1. a Institute of General Physiology , University of Siena , Via A. Moro, Siena , 53100 Phone: Fax: E-mail:
2. b Institute ofThoracic and Cardiovascular Surgery
3. c Department of Ophthalmology of the University of Siena
4. d Servizio Trasfusionale , Azienda Ospedaliera Senese , Siena , Italy Phone: Fax: