1. Faculty of Veterinary Medicine, Okayama University of Science, 1-3 Ikoinooka, Imabari, Ehime 794-8555, Japan
2. Department of Physiological Chemistry, Biocenter, University of Wűrzburg, Am Hubland, Wűrzburg 97074, Germany
3. National Institute for Basic Biology, Nishigonaka 38, Myodaiji, Okazaki, Aichi 444-8585, Japan