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Biomedical subjects

H Hashimoto

Publications and source records attributed to H Hashimoto.

At least 1,351 records · Page 75Linked to original sources
PubMed1979

Influence of temperature on the sensitivity of the adrenoceptors in the isolated atria of guinea pigs and rats.

The influence of the bath temperature on the responsiveness to sympathomimetic amines was studied with isolated guinea pig and rat atria. In electrically driven guinea pig left atria, the dose-response curve for the positive inotropic effect of isoproterenol (ISO) was shifted to the left by lowering the temperature from 36 to 24 degrees C. The positive inotropic effect of phenylephrine (PHE) in lower concentrations was attenuated by lowering the temperature. Phentolamine markedly inhibited the PHE response at 36 and 32 degrees C, whereas it produced no inhibition at 24 degrees C. Similar changes were observed with rat left atria. In guinea pig left atria, propranolol inhibited the response to PHE more effectively at 24 degrees C than 32 degrees C. With guinea pig and rat atria the dose--response curve for the positive inotropic effect of PHE in the presence of phentolamine was shifted to the left by lowering the temperature. The results suggest that lowering the temperature of the bath solution diminished the positive inotropic effect of PHE mediated by alpha-adrenoceptors and potentiated that mediated by beta-adrenoceptors.

Animals↗
PubMed1979

Integration of temperature-sensitive nonconjugative plasmid carrying kanamycin gene into conjugative R plasmids.

A nonconjugative R plasmid, rMS3, whose molecular weight was 2.4 X 10(7) daltons, possessed a kanamycin resistance gene and was thermosensitive in its maintenance in Escherichia coli strains. We mobilized rMS3 with a conjugative R plasmid, R100 or T-tet, and obtained cointegrates carrying all the parental resistance markers. Various markers of the cointegrates were frequently deleted by P1 transduction and the deletion patterns among the different cointegrates were differed from each other. The cointegrates were thermoresistant, but the thermosensitive replicon could be segregated from the thermoresistant cointegrate by deletion. Some cointegrates between rMS3 and T-tet showed a derepressed state of transferability because of the integration of rMS3 and T-tet showed a derepressed state of transferability because of the integration of rMS3 into the regulator gene of the transfer loci. The genome size of the cointegrate so far tested was the sum of the sizes of the parental plasmids, indicating that the whole genome of rMS3 could integrate into various sites of the conjugative plasmids R100 and T-tet.

Biophysical Phenomena↗
PubMed1979

Deletion mutants from R plasmids with increased copy number.

Rms 201-12 and Rms 201-46 are R mutants with increased copy number, and are derived from a conjugative plasmid Rms 201 that encodes resistance to five drugs, ampicillin (Apc), tetracycline (Tc), chloramphenicol (Cm), streptomycin (Sm), and sulfonamides (Sa). The mutants expressed increased levels of resistance to Apc, Sm, and Cm, and a decreased level of resistance to Tc than those of the parent Rms 201 plasmid. When the Rms 201-12+ or Rms 201-46+ cells were inoculated onto plates containing a high concentration of Tc, colonies developed on the plate at a frequency of 10-3 to 10-4 after overnight incubation. The cells grown on the Tc plate carried a tet (Tc gene)-deleted R mutant besides tet-possessing Rms 201-12 or Rms 201-46, and we isolated the tet-deleted R mutant by purifying the R+ cells on drug-free plates. On the other hand, various deletion mutants possessing tet were isolated by prolonged culture of the cells. We have presented a circular gene order of Rms 201 by comparing the genetic markers of all deletion mutants derived from Rms 201, Rms 201-46, and Rms 201-12. The gene(s) regulating the copy number was closely linked to the rep gene. The gene(s) specifying entry exclusion was jointly lost with the tra region.

Anti-Bacterial Agents↗
PubMed1979

Comparison of the protective action of glutathione and cysteamine on radiation-induced mitotic delay in cultured S-5 cells.

The protective effect of glutathione (GSH) and cysteamine (MEA) on radiation-induced mitotic delay in cultured mammalian L-5 cells was studied. Cells treated with 20 mM of GSH during irradiation with 2 Gy (200 rad) showed faster recovery of the mitotic index than control cells irradiated without chemical treatment; however, GSH had no effect on mitotic delay time. Inhibition of mitosis was observed with 80, 100, and 120 mM of GSH. Cells treated with 5 mM of MEA during irradiation also showed faster recovery of the mitotic index than the controls, but in addition the delay time was shortened. Progression of G2-phase cells treated with 5-fluorouracil to mitosis after irradiation was protected by MEA but not by GSH. Progression of S-phase cells labeled with 3H-thymidine to mitosis was accelerated by both agents during irradiation.

Animals↗