The transplacental supply of nutrients is interrupted at birth, which diverts maternal metabolism to lactation. After birth, energy homeostasis is rapidly regained through milk nutrients which supply the newborn with the fatty acids and ketone bodies required for neonatal development. However, immediately after birth and before the onset of suckling there is a time lapse in which the newborn undergoes a unique kind of starvation. During this period glucose is scarce and ketone bodies are not available owing to the delay in ketogenesis. Under these circumstances, the newborn is supplied with another metabolic fuel, lactate, which is utilized as a source of energy and carbon skeletons. Neonatal rat lung, heart, liver and brain utilize lactate for energy production and lipogenesis. Lactate is also utilized by the brain of human babies with type I glycogenosis. Both rat neurons and astrocytes in primary culture actively use lactate as an oxidizable substrate and as a precursor of phospholipids and sterols. Lactate oxidation is enhanced by dichloroacetate, an inhibitor of the pyruvate dehydrogenase kinase in neurons but not in astrocytes, suggesting that the pyruvate dehydrogenase is regulated differently in each type of cell. Despite the low activity of this enzyme in newborn brain, pyruvate decarboxylation is the main fate of glucose in both neurons and astrocytes. The occurrence of a yeast-like pyruvate decarboxylase activity in neonatal brain may explain these results.
The concentrations of the major metabolites for nitrogen excretion and/or transport in maternal and fetal blood and amniotic fluid during the last 2 days of gestation were investigated. Alanine, glutamine, ammonia and allantoin accumulated in amniotic fluid during late gestation. Urea concentrations increased in amniotic fluid though only during the last day of gestation, suggesting that urea is taken up by the mother through the amniotic membranes. Glutamate did not accumulate in amniotic fluid during late gestation although high concentrations of it were found in fetal blood in the same circumstances, suggesting the occurrence of a mechanism for preventing fetal glutamate disposal.
The MN blood group distribution has been determined in 3,100 inhabitants from practically all Spain (Iberian peninsula and Canary Islands). The mean values of the relative MN frequencies are: M = 23.42%, N = 22.48%; MN = 54.10%. These frequencies are evidently within the European population range.
The effect of experimental hypoxia on blood glutamine, glutamate, urea, ammonia, allantoin, hypoxanthine, xanthine, urate, orotate and lactate concentrations and on PO2, PCO2 and, pH m term delivered newborn rats during the first 4 h after delivery were studied. Hypoxia increased blood glutamine, glutamate, allantoin and ‘xanthines’ (hypoxanthine + xanthine + uric acid) concentrations but decreased blood urea and ammonia concentrations. These results suggest that hypoxia inhibited ureogenesis by decreasing the ammonia available for urea synthesis.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.