• YAKHAK HOEJI
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• v.37 no.4
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• pp.350-355
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• 1993

The preparation of Streptococcus faecalis RSI is used as a medicinal preparation for human intestinal disorders. But the microbe in this preparation is very sensitive to rifampicin. If this preparation is taken with rifampicin, its therapeutic effect can not be expected. To develope rifampicin resistant mutants, the rifampicin sensitive strain S. faecalis RSI was treated with Nmethyl-N'-nitro-N-nitrosoguanidine(MNNG). Twelve strains of the MNNG-induced mutants showed distinct resistance to rifampicin and five mutants were selected for further studies. They also exhibited identical characteristics with the parent S. faecalis RSI when they were tested for lactic acid formation and growth inhibition of E. coli. From in vitro test, it was identified that rifampicin is not inactivated by certain factors of the rifampicin resistant mutants. Conclusively, the rifampicin resistant mutants are efficient strains that have insensitivity against rifampicin and original biochemical characteristics of the parent strain.

• Environmental Mutagens and Carcinogens
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• v.18 no.2
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• pp.71-76
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• 1998

Exposure to environmental toxicants can cause cellular problems including the interference of DNA repair processes which may lead to the development of cancer. The existence of toxicant-induced DNA repair abnormality was investigated using mice exposed in vivo to genotoxic chemicals and then challenging their exposed lymphocytes in vitro with bleomycin. The repair of bleomycin-induced DNA damage as estimated by the frequency of chromosome aberrations was determined. Our data indicates that the observed aberration frequencies after in vivo exposure to N-methyl-N'-nitro-N-nitnsoguanidine (MNNG) and in vitro challenge with bleomycin are consistently higher than expected. The enhanced response is not due to the induction of chromosome damage by 25 or 50 mg/kg MNNG since the chemical did not cause chromosome aberrations in lymphocytes of these mice. The observed response after the combined exposure to benzo[a]pyrene (BP) and bleomycin was significantly lower than expected with low in vivo doses of BP (50 mg/kg) and then significantly higher than expected with the high doses (200 mg/kg). We interpret our data to indicate that in vivo exposure to genotoxic agents can cause abnormal DNA repair activities. The response is, however, independent of the clastogenic activities of the inducing chemicals, but dependent upon the inducing agents and on the exposure doses.

• Journal of Life Science
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• v.23 no.8
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• pp.963-969
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• 2013

Although it is popularly believed that vitamin C protects cells from various genotoxicants, the degrees and mechanisms of itsprotective actions are not fully understood. In this study, vitamin C's protective effects against various genotoxicants were quantified, together with subsequent analyses on the mechanisms of these protective effects. Comet assay was employed to measure the degree of DNA damage in Chinese hamster ovary cells (CHO-K1) exposed to five genotoxicants, $H_2O_2$, $HgCl_2$, N-methyl-N-nitro-N-nitrosoguanidine (MNNG), 4-nitroquinoline-1-oxide (4NQO), and UV-irradiation. In cases cells were treated with $H_2O_2$, $HgCl_2$, and 4NQO together with vitamin C, the damage to DNA decreased to the level of the control group. In cases of UV-irradiation, the protective effect of vitamin C appeared, but did not reach the control levels. Interestingly, vitamin C did not have protective effects against the genotoxicity of MNNG. The degrees of DNA damage of cells treated with vitamin C prior to exposure togenotoxicants were 28~49% lower than those of cells treated with vitamin C after being exposed to genotoxicants. In conclusion, vitamin C had strong antioxidanteffects against genotoxicants by being a primary antioxidant blocking genotoxicity reaching the cells, rather than being a secondary antioxidant acting on post-exposure DNA repair processes. However, vitamin C's protective effects appearto be limited, as there are genotoxicants, such as MNNG, whosegenotoxicityis not affected by vitamin C. Therefore, the results of this study warrant furtherstudies on toxic mechanisms of genotoxicants and their interactions with protective mechanisms of vitamin C.

