Biomedical subjects

M A Driancourt

Publications and source records attributed to M A Driancourt.

At least 37 records · Page 2Linked to original sources

PubMed1998

Multiple pituitary and ovarian defects in Krox-24 (NGFI-A, Egr-1)-targeted mice.

The zinc finger transcription factor Krox-24 (NGFI-A, Egr-1) is encoded by an immediate-early serum response gene expressed in various physiological situations and tissues. To investigate its function, we have created a null allele. Mice homozygous for the mutation have a reduced body size, and both males and females are sterile. These phenotypes were related to defects in the anterior pituitary of both sexes and in the ovary. In the pituitary, two cell lineages expressing Krox-24 are differentially affected by the mutation: somatotropes present abnormal cytological features and are reduced in number, consistent with the decreased GH content observed in these animals; in contrast gonadotropes are normal in number, but specifically fail to synthesize the beta-subunit of LH. In the ovary, LH receptor expression is prevented, indicating an involvement of Krox-24 at two levels at least of the pituitary-gonadal axis. Our data, together with the results of a previous report describing another Krox-24 mutant allele, suggest that Krox-24 may have two distinct molecular functions in the anterior pituitary: transcriptional activation of the LHbeta gene in gonadotropes and control of cell proliferation and/or survival in somatotropes by unknown mechanisms.

Animals↗

PubMed1998

Effect of follicle size and of the FecB Booroola gene on oocyte function in sheep.

Booroola ewes have a major gene that affects ovulation rate. Gene expression has consequences on ovarian somatic cells but it is unknown whether it also affects germ cells in the adult ovary. Hence, the present study examined (1) whether oocyte growth was similar in FecBFecB and Fec+ Fec+ oocytes during preantral and antral follicular growth, (2) whether the patterns of proteins neosynthesized by oocytes of these two genotypes were identical, (3) whether the ability of the oocytes to resume meiosis was unaffected by genotype and (4) whether, after IVF, oocytes from both genotypes could develop to the blastocyst stage at similar rates. Histological examination of the respective sizes of the oocyte and of the follicle demonstrated that oocytes were larger in FecBFecB versus Fec+ Fec+ preantral follicles. Resolution of the proteins neosynthesized by FecBFecB and Fec+ Fec+ oocytes by one-dimensional PAGE and image analysis demonstrated that quantitative (but not qualitative) differences could be observed between genotypes for bands at 74, 59, 35 and 25 kDa. In addition, a genotype by oocyte size interaction was detected for two additional bands at 45 and 43 kDa. After 24 h of culture in vitro in TCM-199 plus 100 ng ml-1 FSH plus 10% sheep follicular fluid, oocytes from FecBFec+ follicles gained the ability to resume meiosis at a smaller size and a higher proportion of them reached metaphase II irrespective of the size class studied compared with Fec+ Fec+ follicles. In addition, the developmental rate of eggs after IVF was also affected by follicle size and genotype, since FecBFec+ oocytes originating from 1.0-3.5 mm follicles had a greater ability (P < 0.05) to develop to the blastocyst stage than Fec+ Fec+ oocytes. It is concluded that the FecB gene, in addition to its effects on granulosa cell maturation, also affects oocyte development and function. Whether these alterations are related requires further investigation.

Animals↗

PubMed1998

Luteinization and proteolysis in ovarian follicles of Meishan and Large White gilts during the preovulatory period.

