Ovulation induction by antiestrogens in an Indian tropical vespertillionid bat, Scotophilus heathi

The ovulation induction property of ICI 182,780 a pure antiestrogen and enclomiphene citrate (ENC) was carried out in Scotophilus heathi, an Indian tropical vespertillionid bat, during December to February i.e., preovulatory period. This bat ovulates two ova naturally and shows ovulatory asynchrony. The study showed that 100 ìg of ENC followed by 10 IU hCG resulted in significantly lower number of ovulation. Whereas, the pure antiestrogen ICI 182,780 at a dose of 100 ìg followed by 10 IU hCG resulted in ovulation induction (4.2 +/- 0.4), which is significantly different in comparison to other groups. This is possibly the first report of ovulation induction using this pure antiestrogen i.e., ICI 182,780 in any bat as well as in any animal model that exhibits temporary anovulation similar to polycystic ovary disease (PCOD). This antiestrogen may be useful to induce ovulation in PCOD patients.     

Reversal of indomethacin blockade of ovulation in gilts by prostaglandins

Prepubertal gilts given 750 IU pregnant mares′ serum gonadotropin (PMSG) followed 72 h later by 500 IU human chorionic gonadotropin (hCG) to induce follicular growth and ovulation fail to ovulate when 10 mg/kg indomethacin (INDO) is injected 24 h after hCG administration. This study examines the effects of administration of exogenous prostaglandins F_2α and E₂ (PGF_2α and PGE₂) alone or in combination, and at various times prior to the expected time of ovulation, on the INDO blockade of ovulation in PMSG/hCG-treated gilts. Occurrence of ovulation was determined by visual observation at laparotomy 48 h after hCG. When 5 mg or 10 mg PGF_2α was injected at each of 38, 40 and 42 h after hCG injection, 63% and 79%, respectively, of preovulatory follicles ovulated. In contrast, injection of 5 mg PGE₂ or 5 mg PGE₂ plus 5 mg PGF_2α induced ovulation in 0% and 24% of preovulatory follicles, respectively. In control groups, 100% of folicles in PMSG/hCG-treated gilts ovulated whereas none did so in PMSG/hCG/INDO-treated animals. These results indicate that administration of PGF_2α can induce ovulation in the PMSG/hCG/INDO-treated prepubertal gilt and suggest that PGE₂ is ineffective and may be antagonistic to PGF_2α in overcoming the ovulation blocking effect of INDO.     

Optimisation of an oviposition protocol employing human chorionic and pregnant mare serum gonadotropins in the Barred Frog Mixophyes fasciolatus (Myobatrachidae)

ABSTRACT: BACKGROUND: Protocols for the hormonal induction of ovulation and oviposition are essential tools for managing threatened amphibians with assisted reproduction, but responses vary greatly between species and even broad taxon groups. Consequently, it is necessary to assess effectiveness of such protocols in representative species when new taxa become targets for induction. The threatened genus Mixophyes (family Myobatrachidae) has amongst the highest proportion of endangered species of all the Australian amphibians. This study developed and optimised the induction of oviposition in a non-threatened member of this taxon, the great barred frog (Mixophyes fasciolatus). METHODS: Gravid female M. fasciolatus were induced to oviposit on one or more occasions by administration of human chorionic gonadotropin (hCG) with or without priming with pregnant mare serum gonadotropin (PMSG). Treatments involved variations in hormone doses and combinations (administered via injection into the dorsal lymph sacs), and timing of administration. Pituitary homogenates from an unrelated bufonid species (Rhinella marina) were also examined with hCG. RESULTS: When injected alone, hCG (900 to 1400 IU) induced oviposition. However, priming with two time dependent doses of PMSG (50 IU, 25 IU) increased responses, with lower doses of hCG (200 IU). Priming increased response rates in females from around 30% (hCG alone) to more than 50% (p = 0.035), and up to 67%. Increasing the interval between the first PMSG dose and first hCG dose from 3 to 6 days also produced significant improvement (p<0.001). Heterologous pituitary extracts administered with hCG were no more effective than hCG alone (p = 0.628). CONCLUSIONS: This study found that M. fasciolatus is amongst the few amphibian species (including Xenopus (Silurana) and some bufonids) that respond well to the induction of ovulation utilising mammalian gonadotropins (hCG). The optimal protocol for M. fasciolatus involved two priming doses of PMSG (50 IU and 25 IU) administered at 6 and 4 days respectively, prior to two doses of hCG (100 IU), 24 hours apart. This study is also the first to demonstrate in an amphibian species that responds to mammalian gonadotropins that an increase in the ovulation rate occurs after priming with a gonadotropin (PMSG) with FSH activity.     

