each other and to the gelatin (chemistry) A colourless (USA: VOLUME of products, at the same colorless) and TRANSPARENT substance TEMPERATURE and PRESSURE. It was made from the COLLAGEN of the named after the French chemist and CONNECTIVE TISSUE of animals. It physicist Joseph Gay-Lussac (1778–1850). has the consistency of jelly.

GBG (biochemistry) An abbreviation See COLLOID. of ‘G’onadal steroid-‘B’inding ‘G’lobulin. gen. (1, 2 classification; 3 genetics; G-CSF (physiology) An abbreviation 4 anatomy) 1 An abbreviation of ‘gen’eric. of ‘G’ranulocyte—‘C’olony ‘S’timulating 2 An abbreviation of ‘gen’us. 3 An ‘F’actor. abbreviation of ‘gen’etic. 4 An abbreviation of ‘gen’ital. Gd (chemistry) The CHEMICAL SYMBOL for GADOLINIUM. gene (genetics) The BASIC UNIT of HEREDITY. A GENE is a sequence of Ge (chemistry) The CHEMICAL SYMBOL DNA, occupying its own place, or LOCUS, for GERMANIUM. on a CHROMOSOME. Most genes are structural, i.e. they code for a particular Geiger counter (radiology) Instrument PROTEIN; these genes are divided into for detecting atomic and sub-atomic particles housekeeping and LUXURY GENES. Other (e.g. ALPHA PARTICLES and BETA genes code for the RNA molecules that PARTICLES), used for RADIOACTIVITY are necessary for PROTEIN SYNTHESIS,

161 GENE AMPLIFICATION GENE LIBRARY and others again provide recognition gene divergence (genetics) The process markers for the polymerase ENZYMES by which a sequence of related genes involved in GENE REGULATION. A GENE arises from an original single GENE may exist in two or more alternative that has been duplicated a number of forms, called ALLELES. Genes do not times and then undergone divergent change except in the very rare event of changes in the different copies. MUTATION. There are many genes in the human GENOME that have been gene dosage (genetics) The number passed unchanged down the generations of times that a GENE is represented for millions of years. in an organism’s CELLS, or total GENOME. It can range from as low as one, if See also MUTATION. there is a single-copy GENE on the X CHROMOSOME in animals, to many gene amplification (genetics) The process thousands for a highly duplicated GENE. by which extra copies of a GENE that is needed temporarily are made. This gene expression (genetics) The can occur naturally, e.g. in Drosophila production of RNA and cellular proteins. females who when required multiply ten fold the genes that code for the proteins gene flow (genetics) The movement that compose the membranes of their of genes from one population into a eggs. Gene amplification can also be neighbouring one. It may happen by artificially induced, and has been observed interbreeding or migration or both. in mice, who respond to a sub-lethal dose of CADMIUM by multiplying copies gene frequency (genetics) The FREQUE- of the genes coding for the PROTEIN NCY with which a particular ALLELE occurs metallothioncin that neutralizes the at a given LOCUS. It is expressed as a POISON. decimal: if there are only two ALLELES, the GENE frequencies could be, for example, gene cloning (genetics) The technique 0.1 and 0.9 (the total must add up to 1). of taking a complete GENE from an EVOLUTION is really a matter of changing organism’s GENOME and inserting it, GENE frequencies: the old ALLELE gets via a plasmid, into a HOST BACTERIAL rarer as the new one comes in, and finally CELL. To make sure that the GENE will the new one may become fixed, so that be expressed by the BACTERIAL CELL, there is a complete change in the genetic regulatory regions as well as the coding constitution of the population in respect sequence of the GENE must be included. of that LOCUS. Taken over a sufficient This technique, perhaps the most BASIC number of loci (which could perhaps be one in GENETIC ENGINEERING, can rather few), this gives rise to a new SPECIES. be used to produce large amounts of Changes in GENE FREQUENCY are brought the PRODUCT of any GENE that has about by NATURAL SELECTION, GENE been isolated. Human genes have been FLOW, founder effect and GENETIC DRIFT. cloned in ESCHERICHIA COLI to produce once scarce proteins for TREATMENT gene library (genetics) A collection of of people whose own GENE is defective; the genes from a SPECIES, maintained these proteins include GROWTH as GENE clones. It is different from a HORMONE and INSULIN. DNA library in that the items stored are whole genes, not DNA fragments.

162 GENE POOL GENERIC gene pool (genetics) The total number of ‘choices’ made by GENE SWITCHing of ALLELES in an interbreeding population. are irreversible. gene product (genetics) The MOLECULE gene therapy (medical/genetics) The that is made from the information in TREATMENT of disorders by altering a single GENE. In the majority of cases the genetic material in a CELL, e.g. it is a PROTEIN or POLYPEPTIDE, by microinjection of favourable genes but some genes code for a sequence into a GERM CELL. Genetic disorders of RNA. See PROTEIN SYNTHESIS. that could possibly be suitable for this approach Include HAEMOPHILIA (USA: gene regulation (genetics) The various hemophilia), severe combined immune systems by which genes that are not deficiency, sickle-CELL ANAEMIA (USA: constitutive i.e. in use all the time, are sickle-cell anemia), and THALASSAEMIA switched on and off. GENE REGULATION (USA: thalassemia). is the means by which CELLS specialize into the very many different CELL types genera (biology) Plural of GENUS. found in even quite simple organisms, and by which organisms respond moment general formula (chemistry) Expression by moment to changes in their external representing the common CHEMICAL and internal ENVIRONMENT. Most of FORMULA of a GROUP of compounds what is known about regulation has e.g. C nH2n+2 is the GENERAL FORMULA been discovered in prokaryotes, and for an ALKANE. A SERIES of compounds EUKARYOTE GENE REGULATION is of the same GENERAL FORMULA still hardly understood. The key feature constitute an HOMOLOGOUS SERIES. in prokaryotes is the OPERON, a sequence of DNA in which the regulatory genes generally regarded as safe (GRAS) and the several structural genes e.g. (toxigenicity) Term used by the Food for a metabolic process, are in a line, and Drug Administration applied to one next to the other. Some operons substances that are not known to cause are inducible, that is they are not harm when used as directed. transcribed until they are switched on by the presence of some MOLECULE generation time (1 genetics; 2 microbiol- within the CELL. Others are repressible, ogy) 1 The AVERAGE time in a SPECIES i.e. they are normally transcribed until between the birth of an individual and they are switched off by some MOLECULE its production of offspring. 2 The time within the CELL. within a population of CELLS (e.g. MICROORGANISMS) that it takes for gene splicing (genetics) See RECOM- them to undergo DIVISION to form BINANT DNA. pairs of DAUGHTER CELLS; i.e. the doubling time. gene switch (genetics) The moment when a developing organism changes generic (classification) The official name over from one GENE, or SET of genes, of a drug is the generic name, as opposed to another related one. A classic example to the brand name given it by the is the change in humans from foetal manufacturer. HAEMOGLOBIN (USA: fetal hemaglobin) to the adult equivalent. The SERIES

163 GENET GENETIC MAP genet (genetics) An organism raised clonally is often used. The technique is also from a single ZYGOTE. See CLONE. used in the study of genetic material.

See also ORTET. genetic fingerprinting (genetics) A technique which distinguishes the genetic code (genetics) A code which individuality of an individuals DNA. Devised consists of three NUCLEOTIDE bases by the British geneticist Alec Jeffreys occurring in a DNA or RNA MOLECULE. (1950-), GENETIC FINGERPRINTING It determines which AMINO ACID is is the ANALYSIS of the Alu sequence incorporated into a PROTEIN at a given that is present in many repeats in the point in the sequence. The code thus human GENOME. The number of repeats, contains instructions for all ENZYMES their position in the GENOME and their produced in the CELL, and consequently exact sequence differs from one person the characteristics of the organism. to another. The repeats are digested with restriction endonucleases and genetic death (genetics) The death of identified by SOUTHERN BLOTTING. a GENE, in the sense that the individual The technique has been used in forensic who carried it failed to reproduce. This science in two ways. First it can identify may have been because the individual with certainty whether a SAMPLE of itself died as a result of carrying the BLOOD, SALIVA or SEMEN came from GENE, but not necessarily. From the a particular individual. Second, it can genetical point of view, it is the fact that establish whether a child is or is not fertility was reduced to zero that counts. the offspring of an alleged mother or father, given that the genetic fingerprint genetic distance (genetics) A measure of the other parent is available. of the amount of relatedness of two individuals or populations, in terms of genetic load (genetics) The hidden the probability of their possessing the burden on a population of deleterious same ALLELES at a LOCUS or loci. RECESSIVE MUTATIONS. While these ALLELES are in the HETEROZYGOUS genetic drift (genetics) Random fluctuation state, they do no harm, but once they in the FREQUENCY of particular genes meet in the HOMOZYGOUS state, they in a population. It becomes an important damage the individual and therefore effect in small populations when drift the population. can cause the loss of an ALLELE from the GENE POOL even though it was a genetic map (genetics) A diagram that useful one. shows the position on a CHROMOSOME of the various genes that are known to genetic engineering (genetics) be on it. A method has been devised Manipulation of genetic material such using the FREQUENCY of crossing-over as DNA for practical use, e.g. the between two genes as a measure of introduction of foreign genes into MICRO- how far apart they are on a CHROMOSOME: ORGANISMS for the production of a two genes exactly next to each other useful PROTEIN (such as human will very seldom have a cross-over between INSULIN). The DNA so produced is them, but genes at opposite ends of a called RECOMBINANT DNA, and the CHROMOSOME will be separated by term ‘RECOMBINANT DNA technology’ any cross-over along the length of the

164 GENETIC SCREENING GENOME

CHROMOSOME. The BASIC technique at present, understood. The ethical issue of mapping is therefore to make large will have to be confronted, as to whether numbers of crosses involving two or it is justifiable to exclude a person more loci at which there are distinguishable from a job or benefit because of his or variant ALLELES, and to RECORD the her GENOTYPE. On the face of it, there number of times that RECOMBINATION does not seem to be much difference of the original types has taken place. between GENETIC SCREENING and The FREQUENCY of the crossovers is ordinary medical screening, where the expressed as a PERCENTAGE, and one civil rights of the person not to be PERCENTAGE point is known as a MAP discriminated against has to be weighed UNIT. When three or more loci are mapped against the civil rights of other people in this way, the MAP UNITS add up as who may be put at risk by that person’s they should. For example, if LOCUS A medical condition. and LOCUS B have a 7 per cent cross- over FREQUENCY between them, and genetic variance (genetics) The proportion LOCUS B and LOCUS C have 10 per of the total VARIANCE of a trait that is cent, loci A and C have crossovers in due to genes. It may have several 17 per cent of instances. Other methods components, due to the ADDITIVE of locating genes on chromosomes include EFFECTS of separate genes, or dominance, deletion mapping, and restriction mapping. or INTERaction. The rest of the VARIANCE is environmentally produced. The relative genetic screening (genetics) There contribution of genetic factors to VARIANCE are two different types of GENETIC is not a fixed feature of any trait. See SCREENING. The first is the search HERITABILITY. within a well-defined population or community for carriers of a deleterious genetics (genetics) Study of inheritable RECESSIVE GENE, in ORDER to advise characteristics of organisms; i.e. them of the risk of having an affected HEREDITY. child. This can only be done if (a) the community can be identified as having genito-urinary (GU) (anatomy) Pertaining a significantly HIGH FREQUENCY of to both the reproductive structures and the MUTANT GENE; (b) there is a simple the urinary tract. and cheap test to identify carriers; (c) there is a prenatal test to be used for genocopy (genetics) A genetically pregnancies at risk; and (d) the procedure determined CHARACTER that mimics is acceptable to the community. Given the appearance of another genetically these conditions, GENETIC SCREENING determined CHARACTER, though caused can be successful in reducing the number by an ALLELE at a different LOCUS. of babies born with a particular DEFECT. The second type of GENETIC SCREENING genome (genetics) The total amount is the genetic inspection of persons of genetic information that an organism for employment, insurance assessment possesses; the sum of its genes. In and other commercial transactions. This eukaryotes, this means the entire SET is more a problem for the future than of genes in a HAPLOID SET of for the present, as genetic factors affecting chromosomes. The GENOME of a VIRUS employment (e.g. susceptibilities to may be made up of either DNA (single particular workplace hazards) are not, or double stranded) or RNA; it can be

165 GENOTYPE GERM LAYER as small as 3500 BASE-pairs and may genus (gen.) (taxonomy) In biological contain as few as three genes.The GENOME CLASSIFICATION, one of the groups of a PROKARYOTE (BACTERIA, etc.) into which a FAMILY is divided, and is contained in a doublestranded DNA which is itself divided into SPECIES. MOLECULE (not strictly a CHROMOSOME), and contains from about 750,000 to See also BINOMIAL NOMENCLATURE. 4,500,000 BASE-pairs, comprising up to about 1500 genes. This MOLECULE geometric isomerism (chemistry) Form is extremely compact. The eukaryotes of stercoisomerism that results from have even larger genomes, and in general, there being no free rotation about a the higher up the evolutionary scale, BOND between two atoms. Groups the larger the GENOME (but with exceptions: attached to each ATOM may be on the some SPECIES of amphibians and fish same side of the BOND (the cis-ISOMER) have genomes nearly 40 times larger or on opposite sides (the trans-ISOMER). than the AVERAGE for mammals). The Also termed: cistrans isomerism. size of the GENOME bears no simple relationship to the number of chromosomes: geometric mean (statistics) A measure closely related SPECIES may have either of central tendency, arrived at by taking a large number of small chromosomes the nth ROOT of the PRODUCT of all or vice versa, for roughly the same- scores, where n is the number of scores. sized GENOME. Humans have a GENOME Contrast ARITHMETIC MEAN. of about 2900 million basepairs of DNA, which, if it were all in one DNA MOLECULE, geometric progression (statistics) Se- would be 1 METRE long. (This is the quence of numbers whose sucessive HAPLOID total; each of our body CELLS members differ by a CONSTANT multiplier. has twice this amount.) It would be physically E.g. for the geometric progression, 2, possible for there to be as many as 8, 32, 128,…the common multiplier is 4. one million genes encoded in that much DNA, but in common with other eukaryotes, See also ARITHMETIC PROGRESSION. humans have many instances of repetitive sequences of DNA that do not seem to geometric series (statistics) SERIES have any meaning, and the actual number whose terms form a GEOMETRIC of WORKING genes is probably much PROGRESSION. lower. There are also many genes that are present in multiple copies. germ cell (genetics) See GAMETE. genotype (genetics) Genetic constitution germ (microbiology) Imprecise term of an organism, i.e. the characteristics for a MICRO-ORGANISM that can cause specified by its ALLELES. It is the outward disease; a PATHOGEN. GERMS include appearance of the organism, as opposed BACTERIA; PROTOZOA; VIRUSES. to the way its genes are expressed (which is the PHENOTYPE). germ layer (histology) Layer of CELLS present in an EMBRYO. In triploblastic gentian violet (chemistry) An ANILINE organisms the layers consist of dye used by microscopists as a stain. ECTODERM, MESODERM and endoderm, As crystal violet it may be used on unbroken which each give rise to particular tissues. SKIN as an ANTISEPTIC.

166 GERMAN MEASLES GIGABYTE german measles (medical/virology) giant pyramidal cell (cytology) See See RUBELLA. BETZ CELL. germanium Ge (chemistry) Grey-white giardiasis (parasitology) A protozoan semi-metallic ELEMENT in GROUP IVA INFECTION with Giardia lamblia, a of the PERIODIC TABLE, which occurs PARASITE with flagellae found in the in some SILVER ores. It is an important SMALL INTESTINE. It produces cysts, semiconductor, used for making solid- which are passed in the FAECES (USA: state diodes and transistors. Its OXIDE FECES) and spread by contaminated is used in optical instruments and INFRA- food and WATER. The organism is found RED cameras. At. no. 32; r.a.m. 72.59. worldwide, but is most common in the hotter countries. It causes ACUTE or germinal stage (physiology) The first CHRONIC DIARRHOEA (USA: chronic stage of embryonic development, which diarrhea), and is a cause of TRAVELLER’S lasts about two weeks, during which DIARRHOEA (USA: traveller’s diarrhea) there is little cellular differentiation in some cases. It is also liable to infect in the human EMBRYO. those with immune deficiency syndromes. The condition is treated with gerontology (physiology) The study metronidazole or tinidazole; cases of of aging. cyst carriers who have no symptoms may also be treated with these drugs. gestation (physiology) The process of carrying the EMBRYO and fetus from GIBiol. (education) An abbreviation conception to birth. The duration of of ‘G’raduate of the ‘I’nstitute of ‘Biol’ogy. PREGNANCY. Giemsa for helicobacter pylori (histology) gestational diabetes (biochemistry) A histological staining technique that ABNORMAL GLUCOSE TOLERANCE may be used to make helicobacter pylori during PREGNANCY with return to visible under the MICROSCOPE. NORMAL after delivery. Giemsa stain (histology) A histological GeV (measurement) An abbreviation staining technique that may be used of ‘G’iga-‘e’lectron-‘V’olt, which is 109 to make BLOOD CELLS and PARASITES ELECTRON volts. visible under the MICROSCOPE.

GFR (physiology) An abbreviation of GIFT (medical) An abbreviation of ‘G’amete ‘G’lomerular ‘F’iltration ‘R’ate. ‘I’ntra-‘F’allopian ‘T’ransfer. A form of assisted REPRODUCTION in which EGG gg (immunology) An abbreviation of and SEMEN are deposited in the ‘g’amma ‘g’lobulin. FALLOPIAN TUBE via the laparoscope.

GH (biochemistry) An abbreviation for giga- (G) (measurement) A prefix meaning ‘G’rowth ‘H’ormone. 1,000,000,000 [one BILLION], used with units of measurement. GI (anatomy) An abbreviation of ‘G’astro‘I’ntestinal. gigabyte (G) (computing) A COMPUTER term denoting one BILLION bytes or

167 GIGANTISM GLAUBER’S SALT

1,000 megabytes of information or (EXOCRINE GLAND) into tubular organs STORAGE space. or onto the body surface. gigantism (medical/biochemistry) The state glanders (bacteriology) A disease of of having abnormally large bones, caused horses, donkeys and mules, which is by an excess of GROWTH HORMONE. due to INFECTION by the BACTERIUM Pseudomonas mallei, which has virtually GIH (physiology/biochemistry) An been eliminated in the Western world. abbreviation of ‘G’rowth HORMONE- It can be passed on to man, and the ‘I’nhibiting ‘H’ormone. disease is almost invariably fatal.

Gimenez stain (histology) A histological glands (histology) A specialised GROUP staining technique that may be used of CELLS which secrete or excrete to make helicobacter pylori visible under substances which are not the same the MICROSCOPE. as those needed for their own METABOLISM, and which act on other gingivitis (medical) INFLAMMATION tissues and in places other than the of the gums. GLAND itself. GLANDS are ‘exocrine’, when the SECRETION is removed through GIP (physiology/biochemistry) An a duct, or ‘endocrine’, when it passes abbreviation of ‘G’astric ‘I’nhibitory into the bloodstream. The word is also ‘P’eptide. used to MEAN a LYMPH NODE.

GIU (biochemistry) An abbreviation of glandular fever (virology) See infective ‘G’lucose ‘I’n the ‘U’rine. See DIABETES mononucleosis. MELLITUS. glass electrode (laboratory equipment) g/I (measurement) grams per LITRE. GLASS MEMBRANE ELECTRODE used to measure HYDROGEN ION CONCEN- Gla (biochemistry) A symbol for gamma- TRATION or PH. carboxyglutamic acid. glass (chemistry) Hard brittle AMORPHOUS glabrous (microbiology) Smooth. MIXTURE of the silicates of SODIUM and CALCIUM, or of POTASSIUM and CALCIUM. glacial (chemistry) Describing a COMPOUND In some particularly strong or HEAT-resistant of ICE-like CRYSTALLINE form, especially forms of GLASS, BORON replaces some that of the SOLID form of a LIQUID, e.g. of the atoms of SILICON. GLASS is usually GLACIAL ACETIC (ethanoic) ACID. TRANSPARENT or TRANSLUCENT. glacial acetic acid (chemistry) glass wool (chemistry) Material that CRYSTALLINE form of acetic (ethanoic) consists of fine GLASS fibres (USA: ACID below its FREEZING POINT. glass fibers), used in filters, as a thermal INSULATOR and for making fibreglass gland (anatomy) In animals, ORGAN (USA: fiberglass). that synthesizes and secretes specific chemicals, either directly into the bloodstream Glauber’s salt (chemistry) An alternative (ENDOCRINE GLAND) or through a duct term for SODIUM SULPHATE (USA:

168 GLAUCOMA GLP sodium sulfate), named after the German formerly known as BRIGHT’S DISEASE. physician Johann Glauber (1603–68). See KIDNEY. glaucoma (medical) a disease of the glomerulus (anatomy) Ball of capillaries EYE occurring usually after middle age, located in the BOWMAN’S CAPSULE in which the PRESSURE of the FLUID of the KIDNEY. inside the EYE rises and damages the OPTIC NERVE and the RETINA glomus tumour (histology) there are because the NORMAL drainage passages normally in the fingertips, and other at the margin of the IRIS are blocked parts of the body such as the ears and the AQUEOUS HUMOUR cannot and the face, communications between escape. small arteries and veins which when open allow the BLOOD to bypass the GLC (chemistry) An abbreviation of CAPILLARY vessels. These are called ‘G’as-‘L’iquid ‘C’hromatography. See glomus bodies and are concerned with CHROMATOGRAPHY. the regulation of SKIN TEMPERATURE. Occasionally they form very small pink gleo (medical/bacteriology) A slight tumours, which are extremely tender watery penile DISCHARGE typical of and painful; they may occur under the CHRONIC GONORRHOEA. NAIL, and only respond to surgical removal. (USA: glomus tumor). GLI (biochemistry) An abbreviation of ‘GLI’centin. gloss. (literary terminology) An abbreviation of ‘gloss’ary. glia (medical) An abbreviation of neuro‘glia’. glossina (parasitology) The TSETSE FLY, a biting fly which transmits the glioma (histology) A TUMOUR (USA: trypanosomes of African sleeping sickness. tumor) of the BRAIN or SPINAL CORD arising from neuroglial TISSUE. glossitis (medical) INFLAMMATION of the TONGUE. Gln (biochemistry) An abbreviation of ‘Gl’utami‘n’e. glottis (anatomy) Front opening of the LARYNX, through which AIR passes globins (biochemistry) A GROUP of from the PHARYNX to the TRACHEA proteins involved in the transport of (windpipe) of vertebrates. OXYGEN in BLOOD, muscles, etc. See HAEMOGLOBIN. glove box (laboratory equipment) Closed box that has gloves fixed into holes globulin (chemistry) WATER-INSOLUBLE in the walls, and in which operations PROTEIN that is SOLUBLE in AQUEOUS involving hazardous substances, such SOLUTIONS of certain salts. Globulins as RADIOACTIVE materials or toxic generally contain glycin and are coagulated chemicals, may be carried out safely. by HEAT; e.g. IMMUNOGLOBULIN. Also termed: dry box. glomerulonephritis (medical) A disease GLP (quality standards) An abbreviation of the kidneys affecting the glomeruli, of ‘G’ood ‘L’aboratory ‘P’ractice.

169 GLP-1 GLUE EAR

GLP-1 (biochemistry) An abbreviation of ENZYME involved in the METABOLISM ‘G’lucagon‘L’ike ‘P’olypeptide-1. of carbohydrates. Inability to produce this ENZYME is inherited as an X- GLP-2 (biochemistry) An abbreviation of linked RECESSIVE. Under NORMAL ‘G’lucagon‘L’ike ‘P’olypeptide-2. circumstances, people with this GENE show no ill effects, but when they eat Glu (biochemistry) An abbreviation of broad beans (also known as fava beans), ‘Glu’tamic acid. they suffer a severe bout of haemolytic ANAEMIA (USA: hemolytic anemia) glucagon (biochemistry) A pancreatic (ANAEMIA caused by the destruction HORMONE that increases BLOOD SUGAR of RED BLOOD CELLS).The GENE LEVEL. A POLYPEPTIDE HORMONE causing G6PD deficiency is found at that, like INSULIN, is synthesized and frequencies of up to 30 per cent in secreted by the ISLETS OF LANGERHANS countries around the Mediterranean in the PANCREAS. Produced in (Sardinia, Greece, Israel), in parts of RESPONSE to low BLOOD PRESSURE, Africa (especially the Congo Basin) it stimulates GLYCOGEN breakdown and in India, and it seems likely that in the LIVER, with release of GLUCOSE its distribution is connected with that into the bloodstream. Its ACTION is of MALARIA, because the trait gives therefore opposite to that of INSULIN some resistance to malarial INFECTION (which reduces BLOOD GLUCOSE levels). (as do the genes for sickle-CELL ANAEMIA [USA: side cell anemia] and glucocorticoids (biochemistry) STEROID THALASSAEMIA [USA: thalassemia]). HORMONES (e.g. HYDROCORTISONE) secreted by the ADRENAL CORTEX glucoside (chemistry) See GLYCOSIDE. that promote the conversion of fats and proteins to GLYCOGEN and GLUCOSE. glucostatic theory (biochemistry) The theory that eating is regulated by the glucoreceptor (biochemistry) A hypotheti- BRAIN’S monitoring of the rate at which cal RECEPTOR sensitive to the LEVEL GLUCOSE is removed from the BLOOD of GLUCOSE in the BLOOD, thought (as measured by the difference in GLUCOSE to exist in the HYPOTHALAMUS. levels between arteries and veins): the lower the rate the more the ANIMAL eats. glucose (chemistry) C6H12O6 MONO- Low use of GLUCOSE indicates that the SACCHARIDE CARBOHYDRATE, a SOLUBLE BLOOD levels are low and are being colourless (USA: colorless) CRYSTALLINE replaced by GLUCOSE derived from fats. SUGAR (HEXOSE). It is the substance into which all higher carbohydrates are glue ear (medical) Secretory otitis media, converted in the body; it is the-main source found in children between six months of ENERGY when it is broken down into and 10 years old. A FACTOR in the WATER and CARBON DIOXIDE. It is absorbed development of this condition is CHRONIC without having to be digested. Also termed: blockage of the EUSTACHIAN TUBE, and DEXTROSE; grape SUGAR. another is INFECTION of the middle ear, which may have been successfully treated. glucose-6-phosphate dehydrogenase The symptom is deafness, for the MIDDLE deficiency (G6PD deficiency) (genetics/ EAR becomes full of a sticky thick material biochemistry) A hereditary lack of an which interferes with the movement of

170 GLUE SNIFFING GLYCOGEN the ear-drum and the ossides. Many mild GLUT (physiology/biochemistry) An cases resolve spontaneously, but it may abbreviation of ‘GLU’cose ‘T’ransporter. be necessary to insert a small hollow plastic tube called a grommet into the glutamic acid (biochemistry) An AMINO ear-drum to allow ventilation of the middle ACID that is the PRECURSOR of GABA. ear. This small operation may be accompanied It is thought to be a NEUROTRANSMITTER. by removal of the ADENOIDS. gluten (chemistry) PROTEIN that occurs glue sniffing (medical) The practice of in cereals, particularly wheat flour. People inhaling the vapors of glue, presumably with coeliac disease cannot tolerate GLUTEN, for their CNS effects. Although there may and have to eat a GLUTEN-free diet. be multiple solvents in glue, the alkylbenzene TOLUENE is usually a major constituent. Gly (biochemistry) An abbreviation of Even at low concentrations, TOLUENE ‘Gly’cine. produces fatigue, weakness and confusion. ACIDOSIS, potentially due to acidic glyceride (chemistry) ESTER of GLYCEROL metabolises of TOLUENE, has been reported with an ORGANIC ACID. The most important in humans abusing glue solvents. Inhalation glycerides are FATS AND OILS. of the vapors of glue containing BENZENE or HEXANE may result in hematological glycerol (chemistry) HOCH2CH(OH)-CH2OH effects or PERIPHERAL neuropathies. Colourless (USA: colorless) sweet syrupy LIQUID, a trihydric ALCOHOL that occurs See also TOLUENE. as a constituent of FATS AND OILS (from which it is obtained). It is used in glutamate (MONOSODIUM GLUTAMATE, foodstuffs, medicines and in the preparation MSG) (biochemistry) An excitatory AMINO of alkyd resins and nitroglycerine (glyceryl ACID NEUROTRANSMITTER. It has been trinitrate). Also termed: glycerin; glycerine; demonstrated that NEONATAL animals propan-1,2,3-triol. are sensitive to large doses of GLUTAMATE, which cause permanent lesions of the glycine (biochemistry) CH2(NH2)CO2H HYPOTHALAMUS, resulting in profound Simplest AMINO ACID, found in many neuroendocrine deficits. Toxicity presumably proteins and certain ANIMAL excretions. involves increased availability of It is a PRECURSOR in the biological GLUTAMATE due to an immaturity of SYNTHESIS of purines, porphyrins and the BLOOD-BRAIN barrier or removal CREATINE. It is also a COMPONENT of mechanisms, followed by death of neurons glutathione and the BILE SALT glycocholate. due to prolonged excitatory stimulation. It acts as a NEUROTRANSMITTER at Infantile mice are also reported to have inhibitory NERVE synopses in vertebrates. retinopathies after large doses of Also termed: aminoacetic ACID; amino GLUTAMATE. Some humans are sensitive ETHANOIC ACID. to ingestion of large amounts of GLUTAMATE added as a food flavour enhancer (USA: glycogen (biochemistry) A POLYSAC- flavor enhancer) and experience headaches CHARIDE stored in the LIVER, which or ‘CHINESE RESTAURANT SYNDROME’. when required can be broken down into GLUCOSE for release into the See also CHINESE RESTAURANT BLOOD stream under the control of SYNDROME. ADRENALINE (USA: epinephrine).

171 GLYCOL GOITRE

AMYLASE ENZYMES convert it to glycosuria (biochemistry) An excess GLUCOSE, for use in METABOLISM. of GLUCOSE in the URINE indicating that the BLOOD levels of GLUCOSE glycol (chemistry) An alternative term have risen, usually above 10 mmol/1. for any DIOL or, specifically, ETHYLENE GLYCOL (ethanediol). glycosylase (biochemistry) An ENZYME which recognizes and removes physically glycol ethers (chemistry) A CLASS or chemically modified bases (e.g. alkyl of ALIPHATIC COMPOUNDS containing purines) from the SUGAR phosphate both a HYDROXYL GROUP (-OH) and DNA chain leaving behind a hole (an an ETHER (-C-O-C-) LINKAGE (e.g. abasic site). ETHYLENE GLYCOL monomethyl ETHER, HOCH,CH,OCH,). Widely used glycosylation (biochemistry) The as solvents, they are MISCIBLE with attachment of a CARBOHYDRATE WATER and organic solvents. GLYCOL MOLECULE to another MOLECULE such ETHERS are not toxic ACUTEly, but as a PROTEIN. toxicity of some members of the SERIES has been noted in both humans and gm (measurement) An abbreviation of animals. ‘g’ra‘m’. Also termed gramme; g. glycolipid (biochemistry) Member of a gm mol; g.mol. (measurement) gram- FAMILY of compounds that contain a MOLECULE, MOLECULAR WEIGHT in SUGAR linked to FATTY ACIDS. Glycolipids grams. are present in higher plants and NEURAL TISSUE in animals. Also termed: glycosyl- GM tube (radiology/physics) An acylglycerol; glycosyldiacylglycerol. abbreviation of ‘G’eiger ‘M’üller tube. glycolysis (biochemistry) Conversion GMAG (governing body) An abbreviation of glucose to lactic or PYRUVIC ACID of ‘G’enetic ‘M’anipulation ‘A’dvisory with the release of ENERGY in the ‘G’roup. form of ADENOSINE TRIPHOSPHATE (ATP). In animals it may occur during GM-CSF (physiology) An abbreviation short bursts of muscular activity. of ‘G’ranulocyte-‘M’acrophage ‘C’olony- ‘S’timulating ‘F’actor. glycoproteins (biochemistry) Proteins with CARBOHYDRATE groups attached GnRH (physiology/biochemistry) An at specific locations. They include BLOOD abbreviation of ‘G’o‘n’adotropin- GLYCOPROTEINS, some HORMONES ‘R’eleasing ‘H’ormone. and ENZYMES. goblet cell (cytology) Mucus-secreting glycoside (chemistry) COMPOUND CELL in MUCOUS MEMBRANES. formed from a MONOSACCHARIDE in which an alcoholic or phenolic GROUP goitre (medical/biochemistry) A swelling replaces the first HYDROXYL GROUP. of the THYROID gland in the neck. If the MONOSACCHARIDE is GLUCOSE, Goitres may be associated with under it is termed a GLUCOSIDE. or over-activity of the gland, or a deficiency of iodine in the diet.

172 GOLD AU GONOCOCCUS gold Au (chemistry) Soft yellow metallic gonad (anatomy) Reproductive ORGAN ELEMENT in GROUP IB of the PERIODIC of an ANIMAL, e.g. OVARY or TESTIS, TABLE. It occurs as the free METAL in which ova (eggs) and SPERM are in lodes and placer deposits. Most gold formed respectively. GONADS may also is held in currency reserve stocks, FUNCTION as ENDOCRINE GLANDS, although some is used, usually as an secreting SEX HORMONES. ALLOY in dentistry and in electroplating electronic circuits and components. gonadal (anatomy) Pertaining to the At. no. 79; r.a.m. 196.9665. GONADS.

Golgi apparatus (cytology) Organale See also GONAD. that occurs in most EUKARYOTIC CELLS as stacks of flattened MEMBRANE- gonadotrophic hormone (biochemistry) bounded sacs. It is involved in the The ANTERIOR PITUITARY HORMONES formation of ZYMOGEN granules, that promote GROWTH or activity of SYNTHESIS and transport of secretory the GONADS, controlling the initiation POLYSACCHARIDES (e.g. CELLULOSE of puberty, the MENSTRUAL CYCLE in CELL plate or SECONDARY CELL and LACTATION in females and SPERM- wall formation) and formation of MUCUS formation in males. It is produced by in GOBLET CELLS; assembly of the PITUITARY GLAND. It is also used GLYCOPROTEINS; packing of for the TREATMENT of infertility in HORMONES in NERVE CELLS that women. Also termed: GONADOTROPHIN. carry out neurosecretion; formation of lysosomes.3 and probably production gonadotrophin (biochemistry) See of the PLASMA MEMBRANE. The synaptic GONADOTROPHIC HORMONE. vesicles and their contents are manufactured in the GOLGI APPARATUS. gonadotrophin releasing hormone It was named after the Italian histologist (GNRH) (physiology/biochemistry) An Camillo Golgi (1843–1926). Also termed: hypothalamic HORMONE that acts on Golgi body; Golgi complex. the pituitary gland to release the gonadotrophins, i.e. luteinizing HORMONE, Golgi cell (cytology) A large interneuron LH and follicle-stimulating HORMONE, found in the CEREBELLUM. Activated FSH. by mossy fibres (USA: mossey fibers), climbing fibres (USA: climbing fibers), gonads (anatomy) The organs that and parallel fibres (USA: parallel fibers), produce spermatozoa and ova, i.e. the they inhibit the GRANULE CELLS. TESTIS and OVARY.

Golgi stain (histology) A histological goniometer (crystallography) Instrument staining technique that may be used for measuring angles, particularly the to make NERVE CELLS visible under angles between the faces of crystals. the MICROSCOPE. It is a SILVER stain which percolates to all parts of a living gonococcus (bacteriology) The Gram- NERVE CELL. negative BACTERIUM, Neisseria gonorrhoeae, that causes gonorrhea gomori trichrome (histology) CONNEC- and is often found in pairs (diplococcus) TIVE TISSUE stain for MUSCLE BIOPSY. within WHITE BLOOD CELLS.

173 GONORRHOEA GRA gonorrhoea (medical) A common including facilities, personnel training, SEXUALLY TRANSMITTED DISEASE, DATA gathering, laboratory inspections, caused by the GONOCOCCUS Neisseria ANIMAL health and welfare, chemical gonorrhoeae. In the male, a DISCHARGE ANALYSIS and SAMPLE preparation. from the PENIS with pain on passing water begins between two and ten days goodness of fit (statistics) The extent after INFECTION. The DISCHARGE is to which DATA points match theoretical thick and yellow. If it is left untreated, expectations. the DISCHARGE turns clear and sticky; the EPIDIDYMIS of the testicle may become Gordon & Sweets stain (histology) inflamed, and lymphatic GLANDS draining A histological staining technique that the AREA are enlarged and painful. Most may be used to make reticulin visible importantly a stricture may develop in under the MICROSCOPE. the URETHRA, causing later difficulty in passing WATER. In women there is gout (medical) A disease associated a DISCHARGE from the URETHRA and with a high LEVEL of URIC ACID in the VAGINA, but these are not infrequently BLOOD, causing painful INFLAMMATION unnoticed; in children, usually the victims usually of one joint, the first JOINT of of sexual assault, the external genitalia the great toe, which suddenly becomes may show signs of INFLAMMATION. The red, swollen and ACUTEly painful. The most important complication in women disease is commonest in men, the first is pelvic inflammation involving the attack occurring between the ages of FALLOPIAN TUBES, for this leads to 30 and 60 but it is not found in boys pain, possibly an ABSCESS, CHRONIC before the age of puberty, nor in women INFLAMMATION and infertility. Because until after the MENOPAUSE. Other joints the symptoms of the original INFECTION may be affected such as the ankle, elbow, may be overlooked it is important that knee and wrist, but only one at a time. the slightest suspicion of exposure should It may be associated with stones in the call for medical attention. It is uncommon KIDNEY, and sufferers are usually now for newborn infants to acquire overweight. INFECTION of the eyes from the mother, but once ths was a cause of blindness. GP (1, 2 medical; 3 education) 1 An TREATMENT has been revolutionised abbreviation of ‘G’eneral ‘P’aralysis. by antibiotics: ampicillin or amoxycillin, 2 An abbreviation of ‘G’eneral ‘P’ractitioner. in one large dose of 3.5 g together 3 An abbreviation of ‘G’raduate in with probenecid, which reduces the ‘P’harmacy. Also termed G PH. EXCRETION of PENICILLIN, is effective except in cases where the organism is G6PD (biochemistry) An abbreviation PENICILLIN-resistant, when spectinomycin of ‘G’lucose ‘6’-‘P’hosphate ‘D’ehydroge- or cefuroxime may be used. Prophylactic nase. EYE-drops are used on newborn babies. gpl (measurement) An abbreviation of good laboratory practices (GLP) (quality ‘g’rams ‘p’er ‘l’itre. standards) Regulations governing good LABORATORY practices are in effect GRA (physiology/biochemistry) Abbre- in the UK, USA and OECD, covering viation of ‘G’lucocorticoid-‘R’emediable all phases of LABORATORY testing, ‘A’ldosteronism.

174 GRAAFIAN FOLLICLE GRANULAR LAYER

Graafian follicle (histology) FLUID- gram molecule (measurement) MOLECULAR filled ball of CELLS in the mammalian WEIGHT of a substance in grams; 1 mole. OVARY inside which an OOCYTE develops. It matures periodically and gram (measurement) UNIT of MASS in then bursts at the surface of the OVARY the METRIC SYSTEM, a fundamental UNIT (at OVULATION) to release an OVUM in the e.g.s. system and equal to 1/1000 (EGG). The FOLLICLE then temporarily kg. Also termed: gramme. See SI UNITS. becomes a SOLID body, the CORPUS LUTEUM. It was named after the Dutch Gram/Twort stain (histology) A histologi- anatomist Regnier de Graaf (1641– cal staining technique that may be 73). Also termed: OVARIAN FOLLICLE. used to make BACTERIA visible under the MICROSCOPE. gradient (1,2 mathematics) 1 Amount of inclination of a line (or a curve at a Gram’s stain (bacteriology) A staining particular point) to the horizontal; its technique that may be used to make slope. 2 Rate of rise or fall of a VARIABLE BACTERIA visible under the MICROSCOPE. quantity such as TEMPERATURE or The staining method is to use crystal PRESSURE. violet, then IODINE SOLUTION, then ETHANOL or ETHANOL-acetone, and graft (medical) Transplantation of an ORGAN then COUNTER-stain. The BACTERIA or TISSUE from one organism into the which are stained purple are called Gram- body of another or from one position on POSITIVE, those which have been or in the body to another. A HOMOGRAFT decolourised (USA: decolorized) and have is a GRAFT where the RECIPIENT and taken up the COUNTER-stain Gram- the DONOR are of the same SPECIES; negative. The different uptake of stain a HETEROGRAFT is one carried out is due to differences in cell-wall structure. between two different SPECIES. This method of staining separates BACTERIA into two large groups, Gram-POSITIVE Graham’s law (physics) Velocity of and Gram-negative. Named after the Danish DIFFUSION of a GAS is inversely propor- physician, H.Gram (1853–1938). tional to the SQUARE ROOT of its DENSITY. It was named after the British chemist grand mal (medical) A major epileptic Thomas Graham (1805–69). seizure with both tonic and clonic convulsions and loss of consciousness. grain (1,2 measurement) 1 Small WEIGHT Contrast PETIT MAL. in apothecaries’ and troy WEIGHT (in which it equals 1/5760 Ib), and in granisetron (pharmacology) An ANTI- AVOIRDUPOIS WEIGHT (in which it EMETIC and ANTINAUSEANT drug which, equals 1/7000 Ib). It is equivalent to administered orally, by injection or infusion, 0.0648 grams. 2 One-quarter of a (metric) acts by blocking the action of the natural carat, equal to 0.050 grams. mediator SEROTONIN. gram (g or gm) (measurement) The BASIC granular layer (1,2 histology) 1 Either UNIT of WEIGHT in the METRIC SYSTEM, of two layers of NERVE CELLS in the defined as the MASS of 1 CUBIC millilitre CEREBRAL CORTEX; numbered from (USA: milliliter) of WATER at 4°C [39°F]. the surface inwards, the external 1000g=1 kg. 1oz.=28.35 gm. GRANULAR LAYER is the second layer

175 GRANULATION TISSUE GRISEOFULVIN and the internal GRANULAR LAYER is gravimetric analysis (chemistry) QUANTI- the fourth layer; the name derives from TATIVE chemical ANALYSIS made the large number of golgi type 11 CELLS ultimately by weighing substances. or GRANULE CELLS in these layers. 2 The innermost of the three layers of gravitation (physics) An alternative the CEREBELLUM, which contains term for the FORCE of gravity. GRANULE CELLS and receives an input from the mossy fibres (USA: mossy fibers). gray (Gy) (chemistry) Amount of absorbed RADIATION dose in SI UNITS, equal granulation tissue (histology) the to supplying 1 JOULE of ENERGY per TISSUE formed by fibroblasts and kg. It is equivalent to 100 rad (the endothelial CELLS which grows over UNIT it superseded). a raw surface in the process of healing. Greco latin square (statistics) A latin granule cell (cytology) A small stellate square in which there are two conditions CELL; the name ‘granule’ is used because each with the same number of values, these CELLS look granular under a and in which each COMBINATION of MICROSCOPE. The expression values appears once in each row and ‘GRANULE CELL’ is preferred to ‘stellate CELL’ for the GRANULE CELLS in once in each column. the GRANULAR LAYERS of the CORTEX and CEREBELLUM. green vitriol (chemistry) Old name for IRON(II) SULPHATE (USA: iron(II) sulfate) granuloma (histology) Aggregation and (FERROUS SULPHATE [USA: ferrous proliferation of MACROPHAGES to form sulfate]). small (usually microscopic) nodules. grey matter (anatomy) Any region of grape sugar (chemistry) An alternative the CENTRAL NERVOUS SYSTEM term for GLUCOSE. containing many CELL bodies and their processes, and having unmyelinated graph (statistics) Mathematical diagram axons. All parts of a CELL look grey that shows how one quantity varies in except for a myelinated AXON. The relation to another. expression usually refers to the layers of the CEREBRAL CORTEX, but GREY See also BAR CHART; HISTOGRAM; MATTER also exists in the cerebellar PIE CHART. CORTEX and SPINAL CORD. GRAS (toxicology) An abbreviation of ‘G’enerally ‘R’ecognised ‘A’s ‘S’afe. GRH (physiology/biochemistry) An abbreviation of ‘G’rowth HORMONE- Grave’s disease (medical) See ‘R’eleasing ‘H’ormone. HYPERTHYROIDISM. Grimelius stain (histology) A histological gravid (medical) Pregnant; primigravida, staining technique that may be used one who is in her first PREGNANCY. to make argyrophil CELLS visible under the MICROSCOPE. gravidity (medical) The number of pregnancies. Includes the CURRENT griseofulvin (pharmacology) An ANTIBIOTIC one if the woman is pregnant. active against FUNGUS INFECTION when

176 GROCOTT HEXAMINE SILVER STAIN GUANINE given by mouth. It is concentrated in KERATIN, CELL size or, much more usually, by and is therefore useful for infections involving an increase in CELL number. Most the SKIN and nails. It is used in intractable organisms have a SPECIES-typical or widespread infections, and TREATMENT GROWTH rate and final size, both of has to be continued for a month or more. which are, to some extent, genetically It should not be taken during PREGNANCY. controlled, as is shown by the fact that they can be changed by artificial Grocott hexamine silver stain (histology) selection, but are also much influenced A histological staining technique that by environmental factors. Some fishes may be used to make FUNGI visible and reptiles grow all their lives. under the MICROSCOPE. growth hormone (biochemistry) A GRP (physiology/biochemistry) Abbrevia- PROTEIN HORMONE produced by the tion of ‘G’astrin-‘R’eleasing ‘P’olypeptide. PITUITARY GLAND in the BASE of the SKULL that controls GROWTH and GRPP (biochemistry) An abbreviation differentiation in animals. Either deficiency of ‘G’licentin-‘R’elated ‘P’oly‘P’eptide. of it or excess production can be genetically determined, the former causing gross weight (gr wt) (measurement) a form of dwarfism and the latter The entire WEIGHT of a PRODUCT, GIGANTISM (excess GROWTH in including its container. Found on childhood) and ACROMEGALY packaging and labelling. (enlargement of the JAW, hands and feet in adult life). The dwarfism can ground state (physics) Lowest ENERGY be treated with human GROWTH state of an ATOM or MOLECULE, from HORMONE, which formerly had to be which it can be raised to a higher obtained from human cadavers but can ENERGY state by EXCITATION. now be made by GENE CLONING. Also termed: SOMATOTROPHIN. See also ENERGY LEVEL. Grp (general terminology) An abbreviation group (chemistry) Column, or vertical of ‘Gr’ou‘p’. row, of elements in the PERIODIC TABLE (horizontal rows are PERIODS). The GTP (biochemistry) An abbreviation GROUP number (I to VIII and 0) indicates of ‘G’uanosine ‘T’ri‘P’hosphate. the number of electrons in the ATOM’S outermost shell. GU (medical) An abbreviation of ‘G’enito- ‘U’rinary. grouping (statistics) Assigning DATA to CLASS intervals. guanethidine monosulphate (pharmacology) An ADRENERGIC neurone blocker, grouping error (statistics) Any statistical which is an ANTISYMPATHETIC class error introduced by the way in which of drug that prevents release of DATA are grouped, e.g. by GROUPING NORADRENALINE from sympathetic in such a way that the distribution of nerves. Administered orally or by injection scores within a GROUP is not NORMAL. it is used as an ANTIHYPERTENSIVE.

growth (genetics) Increase in size of guanine (molecular biology) C5H 5N 5O an organism, either by an increase in Colourless (USA: colorless) CRYSTALLINE

177 GUMMA GYRUS

ORGANIC BASE (a PURINE DERIVATIVE) termed: CALCIUM SULPHATE DIHYDRATE that occurs in DNA. (USA: calcium sulfate dihydrate). gumma (medical/bacteriology) A hard gyromagnetic ratio (physics) Ratio granulomatous swelling occurring in the of the magnetic moment of an ATOM third stage of syphilis anywhere in the or NUCLEUS to its angular momentum. body. It develops anything between one and ten years after the primary INFECTION. gyrus (anatomy) One of the convolutions on the surface of the BRAIN. gust (measurement) A UNIT used in scales of TASTE; one GUST is produced by a 1 per cent SUCROSE SOLUTION. gustation (physiology) The sense of TASTE. gustometer (measurement) A device for measuring TASTE thresholds. It consists of a U-tube with a small hole at the bottom; the tube is placed upright on a particular part of the TONGUE, and a SOLUTION is poured through it: the TONGUE is thus exposed to a CONSTANT amount of SOLUTION. gut (anatomy) An alternative term for ALIMENTARY CANAL. gyn. (1,2 medical) An abbreviation of 1 ‘gyn’aecology (USA: gynecology). Also termed gynae.; gynacol. 2 ‘gyn’aecologist (USA: gynecologist). gynaecologist (medical) A medical doctor specialising in GYNAECOLOGY (USA: gynecology). (USA: gynecologist). gynaecology (gyn.; gynac.; gynacol) (medical) That branch of medicine dealing with the diseases of women, especially concerning the reproductive system of women. (USA: gynecology).

gypsum (chemistry) CaSO4.2H2O Very soft CALCIUM mineral, a form of CALCIUM SULPHATE (USA: calcium sulfate), used in making cement and plasters. Also

178 H

H (1 chemistry; 2 biochemistry) 1 The haematogenous (microbiology) Dissemi- CHEMICAL SYMBOL for HYDROGEN. nated by the bloodstream. (USA: 2 An abbreviation of ‘H’istidine. hematogenous). h (1 measurement; 2 physics) 1 An haematology (haematology) The branch abbreviation of ‘h’our. 2 Symbol for of medicine which deals with the BLOOD PLANCK’S CONSTANT. and its disorders. (USA: hematology).

HA (biochemistry) General symbol for haematoma (medical) A swelling an acid. containing BLOOD effused into the tissues, usually as the result of injury. habituation (physiology) Process by (USA: hematoma). which the NERVOUS SYSTEM becomes accustomed to a particular STIMULUS haematopoietic STEM CELLS (cytology) and after a time is no longer irritated (USA: hematopoietic stem cells). See by it; e.g. the feel of one’s clothes or STEM CELLS. the background noise of machinery. haematoxylin & eosin (H&E) (histology/ haem. (1, 2 haematology) An abbreviation haematology) A MIXTURE of HAEMATOXYLIN of 1’haem’oglobin (USA: HEMOGLOBIN); (USA: hematoxylin) in DISTILLED WATER 2 ‘haem’orrhage (USA: hemorrhage). and an AQUEOUS eosin SOLUTION; a (USA: hem). stain used routinely for examination of tissues. (USA: hematoxylin & eosin). haem (chemistry) IRON-containing GROUP of atoms attached to a POLYPEPTIDE haematoxylin (histology) An ACID colour- chain; e.g. in HAEMOGLOBIN (USA: ing (USA: coloring) MATTER from the hemaglobin) and MYOGLOBIN. (USA: heme). heartwood. A histological stain that may be used to make CELL nuclei haemagglutination (haematology/immu- visible under the MICROSCOPE. (USA: nology) The AGGLUTINATION of RED hematoxylin). BLOOD CELLS caused by certain antibodies, VIRUS particles, or high MOLECULAR haematuria (medical) The presence of WEIGHT POLYSACCHARIDES. (USA: BLOOD in the URINE. (USA: hematuria). hemagglutination). haemocyanin (haematology) The BLOOD haemangioma (histology) A TUMOUR PIGMENT that contains COPPER as (USA: tumor) composed of BLOOD its PROSTHETIC GROUP for the transport VESSELS. (USA: hemANGIOMA). See of OXYGEN. It is confined to lower ANGIOMA. animals. e.g. molluscs. (USA: hemocyanin).

179 HAEMOCYTOMETER HALF-CELL haemocytometer (haematology) Appara- the BLOOD is bright red, and may spurt tus for counting BLOOD CELLS. (USA: out with the beat of the HEART; venous hemocytometer). BLOOD is darker and escapes in a steady stream; CAPILLARY BLOOD oozes from haemodialysis (medical) See DIALYSIS. the damaged tissues. (USA: hemorrhage). haemoglobin (Hb) (medical) The OXYGEN haemostasis (medical) The process of carrying PIGMENT of the RED BLOOD stopping BLOOD flow. (USA: hemostasis). CELLS (ERYTHROCYTES). It is a CONJUGATED PROTEIN containing four haemothorax (medical) BLOOD in the haem groups (USA: heme groups) and PLEURAL cavity, the space between the GLOBIN. A MOLECULE of HAEMOGLOBIN chest wall and the LUNG. It may he the contains 4 GLOBIN POLYPEPTIDE result of a penetrating WOUND or injury, chains—designated alpha, beta, gamma or the presence of a MALIGNANT TUMOUR and delta. In the adult, haemoglobin A (USA: malignant tumor). (USA: hemothorax). predominates (alpha2, beta2). (USA: hemoglobin). hafnium Hf (chemistry) Silvery metallic ELEMENT in GROUP IVB of the PERIODIC haemoglobinuria (haematology) Appear- TABLE (a TRANSITION ELEMENT), used ance of HAEMOGLOBIN (USA: hemaglobin) to make control rods for nuclear reactors. in the URINE. (USA: hemoglobinuria). At. no. 72; r.a.m. 178.49. haemolysis (haematology) Breakdown Haga-Yamagchi methenamine silver of RED BLOOD CELLS (ERYTHROCYTES) stain (histology) A histological staining which results in the release of technique that may be used to make HAEMOGLOBIN (USA: hemaglobin) from senile plaques visible under the the red CELLS and its appearance in MICROSCOPE. PLASMA. (USA: hemolysis). hahnium Ha (chemistry) ELEMENT no. haemophilia (medical/haematology) A 105 (a post-ACTINIDE). It is a RADIOACTIVE hereditary bleeding disorder caused METAL with short-lived isotopes, made by a deficiency in the ability to synthesise in very small quantities by bombardment one or more of the BLOOD COAGULATION of an ACTINIDE with atoms of an ELEMENT proteins, e.g. FACTOR VIII (HAEMOPHILIA such as CARBON or OXYGEN. A) (USA: hemophilia A) or FACTOR IX (HAEMOPHILIA B) (USA: hemophilia hair (1, 2 anatomy) 1 DERIVATIVE of B). Sufferers are at CONSTANT risk of ECTODERM composed of INSOLUBLE bleeding excessively from even minor proteins or keratins. Its role in mammals injuries. (USA: hemophilia). includes assisting regulation of body temperature. 2 In plants, any of various haemoptysis (medical) The spitting outgrowths from the EPIDERMIS, e.g. of BLOOD or BLOOD-stained sputum. ROOT HAIRS, which absorb WATER. (USA: hemoptysis). Also termed: trichome. haemorrhage (medical) Bleeding, which half-cell (physics) Half of an ELECTROLYTIC may be internal or external, arterial, CELL, consisting of an ELECTRODE venous or CAPILLARY. In arterial bleeding immersed in an ELECTROLYTE.

180 HALF-LIFE HARDNESS OF WATER half-life (1, 2 measurement/radiology) 1 halogenoalkane (chemistry) A HALOGEN Time taken for something whose DECAY DERIVATIVE of an ALKANE, GENERAL is exponential to reduce to half its value. FORMULA CnH2n+ 1X, where X is a 2 More specifically, time taken for half HALOGEN (FLUORINE, CHLORINE, the nuclei of a RADIOACTIVE substance BROMINE or IODINE). Also termed: to DECAY spontaneously. The HALF-LIFE HALOALKANE; monohaloge-noALKANE. of some unstable substances is only a few seconds or less, whereas for other halophilic (biology) Exhibiting a preference substances it may be thousands of years; for an ENVIRONMENT containing SALT e.g. LAWRENCIUM has a HALF-LIFE of (e.g. sea-WATER). The term is usually 8 seconds, and the ISOTOPE PLUTONIUM- applied to BACTERIA. 239 has a HALF-LIFE of 24,400 years. halothane (pharmacology) An inhalant halide (chemistry) A BINARY COMPOUND general anaesthetic drug, which is used containing a HALOGEN: a FLUORIDE, for induction and maintenance of CHLORIDE, BROMIDE or IODIDE. anaesthesia during surgery. halite (chemistry) Naturally occurring haploid (cytology) Having half the number form of SODIUM CHLORIDE. Also termed: of chromosomes of the organism in COMMON SALT; ROCK SALT. the CELL NUCLEUS. The HAPLOID state is found in gametes (resulting from Hall effect (physics) Production of a MEIOSIS), the gametophyte generation VOLTAGE in a semiconductor or METAL and spores. It occurs after MEIOSIS carrying an ELECTRIC CURRENT in or REDUCTION DIVISION. a strong transverse MAGNETIC FIELD. It was named after the American physicist See also DIPLOID. Edwin Hall (1855–1938). hard copy (computing) Document that haloalkane (chemistry) An alternative people can read (e.g. a PRINT-OUT term for HALOGENOALKANE. in plain language). haloform (chemistry) An ORGANIC hard disk (computing) Rigid MAGNETIC DISK that provides DATA and PROGRAM COMPOUND of the type CHX3, where X is a HALOGEN (CHLORINE, BROMINE STORAGE for computers, including or IODINE); e.g. CHLOROFORM microcomputers. HARD DISKS can hold (TRICHLOROMETHANE), IODOFORM a high DENSITY of DATA. Also termed: (TRIIODOMETHANE). The compounds DISKETTE. are prepared by the ACTION of the HALOGEN on heating with ETHANOL See also FLOPPY DISK. in the presence of SODIUM HYDROXIDE. hardness of water (chemistry) Property halogen (chemistry) ELEMENT in GROUP of water that prevents it forming a VIIA of the PERODIC TABLE: FLUORINE, lather with soap because of the presence CHLORINE, BROMINE, IODINE or ASTATINE. of dissolved compounds of calcium or magnesium. halogenation (chemistry) A CHEMICAL REACTION that involves the addition See also SOFT WATER of a HALOGEN to a substance.

181 HARDWARE HEALTH AND SAFETY EXECUTIVE hardware (computing) Electronic, electri- Hct (haematology) An abbreviation of cal, magnetic and mechanical parts ‘H’aemato‘c’ri‘t’ (USA: Hematocrit). that make up a COMPUTER system. HDL (biochemistry) An abbreviation See also SOFTWARE. of ‘H’igh-‘D’ensity ‘L’ipoPROTEIN. harmonic progression (mathematics) H & E (histology/haematology) An abbre- SERIES of numbers whose reciprocals viation of ‘h’aematoxylin & ‘e’osin. have a CONSTANT difference (form an ARITHMETIC PROGRESSION), e.g. He (chemistry) The CHEMICAL SYMBOL 1/1+1/2 +1/3+1/4. for HELIUM.

Haversian canal (anatomy) Any of the head (computing) In a tape recorder, numerous channels that occur in BONE video recorder, record player or TISSUE, containing BLOOD VESSELS COMPUTER input/output device, an and NERVES. An organic MATRIX is electromagnetic COMPONENT that can laid down in layers encircling each read, erase or write signals off or onto Haversian canal. It was named after tapes and disks. the English physician Clopton Havers (1650–1702). Health and Safety at Work Act (legislation) important UK legislation of 1974, Hb (haematology) An abbreviation of resulting from the recommendations of ‘H’aemo‘g’lobin (USA: HEMOGLOBIN). the Robens committee in July 1972, that covers all aspects of safety at the workplace hb (general terminology) An abbreviation including the POTENTIAL exposure of of ‘h’uman ‘b’eing. workers to toxic and infectious substances.

HBE (physiology) An abbreviation of Health and Safety Commission (govern- ‘H’is ‘B’undle ‘E’lectrogram. ing body) A commission, consisting of employers’ and union representatives,

HbO2 (physiology/biochemistry) A symbol that was established under the UK for Oxyhemoglobin. Health and Safety at WORK Act. The Commission, which is advised by various HBV (virology) An abbreviation of advisory committees on health hazards ‘H’epatitis ‘B’ ‘V’irus. in the workplace from toxic chemicals and infectious agents, and related hazards HCC (biochemistry) An abbreviation to the public, has overall powers to of 25-‘H’ydroxy‘C’hole‘C’alciferol. propose health and safety regulations and to approve codes of practice. It hCG (physiology/biochemistry) An is directly responsible to the Secretary abbreviation of ‘h’uman ‘C’horionic of State for Employment. See HEALTH ‘G’onadotropin. AND SAFETY AT WORK ACT. hCS (physiology/biochemistry) An Health and Safety Executive (governing abbreviation of ‘h’uman ‘C’horionic body) The body that enforces the statutory ‘S’omatomammotropin. duties laid down in the UK Health and Safety at WORK Act. The Executive is

182 HEART HEAT OF REACTION responsible to the Health and Safety Failure may be mainly of the right or Commission. left side, the latter being the most common, following disease of the mitral heart (anatomy) An ORGAN chiefly or aortic valves, coronary insufficiency consisting of CARDIAC MUSCLE that or high BLOOD PRESSURE. in vertebrates is responsible for pumping BLOOD into a system of arteries. BLOOD heat (physics) Form of ENERGY, the ENERGY returns to the heart from the tissues via of motion (KINETIC ENERGY) possessed veins, and is passed to the lungs to by the atoms or molecules of all substances become reoxygenated. The mammalian at temperatures above ABSOLUTE ZERO. HEART is divided into four chambers, the right and left atria (auricles) and heat capacity (physics) Quantity of right and left ventricles, so that deoxygenated HEAT required to produce UNIT rise and oxygenated BLOOD remain separate. of TEMPERATURE in an OBJECT. It demonstrates inherent rhythmicity of contraction because of the presence of heat of activation (physics) Difference PACEMAKER TISSUE, such as the sinoatrial between the values of the thermodynamic NODE. The NEUROTRANSMITTER functions for the activated complex ACETYLCHOLINE slows the heart and and the reactants for a CHEMICAL reduces the FORCE of contraction, whereas REACTION (all the substances being NORADRENALINE (USA: norepinephrine) in their STANDARD STATES). quickens the heart and increases the FORCE. Drugs and toxicants affecting heat of atomization (measurement) cholinergic and ADRENERGIC transmission Amount of HEAT that is required to can therefore affect CARDIAC FUNCTION convert 1 mole of an ELEMENT into and subsequently BLOOD PRESSURE. the gaseous state. Atherosclerotic agents affect coronary arteries and can result in HYPERTENSION heat of combustion (measurement) HEAT and heart attacks. change that accompanies the complete COMBUSTION of 1 mole of a substance. heartbeat (physiology) The alternate contraction and relaxation of the HEART, heat of formation (measurement) HEAT corresponding to DIASTOLE and SYSTOLE. change that occurs when 1 mole of a COMPOUND is formed from its elements, heartburn (medical) A burning pain felt in their NORMAL states. behind the BREASTBONE extending into the THROAT. It is associated with conditions heat of neutralization (measurement) that allow REFLUX of the ACIDcontents HEAT change that occurs when 1 mole of the STOMACH into the lower of AQUEOUS HYDROGEN IONS are OESOPHAGUS (USA: esophagus), such neutralized by a BASE in DILUTE as HIATUS HERNIA. It is relieved by SOLUTION. ALKALIS (USA: alkalies), e.g. ALUMINIUM HYDROXIDE or MAGNESIUM CARBONATE. heat of reaction (measurement) HEAT change that occurs when the MOLAR heart failure (medical) Failure of the quantities (lowest possible multiples HEART to carry out its function properly of 1 mole) of reactants as stated in because of congenital or acquired disease. a CHEMICAL EQUATION react together.

183 HEAT OF SOLUTION HEMIHYDRATE heat of solution (measurement) HEAT (the RARE GASes), which occurs in change that occurs when 1 mole of a some natural GAS deposits. It is INERT substance is dissolved in so much WATER and noninflammable, used to fill airships that further DILUTION with WATER and balloons (in preference to inflammable produces no further HEAT change. HYDROGEN) and in HELIUM-OXYGEN ‘AIR’ mixtures for divers (in preference Heberden’s nodes (medical) Small to the NITROGEN-OXYGEN MIXTURE hard swellings on the finger joints which of real AIR, which can cause the bends). occurs in some cases of osteoarthritis. It is also used in GAS lasers. LIQUID Named after the English physician, HELIUM is employed as a COOLANT W. Heberden (1767–1845). in CRYOGENICS. At. no. 2; r.a.m. 4.0026. hecto- (measurement) Metric prefix helix (molecular biology) A spiral shape. for a multiple of 102; denotes 100 times. The shape of the thread of a bolt or screw. It occurs in nature as the three- height (ht or hgt) (measurement) The dimensional structure of DNA, which LINEAR measurement of an OBJECT is a double HELIX. The alpha HELIX, from top to bottom. described by Linus Pauling, is the secondary structure of many proteins, Heinz bodies (haematology) Dark- i.e. they are twisted threads that are staining bodies found in ERYTHROCYTES subsequently folded into a particular that lie on the inner surface. three-dimensional shape.

Heisenberg uncertainty principle ‘HELLP’ syndrome (medical) Variant (physics) The precise position and of pre-eclampsia typified by HAEMOLYSIS momentum of an ELECTRON cannot (USA: hemolysis) (H), elevated LIVER be determined simultaneously. It was (EL) ENZYMES, and low platelets (LP). named after the German physicist Werner Heisenberg (1901–1976). helminths (parasitology) Parasitic WORMS. See WORMS. Hela cells (cytology) A line of human CANCER CELLS that has been maintained hemianaesthesia (medical) The loss of in culture since 1951 and has been sensation on one side of the body; it is much used in CANCER research. It is caused by UNILATERAL damage to the named after the patient from whom somaesthetic system (USA: hemianesthesia). the CELLS were taken, Henrietta Lacks in 1951, who had CANCER of the CERVIX. hemianopia (medical) Loss of vision See TISUUE CULTURE. in the right or left half of the visual FIELD of one or both eyes. It is caused heliotherapy (medical) TREATMENT by UNILATERAL damage to the visual by exposure to natural sunlight. Once CORTEX, OPTIC radiations, or OPTIC popular but now confined to cases of chiasm. Also termed hemiopia. psoriasis for which it can be greatly benificial. hemihydrate (chemistry) COMPOUND containing one WATER MOLECULE for helium He (chemistry) Gaseous ELEMENT every two molecules of the COMPOUND; in GROUP O of the PERIODIC TABLE e.g. CaSO4.1/2H2O.

184 HEMIOPIA HEPTANE hemiopia (medical) See HEMIANOPIA. FATTY ACIDS and GLYCEROL) pass from the INTESTINE lining for transport hemiplegia (medical) Paralysis of one to the LIVER. side of the body; it is caused by UNILATERAL damage to part of the hepatic (anatomy) Relating to the LIVER. motor system, usually caused by a STROKE. hepatitis (medical/virology) INFLAMMATION hemoglobin (haematology) See HAEMO- of the LIVER, caused by VIRUS INFECTION, GLOBIN. many drugs, and various chemicals including ALCOHOL. VIRUSES causing HEPATITIS hemp plant (toxicology) Cannabis sativa are described as A, B, C, D, E, non-A or Cannabis indica, the plant from which and non-B. hashish and MARIJUANA are derived. hepatoma (histology) A MALIGNANT henry (H) (measurement) SI UNIT of tumor of the LIVER. electrical INDUCTANCE, defined as the INDUCTANCE that produces an induced hepatomegaly (medical) Enlargement ELECTROMOTIVE FORCE of 1 VOLT of the LIVER. for a CURRENT change of 1 AMPERE per second. It was named after the American hepatosplenomegaly (medical) Enlarge- physicist Joseph Henry (1797–1878). ment of the LIVER and SPLEEN.

Henry’s law (physics) WEIGHT of GAS hepatotoxicants (toxicology) Chemicals dissolved by a LIQUID is proportional that cause adverse effects on the LIVER. to the GAS PRESSURE. It was named after the British chemist William Henry See also HEPATOTOXICITY. (1774–1836). hepatotoxicity (toxicology) Adverse effects heparin (haematology) A substance found on the LIVER. The LIVER is particularly in many tissues of the body, but mostly susceptible to chemical injury because in the LIVER, which prevents the clotting of its anatomical relationship to the of BLOOD by interfering with the formation most important portal of entry, the of THROMBIN from prothrombin. It is used GASTROINTESTINAL tract, and its high in medicine to prevent clotting, and acts CONCENTRATION of XENOBIOTIC quickly; but the ACTION is shortlived, metabolizing enyzmes. Many of these and it has to be given by injection, either ENZYMES, particularly the CYTOCHROME into the veins or under the SKIN. It is P450-dependent monooxygenase system, particularly useful in CARDIAC surgery metabolize xenobiotics to produce reactive and renal DIALYSIS. If HAEMORRHAGE intermediates that can react with (USA: hemorrhage) should be provoked, ENDOGENOUS macromolecules such the ANTIDOTE is protamine SULPHATE as proteins and DNA to produce adverse (USA: protamine sulfate). See COAGULATION effects. of the BLOOD.

heptane (chemistry) C7H16 LIQUID ALKANE hepatic portal system (physiology) In HYDROCARBON, the seventh member vertebrates, system of BLOOD capillaries of the methane SERIES, present in petrol. into which dissolved foods (except for

185 HEPTAVALENT HERPES VIRUS heptavalent (chemistry) With a VALENCY heroin (H) (toxicology/pharmacology) of seven. Also termed: SEPTIVALENT. Diamorphine, a highly addictive opiate derived from MORPHINE. heredity (genetics) The process by which characteristics are genetically herpes (medical) INFLAMMATION of transmitted from one generation to the the SKIN characterized by clusters of next. See GENETICS. small vesicles (e.g. HERPES simplex). heritability (genetics) The proportion herpes gestationis (medical) SKIN of the VARIABILITY of the PHENOTYPE disease of PREGNANCY. of a trait that is attributable to genetic factors. HERITABILITY is not a fixed herpes simplex virus 1 (HSV-I) (virology) property of the genes concerned but A VIRUS that results in cold sores or depends in each situation on how much FEVER blisters, most often on the mouth VARIATION there is both in genotypes or around the eyes. Like all HERPES and in the ENVIRONMENT. VIRUSES, it may lie dormant for months or years in NERVE tissues and flare hermaphrodite (genetics) An ANIMAL up in times of STRESS, TRAUMA, that has the reproductive organs of INFECTION or IMMUNOSUPPRESSION. both sexes. Animals that are normally It may also cause a mild form of hermaphroditic include flatworms, MENINGITIS, or a much more dangerous LEECHES, land snails, some fish and encephalitis which follows a first some flies. They are capable of self- INFECTION, and is not likely to affect FERTILIZATION, unless they are those with cold sores or other types of sequential hermaphrodites (i.e. they HERPES. have first one SET of sex organs, then the other). Hermaphrodites do not have herpes simplex virus 11 (HSV-11) (virology) SEX CHROMOSOMES. In humans, A VIRUS that causes painful sores on hermaphroditism is a rare abnormality. the genitals or ANUS. It is one of the The person has both ovarian and testicular most common SEXUALLY TRANSMITTED TISSUE, which may occur as (a) one DISEASES in the United States. OVARY plus one TESTIS, (b) two ovotestes or (c) one ovotestis plus either an OVARY herpes varicella zoster virus (HVZ) or a TESTIS; the external genitalia are (virology) The VARICELLA VIRUS causes ambiguous. The condition is the result chicken pox in children and may reappear of a single OVUM being fertilized in adulthood as herpes zoster. Herpes simultaneously by an X and a Y SPERM, zoster, also called SHINGLES, is so that the person is a CHIMAERA of characterized by small, painful blisters XX and XY CELLS. See SEX on the SKIN along NERVE pathways. DETERMINATION. The most dangerous AREA for the disease to appear is in the face and forehead, hernia (medical) The ABNORMAL protrusion for the EYE may be involved and this of one structure through another. The may LEAD to complications. commonest type is protrusion of part of the abdominal contents through the herpes virus (virology) Any of a GROUP abdominal wall. of ANIMAL DNA VIRUSES responsible for various diseases; e.g. chickenpox

186 HERTZ HETEROGENEOUS

(VARIOLA) and HERPES simplex (coldsore), HETEROCHROMATIN is more intensely and HERPES ZOSTER (SHINGLES). Their coloured (USA: colored) when stained GENOME is double-stranded DNA. than ordinary CHROMATIN (euchromatin).

See also HERPES SIMPLEX VIRUS 1 heterochrony (measurment) A difference (HSV-I); HERPES SIMPLEX VIRUS 11 in the rate or timing of events. (HSV-11); HERPESVARICELLA ZOSTER VIRUS (HVZ). heterocyclic (chemistry) Describing a CYCLIC ORGANIC COMPOUND that hertz (Hz) (measurement) SI UNIT of contains atoms other than CARBON FREQUENCY. 1 Hz=1 CYCLE per second. in the ring, e.g. PYRIDINE. It was named after the German physicist Heinrich Hertz (1858–94). See also HOMOCYCLIC;

Hess’s law (chemistry) Total ENERGY heteroduplex (molecular biology) A change resulting from a CHEMICAL NUCLEIC ACIDmolecule that consists REACTION is dependent only on the of two strands of different genetic origins. initial and final states, and is independent It can be either a double-stranded DNA of the REACTION route. It was named MOLECULE or a DNA-RNA COMBINATION. after the Austrian-born American physicist Where the sequences are HOMOLOGOUS, Victor Hess (1883–1964). the two strands will link; non- HOMOLOGOUS sequences can then be heterarchy (computing) The CHARAC- seen under the ELECTRON MICROSCOPE TERISTIC of a COMPUTER PROGRAM looking like bubbles. Examination of a that does not process DATA merely through HETERODUPLEX made from DNA strands successively higher levels, but can call from wild-type and MUTANT-type DNA many different routines to help in the will show where there are deletions or processing of the DATA at each LEVEL, insertions; this is called ‘HETERODUPLEX including routines from higher levels. mapping’. hetero- (biology) Prefix denoting other heterogametic (genetics) Describing an or different. organism that produces two kinds of gametes, each possessing a different SEX See also HOMO-. CHROMOSOME. These are usually produced by the male; e.g. in human males half heterochromatic flicker photometer the sperms contain an X-CHROMOSOME (physics) See PHOTOMETER. and half a Y-CHROMOSOME. The opposite is HOMOGAMETIC. heterochromatin (molecular biology) CHROMATIN, the substance of which heterogeneous nuclear RNA (genetics) chromosomes are made, that is in a The RNA MOLECULE that reads the DNA highly condensed state because the code in eukaryotes. See MESSENGER RNA. DNA, not being actively transcribed, can be packed densely around the heterogeneous Relating to more than HISTONES. Examples are the DNA in one PHASE, e.g. describing a CHEMICAL the centromeres and in Barr bodies. REACTION that involves one or more solids Because of its more condensed state, in addition to a GAS or a LIQUID PHASE.

187 HETEROGRAFT HEXADECIMAL

See also HOMOGENEOUS. who, at two given loci, has unlike ALLELES. Contrast HOMOZYGOTE. heterograft (medical) See GRAFT. heterozygous advantage (genetics) the heterokaryon (genetics) A CELL or situation where an organism that is individual that contains two nuclei, each HETEROZYGOUS at a given LOCUS of different genetic ORIGIN. It can happen has greater genetic fitness than either naturally when CELLS of two different of the two homozygotes. It is one way FUNGI FUSE, and it can be artificially in which two different ALLELES can be induced by mixing the CELLS of higher maintained within a population at STABLE organisms in vitro. frequencies: neither is better on its own, but the two in COMBINATION are the heterolytic fission (chemistry) Breaking most successful GENOTYPE, and therefore of a two-ELECTRON COVALENT BOND neither ALLELE is lost from the population. to give two fragments, with one fragment The classic example of this is sickle- retaining both electrons. Also termed: CELL ANAEMIA (USA: sickle-cell anemia) heterolytic CLEAVAGE. in humans, in which homozygotes for the MUTANT ALLELE have severe ANAEMIA See also HOMOLYTIC FISSION. (USA: anemia), homozygotes for the NORMAL ALLELE are liable to get MALARIA, heterosis (genetics) The technical term but HETEROZYGOTES are neither anaemic for the phenomenon more generally (USA: anemic) nor subject to MALARIA. known as HYBRID VIGOUR. In a more general sense, organisms that are HETEROZYGOUS at many loci are heterosome (genetics) The X or Y at an advantage over more HOMOZYGOUS CHROMOSOME, each of which, unlike ones; this is known as HYBRID VIGOUR. the other chromosomes can pair with See POLYMORPHISM. a different CHROMOSOME. Compare AUTOSOME. heterozygous (genetics) Describing an organism that possesses two dissimilar heterotroph (microbiology) Organism ALLELES in a pair of chromosomes. A that requires an organic CARBON source. DOMINANT ALLELE can be expressed in the HETEROZYGOUS or HOMOZYGOUS heterotrophism (physiology) MODE state, but a RECESSIVE ALLELE can be of nutrition exhibited by most animals, expressed only in the HOMOZYGOUS state. FUNGI, BACTERIA and some flowering plants. It involves the intake of organic heuristic (philosophy) Describing an substances from the ENVIRONMENT approach to problem-solving that is due to the inability of the organism to based on trial and error rather than synthesize them from inorganic materials. theory. The term is sometimes used to describe COMPUTER programs that See also AUTOTROPHISM. can ‘learn’ from their mistakes. heterozygote (genetics) An organism having hexadecimal (computing) Describing two different ALLELES at the same LOCUS a number system based on 16 (its on a pair of chromosomes. The term ‘double digits are 1–9, A, B, C, D, E, F), commonly HETEROZYGOTE’ refers to an individual used in DIGITAL COMPUTERS.

188 HEXAMINE HIGH-RISK GROUPS

hexamine (chemistry) C6H12N4 ORGANIC 5-HIAA (biochemistry) An abbreviation COMPOUND made by condensing of 5-‘H’ydroxy‘I’ndole‘A’cetic ‘A’cid. METHANAL (FORMALDEHYDE) with AMMONIA, used as a camping fuel hiatus hernia (medical) Protrusion of and ANTISEPTIC drug. It can be nitrated the upper part of the STOMACH through to make the high explosive cyclonite. the diaphram MUSCLE through which Also termed: hexamethyle-netetramine. the OESOPHAGUS (USA: esophagus) passes. (USA: hiatal HERNIA). hexane (chemistry) C6H 14 Colourless (USA: colorless) LIQUID ALKANE, used high blood pressure (medical) See as a SOLVENT, HYPERTENSION. hexanedioic acid (chemistry) An high frequency (HF) (1, 2 physics) 1 alternative term for adipic ACID. A radio FREQUENCY with a range of 3 to 30 megahertz. 2 Rapidly alternating hexose (chemistry) MONOSACCHARIDE ELECTRIC CURRENT or WAVE. CARBOHYDRATE (SUGAR) that contains six CARBON atoms and has the high iron diamine stain (histology)

GENERAL FORMULA C6H 12O 6; e.g. A histological staining technique that GLUCOSE and FRUCTOSE. may be used to make sulphomucins (USA: sulfomucins) visible under the Hf (chemistry) The CHEMICAL SYMBOL MICROSCOPE. for HAFNIUM. highest common factor (HCF) (mathe- hf (physics) An abbreviation of ‘h’igh matics) Of two or more numbers is ‘f’requency. the largest number that divides exactly into each of them; e.g. the HCF of 21, HFG (physics) An abbreviation of ‘H’igh 35 and 63 is 7. ‘F’requency ‘G’as. Highmans congo red stain (histology) Hg (chemistry) The CHEMICAL SYMBOL A histological staining technique that for MERCURY. The symbol is derived may be used to make amyloid visible from Latin hydragyrum, meaning under the MICROSCOPE. MERCURY. high-pass filter (physics) A FILTER hg (measurement) An abbreviation of that transmits from a waveform only ‘h’ecto‘g’ram. the frequencies higher than a specified FREQUENCY. HGH (biochemistry) An abbreviation of ‘H’uman ‘G’rowth ‘H’ormone. high-risk behaviour (epidemiology) A term used to describe certain activities hgt (measurement) An abbreviation that increase the risk of disease exposure. of ‘h’ei‘g’h‘t’. Also termed ht. (USA: high-risk behavior). hi temp (measurement) An abbreviation high-risk groups (epidemiology) Those of ‘hi’gh ‘temp’erature. groups of people that show a behavioural risk for exposure to a disease or condition.

189 HIGH VOLTAGE HISTONE high voltage (HV) (physics) Marked histamine (biochemistry) ORGANIC COM- on wires carrying a high load of POUND that is released from CELLS in ELECTRICITY to indicate danger of CONNECTIVE TISSUE during an allergic electrocution. REACTION. It causes DILATION of capillaries and constriction of bronchi. See ALLERGY. HIOMT (biochemistry) An abbreviation of ‘H’ydroxy‘I’ndole-‘O’- histamine N-methyItransferase (bio- ‘M’ethyl‘T’ransferase. chemistry) See n-METHYLATION.

H-ion (chemistry) An abbreviation of histidine (His.) (chemistry) (C3H3N2)-

‘H’ydrogen ‘ION’. CH2CH(NH2)COOH CRYSTALLINE SOLUBLE SOLID, an OPTICALLY ACTIVE BASIC hip joint (anatomy) The ball-and-socket ESSENTIAL AMINO ACID. Also termed: JOINT between the ballshaped HEAD 2-amino-3-imidazolylPROPANOIC ACID. of the FEMUR, the thigh-BONE, and the acetabulum, a cup-shaped hollow histocompatibility (histology) See T CELLS. in the side of the PELVIS. histocompatibility complex (genetics) hippocampus (histology) Structure of The system whereby the body recognizes NERVE TISSUE within the VERTEBRATE as foreign any TISSUE other than its BRAIN. It is implicated in emotions own. It is medically important in that and also possibly in MEMORY, since differences between DONOR and bilateral removal in humans produces RECIPIENT LEAD to the rejection of severe and permanent anterograde transplants. Each of the individual’s deficits in MEMORY. own CELLS has on its surface a number of specific proteins, the histocompatibility Hirschaprung’s disease (medical) See antigens (also known as HLA, HUMAN MEGACOLON. LEUCOCYTE ANTIGENS), of which there are six different types, each with dozens hirsutism (medical) The GROWTH of of allelic variants. The probability of superfluous HAIR, especially in women. any two people other than identical It is due to androgenic HORMONES, twins having exactly the same and commonly starts soon after the COMBINATION is correspondingly remote. onset of the MENSES. If the PERIODS are NORMAL, there is very little likelihood histogram (statistics) A chart containing of underlying disease, but if they cease adjacent parallel bars, usually vertical, or are very irregular there may be whose lengths represent the FREQUENCY some cause such as a polycystic OVARY. DISTRIBUTION on a continuous DIMENSION.

Hirudinea (biology) CLASS of annelids histology (histology) The study of the consisting of the LEECHES, some of structure of TISSUE particularly at the which are BLOOD-sucking. microscopic LEVEL.

His. (biochemistry) An abbreviation histone (biochemistry) One of a GROUP of ‘His’tidine. of small proteins with a large proportion of BASIC AMINO ACIDS, e.g. ARGININE or lycine. Histones are found in combination

190 HISTOPLASMOSIS HOMEO. with NUCLEIC ACID in the CHROMATIN hndbk (general terminology) An of EUKARYOTIC CELLS. abbreviation of ‘h’a‘n’d‘b’oo‘k’. histoplasmosis (mycology) A FUNGUS hnRNA (genetics) An abbreviation of INFECTION by the organism Histoplasma ‘h’eterogeneous ‘n’uclear ‘RNA’. capsulatum. The FUNGUS is found in the soil where bird excreta are present, Ho (chemistry) The CHEMICAL SYMBOL and if it is inhaled affects the lungs, for HOLMIUM. but may spread throughout the body. Symptoms usually include FEVER, HOC (chemistry) An abbreviation of shortness of breath, cough, WEIGHT ‘H’eavy ‘O’rganic ‘C’hemical. loss and physical exhaustion. Hodgkin’s disease (medical/histology) hit (computing) The detection of a signal A disease of the reticular and lymphatic when it is there. tissues of the body. It causes painless enlargement of the LYMPH GLANDS HIV (virology) An abbreviation of ‘H’uman and may be accompanied by a FEVER ‘I’mmunodeficiency ‘V’irus. and night sweats. As the disease spreads LYMPH GLANDS become enlarged, and hives (immunology) NETTLE RASH the SPLEEN and later the LIVER may or URTICARIA. also become enlarged. Named after the English physician, T.Hodgkin (1798– HIV-positive (virology) Presence of 1866). the human immunodeficiency VIRUS in the body. holandric (genetics) Occurring only in males, i.e. a GENE that is on the HLA (haematology) An abbreviation Y CHROMOSOME. of ‘H’uman ‘L’eucocyte ‘A’ntigen. holmium Ho (chemistry) Silvery metallic HLA system (immunology) An abbrevia- ELEMENT in GROUP IIIB of the PERIODIC tion of ‘h’uman ‘I’eucocyte ‘a’ntigen TABLE (one of the LANTHANIDES). At. system. no. 67; r.a.m. 164.9303.

HMG-CoA reductase (biochemistry) holoenzyme (biochemistry) ENZYME An abbreviation of 3-‘H’ydroxy-3-‘M’ethyl- that forms from the COMBINATION of ‘G’lutaryl ‘Co’enzyme ‘A’ ‘reductase’. a COENZYME and an APOENZYME. The former determines the nature and HMO (medical) An abbreviation of ‘H’ealth the latter the specificity of a REACTION. ‘M’aintenance ‘O’rganisation. homatropine (pharmacology) An HNC (education) An abbreviation of ALKALOID derived from ATROPINE, ‘H’igher ‘N’ational “C’ertificate. used to DILATE the pupil of the EYE.

HND (education) An abbreviation of homeo. (medical) An abbreviation of ‘H’igher ‘N’ational ‘D’iploma. ‘homeo’pathic.

191 HOMEOSTASIS HOMOLOGOUS homeostasis (physiology) The tendency value of HOMOEOPATHY is divided. of a physiological system to maintain Also termed: homeopathy. itself in BALANCE, whatever the changes in the internal or external ENVIRONMENT. homogametic (genetics) Describing an From the Greek ‘homoio’, meaning ‘equal’, organism with HOMOLOGOUS SEX and ‘stasis’, meaning ‘state’. CHROMOSOMES (e.g. XX). This sex can HOMEOSTASIS is an evolved mechanism, only produce one type of GAMETE, with operated by the switching off and on a single X CHROMOSOME, and therefore of many genes. An example is maintenance does not determine the sex of the offspring. of body TEMPERATURE or the BALANCE In humans the female is the HOMOGAMETIC of salts in the BLOOD. sex. See HETEROGAMETIC; BARR BODY. homeotic mutation (genetics) A MUTATION homogeneity of variance (statistics) that replaces a NORMAL structure with Similarity of VARIANCE, i.e. lack of a another structure that is also NORMAL significant difference in VARIANCE. Most but is in the wrong place. parametric tests are only valid if the samples being compared are from homo- (biology) Prefix denoting the populations with the same VARIANCE. same or similar. homogeneous (1 biology; 2 chemistry; See also HETERO-. 3 mathematics) 1 In biology, describing similar structures found in different SPECIES homo sapiens (genetics) The SPECIES that are thought to have originated from to which all human beings alive belong a common ancestor. 2 In chemistry, relating HOMO SAPIENS has 22 pairs of to a single PHASE (e.g. describing a autosomal chromosomes plus two SEX CHEMICAL REACTION in which all the CHROMOSOMES (XX or XY); the amount reactants are solids, or liquids or gases); of DNA in each human SOMATIC CELL describing a system of uniform composition. is about 6 picograms, and if fully extended 3 In mathematics, describing a would be about 1.9 metres long. The POLYNOMIAL whose terms all have the number of genes is ESTIMATED at same DEGREE; e.g. 2x3-3x2y+ xy2+5y3 somewhere in the region of 100,000. is HOMOGENEOUS (of DEGREE 3). homocyclic (chemistry) Describing a See also HETEROGENEOUS. chemical COMPOUND that contains one or more closed rings comprising CARBON homograft (medical) A GRAFT taken and HYDROGEN atoms only, e.g. from another individual of the same BENZENE. Also termed: CARBOCYCLIC. SPECIES. Also called an allograft.

See also HETEROCYCLIC. homoiothermic (physiology) Describing animals that maintain a more-or-less homoeopathy (medical) System of CONSTANT body TEMPERATURE (e.g. ALTERNATIVE MEDICINE that treats mammals, birds). Also termed: WARM- disorders by introducing substances BLOODED. into the body that provoke similar symptoms and so encourage the body’s homologous (biology) Describing things own defences. Medical opinion on the with common ORIGIN, but not necessarily

192 HOMOLOGOUS CHROMOSOMES HORSERADISH PEROXIDASE the same appearance or FUNCTION See also HETEROZYGOUS. (e.g. the arms of a human and the wings of a bat). hookworm infestation (parasitology) Ancylostomiasis. Parasitisation by one See also ANALOGOUS. of the roundworms (nematodes) Ancylos- toma duodenale or Necator americanus, homologous chromosomes (genetics) the members of a pair of chromosomes horizontal cells of Cajal (cytology) that carry the same genes but not always FUSIFORM CELLS in the plexiform the same ALLELES for a given CHARACTER layer of the CORTEX whose dendrites as the other member of the pair. All the spread horizontally in opposite directions. AUTOSOMES come in HOMOLOGOUS pairs. In the case of the SEX horizontal transmission (genetics) The CHROMOSOMES, the X and the Y are transmission of DNA by viral INFECTION not HOMOLOGOUS as they do not carry into CELLS. NORMAL genetic transmission the same GENE sequence, but two X is VERTICAL TRANSMISSION. See CHROMOSOMES are HOMOLOGOUS TRANSDUCTION. with each other. See MEIOSIS. hormone (biochemistry) A chemical released homologous series (chemistry) FAMILY by an ENDOCRINE GLAND and carried of organic chemical compounds with round in the bloodstream to alter the the same GENERAL FORMULA; e.g. BEHAVIOUR (USA: behavior) of other ALKANES, ALKENES and alkynes. specific target CELLS or tissues. STEROID HORMONES are small LIPID molecules homologue (1 chemistry; 2 biology) that enter the target CELLS; they include 1 A member of a HOMOLOGOUS SERIES. the SEX HORMONES. Other HORMONES 2 A HOMOLOGOUS CHROMOSOME. are polypeptides (chains of AMINO ACIDS shorter than proteins) which bind on to homolytic fission (chemistry) Breaking the outside of the target CELL; they of a two-ELECTRON COVALENT BOND include GROWTH HORMONE and INSULIN. in such a way that each fragment retains Many HORMONES can be synthesised one ELECTRON of the BOND. Also to provide TREATMENT for patients with termed: homolytic CLEAVAGE. a deficiency; some can now also be produced by GENE CLONING. See also HETEROLYTIC FISSION. hormone replacement therapy (HRT) homozygote (genetics) An organism (pharmacology) A drug treatment, which having two identical ALLELES at the may be administered orally, or topically, same site on a pair of chromosomes. for women to supplement the diminished production of the sex HORMONE homozygous (genetics) Having the same OESTROGEN during the MENOPAUSE. two ALLELES for a given GENE. Two organisms that are HOMOZYGOUS for the same horseradish peroxidase (biochemistry) ALLELES breed true for the CHARACTER An ENZYME that is taken up by NERVE in question, thus producing progeny which CELLS and that flows in a retrograde are HOMOZYGOUS and identical to the direction from AXON terminals to the parent with respect to that GENE. CELL BODY and dendrites; after being

193 HOSP. HUMIDITY made RADIOACTIVE, it can be used ht (measurement) An abbreviation of to identify the location of CELL bodies ‘h’eigh‘t’. Also termed hgt. whose axonal terminals are elsewhere. H-T, HT (measurement) An abbreviation hosp. (medical) An abbreviation of of ‘H’igh-‘T’emperature. ‘hosp’ital. HTLV (virology) An abbreviation of host (1,2 biology) 1 The RECIPIENT ‘H’uman ‘T’-CELL ‘L’eukaemia (USA: of a GRAFT or transplant. 2 The CELL, leukemia) ‘V’irus. organism or person that is infected by some PATHOGEN or PARASITE, HTRF (biochemistry) An abbreviation e.g. a BACTERIUM invaded by a VIRUS. for ‘H’ypo-‘T’halamic-‘R’eleasing ‘F’actors. See PARASITISM. human equivalent dose (pharmacology/ hot spot (molecular biology) A site in toxicology) A dose which, when a DNA MOLECULE where MUTATIONS administered to humans, produces an or recombinations occur with much effect equal to that produced by a higher FREQUENCY than elsewhere. given dose in another ANIMAL. housekeeping genes (genetics) A GENE human leucocyte antigens (HLA) that has a PRODUCT essential for the (haematology) PROTEIN markers of self NORMAL metabolic requirements of any used in histocompatibility testing. It plays CELL. These genes are active in most a most important part in determining or all CELLS, in contrast to the CELL- whether transplanted tissues will be rejected specific LUXURY GENES. The parts of by the RECIPIENT, and some HLA types the CHROMOSOME where they are situated also correlate with certain AUTO-IMMUNE show up as LIGHT-staining interbands. DISEASES. For example, ANKYLOSING SPONDYLITIS is 120 times more likely hPL (physiology/biochemistry) An to occur in people with ALLELE B27. abbreviation of ‘h’uman ‘P’lacental ‘L’actogen. human t-cell leukaemia virus (HTLV) (virology) Any of several retroviruses HPLC (biochemistry) An abbreviation of that infect T-CELLS, causing a rare strain ‘H’igh ‘P’erformance ‘L’iquid ‘C’hromatography. of LEUKAEMIA (USA: leukemia) to develop. (USA: human T-cell leukemia virus). HPRT (immunology) An abbreviation of ‘H’ypoxanthine ‘P’hospho ‘R’ibosyl humerus (anatomy) Upper BONE in ‘T’ransferase. the forelimb of a tetrapod VERTEBRATE; in human beings, the upper arm BONE. HSC (governing body) An abbreviation of ‘H’ealth and ‘S’afety ‘C’ommission. humi. (physics) An abbreviation of ‘humi’dity. HS-CoA (physiology/biochemistry) A symbol for reduced coenzyme A. humidity (physics) Measure of the amount of WATER VAPOUR in a GAS, e.g. the HSS (society) An abbreviation of ‘H’istory AIR, usually expressed as a PERCENTAGE. of ‘S’cience ‘S’ociety. RELATIVE HUMIDITY is the amount of

194 HUMORAL IMMUNITY HYDATID DISEASE

VAPOUR divided by the maximum amount HEART problems leading to death at of VAPOUR the GAS will hold (at a the age of 8–10. CARRIER females particular TEMPERATURE). can be identified biochemically, as can affected foetuses (USA: fetuses). About humoral immunity (immunology) The 1 in 100,000 babies has Hurler’s syndrome. production of antibodies for defense against INFECTION or disease. HV (physics) An abbreviation of ‘H’igh ‘V’oltage. hundredweight (cwt) (measurement) UNIT of MASS equal to 112 Ib or 50.85 HVA (biochemistry) An abbreviation kg (USA: equal to 100 Ib or 45.40 kg). of ‘Homo‘V’anillic ‘A’cid.