This experiment was conducted to determine why follicles luteinize faster in the Meishan breed than in the Large White breed of pig. Follicles were recovered during the late follicular phase from ovaries of both breeds before and after administration of hCG given to mimic the LH surge. First, the patterns of cholesterol transporters (high and low density lipoproteins: HDL and LDL) were compared. Cholesterol transporters detected in follicular fluid consisted of HDL only. Similar amounts of Apolipoprotein A-I were found in all samples. There was no obvious breed effect on minor lipoproteins found in the HDL-rich fraction, and this pattern was altered similarly by hCG in the two breeds. The LDL-rich samples of serum from both breeds contained similar amounts of protein. Second, three steroidogenic enzymes, adrenodoxin, 17 alpha-hydroxylase-lyase (P450(17) alpha) and 3 beta-hydroxysteroid-dehydrogenase (3 beta-HSD) were detected by immunohistochemistry and quantified by image analysis on sections of the two largest follicles. Before hCG treatment, theca interna cells demonstrated immunoreactivities for adrenodoxin (strong), P450(17) alpha and 3 beta-HSD (very strong), whereas granulosa cells displayed immunoreactivities for adrenodoxin only. After hCG treatment, the localization of the enzymes was unchanged but the staining intensity of adrenodoxin on granulosa cells and 3 beta-HSD on theca cells increased (P < 0.01 and P < 0.05, respectively). Breed effects were detected for the amounts of adrenodoxin in theca cells (Meishan > Large White; P < 0.05) and of 17 alpha-hydroxylase (Large White > Meishan, P < 0.01). Breed x treatment interactions were never detected. Finally, gelatinases, plasminogen activator, plasminogen activator inhibitor, tissue inhibitors of metalloproteases (TIMP-1 and TIMP-2) were visualized by direct or reverse zymography or western blotting. Whatever the stage relative to LH administration, follicular fluid from Large White gilts contained more TIMP-1, and TIMP-2 (P < 0.02 and P < 0.01, respectively). No breed effect was detected for the amounts of gelatinases and plasminogen activator inhibitor 1. However, for these parameters, a significant breed x time interaction was obvious, as the Meishan follicles had a greater response to hCG (P < 0.01). Since proteolysis plays a key role in the bioavailability of growth factors such as insulin-like growth factor 1, fibroblast growth factor and transforming growth factor beta, which have the ability to alter gonadotrophin-induced progesterone production in pigs, the differences observed in its control in the present study may explain, at least in part, the different patterns of luteinization observed in Meishan and Large White follicles.

3-Hydroxysteroid Dehydrogenases↗

PubMed1997

Lack of effects of growth hormone administration on ovarian function of lactating goats.

Exogenous growth hormone (GH, 5 mg d-1) was given daily to lactating goats for 4 weeks (Experiment 1) and 100 days (Experiment 2). Treatment effects on milk production and milk composition were assessed. At the end of treatment, goats were slaughtered and one ovary was processed for histological analysis while the largest follicles of the other ovary were dissected, measured and incubated in vitro (Experiment 1). In Experiment 2, following a synchronisation treatment, a superovulatory regime of pregnant mare's serum gonadotrophin (eCG) was given and ovulation rate measured at laparoscopy. In both experiments, GH administration raised milk yield (28.6% and 17% in Experiments 1 and 2 respectively). Circulating IGF1 concentrations were also increased following treatment. In contrast, no treatment effects were detected on the ovaries. In Experiment 1, the total population of antral follicles, their atresia, the number in specific size classes and the size of the largest healthy or atretic follicles were similar in control and GH treated ovaries. In addition, steroidogenesis (oestradiol and testosterone) by large follicles was also unaffected by treatment. In Experiment 2, eCG induced ovulation rate (control 6.9 +/- 7.6, treated 4.2 +/- 2.8) was also similar between groups. It is concluded that GH administration to lactating goats, while increasing milk production has no detrimental or positive consequences on ovarian function.

Animals↗

PubMed1997

Alterations in follicular maturation associated with within-breed variation in ovulation rate in Chios sheep.

