The use of propidium iodide in cytochemical studies of interphase chromatin structure

Different cytochemical conditions of using Propidium Iodide, a phenanthridinic fluorochrome specific for double-stranded nucleic acids, have been considered to study some structural aspects of the interphasic chromatin. Some molecular properties of the dye allow to define the structure of chromatin fibre (degree of condensation) by means of thermal denaturation of DNA, fluorochromization after extraction of different chromatin components and fluorochromization in condition of low dye-substrate molar ratio (relative unsaturation of DNA). Different biological situations such as cell specialization, neoplastic transformation and life cycles have been examined choosing some typical models (hepatocytes, nucleated erythrocytes, lymphocytes, endometrial cells).