Developmental changes of plasma inhibin, gonadotropins, steroid hormones, and thyroid hormones in male and female Shao ducks

Plasma samples from developing male and female Shao ducks were assayed for immunoreactive (ir-) inhibin, follicle-stimulating hormone (FSH), luteinizing hormone (LH), steroid hormones, and thyroid hormones. In the male, plasma ir-inhibin significantly increased between 75 and 155 days posthatch, and then decreased slightly at day 165. Plasma FSH of male ducks decreased from day 35 to day 55, followed by progressive elevation until day 95. Plasma FSH of male ducks fell significantly at days 135 and 165, while plasma ir-inhibin rose to high level. In female ducks, plasma ir-inhibin remained low until the start of lay, and thereafter significantly increased at day 135. Plasma FSH fluctuated before day 95 and significantly rose at day 115, and decreased thereafter. In males, plasma LH did not vary significantly before day 135, however, plasma testosterone significantly increased from day 95 onwards. No changes in plasma LH were observed during development of female ducks. Plasma estradiol-17beta gradually increased reaching a peak level at day 135. Plasma progesterone did not vary significantly before day 135 and thereafter significantly increased. Both sexes showed a similar pattern in changes of plasma thyroid hormones during sexual development. There was a significant increase in plasma thyroxine (T4) at day 95, thereafter decreased. Plasma triiodothyronine (T3) was at high level at the earlier stage of development and significantly decreased at day 55. Significant increase in plasma T3 in male and female ducks was observed at 135 and 115 days, respectively. In conclusion, these results demonstrated that the rise in inhibin is correlated with age of sexual maturity in the female while the rise in inhibin significantly precedes sexual maturity in the male. There was a progressive increase in plasma steroid hormones towards sexual maturity, and there was no sex difference in the time course of thyroid hormones.

Induction of superovulation by immunoneutralization of endogenous inhibin in immature rats

The effects of passive immunoneutralization of endogenous inhibin on ovulation rate in immature rats were investigated. Efficiency of superovulation on production of fertilized oocytes was compared between the inhibin antiserum (inhibin-AS) and equine chorionic gonadotropin (eCG) protocols. Immature female Wistar strain rats were superovulated with a single injection of 100-200 microl inhibin-AS, with and without an injection of human chorionic gonadotropin (hCG). A total of 77.8% of the 26-30-day-old rats treated with a single injection of 100-200 microl inhibin-AS ovulated 72 h after treatment, while rats given normal goat serum (NGS; 200 microl) did not ovulate. At 28 days of age, all of the inhibin-AS treated rats ovulated when additional hCG treatment was given, whereas the number of ovulated oocytes was not affected. The number of ovulated oocytes in the inhibin-AS-hCG treated groups was significantly higher than that of the NGS-hCG treated group. In addition, plasma concentrations of FSH in the inhibin-AS-hCG treated group significantly increased compared with the NGS treated group. While the percentage of mated rats in the 200 microl inhibin-AS-hCG treated group was significantly lower than that of the 15 IU eCG-hCG treated group, the fertilization rate was comparable between the two groups. The number of fertilized oocytes in the 200 microl inhibin-AS-hCG treated group was significantly higher in comparison with the 15 IU eCG-hCG treated group. These results suggest that immunoneutralization of endogenous inhibin could be a reliable method for induction of superovulation to collect a large number of normally fertilized oocytes in immature rats.

The Stimulatory Role of Estrogen on Sperm Motility in the Male Golden Hamster (Mesocricetus auratus)

To clarify the physiological roles of estrogens in the regulation of sperm motility in the golden hamster, two different approaches were used. In the first experiment, silastic tubes containing either low (low E2 group) or high (high E2 group) amount of estradiol-17beta were implanted (Exp 1). In the second experiment, male golden hamsters were actively immunized against estradiol-17beta (Exp 2). In Exp 1, all sperm motility parameters (including motility, straight velocity, curvilinear velocity, beat/cross frequency, and mean amplitude of lateral head displacement) were significantly increased except linear index in the high E2 group as compared with controls at 20 days after the treatment. In the high E2 group, plasma concentrations of luteinizing hormone (LH) significantly increased, whereas levels of circulating testosterone decreased significantly. Plasma concentrations of follicle-stimulating hormone (FSH) and immunoreactive inhibin were not affected by the treatment with estradiol-17beta. In the Exp 2, titer of circulating antibodies to estradiol-17beta consistently increased after the second immunization until the end of experiment (16 weeks). The sperm motility, straight velocity, and curvilinear velocity were significantly decreased after active immunization to estradiol-17beta. Concentrations of circulating LH and FSH were also decreased significantly by the treatment. In conclusion, the current observations indicate that estradiol-17beta affects sperm motility in adult male golden hamsters.