Within-breed comparisons may be helpful to identify, in a given genetic background (Chios sheep), ovarian strategies and control mechanisms associated with altered ovulation rate. High and low ewes were identified from two large groups (n = 27 and n = 33 in Exp. 1 and Exp. 2 respectively) of Chios ewes submitted to repeated laparoscopies (24 times in Exp. 1 and six times in Exp. 2). High ovulatory ewes (n = 6 and n = 7 in Exp. 1 and Exp. 2 respectively) had mean ovulation rates of 4.3 (Exp. 1) and 4.2 (Exp. 2) while low ovulatory ewes (n = 6 and n = 7 in Exp. 1 and Exp. 2 respectively) had mean ovulation rates of 2.5 (Exp. 1) and 1.9 (Exp. 2). In Exp. 1, follicular function was compared in these two groups of ewes using follicles obtained at 30 h following luteolysis in the same ewes before and after unilateral ovariectomy (ULO). In Exp. 2, circulating follicle stimulating hormone (FSH) concentrations were measured from the end of the luteal phase up to the preovulatory surge in high and low ewes. Thereafter, to demonstrate a causal link between high FSH and high ovulation rate, pituitary downregulation was achieved by a 17-day gonadotrophin releasing hormone (GnRH) agonist treatment and the ovarian response to similar amounts of exogenous gonadotrophins compared between high and low ewes. Numbers of oestrogenic (in vitro oestradiol > 250 pg ml-1 h-1) follicles on the first ovary removed (Exp. 1) were 2.16 +/- 0.5 vs. 1.33 +/- 0.17 in high and low ewes (P = 0.1). Following ULO, these numbers were 3.33 +/- 0.33 and 2.5 +/- 0.18 (P < 0.05 between high and low ewes). There were no significant differences between the first and second ovaries for any of the parameters studied. Follicles from high ovulatory ewes (n = 33) differed from those of low ovulatory ewes (n = 23) by a smaller size (P < 0.01), a reduced number of granulosa cells (P < 0.01) together with decreased oestradiol (P < 0.05) and testosterone (P < 0.01) production in vitro. However, steroid production per cell (oestradiol per granulosa cell, testosterone per thecal cell) was similar in the two groups of sheep. FSH concentrations (Exp. 2) in high ovulatory ewes were significantly higher than those of low ovulatory ewes during the late luteal phase, and the decrease in FSH concentrations was steeper (1.4 ng) during the early follicular phase for high ovulatory ewes than low ovulatory ewes. Chemical hypophysectomy achieved by a 17-day treatment with a GnRH agonist demonstrated that these high FSH concentrations may be important to generate the high ovulation rate of the 'high' ewes as ovulation rate of high and low ewes was similar following chemical hypophysectomy followed by administration of similar amounts of exogenous gonadotropins to both groups of ewes. It is concluded that, despite different genetic control of their high ovulation rate (Chios-polygenic; Booroola-major gene), alterations in follicular function and its control are very similar in high ovulatory Chios and in FecB carriers.

Analysis of Variance↗

PubMed1997

Influence of sex ratio during multiple pregnancies on productive and reproductive parameters of lambs and ewes.

Because twin (and sometimes triplet) births commonly occur in sheep, interactions between foetuses of opposite sex may occur during life in utero and affect adult productive or reproductive performance. This was investigated by comparing growth, milk production and reproductive features of female lambs born as twins with a sister (FF) or a brother (FM) or born as triplets with two sisters (FFF), one brother and one sister (FFM) or two brothers (FMM). Birth weight, age and weight at puberty and milk production during the first lactation were similar between FF and FM lambs as well as between FFF, FFM and FMM lambs. Most of the reproductive parameters were unaffected by the sex ratio in utero. Ovarian development during the postnatal and prepubertal periods was identical between groups as demonstrated by the lack of differences in follicle-stimulating hormone concentrations and ovarian response to human chorionic gonadotropin. Adult ovulation rate and litter size at first lambing were also not related to sex ratio in utero. In contrast, embryonic mortality measured by the difference between ovulation rate and litter size was significantly (P < 0.05) increased in FMM lambs compared to FFF and FFM lambs. The same was observed for FF versus FM lambs. It is concluded that sex ratio in utero may have to be entered in programmes evaluating genetic merit for embryo survival in sheep.

Aging↗

PubMed1996

Relationships between follicle-stimulating hormone, follicle growth and ovulation rate in sheep.

The changes in follicle-stimulating hormone (FSH) concentration required to affect follicle growth and ovulation rate within individual ewes were examined. Relationships between peripheral FSH concentrations during the late-luteal and follicular phase and subsequent ovulation rates were investigated in 22 ewes from 4 breeds over 3 successive cycles (Experiment 1). Ewes were grouped as follows: Group 1 (n = 6), ewes exhibiting the same ovulation rate at each oestrous cycle: Group 2 (n = 5), ewes with three different ovulation rates at each oestrous cycle; and Group 3 (n = 11), ewes with the same ovulation rate at two oestrous cycles and a different ovulation rate on one occasion. Data from ewes in Group 1 and 3 provided estimates on the variation in FSH concentrations between cycles which were not large enough to alter ovulation rate (range, 0-67% variation in FSH concentration). In Group-2 ewes, there was no consistent association between increases in ovulation rate and the proportional increases in FSH concentrations. Differences in FSH concentrations were often less than those that did not alter ovulation rate in Group-I ewes. Furthermore, only 3 of 11 Group-3 ewes demonstrated high FSH concentrations associated with high ovulation rate (or low FSH concentrations and low ovulation rate) when compared with the concentrations found at the two cycles in which ovulation rate was similar. Hence, there was little evidence that FSH concentrations during the late-luteal and follicular phase are associated with changes in ovulation rate within individual ewes. In Experiment 2, follicles of similar size obtained from the same ewe (FecBFec+ and Romanov) showed markedly different responses in vitro to graded doses of FSH as measured by aromatase activity. It is concluded that, within a ewe, the large variability between gonadotrophin-dependent follicles in their requirement for FSH prevented the expression of any thresholds of ovarian response to FSH.

