Percentage Of Atretic Follicles Research Articles

Chronic stress causes ovarian fibrosis to impair female fertility in mice

ObjectiveChronic psychological stress is associated with impaired follicular development and ovarian dysfunction. Many aspects of this dysfunction and the underlying mechanisms remain unclear. Using a chronic unpredictable mild stress (CUMS) mouse model, we investigate the influence of chronic stress on ovarian function and explore potential mechanisms. MethodsA CUMS mouse model was constructed over eight months, covering the period from sexual maturity to the onset of declining fertility in mice. At the end of the 2nd, 4th, 6th, and 8th months of exposure to CUMS, behavioral and physiological assays, including the sucrose preference test, tail suspension test, and serum corticosterone levels, were conducted to validate the effectiveness of the stress model. Fertility and ovarian function were assessed by analyzing the estrous cycle, number of offspring, sex hormone levels, follicle counts, granulosa cell proliferation and apoptosis, and the expression levels of fibrosis markers. Furthermore, proteomic analyses were performed on the ovaries to investigate the molecular mechanisms of ovarian fibrosis induced by CUMS. ResultsWith continued CUMS exposure, there was a gradual decline in both the ovary-to-body weight ratio and the number of offspring. Moreover, the percentage of atretic follicles was notably higher in the CUMS-exposed groups compared to the control groups. It is noticeable that CUMS triggered granulosa cell apoptosis and halted proliferation. Additionally, increased expression of α-SMA and Collagen I in the ovaries of CUMS-exposed mice indicated that CUMS could induce ovarian fibrosis. Proteomic analysis provided insights into the activation of specific biological processes and molecules associated with fibrosis induced by chronic stress. ConclusionsOur results strongly suggest that exposure to CUMS induces ovarian fibrosis, which influences follicular development and ultimately contributes to fertility decline. These findings offer novel perspectives on the impact of chronic stress on ovarian dysfunction.

Baicalein Ameliorates Chronic Stress-Mediated Ovarian Dysfunction by Upregulating the Expression of Gamma-Aminobutyric Acid B2 Receptor

Background: The aim of this study is to assess the effect of baicalein on chronic stress-mediated ovarian dysfunction in a mouse model. Methods: Forty female C57BL/6 mice were randomly divided into four groups as follows: the normal saline group (control, n = 10), the daily stress group (daily stress, n = 10), the baicalein group (baicalein, n = 10), and the daily stress + baicalein group (daily stress + baicalein, n = 10). For the daily stress model, we used a restricted stress model. Baicalein (10 mg/kg) was administered by gavage every day, and control mice received normal saline equivalently. Biopsy specimens were harvested after 4 weeks. Measurement of norepinephrine (NE) in serum was performed to assess the psychological stress level of the mice. In addition, histological changes of the uterus and ovaries and the levels of anti-Mullerian hormone (AMH) in serum were assessed to evaluate changes in ovarian function. To detect the underlying mechanisms of the amelioration of baicalein in chronic stress-mediated ovarian dysfunction, immunohistochemical methods, and quantitative real-time polymerase chain reaction were applied to determine the expression of gamma-aminobutyric acid (GABA) receptors. Results: Compared with values in the control group, serum NE concentrations were significantly increased (P < 0.001), AMH concentrations were markedly decreased (P < 0.01), the thickness of the endometrium was clearly reduced, and the percentage of atretic follicles was significantly increased in the daily stress group (P < 0.001), indicating that the chronic stress model was successfully established. In contrast, compared with values in the daily stress group, serum NE concentrations were significantly reduced (P < 0.001), AMH concentrations were significantly enhanced (P < 0.05), the thickness of the endometrium was clearly increased, and the percentage of atretic follicles was significantly reduced (P < 0.001) in the daily stress + baicalein group, indicating that baicalein clearly attenuated the ovarian dysfunction mediated by chronic stress. Moreover, the expression of the GABAB2receptor in the daily stress group was significantly reduced (P < 0.01). In contrast, treatment with baicalein resulted in increased expression of the GABAB2receptor (P < 0.01). Conclusions: Treatment with baicalein ameliorates the enhancing effect of chronic stress on ovarian dysfunction, and the mechanism can be attributed, in part, to the increased expression of the GABAB2receptor.

