Endocrinological responses during suckling in Hatano high- and low-avoidance rats

Hatano high-avoidance (HAA) and low-avoidance (LAA) animals were originally selected from Sprague-Dawley rats for good and poor active avoidance learning in a shuttle box. We studied the endocrinological profile in lactating rats to determine the effect of suckling during mid-lactation in HAA and LAA rats. The pups were separated from their mother rats 6 h before the onset of suckling and blood samples were drawn from unanaesthetized mother rats via a jugular cannula at 0, 5 and 15 min after the suckling stimulus and then 15, 45 and 105 min after pups were removed. Plasma concentrations of oxytocin in HAA rats were significantly higher than in LAA rats during the suckling period. Plasma concentrations of prolactin and ACTH in HAA rats were significantly higher than in LAA rats during the suckling period, and at 15 min and 45 min after the pups were removed. However, there were no strain differences in circulating corticosterone between the two lines, indicating that the response of the hypothalamo-pituitary axis to the suckling stimulus was greater in HAA rats than in LAA rats, whereas the ACTH-induced adrenal response of corticosterone release was higher in LAA rats than in HAA rats. Since dopamine from the median eminence inhibits prolactin secretion from the lactotrophs of the anterior pituitary, and tuberoinfundibular dopaminergic neurones are partially regulated by the level of circulating prolactin, we evaluated the activity of tyrosine hydroxylase (TH), the rate-limiting enzyme in dopamine biosynthesis. TH, measured by the accumulation of 3,4-dihydroxyphenylalanine, was significantly higher in HAA rats than in LAA rats before the suckling stimulus. After the suckling stimulus, TH activity in HAA rats was significantly lower than before suckling, whereas TH activity in LAA rats was not changed. These findings clearly demonstrated that apparent differences between the two Hatano lines exist in endocrinological profiles during suckling. These strain differences probably originate from neurotransmitter changes, such as dopamine.

Immunization against endogenous inhibin increases normal oocyte/embryo production in adult mice

The objectives of the present study were to induce super-ovulation in adult mice by immunoneutralization of endogenous inhibin and to investigate embryo development in vivo and in vitro. Adult female mice of the ddY strain at 3 mo of age were superovulated with a single ip injection of inhibin antiserum (inhibin-AS; 50, 100, or 200 micro L) at 12:00 h on metestrus of the 4-d estrous cycle. The control group was treated with 100 micro L normal goat serum (control serum). Five mice were sacrificed every 6 h and blood samples were collected for hormonal assay. Individual female mice were bred in the afternoon of proestrus with individual fertile males. Embryos were collected at 08.00 h on d 2 post-coitus and cultured in KSOM solution. Treatment with inhibin-AS significantly increased the concentrations of plasma FSH. Furthermore, there was a significant elevation in plasma concentrations of estradiol-17beta and progesterone in the inhibin-immunized groups in comparison with controls. The superovulated oocytes that were fertilized normally in vivo were able to develop normally to blastocysts in vitro. The number of oocytes and blastocysts developed in animals treated with inhibin-AS was significantly higher than that for mice treated with control serum. Moreover, the rate of fertilization and the rate of blastocyst development were similar in inhibin-AS treated and control groups. These results indicate that immunoneutralization of endogenous inhibin induces superovulation in adult mice without additional treatment with human chorionic gonadotropin (hCG). In addition, the superovulated oocytes obtained by administration of inhibin-AS have normal embryonic developmental competence.

Differential responses of the hypothalamo-pituitary-adrenocortical axis to acute restraint stress in Hatano high- and low-avoidance rats

The high- and low-avoidance animal (HAA and LAA respectively) strains of Hatano rats were originally selected and bred from Sprague-Dawley rats for their performance in the shuttle-box task. The present study focused on the activity of the hypothalamo-pituitary-adrenocortical (HPA) axis of HAA and LAA rats in response to restraint stress. The restraint stress induced an elevation in plasma concentrations of ACTH, prolactin, corticosterone and progesterone. Peak levels of plasma ACTH during stress conditions were significantly higher in HAA rats than in LAA rats, while peak levels of prolactin were significantly lower in HAA rats than in LAA rats. Under stress conditions, ACTH and prolactin synthesis in the anterior pituitary glands was significantly higher in HAA rats compared with LAA rats. The peak plasma concentrations of corticosterone, during restraint stress, were significantly higher in LAA rats compared with HAA rats. These results indicate that the response of the hypothalamo-pituitary axis to acute restraint stress is greater in HAA rats than in LAA rats, whereas the ACTH-induced adrenal response of corticosterone release is higher in LAA rats than in HAA rats. On the other hand, prolactin secretory activity is higher in LAA rats compared with HAA rats. These differences in endocrine responses to stress may be involved in the regulation of the avoidance responses in the shuttle-box task.

