Reduced Ovulation Rate Research Articles

Constant darkness negatively affects the outcome of hormonally induced reproduction in cultured Eurasian perch females

This study aimed to assess the effect of constant darkness applied to fish during controlled breeding on reproductive traits in domesticated females of Eurasian perch. Based on the assumption that keeping fish in constant darkness during the reproduction operation may reduce stress, suspected to be responsible for variable spawning effectiveness in this species. Two conditions were assessed (16 h light per day [group 16L] and constant darkness [group 0L], two tank replicates per condition). The reproductive protocol involved a 7-day-long adaptation period for group 0L where photoperiod was reduced by 2.3 h a day down to constant darkness. After the adaptation period, two hormone injections (salmon gonadoliberin analogue) were applied to both groups: priming (10 µg/kg) and resolving (25 µg/kg) with a 7-day interval between them. During the study, morphometric indices were recorded and blood, brain, and pituitary samples were collected to assess stress markers and determine hypothalamic-pituitary-gonadal axis functioning via measuring blood plasma hormones, as well as gonadoliberin and gonadotropins (luteinising hormone [LH] and follicle-stimulating hormone [FSH]) transcript abundance (n = 7 for each group at each sampling point). In addition, kinetics of the final oocyte maturation (FOM) process, ovulation rate, and egg quality of each group was monitored (n = 12 for each group). The results indicated that there were no differences in terms of morphometry, FOM kinetics, and most stress indices between groups throughout the experiment, except haematocrit, which increased immediately following the acclimation period in fish kept in darkness. Constant darkness negatively affected plasma levels of 17α,20β-dihydroxy-4-pregnen-3-one (DHP) and LH transcript expression at the time of the second hormone injection. This indicated that exposure to constant darkness negatively affected priming of the hormonal dose applied, resulted in the disruption of ovulation, and reduced ovulation rates (50%) for group 0L, as compared to 16L (91%). The findings of this study clearly indicate that constant darkness may have significant deleterious effects on reproductive traits throughout out-of-season induced, hormonally supported, controlled reproduction. Therefore, we advise against the use of constant darkness when managing broodstock reproduction in domesticated Eurasian perch.

Prenatal exposure to bisphenols affects pregnancy outcomes and offspring development in rats

The objective of this study was to evaluate the effects of gestational exposure to low doses of bisphenol A (BPA), bisphenol S (BPS), and bisphenol F (BPF) on pregnancy outcomes and offspring development. Pregnant Sprague-Dawley rats were orally dosed with vehicle, 5 μg/kg body weight (BW)/day of BPA, BPS and BPF, or 1 μg/kg BW/day of BPF on gestational days 6–21. Pregnancy and gestational outcomes, including number of abortions and stillbirths, were monitored. Male and female offspring were subjected to morphometry at birth, followed by pre- and post-weaning body weights, post-weaning food and water intakes, and adult organ weights. Ovarian follicular counts were also obtained from adult female offspring. We observed spontaneous abortions in over 80% of dams exposed to 5 μg/kg of BPF. BPA exposure increased Graafian follicles in female offspring, while BPS and BPF exposure decreased the number of corpora lutea, suggesting reduced ovulation rates. Moreover, BPA exposure increased male kidney and prostate gland weights, BPF decreased epididymal adipose tissue weights, and BPS had modest effects on male abdominal adipose tissue weights. Prenatal BPS exposure reduced anogenital distance (AGD) in male offspring, suggesting possible feminization, whereas both BPS and BPA induced oxidative stress in the testes. These results indicate that prenatal exposure to BPF affects pregnancy outcomes, BPS alters male AGD, and all three bisphenols alter certain organ weights in male offspring and ovarian function in female offspring. Altogether, it appears that prenatal exposure to BPA or its analogues can induce reproductive toxicity even at low doses.

Sustained ERK1/2 signaling is necessary for follicular rupture during ovulation in mice.

