[Effects of the maturity of human oocytes on fertilization and embryonic development: application of oocyte maturation in medium containing follicle-stimulating hormone].

A total of 2,145 oocytes from 355 IVF cycles were classified as overmature (O), mature (M), transitional (T), immature (I) and abnormal (A) according to the morphology of the corona radiata. The rates of fertilization (%F) and embryonic development (%D) per oocyte were the highest in the M group, and decreased significantly with the decreasing maturity of the oocytes (T and I) and were the lowest in the A group. Decreases in %F and %D were also observed in the O group. %F and %D were significantly higher in oocytes with a polar body (PB) than without a PB. Mature oocytes classified according to the morphology of the corona radiata had significantly higher %F and %D than those classified according to the morphology of the cumulus oophorus. %F and %D were increased when T-oocytes without a PB and I-oocytes were matured in vitro for 18-24 hours in medium supplemented with FSH. A normal female baby was delivered, following IVF-ET of two T-oocytes matured in vitro with FSH.

Administration of human chorionic gonadotropin for in vitro fertilization-embryo transfer based on the serum luteinizing hormone (LH) concentration: the importance of synchronization with endogenous LH rises.

OBJECTIVE: To examine whether synchronized administration of hCG at the onset of the endogenous LH rise promotes successful IVF. DESIGN: A prospective randomized study. SETTING: In vitro fertilization program at a university hospital. PATIENTS: A total of 208 IVF cycles in 148 patients. INTERVENTIONS: Serum LH concentrations were measured daily and hMG was administered daily. Independent of follicle size and E2 concentration, hCG was administered as soon as the LH concentration exceeded the J level, defined as the minimum value + (the day 3 value-the minimum value) x 1/3(J group). Alternatively, hCG was administered when the serum LH concentration turned to increase but was still less than the J level, or 1 day after the serum LH concentration exceeded the J level (non-J group). RESULTS: The rates of total and ongoing pregnancy per cycle were significantly higher in the J group (35.6% and 26.0%, respectively, n = 104) than in the non-J group (21.2% and 12.5%, respectively, n = 104). Pregnancies in the J group were achieved over a wide range of dominant follicle diameters (13 to 25 mm), E2 levels (198 to 1,700 pg/mL; conversion factor to SI units, 3.671), and E2 level per follicle > or = 12 mm (24 to 225 pg/mL per follicle) recorded on the day of hCG administration. CONCLUSION: Synchronized administration of hCG in accordance with endogenous LH rises produces a high rate of pregnancy in IVF.

Hydatidiform mole with a surviving coexistent fetus following in-vitro fertilization.

A case of a hydatidiform mole with a surviving coexistent fetus following in-vitro fertilization and embryo transfer is reported. The diagnosis was established at 12 weeks gestation and pregnancy was maintained until 31 weeks, during which time transient hyperthyroidism and lung metastasis developed. No difference was observed in pronucleus formation and early embryonic development between the two embryos, which resulted in a complete mole and a normal fetus. DNA finger-print analysis, karyotype analysis and histopathological examination confirmed that the pregnancy was a twin of a complete mole and a normal conception. DNA fingerprint analysis was performed with a single-locus probe cocktail. All DNA bands from the tumour were of paternal origin, and the bands from the placenta were of paternal and maternal origin.

Prolactin inhibits ovulation by reducing ovarian plasmin generation.

