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Search for other papers by R. M. LIPTRAP in
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SUMMARY
Corticotrophin (ACTH), hydrocortisone or prednisolone trimethylacetate were administered daily to sows from 24 hr. before oestrus or from day 14 of the cycle until the end of oestrus. Treatment beginning on day 14 delayed the peak in urinary oestrogen excretion normally seen, postponed the onset of oestrus by 1–3 days and shortened the duration of oestrus. Treatment begun before oestrus did not appear to alter the pattern of oestrogen excretion but shortened the duration of oestrus. Administration of ACTH, but not that of corticosteroids, also interfered with ovulation.
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SUMMARY
Human chorionic gonadotrophin (HCG) was given to patients at mid-cycle before the endogenous LH surge. Graafian follicles were aspirated 32–33 h later, before ovulation was expected, and the levels of several steroids in follicular fluid and in matching serum samples were measured by radioimmunoassay. Two types of Graafian follicle were identified at laparoscopy, based on the nature of the oocyte, granulosa cells and follicular fluid withdrawn from the follicles. Some were large, preovulatory and presumably becoming luteinized while others were generally smaller, non-ovulatory and still growing.
The concentrations of dehydroepiandrosterone (DHEA) and 17α-hydroxypregnenolone (Δ5 intermediates), androstenedione and testosterone were higher in non-ovulatory follicles, whereas large follicles usually contained high levels of progesterone, 17α-hydroxyprogesterone, pregnenolone and oestradiol-17β. A cluster analysis of these data grouped follicles into two distinct clusters, which accorded with their identification as ovulatory or non-ovulatory at laparoscopy.
Levels of progesterone, 17α-hydroxyprogesterone and oestradiol-17β in follicular fluid were high in preovulatory follicles in comparison with plasma. Results in two patients indicated that plasma levels of these steroids were determined by the preovulatory follicle. Levels of plasma Δ5 steroids were closer to follicular fluid concentrations, whereas DHEA was higher in plasma.
The role of the theca and granulosa is discussed in relation to the synthesis of progesterone and oestradiol-17β in follicles as ovulation approaches.
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SUMMARY
The induction of ovulation and follicular luteinization in the guinea-pig by follicle-stimulating (FSH) and luteinizing (LH) hormones was studied in the intact and in the hypophysectomized animal. Follicular luteinization could be produced as early as day 8 of the oestrous cycle by 250 mu. FSH, but not before day 10 by 400 mu. LH, while either FSH or LH caused ovulation when given on day 12 or later. When injected on day 13, luteinization could be induced with 62·5 mu. FSH or 200 mu. LH. Luteinization of follicles also occurred when 400 mu. LH or 250 mu. FSH was given immediately after hypophysectomy on day 13, but when hormone treatment was delayed for 4·5 h after surgery the incidence of luteinization was greatly reduced. Combined treatment with 200 mu. LH and 125 mu. FSH, by contrast, readily caused luteinization. It is concluded that ovarian follicles are resistant to luteinization during the first half of the oestrous cycle and that the response to LH late in the cycle is dependent upon the maintenance of follicular responsiveness by endogenous gonadotrophin.
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SUMMARY
In the guinea-pig, when bilateral oestrogen implants were placed in the medial basal hypothalamus, anterior hypothalamus or suprachiasmatic area on day 10 of the oestrous cycle, ovarian changes indicative of gonadotrophin secretion were observed on day 15. Similarly located cholesterol implants and oestrogen implants outside this region were without effect. The gonadotrophin release was likely to have been induced by an action of the steroid at the hypothalamic, rather than the pituitary level, since bilateral implants of oestrogen in the pars distalis caused ovarian activation in only one out of eight animals. Signs of normal ovulation were evident in only three out of 19 animals in which oestrogen was implanted in the medial basal hypothalamus on day 10 and left in place for 10 days. The ovaries of some other animals bore the traces of luteal bodies formed in response to the initial exposure to oestrogen; other ovaries contained only large healthy or atretic follicles and spontaneous ovulation was apparently blocked. It is concluded that exposure of the hypothalamo-hypophysial system of the guinea-pig to an increased amount of oestrogen initially stimulates and then inhibits ovulatory gonadotrophin secretion. Tonic gonadotrophin secretion is unaffected.
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SUMMARY
Superovulation can be induced in the immature rat by PMS alone or PMS followed by HCG. Treatment with PMS alone caused an initial average response of 2·8 ova at an age of 20 days and a maximum average response of 70·8 ova at age 28. Treatment with PMS and HCG resulted in an initial average response of 0·3 ova at age 18 days and an average maximum of 61 ova at 22 days of age. A marked drop to approximately 8–10 ova was noted at 45 days of age following both types of treatment. Hypophysectomy revealed that the pituitary gland was necessary for the release of ova following injection of PMS alone. Removal of the pituitary gland as late as 52 hr. after injection of PMS prevented ovulation. Inhibition of ovulation by treatment with dibenamine, SKF-501, atropine and 'Nembutal' following injection of PMS alone led to the concept that superovulation following PMS involves a neural link that is responsible for the endogenous release of LH.
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ABSTRACT
The mechanisms responsible for the 24-h difference in the time of the next ovulation after litter removal between early and late lactating rats were investigated.
