The investigation of chromatin-bound lipids, particularly free and esterified cholesterol, will be continued from the standpoint of amounts present in normal rats, after cholesterol feeding for varying periods of time, after starvation, bile duct ligation or cannulation, etc. The rate of appearance of exogenous cholesterol in the chromatin-bound fraction will be determined by administering labeled cholesterol. Tissues other than liver will also be examined for purposes of comparison. The possible contamination of the chromatin will be studied by EM, by assays of membrane enzymes. Studies on the role of receptor proteins in the cytoplasm capable of binding cholesterol and carrying it into the nucleus will be continued. The role of phospholipids bound to chromatin will be investigated using approaches similar to those used for cholesterol.