Animals↗

PubMed1996

Aromatase activity of ovine follicular walls: technical validation and physiological control.

Since aromatase activity quickly disappears in cultured sheep granulosa cells, its control is poorly understood. As a result, an aromatase assay was developed using cultures of follicular walls and measuring the amount of 3H2O generated from 3H-testosterone. Chromatography and mass spectrometry analysis demonstrated that 3H2O production was indeed associated with the production of oestradiol-17 beta. Optimization of the assay demonstrated: (1) a steady increase in the amount of 3H2O produced over at least 12 h; and (2) highly significant correlations between the amounts of 3H2O measured and the weight of the follicular wall or the amount of 3H-testosterone provided. Furthermore, a highly significant correlation (r = 0.82) was observed between the amount of 3H2O produced and the concentration of oestradiol in the same samples. The effects of follicle-stimulating hormone (FSH), luteinizing hormone (LH) and oestradiol on aromatization by follicles at two specific stages of maturation (recruitment, 12 h after luteolysis; dominance, 36 h after luteolysis) were then assessed. At recruitment and dominance, FSH was able to modulate aromatase activity similarly, increasing and decreasing the activity at low concentrations and high concentrations respectively. At recruitment and dominance, oestradiol had no stimulatory effect on basal aromatase activity and even blocked the stimulatory effects of FSH on aromatase at recruitment. LH significantly inhibited the FSH-stimulated aromatase activity of dominant follicles. It is concluded that: (1) FSH may induce the recruitment of follicles by increasing aromatase activity; and (2) neither oestradiol nor LH stimulate the aromatase activity of follicles which could explain maintenance of the dominant follicle.

Animals↗

PubMed1996

Analysis by two-dimensional electrophoresis of proteins secreted by sheep ovarian follicles: effects of the FecB gene, follicle size and atresia.

Proteins secreted by sheep ovarian follicles at different stages of maturation (small healthy, large healthy or large atretic) and originating from ewes with different ovulation rates (homozygous carriers or noncarriers of the FecB gene) were analysed by two-dimensional electrophoresis (PAGE) followed by computerized image analysis. Follicles were incubated intact for 1 h to assess steroidogenesis, and then incubated for 24 h in the presence of [35S]methionine. Secreted proteins were then resolved by iso-electric focusing followed by migration on 10% acrylamide slab gels and fluorography. Incorporation of label into proteins was similar irrespective of genetic type or health status of the follicles (4-6%). Small follicles incorporated significantly less (P < 0.05) label. Over 100 spots were detected on the fluorographs. The presence of the FecB gene induced qualitative and quantitative changes in the follicular protein patterns. Frequency of detection of spots 116 and 129 was significantly higher (P < 0.01) in Fec+Fec+ compared with FecBFecB follicles (80% versus 8%). In addition, amounts of proteins present in spots 2 and 12 were increased in FecBFecB follicles, while those in spots 9 and 21 were decreased. Size and atresia affected protein patterns only quantitatively. Increased amounts of proteins in spots 1, 10, 38, 44 and 113 were associated with atresia (P < 0.05). Follicle enlargement was associated with increased (P < 0.05) amounts of proteins in spots 5 and 6 and decreased amounts of proteins in spot 16. Amounts of three proteins (33, 40 and 58) were related positively to oestradiol production in vitro before labelling.

Animals↗

PubMed1996

Comparison of cellular distribution of LH receptors and steroidogenic enzymes in the porcine ovary.

