木材横断面六棱规则细胞数学描述理论研究

本文采用微观力学和细胞学理论,在横观各向同性的假设下,提出了一种木材规则细胞主方向截面形状描述的理论方法。应用本文提出的理论,可以根据纤维、木质素、细胞直径和排列的程度,绘出理想状态下木材的主方向规则细胞结构形状,为木材学运用数学手术深入到细胞结构研究的深度提供了一种新的数学方法,并且可以为定量解释木材规则细胞变异后材性与性能提高的原因提供定量解释的数学手段。     

植物细胞中间纤维角蛋白性质的分析

角蛋白是植物细胞中间纤维的主要。应用选择性抽提和生物化学技术,分离纯化了豌豆根尖细胞５８、５２ｋＤ、白菜叶５２ｋＤ和胡萝卜悬浮细胞６４ＫＤ角蛋白,测定了它们的氨基酸组成,结果表明上述角蛋白与动物细胞中间纤维角蛋白 氨基酸组成有较大的相似性。比较了动、植物细胞角蛋白肽谱、结果显示它们之间存在较大的差异,但是植物细胞嶂角蛋白肽谱比较一致,这提示它们属于同一蛋白家族,为植物中间纤维及其蛋白 存在提供了新     

微原纤维

微原纤维有Ⅵ型胶原蛋白微原纤维和原纤维蛋白微原纤维二种。前者广泛存在于固有结缔组织中,确切功能尚不清楚。原纤维蛋白微原纤维由原纤维蛋白、微原纤维相关蛋白、潜在转化生长因子β结合蛋白等成分构成,主要作为弹性纤维的组成部分,并参与弹性纤维的形成,其次是单独地分布于器官的细胞外基质中,提供一种柔韧性的连接方式。原纤维蛋白的基因突变可引发马凡综合征及相关的微原纤维病。     

PtK2细胞的核骨架—核纤层—中间纤维体系

本文用选择性系列抽提的方法结合整装细胞电技术和ＤＧＤ包埋－去包埋超薄切片技术,在电镜下清晰地显示了ＰｔＫ细胞的核骨架－核纤层－中间纤维绵精细结构。处于分裂中期的细胞经抽提后看到,染色体残３余与中间纤维仍然保持一定的联系。用免疫荧光技术对提提后的ＰｔＫ２细胞进行分析结果表明：其中间纤维能同时与ＡＥ１和ＡＥ３反应;能一ＬａｍｉｎＢ反应的单抗可以特异地定位于其核周,而ＬａｍｉｎＡ（Ｃ）的单抗除了与其核纤     

影响动物细胞有丝分裂方向的因素应力纤维在纺锤体定位中的作用

细胞的有丝分裂与细胞的增殖、分化及胚胎发育、组织器官形成、损伤组织的修复和疾病的发生有关.各种物理因素、细胞所处的微环境(包括细胞外基质、细胞粘附)等,以及胞内的多种信号因子均能对细胞的有丝分裂方向产生影响.大量文献表明,应力纤维的排列为有丝分裂中心粒分离和定位提供轨道,最终影响纺锤体和有丝分裂的定向.本实验室的micro-pattern和静态单轴拉伸应变实验进一步提示了应力纤维的排布方式是影响有丝分裂方向的重要因素.本文围绕着应力纤维的排布对有丝分裂方向的影响这一研究观点,综述分析了整合素介导的细胞外粘附-黏着斑的组装-应力纤维的排布-有丝分裂纺锤体定向等一系列影响贴壁哺乳动物细胞有丝分裂定向的过程.并根据酵母模型,对哺乳动物细胞有丝分裂定向过程的分子机制进行了介绍;在该过程中肌球蛋白、动力蛋白和kar9等蛋白质起到重要作用.     

植物细胞中间纤维角蛋白性质的分析

角蛋白是植物细胞中间纤维的主要成分。应用选择性抽提和生物化学技术,分离纯化了豌豆根尖细胞58-、52 kD、白菜子叶52kD和胡萝卜悬浮细胞64kD角蛋白,测定了它们的氨基酸组成,结果表明上述角蛋白与动物细胞中间纤维角蛋白的氨基酸组成有较大的相似性。比较了动、植物细胞角蛋白的肽谱,结果显示它们之间存在较大的差异,但是植物细胞间角蛋白的肽谱比较一致,这提示它们属于同一蛋白家族,为植物中间纤维及其角蛋白的存在提供了新的论据。     

