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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 31 (1992), S. 287-296 
    ISSN: 1040-452X
    Keywords: Phosphorylation ; Protein synthesis ; Pronuclei ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The nuclear restructuring that occurs between insemination and full pronuclear formation in pig eggs is accompanied by posttranslational changes to specific egg proteins. Sperm penetration begins in vitro at 3 hr postinsemination (hpi). By 5 hr, decondensing sperm heads and anaphase II plates are observed in 50% of eggs, and, by 8 hpi, both male and female pronuclei have formed. Three consistent changes to the pattern of newly synthesised proteins are triggered in this period; they affect the 46K, 25K, and 22K polypeptides. Changes are also triggered in the 180-200K polypeptides and in the 14K polypeptides, but these are highly variable. The same changes in the prefertilization pattern were observed when prelabelled eggs were used and new protein synthesis was suppressed. The first and most abrupt change involves the apparent catabolic elimination of a group of 46K unphosphorylated polypeptides (pl 7.3-6.4), whose synthesis was greatest before germinal vesicle breakdown but declined slowly in the final phase of maturation, then declined precipitously after activation. Ageing (beyond maturation) also leads to the disappearance of these polypeptides. The progressive disappearance of a set of 25K polypeptides and the concomitant appearance of a dominant 22K polypeptide is the most characteristic fertilization-induced modification to porcine egg proteins. These modifications begin within 1 hr of sperm penetration or activation, are specific to the pig, and involve heavily phosphorylated polypeptides (25K, pl 6.7-6.0) whose synthesis is begun in the early metaphase I stage. Dual ([35S] and [32P]) labelling, protein blocking experiments, and use of alkaline phosphatase suggest that dephosphorylation selectively affects these 25K polypeptides and is mainly or wholly responsible for converting them (completely within 6 hr) to a single, new (22K, pl 7.6) species that is positively charged. The 25K/22K polypeptide modification has a close temporal relationship with the formation of the male and female pronuclei.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    ISSN: 1040-452X
    Keywords: EGF ; Gonadotropin ; Follicular shell ; Fertilization ; Male pronucleus ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Epidermal Growth Factor (EGF) has been reported to stimulate nuclear maturation in porcine oocytes (Sommer et al., 1992). The objective of this experiment was to test the effect of EGF alone or in combination with gonadotropins and follicular shell coculture, on cytoplasmic maturation of oocytes in vitro. A preliminary experiment tested the effective dose of EGF for stimulation of oocyte nuclear maturation in our culture system. Nuclear maturation rates (MII%) of 67.2 ± 4.6, 81.1 ± 8.6, and 80.7 ± 5.1 for oocyte complexes cultured in the presence of 0.1, 1, and 10 ng/ml EGF, respectively, were significantly higher (P 〈 0.05) than for oocytes cultured in the absence of EGF (18.1 ± 9.4%). In the main experiment a 2 × 2 × 2 factorial random complete block design was used to examine the effect of EGF (1.0 ng/ml) alone or in combination with gonadotropins and follicular shell coculture on cytoplasmic maturation. Cytoplasmic maturation was evaluated by the ability of oocytes to decondense sperm nuclei after sperm penetration. EGF alone did not stimulate cytoplasmic maturation in oocytes in vitro (P 〉 0.05). However, EGF showed a positive interaction (P 〈 0.05) with gonadotropin treatment on male pronuclear formation. We conclude that EGF alone can stimulate nuclear maturation in pig oocytes, and EGF can interact with gonadotropins to enhance cytoplasmic maturation. A high level of cytoplasmic maturation of in vitro matured pig oocytes could be achieved using a combination of EGF, gonadotropin, and follicular shell supplementation to the culture environment. © 1994 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
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  • 3
    ISSN: 1040-452X
    Keywords: Fertilization ; Pig Oocyte ; Meiosis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: In vitro matured porcine oocytes were used to test the importance of protein synthesis for sperm penetration, the second meiotic division, and pronuclear development. Experiments were carried out to measure rates of protein synthesis inhibitors (35 μM or 350 μM cycloheximide or a combination of inhibitors) (study 1); to test for sperm penetration and pronuclear development when protein synthesis was inhibited during fertilization (study 2); to test for oocyte meiosis, sperm penetration, and female and male pronuclear development when protein synthesis was inhibited during maturation (oocyte maturation in vitro with addition of inhibitor at 0, 24, or 36 hr of culture) (study 3); and to analyze the changes in the pattern of protein synthesis during these phases. Sperm penetration, oocyte meiosis, and female pronuclear development were not affected by the total inhibition of protein synthesis during fertilization. By contrast, inhibiting protein synthesis during maturation severely impaired the completion of meiosis and pronuclear development. Although inhibition of protein synthesis after 36 hr of maturation culture did not totally block male pronuclear development (MPN), the rate of MPN formation was lower than for controls (52% vs. 72%, P 〈 0.05). However, protein synthesis was absolutely essential between 24 and 36 hr for the formation of MPN after decondensation. This period of maturation coincided with the dominant phase of protein reprogramming in the oocyte. © 1992 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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