DOCSLIB.ORG

The Conscious Cell

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
The Conscious Cell The Conscious Cell LYNN MARGULIS Department of Geosciences, University of Massachusetts, Amherst, Massachusetts 01003-5820, USA ABSTRACT: The evolutionary antecedent of the nervous system is “microbial consciousness.” In my description of the origin of the eukaryotic cell via bacte- rial cell merger, the components fused via symbiogenesis are already “con- scious” entities. I have reconstructed an aspect of the origin of the neurotubule system by a hypothesis that can be directly tested. The idea is that the system of microtubules that became neurotubules has as its origin once-independent eubacteria of a very specific kind. Nothing, I claim, has ever been lost without a trace in evolution. The remains of the evolutionary process, the sequence that occurred that produced Cajal’s neuron and other cells, live today. By study of obscure protists that we take to be extant decendants of steps in the evolution of cells, we reconstruct the past directly from living organisms. Even remnants of “microbial mind” can be inferred from behaviors of thriving microorgan- isms. All of the eukaryotes, not just lichens or an animal’s neurons, are prod- ucts of symbiogenesis among formerly free-living bacteria, some highly motile. Eukaryotes have evolved by the inheritance of acquired genomes; they have gained all their new features by ingesting and not digesting whole bacterial cells with complete genomes. KEYWORDS: Borrelia; Karyomastigonts; Mixotricha; Nuclear origins; Spirosymplokos; Evolutionary novelties; Minimal cell; Symbiosis Almost one hundred years ago, Ramón y Cajal in his Historia de Vacaciones wrote1: It is certain that science, internally rebellious, seemingly against fate, has invented the microscope with the aim of surprising such small enemies. Yet this already represents an intellectual gain by the microbe. This microscope, this toy—still imperfect because of limitations of its resolving power—from it escape millions of infinitesimal lives; ul- tramicroscopical bacteria have their bacteria, the impalpable dust of myriad lives dis- persed in the air, the water and on the land, the imperceptible intracellular colonies, a kind of symbiotic federation that only now begin to dawn as if they were risky conjec- tures in the minds of some audacious wise men. One day perhaps it will be legal to track the morphology and customs of such diminutive and ultramicroscopic beings that bor- der on the void even though they are so much larger than molecular constructions. And thus, in all, science can never deplete the domains of life. The invisible, infinitely more important than the visible, infinitely delicate and still unknown, will surround us al- ways. Each age will have its inaccessible enemies because the steed of progress gal- lops, spurred only by the heel of death.1 What is the “statue interior,” the “statue inside” that François Jacob2 alludes to in his autobiography, The Statue Within? What is “the invisible infinitely more impor- tant than the visible”? (FIG. 1). This is what I plan to discuss in this paper. Address for correspondence: Morrill Science Center, University of Massachusetts, Amherst, Massachusetts 01003-5820. 55 56 ANNALS NEW YORK ACADEMY OF SCIENCES FIGURE 1. Top: statue of Ramón y Cajal (by sculptor Mariano Benlliure, 1924). Bot- tom: close-up of three Nobel prize winners—Murray Gell-Mann, François Jacob, and Gerald Edelman [left to right]—at the base of the statue. MARGULIS: THE CONSCIOUS CELL 57 Illustrious predecessors to my commentary, as well as to the nervous system, abound. The illustrious predecessor to the nervous system is “microbial conscious- ness.” When I describe the origin of the eukaryotic cell via bacterial cell merger, I emphasize that the components that fused in symbiogenesis are already “conscious” entities. I speak within the evolutionary context developed for us by one of my illus- trious predecessor scientists: Professor Harold J. Morowitz.3 I present an aspect of the origin of the neurotubule system by a hypothesis that can be directly tested. The idea is that the system of microtubules that became neurotubules has as its origin once-independent eubacteria of a very specific kind. In our films I show live beings that help us comprehend how evolution has proceeded since the beginning.4 Noth- ing, I claim, has ever been lost without a trace in evolution. The remains of the evo- lutionary process, the sequence that occurred that produced Cajal’s neuron and other cells, persist today. By study of what thrives now we can reconstruct the past directly from living organisms, even “microbial mind.”5 SYMBIOSIS AND THE EVOLUTION OF EUKARYOTIC CELLS The protein synthetic system, the cytoplasm of your favorite cell, the neuron, as the cytoplasm of all eukaryotic cells, we claim is archaebacterial in origin. We pos- tulate that the protein synthetic system of eukaryotic cells mainly derives from a type of archaebacterium