Ultrasonography of the female reproductive organs in farmed ostriches (Struthio camelus spp.)

The main objective of this study was to determine whether transcutaneous ultrasonography could be used as a diagnostic tool to monitor the reproductive organs of female breeding ostriches. An additional aim was to investigate whether the use of this technique could facilitate prediction of the start or end of the egg production season. A technique for on-farm ultrasound scanning is described and examples of ultrasonographic images of different ovarian structures, developing ova and eggs within the genital tract are presented. These data were obtained by scanning mature female breeding ostriches (n=8). In vivo scanning took place a day prior to slaughter, and immediately after slaughter the reproductive organs were scanned in vitro in a water bath. By comparing ultrasonographic images with post mortem ovarian morphology, it appeared that the following morphological structures can be identified using ultrasonography: ovarian follicles of different sizes (diameter (phi) 1-9 cm), atretic follicles, post-ovulatory follicles (POFs), ova at different stages of development and eggs within the genital tract. Of the number of follicles counted during post mortem investigation, 58% (95% confidence interval 0.41-0.79) had been detected during previous in vivo examination. In the second part of our study, ultrasonographic scans were made at weekly intervals in two farmed female ostriches (n=2) during the breeding season in order to determine the predictive value of the technique. By comparing the images of ovarian activity with individual egg production of these hens, preliminary evidence was obtained that scanning might be of value in predicting egg production, especially at the start and the end of the breeding season. It is concluded that transcutaneous ultrasound scanning in mature female breeding ostriches is an easy, noninvasive technique for the monitoring of ovarian (in)activity, for visualization of different functional ovarian structures, for following the development of individual ova and for visualization of an egg with calciferous shell within the oviduct, and that this technique will be a valuable tool in future research on reproductive physiology and pathology, and the development of more advanced reproductive technologies, such as artificial insemination.     

Endocrine regulations of reproductive seasonality, follicular development and incubation in Magang geese

This study investigated the regulatory mechanisms of seasonal breeding, developments of ovarian follicles and incubation in Magang geese, a short day breeding bird. Throughout the year, plasma PRL concentrations increased in non-breeding season in spring and summer (from April to early August), and remained low in the rest of the year, while LH concentrations peaked in August and September and remained low in non-breeding season (March to June). Lengthening photoperiod increased PRL and decreased LH secretions, which inhibited follicular development, terminated lay and induced moulting, while shortening photoperiod decreased PRL and increased LH secretion and reinitiated lay. Long photoperiod stimulated PRL secretion occurred with increased gene expressions of PRL in the pituitary gland and VIP in the hypothalamus, but inhibition of LH secretion was without decreases in gene expressions of LH beta subunit and GnRH. Under breeding conditions, terminating incubation decreased PRL but increased LH concentrations and resumed lay in 24 days following recruitment of about 10 large white follicles into hierarchical development. Plasma concentrations of progesterone and inhibin peaked at peak lay, whereas LH concentrations exhibited a bi-phasic pattern with troughs at peak lay and incubation when PRL concentrations were high. Ninety percent geese exhibited incubation behaviour after laying one clutch of approximately eight eggs in approximately 30 days. In conclusion the seasonal reproductive activities in Magang geese is directly inhibited by long photoperiod and directly stimulated by short photoperiod via PRL and LH secretions, whose interplays also cause occurrences of four to five lay and incubation cycles in the breeding season.     

Frequency of luteinizing hormone surges and egg production rate in turkey hens

Whether the interval between preovulatory surges of LH was different between lines of turkey hens with either poor (RBC3 line, peak at 55%) or excellent rate of egg production (Egg line, peak at 85%) was examined. Laying hens were cannulated and bled hourly for 10 days at peak of production. A constant light photoschedule was used to avoid diurnal masking of innate circadian rhythms. The mean interval between LH surges in the RBC3 line was longer than in the Egg line and had a higher coefficient of variation. A few longer LH surge intervals (72 h) were found in some RBC3 line hens (2 of 7 hens), but none were found in Egg line hens (0 of 11 hens). All progesterone (P4) surges were coupled with LH surges, but not all LH-P4 surges were coupled with ovipositions (blind LH-P(4) surges). The percentage of blind LH-P4 surges was not different between lines. The baseline concentration of LH was higher in Egg line than RBC3 line hens, but LH surge amplitude, and surge duration were not different. The baseline and surge amplitude concentrations of P4 were not different between lines, nor was the concentration of estradiol-17beta. The longer interval between LH surges was the major factor tested that was associated with the poorer egg production rate in RBC3 line hens in comparison to Egg line hens. A higher incidence of blind LH surges further contributed to lower egg production in RBC3 line turkey hens.     

