Fig. 6.

SQ induces PS externalization and DNA fragmentation. (A) Parasites were treated without (c) and with 50 and 100 μM SQ in HBS for 1 h, costained with Alexa Fluor 488-conjugated annexin V and PI, and analyzed by flow cytometry (FL1 versus FL3) as described in Materials and Methods. Representative dot plots are divided into four quadrants. The percentage of cells in each quadrant is expressed as the mean ± SD for three independent experiments. Viable cells that did not bind annexin V or incorporate PI are represented in the lower left quadrant of each dot plot. The bottom right quadrants indicate apoptotic cells. The percentages of cells in these quadrants, expressed as means ± SD for three independent experiments, were significantly different from control values by t test (P < 0.02) only for parasites treated with 100 μM SQ. (B) SQ causes an increase of parasites in the sub-G₁ phase. DNA fragmentation was quantified by measuring the percentage of cells in the sub-G₁ DNA region. The DNA content degradation profiles of parasites were determined by flow cytometry and PI staining. Parasites were incubated without (c) or with 50 and 100 μM SQ for 24 h and then loaded with PI as described in Materials and Methods. The distribution of DNA content was analyzed by flow cytometry. The percentages of cells in the sub-G₁ phase, expressed as means ± SD for three independent experiments, were significantly different from control values by t test (P < 0.02).