called Thermoplasma. The undulipodium, that is, the microtubular system in its [9(2)+2] array, the shaft called the axoneme, evolved from motile eubacteria close to the genus Spirocheta. The simplified equation, by hypothesis, is Thermoplasma (archaebacteria) + Spiro- cheta (eubacteria) = the first protist. This motile, nucleated cell, the first protist, re- sembled mastigotes like extant Mastigamoeba or Trichomonas. The first merger occurred in the absence of oxygen, prior to acquisition of mitochondria. The earliest microbes, both bacteria and protists, were already greatly sensitive to their environ- ment. The earliest protists bore, in their cells, the karyomastigont. The organelle sys- tem, the karyomastigont, is found in many extant protists. The karyomastigont comprises a nucleus and a nucleus connector or rhizoplast that links the nucleus to centrioles and axonemes. The karyomastigont, in our opinion,6 preceded the unat- tached nucleus. The nucleus as a double membrane-bounded sphere in the cytoplasm originated when it was severed from the karyomastigont. This scheme posits that spirochete plus thermoplasma generated basal new eukaryotes: protists with karyo- mastigonts. When the karyomastigont was cut, the nucleus, an organelle that from the beginning represented DNA from two different sources (archaebacterial and eu- bacterial), was released. From protists evolved the cells of all animals, plants and those of all other familiar eukaryotic organisms.6,7 The timeline has been given to us by the geochronologists: four eons. The origin of life is still a big question mark. The units by which we represent the ancient his- tory are tens of millions of years (FIG. 2). The fossil record of the marine animals begins with the “Cambrian explosion” 541 millions years ago. The Mesozoic age of reptiles began 225 mya. The age of mammals, the Cenozoic, occupies the last portion, 65–0 mya. People are not even visible on this scale. We count in thousands of millions of years. The entire “Precam- 58 ANNALS NEW YORK ACADEMY OF SCIENCES brian,” the long period prior to any animal or plant, is the age of bacteria and proto- ctists. The eukaryote fossil record begins about 2,000 million years ago. The first hard-shelled marine animals appeared at 541 million years ago. This dates the evo- lution of hard parts. Brains appear later, but consciousness, awareness of the sur- rounding environment, starts with the beginning of life itself, which is the point of this paper. The origin of life is represented in FIGURE 2 as a question mark. The earliest cells generated the two great groups of bacteria: the one to which Thermoplasma belongs (archaebacteria) and the one to which the spirochetes belong (eubacteria). The pro- cess of symbiogenesis in the evolution of nucleated cells began about 2,000 mya. The emergent property of the symbiont fusion was the origin of all larger forms of life. We concentrate here on only one of the many, many evolutionary transitions in the origin of ourselves: we mammals who talk too much. Let us review the very earliest life forms from the point of view of their chemistry. This simplified diagram is based completely on the analysis that Morowitz made some 25 years ago: the minimal cell (FIG. 3).3 The minimal cell must be surrounded by a membrane of its own making. In today’s world, on Earth at least, the cell makes its own genetic material, DNA. Of course it synthesizes messenger RNA coded off that DNA, as well as transfer RNAs, and the rest of ribosomal RNAs to make the ri- bosomal system that synthesizes more proteins that make more DNA. All cells re- quire sources of carbon, nitrogen, oxygen, hydrogen, phosphorus, and sulfur. A source of energy too is required by all life. Life’s energy system is always visible light or chemical (inorganic or organic chemical) only. No other known sources of energy for cells exist besides photo- and chemical. All of life’s chemical transforma- tion occurs in a watery matrix. The minimal system, at least on Earth today, dia- FIGURE 2. History of life on geological time scale (by Kathryn Delisle). MARGULIS: THE CONSCIOUS CELL 59 grammed in FIGURE 3, suggests that any organelle that began as a free-living microbe at first contained FIGURE 3’s entire complement of features. In cells of green hydra, for example, the green animal’s gastrodermal cell is clear- ly a product of symbiogenesis: the cnidarian animal and the alga. But three genomes occur in the Chlorella, the green algal cell: nucleocytoplasm, chloroplast, mitochon- drion. At least two coexist in the hydra cell: nucleocytoplasm and mitochondrion. Thus the single digestive system cell of the animal is a composite of at least five ge- nomes. The point is that all eukaryotic cells, including the neuron, all are products of more than a single genome with more than one single ancestor. All are complex, all are heterogenomic with multiple ancestors. All eukaryotes, all nucleated organ- isms, are composed of cells that are products of symbiogenetic mergers.