Effects of chronic heat stress on granulosa cell apoptosis and follicular atresia in mouse ovary.

BackgroundHeat stress is known to alter follicular dynamics and granulosa cell function and may contribute to the diminished reproductive efficiency commonly observed in mammals during the summer. Although several investigators have studied heat-induced ovarian injury, few reports have focused on the effects of chronic heat stress on ovarian function and the molecular mechanisms through which it induces ovarian injury.MethodsIn Exp. 1, 48 female mice were assigned to a control or heat-stressed treatment. After exposure to a constant temperature of 25 °C for 7, 14, 21 or 28 d (n = 6) or to 42 °C for 3 h per d for 7, 14, 21 or 28 d (n = 6), the mice were euthanized and their ovaries were analyzed for follicular atresia, granulosa cell apoptosis, changes in the abundance of HSP70 protein and serum concentrations of estradiol. In Exp. 2, the expression of HSP70 and aromatase was quantified in antral follicles cultured in vitro at 37 or 42 °C for 24 h. In Exp. 3, granulosa cells from ovaries maintained at 37 or 41 °C for 2 h were analyzed for their expression of HSP70, Bim, caspase-3 and cleaved caspase-3.ResultsIn Exp. 1, body weight and food intake of heat-stressed mice decreased (P < 0.05) compared with control mice while the concentration of estradiol in serum was lower (P < 0.05) in heat-stressed mice than in control mice. Compared with control mice, the percentage of atretic follicles and the number of antral follicles with severe apoptotic signals were increased (P < 0.05) after 21 d of heat-stressed treatment. HSP70 protein was more abundant (P < 0.05) in heat-stressed mice than control mice. In Exp. 2, heat stress increased HSP70 and decreased aromatase proteins (P < 0.05) in antral follicles. In Exp. 3, TUNEL-positive granulosa cells from heat-stressed ovaries were observed concomitant with a significant increase in HSP70, Bim and cleaved caspase-3 protein.ConclusionHeat-stress in mice decrease estradiol in serum and aromatase in antral follicles but increased number of atretic follicles and granulosa cell undergoing apoptosis which may explain the decreased fertility commonly observed in heat-stressed animals.

Inhibition of platelet-derived growth factor (PDGF) receptor affects follicular development and ovarian proliferation, apoptosis and angiogenesis in prepubertal eCG-treated rats

The platelet-derived growth factor (PDGF) system is crucial for blood vessel stability. In the present study, we evaluated whether PDGFs play a critical intraovarian survival role in gonadotropin-dependent folliculogenesis. We examined the effect of intrabursal administration of a selective platelet-derived growth factor receptor (PDGFR) inhibitor (AG1295) on follicular development, proliferation, apoptosis and blood vessel formation and stability in ovaries from rats treated with equine chorionic gonadotropin (eCG). The percentages of preantral follicles (PAFs) and early antral follicles (EAFs) were lower in AG1295-treated ovaries than in control ovaries (p < 0.01–0.05). The percentage of atretic follicles (AtrFs) increased in AG1295-treated ovaries compared to control (p < 0.05). The ovarian weight and estradiol concentrations were lower in AG1295-treated ovaries than in the control group (p < 0.01 and p < 0.05, respectively), whereas progesterone concentrations did not change. AG1295 decreased the proliferation index in EAFs (p < 0.05) and increased the percentage of nuclei positive for cleaved caspase-3 and apoptotic DNA fragmentation (p < 0.01–0.05). AG1295 increased the expression of Bax (p < 0.05) without changes in the expression of Bcl-2 protein. AG1295-treated ovaries increased the cleavage of caspase-8 (p < 0.05) and decreased AKT and BAD phosphorylation compared with control ovaries (p < 0.05). AG1295 caused a decrease not only in the endothelial cell area but also in the area of pericytes and vascular smooth muscle cells (VSMCs) in the ovary (p < 0.05). Our findings suggest that the local inhibition of PDGFs causes an increase in ovarian apoptosis through an imbalance in the ratio of antiapoptotic to proapoptotic proteins, thus leading a larger number of follicles to atresia. PDGFs could exert their mechanism of action through an autocrine/paracrine effect on granulosa and theca cells mediated by PDGFRs. In conclusion, these data clearly indicate that the PDGF system is necessary for follicular development induced by gonadotropins.

