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Biomedical subjects

K Taya

Publications and source records attributed to K Taya.

At least 109 records · Page 6Linked to original sources
PubMed1995

Effects of oil adjuvant on systemic response to Escherichia coli lipopolysaccharide in swine.

Intramuscular injection of 0.1 mg/kg of Escherichia coli lipopolysaccharide (LPS) mixed with Freund's complete adjuvant (LPS+FCA) in piglets mitigated the leukopenia and TNF-alpha and cortisol levels in the serum compared with that of LPS suspended in LPS-free saline. The endotoxin level in the serum of the LPS+FCA was remarkably reduced. These results suggest that the addition of oil adjuvant mitigate the systemic toxicity of LPS.

Animals↗
PubMed1995

Follicular dynamics and secretion of inhibin and oestradiol-17 beta during the oestrous cycle of the hamster.

Plasma and ovarian levels of inhibin were determined by a radioimmunoassay (RIA) at 3-h intervals throughout the 4-day oestrous cycle of hamsters. Plasma concentrations of FSH, LH, progesterone, testosterone and oestradiol-17 beta were also determined by RIAs. In addition, hamsters were injected at various times with human chorionic gonadotrophin (hCG) to determine the follicular development. The changes in plasma concentrations of FSH after injection of antisera to oestradiol-17 beta (oestradiol-AS) and inhibin (inhibin-AS) on the morning of day 2 (day 1 = day of ovulation) were also determined. Plasma concentrations of inhibin showed a marked increase on the afternoon of day 1, remained at plateau levels until the morning of day 4, then increased abruptly on the afternoon of day 4 when preovulatory LH and FSH surges were initiated. A marked decrease in plasma concentrations of inhibin occurred during the process of ovulation after the preovulatory gonadotrophin surges. An inverse relationship between plasma levels of FSH and inhibin was observed when the secondary surge of FSH was in progress during the periovulatory period. Plasma concentrations of oestradiol-17 beta showed three increase phases and these changes differed from those of inhibin. Changes in plasma concentrations of oestradiol-17 beta correlated well with the maturation and regression of large antral follicles. Follicles capable of ovulating following hCG administration were first noted at 2300 h on day 1. The number of follicles capable of ovulating reached a maximum on the morning of day 3 (24.8 +/- 0.6), and decreased by 0500 h on day 4 (15.0 +/- 1.1), corresponding to the number of normal spontaneous ovulations.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

A role of prostaglandin in the secretion of inhibin and oestradiol-17 beta in equine chorionic gonadotrophin-primed rats.

The role of prostaglandins in the secretion of inhibin and oestradiol-17 beta was examined in immature female rats treated with equine chorionic gonadotrophin. Administration of prostaglandin (PG) F2 alpha to animals whose serum and ovarian levels of inhibin and oestradiol-17 beta had been suppressed by indomethacin given 24 h after equine chorionic gonadotrophin prevented the inhibition or restored the levels to normal. Initiation of PGF2 alpha replacement immediately after treatment with indomethacin was more effective. The results are consistent with the hypothesis that PGs play a regulatory role in the synthesis and secretion of inhibin and oestradiol-17 beta by the rat ovary.

Animals↗
PubMed1993

Inhibition by indomethacin of the already accelerated secretion of inhibin and estradiol in equine chorionic gonadotropin-primed immature female rats.

In immature female rats, the secretion of ovarian inhibin and estradiol is greatly accelerated by equine chorionic gonadotropin (eCG) treatment. The present study has been carried out to determine whether or not the levels of the two hormones are inhibited by a single s.c.-injection of indomethacin (INDO) 24 h after eCG administration. The levels of ovarian hormones and gonadotropins were measured by double-antibody radioimmunoassay using 125I-labeled radioligands. The serum levels of inhibin and estradiol were considerably inhibited within 24 and 12 h, respectively, after INDO injection. In addition, the serum levels of follicle-stimulating hormone (FSH) after INDO injection remained lower than the basal levels before eCG treatment. The luteinizing hormone (LH) levels were significantly reduced within 12 h after INDO treatment. The results demonstrate that the levels of inhibin and estradiol, even in the situation where the production of both hormones is already accelerated by eCG pretreatment, are suppressed by an inhibitor of prostaglandin (PG) synthesis, suggesting that locally produced PGs may play a role in the regulation of the production of both hormones in the ovary.

