Although hematozoa have been described from many different host species, little is known about the infection and its relationship to the physiology of the host. We studied a hematozoan, regarded as a species of Lainsonia Landau, 1973 (Lankestereliidae), which infects the monocytes of the lizard Ameiva ameiva. The infected animals show a huge monocytosis and morphological changes in the monocytes. Ultrastructurally, the parasite has an apical complex, dense bodies, electron lucent structures, plasma membrane projections and folding which may be involved with nutrition. The parasite occupies a parasitophorous vacuole (PV) exhibiting high electron density at its membrane. Mitochondria and the Golgi complex of the monocytes were concentrated around the PV, and the cytoplasm was totally occupied by a vimentin type of intermediate filament radiating from (or to) the cytosolic surface of the PV. Vimentin was identified by diameter measurement, immunofluorescence and immunoelectron microscopy. These observations indicate that this infection alters the physiological state of the host and suggest that this parasite has the ability to modify monocyte vimentin assembly.

The present work showed the presence of a megasome in Leishmania (Leishmania) chagasi amastigotes. Transmission electron microscopy analysis of ultrathin serial sections and three-dimensional reconstruction allowed visualization of large structures in amastigote forms of L. (L.) chagasi and a multivesicular tubule-lysosome structure in metacyclic promastigotes. Morphometric data showed that the relative volume occupied by the megasome and the multivesicular tubule (MVT)-lysosome structures was about 5% and 3.2%, respectively, in amastigotes and promastigotes of L. (L.) chagasi. Further characterization of the megasome in L. (L.) chagasi amastigotes was carried out by immunolabeling of cysteine proteinase, whereas the lysosomal content of amastigotes and promastigotes was confirmed by arylsulfatase cytochemistry.

No abstract