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Systemic scleroderma (SSd) is a connective tissue disorder accompanied by generalized fibrosis. A disturbance of the synthesis and production of matrix glycoproteins, such as collagens, fibronectin, and proteoglycans, by connective tissue cells is typical for this disease. We previously demonstrated a decrease in the ganglioside content of cultured skin fibroblasts from patients with SSd. In this work the contents of sialoglycoproteins and sialoglycolipids in blood sera of patients with SSd were estimated. Simultaneously, the level of asialofetuin-sialyltransferase activity in blood plasma of three groups of patients--those with SSd, Raynaud's phenomenon, and with localized scleroderma--was investigated. CMP-5-acetamido-9-deoxy-9-fluoresceinylthioureidoneuraminic acid was used as a substrate for the enzyme assay. It was shown that the concentration of total sialic acid was increased and the concentration of lipid-bound sialic acid was slightly decreased in the blood sera of patients with SSd. A correlation between the lipid-bound sialic acid level and the severity of disease was observed; there was no correlation between severity of disease and total sialic acid. Sialyltransferase assay showed a decrease in the activity level in all three groups of patients. The greatest decrease (2-fold) of this activity was observed in patients with Raynaud's phenomenon. Our data suggest that in SSd and similar diseases the process of glycoconjugate sialylation is disturbed. These changes may considerably affect the mechanisms of regulation of metabolism and cellular interactions.

A comparative investigation of glycosphingolipids and phospholipids of cultured skin fibroblasts from healthy donors and patients with progressive systemic sclerosis (SSc) was performed.Culture techniques, qualitative and quantitative lipid analyses, determination of neuraminidase activity, and immunofluorescence microscopy were used.The quantitative content of individual phospholipids in the fibroblasts of SSc patients (PF) was equally elevated, on the average 2.8 times in comparison with the fibroblasts of healthy donors (DF). The total content of neutral glycosphingolipids was slightly elevated only because of a 1.5-fold increase of monoglucosylceramide in PF. A decrease in the amount of the gangliosides GM3 and GM1 and the absence of the disialogangliosides in PF in comparison with DF, were demonstrated. Immunofluorescent assay also showed a decrease of ganglioside epitopes on the cellular surface of PF in comparison with DF. The GM3-neuraminidase activity of PF homogenates was increased two-fold in comparison to normal values.These results are discussed in connection with abnormalities in membrane receptor functions, alterations in the cell phenotype and AMP-cyclase system activity, as well as hyperproduction of extracellular matrix proteins by PF.