Immunohistological study for estrogenic activities of nitrophenols in diesel exhaust particles

We recently isolated 3-methyl-4-nitrophenol (4-nitro-m-cresol; PNMC) and 4-nitro-3-phenylphenol (PNMPP) from diesel exhaust particles (DEP) and identified them as vasodilators and xenoestrogens. The estrogenic activity of PNMC and PNMPP was further examined by using immunohistochemical staining of proliferating cell nuclear antigen (PCNA) in uterine luminal epithelium of ovariectomized 25-d-old immature female rats injected with PNMC and PNMPP subcutaneously for 2 d. Significant increases were observed in uterine luminal epithelium in PCNA positive cells of animals receiving 10 and 100 mg/kg PNMC and 0.1 mg/kg PNMPP compared with controls. These results clearly show the estrogenic activity of PNMC and PNMPP by cell proliferation on the uterine luminal epithelium.

Secretion of leptin throughout pregnancy and early postpartum period in Japanese monkeys: placenta as another potential source of leptin

Leptin is one of the most important factors linking nutrition and reproduction. In the present study, plasma concentrations of leptin during pregnancy and early lactation in the Japanese monkey were determined. Plasma concentrations of gonadotropins, immunoreactive (ir-)inhibin, and steroid hormones were also measured. Plasma concentrations of leptin significantly increased during the second quarter of pregnancy and progressively elevated throughout pregnancy. During the fourth quarter of pregnancy, leptin levels reached up to 89 and 64 times of those during prepregancy and first quarter of pregnancy periods, respectively. After parturition, the circulating leptin level abruptly decreased. During the first 10 d of lactation, its average level decreased to the levels of the second quarter of pregnancy. Plasma irinhibin and estradiol-17beta were elevated throughout the pregnancy and decreased after parturition, and both of them were positively correlated with leptin levels during the whole pregnancy and early lactation. Plasma concentrations of progesterone significantly increased during the first quarter of pregnancy and kept at a higher level compared with prepregnancy and sharply decreased after parturition. Placental homogenates contain a large amount of leptin protein. These results suggest that placenta secretes a large amount of leptin and may be another source of leptin during pregnancy in Japanese monkeys. In addition, high correlations among leptin, irinhibin, and estradiol-17beta during these stages suggest that these hormones may have important regulating roles on leptin secretion during pregnancy in the Japanese monkey.

Cyclic changes in messenger RNAs encoding inhibin/activin subunits in the ovary of the golden hamster (Mesocricetus auratus)

To elucidate changing patterns of inhibin/activin subunit mRNAs in the ovary of the golden hamster (Mesocricetus auratus) during the oestrous cycle, inhibin/activin subunit cDNAs of this species were cloned and ribonuclease protection assay and in situ hybridization were carried out. Inhibin alpha-subunit mRNA was localized in granulosa cells of primary, secondary, tertiary and atretic follicles throughout the 4-day oestrous cycle. It was also expressed in luteal cells on days 1 (oestrus), 2 (metoestrus) and 3 (dioestrus). betaA-subunit mRNA was localized in granulosa cells of large secondary (>200 microm) and tertiary follicles throughout the oestrous cycle. betaB-subunit mRNA was confined to granulosa cells of large secondary and tertiary follicles. Both alpha- and betaA-subunit mRNAs were also found in ovarian interstitial cells and theca interna cells of tertiary and atretic follicles in the evening of day 4 (pro-oestrus). A striking increase in betaA-subunit mRNA levels was also observed during the preovulatory period. The expression pattern of betaA-subunit mRNA during the preovulatory period is unique and not found in other species. An i.v. injection of anti-luteinizing hormone-releasing hormone (LHRH) serum before the LH surge abolished the expression of alpha- and betaA-subunit mRNAs in ovarian interstitial cells and theca interna cells. The treatment also abolished the preovulatory increase in betaA-subunit mRNA. Furthermore, administration of human chorionic gonadotrophin (hCG), which followed the injection of anti-LHRH serum, restored the expression patterns of alpha- and betaA-subunit mRNAs. The present study revealed that the golden hamster showed a unique expression pattern of betaA-subunit mRNA in response to the LH surge.