Abolition of the LH-induced ERK1/2 pathway leads to dramatic changes in gene expression in granulosa cells, subsequently abrogating ovulation. Here we explored whether sustained ERK1/2 signaling beyond immediate-early hours of the LH surge is important for ovulation in mice. First, we examined the effect of inhibition of ERK1/2 activity at 4 h after hCG stimulation on ovulation in superovulated immature mice. Treatment with the ERK1/2 pathway inhibitor PD0325901 at 4 h post-hCG disrupted follicular rupture without altering cumulus expansion, oocyte meiotic maturation and luteinization. Profiling the expression pattern of genes of the RSK family of ERK1/2 signal mediators revealed that RSK3, but not other isoforms, was induced by hCG treatment. Further, RSK3-knockout mice were sub-fertile with reduced ovulation rate and smaller litter size compared to WT mice. Given that PD0325901 inhibits all mediators of ERK1/2 signaling, we chose to evaluate the gene expression underlying deficient follicular rupture in ERK1/2 inhibited mice. We found that inhibition of ERK1/2 signaling at 4 h post-hCG resulted in an imbalance in the expression of genes involved in extracellular matrix degradation and leukocyte infiltration necessary for follicular rupture. In conclusion, our data demonstrate that sustained ERK1/2 signaling during ovulation is not required for cumulus expansion, oocyte meiotic maturation and luteinization, but is required for follicular rupture.

Reproduction and reproductive tract morphology of male and female pigs whose mothers were heat stressed during the second month of gestation.

The primary objective was to assess the development of fetal gonads and measure the subsequent reproductive capacity of boars and gilts whose mother was either subjected to gestational heat stress (GHS) or thermoneutral (GTN; control) conditions during pregnancy. Gilts were subjected to either GHS (28 to 38 °C; 65% to 88% relative humidity [RH]; n = 30) or GTN (17 to 22 °C; 56% to 65% RH; n = 29) for the second month of gestation (a period that coincides with a critical window of gonadal development). A subset of GHS (n = 12) and GTN (n = 11) gilts was sacrificed immediately following treatment for the collection of pregnancy data. The remaining gilts (n = 18 GHS and n = 18 GTN) were allowed to farrow. Female offspring from the farrowed gilts were studied through puberty, first insemination, and early pregnancy when fetal tissues were again collected. During the treatment period, GHS gilts had greater (P < 0.001) rectal temperature and respiration rate at both measurement time points (morning and afternoon) compared with GTN gilts. When assessed at the end of the second month of gestation, the total number of viable fetuses did not differ (P > 0.10) for GHS vs. GTN. Likewise, the weight of the fetus, placenta, fetal testes, and fetal ovaries were similar (P > 0.10) for GHS and GTN pregnancies. There was a tendency for an effect of treatment (63.3 ± 2.3 vs. 70.1 ± 2.6; GHS vs. GTN; P < 0.073) on the number of oogonia per histological section in the fetal ovaries. There was no effect of treatment on the number of prespermatogonia per histological section in the fetal testis. For gilts farrowing after treatment, litter size, piglet birth weight, and weaning weight were similar (P > 0.10) for the GHS and GTN gilts. Testes collected from castrated GHS boars had fewer prespermatogonia per seminiferous tubule cross section (P < 0.049). Female offspring from the GHS (n = 30) or GTN (n = 37) sows reached puberty at a similar age, and their pregnancies (ninth week of gestation) had fewer corpora lutea (15.6 ± 0.5 vs. 17.1 ± 0.4; GHS vs. GTN; P < 0.038) but the number of fetuses was similar for GHS and GTN. In summary, compared with GTN, GHS during a critical window of gonadal development tended to reduce the number of oogonia in the fetal ovary, reduced the number of prespermatogonia in the neonatal testes, and reduced ovulation rate at first pregnancy in gilts.

An Extended Photoperiod Increases Milk Yield and Decreases Ovulatory Activity in Dairy Goats.

Simple SummaryShort day length is associated with reduced milk yield in dairy ruminants possibly as animals prepare for the subsequent reproductive cycle. This study was conducted to determine the effect of an artificially increased daylength on milk production and ovulation in lactating goats. Increased daylength increased milk yield although the responses were only apparent during late lactation. Increased daylength reduced ovulation rate as lactation advanced although this reduction could be partially mitigated by exposing the lactating females to entire males. These findings suggest that artificially extending daylength can increase milk production and persistence while decreasing ovulatory activity in dairy goats.Short day length is associated with reduced milk production in dairy ruminants. Dairy ruminants have been kept in lit sheds during winter to extend the day length and stimulate milk production. However, there studies are few on the effect of an extended photoperiod on the ensuing reproductive performance of dairy goats. The aim of this study was to examine the effect of long day photoperiod (LDPP) and exposure to bucks on milk production and plasma progesterone and prolactin in dairy goats. The study was conducted in 122 non-pregnant lactating dairy goats over 18 weeks from April to August (late autumn and winter in the Southern Hemisphere). The goats were kept in open sided sheds in which the control treatment received ambient lighting while the LDPP treatment received 16 h of light, including artificial lighting. In June, July and August synchronised does were randomly assigned each month to the presence or absence of a buck and ovulatory activity determined from plasma progesterone. Plasma progesterone concentrations were reduced (0.73 vs. 0.46 pmol, p < 0.001) while prolactin concentrations were increased (0.095 vs. 1.33 ng/mL, p < 0.001) in LDPP goats. The former response was most marked in late winter (0.58 vs. 0.004 pmol, p < 0.001) indicating a lack of functional corpora lutea. While there was no overall effect of buck exposure on plasma progesterone concentrations there was a three-way interaction such that plasma progesterone concentrations were increased (p < 0.05) by exposure to bucks in LDPP goats in August (late winter) but not at other times. Milk production was increased in LDPP goats over the latter stages of the study (1. 55 vs. 1.82 L/d, p < 0.05). Also, persistency of lactation was greater in LDPP goats with fewer goats drying off (13 vs. 0%, p < 0.05). These findings suggest that LDPP can increase milk production and persistence while decreasing ovulatory activity in dairy goats.