Estrogenic Activities of Nitrophenols in Diesel Exhaust Particles1

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. Because these compounds are alkylphenolic derivatives that might mimic hormones, we evaluated their estrogenic activity by using recombinant yeast screens, myometrial contractility assays, and in vivo uterotrophic assays. Recombinant yeast screen assays showed that both PNMC and PNMPP possess estrogenic activity. Furthermore, ovariectomized 25-day-old immature female rats injected with PNMC and PNMPP subcutaneously for 2 days showed significant increases in uterine weight among those receiving 100 mg/kg PNMC and 0.1 and 1.0 mg/kg PNMPP. To clarify further the estrogenic activity of PNMC and PNMPP, rat uterine horns were monitored in organ bath chambers for myometrial contractility in response to oxytocin (OT). Significant differences occurred in the initial and maximum contractilities to OT at 0.25 and 25 mIU/ml in uterine horns obtained from animals treated with 100 mg/kg PNMC and in the maximum contractilities to OT at 0.025, 0.25, and 25 mIU/ml in those from rats treated with 0.1 mg/kg PNMPP. These results clearly demonstrated that PNMC and PNMPP in DEP have estrogenic activity both in vitro and in vivo and might therefore be considered as endocrine-disrupting chemicals.

A new alternative method for superovulation using passive immunization against inhibin in adult rats

The present study was undertaken to investigate the effects of passive immunoneutralization of endogenous inhibin on ovulation rate and embryo development in vivo and in vitro to establish a new alternative superovulation method in the adult rat. Female adult rats of Wistar strain were superovulated with a single injection of inhibin antiserum (inhibin-AS; 100 or 400 microl) or an injection of 20 IU eCG followed by an injection of 10 IU hCG. Untreated animals served as controls. Embryos were collected from oviducts or uteri on Days 1-5 of pregnancy, and the number of embryos and implantation sites were observed. On Day 1 of pregnancy, the two-cell-stage embryos were cultured and embryos from the 100-microl inhibin-AS group and the control group were transferred to recipient females to determine developmental competence. There were no significant differences between groups in fertilization rate. The numbers of normal embryos in the inhibin-AS-treated groups were significantly higher than the control and the eCG-hCG-treated groups throughout Days 1-4 of pregnancy. The number of implantation sites observed on Day 5 of pregnancy in the inhibin-AS-treated groups was significantly higher than both the control and the eCG-hCG-treated groups. Furthermore, the rate of blastocyst development in vitro in the inhibin-AS-treated groups and posttransfer viability in the 100-microl-inhibin-AS group were comparable with those of the control group. These results indicate that immunoneutralization of endogenous inhibin is a new practical alternative for induction of superovulation as a substitution for eCG-hCG method in the adult rat.

Long-Term Treatment Effects of Pueraria mirifica Phytoestrogens on Parathyroid Hormone and Calcium Levels in Aged Menopausal Cynomolgus Monkeys

To determine the effect of Pueraria mirifica (PM) on serum parathyroid hormone (PTH) and calcium levels on aged menopausal monkeys (Macaca fascicularis), subjects were treated with 10, 100, or 1,000 mg/day of PM. Blood samples were collected every 5 days for 30, 90, and 60 days during pre-treatment, treatment, and post-treatment periods, respectively. Sera were assayed for PTH, estradiol, and calcium levels. PM-1,000 had the strongest effect on the decrease in PTH (0.001<P< or =0.05) and calcium levels (0.001<P< or =0.03) during the treatment period. PTH levels remained low for the first 15 days of the post-treatment period (0.01< or =P < or =0.05). PM-10 induced a significant decrease in PTH level on day 80 (P=0.02) during the treatment period and a significant decrease in calcium level on day 75 (P<0.01). There were no changes in serum PTH and calcium levels throughout the study period in the PM-100 group. Estradiol levels decreased significantly during the treatment period in all treatment groups. The results suggest that long-term treatment with 1,000 mg/day of PM decreases serum PTH and calcium levels in aged menopausal monkeys, indicating that PM ameliorates bone loss caused by estrogen deficiency.

