1. From the Department of Ophthalmology, University Medical Center, Johannes Gutenberg University Mainz, Mainz, Germany;
2. the Department of Internal Medicine II, University Medical Center Regensburg, Regensburg, Germany;
3. the Cardiovascular Physiology Centre for Biomedicine and Medical Technology Mannheim, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany;
4. the Institute of Vegetative Physiology, Charité-Universitätsmedizin Berlin, Berlin, Germany; and
5. the Molecular Signaling Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland.