Micro hole-based cell chip with impedance spectroscopy

Electric fields can be used for the characterisation and manipulation of single biological cells. One approach to avoid the effect of electrode polarisation is to position cells on micro holes and to apply the electrical fields via the micro holes. For a correct characterisation and optimal manipulation, the electrical properties of the micro hole/cell interface must be understood. In this article, the electrical characteristics of a micro hole-based cell chip were investigated. By FEM simulation, it was estimated that the impedance measurement with micro hole-based chip is most dependent on the cell adhesion/spread rather than the intra-cellular space (contribution of intra-cellular space to the total impedance: 0.07% at 1 kHz, 0.3% at 1 MHz). The effective frequency range in which the impedance related with cell state on the hole considerably influences total measured impedance was below several kiloHertz. From the experiments, it was shown that the impedance of cell cultured on the hole at the low frequency range is increased during the increase of cultivation period, but is sensitively decreased after applying only several nanolitres of culture medium including 5% dimethlysulfoxide. This micro hole-based chip has a potential for monitoring the cell growth and the membrane integrity of even single cell without any labelling.     

An analysis of the sources of musculoskeletal system impedance

When antagonistic muscles co-contract, the impedance of musculoskeletal systems to applied loads is known to increase. In this paper a physiologically-based, higher-order, nonlinear antagonistic muscle-joint model is utilized to clarify the sources of impedance modulation during a variety of tasks, ranging from resisting transient loads to holding steady loads to making fast movements in unpredictable surroundings. It is shown that impedance modulation occurs automatically as a function of the specific operating ranges utilized during a given task by each of four different muscle-joint mechanical relations. The relative contribution of each relation depends on the type of task, with impedance during quasi-static conditions sensitive to muscle tension-length and sometimes joint parallel elastic properties and during dynamic tasks dominated by the series element and muscle force-velocity properties. Elimination of any of these causes a decrease in built-in biomechanical capabilities. These findings raise questions concerning past theories on stiffness-impedance modulation which appear to underestimate the role of inherent biomechanical properties.     

Integration of single-cell trapping and impedance measurement utilizing microwell electrodes

The ability to research individual cells has been seen as important in many kinds of biological studies. In the present study, cell impedance analysis is integrated into a single-cell trapping structure. For the purpose of precise positioning, a cell manipulation and measurement microchip, which uses an alternating current electrothermal effect (ACET) and a negative dielectrophoresis (nDEP) force to move a particle and cell on measurement electrodes, is developed. An ACET and an nDEP can be easily combined with subsequent analyses based on electric fields. A microwell presented in a previous study is separated into two parts, which are regarded as the measurement electrodes. The original structure is modified for precise positioning. Numerical simulations and analyses are conducted to compute and analyze the effects of the structural parameters. The results of simulations and analyses are used to obtain the optimum structure for the cell. The capture range of the microwell can be designed for cells of various sizes. In order to demonstrate the precision of the positioning, a particle is captured, measured, and released twice. The results show that the impedance error of the particle is about 3%. Finally, the developed structure is applied to trap and measure the impedance of a HeLa cell.     

Contribution of large airway to the input impedance of the respiratory system

To evaluate the contribution of the large airway to total respiratory impedance, we develop a one-dimensional model of pressure and flow in these airways by coupling conservation of mass and momentum equations with the geometric information obtained by the acoustic reflection technique. We use this model to calculate the impedance of the respiratory system distal to the carina from impedance data estimated at the airway opening by the forced oscillation technique. Simulations show that the real part of the impedance distal to the carina is uniformly decreased from the impedance at the airway opening, indicating a resistive loss, while the imaginary part is increased as a function of frequency. We estimate parameter values for a six-parameter two-compartment lung model and for a three-parameter reduction of this model before and after the application of the upper airway data to the impedance spectrum. Although compliance terms seem to be minimally affected by the manipulation of the data, resistance and inertance terms are influenced in a fashion that suggests that the resistive contribution of the upper airway to total respiratory impedance is significant. Furthermore it appears that the elastic nature of the walls of the upper airway also impact on estimates of total respiratory impedance at the airway opening.     