Changes in plasma concentrations of luteinizing hormone,progesterone, and estradiol-17beta in peripubertal turkey hens under constant or diurnal lighting

Possible circadian fluctuations and long-term changes in concentrations of reproductive hormones in peripubertal female birds is poorly documented in comparison with mammalian species. Our objective was to document changes in concentrations of several reproductive hormones the several days before and after initial pubertal preovulatory surges of LH in turkey hens photostimulated with either constant (24L:0D) or diurnal (14L:10D) lighting. The hens were cannulated for hourly blood sampling, starting 10 days after photostimulation and continuing until all hens had laid at least two eggs. First eggs were oviposited between 16 and 24 days after photostimulation, and egg production ranged from two to nine eggs/hen during the experimental period. With both lighting treatments, concentrations of LH declined slightly, concentrations of progesterone (P(4)) increased, and concentrations of estradiol-17beta (E(2)) were constant the 3-4 days prior to initial LH surges with no circadian fluctuations in hormone concentrations. Most (10 of 13) initial preovulatory surges of LH were coupled with ovulations, and all LH surges were coupled with P(4) surges. Those LH and P(4) surges not coupled with ovulations (blind surges) occurred with both lighting treatments, but the incidence of blind surges was higher with diurnal lighting. The interval between LH and P(4) surges was longer between the first and second surges than between subsequent surges, when the interval was approximately 26 h. The duration of LH surges (7.4 +/- 3.0 h) was shorter than that of P(4) surges (10.0 +/- 2.0 h). We conclude that, in the peripubertal female turkey, 1) prior to puberty (first LH-P(4) surges), there are no circadian fluctuations in concentrations of LH, P(4), and E(2), 2) 3 days prior to initial LH surges, E(2) concentrations are stable, LH concentrations decline slightly, and P(4) concentrations increase, and 3) surges of LH are coupled to surges of P(4) but LH-P(4) surges are not always coupled to ovipositions (blind surges), possibly because of internal ovulations.     

Changes in gonadotrophin secretion and ovarian antral follicular activity in seasonally breeding sheep throughout the year

Overall, significantly more antral follicles greater than or equal to 1 mm diameter were present in Romney ewes during anoestrus than in the breeding season (anoestrus, 35 +/- 3 (mean +/- s.e.m.) follicles per ewe, 23 sheep; Day 9-10 of oestrous cycle, 24 +/- 1 follicles per ewe, 22 sheep; P less than 0.01), although the mean numbers of preovulatory-sized follicles (greater than or equal to 5 mm diam.) were similar (anoestrus, 1.3 +/- 0.2 per ewe; oestrous cycle, 1.0 +/- 0.1 per ewe). The ability of ovarian follicles to synthesize oestradiol did not differ between anoestrus and the breeding season as assessed from the levels of extant aromatase enzyme activity in granulosa cells and steroid concentrations in follicular fluid. Although the mean plasma concentration of LH did not differ between anoestrus and the luteal phase of the breeding season, the pattern of LH secretion differed markedly; on Day 9-10 of the oestrous cycle there were significantly more (P less than 0.001) high-amplitude LH peaks (i.e. greater than or equal to 1 ng/ml) in plasma and significantly fewer (P less than 0.001) low amplitude peaks (less than 1 ng/ml) than in anoestrous ewes. Moreover, the mean concentrations of FSH and prolactin were significantly lower during the luteal phase of the cycle than during anoestrus (FSH, P less than 0.05, prolactin, P less than 0.001). It is concluded that, in Romney ewes, the levels of antral follicular activity change throughout the year in synchrony with the circannual patterns of prolactin and day-length. Also, these data support the notion that anovulation during seasonal anoestrus is due to a reduced frequency of high-amplitude LH discharges from the pituitary gland.     

