MECHANISMS FOR THE MAINTENANCE OF LIFE IN THE NEWBORN DURING ANOXIAl

In a previous publication the extraordinary tolerance of the newborn of various species to anoxia was described (1). Mature animals succumb after breathing undiluted nitrogen for approximately 3 minutes while the average values for newborn animals are: rats, 50 minutes; cats, 25 minutes; dogs, 23 minutes; rabbits, 17 minutes; and guinea pigs, 7 minutes. Various factors permitting this prolonged survival were discussed. These include a, degree of development at the time of birth, i.e., the guinea pig is more advanced than the rat; b, rate of cerebral metabolism which is lower in the infant than in the adult, and c, anaerobic sources of energy. The last of these factors is the subject of the present investigation. It is well established that the process of glycolysis may afford energy. The anaerobic breakdown of carbohydrate with a release of energy occurs in the series of transformations; glucose phosphate --+ triose phosphate + phosphoglyceric acid -+ pyruvic acid -+ lactic acid. These changes are ininhibited by fluoride at phosphoglyceric acid and by iodoacetate at triose phosphate. IYIETH~D. As in the previous study, animals were placed in a jar in which nitrogen was substituted for air. Sodium iodoacetate, 0.18 mgm. per gram or sodium fluoride, 0.5 mgm. per gram, was injected subcutaneously. Both the carbohydrat,e stores and the level of the blood sugar were altered in different experiments, hypoglycemia being induced by the injection of insulin and hyperglycemia by the intraperitoneal injection of glucose. The lactic acid contents of the brain and of the whole animal were determined before and after exposure to nitrogen. Some of the animals were injected with iodoacetate and others served as controls. To stop glycolysis the isolated head or whole body was rapidly frozen in dry ice and ether. The frozen material was then triturated in a solution of 2 per cent iodoacetate and the lactic acid contents of the tissues and t/he suspending fluid were estimated by the method of Friedemann, Cotonio and Shaffer (2). In order to dissociate t,he effects on brain from those on other organs, newborn