1. Departamento de Bioquímica y Biología Molecular, Universidad de Salamanca, Edificio Departamental, Avda. del Campo Charro, 37007 Salamanca, Spain
2. Department of Neurochemistry, Institute of Neurology, Queen Square, London WC1N 3BG, U.K.
3. Department of Clinical Biochemistry, National Hospital for Neurology and Neurosurgery, Queen Square, London WC1N 3BG, U.K.