NUCLEOLAR ORGANIZER REGIONS IN AKODON-ARVICULOIDES (CRICETIDAE, RODENTIA) - EVIDENCE FOR THE ACTIVITY OF RDNA GENES IN BOTH X-CHROMOSOMES OF FEMALES - Yonenagayassuda, Y.; Assis, MDL; Kasahara, S.; Labbate, M.; Souza, M. J. (Karger, 1983)