不同基底硬度对人肝癌细胞黏附、铺展和迁移的影响

目的研究不同基底硬度对肝癌细胞黏附、铺展和迁移行为的影响及对细胞骨架装配方式和细胞表面黏附蛋白整合素β1表达的调控,探讨基底的力学特性在肝癌细胞恶性转移过程中的作用。方法通过调节丙聚酰胺和双丙烯酰胺的比率制备不同硬度的聚丙烯酰胺基底,并在基底表面裱衬2.5μg/mL纤维连接蛋白为细胞提供黏附位点;用显微观察并记录不同硬度基底上细胞黏附、铺展和迁移的变化,并用Image J软件定量分析;分别运用免疫荧光和流式细胞仪的方法检测不同基底硬度对肝癌细胞骨架装配和细胞表面整合素β1表达的影响。结果硬基底利于肝癌细胞的黏附和铺展并缩短细胞的铺展时间。过软(1.1 kPa)或过硬(玻璃)的基底都不利于肝癌细胞的迁移,肝癌细胞在中间硬度的基底上(10.7 kPa)迁移速率最高。硬基底促进细胞骨架的装配和整合素β1表达。结论基底硬度通过调节细胞骨架装配和整合素的表达从而影响肝癌细胞的黏附、铺展和迁移。     

原子力显微镜在细胞与生物大分子超微结构和力学研究中的应用

作为微纳米科学理论与技术迅猛发展的代表,原子力显微镜(atomic force microscopy,AFM)在其25年的发展过程中极大地推进了生物学在微纳米尺度上的拓展,为微纳米生物学的诞生与发展提供了重要技术手段。本文在介绍AFM基本原理和检测模式的基础上,结合作者在该领域的研究成果和工作经验,从生物结构与形态学研究、表面物化性质表征、生物大分子的力学操纵三方面综述了AFM在细胞与生物大分子超微结构与生物力学特性研究中的具体应用,并重点探讨了AFM在细胞与生物大分子科学研究中亟待改进和解决的科学与技术问题,提出了一些探讨性的见解和建议。     

PVA /HA复合水凝胶力学性能分析及有限元模拟

目的通过实验与有限元模拟对羟基磷灰石(HA)改变聚乙烯醇/羟基磷灰石(PVA/HA)复合水凝胶的力学性能本质及其承载特性进行研究。方法在UMT试验机上进行PVA/HA复合水凝胶的压缩及应力松弛实验。通过模拟与实验结果相结合,研究PVA/HA复合水凝胶的承载特性及HA对其性能的影响。结果随着HA含量的增加,PVA/HA复合水凝胶的压缩模量先增大后减小,而渗透系数先减小后增大;HA含量为3%的PVA/HA复合水凝胶压缩模量最大、渗透系数最小,分别为1.25 MPa和1.59×10-3 mm4.N-1.s-1。PVA/HA复合水凝胶的液体承载比例随着施载时间的增加呈现先增加后减小的非线性变化,加入HA的PVA/HA复合水凝胶的液体承载比例明显增加。应力松弛速率随着HA含量增加呈先上升后下降趋势,下压相同位移HA,含量为3%时,PVA/HA复合水凝胶所能分散的应力更多。结论 PVA/HA复合水凝胶内部的承载特性影响着其力学性能,HA含量为3%时的PVA/HA复合水凝胶力学性能最优,更接近于天然关节软骨的力学性能。     

生物硬组织材料力学研究方法进展

研究生物硬组织材料的力学性质对于预防和治疗骨科和口腔疾病具有重要意义。同时,经过长期的进化,生物材料具有独特的力学性质,研究这些材料的结构与力学性质可以为工程材料的设计提供解决方案。与工程材料不同,生物材料的力学研究需要采用特殊的方法来准确描述其力学性质。本文针对生物硬组织材料力学性质的研究方法进行综述,包括生物硬组织材料的常规力学实验方法、断裂力学和压痕测试技术,以及微观和宏观力学数值模拟技术。     