Estrogenic and Anti-androgenic Activity of Nitrophenols in Diesel Exhaust Particles (DEP)

We recently isolated 4-nitrophenol, 2-methyl-4-nitrophenol, 3-methyl-4-nitrophenol, and 4-nitro-3-phenylphenol from diesel exhaust particles (DEP) and identified them as vasodilators. Because these compounds are alkylphenolic derivatives that might mimic hormones, we evaluated their estrogenic activity by human estrogen receptor (hER)-yeast screen assay. All of these nitrophenol derivatives except 2-methyl-4-nitrophenol exhibited estrogenic activity. Some estrogenic compounds are also anti-androgenic, so we measured the anti-androgenic activity of the same compounds by human androgen receptor (hAR)-yeast screen assay. We found anti-androgenicity in all four nitrophenols. Nitrophenols in DEP possess not only vasodilatory activity but also estrogenic and anti-androgenic activity.

Passive Immunoneutralization of Endogenous Inhibin Increases Ovulation Rate in Miniature Shiba Goats

We reported previously that passive immunization against inhibin enhances follicular growth and increases the ovulation rate. However, the ovulation rate was not comparable to the number of follicles. Therefore, the aim of this study was to attempt to increase the ovulation rate by increasing the interval between inhibin immunization and PGF2alpha injection. Five miniature Shiba goats were treated with 10 ml inhibin antiserum (inhibin-AS) developed against [Tyro30]-inhibin alpha (1-30). A control group (n=5) was treated with normal goat serum. All animals were injected intramuscularly with 125 microg PGF2alpha 72 h after treatment to induce estrus and ovulation. Blood samples were collected for hormonal assay and the ovulation rate was determined by laparotomy. In contrast to the control group, there was a significant increase in plasma concentrations of FSH in the immunized group. After luteolysis, plasma concentrations of estradiol-17beta increased markedly to a preovulatory peak about 2 folds higher (P<0.01) than that of controls. In addition, the ovulation rate was greater in the immunized group (14.4 +/- 2.2) than in the control group (2.2 +/- 0.6), and the mean number of follicles > or = 4 mm in diameter was 10.0 +/- 0.8 in the inhibin-AS group compared with 2.4 +/- 0.3 in control group. The present results demonstrate that immunoneutralization of endogenous inhibin increased FSH secretions in miniature shiba goats. The increased FSH secretion enhanced follicular growth and increased the ovulation rate. Additionally, increasing the interval between inhibin-AS and PGF2alpha injections (to 72 h) resulted in a greater ovulation rate compared with the previous protocol (48 h). Therefore, inhibin-AS treatment proved to be an effective alternative to exogenous gonadotropin methods for induction of superovulation in goats.

Expression of Nerve Growth Factor (NGF), and Its Receptors trkA and p75 in Ovaries of the Cyclic Golden Hamster (Mesocricetus auratus) and the Regulation of Their Production by Luteinizing Hormone

In the present study, changes in localization of nerve growth factor (NGF) and its receptors, trkA and p75 in the ovary were investigated during the estrous cycle of the golden hamster. The effect of LH surge on changes in localization of NGF, trkA and p75 in the ovary was also investigated. NGF and its receptors trkA and p75 were localized in oocytes, granulosa cells and theca cells of various stages of follicles throughout the estrous cycle. NGF and its two receptors were also present in numerous interstitial cells and luteal cells. The number of interstitial cells staining positively for NGF and its two receptors was greater in ovaries of day 1 (day 1=day of ovulation) than the other days during the estrous cycle. Treatment with the antiserum against luteinizing hormone releasing hormone (LHRH-AS) at 1100 h on day 4 completely blocked ovulation. There were few positive reactions for NGF and its two receptors in interstitial cells 24 hr after LHRH-AS injection. The effect of LHRH-AS treatment was blocked by a single injection of 10 IU human chorionic gonadotropin. The distinct widespread distribution of NGF and its two receptors in the ovary of golden hamsters suggest that NGF may be an important growth factor for regulation of ovarian function. Furthermore, the LH surge may be an important factor for inducing production of NGF and its two receptors in interstitial cells of the cyclic golden hamster.

