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  • 1
    Electronic Resource
    Electronic Resource
    Naturally occurring tubulin-containing paracrystals in Allogromia: Immunocytochemical identification and functional significance (1986)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 6 (1986), S. 363-375 
    Details
    ISSN: 0886-1544
    Keywords: Allogromia ; cytoplasmic transport ; microtubules ; reticulopod withdrawal ; tubulin-containing paracrystal ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Bundles of microtubules (MTs) are readily visualized in vivo by videomicroscopy in highly flattened reticulopodia of the foraminiferan protozoan Allogromia sp. strain NF. In this report we use videomicroscopy, immunocytochemistry, and high-voltage electron microscopy to characterize the dynamic changes that occur in this extensive MT cytoskeleton, and in the associated cytoplasmic transport, during induced withdrawal and subsequent reextension of reticulopodia. Within seconds after application of the withdrawal stimulus (seawater substitute made hypertonic with MgCl2) intracellular bidirectional transport along linear MT-containing fibrils ceases and is replaced by an inward, constant-velocity flow of cytoplasm along the fibrils. As withdrawal continues, most fibrils become wavy and coalesce to form phase-dense pools. These wavy fibrils and phase-dense pools contain a paracrystalline material and few if any MTs. Same-section correlative immunofluorescence and high-voltage electron microscopy reveal that the paracrystalline material contains tubulin. During recovery linear fibrils (MTs) rapidly extend from the phase-dense pools (paracrystals), which concurrently shrink in size, thus reestablishing normal network morphology and motility. We conclude that the MT cytoskeleton in Allogromia reticulopodia is transfonned during withdrawal into a tubulin-containing paracrystal, which serves as a temporary reservoir of MT protein and an initiation site for MT regrowth.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970060403
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  • 2
    Electronic Resource
    Electronic Resource
    A new model of reticulopodial motility and shape: Evidence for a microtubule-based motor and an actin skeleton (1986)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 6 (1986), S. 2-14 
    Details
    ISSN: 0886-1544
    Keywords: Allogromia ; reticulopods ; cytoskeleton ; microtubules ; actin ; saltatory transport ; cell shape ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Cytoskeletal inhibitors were used as probes to test the involvement of microtubules and actin microfilaments in the development, motility, and shape maintenance of the pseudopodial networks (i e, reticulopodia) of the foraminifers Allogromia sp strain NF and Allogromia laticcllaris. Agents that disassemble cytoplasmic microtubules (cold, colchicine, and nocodazole) arrest all movement but have variable effects on reticulopodial shape. Electron microscopy reveals a granulofibrillar matrix but few, if any, microtubules in these motility-arrested reticulopods. Allogromiids treated with cytochalasin B or D lose substrate adhesion and undergo dramatic changes in shape and motile behavior, highlighted by the coalescence of reticulopodial cytoplasm into irregularly shaped bodies with chaotic motility. Serial semithick sections of such preparations, viewed by high-voltage electron microscopy, document a striking rearrangement of microtubules within these cytochalasin-induced bodies. All aspects of cytochalasin-altered motility are completely inhibited by colchicine. Actin is present in reticulopodia, as determined by staining with rhodamine-phalloidin; this staining is not observed in cytochalasin-treated organisms. These data provide compelling evidence that microtubules are required for reticulopodial motility. An actin-based cytoskeleton is thought to play a role in maintaining shape, mediating pseudopod/substrate adhesion, and coordinating the various microtubule-dependent processes.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970060103
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  • 3
    Electronic Resource
    Electronic Resource
    Microtubule-dependent reticulopodial motility: Is there a role for actin? (1986)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 6 (1986), S. 146-152 
    Details
    ISSN: 0886-1544
    Keywords: Allogromia ; microtubules ; microtubule-associated protein (MAP-2) ; actin ; cyanideinsensitive respiration ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We summarize our recent immunocytochemical characterization of the reticulopodial cytoskeleton of two allogromiid foraminifers and our pharmacologic dissection of its motility. The reticulopodial microtubule cytoskeleton stained with an antiserum to brain microtubule-associated protein 2. Polymeric actin was localized in the reticulopodia by rhodamine-phalloidin staining. Microtubule inhibitors reversibly inhibited all aspects of motility; cytochalasins induced altered morphology and disorganization of motility but did not inhibit pseudopodial movements or intracellular transport. Simultaneous application of KCN and salicylhydroxamic acid (an alternative oxidase inhibitor) rapidly blocked all movement, indicating that motility is dependent on metabolic energy and that an alternative oxidative pathway functions in allogromiids. Micromanipulation and laser microsurgical experiments revealed tension throughout the reticulopodium. Our results suggest that microtubules are active components of the reticulopodial motile machinery. Actin may mediate substrate adhesion, whole-cell locomotion, pseudopodial tension, and coordination of the microtubule-based motility.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970060212
