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H D Webster

Publications and source records attributed to H D Webster.

92 records · Page 6Linked to original sources
PubMedDate not supplied

Characterization of two subcellular fractions isolated from myelinated axons.

Myelin and a heavy membrane fraction (1.0/1.2 fraction) were isolated from rabbit white matter by a slight modification of the procedure for bovine CNS. The specific activities of acetylcholinesterase and Na+, K+-ATPase were higher in the 1.0/1.2 fraction than in myelin. In contrast, the cerebroside content and 2'3'-cyclic nucleotide 3'-phosphohydrolase activity in the 1.0/1.2 fraction were 4.5 and 3.4 times lower than in myelin. Total lipids accounted for only 30% of the 1.0/1.2 fracton's dry weight; for myelin, they represented 70%. Polacrylamide gel electrophoresis showed the presence of many high molecular weight proteins and glycoproteins in the 1.0/1.2 fraction but myelin components were practically missing. Cytochrome c oxidase and NADPH-cytochrome c reductase activities suggested about 15% contamination in the 1.0/1.2 fraction but less than 5% for myelin. In electron micrographs of the 1.0/1.2 fraction, there were many membraneous profiles that varied in size, some mitochondrial fragments, and only a few lamellar whorls of compact myelin. The results suggest that the 1.0/1.2 fraction is different from other myelin-related fractions and is probably enriched in axolemma.

Animals↗
PubMedDate not supplied

Immunocytochemical study of P0 glycoprotein, P1 and P2 basic proteins, and myelin-associated glycoprotein (MAG) in lesions of idiopathic polyneuritis.

To investigate the mechanism of myelin breakdown in idiopathic polyneuritis, paraffin and Epon sections of lesions were immunostained with antisera to four proteins in myelin sheaths. Three of these (P0, P2, and BP) are constituents of compact myelin whereas myelin-associated glycoprotein (MAG) is restricted to membranes near Schwann cell cytoplasm in periaxonal and paranodal regions and in Schmidt-Lanterman clefts. In early lesions, there were focal abnormalities in P2, P0, and BP immunostaining of paranodal and internodal myelin. No single protein was affected selectively and lesions occurred in fibres of all sizes, not just in larger fibres selectively stained by P2 antiserum. Early changes in MAG immunostaining occurred only in regions where myelin immunostaining also was abnormal. More severe, late changes in the distribution of P0, P2, and BP and MAG were consistent with the sequence of myelinated fibre alterations seen in segmental demyelination and Wallerian degeneration. In regenerating fibres, MAG antiserum stained periaxonal regions intensely; thin regenerating myelin sheaths were stained by P0, and BP antisera, but not by P2 antiserum. The results show that myelin sheath changes are identified more easily in immunostained sections than in conventional histological preparations. Our data also suggest that in idiopathic neuritis, myelin sheaths are the primary target and that the breakdown of myelin and its proteins is not secondary to Schwann cell damage.

Adult↗