Load more

Recommended publications
  • Brain-Specific Expression of MAP2 Detected Using a Cloned Cdna Probe Sally A
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by PubMed Central Brain-specific Expression of MAP2 Detected Using a Cloned cDNA Probe Sally A. Lewis,* Alfredo Villasante,* Peter Sherline,* and Nicholas J. Cowan* *Department of Biochemistry, New York University Medical Center, New York, New York 10016; *Division of Endocrinology, Cornell University Medical College, New York, New York 10021 Abstract. We describe the isolation of a set of over- consistent with the coding capacity required by a lapping cDNAs encoding mouse microtubule associ- 250,000-D protein. ated protein 2 (MAP2), using an anti-MAP antiserum The MAP2-specific cloned cDNA probes were used to screen a mouse brain cDNA expression library in RNA blot transfer experiments to assay for the cloned in bacteriophage hgt 11. The authenticity of presence of MAP2 mRNA in a variety of mouse tis- these clones was established by the following criteria: sues. Though brain contained abundant quantities of (a) three non-identical clones each expressing a MAP2 mRNA, no corresponding sequences were de- MAP2 immunoreactive fusion protein were independ- tectable in RNA prepared from liver, kidney, spleen, ently isolated from the expression library; each of stomach, or thymus. We conclude that the expression these clones cross-hybridized at the nucleic acid level; of MAP2 is brain-specific. (b) anti-MAP antiserum was affinity purified using Use of the MAP2 specific cDNA probes in genomic nitrocellulose-bound fusion protein; these antibodies Southern blot transfer experiments showed the pres- detected only MAP2 in an immunoblot experiment of ence of a single gene encoding MAP2 in mouse.
    [Show full text]
  • Immunolocalization and Molecular Properties of a High Molecular Weight Microtubule-Bundling Protein (Syncolin) from Chicken Erythrocytes E Feick, R
    Immunolocalization and Molecular Properties of a High Molecular Weight Microtubule-bundling Protein (Syncolin) from Chicken Erythrocytes E Feick, R. Foisner, and G. Wiche Institute of Biochemistry, University of Vienna, 1090 Vienna, Austria Abstract. A protein of apparent molecular weight was displaced from the polymer by salt. Brain as well 280,000 (syncolin), which is immunoreactive with an- as erythrocyte microtubules, reconstituted with taxol tibodies to hog brain microtubule-associated protein from MAP-free tubulin and purified syncolin, were ag- (MAP) 2, was purified from chicken erythrocytes. Im- gregated into dense bundles containing up to 15 Downloaded from http://rupress.org/jcb/article-pdf/112/4/689/1060909/689.pdf by guest on 29 September 2021 munofluorescence microscopy of bone marrow cells microtubules, as determinedby'etectron microscopy. revealed the presence of syncolin in cells at all stages On the ultrastructural level, syncolin molecules were of erythrocyte differentiation. In early erythroblasts visualized as globular or ringlike structures, in con- syncolin was diffusely distributed throughout the trast to the thin, threadlike appearance of filamentous cytoplasm. At later stages it was found along microtu- MAPs, such as brain MAP 2. According to ultrastruc- bules of the marginal band, as confirmed by immuno- tural measurements and gel permeation chromatogra- electron microscopy. The association of syncolin with phy, syncolin's molecular weight was ,',,1 x 106. It is the marginal band was dependent on the integrity of suggested that syncolin's specific function is the cross- microtubules, as demonstrated by temperature- linking of microtubules in the marginal band and, by dependent de- and repolymerization or marginal band implication, the stabilization of this structure typical microtubules.
