p-Phenylenediamine: An Adjunct to and a Substitute for Osmium Tetroxide

Abstract

p-Phenylenediamine (PPD) has been used to retard photobleaching in fluorescence microscopy, to increase the intensity of osmium staining , and to improve lipid preservation . Phend et al. used PPD to improve post-embedding immunolocalization in epoxy-embedded specimens; more recently, Brorson et al. recommended including 1% (wt/vol) PPD in all dehydration steps for post-embedding immunolocalization. Experience with a number of animal tissues and microorganisms has resulted in the following protocol, which has been used to improve post-embedding immunolocalization in specimens embedded in either epoxy resins or acrylic resins such as LR White and LR Gold.