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Biomedical subjects

H Takeshima

Publications and source records attributed to H Takeshima.

At least 235 records · Page 13Linked to original sources
PubMed1981

A new antitumor antibiotic, stubomycin.

A new antibiotic, stubomycin, was isolated from the culture broth and mycelia of Streptomyces strain No. KG-2245. Stubomycin was prepared as colorless plates and has the empirical formula C29H35NO5. The antibiotic possesses growth inhibitory activity against Gram-positive bacteria and transplantable murine tumors, such as Ehrlich carcinoma, and leukemia P388. The antibiotic also shows direct cytotoxic activity against HeLa cells in vitro.

Animals↗
PubMed1979

The mode of action of a new antitumor antibiotic, sporamycin.

Sporamycin, an antitumor antibiotic, primarily inhibited DNA synthesis, while RNA and protein synthesis were not significantly affected in HeLa S3 cells. The antibiotic also caused strand scission of cellular DNA. However, the effects were not observed when the cells were incubated at 0 degrees C before washing and subsequently incubated at 37 degrees C. The Tm of calf thymus DNA decreased when incubated with sporamycin in vitro. Sporamycin did not affect DNA synthesis in vitro catalyzed by partially purified DNA polymerase alpha, beta, and gamma derived from EHRLICH ascites cells.

Animals↗
PubMed1977

Studies on the biosynthesis of 16-membered macrolide antibiotics using carbon-13 nuclear magnetic resonance spectroscopy.

The origin of the skeletal carbons in the lactone ring of 16-membered macrolide antiobiotics has been studied. 13C-labeled antibiotics leucomycin and tylosin, have been obtained from the culture broth of Streptomyces kitasatoensis 66-14-3 and Streptomyces fradiae C-373, respectively in the presence of appropriate 13C-labeled precursors, and 13C NMR spectra of the antibiotics thus obtained have been measured. It was shown that the aglycone of leucomycin A3 is derived from five acetates, one propionate, one butyrate, and an unknown precursor corresponding to two carbons. The formyl carbon which is characteristic of the basic 16-membered macrolides orginates from C-4 butyrate. On the other hand, the aglycone of tylosin is formed from two acetates, five propionates and one butyrate. Butyric acid and ethylmalonic acid are metabolized to propionyl-CoA or methylmolonyl-CoA through a pathway involving methylmalonyl-CoA mutase, and subsequently incorporated into the lactone ring of tylosin.

Acetates↗
PubMed1977

Inhibition of the biosynthesis of leucomycin, a macrolide antibiotic, by cerulenin.

Cerulenin, an inhibitor of fatty acid synthesis, specifically inhibits the biosynthesis of leucomycin, a 16-membered macrolide antibiotic, in both growing cells and resting cells of Streptomyces kitasatoensis. In growing cells, the production of leucomycin was inhibited as long as cerulenin remained in the culture. In resting cells, 50 percent inhibition was achieved with a cerulenin concentration of 1.5 microgram/ml. Cells in which leucomycin synthesis was inhibited for 9 h remained capable of leucomycin synthesis upon removal of the inhibitor. Cerulenin specifically inhibits the incorporation of [14C]acetate into leucomycin but does not affect total protein or RNA synthesis. The uptake of [14C]acetate was not inhibited under conditions which completely inhibited the incorporation of acetate into leucomycin. Since cerulenin is known to block the condensation of malonyl-CoA subunits in the formation of fatty acids, it can be concluded that the aglycone of leucomycin is synthesized via the polyketide pathway by condensation steps similar to those involved in fatty acid biosynthesis.

Acetates↗
PubMed1977

Antitumor activity of a new antitumor antibiotic, sporamycin.

Sporamycin is an antitumor antibiotic isolated from the culture filtrate of Streptosporangium strain No. PO-357. Hydrolysate of the antibiotic showed at least 12 kinds of amino acid, and the molecular weight was calculated approximately as 8,500 approximately 9,000. Antitumor activities of Sporamycin were examined on murine tumors according to different schedules of treatment. After nine daily doses of the antibiotic had been given to dd mice bearing Ehrlich ascites carcinoma, significant increase of lifespan was observed at doses of 5.0 approximately 1.3 mg/kg. A marked decrease in tumor size of sarcoma-180 transplanted subcutaneously was observed when the mice were treated by daily or single injection of Sporamycin. Against leukemia P-388 and L-1210 inoculated intraperitoneally into CDF1 mice, the antibiotic increased lifespan of leukemic mice. The antibiotic also inhibited significantly the growth of human tumor cells in vitro.

Amino Acids↗
PubMed1976

Mechanism of action of acetyl kidamycin. I. Interaction with DNA.

Acetyl kidamycin, an antitumor antibiotic, was strongly bound to DNA in vitro, consequently, the melting temperature of DNA was significantly increased, and its buoyant density was decreased. From these results, it was suggested that acetyl kidamycin stabilized residual links between complementary strands by binding to DNA. An additional action was observed in that acetyl kidamycin caused single-strand scission of DNA in an alkaline sucrose density gradient solution.

Animals↗
PubMed1976

Mechanism of action of acetyl kidamycin. II. Inhibition of RNA synthesis in HeLa cells.

The effects of acetyl kidamycin on RNA synthesis in HeLa cells were investigated. Acetyl kidamycin inhibited the synthesis of 45S pre-rRNA, heterogeneous nuclear RNA (HnRNA) and small molecular weight RNAs, though not to the same degree. The processing of 45S pre-rRNA into 18S and 28S rRNA and that of HnRNA into mRNA were not affected.

Antibiotics, Antineoplastic↗