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  • 4
    Electronic Resource
    Electronic Resource
    Primary cilia cycle in PtK1 cells: Effects of colcemid and taxol on cilia formation and resorption (1987)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 7 (1987), S. 187-197 
    Details
    ISSN: 0886-1544
    Keywords: mitosis ; centrosome ; centriole ; cytoplasmic microtubules ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The effects of colcemid (0.16-1.0 μM) and taxol (10 μM) on the primary cilia cycle in PtK1 cells were studied by antitubulin immunofluorescence microscopy and by high-voltage electron microscopy of serial 0.25-μm sections. Although these dings induce a fully characteristic rearrangement (taxol) or disassembly (colcemid) of cytoplasmic microtubulcs, neither affects the structure of primary cilia formed prior to the treatment or the resorption of primary cilia during the initial stages of mitosis. Cells arrested in mitosis by taxol or colcemid remain in mitosis for 5-7 h at 37°C and then form 4N “micronucleated” restitution nuclei. Formation of primary cilia in these micronucleated cells is blocked by colcemid in a concentration-dependent fashion: normal cilia with expanded (ie, bulbed) distal ends form at the lower (0.16-0.25 μM) concentrations, while both cilia formation and centriole replication are inhibited at the higher (≥ 1.0 μM) concentrations. However, even in the presence of 1.0 μM colcemid, existing centrioles acquire the appendages characteristically associated with ciliating centrioles and attach to the dorsal cell surface. Continuous treatment with colcemid thus produces a population of cells enriched for the early stages of primary cilia formation. Micronucleated cells formed from a continuous taxol treatment contain two normal centriole pairs, and one or both parenting centrioles possess a primary cilium. Taxol, which has been reported to stabilize microtubules in vitro, does not inhibit the cell-cycle-dependent assembly and disassembly of axonemal microtubules in vivo.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970070302
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  • 5
    Electronic Resource
    Electronic Resource
    Optical approaches to the study of foraminiferan motility (1988)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 10 (1988), S. 126-136 
    Details
    ISSN: 0886-1544
    Keywords: microtubules ; Allogromia ; intracellular transport ; surface motility ; actin ; morphogenesis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Microtubules are the major cytoskeletal component of foraminiferan reticulopodia. Video-enhanced differential interference contrast light microscopy has demonstrated that the microtubules serve as the intracellular tracks along which rapid bidirectional organelle transport and cell surface motility occurs. Microtubules appear to move, both axially and laterally within the pseudopodial cytoplasm, and these microtubule translocations appear to drive the various reticulopodial movements. F-actin is localized to discrete filament plaques form at sites of pseudopod-substrate adhesion. Correlative immunofluorescence and electron microscopy reveals a structural interaction between microtubules and the actin-containing filament plaques. Our recent data on reticulopodial motility are discussed in an historical context, and a model for foram motility, based on motile microtubules, is presented.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970100117
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  • 6
    Electronic Resource
    Electronic Resource
    Electron microscopy of semithick sections: Advantages for biomedical research (1985)
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 2 (1985), S. 11-28 
    Details
    ISSN: 0741-0581
    Keywords: Ultrastructure ; Semithick sections ; Three-dimensional ; Serial sections ; Stereomicroscopy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Many transmission electron microscopes are available which can be used to examine biological material in 0.25-0.50-μm-thick sections. When compared to the traditional thin section, these “semithick” sections possess a number of inherent advantages: They can be screened for content with the phase contrast light microscope, they facilitate many types of studies requiring an analysis of serial sections, and they are frequently the optimum thickness for stereomicroscopy. Structures such as microtubule-associated components, as well as structural relationships between cellular constituents, may also be clearly visible in semithick sections which are not visible, or go unnoticed, in thin sections. Together these advantages enable an investigator to obtain a more complete three-dimensional picture of a cell or cell component in a significantly (i.e., up to 90%) shorter period of time than would be required if thin sections were used. Semithick sections may, therefore, make a study feasible which is not approachable, or which is approachable only with great difficulty, by conventional thin sectioning techniques.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jemt.1060020103
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