QUATERNARY AMMONIUM COMPOUNDS IN CONNECTIVE TISSUE HISTOCHEMISTRY: I. SELECTIVE UNBLOCKING

Certain features of an accepted biochemical system for fractionating biological polyanions were adapted for more precise identification of acid mucopolysaccharides in histological preparations. Tissue studies were based on two major steps: (1) complete blocking of all polyanions by a quaternary ammonium detergent and (2) selective unblocking by increasing concentrations of an electrolyte. Critical stages were visualized by suitable stains for acid mucopolysaccharides. Results with tissues and certain polyanion models showed that both acid mucopolysaccharide and nucleic acid structures behaved histochemically, under proper conditions, as predicted from the biochemical reactions of such polyanions as hyaluronic acid, chondroitin sulfate, heparin, deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). Chemical fixation involving formaldehyde seriously altered the expected positions of nucleic acid structures in the unblocking sequence; this was corrected by use of cetylpyridinium chloride in the fixing solution. Considering the biochemical background of these methods and several different histochemical applications already accomplished, numerous possibilities are open for extending the fundamental and practical uses of quaternary ammonium compounds in microscopic studies.