Force-length relations in isolated intact cardiomyocytes subjected to dynamic changes in mechanical load

2007 ◽  
Vol 292 (3) ◽  
pp. H1487-H1497 ◽  
Author(s):  
Gentaro Iribe ◽  
Michiel Helmes ◽  
Peter Kohl
Keyword(s):  
Carbon Fibers ◽  
Mechanical Load ◽  
Present System ◽  
Dynamic Force ◽  
Time To Peak ◽  
Computer Controlled ◽  
Whole Heart ◽  
Cell Force ◽  
Cardiomyocyte Mechanics ◽  
Work Loop

We developed a dynamic force-length (FL) control system for single intact cardiomyocytes that uses a pair of compliant, computer-controlled, and piezo translator (PZT)-positioned carbon fibers (CF). CF are attached to opposite cell ends to afford dynamic and bidirectional control of the cell's mechanical environment. PZT and CF tip positions, as well as sarcomere length (SL), are simultaneously monitored in real time, and passive/active forces are calculated from CF bending. Cell force and length were dynamically adjusted by corresponding changes in PZT position, to achieve isometric, isotonic, or work-loop style contractions. Functionality of the technique was assessed by studying FL behavior of guinea pig intact cardiomyocytes. End-diastolic and end-systolic FL relations, obtained with varying preload and/or afterloads, were near linear, independent of the mode of contraction, and overlapping for the range of end-diastolic SLs tested (1.85–2.05 μm). Instantaneous elastance curves, obtained from FL relation curves, showed an afterload-dependent decrease in time to peak elastance and slowed relaxation with both increased preload and afterload. The ability of the present system to independently and dynamically control preload, afterload, and transition between end-diastolic and end-systolic FL coordinates provides a valuable extension to the range of tools available for the study of single cardiomyocyte mechanics, to foster its interrelation with whole heart pathophysiology.

scholarly journals Development of computer-controlled atmospheric pressure plasma structuring for 2D/3D pattern on fused silica

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Duo Li ◽  
Peng Ji ◽  
Yang Xu ◽  
Bo Wang ◽  
Zheng Qiao ◽  
...  
Keyword(s):  
Atmospheric Pressure ◽  
Mechanical Load ◽  
Removal Rate ◽  
Atmospheric Pressure Plasma ◽  
Fused Silica ◽  
Phase Plate ◽  
Gaussian Shape ◽  
Lens Array ◽  
Pressure Plasma ◽  
Computer Controlled

AbstractFused silica with structured and continuous patterns is increasingly demanded in advanced imaging and illumination fields because of its excellent properties and functional performance. Atmospheric pressure plasma, based on pure chemical etching under atmospheric pressure, is developed as a promising fabrication technique for fused silica due to its deterministic high material removal rate, controllable removal imprint and no mechanical load. The stable and controllable Gaussian-shape removal function makes computer-controlled plasma tool potential to generate complex structures with high accuracy, efficiency and flexibility. In the paper, computer-controlled atmospheric pressure plasma structuring (APPS) is proposed to fabricate 2D/3D patterns on fused silica optics. The capacitively coupled APPS system with a double-layer plasma torch and its discharge characteristics are firstly developed. By means of multi-physics simulation and process investigation, the stable and controllable Gaussian-shape removal function can be achieved. Two different structuring modes, including discrete and continuous APPS, are explored for 2D/3D patterns. A series of structuring experiments show that different kinds of 2D patterns (including square lens array, hexagon lens array and groove array) as well as complex 3D phase plate patterns have been successfully fabricated, which validates the effectiveness of the proposed APPS of 2D/3D patterns on fused silica optics.

scholarly journals Relating components of pressure-volume area in Suga's formulation of cardiac energetics to components of the stress-time integral

2012 ◽  
Vol 113 (7) ◽  
pp. 988-995 ◽  
Author(s):  
J.-C. Han ◽  
A. J. Taberner ◽  
K. Tran ◽  
D. P. Nickerson ◽  
M. P. Nash ◽  
...  
Keyword(s):  
Oxygen Consumption ◽  
Time Profile ◽  
Cardiac Energetics ◽  
Time Integral ◽  
Single Twitch ◽  
Triangular Region ◽  
Force Time ◽  
Whole Heart ◽  
Ventricular Trabeculae ◽  
Work Loop