Different Effects of Pueraria mirifica, a Herb Containing Phytoestrogens, on LH and FSH Secretion in Gonadectomized Female and Male Rats

To investigate the effect of Pueraria mirifica (P. mirifica) containing phytoestrogens on reproductive systems, both sexes of rats were gonadectomized and treated orally with 0, 10, 100, and 1,000 mg/kg BW per day of P. mirifica suspended in water (abbreviated as P-0, P-10, P-100, and P-1000), respectively. The treatment schedule was separated into 3 periods: pre-treatment, treatment, and post-treatment. The duration for each period was 14 days. Blood samples were taken once a week. Serum LH and FSH levels were significantly increased within 1 week after gonadectomy; and there were no changes after administration of P-0, P-10, and P-100. However, the increase of LH levels in both sexes and FSH levels in females were attenuated within 1 week after P-1,000 treatment. The attenuation of LH levels in males was smaller than that of females. The decrease of gonadotropin levels was recovered within 1 week in males and 2 weeks in females, respectively, during the post-treatment period. The increase of uterine weight and vaginal cornification were observed in female rats treated with P-100 and P-1,000, whereas only the increase of epididymis weight was found in male rats treated with P-1,000. From this study, it can be concluded that P. mirifica can influence the reproductive functions in both sexes of rats, but the response in females is greater than in males.

Effect of Active Immunization of Pony Mares against Recombinant Porcine Inhibin .ALPHA. Subunit on Ovarian Follicular Development and Plasma Steroids and Gonadotropins

Two pony mares were immunized against recombinant porcine inhibin alpha subunit three times with 39 day intervals. Clinical findings and endocrinological changes before immunization were taken as the control. The first significant rise in the anti-inhibin titre (P<0.05) in the circulation was found 27 days after the first injection. Maximum binding activity was reached by the 12th day after the second booster dose. The number of small, medium and large sized follicles had increased significantly compared to before immunization (11.75 +/- 4.30, 2.75 +/- 0.69 and 2.51 +/- 0.63 vs 6.50 +/- 1.43, 1.83 +/- 0.44 and 1.33 +/- 0.38, respectively), but the ovulation rate remained unchanged after immunization. The average plasma concentration of FSH and estradiol-17beta during the estrous cycle increased significantly (P<0.05) after immunization. These results suggest that immunization against inhibin is a useful tool to increase the number of ovarian follicles during the estrous cycle of pony mares. Moreover, the present study supported the concept that inhibin plays a major role in the control of follicular growth through its inhibitory effect on FSH secretion synergistically with steroid hormones.

Estrogenic Effects of Pueraria mirifica on the Menstrual Cycle and Hormone-Related Ovarian Functions in Cyclic Female Cynomolgus Monkeys

This study investigated the estrogenic effect of Pueraria mirifica (P. mirifica) on menstrual cycle length and hormone-related ovarian function. Nine normal cyclic monkeys (Macaca fascicularis) were separated into 3 groups; each group was force fed with a single dose of 10, 100, and 1,000 mg of P. mirifica. The experimental schedule was separated into the pre-treatment and post-treatment periods. Blood samples were collected on days 3, 9 - 14, 19, 24, 29, and every 10 days until the next menstruation for one and two menstrual cycles during two consecutive periods and assayed for serum levels of gonadotropins and ovarian hormones. The result showed a significant increase in lengths of the follicular phase and total menstrual cycle in monkeys treated with 1,000 mg of P. mirifica, but no change in menstrual cycle length in monkeys treated with 10 and 100 mg of P. mirifica. Serum levels of follicle stimulating hormone, luteinizing hormone, estradiol, progesterone, or immunoreactive-inhibin did not change during the first and second menstrual cycles of the post-treatment period for all monkey groups. Our findings demonstrate that although changes in hormonal levels could not be observed in this study, a single dose of 1,000 mg of P. mirifica can disturb ovarian function and menstrual cycle in monkeys.

