RICHARD-ALLAN SCIENTIFIC COMPANY 88023 Epredia

Modified Grocott’s Methenamine Silver Stain Kit (Chromic Acid) is intended for use as an aid to identify fungal organisms and basement membranes in tissue sections for the diagnosis of general pathology specimens. Fungal cell walls are rich in polysaccharides known as glucans. Treatment with either periodic acid or chromic acid oxidizes these polysaccharides to form aldehyde groups; however, chromic acid is the stronger oxidizer. Chromic acid will achieve a greater degree of oxidation, rendering some chemical groups non-reactive with silver so that they are not demonstrated within the final stain. This greater level of oxidation also results in reduced background staining of basement membranes and collagen fibers, as well as more effective demonstration of Pneumocystis jiroveci (formerly classified as Pneumocystis carinii) and Histoplasma capsulatum (the causative organism of Histoplasmosis). After oxidation, Sodium Metabisulfite Solution removes residual Chromic Acid Solution from the tissue. The aldehyde groups react with the silver ions present in the Working Methenamine Silver Solution and reduce them to form visible metallic silver. Gold Chloride Solution tones the sections and intensifies the reduced silver by forming a silver-gold complex. Sodium Thiosulfate Solution removes any unreduced silver from the tissue sections, followed by Fast Green Stain Solution which produces a light green background to further enhance contrast.