Previous studies have shown a heterogeneous expression of LH receptors in various structures of the porcine ovary. Specially striking was the existence in the preovulatory follicle of inner layers of theca interna cells devoid of LH receptor and the confinement in the corpus luteum of the LH receptor to the external cellular layers. In the present study, we have compared the steroidogenic capabilities of LH receptor-positive and -negative cells using immunocytochemistry for side-chain cleavage P450, 3 beta-hydroxysteroid-dehydrogenase, 17 alpha-hydroxylase P450 and aromatase P450. We have also examined, using the same methods, the evolution of the various cell types after ovulation and during the development of the corpus luteum. In preovulatory follicles the inner layers of theca cells which were not labelled with anti-LH receptor antibodies appeared to express the steroidogenic enzymes in a way similar to that of the outer LH receptor-positive cell layers. Ovulation per se did not change the distribution of LH receptors (present in the outer luteal cells and in the granulosa) or of steroidogenic enzymes. However, 48 h after follicular rupture there as a marked decrease in overall labelling with anti-LH receptor antibody, and especially a disappearance of immunostaining in the luteal cells of granulosa origin. In the mid-luteal phase (6 days after ovulation), the receptor content seemed to increase in the peripheral luteal cells derived from the theca but the receptor did not reappear in the granulosa-derived luteal cells. Thus the down-regulation of LH receptor appeared to be reversible in the external thecal layers but irreversible in the granulosa cells. Furthermore, the distribution of the various steroidogenic enzymes in the corpora lutea delineated granulosa-derived from theca-derived cells and showed that only the external layers of the latter expressed the LH receptor. These results showed the existence in the preovulatory follicle of two theca interna regions expressing the same steroidogenic enzymes but possibly submitted to a different hormonal control. Furthermore, the cells derived from these two regions as well as the cells of granulosa origin showed a distinct pattern of variation of LH receptivity during the development of the corpus luteum. During these studies we also observed that, in the interstitial tissue, only a minority of cells which derived from remnants of atretic follicles expressed both the LH receptor and the steroidogenic enzymes.

3-Hydroxysteroid Dehydrogenases↗

PubMed1996

Alterations in follicular function associated with selection on ovulation rate in Finn ewes.

Finn ewes have been selected on ovulation rate to produce three lines with approximate ovulation rates of 5 (High), 3 (Control), and 2.5 (Low). The associated alterations in follicular function were investigated in three experiments. The function of large estrogenic follicles (Exp. 1) was assessed by measuring in vitro output of steroids and inhibin after a 1-h culture period. Follicles from High line ewes contained fewer (P < .01) granulosa cells than follicles from Low line ewes. Estradiol output per granulosa cell and testosterone output per thecal cell were greater for High than for Low line follicles (P < .01 and < .05, respectively). In contrast, inhibin output, expressed per follicle or per granulosa cell, did not differ between lines. In Exp. 2, cell proliferation in small follicles from the three lines was assessed after incubation of follicles in the presence of [3H]thymidine and in the presence or absence of FSH. The slope of the linear regression relating labeling index of the granulosa cells and follicle size differed significantly between High and Low lines with a significant negative coefficient for High line and a nonsignificant positive slope in the Low line. In Exp. 3, follicular fluid and serum proteins were compared between High and Low lines with 2D PAGE. A line difference was detected for a serum protein (40 kDa, pI = 6). High line had one spot, whereas Low line had three spots on 2D PAGE. This protein was not apolipoprotein E. Furthermore, the pattern of lipoproteins (high-density and low-density lipoproteins) in serum was similar between High and Low line sheep. The results indicate that selection for High ovulation rate was associated with smaller follicles that contained fewer granulosa cells per thecal cell. Aspects of function of estrogenic follicles (estradiol but not inhibin production) were also changed by selection.

Animals↗

PubMed1996

Follicular growth and maturation in hyperprolific and large white sows.

