Metabolic profile of pre-pregnancy,pregnancy and early lactation in multiple lambing Sakiz ewes. 1. Changes in plasma glucose, 3-hydroxybutyrate and cortisol levels

Twenty synchronized Sakiz ewes aged 3-4 years were used in the study. Blood samples were taken once in pre-pregnancy and at the 100th day of pregnancy. At the 120th day of pregnancy and on the 10th day of lactation, blood samples were collected every 2 h for 24 h from only 10 ewes. Plasma cortisol levels were analyzed by radioimmunoassay. Plasma glucose and 3-hydroxybutyrate levels were determined spectrophotometrically. Plasma cortisol level slightly increased at the 100th day of pregnancy, decreased during late pregnancy and continued to decrease during lactation. Plasma glucose and 3-hydroxybutyrate levels were not significantly different during pre-pregnancy, pregnancy and the early lactation periods. In conclusion, the results showed that metabolic disorders such as pregnancy toxaemia did not occur in ewes fed a balanced ration sufficient in energy and protein levels even in a multiple lambing breed of ewes.     

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 pre-pregancy 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 ir-inhibin and estradiol-17β 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 pre-pregnancy 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, ir-inhibin, and estradiol-17β during these stages suggest that these hormones may have important regulating roles on leptin secretion during pregnancy in the Japanese monkey.     

Plasma luteinizing hormone and progesterone in the adult female pig during the oestrous cycles, late pregnancy and lactation, and after ovariectomy and pentobarbitone treatment.

In a series of experiments on female miniature pigs, the pattern of plasma LH and progesterone levels during the oestrous cycle, late pregnancy and lactation and after ovariectomy were characterized, and the effect of pentobarbitone treatment was tested. The preovulatory surge of LH occurred in seven out of eight animals between 00.00 and 12.0 h on day 0 of the oestrous cycle (day 1 of standing heat). Plasma progesterone strated to decline 8 days before oestrus and reached its lowest value 5 days before the preovulatory LH peak. Increases in progesteron concentration were already noticeable 48 h after the LH surge. During late pregnancy, parturition and lactation, plasma LH was low and showed only minor fluctuations, while plasma progesterone declined 4 to 5 days before parturition. Both hormones remained at low levels throughout lactation. Three weeks before parturition increases in LH were always followed by an increase in progesterone. This dependency was greatly diminished immediately before delivery. Four to 12 days after weaning the animals came into oestrus which was followed by an increase in LH and later an increase in progesterone concentrations. Ovariectomy during dioestrus resulted in a steady increase in plasma LH levels of 35-39 days. Ovariectomy caused abortion if performed on day 100 of pregnancy. It was followed by a rapid increase of plasma LH concentration. Normal parturition (around day 115) and lactation took place when animals were spayed on day 112 of pregnancy. In this case, plasma LH levels remained even lower than before ovariectomy as long as lactation was maintained. Immediately after weaning a rapid increase in the normal postovariectomy pattern of LH secretion was observed. Pentobarbitone anaesthesia (30-35 mg/kg body wt, initial dose), during pro-oestrusoestrus, for less than 5 h had no effect on the preovulatory LH increase. However, pentobarbitone anaesthesia for more than 6 h inhibitied the LH peak and ovulation if the animal was under deep anaesthesia before 24.00 h on the day before oestrus. Pentobarbitone treatment of ovariectomized pigs resulted in a clear decrease in LH levels 40 min after a single i.v. dose.     

In vivo steroidogenic effects of homologous pituitary ventral lobe extract in the spiny dogfish, Squalus acanthias

Pregnant Squalus acanthias were injected intravenously with aqueous extract equivalent to three pituitary ventral lobes (VL). Blood samples were withdrawn by caudal sinus puncture at intervals over a period of 72 hr and plasma progesterone, testosterone, and estradiol-17 beta measured by radioimmunoassay. Early pregnancy animals (Stage A) failed to respond, but mid-pregnancy animals (Stage C) responded to VL with significant increases in plasma steroids. Plasma progesterone and testosterone were increased sevenfold and plasma estradiol-17 beta fourfold by 10-24 hr postinjection. These studies demonstrate pregnancy stage-dependent differences in gonadal sensitivity to a pituitary ventral lobe gonadotropic moiety.     

