Hidesuke Shimizu

The genotoxicity of a variety of aniline derivatives in a DNA repair test with primary cultured rat hepatocytes

The genotoxicity of a variety of aniline derivatives was examined by a DNA repair test with rat hepatocytes. Out of 37 aniline derivatives, 6 chemicals, i.e., 2,4,6-trimethylaniline (mesidine), 2,4-xylidine, 3,5-diaminobenzoic acid, 3,4-diaminochlorobenzene, 2-chloro-4-methylaniline and 4-chloro-N-methylaniline, elicited positive DNA repair responses. The results are in agreement with the bacterial mutagenicities with or without norharman of these compounds. Positive compounds of unknown carcinogenicity in the present assay, i.e., 3,5-diaminobenzoic acid, 2-chloro-4-methylaniline and 4-chloro-N-methylaniline are suspected of being potentially carcinogenic.

Induction of aberrant crypt foci in C57BL/6N mice by 2-amino-9H-pyrido [2,3-b]indole (AαC) and 2-amino-3,8-dimethylimidazo [4,5-f]quinoxaline (MeIQx)

The inductions of aberrant crypt foci (ACF) by two carcinogenic heterocyclic amines (HCAs), 2-amino-9H-pyrido[2,3-b]indole (A alphaC) and 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), were studied in the large intestine of C57BL/6N mice. Seven-week-old mice were fed a diet supplemented with 500 or 800 ppm of A alphaC, or 400 or 600 ppm of MeIQx for 7 weeks, followed by a basal diet for another 7 weeks. A alphaC at 800 ppm induced 8.0 +/- 1.9 and 7.8 +/- 2.5 ACF in female and male mice, respectively. MeIQx at 600 ppm induced 2.8 +/- 1.8 and 1.6 +/- 0.8 ACF in females and males, respectively. At lower concentrations of A alphaC and MeIQx, many fewer ACF were induced. No ACF were induced in the control group. The size of ACF (number of aberrant crypts/ACF) in all experimental groups was between 1.0 and 1.5. More than half the A alphaC-induced ACF were located in the region about 20-40% of the distance from the ileocecal portion to the anus. Although both of these HCAs were reported to induce tumors in the liver and other organs, but not in the large intestine, of CDF1 mice, these findings suggest that both these HCAs, and especially A alphaC, induce large intestinal tumors in C57BL/6N mice.

Carbamylhydrazine hydrochloride as a lung and blood vessel tumour inducer in Swiss mice

Abstract Administration of 0·0625% carbamylhydrazine hydrochloride in the drinking water of 6 -week-old, randomly bred Swiss albino mice for the remainder of their lifetimes, enhanced the development of tumors of the lungs and blood vessels. As compared with the untreated controls, the incidence of lung tumors rose from 21 to 50% in the females and from 23 to 30% in the males, while the incidence of blood vessel tumors increased from 5 to 18% in females, but not in the males. The study thus proves for the first time the tumorigenicity of this important industrial-laboratory chemical. The tumor-inducing capabilities of substituted hydrazines as a class and their possible environmental significance are discussed.

Genotoxicity of a variety of hydrazine derivatives in the hepatocyte primary culture/DNA repair test using rat and mouse hepatocytes

The genotoxicity of a variety of hydrazine derivatives was examined in the DNA‐repair test on rat or mouse hepatocytes. Out of 32 hydrazine derivatives, 6 chemicals, i.e., N‐acetyl‐4‐(hydroxymethyl)phenylhydrazine, 1,2‐dimethylhydrazine ‐ 2HCl, 1‐hydrazinophthalazine ‐ HCl, methylhydrazine‐sulfate, p, p′‐oxybisbenzene disulfonylhydrazide and phenylhydrazine‐HCl, elicited positive DNA repair responses in the test on rat hepatocytes. In the test on mouse hepatocytes, 4 more hydrazine derivatives, i.e., 1,1‐dimethylhydrazine, hydrazine hydrate, hydrazine sulfate and 2‐methyl‐4‐chlorophenoxyacetic acid hydrazide‐HCl also generated positive responses, in addition to the 6 positive compounds in the rat assay. These results suggest that mouse hepatocytes are more susceptible to the genotoxicity of hydrazine derivatives, and that the species differences in genotoxicity appear to he in agreement with the in vivo carcinogenicity of these agents.

