1. Endocrinology and Diabetes Unit (T.T.T., S.H, B.A.), Department of Medicine, University of Wuerzburg, D-97080 Wuerzburg, Germany;
2. Max-Planck Institute for Immunobiology (G.N., M.H.), D-79108 Freiburg, Germany;
3. Institute for Developmental Biology (K.B.R.), University of Cologne, D-50923 Cologne, Germany;
4. Department of Physiological Chemistry I (C.W.), University of Wuerzburg, D-97074 Wuerzburg, Germany