PDCD5在类风湿关节炎成纤维样滑膜细胞凋亡中表达上调

为了研究程序化细胞死亡因子5(PDCD5)在类风湿关节炎成纤维样滑膜细胞凋亡中的作用,在不同的时间加入有效剂量100 nmol/L雷公藤内醇酯（triptolide）后,采用实时定量PCR、RT-PCR、Western 印迹和直接免疫荧光染色方法检测体外分离培养的类风湿关节炎成纤维样滑膜细胞中PDCD5在mRNA和蛋白水平的表达及蛋白表达特征.在雷公藤内醇酯诱导类风湿关节炎成纤维样滑膜细胞凋亡的过程中,PDCD5mRNA表达水平明显地渐次增加,呈现一种明确的时间依赖性递增表达模式,而PDCD5蛋白有时间依赖性表达上调持续16 h,并维持在相对恒定水平.直接免疫荧光染色结果显示,在正常体外培养的类风湿关节炎成纤维样滑膜细胞中,PDCD5蛋白的表达较弱,且主要分布在细胞浆.经雷公藤内醇酯处理4 h后,大多数细胞有PDCD5蛋白的聚集,直至12 h,细胞核周围PDCD5蛋白聚集显著增强.36 h后,PDCD5蛋白以核固缩的形式存在于凋亡的RA FLS中,细胞核染色质明显浓缩,片段化并出现了凋亡小体.上述结果表明,在类风湿关节炎成纤维样滑膜细胞凋亡的过程中,PDCD5表达上调并在凋亡早期出现核转位,PDCD5蛋白核转位要早于凋亡小体形成.PDCD5蛋白核转位是类风湿关节炎成纤维样滑膜细胞凋亡的早期事件,PDCD5不仅参与了类风湿关节炎成纤维样滑膜细胞的凋亡过程,而且在类风湿关节炎滑膜增生的凋亡调节中起到重要调节作用.     

不同条件对植物中间纤维体外装配的影响(简报)

细胞骨架的研究是当今细胞生物学中最为活跃的领域之一,而中间纤维是三种主要骨架纤维中研究较少的一种。从60年代发现至今,人们对动物细胞中间纤维的研究已经比较深入,近来又发现它在基因表达等重要生命活动中起一定的作用。中间纤维有一个显著的特征,就是能够在体外进行自我装配,不需要核苷酸和结合蛋白参加,也不依赖于蛋白质的浓度。植物细胞中是否存在中间纤维一直是未解决的问题。从80年代起,有一些研究发现在高等植物细胞中存在能与动物细胞中间纤维抗体进行     

PtK2细胞的核骨架—核纤层——中间纤维体系

本文用选择性系列抽提的方法结合整装细胞电镜技术和DGD包埋-去包埋超薄切片技术,在电镜下清晰地显示了PtK 2细胞的核骨架-核纤层-中间纤维体系的精细结构。处于分裂中期的细胞经抽提后可以看到,染色体残余与中间纤维仍然保持一定的联系。用免疫荧光技术对抽提后的PtK 2细胞进行分析结果表明:其中间纤维能同时与AE1和AE3反应;能与Lamin B反应的单抗可以特异地定位于其核周,而Lamin A(C)的单抗除了与其核纤层蛋白有很强的反应外还与中间纤维有交叉反应。此外,在分裂期细胞中可以看到Lamin A(C)可能与染色体能特异结合;与HeLa细胞不一样。PtK 2细胞的核骨架成份不能与280kD的核骨架蛋白单抗反应。双向电泳结果显示出PtK 2细胞的核骨架-核纤层-中间纤维体系的组成成份与HeLa细胞相比有较大的差异,而且这种差异主要反映在核骨架组份上,TdR的处理也能导致其组份发生变化。     

自组装IKVAV多肽纳米纤维支架凝胶及其对嗅鞘细胞的作用

旨在观察自组装IKVAV多肽纳米纤维支架凝胶对鼠嗅鞘细胞(OECs)的作用。通过调整IKVAV溶液pH值并加入培养液触发多肽自组装为支架凝胶, 用原子力显微镜检测IKVAV分子可以自组装成编织状纳米纤维(直径为3~5 nm)。采用原代分离培养方法获得OECs单细胞悬液后, 使用差速贴壁法两次纯化OECs且在第12天通过免疫染色计数OECs纯度为85%。将IKVAV多肽纳米纤维支架凝胶与OECs复合培养, 倒置显微镜下观察OECs生长良好, Calcein-AM/PI活、死细胞染色表明活细胞数达95%。CCK-8法间接细胞计数证实IKVAV多肽可促进OECs的黏附, 对OECs增殖没有影响。由此可见IKVAV多肽可以自组装成纳米纤维支架凝胶且对OECs有良好的生物相容性及黏附作用, 可作为神经组织工程支架材料。     

Possibility of using waste tire composites reinforced with rice straw as construction materials