Stimulation of folliculogenesis in domestic cats with human FSH and LH

Folliculogenesis in response to exogenous stimulation by human urinary follicle stimulating hormone (huFSH) and human menopausal gonadotropin (hMG) was evaluated in the domestic queen (Felis catus). The role of LH and/or FSH in folliculogenesis was examined by measuring concentrations of estradiol 17beta (E(2)) and progesterone (P) in the serum. Additionally, changes in the number and size of follicles from before the administration of exogenous hormones to surgical oocyte collection were monitored. Findings indicated that in queens receiving huFSH or hMG followed by human chorionic gonadotropin (hCG) to induce ovulation, the numbers of follicles from 1 to 3 mm increase with statistical significance (P<0.005) from before the initiation of treatment to surgical collection of oocytes. Although E(2) concentrations in cats receiving hMG increased above baseline by the third exogenous hormone injection, mean E(2) concentrations did not increase in the groups that received both huFSH and hCG, or hCG only, until after the administration of hCG. This suggests that the exogenous administration of LH contained in both hMG and hCG was necessary for E(2) to rise to levels associated with estrus.     

Influence of ovaries and photoperiod on reproductive function in the mare.

A 16 h daily photoperiod hastened the onset of the ovulatory season (first ovulation); gonadotrophin and follicular changes prior to the onset were similar in intact light-treated and control mares. A preovulatory decline in FSH concentrations before the onset of the ovulatory season preceded the decrease in number of follicles (15--25 mm) and the rise in LH concentrations which was temporally associated with the growth of an ovulatory follicle. Seasonal changes of FSH and LH concentrations were found in ovariectomized mares and were influenced by photoperiod. During the anovulatory season, there was no ovarian influence on gonadotrophin concentrations. However, during the ovulatory season the ovaries exerted a positive influence on seasonally elevated LH concentrations during oestrus and a negative influence during dioestrus. The ovaries exerted a negative influence on seasonally elevated FSH concentrations throughout the oestrous cycle. The onset of the ovulatory season occurred at the time of the first sustained increase in LH concentrations resulting from positive seasonal (increasing photoperiod) and ovarian influences.     

Initiation of follicular maturation during mid-pregnancy by the administration of LH in the rat

Pregnant rats were injected twice daily for 1-3 days (Days 13-16 of pregnancy) with various doses of ovine LH. Follicular maturation was determined by the ability of the follicles to ovulate in response to 10 i.u. hCG as well as by endogenous production of oestradiol-17 beta and inhibin. In control animals, no ovulation was induced by hCG given on Day 16 of pregnancy. An injection of hCG on Day 16 of pregnancy, however, induced ovulation in LH-treated animals (6.25-50.0 micrograms LH per injection, s.c. at 12-h intervals from Days 13 to 16). Concentrations of oestradiol-17 beta and inhibin activity in ovarian venous plasma increased after the administration of LH, indicating that development of ovulatory follicles had been induced. Abolishing the decline in plasma LH values therefore induced maturation of a new set of follicles or prevented the atresia of large antral follicles usually seen at this time of pregnancy. Plasma and pituitary concentrations of FSH decreased in LH-treated animals compared with those in control animals. Concentrations of progesterone, testosterone and oestradiol-17 beta in the peripheral plasma were not significantly different between the two groups. These results suggest that the increase in inhibin secretion from the ovary containing maturing follicles after LH treatment may suppress the secretion of FSH from the pituitary gland. These findings indicate that (1) the development of ovulatory follicles can be induced by the administration of exogenous LH during mid-pregnancy in the rat and (2) basal concentrations of FSH are enough to initiate follicular maturation even in the presence of active corpora lutea of pregnancy, when appropriate amounts of plasma LH are present.     

Growth,antrum formation,and estradiol production of bovine preantral follicles cultured in a serum-free medium

The objective of this study was to identify factors that would allow the establishment of a serum-free culture system that could support follicular and oocyte growth, antrum formation, and estradiol-17beta (E(2)) production in preantral follicles of bovine ovaries. Large preantral follicles (145-170 micro m in diameter) were microsurgically dissected from ovaries, embedded in 0.15% type I collagen gels, and maintained in a serum-free medium for up to 13 days at 38.5 degrees C in 5% CO(2) in air. This culture environment allowed most preantral follicles to maintain a three-dimensional structure with the presence of a thecal layer and basement membrane surrounding the granulosa cells throughout the entire culture period. The effects of insulin, insulin-like growth factor (IGF)-I, IGF-II, FSH, and LH on preantral follicle growth were investigated in serum-free medium. Follicular diameters were significantly larger in the presence of insulin, IGF-I, IGF-II, or FSH after 13 days in culture. Oocyte diameters were also significantly larger in the presence of all hormones tested. The single addition of insulin, IGF-I, or FSH induced antrum formation between Days 7 and 13 of culture. Insulin progressively induced E(2) secretion by follicles after antrum formation, but IGF-I and FSH had no apparent effect. FSH and LH caused an increase in oocyte diameter in the presence of insulin. The addition of three hormones (insulin, FSH, and LH) initiated antrum formation and E(2) production earlier than insulin-containing medium alone. Furthermore, maximal E(2) secretion was maintained steadily between 7 and 13 days in this culture condition. From these results, we have demonstrated that insulin, FSH, and LH play substantial roles in the growth and development of bovine large preantral follicles in a serum-free medium.     