160 Increasing gonadotrophin-releasing hormone dose at initiation of a 5-day CO-Synch protocol increases ovulatory response but not fertility in yearling beef heifers

Heifers typically have a reduced ovulation rate following gonadotrophin-releasing hormone (GnRH) application at initiation of a CO-Synch + controlled internal drug release (CIDR) protocol. Thus, the objective of the present study was to determine whether increasing the dose of GnRH at initiation of a 5-day CO-Synch protocol in beef heifers would improve ovulation rate and therefore increase pregnancies per AI (P/AI). Angus yearling heifers (n=299) at five locations in Ohio (United States) were randomised to receive either 100µg (single; n=149) or 200µg (double; n=150) of gonadorelin acetate (Gonabreed, Parnell) at initiation of a 5-day CO-Synch. On Day −8, heifers received a new intravaginal progesterone-releasing device (1.38g of progesterone; CIDR, Zoetis) and either a single or double dose of GnRH as described above. Five days later (Day −3), devices were removed, 1000µg of cloprostenol sodium (Estroplan, Parnell) was administered, and an oestrous detection patch was applied (Estrotect, Rockway Inc.). Sixty hours after device removal, AI was performed concurrently with the administration of 100µg of GnRH. Pregnancy was determined using ultrasonography 35 days after AI. Ovaries from a subset of animals (n=178) were examined on Days −8 and −3 using ultrasonography to determine the presence of corpora lutea (CL) and the size of the largest follicle. Data were analysed using the GLIMMIX procedure of SAS ver. 9.4 (SAS Institute Inc.). Oestrous expression was similar (P=0.50) between heifers treated with a single (49.0%) or double (52.7%) dose of GnRH. Overall, P/AI was similar (P=0.35) between heifers receiving a single (43.6%; 65/149) or double (38.7%; 58/150) dose of GnRH at initiation of the protocol. However, increasing the dose of GnRH resulted in a greater (P=0.04) ovulation rate in heifers in the double-dose group (40.9%; 36/88) compared with those in the single-dose group (26.1%; 23/88). In addition, heifers with a CL at the time of treatment had reduced ovulatory response to GnRH treatment (16.0%) compared with heifers without a CL (53.7%; P=0.001); however, there was no treatment×CL presence interaction (P=0.69). Heifers that did not ovulate to the initial GnRH treatment had a greater (P=0.0008) diameter of the largest follicle on Day −3 compared with heifers that did ovulate (11.4±0.2 vs. 10.0±0.3). Furthermore, heifers that did ovulate after the initial GnRH had greater (P=0.04) P/AI (52.5%) than heifers that did not ovulate (40.2%), and heifers with a CL on Day −8 tended (P=0.07) to have greater P/AI (47.9%) than heifers without a CL (40.2%). In addition, heifers with a CL present on Day −3 had greater (P=0.04) P/AI (48.2%) than heifers without a CL (31.7%). In summary, increasing the dose of GnRH at initiation of a 5-day CO-Synch did not affect fertility to fixed-time AI but enhanced ovulation rate in beef heifers. Furthermore, heifers that did ovulate at initiation of the protocol or that had a CL at device insertion or removal had greater fertility to fixed-time AI. Thus, alternative strategies that maximise ovulation at initiation of the synchronisation protocol are needed.

PHYSIOLOGY AND ENDOCRINOLOGY SYMPOSIUM: Factors influencing follicle development in gilts and sows and management strategies used to regulate growth for control of estrus and ovulation1.