The present study was undertaken to investigate the effects of prolactin (PRL) on gonadotropin-induced ovulation and the biosynthesis of prostaglandin (PG), leukotriene (LT), and plasmin in in vitro perfused rabbit ovaries. The addition of PRL to the perfusate inhibited hCG-induced ovulation in vitro in a dose-dependent manner. Although exposure to hCG significantly increased PGF2 alpha, PGE2, and LTB4 production by perfused rabbit ovaries, PRL did not affect the secretion rates of PGs and LTB4 stimulated by hCG administration. The ovarian plasmin generation was determined by measuring the amount of plasmin bound to its major inhibitor, alpha 2-plasmin inhibitor (alpha 2PI-Plm). Exposure to hCG enhanced biphasically the ovarian secretion rate of alpha 2 PI-Plm, while PRL at a dose of 10(3) ng/ml significantly inhibited the hCG-stimulated generation of alpha 2 PI-Plm in ovaries throughout the entire perfusion period. A significant correlation was observed between ovulatory efficiency and ovarian plasmin generation in the PRL-treated ovaries. Additionally, PRL inhibited intrafollicular concentrations of alpha 2 PI-Plm in hCG-treated ovaries in a dose-dependent manner. These observations substantiate an essential role for a plasma-generating system in the cascade of events leading to ovulation. In conclusion, PRL may act directly on the ovary and block ovulation, at least in part, via the inhibition of ovarian plasmin generation.

Effects of photoperiod and temperature on gonadal activity and plasma steroid levels in an autumn-spawning bitterling, Acheilognathus rhombea, during different phases of its annual reproductive cycle.

The kanehira bitterling, Acheilognathus rhombea, which breeds during autumn in the underyearlings and during summer and autumn in the yearlings, was exposed to various photoperiodic and temperature regimes during different phases of its annual reproductive cycle. In early autumn, gonadal development and increase in plasma levels of female estradiol-17 beta (E2) and male testosterone (T) of underyearling fish occurred under the short day length condition (12L12D). In early winter, gonadal regression (GSI reduction in both sexes, termination of vitellogenesis in females, and termination of spermatogonia proliferation in males) and decrease in plasma levels of E2 in females and T in males were induced by the low-temperature treatment (13 degrees), while gonadal maturity was maintained under the moderate temperature (20 degrees). The low temperature did not prevent oocyte maturation and ovulation in females and spermiogenesis and spermiation in males, indicating that temperature effect on gonadal activity is quite different among the maturational stages. The gonadal development of yearling fish did not progress during spring, even under the short day length condition combined with moderate temperature, which suggests that this species is in the refractory period during this season. In early summer, however, the autonomous gonadal maturation of yearling fish kept under moderate temperature progressed even under the long day length condition (15L9D). It is concluded that the causative factor in the initiation of the spawning period of the underyearling fish is the short day length in autumn, and that the causative factor in the termination of the spawning period is the low temperature in winter. An internal factor such as circannual rhythm in the yearlings is probably involved in the refractoriness to the photoperiod during spring and the subsequent earlier maturation during summer.

Circadian rhythms of melatonin secretion from superfused goldfish (Carassius auratus) pineal glands in vitro.

A flow-through, whole-organ culture (superfusion) system was developed, and goldfish pineal glands were maintained at 25 degrees under light-dark (LD) 12:12 cycles, reversed LD 12:12 cycles, continuous dark (DD), or continuous light (LL) conditions for 48 hr. Under LD 12:12 and reversed LD 12:12 cycles, superfused pineal glands showed a rhythmic melatonin secretion: Scotophase was associated with high titers and photophase with low titers. The melatonin secretion rhythms persisted for two cycles under DD conditions, whereas nocturnal rises were suppressed under LL conditions. After the transition from LL to DD conditions on the third day, melatonin showed a nocturnal increase. These results indicate that melatonin secretion from the superfused goldfish pineal gland is directly photosensitive and that the goldfish pineal gland harbors a circadian oscillator which generates melatonin secretion rhythms.

Steroid profiles during spawning in male common carp.

