Peripheral and intragonadal actions of inhibin-related peptides.
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Animals↗
Biomedical subjects
R J Scaramuzzi
Publications and source records attributed to R J Scaramuzzi.
Nutrient effects on ovulation rate, ovarian function and the secretion of gonadotrophic and metabolic hormones in sheep.
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Animal Nutritional Physiological Phenomena↗
Steroid secretion rates and plasma binding activity in androstenedione-immune ewes with an autotransplanted ovary.
Mature Merino ewes in which the left ovary and its vascular pedicle had been autotransplanted to the neck were divided into control (N = 5) and immunized groups (N = 6). The immunized ewes were treated (2 ml s.c.) with Fecundin 1 and 4 weeks before the start of blood sampling. Ovarian and jugular venous blood was collected every 10 min at two stages of the follicular phase (21-27 h and 38-42 h after i.m. injection of 125 micrograms of a prostaglandin (PG) analogue) and during the mid-luteal phase (8 h at 15-min intervals). The ewes were monitored regularly for luteal function and preovulatory LH surges. Hormone concentrations and anti-androstenedione titres were assayed by RIA and ovarian secretion rates of oestradiol-17 beta, progesterone and androstenedione were determined. After the booster immunization, progesterone increased simultaneously with titre in immunized ewes, reaching 30 ng/ml at the time of PG injection when median titre was 1:10,000. All ewes responded to PG with LH surges 42-72 h later: 2 of the immunized ewes then had a second LH surge within 3-4 days at a time when peripheral progesterone values were 2-3 ng/ml. The frequency of steroid and LH pulses was greater in immunized ewes (P less than 0.05) during the luteal phase but not the follicular phase. The secretion rate of androstenedione was 6-10 times greater (19-37 ng/min; P less than 0.001) in immunized ewes at all sampling stages. Progesterone secretion rates were 3 times greater (16 micrograms/min; P less than 0.001) during the luteal phase in immunized ewes. The amplitude of oestradiol pulses was significantly reduced in immunized ewes (4.8 vs 2.1 ng/min at +24 h and 6.5 vs 2.8 ng/min at +40 h in control and immunized ewes, respectively: P less than 0.05) during the follicular phase. However, the mean secretion rate of oestradiol at each phase of the cycle was not significantly different between treatment groups. Analysis of bound and free steroid using polyethylene glycol showed that greater than 98% of peripheral and ovarian venous androstenedione and 86% of peripheral progesterone was bound in immunized ewes but there was no appreciable binding (less than 0.1%) in control ewes. Similarly, 50% of ovarian venous oestradiol was bound in immunized ewes compared to 15% in control ewes. We conclude that immunization against androstenedione increases the secretion rate of androstenedione and progesterone but not of oestradiol.(ABSTRACT TRUNCATED AT 400 WORDS)
Androstenedione↗
Ovarian secretion rates and peripheral concentrations of inhibin in normal and androstenedione-immune ewes with an autotransplanted ovary.
