Microfabricated arrays of elastomeric posts to study cellular mechanics

2004 ◽  
Author(s):  
Olivia du Roure ◽  
Caroline Dequidt ◽  
Alain Richert ◽  
Robert H. Austin ◽  
Axel Buguin ◽  
...  
Keyword(s):  
Cellular Mechanics ◽  
Microfabricated Arrays

Measuring surface potential components necessary for transmembrane current computation using microfabricated arrays

2005 ◽  
Vol 289 (6) ◽  
pp. H2468-H2477 ◽  
Author(s):  
J. James Wiley ◽  
Raymond E. Ideker ◽  
William M. Smith ◽  
Andrew E. Pollard
Keyword(s):  
Spatial Resolution ◽  
Current Density ◽  
Potential Gradient ◽  
Electrode Spacing ◽  
Back Side ◽  
Transmembrane Current ◽  
Fine Wire ◽  
Microfabricated Arrays ◽  
Potential Gradients ◽  
Unipolar Electrograms

This study was designed to test the feasibility of using microfabricated electrodes to record surface potentials with sufficiently fine spatial resolution to measure the potential gradients necessary for improved computation of transmembrane current density. To assess that feasibility, we recorded unipolar electrograms from perfused rabbit right ventricular free wall epicardium ( n = 6) using electrode arrays that included 25-μm sensors fabricated onto a flexible substrate with 75-μm interelectrode spacing. Electrode spacing was therefore on the size scale of an individual myocyte. Signal conditioning adjacent to the sensors to control lead noise was achieved by routing traces from the electrodes to the back side of the substrate where buffer amplifiers were located. For comparison, recordings were also made using arrays built from chloridized silver wire electrodes of either 50-μm (fine wire) or 250-μm (coarse wire) diameters. Electrode separations were necessarily wider than with microfabricated arrays. Comparable signal-to-noise ratios (SNRs) of 21.2 ± 2.2, 32.5 ± 4.1, and 22.9 ± 0.7 for electrograms recorded using microfabricated sensors ( n = 78), fine wires ( n = 78), and coarse wires ( n = 78), respectively, were found. High SNRs were maintained in bipolar electrograms assembled using spatial combinations of the unipolar electrograms necessary for the potential gradient measurements and in second-difference electrograms assembled using spatial combinations of the bipolar electrograms necessary for surface Laplacian (SL) measurements. Simulations incorporating a bidomain representation of tissue structure and a two-dimensional network of guinea pig myocytes prescribed following the Luo and Rudy dynamic membrane equations were completed using 12.5-μm spatial resolution to assess contributions of electrode spacing to the potential gradient and SL measurements. In those simulations, increases in electrode separation from 12.5 to 75.0, 237.5, and 875.0 μm, which were separations comparable to the finest available with our microfabricated, fine wire, and coarse wire arrays, led to 10%, 42%, and 81% reductions in maximum potential gradients and 33%, 76%, and 96% reductions in peak-to-peak SLs. Maintenance of comparable SNRs for source electrograms was therefore important because microfabrication provides a highly attractive methods to achieve spatial resolutions necessary for improved computation of transmembrane current density.

scholarly journals Temporal and mutation-specific alterations in Ca2+ homeostasis differentially determine the progression of cTnT-related cardiomyopathies in murine models

2009 ◽  
Vol 297 (2) ◽  
pp. H614-H626 ◽  
Author(s):  
Pia J. Guinto ◽  
Todd E. Haim ◽  
Candice C. Dowell-Martino ◽  
Nathaniel Sibinga ◽  
Jil C. Tardiff
Keyword(s):  
Hypertrophic Cardiomyopathy ◽  
Ventricular Myocytes ◽  
Troponin T ◽  
Early Time ◽  
Left Ventricular ◽  
Familial Hypertrophic Cardiomyopathy ◽  
Compensatory Mechanism ◽  
Missense Mutations ◽  
Tail Domain ◽  
Cellular Mechanics