The profiles of testosterone (T) 11-ketotestosterone (11-KT), 17 alpha-hydroxy-4-pregnen-3-one (17-P), and 17 alpha,20 beta-dihydroxy-4-pregnen-3-one (17,20 beta-P) were determined in groups of spermiating male common carp (Cyprinus carpio) which were or were not mated with females and subjected to an increase in water temperature, a treatment which usually induces females to spawn. The steroid levels were correlated with changes in gonadotropin (GtH). All males mated with ovulatory females showed a GtH surge and spawned. Two distinct classes of these spawned males were differentiated based on their initial androgen levels and hormone profiles. Androgen levels were initially elevated in the "high" males. In these fish there was a very rapid shift in the steroidogenic pathway from androgen to progestogen production coincident with the GtH surge. In the "low" males, 17-P levels rose significantly in response to the GtH surge, but there was no steroidogenic shift. In the males mated with nonovulatory females, the levels of 17-P, 17,20 beta-P, T, and 11-KT all increased coincident with a small rise in GtH; there was no steroidogenic shift. In the unmated males, the steroid profiles were similar to those in the nonspawned fish, except that T and 11-KT levels were significantly lower in comparison. In all groups, 17-P rose higher than 17,20 beta-P, and 11-KT was generally the predominant androgen. A model is proposed which explains the steroidogenic shift in the "high" males. This involves the inhibition of androgen biosynthesis by 17,20 beta-P or by a related progestogen.

Differences in salmon GnRH and chicken GnRH-II contents in discrete brain areas of male and female rainbow trout according to age and stage of maturity.

We have developed sensitive and specific radioimmunoassays (RIA) for salmon gonadotropin-releasing hormone (sGnRH) and chicken GnRH-II (cGnRH-II). Synthetic sGnRH and cGnRH-II(2-10) were conjugated to bovine serum albumin and injected into rabbits to raise specific antisera. The antiserum against sGnRH showed cross-reactivities of 1.58 and 0.08% for cGnRH-II and lamprey GnRH, respectively. The antiserum against cGnRH-II showed cross-reactivities of 0.05 and 0.01% for sGnRH and lamprey GnRH, respectively. Both antisera were observed not to cross-react with mammalian GnRH and cGnRH-I or other peptide hormones. Synthetic sGnRH and cGnRH-II were iodinated using the chloramine-T method. The iodinated GnRH was purified by HPLC using a reverse-phase C18 column. The RIA system was developed as a double antibody method. Brain extracts of rainbow trout showed displacement curves which were parallel to the sGnRH and cGnRH-II standards in each RIA. HPLC analysis followed by RIA has revealed that rainbow trout brain contains two types of GnRH: sGnRH and cGnRH-II. Total sGnRH content in the brain was about three-fold higher than that of cGnRH-II. In the olfactory bulbs, telencephalon, optic tectum-thalamus, hypothalamus, and pituitary, sGnRH content (per region) was higher than cGnRH-II content, whereas cerebellum and medulla oblongata contained much more cGnRH-II than sGnRH. sGnRH content in the optic tectum-thalamus and pituitary was the highest in 1-year-old immature fish and 3-year-old mature fish, respectively. Medulla oblongata showed the highest cGnRH-II content in all groups. sGnRH concentrations (per milligram of protein) were high in the pituitary and intermediate in the olfactory bulbs, hypothalamus, and telencephalon. In all groups, the cGnRH-II concentration was high in the medulla oblongata, whereas the concentration in the olfactory bulbs and pituitary gland was below the detectable limit in most individuals.

Ecdysteroid fluctuations during embryogenesis in the giant freshwater prawn, Macrobrachium rosenbergii.

Ecdysteroid levels during the embryogenesis of the giant freshwater prawn, Macrobrachium rosenbergii, were determined by radioimmunoassay and high-performance liquid chromatography. Ecdysteroids consisting of significant amounts of 20-hydroxyecdysone and high-polarity products (HPP) and lesser amounts of ecdysone and low-polarity products (LPP) were detected in mature ovaries and newly laid eggs. All ecdysteroid groups decreased gradually during the nauplius phase. With the formation of the compound eye and the appearance of the carapace and other body-like structures, marking morphogenesis to the zoeal stage, embryos showed the beginning of a continuous and dramatic increase in ecdysteroid concentrations sustained until larval hatchout. Ecdysteroid levels at hatchout were above 20-fold greater than ecdysteroid levels in newly laid eggs. More specifically, HPP and 20-hydroxyecdysone increased concomitantly, with a decrease in 20-hydroxyecdysone only at the end of the embryogenic period, while ecdysone and LPP levels remained low or undetectable. It may be postulated that the presence of ecdysteroids in ovaries and eggs represents a reserve of maternal ecdysteroids which are necessary at the commencement of embryonic development; with the differentiation of embryonic tissue capable of ecdysteroid synthesis, ecdysteroids increase rapidly to play a role in later embryonic development.