Hunterian chancre (medical) The primary hyaluronidase (biochemistry) A naturally sore of syphilis, which has an ulcerated occurring ENZYME which has the property hard BASE. The DISCHARGE is thin of breaking down hyaluronic ACID. and watery. Named after the London surgeon, J.Hunter (1728–93). hybrid (genetics) The offspring of parents that are genetically unlike, particularly Hunter’s syndrome (genetics) A human of parents of different SPECIES or of disease caused by an X-linked different varieties within a SPECIES. RECESSIVE ALLELE. The biochemical problem (as with HURLER’S SYNDROME) hybrid DNA (molecular biology) DNA that is that the patient is unable to break is artificially made in vitro by mixing two down mucopolysaccharides, large strands of DNA (or one of DNA and one compounds of sugars that combine of RNA) of different genetic origins. It is with proteins and are important in NERVE not the same as RECOMBINANT DNA. CELL function. A build-up of these molecules leads to mental deterioration hybrid vigour (genetics) The phenomenon and deafness, as well as various in which the HYBRID is more vigorous disfiguring symptoms. Women in families than either of its parental strains resulting where the disease has occurred can from an increase in genetical VARIATION. be tested to see whether they are carriers; and prenatal diagnosis is reliable. hybridization (1,2 genetics) 1 Crossing of animals or plants to produce a HYBRID. Huntingtons chorea (medical/genetics) 2 COMBINATION of ATOMIC ORBITALS A human disease caused by a single to produce HYBRID orbitals. DOMINANT ALLELE. The underlying mechanism is not known, but the disease hybridoma (immunology/genetics) An is a distressing one consisting of artificially produced HYBRID CELL, involuntary movements and mental combining a NORMAL lymphocyte and deterioration. a myeloma (cancerous) LYMPH CELL, and used in the preparation of Hurler’s syndrome (genetics) A human MONOCLONAL antibodies. disease caused by a RECESSIVE ALLELE. The biochemical problem is the same hydatid disease (parasitology) INFECTION as in HUNTER’S SYNDROME, but the with the dog TAPEWORM, Echinococcus effects are worse, with dwarfism and granulosus.

195 HYDATIDIFORM MOLE HYDROGEN hydatidiform mole (medical) A disease hydrocarbon (chemistry) ORGANIC COM- of the superficial layer of the CHORION, POUND that contains only CARBON and the outer of the two membranous layers HYDROGEN. The chief naturally occurring covering the FOETUS (USA: fetus) in HYDROCARBONS are bitumen, coal, the UTERUS, in which the UTERUS methane, natural GAS and petroleum. Most becomes full of vesicles like grapes; of these, and HYDROCARBONS derived it results from ABNORMAL development from them, are used as fuels. The ALIPHATIC of the fertilized OVUM. COMPOUNDS form three HOMOLOGOUS SERIES: ALKANES, ALKENES and alkynes. hydrargyrum (chemistry) MERCURY. Aromatic HYDROCARBONS are CYCLIC compounds. See AROMATIC COMPOUNDS. hydrate (chemistry) Chemical COMPOUND that contains WATER OF CRYSTALLIZATION. hydrocephalus (medical) An ABNORMAL amount of CEREBROSPINAL FLUID hydrated (1,2 chemistry) 1 Describing within the ventricles of the BRAIN, a substance after TREATMENT with WATER. eventually leading to malformation of 2 Describing a COMPOUND that contains BRAIN TISSUE. chemically bonded WATER, a HYDRATE. hydrochloric acid (chemistry) HCI hydrated lime (chemistry) An alternative Colourless (USA: colorless) acidic term for CALCIUM HYDROXIDE. AQUEOUS SOLUTION of HYDROGEN CHLORIDE, a STRONG ACID that hydration (chemistry) Attachment of dissolves most metals with the release WATER to the particles (particularly ions) of HYDROGEN; its salts are chlorides. of a SOLUTE during the dissolving process. It is contained in NORMAL STOMACH juices in a diluted form. hydrazine (chemistry) NH2NH2 Colourless (USA: colorless) LIQUID, a powerful REDUCING hydrocortisone A STEROID HORMONE AGENT used in organic SYNTHESIS. secreted by the ADRENAL CORTEX. It may be used to treat rheumatism hydrazone (chemistry) Member of a and inflammatory and allergic conditions. FAMILY of ORGANIC COMPOUNDS that contain the GROUP -C=NNH2. Hydrazones hydrocyanic acid HCN (chemistry) Very are formed by the ACTION of HYDRAZINE poisonous SOLUTION of HYDROGEN on an ALDEHYDE or KETONE, and CYANIDE in WATER. Its salts are cyanides. are used in identifying them. Also termed: prussic ACID. hydride (chemistry) COMPOUND formed hydrofluoric acid HF (chemistry) Colour- between HYDROGEN and another less (USA: colorless) corrosive AQUEOUS

ELEMENT (e.g. CALCIUM HYDRIDE, CaH2). SOLUTION of HYDROGEN FLUORIDE; its salts are fluorides. It is used for etching hydro- (biology) Prefix denoting WATER. GLASS (and must be stored in plastic bottles). hydrobromic acid HBr (chemistry) hydrogen H (chemistry) Gaseous ELEMENT Colourless (USA: colorless) acidic usually given its own place at the beginning AQUEOUS SOLUTION of HYDROGEN of the PERIODIC TABLE, but sometimes BROMIDE; its salts are bromides. assigned to GROUP IA, colourless (USA:

196 HYDROGEN BOND HYDROGEN SULPHIDE colorless), odourless (USA: odorless) and PLATINUM). It is immersed in a MOLAR highly inflammable, it is the lightest GAS ACID solution and used for determining known and occurs abundantly in STANDARD ELECTRODE POTENTIALS.

COMBINATION in WATER (H2O), coal and Also termed: HYDROGEN HALF-CELL. petroleum (mainly as HYDROCARBONS) and living things (mainly as carbohydrates). hydrogen fluoride HF (chemistry) Colour- In addition to the common form (sometimes less (USA: colorless) fuming LIQUID, called protium, r.a.m. 1.00797) there are which is extremely corrosive and dissolves two other isotopes: DEUTERIUM or heavy in WATER to form HYDROFLUORIC ACID. HYDROGEN (r.a.m. 2.01410) and the RADIOACTIVE TRITIUM (r.a.m. 3.0221). hydrogen half-cell (physics) An alterna- At. no. 1; r.a.m. (of the naturally occurring tive term for HYDROGEN ELECTRODE. MIXTURE of isotopes) 1.0080. hydrogen halide (chemistry) COMPOUND hydrogen bond (chemistry) Strong of HYDROGEN and a HALOGEN; e.g. CHEMICAL BOND that holds together HYDROGEN FLUORIDE, HF. some molecules that contain HYDROGEN, e.g. WATER molecules, which become hydrogen ion H+ (chemistry) Positively- associated as a result. A HYDROGEN charged HYDROGEN ATOM; a PROTON. ATOM bonded to an electronegative A CHARACTERISTIC of an ACID is ATOM interacts with a (non-bonding) the production of HYDROGEN IONS, lone pair of electrons on another which in AQUEOUS SOLUTION are electronegative ATOM. HYDRATED to HYDROXONIUM IONS, + H3O . HYDROGEN ION CONCENTRATION hydrogen bromide HBr (chemistry) is a measure of acidity, usually expressed Pale yellow GAS which dissolves in on the PH SCALE. WATER to form HYDROBROMIC ACID.

hydrogen peroxide (chemistry) H2O 2 hydrogen chloride HCI (chemistry) Colourless (USA: colorless) syrupy LIQUID Colourless (USA: colorless) GAS which with strong oxidizing powers, SOLUBLE dissolves readily in WATER to form in WATER in all proportions. DILUTE HYDROCHLORIC ACID. It is made by solutions are used as an OXIDIZING treating a CHLORIDE with concentrated AGENT, disinfectant and BLEACH. SULPHURIC ACID (USA: sulfuric acid) or produced as a BY-PRODUCT of hydrogen spectrum (physics) SPECTRUM electrolytic processes involving chlorides. produced when an electric DISCHARGE is passed through HYDROGEN GAS. hydrogen cyanide HCN (chemistry) Colourless The HYDROGEN molecules dissociate (USA: colorless) poisonous GAS, which and the atoms emit LIGHT at a SERIES dissolves in WATER to form HYDROCYANIC of CHARACTERISTIC frequencies. ACID (prussic acid). It has a CHARACTERISTIC SMELL of bitter almonds. See also BALMER SERIES.

hydrogen electrode (physics) HALF-CELL hydrogen sulphide H2S (chemistry) that consists of HYDROGEN GAS bubbling Colourless (USA: colorless) poisonous around a PLATINUM ELECTRODE, covered GAS With a CHARACTERISTIC SMELL in PLATINUM black (very finely divided (when impure) of bad eggs. It is formed

197 HYDROGENATION HYDROXIDE by rotting SULPHUR (USA: sulfur) containing chemicals that are WATER-SOLUBLE organic MATTER and the ACTION of or to the regions of chemicals that acids on sulphides (USA: sulfides). are polar and therefore attracted to WATER. HYDROPHILIC compounds do hydrogenation (chemistry) Method of not diffuse easily through membranes. chemical SYNTHESIS by adding HYDROGEN to a substance. It forms hydrophobia (virology) Popular name the basis of many important industrial for RABIES, though it in fact only refers processes, such as the conversion of to one of the symptoms, the irrational LIQUID oils to SOLID fats. fear of WATER. hydrogencarbonate (chemistry) Acidic hydrophobic (chemistry) WATER- SALT containing the ION HCO . Also 3- repellent; having no attraction for WATER. termed: BICARBONATE. hydrophobic binding (biochemistry) hydrogen sulphate (chemistry) Acidic When two non-polar groups come together SALT containing the ION HSO . Also 4- they exclude the WATER between them, termed: BISULPHATE (USA: bisulfate). and this mutual exclusion of WATER (USA: hydrogen sulfate). results in a HYDROPHOBIC interaction. hydrogen sulphite (chemistry) Acidic In the aggregate they present the least possible disruption of interactions among SALT containing the ION HSO3-. Also termed: BISULPHITE (USA: bisulfite). polar WATER molecules, and thus can (USA: hydrogen sulfite). LEAD to STABLE complexes. Some authorities consider this a special case hydrolysis (biochemistry) CLEAVAGE involving VAN DER WAALS’ FORCES. of a MOLECULE by the addition of The minimization of thermodynamically WATER, with a HYDROXYL GROUP unfavourable (USA: unfavorable) contact (-OH) from the WATER taking part in of a polar GROUPING with WATER the REACTION; e.g. esters hydrolyse molecules provides the major stabilizing to form ALCOHOLS and acids. effect in HYDROPHOBIC interactions. hydrolytic enzymes (biochemistry) Any hydrops fetalis (medical) Accumulation ENZYME capable of splitting a MOLECULE of FLUID in the body cavities and into components by inserting WATER. SUBCUTANEOUS TISSUES of the fetus. HYDROLYTIC ENZYMES include lysosomal Causes include Rhesus disease. ACID hydrolases and a number of the ENZYMES in PROTEIN, CARBOHYDRATE, hydrosol (chemistry) AQUEOUS SOLUTION LIPID and NUCLEIC ACID CATABOLISM. of a COLLOID. hydrometer (physics) Instrument for hydrous (chemistry) Containing WATER. measuring the DENSITY of a LIQUID. It consists of a weighted GLASS bulb hydroxide (chemistry) COMPOUND of with a long graduated stem, which floats a METAL that contains the HYDROXYL in the LIQUID being tested. GROUP (-OH) or the HYDROXIDE ION (OH). Many METAL hydroxides are bases. hydrophilic (biochemistry) Possessing an AFFINITY for WATER. Refers to

198 HYDROXONIUM ION HYPOCHLOROUS ACID hydroxonium ion (chemistry) HYDRATED It can be corrected by spectacles or contact + HYDROGEN ION, H3O . lenses made from converging (CONVEX) lenses. Also termed: hyperopia. hydroxybenzene (chemistry) An alternative term for PHENOL. See also MYOPIA. hydroxybenzoic acid (chemistry) An hyperphoshataemia (haematology/bio- alternative term for SALICYLLIC ACID. chemistry) Elevated levels of phosphates in the blood. (USA: hyperphoshatemia). hydroxyl group (-OH) (chemistry) GROUP containing OXYGEN and HYDROGEN, hypersensitivity (immunology) Over- characteristics of ALCOHOLS and some REACTION by the IMMUNE SYSTEM. It hydroxides. involves the mounting of a large-scale immunological defence against antigens hydroxypropionic acid (chemistry) An that are in low CONCENTRATION and alternative term for LACTIC ACID. are possibly not harmful to the organism in that low CONCENTRATION though hygrometer (physics) Instrument for they would be at a higher one. See ALLERGY. measuring the HUMIDITY of AIR, the amount of WATER VAPOUR in the ATMOS- hypertension (medical) High arterial PHERE. BLOOD PRESSURE. hygroscope (physics) Instrument for hyperthyroidism (biochemistry) See indicating the HUMIDITY of AIR. THYROID. hygroscopic (chemistry) Having the hypertrophy (histology) Increased size tendency to absorb moisture from the of an ORGAN due to enlargement of ATMOSPHERE. individual CELLS.

Hyl (biochemistry) An abbreviation of hypha (mycology) Microscopic hollow ‘Hy’droxy‘I’ysine. FILAMENT CHARACTERISTIC of FUNGI. Hyphae form a NETWORK called a MYCELIUM. Hyp (biochemistry) An abbreviation of 4-‘Hy’droxy‘p’roline. hypo (chemistry) Popular name for SODIUM THIOSULPHATE (USA: sodium hyperaemia (haematology) Congestion thiosulfate). of a part with BLOOD. (USA: hyperemia). hypocalcaemia (biochemistry) A low hyperchlorhydria (biochemistry) Excess LEVEL of CALCIUM in the BLOOD. of HYDROCHLORIC ACID in the STOMACH. hypochlorite (chemistry) SALT of hypermetropia (medical) Longsighted- HYPOCHLOROUS ACID (containing the ness, a VISUAL DEFECT in which the ION CIO-). Hypochlorites are used as eyeball is too short (front to back) so bleaches and disinfectants. that LIGHT rays entering the EYE from nearby objects would be brought to a hypochlorous acid (chemistry) (HOCI) FOCUS at a point behind the RETINA. A weak LIQUID ACID stable only in

199 HYPOGLYCAEMIA HYSTEROSALPINGOGRAM

SOLUTION, used as an OXIDIZING AGENT hypothalamus (anatomy) Floor and and BLEACH. Its salts are hypochlorites. sides of the VERTEBRATE FOREBRAIN, Also termed: chloric(I) ACID. which is concerned with physiological coordination of the body; e.g. regulation hypoglycaemia (biochemistry) A low LEVEL of body TEMPERATURE, HEART rate, of GLUCOSE in the BLOOD and symptoms BREATHING rate, BLOOD PRESSURE, are likely to appear if the LEVEL falls sleep pattern as well as drinking, eating, below 2.5 mmol/1. By far the most common WATER EXCRETION and other metabolic cause of this is failure in a diabetic to functions. cover the dose of INSULIN or similar drug with food, although there are a hypothermia (medical) Abnormally low number of rare conditions that can lower body TEMPERATURE. the BLOOD SUGAR. (USA: hypoglycemia). hypothesis (philosophy) A provisional hypokalaemia (biochemistry) Abnormally scientific explanation that is unproved, low LEVEL of POTASSIUM in the BLOOD. but either thought of as probably true (USA: hypokalemia). or used as a basis for further investigation. hyponatraemia (biochemistry) Abnormally hypothyroidism (biochemistry) See low LEVEL of SODIUM in the BLOOD. THYROID. (USA: hyponatremia). hypotonic (biochemistry) Having a lower hypophysis (anatomy) An alternative CONCENTRATION of a SOLUTE, used term for PITUITARY. of one SOLUTION with reference to another. Compare hypertonic. hypoplasia (histology) Underdevelopment of a TISSUE or ORGAN. hypotrophy (medical) See ATROPHY. hyposulphuric acid (chemistry) An hypovolaemia (medical) A decrease alternative term for DITHIONIC ACID. in the VOLUME of FLUID in the (USA: hyposulfuric acid). EXTRACELLULAR spaces, which can be caused by lack of WATER or severe hypotension (medical) Abnormally low bleeding and which produces volumetric BLOOD PRESSURE. thirst. (USA: hypovolemia). hypoth. (biology) An abbreviation of hypoxaemia (medical) Deficiency of ‘hypoth’esis. OXYGEN in the BLOOD. (USA: hypoxemia). hypothalamic-releasing factors (HTRF) hysterectomy (medical) Surgical removal (biochemistry) HORMONES produced by of the UTERUS. NERVE CELLS in the HYPOTHALAMUS that selectively promote the release of hysterosalpingogram (radiology) X-RAY five PITUITARY HORMONES: ADRENO- examination to outline the cavity of the CORTICOTROPHIN, LUTEINIZING HOR- UTERUS and lumina of the FALLOPIAN MONE, THYROTROPHIN, FOLLICLE- TUBES by the injection of RADIO-OPAQUE STIMULATING HORMONE, and GROWTH dye. HORMONE.

200 HYSTEROSCOPY HZ hysteroscopy (medical) Inspection of the uterine cavity through a fibreoptic (USA: fiberoptic) scope.

Hz (measurement) An abbreviation of ‘H’ert‘z’.

201 I

I (1 measurement; 2 biochemistry) 1 ice (chemistry) WATER in its SOLID An abbreviation for ‘I’ntensity. 2 A symbol state (i.e. below its FREEZING POINT, for Isoleucine. 0°C). It is less dense than WATER, because HYDROGEN BONDS give its I Biol (society) Institute of Biology. crystals an open structure, and it therefore floats on WATER. This also means that I (chemistry) The CHEMICAL SYMBOL WATER expands on FREEZING. for IODINE. ice point (measurement) FREEZING IAMS (society) An abbreviation of POINT of WATER, 0°C, used as a FIXED ‘I’nternational ‘A’ssociation of ‘M’icro- POINT on TEMPERATURE SCALES. biological ‘S’ocieties/‘S’tudies. Iceland spar (chemistry) Very pure IAP (education) An abbreviation of TRANSPARENT form of calcite (CALCIUM ‘I’nternational ‘A’cademy of ‘P’athology. CARBONATE), noted for the property IARC (education) An abbreviation of of DOUBLE REFRACTION. ‘I’nternational ‘A’gency for ‘R’esearch I cells (physiology) A symbol for on ‘C’ancer. Inspiratory neurons. iatrogenic (medical) Caused by medical ICRO (education) An abbreviation of TREATMENT or mistreatment. ‘I’nternational ‘C’ell ‘R’esearch ‘O’rganiz- IB (medical) An abbreviation of ‘I’nfectious ation. ‘B’ronchitis. ICSH (biochemistry) An abbreviation IBC (education) An abbreviation of of ‘I’nterstitial ‘C’ell-‘S’timulating ‘H’or- ‘I’nternational ‘B’iotoxicological ‘C’entre. mone. ibid (literary terminology) Latin, meaning, ICU (medical) An abbreviation of ‘in the same place’. Refers to the source ‘I’ntensive ‘C’are ‘U’nit. most recently cited. Found in footnotes and text of dissertations, theses, papers, id (measurement) An abbreviation of and the like. ‘i’nner ‘d’iameter. ibp (physics) An abbreviation for ‘initial IDAV (virology) An abbreviation of ‘b’oiling ‘p’oint. ‘I’mmune ‘D’eficiency-‘A’ssociated ‘V’irus.

ICD (taxonomy) An abbreviation for IDDM (medical/biochemistry) An ‘I’nternational ‘C’lassification of ‘D’is- abbreviation of ‘I’nsulin-‘D’ependent eases. ‘D’iabetes ‘M’ellitus.

202 IDIOGRAM IMAGE idiogram (genetics) A formal representa- IJP (physiology) An abbreviation of tion of all the chromosomes in an ‘I’nhibitory ‘J’unction ‘P’otential. individual’s KARYOTYPE, usually consisting of photographed chromosomes IL (physiology/biochemistry) Abbrevia- from a single CELL-DIVISION, which tion of ‘I’nter‘L’eukin. have been cut out and arranged in ORDER. Preparation of an IDIOGRAM IIe (biochemistry) An abbreviation of is an essential step in diagnosing ‘I’so‘le’ucine. CHROMOSOME abnormalities. ileitis (medical) INFLAMMATION of the idiopathic (medical) A term applied ILEUM. It occurs in a localised AREA in to diseases when their cause is unknown, the last part of the ILEUM, which forms or of spontaneous ORIGIN. the last three-fifths of the SMALL INTESTINE, and may extend into the COLON. Named idiotypes (immunology) The unique after the American surgeon, B.B.Crohn and CHARACTERISTIC parts of an (1874–1983), it is often called Crohn’s ANTIBODY’S VARIABLE REGION, which disease. can themselves serve as antigens. ileum (anatomy) Last SECTION of the IDL (biochemistry) An abbreviation of SMALL INTESTINE continuous with ‘I’ntermediate-‘D’ensity ‘L’ipopROTEIN. the JEJUNUM above and the COLON below, where both DIGESTION and IDU (medical) An abbreviation of ‘I’njection ABSORPTION take place. ‘D’rug ‘U’ser. i.e. (literary terminology) An abbreviation of ‘i’d ‘e’st. Latin, meaning See also DUODENUM; JEJUNUM. ‘that is’. Used to clarify or restate what has been said or written. illuminance (physics) The amount of LIGHT falling per UNIT AREA on a surface as IF (immunology) An abbreviation of measured by PHOTOMETRY; the standard ‘I’nter‘F’eron. Also termed: IFN. UNIT of measurement is the LUX.

IFEMS (society) An abbreviation of illuminometer (physics) A device for ‘I’nternational ‘F’ederation of ‘E’lectron measuring LUMINANCE by matching ‘M’icroscope ‘S’ocieties. a comparison FIELD of known brightness to the standard. IFN (physiology/biochemistry) An abbreviation of ‘I’nter‘F’ero‘N’. Also ILT (medical) An abbreviation of termed IF. ‘I’nfectious ‘L’aryngo-‘T’racheitis.

IGF-I, IGF-II (physiology/biochemistry) image (optics) Point from which rays An abbreviation of ‘I’nsulin-like ‘G’rowth of LIGHT entering the EYE appear to ‘F’actors I and II. have originated. A REAL IMAGE, e.g. one formed by a CONVERGING LENS, 123I-IMP (biochemistry) An abbreviation can be focused on a screen; a virtual of ‘ 123I’-labeled ‘I’odoa‘MP’hetamine. IMAGE, e.g. one formed in a plane mirror, can be seen only by the eyes of the observer and has no physical existence.

203 IMAGE CONVERTER IMMUNE SYSTEM image converter (physics) ELECTRON immun. (immunology) An abbreviation TUBE for converting INFRA-RED or of ‘immun’ity/‘immun’isation/‘immun’ology. other invisible images into visible images. immune complex (immunology) A cluster IMI (medical) An abbreviation of of interlocking antigens and antibodies. ‘I’ntra‘M’uscular ‘I’njection. immune response (immunology) The imidazole amines (biochemistry) A REACTION of the IMMUNE SYSTEM CLASS of biogenic amines containing to invasion by a foreign substance an IMIDAZOLE ring, e.g. HISTAMINE. (ANTIGEN). It involves the production of specific ANTIBODY molecules, which imidazole (biochemistry) C3H 4N 2 An combine with the ANTIGEN to form Aromatic HETEROCYCLIC COMPOUND an ANTIGEN-ANTIBODY complex. whose ring contains three CARBON Antibodies may be present in body atoms and two NITROGEN atoms. Also fluids or carried by LYMPHOCYTES. termed: glyoxaline. immune status (immunology) The state imide (chemistry) ORGANIC COMPOUND of the body’s natural defense to diseases. derived from an ACID ANHYDRIDE, It is influenced by HEREDITY, age, GENERAL FORMULA R-CONHCO-R’, past illness history, diet and physical where R and R’ are organic radicals. and mental health. It includes production Also termed: IMIDO COMPOUND. of circulating and local antibodies and their mechanism of ACTION. imido compound (chemistry) An alternative term for IMIDE. immune system (immunology) The system by which the body overcomes infections imido-urea (chemistry) An alternative and other invasions by foreign bodies. term for guanidine. ‘Natural’, or ‘non-specific’, IMMUNITY works by PHAGOCYTOSIS and by the ACTION imine (chemistry) Secondary AMINE, of the PROTEIN INTERFERON. ‘Specific an ORGANIC COMPOUND derived from IMMUNITY’, i.e. a RESPONSE to one AMMONIA, GENERAL FORMULA RNHR’, particular infective agent (all of which, where R and R’ are organic radicals. whether VIRUSES, BACTERIA, PARASITES, Also termed: IMINO COMPOUND. or non-living particles are known as antigens in this context), is most highly developed imino compound (chemistry) An in vertebrates, including humans. It is of alternative term for IMINE. two kinds: ‘HUMORAL IMMUNITY’, in which ANTIBODY molecules circulate in the LYMPH IML (physiology) An abbreviation of and BLOOD; and ‘CELL-mediated’ ‘I’nter‘M’edio‘L’ateral gray column. IMMUNITY, in which LYMPH CELLS directly bind to the antigens. In HUMORAL IMMUNITY, immiscible (chemistry) Describing two the arrival of the ANTIGEN stimulates or more liquids that will not mix (when the appropriate line of B LYMPHOCYTES shaken together they separate into in the BONE MARROW; these CELLS, layers); e.g. oil and WATER. and their descendants in the LYMPH NODES and SPLEEN, produce the specific ANTIBODY molecules which bind on to the antigens,

204 IMMUNISATION IMMUNOGLOBULIN either making them incapable of infective MUCOUS MEMBRANES. Active mechanisms ACTION or holding them in lumps so include PHAGOCYTOSIS by LEUCOCYTES that they can be easily engulfed and dissolved and the IMMUNE RESPONSE in animals. by the large MACROPHAGE CELLS (this Plants can have IMMUNITY, e.g. by means is facilitated by a GROUP of proteins of phytoalexins. collectively known as complement, activated by the ANTIBODY-ANTIGEN complex). immunoassay (immunology) Any of a number CELL-mediated IMMUNITY is similar, with of assays based on the binding of ANTIBODY the ANTIGEN binding being done by T to ANTIGEN. Often the ANTIBODY is linked LYMPHOCYTES which originate in the to a marker such as a FLUORESCENT THYMUS GLAND. The HUMORAL MOLECULE, a RADIOACTIVE MOLECULE IMMUNITY produced by circulating or an ENZYME. Immunoassays include ANTIBODY is most effective against infections RADIAL IMMUNODIFFUSION and by BACTERIA and VIRUSES while they immunoelectrophoresis, both of which utilise are outside the CELLS; CELL-mediated ANTIBODY incorporated into a uniform IMMUNITY is better against VIRUSES GEL; radioimmunoassay where the ANTIBODY inside CELLS, PARASITES, CANCER CELLS is linked to a RADIOACTIVE TRACER; and foreign TISSUE. See AUTO-IMMUNE and ENZYME-linked immunosorbent assay DISEASES; IMMUNISATION. (elisa) where the ANTIBODY is linked to an ENZYME. immunisation (immunology) The technique of artificially creating ACTIVE IMMUNITY immunocompetent (immunology) Capable by injecting the patient with non-virulent of developing an IMMUNE RESPONSE antigens that resemble the disease-causing pathogens. A specific ANTIBODY or immunofluorescence technique (immunol- IMMUNOGLOBULIN is formed in ogy) A method of locating targets by RESPONSE and may persist in the body, linking them to ANTIBODY tagged with preventing further INFECTION by the FLUORESCENT dyes so that they can same organism. Some diseases have a be made visible under a FLUORESCENT- more lasting IMMUNITY than others: the MICROSCOPE. acquired IMMUNITY to MEASLES and mumps is generally lifelong, but in some immunoglobulin (biochemistry) Large cases (e.g. flu) it is very shortlived. This globular proteins found in the body fluids. is probably because of changes in the The BASIC UNIT of IMMUNOGLOBULIN VIRUS responsible, which affect its antigenic structure consists of four POLYPEPTIDE properties.The term is also used for giving chains, two identical LIGHT chains and passive IMMUNITY by the injection of two identical heavy chains, which are ANTISERUM. IMMUNISATION can also disulphide bonded (USA: disulfide bonded) MEAN any experimental process in which to form two identical ANTIGEN-binding animals are injected with some substance (VARIABLE) regions. Humans possess to which they acquire IMMUNITY. five distinct classes of IMMUNOGLOBULIN (IgG, IgA, IgM, IgD, IgE) distinguishable immunity (immunology) Protection by an by differences in the carboxy-terminal organism against INFECTION. Defence portion of the heavy chain. may be divided into passive and active IMMUNOGLOBULIN is a GENERIC term. mechanisms. Passive processes prevent Immunoglobulins known to bind specifically the entry of foreign invasion, e.g. SKIN,

205 IMMUNOL. IMPULSE with a particular ANTIGEN are referred (d.c.) it is equal to the resistance (R). to as antibodies. For ALTERNATING CURRENT (a.c.) the reactance (X) also has an effect, such See also ANTIBODY. that Z2=R2+X2, or Z=R+iX, where i2=-1. immunol. (immunology) An abbreviation imperial system (measurement) Compre- of ‘immunol’ogy. hensive system of weights and measures (feet and inches, AVOIRDUPOIS weights, immunology (immunol.) (immunology) pints and gallons, etc.) that was formerly The scientific study of IMMUNITY, antigens used throughout the British Empire. and antibodies and their role in immune SI UNITS have replaced the IMPERIAL mechanisms and INFECTION. SYSTEM for scientific measurement. immunostimulants (immunology) Agents impermeable (physics) Describing a that boost the natural IMMUNE RESPONSE. substance that will not allow a FLUID Therapeutic IMMUNOSTIMULANTS have (GAS or LIQUID) to pass through it been used in CANCER treatments to restore (e.g. granite is IMPERMEABLE to WATER). or augment the antitumor RESPONSE. impetigo (medical) An INFECTION of immunosuppression (immunology) The the SKIN, particularly of the face, with state of an altered IMMUNE SYSTEM that streptococci or staphylococci, which may LEAD to impaired immune FUNCTION. is found in children and is very contagious. Drugs such as CYTOTOXIC drugs that inhibit CELL DIVISION are powerful implantation (physiology) Process in immunosuppressants and depression of which a fertilized OVUM (EGG) or immune FUNCTION can LEAD to increased EMBRYO becomes attached to the lining susceptibility to BACTERIAL, viral and of the UTERUS (womb) of a mammal. parasitic infections, and possibly increased It is the beginning of PREGNANCY. INCIDENCE of NEOPLASM. implicit function (mathematics) VARIABLE immunosuppressive (pharmocology) x is an IMPLICIT FUNCTION of y when Describing a drug that suppresses the x and y are connected by a FUNCTION IMMUNE RESPONSE, given to recipients that is not explicit (i.e. in which x is not of transplanted organs to minimize that directly expressed in terms of y). chance of rejection. improper fraction (mathematics) FRACTION immunosuppressor (immunology) A CELL whose upper part (NUMERATOR) is larger or SOLUBLE mediator that suppresses than the lower part (DENOMINATOR) e.g. IMMUNE RESPONSES. Immunosuppressors 7/3, 11/4, 3/25. It is always greater than may FUNCTION to regulate IMMUNE 1, as can be seen by converting it to a RESPONSES, preventing excessive, mixed number (the previous examples potentially TISSUE-damaging responses. become 2 1/3, 2 3/4, 1 7/25). impedance (Z) (physics) Property of impulse (1 biology; 2 physics) 1 In biology, an electric CIRCUIT or CIRCUIT transmission of a message along a NERVE COMPONENT that opposes the passage FIBRE (USA: nerve fiber). The NERVE of a CURRENT. For DIRECT CURRENT IMPULSE is an electrical phenomenon

206 IMR INCOMPLETE DOMINANCE which results in DEPOLARIZATION of of a substance; e.g. the FILAMENT in the NERVE MEMBRANE. This ACTION an electric lamp is incandescent. POTENTIAL lasts for a millisecond before the RESTING POTENTIAL is restored. See also LUMINESCENCE. See also ALL-OR-NONE RESPONSE. 2 In physics, when two objects collide, inch (measurement) UNIT of length over the PERIOD of impact there is a equal to 1/12 of a foot; 1 in=25.4 mm. large reactionary FORCE between them whose time INTEGRAL is the IMPULSE incid. (general terminology) An abbrevia- of the FORCE (equal to either OBJECT’S tion of ‘incid’ental. change of momentum). incidence (epidemiology) The rate of IMR (statistics) An abbreviation of ‘I’nfant occurrence of new cases of a disorder ‘M’ortality ‘R’ate. over a given PERIOD of time, usually expressed as the number of new cases IMS (chemistry) An abbreviation of per 100,000 members of the population. ‘I’ndustrial ‘M’ethylated ‘S’pirit. incisor (anatomy) Chisel-shaped cutting In. (biochemistry) An abbreviation of TOOTH of mammals located at the ‘In’ulin. front of the upper and lower JAWS; human beings have eight incisors. They inborn errors of metabolism (genetics/ grow continually in rodents, which use biochemistry) A GROUP of disorders them for gnawing. in which the BASIC cause is the lack of an ENZYME involved in NORMAL inclusion bodies (virology) Microscopic METABOLISM. These disorders are almost bodies, usually within body CELLS, always inherited as recessives. For thought to be VIRUS particles in example, if the NORMAL GENE coding for the ENZYME is T, and the MUTANT morphogenesis. GENE is t, a HETEROZYGOUS person Tt will be healthy because the T GENE incompatibility (haematology) Mismatch- can produce sufficient quantities of the ing of biochemical components, e.g. ENZYME; whereas the person with between BLOOD GROUPS or between GENOTYPE tt will be without the genetic a transplanted DONOR ORGAN and means to produce the ENZYME and its RECIPIENT or between a scion will therefore have a block in a metabolic and the plant on which it is grafted. pathway. Most patients with these disorders With an ORGAN transplant it can LEAD can be treated with diets that avoid to immunological rejection (counteracted taking in the substance that cannot be by IMMUNOSUPPRESSIVE drugs). metabolized. See ALKAPTONURIA; CYSTINURIA; PHENYLKETONURIA. incomplete dominance (genetics) The condition in which neither of a pair of inbreeding (biology) REPRODUCTION ALLELES completely masks the presence between closely related organisms of a of the other phenotypically. SPECIES. See also PHENOTYPE; DOMINANT. incandescence (physics) LIGHT emission that results from the high TEMPERATURE

207 INCR. INDUCED MAGNETISM incr. (general terminology) An abbrevia- survives only in certain environments; tion of ‘incr’ease. its presence gives information about the ENVIRONMENT e.g. the presence in WATER incubation period (1 medical; 2 micro- of certain BACTERIA that normally live biology) 1 The time elapsing between in FAECES (USA: FECES) indicates that INFECTION with the organisms of a the WATER is polluted with sewage. disease and the appearance of symptoms. In any given disease it is relatively indigenous flora (microbiology) NORMAL CONSTANT. People who have been or resident flora. exposed to an INFECTIOUS DISEASE and may be incubating it and who may indigo (chemistry) C16H 10N 2O 2 A blue become infectious, are known as contacts. organic dye, a DERIVATIVE of INDOLE, 2 The time PERIOD that AGAR plates, that occurs as a GLUCOSIDE in plants TISSUE CULTURES etc are held in of the GENUS Indigofera. incubators before being examined. indirect peroxidase technique (histology) incus (anatomy) One of the EAR Immunohistochemical technique for OSSICLES. An alternative term: anvil. visualising material from FROZEN SECTION. independent assortment (genetics) indirect-transmission (epidemiology) The second of MENDEL’S LAWS, which The transmission of a disease to a states that genes are transmitted susceptible person by means of vectors independently from parents to offspring or by airborne route. and assort freely. Thus there is an equal chance of any particular GENE being indium In (chemistry) Silvery-white transmitted to the gametes. It does not metallic ELEMENT of GROUP IIIA of apply to genes that exhibit LINKAGE. the PERIODIC TABLE, used in making mirrors and semiconductors. At. no. independent variable (mathematics) If 49; r.a.m. 114.82. y is a FUNCTION of x, i.e. y=f(x), x is the INDEPENDENT VARIABLE of the indole (biochemistry) C8H7N Colourless FUNCTION (and y is the dependent one). (USA: colorless) organic SOLID, a HETEROCYCLIC AROMATIC COMPOUND index (mathematics) An EXPONENT consisting of fused BENZENE and or POWER; e.g. in the terms 54 and PYRROLE rings, normally found in FAECES x-1/2, 4 and 1/2 are indices. Multiplication (USA: FECES) which is in part responsible is achieved by adding indices (e.g. for the CHARACTERISTIC SMELL. Also x3×x2 =x3+2=x5); DIVISION by subtracting termed: BENZPYRROLE. indices (e.g. x3 B x2=x 3-2=x). indole amines (biochemistry) A CLASS indicator (1 chemistry; 2 biology) 1 In of biogenic AMINE formed by the chemistry, substance that changes COLOUR COMBINATION of INDOLE with an AMINE (USA: color) to indicate the end of a GROUP. They are NEUROTRANSMITTERS CHEMICAL REACTION or the pH of a and include SEROTONIN. SOLUTION; e.g. LITMUS. Indicators are commonly used in titrations in VOLUMETRIC induced magnetism (physics) Creation ANALYSIS. 2 In biology, organism that of a MAGNET by aligning the MAGNETIC

208 INDUCED RADIOACTIVITY INERTIA

DOMAINS in a ferromagnetic substance 1 ELECTROMAGNETIC INDUCTION is by placing it in the MAGNETIC FIELD of the production of an ELECTRIC CURRENT a permanent MAGNET or ELECTROMAGNET. in a CONDUCTOR by means of a varying MAGNETIC FIELD near it. 2 MAGNETIC induced radioactivity (physics) An alter- INDUCTION is the production of a native term for ARTIFICIAL RADIOACTIVITY. MAGNETIC FIELD in an unmagnetized METAL by a nearby MAGNETIC FIELD. inducer (molecular biology) A MOLECULE 3 Electrostatic INDUCTION is the that binds to a represser to turn on the production of an ELECTRIC CHARGE TRANSCRIPTION of an inducible OPERON. on an OBJECT by a charged OBJECT The INDUCER is usually a small brought near it. MOLECULE, smaller than the represser, a PROTEIN, but able to alter the letter’s induction heating (physics) Heating CONFIGURATION so that it dissociates effect that arises from the ELECTRIC from the OPERATOR region and allows CURRENT induced in a conducting material TRANSCRIPTION to proceed. The by an alternating MAGNETIC FIELD. INDUCER is often the SUBSTRATE of the ENZYME whose production is being inductor (1 chemistry; 2 physics) 1 induced. See GENE REGULATION. Substance that accelerates a CHEMICAL REACTION between two other substances inducible enzyme (molecular biology) by reacting rapidly with one of them. An ENZYME which is produced only 2 Any COMPONENT of an electrical when its SUBSTRATE is present to CIRCUIT that possesses significant act as INDUCER. The opposite is a INDUCTANCE. Also termed: choke; coil. repressible ENZYME. See OPERON; GENE REGULATION. induration (histology) ABNORMAL hardness of a TISSUE or part resulting inductance (1 physics; 2 measurement) from HYPERAEMIA (USA: hyperemia) 1 Property of a CURRENT-carrying electric or INFLAMMATION, as in a reactive CIRCUIT or CIRCUIT COMPONENT that tuberculin SKIN test. causes it to form a MAGNETIC FIELD and store magnetic ENERGY. 2 Measurement inert (chemistry) Chemically nonreactive, of ELECTROMAGNETIC INDUCTION. e.g. GOLD is INERT in AIR at NORMAL temperatures. induction (medical) Setting in motion or beginning, used mostly of anaesthesia inert gas (chemistry) Member of GROUP (USA: anesthesia) or LABOUR (USA: labor). 0 of the PERIODIC TABLE; the unreactive elements HELIUM, NEON, ARGON, induction coil (physics) Type of transformer KRYPTON, XENON and RADON. Also for producing high-VOLTAGE ALTERNATING termed: NOBLE GAS; RARE GAS. CURRENT from 3 low-VOLTAGE source. INDUCTION COILS can be used to produce inertia (physics) Resistance offered a HIGH VOLTAGE PULSE, e.g. for FIRING by an OBJECT to a change in its state spark plugs in a petrol engine. of rest or motion. INERTIA is a property of the MASS of an OBJECT. induction (1, 2 physics) MAGNETIZATION or electrification produced in an OBJECT.

209 INFARCTION INFRA-RED RADIATION infarction (medical) When an ARTERY inflammation (medical) Localised is suddenly blocked by THROMBOSIS protective response elicited by injury or by an embolus and there is no alternative or destruction of tissues, which serves circulation to keep the tissues nourished. to destroy, dilute, or wall off both the injurious agent and the injured tissue. infection (microbiology) Invasion by and multiplication of MICRO-ORGANISMS inflammatory response (immunology) in body TISSUE which may or may not Redness, warmth and swelling in RESPONSE result in overt disease. The organisms to injury or INFECTION; the result of concerned are called pathogens, and increased BLOOD flow and a gathering include BACTERIA, VIRUSES, PROTOZOA, of immune CELLS and secretions. It involves WORMS, and FUNGI. DILATION of BLOOD VESSELS, migration of LEUCOCYTES to the site of injury, infectious disease (microbiology) A and movement of FLUID and PLASMA disease which is caused by MICRO- PROTEINS into the inflamed TISSUE. ORGANISMS or VIRUSES living in or on the body as PARASITES. See inflection (optics) Point on a curve INFECTION. where it changes from being CONCAVE to CONVEX (or CONVEX to CONCAVE). infective endocarditis (medical) INFECTION of the lining of the HEART, influenza (virology) ACUTE INFECTION with which may be ACUTE or subACUTE. the respiratory VIRUS influenza A, B or C. The INCIDENCE of the disease is seasonal. inferential statistics (statistics) The branch of statistics that enables one to info. (general terminology) information. assess the VALIDITY of a conclusion drawn from the DATA, e.g. whether two information retrieval (computing) Science means are significantly different from of storing and accessing DATA, which one another, or whether there is a significant may use microfilm, microfiche, magnetic correlation between two variables. Contrast tape and COMPUTER STORAGE DEVICES. DESCRIPTIVE STATISTICS. informed consent (biology) Agreement inferior (anatomy) Towards the lower to take part in an experiment or medical part of the body, the BRAIN or any trial, or to receive a medical procedure, other ORGAN. Contrast superior. with sufficient knowledge of the protocol and risks to reach a rational decision. infestation (parasitology) The presence on or in the body of PARASITES mites infradian rhythm (biology) Any biological and fleas, or other MULTICELLULAR rhythm with cycles longer than a day, organisms, such as TICKS. e.g. the MENSTRUAL CYCLE. infinity (8) (mathematics) Quantity that infra-red radiation (physics) ELECTRO is larger than any quantified concept. MAGNETIC RADIATION in the WAVELENGTH It may be considered as the RECIPROCAL range from 0.75 µm to 1 mm approximately; of zero. between the visible and MICROWAVE regions of the ELECTROMAGNETIC SPECTRUM. infl. (general terminology) Inflammable. It is emitted by all objects at temperatures

210 INFRASOUND INSECTICIDE above ABSOLUTE ZERO, as HEAT (thermal) inorganic chemistry (chemistry) Study RADIATION. of non-CARBON based compounds and their reactions. infrasound (physics) Sound waves with a FREQUENCY below the THRESHOLD of See also ORGANIC CHEMISTRY. human hearing, i.e. less than about 20 Hz. inorganic compound (chemistry) A inheritance (genetics) The acquisition COMPOUND that does not contain of a CHARACTERISTIC through genetic CARBON, with the exception of factors or the characteristics so acquired. CARBON’S oxides, metallic carbides, carbonates and hydrogencarbonates. inhibition (biology) The prevention of life or deactivation of a process. See also ORGANIC COMPOUNDS. inj (1, 2 medical) 1 An abbreviation input device (computing) Part of a of ‘inj’ection. 2 An abbreviation of ‘inj’ury. COMPUTER that feeds in with DATA and PROGRAM instructions. The many injection drug user (IDU) (medical) types of INPUT DEVICES include a Someone who uses drugs that are injected KEYBOARD, punched CARD READER, into the body. paper tape reader, OPTICAL CHARACTER RECOGNITION, LIGHT innate (genetics) Genetically caused; pen (with a VDU) and various types INNATE characteristics sometimes only of devices equipped with a read HEAD appear quite late in life. to input magnetically recorded DATA (e.g. on MAGNETIC DISK, tape or drum). inner diameter (id) (measurement) The distance from the centre (USA: insecticide (parasitology) Substance used center) of the opening of a tube to to kill insects of agricultural or public the inside edge of the material the health importance. There are two main tube is made from. types: those that are eaten (with food) or inhaled by insects, and those that kill inner ear (anatomy) FLUID-filled part by contact. Important classes of insecticides of the EAR that contains both the organs include: chlorinated HYDROCARBONS that convert sound to NERVE IMPULSES (including DOT analogs, chlorinated and the organs of BALANCE. ALICYCLIC COMPOUNDS, cyclodicnes and chlorinated terpenes); organophosphates; innocent (histology) A term sometimes carbamates; thiocyanates; dinitrophenols; used of BENIGN as opposed to MALIGNANT botanicals (including pyrethroids, rotenoids tumours (USA: maglignant tumors). and nicotinoids); JUVENILE HORMONE analogs; GROWTH regulators; and inorganics inoculation (medical) Accidental or (including arsenicals and fluorides). Non- intentional introduction of foreign MATTER biodegradable insecticides may persist into a living organism or culture medium. for a long time and become concentrated Used of the injection of vaccines to in food chains, where they have a damaging prevent disease. See VACCINE. ecological effect.

211 INSEMINATION INTERACTION VARIANCE insemination (medical) The transfer reducing BLOOD GLUCOSE. A PROTEIN of SEMEN into the VAGINA naturally isulin is produced by the beta-CELLS or artificially. of the pancreatic ISLETS OF LANGERHANS and consists of two insertion (molecular biology) The addition PEPTIDE chains. A deficiency of INSULIN of one or more BASE-pairs into a DNA results in the disorder DIABETES sequence. The effect of a small INSERTION MELLITUS, whose symptoms include may be a FRAMESHIFT MUTATION, excessive thirst and high levels of but a larger INSERTION can upset GENE GLUCOSE in the BLOOD and URINE. REGULATION around it, either by activating genes that should be inactive or vice integer (mathematics) Whole number; versa. See INSERTIONAL INACTIVATION. it may be POSITIVE or negative. insertional inactivation (genetics) A integral (1,2 mathematics) 1 Value technique used in GENETIC ENGINEERING that results from the process of to prevent expression of a GENE by INTEGRATION. 2 Describing a whole inserting a foreign DNA sequence adjacent number value. to it or in its coding region. integration (mathematics) In CALCULUS, the process of summation of the SERIES in situ (biology) In the NORMAL or of infinitely small quantities that make natural location. up the difference between two values of a given FUNCTION. It is the inverse insoluble (chemistry) Describing a of differentiation and is used in the substance that does not dissolve in a SOLUTION of such problems as finding given SOLVENT; not capable of forming the AREA enclosed by a given curve or a SOLUTION. the VOLUME enclosed by a given surface.

Inst. (education) An abbreviation of intensity (physics) POWER of sound, LIGHT ‘Inst’itute/‘Inst’itution. or other WAVE-form (e.g. the loudness of a sound or the brightness of LIGHT), insulation (physics) Layer of material determined by the AMPLITUDE of the WAVE. (an INSULATOR) used to prevent the flow of ELECTRICITY or HEAT. Intensive Care Unit (ICU) (medical) The SECTION of a hospital where critically insulator (physics) Substance that is ill patients are monitored around the clock. a poor CONDUCTOR of ELECTRICITY or HEAT; a non-CONDUCTOR. Most interaction (1 general; 2 physics) 1 non-metallic elements (except CARBON) The effect which two or more substances, and polymers are good insulators. The such as drugs, have on each other. 2 presence of entrapped AIR (as in a In atomic physics, exchange of ENERGY foam plastic or woollen garment) increases between a PARTICLE and a second the effectiveness of a thermal INSULATOR. one or ELECTROMAGNETIC RADIATION. insulin (biochemistry) A HORMONE interaction variance (statistics) The secreted in the PANCREAS that is proportion of the total VARIANCE caused responsible for increasing the PERME- by the INTERaction of the INDEPENDENT ABILITY of CELLS to GLUCOSE, thereby VARIABLES.

212 INTERCELLULAR INTERNAL RESISTANCE intercellular (biology) Between CELLS; interkrometer (physics) Instrument that e.g. INTERCELLULAR FLUID surrounds makes use of INTERFERENCE for CELLS, maintaining a CONSTANT internal measuring such things as wavelengths ENVIRONMENT. and other small distances.

See also INTRACELLULAR. intermediate (1, 2 chemistry) 1 In industrial chemistry, COMPOUND to be subjected intercostal muscle (histology) Any of to further chemical TREATMENT to produce the muscles between a mammal’s ribs, finished products such as dyes and which are important in BREATHING pharmaceuticals. 2 Short-lived SPECIES movements. in a complex CHEMICAL REACTION. intercross (genetics) a cross between intermediate compound (chemistry) two individuals or strains that are COMPOUND of two or more metals themselves HYBRID. See F2. that are present in definite proportion although they frequently do not follow intercurrent (medical) Term applied to NORMAL VALENCE rules. a second disease or INFECTION occurring during the course of the original disease. intermediate host (parasitology) Required HOST in the LIFE CYCLE in which essential interface (1 physics; 2 computing) 1 In larval development must occur before a physics, boundary of contact (the common PARASITE is infective to its definitive HOST surface) of two adjacent phases, either or to additional INTERMEDIATE HOSTS. or both of which may be SOLID, LIQUID or a GAS. 2 The point at which two systems, intermolecular force (physics) FORCE or two parts of one system, interact. that binds one MOLECULE to another. INTERMOLECULAR FORCES are much interference (physics) INTERaction weaker than the bonding forces holding between two or more waves of the together the atoms of a MOLECULE. same FREQUENCY emitted from coherent sources. The waves may See also VAN DER WAALS’ FORCE. reinforce each other or tend to cancel each other; the resultant WAVE is the internal conversion (physics) Effect on ALGEBRAic sum of the COMPONENT the NUCLEUS of an ATOM produced by waves. The phenomenon occurs with a gamma-RAY PHOTON emerging from ELECTROMAGNETIC WAVES and it and giving up its ENERGY on meeting sound. an ELECTRON of the same ATOM. interferon (IF) (immunology) A PROTEIN internal energy (physics) Total quantity produced by the body to counteract a of ENERGY in a substance, the sum of its viral INFECTION by slowing or stopping KINETIC ENERGY and POTENTIAL ENERGY. the VIRUS from replicating. Its ACTION is not specific to any particular GROUP internal friction (physics) See VISCOSITY. of VIRUSES. Genes for human interferons have been cloned so the proteins can internal resistance (physics) ELECTRICAL be produced in bulk. RESISTANCE in a CIRCUIT of the source of CURRENT, e.g. a CELL.

213 INTERNATIONAL CANDLE INTERSTITIAL COMPOUND international candle (measurement) The intersex (genetics) A broad term covering former UNIT of LUMINOUS INTENSITY. various conditions in which an individual does not have NORMAL reproductive International Classification of Diseases organs but is not a HERMAPHRODITE. (ICD) (governing body) A CLASSIFICATION, Male pseudohermaphroditism is the made by the World Health Organization, of condition in which there are TESTES diseases including mental disorders. (probably internal) but the external genitalia appear more or less female; the cause intereceptor (physiology) A RECEPTOR can be CHROMOSOME abnormality, a located in or on an internal ORGAN. single GENE (as in testicular feminization) or HORMONE imbalance in utero. Female interphase (cytology) State of CELLS pseudohermaphroditism, in which there when not undergoing DIVISION. Preparation is a COMBINATION of NORMAL ovaries for DIVISION (MITOSIS) is carried out and more or less male external genitalia, during this PHASE, including REPLICATION is not caused by CHROMOSOME of DNA and CELL constituents. disorders, but by a SERIES of RECESSIVE ALLELES, with a combined FREQUENCY interpolation (statistics) Inferring a of about one in 7000 births. HORMONE value or values for points on a DIMENSION imbalance in utero can also be responsible. from the obtained values of points lying to each side. Compare EXTRA-POLATION. See also KLINEFELTER’S SYNDROME. interpose (genetics) The stage on the interstitial atom (chemistry) ATOM CELL CYCLE between divisions. This that is in a position other than a NORMAL is the PHASE during which the LATTICE place. chromosomes are active in synthesising proteins. interstitial cells (cytology) In mammals, CELLS present in the male and female interpreter (computing) A PROGRAM that GONADS. In males they are found between translates another PROGRAM written in the TESTIS tubules and in females in a high-LEVEL language into MACHINE the OVARIAN FOLLICLE. When stimulated CODE and executes each instruction before by LUTEINIZING HORMONE, they produce translating the next. An INTERPRETER ANDROGENS in males and OESTROGEN is slower in execution than a COMPILER (USA: estrogen) in females. and the user’s PROGRAM must be translated afresh every time it is run. interstitial cell-stimulating hormone (ICSH) (biochemistry) A gonadotropin from the interquartile range (IQR) (statistics) ADENOHYPOPHYSIS that stimulates the In a FREQUENCY DISTRIBUTION, the testicular INTERSTITIAL CELLS to produce difference between the upper and lower ANDROGENS. It is equivalent to quartiles; hence it contains the middle LUTEINIZING HORMONE (LH) in the female. 50 per cent of cases. Its SECRETION is stimulated by hypothalamic gonadotropin releasing HORMONE (GnRH). intersegmental tracts (anatomy) Short tracts connecting different segments interstitial compound (chemistry) The of the SPINAL CORD. chemical COMPOUND formed by penetration of non-metallic atoms of small

214 INTERTRIGO INVERSE SQUARE LAW

DIAMETER between the atoms of a METAL the same CHROMOSOME) during MEIOSIS. (usually a TRANSITION ELEMENT). Because the sister chromatids are identical, there is no genetic effect, unlike in the NORMAL intertrigo (medical) Erythematous SKIN process of RECOMBINATION, when non- eruption of adjacent SKIN parts. sister chromatids from HOMOLOGOUS CHROMOSOMES exchange genetic material. interval scale (measurement) A scale having equal intervals, but no zero point intracranial (medical) Inside the SKULL. e.g. Centigrade. intradermal (medical) In the SKIN. intervening variable (statistics) A VARIABLE operating within a theoretical model that intramuscular (medical) Inside a MUSCLE. mediates the effects of the INDEPENDENT VARIABLES on the dependent variables. intrauterine device (IUD) (medical) There may be several INTERVENING A birth control device consisting of a VARIABLES all interacting with one another. plastic coil placed in the UTERUS to The value of an INTERVENING VARIABLE prevent conception. An improperly fitted is usually affected by more than one IUD can cause uterine bleeding. INDEPENDENT VARIABLE and it may in turn affect several dependent variables. intravenous (IV) (medical) Directly into a VEIN. intestine (anatomy) The ALIMENTARY CANAL after it leaves the STOMACH. It intubation (medical) The introduction is divided into small and LARGE INTESTINE; of a tube into the body, used mostly the SMALL INTESTINE is the longer, of the process of inserting a tube into and is continuous with the STOMACH the TRACHEA to maintain an airway at the gastro-duodenal junction. The SMALL during the administration of an INTESTINE is concerned with the further ANAESTHETIC (USA: anesthetic), or DIGESTION of food and the ABSORPTION for the purpose of artificial RESPIRATION into the bloodstream of already digested by a BREATHING machine. AMINO ACIDS and monosaccharides. The LARGE INTESTINE is mainly concerned in utero (biology) Within the UTERUS. with the ABSORPTION of WATER from semi-SOLID indigestible remains, which inverse function (mathematics) Mathe- form the FAECES (USA: FECES). matical FUNCTION of such a nature in respect to another operation, relation, intracellular fluid (cytology) The FLUID etc. that the starting point of one contained within the CELL MEMBRANE. FUNCTION is the conclusion of the other, and vice versa. A FUNCTION intracellular (cytology) Occurring within that is opposite in effect or nature, the boundary of a CELL or CELLS. e.g. inverse hyperbolic functions and inverse trigonometrical functions. See also INTERCELLULAR. inverse square law (physics) The LAW intrachromosomal recombination (genet- that the INTENSITY of a WAVE, e.g. ics) Exchange of sequences of DNA LIGHT or ACOUSTIC waves, travelling between sister chromatids (i.e. two halves of in a homogenous medium decreases

215 INVERSION IODINE in proportion to the square of the distance that happen in a living organism. It does from the source. For instance in OPTICS, not imply that the process described is the quantity of LIGHT from a given source as it occurs in natural conditions, because on a surface of definite AREA is inversely the word is applied to what happens in proportional to the square of the distance experiments; it is used solely in contrast between the source and the surface. to what happens in vitro. It is strictly speaking an adverb, but is often used inversion (1 genetics; 2 chemistry) 1 adjectivally. Contrast IN VITRO. A MUTATION consisting of the reversal of the ORDER of the genes in part of involuntary muscle (histology) MUSCLE a CHROMOSOME. 2 Splitting of DEXTRO- not under conscious control, located in ROTATORY higher sugars (e.g. SUCROSE) internal organs and tissues, e.g. in the into equivalent amounts of LAEVORO- ALIMENTARY CANAL and BLOOD TATORY lower sugars (e.g. FRUCTOSE VESSELS. Also termed: SMOOTH MUSCLE. and GLUCOSE). See also VOLUNTARY MUSCLE. invert sugar (chemistry) A natural DISACCHARIDE SUGAR that consists involution forms (microbiology) Abnor- of a MIXTURE of GLUCOSE and FRUCTOSE, mally shaped BACTERIAL CELLS found in many fruits. occurring in an aging culture population. invertebrate (biology) ANIMAL that IOAT (society) An abbreviation of does not possess a BACKBONE. ‘I’nternational ‘O’rganisation ‘A’gainst ‘T’rachoma. See also VERTEBRATE. IoB (society) An abbreviation of ‘I’nstitute inverted-U curve (statistics) A curve ‘o’f ‘B’iology. that looks like a letter U upside-down, starting low, reaching a peak and then iodide (chemistry) COMPOUND of declining; when performance on a task IODINE and another ELEMENT; SALT is plotted against arousal LEVEL or drive of hydriodic ACID (HI). strength such curves are frequently obtained. iodine I (chemistry) Non-metallic ELEMENT in vitro (biology) From the Latin, meaning in GROUP VIIA of the PERIODIC TABLE ‘in GLASS’. A term for processes that (the halogens), extracted from Chile happen in a controlled ENVIRONMENT SALTPETRE (in which it occurs as an outside of a living organism. It is strictly iodate impurity of SODIUM NITRATE) speaking an adverb but is often used and certain seaweeds. It forms purple- adjectivally. Contrast IN vivo. black crystals that sublime on heating to produce a violet VAPOUR. It is essential in vitro fertilization (medical) The for the SECRETION of the THYROID technique of fertilizing one or several HORMONES THYROXINE and triiodo- ova with SPERM outside the body of thyronine, usually present in sufficient the female, in a GLASS culture dish. quantities in NORMAL diets. IODINE and its ORGANIC COMPOUNDS are in vivo (biology) From the Latin, meaning used in medicine; SILVER IODIDE is ‘in a living thing’. A term used for processes

216 IODINE NUMBER IONIZATION used in PHOTOGRAPHY. At. no. 53; ion pair (chemistry) Two charged fragments r.a.m. 126.9044. that result from simultaneous IONIZATION of two unchanged ones, a POSITIVE iodine number (chemistry) Number that and a negative ION. indicates the amount of IODINE taken up by a substance, e.g. by fats or oils; ion pump (physics) High-VACUUM PUMP it gives a measure of the number of for removing a GAS from a system by UNSATURATED bonds present. Also termed: ionizing its atoms or molecules and IODINE value; IODINE ABSORPTION. adsorbing the resulting ions on a surface. iodoform (chemistry) An alternative ionic bond (physics) Electrostatic term for TRIIODOMETHANE. attraction that occurs between two oppositely charged ions, e.g. proteins ion (chemistry) ATOM or MOLECULE binding with METAL ions. The DEGREE that has POSITIVE or negative ELECTRIC of binding varies with the chemical nature CHARGE because of the loss or GAIN of each COMPOUND and the net CHARGE. of one or more electrons. Many INORGANIC DISSOCIATION of IONIC BONDS usually COMPOUNDS dissociate into ions when occurs readily, but some members of they dissolve in WATER. Ions are the the TRANSITION GROUP of metals exhibit ELECTRIC CURRENT-carriers in ELEC- high association constants (i.e. low Kd TROLYSIS and in DISCHARGE tubes. values) and exchange is slow. Also termed: ELECTROVALENT BOND. ion channels (physiology/pharmacology) Channels or pores composed of PROTEINS See also COVALENT BOND. that allows exchange of ions or water between the CYTOPLASM and the ionic crystal (crystallography) Crystal EXTRACELLULAR fluid. Ion channels composed of ions. Also termed: are vital in the control of CELL volume ELECTROVALENT CRYSTAL; POLAR and the activity of electrically excitable CRYSTAL. CELLS. Conformation changes within the PROTEIN channel lead to opening ionic product (chemistry) PRODUCT (in or closing of the pore. Some drugs bind moles per LITRE) of the concentrations to sites on the EXTRACELLULAR surface of the ions in a LIQUID or SOLUTION, of the ion channel to influence channel e.g. in SODIUM CHLORIDE SOLUTION, opening or closing, other drugs influence the IONIC PRODUCT of SODIUM CHLORIDE channel opening following interaction is given by [Ma+] [CI-]. In a pure LIQUID, with a G-PROTEIN coupled receptor. it results from the DISSOCIATION of molecules in the LIQUID. ion exchange (chemistry) REACTION in which ions of a SOLUTION are retained ionic radius (crystallography) RADIUS by oppositely-charged groups covalently of an ION in a crystal. bonded to a SOLID support, such as ZEOLITE or a SYNTHETIC RESIN. The ionization (chemistry/physics) Formation process is used in WATER softeners, of ions. It is generally achieved by chemical desalination plants and for ISOTOPE or electrical processes, or by separation. DISSOCIATION of ionic compounds in SOLUTION, although at extremely high

217 IONIZATION CHAMBER IRON(III) OXIDE temperatures (such as those in stars) CHOROID make up the uveal tract, and HEAT can cause IONIZATION. they have the same BLOOD supply, so that INFECTION can easily spread from ionization chamber (physics) Apparatus one to the other. There are a number of consisting of a GAS-filled container causes, including HERPES, syphilis and with a pair of high-VOLTAGE electrodes. TOXOPLASMOSIS. It is used to study the IONIZATION of gases or IONIZING RADIATION. iron Fe (chemistry) SILVER-grey magnetic metallic ELEMENT in GROUP VIII of the ionization potential (chemistry) ELECTRON PERIODIC TABLE (a TRANSITION ELEMENT). bonding ENERGY, the ENERGY required It is the fourth most abundant ELEMENT to remove an ELECTRON from a NEUTRAL in the EARTH’S crust and probably forms ATOM. much of the CORE. It is also the most widely used METAL, particularly (ALLOYed ionizing radiation (radiology) RADIATION with CARBON and other elements) in steel. of sufficiently high ENERGY to produce It occurs in various ores, chief of which ions in the medium through which it passes, are haematite (USA: hematite), limonite e.g. high-ENERGY (electrons, protons) and magnesite, which are refined in a or short-WAVE RADIATION (UV, X-RAYS). blast furnace to produce pig IRON. Inorganic IRON compounds are used as pigments; IPA (chemistry) An abbreviation of the BLOOD PIGMENT HAEMOGLOBIN ‘I’so‘P’ropyl ‘A’lcohol, also termed (USA: hemaglobin) is an organic IRON ISOPROPANOL. COMPOUND. At. no. 26; r.a.m. 55.847.

IPSP (physiology) An abbreviation of iron(II) (chemistry) An alternative term ‘I’nhibitory ‘P’ostS’ynaptic ‘P’otential. for FERROUS.

iridium Ir (chemistry) Steel-grey metallic iron(II) sulphate (chemistry) FeSO4.7H2O. ELEMENT in GROUP VIII of the PERIODIC Green CRYSTALLINE COMPOUND, used TABLE (a TRANSITION ELEMENT). It in making inks, in printing and as a wood is used (with PLATINUM or OSMIUM) in preservative. A white MONOHYDRATE hard ALLOYS for bearings, surgical tools is also known. Also termed: FERROUS and crucibles. At. no. 77; r.a.m. 192.22. SULPHATE (USA: ferrous sulfate). (USA: iron(II) sulfate) iris (anatomy) Pigmented part of the human EYE that controls the amount iron(III) (chemistry) An alternative term of LIGHT entering the EYE. for FERRIC.

See also IRIS DIAPHRAGM. iron(III) chloride (chemistry) FeCI3.6H2O Brown CRYSTALLINE COMPOUND, used iris diaphragm (photography) Adjustable as a CATALYST, a mordant and for etching APERTURE in a camera or incorporated COPPER in the manufacture of printed in a LENS to control the amount of circuits. Also termed: FERRIC CHLORIDE. LIGHT passing through the LENS.

iron(III) oxide (chemistry) Fe2O 3. Red iritis (medical) INFLAMMATION of the INSOLUBLE COMPOUND, the principal IRIS. The IRIS, CILIARY BODY and constituent of haematite (USA: hematite).

218 IRRADIANCE ISOCHROMOSOME

It is used as a PIGMENT, CATALYST by spasm or disease of the BLOOD and polishing COMPOUND. Also termed: VESSELS or failure of the general FERRIC OXIDE. circulation; if it is prolonged and severe, the TISSUE dies. (USA: ischemia). irradiance (physics) The POWER of LIGHT falling on an AREA of a surface. It can ischiorectal abscess (medical) An be measured in watts per square METRE. ABSCESS occurring between the RECTUM and the ischium, part of the PELVIS. irradiation (1 physics; 2 radiology) 1 RADIANT ENERGY per UNIT of ISCP (society) An abbreviation of intercepting AREA. 2 TREATMENT by ‘I’nternational ‘S’ociety of ‘C’linical exposure to RADIATION of any kind, ‘P’athology. but usually refers to TREATMENT by ionising RADIATION. See RADIATION. ISGE (society) An abbreviation of ‘I’nternational ‘S’ociety of ‘G’astro- irrational number (mathematics) REAL ‘E’nterology. NUMBER that cannot be expressed as a FRACTION, i.e. as the ratio of ISH (society) An abbreviation of two integers; e.g. p, 2. ‘I’nternational ‘S’ociety of ‘H’aematology. irreversible reaction (chemistry) CHEMICAL ISHAM (society) An abbreviation of REACTION that takes place in one direction ‘I’nternational ‘S’ociety for ‘H’uman only, therefore proceeding to completion. and ‘A’nimal ‘M’ycology. irrigation (medical) The washing-out islets of langerhans (histology/biochem- of a cavity or WOUND by a stream of istry) Clusters of specialized secretory WATER or other LIQUID. CELLS in the PANCREAS. They control the LEVEL of GLUCOSE in the BLOOD irritability (physiology) Ability to respond by secreting the HORMONES INSULIN to a STIMULUS, evident in all living and GLUCAGON. material. isobar (1, 2 physics) 1 Curve that relates irritants (toxicology) Any non-corrosive to qualities measured at the same substance that, on immediate, prolonged PRESSURE. 2 One of a SET of atomic or repeated contact with NORMAL living nuclei having the same total of protons TISSUE produces a local inflammatory and neutrons (i.e. the same NUCLEON REACTION. NUMBER or MASS NUMBER) but different numbers of protons and therefore different ISCB (society) An abbreviation of identities. ‘I’ternational ‘S’ociety for ‘C’ell ‘B’iology. isochromosome (genetics) an ABNORMAL ISCERG (society) An abbreviation of CHROMOSOME in which two identical arms ‘I’nternational ‘S’ociety for ‘C’linical have become joined at the CENTROMERE ‘E’lectro‘R’etino‘G’raphy. because the CENTROMERE divided transversely and not longitudinally during ischaemia (medical) Inadequate BLOOD CELL DIVISION. supply to a part of the body, caused

219 ISOCHRONY ISOTONIC isochrony (physics) The property of is not spread. 2 The GROWTH and having the same time interval. separation of MICRO-ORGANISMS. isocyanide (chemistry) A COMPOUND isoleucine (biochemistry) CRYSTALLINE of GENERAL FORMULA R-NC, rather AMINO ACID; it is a constituent of than R-CN, where R is an organic or proteins, and essential in the diet of inorganic RADICAL. Also termed: human beings. ISONITRILE; CARBYLAMINE. isomer (chemistry) Substance that isoelectric point (pl) (biochemistry) exhibits chemical ISOMERISM. The HYDROGEN ION CONCENTRATION (pH) at which a SPECIES (AMINO ACID, isomerism (1 chemistry; 2 physics) 1 PROTEIN or COLLOID) is electrically In chemistry, the existence of substances NEUTRAL. that have the same molecular composition (and therefore the same CHEMICAL See also ISOELECTRIC FOCUSING. FORMULA), but different structures. See also OPTICAL ISOMERISM. 2 In isoelectric focusing (biochemistry) physics, the existence of atomic nuclei A method used to separate mixtures with the same ATOMIC NUMBERS and containing proteins of different pl. The the same MASS NUMBERS, but different migration of ampholytes (e.g. proteins) ENERGY states. occurs through a pH GRADIENT under an applied ELECTRIC FIELD. Molecules isoniazid (pharmacology) A powerful possessing an ELECTRIC CHARGE drug used in the TREATMENT of migrate towards a region in which they TUBERCULOSIS. are isoelectric. isonitrile (chemistry) An alternative See also ISOELECTRIC POINT. term for ISOCYANIDE.

isoenzymes (biochemistry) A SET of isopropanol (chemistry) (CH3) 2CHOH ENZYMES all carrying out the same One of the two isomers of PROPANOL. CHEMICAL REACTION. Several Also termed: ISOPROPYL ALCOHOL. ISOENZYMES may be present within the same organism, as they are coded isopropyl alcohol (chemistry) An for by genes at different loci. Also alternative term for ISOPROPANOL. termed ISOZYMES. Compare ALLOZYME. isothermal process (physics) Process isogamy (biology) Sexual FISSION of that occurs at a CONSTANT or uniform gametes that are similar in structure TEMPERATURE; e.g. the compression and size. It occurs in some PROTOZOA, of a GAS under CONSTANT TEMPERATURE FUNGI and ALGAe. conditions.

See also ANISOGAMY. See also ADIABATIC PROCESS. isolation (1 medical; 2 microbiology) isotonic (chemistry) solutions which 1 The separation of an infective patient have the same OSMOTIC PRESSURE. from others, so that the infecting organism Such solutions will not bring about

220 ISOTOPE IV

DIFFUSION one into the other through IUBS (society) An abbreviation of an intervening MEMBRANE. ‘I’nternational ‘U’nion of ‘B’iological ‘S’ciences. isotope (physics) A chemical ELEMENT which has the same ATOMIC NUMBER IUCD (medical) An abbreviation of ‘I’ntra- as another, but a different ATOMIC ‘U’terine ‘C’ontraceptive ‘D’evice. MASS. It has the same number of protons in the NUCLEUS, but a different number IUCr (society) An abbreviation of of neutrons. RADIOACTIVE ISOTOPES ‘I’nternational ‘U’nion of ‘Cr’ystallography. change into another ELEMENT over the course of time, the change being IUD (medical) An abbreviation of accompanied by the emission of ‘I’ntra‘U’terine ‘D’evice. ELECTROMAGNETIC RADIATIONS. IUPAB (society) An abbreviation of isotopic number (chemistry) Difference ‘I’nternational ‘U’nion of ‘P’ure and between the number of neutrons in ‘A’pplied ‘B’iophysics. an ISOTOPE and the number of protons. Also termed: NEUTRON EXCESS. IUT (medical) An abbreviation of ‘I’ntra ‘U’terine ‘T’ransfusion. isotopic weight (chemistry) ATOMIC WEIGHT of an ISOTOPE. Also termed: IV (medical) An abbreviation of isotopic MASS. ‘I’ntra‘V’enous. isotropic (chemistry) Describing a substance whose physical properties are the same in all directions (e.g. most liquids). isozymes (biochemistry) See ISOENZYMES.

ISV (quality standards) An abbreviation of ‘I’nternational ‘S’cientific ‘V’ocabulary.

ITP (biochemistry) An abbreviation of ‘I’nosine ‘T’ri‘P’hosphate.

IU (measurement) An abbreviation of ‘I’nternational ‘U’nit(s)

IUAT (society) An abbreviation of ‘I’nternational ‘U’nion ‘A’gainst ‘T’uberculosis.

IUB (society) An abbreviation of ‘I’nternational ‘U’nion of ‘B’iochemistry.

221 J

J (measurement) An abbreviation of jejunitis (medical) INFLAMMATION of ‘j’oule. the JEJUNUM.

Jacksonian epilepsy (medical) Focal jejunum (anatomy) Part of the INTESTINE epilepsy usually the result of a localised of mammals, located between the AREA of disease e.g. TUMOUR (USA: tumor), DUODENUM and the ILEUM, the main or injury in the motor CORTEX of the BRAIN, FUNCTION of which is ABSORPTION. the attack begins in a definite place and spreads from there in a definite Jerne plaque assay (immunology) A PROGRESSION. Named after the English method of quantitating ANTIBODY- neurologist, J.H.Jackson (1835–1911). producing CELLS.

J exon (immunology) See J GENE. jail fever (microbiology) See TYPHUS. JG cells (histology) An abbreviation Jakob-Creutzfeldt disease (medical) of ‘J’uxta‘G’lomerular CELLS. See Creutzfeldt-Jakob disease. J gene (immunology) A short sequence jaundice (medical) A condition character- of DNA coding for part of the hyper- ised by a yellow appearance of the whites VARIABLE REGION of IMMUNO- of the eyes, the SKIN and MUCOUS GLOBULIN LIGHT or heavy chains near MEMBRANES. This discolouration (USA: to the site of joining to the CONSTANT discoloration) is due to the presence region. Also termed J EXON. of excess BILIRUBIN in the BLOOD. JAUNDICE is a common symptom of jigger (parasitology) A flea Tunga disorders of the GALL BLADDER or penetrans which burrows into the SKIN LIVER. jaws (1, 2 anatomy) 1 In vertebrates, of the feet, causing intense irritation bony structure enclosing the mouth, often and ulceration. furnished with TEETH for grasping prey and/or chewing food, consisting of an jnl (literary terminology) An abbreviation upper MAXILLA and lower MANDIBLE. of ‘j’our‘n’a‘l’. Also termed jl/jour. 2 In invertebrates, grasping structure surrounding the mouth. joint (anatomy) Point of articulation of limbs or bones. The bones are J/deg. (measurement) An abbreviation connected to each other by CONNECTIVE of ‘J’oule per ‘deg’ree. TISSUE ligaments, and are well lubricated. Common types of joints include ball- jejunectomy (medical) Excision of part and-socket joints (e.g. the HIP JOINT), of the JEJUNUM. hinge joints (e.g. the elbow) and sliding joints (e.g. between vertebrae).

222 JOINT PROBABILITY JUVENILE joint probability (statistics) The journal (jour.) (literary terminology) probability that two or more events A scientific/medical etc. newspaper or will occur together. periodical.

Jonckheere test (statistics) A non- J region (immunology) An abbreviation parametric planned comparison trend of ‘j’oining ‘region’. The part of an test of the HYPOTHESIS that the values IMMUNOGLOBULIN MOLECULE that of a VARIABLE of different samples lies between the CONSTANT and the are ordered in a specific sequence. VARIABLE REGIONS.

Jones methenamine silver stain jugular vein (anatomy) One of a pair (histology) A histological staining of veins draining the BRAIN and joining technique that may be used to make with the subclavian veins before discharging basement MEMBRANE and mesangium into the ANTERIOR VENA CAVA. visible under the MICROSCOPE. jumping genes (genetics) Genes that joule (J) (measurement) The SI UNIT move within chromosomes. They influence of ENERGY, WORK and quantity of the regulation of GENE activity, probably HEAT. Equal to the WORK done when by physically removing a GENE from one NEWTON of FORCE moves an its PROMOTER. See OPERON. OBJECT one METRE. Named after James Prescott Joule (1818–89). junk DNA (genetics) Sequences of DNA in the GENOME that have no joule’s law (1, 2 physics) 1 INTERNAL apparent genetic FUNCTION. Also known ENERGY of a given MASS of GAS is as ‘SELFISH DNA’. dependent only on its TEMPERATURE and is independent of its PRESSURE jurisprudence (medical) Medical jurispru- and VOLUME. 2 If an ELECTRIC dence, or forensic medicine, concerned CURRENT/flows through a resistance with any aspect of medicine which relates R for a time t, the HEAT produced Q, to the LAW. in joules, is given by Q= I 2Rt. juv. (general terminology) An abbrevia- Joule-Thompson effect (physics) When tion of ‘juv’enile. a GAS is allowed to undergo adiabatic expansion through a porous plug, the juvenile (juv.) (general terminology) TEMPERATURE of the GAS usually A minor; someone who has not reached drops. This results from the WORK the age of majority. done in breaking the INTERMOLECULAR FORCES in the GAS, and is a DEVIATION from JOULE’S LAW. The effect is important in the LIQUEFACTION OF GASES by cooling. Also termed: Joule-Kelvin effect. See ADIABATIC PROCESS. jour. (literary terminology) An abbreviation of ‘jour’nal.

223 K

K (1 chemistry; 2 measurement; 3 kallikrein, which circulates in an inactive biochemistry) 1 CHEMICAL SYMBOL form, and which with high-molecular- for POTASSIUM, derived from Latin: Kalium. WEIGHT kininogen also catalyse the 2 An abbreviation of ‘K’ilodalton/‘K’elvin/ activation of FACTOR XII; and TISSUE ‘K’ilobyte/‘K’ilogram. 3 A symbol for lysine. kallikrein, which is located primarily on the apical membranes of CELLS concerned KE (physiology/biochemistry) A symbol with transcellular ELECTROLYTE transport. for exchangeable body POTASSIUM. kanamycin (pharmacology) A broad Kahn test (bacteriology) A serological SPECTRUM aminoglycoside ANTIBIOTIC test formerly used in the diagnosis of derived from a soil actinomycete. syphilis, now superseded by the VENEREAL KANAMYCIN is active against gram- DISEASE Research Laboratories test negative organisms but is now largely (VDRL test). Named after the Lithuanuan- replaced by gentamicin. The aminoglyco- born American serologist, Reuben Leon sides can cause deafness, tinnitus and Kahn (1887–1979). KIDNEY damage.

Kala azar (microbiology) one of the forms kaolin (chemistry) ALUMINIUM silicate, of LEISHMANIASIS, caused by Leishmania or china clay. It is used in the TREATMENT organisms and spread to humans by of mild DIARRHOEA (USA: diarrhea). the bite of sandflies. KALA AZAR occurs mainly in the Mediterranean AREA and kaolinite (chemistry) HYDRATED ALUMINIUM in India, but is spreading westward into silicate mineral. Europe. There is FEVER, ANAEMIA (USA: anemia), LYMPH NODE swelling, Kaposi’s sarcoma (medical) A MALIGNANT enlargement of the SPLEEN and LIVER, GROWTH formerly known to affect African damage to the BONE MARROW, children and Mediterranean men over the MALNUTRITION and loss of immune age of 50, who developed the TUMOUR CAPACITY (IMMUNOSUPPRESSION). The (USA: tumor) on the legs. In the 1980s condition can be diagnosed by the elisa it became apparent that the TUMOUR test and is treated with drugs containing was associated with the immunoDEFICIENCY ANTIMONY. Also known as VISCERAL DISEASE AIDS. Now about a quarter of LEISHMANIASIS. those suffering with AIDS present with the TUMOUR (USA: tumor), which is thought kallikreins (biochemistry) Proteases that to be due to a VIRUS INFECTION. release the peptides bradykinin and lysylbradykinin from the PRECURSOR Kartagener’s syndrome (medical) The proteins, high-molecular-WEIGHT kininogen COMBINATION of CONGENITAL malfunction and low-molecular-WEIGHT kininogen. of the brush borders of the respiratory There are two KALLIKREINS: PLASMA HAIR CELLS (cilia) with bronchiectasis,

224 KARYAPSIS KAYSER-FLEISCHER RING sinusitis and reversal (TRANSPOSITION) by their size and CENTROMERE position, of the internal organs of the body. and for convenience are usually shown in a specific ORDER in an IDIOGRAM. karyapsis (cytology) See KARYOGAMY. Kastenbaum-Bowman test (statistics) karyo- (cytology) Combining form A test of statistical significance used denoting a CELL NUCLEUS. From the in calculation of MUTATION frequencies. Greek karuon, meaning ‘a nut’. katal (measurement) A UNIT of ENZYME karyogamy (cytology) the coming together activity in the SI system. 1 international and fusing of the nuclei of gametes. UNIT is equal to 16.6 nanokatal. karyogenesis (cytology) The formation Katayama syndrome (medical/parasitol- of a CELL NUCLEUS, ogy) A SET of allergic phenomena associated with the penetration of the SKIN and karyokinesis (cytology) See MITOSIS. invasion of the body by the larval stage (cercariae) of SCHISTOSOMIASIS. The karyolymph (cytology) The FLUID in effects include local itching, URTICARIA, the NUCLEUS of a CELL. FEVER, headache, MUSCLE aches, abdominal pain, cough, patchy pneumonia karyolysis (cytology) Destruction of and enlargement of the SPLEEN. a CELL NUCLEUS. Kawasaki disease (medical) A world- karyomegaly (cytology) An increase wide disease of infants and young children in the size of the nuclei of the CELLS that causes FEVER, swollen LYMPH NODES, of a TISSUE. a MEASLES-like rash, red eyes, inflamed TONGUE, dry cracking lips, peeling SKIN karyon (cytology) The CELL NUCLEUS. and, in just under half the cases, local widening (aneurysms) in the coronary karyoplasm (cytology) The PROTOPLASM arteries. These are usually transient but of the CELL NUCLEUS. 10 per cent have long-term involvement of the coronaries. The disease is probably karyorrhexis (cytology) Rupture of the a RETROVIRUS INFECTION possibly spread CELL NUCLEUS in which the CHROMATIN by house-dust mites or cat fleas. ASPIRIN disintegrates. has been found useful in the TREATMENT and appears to reduce the INCIDENCE karyosome (cytology) A spherical MASS of HEART complications. Less than 1 of aggregated CHROMATIN material per cent of affected children die from in a resting (INTERPHASE) NUCLEUS. the disease and most make a complete recovery. karyotype (genetics) The chromosomal constitution of an individual as seen in Kayser-Fleischer ring (toxicology) A the NUCLEUS of a SOMATIC CELL. It golden-yellow coloured (USA: colored) provides information about the SPECIES ring seen near the edge of the corneas or strain, because a KARYOTYPE is on examination with a slit-lamp CHARACTERISTIC to the CELL of a particular MICROSCOPE in WILSON’S DISEASE. organism.The chromosomes are classified The ring is due to a deposition of COPPER.

225 K BAR KERATINIZATION k bar (measurement) An abbreviation the British physicist Lord KELVIN (William of ‘k’ilo‘BAR’. Thomson) (1824–1907). kc (measurement) An abbreviation of See also KELVIN TEMPERATURE. ‘k’ilo‘c’ycle. Kelvin effect (physics) An alternative Kcal (measurement) An abbreviation term for the Thomson effect. of ‘K’ilo ‘cal’orie. Also termed k.cal. Kelvin temperature (measurement) K cells (immunology) An abbreviation Scale of TEMPERATURE that originates of ‘K’iller CELLS. at ABSOLUTE ZERO, with the triple point of WATER defined as 273.16K. K complex (physiology) An isolated The FREEZING POINT of WATER (on slow WAVE occurring in the ELECTROEN- which the CELSIUS SCALE is based) CEPHALOGRAM, usually during stage is 273.15K. Also termed: KELVIN II sleep. thermodynamic scale of TEMPERATURE.

Kda (measurement) An abbreviation Kendall’s coefficient of concordance of ‘K’ilo‘da’lton. (W) (statistics) A measure of the extent to which two or more rank orderings Kell blood group system (haematology) agree with one another. Complete agreement A FAMILY of RED BLOOD CELL antigens between the rankings gives W=1; lack designated as the allotypes KK, Kk, of agreement gives W=0 (or nearly 0). kk and K-k-. Antibodies to the K-ANTIGEN occur in about 10 per cent of people Kendall’s tau coefficient (statistics) in England and can cause red CELL A COEFFICIENT of rank correlation breakdown, haemolytic (USA: hemolytic), between two sets of scores based on transfusion reactions. The GROUP system the number of inversions of ranks in is next in importance to the ABO and one ranking compared with the other. rhesus systems and is named after a woman whose SERUM contained the kerat-, kerato- (histology) Combining antibodies. form denoting CORNEA or horny keratosis. From the Greek ‘keras’, meaning horn. keloid (histology) An overgrowth of scar TISSUE at the site of a cut or burn. keratin (biochemistry) A fibrous PROTEIN The scar, instead of disappearing, spreads containing SULPHUR (USA: sulfur), the and sends out offshoots like claws which substance of which horn, HAIR, the pucker the surrounding SKIN. outer layer of the SKIN, and the nails are composed. It is also part of the kelvin (K) (measurement) SI UNIT of structure of the ENAMEL of the TEETH. thermodynamic TEMPERATURE with OK being ABSOLUTE ZERO [-273.15°C or keratinization (histology) Replacement -459.7°F]. One KELVIN DEGREE is equal of the CYTOPLASM of CELLS in the to one Celsius DEGREE. The FREEZING EPIDERMIS by KERATIN, thus resulting POINT of WATER is 273.15K, 32°F, and in hardening of SKIN. Also termed: 0°C. The BOILING POINT of WATER is CORNIFICATION. 373.15K, 212°F, and 100°C. Named after

226 KERATITIS KETONE keratitis (medical) INFLAMMATION of ketene (chemistry) Unstable ORGANIC the outer LENS of the EYE, the CORNEA. COMPOUND of GENERAL FORMULA

This implies a prior invasion of the CORNEA R2CCO, where R is an organic RADICAL. with BLOOD VESSELS (vascularization). KETENES react with other UNSATURATED KERATITIS commonly follows inadequately COMPOUNDS to form 4-membered rings. or incorrectly treated infections with cold sore (HERPES simplex) VIRUSes and ketoacidosis (biochemistry) ACIDOSIS is also a feature of TRACHOMA and resulting from the accumulation of CONGENITAL syphilis. There is pain, KETONE bodies in the BLOOD. watering and ACUTE sensitivity to LIGHT. Vision is severely affected if the centre ketoconazole (pharmacology) An IMIDA- (USA: center) of the CORNEA is involved. ZOLE antifungal drug. Ketoconazole is absorbed into the BLOOD from the keratometer (measurement) An instru- INTESTINE and can be used to treat ment for measuring the RADIUS OF internal (systemic) fungal infections CURVATURE of the CORNEA. as well as SKIN fungal infections. It can, however, damage the LIVER. keratoscope (medical) An instrument for examining the CORNEA that makes keto-enol tautomerism (chemistry) The it possible to detect irregularities of existence of a chemical COMPOUND curvature. in two double-bonded structural forms, keto and ENOL, which are in EQUILIBRIUM. kernicterus (biochemistry) The staining The keto changes to the ENOL by the with BILIRUBIN of the basal ganglia migration of a HYDROGEN ATOM to of the BRAIN in infants suffering from form a HYDROXYL GROUP with the haemolytic (USA: hemalytic) disease KETONE OXYGEN; the position of the of the newborn. It may cause toxic DOUBLE BOND also changes. degeneration of the NERVE CELLS with resulting disabilities including ketogenesis (biochemistry) The formation spasticity and mental DEFECT. of ACID KETONE bodies, as in uncontrolled DIABETES, starvation or as a result Kernig’s sign (medical) An indication of a diet with a very high fat content. of irritation of the membranes surrounding the BRAIN and SPINAL CORD (the ketogenic (biochemistry) (of an AMINO MENINGES) as in MENINGITIS. Inability ACID) Giving rise to KETONE bodies. to straighten the leg at the knee joint when the thigh is flexed at right angles ketonaemia (biochemistry) Raised to the trunk. KETONES in the BLOOD. Low levels are NORMAL. (USA: ketonemia). Kerr cell (physics) Chamber of LIQUID between two crossed polaroids that ketone (chemistry) Member of a FAMILY darkens or lightens in an ELECTRIC of ORGANIC COMPOUNDS of GENERAL FIELD (applied between two electrodes). FORMULA RCOR’, where R and R’ are It can be used as a shutter or to modulate organic radicals and =CO is a CARBONYL a LIGHT beam. It was named after the GROUP. KETONES may be made in various British physicist John Kerr (1824–1907). ways, such as the OXIDATION of a secondary ALCOHOL; e.g. OXIDATION

227 KETOSIS KIDNEY TRANSPLANT of ISOPROPANOL gives ACETONE kg f (measurement) An abbreviation

(propanone) (CH3) 2CO. Ketones are of ‘k’ilo‘g’ram ‘f’orce. produced in the body by the imperfect breakdown of stored fats in severe kH (measurement) An abbreviation of DIABETES MELLITUS and starvation. ‘k’ilo‘H’ertz. Also termed kHz.

See also DIABETES MELLITUS. kidney (anatomy) One of a pair of excretory organs that FILTER waste products ketosis (biochemistry) Poisoning caused (particularly nitrogenous waste) from the by an accumulation of KETONES BLOOD and concentrate them in URINE. (acetoace-tate, D-O-hydroxybutyrate, Kidneys also have an important FUNCTION ACETONE) in the BLOOD. in the regulation of the BALANCE of WATER and salts in the body. The main ketotic (biochemistry) Pertaining to processes of the KIDNEY occur in a KETOSIS. large number of tubular structures called Kety method (physiology) Method for nephrons. WATER and waste products measuring cerebral BLOOD flow. The pass from the kidneys to the BLADDER AVERAGE cerebral BLOOD flow in young via the ureters. adults is 54mL/100g/min. The Kety method gives no information about regional kidney cysts (histology) Small, FLUID- differences in BLOOD flow. filled cavities in, the kidneys that are common and BENIGN and usually cause keV (measurement) An abbreviation neither symptoms nor danger. of ‘k’ilo-‘e’lectron ‘V’olt, a UNIT of PARTICLE ENERGY equivalent to 103 kidney failure (medical) The stage ELECTRON volts. in KIDNEY disease in which neither ORGAN is capable of excreting body keyboard (computing) COMPUTER waste products fast enough to prevent INPUT DEVICE which a human their accumulation in the BLOOD. OPERATOR uses to type in DATA as ALPHANUMERIC characters. It consists kidney stones (biochemistry) CRYSTAL- of a standard KEYBOARD, usually with LIZATION out of various substances additional FUNCTION keys. dissolved in the URINE. Stones may occur in inherited disorders in which Kf (physiology/biochemistry) A symbol ABNORMAL amounts of substances such for glomerular ultrafiltration coefficient. as CYSTINE and XANTHINE are excreted, but most KIDNEY STONES contain various kg (measurement) An abbreviation of combinations of CALCIUM, MAGNESIUM, ‘k’ilo‘g’ram. PHOSPHORUS, and oxilate. kg cal (measurement) An abbreviation of ‘k’ilo‘g’ram ‘cal’oric. kidney transplant (medical) The INSERTION of a donated KIDNEY into the body and kg cum (measurement) An abbreviation connection of its BLOOD VESSELS to of ‘k’ilo‘g’rams per ‘cu’bic ‘m’etre. the HOST vessels and its URETER to the HOST BLADDER. kg m (measurement) An abbreviation of ‘k’ilo‘g’ram ‘m’etre.

