1. Environmental Health Science Laboratory, Sumitomo Chemical Company, Ltd, Osaka 554-8558, Japan
2. Bioscience Research Laboratory, Sumitomo Chemical Company, Ltd, Osaka 554-8558, Japan
3. Faculty of Health and Medical Sciences, University of Surrey, Guildford GU2 7XH, UK
4. Department of Pathology and Microbiology, Havlik-Wall Professor of Oncology, University of Nebraska Medical Center, 983135 Nebraska Medical Center, Omaha, Nebraska 68198-3135, USA