1. Nara Medical University, Kashihara, Nara, Japan
2. Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma, USA
3. This manuscript is dedicated to Professor Yoichi Konishi who sadly passed away on December 21, 2012 between submission of the article and its acceptance for publication.
4. San-Ei-Gen F.F.I. Inc., Chuo-ku, Osaka, Japan
5. Japan Bioassay Research Center, Japan Industrial Safety and Health Association, Hadano, Kanagawa, Japan