Plasma oxytocin and steroid concentrations during late pregnancy, parturition and lactation in the miniature pig.

Plasma oxytocin concentrations were measured during late pregnancy, parturition and lactation in the miniature pig. Measurements were made of plasma oestradiol, oestrone and progesterone to determine whether there was any relationship between the concentrations of oxytocin and these steroids in the circulation. Plasma oxytocin concentrations were low or undetectable in late pregnancy. Rises of up to 68.8 mum./ml were seen at the time of delivery of the foetuses and at the expulsion of the placenta. The only steroid that seemed to relat to oxytocin release was progesterone. Oxytocin release was consistently seen when progesterone concentrations had fallen to below 10 ng/ml but no increase in concentration was observed while oestrone and oestradiol increased to their maximum concentrations of 3.86--11.6 and 0.43--0.70 ng/ml respectively. During lactation, when both oestrogen and progesterone concentrations were low, suckling caused the levels of oxytocin to increase to 7.4 muu./ml. These increases were greater during the first 2 weeks of lactation than later.     

An examination of the proposed roles of placental lactogen in the ewe by means of antibody neutralization

The physiological role of placental lactogen (PL; chorionic somatomammotrophin) in the ewe has been investigated by infusion of ewes (n = 3) on day 131 of pregnancy with sufficient ovine PL (oPL) antibody to neutralize circulating oPL for at least 12 h. Effectiveness of the antibody neutralization was defined both in vitro and in vivo according to rigorous criteria. Control ewes (n = 3) were infused simultaneously with an equivalent amount of pooled goat gamma globulin. Since both sets of ewes had previously been catheterized with jugular, utero-ovarian and femoral vein catheters and a femoral arterial catheter, it was possible to measure whole body glucose kinetics as well as muscle and uterine glucose, free fatty acid (FFA) and 3-hydroxybutyrate extraction. In addition, plasma levels of insulin, GH, prolactin, insulin-like growth factor-I (IGF-I), IGF-II, progesterone and cholesterol were determined in femoral arterial samples. Neutralization of maternal oPL did not significantly affect whole body glucose metabolism, uterine and muscle glucose extraction, or 3-hydroxybutyrate extraction by muscle. A trend towards lower plasma FFA levels was observed after prolonged infusion, but was not statistically significant. However, plasma insulin levels rose significantly during antibody infusion after an early fall. These observations are rationalized in terms of the known requirements of ruminant metabolism during pregnancy, and contrasted with the accepted model for the role of human PL in the metabolic adjustments of pregnancy. No change in plasma IGF-I, IGF-II or GH was observed, providing no support for the concept that oPL is responsible for maternal somatomedin generation during pregnancy. Similarly, plasma prolactin did not differ between antibody-treated and control groups. Finally, antibody neutralization had no influence on either plasma progesterone or cholesterol, mitigating against a role for oPL in progesterone production during late pregnancy in the ewe.     

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)     

Morphological and endocrine correlates of the reproductive cycle of the aplacental viviparous dogfish, Squalus acanthias

Pregnant female spiny dogfish were captured off the coasts of Maine and Massachusetts and morphometric and gravimetric analyses of the liver, gonad, and reproductive tract correlated with the reproductive cycle. Plasma samples were taken and circulating steroids (progesterone, testosterone, and estradiol) were measured by radioimmunoassay. Clear-cut temporal variations in plasma steroid levels were observed, which correlated with the ovarian cycle. Testosterone and estradiol-17 beta levels were low (100-200 pg/ml plasma) in early pregnancy when ovarian follicles were small but increased to about 10 ng/ml as follicles grew and gestation progressed. By contrast, plasma progesterone was high (2-6 ng/ml) in early to mid-pregnancy when corpora lutea were active and declined toward term (less than 1.0 ng/ml).     

