The hamster (mesocricetus auratus) as experimental model in chagas' disease: parasitological and histopathological studies in acute and chronic phases of Trypanosoma cruzi infection

This research characterizes the acute and chronic phases of Chagas ' disease in hamster through parasitological and histopathological studies. The acute phase was achieved with 44 young hamsters injected intraperitoneally with 100.000 blood trypomastigotes of Benedito and Y strains of T. cruzi. The chronic phase was induced in 46 hamsters injected intraperitoneally with 35.000 trypomastigotes ofVicentina, Benedito and Y strains. Animals were sacrificed at regular intervals of 24 hours of acute phase and from the 3rd to the 10th month of infection ofchronic phase. In the acute phase, parasites were easily recoveredfrom all animals and there was an inflammatory reaction characterized by mononuclear and polymorphous leukocyte infiltration of variable degree in the majority of tissues and organs, specially in the connective loose and fatty tissues, smooth muscle myocardium and skeletal muscle. In the chronic phase the lesions occurred in the same tissues and organs, but the inflammatory response was less severe and characterized by mononuclear infiltration mainly with focal or zonalfibrosis in the myocardiun. In 50% of infected animals parasites were found inmyocardiun and recoveredfrom pericardic, peritoneal and ascitic fluids in some animals. Signs of heart failure, sudden death and enlargement of bowel were observed regularly. We concluded that the hamster is an useful model for Chagas' disease studies.

The hemorrhagic syndrome of leptospirosis: an experimental study in guinea pigs

The hemorrhagic syndrome of leptospirosis was studied in guinea pigs. The study correlates hematological, histopathological and immunohistochemical alterations in sixty animals inoculated by the intraperitoneal route with lml of the culture of virulent strain of Leptospira interrogans serovar copenhageni. Leptospirae antigens were detected by immunoperoxidase, chiefly in liver, kidney and heart muscle capillaries. Possible pathogenic mechanisms responsible for hemorrhagic syndrome are discussed with emphasis on toxic and anoxic attacks causing damage to endothelia, platelet depletion and alterations to hemostasia rates: prothrombin time [FT], partial thromboplastin time [PIT] and fibrinogen concentrations. Tide clinical-laboratoiy picture is compatible with the histopathological observation of disseminated intravascular coagulation [D1C] in most of the guinea pigs from day 4 of infection.

Hipersensibilidade tardia a antígeno de Trypanosoma cruzi: I - estudo experimental em coelhos

Reações de hipersensibilidade cutânea tardia em coelhos infectados com Trypanosoma cruzi homólogo ou heterólogo, foram obtidas pela injeção de 50µg de proteína do antígeno T12E, derivado de um clone do parasito. A especificidade do teste foi indicada pela ausência de reação em coelhos controles normais que receberam a mesma quantidade de antígeno na pele. A injeção intradérmica do antígeno, em cinco ocasiões, não induziu reação cutânea positiva ou soroconversão dos exames de hemaglutinação e aglutinação, em coelhos controles normais. Por outro lado, coelhos chagásicos submetidos a série de cinco testes cutâneos, com intervalos de uma semana, não exibiram alteração da intensidade das reações de hipersmsibilidade ou dos perfis dos títulos de anticorpos séricos. Os registros eletrocardiográficos também não foram alterados pelos testes cutâneos em coelhos normais e chagásicos. A inocuidade do antígeno T12E foi confirmada em experimentos realizados em 36 coelhos chagásicos e 19 coelhos controles normais. Esse estudo mostra que o teste cutâneo com o antígeno T12E pode ser útil no diagnóstico, além de servir como indicador de morbidade da doença.

Biodemes and zymodemes of Trypanosoma cruzi strains: correlations with clinical data and experimental pathology

With the objective of establishing biological and biochemical characteristics of a significant number of Trypanosoma cruzi strains from different geographical areas, 138 strains isolated from naturally infected humans, triatomine or vertebrate hosts were studied; 120 were isolated from different areas of Brazil and 18 from other South and Central American countries. Inocula from triatomine or culture forms were injected into suckling Swiss mice, followed by passages into mice 10 to 12 g. Biological characters and histopathological study permitted the inclusion of the strains into three Types or biodemes: I, II, III. Isoenzymic analysis confirmed a correspondence between the biodemes and zymodemes : Type I and Z2b, Type II and Z2, Type III and Z1. Results showed the ubiquitary distribution of the several types of strains. The predominance of the same Type and zymodeme in one geographical area was confirmed : Type II strains among the human cases from eastern Bahia and east of Goiás; Type III strains from humans of north Brazil and Central America and from silvatic vectors or vertebrates from other geographical areas. The biological types of strains correlate with different histopathological lesions considering cardiac involvement and neuronal lesions. These findings suggest that the biological behavior together with isoenzymes patterns and pathological pictures in the vertebrate host can be an important tool for establishing correlations between strains behavior and clinico-pathological manifestations of Chagas' disease in different geographical areas.