Active immunization of sheep against androstenedione results in an increase in ovulation rate that is associated with increased plasma levels of LH and progesterone, but not FSH. Although immunized ewes have more activated follicles the secretion rate of oestradiol is not increased. An experiment was conducted to examine the effect of androstenedione immunity on the ovarian secretion and peripheral plasma concentrations of inhibin. Merino ewes in which the left ovary had been autotransplanted to a site in the neck were divided into control (n = 5) and androstenedione-immune (n = 6) groups. Ovarian and jugular venous blood was collected every 10 min at two stages of the follicular phase, 21-27 h and 38-42 h after a luteolytic dose of an analogue of prostaglandin F2 alpha (PG), and every 15 min for 6 h on day 10 of the subsequent luteal phase. The ewes were monitored regularly for luteal function by measurement of the concentration of progesterone and preovulatory LH surges. The concentration of inhibin in jugular and ovarian venous plasma was determined by radioimmunoassay and ovarian secretion rates and peripheral concentrations are expressed as pg of 1-26 peptide fragment of the alpha chain. The ovarian secretion rate of inhibin tended to be greater in androstenedione-immune ewes at all stages of the oestrous cycle measured, with this difference being statistically significant (P less than 0.05) during the luteal phase (100 +/- 40 and 260 +/- 80 (S.E.M.) pg/min for control and immune groups respectively). The pattern of ovarian inhibin secretion exhibited pulsatile-like fluctuations which were not associated with LH pulses. Peripheral concentrations of inhibin were generally higher in immunized than in control ewes with this difference being significant (P less than 0.01) from day 4 to 14 of the luteal phase (59 +/- 5 and 110 +/- 7 ng/l for control and immune respectively). The ovarian secretion rate of immunoactive inhibin was greater (P less than 0.01) during the follicular phase than during the luteal phase in both groups of ewes, and peripheral concentrations of inhibin increased (P less than 0.001) following injection of PG in ewes from both treatment groups. We concluded that androstenedione immunity results in an increase in ovarian inhibin secretion, an effect that can probably be attributed to the greater number of large oestrogenic follicles present in the ovaries of these ewes.(ABSTRACT TRUNCATED AT 400 WORDS)
Androstenedione↗
Seasonal modification of ovine pineal function. I. Interaction of gonadal steroids and sympathetic innervation on beta-adrenoceptors.
The results of a seasonal study of the regulation by steroids of ovine pineal beta-adrenoceptors are reported. The effects of ovariectomy, steroid implants and superior cervical ganglionectomy were investigated in Merino ewes. The results confirm earlier observations showing a seasonal variation in the sensitivity of the receptors to modification by gonadal steroids. A marked difference in receptor density and affinity between the follicular and luteal phases of the estrous cycle is shown for the first time, a difference which can be modified by appropriate steroid-related treatments. A season-dependent antagonism between the sympathetic innervation of the gland (presumably acting via the neurotransmitter noradrenaline) and gonadal steroids in the regulation of ovine pineal beta-adrenoceptor function is also shown.
Animals↗
Seasonal modification of ovine pineal function. 2. Steroidal effects on melatonin and prolactin profiles.
Pineal beta-adrenoceptor density and affinity in ewes are modified in a season-dependent manner by gonadal steroids and by the sympathetic innervation of the gland. The present study was undertaken to relate the steroidal effects on the receptors to post receptor endocrine events, and to investigate the influence of the sympathetic innervation of the pineal gland on these events. Plasma melatonin and prolactin profiles were determined during anestrus and during the normal breeding season in ewes subjected to sympathetic denervation of the pineal and/or a range of steroid-related treatments. Wherever valid comparisons could be drawn between effects of the treatments on beta-adrenoceptor variables and on circulating hormone levels, similar effects were noted. Further, ganglionectomy influenced hormone profiles similarly to estradiol under all conditions tested. It appears that gonadal steroids (estradiol) and the sympathetic neurotransmitter noradrenaline have opposing actions on prolactin levels, just as they have on pineal beta-adrenoceptor binding affinity. These findings suggest that steroid-mediated changes in receptor number and affinity are reflected in post receptor endocrine events. In addition, other factors (e.g. photoperiodic information transmitted via the sympathetic innervation) also play important roles in the regulation of the observed hormonal profiles. A steroid-mediated feedback regulation of pituitary prolactin release, partly direct and partly via pineal melatonin release, is suggested.
Anestrus↗
Polyploid abnormalities in day 3 and day 5 merino sheep embryos.
The chromosome complement was assessed in Merino sheep embryos collected at 3 and 5 days after the onset of oestrus. Donor ewe treatments were: untreated, or immunized against androstenedione (day 3); and untreated, or treated with follicle-stimulating hormone (FSH), or treated with FSH plus immunization against androstenedione (day 5). No significant differences in the frequency of chromosomally abnormal embryos between treatment groups within each age group were observed, so the data have been combined. Euploid abnormalities were observed in 10.8% of the day-3 embryos (4/37), with the abnormalities being one 1n, one 3n and two 5n. Embryos with euploidy (10%) were also observed at day 5, with three 1n/2n mosaics and a 3n embryo present in a sample of 40. These data suggest that chromosomally aberrant embryos are not lost before day 5 of development.