Decreased granulosa cell luteinizing hormone sensitivity and altered thecal estradiol concentration in the aged hen, Gallus domesticus

Few studies have examined the effect of age on the ovulation cycle of the hen. Our aim was to determine if changes in the ovary account for the decrease in egg production with age. Young hens (28-38 wk of age) laying at least 20 eggs per sequence and old hens (53-63 wk of age) laying 3-6 eggs per sequence were used. We determined luteinizing hormone (LH) sensitivity of the ovary of young and old hens by measuring LH stimulable adenylyl cyclase (AC) activity of the granulosa layer. We also measured theca- and granulosa-layer weights and steroid concentrations of these layers and of the serum in young and old hens. Mean basal AC activity (pg/min/mg protein) for the largest (F1) and second largest (F2) follicles from young and old hens did not differ. A significant dose-response relationship to LH was present in all groups, and AC responsiveness to increasing doses of LH was greater in the F1 and F2 follicles of young hens than in the same follicles of old hens. The F4 and F5 follicles of young hens had a significantly greater estradiol (E2) concentration (pg/mg theca protein) compared to old hens, while the E2 concentration in the F2 follicle was greater in old hens. The theca layer of the F1 follicle of old hens weighed significantly more than that of young hens, whereas the theca layer of the F3, F4 and F5 follicles from young hens weighed more than those of old hens.(ABSTRACT TRUNCATED AT 250 WORDS)     

Acute decrease in vitellogenin synthesis by deprivation of food and water in laying hens

Vitellogenin synthesis during a decrease in egg production caused by depriving food and water was investigated in Single Comb White Leghorn hens. They were transferred from long days of 14L: 10D to short days of 10L: 14D 5 days before food and water deprivation. Then food was deprived for 5 days and water for 2 days. The body weight was markedly decreased by the treatment and reached its minimum after 5 days. The egg production rate which was 85% before the treatment was nil after 4 days. On day 3 the circulating vitellogenin concentrations, measured by a newly established RIA system, was markedly decreased by deprivation of food and water to 22% of the pretreatment level. The concentrations remained less than 10% during cessation of egg laying. Serum luteinizing hormone (LH) and progesterone concentrations decreased gradually, but estradiol 17 beta (E2) decreased abruptly. This acute decrease closely coincided with the decrease in egg production and the weight of the oviduct and ovary. These concentrations were gradually increased after day 16 and returned to the normal level after 46 days. Circulating thyroxine (T4) and triiodothyronine (T3) concentrations gradually increased from the beginning of the change in the day length and peaked on day 7 or 9, whereas reverse (r)T3 rapidly increased. The concentrations again decreased at the beginning of molting which occurred later due to the deprivation of food and water. Thus, these results demonstrated for the first time that the decrease in egg production induced by deprivation of food and water closely related to the decrease in vitellogenin synthesis as well as gonadal and pituitary functions. Further, recovery of egg production was coupled with the increase in the ovary and oviduct weight, and circulating LH, E2, progesterone, and vitellogenin.     

