Time-resolved equatorial X-ray diffraction studies of skinned muscle fibres during stretch and release 1 1Edited by J. Karn

Hoskins, B.; Ashley, C. C.; Pelc, Radek; Rapp, Gert; Griffiths, Peter

doi:10.1006/jmbi.1999.2857

Cited by 10 publications

(22 citation statements)

References 51 publications

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“…There is evidence that the contractile process itself can generate lateral forces (16). There also is evidence that the extracellular collagen network in the myocardium may contribute to cross-fiber stresses by tethering adjacent myocytes; Lamberts et al (20) demonstrated these tethers to be important components in both diastolic and systolic function of the myocardium.…”

Section: Discussionmentioning

confidence: 99%

MRI-based finite-element analysis of left ventricular aneurysm

Walker

Ratcliffe²,

Zhang³

et al. 2005

American Journal of Physiology-Heart and Circulatory Physiology

191

190

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Tagged MRI and finite-element (FE) analysis are valuable tools in analyzing cardiac mechanics. To determine systolic material parameters in three-dimensional stress-strain relationships, we used tagged MRI to validate FE models of left ventricular (LV) aneurysm. Five sheep underwent anteroapical myocardial infarction (25% of LV mass) and 22 wk later underwent tagged MRI. Asymmetric FE models of the LV were formed to in vivo geometry from MRI and included aneurysm material properties measured with biaxial stretching, LV pressure measurements, and myofiber helix angles measured with diffusion tensor MRI. Systolic material parameters were determined that enabled FE models to reproduce midwall, systolic myocardial strains from tagged MRI (630 +/- 187 strain comparisons/animal). When contractile stress equal to 40% of the myofiber stress was added transverse to the muscle fiber, myocardial strain agreement improved by 27% between FE model predictions and experimental measurements (RMS error decreased from 0.074 +/- 0.016 to 0.054 +/- 0.011, P < 0.05). In infarct border zone (BZ), end-systolic midwall stress was elevated in both fiber (24.2 +/- 2.7 to 29.9 +/- 2.4 kPa, P < 0.01) and cross-fiber (5.5 +/- 0.7 to 11.7 +/- 1.3 kPa, P = 0.02) directions relative to noninfarct regions. Contrary to previous hypotheses but consistent with biaxial stretching experiments, active cross-fiber stress development is an integral part of LV systole; FE analysis with only uniaxial contracting stress is insufficient. Stress calculations from these validated models show 24% increase in fiber stress and 115% increase in cross-fiber stress at the BZ relative to remote regions, which may contribute to LV remodeling.

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Section: Discussionmentioning

confidence: 99%

MRI-based finite-element analysis of left ventricular aneurysm

Walker

Ratcliffe²,

Zhang³

et al. 2005

American Journal of Physiology-Heart and Circulatory Physiology

191

190

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“…It has been suggested that the intensity ratio, I 1,1 /I 1,0 , provides an estimate of the fraction of myosin heads bound to actin during muscle contraction (31,32). Evaluation of the fraction of actin-bound myosin heads based on this ratio is still used (33). However the equatorial intensities depend not only on the number of myosin heads bound to actin, but also on several other parameters.…”

Section: Equatorial Reflectionsmentioning

confidence: 99%

Insight into the actin-myosin motor from x-ray diffraction on muscle

Bershitsky

Ferenczi²,

Koubassova³

et al. 2009

Front Biosci

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The origin of reflections in the x-ray diffraction pattern from striated muscle and their use for understanding the structural organization of the contractile machinery are presented and discussed. Results of x-ray diffraction experiments obtained by a number of research groups using a variety of protocols revealed structural changes in contracting muscles which are interpreted in terms of molecular movements that underlie force generation. Some of these data are in line with the widely accepted 'lever arm' hypothesis which links force generation to a tilt of the light chain domain of the myosin head with respect to its motor domain. However, changes in the layer line intensities observed in response to various perturbations cannot be explained by tilting of the lever arm. Such changes, first revealed in response to temperature jumps, are interpreted as a transition of non-stereo-specifically attached myosin heads to a stereo-specifically bound state. The new 'roll and lock' model considers force-generation as a two-stage process: initial stereo-specific locking of myosin heads on actin is followed by the lever arm tilt.

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“…Previous experience has shown this to be sufficient time to permeabilize fully the fibres whilst maintaining good structural integrity as evidenced by the X-ray diffraction pattern [18,19]. The fibre was then suspended in a chamber containing approximately 70 µl of relaxing solution held in by capillary action.…”

Section: Experimental Protocolmentioning

confidence: 99%

“…Sarcomere length was set at 2.2 µm. In some experiments the fibres were attached to the hooks by cyanoacrylate glue (see [18,30]). …”

Section: Animalsmentioning

confidence: 99%

The effects of the inotropic agent EMD 57033 on activation and relaxation kinetics in frog skinned skeletal muscle

Lipscomb-Allhouse

Mulligan

Ashley

2001

Pfl�gers Archiv European Journal of Physiology

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The effect of the cardiotonic sensitizing drug EMD 57033 was studied in frog skinned skeletal muscle fibres at 12 degrees C to provide a baseline for skeletal muscle studies and for comparison with cardiac fibres. The activation and relaxation of fibres were induced by laser flash photolysis of the caged calcium NP-EGTA, and caged calcium chelator diazo-2 respectively. EMD 57033 (10 microM) slightly increased the rate of relaxation (rate constant k1 changing from 24.0 +/- 2.9 s-1 in control to 28.1 +/- 3.2 s-1) but had no significant effect on the rate of activation (k1 = 9.6 +/- 0.9 s-1 in control conditions, 9.7 +/- 1.6 s-1 with EMD 57033). The effect of the optical isomer of EMD 57033, EMD 57439, was examined on steady-state force and relaxation rate. EMD57439 (10 microM) slowed the rate of relaxation (k1 = 20.5 +/- 2.4 s-1) but had no effect on the maximal calcium-activated force whereas EMD 57033 increased it by 16.5 +/- 5.7%. These results are compared to earlier results from this laboratory in guinea-pig skinned trabeculae, and a possible model for the action of EMD 57033 whereby the drug enhances force per cross-bridge is discussed.

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Time-resolved equatorial X-ray diffraction studies of skinned muscle fibres during stretch and release 1 1Edited by J. Karn

Cited by 10 publications

References 51 publications

MRI-based finite-element analysis of left ventricular aneurysm

MRI-based finite-element analysis of left ventricular aneurysm

Insight into the actin-myosin motor from x-ray diffraction on muscle

The effects of the inotropic agent EMD 57033 on activation and relaxation kinetics in frog skinned skeletal muscle

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