Retinol induces density-dependent growth inhibition and changes in glycolipids and LETS.
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Biomedical subjects
Publications and source records attributed to L M Patt.
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A mannosyltransferase has been detected in suspensions of BALB/c fibroblasts incubated with GDP-[14C] mannose. The experimental evidence indicates the cell surface as the most likely site for the enzyme. The transferase synthesizes both glycolipids and glycoproteins. The lipid compounds have properties suggestive of lipid-linked mono- and oligosaccharides which can function as intermediates in glycoprotein synthesis. The formation of these compounds by a cell surface enzyme suggests that lipid-linked intermediates may play an important role in the glycosylation of membrane components.
In this communication, we have demonstrated that hydrolysis of the nucleotide sugar can cause errors in the detection of an ectoglycosyltransferase. Spleen cell suspensions can incorporate radioactivity when incubated with labeled UDP-galactose, but all the activity is due to decomposition of the nucleotide sugar and uptake of the free sugar. The fibroblast cell lines can incroporate carbohydrate directly from UDP-galactose. Several criteria are presented with can be used to demonstrate that a nucleotide sugar is the direct carbohydrate donor.
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The ability of suspensions of BALB/c cells to catalyze the incorporation of nucleotide sugars into complex polysaccharides has been compared. These cells have previously been characterized for concanavalin A-induced agglutinability, tumorigenicity, and malignancy. All of the cell lines tested catalyze transfer of the sugar moieties of cytosine 5-monophosphate N-acetylneuraminic acid, uridine 5-diphosphate galactose, uridine 5-diphosphate N-acetylgalactosamine, uridine 5-diphosphate N-acetylglucosamine, uridine 5-diphosphate glucose, and guanidine 5-diphosphate monnose into glycoproteins and glycolipids. While some transformed lines exhibit alterations in transferase levels, others cannot be distinguished from normal cells. Normal cells, transformed cells that cause tumors that regress, and transformed cells that cause tumors that kill an immunologically competent host show growth-dependent changes in transferase activities. Determining the ability to catalyze carbohydrate transfer is insufficient for predicting the tumorigenic and malignant properties of a cell line.
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