Cycloheximide-induced ultrastructural changes in hepatocyte nuclei in partially hepatectomized rats.

Nearly all the chromatin in regenerating rat hepatocytes appears to decondensed form 24 h after partial hepatectomy. When cycloheximide (CXM) is administered to partially hepatectomized rats, a marked condensation of chromatin occurs; 4 h after administration the quantity of condensed chromatin present is much higher than that found in the hepatocytes of sham-operated, untreated rats. No segregation or fragmentation of the nucleolus were, however, observed; this shows that the condensation of chromatin is not by itself sufficient to induce the segregation and fragmentation of the nucleolus. The mechanism governing CMX-induced chromatin condensation in regenerating hepatocytes is discussed.