Histologic effects of amniotic fluid in the early phases of bone healing: an experimental study on rabbits

The purpose of this study was to demonstrate the histological effects of amniotic fluid on bone healing in the rabbit fetus. Fetal femurs (n=34) were fractured in the diaphysis and two experimental groups were established. In group A fetuses (n=18), the fracture ends were bathed in amniotic fluid through their unsutured skin wounds. In group B fetuses (n=16), the fracture sites were isolated from amniotic fluid by suturing the wound edges. Nonoperated fetuses were used as control group (n=9). The fetuses were sacrificed on the first, third and seventh postoperative days for histological studies. Histological examination of the specimens was performed to detect inflammation, fibroblastic proliferation, bone cellularity, callus and cartilage formation. The results were compared, using the Fisher exact chi square test criteria, where no statistically significant differences were detected between group A and group B ( P>0.05). Received: 24 March 1999 / Accepted: 15 September 1999     

Preventive effect of nicardipine on hyperplastic changes in venous bypass grafts

Nicardipine is a relatively new calcium channel blocker with important properties that could result in attenuation of the adverse proliferative changes in autogenous vein bypass grafts. In this experimental, randomized, controlled study, the effect of nicardipine on the pathologic findings in aortoaortic bypass grafts was assessed. Forty-two male rabbits (Orycytolagus cuniculus) were randomized to three groups: group 1 received nicardipine and groups 2 and 3 placebo for 4 weeks, after which an aortoaortic bypass was realized with an autogenous inferior vena cava segment. During the following 4 weeks, groups 1 and 2 received nicardipine, and placebo was continued in group 3. The animals were sacrificed at the end of the study to permit removal and evaluation of the bypass grafts. The mean intimal and medial thickness values for groups 1 and 2 were lower than those for group 3, indicating that nicardipine has a significant preventive effect on the hyperplastic changes in venous bypass grafts compared to placebo. The mean intimal and medial thickness values of group 1 were also lower than those of group 2, and the differences carried statistical relevance, suggesting that the use of nicardipine before grafting could potentiate its protective effect. To provide stimulus for further research, an attempt is made to relate the hyperplasia-preventing effect of nicardipine to possible mechanisms.

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Resumen La nicardipina (N) es un bloqueador de calcio relativamente nuevo con importantes propiedades que pueden resultar en la atenuación de los cambios adversos de tipo proliferativo que ocurren en los injertos con vena autógena. En el presente estudio experimental, randomizado y controlado, se valoró el efecto de la N sobre los hallazgos patológicos en injertos aorto-aórticos. Los conejos utilizados en el estudio fueron divididos en 3 grupos: el Grupo I recibió N, mientras los grupos 2 y 3 recibieron placebo por 4 semanas, después de lo cual se practicó un injerto aorto-aórtico con segmento de vena cava inferior. En las 4 semanas siguientes, los grupos 1 y 2 recibieron N, mientras se continuaba la administración de placebo al grupo 3. Los animales fueron sacrificados al final del estudio para remover y valorar los injertos. El grosor promedio de la íntima y de la media en los grupos 1 y 2 fue menor que en el grupo 3, lo cual es indicativo de que la N posee un efecto preventivo de significación sobre los cambios hiperplásicos en los injertos de vena, en comparación con el placebo. El grosor promedio de la íntima y de la media también fue menor en el grupo 1 que en el grupo 2, y la diferencia tuvo significación estadística, lo cual sugiere que el uso de N antes de injertar puede potenciar su efecto protector. En el presente artículo se intenta relacionar el efecto preventivo de la hiperplasia de la N con algunos mecanismos probables, con miras a estimular más investigación sobre el tema.

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Résumé La nicardipine (N) est une enzyme de conversion rélativement nouvelle capable d'atténuer la prolifération néfaste des greffons veineux autogènes. Dans cette étude expérimentale, randomisée et contrÔlée, on a évalué l'effet de la N sur les pontages aortoaortiques prothétiques pathologiques. Quarante-deux lapins mâles, de l'espèce Orycytolagus cuniculus, ont été randomisés en 3 groupes. Seul le groupe 1 a reÇu de la N, alors que les deux autres groupes ont reÇu du placebo pendant 4 semaines. Un pontage aortoaortique a ensuite été réalisé en utilisant la veine cave autogène. Pendant les quatre semaines suivantes, les groupes 1 et 2 ont reÇu de la N, alors que les lapins du groupe 3 ont continué de recevoir du placebo. Tous les animaux ont été sacrifiés à la fin de l'expérimentation, les greffons ont été prélevés et examinés. L'épaisseur moyenne de l'intima et de la média étaient diminuée dans les groupes 1 et 2 par rapport au groupe 3, attestant du pouvoir de la N à réduire l'hyperplasie des greffons veineux. De mÊme, l'épaisseur moyenne de l'intima et de la média dans le groupe 1 était réduite par rapport aux groupes 2 et 3. Cette différence était statistiquement significative, suggérant que l'utilisation de N avant de réaliser un pontage avait un effet potentialisateur. Les mécanismes événtuellement capables d'expliquer l'effet d'inhibition sur l'hyperplasie sont évoqués, afin de stimuler la recherche à l'avenir.

     

Trypanosoma cruzi infection in rats induced early lesion of the heart noradrenergic nerve terminals by a complement-independent mechanism

Summary The acute phase of the experimental Chagas' disease in rats induces extensive lesion of the heart sympathetic nerve terminals. Because of evidence indicating the involvement of immune reactions in neuron destruction provoked by Chagas' disease, we tested the effects of depleting the complement system by cobra venom factor upon the sympathetic denervation. The serum hemolytic activity against sensitized sheep erythrocytes ensured the efficacy of the anticomplementary treatment. Glyoxylic acid-induced histofluorescence and electron-microscopic methods allowed the study of the heart noradrenergic nerves.T. cruzi infection caused marked rarefaction of fluorescent nerve terminals at day 10 of infection and the ultrastructural study guaranteed that this rarefaction involved lesion of noradrenergic terminals. The complement depletion failed to prevent this early heart noradrenergic denervation, excluding the participation of complement-mediated lysis as a main mechanism.