228 KILLER CELLS KINETIC THEORY killer cells (immunology) A subclass kilowatt-hour (kwh or kwhr) (measure- of large, granular LYMPHOCYTES. These ment) A UNIT of measure equal to are important elements in the IMMUNE 1,000 watts of POWER over the PERIOD SYSTEM and are the final effectors of an hour. Also termed: UNIT. in the process by which damaged, infected or MALIGNANT CELLS are recognized kinaesthesis (physiology) Process by and destroyed. which sensory CELLS in muscles and organs relay information concerning kilo- (measurement) Metric prefix meaning the relative position of the limbs and a thousand times (x 103) used with the general orientation of an organism units of measurements. in space; a type of biological FEEDBACK. kilobase (molecular biology) A UNIT kinase (chemistry) ENZYME that causes of length of DNA or RNA of 1000 bases, PHOSPHORYLATION by ATP. used in describing genes or shorter sequences. When measuring double kinematic viscosity (v) (physics) The stranded DNA, it is actually BASE- COEFFICIENT of VISCOSITY of a FLUID PAIRS that are counted, so that the divided by its DENSITY. UNIT is comparable with counting bases in a single-stranded MOLECULE. kinesis (biology) The simplest kind of orientation BEHAVIOUR (USA: behavior) kilobyte (K) (computing) A COMPUTER that occurs in RESPONSE to a STIMULUS term denoting 1,024 bytes of information (e.g. the CONCENTRATION of a nutrient or STORAGE space. or an irritant). The speed of an ANIMAL’S random motion increases until the kilocalorie (Kcal) (measurement) 1,000 STIMULUS reduces. small calories [cal] or one large CALORIE [Call. This is a scientific UNIT of ENERGY See also TAXIS. required to burn off consumed food. kinetic energy (physics) The ENERGY kilogram (kg) (measurement) SI UNIT possessed by an OBJECT because of of MASS, equal to 1,000 grams. 1 kg= its motion, equal to 1/2mv2, where m= 2.2046 Ib. MASS and v=velocity. The KINETIC ENERGY of the particles that make kilohertz (kHz) (measurement) A UNIT up any SAMPLE of MATTER determine of FREQUENCY equal to 1,000 hertz, its HEAT ENERGY and therefore its or 1,000 cycles per second. TEMPERATURE (except at ABSOLUTE ZERO, when both are equal to zero). kilojoule (kj) (measurement) UNIT of See KINETIC THEORY. ENERGY equal to 1,000 joules. kinetic theory (physics) Theory that accounts kilometre (km) (measurement) UNIT for the properties of substances in terms of length equal to 1,000 metres. 1 km= of the movement of their COMPONENT 0.62137 miles. (USA: kilometer). particles (atoms or molecules). The theory is most important in describing the kilowatt (kw) (measurement) A UNIT BEHAVIOUR (USA: behavior) of gases of electrical POWER equal to 1,000 watts. (when it is referred to as the KINETIC

229 KINETICS KOCH’S POSTULATES

THEORY of gases). An ideal GAS is assumed KININASE II is the same ENZYME as to be made of perfectly elastic particles the angiotensin-converting ENZYME, that collide only occasionally with each which removes His-Leu from the C- other. Thus, e.g. the PRESSURE exerted terminal end of angiotensin I. by a GAS on its container is then the result of GAS particles colliding with the Kirchhoff’s laws (1, 2 physics) Extensions walls of the container. of OHM’S LAW that are used in the ANALYSIS of complex electric circuits. 1 The sum See also KINETIC THEORY. of the currents flowing at any junction is zero. 2 Around any closed path, the sum kinetics (chemistry) Study of the rates at of the EMFS equals the sum of the products which CHEMICAL REACTIONS take place. of the currents and impedances. kinetochore (cytology) The point of kissing bug (parasitology) The reduviid attachment of the spindle in a CELL. BUG that transmits chagas’ disease, it is so called because its nocturnal kingdom (biology) Highest rank in the bite is barely felt. CLASSIFICATION of living organisms, which encompasses phyla (for animals) kJ (measurement) An abbreviation of and divisions (for plants). Criteria determining ‘k’ilo‘j’oule. members of a KINGDOM are broad, and consequently members are very diverse. Klinefelter’s syndrome (genetics) A Traditionally, there were two kingdoms: disorder, limited to males, caused by the plants and the animals. However, having an extra X CHROMOSOME (YXY); FUNGI, protists and prokaryotes are now the male characteristics tend to be often placed in kingdoms of their own. diminished, and there is a predisposition to mental illness and mental retardation. kinins (biochemistry) VASODILATOR HORMONES. Two related VASODILATOR klino-taxis (biology) Movement of an peptides called KININS are found in ANIMAL in RESPONSE to LIGHT. the body. One is the nanapeptide brabykinin and the other is the decapeptide knowledge base (computing) The part lysylbradykinin, also known as kalidin. of an expert system in which the expert knowledge is stored. kininase I (biochemistry) An ENZYME involved in the cardiovasular regulatory Koch’s postulates (bacteriology) A mechanism. A carboxypeptidase that SET of criteria to be obeyed before it metabolizes the KININS bradykinin and is established that a particular organism lysylbradykinin to inactive fragments causes a particular disease. The organism by removing the C-terminal Arg. must be present in every case and must be isolated, cultured and identified; kininase II (biochemistry) An ENZYME, it must produce the disease when a like KININASE I, involved in the pure culture is given to susceptible cardiovasular regulatory mechanism. animals; and it must be recoverable It is a dipeptidylcarboxypeptidase that from the diseased ANIMAL. Named inactivates bradykinin and lysylbradykinin after the German BACTERIOLOGIST, by removing Phe-Arg from the C terminal. R.Koch (1843–1910).

230 KOPLIK’S SPOTS KWASHIORKOR

Koplik’s spots (virology) Tiny white in GAS-filled lamps and DISCHARGE spots, surrounded by a red BASE, tubes. At. no. 36; r.a.m. 83.80. occurring on the inside of the cheeks and the inner surface of the lower lip Kupffer cells (histology) The CELLS during the INCUBATION PERIOD of that line the fine BLOOD sinuses MEASLES. Named after the American (capillaries) of the LIVER and act as paediatrician, H. Koplik (1858–1927). scavengers to remove BACTERIA and other foreign material. Named after Korsakoff’s syndrome (medical) A the German anatomist, K.W.von Kupffer condition that follows delirium and toxic (1829–1902). states. Often due to alcoholism. kurchatovium (chemistry) An alternative Kr (chemistry) The CHEMICAL SYMBOL term for the post-ACTINIDE ELEMENT for KRYPTON. RUTHERFORDIUM.

Krause end bulb (histology) An Kuru (medical) A disease of the BRAIN encapsulated SKIN RECEPTOR probably caused by a transmissible slow VIRUS, sensitive to cold. found in Papua New Guinea in 1957. It is fatal, and affects the CEREBELLUM Krebs cycle (biochemistry) A cyclical and other parts of the BRAIN, resulting sequence of 10 bioCHEMICAL REACTIONS, in progressive unsteadiness and inability brought-about by mitochondrial ENZYMES, to control movements. The disease was that involves the OXIDATION of a passed on by the practice of cannibalism MOLECULE of acetyl-CoA, to two molecules and is thought to be caused by a prion. of CARBON DIOXIDE and WATER. It forms the second stage of AEROBIC kV (measurement) An abbreviation of RESPIRATION, in which PYRUVATE or ‘k’ilo‘V’olt. LACTIC ACID produced by GLYCOLYSIS is oxidized to CARBONDIOXIDE and WATER, kVA (measurement) An abbreviation thus producing a large amount of ENERGY of ‘k’ilo‘V’olt-‘A’mpere. in the form of ATP molecules. It was named after the German-born British Kveim test (medical) A test for biochemist Hans Krebs (1900–82). Also SARCOIDOSIS involving the introduction termed: CITRIC ACID cycle; TRICAR- of some TISSUE, prepared from a person BOXYLIC ACID CYCLE. suffering from the condition, into the SKIN. A typical TISSUE REACTION Kruskal-Wallace test (statistics) A occurs after a few weeks. Named after nonparametric rank test of the HYPO- the Norwegian physician, Morton Ansgar THESIS that two or more independent Kveim (1892–1966). samples have been drawn from the same population. kw (measurement) An abbreviation of ‘k’ilo‘w’att. krypton Kr (chemistry) Gaseous nonmetallic ELEMENT of GROUP 0 of the kwashiorkor (biochemistry) A severe PERIODIC TABLE (the RARE GASes), nutritional disorder of infants and young which occurs in trace quantities in AIR children which occurs when diet is (from which it is extracted). It is used extremely deficient of PROTEIN.

231 KYASANUR FOREST DISEASE KYASANUR FOREST DISEASE

Kyasanur forest disease (virology) An arbovirus haemorrhagic FEVER (USA: hemorrhagic fever) that occurs in Mysore State, India, in the villages around the Kyasanur forest. The disease is caused by a VIRUS of the same GROUP as that causing Japanese B encephalitis and the INFECTION is transmitted by TICK bite.

232 L

L (biochemistry) A symbol for leucine. LABOUR (USA: LABOR) pains begin. LABOUR is divided into three stages: DILATION of the I (measurement) An abbreviation of CERVIX, the neck of the womb; delivery of ‘I’itre (USA, liter). the child; and expulsion of the PLACENTA, the AFTER BIRTH. (USA: LABOR). L- (biochemistry) A symbol for geometric isomer of D-form of chemical compound. labyrinth (anatomy) Part of the INNER EAR of vertebrates, containing the La (chemistry) The CHEMICAL SYMBOL COCHLEA and vestibular apparatus. for LANTHANUM. Also known as the INNER EAR. lab. (general terminology) An abbrevia- labyrinthitis (medical) INFLAMMATION tion of ‘lab’oratory. of the INNER EAR, which causes vertigo, label (chemistry) An ISOTOPE (RADIO- nausea and vomiting. ACTIVE or STABLE) that replaces a STABLE Lac operon (genetics) The GROUP of ATOM in a COMPOUND. The course of a genes in ESCHERICHIA COLI that controls chemical or bioCHEMiCAL REACTION or the METABOLISM of LACTOSE. It was physical process can be followed by tracing the first OPERON to be discovered, and the RADIOACTIVITY using a COUNTER was found by Jacob and Monod in 1961. or, in the case of STABLE isotopes, a MASS SPECTROMETER. lacrimal gland (anatomy) GLAND that labiate (biology) Having lips or structures produces tears. FLUID is continuously resembling lips. secreted to protect and moisten the CORNEA; it also contains the labile (chemistry) Liable to change; usually BACTERICIDAL ENZYME LYSOZYME. applied with respect to particular conditions, Also termed: lachrimal GLAND. e.g. HEAT-LABILE. ß-lactam (pharmacology) Member of labium (anatomy) One of the folds of a GROUP of antibiotics that include flesh at the entrance to the VAGINA. the PENICILLINS. laboratory (lab) (general terminology) lactate (1 chemistry; 2 biology) 1 SALT A room for scientific experiments and or ESTER of LACTIC ACID (2-hvdroxy demonstrations. PROPANOIC ACID). 2 To produce milk. labour (physiology) PARTURITION, the process lactation (physiology/biochemistry) The of giving birth. When PREG-NANCY in the production of milk. May be physiological human has lasted for more or less 280 days (after PREGNANCY) or pathological the contractions of the UTERUS known as (galactorrhoea).

233 LACTEAL LAMBERT’S LAW lacteal (physiology) LYMPH VESSEL It is a REDUCING SUGAR. Also termed: of the villi in the INTESTINE of vertebrates. milk-SUGAR. Fat passes into the LACTEALS as an EMULSION of globules to be circulated laevorotatory (/-) (chemistry) Describing in the LYMPHATIC SYSTEM. a COMPOUND With OPTICAL ACTIVITY that causes the plane of POLARIZED lactic acid (biochemistry) CH3CH(OH)- LIGHT to rotate in an anti-clockwise direction. COOH Colourless (USA: colorless) LIQUID ORGANIC ACID. A MIXTURE of (+)- laevulose (chemistry) Fruit SUGAR, also LACTIC ACID (DEXTROROTATORY) and called FRUCTOSE. A MONOSACCHARIDE (-)-LACTIC ACID (LAEVOROTATORY) CARBOHYDRATE. is produced by BACTERIAL ACTION on the SUGAR LACTOSE in milk during lag phase (microbiology) PERIOD of slow souring. The (+)-form is produced in microbial GROWTH, which occurs follow- animals when ANAEROBIC RESPIRATION ing INOCULATION of the culture medium. takes place in muscles because of an insufficient OXYGEN supply during Lamarckism (genetics) Discredited theory vigorous activity. LACTIC ACID is used proposed by the French natuarlist Jean- in the chemical and textile industries. Baptiste Lamarck (1744–1829) that Also termed: 2-hydroxyPROPANOIC ACID. evolutionary change could be achieved by the transmission of acquired lactic dehydrogenase (LDH) (biochemis- characreristics from parents to offspring. try) An ENZYME that catalyses the The theory was superseded by Darwinism. REDUCTION of PYRUVATE to LACTATE. The ENZYME is found in all CELLS capable lambda (genetics) One of the most intensively of GLYCOLYSIS. LDH exists as several studied of the bacteriophages. It attacks different ISOZYMES, and different tissues ESCHERICHIA COLI. The GENOME is have either different ISOZYMES or different double-stranded DNA, but with single- sets of ISOZYMES. Release of LDH into stranded, mutually complementary ‘tails’ the BLOOD is a sign of TISSUE damage that join up to make a circular DNA after and can occur under many circumstances entry into the HOST CELL. (e.g. MYOCARDIAL INFARCTION, HEPATOTOXICITY, nephrotoxicity, etc.). lambda particle (physics) Type of Identification of the particular isozyme can ELEMENTARY PARTICLE with no ELECTRIC be used to identify the ORGAN involved. CHARGE. For example, the SERUM CONCEN- TRATION of LDH, is increased in LIVER lambda point (chemistry) TEMPE-RATURE injury, whereas LDH and LDH are increased at which LIQUID HELIUM (HELIUM I) in KIDNEY injury. becomes the superfluid known as HELIUM II. lactoflavin (biochemistry) An alternative Lambert’s law (physics) Equal fractions term for RIBOFLAVIN. of incident LIGHT RADIATION are absorbed by successive layers of equal thickness lactose (chemistry) C12H 22O 11 White of the LIGHT-absorbing substance. It CRYSTALLINE DISACCHARIDE SUGAR was named after the German mathematician that occurs in milk, formed from the and physicist Johann Heinrich Lambert union of GLUCOSE and GALACTOSE. (1728–77).

234 LAMINAR FLOW LATENT TRAIT laminar flow (physics) Streamlined, larynx (anatomy) Region of TRACHEA or non-turbulent, flow in a GAS or LIQUID. (windpipe) that usually houses the VOCAL CORDS (composed of MEMBRANE folds lanolin (chemistry) Yellowish sticky substance that vibrate to produce sounds). obtained from the grease that occurs naturally in wool. It is used in cosmetics, laser (physics) An abbreviation of ‘I’ight as an ointment and in treating leather. ‘a’mplification by ‘s’timulated ‘e’mission Also termed: lanoline; WOOL FAT. of ‘r’adiation. lanthanide (chemistry) Member of the Lassa fever (virology) Lassa FEVER is GROUP IIIB elements of ATOMIC NUMBER a VIRUS INFECTION carried by the rat 57 to 71. The properties of these metals Mastomys natalensis found in sub-Saharan are very similar, and consequently they Africa. First seen in a town called Lassa are difficult to separate. Also termed: in northern Nigeria in 1969, the INFECTION lanthanoid; rare-EARTH ELEMENT. is thought to be spread to humans by contamination of food by rat’s URINE, lanthanum (La) (chemistry) SILVER- and from person to person by contact white metallic ELEMENT in GROUP IIB with BLOOD or other body fluids. of the PERIODIC TABLE, the parent ELEMENT of the LANTHANIDE SERIES. late genes (virology/genetics) Genes It is used in making lighter flints. At. that are expressed late in the process no. 57; r.a.m. 138.9055. of a VIRUS infecting a BACTERIAL CELL. They usually code for the PROTEIN(S) laparoscopy (medical) Inspection of that make up the VIRUS’S coat. intra-abdominal structures through a FIBREOPTIC (USA: fiberoptic) scope. latency period (biology) The PERIOD Very widely used in GYNAECOLOGY of time between the application of an (USA: gynecology). agent to a living organism and a demonstrable effect of such application. LaPlace law (physics) An alternative term for AMPERE’S LAW. latent heat (physics) HEAT ENERGY that is needed to produce a change large intestine (anatomy) See COLON; of state during the melting (SOLID- INTESTINE. to-LIQUID change) or vaporisation (USA: vaporization) (LIQUID-to VAPOUR/GAS Larmor precession (physics) ORBITAL change) of a substance; it causes no motion of an ELECTRON about the rise in TEMPERATURE. This HEAT NUCLEUS of an ATOM when it is subjected ENERGY is released when the substance to a small MAGNETIC FIELD. The reverts to its former state (by FREEZING/ ELECTRON processes about the direction solidifying or condensing/liquefying). of the MAGNETIC FIELD. It was named after the British physicist Joseph Larmor latent trait (genetics) Any trait that is (1857–1942). not expressed in an organism’s PHENOTYPE, but that can be passed on through its laryngitis (medical) INFLAMMATION of genes to descendants. the LARYNX, usually caused by a VIRUS INFECTION such as in the common cold.

235 LATERAL LAW OF MASS ACTION

lateral (anatomy) Lying towards the side; lauric acid (chemistry) CH3(CH2)10COOH away from the mid-line. Contrast MEDIAL. White CRYSTALLINE CARBOXYLIC ACID, used in making soaps and detergents. lateral dorsal nucleus (cytology) A Also termed: DODECANOIC ACID; NUCLEUS that projects to the cingulate dodecylic ACID. gyrus. lavage irrigation (medical/toxicology) lateral horn (histology) GREY MATTER Usually used in referring to GASTRIC lying on either side of the SPINAL CORD LAVAGE, the washing out of the STOMACH between the DORSAL and VENTRAL horns, through a STOMACH tube for severe and forming part of the autonomic system. ALCOHOLic intoxication or poisoning. latex (chemistry) Milky FLUID produced law (science) A simple statement or in some plants after damage, containing mathematical expression for the sugars, proteins and ALKALOIDS. It generalisation (USA: generalization) of is used in manufacture, e.g. of rubber. results relating to a particular phenomenon A SUSPENSION of SYNTHETIC rubber or known facts. is also called LATEX. law of constant composition (physics/ latin square design (statistics) An chemistry) In any given chemical experimental design whose aim is to COMPOUND, the same elements are remove experimental error due to VARIATION always combined in the same proportions arising from two sources. The design is by MASS. identified with the rows and columns of a square. The number of conditions arising law of equivalent proportions (chemistry) from each source and the number of When two elements both form chemical treatments are the same, and each compounds with a third ELEMENT, a TREATMENT occurs once in each column COMPOUND of the first two contains them and row. in the relative proportions they have in compounds with the third one e.g. CARBON LATS (physiology/biochemistry) An combines with HYDROGEN to form methane, abbreviation of ‘L’ong-‘A’cting ‘T’hyroid CH4, in which the ratio of CARBON to ‘S’timulator. HYDROGEN is 12:4; OXYGEN also combines

with HYDROGEN to form WATER, H2O, in lattice energy (crystallography) Strength which the ratio of OXYGEN to HYDROGEN of an IONIC BOND; the ENERGY required is 16:2. CARBON and OXYGEN form the for the separation of the ions in 1 mole COMPOUND CARBON MONOXIDE, CO, of a crystal to an infinite distance from in which (and in accordance with the LAW) each other. Also termed: LATTICE ENTHALPY. the ratio of CARBON to OXYGEN is 12:16. Also termed: LAW of RECIPROCAL lattice (crystallography) Regular three- proportions. dimensional NETWORK of atoms, ions or molecules in a crystal. Also termed: law of mass action (chemistry) The driving CRYSTAL LATTICE. FORCE of a HOMOGENEOUS CHEMICAL REACTION is proportional to the ACTIVE laughing gas (chemistry) An alternative MASSes of the reacting substances. term for DINITROGEN OXIDE.

236 LAW OF OCTAVES LEAD law of octaves (chemistry) When the Id (toxicology) An abbreviation of ‘I’ethal elements are arranged in ORDER of their ‘d’ose. RELATIVE ATOMIC MASSes, any One ELEMENT has properties similar to those LD5O (toxicology) A term used to denote of the ELEMENT eight places in front of the dose of a substance that will kill it and eight places behind it in the list. 50 per cent of the organisms receiving It is a rejected idea of the relationship it. LD50 tests are used on LABORATORY of elements. Also termed: Newland’s LAW. animals for testing the toxicity of drugs, toilet preparations, cosmetics, etc. See also PERIODIC TABLE. designed for human use. law of reciprocal proportions (chemistry) LDH (physiology/biochemistry) An abbre- An alternative term for the LAW of viation of ‘L’actate ‘D’e‘H’ydrogenase. equivalent proportions. LDL (biochemistry) An abbreviation lawrencium (Lr) (chemistry) RADIOACTIVE of ‘L’ow-‘D’ensity ‘L’ipoPROTEIN. ELEMENT in GROUP IIIB of the PERIODIC TABLE (the last of the ACTINIDES). At. no. Le Chatelier’s principle (physics) If 103; r.a.m. 257 (most STABLE ISOTOPE). a change occurs in one of the factors (such as TEMPERATURE or PRESSURE) laws of reflection of light (1,2 physics) under which a system is in EQUILIBRIUM, 1 The ANGLE OF REFLECTION equals the system will tend to adjust itself so the ANGLE OF INCIDENCE. 2 The as to counteract the effect of that change. reflected RAY is in the same plane as It was named after the French physicist the incident RAY and the NORMAL at Henri Le Chatelier (1850–1936). Also the point of INCIDENCE. termed: Le Chatelier-Braun principle. laws of refraction of light (1,2 optics) 1 For leaching (chemistry) Washing out of a two particular media, the ratio of the sine of SOLUBLE material from a SOLID by a the ANGLE OF INCIDENCE to the sine of the suitable LIQUID. ANGLE OF REFRACTION is CONSTANT (the REFRACTIVE INDEX). This is a lead dioxide (chemistry) An alternative statement of Snell’s LAW. 2 The refracted term for LEAD(IV) OXIDE. RAY is in the same plane as the incident RAY and the NORMAL at the point of INCIDENCE. lead equivalent (radiology) FACTOR that compares any form of shielding against LCAT (physiology/biochemistry) ‘L’ecithin- RADIOACTIVITY to the thickness of LEAD ‘C’holesterol ‘A’cyl‘T’ransferase. that would provide the same measure of protection. LCD (physics) An abbreviation of ‘l’iquid- ‘c’rystal ‘d’isplay. lead monoxide (chemistry) An alternative term for LEAD(II) OXIDE. LCM (mathematics) An abbreviation of ‘l’owest ‘c’ommon ‘m’ultiple. lead (Pb) (chemistry) SILVER-blue poisonous metallic ELEMENT in GROUP IVA of the LCR (physiology) An abbreviation of PERIODIC TABLE, obtained mainly from its ‘L’ocus ‘C’ontrol ‘R’egion. SULPHIDE (USA: sulfide) ore galena.

237 LEAD TETRAETHYL(IV) LEISHMAN-DONOVAN BODY

Various isotopes of LEAD are final elements and found in large amounts in the BRAIN in RADIOACTIVE DECAY SERIES. The and NERVES as well as SEMEN and METAL is used in building, as shielding the YOLK of eggs. Also termed: against IONIZING RADIA-TION, as PHOSPHATIDYL CHOLINE. electrodes in ACCUMU-LATORS and in various ALLOYS (such as solder, metals for lectins (biochemistry) A general term bearings and type METAL). Its INORGANIC for proteins or GLYCOPROTEINS of non- COMPOUNDS are employed as pigments; immune ORIGIN that have multiple highly tetraethyllead is used as an anti-knock agent specific CARBOHYDRATE-binding sites. in petrol. At. no. 82; r.a.m. 207.19. LED (physics) An abbreviation of ‘L’ight- lead tetraethyl(IV) (chemistry) An alterna- ‘E’mitting ‘D’iode. tive term for tetraethyllead. leeches (biology) The medicinal leech, Hirudo medicinalis, can sometimes help lead(II) (chemistry) An alternative term in the technique of SKIN grafting by for PLUMBOUS. reducing swelling in the grafted SKIN. lead(II) oxide (chemistry) PbO Yellow LEED (physics) An abbreviation of ‘L’ow- CRYSTALLINE substance, used in the ‘E’nergy ‘E’lectron ‘D’iffraction. manufacture of GLASS. Also termed: LEAD MONOXIDE; litharge. legionaires disease (medical/bacteriology) Pneumonia caused by the BACTERIA lead(IV) (chemistry) An alternative term Legionella pneumophila. The disease for PLUMBIC. cannot be spread from person to person, but only in infected drops of WATER such lead(IV) oxide (chemistry) PbO Brown 2 as appears in some cooling towers and AMORPHOUS SOLID, a strong oxidising condensers in air-conditioning systems, (USA, oxidizing) agent, used in lead- which can give out AIR infected with the acid accumulators. Also termed: LEAD BACTERIA in fine drops of WATER. DIOXIDE; LEAD PEROXIDE. leiomyoma (histology) a TUMOUR (USA: leader sequence (molecular biology) tumor) of the unstriped or INVOLUNTARY The part of a MOLECULE of MESSENGER MUSCLE in an internal ORGAN. RNA between the 5’ end and the start of the coding sequence. It contains leiomyosarcoma (histology) MALIGNANT sequences that are concerned with binding TUMOUR (USA: maglignant tumor) of to the RIBOSOME. the UTERUS which may arise in fibroids. leaders (histology) The popular name Leishman stain (histology) A histological for tendons. staining technique that may be used to make BLOOD CELLS and PARASITES lecithin (biochemistry) Type of PHOS- visible under the MICROSCOPE. PHOLIPID, a GLYCERIDE in which one ORGANIC ACID residue is replaced by Leishman-Donovan body (microbiology) a GROUP containing phosphoric ACID Small, round INTRACELLULAR form (called and the BASE CHOLINE. It is a major amastigote or leishmanial stage) of COMPONENT of a CELL MEMBRANE Leishmania sp. and Trypanosoma cruzi.

238 LEISHMANIASIS LETHAL MUTATION

Leishmaniasis (medical/microbiology) leptokurtic (statistics) Of a FREQUENCY INFECTION with a protozoon of the DISTRIBUTION, having a sharper peak GENUS Leishmania, which is found than a reference distribution such as in dogs and rodents and transmitted the NORMAL curve. by sandflies. The INFECTION may be of the SKIN, where it produces indolent Leptospira (bacteriology) BACTERIA sores, or it may be in the internal like very fine corkscrews which are in organs. Named after the English CONSTANT motion. BACTERIOLOGIST, Sir W.Leishman (1865–1926). See KALA AZAR. leptotene (genetics) One of the stages in MEIOSIS. One of the two processes lens (optics) Any TRANSPARENT substance of CELL DIVISION. with two opposite surfaces that refract LIGHT, most often used of a disc having LES (physiology) An abbreviation of a spherical curvature on one or both ‘L’ower ‘E’sophageal ‘S’phincter. sides, which through REFRACTION can be used to form an IMAGE, to magnify Lesch-Nyhon syndrome (genetics) A an IMAGE, etc. By analogy also a CURRENT- human disease inherited as an X-linked carrying coil that focuses a beam of RECESSIVE. It therefore affects boys electrons (as in an ELECTRON who have inherited it from CARRIER MICROSCOPE). The mammalian EYE mothers. The actual MUTATION is a contains a single LENS with CONVEX failure to produce the ENZYME faces, lying behind the CORNEA. By hypoxanthine phosphoribosyl transferase changing its convexity, it brings the IMAGE (HPRT), which is part of the process of objects at different distances into correct for metabolising purines; build-up of FOCUS on the RETINA. The refractive only partly metabolised purines leads POWER of the human LENS is about to mental retardation and cerebral palsy. 20 diopters. See ACCOMMODATION. The condition is very rare. Female relatives of a sufferer, who may be carriers, Lenz’s law (physics) When a wire moves can have a FOETUS (USA: fetus) in a MAGNETIC FIELD, the ELECTRIC prenatally diagnosed, as the lack of CURRENT induced in the wire generates HPRT can be detected from conception. a MAGNETIC FIELD that tends to oppose the motion. It was named after the Russian lesion (medical) A region of damage physicist Heinrich Lenz (1804–65). to an ORGAN, whether produced deliberately or by PATHOLOGY. LEPRA (society) An abbreviation of ‘LEP’rosy ‘R’elief ‘A’ssociation. lethal mutation (genetics) Any MUTATION that has such a severe effect on the organism leprosy (medical/bacteriology) Also known as to cause early death. From the genetic as Hansen’s disease, LEPROSY is caused point of view, a MUTATION is considered by BACTERIA called Mycobacterium ‘lethal’ if the death occurs at any time before leprae. It now occurs in many tropical the individual reaches reproductive age. and subtropical countries, but has Common usage in relation to humans, disappeared from Northern Europe. Named however, includes only those MUTATIONS after the Norwegian physician, Gerhard that cause death before birth or in early Henrik Hansen (1841–1912). infancy. LETHAL MUTATIONS can be

239 LEU. LEUCOPENIA

DOMINANT, RECESSIVE or X-linked, and is common. The only harm it causes is there are some known as ‘semi-lethals’. the social embarrassment of the patient; LETHAL MUTATIONS are quite common in but the blemish may often be camouflaged humans. Approximately 20 per cent of by ‘make-up’. It may affect coloured pregnancies end in spontaneous (USA: colored) people; about one in ABORTION (MISCARRIAGE), with either three patients are cured spontaneously. LETHAL MUTATIONS or CHROMOSOME abnormalities responsible for most cases. leucoplakia (medical) A condition in which the patient develops thickened Leu. (biochemistry) An abbreviation white patches on the TONGUE, cheeks of ‘Leu’cine. or gums which cannot be scraped off. In many cases no cause is found, but leucine (Leu.) (biochemistry) (CH3)2CH- leucoplakia is a precancerous condition

CH2CH(NH2)COOH Colourless (USA: and a number of cases develop colorless) CRYSTALLINE AMINO ACID; MALIGNANT change. a constituent of many proteins. Also termed: 2-amino-4-methylpentanoic acid. leukaemia (haematology) A MALIGNANT disease involving overproduction of WHITE leucine-amino peptidase stain BLOOD CELLS. LEUKAEMIA (USA: (histology) An ENZYME histochemical leukemia) may be ACUTE or CHRONIC, staining technique. and according to the type of CELL involved can be divided into myeloid or lymphatic. leuco- (general terminology) Prefix ACUTE LYMPHATIC LEUKAEMIA is mostly denoting white; e.g. LEUCOCYTE. (The a disease of children, and ACUTE myeloid prefix is spelled leuk in LEUKAEMIA.) LEUKAEMIA a disease of those over 55; the CHRONIC leukaemias occur in leucocyte (haematology) Any kind of people over 40. In ACUTE disease, there WHITE BLOOD CELL. They are classified is failure of the NORMAL FUNCTION as polymorphonuclear LEUCOCYTES of the BONE MARROW, leading to a or polymorphs, LYMPHOCYTES and lack of RED BLOOD CELLS, platelets monocytes. Granulocytes are further divided necessary for BLOOD clotting, and white into neutrophils, basophils or eosinophils, CELLS necessary to fight disease, so according to their staining characteristics. that the patient becomes anaemic (USA: In health they number approximately 4 anemic), and liable to develop infections to 11×109 per LITRE in the BLOOD, and haemorrhages (USA: hemorrhages). 60–70 per cent of which are neutrophils. In addition the LIVER and SPLEEN are Their number is raised (leucocytosis) enlarged, as are the LYMPH GLANDS. in inflammatory conditions and abnormally In all leukaemias, the diagnosis is made low (leucopenia) in other conditions, by examination of the BLOOD. (USA: such as poisoning of the BONE MARROW leukemia). by drugs. (USA: leukocyte). leucocytosis (haematology) Elevated leucoderma (medical) A condition of WHITE BLOOD CELL count. (USA: the SKIN in which patches of white appear. leukocytosis). It may be caused by diseases such as pityriasis versicolor or LEPROSY, or by leucopenia (haematology) Low WHITE vitiligo, an autoimmune condition which BLOOD CELL count. (USA: leukopenia).

240 LEUCORRHOEA LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION leucorrhoea (medical) An ABNORMAL life cycle (biology) Progressive sequence white DISCHARGE from the VAGINA. of changes that an organism undergoes (USA: leukorrhoea). from FERTILIZATION to death. In the course of the CYCLE a new generation level (statistics) A sub-CLASSIFICATION is usually produced. REPRODUCTION of a FACTOR. The LEVEL of a FACTOR may be sexual or ASEXUAL, both MEIOSIS corresponds to the value of an and MITOSIS may occur. independent or INTERVENING VARIABLE. A ‘fixed LEVEL’ is any one LEVEL of ligament (histology) The tough elastic a FACTOR where all possible levels CONNECTIVE TISSUE that hold the are investigated. A ‘random LEVEL’ bones together and stabilise the joints. is a LEVEL chosen to be representative of the FACTOR levels where only some ligand (1 chemistry; 2 biochemistry) 1 Any levels are investigated. MOLECULE or ION that has at least one ELECTRON pair that donates its electrons to levelling effect (statistics) The tendency a METAL ION or other ELECTRON acceptor, after many trials for scores to cluster often forming a CO-ORDINATE BOND. 2 Any closely around the MEAN. MOLECULE that interacts with or binds to a RECEPTOR that has an AFFINITY for it. Lewis acid and base (chemistry) Concept of acids and bases in which an ACID is ligase (biochemistry) ENZYME that repairs defined as a substance capable of accepting damage to the strands that make up a pair of electrons, whereas a BASE is DNA, widely used in RECOMBINATION able to donate a pair of electrons to a techniques to seal the joins between BOND. It was named after the American DNA sequences. chemist Gilbert Lewis (1875–1946). ligation (molecular biology) The joining LFO (physics) An abbreviation of ‘L’ow together of separate sequences of DNA ‘F’requency ‘O’scillator. by DNA LIGASE ENZYMES. It occurs during REPLICATION, DNA repair, and is also LH (biochemistry) An abbreviation of widely used in GENETIC ENGINEERING ‘L’uteinising ‘H’ormone. to stick DNA molecules together IN VITRO.

LHRF (biochemistry) An abbreviation ligature (medical) A piece of material, of ‘L’uteinising ‘H’ormone ‘R’eleasing e.g. thread or catgut, used to tie off BLOOD ‘F’actor. VESSELS or other structures.

LHRH (physiology/biochemistry) An light (physics) Visible part of the abbreviation of ‘L’uteinizing ‘H’ormone- ELECTROMAGNETIC SPECTRUM, of wave- ‘R’eleasing ‘H’ormone. lengths between about 400 and 760 nanometres. Li (chemistry) The CHEMICAL SYMBOL for LITHIUM. light amplification by stimulated emission of radiation (LASER) (physics) libido (physiology) The sexual IMPULSE. A device that causes particles of a substance to amplify ELECTRO- MAGNETIC WAVES into the VISIBLE

241 LIGHT INTENSITY LINEAR ACCELERATOR

SPECTRUM. The powerful beam of LIGHT the PRECIPITATION of CALCIUM ENERGY produced is increasingly used in CARBONATE; after prolonged bubbling surgery, and has proved particularly useful the SOLUTION goes clear again due in OPHTHALMIC operations because the to the formation of SOLUBLE CALCIUM EYE is largely devoid of significant optical HYDROGENCARBONATE). scatter, unlike other tissues, so that an optical beam can be focused on TISSUE limit (mathematics) Value to which a deep inside the EYE; COAGULATION and sequence or SERIES tends as more cutting is then possible without the risk of and more terms are included. INFECTION. limiting friction (physics) Maximum light intensity (physics) The RADIANT value of a frictional FORCE. ENERGY emitted per UNIT time. The SI UNIT of measurement is the WATT. limiting step (chemistry) An alternative Contrast LUMINOUS INTENSITY. term for RATE-DETERMINING STEP. light meter (physics) Instrument for line breeding (genetics) The technique measuring levels of illumination (e.g. of breeding from animals as closely in PHOTOGRAPHY), usually by means related as possible. of a PHOTOCELL. linea alba (histology) A whitish line light-emitting diode (LED) (physics) running down the middle of the muscular Semi-conducting DIODE that gives off wall of the ABDOMEN, formed by the LIGHT, used to form letters and numbers junction of the flat tendons of the external on a DISPLAY panel. oblique, internal oblique and transverse muscles after they have split to enclose lignocaine (pharmacology) A commonly the two longitudinal rectus muscles. used local ANAESTHETIC (USA: anesthetic). lineage (genetics) A sequence of likelihood ratio (statistics) The ratio SPECIES through evolutionary time, of the likelihood of obtaining an observed from the ancestral SPECIES to its present- SET of DATA under one HYPOTHESIS day descendants. to the likelihood of obtaining the same DATA under another. It is widely used linear (1 statistics; 2 mathematics) 1 in significance tests. Pertaining to a straight line or plane. 2 Describing an equation of the first lime (chemistry) General term for ORDER. (See LINEAR EQUATION). QUICKLIME (CALCIUM OXIDE, CaO), slaked LIME and HYDRATED LIME (both linear absorption coefficient (physics)

CALCIUM HYDROXIDE, Ca(OH)2). They Measure of a medium’s ability to absorb are obtained from limestone. a beam of RADIATION passing through it, but not to scatter or diffuse it. lime water (chemistry) A SOLUTION of CALCIUM HYDROXIDE (Ca(OH)2) linear accelerator (physics) Apparatus in WATER, used as a test for CARBON for accelerating charged particles. DIOXIDE (which turns LIME WATER milky when bubbled through it due to

242 LINEAR ATTENUATION COEFFICIENT LIPID linear attenuation coefficient (physics) Lineweaver-Burk plot (statistics) One Measure of a medium’s ability to diffuse of several ways of linearising ENZYME- and absorb a beam of RADIATION passing or RECEPTOR-binding DATA, based on through it. derivations of the LAW of MASS ACTION. linear energy transfer (LET) (physics) linkage (genetics) Occurrence of two LINEAR rate of ENERGY DISPERSION genes on the same CHROMOSOME. of separate particles of RADIATION Genes that are close together are likely when they penetrate an absorbing medium. to be inherited together; genes that are further apart may become separated linear equation (mathematics) Algebraic during CROSSING OVER. equation of the first ORDER. In CO- ORDINATE geometry, the equation of linkage group (genetics) A GROUP a straight line, GENERAL FORMULA of genes that can be observed to be y=mx+c, where m is the GRADIENT linked together rather than to assort (slope) of the line and c (a CONSTANT) independently. In practice, a LINKAGE is its intercept with the Y-AXIS. GROUP means a GROUP of genes all on the same CHROMOSOME. linear function (1 statistics; 2 general terminology) 1 A sum of weighted Linnaean system (biology) System that variables; they can be graphically classifies and names all organisms expressed as a line or plane. 2 Any according to scientific principles. Each FUNCTION describing the relationship SPECIES has two names; the first indicates of output to input in a LINEAR SYSTEM. the organism’s general type (GENUS), the second names the unique SPECIES. It was linear molecule (chemistry) MOLECULE named after the Swedish botanist Carolus whose atoms are arranged in a line. Linnaeus (1707–78). Also termed: BINOMIAL CLASSIFICATION. linear regression (statistics) Fitting a straight line to the DATA points produced when lipaemia (biochemistry) Abnormally high one VARIABLE is plotted against another. LIPID LEVEL in the BLOOD. (USA, lipemia). linear system (statistics) A system in lipase (biochemistry) In vertebrates, which the output varies in direct proportion an ENZYME in intestinal juice and to the input, and in which if there is pancreatic juice that catalyses the more than one input, the RESPONSE HYDROLYSIS of fats to GLYCEROL is proportional to the weighted sum of and FATTY ACIDS. the inputs. lipid (biochemistry) Member of a GROUP linear transformation (statistics) A TRANS- of naturally occurring fatty or oily FORMATION of scores (e.g. test scores) compounds that share the property of being that changes their MEAN and STANDARD SOLUBLE in organic solvents, but DEVIATION, but retains other aspects sparingly SOLUBLE in WATER; they are of the original distribution. Compare an important part of the CELL MEMBRANE. NORMALIZATION. Also, all LIPIDS yield MONOCARBOXYLIC ACIDS on HYDROLYSIS.

243 LIPOLYTE LITHIUM lipolyte (cytology) LIPID-containing CELL. Large groups of its molecules maintain Also termed: fat CELL. their mobility but nevertheless also retain a form of structural relationship. Some lipoma (histology) A harmless TUMOUR LIQUID CRYSTALS change COLOUR (USA: (USA: tumor) composed of fat CELLS color) according to the TEMPERATURE. often occurring just below the SKIN. liquid-crystal display (LCD) (physics) A lipoprotein (biochemistry) A molecule device displaying letters and numbers on consisting of a protein complexed with a objects such as control panels. These images lipid. They exist in a wide range of forms. are produced when an electrical FIELD Some have a transport function within causes a CAPSULE of TRANSPARENT cells, and others have roles in the metabolism LIQUID CRYSTAL to become OPAQUE. of cholesterol, particularly in the context of some forms of heart disease. See also LIGHT-EMITTING DIODE (LED). liposome (cytology) Droplet of fat in liquid-liquid extraction (chemistry) An the CYTOPLASM of a CELL, particularly alternative term for SOLVENT EXTRACTION. that of an EGG. Listeria (bacteriology) A GENUS of liq. (general terminology) An abbreviation BACTERIA associated with FOOD of ‘liq’uid. POISONING, L. monocytogenes being a member of this GENUS. The sources liquefaction of gases (chemistry) All of the organism include tissues, URINE gases can be liquefied by a COMBINATION and milk of infected animals and the of cooling and compression. The greater foods commonly associated with outbreaks the PRESSURE, the less the GAS needs include milk and milk products, eggs, to be cooled, but there is for each GAS a meat and poultry. certain CRITICAL TEMPERATURE below which it must be cooled before it can be liter (measurement) See LITRE. liquefied. litharge (chemistry) An alternative term liquid (liq.) (physics) FLUID that, without for LEAD(II) OXIDE. changing its VOLUME, takes the shape of its container. According to the KINETIC lithium (Li) (chemistry) SILVER-white THEORY, the molecules in a LIQUID metallic ELEMENT in GROUP IA of the are not bound together as rigidly as PERIODIC TABLE (the ALKALI METALS), those in a SOLID but neither are they the SOLID with the least DENSITY. Its as free to move as those of a GAS. compounds are used in lubricants, ceramics, It is therefore a PHASE that is drugs and the plastics industry. LITHIUM, INTERMEDIATE between a SOLID and when given as a SALT partially replaces a GAS. SODIUM in body tissues, thus affecting the PERMEABILITY of membranes. It liquid crystal (chemistry) COMPOUND is used to reduce mania, and on a long- that is LIQUID at room TEMPERATURE term basis, to alleviate manic-depressive and ATMOSPHERIC PRESSURE but shows illness. At. no. 3; r.a.m. 6.941. characteristics normally expected only from SOLID CRYSTALLINE substances.

244 LITHIUM ALUMINIUM HYDRIDE LIVER FLUKE lithium aluminium hydride (chemistry) FATTY ACIDS. It also carries out many

LiAIH4 Powerful REDUCING AGENT, used in reactions of intermediary METABOLISM. It ORGANIC CHEMISTRY. Also termed: is responsible for the EXCRETION of LITHIUM tetrahydridoaluminate(III). BILIRUBIN and biliverdin, products formed by DEGRADATION of haem (USA: heme). litmus (chemistry) Dye made from certain lichens, used as an INDICATOR to distinguish liver enzymes, in blood (serum enzymes) acids from ALKALIS (USA: alkalies). (biochemistry) The measurement of NEUTRAL LITMUS SOLUTION or LITMUS HEPATIC ENZYMES released into the paper is naturally violet-blue; acids turn BLOOD as a consequence of injury has it red, ALKALIS (USA: alkalies) turn it proven to be a sensitive INDICATOR of blue. HEPATOTOXICITY. Since the ENZYMES may be of cytoplasmic or ORGANELLE litre (I) (measurement) A BASIC UNIT ORIGIN, such measurements may also help of CAPACITY in the METRIC SYSTEM, define the subcellular site of damage. One determined by VOLUME of DISTILLED or more of the following ENZYMES are WATER at 4° Celsius. (USA, liter). 1 measured: ALKALINE PHOSPHATASE; 5- LITRE=1.7598 pints. nucleotidase; LEUCINE aminopeptidase; glutamyl transpeptidase; LACTIC liver (anatomy) In vertebrates, a large ORGAN DEHYDROGENASE ISOZYMES; isocitrate in the ABDOMEN, the main FUNCTION of DEHYDROGENASE; ALCOHOL DE- which is to regulate the chemical composition HYDROGENASE; FRUCTOSE mono-or of the BLOOD by removing surplus diphosphate aldolase; arginase; QUININE carbohydrates and AMINO ACIDS, converting OXIDASE; 0-hydroxybutyrate DE- the former into GLYCOGEN for STORAGE HYDROGENASE; glutamic-pyruvic and the latter into UREA for EXCRETION. transAMINASE; glutamic-oxaloacetic Its glandular SECRETION is known as BILE, transAMINASE; SORBITOL DE- and it is secreted into the SMALL INTESTINE HYDROGENASE. Some of these are via the common BILE DUCT. In those measured only rarely; the ones utilized most SPECIES having a gallBLADDER, including commonly being the two transaminases. humans, the common BILE DUCT originates at the point at which the HEPATIC duct, liver fluke (parasitology) Clonorchis, Fasciola draining the intra-HEPATIC BILE passages, and Opisthorcis are GENERA of FLUKES and comes together with the cystic duct which infect the LIVER of humans. They that connects the gallBLADDER to the live in the BILIARY tract, and their common duct. BILE salts FUNCTION in INTERMEDIATE HOSTS are snails. the DIGESTION of fats in the SMALL Clonorchis and Opisthorcis find a further INTESTINE. The LIVER is supplied with secondary HOST in freshwater fish, and BLOOD via the HEPATIC ARTERY and the the INFECTION occurs where people HEPATIC PORTAL VEIN, and drains into eat raw fish, particularly in the Far East. the INFERIOR VENA CAVA via HEPATIC FLUKES may infect fish-eating mammals veins. The LIVER receives BLOOD, via the other than man, such as cats and dogs. HEPATIC PORTAL VEIN, from the SMALL Fasciola is the sheep LIVER FLUKE, INTESTINE, thus receiving the products of and the snail infects vegetation and WATER; DIGESTION and ABSORPTION of food. It in sheep and cattle raising countries forms GLYCOGEN from GLUCOSE, proteins the INFECTION spreads to humans through from AMINO ACIDS and glycerides from infected WATER. See FLUKES.

245 LL LOGIC

LL (general terminology) An abbreviation can be drawn through adjacent positions of ‘L’ower ‘L’imb. of a point, each position of that point satisfying a particular SET of conditions. LMA (physics) An abbreviation of ‘L’ow 2 Position of a GENE on a CHROMOSOME, ‘M’oisture ‘A’vidity. (pl. ‘loci’).

LMRSH (education) An abbreviation lodestone (chemistry) Fe3O 4 Naturally of ‘L’icentiate ‘M’ember of the ‘R’oyal occurring magnetic OXIDE of IRON. ‘S’ociety for the ‘P’romotion of ‘H’ealth. Also termed: loadstone; magnetite. loa loa (parasitology) A filarial worm LOEL (toxicology) An abbreviation of of West Africa, which infests the SUB- ‘L’owest ‘O’bserved ‘E’ffect ‘L’evel. CUTANEOUS TISSUES, causes transient swellings (Calabar swellings) and intense log (mathematics) An abbreviation of itching, and is sometimes seen crossing ‘log’arithm to base 10. the EYE beneath the CONJUNCTIVA. It is spread by the mango fly, and treated logarithm (mathematics) Number related with diethylcarbamazine citrate. See to an ordinary number in such a way FILARIASIS. that addition or subtraction of logarithms corresponds to multiplication or DIVISION lobe (anatomy) A well-defined part of of ordinary numbers. Logarithms are given an ORGAN, by virtue of their shape, to a particular BASE. The LOGARITHM by partitions of CONNECTIVE TISSUE, of a number to a given BASE is the or by fissures in the ORGAN. The BRAIN, POWER to which the BASE must be lungs, LIVER and THYROID GLAND raised to give the number, i.e. if y is a are for example made up of lobes. number and x is the BASE, y=xn where n is the LOGARITHM of y to the BASE loc. cit. (literary terminology) An x; e.g. the LOGARITHM of 100 to the abbreviation of ‘loc’o ‘cit’ato. Latin, BASE 10 is 2, because 102 is 100. meaning ‘in the place cited’. Used in papers and dissertations to cite a WORK See also CHARACTERISTIC; COMMON previously referred to. LOGARITHM; NATURAL LOGARITHM. local anaesthesia (medical) Anaesthesia logarithmic phase (microbiology) of a localised AREA of the body, as PERIOD of maximal GROWTH rate of opposed to general anaesthesia, when a MICROORGANISM in a culture medium. the whole body is rendered insensitive to pain (USA: local anesthesia). logarithmic scale (measurement) NON- LINEAR scale of measurement. For lochia (physiology) The NORMAL COMMON LOGARITHMS (to the BASE DISCHARGE from the womb after childbirth. 10), an increase of one UNIT represents It may last for one or two weeks. a tenfold increase in the quantity measured. lockjaw (bacteriology) See TETANUS. logic (1 mathematics; 2 computing) 1 The use of methods from mathematics locus (1 mathematics; 2 genetics) 1 Path and formal LOGIC to analyse the traced by a moving point, i.e. a line that underlying principles on which

246 LONE PAIR OF ELECTRONS LP mathematical systems are based. 2 In than on the body. Pthirus pubis is the electronic DATA-processing systems, crab LOUSE, found in the pubic HAIR the principles that define the interactions and usually spread by sexual intercourse. of DATA in the form of physical entities. low birthweight (physiology) Birthweight lone pair of electrons (chemistry) Pair less than 2.5 kg. Babies either preterm of unshared electrons of opposite spin (two thirds) or small-for-dates (one third). (in the same ORBITAL) that under suitable conditions can form a CO-ORDINATE BOND lowest common denominator (mathe- e.g. the NITROGEN ATOM in AMMONIA matics) Number that is the LOWEST has a lone pair of electrons; the OXYGEN COMMON MULTIPLE of all the denominators in WATER has two lone pairs. of a SET of fractions, necessary in ORDER to add or subtract the fractions; e.g. the long sight (medical) An alternative LOWEST COMMON DENOMINATOR of term for HYPERMETROPIA. 1/2, 1/3 and 1/4 is 12 (because these fractions can be expressed as 6/12, 4/ longitudinal study (statistics) Any study 12 and 3/12, and thereby added). of a GROUP of people over a long PERIOD of time, usually years. It avoids lowest common multiple (LCM) the problems that arise in retrospective (mathematics) Smallest number that studies and in cross-sectional studies, all the members of a GROUP of numbers but cannot take into account the effects will divide into; e.g. the LOWEST COMMON of repeated testing. MULTIPLE of 2, 3, 4 and 5 is 60. loop diuretics (pharmacology) DIURETICS low-pass filter (physics) A FILTER such as ethacrnic acid which act on that transmits from a waveform only the ascending tubules of the loop of frequencies below a given FREQUENCY. Henlé, inhibiting resorption of SODIUM, some POTASSIUM and water. Lowry-Brönsted theory (chemistry) Concept of acids and bases in which an ACIDis loptotene (genetics) Stage of PROPHASE defined as a substance with a tendency in the first CELL DIVISION in MEIOSIS. to lose a PROTON and a BASE as a At this stage, chromosomes can be substance with a tendency to GAIN an seen to carry chromomeres. ELECTRON. It was named after the British chemist Thomas Lowry (1874–1936) and louse (parasitology) A parasitic insect. the Danish chemist Johannes Brönsted There are many varieties of lice, but (1879–1947), who proposed it independently. only two which breed on man, Pediculus Also termed: Brönsted-Lowry theory. and Pthirus. Pediculus humanus capitis lives on the HEAD, and is common in See also LEWIS ACID AND BASE. schools, where it is spread by direct contact and by combs and hairbrushes. LOX (physics) An abbreviation of ‘L’iquid Pediculus humanus humanus is the ‘OX’ygen. body LOUSE, bigger than the HEAD LOUSE and capable of spreading Lp (general terminology) An abbreviation TYPHUS, relapsing FEVER and trench of ‘L’im‘p’. FEVER. It lives in the clothes rather

247 LP LUMINANCE

Ip (medical) An abbreviation of ‘l’atent luciferin (biochemistry) Substance that ‘p’eriod. occurs in the LIGHT-producing ORGAN of some animals, e.g. firefly. When oxidized Lr (chemistry) The CHEMICAL SYMBOL (through the ACTION of LUCIFERASE) for LAWRENCIUM. it produces BIOLUMINESCENCE.

LRCVS (education) An abbreviation Lugol’s iodine (chemistry) A SOLUTION of ‘L’icentiate of the ‘R’oyal ‘C’ollege of IODINE 5 per cent and POTASSIUM of ‘V’eterinary ‘S’urgeons. IODIDE 10 per cent in WATER.

LRIC (education) An abbreviation of lum. (1 medical; 2 physics) 1 An ‘L’icentiate of the ‘R’oyal ‘I’nstitute of abbreviation of ‘lum’bago. 2 An ‘C’hemistry. abbreviation of ‘lum’inous.

LRP (physiology/biochemistry) An lumbar (anatomy) Pertaining to the abbreviation of ‘L’DL ‘R’eceptor-related lower back, a region that comes between ‘P’rotein. the sacral and thoracic regions.

LSD (pharmacology) An abbreviation lumbar puncture (medical) The introduc- of ‘L’y‘S’ergic ACID ‘D’iethylamide. tion of a hollow needle into the spinal canal in ORDER to draw off a specimen LSHTM (education) An abbreviation of CEREBROSPINAL FLUID for of ‘L’ondon ‘S’chool of ‘H’ygiene and LABORATORY examination, or to introduce ‘T’ropical ‘M’edicine. drugs, spinal ANAESTHETICS (USA: spinal anesthetics) or RADIO-OPAQUE LTD (medical) An abbreviation of ‘L’ong- substances for X-RAY investigations. ‘T’erm ‘D’epression. The puncture is made between the third and fourth or fourth and fifth LUMBAR LTH (1 biochemistry; 2 education) 1 vertebrae, where the point of the needle An abbreviation for ‘L’uteo‘T’ropic cannot harm the SPINAL CORD, for it ‘H’ormone. 2 An abbreviation of ‘L’icentiate ends at the LEVEL of the second spinal in ‘T’ropical ‘M’edicine. VERTEBRA. The puncture is usually made under LOCAL ANAESTHESIA (USA: LTP (physiology) An abbreviation of local anesthesia). ‘L’ong-‘T’erm ‘P’otentiation. lumen (1 physics; 2 biology) 1 The SI Lu (chemistry) The CHEMICAL SYMBOL UNIT of LUMINOUS FLUX, equal to for LUTETIUM. the amount of LIGHT emitted by source of 1 candela through UNIT SOLID angle. lubricant (physics) Any substance used 2 The space enclosed by a duct, VESSEL to reduce friction between surfaces or tubular ORGAN. in contact; e.g. oil, graphite, molybdenum disulphide (USA: molybdenum bisulfide), luminance (L) (physics) The photometric silicone grease. INTENSITY of the LIGHT emitted or reflected by a surface per UNIT AREA. The standard luciferase (biochemistry) ENZYME that UNIT is candela per square METRE. initiates the OXIDATION of LUCIFERIN.

248 LUMINESCENCE LUTETIUM luminescence (physics) Emission of LIGHT lung (anatomy) The paired or single by a substance without any appreciable RESPIRATORY ORGAN located in the rise in TEMPERATURE. See BIOLUMINE- THORAX. Its surface contains a large SCENCE; FLUORESCENCE; INCANDE- AREA of thinly folded, moist EPITHELIUM SCENCE; PHOSPHORESCENCE. MEMBRANE so that it occupies little VOLUME. This MEMBRANE is richly supplied by luminosity (physics) The apparent BLOOD capillaries which allow for efficient brightness of a surface or LIGHT source. and easy gaseous exchange. AIR enters It tends to be used to MEAN the apparent and leaves lungs through the BRONCHUS, INTENSITY of a LIGHT as derived from which branches into bronchioles ending the luminous efficiency FUNCTION. in clusters of alveoli, where the main gaseous exchange takes place. The luminosity curve (physics) A curve respiratory system consists of the lungs, showing the relative RADIANT POWER AIR passages, the muscles that control needed by LIGHT of different wavelengths BREATHING, and the PLEURAL cavities. in ORDER for them to appear equally bright. lupus (medical) LUPUS vulgaris is TUBERCULOSIS of the SKIN, now luminous efficiency function (physics) increasingly rare; it occurs mostly on A FUNCTION that can be applied to the face and nose, taking the form of LIGHT of any MIXTURE of wavelengths small nodules which leave scars behind. to yield its apparent brightness or It responds to the anti-tubercular drugs. LUMINOSITY. It weights the INTENSITY of each WAVELENGTH according to the luteal phase (physiology) The stage of sensitivity of a hypothetical standard the MENSTRUAL CYCLE that starts with observer to that WAVELENGTH e.g. yellow OVULATION and ends, unless FERTILIZATION LIGHT receives a higher weighting than occurs, with the onset of MENSTRUATION; blue. Different functions are used for during this stage PROGESTERONE is scotopic, mesopic, and photopic conditions. secreted by the CORPUS LUTEUM. The photometric functions are only an approximation to those of real observers. luteinizing hormone (LH) (biochemistry) Compare LUMINOSITY CURVE. GLYCOPROTEIN HORMONE that is secreted by the PITUITARY under regulation luminous flux (physics) The total amount by the HYPOTHALAMUS. In females, it of LIGHT per UNIT time emitted from stimulates the formation of the CORPUS a source, as measured by PHOTOMETRY; LUTEUM and GRAAFIAN FOLLICLE, which the standard UNIT of measurement is in turn stimulates OESTROGEN (USA: the LUMEN. See PHOTOMETRY. estrogen) production. LH is also essential for OVULATION. In males, it stimulates luminous intensity (physics) The INTERSTITIAL CELLS of the TESTIS to LUMINOUS FLUX emitted per UNIT SOLID produce ANDROGENS. angle (steradian) by a LIGHT source; the standard UNIT of measurement is luteotrophin (biochemistry) An alternative the candela. See PHOTOMETRY. term for PROLACTIN. lunar caustic (chemistry) SILVER NITRATE. lutetium (Lu) (chemistry) Metallic ELEMENT in GROUP IIIB of the PERIODIC TABLE

249 LUX LYMPH NODE

(one of the LANTHANIDES). The irradiated Lyman series (physics) SERIES of lines METAL is a BETA-PARTICLE emitter, in SPECTRUM of HYDROGEN. It was named used in catalytic processes. At. no. 71; the physicist Theodore Lyman (1874–1954). r.a.m. 174.97. Lyme disease (microbiology) First de- lux (measurement) SI UNIT of illumination, scribed as the result of cases occurring equal to one LUMEN per square METRE. in Lyme in the USA in 1977, the disease Also termed: METRE-CANDLE. is caused by the MICRO-ORGANISM Borrelia bergdorferi, and spread by TICKS, See also PHOTOMETRY. mosquitoes and biting flies. The disease may continue, some months after the luxol fast blue/cresyl violet stain original INFECTION, to involve the joints, (histology) A histological staining especially the knee; the HEART, with technique that may be used to make irregular PULSE, shortness of breath myelin and nissl substance visible under and pain in the chest; and the central the MICROSCOPE. and PERIPHERAL NERVOUS SYSTEM, with encephalitis and neuritis. Similar luxury gene (genetics) A term rarely illnesses have occurred in Europe where used nowadays. A GENE that codes the TICK Ixodes ricinus is found to for a PRODUCT specific to one particular carry the disease, possibly from dogs. type of CELL, in contrast to HOUSE- KEEPING GENES. An example of a lymph (histology) The FLUID found in LUXURY GENE would be the GENE the LYMPH vessels; it is clear and slightly for INSULIN, which is active only in yellow, containing LYMPH CELLS and, certain CELLS in the PANCREAS, though if it derives from intestinal vessels, particles present in all CELLS. LUXURY GENES of fat. It is similar in SALT CONCENTRATION are switched off in all CELLS except to PLASMA, but possesses a lower the ones where their FUNCTION is needed. PROTEIN CONCENTRATION. It originates While they are inactive, the DNA of in the TISSUE spaces, being derived LUXURY GENES is highly condensed from the FLUID which filters through as HETEROCHROMATIN, and it shows the walls of the CAPILLARY BLOOD up as a dark-staining band. VESSELS. It may contain particles as big as BACTERIA if it is draining from Iv (physics) An abbreviation of ‘l’ow an infected AREA. ‘v’oltage.

LVET (physiology) An abbreviation of lymph node (histology) Flat, oval structure ‘L’eft ‘V’entricular ‘E’jection ‘T’ime. made of LYMPHOID TISSUE that lies in the lymphatic vessels and occurs LVI (physics) An abbreviation of ‘L’ow in clusters in the neck, armpit or groin. ‘V’iscosity ‘I’ndex. Its main FUNCTION is the manufacture of antibodies and leucocytes. LYMPH LVS (education) An abbreviation of NODES also act as a defence barrier ‘L’icentiate in ‘V’eterinary ‘S’cience. against the spread of INFECTION by filtering out foreign bodies and BACTERIA, lye (chemistry) SOLUTION of strong thus preventing their entry into the CAUSTIC ALKALI (e.g. POTASSIUM bloodstream. Also termed: LYMPH GLAND. HYDROXIDE, SODIUM HYDROXIDE). Also known as LYMPH GLANDS.

250 LYMPHADENITIS LYMPHOKINES lymphadenitis (histology) INFLAMMATION maturation. The two major classes of of LYMPH GLANDS, or nodes. LYMPHOCYTES, which are morphologically indistinguishable, are the B CELLS, the lymphadenopathy (medical) Disease EFFECTOR CELLS of the humoral IMMUNE of the LYMPH NODES. RESPONSE, and T CELLS, the EFFECTOR CELLS of the cellular IMMUNE RESPONSE. lymphatic leukaemia (haematology) LYMPHOCYTES circulate through the BLOOD See LEUKAEMIA. stream and lymphatic vessels, passing through the SPLEEN and LYMPH NODES, lymphatic system (histology) TISSUE which have filtered and retained ANTIGEN FLUID, consisting mainly of FLUID forced for presentation to the B and T CELLS. out of the capillaries by the PRESSURE They enter the LYMPH NODES from the of circulating BLOOD, is known as LYMPH, bloodstream via high endothelial venules and is in part recirculated by a system (HEV) in the NODE, percolate through known as the LYMPHATIC SYSTEM. The the LYMPH NODE and exit via the EFFERENT LYMPHATIC SYSTEM arises as capillaries lymphatics that drain into the venous system in the tissues that come together to at the thoracic duct. The SPLEEN is primarily form an interconnecting NETWORK of a BLOOD-filtering ORGAN, and LYMPHO- progressively larger vessels, similar to CYTES enter and exit via the capillaries. veins in structure. Flow is maintained largely by contraction of body muscles See also B CELLS; T CELLS. with valves preventing back flow; the system empties into the VENA CAVA lymphogranuloma (medical/microbiology) via the thoracic duct. As LYMPH moves Lymphogranuloma venercum is a through the system it passes through SEXUALLY TRANSMITTED DISEASE LYMPH NODES (LYMPH GLANDS is not Caused by INFECTION with the organism correct usage). LYMPH NODES contain Chlamydia trachomatis. The INFECTION T and B CELLS derived from the BONE is found in Africa, the Caribbean, South MARROW STEM CELLS and remove America and South-East Asia. foreign particles by PHAGOCYTOSIS. The SPLEEN and the THYMUS are both lymphoid tissue (histology) TISSUE largely composed of LYMPHOID TISSUE. found in dense aggregations in LYMPH NODES, tonsils, THYMUS and SPLEEN. See also B CELLS; SPLEEN; THYMUS. It produces LYMPHOCYTES and macrophagocytic CELLS, which ingest lymphocytes (haematology) The primary BACTERIA and other foreign bodies. nucleated CELLS of the LYMPHATIC SYSTEM. Also termed: lymphatic TISSUE. Resting LYMPHOCYTES are small, densely staining and have little CYTOPLASM. Activated lymphokines (biochemistry) Biologically LYMPHOCYTES enlarge and have increased active molecules produced by LYMPHOCYTES CYTOPLASM. LYMPHOCYTES comprise that have diverse effects on many different 20–80 per cent of the nucleated BLOOD CELL types. They can be produced in CELLS and more than 99 per cent of the RESPONSE to stimulation by ANTIGEN, CELLS in the LYMPHATIC SYSTEM. CELL contact or other LYMPHOKINES. LYMPHOCYTES originate from STEM CELLS The majority of LYMPHOKINES have been in the BONE MARROW and migrate to defined only functionally, although the secondary lymphoid organs for further structures of a few, such as interleukin

251 LYMPHOMA LYSOZYME are known. Most LYMPHOKINES have actions lysergic acid diethytamide (LSD) on several different target CELLS. (pharmacology) A SYNTHETIC substance, similar to some FUNGUS ALKALOIDS, lymphoma (medical) A number of conditions which provokes hallucinations and extreme that involve swelling of the LYMPH NODES mental disturbance if taken, even in which is not caused by INFLAMMATION, extremely small quantities. METASTATIC MALIGNANT disease or HODGKIN’S DISEASE, have been called lysergide (pharmacology) See LSD. lymphomas. They are rare, and the diagnosis is made on microscopical examination lysine (chemistry) H2N(CH2)4CH(NH2)- of LYMPH NODES removed at BIOPSY. COOH ESSENTIAL AMINO ACID that TREATMENT is by RADIOTHERAPY or occurs in proteins and is responsible CHEMOTHERAPY, according to the particular for their BASE-neutralizing powers needs of each case. because of its two -NH2 groups. Also termed: diaminocaproic acid. Lyon hypothesis (genetics) The theory that, in female mammals (SEX lysis (biology) The break-up of a CELL CHROMOSOMES XX), one X in each after the rupture of its CELL wall. This CELL is inactivated so as to achieve can be the result of attack by chemicals dosage compensation, the individual (e.g. detergents) or INFECTION (as then having the same amount of X- happens when BACTERIA are invaded CHROMOSOME activity as the male by bacteriophages), or the CELL may (XY). The X CHROMOSOME to be simply dissolve itself (AUTOLYSIS). inactivated is chosen at random, and this happens in different tissues at different See also VIRUS. times during the development of the EMBRYO (EMBRYOGENESIS). Once one lysogeny (genetics) The colonisation X has been inactivated in one CELL, of a HOST CELL by a VIRUS, which all CELLS derived from that CELL will gets itself replicated by the HOST’S have the same X inactivated. The female genetic machinery. mammal is a naturally occurring MOSAIC. The inactivated X CHROMOSOME can lysosome (cytology) MEMBRANE-bound be seen microscopically as the BARR ORGANELLE of eukaryotes that contains BODY. The theory is called after the a range of digestive ENZYMES, such British geneticist Mary F.Lyon. Also termed: as proteases, phosphatases, lipases inactive-X hypothesis. and nucleases. The functions of lysosomes include contributing ENZYMES to WHITE lyophilic (chemistry) Possessing an BLOOD CELLS during PHAGOCYTOSIS AFFINITY for liquids. and the destruction of CELLS and TISSUE during NORMAL development. lyophilized (chemistry) Freeze dried. Lysosomes may be produced directly from the ENDOPLASMIC RETICULUM lyophobic (chemistry) LIQUID-repellent, or by BUDDING of the GOLGI having no attraction for liquids. APPARATUS.

Lys (biochemistry) An abbreviation of lysozyme (biochemistry) ENZYME in ‘Lys’ine. SALIVA, EGG white, tears and MUCUS.

252 LYSOZYME LYSOZYME

It catalyses the destruction of BACTERIAL CELL walls by HYDROLYSIS of their mucopeptides, and thus has a BACTE- RICIDAL effect.

253 M

M (1 general terminolgy; 2 biochemistry) to appear the same brightness as the 1 An abbreviation of ‘M’ale. 2 An LIGHT from the surface. abbreviation of ‘M’ethionine. machine code (computing) The BASIC m (measurement) An abbreviation of SET of instructions for a COMPUTER, ‘m’etre (USA: meter). which are in BINARY CODE and can be directly implemented by the CENTRAL ma (general terminology) An abbreviation PROCESSOR. They are limited in both of ‘m’enstrual ‘a’ge. number and scope. These instructions are used to construct the more complex MA (general terminology) An abbreviation and versatile instructions of high-LEVEL for ‘M’ental ‘A’ge. languages, which must be translated back into MACHINE CODE when a higher- mA (physics) milliAMPERE. LEVEL PROGRAM is run. mAb (immunology) An abbreviation of machine language (computing) See ‘m’onoclonal ‘A’nti‘b’ody. MACHINE CODE. mabp (physiology) An abbreviation of macro (computing) A procedure or ‘m’ean ‘a’rterial ‘b’lood ‘p’ressure. OPERATOR built from a sequence of other procedures or operators. Macchiavello stain (histology) A histological staining technique that may macro- Prefix meaning large or long be used to make RICKETTSIAE, viral in size or duration. inclusions, visible under the MICROSCOPE. macrocephaly (medical) A CONGENITAL MACD (education) An abbreviation of disorder in which the HEAD is swollen ‘M’ember of the ‘A’ustralasian ‘C’ollege through excess CEREBROSPINAL FLUID of ‘D’ermatologists. and the person is mentally retarded. maceration (histology) The softening macrocyclic (chemistry) Describing of a SOLID by FLUID. In medicine, a chemical COMPOUND whose molecules the softening and damaging of the have a large ring structure. tissues by WATER, as in the case of a corpse many hours drowned. macrolides (pharmacology) See ANTIBIOTIC. Macheth illuminometer (physics) A device for measuring LUMINANCE; an macromolecule (chemistry) Very large observer views a surface through it MOLECULE containing hundreds or and adjusts a LIGHT of known INTENSITY thousands of atoms; e.g. natural polymers

254 MACRONUTRIENT MAGNESIUM CHLORIDE such as CELLULOSE, rubber and STARCH, foot swells and its tissues and bones and SYNTHETIC ones, including plastics. become riddled with sinuses caused by INFECTION with a FUNGUS. It is macronutrient (biology) Food substance one of a GROUP of CHRONIC infections needed in fairly large amounts by living called mycetomas, caused by FUNGI organisms, which may be an inorganic or ACTINOMYCETES. The disease may ELEMENT (e.g. PHOSPHORUS or attack many areas of the body but the POTASSIUM in plants) or an ORGANIC legs and feet are most commonly affected. COMPOUND (e.g. AMINO ACIDS and carbohydrates in animals). mag (physics) An abbreviation of ‘mag’net/ ‘mag’netic/‘mag’netism. See also VITAMINS; TRACE ELEMENT. magnesia (chemistry) MAGNESIUM macrophages (cytology) Large CELLS OXIDE, MgO, particularly a form that present in CONNECTIVE TISSUE and has been processed and purified. It in the walls-of BLOOD VESSELS. They is used as an ANTACID. can be found in the PLEURAL and peritoneal cavities, the lungs (ALVEOLAR magnesium (chemistry) A metallic MACROPHAGES), the LIVER (KUPFFER ELEMENT used in medicine in the form CELLS), CONNECTIVE TISSUE of its salts: MAGNESIUM CARBONATE, (histiocytes), the LYMPH NODES and HYDROXIDE and trisilicate are used other tissues. MACROPHAGES are highly as antacids in the TREATMENT of PEPTIC phagocytic and serve in the first line of ULCERS and GASTRITIS. MAGNESIUM defence against MICROORGANISMS. They HYDROXIDE MIXTURE (milk of form part of the reticulo-endothelial system. MAGNESIUM) has a slight laxative ACTION, and MAGNESIUM SULPHATE (USA: MACS (education) An abbreviation of magnesium sulfate) (EPSOM SALTS) a ‘M’ember of the ‘A’merican ‘C’hemical more powerful one. The ELEMENT is a ‘S’ociety. constituent of chlorophyll, and so an essential part of life; it is essential for macula (anatomy) Any small blemish, human beings, playing a part in the used in anatomy to MEAN an AREA functioning of NERVES and muscles, distinguishable from its surroundings and in ENERGY METABOLISM. A NORMAL by its COLOUR (USA: color) or other diet supplies the requirements. peculiarity e.g. the MACULA of the RETINA is a YELLOW SPOT at the back of the magnesium carbonate (chemistry) MgCO3 RETINA, which has in it a central depression White CRYSTALLINE COMPOUND, called the FOVEA, where the RETINA SOLUBLE in acids and INSOLUBLE in is thinnest and the vision most ACUTE. WATER and ALCOHOL, which occurs naturally as magnesite and dolomite. It macule (histology) A flat discoloured is used, often as the BASIC CARBONATE, (USA: discolored) spot in the SKIN, as an ANTACID. as distinct from a papule, which is a raised spot. magnesium chloride (chemistry) MgCI2 White CRYSTALLINE COMPOUND obtained Madura foot (medical/mycology) A from sea-WATER and the mineral carnallite, disease of the tropics in which the used as a source of MAG ESIUM.

255 MAGNESIUM HYDROXIDE MAGNETIC INDUCTION magnesium hydroxide (pharmacology) netic ring wound with wires; a CURRENT

Mg(OH)2 White CRYSTALLINE COMPOUND, flowing in the wires polarizes the CORE, used as an ANTACID. which can therefore adopt one of two states (making it a bistable device). magnesium Mg (chemistry) Reactive SILVER-white metallic ELEMENT in GROUP magnetic disk (computing) Device for IIA of the PERIODIC TABLE (the ALKALINE direct-access STORAGE and retrieval EARTHS). It burns in AIR with a brilliant of DATA, used in computers and similar WHITE LIGHT, and is used in flares systems. It consists of a rotatable flexible and lightweight ALLOYS. It is the METAL or rigid plastic disc (i.e. a floppy or ATOM in chlorophyll and an important HARD DISK) coated on one or both TRACE ELEMENT in plants and animals. surfaces with magnetic material, such At. no. 12; r.a.m. 24.305. as IRON OXIDE. DATA is stored or retrieved through one or more read/write heads. magnesium oxide (chemistry) MgO White Also termed: magnetic disc. CRYSTALLINE COMPOUND INSOLUBLE in WATER and ALCOHOL, made by magnetic domain (physics) GROUP heating MAGNESIUM CARBONATE. It of atoms with aligned magnetic moments is used as a refractory and ANTACID. that occur in a ferromagnetic material. Also termed: MAGNESIA. There are many randomly oriented domains in a permanent MAGNET. magnesium silicate (chemistry) See TALC. magnetic drum (computing) COMPUTER magnesium sulphate (pharmacology) See STORAGE DEVICE consisting of a EPSOM SALT. rotatable drum coated with magnetic material, such as IRON OXIDE. DATA magnet (physics) OBJECT possessing is stored or retrieved through one or the property of MAGNETISM, either more read/write heads. permanently (a permanent MAGNET, made of a ferromagnetic material) or magnetic field (physics) FIELD of FORCE temporarily under the influence of another in the space around the magnetic poles MAGNET or the MAGNETIC FIELD of a MAGNET. associated with an ELECTRIC CURRENT (an ELECTROMAGNET). magnetic field strength (physics) An alternative term for MAGNETIC INTENSITY. See also PARAMAGNETISM. magnetic flux (physics) Measure of the magnetic amplifier (physics) TRANSDUCER total size of a MAGNETIC FIELD, defined so arranged that a small controlling DIRECT as the scalar PRODUCT of the flux DENSITY CURRENT input can produce large changes and the AREA. Its SI UNIT is the WEBER. in coupled ALTERNATING CURRENT circuits. magnetic flux density (physics) PRODUCT magnetic circuit (physics) Completely of MAGNETIC INTENSITY and PERME- closed path described by a given SET ABILITY. Its SI UNIT is the tesla (formerly of lines of MAGNETIC FLUX. WEBER m-2). magnetic core (computing) COMPUTER magnetic induction (physics) In a magnetic STORAGE DEVICE consisting of a ferromag material, MAGNETIZATION induced in

256 MAGNETIC INTENSITY MALARIA it, e.g. by placing it in the electromagnetic FIELD, used, e.g. in prospecting for field of a CURRENT-carrying coil or by minerals. stroking it with a permanent MAGNET. magneton (measurement) UNIT for the magnetic intensity (physics) Magnitude magnetic moment of an ELECTRON. of a MAGNETIC FIELD. Its SI UNIT is Also termed: Bohr-magneton. the AMPERE m-2. Also termed: MAGNETIC FIELD STRENGTH; magnetizing FORCE. magnification (optics) The ratio y’/y, where y is the height of an OBJECT magnetic lens (microscopy) Arrangement perpendicular to the OPTICAL AXIS of electromagnets used to FOCUS a and y’ is the corresponding height of beam of charged particles (e.g. electrons its magnified IMAGE. For a single LENS in an ELECTRON MICROSCOPE). this is equivalent to the ratio of the IMAGE distance to the OBJECT distance. magnetic resonance imaging (MRI) (physics) See NUCLEAR MAGNETIC maintenance level (physiology) The RESONANCE I(NMR) MAGING. magnetism LEVEL of GROWTH at which further (physics) Presence of magnetic properties physical development ceases. in materials. Diamagnetism is a weak effect common to all substances and major histocompatibility complex (genetics) results from the ORBITAL motion of electrons. The GROUP of genes that control the In certain substances this is masked by HLA (human LEUCOCYTE ANTIGEN) system. a stronger effect, PARAMAGNETISM, due to ELECTRON spin. Some paramagnetic See also IMMUNE SYSTEM. materials such as IRON also DISPLAY FERROMAGNETISM, and are permanently mal (medical) Sickness, disease. magnetic. malaise (medical) A vague feeling of magnetization (physics) Difference general discomfort. between the ratio of the MAGNETIC INDUCTION to the permeability and malaria (parasitology) An INFECTIOUS the MAGNETIC INTENSITY; its SI UNIT DISEASE in which the RED BLOOD CELLS is the AMPERE m-1. It represents are attacked by the Protozoan PARASITE departure from randomness of MAGNETIC Plasmodium, which is transmitted from DOMAINS. one infected person to another by Anopheles mosquitoes. MALARIA is common in tropical magnetochemistry (chemistry) Study areas, and used also to be common of the magnetic properties of chemicals. around the Mediterranean until mosquito numbers were reduced, partly through magnetohydrodynamics (MHD) (physics) loss of their habitat as marshes were Branch of physics that deals with the drained and partly by insecticidal campaigns. BEHAVIOUR (USA: behavior) of a In those areas still affected by MALARIA, conducting FLUID under the influence prevention is better than cure, and of a MAGNETIC FLUX. SYNTHETIC QUININE-like drugs are effective in deterring the Plasmodium magnetometer (physics) Instrument PARASITE. MALARIA, which causes high for measuring the strength of a MAGNETIC FEVER that often recurs for years after

257 MALIC ACID MAMMALIAN CELL MUTATION TESTS the original INFECTION, is a dangerous defective GENE from one parent to disease, so it is not surprising that in more complex genetic patterns. VOLATILE areas where it is (or was) ENDEMIC gaseous inhalation anaesthetics, as well genes that confer protection against it as the MUSCLE relaxant succinylcholine, have been selected for and are common can trigger it, whereas injectable local in the population. Unfortunately, in most anesthetics, barbiturates, opioids, other cases these genes ‘buy’ protection against SEDATIVE-hypnotics, and NITROUS MALARIA at the cost of giving people OXIDE, are safe for persons susceptible who are HOMOZYGOUS for the GENE to this disorder. another disease: the two best examples are sickle-CELL ANAEMIA (USA: sickle- malignant tertian malaria (microbiology) cell anemia) and THALASSAEMIA (USA: MALARIA caused by Plasmodium thalassemia), and another is GLUCOSE- falciparum. 6-PHOSPHATE DEHYDROGENASE deficiency (but one ANTIGEN in the Duffy malleus (anatomy) A small hammer- BLOOD GROUP SERIES seems to give shaped BONE in the MIDDLE EAR, protection without deleterious effects) one of the OSSICLES. It is SET in motion by the EAR DRUM and transmits malic acid (chemistry) COOHCH2CH(OH)- sound vibrations to the INCUS. COOH Colourless (USA: colorless) CRYSTALLINE CARBOXYLIC ACID with Mallory cell (physics) An alternative an agreeable sour TASTE resembling term for MERCURY CELL. that of apples, found in unripe fruit. It is used as a flavouring agent. malnutrition (biochemistry) A condition arising from deficiency in the diet or malignant (medical) When used of a deficiency in the ABSORPTION or TUMOUR (USA: tumor) it means METABOLISM of food. cancerous; the term is also applied to dangerous conditions which progress Malpighian body (anatomy) Part of rapidly such as MALIGNANT MALARIA the mammalian KIDNEY, BOWMAN’S or MALIGNANT HYPERTENSION. CAPSULE and GLOMERULUS. Its FUNCTION is to FILTER BLOOD. It malignant hyperthermia (medical) was named after the Italian biologist MALIGNANT HYPERTHERMIA ia a lethal Marcello Malpighi (1628–1694). complication related to anaesthesia (USA: anesthesia). This SYNDROME is a CHAIN Malta fever (bacteriology) See BRU- REACTION of abnormalities triggered CELLOSIS. in susceptible individuals by commonly used general anaesthetics. The signs maltose (chemistry) C12H22O11 Common include greatly increased body DISACCHARIDE SUGAR, composed of METABOLISM, MUSCLE rigidity, and two molecules of GLUCOSE. It is found eventual hyperthermia that may exceed in STARCH and GLYCOGEN, and used 44°C. Death can result from CARDIAC in the food and brewing industries. arrest, BRAIN damage, internal hemorrhaging or failure of other body mammalian cell mutation tests systems. Susceptibility is inherited, (toxicology) The mutagenicity of chemicals although the basis varies from a single is tested in cultured mammalian CELLS,

258 MAMMARY GLAND MANTISSA such as Chinese hamster OVARY CELLS manganese Mn (chemistry) Metallic or mouse LYMPHOMA CELLS. ELEMENT in GROUP VIIA of the PERIODIC TABLE, used mainly for making special mammary gland (histology) The GLAND ALLOY steels and as a deOXIDIZING in the female breast that secretes milk. AGENT. It is also an essential TRACE ELEMENT for plants and animals. At. mammillary bodies (histology) Two no. 25; r.a.m. 54.9380. protrusions at the bottom of the POSTERIOR HYPOTHALAMUS—the MEDIAL and manganese(IV) oxide (chemistry) MnO2 LATERAL mammillary nuclei. They are Black AMORPHOUS COMPOUND, used implicated in emotion and the sexual drive. as OXIDIZING AGENT, CATALYST and depolarizing agent in dry batteries. mammogram (radiology) A radiological Also termed: MANGANESE DIOXIDE. examination of the breast to identify or exclude tumours (USA: tumors). It manganic (chemistry) An alternative is simple, and recommended as a three- term for MANGANESE(III) in MANGANESE yearly routine in women between the compounds. ages of 50 and 65. manganous (chemistry) An alternative man. (general terminology) An abbrevia- term for MANGANESE(II) in MANGANESE tion of ‘man’ual. A guidebook explaining compounds. the use of a PRODUCT or the operations of an organisation. Mann Whitney U Test (statistics) A nonparametric test of whether two mandible (anatomy) The lower jawbone. independent samples come from the same population. It is equivalent to Wilcoxon’s mandibular nerve (anatomy) Sensory test. The test compares each value in nerve which supplies the TEETH, the one SAMPLE with each value in the other temple, the floor of the mouth and but does not require ranking, as in Wilcoxon’s the back part of the TONGUE. ALGORITHM. It is a nonparametric version of a T-TEST for independent samples. manganese Mn (chemistry) An ELEMENT Compare KRUSKALWALLACE TEST. that is essential as a cofactor for many ENZYMES, including hexokinase, mannitol (chemistry) HO.CH2(CHOH)4- XANTHINE OXIDASE and SUPEROXIDE CH2OH SOLUBLE hexahydric ALCOHOL dismutase. Although the ELEMENT is that occurs in many plants, and is essential for life, only MINUTE quantities used in medicine as a diuretic. are needed; no cases of MANGANESE deficiency have been recorded. It may manometer (physics) A device for be used in medicine in the form of measuring FLUID PRESSURE. POTASSIUM PERMANGANATE as an ANTISEPTIC. If MANGANESE fumes or manoptoscope (measurement) A device dust are inhaled to excess, patients develop for measuring EYE dominance. a condition very like Parkinson’s disease. mantissa (mathematics) Fractional part manganese dioxide (chemistry) An alternative of a LOGARITHM (the other part is the term for MANGANESE (IV) OXIDE. CHARACTERISTIC); e.g. in the LOGARITHM 2.3010, the .3010 part is the MANTISSA.

259 MANTOUX TEST MARROW

Mantoux test (bacteriology) A test infected body fluids, and the same is for INFECTION with tuberculosis. An true of INFECTION from man to man. injection of a SOLUTION of purified PROTEIN DERIVATIVE of tuberculin Marchi stain (histology) A histological (PPD) is made into the SKIN, and a stain that makes myelinated NERVE POSITIVE REACTION of INFLAMMATION FIBRES (USA: nerve fibers) visible. in the SKIN over 10 mm in size is likely to indicate an INFECTION. The Marfan’s Syndrome (medical/genetics) Heaf test is a VARIATION of the MANTOUX An inherited SYNDROME characterised TEST. Named after the French physician, by long thin fingers, toes, arms and Charles Mantoux (1877–1947). legs, increased height, deformity of the SPINE and BREASTBONE, and abnormality MAO (biochemistry) An abbreviation of the HEART and eyes. The aortic VALVE for ‘M’ono‘A’mine ‘O’xidase. in the HEART is incompetent, and the LENS of the EYE is dislocated. These MAOI (biochemistry) An abbreviation various effects are the result of a single for ‘M’ono‘A’mine ‘O’xidase ‘I’nhibitors. DOMINANT GENE, though the biochemical mode of action is not known. The symptoms map unit (genetics) A measure of the do not cause any ill health until middle distance between two loci on the same age, when the HEART deformities often CHROMOSOME. Loci are 1 MAP UNIT prove fatal; thus people with the apart if cross-over occurs between them SYNDROME have usually already had in 1 per cent of cases. A MAP UNIT children by the time they are diagnosed, has the formal name of centimorgan. and the GENE has been passed on to the next generation. About one person marasmus (medical) Progressive wasting in 25,000 has Marfan’s SYNDROME. away, particularly in infants. Named after the French physician, Bernard Jean Antonin Marfan (1858–1942). Marburg disease (virology) A VIRUS INFECTION first described in 1967 when marihuana (toxicology) An alternative it affected LABORATORY workers in spelling of MARIJUANA. Marburg who had been in contact with a GROUP of vervet monkeys from Uganda. marijuana (toxicology) A NARCOTIC In 1976 there was an outbreak of severe prepared from hemp. It has mildly haemorrhagic FEVER (USA: hemorrhagic hallucinogenic effects. fever) in the Sudan and Zaire which was found to be caused by a VIRUS marrow (histology) The MARROW of identical with the Marburg VIRUS, but the bones in an adult is red or yellow. carrying a different ANTIGEN. This was Red MARROW is found in the SKULL, called the Ebola VIRUS. Both infections ribs, PELVIS, BREASTBONE, the bodies are now referred to as African haemorrhagic of the vertebrae and the ends of the FEVER, and a number of cases have long bones. It is actively engaged in occurred. Although the cases at Marburg making the CELLS of the BLOOD. Yellow were connected with monkeys, it has MARROW is full of fat; in early life, it not been proved that monkeys are the is active and red, but by the end of carriers of the disease. INFECTION from the PERIOD of GROWTH it has become monkey to man was by contact with inactive. In times of crisis it is still

260 MARTINOTTI CELLS MAST CELLS capable of regaining activity, and it mass spectrograph (physics) VACUUM then becomes red again. system in which POSITIVE rays of charged atoms (ions) are passed through electric Martinotti cells (cytology) Spindle-shaped and MAGNETIC FIELDS so as to separate cells with CELL bodies in the internal them in ORDER of their CHARGE/MASS GRANULAR LAYER of the CORTEX, ratios on a photographic plate. It measures and with axons extending to the CELL precisely the RELATIVE ATOMICMASS bodies of the outer pyramidal layer. es of isotopes.

MAS (education) An abbreviation of mass spectrometer (physics) MASS ‘M’aster of ‘A’pplied ‘S’cience. Also SPECTROGRAPH that uses electrical termed MASc. methods rather than photographic ones to detect charged particles. maser (physics) An abbreviation of ‘m’icrowave ‘a’mplification by ‘s’timulated mass spectrum (physics) Indication ‘e’mission of ‘r’adiation. A precise of the distribution in MASS, or in mass/ ENERGY-emitting device that amplifies charge ratio, of ionized atoms or molecules ELECTROMAGNETIC WAVES into the produced by a MASS SPECTROGRAPH. MICROWAVE SPECTRUM. massage (medical) A manipulative mass (physics) Quantity of MATTER TREATMENT used in physiotherapy. in an OBJECT, and a measure of the The masseur or masseuse uses passive extent to which it resists ACCELERATION movements of the muscles, limbs and if acted on by a FORCE (i.e. its INERTIA). joints, and by stroking, pinching, pressing The SI UNIT of MASS is the KILOGRAM. and kneading stimulates the tissues.

See also WEIGHT. mass-energy equation (physics) A deduction from Einstein’s special theory mass decrement (chemistry) See MASS of RELATIVITY that ENERGY has MASS; DEFECT. E= mc2, where E is the ENERGY, m is the amount of MASS, and c the speed mass defect (1, 2 chemistry) 1 Difference of LIGHT. between the MASS of an atomic NUCLEUS and the masses of the particles Masson/Fontana stain (histology) A that make it up, equivalent to the BINDING histological staining technique that may ENERGY of the NUCLEUS (expressed be used to make MELANIN visible under in MASS units). 2 MASS of an ISOTOPE the MICROSCOPE. minus its MASS NUMBER. Also termed: mass decrement; mass excess. massons trichome (histology) A histological staining technique that may mass number (A) (chemistry) Total number be used to make CONNECTIVE TISSUE of protons and neutrons in an atomic visible under the MICROSCOPE. NUCLEUS. Also termed: NUCLEON NUMBER. mast cells (cytology) Large CELLS found in many places in the body, See also ISOTOPE. particularly in CONNECTIVE TISSUES and the mucosal surfaces. If they are

261 MASTECTOMY MATERNAL EFFECT damaged, or activated by an ANTIBODY- mastoiditis (medical) INFLAMMATION ANTIGEN REACTION, they release of the AIR CELLS in the mastoid process HISTAMINE and other substances which of the temporal BONE, once not increase the passage of FLUID from uncommon in association with middle the BLOOD VESSELS, lower the BLOOD EAR disease, but since the advent of PRESSURE, increase SECRETION from antibiotics rarely seen. the MUCOUS MEMBRANES, and contract SMOOTH MUSCLES. They also attract mat. (medical) An abbreviation of WHITE BLOOD CELLS. Massive ‘mat’ernity. activation of the MAST CELLS results in anaphylactic shock. matched groups (statistics) Groups assigned to different experimental mastectomy (medical) The removal conditions but not differing in other of the breast. Simple MASTECTOMY ways, e.g. in IQ or age, that might be is the removal of the breast alone; relevant to the outcome of the experiment. RADICAL MASTECTOMY, which may The expression is sometimes used of be carried out for CANCER, involves the MATCHED PAIRS METHOD, which removal of the breast together with is a special case. the muscles on which it lies and the LYMPH NODES in the armpit. matched pairs method (statistics) Obtaining two MATCHED GROUPS by mastic (microscopy) A RESIN derived matching each member of one GROUP from the tree Pisiacia lentiscus, used against a member of the other GROUP in microscopy and dentistry. by reference to qualities other than those under investigation. masticatory nerve (histology) An alternative term for MANDIBULAR NERVE. matched sample (1 statistics; 2 general terminology) A SAMPLE chosen in such mastitis (medical) ACUTE MASTITIS a way that each member of it is the is an INFLAMMATION of the breast same on some CHARACTERISTIC or which most commonly occurs in nursing characteristics (other than those being mothers in association with cracked investigated) as a member of another or depressed nipples. TREATMENT is SAMPLE to be compared with it; e.g. by PENICILLIN; feeding from the NORMAL the same subjects may each be run under breast may not have to be stopped, two conditions. In this case a paired although the milk should be expressed comparison test can be run on the differences manually from the infected breast while in the effects of the two conditions. Contrast it is inflamed. CHRONIC MASTITIS is independent samples. 2 A SAMPLE chosen not an INFECTION, but a name used in such a way that its members are on for changes which produce BENIGN AVERAGE the same on some category lumps in the breast, possibly in association as those of another SAMPLE, but are with cysts; the changes are probably not necessarily matched pair by pair. dependent on hormonal imbalance, for it is found that the condition is improved maternal effect (genetics) The situation by the contraceptive pill. in which the PHENOTYPE of the offspring is determined not by its own GENOTYPE but by its mother’s. There is some

262 MATERNAL INHERITANCE MAXIMUM LIKELIHOOD PRINCIPLE evidence to suggest that left-handedness mating increase homozygosity; outbreeding in humans is inherited in this way. and negative assortative mating increase heterozygosity. See also MATERNAL INHERITANCE. matrix (1 biology; 2 mathematics) 1 maternal inheritance (genetics) Any EXTRACELLULAR substance that embeds effect on the offspring that is not genetically and connects CELLS, e.g. CONNECTIVE transmitted but is passed on through TISSUE. 2 Square or rectangular ARRAY the CYTOPLASM of the EGG, i.e. of elements, e.g. numbers. cytoplasmic INHERITANCE. MATERNAL INHERITANCE is the explanation of the matter (physics) Substance that occupies situation in which a cross between a space and has the property of INERTIA. Strain A female and a Strain B male These two characteristics distinguish gives a different result from a cross MATTER from ENERGY, the various between a Strain B female and a Strain forms of which make up the rest of A male (assuming that X-LINKAGE has the material universe. been ruled out). See also MASS. See also MATERNAL EFFECT. max. (measurement) An abbreviation mathematical probability (mathematics) of ‘max’imum. The highest amount Expression of the extent to which an possible. event is likely to occur, given a value between 0 (an impossibility) and 1 (a maxilla (anatomy) The BONE of the certainty); e.g. the probability of getting upper JAW, which also takes part in a 6 on one roll of a dice is 1/6 or 0.16666… the formation of the orbit or EYE-socket, the nose and the hard palate. It contains mathematics (mathematics) Branch the maxillary ANTRUM or SINUS, a of science concerned with the study hollow cavity which communicates with of numbers, quantities and space. the nose and is liable to become inflamed in sinusitis. mating system (genetics) The system within a population by which mates maximum and minimum thermometer are chosen. At one extreme are (physics) THERMOMETER that records PARTHENOGENESIS and self- the maximum and minimum temperatures FERTILIZATION; at the other is random attained during a given PERIOD of time. mating. There may be systematic INBREEDING or outbreeding, or maximum individual risk (MIR) (toxicology) assortative mating in respect of one Increased risk for an individual exposed or more traits. Some MATING SYSTEMS to the highest measured or predicted involve equal numbers of both sexes; CONCENTRATION of a TOXICANT. in others, members of one sex have multiple mates. All MATING SYSTEMS maximum likelihood principle (statistics) have an effect on the genetic constitution The principle that we should estimate of the succeeding generations: under the value of a population parameter random mating, it stays the same; as the value which maximizes the INBREEDING and POSITIVE assortative likelihood of the obtained DATA.

