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PubMed1982

Electrical activity of the infundibulum in relation to ovulation in the chicken.

Electrical activity was recorded from the smooth muscle layer of the infundibulum of unanaesthetized hens during the ovulation cycle. There were low-frequency isolated spike potentials throughout the cycle except for the period near ovulation. There were intermittent bursts of spike potentials about 1 h before ovulation and then an increased frequency of spike potentials near the time of ovulation. These may be related to the activity of the infundibulum engulfing the shed ovum. The frequency of electrical activity tended to decrease shortly after ovulation, but then increased again for a few hours. Premature ovulation induced by progesterone i.m. was associated with similar electrical changes.

Action Potentials↗
PubMed1983

Effect on oestrus and ovulation of exposing creole goats to the male at three times of the year.

The characteristics of the oestrous and ovarian cycles of local goats were studied over 2 years, on 96 females in March, 60 in July and 100 in November. After 3 weeks of separation between sexes, the females with inactive ovaries were identified and harnessed males were introduced. Detection of oestrus was undertaken daily and the date and rate of ovulation were checked at laparoscopies. The proportion of females with non-cyclic ovaries before the mating period varied according to the season and whether the females were nulliparous or suckling. Among the females with inactive ovaries before the mating period, 97% ovulated 2 . 8 days after the introduction of males; 68% of these initial ovulations were accompanied by oestrus and 76% resulted in short luteal phases (5 . 3 days) followed by a second ovulation accompanied by oestrus 89% of the time. The proportions of initial ovulations with oestrus and of initial ovulations followed by a short luteal phase were in linear relationship with the proportion of females with non-cyclic ovaries before the mating period. For the females with cyclic ovaries before the mating period, the distribution of first oestrus during the 8 days after the introduction of males was significantly different from the expected uniform distribution. A possible luteolytic action of teasing was suspected. The fertility of females in all groups was high (greater than 79%). Litter size was not different for non-cyclic and for cyclic females.

Animals↗
PubMed1983

Genetic variation in spontaneous ovulation rate and LH receptor induction in mice.

Selection for litter size (Line S1) and for post-weaning body weight gain (Line G) increased spontaneous ovulation rate in mature females by 69 and 73%, respectively, over that of randomly bred control mice (Line C). Inbreeding from S1 mice with selection for litter size produced highly inbred lines with elevated ovulation rates. Inbreeding from Line C mice produced a 21% divergence among lines, but did not depress the mean ovulation rate. Crosses of these lines revealed little heterosis in ovulation rate. LH receptors were induced by treating females from 22 days of age with diethylstilboestrol for 4 days and FSH for 2 days. The in-vitro binding of 125I-labelled hCG per microgram DNA decreased 56% in response to selection for litter size and increased 57% in response to selection for body weight gain, indicating high susceptibility of this trait to genetic change. Inbreeding from Line C mice produced a 135% divergence amongst lines, but did not depress the mean LH receptor induction. Body weight had significant effects on ovulation rate and LH receptor induction. These results show that selection for litter size and for rapid post-weaning body weight gain increases ovulation rate, but we suggest that different mechanisms are involved in these responses.

Animals↗
PubMed1987

Studies of ovulation in the perfused ovary of the fowl (Gallus domesticus).

A system was developed for the in-vitro perfusion of the fowl ovary. The ovaries were isolated 16-18 h before expected ovulation of the first follicle of a clutch sequence and perfused at 41 degrees C with Eagle's culture medium containing L-thyroxine and insulin. The efferent perfusion pressure was maintained at 30-40 mmHg. This model was used to investigate the mechanism of ovulation. Addition of LH (1 U) to the perfusate induced ovulation (46%) but LH (1 U) + FSH (1 U) was more effective (88%; P less than 0.05). Progesterone at 100 micrograms alone also induced ovulation (80%). Clomiphene prevented gonadotrophin-induced ovulation. These results suggest that progesterone may act directly on the ovary as a final hormone to induce ovulation in the domestic fowl.

