[1] Univ Ulm, Childrens Hosp, Dept Pediat, D-89069 Ulm, Germany
[2] Temple Univ, Sch Med, Dept Physiol, Philadelphia, PA 19122 USA
[3] Temple Univ, Sch Med, Dept Pediat, Philadelphia, PA 19122 USA
[4] Ruhr Univ Bochum, Dept Pathol, D-4630 Bochum, Germany