Nutritionally induced anovulation in beef Heifers: ovarian and endocrine function during realimentation and resumption of ovulation.
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Nutritionally induced anovulatory and cyclic Angus x Hereford heifers were used to evaluate follicular growth and concentrations of hormones and metabolites during anovulation and resumption of ovulation. Anovulatory heifers were fed to gain 0.6 (LGAIN) or 1.5 (HGAIN) kg/day until resumption of ovulation, and heifers with normal estrous cycles were fed a maintenance diet (M). Follicles >/= 4 mm in diameter were measured by daily ultrasonography in HGAIN and LGAIN heifers during one follicular wave before realimentation (Wan) and in two waves (W-2, W-1) immediately before the wave resulting in first ovulation or luteinization (W0). Ovaries of M heifers were evaluated to determine the day of ovulation of the second-wave dominant follicle (DF). Resumption of ovulation after realimentation occurred 23 days earlier in HGAIN than in LGAIN. Maximum diameter, growth rate, and persistence of dominant follicles increased, while persistence of first subordinate follicles decreased between anovulation and resumption of ovulation in anovulatory heifers. Concentrations of LH in serum were similar for HGAIN and LGAIN and gradually increased during realimentation. The increase in estradiol before the first ovulation was less in realimented heifers compared with cyclic heifers. Concentrations of insulin-like growth factor-I (IGF-I) in HGAIN and LGAIN gradually increased during realimentation but were lower than concentrations of IGF-I in cyclic heifers at ovulation. Increased diameter, growth rate, and persistence of the DF were associated with increased concentrations of LH, estradiol, and IGF-I during the transition from nutritionally induced anovulation to resumption of ovulatory cycles. (+info)
Reproductive hormone profiles in mares during the autumn transition as determined by collection of jugular blood at 6 h intervals throughout ovulatory and anovulatory cycles.
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The aim was to define precisely the FSH secretion pattern in mares during the two ovulatory cycles before, and for 24 days after, the last ovulation of the season and to compare this with the profiles of other reproductive hormones and follicular growth to identify changes which may lead to the termination of follicular cycles. Jugular blood was collected every 6 h from ten light horse mares for 6 weeks in autumn. Samples were assayed for FSH, LH, prolactin, inhibin, oestrone conjugates and progesterone. Luteolysis occurred earlier and periovulatory oestrone, but not inhibin, concentrations were significantly lower in the last than in the second to last cycles. In ovulatory and anovulatory cycles, daily mean FSH concentrations were low at the expected time of ovulation and high between days 9 and 11 (day 0 = ovulation), which were usually after luteolysis. However, the periovulatory FSH nadir was prolonged in the last compared with the second to last cycles, and the difference between peak and trough values was not significant in anovulatory cycles. Between day 5 and day 8, the FSH interpulse interval was approximately 2 days, and did not vary in successive cycles. The LH profile also showed progressive changes as mares entered acyclicity; the surge terminated sooner in the last than in the second to last cycles, and failed to occur when expected in acyclicity. Sporadic prolactin pulses occurred at luteolysis in a similar proportion of ovulatory and anovulatory cycles. These results indicate that inadequate gonadotrophin stimulation in early dioestrus may be a critical event leading to suboptimal follicular and luteal development, and eventually acyclicity. Moreover, the time relationships amongst changes in pituitary and ovarian hormones and follicular growth become increasingly disrupted during the autumn transition, which may contribute to the cessation of cyclicity. (+info)
Anovulation in non-reproductive female Damaraland mole-rats (Cryptomys damarensis).
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Within colonies of Damaraland mole-rats (Cryptomys damarensis), anovulation in non-reproductive females is thought to play an important role in maintaining reproductive skew. Pituitary sensitivity and ovarian structure were examined in three groups of females that differed with respect to their social environment and breeding status to determine whether anovulation is due to inhibitory social cues or is merely the result of a lack of copulatory stimulation. The contribution of gonadal steroid negative feedback to neuroendocrine differences in the reproductive systems of the respective groups was also investigated. LH secretion after a 0.5 micrograms GnRH challenge in females that had been removed from the presence of the breeding individuals for at least 6 months (removed non-reproductive females) was significantly higher than in non-reproductive females in the colony, but significantly lower than in reproductive females. In both removed non-reproductive females and reproductive females, corpora lutea were observed in ovaries of seven of eight females, indicating that ovulation occurs spontaneously in subordinate females on removal from the breeding pair. Circulating progesterone concentrations in removed non-reproductive females were significantly higher than in non-reproductive females, indicating that circulating progesterone is not responsible for infertility in non-reproductive females. Indeed, after hystero-ovariectomy, reproductive females continued to show significantly greater GnRH-stimulated LH secretion than non-reproductive females. Thus, differential inhibition of gonadotrophin secretion in breeding and non-breeding females occurs independently of gonadal steroids. It is concluded that female Damaraland mole-rats are spontaneous ovulators and that anovulation results from inhibitory social cues within the colony, not a lack of copulatory stimulation. Since non-reproductive females are infertile, inhibition of the hypothalamo-pituitary-gonadal axis has the potential to play a causal role in maintaining reproductive skew in colonies of C. damarensis. (+info)
Functional compensation by Egr4 in Egr1-dependent luteinizing hormone regulation and Leydig cell steroidogenesis.
