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J J Eppig

Publications and source records attributed to J J Eppig.

At least 109 records · Page 6Linked to original sources
PubMed1984

Sulfated glycosaminoglycans inhibit hyaluronic acid synthesizing activity in mouse cumuli oophori.

Prior to ovulation, the cumulus cells that surround the oocyte become embedded in a matrix containing hyaluronic acid (HA). Sulfated glycosaminoglycans (GAGs) prevent the hormonally stimulated deposition of this matrix in vitro. The goal of this project was to determine the effect of sulfated GAGs on the HA-synthesizing activity of the cumuli oophori. This activity was measured in lysates of mouse cumuli oophori after stimulation of isolated cumulus cell-oocyte complexes with follicle-stimulating hormone (FSH) in the presence or absence of sulfated GAGs. FSH treatment resulted in a 5-fold stimulation of HA-synthesizing activity by 3 h in vitro. This induction was inhibited in a dose-dependent manner by heparin and chondroitin sulfate B. However, addition of heparin or chondroitin sulfate B to the assay mixtures containing lysates of FSH-stimulated cumuli oophori had no effect on the HA-synthesizing activity. Heparin also suppressed HA-synthesizing activity stimulated by dibutyryl cyclic adenosine monophosphate. Heparin inhibited the continued increase in hyaluronic acid synthesizing activity when added to cultures after 3 h of FSH stimulation. Also, addition of heparin to cultures of cumuli oophori after 3 or 6 h of incubation in medium containing FSH resulted in only partial cumulus expansion. These results indicate that sulfated GAGs, which are found in ovarian follicular fluid and are a component of extracellular matrix, inhibit some cellular process(es) that results in increased HA-synthesizing activity. The sulfated GAGs also have the ability to suppress HA-synthesizing activity after it has been induced to levels that result in partial cumulus expansion. However, the sulfated GAGs are not direct enzyme inhibitors.

Animals↗
PubMed1984

Chemical signals that regulate mammalian oocyte maturation.

The nature and functions of the chemical signals involved in the acquisition of competence to resume meiosis, and the maintenance of meiotic arrest in antral follicles are the subjects of this paper. Evidence indicating that gonadotropins are not required for the development of competence to undergo spontaneous maturation is discussed. However, gonadotropins may promote optimal conditions for oocyte development via an estrogen-dependent action on follicular cells. Evidence for the participation of cyclic AMP (cAMP), steroids and a putative maturation-inhibiting factor in the maintenance of meiotic arrest in mammalian oocytes is discussed. Cyclic AMP seems to play a critical role in the maintenance of meiotic arrest by actions in both granulosa/cumulus cells and oocytes. However, cAMP does not appear to equilibrate between cumulus cells and oocytes. In the granulosa/cumulus cells, cAMP may promote the generation/activation of a maturation-inhibiting factor which is transferred to the oocyte. Oocyte cAMP appears to be produced in the oocyte itself. The putative maturation-inhibiting factor may be maintained in an active form by a cAMP-dependent process in the oocyte. Alternatively, the putative maturation-inhibiting factor may play a role in maintaining oocyte cAMP levels. Some steroid hormones act synergistically with a cAMP-dependent process in the oocyte to maintain meiotic arrest. However, the physiological significance of this observation remains in question.

Animals↗
PubMed1984

Cyclic adenosine monophosphate and ovarian follicular fluid act synergistically to inhibit mouse oocyte maturation.

The relationship between cAMP and the capacity of two partially-purified fractions of porcine follicular fluid (PFF) to suppress mouse oocyte maturation was investigated. The fractions used were: 1) a low molecular weight filtrate (less than 10,000) derived from Amicon PM10 filtration of PFF (PM10), and 2) a fraction from Bio-Gel P2 chromatography of the PM10 filtrate (Bio-Gel) that has meiotic inhibitory activity in porcine oocytes. PM10 alone produced a transient inhibition of the maturation of both cumulus cell-enclosed and denuded mouse oocytes, as manifested by germinal vesicle breakdown. The addition of FSH or (Bu)2cAMP to medium containing either of the PFF fractions resulted in dramatic synergism of the inhibitory effect of PFF alone in cumulus cell-enclosed oocytes. Forskolin or (Bu)2cAMP promoted a similar synergistic response with either PFF fraction in denuded oocytes. The degree of inhibition was consistently greater in cumulus cell-enclosed than in denuded oocytes. The putative inhibitor was dialyzable through tubing having a nominal molecular weight cutoff of 1,000. Proteolysis, acid hydrolysis, or ether extraction of PM10 did not reduce its inhibitory synergism with (Bu)2cAMP. However, inhibition was completely abolished by charcoal extraction. Steroid hormones did not mimic the PM10-induced synergism when added to (Bu)2cAMP-containing medium in a concentration at least 14-fold greater than that present in PM10-supplemented medium. In conclusion, our results demonstrate the presence of a factor(s) in PFF that acts synergistically with a cAMP-dependent process to inhibit oocyte maturation in vitro. Furthermore, although PFF fractions suppressed the maturation of both denuded and cumulus cell-enclosed oocytes, cumulus cells appear to mediate the inhibitory activity of PFF. The data also suggest that the PFF inhibitor is a small (mol wt less than 1,000) hydrophobic molecule but not a peptide or nonpolar lipid.

1-Methyl-3-isobutylxanthine↗
PubMed1983

Inhibition of oocyte maturation in the mouse: participation of cAMP, steroid hormones, and a putative maturation-inhibitory factor.