Protective effect of proanthocyanidin against oxidative ovarian damage induced by 3-nitropropionic acid in mice

Oxidative stress, which poses a threat to reproductive health, causes many serious female reproductive diseases. In this study, we investigated whether proanthocyanidins (PC) have a protective effect against oxidative stress-induced ovarian damage. Forty female ICR mice were randomized into 4 groups: a control group, a control plus PC group, a 3-nitropropionic acid (3-NPA) group, and a 3-NPA plus PC group. An ovarian oxidative stress model induced by 3-NPA was constructed using female ICR mice. After the animals were sacrificed, their ovaries were collected to measure reactive oxygen species (ROS) levels, the activities of superoxide dismutase (SOD) and catalase (CAT), and the mRNA expression levels of relevant granulosa cell apoptosis genes (Bcl-2, Bax, Bim, FasL, and caspase-3). We also conducted a histological evaluation of granulosa cell apoptosis and follicular atresia. The results showed that compared to the 3-NPA group, ROS levels and activities of T-SOD and CAT in the 3-NPA plus PC group were significantly decreased (P < 0.05), while the ratio of Bcl-2 to Bax in the 3-NPA plus PC group were significantly increased (P < 0.05). mRNA expression levels of Bim, FasL, and caspase-3 in the 3-NPA plus PC group were significantly decreased (P < 0.05), and the percentage of atretic follicles and granulosa cell apoptosis in the 3-NPA plus PC group was significantly decreased (P < 0.05). Collectively, these data indicate that PC has significant protective effects against damage induced by oxidative stress in mouse ovaries. The mechanisms of protection may be related to antioxidation and apoptosis reduction.

Decreased ovarian reserve in female Sprague–Dawley rats induced by isotretinoin (retinoic acid) exposure

Isotretinoin is a retinoid widely used for the treatment of severe nodulocystic acne. Although it has broad side effects, there is no well-designed study about its effects on the ovary. This study investigated possible toxic effects of isotretinoin on female gonads. A total of 30 female rats were randomly divided into three equal groups according to the dose of isotretinoin they were administered: 0mg/kg/day (group 1), 7.5mg/kg/day (group 2) or 15mg/kg/day (group 3). Thirty days after the treatment, the effects of isotretinoin on the ovaries were evaluated with serum anti-Müllerian hormone (AMH) concentrations, apoptosis by TUNEL assay and immunohistochemical observations by proliferating cell nuclear antigen (PCNA). The percentage of atretic follicles was calculated for each stage of folliculogenesis. The serum AMH concentrations were found to be lower in both isotretinoin groups. The percentage of atretic follicles in both isotretinoin groups was higher than the control. The number of PCNA-positive granulosa cells was decreased in the isotretinoin groups. The number of ovarian follicles with apoptotic granulosa cells was increased in the experimental groups. These data are the first to identify that exposure of isotretinoin may be responsible for decreased ovarian reserve and toxic effects on rat ovaries.Isotretinoin (13-cis-retinoic acid) is a retinoid that is widely used for the treatment of severe acne. Although it has a broad side effects profile, no well-designed study about its effects on the ovary has been published. This study was designed to investigate possible toxic effects of isotretinoin on female gonads. A total of 30 female rats were divided into three equal groups according to the dose of isotretinoin to be administered: 0mg/kg/day (group 1), 7.5mg/kg/day (group 2) or 15mg/kg/day (group 3). Thirty days after the treatment, ovarian effects of isotretinoin were evaluated with serum anti-Müllerian hormone (AMH) concentrations and immunohistochemical examination. The percentage of atretic follicles was calculated for each stage of folliculogenesis. The serum AMH concentrations were lower in both isotretinoin groups. The percentage of atretic follicles in both isotretinoin groups was higher than the control. The number of proliferating cell nuclear antigen-positive granulosa cells was decreased in the isotretinoin groups. The number of ovarian follicles with apoptotic granulosa cells was increased in the experimental groups. These data are the first to identify that exposure of isotretinoin may be responsible for decreased ovarian reserve and toxic effect on rat ovaries.