Animals↗
PubMed1987

Induction of oestrus and ovulation in farmed fallow deer (Dama dama) by using progesterone and PMSG treatment.

Twenty non-lactating fallow does were each treated with an intravaginal progesterone device (CIDR) for 14 days followed by an i.m. injection of 500 i.u. PMSG, 3-4 weeks before the expected start of the natural rut. An additional 7 does received no treatments and were used as controls. Induced oestrus was observed for 19 (95%) of the treated does, the onset occurring between 48 and 76 h after CIDR removal/PMSG administration. Laparoscopic examination 12 days after CIDR removal revealed ovulation rates ranging from 1 to 4 in treated does. Non-ovulating luteinized follicles were also a feature of PMSG treatment and there was a significant inverse relationship between ovulation rate and numbers of luteinized follicles. Only 3 (14.3%) of the treated does conceived at or near the induced oestrus, the remainder returning to oestrus 21-27 days later. Mid-cycle progesterone concentrations were positively related to ovulation rate. All control does showed evidence of a recent single ovulation at laparoscopy, although first oestrus did not occur until 7-15 days later, indicating the occurrence of silent ovulations before the natural breeding season.

Animals↗
PubMed1988

FSH-induced ovulation in intact and hypophysectomized mice.

A single, ovulatory dose of 25 micrograms of a highly purified preparation of ovine FSH caused ovulation in 89% of hypophysectomized and 91% of intact female mice primed 48 h earlier with PMSG; the number of oocytes recovered (29.4 +/- 4.7 and 22 +/- 2.7/mouse ovulating, respectively) compared favourably with the 20.0 +/- 2.9 oocytes per ovulating female recovered from animals that received PMSG + hCG. After oFSH injection, 82% of oocytes released were fertilized and developed to blastocysts. That the trace contamination (less than 0.2%) of the oFSH with oLH was not responsible for the ovulation was shown by the markedly reduced number of oocytes collected from ovulating females that were injected with equivalent low levels of hCG (0.001 micrograms) or oLH (1 microgram) (9.0 +/- 3.3 and 8.0 +/- 3.1, respectively). These results demonstrate that oFSH is as effective as LH in inducing ovulation of competent oocytes in the mouse.

Animals↗
PubMed1988

The number of spermatozoa, the number of ovulations per ewe, and immunization against androstenedione affect fertility and prolificacy of sheep.

Ewes that were untreated, fed lupins or fed lupins and immunized against androstenedione were artificially inseminated. The percentage of ewes pregnant at 36-45 days after insemination (fertility) was 8% higher in ewes that had more than one ovulation than in those that had only one ovulation. Maximum fertility was achieved with 50 x 10(6) spermatozoa and this did not vary with the number of ovulations that ewes had. Among the pregnant, twin-ovulating ewes, embryo survival increased as the number of spermatozoa inseminated increased from 25 x 10(6) to 400 x 10(6). Immunization of ewes against androstenedione increased ovulation rate but reduced fertility, and reduced embryo survival among twin-ovulation ewes.

Androstenedione↗
PubMed1988

Importance of non-olfactory ram stimuli in mediating ram-induced ovulation in the ewe.

In Exp. 1, 4 groups of 50 recently weaned ewes were exposed to various degrees of contact with rams for 65 days, followed by exposure to novel rams for 4 days. Ovarian activity in the ewes was determined by laparoscopy on Days 29, 65 and 69 of treatment. There were no treatment differences in the percentage of ewes ovulating on Day 4 whereas by Day 29 more ewes in clear fenceline and full ram contact were ovulating compared to controls (P less than 0.05, P less than 0.001). After 65 days ovarian activity was significant only in those ewes in full contact with rams (P less than 0.001). Between 89 and 95% of ewes remaining anovulatory after 65 days ovulated after 4 days of full contact with novel rams. In Exp. 2, 4 groups of about 30 anovulatory ewes were exposed to various degrees of contact with rams for 5 days. Ovarian activity was assessed before and after treatment by laparoscopy. After 5 days, more ewes were ovulating in response to full ram contact than in any other treatment (P less than 0.05) and more ewes in fenceline contact with rams or with rams plus ewes were ovulating than in the isolated control treatment (P less than 0.01). In Exp. 3, 6 groups of about 40 anovulatory ewes were exposed to face masks with and without rams' wool and/or various degrees of contact with rams for 5 days. More ewes were ovulating after 5 days in the group in full physical contact with rams than in any other group (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Ability of progesterone to reverse anti-androgen (hydroxyflutamide)-induced interference with the preovulatory LH surge and ovulation in PMSG-primed immature rats.

