Sialic basement

As regards the function of this electronegative shield in some cell-types, membrane sialic acids prevent aggregation due to electrostatic repulsion in, for example, blood platelets, erythrocytes, and carcinoma cells in culture,418 whereas, in others, for example, chick, embryonic muscle-cells,422 aggregation is facilitated, most probably by Ca24 bridges. Sialic acid was also shown to be involved in the attachment both of endothelium and epithelium to glomerular basement-membranes of rat kidney.423... 

Sialic acid is apparently ubiquitous in tissues, but is only demonstrable, histochemically, in certain well defined areas. Principally these are the epithelial secretions, although basement membranes (e.g. of the kidney glomeruli), are clearly delineated by those techniques appropriate for the demonstration of sialic acids. Sialic acids occurring in other glycoproteins (e.g. plasma proteins, cell membrane components) may contribute to the diffuse background staining, but due to their low concentration in tissue sections are not readily defined, on a... 

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