Endocrine-active compound evaluation: Qualitative and quantitative histomorphological assessment of zebrafish gonads after bisphenol-A exposure

There is great social concern about the risk involved from exposure to BPA as an endocrine disrupter in humans, as well as the possible repercussion of this chemical on the environment. In this study, the short-term effects of BPA at a gonadal level were assessed by means of different biomarkers in a model animal organism in vogue, the zebrafish (Danio rerio). For this purpose, 60 female zebrafish aged 16 weeks were used. These were exposed for 14 days in aquariums (following OECD Directive no.204) to BPA concentrations of 1, 10, 100 and 1000μg/L, in addition to a control batch. After the exposure period, the zebrafish were sacrificed and samples taken for a histopathological study by light and electron microscopy and morphometric analysis. During the fourteen days of exposure, water samples were taken from the aquariums to analyze the BPA levels. The BPA concentration in the fish and the water was determined by LC–MS/MS.The gonads of the zebrafish exposed to the BPA had a normal external appearance and there were no variations in their size or body weight. An accumulation of BPA was produced in the zebrafish tissues, and this increased as the BPA concentration to which the fish were exposed did. In the histopathological and morphometric studies, multiple alterations were observed in the zebrafish ovaries, particularly highlighting the vacuolization of the follicular cytoplasm, a great degeneration of all the cell components, and an important increase in the percentage of atretic follicles as from concentrations of 100 and 1000μg/L of BPA, verified by morphometry.These data indicate that morphological endpoints are sufficiently sensitive to individuate early effects of environmental concentration of BPA on gonads after two weeks of exposure.

Effect of sublethal hexavalent chromium exposure on the pituitary‐ovarian axis of a teleost, Channa punctatus (Bloch)

Exposure to sublethal hexavalent chromium (as 2 and 4 mg L⁻¹ potassium dichromate for 1 and 2 months) during late preparatory to mid prespawning phase of annual reproductive cycle severely affected the pituitary-ovarian axis of a teleost Channa punctatus. Gonadosomatic index (GSI), ovarian histopathology, immunocytochemistry of the pituitary gonadotrophs (LHβ-immunoreactive cells), and serum 17β-estradiol level revealed distinct dose and duration-dependent effects. Gonadosomatic index was declined. Diameter of ovary as well as ovarian follicles was reduced along with a distinct variation in the percentage of follicles. The greater percentage of previtellogenic follicles (stage I) and decline in vitellogenic ones (stage II and stage III) compared to control indicated the arrest of follicular development. The percentage of atretic follicles was also increased indicating toxic impact of metal on ovary. Decreased serum level of ovarian steroid 17β-estradiol further indicated the same. Chromium interference of the pituitary was demonstrated as atrophy and less immunointensity of LH-immunoreactive gonadotrophs. Thus, the hexavalent chromium impaired the pituitary-ovarian axis affecting at the sites of both pituitary and ovary.

Increased ovarian follicle atresia in obese Zucker rats is associated with enhanced expression of the forkhead transcription factor FOXO1

It is well established that hyperinsulinemia, resulting from insulin resistance, plays a role in the pathophysiology of polycystic ovary syndrome (PCOS). The aim of this study was to investigate if ovarian follicular development and atresia are impaired in obese hyperinsulinemic (fa/fa) Zucker rats. To gain insight into the molecular mechanism of follicular atresia, we also examined the expression and localization of forkhead transcription factor FOXO1, a major regulator of cell fate decisions such as differentiation, cell-cycle arrest, and cell death. Serum insulin but not gonadotropin levels were significantly higher in obese (fa/fa) rats when compared to lean controls. Total ovarian follicle number and the percentage of atretic follicles were also significantly increased in obese (fa/fa) rats. Follicle atresia was associated with nuclear accumulation of FOXO1 transcription factor in TUNEL-positive granulosa cells. These results suggest a role for FOXO1 in granulosa cell apoptosis and increased ovarian follicle atresia associated with hyperinsulinemia.