Secretion of inhibin A and inhibin B throughout pregnancy and the early postpartum period in chimpanzees

Plasma concentrations of inhibin A and inhibin B during pregnancy and early lactation in chimpanzees were determined by enzyme-linked immunosorbent assay (ELISA). Plasma samples were taken from five pregnant chimpanzees at 6-9, 10, 20 and 25 weeks of pregnancy, and following parturition. Throughout pregnancy and the early postpartum period, circulating inhibin A and inhibin B concentrations remained low, at similar levels to those during the normal menstrual cycle in chimpanzees. Concentrations of inhibin A in the placental homogenate were high enough to be measured by the ELISA and by bioassay, whereas circulating inhibin bioactivities in late pregnancy were too low to be measured. Plasma concentrations of FSH remained low with no significant changes throughout pregnancy and the postpartum period. Plasma concentrations of oestradiol-17beta and progesterone at 25 weeks of pregnancy were much higher than normal menstrual cycle levels. It was concluded that in chimpanzees the levels of circulating inhibin A and inhibin B remained low throughout pregnancy and the early postpartum period, and that the concentrations of bioactive dimeric inhibin did not increase towards the end of pregnancy. The suppression of circulating FSH levels during pregnancy is suggested to be controlled by steroid hormones that increased significantly in late pregnancy, and the present findings further suggest that the secretory pattern and role of inhibin during pregnancy in chimpanzees may be different from that in human and other primates.     

Plasma hormones and pituitary luteinizing hormone in the rat during the early stages of pregnancy and after post-coital treatment with tamoxifen (ICI 46,474).

Plasma levels of oestradiol-17beta, progesterone and luteinizing hormone (LH) and pituitary levels of LH have been measured during the first 6 days of pregnancy, in normal rats and in rats receiving two doses of Tamoxifen (trans-1-(rho-beta dimethylamino-ethoxyphenyl)-1-2-diphenylbut-1-ene) on day 2 of pregnancy. In normal rats oestradiol rose strongly from early on day 3 to reach a peak concentration between 22.00 h on day 3 and 08.00 h on day 4. Progesterone concentrations rose from day 2 to reach peak values on day 3-4. In animals in which implantation was delayed 20-24 h by administration of Tamoxifen (0.1 mg/kg) orally on day 2 the increased level of plasma oestrogen was also delayed by 20 h. A higher dose of Tamoxifen (0.2 mg/kg) on day 2, which prevented implantation, completely eliminated the increase in plasma oestradiol. Neither dose of Tamoxifen affected the levels of progesterone. In both normal rats and rats treated with 0.1 mg Tamoxifen/kg, plasma LH levels declined by day 3 while pituitary levels rose steadily. There was no detectable change in either plasma or pituitary LH levels, accompanying the increase in plasma oestradiol in the normal rats. In animals receiving Tamoxifen (0.2 mg/kg), plasma LH increased to a maximum by day 4 while levels of pituitary LH decreased. The results show that the oestrogen "surge" of early pregnancy, occurs normally about midnight on day 3 and not late on day 4 as previously thought. It is considered that the plasma oestradiol peak in early pregnancy results from an increased release of FSH rather than an increased release of LH. Tamoxifen may owe part of its antifertility action to a capacity to inhibit the synthesis of oestradiol from progesterone.     

Difference in the response of follicular maturation and ovulation between early and late lactating rats after removal of the litter

The mechanisms responsible for the 24-h difference in the time of the next ovulation after litter removal between early and late lactating rats were investigated. At 11.00 h on day 5 of lactation, concentrations of oestradiol-17 beta and inhibin activity in ovarian venous plasma were lower than those on day 17, corresponding to the absence of healthy Graafian follicles. After removal of the litter on day 5 of lactation a small surge of FSH with a steady increase in basal levels of LH occurred to initiate follicular maturation, and ovulation occurred 4 days later. After removal of the litter on day 17 of lactation a surge of FSH was not observed, due to high levels of inhibin activity in ovarian venous plasma, until the time of preovulatory surges of gonadotropin which occurred 2 days later and resulted in ovulation the next morning. Prolactin concentrations decreased similarly in both groups abruptly after removal of the litter. A decrease in plasma concentrations of progesterone occurred 42 h after removal of the litter on day 5, though it occurred 18 h after removal of the litter on day 17. These results indicate that the 24-h delay of ovulation after litter removal on day 5 of lactation, as compared with the time of ovulation after litter removal on day 17, is due probably to the absence of healthy antral follicles and high activity of corpora lutea secreting progesterone at the time of litter removal.     