Hydraulic input impedance measurements in physical models of the arterial wall

A white noise method was used to measure the hydraulic input impedance and transmission characteristics in physical models of an arterial system made of single, unbranched latex tubes. The experimentally obtained impedance curves show a rise in modulus and a positive phase at high frequencies in the absence of wave reflections. Using the impedance moduli in the presence of wave reflections, wave velocity and attenuation were calculated. The influence of wall nonlinearity on hydraulic impedance was also examined. It is concluded that, in the model used neither wave reflections nor wall nonlinearity can account for the deviations of the experimental impedance curves from the theoretically predicted ones. Impedance moduli in the presence of reflections may be used to study transmission characteristics (wave velocity and attenuation) of the model.     

A computational model of limb impedance control based on principles of internal model uncertainty

Efficient human motor control is characterized by an extensive use of joint impedance modulation, which is achieved by co-contracting antagonistic muscles in a way that is beneficial to the specific task. While there is much experimental evidence available that the nervous system employs such strategies, no generally-valid computational model of impedance control derived from first principles has been proposed so far. Here we develop a new impedance control model for antagonistic limb systems which is based on a minimization of uncertainties in the internal model predictions. In contrast to previously proposed models, our framework predicts a wide range of impedance control patterns, during stationary and adaptive tasks. This indicates that many well-known impedance control phenomena naturally emerge from the first principles of a stochastic optimization process that minimizes for internal model prediction uncertainties, along with energy and accuracy demands. The insights from this computational model could be used to interpret existing experimental impedance control data from the viewpoint of optimality or could even govern the design of future experiments based on principles of internal model uncertainty.     

ELECTRIC IMPEDANCE OF SUSPENSIONS OF ARBACIA EGGS

Apparatus has been designed and constructed for the measurement of the electric impedance of suspensions of Arbacia eggs in sea water to alternating currents of frequencies from one thousand to fifteen million cycles per second. This apparatus is simple, rugged, compact, accurate, and rapid. The data lead to the conclusions that the specific resistance of the interior of the egg is about 90 ohm cm. or 3.6 times that of sea water, and that the impedance of the surface of the egg is probably similar to that of a "polarization capacity". The characteristics of this surface impedance can best be determined by measurements of the capacity and resistance of suspensions of eggs. No specific change has been found in the interior resistance or the surface impedance which can be related either to membrane formation or to cell division.     

枯草芽孢杆菌无标记遗传操作技术研究进展

枯草芽孢杆菌是革兰氏阳性菌的模式生物,长期以来在代谢工程和工业微生物领域扮演重要角色。枯草芽孢杆菌无标记遗传操作技术对后基因组时代的基因功能研究和菌株生理特性的改造起着关键作用。综述枯草芽孢杆菌无标记遗传操作所使用的负筛选标记基因,总结目前主流的无标记遗传操作的策略,并提出枯草芽孢杆菌无标记遗传操作技术面临的主要问题和发展方向。     

Activation of rabbit oocytes: the impact of the Ca2+ signal regime on development

Postfertilization manipulation of mammalian embryos results in various developmental alterations. To determine whether the manipulation of the Ca2+ regime causing oocyte activation is a valuable experimental means in helping understand the biological process by which embryos integrate signals from outside and later regulate gene expression, we linked Ca2+ signal parameters i.e. amplitude, number and frequency, with the efficiency and quality of postimplantation development. Freshly ovulated rabbit oocytes were subjected to repetitive and modulated Ca2+ influx. The results provide three major pieces of information. Firstly, the Ca2+ stimulus is the most efficient signal activating mammalian eggs when it is applied in a repetitive manner, the amplitude being the crucial factor. Secondly, the dynamics of early cleavage does not appear to be determined by either the frequency or the amplitude of modulation of the Ca2+ signal that activates the oocyte. Thirdly, amplitude and temporal modulation of the Ca2+ signal in the early minutes influences the developmental performance and the morphology of the rabbit parthenogenetic conceptus at day 11.5 of pregnancy. The results demonstrate the importance of epigenetic events during postfertilization as well as the possible uses of Ca2+ modulation in studying long term developmental effects.     

Physiological model analysis of involuntary human-voice tremor

Frequency variations in the human voice result from voluntary and involuntary changes in the parameters of the vocal system. The present work deals with involuntary frequency perturbations from two theoretical aspects: 1) the influence of pitch period variations on frequency changes in the band-limited signal which results from the resonant characteristics of the vocal tract; 2) the physiological parameters of the vocal system which are potentially able to govern involuntary frequency changes. It is shown that the modulation function of the vocal-cord wave can theoretically be derived from its harmonics using FM demodulation techniques, and that higher distortion may appear at higher harmonics. It is also shown that involuntary geometrical changes of the vocal tract and its terminal impedance as well as tension and initialarea changes of the vocal cord—changes well within the physiological range—can influence frequency changes in the human voice. The present results are correlated with our reported experimental findings on involuntary voice tremor, used in psychological stress evaluation. The role of the central nervous system, and possible mechanisms for these phenomena, are discussed.     

