The photomicrographs of FOA-resistant and wild-type parasites during serial passaging in the absence of drug.

<p>A and B show FOA-resistant parasite at passages 2 and 12 respectively, with dark/condensed chromatin dot & cell shrinkage characterized by small and more dense cytosol (red arrowheads), confirming that the death phenomenon was a persistent feature of the FOA-resistant parasite line. The wild-type parasite (C) shows the typical ellipsoidal morphology and full cytoplasm.</p

Resistance induces internucleosomal DNA fragmentation in FOA-resistant parasite grown in mice without drug.

<p>Polyacrylamide gel electrophoretic fraction of DNA was done in two independent experiments, A and B. In A, lanes 1 represent DNA extracted from the wild-type parasite that shows no cleavage, while lanes 2 represent cleaved DNA of FOA-resistant parasite, with the main band at ≈200 bp. Similar results are represented in B, where the wild-type shows no cleaved DNA (lanes 1), while FOA-resistant parasite shows cleaved DNA and a clear band at ≈200 bp (lanes 2). Lane M is the molecular size marker (pSG5/Hinf I and φX174/HincII for A, and pSG5/Hinf I for B).</p

Parasitaemia patterns of mice infected with FOA-resistant parasite and orally treated with FOA.

<p>The mice were treated twice daily for 3 days with FOA (40 mg/kg cumulative dose) at passages 2, 5, 10 and 12. Note that the patterns mirror each other, confirming that the acquired FOA-resistance is stable. The discontinuous curve indicates that following FOA administration to mice infected with the wild-type parasite, no parasites could be observed under the microscope until day 14 p.i when recrudescent parasites were observed.</p

Electron micrographs of FOA-resistant and wild-type parasites grown in mice in the absence of drug.

<p>In (B), the trophozoite of the wild-type parasite shows normal ultrastructural morphology with various compartments and organelles well defined by membranes that have retained their integrity. In (A), late schizont of FOA-resistant parasite is seen with intact plasmalemma housing non-viable segmenters/merozoites that appear as electron dense bodies probably due to compaction of nuclear chromatin and condensation of cytoplasm. (C) is an immuno-gold electron micrograph adapted from Bhowmick et al. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0021251#pone.0021251-Bhowmick1" target="_blank">[114]</a> showing a similar ‘syncytial’ cell from <i>P. falciparum</i> with viable merozoites. Note the distinct nucleus of segmenters. Abbreviations: CN, condensed segmenter; E, erythrocyte; FV, food vacuole; IPV, intraparasitic vacuole; M, mitochodria; N, nucleus; NM, nuclear membrane; PM, plasma membrane; PV, parasitophorous vacuole; PVM, parasitophorous vacuolar membrane; VL, vacuolization.</p