In Exp. 1, PMSG was injected to 26-day-old prepubertal rats to induce ovulations. On Day 2 (2 days later, the equivalent of the day of pro-oestrus) they received at 08:00 h 5 mg hydroxyflutamide or vehicle and at 12:00 h 2 mg progesterone or testosterone or vehicle. Animals were killed at 18:00 h on Day 2 or at 09:00 h on Day 3. Progesterone but not testosterone restored the preovulatory LH surge and ovulation in hydroxyflutamide-treated rats. In Exp. 2, 2 mg progesterone or testosterone were injected between 10:30 and 11:00 h on Day 2, to advance the pro-oestrous LH surge and ovulation in PMSG-primed prepubertal rats. Injection of hydroxyflutamide abolished the ability of progesterone to advance the LH surge or ovulation. Testosterone did not induce the advancement of LH surge or ovulation. In Exp. 3, ovariectomized prepubertal rats implanted with oestradiol-17 beta showed significantly (P less than 0.01) elevated serum LH concentrations at 18:00 h over those observed at 10:00 h. Progesterone injection to these animals further elevated the serum LH concentrations at 18:00 h, in a dose-dependent manner, with maximal values resulting from 1 mg progesterone. Hydroxyflutamide treatment significantly (P less than 0.003) reduced the serum LH values in rats receiving 0-1 mg progesterone but 2 mg progesterone were able to overcome this inhibition. It is concluded that progesterone but not testosterone can reverse the effects of hydroxyflutamide on the preovulatory LH surge and ovulation. It appears that hydroxyflutamide may interfere with progesterone action in induction of the LH surge, suggesting a hitherto undescribed anti-progestagenic action of hydroxyflutamide.

Anilides↗
PubMed1989

Effects of oestradiol implants on the ovulation rate of the ewe.

In a series of 5 experiments, ewes were treated with implants releasing oestradiol-17 beta and the effects on ovulation rate were observed. Large doses of oestradiol-17 beta (greater than 20 micrograms/day) produced anovulation while smaller amounts only reduced the proportion of twin ovulations. Amounts of exogenous oestradiol comparable to ovarian production rate in the luteal phase (less than 1 microgram/day) produced a significant (P less than 0.01) suppression in ovulation rate. Treatment during the follicular phase of the oestrous cycle was most effective, but treatment during the luteal phase alone also appeared to suppress ovulation rate. Furthermore, in 2 of 3 experiments ewes treated with low amounts of oestradiol during the first half of the luteal phase were less likely to have multiple ovulations at the subsequent oestrous period. The results support the hypothesis that oestrogen is involved in the physiological control of ovulation rate in the ewe, but this action is probably not restricted to the assertion of dominance by a maturing follicle during the follicular phase.

Animals↗
PubMed1990

Increased ovulation rate in gilts after oral administration of epostane.