Steroidogenic and maturation-inducing potency of native gonadotropic hormones in female chub mackerel, Scomber japonicus

ABSTRACT: BACKGROUND: The gonadotropins (GtHs), follicle-stimulating hormone (FSH) and luteinizing hormone (LH) are produced in the pituitary gland and regulates gametogenesis through production of gonadal steroids. However, respective roles of two GtHs in the teleosts are still incompletely characterized due to technical difficulties in the purification of native GtHs. METHODS: Native FSH and LH were purified from the pituitaries of adult chub mackerel, Scomber japonicus by anion-exchange chromatography and immunoblotting using specific antisera. The steroidogenic potency of the intact chub mackerel FSH (cmFSH) and LH (cmLH) were evaluated in mid- and late-vitellogenic stage follicles by measuring the level of gonadal steroids, estradiol-17beta (Epsilon2) and 17,20beta-dihydroxy-4-pregnen-3-one (17,20beta-P). In addition, we evaluated the maturation-inducing potency of the GtHs on same stage follicles. RESULTS: Both cmFSH and cmLH significantly stimulated E2 production in mid-vitellogenic stage follicles. In contrast, only LH significantly stimulated the production of 17,20beta-P in late-vitellogenic stage follicles. Similarly, cmLH induced final oocyte maturation (FOM) in late-vitellogenic stage follicles. CONCLUSIONS: Present results indicate that both FSH and LH may regulate vitellogenic processes, whereas only LH initiates FOM in chub mackerel.     

Relationship between the appearance of preantral follicles in the fetal ovary of Antarctic minke whales (Balaenoptera bonaerensis) and hormone concentrations in the fetal heart, umbilical cord and maternal blood

The present study aimed to determine the relationship among changes in the number of preantral follicles and concentrations of follicle-stimulating hormone (FSH), luteinizing hormone (LH), progesterone (P4), androstenedione (A) and estradiol-17beta (E2) in the fetal heart, umbilical cord and maternal blood. Primordial follicles had already appeared in a 20 cm fetus and primary follicles were observed in a 50 cm fetus. In a 70 cm fetus, the number of primordial and primary follicles increased rapidly and secondary follicles were present. The concentrations of LH and FSH did not change between 20 cm and 160 cm in fetal length. When the fetal length became > 70 cm, serum levels in the fetus, umbilical cord and mothers, and E2 levels in umbilical cord increased synchronously (p < 0.05). These results showed increases in the number of preantral follicles in the Antarctic minke whale fetal ovary along with fetal growth during the early gestation period. These findings suggest that the change in preantral follicles was associated with changes in the concentration of steroids in early gestation periods. The changes in steroid concentrations in the fetal and umbilical cord blood and the increased number of preantral follicles were coincident at around 70 cm in fetal length, whereas the growth and differentiation of primordial and primary follicles appeared to be independent of FSH and LH.     

Concentrations of steroids and expression of messenger RNA for steroidogenic enzymes and gonadotropin receptors in bovine ovarian follicles of first and second waves and changes in second wave follicles after pulsatile LH infusion

The objectives were to compare expression of mRNA for cytochrome P450 cholesterol side-chain cleavage (P450scc), cytochrome P450 17alpha-hydroxylase (P450c17), cytochrome P450 aromatase (P450arom), 3beta-hydroxysteroid dehydrogenase Delta(4), Delta(5) isomerase (3beta-HSD), FSH receptor (FSHr) and LH receptor (LHr) in bovine ovarian follicles of the first and second waves of the bovine oestrous cycle and to determine if LH infusion changes growth, steroidogenesis and gene expression in second wave follicles. Transrectal ultrasonography was used to examine follicular size changes during the oestrous cycle in non-lactating Holstein cows (n=31). Saline or purified bovine LH was infused intravenously into cows at emergence of follicular waves for 2 or 4 days using a computer-controlled syringe pump (n=5-6 per treatment). Treatments were: wave 1, saline (W1S); wave 2, saline (W2S) or LH (25 microg/h; W2LH). During infusion, blood samples were collected at 12min intervals for 8h via i.v. catheters for measurement of serum LH concentrations. Ovaries were removed from cows on days 2 or 4 after emergence of follicular waves. Follicles were frozen and stored at -80 degrees C. Follicular fluid (FF, 50 microl) was collected for determination of progesterone (P4), oestradiol-17beta (E2) and androstenedione (A4) concentrations. Frozen sections (14 microm) were used for in situ hybridization to measure expression of mRNA (% pixel intensity) for P450scc, P450c17, P450arom, 3beta-HSD, FSHr, and LHr. LH infusion resulted in a serum LH pattern (high frequency) similar to the early luteal phase. There were no significant differences in size of follicles among the three treatment groups. Follicular fluid concentrations of E2 and A4 in W2S were lower than those of W1S on day 2 of a follicular wave. LH infusion into cows during the midluteal phase increased follicular fluid E2 and A4 concentrations in second wave follicles on day 2 of a follicular wave (W2LH) compared to those of W2S. The increase in follicular fluid E2 on day 2 in wave 2 follicles after LH infusion occurred possibly through an increase in mRNA expression of P450c17 and 3beta-HSD. In conclusion, follicular fluid concentrations of E2 and A4 were lower in W2S than in W1S and E2 and A4 concentrations were restored by infusion of LH in W2LH with an increase in mRNA expression of P450c17 and 3beta-HSD.     