GnRH treatment at CIDR insertion influences ovarian follicular dynamics in Japanese black cows

Ovarian follicular dynamics and estrous synchronization after Gonadotropin-releasing hormone (GnRH) treatment at Controlled Internal Drug Releasing device (CIDR) insertion were investigated in Japanese Black cows. CIDR was inserted for eight cows at 7 days after estrus. Cows were allocated to either Group A: 8-day CIDR insertion with GnRH treatment on d 0 (n=4, d 0=CIDR insertion) or Group B: 8-day CIDR insertion (n=4). Both groups were injected with prostaglandin F2alpha (PGF2alpha) on d 7. Ultrasonography and blood sampling were performed twice daily. Intensive sampling was performed every 15 min for 8 hr to determine the pulsatile release of LH on d -1, d 5 and d 10. Three of four cows showed intermediate ovulation within 2 days after GnRH treatment during CIDR insertion in Group A, whereas no ovulation was found in Group B. Three of four cows in Group A and all four cows in Group B ovulated after CIDR removal. Plasma progesterone concentrations from d 3 to d 7 in three intermediate ovulatory cows in Group A (8.4 +/- 1.6 ng/ml) was significantly higher than those in Group B (4.1 +/- 1.2 ng/ml; 4 cows) during CIDR insertion (P<0.01). Interval to estrus and ovulation after CIDR removal was observed at 60.0 +/- 12.0 hr and 76.0 +/- 6.9 hr in three cows in Group A, and 75.0 +/- 15.1 hr and 93.0 +/- 20.5 hr in Group B, respectively. There was a significant increase in LH pulse frequency on d 10 compared on d -1 or d 5 in both groups (P<0.05), in addition those on d 10 in Group A tended to be higher than in Group B. As a result, GnRH treatment at CIDR insertion at 7 days after estrus induced intermediate ovulation with formation of corpus luteum (CL) and rather synchronized emergence of ovulatory follicle during CIDR insertion. These induced CL increased plasma progesterone concentrations and contributed to precise synchronization.

Active immunization against inhibin improves superovulatory response to exogenous FSH in cattle

The effect of active immunization against inhibin on the response to superovulatory treatment by porcine FSH (pFSH) was investigated in cattle. Japanese black cows were sc injected with 1 mg of porcine inhibin alpha-subunit fragment (1-26) conjugated with rabbit serum albumin (inhibin-immunized group; n=14) or rabbit serum albumin alone (control group; n=12) in Freund's complete adjuvant. Booster injections (half the amount of the primary injection) were given 35 and 70 days after the primary injection. All cows were superovulated three times with pFSH. Three days after each injection of the antigen, a progesterone-releasing intravaginal device (CIDR-B) was inserted vaginally into all animals and left in place for 10 days. Forty-eight hours before CIDR-B removal, all animals were sc injected with 30 mg pFSH dissolved in 40% polyvinylpyrrolidone, and im injected with 750 microg of PGF2alpha at CIDR-B removal. Cows were artificially inseminated twice during estrus, and ova or embryos were collected 7 or 8 days after estrus. The number of corpora lutea, the number of ova or embryos and the number of transferable embryos in inhibin-immunized cows (12.1+/-1.2, 11.1+/-1.3 and 6.2+/-1.0, respectively) were significantly greater than those in the controls (8.2+/-1.0, 5.7+/-1.1 and 3.1+/-0.7, respectively). These results indicate that active immunization against inhibin enhanced ovarian response to the usual superovulatory treatment in cattle. Therefore, immunization against inhibin may be a useful approach for improving the response to superovulation in cattle.

Immunolocalization of steroidogenic enzymes in the corpus luteum and placenta of the Japanese Shiba goat

In this study, we performed immunohistochemistry of cholesterol side-chain cleavage cytochrome P450 (P450scc), 3beta-hydroxysteroid dehydrogenase (3betaHSD), cytochrome 17alpha-hydroxylase P450 (P450c17), and cytochrome P450 aromatase (P450arom) in the corpus luteum and placenta of Shiba goats. The aim was to clarify the steroidogenic capability of the corpus luteum and placenta of Shiba goats. Ovaries containing corpora lutea were obtained from four adult Shiba goats during the luteal phase (day10; n=2) and pregnancy (90 and 120 days of gestation). Placenta was obtained from one Shiba goat on day 120 of gestation. The sections of the ovaries and placentae were immunostained using the avidin-biotin-peroxidase complex method (ABC) with polyclonal antibodies generated against steroidogenic enzymes of mammalian origin. All luteal cells expressed P450scc, 3betaHSD, P450c17 and P450arom. The distribution of P450scc, 3betaHSD, P450c17 and P450arom were not different during the luteal phase and pregnancy. P450arom showed a weak positive staining in late pregnancy (120 days). In addition, immunoreactions for P450c17 and P450arom were observed in syncytiotrophoblast of the placenta of one Shiba goat. These results indicate that, in Shiba goats, corpus luteum is not only an important source of progesterone but also has the ability to synthesize androgen and estrogen during the luteal phase and pregnancy. Also the placenta has the ability to synthesize androgen and estrogen in late pregnancy.