In Phase I of this study to enhance ovulation rate and hence litter size, gilts received 0 (sham control), 0.625, 1.25, 2.5 or 5.0 mg epostane/kg body weight on Days 10, 11 and 12 of the oestrous cycle (5 gilts/group). After epostane treatment, plasma progesterone concentrations were reduced (P less than 0.01) in a dose-related manner, % progesterone decline = 21.30 x square root of (dose) + 10.45, R2 = 0.70, but recovered to pretreatment levels by 24 h. In Phase II the effects of epostane on ovulation rate and litter size were tested at two study centres. At each centre 108 gilts were treated with the same doses of epostane as used in Phase I and the doses were given for 7 days (Days 15-21) or 12 days (Days 10-21) during the first oestrous cycle. Gilts were inseminated twice during the oestrus after treatment and were slaughtered 30 days later. Mean (+/- s.d.) ovulation rate was 16 +/- 2.7 (N = 8) and 21 +/- 4.0 (N = 61) for control and epostane-treated gilts in Centre A and 12 +/- 2.4 (N = 5) and 17 +/- 3.8 (N = 55) respectively in Centre B (P less than 0.01 for both) and was dose related (ovulation rate = 3.38 x square root of (dose) + 16.17, R2 = 0.31). The effects of 7- or 12-day epostane treatment on ovulation rate were not different (P greater than 0.05), indicating that effects of treatment after Day 14 of the oestrous cycle are most important to subsequent ovulation frequency.(ABSTRACT TRUNCATED AT 250 WORDS)

Androstenols↗
PubMed1990

Vasoactive intestinal polypeptide in the PMSG-primed immature rat ovary and its effect on ovulation in the isolated rat ovary perfused in vitro.

The immature rat ovary contains VIP immunoreactive nerve fibres sparsely distributed around blood vessels, in the interstitial gland and around follicles. The VIP concentration, measured radioimmunologically, decreased significantly after PMSG treatment (10 i.u.), probably due to ovarian enlargement and oedema, while the total VIP content (total of 0.12 pmol in both ovaries) did not change after PMSG priming. The ovulatory effect of VIP was studied using in-vitro perfused ovaries from immature 28-day-old rats primed with 10 i.u. PMSG. In all ovaries perfused, VIP (10(-7) M) induced ovulations with a rate of 2.33 +/- 0.56. The ovulation rate was significantly lower than that of ovaries stimulated by LH (0.1 microgram/ml) (5.20 +/- 0.86 ovulations per ovary). No synergistic effect on the ovulation rate was seen when LH and VIP were administered together (5.20 +/- 0.49 ovulations per ovary). The results suggest that the neuropeptide VIP may represent one of the local factors involved in the ovulation process.

Animals↗
PubMed1993

Effect of immunization against synthetic peptide sequences of bovine inhibin alpha-subunit on ovulation rate and twin-calving rate in heifers.

Three peptide sequences from the bovine inhibin alpha-subunit (P1: 18-30; P2: 63-72 and P3: 107-122) were synthesized and conjugated to human serum albumin (HSA). Hereford cross-heifers (n = 5 per group) were injected with 3 mg of one of the peptide conjugates, followed by three booster injections at intervals of 11 weeks. Control heifers (n = 5) were injected with HSA only. Antibodies recognizing both the individual peptides and 32 kDa bovine inhibin were generated and ovulation rate was increased in peptide immunized heifers. In group P1, 1 of 5 heifers responded with an increased ovulation rate whereas in groups P2 and P3, 5 of 5 and 4 of 5 heifers, respectively, had an increased ovulation rate. In group P2, in the first oestrous cycle following booster injections 2 and 3, 4 of 5 and 3 of 5 heifers, respectively, responded with twin ovulations, whereas a fourth heifer had three ovulations following booster injection 3. After breeding following booster injection 3, 3 of 5 heifers in group P2 and 1 of 5 in group P3 gave birth to twin calves. This study demonstrates the potential of immunizing against synthetic peptide sequences of the alpha-subunit of bovine inhibin to increase ovulation and twinning rates in cattle.

Animals↗
PubMed1993

Induced ovulation of the first postpartum dominant follicle in beef suckler cows using a GnRH analogue.