263 MAXIMUM RESIDUE LIMIT MDR maximum residue limit (MRL) (toxicology) mcg (measurement) An abbreviation The LIMIT on the amount of an ‘additive’ of ‘m’i‘c’ro‘g’ram. (1/1,000,000 of a that may be present in food. gram). Scientifically expressed as µg. maxwell (measurement) C.g.s. UNIT Mcnemar’s test (statistics) A non- of MAGNETIC FLUX, the SI UNIT being parametric test for the significance of the WEBER. 1 maxwell=10-8 WEBER. the difference between two proportions It was named after the British physicist in MATCHED SAMPLES, usually used James Clerk Maxwell (1831–79). when the same SET of subjects are tested at two different times. May Grunwald-Giemsa (histology) A histological stain for AIR dried cytology MCPA (education) An abbreviation of preparations. ‘M’ember of the ‘C’ollege of ‘P’athologists of ‘A’ustralia. MB (education) An abbreviation of ‘M’edicinae ‘B’accalaureus. [Latin, MCRA (education) An abbreviation of meaning ‘Bachelor of Medicine’.] ‘M’ember of the ‘C’ollege of ‘R’adiologists of ‘A’ustralia. mb (measurement) An abbreviation of ‘m’illi‘b’ar. M-CSF (physiology) An abbreviation of ‘M’acrophage ‘C’olony-‘S’timulating MBAC (education) An abbreviation of ‘F’actor. ‘M’ember of the ‘B’ritish ‘A’ssociation of ‘C’hemists. MD (1, 2 education; 3 medical) 1 An abbreviation of ‘M’edical ‘D’epartment. mbc (physiology) An abbreviation of 2 An abbreviation of ‘M’edicinae ‘D’octor. ‘m’aximum ‘b’reathing ‘c’apacity. [Latin, meaning, ‘Doctor of Medicine’. The graduate DEGREE awarded to a MBCO (education) An abbreviation of student who has successfully completed ‘M’ember of the ‘B’ritish ‘C’ollege of a predetermined course of study in ‘O’phthalmic ‘O’pticians/‘O’ptometrists. medicine.] 3 An abbreviation of ‘M’uscular ‘D’ystrophy. mbp (physiology) An abbreviation of ‘m’ean ‘b’lood ‘p’ressure. Md (chemistry) The CHEMICAL SYMBOL for ELEMENT 101, MENDELEVIUM. mbr (general terminology) An abbreviation of ‘m’em‘b’e‘r’. MDM (pharmacology) See MDMA. mc (1, 2 measurement) 1 An abbrevia- MDMA (pharmacology) An abbreviation tion of ‘m’ega‘c’ycle. 2 An abbreviation of ‘M’ETHYLENE‘D’ioxy-‘M’eth‘A’mphet- of ‘m’illi‘c’uries, a measurement for amine. An antidepressant used in RADIUM. THERAPY. Commonly referred to as Ecstasy. M cells (histology) An abbreviation of ‘M’icrofold ‘CELLS’. mdr (physiology) An abbreviation of ‘m’inimum ‘d’aily ‘r’equirement.

264 MDSC MED

MDSc (education) An abbreviation of affects children between the ages of ‘M’aster of ‘D’ental ‘Sc’ience. three and six; up to a year old, children are protected by the antibodies passed ME (1 forensics; 2 physiology) 1 An to them by their mother. The infecting abbreviation of ‘M’edical ‘E’xaminer. organism is a paramyxovirus, which 2 An abbreviation of ‘M’etabolizable is spread in droplets by coughing or ‘E’nergy, sneezing. One attack of MEASLES confers IMMUNITY for life. mean (statistics) The arithmetical AVERAGE, i.e. the sum of all the values meatus (anatomy) Duct or channel between divided by the number of individuals. body parts, e.g. external AUDITORY MEATUS, the opening to the EAR. See also MEDIAN; MODE; NORMAL DISTRIBUTION. mechanoreceptor (physiology) A RECEPTOR sensitive to a mechanical mean average (mathematics) See FORCE, e.g. PRESSURE receptors, ARITHMETIC MEAN; GEOMETRIC MEAN. hair-cells, MUSCLE receptors. mean corpuscular haemoglobin (haema- Meckel’s diverticulum (histology) A tology) A measure of the HAEMOGLOBIN hollow blind appendage sometimes found (USA: hemaglobin) content of RED BLOOD growing from the SMALL INTESTINE CELLS. (USA: mean corpuscular hemaglobin). about 50 cm from the ileo-caecal junction. It varies in size, the AVERAGE length mean corpuscular volume (haematology) being about 5 cm. It is the remains of A measure of the VOLUME of RED a structure in the EMBRYO called the BLOOD CELLS. vitellointestinal duct, which in the early stages of development connects the mean deviation (statistics) Of a GROUP YOLK SAC to the midgut. It may be of numbers, the sum of all deviations connected to the UMBILICUS by a fibrous from the ARITHMETIC MEAN divided cord. In later life it may be the seat of by the quantity of numbers in the GROUP. INFECTION, or ulceration, because in some cases it contains GASTRIC CELLS. mean life (1 satistics; 2 physics) 1 It is possible for the GUT to become AVERAGE time for which the unstable twisted round a persisting connection NUCLEUS of a radioisotope exists before to the UMBILICUS, causing an obstruction. decaying. 2 AVERAGE time of survival Named after the German anatomist, of an ELEMENTARY PARTICLE, ION, Johann Friedrich Meckel II (1781–1833). etc. in a given medium or of a CHARGE CARRIER in a semiconductor. meconium (physiology) A dark green semi-FLUID material consisting of BILE, mean square (statistics) The ARITHMETIC MUCUS, desquamated CELLS, and debris MEAN of the squared deviations from discharged from the infant’s BOWEL the MEAN, i.e. the VARIANCE. at birth or immediately afterwards. measles (virology) An ACUTE VIRUS MED (pharmacology) An abbreviation INFECTION which appears in epidemics, of ‘M’inimal ‘E’ffective ‘D’ose. often in the winter and spring. It commonly

265 MED. MEDICINES ACT med. (1 medical; 2 statistics) 1 An median eminence (histology) A swelling abbreviation of ‘med’ical/‘med’icine. at the BASE of the HYPOTHALAMUS 2 An abbreviation of ‘med’ium/‘med’ian. that releases HORMONES into the portal circulation of the ANTERIOR PITUITARY. medial (anatomy) Toward the mid-line of the body or of an ORGAN. Contrast median lethal dose (toxicology) See LATERAL. LD50. medial dorsal nucleus (cytology) An median nerve (histology) One of the alternative term for dorsomedial NUCLEUS. NERVES of the arm. It originates in the brachial PLEXUS of NERVES in medial forebrain bundle (MFB) (histology) the ROOT of the neck, runs down the A tract of axons passing through the upper arm, passes in front of the elbow, LATERAL HYPOTHALAMUS and running down the forearm and ends in the palm in both directions between the FOREBRAIN of the hand. and brainstem. It has many connections with the limbic system and self-stimulation median test (statistics) A nonparametric can readily be obtained from it. test for the significance of the difference between two or more samples. The medial geniculate nucleus (cytology) MEDIAN for all samples combined is A NUCLEUS in the THALAMUS relaying calculated; in each SAMPLE the number AUDITORY information received from of values above and below the combined the INFERIOR colliculus to the CORTEX. MEDIAN is found and the results are evaluated by a chi square test. medial hypothalamic area (histology) A region of the HYPOTHALAMUS, mediastinum (anatomy) The space in stimulation of which tends to arouse the chest between the two lungs. It the parasympathetic system. contains the HEART and great vessels, the OESOPHAGUS (USA: esophagus), medial lemniscus (histology) A NERVE the lower end of the TRACHEA, the tract which is part of the lemniscus and thoracic duct, various NERVES, the which conveys somaesthetic information THYMUS GLAND and LYMPH NODES. from the MEDULLA to the THALAMUS. Medical Examiner (ME) (medical) A medial plane (histology) The vertical forensics specialist, coroner, or other plane that divides the body into two official authorized to perform autopsies. symmetrical halves. medial rectus (histology) An extraocular Medical Research Council (MRC) (govern- MUSCLE that pulls the EYE inward ing body) A government organization towards the nose. that supports MRC research institutes in the UK, as well as providing funds median (1 statistics; 2 anatomy) 1 for research projects carried out at The value in a distribution that comes universities. half-way between the highest and the lowest. See also MEAN; MODE; NORMAL Medicines Act (legislation) UK legislation, DISTRIBUTION. 2 An alternative term passed in 1968, that restricts the supply for MEDIAL.

266 MEDITERRANEAN FEVER MEIOSIS and manufacture of all medicines to megabyte (computing) A COMPUTER license-holders. term denoting a million bytes of STORAGE space. Mediterranean fever (bacteriology) See BRUCELLOSIS. megacolon (histology) ABNORMAL enlargement of the COLON, which may med. lab. (general terminology) An happen in consequence of prolonged abbreviation of ‘med’ical ‘lab’oratory. use of certain laxatives such as senna and cascara. It may be CONGENITAL Med.RC (education) An abbreviation as in Hirschsprung’s disease (aganglionic of ‘Med’ical ‘R’esearch ‘C’ouncil. Also MEGACOLON) where there are no NERVE termed MRC. GANGLION CELLS in the wall of the RECTUM and the absence of NERVE Med Sc D (education) Doctor of Medical CELLS may extend upwards into the Science, COLON. The affected part of the GUT Med. Tech. (education) An abbreviation causes failure of PERISTALSIS and of ‘Med’ical ‘Tech’nology. obstruction, above which the COLON becomes loaded with FAECES (USA: medulla (1,2 histology) 1 The inner feces) and grossly distended. Named part of a structure or ORGAN or TISSUE after the Danish physician, Harald (e.g. adrenal MEDULLA). See also Hirschsprung (1830–1916). CORTEX. 2 An alternative term for MEDULLA OBLONGATA. megahertz (MHz) (measurement) UNIT of FREQUENCY of one million hertz. medulla oblongata (anatomy) The lower of the two divisions of the hindbrain; megloblastic anaemia (haematology) it is immediately above the SPINAL An ANAEMIA (USA: anemia) due to

CORD and below the pons. It contains deficiency of VITAMIN B12 or FOLIC many NERVE tracts, and also the ACID. In this type of ANAEMIA the autonomic nuclei implicated in the control red CELLS are immature and larger of BREATHING, HEARTBEAT, and is than NORMAL. See PERNICIOUS concerned with the coordination of NERVE ANAEMIA. (USA: megloblastic anemia) IMPULSES from hearing, touch and TASTE receptors. megrim (medical) Another term for headache; migraine. medullary layer (histology) The innermost of the three layers of the cerebellar meibomian cyst (histology) A cyst on CORTEX. the inside of the eyelid caused by blockage of-the duct from one of the meibomian medullary sheath (histology) An GLANDS which normally open at the alternative term for myelin. edge of the eyelid. Named after the German anatomist, Heinrich Meibom medullated nerve fibre (histology) See (1638–1700). NERVE FIBRE. meiosis (genetics) The central event in mega- (measurement) Metric prefix HEREDITY. Type of CELL DIVISION in meaning million times;×106 (e.g. which the number of chromosomes in megahertz). the DAUGHTER CELLS is halved; thus

267 MEIOTIC MELTING POINT they are in the HAPLOID state. Two natural (i.e. from the sun) or artificial, and successive divisions occur in the process, is catalysed by the ENZYME tyrosinase, giving four DAUGHTER CELLS. The first lack of which causes ALBINISM. DIVISION takes place in four stages: PROPHASE, METAPHASE, ANAPHASE melanism (biochemistry/histology) and TELOPHASE. The second DIVISION Occurrence in populations of dark- has three stages: METAPHASE, coloured (USA: colored) individuals having ANAPHASE and TELOPHASE. In animals an excess of MELANIN in their tissues. MEIOSIS occurs in the formation of gametes, e.g. eggs and SPERM. Also melanocyte (histology) A pigmented termed: REDUCTION DIVISION. CELL in the SKIN containing MELANIN.

See also MITOSIS. melanocyte-stimulating hormone (MSH) (biochemistry) A PEPTIDE HORMONE meiotic (genetics) Describing or referring produced by the INTERMEDIATE LOBE to MEIOSIS. of the PITUITARY that increases production of MELANIN. meiotic drive (genetics) Any mechanism that causes unequal proportions of the melanoma (histology) A TUMOUR (USA: possible gametes to be formed at MEIOSIS. tumor) of CELLS containing MELANIN. One example is B chromosomes, which The TUMOUR is MALIGNANT, and tend to be included preferentially in produces secondary deposits. It occurs the OVUM during MEIOSIS in the female. most often on the legs in women, and on the neck, HEAD and trunk in men. Meissner’s corpuscle (physiology) A The darker the SKIN, the less likely it SKIN RECEPTOR thought to be sensitive is to develop a MELANOMA; the to PRESSURE. INCIDENCE varies according to the amount of ULTRAVIOLET RADIATION meknuria (histology) Dark-coloured to which the SKIN is exposed, but it (USA: dark-colored) URINE, or URINE is not more common in outdoor than which turns dark if left standing, found indoor workers, being related more to in cases of melanotic tumours (USA: sunbathing. ULTRAVIOLET RADIATION melanotic tumors), and the rare conditions is not the only FACTOR concerned in of alcaptonuria and porphyria. the development of the TUMOUR, for it may develop in those who never expose melaena (haematology) Black motions, the SKIN to the sun. MALIGNANT caused by altered BLOOD originating from melanomas may arise in previously existing HAEMORRHAGE (USA: hemorrhage) in moles, and if one starts to grow, bleed the STOMACH or intestines, by IRON or change in any way, medical advice taken as a medicine, or by some red wines. is necessary. melanin (biochemistry) The black or dark melatonin (biochemistry) A substance brown PIGMENT that gives COLOUR found in the PINEAL GLAND that is (USA: color) to SKIN, HAIR and eyes in implicated in CIRCADIAN RHYTHMS. animals, including humans. MELANIN production in melanocytes is stimulated melting point (physics) TEMPERATURE by ULTRAVIOLET RADIATION, either at which a SOLID begins to liquefy, a

268 MELTING PROFILE MENDELEVIUM fixed (and therefore CHARACTERISTIC) said; but a deficient MEMORY may be TEMPERATURE for a pure substance. an early sign of cerebral disease such as ALZHEIMER’S DISEASE. melting profile (genetics) A GRAPH that shows how much DNA in a SAMPLE melts See also AMNESIA, KORSAKOFF’S over time in an increasing TEMPERATURE. SYNDROME. DNA melts in the range 60–80°C (140– 175°F). DNA with a preponderance of A- memory cells (immunology) MEMORY, or T BASE-pairs melts at lower temperatures the ability to mount a quantitatively and than DNA with more G-Cs, so the MELTING qualitatively different RESPONSE upon PROFILE gives a crude indication of the secondary exposure to a specific ANTIGEN, composition of the SAMPLE. is one of the hallmarks of the VERTEBRATE IMMUNE RESPONSE. In the humoral, or membrane (1 physics; 2 biology) 1 ANTIBODY, secondary RESPONSE, Any thin material, e.g. plastic FILM. 2 ANTIBODY is produced more quickly, in Structure that forms a dynamic larger quantities, for a longer PERIOD of INTERFACE, e.g. the outer MEMBRANE time, and of different classes and affinities between a CELL and its surroundings. than in a primary RESPONSE. The The structure may be selective in allowing secondary RESPONSE in CELL-mediated the passage of certain molecules through IMMUNITY produces faster elimination of (e.g. a -PERMEABLE MEMBRANE) or viral antigens, faster and more severe specific (e.g. in ACTIVE TRANSPORT). delayed-type HYPERSENSITIVITY reactions Membranes are widely distributed and and decreased GRAFT rejection time. The very important in all organisms. ability to mount a secondary IMMUNE RESPONSE is due to the generation of See also PLASMA MEMBRANE. ANTIGEN-specific MEMORY CELLS during the primary RESPONSE. MEMORY B membrane potential (physics) The CELLS and probably MEMORY T CELLS, VOLTAGE difference between the inside as well as EFFECTOR B CELLS (PLASMA and outside of a CELL’S MEMBRANE, CELLS) and EFFECTOR T CELLS particularly of a NERVE MEMBRANE. (CYTOTOXIC T CELLS) are produced from naive B and T CELLS during the primary membranous labyrinth (anatomy) See RESPONSE to that ANTIGEN. The EAR. EFFECTOR CELLS are generally short-lived, but a CLONE of long-lived ANTIGEN-primed memo. (general terminology) An abbre- MEMORY CELLS is thought to survive and viation of ‘memo’randum. provide for the heightened secondary RESPONSE by bypassing the early stages memory (1 computing; 2 medical) 1 of clonal expansion. Part of a COMPUTER that stores DATA and instructions (programs), usually See also IMMUNE SYSTEM. referring to the immediate access store. See also RANDOM ACCESS MEMORY menarche (physiology) The first appear- (RAM); READ-ONLY MEMORY (ROM). ance of the menstrual PERIODS. 2 Defects in MEMORY may result from faulty perception during preoccupation mendelevium Md (chemistry) RADIO- with other matters and paying little ACTIVE ELEMENT in GROUP IIIB of attention to what is going on or being the PERIODIC TABLE (one of the

269 MENDELISM MENINGITIS

ACTINIDES); it has several isotopes, from outside to inside, the dura mater, with half-lives of up to 54 days. At. no. arachnoid layer, and pia mater. 101; r.a.m. 258 (most STABLE ISOTOPE). meningioma (histology) A fibrous TUMOUR Mendelism (genetics) Study of IN- (USA: tumor) arising from the MENINGES; HERITANCE, and therefore genetics. The it is not MALIGNANT unless it penetrates principles of genetics put forward by the SKULL, when the portion that breaks the Austrian monk Gregor Mendel (1822– through may give rise to secondary tumours, 84), who postulated the existence of but removal may prove difficult and genes, both DOMINANT and RECESSIVE, dangerous when the TUMOUR grows and the rules governing their transmission. about the BASE of the BRAIN. It produces See MENDEL’S LAWS. symptoms according to its position by direct pressure on the BRAIN, and it See also HEREDITY. also competes with the BRAIN for the limited space within the skull, thus producing Mendel’s laws (genetics) Conclusions symptoms of increased INTRACRANIAL drawn from WORK on INHERITANCE carried PRESSURE such as severe headache, out by Gregor Mendel in breeding experiments. deterioration of vision, and in extreme The first is the LAW of SEGREGATION: cases vomiting and disturbance of an inherited CHARACTERISTIC is controlled consciousness. The TREATMENT is surgical by a pair of factors (ALLELES), which removal; the operation for removal of a separate and become incorporated into MENINGIOMA on the upper surface of different gametes. The second is the LAW the BRAIN is one of the most satisfactory of INDEPENDENT ASSORTMENT: the in neurosurgery. separated factors are independent of each other when gametes form. meningitis (medical/microbiology) INFLAM- MATION of the MENINGES, membranes Ménière’s disease (medical) A disorder that cover the BRAIN and SPINAL CORD. of the INNER EAR, causing recurrent It is possible for the MENINGES to become ACUTE vertigo, deafness and tinnitus. infected as a result of injury to the SKULL, As time goes by, the deafness becomes or INFECTION of the MIDDLE EAR, but worse but the attacks of giddiness improve. in general MENINGITIS is caused by a The noises in the EAR are usually present VARIETY of BACTERIA, VIRUSES and all the time, but are worse during the sometimes FUNGI. The symptoms of attacks of giddiness, which are bad enough MENINGITIS are in general headache, to make the patient vomit and collapse. FEVER, nausea, vomiting, backache, and Attacks last about a day, but are liable dislike of LIGHT (photophobia). There is to come in groups, with intervals of a few stiffness of the neck, and in children possibly weeks or months. Those affected are usually convulsions, and there may be a history 40 or 50 years old. The cause is thought of respiratory INFECTION. Often the to be excessive FLUID in the INNER EAR. meningeal irritation is due to a VIRUS Named after the French physician, Prosper INFECTION, the commonest being mumps; Ménière (1799–1862) See EAR. MEASLES can be responsible, as can a VARIETY of other VIRUSES, including meninges (histology) The three layers the HERPES VIRUS, but they do not usually of protective TISSUE that enclose the cause accompanying INFECTION of the BRAIN and SPINAL CORD, which are, BRAIN (encephalitis) and recovery is the

270 MENISCUS MENTHOL rule. INFECTION due to the poliomyelitis or there may be a DEFECT in the clotting VIRUS is now rarely seen because of mechanism of the BLOOD. Any bleeding the success of the IMMUNISATION which happens after the MENOPAUSE programme, and it is hoped that mumps is also a sign that investigation is needed. and MEASLES will for the same reason become increasingly rare. BACTERIAL menorrhea (medical) The NORMAL MENINGITIS is usually caused by Neisseria DISCHARGE of the MENSES. meningitidis, STREPTOCOCCUS pneumoniae or Haemophilus influenzae. menses (medical) The monthly flow of INFECTION is spread by droplets from BLOOD from the genital tract of a woman. the nose and is encouraged by crowded conditions. In meningococcal infections menstrual age (medical) The age of (spotted FEVER) patients, who are often the fetus, starting from the beginning under five years old, may develop a rash. of the mother’s last MENSTRUATION. The diagnosis is confirmed by LUMBAR PUNCTURE. Since the introduction of menstrual cycle (physiology) HORMONE- antibiotics the mortality of BACTERIAL regulated CYCLE of female reproductive MENINGITIS has decreased from about BEHAVIOUR (USA: behavior) during which 75 per cent to less than 5 per cent. Tuberculous OVULATION occurs; it occurs in some MENINGITIS has become rare in the West, primates, including human beings. The but is still to be found in developing countries end of the CYCLE is marked by a monthly where it is a serious disease. shedding of the endometrium (lining of the womb) accompanied by a DISCHARGE meniscus (1 anatomy; 2 physics) 1 A of BLOOD from the VAGINA, known as semicircular or crescentic CARTILAGE MENSTRUATION. The CYCLE begins in a JOINT, usually used to refer to the with the MENARCHE at the beginning semilunar cartilages in the knee. 2 Curved of puberty and ends at the MENOPAUSE. surface of a LIQUID where it is in contact Also termed: sexual CYCLE. with a SOLID. The effect is due to SURFACE TENSION. See also OESTROUS CYCLE. menopause (physiology) Final cessation menstruation (physiology) See MENSTRUAL of MENSTRUATION. The CAPACITY for CYCLE. REPRODUCTION in women begins to decrease at about the age of 40 to 45, mensuration (measurement) Science and the PERIODS cease at about 50, of measurement. either abruptly or more frequently gradually, with increasing intervals between. There mental age (MA) (medical) A measure is a gradual change in the FUNCTION of mental ability derived from tests. The of the ovaries, and there is a decrease score is expressed as the AVERAGE in the LEVEL of oestrogens (USA: estrogens) age at which children on AVERAGE perform in the BLOOD. See MENSTRUAL CYCLE. as well as the person being tested.

menorrhagia (medical) Excessive BLOOD menthol (chemistry) C10H19OH White SOLID loss at the monthly PERIOD. It may be ALICYCLIC COMPOUND. It is an ALCOHOL due to a number of factors: nervous with a minty SMELL and TASTE, used and emotional causes are not uncommon, as a flavouring and in medicines.

271 MERCAPTAN MESON mercaptan (chemistry) An alternative as cinnabar, used as a PIGMENT term for a thiol. (vermilion) and source of MERCURY. (USA: mercury(II) sulfide). mercuric (chemistry) An alternative term for MERCURY(II). mercury-vapour lamp (physics) Lamp that uses a MERCURY ARC in a QUARTZ mercurous (chemistry) An alternative tube; it produces ULTRAVIOLET RADIATION. term for MERCURY(I). mescaline (pharmacology/toxicology) mercury Hg (chemistry) Dense LIQUID Powerful drug derived, from the Mexican metallic ELEMENT in GROUP IIB of the mescal cactus (peyote), which has a PERIODIC TABLE (a TRANSITION similar effect to LYSERGIC ACID ELEMENT), used in lamps, batteries, switches DIETHYLamide (LSD), and causes and scientific instruments. It ALLOYS with hallucinations and mental disturbance. most metals to form AMALGAMS. Its compounds are used in drugs, explosives mesencephalon (anatomy) An alternative and pigments. Also termed: QUICKSILVER. term for mid-BRAIN. At. no. 80; r.a.m. 200.59. mesentery (histology) Vertical fold of mercury arc (chemistry) Bright blue-green TISSUE on the inner surface of the LIGHT obtained from an electric DISCHARGE body wall of animals, which supports through a VAPOUR of MERCURY. internal organs or associated structures. mercury cell (1, 2 physics) 1 ELEC- meso- (biology) Prefix meaning middle. TROLYTIC CELL that has a CATHODE made of MERCURY. See POLAROGRAPHY. mesoderm (histology) TISSUE in an 2 DRY CELL that has a MERCURY ANIMAL EMBRYO that develops into ELECTRODE. Also termed: Mallory cell. tissues between the GUT and ECTODERM. mercury(II) oxide (chemistry) HgO Red mesomerism (chemistry) Phenomenon or yellow COMPOUND, slightly SOLUBLE in which a chemical COMPOUND can in WATER, which reduces to metallic adopt two or more different structures MERCURY on heating. Also termed: by the alteration of (covalent) bonds, MERCURIC OXIDE. the atoms in the molecules remaining in the same relationship to each other. mercury(I) chloride (chemistry) HgCI Also termed: RESONANCE. White CRYSTALLINE COMPOUND, used as an INSECTICIDE and in a MERCURY See also TAUTOMERISM. CELL. Also termed: MERCUROUS CHLORIDE; CALOMEL. meson (physics) Member of a GROUP of unstable ELEMENTARY PARTICLES mercury(II) chloride (chemistry) HgC12 with masses INTERMEDIATE between Extremely poisonous white COMPOUND. those of electrons and nucleons, and Also termed: MERCURIC CHLORIDE; with POSITIVE, negative or zero CHARGE. CORROSIVE SUBLIMATE. MESONS are emitted by nuclei that have been bombarded by high-ENERGY electrons. mercury(II) sulphide (chemistry) HgS Red COMPOUND, which occurs naturally

272 MESSENGER RNA METHANAL messenger RNA (mRNA) (molecular metallocene (chemistry) Member of biology) RIBONUCLEIC ACID that a GROUP of chemicals formed between conveys instructions from DNA by copying a METAL and an AROMATIC COMPOUND the code of DNA in the CELL NUCLEUS in which the OXIDATION state of the and passing it out to the CYTOPLASM. METAL is zero; e.g. FERROCENE. It is translated into a POLYPEPTIDE chain formed from AMINO ACIDS which metalloid (chemistry) An ELEMENT join in a sequence according to the with physical properties resembling instructions in the messenger RNA. those of metals and chemical properties typical of NON-METALS (e.g. ARSENIC, See also TRANSCRIPTION. GERMANIUM, SELENIUM). Many meta- lloids are used in semiconductors. Met. (pharmacology) An abbreviation of ‘Met’hionine. metallurgy (chemistry) Scientific study of metals. metabolism (biochemistry) CHEMICAL REACTIONS that occur in CELLS and metaphase (genetics) Second stage are a CHARACTERISTIC of all living of MITOSIS and MEIOSIS, in which organisms. Metabolic reactions are chromosomes are lined up along the initiated by ENZYMES and liberate equator of the nuclear spindle. Also ENERGY in a usable form. ORGANIC termed: ASTER PHASE. COMPOUNDS may be broken down to simple constituents (CATABOLISM) metaplasia (cytology) TRANSFORMATION and used for other processes. Simple of one NORMAL TISSUE type into another compounds may be built up to more as a RESPONSE to a disease or complex ones (ANABOLISM). ABNORMAL condition. metabolite (biochemistry) A MOLECULE metastasis (histology) Process by which participating in METABOLISM, which disease-bearing CELLS are transferred may be synthesized in an organism or from one part of the body to another via taken in as food. Autotrophic organisms the LYMPH and BLOOD VESSELS; the need only to take in inorganic metabolises; term is usually applied to the spread of heterotrophs also need organic metabolises. cancers. The term also applies to the newly diseased AREA arising from the process. metal (chemistry) Any of a GROUP of elements and their ALLOYS with general metastatic (chemistry) Describing properties of strength, hardness and the electrons that leave an ORBITAL shell, ability to conduct HEAT and ELECTRICITY either entering another shell or being (because of the presence of FREE absorbed into the NUCLEUS. ELECTRONS). Most have high MELTING POINTS and can be polished to a shiny metatarsal (anatomy) One of the ROD- finish. Metallic elements (about 80 per shaped bones that forms the lower hind cent of the total) tend to form cations. limb or part of the hind foot in tetrapods and the arch of the foot in human beings. See also METALLOID. methanal (chemistry) HCHO An alternative term for FORMALDEHYDE.

273 METHANOIC ACID MICRO- methanoic acid (chemistry) HCOOH methylbenzene (chemistry) An alternative An alternative term for FORMIC ACID. term for TOLUENE. methylbenzene (chemistry) An alternative methylbutadiene (chemistry) An alterna- term for TOLUENE. tive term for isoprene. methanol (chemistry) CH OH Simplest 3 methylene blue (chemistry) Blue dye PRIMARY ALCOHOL, a poisonous LIQUID used as a pH INDICATOR. used as a SOLVENT and added to ETHANOL to make METHYLATED SPIRITS. Also methylphenol (chemistry) CH C H OH termed: METHYL ALCOHOL; WOOD SPIRIT. 3 6 4 DERIVATIVE of PHENOL in which one of the hydrogens of the BENZENE RING methionine (chemistry) CH3S(CH2)2CH- has been substituted by a methyl GROUP. (NH2)COOH SULPHUR (USA: sulfur) containing AMINO ACID; a constituent There are three isomers (ortho-, meta- of many proteins. Also termed: 2-amino- and para-), depending on the positions 4-methylthiobutanoic ACID. of the substituents in the ring. Also termed: cresol. methyl alcohol (chemistry) An alternative term for METHANOL. metre (m) (measurement) SI UNIT of length. 1 m=39.37 inches. (USA: meter). methyl chloroform (chemistry) An alternative term for 1,1,1-trichloroethane. metre-candle (measurement) An alternative term for LUX. (USA: meter- methyl cyanide (chemistry) An alternative candle). term for acetonitrile. methyl orange (chemistry) Orange dye metric system (measurement) Decimal- used as a pH INDICATOR. based system of units. See SI UNITS. methyl red (chemistry) Red dye used MGP (physiology/biochemistry) An as a PH INDICATOR. abbreviation of ‘M’atrix ‘G’la ‘P’rotein. methyl salicylate (chemistry) Methyl MHC (1, 2 physiology) 1 An abbreviation ESTER of SALICYLLIC ACID, used in of ‘M’ajor ‘H’istocompatibility ‘C’omplex; medicine. Also termed: oil of wintergreen. 2 An abbreviation of ‘M’yosin ‘H’eavy ‘C’hain. methylamine (chemistry) CH3NH2 Simplest primary AMINE, a GAS smelling mho (measurement) UNIT of CONDUC- like ammonia, used in making herbicides. TANCE. Also termed: RECIPROCAL OHM. methylaniline (chemistry) An alternative term for TOLUIDINE. MHPG (biochemistry) An abbreviation of 3-‘M’ethoxy-4-‘H’ydroxy‘P’heny‘G’lycol. methylated spirits (chemistry) General SOLVENT consisting of ABSOLUTE ALCOHOL. micro- (measurement) Metric prefix meaning a millionth;×10-6 (e.g. microfarad). methylation (chemistry) A CHEMICAL It is sometimes represented by the REACTION in which a methyl GROUP Greek letter µ (e.g. µF). is added to a chemical COMPOUND.

274 MICROBALANCE MIFEPRISTONE microbalance (equipment) A BALANCE microtubule (histology) MINUTE capable of weighing very small masses cylindrical unbranched tubule composed (e.g. down to 10-5 mg). of globular PROTEIN subunits found either singly or in groups in the microbe (microbiology) Imprecise term CYTOPLASM of EUKARYOTIC CELLS, for any MICRO-ORGANISM. in which it has the skeletal FUNCTION of maintaining their shape. Microtubules microbiology (microbiology) Biological are also associated with spindle formation, study of MICRO-ORGANISMS. and hence are responsible for chromosomal movement during NUCLEAR DIVISION. micrometre (measurement) Small UNIT of length equal to 10-6 m, formerly called microwave (physics) ELECTROMAGNETIC a micron. (USA: micrometer). RADIATION with 3 WAVELENGTH in the approximate range I mm to 0.3 m, micron (µ) (measurement) Former name i.e. between INFRA-RED RADIATION for the micrometre. and radio waves. micronutrient (biochemistry) General term for any of the TRACE ELEMENTS or microwave spectroscope (physics) VITAMINS. Study of atomic and/or molecular resonances in the MICROWAVE region. micro-organism (microbiology) Organism that may be seen only with the aid of midazolam (pharmacology) A benzodia- a MICROSCOPE. MICRO-ORGANISMS zepine drug that, administered by include microscopic FUNGI and ALGAe, injection, can be used as an ANXIOLYTIC BACTERIA, VIRUSES and single-celled and sedative in preoperative medication. animals (e.g. protozoans). mid-brain (anatomy) Part of BRAIN microprocessor (computing) See COM- that connects the fore-BRAIN to the PUTER. hind-BRAIN, concerned with processing visual information passed from the fore- microscope (microscopy) Instrument BRAIN. Fishes, amphibians and birds that produces magnified images of have a well developed mid-BRAIN roof, structures invisible to the naked EYE. the tectum, which forms the INTEGRATION There are two major optical types: the centre (USA: center) of their BRAIN. simple MICROSCOPE, consisting of one Mammals have a less well developed short focal-length CONVEX LENS giving mid-BRAIN. Also termed: mesencephalon. a virtual IMAGE, and the COMPOUND MICROSCOPE, consisting of two short middle ear (anatomy) AIR-filled part focal-length CONVEX lenses which of the EAR that is inside the EAR combine to give high MAGNIFICATION. DRUM and transmits sound waves from Highest magnifications are produced the OUTER EAR to the INNER EAR. by an ELECTRON MICROSCOPE. Also termed: tympanic cavity. microtome (histology) Instrument for mifepristone (pharmacology) A uterine cutting thin slices (of the ORDER of stimulant that, administered orally or a few micrometres) of biological materials topically via vaginal pessaries, is used for microscopic examination. for termination of uterine PREGNANCY.

275 MIL MITOCHONDRION mil (1, 2 measurement) 1 A millilitre. mineral acid (chemistry) InORGANIC 2 One-thousandth of an INCH, equivalent ACID such as sulphuric (USA: sulfuric), to 0.0254 mm. hydrochloric or NITRIC ACID. mile (measurement) UNIT of length mineral oil (chemistry) HYDROCARBON equal to 1,760 yards or 5,280 feet. 1 oil obtained from mineral sources or mile= 1.60934 kilometres. A nautical petroleum (as opposed to an ANIMAL mile is 6,080 feet (=1.85318 km). oil or vegetable oil). milk sugar (chemistry) An alternative mineral salts (chemistry) Dissolved term for LACTOSE. salts that occur in soil, derived from weathered rock and decomposed plants. milk teeth (anatomy) First of two sets They contain essential nutrients for of TEETH possessed by most mammals. plant GROWTH, which are in turn utilized Human beings have 20 MILK TEETH. by herbivores (and carnivores that feed Also termed: deciduous TEETH. on them). milli- (measurement) Metric prefix mean- minute (1, 2 measurement) 1 UNIT ing a thousandth;×10-3 (e.g. milligram). of time equal to 1/60 of an hour. 2 UNIT of angular measure equal to 1/ milligram (mg) (measurement) Thou- 60 of a DEGREE. Both types of minutes sandth of a gram. are made up of 60 seconds. millilitre (ml) (measurement) Thousandth MIS (physiology/biochemistry) An of a LITRE, equivalent to a CUBIC abbreviation of ‘M’üllerian ‘I’nhibiting centimetre (cc or cm3). ‘S’ubstance. millimetre (mm) (measurement) Thou- miscarriage (medical) An alternative sandth of a METRE, equal to a tenth term for a spontaneous ABORTION. of a centimetre. 1 mm=0.03937 inches. (USA: millimeter). miscible (chemistry) Describing two or more liquids that will mutually dissolve millimetre of mercury (mmHg) (measure- (mix) to form a single PHASE. They ment) UNIT of PRESSURE, equal to can be separated by FRACTIONAL 1/760 atmospheres. (USA: millimeter DISTILLATION. of mercury). MIT (biochemistry) An abbreviation of milrinone (pharmacology) A phosphodi- ‘M’ono‘I’odo‘T’yrosine. esterase inhibitor which can be administered by INTRAVENOUS injection mitochondrion (cytology) CELL ORGANELLE or infusion to treat congestive HEART in the CYTOPLASM of EUKARYOTIC CELLS, FAILURE and in acute HEART FAILURE. concerned with AEROBIC RESPIRATION and hence ENERGY production from the min (measurement) An abbreviation REDUCTION of ATP to ADP. Its shape of ‘min’ute(s). varies from spherical to cylindrical. Large concentrations of mitochondria are observed in areas of high ENERGY consumption,

276 MITOSIS MOLECULAR BIOLOGY such as MUSCLE TISSUE. Also termed: molar (1 chemistry; 2 anatomy) 1 Describing CHONDRIOSOME. a quantity of a substance that is proportional to its MOLECULAR WEIGHT (a mole). mitosis (genetics) The usual type of See MOLARITY. 2 MOLAR TOOTH. CELL DIVISION in which the parent NUCLEUS splits into two identical molar concentration (chemistry) See daughter nuclei, which contain the same MOLARITY. number of chromosomes and identical genes to that of the parent NUCLEUS. molar conductivity (physics) Electrical Also termed: KARYOKINESIS. CONDUCTIVITY of an ELECTROLYTE with a CONCENTRATION of 1 mole of See also MEIOSIS. SOLUTE per LITRE of SOLUTION. Expressed in siemens cm2 mol-1. mixed number (mathematics) Sum of a whole number (INTEGER) and a molar heat capacity (measurement) HEAT FRACTION (e.g. 3 2/3, 12 15/16). required to increase the TEMPERATURE of 1 mole of a substance by 1 KELVIN. mixture (chemistry) COMBINATION of Expressed in joules K-1 mol-1. two or more substances that do not react chemically and can be separated molar solution (chemistry) SOLUTION by physical methods (e.g. a SOLUTION). that contains 1 mole of SOLUTE in 1 LITRE of SOLUTION. m.k.s. unit (measurement) METRE- KILOGRAM-second UNIT, a metric UNIT molar tooth (anatomy) One of the used in science in preference to c.g.s. rearmost TEETH of a mammal, used units and now superseded by SI UNITS. for crushing and grinding food. They Also termed: MKS UNIT; Giorgi UNIT are absent from the MILK TEETH. (after the Italian physicist Giovanni Giorgi (1871–1950), who devised it). molar volume (chemistry) VOLUME occupied by 1 mole of a substance M Med (education) Master of Medicine; under specified conditions. -(Sc.) Master of Medical Science molarity (M) (chemistry) CONCENTRATION mode (statistics) Of a GROUP of numbers, of a SOLUTION given as the number of the number that occurs most often in moles of SOLUTE in a LITRE of SOLUTION. the GROUP. mole (mol) (chemistry) SI UNIT of amount See also MEDIAN. of substance. In chemistry, it is the amount of a substance in grams that corresponds modem (computing) Acronym of to its MOLECULAR WEIGHT, or the amount ‘mo’dulator/‘dem’odulator, a device for that contains particles equal in number transmitting COMPUTER DATA over to the AVOGADRO CONSTANT. Also long distances (e.g. by telephone line). termed: gram-MOLECULE. molality (m) (chemistry) CONCENTRATION molecular biology (molecular biology) of a SOLUTION given as the number of moles Study of biological macromolecules of SOLUTE in a KILOGRAM of SOLVENT. (e.g. NUCLEIC ACIDS, proteins).

277 MOLECULAR FORMULA MONOCHROMATIC LIGHT molecular formula (chemistry) Method atoms may be joined by COVALENT BONDS, of describing the composition of a DATIVE BONDS or bonds. MOLECULE of a chemical COMPOUND, using the CHEMICAL SYMBOLS of the monatomic (chemistry) Describing a constituent elements with numerical MOLECULE that contains only one ATOM suffixes that indicate the number of (e.g. the RARE GASes). atoms of each ELEMENT in the mongolism (medical) An alternative MOLECULE e.g. H2O and Na2SO4 are the MOLECULAR FORMULAe of WATER term for DOWN’S SYNDROME. and SODIUM SULPHATE (USA: sodium sulfate), respectively. The MOLECULAR Mono- (general terminology) Prefix mean- FORMULA gives no indication how the ing one (e.g. monobasic). COMPONENT atoms are arranged. monoamine-oxydase inhibitors (MAOIs) See also EMPIRICAL FORMULA; (Pharmacology/biochemistry) Drugs STRUCTURAL FORMULA. sometimes used in cases of depression. They take about three weeks to become molecular orbital (chemistry) Region effective, and have the disadvantage in space occupied by a pair of ELECTRONS that they interact with certain substances to stimulate the release of NORADRE- that form a COVALENT BOND in a NALINE (USA: norepinephrine) at the MOLECULE, formed by the overlap of NERVE endings; this results in a sudden two ATOMIC ORBITALS. dangerous elevation of the BLOOD PRESSURE. The main substance liable molecular oxygen (chemistry) O 2 to produce this effect is tyramine, which DIATOMIC molecular form of OXYGEN. is found in many foods, e.g. cheese, or meat or YEAST extracts. Substances molecular sieve (chemistry) Method used in proprietary cough medicines of separating substances by trapping and cold cures may have the same (absorbing) the molecules of one within effect. The principal MAOIs are phenelzine cavities of another, usually a natural and isocarboxazid. or SYNTHETIC ZEOLITE. MOLECULAR SIEVES are used in ION EXCHANGE, Monobasic acid (chemistry) ACID that desalination and as supports for catalysts. on solvation produces 1 mole of HY

DROXONIUM ION (H3O+) per mole of molecular spectrum (physics) See ACID; an ACID with one replaceable SPECTRUM. HYDROGEN ATOM in its MOLECULE (e.g. HYDROCHLORIC ACID, HCI, and molecular weight (chemistry) See NITRIC ACID, HNO3). It cannot therefore RELATIVE MOLECULAR MASS. form ACID salts. molecule (chemistry) GROUP of atoms held monocarboxylic acid (chemistry) CARBOX- together in fixed proportions by CHEMICAL YLIC ACID with only one carboxylic GROUP

BONDS; the fundamental UNIT of a chemical (e.g. acetic (ethanoic) ACID, CH3COOH). COMPOUND. The simplest molecules are DIATOMIC molecules, consisting of two monochromatic light (physics) LIGHT atoms (e.g. O2, HCI); the most complex are of a single WAVELENGTH. biochemicals and macromolecules. The

278 MONOCHROMATOR MOSELEY’S LAW

monochromator (physics) See SPEC- monosaccharide (chemistry) CnH 2nO n TROMETER. Member of the simplest GROUP of carbohydrates, which cannot be hydrolysed monoclinic (crystallography) Crystal to any other smaller units; e.g. the sugars form in which all three axes are unequal, GLUCOSE, FRUCTOSE. with one of them perpendicular to the other two, which intersect at an angle monosodium glutamate (MSG) (chemis- inclined at other than a right-angle. try) White CRYSTALLINE SOLID, 3 SODIUM SALT of the AMINO ACID GLUTAMIC monoclonal (immunology) Derived from ACID, made from soya bean PROTEIN a single parent CLONE. and used as a flavour enhancer. Eating it can cause an allergic REACTION in monoclonal antibody (immunology) certain susceptible people. ANTIBODY produced by a single-CELL CLONE and hence consisting of a single monovalent (chemistry) Having a AMINO ACID sequence. Such CELL clones VALENCE of one. Also termed: UNIVALENT. are produced by the artificial FUSION of cancerous and ANTIBODY-forming CELLS morphine (pharmacology) SEDATIVE, from the mouse SPLEEN. The HYBRID NARCOTIC ALKALOID drug isolated CELLS are grown in vitro as clones of from OPIUM, used for pain relief. Also cells, with each producing only a single termed: morphia. type of ANTIBODY MOLECULE.

morpholine (chemistry) C4H 9O HET- monocyte (haematology) Largest phago- EROCYCLIC secondary AMINE, used cytic LEUCOCYTE, of order of about as a SOLVENT. 10 to 12 micrometres. Monocytes have monogranulated CYTOPLASM with a morphology (biology) Study of the large oval NUCLEUS. ORIGIN, development and structures of organisms. monohydrate (chemistry) Chemical COMPOUND (a HYDRATE) that contains mosaic (genetics) Organism derived 1 mole of WATER OF CRYSTALLIZATION from a single EMBRYO that displays in each of its molecules e.g. IRON(II) the characteristics of different genes SULPHATE (USA: iron(II) sulfate) forms in different parts of its body. See CHIMAERA. a MONOHYDRATE, FeSO4.H2O. Moseley’s law (physics) The X-RAY monohydric (chemistry) Describing a SPECTRUM of an ELEMENT can be chemical COMPOUND that has one divided into several distinct line SERIES: HYDROXYL GROUP in each of its K, L, M and N. The LAW states that for molecules (e.g. ETHANOL, C2H 5OH, is certain elements the SQUARE ROOT a MONOHYDRIC ALCOHOL). of the FREQUENCY f of the CHARACTERISTIC X-RAYS of one of monomer (chemistry) Small MOLECULE that these SERIES is directly proportional can polymerize to form a larger MOLECULE. to the ELEMENT’S ATOMIC NUMBER See POLYMER. Z. It was named after the British physicist Henry Moseley (1887–1915).

279 MOTILE MUTAGEN motile (biology) Describing an organism mucin (biochemistry) Any of a number or structure that can move. of GLYCOPROTEINS that occur in MUCUS. motor neurone (cytology) NERVE CELL mucous membrane (histology) Moist, that transmits impulses from the SPINAL Mucus-lined EPITHELIUM which itself CORD or the BRAIN to a MUSCLE. lines VERTEBRATE internal cavities, Also termed: motor neuron; motor NERVE. including the alimentary, respiratory and reproductive tracts, which are continuous MPGF (physiology/biochemistry) An with the outer ENVIRONMENT. abbreviation of ‘M’ajor ‘P’ro‘G’lucagon ‘F’ragment. mucus (cytology) Slimy substance secreted by the GOBLET CELLS of MUCOUS MPP+ (biochemistry) An abbreviation MEMBRANE. It lubricates and protects of 1-‘M’ethyl-4-‘P’henyl‘P’yridinium. the epithelial layer on which it is secreted.

MPR (physiology/biochemistry) An multicellular (biology) Describing plants abbreviation of ‘M’annose-6-‘P’hosphate and animals that have bodies consisting ‘R’eceptor. of many CELLS. m pt (physics) An abbreviation of ‘m’elting multi-CSF (physiology/biochemistry) ‘p’oint. An abbreviation of ‘multi’potential ‘C’olony- ‘S’timulating ‘F’actor. MPTP (biochemistry) An abbreviation of 1-‘M’ethyl-4-‘P’henyl-1,2,5,6-‘T’etra- multifactorial inheritance (genetics) Exis- hydro‘P’yridine. tence of more than two ALLELES for one GENE; e.g. as in A, B, O blood grouping. MRI (physics) An abbreviation of ‘M’agnetic ‘R’esonance ‘I’imaging. multimeter (physics) Instrument that can be used as a galvanometer, AMMETER mRNA (physiology/biochemistry) An and VOLTMETER. abbreviation of ‘m’essenger ‘RNA’. multiple bond (chemistry) CHEMICAL M.Sc. (education)—(Med.) Master of BOND that contains more electrons than Science in Medicine; -(Med.Sc.) Master a SINGLE BOND (which contains 2 of Science in Medical Science; -(N) electrons); e.g. a DOUBLE BOND (4 Master of Science in Nursing; -(Nutr.) electrons) or a TRIPLE BOND (6 electrons). Master of Science in Nutrition; -(Pharm.) Master of Science in Pharmacy; -(V. muscle (histology) ANIMAL TISSUE of Sc.) Master of Veterinary Science. that contracts (by means of MUSCLE fibres [USA: muscle fibers]) to produce MSH (physiology/biochemistry) Abbre- movement, tension and mechanical viation of ‘M’elanocyte-‘S’timulating ENERGY. See INVOLUNTARY MUSCLE; ‘H’ormone. VOLUNTARY MUSCLE.

MT (biochemistry) An abbreviation of mutagen (toxicology) Chemical or 3-‘M’ethyoxy‘T’yramine. physical agent that induces or increases the rate of MUTATION; e.g. ETHYL

280 MUTANT MYXOEDEMA methane sulphonate (USA: ethyl methan- mycotoxin (toxicology/mycology) TOXIN sulfonate), ultra-violet LIGHT, X-RAYS produced by a FUNGUS. and gamma-rays. myelin sheath (cytology) Thin fatty layer mutant (molecular biology) Organism of membranes, produced by SCHWANN that arises by MUTATION. CELLS, that covers the AXON of most VERTEBRATE neurones (NERVE CELLS). mutarotation (chemistry) Change in the OPTICAL ACTIVITY of a SOLUTION containing myeloid tissue (histology) TISSUE photo-active substances, such as sugars. usually present in BONE MARROW which produces RED BLOOD CELLS mutation (molecular biology) Alteration and other BLOOD constituents. in the sequence of bases encoded by DNA, resulting in a permanent inheritable myocardial (anatomy) Relating to MYO- change in the GENE and consequently CARDIUM. the PROTEIN encoded. MUTATIONS may occur in different ways and may be induced myocardium (histology) MUSCLE by a MUTAGEN or occur spontaneously. TISSUE of the VERTEBRATE HEART. A MUTATION can be detrimental, e.g. those thought to be involved in myoglobin (biochemistry) In VERTEBRATE CARCINOGENESIS (formation of CANCER). MUSCLE FIBRE (USA: muscle fiber), a haem However, some MUTATIONS can be (USA: heme) PROTEIN capable of binding advantageous, e.g. in EVOLUTION, where with one ATOM of OXYGEN per MOLECULE. favourable characteristics may be endowed. myology (histology) Study of muscles. mutualism (biology) Relationship between two organisms from which each benefits myopia (medical) Short-sightedness, (e.g. CELLULOSE-digesting MICRO- a VISUAL DEFECT in which the eyeball ORGANISMS and animals, such as is too long (front to back) so that rays ruminants, whose GUT they inhabit). of LIGHT entering the EYE from distant objects are brought to a FOCUS in See also SYMBIOSIS. front of the RETINA. It can be corrected with spectacles or contact lenses made MVV (physiology) An abbreviation of from diverging (CONCAVE) lenses. ‘M’aximal ‘V’oluntary ‘V’entilation. See also HYPERMETROPIA. mycelium (mycology) MASS of hyphae that form the body of a FUNGUS. myosin (biochemistry) Fibrous PROTEIN which, with ACTIN, makes up MUSCLE. mycology (mycology) Scientific study Movement of MYOSIN fibres (USA: myosin of FUNGI. fibers) between ACTIN fibres (USA: actin fibers) causes MUSCLE contraction. Mycota (taxonomy) Division (PHYLUM) that includes the FUNGI, usually included myxoedema (medical/biochemistry) A in the plant KINGDOM but sometimes disorder caused by lack of HORMONES accorded a KINGDOM of its own. from the THYROID GLAND; if present at birth it causes cretinism.

281 N

N (biochemistry) A symbol for asparagine. nanosecond (nS) (measurement) One billionth of a second. Also termed nsec. Na (chemistry) The CHEMICAL SYMBOL for SODIUM. The symbol is derived naphthalene (chemistry) C10H8 SOLID from Latin natrium. aromatic HYDROCARBON that consists of two fused BENZENE RINGS, NA (1, 2 general terminology) 1 An INSOLUBLE in WATER but SOLUBLE abbreviation of ‘N’ot ‘A’pplicable. 2 in hot ETHANOL. It is 3 starting material An abbreviation of ‘N’ot ‘A’vailable. in the manufacture of dyes.

NaE (physiology/biochemistry) A symbol Napierian logarithm (mathematics) LOGA- for exchangeable body SODIUM. RITHM to the BASE e (e=2.71828…), named after the Scottish mathematician NAD (biochemistry) An abbreviation of John Napier (1550–1617). Also termed: ‘N’ictinamide-‘A’denine ‘D’inucleotide. CO- NATURAL LOGARITHM. ENZYME form of the VITAMIN NICOTINIC ACID, necessary in certain ENZYME- narc. (biochemistry) An abbreviation catalysed OXIDATION-REDUCTION of ‘narc’otic. REACTIONS in CELLS. Its reduced form is a PRECURSOR in the fixation of narcosis (medical) A state of uncon- CARBON DIOXIDE in chloroplasts during sciousness or extreme drowsiness induced PHOTOSYNTHESIS. by a NARCOTIC drug.

NADP (biochemistry) An abbreviation narcotic (pharmacology) ANALGESIC of ‘N’icotinamide-‘A’denine ‘D’inucleotide drug that, in addition to killing pain, ‘P’hosphate. causes loss of sensation or consciousness (e.g. MORPHINE and other opiates). nail (histology) Layer of KERATIN that grows on the upper surface of the fingers narcotic antagonist (pharmacology) of human beings and other primates Any drug that reduces the effects of (except tree-shrews, which have claws). a NARCOTIC. nano- (measurement) Prefix meaning nares (anatomy) The external openings a thousand-millionth;×10-9; e.g. 1 of the nose; the nostrils. NANOSECOND is 10-9s. NAS (education) An abbreviation of nanometre (measurement) Thousand- ‘N’ational ‘A’cademy of ‘S’cience. millionth of a METRE (USA: meter).; 10-9 m. It is the usual UNIT for wavelengths nasal cavity (anatomy) Cavity located of LIGHT. (USA: nanometer). in the HEAD of tetrapods, containing the OLFACTORY SENSE ORGANS.

282 NASOPHARYNGEAL NEON nasopharyngeal (anatomy) Pertaining NB (general terminology) An abbreviation to the part of the PHARYNX above of ‘N’ota ‘B’ene, Latin, meaning ‘note the LEVEL of the SOFT PALATE. well’.

National Science Foundation (NSF) near infra-red or ultraviolet (physics) Parts (governing body) An American gover- of the INFRA-RED or ULTRAVIOLET regions nment agency supporting research and of the ELECTROMAGNETIC SPECTRUM education programmes (USA: programs) that are close to the visible region. to encourage interest in science. nearsightedness (medical) An alternative natural abundance (chemistry) Relative term for MYOPIA. proportion of the various isotopes in a naturally occurring SAMPLE of an ELEMENT. NEFA (physiology/biochemistry) An abbreviation of ‘Non‘E’sterified free natural cytotoxic cells (immunology) ‘F’atty ‘A’cid. See KILLER CELLS. negative feedback (cybermetics) See natural logarithm (mathematics) An FEEDBACK. alternative term for NAPIERIAN LOGARITHM. negative number (mathematics) Number natural number (mathematics) One less than zero. of the SET of ordinary counting numbers (e.g. 1, 2, 3, 4, etc.). Nematoda (parasitology) PHYLUM of INVERTEBRATE animals that contains natural selection (genetics) One of round, thread and eel WORMS. They the conclusions drawn by the British have unsegmented bodies that taper naturalist Charles Darwin (1809–82) at each end. Many nematodes are from the theory of EVOLUTION: certain PARASITES (e.g. filaria). organisms with particular characteristics are more likely to survive and hence nematode (parasitology) Worm of the pass on their characteristics to their PHYLUM NEMATODA. offspring, i.e. survival of the fittest. Thus the characteristics of a population neo- (general terminology) Prefix meaning are controlled by this process. new.

Naumenko/Feigin stain (histology) neodymium Nd (chemistry) Metallic Histological staining technique for ELEMENT in GROUP IIIB of the PERIODIC astrocytes. TABLE (one of the LANTHANIDES), used in special GLASS for lasers. At.no. Nauta stain (histology) Histological 60; r.a.m. 144.24. staining technique. A SILVER stain that is taken up by degenerating axons, neo-Lamarckism (genetics) See and hence identifies dead or degenerating LAMARCKISM. neurons. neon Ne (chemistry) Gaseous nonmetallic Nb (chemistry) The CHEMICAL SYMBOL ELEMENT in GROUP 0 of the PERIODIC for NIOBIUM. TABLE (the RARE GASes) which occurs

283 NEONATAL NETTLE RASH in trace quantities in AIR (from which nerve cell (cytology) An alternative it is extracted). It is used in DISCHARGE term for a NEURONE. tubes (for advertising signs) and INDICATOR lamps. At. no. 10; r.a.m. 20.179. nerve cord (histology) Cord of nervous TISSUE in invertebrates that forms part neonatal (medical) Concerning the of their CENTRAL NERVOUS SYSTEM. newborn. nerve fibre (histology) Extension of a neoplasm (histology) TUMOUR (USA: NERVE CELL. NERVE FIBRES (USA: nerve tumor) or GROUP of CELLS with uncon- fibers) may be surrounded by a MYELIN trolled GROWTH. It may be BENIGN and SHEATH (except at the nodes of Ranvier), localized, or if CELLS move from their as in many vertebrates; or they may be NORMAL position in the body and invade unmyelinated and bound by a PLASMA other organs the TUMOUR is MALIGNANT. MEMBRANE. (USA: nerve fiber).

See also CANCER; METASTASIS. nerve impulse (physiology) Electrical signal conveyed by a NERVE to carry information NEP (biochemistry) An abbreviation throughout the NERVOUS SYSTEM. of ‘N’eutral ‘E’ndo‘P’eptidase. External stimuli trigger NERVE IMPULSES in RECEPTOR CELLS, and travel along nephritis (medical) INFLAMMATION AFFERENTS towards the CENTRAL of the KIDNEY. NERVOUS SYSTEM. Alternatively the impulses are generated within the nephroblastoma (medical) A MALIGNANT CENTRAL NERVOUS SYSTEM and travel TUMOUR (USA: malignant tumor) of along efferents towards organs and tissues the KIDNEY arising from primative kidney- (e.g. along motor NERVES to muscles). forming tissue. Also termed Wilm’s tumour. (USA: Wilm’s tumor). nervous system (anatomy) System that provides a rapid means of communication nephron (histology) Functional filtering within an organism, enabling it to be UNIT of the VERTEBRATE KIDNEY, aware of its surroundings and to react consisting of BOWMAN’S CAPSULE accordingly. In most animals it consists and the GLOMERULUS. of a CENTRAL NERVOUS SYSTEM (CNS) that integrates the sensory input from neptunium Np (chemistry) RADIOACTIVE PERIPHERAL NERVES which transmit ELEMENT in GROUP IIIB of the PERIODIC stimuli from receptors (afrerents) to TABLE (one of the ACTINIDES); it has the CNS, allowing the appropriate several isotopes. At. no. 93; r.a.m. 237 (most RESPONSE from the electors. STABLE ISOTOPE). net weight (nt wt) (measurement) Used nerve (anatomy) Structure that carries on packaging and labelling to show nervous impulses to and from the the WEIGHT of the PRODUCT itself, CENTRAL NERVOUS SYSTEM, consisting not including the WEIGHT of the packaging of a bundle of NERVE FIBRES (USA: the PRODUCT is stored in. nerve fibers). nettle rash (immunology) See URTICARIA. See also NERVE FIBRE; NEURONE.

284 NETWORK NEUROTOXICOLOGY network (physics/computing) System mental diseases that have no known of interconnected points and their pathological basis. connections; e.g. a grid of ELECTRICITY supply lines or a SET of interconnected neuroma (histology) A TUMOUR (USA: terminals online to one or more computers. tumor) composed of NERVE CELLS or NERVE FIBRES (USA: nerve fibers); a neur. (medical) An abbreviation of TUMOUR growing from a NERVE. ‘neur’ological/‘neur’ology. Also termed neurol. neuromuscular junction (anatomy) The INTERFACE between a motor NERVE neural (anatomy) Pertaining to NERVE FIBRE (USA: motor nerve fiber) and CELLS or neurons, or pertaining to a skeletal MUSCLE. the NERVOUS SYSTEM. neurone (cytology) BASIC CELL of the neurinoma (histology) a BENIGN NERVOUS SYSTEM which transmits TUMOUR (USA: benign tumor) arising NERVE IMPULSES. Each CELL BODY from the sheath of a NERVE. Also typically possesses a NUCLEUS and fine termed a neurofibroma. processes: short dendrites and a long AXON. The AXON carries impulses to neuro. (medical) An abbreviation of distant EFFECTOR CELLS and other ‘neuro’tic. neurones. Neurones also make functional contacts over the surface of shorter, thread- neuroanatomy (anatomy) The study like projections from the CELL BODY of the structure of the NERVOUS SYSTEM, (dendrites). Also termed: neuron; NERVE its constituents, and their connections. CELL. neurochemistry (biochemistry) The neuropathology (medical) The branch study of the chemistry of neurons. of PATHOLOGY that is concerned with diseases of the NERVOUS SYSTEM. neuroglia (histology) CONNECTIVE TISSUE between NERVE CELLS (neurones) of neuropharmacology (pharmacology) the BRAIN and SPINAL CORD. The study of the effects of drugs on the NERVOUS SYSTEM. neurohumour (biochemistry) Any chemical substance specifically secreted by neurosecretory cell (biochemistry) A neurons, particularly substances involved neuron that secretes a HORMONE into in synaptic transmission such as the EXTRACELLULAR FLUID. NEUROTRANSMITTERS. neurosurgery (medical) The medical speciality neurol. (medical) See neur. concerned with surgery on the NERVOUS SYSTEM, particularly on the BRAIN. neurology (medical) A medical speciality dealing with the diagnosis and neurotoxicology (biochemistry) The branch TREATMENT of patients with damage of toxicology that deals with toxicants to, or disorders of, the NERVOUS affecting the central and/or PERIPHERAL SYSTEM, and with the causation of NERVOUS SYSTEM and with the nature the symptoms. It is not concerned with and mechanisms of the process of toxic

285 NEUROTRANSMITTER NEWTON’S FORMULA injury and recovery of these aspects of outside the NUCLEUS they have a MEAN the NERVOUS SYSTEM. LIFE of about 12 minutes. neurotransmitter (biochemistry) Chemical neutron diffraction (chemistry) Technique released by NEURONE endings to either for determining the crystal structure of induce or inhibit transmission of NERVE solids by DIFFRACTION of a beam of IMPULSES across a SYNAPSE. neutrons. Similar in principle to ELECTRON NEUROTRANSMITTERS are typically DIFFRACTION, it can be used as a stored in small vesicles near the SYNAPSE substitute for X-RAY CRYSTALLOGRAPHY. and released in RESPONSE to arrival of an IMPULSE. There are more than neutron excess (chemistry) An alternative 100 different types, e.g. acetylcholine, term for ISOTOPIC NUMBER. NORADRENALINE (USA: norepinephrine) and SEROTONIN. Also termed: transmitter. neutron flux (chemistry) PRODUCT of the number of free neutrons per neurotrophic (biology) Having a selective UNIT VOLUME and their MEAN speed. AFFINITY for NERVE tissue. RABIES for Also termed: NEUTRON FLUX DENSITY. example, is caused by a NEUROTROPHIC VIRUS. neutron number (chemistry) Number of neutrons in an atomic NUCLEUS, the neutral (1 physics; 2 chemistry) 1 Having difference between the NUCLEON NUMBER neither POSITIVE nor negative electrical of an ELEMENT and its ATOMIC NUMBER. CHARGE; e.g. a NEUTRON is a NEUTRAL SUBATOMIC PARTICLE. 2 Describing neutropaenia (haematology) See a SOLUTION with PH equal to 7 (i.e. AGRANULOCYTOSIS. neither acidic nor ALKALINE). neutrophil (haematology) A granular neutral oxide (chemistry) OXIDE that leucocyte important in the IMMUNE is neither an ACIDIC OXIDE nor a SYSTEM because it ingests BACTERIA, BASIC OXIDE (e.g. DINITROGEN OXIDE whose PROTOPLASM can be stained

[N2O], WATER [H2O]). by NEUTRAL dyes. Neutrophils have a NUCLEUS with 3 to 5 lobes connected. neutralization (chemistry) CHEMICAL REACTION between an ACID and a newton (N) (measurement) SI UNIT BASE in which both are used up; the of FORCE, defined as the FORCE that products of the REACTION are a SALT provides a MASS of 1 kg with an and WATER. The completion of the ACCELERATION of 1 m s-2. It was named REACTION (end-point) can be detected after the British mathematician and by an INDICATOR. physicist Isaac NEWTON (1642–1727). neutron (chemistry) Uncharged PARTICLE Newton per metre (N/m) (measurement/ that is a constituent of the atomic NUCLEUS, physics) A UNIT of SURFACE TENSION. having a rest MASS of 1.67482 ×10-27 kg (USA: Newton per meter). (similar to that of a PROTON). Free neutrons are unstable and disintegrate by BETA Newton’s formula (optics) For a LENS, DECAY to a PROTON and an ELECTRON; the distances p and q between two

286 NEWTON’S RINGS NIOBIUM conjugate points and their respective nickel-iron accumulator (physics) Rechar- foci (f) are related by pq=f 2. gable ELECTROLYTIC CELL (BATTERY) with a POSITIVE ELECTRODE of NICKEL Newton’s rings (optics) Circular INTERFER- OXIDE and a negative ELECTRODE ENCE fringes formed in a thin gap between of IRON, in a POTASSIUM HYDROXIDE two reflective media, e.g. between a LENS ELECTROLYTE. Also termed: EDISON and a GLASS plate with which the LENS ACCUMULATOR; NIFECELL. is in contact. There is a central dark spot around which there are concentric Nicol prism (optics) Pair of calcite crystals dark rings. glued together and cut in such a way that they polarize a beam of LIGHT N gen (microbiology) An abbreviation passing through them. It was named of ‘N’ew ‘gen’us. after the British physicist William Nicol (1768–1851). See POLARIZED LIGHT. NGF (physiology/biochemistry) An abbreviation of ‘N’erve ‘G’rowth ‘F’actor. nicotine (biochemistry) Poisonous ALKALOID, found in tobacco, which niacin (biochemistry) VITAMIN B3, the potentially binds to the RECEPTOR for only one of the B VITAMINS that is the NEUROTRANSMITTER acetylcholine. synthesized by ANIMAL tissues. It is It is used as an INSECTICIDE. used by the body to manufacture the ENZYME nictinamide-adenine dinucleotide nicotinic acid (biochemistry) An alterna- (NAD), and a deficiency causes the disease tive term for NIACIN. pellagra. Also termed: NICOTINIC ACID. NIDA (education) An abbreviation of NIAID (education) An abbreviation of ‘N’ational ‘I’nstitute of ‘D’rug ‘A’buse. ‘N’ational ‘I’nstitute of ‘A’llergy and ‘I’nfectious ‘D’iseases. NIDDM (medical/biochemistry) Abbre- viation of ‘N’on-‘I’nsulin-‘D’ependent NIC (chemistry) An abbreviation of ‘D’iabetes ‘M’ellitus. ‘Nl’tro‘C’ellulose. NIDR (education) An abbreviation of niche (physiology) Status or way of life ‘N’ational ‘I’nstitute of ‘D’ental ‘R’esearch. of an organism (or GROUP of organisms) within an ENVIRONMENT, which it cannot NiFe cell (physics) An alternative term share indefinitely with another competing for NICKEL-IRON ACCUMULATOR. organism. Also termed: ECOLOGICAL NICHE. NIH (institute) An abbreviation of ‘N’ational nickel Ni (chemistry) SILVER-yellow metallic ‘I’nstitutes of ‘H’ealth. ELEMENT in GROUP VIII ofthe PERIODIC TABLE (a TRANSITION ELEMENT). It niobium Nb (chemistry) Metallic ELEMENT is used in VACUUM tubes, electroplating in GROUP VB of the PERIODIC TABLE and as a CATALYST, and its ALLOYS (a TRANSITION ELEMENT). Its ALLOYS (e.g. stainless steel, cupronickel, German are used in high-TEMPERATURE SILVER, NICKEL SILVER) are used in applications and superconductors. At. making cutlery, hollow-ware and coinage. no. 41; r.a.m. 92.9064. At. no. 28; r.a.m. 58.71.

287 NITRATE NITROGEN FIXATION nitrate (chemistry) SALT of NITRIC ACID, nitro compound (chemistry) ORGANIC containing the NO3 ANION. NITRATES COMPOUND in which a nitro GROUP are employed as OXIDIZING AGENTS (-NO2) is present in the BASIC molecular and commonly used as fertilizers, which structure. Usually made by NITRATION, may give rise to pollution of WATER supplies. some NITRO COMPOUNDS are commercial explosives. nitration (chemistry) CHEMICAL REACTION in which a nitro GROUP (-NO2) is incorpo- nitrobenzene (chemistry) C6H 5NO2 An rated into a chemical structure, to make aromatic LIQUID ORGANIC COMPOUND a NITRO COMPOUND. NITRATION of in which one of the HYDROGEN atoms ORGANIC COMPOUNDS is usually achieved in BENZENE has been replaced by a using a MIXTURE of concentrated nitric nitro GROUP (-NO2). It is used to make and SULPHURIC ACIDS (USA: sulfuric ANILINE and dyes. acid) (known as nitrating MIXTURE). nitrocellulose (chemistry) An alternative nitre (chemistry) Old term for POTASSIUM term for CELLULOSE trinitrate.

NITRATE, KNO3, also commonly known as SALTPETRE. nitrogen N (chemistry) Gaseous nonmetallic ELEMENT in GROUP VA of nitric acid (chemistry) HNO3 Strong the PERIODIC TABLE. It makes up extremely corrosive MINERAL ACID. It about 80 per cent of AIR by VOLUME, is manufactured commercially by the catalytic and occurs in various minerals (particularly OXIDATION of AMMONIA to NITROGEN NITRATES) and all living organisms. MONOXIDE (NITRIC OXIDE) and dissolving It is used as an INERT filler in electrical the latter in WATER. Its salts are NITRATES. devices and cables, and is an essential The main use of the ACID is in making plant nutrient. At. no. 7; r.a.m. 14.0067. explosives and fertilizers. nitrogen cycle (biochemistry) Circulation nitric oxide (chemistry) An alternative of NITROGEN and its compounds in term for NITROGEN MONOXIDE. the ENVIRONMENT. The main reservoirs of NITROGEN are NITRATES in the nitrification (chemistry) Conversion of soil and the GAS itself in the AMMONIA and nitrites to NITRATES by the ATMOSPHERE (formed from NITRATES ACTION of nitrifying BACTERIA. It is one of by DENITRIFICATION). NITRATES are the important parts of the NITROGEN CYCLE, also taken up by plants, which are because NITROGEN cannot be taken up eaten by animals, and after their death directly by plants except as NITRATES. the NITROGEN-containing proteins in plants and animals form AMMONIA, nitrile (chemistry) Member of a GROUP of which NITRIFICATION converts back ORGANIC COMPOUNDS that contain the into NITRATES. Some atmospheric NITRITE GROUP (-CN). Also termed: NITROGEN undergoes fixation by CYANIDE. lightning or BACTERIAL ACTION, again leading to the eventual formation of nitrite (chemistry) SALT of NITROUS nitrogen dioxide NO2.

ACID, containing the NO2 ANION. Nitrites are used to preserve meat and meat nitrogen fixation (biology) See FIXATION products. OF NITROGEN.

288 NITROGEN MONOXIDE NON-METAL nitrogen monoxide (chemistry) NO nobelium No (chemistry) RADIOACTIVE Colourless (USA: colorless) GAS made ELEMENT in GROUP IIIB of the PERIODIC commercially by the catalytic OXIDATION TABLE (one of the ACTINIDES); it has of AMMONIA and used for making NITRIC various isotopes with half-lives of up to ACID. It reacts with OXYGEN (e.g. in 3 min. At. no. 102; r.a.m. 255 (most STABLE AIR) to form nitrogen dioxide. Also ISOTOPE). termed: NITRIC OXIDE. noble gas (chemistry) Any of the elements nitrogen oxides (chemistry) Compounds in GROUP 0 of the PERIODIC TABLE: containing NITROGEN and OXYGEN HELIUM, NEON, ARGON, KRYPTON, in various ratios, including N2O, NO, XENON and RADON. They have a complete

N 2O 3, NO2, N2O 4, N2O 3, N2O 5, NO3 and SET of outer electrons, which gives them

N 2O6. The most important are great chemical stability (very few NOBLE DINITROGEN OXIDE, NITROGEN GAS compounds are known); RADON DIOXIDE and NITROGEN MONOXIDE. is RADIOACTIVE. Also termed: INERT GAS; RARE GAS. nitro-reduction (biochemistry/microbiology) The REDUCTION of aromatic amines noble metal (chemistry) Highly unreactive by either BACTERIAL or mammalian METAL, e.g. GOLD and PLATINUM. nitroreductase systems. nocturia (medical) Excessive urination nitrous acid (chemistry) HNO2 Weak, at night. unstable MINERAL ACID, made by treating a SOLUTION of one of its salts (nitrites) node (1 anatomy; 2 mathematics; 3 with an ACID. physics) 1 Thickening or junction of an anatomical structure, e.g. LYMPH nitrous oxide (chemistry) An alternative NODE (GLAND), sinoatrial NODE, NODE term for DINITROGEN OXIDE. OF RANVIER. 2 Meeting point of one or more arcs on a NETWORK. 3 Stationary nits (microbiology) The EGG containers point (i.e. point with zero AMPLITUDE) of lice. See LOUSE. on a standing WAVE.

NK (general terminology) An abbreviation node of ranvier (histology) One of of ‘N’ot ‘K’nown. several regular constrictions along the MYELIN SHEATH of a NERVE FIBRE nm (measurement) An abbreviation for (USA: nerve fiber). It was named after ‘n’ano‘m’etre. the French histologist Louis-Antoine Ranvier (1835–1922). NMDA (biochemistry) An abbreviation of ‘N’-‘M’ethyl-‘D’-‘A’spartate. non-homologous chromosomes (genetics) Any CHROMOSOMES that do not have nmr (physics) Abbreviation of ‘n’u-clear an exactly matching pair. The main example ‘m’agnetic ‘r’esonance. is the SEX CHROMOSOMES, in which No (chemistry) The CHEMICAL SYMBOL the X and Y are non-HOMOLOGOUS. for NOBELIUM. non-metal (chemistry) Substance that does not have the properties of a METAL. Nonmetallic elements are usually gases

289 NON-NEWTONIAN FLUID NORM.

(e.g. NITROGEN, halogens, NOBLE GASes) GENETIC CODE; NONSENSE CODON; or low-MELTING POINT solids, e.g. PROTEIN SYNTHESIS. PHOSPHORUS, SULPHUR (USA: sulfur), IODINE; BROMINE is exceptional in being non-specific urethritis (medical/micro- LIQUID at ordinary temperatures. They biology) One of the most commonly have poor electrical and THERMAL encountered SEXUALLY TRANSMITTED CONDUCTIVITY, form ACIDIC OXIDES, DISEASES which produces FREQUENCY do not react with acids and tend to form of micturition, some pain and a COVALENT BONDS. In ionic compounds DISCHARGE. It is in many cases caused they usually form anions. by the organism Chlamydia trachomatis, the organism of TRACHOMA, in others non-Newtonian fluid (physics) FLUID possibly by Ureaplasma urealyticum; the that consists of two or more phases at TREATMENT is by TETRACYCLINES or the same time. The COEFFICIENT of erythromycin. VISCOSITY is not a CONSTANT but is a FUNCTION of the rate at which the nonsporulating (microbiology) Does FLUID is sheared as well as of the relative not produce spores. CONCENTRATION of the phases. nonstoichiometric compound (chemistry) non-parametric (statistics) Describing Chemical whose molecules do not contain significance tests that do not involve the small whole numbers of atoms. assumptions of normality or HOMOGENEITY OF VARIANCE. In such tests, no assumptions See also STOICHIOMETRIC COMPOUND. are made about the distribution or parameters of the population from which the observations non-viable (microbiology) Not capable were sampled. The chi-square test is an of independent life. example of a commonly employed NON- PARAMETRIC test. Contrast PARAMETRIC. noradrenaline (biochemistry) HORMONE secreted by the MEDULLA of the ADRENAL nonsense codon (genetics) One of the GLANDS for the regulation of the CARDIAC three codons that specify the end of a MUSCLE, glandular TISSUE and SMOOTH genetic message. These codons do not MUSCLES. It is also a NEUROTRANSMITTER code for any AMINO ACID but signal in the SYMPATHETIC NERVOUS SYSTEM, the TERMINATION of the PROTEIN being where it acts as a powerful vasoconstrictor synthesised. They are UAG (‘amber’), on the vascular SMOOTH MUSCLES. In UAA (‘OCHRE’) and UGA (‘opal’). Also the BRAIN, levels of NORADRENALINE known as ‘stop codon’. See GENETIC (USA: norepinephrine) are related to NORMAL CODE; PROTEIN SYNTHESIS. mental FUNCTION, e.g. lowered levels LEAD to mental depression. (USA: nonsense mutation (genetics) A norepinephrine). MUTATION in which a codon that codes for an AMINO ACID is changed to a norepinephrine (biochemistry) An alterna- codon that codes for ‘stop’, resulting tive term for NORADRENALINE. in a shortened PROTEIN. The DEGREE to which the PROTEIN is shortened norm. (general terminology) An abbrevia- depends on how far along the GENE tion of ‘norm’al. the NONSENSE MUTATION occurs. See

290 NORMAL NREM SLEEP normal (1 mathematics; 2 chemistry) 1 except that the NUCLEIC ACID being A plane or line that is perpendicular to transferred is RNA and not DNA. NUCLEIC another. At any point on a curve, the ACIDS, previously resolved by agarose NORMAL is perpendicular to the tangent GEL ELECTROPHORESIS, are to the curve at that point. 2 Describing transferred to a NITROCELLULOSE a SOLUTION that contains 1 gram- FILTER by CAPILLARY ACTION. They are equivalent of SOLUTE in 1 LITRE of then bound to the sheet by heating and SOLUTION. It is denoted by the symbol can be probed with RADIOACTIVE labelled N and its multiples (thus 3N is a (USA: labeled) NUCLEIC ACIDS followed CONCENTRATION of 3 times NORMAL; by AUTORADIOGRAPHY. Whereas N/10 or decinormal is a CONCENTRATION SOUTHERN BLOTTING was called after of one-tenth NORMAL). its inventor, NORTHERNBLOTTING got its name by analogy. normal distribution (statistics) The statistical distribution in which the FREQUENCY See also WESTERN BLOTTING. of occurrences of values decreases with their distance from the MEAN. When plotted nos. (general terminology) Numbers. as a GRAPH, a NORMALDISTRIBUTION The plural of no. looks symmetrically bell-shaped. The MEAN (the AVERAGE of all the individual values), not applicable (NA) (general terminology) the MODE (the value that occurs most Term used in tables and charts to indicate often) and the MEDIAN (the half-way point that the information is not pertinent. between the highest and the lowest values) all coincide. The STANDARD DEVIATION not available (NA) (general terminology) is a measure of how steep-sided the ‘bell’ Term used in tables and charts to indicate is. In biological DATA, many traits that that the information is not available. show continuous VARIATION conform to a NORMAL DISTRIBUTION, Also termed notifiable diseases (microbiology) Gaussian distribution. Certain communicable diseases that are by LAW notifiable to the appropriate normalization (statistics) Transforming authority. DATA by mathematical operations to make them fit a preconceived pattern. Np (chemistry) The CHEMICAL SYMBOL for neptunium. normoblast (haematology) Immature RED BLOOD CELL which still has a NUCLEUS. NPH insulin (physiology/biochemistry) As the CELL matures and enters the An abbreviation of ‘N’eutral ‘P’rolamine bloodstream, the NUCLEUS breaks up, ‘H’agedorn insulin. and the CELL containing the remains of the NUCLEUS is called reticulocyte. Finally, NPN (physiology/biochemistry) An when it is mature, the RED BLOOD CELL abbreviation of ‘N’on‘P’rotein ‘N’itrogen. has no NUCLEUS. Normoblasts are not seen in the circulation unless new red npt (physics) An abbreviation of ‘n’ormal CELLS are being formed abnormally quickly. ‘p’ressure and ‘t’emperature.

Northern blotting (biochemistry) A similar NREM sleep (physiology) An abbreviation procedure to SOUTHERN BLOTTING, of ‘N’on‘R’apid ‘E’ye ‘M’ovement sleep.

291 NS NUCLEAR MEDICINE nS (measurement) An abbreviation of nuclear division (genetics) See MEIOSIS; ‘n’ano‘s’econd. MITOSIS.

NSAID (pharmacology) An abbreviation nuclear envelope (cytology) The double of ‘N’on-‘S’teroidal ‘A’nti-‘I’nflammatory MEMBRANE that surrounds the NUCLEUS ‘D’rugs. of EUKARYOTIC CELLS.

NSF (governing body) An abbreviation nuclear force (chemistry) Strong FORCE of ‘N’ational ‘S’cience ‘F’oundation. that operates during interactions between certain SUBATOMIC PARTICLES. It holds NSILA (physiology/biochemistry) An together the protons and neutrons in abbreviation of ‘N’on‘S’uppressible an atomic NUCLEUS. ‘I’nsulin‘L’ike ‘A’ctivity. nuclear isomerism (chemistry) Property NSILP (physiology/biochemistry) An exhibited by nuclei with the same MASS abbreviation of ‘N’on‘S’uppressible NUMBER and ATOMIC NUMBER but ‘I’nsulin‘L’ike ‘P’rotein. different RADIOACTIVE properties. nsp (microbiology) An abbreviation of nuclear magnetic resonance (nmr) ‘n’ew ‘sp’ecies. (physics) An effect observed when radio- frequency radiation is absorbed by matter. NSS (chemistry) An abbreviation of NUCLEAR MAGNETIC RESONANCE ‘N’ormal ‘S’aline ‘S’olution. spectroscopy is used in chemistry for the study of molecular structure. nt (physics) An abbreviation of ‘n’ormal ‘t’emperature. See also NUCLEAR MAGNETIC RESO- NANCE IMAGING. N terminal (biochemistry) A term for the end of peptide or PROTEIN having nuclear magnetic resonance (nmr) a free-NH2 group. imaging (medical/physics) A technique of imaging by computer using a strong NTP (physics) An abbreviation of ‘N’ormal magnetic field and radio frequency signals ‘T’emperature and ‘P’ressure. to examine thin slices of the body. It has the advantage over computed See also STANDARD TEMPERATURE tomography in that no X-rays are used, AND PRESSURE (STP). thus no biological harm is thought to be caused to the subject. NTS (physiology) An abbreviation of ‘N’ucleus of the ‘T’ractus ‘S’olitarius. See also NUCLEAR MAGNETIC RESO- NANCE nt wt (physics) An abbreviation of ‘n’e‘t’ ‘w’eigh‘t’. nuclear medicine (medical/radiology) The use of RADIOACTIVE substances in medicine. nuclear barrier (chemistry) Region of high A common use of a RADIOACTIVE substance POTENTIAL ENERGY that a charged in the TREATMENT of disease is the use PARTICLE must pass through in ORDER of RADIOACTIVE IODINE in THYRO- to enter or leave an atomic NUCLEUS. TOXICOSIS.

292 NUCLEAR MEMBRANE NUCLEUS nuclear membrane (cytology) MEMBRANE lone pair of electrons such as AMMONIA that encloses the NUCLEUS of a CELL. (NH3). nuclease (biochemistry) Type of ENZYME See also ELECTROPHILE. that splits the ‘chain’ of the DNA MOLECULE. Nucleases that act at specific nucleophilic reagent (chemistry) Chemical sites are called RESTRICTION ENZYMES. REACTANT that contains ELECTRON-rich groups of atoms. nucleic acid (molecular biology) Complex ORGANIC ACID of high MOLECULAR nucleophilic substitution (chemistry) SUB- WEIGHT consisting of chains of STITUTION REACTION that involves a nucleotides. NUCLEIC ACIDS commonly NUCLEOPHILE. occur, CONJUGATED with proteins, as nueleoproteins, and are found in nucleoprotein (molecular biology) A CELL nuclei and PROTOPLASM. They COMPOUND that is a COMBINATION are responsible for storing and transferring of a NUCLEIC ACID (DNA, RNA) and the GENETIC CODE. See DNA a PROTEIN. For example, in EUKARYOTIC (DEOXYRIBONUCLEIC ACID); RNA CELLS DNA is associated with HISTONES (RIBONUCLEIC ACID). and protamines; RNA in the CYTOPLASM is associated with PROTEIN in the nucleoid (cytology) In a PROKARYOTIC form of the ribosomes. CELL, the DNA-containing region, similar to the NUCLEUS of a EUKARYOTIC nucleoside (molecular biology) COMPOUND CELL but not bounded by a MEMBRANE. formed by partial HYDROLYSIS of a NUCLEOTIDE. It consists of a BASE, such nucleolus (cytology) Spherical body that as PURINE or PYRIMIDINE, linked to a occurs within nearly all nuclei of SUGAR, such as RIBOSE or DEOXYRIBOSE; EUKARYOTIC CELLS. It is associated e.g. ADENOSINE, cytidine and uridine. with RIBOSOME SYNTHESIS and is thus abundant in CELLS that make large nucleotide (molecular biology) COMPOUND quantities of PROTEIN. It contains PROTEIN that consists of a SUGAR (RIBOSE or DNA and much of the nuclear RNA. DEOXYRIBOSE), BASE (PURINE, PYRIMIDINE or PYRIDINE) and phosphoric nucleon (chemistry) A comparatively ACID. These are the BASIC units from massive PARTICLE in an atomic which NUCLEIC ACIDS are formed. NUCLEUS; a PROTON or NEUTRON. nucleus (1 chemistry/physics; 2 cytology) nucleon number (chemistry) Total number 1 The most massive, central part of of neutrons and protons in an atomic the ATOM of an ELEMENT, having a NUCLEUS. See MASS NUMBER. POSITIVE CHARGE given by Ze, where Z is the ATOMIC NUMBER of the ELEMENT nucleophile (chemistry) ELECTRON-rich and e the CHARGE on an ELECTRON. chemical REACTANT that is attracted by It is composed of chiefly protons and ELECTRON-DEFICIENT COMPOUNDS. (except for HYDROGEN) neutrons, and Examples include an ANION such as is surrounded by orbiting electrons. See CHLORIDE (CI-) or a COMPOUND with a also ISOTOPE. 2 The largest CELL ORGANELLE (about 20 micrometres

293 NUCLEOPHILIC ADDITION NZASC in DIAMETER), found in nearly all EUKARYOTIC CELLS. It is spherical to oval, containing the genetic material DNA, and hence controlling all CELL activities. A NUCLEUS is absent from mature mammalian ERYTHROCYTES (RED BLOOD CELLS) and the mature sieve-tube elements of plants. It is surrounded by a double MEMBRANE that forms the NUCLEAR ENVELOPE. nucleophilic addition (chemistry) A CHEMICAL REACTION in which a nucleophile adds onto an ELECTROPHILE. null method (measurement) Any measuring system that establishes an unknown value from other known values, when a particular instrument registers zero, e.g. a POTENTIOMETER. Also termed: ZEROMETHOD. numeral (mathematics) A symbol that represents a number; e.g. Arabic NUMERALS 1, 2, 3, 4, 5, 6 etc. or ROMAN NUMERALS I, II, III, IV, V, VI etc. numerator (mathematics) Top part of a FRACTION (the lower part being the DENOMINATOR).

NZAB (society) An abbreviation of ‘N’ew ‘Z’ealand ‘A’ssociation of ‘B’acteriologists.

NZASc (society) An abbreviation of ‘N’ew ‘Z’ealand ‘A’ssociation of ‘Sc’ientists.

294 O

object (optics) With a mirror, LENS octadecanoic acid (chemistry) An or optical instrument, the source of alternative term for STEARIC ACID. LIGHT rays that form an IMAGE. octahedral compound (chemistry) A objective (microscopy) LENS of an chemical COMPOUND whose molecules optical system (e.g. MICROSCOPE) have a central ATOM joined to six atoms that is nearest the OBJECT. or groups located at the vertices of an octahedron. obligate anaerobe (microbiology) MICROORGANISM that grows only in octahydrate (chemistry) A chemical complete or nearly complete absence containing eight molecules of WATER of AIR or MOLECULAR OXYGEN. OF CRYSTALLIZATION. See HYDRATE.

OBP (physiology/biochemistry) Abbrevia- octanoic acid (chemistry) C7H15COOH tion of ‘O’dorant-‘B’inding ‘P’rotein. Colourless (USA: colorless) oily CARBOX- YLIC ACID, used in the manufacture obtuse (mathematics) Describing an of dyes and perfumes. Also termed: angle that is more than 90 degrees CAPRYLIC ACID. but less than 180 degrees. octet (chemistry) STABLE GROUP of occlusion (1 biology; 2 chemistry) 1 eight electrons; the CONFIGURATION Closure of an opening (e.g. the way of the outer ELECTRON shell of most an ANIMAL’S TEETH meet when the RARE GASes, and the arrangement mouth closes). 2 ABSORPTION of a achieved by the atoms of other elements GAS on a SOLID MASS or on the as a result of most cases of CHEMICAL surface of SOLID particles by forming COMBINATION between them. Also a SOLID SOLUTION, by the formation termed: ELECTRON OCTET. of a chemical COMPOUND, or by the CONDENSATION of the GAS on the odd-even nucleus (chemistry) Atomic surface of the SOLID. NUCLEUS with an odd number of protons and an even number of neutrons. ochre (chemistry) Mineral of clay and

IRON(III) OXIDE (Fe2O 3), used as a odd-odd nucleus (chemistry) Atomic LIGHT yellow to brown PIGMENT. NUCLEUS with an odd number of both protons and neutrons; it is usually OCR (computing) An abbreviation of unstable. ‘o’ptical ‘c’haracter ‘r’ecognition. oedema (medical) A swelling due to octa-l octo- (general terminology) Prefix the accumulation of excess tissue fluid. meaning eight. (USA: edema).

295 OESOPHAGUS ONCOGENIC oesophagus (anatomy) Muscular tube oil of wintergreen (chemistry) An between the PHARYNX and STOMACH alternative term for METHYL SALICYLATE. (the gullet), through which food passes by PERISTALSIS. (USA: esophagus). -ol (chemistry) Chemical suffix that denotes an ALCOHOL or PHENOL. oestrogen (biochemistry) Female SEX HORMONE, a member of a GROUP of oleate (chemistry) ESTER or SALT of STEROID HORMONES that act on the OLEIC ACID. sex organs. The most important is oestradiol, which is responsible for the GROWTH olefin (chemistry) An alternative term and activity of much of the female for ALKENE. reproductive system. (USA: estrogen).

oleic acid (chemistry) C17H 33COOH oestrous cycle (physiology) Reproductive UNSATURATED FATTY ACID that occurs CYCLE of female mammals during which in many FATS AND OILS. It is a colourless there is a PERIOD of oestrus or ‘HEAT’, (USA: colorless) LIQUID that turns yellow when OVULATION occurs and the female on exposure to AIR, and is used in may be successfully impregnated by varnishes. a male to achieve FERTILIZATION. The

CYCLE is regulated by HORMONES. oleum (chemistry) H2S2O7 Oily SOLUTION (USA: estrous cycle). of SULPHUR TRIOXIDE (USA: sulfur

trioxide) (SO3) in concentrated See also MENSTRUAL CYCLE. SULPHURIC ACID (USA: sulfuric acid). Also termed: DISULPHURIC ACID (USA: OGF (physiology/biochemistry) An disulfuric acid); fuming SULPHURIC abbreviation of ‘O’varian ‘G’rowth ACID (USA: fuming sulfuric acid). ‘F’actor. olfaction (physiology) Process of smelling. ohm W (measurement) The SI UNIT In vertebrates, the incoming NERVE of ELECTRICAL RESISTANCE. It is IMPULSES from the OLFACTORY SENSE the resistance of a CONDUCTOR in ORGANS are processed in the OLFACTORY which the CURRENT is 1 AMPERE lobes of the BRAIN. when a POTENTIAL DIFFERENCE of 1 VOLT is applied across it. It was olfactory (physiology) Concerning the named after the German physicist Georg sense of SMELL. OHM (1787–1854). oligo- (general terminology) Prefix that Ohm’s law (physics) Relationship stating denotes small or few in number. that the VOLTAGE across a CONDUCTOR is equal to the PRODUCT of the oligomer (chemistry) POLYMER formed CURRENT flowing through it and its from the COMBINATION of a few MONOMER resistance. It is written V=IR, where V is molecules. VOLTAGE, I CURRENT and R resistance. oncogenic (toxicology) CANCER-producing. oil of vitriol (chemistry) Old name for SULPHURIC ACID (USA: sulfuric acid). See also CARCINOGENIC.