• Molecular & Cellular Toxicology
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• v.3 no.2
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• pp.98-106
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• 2007

Genotoxic stress triggers a variety of biological responses including the transcriptional activation of genes regulating DNA repair, cell survival and cell death. In this study, we investigated to examine gene expression profiles and genotoxic response in TK6 cells treated with DNA damaging agents MNNG (N-methyl-N'-nitrosoguanidine) and hydrogen peroxide $(H_2O_2)$. We extracted total RNA in three independent experiments and hybridized cRNA probes with oligo DNA chip (Applied Biosystems Human Genome Survey Microarray). We analyzed raw signal data with R program and AVADIS software and identified a number of deregulated genes with more than 1.5 log-scale fold change and statistical significancy. We indentified 14 genes including G protein alpha 12 showing deregulation by MNNG. The deregulated genes by MNNG represent the biological pathway regarding MAP kinase signaling pathway. Hydrogen peroxide altered 188 genes including sulfiredoxins. These results show that MNNG and $H_2O_2$ have both uniquely regulated genes that provide the potential to serve as biomarkers of exposure to DNA damaging agents.

• Korean Journal of Food Science and Technology
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• v.22 no.6
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• pp.625-631
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• 1990

This study was carried out to investigate the antimutagenic effects of five kinds of apple enzymatic browning reaction products(AEBRP) on mitomycin C (MMC), N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), 4-nitroquinoline-1-oxide(4NQO), benzo(${alpha}$)pyrene(B(${alpha}$)P) and 3-amino-1,4-dimethyl-5H-pyri-do [4,3-b]indol (Trp-P-1). In spore rec-assay using B. subtilis Hl7($rec^+$) and M45($rec^-$), homocatechol-AEBRP and hydroquinone-AEBRP showed strong antimutagenic effects on MMC and MNNG as the concentration of AEBRP increased. In the Ames test using S. typhimurium TA98 and TA100, hydroxyhydroquinone-AEBRP and pyrogallol-AEBRP showed strong antimutagenic effects on Trp-p-1 and B(${alpha}$)p in TA98 and TA100 in the presence of S-9 mix. Most of AEBRPs suppressed about 50% to 80% the mutagenesis in S. typhimurium TA98 induced by MNNG, however, AEBRPs except hydroxyhydroquinone-AEBRP showed antimutagenic effects of about 94% in TA100. Antimutagenic effects of the five kinds of AEBRPs on 4-NQO were more or less weak, in particular homocatechol-AEBRP exhibited the inhibitory effect of about 48% in TA98, and homocatechol-AEBRP and hydroquinone-AEBRP showed inhibitory effects of about 46% to 58% in TA 100.

• Journal of the Korean Society of Food Science and Nutrition
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• v.37 no.6
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• pp.691-695
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• 2008

The study was carried out to evaluate the antimutagenic effects in methanol extracts of Korean soybean paste (doenjang) added with various kinds of water (germanium water, painted maple sap) or salt (sun-dried salt, roasted salt, one time bamboo roasted salt, nine times bamboo roasted salt). Methanol extracts of germanium water doenjang (Ge-D) and painted maple sap (Acer mono Max) doenjang (PM-D) exhibited significant inhibitory activity ($56{\sim}62%$) against aflatoxin $B_1$ ($AFB_1$) by adding of 1 mg/plate in Ames test. Also, methanol extracts of Ge-D and PM-D showed stronger antimutagenic activity toward N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in SOS chromotest than traditional doenjang (TD). Methanol extracts of doenjang made with four kinds of salt revealed antimutagenic activity toward MNNG; especially, doenjang extracts using one-time bamboo roasted salt (B1-D) showed 94% inhibition at the concentration of 5 mg/plate. Methanol extracts of B1-D also had the strongest inhibitory effect against MNNG of doenjang made with different salts in SOS chromotest. As the results indicate, the various kinds of water and salt have had separate effects on the antimutagenic activity of doenjang; therefore, further research on various physiological functions of water or salt added traditional doenjang is needed.