The concept of pressure-volume area (PVA) in whole heart studies is central to the phenomenological description of cardiac energetics proposed by Suga and colleagues ( Physiol Rev 70: 247–277, 1990). PVA consists of two components: an approximately rectangular work loop (W) and an approximately triangular region of potential energy (U). In the case of isovolumic contractions, PVA consists entirely of U. The utility of Suga's description of cardiac energetics is the observation that the oxygen consumption of the heart (V̇o2) is linearly dependent on PVA. By using isolated ventricular trabeculae, we found a basis on which to correlate the components of stress-length area (SLA; i.e., the 1-D equivalent of PVA) with specific regions of the stress-time integral (STI; i.e., the area under the force-time profile of a single twitch). In each case, proportionality obtains and is robust, independent of the type of twitch contraction (isometric or isotonic), and insensitive to changes of preload or afterload. We apply our results by examining retrospectively the interpretations reached in three independent studies published in the literature.

Minor preload dependence of O2 consumption of unloaded contraction in dog heart

1989 ◽  
Vol 256 (5) ◽  
pp. H1289-H1294 ◽  
Author(s):  
Y. Yasumura ◽  
T. Nozawa ◽  
S. Futaki ◽  
N. Tanaka ◽  
H. Suga
Keyword(s):  
Mechanical Load ◽  
Mechanical Energy ◽  
Systolic Pressure ◽  
Ventricular Volume ◽  
Dog Heart ◽  
End Diastolic Volume ◽  
Pressure Development ◽  
Total Mechanical Energy ◽  
Whole Heart ◽  
Length Dependent Activation

We studied whether end-diastolic volume (EDV) would affect myocardial oxygen consumption (VO2) of mechanically unloaded contraction in the cross-circulated dog heart, as expected from the concept of the myocardial length-dependent activation. We made preloaded but maximally unloaded contractions from different EDVs by quickly releasing ventricular volume to eliminate systolic pressure development and hence to minimize the VO2 for mechanical load during the contraction. We then studied the relation between VO2 and EDV. The VO2 of the almost unloaded contraction from a relatively large EDV slightly exceeded the VO2 of the isovolumic contraction at V0, where V0 is the volume at which peak isovolumic pressure was zero. However, the excess VO2 could be ascribed to the residual systolic pressure-volume area (PVA) adversely produced from the large EDV, where PVA is a measure of the total mechanical energy generated during contraction. Therefore, we considered that VO2 was practically little dependent on EDV. We interpreted this finding as an indication that an increase, if any, in VO2 due to the length-dependent activation of the excitation-contraction coupling was practically negligible in the whole heart preparation.

Conformal 3D Printing of Sensors

2015 ◽  
Author(s):  
Gaurav Siwach ◽  
Rahul Rai
Keyword(s):  
Mechanical Properties ◽  
Carbon Fiber ◽  
Carbon Fibers ◽  
Mechanical Load ◽  
3D Printer ◽  
Load Testing ◽  
Strain Sensing ◽  
Resistivity Variation ◽  
Acrylate Resin ◽  
Short Carbon

A sensor is unobtrusive if it doesn’t interfere with the design, mechanical properties, and the functionality of the structure it is integrated with. This paper discusses the development of unobtrusive piezo-resistive sensors and their production using additive manufacturing. Short carbon fibers were dispersed in an acrylate resin and subsequently cured with UV DLP 3D printer to be used as a strain-sensing device. Varying the amount of carbon fiber resulted in resistivity variation of the composite. The composite was found to be piezo-resistive, and gauze factor at a concentration of 12% carbon fiber by volume was obtained through mechanical load testing.

scholarly journals Spontaneous calcium oscillations during diastole in the whole heart: the influence of ryanodine reception function and gap junction coupling