Early Pregnancy Diagnosis by Means of Ultrasonography as a Method of Improving Reproductive Efficiency in Goats

Eighteen cyclic Shiba goats were used in this study. Estrus was synchronized with a single injection of 125 microg of a synthetic analogue of prostaglandin F(2)alpha (PGF(2)alpha) after detection of at least one corpus luteum by B-mode ultrasonography. Blood samples were collected from each animal on days 0, 7 and 21 post-mating for progesterone assay. Animals in estrus were either allowed to be mated by fertile bucks twice during estrus (group I; n=12) or not at all (group II; n=6). Ultrasonographic examinations were performed transrectally or transabdominally using a real-time B-mode scanner equipped with a 7.5 or 5 MHz transducer. All animals exhibited estrus 56.0 +/- 2.7 h after injection of PGF2alpha. The results show that the accuracy of the progesterone assay in diagnosing pregnancy on day 21 after mating was 80% for pregnancy and 100% for non-pregnancy, retrospectively. Ultrasonographic examinations showed that gestational sac and embryos heartbeats were detected on days 20.2 +/- 0.6 and 24.3 +/- 0.7 of gestation, respectively. Placentomes were detected on day 35.4 +/- 1.0 of gestation as small nodules (0.7 +/- 0.2 cm in size). At two months pregnancy, skeletal structures like skull, thorax and long bones were clear. Biparietal diameter of the skull and length of long bones could be used as an estimate of gestational age. The accuracy of detection of fetal number using real-time B-mode ultrasonography was 91.7% on day 60 of gestation. In conclusion, progesterone assay at day 21 post-mating (cut-off value, 1 ng/ml) can be used for pregnancy diagnosis in goats. However, B-mode transrectal ultrasonography was more efficient due to detection of embryo and confirmation of its viability by heartbeats. In addition, fetal number and gestational age could be determined only by ultrasonography.

NMDA receptor antagonists reduce restraint-induced release of prolactin in male rats

OBJECTIVE

To investigate the effects of N-methyl-D-aspartate (NMDA) receptor antagonists on restraint-induced release of prolactin (PRL) in male Wistar rats of different ages.

DESIGN

Rats were implanted with a brain ventricular for icv injection, and with a jugular vein cannula for iv injection. Competitive NMDA receptor antagonist AP-5 and noncompetitive NMDA receptor blocker MK-801 was injected via brain cannula or vein cannula and was restrained for 3 hours. The blood sample was collected through vein cannula during the restraint. The plasma concentration of prolactin was measured by RIA.

RESULTS

The restraint-induced PRL release in the adult rat (12-weeks) was significantly suppressed by MK-801 (50 microg/rat, icv; or 5 mg/kg, iv) and was partially inhibited by pretreatment of AP-5 (50, 100 microg/rat, icv), but was not changed by systemic administration of AP-5 (10 mg/kg, iv). MK-801 (5 mg/kg, iv) prevented the restraint-induced PRL release in the peripuberal rat (45-days) and in the middle-aged rat (16-months).

CONCLUSION

Central NMDA receptors mediate restraint-induced PRL release in the male rat.

Endocrinologic comparison of activin a secretion during pregnancy and early lactation in Japanese monkeys, chimpanzees, and humans

Secretion of activin A in Japanese monkeys and chimpanzees during pregnancy and early postpartum periods was investigated, and the results were compared with those in humans. Plasma activin A increased throughout pregnancy in Japanese monkeys, and the level was significantly higher in the third and fourth quarters than in the first quarter. After parturition in the Japanese monkey, circulating activin A decreased to levels seen during the normal menstrual cycle. In chimpanzees, plasma activin A remained low until the third quarter of pregnancy and abruptly increased in the fourth quarter. After parturition in chimpanzees, however, circulating activin A concentrations still remained as high as levels in the fourth quarter until 42 h after parturition, then decreased to nadir levels at 1 mo after parturition, suggesting that activin A in chimpanzees may be secreted from other organs such as uterus in addition to placenta. Positive staining with inhibin/ activin alpha-, betaA-, and betaB-subunit antisera was observed in the cytoplasm of the syncytiotrophoblast of term placenta in the Japanese monkey, chimpanzee, and human. These results demonstrated that circulating activin A gradually increased from early pregnancy in Japanese monkey, whereas an abrupt increase occurred at late pregnancy in chimpanzees. These results also demonstrated that the syncytiotrophoblast of placenta is the source of activin A in Japanese monkeys and chimpanzees as well as humans.