Ovulation block by Pueraria mirifica: a study of its endocrinological effect in female monkeys

Pueraria mirifica (PM), a Thai herb containing phytoestrogens, may act as estrogen and disturb reproduction. To investigate the effect of PM on the menstrual cycle length and related hormones, nine adult female monkeys (Macaca fascicularis) were separated into three groups. Each group (n = 3) was fed with 10, 100, and 1000 mg/d of PM for three menstrual cycles. The menstrual cycle length increased significantly in monkeys treated with PM-10 and PM-100 and disappeared completely in monkeys treated with PM-1000. Serum follicle stimulating hormone, luteinizing hormone, estradiol, progesterone, and irinhibin were lower during the treatment period in a dose-dependent manner. Changes in menstrual cycle length and the hormonal levels recovered during the post-treatment period only in monkeys treated with PM-10 and PM-100. PM greatly influences menstrual cycles and may suppress ovulation by lowering serum levels of gonadotropins.

Maternal exposure to low doses of bisphenol a has no effects on development of female reproductive tract and uterine carcinogenesis in Donryu rats

Effects of maternal exposure to low doses of bisphenol A (BPA), including those comparable with human exposure levels, on growth and development of the female reproductive system and uterine carcinogenesis in Donryu rats were investigated. Dams were administered BPA (0, 0.006 and 6 mg/kg/day) daily by gavage from gestation day 2 up to the day before weaning (postnatal day 21 at offspring). The serum levels of BPA were significantly elevated in the dams receiving 6 mg/kg/day, however, BPA levels in the milk of dams, and those in the serum and liver of offspring were similar between control and treated groups. The treatment did not exert any influences on uterine development including weight, gland genesis and estrogen receptor alpha expression, vaginal opening and gonadotropin secretion in the female offspring up to puberty. After maturation, no effects were evident with regard to estrous cyclicity in female offspring treated with BPA. In addition, the treatment had no effects on age-related morphological changes of the reproductive and endocrine organs and uterine carcinogenesis until 15 months of age. The results demonstrate that maternal exposure to BPA at levels comparable to human exposure did not have any effects on the female reproductive system of offspring in rats. In addition, BPA was also found in the serum, milk and liver of control dams and pups, and low levels of BPA were detected in drinking water and pellet diet. The present study showed that the experimental animals were also exposed to environmental BPA in the animal room.

Effects of hypothyroidism on the estrous cycle and reproductive hormones in mature female rat

The present study was undertaken to examine the systemic role of thyroid hormones by analyzing changes in reproductive functions in hypothyroid female rats. Serum concentrations of triiodo-thyronine (T3) significantly decreased 1 week after the initiation of propyl-thiouracil treatment or thyroidectomy. The estrous cycle became irregular 3 and 2 weeks after the initiation of propyl-thiouracil treatment and thyroidectomy, respectively. Serum luteinizing hormone (LH) levels significantly reduced in both groups on the day of diestrus-1 about 1 month later. Hypothyroid rat shows the high progesterone and low testosterone levels. No significant changes in inhibin and estradiol levels were detected. The serum levels of FSH decreased in the thyroidectomy group. The irregular estrous cycle and the above changes in hormone levels were recovered by administration of T4. Compensatory secretions of FSH and LH induced by ovariectomy were enhanced by thyroidectomy and suppressed by T4 treatment. These results suggest that thyroid hormones play a role in the regulation of reproductive hormones secretion in the cyclic rat ovary.

