B-NPOx was more effective than Et-NPOX, Bz and Nx in terms of its ability to reduce amastigote nests in infected mice. (A) The effects of B-NPOx, Et-NPOx and Bz (daily dosing at 100 mg/kg for 30 or 50 days) on the amastigote nests were evaluated using tissue slices (3 μm thick) of the heart and skeletal muscles of mice infected with the Nayarit and Miguz strains of T. cruzi (these mice were the same than those studied in Figure 3). The tissue slices were stained with hematoxylin/eosin and analyzed by light microscopy. Fifty randomly selected microscopic fields from at least three mice were examined to quantify the number of amastigote nests. The mean number of amastigote nests in the infected/untreated group was set as 100%. Data were analyzed with one-way ANOVA followed by Tukey’s multiple comparisons test. ***p ≤ 0.001, **p ≤ 0.01, *p ≤ 0.05, compared with the infected/untreated mice. (B) Histological studies of the myocardium and skeletal muscle of mice infected with the NINOA strain of T. cruzi. Samples of the myocardium (a, b) and skeletal muscle (c, d) from infected/untreated mice (a, c) or of mice (b, d) treated with B-NPOx at 100 mg/kg over 50 days. Tissue slices stained with hematoxylin/eosin were analyzed at 40× magnification. The arrows indicate the amastigote nests. The images are representative of three different experiments.