ELSEVIER Mutation Research 33X (IYYS) 51-57 DNAging Genetic Instability and Aging Effect of aging on spontaneous micronucleus frequencies in peripheral blood of nine mouse strains: the results of the 7th collaborative study organized by CSGMT/JEMS * MMS* Sei-ichi Sato ‘.I, Masako Taketomi “, Madoka Nakajima “*I, Michiyo Kitazawa b, Hiroyasu Shimada ‘, Satoru Itoh ‘, Miyuki Igarashi ‘, Naohiko Higashikuni d, Shizuyo Sutou d, Yu F. Sasaki ‘, Makoto Hayashi ‘.‘,*, Toshio Sofuni f, Takafumi Higashiguchi g, Shinji Nito g, Yasushi Kondo g, Sachiko Honda h,l, Mikiko Hayashi h, Yasuhiro Shinagawa h, Eiichi Nakajima ‘, Yoshie Oka ‘, Kayoko Shimoi j, Yumiko Hokabe j, Akira Morita j, Naohide Kinae j, Masaki Takeuchi k, Haruyoshi Hirono k, Eiji Yamamura k, Koichi Tamai ’ ” Toxicology Research Laboratories, C‘entrtd Phurmaceuttcul Reseurch Institute, Japan To&co Inc., 23 Nakogi, Hatano 257, Japan h Biosafety Reseurch Center, Foods, Drugs und Pesttcides. 5-82-2, Arahamu Shioshinden, Fukude-rho, Iwata-gun, Shizuoku 437-12 Jupnn ‘ Drug Safety Reseurch Center. Der elopmcnt Research Laboratones Datrchi Phurmrtceutical Co., Ltd., I- 16-13, Kitakasai, Edogawu-ku. Tokyo 134, Jupun ” Itohum Centrul Research Institute, I-2 Kuhoguoka. Moriya. Ibaraki 302.01, Japan Faculty of C’hemicul and Btologucd Engineering, Huchmohe N~t~onul College of Technology, Tumonoki Uwunotai 16-1, Hachinohe, Aomori 039. I I, Jupan ’ Dit ision of Genrttc~.r und Mutugenests, .Nationul lnstttute of Heulth Scrences, I-IX-1 Kamiyoga, Setagayu-ku, Tokyo 158, Japan ’ Safety Reseurch Luhorutory. Tunuhe Seiyaku Co., Ltd., 16-89. Kashtmu 3.Chome. Yodogawa-ku. Osaku 532, Japan h To~mcr Institute of Health, 17-l. Nakatatkoyamu, Kosugr-machi, Toyama 939-03, Japan ’ Pharmaceutrruls Research Center, Toyoho Co.. Ltd., 2-l-I Katata, Ohtsu, Shiga 520-02. Japan phoratory of Food Hygiene, School of Food and Nutritionul Sciemes, Unir~ersity of Shizuoka, S2-1. Yada, Shizuoka-shi, 422, Japan Toxicology Luhorutories, Yoshitomi Phurmuceuticul Industrres. Ltd., 955 Koiwai, Yoshitomi-cho, Chikujo-gun, Fukuoka-ken 871, Jupun ’ Depurtmrnt of .~luttrgmetrr. Heulth S~~rences Research Instrtute. 106. (;odo-cho, Hodoguyu-ku, Yokohama 240, Japan Accepted 15 May 1995 The Collaborative Study Group for the Micronucleus Test (CSGMT). a subgroup of the Mammalian Mutagenesis Study Group (MMS), a suborganization in the Environmental Muta- gen Society of Japan (JEMS). * Corresponding author. Tel: + 81.3-3700-1141[435]; Fax: + 81-3-3700-2348; E-mail hayashi(anihs.go.jp. ’ Member of organizing committee; S.S.: organizer-in-chief. 0921~8734/95/$09.50 P lYY5 Elsevier Science B.V. All right\ resetved SSDI 0921.8734(95)0001 I-Y