    [Show full text]
  • And High-Molecular-Weight Forms of MAP2 in the Developing Cerebellum
    The Journal of Neuroscience, December 1999, 8(12): 4503-4512 The Sequential Appearance of Low- and High-Molecular-Weight Forms of MAP2 in the Developing Cerebellum R. P. Tucker,’ L. I. Binder,’ C. Viereck,’ B. A. Hemmings,’ and A. I. Matus’ ‘Friedrich Miescher Institute, CH-4002 Basel, Switzerland, and *Department of Cell Biology and Anatomy, School of Medicine and Dentistry, University of Alabama at Birmingham, Birmingham, Alabama 35294 Mammalian microtubule-associated protein 2 (MAPS) exists shown that a number of MAPS promote the assemblyof tubulin in high-molecular-weight (M, -280,000) and low-molecular- into microtubulesand stabilize the resulting microtubulesagainst weight (M, -70,000) forms, with the latter protein being more the depolymerizing effects of cold and various pharmacological abundant in embryonic brain homogenates than in prepa- agents(Olmsted, 1986; Matus, 1988). The most abundant MAP rations from mature brain (Riederer and Matus, 1985). In the in the mammalian CNS, MAP2, displays each of these char- current study, we have shown that avian MAP2 also exists acteristics: (1) There are 2 closely related high-molecular-weight as both high- (M, -260,000) and low-molecular-weight (M, (HMW) forms of MAP2, MAP2a, and MAP2b, which change -65,000) forms whose relative abundance changes during in relative abundanceduring development (Binder et al., 1984; brain maturation, indicating a conserved function for these Burgoyne and Cummings, 1984);(2) MAP2 is found in dendrites proteins during vertebrate neuronal morphogenesis. Using and only rarely in axons (e.g., Cacereset al., 1984; DeCamilli indirect immunohistochemistry, we have determined the cel- et al., 1984; Huber and Matus, 1984b); and (3) MAP2 stabilizes lular distribution of the high- and low-molecular-weight forms and promotes the assembly of microtubules in vitro (Murphy of MAP2 in the developing avian cerebellum.
    [Show full text]
  • Evidence for Conformational Change-Induced Hydrolysis of Β-Tubulin-GTP
    bioRxiv preprint doi: https://doi.org/10.1101/2020.09.08.288019; this version posted September 10, 2020. The copyright holder for this preprint (which was not certified by peer review) is the author/funder. All rights reserved. No reuse allowed without permission. Evidence for conformational change-induced hydrolysis of β-tubulin-GTP Mohammadjavad Paydar1 and Benjamin H. Kwok1† 1 Institute for Research in Immunology and Cancer (IRIC), Département de médecine, Université de Montréal, P.O. Box 6128, Station Centre-Ville, Montréal, QC H3C 3J7, Canada. † Corresponding author: B. H. Kwok: [email protected] Keywords: Kinesin, Kif2A, MCAK, motor protein, microtubules, tubulin, GTP hydrolysis Abbreviations NM: Neck+Motor MD: Motor domain MT: Microtubule Running title: Tubulin GTP hydrolysis 1 bioRxiv preprint doi: https://doi.org/10.1101/2020.09.08.288019; this version posted September 10, 2020. The copyright holder for this preprint (which was not certified by peer review) is the author/funder. All rights reserved. No reuse allowed without permission. ABSTRACT Microtubules, protein polymers of α/β-tubulin dimers, form the structural framework for many essential cellular processes including cell shape formation, intracellular transport, and segregation of chromosomes during cell division. It is known that tubulin-GTP hydrolysis is closely associated with microtubule polymerization dynamics. However, the precise roles of GTP hydrolysis in tubulin polymerization and microtubule depolymerization, and how it is initiated are still not clearly defined. We report here that tubulin-GTP hydrolysis can be triggered by conformational change induced by the depolymerizing kinesin-13 proteins or by the stabilizing chemical agent paclitaxel. We provide biochemical evidence that conformational change precedes tubulin-GTP hydrolysis, confirming this process is mechanically driven and structurally directional.
    [Show full text]
  • Axonal Transport and the Eye
    Br J Ophthalmol: first published as 10.1136/bjo.60.8.547 on 1 August 1976. Downloaded from Brit. 7. Ophthal. (1976) 60, 547 Editorial: Axonal transport and the eye Since the earliest days of histology, it has been and proteins, and are predominantly found in the known that the neurons have a large amount of particulate fraction of nerve homogenates. The basophilic material in the cell body. More recently slower transported material is mainly soluble this has been shown to be due to masses of rough protein (McEwen and Grafstein, I968; Kidwai and endoplasmic reticulum which are responsible for a Ochs, I969; Sj6strand, 1970). Much of the former high rate of protein synthesis of neurons. Since the and more than 6o per cent of the latter is probably earliest days of the microscopy of living cells in neurotubular protein (tubulin), and the neurotubules vitro, particulate movement within these cells has are thought to play a major part in axonal transport been recognized, particularly in neurons (Nakai, (Schmitt and Samson, I968). The neurotubules I964). The last 30 years have seen the gradual have a similar structure to actin, and are linked to accumulation of the knowledge required to explain high-energy phosphate compounds. Myosin-like these two observations. In the last io years in proteins are also found in axoplasm. It is suggested particular, the development of radioactive tracer that moving material might in part roll along the techniques has revealed much information on the neurotubules, or that the neurotubules themselves movement of protein and other substances within might move by a mechanism involving myosin- axons, a process termed axonal transport (Barondes, guanosine triphosphate-neurotubule cross bonds I967).