Optimal dose of human chorionic gonadotropin for inducing ovulation in the ferret

The optimal dose of human chorionic gonadotropin (hCG) for induction of ovulation was determined by comparing the ovulatory response of 119 mated ferrets (controls) with that of estrous females induced to ovulate with five different dosages of hCG. Copulation induced formation of 12.7 ± 4.5 corpora lutea (CL) in all 119 females and resulted in a 90.7% conception rate as evidenced by finding approximately eight blastocysts/female in the uteri of 108 ferrets. All doses of hCG tested induced ovulation; however, the lower doses (50 and 75 IU) resulted in a lesser percentage of females ovulating. The highest doses of hCG (150 and 300 IU) resulted in fewer CL/female being formed. The optimal dose of hCG for simulating copulation induced ovulation was 100 IU. Tubal transport of unfertilized oocytes in pseudopregnant females was found to be significantly retarded when compared to the rate of transport of embryos in the control group.     

Control of ovulation with a GnRH analog in gilts and sows

Methods for the control of ovulation with GnRH or the GnRH analog D-Phe6 -LHRH (GnRH-A), were evaluated in gilts and sows as the last step in development of a fixed-time Al protocol. This involved 3 field trials using 2,744 gilts (10 units) and 71,628 sows (33 units). In Trial 1, the GnRH-A (75 microg) was given subsequent to treatment with altrenogest for cycle control or eCG for the stimulation of uniform follicle development in gilts. The release of LH was followed by ovulations which commenced within 36.4 +/- 3.3 hr and were terminated at 39.0 +/- 2.8 hr after administration of GnRH-A. This degree of synchronization of ovulations enabled the use of fixed-time AI. Consequently, subsequent to pretreatment with altrenogest and eCG, in 10 production units 1,285 gilts received 50 microg GnRH-A and 1,459 gilts 500 IU hCG serving as positive controls (Trial 2); all the gilts were inseminated 24 and 42 hr after treatment. Pregnancy rate and piglet index (n of piglets per 100 first inseminations) following GnRH-A vs hCG were 78.8% and 779 vs 74.4% and 728, respectively (P < 0.05). In field trials with first litter gilts and multiparous sows (33 units holding from 250 to 6,000 sows), 1,000 IU eCG was used for estrus control after weaning and 25 microg or 50 microg GnRH-A were given 55 to 58 hours after eCG (n = 19,954 and 20,701) (Trial 3). Sows treated during the same time period with 300 microg GnRH plus 300 IU. hCG (n = 30,973) served as positive controls; all sows were inseminated 24 and 42 hours after treatment. Pregnancy rates for 50 microg GnRH-A, 25 microg GnRH-A and 300 microg GnRH plus 300 IU hCG were 83.0%, 81.7% and 80.7%, and the piglet indices 913, 899 and 880, respectively (P < 0.05). Unit size and parity had significant effects on fertility and productivity. In all studies, results with 50 microg GnRH-A were superior. In year-long studies, highest levels of fertility in response to these treatments were seen from December to May.     

