Sialic acids spleen

Gangliosides appear to be confined to the animal kingdom. In man, cattle, horse, main ganglioside outside brain is Lactl A -Glycolyl-neuraminic acid is chief sialic acid in erythrocyte and spleen ganglioside of horse and cattle. 

Sialidase-treated erythrocytes from rats, unlike the normal erythrocytes, preferentially adhered to mononuclear spleen cells and Kupffer cells of the liver. This recognition manifests itself, both in autologous and homologous systems, by the adhesion of complementary cells in the form of rosettes. This process may be the normal physiological mechanism for removing circulating erythrocytes that have a decreasing proportion of sialic acid residues. 

Fig. 7. Oral administration of sialic acids to mice. The sum of remaining radioactivity in blood, liver, spleen, kidney, and brain after oral application each of 2 mg [2-i4C,9- H]Neu5Ac, 2 mg [2-i4C,9-3H]Neu5Gc and 0.087 mg pH]Neu5Ac2en to fasted mice (strain C57) is shown (NOhle and Schauer 1981, NOhleet al. 1982). Symbols O from...

Kean (1970) found that CMP-sialic acid synthetase was located in the nuclei isolated from rat liver, kidney, brain, and spleen and hog retina. The subcellular location of this enzyme in the nucleus was well documented and is surprising in the light that CMP-sialic acid is utilized in a different geographic location in the cell (see Section III, C). This subcellular separation of the enzymes for synthesizing and utilizing CMP-sialic acid may represent an important control mechanism for sialic acid metabolism. 

Tissue surveys revealed the widespread presence of an enzyme which would transfer sialic acid from CMP-sialic acid to lactose. The enzyme was found in rat spleen, testes, kidney, lung, brain, and liver. More importantly, this work led investigators to look at milk and colostrum as sources of the glycosyltransferases. These secretions turned out to contain large amounts of soluble glycosyltransferases—a great boon. 

The role of sialic acid in the interaction between cells of different origin has been far less studied than in the interaction between identical cells. Cormack (1970) observed a decreased attachment of neuraminidase-treated Walker 25 tumor cells to the mesothelial membrane of rat, but the interpretation of this experiment performed in vivo is complicated by the resynthesis of sialic acid residues at the surface of the treated cell. Weiss and Cudney (1971) found no effect of neuraminidase on the immunolysis of mastocytoma P815 cells by sensitized spleen cells, and it is doubtful that sialic acid residues play a direct role in the interaction between different cells. It may play an indirect one, however, for example, by masking receptor sites at the surface of either human peripheral blood lymphocytes, or sheep red blood cells, as shown by the increased stability of the rosettes formed by these cells upon neuraminidase treatment (Galili and Schlesinger, 1974). 

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