Insulin-Like Growth Factor-I as a Follicular Growth Promoter during Early Pregnancy in Thoroughbred Mares

To elucidate the physiological role of insulin-like growth factor-I (IGF-I) during early pregnancy in mares, number of ovarian follicles was monitored ultrasonically during different stages of the first trimester of pregnancy in 36 thoroughbred mares. From 9 of 36 mares, blood samples were collected weekly from the mating day till the end of the first trimester of pregnancy and plasma IGF-I profiles were examined with other hormones, like follicle stimulating hormone (FSH), luteinizing hormone (LH), ir-inhibin, progesterone and estradiol-17beta. Plasma IGF-I level fluctuated throughout the studied period with four peaks on the 7th, 28th, 49th and 84th days of pregnancy. Plasma IGF-I showed a positive correlation with plasma FSH (P<0.05), whereas no correlation was found with other hormones during the studied period. Plasma IGF-I had no correlation with the foetal size, but positive correlation with the number of large (> 30 mm) and medium (10-30 mm) follicles. These results suggested that IGF-I might produce from the medium and large follicles during early pregnancy and promote to develop their growth via pituitary FSH mediated effects in the mares.

Plasma Concentrations of Immunoreactive (ir)-Inhibin, Gonadotropins and Steroid Hormones during the Ovulatory Cycle of the Duck

The present study was undertaken to determine changes in circulating levels of immunoreactive (ir)-inhibin, FSH, LH, estradiol-17beta, progesterone, and testosterone during the ovulatory cycle of Shao ducks. Serial blood samples were taken from two groups of laying ducks for measurement of ir-inhibin, gonadotropins, and steroid hormones at 2 h intervals for 24 h. Plasma concentrations of ir-inhibin did not change significantly during the ovulatory cycle. The highest level of plasma ir-inhibin was observed 6 h prior to ovulation, which coincided with a decreased level of plasma FSH. One FSH surge was found 12 h after ovulation. Estradiol-17beta, progesterone, and testosterone were also determined during the ovulatory cycle. Two peak values were detected for estradiol-17beta 8 h before ovulation and 4 h after ovulation, while progesterone started to increase 4 h before ovulation and reached a peak at ovulation. The highest level of plasma testosterone was detected around the time of ovulation. These results suggest that inhibin may be involved in the control of FSH secretion during the ovulatory cycle. In addition, both LH and progesterone are of importance in the ovulation process of Shao ducks.

Effects of Hypothyroidism on Gonadal Function after Transition of Short Day Photoperiod in Male Golden Hamsters (Mesocricetus auratus)

Thyroid hormones permit the annual reproductive transition of seasonal breeders. Although, precise function of thyroid hormones in seasonal breeding is not well understood. In the present study, we examined effects of hypothyroidism on the hypothalamus-pituitary-gonadal axis in adult male golden hamsters after transition of the short-day photoperiod (SD; 8 h light: 16 h dark) condition. We confirmed that hypothyroid, which had been induced by administration of thiouracil in drinking water for 4 weeks, did not have direct effects on testes in male hamsters under the long-day photoperiod. Plasma concentrations of free T3 and T4 decreased 15 weeks after transition of SD condition. Plasma concentrations of testosterone in the hypothyroid group decreased earlier than in the control group after the transition from LD to SD. In animals treated with testosterone after castration, plasma concentrations of LH in the hypothyroid group decreased earlier than in the control group after the transition of SD. On the other hand, pituitary response to GnRH for LH release did not change in castrated hamsters as a result of hypothyroidism. These results suggest that thyroid hormones act the hypothalamus and might be required to maintain GnRH secretion in male golden hamsters.

Immunolocalization of Nerve Growth Factor (NGF) and Its Receptors (TrkA and p75LNGFR) in the Reproductive Organs of Shiba Goats

The objective of this study was to determine the immunolocalization of NGF and its receptors (TrkA and p75LNGFR) in the reproductive tract of the Japanese Shiba goats. Five adult goats were used in this study and sections of ovaries, uteri and oviducts were immunostained by the avidin-biotin-peroxidase complex method (ABC). The results showed that NGF and its receptors (TrkA and p75LNGFR) were expressed in granulosa cells, theca cells, interstitial cells and lutein cells in ovaries. Immunoreactions for NGF, TrkA and p75LNGFR were also detectable in epithelial cells and muscle cells of the ampulla and isthmus of the oviduct, and in epithelial cells and uterine glands of the uterus. These results strongly suggest autocrine and paracrine regulation of reproductive function by NGF in the reproductive tract of female Shiba goats.