Animals↗
PubMed1993

Age-related changes in blood concentrations of FSH, LH and testosterone and testicular morphology in a new rat sterile mutant with hereditary aspermia.

A new rat mutant showing aspermia was investigated. Groups of 4-7 mutant male rats were killed at 3, 5, 10, 15 and 25 weeks of age. Examination by microscope showed apparent abnormalities in the seminiferous epithelium from 3 weeks of age onward. Inclusion-like bodies were observed in the cytoplasm of pachytene spermatocytes from 3 weeks old and instead of spermiation, polynuclear giant cells were formed within the seminiferous epithelium after 5 weeks of age. Histological analysis of seminiferous epithelium of adult mutant rats also showed a marked decrease in the number of preleptotene, leptotene and pachytene spermatocytes and tubules containing only spermatogonia and Sertoli cells in the seminiferous epithelium increased with age. However, the combination of other cellular elements of germ cells in the seminiferous epithelium was similar to that in normal rats and the distribution rate of these seminiferous tubules was close to that of normal rats, indicating that cyclicity of seminiferous epithelium was still maintained in the mutant rats despite the lack of spermiation. Plasma concentrations of FSH and LH were significantly higher in the mutant male rats than in normal male rats at 5 and 10 weeks of age onward, respectively. Plasma concentrations of testosterone were lower in the mutant male rats than in normal male rats. Silastic capsules containing testosterone were implanted into the unilateral testis of adult mutant male rats and animals were autopsied 5 weeks later. However, intratesticular administration of testosterone did not affect restoration of spermatogenesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1993

Evidence that inhibin is an important factor in the regulation of FSH secretion during the mid-luteal phase in cows.

To investigate the physiological importance of inhibin in the regulation of FSH secretion in cows, seven cyclic cows were treated with an inhibin antiserum raised against bovine 32 kDa inhibin in a castrated goat. The same animals treated with a castrated goat serum (control serum) served as controls. On day 12 of the oestrous cycle (day 0 = day of oestrus), four of seven cows were injected with 100 ml inhibin antiserum first, and the remaining three cows with 100 ml control serum first. Twelve days after the second oestrus following the first serum injection (42-46 days after the first serum injection), the former four cows were injected with control serum and the latter three with inhibin antiserum. Follicular development after the injections of control serum or inhibin antiserum was assessed by daily ultrasonographic examination. Treatment with inhibin antiserum resulted in a marked increase (P < 0.01) in plasma concentrations of FSH and oestradiol-17 beta but not LH or progesterone, compared with those after treatment with control serum. Plasma concentrations of FSH increased significantly (P < 0.01) at 8 h after injection of anti-inhibin serum when compared with the control value. Concentrations of FSH in the plasma remained high for 72 h, then declined to the control level by 84 h, concomitant with an abrupt decrease in the titre of free inhibin antibody in the plasma. High concentrations of oestradiol-17 beta were observed between 36 and 96 h after treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Involvement of inhibin in the regulation of FSH secretion in prepubertal bulls.

To investigate the physiological importance of inhibin in the regulation of FSH secretion in prepubertal bulls, animals (6-month-old) were passively immunized against inhibin. Five animals were given an i.v. bolus injection of 50 ml inhibin antiserum raised against bovine 32 kDa inhibin in a castrated male goat, and four bulls were given the same amount of castrated male goat serum (control serum) as controls. Treatment with the inhibin antiserum resulted in a marked increase (P < 0.01) in plasma concentrations of FSH within 12 h compared with control animals, and FSH levels in immunized animals remained high until 168 h after the injection. Concentrations of plasma LH and testosterone in the immunized animals were not different from those in the control animals. The present findings provide strong evidence that inhibin plays an important role in the inhibitory regulation of FSH secretion in prepubertal bulls.