The shift from C-19 to C-21 steroid synthesis in spawning male common carp, Cyprinus carpio, is regulated by the inhibition of androgen production by progestogens produced by spermatozoa.

There is a rapid shift in the steroidogenic pathway from androgen to progestogen production in spawning male common carp, Cyprinus carpio. Experiments were conducted to determine the mechanism regulating this shift using in vitro cultures of testicular fragments and isolated sperm of spermiating male carp. The levels of 11-ketotestosterone (11-KT) continually increased for 48 h with or without gonadotropin (GtH) stimulation, suggesting that 11-KT is the principal androgen produced by carp testes. Ovine prolactin (oPRL) enhanced GtH-stimulated 11-KT production, but by itself had no effect. Gonadotropin, carp pituitary extract, and pregnenolone all enhanced the production of 11-KT, testosterone (T), and 17 alpha-hydroxyprogesterone (17-P) in a dose-dependent manner. No 17 alpha,20 beta-dihydroxy-4-pregnen-3-one (17,20 beta-P) was detected in response to any of these agents; 17 alpha,20 alpha-dihydroxy-4-pregnen-3-one (17,20 alpha-P) was not measured. Both 17,20 beta-P and 17,20 alpha-P inhibited 11-KT production in a dose-dependent manner in the presence of either GtH, 17-P, or T. Isolated sperm and testicular fragment preparations both produced 17,20 beta-P and approximately tenfold more 17,20 alpha-P when incubated with 17-P. Only testicular fragments, however, produced 11-KT. We conclude that androgen synthesis occurs only within somatic cells of common carp testes. GtH, and perhaps PRL, stimulates the production of steroid precursors that, under normal physiological conditions, are metabolized to androgens.(ABSTRACT TRUNCATED AT 250 WORDS)

Development of sensitivity to maturation-inducing steroids and gonadotropins in the oocytes of the tobinumeri-dragonet, Repomucenus beniteguri, Callionymidae (Teleostei).

The effectiveness of steroids and gonadotropins (GtHs) in inducing final oocyte maturation was examined at different times of the day (0100, 0500, 0700, 0900, 1100, 1300, 1700, 2100 hr) in a daily spawning marine teleost, the tobinumeri-dragonet, Repomucenus beniteguri. The responsiveness of oocytes to GtHs and steroids was different at various times of day. The sensitivity of oocytes to hormones was apparent only during a certain period of the day (0100-0900 hr). Germinal vesicle breakdown (GVBD) could be induced by GtHs but not by steroids at 0100 hr. At 0500 hr, not only GtHs but also steroids at higher doses induced GVBD and ovulation. Oocytes underwent GVBD and ovulation at low doses of steroids at 0900 hr. GVBD and ovulation spontaneously occurred at 1100 and 1300 hr without any hormonal treatment. In addition, diameter and histological changes of ovarian oocytes were investigated. Ovarian oocytes were smaller than 420 microns, and only one oocyte group existed in distribution of oocyte frequency at 2100 and 0100 hr. With the increase in size of oocytes, two distinct groups appeared at 0500 hr. Larger oocytes completed GVBD at 1100 hr. Ovulation occurred between 1300 and 1700 hr and oviposition was completed between 1700 and 2100 hr daily. These results clearly show that the oocyte of the dragonet possesses a daily maturation rhythm. Responsiveness of oocytes to GtHs appeared earlier than responsiveness to steroids. This suggests that sensitivity to steroids is induced by GtH.

