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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 38 (1994), S. 85-90 
    ISSN: 1040-452X
    Keywords: Meiosis ; p34cdc2 ; Cyclin B ; Histone H1 kinase ; Okadaic acid ; Phosphatase 1 and 2A ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Growing pig oocytes (≤90 μm in diameter) are unable to resume meiosis in vitro. The objective of our present experiments has been to identify the reasons for meiotic competence in these cells. By comparing histone H1 kinase activity in growing and fully grown oocytes we demonstrate that incompetence is associated with an inability to activate H1 kinase in growing oocytes. Immunoblotting was used to determine whether this kinase inactivity resulted from a lack of either p34cdc2 protein or B-type cyclin. The results established that each of these cell cycle molecules are present in comparable amounts in both growing and fully grown oocytes. In the third series of studies experiments were carried out in an attempt to induce p34cdc2 activation during growth. Treatment with okadaic acid, an inhibitor of phosphatase 1 and 2A known to stimulate and accelerate the transition into M-phase of the meiotic cycle in a number of different species, was able to induce p34cdc2 kinase activity and facilitated the G2- to M-phase in growing oocytes.We conclude that although growing oocytes in pigs have sufficient key cell cycle components for the G2 to M transition, they remain incapable of converting these components to active maturation-promoting factor (MPF) until growth is virtually completed. Inhibition of phosphatase 1 or 2A induces the formation of active MPF during growth by an as yet unidentified pathway. © 1994 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 27 (1990), S. 216-223 
    ISSN: 1040-452X
    Keywords: In vitro culture ; uterine secretions ; rabbit blastocysts ; medium treatments ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The development of cultured rabbit preimplantation embryos grown in standard media (Ham's F-10 or BSM II supplemented with bovine serum albumin (BSA) or homologous serum) or in Ham's medium supplemented with uterine flushings was compared. The uterine flushings derived from donors of 0.5-6 years of age. Uterine flushing supplemented media were used natively or after treatments like sterilization by filtration, lyophilization, three times freezing/thawing, heat denaturation, dialysis, or ultrafiltration. Compared with in vivo controls, embryonic growth was substantially reduced during in vitro culture, demonstrably by smaller diameters and impaired cell proliferation (measured by thymidine incorporation). The growth retardation was more pronounced in blastocyts (recovered at day 4 post coitum [p.c.]) than in morulae (recovered at day 3 p.c.). Development in uterine flushing media was notably better than in standard media but did not comply with in vivo development. Highest thymidine incorporation was observed in media with increased concentrations of uterine secretions and after sequential supplementation of flushings from subsequent progestational stages. Advanced donor ages, heating up to 80°C, freezing, and lyophilizing did not affect incorporation data statistically significantly, whereas sterilization by filtration, ultrafiltration, and dialysis led to a significantly reduced thymidine incorporation in the cultured embryos. The positive effects of uterine flushing supplementation are attributed to the supply of components more adjusted to the needs of the cultured embryos and/or to a reduction of pathological effects in vitro like washing out of nutritive and regulatory components from the embryo into the surrounding culture medium.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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