Survival role of locally produced acetylcholine in the bovine corpus luteum.

The present study was conducted to explore the source of acetylcholine (ACH) in the corpus luteum (CL) and to test our hypothesis of an antiapoptotic role of ACH in the bovine CL and, further, to investigate whether nerve growth factor (NGF), insulin-like growth factor 1 (IGF1), and transforming growth factor beta1 (TGFB1) influence the expression of choline acetyltransferase (CHAT), the biosynthetic enzyme of ACH, in cultured bovine luteal cells. Protein expression and immunolocalization of CHAT were carried out at different stages throughout the luteal phase and in cultured luteal and endothelial cells. ACH was measured in luteal tissue at the different luteal stages and in luteal cells cultured for 8 and 24 h. Cell viability and TUNEL assays were performed on cultured midluteal cells treated with or without tumor necrosis factor alpha (TNF)/interferon gamma (IFNG) in the presence of ACH and its muscarinic (atropine) and nicotinic (mecamylamine) receptor antagonists. The CL was devoid of cholinergic nerve fibers. CHAT immunostaining was evident in luteal, endothelial, and stromal cells in luteal tissue sections and in cultured luteal and endothelial cells. CHAT protein was expressed throughout the cycle without any significant changes. ACH concentration in luteal tissue was not changed during the luteal stages but increased over time and with increased cell numbers in luteal cell cultures. ACH increased cell viability and prevented cell death induced by TNF/IFNG. Atropine significantly attenuated ACH action, whereas mecamylamine had no effect. TNF/IFNG treatment downregulated CHAT expression, whereas NGF, IGF1, and TGFB1 upregulated CHAT expression, in cultured luteal cells. The overall findings strongly suggest a nonneural source and antiapoptotic role of ACH in the bovine CL. Locally produced ACH appears to be regulated by NGF, IGF1, and TGFB1.

The absence of corpus luteum formation alters the endocrine profile and affects follicular development during the first follicular wave in cattle.

We previously established a bovine experimental model showing that the corpus luteum (CL) does not appear following aspiration of the preovulatory follicle before the onset of LH surge. Using this model, the present study aimed to determine the profile of follicular development and the endocrinological environment in the absence of CL with variable nadir circulating progesterone (P(4)) concentrations during the oestrous cycle in cattle. Luteolysis was induced in heifers and cows and they were assigned either to have the dominant follicle aspirated (CL-absent) or ovulation induced (CL-present). Ultrasound scanning to observe the diameter of each follicle and blood collection was performed from the day of follicular aspiration or ovulation and continued for 6 days. The CL-absent cattle maintained nadir circulating P(4) throughout the experimental period and showed a similar diameter between the largest and second largest follicle, resulting in co-dominant follicles. Oestradiol (E(2)) concentrations were greater in the CL-absent cows than in the CL-present cows at day -1, day 1 and day 2 from follicular deviation. The CL-absent cows had a higher basal concentration, area under the curve (AUC), pulse amplitude and pulse frequency of LH than the CL-present cows. After follicular deviation, the CL-absent cows showed a greater basal concentration, AUC and pulse amplitude of growth hormone (GH) than the CL-present cows. These results suggest that the absence of CL accompanying nadir circulating P(4) induces an enhancement of LH pulses, which involves the growth of the co-dominant follicles. Our results also suggest that circulating levels of P(4) and E(2) affect pulsatile GH secretion in cattle.

[Physiology of ovulation and mode of action of contraceptive pills]. / Physiologie de l'ovulation et mode d'action de la contraception.

Follicular ovulation occurs at most 400 times in a woman's lifetime. This process involves enzymatic destruction of the cells surrounding the oocytes, called cumulus oophorus. The three different partners in order to obtain normal ovulation are the oocytes, the mature follicle containing adequate LH receptors and the hormones, especially progesterone and the preovulatory LH surge. Contraceptive pills available so far contain ethynyl estradiol, in order to regulate bleedings. The different progestins in the contraceptive pill exert an antigonadotropic effect and therefore inhibit follicular recruitment. As third generation progestins exert a stronger antigonadotropic effect than previous progestins, the dose of ethynyl estradiol has been lowered in the past 50 years.

Neuroendocrinology briefings 12: The maternal brain.

The mother's brain is prepared by the hormones of pregnancy to show the strong maternal feelings that ensure the newborn is cared for. These hormones induce a cascade of changes in the brain, reducing stress reactions, evoking maternal behaviour and preparing the neuroendocrine circuits that drive the birth process and ensure that the suckling infant gets milk. The nerve cells that make oxytocin are involved in all of these aspects of motherhood, and details are emerging of how their performance is adapted by pregnancy.

The role of luteal steroid hormones in the regulation of the estrous cycle of high fecundity Olkuska sheep.

