In vitro and in vivo assays of 3,5-disubstituted-tetrahydro-2H-1,3,5-thiadiazin-2-thione derivatives against Trypanosoma cruzi

Cytotoxicity assays of 24 new 3,5-disubstituted-tetrahydro-2H-1,3,5-thiadiazin-2-thione derivatives were performed. The 17 compounds with higher anti-epimastigote activity and lower cytotoxicity were, thereafter, screened against amastigote of Trypanosoma cruzi. Out of these 17 derivatives S-2d was selected to be assayed in vivo, because of its remarkable trypanocidal properties. To determine toxicity against J774 macrophages, a method based on quantification of cell damage, after 24 h, was used. Cell respiration, an indicator of cell viability, was assessed by the reduction of MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] to formazan. Anti-amastigote activity was estimated after 48 h by microscopic counts of May Grünwald-Giemsa-stained monolayers. Nifurtimox and benznidazole were used as reference drugs. For the in vivo experiences, mice were infected with 10(4) blood trypomastigotes and then treated during 15 days with S-2d or nifurtimox by oral route. All of the compounds were highly toxic at 100 micro g/ml for macrophages and a few of them maintained this cytotoxicity even at 10 microg/ml. Of the derivatives assayed against amastigotes 3k and S-2d showed an interesting activity, that was held even at 1microg/ml. It is demonstrated that the high anti-epimastigote activity previously reported is mainly due to the non-specific toxicity of these compounds. In vivo assays assessed a reduction of parasitemia after administration of S-2d to infected mice.     

Relation between hepatitis B carrier status and antibody against synthetic Plasmodium falciparum erythrocyte surface (pf155 - RESA) antigen

A survey on Plasmodium infection was carried out in gold mine camps located in the Brazilian Amazon. Antibody against P. falciparum ring-infected erythrocyte surface antigen (RESA) was quantified by an enzyme-immunoassay in order to assess P. falciparum exposure. Hepatitis B, a common infection in this area, was also investigated by serologic markers. Among 520 sampled subjects, 517 (99.4%) admitted previous symptomatic malaria, 106 (20.4%) had positive thick smears for malaria, 82.9% had HBV markers, and 7.1% were HBsAg positive. Anti-RESA titers was significantly lower in HBV carriers than in people with resolved HBV infection suggesting that the anti-RESA immune response could be supressed by HBV carrier status. Moreover, immunedeficient responses to both infections may take place in some subjects causing concomitant lower anti-RESA response and incapacity to clear HBV.     

Phorcotabanus cinereus (Wiedemann, 1821) (Diptera,Tabanidae), an ornithophilic species of Tabanid in Central Amazon,Brazil

In Central Amazon, Brazil, the tabanid Phorcotabanus cinereus (Wiedemann) was recorded attacking the native duck Cairina moschata (Linnaeus) (Anseriformes, Anatidae). The flight and behavior of the tabanid during the attacks and the host's defenses were videotaped and analyzed in slow motion. The tabanid was recorded flying rapidly around the heads of the ducks before landing. Landing always took place on the beak, and then the tabanid walked to the fleshy caruncle on the basal part of the beak to bite and feed. Firstly the duck defends itself through lateral harsh head movements, and then, when it is being bitten, it defends itself by rubbing its head on the body, or dipping the head into water, when swimming. If disturbed, the fly resumed the same pattern of flight as before and would generally try to land again on the same host and bite in the same place. This feeding activity was observed predominantly between 9:30 am and 4:30 pm and always in open areas, near aquatic environments, from June 1996 to January 1997, the dry season in Central Amazon. To test the attractiveness of other animals to P. cinereus, mammals, caimans and domestic and wild birds were placed in suitable habitat and the response of P. cinereus observed. P. cinereus did not attack these animals, suggesting that this species has a preference for ducks, which are plentiful in the region.     

Prevalence of Trypanosoma lewisi in Rattus norvegicus from Belo Horizonte,State of Minas Gerais,Brazil

From April 1984 to March 1985, a Trypanosoma lewisi prevalence of 21.7% was found in 429 Rattus norvegicus trapped in Belo Horizonte, State of Minas Gerais, Brazil. The infection rates were higher in male and young rats and could be attributed to ecological and behavioral factors. T. lewisi was observed in rats measuring between 60 and 250 mm. Data about monthly T. lewisi infections throughout the year are presented for the first time in Brazil, with the highest prevalences observed in the warm-rainy season (October to March).     

Temperature influence on embryonic development of Anopheles albitarsis and Anopheles aquasalis

Temperature influence on the embryonic development of Anopheles aquasalis and An. albitarsis was investigated. At 26 degrees C, 75% and 60% of respectively An. aquasalis and An. albitarsis eggs hatched, with one peak of eclosion, between the 2nd and 3rd day after oviposition. At 20 +/- 2 degrees C, around 66-70% of An. aquasalis eggs hatched, with one eclosion peak, on the 5th day. On the other hand, An. albitarsis eclosion at 21+/- 2 degrees C decreased to 10-22%, with two eclosion peaks, on the 4th-5th day and on the 9th-12th day. These data indicate a stronger temperature influence over An.albitarsis than over An. aquasalis embryos.     