Androstenedione↗
The sheep corpus luteum secretes inhibin.
An experiment was performed in 20 Merino ewes in which ovarian venous blood was collected by venepuncture at surgery and at two stages of the oestrous cycle. The ovarian venous concentrations of inhibin, oestradiol-17 beta and progesterone were determined. The results demonstrate that during the luteal phase of the oestrous cycle the ovarian venous blood draining an ovary containing luteal tissue contains significantly more inhibin bioactivity than ovarian venous blood from an ovary not containing luteal tissue. During the follicular phase the concentration of inhibin bioactivity in ovarian venous blood was reduced compared with the luteal phase. From this data we conclude that the sheep corpus luteum secretes inhibin bioactivity into the ovarian venous blood.
Animals↗
Secretion of bioactive inhibin by the ovary of the Booroola Merino ewe with or without a copy of the fecundity (F) gene.
The secretion rates of bioactive inhibin, oestradiol and progesterone were measured during the mid-luteal phase and at various times during the follicular phase of the cycle by a sensitive bioassay using sheep pituitary cells in culture in 12 Booroola ewes with and without copies of the Fecundity (F) gene in which the left ovary had been auto-transplanted to the neck. Inhibin secretion was high during the luteal phase and fell in the early follicular phase in all genotypes (P less than 0.01). In Booroola ewes with a F/- genotype, inhibin secretion then increased again, towards luteal rates, in the mid and late follicular phases. In Booroola ewes without a copy of the F gene (+/+) inhibin secretion remained low at all three sampling times in the follicular phase. The secretion rate of inhibin at 36 h (P less than 0.1) and 48 h (P less than 0.01) were significantly lower in ewes from the +/+ (no copy of the gene) ewes than in F/- (one copy of the gene) ewes. Oestradiol secretion was low during the luteal phase and increased steadily during the early (24 h) to a plateau in the mid (36 h; P less than 0.01) and late (48 h; P less than 0.05) follicular phase. Progesterone secretion was high during the luteal phase, and decreased to a very low rate by 24 h after prostaglandin (PG) treatment (P less than 0.001) and remained low. At 24 h after PG the concentration of FSH was significantly lower (P less than 0.01) than that during the luteal phase and remained suppressed until the onset of the LH surge.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Control of fertility and fecundity of sheep by means of hormonal manipulation.
The results of four experiments are presented in summary form. The data are considered in relationship to the improvement of the fecundity and fertility of the Australian ewe breeding flock. In the first, three commonly used methods of oestrous synchronization were examined and showed differences that are attributed to the different patterns of hormonal changes associated with the methods demonstrated. The second experiment looked at the use of active immunization against testosterone and concluded that this method can improve fecundity but not fertility. The third experiment, a group of five trials, studied the use of progestagen sponges and PMSG in anoestrous ewes as a means of inducing normal fertility. The extensive data produced in this experiment allowed the relationships between ovulation rate and fertility and between fertility and prolificacy (fecundity) to be examined. Fertility appeared greatest when the mean flock ovulation rate was about 2.5. At this ovulation rate prolificacy was also improved and a high proportion of twins were produced. We concluded that high fertility and low prolificacy (i.e. of 1.00) are an unlikely combination. In the final experiment the effect of post-mating hormonal supplementation on fertility was examined and a number of earlier reports were confirmed by showing that fertility can be improved with supplementary progesterone between days 10 and 25 post-mating. The effect appears to be modified by hormonal and nutritional factors.
Animals↗
Ovarian response to PMSG and GnRH in ewes immunised against oestradiol-17 beta.