Factors that affect follicle health and growth can influence estrus, ovulation, conception, and litter size. Since the majority of the breeding herd is composed of sows, production schedules are established based on synchronized follicle growth following weaning. Insemination of sows over a 3- to 4-d period after weaning facilitates farrowing over fewer days and helps improve the uniformity of pigs at weaning. Synchronized inseminations of the group are reduced when disturbance to the follicular phase results in delayed estrus. The failure of >15 follicles to uniformly progress beyond the 6.0 mm size within 4 d during the follicular phase is associated with delayed estrus and ovulation, reduced ovulation rate, and reduced farrowing rate. In sows, the follicular phase is initiated at weaning by removal of the suckling inhibition, whereas in cycling gilts, luteolysis and clearance of progesterone begins the process. The timing and patterns of follicle-stimulating hormone and luteinizing hormone stimulation to the ovary determine follicle health and selection for ovulation. Interestingly, abnormal wean-to-estrus intervals in sows and deviations from a 19- to 22-d estrous cycle in gilts are associated with reduced fertility. However, in both cases, it is not entirely clear whether the abnormal intervals are a direct result of problems occurring prior to or only during the follicular phase. In prepubertal gilts, the signal for initiating the follicular phase remains elusive, but could reside in differential sensitivity and response to hormone signals at the level of the ovary and brain. Although the mechanisms are not clear, factors such as boar exposure, stress, feed intake, growth rate, and birthweight have been shown to stimulate an early follicular phase. In contrast, inhibitors to follicle growth have been associated with season, heat stress, photoperiod, negative energy balance, poor body condition, slow growth, fewer parities, and short lactation length. Hormonal aids for inducing and delaying the follicular phase, as well as for inducing ovulation are available to aid in synchronized breeding schedules.

\u03b1-SNAP is expressed in mouse ovarian granulosa cells and plays a key role in folliculogenesis and female fertility

The balance between ovarian folliculogenesis and follicular atresia is critical for female fertility and is strictly regulated by a complex network of neuroendocrine and intra-ovarian signals. Despite the numerous functions executed by granulosa cells (GCs) in ovarian physiology, the role of multifunctional proteins able to simultaneously coordinate/modulate several cellular pathways is unclear. Soluble N-ethylmaleimide-sensitive factor (NSF) attachment protein (α-SNAP) is a multifunctional protein that participates in SNARE-mediated membrane fusion events. In addition, it regulates cell-to-cell adhesion, AMPK signaling, autophagy and apoptosis in different cell types. In this study we examined the expression pattern of α-SNAP in ovarian tissue and the consequences of α-SNAP (M105I) mutation (hyh mutation) in folliculogenesis and female fertility. Our results showed that α-SNAP protein is highly expressed in GCs and its expression is modulated by gonadotropin stimuli. On the other hand, α-SNAP-mutant mice show a reduction in α-SNAP protein levels. Moreover, increased apoptosis of GCs and follicular atresia, reduced ovulation rate, and a dramatic decline in fertility is observed in α-SNAP-mutant females. In conclusion, α-SNAP plays a critical role in the balance between follicular development and atresia. Consequently, a reduction in its expression/function (M105I mutation) causes early depletion of ovarian follicles and female subfertility.

Reduced ovulation rate, failure to be mated and fertilization failure/embryo loss are the underlying causes of poor reproductive performance in juvenile ewes

A ewe that is mated as a juvenile (producing a lamb at 1year of age) will produce an average of only 0.6 lambs to weaning, compared to an average of 1.2 lambs in adult ewes. Understanding the underlying causes of this low reproductive efficiency and designing methods to improve or mitigate these effects could potentially increase adoption of mating juvenile ewes.In Experiment 1, 2 Cohorts of ewes, born a year apart, were mated in order to lamb at 1 and 2 years of age and the performance of the ewes at each age was compared. Onset of puberty, mating by the fertile ram, ovulation rate, early pregnancy (day 30–35) litter size, number of lambs born and number of lambs weaned were measured. In juvenile ewes, by day 35 of pregnancy, 43% of ova had failed to become a viable embryo and this early loss was the largest contributor to the poor reproductive performance observed. Compared with young adult ewes, ovulation rate was lower (p<0.001), fewer ova were exposed to sperm (p<0.001) and fertilization failure/embryo loss was increased (p<0.001) in juveniles.In Experiment 2, the early pregnancy litter size of juveniles was shown to be greater (p<0.001) in those ewes with a greater ovulation rate (p<0.001). Attaining puberty prior to introduction of the fertile ram was associated with an increased pregnancy rate (p<0.001).In juvenile ewes, failure to mate with the ram, lower ovulation rate and increased fertilisation failure/embryo loss underlie their poor reproductive performance.