At 11.00 h on day 5 of lactation, concentrations of oestradiol-17β and inhibin activity in ovarian venous plasma were lower than those on day 17, corresponding to the absence of healthy Graafian follicles. After removal of the litter on day 5 of lactation a small surge of FSH with a steady increase in basal levels of LH occurred to initiate follicular maturation, and ovulation occurred 4 days later. After removal of the litter on day 17 of lactation a surge of FSH was not observed, due to high levels of inhibin activity in ovarian venous plasma, until the time of preovulatory surges of gonadotrophin which occurred 2 days later and resulted in ovulation the next morning. Prolactin concentrations decreased similarly in both groups abruptly after removal of the litter. A decrease in plasma concentrations of progesterone occurred 42 h after removal of the litter on day 5, though it occurred 18 h after removal of the litter on day 17.
These results indicate that the 24-h delay of ovulation after litter removal on day 5 of lactation, as compared with the time of ovulation after litter removal on day 17, is due probably to the absence of healthy antral follicles and high activity of corpora lutea secreting progesterone at the time of litter removal.
J. Endocr. (1987) 113, 271–276
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SUMMARY
Seasonal variation in the ovulation rate and incidence of ovulation was examined in 15 Romanov and 15 Solognote ewes by endoscopy. The ovulation rate of the Romanovs was found to be related to the incidence of ovulation (r = 0·78) and to the incidence of oestrus as measured by daily teasing with aproned entire rams (r = 0·83). The ovulation rate of the Romanovs was greater than that of the Solognotes, and was 2·6 and 1·1 corpora lutea in the two breeds, respectively, in the autumn. The durations of the breeding season and of oestrus of the Romanovs exceeded those of the Solognotes.
The characteristics of the preovulatory discharge of luteinizing hormone (LH) and the daily plasma LH levels were studied by radioimmunoassay in the Romanov and Solognote ewes and in ewes of the Berrichon and Berrichon × Romanov breeds. The interval between the onset of oestrus and the discharge of LH was greater in the Romanovs (17·6 h) than in the other breeds (mean = 7·5 h). The total release of LH, however, was not related to the number of corpora lutea formed.
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Department of Anatomy, Louisiana State University Medical Center, New Orleans, Louisiana 70112, U.S.A.
(Received 12 April 1977)
It is known that a functional interaction exists between the adrenal and ovarian systems, albeit complex and not well understood. Removal of progesterone derived from the adrenal gland disrupts the synchronous discharge of luteinizing hormone (LH) and consequently the events associated with reproduction (Mann, Korowitz & Barraclough, 1975). Adrenalectomy of female rats also delays the onset of puberty, disrupts the normal oestrous cycle and decreases the number of ova shed and the size of the litter (Ramaley, 1974). Previously we reported that unilaterally ovariectomized rats which had been bilaterally adrenalectomized for 30 days did not, after one oestrous cycle, show compensatory ovulation or ovarian hypertrophy; rats adrenalectomized and ovariectomized for 30 days did, however, display both phenomena (Peppler & Jacobs, 1976). While continuing these studies on adrenal gland–ovary interrelationships, we collected data which
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SUMMARY
An assay method depending on the induction of ovulation in immature mice has been applied to the assay of human urinary gonadotrophin, human chorionic gonadotrophin, pregnant mare serum gonadotrophin, and sheep and rat pituitary gonadotrophins. Valid parallel line assays were obtained in all cases, and the sensitivity and precision of the assay were such as to make it suitable for application to clinical studies.
Experiments with mixtures of gonadotrophins, and the use of a barbiturate to suppress gonadotrophin secretion, indicate that the assay was not specific for LH. It is suggested that the lack of specificity may be due in part to the secretion of a variable amount of gonadotrophin by the pituitaries of the test animals.
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Abstract
In the first experiment, mature female Wistar rats, displaying a regular 4-day oestrous cycle, were killed in succession every 2 or 3 h on the day of pro-oestrus and oestrus until the time of ovulation. In the second experiment, immature female Wistar rats (aged 24 days) were injected s.c. with 30 IU pregnant mare serum gonadotrophin (PMSG) and 56 h later with 20 IU human chorionic gonadotrophin (hCG). They were killed in groups at 0, 24, 48, 56 and 57 h, and then every 2 h until 72 h. Excised ovaries were homogenized and analysed for steroid content or they were submitted to a routine histological procedure. The cyclic and PMSG/hCG-treated rats exhibited some similarities and differences in the general pattern of steroid content. Either a presumptive endogenous LH surge or administration of hCG resulted in an increase in the ovarian androgen concentration which preceded a rise in progesterone; the progesterone peak, in turn, was accompanied by a fall in the amount of androgens and oestradiol. However, in comparison with cyclic rats, superovulated animals displayed a significantly higher ovarian androgen level for a prolonged period; ovarian oestradiol concentration was also raised while the progesterone content was much lower. Histological analysis revealed large differences between the ovaries of superovulated and cyclic rats, especially with regard to the maturing follicles. The majority of PMSG/hCG-derived follicles showed hypertrophied theca interna and degenerated or luteinized granulosa. A large number of preovulatory follicles did not ovulate. These results clearly indicate that PMSG/hCGinduced follicles are not equal to the follicles developing during a normal oestrous cycle. This should be taken into consideration when using superovulated animals in experiments.
Journal of Endocrinology (1994) 141, 91–100