The effects of a low dose of cabergoline on induction of estrus and pregnancy rates in anestrous bitches

This is the first report of successful induction of normal estrus and ovulation in breeder bitches with as a low dose as 0.6 microg/kg/day of cabergoline formulation marketed for use in women. Sixty-one pure breed bitches from various breeds were used in the study at their already determined periods of anestrus. Twenty-four dogs formed the control group, while 37 bitches were administered with two different doses of cabergoline (recommended dose group, n=10, 5 microg/kg/day and low dose group, n=27, 0.6 microg/kg/day). Induced estrus rates and mean treatment and proestrus durations of dogs in these two dose groups were compared. At the second phase of the study, the effects of 500 IU human chorionic gonadotropin (hCG) administered on days 1 and 3 of estrus induced by the low dose of cabergoline, on the duration of behavioral estrus, ovulation rates, pregnancy rates and the number of offspring were investigated. For this purpose, the dogs with signs of proestrus (22/27) following the treatment in the low dose group were assigned into two subgroups. Five hundred IU of hCG (Pregnyl, Organon, Turkey) was intramuscularly administered to eight of these dogs [low dose (hCG+) group] on days 1 and 3 of estrus. The remaining 14 dogs were not treated with hCG [low dose (hCG-) group]. An aqueous solution of cabergoline (Dostinex, Pharmacia, Italy) was orally administered until 2 day after the onset of proestrus or for a maximum of 42 days. Blood samples were taken daily from all treatment and 11 control bitches during the first five days of behavioral estrus to measure progesterone concentrations. In the recommended dose and low dose groups, estrus was induced between days 8-45 and 4-48 (mean: 23.63+/-14.33 and 24.41+/-14.31 days), in the ratio of 80.0 and 81.5%, respectively (p>0.05). In both dose groups, post-treatment interestrous intervals were significantly shorter than both those of the control group and their own pre-treatment interestrous intervals (p<0.05). Ovulation rates, pregnancy rates and mean number of offspring delivered by the dogs in the recommended dose, low dose (hCG-), low dose (hCG+) and control groups were found to be similar (p>0.05). However, the mean duration of behavioral estrus of the dogs in the low dose (hCG+) group was found to be significantly longer compared to dogs in all other groups (p<0.05). In both dose groups, no correlation could be found between the anestrus stages and treatment durations (p>0.05). Shortly, it has been concluded from the study that (1) normal and fertile estrus can be induced more economically in bitches during different stages of anestrus using as a low dose of 0.6 microg/kg of cabergoline formulation marketed for use in women, and that (2) hCG injections on days 1 and 3 of the estrus induced by this method has no positive effects on the ovulation rates, pregnancy rates and the number of offspring per pregnancy.     

Induction of estrus in pubertal miniature gilts

Genetic engineering of miniature pigs has facilitated the development of numerous biomedical applications, such as xenotransplantation and animal models for human diseases. Manipulation of the estrus is one of the essential techniques for the generation of transgenic offspring. The purpose of the present study was to establish a useful method for induction of the estrus in miniature gilts. A total of 38 pubertal miniature gilts derived from 4 different strains were treated with exogenous gonadotropins. Estrus and ovulatory response were examined after treatment with pregnant mare serum gonadotropin (PMSG) and human chorionic gonadotropin (hCG) as 200 IU PMSG and 100 IU hCG, 300 IU PMSG and 150 IU hCG, or 1,500 IU PMSG only, followed by 100, 150 or 750 IU hCG 72 h later, respectively. The optimal protocol was determined to be the combination treatment of 200 IU PMSG and 100 IU hCG followed by 100 IU hCG. The administration of 200 IU PMSG and 100 IU hCG was effective in inducing estrus regardless of the strain, although there was a strain difference in the ovulatory response. These results indicate that treatment with a low-dose combination of PMSG and hCG provides one of the simplest methods for induction of estrus and ovulation in pubertal miniature pigs.     