Loss of vascular endothelial growth factor A (VEGFA) isoforms in granulosa cells using pDmrt-1-Cre or Amhr2-Cre reduces fertility by arresting follicular development and by reducing litter size in female mice.

Because VEGFA has been implicated in follicle development, the objective of this study was to determine the effects of granulosa- and germ cell-specific VEGFA loss on ovarian morphogenesis, function, and female fertility. pDmrt1-Cre mice were mated to floxed VEGFA mice to develop granulosa-/germ cell-specific knockouts (pDmrt1-Cre;Vegfa -/-). The time from mating to first parturition was increased when pDmrt1-Cre;Vegfa -/- females were mated to control males (P = 0.0008) and tended to be longer for heterozygous females (P < 0.07). Litter size was reduced for pDmrt1-Cre;Vegfa -/- females (P < 0.007). The time between the first and second parturitions was also increased for heterozygous females (P < 0.04) and tended to be increased for pDmrt1-Cre;Vegfa -/- females (P < 0.07). pDmrt1-Cre;Vegfa -/- females had smaller ovaries (P < 0.04), reduced plasma estradiol (P < 0.007), fewer developing follicles (P < 0.008) and tended to have fewer corpora lutea (P < 0.08). Expression of Igf1r was reduced (P < 0.05); expression of Foxo3a tended to be increased (P < 0.06); and both Fshr (P < 0.1) and Sirt6 tended to be reduced (P < 0.06) in pDmrt1-Cre;Vegfa -/- ovaries. To compare VEGFA knockouts, we generated Amhr2-Cre;Vegfa -/- mice that required more time from mating to first parturition (P < 0.003) with variable ovarian size. Both lines had more apoptotic granulosa cells, and vascular staining did not appear different. Taken together these data indicate that the loss of all VEGFA isoforms in granulosa/germ cells (proangiogenic and antiangiogenic) causes subfertility by arresting follicular development, resulting in reduced ovulation rate and fewer pups per litter.

Tocotrienol preserves ovarian function in cyclophosphamide therapy

Cyclophosphamide (CPA) chemotherapy leads to ovarian failure and infertility. Tocotrienol (T3) is an antioxidant and anti-inflammatory agent. The role of T3 in ovarian protection throughout chemotherapy remains unclear. To investigate the role of T3 in the preservation of female fertility in CPA treatment. Sixty female mice were divided into five treatment groups, namely, normal saline, corn oil only, T3 only, CPA and CPA + T3. The treatment was given for 30 days, followed by administration of gonadotrophin to induce ovulation. After killing, both ovaries were collected and examined histologically. There was significant reduction in ovarian size in the CPA group compared with the normal group (CPA versus normal, mean area ± SD; 0.118 ± 0.018 vs. 0.423 ± 0.024 cm(2); p ≤ 0.005), whilst concurrent administration of T3 with CPA leads to conservation of ovarian size (CPA + T3 vs. CPA, mean area ± SD; 0.285 ± 0.032 vs. 0.118 ± 0.018 cm(2); p ≤ 0.005). Ovaries in CPA group showed abnormal folliculogenesis with accompanied reduced ovulation rate, follicular oedema, increased vascularity and inflammatory cell infiltration. These changes were reversed by concurrent T3 administration. Co-administration of T3 with CPA confers protection of ovarian morphology and function in vivo. These findings contribute to the further elucidation of CPA effect on ovary and suggest the potential of T3 use in preserving fertility in chemotherapy.

Cryptotanshinone reverses ovarian insulin resistance in mice through activation of insulin signaling and the regulation of glucose transporters and hormone synthesizing enzymes

