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Membrane Tension (membrane + tension)
Selected AbstractsCausal mapping as a tool to mechanistically interpret phenomena in cell motility: Application to cortical oscillations in spreading cellsCYTOSKELETON, Issue 9 2006Gabriel E. Weinreb Abstract Biological processes that occur at the cellular level and consist of large numbers of interacting elements are highly nonlinear and generally involve multiple time and spatial scales. The quantitative description of these complex systems is of great importance but presents large challenges. We outline a new systems biology approach, causal mapping (CMAP), which is a coarse-grained biological network tool that permits description of causal interactions between the elements of the network and overall system dynamics. On one hand, the CMAP is an intermediate between experiments and physical modeling, describing major requisite elements, their interactions and paths of causality propagation. On the other hand, the CMAP is an independent tool to explore the hierarchical organization of cell and the role of uncertainties in the system. It appears to be a promising easy-to-use technique for cell biologists to systematically probe verbally formulated qualitative hypotheses. We apply the CMAP to study the phenomenon of contractility oscillations in spreading cells in which microtubules have been depolymerized. The precise mechanism by which these oscillations are governed by a complex mechano-chemical system is not known but the data observed in experiments can be described by a CMAP. The CMAP suggests that the source of the oscillations results from the opposing effects of Rho activation leading to a decreased level of myosin light chain phosphatase and a cyclic calcium influx caused by increased membrane tension and leading to a periodically enhanced activation of myosin light chain kinase. Cell Motil. Cytoskeleton 2006. © 2006 Wiley-Liss, Inc. [source] Cell distribution of stress fibres in response to the geometry of the adhesive environmentCYTOSKELETON, Issue 6 2006Manuel Théry Abstract Cells display a large variety of shapes when plated in classical culture conditions despite their belonging to a common cell type. These shapes are transitory, since cells permanently disassemble and reassemble their cytoskeleton while moving. Adhesive micropatterns are commonly used to confine cell shape within a given geometry. In addition the micropattern can be designed so as to impose cells to spread upon adhesive and nonadhesive areas. Modulation of the pattern geometry allows the analysis of the mechanisms governing the determination of cell shape in response to external adhesive conditions. In this study, we show that the acquisition of cell shape follows two stages where initially the cell forms contact with the micropattern. Here, the most distal contacts made by the cell with the micropattern define the apices of the cell shape. Then secondly, the cell borders that link two apices move so as to minimise the distance between the two apices. In these cell borders, the absence of an underlying adhesive substrate is overcome by stress fibres forming between the apices, which in turn are marked by an accumulation of focal adhesions. By inhibiting myosin function, cell borders on nonadhesive zones become more concave, suggesting that the stress fibres work against the membrane tension in the cell border. Moreover, this suggested that traction forces are unevenly distributed in stationary, nonmigrating, cells. By comparing the stress fibres in cells with one, two, or three nonadherent cell borders it was reasoned that stress fibre strength is inversely proportional to number. We conclude that cells of a given area can generate the same total sum of tractional forces but that these tractional forces are differently spaced depending on the spatial distribution of its adherence contacts. Cell Motil. Cytoskeleton 2006. © 2006 Wiley-Liss, Inc. [source] Behavior of Nonselective Cation Channels and Large-Conductance Ca2+ -Activated K+ Channels Induced by Dynamic Changes in Membrane Stretch in Cultured Smooth Muscle Cells of Human Coronary ArteryJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 1 2003PH.D., SHENG-NAN WU M.D. Stretch-Activated Ion Channels. Introduction: The effects of membrane stretch on ion channels were investigated in cultured smooth muscle cells of human coronary artery. Methods and Results: In the cell-attached configuration, membrane stretch with negative pressure induced two types of stretch-activated (SA) ion channels: a nonselective cation channel and a large-conductance Ca2+ -activated K+ (BKCa) channel. The single-channel conductances of SA cation and BKCa channels were 26 and 203 pS, respectively. To elucidate the mechanism of activation of these SA channels and to minimize mechanical disruption, a sinusoidal change in pipette pressure was applied to the on-cell membrane patch. During dynamic changes in pipette pressure, increases in SA cation channel activity was found to coincide with increases in BKCa channel activity. In the continued presence of cyclic stretch, the activity of SA cation channels gradually diminished. However, after termination of cyclic stretch, BKCa channel activity was greatly enhanced, but the activity of SA cation channels disappeared. Conclusion: This study is the first to demonstrate that the behavior of SA cation and BKCa channels in coronary smooth muscle cells is differentially susceptible to dynamic changes in membrane tension. [source] Turgor pressure, membrane tension and the control of exocytosis in higher plantsPLANT CELL & ENVIRONMENT, Issue 9 2000Wieland Fricke ABSTRACT Both turgor pressure and differences in membrane tension are capable of providing an energy input into exocytosis, the process of fusion of Golgi vesicles with the cell membrane in plants. It is shown that the contribution of turgor pressure is much larger than that of membrane tension, so that the exocytotic process is not likely on thermodynamic grounds to be reversible unless another source of energy is made available. However, recycling of membrane material as flattened, empty vesicles is energetically possible and is likely to be favoured when the magnitude of membrane tension in the cell membrane is low. Thus the outward flows of membrane and cell wall material are in principle linked to turgor, whereas membrane tension influences the inward flow of membrane material. [source] | ||||||||||