1. From the Laboratory for Physiology (A.H.C.G., N.L., E.M.W., P.K., V.W.M.v.H.), Institute for Cardiovascular Research, VU University Medical Center, Amsterdam, the Department of Hematology (A.H.C.G., D.C.R.), Erasmus University Medical Center, Rotterdam, and the Department of Biomedical Research (P.K.), TNO Quality of Life, Leiden, The Netherlands.