Yoshino, Tomio; Nishiguchi, Yukari; Katou, Keiko.
Studies have been carried out on the amount of hydrogen chloride formed by the radiolysis of some chloroalkanes and the energy absorbed in the solutions. The samples were prepared by dissolving p-dimethylaminoazobenzene as a dye (1.0 x 10 -4 mol/dm 3 ) in the chloroalkanes, and were irradiated at a dose of 2500 R at 20degC. The amount of hydrogen chloride formed in the irradiated sample was determined spectrophotometrically. The absorbed dose of the irradiated sample was calculated from the equation, D M =8.77 x 10 -3 x (Z/A) M /(Z/A) A x R A (Gy). G(HCl) values for hydrogen chloride formed in the solutions of chloroform, 1,2,3-trichloropropane and 1,2-dichloroethane were 10.2, 8.5 and 5.7, respectively. On the other hand, the dielectric constants of the above chloroalkanes measured were 4.3, 7.8 and 10.7, respectively, being in inverse proportion to G(HCl). These results seem to suggest that the formation of hydrogen chloride and its reaction with the dye in the irradiated solution are influenced by the dielectric constant of chloroalkane. (author)
Koizumi, Shinji; Ohno, Shotaro; Otsuka, Fuminori
Gene expression processes are now recognized as important targets of the toxic effects exerted by industrial chemicals. The transient transfection assay is a powerful tool to evaluate such effects. Thus, we developed a versatile assay system by constructing a basic reporter plasmid in which the regulatory DNA sequence to be studied can easily be substituted. To verify the performance of this system, reporter plasmids carrying any of the three distinct regulatory sequences, estrogen responsive element (ERE), glucocorticoid responsive element (GRE) and xenobiotic responsive element (XRE) were constructed. After transfection of human cells, these plasmids successfully expressed the relevant reporter genes in response to specific inducers, β-estradiol, dexamethasone and 3-methylcholanthrene, respectively. Several industrial chemicals were assayed using these reporter plasmids, and the ability of p-dimethylaminoazobenzene to elevate GRE- and XRE-mediated transcription was detected. α-Naphthylamine and o-tolidine were also observed to increase the XRE-mediated response. The transfection assay system established here will be useful to evaluate the effects of a wide variety of industrial chemicals.
Evaluation of a liver micronucleus assay in young rats (IV): a study using a double-dosing/single-sampling method by the Collaborative Study Group for the Micronucleus Test (CSGMT)/Japanese Environmental Mutagen Society (JEMS)-Mammalian Mutagenicity Study Group (MMS).
Takasawa, Hironao; Suzuki, Hiroshi; Ogawa, Izumi; Shimada, Yasushi; Kobayashi, Kazuo; Terashima, Yukari; Matsumoto, Hirotaka; Oshida, Keiyu; Ohta, Ryo; Imamura, Tadashi; Miyazaki, Atsushi; Kawabata, Masayoshi; Minowa, Shigenori; Maeda, Akihisa; Hayashi, Makoto
A collaborative study was conducted to evaluate whether a liver micronucleus assay using four-week-old male F344 rats can be used to detect genotoxic rat hepatocarcinogens using double-dosing with a single-sampling 4 days after the second dose. The assay methods were thoroughly validated by the seven laboratories involved in the study. Seven chemicals, 2,4-diaminotoluene, diethyl nitrosamine, p-dimethylaminoazobenzene, 1,2-dimethylhydrazine dihydrochloride, 2,4-dinitrotolunene, 2,6-dinitrotoluene and mitomycin C, known to produce positive responses in the single-dosing/triple-sampling method were selected for use in the present study, and each chemical was examined in two laboratories with the exception of 2,4-dinitrotolunene. Although several of the compounds were examined at lower doses for reasons of toxicity than in the single-dosing/triple-sampling method, all chemicals tested in the present study induced micronuclei in liver cells indicating a positive result. These findings suggest that the liver micronucleus assay can be used in young rats to detect genotoxic rat hepatocarcinogens using a double-dosing/single-sampling procedure. Further, the number of animals used in the liver micronucleus assay can be reduced by one-third to a half by using the double-dosing/single-sampling method. This reduction in animal numbers also has significant savings in time and resource for liver perfusion and hepatocyte isolation. Copyright 2010 Elsevier B.V. All rights reserved.