Naturally occurring mutations in cardiac troponin T (cTnT) result in a clinical subset of familial hypertrophic cardiomyopathy. To determine the mechanistic links between thin-filament mutations and cardiovascular phenotypes, we have generated and characterized several transgenic mouse models carrying cTnT mutations. We address two central questions regarding the previously observed changes in myocellular mechanics and Ca2+ homeostasis: 1) are they characteristic of all severe cTnT mutations, and 2) are they primary (early) or secondary (late) components of the myocellular response? Adult left ventricular myocytes were isolated from 2- and 6-mo-old transgenic mice carrying missense mutations at residue 92, flanking the TNT1 NH2-terminal tail domain. Results from R92L and R92W myocytes showed mutation-specific alterations in contraction and relaxation indexes at 2 mo with improvements by 6 mo. Alterations in Ca2+ kinetics remained consistent with mechanical data in which R92L and R92W exhibited severe diastolic impairments at the early time point that improved with increasing age. A normal regulation of Ca2+ kinetics in the context of an altered baseline cTnI phosphorylation suggested a pathogenic mechanism at the myofilament level taking precedence for R92L. The quantitation of Ca2+-handling proteins in R92W mice revealed a synergistic compensatory mechanism involving an increased Ser16 and Thr17 phosphorylation of phospholamban, contributing to the temporal onset of improved cellular mechanics and Ca2+ homeostasis. Therefore, independent cTnT mutations in the TNT1 domain result in primary mutation-specific effects and a differential temporal onset of altered myocellular mechanics, Ca2+ kinetics, and Ca2+ homeostasis, complex mechanisms which may contribute to the clinical variability in cTnT-related familial hypertrophic cardiomyopathy mutations.

Interval Coding. II. Dendrite-Dependent Mechanisms

2007 ◽  
Vol 97 (4) ◽  
pp. 2744-2757 ◽  
Author(s):  
Brent Doiron ◽  
Anne-Marie M. Oswald ◽  
Leonard Maler
Keyword(s):  
Neural Coding ◽  
Pyramidal Neurons ◽  
Temporal Structure ◽  
Spike Trains ◽  
Sensory Cells ◽  
Cellular Mechanics ◽  
Dynamic Stimuli ◽  
Multiple Dimensions ◽  
Sensory Modalities ◽  
The Rich

The rich temporal structure of neural spike trains provides multiple dimensions to code dynamic stimuli. Popular examples are spike trains from sensory cells where bursts and isolated spikes can serve distinct coding roles. In contrast to analyses of neural coding, the cellular mechanics of burst mechanisms are typically elucidated from the neural response to static input. Bridging the mechanics of bursting with coding of dynamic stimuli is an important step in establishing theories of neural coding. Electrosensory lateral line lobe (ELL) pyramidal neurons respond to static inputs with a complex dendrite-dependent burst mechanism. Here we show that in response to dynamic broadband stimuli, these bursts lack some of the electrophysiological characteristics observed in response to static inputs. A simple leaky integrate-and-fire (LIF)-style model with a dendrite-dependent depolarizing afterpotential (DAP) is sufficient to match both the output statistics and coding performance of experimental spike trains. We use this model to investigate a simplification of interval coding where the burst interspike interval (ISI) codes for the scale of a canonical upstroke rather than a multidimensional stimulus feature. Using this stimulus reduction, we compute a quantization of the burst ISIs and the upstroke scale to show that the mutual information rate of the interval code is maximized at a moderate DAP amplitude. The combination of a reduced description of ELL pyramidal cell bursting and a simplification of the interval code increases the generality of ELL burst codes to other sensory modalities.

Dissecting cellular mechanics: Implications for aging, cancer, and immunity

2019 ◽  
Vol 93 ◽  
pp. 16-25 ◽  
Author(s):  
Michael J. Harris ◽  
Denis Wirtz ◽  
Pei-Hsun Wu
Keyword(s):  
Cellular Mechanics

scholarly journals Cellular Mechanics and Therapeutic Resistance of the Cancer Relapse

2017 ◽  
Vol 1 (11) ◽  
pp. 1-12
Author(s):  
Emad Y. Moawad
Keyword(s):  
Low Dose ◽  
Cultured Cells ◽  
Therapeutic Resistance ◽  
Primary Cancer ◽  
A431 Cells ◽  
Second Line Therapy ◽  
Cellular Mechanics ◽  
Cancer Relapse ◽  
Subcutaneous Tissues ◽  
The Right

