Role of melanin in the pathogenesis of cutaneous sporotrichosis.

In this study, we evaluate the clinical, histopathological and ultra structural aspects of the infection by field strain (MEL(+)) and mutated strain (MEL(-)) of Sporothrix schenckii. The development of sporotrichosis at the inoculation sites was similar for both groups of animals after the second week of the experimental period. Statistical differences appeared only at weeks 3 and 5. The pigmented isolate had greater tissue invasive capacity, promoting the formation of multifocal granulomas, whereas the albino isolate induced an enhanced inflammatory response, restraining the agent to the core of the granulomas.

Homologues of the 24-kDa flagellar Ca(2+)-binding protein gene of Trypanosoma cruzi are present in other members of the Trypanosomatidae family.

A full-length cDNA encoding the 24-kDa flagellar Ca(2+)-binding protein (FCaBP) of the Dm28c clone of Trypanosoma cruzi was cloned and characterized. Comparison of the deduced amino acid sequence with those of the FCaBPs of other T. cruzi strains revealed greater than 97% sequence conservation. FCaBP-like genes are found in Trypanosoma conorhini, Trypanosoma freitasi, Trypanosoma lewisi, Herpetomonas megaseliae, Leptomonas seymouri, and Phytomonas serpens, but not in Crithidia deanei, Leishmania amazonensis, or Endotrypanum schaudinni: Among various T. cruzi strains, FCaBP genes are located on chromosomes of different size, although all strains possess multiple FCaBP genes organized as tandemly arranged gene families. Northern and Western blot analyses revealed that FCaBP mRNAs are produced in all organisms possessing FCaBP-hybridizing sequences, indicating that expression of FCaBP or an FCaBP-like protein is common to a number of trypanosomatid species.

Heterogeneity of metalloprotease expression in Trypanosoma cruzi.

Expression of metalloprotease activities during metacyclogenesis of a series of strains and clones of Trypanosoma cruzi was investigated using SDS-polyacrylamide gel electrophoresis with a range of different co-polymerized proteolytic substrates. A complex pattern of metalloprotease expression, with considerable quantitative and qualitative variability between strains and life-cycle stages, was apparent. This is in contrast to previously published data, and data presented in this study, which demonstrate a high degree of conservation of expression of cysteine proteases in different strains and clones of T. cruzi. All the metalloprotease activities identified partitioned into the detergent phase of a Triton X-114 extract, suggesting that they are membrane-bound. Developmental regulation of expression during metacyclogenesis, either in terms of quantity, or in terms of difference in relative amounts of different isoforms, was apparent for all isolates studied except CL14. However, a clearly metacyclic-specific/metacyclic-enriched metalloprotease was detected only in T. cruzi Dm28c and 383, and our results demonstrate that a metacyclic-specific metalloprotease common to all isolates of the parasite could not be detected, at least at this level of analysis.

Ultrastructural aspects of Trypanosoma (Megatrypanum) freitasi in co-cultivation with mammalian cells.

Cultures of Trypanosoma (Megatrypanum) freitasi with L929 mouse fibroblasts at 27.5 degrees C were examined by scanning and transmission electron microscopy in an attempt to clarify the processes of colony formation by the epimastigotes and of their attachment to substrata. It was seen that the flagellates occupy intercellular spaces and do not associate with intact fibroblasts. As the trypanosome population increases, ever larger portions of the substratum are cleared of fibroblasts and occupied by conglomerates of epimastigote colonies consisting of about a dozen organisms that attach to the substratum by their anterior extremities and form pyramidal clusters. Attachment of the epimastigotes involves the flagellar membrane, which becomes extraordinarily enlarged and assumes various aspects of broad sheets, filaments and loops over the substratum or along the flagellum, which exhibits a shortened axoneme. Desmosome or hemidesmosome plaques are present when the attachment takes place between membranes or between the membrane and the substratum.

Continuous growth and differentiation of Trypanosoma (Megatrypanum) freitasi Rego, Magalhães & Siqueira, 1957, in vitro.

Trypanosoma (Megatrypanum) freitasi, a parasite of didelphid opossum, was known to be very difficult to cultivate in conventional media. Co-cultivation with L929 cell line in Baltz's medium at 27.5 degrees C resulted in luxuriant growth of the trypanosome with the production of epimastigote colonies that adhered to the surface of culture flasks or tubes, and transformation into metacyclics. Further transformation was stimulated by raising the incubation temperature. At 37 degrees C the population was of the bloodstream type and resistant to lysis by complement.

Biological aspects of the Dm 28c clone of Trypanosoma cruzi after metacyclogenesis in chemically defined media.

The biological characterization of the Trypanosoma cruzi clone Dm 28c in terms of its growth in LIT medium, cell-cycle, infectivity to mice and interaction with professional and non-professional phagocytic cells shows that it behaves as a bona fide T. cruzi representant. The biological properties of this myotropic clone do not change according to the origin of the trypomastigote forms (i. e., from triatomines, infected mice, cell-culture or from the chemically defined TAUP and TAU3AAG media). In addition Dm 28c metacyclic trypomastigotes from TAU3AAG medium display a high infectivity level to fibroblasts and muscle cells. Experiments on binding of cationized ferritin to trypomastigotes surface show the existence of cap-like structures of ferritin in regions near the kinetoplast, however the nature and role of these anionic sites remain to be determined. The results indicate that metacyclic trypomastigotes from the Dm 28c clone obtained under chemically defined conditions reproduce the biological behaviour of T. cruzi, rendering this system very suitable for the study of cell-parasite interactions and for the isolation of trypanosome relevant macromolecules.