2011 ◽  
Vol 300 (5) ◽  
pp. H1822-H1828 ◽  
Author(s):  
Bradley N. Plummer ◽  
Michael J. Cutler ◽  
Xiaoping Wan ◽  
Kenneth R. Laurita
Keyword(s):  
Calcium Release ◽  
Calcium Oscillations ◽  
Cytoplasmic Calcium ◽  
Cell Coupling ◽  
Cellular Mechanisms ◽  
Open Probability ◽  
Temporal Synchronization ◽  
Time To Peak ◽  
Triggered Arrhythmias ◽  
Whole Heart

Triggered arrhythmias due to spontaneous cytoplasmic calcium oscillations occur in a variety of disease conditions; however, their cellular mechanisms in tissue are not clear. We hypothesize that spontaneous calcium oscillations in the whole heart are due to calcium release from the sarcoplasmic reticulum and are facilitated by calcium diffusion through gap junctions. Optical mapping of cytoplasmic calcium from Langendorff perfused guinea pig hearts ( n = 10) was performed using oxygenated Tyrode's solution (in mM): 140 NaCl, 0.7 MgCl, 4.5 KCl, 5.5 dextrose, 5 HEPES, and 5.5 CaCl2 (pH 7.45, 34°C). Rapid pacing was used to induce diastolic calcium oscillations. In all preparations, pacing-induced multicellular diastolic calcium oscillations (m-SCR) occurred across most of the mapping field, at all pacing rates tested. Ryanodine (1 μM) eliminated all m-SCR activity. Low-dose caffeine (1 mM) increased m-SCR amplitude (+10.4 ± 4.4%, P < 0.05) and decreased m-SCR time-to-peak (−17.4 ± 6.7%, P < 0.05) and its temporal synchronization (i.e., range) across the mapping field (−26.9 ± 17.1%, P < 0.05). Surprisingly, carbenoxolone increased the amplitude of m-SCR activity (+14.8 ± 4.1%, P < 0.05) and decreased m-SCR time-to-peak (−11.3 ± 9.6%, P < 0.01) and its synchronization (−37.0 ± 19.1%, P < 0.05), similar to caffeine. In isolated myocytes, carbenoxolone (50 μM) had no effect on the frequency of aftercontractions, suggesting the effect of cell-to-cell uncoupling on m-SCR activity is tissue specific. Therefore, in the whole heart, overt m-SCR activity caused by calcium release from the SR can be induced over a broad range of pacing rates. Enhanced ryanodine receptor open probability and, surprisingly, decreased cell-to-cell coupling increased the amplitude and temporal synchronization of spontaneous calcium release in tissue.

A Facility For Evaluation of Actuators Based on Giant Magnetostrictive Materials

1994 ◽  
Vol 360 ◽  
Author(s):  
H. Tiberg ◽  
G. Engdahl
Keyword(s):  
Mechanical Load ◽  
High Stress ◽  
Measurement Procedure ◽  
Test Rig ◽  
Mechanical Loads ◽  
Magnetostrictive Materials ◽  
Giant Magnetostrictive Materials ◽  
Computer Controlled ◽  
Set Up ◽  
Future Evaluation

AbstractThe recent development of actuators based on giant magnetostrictive materials in for instance hydroacoustic transducers has caused an increase in output forces from the drive elements used. The high stress levels make testing of the actuators with well defined mechanical loads difficult. The need for standards and improved evaluation methods has therefore become evident.Based on experiences from earlier test facilities a new set-up has been designed with the intention to obtain- higher resonance frequency- facilitated assembly of test objects- increased operating forces- flexible choice of mechanical loads- computer controlled measurement procedure- controllable environmental conditions, for instance temperature.In order to achieve the specifications, the test rig involves hydraulics for prestressing and clamping of the test object and the mechanical load. A method of mechanically disconnecting the prestress device from the fixture gives lower mass to stiffness ratio in the fixture and therefore a better high frequency performance.The presented test rig is considered to have the prerequisites of serving as a platform for future evaluation and standardization of actuators.