Animals↗
PubMed1993

Suppression of basal secretion of FSH inhibits follicular development and maturation during the oestrous cycle of the rat.

The role of basal FSH secretion during the rat oestrous cycle in regulating ovulation was examined by suppressing FSH secretion using charcoal-treated porcine follicular fluid (pFF). Although 0.5 ml pFF given at 05.00 and 11.00 h on the day of pro-oestrus had no effect on ovulation, 0.5 ml pFF given five times at 6-h intervals from 11.00 h on dioestrus to 11.00 h on pro-oestrus completely eliminated ovulation on the morning of the next oestrus. When 0.25 ml pFF was given on the same schedule, all animals ovulated a significantly decreased number of oocytes (9.0 +/- 0.8) at the next oestrus. During the period of pFF treatment, the number of follicles capable of ovulating in response to human chorionic gonadotrophin (hCG) decreased (7.6 +/- 0.7 at 05.00 h on pro-oestrus) and plasma levels of oestradiol showed a peak level 6 h later than in controls treated with 0.5 ml steroid-free porcine serum. Treatment with pFF suppressed plasma FSH concentrations in a dose-dependent manner, although plasma LH was inhibited irregularly. Supplementary administration of LH throughout the treatment period and 0.5 ml pFF resulted in ovulation of one to three oocytes in response to hCG in only three out of ten animals. These results suggest that basal secretion of FSH during the rat oestrous cycle plays an essential role in follicular development and maturation towards ovulation, and that the levels of FSH secretion may contribute to the maturation of normal numbers of follicles for ovulation.

Animals↗
PubMed1993

PC-766B, a new macrolide antibiotic produced by Nocardia brasiliensis. I. Taxonomy, fermentation and biological activity.

An actinomycete strain SC-4710, a new soil isolate, was found to produce a new macrolide antibiotic, PC-766B. Chemotaxonomic analysis of the producing organism revealed that the cells of SC-4710 had type IV cell wall, type A whole cell sugar pattern, type PII phospholipids, menaquinone MK-8(H4), cellular fatty acids comprising straight-chain saturated, unsaturated and tuberculostearic acids, and mycolic acids. The strain was identified as Nocardia brasiliensis (Lindenberg) Pinoy. The antibiotic, PC-766B, was active against Gram-positive bacteria, and some fungi and yeasts, but inactive against Gram-negative bacteria. It also showed antitumor activity against murine tumor cells in vitro and in vivo, and a weak inhibitory activity against Na+, K(+)-ATPase in vitro.

Animals↗
PubMed1992

Indomethacin inhibits the secretion of inhibin and oestradiol-17 beta stimulated by pregnant mare serum gonadotrophin in the immature female rat.

The involvement of prostaglandins (PGs) in the regulation of inhibin and oestradiol-17 beta secretion from the ovary was studied by determining the effects of indomethacin and/or pregnant mare serum gonadotrophin (PMSG) on the levels of ovarian hormones in immature female rats. An increase in serum and ovarian levels of inhibin and oestradiol-17 beta was observed with a reciprocal reduction in serum follicle-stimulating hormone (FSH) levels from within 26 to 50 h after a single injection of 5 IU PMSG (s.c.) when the rats were 26 days of age. Administration of indomethacin to suppress PGs synthesis, simultaneously with PMSG, resulted in a substantial reduction in the levels of ovarian PGF2 alpha and serum inhibin and oestradiol-17 beta, which were both enhanced by PMSG treatment, 24 h after treatment with drugs. Indomethacin also reduced the basal serum level of inhibin. In the indomethacin-treated animals, the serum level of FSH was significantly increased regardless of the treatment with PMSG, indicating that the negative feedback regulation between FSH and inhibin is operating in these animals. These results demonstrate the inhibitory effects of indomethacin on PMSG-enhanced inhibin and oestradiol-17 beta production, suggesting that PGs play a regulatory role in the secretion of inhibin and oestradiol-17 beta from the gonadotrophin-stimulated ovary.

