Gallocyanin-Chrome Alum: II. Histochemistry and Specificity

Abstract

Paraffin sections 6-8 μ thick of cat and albino rat spinal cord fixed in CaCl₂-formalin or plain formalin were stained with Einarson's 1932 preparation of gallocyanin-chrome alum for 12-15 hr after the following procedures: methylation, deamination, the Wiley reaction, iodine treatment, 10% perchloric acid and combinations of these procedures. A comparison was made between gallocyanin-chrome alum and the chrome alum lakes of certain other oxazine dyes and hematoxylin. Tests for protein concentrations at the sites where gallocyanin-chrome alum ordinarily stains consisted of histochemical reactions for carboxyls, amino groups, tyrosine and histidine. Methylation, deamination, and the Wiley reaction as well as perchloric acid treatment decreased the staining of gallocyanin-chrome alum. We were unable to abolish staining completely with any combination of blocking reactions. Other dyes mordanted with chrome alum did not exhibit limited progressive staining like gallocyanin but stained in a nonspecific manner. Protein concentrations were demonstrated at all sites of gallocyanin-chrome alum staining. It was concluded that gallocyanin-chrome alum is an excellent nuclear stain for routine use because of its limited progressivity but that it can not be considered specific for any substance.