The purpose of this study is to investigate the biochemical basis of and mechanism for maturation and stabilization of surfactant function in the developing rabbit and human fetus and newborn, and to apply the information to human clinical examples. The developmental patterns of the enzymes for the synthesis and for the hydrolysis of the surfactant phospholipids are being studied. Synthesis of surfactant in diabetic models (both streptozotocin and hyperglycemic) in rabbits is being evaluated. The alveolar geometry scanning (EM), surface characteristics, and surfactant phospholipid components are being correlated in the rabbit. Further studies will be done on the production and requirements of surfactant postnatally, especially in infants with RDS, and correlating these in infants with RDS and PDA. A special study also is being done correlating phospholipids, premature labor, and perinatal infection.