Effects of chronic LHRH-a + 17-methyltestosterone or LHRH-a + testosterone therapy on oocyte growth in the striped mullet (Mugil cephalus).

The striped mullet (Mugil cephalus) exhibits a restricted spawning season and matures only once per spawning cycle. In vivo monitoring of ovarian maturation of individual females during the season reveals that timing of full maturity varies. A small percentage of females that mature early can be induced to spawn and will remature. Such females can be spawned a second time within the same season. Chronic administration of luteinizing hormone-releasing analog (LHRH-a) + testosterone results in accelerated egg growth. The majority of females undergoing this therapy mature at least a month before control fish. When these females are induced to spawn, a higher percentage remature and can be spawned again. The double spawnings of both control and LHRH-a + testosterone-treated females occur without any appreciable loss in egg quality. Administration of LHRH-a + 17 alpha-methyltestosterone essentially inhibits egg growth. Steroid profiles from females undergoing this therapy exhibit a significant drop in circulating testosterone and estradiol 17 beta, compared to control and LHRH-a + testosterone-treated females. Hypotheses for the poor performance of this therapy are discussed.

Melatonin secretion from goldfish pineal gland in organ culture.

Pineal glands were removed from goldfish reared under 12L-12D at 25 degrees for 2 weeks. These were incubated for 6 days under (1) normal 12L-12D (lights on 0600-1800 hr), (2) reversed 12L-12D (lights on 1800-0600 hr), (3) continuous dark, or (4) continuous light condition at 25 degrees. The incubation medium was changed at 12-hr intervals (0600-1800 and 1800-0600 hr) and secreted melatonin (MLT) was measured by RIA. Under 12L-12D or reversed 12L-12D, MLT secretion was active in the dark phase and was suppressed in the light phase of a given photoperiod. Under a continuous dark condition, a large amount of MLT was secreted into the medium, although the amount gradually decreased. The MLT secretion was more active in the period corresponding to the dark phase of the acclimatory photoperiod than in the period corresponding to the light phase. This pattern in secretion remained for 4 days. Under a continuous light condition, MLT secretion was suppressed, but the secretion was rapidly increased after changing the photoperiod from the light to the dark condition. These findings clearly indicate that MLT secretion in the organ-cultured pineal gland is photosensitive. It is active under dark and inactive under light conditions. The existence of a circadian rhythm in MLT secretion is also suggested.

Effects of photoperiod and temperature on gonadal maturation, and plasma steroid and gonadotropin levels in a cyprinid fish, the honmoroko Gnathopogon caerulescens.

The honmoroko (Gnathopogon caerulescens), a small, spring-summer-breeding cyprinid fish, was exposed to various temperature and photoperiod regimes during different phases of its annual reproductive cycle. In autumn, a clear photoperiodism was seen, especially at warm temperatures (18-24 degrees). The gonadosomatic index, plasma gonadotropin (GtH), and gonadal steroids were higher in fish held at long photoperiod (15L/9D) than in those held at short photoperiod (12L/12D); the differences were greater as the temperature increased. In early spring, gonadal recrudescence progressed at temperatures above 7 degrees, regardless of photoperiod. Photoperiod did not affect plasma GtH and gonadal steroid levels at this time of the year. During its spawning season, a long photoperiod (15L/9D) was again required to maintain gonadal activity and high plasma GtH and gonadal steroid levels, especially at high temperature (25 degrees). In early summer, high temperatures (25 and 30 degrees) suppressed gonadal activity; however, gonadal steroid levels were not depressed, and plasma GtH levels actually increased. The data suggest that under natural conditions, high water temperatures in summer may act directly at the gonadal level, and is probably the factor which terminates the breeding season for this species. The results of these four experiments indicate that the honmoroko exhibits a photoperiodic response during the autumn month and its spawning season, and is dependent on the water temperature. The effects of photoperiod on gonadal maturation appear to be GtH mediated, whereas the suppressive effects of high temperature are not.

