FIG. 6.

Analysis of the NO-induced apoptosis-like process in extracellular amastigotes by a cytofluorometry YOPRO-1 differential staining technique. Parasites were incubated for 6 h in 0.01 M PBS (pH 7.2) (negative control, not shown), treated for 10 min by 0.1% sodium dodecyl sulfate (necrosis control, A and B), and treated for 24 h with 50 μg of potassium antimonyl tartrate/ml (apoptosis control, C and D). Amastigotes were, respectively, incubated in 0.01 M PBS (pH 4.5) as an internal control (a 6-h incubation is depicted in E and F) and treated with 5 mM NaNO₂ for 2 h (G and H), 4 h (I and J), or 6 h (K and L). The apoptotic cell percentage (R2), corresponding to both reduced forward scatter and high fluorescence intensity, is indicated in each experimental condition. M1 shows the peak of fluorescence intensity in panels B, D, F, H, J, and L. The experiment was done three times in duplicate.