X射线致HeLa细胞损伤过程中NADPH氧化酶的作斥

以HeLa细胞为实验材料，探讨了NADPH氧化酶在X射线诱导细胞损伤过程中的作用。结果显示，12Cry X射线辐照后细胞内活性氧（ROS）明显增加，在用NADPH氧化酶抑制剂处理后再辐照，则细胞内ROS降低到未辐照水平；同时辐照后NADPH氧化酶细胞质亚基p47^phox在细胞质积聚并和细胞膜亚基gp91^phox结合；Western blotting检测结果显示，NADPH氧化酶的关键亚基gp91^phox的表达量明显增加。以上结果说明，NADPH氧化酶可以被X射线激活，由其介导产生的ROS在X射线诱导HeLa细胞损伤过程中扮演重要角色。     

卡维地洛载入酵母细胞微囊的制备和体外释放

酵母细胞通过被十六烷基三甲基溴化铵(CTAB)进行透性化处理之后,很好的增加了细胞膜的通透性,从而使药物分子更容易的进入细胞中.利用电子显微镜和透射电镜考察透性化后细胞的形态和细胞内部结构、紫外测定载药量和释放度.结果表明用酵母细胞经过CTAB处理之后细胞仍保持完整性,平均载药量为32.24％,卡维地洛在pH1.2,48h内体外累积释放为94.07％.     

模型化研究药物小分子阻滞细胞周期

基于扩散动力学与细胞信号传导动力学，研究药物小分子对细胞周期的阻滞特性.理论模型考虑药物小分子穿越细胞膜输运的动力学特性，以及进入细胞内的药物分子对细胞周期的阻滞效应.研究发现，穿越细胞膜内层进入细胞内的药物分子，将会在很大程度上决定药物分子对相关的靶向基因、蛋白的阻滞功效.细胞膜对药物分子的输运特性，是影响药物分子阻滞细胞周期的关键因素.另外，药物分子的降解程度，将会改变药物分子与靶向基因、蛋白作用时间，进而改变对相关细胞生长增殖的抑制效应.通过对模型中各参数的敏感度分析，我们确认了药物分子穿越细胞膜、进入细胞内过程的多种因素对细胞周期的抑制效应.本文理论结果符合模拟、实验观测，进一步深刻揭示了药物小分子阻滞细胞周期的物理机制，可为设计确切的疗法药物提供必要的参考和新方案.     

氢化物发生-原子荧光光谱法研究嗜热四膜虫对阿散酸饲料添加剂及其环境降解物的砷吸收

用以单细胞原生动物嗜热四膜虫对阿散酸及其降解物的砷吸收模型,研究了饲料添加剂阿散酸及其环境降解物对生物体的影响.四膜虫在含有阿散酸及其降解物的培养基中培养72 h后,洗去培养基,收集细胞.将虫体裂解,分离细胞膜和细胞内质液,经消解.用流动注射氢化物发生-原子荧光光谱法(HG-AFS)分别测定了细胞膜上和细胞膜内的砷.结果表明,阿散酸及其环境降解物可被细胞膜吸收并进入细胞内,且降解产生的无机砷比阿散酸更易被吸收,生物体通过细胞的砷吸收引起毒害.     

近红外光刺激神经细胞钙离子光激活

钙离子(Ca~(2+))是细胞的主要信息传输通道,研究Ca~(2+)激活对阐述亚细胞层次生物过程具有重要意义,光激活是目前研究细胞内Ca~(2+)传输和控制的主要方式之一.本文利用近红外脉冲激光刺激标记有金纳米棒(gold nanorods, GNRs)的人神经母细胞瘤细胞(SH-SY5Y)的Ca~(2+)信号传导,并利用钙离子指示剂(Fluo-4,AM)对其进行双光子荧光成像.实验采用功率为0.5 m W,波长为800 nm的激发光,平均10 s就可实现Ca~(2+)光激活,标记GNRs的神经细胞Ca~(2+)释放速度是未标记GNRs的6倍.研究结果表明GNRs通过局域表面等离子体共振将脉冲激光瞬间转化为热量,改变膜电容,使细胞膜去极化并引发动作电位,使细胞外Ca~(2+)流入,证明了借助GNRs来增强神经细胞Ca~(2+)激活的可行性,为神经细胞离子通道研究提供了一种光学手段.     