To investigate the effects of cryptotanshinone (CRY), an active component of Chinese medicine, on ovarian androgen production, insulin resistance (IR), and glucose metabolism in mice. Animal model and invitro tissue model. University-affiliated laboratory. Mice. Ovarian IR was induced by dexamethasone (DEX) invivo. Animals were randomized to receive CRY treatment for 3days or not. Ovulation rates, serum steroid levels, and glucose uptake in ovaries were quantified, and proteins in the phosphatidylinositol 3-hydroxy kinase pathway were measured. Invitro ovarian IR was also induced by DEX for 3days. Ovarian steroid hormone secretion and glucose uptake were measured, and the hormone-synthesizing enzymes were determined by semiquantitative reverse transcription-polymerase chain reaction. Ovarian glucose uptake, invivo ovulation rate, serum and culture medium steroid level, and molecular expression of phosphatidylinositol 3-hydroxy kinase and steroidogenic enzymes. Dexamethasone significantly increased ovulation rates invivo and increased T and E2 production and decreased ovarian glucose uptake invivo and invitro. Cryptotanshinone significantly reduced ovulation rates invivo and decreased T and estrogen production invitro. Cryptotanshinone attenuated the inhibition of DEX on AKT2 and suppressed the up-regulation of CYP11 and CYP17 expression by DEX. Cryptotanshinone reversed DEX-induced androgen excess and ovarian IR in mice through activation of insulin signaling and the regulation of glucose transporters and hormone-synthesizing enzymes. This suggests a potential role for CRY in treating the ovulatory dysfunction associated with PCOS.

Role of leptin receptors in granulosa cells during ovulation

Leptin is an important hormone influencing reproductive function. However, the mechanisms underpinning the role of leptin in the regulation of reproduction remain to be completely deciphered. In this study, our objective is to understand the mechanisms regulating the expression of leptin receptor (Lepr) and its role in ovarian granulosa cells during ovulation. First, granulosa cells were collected from superovulated mice to profile mRNA expression of Lepr isoforms (LeprA and LeprB) throughout follicular development. Expression of LeprA and LeprB was dramatically induced in the granulosa cells of ovulating follicles at 4 h after human chorionic gonadotropin (hCG) treatment. Relative abundance of both mRNA and protein of CCAAT/enhancer-binding protein β (Cebpβ) increased in granulosa cells from 1 to 7 h post-hCG. Furthermore, chromatin immunoprecipitation assay confirmed the recruitment of Cebpβ to Lepr promoter. Thus, hCG-induced transcription of Lepr appears to be regulated by Cebpβ, which led us to hypothesise that Lepr may play a role during ovulation. To test this hypothesis, we used a recently developed pegylated superactive mouse leptin antagonist (PEG-SMLA) to inhibit Lepr signalling during ovulation. I.p. administration of PEG-SMLA (10 μg/g) to superovulated mice reduced ovulation rate by 65% compared with control treatment. Although the maturation stage of the ovulated oocytes remained unaltered, ovulation genes Ptgs2 and Has2 were downregulated in PEG-SMLA-treated mice compared with control mice. These results demonstrate that Lepr is dramatically induced in the granulosa cells of ovulating follicles and this induction of Lepr expression requires the transcription factor Cebpβ. Lepr plays a critical role in the process of ovulation by regulating, at least in part, the expression of the important genes involved in the preovulatory maturation of follicles.

Periovulatory Expression of Hydrogen Peroxide-Induced Sulfiredoxin and Peroxiredoxin 2 in the Rat Ovary: Gonadotropin Regulation and Potential Modification

Reactive oxygen species are involved in ovulation. The aim of this study was to examine gonadotropin regulation of antioxidant enzyme sulfiredoxin (Srx) and peroxiredoxin 2 (PRDX2) expressions and modification during the ovulatory process in rats. Administration of antioxidants in vivo reduced ovulation rate and cumulus expansion. LH treatment increased H(2)O(2) levels within 15 min, which, in turn, induced Srx gene expression in cultured preovulatory follicles. Treatment of preovulatory follicles with catalase suppressed the stimulatory effect of LH on Akt phosphorylation. LH- or H(2)O(2)-stimulated Srx mRNA levels were suppressed by inhibitors of antioxidant agents and MAPK kinase. An in vivo injection of equine chorionic gonadotropin-human chorionic gonadotropin (hCG) stimulated Srx mRNA within 1 h in granulosa but not thecal cells of preovulatory follicles. Srx protein levels were stimulated from 3 h post-hCG injection. Immunofluorescence analysis revealed that oocytes expressed the Srx protein. Furthermore, hCG treatment increased Srx expression in mural granulosa, theca and cumulus cells, but the Srx protein was not detected in corpora lutea. Gene expression of PRDX2, identified as an Srx-dependent modified enzyme, was stimulated by gonadotropins. In situ hybridization analysis demonstrated that PRDX2 mRNA was detected in oocytes and theca cells as well as granulosa cells of some antral and preovulatory follicles. High levels of PRDX2 mRNA were detected in corpora lutea. Total levels of PRDX2 protein were not changed by gonadotropins. However, levels of hyperoxidized PRDX2 increased within 2-3 h after the hCG injection. Taken together, gonadotropin stimulation of Srx expression and PRDX2 modification in the ovary suggest the existence of an antioxidant system to maintain H(2)O(2) production and elimination during the periovulatory period.

