PubMed Health⌕ Search

Biomedical subjects

J J Eppig

Publications and source records attributed to J J Eppig.

At least 19 recordsLinked to original sources
PubMed1995

Unusual cytoskeletal and chromatin configurations in mouse oocytes that are atypical in meiotic progression.

Meiotic maturation progresses atypically in oocytes of strain LT/Sv and I/LnJ mice. LT/Sv occytes show a high frequency of metaphase I-arrest and parthenogenetic activation. I/LnJ oocytes display retarded kinetics of meiotic maturation and a high frequency of metaphase I-arrest. Some I/LnJ oocytes fail to resume meiosis. Changes in the configuration of chromatin, microtubules, and centrosomes are associated with specific stages of meiotic progression. In this study, the configuration of these subcellular components was examined in LT/Sv, I/LnJ, and C57BL/6J (control) oocytes either freshly isolated from large antral follicles or after culture for 15 hr to allow progression of spontaneous meiotic maturation. Differences were found in the organization of chromatin, microtubules, and centrosomes in LT/Sv and I/LnJ oocytes compared to control oocytes. For example, rather than exhibiting multiple cytoplasmic and nuclear centrosomes as in the normal germinal vesicle-stage oocytes, LT/Sv oocytes typically contain a single large centrosome. In contrast, I/LnJ oocytes displayed many small centrosomes. The microtubules of normal germinal vesicle-stage oocytes were organized as arrays or asters, but microtubules were shorter in LT/Sv oocytes and absent from I/LnJ oocytes. After a 15-hr culture, centrosomal material of normal metaphase II oocytes was organized at both spindle poles. In contrast, metaphase I-arrested LT/Sv oocytes exhibited an elongated spindle with centrosomal material appearing more organized at one pole of the spindle. Both control and LT/Sv oocytes displayed cytoplasmic centrosomes.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Translational regulation of the gradual increase in histone H1 kinase activity in maturing mouse oocytes.

In maturing mouse oocytes, p34cdc2-associated histone H1 kinase activity gradually increases until it reaches its maximum at metaphase I (Choi et al., 1991: Development 113:789-795). In this study, treatment of oocytes with cycloheximide resulted in a failure to increase the level of histone H1 activity above that detected at approximately the time of germinal vesicle breakdown (GVB), which is approximately 20-30% of the level normally achieved at metaphase I. Cyclin B was detected in GV-stage oocytes, but there was a 2-2.5-fold increase in the amount of cyclin B in maturing oocytes from GV-stage to metaphase I and a burst of cyclin B synthesis during the first 3 hr of maturation. Okadaic acid-treatment of mouse oocytes did not accelerate activation of histone H1 kinase but rather arrested its activity at the same level observed in cycloheximide-treated oocytes. Thus the components of the p34cdc2 kinase activating system in mouse oocytes are apparently not present in GV-stage oocytes in an amount or configuration that would allow maximum kinase activation when meiosis is reinitiated by okadaic acid. Importantly, okadaic acid-treatment dramatically inhibited protein synthesis. Therefore, the inhibition of protein synthesis by okadaic acid probably abrogates the possibility of de novo synthesis of the regulators of p34cdc2 kinase required to drive its activity to the maximum level normally achieved by metaphase I. It is concluded that there is a critical point in driving the continued activation of histone H1 kinase that occurs at approximately the time of GVB. Progression beyond this point requires de novo protein synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Synthesis and accumulation of p34cdc2 and cyclin B in mouse oocytes during acquisition of competence to resume meiosis.

This study tests the hypothesis 033 that growing murine oocytes, which are incompetent to resume meiosis, are deficient in their content of p34cdc2 and/or cyclin B, the two subunits of maturation promoting factor (MPF). Accumulation of the two MPF components occurred in an asynchronous manner in growing oocytes. Cyclin B content reached maximal levels in oocytes that were not yet competent to undergo germinal vesicle breakdown (GVB), the first obvious morphological manifestation of the resumption of meiosis. Thus, the amount of cyclin B is not the limiting factor rendering these growing oocytes incompetent to undergo GVB. In contrast, synthesis and accumulation of p34cdc2 increased during the period of oocyte growth in vivo when they became competent to undergo GVB. A similar increase in the amount of p34cdc2 also occurred in cultured granulosa cell-free oocytes despite the lack of oocyte growth, but these cultured oocytes did not become GVB competent. Thus, the accumulation of p34cdc2 is probably necessary, but not sufficient, for mouse oocytes to become competent to undergo GVB. This accumulation occurs autonomously in oocytes independently of growth or of the participation of follicular somatic cells.