Endocrine disruption and ovarian morphometric responses in rats following exposure to tetradifon

We have investigated whether exposure to tetradifon causes ovary injuries, disrupts folliculogenesis in rat and whether ovary hormones (estrogen and progesterone) to be affected by this endocrine-active agent. Female rats were exposed orally to a dose of 28.9 mg/kg/day for 6 or 12 weeks. After sacrifice, ovary glands were examined for morphometric changes. The serums were used to determine levels of 17β-estradiol and progesterone. Results showed no sign of toxicity. However, tetradifon promoted a significant increase in the percentage of atretic follicles in the 12-weeks treated rats. Number and the diameter of mature follicles (tertiary and preovulatory) were markedly diminished together with a reduction of the relative weight of ovaries. Compared with controls, the treated rats exhibited significant reduction in serum 17β-estradiol and progesterone levels. These results suggest an endocrine disruption by tetradifon which may interfere with ovarian follicles development in rat.

Sympathetic pharmacological denervation in ageing rats: effects on ovulatory response and follicular population

The present study analyses the participation of ovarian innervation during reproductive senescence. We use the model of acute peripheral pharmacological sympathetic denervation with guanethidine in young (3 months old), middle-aged (12 months old) or old (18 months old) rats with spontaneous or induced ovulation. Ovarian levels of norepinephrine (NE) were measured by HPLC and the oestrous cycle, the number of ovulating animals and the percentage of atretic follicles were also assessed. Aged animals showed a progressive reduction in ovulatory capacity and an increase in ovarian NE content. Acute denervation increased the percentage of healthy follicles in 12- and 18-month-old rats compared with control adult animals. Combined treatment of denervation plus stimulation with gonadotrophins doubled the number of ova shed in young adult rats and restablished a partial ovulation in 12-month-old rats. The results suggest that ovarian noradrenergic innervation plays a modulator role in ovarian physiology during the ageing ovary process. The action of ovarian noradrenergic innervation seems to be associated with folliculogenesis and the ovarian response to gonadotrophins.

Rapid Communication ELEVATED OVARIAN AND THYMIC CELL APOPTOSIS IN WILD COTTON RATS INHABITING PETROCHEMICALCONTAMINATED TERRESTRIAL ECOSYSTEMS

The objective of this study was to determine the rates of apoptotic cell death in ovary and thymus collected from wild female cotton rats ( Sigmodon hispidus ) inhabiting five petrochemical-contaminated and five ecologically matched reference sites in Oklahoma. Overall comparison of reference and contaminated sites, using individual sites as replicates, revealed a significantly increased rate of ovarian cell apoptosis in cotton rats inhabiting contaminated sites. In comparison to rats from reference sites, the number of uterine scars was lower in rats collected from the contaminated sites. There were no significant differences in the percentage of atretic follicles among animals collected from reference and contaminated sites. The rate of thymocyte apoptosis was elevated at one of five contaminated sites, although the overall rate of thymocyte apoptosis was not significantly different when comparing all sites. To our knowledge, this is the first study documenting elevated rates of ovarian and thymic cell apoptosis in wild mammals exposed chronically to environmental toxicants.

Study of preantral follicle population in situ and after mechanical isolation from caprine ovaries at different reproductive stages