Undernutrition during early follicle development has irreversible effects on ovulation rate and embryos

This study assessed carry-over effects of energy level during the early antral phase and subsequent follicular phase on follicle recruitment and ovulation rate. Gilts (n=45) were fed a standard diet to a low (L, ~1.2kg day(-1)) or high (H, ~2.7kg day(-1)) level during the early antral (luteal) phase, and subsequently fed a H or L feed level during the follicular phase, resulting in four treatment groups (HH, HL, LH and LL). Follicle size at the end of the luteal phase was greater for gilts fed a high feed level previously (3.3vs3.0mm; P<0.05). During the follicular phase, high feeding increased follicle size at Day 5 (6.9vs6.2mm; P<0.005) and plasma oestradiol concentration (P<0.05). Nevertheless, a low feed level during the luteal phase reduced ovulation rate (14.4vs13.2; P<0.05) and embryo number (12.6vs10.5; P<0.05), and this was not counteracted by feed level during the follicular phase. Plasma progesterone concentration after ovulation was lower for LL gilts than for other treatments (P<0.05). These results indicate that undernutrition during early antral follicle development may have a residual effect on follicle recruitment and quality.

Reproductive performance and fertility in male and female adult mice chronically treated with hexarelin

Hexarelin (HEXr), a synthetic ghrelin analogue, has been associated with modifications of reproductive physiology. In previous studies of adult mice, we detected that HEXr induced significantly reduced ovulation rate and significant correlation coefficients between sexual maturation and corporal weight in offspring. In this study, we investigated the effects of chronic HEXr administration on sperm concentration and functional activity, oestrous cyclicity and pregnancy index, in addition to the number of fetuses and its correlation with the number of corpora lutea. Adult Albino swiss mice were injected (sc) daily with HEXr: 100 μgkg(-1) day(-1) (HEXr D1) or 200 μgkg(-1) day(-1) (HEXr D2) for 53 days in males and 30 days in females. We detected a significantly decreased ratio in the number of fetuses per corpora lutea in females treated with HEXr D2 for 30 days before mating and during the first 6 days of pregnancy, in addition to a downward trend in the pregnancy index and percentage of females impregnated by each male treated with both doses of the analogue. Although we did not find any significant effect on additional parameters evaluated in both genders, we propose certain effects of HEXr on the implantation process and/or early development of embryos and over the in vivo reproductive capability of males.

Effect of excessive, hormonally induced intrauterine crowding in the gilt on fetal development on day 40 of pregnancy

Selection for litter size may result in an increase in uterine crowding due to a faster increase in ovulation rate than in litter size. Increased ovulation rate does not result in a proportionally increased number of piglets born alive. In this study, the effect of ovulation rate on vitality characteristics of fetal-placental units at d 40 of pregnancy was investigated. For this, 43 Large White gilts were treated with hormones to induce superovulation. Average ovulation rate was 45.16 +/- 13.22; average number of vital fetuses at d 40 of pregnancy was 17.09 +/- 3.61 that weighed 11.26 +/- 1.99 g; their placenta weighed 31.88 +/- 14.79 g; and they occupied 11.69 +/- 4.90 cm of the uterus. Loss in oocytes (i.e., that did not result in a vital fetus at d 40) increased with increasing ovulation rate and occurred before (early mortality; P = 0.0003) and after implantation (late mortality, i.e., traces visible at d 40; P < 0.0001). With respect to the vital fetuses, increased ovulation rate resulted in decreased fetal (P = 0.0008) and placental weight (P = 0.0008) and decreased length of the area in the uterus that was occupied by the placenta (P = 0.0011). Strong correlations existed between placental and fetal weight [0.68; 95% confidence interval (CI) = 0.64 to 0.72], and placental weight and length (0.78; 95% CI = 0.74 to 0.82). Fetal-placental characteristics were weakly correlated to distance to the implantation sites of neighboring fetuses, a measure of crowdedness [-0.002 (95% CI = -0.042 to 0.038) with fetal weight to 0.16 (95% CI = 0.12 to 0.20) with placental length]. Increased ovulation rates, but more specifically increased late mortality rates, have negative effects on the remaining vital fetuses with respect to the fetal (P = 0.0085) and placental weight (P < 0.0001) and length of the implantation site (P = 0.0016). The most extreme effect was on placental weight, in which a uterus with <10 cases of late mortality was on average 25% greater than placental weight in a uterus with >18 cases of late mortality (P < 0.0001). Furthermore, increased ovulation rates resulted in decreased within litter variation for fetal (P = 0.0018) and placental weight (P = 0.0084). At increased ovulation rates, the number of live fetuses remained similar, but placental development is impaired and the growth of the fetus is retarded compared with reduced ovulation rate, with effects likely lasting into adult life.