Animals↗
PubMed1992

Changes in peripheral levels of bioactive and immunoreactive inhibin, estradiol-17 beta, progesterone, luteinizing hormone, and follicle-stimulating hormone associated with follicular development in cows induced to superovulate with equine chorionic gonadotropin.

Changes in concentrations of bioactive and immunoreactive (ir-) inhibin, estradiol-17 beta, progesterone, LH, and FSH in peripheral blood were determined in cows induced to superovulate with eCG. The pattern of follicular growth was also characterized by daily ultrasonographic examination. Hormonal profiles and follicular development during the intact estrous cycle of the same animals before eCG treatment served as controls. Equine CG increased the number of follicles of various sizes (small, greater than or equal to 4 less than 7, medium, greater than or equal to 7 less than 10; large, greater than or equal to 10 mm in diameter) by 4 days after administration. The second growth of large follicles occurred within 1 day after superovulation. Inhibin bioactivity in jugular vein blood was detectable 48 h after eCG injection (44 h before LH peak), whereas it was not detected before administration of eCG or during control cycles. Circulating levels of bioactive inhibin further increased during the two waves of growth of large follicles. The highest activity of inhibin was noted at the time of the preovulatory LH peak (0 h). Thereafter, bioactivity of inhibin in peripheral plasma dropped from 0 to 24 h after the LH peak, and the activity increased again at 72 h compared to the value at -44 h. Plasma levels of ir-inhibin showed a pattern similar to changes in bioactive inhibin in the eCG-treated cows. Plasma concentrations of estradiol-17 beta also increased concomitantly with two waves of growth of large follicles. There was no correlation between plasma levels of progesterone and inhibin.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Ovarian follicular dynamics and concentrations of oestradiol-17 beta, progesterone, luteinizing hormone and follicle stimulating hormone during the periovulatory phase of the oestrous cycle in the cow.

Changes in the plasma concentration of oestradiol-17 beta, progesterone, luteinizing hormone (LH) and follicle stimulating hormone (FSH) were characterized during the transition from the luteal to the follicular phase, the periovulatory period and the early luteal phase in five cycling cows. The pattern of growth and the regression of follicles and corpora lutea in the ovary of the same animals were also assessed by daily ultrasonographic examinations. Two waves of follicular growth (ovulatory and non-ovulatory) occurred in all animals. The ovulatory follicular wave started from 4 days before the preovulatory surges of LH and FSH and the wave of next growth of a dominant follicle (non-ovulatory follicle) started within one day after ovulation. Changes in plasma levels of oestradiol-17 beta correlated well with the growth of both ovulatory and non-ovulatory dominant follicles. Suppression of FSH concentration during the follicular phase was inversely related to the increase in plasma concentration of oestradiol-17 beta. These results suggest that, in the cow, ovulatory dominant follicles suppress FSH secretion by increasing the concentration of oestradiol-17 beta (and probably also inhibin) during the follicular phase.

Animals↗
PubMed1991

Seasonal changes in plasma concentrations of immunoreactive inhibin and testicular activity in male Japanese monkeys.

