Fluorescent staining of nuclei and amyloid substance. Two useful properties of p-phenylenediamine.

Mounting immunofluorescent slides in an oxidized solution of p-phenylenediamine in 90% glycerol, resulted in brown fluorescent staining of nuclei. This contrasts well with the fluorescence of fluorescein and rhodamine conjugates and facilitates excellent morphological localization of antigens. The antifading effect of p-phenylenediamine is maintained in this oxidized solution. In addition, amyloid substance gives a bright yellow-orange fluorescence with this medium. This method of staining is more sensitive and less time consuming than the usual methods for amyloid. Alternative techniques to keep the antifading effect without either nuclear or amyloid counterstain (for identification of nuclear antigens), or to show up amyloid deposits without nuclear counterstain (for small amyloid deposits) are described.