Induction of gonadotropin surge by steroid hormone implantation in ovariectomized and sexually regressed female goldfish.

Involvement of steroid hormones in the occurrence of the ovulatory gonadotropin (GtH) surge was studied in goldfish. Ovariectomized female goldfish were implanted with an empty Silastic capsule or a capsule containing testosterone or estradiol, and kept below 12 degrees for 3 months (Experiment 1). Some of the steroid implanted fish showed a GtH surge which was quite similar to the normal ovulatory GtH surge in response to a water temperature rise from 12 to 20 degrees, whereas no surge was observed in fish with empty capsules. When sexually regressed female goldfish were implanted with the capsules containing testosterone or estradiol and kept at 12 degrees for 6 weeks out of spawning season, the GtH surge was also observed in these fish after the water temperature rise to 20 degrees (Experiment 2). The GtH surge was observed in a larger number of testosterone-implanted fish than in the estradiol-treated fish in both experiments. These results strongly suggest that the high plasma level of testosterone observed before ovulation is an important physiological requisite for the occurrence of the ovulatory GtH surge in goldfish.

Involvement of steroid hormones in the preovulatory gonadotropin surge in female goldfish.

Goldfish,Carassius auratus, spawn several times within a spawning season. A gonadotropin (GtH) surge occurs at the time of ovulation in this cyprinid species. This ovulatory GtH surge mediates the processes of final oocyte maturation and ovulation, and occurs at the end of each spawning cycle. Within a cycle, there is a shift in the predominant plasma steroid from estradiol to testosterone, and finally 17α, 20ß-dihydroxy-4-pregnen-3-one at the time of the ovulatory GtH surge. High levels of testosterone were always observed before ovulation. When ovariectomized or sexually regressed female goldfish were implanted with testosterone, they exhibited a GtH surge which was similar to those normally observed at ovulation. These results strongly suggest that elevated plasma testosterone is an important physiological requirement for the occurrence of the GtH surge.

Development of sensitivity to maturation-inducing steroids in the oocytes of the daily spawning teleost, the kisu Sillago japonica.

The responsiveness of oocytes to 17 alpha,20 beta-dihydroxy-4-pregnen-3-one (17 alpha,20 beta-diOH-P), 17 alpha-hydroxyprogesterone (17 alpha-OH-P), and silver carp gonadotropin (GtH) was examined in vitro at seven different times of the day (0100, 0500, 0800, 1000, 1300, 1700, 2100 hr) in a daily spawning teleost, the kisu Sillago japonica. 17 alpha,20 beta-DiOH-P, 17 alpha-OH-P, and GtH were effective in inducing germinal vesicle breakdown (GVBD) and ovulation in kisu oocytes. However, the oocytes of the kisu responded to these hormones during a limited time of the day (2100-1000 hr), and their responsiveness to steroids and GtH was different with the sampling time. After a 20-hr incubation, the oocytes with yolk globules were classified into four stages based on their responses (GVBD) to GtH and steroids. Stage A, the oocytes did not respond to either GtH or steroids. These unresponsive oocytes were observed in all the ovaries examined. Stage B, GVBD could be induced by GtH but not by steroids. These oocytes were found in the ovaries collected from 2100 to 1000 hr. Stage C, GVBD could be induced by both GtH and steroids. These oocytes were found only between 0800 and 1000 hr. Stage D, oocytes spontaneously underwent GVBD without hormones. These oocytes were found between 1300 and 1700 hr. Ovulated oocytes were found in the ovaries collected during 1700-0500 hr. These results indicate that the kisu possesses a daily rhythm in oocyte development from stage A to stage D, and that the sensitivity to 17 alpha,20 beta-diOH-P appears at stage C.(ABSTRACT TRUNCATED AT 250 WORDS)

Daily cycles in plasma melatonin levels under long or short photoperiod in the common carp, Cyprinus carpio.