基于膨隆实验的血管非线性力学特性确定方法

目的基于实验测试和数值模拟结果,建立反方法确定血管的非线性力学特性。方法采用自行设计的实验装置,对血管进行压力加载,获取血管膨隆的实验数据;假设血管材料特性符合超弹性Ogden模型,建立血管膨隆的有限元模型,然后结合实测数据及数值模拟结果,利用优化算法建立反方法确定血管的力学特性。结果得到了描述兔腹主动脉非线性力学特性的Ogden模型一阶和二阶的材料参数,其中一阶Ogden模型参数α=10.86±1.98。经验证兔腹主动脉的力学特性可用超弹性力学模型描述。结论基于实验测试和数值模拟方法建立的反方法可用来识别血管的非线性力学特性。     

青少年健康相关危险行为问卷的编制及信效度检验

目的:编制青少年健康相关危险行为问卷(AHRBI)并检验其信效度。方法:在文献分析的基础上,并结合前期实证研究结果,确定健康相关危险行为的6个维度。在长沙、苏州、成都和银川四地以班级为单位,共调查普通中学初一至高三的学生5755名(其中男生2997名);另外方便抽取长沙附近3所特训学校学生323名[平均年龄(15±2)岁,男生256名]。采用Zuckerman-Kuhlman人格量表(ZKPQ)中的冲动感觉寻求(ISS)和攻击敌意(AH)两个分量表以及Barratt冲动量表(BIS)作为效标。从普通中学学生样本中,分别抽取329人和347人间隔4周和8周后进行重测。结果:通过项目分析确定38个条目,每个分量表5～10个。除健康妥协行为的Cronbachα系数为0.40外,其他5个分量表的Cronbachα系数均在0.75以上。全量表及各分量表间隔4周和8周的重测系数分别在0.55～0.80和0.53～0.76之间。验证性因素分析显示,二阶单因子模型的各拟合指标分别为S-Bχ2=3933.23,df=623,NNFI=0.88,CFI=0.89,RM SEA(90%CI)=0.029(0.029,0.031)。效标关联效度分析显示攻击暴力、破坏纪律和吸烟饮酒得分与效标间的相关系数在0.06～0.43之间,而无保护性行为、自杀自残和健康妥协与效标间的相关系数在-0.06～0.27之间。特训学校学生在所有6个分量表上的得分高于普通中学学生(Cohen's d值在0.67至2.88之间)。结论:本研究编制的青少年健康相关危险行为问卷包含38个条目测查6个方面的危险行为,具有较好的心理测量学特性。     

Influence of perfusion and compression on the proliferation and differentiation of bone mesenchymal stromal cells seeded on polyurethane scaffolds

In the present study, a porous meniscal-shaped scaffold consisting of polyurethane (PU)-based 1, 4-butanediisocyanate (BDI), which provided a 3-D culture condition for human bone mesenchymal stromal cells (hBMSC) was employed. A bioreactor was utilized to produce perfusion and mechanical stimulations. The viability, proliferation and fibro-cartilaginous differentiation of the hBMSC cultured on the PU-based meniscal scaffold were investigated during the perfusion and mechanical stimulation process. In addition, the mechanical properties of the cell-laden scaffolds were examined as well. Our finding indicated that the perfusion (10 ml/min) and on-off cyclic compressions mechanical stimulation (10% strain, 0.5 Hz, 4 times/day, 2 h/time with 4 h of rest thereafter) maintained the viability and promoted the proliferation of hBMSC over 2 weeks. The on-off cyclic compression caused a 1.85 fold increase in equilibrium modulus. Meanwhile, type I procollagen produced by hBMSC was increased for 3.02-fold after 2 weeks culture. On the other hand, the irrigating medium enhanced the synthesis of type III procollagen for 2.24-fold after 2 weeks. Tensile modulus was elevated for 2.02-fold in perfusion group after 1 week, which was decreased after 2 weeks unexpectedly. Our study suggests that the perfusion and on-off compression are promising to enhance the functional properties of the hBMSC-laden PU-based meniscal scaffold.     

