Assuntos

RESUMO

Leishmania mexicana mexicana promastigotes, axenic amastigotes, and amastigotes derived from Vero cells were examined for de novo purine synthesis and mechanisms of purine salvage. Both promastigotes and axenic amastigotes were incapable of de novo purine synthesis, as shown by the lack of [14C]formate and [14C]glycine incorporation into purine nucleotide pools. However, the ready incorporation of [14C]hypoxanthine, [14C]adenine, and [14C]guanine suggested that purine salvage pathways were operating. In addition, a significant percentage (greater than or equal to 60%) of the total label from these purine precursors was associated with adenylate nucleotides. Nucleotide pool levels of axenic amastigotes were consistently greater but the specific activities were less than those of promastigotes, suggesting a slower rate of purine metabolism in the axenic amastigote form. Similar results were obtained from amastigotes isolated from infected Vero cells.

Assuntos

RESUMO

The susceptibility of 12 strains of inbred mice representing a broad genetic spectrum to infection of Leishmania braziliensis, L. mexicana and L. aethiopica was determined. Levels of susceptibility were evaluated by gross morphology of lesions, evidence of resolution, persistence of parasites at the site of inoculation, and visceralization to the spleen or liver following inoculation in noses. Very different patterns of responses were noted among the infections with the three species of Leishmania. Among the strains of inbred mice infected with L. braziliensis, patterns of cutaneous lesion development indicated a broad range of susceptibilities and responses. Two strains of inbred mice (AKR/J and CBA/J) showed only a slight and transient swelling of the nose. The SWR/J, C57L/J, A/J, A/HeJ and DBA/1J showed initial swellings or nodules which eventually resolved. In contrast, the BALB/cJ mice were ranked as most susceptible, based on progressive dermal lesions and visceralization. Four strains of inbred mice (C3H/HeJ, C57BL/6J, CBA/J and CBA/CaJ) showed no evidence of infection. Lesion development in most strains of inbred mice infected with L. mexicana occurred later than with L. braziliensis but was then more rapidly progressive with no indication of resolution. Two strains (C3H/HeJ and C57BL/6J) showed no evidence of infection. Only slight swellings of the nose were seen in the 12 strains of inbred mice infected with L. aethiopica; however, parasites were isolated by culture from apparently normal noses in five groups (A/HeJ, AKR/J, BALB/cJ, DBA/2J and SWR/J).

Assuntos

RESUMO

Promastigotes of Leishmania braziliensis panamensis absorbed the purines adenine, hypoxanthine, adenosine and inosine by a combination of diffusion and mediated components. When the uptake rates for these substrates were corrected for diffusion and compared, the purine bases adenine and hypoxanthine were transported at a significantly slower rate than the purine nucleosides adenosine and inosine. Competitive interactions among those purines tested confirmed the presence of mediated and diffusion components and suggested that three transport loci may be operating (Fig. 6). The first transport locus, designated Locus 1, transported inosine, Locus 2, the purine bases hypoxanthine and adenine and Locus 3, adenosine. In addition, adenine and hypoxanthine inhibited the uptake of one another competitively. A comparison of Ki values derived from double reciprocal plots of labelled hypoxanthine and adenine uptake in the presence of the unlabelled substrates as inhibitors suggested that adenine has a greater affinity for the transport locus.

Assuntos

RESUMO

The interaction between macrophagelike cells (P388D murine tumor cells) and Leishmania braziliensis panamensis promastigotes was studied in vitro under various conditions by light and electron microscopy. When the macrophagelike cells and L braziliensis promastigate were incubated together for 2 minutes, 90% of the promastigotes were attached to the macrophagelike cells by the tip of the flagella. The macrophagelike cells did not form pseudopods or aggregated microfilaments around the inserted flagellum. After a 5-minute incubation period, the parasites attached to the macrophagelike cells did not show preferred orientation. At this time, numerous pseudopods and aggregated microfilaments of the macrophagelike cells were seen around the invading parasites. When the relationship between the cytochalasin B-treated promastigotes and the macrophagelike cells were examined, no interaction of the promastigote flagella with macrophagelike cells was observed at 2 minutes. After a 5-minute incubation period, 50% of the attached parasites adhered to a macrophagelike cell without any particular orientation. When the interaction between the promastigotes and cytochalasin B-treated macrophagelike cells were examined, the cytochalasin B-treated cells showed fewer pseudopods than the untreated cells, and the number of parasites attached to them was reduced considerably after a 5-minute incubation period. This data demonstrated, for the first time, that the mode of entry by Leishmania promastigotes into macrophagelike cells is dependent on the activation of the macrophagelike cells following the attachment of Leishmania promastigotes.

Assuntos

Assuntos

RESUMO

Thirty-four Mystromys albicaudatus were injected intradermally with Leishmania braziliensis promastigotes and examined and killed during a 12-week period. All animals developed single cutaneous lesions at the sites of inoculation that began as a papular thickening in the dermis and progressed to a 2.0 cm crateriform ulcer. The histopathology of these lesions was characterized by granuloma formation and diffuse infiltrates of lymphocytes and plasma cells. Parasites were most frequently observed in vacuolated macrophages immediately underlying the necrotic debris of the ulcer. Histiocytes in which amastigotes were not identified were noted in aggregates at the margins of the inflammation. Russell's bodies were observed at 6 weeks post-infection, and discrete lymphocytic infiltrates bordered the inflammation at 12 weeks post-infection. It is suggested that M. albicaudatus is an excellent model of American cutaneous leishmaniasis.

Assuntos

RESUMO

In November 1977, 627 soldiers belonging primarily to the First Battalion, 82nd Airborne Division, stationed at Fort Bragg, were sent to the Canal Zone, Panama, for jungle warfare training. A medical surveillance program incorporating pre- and post-evaluations over a 6-month period with dermatologic examinations, questionnaires, and serologic tests was established. Ten cases of cutaneous leishmaniasis (1.6/100 men) were diagnosed by positive Leishmania culture. The demonstrated lack of sensitivity and specificity of the indirect fluorescent antibody test and the direct agglutination test render these serological methods useless as diagnostic screening methods in the early stages of this disease.

Assuntos