Investigation of testicular toxicity of nefiracetam, a neurotransmission enhancer, in rats

Testicular toxicity of nefiracetam (N-(2,6-dimethylphenyl)-2-(2-oxo-1-pyrrolidinyl) acetamide), a neurotransmission enhancer, was investigated in male Slc:SD rats. Nefiracetam was orally administered daily at 1500 mg/kg for 4 weeks, and the animals were killed sequentially during the course of administration to determine testicular histopathological changes and sperm head counts (SHC), and hormonal changes. Retention of step 19 spermatids, sporadic degeneration of pachytene spermatocytes and step 7 spermatids in the stage VII seminiferous tubules, and a decrease in SHC were seen as earliest changes after 1 week of administration. These changes gradually advanced up to atrophy of seminiferous tubules with multinucleated-giant-cell formation after 4-week administration. Serum and testicular testosterone levels were decreased, but recovered to the control levels within a day following a single administration, and the decreases were repeated after 1-week administration. These results suggest that nefiracetam-induced earliest changes could be caused by the decreased level of testicular testosterone.

Endocrinological changes before and after removal of the granulosa theca cell tumor (GTCT) affected ovary in 6 mares

To clarify the endocrinological characteristics of the mares with granulosa theca cell tumor (GTCT), peripheral plasma samples from the 6 mares affected with GTCT were collected before and after the surgical removal of the affected ovary. Concentrations of testosterone (T), follicle stimulating hormone (FSH), luteinizing hormone (LH), immunoreactive-inhibin (ir-INH), progesterone (P) and estradiol-17beta (E(2)) in the plasma samples were measured by radioimmunoassay. Before removal of GTCT in all cases, the concentrations of T were significantly higher than those of normal mares at the breeding and non-breeding seasons, whereas plasma concentrations of FSH, LH, ir-INH, P and E(2) were lower. After surgical removal of the affected ovary, the circulatory concentrations of T was declined, but the concentrations of other hormones were constantly low as compared with those of normal mares. The present study suggests that 1) the source of higher T may be due to the abnormal follicles in ovary of GTCT, 2) in the case of GTCT the elevated level of T is observed due to the lack of aromatase, and 3) the high level of T is a typical characteristics for GTCT in mares. It is also suggested 4) due to the elevated levels of T the concentrations of gonadotropins may be suppressed.

Ovarian dynamics and their associations with peripheral concentrations of gonadotropins, ovarian steroids, and inhibin during the estrous cycle in goats

Ovarian changes determined by daily transrectal ultrasound and its relationship with FSH, LH, estradiol-17beta, progesterone, and inhibin were investigated in six goats for three consecutive interovulatory intervals. Estrous cycles were synchronized using two injections of prostaglandin F2alpha analogue 11 days apart. All follicles 3 mm or greater in diameter and corpora lutea were measured daily. A follicular wave was defined as one or more follicles growing to 5 mm or greater in diameter. The day that the follicles reached 3 mm in diameter was defined as the day of wave emergence, and the first wave after ovulation was defined as wave 1. During the interovulatory interval (mean +/- SEM, 21.3 +/- 0.4 days; n = 18), follicular waves emerged at 0.3 +/- 0.5, 6.5 +/- 0.2, and 12.1 +/- 0.4 days for wave 1, wave 2, and wave 3, respectively, in goats with three waves of follicular development and at -0.6 +/- 0.3, 4.7 +/- 0.2, 9.4 +/- 0.5, and 13.4 +/- 0.5 days for wave 1, wave 2, wave 3, and wave 4, respectively, in goats with four waves of follicular development (Day 0 = the day of ovulation). The mean diameter of the largest follicle of the ovulatory wave was significantly larger than those of the largest follicles of the other waves. Corpora lutea could be identified ultrasonically at Day 3 postovulation and attained 12.1 +/- 0.3 mm in diameter on Day 8. Transient increases in plasma concentrations of FSH were detected around the day of follicular wave emergence. The level of FSH was negatively correlated with that of inhibin. These results demonstrated that follicular waves occurred in goats and that the predominant follicular wave pattern was four waves with ovulation from wave 4. These results also suggested that the emergence of follicular waves was closely associated with increased secretion of FSH.

