The effect of laboratory maintenance of Panstrongylus megistus on its flight activity

In this study we compared two lines of #P. megistus$ which differed only by its laboratory maintenance time. PM1 (more than five generations in insectarium) and PM2 (one or two generations under laboratory conditions). The parameters studied were temperature (tp), humidity (hm), the weight/length ratios (nutritional status, w/l), isoenzyme electrophoresis at 7 locus (ME, GPI, LDH, ICD and alfa-GPD), as well as enzymatic activity of alfa-glycerophosphate dehydrogenase (alfa-GPD ac.), a crucial flight activity related enzyme. Insects were processed according to SCHOFIELD (1980) and observed througth a period of 30 days. The temperature and humidity were measured daily at the safe time, and the insects that had flighted, "good" flyers (gf), were also measured for the determination of the nutritional status. Muscle extraction was made for isoenzyme and alfa-GPD enzymatic studies. At the end of this period the same number of insects that did not fly, "bad" flyers (bf), were used as control and submitted to the same analysis. No isoenzyme difference was observed between gf and bf for the two populations. Main external factors influencing flight activity were w/l (PM1 P=0.0027; PM2 P=0.0209) and tp (PM1 P=0.0814; PM2 P=0.0118). However, PM1 and PM2 strongly differed with respect to alfa-GPD activity : it was the main difference found between PM1-gf and PM1-bf (P=0.0001), whereas it did not present any evidence for heterogeneity in PM2 (P=0.5995). We used two multivariate approaches to verify the differences between gf and bf (logistic regression and canonical variate analysis, CVA). Logistic regression was able to separate "good" from "bad" flyers of the old established laboratory strain (PM1) using as the unique parameter value the alfa-GPD activity (87 to 93% of correct attribution), while it reached lower scores (78 to 86%) in PM2, needing the combination of two or more parameters excluding alfa-GPD activity. (Résumé d'auteur

Endothelin-1 receptors play a minor role in the protection against acute Trypanosoma cruzi infection in mice

Chagas' disease, caused by the protozoan Trypanosoma cruzi, is a major cause of cardiovascular disability in countries where it is endemic. Damage to the heart microvasculature has been proposed to be an important factor in the pathogenesis of heart dysfunction. Endothelin-1 (ET-1) is a potent vasoconstrictor and exerts its effects via specific ET A and ET B receptors. A few studies have suggested a role for ET-1 and its receptors in the pathogenesis of Chagas' disease. We investigated the effects of treatment with bosentan, an ET A/ET B receptor antagonist, on the course of T. cruzi infection (Y strain) in C57Bl/6 mice. Treatment with bosentan (100 mg kg-1 day-1) was given per os starting day 0 after infection until sacrifice. Bosentan significantly increased myocardial inflammation, with no effects on parasitemia. Although the total number of nests was similar, a lower number of intact amastigote nests was found in the heart of bosentan-treated animals. Bosentan failed to affect the infection-associated increase in the cardiac levels of the cytokines IFN-g and TNF-a and the chemokines CCL2/MCP-1, CCL3/MIP-1a and CCL5/RANTES. In vitro, pre-incubation with ET-1 (0.1 µM) 4 h before infection enhanced the uptake of the parasites by peritoneal macrophages, and this effect was abrogated when macrophages were pre-treated with bosentan (1 µM) 15 min before incubation with ET-1. However, ET-1 did not alter killing of intracellular parasites after 48 h of in vitro infection. Our data suggest that bosentan-treated mice have a delay in controlling parasitism which is compensated for exacerbated inflammation. Infection is eventually controlled in these animals and lethality is unchanged, demonstrating that ET-1 plays a minor role in the protection against acute murine T. cruzi infection

In vitro and in vivo experimental models for drug screening and development for Chagas disease

Chagas disease, a neglected illness, affects nearly 12-14 million people in endemic areas of Latin America. Although the occurrence of acute cases sharply has declined due to Southern Cone Initiative efforts to control vector transmission, there still remain serious challenges, including the maintenance of sustainable public policies for Chagas disease control and the urgent need for better drugs to treat chagasic patients. Since the introduction of benznidazole and nifurtimox approximately 40 years ago, many natural and synthetic compounds have been assayed against Trypanosoma cruzi, yet only a few compounds have advanced to clinical trials. This reflects, at least in part, the lack of consensus regarding appropriate in vitro and in vivo screening protocols as well as the lack of biomarkers for treating parasitaemia. The development of more effective drugs requires (i) the identification and validation of parasite targets, (ii) compounds to be screened against the targets or the whole parasite and (iii) a panel of minimum standardised procedures to advance leading compounds to clinical trials. This third aim was the topic of the workshop entitled Experimental Models in Drug Screening and Development for Chagas Disease, held in Rio de Janeiro, Brazil, on the 25th and 26th of November 2008 by the Fiocruz Program for Research and Technological Development on Chagas Disease and Drugs for Neglected Diseases Initiative. During the meeting, the minimum steps, requirements and decision gates for the determination of the efficacy of novel drugs for T. cruzi control were evaluated by interdisciplinary experts and an in vitro and in vivo flowchart was designed to serve as a general and standardised protocol for screening potential drugs for the treatment of Chagas disease