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I Oki

Publications and source records attributed to I Oki.

At least 19 recordsLinked to original sources
PubMed1989

Temporal changes of plasma erythropoietin level in hypobaric hypoxic mice and the influence of an altered blood oxygen affinity.

Temporal changes of plasma erythropoietin (Epo) in mice exposed to hypobaric hypoxia were studied by a fetal mouse liver cell culture method. Since a colony formation inhibitory activity was found in the mouse plasma, thirteen pretreatment procedures for bioassay were compared and the procedure of shaking with chloroform followed by dialysis was concluded to be the best. When normal mice (P50 = 40.4 +/- 2.2 Torr) were exposed to hypoxia of 350 Torr, the plasma Epo level was elevated, with peak at the 2nd to 3rd day, and afterwards declined gradually. On the contrary, cyanated mice (P50 = 30.1 +/- 1.5 Torr) showed much less of the Epo response when exposed to 350 Torr. Under 200 Torr hypoxia, both mice exhibited a similar and remarkable extent of the response. These results suggest that the renal Epo-producing tissue or its oxygen-sensing system is less hypoxic in cyanated mice than in normal mice under 350 Torr, and that the physiologically optimal oxygen affinity of blood is variable depending on hypoxic degrees. The fact that the inhibitory activity showed an inverse temporal change to that of Epo, suggested a possible important role of this activity in the regulation of erythropoiesis under hypoxia.

Administration, Oral↗
PubMed1988

Harman and norharman induce SOS responses and frameshift mutations in bacteria.

Norharman and harman, beta-carboline derivatives with comutagenic activity in Salmonella typhimurium, were examined for their activity to induce SOS responses in S. typhimurium using the umu-test and mutations in Escherichia coli. The inducibility of the umuC gene by norharman and harman was assayed by measuring the levels of beta-galactosidase activity in tester cells harbouring the umuC'-'lacZ fusion gene on a plasmid. In the umu-test, both norharman and harman weakly induced umuC gene expression at 25-100 and 50-150 micrograms/ml, respectively. In the mutation test using reversion from trpE9777 to Trp+, harman was relatively more potent than norharman in inducing the mutations. These results indicate that norharman and harman induce SOS responses as well as reversion of trpE9777 frameshift mutation in bacteria.

Alkaloids↗
PubMed1987

SOS-inducing activity of chemical carcinogens and mutagens in Salmonella typhimurium TA1535/pSK1002: examination with 151 chemicals.

The umu test system is a newly developed method to evaluate genotoxic activities of a wide variety of environmental carcinogens and mutagens (Oda et al., 1985). In the present study, we further examined the abilities of 151 chemicals to induce umu gene expression in Salmonella typhimurium TA1535/pSK1002. Among the chemicals examined, 72 compounds induced umu gene expression, which could be defined on a basis of increased beta-galactosidase activity by 2-fold over the background level. The potent genotoxic compounds without metabolic activation were adriamycin, bleomycin, daunorubicin, 1,3-dinitropyrene, 1,6-dinitropyrene, 1,8-dinitropyrene, N-ethyl-N'-nitro-N-nitrosoguanidine, furylfuramide, methyl methanesulfonate, N-methyl-N'-nitro-N-nitrosoguanidine, mitomycin C, 1-nitropyrene and 4-nitroquino-line-1-oxide. In the presence of S9, aflatoxin B1, 2-aminoanthracene, Glu-P-1, IQ, MeIQ, MeIQx, Trp-P-1 and Trp-P-2 also induced umu gene expression markedly. Several chemicals such as 2-acetylaminofluorene, 9-aminoacridine, azobenzene, benzanthracene, benzidine, diethyl nitrosamine, 1-nitronaphthalene, paraquat, potassium dichromate and sodium nitrite were weakly genotoxic and the induction by these compounds could be detected only when the incubation time was prolonged from 2 h to 5 h. Data are also presented that some of the chemicals such as dimethyl sulfoxide, m-dioxan, 5-fluorouracil and paraquat, which have been reported to be non-mutagenic in Ames/Salmonella assay, were found to be active in inducing umu gene expression, while the known mutagenic compounds including acrylonitrile, 4,4'-dinitrobiphenyl, furfural, methylene chloride, 1-naphthylamine, sodium azide, o-tolidine and o-toluidine were non-genotoxic in the present assay system.

Biotransformation↗
PubMed1985

Evaluation of the new system (umu-test) for the detection of environmental mutagens and carcinogens.

The umu operon in Escherichia coli is responsible for chemical and radiation mutagenesis, and the expression of the operon itself is inducible by these DNA-damaging agents. The principle of the umu-test is based on the ability of the DNA-damaging agents, most of which are potential carcinogens, to induce the umu operon. A plasmid (pSK1002) carrying a fused gene umuC'-'lacZ was introduced into Salmonella typhimurium TA1535. The strain TA1535/pSK1002 enabled us to monitor the levels of umu operon expression by measuring the beta-galactosidase activity in the cells produced by the fusion gene. Using this strain, a simple, inexpensive, and sensitive system, the umu-test, for the screening of environmental mutagens and carcinogens was developed. 38 chemicals with different structures and modes of action, including 31 known animal carcinogens, were examined by the test to evaluate the system. The threshold sensitivity of the umu-test was approximately equal to that of the Ames test for chemicals genotoxic in both tests. By the umu-test, using the single tester strain, we detect many types of DNA-damaging agents for which the Ames test requires several tester strains. Furthermore, the umu-test provides a potential practical advantage for the screening of various environmental samples containing amino acids and nutrients such as urine, serum and foods.

Animals↗