The hypothesis that cumulus cells inhibit oocyte maturation by a cAMP-dependent process was tested (R.M. Schultz, R. Montgomery, P.F. Ward-Bailey, and J.J. Eppig (1983). Dev. Biol. 95, 294-304.). Treatment of isolated cumulus cell-oocyte complexes with follicle-stimulating hormone (FSH) resulted in a dose-dependent increase in both cumulus cell cAMP levels and in the extent of inhibition of germinal vesicle breakdown (GVBD), the first morphological manifestation of oocyte maturation. Furthermore, it was found that concentrations of a membrane-permeable analog of cAMP, dibutyryl cAMP (dbcAMP), that were below those required for complete meiotic inhibition had a greater inhibitory effect on cumulus cell-enclosed oocytes than on denuded oocytes. Cumulus cell-enclosed and denuded oocytes matured at the same time in the absence of dbcAMP. Ablation of the gap junctions that couple cumulus cells to the oocyte abolished the maturation-inhibitory action of cumulus cells that was promoted either by FSH or low concentrations of dbcAMP. These results are consistent with the hypothesis that inhibition of oocyte maturation is mediated by a factor of granulosa/cumulus cell origin, other than cAMP, which requires cAMP for its activity and/or generation, and an intact intercellular coupling pathway between cumulus cells and the oocyte. A variety of steroid hormones potentiated the FSH-induced inhibition of maturation in cumulus cell-enclosed oocytes. In addition, steroid hormones inhibited maturation in denuded oocytes, but only when oocyte cAMP levels were elevated by cAMP analogs or forskolin. Steroids alone did not inhibit maturation of either cumulus cell-enclosed or denuded oocytes. Moreover, the steroids alone or in combination with FSH did not affect metabolic coupling between the cumulus cells and oocytes, nor did testosterone affect the forskolin-induced level of cAMP in denuded oocytes. Therefore, it is proposed that the oocyte is a site for the synergistic activity of steroid hormones with a cAMP-dependent process in inhibiting maturation. Results of these studies are discussed in terms of the roles of intercellular communication, cAMP, a putative maturation-inhibiting factor, and steroid hormones in the inhibition of maturation of mouse oocytes.

1-Methyl-3-isobutylxanthine↗
PubMed1981

Ovarian glycosaminoglycans: evidence for a role in regulating the response of the oocyte-cumulus cell complex to FSH.

The effects of sulfated glycosaminoglycans (GAGs) on FSH-stimulated cumulus expansion and hyaluronic acid (HA) synthesis were tested using cumuli oophori isolated from mice. It was found that heparin (Hep), heparin sulfate (HeS) and chondroitin sulfates (CSs) A,B, and C inhibited FSH-stimulated cumulus expansion and HA synthesis. The relative potencies of these GAGs in inhibiting HA synthesis was as follows: Hep greater than HeS congruent to CS-B greater than CS-C greater than CS-A. The GAGs did not block spontaneous oocyte meiotic maturation. It is suggested that the GAGs may function in vivo to block the response of the cumulus cells to FSH indigenous to the Graafian follicle prior to the preovulatory gonadotropin surge.

Animals↗
PubMed1979

A comparison between oocyte growth in coculture with granulosa cells and oocytes with granulosa cell-oocyte junctional contact maintained in vitro.

Evidence is presented that strongly supports the hypothesis that the junctional association between oocytes and granulosa cells must be maintained to promote oocyte growth and development in vitro and that the coculture of oocytes with granulosa cells is not a sufficient condition for oocyte development. Furthermore, it is shown that incorporation of uridine and leucine by oocytes into TCA-insoluble material is significantly greater in granulosa cell-enclosed oocytes than in cocultured oocytes.

Animals↗
PubMed1979

Ultrastructural and morphometric studies of delta cells in pancreatic islets from C57BL/Ks diabetes mice.

An ultrastructural and immunocytochemical study was undertaken to elucidate the temporal and quantitative aspects of the changes occurring in the delta cells in the pancreatic islets of C57BL/KsJ db/db (diabetes) mice. Electron microscopy revealed that prior to the major topographical redistribution of delta cells from their peripheral location to the islet interior, long delta cell filopodial extensions penetrated into the islet, greatly increasing the area of surface contact between delta cells and hypersecretory beta cells. Coincident with delta cells redistribution in islets of 8 to 10 week diabetes mice, the mean number of delta cells per islet had increased significantly. In contrast, their volume density had decreased, indicating incomplete compensation for beta cell hyperplasia which had commenced approximately 4 weeks earlier. In the 14 week mutants, numbers of delta cells per islet and islet volume reached maximum values while delta cell volume density had been restored to a control level. Delta cell volume density exhibited a 2-fold increase in the mutants at 20 weeks that coincided with massive beta cell necrosis. However, a decline in the number of delta cells per islet (173.6 +/- 20.9 at 14 weeks versus 91.2 +/- 20 weeks) suggests that islet degeneration in terminal stages of the syndrome also includes some loss of these cells.

Animals↗
PubMed1979

Endocrine pancreatic cells of postnatal "diabetes" (db) mice in cell culture.

Ultrastructural characteristics as well as secretory and biosynthetic behavior of monolayer pancreatic cell cultures established from 4-day-old C57BL/KsJ misty diabetic (m db/m db) mice have been studied in comparison to normal littermate controls. Hypersecretion of glucagon by alpha-cells from BL/Ks misty diabetic mice after 2 days in vitro was found to precede any hyperfunction of the insulin-secreting beta-cells. The increased level of glucagon-release in BL/Ks cell cultures from diabetic mice was accompanied by a greatly enhanced level of incorporation of [3H]tryptophan into glucagon-like molecules whose specific radioactivity was up to 15-fold higher than that observed in cultures from genetic controls. The finding of an alpha-cell dysfunction in cultures established from preweaning diabetic BL/Ks mice suggests that glucagon could play an early role in shaping the events that culminate in the expression of frank diabetes in this inbred strain.

Animals↗