Induction of differentiation in Herpetomonas samuelpessoai by dimethylsulfoxide.

Dimethylsulfoxide (DMSO) induces in Herpetomonas samuelpessoai, grown in a chemically defined medium at 28 degrees C the transformation of promastigotes into paramastigotes and opisthomastigotes. This effect was dependent on the period of cultivation and the concentration of DMSO. Initially, DMSO induced the appearance of paramastigotes and later, of opisthomastigotes. Approximately 43% opisthomastigotes were obtained after growth of the protozoan for 96 h at 28 degrees C in a medium containing 3% DMSO. No ultrastructural changes were observed on DMSO-treated cells. Based on these results and others previously described, the process of differentiation in Herpetomonas is compared and analyzed with that occurring in Trypanosoma.