Abstract
The cationic carbocyanine dye l-ethyl-2-[3-(l-ethylnaphtho[l,2d]thiazolin-2-ylidene)-2-methylprolpenyl]-naphtho[1, 2d]thiazolium bromide stains several classes of macromolecules differentially in histologic sections. Most proteins are red at pH 4.3 and pink or unstained at pH 2.8. The caseins are blue at pH 4.3 and unstained at pH 2.8. Nuclei stain purple, mast cells stain red-purple, cartilage stains purple and mucoproteins stain blue-green at both hydrogen ion concentrations. The nature of some of the macromolecules involved in these color reactions has been determined by the use of chemical and enzymatic procedures and by staining films of glycosaminoglycuronoglycans, proteins and conjugated proteins. The method requires less than 1 hr staining time for most tissues; the stain is stable when kept in the dark and has the advantage of distinguishing several macromolecules in tissues simultaneously. The simplicity of the method and the ability to discriminate classes of macromolecules in tissues should make this stain valuable in pathologic diagnosis.