Steroid profiles of the female tilapia, Oreochromis mossambicus, and correlation with oocyte growth and mouthbrooding behavior

Plasma levels of progesterone, 17 alpha-OH-progesterone, testosterone, and estradiol-17 beta were measured by radioimmunoassay during the ovarian cycles of two groups of female tilapia, Oreochromis mossambicus. One group included females that successfully mouthbrooded fry, while the other group consisted of females in which the zygotes were either removed or swallowed within 1 day after spawning. The mouthbrooders had a longer ovarian cycle (about 40 days) and were sampled 1, 3, 5, 7, 10, 15, 20, 25, 30, 35, and 40 days after spawning. The non-mouthbrooders had an ovarian cycle of about 25 days. They were sampled 3, 5, 7, 10, 15, 20, and 25 days after spawning. Initial peaks in levels of testosterone, estradiol-17 beta, and progesterone occurred later in the cycle of mouthbrooders. The first peak of testosterone and estradiol-17 beta occurred at 15 days after spawning. While estradiol-17 beta levels remained high, testosterone levels fell at 25 days after spawning, and increased again just prior to spawning. In the latter phase of mouthbrooding (15-25 days after spawning), the oocytes in the ovary did not increase in size, and testosterone and estradiol levels were high. During this time, estradiol may have a function other than stimulating vitellogenesis, such as an involvement (with testosterone?) in parental behavior, or protecting the oocytes from atresia. In non-mouthbrooders, testosterone, estradiol-17 beta, and progesterone levels initially peaked at 10 days after spawning, then dropped at 15 days after spawning. At the end of the cycle, testosterone and estradiol-17 beta levels increased again. The drop in estradiol levels is contrary to the profile seen in mouthbrooders. Also in mouthbrooders, progesterone levels did not rise until 25 days after spawning, then decreased and peaked again towards the end of the cycle. 17 alpha-OH-progesterone concentrations were low, with a single peak at 7 days after spawning in non-mouthbrooders, and at 40 days after spawning in mouthbrooders. There appears to be a relationship between the delayed initial peaks of the steroid hormones measured, oocyte growth arrestment, and longer-lived postovulatory follicles in mouthbrooding female tilapia.     

Peripheral blood levels of immunoreactive inhibin during pseudopregnancy, pregnancy and lactation in the rat

Concentrations of inhibin in peripheral blood were determined by radioimmunoassay in pseudopregnant, pregnant and lactating rats and correlated with the status of follicular development, luteal function in the ovaries and placental function. In pseudopregnant rats, plasma concentrations of inhibin remained relatively high from days 2 to 12 of pseudopregnancy and no significant changes occurred throughout pseudopregnancy. In pregnant rats, a marked decline in plasma concentrations of inhibin occurred between days 6 and 14 followed by an abrupt increase on days 20 and 21. In lactating rats, plasma concentrations of inhibin were consistently lower in dams nursing eight pups than in dams nursing two pups. Plasma concentrations of inhibin remained low during the early stages of lactation followed by a significant increase during the late stages in dams nursing eight pups. These changes in inhibin during the period of lactation correlated with those of plasma concentrations of LH, but not with those of oestradiol-17 beta, testosterone and progesterone. Throughout pseudopregnancy, pregnancy and lactation, on the other hand, plasma concentrations of FSH were within the range of dioestrous levels. These findings indicate that concentrations of inhibin in peripheral plasma vary with the number of healthy antral follicles and no positive correlation was observed with luteal function during the luteal phase in rats. The results also suggest that inhibin is a more direct index of follicular development than oestradiol-17 beta in rats.     