There is a low incidence of ovulation of the first dominant follicle that develops in the early postpartum period of beef suckler cows, which prolongs the interval from calving to first ovulation. The objective of this study was to determine whether a single injection of a GnRH analogue would ovulate the first postpartum dominant follicle. Limousin x Friesian beef suckler cows were assigned at parturition, over two years (16 cows in year 1; 19 cows in year 2), to one of three treatments: (1) untreated (control; n = 12), (2) GnRH analogue (20 micrograms buserelin i.m.) administered in the growing-plateau phase of the first postpartum dominant follicle (GnRH-G; n = 12) and (3) GnRH analogue administered in the declining phase of the first postpartum dominant follicle (GnRH-D; n = 11). From day 8 or 9 post partum, the ovaries of each cow were examined daily by ultrasound to determine the time of GnRH injection and ovulation. Blood samples were collected daily for progesterone measurement to confirm ovulation and in year 2 to determine the duration of the first oestrous cycle. The mean (+/- SEM) number of days from parturition to development of the first dominant follicle was 11.0 +/- 0.3, 10.3 +/- 0.5 and 10.1 +/- 0.7 for cows assigned to treatments 1-3, respectively (P > 0.05). The proportion of cows ovulating the first dominant follicle was higher (P < 0.05) following GnRH treatment (12 of 12 and 7 of 10; GnRH-G and GnRH-D, respectively) than with controls (2 of 12).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Stimulation of in vitro ovulation and contraction of brook trout (Salvelinus fontinalis) follicles by adrenaline through alpha-adrenoreceptors.

The effects of adrenaline and adrenoreceptor antagonists on ovulation and follicle wall contraction were investigated in brook trout (Salvelinus fontinalis) follicles using in vitro incubation systems. Adrenaline significantly stimulated a dose-dependent increase in ovulation and follicle contraction at concentrations between 1.0 and 100 mumol l-1. The ovulatory and contractile effects of 10 mumol adrenaline l-1 could be blocked by the alpha 1-adrenoreceptor antagonists WB-4101 and benoxathian, and by the alpha 2-antagonist yohimbine. WB-4101 was the most potent blocker, significantly inhibiting ovulation and contraction at 1.0 mumol l-1. In contrast, the beta-antagonist propranolol (100-0.001 mumol l-1) was totally ineffective in blocking adrenaline-induced ovulation and follicle contraction. The results indicate that there is a strong correlation between the effects of adrenaline on ovulation and contraction. In addition, the antagonist studies indicate that adrenaline stimulates ovulation and follicle contraction of brook trout follicles through alpha-adrenoreceptors.

Adrenergic alpha-Antagonists↗
PubMed1995

Effect of immunization against synthetic peptide sequences of the alpha N-subunit of bovine inhibin on ovulation rate, gonadotrophin concentrations and fertility in heifers.

The effects of immunizing cattle against either of two peptides from the amino terminal peptide (alpha N) of the alpha 43-subunit of bovine inhibin on ovulation rate, gonadotrophin concentration and fertility were investigated. Two peptide sequences from the alpha N-subunit of bovine inhibin (P1N, bI alpha-(8-20) and P2N, bI alpha-(153-167)) were synthesized and conjugated to human serum albumin (HSA). Hereford-cross heifers (n = 5 per group) were given an initial injection of 3 mg of one of the peptide conjugates, followed by three booster injections (1.5 mg) at intervals of 11 weeks. Control heifers (n = 5) were injected with HSA only. Blood samples were taken once a week to measure antibody titre and every hour at about the time of the first oestrus and during the mid-luteal phase after the second booster injection, to measure FSH and LH concentrations. Ovulation rate was measured by ultrasonography. Gonadotrophin concentrations were analysed for four periods relative to the peak (time = 0 h) of the preovulatory LH surge as follows: pre-surge: -16 to -5 h; surge: -4 to 4 h; post-surge: 5 to 16 h and a period of 12 h during the mid-luteal (days 10-12) phase. Antibodies that bound to the individual peptides were generated and the ovulation rate increased (P < 0.05) in immunized heifers. Control heifers had one ovulation at all ovulatory cycles monitored. In group P1N, one heifer had two ovulations at each of the six cycles monitored, while another heifer had two ovulations at one cycle.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1996

Timing of ovulation after gonadotrophin induction and its importance to successful intrauterine insemination in the tiger (Panthera tigris).