The purposes of this study were to estimate the population of caprine preantral follicles, and to evaluate quantitatively and qualitatively the efficiency of a specific mechanical method for the isolation of preantral follicles from mixed breed goats at different reproductive stages. On average, 37,646+/-4277 preantral follicles were present in goat ovaries, and 13,631+/-2399 preantral follicles were obtained after isolation. The number of preantral follicles isolated or in situ was not significantly affected by the reproductive stage. The mean recovery rate per ovary ([number of isolated follicles/number of in situ follicles] x 100) of isolated follicles was 36.2%. The distribution of follicles in situ was 67.8% primordial, 25.8% primary and 6.4% secondary; the respective distribution after isolation was 93.8%, 5.2% and 1.0%. In this study, many polyovular follicles were also observed, mainly in prepubertal goat ovaries. Histological analysis showed that few preantral follicles were atretic in situ (4.83%+/-0.35) or after the isolation procedure (4.67%+/-0.65) in the three reproductive stages. The percentage of atretic follicles was not affected either by the mechanical method or by the reproductive stage. It is concluded that a large number of preantral follicles can be successfully isolated mechanically, with a high recovery rate and a low rate of follicular atresia, irrespective of the reproductive stage of the caprine female.

Effect of passive immunization with buffalo follicular fluid antisera on ovarian activity in guinea pigs.

Ovarian activity and follicular populations were studied in guinea pigs (Cavia porcellus) following administration of antisera against buffalo follicular fluid (buFF). Antibodies were raised in rabbits and the titre tested by immunodiffusion assay. Fourteen guinea pigs cycling normally were randomized into two groups. Animals in Group I (n = 8) were treated (i.p.) with 0.5 ml antisera and in Group II (control, n = 6) with the same volume of normal rabbit serum at 12 h intervals on the 10th and 11th day of their oestrous cycle. They were sacrificed 24 h after onset of estrus when ovulation points were counted and ovaries processed for microscopical examination. Treatment with buFF-antisera increased ovulation rate (3.6 vs. 2.0; p < 0.01) but had no significant effect on the total number of follicles. However, the treatment reduced the percentages of atretic follicles in all size classes. These results indicated that the administration of a buFF-antisera produced in the rabbits increased ovulation rate in guinea pigs by reducing the incidence of atresia.

Significance of oestradiol for follicular development in hypogonadotrophic immature rats treated with FSH and hCG.

Administration of hCG (0.5 i.u.) to immature female rats that were made hypogonadotrophic by injections of an LHRH-antagonist at 22, 24, 26 and 28 days of age and in which follicular development was induced by FSH (10 i.u., given from day 26 until day 29) stimulates follicles to grow to their preovulatory size with a low amount of atresia. To investigate whether this effect of hCG on follicular growth is due to stimulation of oestradiol production, intraovarian concentrations of oestradiol were suppressed by an aromatase inhibitor and oestradiol action was blocked by an oestrogen antagonist; both of these were administered from day 25 until day 29. By day 30 this treatment had resulted in an increase in the percentage of atretic follicles. In turn, oestradiol benzoate (100 micrograms or 1000 micrograms day-1), given from day 26 until day 29 in rats treated with 10 i.u. FSH, resulted in (1) an increase in the total number of antral follicles, (2) an increase in follicular size and (3) a decrease in the percentage of atretic follicles. Although the administration of 1000 micrograms oestradiol benzoate can mimic the effects of 0.5 i.u. hCG on follicular growth to a large extent, the number of follicles with a diameter > 575 microns in rats treated with FSH plus oestrogen was smaller than that in rats treated with FSH plus hCG (10 +/- 2 and 24 +/- 2, respectively). Furthermore, a single injection of 10 i.u. hCG given on day 29 was used to induce ovulation: fewer ova were found in rats treated with FSH plus 1000 micrograms oestrogen than in rats treated with FSH plus hCG (15.2 +/- 2.1 and 46.5 +/- 1.6, respectively). From these studies, it is concluded that the effects of hCG on follicular growth and atresia can be largely attributed to the mitotic and anti-atretic effect of oestradiol. However, part of the effect of hCG cannot be explained on the basis of oestradiol action.