Forty-six adult merino ewes were immunised against oestradiol-17 beta-6 carbomethyloxime:human serum albumin and 48 comparable ewes were used as controls in an experiment to study the effects of gonadotrophin releasing hormone (GnRH) on ovulatory responses after treatment with pregnant mare's serum gonadotrophin (PMSG). All the ewes were treated with progestogen sponges for 14 days and received 1500 iu PMSG on the 12th day. Twenty-four control and 24 immunised ewes received 25 micrograms GnRH 21.5 hours and 23 hours after the sponges were withdrawn. Plasma samples were collected between 17 and 50 hours after the sponges were withdrawn and assayed for luteinising hormone (LH). Immunisation reduced the proportion of ewes which ovulated and their rate of ovulation. Injection of GnRH increased the proportion of immunised ewes ovulating (P less than 0.0005) and their rate of ovulation (P less than 0.0001). More unovulated follicles were observed in immunised ewes regardless of GnRH treatment (P less than 0.0001). The rate of recovery of eggs was reduced after immunisation. Treatment with GnRH produced a surge of LH of equal magnitude in the control and immunised ewes although not as many immunised ewes ovulated.
Animals↗
Effect of immunization against progesterone on oestrus, cycle length, ovulation rate, luteal regression and LH secretion in the ewe.
The effects of active immunization against progesterone on reproductive activity were studied in Merino ewes. Immunization against progesterone caused a shortening (P less than 0.01) of the interval between ovulations from 17-18 days (controls) to between 6 and 10 days (immunized group); this was associated with a corresponding reduction in the interval between LH surges. The immunized ewes also had higher (P less than 0.05) ovulation rates (1.72) than controls (1.25) and exhibited a reduced (P less than 0.01) incidence of oestrus (26% v. 95%). Many immunized ewes continued to ovulate despite the persistence of corpora lutea from earlier ovulations which led to an accumulation on the ovaries of many corpora lutea of different ages. The frequency of LH pulses in ewes immunized against progesterone (1.8 +/- 0.2 pulses/4 h) was significantly (P less than 0.001) higher than that of control ewes (0.3 +/- 0.1 pulses/4 h). This study highlights the importance of progesterone in the control of oestrus, ovulation, ovulation rate, luteal regression and the secretion of LH in the ewe.
Animals↗
Plasma concentrations of luteinising hormone during the ovulatory cycle in hens selected for reduced oviposition interval and maintained in continuous light or a 24 h light:dark cycle.
Plasma luteinising hormone (LH) concentrations were measured during the ovulatory cycle in lines of Australorps and White Leghorns selected for reduced oviposition interval and maintained under continuous light and noise. Selection significantly increased plasma LH concentrations in mid-sequence ovulatory cycles of Australorps but not in the White Leg-horns. Selection in the Australorps apparently increased the rate of ovarian follicular maturation, resulting in more frequent LH peaks. The effect of selection on plasma LH concentrations is a function of the lighting condition to which the hens are exposed.
Animals↗
Fertilization and early embryonic development in androstenedione-immunized Merino ewes.
Ewes were immunized against androstenedione (Fecundin) and assigned to be mated 14 days (179 ewes Group C) or 25 days (174 ewes Group B) after a booster immunization with Fecundin. The anti-androstenedione titres at these times were 6790 and 3240 respectively (P less than 0.01). The remaining 169 ewes were untreated controls (Group A). Ewes were mated to entire rams (12 rams to 180 ewes) at their second oestrus after synchronization of oestrus. Immunization against androstenedione caused a shortening of the time from sponge removal to mating (Day 0) and a decrease in the percentage of ewes mated by the rams. Also, ovulation rate was increased after immunization (P less than 0.01), being 1.42, 2.16 and 1.93 for Groups A, C and B respectively. Egg recovery rates on Day 2 were lower in immunized ewes and there was some indication that fertilization rates were lowered. On Day 13 after mating a higher proportion of blastocysts was recovered from ewes in Group A than from those in Groups B and C. Immunization resulted in lower fertilization rates and smaller blastocysts with lower mitotic indexes (P less than 0.01). At Days 24-32 of pregnancy fetal weight was lower in the immunized ewes. At all sampling stages, the proportion of ewes pregnant (fertility) was lowered in immunized ewes. The results of the present study show that significant reproductive wastage occurs in androstenedione-immunized Merino ewes, with lower rates of embryo recovery and delayed embryonic development being found in comparison to controls.(ABSTRACT TRUNCATED AT 250 WORDS)
Androstenedione↗
Polyploid cells in blastocysts and early fetuses from Australian Merino sheep.
