用正交异性算法仿真的肌力对股骨再造的影响

肌力与骨骼的生长(即"骨再造")有密切关系。该文基于CT数据建立股骨有限元模型,用正交异性算法仿真了肌力对骨再造的影响。骨再造仿真中,由复杂到简单共设置三组肌力载荷工况,使用正交异性算法结合有限元分析。结果表明,复杂肌力比简单肌力的仿真结果更符合股骨的真实密度分布和结构。肌力可以在一定程度上调节局部骨量大小和骨小梁的排列,对股骨近端影响较大,对中端和末端影响较小。对肌力做适当的简化不会影响骨密度分布和内部结构,但过于简化的肌力将显著影响局部骨量大小和骨小梁排列方向。     

西藏新型国有企业文化建设中的交互影响因素与融合

文章分析了传统国有企业文化、现代西方企业文化、西藏传统文化等方面对西藏新型国有企业文化建设的影响,指出转型和变革所带来的文化动荡能否在短时间内通过梳理、整合和重塑并形成新的企业文化,将决定西藏新国企在未来的发展中是否能够迅速形成新的核心竞争力,在市场竞争中取得优势,决定着西藏国有企业改革的成败。     

Modeling the electrostatic potential of asymmetric lipopolysaccharide membranes: The MEMPOT algorithm implemented in DelPhi

Four chemotypes of the rough lipopolysaccharides (LPS) membrane from Pseudomonas aeruginosa were investigated by a combined approach of explicit water molecular dynamics (MD) simulations and Poisson–Boltzmann continuum electrostatics with the goal to deliver the distribution of the electrostatic potential across the membrane. For the purpose of this investigation, a new tool for modeling the electrostatic potential profile along the axis normal to the membrane, MEMbrane POTential (MEMPOT), was developed and implemented in DelPhi. Applying MEMPOT on the snapshots obtained by MD simulations, two observations were made: (a) the average electrostatic potential has a complex profile but is mostly positive inside the membrane due to the presence of Ca²⁺ ions, which overcompensate for the negative potential created by lipid phosphate groups; and (b) correct modeling of the electrostatic potential profile across the membrane requires taking into account the water phase, while neglecting it (vacuum calculations) results in dramatic changes including a reversal of the sign of the potential inside the membrane. Furthermore, using DelPhi to assign different dielectric constants for different regions of the LPS membranes, it was investigated whether a single frame structure before MD simulations with appropriate dielectric constants for the lipid tails, inner, and the external leaflet regions, can deliver the same average electrostatic potential distribution as obtained from the MD‐generated ensemble of structures. Indeed, this can be attained by using smaller dielectric constant for the tail and inner leaflet regions (mostly hydrophobic) than for the external leaflet region (hydrophilic) and the optimal dielectric constant values are chemotype‐specific. © 2014 Wiley Periodicals, Inc.     

Numerical analysis of a contact problem including bone remodeling

In this work, a contact problem between an elastic body and a deformable obstacle is numerically studied. The bone remodeling of the material is also taken into account in the model and the contact is modeled using the normal compliance contact condition. The variational problem is written as a nonlinear variational equation for the displacement field, coupled with a first-order ordinary differential equation to describe the physiological process of bone remodeling. An existence and uniqueness result of weak solutions is stated. Then, fully discrete approximations are introduced based on the finite element method to approximate the spatial variable and an Euler scheme to discretize the time derivatives. Error estimates are obtained, from which the linear convergence of the algorithm is derived under suitable regularity conditions. Finally, some 2D numerical results are presented to demonstrate the behavior of the solution.     

Etoposide interferes with the process of chromatin condensation during alga Chara vulgaris spermiogenesis

DNA topoisomerase II plays an essential role in animal spermiogenesis, where changes of chromatin structure are connected with appearance of transient DNA breaks. Such topo II activity can be curtailed by inhibitors such as etoposide and suramine. The aim of the present study was to investigate, for the first time, the effect of etoposide on spermatid chromatin remodeling in the green alga Chara vulgaris. This inhibitor prolonged the early spermiogenesis stages and blocked the formation of the phosphorylated form of histone H2AX at stages VI–VII. The lack of transient DSBs at these stages impairs the elimination of supercoils containing nucleosomes which lead to disturbances in nucleoprotein exchange and the pattern of spermatid chromatin fibrils at stages VI–VIII. Immunofluorescent and ultrastructural observations revealed that during C. vulgaris spermiogenesis topo II played an important role similar to that in mammals. Some corresponding features had been pointed out before, the present studies showed further similarities.     

显微损伤修复过程中骨组织纳米力学性能的变化

人工关节置换、骨折内固定等骨科植入物手术会在其周围造成显微损伤,这些机械性显微损伤会降低植入物周围骨的质量,影响其与植入物界面之间的结合强度,并进而影响植入物的长期稳定性.通过在山羊胫骨植入螺钉建立显微损伤模型,比较螺钉植入近端和远端两种不同情况下机械性显微损伤的产生和修复,以及修复过程中骨微观力学性能和骨组织元素成分的变化.结果发现:显微损伤产生和修复过程中,局部骨组织的硬度和弹性模量都呈现下降趋势;随着显微损伤修复的逐渐完成,其微观力学性能又有所恢复.     

p53-dependent upregulation of PIG3 transcription by γ-ray irradiation and its interaction with KAP1 in responding to DNA damage

PIG3 (p53-inducible gene 3), originally identified as one of a set of genes induced by p53 before the onset of apoptosis, was assumed to contribute to early cellular response to DNA damage. Here, we studied the relation between p53 status and the increased expression of PIG3 by ionizing radiation (IR), and the related clues regarding the involvement of PIG3 in the cellular response to IR-induced DNA damage signaling. We demonstrated that the pentanucleotide microsatellite sequence was responsible for the p5...     

近视巩膜生物力学研究进展

 近视是一种最为常见的具有致盲可能性的眼部疾患，其发病机制目前尚不完全明晰。巩膜可直接决定眼轴的长度，是近视形成的最终效应器。本文以巩膜为切入点，综述近视发生时巩膜组织生物力学性质的变化、相应巩膜组织成分的改变与原因，以及目前临床上针对性的近视治疗方案，展望了该研究领域的发展方向和趋势。     

Multiscale molecular dynamics simulations of membrane remodeling by Bin/Amphiphysin/Rvs family proteins

Membrane curvature is no longer thought of as a passive property of the membrane; rather, it is considered as an active, regulated state that serves various purposes in the cell such as between cells and organelle definition. While transport is usually mediated by tiny membrane bubbles known as vesicles or membrane tubules, such communication requires complex interplay between the lipid bilayers and cytosolic proteins such as members of the Bin/Amphiphysin/Rvs(BAR) superfamily of proteins. With rapid developments in novel experimental techniques, membrane remodeling has become a rapidly emerging new field in recent years. Molecular dynamics(MD) simulations are important tools for obtaining atomistic information regarding the structural and dynamic aspects of biological systems and for understanding the physics-related aspects. The availability of more sophisticated experimental data poses challenges to the theoretical community for developing novel theoretical and computational techniques that can be used to better interpret the experimental results to obtain further functional insights. In this review, we summarize the general mechanisms underlying membrane remodeling controlled or mediated by proteins. While studies combining experiments and molecular dynamics simulations recall existing mechanistic models, concurrently, they extend the role of different BAR domain proteins during membrane remodeling processes. We review these recent findings, focusing on how multiscale molecular dynamics simulations aid in understanding the physical basis of BAR domain proteins, as a representative of membrane-remodeling proteins.