Seasonal changes in plasma immunoreactive (ir-) inhibin, testosterone, LH, and FSH concentrations were examined in five sexually mature male Japanese monkeys (Macaca fuscata fuscata) housed indoors individually, to explore the reproductive cyclicity in the male. Blood samples were collected monthly throughout one year, and testicular size, semen volume, and number of sperm in the semen were ascertained at the same time in the same animals. Semen samples were obtained by penile electrostimulation. The results showed a clear seasonal increase in all parameters: plasma ir-inhibin, testosterone, testicular size, semen volume, and total number of sperm in the liquid portion of the semen during the autumn and winter months in synchrony with the natural breeding season. In contrast, plasma LH and FSH remained unchanged throughout the year, although plasma FSH tended to increase during the breeding season concomitant with an increase in plasma ir-inhibin. A significant positive correlation between FSH and ir-inhibin was observed in two of five monkeys. The positive correlations between plasma ir-inhibin and testicular activities during both the developing and regressing phases of the testicular cycle indicate that plasma ir-inhibin is a useful indicator of testicular activity as well as an indicator of Sertoli cell function in the Japanese monkey.

Animals↗
PubMed1991

Marked seasonal changes in response to the negative feedback action of estradiol on luteinizing hormone secretion in the female Japanese monkey.

The seasonal changes in response to the negative feedback action of estradiol on LH secretion were studied in two groups of ovariectomized Japanese monkeys (Macaca fuscata fuscata; n = 6). Blood samples were collected two to three times a week, and changes in serum concentrations of LH, estradiol, and progesterone were examined. Before ovariectomy (OVX), serum LH was maintained at about 320 pg/ml regardless of the season (breeding season: autumn and winter). After OVX and simultaneous treatment sc with a Silastic implant of estradiol during the first breeding season, serum LH increased rapidly and remained high. As spring arrived, serum LH decreased abruptly and remained low. The removal of implants during the subsequent nonbreeding season resulted in an increase in serum LH similar to that during the previous breeding season after OVX and estradiol treatment. After the reinsertion of implants during the same nonbreeding season, serum LH reverted to previous low levels. As autumn arrived (second breeding season), serum LH rose again and remained high under the presence of implants. In the first subset of animals (n = 3), the implants were left in place until the subsequent mid-nonbreeding season when they were removed, and reinserted during the same non-breeding season. The findings closely corresponded to the previous results. In these animals, the implants were removed during the third breeding season, which resulted in a significant increase in serum LH. The second subset of animals (n = 3) underwent removal of implants during the second breeding season, which resulted in a further increase in serum LH, but the difference was not significant. In both subsets of animals, the timing of the increase and decrease in serum LH under the presence of implants virtually coincided with the onset and end of the breeding season in ovary-intact animals. Serum estradiol after OVX was maintained at levels similar to those in intact animals (80-100 pg/ml) under the presence of implants, but removal of implants resulted in decrease in serum estradiol to around 30 pg/ml within 1 week. Serum progesterone after OVX was maintained at low levels (less than 0.2 ng/ml) regardless of the presence of estradiol implants. These results clearly indicate a marked seasonal difference in serum LH concentrations in ovariectomized monkeys in response to constant serum estradiol. It is suggested that seasonal breeding of the Japanese monkey is governed by biannual changes in the response of the hypothalamo-hypophysial axis to the negative feedback action of estradiol.

Animals↗
PubMed1991

Mechanisms responsible for suppression of FSH and LH during lactation in the rat.

