Cytological analysis of the effect of treatments visualizing the chromosome core on non-histone nuclear proteins

A silver-stainable chromatid core is visualized under the light microscope on human leukocyte chromosomes by treating fixed chromosomes with 2M NaCl.An aminoacid which is not part of histone composition, 3H-tryptophan, is used to label the synthesis and location of non-histone proteins and to study the effect on these proteins of treatment with 2M NaCl and 0.2N HCl to visualize the core. 2M NaCl is shown to remove from nuclei and chromosomes an appreciable fraction of acid proteins, as well as all those synthesized during the two hours preceding the metaphase. 3H-Try labelling seems to preferentially affect only one chromatid per chromosome. The silver-stainable halocs appearing around numerous nuclei after treatment with 2M NaCl and 0.2N HCl are found to be labelled by 3H-Try and not by 3H-TdR.