The basic objective of this study is to determine what effect dietary restriction has on the transfer of genetic information throughout the life span of male Fischer F344 rats. At six weeks of age, the rats were placed on two dietary regimens. The rats are fed a synthetic diet either ad libitum or sixty percent of ad libitum. The translational and transcriptional activities of liver and kidney tissues from the rats on the two dietary regimens are assessed by measuring the incorporation of (3H)-valine and (3H)-orotic acid into acid-insoluble material by isolated hepatocytes and isolated kidney cells prepared by in situ collagenase perfustion. The translational activities of the brain and testes from these rats are determined by measuring the cell-free incorporation of (3H)-valine into acid-insoluble material by the post-mitochondrial supernatant obtained from these two tissues. In addition, several other investigators are studying additional biological processes in varous tissues from the rats on the two dietary regimens. the effect of dietary restriction on heart mitochondria is determined by measuring the numerical density of mitochondria from samples of heart tissue and the rate of respiration by isolated heart mitochondria. The immune response and skeletal muscle cellularity also are measured in these two groups of rats.