FIG 7.

SQ109 effects on epimastigotes. (A) Effects of various concentrations of SQ109, added at 24 h, on the growth of T. cruzi epimastigotes (Y strain, TcII) treated with SQ109 for 120 h at 28°C. The parasites were cultured in the absence (control) or presence of SQ109 (from 0.5 to 10 μM). The experiments were performed in triplicate, and the bars represent the standard deviations. (B to D) Light microscopy of epimastigotes treated with SQ109. (B) Untreated parasite with kinetoplast (k) shown. Epimastigotes were treated with 4.6 μM SQ109 for 24 h (C) and 48 h (D) and showed rounding of the cell body and the presence of vacuoles in the cytoplasm (arrows). Scale bars = 5 μm (B to D). (E to H) Effects of SQ109 on T. cruzi morphology, as revealed by SEM. SQ109 causes drastic morphology alterations in T. cruzi epimastigotes treated with 4.6 μM SQ109 after 24 and 48 h of treatment. (E) Untreated epimastigotes have a typical elongated shape with a smooth cell surface. (F and G) Epimastigotes treated for 24 h show plasma membrane alterations, rounding of the cell body (arrowhead), and depression of the cell surface (arrows). (H) Epimastigotes treated for 48 h with SQ109 show large plasma membrane depressions (arrows), which were seen also in some cells at shorter times. Scale bars = 2.5 μm (E to H). As with trypomastigotes, the observation of major changes in cell morphology within a short time span (24 h) suggests that the inhibition of enzymes involved in sterol biosynthesis may not be involved.