In vitro and in vivo anti-Trypanosoma cruzi activity of a novel nitro-derivative

Nitroarylidenemalononitriles and their cyanoacetamide derivatives with remarkable anti-epimastigote properties, were synthesized attempting to obtain new 3,5-diamino-4-(5'-nitroarylidene)-4H-thiadiazine 1,1-dioxide derivatives, which in previous reports had shown anti-Trypanosoma cruzi activity. Tests to evaluate the cytotoxicity of compounds were performed on J774 macrophages. 5-nitro-2-thienyl-malononitrile (5NO2TM), was the only product which maintained a high anti-epimastigote activity at concentrations in which it was no longer cytotoxic, thus it was assayed against intracellular amastigotes. Its anti-amastigote activity was similar to that of nifurtimox. Afterwards in vivo toxicity and anti-chagasic activity were determined. A reduction in parasitemia was observed.     

Hantavirus pulmonary syndrome in Uberaba,Minas Gerais,Brazil

This report describes the epidemiological and clinical-evolutive characteristics of eight patients with hantavirus pulmonary syndrome (HPS) in Uberaba, Minas Gerais, Brazil. A positive history of contact with rodents was present in 100% of the cases. The time between the onset of symptoms and hospital care was, on average, 3.6 days. All patients showed clinical and laboratory findings suggestive of HPS. Elevated urea and creatinine levels were observed in 6 (75%) cases, PO2 was < 60 mmHg in 100% of the cases, and a chest X-ray demonstrated a bilateral interstitial-alveolar infiltrate. The diagnosis was confirmed by the detection of IgM antibodies against Sin Nombre virus by ELISA. Three patients died as a direct consequence of HPS.     

Charaterization of Leishmania major Friedlin telomeric terminus

Here we have characterized Leishmania major (Friedlin) telomeric terminus (the very end) using recombinants obtained by a vector-adaptor cloning protocol. As in L. donovani, the last nine nucleotides of L. major terminus are 5'-GGTTAGGGT-OH 3', differing from Trypanosoma cruzi and T. brucei terminus 5'GGGTTAGGG-OH 3', thus indicating that these sequences are genus specific. We have also made a comparative analysis between L. major and L. donovani telomere-associated sequences, and described a novel non-repeated telomeric associated sequence common to L. major low molecular weight chromosomal bands.     

Differences in sperm migration through cervical mucus in vitro relates to sperm colonization of the oviduct and fertilizing ability in goats

Sperm migration in estrous cervical mucus can be used to measure the ability of spermatozoa to migrate through the genital tract. The relationship of this test with the sperm colonization of the isthmus, and its impact on fertility has not been evaluated in goats. Our objectives were to determine the differences among spermatozoa of different bucks in their ability to penetrate homologous cervical mucus in vitro and to determine the relationship between sperm displacement through cervical mucus and the ability of spermatozoa to colonize the oviduct and penetrate IVM oocytes, in vivo. Sperm migration in cervical mucus was assessed in flat capillary tubes with a phase contrast microscope. In the first experiment, fresh semen was used to establish differences between males in the ability of their spermatozoa to migrate in cervical mucus. In the second experiment, goats in estrus were inseminated with fresh spermatozoa from males with significant differences in mucus migration ability, and sperm numbers were evaluated at the UTJ. In the third experiment, the fertilization efficiency of IVM oocytes transferred to the oviduct of estrous females inseminated with semen from the same males as earlier, was used to assess the relationship between the mucus migration test and the in vivo fertilization performance of their spermatozoa. Spermatozoa from different males varies significantly in sperm migration efficiency in cervical mucus (15.5a +/- 1.2; 14.9a +/- 1.4; 17.5ab +/- 1.2; 17.0ab +/- 1.5; 19.7b +/- 1.2; 20.1b +/- 1.4 mm; media +/- S.E.M. for males A-F, respectively, P < 0.05). Spermatozoa from males with different mucus migration efficiency values produced different sperm populations at the oviduct reservoir of inseminated females (1,233 +/- 92.3 versus 28.8 +/- 17.0 spermatozoa of males with high and low relative migration efficiency, respectively, P < 0.02). Spermatozoa from males with different mucus migration efficiency values have different fertilization rates of IVM oocytes transferred to oviduct (47/96 (49.0%) versus 25/91 (27.5%) for males with high and low relative migration efficiency, respectively, P < 0.05). Cumulative results suggest that sperm migration in cervical mucus is related to the ability of spermatozoa to colonize the oviduct and to fertilize matured oocytes in vivo.