Mechanisms responsible for suppression of FSH and LH secretion during lactation were investigated in rats, with special reference to the suckling stimulus and ovarian inhibin. Concentrations of immunoreactive inhibin in the peripheral plasma and bioactive inhibin in ovarian venous plasma were always low on days 3 and 5 of lactation in dams nursing eight pups, whereas values were always high on days 17 and 20 of lactation in dams nursing eight pups and on day 5 of lactation in dams nursing two pups. There was an FSH surge within 48 h after removal of litters on days 3 and 5 of lactation in dams nursing eight pups, whereas plasma concentrations of FSH were unchanged within 48 h by removal of litters on days 17 and 20 of lactation in dams nursing eight pups and on day 5 of lactation in dams nursing two pups. Plasma LH concentrations increased significantly compared with those of control animals within 24 h after removal of the litter on any day of lactation, regardless of the litter size. Plasma FSH levels increased within 6 h after bilateral or unilateral ovariectomy in lactating rats only on the days when plasma concentrations of inhibin were high before ovariectomy, such as day 17 of lactation in dams nursing eight pups and on day 5 of lactation in dams nursing two pups, whereas the mean concentrations of plasma LH showed no significant increase within 12 h after bilateral ovariectomy in these lactating rats. Treatment with progesterone or oestradiol-17 beta after unilateral ovariectomy did not inhibit the increase in plasma FSH levels, while the increase in plasma concentrations of FSH after surgery was completely inhibited by injecting inhibin (porcine follicular fluid). Treatment with steroid hormones inhibited the basal levels of LH in unilateral ovariectomized lactating rats. Plasma FSH concentrations increased sharply within 6 h after a single i.v. injection of anti-inhibin serum on days 10, 15 and 20 of lactation in dams nursing eight pups and on day 5 of lactation in dams nursing two pups, whereas only a small but significant increase in concentrations of FSH was noted 6 h after the antiserum treatment on day 5 of lactation in dams nursing eight pups. Concentrations of plasma LH were unchanged by treatment with antiserum in lactating rats throughout lactation.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1990

Immunoreactive inhibin levels in peripheral blood during the breeding season in the female Japanese monkey.

Serum levels of immunoreactive inhibin as well as FSH, LH, estradiol-17 beta, and progesterone were measured by RIA in four mature female Japanese monkeys (Macaca fuscata fuscata) during the breeding season and subsequent transition into the nonbreeding season. During the breeding season, each monkey showed 2-6 ovulations, which were inferred from underlying endocrine events. The concentrations of serum inhibin increased during the luteal phase, but were low during the follicular phase. Such changes in serum inhibin levels correlated positively with those in serum progesterone levels. Basal levels of serum inhibin also increased during the breeding season, decreased during transition from the breeding season, and were low during the nonbreeding season. The parallel change in serum levels of inhibin and progesterone together with the increased basal levels of serum inhibin during this period suggests that both the CL and antral follicles are sources of circulating inhibin. Decreases in serum FSH levels during the luteal phase suggest that secretion of FSH is controlled by an inhibitory action of ovarian inhibin in addition to steroid hormones.

Animals↗
PubMed1990

Changes in circulating inhibin levels during pregnancy and early lactation in the Japanese monkey.

Changes in immunoreactive (ir-) inhibin concentrations in serum throughout pregnancy and early lactation up to one month after parturition were characterized in 6 Japanese monkeys (Macaca fuscata fuscata) by a heterologous radioimmunoassay (RIA) based on a bovine RIA. Serum levels of FSH, LH/monkey chorionic gonadotropin (mCG), estradiol-17 beta, and progesterone were also monitored for the entire period. Ir-inhibin levels in the serum were low (under 0.5 ng/ml) before conception. Three marked increases in serum ir-inhibin levels were found during pregnancy. The first increase was noted during early pregnancy, with a peak (2.2 +/- 0.2 ng/ml) at Day 22 of pregnancy (Day 0 = day of LH surge). The second increase was noted after Day 38 until Day 72 of pregnancy, when a peak value was noted (19.0 +/- 1.4 pg/ml). Plateau levels were maintained until late pregnancy, and a final rise was evident near the term with a peak (36.7 +/- 3.8 ng/ml) at Day 158 of pregnancy, 5 days before parturition. After parturition, ir-inhibin levels in the serum plummeted to nonpregnant levels within one day, and were maintained during early lactation. The first rise in serum inhibin during pregnancy was parallel to the rise of mCG and estradiol-17 beta, and the second and third rise were well correlated with serum estradiol-17 beta. Serum FSH was maintained at low levels throughout pregnancy, followed by a slight increase after parturition when serum inhibin decreased abruptly. Both bioactivity and immunoreactivity of inhibin were detected in the placental homogenates obtained at 120 days of pregnancy.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