Glycemia, ketonemia, and brain enzymes of ketone body utilization in suckling and adult rats undernourished from intrauterine life

Differentiation dependent activation of the myelin genes in purified oligodendrocytes is highly resistant to hypoglycemia

We have previously demonstrated that the developmental upregulation of myelin-specific genes in mixed glial cultures is strongly attenuated by hypoglycemia. The present study was designed to evaluate the effect of hypoglycemia on differentiation-dependent upregulation of myelin genes in purified oligodendrocyte cultures. The expression of major myelin protein genes, i.e., proteolipid protein (PLP), basic protein (BP) and myelin associated glycoprotein (MAG) were monitored by Northern blot analysis. In control cultures maintained at 6 mg/ml of glucose, the expression of all the genes upregulated rapidly, and plateaued at approximately day 4. A similar pattern of differentiation-dependent upregulation was observed for the gene encoding a lipogenic enzyme, i.e., malic enzyme (ME). In contrast to mixed glial cultures, however, this developmental gene upregulation was not significantly affected by severe hypoglycemia (approximately 0.02 mg/ml). The results indicate that the effect of glucose deprivation on oligodendrocyte genes observed in mixed glial cultures is mediated by other cells. The upregulation of the genes in differentiating oligodendrocytes was accompanied by the production of myelin-related membrane that was isolated by density gradient fractionation. In contrast to the effect on gene expression, this anabolic activity was highly dependent on glucose, as seen from a profound suppression by severe hypoglycemia.

Undernutrition and Postnatal Development of Brain Oxidative Metabolism in Limbic Structures: A Quantitative Study

The effects of food restriction during gestation, lactation and post-weaning were studied in rat brain structures (14,21 and 30 days). Oxidative metabolism was quantified in neurons from the anterior thalamus and mammillary bodies using a quantitative histochemical method for cytochrome c oxidase (CO). In all the rat brains studied, a significant increase in activity occurred in the control group from 14 to 21 days after birth which then remained constant up to 30 days. A similar pattern was observed in the undernourished group, although in the anterodorsal and anteromedial thalamic nuclei the rise in CO only occurred between day 14 and 30 and there were no significant age-related changes in the lateral mammillary nucleus. Undernutrition produced a significant drop in CO activity after 21 days in all the nuclei except the lateral mammillary nucleus. In the latter nucleus and also in the pars medialis of the medial mammillary nucleus this parameter decreased at 30 days. Our results suggest that undernutrition and nutritional rehabilitation have different effects on the diencephalic regions studied, which depends on age and region.