Effect of the stage of pregnancy and post-partum on the number of gonadotrophin responsive follicles in ewes

The present study was designed to study follicular growth and its interactions with the corpus luteum of pregnancy in sheep during early, middle and late pregnancy and during postpartum anestrus. Ewes with 1 or 2 corpora lutea in one ovary were selected from a larger group of Serres ewes. All pregnant ewes were randomly allocated to two groups, with 10 to 12 ewes per group. Ewes of Group I were treated with 750 IU hCG at Day 25 or 45 or 70 or 100 or 125 of pregnancy. In Group II, ewes were treated with a combination of 1000 IU PMSG + 750 IU hCG either at Day 25 or 45 or 70 or 100 of pregnancy. The results demonstrated the presence of gonadotrophin-responsive follicles during early pregnancy (Days 25 to 45), reduction of their number during mid-pregnancy (Days 70 to 100), and their disappearance during late pregnancy (Day 125). Administration of hCG to Serres ewes at 10 and 20 days postpartum induced ovulation of a high proportion of ewes at 10 days postpartum (62%) with a further increase observed at 20 days postpartum (75%). During pregnancy, as well as during the postpartum period, there was no significant difference in the number of ovulations induced according to the location of the corpus luteum of pregnancy. These data demonstrate that the presence of the corpus luteum of pregnancy does not affect the number of gonadotrophin-responsive follicles until Day 100 of pregnancy. However, during late pregnancy such follicles were no longer present in the ovaries. Gonadotrophin-responsive follicles were again present as soon as Day 10 postpartum.     

Use of buserelin to induce ovulation in the cyclic mare

Inducing ovulation in a cyclic mare is often necessary. For this purpose, hCG has been used commonly, but the response can be reduced after successive administrations. The aims of this study were to test the effectiveness of buserelin in hastening ovulation in estrus mares, and its influence on fertility; and to investigate the effect of treatment on LH secretion. Five crossover trials were designed to compare the effect of two treatments: buserelin (40 microg in 4 doses i.v. at 12 h intervals) vs placebo (Experiments 1 and 2); buserelin 40 microg (in 4 doses i.v.) vs 20 microg (Experiment 3); buserelin (4 doses of 20 microg i.v.) vs hCG (1 dose of 2,500 IU i.v.) (Experiment 4); or buserelin (3 doses of 13.3 microg at 6 h interval) vs hCG (Experiment 5). In Experiment 2, blood samples were taken hourly until ovulation, for LH measurements. In Experiment 1, buserelin treatment significantly hastened ovulation. Reduction of the dose by half (Experiment 3) did not alter the effectiveness. In Experiments 4 and 5, buserelin was as effective as hCG in inducing ovulation between 24 and 48 h after initiation of treatment. Buserelin treatment induced a rise in LH concentration during the 48 h period of the experiment, and LH concentrations before ovulation were significantly higher in buserelin treated cycles than in placebo cycles. These experiments demonstrated the usefulness of two new protocols of administration of buserelin, as an alternative to hCG for induction of ovulation. One hypothesis explaining the mechanism of action is that the persistant rise in LH concentration could modify the ratio of biological/immunological LH, as it occurs physiologically, thereby hastening ovulation.     

Premature elevation of progesterone shortens duration of ovulation in PMSG/hCG-treated prepuberal gilts

A surge of LH during the follicular phase triggers multiple pathways, including progesterone and prostaglandin synthesis before culminating in ovulation. Progesterone has been shown to be involved in the ovulatory process in many species. In prepuberal gilts treated with PMSG/hCG the follicular progesterone level has been shown to increase sharply before ovulation. This study was conducted to investigate whether premature elevation of progesterone can accelerate the ovulatory process in Large White PMSG/hCG-treated prepuberal gilts. Fifty-four Large White gilts were treated with 1000 IU, i.m. PMSG to stimulate follicular growth, followed 72 h later by 500 IU, i.m. hCG to induce ovulation. Gilts in the treatment group (n = 27) were given progesterone intermuscularly at 24 and 36 h after hCG. Ovaries were exteriorized to observe ovulation points during laparotomy under general anesthesia at 38 to 50 h after hCG. Ovulation in both groups commenced by 40.05 h after hCG and was completed by 47.71 h in the control group and by 42.87 h after hCG in the treated group. Progesterone shortened (P < 0.01) ovulation time by 4.84 h and the time required (P < 0.01) for the median proportion of follicles to ovulate (40.7 vs 43.5 h after hCG). Progesterone also increased (P < 0.01) the plasma progesterone concentration without altering follicular progesterone concentration.     