Seasonal and steroid-dependent effects on the modulation of LH secretion in the ewe by intracerebroventricularly administered beta-endorphin or naloxone

The natural opioid ligand, beta-endorphin, and the opioid antagonist, naloxone, were administered intracerebroventricularly (i.c.v.) to evaluate effects on LH secretion in ovariectomized ewes and in ovariectomized ewes treated with oestradiol-17 beta plus progesterone either during the breeding season or the anoestrous season. Ovary-intact ewes were also studied during the follicular phase of the oestrous cycle. Jugular blood samples were taken at 10-min intervals for 8 h and either saline (20-50 microliters), 100 micrograms naloxone or 10 micrograms beta-endorphin were injected i.c.v. after 4 h. In addition, luteal phase ewes were injected i.c.v. with 25 micrograms beta-endorphin(1-27), a purported endogenous opioid antagonist. In ovariectomized ewes, irrespective of season, saline and naloxone did not affect LH secretion, but beta-endorphin decreased the plasma LH concentrations, by reducing LH pulse frequency. The effect of beta-endorphin was blocked by administering naloxone 30 min beforehand. Treating ovariectomized ewes with oestradiol-17 beta plus progesterone during the breeding season reduced plasma LH concentrations from 6-8 micrograms/l to less than 1 microgram/l. In these ewes, saline did not alter LH secretion, but naloxone increased LH pulse frequency and the plasma concentrations of LH within 15-20 min. During anoestrus, the combination of oestradiol-17 beta plus progesterone to ovariectomized ewes reduced the plasma LH concentrations from 3-5 micrograms/l to undetectable levels, and neither saline nor naloxone affected LH secretion. During the follicular phase of the oestrous cycle, naloxone enhanced LH pulse frequency, which resulted in increased plasma LH concentrations; saline had no effect.(ABSTRACT TRUNCATED AT 250 WORDS)     

Endometrial progesterone concentrations during the menstrual cycle.

Endometrial progesterone concentrations have been determined during the menstrual cycle and compared to plasma progesterone and estradiol-17 beta concentration. There is a good relationship between endometrial and plasma progesterone concentrations but none between endometrial progesterone and estradiol-17 beta concentration.     

Plasma and follicular tissue steroid levels in the elasmobranch fish, Torpedo marmorata.

Steroid concentrations in plasma and follicular tissues (theca plus granulosa layers) were determined by radioimmunoassay in the aplacental viviparous ray, Torpedo marmorata, during various stages of the reproductive cycle. Steroids in the uterine fluid of pregnant animals and in preovulatory atretic follicles were also measured. In the follicular tissue of cyclic animals, levels of progesterone were always lower than those of estradiol-17 beta and androgens (testosterone plus 5 alpha-dihydrotestosterone). Estradiol-17 beta and androgen levels increased as the animals approached the ultimate maturational stage before ovulation. Androgens were not detectable in plasma, while estradiol-17 beta increased dramatically before ovulation. In pregnant animals, only small ovarian follicles (less than 5 mm in diameter) were observed, and these had hormone concentrations that were similar to those of the small follicles of cyclic animals. Progesterone was the only steroid detected in the uterine fluid of pregnant animals. In completely sclerotic atretic follicles of pregnant animals, steroids were not detected. Progesterone was the main hormone in atretic follicles undergoing yolk resorption. This suggests that the latter may contribute to the elevated plasma progesterone concentrations of pregnant animals.     

Composite microassays of plasma progesterone, 17alpha-OH-progesterone, estrone, 17beta-estradiol and estriol in normal adult women. II.Steroid patterns in normal pregnancy, labor and the puerperium (author's transl)]

Plasma progesterone, 17alpha-OH-progesterone, estrone, 17beta-estradiol and estriol in human normal pregnancy, labor and the puerperium were measured simultaneously with radioimmunoassay or competitive protein binding assay. The steroids were extracted from the sample plasma with diethyl either, and were separated through two steps of sephadex LH-20 microcolumn chromatography prior to the assays. From the beginning to the 25th week of pregnancy, a gradual rise in the levels of plasma progesterone was noted, followed by a steep increase toward term with a level of 150-250 ng/ml at the end of gestation. The levels of 17alpha-OH-progesterone during the 7th or 8th week of pregnancy were 2-3 ng/ml, which was above the normal range in the luteal phase, followed by a gradual decrease during 15-25 weeks of gestation. Thereafter, an increase toward term was seen with a mean level of 6-10 ng/ml in the 40th week. From the beginning to the end of pregnancy, plasma levels of estrone, 17beta-estradiol, and estriol increased from less than 0.5 ng/ml to 2-4 ng/ml, from 1-2.5 ng/ml to 6-10 ng/ml, and from less than 1 ng/ml to 6-10 ng/ml, respectively. The disappearance of steroids from maternal peripheral blood in the puerperium was rapid. The half time of progesterone, 17alpha-OH-progesterone, estrone, 17beta-estradiol, and estriol were 72 min, 68 min, 27 min, 27 min, and 48 min, respectively. Analysis of the interrelation between several kinds of steroids of pregnancy, labor, and the puerperium with simultaneous microassays will contribute to the clarification of some important physiological and pathological aspects of feto-placental-maternal functions and steroidogenic functions of the corpus luteum in pregnancy.     

