Abstract
Central nervous system and peripheral nerve myelin were studied with lipid and polysaccharide staining reactions, used in conjunction with enzyme digestions and solvent extractions. The colloidal iron (ferriphilic) and acridine orange reactions of myelin appeared to be due to an acidic sphingolipid (sphingomyelin and/or sulfatide). Acetone and trypsin unmasked the ferriphilic substance in fixed myelin, whereas phospholipase A increased the ferriphilia and acridine orange fluorescence of unfixed myelin. Both reactions were extinguished in fixed and unfixed myelin by preliminary extraction with choloroform-methanol. Trypsin removed considerably more lipids from unfixed than fixed myelin; it removed more cholesterol and less sphingomyelin than other lipids of fixed myelin. From these observations a model is presented of the intermolecular relationships between lipids and trypsin-resistant/trypsin-sensitive proteins in the myelin sheath.