Comparative Physiologic Studies in Chronically Catheterized Sheep and Guinea Pigs: A. Studies in sheep include fetal carbohydrate and amino acid metabolism during maternal fasting and during a graded reduction in uterine flow. The measurements include umbilical uptake of carbohydrates and amino acids as well as turnover rates of glucose and lactate. Placental metabolism in vivo during fasting will be studied. The rate of protein synthesis and protein turnover in the early fetus and in individual fetal organs will be studied. The role of ammonia production by the placenta on fetal nitrogen balance in early fetal development, & the urea production rate will be studied. The role of estrogen binding sites in the regulation of uterine blood flow will be evaluated. B. Studies in the guinea pig include the development of techniques permitting studies of maternal and fetal metabolism under chronic unstressed conditions. The turnover rates of substrates in the pregnant animal at different gestational ages coupled with measurements of substrate flow to the uterus will be made. The latter will be compared 1) with total accretion of calories, carbon and nitrogen in the fetuses and uterus, and 2) with the turnover rate of these same compounds in the mother. Uterine blood flow will be studied noting variability of flow within litters and its relationship to the rate of protein synthesis. Developmental Immunology: The development of lymphocyte control mechanisms will be studied in fetal and newborn sheep in order to establish their timing and to investigate environmental stimuli which could influence them. CLINICAL STUDIES: The pharmacokinetics of furosemide and aminoglycosides in newborn infants and their relationship to hearing loss will be evaluated, as will the relationship of bilirubin concentrations to hearing loss. Fetal/placental weight ratios will be studied in relationship to neonatal mortality and morbidity, and to several metabolic characteristics of the placenta in vitro. The diagnosis and management of intracranial hemorrhage and the role of galactose in neonatal nutrition will also be investigated.