{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2023,10,13]],"date-time":"2023-10-13T11:56:16Z","timestamp":1697198176600},"reference-count":50,"publisher":"The Endocrine Society","issue":"9","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2000,9,1]]},"abstract":"<jats:title>Abstract<\/jats:title>\n               <jats:p>Androstenedione treatment of pregnant monkeys at 0.8 of gestation reproduces endocrine, biophysical, and biochemical changes similar to those measured during spontaneous, term labor in the pregnant monkey. In the pregnant baboon, the spontaneous onset of labor at term has been attributed to a forward shift in the nocturnal estradiol surge relative to that of progesterone in maternal plasma. This study investigated whether androstenedione treatment of the pregnant baboon at 0.7\u20130.8 of gestation promotes a premature forward shift in the nocturnal surge of maternal plasma estradiol relative to progesterone and whether this shift is associated with premature increases in nocturnal myometrial activity. Eight pregnant baboons were prepared surgically under general anesthesia with vascular catheters and myometrial electromyogram electrodes between 121 and 139 days of gestation (term is ca. 185 days). Catheters were maintained patent by continuous infusion of heparinized saline from the time of surgery until one of two treatments began following at least 9 days of postoperative recovery. In four baboons (Group I), the saline administration was replaced by a continuous infusion of 10% intralipid vehicle during Day 1 of the experimental protocol. During Day 2 and Day 3, the intralipid infusion was switched for a continuous infusion of androstenedione dissolved in intralipid set at a low (0.8 mg\u00b7kg\u22121\u00b7h\u22121) and at a high (1.6 mg\u00b7kg\u22121\u00b7h\u22121) dose, each delivered for 24 h. The other four pregnant baboons (Group II) received 10% intralipid vehicle for Days 1, 2, and 3 of the experimental protocol. One baboon from Group I received an additional dose of 0.4 mg\u00b7kg\u22121\u00b7h\u22121 for 24 h before the low and the high dose of androstenedione. In each baboon, during each experimental day, maternal arterial blood samples (1 ml) were taken at 1 h intervals for 12 h, starting 3 h before the onset of darkness in the animal\u2019s environment, for measurement of maternal plasma estradiol and progesterone concentrations via RIA. Myometrial contractions were counted during each night-time period of the experimental protocol. All pregnant baboons demonstrated increases in maternal plasma estradiol and progesterone concentrations at night-time. Androstenedione had a dose-dependent effect in elevating day-time maternal plasma estradiol concentrations and in promoting a forward shift in the nocturnal surge of maternal plasma estradiol without affecting the nocturnal progesterone profile in maternal plasma. Maternal treatment with androstenedione also led to an increase in nocturnal myometrial contraction activity. We conclude that androstenedione treatment of the pregnant baboon at 0.7\u20130.8 of gestation promotes a premature forward shift in the nocturnal estradiol surge relative to that of progesterone in maternal plasma and that this shift is associated with an increase in nocturnal myometrial contraction activity, in a similar way to that measured during spontaneous onset of labor at term in this species.<\/jats:p>","DOI":"10.1210\/endo.141.9.7677","type":"journal-article","created":{"date-parts":[[2014,1,8]],"date-time":"2014-01-08T16:11:02Z","timestamp":1389197462000},"page":"3296-3303","source":"Crossref","is-referenced-by-count":3,"title":["Androstenedione Treatment of Pregnant Baboons at 0.7\u20130.8 of Gestation Promotes a Premature Forward Shift in the Nocturnal Maternal Plasma Estradiol Surge Relative to Progesterone and Increases Myometrial Contraction Activity*"],"prefix":"10.1210","volume":"141","author":[{"given":"Dino A.","family":"Giussani","sequence":"first","affiliation":[{"name":"The Physiological Laboratory (D.A.G.), University of Cambridge, Downing Street, Cambridge CB2 3EG, United Kingdom"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Susan L.","family":"Jenkins","sequence":"additional","affiliation":[{"name":"Laboratory for Pregnancy & Newborn Research (S.L.J., J.A.W., J.D.T., P.W.N.), College of Veterinary Medicine, Cornell University, Ithaca, New York 14853-6401"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"James A.","family":"Winter","sequence":"additional","affiliation":[{"name":"Laboratory for Pregnancy & Newborn Research (S.L.J., J.A.W., J.D.T., P.W.N.), College of Veterinary Medicine, Cornell University, Ithaca, New York 14853-6401"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jennifer D.","family":"Tame","sequence":"additional","affiliation":[{"name":"Laboratory for Pregnancy & Newborn Research (S.L.J., J.A.W., J.D.T., P.W.N.), College of Veterinary Medicine, Cornell University, Ithaca, New York 14853-6401"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Peter W.","family":"Nathanielsz","sequence":"additional","affiliation":[{"name":"Laboratory for Pregnancy & Newborn Research (S.L.J., J.A.W., J.D.T., P.W.N.), College of Veterinary Medicine, Cornell University, Ithaca, New York 14853-6401"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"80","reference":[{"key":"2020071622355667500_R1","doi-asserted-by":"crossref","first-page":"208","DOI":"10.1038\/229208a0","article-title":"Sharp increase in free circulating oestrogens immediately before parturition in sheep.","volume":"229","author":"Challis","year":"1971","journal-title":"Nature"},{"key":"2020071622355667500_R2","first-page":"111","article-title":"The mechanism of initiation of parturition in the ewe.","volume":"29","author":"Liggins","year":"1973","journal-title":"Recent Prog Horm Res"},{"key":"2020071622355667500_R3","first-page":"66","volume-title":"Fetal Endocrinology.","author":"Novy","year":"1981"},{"key":"2020071622355667500_R4","doi-asserted-by":"crossref","first-page":"629","DOI":"10.1210\/jcem-58-4-629","article-title":"Daily hormonal changes in the maternal, fetal, and amniotic fluid compartments before parturition in a primate species.","volume":"58","author":"Walsh","year":"1984","journal-title":"J Clin Endocrinol Metab"},{"key":"2020071622355667500_R5","doi-asserted-by":"crossref","first-page":"1487","DOI":"10.1016\/S0002-9378(12)90790-5","article-title":"Foward shift in the initiation of the nocturnal estradiol surge in the pregnant babon: is this the genesis of labor?","volume":"165","author":"Wilson","year":"1991","journal-title":"Am J Obstet Gynecol"},{"key":"2020071622355667500_R6","doi-asserted-by":"crossref","first-page":"247","DOI":"10.1095\/biolreprod18.2.247","article-title":"Serum estradiol in mid and late gestation and estradiol\/progesterone ratio in baboons near parturition.","volume":"18","author":"Albrecht","year":"1978","journal-title":"Biol Reprod"},{"key":"2020071622355667500_R7","first-page":"533","article-title":"Endocrine functions of the human fetus and placenta.","volume":"53","author":"Dieczfalusy","year":"1974","journal-title":"Am J Obstet Gynecol"},{"key":"2020071622355667500_R8","doi-asserted-by":"crossref","first-page":"52","DOI":"10.1016\/S0146-0005(95)80047-6","article-title":"Control of human parturition.","volume":"19","author":"Olson","year":"1995","journal-title":"Semin Perinatol"},{"key":"2020071622355667500_R9","doi-asserted-by":"crossref","first-page":"1095","DOI":"10.1016\/0002-9378(72)90185-8","article-title":"Plasma estrone, estradiol, estriol, progesterone and 17-hydroxy-progesterone in human pregnancy. 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