Altered secretion of gonadotropins and steroids resulting from delayed ovulation in the rat.

Rats were killed by decapitation at 3-h intervals during a 48-h delay of ovulation induced by sodium pentobarbital, as well as during the ensuing delayed proestrus, estrus and the first 4 days of gestation. Control animals were killed at the same intervals following injections of vehicle. Blood was collected and analyzed for LH, FSH, prolactin, progesterone and estradiol-17beta to determine if alterations in hormonal levels could account for the abnormal embryonic development which follows delayed ovulation. Hormonal concentrations in plasma were measured by radioimmunoassay except for progesterone, which was determined by competitive protein binding. Embryos were examined to verify the occurrence of abnormal development. Rate of oocyte maturation was studied in serial sections of ovaries from all animals killed at 30-min intervals on the afternoon of proestrus. Oocytes remained in meiotic arrest during the 48-h delay of ovulation, but resumed maturation at the expected time on the afternoon of the preovulatory surge of gonadotropins. Following delayed ovulation there was a significant increase in fertilized ova that were undergoing degeneration (6.5 vs 1.9%), abnormal development (3.7 vs 0.7%), and retarded development (3.1 vs 0.2%). A number of alterations in hormonal levels occurred during the prolonged preovulatory period. The proestrous surge of LH in plasma was completely suppressed on both days of treatment with Nembutal, but exhibited a normal preovulatory peak on the following day. FSH showed a small but significant rise on both days of treatment. Peak concentrations of FSH on the following day were not different in magnitude from the normal preovulatory surge, although the duration of this surge was shortened by 12 h. Prolactin and progesterone concentrations in plasma were only partially suppressed on the days of treatment, while on the following day preovulatory levels of prolactin were significantly greater than in controls. The proestrous peak levels of estradiol occurred prior to the first Nembutal injection and declined more gradually after this treatment. Plasma levels of estradiol remained above basal levels during the period of delayed ovulation with peaks of short duration at 15u0 h on the day of second treatment and the day prior to ovulation. Plasma levels of these 5 hormones during the first 4 days of gestation were not altered by delayed ovulation.     

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.     

Plasma Levels of Immunoreactive Melatonin, Estradiol, Progesterone, Follicle Stimulating Hormone, and β-Human Chorionic Gonadotropin During Pregnancy and Shortly After Parturition in Humans

Plasma concentrations of immunoreactive melatonin, estradiol, progesterone, follicle stimulating hormone (FSH), and beta-human chorionic gonadotropin (beta hCG) were studied between 1000 and 1230 h in 105 Chinese females during six periods of normal pregnancy and 1-5 min after normal delivery. We have also examined the midday levels of immunoreactive melatonin in the cord blood of fetuses and plasma collected 1-5 min after and 24 h after delivery from their mothers. Concentrations of hormone immunoreactivities were determined by radioimmunoassay, and distinct fluctuations of all hormones were recorded during pregnancy. In the pregnant females, there were significant negative correlations between melatonin and estradiol, melatonin and progesterone, beta hCG and progesterone, and beta hCG and estradiol, and positive correlations between melatonin and FSH and progesterone and estradiol. Furthermore, plasma melatonin levels in the cord blood demonstrated no sex difference and were significantly lower than and correlated positively with the levels in their mothers. Our results suggest that sex steroids may inhibit and FSH may potentiate circulating melatonin levels in gravid women; changes in the levels of melatonin during pregnancy may affect the in utero development of the human embryo; and circulating melatonin in the mother may be the major source of blood melatonin in the fetus before parturition.