In vivo binding of the Cry11Bb toxin of Bacillus thuringiensis subsp. medellin to the midgut of mosquito larvae (Diptera: Culicidae)

Bacillus thuringiensis subsp. medellin produces numerous proteins among which 94 kDa known as Cry11Bb, has mosquitocidal activity. The mode of action of the Cry11 proteins has been described as similar to those of the Cry1 toxins, nevertheless, the mechanism of action is still not clear. In this study we investigated the in vivo binding of the Cry11Bb toxin to the midgut of the insect species Anopheles albimanus, Aedes aegypti, and Culex quinquefasciatus by immunohistochemical analysis. Spodoptera frugiperda was included as negative control. The Cry11Bb protein was detected on the apical microvilli of the midgut epithelial cells, mostly on the posterior midgut and gastric caeca of the three mosquito species. Additionally, the toxin was detected in the Malpighian tubules of An. albimanus, Ae. aegypti, Cx. quinquefasciatus, and in the basal membrane of the epithelial cells of Ae. aegypti midgut. No toxin accumulation was observed in the peritrophic membrane of any of the mosquito species studied. These results confirm that the primary site of action of the Cry11 toxins is the apical membrane of the midgut epithelial cells of mosquito larvae.

Fibrotic sequelae in pulmonary paracoccidioidomycosis: histopathological aspects in BALB/c mice infected with viable and non-viable Paracoccidioides brasiliensis propagules

Patients with paracoccidioidomycosis often present pulmonary fibrosis and exhibit important respiratory limitations. Based on an already established animal model, the contribution of viable and non-viable P. brasiliensis propagules to the development of fibrosis was investigated. BALB/c male mice, 4-6 weeks old were inoculated intranasally either with 4x10(6 )viable conidia (Group I), or 6.5x10(6) fragmented yeast cells (Group II). Control animals received PBS. Six mice per period were sacrificed at 24, 48, 72h (initial) and 1, 2, 4, 8, 12 and 16 weeks post-challenge (late). Paraffin embedded lungs were sectioned and stained with H&E, trichromic (Masson), reticulin and Grocott's. During the initial period PMNs influx was important in both groups and acute inflammation involving 34 per cent to 45 per cent of the lungs was noticed. Later on, mononuclear cells predominated. In group I, the inflammation progressed and granulomas were formed and by the 12th week they fussed and became loose. Thick collagen I fibers were observed in 66.6 per cent and 83.3 per cent of the animals at 8 and 12 weeks, respectively. Collagen III, thick fibers became apparent in some animals at 4weeks and by 12 weeks, 83 per cent of them exhibited alterations in the organization and thickness of these elements. In group II mice, this pattern was different with stepwise decrease in the number of inflammatory foci and lack of granulomas. Although initially most animals in this group had minor alterations in thin collagen I fibers, they disappeared by the 4th week. Results indicate that tissue response to fragmented yeast cells was transitory while viable conidia evoked a progressive inflammatory reaction leading to granuloma formation and to excess production and/or disarrangement of collagens I and III; the latter led to fibrosis.

Tratamiento de amebiasis intestinal con Secnidazol. II. Estudio doble ciego en portadores asintomáticos

Se estudiaron 100 portadores asintomáticos de Entoameba histolytica o de Entameba hartmanni, ameba no patógena que frecuentemente se confunde con la primera. Se dividieron al azar en dos grupos que recibieron secnidazol o placebo en dosis única. El secnidazol se administró, de acuerdo con la edad, a una dosis promedio de 30 mg/kg. Se hicieron controles parasitológicos post-tratamiento a la una y dos semanas y se encontró que hubo negativización en 56 por ciento de los que recibieron antiamibiano y solo en 24 por ciento de los que recibieron placebo. La tolerancia fue buena, no hubo reacciones tóxicas.

Estudio comparativo de los métodos de Kato Katz y de Beaver modificado para el recuento de huevos de helmintos / Comparative study of the Kato Katz method and the modified Beaver technic for parasite egg count

Después de revisar varios trabajos sobre métodos de recuento de huevos de helmintos, analizamos el de Kato Katz y lo comparamos son el método de Beaver modificado. Para este estudio escogimos una comunidad para recuperación de gamines, con una población de 250 estudiantes y 13 profesores, a todos los cuales se les hizo estudio de materia fecal por los dos métodos. El método de Kato Katz detectó más infecciones por Trichuris trichiura, uncinarias y Ascaris Iumbricoides, con diferencia estadíticamente significativa para los dos primeros