SPECTRA: A program for processing electron images of crystals

1992 ◽  
Vol 50 (1) ◽  
pp. 132-133
Author(s):  
M.F. Schmid ◽  
R. Dargahi ◽  
M. W. Tam
Keyword(s):  
Lattice Distortion ◽  
Data Transfer ◽  
Reciprocal Lattice ◽  
Data Entry ◽  
Image Data ◽  
Distortion Correction ◽  
Specimen Preparation ◽  
Electron Image ◽  
Computer Controlled ◽  
Program Modules

Electron crystallography is an emerging field for structure determination as evidenced by a number of membrane proteins that have been solved to near-atomic resolution. Advances in specimen preparation and in data acquisition with a 400kV microscope by computer controlled spot scanning mean that our ability to record electron image data will outstrip our capacity to analyze it. The computed fourier transform of these images must be processed in order to provide a direct measurement of amplitudes and phases needed for 3-D reconstruction.In anticipation of this processing bottleneck, we have written a program that incorporates a menu-and mouse-driven procedure for auto-indexing and refining the reciprocal lattice parameters in the computed transform from an image of a crystal. It is linked to subsequent steps of image processing by a system of data bases and spawned child processes; data transfer between different program modules no longer requires manual data entry. The progress of the reciprocal lattice refinement is monitored visually and quantitatively. If desired, the processing is carried through the lattice distortion correction (unbending) steps automatically.

EXELFS Studies of Carbon Fibers

1990 ◽  
Vol 48 (2) ◽  
pp. 72-73
Author(s):  
V. Serin ◽  
K. Hssein ◽  
G. Zanchi ◽  
J. Sévely
Keyword(s):  
Carbon Fibers ◽  
Energy Analysis ◽  
Electron Excitation ◽  
Complex Structures ◽  
High Modulus ◽  
Promising Technique ◽  
X Ray ◽  
Fine Structures ◽  
X Ray Absorption

The present developments of electron energy analysis in the microscopes by E.E.L.S. allow an accurate recording of the spectra and of their different complex structures associated with the inner shell electron excitation by the incident electrons (1). Among these structures, the Extended Energy Loss Fine Structures (EXELFS) are of particular interest. They are equivalent to the well known EXAFS oscillations in X-ray absorption spectroscopy. Due to the EELS characteristic, the Fourier analysis of EXELFS oscillations appears as a promising technique for the characterization of composite materials, the major constituents of which are low Z elements. Using EXELFS, we have developed a microstructural study of carbon fibers. This analysis concerns the carbon K edge, which appears in the spectra at 285 eV. The purpose of the paper is to compare the local short range order, determined by this way in the case of Courtauld HTS and P100 ex-polyacrylonitrile carbon fibers, which are high tensile strength (HTS) and high modulus (HM) fibers respectively.

Applications of CCEM to Environmental Health Problems

1985 ◽  
Vol 43 ◽  
pp. 102-103
Author(s):  
R. J. Lee ◽  
J. S. Walker
Keyword(s):  
Electron Microscopy ◽  
Image Analysis ◽  
Environmental Health ◽  
Computer Control ◽  
External Agent ◽  
External Agents ◽  
Computer Controlled ◽  
Primitive State ◽  
Textural Changes ◽  
General Aspects

Electron microscopy (EM), with the advent of computer control and image analysis techniques, is rapidly evolving from an interpretative science into a quantitative technique. Electron microscopy is potentially of value in two general aspects of environmental health: exposure and diagnosis.In diagnosis, electron microscopy is essentially an extension of optical microscopy. The goal is to characterize cellular changes induced by external agents. The external agent could be any foreign material, chemicals, or even stress. The use of electron microscopy as a diagnostic tool is well- developed, but computer-controlled electron microscopy (CCEM) has had only limited impact, mainly because it is fairly new and many institutions lack the resources to acquire the capability. In addition, major contributions to diagnosis will come from CCEM only when image analysis (IA) and processing algorithms are developed which allow the morphological and textural changes recognized by experienced medical practioners to be quantified. The application of IA techniques to compare cellular structure is still in a primitive state.

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