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  • 1
    ISSN: 0886-1544
    Keywords: sarcoplasmic reticulum ; mitochondira ; mitotic spindle ; cytoskeleton ; cytokinesis ; fluorescent membrane dyes ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The dynamic changes of the endoplasmic reticulum (ER) in interphase and mitotic cells was detected by the vital fluorescent dye 3,3′-dihexyloxacarbocyanine iodide. Two types of arrays characterize the continuous ER system in the non-muscle PtK2 cell: (1) a lacy network of irregular polygons and (2) long strands of ER that are found aligned along stress fibers. In cross-striated myotubes there was a periodic localization of fluorescence over each I-band corresponding to the positions of the terminal cisternae of the sarcoplasmic reticulum (SR). In contrast to the arrangement in muscle cells, the aligment of the long strands of ER along stress fibers showed no strict periodicity that could be correlated with the sarcomeric units of the stress fibers. The ER and SR arrays seen in living cells were also detected in fixed cells stained with antibodies directed against proteins of the endoplasmic reticulum and sarcoplasmic reticulum, respectively. Observations of vitally stained PtK2 cells at 1 to 2 minute intervals using low light level video cameras and image processing techniques enabled us to see the polygonal ER units form and undergo changes in their shapes. During cell division, the ER, rhodamine 123-stained mitochondria, and phagocytosed fluorescent beads were excluded from the mitotic spindle while soluble proteins were not. No obvious concentration or alignment of membranes could be found associated with the contractile proteins in the cleavage furrow. After completion of cell division there was a redeployment of the ER network in each daughter cell.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0886-1544
    Keywords: cleavage furrows ; cytokinesis ; actin ; phalloidin ; myosin ; filamin ; talin ; attachment plaques ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: PtK2 cells of exceptionally large size were microinjected with fluorescently labeled probes for actin, myosin, filamin, and talin in order to follow the assembly of the contractile proteins into the cleavage furrows. Whereas in cells of normal size, there is usually a diffuse pattern of localization of proteins in the cleavage furrow, in these large, flat cells the labeled proteins localized in fibers in the cleavage furrow. Often, the fibers were striated in a pattern comparable to that measured in the stress fibers of the same cell type. The presence of talin in discrete plaques along fibers in the cleavage furrows of the large cells suggests a further similarity between cleavage furrow and stress fiber structure. The presence of filamin in the cleavage furrows also suggests the possibility of an overlapping mechanism in addition to that of a talin mediated mechanism for the attachment of actin filaments to the cell surfaces in the cleavage furrow. A model is presented that emphasizes the interrelationships between stress fibers, myofibrils, and cleavage furrows. © 1994 Wiley-Liss, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0886-1544
    Keywords: cytokinesis ; microinjection ; cleavage furrow ; mitosis ; midbody ; stress fibers ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Actin and the light chains of myosin were labeled with fluorescent dyes and injected into interphase PtK2 cells in order to study the changes in distribution of actin and myosin that occurred when the injected cells subsequently entered mitosis and divided. The first changes occurred when stress fibers in prophase cells began to disassemble. During this process, which began in the center of the cell, individual fibers shortened, and in a few fibers, adjacent bands of fluorescent myosin could be seen to move closer together. In most cells, stress fiber disassembly was complete by metaphase, resulting in a diffuse distribution of the fluorescent proteins throughout the cytoplasm with the greatest concentration present in the mitotic spindle. The first evidence of actin and myosin concentration in a cleavage ring occurred at late anaphase, just before furrowing could be detected. Initially, the intensity of fluorescence and the width of the fluorescent ring increased as the ring constricted. In cells with asymmetrically positioned mitotic spindles, both protein concentration and furrowing were first evident in the cortical regions closest to the equator of the mitotic spindle. As cytokinesis progressed in such asymmetrically dividing cells, fluorescent actin and myosin appeared at the opposite side of the cell just before furrowing activity could be seen there. At the end of cytokinesis, myosin and actin were concentrated beneath the membrane of the midbody and subsequently became organized in two rings at either end of the midbody.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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