Electron cytochemical study of carbohydrate components in cultured nerve and glial cells of the snail Helix pomatia

Electron microscopic evidence for multiple types of secretory vesicles in bovine chromaffin cells

It has been previously shown that the neuron-like chromaffin cells from the bovine adrenal medulla are heterogeneous. Among other differences, the cells also differed in secretory vesicles represented in their cytoplasm. The present study investigates the types of secretory vesicles in bovine chromaffin cells by electron microscopy. Morphometric analysis revealed five types of electron-dense secretory vesicles in chromaffin cells. These were as follows: elementary large catecholamine-storing chromaffin granules of rounded shape, large dense core vesicles of ovoid and rod-like shapes, small dense core vesicles as well as ribosome-coated vesicles of intermediate density. Among the electron-lucent vesicles there were small synaptic-like microvesicles, endocytotic clathrin-coated vesicles, growth cone vesicles, and emptied large light core vesicles. The structural and functional backgrounds of different types of secretory vesicles are described, focusing on their formation and potential role.

Electron cytochemical study of carbohydrate components in different types of cultured glial cells of snail Helix pomatia

Using a variety of colloidal gold-labelled lectins with different sugar specificities, the structure and topography of carbohydrate determinants of the surface membrane of in vitro cultured glial and nerve cells of the snail Helix pomatia have been electron cytochemically studied. Heterogeneity of carbohydrate pools among different types of glial cells and between glial and nerve cells was established. It was found that satellite glial cells having the ultrastructural signs of cells with high metabolic level (type II cells) selectively bind GNA which is specific to terminal alpha-D-mannose residues and do not bind other mannose-specific lectins, Con A and LCA. GNA determinants are absent in satellite type I glial cells, fibrous glial cells, microglia and neurons. It has been found that glial cells (satellite type I and II glial cells, filamentous glial cells and microglial cells) do not bind PVA and LABA. LTA did not bind to any glial cells and binds weakly to neurons. Con A and WGA determinants which are abundant on the neurons are completely absent on satellite type II glial cells but present on satellite type I glial cells and filamentous glial cells. Microglial cells contain Con A and LCA determinants and the density of PNA determinants on these cells is the highest compared to other types of glial cells or neurons. It is concluded that some lectin determinants (for RCA-1, PNA, LPA) are present on all types of glial cells, while another determinant (GNA) is specific for a definite type of glial cells and can serve as a marker of these cells. The role of specific carbohydrate determinants in the functioning of a neuron-glial complex is discussed.