The newborn mammalian brain of several species has been shown to have a lower average rate of energy metabolism and a narrower range of rates in its various components than is found in maturity. In a further study of cerebral energy metabolism during development, we have employed the [14C]deoxyglucose method for measuring local cerebral glucose utilization in fetal and neonatal sheep. After establishing the lumped constant to be 0.40 and finding the rate constants for the kinetic behavior of deoxyglucose in plasma and brain to be close to those in other species, we measured the rates of glucose utilization in 44 regions of the brain. The rates were low and homogeneous in midgestation, except for those of brain stem nuclei of the auditory and vestibular systems and those of the hippocampus which were relatively high. In the last 7 wk, local rates rose approximately threefold. After birth there was a further average increase of 50% above full-term levels. The study shows that cerebral energy metabolism rises in most structures during prenatal maturation, a time when sensory stimulation is at a relatively low level and behavioral responses are minimal.

No abstract

Prostaglandin D2 (PGD2) is a powerful antiaggregatory agent and contracts various types of smooth muscle preparations, including isolated canine and bovine pulmonary vessels. Pulmonary vascular responses of anesthetized fetal and adult goats and newborn lambs to PGD2 were evaluated in situ by means of an isolated perfused lower left lobe preparation. These experiments indicate that PGD2 is a pulmonary vasodilator in fetal goats, both a pulmonary vasodilator and vasoconstrictor in newborn lambs depending on the dose used, and a pulmonary vasoconstrictor in adult goats. Evidence is presented of an age-related change in pulmonary vascular response to prostaglandins. The responses of the pulmonary vasculature are dose dependent; however, there is not a significant dose-dependent relationship for systemic arterial pressure or heart rate with intrapulmonary infusions of PGD2. The inhibition of prostaglandin synthesis potentiates the pulmonary response to PGD2 in fetal goats. In contrast with other prostaglandins, PGI2, PGE2, and PGE1, which dilate both the fetal pulmonary and systemic circulations, PGD2 has minimal action on the systemic circulation over a wide range of doses.

Summary Thirteen chronically catheterized pregnant sheep were given intravenous infusions of 10 per cent ethyl alcohol in 5 per cent dextrose solution (15 ml/kg over two hours). Samples of blood from maternal femoral artery, uterine vein, and fetal brachiocephalic artery were drawn at hourly intervals before, during and after the infusions. Plasma was analyzed for alcohol concentration, protein concentration, haematocrit, PCO2 and pH. Maternal and fetal arterial blood pressures were monitored continuously. There were no significant differences between maternal and fetal arterial blood alcohol levels at any sampling interval nor was there any difference in elimination constants. Alcohol infusion did not produce any significant change in plasma protein concentration, haematocrit, PCO2 and pH, and mean arterial blood pressure in either mother or fetus. However, both maternal and fetal heart rate increased significantly following alcohol infusion.