Growth related changes in sugar determinants on the surface of C6 glioma cells in culture: a cytochemical lectin-binding study.

The cell surface sugar determinants (CSSD) were examined in C6 glioma cells in cultures at different conditions of growth by peroxidase conjugates of the lectins: peanut agglutinin (PNA), Ricinus communis agglutinin (RCA), Helix pomatia agglutinin (HPA), wheat germ agglutinin (WGA), lentil agglutinin (LCA), laburnum bork agglutinin (LABA), and lotus agglutinin (TPA). It was found that the cells bound more intensively WGA, LCA, and RCA compared to PNA, HPA; the weakest staining was provided by LABA and TPA. Binding intensity for PNA significantly increased after pretreatment of the cells with neuraminidase. This indicates that a part of the beta-D-galactose residues on the surface membrane of C6 glioma cells is covered by sialic acid. The process of sialization was increased during the culturing of C6 glioma cells. Addition of cis-DDP or dBcAMP to cultures growing in medium with 10% of CS increased the number of Gal residues which are not covered by sialic acid. The expression of beta-D-galactose (Gal), N-acetyl-D-galactosamine (NAcDGal), and fucose (Fuc) residues appeared to be most responsive to changes in growth conditions and degree of cell differentiation. The expressions of N-acetyl-D-glucosamine (NAcDGlc) and mannose (Man) residues were high and seems did not depend on changing of the conditions of culturing. In C6 glioma cells cultures in which the rate of cell division, formation of the cell processes, and adhesiveness of the cells to the substratum were reduced by growing cells in MEM+, expression of beta-Gal, NAcDGal, and Fuc was considerably reduced. The decrease of expression of beta-Gal, NAcDGal, and Fuc on the surface of cell membrane was more pronounced in MEM+ with 1% of CS than in MEM+ with 10% of CS. In DbcAMP and cis-DDP treated cultures, grown in medium with 1% serum, in which cell division was inhibited without obvious changes in cell adhesiveness to the substratum, binding of PNA and HPA was increased due to higher expression of beta-Gal and NAcDGal. From these observations it was concluded that the pattern of expression of sugar residues on the cell surface varies according to the biological state of the cells and are easily affected by tissue culture conditions.

Cytoskeleton-mediated, age-dependent lateral topography of lectin-gold-labelled molecules on the plasma membrane of cultured neurons: a statistical view.

In dissociated spinal cord neurons (12-day-old mouse embryo, monolayer culture), an electron microscopic study was carried out to examine quantitatively the rearrangement of wheat-germ agglutinin-gold-labelled molecules on the neuronal somatic surface at two developmental stages (on the fifth and 15th days in vitro), and after cytoskeletal interruptions. In tests, before labelling the cultures were incubated with colchicine or cytochalasin in order to affect microtubules or mostly actin filaments, respectively. Samples of electron micrographs that display soma membrane (profile) fragments were quantified. A set of stochastic geometry approaches was accomplished, which allowed statistical and stereological analysis of labelling. Images that illustrate the lateral (surface) patterns of label were simulated. On the fifth day in vitro, both colchicine and cytochalasin were found to cause an increase in the surface density and aggregation of wheat-germ agglutinin label relative to controls, the effect of cytochalasin being significantly more profound. By the 15th day in vitro, treatment with both drugs led to a similar tendency towards heavy aggregation of wheat-germ agglutinin labels. In contrast, neuron processes showed an opposite tendency of label rearrangement, which suggests lateral migration of labelled molecules, as a result of drug action. Possible molecular mechanisms involved in the phenomena are discussed.