Reduction of Primordial Follicles Caused by Maternal Treatment with Busulfan Promotes Endometrial Adenocarcinoma Development in Donryu Rats

Ovarian dysfunction leading to hormonal imbalance plays a crucial role in uterine carcinogenesis in rats as well as women. However, the effects of a reduction in primordial follicles at birth on uterine adenocarcinoma development have hitherto not been determined. The present study was therefore conducted using female Donryu rats, a high incidence rat strain of uterine adenocarcinoma. The animals were maternally exposed to 2.5 or 5.0 mg/kg of busulfan on gestation day 14 to reduce primordial follicles, and were then initiated by intrauterine treatment with N-ethyl-N'-nitro-N-nitrosoguanidine at 11 weeks of age. Both busulfan treatment doses caused earlier occurrence of persistent estrus, with dose-dependence as compared to controls. At 15 months of age, the rats were euthanized. The incidence of uterine adenocarcinomas and multiplicity of uterine neoplastic lesions were significantly increased by the 5.0 mg/kg, but not the 2.5 mg/kg busulfan treatment. Morphologically, the ovaries exposed to busulfan treatment exhibited severe atrophy, with few or no follicles and corpus lutea. Serum 17beta-estradiol (E2), progesterone, and inhibin levels were significantly decreased in the busulfan treatment groups, with a clear dose-relation. Interestingly, only the 5.0 mg/kg busulfan treatment elevated the E2/progesterone ratio. These results provide evidence that the reduction of primordial follicles promotes uterine adenocarcinoma development in rats in association with an earlier occurrence of the persistent estrus status.

Immunolocalization of Steroidogenic Enzymes P450scc, 3.BETA.HSD, P450c17, and P450arom in Goettingen Miniature Pig Testes

The objective of this study was to investigate immunolocalization of steroidogenic enzymes in Göttingen miniature (GM) pig testes. Testes of 6 adult GM pigs were obtained in September 1996 (n=2), February (n=2) and June (n=2), 1997. Steroidogenic enzymes were immunolocalized using polyclonal antisera raised against bovine adrenal cholesterol side-chain cleavage cytochrome P450 (P450scc), human placental 3beta-hydroxysteroid dehydrogenase (3betaHSD), porcine testicular 17alpha-hydroxylase cytochrome P450 (P450c17), and human placental aromatase cytochrome P450 (P450arom). Histologically, all types of spermatogenic cells including mature-phase spermatozoa in seminiferous tubules were observed in all testes throughout the year. Moreover, P450scc, 3betaHSD, P450c17and P450arom were identified in Leydig cells but not in Sertoli cells of all testes. These results suggested that adult GM pig testes have the ability to produce germ cells throughout the year, and the synthesis of progestin, androgen and estrogen occurs in the Leydig cells of GM pig testes.

Immunolocalization of Inhibin/Activin Subunits in the Shiba Goat Fetal, Neonatal, and Adult Testes

The objective of this study was to investigate the cellular immunolocalization of inhibin alpha and inhibin/activin (betaA and betaB) subunits in the fetal, neonatal and adult testes of Shiba goats. The testes were obtained from a fetus at 90 days, a neonate at 15 days, and two adult Shiba goats (both of 3 years old). The sections of testes were immunostained by the avidin-biotin-peroxidase complex method (ABC) using polyclonal antisera raised against porcine inhibin alpha, inhibin/activin betaA, and inhibin/activin betaB. Inhibin alpha and inhibin/activin (betaA and betaB) subunits were expressed in Leydig cells, but not in the Sertoli cells of the fetus with a weak immunostaining. An increase in the number of positive cells and a more intense immunohistochemical signal for inhibin alpha and inhibin/activin (betaA and betaB) subunits were observed in the Leydig cells of neonatal testes. Moreover, inhibin alpha, betaA, and betaB subunits were expressed in the Sertoli cells and Leydig cells of adult testes, respectively. These results suggest that Shiba goats testes have the ability to synthesize inhibins in the fetus, neonate, and adult, and the cellular localization of inhibin/activin subunits showed age-related changes in fetal, neonatal, and adult testes of Shiba goats.

Follicular and Hormonal Dynamics during the Estrous Cycle in Goats

Transrectal ultrasonography of ovaries was performed daily in 6 goats for 3 consecutive estrous cycles. Blood samples collected daily were measured for concentrations of FSH, inhibin A, and estradiol-17beta. Follicular and hormonal data were analyzed for associations between the follicular waves and hormonal concentrations. During the interovulatory intervals, follicular growth and regression occurred in a wave like pattern (2-5 waves), and the predominant patterns were three and four follicular waves. In addition, there was no significant difference among the diameters of dominant follicles during the growth phase of the follicular waves. The number of 3 mm follicles peaked on days 0, 7, and 11 in interovulatory intervals that had three follicular waves and on days -1, 5, 11, and 15 in those that had four follicular waves. Plasma concentrations of FSH increased around the day of follicular wave emergence and declined with the growth of follicles. Circulating FSH increased again concomitant with regression of dominant follicles in the anovulatory wave, whereas FSH levels remained low in the ovulatory wave. Inhibin A was negatively correlated with FSH, while it was positively correlated with estradiol-17beta, suggesting that inhibin A is a product of healthy growing follicles and that it contributes to the suppression of FSH secretion. In conclusion, the growth of ovarian follicles in goats exhibits a wave-like pattern, and follicular dominance is less apparent in goats. Moreover, inhibin A may be a key hormone for regulation of the follicular wave through suppression of FSH secretion in goats.

