RESUMO
Connexins are protein subunits that oligomerize into hexamers called connexons, gap junction hemichannels or just hemichannels. Because some gap junction channels are permeable to negatively and/or positively charged molecules up to approximately 1kDa in size, it was thought that hemichannels should not open to the extracellular space. A growing amount of evidence indicates that opening of hemichannels does occur under both physiological and pathological conditions in astrocytes and other cell types. Electrophysiological studies indicate that hemichannels have a low open probability under physiological conditions but may have a much higher open probability under certain pathological conditions. Some of the physiological behaviours of astrocytes that have been attributed to gap junctions may, in fact, be mediated by hemichannels. Hemichannels constituted of Cx43, the main connexin expressed by astrocytes, are permeable to small physiologically significant molecules, such as ATP, NAD+ and glutamate, and may mediate paracrine as well as autocrine signalling. Hemichannels tend to be closed by negative membrane potentials, high concentrations of extracellular Ca2+ and intracellular H+ ions, gap junction blockers and protein phosphorylation. Hemichannels tend to be opened by positive membrane potentials and low extracellular Ca2+, and possibly by as yet unidentified cytoplasmic signalling molecules. Exacerbated hemichannel opening occurs in metabolically inhibited cells, including cortical astrocytes, which contributes to the loss of chemical gradients across the plasma membrane and speeds cell death.
Assuntos
Astrócitos/fisiologia , Junções Comunicantes/fisiologia , Conexinas/fisiologia , Eletrofisiologia , Humanos , Ativação do Canal Iônico/fisiologia , Transdução de Sinais/fisiologiaRESUMO
BACKGROUND: Objective structured clinical examination has advantages over traditional oral examination of medical student. However, it is not routinely used in Chile. AIM: To describe the objective structured clinical examination system and report the results of its first use with Chilean medical students. MATERIAL AND METHODS: Thirteen interns ware evaluated at the end of their surgical rotation, using the objective structured clinical examination. Thirteen stations were structured for this examination: one for history taking, two for physical examination, four for problem solving and knowledge, one for radiological interpretation, one for instrumental recognition, one for skills and one for text comprehension. There were a total of 88 questions. RESULTS: All students exceeded 60% of requirements. Mean approval score was 73%. The higher score was 80% and the lower 61%. Ten students had a score over 70%. The method was well accepted by teachers and students. CONCLUSIONS: This first local experience with the objective structured clinical examination was successful.
Assuntos
Competência Clínica , Educação de Graduação em Medicina , Internato e Residência , Chile , Currículo , Avaliação Educacional/métodos , Estudos de Avaliação como Assunto , Cirurgia Geral/educação , HumanosRESUMO
Los resultados observados en esta serie de 18 casos evaluados en 3 años demuestran: que la atención del traumatismo abdominal en un Servicio de Urgencia, que cuenta con la adecuada infraestructura de recursos humanos y tecnológicos, redunda en un diagnóstico y terapéutica precoces. Una menor incidencia de complicaciones. Rehabilitación precoz. Alto índice de sobrevida