Animals↗
PubMed1995

Preimplantation development of mouse embryos in KSOM: augmentation by amino acids and analysis of gene expression.

Simplex optimization has generated several media that have improved the development of mouse preimplantation embryos in vitro. One objective of this study was to compare the development of preimplantation mouse embryos in one of these computer-optimized media, KSOM, with embryos that developed in vivo, in terms of the relative abundances of specific mRNAs involved in metabolism, transcription, and cell proliferation. First, however, since studies have indicated an improvement of other simple embryo culture media by addition of amino acids, the effects of the addition of amino acids to KSOM (KSOM/AA) on preimplantation development were assessed. We find that addition of both essential and nonessential amino acids to KSOM augments development in vitro, as compared to development supported by KSOM without amino acids. This augmentation is observed starting at the blastocyst stage, and is associated with increased rate of development to the blastocyst stage, increased frequency of hatching, and increased number of cells in the blastocysts. Reverse-transcription PCR was then used to assess the relative abundance of mRNAs for actin, glyceraldehyde-3-phosphate dehydrogenase, Na+, K(+)-ATPase, Sp1, TATA box-binding protein TBP, IGF-I, IGF-II, IGF-I receptor, and IGF-II receptor in embryos that developed in vivo and in vitro using KSOM/AA. Eight out of 9 of these mRNAs were present in the 8-cell embryos and blastocysts raised in KSOM/AA in amounts that were indistinguishable from those in embryos that developed in vivo. It is concluded that KSOM/AA provides an environment in which preimplantation mouse embryos can undergo development that is quantitatively similar to that occurring in vivo.

Amino Acids↗
PubMed1995

Factors affecting the developmental competence of mouse oocytes grown in vitro: oxygen concentration.

The purpose of this study was to assess the effects of oxygen concentration on the developmental competence of mouse oocytes grown in vitro because oxygen has been shown to affect the nuclear maturation of oocytes (Haidri et al., 1971: J Reprod Fertil 26:409-411) and preimplantation embryo development (Whitten, 1971: Adv Biosci 6:129-139). Oocyte--granulosa cell complexes were isolated from the preantral follicles of 12-day-old mice and cultured for 10 days in serum-free medium equilibrated with 5, 10, 15, or 20% O2. Five percent CO2 was used for all groups. Oocytes from all groups were then matured and fertilized, and preimplantation embryos cultured using 5% O2. With increased oxygen tension, there were dramatic decreases in the percentage of (1) oocytes that survived in vitro culture, (2) surviving oocytes that could resume meiosis and undergo germinal vesicle breakdown (GVB), and then cleave to the two-cell stage, and (3) two-cell-stage embryos that completed the blastocyst transition. For example, 42% of the oocytes grown in a 5% O2 atmosphere cleaved to the two-cell stage compared with only 3% when the oocytes grew in an atmosphere of 20% O2. These dramatic effects of elevated oxygen were mitigated by either increased numbers of the oocyte-granulosa cell complexes in the culture or increased concentration of oxygen late in the culture period, after the oocytes became surrounded by greater numbers of granulosa cells. When the culture period was extended for 4 days beyond the standard 10 day cultures used in the experiments described above, there was an increased occurrence of precocious GVB or failure of the somatic cells to maintain meiotic arrest. This was prevented by increased oxygen concentration. Nevertheless, extending the time of culture even in the presence of elevated oxygen failed to increase oocyte growth to the equivalent of in vivo-grown oocytes or to improve the developmental competence of the in vitro-grown oocytes. It was concluded that concentrations of O2 above 5% have a deleterious effect on oocyte development during the early stages of culture. However, increasing the concentration on O2 during the later stages, in conjunction with other treatments to promote normal granulosa cell development and function and their interaction with the oocyte, may be critical to promote normal oocyte development in vitro.

Animals↗
PubMed1995

In vitro maturation and fertilization of oocytes isolated from aged mice: a strategy to rescue valuable genetic resources.