Effects of follicle-stimulating hormone with and without luteinizing hormone on serum hormone concentrations, follicle growth, and intrafollicular estradiol and aromatase activity in gonadotropin-releasing hormone-immunized heifers

To evaluate the roles of FSH and LH in follicular growth, GnRH-immunized anestrous heifers (n = 17) were randomly assigned (Day 0) to one of three groups (n = 5 or 6). Group 1 received i.m. injections of 1.5 mg porcine FSH (pFSH) 4 times/day for 2 days; group 2 received i.v. injections of 150 microg pLH 6 times/day for 6 days; group 3 received both pFSH and pLH as described for groups 1 and 2. After slaughter on Day 6, measurements were made of follicle number and size, and follicular fluid concentrations of progesterone (P(4)), estradiol (E(2)), and aromatase activity. Injection of pFSH increased (P: < 0.01) the serum concentrations of FSH between 12 and 54 h. Infusion of pLH increased (P: < 0.05) mean and basal concentrations of LH and LH pulse frequency. Serum E(2) concentrations were higher (P: < 0.05) for heifers given pFSH + pLH than those given either pFSH or pLH alone. There was no difference (P: > or = 0.24) between treatments in the number of small follicles (<5 mm). Heifers given pFSH or pFSH + pLH had more (P: < or = 0.02) medium follicles (5.0-9.5 mm) than those that were given pLH alone (none present). Heifers given pFSH + pLH had more (P: = 0.04) large follicles (> or =10 mm) than those given either pLH or pFSH alone (none present). Overall, only 1 of 35 small follicles and 2 of 96 medium follicles were E(2)-active (i.e., E(2):P(4) >1.0), whereas 18 of 21 large follicles (all in the pFSH + pLH treatment) were E(2)-active; of these, 8 of 18 had aromatase activity. Concentrations of E(2) and E(2) activity in follicular fluid were correlated (r > or = 0.57; P: < 0.0001) with aromatase activity in heifers given pLH + pFSH. In conclusion, pLH failed to stimulate follicle growth greater than 5 mm; pFSH stimulated growth of medium follicles that were E(2)-inactive at slaughter and failed to increase serum E(2) concentrations; whereas pFSH + pLH stimulated growth of medium follicles and E(2)-active large follicles, and a 10- to 14-fold increase in serum E(2) concentrations.     

Seasonal variation in oestrus, the secretion of oestrogen and progesterone and LH levels before ovulation in the ewe

Ewes with cervical ovarian autotransplants were studied after PGF-2alpha-induced luteal regression in November and February (mid- and late-breeding season) and June (anoestrum). Progesteron and oestradiol-17beta secretion rates and LH concentrations were determined in serial ovarian venous blood samples and the ewes were frequently tested for oestrus. All 4 ewes in November and 3 of the 4 ewes in February exhibited oestrus and endocrine changes indicative of ovulation. The remaining ewe in February and the three ewes in June failed to show elevated oestradiol-17beta secretion rates after luteal regression, indicating the absence of follicles in the final stages of maturation. The preovulatory rise in the oestradiol-17beta secretion rate, the LH surge and the display of oestrus all occurred earlier, with respect to the PGF-2alpha infusion, in November than in February, suggesting a greater stimulation of folliculogenesis, and therefore a greater availability of maturing follicles, in November than in February.     

Elevated peripheral concentrations of LH block ovulation and increase thecal and serum progesterone in the hamster

