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  • Centrosome  (2)
  • Polyspermy  (1)
  • 1
    ISSN: 1040-452X
    Keywords: Sperm ; Aster ; Bovine ; Centrosome ; Polyspermy ; Adrogenote ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Chromatin and microtubule configurations during the first cell cycle of bovine zygotes were analyzed by DNA staining and microtubule immunolocalization using an IVM/IVF system and oocytes matured and fertilized in vivo, in order to investigate the origin of the active centrosome and to characterize the nuclear and the cytoplasmic changes following bovine fertilization. Our results suggest that the paternal centrosome is active during early zygotic development, forming a conspicuous sperm aster soon after fertilization. We also report that polyspermy in bovine eggs, leads to the formation of numerous sperm asters with different degrees of association with the chromatin. The maternal structures in both monospermic and polyspermic zygotes can be lost or degenerate. Consequently, these cells may resume the first cell cycle as androgenotes, very often with several types of mitotic activity taking place in different regions of the cell cytoplasm at the same time. As indicated by a comparison of monospermic and polyspermic fertilization rates to rates of development, it is possible that some androgenetic embryos cleave and develop to the blastocyst stage. © 1993 Wiley-Liss, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1040-452X
    Keywords: Spindle ; Oocyte ; Mammalian ; Centrosome ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Artificial activation and nuclear transfer in rabbit oocytes have been used in past years in an attempt to develop viable techniques for cloning in cattle. The procedures established in our laboratory, using the rabbit as a model, consistently lead to high rates of development to the blastocyst stage. However, the rate of embryos developing to term is considerably lower. In the present study, we undertook a detailed immunocytochemical study of the patterns of both microtubules and chromatin during the first cell cycle of electrical pulse-activated oocytes and of nuclear transfer embryos. Our goal was to investigate the responses of the cell to the different stimuli applied and to establish the sequence of events leading to first cleavage in the absence of normal fertilization. Our results show that, in both electrically activated oocytes and nuclear transfer embryos, although the initial development patterns are rather unusual, embryos become synchronized at the time of the formation of a pronuclear-like structure, and then organize metaphase spindles and cleave. These spindles consistently present small defects, suggesting that problems in the formation of the mitotic apparatus during the first cell cycle may have a long-term effect leading to embryo mortality. © 1993 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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