Effects of hypoglycemia on rat brain polyribosome sedimentation pattern.

Insulin-induced hypoglycemia provokes polyribosome disaggregation and accumulation of monomeric ribosomes in the brain of rats with hypoglycemic paresis and coma. The extent of brain polyribosome disaggregation depends on the decrease of blood glucose concentration, and in comatose animals on the duration of hypoglycemia. Cycloheximide prevents the disaggregation of brain polyribosomes induced by hypoglycemia, indicating that hypoglycemia affects brain protein synthesis, decreasing the rate of initiation relative to the rate of elongation of polypeptide chain synthesis.

Effects of cadmium on mouse liver polyribosome function.

The distribution of ribosomes between their various functional states (native subunits, unprogrammed ribosomes, monoribosomes and polyribosomes) was analyzed in livers of cadmium-treated (CdCl2, 20 umol/kg, l h) and control mice. The ribosomes with double-labelled RNA were separated by sucrose density-gradient centrifugation in zonal rotor, and monomeric ribosome fraction was subsequently isolated and analyzed by selective dissociation of unprogrammed ribosomes. The analysis shows that the increase in monomeric ribosomes, occurring during polyribosome disaggregation in livers of cadmium-treated mice, entirely due to the increase of the unprogrammed ribosome fraction at the expense of polyribosomes.

Effects of mercury bichloride on mouse kidney polyribosome structure and function.

Polyribosome sedimentation pattern and their in vitro protein synthetic ability were investigated in kidneys of mice treated with a single injection of HgCl2. Mercury bichloride, after 1 h, evokes polyribosome disaggregation, the extent of which is logarithmically correlated with the dose in the range of 2.5-20 micromoles/kg.