296 ONCOLOGY OPTICAL CHARACTER READER oncology (histology) The study of ophthalmic (medical) Pertaining to MALIGNANT tumours (USA: maglignant the EYE. tumors). ophthalmology (medical) The branch oncovirus (virology) An alternative of medicine dealing with the EYE and term for RETROVIRUS. its diseases. on-line (computing) Describing part of a opium (pharmacology) Dried juice from COMPUTER (e.g. an INPUT DEVICE) that a SPECIES of poppy; a bitter nauseous- is linked directly to and under the control tasting brown MASS with a heavy, of the CENTRAL PROCESSOR. CHARACTERISTIC SMELL. Its NARCOTIC ACTION, for which it is used oocyte (biology) CELL at a stage of both medicinally and as an abused drug, oogenesis before the complete develop- depends on the ALKALOIDS it contains. ment of an OVUM. A primary OOCYTE undergoes the first MEIOTIC DIVISION See also MORPHINE. to give the secondary OOCYTE, which after the second MEIOTIC DIVISION optic (optics) Concerning the EYE and produces an OVUM. See MEIOSIS. vision. opaque (physics) Not allowing a WAVE optic nerve (histology) CRANIAL NERVE motion (e.g. LIGHT, sound, X-RAYS) of vertebrates that transmits stimuli to pass; not transmitting LIGHT, not from the EYE to the BRAIN. TRANSPARENT. optical activity (chemistry) Phenomenon operand (mathematics) An entity or exhibited by some chemical compounds quantity on which a mathematical which, when placed in the path of a beam OPERATOR acts. of plane-POLARIZED LIGHT, are capable of rotating the plane of POLARIZATION operator (1 mathematics; 2 molecular to the left (LAEVOROTATORY) or right biology) 1 Symbol or term that represents (DEXTROROTATORY). Also termed: a mathematical operation to be carried OPTICAL ROTATION. out on a particular OPERAND. 2 Region of DNA to which a MOLECULE or optical axis (optics) Line that passes represser may bind to regulate the through the OPTICAL CENTRE (USA: activity of a GROUP of closely linked optical center) and the CENTRE OF structural genes. CURVATURE (USA: center of curvature) of a spherical LENS or mirror. Also operon (genetics) Groups of closely termed: principal AXIS. linked structural genes which are under control of an OPERATOR GENE. The optical centre (optics) Point at the OPERATOR may be switched off by a centre of a LENS through which a represser, produced by a regulator GENE RAY continues straight on and undeviated. separate from the OPERON. Another (USA: optical center). substance, the EFFECTOR, may inactivate the represser. optical character reader (computing) COMPUTER INPUT DEVICE that ‘reads’

297 OPTICAL CHARACTER RECOGNITION ORGANELLE printed or written ALPHANUMERIC order (taxonomy) In biological CLASSI- characters and feeds the information into FICATION, one of the groups into which a COMPUTER system. a CLASS is divided, and which is itself divided into families; e.g. Lagomorpha optical character recognition (OCR) (lagomorphs), Rodentia (rodents). (computing) Technique that uses an OPTICAL CHARACTER READER. order of reaction (chemistry) CLASSI- FICATION of CHEMICAL REACTIONS optical fibre (optics) See FIBRE OPTICS. based on the POWER to which the CONCENTRATION of a COMPONENT optical glass (microscopy) Very pure of the REACTION is raised in the RATE GLASS free from streaks and bubbles, LAW. The overall ORDER is the sum used for lenses, etc. of the powers of the concentrations. optical isomerism (chemistry) Property ordinal number (mathematics) Number of chemical compounds with the same that indicates the rank of a quantity; molecular structure, but different e.g. 1st, 2nd, 3rd, etc. (as opposed to configurations. Because of their molecular ordinary counting or CARDINAL asymmetry they exhibit OPTICAL NUMBERS: 1, 2, 3, etc.). ACTIVITY. ordinate (mathematics) In CO-ORDINATE optically active (chemistry) Describing geometry, the y CO-ORDINATE of a a substance that exhibits OPTICAL ACTIVITY. point (distance to the X-AXIS). The other (x) CO-ORDINATE is the ABSCISSA. optical rotation (chemistry) An alternative term for OPTICAL ACTIVITY. organ (anatomy) Specialized structural and functional UNIT made up of various optics (optics) Branch of physics tissues, in turn formed of many CELLS, concerned with the study of LIGHT. found in animals and plants; e.g. HEART, KIDNEY, leaf. oral (anatomy) Concerning the mouth and, in some contexts, speech. organ culture (histology) Maintenance of an ORGAN in vitro (after removal orange oxide (chemistry) An alternative from an organism) by the artificial creation term for URANIUM(VI) OXIDE. of the bodily ENVIRONMENT. orbital (chemistry) Region around the organ of corti (anatomy) ORGAN NUCLEUS of an ATOM in which there is high concerned with hearing, located in the probability of finding an ELECTRON. See COCHLEA of the EAR. It was named ATOMIC ORBITAL; MOLECULAR ORBITAL. after the Italian anatomist Alfonso Corti (1822–88). orbital electron (chemistry) ELECTRON that orbits the NUCLEUS of an ATOM. organelle (histology) Discrete MEMBRANE- Also termed: planetary ELECTRON. See bound structure that performs a specific ATOMIC ORBITAL; MOLECULAR ORBITAL. FUNCTION within a EUKARYOTIC CELL; e.g. NUCLEUS, MITOCHONDRION, chloroplast, ENDOPLASMIC RETICULUM.

298 ORGANIC ACID OSMIUM organic acid (chemistry) An ORGANIC also carry it. The organism causes COMPOUND that can give up protons to headache, FEVER and coughing, and a BASE; e.g. CARBOXYLIC ACIDS, PHENOL. the INFECTION may proceed to pneumonia, or enlargement of the LIVER and SPLEEN. organic base (chemistry) An ORGANIC COMPOUND that can donate a pair of ortet (genetics) The original organism electrons to a BOND; e.g. amines. from which a CLONE is derived. organic chemistry (chemistry) Study orth. (medical) An abbreviation of of ORGANIC COMPOUNDS. ‘orth’opaedic (USA: orthopedic). organic compound (chemistry) COMPOUND ortho- (chemistry) Prefix that denotes a of CARBON, with the exception of its BENZENE COMPOUND with substituents oxides and metallic carbonates and carbides. in the 1, 2 positions. Other elements are involved in ORGANIC COMPOUNDS, principally HYDROGEN See also PARA-. and OXYGEN but also NITROGEN, the halogens, and SULPHUR (USA: sulfur). orthoarsenic acid (chemistry) See ARSENIC ACID. organic cyanide (chemistry) See NITRILE. orthopaedic (orth.) (medical) Relating organometallic compound (chemistry) to the medical science of treating injured A chemical COMPOUND in which a bones and muscles (USA: orthopedic). METAL is directly bound to CARBON in an organic GROUP. orthophosphoric acid (chemistry) An alternative term for PHOSPHORIC(V) ACID. organosilicon compound (chemistry) A chemical COMPOUND in which SILICON Os (chemistry) The CHEMICAL SYMBOL is directly bound to CARBON in an organic for OSMIUM. GROUP. oscillator (physics) Device or electronic origin (mathematics) In CO-ORDINATE CIRCUIT for producing an ALTERNATING geometry, the point where the x- and CURRENT of a particular FREQUENCY, y-axes cross (and from which CARTESIAN usually controlled by altering the value of CO-ORDINATES are measured). a CAPACITOR in the OSCILLATOR CIRCUIT.

ornithine (chemistry) NH2(CH2)3CH(NH2)- oscilloscope (physics) An instrument COOH AMINO ACID, involved in the incorporating a cathode-ray tube, time- formation of UREA in animals. Also base generators, triggers etc. for termed: 1,6-diaminovaleric ACID. displaying a wide range of waveforms by electron beam. ornithosis (medical/microbiology) A disease carried by birds and transmitted osm (measurement) An abbreviation to man, caused by the organism Chlamydia of ‘osm’ole(s). psitiaci. The organisms can be carried by budgerigars, parrots, pigeons, poultry, osmium Os (chemistry) Metallic ELEMENT sea-birds and other more exotic birds in GROUP VIII of the PERIODIC TABLE (a

299 OSMIUM(IV) OXIDE OVIDUCT

TRANSITION ELEMENT). The densest ossicles (anatomy) Small bones; usually ELEMENT, it is used in hard ALLOYS and used to refer to the small bones of as a CATALYST. At. no. 76; r.a.m. 190.2. the MIDDLE EAR.

osmium(iv) oxide (chemistry) OsO4 ossification (histology) Process by which VOLATILE CRYSTALLINE SOLID with a BONE is formed, especially the TRANSFOR- CHARACTERISTIC penetrating odour MATION of CARTILAGE into BONE. (USA: odor) reminiscent of CHLORINE. It is used in the preparation of tissues for OST (governing body) An abbreviation observation with an ELECTRON of ‘O’ffice of ‘S’cience and ‘T’echnology. MICROSCOPE. Its AQUEOUS SOLUTIONS are used as a CATALYST in organic outer ear (anatomy) Part of the EAR reactions. Also termed: OSMIUM tetroxide. that transmits sound waves from external AIR to the EAR DRUM. osmoregulation (physiology) Process that controls the amount of WATER and output device (computing) Part of a ELECTROLYTE (salts) CONCENTRATION COMPUTER that presents DATA in a 5n an ANIMAL’S body. In a saltwater form that can be used by a human ANIMAL, there is a tendency for WATER OPERATOR; e.g. a PRINTER, visual to pass out of the body by OSMOSIS, which DISPLAY UNIT (VDU), chart plotter, is prevented by OSMOREGULATION by etc. A machine that writes DATA onto the kidneys. In freshwater animals, a portable magnetic medium (e.g. OSMOREGULATION by the kidneys (or by MAGNETIC DISK or tape) may also CONTRACTILE VACUOLEs in simple be considered to be an OUTPUT DEVICE. creatures) prevents WATER from passing into the ANIMAL by OSMOSIS. oval window (histology) Membranous AREA at which the ‘sole’ of the stirrup osmosis (physics) Movement of a (stapes) BONE of the INNER EAR makes SOLVENT from a DILUTE to a more contact with the COCHLEA. Also termed: concentrated SOLUTION across a semi- fenestra ovalis. PERMEABLE (or differentially PERMEABLE) MEMBRANE, thus tending ovarian follicle (histology) An alternative to equal the CONCENTRATION of the term for GRAAFIAN FOLLICLE. SOLUTE on either side. ovary (anatomy) Female reproductive osmotic diuretics (pharmacology) Inert ORGAN. In vertebrates, there is a pair DIURETIC compounds such as MANNITOL of ovaries, which produce the ova (eggs) which are secreted into the KIDNEY and SEX HORMONES. proximal tubules and not resorbed. They therefore carry water and salts with ovary ossicle (anatomy) An alternative them into the URINE. term for an EAR OSSICLE. osmotic pressure (physics) The PRESSURE oviduct (anatomy) Tube that conducts required to prevent OSMOSIS i.e. the released ova (eggs) from the ovaries after flow of WATER through a SEMIPERMEABLE OVULATION. Also termed: FALLOPIAN TUBE. MEMBRANE to the side on which there is a greater CONCENTRATION of a SOLUTE.

300 OVLT OXYGEN

OVLT (physiology) An abbreviation of OXIDATION NUMBER indicates that an ‘O’rganum ‘V’asculosum of the ‘L’amina ELEMENT is in an oxidized state; the higher ‘T’erminalis. the OXIDATION NUMBER, the greater is the extent of OXIDATION. Conversely, a ovulation (physiology) In vertebrates, negative OXIDATION NUMBER shows that DISCHARGE of an OVUM (EGG) from an ELEMENT is in a reduced state. a mature GRAAFIAN FOLLICLE at the surface of an OVARY. In mature human oxidation-reduction reaction (chemistry) females, OVULATION occurs from An alternative term for a REDOX REACTION. alternate ovaries at about every 28 days until the MENOPAUSE occurs. oxide (chemistry) COMPOUND of OXYGEN and another ELEMENT, usually made ovum (cytology) Unfertilized non-MOTILE by direct COMBINATION or by heating female GAMETE produced by the OVARY. a CARBONATE or HYDROXIDE. Also termed: EGG CELL; EGG. See also ACIDIC OXIDE; BASIC OXIDE; oxalate (chemistry) ESTER or SALT NEUTRAL OXIDE. of OXALIC ACID. oxidizing agent (chemistry) Substance oxalic acid (chemistry) (COOH)2.2H2O that causes OXIDATION. Also termed: White CRYSTALLINE poisonous ELECTRON acceptor. DICARBOXYLIC ACID. It occurs in rhubarb, wood sorrel and other plants oxime (chemistry) COMPOUND containing of the Oxalis GENUS. It is used in the GROUP -NH2OH, derived by the dyeing and VOLUMETRIC ANALYSIS. CONDENSATION of an ALDEHYDE or

Also termed: ETHANEDIOIC ACID. KETONE with hydroxylamine (NH2OH). oxatyl (chemistry) An alternative term 2-oxopropanoic acid (chemistry) An for CARBONYL GROUP. alternative term for PYRUVIC ACID. oxidase (biochemistry) Collective name oxyacid (chemistry) ACID in which the for a GROUP of ENZYMES that promote acidic (i.e. replaceable) HYDROGEN ATOM OXIDATION within plant and ANIMAL CELLS. is part of a HYDROXYL GROUP, e.g. organic CARBOXYLIC ACIDS and phenols, oxidation (chemistry) Process that and inorganic acids such as involves the loss of electrons by a PHOSPHORIC(V) ACID and SULPHURIC substance; the COMBINATION of a ACID (USA: sulfuric acid). substance with OXYGEN. It may occur rapidly (as in COMBUSTION) or slowly oxygen O (chemistry) Gaseous nonmetal- (as in rusting and other forms of corrosion). lic ELEMENT in GROUP VIA of the PERIODIC TABLE. A colourless (USA: oxidation number (chemistry) Number of colorless) odourless (USA: odorless) GAS, electrons that must be added to a CATION it makes up about 20 per cent of AIR by or removed from an ANION to produce a VOLUME, from which it is extracted, and NEUTRAL ATOM. An OXIDATION is essential for life. It is the most abundant NUMBER of zero is given to the elements ELEMENT in the EARTH’S crust, occurring themselves. In compounds, a POSITIVE in all WATER and most rocks. It has a

301 OXYGEN DEBT OZONE

triatomic ALLOTROPE, OZONE (O3). At. no. 8; r.a.m. 15.9994. oxygen debt (physiology) Physiological condition that induces ANAEROBIC RESPIRATION in an otherwise AEROBIC organism. It occurs during ANOXIA, caused e.g. by violent exercise. oxyhaemoglobin (haematology) PRODU- CT of RESPIRATION formed by the COMBINATION of OXYGEN and HAEMOGLOBIN (USA: hemaglobin). (USA: oxyhemoglobin).

ozone (chemistry) O3 ALLOTROPE of OXYGEN that contains three atoms in its MOLECULE. It is formed from OXYGEN in the upper ATMOSPHERE by the ACTION of ULTRAVIOLET RADIATION, where it also acts as a shield that prevents excess ULTRAVIOLET RADIATION reaching the EARTH’S surface. It is a powerful OXIDIZING AGENT, often used in ORGANIC CHEMISTRY.

302 P

P (biochemistry) An abbreviation of pachymeningitis (histology) INFLAMMATION ‘P’roline. of the dura mater of the BRAIN. See MENINGITIS. P450 (genetics) A GENE superfamily, consisting of large groups of genes pachytene (genetics) A stage in PROPHASE that code for proteins (CYTOCHROMES) or first DIVISION of MEIOSIS, in which which metabolise drugs or other foreign the paired chromosomes shorten and chemicals. The P450 CYTOCHROMES thicken, appearing as two chromatids. are coded for by 20 different families of genes, ten of which are the same Pacinian corpuscle (histology) A small in all mammals. Any one mammalian structure about 4 mm long found below SPECIES may have between 60 and the SKIN and in other parts of the 200 individual P450 genes, each making body,which in SECTION is like an oval a unique CYTOCHROME. The drug or onion. It is attached to a sensory NERVE chemical acts in many cases as the FIBRE (USA: nerve fiber), and is sensitive INDUCER for the relevant P450 GENE. to PRESSURE. The structure is named In humans, POLYMORPHISMS of P450 after the Italian anatomist, F.Pacini genes are responsible for many of the (1812–83). examples of patients’ VARIABLE responses to clinical drugs. packing fraction (radiology) Difference between the actual MASS of an ISOTOPE P (physiology/biochemistry) An abbre- 50 and the nearest whole number divided viation of partial pressure of O at 2 by the MASS NUMBER. which haemoglobin (USA: hemoglobin) is half-saturated with O . 2 paediatrics (medicine) The medical p (1, 2 physics; 3 chemistry) 1 An speciality concerned with childhood abbreviation of ‘p’article; 2 An abbreviation diseases and disorders. (USA: pediatrics). of ‘p’roton; 3 An abbreviation of ‘p’ara. PAF (physiology/haematology) An abbre- Pa (1 chemistry; 2 measurement) 1 viation of ‘P’latelet-‘A’ctivating ‘F’actor. The CHEMICAL SYMBOL for ELEMENT 91, PROTACTINIUM. 2 An abbreviation PAH (biochemistry) An abbreviation of ‘Pa’scal (SI unit of pressure). of ‘P’ara-‘A’mino‘H’ippuric acid.

PABA (chemistry) An abbreviation of palladium Pd (chemistry) SILVER-white ‘P’ara-‘A’mino‘B’enzoic ‘A’cid. An metallic ELEMENT in GROUP VIII of the ORGANIC ACID found in YEAST. It PERIODIC TABLE (a TRANSITION absorbs ULTRAVIOLET RADIATION and ELEMENT), used as a CATALYST and in is used in suntan lotions. making jewellery. At. no. 46; r.a.m. 106.4.

303 PALMITIC ACID PARASITISM

palmitic acid (chemistry) C15H31COOH para- (1, 2 chemistry) 1 Prefix that denotes Long-chain CARBOXYLIC ACID which the form of DIATOMIC MOLECULE in occurs in oils and fats (e.g. palm oil) as which both nuclei have opposite spin its glyceryl ESTER, used in making SOAP. directions. 2 Relating to the 1, 4 positions in the BENZENE RING. Also termed p-. PAM (physiology/haematology) An abbreviation of ‘P’ulmonary ‘A’lveolar See also meta-, ortho-. ‘M’acrophage. paraffin wax (chemistry) MIXTURE of pancreas (anatomy) GLAND situated SOLID paraffins (ALKANES) which takes near the DUODENUM that has digestive the form of a white TRANSLUCENT SOLID and endocrine functions. The ENZYMES that melts below 80°C. It is used to AMYLASE, trypsin and LIPASE are make candles. Also termed: PETROLEUM released from it during DIGESTION. WAX. Special groups of CELLS (the ISLETS OF LANGERHANS) produce the paraformaldehyde (chemistry) An HORMONES INSULIN and glueagon alternative term for POLYMETHANAL. for the control of BLOOD SUGAR levels.

paraldehyde (chemistry) (CH3CHO)3 pandemic (epidemiology) Describing A CYCLIC TRIMER formed by the a disease that affects people or animals polymerization of ACETALDEHYDE throughout the world. (ETHANAL), used as a sleep-inducing drug. Also termed: ETHANAL TRIMER. See also ENDEMIC; EPIDEMIC. parallel circuit (physics) Electrical circuit pantothenic acid (biochemistry) A con- in which the voltage supply is connected stituent of COENZYME A, a CARRIER to each side of all the components so of ACYL GROUPS in biochemical processes. that only a fraction of the total current It is required as a B VITAMIN by many flows through each of them. organisms, including vertebrates and YEAST. See also SERIES CIRCUIT. papain (biochemistry) Proteolytic ENZYME, which digests proteins, found in various paramagnetism (physics) Property of fruits and used as a meat tenderizer. substances that possess a small permanent magnetic moment because paper chromatography (chemistry) Type of the presence of odd (unpaired) of CHROMATOGRAPHY in which the electrons; the substance becomes mobile PHASE is LIQUID and the magnetized in a MAGNETIC FIELD as stationary PHASE is porous paper. the magnetic moments align. Compounds are separated on the paper, and can then be identified. parasite (parasitology) Organism that forms the beneficial partner in PARASITISM. papovavirus (virology) Member of a GROUP of double-stranded DNA parasitism (parasitology) The intimate VIRUSES which infect the CELLS of relationship between two organisms higher vertebrates, in which they can in which one (the PARASITE) derives cause tumours (USA: tumors). benefit from the other (the HOST),

304 PARASYMPATHETIC NERVOUS SYSTEM PASCAL usually to obtain food or physical support. can be produced by PARTHENOGENESIS, PARASITISM can have minor or major as no Y chromosome is present. effects on the survival of the HOST. partial derivative (mathematics) The See also COMMENSALISM; SYMBIOSIS. DERIVATIVE of a FUNCTION with respect to one of its variables, all other variables parasympathetic nervous system (anat- in the FUNCTION being taken as omy) Branch of the AUTONOMIC CONSTANT. Also termed: partial differential. NERVOUS SYSTEM used in involuntary activities, for which ACETYLCHOLINE partial fraction (mathematics) One is the transmitter substance. Effects of the COMPONENT fractions into which of the PARASYMPATHETIC NERVOUS another FRACTION can be separated SYSTEM generally counteract those (so that the sum of the partial fractions of the SYMPATHETIC NERVOUS SYSTEM. equals the original FRACTION). parathyroid (anatomy) Four ENDOCRINE partial pressure (physics) See GLANDS embedded in the THYROID DALTON’SLAW OF PARTIAL PRESSURES. in the neck which release a HORMONE that controls the levels of CALCIUM in particle (physics) MINUTE portion of the BLOOD. MATTER, often taken to mean an ATOM, MOLECULE or ELEMENTARY PARTICLE parietal cells (histology) Large CELLS or SUBATOMIC PARTICLE. in the lining of the STOMACH that secrete hydrochloric acid. particle physics (physics) Branch of science concerned with the properties Parkinson’s disease (medical) A disease of ELEMENTARY PARTICLES. of the nervous system first described by the British physician James Parkinson partition coefficient (chemistry) Ratio (1775–1824). PARKINSON’S disease is of the concentrations of a single SOLUTE a result of a degenerative process in in two IMMISCIBLE solvents, at the substantia nigra, a pigmented NUCLEUS EQUILIBRIUM. It is independent of in the BRAIN stem, which employs the the actual concentrations. substance DOPAMINE as the transmitter of nerve impulses to the corpus striatum, parturition (physiology) Birth of a full- one of the basal ganglia of the BRAIN, growth FOETUS (USA: fetus) at the in which there is consequuently a deficiency completion of PREGNANCY (GESTATION). of DOPAMINE. PAS (histology) Abbreviation of ‘P’eriodic parthenogenesis (biology) The develop- ‘A’cid—‘S’chiffs stain. ment of an unfertilized egg into an adult organism. Virgin birth. This occurs pascal (Pa) (measurement) SI UNIT of naturally in bees and ants and in some PRESSURE, equal to a FORCE of 1 animal species development of an ovum NEWTON per square METRE (N m-2). It can be induced chemically or by pricking was named after the French physicist and with a fine glass fibre (USA: glass fiber). mathematician Blaise Pascal (1623–62). The result is a clone of the mother cell identical in all respects. Only females

305 PASTEURIZATION PECTIN pasteurization (microbiology) Process Paul-bunnell test (virology) A BLOOD of heating food or other substances test for infectious mononucleosis under controlled conditions. It was (GLANDULAR FEVER). Nameed after developed by the French chemist Louis American physicians, J.Paul (1893–1971) Pasteur (1822–95) to destroy pathogens. and W.W.Bunnell (1902–1966). It is widely used in industry, e.g. milk production. Pb (chemistry) The CHEMICAL SYMBOL for ELEMENT 82, LEAD. The symbol patella (anatomy) BONE in front of is derived from Latin: plumbum. the knee JOINT. Also termed: kneecap. PBI (biochemistry) An abbreviation of path. (general terminology) An abbrevia- ‘P’rotein-‘B’ound ‘I’odine. tion of ‘path’ology. p-block elements (chemistry) 30 pathetic nerve (histology) An alternative nonmetallic elements that form Groups term for trochlear NERVE. IIB, IVB, VB, VIB, VIIB and 0 of the PERIODIC TABLE (HELIUM is Usually pathogen (microbiology) An organism, excluded), so called because their 1 or other agent, capable of causing disease. to 6 outer electrons occupy p-orbitals. Commonly used of MICRO-ORGANISMS such as BACTERIA and VIRUSES. P cells (1, 2 physiology) An abbreviation of ‘P’rincipal CELLS in the renal tubules; pathogenesis (microbiology) The ORIGIN 2 An abbreviation of ‘P’acemaker CELLS and course of a disease. of sinoatrial and atrioventricular nodes. pathogenic (microbiology) Producing PCR (biochemistry) An abbreviation disease. of ‘P’olymerase ‘C’hain ‘R’eaction. pathognomonic (medical) Indicative of, pd (physics) An abbreviation of ‘p’otential or CHARACTERISTIC of, a particular illness. ‘d’ifference. pathognomy (1,2 medical) 1 The study PDGF (physiology/biochemistry) An of how to recognize an illness from abbreviation of ‘P’latelet-‘D’erived ‘G’rowth its symptoms. 2 Symptom or symptoms ‘F’actor. of an illness. PE (statistics) An abbreviation for pathologic (medical) Due to or involving a ‘P’robable ‘E’rror. morbid condition, as a PATHOLOGIC state. PEC (physics) An abbreviation of ‘P’hoto pathology (path.) (medical) The study of ‘E’lectric ‘C’ell. morphological changes CHARACTERISTIC of ABNORMAL states, including both peck (measurement) UNIT of dry CAPACITY physiological (ENDOGENOUS) effects, equal to a quarter of a BUSHEL, or 2 effects caused by PATHOGENIC organisms gallons (=9.092 LITRES). and the adverse effects of EROGENOUS physical and chemical agents. It includes pectin (chemistry) Complex POLYSAC- changes at the LEVEL of gross anatomy. CHARIDE DERIVATIVE present in plant

306 PECTORAL PENIS

CELL walls, to which it gives rigidity. It pelvic (anatomy) Concerning the part can be converted to a GEL form in sugary of the rear end of a VERTEBRATE’S ACID SOLUTION. body which supports the hindlimbs. pectoral (medical) Relating to the chest. pelvis (1, 2 anatomy) 1 Part of the SKELETON (PELVIC girdle) to which pectoral (anatomy) Concerning the part a VERTEBRATE’S hindlimbs are joined. of the front end of a VERTEBRATE’S 2 Cavity in the KIDNEY which receives body which supports the shoulders and URINE from the tubules and drains it forelimbs. into the URETER. pediat. (medical) An abbreviation of pemphigus (medical) A term used for ‘pediat’rics SKIN diseases in which blisters develop. pediatrics (medical) See PAEDIATRICS. penetrance (genetics) The FREQUENCY with which a DOMINANT ALLELE is pediculosis (parasitology) INFESTATION expressed in the PHENOTYPE of the with lice. See LOUSE. individual carrying it. A completely penetrant ALLELE is expressed in every case, pedigree (genetics) A diagram represent- and this is normally the position with ing the genetic relationships between DOMINANT ALLELES having major effects. individuals. Usually drawn up with An ALLELE is said to have incomplete reference to one (or a few) specific PENETRANCE if it is not always expressed traits, the PEDIGREE uses conventional (this will depend on the genetic background symbols to show the sex of the individuals and on the ENVIRONMENT). (usually squares for males, circles for females); a diagonal line through their penicillin (pharmacology) Member of symbol shows that the person is deceased. a CLASS of antibiotics produced by Whether or not the individual is affected moulds (USA: molds) of the GENUS with the trait in question is shown by Penicillium. It inhibits GROWTH of some having their symbol SOLID or open, BACTERIA by interfering with CELL- perhaps with HETEROZYGOTES (proven wall BIOSYNTHESIS. or surmised) shaded. penicillinase (beta-lactamase I) (microbi- peduncle (histology) Any bundle of NERVE ology) ENZYME produced by some FIBRES (USA: nerve fibers) in the BRAIN. BACTERIAL SPECIES, which inactivates the antimicrobial activity of certain PEEP (physiology) An abbreviation of PENICILLINS (e.g. PENICILLIN G). ‘P’ositive ‘E’nd-‘E’xpiratory ‘P’ressure breathing. penis (anatomy) The male sex ORGAN through which SEMEN and URINE are PEG (chemistry) An abbreviation of discharged by way of the URETHRA. ‘P’oly‘E’thylene ‘G’lycol. The shaft of the PENIS contains spongy TISSUE which fills with BLOOD during PEL (toxicology) An abbreviation of sexual excitement: the ensuing erection ‘P’ermissible ‘E’xposure ‘L’evel. See makes sexual intercourse possible. PERMISSIBLE DOSE.

307 PENTAHYDRATE PERCENTAGE COMPOSITION pentahydrate (chemistry) A chemical conditions, brings about the partial containing five molecules of WATER OF HYDROLYSIS of polypeptides which breaks

CRYSTALLIZATION (e.g. CUSO4.5H2O). down PROTEIN in the food.

pentane (chemistry) C5H 12 LIQUID peptic ulcer (medical) Ulcers in the ALKANE, extracted from petroleum and STOMACH and DUODENUM are referred used as a SOLVENT and in organic to as PEPTIC ULCERS. Duodenal ulcers SYNTHESIS. It has three isomers. are more common than those in the STOMACH, and more common in men pentanoic acid (chemistry) CH3(CH2) 3 than women, who are more liable to develop -COOH LIQUID CARBOXYLIC ACID with duodenal ulcers after the MENOPAUSE. a pungent odour (USA: odor), used in perfumes. Also termed: valeric ACID. peptidase (biochemistry) ENZYME, often secreted in the body (e.g. by the pentavalent (chemistry) Having a INTESTINE), which degrades peptides VALENCE of five. into free AMINO ACIDS, thus completing the DIGESTION of proteins. pentazocine (pharmacology) Mixed opioid AGONIST-ANTAGONIST used as an peptide (biochemistry) Compounds that ANALGESIC. This is a NARCOTIC and, consist of a relatively small number of in the UK and US, a controlled substance. AMINO ACIDS linked covalently through PEPTIDE BONDS (-NH-CO-). The PEPTIDE pentose (chemistry) A MONOSACCHARIDE BOND is formed by the elimination of CARBOHYDRATE (SUGAR) that contains the atoms of WATER from the AMINO five CARBON atoms and has the GENERAL GROUP of one AMINO ACID and the

FORMULA C5H10O5; e.g. RIBOSE and CARBOXYL GROUP of another. Peptides XYLOSE. Also termed: pentaglucose. polymerize to form proteins. pentyl group (chemistry) An alternative peptide bond (biochemistry) A BOND term for AMYL GROUP. joining AMINO ACIDS to form peptides or proteins. pentylenetetrazole (pharmacology) Once believed to be a useful CNS stimulant percentage (statistics) A FRACTION as well as an ANALEPTIC agent. Because expressed in hundredths (with the its effective dose is similar to doses DENOMINATOR omitted) e.g. one half=1/ that induce seizures, its only present 2 =50/100=50 per cent (often written utility is as a diagnostic aid in screening 50%). for latent epileptogenic foci, in characterizing the underlying cerebral percentage composition (chemistry) Make- disorders in individuals with documented up of a chemical COMPOUND expressed cases of epilepsy and in BASIC research. in terms of the percentages (by MASS) of each of its COMPONENT abbreviation

PEP (physiology) An abbreviation of of elements e.g. ETHANE (C2H6), ETHENE

‘P’re‘E’jection ‘P’eriod. (C2H4) both consist of CARBON and HYDROGEN but their respective approximate pepsin (biochemistry) ENZYME produced PERCENTAGE COMPOSITIONS are: in the STOMACH which, under ACID ETHANE, 80 per cent CARBON+20 percent

308 PERCENTILE PERINATAL MORTALITY RATE

HYDROGEN; ETHENE 85 per cent CARBON ACTION of the HEART may be affected. + 15 per cent HYDROGEN. It may then be necessary to aspirate the FLUID. percentile (statistics) Hundredth part of a range of statistics (DATA) of equal pericardium (anatomy) The membranous FREQUENCY e.g. the 80th PERCENTILE sac which contains the HEART. It has is the value below which 80 per cent two layers, between which is a CAPILLARY of all the values fall. The 50th PERCENTILE space containing a FILM of FLUID. is the MEDIAN. This provides lubrication to assist the free movement of the HEART in relation perdisulphuric(VI) acid (chemistry) to neighbouring structures. The outermost

H2SO5 White CRYSTALLINE COMPOUND, part of the PERICARDIUM is fibrous. used as a powerful OXIDIZING AGENT. Also termed: CARO’S ACID; persulphuric pericentric (genetics) See INVERSION. acid (USA: perdisulfuric(VI) acid; peroxomonosulphuric acid (USA: perichondrium (histology) The thin peroxomonosulfuric acid). MEMBRANE which covers CARTILAGE, except on free joint surfaces. perfect gas (chemistry) An alternative term for ideal GAS. pericranium (histology) The periosteal MEMBRANE covering the SKULL. See also KINETIC THEORY. perikaryon (cytology) An alternative perfect number (mathematics) Number term for CELL BODY. that equals the sum of all its factors (except the number itself e.g. 28 (=1+ 2+4+7+14) perilymph (anatomy) The FLUID found and 496 (=1+2+ 4+8+16+31+62+124+248) in the INNER EAR separating the are PERFECT NUMBERS. MEMBRANE of the LABYRINTH from the surrounding BONE. It does not communicate periarteritis nodosa (histology) with the ENDOLYMPH, the FLUID inside INFLAMMATION of the outer part of the membranous LABYRINTH. See EAR. the wall of an ARTERY and the tissues immediately roundabout. perilymph (anatomy) FLUID that surrounds the COCHLEA of the EAR. periarthritis (histology) INFLAMMATION of the tissues surrounding a JOINT. perimeter (medical) A device for measuring sensitivity of each part of pericarditis (medical) INFLAMMATION the RETINA. of the PERICARDIUM, the MEMBRANE surrounding the HEART. It may occur perimetry (medical) Measurement of in association with coronary THROMBOSIS, the outer limits of the FIELD of vision VIRUS INFECTION, TUBERCULOSIS, of each EYE. rheumatic HEART disease or BACTERIAL INFECTION, or as the result of injury. perinatal mortality rate (statistics) There is pain in the chest, and if there The number of stillbirths (babies born is an EFFUSION of FLUID between the dead after 28 weeks) plus NEONATAL two layers of the PERI CARDIUM the deaths (babies born alive but dying

309 PERINATAL PERIOD PERIPHERAL NEUROPATHY within aweek, regardless of gestational periodic table (chemistry) Arrangement age at delivery) expressed as a proportion of elements in ORDER of increasing of 1000 total births. ATOMIC NUMBER, with elements having similar properties, i.e. in the same perinatal period (physiology) The FAMILY, in the same vertical column develop-mental PERIOD preceding birth; (GROUP). Horizontal rows of elements the last third of GESTATION. are termed PERIODS. perinephric (medical) Surrounding the periodicity (chemistry) Regular increases KIDNEY. and decreases of physical values for elements known to have similar chemical perineum (anatomy) The fork, strictly properties. the region between the genital organs in front and the ANUS behind. periods (physiology) See MENSTRUATION. period (1 chemistry; 2 physics) 1 One periorbita (medical) Periosteum of the of the seven horizontal rows of elements bones of the orbit or EYE socket, in the PERIODIC TABLE. 2 Time taken (periorbital, adj.). to complete a regular CYCLE. periosteum (histology) The thin MEMBRANE periodic acid—Schiff orange G of CONNECTIVE TISSUE that surrounds (histology) A histological staining the bones. technique that may be used to make PITUITARY CELL types visible under periostitis (medical) INFLAMMATION of the MICROSCOPE. the periosteum. It may follow injury, when the periosteum is stripped from the BONE periodic acid—Schiff (PAS) (histology) and there is an extravasation of BLOOD, A histological staining technique that an open fracture, or BACTERIAL INFECTION may be used to make mucins and in neighbouring tissues; it can be caused CARBOHYDRATE groups, fungi etc. by TUBERCULOSIS and syphilis. visible under the MICROSCOPE. peripheral (1 computing, 2 medical) 1 periodic disease (medical) Recurrent Any device attached to COMPUTER but polyscrositis: a disease of unknown not forming part of the central processor cause, inherited as a RECESSIVE trait, or CORE store, e.g. a DISK, printer, visual commonest among Arabs, Armenians, DISPLAY UNIT. 2 A term applied to structures Jews and Turks, which usually starts towards the outer parts or extremities, before the age of 20; the patient suffers e.g. the PERIPHERAL as opposed to a VARIETY of symptoms. the CENTRAL NERVOUS SYSTEM. periodic function (mathematics) FUNCTION peripheral nervous system (anatomy) that returns to the same value at regular That portion of the NERVOUS SYSTEM intervals. consisting of the NERVES and ganglia outside of the SPINAL CORD and BRAIN periodic law (chemistry) Properties (CENTRAL NERVOUS SYSTEM, CNS). of elements are a PERIODIC FUNCTION of their ATOMIC NUMBERS. Also termed: peripheral neuropathy (medical) A disorder Mendeleev’s LAW. of the PERIPHERAL NERVOUS SYSTEM.

310 PERIPHERAL UNIT PERMEABILITY

SOMATIC motor, sensory, and autonomic peritonitis (medical) INFLAMMATION NEURONES may be equally or preferentially of the PERITONEUM. affected. Clinical manifestations reflect the distribution of the pathological changes peritonsillar abscess (microbiology) among SOMATIC motor, sensory and (QUINSY) An ABSCESS round the autonomic NEURONES and include TONSIL, usually occurring as the result MUSCLE weakness, MUSCLE ATROPY, of ACUTE INFECTION of the tonsils. sensory disturbances and autonomic dysfunction. Neuropathies may be classified periventricular (medical) Near the by AETIOLOGY (USA: etiology) as toxic, ventricles of the BRAIN. metabolic, hereditary, autoimmune, ischaemic, traumatic, neoplasmic, infectious Perl’s prussian blue ferric stain (histol- or IDIOPATHIC. ogy) A histological staining technique that may be used to make FERRIC peripheral unit (computing) Equipment IRON visible under the MICROSCOPE. that can be linked to a COMPUTER, including input, output and STORAGE DEVICES. permanent gas (chemistry) GAS that is incapable of being liquefied by peristalsis (physiology) The process PRESSURE alone; a GAS above its by which the contents are propelled CRITICAL TEMPERATURE. along tubular organs, as in the intestines; contractions of the MUSCLE in the permanent magnet (physics) Ferromag- walls of the GUT pass in a WAVE-like netic OBJECT that retains a permanent motion along its length, being controlled MAGNETIC FIELD and the magnetic by the nervous PLEXUS present there, moment associated with it after the e.g. in the OESOPHAGUS or INTESTINE magnetizing FIELD has been removed. to push food along. permanent teeth (anatomy) Second peristriate cortex (histology) An SET of TEETH used by most mammals alternative term for parastriate CORTEX. in adult life (after they have displaced the first SET of milk or deciduous TEETH). peritoneal dialysis (medical) See DIALYSIS. permanganate bleach (histology) A histological staining technique used peritoneoscopy (laparoscopy) (medical) for removing MELANIN. The examination of the peritoneal cavity and abdominal organs through an permeability (1, 2 physics) 1 Rate at ENDOSCOPE passed through the which a substance diffuses through a abdominal wall. porous material. 2 Extent to which a substance can pass through a peritoneum (histology) The MEMBRANE MEMBRANE. Membranes may be semi- covering the inner walls of the abdominal PERMEABLE, e.g. PLASMA MEMBRANE, cavity and the organs it contains. There which allows small molecules such as are two layers, the MEMBRANE covering those of WATER to pass through. 3 the wall of the cavity is the parietal layer, MAGNETIZATION developed in a material and that covering the abdominal organs placed in a MAGNETIC FIELD, equal the VISCERAL layer. to the flux DENSITY produced divided

311 PERMEABLE PH by the MAGNETIC FIELD STRENGTH. persulphate (chemistry) SALT of PER- Also termed: magnetic PERMEABILITY. DISULPHURIC(VI) ACID (USA: persulfuric(VI) acid), used as an permeable (physics) Porous; describing OXIDIZING AGENT. (USA: persulfate). something (e.g. a MEMBRANE) that exhibits PERMEABILITY. persulphuric acid (chemistry) An alternative term for perdisulphuric(VI) permissible dose (toxicology) That acid (USA: perdisulfuric(VI) acid). (USA: dose of a chemical that may be received persulfuric acid). by an individual without expectation of an adverse effect. pertussis (medical/bacteriology) An acute, highly infectious, disease of early childhood permutation (mathematics) Number of acquired by droplet infection and caused ways a SET of numbers can be arranged by the bacteria Bordetella pertusis. Also and ordered. For n numbers, there are termed: whooping cough. n! ways of arranging them n at a time, and n!/(n-r)! ways of arranging them r pesticide (toxicology) COMPOUND used at a time (n! stands for FACTORIAL n). in agriculture to destroy organisms that can damage crops or stored food, especially pernicious anaemia (medical/haematol- insects and rodents. Pesticides include ogy) A condition resulting from the inability FUNGICIDES, herbicides and insecticides. of the bone marrow to produce normal The effects of some of them, e.g. organic red blood cells because of the deprivation CHLORINE compounds such as dichloro- of a protein released by gastric glands, diphenyl-trichloroethane (DOT), can be called the intrinsic factor, which is necessary detrimental to the ECOSYSTEM. for the absorption of vitamin B12 from food. An auto-immune mechanism may petri dish (laboratory equipment) Sterilizable be responsible. (USA: pernicious anemia). circular GLASS plate with a fitted lid used in microbiology for holding media on which peroxide (1,2 chemistry) 1 OXIDE of MICRO-ORGANISMS may be cultured. It an ELEMENT containing more OXYGEN was named after the German than does the NORMAL OXIDE of the BACTERIOLOGIST Julius Petri (1852–1921). ELEMENT. 2 OXIDE, containing the 2- O 2 ION, that yields HYDROGEN petroleum wax (chemistry) An alternative PEROXIDE On TREATMENT with an term for parafin WAX. ACID. Peroxides are powerful OXIDIZING AGENTS. P factor (physiology) An abbreviation of hypothetical ‘P’ain producing substance peroxomonosulphuric acid (chemistry) produced in ischemic muscle. An alternative term for perdisulphuric (VI) ACID (USA: perdisulfuric acid). PGO spikes (physiology) An abbreviation (USA: peroxomonosulfuric acid). of ‘P’onto-‘G’eniculo-‘O’ccipital spikes in rapid eye movement sleep. Perspex (chemistry) Trade name for the plastic polymethyl methacrylate. PH (chemistry) Hydrogen ion concentration (grams of hydrogen ions per litre) expressed as its negative logarithm; a

312 PH SCALE PHENOL measure of acidity and alkalinity. E.g. to the OESOPHAGUS when the a hydrogen ion concentration 10-4 grams EPIGLOTTIS closes the entrance of per litre corresponds to a pH of 4, and the TRACHEA. is acidic. A pH of 7 is neutral while a pH of more than 7 is alkaline. phase (1 chemistry; 2 physics) 1 Any HOMOGENEOUS and physically distinct pH scale (chemistry) Scale that indicates part of a chemical system that is separated the acidity or alkalinity of a SOLUTION. from other parts of the system by definite See PH. boundaries, e.g. ICE mixed with WATER. 2 The part of a periodically varying phage (microbiology) See BACTERIOPHAGE. waveform that has been completed at a particular moment, there being 360° phagocyte (cytology) CELL that exhibits or 2p RADIANS in a full CYCLE. PHAGOCYTOSIS. phase contrast microscope (microscopy) phagocytosis (cytology) Engulfment MICROSCOPE that uses the principle of external SOLID material by a CELL, that LIGHT passing through materials e.g. PHAGOCYTE. It is also the method of different refractive indices undergoes by which some UNICELLULAR organisms a change in PHASE, transmitting these (e.g. PROTOZOA) feed. changes as different intensities of LIGHT given out by different materials. phalanges (anatomy) Bones in the digits of the hand or foot. phase rule (physics) The number of degrees of freedom (F) of a HETERO- pharmacodynamics (pharmacology) GENEOUS system is related to the The study of the effects of drugs upon number of components (C) and of phases the body. (P) present at EQUILIBRIUM by the equation P+F=C+2. pharmacokinetics (pharmacology) The study of how drugs are absorbed into, Phe (biochemistry) An abbreviation of distributed and broken down in, and ‘Phe’nylalanine. excreted from, the body.

phenanthrene (chemistry) C14H10 Tricyclic pharmacology (pharmacology) The study aromatic ORGANIC COMPOUND consisting of the action of drugs on living organisms; of three BENZENE RINGS fused together, drug development, their use; their adverse the BASIC SKELETON of steroids and effects and their beneficial effects. many other biologically active compounds.

pharmacy (general terminology) Prepara- phenol (chemistry) C6H5OH Colourless tion and dispensing of drugs, and the (USA: colorless) CRYSTALLINE SOLID place where this is done. which turns pink on exposure to AIR and LIGHT. It has a CHARACTERISTIC, pharynx (anatomy) AREA that links rather sweet odour (USA: odor). It is the BUCCAL CAVITY (mouth) to the used as an ANTISEPTIC and disinfectant, OESOPHAGUS (gullet) and the nares and in the preparation of dyes, drugs, (back of the nostrils) to the TRACHEA etc. Also termed: CARBOLIC ACID; (windpipe). Food passes via the PHARYNX HYDROXYBENZENE. Other compounds

313 PHENOLPHTHALEIN PHOSPHIDE with one or more hydroxy groups bound accumulate in the body and can cause directly to a BENZENE RING are also brain damage with mental retardation. known as phenols. They give reactions In the UK babies are screened at birth typical of ALCOHOLS (e.g. they form by the Guthrie test and about 1 in 16,000 esters and ethers), but they are more is found to have the condition. acidic and form salts by the ACTION of strong ALKALIS (USA: strong alkalies). pheromone (biochemistry) Chemical substance produced by an organism phenolphthalein (chemistry) An ORGANIC which may influence the BEHAVIOUR COMPOUND that is used as a laxative and (USA: behavior) of another; e.g. in moths, as an INDICATOR in VOLUMETRIC pheromones act as sexual attractants; ANALYSIS. It is red in ALKALIS (USA: alkalies) in social insects such as bees, pheromones and colourless (USA: colorless) in acids. have an important role in the development and BEHAVIOUR of the COLONY. phenotype (genetics) Outward appearance and characteristics of an organism, phon (acoustics) UNIT of loudness of or the way genes express themselves in sound (given as the number of decibels an organism. Organisms of the same it appears to be above a reference tone PHENOTYPE may possess different of known FREQUENCY and INTENSITY). genotypes; e.g. in a HETEROZYGOUS phosgene (chemistry) COCI Colourless organism two ALLELES of a GENE may 2 be present with the expression of only one. (USA: colorless) GAS with penetrating and suffocating SMELL. It was formerly used as a war GAS, and is now used phenyl group (chemistry) C6H5- MONO- VALENT RADICAL derived from BENZENE. in organic SYNTHESIS. Also termed: CARBONYL CHLORIDE. phenyl methyl ketone (chemistry) An alternative term for ACETOPHENONE. phosphate (chemistry) SALT of PHOS- 3- PHORIC(V) ACID, containing the ION PO4 3-phenylpropenoic acid (chemistry) . Many phosphates occur naturally in minerals An alternative term for cinnamic ACID. (e.g. APATITE, CALCIUM PHOSPHATE) and in biological systems, and some are phenylalanine (chemistry) C6H5CH2CH- of enormous commercial and practical

(NH2)COOH ESSENTIAL AMINO ACID importance, e.g. AMMONIUM PHOSPHATE that possesses a BENZENE RING. fertilizers and ALKALI PHOSPHATE buffers. Also termed: orthophosphate. Because phenylamine (chemistry) An alternative PHOSPHORIC(V) ACID is a tribasic ACID, term for ANILINE. 2- it also forms hydrogenphosphates, HPO4 and dihydro-genphosphates, H PO -. phenylethylene (chemistry) An alternative 2 4 term for styrene. phosphatidyl choline (biochemistry) An alternative term for LECITHIN, a phenylketonuria (biochemistry) An PHOSPHOLIPID constituent of PLASMA autosomal recessive inherited deficiency MEMBRANES. of the liver enzyme phenylalanine hydroxylase that converts the amino phosphide (chemistry) A chemical COM- acid phenylalanine into tyrosine. POUND of PHOSPHORUS and another Phenylalanine and its toxic derivatives ELEMENT.

314 PHOSPHOLIPID PHOSPHORYLATION phospholipid (chemistry) Member of an essential nutrient for plants. PHOSPHORUS a CLASS of complex LIPIDS that are is made by heating CALCIUM PHOSPHATE major components of CELL MEMBRANES. (with CARBON and sand) in an electric They consist of molecules containing a furnace. It is used in matches and for PHOSPHORIC(V) ACID ESTER of making fertilizers. At. no. 15; r.a.m. 30.9738. GLYCEROL (i.e. phosphoglycerides), the remaining HYDROXYL GROUPS of the phosphorus(III) oxide (chemistry) P2O3 GLYCEROL being esterified by FATTY White waxy SOLID which readily reacts with ACIDS. Also termed: phosphoglyceride; OXYGEN to form PHOSPHORUS(V) OXIDE. phosphatide; GLYCEROL phosphatide. Also termed: PHOSPHORUS trioxide.

+ phosphonium ion (chemistry) ION PH4 . phosphorus(III) bromide (chemistry) PBr3 Colourless (USA: colorless) LIQUID, used phosphor (chemistry) Substance capable of in organic SYNTHESIS to replace a LUMINESCENCE or PHOSPHORESCENCE, HYDROXYL GROUP with a BROMINE ATOM. as used to coat the inside of a television Also termed: PHOSPHORUS tribromide. screen or FLUORESCENT LAMP. phosphorus(III) chloride (chemistry) phosphorescence (chemistry) Emission of PCI3 Colourless (USA: colorless) fuming LIGHT, generally VISIBLE LIGHT, after LIQUID, used to make ORGANIC ABSORPTION of LIGHT of another COMPOUNDS of PHOSPHORUS. Also WAVELENGTH, usually ULTRAVIOLET termed: PHOSPHORUS trichloride. RADIATION or near ULTRAVIOLET RADIATION or ELECTRONS. Phospho-rescence continues phosphorus(V) bromide (chemistry) after the stimulating source is removed. PBr5 Yellow CRYSTALLINE SOLID, used as a brominating agent. Also termed: See also FLUORESCENCE; LUMINE- PHOSPHORUS pentabromide. SCENCE.

phosphorus(V) chloride (chemistry) PCI5 phosphoric(V) acid (chemistry) H3PO4 Yellowish-white CRYSTALLINE SOLID, Tribasic ACID, a colourless (USA: colorless) used as a chlorinating agent. Also termed: CRYSTALLINE SOLID, made by dissolving PHOSPHORUS pentachloride. PHOSPHORUS(V) OXIDE in WATER.

It is used to form a corrosion-resistant phosphorus(V) oxide (chemistry) P2O5 layer on steel. Its salts, the phosphates, HYGROSCOPIC white powder which readily are of great biological and commercial reacts with WATER to form PHOSPHORIC(V) importance. Also termed: phosphoric ACID. It is used as a DESICCANT. Also ACID; ORTHOPHOSPHORIC ACID. termed: PHOSPHORUS pentoxide. phosphorus P (chemistry) Nonmetallic phosphorylation (chemistry) Process by ELEMENT in GROUP VA of the PERIODIC which a PHOSPHATE GROUP is transferred TABLE. It exists as several ALLOTROPES, to a MOLECULE of an ORGANIC COM- chief of which are red PHOSPHORUS POUND. In some sub-stances, e.g. atp, a and the poisonous and spontaneously high-ENERGY BOND may be formed by inflammable white or yellow PHOSPHORUS. PHOSPHORYLATION, which is essential for It occurs in many minerals (particularly ENERGY-transfer in living organisms. It is an phosphates) and all living organisms; it is important biochemical end-REACTION which

315 PHOTOCELL PHOTOMICROGRAPH modifies the CONFORMATION of molecules photographic fixing (PHOTOGRAPHY) such as ENZYMES, receptors, etc. The process for removing unexposed SILVER halides after development of a photocell (physics) Device that converts photographic EMULSION. It involves LIGHT into an ELECTRIC CURRENT. It can dissolving the SILVER salts by immersing be used for the detection and measurement the developed FILM in a fixing bath consisting of LIGHT. Also termed: PHOTOELECTRIC of a SOLUTION of SODIUM or ammonium CELL; photoemissive CELL. thiosulphate (USA: ammonium thiosulfate). photochemical reaction (chemistry) photography (photography) Process A CHEMICAL REACTION that is initiated of taking photographs by the chemical by the ABSORPTION of LIGHT. The ACTION of LIGHT or other RADIATION most important phenomenon of this on a sensitive plate or FILM made of type is PHOTOSYNTHESIS. It is also GLASS, coated with a LIGHT-sensitive the basis of PHOTOGRAPHY. EMULSION. celluloid or other TRANS- PARENT material LIGHT causes changes photochemistry (chemistry) Branch of in particles of SILVER salts in the chemistry concerned with the ACTION of EMULSION which, after development LIGHT in initiating CHEMICAL REACTIONS. (in a REDUCING AGENT), form grains of dark metallic SILVER to produce a photoconductivity (physics) Change negative IMAGE. Unaffected SILVER in electrical CONDUCTIVITY of a salts are removed by fixing (in a SOLUTION substance when it is exposed to LIGHT; of ammonium or SODIUM THIOSULPHATE e.g. SELENIUM, used in photoelectric [USA: sodium thiosulfate]). LIGHT METERS. photoionisation (chemistry) IONIZATION photoelectric cell (physics) An alternative of atoms or molecules by LIGHT or term for PHOTOCELL. other ELECTROMAGNETIC RADIATION. photoelectric effect (chemistry) A photoluminescence (chemistry) LIGHT phenomenon that occurs with some semi- emission by a substance after it has itself metallic materials. When photons strike been exposed to VISIBLE LIGHT or INFRA- them they are absorbed and the energized RED or ULTRAVIOLET RADIATION. electrons produced flow in the material as an ELECTRIC CURRENT. It is the photolysis (chemistry) PHOTOCHEMICAL basis of photocells and instruments that REACTION that results in the DECOM- employ them, such as photographers’ POSITION of a substance. LIGHT METERS and burglar alarms. photometer (physics) Instrument for photoelectron (chemistry) An ELECTRON measuring the INTENSITY of LIGHT. produced by the PHOTOELECTRIC EFFECT or by PHOTOIONISATION. photometry (measurement) Measurement of the INTENSITY of LIGHT. photoemission (chemistry) Emission of photoelectrons by the PHOTOELECTRIC photomicrograph (microscopy/photogra- EFFECT or by PHOTOIONISATION. phy) Photograph obtained through a MICROSCOPE.

316 PHOTOMULTIPLIER PHYSICAL CHANGE photomultiplier (physics) PHOTOCELL and oxygen. Hydrogen is subsequently of high sensitivity used for detecting combined with carbon dioxide in the very small quantities of LIGHT dark stage to form carbohydrates. RADIATION. It consists of SERIES of Photosynthetic bacteria use different electrodes in an evacuated ENVELOPE, sources of hydrogen in the process. which are used to amplify the emission CURRENT by ELECTRON multiplication. photovoltaic cell (physics) An alternative Also termed: ELECTRON MULTIPLIER. term for a PHOTOCELL.

photon (physics) QUANTUM of ENERGY phthalic acid (chemistry) C6H4(COOH)2 in ELECTROMAGNETIC RADIATION, White CRYSTALLINE SOLID which on such as LIGHT or X-RAYS. The amount heating converts to its ANHYDRIDE. of ENERGY per PHOTON is hv, where It is used in organic SYNTHESIS and h is PLANCK’S CONSTANT and v is to make polyester resins. Also termed: the FREQUENCY of the RADIATION. BENZENE-1,2-DICARBOXYLIC ACID. photoneutron (physics) NEUTRON phthalocyanine (chemistry) Member resulting from the INTERACTION of a of an important CLASS of SYNTHETIC PHOTON with an atomic NUCLEUS. organic dyes and pigments. They are blue to green and used for colouring photophosphorylation (biology) Process (USA: coloring) paints, printing inks, during PHOTOSYNTHESIS that results SYNTHETIC plastics and fibres (USA: in the formation of ATP from ENERGY fibers), rubber, etc. derived from sunlight via chlorophyll. The reactions also produce HYDROGEN, which phytogeny (taxonomy) Relationship is used in COMBINATION with CARBON between groups of organisms (e.g. DIOXIDE to make sugars. Also termed: members of a PHYLUM) based on the photosynthetic PHOSPHORYLATION. closeness of their evolutionary descent.

See also PHOSPHORYLATION-3 PHOTO- phylum (taxonomy) In biological SYNTHESIS. CLASSIFICATION, one of the groups into which the ANIMAL KINGDOM is photoreceptor (physics) A RECEPTOR divided. The members of the GROUP, consisting of sensory CELLS that are although often quite different in form stimulated by LIGHT, e.g. LIGHT-sensitive and structure, share certain common CELLS in the EYE. features; e.g. the PHYLUM Arthropoda (arthropods) includes all animals with photosynthesis (biology) Type of jointed legs and an exoskeleton. Phyla autotrophic nutrition employed by green are subdivided into classes. The equivalent plants which involves the synthesis of a PHYLUM in the plant KINGDOM of organic compounds (mainly sugars) is a DIVISION. from carbon dioxide and water. Sunlight is used as a source of energy, which physical change (chemistry) Reversible is trapped by chlorophyll present in alteration in the properties of a substance chloroplasts. The process consists of that does not affect the composition a light stage, in which energy is converted of the substance itself (as opposed into ATP and water is split into hydrogen to a chemical change, which is difficult

317 PHYSICAL CHEMISTRY PINEAL GLAND to reverse and in which composition a given number of items of information; is affected). e.g. if a barrel is used to symbolize a million gallons of oil, a row of 7 barrels physical chemistry (chemistry) Branch represents 7 million gallons. It is thus of chemistry concerned with the physical a sort of pictorial BAR CHART. properties of substances. pie chart (statistics) A method of physical states of matter (chemistry) graphically representing statistical DATA Three kinds of substances that make that consists of a circular diagram divided up MATTER: gases, liquids and solids. into sectors whose size (determined by the angle they subtend at the centre physics (physics) Science concerned [USA: center]) represents a number with the properties of MATTER, ENERGY of items of information, calculated as and RADIATION, particularly in processes a PERCENTAGE of the whole; e.g. an involving no change of chemical item allocated a quadrant (quarter of composition. the PIE CHART) represents 25 per cent of the whole. physiology (physiology) Branch of biology that is concerned with the functioning piezoelectric effect (physics) Production of living organisms (as opposed to of a measurable ELECTRIC CURRENT anatomy, which deals with their structure). by some crystals when they are subjected to mechanical compression. Pi p (mathematics) Symbol for the ratio between the CIRCUMFERENCE of a circle piezoelectricity (physics) ELECTRICITY and its DIAMETER. It is an IRRATIONAL produced by the PIEZOELECTRIC EFFECT. NUMBER with the value 3.1415926536… pigment (chemistry) INSOLUBLE Pi (biochemistry) An abbreviation of colouring (USA: coloring) material, used ‘P’hosphate- ‘i’norganic. for imparting various colours to paints, paper, polymers, etc. (SOLUBLE colouring picrate (chemistry) 1 SALT of PICRIC ACID materials are dyes). Some naturally 2 CHARGE-transfer complex of PICRIC occurring coloured substances are also ACID with aromatic HYDROCARBONS, known as pigments; e.g. green chlorophyll amines and phenols; picrates are frequently in plants and red HAEMOGLOBIN (USA: used to identify these classes of compounds. hemoglobin) in BLOOD. See AROMATIC COM-POUND. PIH (physiology/biochemistry) An picric acid (chemistry) C6H2(NO3)3OH abbreviation of ‘P’rolactin-‘I’nhibiting Yellow CRYSTALLINE SOLID obtained ‘H’ormone. by nitrating PHENOL SULPHONIC ACID (USA: phenol sulfonic acid). It has been pineal gland (anatomy) Club-shaped, used as an ANTISEPTIC, dye and explosive. elongated outgrowth from the roof of Also termed: 2,4,6-TRINI-TROPHENOL. the VERTEBRATE FOREBRAIN. It may act as a third EYE in some lower bony pictogram (statistics) A method of fishes; in other vertebrates it serves as graphically representing statistical DATA a HORMONE-producing ORGAN whose that uses symbols, each representing secretory FUNCTION is regulated by LIGHT

318 PINNA PLASMA MEMBRANE entering the body via the eyes. In human Planck’s constant (h) (physics) Funda- beings its role is not clear. Also termed: mental CONSTANT that relates the pineal body; EPIPHYSIS. ENERGY of a QUANTUM of RADIATION to the FREQUENCY of the OSCILLATOR pinna (anatomy) The part of the EAR that emits it. The relationship is E=hv, that extends beyond the SKULL, consisting where E is the ENERGY of the QUANTUM of a cartilaginous flap. It covers and and v is its FREQUENCY. Its value is protects the opening of the EAR. 6.62559×10-34 JOULE second. It was named after the German physicist Max pinocytosis (cytology) Uptake of particles Planck (1858–1947). and macromolecules by living CELLS. Also termed: endocytosis. Planck’s radiation law (physics) An OBJECT cannot emit or absorb ENERGY, pint (measurement) UNIT of LIQUID in the form of RADIATION, in a continuous measure equal to 20 FLUID ounces manner; the ENERGY can be taken up or one-eighth of a gallon. 1 pint=0.56826 or given out only as INTEGRAL multiples LITRES. of a definite amount, known as a QUANTUM. Also termed: Planck’s LAW of RADIATION. pipette (laboratory equipment) Device for transferring a known VOLUME of plasma (1 physics; 2 haematology) 1 LIQUID. It consists of a GLASS tube, STATE OF MATTER in which the atoms often with a swelling at its centre (USA: or molecules of a substance are broken center), and may have a rubber bulb into electrons and POSITIVE ions. All or GLASS ‘cylinder’ at one end. Pipettes substances pass into this STATE OF MATTER are used in VOLUMETRIC ANALYSIS. when heated to a very high TEMPERATURE, e.g. in an electric ARC or in the interior pituitary (anatomy) ENDOCRINE GLAND of a star. 2 Colourless (USA: colorless) situated at the BASE of the BRAIN in FLUID portion of BLOOD or LYMPH from vertebrates, responsible for the production of which all CELLS have been removed. many HORMONES. The ANTERIOR (front) LOBE produces GROWTH HORMONE, plasma cell (cytology) Large EGG-shaped LUTEINIZING HORMONE, FOLLICLE- CELL with granular, basophilic stimulating HORMONE, thyrotrophic CYTOPLASM except for a clear AREA HORMONE, lactogenic HORMONE and around the small eccentrically placed ACTH. The POSTERIOR (rear) LOBE NUCLEUS. Its FUNCTION is believed secretes oxytocin and VASOPRESSIN to be ANTIBODY SYNTHESIS. Also termed: produced in the HYPOTHALAMUS. Also plasmacyte. termed: PITUI-TARY GLAND; HYPOPHYSIS. plasma membrane (histology) Thin layer pk value (mathematics) Negative of TISSUE consisting of fat and PROTEIN LOGARITHM of the EQUILIBRIUM that forms a boundary surrounding the CONSTANT for the DISSOCIATION of an CYTOPLASM of EUKARYOTIC CELLS ELECTROLYTE in AQUEOUS SOLUTION. and its organelles. It is a differentially PERMEABLE MEMBRANE that separates placenta (anatomy) Vascular ORGAN adjacent CELLS and cavities. Also termed: that attaches the FOETUS (USA: fetus) cytoplasmic MEMBRANE. to the wall of the UTERUS (womb).

319 PLASMA PROTEIN POISON plasma protein (haematology/biochemis- pleura (anatomy) Double MEMBRANE try) PROTEIN in the PLASMA of BLOOD that covers the lungs and lines the chest (e.g. antibodies and various HORMONES). cavity, with FLUID between the membranes. Also termed: PLEURAL membranes. plasmasol (cytology) An alternative term for ENDOPLASM. pleural (anatomy) To do with the lungs. plaster of Paris (chemistry/medical) plexus (anatomy) NETWORK of interlacing

CaS4O1/2H2O CALCIUM SULPHATE NERVES. HEMIHYDRATE (USA: calcium sulfate hemihydrate), obtained by heating plumbic (chemistry) An alternative term GYPSUM. When WATER is added, it for LEAD(IV). sets hard, reforming GYPSUM. In doing so, it does not expand or contract much, plumbous (chemistry) An alternative and is therefore valuable as a moulding term for LEAD(II). (USA: molding) material, particularly as a splint for broken bones and in Plutonium Pu (chemistry) RADIOACTIVE the building industry. ELEMENT in GROUP 1MB of the PERIODIC TABLE (one of the ACTINIDES), produced platelet (haematology) Small non- from URANIUM-238 in a breeder REACTOR. nucleated oval or round fragment of It has several isotopes (with half-lives CELLS from the red BONE MARROW of up to 76 million years), some of which found in mammalian BLOOD. There (e.g. Pu-239) undergo nuclear FISSION; are about 250,000 to 400,000 per mm3 all are very poisonous. At. no. 94; r.a.m. in human BLOOD, which are required 244 (most STABLE ISOTOPE). to initiate BLOOD clotting by disintegrating and liberating thrombokinase. In some PMN (haematology) An abbreviation vertebrates platelets are represented of ‘P’oly‘M’orphonuclear ‘N’eutrophilic by THROMBOCYTES, which are small leukocyte. spindle-shaped nucleated CELLS. pneumatic (physics) Operated by AIR platinum Pt (chemistry) Valuable SILVER- PRESSURE. white metallic ELEMENT in GROUP VIII of the PERIODIC TABLE (a TRANSITION PNMT (biochemistry) An abbreviation of ELEMENT). It is used for making jewellery, ‘P’henylethanolamine-‘N’-‘M’ethyl‘T’rans- electrical contacts and in scientific ferase. apparatus. At. no. 78; r.a.m. 195.09. poikilothermic (biology/physiology) Platyhelminthes (parasitology) PHYLUM Describing an ANIMAL that is cold-blooded of simple invertebrates; flatworms. Parasitic and relies on the HEAT of the ENVIRONMENT platyhelminths include FLUKES and to warm its body; e.g. among vertebrates, fish, tapeworms. amphibians and reptiles.

PLC (biochemistry) An abbreviation See also HOMOIOTHERMIC. of ‘P’hospho‘L’ipase ‘C’. poison (1 chemistry; 2 toxicology) 1 Substance that destroys the activity

320 POLAR BOND POLY- of a CATALYST. 2 Substance that when consisting of a plate of tourmaline crystal Introduced into a living organism in cut in a special way, through a NICOL any way destroys life or causes injury PRISM or by using a Polaroid sheet. to health; a TOXIN. Substances that are OPTICALLY ACTIVE have the property of rotating the plane polar bond (chemistry) COVALENT BOND of polarized LIGHT. in which the bonding electrons are not shared equally between the two atoms. polarography (chemistry) Method of chemical ANALYSIS for substances in polar crystal (crystallography) Crystal DILUTE SOLUTION in which CURRENT is that has IONIC BONDS between its measured as a FUNCTION of POTENTIAL atoms. Also termed: IONIC CRYSTAL. between MERCURY elec-trodes in an ELECTROLYTIC CELL containing the polar molecule (chemistry) MOLECULE SOLUTION. that is polarized even in the absence of an ELECTRIC FIELD. See POLARIZATION. Polaroid (photography) Trade name for a thin TRANSPARENT FILM that produces polarimeter (physics) Instrument for plane POLARIZED LIGHT when LIGHT measuring the OPTICAL ACTIVITY of is passed through it. a substance. Also termed: polariscope. pole (physics) ELECTRODE (particularly polarimetry (measurement) Measurement of a BATTERY). of OPTICAL ACTIVITY, used in chemical ANALYSIS. pollen (biology) Dust-like microspore of a seed plant produced by microsporangium polarity (physics) Designation that something cones in gymnosperms and by anthers in is either positively or negatively charged angiosperms. Each grain contains male (e.g. the CATHODE in an ELECTROLYTIC gametes. If these gametes are carried by CELL has negative POLARITY). an external agent such as wind, insects or WATER to the ovules of gymnosperms or polarization (1 chemistry; 2, 3 physics) to the stigma of angiosperms, they produce 1 Separation of the POSITIVE and negative FERTILIZATION. In susceptible (i.e. charges of a MOLECULE. 2 Lining up sensitive) people, POLLEN can be a of the electric and MAGNETIC FIELDS powerful ANTIGEN that results in a of an ELECTROMAGNETIC WAVE, e.g. vigorous ALLERGIC RESPONSE. Also as in POLARIZED LIGHT. Only transverse termed: FARINA. See ALLERGY. waves can be polarized. 3 Formation of GAS bubbles or a FILM of deposit polonium Po (chemistry) RADIOACTIVE on an ELECTRODE of an ELECTROLYTIC metallic ELEMENT in GROUP VIA of the CELL, which tends to impede the flow PERIODIC TABLE, used as a source of of ELECTRIC CURRENT. alpha-particles. It has 27 isotopes, more than any other ELEMENT, with half-lives polarized light (optics) LIGHT waves of up to 100 years. At. no. 84; r.a.m. 209 (which normally oscillate in all possible (most STABLE ISOTOPE). planes) with fixed orientation of the electric and MAGNETIC FIELDS. It may be created poly- (general terminology) A prefix by passing the LIGHT through a polarizer meaning many (e.g. polychaete, polygon).

321 POLYAMIDE POLYSACCHARIDE polyamide (chemistry) CONDENSATION polymethyl methacrylate (chemistry/ POLYMER in which the units are linked optics) TRANSPARENT colourless (USA: by AMIDE groups (-CONH-); e.g. proteins, colorless) thermoplastic. Its optical HAIR, wool fibres (USA: wool fibers), properties of high transmission of LIGHT nylon. and high internal REFLECTION, coupled with great strength, are responsible polybasic (chemistry) Describing an for its use in place of GLASS. Also ACID with two or more acidic (replaceable) termed: PERSPEX. HYDROGEN atoms in its MOLECULE; e.g. PHOSPHORUS(V) (orthophosphoric) polymorphism (1 chemistry; 2 biology)

ACID, H3PO4, with three replaceable 1 Occurrence of a substance in more hydrogens, is tribasic. than one CRYSTALLINE form. 2 Occurrence of an organism in more than one structural polycyclic (chemistry) Describing a form during its LIFE CYCLE. substance that has more than one ring of atoms in its MOLECULE. polynomial (mathematics) An ALGEBRAic expression with only one VARIABLE. polyhydric alcohol (chemistry) ALCOHOL that contains three or more HYDROXYL polynucleotide (chemistry) POLYMER GROUPS. of many nucleotides. polyhydric (chemistry) Containing a polypeptide (chemistry) Chain of AMINO number of HYDROXYL GROUPS. ACIDS which is a BASIC constituent of proteins. It may be broken down by polymer (chemistry) Long-chain ENZYME ACTION (DIGESTION) to form MOLECULE built up of a number of smaller peptides. The functionally significant molecules called monomers, joined linking and folding of polypeptides makes together by POLYMERIZATION. Natural up the three-dimensional structure of polymers include STARCH, CELLULOSE a PROTEIN. and rubber. SYNTHETIC polymers include all kinds of plastics. polyploidy (genetics) Condition in which a CELL or organism has three to four polymerization (chemistry) Process of times the NORMAL HAPLOID or gametic joining together of small molecules, called number. It is often made use of in plant monomers, to form larger molecules, polymers, breeding because it results in the often in the presence of a CATALYST. In production of larger and more vigorous CONDENSATION POLYMERIZATION, two crops. Because it disturbs the sex- types of MONOMER molecules condense determining mechanism, POLYPLOIDY is to form long chains, with the elimination rare in animals, and would result in sterility. of a small MOLECULE, such as WATER. In addition POLYMERIZATION, long chains polypus Pendulous but usually BENIGN are formed by molecules of a single TUMOUR (USA: benign tumor) that grows MONOMER joining together. from MUCOUS MEMBRANE (e.g. in the nose or womb). Also termed: polyp. polymethanal (chemistry) POLYMER formed from METHANAL (FORMA-LDEHYDE). Also polysaccharide (chemistry) High MOLECU- termed: PARAFORMA-LDEHYDE. LAR WEIGHT CARBOHYDRATE, linked by

322 POLYVALENT POTASSIUM BROMIDE

GLYCOSIDE bonds, that yields a large than zero. 2 Describing an ELECTRIC number of MONOSACCHARIDE molecules CHARGE or ION that is attracted by (e.g. simple sugars) on HYDROLYSIS or a negative one. ENZYME ACTION. The most common POLYSACCHARIDES have the GENERAL positive feedback (general terminology)

FORMULA (C6H 10O 5) n; e.g. STARCH, FEEDBACK in which the output adds CELLULOSE, etc. to the input. polyvalent (1, 2 chemistry) 1 Having positron (physics) ELEMENTARY a VALENCE of more than one. 2 Having PARTICLE which has a MASS equal to that more than one VALENCY. of an ELECTRON, and an electrical CHARGE equal in magnitude, but opposite POMC (biochemistry) An abbreviation in sign, to that of the ELECTRON. of ‘P’ro-‘O’pio‘M’elano‘C’ortin. posterior 1 In bilaterally symmetrical population genetics (genetics) Study animals, the end of the body directed of the theoretical and experimental backwards during locomotion; the rear consequence of Mendelian INHERITANCE or hind end. In bipedal animals (e.g. on population levels, taking into account human beings), it corresponds to the the genotypes, phenotypes, GENE DORSAL side of quadrupeds. frequencies and the MATING SYSTEMS. post-matum (medical) Over-developed; population inversion (chemistry) A condition used of an infant born after its time. in which a higher ENERGY state in an atomic system is more populated with potash (chemistry) A substance that electrons than a lower ENERGY state. contains POTASSIUM, particularly POTASSIUM CARBONATE. porosity (physics) Property of substance that allows gases or liquids to pass potassium K (chemistry) Highly reactive through it. SILVER-white metallic ELEMENT in GROUP IA of the PERIODIC TABLE porphyrin (chemistry) Member of an (the ALKALI METALS). Its compounds important CLASS of naturally occurring occur widely (particularly the CHLORIDE) organic pigments derived from four and have many uses; POTASSIUM is PYRROLE rings. Many form complexes an essential nutrient for plants. The with METAL ions, as in e.g. chlorophyll, METAL is used as a COOLANT in nuclear haem (USA: heme), CYTOCHROME, etc. reactors. At. no. 19; r.a.m. 39.102. portal vein (anatomy) Any VEIN connect- potassium bicarbonate (chemistry) ing two CAPILLARY networks, thus An alternative term for POTASSIUM allowing for BLOOD regulation from hydrogencarbonate. one NETWORK by the others e.g. the HEPATIC PORTAL VEIN connects the potassium bromide (chemistry) KBr INTESTINE with the LIVER. White CRYSTALLINE SALT, used in medicine and PHOTOGRAPHY. positive (1 mathematics; 2 physics) 1 Describing a number or quantity greater

323 POTASSIUM CARBONATE POTENTIAL DIFFERENCE

potassium carbonate (chemistry) K2CO3 organic SYNTHESIS. Its SOLUTION White granular SOLID, used in the dissolves IODINE. manufacture of GLASS and SOAP. Also termed: POTASH. potassium manganate(VII) (chemistry) An alternative term for POTASSIUM potassium chloride (chemistry) KCI PERMANGANATE. Colourless (USA: colorless) or white

CRYSTALLINE SALT, used as a fertilizer potassium nitrate (chemistry) KNO3 and as a dietary SALT (SODIUM CHLORIDE) Colourless (USA: colorless) CRYSTALLINE substitute when SODIUM intake must SALT, a powerful OXIDIZING AGENT. It is be limited. used in the manufacture of GLASS and explosives, and as a food preservative. Also potassium cyanide (chemistry) KCN termed: SALTPETRE; NITRE. White poisonous SOLID, used in metallurgy and electroplating. potassium permanganate (chemistry)

KMnO4 Purple crystals, a powerful potassium ferricyanide (chemistry) OXIDIZING AGENT. It is used in the

K 3Fe-(CN)6 Red crystals, used as a manufacture of chemicals, as a disinfectant chemical REAGENT and in the and FUNGICIDE, and in VOLUMETRIC manufacture of pigments (e.g. Prussian ANALYSIS. Also termed: permanganate of blue). An alternative term: POTASSIUM POTASH; POTASSIUM manganate(VII). hexacyanoferrate(III). potassium-sparing diuretics (pharmacol- potassium ferrocyanide (chemistry) K4Fe- ogy) Weak DIURETICS such as amiloride

(CN)6.3H2O Yellow crystals. Also termed: which act on the distal tubule causing retention POTASSIUM hexacyanoferrate(II). of POTASSIUM. potassium hydrogencarbonate (chemis- potassium thiocyanate (chemistry) try) KHCO3 White granular SOLID, used in KSCN Colourless (USA: colorless) pharmaceuticals. Also termed: HYGROSCOPIC SOLID, used in POTASSIUM BICARBONATE. SOLUTION to test for IRON (III) (FERRIC) compounds, which give a BLOOD-red potassium hydrogentartrate (chemistry) COLOUR (USA: color).

HOOC(CHOH)2 COOK White CRYSTALLINE powder, used in baking powder. Also termed: potency (pharmacology) The strength CREAM OF TARTAR. of a drug based on its effectiveness to cause change. potassium hydroxide (chemistry) KOH Strongly HYGROSCOPIC white SOLID. potential (physics) An alternative term for A strong ALKALI, it is used in the POTENTIAL DIFFERENCE or VOLTAGE. manufacture of soft soaps. Also termed: CAUSTIC POTASH. potential difference (pd) (physics) Difference in electric POTENTIAL between potassium iodide (chemistry) KI two points in an ELECTRIC CURRENT- Colourless (USA: colorless) CRYSTALLINE carrying CIRCUIT, usually expressed in SALT, used in chemical ANALYSIS and volts (V). Also termed: VOLTAGE.

324 POTENTIOMETER PRESSURE potentiometer (1, 2 physics) 1 Instrument precipitate (chemistry) SOLID that forms for measuring POTENTIAL DIFFERENCE in and settles out from a SOLUTION. or ELECTROMOTIVE FORCE 2 VOLTAGE DIVIDER. precipitation (chemistry) Process of PRECIPITATE formation. See DOUBLE potentiometric titration (chemistry) DECOMPOSITION. Method of QUANTITATIVE ANALYSIS, using TITRATION, that involves the precursor (chemistry) INTERMEDIATE measurement of changes in ELECTRODE substance from which another is formed POTENTIAL of an ELECTRODE dipping in a CHEMICAL REACTION. into a SOLUTION. pregnancy (physiology) Time that elapses pound (1 Ib; 2 £) (1, 2 measurement) between FERTILIZATION or IMPLAN- 1 UNIT of WEIGHT equal to 16 ounces; TATION of a fertilized OVUM and an 14 Ib 1 stone, 112 Ib=1 hundredweight ANIMAL’s birth; the time that an ANIMAL (cwt). 1 Ib=0.4536 kg. 2 UNIT of currency spends as an EMBRYO or FOETUS (USA: equal to 100 pence. fetus). Also termed: GESTATION. The time that an EMBRYO reptile or bird spends in power (1 physics; 2 optics; 3 mathe- an EGG between laying and hatching is matics) 1 Rate of doing WORK. The usually termed incubation. SI UNIT of POWER is the WATT (equal to 107 erg s-1 or 1/745.7 horsepower). premolar (anatomy) Grinding and chewing 2 The extent to which a curved mirror, TOOTH located behind the canine TEETH LENS or optical instrument can magnify and in front of the MOLAR TEETH. An an OBJECT. For a simple LENS, POWER adult human being has eight premolars, is expressed in dioptres. 3 An EXPONENT two in each side of each JAW. or INDEX, written as a small superior NUMERAL; e.g. 32 is 3 to the POWER presbyopia (medical) Age-related loss 2 (or 3 squared)=9; 43 is 4 to the POWER of ACCOMMODATION of the human 3 (or 4 cubed)=256; x 5 is x to the EYE. Loss of elasticity of the EYE POWER 5 (or x to the 5th). LENS makes it difficult to FOCUS on near objects. poxvirus (virology) Member of a GROUP of large DNA-containing VIRUSES that See also HYPERMETROPIA. are responsible for smallpox, cowpox and some ANIMAL tumours (USA: tumors). pressure (p) (physics) FORCE applied to, or distributed over, a surface. Measured PRA (physiology/biochemistry) An abbre- as FORCE f per UNIT AREA a; p=f/a. viation of ‘P’lasma ‘R’enin ‘A’ctivity. At a depth d in a LIQUID, the PRESSURE is given by p=gd, where is the LIQUID’S praseodymium Pr (chemistry) Metallic DENSITY, d the depth and g is the ELEMENT in GROUP IIIB of the PERIODIC ACCELERATION of free fall. The SI UNIT TABLE (one of the LANTHANIDES). At. no. of PRESSURE is the PASCAL; other 59; r.a.m. 140.9077. units include bars, millibars, atmospheres and millimetres of MERCURY. PRC (biochemistry) An abbreviation of ‘P’lasma ‘R’enin ‘C’oncentration. See also ATMOSPHERIC PRESIURE.

325 PRESSURE GAUGE PROGRAM pressure gauge (physics) Device for probability distribution of electrons measuring FLUID PRESSURE (e.g. (physics) Probability that an ELECTRON BAROMETER, MANOMETER). within an ATOM will be at a certain point in space at a given time. It predicts primary alcohol/amine (chemistry) the shape of an ATOMIC ORBITAL. ALCOHOL or AMINE with only one ALKYL GROUP or ARYL GROUP. proboscis (biology) Tube-like ORGAN of varying form and functions. In insects, primary cell (physics) ELECTROLYTIC a PROBOSCIS is a filamentous structure CELL (BATTERY) in which the CHEMICAL that projects outwards from the mouthparts, REACTIONS that cause the CURRENT functioning as a piercing and sucking flow are not readily reversible and the device for obtaining LIQUID food. In CELL cannot easily be recharged, e.g. elephants, the PROBOSCIS is the trunk, a DRY CELL. and in some marine animals it is a tube-like PHARYNX that can be protruded. See also SECONDARY CELL. product (1 mathematics; 2 chemistry) primary colour (1, 2 physics) 1 Red, 1 The result of multiplying numbers green and violet, which give all other together. 2 A substance formed as a colours (USA: colors) when LIGHT producing result of a chemical change. them is combined in various proportions. All three mix to give white. 2 PIGMENT proenzyme (biochemistry) An alternative colours red, yellow and blue, which can term for ZYMOGEN. also be combined to give pigments of all other colours. All three mix to give progesterone (biochemistry) C21H30O2 black. (USA: primary color). STEROID SEX HORMONE secreted by the CORPUS LUTEUM of the mammalian prime number (mathematics) INTEGER OVARY, PLACENTA, TESTES and (whole number) divisible only by itself ADRENAL CORTEX. In females it prepares and 1. All PRIME NUMBERS except 2 the UTERUS for the IMPLANTATION of a are odd. fertilized OVUM (EGG) and during PREGNANCY maintains nourishment for principle of flotation (physics) A floating the EMBRYO by developing the OBJECT displaces its own WEIGHT of PLACENTA, inhibiting OVULATION and FLUID (LIQUID or GAS). An OBJECT floats MENSTRUATION, and stimulating the if its WEIGHT equals the upthrust on it. GROWTH of the MAMMARY GLANDS.

See also ARCHIMEDES’ PRINCIPLE. progestogen drugs (pharmacology) A group of drugs chemically and printer (computing) COMPUTER OUTPUT pharmacologically similar to the natural DEVICE that produces HARD COPY as HORMONE progesterone. Administered a printout. There are various kinds, including orally they are used in oral contraceptives (in ORDER of speed) daisy-wheel, dot- and to treat menstrual disorders. MATRIX, line, barrel and LASER. program (computing) Sequence of print-out (computing) Output (HARD COPY) instructions for a COMPUTER. Also termed: from a COMPUTER PRINTER. programme.

326 PROGRESSION PROPENONITRILE

progression (mathematics) Mathematical propanoic acid (chemistry) CH3CH2COOH SERIES of terms. See ARITHMETIC LIQUID CARBOXYLIC ACID. Also termed: PROGRESSION; GEOMETRIC PROG- PROPIONIC ACID. RESSION. propanol (chemistry) ALCOHOL that prokaryote (biology) DNA-containing, occurs as two isomers. 1 n-PROPANOL single-celled organism with no proper C3H7OH is a colourless (USA: colorless) NUCLEUS or ENDOPLASMIC RETI- LIQUID, used as a SOLVENT and in CULUM; e.g. BACTERIA, BLUE-GREEN making toilet preparations. Also termed: ALGAe (cyanophytes). n-propyl ALCOHOL; propan-l-ol. 2

ISOPROPANOL (CH3) 2CHOH is also See also EUKARYOTE. a colourless LIQUID, used for preparing esters, ACETONE (propanone), and prokaryotic (biology) Describing or as a SOLVENT. Also termed: ISOPROPYL resembling a PROKARYOTE. ALCOHOL; propan-2-ol. prolactin (biochemistry) PROTEIN propranolol hydrochloride (pharmacology) HORMONE secreted by the ANTERIOR A BETA-BLOCKER that can be administered PITUITARY. In mammals it stimulates orally or by injection and used as an LACTATION and promotes functional ANTIHYPERTENSIVE, as an ANTI-ANGINA activity of the CORPUS LUTEUM. Also treatment, an ANTI-ARRHYTHMIC, and an termed: LUTEOTROPHIN; mammary ANTITHYROID, antimigraine and axiolytic stimulating HORMONE; mammogen treatment. HORMONE; mammotrophin. 2-propanone (chemistry) An alternative proline (biochemistry) White CRYSTALLINE term for ACETONE. AMINO ACID that occurs in most proteins. propellant (physics) GAS used in an promethium Pm (chemistry) RADIOACTIVE AEROSOL to expel the contents through metallic ELEMENT in GROUP IIIB of the an atomizing jet. PERIODIC TABLE (one of the LANTHANIDES). It has several isotopes 2-propenal (chemistry) An alternative (none of which occurs naturally), with half- term for ACROLEIN. lives of up to 20 years. At. no. 61; r.a.m. 145

(most STABLE ISOTOPE). propene (chemistry) CH3CH=CH2 Colourless (USA: colorless) gaseous promoter (chemistry) Substance used ALKENE (OLEFIN), used in industry to enhance the efficiency of a CATALYST. for the preparation of ISOPROPANOL, Also termed: activator. GLYCEROL, polypropene, etc. Also termed: propylene. proof (measurement) Measure of the ETHANOL (ETHYL ALCOHOL) content propenoic acid (chemistry) An alternative of a SOLUTION (gunpowder moistened term for acrylic acid. with a 100 per cent PROOF SPIRIT will just ignite). A 100 per cent PROOF SOLUTION propenonitrile (chemistry) An alternative is 57.1 per cent ETHANOL by VOLUME term for ACRYLONITRILE. or 49.3 per cent ETHANOL by WEIGHT.

327 PROPER FRACTION PROTON proper fraction (mathematics) FRACTION Prot (biochemistry) An abbreviation whose NUMERATOR is less than its of ‘Prot’ein anion. DENOMINATOR (a FRACTION whose NUMERATOR is larger than its DENOMINATOR protactinium Pa (chemistry) RADIOACTIVE is an IMPROPER FRACTION). ELEMENT in GROUP IIIB of the PERIODIC TABLE (one of the ACTINIDES). It has several prophase (genetics) First stage of CELL isotopes, with half-lives of up to 20,000 years. DIVISION in MEIOSIS and MITOSIS. During At. no. 91; r.a.m. 231.0319. PROPHASE chromosomes can be seen to thicken and shorten and to be composed protease (biochemistry) ENZYME that of chromatids. The spindle is assembled breaks down PROTEIN into its constituent for DIVISION of chromosomes and the peptides and AMINO ACIDS by breaking NUCLEAR MEMBRANE disintegrates. In PEPTIDE linkages (e.g. PEPSIN, trypsin). MEIOSIS the first PROPHASE is extended into several stages. protein (biochemistry) Member of a CLASS of high MOLECULAR WEIGHT polymers propionaldehyde (chemistry) An altern- composed of a VARIETY of AMINO ACIDS ative term for propanal. joined by PEPTIDE linkages. In CONJU- GATED proteins, the AMINO ACIDS are propionic acid (chemistry) An alternative joined to other groups. Proteins are extremely term for propanoic acid. important in the physiological structure and functioning of all living organisms. prostaglandin (biochemistry) Member of a GROUP of UNSATURATED FATTY ACIDS protein synthesis (biochemistry) Process that contain 20 CARBON atoms. They are by which proteins are made in CELLS. A found in all human TISSUE, and particularly MOLECULE of MESSENGER RNA decodes high concentrations occur in SEMEN. Their the sequence of copied DNA on ribosomes activities affect the NERVOUS SYSTEM, in the CYTOPLASM. A POLYPEPTIDE chain circulation, female reproductive organs and is generated by the linking of AMINO ACIDS METABOLISM. Most prostaglandins are in an ORDER instructed by the BASE secreted locally and are rapidly metabolized sequence of MESSENGER RNA. by ENZYMES in the TISSUE. protist (biology) Member of the PROTISTA. prostate gland (anatomy) GLAND located at the BASE of the urinary BLADDER that forms Protista (taxonomy) KINGDOM that contains part of the male reproductive system. The size simple organisms such as ALGAe, of the GLAND and the quantity of its BACTERIA, FUNGI and PROTOZOA, SECRETION are controlled by ANDROGENS. although sometimes MULTICELLULAR Its FUNCTION is SECRETION of a FLUID organisms are excluded. containing ENZYMES and antiglutinating FACTOR, which contributes to the production proton (physics) Fundamental ELE- of SEMEN. MENTARY PARTICLE with a POSITIVE CHARGE equal in magnitude to the negative prosthetic group (biochemistry) Non- ELECTRON CHARGE, and with a rest MASS PROTEIN portion of a CONJUGATED of 1.67252 ×10-27 kg (about 1,850 times that PROTEIN, e.g. haem (USA: heme) GROUP of an ELECTRON). Protons are constituents in HAEMOGLOBIN (USA: hemoglobin). of the NUCLEUS in every kind of ATOM.

328 PROTON NUMBER PTHRP proton number (chemistry) An alternative pseudopodium (biology) Part of an term for ATOMIC NUMBER. AMOEBA (USA: ameba) or similar protozoan that bulges out of its single protonic acid (chemistry) COMPOUND CELL. Pseudopodia are used for locomotion that releases solvated HYDROGEN IONS and to engulf food particles (for in a suitable polar SOLVENT (e.g. WATER). DIGESTION). proton pump (physiology/biochemistry) pseudopregnancy (physiology) In some The enzyme hydrogen-potassium ATP- female mammals, physiological state ase which is involved in the final stage resembling PREGNANCY without the of acid production in the PARIETAL CELLS. formation of embryos. Also termed: FALSE PREGNANCY. proton pump inhibitors (pharmacology) Drugs, e.g. omeprazole, that block the P Surg. (medical) An abbreviation of action of the proton pump in the PARIETAL ‘P’lastic ‘Surg’ery. CELLS of the STOMACH causing a reduction in acid secretion. psychiatry (medical) Study and TREATMENT of disorders of the mind protoplasm (cytology) Material within a (i.e. mental disorders). CELL, i.e. the CYTOPLASM and NUCLEUS. psycho- (general terminology) Prefix Protozoa (taxonomy) Subkingdom or meaning to do with the mind (e.g. PHYLUM of microscopic UNICELLULAR psychiatry, psychology). organisms which range from plant-like forms to types which feed and behave like psychology (psychology) Scientific study animals. They have no fundamental body of the mind. shape but have specialized organelles. BASIC MODE of REPRODUCTION is by PTA (haematology) An abbreviation BINARY FISSION, although multiple of ‘P’lasma ‘T’hromboplastin ‘A’ntecedent FISSION and CONJUGATION occur in (clotting factor XI). some SPECIES. Some protozoans are colonial and many are parasitic, inhabiting PTC (1, 2 physiology) 1 Abbreviation freshwater, marine and damp terrestrial of ‘P’lasma ‘T’hromboplastin ‘C’omponent environments. (clotting factor IX); 2 An abbreviation of ‘P’henyl‘T’hio‘C’arbamide. 5-PRPP (biochemistry) An abbreviation of ‘5’-‘P’hospho‘R’ibosyl ‘P’yro‘P’hosphate. p tgt (chemistry) An abbreviation of ‘p’rimary ‘t’ar‘g’e ‘t’. prussic acid (chemistry) An alternative term for HYDROCYANIC ACID. PTH (physiology/biochemistry) Abbre- viation of ‘P’ara‘T’hyroid ‘H’ormone. P sac (anatomy) Pericardial cavity. The cavity within which the HEART lies. PTHRP (physiology/biochemistry) Abbre- viation of ‘P’ara‘T’hyroid ‘H’ormone- pseudo- (general terminology) Prefix ‘R’elated ‘P’rotein. meaning false (e.g. PSEUDOPREGNANCY).

