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  • oocyte maturation  (3)
  • Analytical Chemistry and Spectroscopy  (2)
  • United States
  • 1985-1989  (5)
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Year
  • 1
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The ratio of the fragment ions at m/z 122 and m/z 123 in the positive ion fast atom bombardment or secondary ion mass spectra of thiamine hydrochloride varies with sample preparation and experimental conditions. For all mass spectra that contained significant abundances of matrix (S) ions [S + H]+, the fragment at m/z 123 is the more abundant of the two ions. If [S + H]+ ions are not observed in the mass spectrum under the conditions selected, the ion at m/z 122 is more abundant. This correlation suggests that hydrogen transfer to the fragment ion occurs in the gas phase, with the composition of the ion-solvent cluster ions in the selvedge region being the key factor. The ratio of the fragment ions at m/z 123 and m/z 122 is thus an indicator of the extent of protonation in the selvedge, the region immediately above the solvent surface created by primary particle bombardment.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0148-7280
    Keywords: oocyte maturation ; follicular fluid ; mouse ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The effects of the putative maturation inhibitor in porcine follicular fluid on gonadotropinstimulated reversal of cyclic adenosine monophosphate (cAMP)-maintained meiotic arrest in mouse oocytes in vitro were assessed in this study. When cumulus cell-enclosed oocytes were cultured in a suboptimal inhibitory concentration of dibutyryl cAMP (dbcAMP), the effect of follicle-stimulating hormone (FSH) on oocyte maturation was initially inhibitory at 3 hr, but stimulatory at 6 hr. Supplementation of the medium with an ultrafiltrate of porcine follicuiar fluid (PM10-filtrate) completely suppressed FSH-promoted reversal of inhibition at 6 hr. Charcoal extraction eliminated this effect of the PM10-filtrate. FSH reversed the inhibition of maturation of cumulus cell-enclosed oocytes maintained by a high concentration of dbcAMP and suboptimal concentrations of the phosphodiesterase inhibitor, 3-isobutyl-1-methyl xanthine (IBMX), during a 21-22-hr culture period. However, the effect of a completely inhibitory concentration of IBMX was not reversed by gonadotropin. A component of serum was also found to inhibit FSH reversal of dbcAMP-maintained meiotic arrest, and this activity was removed by charcoal extraction. In addition, when oocytes were cultured in medium containing a suboptimal concentration of dbcAMP plus a low molecular weight fraction (〈 1,000) of porcine follicular fluid, porcine serum, or fetal bovine serum, a synergistic inhibition of maturation was observed. Experiments with highly purified gonadotropins revealed that reversal of dbcAMP-maintained meiotic arrest occurred only in response to FSH; neither highly purified luteinizing hormone nor human chorionic gonadotropin could mimic this action of FSH. Also, this effect was mediated by the cumulus cells, since FSH could not reverse dbcAMP-maintained meiotic arrest in denuded oocytes. Furthermore, elevating cAMP levels in denuded oocytes augmented, rather than reversed, the inhibitory action of dbcAMP on oocyte maturation. These data therefore suggest that dbcAMP- or IBMX-maintained meiotic arrest in vitro is reversed by an FSH-stimulated, cAMP-dependent process mediated by the cumulus cells and demonstrate that a factor present both in follicular fluid and serum prevents this action of the gonadotropin.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0148-7280
    Keywords: oocyte maturation ; hypoxanthine ; adenosine ; cAMP metabolism ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Hypoxanthine and adcnosine are present in preparations of mouse ovarian follicular fluid, and these purines maintain mouse oocytes in meiotic arrest in vitro (Eppig et al.: Biology of Reproduction 33:1041-1049, 1985). The first hypothesis tested in this study is that purines which maintain meiotic arrest act by maintaining meiosis-arresting levels of cyclic adenosine monophosphatc (cAMP) in the oocyte. Oocyte-cumulus cell complexes were incubated in control medium (no added purines), or medium containing 0.75 mM adenosine, 4 mM hypoxanthine, or both for 3 hr and the percentage of the oocytes that underwent germinal vesicle breakdown (GVB) and the cAMP content of the intact complexes and the oocytes were determined. Adenosine alone had little inhibitory effect on GVB at this time point but sustained higher levels of cAMP in the oocytes. Hypoxanthine maintained 80% of cumulus cell-enclosed oocytes in meiotic arrest and also sustained higher cAMP levels in the oocytes. The additon of adenosine to hypoxanthine-containing medium increased the percentage of oocytes maintained in meiotic arrest, and increased the amount of cAMP in the oocytes above that maintained by either hypoxanthine or adenosine alone. Neither hypoxanthine, adenosine, nor hypoxanthine plus adenosine altered the cAMP content of intact complexes when assayed after 3 hr culture. Microinjection of an inhibitor of the catalytic subunit of cAMP-dcpendent protein kinase induced GVB in denuded oocytes cultured in medium containing hypoxanthine. This purne, therefore, maintained meiotic arrest by sustaining elevated cAMP levels within the oocytes.The second hypothesis tested in this study is that purines maintain meiosis-arresting levels of cAMP, at least in part, by inhibiting cAMP phosphodiestcrase activity. In descending order of potency, 3-isobutyl-l-methylxanthine (IBMX), guanosine, hypoxanthine, adenosine, and xanthosine inhibited cAMP phosphodiesterase in oocyte lysates. Moreover, like the potent phosphodiesterase inhibitor IBMX, hypoxanthine augmented the cAMP meiotic arrest and cAMP accumulation mediated by follicle-stimulating hormone (FSH) in intact complexes. Therefore, inhibition of oocyte phosphodiesterase appears to be one mechanism by which the purines could maintain meiosis-arresting levels of cAMP.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0148-7280
    Keywords: mouse ; oogenesis ; oocyte maturation ; cyclic adenosine monophosphate ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The cyclic adenosine monophosphate (cAMP) content of intact oocyte-cumulus cell complexes at various times after the induction of oocyte maturation in mice in vivo was correlated with the time of commitment by the oocytes to undergo germinal vesicle breakdown (GVB) and metabolic coupling between the oocyte and cumulus cells. Seventy-nine percent of the oocytes either underwent GVB or were committed to do so by 2 h after injection of human chorionic gonadotropin (hCG). This occurred without a decrease in the coupling between cumulus cells and the oocyte and with increasing cAMP levels in the oocyte-cumulus cell complex. Maintenance of threshold levels of cAMP within mammalian oocytes appears essential for the maintenance of meiotic arrest, but data presented here suggest that oocyte maturation in mice is induced by gonadotropins in nonatretic follicles in vivo by some mechanism other than one which decreases the cAMP content of the intact oocyte-cumulus cell complex.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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