Sex influences diaphragm muscle response in exercised mdx mice.

Physical exercise promotes increased muscle damage in the mdx mice, the experimental model of Duchenne muscular dystrophy. Studies suggest that the estrogen level in females makes them less susceptible to muscle injuries. The aim of this study was to characterize the diaphragm (DIA) muscle response to physical exercise in male and female mdx mice. The animals were divided into four groups: female sedentary mdx; male sedentary mdx; female mdx submitted to exercise; and male mdx mice submitted to exercise. Blood samples were used to determine creatine kinase (CK). Regenerated muscle fibers were indicated by the presence of central nucleus and also inflammation areas were determined in DIA muscle sections. The alpha and beta estrogen receptors (ER) were determined by means of immunohistochemistry evaluation in the dystrophic DIA muscle. Male mdx animals submitted to exercise showed increased CK levels and inflammatory area. The quantification of regenerated fibers was higher in male animals, submitted or not to physical exercise. Greater alpha and beta ER expression was verified in the females submitted to exercise in the DIA muscle than in the other experimental groups. Therefore, estrogen may have contributed to the prevention of increased inflammatory process and DIA injury in females submitted to exercise.

Apoptosis in Denervated Skeletal Muscle / Apoptosis en Músculo Estriado Desnervado

The apoptosis phenomenon happens in normal tissues and in many pathological conditions as described by several researchers. Most studied in the 70s, this phenomenon remained almost forgotten in the 90s, when, with the advent of more advanced techniques, returned to laboratories. Thus, electronic microscopy, Comet Assays and histochemistry techniques, among others, were utilized in an effort to elucidate in a thorough way, the mechanisms that lead the cell to "suicide". No one can deny the importance of the knowledge of such phenomenon, so as to control its induction or blocking in the treatment of pathologies such as cancer. In this work, the apoptosis study was aimed at denervated muscles in different periods. Furthermore, two types of skeletal striated muscles were compared: the one called red muscle (soleo) which is resistant to fatigue, having a slow contraction, and the one named white muscle (EDL) of precocious fatigue and fast contraction. Previoulsy carried out in the techniques mentioned above, this work has been accomplished using the TUNEL technique, which is most accepted in the identification of apoptosis. It was demonstrated that this phenomenon takes place in a more marked way, in the beginning of the denervation process. In addition, it was observed that the red muscle responds more intensely to denervation than the white muscle. One can infer that the removal of the main cell function, the contraction, in the case of the skeletal striated muscle, triggers the chain reactions that culminate in apoptosis. Other projects are in process using mutant animals aiming at studying degenerative muscular illnesses and correlating them with denervation.

El fenómeno apoptosis ocurre en tejidos normales y en muchas condiciones patológicas, de acuerdo a lo relatado en varios trabajos. El estudio de este fenómeno tuvo su apogeo en la década del 70, permaneciendo en el olvido hasta la década del 90, momento en el cual comienzan a surgir técnicas más avanzadas, que motivaron su retorno a laboratorios de todo el mundo. Así, técnicas de microscopía electrónica, histoquímica, ensayos cometa, etc., fueron utilizados en los esfuerzos de elucidar de forma más profunda los mecanismos que conllevan a la célula al "suicidio". No se puede negar la importancia del conocimiento de ese fenómeno o, más específicamente, del control de su inducción o bloqueo para el tratamiento de patologías como el cáncer, por ejemplo. El presente trabajo tuvo como objetivo el estudio de apoptosis en músculo inervados, por diferentes periodos. También fueron comparados dos tipos de músculo estriado, el llamado músculo rojo (m. soleo), resistente a la fatiga y de contracción lenta, un músculo blanco (m. EDL) de fatiga precoz y contracción rápida. Este trabajo hace parte de un proyecto mayor ya desarrollado por sus ejecutores, sólo que utilizando la técnica del TUNEL como herramienta principal para identificar la apoptosis. Fue demostrado que tal fenómeno ocurre de forma más acentuada en los momentos iniciales de la desnervación. Además de eso, fue observado que el músculo rojo responde de manera más intensa a la desnervación. Nos parece inferir que la retirada de la principal función celular, en el caso del músculo estriado, la contracción despierta un mecanismo cuya reacción en cadena culmina en apoptosis. Otros proyectos están siendo elaborados con el propósito de utilizar animales mutantes, para estudiar enfermedades musculares degenerativas y correlacionarlas a la desnervación.