The purpose of the present study was to determine the effects of metformin on the inhibition of proliferation, apoptosis, invasion and migration of A172 human glioma cells in vitro and determine the underlying mechanism. The effects of metformin at different concentrations (0, 0.1, 1 and 10 mmol/l) on the inhibition of A172 cell proliferation were detected using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Cell apoptosis was detected by flow cytometry. Caspase-3 activity was analyzed by spectrophotometry. The invasion and migration of cells were detected by Transwell assays. The levels of Bcl-2-associated X protein (Bax), B-cell lymphoma 2 (Bcl-2), AMP-activated protein kinase (AMPK), phosphorylated-(p)AMPK and mechanistic target of rapamycin (mTOR) protein expression were detected by western blot analysis, and changes in the malondialdehyde (MDA) content and activity of superoxide dismutase (SOD) were determined. Compared with the control group, metformin significantly increased the inhibition of proliferation and apoptosis, and significantly reduced the invasion and migration of A172 cells in dose- and time-dependent manners (P<0.05). In addition, compared with the control group, metformin significantly enhanced the activity of caspase-3, increased the expression of AMPK/pAMPK/Bax proteins and reduced the expression of mTOR/Bcl-2 proteins (P<0.05). Metformin increased the MDA content and reduced the activity of SOD in a dose-dependent manner (P<0.05). Metformin may inhibit glioma cell proliferation, migration and invasion, and promote its apoptosis; the effects may be associated with the AMPK/mTOR signaling pathway and oxidative stress.
The corn threshing process is a complex process of contact interaction between thresher mechanical parts and corn ears. The paper analyzed this process with the discrete element method (DEM). A method was set up to calculate the contact forces between thresher mechanical parts (boundary) and corn ears. The conditions for corn kernels threshing were established as well. On this basis, we developed the corn threshing simulation software, and simulated the corn threshing process using the software. The simulation results are close to the actual situation, and the results verify the feasibility and effectiveness of the new method. Thus we have laid the foundation for using the DEM to analyze the corn threshing process and putting forward a novel method for the optimal design of the corn thresher.
A three-dimensional discrete element method analytic model of the corn seed metering device with combination inner-cell was established based on its 3D CAD model, and the three-dimensional particle model of corn seeds was built by using the method of combination spherical particle. The working process of the corn seed metering device was simulated and analyzed by self-developed three-dimensional CAE software. It was observed that the simulative results of the seeding performance, clearing angles and dropping angles of the corn seeds well agreed with the bench test results. A novel method for studying and designing of the corn seed metering device was put forward.
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