1. Institute for Community Medicine (T.I., H.V.), D-17487 Greifswald, Germany
2. Robert Koch Institute (M.T.), 13353 Berlin, Germany
3. Institute of Clinical Chemistry and Laboratory Medicine (H.W.), D-17487 Greifswald, Germany
4. Institute of Physiology (R.R.), University of Greifswald, D-17487 Greifswald, Germany