Impaired regeneration of dystrophin-deficient muscle fibers is caused by exhaustion of myogenic cells

Duchenne muscular dystrophy is one of the most devastating myopathies. Muscle fibers undergo necrosis and lose their ability to regenerate, and this may be related to increased interstitial fibrosis or the exhaustion of satellite cells. In this study, we used mdx mice, an animal model of Duchenne muscular dystrophy, to assess whether muscle fibers lose their ability to regenerate after repeated cycles of degeneration-regeneration and to establish the role of interstitial fibrosis or exhaustion of satellite cells in this process. Repeated degenerative-regenerative cycles were induced by the injection of bupivacaine (33 mg/kg), a myotoxic agent. Bupivacaine was injected weekly into the right tibialis anterior muscle of male, 8-week-old mdx (N = 20) and C57Bl/10 (control, N = 10) mice for 20 and 50 weeks. Three weeks after the last injection, the mice were killed and the proportion of regenerated fibers was counted and reported as a fibrosis index. Twenty weekly bupivacaine injections did not change the ability of mdx muscle to regenerate. However, after 50 weekly bupivacaine injections, there was a significant decrease in the regenerative response. There was no correlation between the inability to regenerate and the increase in interstitial fibrosis. These results show that after prolonged repeated cycles of degeneration-regeneration, mdx muscle loses its ability to regenerate because of the exhaustion of satellite cells, rather than because of an increase in interstitial fibrosis. This finding may be relevant to cell and gene therapy in the treatment of Duchenne muscular dystrophy

Fadiga psiquica: resultados da aplicacao de um metodo alternativo para a identificacao dos agentes etiologicos ligados ao ambiente de trabalho / Psychological fatigue: results of the application of an alternative method in order to identify etiological agents

A fadiga psiquica aparece nos nossos dias como uma doenca social ligada em parte ao ambiente de trabalho. Compromete o individuo e o trabalho, com prejuizo para ambos. O diagnostico de casos pode ser feito pelo medico do trabalho que, na maioria das vezes, identifica a inadaptacao ou mesmo a insatisfacao com o trabalho. O problema maior que apresenta nos casos de diagnostico de fadiga psiquica e o julgamento da importancia de um determinado agente agressivo. Para uma avaliacao geral na empresa, o trabalho interprofissional, principalmente do medico do trabalho e do psicologo industrial, assume proporcoes relevantes No presente estudo, apresenta-se uma alternativa de metodo de identificacao dos agentes etiologicos da fadiga psiquica, principalmente aqueles ligados ao ambiente de trabalho, e os resultados da aplicacao desse metodo durante 18 meses na companhia Forjas Acesita.Os dados apresentam uma caracteristica importante, que e o diagnostico implicito, ou seja o leitor reconhecera nao so o metodo sugerido como tambem tomara conhecimento dos problemas que afetam os recursos humanos da empresa no periodo citado. No final, conclui-se quanto aos aspectos de validade do metodo e propoe-se alteracoes no sentido de aperfeiçoá-lo