Metallothionein content increased in the liver of mice exposed to magnetic fields

Abstract Although recent studies have shown that various stress can induce metallothionein (MT) synthesis in animal tissues, the induction of MT synthesis by exposure to static magnetic fields (SMF) has not been reported. We measured MT levels in the liver, kidney and brain of mice exposed to SMF and also evaluated the effect of SMF exposure on the induction of hepatic MT by treatment with carbon tetrachloride (CCl4). The MT content in the liver was significantly increased by exposure to 4.7 T of SMF for 6, 24, or 48 h, whereas that in the kidney or brain was not changed compared to the control. The combination of CCl4 injection and SMF exposure induced elevation of the hepatic MT content exceeding that induced by either treatment alone. These results indicate that exposure to the strong SMF induces MT synthesis in the liver in mice and enhances the hepatic MT synthesis induced by CCl4 administration.

Effect of estrogen on induction of micronuclei by mutagens in male mice.

The effect of estrogen on the induction of micronucleated polychromatic erythrocytes (MPCE) by mutagens was examined in male mice. In the dose-response study, a dose-related inhibition of the mitomycin C (MMC)-induced MPCE frequency by estradiol (E2) treatment was observed. In the time study, inhibitory effects of E2 on MPCE frequency by MMC were observed when MMC was administered at 0 or 1 day after injection of E2. The most effective protocol for inhibition was when E2 and MMC were used on the same day. Of mutagens other than MMC, only vincristine (VCR) showed a significant decrease in MPCE frequency when used together with E2. Benzo[a]pyrene (BaP) and 5-fluorouracil (5-FU) showed no significant decrease in MPCE frequency. The data suggest that the induction of micronuclei by mutagens is inhibited by treatment with estrogen, and this could result in a sex difference in the sensitivity of mice employed in the micronucleus test. Mechanisms of the inhibitory effects of estrogen are discussed; these might include a suppression of erythropoiesis and a possible effect on the cell membrane permeability of erythroblasts.

Induction of Metallothionein Synthesis in Transplanted Murine Tumors by X Irradiation

Although recent studies have shown that radiation can induce metallothionein (MT) synthesis in normal tissues, the induction of tumor MT synthesis by irradiation has not been reported. We examined the accumulation of MT in the Meth-A tumor (mouse fibrosarcoma cells) transplanted into mice exposed to whole-body X irradiation. In the present study, the MT content in the tumor cells was increased by X irradiation in a dose-dependent manner. The MT level induced in the tumor cells by X irradiation was elevated not only after a single exposure but also after repeated exposures. Several studies have shown that MT is one of the important cellular factors in resistance to various anticancer drugs and ionizing radiation. Thus our results suggest that the radiation-induced MT in the tumor cells may have to be taken into consideration when designing protocols for radio- and chemotherapy.

Collaborative study using the preincubation Salmonella typhimurium mutation assay for airborne particulate matter in Japan. A trial to minimize interlaboratory variation

A collaborative study has been performed over a period of 3 years to develop a suitable method for monitoring the mutagenicity of airborne particulate matter. The study was organized with 8 laboratories and performed in the following steps: (1) selection of a suitable technique for each process involved in the mutagenicity monitoring, (2) developing a tentative protocol by combining systematically the selected techniques, (3) evaluation of the protocol by intra- and inter-laboratory studies, (4) modification of the protocol according to the evaluation, and (5) evaluation of the modified protocol by conducting an interlaboratory study. We found a suitable method for mutagenicity monitoring of particles in the atmosphere. Airborne particles were sampled with a high-volume sampler, the samples were stored at -80 degrees C, extracted by sonication using dichloromethane, solvent-exchanged, and assayed by the preincubation method using Salmonella typhimurium TA98 and TA100. The observed mutagenic activity was normalized with that of an internal standard. Round robin tests revealed that the method resulted in excellent reproducibility. The coefficient of variation for mutagenic activities of airborne particulate samples collected in various districts of Japan were in the range of 14.7 +/- 6.6% to 19.6 +/- 4.0% for strains TA98 and TA100 with and without metabolic activation. We also found that the plate incorporation method was equivalent to the preincubation method for airborne particulate extracts.

Mutagenic activity of N-nitrosomethamphetamine and N-nitrosoephedrine

The mutagenicity of N-nitrosomethamphetamine (NMA) and N-nitrosoephedrine (NEP), which were synthesized in our laboratory, was examined by the modified pre-incubation method of Ames assay using Salmonella typhimurium TA100 and TA98. Both nitroso compounds showed significant mutagenic activity in the presence of hamster S9.

Indium chloride-induced micronuclei in in vivo and in vitro experimental systems.

Indium Chloride‐induced Micronuclei in In Vivo and In Vitro Experimental Systems: Ryo Takagi, et al. Department of Public Health and Environmental Medicine, Jikei University School of Medicine—