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M Ishidate

Publications and source records attributed to M Ishidate.

At least 91 records · Page 5Linked to original sources
PubMed1984

Primary mutagenicity screening of food additives currently used in Japan.

Salmonella/microsome tests (Ames tests) and chromosomal aberration tests in vitro using a Chinese hamster fibroblast cell line were carried out on 190 synthetic food additives and 52 food additives derived from natural sources, all of which are currently used in Japan. Fourteen out of 200 tested in the Ames assay showed positive effects and 54 out of 242 were positive in the chromosome test. Three additives (erythorbic acid, chlorine dioxide and beet red) were positive only in the Ames test, although their mutagenic potentials were relatively weak, while 43 additives were positive only in the chromosome test. Eleven additives (calcium hypochlorite, cinnamic aldehyde, L-cysteine monohydrochloride, Food Green No. 3 (Fast Green FCF), hydrogen peroxide, potassium bromate, sodium chlorite, sodium hypochlorite, sodium nitrite, cacao pigment and caramel) were positive in both the Ames test and the chromosome test. The usefulness of such primary screening tests combining two different genetic end-points, gene mutation and chromosomal aberration, and some correlation between mutagenicity and carcinogenicity of food additives are discussed.

Animals↗
PubMed1983

Species difference in the metabolic activation of phenacetin by rat and hamster liver microsomes.

Phenacetin is mutagenic in Salmonella typhimurium TA 100 when liver 9,000 X g supernatant fractions from PCB-treated hamsters instead of rats are used. A mechanism of the species difference in phenacetin mutagenicity was investigated. By high-performance liquid chromatography analysis, it was found that phenacetin is activated to direct-acting mutagens through N-hydroxylation and deacetylation by hamster liver microsomes. Although no significant species difference was observed in N-hydroxylation, rates of deacetylation were 9 to 150 times higher in hamsters than in rats. The results indicate that the marked species difference in phenacetin mutagenicity is due to the difference in deacetylation activity between rat and hamster liver microsomes.

Animals↗
PubMed1983

An application of Acridine Orange fluorescent staining to the micronucleus test.

Acridine Orange fluorescent staining was applied to the micronucleus test in mice and rats. Micronuclei emitted bright green fluorescence and were easily distinguished from micronucleus-like inclusions or contaminants. In rat bone-marrow cells, micronuclei with green fluorescence could be easily distinguished from granules accidentally dispersed from broken mast cells, which showed bright red fluorescence. Therefore, it is recommended that the Acridine Orange staining method be used to provide more reliable data in the micronucleus test.

Acridine Orange↗
PubMed1982

Difference in liver homogenates from Donryu, Fischer, Sprague-Dawley and Wistar strains of rat in the drug-metabolizing enzyme assay and the Salmonella/hepatic S9 activation test.

Comparison studies for detecting differences between liver microsome and S9 preparations from 4 strains (Donryu, Fischer, Sprague-Dawley, Wistar) of young male rats were carried out with pretreatment of the animals by inducers such as PCBs and PB plus 5,6-BF. Each microsome fraction was assayed for the enzymic activity of metabolism of model substrates such as aniline, benzophetamine, BP, DMN and 7-ethoxycoumarin. The hepatic S9 sample was also compared, as regards its metabolizing ability to activate 9 pre-mutagens (2AA, AAF, o-AAT, BP, DAB, DMBA, DMN, m-PDA, quinoline) to directly acting mutagens in the Salmonella/hepatic S9 activation test by using TA98, TA100 and TA1537 strains with or without cytochrome P450 inhibitors (SKF-525A, metyrapone, 7,8-benzo-flavone). In the enzymic assay with PCBs-induced microsomes, BP hydroxylation a strain-specific difference: the microsomes from Fischer and Wistar rats were more effective for metabolizing BP than those from the other strains of rat. The effect of induction by BP plus 5,6-BF for Fischer rats showed relatively higher enzymic activity in the same induction group. Other microsomes prepared from rats with and without induction by PB plus, 5,6-BF did not show a clear-cut strain dependency in the enzymic activities assayed. In the mutation experiments with hepatic S9 samples, the examination of DAB and quinoline revealed a marked strain difference when S9 samples prepared from PCBs-pretreated and PB-plus-5,6-BF-induced rats were used: the S9 sample from Fischer rats was available for activating the two pre-mutagens to directly acting mutagens. No marked difference in the metabolic activation of the remaining 7-pre-mutagens was observed on other S9 preparations. In examinations of mutagenicity activities with the use of three inhibitors, the two S9 preparations made with the two induction methods showed inhibition profiles closely similar to each other. However, there were minor differences in the profiles by these inhibitors. From these findings it was concluded that Fischer rat-liver S9 is useful for detecting mutagens in the metabolic activation test, when induction by PB plus 5,6-BF was used in the Ames Salmonella test.