Changes in morphological appearance and functional capacity of recruited follicles in cows treated with FSH in the presence or absence of a dominant follicle

This study was designed to determine the effect of the presence of a dominant follicle at the beginning of FSH stimulation on the morphological appearance and functional capacity of recruited follicles during FSH stimulation in cattle. Synchronized nonlactating dairy cows were assigned to 1 of 2 groups and treated with FSH in the presence (n = 5) or absence (n = 6) of a dominant follicle between Days 7 and 12 of the estrous cycle (Day 0 = estrus) to stimulate follicular growth. Dominant follicles were identified by daily ultrasonographic observations, beginning on Day 3 of the estrous cycle. Dominant follicle had an ultrasonographic diameter ≥ 10 mm and were in a growing phase, or maintaining a constant diameter (≥ 10 mm) for less than 4 d. Ovaries were collected at slaughter on the morning of the third day following initiation of the FSH stimulation. All follicles > 2 mm were dissected, classified according to diameter (Class 1: 2 to 4.4 mm; Class 2: 4.5 to 7.9 mm; Class 3: > 8 mm), and incubated individually for 90 min in medium M-199 (37 °C, 5% CO 2). Following incubation, integrity of each follicle was evaluated histologically to assess the level of atresia and biochemically to determine the in vitro release of estradiol (E2) and androstenedione in culture media. On Day 3 of the FSH treatment, mean number of follicles in each class was similar (P > 0.1) between the 2 groups. The percentage of atretic follicles in Classes 1 and 3 on Day 3 of the FSH stimulation did not differ (P > 0.1) between the 2 groups. However, the percentage of atretic follicles in Class 2 was higher (P < 0.005) in cows treated with FSH in presence than in absence of a dominant follicle (60.8 vs 38.2%). The release of E2 in culture media by small Class 1 atretic or healthy follicles, by Class 2 atretic and by Class 3 healthy follicles was not affected (P > 0.1) by the ovarian status. However (P < 0.001), the release of E2 in culture media of Class 2 healthy and Class 3 atretic follicles was less for follicles harvested from cows bearing than from those not bearing a dominant follicle. Within each follicular class, concentrations of androstenedione in the culture media did not differ between the 2 groups (P > 0.1). These results suggest that the presence of a dominant follicle at the beginning of FSH stimulation alters the population of follicles recruited FSH stimulation. This may be associated with the reported decrease of the superovulatory response in cows superovulated in presence of a dominant follicle.

Follicular Atresia, Follicular Fluid Hormones, and Circulating Hormones During the Midluteal Phase of the Estrous Cycle in Pigs1

The incidence of atresia, concentrations of follicular fluid steroids, and circulating concentrations of estradiol, FSH, and progesterone were investigated to determine whether there was any evidence for a wave of follicular activity or atresia between Days 7 and 15 of the estrous cycle in pigs, Cyclic pigs (gilts) were slaughtered on Days 7, 9, 11, 13, and 15 (4, 4, 4, 4, and 3 pigs per day), and 287 follicles > 2 mm were dissected from ovaries to recover follicular fluid and granulosa cells. Apoptotic (Ao) granulosa cells were those containing sub-diploid DNA fluorescence as determined by flow cytometry. follicles with > or = 10% Ao granulosa cells were classified as atretic, and those with < 10% Ao granulosa cells were designated nonatretic. The percentage of atretic follicles (AF) per pig was 35.5 +/- 4.7 (mean +/- SEM), and while the percentage of AF ranged from 12% to 73%, means did not differ significantly among days. Mean follicular estradiol concentration was higher (p < 0.05) in nonatretic follicles (NAF) than in AF; in NAF, the concentration decreased (p < 0.05) from 15 ng/ml on Day 7 to 2.5 ng/ml on Day 11 and then increased (p < 0.05) to 10 ng/ml on Day 15 of the cycle. Mean follicular progesterone concentration was higher (p < 0.05) in AF than in NAF, while follicular androstenedione concentration (20 +/- 1.5 ng/ml, overall mean +/- SEM) did not differ between AF and NAF. Mean plasma estradiol, FSH, and progesterone concentrations did not differ among days of the cycle or differ significantly during the last 42 h before slaughter. Plasma estradiol and FSH concentrations were not significantly correlated with percentage of AF or with follicular steroid concentrations. These results support the notion of continuous growth and atresia of ovarian follicles in pigs independent of changes in plasma FSH and follicular steroid concentration, without evidence for a dominant cohort of follicles during the luteal phase of the estrous cycle.

