Comparison of Interphase and Prophase in Isolated Rat Liver Nuclei

Abstract

IT has often been found that isolated interphase nuclei can be made granular or homogeneous artificially by alteration of the composition of the medium in which they are suspended^1–3; and there is an obvious possibility that this is related to the condensed and decondensed states of chromosomes in prophase and interphase respectively, that is, that the change from interphase to prophase is merely a ‘granulation’ produced by a change in physical properties of the cell sap. The only apparent difference is that artificial granularity in isolated interphase nuclei is of finer texture, that is, the granules are smaller and probably more numerous (though difficult to count) than the chromosomes in natural prophase. A simple explanation of the difference in texture could be based on analogy with crystallization, for example, of proteins, where in some cases fine texture results from too rapid change in the medium. We therefore tried to ‘crystallize’ chromosomes in isolated interphase nuclei by changing the medium continuously over periods up to a few hours, by dialysis or by drop-wise additions with gentle stirring.