Effect of 2-deoxy-D-glucose on Herpetomonas samuelpessoai

Biology of human pathogenic trypanosomatids: epidemiology, lifecycle and ultrastructure

Leishmania and Trypanosoma belong to the Trypanosomatidae family and cause important human infections such as leishmaniasis, Chagas disease, and sleeping sickness. Leishmaniasis, caused by protozoa belonging to Leishmania, affects about 12 million people worldwide and can present different clinical manifestations, i.e., visceral leishmaniasis (VL), cutaneous leishmaniasis (CL), mucocutaneous leishmaniasis (MCL), diffuse cutaneous leishmaniasis (DCL), and post-kala-azar dermal leishmaniasis (PKDL). Chagas disease, also known as American trypanosomiasis, is caused by Trypanosoma cruzi and is mainly prevalent in Latin America but is increasingly occurring in the United States, Canada, and Europe. Sleeping sickness or human African trypanosomiasis (HAT), caused by two sub-species of Trypanosoma brucei (i.e., T. b. rhodesiense and T. b. gambiense), occurs only in sub-Saharan Africa countries. These pathogenic trypanosomatids alternate between invertebrate and vertebrate hosts throughout their lifecycles, and different developmental stages can live inside the host cells and circulate in the bloodstream or in the insect gut. Trypanosomatids have a classical eukaryotic ultrastructural organization with some of the same main organelles found in mammalian host cells, while also containing special structures and organelles that are absent in other eukaryotic organisms. For example, the mitochondrion is ramified and contains a region known as the kinetoplast, which houses the mitochondrial DNA. Also, the glycosomes are specialized peroxisomes containing glycolytic pathway enzymes. Moreover, a layer of subpellicular microtubules confers mechanic rigidity to the cell. Some of these structures have been investigated to determine their function and identify potential enzymes and metabolic pathways that may constitute targets for new chemotherapeutic drugs.

Particularities of mitochondrial structure in parasitic protists (Apicomplexa and Kinetoplastida)

Without mitochondria, eukaryotic cells would depend entirely on anaerobic glycolysis for ATP generation. This also holds true for protists, both free-living and parasitic. Parasitic protists include agents of human and animal diseases that have a huge impact on world populations. In the phylum Apicomplexa, several species of Plasmodium cause malaria, whereas Toxoplasma gondii is a cosmopolite parasite found on all continents. Flagellates of the order Kinetoplastida include the genera Leishmania and Trypanosoma causative agents of human leishmaniasis and (depending on the species) African trypanosomiasis and Chagas disease. Although clearly distinct in many aspects, the members of these two groups bear a single and usually well developed mitochondrion. The single mitochondrion of Apicomplexa has a dense matrix and many cristae with a circular profile. The organelle is even more peculiar in the order Kinetoplastida, exhibiting a condensed network of DNA at a specific position, always close to the flagellar basal body. This arrangement is known as Kinetoplast and the name of the order derived from it. Kinetoplastids also bear glycosomes, peroxisomes that concentrate enzymes of the glycolytic cycle. Mitochondrial volume and activity is maximum when glycosomal is low and vice versa. In both Apicomplexa and trypanosomatids, mitochondria show particularities that are absent in other eukaryotic organisms. These peculiar features make them an attractive target for therapeutic drugs for the diseases they cause.

Alterations induced by the antifungal compounds ketoconazole and terbinafine in Leishmania

The antiproliferative effects and ultrastructural alterations induced in vitro by two antifungal compounds, the azole ketoconazole and the allylamine terbinafine on Leishmania amazonensis are reported. Promastigotes treatment with ketoconazole and terbinafine induced growth arrest and cell lysis in 72 hours. Combination of the two agents produced additive effects on promastigote axenic growth and synergistic effects on intracellular amastigote proliferation. The amastigotes, either axenically grown or infecting murine macrophages, were about 100-fold more sensitive to the drugs. These compounds induced the appearance of large multivesicular bodies, especially after ketoconazole treatment, increased amount of lipid inclusions as well as numerous, polymorphic volutin granules, particularly in terbinafine-treated cells. Multivesicular bodies were observed in close apposition with organelles such as mitochondria, which also showed alterations in the distribution and appearance of cristae, and the formation of paracrystalline arrays within the matrix. Some cells presented large portions of cytoplasm wrapped by endoplasmic reticulum and many parasites also presented myelin-like endoplasmic reticulum profiles. Such alterations together with the strong acid phosphatase activity observed in the multivesicular bodies and volutin granules may indicate the existence of an unusual autophagic process in cells treated with ergosterol biosynthesis inhibitors.

Biological effects of lithium chloride on the insect trypanosomatid Herpetomonas samuelpessoai

Effects of lithium chloride on growth, differentiation and respiration of Herpetomonas samuelpessoai, cultivated in a synthetic medium were studied both at 28 and 37 degrees C. Low concentration of lithium chloride (15 mM) stimulated growth at 37 degrees C. In addition, the protozoon tolerated high concentrations (60-150 mM) of the salt at both incubation temperatures. In general, 15 mM lithium chloride increased and 150 mM decreased oxygen uptake when glucose, glutamic acid and proline were used as substrates. However, at 28 degrees C after incubation for 96 h, the highest concentration increased oxygen uptake in the presence of glucose. Sodium butyrate induced cell differentiation in H. samuelpessoai both at 28 and 37 degrees C. High concentration (150 mM) of lithium chloride inhibited cell differentiation of H. samuelpessoai induced by both controlled growth conditions and butyrate addition. The results obtained are described in this paper.

Studies on the ultrastructure, virus-like particles and infectivity of Leishmania hertigi

Five strains of Leishmania hertigi hertigi isolated in Panama and three strains of L. hertigi deanei isolated in Brazil were studied. Ultrastructural examination of promastigotes grown in culture showed virus-like particles (VLPs), 55--60 nm diameter, in the cytoplasm of all strains. The VLPs were normally either organized in paracrystalline clusters or associated with induced tubules. In some cases the VLPs were associated with dense vesicular bodies. Mitochondria with which the VLPs were associated had enlarged elongate or circular cristae. Elongate 'microbodies' containing rod-like structures were observed in promastigotes grown in culture. Poor infections of promastigotes developed in the midguts of 10% of laboratory-bred Lu. longipalpis following experimental feeding on cultures of L. h. hertigi. VLPs were seen in a promastigote in the midgut of a sandfly five days after feeding. Laboratory mammals proved poor hosts for L. hertigi. Cryptic infections in the visceral organs of immunosuppressed hamsters and immunodeficient 'nude' mice were detectable only by culture. Infections of DS cell and mouse peritoneal macrophage cultures showed amastigotes with a high ribosomal density and deep invaginations of the pellicular layer. VLPs were rarely seen in these amastigotes.