DISCRIMINATION OF THE NUCLEOLUS BY A CRITICAL ELECTROLYTE CONCENTRATION METHOD

A new technique for the visualization of the nucleolus based on a vari ant of the previously reported critical electrolyte concentration meth od for nucleoprotein complexes is proposed. The method consists of tre ating toluidine blue-stained preparations with Mg2+ ions in a concentr ation such that ribonucleoprotein complexes are metachromatically high lighted, while DNA-protein complexes attain their critical electrolyte concentration point, thus losing metachromasy. The technique, which i s applicable to plant and animal cells, is proposed for studies involv ing identification, morphometry and eventually changes in substructure of the nucleolus at the light microscopy level.