Jun'ichi Tohyama

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Sphingolipid activator proteins (saposins A, B, C and D) are small homologous glycoproteins derived from a common precursor protein (prosaposin) encoded by a single gene. They are required for in vivo degradation of sphingolipids with short carbohydrate chains. Six cysteines and one glycosylation site are strictly conserved in all four saposins. Total(More)
We have generated mice doubly deficient in both synthesis and degradation of galactosylceramide by cross-breeding twitcher mice and galactosylceramide synthase (UDP-galactose:ceramide galactosyltransferase, CGT) knockout mice. The prediction that the phenotype of the doubly deficient mice should be the same as the cgt -/- mice, since the degrading enzyme(More)
We have cross-bred twitcher mice (galactosylceramidase deficiency) and acid beta-galactosidase knockout mice (G(M1) gangliosidosis) and found that the acid beta-galactosidase gene dosage exerts an unexpected and paradoxical influence on the twitcher phenotype. Twitcher mice with an additional complete deficiency of acid beta-galactosidase have the mildest(More)
Cytotoxic capacity of psychosine (galactosylsphingosine) was evaluated in comparison with C6-ceramide in cultured fibroblasts and the glia-derived MOCH-1 cells that have characteristics of myelinating cells (1). Psychosine caused cytotoxic cell death and DNA fragmentation at concentrations similar to C6-ceramide and MOCH-1 cells were substantially more(More)
Ceramide is recognized as an intracellular mediator of cell growth, differentiation and apoptosis. Tumour necrosis factor, anti-fas antibody, radiation and anticancer drugs such as actinomycin D are known to induce apoptosis in several cell types through generation of ceramide by activation of the sphingomyelinase pathway or ceramide synthetase. In this(More)
Cross-breeding of mouse mutants, each defective in either synthesis (CGT knockout) or degradation (twitcher) of galactosylceramide, generates hybrids with a genotype of galc -/-, cgt +/-, in addition to doubly deficient mice. They are ideally suited to test the potential usefulness of limiting synthesis of the substrate as a treatment of genetic disorders(More)
UNLABELLED Spontaneously occurring genetic lysosomal storage diseases are as rare in other mammalian species as in man. However, the advent of gene targeting technology has revolutionized the state of animal models of genetic diseases. Nearly all lysosomal storage diseases known in man have been duplicated in the mouse. The technology now allows, not only(More)
3'-Deoxycytidine 5'-triphosphate and 3'-deoxyuridine 5'-triphosphate were synthesized starting from cordycepin in good yield. The inhibitory effects of these nucleotides were examined in comparison with that of cordycepin 5'-triphosphate (3'-dATP) using purified DNA-dependent RNA polymerases I and II from Dictyostelium discoideum cells. Both nucleotide(More)
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