Diurnal variations in plasma arginine vasotocin (AVT) concentrations in the ovine fetus.

Previously we have demonstrated the presence of AVT in the blood of fetal sheep. The source is not clear, but AVT has been identified in fetal pineal and pituitary glands. In view of the circadian secretory pattern of the pineal gland, we questioned whether fetal plasma AVT levels might vary diurnally.

Catecholamine physiology in the ovine fetus. I. Gestational age variation in basal plasma concentrations.

Fifty-five ewes with chronically catheterized singleton gestations were studied to assess changes in basal concentrations of fetal catecholamines with increasing gestational age. All pregnancies were time dated, and measurements of catecholamines were conducted at least 5 days after placement of fetal catheters when fetal metabolic parameters had normalized. Plasma concentrations of catecholamines were measured by radioenzymatic assay.

Fetal catecholamine release in response to labor and delivery.

Umbilical arterial plasma norepinephrine and epinephrine were measured using a sensitive, specific radioenzymatic assay. Plasma catecholamines were correlated with umbilical arterial blood gases, durations of the first and second stages of labor, duration of rupture of the membranes, fetal heart rate tracings, and fetal sex. Significant correlations were observed for plasma norepinephrine versus fetal pH and PO2 and plasma epinephrine versus pH but not PO2.

Developmental changes in pituitary-thyroid function in the human fetus and newborn.

Maturation of the hypothalamic pituitary thyroid axis as reflected in cord serum thyroid hormone concentrations was assessed in premature and full term infants born between 26 and 43 weeks gestation. Measurements of thyroxine (T4), free T4 (FT4), thyrotropin (TSH) and thyroxine binding globulin (TBG) in cord sera were correlated with gestational age, sex and birthweight and compared to similar measurements in well two month old infants and adults. There were significant increases in T4, FT4, and TBG with increasing gestational age (GA) between 26 and 33-35 weeks (P less than 0.

Characterization of the daily oxytocin rhythm in primate cerebrospinal fluid.

The circadian characteristics of the daily rhythm in oxytocin (OT) concentrations in cerebrospinal fluid (CSF) were studied in the rhesus monkey. Monkeys subjected to constant light or constant dark for periods of 3 to 6 days manifested persistence of the CSF OT rhythm. A 12-hr phase shift in the light-dark cycle resulted in a resynchronization of the rhythm to the new lighting schedule within 3 to 4 days.