MARGINAL BAND SYSTEMS IN BLOOD CELLS OF INVERTEBRATES.
Item
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Title
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MARGINAL BAND SYSTEMS IN BLOOD CELLS OF INVERTEBRATES.
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Identifier
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AAI8203308
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identifier
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8203308
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Creator
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NEMHAUSER, IRIS.
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Contributor
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Prof. William D. Cohen
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Date
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1981
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Language
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English
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Publisher
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City University of New York.
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Subject
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Biology, General
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Abstract
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Two major objectives directed the studies described in this dissertation. The first was an attempt at surveying a wide range of invertebrate species in order to determine whether or not such organisms contained in their flattened, elliptical blood cells microtubule marginal bands (MBs) similar to those observed in the erythrocytes of nonmammalian vertebrates and mammalian platelets. The second objective, dependent on the first, involved use of MB-containing invertebrate erythrocytes and clotting cells as experimental tools for elucidation of the structure, function and assembly mechanism(s) of MBs. Use of a modified microtubule polymerization medium containing Triton X-100 facilitated accomplishment of the first objective by providing a means for rapidly assaying the cells of various species for the presence of MBs. This was made possible by the clearing of respiratory pigment and other soluble cellular components from the cells in the lytic medium. Development of a technique for simultaneously lysing and fixing cells prior to embedment made possible the ultrastructural examination of lysed erythrocytes in which the relationships of MB-system components were apparently preserved.;Light microscopic examination of blood from a variety of invertebrates revealed the presence of MB-containing erythrocytes or clotting cells in four phyla comprising six classes. Experiments on the blood cells of selected species, using indirect immunofluorescence with antibulin antibody, demonstrated that these MBs contained tubulin.;MBs are bundles of microtubules circumscribing the cells beneath the plasma membrane in the plane of cell flattening. Light and electron microscopic observation revealed the MB (as in vertebrates) to be a component of a system comprised of the band and a filamentous network, the latter lying subjacent to the plasma membrane and enclosing the other cellular contents. In addition, under the light microscope, phase-dense dots were seen associated with the MBs of the erythrocytes examined.;Members of the Arcidae, or blood clams, were found to have MB-containing erythrocytes that were useful in exploring questions of MB assembly and function. The Arcidae MBs are cold-labile and the phase-dense dots in these species were observed, in thin sections, to be centrioles. Furthermore, cold-disassembled MBs of one of these clam species, Noetia ponderosa were observed, using phase-contrast and electron microscopy as well as indirect immunofluorescence, to reassemble in association with the centrioles when rewarmed. The cells of this species were therefore used in experiments designed to study the possible role of centrioles in MB assembly. Time course rewarming experiments on these erythrocytes demonstrated that during MB reassembly the microtubules grow from the vicinity of the centrioles. This is the first demonstration of centrioles acting as microtubule organizing centers (MTOCs) in MB formation. The findings suggest a model for MB assembly in the Arcidae. The model is supported by results obtained in colchicine experiments on N. ponderosa erythrocytes as well as by the discovery of naturally occurring aberrant MBs in one blood clam species. The proposed model also suggests the means whereby the nascent MB and the network might interact to generate the native flattened elliptical cell shape.;MBs of amebocytes, or clotting cells, of Homarus americanus were shown, using the indirect immunofluorescence technique, to undergo natural disassembly as the cells were morphologically transformed to the amoeboid state during activation. These findings thus provide evidence of a cytoskeletal function for MBs in these cells. It is suggested that invertebrate clotting cells, obtainable in quantity, might serve as useful models for the study of the possible role of MBs in various types of clotting cells including platelets.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
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Program
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Biology
