RESUMO
The paper summarizes the data on proliferation and gravity-related gene expression of osteoblasts that were obtained from an experiment conducted under simulated and real microgravity conditions. Simulated microgravity conditions obtained in a clinostat depress proliferation of both osteoblast-like MC3T3-E1 and HeLa carcinoma cells. This depression of proliferation occurs in a collagen gel culture in which the flow of culture medium by rotation may be reduced. Interestingly, MC3T3-E1 cells which are probably one of target cells to microgravity are more sensitive than the HeLa cells. Simulated microgravity inhibited the epidermal growth factor (EGF)-induced c-fos gene expression in the MC3T3-El cells. To examine in detail the effect of real microgravity on the EGF signal transduction cascade in osteoblasts, MC3T3-E1 cells were cultured in the Cell Culture Experiment Module of the sounding rocket TR-1A6. The EGF-induced c-fos expression in cells was depressed under short-term microgravity conditions in the sounding rocket, while the phosphorylation of mitogen-activated protein kinase (MAPK) was not affected compared with the controls grown on the ground. These results suggest that an action site of microgravity in the signal transduction pathway may be downstream of MAPK.
Assuntos
Expressão Gênica , Genes fos , Osteoblastos/fisiologia , Voo Espacial , Simulação de Ausência de Peso , Ausência de Peso , Animais , Células Cultivadas , Fator de Crescimento Epidérmico/fisiologia , Gravitação , Células HeLa , Humanos , Camundongos , Proteínas Quinases Ativadas por Mitógeno/metabolismo , Osteoblastos/citologia , Osteoblastos/enzimologia , Rotação , Transdução de Sinais/genética , Transdução de Sinais/fisiologiaRESUMO
The present study was undertaken to examine the electrophysiologic effects of nitrous oxide in the dog heart after inducing myocardial infarction, and to compare these with those of other anesthetics. Myocardial infarction was produced by two-stage ligation of the left anterior descending coronary artery in dogs. Seven days after ligation, bipolar electrodes were sutured on the ventricular surface of the infarcted and normal regions for applying electrical stimulation or recording ventricular activation. Ventricular activation time and QT interval on the bipolar electrocardiogram and PQ interval from the standard limb lead II were measured during atrial pacing. Nitrous oxide 80% did not significantly prolong ventricular activation time, PQ interval or QT interval. However, halothane 1 minimum alveolar concentration (MAC), thiopental 5 and 10 mg/kg and fentanyl 30 microg/kg did prolong ventricular activation time; thiopental and fentanyl prolonged the QT interval. Nitrous oxide did not potentiate the effects of fentanyl. Therefore, electrophysiologic effects of nitrous oxide are much weaker compared with those of thiopental, fentanyl or halothane.