329 PULMONARY ARTERY (PYRO)GLU pulmonary artery (anatomy) In mammals, HETEROCYCLIC ring of five CARBON a paired ARTERY that carries deoxygen- atoms and one OXYGEN ATOM. ated BLOOD from the right VENTRICLE of the HEART to the lungs. It is the only See also FURANOSE. ARTERY that carries deoxygenated BLOOD.

pyrazine (chemistry) C4H4N2 HETEROCYCLIC pulmonary (anatomy) Concerning the AROMATIC COMPOUND whose ring contains lungs and BREATHING. four CARBON atoms and two NITROGEN atoms. Also termed: 1, 4-diazine. pulmonary vein (anatomy) A paired

VEIN that carries oxygenated BLOOD pyrazole (chemistry) C3H4N2 HETERO- from the lungs to the right ATRIUM of CYCLIC AROMATIC COMPOUND whose the HEART. It is the only VEIN that ring contains three CARBON atoms and two carries oxygenated BLOOD. NITROGEN atoms. Also termed: 1, 2-diazole.

pulse (1 physics; 2 physiology) 1 Brief pyrene (chemistry) C16H 10 AROMATIC disturbance propagated in a similar way COMPOUND consisting of four BENZENE as a WAVE, but not having the continuous RINGS fused together. periodic nature of a WAVE. 2 Regular expansion of the wall of an ARTERY Pyrex (chemistry) Trade name for a HEAT- caused by the BLOOD PRESSURE waves resistant BOROSILICATE GLASS, used that accompany heartbeats. for domestic and LABORATORY glassware.

pump (equipment) Mechanical device for pyridine (chemistry) C5H5N HETEROCYCLIC transferring liquids or gases, or for LIQUID ORGANIC BASE which occurs in the compressing gases. A simple lift PUMP LIGHT oil FRACTION of coal-tar and in BONE employs ATMOSPHERIC PRESSURE and oil. It forms salts with acids and is important in cannot PUMP a LIQUID vertically more organic SYNTHESIS. than about 10 m (32 feet); a FORCE PUMP does not have this restriction. pyridoxine (chemistry) CRYSTALLINE substance from which the active purine (chemistry) C5H4N4 HETEROCYCLIC COENZYME forms of VITAMIN B6 are NITROGEN-containing BASE from which the derived. It is also utilized as a potent bases CHARACTERISTIC of nucleotides GROWTH FACTOR for BACTERIA. and DNA are derived; e.g. ADENINE,

GUANINE. Other PURINE derivatives pyrimidine (chemistry) C4H4N2 HETERO- include CAFFEINE and URIC ACID. CYCLIC CRYSTALLINE ORGANIC BASE from which bases found in nuelcotides and DNA are putrefaction (microbiology) ANAEROBIC derived; e.g. URACIL, THYMINE and CYTO- DECOMPOSITION of organic MATTER SINE. Its derivatives also include BARBITURIC by microscopic organisms (e.g. BACTERIA, ACID and the BARBITURATE drugs. FUNG, etc.) which results in the formation of incompletely oxidized products. pyro- (general terminology) Prefix that denotes strong HEAT, fire. pyranose (chemistry) Any of a GROUP of MONOSACCHARIDE sugars (hexoses) (pyro)Glu (biochemistry) An abbreviation whose molecules have a six-membered of ‘pyro’‘Glu’tamic acid.

330 PYROELECTRICITY PZI pyroelectricity (chemistry) POLARIZATION of certain crystals by the application of HEAT. pyrolysis (chemistry) DECOMPOSITION of a chemical COMPOUND by HEAT. pyrometer (physics) Instrument for measuring high temperatures, above the range of LIQUID thermometers. pyrometry (measurement) Measurement of high temperatures.

pyrrole (biochemistry) (CH)4NH HETERO- CYCLIC LIQUID ORGANIC COMPOUND whose ring contains four CARBON atoms and one NITROGEN ATOM. An AROMATIC COMPOUND, its derivatives are important biologically; e.g. haem (USA: heme), chlorophyll. pyruvate (chemistry) ESTER or SALT of PYRUVIC ACID.

pyruvic acid (biochemistry) CH3COCOOH Simplest keto-ACID, important in making ENERGY available from ingested food. It is the PRODUCT of the first stage of RESPIRATION (GLYCOLYSIS). If OXYGEN is available, the ACID is broken down in the KREBS CYCLE to yield ENERGY. Also termed: 2-OXOPROPANOIC ACID.

PYY (biochemistry) An abbreviation of ‘P’olypeptide ‘YY’.

PZI (biochemistry) An abbreviation of ‘P’rotamine ‘Z’inc ‘I’nsulin.

331 Q

Q (biochemistry) A symbol for glutamine. (DEGREE) or square POWER, which has two possible solutions, known as the roots q (genetics) Symbol used to designate the of the unknown. The roots may be real long arm of a CHROMOSOME. Thus if a and different, real and the same (coincident) GENE’S LOCUS is given as 22q, this means or imaginary. For the general QUADRATIC that it is on the long arm of CHROMOSOME EQUATION ax2+bx+c=0, the solutions are 22. The short arm is called p. given by x=[-b ± (b2- 4ac)1/2]/2a.

Q&A (literature terminology) An quadriceps (anatomy) The large MUSCLE abbreviation of ‘Q’uestion ‘and’ ‘A’nswer. covering the front of the thigh. It is a COMBINATION of four muscles, the QC (quality standards) An abbreviation vastus medialis, vastus intermediug, of ‘Q’uality ‘C’ontrol. vastus lateralis and rectus femoris.

Q fever (microbiology) An ACUTE febrile quadriplegia (medical) Paralysis of all illness caused by INFECTION with the four limbs. MICRO-ORGANISM Coxiella burnetii, a SPECIES of Rickettsia. The organism quadrivalent (chemistry) Having a normally infects sheep, cattle and goats, VALENCE of four. Also termed: TETRA- passing to them from wild animals via VALENT. TICKS and lice, but humans acquire the INFECTION by inhaling dust from quadruplets (genetics) Four babies dried excreta or drinking infected milk. born together. Human QUADRUPLETS may be identical or non-identical. QSAR (toxicology) An abbreviation of ‘Q’UANTITATIVE ‘S’TRUCTURE ‘A’CTIVITY qual. (1, 2, 3 general terminology) 1 ‘R’ELATIONSHIPS. An abbreviation of ‘qual’ification. 2 An abbreviation of ‘qual’itative. 3 An qty (general terminology) An abbreviation abbreviation of ‘qual’ity. of ‘q’uan‘t’it‘y’. qualitative (chemistry) Dealing with the quadrate (anatomy) One of a pair of qualities or appearance of something only. bones in the upper JAW of amphibians, birds, fish and reptiles that has evolved qualitative analysis (chemistry) Identifica- into the INCUS (an EAR OSSICLE) in tion of the constituents of a substance mammals. or MIXTURE, irrespective of their amount. quadratic equation (mathematics) Alge- quality assurance (quality standards) braic equation of the second ORDER See QUALITY CONTROL.

332 QUALITY CONTROL QUANTUM THEORY quality control (QC) (quality standards) RADIATION (such as LIGHT) and in certain A term used to describe mechanisms contexts the MESON is the QUANTUM and procedures planned as a part of of the nuclear FIELD. experimental protocols that are designed to reduce the possibility of error, particularly quantum electrodynamics (physics) Study human error. INTEGRAL parts of QUALITY of ELECTROMAGNETIC INTERACTIONS, CONTROL include the design of procedures in accordance with the QUANTUM THEORY. in such a way as to minimise the possibility of human error, the collection of DATA quantum electronics (physics) Generation not only on the results of the experiments, or amplification of MICROWAVE POWER, but also on the daily activities, personnel governed by QUANTUM MECHANICS. involved, etc.; and the proper training of all LABORATORY and ANIMAL room quantum evolution (genetics) Evolution- personnel. Activity and results forms ary change in which new SPECIES are must be designed in such a way that formed very rapidly. The circumstance omissions are immediately apparent. in which this is likely to happen is the colonisation of new habitats by small quanta (measurement) Plural of QUANTUM. populations, in which both founder effect and GENETIC DRIFT contribute to genetic quantification (genetics) the application change. of measurement to experimental results. quantum mechanics (physics) Method quantitative (chemistry) Dealing with of dealing with the BEHAVIOUR (USA: quantities of substances, e.g. MASS, behavior) of small particles such as VOLUME, etc., irrespective of their electrons and nuclei. It uses the idea identity. of the PARTICLE WAVE duality of MATTER. Thus an ELECTRON has a dual nature, quantitative analysis (chemistry) Deter- PARTICLE and WAVE, but it behaves mination of the amounts of constituents as one or the other according to the present in a substance or MIXTURE, nature of the experiment. often by weighing or manipulating volumes of solutions. quantum number (physics) INTEGER or half-INTEGRAL number that specifies See also GRAVIMETRIC ANALYSIS; possible values of a quantitized physical VOLUMETRIC ANALYSIS. quantity, e.g. ENERGY LEVEL, nuclear spin, angular momentum, etc. quantitative structure-activity relationships (QSAR) (toxicology) The relation- quantum state (physics) State of an ship between the physical and/or chemical ATOM, ELECTRON, PARTICLE, etc; defined properties of chemicals and their ability by a unique SET of QUANTUM NUMBERS. to cause a particular effect, enter into particular reactions, etc. quantum theory (physics) Theory of RADIATION. It states that RADIANT ENERGY quantum (measurement) UNIT quantity is given out by a radiating body in separate (an indivisible ‘packet’) of ENERGY postulated units of ENERGY known as quanta; the in the QUANTUM THEORY. The PHOTON same applies to the ABSORPTION of is the QUANTUM of ELECTROMAGNETIC RADIATION. The total amount of RADIANT

333 QUARANTINE QUINONE

ENERGY given out or absorbed is always audience can ask specific questions a whole number of quanta. of the speaker or panel. quarantine (medical) The ISOLATION quicklime (chemistry) CaO Whitish powder of people who are suspected of being prepared by roasting limestone, used infected with a particular INFECTIOUS in agriculture and in cements and mortar. DISEASE. Also termed: CALCIUM OXIDE; LIME. quart (measurement) UNIT of LIQUID quicksilver (chemistry) See MERCURY. measure equal to 2 pints. 1qt (imperial) =1.13652 LITRES. quinidine (pharmacology) A drug obtained from the cinchona tree and quartan malaria (microbiology) MALARIA used to treat irregular HEART ACTION. caused by Plasmodium malariae. quinine (pharmacology) An ALKALOID quartile (statistics) Value below which made from the bark of the South American one-quarter of a SET of DATA lies; cinchona tree. It is used against the 25th PERCENTILE. The second chloroquine-resistant strains of Plas- QUARTILE equals the MEDIAN. modium falciparum, the organism of maglignant MALARIA. quartz (chemistry) SiO2 Natural CRYSTALLINE silica (SILICON dioxide), quinine (pharmacology) Colourless (USA: one of the hardest of common minerals. colorless) CRYSTALLINE ALKALOID, Its crystals (which can generate piezoelec- obtained from the bark of the cinchona tricity) are frequently colourless (USA: shrub, once much used in the colorless) and TRANSPARENT. It is used TREATMENT and prevention of MALARIA. as an abrasive and in mortar and cement.

quinoline (chemistry) C9H7N Colourless quasi group (statistics) A collection (USA: colorless) oily LIQUID HETERO- of people, not yet a proper GROUP, CYCLIC BASE. It is an AROMATIC but with the CAPACITY to become one. COMPOUND consisting of fused BENZENE and PYRIDINE rings. quaternary ammonium compound (chemistry) Member of a GROUP of quinolones (pharmacology) A GROUP white CRYSTALLINE solids, SOLUBLE of antibiotics comprising nalidixic ACID in WATER, and completely dissociated and cinoxacin, used in urinary infections, in SOLUTION. These compounds have ciprofloxacin, used in Gram-negative and + - the GENERAL FORMULA R4N X , where some Gram-POSITIVE infections that are R is a long-chain ALKYL GROUP. They resistant to other antibiotics, and enoxacin, have DETERGENT properties. Also termed: which is used in SKIN infections, shigella quaternary ammonium SALT. infections, GONORRHOEA and urinary infections. quenching (chemistry) Rapid cooling. quinone (chemistry) Member of a GROUP Question and Answer (Q&A) (general of CYCLIC UNSATURATED diketones terminolgy) Relating to speeches and in which the DOUBLE BONDS and keto lectures, the time when people in the groups are CONJUGATED. Thus they

334 QUINSY QWERTY are not AROMATIC COMPOUNDS. Many quinones are used as dyes. quinsy (medical) See PERITONSILLAR ABSCESS. quotient (mathematics) Result of DIVISION. qwerty (computing) Description of the standard ALPHANUMERIC KEYBOARD used on typewriters, typesetting machines, WORD PROCESSORS and computers (named after the first six letters on the top rank of letters).

335 R

R (radiology) An abbreviation ‘R’adiologist/ Rad. (radiology) An abbreviation of ‘R’adiology. of ‘Rad’iologist; ‘Rad’iology; ‘Rad’iotherapist; ‘Rad’iotherapy; Ra (chemistry) The CHEMICAL SYMBOL for ELEMENT 88, RADIUM. rada (radiology) An abbreviation of ‘rad’io‘a’ctive. rabies (medical) VIRUS disease, mainly affecting carnivores but which can affect radial immunodiffusion (RID) (immunol- any WARM-BLOODED SPECIES, that ogy) See IMMUNOASSAY. is usually transmitted by bites from infected animals, including foxes, wolves, radial symmetry (general terminology) jackals, mongooses, raccoons, skunks SYMMETRY about any one of several and bats. Also termed: HYDROPHOBIA. lines or planes through the centre (USA: center) of an OBJECT or organism. race (biology) In CLASSIFICATION, alternative term for SUBSPECIES. an See also BILATERAL SYMMETRY. racemic acid (chemistry) RACEMIC radian (rad) (measurement) SI UNIT MIXTURE of TARTARIC ACID. of plane angle; the angle at the centre (USA: center) of a circle subtended racemic mixture (chemistry) Optically by an ARC whose length is equal to inactive MIXTURE that contains equal the RADIUS of the circle. 1 RADIAN=57 amounts of DEXTROROTATORY and degrees (approx.). LAEVOROTATORY forms of an OPTICALLY ACTIVE COMPOUND. radiance (physics) (measurement) The RADIANT INTENSITY of a source in racemization (chemistry) TRANSFOR- a given direction per unit transverse MATION of OPTICALLY ACTIVE compounds AREA. It is usually measured in WATTS into RACEMIC MIXTURES. It can be effected METRE2 per steradian. by the ACTION of HEAT or LIGHT, or by the use of chemical reagents. radiant (physics) Describing something that emits electromagnetic RADIATION rad (1 radiology; 2 measurement) 1 An (e.g. LIGHT, HEAT rays). abbreviation of ‘r’adiation ‘a’bsorbed ‘d’ose. 2 UNIT of ABSORBED DOSE of radiant energy (physics) Electromagnetic IONIZING RADIATION, equivalent to 100 ENERGY, which the part with wavelengths ergs per gram (0.01 J kg1) of absorbing between about 380 and 750 nm is material. The corresponding SI UNIT is visible as LIGHT. the gray.

336 RADIANT FLUX RADIOACTIVE SERIES radiant flux (physics) The rate at which POWER BECQUEREL in SI UNITS. Formerly it is emitted or received by an OBJECT in the was measured in curies. form of ELECTROMAGNETIC RADIATION. radical (1 chemistry; 2 mathematics) 1 radiant heat (physics) HEAT that is A GROUP of atoms within a MOLECULE transmitted in the form of INFRA-RED that maintains its identity through chemical RADIATION. changes that affect the rest of the MOLECULE, but is usually incapable of radiant intensity (physics) The INTENSITY independent existence; e.g. alkyl RADICAL. of energy emitted by a source per UNIT See also FREE RADICAL. 2 Relating to SOLID angle, usually measured in WATT the ROOT of a number or quantity. steradian. radiculitis (histology) INFLAMMATION radiation (physics) ENERGY that travels of a ROOT, applied to INFLAMMATION in the form of ELECTROMAGNETIC of a NERVE ROOT. RADIATION, e.g. radio waves, INFRA- RED RADIATION, LIGHT, ULTRAVIOLET radioactive (radiology) Possessing or RADIATION, X-RAYS and GAMMA RAYS. exhibiting RADIOACTIVITY. The term is also applied to the rays of ALPHA PARTICLES and BETA PARTICLES radioactive decay (radiology) Way in emitted by RADIOACTIVE substances. which a RADIO-ISOTOPE spontaneously PARTICLE rays and short-WAVELENGTH changes into another ELEMENT or ISOTOPE ELECTROMAGNETIC RADIATION may by the emission of alpha or BETA PARTICLES be harmful to tissues as they are IONIZING or GAMMA RAYS. The rate at which it RADIATION. Radiation is one of the causes does so is represented by its HALF-LIFE. of raised MUTATION rates and of increased INCIDENCE of cancers. radioactive equilibrium (radiology) A condition attained when a parent radiation damage. (physics) Alteration RADIOACTIVE ELEMENT produces a of properties of a material that results daughter RADIOACTIVE ELEMENT that from exposure to IONIZING RADIATION. decays at the same rate as it is being formed from the parent. radiation pressure (physics) MINUTE FORCE exerted on a surface by ELECTROMAGNETIC radioactive isotope (chemistry) A form RADIATION that strikes it. of a chemical substance that emits RADIOACTIVITY. radiation sickness (medical/radiology) Illness caused by exposure to excessive radioactive series (radiology) One of RADIATION. ALPHA PARTICLES cannot three SERIES that describe the penetrate SKIN and are not dangerous RADIOACTIVE DECAY of 40 or more internally. GAMMA RADIATION, X-RAYS naturally occurring RADIOACTIVE and neutrons can penetrate the body ISOTOPES of high ATOMIC NUMBER. and are thus the most harmful. They are known (after the ELEMENT at the beginning of each sequence) as radiation unit (radiology) Activity of a the THORIUM SERIES, URANIUM SERIES RADIO-ISOTOPE expressed in units of and ACTINIUM SERIES. disintegrations per second, called the

337 RADIOACTIVE STANDARD RADIUS radioactive standard (radiology) RADIO- RADIATION. An X-RAY photograph is a ISOTOPE of known rate of RADIOACTIVE common example. DECAY used for the CALIBRATION of RADIATION-measuring instruments. radiography (radiology) PHOTOGRAPHY using X-RAYS or GAMMA RAYS, radioactive tracers (radiology) RADIO- particularly in medical applications. ACTIVE ISOTOPES whose passage and BEHAVIOUR (USA: behavior) through radio-isotope (radiology) ISOTOPE that the body is monitored by recording their emits RADIOACTIVITY (IONIZING RADIATION, e.g. 14C, 15N. RADIATION) during its spontaneous DECAY. RADIOISOTOPES are useful radioactive waste (radiology) Hazardous sources of RADIATION (e.g. in RADIO- RADIO-ISOTOPES (FISSION products) GRAPHY) and are used as tracers for that accumulate as waste products in radioactive tracing. a nuclear REACTOR. They have to be periodically removed and stored safely radiology (radiology) Study of X-RAYS, or reprocessed. The term is also applied GAMMA RAYS and RADIOACTIVITY to the waste (‘tailings’) produced by (including RADIO-ISOTOPES), especially as the processing of URANIUM ores. used in medical diagnosis and TREATMENT. radioactivity (radiology) Spontaneous radioluminescence (radiology) FLUO- DISINTEGRATION of atomic nuclei, usually RESCENCE caused by RADIOACTIVITY. with the emission of ALPHA PARTICLES, BETA PARTICLES or GAMMA RAYS. radio-opaque (radiology) Resistant to the penetrating effects of RADIATION, radiobiology (radiology) Study of IONIZING especially X-RAYS, often used to describe RADIATION in relation to living systems. substances injected into the body before It includes the effects of RADIATION on a RADIOGRAPHY examination. living organisms and the use of RADIO- ISOTOPES in biological and medical WORK. radiotherapy (radiology) TREATMENT of disorders (e.g. CANCER) by the use See also RADIOTHERAPY. of IONIZING RADIATION such as X-RAYS or RADIATION from RADIO-ISOTOPES. radiochemistry (radiology) Chemistry of RADIOACTIVE elements and their radium Ra (chemistry) SILVER-white compounds, and use of RADIO-ISOTOPES RADIOACTIVE metallic ELEMENT in GROUP (e.g. for ‘labelling’ in chemical ANALYSIS). IIA of the PERIODIC TABLE (the ALKALINE EARTHS). It has several isotopes, with radiodiagnosis (radiology) Branch of half-lives of up to 1,620 years. It is obtained medical radiology that is concerned from pitchblende (its principal ore), and with the use of X-RAYS or RADIO- used in RADIOTHERAPY and luminous ISOTOPES in diagnosis. paints. At. no. 88; r.a.m. 226.0254. radiograph (radiology) Photographic IMAGE radius (1 mathematics; 2 anatomy) 1 that results from uneven ABSORPTION Distance from the centre (USA: center) by an OBJECT being subjected to penetrating of a circle to the CIRCUMFERENCE, equal to half the DIAMETER or the

338 RADIUS OF CURVATURE RATE CONSTANT

CIRCUMFERENCE divided by 2p. 2 One random access memory (RAM) (comput- of two bones in the forearm of a tetrapod ing) Part of a COMPUTER’S MEMORY VERTEBRATE (the other is the ULNA). that can be written to and read from. radius of curvature (mathematics) Of See also ROM. a point on a curve, the RADIUS of a circle that touches the inside of the curve random sample (statistics) SAMPLE at that point. taken from a large GROUP in such a way that it is representative of the GROUP radon Rn (chemistry) A RADIOACTIVE as a whole. Random sampling is an gaseous ELEMENT in GROUP 0 of the important method of carrying out QUALITY PERIODIC TABLE (the RARE GASes), a CONTROL for MASS-produced articles. RADIOACTIVE DECAY PRODUCT of RADIUM. It has several isotopes, with half-lives of Rankine scale (measurement) A up to 3.82 days. RADON coming out of TEMPERATURE SCALE that expresses the ground, particularly in hard-rock areas, ABSOLUTE TEMPERATURES in degrees is a source of BACKGROUND RADIATION Fahrenheit (ABSOLUTE ZERO=0°R). It that has been recognized as a health hazard. was named after the British engineer and At. no. 86; r.a.m. 222 (most STABLE ISOTOPE). physicist William Rankine (1820–72). raffinate (chemistry) LIQUID that remains rare earth (chemistry) Member of the after a substance has been obtained SERIES of elements, in GROUP IIIB of by SOLVENT EXTRACTION. the PERIODIC TABLE, known also as the LANTHANIDES. Also termed: RARE raffinose (chemistry) C18H32O16 Colourless EARTH ELEMENT. (USA: colorless) CRYSTALLINE TRISACCHARIDE CARBOHYDRATE that rare gas (chemistry) One of the uncommon, occurs in SUGAR beet, which hydrolyses to unreactive and highly STABLE gases the sugars GALACTOSE, GLUCOSE and in GROUP 0 of the PERIODIC TABLE. FRUCTOSE. They are HELIUM, NEON, ARGON, KRYPTON, XENON and RADON. Also r.a.m. (chemistry) An abbreviation of termed: INERT GAS; NOBLE GAS. ‘r’elative ‘a’tomic ‘m’ass (formerly called ATOMIC WEIGHT). RAS (physiology) An abbreviation of ‘R’eticular ‘A’ctivating ‘S’ystem. RAM (computing) An abbreviation of ‘r’andom ‘a’ccess ‘m’emory of a raster (computing) DISPLAY of information COMPUTER. in the form of a grid, usually referring to the IMAGE produced by the parallel scanning Raman effect (physics) Scattering of ACTION of a CATHODE-RAY TUBE. MONOCHROMATIC LIGHT, when it passes through a TRANSPARENT HOMOGENEOUS rate constant (chemistry) CONSTANT medium, into different CHARACTERISTIC of proportionality for the speed of a CHEMICAL wavelengths because of INTERACTION REACTION at a particular TEMPERATURE. with the molecules of the medium. It was It can only be obtained experimentally. named after the Indian physicist Also termed: velocity CONSTANT; specific Chandrasekhara Raman (1888–1970). RATE CONSTANT.

339 RATE-DETERMINING STEP REAL IMAGE rate-determining step (chemistry) The R&D (education) An abbreviation of slowest step of a CHEMICAL REACTION ‘R’esearch ‘and’ ‘D’evelopment. which determines the overall rate, provided the other steps are relatively RDS (medical) An abbreviation of rapid. Thus the KINETICS and ORDER ‘R’espiratory ‘D’istress ‘S’yndrome. OF REACTION are basically those of the rate determining step. Also termed: Re. (measurement) An abbreviation LIMITING STEP. of ‘Re’ynolds’ number. rate equation (chemistry) An alternative reactant (chemistry) Substance that term for RATE LAW. reacts with another in a CHEMICAL REACTION to form new substances. rate law (chemistry) Equation that relates the rate of a CHEMICAL REACTION to reaction (chemistry) An alternative term the CONCENTRATION of the individual for CHEMICAL REACTION. reactants. It has the form rate=k[X]n, where k is the RATE CONSTANT, X is the REACTANT reactive dye (chemistry) Dye that forms and n is the ORDER OF REACTION. It a COVALENT BOND with the FIBRE can only be obtained experimentally. Also MOLECULE (USA: fiber molecule) of termed: RATE EQUATION. the textile being dyed. This provides excellent fastness. Such dyes are used rate of reaction (chemistry) Speed of to dye CELLULOSE fibres (USA: cellulose a CHEMICAL REACTION, usually fibers) (e.g. rayon). expressed as the change in CONCENTRATION of a REACTANT or reactor (chemistry) VESSEL in which PRODUCT per UNIT time. It can be a CHEMICAL REACTION is carried out. affected by TEMPERATURE, PRESSURE and the presence of a CATALYST. read-only memory (ROM) (computing) Part of a COMPUTER’S MEMORY that rational number (mathematics) Number can only be read (and not written to). that may be expressed as a ratio of two integers—i.e. in the form of a FRACTION. See also RANDOM ACCESS MEMORY.

See also IRRATIONAL NUMBER. reagent (1, 2 chemistry) 1 Substance that takes part in a CHEMICAL ray (physics) Beam of any type of REACTION; a REACTANT. 2 Common RADIATION, e.g. LIGHT. LABORATORY chemical used in chemical ANALYSIS and for experiments. rbc (haematology) An abbreviation of ‘r’ed ‘b’lood ‘c’ell(s). real gas (chemistry) GAS that never fully achieves ‘ideal’ BEHAVIOUR (USA: RCBF (physiology) An abbreviation of behavior). ‘R’egional ‘C’erebral ‘B’lood ‘F’low. See also KINETIC THEORY. RCMRO (physiology) An abbreviation of ‘R’egional ‘C’erebral ‘M’etabolic ‘R’ate real image (optics) IMAGE brought for‘O’xygen. to a FOCUS by a LENS, mirror or optical

340 REAL NUMBER RECTIFIER system that can be displayed on a reciprocal wavelength (physics) An screen (as opposed to a virtual IMAGE, alternative term for WAVE NUMBER. which can not). recombinant DNA (molecular biology) real number (mathematics) Any number, Type of DNA that has genes from different POSITIVE or negative, from among all sources, genetically engineered using RATIONAL NUMBERS and IRRATIONAL RECOMBINATION. NUMBERS (as opposed to an imaginary number). recombination (molecular biology) The process by which new combinations of realgar (chemistry) As2S 2 Natural red characteristics not possessed by the parents ARSENIC disulphide (USA: arsenic are formed in the offspring. It results disulfide), used as a PIGMENT and from CROSSING OVER during MEIOSIS in pyrotechnics. to form gametes that unite during FERTILIZATION to form a new individual. receptors (1 chemistry/physics; 2 Genetic engineers have developed pharmacology) 1 Sensory CELLS, which techniques for artificially recombining strands may be part of a GROUP that form a of DNA (to make RECOMBINANT DNA). SENSE ORGAN capable of detecting stimuli. When a RECEPTOR is stimulated record (computing) A number of elements (e.g. by TEMPERATURE or LIGHT), it of DATA that together form one UNIT produces electrical or biochemical of stored information. changes that are relayed to the NERVOUS SYSTEM for processing. 2 PROTEINS recrystallization (1, 2 chemistry) 1 through which many drugs and natural Change from one crystal structure to mediators act to exert their effects. another; it occurs on heating or cooling through a CRITICAL TEMPERATURE. recessive (genetics) Describing a GENE 2 Purification of a substance by repeated that is expressed in the PHENOTYPE CRYSTALLIZATION from SOLUTION. when it is HOMOZYGOUS in a CELL (i.e. there have to be two RECESSIVE rectification (1 chemistry; 2 physics) genes for their effect to be apparent). 1 Purification of a LIQUID using The presence of a DOMINANT ALLELE DISTILLATION. 2 Conversion of ALTER- masks the effect of a RECESSIVE GENE NATING CURRENT (ac) into DIRECT (i.e. in a COMBINATION of a DOMINANT CURRENT (dc) using a RECTIFIER. GENE and a RECESSIVE GENE, the DOMINANT GENE manifests itself. rectified spirit (chemistry) SOLUTION of ETHANOL (ETHYL ALCOHOL) that contains recipient (biology) Organism that receives about 5 to 7 per cent WATER. It is a material from another, e.g. as in the CONSTANT-boiling MIXTURE and the taking up of DNA by one bacterium WATER cannot be removed by DISTILLATION. from another. rectifier (physics) Electrical device for reciprocal (mathematics) The quantity converting an ALTERNATING CURRENT obtained by dividing a number into 1; (ac) into a DIRECT CURRENT (dc). It i.e. the RECIPROCAL of x is the number may take the form of a plate RECTIFIER, l/x. Zero has no RECIPROCAL. a DIODE VALVE or a semiconductor DIODE.

341 RECTILINEAR REFLECTOR rectilinear (mathematics) In or forming reduced pressure distillation (chemistry) a straight line. An alternative term for VACUUM DISTILLATION. rectum (anatomy) Final part of the INTESTINE, through which FAECES (USA: reduced temperature, pressure and volume feces) are passed after reABSORPTION (physics) The ratios of the TEMPERATURE, of WATER. PRESSURE and VOLUME to the CRITICAL TEMPERATURE, CRITICAL PRESSURE and recurring decimal (mathematics) Decimal CRITICAL VOLUME respectively in the that contains a number or block of REDUCED EQUATION OF STATE. numbers that repeat to INFINITY; e.g. the decimal for 2/3=0.666666… reducing agent (chemistry) Substance that causes chemical REDUCTION, often See also TERMINAL DECIMAL. by adding HYDROGEN or removing OXYGEN; e.g. CARBON, CARBON red blood cell (haematology) An alterna- MONOXIDE, HYDROGEN. Also termed: tive term for an ERYTHROCYTE, also ELECTRON DONOR; reluctant. known as a red cell or red corpuscle. reducing sugar (chemistry) Any SUGAR red lead (chemistry) Pb3O 4 Bright red that can act as a REDUCING AGENT. powdery OXIDE of LEAD. An OXIDIZING AGENT, it is used in anti-rust and priming See also BENEDICT’S TEST; FEHLING’S TEST. paints. Also termed: minium; dilead(II); LEAD(IV) OXIDE; LEAD tetraoxide; reductase (biochemistry) ENZYME that triplumbic tetroxide. causes the REDUCTION of an ORGANIC COMPOUND. red tide (biology) Phenomenon that occurs on seas and estuaries when SPECIES reduction (chemistry) CHEMICAL REAC- of red ALGAe multiply abnormally, sometimes TION that involves the GAIN of electrons producing a floating crust several centimetres by a substance; the addition of HYDROGEN thick. The ALGAe produce toxins that or removal of OXYGEN from a substance. POISON shellfish and which can be passed along food chains. REF (physiology/biochemistry) An abbreviation of ‘R’enal ‘E’rythropoietic ‘F’actor. redox reaction (chemistry) CHEMICAL REACTION in which OXIDATION is necessarily reflectance (measurement) Ratio of the accompanied by REDUCTION, and vice versa; INTENSITY of reflected RADIATION to an OXIDATION-REDUCTION REACTION. the INTENSITY of the incident RADIATION. reduced equation of state (physics) An reflection (physics) Change in direction equation of state of a gas in which the of an ELECTROMAGNETIC WAVE (e.g. temperature, pressure and volume are LIGHT) or sound WAVE after it strikes a replaced by their reduced values. See (smooth) surface (e.g. a mirror). See LAWS REDUCED TEMPERATURE, PRESSURE OF REFLECTION. AND VOLUME. reflector (optics) OBJECT or surface that reflects electromagnetic RADIATION

342 REFLEX RELATIVE HUMIDITY

(e.g. LIGHT, radio waves), particularly as LIGHT) in AIR or VACUUM to its speed in one around or inside a lamp to concentrate another medium. The speed depends on the a LIGHT beam. WAVELENGTH of the RADIATION as well as on the DENSITY of the medium. For a reflex (1 biology; 2 mathematics) 1 refracted RAY of LIGHT, it is equal to the Sequence of NERVE IMPULSES that ratio of the sine of the ANGLE OF produce a fast involuntary RESPONSE INCIDENCE i to the sine of the ANGLE OF to an external STIMULUS. 2 Describing REFRACTION r; i.e. n=sin/sinr. Also termed: an angle that exceeds 180 degrees (but REFRACTIVE CONSTANT. is less than 360 degrees). refractometer (physics) Instrument for reflux (chemistry) Boiling of a LIQUID for long measuring the REFRACTIVE INDEX periods of time. Loss by EVAPORATION is of a substance. prevented by using a REFLUX CONDENSER. refrigerant (chemistry) Substance used reflux condenser (chemistry) Vertical as the WORKING FLUID in a refrigerator CONDENSER used in the process of (e.g. AMMONIA, fluon, CFCS). refluxing. It is attached to a VESSEL that contains the LIQUID to be refluxed refrigeration (physics) A method of and condenses the VAPOUR produced maintaining a cool TEMPERATURE in on boiling, which then runs back into a room or container by transferring the VESSEL. HEAT from it to the exterior using a HEAT PUMP. Cooling is caused by the reflux reduction division (genetics) EVAPORATION of a VOLATILE LIQUID An alternative term for MEIOSIS. (REFRIGERANT) into a VAPOUR, which is compressed by a PUMP (compressor) reforming (chemistry) Production of to turn it back to a LIQUID. branched-chain ALKANES from straight- chain ones or the production of AROMATIC regeneration (physiology) Regrowth of COMPOUNDS (e.g. BENZENE) from TISSUE to replace that which has been ALKENES, using cracking or a CATALYST. damaged or lost, e.g. WOUND healing. refraction (physics) Change in direction relative atomic mass (r.a.m.) (physics) of an ENERGY WAVE (e.g. LIGHT, sound) MASS of an ATOM relative to the MASS when it passes from one medium into of the ISOTOPE CARBON-12 (which another in which its speed is different. is taken to be exactly 12). Former name: ATOMIC WEIGHT. refraction of light (optics) Change in direction of a LIGHT RAY as it passes relative density (physics) Ratio of the obliquely from one TRANSPARENT medium DENSITY of a given substance to the to another of different REFRACTIVE INDEX. DENSITY of some reference substance. For liquids, relative densities are usually expressed refractive constant (physics) An alterna- with reference to the DENSITY of WATER at tive term for REFRACTIVE INDEX. 4°C. Former name: SPECIFIC GRAVITY. refractive index (n) (physics) Ratio of the relative humidity (physics) Ratio of the speed of electromagnetic RADIATION (such PRESSURE of WATER VAPOUR present

343 RELATIVE MOLECULAR MASS RESORCINOL in AIR to the PRESSURE the WATER replication (molecular biology) The VAPOUR would have if the AIR were saturated process by which a new complete at the same TEMPERATURE (i.e. to the molecule of DNA is made, by one strand saturated-WATER VAPOUR PRESSURE). being used as a template for the assembly It is expressed as a PERCENTAGE. of another strand. relative molecular mass (chemistry) Sum reproduction (biology) Procreation of of the RELATIVE ATOMIC MASses of all an organism. SEXUAL REPRODUCTION the atoms in a MOLECULE of a substance. involves the FUSION of SEX CELLS Also termed: MOLECULAR WEIGHT. or gametes and the exchange of genetic material, thus bringing new vigour to relative permittivity (physics) The ratio a SPECIES. ASEXUAL REPRODUCTION of the capacitance of a capacitor with does not involve gametes, but usually a specified medium between the plates, the vegetative proliferation of an organism. to the capacitance of the same capacitor with free space between the plates. resin (chemistry) ORGANIC COMPOUND Also termed: dielectric constant. that is generally a viscous LIQUID or semi-LIQUID which gradually hardens relativity (physics) Einstein’s theory; when exposed to AIR, becoming an scientific principle expressing in AMORPHOUS, brittle SOLID. Natural resins, mathematical and physical terms the found in plants, are yellowish in COLOUR implications of the fact that observations (USA: color) and INSOLUBLE in WATER, depend as much on the viewpoint as but are quite SOLUBLE in organic solvents. on what is being observed. SYNTHETIC resins (types of plastics) also possess many of these properties. rem (radiology) An abbreviation of ‘r’öntgen ‘e’quivalent ‘m’an, the quantity resistor (physics) Device that provides of IONIZING RADIATION such that the resistance in electrical circuits. ENERGY imparted to a biological system per gram of living material has the resonance (1 chemistry; 2 physics) 1 same effect as one röntgen. Movement of electrons from one ATOM of a MOLECULE or ION to another ATOM REM sleep (physiology) An abbreviation of that MOLECULE or ION to form a of ‘R’apid ‘E’ye ‘M’ovement (paradoxical) STABLE RESONANCE HYBRID structure sleep. (e.g. as in an AROMATIC COMPOUND). 2 Phenomenon in which a system is renin (biochemistry) ENZYME produced made to vibrate at its natural FREQUENCY by the KIDNEY that constricts arteries as a result of vibrations received from and thus raises BLOOD PRESSURE. another source of the same FREQUENCY.

rennin (biochemistry) ENZYME found resorcinol (chemistry) C6H4(OH)2 CRYS- in GASTRIC JUICE that curdles milk. TALLINE dihydric PHENOL, used in the It is the active ingredient of rennet. SYNTHESIS of drugs, dyes and plastics. Also termed: m-dihydroxybenzene; 1,3- replicase (biochemistry) ENZYME that benzenediol. promotes the SYNTHESIS of DNA and RNA within living CELLS.

344 RESPIRATION RETINOL respiration (1, 2 physiology) 1 Release in a given time. It gives information of ENERGY by living organisms from about the type of food being oxidized; the breakdown of ORGANIC COMPOUNDS. e.g. CARBOHYDRATE has an RQ of In AEROBIC RESPIRATION, which occurs approximately 1, but if the RQ becomes in most CELLS, OXYGEN is required high (i.e. little OXYGEN is available), and CARBON DIOXIDE and WATER are ANAEROBIC RESPIRATION may occur. produced. ENERGY production is coupled to a SERIES of oxidation-reduction reactions, response (physiology) Physical, chemical catalysed by ENZYMES. In ANAEROBIC or behavioural (USA: behavioral) change RESPIRATION (e.g. FERMENTATION), in an organism initiated by a STIMULUS. food substances are only partly broken down, and thus less ENERGY is released resting potential (physiology) POTENTIAL and OXYGEN is not required. 2 An alternative DIFFERENCE between the inner and outer term for BREATHING. surfaces of a resting NERVE, which is about -60 to -80 mV. It occurs when the NERVE respiratory movement (physiology) Move- is not conducting any IMPULSE, and is in ment by an organism to allow the exchange contrast to the ACTION POTENTIAL, which of respiratory gases, i.e. the taking up occurs during the application of a STIMULUS of OXYGEN and release of CARBON and brings about a rise in the POTENTIAL DIOXIDE. In mammals such as human DIFFERENCE to a POSITIVE value. beings this entails BREATHING, involving movements of the chest and DIAPHRAGM. restriction enzyme (biochemistry) ENZYME In fishes, WATER is passed over the (a NUCLEASE) produced by some gills for gaseous exchange. BACTERIA that is capable of breaking down foreign DNA. It cleaves double-stranded DNA respiratory organ (anatomy) ORGAN at a specific sequence of bases, and the DNA in which RESPIRATION (BREATHING) of the BACTERIA is modified for protection takes place. In mammals (e.g. human against DEGRADATION. RESTRICTION beings), the process is carried out in ENZYMES are used widely as tools in the LUNG; in fish, the gills. There gaseous GENETIC ENGINEERING for cutting DNA. exchange takes place (usually of OXYGEN Also termed: restriction endonuclease. and CARBON DIOXIDE). retina (histology) LIGHT-sensitive TISSUE respiratory pigment (biochemistry) Sub- at the back of the VERTEBRATE EYE, made stance that can take up and carry OXYGEN up of a NETWORK of interconnected in areas of high OXYGEN CONCEN- NERVES. The first CELLS in the NETWORK TRATION, releasing it in parts of the are photo-receptors consisting of cones organism with low OXYGEN concentrations (which are sensitive to COLOUR [USA: color]) where it is consumed, i.e. by RESPIRATION or rods (which are sensitive to LIGHT). They in CELLS. In vertebrates the RESPIRATORY contain visual pigments (e.g. RHODOPSIN) PIGMENT is HAEMOGLOBIN (USA: which ultimately cause impulses to be hemoglobin); in some invertebrates it is transmitted to the visual centre (USA: center) HAEMOCYANIN (USA: hemocyanin). of the BRAIN via the OPTIC NERVE. respiratory quotient (RQ) (measurement) retinol (biochemistry) Fat-SOLUBLE Ratio of CARBON DIOXIDE produced VITAMIN found in plants, in which it is formed by an organism to the OXYGEN consumed from CAROTENE. Also termed: VITAMIN A.

345 RETORT RIBONUCLEIC ACID retort (chemistry) Heated VESSEL used Rh factor (haematology) An abbreviation for the DISTILLATION of substances, as of ‘Rh’esus factor. in the separation of some metals. rhesus factor (Rh) (haematology/immun- retrovirus (virology) Member of a GROUP ology) ANTIGEN present in the RED of VIRUSES that contain RNA as their BLOOD CELLS of a majority of human genetic material. They use an RNA-dependent beings, who are thus rhesus POSITIVE DNA polymerase or reverse transcriptase (Rh+). Unlike the ABO BLOOD GROUP ENZYME to carry out TRANSCRIPTION. system, a person with rhesus-negative Many RNA VIRUSES are CARCINOGENIC (Rh-) BLOOD does not possess the rhesus in their hosts, which include mammals. ANTIBODY unless he or she receives Also termed: ONCOVIRUS. rhesus-POSITIVE BLOOD (through transfusion or via the PLACENTA). This reversible process (chemistry) Process can be fatal to a rhesus-POSITIVE FOETUS that can theoretically be reversed by (USA: fetus) in a rhesus-negative mother. an appropriate small change in any of the thermodynamic variables (e.g. rhinovirus (virology) Member of a GROUP PRESSURE, TEMPERATURE). Real natural of VIRUSES that infect the respiratory processes are irreversible. tract of vertebrates and which are one of the main causative agents of the reversible reaction (chemistry) CHEMICAL common cold. REACTION that can go either forwards or backwards depending on the conditions. rhodium Rh (chemistry) SILVER-white metallic ELEMENT in GROUP VIII of the RFLP (physiology/biochemistry) An PERIODIC TABLE (a TRANSITION abbreviation of ‘R’estriction ‘F’ragment ELEMENT), used as a CATALYST and in ‘L’ength ‘P’olymorphism. making thermocouples. At. no. 45; r.a.m. 102.9055. rhabdovirus (virology) Member of a GROUP of VIRUSES that can infect rhodopsin (biochemistry) PROTEIN multi-cellular animals and plants. One (derived from VITAMIN A) in the rods type causes RABIES. of the RETINA of the EYE which acts as a LIGHT-sensitive PIGMENT; the ACTION rhenium Re (chemistry) Rare metallic of LIGHT brings about a chemical change ELEMENT of GROUP VIIB of the PERIODIC that results in the production of a NERVE TABLE (a TRANSITION ELEMENT), used IMPULSE. Also termed: VISUAL PURPLE. in making thermocouples. At no 75; r.a.m. 186.20. riboflavin (biochemistry) Orange WATER- SOLUBLE CRYSTALLINE SOLID, member rheology (physics) Study of flow within of the VITAMIN B complex. It plays an objects under STRESS. important role in GROWTH. Also termed:

riboflavine; LACTOFLAVIN; VITAMIN B2. rheostat (physics) VARIABLE electrical RESISTOR, generally used to control ribonucleic acid (molecular biology) See ELECTRIC CURRENT flow. RNA.

346 RIBOSE ROMAN NUMERALS

ribose (chemistry) C5H10O5 OPTICALLY DNA. It is composed of nucleotides that ACTIVE PENTOSE SUGAR, a contain RIBOSE as the SUGAR. RNA COMPONENT of the aucleotides of RNA contains the bases ADENINE, GUANINE, (RIBONUCLEIC ACID). CYTOSINE and URACIL. MESSENGER RNA takes part in TRANSCRIPTION or ribosome (cytology) PARTICLE present copying of the GENETIC CODE from a DNA in the CYTOPLASM of CELLS, often attached template. TRANSFER RNA and ribosomal to the ENDOPLASMIC RETICULUM, that RNA take part in TRANSLATION or is essential in the BIOSYNTHESIS of PROTEIN SYNTHESIS, all of which occur proteins. Ribosomes are composed of in prokaryotes and eukaryotes. PROTEIN and RNA, and are the site of attachment for MESSENGER RNA during RNA virus (virology)VIRUS that has RNA PROTEIN SYNTHESIS. They may be as its genetic material (instead of DNA). associated in chains called polyribosomes. rock salt (chemistry) Naturally occurring rickets (medical) Disorder that results CRYSTALLINE SODIUM CHLORIDE, an from a deficiency of VITAMIN D. It mainly important raw material in the chemical industry. affects children and can cause deformed limbs. rod (cytology) Type of sensory CELL present in the RETINA of the VERTEBRATE rickettsiae (microbiology) GROUP of MICRO- EYE. It is stimulated by LIGHT and is ORGANISMS, often classified as being part concerned with vision in low illumination. way between BACTERIA and VIRUSES, that The ABSORPTION of LIGHT ENERGY are parasitic on the CELLS of arthropods (photons) by the visual PIGMENT (lice, mites and TICKS) and vertebrates. Some RHODOPSIN present in the ROD causes can cause serious disorders (e.g. TYPHUS in a nervous IMPULSE, which travels along human beings). the OPTIC NERVE to the BRAIN. ringer’s fluid (chemistry) Physiological See also CONE. SALINE SOLUTION used for keeping tissues and organs alive outside the roentgen (R) (measurement) UNIT of body (in vitro). It is similar in composition RADIATION; the amount of X-RAYS or to the FLUID that naturally bathes CELLS GAMMA RAYS that produce a CHARGE and tissues, maintaining a CONSTANT of 2.58×10-4 coulomb of ELECTRICITY internal ENVIRONMENT. It contains in 1 cm3 of dry AIR. It was named after chlorides of SODIUM, POTASSIUM and the German physicist Wilhelm Röntgen CALCIUM. It was named after the British (1845–1923). Also termed: röntgen. physiologist Sydney Ringer (1835–1910). Roentgen rays (radiology) An alternative ringworm (mycology) See TINEA. term for X-RAYS.

RMV (physiology) An abbreviation of ROM (computing) An abbreviation of ‘Respiratory ‘M’inute ‘V’olume. ‘r’ead-‘o’nly ‘m’emory of a COMPUTER.

RNA (molecular biology) An abbreviation of Roman numerals (mathematics) A num- ‘R’ibo‘N’ucleic ‘A’cid, one of the NUCLEIC ber system, originally used by the Romans, ACIDS present in CELLS, the other being based on letters: I=1; V=5; X=10; L=50;

347 RÖNTGEN RUTHERFORDIUM

C=100; D=500; M=1,000. Other numbers rubella (medical) An acute infectious are written using combinations of these; viral disease spread by droplet infection. there is no zero. Complications are rare, except when contracted in the early months of röntgen (chemistry) An alternative term pregnancy, when it may produce foetal for roentgen. (USA: fetal) deformities. Also termed: German measles. root (1, 2 mathematics) 1 Number or quantity that when multiplied by itself rubidium Rb (chemistry) Reactive some specified times gives the number SILVER-white METAL in GROUP IA of again; e.g. the square ROOT of a number the PERIODIC TABLE (the ALKALI is that when multiplied by itself gives METALS), with a naturally occurring the number. 2 SOLUTION of an RADIOACTIVE ISOTOPE (Rb-87). At. ALGEBRAic equation. no. 37; r.a.m. 85.4678. root-mean-square (rms) (mathematics) rule of acceleration (genetics) The AVERAGE equal to the SQUARE ROOT rule that in an organism’s development of the sum of the squares of a number the structures that are formed first of values divided by the total number are the ones most important to the of values. organism’s overall FUNCTION. rotatory (chemistry/optics) OPTICALLY R unit (measurement) 1 An abbreviation ACTIVE; capable of rotating the plane of ‘R’esistance unit in the cardiovascular of POLARIZED LIGHT. system, mmHg divided by ml/s. 2 An abbreviation of ‘R’oentgen unit. rotoscope (physics) An alternative term for STROBOSCOPE. ruthenium Ru (chemistry) SILVER-white metallic ELEMENT in GROUP VIII of the round window (histology) Lower of two PERIODIC TABLE (a TRANSITION membranous areas on the COCHLEA ELEMENT), used to add hardness to of the INNER EAR (the other is the OVAL PLATINUM ALLOYS. At. no. 44; r.a.m. 101.07. WINDOW). Also termed: fenestra rotunda. rutherfordium Rf (chemistry) ELEMENT no. RPF (physiology) An abbreviation of 104. A RADIOACTIVE METAL with at least ‘R’enal ‘P’lasma ‘F’low. three very short-lived isotopes (half-lives up to 70 seconds) made by bombarding an R plasmid (genetics) Any plasmid carying ACTINIDE with CARBON, OXYGEN or NEON a GENE for ANTIBIOTIC resistance. atoms. Also termed: KURCHATOVIUM.

RQ (physiology) An abbreviation of ‘R’espiratory ‘Q’uotient.

R technique (statistics) A FACTOR ANALYSIS based on the correlations between tests that attempts to derive a limited number of factors underlying the correlations.

348 S

S (1 chemistry; 2 biochemistry) 1 The saccharose (chemistry) An alternative CHEMICAL SYMBOL for SULPHUR (USA: term for SACCHARIDE. sulfur). 2 An abbreviation of ‘S’erine. SADR (biochemistry) An abbreviation SA (physiology) An abbreviation of of ‘S’uspected ‘A’dverse ‘D’rug ‘R’eaction. ‘S’pecific ‘A’ctivity. safranine O/ fast green stain (histology) SAB (1 governing body; 2 society) 1 A histological staining technique that An abbreviation of ‘S’cience/‘S’cientific may be used to make CARTILAGE visible ‘A’dvisory ‘B’oard. 2 An abbreviation under the MICROSCOPE. of ‘S’ociety of ‘A’merican ‘B’acteriologists. sagittal fissure (histology) The FISSURE saccharide (chemistry) Simplest type separating the CEREBRAL HEMISPHERES. of CARBOHYDRATE, with the GENERAL SAIMR (institution) An abbreviation FORMULA (C6H12O6), common to many sugars. Also termed: SACCHAROSE. of ‘S’outh ‘A’frican ‘I’nstitute of ‘M’edical ‘R’esearch. See also DISACCHARIDE; MONO- SACCHARIDE. sal ammoniac (chemistry) Old name for AMMONIUM CHLORIDE. saccharimetry (measurement) Measure- ment of the CONCENTRATION of SUGAR salicylate (chemistry) ESTER or SALT in a SOLUTION from its OPTICAL ACTIVITY, of SALICYLLIC ACID. by using a polarimeter. salicyllic acid (chemistry) C6H4(OH)COOH White CRYSTALLINE ORGANIC COM- saccharin (chemistry) C6H4SO2CONH White CRYSTALLINE ORGANIC COMPOUND that POUND, a CARBOXYLIC ACID. It is used is about 550 times sweeter than SUGAR; as an ANTISEPTIC, in medicine, and in an artificial sweetener. It is almost the preparation of AZO DYES. Its acetyl INSOLUBLE in WATER and hence it is ESTER is ASPIRIN. Also termed: 2- used in the form of its SOLUBLE SODIUM HYDROXYBENZOICACID. SALT. Also termed: 2-sulphobenzimide (USA: 2-sulfobenzimide); saccharine. saline (chemistry) Salty; describing a SOLUTION of SODIUM CHLORIDE Saccharomyces cerevisiae (toxicology/ (COMMON SALT). genetics) A common SPECIES of YEAST which is frequently used in in vitro tests for saliva (biochemistry) NEUTRAL or slightly mutagenic POTENTIAL of chemicals, genetic ALKALINE FLUID secreted by the salivary research, commercial GENE CLONING. GLANDS in the mouth. It lubricates food during chewing and aids DIGESTION. It consists of a MIXTURE of MUCUS and

349 SALPINGOSTOMY SANTA the ENZYME AMYLASE (ptyalin), which sample bias (statistics) Any way in which breaks down STARCH to MALTOSE. a SAMPLE is not representative of the population from which it was drawn. salpingostomy (medical) An operation to open the FALLOPIAN TUBES. sampling error (statistics) The difference between any value of a statistic obtained salt (1,2 chemistry) 1 PRODUCT obtained from a SAMPLE of a population. when a HYDROGEN ATOM in an ACID is replaced by a METAL or its equivalent sampling population (statistics) The + (e.g. the AMMONIUM ION NH4 ). It results population from which a SAMPLE is drawn. from the REACTION between an ACID and a BASE. sampling theory (statistics) The principles that govern the selection of representa- See also ACID SALT; BASIC SALT. 2 tive samples. COMMON SALT, SODIUM CHLORIDE. sampling validity (statistics) The extent saltcake (chemistry) An alternative term to which a test appears to SAMPLE those for crude SODIUM SULPHATE (USA: traits under test, and only those traits. sodium sulfate). sampling with replacement (statistics) salting out (chemistry) PRECIPITATION Sampling from a finite population while of a COLLOID (e.g. gelatine) by the addition replacing each item sampled. of large amounts of a SALT. sampling without replacement (statistics) saltpetre (chemistry) An alternative term Sampling from a finite population without for POTASSIUM NITRATE. replacing the items sampled. salvation (chemistry) The attachment sanatorium (medical) A hospital that between SOLVENT and SOLUTE molecules. specialised in the TREATMENT of The greater the POLARITY of the SOLVENT, TUBERCULOSIS. Since the introduction the greater is the attraction between of CHEMOTHERAPY for the disease, SOLUTE and SOLVENT molecules. such hospitals are no longer necessary. sal volatile (chemistry) Old name for sandwich compound (chemistry) AMMONIUM CARBONATE. ORGANOMETALLIC COMPOUND whose molecules consist of two parallel planar samarium Sm (chemistry) Metallic rings with a METAL ATOM centred ELEMENT in GROUP IIIB of the PERIODIC (USA: centered) between them (e.g. TABLE (one of the LANTHANIDES). It is FERROCENE). slightly RADIOACTIVE and arises from FISSION fragments in a nuclear REACTOR, SA node (histology) An abbreviation where it acts as a ‘POISON’. At. no. 62; of ‘S’ino‘A’trial node. r.a.m. 150.35. SANTA (society) An abbreviation of sample (statistics) Part of a population, ‘S’outh ‘A’frican ‘N’ational ‘T’uberculosis usually randomly selected to be ‘A’ssociation. representative of the whole population.

350 SAPONIFICATION SCANDIUM saponification (chemistry) HYDROLYSIS of BONDS; all the atoms in the COMPOUND an ESTER, using an ALKALI, to produce a exert their maximum combining POWER free ALCOHOL and a SALT of ORGANIC ACID. (VALENCY) with other atoms, so that a chemical change can be effected only saponification value (chemistry) Number by a SUBSTITUTION REACTION and of milligrams of POTASSIUM HYDROXIDE not in an ADDITION REACTION. required for the complete SAPONIFICATION of 1 g of the substance being tested. saturated solution (chemistry) SOLUTION Also termed: saponification number. that cannot take up any more SOLUTE at a given TEMPERATURE. saprophyte (microbiology) Organism that feeds on dead or decaying organic MATTER See also SUPERSATURATED SOLUTION. (e.g. many BACTERIA and FUNGI). Saprophytic activity is the first step in saturated vapour pressure (physics) the DECOMPOSITION of dead animals The PRESSURE exerted by a SATURATED and plants, and consequently is important VAPOUR. It is TEMPERATURE dependent. in the recycling of elements. Also termed: saprotroph. saturated vapour (physics) VAPOUR that can exist in EQUILIBRIUM with its parent saprotroph (microbiology) An alternative SOLID or LIQUID at a given TEMPERATURE. term for SAPROPHYTE. saturation (chemistry) Point at which sarcoidosis (medical) A disease of unknown no more of a material can be dissolved, cause featuring GRANULOMAS in many absorbed or retained by another. parts of the body, especially in the LYMPH NODES, LIVER, LUNGS, skin and EYES. SB (education) An abbreviation of ‘S’cientiae ‘B’accalaureus. Latin, meaning See also KVEIM TEST. ‘Bachelor of Science’. sarcoptes (microbiology) A GENUS s-block elements (chemistry) Metallic of acarids, which includes SARCOPTES elements that form Groups IA and IIA of scabiti, the itch mite which causes the PERIODIC TABLE, which include the scabies. ALKALI METALS, ALKALINE EARTHS and the LANTHANIDES and ACTINIDES satellite chromosome (genetics) A (together also known as the RARE EARTHS); part of a CHROMOSOME that is joined HYDROGEN is usually included as well. to the end of the main CHROMOSOME They are so called because their 1 or by a very fine thread of non-condensed 2 outer electrons occupy s-orbitals. CHROMATIN. Sc (chemistry) CHEMICAL SYMBOL satellite DNA (molecular biology) A for SCANDIUM. FRACTION of DNA with significantly different DENSITY and thus BASE composi- scandium Sc (chemistry) Silvery-white tion from most of the DNA in an organism. metallic ELEMENT in GROUP IIIB of the PERIODIC TABLE (a RARE EARTH saturated compound (chemistry) ORGANIC ELEMENT); its OXIDE, Sc2O3, is used as COMPOUND that contains only SINGLE a catalyst. At. no. 21; r.a.m. 44.9559.

351 SCANNER SCOMBROID POISONING scanner (computing) An alternative schizont (microbiology) A stage in the term for OPTICAL CHARACTER READER. development of the MALARIA PARASITE. See MALARIA. scanning electron microscope (microscopy) ELECTRON MICROSCOPE that Schmorl stain (histology) A histological scans the SAMPLE to be examined staining technique that may be used with a beam of electrons. to make lipofuscin visible under the MICROSCOPE. scapula (anatomy) An alternative term for the SHOULDER BLADE. Schwann cell (cytology) CELL that produces the myclin sheath that surrounds scattering of light (physics) Irregular a NERVE CELL (NEURONE). SCHWANN REFLECTION or DIFFRACTION of LIGHT CELLS are in close contact with the rays that occurs when a beam of LIGHT AXON of the NEURONE and are separated passes through a material medium. by gaps called NODES OF RANVIER. It was named after the German physiologist SCE (genetics) An abbreviation of ‘S’ister Theodor Schwann (1810–82). ‘C’hromatid ‘E’xchange. scintillation counter (physics) Device Schiff’s base (chemistry) ORGANIC that counts the INCIDENCE of photons COMPOUND formed when an ALDEHYDE upon a material by the visible or near- or KETONE condenses with a primary VISIBLE LIGHT which is emitted. aromatic AMINE with the elimination of WATER. Also termed: aldimine; AZOME- scintillation spectrometer (physics) THINE. It was named after the German SCINTILLATION COUNTER capable of chemist Hugo Schiff (1834–1915). measuring the ENERGY and the INTENSITY of GAMMA RADIATION emitted Schiff’s reagent (chemistry) REAGENT from a material. for testing for the presence of aliphatic ALDEHYDES, which quickly restore scleroprotein (biochemistry) Member of its magenta COLOUR (USA: color). It a GROUP of fibrous proteins that provide is prepared by dissolving rosaniline organisms with structural materials (e.g. hydrochloride in WATER and passing COLLAGEN, KERATIN). SULPHUR DIOXIDE (USA: sulfur dioxide) through it until the magenta COLOUR sclerotic (histology) Outermost of the is discharged. three layers that form the eyeball (outside the CHOROID and RETINA). schistosomiasis (parasitology) An alternative term for BILHARZIA. SCN (histology) An abbreviation of ‘S’upra‘C’hiasmatic ‘N’ucleus. schizogony (biology) Form of ASEXUAL REPRODUCTION employed by some single scombroid poisoning (toxicology) A celled animals, in which a parent CELL seafood poisoning named for the fish divides into more than two independent FAMILY Scombroidae, which contains CELLS. some of the fish SPECIES frequently causing the toxicosis. The poisoning results See also BINARY FISSION. most frequently from fish such as tuna,

352 SCROFULA SEDATIVE skipjacks, bonitos and mahi-mahi. The second (measurement) 1 SI UNIT of poisoning occurs about 2 to 16 hours time, defined as the duration of following ingestion of fish which have 9,192,631,770 PERIODS of the typically not been kept sufficiently chilled RADIATION between the two hyperfine before cooking, and is the result of the levels of the GROUND STATE of the presence of HISTAMINE and other toxic CAESIUM-133 (USA: cesium-133) ATOM. factors. It is usually not fatal. Abbreviated to sec or s. 2 Angle equal to 1/60 of a MINUTE or 1/360 of a scrofula (medical/microbiology) TUBERCU- DEGREE. LOSIS of the LYMPH NODES in the neck, in which the disease may slowly progress secondary cell (physics) ELECTROLYTIC to the formation of fistulous openings. CELL that must be supplied with ELECTRIC CHARGE before use by passing a DIRECT scrotum (anatomy) Sac present in males CURRENT through it, but it can be of some mammals that contains the recharged over and over again. Also TESTES. Positioned outside the body termed: ACCUMULATOR; STORAGE CELL. cavity so that their TEMPERATURE is cool enough for SPERM production. See also PRIMARY CELL.

SD (statistics) Abbreviation of ‘S’tandard secondary colour (optics) COLOUR ‘D’eviation. (USA: color) obtained by mixing PRIMARY COLOURS. (USA: secondary color). SDA (physiology) An abbreviation of ‘S’pecific ‘D’ynamic ‘A’ction. secondary sexual characteristics (physiology) Features that develop in some animals SDS (computing) An abbreviation of after the onset of puberty, distinguishing ‘S’cientific ‘D’ata ‘S’ystems. males from females but not required for sexual FUNCTION. They result from the SDS-PAGE (chemistry) An abbreviation actions of SEX HORMONES, principally of ‘S’odium ‘D’odecyl ‘S’ulphate—‘P’oly TESTOSTERONE and OESTROGEN (USA: ‘A’crylamide ‘G’el ‘E’lectrophoresis. estrogen). sebaceous gland (anatomy) Small secretion (biochemistry) Release of a GLAND found in large numbers in the substance by a CELL or GLAND with a SKIN of mammals, usually alongside specialized FUNCTION, e.g. SECRETION a HAIR FOLLICLE, that secretes the of digestive ENZYMES by CELLS of the protective SKIN oil SEBUM. SMALL INTESTINE, or SECRETION of HORMONES by the PITUITARY. sebum (biochemistry) Waxy material secreted by SEBACEOUS GLANDS, section (histology) A slice of TISSUE which helps to keep SKIN waterproof. cut for examination under a MICROSCOPE. sec (measurement) An abbreviation sedative (pharmacology) Drug that calms of ‘sec’ond. A UNIT of time equal to without (in NORMAL doses) causing 1/60 of a MINUTE. loss of awareness or consciousness. In larger doses, some sedatives become sleep-inducing drugs.

353 SEDIMENTATION SEMIPERMEABLE MEMBRANE

See also TRANQUILLIZER. FORCE (e.m.f.) in an electric CIRCUIT when the CURRENT is varied. sedimentation (physics) Removal of SOLID particles from a SUSPENSION self-induction (physics) Resistance to by gravitational force or in a CENTRIFUGE. a change in ELECTRIC CURRENT in a CIRCUIT by the creation of a back segregation (genetics) Separation of ELECTROMOTIVE FORCE. a pair of ALLELES in a DIPLOID organism during MEIOSIS in the formation of selfish DNA (molecular biology) Those gametes. A GAMETE receives one of parts of a DNA sequence in a SPECIES the two ALLELES in a DIPLOID organism that serve no apparent useful FUNCTION, because it receives only one of a pair and which are thought to have survived of HOMOLOGOUS CHROMOSOMES. EVOLUTION only because they do not actually harm the organism in any way. selection pressure (genetics) The INTENSITY With which NATURAL SEM (statistics) An abbreviation of SELECTION is acting upon a population ‘S’tandard ‘E’rror of the ‘M’ean. to change the GENE frequencies from one generation to the next. semen (biochemistry) FLUID produced in male reproductive organs of many selective advantage (genetics) The animals. It contains SPERM, and in increase in fitness of one GENOTYPE mammals secretions from the accessory compared to others in the same sex GLANDS. population. semicarbazone (chemistry) CRYSTALLINE selectively permeable membrane (phys- ORGANIC COMPOUND formed when ics) An alternative term for SEMIPERMEABLE an ALDEHYDE or a KETONE reacts

MEMBRANE. with semicarbazide (NH2NHCONH2) with the elimination of WATER. Semicarbazones selenium Se (chemistry) Nonmetallic are used to identify the original ALDEHYDE ELEMENT in GROUP VIA of the PERIODIC or KETONE. TABLE, obtained from flue dust in refineries that use SULPHIDE (USA: sulfide) ores. semicircular canal (anatomy) Part of One of its ALLOTROPES conducts the EAR that is involved in maintaining ELECTRICITY in the presence of LIGHT, BALANCE. and is used in photocells and rectifiers. At. no. 34; r.a.m. 78.96. semiferous tubule (anatomy) One of many tubes within the TESTES in which self-absorption (radiology) Decrease SPERM are made. in RADIATION from a large RADIOACTIVE source due to ABSORPTION by the material seminal vesicle (anatomy) ORGAN in itself of some of the RADIATION produced. the TESTES that is used for storing SPERM. Also termed: self-shielding. semipermeable membrane (physics) self-induced electromotive force (physics) A porous MEMBRANE that permits the Production of an ELECTROMOTIVE passage of some substances but not others; e.g. PLASMA MEMBRANE, which

354 SENSE ORGAN SEROTONIN permits entry of small molecules such chemical compounds (e.g. HOMOLOGOUS as WATER but not large molecules, SERIES) or of numbers or ALGEBRAic allowing OSMOSIS to occur. Such terms (e.g. ARITHMETIC SERIES, membranes are extremely important EXPONENTIAL SERIES, GEOMETRIC in biological systems and are used in SERIES). 2 Describing the arrangement DIALYSIS. Also termed: SELECTIVELY of components in a SERIES CIRCUIT. PERMEABLE MEMBRANE. series circuit (physics) Electrical sense organ (histology) A GROUP of CIRCUIT in which the components are RECEPTOR CELLS specialized to react arranged one after the other so that to (detect) a certain STIMULUS (e.g. the same ELECTRIC CURRENT flows the EYE to LIGHT, the EAR to sound, through each of them. For a SERIES and chemoreceptors in the TONGUE of resistors, the total resistance R is and nose to tastes and smells). equal to the sum of the individual resistors; i.e. R=R1+R2+R3+… For a SERIES senses (physiology) The five primary of capacitors, the RECIPROCAL of the SENSES, common to most vertebrates total CAPACITANCE C is equal to the but sometimes lacking in less highly sum of the reciprocals of the individual evolved animals, are sight, hearing, TASTE, capacitances; i.e. 1/C=1/C,+1/C2+ 1/

SMELL and touch, to which may be C 3+… added the sense of BALANCE. They are effected by various SENSE ORGANS. See also PARALLEL CIRCUIT. septicaemia (medical) Disorder that serine (chemistry) CH2OHCHNH2COOH results from the presence of BACTERIA, White CRYSTALLINE AMINO ACID, or their toxins, in the bloodstream. present in many proteins. Also termed: Also termed: BLOOD POISONING. (USA: 2-amino-3-hydroxypropanoic acid. septicemia). seroconversion (immunology) The point septivalent (chemistry) Having a VALENCY at which an individual exposed to a of seven. Also termed: HEPTAVALENT. VIRUS or other agent becomes serologically POSITIVE. septum (anatomy) Dividing wall found in biological systems, e.g. between serology (immunology) Branch of the nostrils or between the two halves immunology concerned with reactions of the HEART. between antibodies of one organism with antigens of the SERUM of another. sequela (medical) Any abnormality caused by an illness that has ended. serotonin (physiology/pharmacology) Substance derived from TRYPTOPHAN SER (histology) An abbreviation of and found in BLOOD SERUM, used as ‘S’mooth ‘E’ndoplasmic ‘R’eticulum. a NEUROTRANSMITTER and vasoconstrictor. It mediates chemical Ser. (biochemistry) An abbreviation messages on its release to excite or of ‘Ser’ine. inhibit other nerves, and also interacts with a variety of RECEPTORS. A number series (1 chemistry; 2 physics) 1 of important drug classes have been Systematically arranged succession of developed that act by mimicking, modifying,

355 SEROUS CYST ADENOCARCINOMA SEXUAL REPRODUCTION or antagonising serotonin’s actions. Also sexual dimorphism (biology) The termed: 5H; 5-hydroxytryptamine. existence of physical differences between the two sexes, other than the differences serous cyst adenocarcinoma (medical/ in the reproductive organs. histology) The most common MALIGNANT ovarian TUMOUR (USA: maglignant sex hormone (biochemistry) HORMONE ovarian tumor). that determines SECONDARY SEXUAL CHARACTERISTICS and regulates the serum (haematology) Constituent of reproductive BEHAVIOUR (USA: behavior) PLASMA of BLOOD, which contains of an organism. In mammals, the sexual all the substances in PLASMA except CYCLE of the female is controlled by for FIBRINOGEN. such HORMONES. In males the GONADS are regulated. See OESTROUS CYCLE. set (mathematics) A GROUP of things (elements) that have at least one property sex linkage (genetics) Distribution of genes in common; e.g. the SET of all even according to the sex of an organism because numbers or the SET of all people with they are carried on the SEX red HAIR. CHROMOSOMES. In human males a RECESSIVE GENE carried on the X- sex cell (cytology) An alternative term CHROMOSOME will be expressed because for GAMETE. no corresponding ALLELE is present on the Y-CHROMOSOME to mask it. In the sex chromosome (genetics) CHROMOSOME female the corresponding ALLELE will be that carries the genes determining sex. present on the other X-CHROMOSOME, In mammals the female possesses two and for this reason human males have a identical SEX CHROMOSOMES or X- predisposition to RECESSIVE sex-linked chromosomes, whereas in the male the disorders e.g. HAEMOPHILIA (USA: two SEX CHROMOSOMES differ, one being hemophilia), COLOUR BLINDNESS (USA: an X- and the other a Y-CHROMOSOME. color blindness).

See also HETEROGAMETIC; HOMOGAME- sex ratio (measurement) Ratio of the TIC; SEX DETERMINATION. number of males to the number of females in a population. It may be expressed sex determination (genetics) INHERI- as the number of males to every 100 TANCE of particular COMBINATION of SEX females. CHROMOSOMES, which is the deciding FACTOR in whether an organism is male or sexagesimal (mathematics) Describing female. INHERITANCE of a HOMOLOGOUS a number system with the BASE 60. pair of SEX CHROMOSOMES predisposes the organism to one sex (e.g. in mammals, sexual reproduction (physiology) REPRO- the female). INHERITANCE of a pair of DUCTION of an organism that involves dissimilar SEX CHROMOSOMES deter- the FUSION of specialized SEX CELLS mines the other sex (in mammals, the male). or gametes (which are HAPLOID) to form DIPLOID progeny. It is important in bringing See also HETEROGAMETIC; HOMOGAMETIC. new vigour to a SPECIES by the mixing of genetic material from the parents to give a genetically different organism.

356 SEXUALLY TRANSMITTED DISEASE SILICON

See also ASEXUAL REPRODUCTION; sibship (medical) All the brothers and EGG; FERTILIZATION; SPERM. sisters in a FAMILY. sexually transmitted disease (medical) side reaction (chemistry) A CHEMICAL Previously called venereal disease. The REACTION that takes place at the same currently generally preferred term is time as the main REACTION. genitourinary medicine. SIDS (medical) An abbreviation of SFO (anatomy) An abbreviation of ‘S’udden ‘I’nfant ‘D’eath ‘S’yndrome. ‘Sub‘F’ornical ‘O’rgan. siemens (S) (measurement) SI UNIT sg (physics) An abbreviation of ‘s’pecific of electric CONDUCTANCE, formerly ‘g’ravity. expressed in RECIPROCAL ohms (mhos). It was named after the German physicist SGLT 1 (physiology/biochemistry) An Ernst Werner von Siemens (1816–92). abbreviation of ‘S’ODIUM-dependent ‘GL’ucose ‘T’ransporter. sievert (Sv) (measurement) SI UNIT of RADIATION dose equivalent. SGOT (biochemistry) An abbreviation of ‘S’erum ‘G’lutamic-‘O’xaloacetic SIF cells (histology) An abbreviation ‘T’ransaminase. of ‘S’mall, ‘I’ntensely ‘F’luorescent CELLS in sympathetic ganglia. SH (biochemistry) An abbreviation of ‘S’ulp‘H’ydryl (USA: sulfhydryl). significant figure (mathematics) DIGIT that gives information about a number shingles (medical) See HERPES VARICELLA containing it, and not a zero used simply ZOSTER VIRUS (HVZ). to indicate a vacant place at the beginning or end of the number; a DIGIT that shortsightedness (medical) An alternative makes an actual contribution to the term for MYOPIA. number. Also termed: significant DIGIT. shoulder blade (anatomy) An alternative silica gel (chemistry) Porous AMORPHOUS term for SCAPULA. VARIETY of silica (SiO2) which is capable of absorbing large quantities of WATER shunt (1 physics; 2 medical) 1 Device and other solvents. It is used as a that directs an ELECTRIC CURRENT DESICCANT and ADSORBENT. in a known way. 2 A surgically implanted tube or VESSEL that diverts the flow silicon Si (chemistry) Nonmetallic ELEMENT of FLUID (e.g. to by-pass an obstruction). in GROUP IVA of the PERIODIC TABLE, which exists as AMORPHOUS and SIADH (physiology/biochemistry) An CRYSTALLINE ALLOTROPES. It is the abbreviation of ‘S’yndrome of ‘I’nappro- second most abundant ELEMENT, occurring priate hypersecretion of ‘A’nti‘D’iuretic as silicates in clays and rocks. Sand ‘H’ormone (vasopressin). and QUARTZ consist of silica (SILICON

dioxide, SiO2). It is used in making refractory sibling (medical) A brother or sister. materials and TEMPERATURE-resistant GLASS. At. no. 14; r.a.m. 28.086.

357 SILVER SKIN silver Ag (chemistry) SILVER-white metallic single bond (chemistry) COVALENT BOND ELEMENT in GROUP IB of the PERIODIC formed by the sharing of one pair of TABLE (a TRANSITION ELEMENT). It electrons between two atoms. occurs as the free ELEMENT (native) and in various SULPHIDE (USA: sulfide) sinus (anatomy) Irregular cavity or ores. It is used in jewellery, electrical depression that forms part of an ANIMAL’S contacts, batteries and mirrors. SILVER anatomy; e.g. sinuses in the bones of halides are used in photographic emulsions. the face in mammals. At. no. 47; r.a.m. 107.868. siphon (physics) Device consisting of silver bromide (chemistry) AgBr Pale an inverted U-shaped tube that moves yellow INSOLUBLE CRYSTALLINE SALT, a LIQUID from one place to another used for making LIGHT-sensitive place at a lower LEVEL. The tube has photographic emulsions. to be initially filled with LIQUID in ORDER to FUNCTION. silver chloride (chemistry) AgCI White INSOLUBLE CRYSTALLINE SALT, used SI units (measurement) An abbreviation in the manufacture of pure SILVER for ‘S’ystème ‘I’nternational d’Unités, and in photographic emulsions. an international system of scientific units. It has seven BASIC units: METRE silver iodide (chemistry) Agl Pale yellow (m), KILOGRAM (kg), second (s), KELVIN INSOLUBLE CRYSTALLINE SALT, used (K), AMPERE (A), mole (mol) and candela in photographic emulsions. (cd), and two supplementary units RADIAN (rad) and steradian (sr). There are silver nitrate (chemistry) AgNO3 also 18 derived units. Colourless (USA: colorless) CRYSTALLINE SALT, used in VOLUMETRIC ANALYSIS skeleton (anatomy) Structure that supports and SILVER plating, and as a CAUSTIC the tissues and organs of an ANIMAL in medicine (e.g. for removing WARTS). and is attached to muscles to allow locomotion. An endoskeleton is internal, silver oxide (chemistry) Ag2O Brown made of BONE or CARTILAGE, and AMORPHOUS SOLID, only slightly possessed by vertebrates. Exoskeletons SOLUBLE in WATER but SOLUBLE in lie outside the muscles, e.g. in arthropods. AMMONIA SOLUTION. Also termed: Some invertebrates possess a hydrostatic silver(I) oxide. SKELETON which consists of FLUID under PRESSURE. simultaneous equations (mathematics) SET of algebraic equations that are skin (anatomy) ORGAN that protects all true for the same particular values the body from invasion by pathogens. In of their variables. WARM-BLOODED animals the SKIN also takes part in TEMPERATURE regulation, sine wave (physics) Waveform that e.g. through sweating and the constriction represents the periodic oscillations of and DILATION of its BLOOD VESSELS. CONSTANT AMPLITUDE as given by the It consists of epithelial TISSUE and sine of a LINEAR FUNCTION. Also termed: CONNECTIVE TISSUE arranged in two sinusoidal WAVE; sine curve. major layers, the thin outer EPIDERMIS and the thicker underlying DERMIS.

358 SKULL SODIUM BISULPHATE skull (anatomy) Bones that form the soda (chemistry) Imprecise term for a HEAD and face, including the CRANIUM COMPOUND of SODIUM, usually referring and JAWS. to SODIUM CARBONATE. small intestine (anatomy) Part of the See also CAUSTIC SODA; SODA ASH; digestive tract in mammals which is SODA LIME. composed of the DUODENUM and ILEUM, and is the main site of DIGESTION and soda ash (chemistry) Common name ABSORPTION in the GUT. BILE, pancreatic for ANHYDROUS SODIUM CARBONATE. juice and intestinal juice are liberated LIME SOLID MIXTURE of SODIUM in it, to supply many digestive ENZYMES. HYDROXIDE and CALCIUM OXIDE.

See also INTESTINE. sodium Na (chemistry) Soft, silvery- white metallic ELEMENT in GROUP smell (physiology) One of the primary IA of the PERIODIC TABLE (the ALKALI SENSES that enables animals to detect METALS). It occurs widely, principally odours (USA: odors), using chemorecep- as its CHLORIDE (COMMON SALT, tors usually located (in mammals) in NACI) in seawater and as underground OLFACTORY bulbs in the NASAL CAVITY. deposits, from which it is extracted by ELECTROLYSIS. The METALS many smg (biochemistry) An abbreviation of compounds are important in the chemical ‘sm’all ‘g’TP-binding PROTEIN. industry, particularly, in addition to the CHLORIDE, SODIUM HYDROXIDE smooth muscle (histology) Type of (CAUSTIC SODA, NAOH) and SODIUM

MUSCLE in internal organs and tissues, CARBONATE (SODA, Na2CO3). At. no. not under voluntary control. Also termed: 11; r.a.m. 22.9898. INVOLUNTARY MUSCLE.

sodium acetate (chemistry) CH3COONa SMS (medical) An abbreviation of ‘S’tiff- White CRYSTALLINE SOLID, used in ‘M’an ‘S’yndrome. PHOTOGRAPHY and in the manufacture of ETHYL ETHANOATE (acetate) and soap (chemistry) SODIUM or POTASSIUM various pigments. Also termed: SODIUM SALT of a FATTY ACID of high MOLE- ETHANOATE. CULAR WEIGHT (e.g. PALMITIC ACID,

STEARIC ACID). Soaps are made by sodium azide (chemistry) NaN3 White the HYDROLYSIS or SAPONIFICATION poisonous CRYSTALLINE SOLID, used of fats with hot SODIUM HYDROXIDE in the manufacture of detonators. or POTASSIUM HYDROXIDE, giving GLYCEROL as a BY-PRODUCT. They sodium bicarbonate (chemistry) An emulsify grease and act as wetting agents. alternative term for SODIUM HYDRO- GENCARBONATE. See also DETERGENT. sodium bisulphate (chemistry) An alterna- SOD (biochemistry) An abbreviation of tive term for SODIUM HYDROGENSULPHATE ‘S’uper‘O’xide ‘D’ismutase. (USA: sodium hydrogensulfate). (USA: sodium bisulfate).

359 SODIUM BISULPHITE SODIUM PUMP sodium bisulphite (chemistry) An alterna- sodium hydrogencarbonate (chemistry) tive term for SODIUM HYDROGENSULPHITE NaHCO3 White SOLUBLE powder, used (USA: sodium hydrogensulfite). (USA: in making baking powder, powder-based sodium bisulfite). fire extinguishers and antacids. Also termed: SODIUM BICARBONATE; BAKING SODA. sodium borate (chemistry) An alternative term for BORAX. sodium hydrogensulphate (chemistry)

NaHSO4.H2O White SOLID, used in the sodium bromide (chemistry) NaBr White dyeing industry and in the manufacture CRYSTALLINE SOLID, used in medicine. of SULPHURIC ACID (USA: sulfuric acid). Also termed: SODIUM BISULPHATE (USA: sodium carbonate (chemistry) Na2CO3.- sodium bisulfate). (USA: sodium

10H2O White CRYSTALLINE SOLID which hydrogensulfate). exhibits EFFLORESCENCE and forms an ALKALINE SOLUTION in WATER. sodium hydrogensulphite (chemistry)

It is used in GLASS making, as a WATER NaHSO3 White powder, used in medicine softener, and for the preparation of as an ANTISEPTIC, and as a preservative. SODIUM chemicals. Also termed: Also termed: SODIUM BISULPHITE (USA: WASHING SODA; SODA; SODA ASH. sodium bisulfite). (USA: sodium hydrogensulfite). sodium chlorate (chemistry) NaCIO3 White SOLUBLE CRYSTALLINE SOLID. sodium hydroxide (chemistry) NaOH It is a powerful OXIDIZING AGENT, used White DELIQUESCENT SOLID; a as a weed-killer and in the textile industry. STRONG BASE. It is made by the Also termed: SODIUM CHLORATE(V). ELECTROLYSIS of BRINE (SODIUM CHLORIDE SOLUTION). It is used in sodium chloride (chemistry) NaCI White the manufacture of soaps, rayon and SOLUBLE CRYSTALLINE SALT, .extracted paper and many other SODIUM from seawater or underground deposits. It is compounds. Also termed: CAUSTIC used for seasoning and preserving food. SODA; SODA. Industrially, it is used in the manufacture of a wide VARIETY of chemicals, including sodium nitrate (chemistry) NaNO3 White CHLORINE, SODIUM CARBONATE, CRYSTALLINE SALT, used as a food SODIUM HYDROXIDE and HY- preservative and in the manufacture DROCHLORIC ACID. Also termed: of explosives and fireworks. Also termed: COMMON SALT; SALT; sea SALT; table CHILE SALTPETRE; SODA NITRE. SALT.

sodium peroxide (chemistry) Na2O 2 sodium dihydrogenphosphate(V) (chem- Pale yellow powdery SOLID that reacts istry) NaH2PO4 White SOLID, used in readily with WATER to give SODIUM detergents and certain baking powders. HYDROXIDE and OXYGEN. It is an Also termed: SODIUM dihydrogen OXIDIZING AGENT, used as a BLEACH. orthophosphate. sodium pump (physiology) Process sodium ethanoate (chemistry) An alterna- by which POTASSIUM and SODIUM tive term for SODIUM ACETATE. ions are transported across membranes that surround ANIMAL CELLS.

360 SODIUM SILICATE SOLUBILITY

sodium silicate (chemistry) Na2SiO3.5H2O soft water (chemistry) WATER that Colourless (USA: colorless) CRYSTALLINE lathers immediately with SOAP. WATER SOLID, used in various types of detergents from which most of the CALCIUM and and cleaning compounds, and as a bonding MAGNESIUM compounds have been agent in many ceramic cements and removed. in various refractory applications. Also termed: SODIUM metasilicate. See also HARDNESS OF WATER. sodium silicate solution (chemistry) softening of water (chemistry) See A concentrated SOLUTION of SODIUM ION EXCHANGE. silicate in WATER, used to prepare SILICA GEL and precipitated silica. Also termed: software (computing) PROGRAM that WATER GLASS. can be used on a COMPUTER; e.g. executive programs, operating systems and utility sodium sulphate (chemistry) NaSO4.- programs.

10H2O White CRYSTALLINE SALT, used in the manufacture of paper, GLASS, See also HARDWARE. dyes and detergents. Also termed: Glauber’s SALT; SALTCAKE. (USA: sodium sulfate). sol (chemistry) Type of COLLOID consisting of a SOLID dispersed in a LIQUID. It sodium sulphide (chemistry) NaS2 A is usually LIQUID (unlike a GEL, which reddish-yellow DELIQUESCENT AMOR- is a jelly-like SOLID). PHOUS SOLID, used in the manufacture of dyes. (USA: sodium sulfide). solar cell (physics) PHOTOCELL that converts solar ENERGY directly into sodium sulphite (chemistry) Na2SO3 ELECTRICITY. White SOLUBLE CRYSTALLINE SOLID, used in bleaching and PHOTOGRAPHY. solenoid (physics) Cylindrical coil of (USA: sodium sulfite). wire, carrying an ELECTRIC CURRENT, used to produce a MAGNETIC FIELD. It sodium thiosulphate (chemistry) Na2S2O3 may have an IRON CORE that moves, White SOLUBLE CRYSTALLINE SOLID. often to WORK a switch. It is a strong REDUCING AGENT, used as a photographic fixing agent (when it See also RELAY, ELECTRICAL. reacts with unexposed SILVER halides) and in dyeing and VOLUMETRIC ANALYSIS. solid (1 chemistry; 2 mathematics) 1 Also termed: hypo. (USA: sodium thiosulfate). An alternative name for a substance in the solid state. 2 Having or relating to soft palate (anatomy) Rear part of the three dimensions. roof of the mouth, consisting of MUSCLE TISSUE covered by MUCOUS MEMBRANE. solidifying point (physics) An alternative The uvula hangs from the back of the term for FREEZING POINT. SOFT PALATE. solubility (chemistry) Amount of a soft radiation (radiology) RADIATION substance (SOLUTE) that will dissolve of relatively long WAVELENGTH whose in a LIQUID (SOLVENT) at a given penetrating POWER is very limited. TEMPERATURE, usually expressed as

361 SOLUBILITY PRODUCT SPECIFIC CHARGE a WEIGHT per UNIT VOLUME (e.g. gm somatotrophin (biochemistry) An alterna- per LITRE) or a PERCENTAGE. tive term for GROWTH HORMONE.

See also CONCENTRATION. sorbitol (chemistry) ALCOHOL formed by the REDUCTION of GLUCOSE, used solubility product (chemistry) The as a sweetening agent. PRODUCT of the concentrations of the ions of a dissolved ELECTROLYTE when Soret effect (physics) See THERMAL in EQUILIBRIUM with undissolved substance. DIFFUSION. soluble (chemistry) Describing a sub- SOT (society) An abbreviation of ‘S’ociety stance (SOLUTE) that will dissolve in ‘O’f ‘T’oxicology. a LIQUID (SOLVENT). Southern blotting (molecular biology) solute (chemistry) A substance that dissolves DNA blotting. Named after Edwin Mellor in a SOLVENT to form a SOLUTION. Southern (1938-). See WESTERN BLOTTING; NORTHERN BLOTTING. solution (1 chemistry; 2 general terminology) 1 HOMOGENEOUS MIXTURE Southgates mucicarmine stain (histology) of SOLUTE and SOLVENT. 2 Result of A histological staining technique that solving a problem (e.g. finding the unknown may be used for MUCIN. quantity in a mathematical equation). sp (microbiology) An abbreviation of solvent extraction (chemistry) Removal ‘sp’ecies. of a substance from a (usually AQUEOUS) SOLUTION by dissolving it in a (usually species (sp) (taxonomy) Smallest GROUP organic) SOLVENT. The resulting LIQUID commonly used in biological CLASSIFI containing the substance is called a CATION and into which a GENUS is RAFFINATE. Also termed: LIQUID-LIQUID divided. SPECIES are sometimes further EXTRACTION. divided into SUBSPECIES (races). Generally, no more than one type of solvent (chemistry) Substance in which organism is present in one SPECIES. a SOLUTE dissolves; the COMPONENT Members of a SPECIES may breed with of a SOLUTION which is in excess. one another, but cannot generally breed with members of another SPECIES. Rarely, solvolysis (chemistry) CHEMICAL very closely related SPECIES interbreed REACTION between SOLVENT and to produce a HYBRID. SOLUTE molecules. See also BINOMIAL NOMENCLATURE; See also HYDROLYSIS. VARIETY. somatic cell (histology) Any CELL in the specific activity (physics) Number of body other than its gametes, the SPERM in disintegrations of a RADIO-ISOTOPE its TESTES or the eggs in its OVARY. per UNIT time per UNIT MASS. somatic (histology) Of the body. SOMATIC specific charge (physics) Ratio of ELECTRIC CELLS include all CELLS of an organism CHARGE to UNIT MASS of an ELEMENTARY except for the gametes or sex-CELLS. PARTICLE.

362 SPECIFIC GRAVITY SPERMATOZOON specific gravity (physics) Former name spectroscopy (physics) Study of the properties for RELATIVE DENSITY. of LIGHT, using a SPECTROSCOPE; the production and ANALYSIS of spectra. specific latent heat (physics) Amount of LATENT HEAT per UNIT MASS of a substance. spectrum (1, 2 physics) 1 Band, continuous range, or lines of ELEC- specific rate constant (chemistry) See TROMAGNETIC RADIATION emitted RATE CONSTANT. or absorbed by a substance under certain circumstances. 2 Coloured (USA: colored) SPECT (physics) An abbreviation of band of LIGHT or bands of colours ‘S’ingle ‘P’hoton ‘E’mission ‘C’omputed produced by splitting various wavelengths ‘T’omography. of ELECTROMAGNETIC RADIATION, using an OPTICAL PRISM or spectral line (physics) WAVELENGTH DIFFRACTION GRATING. of LIGHT in a line. Particular spectrum colours (physics) Visible colours spectral series (physics) Sequence that are observed in the SPECTRUM of lines in a line SPECTRUM. of WHITE LIGHT (e.g. in a rainbow). (USA: spectrum colors). spectrochemistry (chemistry) Branch of chemistry concerned with the study sperm (cytology) An abbrevistion of of spectra of substances. ‘SPERM’atozoan, the GAMETE (sex- CELL) produced by the male in many spectrometer (physics) SPECTROSCOPE SPECIES of animals (in mammals, in that has some form of photographic or the TESTES). It consists of a HEAD electrical detection device. contsining genetic material in the NUCLEUS (which is HAPLOID) and usually possesses spectrometry (measurement) Measurement cilia or flagelia for movement. of the INTENSITY of SPECTRAL LINES or SPECTRAL SERIES 3S 3 FUNCTION spermatocyte (cytology) CELL from which of WAVELENGTH. SPERM (spermatozoa) are derived through SPERMATOGENESIS. Primary sperma- spectrophotometer (physics) Instrument tocytes are DIPLOID; after MEIOSIS, that measures the INTENSITY of ELEC- secondary spermatocytes which are TROMAGNETIC RADIATION absorbed HAPLOID are formed. These further divide or transmitted by a substance as a to produce spermatids, which differentiate FUNCTION of WAVELENGTH, usually to form SPERM. in the visible, INFRA-RED and ULTRAVIOLET regions of the ELECTROMAGNETIC spermatogenesis (physiology) Formation SPECTRUM. of SPERM in the TESTIS. It commences with the repeated MITOSIS of primordial spectroscope (physics) Instrument for GERM CELLS to form spermatogonia, splitting various wavelengths of which grow to form 3 primary SPER- ELECTROMAGNETIC RADIATION into MATOCYTE. This ultimately forms 3 SPECTRUM, using an OPTICAL PRISM HAPLOID spermstozoa after MEIOSIS. or DIFFRACTION GRATING. spermatozoon (cytology) See SPERM.

363 SPHERICAL ABERRATION SRIF spherical aberration (optics) Type of the organs within the central body cavity ABERRATION in a LENS or mirror. of vertebrates. sphincter (histology) Circular MUSCLE spleen (anatomy) ORGAN present in that controls the flow of a LIQUID or the ABDOMEN of some vertebrates semi-solid through an orifice (e.g. the that aids in defence against invading anal SPHINCTER, round the ANUS). organisms. It produces LYMPHOCYTES and also stores and removes RED BLOOD sphygmomanometer (physics) Instrument CELLS (ERYTHROCYTES) from the for measuring BLOOD PRESSURE. BLOOD system. spinal column (anatomy) See SPINE. spontaneous generation (philosophy) A theory (now disproved) that living spinal cord (anatomy) Part of the CENTRAL MATTER can arise from non-living NERVOUS SYSTEM (CNS) in vertebrates MATTER. Also termed: ABIOGENESIS. that is enclosed within the SPINE. It consists of a hollow NERVE tube containing See also BIOGENESIS. many interconnecting neurones and connected to the SPINAL NERVES. spore (biology) Resting form of an organism that is highly resistant to spinal nerve (histology) Any of several adverse conditions, e.g. in BACTERIA. PERIPHERAL NERVES arising from the SPINAL CORD which are connected to sq cm (measurement) An abbreviation receptors and effectors in other parts of of ‘sq’uare ‘c’enti‘m’eter(s) (USA: centi- the body. meter[s]). spine (anatomy) BACKBONE; dorsally squamous (histology) Scaly or plate- situated bony column composed of like; a type of CELL. vertebrae, which enclose the SPINAL CORD. Also termed: SPINAL COLUMN. squamous cell carcinoma (histology) A MALIGNANT NEOPLASM derived from spirit (1,2 chemistry) 1 A VOLATILE LIQUID SQUAMOUS EPITHELIUM. obtained by DISTILLATION; a VOLATILE DISTILLATE (e.g. aviation SPIRIT). 2 A square root (mathematics) Of a number, SOLUTION that consists of a VOLATILE another number that when multiplied substance dissolved in ETHANOL (ETHYL by itself gives the original number. It ALCOHOL). is indicated by the symbol or the INDEX 1 1/2 (POWER) / 2; e.g. 16 (or 16 )=4. See also METHYLATED SPIRITS. See also ROOT. spirochaete (bacteriology) Member of a GROUP of BACTERIA characterized SR (society) An abbreviation of ‘S’ociety by a spiral shape, some of which are of ‘R’adiographers. parasitic and cause disorders (e.g. syphilis, YAWS, infectious JAUNDICE). SRIF (physiology/biochemistry) Abbre- viation of ‘S’omatotrophin ‘R’elease- splanchnology (biology) Branch of ‘I’nhibiting ‘F’actor. (USA: somatotropin biology and medicine concerned with release-inhibiting factor).