The mechanisms whereby hyperprolific sows achieve their increased ovulation rate (+5 oocytes on average) compared with normal Large White sows were explored in this study. The following specific questions were asked. Is increased ovulation rate related to 1) increased follicular populations within the ovaries or 2) alterations in terminal follicular growth and maturation? The population of antral follicles in six sows of each genotype was studied using histological techniques on ovaries obtained at the preovulatory stage. No difference between the total number of antral follicles, number of healthy or atretic follicles in specific size classes, and in size of the preovulatory follicles could be detected. The number of granulosa cells contained in preovulatory follicles was also similar between genotypes. Terminal follicular growth and maturation were studied in 15 sows of each genotype killed at d 1, 3, or 5 (n = 5.d-1.genotype-1) after the end of Regumate administration (d 0). Small (< or = 3.5 mm) follicles were counted, and follicles > 3.5 mm were dissected, measured, and incubated in vitro. Steroid concentrations (estradiol and testosterone) in culture medium were then measured. The two genotypes differed in the patterns of growth of their ovulatory follicles, because at d 3 all ovulatory follicles were obvious in Large White sows. In contrast, between d 3 and 5, seven additional ovulatory follicles grew in hyperprolific sows. Differences in follicular maturation between genotypes were also detected. Whereas testosterone concentrations in culture medium were similar in the two genotypes, estradiol concentrations were markedly (P < .01) increased in hyperprolific follicles. This indicates that these follicles may have an increased aromatizing ability. How this generates the altered pattern of follicular growth and the increased ovulation rate of hyperprolific sows remains to be established.

Animals↗

PubMed1995

Effects of gonadotrophin deprivation on follicular growth in gilts.

The endocrine and ovarian effects of hypophysectomy (n = 5) and gonadotrophin-releasing hormone (GnRH) antagonist administration (Antarelix) (n = 5) were studied in gilts by comparison with control animals (n = 6). All gilts were given Regumate (20 mg/d for 18 d). The last day of Regumate was day 0. Hypophysectomy and initiation of Antarelix administration (0.6 mg iv twice daily for 7 d) were performed on day 5. All ovaries were obtained at slaughter on day 12. Blood samples were obtained daily from all Antarelix-treated and control sows to measure luteinizing hormone (LH) and follicle stimulating hormone (FSH) concentrations. Frequent sampling was performed on day 10 on control and Antarelix-treated gilts to assess pulsatile LH secretion. Oestrus or LH surge was initiated before the beginning of treatment in 2 hypophysectomized, 4 Antarelix-treated, and 4 control females. Gonadotropins were undetectable in the blood of hypophysectomized sows on day 6. On day 10, pulsatile LH release was blocked in Antarelix-treated gilts. At no time were FSH concentrations significantly affected. Histological observation of the ovaries demonstrated that: (i) similar populations of healthy or total (healthy + atretic) follicles < 1 mm were found in the 3 groups of females; (ii) healthy follicles 1 to 2 mm in diameter were present in Antarelix-treated but not in hypophysectomized gilts; and (iii) healthy follicles > 2 mm were absent in Antarelix-treated and hypophysectomized gilts. The present study suggests the existence of 3 subgroups amongst antral follicles (gonadotropin independent: 0.19 to 1.1 mm; FSH dependent: 1.1 to 2 mm; LH pulses dependent: > 2 mm in diameter).

Animals↗

PubMed1994

Lack of between-follicle interactions in the sheep ovary.

Follicular growth over 2 mm in diameter is mainly regulated by gonadotrophins (FSH and LH). However, it is possible that between-follicle interactions may be involved in ensuring ovulation of a specific number of follicles. The present study tested specific hypotheses regarding: (1) a stimulatory role of atretic follicles on differentiation of follicles of the next wave; (2) a stimulatory role of large follicles in F-gene-carrier Booroola ewes on differentiation of follicles of the same ovulatory cohort; and (3) an inhibitory role of the dominant follicle on differentiation of follicles of the same ovulatory cohort. The end points measured were aromatase activity (all trials) and granulosa cell proliferation (Booroola). The techniques used tested effects of ovarian venous serum or conditioned media or follicle co-culture. Comparison of the effects of similar protein concentrations of serum or media conditioned by healthy versus atretic follicles could not demonstrate a stimulatory role of the atretic follicle. This was further confirmed using ovarian venous serum draining an ovary bearing an atretic follicle. Comparison of the effects of similar protein concentration of serum or media conditioned by F+ or ++ follicles could not demonstrate a stimulatory role of large follicles in F+ewes. This was supported by the observation that ovarian venous serum of F + or ++ ewes had similar effects on aromatase activity. Furthermore, coculture of small follicles with a large follicle of either genotype did not alter granulosa-cell proliferation compared with controls. This suggests that an alteration in the between-follicles regulation does not operate in Booroola sheep to generate their high ovulation rate. Comparison of the effects of similar protein concentrations of serum, follicular fluid from large follicles or media conditioned by large follicles showed that follicular fluid (but not conditioned media) contained an aromatase inhibitor. This suggests that dominant follicles do not secrete the aromatase inhibitor they contain.

