Paclitaxel (Taxol) attenuates clinical disease in a spontaneously demyelinating transgenic mouse and induces remyelination.

Treatment with paclitaxel by four intraperitoneal injections (20 mg/kg) 1 week apart attenuated clinical signs in a spontaneously demyelinating model, if given with onset of clinical signs. If given at 2 months of age (1 month prior to clinical signs), disease was almost completely prevented The astrogliosis, prominent in our model, was reversed by paditaxel as determined by astrocyte counts and quantitation of GFAP. Electron microscopic examination of affected regions at 2.5 months demonstrated that the myelin was generally normal. By 4 months of age, demyelination was common in the superior cerebellar peduncle, maximal at 6 months, but continued to 8 months. In addition to myelin vacuolation and nude axons, the presence of many thin myelin sheaths suggested remyelination or partial demyelination. Although no evidence of oligodendrocyte loss was seen, nuclear changes were observed. To substantiate that remyelination was occurring, we measured MBP (18.5 kDa), MBP-exon II, Golli-MBP, TP8, Golli-MBP-J37, platelet-derived growth factor alpha (PDGFR alpha) and sonic hedgehog (SHH). Of these TP8, PDGFR alpha and SHH were up-regulated in the untreated transgenic. After paditaxel treatment, MBP-Exon II, TP8, PDGFR alpha and SHH were further up-regulated. We concluded that some of the effects of paditaxel were to stimulate proteins involved in early myelinating events possibly via a signal transduction mechanism.

Stimulation of bovine milk galactosyltransferase activity by bovine colostrum N-acetylglucosaminyltransferase I.

Purified bovine milk galactosyltransferase was stimulated by purified bovine colostrum N-acetylglucosaminyltransferase I by more than 10-fold. Only slight stimulation of the N-acetylglucosaminyltransferase I by galactosyltransferase was observed. Heat inactivation destroyed the ability of the N-acetylglucosaminyltransferase I to stimulate the galactosyltransferase. The stimulation of galactosyltransferase was accompanied by a decrease in Km of this enzyme from 9.7 to 3.3. mM and an increase in Vmax from 1.87 to 3.71 nmol galactose transferred/min per mg galactosyltransferase when GlcNAc was the substrate. When the Km for UDPgalactose was determined, it increased from 0.19 to 0.42 mM in the presence of N-acetylglucosaminyltransferase I and the Vmax increased from 0.66 to 2.76 nmol galactose transferred/min per mg galactosyltransferase. In phosphatidylcholine vesicles, no effect on Km values with GlcNAc as substrate was noted, while an increase in the Km of UDPgalactose was observed. The Vmax values were generally higher in the lipid vesicles. Complex formation between galactosyltransferase and N-acetylglucosaminyltransferase I was demonstrated both by glycerol density gradient centrifugation and Bio-Gel P-100 column chromatography. An approximate molecular weight for the complex was obtained on a calibrated Sephadex G-200 column and found to be about 75 000, consistent with a 1:1 complex. The stimulation of galactosyltransferase involved the N-acetyllactosamine synthetase activity of this enzyme and not the lactose synthetase activity, since the latter activity was only slightly affected. Since N-acetylglucosaminyltransferase I is not involved in the lactose synthetase reaction, the stimulation is consistent with the known biosynthetic role of N-acetylglucosaminyltransferase I in the biosynthesis of asparagine-linked oligosaccharides.