Sialylation decrease

Butyrate appears to have its most profound effects on neoplastic cells such as HeLa in addition to morphological and biochemical differentiation, the fatty acid inhibits cell growth (2). Previous studies have established a correlation between decreased ganglioside synthesis and malignant transformation (43-46). Transformed baby hamster kidney and newborn rat kidney cells exhibited a loss of GM3 and sialyl transferase activity (43,44). 

This intracellular concentration of UDP-GlcNAc has also been shown to be important in another respect. An elevated UDP-GlcNAc appears to cause a decrease in sialylation, which may be explained metabolically by the inhibition of CMP-sialic acid transport (Pels Rijcken et al., 1995). This may be the mechanism for the observed decrease in sialylation that has been shown to accompany high levels of ammonia in culture (Yang and Butler, 2000). 

An efficient a-sialylation that took advantage of the highly reactive sialyl donors having C5 cyclic imides, especially phthalimide (NPhth), by virtue of the fixed-dipole moment effects, was also reported [42], For example, the use of the sialyl donor 4 and acceptor 6 at -78°C supplied the sialoside 7 as a only with 92% yield on 50 mg scale. The scale-up in batch process, however, significantly decreased the yield and stereoselectivity. This decrease in sialylation efficiency might be a result of... 

Brinkman-Van der Linden, C.M., Havenaar, E.C., Van Ommen, C.R., Van Kamp, G.J., Gooren, L.J. and Van Dijk, W. (1996) Oral estrogen treatment induces a decrease in expression of sialyl Lewis x on alpha 1-acid glycoprotein in females and male-to-female transsexuals. Glycobiology, 6,407 142. 

As outlined in Section VI, tliis greatly simphfied picture has been confirmed by an extensive series of binding studies with sialyl-Lewis derivatives that had been synthesized as candidate phannaceutical agents. In accordance with the incremental refinement of structure-activity relationships over time, the design of inhibitoiy structures followed a series of models decreasing in complexity. These have been designated the tetrasaccharide, trisaccharide, disaccharide, and monosaccharide... 

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