The ovarian response to equine chorionic gonadotrophin (eCG) and human chorionic gonadotrophin (hCG), the effect of timing of ovulation relative to hCG injection and the use of laparoscopic intrauterine artificial insemination (AI) were examined in two subspecies of tiger (Panthera tigris). Adult female tigers were subjected to the same eCG/hCG treatment followed by laparoscopy under xylazine/diazapam/ketamine HCl anaesthesia at 39-42 h (Group I, n = 9), 46-49 h (Group II, n = 5) or 51-55 h (Group III, n = 5) after hCG. Six of these females, observed to be postovulatory at the time of laparoscopy (Group II, n = 3; Group III, n = 3), were subjected to intrauterine AI. The number of preovulatory follicles observed on the ovaries of Group I females was twofold greater (P < 0.05) than the number observed on ovaries of females in Group II and III. Fewer (P < 0.05) corpora lutea were observed on ovaries of Group I females (1.3 +/- 0.6) compared with the number of corpora lutea in Group II and III (combined average, 7.8 +/- 0.8 corpora lutea per female). Only one of ten females in Groups II and III failed to ovulate by the time of laparoscopy. Four Group I females never ovulated, based on a laparoscopic re-evaluation 4 weeks later. One female inseminated 46 h after hCG (Group II) became pregnant and delivered a healthy cub after a normal gestation. There were no apparent differences between subspecies in response to the same ovulation induction protocol. Results demonstrate the importance of the relationship between exogenous gonadotrophin treatment and onset of anaesthesia for laparoscopic examination and AI in tigers. Data clearly indicate that anaesthesia/laparoscopy conducted too early (39-42 h after hCG) compromises the number of females and proportion of follicles ovulating. In contrast, ovulation success is high if anaesthesia/laparoscopy is performed after this time, and intrauterine insemination can result in healthy young.

Animals↗
PubMed1998

Effect of acute treatment with progesterone on the timing and synchrony of ovulation in Bos indicus heifers treated with a norgestomet implant for 17 days.

The aim of the present study was to develop a treatment protocol for the precise synchronization of oestrus that would avoid the development of persistent dominant ovarian follicles. Bos indicus heifers, in which oestrous cycles had been presynchronized, were allocated randomly, according to the day of their oestrous cycle, to one of five treatment groups. All heifers received a subcutaneous ear implant containing 3 mg of norgestomet for 17 days starting on day 0 and an injection of an analogue of prostaglandin F2 alpha on days 0 and 4. Heifers in group 1 (control group; n = 7) received no other treatment, while heifers in groups 2 (n = 8), 3 (n = 7), 4 (n = 7), and 5 (n = 7) received a single progesterone-releasing controlled internal drug release device (CIDR) for 24 h on days 10, 12, 14 and 16, respectively. Treatment with a single CIDR delayed the mean time of ovulation and the day of emergence of the ovulatory follicle in heifers treated on days 14 and 16 compared with control heifers (P < 0.05). There was less variation in the interval to ovulation in heifers treated on day 10 compared with other treated heifers (P < 0.05). The variation among heifers in the day of emergence of the ovulatory follicle and the age of the ovulatory follicle at ovulation was less for all groups treated with a CIDR than for the control group (P < 0.05). The duration of dominance and variation in the duration of dominance of the ovulatory follicle was less in heifers treated with a CIDR device on days 10 and 16 than for control heifers (P < 0.05). Mean age (days from emergence to ovulation) of the ovulatory follicle did not differ among treatment groups (P > 0.05). Concentrations of LH and oestradiol decreased coincident with increased concentrations of progesterone on the days of CIDR treatment in treated compared with control heifers (P < 0.02) but increased again after removal of the CIDR. A smaller proportion of follicles in the growing phase of follicular development at the time of CIDR treatment become atretic compared with follicles that had reached a plateau phase of follicular growth (14.3% (1/7) versus 90.5% (19/21), respectively; P < 0.001). It was concluded that acute treatment with progesterone can influence the growth pattern of ovarian follicular development. However, the effect varies with the stage of ovarian follicular development. Short term treatment with progesterone 7 days before the end of a 17 day period of norgestomet treatment resulted in precise synchrony of ovulation without the ovulation of a persistent dominant ovarian follicle.

Animals↗