    [Show full text]
  • Tubulin Requires Tau for Growth Onto Microtubule Initiating Sites (Flagella/In Vitro Assembly/Electron Microscopy) GEORGE B
    Reprinted from Proc. Natl. Acad. Sci. USA Vol. 73, No. 11, pp. 4070-4074, November 1976 Cell Biology Tubulin requires tau for growth onto microtubule initiating sites (flagella/in vitro assembly/electron microscopy) GEORGE B. WITMAN, DON W. CLEVELAND, MURRAY D. WEINGARTEN, AND MARC W. KIRSCHNER The Departments of Biology and Biochemistry, Princeton University, Princeton, New Jersey 08540 Communicated by J. T. Bonner, August 9, 1976 ABSTRACT Tubulin purified by phosphocellulose chro- ether)-N,N'-tetraacetic acid (EGTA), 1 mM GTP, 0.5 mM matography and free of accessory proteins will not form mi- MgCl2, and 1 mM mercaptoethanol]. A high-speed supernatant crotubules in the absence or presence of micrdtubule initiating sites (flagellar microtubules). The capacity for growth onto of depolymerized microtubules was prepared by cooling the pre-existing "seeds" can be restored by the addition of small protein at 5 mg/ml in the above buffer at 0° for 30 min and quantities of partially purified tau protein. Larger quantities sedimenting the solution at 190,000 X g for 2 hr. Phosphocel- restore the capacity for spontaneous assembly. These results lulose-purified tubulin was prepared as described (4, 8). Mi- suggest that tubulin requires tau for both initiation and growth crotubule protein in purification buffer was repolymerized and of microtubules and that tau is incorporated into the microtu- centrifuged at 100,000 X g for 40 min at 280. The resulting bule throughout its length. pellets were resuspended in Mes-EDTA buffer (25 mM Mes, pH 6.4,0.5 mM MgCl2, 0.1 mM EDTA, and 1 mM mercapto- The development of procedures for the assembly of microtu- ethanol) to a final concentration of 8-10 mg/ml.
    [Show full text]
  • Axon Growth: Roles of Microfilaments and Microtubules* Kenneth M
    Proceedings of the JVational Academy of Sciences Vol. 66, No. 4, pp. 1206-1212, August 1970 Axon Growth: Roles of Microfilaments and Microtubules* Kenneth M. Yamada, Brian S. Spooner, and Norman K. Wessellst DEPARTMENT OF BIOLOGICAL SCIENCES, STANFORD UNIVERSITY, STANFORD, CALIFORNIA Communicated by Colin S. Pittendrigh, April 27, 1970 Abstract. The motile tips of elongating axons consist of growth cones from which microspikes protrude. Cytochalasin B causes retraction of microspikes, rounding-up of growth cones, and cessation of axon elongation. Drug with- drawal is followed by resumption of growth cone and microspike activity and of axon elongation. In contrast, colchicine causes shortening and retraction of axons, but it does not initially affect the tips. Growth cones and microspikes of elongating axons contain a network of 50 A microfilaments, the pattern of which is altered by cytochalasin treatment. These experiments indicate that both structural integrity of the axon and continuing function of its motile tip are essential elements in axonal elongation. The tips of elongating axons consist of expanded regions called "growth cones" from which project long slender microspikes (filopodia). These microspikes continually wave about, extend, and retract as the growth cone moves over a substratum.1 Although it is assumed that growth cones and microspikes play a significant role in axon extension, it has not been previously possible to analyze their functions. We have investigated the effects of cytochalasin B on axon elongation since this drug halts cell movement,2 a process similar in many respects to growth cone movement. Cytochalasin B is also known to inhibit cytokinesis3 and morpho- genetic movements,4 apparently by disrupting contractile 50 A microfilaments.
