Section on Physiological Controls, Laboratory of Biomedical Sciences, and Section on Developmental Pharmacology, Neonatal and Pediatric Medicine Branch, National Institute of Child Health and Human Development; and Section on Biochemical Mechanisms, Laboratory of Chemistry, and Section on Intermediary Metabolism, Laboratory of Biochemistry and Metabolism, National Institute of Arthritis, Metabolism, and Digestive Diseases, National Institutes of Health, Bethesda, Maryland 20014

Section on Physiological Controls, Laboratory of Biomedical Sciences, and Section on Developmental Pharmacology, Neonatal and Pediatric Medicine Branch, National Institute of Child Health and Human Development; and Section on Biochemical Mechanisms, Laboratory of Chemistry, and Section on Intermediary Metabolism, Laboratory of Biochemistry and Metabolism, National Institute of Arthritis, Metabolism, and Digestive Diseases, National Institutes of Health, Bethesda, Maryland 20014

Section on Physiological Controls, Laboratory of Biomedical Sciences, and Section on Developmental Pharmacology, Neonatal and Pediatric Medicine Branch, National Institute of Child Health and Human Development; and Section on Biochemical Mechanisms, Laboratory of Chemistry, and Section on Intermediary Metabolism, Laboratory of Biochemistry and Metabolism, National Institute of Arthritis, Metabolism, and Digestive Diseases, National Institutes of Health, Bethesda, Maryland 20014

Section on Physiological Controls, Laboratory of Biomedical Sciences, and Section on Developmental Pharmacology, Neonatal and Pediatric Medicine Branch, National Institute of Child Health and Human Development; and Section on Biochemical Mechanisms, Laboratory of Chemistry, and Section on Intermediary Metabolism, Laboratory of Biochemistry and Metabolism, National Institute of Arthritis, Metabolism, and Digestive Diseases, National Institutes of Health, Bethesda, Maryland 20014

Section on Physiological Controls, Laboratory of Biomedical Sciences, and Section on Developmental Pharmacology, Neonatal and Pediatric Medicine Branch, National Institute of Child Health and Human Development; and Section on Biochemical Mechanisms, Laboratory of Chemistry, and Section on Intermediary Metabolism, Laboratory of Biochemistry and Metabolism, National Institute of Arthritis, Metabolism, and Digestive Diseases, National Institutes of Health, Bethesda, Maryland 20014

Section on Physiological Controls, Laboratory of Biomedical Sciences, and Section on Developmental Pharmacology, Neonatal and Pediatric Medicine Branch, National Institute of Child Health and Human Development; and Section on Biochemical Mechanisms, Laboratory of Chemistry, and Section on Intermediary Metabolism, Laboratory of Biochemistry and Metabolism, National Institute of Arthritis, Metabolism, and Digestive Diseases, National Institutes of Health, Bethesda, Maryland 20014