PURPOSE: This project was to determine whether oocytes isolated from virgin aged mice, up to 18 months old, are competent to undergo cytoplasmic maturation in vitro and undergo fertilization and embryonic development. If so, oocyte maturation in vitro could be used as a strategy to rescue valuable genetic resources. RESULTS: Although the number of oocytes recovered from mice was greatly reduced with increasing age, the percentage of oocytes that underwent fertilization, cleavage, and development to the blastocyst stage was essentially unchanged up to 18 months of age. The success of cleavage to the two-cell stage was greater after maturation in vitro (81%) than gonadotropin-induced maturation in vivo (55%). About 20% (20/106) of the embryos derived from oocytes isolated from 18-month-old mice developed to term after embryo transfer. CONCLUSION: Oocytes from virgin aged mice undergo normal cytoplasmic maturation in vitro. Higher percentages of oocytes from aged mice cleave to the two-cell stage after spontaneous maturation in vitro than after gonadotropin-induced maturation in vivo. Therefore, in vitro maturation and fertilization of oocytes could be used to rescue valuable genetic resources that might otherwise be lost because of age-related infertility.

Aging↗
PubMed1995

Induction of precocious germinal vesicle breakdown (GVB) by GVB-incompetent mouse oocytes: possible role of mitogen-activated protein kinases rather than p34cdc2 kinase.

In contrast to fully grown mouse oocytes, growing oocytes released from their preantral follicles are not capable of resuming meiosis spontaneously. However, when these denuded growing oocytes are incubated for 2-3 days in control medium and then treated with okadaic acid, 95% undergo precocious germinal vesicle breakdown (GVB) and chromosome condensation within 24 h. This study shows that both events apparently occur through a p34cdc2 kinase-independent pathway, since activity of this kinase was detected only after the oocytes had undergone okadaic acid-stimulated GVB. In contrast, microtubule-associated or mitogen-activated protein (MAP) kinases 1 and 2 were activated before GVB and their level of activity was correlated with the percentage of oocytes undergoing GVB, suggesting that these kinases may promote GVB and chromosome condensation under these experimental conditions. In addition, it is shown that MAP kinases accumulate during normal oocyte growth in vivo, but not in cultured denuded oocytes in vitro even when these oocytes become competent to undergo okadaic acid-stimulated GVB. Unlike p34cdc2, the accumulation of MAP kinases requires close physical interactions between the oocytes and the granulosa cells but is not necessary for the oocyte to become GVB-competent. Therefore, it MAP kinases are actually involved in the induction of GVB and chromosome condensation during normal oocyte maturation, acquisition of GVB competence requires oocyte-autonomous accumulation of MAP kinase activator(s) rather than the MAP kinases themselves.

Animals↗
PubMed1995

Analysis of the mechanism(s) of metaphase I arrest in maturing mouse oocytes.

Fully grown mouse oocytes are normally competent to progress from prophase I to metaphase II without interruption. However, growing mouse oocytes initially become only partially competent to undergo meiotic maturation. Meiotic maturation in these oocytes does not progress beyond metaphase I. In contrast to the oocytes of most strains of mice, most oocytes of strain LT/Sv mice become arrested at metaphase I even when they are fully grown. The initiation of oocyte maturation is correlated with an increase in p34cdc2 kinase activity that continues to rise until metaphase I. The transition into anaphase I is normally correlated with a decrease in p34cdc2 kinase activity. This study demonstrated that metaphase I arrest in both partially competent growing oocytes and fully grown LT/Sv oocytes is correlated with a sustained elevation of p34cdc2 kinase activity. In fact, p34cdc2 activity continued to increase during the time when activity normally decreased. In normally maturing oocytes, some, but not all, of the cyclin B, the regulatory protein associated with p34cdc2, became degraded in oocytes that entered anaphase I. In contrast, the amount of cyclin B present in the metaphase I-arrested oocytes continued to increase at the time when it was being degraded in normal oocytes progressing to metaphase II. These results suggest that the progression of meiosis is arrested at metaphase I in both groups of oocytes because of continued p34cdc2 kinase activity sustained, at least in part, by restricted degradation of cyclin B.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenine↗
PubMed1994

Acquisition of meiotic competence by denuded mouse oocytes: participation of somatic-cell product(s) and cAMP.

