Differentiation of Herpetomonas megaseliae: effects of hydroxyurea on morphology and growth.

Herpetomonas megaseliae grown in the presence of hydroxyurea showed a decline in population during the first 24 hr, eventually increasing slightly over the 7-day incubation. Throughtout the 7-day incubation period the population of the treated organisms never equaled that of the control organisms. The percentage of promastigotes, as opposed to para-and opisthomastigotes, in the treated cultures did not differ from that in the control cultures through the first 3 days in incubation. Thereafter, the percentage of promastigotes in the treated cultures dropped significantly below that of the controls. At the light microscope level, the treated organisms showed an increase in size with associated striations at the anterior end. A multiflagellate (nondividing) condition was also observed in the hydroxyurea-treated organisms. TEM and SEM studies showed pellicular convolutions, which were interpreted as the striations observed under the light microscope. The differnces in population number, kinetoplast number and position and pellicular morphology between control and experimental cultures suggests that enhanced differentiation and abortive cytokinesis are the net effects of hydroxyurea on Herpetomonas megaseliae.