Animals↗

PubMed1994

Evidence that a non-steroidal factor from corpus luteum of pregnant sheep inhibits aromatase activity of ovarian follicles in vitro.

Porcine and ovine follicular tissues were used to investigate, in vitro, the effect of charcoal-treated aqueous extract from ovine corpora lutea of pregnancy on aromatase activity as determined by the conversion of [3H]testosterone to oestradiol by follicular walls and measurement of 3H2O release. Extract (500 micrograms protein) prepared from corpora lutea of day 112 of pregnancy but not extract (500 micrograms) prepared from ovine fetal cotyledonary tissue obtained at a similar time significantly decreased (P < 0.02) aromatase activity of pig follicles in the absence of FSH. These results demonstrate that a non-steroidal factor in the corpora lutea of late pregnancy directly inhibits aromatase activity. When the effects of different doses (300, 600 or 1200 micrograms) of luteal extract from corpora lutea of day 100 of pregnancy on aromatase activity of pig follicles were studied, the dose by treatment (presence or absence of FSH) interaction was not significant. Luteal extract dose at 300 micrograms did not affect aromatase activity but a significant decrease in activity occurred at 600 micrograms of luteal extract (600 versus 300 micrograms, P < 0.02). There was no further significant increase in the inhibitory effect with 1200 micrograms luteal extract. When the effects of 600 micrograms luteal extract from corpora lutea of days 15, 75 or 100 of pregnancy on aromatase activity of pig follicles were studied, a significant (P < 0.05) stage of pregnancy effect was detected, but the stage of pregnancy by treatment (presence or absence of FSH) interaction was not significant. No effect was noted with day 15 or day 75 luteal extract.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

[Seasonal variations in estrus behavior and ovulatory activity in Chios and Serres ewes in Greece].

Sheep are seasonal breeders, but a lower seasonality has been reported for sheep breeds from the Mediterranean countries enabling spring matings. To further substantiate this, the present study compared seasonal variation in oestrus behaviour and ovulation in two Greek breeds (Chios and Serres) maintained in the same environment. In 27 adult ewes of each breed, oestrus behaviour, the occurrence of ovulation and ovulation rate were monitored during 2 successive years by daily inspection by rams, weekly progesterone assay in circulating blood plasma and monthly ovarian laparoscopy. The periods of anoestrus (109 +/- 8 (wk) vs 178 +/- 5 d) and anovulation (63 +/- 8 vs 149 +/- 6 d) were significantly shorter (P < 0.001 and P < 0.001) and more variable in Chios than in Serres ewes. Furthermore, the percentage of ewes exhibiting oestrus at least once monthly was significantly higher from March to July in Chios than in Serres ewes. Continuous ovulation throughout the year was noted in 5 and 2 Chios ewes during year 1 and 2, respectively. Ovulation rate (3.25 +/- 0.15 vs 1.45 +/- 0.04) was higher in Chios than in Serres ewes (P < 0.001) while duration of oestrus was also longer in Chios ewes (1.8 +/- 0.05 vs 1.5 +/- 0.06 d; P = 0.002). There were significant correlations between the duration of anovulatory periods of the 2 successive years in Chios (r = 0.43) but not Serres ewes. Ovulation rate was positively related to the onset of the sexual season in Serres but not in Chios ewes. The present data suggest that: i) the efficiency of Serres but not in Chios ewes. The present data suggest that: i) the efficiency of spring mating in these breeds is suboptimal since it is a period when the percentage of ewes exhibiting oestrus and ovulation as well as ovulation rate are limited, ii) owing to the large variation in seasonality within Chios ewes and to the good between year correlation in features of seasonality, selection against seasonality in Chios ewes could be worthwhile.

Animals↗

PubMed1992

Endocrine and ovarian responses associated with the first-wave dominant follicle in cattle.