In contrast to fully grown oocytes, growing mouse oocytes are not capable of undergoing germinal vesicle breakdown (GVB) when released from the follicle unless they are first cultured in somatic-cell-conditioned medium. The first objective of this study was to assess the mechanisms by which oocytes in vitro acquire the ability to resume meiosis in conditioned medium. Whereas most of the denuded oocytes that were initially incompetent of undergoing GVD underwent GVB within 4 days of culture in fibroblast-conditioned medium, oocytes cultured in control medium remained in the GV stage although their viability was sustained as judged by morphological appearance and quantitative and qualitative patterns of protein synthesis. This suggested that the effect of somatic-cell-conditioned medium is inductive rather than simply permissive. When GVB-incompetent oocytes were first incubated in control medium for 1-3 days, a larger percentage underwent GVB following exposure to the conditioned medium or okadaic acid. It was therefore concluded that some aspects of the oocytes' developmental program for the acquisition of GVB competence are oocyte-autonomous but external factors provided by the surrounding somatic cells are probably require for oocytes to become fully GVB-competent. The effect of cAMP on acquisition of GVB competence by growing oocytes was also studied. Dibutyryl cAMP dose-dependently promoted the acquisition of GVB competence by initially GVB-incompetent oocytes. Forskolin, an adenylate cyclase activator, acted in similar way and its effect was potentiated by hypoxanthine, a naturally occurring cAMP-phosphodiesterase inhibitor. Thus cAMP, in addition to maintaining meiotic arrest in GVB-competent oocytes, also participates in the acquisition of GVB competence by growing oocytes.

1-Methyl-3-isobutylxanthine↗
PubMed1994

Relationship between the developmental programs controlling nuclear and cytoplasmic maturation of mouse oocytes.

This paper focuses on the relationship between the developmental programs that regulate nuclear and cytoplasmic maturation of mouse oocytes. As oocytes near completion of their growth phase, they become competent to resume meiosis when isolated from the small antral follicles and cultured, but the progression of meiosis in many of these oocytes stops at metaphase I (MI). With further growth and development at the germinal vesicle (GV) stage, however, these oocytes become competent to complete nuclear maturation and progress to metaphase II (MII). In this study, about 44% of the oocytes were arrested at MI after isolation from the small antral follicles of 18-day-old mice and culture for 16 to 17 hr. Upon insemination, these MI-arrested oocytes produced the first polar body, formed pronuclei, cleaved, and developed to the blastocyst stage. Seventy five percent of these blastocysts were triploid, the remainder were diploid. Treatment of MI-arrested oocytes with calcium ionophore resulted in the completion of the first meiotic division and parthenogenetic activation. Moreover, while the pattern of proteins synthesized in MI-arrested oocytes was quite different from that of normal MI oocytes as determined by [35S]methionine labeling and two-dimensional gel electrophoresis, it was similar to that of MII-arrested oocytes. It was therefore concluded that some critical aspects of cytoplasmic maturation can occur in oocytes whose nuclear maturation is arrested at MI. In addition, triggers that promote entry of MII-arrested oocytes into anaphase II are sufficient to drive MI-arrested oocytes into anaphase I and to produce the first polar body when the triggers are generated in mature cytoplasm. The developmental capacity of MII oocytes that matured in vitro after isolation from 18- or 26-day-old mice were compared. The frequency of fertilization and cleavage to the 2-cell stage was equal in both groups. In surprising contrast, the ability to complete the 2-cell stage to blastocyst transition occurred much more frequently when the oocytes were from the 26- than the 18-day-old mice (82 and 27%, respectively). Thus, even though both groups of oocytes had completed nuclear maturation by progressing to MII, oocytes from the smaller follicles of the younger mice were deficient in maternal factors essential for development of embryos beyond the 2-cell stage. Further differentiation of these GV-stage oocytes of small antral follicles is therefore required to produce eggs competent of completing preimplantation development.

Animals↗
PubMed1994

Atypical maturation of oocytes of strain I/LnJ mice.

The maturation of strain I/LnJ oocytes was compared to oocytes of selected inbred strains. The time of germinal vesicle breakdown (GVB) of I/LnJ oocytes was greatly delayed compared to all other strains tested. In addition, 5% of the cumulus cell-enclosed oocytes isolated from antral follicles of I/LnJ mice failed to undergo GVB in vitro and 58% of the oocytes that underwent GVB failed to progress beyond metaphase I. Similar defects in the progression of meiosis occurred when maturation was stimulated in vivo by the administration of exogenous gonadotrophins. When in-vitro matured metaphase II oocytes were selected for in-vitro fertilization, similar percentages of I/LnJ oocytes underwent fertilization and cleavage to the 2-cell stage as oocytes from another inbred stain, C57BL/6J, and similar percentages of 2-cell stage oocytes completed the 2-cell stage to blastocyst transition in vitro. However, unlike C57BL/6J oocytes, a much lower percentage of oocytes that matured in vivo in response to exogenous gonadotrophins underwent fertilization and cleavage to the 2-cell stage than oocytes that underwent maturation in vitro. Likewise, lower percentages of 2-cell stage embryos derived from in-vivo matured I/LnJ oocytes developed to blastocysts than embryos derived from in-vitro matured oocytes. These results show than I/LnJ oocytes are atypical in the progression of both nuclear and cytoplasmic maturation. These defects may account for the poor reproductive performance of I/LnJ mice. Thus, I/LnJ mice might be a useful model for studying infertility resulting from defective oocytes.