Insertion of osmotic minipumps containing 1 mg ovine LH on Day 1 (oestrus) elevated circulating serum concentrations of LH, progesterone and androstenedione when compared with values at pro-oestrus. Ovulation was blocked for at least 2 days at which time there were twice the normal numbers of preovulatory follicles. Follicular and thecal progesterone production in vitro was elevated when compared with that in pro-oestrous controls. Follicular and thecal androstenedione production in vitro was lower than in controls even though serum concentrations of androstenedione were elevated; the higher androstenedione values may be due to the increase in number of preovulatory follicles when compared with pro-oestrous controls. Follicles from LH-treated hamsters aromatized androstenedione to oestradiol and follicular production of oestradiol was similar to that in pro-oestrous follicles despite low follicular androstenedione production in the LH-treated group. Treatment with 20 i.u. hCG on Days 4 or 6 after insertion of an LH osmotic minipump on Day 1 induced ovulation of approximately 30 ova, indicating that the blockade of ovulation was not due to atresia of the preovulatory follicles. Serum progesterone concentrations on Days 2, 4 and 6 in LH-treated hamsters were greater than 17 nmol/l, suggesting that the blockade of ovulation might have been due to prevention of the LH surge by high serum progesterone concentrations.     

Age-related and seasonal variation in the Sertoli cell population, daily sperm production and serum concentrations of follicle-stimulating hormone, luteinizing hormone and testosterone in stallions

Testes and blood samples were obtained from 201 stallions aged 6 months to 20 years in either December-January (nonbreeding season) or June-July (breeding season) to study the effect of age and season on reproductive parameters. Seasonal differences in the Sertoli cell population of adult (4-20 years old) horses were characterized by a 36% larger number of Sertoli cells in the breeding season than in the nonbreeding season. Seasonal elevation in the Sertoli cell population was associated with an increase in testicular weight and daily sperm production per testis (DSP/testis). Concentrations of luteinizing hormone (LH) and testosterone in serum varied with season. Although follicle-stimulating hormone (FSH) concentrations also tended to be higher in the breeding season, this trend was not statistically significant (P less than 0.08). Sertoli cell numbers averaged over both seasons, like testicular weights, increased with age until 4-5 years of age, but were stabilized thereafter. This age-related difference was also associated with increased concentrations of FSH, LH and testosterone, and with increased DSP/testis. The Sertoli cell population was capable of increasing in the adult horse by fluctuating its size with season. The number of elongated spermatids per Sertoli cell over both seasons increased with age up to 4-5 years of age and was stabilized thereafter. Thus, seasonal and/or age-related differences in DSP/testis were associated with significant elevations in serum concentrations of FSH, LH and testosterone, testicular weights, numbers of elongated spermatids per Sertoli cell and elevation of the Sertoli cell population.     

Relationship between the preovulatory luteinizing hormone (LH) surge and androstenedione synthesis of preantral follicles in the cyclic hamster: detection by in vitro responses to LH

Preantral follicles of cyclic hamsters were isolated on proestrus, estrus and diestrus I, incubated for 3 h in 1 ml TC-199 containing 1 microgram ovine luteinizing hormone (LH) (NIH-S22), and the concentrations of progesterone (P), androstenedione (A) and estradiol (E2) determined by radioimmunoassay. At 0900-1000 h on proestrus (pre-LH surge) preantral follicles produced 2.4 +/- 0.3 ng A/follicle per 3 h, less than 100 pg E2/follicle and less than 250 pg P/follicle. At the peak of the LH surge (1500-1600 h) preantral follicles produced 1.8 +/- 0.2 ng P and 1.9 +/- 0.1 A and less than 100 pg E2/follicle. After the LH surge (1900-2000 h proestrus and 0900-1000 h estrus) preantral follicles were unable to produce A and E2 but produced 4.0 +/- 1.0 and 5.0 +/- 1.1 ng P/follicle, respectively. By 1500-1600 h estrus, the follicles produced 8.1 +/- 3.1 ng P/follicle but synthesized A (1.6 +/- 0.2 ng/follicle) and E2 (362 +/- 98 pg/follicle). On diestrus 1 (0900-1000 h), the large preantral-early antral follicles produced 1.9 +/- 0.3 ng A, 2.4 +/- 0.4 ng E2 and 0.7 +/- 0.2 ng P/follicle. Thus, there was a shift in steroidogenesis by preantral follicles from A to P coincident with the LH surge; then, a shift from P to A to E2 after the LH surge. The LH/follicle-stimulating hormone (FSH) surges were blocked by administration of 6.5 mg phenobarbital (PB)/100 g BW at 1300 h proestrus. On Day 1 of delay (0900-1000 h) these follicles produced large quantities of A (2.2 +/- 0.2 ng/follicle) and small amounts of E2 (273 +/- 27 pg/follicle) but not P (less than 250 pg/follicle).(ABSTRACT TRUNCATED AT 250 WORDS)