Inhibition of hCG-induced spawning by alpha-methylparatyrosine, a tyrosine hydroxylase inhibitor, in the catfish Heteropneustes fossilis (Bloch)

In this study, the effect of pharmacological inhibition of catecholaminergic activity on hCG-induced spawning was evaluated and correlated with tyrosine hydroxylase (TH) activity, the rate-limiting enzyme in catecholamine biosynthesis. Gravid female H. fossilis collected in both prespawning and spawning phases were given alpha-methylparatyrosine (alpha-MPT: 250 microg/g body weight, ip, an irreversible inhibitor of TH) and human chorionic gonadotropin (hCG: 100 IU/fish, ip) alone or in combination. The fish were sampled at different intervals for measuring hypothalamic and ovarian TH activity and checking spawning response. The administration of hCG resulted in ovulation and spawning in both phases with a higher response in the spawning phase. The administration of alpha-MPT did not induce any response, like the control fish. In the hCG + alpha-MPT groups, the spawning response of hCG was significantly inhibited and delayed by the inhibitor. The spawning response of hCG was accompanied by a significant increase in both hypothalamic and ovarian TH activity at 6 and 12 h of the injection. However, at 24hr the activity decreased except in the spawning phase. The alpha-MPT treatment inhibited TH activity significantly in a duration-dependent manner. In the hCG + alpha-MPT groups, enzyme activity was inhibited at all duration. The results indicate the involvement of catecholamines during the hCG-induced spawning and the specific functional nature of the involvement needs further investigation.     

Cytogenetic analysis of Day-4 embryos from PMSG/hCG-treated prepuberal gilts

Prepuberal gilts were treated with pregnant mare serum gonadotropin (PMSG) to study the effects of its dosage on ovulation rate, fertilization rate after artificial insemination, embryo viability, and rate of development and incidence of chromosome abnormalities in Day-4 embryos. Gilts received 750 IU, 1250 IU or 1500 IU of PMSG, followed 72 h later by 500 IU human chorionic gonadotropin (hCG). Gilts were inseminated 28 to 30 h following the hCG injection, and resulting embryos were collected on Day 4 post ovulation. Ovulation rate was higher in the 1250 IU group than in the 1500 IU group or the 750 IU group. The 1500 IU dose caused excessive stimulation of the ovary, resulting in the occurrence of large (>10mm diameter) unovulated follicles, reduced fertilization rate and low embryo recovery rate. There was no difference in the incidence of chromosome abnormalities among the three groups, although the 1500 IU group had higher embryonic mortality than the two lower dose groups. A dose of 1250 IU PMSG increased ovulation rate above that achieved by 750 IU and, therefore, increased the number of oocytes or embryos available for transfer or for other studies, without sacrificing embryo viability or increasing the incidence of chromosome abnormalities.     

Effect of periovulatory prostaglandin F2alpha on pregnancy rates and luteal function in the mare.

