Introduction:To evaluate the efficacy of vitamin C in reducing the consequences generated by the production of free radicals in the acute and chronic phases of Chagas disease, two different doses of ascorbic acid were administered orally to 60 mice infected by Trypanosoma cruzi QM2 strain. Methods: The animals were divided into six groups: G1, G2, and G3 for the acute phase study, and G'1, G'2, and G'3 for the chronic stage. The groups G1 and G'1 received 8.6x10 -4 mg/g of vitamin C daily, whereas G2 and G'2 received 7.14x10 -3 mg/g daily. The other groups, G3 and G'3, were considered placebos and received 10µL of mineral water. Results: The study of the acute phase showed statistically significant differences between G1 and the other groups at various count days of the parasitemia evolution. The multiplying parasite was slower in G1 until the 11 th day, but on the 22 nd day it had greater parasitemia than in G2 and G3, and from the 36 th day on, parasitemia stabilized at higher levels. However, when the histopathology of acute and chronic phases is considered, one does not note significant differences. Conclusions: The administration of two different doses of vitamin C was not able to protect mice and to contain the oxidative stress caused by free radicals formed by the metabolism of oxygen (reactive oxygen species) and nitrogen (reactive nitrogen species). Keywords: Ascorbic acid. T. cruzi. Parasitemia. Free radicals. RESUMOIntrodução: Para avaliar a eficácia da vitamina C em reduzir as consequências geradas pela produção de readicais livres na fase aguda e crônica da doença de Chagas, duas diferentes dosagens de ácido ascórbico foram administradas oralmente para 60 camundongos infectados pela cepa QM2 de Trypanosoma cruzi. Métodos: Estes animais foram divididos em seis grupos: G1, G2 e G3 para o estudo da fase aguda e G'1, G'2 e G'3 para o estudo da fase crônica. Diariamente, G1-G'1 recebeu 8.6 x 10 -4 mg/g de vitamina C, G2-G'2 recebeu 7.14 x 10 -3 mg/g. Os outros grupos, G3-G'3, foram considerados placebos e receberam 10µL of de água mineral. Resultados: O estudo da fase aguda mostrou diferenças estatisticamente significativas entre G1 e os outros grupos em vários dias de contagens na evolução da parasitemia, e até o 11 o dia a multiplicação parasitária foi menor em G1, mas no 22 o dia ele tinha parasitemia maior que G2 e G3, e a partir do 36 o , a parasitemia estabilizou em altos níveis. Quando considerado o histopatológico da fase aguda e crônica, não foi notado, entretanto, diferença significativa. Conclusões: Assim, foi encontrado que a administração de duas diferentes dosagens de vitamina C não foi capaz de proteger o camundongo e conter o estresse oxidativo causado pelos radicais livres formados pelo metabolismo do oxigênio (ROS) e nitrogênio (RNS). Palavras-chaves: Acido ascórbico. T. cruzi. Parasitemia. Radicais livres.

SUMMARYThe tissue changes that occur in Chagas disease are related to the degree of oxidative stress and antioxidant capacity of affected tissue. Studies with vitamin C supplementation did not develop oxidative damage caused by Chagas disease in the host, but other studies cite the use of peroxiredoxins ascorbate -dependent on T. cruzi to offer protection against immune reaction. Based on these propositions, thirty "Swiss" mice were infected with T. cruzi QM1 strain and treated with two different vitamin C doses in order to study the parasitemia evolution, histopathological changes and lipid peroxidation biomarkers during the acute phase of Chagas disease. The results showed that the parasite clearance was greater in animals fed with vitamin C overdose. There were no significant differences regarding the biomarkers of lipid peroxidation and inflammatory process or the increase of myocardium in animals treated with the recommended dosage. The largest amount of parasite growth towards the end of the acute phase suggests the benefit of high doses of vitamin C for trypomastigotes. The supplementation doesn't influence the production of free radicals or the number of amastigote nests in the acute phase of Chagas disease.

Introduction:In order to examine the effectiveness of vitamin C (ascorbic acid) in combating the oxidative insult caused by Trypanosoma cruzi during the development of the chronic phase of Chagas disease, Swiss mice were infected intraperitoneally with 5.0 × 104 trypomastigotes of T. cruzi QM1strain.Methods:Mice were given supplements of two different doses of vitamin C for 180 days. Levels of lipid oxidation (as indicated by thiobarbituric acid reactive substances-TBARS), total peroxide, vitamin C, and reduced glutathione were measured in the plasma, TBARS, total peroxide and vitamin C were measured in the myocardium and histopathologic analysis was undertaken in heart, colon and skeletal muscle.Results:Animals that received a dose equivalent to 500 mg of vitamin C daily showed increased production of ROS in plasma and myocardium and a greater degree of inflammation and necrosis in skeletal muscles than those that received a lower dose or no vitamin C whatsoever.Conclusion:Although some research has shown the antioxidant effect of vitamin C, the results showed that animals subject to a 500 mg dose of vitamin C showed greater tissue damage in the chronic phase of Chagas disease, probably due to the paradoxical actions of the substance, which in this pathology, will have acted as a pro-oxidant or pro-inflammatory.

The low number of trypomastigote forms ingested by the newborn mice combined with biological and biochemical characteristics of blood trypomastigotes may explain the lack of transmission in this experiment.

Este estudo teve por objetivo produzir subsídios numéricos para auxiliar a caracterização das formas tripomastigotas de Trypanosoma cruzi quanto às suas dimensões, em razão da dificuldade para classificá-las apenas por seu fenótipo morfológico observado na visualização microscópica. Foi realizado, então, um estudo experimental em 150 formas tripomastigotas, obtidas de cinco cepas de T. cruzi recentemente isoladas, aplicando-se um tratamento estatístico e matemático. Os resultados mostraram que existe forte correlação entre as variáveis comprimento (C) e largura (L), sendo possível definir intervalos para agrupá-las segundo o coeficiente C/L. Assim, as formas pequenas apresentaram C/L menor ou igual a 7,06, as médias apresentaram C/L maior que 7,06 e menor que 8,12 e as grandes apresentaram C/L maior ou igual a 8,12. DESCRITORES: Doença de Chagas. Trypanosoma cruzi. Tripomastigotas.Morfometria. INTRODUÇÃODesde a descrição do protozoário Trypanosoma cruzi em 1909, por Carlos Chagas, as variações das características morfológicas da forma tripomastigota do parasito chamaram a atenção de vários pesquisadores (3, 5, 6, 16, 17). Assim, pesquisas foram realizadas com a intenção de diferenciar esse flagelado das outras espécies do gênero (3, 17).A aplicação de métodos estatísticos com essa finalidade iniciou-se com trabalhos de Pearson (12, 13), que utilizou o teste qui-quadrado para demonstrar que

The low number of trypomastigote forms ingested by the newborn mice combined with biological and biochemical characteristics of blood trypomastigotes may explain the lack of transmission in this experiment.