Cytogenetic examination was made of 103 13-14-day-old blastocysts and 116 24-32-day-old fetuses from untreated and androstenedione-7-HSA-immunized Merino ewes. There were no differences in the chromosome composition of blastocysts or fetuses from treated or untreated ewes and so the data were combined. At Days 13-14 a 1N/2N mosaic and a 2N - 1/2N/4N mosaic embryo were observed. In addition, 52 of the blastocysts were 2N/4N mosaics, with 8 of these also containing 8N cells, and one blastocyst was a 2N/8N mosaic. No aneuploid fetuses were observed, but 80 of the 116 fetuses contained polyploid cells, including 4N, 6N and 8N cells. The polyploid cells observed in the blastocysts and fetuses should not be considered as abnormal cells as they appear to be a normal part of the developmental processes leading to trophoblast formation and fetal differentiation.
Animals↗
Effects of selection for reduced oviposition interval on plasma concentrations of luteinising hormone during the ovulatory cycle in hens on a 24 h lighting cycle.
The effects of selection under continuous light for reduced oviposition interval within a sequence of eggs on plasma luteinising hormone (LH) concentrations during the ovulatory cycle were investigated in lines of Australorps and White Leghorns maintained on a 24-h light:dark cycle. Selection did not significantly alter LH concentrations during mid-sequence cycles in either breed. In the control lines, concentrations were higher in the Australorps than in the White Leghorns before and at peak in mid-sequence cycles. The increase in egg production resulting from selection was associated with an advance in the mean time of lay of mid-sequence eggs in both breeds and, in the Australorps, with more pre-ovulatory LH peaks being initiated at the beginning of the open period of the ovulatory cycle. Selection reduced the time an egg spends in the oviduct and, in the Australorps, significantly reduced the interval between a pre-ovulatory LH peak and the oviposition of the egg currently in the shell gland. We suggest that selection under continuous light for reduced oviposition interval increased the rate of ovarian follicular maturation by a mechanism which did not involve an increase in pre-ovulatory concentration of plasma LH in a 24-h light-dark cycle.
Animals↗
Seasonal changes in the sensitivity of ovine pineal beta-adrenoceptors to steroids.
Immunoneutralization of endogenous gonadal steroids has recently been shown to modify pineal beta-adrenoceptor function in intact Merino ewes. In the current study, interactions between gonadal steroids and these receptors have been further investigated. beta-Adrenoceptor density and binding affinity both showed time-related changes in ewes; the significance of these changes requires further study. Two observations, firstly modification of beta-adrenoceptor function by androstenedione and 17 beta-estradiol in ovariectomized, but not in intact ewes, and secondly that steroid-mediated effects on receptor density and binding affinity in the pineal of ovariectomized Merino ewes could be demonstrated during anestrus, but not during the breeding season for intact ewes, indicate that gonadal steroids may regulate pineal beta-adrenoceptor variables in Merino ewes. It is suggested that gonadal steroids may regulate ovine pineal function in ewes, and that the seasonal differences in sensitivity of luteinizing hormone release to steroid feedback may be mediated in part via effects on the pineal gland.
Androstenedione↗
Occurrence of haploid and haploid/diploid mosaic embryos in untreated and androstenedione-immune Australian Merino sheep.
Chromosome counts were obtained from 73 out of 177 (41%) early cleavage-stage Merino embryos. A further 13 embryos were classified as probably diploid. Chromosome aberrations were found in 8 (11%) embryos, one of which was aneuploid and the remainder (9.6%) had euploid abnormalities. If the probable diploid embryos are included, the incidence of euploid aberrations falls to 8.1%. Of the abnormal embryos there was one aneuploid with 2N = 55, two haploids, four haploid/diploid mosaics and one zygote with 4 haploid metaphase plates. Two additional zygotes had 4 interphase pronuclei. Four of the euploid abnormalities were attributable to the entry of two or more spermatozoa and therefore polyspermy is the largest single factor leading to chromosomally aberrant embryos in this population of Merino ewes.
Androstenedione↗