Histochemical localization of galactose-containing glycoconjugate at peripheral nodes of Ranvier in the rat

Lectin-horseradish peroxidase conjugates were used to study glycoconjugates in paraffin sections of dorsal roots of the rat spinal cord. Griffonia simplicifolia-B4 isolectin (GSA I-B4) and peanut agglutinin (PNA) stained strongly the nodes of Ranvier, localizing, respectively, terminal alpha- and beta-D-galactose. Sialidase digestion did not increase staining with PNA at the node of Ranvier, suggesting the presence of a neutral glycoconjugate. Staining of the nodal but not the internodal axolemma was observed with PNA. The outer surface of the myelin sheath in axons of the dorsal root stained strongly with GSA I-B4 but only weakly with PNA, demonstrating an abundance of terminal alpha-galactose. PNA staining was enhanced in this site by sialidase digestion, showing terminal sialic acid-beta-galactose dimers. The presence of sialic acid here was further evidenced by labeling of these membranes with the lectin derived from the slug, Limax flavus (LFA). Affinity for a high iron diamine-Alcian blue (pH 2.5) sequence demonstrated, in addition, the presence of sulfate esters in glycoconjugates on the outer myelin membrane. GSA I-B4 imparted strong reactivity to nonmyelinated fibers in the dorsal root and the spinal nerve. The present findings appear to reflect several localizations of biochemically described nervous system glycoproteins containing O-glycosidically linked side chains terminated by alpha- and beta-D-galactose.