Myocardiocyte Ultrastructure and Morphometrical Analysis in Hamsters Experimentally Infected withTrypanosoma cruzi

The aim of this work was the study of ultrastructural morphologic and morphometric changes in myocardiocytes from chronic chagasic hamsters (Mesocricetus auratus), comparatively with changes described in other animal models and in human Chagas disease. Four chagasic animals and three nonchagasic controls were studied. Mitochondria changes were the most conspicuous findings, varying from swelling to complete organelle destruction. Noteworthy, T-tubules appeared tortuous and interrupted at the Z-line level and there was dehiscence in intercalated disks, especially in adherens junctions;in addition, the myofibrils were separated from each other by intracellular edema, with mild to accentuated focal lyses. In morphometric analysis, both the numeric density and the area of mitochondria from chagasic and normal control animals were statistically similar; however, the infected hamsters showed statistically significant enlarged sarcomeres and reduced myofibril thickness. Based on the morphologic and morphometric characteristics observed in these experimental animals, one may conclude that heart changes described at light microscopy in human Chagas disease can have a substrate on electron microscopy. Moreover, the hamster also constitutes a useful animal model to pathology studies in Chagas disease on electron microscopy.

Pancreatic hepatocytes in hamsters (Mesocricetus auratus) infected with Trypanosoma cruzi

Hepatocytic metaplasia may be induced in hamsters by carcinogens, and associated with aging, diabetes or chronic pancreatitis. By means of histopathologic and immunohistochemic studies, we observed pancreatic hepatocytes in hamsters infected and reinfected with Trypanosoma cruzi. The change was seen in 18 (19%) out of 94 infected animals, and was not found among 53 controls, Normal islet cells were immunoreactive for neuron-specific enolase and not reactive for NCL-HAS. Metaplastic cells were immunoreactive for NCL-HAS and not reactive for islet hormones and enolase. No relationship was observed between number of inoculations and metaplasia; however, the intensity of the inflammatory process and sequels seems to favor the development of metaplastic cells. Hamsters infected with T. cruzi may be useful to study hepatocytic metaplasia, and contribute to clarify aspects of Chagas' disease and pancreatic changes. Our data indicate that aging, in addition to inflammation and atrophy, plays a role in this change.

Partial epineural burying of nerve grafts with different sizes next to or distant from neurorrhaphy’s site: histological and electrophysiological studies in rat sciatic nerves

The aim of the present study was to compare and correlate histologically and electromyographically the effects of partial epineural burying of sural nerve segments in sectioned and sutured rat sciatic nerves. Sixty adult male Wistar rats were operated on 3 groups: Group 1, sural nerve graft, 9mm long, placed next to neurorrhaphy; Group 2, sural nerve graft, 9mm long, buryied 10mm distant from neurorrhaphy; Group 3, sural nerve graft, 18mm long, set next to neurorrhaphy. The morphological features were examined at light microscope after 3 months in 45 rats. The elements observed were: vascularization, vacuoles in nerve fibers, mastocytes and inflammatory infiltrate. The morphometry was made after 6 months in 15 rats from Group 1, 2 and 3, measuring external nerve fiber diameters and counting myelinated nerve fibers/mm². The electrophysiological study was perfomed after 6 months, registering maximum amplitude and frequency of EMG pontentials, at rest, in extensor digitorum longus muscle. Group 3 rats presented sciatic nerves better conserved morphologically and mean external nerve fiber diameters greater than those from Groups 1 and 2. There were no significant differences in density of nerve fibers/mm², and in the electrophysiological study in rats from Group 1, 2 and 3. The epineural burying of sural nerve grafts with greater length and placed next to the neurorrhaphy’s site had a significantly better regeneration of the histological features than the smaller ones distant from neurorrhaphy.