Changes in the nuclear acidic proteins and chromatin structure in starved and refed Tetrahymena

Abstract

The amount of phenol-soluble nuclear acidic proteins and morphological changes in the nuclear chromatin of the ciliate Tetrahymena pyriformis GL-C were studied following synchronization of the organism by starvation and refeeding. Electron microscopy of starved cells revealed spherical chromatin bodies with rather distinct boundaries. Shortly after refeeding, granular material appeared around the periphery of the chromatin bodies while there was a three-fold increase in the nuclear acidic proteins and a 50% decrease in cellular and nuclear volume. Following this, the chromatin bodies became smaller, more irregular in shape and appeared to radiate more fibrillar material. Additionally, after the initial decrease the nuclear and cellular volumes increased. The changes in nuclear volume and morphology as well as content of nuclear acidic proteins are correlated with previously described changes in the cellular events that lead to genomic activation, DNA synthesis and cell division in this and other eukaryotic cells.