Objective： To investigate the protective effect of mouse astrocyte-conditioned medium （ACM） on hypoxic and mechanically injured neurons by a cell model in vitro, and to explore the possible mechanism. Methods： Th...Objective： To investigate the protective effect of mouse astrocyte-conditioned medium （ACM） on hypoxic and mechanically injured neurons by a cell model in vitro, and to explore the possible mechanism. Methods： The model of hypoxic neuronal injury was caused by 3% 02 in three-gas incubator. Neurons were cultured with ordinary medium or 20% ACM respectively and randomly divided into hypoxic group （hypoxia for 4, 8, 24 h and marked as H4R0, H8R0, H24R0） and hypoxia reoxygenation group （H4R24, H8R24, H24R24）. Mechanical injury model was developed by scratching neurons cultured in 20% ACM or ordinary medium to different degrees. Neu- rons in both medium were divided into normal control group, mild, moderate and severe injury groups. The 20% ACM was added 24 h before hypoxia/reoxygenation or mechanical injury. The morphology and survival of neurons were observed and counted by trypan blue staining. The concentration of NO, lactic dehydrogenase （LDH） and membrane ATPase activity were detected by corresponding kits. Results： It was showed that 20% ACM can obviously promote the survival rate of hypoxia/reoxygenated neurons and scratched neurons as well. The morphology and num- ber of neurons exposed to hypoxia or scratch injury showed great difference between groups with or without ACM treatment. Compared with control group, the concentration of NO and LDH was much lower in hypoxic/reoxygenated neurons treated with 20% ACM, and the ATPase activity was higher. For the mechanical injury model, neurons with moderate injury also revealed a lower NO and LDH concen- tration than the control group. All the differences were sta- tistically significant （P〈0.05）. Conclusion： ACM can promote the survival and func- tional recovery of neurons following hypoxia or scratching to a certain degree. The mechanism may be associated with reducing the synthesis and release of NO and LDH as well as increasing the activity of membrane ATPase.展开更多
Sintered metals are characterized by the high porosity(8%)and voids/micro-cracks in microns.Inelastic behavior of the materials is coupled with micro-crack propagation and coalescence of open voids.In the present work...Sintered metals are characterized by the high porosity(8%)and voids/micro-cracks in microns.Inelastic behavior of the materials is coupled with micro-crack propagation and coalescence of open voids.In the present work the damage evolution of the sintered iron under multi-axial monotonic loading conditions was investigated experimentally and computationally.The tests indicated that damage of the sintered iron initiated already at a stress level much lower than the macroscopic yield stress.The damage process can be divided into the stress-dominated elastic damage and the plastic damage described by the plastic strain.Based on the uniaxial tensile tests an elastic-plastic continuum damage model was developed which predicts both elastic damage and plastic damage in the sintered iron under general multi-axial monotonic loading conditions.Computational predictions agree with experiments with different multi-axial loading paths.A phenomenological continuum damage model for the sintered metal is developed based on the experimental observations to predict the inelastic behavior and damage process to failure under multi-axial loading conditions.The proposed damage model is experimentally verified under different loading conditions.展开更多
文摘Objective： To investigate the protective effect of mouse astrocyte-conditioned medium （ACM） on hypoxic and mechanically injured neurons by a cell model in vitro, and to explore the possible mechanism. Methods： The model of hypoxic neuronal injury was caused by 3% 02 in three-gas incubator. Neurons were cultured with ordinary medium or 20% ACM respectively and randomly divided into hypoxic group （hypoxia for 4, 8, 24 h and marked as H4R0, H8R0, H24R0） and hypoxia reoxygenation group （H4R24, H8R24, H24R24）. Mechanical injury model was developed by scratching neurons cultured in 20% ACM or ordinary medium to different degrees. Neu- rons in both medium were divided into normal control group, mild, moderate and severe injury groups. The 20% ACM was added 24 h before hypoxia/reoxygenation or mechanical injury. The morphology and survival of neurons were observed and counted by trypan blue staining. The concentration of NO, lactic dehydrogenase （LDH） and membrane ATPase activity were detected by corresponding kits. Results： It was showed that 20% ACM can obviously promote the survival rate of hypoxia/reoxygenated neurons and scratched neurons as well. The morphology and num- ber of neurons exposed to hypoxia or scratch injury showed great difference between groups with or without ACM treatment. Compared with control group, the concentration of NO and LDH was much lower in hypoxic/reoxygenated neurons treated with 20% ACM, and the ATPase activity was higher. For the mechanical injury model, neurons with moderate injury also revealed a lower NO and LDH concen- tration than the control group. All the differences were sta- tistically significant （P〈0.05）. Conclusion： ACM can promote the survival and func- tional recovery of neurons following hypoxia or scratching to a certain degree. The mechanism may be associated with reducing the synthesis and release of NO and LDH as well as increasing the activity of membrane ATPase.
基金supported by the National Natural Science Foundation of China(Grant No.51175041)
文摘Sintered metals are characterized by the high porosity(8%)and voids/micro-cracks in microns.Inelastic behavior of the materials is coupled with micro-crack propagation and coalescence of open voids.In the present work the damage evolution of the sintered iron under multi-axial monotonic loading conditions was investigated experimentally and computationally.The tests indicated that damage of the sintered iron initiated already at a stress level much lower than the macroscopic yield stress.The damage process can be divided into the stress-dominated elastic damage and the plastic damage described by the plastic strain.Based on the uniaxial tensile tests an elastic-plastic continuum damage model was developed which predicts both elastic damage and plastic damage in the sintered iron under general multi-axial monotonic loading conditions.Computational predictions agree with experiments with different multi-axial loading paths.A phenomenological continuum damage model for the sintered metal is developed based on the experimental observations to predict the inelastic behavior and damage process to failure under multi-axial loading conditions.The proposed damage model is experimentally verified under different loading conditions.