Inhibin B is the major form of inhibin secreted from testes in male Japanese macaques ( Macaca fuscata)

In order to clarify the cellular source and forms of bioactive inhibin in male Japanese macaques ( Macaca fuscata), circulating concentrations of inhibin A and B, and immunohistochemical localization of inhibin subunits in testis were studied. Plasma concentrations of testosterone were also measured. The present study showed that inhibin B was clearly detected in the plasma of male Japanese macaques. Moreover, concentrations of both inhibin B and testosterone during the breeding (mating) season were significantly higher than those of the non-breeding season. On the other hand, plasma inhibin A was detected neither during the breeding seasons nor during the non-breeding seasons. Positive stainings with alpha and betaB subunit antibodies were observed in the Sertoli cells, however staining with betaA subunit antibody was not observed in the testicular samples. These results indicate that inhibin B is the major circulating inhibin and probably secreting from Sertoli cells in male Japanese macaques.

Spontaneous repair of the atrophic contralateral ovary without ovariectomy in the case of a granulosa theca cell tumor (GTCT) affected mare

A 21 year old thoroughbred mare with granulosa theca cell tumor (GTCT) in the right side and atrophic contralateral ovary was investigated in this study. After arrival at our laboratory on 10th December 1999, the clinical diagnosis of GTCT was examined by rectal palpation and ultrasonographic image of ovaries. Plasma from peripheral blood was collected in the breeding and non-breeding seasons for hormonal analysis. The results showed that the contralateral ovary regained normal activity without any treatment of the GTCT affected ovary and contained follicles showing different sizes 19 months later. However, the affected right ovary, which became smaller after 4 months, was totally inactive without any follicle. The observations clearly demonstrate that without any treatment of the GTCT affected ovary, a mare can return to her normal estrous cycle within a certain period in some GTCT cases.

Localization of inhibin alpha-, betaA- and betaB-subunits and aromatase in ovarian follicles with granulosa theca cell tumor (GTCT) in 6 mares

To clarify the morphological and immunohistochemical characteristics in mares with granulosa theca cell tumor (GTCT), the localization of inhibin subunits (alpha, betaA, betaB) and aromatase in the granulosa cell layers and theca layers in the ovarian follicles were determined by immunohistochemical staining. The follicles were obtained from the ovaries of 6 mares with GTCT and 4 normal mares as controls. Immunohistochemically, inhibin alpha-subunit was localized in the granulosa cells of all follicles showing different sizes in all GTCT cases and betaA- subunit was localized in two GTCT cases in all sized follicles. But inhibin betaB- subunit and aromatase were not localized in GTCT cases. On the other hand, inhibin alpha-, betaA-, and betaB-subunits and aromatase were localized in the large and medium sized follicles, but inhibin betaA- and betaB-subunits and aromatase were not stained in the small sized follicles in normal cases. These findings suggest that some mares with GTCT can secrete dimeric inhibin (inhibin A), but all GTCT cases cannot secrete inhibin B. By the results of aromatase staining it is clear that testosterone is not converted into estradiol due to the lack of aromatase in the GTCT follicles.

Effects of passive immunization of goats against inhibin on follicular development, hormone profile and ovulation rate