基于生物阻抗谱的细胞电学特性研究

生物阻抗谱是一种非侵入式、免标记、能够定量分析的检测技术,将其应用于生物细胞及组织的生理、病理分析中具有很大优势.本文采用数值仿真的方法研究了单细胞电学特性与其结构之间的关系,并通过实验进行了验证.根据细胞的生理特征,依据细胞的双壳模型与单壳模型理论分别建立了不同种类细胞的电学模型,研究了细胞种类、细胞膜、细胞核对细胞电学特性的影响.数值分析结果表明:1)细胞结构尺寸的变化引起细胞电学特性的改变,因此,依据细胞电学特性能够准确实现细胞分类; 2)柯尔-柯尔(Cole-Cole)图上高频与低频的两个半圆弧分别是由细胞质或细胞外液的离子极化、细胞膜与细胞外液之间的界面极化引起的;3)细胞核大小对测量阻抗的影响主要在低频段,是由细胞核与细胞内液的界面极化引起的,当存在细胞膜且当细胞核的核质比小于0.25时可忽略其影响.为验证仿真结果,对20%不同活性的酵母菌进行了实验.实验结果表明,运用本文建立的细胞电学模型,可以准确检测细胞的不同活性.该方法对实现细胞的精准电阻抗检测提供了理论依据,具有重要的应用价值.     

K+离子通道及其研究进展

 细胞是通过细胞膜与外界隔离的,在细胞膜上有很多离子通道,细胞通过这些通道与外界进行离子交换。离子通道在许多细胞活动中都起关键作用,它是生物电活动的基础,在细胞内和细胞间信号传递中起着重要作用。离子通道通过调控细胞内pH值和离子浓度来维持正常的细胞体积及细胞内生物分子活性所需的离子浓度范围。特别是通过改变作为第二信使的钙离子浓度,来调控各种生化过程。生命的很多过程如发育、生长、分泌、兴奋、运动,甚至于学习和记忆都与离子通道功能的正常发挥有直接联系。目前,离子通道的研究已成为分子生物学、分子药理学、生物物理学、神经生物学等多种学科的热点。     

具有双重治疗机制的磁性纳米无定型氧化铁基药物递送系统

合成一种具有pH响应性的聚乙二醇(PEG)修饰无定形介孔氧化铁纳米粒子(AFe-PEG). 这种纳米粒子可以高效负载药物分子如阿霉素(DOX)，构成新型多功能AFe-PEG/DOX药物递送体系. DOX的负载率高达948 mg/g-纳米粒子. 在酸性溶液中，AFe-PEG/DOX纳米粒子不仅可以有效释放DOX，同时可以释放Fe离子进行Fenton反应，将H₂O₂转变成·OH自由基. 体外实验结果表明，AFe-PEG/DOX纳米粒子对HeLa细胞同时具有化疗和化学动力学疗法的疗效. 同时，由于AFe-PEG/DOX 纳米粒子本身的磁性，使其在外部磁场中的细胞内化效率也得到了提高.     

细胞内单颗粒示踪技术的进展

单颗粒示踪（Single particle tracking，SPT）技术是应用显微镜系统对细胞内单个特定荧光或散射颗粒的定位和追踪。由于SPT能够实时监控活细胞内复杂、高度动态的组织结构的变化并提供结构—功能间的动力学关系，因此在细胞生物学上有重要的应用。本文总结了SPT的机理以及在细胞上的应用，首先介绍了SPT的动力学原理，包括单颗粒定位，轨道重建以及轨道分析，然后总结了SPT技术现阶段重点发展的光学材料及仪器，最后阐述了SPT在细胞膜、细胞内信号通路、分子转运机制、遗传信息表达以及病毒感染机制的应用。此外，本文还对SPT技术未来的发展进行了展望。     

细胞内蛋白质磁共振

细胞内的环境异常复杂，其中生物大分子的浓度超过300 mg/mL并占据着大约30%的细胞内空间. 然而，直到目前为止大多数的蛋白质研究仍然在细胞外或是甚至非常稀的缓冲液中进行. 细胞内磁共振（In-cell NMR）提供了一个可以直接非损伤地获取细胞内原子水平信息的方法. 虽然In-cell NMR在近10年里有了较大的发展，但是这一技术尚未成熟. 在该篇综述中，作者首先总结制约这一技术发展的因素以及研究中需要注意的事项，最后讨论了未来的发展方向.     

