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Biomedical subjects

W B Currie

Publications and source records attributed to W B Currie.

At least 55 records · Page 3Linked to original sources
PubMed1978

The effect of passive immunization against estradiol on the regulatory profile and character of labor in the rat.

Treatment of pregnant rats with antiestradiol (A-E2) serum twice a day, starting at 2100 hours on day 19, sharply increased circulating total estradiol (E2) above control values and drastically reduced the biologically active E2 unbound (E2U) to A-E2 in plasma and uterine tissue. This A-E2-induced and--sustained E2U deficiency was not accompanied by similar changes in plasma and tissue progesterone (P), since P decreased similarly in the control and A-E2--treated rats in preparation for parturition. However, in the A-E2 rats the reduction in E2U was accompanied by a small, though significant, decrease in uterine vein prostaglandin F (PGF) during labor. This A-E2--provoked regulatory imbalance significantly altered normal parturition. In comparison with controls, labor in the A-E2 rats was delayed and prolonged by extended intervals between deliveries of individual fetuses of the same litter. The delay in the onset of labor significantly increased the birth weights of the newborn rats. Whether E2U deficiency is directly responsible for the asynchronic myometrial activity that delays and prolongs labor or whether it is mediated by reduced PGF release remains to be determined.

Animals↗
PubMed1977

Caprine placental lactogen: levels of prolactin-like and growth hormone-like activities in the circulation of pregnant goats determined by radioreceptor assays.

Radioreceptor assays for prolactin-like (lactogenic) activity and growth hormone (GH)-like activity have been used to study concentrations of caprine placental lactogen (PL) in the circulation during pregnancy. Both lactogenic and GH-like activities from less than 100 ng/ml (ovine prolactin- and human GH-equivalents) about 60 days after mating to reach peak levels (400-1600 ng/ml) between days 110 and 130 of pregnancy. The levels of both activities increased in essentially the same fashion but during the last 15 days of pregnancy, lactogenic activity declined less than GH-like activity. This divergence was most pronounced at parturition when levels of lactogenic activity increased (approximately 700 ng/ml) despite very low (less than 200 ng/ml) levels of GH-like activity being measured and this probably reflected increased secretion of pituitary prolactin near parturition. When serum from a pregnant goat or a simple alkaline extract of placental cotyledons was fractioned on a column packed with Sephadex G-100, lactogenic and GH-like activities eluted together with distribution coefficients of approximately 0-5-0-6. The possibility that caprine PL serves physiologically as a luteotrophin and/or mammotrophin during pregnancy in goats is discussed.

Animals↗
PubMed1977

Parturition in goats: studies on the interactions between the foetus, placenta, prostaglandin F and progesterone before parturition, at term or at parturition induced prematurely by corticotrophin infusion of the foetus.

Relationships between foetal corticosteroid concentrations, utero-ovarian prostaglandin F (PGF) and maternal peripheral progesterone have been examined in detail in goats shortly before spontaneous parturition at term. Foetal corticosteroids increased during the last 13-11 days of gestation and particularly sharply during the last 3 days and even during advanced labour. About 24 h before parturition, acute releases of PGF were evident in the vein draining the pregnant uterine horn, and these corresponded closely to the time of luteal regression. Further release of PGF occured when progesterone declined to low levels, probably reflecting in the course of labour. The changes observed before premature parturition, induced by infusing ACTH into foetal goats, were similar except for the more rapid increase in foetal corticosteoid concentrations. Immature neonates born after ACTH treatment were viable, placental delivery was normal and lactogenesis occurred in the mothers indicating that the treatment promoted full expression of the critical perinatal events. The early, acute releases of PGF were ipsilateral to the ACTH-infused foetus and were luteolytic provided the corpora lutea were also on that side. Luteolysis failed or was abnormally delayed if the corpora lutea were contralateral and prolonged ACTH treatment of the foetuses in such cases caused foetal death probably because of premature failure of the placenta. Similar findings were noted if ACTH infusion of the foetus was accompanied by simultaneous progesterone treatment of the mothers in order block the induction of labour. It was suggested that placental changes occurring during foetal hypercortisolism might be caused by increased placental oestrogen synthesis and the effect of this on the foeto-maternal junction along with a stimulatory action on PG synthesis in the maternal placenta. Experimental disruption of the normal sequence of events, when labour was blocked by progesterone, proved to be lethal to the foetus if the loss of placental integrity progressed sufficiently. The chain of regulatory signals linking increased activity of the foetal adrenal with parturition thus appears to involve stimulation of oestrogen biosynthesis, PGF release from the maternal placenta and the start of physical changes at the placental junction. Provided the foetus and corpora lutea are ipsilateral, the early releases of PGF effect luteolysis and a withdrawal of progesterone from the maternal circulation. When progesterone concentrations are sufficiently low, labour is initiated and its progress reflected by further release of PGF. The control mechanisms, which also provide for the final maturation of the foetus, clearly enable a close synchronization of the various perinatal events which are essential for the transition from foetal to postnatal life.

Adrenal Cortex Hormones↗
PubMed1976

Release of prostaglandin F, regression of corpora lutea and induction of premature parturition in goats treated with estradiol-17beta.

Premature parturition was induced in five pregnant goats infused intravenously with 4.65-8.4 mg estradiol-17beta but not in one treated with 5.85 mg estradiol-17alpha. A single intramuscular injection of 12 mg estradiol benzoate (8.8 mg estradiol-17beta equivalents) was also effective. These doses were estimated to provide plasma concentrations of estradiol-17beta in the physiological range for animals at sponteneous parturition. Circulating plasma concentrations of progesterone decreased and lactogenesis occurred before all instances of induced parturition but no such changes resulted from infusion of estradiol-17alpha. Placental delivery was normal in all animals but neonates of more than 10 days prematurity were non-viable.

Animals↗
PubMed1975

Secretion rate of prostaglandin F during induced labor in goats.

Relationships between plasma flow and plasma concentrations of prostaglandin F were examined in the utero-ovarian veins of three pregnant goats. Plasma flow, measured by veno-arterial dilution of para-Aminohippurate in two goats, was unchanged or increased slightly when PGF concentrations were elvated by short-term infusions of PGF2alpha into a uterine vein. Utero-ovarian plasma flow was measured during labor in two goats. Flow doubled during advanced labor and then decreased sharply to very low rates during the terminal expulsive phase of stage II labor. A total of 8.3 and 9.5 mg PGF was released into the utero-ovarian vein of two goats during the last 6 hours before fetal delivery and maximal release rates of approximately 100 ug. min-1 were obtained some 5-10 minutes before delivery was completed. The highest plasma concentrations of PGF were detected immediately after completion of fetal delivery when utero-ovarian plasma flows were lowest.

Adrenocorticotropic Hormone↗