All Questions to Be Answered I-Put True Or False(16 Marks)

Alexandria University Medical Research Institute Histochemistry and cell biology Department Semester: Fall Master Degree Academic year: 2019– 2020 Course title: microtechnique 1 Time allowed: 2 hours Course code: 1709701 Date: 31/ 12/ 2019 Final exam(model answer) Total marks: 60 ______All questions to be answered I-Put true or False(16 marks)

1- Zenker's fixatives is highly recommended for fixation of testis, GI tract, and endocrine tissue ( )

2- Fixation by Microwaves irradiation speed fixation and increase time of fixation of some gross specimens( )

3- Formalin is a coagulant fixative while Mercuric chloride is non-coagulant ( )

4- cold formalin will fix tissues faster, and this is often the first step on an automated tissue processor ( )

5- Wet fixed tissues (in aqueous solutions) can be directly infiltrated with paraffin ( )

6- It is highly recommended for Specimen to be left on absorbent surface for some time prior to fixation ( )

7- Cross linking fixatives act by creating ionic chemical bonds between proteins in tissue ( )

8- Glutaraldehyde causes deformation of Beta-helix structure in proteins so is not good for immunoperoxidase staining ( )

9- The oxidizing fixatives can react with various side chains of proteins and other biomolecules and are used mainly as primary fixatives ( )

10- Precipitating fixatives are not good for cytological smears because they act quickly ( )

11- Hepes-glutamic acid buffer-mediated organic solvent protection effect (HOPE) fixative is good for molecular studies as RNA and DNA yields is good in presence of crosslinking proteins ( )

12- The heat in microwave is a secondary factor in tissue fixation process ( )

13- Hypoxia of tissues increases the pH, so there must be buffering capacity in the fixative to prevent excessive acidity ( )

14- Acetone is very fast dehydrant, but a fire hazard, so is safe only for large, hand processed sets of tissues( )

15- In Masson's trichrome all tissues structures stain red collagen fiber will stain green ( T )

16- Argyrophilia dependent upon the reactive groups present in the carbohydrate matrix & upon the proteins of the fibrils themselves ( F )

17- carbohydrate-rich interfibrillar material ( T )

18- Weigert'sResorcin-fuchsin stain elastic fibers stain dark blue to black ( T )

19- Elastic fiber are basophilic ( F )

20- Verhoeff stain result in staining Elastic fiber& nuclei black. Other pink to red ( T )

21- Under normal conditions glycogen is extracytoplasmic ( F )

22- Periodic acid Schiff (PAS) stain, it is specific for glycogen without controls ( F )

23- After completing an experiment, all chemicals wastes should be dumped in the sink ( F )

24- When gathering glassware and equipment for an experiment, you should examine all glassware to check for chips and cracks. ( T )

25- If an acid is splashed on your skin, wash it once with weak base.( F )

26- To remove solid chemicals from a bottle, use your spoon to get the required amount ( F )

27- When working with an experiment under a fume hood, keep fume hood sash as down as far as possible ( T )

28- If liquid chemicals are to be mixed with water, always add the concentrated chemical to water( T )

29- If a fire occurs during a lab period, you should leave your experiment as is and leave the room ( F )

30- It is ok to store oxidizing material near flammable or reactive materials ( F )

31- To prevent inhalation of toxic chemical vapors, do your experiments near an open window ( F )

32- Water bath is much safer source of heat for experiments than open-flames ( T )

II-Choose the correct answer:(8 marks) 1- The term “special stains” refers to a large number of staining techniques, other than ….. a-Masson's trichrome b-H&E c-Van Gieson stain d- all above

2- H& E allow …….. a-the visualization of particular tissue structures b-the visualization of elements c-the visualization of microorganisms that cannot be identified d- all above

3- Special stains are classified into ….. categories a-2 b-3 c-4 d-6

4- The connective tissue stains collagen stains Include …………. a-Masson's trichrome b-Weigert_vanGieson stain c-Sliver impregnation method d-(a&b) 3

5 - In Masson's trichrome After applying nuclear stain the section stained first by a- small Mw acid dye b-small Mw base dye c-small Mw neutral dye d- non of them

6- Reticulin stains include ……… a-Van Gieson stain b-Masson's trichrome c-Weigert_vanGieson stain d-non of them

7- Sliver impregnation method result that Reticular fibers stain ……… a-grey b-black c-red d-non of the above

8- Elastic fiber stains include …….. a-Verhoeff stain b-Weigert's Resorcin-fuchsin stain c- both of them d-non of them

9-Personal eyeglasses provide as much protection as: a-A face shield. b-Safety glasses. c-Splash-proof chemical goggles. d-None of the above.

