R Benigni1, A Giuliani, R Franke, A Gruska. 1. Istituto Superiore di Sanitá, Laboratory of Comparative Toxicology and Ecotoxicology, Viale Regina Elena 299, I-00161 Rome, Italy, and Consulting in Drug Design GbR, Gartenstr. 14, D-16352 Basdorf, Germany.