Doxorubicin-induced ovarian toxicity.

BackgroundYoung cancer patients may occasionally face infertility and premature gonadal failure. Apart from its direct effect on follicles and oocytes, chemotherapy may induce ovarian toxicity via an impact on the entire ovary. The role of doxorubicin in potential ovarian failure remains obscure. Our intention was to elucidate doxorubicin-related toxicity within ovaries.MethodsFemale mice were injected intraperitoneally with 7.5 or 10 mg/kg doxorubicin and their ovaries were visualized in vivo by high resolution MRI, one day and one month following treatment. Ovaries of other treated mice were excised and weighed at the same post-treatment intervals. Ovarian histological sections were stained for TUNEL or active caspase-3 and follicles were counted and categorized. Ovulation rates were evaluated in superovulated female mice treated with doxorubicin.ResultsA single injection of doxorubicin resulted in a major reduction in both ovarian size and weight that lasted even one month post treatment. A dramatic reduction in ovulation rate was observed one week after treatment, followed by a partial recovery at one month. Histological examination revealed positive staining of TUNEL and active caspase-3. We observed a significant reduction in the population of secondary and primordial follicles one month following treatment.ConclusionsOur results may imply a mechanism of chemotherapy-induced ovarian toxicity, manifested by reduced ovulation and accompanied by a reduction in ovarian size, caused probably by an acute insult to the ovary.

Oocyte-specific deletion of complex and hybrid N-glycans leads to defects in preovulatory follicle and cumulus mass development

Complex and hybrid N-glycans generated by N-acetylglucosaminyltransferase I (GlcNAcT-I), encoded by Mgat1, affect the functions of glycoproteins. We have previously shown that females with oocyte-specific deletion of a floxed Mgat1 gene using a zona pellucida protein 3 (ZP3)Cre transgene produce fewer pups primarily due to a reduction in ovulation rate. Here, we show that the ovulation rate of mutant females is decreased due to aberrant development of preovulatory follicles. After a superovulatory regime of 48 h pregnant mare's serum (PMSG) and 9 h human chorionic gonadotropin (hCG), mutant ovaries weighed less and contained approximately 60% fewer preovulatory follicles and more atretic and abnormal follicles than controls. Unlike controls, a proportion of mutant follicles underwent premature luteinization. In addition, mutant preovulatory oocytes exhibited gross abnormalities with approximately 36% being blebbed or zona-free. While 97% of wild-type oocytes had a perivitelline space at the preovulatory stage, approximately 54% of mutant oocytes did not. The cumulus mass surrounding mutant oocytes was also smaller with a decreased number of proliferating cells compared with controls, although hyaluronan around mutant oocytes was similar to controls. In addition, cumulus cells surrounding mutant eggs were resistant to removal by either hyaluronidase or incubation with capacitated sperm. Therefore, the absence of complex and hybrid N-glycans on oocyte glycoproteins leads to abnormal folliculogenesis resulting in a decreased ovulation rate.

Body condition is associated with a shorter breeding season and reduced ovulation rate in subtropical goats

To determine the effect of body condition on the characteristics of the breeding season in female goats from subtropical Mexico, does in either greater- or lesser-body condition ( n = 20/group) were monitored for the expression of estrous behavior, ovulation and ovulation rate between June and April. The commencement of estrus and ovulation occurred earlier ( P < 0.05) in does in greater than lesser body condition. The cessation of estrus and ovulation was later ( P < 0.05) in female goats with greater than those with lesser body condition. Does in greater body condition had more ( P < 0.001) normal estrous cycles than those in lesser body condition. As consequence, does from the greater body condition group had fewer short ( P < 0.001) or long ( P < 0.05) estrous cycles than those of in the lesser body condition group. The ovulation rate was greater ( P < 0.01) in the greater (1.9 ± 0.1) than lesser body condition does (1.6 ± 0.1). In conclusion, female goats in lesser body condition have a shorter breeding season, more abnormal estrous cycles, and fewer ovulations than does in greater body condition.