To examine endocrine and biochemical differences between dominant and subordinate follicles and how the dominant follicle affects the hypothalamic-pituitary-ovarian axis in Holstein cows, the ovary bearing the dominant follicle was unilaterally removed on Day 5 (n = 8), 8 (n = 8), or 12 (n = 8) of synchronized estrous cycles. Follicular development was followed daily by ultrasonography from the day of detected estrus (Day 0) until 5 days after ovariectomy. Aromatase activity and steroid concentrations in first-wave dominant and subordinate follicles were measured. Intact dominant and subordinate follicles were cultured in 4 ml Minimum Essential Medium supplemented with 100 microCi 3H-leucine to evaluate de novo protein synthesis. Five days after unilateral ovariectomy, cows were resynchronized and the experiment was repeated. Follicular growth was characterized by the development of single large dominant follicles, which was associated with suppression of other follicles. Concentrations of estradiol-17 beta (E2) in follicular fluid and aromatase activity of follicular walls were higher in dominant follicles (438.9 +/- 45.5 ng/ml; 875.4 +/- 68.2 pg E2/follicle) compared to subordinate follicles (40.6 +/- 69.4 ng/ml; 99.4 +/- 104.2 pg E2/follicle). Aromatase activity in first-wave dominant follicles was higher at Days 5 (1147.1 +/- 118.1 pg E2/follicle) and 8 (1028.2 +/- 118.1 pg E2/follicle) compared to Day 12 (450.7 +/- 118.1 pg E2/follicle). Concentrations of E2 and androstenedione in first-wave dominant follicles were higher at Day 5 (983.2 +/- 78.2 and 89.5 +/- 15.7 ng/ml) compared to Days 8 (225.1 +/- 78.6 and 5.9 +/- 14.8 ng/ml) and 12 (108.5 +/- 78.6 and 13.0 +/- 14.8 ng/ml). Concentrations of progesterone in subordinate follicles increased linearly between Days 5 and 12 of the estrous cycle. Plasma concentrations of FSH increased from 17.9 +/- 1.4 to 32.5 +/- 1.4 ng/ml between 0 and 32 h following unilateral removal of the ovary with the first-wave dominant follicle. Increases in plasma FSH were associated with increased numbers of class 1 (3-4 mm) follicles in cows that were ovariectomized at Day 5 or 8 of the cycle. Unilateral ovariectomy had no effects on plasma concentrations of LH when a CL was present on the remaining ovary. First-wave dominant follicles incorporated more 3H-leucine into macromolecules and secreted high (90,000-120,000) and low (20,000-23,000) molecular weight proteins that were not as evident for subordinate follicles at Days 8 and 12.(ABSTRACT TRUNCATED AT 400 WORDS)

Androstenedione↗

PubMed1991

Dynamics of ovarian follicular development in cattle during the estrous cycle, early pregnancy and in response to PMSG.

Ovarian follicular dynamics of cattle were examined during the estrous cycle, early pregnancy and in response to PMSG. Number and size of follicles were monitored by ultrasonographic examinations. During the estrous cycle, distinct periods of follicular dominance (measured by the increase in difference in size between the largest and second largest follicle) occurred in both the luteal (Days 6-8) and proestrus (18-22) phases of the estrous cycle (two follicular waves). Associated with the well timed development of the first dominant follicle was a change in distribution of follicle numbers in small (less than 5 mm; increased on Days 2-4), medium (6-8 mm; increased on Days 3-5) and large (greater than or equal to 9 mm; increased on Days 6-9) follicular size classes. Follicular development was greater on the ovary bearing the CL for the period that the CL was present. The dominant follicle formed during the first follicular wave was capable of ovulating (6 of 8 heifers) following an injection of a synthetic analogue of prostaglandin F-2 alpha on Day 9 of the estrous cycle. During early pregnancy (Days 6-34), follicular development (size of largest follicle, number of follicles and total accumulated size of all follicles) on the ovary bearing the CL was suppressed between Days 24 and 34 of pregnancy. This was a local effect in that follicular development was sustained on the contralateral ovary. Therefore, the CL or conceptus may be regulating follicular development in a manner to help prevent luteolysis. Associated with the injection of PMSG was an initial increase in the number of small follicles followed by their recruitment into medium and large size classes leading to ovulation. Number of follicles greater than 5 mm on the Day of estrus was related (r = .97) to the number of subsequent embryos and oocytes collected. Ultrasonography is a valuable technique to monitor ovarian follicular dynamics in cattle, and can thereby be used to infer changes in physiological and endocrine states.

Animals↗