Electron cytochemical study of carbohydrate components in growth cone of cultured nerve cells of the snail Helix pomatia

1. 1. The structure and topography of carbohydrate determinants on the growth cone surface membrane of the snail Helix pomatia nerve cells cultured in vitro have been characterized with a variety of gold-labelled lectins of different sugar specificity. 2. 2. Substantial differences in the pattern of carbohydrate determinants in different parts of growth cone have been revealed. On the surface membrane of organelle-poor veils complex branched sugar chains of N-type were exposed, in other parts of regenerating neuron they were absent. Maturation of veils is accompanied by accumulation of organelles within them and expression on their surface of a considerable number of nonsialylated disaccharide residues of T-F antigen (Galβ l-3GalNac) which can be related to an increased migration ability of these structures. 3. 3. The mature growth cone contains numerous N-acetylglucosamine and considerably less N-acetyllactosamine and N-acetylgalactosamine determinants. 4. 4. All the lectins studied failed to bind to the surface of growth nubbin containing clusters of subplasmalemmal vesicles. 5. 5. The fusion of primary lysosomes with the inner surface of membrane of mature dendrites was found. Decrease or complete disappearance of carbohydrate residues in the fusion region has been observed. The physiological significance of carbohydrate components in neurite growth is discussed.