The objective of this study was to determine whether periovulatory treatments with PGF2alpha affects the development of the CL, and whether the treatment was detrimental to the establishment of pregnancy. Reproductively sound mares were assigned randomly to one of the following treatment groups during consecutive estrus cycles: 1. 3,000 IU hCG within 24 hours before artificial insemination and 500 microg cloprostenol (PGF2alpha analogue) on Days 0, 1, and 2 after ovulation (n=8), 2. 2 mL sterile water injection within 24 hours before artificial insemination and 500 microg cloprostenol on Days 0, 1, and 2 after ovulation (n=8); 3. 3,000 IU hCG within 24 hours before artificial insemination and 500 microg cloprostenol on Day 2 after ovulation (n=8); or 4. 3,000 IU hCG within 24 hours before artificial insemination and 2 mL of sterile water on Days 0, 1, and 2 after ovulation (controls; n=8). Blood samples were collected from the jugular vein on Days 0, 1, 2, 5, 8, 11, and 14 after ovulation. Plasma progesterone concentrations were determined by the use of a solid phase 125I radioimmunoassay. All mares were examined for pregnancy by the use of transrectal ultrasonography at 14 days after ovulation. Mares in Group 1 and 2 had lower plasma progesterone concentrations at Day 2 and 5, compared to mares in the control group (P < 0.001). No difference was detected between group 1 and 2. Plasma progesterone concentrations in group 3 were similar to the control group until the day of treatment, but decreased after treatment and were significantly lower than the control group at Day 5 (P < 0.001). Plasma progesterone concentrations increased in all treatment groups after Day 5, and were comparable among all groups at Day 14 after ovulation. Cloprostenol treatment had a significant effect on pregnancy rates (P < 0.01). The pregnancy rate was 12.5% in Group 1, 25% in Group 2, 38% in Group 3, and 62.5% in Group 4. It was concluded that periovulatory treatment with PGF2alpha has a detrimental effect on early luteal function and pregnancy.     

孕马血清促性腺激素和氯地酚对猕猴超数排卵效果的观察

用孕马血清促性腺激素,总剂量为1550—2000单位,分4—7天处理猕猴,可促使其每侧卵巢出现滤泡超数发育,随后静脉注射入绒毛膜促性腺激素2500单位,在24小时内,猕猴即可出现超数排卵。     

Efficacy of exogenous gonadotrophic hormones to induce estrus in anestrous gilts

The objective of this study was to examine the response of anestrous gilts to injections of pregnant mare's serum gonadotrophin (PMSG) alone or in combination with human chorionic gonadotrophin (hCG). One hundred and eighty gilts which had failed to exhibit estrus by about 33 wk of age were given one of the following treatments: no injection, 500 IU PMSG, 1000 IU PMSG or 400 IU PMSG + 200 IU hCG. A greater number of gilts injected with 1000 IU PMSG exhibited estrus within nine days of treatment than control gilts (21/37 vs 13/41, X(2) = 5.0, P<0.05). In addition, gilts injected with 1000 IU PMSG exhibited oestrus significantly earlier than gilts receiving the other treatments. In comparisons of the proportion of gilts ovulating within 9 d of treatment and the treatment-to-ovulation interval, there were no significant differences between the three exogenous hormone treatments. There was also no significant effect of treatment on farrowing rate or subsequent litter size. The results of our study indicate that treatment of anestrous gilts with 1000 IU PMSG effectively induces ovulation and fertile estrus. Inadequate expression of estrus often accompanied the ovulation induced by the lower dosages of PMSG used with and without hCG in this experiment.     

Effect of histamine and histamine blockers on the ovulatory process in the vitro perfused rabbit ovary

An increase in the content of histamine in the ovary following luteinizing hormone (LH) release and the inhibition of ovulation in the rabbit by antihistamines suggest that histamine may be involved in the ovulatory process. The effects of various doses of histamine and antihistamines on ovulation were investigated using the in vitro perfused rabbit ovary system. Histamine (100 ng/ml) added to the perfusate at hourly intervals induced ovulation, although at a rate below that observed following human chorionic gonadotropin (hCG) administration. Cimetidine (10 micrograms/ml), an H2 blocker, inhibited histamine-induced ovulation, while the H1 blocker, chlorpheniramine (66.7 micrograms/ml), failed to do so. Neither cimetidine nor chlorpheniramine was able to block ovulation following hCG (50 IU). In all experimental groups in which histamine was used to induce ovulation, both extruded ova and follicular oocytes remained in an immature stage and displayed little evidence of degeneration. In contrast, a high percentage of ova exposed to hCG were mature. Ovarian edema was increased in ovaries in which ovulation occurred, regardless of treatment. A linear correlation was noted between ovulatory efficiency and degree of ovarian edema. Histamine may be an intermediary in the mechanism of follicular rupture, but does not support ovum maturation. However, the inability of H1 and H2 antagonists to block hCG-induced ovulation raises questions regarding the role of histamine in the physiologic process of ovulation.     

