Lectin cytochemical evaluation of somatosensory neurons and their peripheral and central processes in rat and man

Summary Paraffin sections of the trigeminal nerve root of the rat, and human spinal nerve root and trigeminal ganglion were stained with a battery of lectin-horseradish peroxidase conjugates to localize and characterize glycoconjugate (GC) in situ. In the rat the myelin sheath of the peripheral segment contained GC with sialic acid most probably linked to the penultinate disaccharide galactose(1 4)-N-acetylglucosamine (Gal(1 )-GlcNAc), and complex type N-glycosidic side chains. The myelin sheath in the central segment differed in containing little if any of the GC named above and in containing GC with terminal -Gal linked to N-acetylgalactosamine (GalNAc), terminal GalNAc and fucose. Schwann cells stained for GC with GlcNAc or mannose whereas oligodendroglia stained for GC with the terminal disaccharide Gal-(1 3)-GalNAc and N-glycosidic side chains, especially in presumed Golgi zones, but also in processes continued as the outer myelin sheath. The human myelin sheath in the central segment differed from that of the rat in not staining with lectins specific for fucose and terminal GalNAc. Sialic acid and terminal -Gal were seen in the human central segment but these sugars appeared to bind to astroglial structures rather than to the myelin sheath as in the rat. Astrocytes in both rat and man were stained by two fucose-binding lectins. Several lectins revealed affinity for GC in the neurilemmal sheath, and staining of this structure was stronger in the human specimens. Neurons in the human trigeminal ganglion ranged from unstained to strongly positive for fucoconjugate in cytoplasmic bodies and plasmalemma. Positive ganglion cells gave rise to unmyelinated fibers which also stained for fucoconjugate. Remak fibers and their extensions into the substantia gelatinosa of the human spinal cord stained strongly for content of fucose.The stronger lectin affinity for N-glycosidic core sugars in the peripheral as compared with the central segment suggests that lectins localize P_o protein in peripheral myelin. The reactivity for several sugars in the central segment can possibly be attributed to myelin-associated glycoprotein (MAG) of central myelin, but lectin staining for GalNAc shows in addition a biochemically unrecognized GC with O-glycosidic linked oligosaccharides in myelin. The lectin cytochemistry indicates that the 170 K Dalton glycoprotein with PNA affinity obtained from rat sciatic nerves occurs in nodes of Ranvier.This research was supported by NIH Grants AM-10956, HL-29775 and United Health and Medical Research Foundation of South Carolina, Inc. Grant No. 79