The study was undertaken to investigate the steroid hormone production by sheep luteal cells. Corpora lutea were collected from 30 Olkuska sheep on Days 3, 6, 9, 12 and 15 of the estrous cycle during the reproductive season. In Experiment 1, steroid hormone concentration was estimated in extracts of CL. In Experiment 2, luteal cells were cultured in vitro for 24 h. Luteal cells isolated on Days 9 and 12 secreted high amounts of progesterone and androgens but smaller amounts of estradiol. Concentration of these steroids in CL extracts collected on the same days showed the same trend. In CL harvested on Day 15, a decrease in androgens and progesterone as well as a significant increase in estradiol were observed in culture media and in extracts. Judging from the high amounts of estradiol and low amounts of androgen observed at the end of the luteal phase, we speculate that the steroid hormones secreted by the regressing CL may play an active role in the regulation of the estrous cycle in the Olkuska sheep with autocrine influence on the luteal activity or a possible paracrine action on follicular growth. In the third Experiment, the possibility of heterogeneity in the multiple corpora lutea population of prolific Olkuska sheep was investigated. Differences were found in the level of progesterone and estradiol secretion by individual corpora lutea recovered from the same animal, which also varied in terms of weight. This is the first study which shows the existence of intra-ovarian and individual heterogeneity between corpora lutea recovered from ewes during the normal estrous cycle.

[Aids in the management of pathological pregnancies. Advances in current knowledge of corpus luteum function]. / Hjälp vid handläggning av patologiska graviditeter. Ny kunskap om gulkroppens funktion.

Technological advances during the past decade have yielded new knowledge of luteal function and its regulation. A number of new substances with luteotrophic and lutcolytic properties have been identified in the corpus luteum, and the picture which emerges of the mechanisms responsible for physiological luteolysis is becoming increasingly complex. As luteal function/regulation during the menstrual cycle in the absence of pregnancy differs both from that in normal pregnancy, and from that in pathological pregnancy, these advances in our knowledge should prove clinically useful, particularly with regard to the early diagnosis and management of pathological pregnancy.

[Physiopathology of the menopause]. / Physiopathologie de la ménopause.

The menopause constitutes a considerable physiological alteration for the woman. The pre-menopausal period is essentially marked by luteal failure. The actual menopause, which coincides with the cessation of menstruation, corresponds to disturbance of the hypothalamo-hypophyseo-ovarian axis, of which the most dramatic manifestations are hot flushes and psychiatric disturbances. The post-menopausal period may be marked by peripheral and metabolic disorders.

Ovarian follicular and luteal physiology.

Follicular maturation and development is a complex process of interrelated intra- and extraovarian events that ultimately lead to ovulation of a mature oocyte and transformation of the ruptured follicle into a corpus luteum. The primordial follicle consists of an immature oocyte arrested in the dictyate stage of meiosis, surrounded by a single layer of relatively undifferentiated granulosa cells. The oocyte remains in the immature state because of many factors, one of which is the oocyte maturation inhibitor (OMI) secreted by granulosa cells. The oocyte subsequently increases in size, and as the antrum forms it becomes surrounded by cumulus cells. The cumulus cells may be intimately involved in the action of O,I to arrest the oocyte in the immature state within the follicle, as well as the resumption of meiosis during the LH surge. The compartments of the follicle that change most dramatically during follicular maturation are the cells lining the follicle--the granulosa and thecal cells. Under the influence of estrogen and FSH, the granulosa cells proliferate and also acquire FSH receptors. At this time, the thecal compartment differentiates and surrounds the granulosa cells, but remains separated from them by a basement membrane. Steroid secretion by the antral follicle involves the interplay of androgens, estrogens, and progestins. Both the granulosa and thecal cell compartments contribute to follicular fluid and serum levels of steroids; the interaction of both cell types may be necessary for estrogen and progesterone secretion in some species. As a consequence of the presence of an elevated number of FSH receptors, the granulosa cells of the small antral follicle are able to respond to FSH in many ways, including increased cyclic AMP accumulation, activation of the aromatase system, and induction of LH receptors, which permits the granulosa cells to later respond to LH. The mechanism by which thecal cells acquire their LH receptors is presently unknown. The granulosa cells of the follicle may indirectly control their own maturation and the number of follicles maturing through the secretion of follicular inhibin, which decreases the pituitary output of FSH. Even though the granulosa cells have acquired large numbers of LH receptors, they are prevented from luteinizing prematurely by factors in follicular fluid, including estrogen and a luteinizing inhibitor (LI). As serum LH levels increase during the preovulatory LH surge, a number of events occur: resumption of oocyte meiosis, transformation of the steroid enzyme complex from estrogen to progesterone secretion, follicular rupture, and formation of the corpus luteum. Granulosa cells form the bulk of the corpus luteum, which secretes elevated amounts of progesterone for a fixed time period depending on the species. Before ovulation the preovulatory follicle must be exposed to and respond to adequate LH and FSH levels in order for the eventual corpus luteum to secrete elevated amounts of progesterone for its normal lifespan...

Hormonal regulation of intraocular pressure.

A detailed review of the hormonal effects on intraocular pressure is presented. There is evidence that corticotropin, vasopressin, thyroxin, insulin, glucocorticoids and mineralocorticoids may play a role in the physiologic regulation of intraocular pressure. Growth hormone, melanocyte stimulating hormone, progesterone, estrogen, chorionic gonadotropin and relaxin may influence intraocular pressure when administered in pharmacologic doses. Whether the key to understanding primary open-angle glaucoma lies in recognizing abnormal endocrine mechanisms, especially involving glucocorticoids, remains unclear at the present time.