Sialic acids release

Exact analysis of sialic acid is required in biologieal experiments where the biological role of sialic acid is frequently studied with the aid of sialidases, and the amount of sialic acids released is determined. This is also important for periodate oxidation studies on biological systems, where modification of sialic acids by periodate is only assumed, but chemical analysis of this effect by isolation and analysis of the modified sialic acids is seldom performed. These uncertainties in determinations of sialic acid can be overcome by the purification procedures already described. Furthermore, it must be stressed that unequivocal determination of the structure of a sialic acid, especially... 

Sialic acids, released from human lymphocytes by hydrolysis, have been determined in the nanomolar range by a modified periodic acid - thiobarbituric acid assay. ... 

Combination of ion-exchange purification with ether or hexane extraction has proved to be necessary in quantitation of sialic acids released by mild acid hydrolysis from membrane preparations (Schauer er al 1975, Schauer 1978 see also chapter C). The extraction removes lipid material which would otherwise yield similar pigments in the assay, and which is not always removed after ion-exchange chromatography. 

Fidgen, K. J., 1973, An improved automated method for the estimation of sialic acid released in the neuraminidase assay. Anal. Biochem. 54 349. 

Following the early observation of Klenk and Yamakawa and their associates, the presence of sialic acid residues at the surface of numerous cells was established, either by action of neuraminidase followed by determination of the cell electrophoretic mobility or by determination of the sialic acid released. For example, sialic acid residues were detected at the surface of EMich ascites tumor cells (Wallach and Eylar, 1961 Cook et aL, 1962), hamster kidney fibroblasts transformed by polyoma virus (Forrester et aL, 1964), squamous epithelial cells (Berwick and Coman, 1962), solid and ascites sarcoma cells (Cook et aL, 1963 Wallach and de Perez Esandi, 1964), normal and malignant rat liver cells (Kalant et aL, 1964), cells from human bronchial carcinoma, cells from rat myeloma, HeLa cells, and L-strain mouse fibroblasts (Fuhrmann etaL, 1962). 

The role of viral neuraminidase in viral adsorption, hemagglutination, infectivity, and virus release has been studied extensively. Studies of sialic acid release have revealed two distinct stages in infectivity (Fresen and Ubendorfer, 1973 Tsvetkova and Lipkind, 1973). For... 

Table I lists nonhormonal plasma sialoglycoproteins, and when known, their molecular weight, number of sialic acid residues per mole, and carbohydrate content. Sialic acid content was estimated by either the Warren procedure (1959) or by treatment with microbial sialidase and measurement of sialic acid release and concomitant change in electrophoretic mobility or isoelectric point. Some of the physical and biological changes observed in the plasma sialoglycoproteins after removal of sialic acid residues are described below.

Decrease in electrophoretic mobility, loss of sialic acid Increased anti-A, -B, -H, -D and -C agglutinability Enhanced blastogenic response Enhanced cytotoxicity Delay of skin graft rejection Pregnancy rejection More sialic acid release from tumor cells... 

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