364 SRNA STARCH

SRNA (biochemistry) An abbreviation standard error (statistics) An alternative of ‘S’oluble ‘R’ibo‘N’ucleic ‘A’cid. term for STANDARD DEVIATION.

SRY (genetics) An abbreviation of product standard solution (chemistry) SOLUTION of ‘S’ex-determining ‘R’egion of ‘Y’ of definite CONCENTRATION, i.e. having chromosome. a known WEIGHT of SOLUTE in a definite VOLUME of SOLUTION. SS (society) An abbreviation of Royal ‘S’tatistical ‘S’ociety. standard state (chemistry) ELEMENT in its most STABLE physical form at a SS 14 (biochemistry) An abbreviation specified TEMPERATURE and a PRESSURE of ‘S’omato‘S’tatin 14. of 101,325 pascals (760 mm Hg).

SS 28 (biochemistry) An abbreviation standard temperature and pressure of ‘S’omato‘S’tatin 28. (s.t.p. or STP) (physics) SET of standard conditions of TEMPERATURE and SSRI (pharmacology) An abbreviation PRESSURE. By convention, the standard of ‘S’elective ‘S’erotonin ‘R’euptake TEMPERATURE is 273.15 K (0°C) and ‘I’nhibitors. the standard PRESSURE is 101,325 pascals (760 mm Hg). ssp. (microbiology) An abbreviation of ‘s’ub ‘sp’ecies. stannic chloride (chemistry) An alternative term for TIN(IV) CHLORIDE. stable (1 chemistry; 2, 3 physics) 1 Relatively INERT (e.g. describing a RARE GAS) or stannous (chemistry) Also termed: hard to decompose (e.g. describing an TIN(IV). OXIDE such as silica). 2 In atomic physics, describing an ISOTOPE or NUCLEUS stannous chloride (chemistry) An that shows no tendency to decompose alternative term for TIN(II) CHLORIDE. (e.g. by emitting RADIOACTIVITY). 3 Describing a type of EQUILIBRIUM that staphylococcus (bacteriology) Type of does not have a tendency to shift (as gram-POSITIVE BACTERIUM characterized opposed to unstable EQUILIBRIUM). by its shape, which takes the form of irregular clusters (resembling a miniature standard deviation (statistics) Measure bunch of grapes). Staphylococci cause of the spread of a SET of numbers about various inflammatory disorders (e.g. BOILS, their ARITHMETIC MEAN. It is the IMPETIGO, osteomyelitis). SQUARE ROOT of the MEAN (AVERAGE) of the squares of all the deviations from starch (chemistry) (C6H 10O 5)n Complex the MEAN value of the SET (ROOT-MEAN- POLYSACCHARIDE CARBOHYDRATE, SQUARE value). It is a measure of the a POLYMER of GLUCOSE, that occurs compactness of a SET of numbers. Also in all green plants, where it serves as termed: STANDARD ERROR. a reserve ENERGY material. It forms GLUCOSE on complete HYDROLYSIS. standard electrode potential (physics) Also termed: AMYLUM. ELECTRODE POTENTIAL specified by comparison with a standard ELECTRODE.

365 STAT STERILIZATION stat (general terminology) (Do) immedi- stereoisomer (chemistry) One of two ately. or more isomers with the same MOLECULAR FORMULA, but different configurations state of matter (physics) An alternative (arrangements of atoms). term for physical STATE OF MATTER. stereoisomerism (chemistry) ISOMERISM statistical analysis (statistics) Evaluation of compounds of the same MOLECULAR of DATA by the use of statistics. FORMULA that results when the spatial arrangement of the atoms within the statistics (statistics) Branch of science molecules are different. concerned with the collection and CLASSIFICATION of numerical DATA See also GEOMETRIC ISOMERISM; and facts, and their interpretation in OPTICAL ISOMERISM. mathematical terms, especially the determination of probabilities. stereoregular (chemistry) Describing a COMPOUND that has a regular spatial STD (medical) An abbreviation of arrangement of atoms within its ‘S’exually ‘T’ransmitted ‘D’isease. MOLECULE. steam point (physics) NORMAL BOILING stereoscope (physics) Optical instrument POINT of WATER; it is taken to be a that gives a three-dimensional illusion TEMPERATURE of 100°C (at NORMAL of depth, normally from a pair of flat PRESSURE). photographs. stearate (chemistry) ESTER or SALT stereoscopic (physics) Describing an of STEARIC ACID. instrument or system of vision that allows objects to be viewed in three See also SOAP. dimensions.

stearic acid (chemistry) CH3(CH2)16COOH stereospecific (chemistry) Describing Long-chain FATTY ACID (a CARBOXYLIC a CHEMICAL REACTION in which a ACID) that occurs in most FATS AND different PRODUCT is formed from each OILS. Its SODIUM and POTASSIUM geometric ISOMER of the REACTANT. salts are constituents of soaps. Also termed: OCTADECANOIC ACID. steric effect (chemistry) Phenomenon in which the shape of a MOLECULE stem cell (cytology) A cell that gives affects its CHEMICAL REACTIONS. rise to a particular type of cell, as occurs in haematopoiesis (USA: hematopoiesis). sterilization (1 microbiology; 2 medical) 1 TREATMENT of an apparatus or stereochemistry (chemistry) Branch of substance (e.g. food) so that it contains chemistry concerned with the study of no MICROORGANISMS that could cause the spatial arrangement of the atoms disease or spoilage, usually by means within a MOLECULE and the way that of high temperatures, GAMMA RADIATION, these affect the properties of the MOLECULE. etc. 2 Surgical TREATMENT of an ANIMAL so that it cannot have offspring (e.g. in mammals by cutting or tying the FALLOPIAN

366 STERNUM STPD

TUBES of the female or vasa deferentia stimulus (physics) Environmental FACTOR of the male; removing the ovaries or that is detected by a RECEPTOR and TESTES is a more drastic way of achieving induces a RESPONSE from an EFFECTOR. the same effect). stoichiometric compound (chemistry) sternum (anatomy) BONE in tetrapod A chemical whose molecules have the vertebrates on the VENTRAL side of COMPONENT elements present in exact the THORAX, parallel to the SPINE, to proportions as demanded by a simple which most of the ribs are attached. MOLECULAR FORMULA. Also termed: BREASTBONE. stoichiometric mixture (chemistry) A steroid (biochemistry) Any of a GROUP MIXTURE of reactants that in a CHEMICAL of naturally occurring tetracyclic organic REACTION yield a STOICHIOMETRIC compounds, widely found in ANIMAL tissues. COMPOUND with no excess REACTANT. Most have very important physiological activities (e.g. adrenal HORMONES, BILE stoichiometry (chemistry) Branch of acids, SEX HORMONES, sterols). Some chemistry that deals with the relative can be made synthetically (e.g. for use quantities of atoms or molecules taking as contraceptive pills). place in a REACTION. sterol (biochemistry) Subgroup of steroids stomach (anatomy) Muscular sac present or STEROID ALCOHOLS. They include in vertebrates in which food is partly CHOLESTEROL, abundant in ANIMAL digested and stored after passage through tissues, which is the PRECURSOR of OESOPHAGUS (gullet). HYDROCHLORIC many other steroids. ACID is secreted in the STOMACH, as is the ENZYME PEPSIN, which begins stethoscope (medical) An instrument the DIGESTION of proteins. through which the physician listens to sounds made by internal organs (e.g. storage (computing) COMPUTER HEART, lungs). MEMORY CAPACITY.

STH (physiology/biochemistry) An storage cell (physics) An alternative abbreviation of ‘S’omato‘T’rophin, growth term for SECONDARY CELL. ‘H’ormone (USA: somatotropin growth hormone). storage device (computing) An alternative term for a COMPUTER MEMORY or store. still (chemistry) Apparatus for the DISTILLATION of liquids. See also RANDOM ACCESS MEMORY (RAM); READ-ONLY MEMORY (ROM). stimulated emission (physics) Process by which a PHOTON causes an ELECTRON STP or s.t.p. (physics) An abbreviation in an ATOM to drop to a lower ENERGY of ‘s’tandard ‘t’emperature and ‘p’ressure. LEVEL and emit another PHOTON. It is the principle of the LASER. STPD (physics) An abbreviation of ‘S’tandard ‘T’emperature and ‘P’ressure (0°C, 760mm Hg), ‘D’ry.

367 STR. STRYCHNINE str. (microbiology) An abbreviation of stroma (histology) The TISSUE that forms ‘str’eptococcus. the supporting framework of an ORGAN, as distinct from the parenchyma, the stratum (histology) Layer of CELLS functioning TISSUE. or TISSUE. strong acid (chemistry) ACID that is strep. (microbiology) An abbreviation completely dissociated into its COMPONENT of ‘strep’tococcus. ions (e.g. HYDROCHLORIC ACID). streptococcus (bacteriology) Type of GRAM- strong base (chemistry) BASE that is POSITIVE BACTERIUM characterized by completely dissociated into its COMPONENT its shape, which takes the form of a ions (e.g. SODIUM HYDROXIDE). chain. Streptococci cause various disorders (e.g. erysipelas, scarlet fever). strontium Sr (chemistry) Silvery-white metallic ELEMENT in GROUP IIA of the streptomycin (pharmacology) ANTIBIOTIC PERIODIC TABLE (one of the RARE EARTH that works by inhibiting PROTEIN elements). STRONTIUM compounds impart SYNTHESIS in BACTERIAL CELLS. a bright red COLOUR (USA: color) to a flame, and are used in flares and fireworks. stress (biology) Any environmental At. no. 38; r.a.m. 87.62. FACTOR, or COMBINATION of factors, that has adverse effects on the structure strontium unit (measurement) Measure or BEHAVIOUR (USA: behavior) of an of the CONCENTRATION of the RADIO- organism. ISOTOPE STRONTIUM-90 in substances such as BONE, milk or soil relative to striated muscle (histology) MUSCLE their CALCIUM content. that contains well-aligned threads of PROTEIN, which enable it to contract See also STRONTIUM. strongly in a particular direction. Also termed: VOLUNTARY MUSCLE. structural formulae (chemistry) Shorthand description of a chemical compound stroboscope (physics) An instrument that indicates the arrangement of the consisting of a rapidly flashing lamp, atoms in its molecules as well as its employed for measuring speeds of rotation. composition e.g. H2O. It can also be used, by controlling the rate of flashing, to view objects that See also EMPIRICAL FORMULA; are moving rapidly with periodic motion MOLECULAR FORMULA. and to see them as if they were at rest. Also termed: rotoscope. structural isomerism (chemistry) The ISOMERISM of chemical compounds stroke (medical) Sudden damage to the that have the same MOLECULAR VASCULAR SYSTEM in the BRAIN, caused FORMULA but different structural formulae. by the rupture or blockage of a BLOOD- Structural isomers have different physical VESSEL and usually resulting in impairment and chemical properties. or loss of some functions. strychnine (chemistry) White CRYSTALLINE INSOLUBLE ALKALOID with a bitter TASTE,

368 STX SUCROSE one of the most powerful poisons known. substituent (chemistry) ATOM or GROUP Also termed: VAUQUELINE. that replaces another ATOM or GROUP in a MOLECULE of a COMPOUND. STX (toxicology) An abbreviation of ‘S’axi‘T’o‘X’in. substitution product (chemistry) PRODUCT formed from substitution. subatomic particle (physics) PARTICLE that is smaller than an ATOM or forms part substitution reaction (chemistry) A of an ATOM (e.g. ELECTRON, NEUTRON, CHEMICAL REACTION that involves the NUCLEUS, PROTON). Sometimes also direct replacement of an ATOM or GROUP called an ELEMENTARY PARTICLE. in a MOLECULE of a COMPOUND (usually an ORGANIC COMPOUND) by some subclinical infections (medical/microbiol- other ATOM or GROUP; e.g. the REACTION ogy) Infections with minimal or no apparent in which an ATOM of CHLORINE replaces symptoms. an ATOM of HYDROGEN in a MOLECULE

of BENZENE (C6H6) to form a MOLECULE subcutaneous (medical) Beneath the of chlorobenzene (C6H5CI). Also termed: surface of the SKIN, but not necessarily DISPLACEMENT REACTION. beneath all the layers of SKIN, usually applied to injections. substrate (1 biochemistry; 2 biology) 1 The MOLECULE or COMPOUND upon subcutaneous tissue (histology) Layer which an ENZYME acts. Each SUBSTRATE of TISSUE below the DERMIS of the is specific to its own ENZYME, and SKIN. It often contains deposits of fat. vice versa. 2 Substance upon which an organism grows or is attached to. sublimate (chemistry) SOLID formed by the process of SUBLIMATION. succinic acid (chemistry) (CH2COOH)2 White CRYSTALLINE DICARBOXYLIC sublimation (chemistry) Direct conversion ACID, used in the manufacture of dyes of a SOLID substance to its VAPOUR and in organic SYNTHESIS. It is an state on heating without melting taking INTERMEDIATE in the KREBS CYCLE place (e.g. SOLID CARBON DIOXIDE (CITRIC ACID or TRICARBOXYLIC ACID (DRY ICE). The VAPOUR condenses CYCLE). Also termed: BUTANEDIOIC to give a SUBLIMATE. The process is ACID; ethylenedicarboxylic ACID. used to purify various substances. sucrase (biochemistry) ENZYME that sub-shell (physics) Subdivision of an breaks down SUCROSE into simpler ELECTRON shell. sugars. Also termed: invertase. subspecies (taxonomy) A GROUP of sucrose (chemistry) C12H22O11 White organisms within a SPECIES that have OPTICALLY ACTIVE SOLUBLE CRY- certain characteristics not possessed STALLINE DISACCHARIDE which is by other members of the SPECIES. Breeding obtained from SUGAR cane and SUGAR- may occur between members of different beet; ordinary SUGAR, used to sweeten subspecies. Also termed: RACE. food. It is hydrolysed to FRUCTOSE and GLUCOSE. Also termed: CANE- SUGAR; beet-SUGAR; SUGAR.

369 SUDDEN INFANT DEATH SYNDROME SULPHUR DIOXIDE sudden infant death syndrome (SIDS) sulphonation (chemistry) A SUBSTITUTION (medical) A term applied to babies who REACTION that involves the replacement die unexpectedly and of undetermined of a HYDROGEN ATOM by the SULPHONIC cause, usually during sleep. Also called ACID GROUP (USA: sulfonic acid group). cot (USA: crib) death. (USA: sulfonation). sugar (1, 2 chemistry) 1 CRYSTALLINE sulphonic acid (chemistry) ACID that

SOLUBLE CARBOHYDRATE with a sweet contains the GROUP -SO3H. Organic TASTE; usually a MONOSACCHARIDE SULPHONIC ACIDS (USA: sulfonic acids) or DISACCHARIDE. 2 Common name are used in the manufacture of dyes, for SUCROSE. detergents and drugs. (USA: sulfonic acid). sulphate (chemistry) ESTER or SALT sulphonium compound (chemistry) A of SULPHURIC ACID (USA: sulfuric acid). COMPOUND of the EMPIRICAL FORMULA

(USA: sulfate). R3SX, where R is an organic RADICAL and X is an electronegative ELEMENT sulphation (chemistry) Conversion of or RADICAL. (USA: sulfonium compound). a substance into a SULPHATE (USA: sulfate). (USA: sulfation). sulphoxide (chemistry) COMPOUND of EMPIRICAL FORMULA RSOR’, where R sulphide (chemistry) BINARY COMPOUND and R’ are organic radicals. (USA: sulfoxide). containing SULPHUR (USA: sulfur); a SALT of HYDROGEN SULPHIDE (USA: sulphur S (chemistry) Yellow nonmetallic hydrogen sulfide). Organic sulphides SOLID ELEMENT in GROUP VIB of the (USA: sulfides) are called THIOETHERS. PERIODIC TABLE, which forms several (USA: sulfide). ALLOTROPES including alpha- (rhombic) SULPHUR (USA: sulfur) and beta- sulphite (chemistry) ESTER or SALT (MONOCLINIC) SULPHUR. It occurs as of SULPHUROUS ACID (USA: sulfurous the free ELEMENT in volcanic regions acid). (USA: sulfite). and as underground deposits and as sulphates and sulphides, which include 2-sulphobenzimide (chemistry) An important minerals (e.g. galena, PbS, alternative term for SACCHARIN. (USA: and pyrites, FeS2). Chemically it behaves sulfobenzimide). like OXYGEN, and can replace it in ORGANIC COMPOUNDS (e.g. sulphonamide (pharmacology) Member THIOETHERS and thiols). SULPHUR is of a CLASS of SYNTHETIC anti- used to make SULPHURIC ACID, matches, BACTERIAL drugs which act by ENZYME gunpowder, drugs, FUNGICIDES and dyes, INHIBITION. They are amides derived and in the vulcanization of rubber. At. from SULPHONIC ACIDS (USA: sulfonic no. 16; r.a.m. 32.06. (USA: sulfur). acids). (USA: sulfonamide). sulphur dichloride oxide (chemistry) sulphonate (chemistry) ESTER or SALT An alternative term for thionyl CHLORIDE. of a SULPHONIC ACID (USA: sulfonic (USA: sulfur dichloride oxide). acid). (USA: sulfonate).

sulphur dioxide (chemistry) SO2 Colourless (USA: colorless) poisonous

370 SULPHUR DYE SUPEROXIDE

GAS with a strong pungent odour (USA: acids, fertilizers, explosives, ACCUMU- odor), made by burning SULPHUR (USA: LATORS, petrochemicals, etc. Its salts are sulfur), roasting SULPHIDE (USA: sulfide) sulphates (USA: sulfates). Also termed: ores or by the ACTION of acids on VITRIOL; oil of VITRIOL; HYDROGEN sulphites (USA: sulfites). It is also SULPHATE (USA: hydrogen sulfate). produced when SULPHUR containing (USA: sulfuric acid). compounds, such as fossil fuels, are burned, and from this source is a major sulphurous acid (chemistry) H2SO3 atmospheric pollutant. It is used to Colourless (USA: colorless) AQUEOUS make SULPHURIC ACID (USA: sulfuric SOLUTION of SULPHUR DIOXIDE (USA: acid) and, in AQUEOUS SOLUTION, sulfur dioxide), used as a BLEACH and as a BLEACH. It is also termed: a REDUCING AGENT. Its salts are sulphites SULPHUR(IV) OXIDE (USA: sulfur(IV) (USA: sulfites). (USA: sulfurous acid). oxide). (USA: sulfur dioxide). superconductivity (physics) A large sulphur dye (chemistry) Dye made by increase in electrical CONDUCTIVITY heating certain ORGANIC COMPOUNDS exhibited by certain metals and ALLOYS with SULPHUR (USA: sulfur) or ALKALI at a TEMPERATURE a few degrees polysulphides (USA: polysulfides), used above ABSOLUTE ZERO. Also termed: for dyeing industrial fabrics. (USA: sulfur supraconductivity. dye). superconductor (physics) METAL that sulphur(IV) oxide (chemistry) An alterna- exhibits SUPERCONDUCTIVITY. tive term for SULPHUR DIOXIDE (USA: sulfur dioxide). (USA: sulfur(IV) oxide). supercooling (chemistry) Metastable state of a LIQUID in which its TEMPERATURE sulphur(V1) oxide (chemistry) An alterna- has been brought below the NORMAL tive term for SULPHUR TRIOXIDE (USA: FREEZING POINT without any solidification sulfur trioxide). (USA: sulfur(VI) oxide). or CRYSTALLIZATION occurring.

sulphur trioxide (chemistry) SO3 VOLATILE superheated steam (chemistry) Steam white SOLID made by the catalytic (under PRESSURE) at a TEMPERATURE OXIDATION of SULPHUR DIOXIDE (USA: above the BOILING POINT of WATER sulfur dioxide), usually stored in sealed (100°C). See SUPERHEATING. tubes. It reacts with WATER to form SULPHURIC ACID (USA: sulfuric acid). Also superheating (chemistry) Metastable state termed: SULPHUR (VI) OXIDE (USA: of a LIQUID or GAS that has been heated sulfur(VI) oxide). (USA: sulfur trioxide). above its BOILING POINT in the LIQUID state, by increasing the PRESSURE above sulphuric acid (chemistry) H2SO4 A that of the ATMOSPHERE. Also termed: corrosive, colourless (USA: colorless), oily overheating. LIQUID ACID, made mainly from SULPHUR DIOXIDE (USA: sulfur dioxide) supernatant liquid (chemistry) Clear LIQUID by the contact process. It is a DESICCANT, that lies above a sediment or PRECIPITATE. and when hot a powerful OXIDIZING AGENT. It is produced in large quantities superoxide (chemistry) 1 COMPOUND that and used in the manufacture of other yields the FREE RADICAL O2, which is highly

371 SUPERSATURATED SOLUTION SYNERGY toxic to living CELLS. 2 OXIDE that yields in the SKIN. EVAPORATION of SWEAT both HYDROGEN PEROXIDE and OXYGEN aids in cooling the body. Also termed: on TREATMENT with an ACID. perspiration.

See also PEROXIDE. symbiosis (biology) Association between two organisms of different SPECIES in supersaturated solution (chemistry) which both partners benefit. An unstable SOLUTION that contains more SOLUTE than a SATURATED See also COMMENSALISM; PARASITISM; SOLUTION would contain at the same SAPROPHYTE. TEMPERATURE. It easily changes to a SATURATED SOLUTION when the excess symmetry (mathematics) The property SOLUTE is made to crystallize. of being symmetrical, i.e. having the same shapes on each side of or around a surface active agent (chemistry) An point, AXIS or plane. alternative term for SURFACTANT. sympathetic nervous system (anatomy) surface tension (physics) FORCE per Branch of the AUTONOMIC NERVOUS UNIT length acting along the surface of SYSTEM that is structurally different a LIQUID at right-angles to any line drawn to the PARASYMPATHETIC NERVOUS in the surface. It has the effect of making SYSTEM. NORADRENALINE (USA: a LIQUID behave as if it has a surface norepinephrine) is produced at the end SKIN (which can support e.g. small aquatic of sympathetic nerve fibres (USA: insects), and is responsible for CAPILLARITY sympathetic nerve fibers), unlike the and other phenomena. It is measured in parasympathetic system. Effects produced newtons per METRE (N m-1). by each system are generally antagonistic. surfactant (chemistry) Substance that synapse (histology) Point of connection reduces the SURFACE TENSION of a between neurones (NERVE CELLS). LIQUID, used in detergents, wetting It consists of a gap between the mem- agents and foaming agents. Also termed: branes of two CELLS, across which SURFACE ACTIVE AGENT. impulses are transmitted by a transmitter substance (e.g. acetylcholine). Specialized suspension (chemistry) MIXTURE of synapses occur at NERVE-MUSCLE INSOLUBLE small SOLID particles and junctions. a FLUID in which the INSOLUBLE substance stays evenly distributed throughout the See also NEUROTRANSMITTER. FLUID (because of molecular collisions and the FLUID’S VISCOSITY, which prevent syndrome (medical) SET of symptoms PRECIPITATION). Also termed: suspensoid. occurring together all thought to be produced by the same illness, (e.g. suspensory ligament (anatomy) One nephrotic SYNDROME). of the structures that hold the LENS of the EYE in position. synergy (biology) Collective ACTION of two or more things (e.g. drugs, muscles) sweat (physiology) A watery FLUID that is more effective than it would be containing salts secreted from GLANDS

372 SYNOVIAL FLUID SYSTOLE if they acted on their own. Also termed: synergism. synovial fluid (anatomy) LIQUID secreted by a SYNOVIAL MEMBRANE. synovial membrane (anatomy) Lining of the CAPSULE that encloses a JOINT between bones. It secretes SYNOVIAL FLUID, which acts as a LUBRICANT to prevent friction in the JOINT during movement. synthesis (chemistry) Formation of a chemical COMPOUND by combining elements or simpler compounds; the building of compounds through a planned SERIES of steps. synthetic (chemistry) Formed by artificial means; describing a chemical COMPOUND that has been produced by SYNTHESIS. systole (physiology) The contraction phase of the cardiac cycle, as opposed to the DIASTOLE.

373 T

T (biochemistry) A symbol for THREONINE. in talcum powder, in medicine and in ceramic materials. Also termed: French CHALK; T4 (1 genetics; 2 biochemistry) 1 One of MAGNESIUM SILICATE MONOHYDRATE. the most intensively studied of the bacteriophages. It only attacks ESCHERICHIA talus (anatomy) The ankle BONE. COLI. The GENOME is doublestranded DNA, LINEAR, but with matching ends tandum duplication (genetics) A form of that can join up to make a circular DNA duplication in which part of a CHRO- MOLECULE after entry into the HOST MOSOME duplicates itself, the second CELL. 2 THYROXINE. See THYROID. copy being inserted in line with the first. t (general terminology) An abbreviation tanin (chemistry) Yellow substance that of ‘t’ime. is a member of a CLASS of ORGANIC COMPOUNDS, of vegetable ORIGIN (e.g. TAB (immunology) An abbreviation of in tree bark, oak galls and tea), that ‘t’yphoid, paratyphoid ‘A’ and paratyphoid are derivatives of POLYHYDRIC BENZOIC ‘B’ (VACCINE). ACIDS. They are used in tanning hides to make leather. tabes dorsalis (medical/microbiology) Degeneration of neurons in the SPINAL See also TANNIC ACID. CORD, caused by syphilis. tannic acid (chemistry) White AMORPHOUS tachycardia (medical) Rapid HEARTBEAT, SOLID ORGANIC ACID, a member of above 100 beats per MINUTE. the CLASS of compounds called tannins. It is used in tanning and for making inks taenia (microbiology) A GENUS of tapeworms. and dyes. Also termed: tannin. A parasitic worm which is long and flat, like a piece of tape; it is divided into tantalum Ta (chemistry) Hard blue-grey segments. TAENIA saginata and TAENIA metallic ELEMENT in GROUP VA of the solium are those important in medicine, PERIODIC TABLE (a TRANSITION ELE- for man is the only natural HOST. MENT), used in electronic and chemical equipment, and for making surgical instruments. tail (statistics) The extreme part of a At. no. 73; r.a.m. 180.9479. distribution, which when represented graphically looks like a tail. tapeworm (parasitology) See TAENIA.

talc (chemistry) 3MgO.4SiO2.H2O Finely target dose (biochemistry) The amount powdered HYDROUS MAGNESIUM or CONCENTRATION of a chemical that SILICATE. Soft white or grey-green mineral. gets to the site of ACTION, causing a Its purified form is a white powder, used measurable effect.

374 TARONE TEST TAXON tarone test (statistics) A statistical test reactivity to TARTRAZINE, and other used in carcinogenicity studies to evaluate benzoates, and individuals sensitive to the significance of the time of observation TARTRAZINE are frequently sensitive to of TUMOUR rather than death as an ASPIRIN. Allergic reactions include asthma, endpoint. This test is only appropriate rhinitis, URTICARIA and angioedema, and under certain defined conditions such these may be life-threatening. Pharmaceu- as when the number of animals dying ticals containing this COLOUR (USA: color) early with a lethal TUMOUR (USA: tumor) are therefore labelled. is large and control survival has been large. taste bud (physiology) Small SENSE ORGAN containing chemoreceptors for the sense tarsal (anatomy) BONE that occurs in of TASTE, located in the mouth (particu- the feet of tetrapods. Human beings have larly on the upper surface of the TONGUE). seven tarsals in each foot, one of them modified to form the heel BONE (calca- taste (physiology) Sense that enables neum). animals to detect flavours, which in mammals involves TASTE BUDS. tartar emetic (chemistry) POTASSIUM antimonyl TARTRATE, K.SbO.C4H 4O 6.- TATA box (genetics) A sequence found

1/2H2O, a poisonous COMPOUND used in EUKARYOTE genes. Part of the as an INSECTICIDE and as mordant PROMOTER region, it occurs about 35 in dyeing. BASE-pairs UPSTREAM from the point at which RNA TRANSCRIPTION is to start. tartaric acid (chemistry) HOOC.CH(OH)- PROKARYOTES have a ‘Pribnow box’. CH(OH).COOH A white CRYSTALLINE hydroxycarboxylic acid that occurs in tautomerism (chemistry) EQUILIBRIUM grapes and other fruits. It is used in between two organic isomers. It usually dyeing and printing. Its salts, the tartrates, involves a shift in the point of attachment are used as buffers and in medicine. of a mobile HYDROGEN ATOM and a Also termed: 2,3-dihydroxybutanedioic shift in the position of a DOUBLE BOND acid; DIHYDROXYSUCCINIC ACID. in a MOLECULE. Also termed: DYNAMIC ISOMERISM. tartrate (chemistry) ESTER or SALT of TARTARIC ACID. taxis (biology) Orientation of an organism, involving movement, with tartrazine (toxicology) A food colour (USA: respect to a STIMULUS from a specific food color) that is often used in dairy direction. products, juices, jams and marmalades, ketchup (USA: catsup), pickles, etc.; as See also CHEMOTAXIS. well as in pharmaceuticals. The major METABOLITE is sultannilic acid, with lesser taxon (genetics) Any GROUP of living amounts of p-acetoamidobenzenesulphonic things, from the viewpoint of CLASS- acid (USA: p-acetoamidobenzenesulfonic IFICATION. The key TAXON is the acid). A small, but significant number SPECIES; the higher taxa are for animals: (about 1 to 5 per cent) of individuals GENUS, FAMILY, ORDER, CLASS, with ASPIRIN sensitivity also have cross- PHYLUM, KINGDOM. (pl. taxa).

375 TAXONOMY TELOPHASE taxonomy (genetics) Study of the Te (chemistry) The CHEMICAL SYMBOL CLASSIFICATION of living organisms. for ELEMENT 52, TELLURIUM. The arrangement of taxa into a system of CLASSIFICATION. A MODEM technique TEA (biochemistry) An abbreviation of is numerical TAXONOMY, in which all ‘T’etra‘E’thyl‘A’mmonium. attributes of the PHENOTYPE metric, biochemical or whatever, are given equal tech. (general terminology) Technical. weighting, and groupings are worked out by COMPUTER. technetium Tc (chemistry) Artificial RADIOACTIVE metallic ELEMENT in TB (bacteriology) An abbreviation of GROUP VIIA of the PERIODIC TABLE ‘T’u‘B’erculosis. (a TRANSITION ELEMENT), which occurs among the FISSION products of URANIUM. Tb (chemistry) The CHEMICAL SYMBOL It has several isotopes, with half-lives for TERBIUM. of up to 2.12×105 years. At. no. 43; r.a.m. 99 (most STABLE ISOTOPE). TBG (physiology/biochemistry) An abbreviation of ‘T’hyroxine-‘B’inding teeth (anatomy) See TOOTH. ‘G’lobulin. teflon (chemistry) Trade name for TBPA (physiology/biochemistry) An polytetrafluoroethene (PTFE). abbreviation of ‘T’hyroxine-‘B’inding ‘P’re‘A’lbumin. telangiectasis (histology) A red spot on the SKIN formed by dilated CAPILLARY TBW (physiology) An abbreviation of ‘T’otal or terminal arterial BLOOD VESSELS. ‘B’ody ‘W’ater. telluride (chemistry) BINARY COMPOUND Tc (chemistry) The CHEMICAL SYMBOL that contains TELLURIUM. for ELEMENT 43, TECHNETIUM. tellurium Te (chemistry) Silvery-white TCA (chemistry) An abbreviation of semi-metallic ELEMENT in GROUP VIB ‘T’ri‘C’hloroacetic ‘A’cid. of the PERIODIC TABLE, obtained as a BY-PRODUCT of the extraction of GOLD, T cell (immunology) An abbreviation of SILVER and COPPER. It is used as a ‘T’hymus-derived CELL. CATALYST and to add hardness to ALLOYS of LEAD or steel. At. no. 52; r.a.m. 127.60. T8 cells (immunology) A subset of T CELLS that may kill VIRUS infected CELLS telodendria (histology) The very fine and suppress immune FUNCTION when terminal branches of an AXON. the INFECTION is over. telophase (cytology) Final PHASE of CELL TCP (pharmacology) Trichloro-phenyliodo- DIVISION that occurs in MITOSIS and methyl-salicyl. MEIOSIS. During TELOPHASE chromatids, on reaching the poles of the CELL, become TDN (biochemistry) An abbreviation of densely packed and the CELL divides. ‘T’otal ‘D’igestible ‘N’utrients. In ANIMAL CELLS, the PLASMA

376 TEMP. TERM

MEMBRANE constricts. In plants, a wall tenesmus (medical) Straining painfully divides the CELL in two. but ineffectively to pass a motion or pass URINE. temp. (measurement) An abbreviation of ‘temp’erature. tenosynovitis (histology) INFLAMMATION of the sheath of a TENDON. temperature (measurement) The DEGREE of hotness or coldness, a tenoxicam (pharmacology) A non-steroidal measure of the AVERAGE KINETIC ANTI-INFLAMMATORY drug (NSAID) ENERGY of its atoms or molecules. which, administered orally or by injection, The AVERAGE body TEMPERATURE is used as a non-narcotic ANALGESIC in health is 37°C (98.6°F). It is a little and ANTIRHEUMATIC to treat pain and lower in the morning and higher in inflammation in rheumatic disease and the evening. other musculoskeletal conditions. temperature coefficient (physics) Change teratogen (toxicology) Any substance, in a physical quantity with change in natural or artificial, that causes TEMPERATURE, usually given as per ABNORMAL development of an EMBRYO. DEGREE rise of TEMPERATURE. teratology (medical) Study of birth defects. See also TEMPERATURE SCALE. The study of ABNORMAL development between conception and birth. temperature gradient (physics) DEGREE or measured rate of the TEMPERATURE teratoma (histology) A TUMOUR (USA: change between two points of reference tumor) composed of embryonic tissues in a substance or in an AREA. including all three layers of developing CELLS, endoderm, MESODERM and temperature scale (physics) Method ECTODERM. A SOLID TERATOMA may of expressing TEMPERATURE. There contain pieces of BONE, NERVE or are various scales, based on different INTESTINE, and is usually MALIGNANT; FIXED POINTS. The Fahrenheit scale it may develop in the TESTIS, or in has largely been replaced by the CELSIUS other places, and must be removed. SCALE (formerly centigrade), all of which Cystic teratomas may contain various express temperatures in degrees (°F rudimentary tissues such as SKIN, HAIR and °C). In science, temperatures are and TEETH, and are not MALIGNANT; frequently expressed in KELVIN (K), the they may contain ECTODERM to the thermodynamic UNIT of TEMPERATURE exclusion of other tissues, and are then in SI UNITS. called dermoid cysts. tendon (histology) Strong CONNECTIVE terbium Tb (chemistry) Silvery-grey metallic TISSUE that attaches muscles to bones. ELEMENT in GROUP IIIA of the PERIODIC It consists of COLLAGEN fibres (USA: TABLE (one of the LANTHANIDES), used collagen fibers). in making semiconductors and phosphors. At. no. 65; r.a.m. 158.9254. See also LIGAMENT. term (medical) A definite PERIOD of time, in medicine usually applied to the

377 TERMINAL DECIMAL TETANY duration of a PREGNANCY; full term is HAIR and strong muscles. It also raises 282 days from the first day of the last the sexual drive in males, and increases menstrual PERIOD. aggression in some SPECIES, probably including man. terminal decimal (mathematics) Decimal quantity that has a finite number of digits tetanic (medical) Pertaining to the after the decimal point. frequently repeated stimulation of a neuron or GROUP of neurons. See also RECURRING DECIMAL. tetanospasmin (toxicology/bacteriology) terminal fronsferase (genetics) An See TETANUS TOXIN. ENZYME that synthesises a ‘tail’ on to a DNA MOLECULE. It is used in GENETIC tetanus (lockjaw) (medical/bacteriology) ENGINEERING to add a poly-A tail (one A disease caused by the MICRO-ORGANISM that consists only of repeated As) to Clostridium tetani. The spores of this the end of one DNA MOLECULE and a organism are found in the bowels of many poly-T tail (one that consists only of animals, including man, and are very repeated Ts) to the end of another so common in the soil. The bacilli are Gram- that they join up. POSITIVE and ANAEROBIC, that is, they will only grow in the absence of OXYGEN. terminal (computing) An INPUT DEVICE INFECTION occurs through a WOUND or OUTPUT DEVICE that can handle DATA. or ABRASION in the SKIN; it need only be a very minor WOUND, and in some termination (medical) Commonly used cases no entry WOUND can be found. to MEAN TERMINATION of PREGNANCY, The organism produces a TOXIN called or ABORTION. tetanospasmin, which spreads to the SPINAL tesla (measurement) SI UNIT of MAGNETIC CORD and the BRAIN, both through the FLUX DENSITY, named after the Croatian- BLOOD and along the NERVES. born American physicist Nikola Tesla tetanus toxin (toxicology/bacteriology) A (1857–1943). 150,000 dalton neurotoxic PROTEIN testes (anatomy) Plural OF TESTIS. composed of one heavy and one LIGHT PEPTIDE chain linked by a disulphide (USA: testis (anatomy) The male GONAD whose disulfide) BOND. It is HEAT-LABILE and primary structures are the seminiferous easily oxidized. Also termed: tetanospasmin. tubules in which SPERMATOGENESIS occurs and the INTERSTITIAL CELLS tetany (medical) Not to be confused with (Leydig CELLS) which secrete ANDROGENS. TETANUS, TETANY is a condition in which there is ABNORMAL excitability of the testosterone (biochemistry) SEX NERVES and muscles. The condition is HORMONE. The most active ANDROGEN caused by lack of CALCIUM ions in the HORMONE. It is produced by the TESTES BLOOD, and may be due to deficiency in the male, in small quantities by the of the PARATHYROID GLANDS, lack of ovaries in the female, and by the VITAMIN D or deficient ABSORPTION of ADRENAL CORTEX in both sexes. It CALCIUM; it may also be due to ALKALOSIS stimulates the development of the male of the BLOOD from taking excess of ALKALIS reproductive organs and of male (USA: alkalies), as may happen in the secondary sex characteristics like body over-enthusiastic TREATMENT of a PEPTIC

378 TETRABENAZINE THALASSAEMIA

ULCER or a bout of hysterical over- tetrahydrate (chemistry) A chemical BREATHING. See CALCIUM. containing four molecules of WATER OF CRYSTALLIZATION. tetrabenazine (pharmacology) A drug that administered orally reduces the amount tetraploid (genetics) Describing an organism of DOPAMINE in the nerves in the BRAIN. that has four sets of HO MOLOGOUS It is used to lessen the extent of involuntary CHROMOSOMES. movements in cases of HUNTINGDON’S CHOREA and related disorders. See also DIPLOID; HAPLOID.

tetrachloroethene (chemistry) CCI2=CCI2 tetravalent (chemistry) Having a VALENCE LIQUID HALOGENOALKENE, used as a of four. Also termed: QUADRIVALENT. SOLVENT (especially as a de-greasing agent). Also termed: ETHYLENE TETRACHLORIDE; tetrodotoxin (TTX) (toxicology) A TOXIN TETRACHLOROETHYLENE. contained in the OVARY and LIVER of puffer fish, in the eggs of the California tetrachloroethylene (chemistry) An newt and in some other animals. It is alternative term for TETRACHLOROETHENE. used as a chemical tool for the study of ION channels. The LD50 in mice is 10 tetrachloromethane (chemistry) CCI4 mg/kg. It is a TOXICANT of NERVE and Colourless (USA: colorless) LIQUID MUSCLE by blocking SODIUM channels, HALOGENOALKANE, used as a SOLVENT, this ACTION causing NERVE and MUSCLE cleaning agent and in fire extinguishers. paralysis. Symptoms include weakening Also termed: CARBON TETRACHLORIDE. of VOLUNTARY MUSCLES, respiratory failure from paralysis of the DIAPHRAGM tetracycline (pharmacology) Member of and HYPOTENSION. There is no ANTIDOTE. a CLASS of antibiotics which act by inhibiting THERAPY involves artificial RESPIRATION. PROTEIN SYNTHESIS in BACTERIA. They have a broad SPECTRUM of activity, TF/P (physiology/biochemistry) An but many organisms have developed abbreviation of concentration of a substance resistance to them and they are not as in renal ‘T’ubular ‘F’luid divided by its widely used as they once were. concentration in ‘P’lasma. tetrad (1, 2 genetics) 1 Four CELLS formed TGFA (physiology) An abbreviation of after the second DIVISION in MEIOSIS ‘T’ransforming ‘G’rowth ‘F’actor ‘A’lpha. is complete. 2 Four spores formed by MEIOSIS in a SPORE mother CELL, often Th (chemistry) The CHEMICAL SYMBOL seen in FUNGI. See TETRAD ANALYSIS. for THORIUM. tetrahedral compound (chemistry) A thalamus (anatomy) Part of the FOREBRAIN COMPOUND that has a central ATOM of vertebrates that is concerned with joined to other atoms or groups at the the routing of nervous impulses to and four corners of a tetrahedron. It is the from the SPINAL CORD. CONFIGURATION of CARBON in many SATURATED COMPOUNDS. thalassaemia (haematology) An inherited DEFECT in the formation of HAEMOGLOBIN (USA: hemaglobin) common in Mediterranean

379 THALIDOMIDE THERMOBAROGRAPH countries and Africa; there are a number therap. (general terminology) An abbre- of types, of which the most important is viation of ‘therap’eutic. beta-THALASSAEMIA (USA: beta- thalassemia). This produces profound therapeutic index (T1) (pharmacology) ANAEMIA (USA: anemia) in children, which A numerical estimate of the relationship if not treated by transfusions is often between the toxic dose of a drug and fatal. (USA: thalassemia). its therapeutic dose. thalidomide (toxicology/pharmacology) therapeutic window (pharmacology) Formerly used therapeutically as a The range of PLASMA levels of a drug SEDATIVE hypnotic; currently used to within which optimal therapeutic effects treat LEPROSY. THALIDOMIDE is a are obtained; below the range the drug TERATOGEN; major morphological has too little beneficial effect, while abnormalities result from exposure during too high concentrations may either the first trimester of PREGNANCY. Its produce serious side effects or reduce mode of action involves the formation the therapeutic effect. of a toxic arene OXIDE METABOLITE. therapeutics (pharmacology) The study thallium TI (chemistry) A silver-grey of the science of treating disease. metallic ELEMENT in GROUP IIIB of the PERIODIC TABLE, used in electronic therapy (pharmacology) The TREATMENT equipment and to make pesticides. At. of disease. no. 81; r.a.m. 204.39. thermal conduction (physics) Transmis- THC (toxicology) An abbreviation of sion of HEAT by materials. ‘T’etra‘H’ydro‘C’annabinol. thermal conductivity (physics) Thermal T helper cells (immunology) A subset conducting POWER of a material. of T CELLS that carry the T4 marker and are essential for turning on ANTIBODY thermal diffusion (physics) Process of production, activating CYTOTOXIC T forming a concentration gradient in a CELLS and initiating many other IMMUNE fluid mixture by the application of a RESPONSES. temperature gradient. Also termed: Soret effect. theophylline (pharmacology) A xanthine that is used as a bronchodilator drug. thermistor (physics) TEMPERATURE- Administered orally or by injection it sensitive semiconductor device whose is mainly used as an ANTI-ASTHMATIC resistance decreases with an increase and for the treatment of bronchitis. in TEMPERATURE, used in electronic thermometers and switches. theorem (philosophy) General conclusion in science or mathematics which makes thermobarograph (physics) Instrument certain assumptions in ORDER to explain for measuring and recording the observations. TEMPERATURE and PRESSURE of the ATMOSPHERE. It consists of a thermograph See also HYPOTHESIS; LAW. and a BAROGRAPH.

380 THERMOCHEMISTRY THIAZIDE AND THIAZIDE-LIKE DIURETICS thermochemistry (chemistry) Branch may help in the diagnosis of diseases of chemistry that deals with the study such as CANCER of the breast. of HEAT changes in relation to CHEMICAL REACTIONS. The measurement of heats thermolabile (biology) Adversely affected of REACTION, specific HEAT capacities by HEAT (as opposed to thermostable, and BOND energies falls within its not affected by HEAT). scope. thermometer (measurement) An instrument thermocouple (physics) A device for for measuring TEMPERATURE. The measuring TEMPERATURE which relies common LIQUID in-GLASS THER- on the Seebeck effect: a heated junction MOMETER relies on the expansion of between two dissimilar metals produces the LIQUID (e.g. MERCURY or dyed a measurable ELECTROMOTIVE FORCE ALCOHOL) in a calibrated sealed GLASS (e.m.f.) which depends on the TEM- CAPILLARY tube. PERATURE of the junction. thermopile (physics) A TEMPERATURE- thermodynamic temperature (physics) measuring device consisting of several An alternative term for ABSOLUTE thermocouples connected in SERIES, TEMPERATURE. with one SET of junctions blackened so as to absorb thermal RADIATION. thermodynamics (physics) Branch of physics concerned with the study of the thermoreceptors (measurement) Sensory effects of ENERGY changes in physical receptors sensitive to TEMPERATURE. systems and the relationship between various forms of ENERGY, principally thermoregulation (physiology) The control HEAT and mechanical ENERGY. of the body’s TEMPERATURE: the main regulating centre (USA: center) is in the thermoelectricity (physics) ELECTRICITY HYPOTHALAMUS, which contains produced from HEAT ENERGY, as in a THERMO-RECEPTORS and can control THERMOCOUPLE. VASODILATION, sweating, etc. thermograph (physics) THERMOMETER THI (physics) An abbreviation of that records variations in TEMPERATURE ‘T’emperature ‘H’umidity ‘I’ndex. over a PERIOD in time on a GRAPH; a self-registering THERMOMETER. thiamine (chemistry) White WATER- SOLUBLE CRYSTALLINE B VITAMIN, thermography (physics) Variations of found in cereals and YEAST. Deficiency TEMPERATURE over the surface of a of THIAMINE causes the disorder beri- body can be recorded by using photographic beri in human beings. Also termed: thiamin;

FILM sensitive to INFRA-RED RADIATION. ANEURIN; VITAMIN B1. The technique is called thermography, and the RECORD a thermogram. Because thiazide and thiazide-like diuretics the surface TEMPERATURE of the body (pharmacology) Commonly used DIURETICS is determined by the state of the local such as chlorothiazide which act by inhibiting circulation, and variations in the BLOOD SODIUM reabsorption at the distal tubule supply to a part can be produced by of the KIDNEY. Their action may cause underlying disease processes, thermography POTASSIUM loss from the blood. They

381 THIAZINE THRESHOLD are used in the TREATMENT of HIGH thoracoscopy (medical) The inspection BLOOD PRESSURE and HEART failure. of the interior of the thoracic cavity through an ENDOSCOPE. thiazine (chemistry) Member of a GROUP of HETEROCYCLIC compounds that contain thoracotomy (medical) The operation SULPHUR (USA: sulfur) and NITROGEN of opening the wall of the chest. (in addition to CARBON) in the ring. thorax (anatomy) Region of the body thin-layer chromatography (TLC) (bio- that contains the HEART and lungs; the chemistry) A chromatographic separation chest. It is separated from the ABDOMEN technique using a LIQUID mobile PHASE by the DIAPHRAGM. that moves by CAPILLARY ACTION through a thin layer of sorbent coated on an thoria (chemistry) An alternative term INERT, ridgid backing material or plate. for THORIUM DIOXIDE. Once separated, they can be identified.

thorium dioxide (chemistry) ThO2 White thio- (chemistry) Prefix denoting the INSOLUBLE powder, used as a refractory presence of SULPHUR (USA: sulfur) in and in non-silica OPTICAL GLASS. Also a COMPOUND. termed: THORIA. thiocarbamide (chemistry) An alternative thorium Th (chemistry) Silvery-white term for THIOUREA. RADIOACTIVE ELEMENT in GROUP IIIA of the PERIODIC TABLE (one of the thioether (chemistry) Member of a class ACTINIDES). It has several isotopes, of organic compounds, ANALOGOUS to with half lives of up to 1.39×1010 years. ethers, in which SULPHUR (USA: sulfur) THORIUM-232 captures slow, or thermal, takes the place of OXYGEN. Also termed: neutrons and is used to ‘breed’ the fissile alkyl or aryl SULPHIDE (USA: aryl sulfide). URANIUM-233. Its refractory OXIDE

(THORIA, ThO2) is used in GAS mantles. thiopentone sodium (pharmacology) A At.no. 90; r.a.m. 232.0381. barbiturate drug which, administered by injection, is used as a general anaesthetic Thr (biochemistry) An abbreviation of for induction and maintenance of anaesthesia ‘Thr’eonine. during operations of short duration. threadworm (parasitology) PARASITES thiourea (chemistry) NH2CSNH2 Colourless called Oxyuris vermicularis. Also termed: (USA: colorless) CRYSTALLINE ORGANIC pinworm. See WORMS. COMPOUND, the SULPHUR (USA: sulfur) analogue of UREA. Its conversion to its threonine (biochemistry) AMINO ACID that ISOMER ammonium thiocyanate on heating is essential in the diet of animals. Also was the first demonstration of an ORGANIC termed: 2-amino-3-hydroxybutanoic ACID. COMPOUND being changed directly into an inorganic one. It is used in medicine threshold (physics) The value of a physical and as a photographic sensitizer. Also STIMULUS at which it becomes detectable, termed: THIOCARBAMIDE. ‘absolute threshold’, or the minimum difference in the values of two stimuli lying on the same DIMENSION at which

382 THROAT THYMINE they can be discriminated, ‘difference autoimmune REACTION following the threshold’. Within limits the value assigned COMBINATION of such agents as ASPIRIN, to a THRESHOLD is arbitrary: it is usually digoxin, antihistamines or sulphonamides taken to be that at which the STIMULUS (USA: sulfonamides) with PLATELET proteins (or the difference between two stimuli) to form antigens. is detected on 50 per cent of presentations. thrombophlebitis (haematology) INFLAM- throat (medical) A common site of MATION of a VEIN with consequent INFECTION involving the tonsils alone THROMBOSIS, the formation of a clot. or more usually the whole of the THROAT, It is quite common in varicose veins, when it is called pharyngitis. The which become red and tender and sometimes INFECTION is most often due to a VIRUS; painful enough to make walking difficult. this may be complicated by secondary INFECTION with haemolytic streptococci, thrombosis (haematology) The formation Haemophilus influenzae or STREP- of a clot or THROMBUS in a BLOOD TOCOCCUS pneumoniae. VESSEL. It may occur in arteries, particularly when the wall has been roughened by thrombin (biochemistry) An ENZYME atheroscierosis, or in the veins, especially concerned with the conversion of when the BLOOD flow is stagnant or FIBRINOGEN into FIBRIN in the clotting sluggish. of BLOOD following injury. See COAGULATION of the BLOOD. thrombus (medical) A SOLID MASS formed from the constituents of BLOOD within thrombocytes (platelets) (haematology) the BLOOD VESSELS or the HEART. The smallest of the formed elements in Thrombi that form within the rapidly moving the BLOOD. They are fragments of arterial circulation are composed largely megakaryocytes, giant PRECURSOR of FIBRIN and platelets with only a few CELLS. Platelets adhere to COLLAGEN trapped red and white CELLS, (pl. thrombi). fibres (USA: collagen fibers) exposed at points of BLOOD VESSEL injury. thrush (mycology) A disease character- Additional platelets aggregate at this ised by the formation of whitish spots in point to form a PLATELET plug, which the mouth. It is caused by the FUNGUS is the first step in HAEMOSTASIS (USA: Candida albicans. hemostasis). They release factors to promote COAGULATION. A typical thulium Tm (chemistry) Silvery-white metallic PLATELET count is 250,000 per CUBIC ELEMENT in GROUP IIA of the PERIODIC millimetre (USA: CUBIC millimeter). TABLE (one of the LANTHANIDES). Its ASPIRIN interferes with PLATELET RADIOACTIVE ISOTOPES emit GAMMA aggregation and may be useful in preventing RAYS and X-RAYS and are used in portable clot formation. RADIOGRAPHY equipment. At. no. 69; r.a.m. 168.9342. See also THROMBOCYTOPENIA.

thymine (chemistry) C5H6N2O2 Colourless thrombocytopenia (haematology) A (USA: colorless) CRYSTALLINE HETE- condition of low PLATELET concentrations, ROCYCLIC COMPOUND, one of the resulting in excessive bruising and bleeding pyrimidines. It is found in the nucleotides from WOUNDS. This can result from an of DNA (along with CYTOSINE, ADENINE

383 THYMOL THYROTROPHIN and GUANINE). In RNA the corresponding THYROID HORMONE SYNTHESIS and BASE is URACIL. Also termed: 5-methyluracil; SECRETION are under the control of 5-methyl-2,4-dioxopyrimidine. THYROID-STIMULATING HORMONE from the ADENOHYPOPHYSIS. HYPOTHY- thymol (chemistry) C10H14O Colourless ROIDISM in the infant causes cretinism and (USA: colorless) CRYSTALLINE ORGANIC in the adult myxedema. HYPERTHY- COMPOUND found in the oils of thyme ROIDISM leads to Graves’ disease. The and mint. It is used in ANTISEPTIC mouth third HORMONE from the THYROID washes. Alternative names: 2-hydroxy- GLAND, CALCITONIN, decreases BLOOD p-cymene, 2-hydroxy-1-isopropyl-4-methyl- CALCIUM levels and acts antagonistically benzene. to PARATHYROID HORMONE in CALCIUM HOMEOSTASIS. CALCITONIN SECRE- thymus (anatomy) Twin-lobed ENDOCRINE TION is controlled by BLOOD CALCIUM GLAND, situated in the chest near the levels and not by THYROID-stimulating HEART, that plays an important role in HORMONE. In human beings, under- the IMMUNE RESPONSE. After birth it secretion (HYPOTHYROIDISM) causes produces many LYMPHOCYTES and cretinism in children and MYXOEDEMA in induces them to develop into ANTIBODY- adults; overproduction (HYPERTHY- producing CELLS. It declines after puberty ROIDISM) may cause THYROTOXICOSIS, and atrophies in older adults. resulting in goitre. IODINE is needed in the diet for efficient functioning of the THYROID; See also LYMPHATIC SYSTEM; T CELLS. deficiency of IODINE may cause the GLAND to swell and form a goitre. thymus-derived cell (T-CELL) (haematology) A LYMPH CELL of the body that thyroid-stimulating hormone (TSH) fights against INFECTION and foreign particles. (biochemistry) Alternative name for THYROTROPHIN. thyroid (biochemistry) An ENDOCRINE GLAND, located in the neck region, that thyrotoxicosis (medical) Graves’ disease produces three HORMONES: THYROXINE is the commonest cause of this overaction (tetraiodothyronine, T4); triiodothyronine of the THYROID GLAND. It is five times (T3); thyrocalcitonin (CALCITONIN). The more common in women than men, and former two are the classic ‘THYROID is thought to be an AUTO-IMMUNE DISEASE; HORMONES’. THYROXINE is the it runs in families. The THYROID GLAND CLEAVAGE PRODUCT of thyroglobulin is enlarged. Investigation shows high levels found in the THYROID GLAND COLLOID. in the BLOOD of the THYROID HORMONES THYROXINE represents the predominant T3 and T4 and a low value of the PITUITARY circulating form. The L-form is the THYROID HORMONE TSH. Named after the Dublin HORMONE, whereas the D-form has an physician, R. Graves (1796–1853). anticholesteremic ACTION. THYROXINE is metabolized within target CELLS to T3, thyrotrophin TSH (biochemistry) A tropic which is five times more active than T4. T3 HORMONE from the ADENOHYPOPHYSIS binds to nuclear receptors where it activates that causes the THYROID GLAND to genes. Its primary actions are to increase proliferate, absorb more IODINE and METABOLISM, to increase PROTEIN synthesise and secrete the THYROID SYNTHESIS, stimulate BASAL METABOLIC HORMONES THYROXINE and triiodothyro- RATE and increase HEAT production. nine, but not thyrocalcitonin. TSH

384 THYROXIN TIN(II) CHLORIDE

SECRETION is under the control of LYME DISEASE, TYPHUS, spotted lever, THYROTROPHIN-releasing FACTOR (TRF) Q FEVER, and babesiosis which is a (USA: thyrotropin-releasing factor) from the protozoan parasitic disease common in HYPOTHALAMUS. Thyrotrophin is a wild and domestic animals in tropical GLYCOPROTEIN, consisting of two large and subtropical countries, passed on PEPTIDE units (one of which is similar to to man by hard TICKS. LH and FSH). (USA: thyrotropin). Also termed: THYROID-STIMULATING HORMONE. tidal volume (physiology) The VOLUME of GAS inspired or expired during each thyroxin (biochemistry) White CRYSTALLINE respiratory CYCLE. It is an INDICATOR ORGANIC COMPOUND, an IODINE- of the depth of BREATHING. containing AMINO ACID derived from TYROSINE. It is a HORMONE secreted time series (statistics) DATA tabulated by the THYROID, which promotes GROWTH by the time which successive observations in immature organisms and increases are made. metabolic rate in PERIODS of increased activity. time-lapse photography (photography) Technique for producing a speeded-up thyroxine (T4) (biochemistry) See THYROID. FILM, achieved by introducing a delay between each frame exposed during Ti (chemistry) The CHEMICAL SYMBOL filming. It is used to FILM very slow- for TITANIUM. moving or slow-developing processes.

TI (pharmacology) An abbreviation of tin Sn (chemistry) Soft silvery-white ‘T’herapeutic ‘I’ndex. metallic ELEMENT in GROUP IVB of the PERIODIC TABLE, which forms three tiaprofenic (pharmacology) A non-steroidal ALLOTROPES. It occurs mainly as TIN(IV)

ANTI-INFLAMMATORY drug (NSAID) which, OXIDE, SnO2, in ores such as cassiterite administered orally, is used to treat pain (tinstone). It is used mainly as a protective and inflammation in rheumatic disease coating for steel (TIN plate) and in and other musculoskeletal conditions. making ALLOYS with LEAD (solder, type METAL, pewter). Its compounds are tibia (anatomy) One of the two bones used as catalysts, FUNGICIDES and below the knee in a tetrapod VERTEBRATE mordants. Metallic TIN and inorganic (the other is the FIBULA); the shinbone. TIN compounds are not toxic to humans. Some organo-TIN compounds are toxic. tibolone (pharmacology) A drug that, At. no. 50; r.a.m. 118.69. administered orally, has both OESTROGEN and PROGESTOGEN activity. It can be used tin(II) (chemistry) An alternative term to treat menopausal problems in HORMONE for stannous. REPLACEMENT THERAPY (HRT). tin(IV) (chemistry) An alternative term tick (parasitology) A BLOOD-sucking for stannic. insect. They may be separated into hard,

Ixodidae, and soft, Argasidae, TICKS. tin(II) chloride (chemistry) SnCI2 White TICKS carry several diseases, among SOLUBLE SOLID. A REDUCING AGENT, them encephalitis, relapsing FEVER, it is used as a CATALYST in organic reactions

385 TIN DIOXIDE TISSUE TYPING and as an anti-sludge agent for oils. Also discolored) patches, that results from termed: stannous chloride; tin salt. an INFECTION by a FUNGUS. tin dioxide (chemistry) An alternative tinnitis (medical) An abnormality of hearing term for TIN(IV) OXIDE. in which an apparent persistent ringing sound is heard when in fact no such tin disulphide (chemistry) An alternative sound is present. term for TIN(IV) SULPHIDE (USA: tin(IV) sulfide). (USA: tin disulfide). tis. (general terminology) An abbreviation of ‘tis’sue. tin(IV) hydride (chemistry) SnH4 Unstable GAS, used as a REDUCING AGENT in tissue (histology) The tissues are the ORGANIC CHEMISTRY. Also termed: substance of the body; particular tissues stannane. such as connective or fatty TISSUE are collections of CELLS of the same type tin(IV) oxide (chemistry) SnO2 White specialised in the same way to carry CRYSTALLINE SOLID, used as a PIGMENT out a particular FUNCTION. In higher and as a refractory material. Also termed: organisms tissues may combine to form TIN DIOXIDE. a highly specialized ORGAN.

tin(IV) sulphide (chemistry) SnS2 Yellow tissue culture (biology) Process by INSOLUBLE SOLID, used as a PIGMENT. which CELLS or tissues are maintained Also termed: TIN DISULPHIDE (USA: outside the body (in vitro) in a suitable tin disulfide). (USA: tin(IV) sulfide). medium. The material is kept at a suitable TEMPERATURE, PH and OSMOTIC tin salt (chemistry) An alternative term PRESSURE. The composition of the for TIN(II) CHLORIDE. medium depends on the type of TISSUE CULTUREd. Depending on the type of tincal (chemistry) Naturally occurring CELL, a culture may be able to go on crude BORAX. indefinitely, with CELLS dividing from time to time. CANCER CELLS (or NORMAL tinea (mycology) A superficial FUNGUS CELLS that have undergone TRANS- INFECTION of the SKIN. TINEA pedis FORMATION in culture) will go on dividing is athlete’s foot, caused by the organisms infinitely often, but most differentiated Trichophyton rub rum and T. interdigitale, CELLS seem to lose the ability to divide which produce moist itching lesions after 30–40 divisions; this is known as commonest between the toes, and the Hayflick phenomenon. sometimes blisters on the soles of the feet. T. rubrum may cause scaly patches tissue fluid (biology) An alternative term on the toes and feet, and attack the for LYMPH. nails. Infections of the groin are caused by T. rubrum or Epidermophyton floccosum, tissue typing (histology) The identifica- and are more common in males. tion of histocompatibility antigens in DONOR and RECIPIENT prior to transplant tinea (medical/mycology) RINGWORM, surgery. a SKIN disorder characterized by raised, roughly circular and discoloured (USA:

386 TITANIA TM titania (chemistry) An alternative term pyrimidines from the medium so that for TITANIUM(IV) OXIDE. these pyrimidines may be converted into NUCLEIC ACIDS. A MUTATION at this titanic chloride (chemistry) An alternative LOCUS prevents uptake of pyrimidines, term for TITANIUM(IV) CHLORIDE. both NORMAL and toxic, such as bromodeoxyuridine or trifluorothymidine; titanium Ti (chemistry) A silvery-white with toxic pyrimidines, such a MUTATION metallic ELEMENT in GROUP IVA of allows GROWTH of the cultured CELLS the PERIODIC TABLE (a TRANSITION since they can produce pyrimidines by ELEMENT). Its corrosion-resistant lightweight de novo SYNTHESIS. This concept is ALLOYS are employed in the aerospace utilised in some mutagenicity tests in industry. Naturally occurring CRYSTALLINE which cultured mammalian CELLS are forms of TITANIUM(IV) OXIDE (titania, exposed to toxic pyrimidines in addition

TiO2) are the semi-precious gemstone to possible mutagens; GROWTH of these rutile. The powdered OXIDE is used as CELLS indicates that a MUTATION in a white PIGMENT and a DIELECTRIC the TK LOCUS has occurred. in capacitors. At. no. 22; r.a.m. 47.90. TI (chemistry) The CHEMICAL SYMBOL titanium tetrachloride (chemistry) An for ELEMENT 81, THALLIUM. alternative term for TITANIUM(IV) CHLORIDE. TLC (biochemistry) An abbreviation of titrant (chemistry) Chemical SOLUTION ‘T’hin-‘L’ayer ‘C’hromatography. of known CONCENTRATION, i.e. a STANDARD SOLUTION, which is added TLV (toxicology) An abbreviation of during the course of a TITRATION. ‘T’hreshold ‘L’imit ‘V’alue. titration (chemistry) A technique in T lymphocytes (immunology) A GROUP VOLUMETRIC ANALYSIS in which one of WHITE BLOOD CELLS involved in chemical SOLUTION of known CONCE- the IMMUNE SYSTEM. They have on NTRATION is added (using a BURETTE) to their surfaces receptors that recognize a known VOLUME of another chemical histocompatibility antigens on the surfaces SOLUTION of unknown CONCENTRATION of CELLS, so that they bind on to these (measured by a PIPETTE), and the antigens on any foreign CELL that enters CHEMICAL REACTION followed by the body. They are therefore the main observing changes in COLOUR (USA: color), part of the body’s RESPONSE to transplants. PH, etc. An INDICATOR may be added to T LYMPHOCYTES (so called because indicate the end-point of the REACTION, they originate in the THYMUS) recognize which allows the unknown CONCEN- the antigens by sequence (unlike B TRATION to be determined. LYMPHOCYTES). T LYMPHOCYTES also release factors that induce proliferation titre (measurement) RECIPROCAL value of of T LYMPHOCYTES and B LYMPHOCYTES. the highest possible DILUTION that illicits a RESPONSE or REACTION. (USA: titer). Tm (1 chemistry; 2 physiology) 1 The CHEMICAL SYMBOL for ELEMENT 69, Tk locus (thymidine KINASE LOCUS) THULIUM. 2 An abbreviation of renal (biochemistry) The TK LOCUS allows ‘T’ubular ‘m’aximum. cultured mammalian CELLS to incorporate

387 TN TON

Tn (chemistry) The CHEMICAL SYMBOL Tollens’ reagent (chemistry) Ammoniacal for thoron. SOLUTION of SILVER OXIDE used as a test for ALDEHYDES, which reduce it TNF (histology/biochemistry) An abbreviation to deposit a mirror of SILVER. It was of ‘T’umour ‘N’ecrosis ‘F’actor (USA: tumor named after the German chemist Bernhard necrosis factor). Tollens (1841–1918).

tocopherol (biochemistry) A VITAMIN toluene (chemistry) C6H5CH3 Colourless isolated from plants that increases fertility (USA: colorless) aromatic organic LIQUID in rats. Deficiency of it causes wasting that occurs in coal-tar, used as an industrial of muscles in animals. It has been found SOLVENT and starting point for making to have ANTIOXIDANT activity, and it explosives. Also termed: METHYLBENZENE. is important in maintaining membranes.

Also termed: VITAMIN E, toluidine (chemistry) CH3C6H4NH2 One of three isomeric aromatic amines, used tolbutamide (pharmacology) A sulphonyl- in the manufacture of dyes and drugs. urea drug used as an orally administered The ortho- and meta- forms are colourless treatment in non-insulin-dependent (USA: colorless) liquids; the para- ISOMER DIABETES MELLITUS. is a colourless CRYSTALLINE SOLID. Also termed: AMINOTOLUENE; METHY- tolerance (1 pharmacology; 2 immunology) LANILINE. 1 An ADAPTATIONal state when, after repeated exposure, a given dose of toluidine blue in sorensons PH 6.8 an agent produces a decreased effect buffer (histology) A histological staining or, conversely, when increasingly larger technique that may be used to make doses are necessary to obtain the effects helicobacter pylori visible under the observed with the original dose. Two MICROSCOPE. mechanisms of acquired pharmacological TOLERANCE are generally recognized: toluidine blue stain (histology) A (a) dispositional; (b) pharmacodynamic. histological staining technique that may Dispositional TOLERANCE results from be used to make amyloid visible under alterations in the pharmacokinetic the MICROSCOPE. properties of the agent. Pharmacodynamic TOLERANCE results from adaptive tomogram (radiology) An X-RAY taken changes within affected systems, such to show structures lying in a selected that the RESPONSE is reduced in the plane in the body. presence of the same CONCENTRATION of the agent. TOLERANCE may not develop tomography (medical) Any non-invasive uniformly to all the actions of an agent. technique that yields information about The toxicological manifestation of the different spatial parts of the BRAIN, TOLERANCE development is typically particularly about successive slices expressed as a progressive increase through it. in the LD50 for a given agent, although it should be recognized that TOLERANCE ton (measurement) UNIT of MASS equal development is not absolute. 2 A state to 20 cwt or 2,240 Ib (an imperial, or of nonresponsiveness to a particular long, ton); a short ton equals 2,000 Ib. ANTIGEN or GROUP of antigens.

388 TONGUE TOXIN

See also TONNE. toxic shock syndrome (TSS) (medical/ bacteriology) A life-threatening but rare tongue (anatomy) Muscular ORGAN condition caused by the damaging effect located in the BUCCAL CAVITY (mouth) of toxins of STAPHYLOCOCCUS aureus of some animals, used for manipulating SPECIES on the lining of BLOOD food (and in human beings involved in VESSELS. The condition has been linked speech). to sanitary tampon use. tonne (measurement) UNIT of MASS toxicant (toxicology) Any chemical, of equal to 1,000 kilograms. 1 tonne= natural or SYNTHETIC ORIGIN, capable 23204.62 Ib, slightly less than the of causing a deleterious effect on a imperial ton (2,240 Ib). Also termed: living organism. The term TOXIN should metric ton. never be used as an alternative term for TOXICANT, being properly reserved tonsil (anatomy) One of a pair of LYMPHOID for only those toxicants synthesised TISSUE regions at the back of the mouth metabolically by a living organism. which help to prevent INFECTION by producing LYMPHOCYTES. toxicara (parasitology) An INFESTATION with TOXICARA canis, a worm that lives tooth (anatomy) A hard structure in the intestines of dogs and foxes. embedded in the JAW BONE and adapted The eggs are passed in the excreta, for cutting and grinding food. TEETH and if humans eat contaminated food are composed of a cavity containing the larvae travel through the lungs and capillaries and NERVE endings, a layer LIVER but normally do no harm and of DENTINE and a tough outer layer die in about a year. Occasionally however of ENAMEL. they reach the EYE, where they can SET up a granulomatous INFLAMMATION See also CANINE TOOTH; INCISOR; and affect the RETINA, causing a squint MOLAR TOOTH; PREMOLAR. and loss of vision. torasemide (pharmacology) A powerful toxicol. (toxicology) An abbreviation DIURETIC drug of the LOOP DIURETIC of ‘toxicol’ogical; ‘toxicol’ogist; ‘toxi- type which can be administered orally, col’ogy. by injection or infusion. It is used to treat OEDEMA (USA: edema), oliguria, toxicology (toxicology) The science and as a ANTIHYPERTENSIVE. that deals with poisons (toxicants) and their effects. A POISON is defined as torr (measurement) UNIT of PRESSURE any substance that causes a harmful equivalent to that produced by a 1 mm effect, either by accident or design, column of MERCURY. It is equal to 133.3 when administered to a living organism. newtons m-2. toxicosis (toxicology) The state of having toxaemia (bacteriology) The presence of been poisoned. BACTERIAL toxins in the BLOOD. TOXAEMIA of PREGNANCY is a different condition, toxin (1, 2 toxicology) 1 A POISON; and is now called eclampsia. (USA: toxemia). usually applied to those produced by

389 TOXOID TRANS CONFIGURATION a living organism. 2 Any harmful TPNH (biochemistry) An abbreviation substance. of reduced ‘T’ri‘P’hosphopyridine ‘N’ucleotide. toxoid (toxicology) A BACTERIAL TOXIN so modified that it has lost its poisonous Tr (chemistry) CHEMICAL SYMBOL for properties, but can still act as an ANTIGEN TERBIUM. to provoke the formation of antibodies; TETANUS TOXOID is, for example, used trace element (biochemistry) ELEMENT by injection to induce IMMUNITY to essential to METABOLISM, but necessary TETANUS, but it does not produce only in very small quantities (e.g. COPPER symptoms of the disease. and COBALT in animals, molybdenum in ants). Such elements are usually toxoplasmosis (parasitology) INFECTION poisonous if large quantities are ingested. with the protozoan PARASITE Toxoplama gondii. Human beings may become infected trachea (anatomy) Tube through which from cats or by eating meat containing AIR is drawn into the lungs; windpipe. TISSUE cysts which has been badly cooked; the disease is common in sheep. tracheotomy (medical) The operation In the vast majority of cases the of cutting an opening into the TRACHEA. INFECTION does no harm and passes unrecognized, but in some there may trachoma (medical/microbiology) An be enlargement of the LYMPH NODES INFECTION of the EYE, caused by and rarely a rash, with general MALAISE the MICROORGANISM Chlamydia which may last weeks; the disease trachomatis. Commonest in tropical Africa resembles infectious mononucleosis. and India, it is worldwide the largest It usually resolves without trouble, but single cause of human sight loss. it may infect those suffering from IMMUNOSUPPRESSIVE disorders such tranexamic acid (pharmacology) An as AIDS or those who are taking antifibrinolytic drug which administered IMMUNOSUPPRESSIVE drugs, when orally or by injection, acts by inhibiting the disease may affect the BRAIN and plasminogen, which is one of the blood’s produce encephalitis. Most importantly, natural ANTICOAGULANT factors. It however, mothers who become infected is used to stem bleeding in circumstances during PREGNANCY may pass the such as excessive period bleeding INFECTION on to the child. This may (MENORRHAGIA). result in MISCARRIAGE, or the child may be born with abnormalities of the tranquillizer (pharmacology) Drug that CENTRAL NERVOUS SYSTEM which acts on the CENTRAL NERVOUS are apparent at birth or become apparent SYSTEM (CNS), used for calming people later, perhaps after several years. and animals without affecting consciousness. TPA (physiology/biochemistry) An abbreviation of ‘T’issue ‘P’lasminogen See also SEDATIVE. ‘A’ctivator. trans configuration (genetics) One of TPN (biochemistry) An abbreviation of the two possible arrangements for the ‘T’ri‘P’hosphopyridine ‘N’ucleotide. ALLELES in an individual that is

390 TRANSAMINATION TRANSITION ELEMENT

HETEROZYGOUS for MUTATIONS at two of specific amino acids in the SYNTHESIS linked loci. Trans (from the Latin meaning of proteins. AMINO ACIDS are placed ‘across’) means that one of the MUTANT in a specific ORDER by the transfer RNA ALLELES is on one CHROMOSOME and molecules according to instructions in the other is on the HOMOLOGOUS the MESSENGER RNA, to form a CHROMOSOME, i.e. the two chromosomes POLYPEPTIDE chain. are a+and +b. The opposite is cis. Also termed: repulsion. transferases (biochemistry) See ENZYMES. transamination (chemistry) Removal and transference number (physics) An transference of an AMINO GROUP from alternative term for TRANSPORT NUMBER. one COMPOUND (usually an AMINO ACID) to another. transformation (genetics) This has two meanings in genetics. (1) A permanent transcendental (1, 2 mathematics) 1 change in the genetic characteristics of IRRATIONAL NUMBER that is not the one BACTERIUM by exposure to DNA ROOT of a POLYNOMIAL equation. 2 of a different ORIGIN. It was the phenomenon FUNCTION that is not a finite POLYNOMIAL of TRANSFORMATION that led Avery to equation (e.g. logarithmic). the discovery that DNA was the MOLECULE responsible for carrying genetic information. transcription (molecular biology) The (2) A change in an ANIMAL CELL in process by which one strand of DNA is TISSUE CULTURE so that it grows and copied into a single strand of RNA; the divides in the same way as a CANCER first step in PROTEIN SYNTHESIS. The CELL, possibly due to activation of a RNA MOLECULE is synthesized by RNA viral GENE. The relationship of this polymerase, copying the DNA message phenomenon to CANCER is not understood. by following the base-pairing rules. The polymerase first recognizes the PROMOTER transformation constant (radiology) An region, and actual TRANSCRIPTION begins alternative term for DISINTEGRATION at the start codon a few bases further CONSTANT. downstream (going from the 5’ towards the 3’ end of the DNA strand). See transition (molecular biology) A MUTATION GENETIC CODE. in which a PURINE BASE (ADENINE, GUANINE) is replaced with another PURINE, transducer (physiology) A device that or a PYRIMIDINE (CYTOSINE, THYMINE) receives a signal in one physical form with another PYRIMIDINE. and outputs it in another; e.g. sensory receptors signal the STIMULUS received See also TRANSVERSION. by a change in their MEMBRANE POTENTIAL. transition element (chemistry) Member transduction (genetics) The transfer of of a large GROUP of elements that have genetic information from one BACTERIUM partly filled inner ELECTRON shells, which to another when it is carried by a gives them their distinctive physical and BACTERIOPHAGE. chemical properties (particularly VARIABLE VALENCY and the tendency to form coloured transfer RNA (molecular biology) Small [USA: colored] compounds). They occupy MOLECULE of RNA that acts as a CARRIER Groups IIIA, IVA, VA, VIA, VIIA, VIII, IB

391 TRANSITION POINT TRANYLCYPROMINE and IIB of the PERIODIC TABLE. Many See also TRANSLUCENT. of these elements and their compounds are used as catalysts. transport number (physics) In ELEC TROLYSIS, FRACTION of the total transition point (1, 2 chemistry) 1 CURRENT carried by a particular ION TEMPERATURE at which the TRANS- in the ELECTROLYTE. Also termed: FORMATION of one form of a substance TRANSFERENCE NUMBER. into another form can occur (usually one CRYSTALLINE modification into another). 2 transposition (genetics) The movement TEMPERATURE at which two SOLID phases of a transposer or other movable sequence exist at EQUILIBRIUM. 3 TEMPERATURE at of DNA from one place in the GENOME which a change to SUPERCONDUCTIVITY to another. happens in a substance. transposon (genetics) A moveable genetic transition temperature (chemistry) The ELEMENT similar to a JUMPING GENE. TEMPERATURE above and below which They are found in the GENOME of different ALLOTROPES are STABLE. BACTERIA, and are involved in the resistance to antibiotics. Unlike JUMPING GENES, translation (biochemistry) Process by which transposers leave a copy of themselves PROTEIN is synthesized in CELLS. It occurs in the original position when they move the ACTION of MESSENGER RNA, which to a new site. They make it possible for attaches to a RIBOSOME in the ANTIBIOTIC resistance to be spread very CYTOPLASM. TRANSFER RNA molecules rapidly, not only within a single strain of which are attached to a specific AMINOACID BACTERIA, but from one GENUS to another. then line up according to the sequence of See CONJUGATION. AMINO ACIDS encoded in the MESSENGER RNA to form a POLYPEPTIDE chain. Also transtracheal aspiration (medical) The termed: PROTEIN SYNTHESIS. passage of needle and plastic catheter through the TRACHEA for obtaining lower translocation (genetics) A MUTATION respiratory tract secretions. consisting of the transfer of part of a CHROMOSOME to another part of the transudate (cytology) Similar to exudate, same CHROMOSOME or of a different but with low PROTEIN content. CHROMOSOME. transversal (general terminology) Line translucent (chemistry) Describing a that intersects another SET of lines. substance that transmits and diffuses LIGHT, but which does not allow a well- transversion (molecular biology) A MUTA- defined IMAGE to be seen through it TION in which a PURINE BASE (ADENINE, with little or no diffusion. GUANINE) is substituted for a PYRIMIDINE one (eytosine, THYMINE), or vice versa. See also TRANSPARENT. See also TRANSITION. transparent (chemistry) Describing a substance that allows LIGHT (or other tranylcypromine (pharmacology) An ANTI- RADIATION) to pass through it with little DEPRESSANT drug of the monoamine- or no diffusion.

392 TRAP TRICHLOROMETHANE oxidase inhibitor (MAOI) class which is triatomic molecule (chemistry) MOLECULE administered orally. of an ELEMENT that consists of three

atoms, e.g. OZONE, O3. TRAP (physiology/biochemistry) An abbreviation of ‘T’hyroid ‘R’eceptor triazine (chemistry) C3H3N3 One of a GROUP ‘A’uxiliary ‘P’rotein. of isomeric HETEROCYCLIC ORGANIC COMPOUNDS with three NITROGEN atoms trauma (medical) An injury or WOUND. and three CARBON atoms in the ring. TRIAZINE derivatives are used as plastics, travellers diarrhoea (medical) A term dyes and herbicides. applied to the short attacks of DIARRHOEA which afflict many people when they tricarboxylic acid cycle (biochemistry) first arrive in a warm country. Most cases An alternative term for KREBS CYCLE. are due to a type of ESCHERICHIA COLI which produces a TOXIN which trichinosis (parasitology) An INFECTION affects the BOWEL. (USA: traveller’s with the worm Trichinella spiral is, which diarrhea). infects pigs and is acquired by eating undercooked pork. treatment (pharmacology) See THERAPY. trichloroacetic acid (TCA) (chemistry) trematodes (parasitology) FLUKES. A colourless (USA: colorless), HYGROSCOPIC SOLID, used as a herbicide (SODIUM treponema (bacteriology) A GENUS of trichloroacetate) and as an INTERMEDIATE spirochactes, MICRO-ORGANISMS formed in PESTICIDE manufacture. TCA is also like a very thin coiled thread that can used in in vitro LABORATORY studies to bend and spin on its long AXIS. stop ENZYME reactions by PRECIPITATION TREPONEMA pertenue causes YAWS, of proteins. It is corrosive to the SKIN TREPONEMA pallidum syphilis and and eyes, but is not otherwise hazardous. TREPONEMA carateum pinta. trichloroacetaldehyde (chemistry) An TRH (physiology/biochemistry) An alternative term for TRICHLOROETHANAL. abbreviation of ‘T’hyrotrophin-‘R’eleasing

‘H’ormone (USA: thyrotropin-releasing trichloroethanal (chemistry) CCI3CHO hormone). Pungent colourless (USA: colorless) oily LIQUID ALDEHYDE, which forms a SOLID HYDRATE triamcinolone acetonide (pharmacology) (TRICHLOROETHANEDIOL). Also termed: A synthetic corticosteroid with ANTI- CHLORAL; TRICHLOROACETALDEHYDE. INFLAMMATORY and anti-allergic properties.

trichloroethanediol (chemistry) CI3CCH- triamterene (pharmacology) A mild (OH)2 White CRYSTALLINE ORGANIC DIURETIC drug of the POTASSIUM-sparing COMPOUND, used as a SEDATIVE. Also type, which causes the retention of termed: CHLORAL HYDRATE. POTASSIUM. It is used as a DIURETIC, to treat OEDEMA (USA: edema), as an trichloromethane (chemistry) CHCI3 ANTIHYPERTENSIVE, and in congestive Colourless (USA: colorless) VOLATILE LIQUID HEART FAILURE treatment. HALOFORM, used as an ANAESTHETIC

393 TRICHOMONAS TRIPLOIDY

(USA: anesthetic) and as a SOLVENT. is limited, the amount of TRIGLYCERIDE Also termed: CHLOROFORM. stored appears to be essentially unlimited.

trichomonas (parasitology) TRICHOMONAS triiodomethane (chemistry) CHI3 Yellow vaginalis is a protozoan PARASITE which CRYSTALLINE SOLID HALOFORM, used causes INFLAMMATION of the VAGINA as an ANTISEPTIC. Also termed: in women and URETHRITIS in men. It is IODOFORM. commonly passed on in sexual intercourse. trimer (chemistry) Chemical formed by trichuris (parasitology) The WHIPWORM, the COMBINATION of three similar a small roundworm. (MONOMER) molecules. tricyclic antidepressants (pharmacology) trimetaphan camsylate (pharmacology) One of the three main classes of A ganglion blocker drug which is administered ANTIDEPRESSANT drugs that are used by injection or INTRAVENOUS infusion to relieve the symptoms of depressive and lowers BLOOD PRESSURE by reducing illness. Chemically they are mainly vascular tone normally induced by the dibenzazepine or dibenzcycloheptene SYMPATHETIC NERVOUS SYSTEM. It derivatives and examples include is short-acting and can be used as a amitriptyline hydrochloride and imipramine hypotensive for controlled BLOOD hydrochloride. PRESSURE during surgery. triglyceride (chemistry) ESTER of trinitrophenol (chemistry) An alternative GLYCEROL, in which all three HYDROXYL term for PICRIC ACID. GROUPS have been substituted by ESTER groupings from FATTY ACIDS. Many fats trinomial (chemistry) POLYNOMIAL with are TRIGLYCERIDES. only three terms. triglycerides (biochemistry) NEUTRAL triple bond (chemistry) COVALENT BOND fat comprises three FATTY ACIDS esterified formed by the sharing of three pairs of to GLYCEROL. The FATTY ACIDS may electrons between two atoms. be saturated or UNSATURATED, and the most common ones are stearic, oleic triploidy (genetics) The condition of having and PALMITIC ACIDS. This is the primary three copies of every CHROMOSOME, STORAGE form of LIPID as an ENERGY a form of POLYPLOIDY. TRIPLOIDY does reserve. TRIGLYCERIDES are synthesised not occur in nature as a permanent feature in ADIPOSE TISSUE from GLYCEROL of a SPECIES, as triploid organisms PHOSPHATE, derived from GLUCOSE, have very low fertility. This is because and from FATTY ACIDS, either derived at MEIOSIS there are three chromosomes from acetyl CoA formed from GLUCOSE trying to find partners for a process that or absorbed from the PLASMA after they only works with two, so the DIVISION are released from LIPOPROTEINS. is usually a failure. However, triploid TRIGLYCERIDE SYNTHESIS in adipose organisms are just as capable of NORMAL CELLS is dependent upon INSULIN- GROWTH as any others (MITOSIS is stimulated uptake of PLASMA GLUCOSE. not impeded at all, since the process Whereas the amount of GLYCOGEN that consists of each CHROMOSOME dividing can be stored as an ENERGY reserve itself in half, irrespective of any partner).

394 TRISACCHARIDE T/S RATIO

Artificially produced triploids can be Tryp. (biochemistry) An abbreviation of commercially useful. One example of ‘Tr y p ’tophan. this is the banana, the trees of which are bred as triploids from stocks of a trypan blue (biochemistry) A vital dye that TETRAPLOID and a DIPLOID strain. The is used to determine the viability of isolated triploid hybrids grow well, but their seeds CELLS. Living CELLS exclude the dye, never develop properly, so that the inside whereas nonviable CELLS do not. of the banana is not full of inedible seeds as it is in a NORMAL banana. trypanosomiasis (parasitology) INFES- TATION with Trypanosomes, small trisaccharide (chemistry) CARBOHYDRATE PARASITES spread by the TSETSE FLY. consisting of three joined monosaccha- Trypanosoma brucei gambiewe causes rides. sleeping sickness in West Africa, and Trypanosoma brucei rhoesiense causes trisomy (genetics) The state of having the disease in East Africa. three representatives of a given CHROMOSOME instead of the usual pair, See also CHAGAS DISEASE. as in TRISOMY 21 (DOWN’S SYNDROME). tryptophan (biochemistry) An ESSENTIAL tritium (chemistry) A RADIOACTIVE AMINO ACID ISOTOPE of HYDROGEN, with MASS NUMBER 3 and ATOMIC MASS 3.016. tryptophan (biochemistry) An ESSENTIAL Its HALF-LIFE is 12.5 years. TRITIUM AMINO ACID which is a PRECURSOR is used extensively as a radiolabel of SEROTONIN, that contains an aromatic tracer in toxicity studies. GROUP, needed in animals for proper GROWTH and development. triton (chemistry) Atomic NUCLEUS of TRITIUM, consisting of two neutrons and tsetse fly (parasitology) See TRY- one PROTON. PANOSOMIASIS. trivalent (chemistry) Having a VALENCE TSF (haematology) An abbreviation of three. Also termed: tervalent. of ‘T’hrombopoietic ‘S’timulating ‘F’actor, thrombopoietin. tRNA (molecular biology) An abbreviation of ‘t’ransfer (or soluble) ‘R’ibo‘N’ucleic TSH (physiology/biochemistry) An ‘A’cid. abbreviation of ‘T’hyroid-‘S’timulating ‘H’ormone. trop. med. (medical) An abbreviation of ‘trop’ical ‘med’icine. TSI (physiology/immunology) abbreviation of ‘T’hyroid-‘S’timulating ‘I’mmuno- trophozoite (microbiology) Feeding, MOTILE globulins. stage of PROTOZOA. T/S ratio (physiology/biochemistry) An tropical sore (medical) A slow-healing abbreviation of ‘T’hyroid/‘S’erum iodide ulcer in the SKIN caused by Leishmania ratio. major or Leishmania tropica. See LEISHMANIASIS.

395 TSS TURNBULL STAIN

TSS (microbiology) An abbreviation of destroys the tissues which it involves, ‘T’oxic ‘S’hock ‘S’yndrome. which are principally those of the LUNG. t-test (statistics) A parametric test for tubocurarine chloride (pharmacology) assessing hypotheses about population A non-depolarising skeletal muscle means. It is most commonly used when relaxant drug which is administered the null HYPOTHESIS is that two by injection to induce muscle paralysis populations have the same MEAN value during surgery. on some VARIABLE of interest. The form of the test used in this case depends tularaemia (medical/bacteriology) A rare on whether independent samples are disease in human beings caused by drawn from each population, or whether the BACTERIA Franciselia tularensis, samples are matched in some way (e.g. named after Tulare in California where thereby having the same subjects each the disease was first identified. It occurs perform under two conditions). Though principally in rodents but may affect the test is based on assumptions of other animals, and is spread to man normality and homogeneity of population by TICKS, flies and mosquitoes, or by variances, it is relatively robust against touching infected animals. departures from these assumptions. tumour (histology) An overt NEOPLASM, TTX (biochemistry) An abbreviation of either BENIGN (e.g. a POLYPUS) or ‘T’etrodo‘T’o‘X’in. MALIGNANT (i.e. cancerous). (USA: tumor).

Tu (chemistry) The CHEMICAL SYMBOL See also CARCINOGENESIS; NEOPLASM. for THULIUM. tumour suppressor genes (genetics) Tuberc. (medical) An abbreviation of The PROTEIN products of TUMOUR ‘Tuberc’ulosis. SUPPRESSOR GENES inhibit the PROGRESSION of CELLS in the DIVISION tuberculosis (medical) A disease caused CYCLE. MUTATIONS in TUMOUR by INFECTION with the MICRO-ORGANISMS SUPPRESSOR GENES may bring about Mycobacterium TUBERCULOSIS or the formation of proteins that cannot Mycobacterium bovis, of which the first suppress CELL DIVISION. Inactivating is responsible for most human infections. MUTATIONS in the GERM CELLS bring The MICROORGANISMS provoke the about a predisposition to certain form formation of tubercles, collections of of CANCER, e.g. familial retinoblastoma, MACROPHAGES, which are WHITE BLOOD familial polyposis, etc. SOMATIC CELLS and TISSUE CELLS able to engulf MUTATIONS in tumor suppressor genes BACTERIA and form epithelioid CELLS; may also play a role in TUMOUR PRO these may FUSE to form giant CELLS, GRESSION (USA: tumor progression). which are CHARACTERISTIC of the tubercle. (USA: tumor suppressor genes). The MACROPHAGES are activated by T LYMPHOCYTES, by the invading organisms Turnbull stain (histology) Histological and by the activity of other MACROPHAGES. staining technique which may be used When the tubercle has formed, the centre to make FERROUS IRON visible under (USA: center) breaks down, a process the microscope. called caseation. The disease process

396 TURNER’S SYNDROME TYROSINE

Turner’s syndrome (genetics) The Tyr (biochemistry) An abbreviation of condition in which a female has GENOTYPE ‘Tyr’osine. XO, i.e. only one SEX CHROMOSOME. A TURNER’S SYNDROME girl looks fairly tyrosine (chemistry) White CRYSTALLINE NORMAL, but with short stature and a ORGANIC COMPOUND, a naturally wide ‘webbed’ neck; the ovaries are occurring ESSENTIAL AMINO ACID present but undeveloped so she is not that is a PRECURSOR for ADRENERGIC fertile. transmitters, e.g. ADRENALINE (USA: epinephrine) and NORADRENALINE two-tailed test (statistics) A statistical (USA: norepinephrine). test of an HYPOTHESIS whose regions of rejection are placed at both ends (or tails) of the distribution of the test statistic, e.g. when the alternative to the null HYPOTHESIS is that the MEAN of one population differs from that of the other, regardless of whether it is higher or, lower. Contrast one-tailed test. type I error (statistics) Rejection of the null HYPOTHESIS when it is in fact true. type II error (statistics) Acceptance of the null HYPOTHESIS when it is in fact false. typhoid fever (medical/bacteriology) A serious disease caused by Salmonella typhi, found throughout the world but commonest where sanitation and WATER supplies are less than first CLASS. The INFECTION is spread by contamination of food or WATER by the excreta of patients suffering or recovering from the disease, or of those carrying the disease but apparently in health. It is confined to human beings. typhoid, paratyphoid A and paratyphoid B vaccine (TAB) (medical) A triple VACCINE to prevent these infections. typhus (Gail FEVER) (medical/microbiology) An INFECTION caused by Rickettsia prowazekii and spread by lice.

397 U

U (1 chemistry; 2 measurement) 1 The ultramicroscope (microscopy) Instrument CHEMICAL SYMBOL for URANIUM, for viewing sub-microscopic objects, e.g. ELEMENT 92. 2 An abbreviation of ‘U’nit(s). particles of smoke and fog.

UCHD (medical) An abbreviation of ‘U’sual ultrasonic (physics) Describing a band ‘C’hild‘H’ood ‘D’iseases. of sound frequencies of about 2×109 hertz, which are just above the upper UCL (physics) An abbreviation of ‘U’pper LIMIT of NORMAL human hearing. ‘C’ontrol ‘L’imit. ULTRASONIC ENERGY is used in sonar, for degreasing (in conjunction with a UDPG (biochemistry) An abbreviation suitable SOLVENT) and for scanning soft of ‘U’ridine ‘D’i‘P’hospho‘G’lucose. tissues in medical diagnosis. Also termed: supersonic. UDPGA (biochemistry) An abbreviation of ‘U’ridine ‘D’i‘P’hospho‘G’lucuronic ‘A’cid. ultraviolet radiation (UV) (physics) ELECTROMAGNETIC RADIATION with UFA (physiology/biochemistry) An wavelengths in the range 4×10-7 to 4× abbreviation of ‘U’nesterified free ‘F’atty 10-9m, the region between VISIBLE LIGHT ‘A’cid. and X-RAYS. Also termed: ultraviolet light.

