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To investigate the possible role of melatonin in the regulation of the human menstrual cycle, the circadian pattern of melatonin was determined in the follicular and luteal phases of 10 normal women. Four-hourly sampling was used to derive a melatonin index which described the total exposure to melatonin for 24 h. This sampling procedure adequately(More)
Granulosa cells, aspirated from the follicles of patients undergoing treatment for in-vitro fertilization, were cultured in serum-supplemented medium. Adrenaline and noradrenaline stimulated a dose-related increase in progesterone secretion with a maximum stimulation at 10(-5) M, a response that was prevented by the beta-antagonist, propranolol. Adrenaline(More)
Melatonin, at concentrations and periods of exposure reflecting those present during the circadian cycle, was investigated for its influence on steroid production by granulosa cells cultured in serum-supplemented medium. At high (200 pg/ml) but not low (20 pg/ml) physiological concentrations, melatonin significantly stimulated progesterone production by(More)
The ability of melatonin to stimulate luteal steroidogenesis directly in the ewe was investigated by using a perfusion cannula system in vivo and luteinised granulosa cells in vitro. Exposure to human chorionic gonodotrophin (hCG) or ovine luteinising hormone (oLH), as positive controls, significantly stimulated progesterone secretion by the perfused corpus(More)
Although recent data for several species of primate, including human and marmoset, indicate that the corpus luteum secretes high levels of radioimmunoassayable inhibin, the nature of the immunoreactive (ir) inhibin detected has not been established. In this study, plasma ir-inhibin levels during the ovarian cycle of the marmoset (n = 12 animals) were(More)
It is well documented that prostaglandin F2 alpha (PGF2 alpha) inhibits progesterone production in luteal cells, but its mode of action is uncertain. It has recently been suggested that PGF2 alpha acts by activating the calcium and phospholipid-dependent protein kinase, protein kinase C (PKC). This hypothesis has been tested by comparing the site and mode(More)
Genes for chorionic gonadotrophin (CG) are transcribed by the 16-cell embryo stage in humans, but there is no clear evidence of CG secretion as a bioactive dimer before attachment and trophoblast outgrowth stages of implantation. The studies summarized question the timing of CG expression and secretion, the possible roles of CG for intraembryonic(More)
During the peri-implantation period of pregnancy in primates, chorionic gonadotrophin (CG) is the first clear signal of the embryo's presence and viability. In the marmoset (Callithrix jacchus) implantation begins on Day 11-12 after ovulation and CG is secreted by the embryo from this time. The inner cell mass is necessary for the normal secretion of CG by(More)
The effect of prolonged exposure to exogenous melatonin on the reproductive status and growth rate of ewe lambs was investigated. Ewe lambs (born late March) were given intravaginal melatonin implants on 4 July (group J, n = 10) during anoestrus, or 20 December (group D, n = 10) during the breeding season. A third group (group C, n = 7) received empty(More)