1. From the Laboratory for Physiology (A.B., J.v.d.V., J.G.F.B., G.J.M.S., W.J.P.), Institute for Cardiovascular Research, VUMC, Amsterdam, the Netherlands, and the Division of Clinical Physiology (A.B., Z.P., I.E.), Institute of Cardiology, UDMHSC, Debrecen, Hungary.