Agricultural lignocellulosic fiber (rice straw)-waste tire particle composite boards were manufactured for use as insulation boards in construction, using the same method as that used in the wood-based panel industry. The manufacturing parameters were: a specific gravity of 0.8 and a rice straw content (10/90, 20/80 and 30/70 by wt.% of rice straw/waste tire particle). A commercial polyurethane adhesive for rubber was used as the composite binder. The water proof, water absorption and thickness swelling properties of the composite boards were better than those of wood particleboard. Furthermore, the flexibility and flexural properties of the composite boards were superior to those of other wood-based panel products. The composite boards also demonstrated good acoustical insulation, electrical insulation, anti-caustic and anti-rot properties. These boards can be used to prevent impact damage, are easily modifiable and are inexpensive. They are able to be used as a substitute for insulation boards and other flexural materials in construction.     

To model or not to model?

In theory, the combination of mathematical modeling with experimental studies can be a powerful and compelling approach to understanding cell biology. In practice, choosing appropriate problems, identifying willing and able collaborators, and publishing the resulting research can be remarkably challenging. To provide perspective on the question of whether and when to combine modeling and experiments, a panel of experts at the 2010 ASCB Annual Meeting shared their personal experiences and advice on how to use modeling effectively.     

Three-dimensional mathematical model analysis of the patellofemoral joint

This paper is concerned with a mathematical model analysis of the patellofemoral joint in the human knee, taking into account the articular surface geometry and mechanical properties of the ligament. It was made by the application of a computer-aided design theory (previously studied) and it was possible to express the articular surface geometries in a mathematical formulation and hence elucidate the joint movement mechanics. This method was then applied to a three-dimensional geometrical model of the patellofemoral joint. For the modelling of tendofemoral contact at large angles of knee flexion, the geodestic line theory was adopted. Applying the Newton-Raphson method and the Runge-Kutta Gil method to the model, variables such as patellar attitudes, patellofemoral contact force and tensile force of the patellar ligament for various knee flexion angles were computed. Applying the Hertzian elastic theory, contact stress was also computed. These results showed good agreement with the previously reported experimental results. As an application for the model, some parameter analyses were performed in terms of the contact stress variations and compared with those of the normal knee. The simulation results indicated that both the Q-angle increase and decrease increased contact stress, the patella alta showed undulating variations of stress while the patella infera showed little change of stress, and the tibial tuberositas elevation showed 20-30% reduction of stress.     

Cellular Pressure and Volume Regulation and Implications for Cell Mechanics

In eukaryotic cells, small changes in cell volume can serve as important signals for cell proliferation, death, and migration. Volume and shape regulation also directly impacts the mechanics of cells and tissues. Here, we develop a mathematical model of cellular volume and pressure regulation, incorporating essential elements such as water permeation, mechanosensitive channels, active ion pumps, and active stresses in the cortex. The model can fully explain recent experimental data, and it predicts cellular volume and pressure for several models of cell cortical mechanics. Moreover, we show that when cells are subjected to an externally applied load, such as in an atomic force microscopy indentation experiment, active regulation of volume and pressure leads to a complex cellular response. Instead of the passive mechanics of the cortex, the observed cell stiffness depends on several factors working together. This provides a mathematical explanation of rate-dependent response of cells under force.     

Cellular Pressure and Volume Regulation and Implications for Cell Mechanics

In eukaryotic cells, small changes in cell volume can serve as important signals for cell proliferation, death, and migration. Volume and shape regulation also directly impacts the mechanics of cells and tissues. Here, we develop a mathematical model of cellular volume and pressure regulation, incorporating essential elements such as water permeation, mechanosensitive channels, active ion pumps, and active stresses in the cortex. The model can fully explain recent experimental data, and it predicts cellular volume and pressure for several models of cell cortical mechanics. Moreover, we show that when cells are subjected to an externally applied load, such as in an atomic force microscopy indentation experiment, active regulation of volume and pressure leads to a complex cellular response. Instead of the passive mechanics of the cortex, the observed cell stiffness depends on several factors working together. This provides a mathematical explanation of rate-dependent response of cells under force.     