Estimation of biophysical properties of cell exposed to electric field

Excitable media,such as cells,can be polarized and magnetized in the presence of an external electromagnetic field.In fact,distinct geometric deformation can be induced by the external electromagnetic field,and also the capacitance of the membrane of cell can be changed to pump the field energy.Furthermore,the distribution of ion concentration inside and outside the cell can also be greatly adjusted.Based on the theory of bio-electromagnetism,the distribution of field energy and intracellular and extracellular ion concentrations in a single shell cell can be estimated in the case with or without external electric field.Also,the dependence of shape of cell on the applied electronic field is calculated.From the viewpoint of physics,the involvement of external electric field will change the gradient distribution of field energy blocked by the membrane.And the intracellular and extracellular ion concentration show a certain difference in generating timevarying membrane potential in the presence of electric field.When a constant electric field is applied to the cell,distinct geometric deformation is induced,and the cell triggers a transition from prolate to spherical and then to oblate ellipsoid shape.It is found that the critical frequency in the applied electric field for triggering the distinct transition from prolate to oblate ellipsoid shape obtains smaller value when larger dielectric constant of the cell membrane and intracellular medium,and smaller conductivity for the intracellular medium are used.Furthermore,the effect of cell deformation is estimated by analyzing the capacitance per unit area,the density of field energy,and the change of ion concentration on one side of cell membrane.The intensity of external applied electric field is further increased to detect the change of ion concentration.And the biophysical effect in the cell is discussed.So the deformation effect of cells in electric field should be considered when regulating and preventing harm to normal neural activities occurs in a nervous system.     

蜂毒肽浓度和磷脂组分对巨囊泡泄露的影响

蜂毒肽作为一种广谱抗菌肽已经得到广泛认知,用蜂毒肽构建载药体系攻击癌细胞研究正在兴起.基于仿生物膜模型探索其破坏机理,可以避免潜在活性细胞过程的影响.在此,我们选用细胞尺寸的单层巨囊泡膜模型,可在光学显微镜下直接观察和操作,获得仿正常细胞膜和仿癌细胞膜在不同蜂毒肽浓度刺激下的响应.研究得出,低浓度蜂毒肽诱导囊泡泄露实验表明中性磷脂囊泡以孔模式为主泄露,负电性磷脂囊泡以爆裂模式为主泄露;高浓度蜂毒肽诱导囊泡泄露实验表明负电性磷脂相较于中性磷脂可延迟蜂毒肽作用效果;蜂毒肽色氨酸残基荧光光谱表明囊泡膜表面蜂毒肽吸附量以及泄露模式依赖于磷脂组分.此外,推断了蜂毒肽对不同组分磷脂膜的破坏作用模型.研究为蜂毒肽在肿瘤细胞的作用机制及其衍生物的优化设计提供参考.     

Relative quantification of cellular sections with molecular depth profiling ToF-SIMS imaging

We report the use of secondary ion mass spectrometry (SIMS) imaging to quantify the relative difference in the amount of lipid between two sections, the plasma membrane and the cytoplasm, of single cells from two different populations. Cells were each labeled with lipophillic dyes, frozen, fractured and analyzed in a ToF-SIMS mass spectrometer equipped with a 40 keV C₆₀⁺ ion source. In addition to identifying cells from separate populations, the lipophilic dyes can be used as a marker for the outer leaflet of the cell membrane and therefore as a depth finder. Here, we show that it is possible to compare the amount of lipids with particular headgroups in the cell membrane of a treated cell to the membrane of a control cell. Following erosion of the cell membranes, the amount of the two specific lipid head groups in the cytoplasm of the treated cell can be compared to those lipids in a control cell. Here we take the first step in this experimental design and display the ability to analyze multiple sections of frozen cells following a single fracture.     

维生素C对生物膜流动性的影响的ESR波谱的研究

本文使用TEMPO和脂肪酸氮氧自由基自旋标记脂质体和正常的与癌变的鼠肝细胞膜,研究了V_c对膜流动性的影响,探讨有关V_c抗肿瘤作用的机理。实验表明:V_c可以影响膜类脂和膜蛋白的运动,提高癌变细胞膜的流动性,并随V_c浓度的增加其作用速度加快,但对正常肝细胞膜流动性则无明显影响。此外,在一定浓度范围内,V_c对正常的与癌变的肝细胞膜的掺入能力有显著差异。     

Diffusion and the physics of chemoreception

This review provides a manual which enables the reader to perform calculations on the rate with which a biological cell can capture certain chemical compounds (ligands) which are essential to its survival and which diffuse in its environment. After a discussion of spatial diffusion and the capture of ligands by a single receptor in the cell membrane, the theory of one-stage chemoreception is developed for the general case in which the cell is spherical and arbitrary forces act between the ligand and the cell. Our method can also be applied to cells with other shapes. Next we discuss membrane diffusion and develop a theory of two-stage chemoreception. Some hydrodynamic effects are also discussed.     