Optimum dose of LH-RH analogue Fertirelin Acetate for the induction of superovulation in mice.

The optimum dose for establishing superovulation in mice of Fertirelin Acetate (FA), an LH-RH analogue, was examined. Mice were subcutaneously injected with 5 IU of hCG at 17:00 (Day 0), and with various doses of FA (0.001 to 1.0 microg) five times at 4 h intervals on and after 22:00 on Day 0. To induce ovulation, 5 IU of hCG was again injected subcutaneously at 17:00 on Day 2. In the groups administered with doses ranging from 0.01 to 0.5 microg of FA, the number of ovulated eggs was significantly (p<0.05) larger than in the control group (12.9 +/- 5.9). The greatest number of ovulated eggs (22.6 +/- 7.3) was obtained in the group administered with 0.025 microg of FA. The results indicate that the effective dose of LH-RH analogue, FA, is between 0.1 and 0.5 microg for superovulation induction in mice.     

Effect of superovulation induction on embryonic development on day 5 and subsequent development and survival after nonsurgical embryo transfer in pigs

To evaluate the effects of eCG dosage on recovery and quality of Day 5 embryos and on subsequent development and survival after embryo transfer, batches of 5 to 10 donor sows were treated with 1000 or 1500 IU eCG. Recipients from the same batch were synchronously treated with 800 IU eCG. Ovulation was induced with 750 IU hCG (72 h after eCG) in donors and recipients. Donors were inseminated and embryos were collected at 162 h after hCG (120 h after ovulation). Ovulation rate was lower using 1000 IU eCG (28.5+/-11.7; n=48) than 1500 IU eCG (45.7+/-20.3; n=32; P<0.0001). Embryo recovery rate (82.9+/-16.9%) and percentage expanded blastocysts (56.2+/-31.4%) were similar (P>0.05). Expanded blastocysts from each group of sows were pooled into 2 groups within eCG treatment, containing embryos from normally ovulating sows (< or = 25 corpora lutea [CL]) or from superovulated sows (> 25 CL). Average diameter and number of cells of a random sample of the expanded blastocysts per pool were recorded. The average diameter of blastocysts (160.5+/-11.5 microm) was not affected by eCG dosage or ovulation rate (P>0.10). The average number of cells per embryo was higher in the 1000 IU eCG group (84.3+/-15.3) than in the 1500 IU eCG group (70.2+/-1.9; P<0.05) but was similar for normal and superovulated donors within each eCG group (P>0.10). Of the 4 groups, litters of 28 to 30 blastocysts were nonsurgically transferred to 27 synchronous recipients. Pregnant recipients were slaughtered on Day 37 after hCG treatment to evaluate embryonic development and survival. Pregnancy rate for the 1000 and 1500 IU eCG donor groups was 71% (10/14) and 46% (6/13; P>0.10), respectively. The number of implantations and fetuses for the 1000 IU eCG groups was 12.9+/-3.0 and 11.1+/-2.7, and 14.2+/-7.0 and 10.5+/-4.6, respectively, for the 1500 IU eCG groups (P>0.10). After post-priory categorizing the litters of blastocysts to below or above the average diameter (158 microm) of the transferred embryos, irrespective of eCG dosage or ovulation rate, the pregnancy rate was 43% (6/14) and 77% (10/13; P<0.10), respectively. Post-priory categorizing the transferred litters to below or above the average number of cells per embryo litter, irrespective of eCG dosage or ovulation rate, showed no differences in pregnancy rates or number of implantations and fetuses (P>0.10). It was concluded that eCG dosage affects embryonic development at Day 7 after hCG, and this effect was not due to ovulation rate. Embryonic survival after nonsurgical transfer was not related to eCG dosage but tended to be related to the diameter of the blastocysts.     

