Regulation of axoplasmic transport

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1) Flow pattern of cytoskeletal proteins in axons was analysed by SDS-polyacrylamide gel electrophoresis coupled with fluorography, after labelling the art L5 ganglion with L-[^<35>S] methionine. A portion of tubulin migrated at 3.2 mm/day; this portion contrained most of intra-axonal tau factors, and was depolymerised by colchicine and at low temperature. The remaining portion of tubulin migrated at 1.8 mm/day, contained less tau factors, and comparatively resistant to colchicine and low temperature. This portion is considered to serve as a nucleus in polymer isation of ihtra-axonal tubulin in situ.2) GD1<alpha>, a ganglioside species in Xenopus sciatic nerve, was found to migrate at a slow rate i.e. at around 1 mm/day at 15゜C, in sharp contrast to rapid transport of gangliosides so far reported in various animal species. Heterogeneity of ganglioside transport was thus indicated. Further, transport of CMP-sialic acid was found, suggesting the possibility of additional sialosylation of the ganglioside in axon terminals.3) Co-existence of choline acetyltransferase and glutamic acid decarboxylase was found in the anterior horn cells in various species by using ultramicroassay techniques newly. developed in this laboratory. This raises the possibility of <gamma>-aminobutyric acid to play a role other than a naeurotransmitter in this purely cholinergic neurone.