Ultrasound exposure in the presence of hematoporphyrin induced loss of membrane integral proteins and inactivity of cell proliferation associated enzymes in sarcoma 180 cells in vitro

Ultrasonically induced effects of hematoporphyrin (HPD) on cell damage and membrane protein alteration of S180 isolated tumor cells in vitro were investigated, and the potential mechanisms of sonodynamic therapy (SDT) inhibiting tumor growth were discussed. Tumor cells suspended in air-saturated PBS (pH 7.2) were exposed to ultrasound at 1.8 MHz for up to 180 s in the presence and absence of HPD. The viability of cells was determined by a trypan blue exclusion test. To estimate the damage effects of SDT on plasma membrane of tumor cells primarily, membrane integral proteins (EGFR, Ras, Fas, FasL) and cell proliferation associated enzymes (adenylate cyclase and guanylate cyclase) were checked with immunochemical methods. The results indicated that the intensity threshold for ultrasonically induced cell damage at 1.8 MHz was 3 W/cm². At this condition, the expression of the integral proteins was obviously inhibited and the activity of the enzymes was decreased post ultrasound treatment in the presence of 20 μg/ml HPD. Loss of the membrane proteins and inactivity of AC and GC post SDT was time-dependent. This paper reveals SDT can cause the loss of tumor cell membrane integral proteins and inactivity of the enzymes associated with cell proliferation which might be attributed to a sonochemical activation mechanism. The mechanisms by that tumor growth is inhibited by SDT can be understood as that the growth signaling pathway is partially interdicted and the resistance of tumor cells to the specifically activated immune cells is weakened.     

Fractal properties of macrophage membrane studied by AFM

Complexity of cell membrane poses difficulties to quantify corresponding morphology changes during cell proliferation and damage. We suggest using fractal dimension of the cell membrane to quantify its complexity and track changes produced by various treatments. Glutaraldehyde fixed mouse RAW 264.7 macrophage membranes were chosen as model system and imaged in PeakForce QNM (quantitative nanomechanics) mode of AFM (atomic force microscope). The morphology of the membranes was characterized by fractal dimension. The parameter was calculated for set of AFM images by three different methods. The same calculations were done for the AFM images of macrophages treated with colchicine, an inhibitor of the microtubule polymerization, and microtubule stabilizing agent taxol. We conclude that fractal dimension can be additional and useful parameter to characterize the cell membrane complexity and track the morphology changes produced by different treatments.     

Transformation optics for efficient calculation of transmembrane voltage induced on cells

We present a novel efficient approach in calculating induced transmembrane voltage(ITV) on cells based on transformation optics. As cell membrane is much thinner than the dimension of a typical cell, discretizing the membrane needs numerous meshes. Using an anisotropic medium based on transformation optics, the thickness of the membrane can be exaggerated by at least one order, which eliminates rigorous mesh refinement and reduces unknowns greatly. The accuracy and efficiency of the proposed method are verified by a cylindrical cell model. Moreover, the influence on ITV with bound water(BW) layers is also studied. The results show that when cells are exposed to nanosecond electric field, BW layers should be rigorously considered in calculating ITV.     

Monitoring membrane rafts in colorectal cancer cells by means of correlative fluorescence electron microscopy (CFEM)

Detergent-resistant membrane (DRM) rafts have been shown to play a pivotal role in regulating key cell biological processes, such as signal transduction, cellular transport and cell survival. The fine structure of membrane rafts are studied using various different imaging approaches and the outcomes are largely dependent on the detection methodology applied. All these microscopy techniques which employ light-, laser- and photon-optics, electrons as well as atomic force probing are characterized on their turn by their strengths and limitations for membrane raft identification. This explains in part the diversity of definitions available to describe these peculiar membrane structures. We present herewith an alternative and uncomplicated microscopy tool to study fluorescently labelled DRMs with information at the transmission electron microscopical level of the same cell, enabling us to obtain a snapshot of the morpho-functional relationships between the cell's interior and DRMs. The proposed approach of correlative fluorescence electron microscopy (CFEM) can therefore be considered as an additional alternative imaging approach to unravel DRM structure–function relationships from micro- to nanometre length scales, from the cell to the molecule.