The Ovarian Cycle in an Oviparous Gymnophione Amphibian, Ichthyophis beddomei (Peters)

The ovarian cycle in an oviparous gymnophione amphibian, Ichthyophis beddomei (Peters), was studied in captivity for 12 consecutive months from June, 1984 to May, 1985. A significant increase in the relative weight of the ovary, ovarian follicular diameter, recruitment of 70-80% of previtellogenic follicles (PVF) to vitellogenesis, and a significant decrease in the percentage of atretic follicles (AF) during August-November indicate that August-November might be the prebreeding phase of the ovarian cycle. The presence of the maximum number of the largest vitellogenic follicles (VF), the reduced number of AF, the minimum number of PVF, and presence of dividing oogonia during December-February suggest that the latter might be the breeding phase

Ovarian follicular development during early pregnancy in cattle.

On the day of oestrus (Day 0), 23 cows were assigned randomly to 4 groups in a 2 X 2 factorial experiment. Main effects were cow status [pregnant (P) versus non-pregnant (NP; not mated)] and day (Day 17 versus Day 34) when cows were slaughtered and ovaries collected; i.e. Groups NP-17 (N = 6), NP-34 (N = 5), P-17 (N = 6) and P-34 (N = 6). To mimic CL maintenance associated with presence of a conceptus in Group P-34, cows assigned to Group NP-34 were hysterectomized between Days 4 and 6 after oestrus. Pregnancy in Groups P-17 and P-34 (recovery of conceptus) and CL maintenance between day of surgery and Day 34 in Group NP-34 were confirmed. In Group NP-17, all cows except one were slaughtered before luteolysis. CL-bearing ovaries were serially sectioned (10 microns) and follicles (greater than 0.15 mm) were counted and measured using routine histological techniques. For each size class of follicles, the percentages of follicles were similar (P greater than 0.1) on Days 17 and 34. The percentage of non-atretic follicles (less than 4 pycnotic bodies) was lower (P less than 0.002) in pregnant than non-pregnant groups in the smallest class of antral follicles (0.16-0.28 mm) but was higher (P less than 0.03) in larger classes (0.68-3.67 mm) for pregnant groups. Percentages of atretic follicles were 3.7 and 4.9 (P greater than 0.1) for follicles of 0.16-0.67 mm, 91.1 and 78.9 for follicles of 0.68-3.67 mm (P less than 0.04) and 5.1 and 16.1 (P less than 0.05) for follicles of 3.67-78.56 mm in pregnant and non-pregnant groups respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of alterations in pulsatile luteinizing hormone release on ovarian follicular atresia and steroid secretion on diestrus 1 in the rat estrous cycle.

This study examined the importance of pulsatile luteinizing hormone (LH) release on diestrus 1 (D1; metestrus) in the rat estrous cycle to ovarian follicular development and estradiol (E2) secretion. Single injections of a luteinizing hormone-releasing hormone (LHRH) antagonist given at -7.5 h prior to the onset of a 3-h blood sampling period on D1 reduced mean blood LH levels by decreasing LH pulse amplitude, while frequency was not altered. Sequential injections at -7.5 and -3.5 h completely eliminated pulsatile LH secretion. Neither treatment altered the total number of follicles/ovary greater than 150 mu in diameter, the number of follicles in any size group between 150 and 551 mu, or plasma E2, progesterone, or follicle-stimulating hormone (FSH) levels. However, both treatments with LHRH antagonist significantly increased the percentage of atretic follicles in the ovary. These data indicate that: 1) pulsatile LH release is an important factor in determining the rate at which follicles undergo atresia on D1; 2) reductions in LH pulse amplitude alone are sufficient to increase the rate of follicular atresia on D1; 3) an absence of pulsatile LH release for a period of up to 10 h on D1 is not sufficient to produce a decline in ovarian E2 secretion, most likely because the atretic process was in its early stages and had not yet affected a sufficient number of E2-secreting granulosa cells to reduce the follicle's capacity to secrete E2; and 4) suppression or elimination of pulsatile LH release on D1 is not associated with diminished FSH secretion.