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The Egr family of zinc finger transcription factors, whose members are encoded by Egr1 (NGFI-A), Egr2 (Krox20), Egr3, and Egr4 (NGFI-C) regulate critical genetic programs involved in cellular growth, differentiation, and function. Egr1 regulates luteinizing hormone beta subunit (LHbeta) gene expression in the pituitary gland. Due to decreased levels of LHbeta, female Egr1-deficient mice are anovulatory, have low levels of progesterone, and are infertile. By contrast, male mutant mice show no identifiable defects in spermatogenesis, testosterone synthesis, or fertility. Here, we have shown that serum LH levels in male Egr1-deficient mice are adequate for maintenance of Leydig cell steroidogenesis and fertility because of partial functional redundancy with the closely related transcription factor Egr4. Egr4-Egr1 double mutant male mice had low steady-state levels of serum LH, physiologically low serum levels of testosterone, and atrophy of androgen-dependent organs that were not present in either Egr1- or Egr4-deficient males. In double mutant male mice, atrophic androgen-dependent organs and Leydig cell steroidogenesis were fully restored by administration of exogenous testosterone or human chorionic gonadotropin (an LH receptor agonist), respectively. Moreover, a normal distribution of gonadotropin-releasing hormone-containing neurons and normal innervation of the median eminence in the hypothalamus, as well as decreased levels of LH gene expression in Egr4-Egr1-relative to Egr1-deficient male mice, indicates a defect of LH regulation in pituitary gonadotropes. These results elucidate a novel level of redundancy between Egr4 and Egr1 in regulating LH production in male mice. (+info)
Patient selection for assisted reproductive technology treatments.
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Assisted reproductive technologies refer to procedures in which the oocyte is handled or manipulated in vitro before replacement, either as an oocyte or an embryo. Because of rapid advances in this area, infertile couples may seek direct referral for assisted reproductive treatments, instead of trying simpler measures such as ovulation induction and intrauterine insemination. It is important to establish whether these conventional infertility treatments are appropriate, as such treatments are generally safer, less stressful, and more affordable. On the other hand, subjecting infertile couples to unnecessary delay by offering inappropriate treatments-for example, ovulation induction for tubal infertility or intrauterine insemination for severe male-factor infertility-would reduce the overall chance of success because of the age-related decline in female fecundity. The choice of infertility treatments thus depends on a balance of factors: the chance of pregnancy without treatment; the chance with simpler and safer, but less successful, infertility treatments; or the chance with the more complex and costly, but more effective, assisted reproductive treatments. The factors that should be taken into consideration include the age of the woman, the duration of infertility, the causes of infertility, the availability and cost of alternative treatments, and-most importantly-the acceptability. (+info)
Use of clomiphene and luteinizing hormone/follicle stimulating hormone-releasing hormone in investigation of ovulatory failure.
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A luteinizing hormone/follicle-stimulating hormone-releasing hormone (LH/FSH-RH) test was performed in 70 women with amenorrhoea or anovulatory infertility, or both, and a clomiphene stimulation test was also performed in 24 of these patients. Most patients responded to LH/FSH-RH with significant increases in LH and FSH. In women with gonadal dysgenesis or premature ovarian failure exaggerated responses were observed after LH/FSH-RH and there was no change in high basal LH levels after clomiphene. Patients with absent or impaired responses to LH/FSH-RH failed to respond to clomiphene. All patients with anovulatory menstrual cycles responded to both LH/FSH-RH and clomiphene, while seven out of 13 amenorrhoeic patients with a normal LH/FSH-RH response showed an early LH rise during clomiphene treatment and six were unresponsive. These results suggest a difference between the two groups at hypothalamic level with consequent therapeutic implications. (+info)
Assessing the status of intrauterine insemination before forming a medically assisted conception unit.
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A survey in 1996 of our female patients suggest that the three commonest causes of infertility were endometriosis, anovulation and idiopathic which comprises of about 70% of all the patients. In the male patients, sperm morphology evaluation by critical criteria showed that abnormal morphology was present in 71% while 87% of all the semen analysis were abnormal. The objective of this study was to assess the status of IUI before proceeding to formulate patient protocols for IVF in a tertiary infertility referral unit. A retrospective study of patients data was done from Jan 1995 to Dec 1996. Ovarian stimulation by clomiphene for anovulatory and idiopathic patients was performed on couples with at least one patent fallopian tube. Ovulation induction was by an intramuscular injection of 5000 i.u of HCG after follicular maturation. IUI was performed approximately 36-40 hours later. A total of 74 couples received 114 treatment cycles producing a total of 9 conceptions. The conception rate of IUI was therefore 7.89% per cycle and 12.16% per couple with the cumulative pregnancy rate of 28.21%. Associated success features of IUI found in this study were the age of the woman and the semen parameters of the husband. (+info)
Hormones, nutrition, and cancer.
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The effects of obesity on steroid metabolism in women with breast and uterine cancer have been considered. Obesity may increase plasma estrone by two mechanisms, a higher rate of secretion of the estrone precursor, androstenedione, and a higher rate of conversion of androstenedione to estrone. Obesity may alter routes of metabolism of androgens and estrogens. The excretion of specific urinary metabolites can therefore be altered by obesity alone. Thus, steroid indices of relative cancer risk or responsiveness must be constructed with due attention to obesity, one of many important variables. (+info)