A radioimmunoassay (RIA) for plasma melatonin (MLT) was simplified for use with the common carp (Cyprinus carpio). Plasma was partially purified with Sep-Pak C18 cartridge before RIA. The inhibition curves for the Sep-Pak C18 fraction from the plasma of carp, goldfish (Carassius auratus), yellow tail (Seriola quinqueradiata), Japanese eel (Anguilla japonica), bora (Mugil cephalus cephalus), kisu (Sillago japonica), ishigarei (Kareius bicoloratus), and shimaisaki (Rhyncopelates oxyrhynchus) were parallel with the MLT standard curve. There was a highly significant correlation between MLT added to carp plasma and that which was recovered (r = 0.997, P less than 0.01). Intraassay coefficients of variation at low, medium, and high levels were 4.7, 5.2, and 6.4, respectively. Interassay coefficients of variation at low, medium, and high levels were 11.8, 8.2, and 24.1%, respectively. The lower limit of detection was 11 pg/tube. Plasma MLT levels were investigated every 2 hr in carp under 16L-8D and 8L-16D at 24 degrees. Under both photoperiods, MLT levels showed marked daily patterns, i.e., the levels were high (220-540 pg/ml) during the dark phase and low (23-104 pg/ml) during the light phase. Tricaine methanesulfonate markedly interfered with the MLT measurements, while ethylcarbamate did not show any significant influence. Sexual difference in plasma MLT levels in carp was not observed. These observations suggest that MLT is an important hormone in photoperiodism and/or a circadian rhythm in fish.

Hormone changes during the ovulatory cycle in goldfish.

Hormone profiles during the ovulatory cycle were studied in goldfish. Blood samples were taken from female goldfish every 4 days between 1400 and 1700 hr during the course of repeated ovulations for a duration of 3 months, and plasma hormone levels of 3 days before and after ovulation were compared. Plasma gonadotropin (GtH) levels did not show significant changes except a surge for ovulation, but tended to show higher levels before the surge than those after the surge. Plasma testosterone before ovulation showed significantly higher levels compared with those after ovulation. Plasma estradiol-17 beta (E2) levels remained low for 3 days prior to ovulation. Postovulation E2 levels that were significantly higher than the preovulation levels were kept elevated and declined on the third day after ovulation. These results indicate that E2 is mainly produced in the first part of the ovulatory cycle and testosterone in the latter part followed by the GtH surge and ovulation at the end of the cycle. This shift in steroid pattern from E2 to testosterone seems to be similar to those observed in salmonid fishes except for the time scale. The synchrony of ovulation in goldfish is also discussed in relation to physiological and external factors which influence the occurrence of ovulation.

Hormone changes during ovulation and effects of steroid hormones on plasma gonadotropin levels and ovulation in goldfish.

Plasma hormone changes during ovulation and the effects of steroid hormones on plasma gonadotropin (GtH) levels and ovulation were studied in the female goldfish. Ovulation was induced by raising water temperature from 12 to 20 degrees. Plasma gonadotropin levels exhibited a gradual rise during the latter half of the light phase. This was then followed by a surge in GtH, showing a peak at the time of ovulation in the dark phase. After ovulation, GtH levels decreased rapidly by the next light phase. Plasma 17 alpha,20 beta-dihydroxy-4-pregnen-3-one (17 alpha,20 beta-diOH-P) and testosterone showed a peak before ovulation, and then decreased by the time of ovulation. Estradiol-17 beta (E2) showed moderate levels during the GtH surge. No marked decrease of E2 levels was observed before the commencement of the GtH surge. Administration of testosterone or E2 prior to elevating the water temperature did not inhibit the occurrence of the GtH surge and ovulation. Likewise, administration of neither 17 alpha-hydroxyprogesterone nor 17 alpha,20 beta-diOH-P affected plasma GtH levels at 20 degrees. The present study shows a clear picture of the hormone changes that occur during spontaneous ovulation in goldfish. The results of administering steroids prior to ovulation does not support the hypothesis that a decline in E2 levels triggers the GtH surge and ovulation.