The aims of this study are to investigate the variation in the mechanical behaviour of the primary cancer from cancer relapse, and measuring the therapeutic resistance acquired by cancer relapse. A431-cultured cells were irradiated for 7 months until 85 Gy. Then, a selected single cell was left to grow as stable A431-R cell line. 106 cells of A431 cells and 106 of A431-R cells suspended in 100 μL of medium were injected into subcutaneous tissues on the right thigh of athymic mice to generate tumor xenografts models of primary cancer (A431-P) and cancer relapse (A431-R). Radiotherapy of a low-dose of 30Gy was applied on xenoimplanted tumors after one week from inoculation. A mock process was performed on untreated groups of mice for controls. Tumor size was monitored starting from inoculation and tumor growth was measured along 42 days. Rates of mitosis and apoptosis and the histologic grade (HG) that characterize the tumor response were determined as described in earlier studies. Alterations induced on tumor HG in the treated models were 100% identical to the energy of the applied doses. The differences in response energy between cancer relapse and primary cancer irrespectively of the treatment (untreated vs. treated) or origin of the cells (A431-P vs. A431-R) in all phases of tumor responses (growth, shrinkage or regrowth) were 100% identical to the total differences in the administered regimens applied on those groups during those phases. Cancer relapse is characterized by a delay in growth before second line therapy for its relatively lower rate of mitosis compared by the primary cancer inducing a corresponding delay in the early detection. The therapeutic resistance of the cancer relapse is equivalent to the energy of the doses which have been delivered in the prior therapies, and requires increasing the administered dose by an amount equivalent to that resistance.

scholarly journals The Functional Implications of Endothelial Gap Junctions and Cellular Mechanics in Vascular Angiogenesis

Cancers ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 237 ◽  
Author(s):  
Takayuki Okamoto ◽  
Haruki Usuda ◽  
Tetsuya Tanaka ◽  
Koichiro Wada ◽  
Motomu Shimaoka
Keyword(s):  
Endothelial Cells ◽  
Cell Migration ◽  
Gap Junctions ◽  
Gap Junction ◽  
Cancer Cells ◽  
Tumor Development ◽  
Tube Formation ◽  
Cellular Mechanics

Angiogenesis—the sprouting and growth of new blood vessels from the existing vasculature—is an important contributor to tumor development, since it facilitates the supply of oxygen and nutrients to cancer cells. Endothelial cells are critically affected during the angiogenic process as their proliferation, motility, and morphology are modulated by pro-angiogenic and environmental factors associated with tumor tissues and cancer cells. Recent in vivo and in vitro studies have revealed that the gap junctions of endothelial cells also participate in the promotion of angiogenesis. Pro-angiogenic factors modulate gap junction function and connexin expression in endothelial cells, whereas endothelial connexins are involved in angiogenic tube formation and in the cell migration of endothelial cells. Several mechanisms, including gap junction function-dependent or -independent pathways, have been proposed. In particular, connexins might have the potential to regulate cell mechanics such as cell morphology, cell migration, and cellular stiffness that are dynamically changed during the angiogenic processes. Here, we review the implication for endothelial gap junctions and cellular mechanics in vascular angiogenesis.

Invited Review: Engineering approaches to cytoskeletal mechanics

2000 ◽  
Vol 89 (5) ◽  
pp. 2085-2090 ◽  
Author(s):  
Dimitrije Stamenović ◽  
Ning Wang
Keyword(s):  
Cell Biology ◽  
Theoretical Models ◽  
Force Balance ◽  
Mechanical Forces ◽  
Cellular Functions ◽  
Cellular Mechanics ◽  
Recent Developments ◽  
Biochemical Mechanisms ◽  
Underlying Mechanisms ◽  
Biochemical Signals

An outstanding problem in cell biology is how cells sense mechanical forces and how those forces affect cellular functions. Various biophysical and biochemical mechanisms have been invoked to answer this question. A growing body of evidence indicates that the deformable cytoskeleton (CSK), an intracellular network of interconnected filamentous biopolymers, provides a physical basis for transducing mechanical signals into biochemical signals. Therefore, to understand how mechanical forces regulate cellular functions, it is important to know how cells respond to changes in the CSK force balance and to identify the underlying mechanisms that control transmission of mechanical forces throughout the CSK and bring it to equilibrium. Recent developments of new experimental techniques for measuring cell mechanical properties and novel theoretical models of cellular mechanics make it now possible to identify and quantitate the contributions of various CSK structures to the overall balance of mechanical forces in the cell. This review focuses on engineering approaches that have been used in the past two decades in studies of the mechanics of the CSK.

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