The constitution of the Japanese Environmental Mutagen Society (JEMS) says, “The society aims to encourage basic research on mutagens in humans, other organisms, and the environment, especially mutagens that affect public health. It also aims to further good communication and the transfer of research techniques in related subjects” (Chapter 4). I believe that JEMS should follow these written objectives of the society precisely and honestly. The main theme of the 31st JEMS annual meting is, “Challenges to Internationalization and Humanization”, and it is the current requirement to the society that member want. On the matter of “Internationalization”, we held the 8th ICEM at Shizuoka last year under the most difficult circumstances and had great success, providing evidence that JEMS is effective internationally. We also played an important role in having our research in this field reflected in regulation considered in international harmonizing activities (i.e., International Workshop on Genotoxicity Testing). On the other hand, to take care global problems, e.g., air and water, international cooperation is important. Our society, however, has made little effort to cooperate with the Asian EM societies with except for a few individuals. JEMS should seek ways to collaborate on problems we share with these countries. We could possibly be a hub for communication between societies that are located in Asian countries. In an effort to do that, we organized the “Asian Environmental Mutagen Societies Forum”, hoping that it would eventually head to an Asian Association of Environmental Mutagen Societies. The topic of “Humanization” is a most important one. The ultimate goal of our field is the maintaining the highest possible quality of life (QOL), and that includes maintains the environment that affects our QOL directly or indirectly in good condition. For this purpose our society should focus more on human risk assessment, including exposure assessments of environmental mutagens, and molecular epidemiology. In addition to the main issues mentioned above, our society should orient our research more to the genome than to the detection of environmental mutagens. Also, I think that the society should contribute to regulatory requirement. This includes organizing validation studies of novel technology and establishing strategies on how to evaluate and interpret test data. From the administrative viewpoint, the organization of JEMS should be more transparent and the responsibilities of the executive and the council should be clarified. Moreover, we need to establish a mechanism for gathering opinions from the membership. On the web, we have started to improve our Home Page and mailing system to permit better communication between the executive board and society members and also among members. Lastly, I would like to mention the society’s important research activities. Our sub-organizations include the Mammalian Mutagenicity Study Group (MMS), the Bacterial Mutagenicity Study Group (BMS), the Nongenotoxic Carcinogen Study Group (NGCS), the Antimutagenesis and Anticarcinogenesis Study Group (AAS), the FISH Study Group, and Mutag 21. Activation of JEMS, we support all thee groups as official activities of JEMS. Finally, I believe, the most important factor for an active society is the individual contribution of each society member.
The individual chromosomes in animal and plant interphase cell nuclei are discretely highly compartmentalized called “chromosome territories” that are visualized by 3D-FISH techniques. The chromosome territories are mutually exclusive without mixing each other, formed in essential components of the higher order chromatin architecture. Here I reviewed historical aspects of studies on the chromosome territory and recent advancement of studies on the chromosome positioning in relation to nuclear architecture. Chromosome positioning in the interphase cell nuclei has been investigated with regard to the following two aspects : radial positioning or relative positioning. It has been generally considered that the former radial positioning of a given chromosome territory is correlated with its size, its gene-density, and replication timing, namely comprehended as non-random distribution. From a series of 3D-FISH studies on the primate and chicken cell nuclei, the topology of the radial positioning of human chromosomes 18 and 19 homologs shows highly evolutionarily conserved during the evolution, but its functional significance is still within the speculation. On the other hand, the relative positioning has much affects to the translocation frequencies between adjacent two chromosomes, that was experimentally indicated by the mouse lymphoma cell nuclei, but in human lymphocytes the majority of reports suggested the random organization without particular patterns except for some clusters formed between homologous chromosomes. In future studies higher order nuclear architecture in relation to chromosome territory will be more elucidated by 3D-FISH techniques combined with living cell (in vivo) approaches by means of visualizing various nuclear molecules.
Research studies in drug discovery are progressing with high speed due to the introduction of combinatorial chemistry and robotics. Therefore, genotoxicity screening assays which can be conducted with a small amount of compound, in a short time, and which could predict the Ames test results are required in the early stage of research. We therefore established potentially useful assays that could be run in microwell plates. The fluctuation Ames test (FAT) using 384-well plates and Salmonella typhimurium TA98 and TA100, and the SOS/umu assay (SOS) using 96-well plates with S. typhimurium TA1535/pSK1002 and NM2009 as based on FAT reports from Gatehouse et al. (1979) and Gee et al. (1998) and on SOS reports from Reifferscheid et al. (1991) were developed. Seventeen Ames positive mutagens were tested with both assays in the presence and absence of S9 mix. The percentage of correctly predicted compounds was 88 % (15/17), 88 % (15/17), and 94 % (16/17) in the FAT, SOS and FAT + SOS, respectively. The amount of compound required for the Ames test (pre-incubation method with TA98 and TA100), FAT, and SOS is 100 mg, 5 mg, and 1 mg, respectively. Practical numbers of compounds tested and cost of testing one compound is 12, 20, and 54 compounds per week, and ¥20000, ¥6400, and ¥2400, respectively. The FAT and SOS are also able to be automated, and are therefore considered useful as high throughput genotoxicity screening assays.
The micronucleus assay was conducted with 7 chemicals (2-acetylaminofluoren [2-AAF], 1-β-D-arabinofuranosylcytosine [Ara-C], colchicine, cyclophosphamide [CP], methyl methanesulfonate [MMS], potassium bromate [KBrO3], urethane) in male and female rats to determine whether the results varied with sex. Each chemical was administered twice orally, 24 h apart, to 5 rats in each of 3 dosage groups and collected bone marrow and peripheral blood 24 h later. Sex differences were observed in micronucleus induction in both polychromatic erythrocytes (bone marrow) and reticulocytes (peripheral blood), which we attributed to a sex difference in hematopoiesis. In spite of those differences, both sexes showed positive responses. We concluded that the rat is suitable for the micronucleus assay regardless of sex.
Lac+ reversion assay with the E. coli strains WP3101P-WP3106P, derivatives of WP2uvrA/pKM101, have been used to determine mutational specificity of mutagens. A minimal glucose medium supplemented with tryptophan (MGT) is used as a preculture medium in the Lac+ reversion assay. Nutrient broth (NB), on the other hand, is usually used for Trp+ reversion assay with the strain WP2uvrA/pKM101. To improve the test procedure using a common preculture medium, we investigated the sensitivity of tester strains WP3101P-WP3106P against 11 kinds of mutagens when they were precultured in NB or MGT medium. In the Lac+ reversion assay, cells grown in MGT were as sensitive to MNNG, ENNG, EMS, and N4-aminocytidine as those grown in NB. However, mutagenicities of MMS, captan, 5-diazouracil, and Na-azide were scarcely detected with NB-cultured cells. In contrast, cells grown in MGT were less sensitive to several mutagens in the Trp+ reversion assay than cells grown in NB. Therefore the use of a common preculture medium is not recommended for the Lac+ and Trp+ reversion assays.