We studied the effect of an acute 4-h period of hyperinsulinemia (H) on net utilization rates (AAUR(net)) of 21 amino acids (AA) in 17 studies performed in 13 late-gestation fetal sheep by use of a novel fetal hyperinsulinemic-euglycemic-euaminoacidemic clamp. During H [84 +/- 12 (SE) microU/ml H, 15 +/- 2 microU/ml control (C), P < 0. 00001], euglycemia was maintained by glucose clamp (19 +/- ...

Ontogenic changes in baseline and 24-h rhythms of fetal arterial blood pressure (FABP) and heart rate (FHR) and their regulation by the fetal adrenal were studied in 18 fetal sheep chronically instrumented at 109-114 days gestation (GA). In the long-term study, FABP and FHR were continuously recorded from 120 days GA to spontaneous term labor (>145 days GA) in five animals. Peak times (PT) and ...

High levels of circulating catecholamines are found in the fetus, and fetal stress and birth induce a marked surge in catecholamine secretion. Little is known about the role of catecholamines on the fetal pulmonary circulation. To determine the effects of catecholamines on the pulmonary vascular tone, we tested the hemodynamic response to norepinephrine and dopamine infusion in chronically prep...

OBJECTIVE Four days of hypoxia produce an extensive fetal polyuria with little change in amniotic fluid volume in the ovine fetus. We hypothesized that fetal swallowing and intramembranous absorption would increase with prolonged hypoxia to offset the polyuria. STUDY DESIGN After a 24-hour normoxic period, nine ovine fetuses were subjected to 4 days of hypoxia induced by lowering maternal ins...

By late gestation, the maturing hypothalamo-pituitary-adrenal (HPA) axis aids the fetus in responding to stress. Hypoxia represents a significant threat to the fetus accompanying situations such as preeclampsia, smoking, high altitude, and preterm labor. We developed a model of high-altitude (3,820 m), long-term hypoxia (LTH) in pregnant sheep. We describe the impact of LTH on the fetal HPA axi...

Although vascular endothelial growth factor (VEGF) plays a vital role in lung vascular growth in the embryo, its role in maintaining endothelial function and modulating vascular structure during late fetal life has not been studied. We hypothesized that impaired lung VEGF signaling causes pulmonary hypertension, endothelial dysfunction, and structural remodeling before birth. To determine wheth...

Information on the effects of injury on neovascularization in the immature brain is limited. We investigated the effects of ischemia on cerebral cortex neovascularization after the exposure of fetuses to 30 minutes of cerebral ischemia followed by 48 hours of reperfusion (I/R-48), 30 minutes of cerebral ischemia followed by 72 hours of reperfusion (I/R-72), or sham control treatment (Non-I/R). ...

This study was designed to test the hypothesis that long-term hypoxia (LTH) increases fetal plasma leptin and fetal adipose or placental leptin expression and alters hypothalamic and adrenocortical leptin receptor (OB-R) expression. Pregnant ewes were maintained at high altitude (3,820 m) from day 30 to approximately 130 days of gestation. Reduced Po2 was maintained in the laboratory by nitroge...

To determine the role of the renal nerves on renin secretion and expression in the mature ovine fetus, we performed bilateral renal denervation on eight fetuses of time-dated pregnant ewes (126.8 +/- 0.6 days gestation) and compared renin in them to seven fetuses that underwent sham denervation (126.7 +/- 0.6 days gestation). Fetal arterial and venous catheters were implanted, and after 5-7 day...