1. Department of Clinical and Experimental Medicine, University of Verona, Policlinico G.B. Rossi, 37134 Verona, Italy
2. Vitamin Metabolism Laboratory, Jean Mayer U.S. Department of Agriculture Human Nutrition Research on Aging at Tufts University, Boston, MA 02111
3. Institute of Biology and Genetics, University of Verona, Policlinico G.B. Rossi, 37134 Verona, Italy
4. Institute of Clinical Chemistry, University of Verona, Policlinico G.B. Rossi, 37134 Verona, Italy