• Korean Journal of Food Science and Technology
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• v.32 no.6
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• pp.1426-1432
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• 2000

The effects of raw anchovy, salted raw anchovy (20% salt+anchovy), 6- and 12-month fermented anchovy (20% salt added) on the N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced mutagenicities were evaluated using Salmonella assay and the SOS chromotest. The methanol extracts from raw, salted and the fermented anchovy (FA) sample increased the revertants of Salmonella typhimurium TA100 at the level of $0.125{\sim}5\;mg/plate$ in Ames test. The salted raw anchovy extract induced the largest number of the revertants. All the FA extracts had comutagenic effect on the MNNG. Twelve-month FA juice exerted the lowest comutagenic activity among the FA samples. The comutagenicity of 12-month FA was due to the synergistic effect of salt and histidine which teem in FA. Thus the Ames test using histidine requiring mutant, S. typhimurium, is not appropriate to determine the mutagenicity of FA which is rich in histidine. In SOS chromotest using E coli, raw, salted and fermented anchovy extracts did not show any mutagenicity in the absence of MNNG. The raw and fermented anchovy samples blocked the SOS response of E. coli PQ37 induced by MNNG, while raw salted anchovy increased the SOS induction factor. Twelve-month FA juice showed higher antimutagenic effects than 6-month FA samples (both solid and liquid). The ripened (12-month) FA along with raw anchovy in the SOS chromotest exhibited antimutagenic activity.

• Microbiology and Biotechnology Letters
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• v.20 no.6
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• pp.707-710
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• 1992

Bacillus stearothermophilus No.239 isolated from soil was mutated with N-methyl-N'nitro-N-nitrosoguanidine (MNNG) to yield a series of mutants with increasing levels of cyclomalto-dextrin glucanotransferase (EC 2.4.1.19` CGTase) production. After five consecutive mautation steps, a mutant MNNG 8 with about 14 times of CGTase activity than the parent strain was obtained.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2001.11a
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• pp.168-170
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• 2001

생물 계면활성제의 개발을 위해 MNNG(N-Methyl-N-Nitro- Nitrosoguanidine), EMS, UV radiator random mutation을 통해 가장 우수한 biosurfactant 생산 균주를 선별하였는데 MNNG를 처리한 균주가 유화활성 1.950, 표면장력 29.0dyne/cm으로 공시균주인 Pseudomonas aeruginosa EL-MS 유화활성 0.456과 표면장력 33.0dyne/cm에 비해 우수하였다.

• Korean Journal of Food Science and Technology
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• v.30 no.2
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• pp.450-455
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• 1998

Pine has been known as a traditional medicinal plant and as showing a physically beneficial function to a human being. Therefore, this study was performed to investigate the physiological activities of main pine neddles. Ethanol extracts from pinus needles did net exhibit any mutagenicity. On the contrary, inhibitory effects of ethanol extract were observed on mutagenicity induced by N-methyl-N'-nitro-N-nitrosoguanidine(MNNG), 4-nitroquinoline-1-oxide (4NQO), 3-amino-1,4-dimethyl-5H-pyrido-(4,3-b)indol (Trp-P-1) and benzo(a)pyrene $(B({\alpha})P)$ using Salmonella typhimurium reversion assay. On direct-acting mutagen (MNNG, 4NQO) and indirect-acting mutagen (Trp-P-1, $(B({\alpha})P)$, we observed higher inhibitory effect. Stepwise fractionation of the ethanol extract was done by using ether, chloroform, ethyl acetate, butanol and water to obtain effective fraction. Among them, water fractions $(100\;{\mu}g/plate)$ of Pinus thunbergii, Pinus rigida, Pinus densiflora and Pinus koraiensis showed high inhibition of 91.65%, 94.7%, 84.22% and 79.02%, respectively, on the mutagenicity of MNNG in Salmonella typhimurium TA100.