This study was conducted to investigate the effect of immunoneutralization against endogenous inhibin on FSH secretion and ovulation rate, with the aim of developing a new superovulation method using inhibin antiserum in goats. Two groups of goats received an i.v. injection of either 10 ml normal goat serum (control; n = 6) or 10 ml inhibin antiserum developed against [Tyr(30)]-inhibin alpha (1-30) (n = 6) 48 h before treatment with prostaglandin F(2alpha) (PGF(2alpha)). Blood samples were collected at 6 h intervals and ovaries were examined each day using a B-mode ultrasound scanner equipped with a 7.5 MHz transducer during the experimental period. Immunization against inhibin resulted in a four- to fivefold increase (P < 0.01) in plasma concentrations of FSH. After luteolysis, plasma concentrations of oestradiol increased markedly to reach a preovulatory peak, which was about two times higher (P < 0.01) than that of the controls. The treatment was accompanied by a significant increase in the total number of follicles of > or = 3 mm in diameter at 24 (8.2 +/- 0.4 in inhibin antiserum group versus 4.8 +/- 0.3 in control group) and 96 h later (13.5 +/- 1.0 in inhibin antiserum group versus 5.3 +/- 0.6 in control group). The ovulation rate was significantly (P < 0.01) higher in goats treated with inhibin antiserum (4.2 +/- 0.5; n = 6) than in control goats (1.8 +/- 0.3; n = 6). These results indicate that inhibin is an important factor in the regulation of FSH secretion in goats and demonstrate that passive immunization against inhibin at 48 h before treatment with PGF(2alpha) induces the development of more follicles and increases ovulation rate. Thus, inhibin antiserum treatment may be an alternative to the use of exogenous gonadotrophins for induction of superovulation in goats.

Effects of passive immunization of goats against inhibin on follicular development, hormone profile and ovulation rate

This study was conducted to investigate the effect of immunoneutralization against endogenous inhibin on FSH secretion and ovulation rate, with the aim of developing a new superovulation method using inhibin antiserum in goats. Two groups of goats received an i.v. injection of either 10 ml normal goat serum (control; n = 6) or 10 ml inhibin antiserum developed against [Tyr(30)]-inhibin alpha (1-30) (n = 6) 48 h before treatment with prostaglandin F(2alpha) (PGF(2alpha)). Blood samples were collected at 6 h intervals and ovaries were examined each day using a B-mode ultrasound scanner equipped with a 7.5 MHz transducer during the experimental period. Immunization against inhibin resulted in a four- to fivefold increase (P < 0.01) in plasma concentrations of FSH. After luteolysis, plasma concentrations of oestradiol increased markedly to reach a preovulatory peak, which was about two times higher (P < 0.01) than that of the controls. The treatment was accompanied by a significant increase in the total number of follicles of > or = 3 mm in diameter at 24 (8.2 +/- 0.4 in inhibin antiserum group versus 4.8 +/- 0.3 in control group) and 96 h later (13.5 +/- 1.0 in inhibin antiserum group versus 5.3 +/- 0.6 in control group). The ovulation rate was significantly (P < 0.01) higher in goats treated with inhibin antiserum (4.2 +/- 0.5; n = 6) than in control goats (1.8 +/- 0.3; n = 6). These results indicate that inhibin is an important factor in the regulation of FSH secretion in goats and demonstrate that passive immunization against inhibin at 48 h before treatment with PGF(2alpha) induces the development of more follicles and increases ovulation rate. Thus, inhibin antiserum treatment may be an alternative to the use of exogenous gonadotrophins for induction of superovulation in goats.

Ovarian and hormonal response of female goats to active immunization against inhibin

This study was conducted to evaluate the effect of active immunization against inhibin on hormonal levels and the ovulation rate in goats. Ten adult Shiba goats (Capra hircus) in two groups were used in this study. The first group was injected with inhibin vaccine (immunized, n=5) and the second group was injected with Freund's adjuvant (control, n=5) followed by three booster injections at 4-week intervals. After the third booster injection, three consecutive periods of oestrus were induced using prostaglandin F(2alpha) at intervals of 11 days. Blood samples were collected at 2-6 h intervals and the ovaries were monitored using B-mode ultrasonography. All inhibin-immunized goats generated antibodies that bound (125)I-labelled bovine inhibin and their FSH concentrations were significantly higher than corresponding values in the control group. Also, inhibin-immunized goats had significantly higher preovulatory oestradiol-17beta (P<0.01) and higher concentrations of progesterone in the luteal phase (P<0.05). Immunization of goats against inhibin resulted in a significant (P<0.01) increase in ovulation rate (control: 1.7+/-0.3 vs immunized: 7.6+/-1.1). These results demonstrate that active immunization against inhibin enhances ovarian follicular development and ovulation rate by promoting an increase in pituitary FSH secretion. Therefore, immunization against inhibin may be a useful alternative to the conventional approach of superovulation in goats.