Multi‐Functional Transparent Luminescent Configuration for Advanced Photovoltaics

The conversion and manipulation of light via luminescent down‐shifting (LDS) show promise in numerous applications. An elegant combination of lanthanide‐doped polymer‐derived ceramics incorporated with versatile nanopatterns is demonstrated using direct nanoimprint techniques. The prompt formation of nanoscale photonic structures enhances the fluorescence emission from the LDS while retaining the material's optical transparency. The functionality of this material is further expanded to accommodate surface energy modulation by nanopatterns. The practical applicability of this platform in photovoltaic devices is evaluated, showing distinctively enhanced efficiency and lifetime mainly attributed to the nanopattern assisted strong LDS property. Moreover, to efficiently combine two lanthanide emissions, so called a “double imprint” approach is devised by superpositioning two LDS nanopatterned arrays. Combined with the multi‐functionality such as prominent LDS characteristics, color tunability, and surface energy modulation, the developed LDS platform offers promise for esthetic building‐integrated photovoltaics.     

Macrophage plasminogen activator: induction by concanavalin A and phorbol myristate acetate

The synthesis and secretion of plasminogen activator by cultured macrophages can be induced and stimulated by concanavalin A and by phorbol myristate acetate, and inhibited by such agents as glucocorticoids, mitotic inhibitors and compounds affecting cAMP metabolism. By the manipulation of stimulatory and inhibitory influences, enzyme production can be modulated continuously over a 200 fold range. In the same way, the proportion of cells that secrete detectable levels of enzyme can be varied from 1–90%. No comparable modulation of lysozyme or acid hydrolase production is observed under the same conditions. These results suggest that the physiological control of macrophage plasminogen activator production is achieved by the interacting effects of mutually antagonistic stimuli; this emphasizes the utility of this enzyme for the study of regulatory phenomena, including those relating to inflammation.     

Sodium Channel Toxins and Neurotransmitter Release

Voltage-dependent sodium channels (VDSC) are an important class of ion channels in excitable cells, where they are responsible for the generation and conduction of action potential. In addition, the release of neurotransmitters from nerve terminals is influenced by sodium channel activity. The function of VDSC is subject to modulation by various neurotoxins, such as scorpion toxins, which have long been used as tools in the investigation of neurotransmitter release. This opens an interesting perspective concerning modulation of neurotransmission via pharmacological manipulation of sodium channel properties, which can lead to a better understanding of their physiological and pathological roles. Here we briefly review the studies of neurotoxins acting on sodium channels, focusing primarily on the view of the mechanisms of neurotransmitter release.     

中医推拿（滚）法生物力学研究——手法运动学实测及分析中医推拿（滚）法生物力学研究——手法运动学实测及分析中医推拿（滚）法生物力学研究——手法运动学实测及分析中医推拿（滚）法生物力学研究——手法运动学实测及分析

目的 实测中医推拿（滚）法的运动过程,归纳（滚）法手法运动学的主要特征.方法 邀请推拿领域的专家,在其手背上选取标记点,拍摄专家进行（滚）法推拿时的动态影像并提取坐标数据.将坐标系建立在测试者手法运动初始时刻的手上,并对坐标和时间进行归一化,用统计的手段对数据进行分析、归纳.结果 描绘了（滚）法手法的三维运动轨迹、位移-时间关系图、速度-时间关系图和旋转角-时间关系网,根据其运动学特点提出了14个特征时间点,并采用聚类分析方法对14个特征时间点进行归并,最终定量得到了具有共性的（滚）法手法的5个特征时刻,将（滚）法周期划分为四个具有不同运动特点的阶段,并提出（滚）法有持续1/5-1/4左右的时间具有作用面积大、作用力度大的特点.结论 从（滚）法特征时刻入手,对其运动学特征进行了归纳总结.提取了（滚）法运动学中的共性特征,得到了一些定量的结果.     