UHF (physics) An abbreviation of ‘U’ltra‘H’igh ultronics (physics) Sound waves which ‘F’requency. are of a FREQUENCY above the range of audible sound, which lies between UL (histology) An abbreviation of 20 and 20,000 cycles per second. ‘U’nstirred ‘L’ayer. umbilical cord (anatomy) In EMBRYOLOGY, ulf (1, 2 physics) 1 An abbreviation of vascular structure that contains the umbilical ‘u’ltra ‘l’ow ‘f’requency. 2 An abbrevia- arteries and veins, connecting the FOETUS tion of ‘u’pper ‘l’imiting ‘f’requency. (USA: fetus) to the PLACENTA. ulna (anatomy) Rearmost (and usually umbilicus (anatomy) The navel. larger) of the two bones in the lower forelimb of a tetrapod VERTEBRATE (the uncertainty principle (physics) It is other BONE is the RADIUS). impossible to determine simultaneously with ACCURACY both the position and ultrahigh frequency (UHF) (physics) A the momentum of a moving PARTICLE. radio FREQUENCY between 300 and The LIMIT of ACCURACY may be given

3,000 megahertz. by the relation pxx > h/2p, where px is the uncertainty in the momentum, x the uncertainty in position and h is PLANCK’S

398 UNDULANT FEVER URAEMIA

CONSTANT. Also termed: Heisenberg during the MEIOTIC DIVISION. See UNCERTAINTY PRINCIPLE. MEIOSIS. 2 MONOVALENT. undulant fever (medical/bacteriology) univariate (statistics) Having only one See BRUCELLOSIS. VARIABLE. uniaxial crystal (crystallography) Doubly- universal indicator (chemistry) MIXTURE refracting crystal in which there is only of chemical indicators that give a definite one direction of single REFRACTION. for various values of PH. See DOUBLE REFRACTION. unkn (general terminology) An abbreviation unicellular (biology) Describing an organism of ‘unk’now‘n’. that consists of only one CELL (e.g. PROTOZOANS, BACTERIA). unpub (literary terminology) An abbreviation of ‘unpublished. uniform distribution (statistics) A FREQUENCY DISTRIBUTION in which unsaturated (1,2 chemistry) 1 Describing all classes or values have the same an ORGANIC COMPOUND with doubly FREQUENCY or probability. or triply bonded CARBON atoms. See also SATURATED COMPOUND. 2 Describing unilateral (medical) Pertaining to one a SOLUTION that can dissolve more side of the body or one hemisphere of SOLUTE before reaching SATURATION. the BRAIN. up. (general terminology) An abbreviation unimodal (statistics) of a distribution, of ‘up’per. having only one MODE, which, if the DATA are represented graphically, upstream (molecular biology) Further corresponds to there being only one peak. back on a DNA MOLECULE, in respect of the direction in which the sequence unimolecular reaction (chemistry) is being read. See REPLICATION. CHEMICAL REACTION that involves only one type of MOLECULE as the REACTANT. Ur (chemistry) An abbreviation of ‘Ur’anium. unit (1, 2 measurement) 1 A standard quantity in which something is measured, uracil (molecular biology) C4H4N 2O 2 e.g. decibel, or WAVELENGTH. 2 A single PYRIMIDINE BASE; one of the four UNIT. 3 An alternative term for KILOWATT- NUCLEOTIDE bases in RNA; in DNA HOUR, the UNIT that measures consump- the corresponding BASE is THYMINE. tion of ELECTRICITY. Also termed: 2,6-dioxypyrimidine. unit cell (crystallography) Smallest GROUP uraemia (biochemistry) Excess of UREA of atoms, ions or molecules whose three and other NITROGEN containing dimentional repetition at regular intervals compounds, principally CREATININE, in produces a CRYSTAL LATTICE. the BLOOD. The condition is the result of KIDNEY FAILURE, except in cases univalent (1 cytology; 2 chemistry) 1 where there is failure of the circulation Single CHROMOSOME that separates from any cause, when the state is described

399 URANIUM UROL.

as pre-renal URAEMIA; such cases may urethane (chemistry) CO(NH2)OC2H5 Highly recover when the circulatory collapse is toxic, inflammable organic used in veterinary remedied. Also termed ‘azotaemia’. medicine, biochemical research and as a chemical INTERMEDIATE. Also termed: uranium U (chemistry) RADIOACTIVE ETHYL CARBAMATE; ETHYL URETHANE. grey metallic ELEMENT in GROUP IIIA of the PERIODIC TABLE (one of the urethra (anatomy) Tube through which ACTINIDES), obtained mainly from its URINE is discharged to the exterior from ore uraninite (which contains URANIUM(IV) the urinary BLADDER of most mammals.

OXIDE, UO2). It has three natural and several artificial isotopes with half-lives urethritis (medical) INFLAMMATION of the of up to 4.5× 109 years. URANIUM-235 URETHRA, the canal through which URINE undergoes nuclear FISSION and is used is discharged e.g. gonococcal URETHRITIS. in nuclear weapons and reactors; URANIUM-238 can be converted into URF (physiology) An abbreviation of ‘U’terine- the fissile PLUTONIUM-239 in a breeder ‘R’elaxing ‘F’actor; relaxin. REACTOR. At. no. 92; r.a.m. 238.029. URI (medical) An abbreviation of ‘U’pper urates (biochemistry) Salts of URIC ‘R’espiratory ‘I’nfection. ACID, the result of the breakdown of purines, which are compounds which uric acid (biochemistry) C5H4N4O3 White have an important role in METABOLISM. CRYSTALLINE ORGANIC ACID of the URATES are normally present in the PURINE GROUP, the end-PRODUCT and BLOOD, but when the BLOOD LEVEL the principal excretory PRODUCT of PURINE is too high crystals may form; in the METABOLISM. Defects in URIC ACID joints they give rise to GOUT, and in metabolism and EXCRETION appear to the kidneys to stones. be associated with a number of disease states, and it frequently occurs as a urea (biochemistry) H2NCONH2 White COMPONENT of renal calculi. URIC ACID CRYSTALLINE ORGANIC COMPOUND, deposition in the joints is the principal found naturally in the URINE of mammals cause of GOUT. Also termed: 2,6,8- as the natural end-PRODUCT of the trihydroxypurine. METABOLISM of proteins. It is also manufactured commercially from CARBON urine (biochemistry) LIQUID, produced DIOXIDE and AMMONIA under high in the kidneys and stored in the urinary PRESSURE. It is used in plastics, adhesives, BLADDER, that contains UREA and other fertilizers and ANIMAL-feed additives. excretory products. It is discharged to Also termed: CARBAMIDE. the outside via the URETHRA. urease (chemistry) ENZYME that occurs urobilinogen (biochemistry) A DERIVATIVE in plants (e.g. soya beans) and acts as of BILIRUBIN formed by the GUT microflora; a CATALYST for the HYDROLYSIS of this COMPOUND is colourless (USA: UREA to AMMONIA and CARBON DIOXIDE. colorless). ureter (anatomy) One of a pair of ducts urol. (medical) An abbreviation of that carry URINE from the kidneys to ‘urol’ogy. the BLADDER.

400 UROLOGY UVL urology (medical) The branch of medicine that deals with diseases of the urinary tract in both sexes, and those of the genital organs in the male. urticaria (nettle-rash) (immunology) Swelling and redness of the SKIN, usually with itching, caused by an allergic REACTION which results in the liberation of HISTAMINE in the SKIN.

US (physiology) An abbreviation of ‘U’nconditioned ‘S’timulus. u-shaped curve (statistics) Any GRAPH of a distribution that is shaped like a U.

USPHS (governing body) An abbreviation of ‘U’nited ‘S’tates ‘P’ublic ‘H’ealth ‘S’ervice. usu. (general terminology) An abbreviation of ‘usu’ally. uterus (anatomy) Muscular ORGAN located in the lower ABDOMEN of female mammals, in which a fertilized OVUM develops into a FOETUS (USA: fetus) prior to birth. Also termed: womb.

UTP (biochemistry) An abbreviation of ‘U’ridine ‘T’ri‘P’hosphate.

UV (physics) An abbreviation of ‘U’ltra‘V’iolet.

UVL (physics) An abbreviation of ‘U’ltra‘V’iolet ‘L’ight.

401 V

V (1 chemistry; 2 biochemistry) 1 The CUBIC METRE; intergalactic space may have CHEMICAL SYMBOL for ELEMENT 23, an almost perfect VACUUM (although it does VANADIUM. 2 A symbol for valine. contain some SUBATOMIC PARTICLES). vaccination (immunology) The artificial vacuum pump (equipment) An alternative production of ACTIVE IMMUNITY by the term for DIFFUSION PUMP. injection of a VACCINE. The word ‘VACCINATION’ is derived from the Latin vagina (anatomy) The canal which leads for ‘cow’, and was coined by the British from the external female genitalia to physician Edward Jenner (1749–1823) the CERVIX. to describe his idea of injecting patients with cowpox VIRUS to protect them against vaginitis (medical) INFLAMMATION of smallpox (a very similar VIRUS). A VACCINE the VAGINA. The commonest causes are now means any SUSPENSION of dead INFECTION with TRICHOMONAS vagina/ or non-virulent VIRUSES or BACTERIA is or Candida albicans, or ATROPHY used in IMMUNISATION. that occurs with age as the result of lack of OESTROGEN (USA: estrogen). vaccine (immunology) A preparation of dead organisms, ATTENUATED live vagus nerve (anatomy) In vertebrates, organisms, live virulent organisms, or tenth CRANIAL NERVE, which forms the parts of MICRO-ORGANISMS which are major NERVE of the PARASYMPATHETIC either injected or ingested into the body, NERVOUS SYSTEM, supplying motor where they stimulate the production of NERVE FIBRES (USA: nerve fibers) to antibodies and so confer IMMUNITY against the STOMACH, kidneys, HEART, LIVER, INFECTION. Less commonly, vaccines lungs and other organs. are used in treating a disease. Val. (biochemistry) An abbreviation of vac. pmp (physics) An abbreviation of ‘Val’ine. ‘vac’uum ‘p’u‘mp’. valence band (1,2 chemistry) 1 Highest vacuity (anatomy) Any gap between the ENERGY LEVEL in an INSULATOR or bones of a SKULL. semiconductor that can be filled with electrons. 2 Region of electronic ENERGY vacuole (biology) An alternative term LEVEL that binds atoms of a crystal together. for a VESICLE. valence band (chemistry) CHEMICAL BOND See also CONTRACTILE VACUOLE. formed by the INTERACTION of VALENCE ELECTRONS between two or more atoms. vacuum (physics) Space containing no MATTER. A good LABORATORY VACUUM valence electron (chemistry) ELECTRON still contains about 1014 molecules of AIR per in an outer shell of an ATOM which

402 VALENCE VARIABILITY participates in bonding to other atoms to make CONNECTIVE TISSUE visible to form molecules. under the MICROSCOPE. valence (chemistry) POSITIVE number vanadium V (chemistry) Silvery-grey metallic that characterizes the combining POWER ELEMENT in GROUP VA of the PERIODIC of an ATOM of a given ELEMENT to TABLE (a TRANSITION ELEMENT), used the number of HYDROGEN atoms or to make special steels. VANADIUM(V) their equivalent (in a CHEMICAL OXIDE, V2O5, is used as an industrial REACTION). For an ION, the VALENCE CATALYST and in ceramics. At. no. 23; equals the CHARGE on the ION. Also r.a.m. 50.9414. termed: VALENCY. van’t Hoff’s law (physics) OSMOTIC valency (chemistry) See VALENCE. PRESSURE of a SOLUTION is equal to the PRESSURE that would be exerted validation (biology) The process of by the SOLUTE if it were in the gaseous establishing that a theory or test is valid. PHASE and occupying the same VOLUME as the SOLUTION at the same validity (biology) The extent which a TEMPERATURE. It was named after test or experiment genuinely measures the Dutch chemist Jacobus van’t Hoff what it purports to measure. (1852–1911). valine (biochemistry) C5H11NO2 One vapour (chemistry) A GAS when its of the ESSENTIAL AMINO ACIDS required TEMPERATURE is below the CRITICAL for NORMAL GROWTH in animals. Also TEMPERATURE; a VAPOUR can thus be termed: 2-AMINOISOVALERIC ACID; 2- condensed to a LIQUID by PRESSURE alone. amino-3-methylbutyric ACID. vapour density (physics) DENSITY of valve (anatomy) Flap of TISSUE that a GAS relative to a reference GAS, controls movement of FLUID through a such as HYDROGEN, equal to the MASS tube, duct or APERTURE in one direction, of a VOLUME of GAS divided by the e.g. as between the chambers of the MASS of an equal VOLUME of HYDROGEN HEART or in the veins. at the same TEMPERATURE and PRESSURE. It is also equal to half the van der Waals forces (physics) Very RELATIVE MOLECULAR MASS. weak forces acting between the NUCLEUS of one ATOM and the electrons of another vapour pressure (physics) PRESSURE ATOM (i.e. between dipoles and induced under which a LIQUID and its VAPOUR dipoles). The attractive forces arise coexist at EQUILIBRIUM. Also termed: from slight distortions induced in the SATURATION VAPOUR PRESSURE. ELECTRON clouds surrounding each NUCLEUS as two atoms are brought var. (1 statistics; 2 general terminology) close together. Named after the Dutch 1 An abbreviation of ‘var’iable. 2 An physicist Johannes Diderik van der abbreviation of ‘var’ious. Waals (1837–1923). variability (statistics) The spread of scores van Gieson stain (histology) A histologi- in a SAMPLE or the extent to which cal staining technique that may be used they differ from the MEAN.

403 VARIABLE VASOPRESSIN variable (1 mathematics; 2 computing) vasc. (histology) An abbreviation of 1 Something that is not CONSTANT. 2 ‘vasc’ular. Block of DATA that is stored at different vascular accident (medical) An alternative locations during the operation of a term for STROKE. PROGRAM. vascular system (anatomy) A system variable number tandem repeats (VNTRs) of interlinked FLUID-filled vessels, e.g. (molecular biology) The repeated sequences the BLOOD VASCULAR SYSTEM. of DNA that vary from one individual to another and are the basis for GENETIC vasculitis (medical) INFLAMMATION of FINGERPRINTING. a VESSEL. variable region (immunology) See V vasoconstriction (physiology) REDUCTION REGION. in DIAMETER of a BLOOD VESSEL due to contraction of the SMOOTH MUSCLES in its variance (statistics) For a SET of numbers, walls. It may be induced by the SECRETION the MEAN of the squares of the deviations of ADRENALINE (USA: epinephrine) in of each number from the ARITHMETIC RESPONSE to pain, fear, decreased BLOOD MEAN of the SET. Its SQUARE ROOT PRESSURE, low external TEMPERATURE, is the STANDARD DEVIATION. etc. or result from stimulation by vasoconstrictor NERVE FIBRES (USA: nerve fibers). variation (biology) Differences between members of the same SPECIES, which vasodilation (physiology) Increase in may be either continuous (having a NORMAL DIAMETER of small BLOOD VESSELS DISTRIBUTION about a SPECIES MEAN, due to relaxation of the SMOOTH MUSCLES e.g. height and WEIGHT) or discontinuous in their walls. It is induced in RESPONSE (having different specific characteristics to exercise, HIGH BLOOD PRESSURE, with no INTERMEDIATE forms, e.g. BLOOD high external TEMPERATURE, etc. or types). results from stimulation by VASODILATOR NERVE FIBRES (USA: nerve fibers). Also varicella (virology) Chicken-pox. termed: vasodilatation. variety (taxonomy) Any sub-DIVISION of vasodilator (medical) An agent that causes a SPECIES, e.g. breed, RACE, strain, etc. dilatation of the BLOOD VESSELS. variola (virology) Any of the diseases vasomotor (physiology) Pertaining to caused by the poxviruses. VARIOLA major the motor control of the DIAMETER of is an alternative term for smallpox. BLOOD VESSELS. vas deferens (anatomy) One of a pair vasomotor nerve (physiology) NERVE of ducts that carry SPERM from the TESTES. of the AUTONOMIC NERVOUS SYSTEM In mammals it joins the URETHRA and that controls the VARIATION in the DIAMETER passes along the PENIS. Plural: vasa of BLOOD VESSELS, e.g. causing them deferentia. Also termed: SPERM duct. to become constricted or dilated. vas. (medical) An abbreviation of vasopressin (biochemistry) PEPTIDE ‘vas’ectomy. HORMONE, secreted by the PITUITARY

404 VASOPRESSOR VENTRICLE

GLAND and HYPOTHALAMUS, that Also termed: CARRIER. 3 A quantity having stimulates WATER resorption in the KIDNEY both magnitude and direction, which can tubules, contraction of the SMOOTH be used to characterise forces. MUSCLES in the walls of BLOOD VESSELS. It is secreted in RESPONSE to low BLOOD vecuronium bromide (pharmacology) PRESSURE. A lack of VASOPRESSIN A non-depolarising skeletal muscle results in DIABETES insipidus. Also termed: relaxant drug which is administered ANTIDIURETIC HORMONE (ADH). by injection to induce muscle paralysis during surgery. vasopressor (biochemistry/physiology) A substance which increases BLOOD vein (anatomy) BLOOD VESSEL that, PRESSURE by narrowing the BLOOD with the exception of the PULMONARY VESSELS. VEIN, carries deoxygenated BLOOD away from CELLS and tissues. vauqueline (chemistry) An alternative term for STRYCHNINE. vena cava (anatomy) Collective term for the precaval (ANTERIOR VENA CAVA) vcm (physics) An abbreviation of ‘v’a‘c’uu‘m’. and postcaval (POSTERIOR VENA CAVA) VEIN. The precaval VEIN is paired, Vd (chemistry) CHEMICAL SYMBOL for and carries eoxygenated BLOOD away VANADIUM. from the HEAD and forelimbs; the postcaval VEIN is single and carries deoxygenated vd (physics) An abbreviation of ‘v’apour BLOOD away from most of the body ‘d’ensity. and hind limbs (or legs) to the HEART.

VDH (medical) An abbreviation of ‘v’alvular venereal disease (medical) See SEXUALLY ‘d’isease of ‘h’eart. TRANSMITTED DISEASE.

VDRL (bacteriology) A BLOOD test for venesection (medical) The cutting of a syphilis named after the VENEREAL VEIN to draw off BLOOD or, more usually, DISEASE Research Laboratories. to insert a cannula for INTRAVENOUS THERAPY. VDT (computing) An abbreviation of ‘V’isual ‘D’isplay ‘T’erminal. ventral (general terminology) Describing something that is on or near the surface VDU (computing) An abbreviation of ‘V’isual of an organism and, in a tetrapod, directed ‘D’isplay ‘U’nit. downwards (on a human being it is directed forwards). vector (1 molecular biology; 2 medicine/ parasitology; 3 mathematics) 1 A plasmid ventral noradrenergic bundle (histology) or other self-replicating DNA MOLECULE A noradrenergic (USA: norepinephrine) that transfers DNA between CELLS in tract running from the brainstem to the nature or in RECOMBINANT DNA technology. HYPOTHALAMUS. In the latter case it may be called a cloning VECTOR or cloning vehicle. 2 An organism ventricle (1,2 anatomy) 1 In mammals, responsible for PARASITE transmission thick-walled muscular lower chamber of between hosts, e.g. the mosquito in MALARIA. the HEART. Contraction of the right

405 VENTURI TUBE VGA

VENTRICLE pumps deoxygenated BLOOD vertebral column (anatomy) Flexible column into the PULMONARY ARTERY, and of closely arranged vertebrae that form contraction of the left VENTRICLE forces an axial SKELETON running from the oxygenated BLOOD into the AORTA. 2 SKULL to the tail. It provides a protective In vertebrates, one of the FLUID-filled channel for the SPINAL CORD. The interconnected cavities within the BRAIN. VERTEBRAL COLUMN becomes larger and stronger towards the POSTERIOR, Venturi tube (physics) Cylindrical pipe which is the major weightbearing region. with a constriction at its centre (USA: Also termed: SPINAL COLUMN; BACKBONE. center). When a FLUID flows through the tube, its rate of flow increases and vertebrata (taxonomy) Major subphylum FLUID PRESSURE drops in the constriction. of Chordata that contains all animals The rate can be calculated from the with a VERTEBRAL COLUMN, i.e. mammals, difference in PRESSURE between the birds, fish, reptiles and amphibians. ends of the tube and at the constriction. Vertebrates are characterized by a well- It was named after the Italian physicist developed BRAIN, complex NERVOUS Giovanni Battista Venturi (1746–1822). SYSTEMS and a flexible endoskeleton of BONE and CARTILAGE. Also termed: venule (anatomy) Small VEIN located Craniata. close to CAPILLARY BLOOD VESSELS, where it collects and conveys deoxygenated vertebrate (taxonomy) A backboned BLOOD from the CAPILLARY NETWORK ANIMAL; a member of the subphylum to a VEIN. VERTEBRATA. verapamil hydrochloride (pharmacology) vertical transmission (genetics) The usual A calcium-channel blocker used as an type of genetic INHERITANCE, from one orally administered ANTI-ANGINA drug generation to the next. It is contrasted in the prevention and treatment of attacks, with HORIZONTAL TRANSMISSION. as an ANTI-ARRHYTHMIC to correct HEART irregularities and as an ANTIHYPERTENSIVE very high frequency (VHF) (physics) A treatment. radio FREQUENCY between 30 and 300 KILOHERTZ. verdigris green (chemistry) BASIC

COPPER(II) CARBONATE, CUCO3.CU(OH)2, vesical (medical) Pertaining to the formed by corrosion of metallic COPPER BLADDER. or its ALLOYS. The term is also used for the similar BASIC COPPER(II) ACETATE, vesicle (1 biology; 2 medical) 1 A small used as a PIGMENT, FUNGICIDE and FLUID-filled sac of VARIABLE ORIGIN, mordant in dyeing. e.g. GOLGI APPARATUS, pinocytotic VESICLE. Also termed: VACUOLE; AIR sac; BLADDER. vermiform appendix (anatomy) An 2 small blister on the SKIN. alternative term for the APPENDIX. vessel (anatomy) Tubular structure that vertebra (anatomy) One of the hollow transports FLUID (e.g. BLOOD, LYMPH). bones or pieces of CARTILAGE that form the VERTEBRAL COLUMN. VGA (computing) An abbreviation of ‘V’ideo ‘G’raphics ‘A’rray.

406 VHF VIRUS

VHF (physics) An abbreviation of ‘Very vinyl group (chemistry) Double-bonded

‘H’igh ‘F’requency. organic GROUP CH2=CH-. viable (biology) Capable of living. VIP (physiology/biochemistry) An abbreviation of ‘V’asoactive ‘I’ntestinal vibration receptor (physiology) The SKIN ‘P’olypeptide. RECEPTOR that responds to vibration, thought to be the PACINIAN CORPUSCLE. viroid (microbiology) A small disease- causing agent, a tight loop of RNA lacking vibrio (bacteriology) A Gram-negative any form of capsid (outer coat). GENUS of BACTERIA which includes the organism causing cholera, VIBRIO virulence (microbiology) The ability of choleras. Another less important VIBRIO a PATHOGEN (a VIRUS, BACTERIUM causing DIARRHOEA (USA: diarrhea) or other MICRO-ORGANISM) to produce and abdominal pain is VIBRIO parahaemalyti- a disease. It depends partly on its CAPACITY cus, which lives in the sea in warm climates to invade the HOST CELL and multiply, and infects fish, crabs and prawns; the and partly on its ability to produce toxins. illness only lasts for a day or two. VIRULENCE tends to be favoured by NATURAL SELECTION, as virulent strains video graphics array (VGA) (computing) are often the most successful at reproducing A type of COMPUTER graphics circuitry themselves; but beyond a certain point that drives a COMPUTER monitor with VIRULENCE is a disadvantage to a strain very high resolution, or the monitor itself. of pathogens, as they may kill their hosts too soon for their own good. vigabatrin (pharmacology) An ANTI- EPILEPTIC drug administered orally to virus (virology) PATHOGENIC MICRO- treat epilepsy. ORGANISM with a DIAMETER between about 20 and 400 nm, visible only under villus (histology) A small protrusion from an ELECTRON MICROSCOPE. It consists the surface of a MEMBRANE. One of of an outer coat (capsid) PROTEIN and many finger-like structures that line the an inner CORE of DEOXYRIBONUCLEIC inside of the SMALL INTESTINE. Villi ACID (DNA) or RIBONUCLEUR ACID (RNA). increase the surface AREA for VIRUSES infect plants, animals and ABSORPTION. Each VILLUS contains BACTERIA. Outside the HOST CELLS a central LACTEAL and a NETWORK of viruses are metabolically inactive (and BLOOD capillaries, which absorb the may be crystallizable), and only when SOLUBLE products of DIGESTION into attached to a CELL or wholly inside it the body. does the viral DNA interfere with the metabolic activities of the CELL, suppressing Vincent’s angina (trench mouth) (medical/ its NORMAL control processes and causing bacteriology) A BACTERIAL INFECTION it to manufacture new PROTEIN coats of the mouth and gums, which ulcerate and NUCLEIC ACID threads identical with and bleed. The INFECTION is mixed, those of the invading VIRUS. Viruses which with Borrelia vincentti and Fusobacterium actively attack and proliferate in CELLS fusiform is predominating. are described as virulent. Those VIRUSES that infect animals include: DNA genomes: adenoviruses, herpesviruses, poxviruses,

407 VISCERA VITREOUS HUMOUR parvoviruses. RNA genomes: reoviruses, CELLS to take place, e.g. the production retroviruses. The VIRUSES that attack of ENERGY, the SYNTHESIS of proteins BACTERIA are called bacteriophages. (for TISSUE-building, HORMONES, etc). Excessive doses of VITAMINS often have viscera (histology) The large internal a deleterious effect, such toxic overdoses organs of the body, e.g. lungs, LIVER being known by the general term, and intestines. hypervitaminosis. visceral (anatomy) Relating to the vitamin A (biochemistry) See RETINOL. VISCERA.

vitamin B1 (biochemistry) See THIAMINE. viscometer (physics) Instrument for measuring VISCOSITY. vitamin B2 (biochemistry) See RIBOFLAVIN. viscosity (physics) Property of a FLUID vitamin C (biochemistry) See ASCORBIC (LIQUID or gases) that makes it resist ACID. flow, resulting in different velocities of flow at different points in the FLUID. vitamin D (biochemistry) See CALCIFEROL. Also termed: INTERNAL FRICTION. vitamin E (biochemistry) See TOCOPHEROL. visible light (physics) LIGHT that can be seen by the human EYE (the VISIBLE vitamin H (biochemistry) See BIOTIN. SPECTRUM), as opposed to INFRA-RED and ULTRAVIOLET RADIATION. vitamin K (biochemistry) An essential fat-soluble vitamin that occurs naturally visible spectrum (physics) Range of in two forms, vitamin k1 (phytomenadione) wavelengths of visible ELECTROMAGNETIC and vitamin K2. Vitamin K1 is found in RADIATION (LIGHT), between about 780 food such as fresh root vegetables, fruit, and 380 nm. dairy products and meat, while vitamin

K2 is synthesised in the INTESTINE by visual defect (medical) See ASTIGMATISM; bacteria and this source supplements the HYPERMETROPIA; MYOPIA. dietary form. Vitamin K is required for blood-clotting factors and is also important visual purple (biochemistry) An alternative for the proper calcification of bone. The term for RHODOPSIN. secretion of bile salts by the LIVER and fat absorption from the INTESTINE is vitamins (biochemistry) A group of required by both forms of vitamin K to substances that are necessary for achieve uptake into the body. Therefore METABOLISM but only in MINUTE quantities. when treating vitamin K deficiency due There are two major groups, WATER- to malabsorption disorders a synthetic

SOLUBLE (e.g. VITAMINS C, B) and fat- form, vitamin K3 (menadiol sodium phosphate), SOLUBLE (e.g. A, D, E, K), which are which is water-soluble and effective when present in foodstuffs and must be taken administered orally, is used. as part of a balanced diet. VITAMINS WORK as CO-ENZYMES within the vitreous humour (anatomy) Firm TRANS- ENZYME system, enabling the various PARENT GEL-like substance in the essential CHEMICAL REACTIONS within EYE, that fills the space behind the

408 VITRIOL V REGION

LENS, thus maintaining the shape of voltage divider (physics) RESISTOR that the eyeball. can be tapped at a point along its length to give a particular FRACTION of the See also AQUEOUS HUMOUR. VOLTAGE across it. Also termed: POTENTIOMETER. vitriol (chemistry) An alternative term for SULPHURIC ACID (USA: sulfuric acid). voltaic cell (physics) Any device that produces an ELECTROMOTIVE FORCE VLDL (biochemistry) An abbreviation of (e.m.f.) by the conversion of chemical ‘V’ery ‘L’ow ‘D’ensity ‘L’ipoPROTEIN. ENERGY to electrical ENERGY, e.g. a BATTERY or ACCUMULATOR. Also termed: VLDLP (chemistry) An abbreviation of GALVANIC CELL. ‘V’ery-‘L’ow-‘D’ensity ‘L’ipo‘P’rotein. See LIPOPROTEINS. voltmeter (physics) An instrument for measuring VOLTAGE or POTENTIAL VLN (physics) An abbreviation of ‘V’ery DIFFERENCE. ‘L’ow ‘N’itrogen. volume (P) (physics) Amount of space VMA (biochemistry) An abbreviation of occupied by a SOLID OBJECT, or the ‘V’anillyl‘M’andelic ‘A’cid (3-methoxy-4- CAPACITY of a hollow VESSEL. hydroxymandelic acid). volumetric analysis (chemistry) Method vocal cord (anatomy) One of a pair of of chemical ANALYSIS that relies on membranous flaps in the LARYNX that the accurate measurement of the reacting are vibrated by AIR from the lungs to volumes of substances in SOLUTION produce sounds. (e.g. by carrying out a TITRATION). volatile (1 chemistry; 2 computing) 1 voluntary muscle (histology) Type of Describing any substance that is readily MUSCLE, connected to the bones, that changed to a VAPOUR and hence lost is under conscious control. It is responsible through EVAPORATION. VOLATILE liquids for most body movements. Also termed: have low BOILING POINTS. 2 Describing STRIATED MUSCLE. stored information that is lost through a POWER cut. Von Kossa stain (histology) A histological staining technique that may be used to volt (V) (measurement) SI UNIT of make CALCIUM visible under the POTENTIAL DIFFERENCE (pd) or MICROSCOPE. ELECTROMOTIVE FORCE (emf), which equals the pd between two points when one VOR (physiology) An abbreviation of coulomb of ELECTRICITY produces one ‘V’estibulo-‘O’cular ‘R’eflex. JOULE of WORK in going from one point to the other. It was named after the Italian V region (immunology) VARIABLE physicist Alessandro Volta (1745–1827). REGION. Part of the heavy and LIGHT chains of an IMMUNOGLOBULIN voltage (P) (physics) Value of a POTENTIAL MOLECULE. It is this region that interacts DIFFERENCE, or the POTENTIAL DIFFE- with the ANTIGEN. RENCE itself.

409 VS V.V.

Vs (medical) An abbreviation of ‘V’ene‘s’ection. vulgar fraction (mathematics) FRACTION in which both NUMERATOR and DENOMI- NATOR are integers (whole numbers). vulva (anatomy) In female mammals, the external opening of the VAGINA. v.v. (literary terminology) An abbreviation of ‘v’ICE ‘v’ersa. Latin, meaning ‘reversal of ORDER’.

410 W

W (1 chemistry; 2 physics; 3 biochemis- axonal degeneration is morphologically try) 1 The CHEMICAL SYMBOL for the similar to WALLERIAN DEGENERATION. ELEMENT tungsten (from its German name: ‘WOLFRAM’). 2 Symbol for the warfarin (pharmacology) ORGANIC UNIT WATT. 3 A symbol for tryptophan. COMPOUND used (as its SODIUM DERIVATIVE) as an ANTICOAGULANT drug Wade/Fite stain (histology) A histological and as a PESTICIDE for killing rats and mice. staining technique that may be used to make the LEPROSY bacilli visible under warm-blooded (biology) An alternative the MICROSCOPE. term for HOMOIOTHERMIC.

Wagner-nelson method (chemistry) Warthin/Starry stain (histology) A Technique to characterise the rate and histological staining technique that may extent of ABSORPTION of a substance. be used to make spirochaetes visible under the MICROSCOPE. Waldenstrom’s macroglobulinaemia (immunology) Disease occurring mainly warts (microbiology/histology) A non- in elderly males, characterised by the maglignant, localised TUMOUR (USA: presence of large amounts of tumor) of the SKIN formed by overgrowth MONOCLONAL IMMUNOGLOBULIN M of the prickle-CELL layer, with or without in the BLOOD, LYMPHOID TISSUE hyperkeratosis, caused by INFECTION enlargement, splenomegaly, a haemorrhagic with the human papilloma VIRUS. WARTS (USA: hemorrhagic) tendency and can affect many parts of the SKIN including depression. The IMMUNOGLOBULIN M the fingers and feet which can be treated is occassionally found to have detectable with a MIXTURE of salicylic and LACTIC ANTIBODY activity e.g. rheumatoid FACTOR. ACIDS in collodion, or by the use of The disease is probably a relatively BENIGN LIQUID NITROGEN. If left they often and slowly progressing form of myelomatosis. disappear in time. (USA: Waldenstrom’s macroglobulinemia). washed red cells (haematology) BLOOD Wallerian degeneration (histology) The COMPONENT in which PLATELET and degeneration of myelinated and unmy- LEUCOCYTE (USA: leukocyte) antigens elinated axons that occurs in a NERVE distal have been removed. to a transaction or crush of the NERVE. MYELIN SHEATHS also degenerate in the washing soda (chemistry) An alternative distal NERVE stump as a consequence of term for HYDRATED SODIUM CARBONATE. the loss of their underlying AXON. Axonal degeneration due to other causes (e.g. Wass. (microbiology/immunology) An neurotoxicants) is often referred to as abbreviation of ‘Wass’ermann REACTION. ‘Wallerian-like’ or ‘Wallerian-type’ if the

411 WASSERMANN REACTION WATT

Wassermann reaction (microbiology/im- See also HARDNESS OF WATER. munology) A BLOOD test formerly used in the diagnosis of syphilis, introduced water of crystallization (chemistry) by the German pathologist, August Paul Definite amount of WATER retained by von Wassermann (1866–1925). A a COMPOUND (usually a SALT) when complement fixation test in which cardiolipin crystallized from SOLUTION. The derived from ox HEART is used as ANTIGEN CHEMICAL FORMULA of the resulting because the BLOOD of individuals with HYDRATE shows the number of molecules syphilis regularly contains ANTIBODY of WATER OF CRYSTALLIZATION which reacts with this substance. However, associated with each MOLECULE of the Wassermann test is not entirely specific HYDRATE; e.g. Na2SO4.7H2O. The WATER for syphilis. False results may be obtained can usually be removed by heating, in cases where there are increased and the resulting COMPOUND is termed IMMUNOGLOBULIN levels, e.g. due to ANHYDROUS. Also termed: WATER OF parasitic INFECTION or in autoimmune HYDRATION. conditions and confirmatory tests using TREPONEMA pallidum itself as the water of hydration (chemistry) The WATER ANTIGEN may need to be made for a present in HYDRATED compounds. These POSITIVE diagnosis. Tests such as the compounds when crystallized from TREPONEMA pallidum haematagglutination SOLUTION in WATER retain a definite assay (TPHA) (USA: Treponema pallidum amount of WATER, e.g. COPPER (II) hematagglutination assay) or a FLUO- SULPHATE (USA: copper (II) sulfate),

RESCEIN-labelled ANTIBODY test (FTA- CuSO4.5H2O. ABS) are now generally used. waterbrash (medical) Regurgitation of a WAT (physics) An abbreviation of ‘W’eight, watery SECRETION containing ACID fluids ‘A’ltitude and ‘T’emperature. from the STOMACH into the OESOPHAGUS (USA: esophagus) and mouth. water (chemistry) H2O Colourless (USA: colorless) LIQUID, one of the oxides of water-in-oil emulsion adjuvant (immunol- HYDROGEN (the other is HYDROGEN ogy) Adjuvant in which the ANTIGEN,

PEROXIDE, H2O2) and the commonest dissolved or suspended in WATER, is substance on the EARTH. It can be made enclosed in tiny droplets within a by burning HYDROGEN or fuels containing continuous PHASE of MINERAL OIL. it in AIR or OXYGEN, or by the ACTION The ANTIGEN SOLUTION constitutes of an ACID on an ALKALI or ALCOHOL. the dispersed PHASE, stabilised by It is a good (polar) SOLVENT, particularly an emulsifying agent such as MANNITOL for ionic compounds, with which it may mono-OLEATE. form SOLID hydrates. It can be decomposed by the ACTION of certain reactive metals watt (W) (measurement) SI UNIT of (e.g. the ALKALI METALS) or by ELE- POWER, equal to 1 JOULE per second CTROLYSIS. WATER is essential for life (j s-1). 745.70 watts=1 horsepower. and forms the major part of most body Wattage is the POWER of an electrical fluids (e.g. BLOOD, LYMPH). It freezes CIRCUIT determined by multiplying at 0°C and BOILS at 100°C (at NORMAL the VOLTAGE by the amperage. It was ATMOSPHERIC PRESIURE), and has named after the British engineer James its maximum DENSITY at 3.98°C. Watt (1736–1819).

412 WATT-HOUR WEIL-FELIX REACTION watt-hour (measurement) Measure of weak acid (chemistry) ACID that shows electric POWER consumption. Also termed: little IONIZATION or DISSOCIATION in UNIT. SOLUTION; e.g. CARBONIC ACID, acetic (ethanoic) ACID. wattmeter (physics) Instrument for measuring POWER consumption in an weak electrolyte (chemistry) An ELECTRO- electric CIRCUIT. POWER consumption LYTE which is only slightly ionised in is usually expressed in WATT-HOURS, moderately concentrated solutions. or units. weaning index (toxicology) An expression wave (physics) Regular (periodic) distur- of survival of offspring to weaning in bance in a substance or in space; e.g. reproductive toxicity tests. The number in an airborne sound WAVE, alternate of offspring surviving to weaning (i.e. regions of high and low PRESSURE travel 21 days in the rat) as a PERCENTAGE through the AIR, although the AIR itself of those alive at four days. does not move along. In an ELECTRO- MAGNETIC WAVE, such as LIGHT, electric weber (Wb) (measurement) SI UNIT of and magnetic waves at rightangles to MAGNETIC FLUX, named after the German each other and the direction of movement physicist Wilhelm WEBER (1804–91). travel through a medium or through space. weight (physics) The FORCE of gravity wave function (mathematics) Equation (9.8 m s-2) acting on an OBJECT at that expresses time and space VARIATION the EARTH’S surface; i.e. WEIGHT=MASS in AMPLITUDE for a WAVE system. X ACCELERATION of free fall (ACCELERATION due to gravity). It is wave number (physics) RECIPROCAL of measured in newtons, pounds-FORCE the WAVELENGTH of an ELECTRO- or dynes. MAGNETIC WAVE. Also termed: RECIPROCAL WAVELENGTH. weights and measures (measurement) See SI UNITS. wavelength (?) (physics) The distance between two successive points at which Weil-Felix reaction (immunology) An a WAVE has the same PHASE e.g. VISIBLE AGGLUTINATION test used in the diagnosis LIGHT has a WAVELENGTH of between of rickettsial infections (TYPHUS etc.) which 400 nm (violet) to 750 nm (red). depends upon a CARBOHYDRATE cross- reacting ANTIGEN shared by wax (chemistry) SOLID or semi-solid organic RICKETTSIAE and certain strains of substance that is 1 an ESTER of a FATTY Proteus. The AGGLUTINATION pattern of ACID, produced by a plant or ANIMAL patients with rickettsial disease against O- (e.g. beeswax, tallow), or 2 a high agglutinable strains of Proteus OX19, OX2 MOLECULAR WEIGHT HYDROCARBON and OXK is diagnostic of the various (e.g. PARAFFIN WAX, from petroleum), rickettsial diseases. Named after the also called mineral WAX. Austrian physician, Edmund Weil (1880– 1922) and the Polish BACTERIOLOGIST, WBC (1,2 haematology) 1 An abbrevia- Arthur Felix (1887–1956). tion of ‘W’hite ‘B’lood ‘C’ell. 2 An abbreviation of ‘W’hite ‘B’lood ‘C’ount.

413 WEIL’S DISEASE WHITE ARSENIC

Weil’s disease (medical/bacteriology) and NIACIN and marked by clouding of Severe form of INFECTION by consciousness and ATAXIA; it can be LEPTOSPIRA interrogans, a SPIRO- caused by ALCOHOLISM. Named after CHAETE which infects rats and other the psychiatrist and neurologist, Karl animals and is passed on to man mainly Wernicke (1848–1905). by contact with rats, their URINE, or WATER contaminated by their URINE. Western blotting (biochemistry) A technique There are a large number of types of for the ANALYSIS and identification of the SPIROCHAETE, and the type commonly proteins in complex mixtures. The proteins responsible for WEIL’S DISEASE is are separated by polyacrylamide GEL LEPTOSPIRA icterohaemorrhagica; it ELECTROPHORESIS and the separated causes damage to the LIVER and the bands then transferred by ‘blotting’ onto kidneys. Named after the German physician a POLYMER MEMBRANE by ELECTRO- Adolf Weil (1848–1916). See LEPTOSPIRA. PHORESIS at 90° to the GEL surface. The proteins bound on the POLYMER Weil’s myelin stain (histology) A his- MEMBRANE can then be identified by tological staining technique that may be REACTION with specific reagents such used to make myelin visible under the as RADIOACTIVE or FLUORESCENT MICROSCOPE. labelled antibodies. The method is very specific and can be used to confirm the Weismannism (philosophy) Idea put results of the ELISA test. It is named by forward by the German biologist August analogy with SOUTHERN BLOTTING. Weismann (1834–1914), who expressed it in terms of the theory of the continuity See also NORTHERN BLOTTING; SOUTHERN of the ‘germ plasm’, which states that BLOTTING. INHERITANCE is affected only by the GERM CELLS (gametes), which is in WFN (professional body) An abbreviation disagreement with the theory of of ‘W’orld ‘F’ederation of ‘N’eurology. INHERITANCE of ACQUIRED CHARAC- TERISTICS as in LAMARCKISM. Wheatstone bridge (physics) Electric CIRCUIT for measuring the resistance See also DARWINISM. of a RESISTOR (by comparing it with three other resistors of known values). wen (histology) A sebaceous cyst. It was named after the British physicist Charles Wheatstone (1802–75). Wernicke-Korsakoff syndrome (medical/ biochemistry) A COMBINATION of whewellite (biochemistry) HYDRATED

WERNICKE’S DEMENTIA and the Korsakoff CALCIUM OXALATE CaC2O4.H2O. It occurs SYNDROME, both of which are thought uncommonly in the mineral world but is to be caused by THIAMINE deficiency. abundant in human calculi. Named after the German psychiatrist and neurologist, Karl Wernicke (1848– whipworm (parasitology) A popular name 1905), and Russian psychiatrist, Sergei for TRICHURIS trichiura. Sergeevich Korsakoff (1854–1900). white arsenic (chemistry) An alternative Wernicke’s dementia (biochemistry) A term for ARSENIC(III) OXIDE (arsenious BRAIN disorder caused by lack of THIAMINE OXIDE). See ARSENIC.

414 WHITE BLOOD CELL WILD STRAIN white blood cell (haematology) See typhoid and paratyphoid fevers. The LEUCOCYTE. organisms used must be MOTILE, smooth and in the specific PHASE. Formalised white light (physics) LIGHT that is composed and alcoholised suspensions are used of a MIXTURE of wavelengths in the respectively for testing for H (flageller) visable SPECTRUM. and O AGGLUTININS. The WIDAL TEST is not likely to be POSITIVE until after white matter (histology) Those parts of the first 10 days of the disease. Prior the CENTRAL NERVOUS SYSTEM IMMUNISATION with TAB VACCINE may containing mainly myelinated fibres (USA: cause FALSE POSITIVE results and for myelinated fibers), which appear white; this reason the test is of limited value e.g. the myelinated fibres of the CORTEX in countries which have an active TAB which run below the GREY MATTER. IMMUNISATION programme. Named after the Algerian born French pathologist George white vitriol (chemistry) An alternative Fernand Isadore Widal (1862–1929). term for ZINC SULPHATE (USA: zinc sulfate). wide-spectrum (microbiology) Of antibiotics etc. effective against a wide range of whitlow (microbiology) A purulent MICRO-ORGANISMS. The term ‘broad- INFECTION of the end of the finger involving SPECTRUM’ is also used. the pulp. The term is also applied to an INFECTION of the SKIN in the region Wilcoxon rank-sum test (statistics) A of the NAIL by HERPES simplex VIRUSES. distribution-free, NON-PARAMETRIC test Also known as FELON. for two independent groups. The DATA from both groups are combined and ranked WHO (governing body) An abbreviation with the lowest value assigned a rank of ‘W’orld ‘H’ealth ‘O’rganisation. of 1. The ranks assigned to each GROUP are then summed, with the test statistic whole blood (haematology) BLOOD which T’ being the sum of the ranks for the has not been broken down into its various smaller GROUP. For small groups (n < components. It is used in transfusion 10), the critical value for T’ can be obtained THERAPY a) in NEONATAL total BLOOD from special tables. If n > 10 for both exchange and b) in cases of ACUTE groups, the distribution approximates massive BLOOD loss. WHOLE BLOOD NORMAL, and the obtained value for T’ is usually collected in citrate-PHOSPHATE- can be assessed using the NORMAL DEXTROSE (CPD) ANTICOAGULANT curve table. preservative SOLUTION. WHOLE BLOOD is suitable for transfusion up to a 21 See also NON-PARAMETRIC. day STORAGE PERIOD. Wilcoxon signed ranks test (statistics) whooping cough (medical/bacteriology) See WILCOXON RANK-SUM TEST. See PERTUSSIS. wild strain (microbiology) A strain of a Widal test (microbiology/immunology) particular type of MICRO-ORGANISM A serological AGGLUTINATION REACTION that has not become LABORATORY adapted. of Salmonella typhi and similar organisms by the patient’s SERUM, used to diagnose

415 WILD TYPE WORD PROCESSOR wild type (genetics) The ALLELE that is in PLATELET membranes is missing. deemed to be the one that occurs in the Sufferers are particularly susceptible SPECIES in its original state, as opposed to to infections from HERPES VIRUSES subsequent MUTATIONS, either spontaneous and lymphoreticular malignancies, especially or induced. The wild-type ALLELE may be of the CENTRAL NERVOUS SYSTEM. either DOMINANT or RECESSIVE in relation witches’ milk (physiology) The milk to a MUTANT ALLELE. Its symbol is+. secreted from the breasts of a newborn baby in RESPONSE to the HORMONES Wilm’s tumour (haematology) See of its mother. NEPHROBLASTOMA. withdrawal symptoms (toxicology) The Wilson’s disease (biochemistry) A rare unpleasant symptoms that are caused disease in which excessive amounts of by ceasing to take a drug of ADDICTION. COPPER are deposited in the BRAIN The symptoms vary with the drug but and LIVER. Named after the British may include restlessness, inability to neurologist, Samuel Alexander Kinnier concentrate, IRRITABILITY, insomnia, Wilson (1878–1937). depression, nausea, and delirium. winchester (equipment) A bottle, com- within-group variance (statistics) The monly used for LIQUID chemicals, with amount of VARIANCE caused by differences a CAPACITY of about 2.25 LITRES. It within a GROUP. was named after the city of winchester, Hampshire, UK. w/o (literature terminology) An abbreviation of ‘w’ith‘o’ut. winter vomiting disease (medical/ virology) A disease caused by parvoviruses wolfram (chemistry) Old name for tungsten. characterised by nausea, vomiting, DIARRHOEA (USA: diarrhea) and giddiness wood spirit (chemistry) An alternative which occurs during the winter months. term for METHANOL. Outbreaks may involve whole families or may affect communities such as schools. wood sugar (chemistry) An alternative The INCUBATION PERIOD is 1 to 2 days, term for XYLOSE. and the condition seldom lasts for more than 3 days. wool fat (chemistry) An alternative term for LANOLIN. Wiskott-Aldrich syndrome (medical/ haematology) An IMMUNE SYSTEM sex- woolsorter’s disease (medical/bacteriol- linked RECESSIVE disease of infants, ogy) An ACUTE LUNG disease due to characterised by THROMBOCYTOPENIA, INFECTION with BACILLUS anthracis, with a haemorrhagic (USA: hemorrhagic) conveyed to humans by inhalation of tendency, eczema, and immunodeficiency spores from infected sheep’s wool. with recurrent infections. Delayed HYPERSENSITIVITY reactions are absent See also ANTHRAX. and there is a defective ANTIBODY RESPONSE to POLYSACCHARIDE word processor (computing) Microcom- antigens, with low immunoglobulin M puter that is programed to help in the levels. A PROTEIN normally present

416 WORK WUCHERERIA preparation of text, for DATA TRANSMISSION or printing. work (W) (physics) The measurement of a FORCE multiplied by the distance moved by the point of application of the FORCE in the direction of the FORCE. It is measured in joules. working (mathematics) Pertaining to something assumed or approximated, e.g. ‘WORKING HYPOTHESIS’.

World Health Organisation (WHO) (governing body) The health agency of the United Nations, WHO is based in Geneva, Switzerland. SET up in 1948 it co-ordinates international health activities, and aims to improve health, particularly of developing countries, through education and information and practical assistance with MASS VACCINATION programmes, public health schemes and medical facilities. worms (microbiology/parasitology) An imprecise term applied to elongated invertebrates with no appendages. Those that infest human beings can be divided into three groups: roundworms or nematodes, tapeworms or cestodes and FLUKES or TREMATODES. wounds (medical) Disruption of the tissues by external agents of a mechanical nature which may be classified as incised, punctured, contusm, lacerated, perforating and penetrating.

WP (computing) An abbreviation of ‘W’ord ‘P’rocessing. wt (measurement) An abbreviation of ‘w’eigh‘t’.

Wuchereria (parasitology) See FILARLASIS; WORMS.

417 X

X (statistics) The ARITHMETIC MEAN. Xe (chemistry) The CHEMICAL SYMBOL for the ELEMENT XENON. xanthene (chemistry) CH2(C6H4)2O Yellow CRYSTALLINE ORGANIC COMPOUND, xenobiotic (toxicology) A general term used as a FUNGICIDE and in making used to describe any chemical interacting dyes. Also termed: tricyclicdibenzopyran. with an organism that does not occur in the NORMAL metabolic pathways of that xanthine (chemistry) C5H4N2O2 ORGANIC organism. COMPOUND that occurs in potatoes, coffee beans, BLOOD and URINE, used xenodiagnosis (parasitology) Procedure industrially as a chemical INTERMEDIATE. involving the feeding of LABORATORY- Also termed: 3 7-dihydro-1 H-PURINE- reared triatomid bugs on patients 2,6-dione; 2,6-DIHYDROXYPURINE. suspected of having Chagas’ disease; after several weeks the FAECES (USA: xanthone (chemistry) CO(C6H4)2O Plant feces) of the bugs are checked for PIGMENT that occurs in gentian and INTERMEDIATE stages of Trypanosoma other flowers, used commercially as an cruzi. INSECTICIDE and dye INTERMEDIATE. Also termed: 9H-xanthen-9-one. xenograft (biology) The grafting of TISSUE to an immunosuppressed ANIMAL of a xanthophyll (chemistry) C40H56O2 Yellow different SPECIES. A convenient method to orange PIGMENT present in the NORMAL to grow human tumours (USA: tumors) chlorophyll MIXTURE of green plants. in experimental animals for further study. Also termed: lutein. xenon Xe (chemistry) Unreactive gaseous x-axis (mathematics) The horizontal AXIS ELEMENT in GROUP O of the PERIODIC on a GRAPH. TABLE (the RARE GASes) which occurs as traces in the ATMOSPHERE, from X chromosome (genetics) One of the which it is extracted. It is used in electronic SEX CHROMOSOMES. In humans the flash tubes and high-INTENSITY ARC female has two X CHROMOSOMES and lamps. At. no. 54; r.a.m. 131.30. the male an X and a Y. The human X CHROMOSOME is the seventh largest in xeroderma pigmentosum (medical/genet- the human KARYOTYPE, nearly three times ics) A disease in which the SKIN is excessively the size of the Y CHROMOSOME. It carries vulnerable to bright sunlight, resulting in a large number of genes, which are said a high INCIDENCE of SKIN cancers. The to be X-linked. See X LINKAGE. underlying cause is an inherited inability to repair the damage to DNA in SKIN x coordinate (mathematics) A value on CELLS, brought about by exposure to the horizontal AXIS of a GRAPH. ULTRAVIOLET RADIATION. The disorder

418 XERORADIOGRAPHY X-RAYS is inherited as an autosomal RECESSIVE, is DOMINANT; its pattern of transmission and is one of the few clear-cut examples is similar, in that a father cannot pass it on of a genetic basis for CANCER. Fibroblasts to his sons. obtained from XERODERMA PIGMENTOSUM patients nave been used in the development XPS (physics) An abbreviation of ‘X’-RAY of MUTATION assays. ‘P’hotoelectron ‘S’pectroscopy. xeroradiography (radiology) A method X-ray crystallography (biochemistry) The of producing radiographs by a dry process. technique used for investigating the three dimensional structure of large molecules xipamide (pharmacology) A DIURETIC such as proteins and NUCLEIC ACIDS. drug of the THIAZIDE-related class. The WAVELENGTH of the X-RAYS used Administered orally it can be used in is similar to the inter-atomic distances ANTIHYPERTENSIVE treatment and in in these molecules, and the position of congestive HEART FAILURE treatment atoms can be deduced from the patterns and associated OEDEMA (USA: edema). of DIFFRACTION seen when X-RAYS are passed through them. X linkage (genetics) The situation in which a GENE is located on the X CHROMOSOME. X-ray diffraction (physics) Pattern of In males, with SEX CHROMOSOMES XY, VARIABLE intensities produced by any ALLELE on the X CHROMOSOME DIFFRACTION of X-RAYS when passed behaves as a DOMINANT, because there through a DIFFRACTION GRATING consisting is no corresponding ALLELE to mask it on of spacings of about 10-8cm, in particular the other CHROMOSOME (the Y does not that formed by the LATTICE of a crystal. behave as HOMOLOGOUS to the X). A male passes on to all his daughters any X-ray fluorescence (physics) Less GENE that he carries on the X penetrating, secondary X-RAYS emitted CHROMOSOME, but his sons will not inherit by a substance when subjected to primary it. A female who carries the same ALLELE X-RAYS or high-ENERGY electrons. The on one of her X CHROMOSOMES will not secondary X-RAYS are CHARACTERISTIC be affected, if the GENE is RECESSIVE as of the bombarded substance. most X-linked genes are. Such a female is known as a CARRIER, and passes on the X-ray spectrum (physics) Line SPECTRUM GENE to half of her offspring, sons and of the INTENSITY of X-RAYS emitted daughters alike: males who receive the GENE when a SOLID target is bombarded with will inherit the condition, females will be electrons. It consists of sharp superimposed carriers. It is possible for a female to inherit lines, which are CHARACTERISTIC of an X-linked GENE simultaneously from her the target atoms, on a continuous background. father (he will have the trait in question) and from her CARRIER mother, but this is X-ray tube (radiology) VACUUM tube rare (how rare depends on the FREQUENCY designed to produce X-RAYS by using an of the X-linked allele in the population). ELECTROSTATIC FIELD which accelerates Over 100 genes are known to be X-linked and directs electrons on to a target. in humans, including COLOUR BLINDNESS (USA: color blindness), Duchenne muscular X-rays (radiology) ELECTROMAGNETIC dystrophy and HAEMOPHILIA (USA: RADIATION produced in a partial hemophilia). Occasionally an X-linked GENE

419 XYLENE XYLOSE

VACUUM by the sudden arrest of high- ENERGY bombarding electrons as they collide with the heavy ATOM nuclei of a target METAL. The X-RAYS produced are thus CHARACTERISTIC of the target’s atoms. X-RAYS have very short wavelengths (103 to 1 nm) and can penetrate solids to varying degrees; this CHARACTERISTIC has made them useful in medicine, dentistry and X- RAY CRYSTALLOGRAPHY. Also termed: rontgen (ROENTGEN) rays; X-radiation.

xylene (chemistry) C6H4(CH3)2 Aromatic LIQUID ORGANIC COMPOUND that exists in three isomeric forms (ortho-, meta- and para-XYLENE), obtained from coaltar and petroleum. They are used as solvents in polyester SYNTHESIS, in microscopy for preparation of specimens and as cleaning agents. Also termed: DIMETHYLBENZENE.

xylose (chemistry) C5H10O5 Naturally occurring PENTOSE SUGAR, found in the form of xylan or as GLYCOSIDES in many plants (e.g. cherry and maple wood, straw, pecan shell, corn cobs and cottonseed hulls). Also termed: WOOD SUGAR.

420 Y

X (statistics) The ARITHMETIC MEAN. Yb (chemistry) The CHEMICAL SYMBOL for YTTERBIUM. Y (1 chemistry; 2 biochemistry) 1 The CHEMICAL SYMBOL for YTTRIUM. 2 Y chromosome (genetics) One of the SEX The symbol for TYROSINE. CHROMOSOMES and the third smallest in the human KARYOTYPE. In humans the Y1 adrenal cells (microbiology) A com- male has an X and a Y, while the female monly used continuous CELL line used has two X CHROMOSOMES. It is the in TISSUE CULTURE systems. presence of the Y CHROMOSOME that causes maleness to develop. The sex- YAC (genetics) An abbreviation of ‘Y’east determining GENE is on the short arm of ‘A’rtificial ‘C’hromosome. the Y CHROMOSOME, and individuals who are XY but have lost the short arm of the yard (measurement) UNIT of length equal Y develop as female, while the longer arm to 3 feet; there are 1,760 yards in 1 of Y CHROMOSOMES can apparently be mile. 1 YARD=0.9144 m. lost with no effect on the PHENOTYPE.

Yates correction (statistics) A correction y coordinate (mathematics) A value on for small samples in the calculation of the vertical AXIS of a GRAPH. chi-square in a 2-by-2 table, in which 0.5 is deducted from each figure exceeding yeast (mycology) A member of a GROUP expectation, and 0.5 is added to each of widespread UNICELLULAR FUNGI of figure that is less than the expected the CLASS Ascomycota. There are a very value. Assuming fixed marginal totals, large number of naturally occurring varieties. which is rarely appropriate, the effect is Some yeasts are pathogens, such as to bring the distribution of the calculated Candida albicans, and cause diseases such chi-square nearer to the continuous as THRUSH in humans. SACCHAROMYCES distribution from which the usual chi- CEREVISIAE is an important LABORATORY square tables are derived. Compare organism, and is the FOCUS of much genetic correction for continuity. research using RECOMBINANT DNA and DNA cloning techniques. yaws (medical/microbiology) A CHRONIC disease of the tropics, especially of Africa yeast artificial chromosome (YAC) and the West Indies, caused by TREPONEMA (genetics) A system used for producing pertenue, a SPIROCHAETE. The disease segments of DNA of more than 200,000 is also known as FRAMBOESIA, and pian. bases. GENETIC ENGINEERING techniques have been used to construct DNA molecules y-axis (mathematics) The AXIS perpen- that contain a YEAST CENTROMERE dicular to and in the horizontal plane and several YEAST genes. Segments of through the X-AXIS in any type of GRAPH. DNA can be inserted into such molecules and, when introduced into YEAST CELLS, 421 YEAST MUTATION TESTS YTTRIUM they behave like chromosomes and divide Yersinia pestis (microbiology) A member in step with the CELL. YACs have become of the GENUS YERSINIA. The agent important HOST vectors for cloning large responsible for bubonic plague, formerly regions of genomes. called Pasteurella pestis. yeast mutation tests (toxicology) In vitro Yersinia pseudotuberculosis (microbiol- test systems used to detect mutagenicity ogy) An organism that is very similar that have been developed with strains of biochemically to YERSINA PESTIS and the YEAST SACCHAROMYCES CERE- that causes infections that have a broad VISIAE which are capable of detecting clinical picture that closely resembles FORWARD MUTATIONS, reverse MUTA- that of YERSINIA ENTEROCOLITICA. TIONS and recombinant events such as RECIPROCAL or non-RECIPROCAL yolk (biology) Part of an OVUM that mitotic RECOMBINATION. stores the nutritive materials, or the yellow central portion of the EGG of birds and yellow fever (medical/microbiology) An reptiles. ACUTE and severe disease ENDEMIC in tropical America and Africa. It is caused yolk sac (microbiology) A tiny bag attached by a flavivirus of the togavirus FAMILY to the EMBRYO that provides early transmitted between humans by the bite nourishment before the PLACENTA is of the mosquito Aedes aegypti. formed. See YOLK SAC ISOLATION. yellow spot (MACULA lutea) (anatomy) yolk sac isolation (microbiology) A An alternative term for FOVEA. technique used for harvesting and increasing yields of chlamydiae and certain Yersinia (microbiology) A GENUS of VIRUSES. All known chlamydiae grow gram-negative ROD-shaped BACTERIA in the YOLK SAC of the embryonated of the FAMILY Enterobacteriaceae. This hen EGG. However, these techniques GENUS contains some important human are relatively slow and will not provide pathogens including YERSINIA PESTIS, an aetiologic diagnosis quickly enough YERSINIA ENTEROCOLICITA and to be clinically relevant. YERSINIA PSEUDOTUBERCULOSIS. ytterbium Yb (chemistry) Silvery-white Yersinia enterocolicita (microbiology) metallic ELEMENT in GROUP IIIA of The agent recognized as a cause of the PERIODIC TABLE (one of the enterocolitis and mesenteric LYMPH- LANTHANIDES), with no commercial uses. ADENITIS. Although some strains apparently At. no. 70; r.a.m. 173.04. produce a HEAT-STABLE enterotoxin that closely resembles that of ESCHERICHIA yttrium Y (chemistry) Grey metallic COLI, Yersinia enterocolitica is considered ELEMENT in GROUP IIIA of the PERIODIC an invasive PATHOGEN. Involvement of TABLE (one of the ALKALINE EARTHS, intestinal LYMPH NODES is common, but often classed with the LANTHANIDES). and the condition is difficult to distinguish It is used in ALLOYS for superconductors from ACUTE appendicitis. Only strains and magnets, and YTTRIUM(VI) OXIDE, pocessing essential VIRULENCE factors Y2O6, is employed in lasers and phosphors. are capable of causing human intestinal At. no.39; r.a.m. 88.9059. disease.

422 YTTRIUM-90 YTTRIUM-90

Yttrium-90 (radiology) An artificially produced RADIOACTIVE ISOTOPE of the ELEMENT YTTRIUM. The ISOTOPE emits BETA RAYS and is used for the TREATMENT of tumours (USA: tumors).

423 Z

z-axis (mathematics) The vertical AXIS CELLS, occuring, e.g. in prolonged fevers in any 3-dimensional CO-ORDINATE system. such as typhoid or in HEPATITIS. Also known as hyaline necrosis. Named after Z DNA (genetics) DNA in which the double the German Pathologist, Friedrich Albert HELIX is wound left-handed rather than von Zenker (1825–89). right-handed as NORMAL. The sugars do not fit together so well in this zeolite (chemistry) HYDRATED ALUMINO- CONFIGURATION, giving the MOLECULE SILICATE mineral, from which the WATER a jagged appearance. Z DNA has been is easily removed, used for making studied in Drosophila chromosomes, and MOLECULAR SIEVES and for ION it has been suggested that it has a role EXCHANGE columns. in GENE REGULATION. zero method (statistics) An alternative zearalenone (toxicology/microbiology) term for NULL METHOD. A MYCOTOXIN produced by the FUNGI Fusarium which is oestrogenic (USA: zero-order correlation (statistics) A estrogenic) and causes hyperoestrogenic correlation performed on the raw DATA (USA: hyperestrogenic) effects. It is found without first removing the effects of any on corn, barley, wheat, hay, oats. related variables. Compare partial correlation.

Zeeman effect (physics) Splitting of zeta potential (physics) POTENTIAL SPECTRAL LINES of a substance into DIFFERENCE that exists across the components of different FREQUENCY INTERFACE between a SOLID PARTICLE when placed in a MAGNETIC FIELD. It and a LIQUID in which it is immersed. was named after the Dutch physicist Also termed: ELECTROKINETIC POTENTIAL. Pieter Zeeman (1865–1943). Ziehl-Neelsen stain (microbiology) Zener current (physics) CURRENT produced Microbiological staining technique that in an INSULATOR in a strong ELECTRIC may be used to make ALCOHOL fast FIELD when its VALENCE BAND electrons bacilli, such as Mycobacterium tuberculosis, are raised to the CONDUCTION BAND. visible under the MICROSCOPE.

Zener diode (physics) Semiconductor zinc Zn (chemistry) Bluish-white metallic DIODE which at a certain negative VOLTAGE ELEMENT in GROUP MB of the PERIODIC produces a sharp breakdown of CURRENT TABLE (a TRANSITION ELEMENT), used and hence may be used as a VOLTAGE to give a corrosion-resistant coating to control device. Also termed: AVALAN- steel (galvanizing), to make dry batteries CHEDIODE; breakdown DIODE. and in various ALLOYS (e.g. brass, bronze). It is an essential TRACE ELEMENT which Zenker’s degeneration (histology) The are needed for ENZYME systems in the degeneration of STRIATED MUSCLE body. Although sufficient is normally present

424 ZINC CHLORIDE ZONE in the diet, deficiency results in stunted ELECTROLYTE in fuel CELLS. At. no. GROWTH, SKIN disease and inadequacy 40; r.a.m. 91.22. of the IMMUNE SYSTEM. At. no. 30; r.a.m. 65.38. zinc sulphide ZnS (chemistry) Occurs naturally as blende, an important ZINC zinc chloride (chemistry) ZnCI2 White ore, and can be prepared as a white HYGROSCOPIC SALT produced com- PRECIPITATE by adding ammonium mercially by heating metallic ZINC in SULPHIDE (USA: ammonium sulfide) or dry CHLORINE GAS. It is used to fireproof HYDROGEN SULPHIDE (USA: hydrogen timber, in BATTERY making, vulcanizing sulfide) to a SOLUTION of a ZINC SALT. and galvanizing, in oil refining, and as It is used as the pigmentary BASE for a FUNGICIDE and CATALYST. white ZINC SULPHIDE (USA: zinc sulfide) which contains up to 60 per cent ZINC zinc oxide (chemistry) ZnO White SULPHIDE and a BALANCE of BARIUM CRYSTALLINE SOLID (yellow when hot) SULPHATE (USA: barium sulfate). It is which can be produced directly by heating also used in FUNGICIDES and phosphors. ZINC in AIR. It is used as a white PIGMENT (USA: zinc sulfide). (Chinese white), in ceramics, cosmetics, pharmaceuticals and floor coverings, and ZN (microbiology) An abbreviation of ‘Z’IEHL- in the manufacture of tyres. It dissolves ‘N’EELSEN STAIN. in ALKALIS (USA: alkalies) to form zincates. Zn (chemistry) The CHEMICAL SYMBOL zinc sulphate (chemistry) ZnSO4.7H2O for ZINC. Colourless (USA: colorless) CRYSTALLINE SALT prepared by dissolving metallic Zollinger-Ellison syndrome (biochemistry/ ZINC in DILUTE SULPHURIC ACID (USA: histology) A severe form of STOMACH sulfuric acid). It is used in the manufacture and duodenal ulceration caused by an of rayon, glue, fertilizers, FUNGICIDES, excessive production of ACID by the wood preservatives, rubber, paint and STOMACH. This is stimulated by one or varnishes. Also termed: white copperas; more slow growing, and often maglignant, WHITE VITRIOL; ZINC VITRIOL. (USA: tumours (USA: tumors) of the PANCREAS, zinc sulfate). known as gastrinomas, that secrete a powerful HORMONE acting on the zincate (chemistry) COMPOUND formed STOMACH. Named after the American by the REACTION of metallic ZINC or surgeons Robert Milton Zollinger (b. 1903)

ZINC OXIDE with an ALKALI; e.g. Na2ZnO2. and Edwin H.Ellison (1918–1970). zirconium Zr (chemistry) Silvery-grey zolpidem tartrate (pharmacology) A metallic ELEMENT in GROUP IVA of hypnotic drug administered orally for the the PERIODIC TABLE (a TRANSITION short term treatment of insomnia. It acts ELEMENT). It is used to clad URANIUM in the same way as the benzodiazepine fuel rods in nuclear reactors. Naturally drugs. occurring CRYSTALLINE ZIRCONIUM(IV)

OXIDE, ZrO2, is the semi-precious gemstone zone (1 chemistry; 2 crystallography; 3 zircon; the OXIDE is also used as an mathematics) 1 Orientation of SOLUTE molecules in a SERIES of tubes in a LIQUID- LIQUID extraction procedure. 2 Crystal

425 ZOOL. ZYMOTIC faces that intersect along parallel edges. and SD the STANDARD DEVIATION. They 3 The part of a sphere that is enclosed have the following properties: (i) their between two parallel planes which intersect sum is zero; (ii) their STANDARD DEVIATION the sphere. Also termed: fresnel. is 1.0. zool. (biology) An abbreviation of zwitterion (chemistry) An ION carrying ‘zool’ogy. both a POSITIVE and a negative CHARGE, e.g. present in SOLID and zoology (biology) Systematic study of LIQUID amino acids such as GLYCINE, the ANIMAL KINGDOM. N +H3CH2COO-. zoomastigophorea (microbiology) A CLASS zygomycocosis (microbiology) A FUNGUS of flagellated PROTOZOA many of which INFECTION in which masses of various cause diseases such as LEISHMANIASIS, FUNGI form in the nasal sinuses, under trichomoniasis and TRYPANOSOMIASIS. the SKIN of the face and in other parts of the body especially in people with zoonosis (microbiology) Any disease of immune deficiency. animals which may be transmitted to human beings. Examples are plague and RABIES; zygosis (genetics) The union of two gametes. ANTHRAX, Q FEVER and salmonella infections; all kinds of worm infestations, zygote (genetics) The individual as it and various VIRUS, rickettsial, leptospiral exists at the moment of fertilization, i.e. and FUNGUS infections; BRUCELLOSIS, the DIPLOID CELL that results from the ORNITHOSIS, and GLANDERS. FUSION of two gametes. See HYBRID. zopiclone (pharmacology) A hypnotic zygotene (genetics) One of the stages drug, which works in the same way as in MEIOSIS. the benzodiazepine drugs, which can be administered orally for the short-term zymase (chemistry) ENZYME that catalyses treatment of insomnia. the FERMENTATION of carbohydrates to ETHANOL (ETHYL ALCOHOL). zoster (virology) See HERPES ZOSTER. zymogen (biochemistry) Inactive zovirax (pharmacology) See ACYCLOVIR. PRECURSOR of an ENZYME. It is activated by the ACTION of a KINASE. Also termed: ZPP (haematology) An abbreviation of PROENZYME. ‘Z’inc ‘P’roto‘P’orphyrin. See FREE ERYTHROCYTE PROTOPORPHYRIN. zymogenesis (biochemistry) The conversion of an ENZYME PRECURSOR Zr (chemistry) The CHEMICAL SYMBOL to the active state. for ELEMENT 40, ZIRCONIUM. zymotic (microbiology) Describing an z-score (statistics) A score expressed agent that causes an INFECTIOUS as the number of units of STANDARD DISEASE. DEVIATION above or below the MEAN, according to the FORMULA, z=(X-M)/ SD, where X is the score, M the MEAN,

426 Appendices

1. Reference Ranges

2. Metric Conversions

3. Organizations of Biomedical Science

4. Select Bibliography and Further Reading Appendix 1 Reference Ranges Blood constituents Values are for adults and refer to plasma/serum except as indicated*

Electrolytes and blood gases

Osmolarity 280–298 mmol/kg

pCO2 (arterial) 4.5–6.1 kPa

pO2 (arterial) 11–15 kPa pH (arterial) 7.35–7.45 Sodium 134–147 mM Potassium 3.5–5.0 mM Chloride 96–106 mM Bicarbonate 21–30mM Phosphate 0.7–1.4 mM Sulphate 0.25–0.38 mM Calcium 2.1–2.7 mM Magnesium 0.7–1.3 mM Copper 1 2–30 µM Zinc 12–24 µM Lead <2.4 µM

Haemoglobin and blood cells

Haemoglobin* 13–17 g/dl (males) 11–15 g/dl (females) Erythrocytes (red cell count)* 4.5–6.5×1012/l (males) 3.9–5.6×1012/l (females) Packed cell volume (PCV)* 0.41–0.53 l/l (males) 0.35–0.48 l/l females) Mean corpuscular volume (MCV) 76–96 fl Mean corpuscular haemoglobin (MCH) 26–33 pg/cell Mean corpuscular haemoglobin 31–35 g/dl concentration (MCHC)* Leukocytes (white cell count)* 4–6×109/l Platelets* 2–4×1011/l Reticulocytes* 0.5–2.5% red cells Glucose 6-phosphate dehydrogenase 5–15 U/g Hb (erythrocyte)* Pyruvate kinase (erythrocyte)* 13–17 U/g Hb Iron 10–30 µM Total iron-binding capacity (TIBC) 40–70 µM

428 Nitrogenous constituents and amino acids

Ammonia 12–60 µM Urea 2.5–7.0 mM Creatinine 53–124 µM Uric Acid 0.18–0.42 µM Alanine 0.2–0.3 mM Glutamine 0.45–0.75 mM Citrulline 10–30 µM Phenylalanine 0–0.12 mM

Organic constituents

Glucose (fasting) 3.5–5.5 mM Lactate 0.6–1.8 mM Pyruvate 0.03–0.11 mM Citrate 0.08–0.16 mM Bilirubin (total) 3–15 µM

Vitamins

Ascorbic acid (C) 20–100 µM Biotin 2.5–5.5 µM

Cholecalciferol (D3) 0.07 µM

Cobalamin (B12) 0.15–0.67 nM Folic acid 15–80 nM Niacin (nicotinic acid) 50 µM Pantothenic acid 1.3 µM Retinol (A) 0.3–2.1 µM

Riboflavin (B2) 0.07–0.1 µM

Thiamine (B1) 0.2–0.3 µM a-Tocopherol (E) 20–45 µM

Lipids (fasting)

Triglyceride 0.6–3.2 mM Cholesterol 3.7–6.8 mM Fatty acids (total) 0.2–0.8 mM

429 Proteins

Total protein 60–84 g/l Albumin 35–50 g/l Globulins (total) 23–35 g/l IgG 7–15 g/l Lipoprotein (HDL) 3–8 g/l Ceruloplasmin 0.2–0.4 g/l

Clotting factors

Fibrinogen 2–4 g/l Plasminogen 0.3 g/l Prothrombin 0.1 g/l

Enzymes*

Acid phosphatase 4–11 Alkaline phosphatase 100–300 Aldolase 2–12 Creatine kinase (CK) 20–150 Lactate dehydrogenase (LDH) 45–90 Amylase 70–300 g-Glutamyl transferase (GGT)†† 7–45 Aspartate transaminase (AST)§ 10–40 Alanine transaminase (ALT)§§ 5–35 Serum lipase 28–280 Cholinesterase 39–51 a-Fucosidase 4.5–14.0 a-Galactosidase 0.22–0.50 b-Galactosidase 0.4–1.1 a-Mannosidase 0.35–0.90 N-Acetyl-a-glucosaminidase 0.15–0.40 N-Acetyl-ß-glucosaminidase 12–25 p-Nitrocatechol sulphatase 0.04–0.12 a-Glucosidase 0.1–0.25

* Enzyme activities in units/l (U/I) † PCV also expressed as %=l/l×100. †† Serum g-glutamyl transpeptidas (g-GT) § Serum glutamate-oxaloacetate transaminase (SGOT) §§ Serum glutamate-pyruvate transaminase (SGPT)

430 Urinary constituents The daily (24 hour) excretion of many constituents will vary considerably from subject to subject depending on diet, age, sex, exercise, etc. Therefore, the values listed in this Appendix are only very approximate.

Volume 1–2 l/day PH 4.8–7.5 (mean 6.0)

Nitrogen compounds

Total nitrogen 600–1400 mmol/day Urea 300–640 mmol/day Ammonia 60–110 mmol/day Uric acid 2–6 mmol/day Creatinine 7–17 mmol/day Amino acids 7–21 mmol/day Protein 0–150 mg/day

Electrolytes

Titratable activity (H+) 15–50 mmol/day Sodium 180–440 mmol/day Potassium 40–80 mmol/day Calcium 5–12 mmol/day Magnesium 4–8 mmol/day Chloride 100–260 mmol/day Sulphate (as S) 18–56 mmol/day Phosphate (as P) 23–52 mmol/day Lead 0–500 nmol/day Copper 0–1.6 µmol/day

Porphyrins d-Aminolævulinic acid 0–40 µmol/day Porphobilinogen 0–16 µmol/day Coproporphyrin 0–380 nmol/day Urobilinogen 0–7 µmol/day Uroporphyrin 0–49 nmol/day

Others

Glucose negative Ketones negative Citrate 1.0–5.7 mmol/day 17-ketosteroids 3–56 µmol/day 17-hydroxysteroids 8–22 µmol/day 431 Appendix 2 Metric conversions

Distance Capacity

1 inch=2.54 centimetres 1 cubic inch=16.387 cubic centimetres 1 foot=0.3048 metre 1 cubic foot=0.0283 cubic metre 1 yard=0.9144 metre 1 cubic yard=0.7646 cubic metre 1 rod=5.0292 metres 1 cubic centimetre=0.061 cubic inch 1 chain=20.117 metres 1 cubic decimetre=0.035 cubic foot 1 furlong=201.17 metres 1 cubic metre=1.308 cubic yard 1 mile=1.6093 kilometre 1 nautical mile=1.8532 kilometre Dry measure (Imperial)

1 millimetre=0.03937 inch 1 pint=0.5506 litre 1 centimetre=0.3937 inch 1 quart=1.136 litres 1 decimetre=0.3281 foot 1 gallon=4.546 litres 1 metre=3.281 feet 1 peck=9.092 litres 1 metre=1.094 yard 1 bushel=36.369 litres 1 decametre=10.94 yards 1 kilometre=0.6214 mile 1 kilometre=0.539 nautical mile Liquid measure (USA)

1 pint=0.473 litre Surface or area 1 quart=0.9463 litre 1 gallon=3.785 litres 1 square inch=6.4516 square 1 peck=8.809 litres centimetres 1 bushel=35.24 litres 1 square foot=929.03 square centimetres 1 square yard=0.8361 square metre Avoirdupois weight 1 acre=4046.9 square metres 1 square mile=259.0 hectares 1 ounce=28.35 grams 1 square centimetre=0.1550 square 1 pound=453.59 grams inch 1 hundredweight=50.802 kilograms 1 square metre=1550 square inches 1 ton=907.18 kilograms 1 acre=119.6 square yards 1 gram=0.035 ounce 1 hectare=2.4711 acres 1 hectogram=3.527 ounces 1 square kilometre=0.3861 square mile 1 kilogram=2.205 pounds 1 ton=1.102 ton (short) Temperature conversion

Celsius°=5/9 (Fahrenheit°-32°) Fahrenheit°=9/5 Celsius°+32° Appendix 3 Organizations of Biomedical Science

Biomedical science incorporates information from a large number of disciplines and worldwide there are many hundreds of associations, societies and other organisations dedicated to various aspects. The following information contains the contact addresses of a selection of key organisations in the United Kingdom, Ireland and the United States of America relevant to biomedical science from which specialised information and assistance may be sought. These are listed under headings indicating the scientific areas in which they are particularly involved. Although it is appreciated that some of the organisations indicated may be involved in many aspects of biomedical scientific practice and research and could legitimately be included under more than one heading, only one entry per organisation has been included. It is hoped, however, that the listing provides a useful guide, as a starting point, to identifying sources of information being sought.

Anatomy American Association of Anatomists (AAA) 9650 Rockville Pike Bethesda Maryland United States of America

British Association of Clinical Anatomists (BACA) Department of Human Anatomy and Cell Biology New Medical School The University of Liverpool Ashton Street Liverpool L69 3GE United Kingdom Biochemistry American Society for Biochemistry and Molecular Biology (ASBMB) 9650 Rockville Pike Bethesda Maryland United States of America

Association of Clinical Biochemists (ACB) 130–132 Tooley Street London SE1 2TU United Kingdom

Biochemical Society 59 Portland Place London W1B 1QW United Kingdom

Biology Institute of Biology (IOB) 20–22 Queensberry Place London SW7 2DZ United Kingdom

Biophysics British Biophysical Society (BBS) Department of Chemistry University of York Heslington York Y01 5DD United Kingdom

Cancer American Institute for Cancer Research (AICR) 1759 R Street NW Washington DC 20009 United States of America

British Association for Cancer Research (BACR) Cotswold Road Sutton Surrey SM2 5NG United Kingdom

434 Cell Biology British Society for Cell Biology (BSCB) Department of Zoology University of Cambridge Downing Street Cambridge CB2 3EJ United Kingdom

Cytology British Society for Clinical Cytology (BSCC) Thorn EMI Central Research Laboratories Dawley Road Hayes Middlesex UB3 1HH United Kingdom

Epidemiology PHLS Communicable Disease Surveillance Centre (CDSC) 61 Colindale Avenue London NW9 5EQ United Kingdom

General Institute of Biomedical Sciences (IBMS) 12 Coldbath Square London EC1R 5HL United Kingdom

Genetics The Genetical Society Department of Biology University of York Heslinton York YO1 5DD United Kingdom

Haematology British Society of Haematology (BSH) 2 Carlton House Terrace London SW1Y 5AF United Kingdom

Histology Anatomical Society of Great Britain and Ireland (ASGBI) Department of Anatomy National University of Ireland Cork Ireland

435 Immunology American Association of Immunologists (AAI) 9650 Rockville Pike Bethesda Maryland United States of America

British Society for Allergy and Clinical Immunology (BSACI) 66 Weston Park Thames Ditton Surrey KT7 OHL United Kingdom

British Society for Immunology (BSI) Triangle House Broomhill Road London SW18 4HX United Kingdom

Medicine American Medical Association (AMA) 515 N State Street Chicago Illinois 60610 United States of America

British Medical Association (BMA) BMA House Tavistock Square London WC1H 9JP United Kingdom

Royal Society of Medicine (RSM) 1 Wimpole Street London W1M 8AE United Kingdom

Microbiology American Society for Microbiology (ASM) 1752 N Street NW Washington DC 20036 United States of America

436 Association of Medical Microbiologists (AMM) Public Health Laboratory Birmingham Heartlands Hospital Bordesley Green East Birmingham B9 5SS United Kingdom

Society for General Microbiology (SGM) Marlborough House Basingstoke Road Spencers Wood Reading RG7 1AE United Kingdom

Microscopy Royal Microscopical Society (RMS) 37/38 St Clements Oxford OX4 1AJ United Kingdom

Mycology British Society for Mycopathology (BSM) MRC Immunology Laboratories Sully Hospital Penarth South Glamorgan CF6 2YA United Kingdom

Neuroscience British Society Clinical Neurophysiology (BSCN) Department of Neurophysiology Middlesex Hospital Mortimer Street London W1N 8AA United Kingdom

Parasitology British Society for Parasitology (BSP) Triangle House Broomhill Road London SW18 4HX United Kingdom

Pharmacology British Pharmacology Society (BPS) 16 Angel Gate City Road London EC1V 2SG United Kingdom

437 Physiology British Biophysical Society (BBS) Department of Chemistry University of York Heslington York YO1 5DD United Kingdom

Physiological Society PO Box 11319 London WC1E 7JF United Kingdom

Public Health Centers for Disease Control and Prevention (CDC) 1600 Clifton Road Atlanta GA 30333 United States of America

Public Health Laboratory Services (PHLS) 61 Colindale Avenue London NW9 5HT United Kingdom

Royal Institute of Health and Hygiene and Society of Public Health 28 Portland Place London W1B 1DE United Kingdom

Radiology British Institute of Radiology (BIR) 36 Portland Place London W1B 1AT United Kingdom

Toxicology British Toxicology Society (BTS) PO Box 249 Macclesfield Cheshire SK11 6FT United Kingdom

438 Virology American Society for Virology (ASV) Howard Hughes Medical Institute Department of Biochemistry, Molecular Biology and Cell Biology Northwestern University 2153 North Campus Drive Evanston IL 60208–3500 United States of America

439 Appendix 4

Select Bibliography and Further Reading List

Books Academic Press Dictionary of Science and Technology, Academic Press Inc, 1992. Anderson KN, Anderson L, Glanze WD, Mosby’s Medical, Nursing, and Allied Health Dictionary, Mosby, 1994. Blackwell’s Dictionary of Nursing, Blackwell Science (UK), 1997. Borowski EJ, Borwein JM, Dictionary of Mathematics, HarperCollins, 1999. Brown JAC, Pears Medical Encyclopaedia, Little, Brown and Company, 2000. Calbreath DF, Clinical Chemistry, WB Saunders Co. Ltd, 1992. Cassell Dictionary of Science, Ward Lock, 1999. Chambers Dictionary of Science and Technology, Chambers, 2000. Clugston MJ (ed), The New Penguin Dictionary of Science, Penguin Books, 1998. Coatrieux, The Biomedical Engineering Dictionary, Academic Press Inc, 2000. Collin PH, Dictionary of Medicine, Peter Collin Publishing, 2000. Collin S, Dictionary of Science and Technology, Peter Collin Publishing, 2000. Compact American Library Medical Dictionary, American Heritage Dictionaries, Houghton Mifflin Co., 1999. Concise Science Dictionary, Oxford University Press, 1996. Daintith J, Oxford’s Dictionary of Chemistry, Oxford University Press, 1996. Dictionary of Science, Brockhampton Press, 1997. Dictionary of the Sciences, Harcourt Publishers Ltd, 2000. Dupayrat J, Dictionary of Biomedical Acronyms and Abbreviations, John Wiley and Sons, 1990. Everitt B, Cambridge Dictionary of Statistics, Cambridge University Press, 1998. Everitt BS, The Cambridge Dictionary of Statistics in the Medical Sciences, Cambridge University Press, 1995.

440 Farr AD, Dictionary of Medical Laboratory Sciences, Blackwell Science (UK), 1988. Fukui S, Schmid R, Dictionary of Biotechnology, Springer-Verlag Berlin and Heidelberg GmbH & Co. KG, 1986. Ganong WF, Review of Medical Physiology, Appleton and Lange, 1995. Gard P, Human Pharmacology, Taylor and Francis, 2001. Gray H, Gray’s Anatomy, Parragon, 1998. Griffin JP, Hematology and Immunology Concepts for Nursing, Appleton Century Crofts, 1986. Hale WG, Margham JP, Saunders VA, Dictionary of Biology, HarperCollins, 1999. Harrap’s Dictionary of Science and Technology, Harrap, 1991. Harrison P, Waites G, Cassell Dictionary of Chemistry, Ward Lock, 1999. Heister R, Dictionary of Abbreviations in Medical Sciences, Springer- Verlag Berlin and Heidelberg GmbH & Co. KG, 1989. Herbert WJ, Wilkinson PC, Dictionary of Immunology, Blackwell Science (UK), 1985. Higgins SJ, Turner AJ, Wood EJ, Biochemistry for the Medical Sciences, Longman Group Ltd, 1994. Hodgson E, Mailman RB, Chambers JE (eds), Dictionary of Toxicology, Macmillan Reference Ltd, 1998. Hodson A, Essential Genetics, Bloomsbury, 1992. Howell DC, Statistical Methods for Psychology, Duxbury Press, 1997. Hull D and Johnson DI, Essential Paediatrics, Churchill Livingstone, 1994. Lafferty P, Rowe J, The Dictionary of Science, Prentice Hall, 1994. Lewis RJ Sr, Hawley’s Condensed Chemical Dictionary, John Wiley and Sons, 1997. McLaren DS, Meguid MM, Nutrition and its Disorders, Churchill Livingstone, 1988. McGraw-Hill, Dictionary of Bioscience, McGraw-Hill Publishing Company 1996. MacPherson G, Black’s Medical Dictionary, A & C Black, 1999. Martin CR, Dictionary of Endocrinology and Related Biomedical Sciences, Oxford University Press Inc, USA, 1995. Merrell S (ed), Medicines, Bloomsbury Publishing Plc, 1995. Millodot M, Dictionary of Optometry and Visual Science, Butterworth- Heinemann, 2000. Muir H, Walker P, Larousse Dictionary of Science and Technology, Kingfisher Chambers Harrap, 1995. Oxfords’ Concise Medical Dictionary, Oxford University Press, 1998. Oxford’s Science Dictionary, Oxford University Press, 1999.

441 Pearce EC, Pearce’s Medical and Nursing Dictionary and Encyclopaedia, Mosby, 1983. Potparic O, Gibson J, A Dictionary of Medical and Surgical Syndromes Parthenon Publishing, 1991. Reuter P, Birkhauser Pocket Dictionary of Biochemistry, Birkhauser Verlag AG, 2000. Rowland LP, Wood DS, Schon EA, et al., Molecular Genetics in Diseases of Brain, Nerve, and Muscle, Oxford University Press, 1989. Roper N, Churchill Livingstone Pocket Medical Dictionary, Harcourt Publishers Ltd, 1988. Roper N, New American Pocket Medical Dictionary, Prentice Hall, 1988. Ross is, Wilson KJW, Foundations of Anatomy and Physiology, Churchill Livingstone, 1984. Smith AD, Datta SP, Smith G, et al., Oxford Dictionary of Biochemistry and Molecular Biology, Oxford University Press, 1997. Stedman’s Concise Medical and Allied Health Dictionary, Lippincott Williams and Wilkins, 1997. Stenesh J, Dictionary of Biochemistry and Molecular Biology, John Wiley and Sons, 1989. The Hutchinson Dictionary of Science, Helicon, 1998. The Wordsworth Dictionary of Science and Technology, Wordsworth Editions Ltd, 1995. Uvarov EB, Isaacs A, Penguin Dictionary of Science, Penguin Books, 1993. Vogt WP, Dictionary of Statistics and Methodology, A Non-Technical Guide for the Social Sciences, Sage Publications Ltd, 1993. Walker P, Chambers Science and Technology Dictionary, Kingfisher Chambers Harrap, 1991. Webster’s New American Dictionary, Merriam-Webster Inc, 1995. Wilson J, Hunt T, Molecular Biology of the Cell, Garland Publishing Inc, 1994. Youngson RM, Dictionary of Medicine, HarperCollins, 1999.

Journals and Periodicals Advances in Applied Probability (Quarterly), Applied Probability Trust. Analyst (Monthly), The Royal Society of Chemistry. Annals of Clinical Biochemistry (Bi-monthly), The Royal Society of Medicine Press Ltd. Aspects of Applied Biology (3 Issues Yearly), Association of Applied Biologists. Biochemical Society Transactions (Bi-monthly), Portland Press Ltd.

442 Biochemist (Bi-monthly), The Biochemical Society. Biomedical Materials (Monthly), International Newsletters. Biomedical News (10 Issues Yearly), Quantum Publishing Ltd. Biomedical Scientist (Monthly), Institute of Biomedical Sciences. Brain: A Journal of Neurology (Monthly), Oxford University Press. British Journal for the Philosophy of Science (Quarterly), Oxford University Press. British Journal of Biomedical Science (Quarterly), The Royal Society of Medicine Press Ltd. British Medical Journal (Weekly), British Medical Association. CLI Clinical Laboratory International (8 Issues Yearly), Pan European Publishing Co. Clinical & Experimental Immunology (Monthly), Blackwell Science Ltd. Comparative Haematology International (Quarterly), Springer-Verlag London Ltd. Current Opinion in Neurobiology (Bi-monthly), Current Biology Ltd. European Clinical Laboratory (Bi-monthly), International Scientific Communications. Experimental Physiology (Bi-monthly), Cambridge University Press. Gene Therapy (Monthly), Stockton Press. Genes & Function (Bi-monthly), Blackwell Science Ltd. Health and Hygiene (Quarterly), The Royal Institute of Public Health and Hygiene. Human and Experimental Toxicology (Monthly), Stockton Press. Infection and Immunity (Monthly), American Society for Microbiology. Immunology Today (Monthly), Elsevier Science Ltd. International Biotechnology Laboratory (Bi-monthly), International Scientific Communications. International Journal of Systematic Bacteriology (Quarterly), The Society for General Microbiology. Journal of Applied Toxicology (Bi-monthly), John Wiley and Sons Ltd. Journal of Bacteriology (24 issues Yearly), American Society for Microbiology. Journal of Comparative Pathology (8 Issues Yearly), WB Saunders Co. Ltd. Journal of Electron Microscopy (Bi-monthly), Oxford University Press. Journal of Gene Medicine (Bi-monthly), John Wiley and Sons Ltd. Journal of Medical Engineering & Technology (Bi-monthly), Taylor and Francis Ltd. Journal of Molecular Recognition (Bi-monthly), John Wiley and Sons Ltd. Journal of Neurovirology (Bi-monthly), Stockton Press. Journal of Pathology (Monthly), John Wiley and Sons Ltd. Journal of Virology (24 issues Yearly), American Society for Microbiology. Laboratory News (Monthly), Quantum Publishing Ltd.

443 Lancet (Weekly), The Lancet Ltd. Luminescence: The Journal of Bioluminescence and Chemical Luminescence (Bi-monthly), John Wiley and Sons Ltd. Medical & Biological Engineering & Computing (Bi-monthly), Peter Peregrinus Ltd. Medical Computing (Bi-monthly), Healthworks Ltd. Medical Mycology (Bi-monthly), Blackwell Science Ltd. Microbial Pathogenesis (Monthly), Academic Press Ltd. Microscopy & Imaging News (Quarterly), Quantum Publishing Ltd. Nature: International Weekly Journal of Science (Weekly), Macmillan Magazines Ltd. Neuropathology and Applied Neurobiology (Bi-monthly), Blackwell Science Ltd. New Scientist (Weekly), Reed Business Information Ltd. NMR in Biomedicine (8 Issues Yearly), John Wiley and Sons Ltd. Optics and Laser Technology (8 Issues Yearly), Elsevier Science Ltd. Optometry Today Inc., The Scottish Optometrist (24 Issues Yearly), Association of Optometrists. Radiology Now (3 Issues Yearly), Franklin Scientific Projects. Receptor & Ion Channel Nomenclature Supplement (Annual), Elsevier Trends Journals. RNA (Monthly), Cambridge University Press. Science (Weekly), American Association for the Advancement of Science. Trends in Neurosciences (Monthly), Elsevier Trends Journals. Ultrasound in Obstetrics & Gynecology (Monthly), The Parthenon Publishing Group Ltd. Visual Neuroscience (Bi-monthly), Cambridge University Press.

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