It was shown in this work that the infectivity of metacyclic forms of Trypanosoma cruzi was affected upon interaction with the monoclonal antibody (10D8), which reacts with a carbohydrate epitope of the 35-and 50-kilodalton (kDa) surface glycoconjugates. The invasion of Vero cells by metacyclic forms of strains Tulahuen and G was inhibited 50 to 67% in the presence of 10D8 (10 ,g/ml), whereas a nonrelated monoclonal antibody to Plasmodium berghei had no such effect. In mice that were inoculated with metacyclic forms preincubated with 10D8 or that had passively received 10D8 before challenge with metacyclic forms, a considerable decrease in the parasitemia levels was observed. The 35-and 50-kDa antigens were detectable by the galactose oxidase and sodium boro[3HJhydride procedure but not by surface iodination or metabolic labeling with [35S]methionine, suggesting that they may be of glycolipid nature. The finding that the 35-and 50-kDa antigens are major bands recognized by sera of mice immunized with killed metacyclic forms and protected against acute infection, in addition to the results with 10D8, indicate that these glycoconjugates may play an important role in the metacyclic form-host cell association that initiates T. cruzi infection.

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O objetivo deste trabalho é mostrar que as questões sobre ética e integridade na pesquisa devem ser abordadas a partir da discussão sobre a responsabilidade do cientista e também da responsabilidade coletiva. Essa noção de responsabilidade coletiva implica uma reflexão sobre os atuais valores atribuídos ao trabalho científico como um todo nos últimos anos, os quais vêm direcionando as decisões de muitos pesquisadores e organismos ligados à pesquisa e aos resultados que dela derivam.

Eye contact is a highly salient and fundamentally social signal. This entails that the mere perception of direct gaze may trigger differentiated neurobehavioral responses as compared to other gaze directions. We investigated this issue using a visual word-spelling task where faces under different gaze directions and head orientations were displayed on-screen concomitantly with the words. We show evidence for automatic increase of skin conductance response (SCR), indicative of arousal, associated with the perception of direct gaze as compared to both averted gaze and closed eyes. Moreover, the perception of averted gaze was associated with an increase of electromyographic (EMG) corrugator activity. These effects were observed in two demanding word-spelling tasks, but not in a simple letter decision task. We propose to interpret these findings in terms of the social value of direct and averted gaze and conclude that some circumstances such as the task at hand may be essential for uncovering the neurobehavioral responses associated with the perception of others' gaze.

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