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  • Cell & Developmental Biology  (2)
  • Wiley-Blackwell  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Protein synthesis in mature human oocytes (1987)
    New York, NY : Wiley-Blackwell
    Gamete Research 18 (1987), S. 97-107 
    Details
    ISSN: 0148-7280
    Keywords: protein synthesis ; oocyte ; human ; electrophoresis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: As a first step toward understanding control of gene expression in early human development, an analysis of protein synthesis and amino-acid transport in unfertilized mature oocytes was initiated. Qualitative patterns of protein synthesis were examined in individual oocytes cultured in medium containing radiolabeled methionine. No differences in synthetic pattern of proteins, resolved by one-dimensional electrophoresis and fluorography, were observed in oocytes analyzed from times varying from 12 to 52 hr following collection by laparoscopy. Contamination by follicular or corona radiata cells was readily distinguished on the basis of increased relative synthesis of a polypeptide with Mr = 44,000, a dominant product of synthesis in follicular cells. Based on the specific activity of the methionine precursor, the absolute rate of synthesis was measured to be about 50 pg/oocytc/hr, a value higher than in mouse unfertilized eggs. No difference in protein synthetic rate was observed in oocytes analyzed at 12 hr postcollection versus later times up to 50 hr postcollection. Competition of methionine uptake by leucine, efflux of radiolabeled methionine from preloaded oocytes into medium containing methionine and uptake of methionine in medium with low sodium ion concentration was observed. These findings are consistent with the presence of an L (leucine-preferring) system for neutral amino acid transport, similar to that in mouse and rabbit eggs. Total protein was measured to be about 150 ng/oocyte, a value five times that of the mouse. These studies provide basic data for further analysis of oocytes and perhaps preimplantation stage embryos in the future.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1120180202
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  • 2
    Electronic Resource
    Electronic Resource
    Amino acid transport and exchange in unfertilized mouse eggs (1986)
    New York, NY : Wiley-Blackwell
    Gamete Research 15 (1986), S. 1-12 
    Details
    ISSN: 0148-7280
    Keywords: methionine uptake ; methionine efflux ; kinetic parameters ; trans-stimulation ; trans-inhibition ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The mouse egg is an ideal model for the kinetic study of neutral amino acid exchange transport in development in that it possesses strong exchange-mediated uptake/efflux with little other efflux. Exchange transport was examined by preloading eggs in unlabeled or labeled amino acid and then measuring subsequent amino acid fluxes. The existence of two L-like (leucine-preferring) systems, a low-affinity exchange system, and a high-affinity weakly exchanging system is suggested by the differences between preloaded and control eggs in uptake specificity and in the kinetic parameters of methionine uptake (respectively, Km = 220 and 69 μM, Vmax = 98 and 32 fmol/min/egg). The Vmax of exchange-mediated efflux of methionine is similar to that for uptake into preloaded eggs, but the Km is about an order of magnitude higher. Preloading in alanine and serine (preferred substrates, along with cysteine, of system ASC) decreased the subsequent uptake of radiolabeled methionine, suggesting some ASC activity in the unfertilized mouse egg. The plateau in accumulation of leucine and phenylalanine, characteristic of simple exchange (mediated by system L), is not shared by methionine, suggesting the existence of another system (possibly an A, or alanine-preferring, system) for the transport of methionine. Amino acid transport in the mouse egg is more complex than previously thought, the egg possessing four interacting systems for the transport of the neutral amino acids.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1120150102
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    Paper (German National Licenses)
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