聚羟基丁酸酯可吸收缝线灭菌方法的实验研究

目的：研究不同的灭菌方法对聚羟基丁酸酯（PHB）可吸收缝线的降解性和力学特性的影响。方法：将聚羟基丁酸酯（PHB）可吸收缝线进行酒精浸泡、环氧乙烷、紫外线照射三种方法进行灭菌处理后,用细菌培养检测灭菌效果,用粘度法测定聚合物分子量从而观察缝线的降解性,用拉伸试验测定缝线的力学特性。结果：①酒精浸泡灭菌组有10%检出细菌,环氧乙烷及紫外线灭菌组未检出细菌;②紫外线照射灭菌和酒精浸泡灭菌组可使缝线黏度下降并具有显著性差异,环氧乙烷对缝线黏度下降的影响没有显著性差异;③经酒精和紫外线灭菌后缝线的断裂强度降低明显,差异具有显著性,经环氧乙烷灭菌后缝线的断裂强度降低无显著性差异。经紫外线灭菌后缝线的断裂伸长率明显降低,差异具有显著性,经酒精和环氧乙烷灭菌后缝线的断裂伸长率无明显降低。结论：环氧乙烷灭菌对PHB可吸收缝线的降解性和力学特性影响较小,是PHB可吸收缝线较理想的灭菌方法。     

Quantitative conductivity and permittivity imaging of the human brain using electric properties tomography

The electric properties of human tissue can potentially be used as an additional diagnostic parameter, e.g., in tumor diagnosis. In the framework of radiofrequency safety, the electric conductivity of tissue is needed to correctly estimate the local specific absorption rate distribution during MR measurements. In this study, a recently developed approach, called electric properties tomography (EPT) is adapted for and applied to in vivo imaging. It derives the patient's electric conductivity and permittivity from the spatial sensitivity distributions of the applied radiofrequency coils. In contrast to other methods to measure the patient's electric properties, EPT does not apply externally mounted electrodes, currents, or radiofrequency probes, which enhances the practicability of the approach. This work shows that conductivity distributions can be reconstructed from phase images and permittivity distributions can be reconstructed from magnitude images of the radiofrequency transmit field. Corresponding numerical simulations using finite‐difference time‐domain methods support the feasibility of this phase‐based conductivity imaging and magnitude‐based permittivity imaging. Using this approximation, three‐dimensional in vivo conductivity and permittivity maps of the human brain are obtained in 5 and 13 min, respectively, which can be considered a step toward clinical feasibility for EPT. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.     

Physical Properties of an Acrylic Resin after Incorporation of an Antimicrobial Monomer

Purpose: This study evaluated the effect of the incorporation of the antimicrobial monomer methacryloyloxyundecylpyridinium bromide (MUPB) on the hardness, roughness, flexural strength, and color stability of a denture base material. Materials and Methods: Ninety‐six disk‐shaped (14‐mm diameter × 4‐mm thick) and 30 rectangular (65 × 10 × 3.3 mm³) heat‐polymerized acrylic resin specimens were divided into three groups according to the concentration of MUPB (w/w): (A) 0%, (B) 0.3%, (C) 0.6%. Hardness was assessed by a hardness tester equipped with a Vickers diamond penetrator. Flexural strength and surface roughness were tested on a universal testing machine and a surface roughness tester, respectively. Color alterations (ΔE) were measured by a portable spectrophotometer after 12 and 36 days of immersion in water, coffee, or wine. Variables were analyzed by ANOVA/Tukey HSD test (α= 0.05). Results: The following mean results (±SD) were obtained for hardness (A: 15.6 ± 0.6, B: 14.6 ± 1.7, C: 14.8 ± 0.8 VHN; ANOVA: p= 0.061), flexural strength (A: 111 ± 17, B: 105 ± 12, C: 88 ± 12 MPa; ANOVA: p= 0.008), and roughness (A: 0.20 ± 0.11, B: 0.20 ± 0.11, C: 0.24 ± 0.08 μm; ANOVA: p= 0.829). Color changes of immersed specimens were significantly influenced by solutions and time (A: 9.1 ± 3.1, B: 14.8 ± 7.5, C: 13.3 ± 6.1 ΔE; ANOVA: p < 0.05). Conclusions: The incorporation of MUPB affects the mechanical properties of a denture base acrylic resin; however, the only significant change was observed for flexural strength and may not be critical. Color changes were slightly higher when resin containing MUPB was immersed in wine for a prolonged time; however, the difference has debatable clinical relevance.