Brain glucose utilization in undernourished rats

Changes in brain temperature and free amino acids in normal and protein deprived suckling rats exposed to room temperature

Previous reports on early-induced protein-calorie malnutrition (PCM) in rats have indicated alterations in the concentration of free amino acids and of protein synthesis in the brain. Recently it was shown that early-induced protein deprivation (PD) retards the development of thermoregulation. This resulted in a failure to maintain a normal rectal temperature after short exposure to room temperature (+22 degrees C) still at the age of 20-25 days corresponding to changes seen in normal rats at an age of 10-15 days. In the present study, 20-day old PD and normal rats where examined with regard to the effect of exposure to room temperature on brain temperature and on brain free amino acids. The results show a similar reduction in brain and rectal temperature of the PD rats occurring within 30 minutes after exposure to room temperature. The reduction was in the range of 5 degrees C. PD rats kept in room temperature for 5 hours and then allowed to recover at 32.5 degrees C showed a slow increase in brain and rectal temperature but normal temperatures were not reached even after 1 hour. The concentration of free amino acids in the brain was examined in rats kept for 1 hour at room temperature or at 32.5 degrees C. In the PD rats kept at 32.5 degrees C, free aspartate and glutamate were reduced whereas taurine, GABA and glycine were increased as compared to their corresponding control rats. As a result of the reduced brain temperature in PD rats exposed to room temperature there was a reduction in free asparagine.(ABSTRACT TRUNCATED AT 250 WORDS)

Functional development of the visual system in normal and protein deprived rats. I. Persistent changes in light-induced cortical evoked response

During an investigation focused on development of visual evoked responses (VER) in normal and protein deprived rats indications of persisting latency differences were found. Since such differences are in variance with previous reports special attention was paid to compare control and protein deprived adult rats. Protein deprivation was induced by feeding rats a diet with 50% reduction in protein content compared with control rat diet from two weeks before onset of gestation until examination. Dependence on experimental variables of latencies and complexity of the VER illustrated the need of a well defined experimental situation. Adult protein deprived rats showed significantly longer latencies to onset and to the first three peaks of the VER and an altered complexity of the response. It is suggested that the observed alterations result from effects of the protein deprivation on early brain development since this and previous studies have shown similar alterations in developing young rats. The divergence in findings between the present and previous reports may be explained by differences in degree of malnutrition and in other experimental conditions.

The influence of protein deprivation during development on amino acid incorporation into cerebral proteins

The incorporation of 3H-valine into protein of cerebrum, liver, and muscle was studied in rats fed a low protein diet. Animals, 15-50 days old, were used to cover the period during and after the most rapid phase of cerebral protein synthesis. The precursor was administered in doses resulting in brain concentrations of free valine in the 0.1-0.3 mM range. Two series of experiments were run and the injected dose varied for comparison of protein synthesis at different concentrations of precursor valine. By concomitant amino-acid analysis it was shown that the concentration of other amino-acids in the brain was not changed by the injected valine. The changes in the amino-acid pool with age in control rats were in agreement with previous findings. Only small alterations were seen in the amino acid pool as an effect of protein deprivation, the results being consistent with those of some previous reports. Uptake of valine into the brain appeared to be decreased only in 15-17-day-old protein-deprived rats. Valine incorporation into cerebral protein was decreased in the youngest age group but no effect was seen in older animals. Liver protein incorporation was slightly decreased by low protein diet but a marked reduction was observed for muscle protein. The changes in brain protein synthesis during normal development were in agreement with previous studies and differed qualitatively from those in liver and muscle.