    [Show full text]
  • Neurons and Associated Cells
    CH02.p3 3/11/05 8:41 AM Page 11 2 Neurons and Associated Cells Neuroplasticity Organelles and Components Neurotrophic Factors and Tropic Factors Structure of Peripheral Nerves and Ganglia Neuroglia (GLIA) Paraneurons Nerve Regeneration Plasticity and Axonal Sprouting resulting excitation rapidly to other portions of NEUROPLASTICITY the nerve cell, and to influence other neurons, muscle cells, and glandular cells. Neurons are Some 100–200 billion ([1–2] × 1011) neu- so specialized that most are incapable of repro- rons (nerve cells), as well as many more glial ducing themselves and they lose viability if cells, are integrated into the structural and denied an oxygen supply for more than a few functional fabric that is the brain. They exhibit minutes. a wide diversity of form and sizes. The neuron is the basic unit of the nervous system and is composed of four structurally defined regions: a cell body (soma) that emits a single nerve ORGANELLES AND COMPONENTS process called an axon, which ends at presy- naptic terminals, and a variable number of Each neuron consists of a large nucleus, a branching processes called dendrites (Figs. 2.1 plasma (cell) membrane and cytoplasm con- and 2.2). Each axon, including its collateral sisting of cytosol (fluid phase of cytoplasm), branches, usually terminates as an arbor of fine and a number of organelles, including the fibers; each fiber ends as an enlargement called endoplasmic reticulum, Nissl substance, Golgi a bouton,which is part of a synaptic junction. apparatus, mitochondria, lysosomes and cyto- At the other end of the neuron, there is a three- skeleton (Figs.
    [Show full text]
  • Cyclic AMP-Dependent Endogenous Phosphorylation of a Microtubule-Associated Protein (Protein Phosphorylation/In Vitro Assembly) ROGER D
    Proc. Nat. Acad. Sci. USA Vol. 72, No. 1, pp. 177-181, January 1975 Cyclic AMP-Dependent Endogenous Phosphorylation of a Microtubule-Associated Protein (protein phosphorylation/in vitro assembly) ROGER D. SLOBODA, STEPHEN A. RUDOLPH, JOEL L. ROSENBAUM, AND PAUL GREENGARD Department of Biology, Kline Biology Tower, Yale University and Department of Pharmacology, Yale University School of Medicine, New Haven, Connecticut 06610 Communicated by Aaron B. Lerner, October 21, 1974 ABSTRACT Microtubules prepared from chick brain were homogenized in a motor-driven glass-Teflon homogenizer homogenates by successive cycles of assembly-disassembly at 00 in 1 ml of polymerization mixture buffer [1 mM MgSO4, were found to contain two high-molecular-weight pro- ether)-N,N'-tetra- teins, designated microtubule-associated protein, and 2 mM ethyleneglycol bis(#-aminoethyl microtubule-associated proteins. Microtubule-associated acetate (EGTA), 1 mM GTP, 100 mM piperazine-N,N'-bis(2- protein2 (apparent molecular weight 300,000 by sodium ethanesulfonic acid) (Pipes) (pH 6.9)] per g wet weight, and dodecyl sulfate-polyacrylamide gel electrophoresis) was the homogenate was centrifuged at 130,000 X g for 1 hr at 40 the preferred substrate for an endogenous cyclic AMP- to yield a crude high-speed supernatant. This supernatant was dependent protein kinase which appeared to be an integral component of the microtubules. The initial rate of phos- diluted with an equal volume of polymerization mixture buffer phorylation of microtubule-associated protein2 was en- containing 8 M glycerol, and incubated at 370 for 30 min to hanced 4- to 6-fold by cyclic AMP, with half-maximal assemble microtubules.