Adverse effects of environmental toxicants, octylphenol and bisphenol A, on male reproductive functions in pubertal rats

It has been proposed that a global decline in sperm counts, semen quality, and several male reproductive disorders are associated with exposure to environmental chemicals. Thus, the present study examined the effects of two estrogenic chemicals, octylphenol (OP) and bisphenol A (BPA), on epididymal sperm counts and sperm motility, luteinizing hormone (LH)-releasing hormone (LHRH)-stimulated plasma LH and steroid hormones, insulin-like growth factor I (IGF-I), and accessory reproductive organs in pubertal male Wistar rats. Fifty-day-old rats in the OP group (n=11) and BPA group (n=11) received daily sc injections of the respective chemical at a dose of 3 mg/kg bw dissolved in 0.2 mL DMSO. Rats in the control group (DMSO group; n=10) received 0.2 mL DMSO alone. After 2 wk of treatment, a jugular blood sample was taken, and, on the next day, a second blood sample was taken 1 h after an sc injection of LHRH (250 ng). After 5 wk of treatment, rats were deeply anesthetized and heart blood was collected. Epididymal sperm motility and sperm head counts were determined. LHRH increased plasma LH to higher levels in all groups, but the increases were significant (p<0.01) in the BPA and OP groups. However, despite higher LH levels after LHRH injection, the incremental responses of testosterone and pro-gesterone in the OP and BPA groups were small compared to those in the DMSO group, which showed a small LH response. After 5 wk of treatment, plasma testosterone levels were significantly (p<0.01) reduced in the OP and BPA groups and this was accompanied by reduced (p<0.05) epididymal sperm counts. However, the chemical-treated groups had high basal progesterone levels. No significant effects of chemicals on sperm motility parameters were noted. The chemical-induced increases (p<0.05) of the weight of ventral prostate gland were coincided with elevated plasma IGF-I levels in the BPA (p<0.05) and OP (p<0.01) groups. The present results demonstrated that OP and BPA can reduce sperm counts resulting from lowered plasma testosterone in male rats just after puberty. The enlarged ventral prostate gland may possibly be associated with increased plasma IGF-I, raising the possibility of a link between these chemicals and prostate diseases because IGF-I has been implicated in the pathogenesis of human prostate cancers.

Effects of re-immunization of heifers against inhibin on hormonal profiles and ovulation rate

To study the effect of re-immunization against inhibin on ovarian response and hormonal profiles, Japanese beef heifers (n = 5) were re-immunized three times with inhibin vaccine (recombinant ovine inhibin α-subunit in oil emulsion, 125 μg ml−1) one year after the primary immunization. Control heifers (n = 5) were injected with placebo (Montanide: Marcol adjuvant alone). Oestrous cycles were synchronized by using prostaglandin F2α (PGF2α) and ovarian response was monitored daily by ultrasonography. Blood samples were collected by jugular venipuncture for assessment of hormonal levels and inhibin antibody titres. In contrast to controls, inhibin re-immunized heifers generated antibodies against inhibin rapidly reaching a peak level 9 days after the first booster injection. The mean concentrations of FSH in re-immunized cows increased significantly in comparison with controls. In addition, there was a significant increase in oestradiol-17β and progesterone levels in re-immunized cows compared with controls. Inhibin re-immunized heifers had a significant increase in small (≥4 < 7 mm), medium (≥7 < 10 mm) and large (≥10 mm in diameter) sized follicles. Moreover, the mean ovulation rate was 5.0 ± 1.1 after the third booster injection in re-immunized heifers compared with control heifers (single ovulation). These results clearly demonstrate that re-immunization of inhibin can be used to enhance ovarian follicular development and ovulation rate. Furthermore, the great number of follicles is a potential source of oocytes that could be harvested for in vitro fertilization and embryo transfer programmes.