Human chorionic gonadotropin and luteinizing hormone-releasing hormone reverse the blockade of ovulation in pregnant mare's serum gonadotropin-primed immature rats by the anti-androgenic drug, hydroxyflutamide

The present study was designed to examine mechanism(s) of the anti-ovulatory action of the anti-androgen, hydroxyflutamide (OH-F). Prepubertal rats were treated with 4 IU pregnant mare's serum gonadotropin (PMSG) (day -2) to induce first estrus and ovulation. They received OH-F in sesame oil or oil alone at 08:00 and 20:00 h on day 0 (the day of proestrus) and ovulations were assessed on the morning of day 1. Eighty-three percent of control animals ovulated with a mean of 7.7 +/- 1.1 corpora lutea per rat. Hydroxyflutamide blocked ovulation in all but 2 of the 12 rats receiving this drug alone. All of OH-F treated rats that received 5 and 25 IU human chorionic gonadotropin (hCG) ovulated with means +/- SEM of 9.1 +/- 0.1 and 7.3 +/- 1.4 corpora lutea per rat, respectively. The dose of 0.2 IU hCG was essentially ineffective, while the effect of 1.0 IU hCG was intermediate. At the dose of 20 ng and above (100 and 500 ng) luteining hormone-releasing hormone (LHRH) completely overcame the ovulation blockade in the OH-F treated animals, while a 4-ng dose was ineffective. At 18:00 h on the day of proestrus, serum LH levels in control animals were 17.56 +/- 2.60 ng/mL, which were 920% above basal levels (1.90 +/- 0.13) indicating a spontaneous LH surge. This surge was suppressed in OH-F treated rats. Injection of LHRH, at the dose of 20 ng and above, reinstated the LH release in OH-F treated animals. Thus, the anti-androgen, OH-F, inhibits ovulation in PMSG-treated immature rats through its interference with the preovulatory LH surge; the inhibition can be reversed by hCG or LHRH. Hydroxyflutamide does not appear to interfere at the level of the pituitary, but may have direct action at the hypothalamic and (or) extrahypothalamic sites involved in the generation of positive feedback signals that control LH release.     

Superovulation in immature and mature Chinese hamsters

Mature female Chinese hamsters ovulate an average of 8.8 ± 1.0 (mean ± SD) eggs per female in each estrous cycle. Superovulation can be induced in both immature and mature females by subcutaneous or intraperitoneal injections of pregnant mare serum gonadotropin (PMSG) and either human chorionic gonadotropin (hCG) or pituitary luteinizing hormone (PLH). The best superovulation in immature females was induced by the administration of 15 IU of PMSG followed 72 hr later by injection of 15 IU of hCG (about 25 eggs per female) or 0.2 mg (200 IU) PLH (about 46 eggs per female). Ovulation started about 13–15 hr after administration of hCG (or PLH) and was completed during the next 5–6 hr. Superovulation in mature females could be induced by injecting PMSG any day of the estrous cycle, but the best superovulation (about 39 eggs per female) was induced by injecting 15 IU of PMSG on day 1 (day of ovulation) followed by the injection of 0.4 mg of PLH 72 hr later. When immature females treated with the best superovulatory protocol were mated on the evening of PLH injection, only 5% of the eggs were found fertilized 50 hr after PLH administration. On the other hand, about 60% of the eggs were found fertilized in mature females mated following treatment with the best superovulatory protocol. The majority (83–85%) of superovulated eggs obtained from both immature and mature females were normally fertilized in vitro.