    [Show full text]
  • NERVE TISSUE Neuron – Nerve Cell
    Department of Histology and Embryology, P. J. Šafárik University, Medical Faculty, Košice NERVE TISSUE: Sylabus for foreign students Author: doc. MVDr. Iveta Domoráková, PhD. Revised by: prof. MUDr. Eva Mechírová, CSc. NERVE TISSUE FUNCTION: Reception, transmission, processing of nerve stimuli. Coordination of all functional activities in the body: - motor function (body movement) - sensory (rapid response to external stimuli) - visceral, endocrine and exocrine glands - mental functions, memory, emotion A) Anatomically nervous system consists of: 1. CNS (central nervous system) – brain, spinal cord 2. PNS (peripheral nervous system) – peripheral nerves and ganglia B) Functionally nervous system is divided into the: 1. Somatic nervous system (sensory and motor innervation) 2. Autonomic nervous system (involuntary innervation of smooth muscles, glands) C) Microscopic structure of the nerve tissue - two types of cells: 1. Nerve cells – neurons 2. Glial cells (supporting, electrical insulation, metabolic function) Neuron – nerve cell - is the structural and functional unit of the nerve tissue - receives stimuli from other cells - conducts electrical impulses to another cells by their processes - chainlike communication - ten bilion of neurons in humans A. Neurons according the shape: Pyramidal (E) star-shaped (D) pear-shaped (G) oval (B) B. Types of neurons according number of the processes 1. multipolar (D,E,G)) 2. bipolar (A) 3. pseudounipolar (B) 4. unipolar C. Neurons - according the function Motor (efferent) neurons – convey impulses
    [Show full text]
  • Ultrastructural Study of the Persistence of Colchicine-Induced Cytological Changes in Harding-Passey Melanoma1
    [CANCER RESEARCH 38. 168-176, January 1978] Ultrastructural Study of the Persistence of Colchicine-induced Cytological Changes in Harding-Passey Melanoma1 Kenneth R. Loader and Edward J. H. Nathaniel2 Department ol Anatomy, Faculty of Medicine, University of Manitoba, Winnipeg, Manitoba, Canada ABSTRACT and characterizing the differentiated state. Since they are not always concordant, it becomes important to recognize Electron microscopic observations were undertaken on the significance of each, and to specify criteria when one Harding-Passey melanoma in control tumors, colchicine- is characterizing differentiation. Cells may be said to be treated tumors, and tumors that were passed through differentiated by morphological, behavioral, chemical or five transplantations in mice subsequent to colchicine developmental criteria." treatment. Evidence of submicroscopic differentiation is observed The untreated Harding-Passey melanoma tumor was in both the nucleus and the cytoplasm. These changes are composed of pleomorphic cells the cytoplasm of which more conspicuous in the cytoplasm (13). Morphological contained tubulovesicular mitochondria and numerous changes in the nucleus during the course of development free and membrane-attached ribosomes. Type A virus have been described by several investigators (3, 22). How particles were observed in both mitotic and interphase ever, the site of functional realization of the cell, together cells. Colchicine-treated tumors exhibited several typical with the respective structural arrangement, resides within colchicine mitotic cells arrested in metaphase. A most the cytoplasm, the primary area of submicroscopic differ significant feature of the colchicine administration was entiation. During differentiation, changes in cellular organ- the appearance of microfilaments in both interphase and elles take place. mitotic cells, a feature not observed in cells of the un The appearance of microfilaments in the tumor cells of treated tumor.
    [Show full text]
  • Estramustine Phosphate Inhibits Germinal Vesicle Breakdown and Induces Depolymerization of Microtubules in Mouse Oocyte Hélène Rime, Catherine Jessus, R
    Estramustine phosphate inhibits germinal vesicle breakdown and induces depolymerization of microtubules in mouse oocyte Hélène Rime, Catherine Jessus, R. Ozon To cite this version: Hélène Rime, Catherine Jessus, R. Ozon. Estramustine phosphate inhibits germinal vesicle breakdown and induces depolymerization of microtubules in mouse oocyte. Reproduction Nutrition Développe- ment, 1988, 28 (2A), pp.319-334. hal-00898793 HAL Id: hal-00898793 https://hal.archives-ouvertes.fr/hal-00898793 Submitted on 1 Jan 1988 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Estramustine phosphate inhibits germinal vesicle breakdown and induces depolymerization of microtubules in mouse oocyte Hélène RIME Catherine JESSUS R. OZON Laboratoire de Physiologie de la Reproduction, Groupe Stéroides, UA-CNRS 555, Université Pierre et Marie Curie, 4, place Jussieu, 75252 Paris Cedex 05, France. Summary. The first meiotic cell division (meiotic maturation) of the dictyate stage of mouse oocytes, removed from the follicle, resumes spontaneously in vitro. This study indicates that estramustine phosphate reversibly blocks meiotic maturation by inhibiting germinal vesicle breakdown. Oocyte cryostat sections were stained with anti-tubulin and two antibodies (anti-MAP1 : JA2 and 5051) which decorated the metaphase spindle during meiotic maturation.
    [Show full text]