Plasma concentrations of ir-inhibin, inhibin A, inhibin pro-alphaC, FSH, and estradiol-17beta during estrous cycle in mares and their relationship with follicular growth

The relationship among plasma levels of immunoreactive (ir)-inhibin, inhibin A, inhibin pro-alphaC, FSH, estradiol-17beta and follicular growth were investigated during the normal estrous cycle in mares. Seven mares were used for two successive normal estrous cycles. Follicular diameters and ovulation were obtained by transrectal ultrasonography, and blood samples were collected daily by jugular venipuncture for hormonal assay. The results showed that inhibin A was inversely correlated (r = -0.59, p < 0.0001) with FSH indicating its contribution to negative feedback control of FSH secretions from the pituitary gland. Estradiol-17beta increased during the follicular phase reaching a peak (37.9 +/- 3.8 pg/mL) 2 d before ovulation. Estradiol-17beta was positively correlated (r = 0.78, p < 0.0001) with inhibin A. The high levels of inhibin A and estradiol-17beta were associated with the growth of the preovulatory dominant follicle and inversely correlated with FSH suggesting that both hormones are products of the large dominant follicles and were responsible for the decline in FSH secretion during the follicular phase of estrous cycle. In conclusion, an inverse relationship between inhibin A and FSH was clearly demonstrated indicating that inhibin A has a key role in the negative feedback control of FSH from the pituitary gland. In addition, inhibin A and estra-diol-17beta secretions were associated with the growth of the preovulatory dominant follicle and were positively correlated.

Histologic Changes in Thyroid Glands from Great Cormorant (Phalacrocorax carbo) in Tokyo Bay, Japan: Possible Association with Environmental Contaminants

We compared morphologic changes in thyroid glands of great cormorants (Phalacrocorax carbo) from the Tokyo Bay and Lake Biwa areas in Japan with presence of residues of polychlorinated dibenzo-dioxins (PCDDs), polychlorinated dibenzo-furans (PCDFs), and coplanar polychlorinated biphenyls (Co-PCBs). Prominent morphologic changes in thyroid glands included increased density of small follicles and increased number of epithelial cells surrounding follicular lumens. The extent of morphologic changes in the thyroid gland was higher in cormorants captured from Tokyo Bay than in those captured from Lake Biwa. Increased thyroid change in cormorants from the Tokyo Bay area was associated with significantly higher levels of PCDFs and Co-PCBs. Thus, we suggest that morphologic changes in thyroid glands from the cormorants are associated with increased levels of dioxin contamination in Japan.

Transrectal ultrasonic diagnosis of ovarian follicular cysts in goats and treatment with GnRH

Cystic ovarian disease is an important cause of reproductive failure. The objective of this study was to evaluate transrectal ultrasonography as a diagnostic tool and gonadotropin-releasing hormone (GnRH) as a therapeutic approach for ovarian follicular cysts in goats. Goats were considered to have a follicular cyst(s) if a non-echoic structure >10 mm in diameter was detected in the absence of corpora lutea (CL) in three ultrasonic examinations performed at 5-day intervals. After diagnosis (Day 0), goats with ovarian follicular cysts (n = 5) were treated with a single bolus injection of 10.5 microg synthetic GnRH followed by administration of 125 microg prostaglandin F2alpha (PGF2alpha) 10 days later. Five blood samples were collected at 5-day intervals for determination of progesterone and estradiol-17beta. For detection of LH surge, blood samples were collected every 2 h. Ovulation rate was determined and pregnancy was confirmed by transrectal ultrasonography. The results showed that transrectal ultrasonography is reliable for diagnosis of ovarian follicular cysts and the mean diameter of the follicular cysts was 12.6 +/- 0.4 mm. Plasma concentrations of progesterone and estradiol-17beta at the time of diagnosis of follicular cysts (Day 0) were 0.7 +/- 0.2 ng/ml and 12.7 +/- 0.9 pg/ml, respectively. The concentration of progesterone increased to 4.0 +/- 0.5 ng/ml 10 days after administration of GnRH indicating luteinization of the ovarian follicular cysts concomitant with a decrease in the concentration of estradiol-17beta (3.5 +/- 0.4 pg/ml). Administration of GnRH to cystic goats resulted in a surge of LH within 2 h of treatment. The interval from PGF2alpha injection to the preovulatory LH surge was 62.8 +/- 1.4 h. All goats exhibited estrus 55.2 +/- 2.3 h after PGF2alpha injection and four goats out of the five ovulated. The ovulation rate was 1.5 +/- 0.3. In conclusion, results of this study suggest that transrectal ultrasonography is a reliable tool for diagnosis of ovarian follicular cysts. In addition, GnRH can be used to effectively treat ovarian follicular cysts in goats with 80% success rate.