10- Good way to test if a container or a piece of equipment is hot, is to: a-Pick the object up. b-Touch the object. c-Place the back of your hand near any object before picking it up. d-Spraying it with cold water to see if it spatters.

11-What is the best way to smell chemicals in lab? a-Take short direct sniffs from the container. b-Take one deep, slow sniff from the container. c-Waft the fumes towards your nose by waving your hand over the mouth of the container. d-Stir and shake the chemical well to allow the odour to come out.

12- If you spill solid chemicals on a balance: a-Clean it immediately using water. b-Brush off any spills. c-Ignore it since you are not trained to handle spilled chemicals. d-Clean it using oil

13- You should always hold containers that have chemicals: a-With a pair of tongs. b-Close to your chest and with a strong grip. c-Away from your body. d-None of the above.

14- Damaged or exposed electric cord: a-Can be used only if you know how to fix it. b-Can be used only with caution and care. c-Should be dried out completely to avoid electric shock. d-None of the above.

15- Small burns from touching hot objects should be: a-Placed under running cold water. b-Covered immediately with a band-aid. c-Massaged gently until it feels better. d-Brought closer to the air conditioner to cool it off.

16-A fire occurs in the laboratory, the first course of action is to: a-Evacuate the entire area. b-Pull the fire alarm box. c-Remove persons from immediate danger. d-Contain the fire by closing doors

III-Match the following (6 marks)

1.Special stains are specific stains for L. connective tissue

2.The connective tissue stains which is used for staining the K.Masson’s trichrome collagen fibers

3.Stains which used for staining the reticulin fibers include I. silver impregnation method

4. Elastic fibers stains include F. Verhoeff's stains

5.Sudan stain is a special stain used for staining H. Fats.

6.Carbohydrates are stained with A. periodic acid Schiff satin (PAS)

7. The formed complex of hematoxylin is J. hemalum

8.Nuclear staining occurs after the in vitro

oxidation of Hematoxylin to E. Hematin.

9.Feulgen reaction is a selective staining for B. DNA

10.During using Feulgen stain we use any fixative

except

IV-Write Briefly on:

1-special stains categories . (5 marks)

1- Specific stains of of particular tissue structures such as connective tissue eg . collagen fibers, reticular fibers and elastic fibers 2- Specific stains for particular tissue elements eg .carbohydrates, iron, mucin and amyloid 3- Specific stains for micro-organisms eg. Bacteria and fungi

2-Classification of carbohydrates. (5 marks)

1) simple carbohydrates : monosaccharides ( Glucose )- oligosaccharides ( lactose)- polysaccharides (glycogen)- 2) mucosubstances : mucopolysaccharides (mucin)- mucoproteins - mucolipids

3- the mechanism of action of Precipitating (denaturing) fixatives. (5 marks)

4- Honing of microtome knife. (5 marks)

o The purpose of honing is to remove fine nicks in the cutting edge of microtome knife. (1 Mark) o The hone is first wiped clean with a soft cloth moistened in xylene, then covered with a thin film of lubricant (a light machine oil). (1 Mark) o The knife is fitted with its own back and laid obliquely on the stone, edge forwards. (1 Mark) o Gentle to firm pressure is made on the knife with the thumbs of forefingers and the knife drawn obliquely forwards on the stone in an easy steady motion. (1 Mark) o When the other end of the stone is reached, the knife is then reversed and drawn towards the operator. Such sequence forms a double stroke, and about 20 to 30 such strokes usually suffices. (1 Mark)

5- Cryostat. (5 marks)

o Cryostat consists of rotary microtome contained within a refrigerated cabinet designed to operate at -5°C to -30°C. The microtome can be operated by various controls fitted outside the cabinet. (1 Mark) o All cryostats incorporate an anti-roll plate either of plastic material (with a low coefficient of friction) or are in the form of a glass plate coated by spraying with similar material. (1 Mark) o Its purpose is to keep the sections flat on the knife blade for subsequent direct mounting onto a slide or cover slip. (1 Mark) o The exact temperature best suited to the preparation of sections in cryostat will vary according to the type of tissue and the section required. (1 Mark) o In general, a cabinet temperature of -15°C to -20°C provides suitable conditions for a wide range of tissues. (1 Mark)

6- Storage of compressed gas cylinders. (5 marks)

o Securely attach all gas cylinders (empty or full) to a wall or a laboratory bench with a clamp or chain in an upright position. (1 Mark) o Store cylinders by gas type, separating oxidizing gases from flammable gases. (1 Mark) o Store gas cylinders in cool, dry, well ventilated areas away from incompatible materials and ignition sources. (1 Mark) o Do not subject any part of a cylinder to a high temperature. (1 Mark) o Always attach valve safety caps when storing cylinders, store empty cylinders separately from full cylinders. (1 Mark)