Applying voting rules to panel-based decision making in LCA

Background, aim, and scope  Cross-category weighting is one possible way to facilitate internal decision making when dealing with ambiguous impact assessment results, with simple additive weighting being a commonly used method. Yet, the question as to whether the methods applied today can, in fact, identify the most “environmentally friendly” alternative from a group perspective remains unanswered. The aim of this paper is to propose a new method for group decision making that ensures the effective identification of the most preferable alternative. Materials and methods  Common approaches to deduce a single set of weighting factors for application in a group decision situation (e.g., arithmetic mean, consensus) are discussed based on simple mathematics, empirical data, and thought experiments. After proposing an extended definition for “effectiveness” in group decision making, the paper recommends the use of social choice theory whose main focus is to identify the most preferable alternative based on individuals’ rankings of alternatives. The procedure is further supplemented by a Monte Carlo analysis to facilitate the assessment of the result’s robustness. Results  The general feasibility of the method is demonstrated. It generates a complete ranking of alternatives, which does not contain cardinal single scores. In terms of effectiveness, the mathematical structure of the procedure ensures the eligibility for compromise of the group decision proposal. The sensitivity analysis supports the decision makers in understanding the robustness of the proposed group ranking. Discussion  The method is based upon an extended definition of effectiveness which acknowledges the eligibility for compromise as the core requirement in group decision contexts. It is shown that multi-attribute decision-making (MADM) methods in use in life cycle assessment (LCA) today do not necessarily meet this requirement because of their mathematical structure. Further research should focus on empirical proof that the generated group results are indeed more eligible for compromise than results generated by current methods that utilize an averaged group weighting set. This is closely related to the question considering under which mathematical constraints it is even possible to generate an essentially different result. Conclusions  The paper describes a new multi-attribute group decision support system (MGDSS) for the identification of the most preferable alternative(s) for use in panel-based LCA studies. The main novelty is that it refrains from deducing a single set of weighting factors which is supposed to represent the panel as a whole. Instead, it applies voting rules that stem from social choice theory. Because of its mathematical structure, the procedure is deemed superior to common approaches in terms of its effectiveness. Recommendations and perspectives  The described method may be recommended for use in internal, panel-based LCA studies. In addition, the basic approach of the method—the combination of MADM methods with social choice theory—can be recommended for use in all those situations where multi-attribute decisions are to be made in a group context.     

肿瘤干细胞分离研究进展

癌症是严重威胁人类生命健康的疾病之一,传统治疗方法未能彻底根除癌症。究其原因是癌症的发病机制复杂,至今尚未完全认识。肿瘤干细胞理论的提出为肿瘤的发生、发展乃至术后复发提供了新的研究思路,同时也为癌症的治疗带来了新的曙光。但由于肿瘤干细胞含量极低、分离困难,给肿瘤干细胞的研究带来诸多不便。目前常用的分离方法为无血清培养法与流式分选法,但二者均存在一定的缺陷,因此亟须建立一种新型有效地分离方法。肿瘤干细胞与普通干细胞有许多相似的信号通路,因此可利用干细胞的微环境筛选分离分化程度较低的肿瘤干细胞。水凝胶由于其独特的性质,目前广泛用于细胞的三维培养。有鉴于此,科研工作者利用水凝胶模拟普通干细胞生长的力学环境筛选、富集肿瘤干细胞。本文就肿瘤干细胞目前常用分离及鉴定方法,同时结合国内外最新的肿瘤干细胞分离方法进行综述。     

A new hypothesis for molecular behavior

In order to understand the living cell, biologists need workable explanations of molecular phenomena. From data in the literature, it is possible to construct a mathematical hypothesis: molecular behavior in the continuum can be represented by a set of simple, logarithmic functions. These functions apply not only to biology, but also to chemistry and to physics.Although empirical in its origins, this hypothesis satisfies criteria which are often associated with good theories. It is comprehensive in its application, and it is mathematically simple. It is easily tested; and it is accurate, when tested. Because it can be correlated with classical atomic and molecular theory, the hypothesis can be used to make strong predictions. The proposal also appears to be consistent with quantum mechanics.     

Equilibria of idealized confined astral microtubules and coupled spindle poles

Positioning of the mitotic spindle through the interaction of astral microtubules with the cell boundary often determines whether the cell division will be symmetric or asymmetric. This process plays a crucial role in development. In this paper, a numerical model is presented that deals with the force exerted on the spindle by astral microtubules that are bent by virtue of their confinement within the cell boundary. It is found that depending on parameters, the symmetric position of the spindle can be stable or unstable. Asymmetric stable equilibria also exist, and two or more stable positions can exist simultaneously. The theory poses new types of questions for experimental research. Regarding the cases of symmetric spindle positioning, it is necessary to ask whether the microtubule parameters are controlled by the cell so that the bending mechanics favors symmetry. If they are not, then it is necessary to ask what forces external to the microtubule cytoskeleton counteract the bending effects sufficiently to actively establish symmetry. Conversely, regarding the cases with asymmetry, it is now necessary to investigate whether the cell controls the microtubule parameters so that the bending favors asymmetry apart from any forces that are external to the microtubule cytoskeleton.