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Biomedical subjects

M Kuwano

Publications and source records attributed to M Kuwano.

At least 325 records · Page 18Linked to original sources
PubMed1976

Effect of l-asparaginase and asparagine deprivation on RNA metabolism in mouse leukemia L 5178Y cells in suspension culture.

We analyzed the effect of asparagine starvation and L-asparaginase on RNA metabolism of mouse leukemia cell lines L5178Y, whose growth is dependent on the presence of asparagine, and L5178Y-R, whose growth is independent of the presence of asparagine. The deprivation of asparagine from the medium inhibited cellular protein synthesis by 30 to 40% of the control value in L5178Y cells, but not in L5178Y-R cells, whereas L-asparaginase inhibited synthesis by more than 80% in both L5178Y and L5178Y-R cells. The decrease in protein synthesis caused by asparagine starvation in L5178Y cells was accompanied by a decrease in ribosomal RNA synthesis. The synthesis of rRNA was also markedly blocked when L5178Y and L5178Y-R cells were exposed to L-asparaginase. The rate of synthesis of pulse-labeled RNA decreased significantly in the cells treated with L-asparaginase, and smaller pieces of polyadenylate containing pulse-labeled RNA (presumptive messenger RNA) appeared among monosomes and polysomes. However, the rate of messenger RNA synthesis was constant during asparagine starvation, and a marked accumulation of monosome was observed.

Animals↗
PubMed1975

Synthesis and degradation of early mRNA in lambda phage.

Using two different Escherichia coli mutants defective in elongation factors EFG and EFTs required for peptide synthesis, lambda phage with or without a tof mutation was analysed for synthesis of early mRNA by DNA-RNA hybridization technique. (1) In CP78G carrying temperature-sensitive elongation factor G, shift-up to high temperature (41 degrees C) in the middle of phage infection did not affect early mRNA synthesis with lambdatof+ phage but did inhibit it with lambdatof- phage. (2) In HAK88 carrying temperature-sensitive elongation factor Ts, shift-up to 41 degrees C dropped total cellular RNA synthesis to below 10-20 percent of the control in the presence or absence of phage infection (stringent control). Under such a condition for suppressed protein synthesis, lambda early mRNA synthesis was completely blocked with both tof+ and tof- phage infection. Thus, stringent control seems to exert its effect on lambda early mRNA synthesis. (3) Addition of chloramphenicol, which is known to relax the stringent control of RNA synthesis, to the culture of phage-infected HAK88 at 41 degrees C resulted in full recovery of tof+-mRNA synthesis, but only in partial recovery to tof --mRNA synthesis. (4) Analysis of the stability of lambda mRNA indicated an exponential decay, and a halflife of tof --mRNA of 6 min when that of tof+-mRNA was 13 min at 37 degrees C.

Chloramphenicol↗
PubMed1975

Potentiation of cytostatic effect of sulfur- or chlorine-containing purines and related ribonucleosides by amphotericin-B on cultured mouse leukemia cells.

Synergistic effects of sulfur-containing purines and related ribonucleosides (6-thioinosine, 6-thioguanine, 6-thiocyanatopurine, 6-methylthioinosine, 6-thiocyanatoguanine, 6-thiocyanatoguanosine, 6-phenacylthioinosine, 6-nitrobenzlythioinosine, 6-(p-chlorobenzyl)thioinosine, 6-(p-nitrobenzyl)thioguanosine, 6-benzylthioinosine, 6-ethylthioinosine, 6-benzylthioguanine, 6-benzylthiopurine, 6-methylthiopurine, and 6-thiocyanatoinosine) and chlorine-containing purine and its ribonucleoside, (6-chloropuine and 6-chloropurine riboside), in combination with the polyene antibiotic, Amphotericin-B, on cell survival and synthesis of DNA were examined in mouse leukemia L5178Y cells. 6-Methylthioinosine, 6-thiocyanatopurine, 6-thiocyanatoinsoine, 6-methylthiopurine, and 6-thiocyanatoguanine (or -guanosine) among sulfur-containing compounds were strongly potentiated by Amphotericin-B, and 6-chloropurine riboside, which is electronically analogous to methylthioinosine, was also enhanced by the polyene. Thiocyanoto or methylthio group at position 6 of the purine ring seems to be important for the polyene-mediated potentiation. 6-Methylthioinosine alone had much greater effect on DNA synthesis of HeLa cells than on L5178Y cells, and Amphotericin-B failed to potentiate the action of 6-methylthioinosine in HeLa cells.

Amphotericin B↗
PubMed1973

Potentiation of 5-fluorouracil, chromomycin A3, and bleomycin by amphotericin B or polymyxin B in transformed fibroblastic cells.

By using cultured, transformed fibroblastic cells, antitumor agents including cytosine arabinoside, thio-tepa, nitrogen mustard N-oxide, mitomycin C, chromomycin A3, 5-fluorouracil, daunomycin, vinblastine, vincristine, and bleomycin A2 were screened for the potentiation of their activity by amphotericin B or polymyxin B. Among them, the action of 5-fluorouracil and chromomycin A3 on ribonucleic acid synthesis was potentiated in their action by amphotericin B, not by polymyxin B. Bleomycin A2 was potentiated in its action on deoxyribonucleic acid and ribonucleic acid synthesis only by polymyxin B.

Amphotericin B↗
PubMed1972

3',5'-cyclic adenosine monophosphate-requiring mutants of Escherichia coli.

Mutants that require exogenous 3',5'-cyclic adenosine monophosphate (cAMP) for exponential growth were isolated from strains deficient in adenyl cyclase. Studies of one strain showed that cAMP is not incorporated into macromolecules; instead, it seems to have a regulatory function, i.e., in media lacking cAMP, cells form ribonucleic acid (RNA) and protein at linear rather than exponential rates. The exact lesion is not known; ribosomes, messenger RNA, and the beta and beta' subunits of RNA polymerase continue to be made in absence of added cAMP.

Adenylyl Cyclases↗