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M Kumasaka

Publications and source records attributed to M Kumasaka.

13 recordsLinked to original sources
PubMed1983

Stimulation of tubulin-dependent ATPase activity in microtubule proteins from porcine brain by taxol.

Taxol, an antimitotic agent that induces microtubule assembly, stimulated tubulin-dependent Mg2+-ATPase activity of microtubule-associated proteins (MAPs). A concentration-dependent increase in the rate of ATP hydrolysis was observed. Taxol acted through its binding to the tubulin molecule on MAP ATPase, and maximal stimulation, which was found at approximately equal concentrations of taxol and tubulin, reached about 140% of the original level in the absence of taxol. Taxol enhanced ATP hydrolysis by a mixture of MAPs and tubulin, and this continued at a steady linear rate even when the polymerization had approached a plateau. In the presence of taxol, a large portion of ATPase activity and protein was recovered in the pellet after centrifugation at 70,000 g for 60 min at 25 degrees C. Both colchicine and podophyllotoxin inhibited taxol-stimulated ATPase activity via the same mechanism by which they inhibited taxol-induced microtubule polymerization. The stimulation by taxol was not found in the presence of Ca2+ alone but required Mg2+. We conclude that tubulin effectively stimulates Mg2+-ATPase activity of MAPs under conditions that induce tubulin polymerization.

Adenosine Triphosphatases↗
PubMed1982

Stimulation of tubulin-dependent ATPase activity in microtubule proteins from porcine brain by vinblas tine.

Vinblastine, a plant alkaloid which inhibits tubulin polymerization, stimulated an ATPase activity in microtubules. When microtubule proteins were separated into microtubule-associated proteins (MAPs) and tubulin by phosphocellulose column chromatography, vinblastine did not stimulate an ATPase activity recovered in the MAPs fraction unless tubulin was present. Therefore, vinblastine is considered to act through its binding to the tubulin molecule on MAPs ATPase. Divalent cations that activate tubulin-dependent MAPs ATPase activity were also required for the stimulation by vinblastine. In the presence of Ca2+ and vinblastine the ATPase activity was most active and the extent of stimulation reached about 200% of the original level in the absence of vinblastine. Half-maximal stimulation was attained when the molar ratio of vinblastine to tubulin was 0.5. The concentration of tubulin for half-maximal stimulation was increased in the presence of vinblastine, while divalent cation requirements were decreased. Several factors such as KCl (100 mM), alkaline pH (pH 7.5), and low temperature (10 degrees C) were not responsible for the disappearance of the stimulation. Vincristine stimulated tubulin-dependent MAPs ATPases activity as vinblastine did, whereas the activity was scarcely affected by colchicine, podophyllotoxin, strychnine, and chlorpromazine. Actin had no effect on MAPs ATPase activity in the absence and presence of vinblastine when it was used in place of tubulin.

Actins↗
PubMed1981

Serologic diagnosis of enterovirus type 71 infections using selected plaque mutants.

Mutants of enterovirus type 71 with respect to plaque size were selected from two American and two Japanese strains, and the antigenic relationship between the mutants was analyzed using immune animal and patients' sera. All four strains were mixtures of m+ (big) and m (minute) plaque mutants that were serologically different from each other. Thus, it appears that selected m+ and m mutants must be used for identification and antigenic analysis of isolates of enterovirus type 71. In patients with hand, foot, and mouth disease, the antibody responses to the m mutants of all four strains were significant, but responses to the m+ mutants were poor or absent. No antibody was detected if the current strain including the m+ mutant was used. Thus, the selected m mutant should be used for serologic diagnosis of infection with enterovirus type 71.

Adolescent↗
PubMed1978

Distribution of antibodies against swine and Hong Kong influenza viruses among pigs in 1977.

The distribution of antibodies against swine and Hong Kong influenza viruses among hogs in Miyagi Prefecture was examined. Of 456 serum specimens collected since July 1977, 12 were found to be positive against swine influenza virus and 6 against Hong Kong influenza virus. Such serological results reveal that swine and Hong Kong influenza viruses coexist in Japanese hogs and suggest that swine influenza virus reappeared in mid-1977.

Animals↗