Gamma irradiation reduces the toxic activities of Crotalus durissus terrificus venom but does not affect their immunogenic activities: Y. Murata,1A. K. Nishikawa,2N. Nascimento,1H. G. Higashi,2W. Dias da Silva2 and J. R. Rogero1 (1Instituto de Pesquisas Energéticas e Nucleares IPEN-CNEN/SP—C.P—11049 Pinheiros—05508—São Paulo—Brasil, and 2Instituto Butantan—C.P. 65—Butantan—05504—São Paulo—Brasil)