Basic Fuchsin as A Nuclear Stain

Five distinct nuclear stains and staining procedures which utilize basic fuchsin as the dye have been studied, compared and tested on a Feulgen-weak fungus, Blastomyces dermatitidis, and other fungi.Aqueous basic fuchsin has been shown to be an excellent, though impermanent, stain with which to study the nuclei of this and other fungi. The conditions under which formaldehyde acts as a mordant for basic fuchsin and produces a permanent nuclear stain have been established.Comparison of crystal violet and basic fuchsin suggests that the mordanting action of the aldehyde operates through the para-amino groups of the dye. Certain other basic dyes were not mordanted by formaldehyde.Gentle acid hydrolysis of the tissues has been found to be essential both to the specificity of the dye as a nuclear stain and to the mordanting effect of the aldehyde.The possible relationship of these observations to the Feulgen reaction is discussed. A protocol for the method developed is presented.