Gut microbiome and cancer immunotherapy

Gut microbiome has received significant attention for its influences on a variety of host functions, especially immune modulation. With the next-generation sequencing methodologies, more knowledge is gathered about gut microbiome and its irreplaceable role in keeping the balance between human health and diseases is figured out. Immune checkpoint inhibitors (ICIs) are one of the most innovational cancer immunotherapies across cancer types and significantly expand the therapeutic options of cancer patients. However, a proportion of patients show no effective responses or develop immune-related adverse events when responses do occur. More important, it is demonstrated that the therapeutic response or treatment-limiting toxicity of cancer immunotherapy can be ameliorated or diminished by gut microbiome modulation. In this review, we first introduce the relationship between gut microbiome and cancer immunotherapy. And then, we expound the impact of gut microbiome on efficacy and toxicity of cancer immunotherapy. Further, we review approaches to manipulating gut microbiome to regulate response to ICIs. Finally, we discuss the current challenges and propose future directions to improve cancer immunotherapy via gut microbiome manipulation.     

Regulatory T cells target chemokine secretion by dendritic cells independently of their capacity to regulate T cell proliferation

The clinical manipulation of regulatory T cells (Tregs) represents a promising strategy for the regulation of unwanted immune responses. It is now becoming clear that Tregs exert multiple effects on different cell targets under particular conditions; however, the interplay between these different factors remains unclear. Using mouse Tregs of known Ag specificity, we report in this study two different levels of Treg-mediated suppression: one that targets T cell proliferation and one that targets dendritic cell-mediated proinflammatory chemokine (CCL3 and CCL4) production. These two effects can be dissociated, and whereas modulation of T cell proliferation depends on the strength of the antigenic stimulus, modulation of chemokine production by dendritic cells does not. We also provide evidence that the bystander effect of Tregs on immune responses observed in vivo may be in great part explained by a decrease in the recruitment of target T cells, and therefore in the magnitude of the response, rather than by a direct effect on their priming or proliferation. Overall, our results shed some light on the different aspects that need to be considered when attempting to modulate Tregs for clinical purposes.     

Temperature dependent alterations of the surface-EMG and ECG: an investigation of the electrical transfer characteristics of the human skin (author's transl)

The influence of local heating of the skin on the integrated EMG (registered with surface and subcutaneous electrodes), the amplitude of the ECG, the skin blood flow, the electrode impedance, the electrode-to-skin impedance, and the tissue impedance is investigated. Except for the increasing skin blood flow each of the variables exhibits a significant reduction with an increase in skin temperature. From these results the existence of two mechanisms is deduced mediating thermal influence on bioelectric signals picked up by surface electrodes: 1. An alteration of the signal source. 2. An alteration of the electric transfer characteristics of the tissue between signal source and electrode. Especially in quantitative surface electromyography the temperature dependence of the signal can be a source of error.     

Plasma membrane microparticles in angiogenesis: role in ischemic diseases and in cancer

Microparticles are small fragments of the plasma membrane released by activated and/or apoptotic cells. In theory, all type of cells can shed microparticles representing a physiological process in the cell life. Mainly, microparticles generation has been studied in different cardiovascular pathologies due to the facility to obtain blood samples from individuals. Although microparticles have been considered as simply markers of several diseases, in the last decade, several studies support the hypothesis that they participate in the regulation of the cardiovascular system function by carrying biological messages between cells. Among the effects of microparticles, recent data show that they can be implicated in the modulation of neovascularization, an essential function of cells from cardiovascular system during either ischemic diseases or cancer development. Whereas during pathologies associated with ischemia an increase of neovascularization may have beneficial effects, anti-angiogenic strategies represent new approaches for manipulation of tumor development. Here, we give an overview of the mechanisms and factors involved in neovascularization, and finally, we look at the role and the consequences of the modulation of this process by microparticles in pathological situations.     

Impedance characteristics of a neuromusculoskeletal model of the human arm II. Movement control

The modulation of neuromusculoskeletal impedance during movements is analysed using a motor control model of the human arm. The motor control system combines feedback and feedforward control and both control modes are determined in one optimization process. In the model, the stiffness varies at the double movement frequency for 2-Hz oscillatory elbow movements and has high values at the movement reversals. During goal-directed two-degrees-of-freedom arm movements, the stiffness is decreased during the movement and may be increased in the initial and final phases, depending on the movement velocity. The stiffness has a considerable curl during the movement, as was also observed in experimental data. The dynamic stiffness patterns of the model can be explained basically by the α−γ coactivation scheme where feedback gains covary with motor control signals. In addition to the modulation of the gain factors, it is argued that the variation of the intrinsic stiffness has a considerable effect on movement control, especially during fast movements. Received: 14 October 1997 / Accepted in revised form: 18 May 1999