Animals↗
PubMed1993

Production of cumulus expansion enabling factor by mouse oocytes grown in vitro: preliminary characterization of the factor.

The objective of this study was to determine whether fully grown oocytes, obtained after isolation from preantral follicles and growth in vitro, secrete paracrine factors affecting granulosa cell development and function. If so, the relative ease in producing oocytes in this way could facilitate the identification and characterization of the factors. As a test of this idea, the ability of in vitro grown oocytes to produce a paracrine factor that is known to enable the isolated cumulus oophorus to undergo expansion in response to follicle stimulating hormone (FSH) was determined. Initial experiments compared culture systems, which differed in the orientation of the oocyte-granulosa cell complexes from preantral follicles to an extracellular matrix, for their ability to support oocyte growth and the acquisition of competence to resume meiosis. The systems for culture on the surface of the matrix produced larger oocytes and the highest percentage of oocytes having competence to resume meiosis. Oocytes grown using this system secreted active cumulus expansion enabling factor, albeit at levels about half that of oocytes grown in vivo. A preliminary characterization of the cumulus expansion enabling factor secreted by the oocytes grown in vitro showed that activity was lost upon treatment with either heat (65 degrees C for 15 min) or proteinase K. Activity did not pass through a membrane having a nominal molecular weight limit (NMWL) of 100 kd but did pass through a membrane having a NMWL of 300 kd. It is concluded that cumulus expansion enabling factor is secreted by oocytes grown in vitro. This factor is probably a protein or depends upon a protein for its activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Secretion of cumulus expansion enabling factor by mouse oocytes: relationship to oocyte growth and competence to resume meiosis.

Fully grown mouse oocytes secrete a factor that enables the surrounding cumulus cells to undergo cumulus expansion upon stimulation of the cumulus cells with follicle-stimulating hormone in vitro. The secretion of the enabling factor by the oocytes is developmentally regulated; it is normally secreted in significant amounts only by oocytes that are competent of undergoing spontaneous germinal vesicle breakdown (GVB) and resuming the first meiotic division. The objective of this study was to determine the relationship, if any, among secretion of this factor, oocyte growth, and the competence to undergo GVB. Three experimental systems were used to assess these relationships. First, 20 to 25% of the oocytes isolated from the small antral follicles of mutant hypogonadal mice were GVB-incompetent even though they had achieved a size typical of GVB-competent oocytes. These large GVB-incompetent oocytes secreted almost as much cumulus expansion enabling factor as the GVB-competent oocytes. Second, GVB-incompetent oocytes cultured under conditions that promote the acquisition of GVB competence but not oocyte growth acquired the ability to secrete the cumulus expansion enabling factor. Third, the precocious activation of maturation promoting factor (MPF) in GVB-incompetent oocytes by okadaic acid did not stimulate the secretion of cumulus expansion enabling factor. It is concluded that the secretion of cumulus expansion enabling factor by oocytes is (1) independent of oocyte growth, (2) independent of competence to undergo GVB, and (3) not induced by the precocious activation of MPF. Thus, although the secretion of the enabling factor normally coincides with the time of acquisition of competence to undergo GVB, the ability to secrete the enabling factor is independent of oocyte maturation. Nevertheless, factors that promote the oocyte's program that leads to competence to undergo GVB probably also promote the ability to secrete the enabling factor.

Animals↗
PubMed1992

Modulation of meiotic arrest in mouse oocytes by guanyl nucleotides and modifiers of G-proteins.