Animals↗
PubMed1982

Effects of 7, 8-benzoflavone and SKF 525-A on the enzyme-mediated mutagenicity of phenylenediamines.

The effects of microsomal enzyme inhibitors (7, 8-BF and SKF 525-A) on the S-9-mediated mutagenicity of o-, m- and p-phenylenediamine were investigated using Salmonella typhimurium TA98. SKF 525-A did not affect the enzyme-mediated mutagenicity of m- and p-phenylenediamine, while 7, 8-BF reduced significantly the mutagenicity of all three isomers of phenylenediamine. When the enzyme reactions in the agar overlayer were stopped successively by adding 7, 8-BF directly onto the plate, the number of revertants increased linearly with time at least for 6 hours. These data suggest that cytochrome P-448 takes a main role in the activation of phenylenediamines and that in the agar layer this microsomal enzyme remain active for a period as long as 6 hours at 37 degrees C.

Animals↗
PubMed1982

Failure to validate the growth of Mycobacterium leprae on M-Y 14b agar medium.

Confirmation experiments on colony formation of M. leprae on the M-Y 14b agar medium developed by Murohashi and Yoshida were carried out for two years independently by individual members of an organized research group, according to the method described by Murohashi and Yoshida. The results obtained can be summarized as follows: a) No colony production by M. leprae on M-Y 14b agar medium was seen. b) No increase in the number of cells of M. leprae on M-Y 14b agar medium during cultivation was seen. c) Light and electron microscopic observation indicated that there was an increase in the number of non-solid bacterial cells and ghost cells with time of cultivation. d) It was found by mouse foot pad inoculation that four of six samples of M. leprae used as inocula were definitely viable. e) By means of mouse foot pad inoculation, it was shown that viability of M. leprae inoculated onto M-Y 14b agar medium was lost within approximately seven weeks of cultivation. From these results, can be definitely concluded that there is no evidence indicating that multiplication of M. leprae took place on M-Y 14b agar medium.

Agar↗
PubMed1981

Mutagenicity studies on alcohol extracts from gamma-irradiated potatoes.

The alcohol extracts freshly prepared from gamma-irradiated potatoes were examined for their mutagenic activity in bacterial and mammalian cell systems. Negative results were obtained from all following test systems: Mutation assays with Salmonella typhimurium His- strains such as TA 100, TA 98, TA 1535, TA 1537, and streptomycin-dependent mutant (SMd) strain, TA 100-10, inductests with Escherichia coli strains, K 12 GY 5027 and K 12 C600, chromosomal aberration tests with Chinese hamster cells in culture, as well as micronucleus tests in mice. In addition, no difference in the mutagenic activities was found between extracts prepared from the irradiated and the unirradiated potatoes, suggesting that no mutagenic substance was produced in potatoes following gamma-irradiation.

Alcohols↗
PubMed1980

Chromosome aberration tests with Chinese hamster cells in vitro with and without metabolic activation--a comparative study on mutagens and carcinogens.

Chromosome aberration tests (CH-test) in vitro were carried out on more than 400 chemicals from our environment, which included carcinogens and other compounds such as food additives, medical drugs, pesticides and those used in laboratories or industries. All results were compared with those obtained by mutation assays with bacteria (Ames test). Nearly half of these chemicals tested were positive either in the CH-tests or in the Ames tests. Among the chemicals being positive in the CH-tests, however, there were some which were negative in the Ames tests but have been proved to be carcinogenic in animals. Mammalian cell systems, therefore, may be not dispensable and are postulated for the primary screening for chemical mutagens and carcinogens in our environment.

Animals↗
PubMed1980

Differential mutagenicities of 6 N-nitroso-N-alkylurea derivatives in Escherichia coli strains with different DNA-repair capacities.

Reverse mutations to prototrophy by, and killing effects of, 6 N-nitroso-N-alkylurea derivatives such as NMU, NEU, NPU, NBU, NIBU and NAU were studied with E. coli strains H/r30R (wild-type), Hs30R (uvrA-), O16 (polA-) and NG30 (recA-). Both strains polA- and recA- were far more sensitive to killing by the 6-compounds than were the wild-type and uvrA- strains, and there was no difference in the sensitivity between the latter 2 strains. NMU was mutagenic in all 4 strains; wild-type, uvrA- and polA- strains were almost equally mutable but the compound was slightly mutagenic in the recA- strain. The other 5 compounds, NEU, NPU, NBU, NIBU and NAU, caused hardly any mutation in the recA- strain. NEU, NPU and NBU were equally mutagenic in the wild-type, uvrA- and polA- strains; however, NIBU and NAU were more mutagenic in the uvrA- than in the wild type or polA-. From the differential mutagenicities and lethalities induced by the 6 N-nitroso-N-alkylureas into the 4 tester strains, mutational patterns of the compounds can be classified into 3 types.

DNA Repair↗