Objective To establish the plane strain model of brain tissues on mid-sagittal plane and discuss the relation between the brain tissue deformation and brain injury. Methods By referring to the computerized tomography pictures of the human body and using plane strain and finite element method (FEM), we applied plane strain hypothesis to establish a model for calculation of the brain tissue deformation caused by rotational inertia loading during vehicle crash accident. Results At the 12th ms, the shear strain field adjacent to parietal lobe reached 0.148 and the maximum positive shear stress located at white material of the cerebellum was up to 8 088.0 Pa. At the 28th ms, the maximum shear stress located at the cerebellum reached 900.9 Pa. Great shear strain existed in the cerebrospinal fluid region all the time and shear stress with large absolute value presented on the boundary of white matter and gray matter. Conclusions Under rotational inertia loading, the shear strain (stress) in brain tissues can lead to diffuse axonal injury. The uneven strain (stress) may cause serious avulsion damage in brain tissues.

Objective To observe the effect of down-regulated CDX2 gene on the migration and invasion abilities of colon cancer cells (SW480 and HT29) and investigate the role and mechanisms of CDX2 gene in occurrence and development of colon cancer metastasis.Methods CDX2 gene in HT29 and SW480 cells was down-regulated using lentivirus RNA interference (RNAi) vector.The interference efficiency of CDX2 was detected by qRT-PCR and Western blotting.The effect of down-regulated CDX2 expression on colon cancer cells'migration and invasion was determined by Transwell and wound heal methods.Then the effects of down-regulated CDX2 on the expressions of epithelial-mesenchymal transition (EMT)-related genes (E-cadherin,ZEB-1,Vimentin,Twist and Snail) were detected by RT-PCR and Western blotting.Results The constructed CDX2 siRNA expression vector could significantly inhibit the expression of CDX2 in HT29 and SW480 cells.Compared with those of the cells transfected with empty vector (LV-NT-shRNA) and non-transfected cells,the migration and invasion abilities of cells transfected with LV-CDX2-shRNA were markedly enhanced (P ＜ 0.05).E-cadherin expression was reduced while expressions of ZEB-1,Vimentin,Twist,and Snail were significantly increased (all P＜0.05).Conclusion Down-regulating the expression of CDX2 can induce the occurrence of EMT,thus enhancing the invasion and migration of colon cancer cells.