Guanyl nucleotide binding-proteins, or G-proteins, are ubiquitous molecules that are involved in cellular signal transduction mechanisms. Because a role has been established for cAMP in meiosis and G-proteins participate in cAMP-generating systems by stimulating or inhibiting adenylate cyclase, the present study was conducted to examine the possible involvement of G-proteins in the resumption of meiotic maturation. Cumulus cell-free mouse oocytes (denuded oocytes) were maintained in meiotic arrest in a transient and dose-dependent manner when microinjected with the nonhydrolyzable GTP analog, GTP gamma S. This effect was specific for GTP gamma S, because GppNHp, GTP, and ATP gamma S were without effect. Three compounds, known to interact with G-proteins, were tested for their ability to modulate meiotic maturation: pertussis toxin, cholera toxin, and aluminum fluoride (AlF4-). Pertussis toxin had little effect on maturation in either cumulus cell-enclosed oocytes or denuded oocytes when meiotic arrest was maintained with dibutyryl cAMP (dbcAMP) or hypoxanthine. Cholera toxin stimulated germinal vesicle breakdown (GVB) in cumulus cell-enclosed oocytes during long-term culture, but its action was inhibitory in denuded oocytes. AlF4- stimulated GVB in both cumulus cell-enclosed oocytes and denuded oocytes when meiotic arrest was maintained with hypoxanthine but was much less effective in dbcAMP-arrested oocytes. In addition, AlF4- abrogated the inhibitory action of cholera toxin in denuded oocytes and also that of follicle-stimulating hormone (FSH) in cumulus cell-enclosed oocytes. Cholera toxin or FSH alone each stimulated the synthesis of cAMP in oocyte-cumulus cell complexes, whereas pertussis toxin or AlF4- alone were without effect. Both cholera toxin and AlF4- augmented the stimulatory action of FSH on cAMP. These data suggest the involvement of guanyl nucleotides and G-proteins in the regulation of GVB, although different G-proteins and mediators may be involved at the oocyte and cumulus cell levels. Cholera toxin most likely acts by ADP ribosylation of the alpha subunit of Gs and increased generation of cAMP, whereas AlF4- appears to act by antagonizing a cAMP-dependent step.

Adenylate Cyclase Toxin↗
PubMed1992

Comparison of embryonic developmental competence of mouse oocytes grown with and without serum.

The first objective of this study was to determine whether oocyte growth in serum-free medium affects the solubility of the zona pellucida to alpha-chymotrypsin digestion, which is an index of zona pellucida "hardening" and reflects the potential penetrability of the zona pellucida by sperm. Oocyte-granulosa cell complexes were isolated from the preantral follicles of 12-day-old mice and cultured for 10 days in medium containing 5% fetal bovine serum (FBS) or in serum-free medium. The zonae pellucidae of oocytes grown in serum-free medium were four times as hard as freshly isolated germinal vesicle (GV)-stage oocytes grown in vivo or oocytes grown in vitro in FBS-containing medium. The hardening of the zonae pellucidae of oocytes grown in serum-free medium was prevented by addition of fetuin. The second objective was to compare the competence to undergo embryogenesis of oocytes that grew in serum-free vs. FBS-containing medium. Approximately 70% of the oocytes underwent maturation regardless of whether the medium was serum-free or contained FBS. Of the mature ova grown in medium containing FBS, 53% cleaved to the two-cell stage after insemination compared with only 6% of the ova grown in serum-free medium. Addition of fetuin to the serum-free medium used for oocyte growth increased the frequency of cleavage to the two-cell stage. Of the embryos derived from oocytes that grew in FBS-containing medium, 70% completed the two-cell stage to blastocyst transition.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Mating stimulates estradiol production by ovaries of the musk shrew (Suncus murinus).

Asian musk shrews (Suncus murinus) are induced ovulators, but exhibit no cyclic changes in reproductive structures or in sexual behavior. Mating behavior is induced by contact with a male. To determine if mating induces changes in ovarian steroidogenesis, ovaries removed from unmated animals and at 3, 10, 15, and 36 h after mating were cultured for 4 h in the presence or absence of gonadotropins (LH + FSH, 1 microgram/ml). Histological analysis revealed no obvious changes in follicular size or appearance at the end of culture in ovaries cultured at 3 and 10 h post-mating, as compared with ovaries from unmated shrews, and mating did not stimulate any discernable changes in steroid secretion in these two groups. However, at the end of the culture period, ovulation had occurred or was occurring in ovaries from 35% of the animals ovariectomized at 15 h after mating, and corpora lutea (CLs) were present in 39% of ovarian pairs obtained 36 h after mating. At 15 h post-mating, ovaries with ovulations secreted three times more estradiol than did ovaries that showed no evidence of stimulation by mating, but there were no differences in testosterone or progesterone production. In contrast, ovaries isolated 36 h post-mating with CLs secreted dramatically more of all three steroids than ovaries without CLs (23, 13, and 52 times more estradiol, testosterone, and progesterone, respectively). These data are consistent with plasma concentrations of estradiol at the time of ovariectomy, which were twice as high at both 15 and 36 h after mating, in animals whose ovaries showed evidence of ovarian stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