TEM analysis of <i>N. caninum-</i>infected HFF cultures in the presence of 2.5 μM of inhibitor 1294 for 5 and 9 days.

<p><b>A–C</b> illustrate two distinct outcomes of treatment with 2.5(PV1 and PV2) in a HFF cell. In <b>B</b>, the higher magnification view of PV1 reveals non-viable remnants of tachyzoite (tach), now largely embedded in a solid matrix (*), and as indicated by arrows, the parasitophorous vacuole membrane has been replaced by a rather amorphous transition zone between PV1 and the host cell cytoplasm. In <b>C</b>, PV2 displays a complex of still viable and presumably proliferating, but non-separating, parasites forming a large multi-nucleated mass, with clearly discernable micronemes (mic), rhoptries (rho), dense granules (dg), and smaller nuclei (nuc). Note the large nuclear mass (NUC) in the center with a large nucleolus marked by the bold arrow. In <b>D</b>, and at a higher magnification in E, a similar multinucleated complex is shown after 9 days of treatment with compound 1294, also displaying a large nuclear mass (NUC), as well as rhoptries, micronemes, dense granules, and an intact parasitophorous vacuole membrane. In <b>F</b>, a non-viable complex with tachyzoite remnants (tach) is shown after 9 days of treatment. Note the difference in electron density of the matrix of PVs containing non-viable parasites (B, F) compared to viable multinucleated complexes (C, D, E). Bars in A = 5 μm; B = 0.8 μm; C = 0.9 μm; D = 2 μm; E = 0.7 μm; F = 0.9 μm.