Controlled Auxotonic Twitch in Papillary Muscle: A New Computer-Based Control Approach

Vidøhus, Vidar; Sys, Stanislas U.; Demolder, M.; Natas, Anders; Angelsen, Bjørn

doi:10.1006/cbmr.2000.1551

Cited by 10 publications

(6 citation statements)

References 32 publications

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“…The end‐systolic and end‐diastolic points at both preloads were fitted using cubic regression (dotted lines). The end‐systolic loci of both isometric contractions and isotonic work‐loop contractions fell on the same line, in agreement with results in isolated papillary muscles (Hisano & Cooper, 1987; Sorhus et al . 2000) and with numerous equivalent demonstrations by Suga and colleagues in isolated whole‐heart preparations (Khalafbeigui et al .…”

Section: Resultssupporting

confidence: 90%

Interventricular comparison of the energetics of contraction of trabeculae carneae isolated from the rat heart

Han

Taberner

Nielsen

et al. 2013

The Journal of Physiology

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Key points• With each beat of the heart, the left and right ventricles must overcome substantially different arterial pressures in order to eject blood.• We have tested whether this difference in mechanical demand is reflected in different metabolic energy expenditure.• Our experimental preparations were trabeculae isolated from both ventricles; our index of metabolic energy expenditure was their heat production in response to electrical stimulation.• We found that the cost of activating contraction (i.e. the production of heat in the absence of force generation) was higher in trabeculae from the left ventricle, thereby conferring a lower mechanical efficiency on that ventricle.• Correction for the activation heat reveals the thermodynamic efficiency of the actomyosin crossbridges; whereas there was no interventricular difference in this fundamental property of cardiac muscle, its dependence on force development is baffling.Abstract We compare the energetics of right ventricular and left ventricular trabeculae carneae isolated from rat hearts. Using our work-loop calorimeter, we subjected trabeculae to stress-length work (W ), designed to mimic the pressure-volume work of the heart. Simultaneous measurement of heat production (Q) allowed calculation of the accompanying change of enthalpy ( H = W + Q). From the mechanical measurements (i.e. stress and change of length), we calculated work, shortening velocity and power. In combination with heat measurements, we calculated activation heat (Q A ), crossbridge heat (Q xb ) and two measures of cardiac efficiency: 'mechanical efficiency' (ε mech = W / H) and 'crossbridge efficiency' (ε xb = W /( H -Q A )). With respect to their left ventricular counterparts, right venticular trabeculae have higher peak shortening velocity, and higher peak mechanical efficiency, but with no difference of stress development, twitch duration, work performance, shortening power or crossbridge efficiency. That is, the 35% greater maximum mechanical efficiency of right venticular than left ventricular trabeculae (13.6 vs. 10.2%) is offset by the greater metabolic cost of activation (Q A ) in the latter. When corrected for this difference, crossbridge efficiency does not differ between the ventricles.

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Section: Resultssupporting

confidence: 90%

Interventricular comparison of the energetics of contraction of trabeculae carneae isolated from the rat heart

Han

Taberner

Nielsen

et al. 2013

The Journal of Physiology

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“…sarcomere lengths while the work-loop ESFLR was derived from afterloaded shortening contractions, all of which commenced at the same initial length (L o ). These simulation results compare well with the experimental data from rat trabeculae (Tran et al, 2016) in Figure 3B and are consistent with other previous studies on rat cardiac myocytes (Iribe et al, 2014), rat trabeculae (Han et al, 2014a,b), rabbit papillary (Sørhus et al, 2000), ferret papillary (Hisano and CooperIV, 1987), and rat papillary (Gülch, 1986), the simulated work-loop ESFLR lies to the right of its isometric counterpart. In Figure 3A, the afterloads for the simulated work-loop contractions (black circles) correspond to isometric contractions of equivalent peak force (gray circles).…”

Section: Simulating Isometric and Work-loop Esflrs Using Dynamic Ca 2+supporting

confidence: 91%

“…The contraction-mode dependence of the cardiac ESFLR has been observed to be independent of experimental temperature (Gülch, 1986;Hisano and CooperIV, 1987;Sørhus et al, 2000;Han et al, 2014a,b;Tran et al, 2016), providing confidence in the predictions of our model, which was parameterized using data at room temperature. Experimental reports from cat papillary (Downing and Sonnenblick, 1964) and frog myocytes (Parikh et al, 1993) at room temperature, which purported to show contraction-mode independence of the ESFLR, was recently refuted in a re-examination of the data using a novel end-systolic zone framework (Han et al, 2019).…”

Section: Model Limitationssupporting

confidence: 65%

“…Contraction-mode independence of the ESPVR is likely an artifact arising from performance of work-loop contractions at low diastolic left ventricular volumes (Han et al, 2019). These findings stand in contrast to those from the hearts of other smaller mammalian species (ferret, rabbit, and rat) (Hisano and CooperIV, 1987;Sørhus et al, 2000;Han et al, 2014a,b;Tran et al, 2016), all of which show contraction-mode dependence.…”

Section: Comparison To Previous Computational Modeling Studiesmentioning

confidence: 84%

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Insights From Computational Modeling Into the Contribution of Mechano-Calcium Feedback on the Cardiac End-Systolic Force-Length Relationship

et al. 2020

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“…4 -6. The principal advantage of the highly reconfigurable hardware and software force-length control system is that we can, with great precision, subject trabeculae to various contraction protocols: fixed-end, isometric, auxotonic (23) or isotonic afterloaded, at any desired preload or afterload. Moreover, the advance of using laser-interferometry for the measurement of displacement and force allows the use of a robust, reliable, and nonthermogenic stainless steel force transducer, placed in close proximity to our heat sensor.…”

Section: Discussionmentioning

confidence: 99%

An innovative work-loop calorimeter for in vitro measurement of the mechanics and energetics of working cardiac trabeculae

Taberner

Han

Loiselle

et al. 2011

Journal of Applied Physiology

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Taberner AJ, Han J-C, Loiselle DS, Nielsen PM. An innovative work-loop calorimeter for in vitro measurement of the mechanics and energetics of working cardiac trabeculae. J Appl Physiol 111: 1798 -1803. First published September 8, 2011 doi:10.1152/japplphysiol.00752.2011.-We describe a unique work-loop calorimeter with which we can measure, simultaneously, the rate of heat production and force-length work output of isolated cardiac trabeculae. The mechanics of the force-length work-loop contraction mimic those of the pressure-volume work-loops experienced by the heart. Within the measurement chamber of a flowthrough microcalorimeter, a trabecula is electrically stimulated to respond, under software control, in one of three modes: fixed-end, isometric, or isotonic. In each mode, software controls the position of a linear motor, with feedback from muscle force, to adjust muscle length in the desired temporal sequence. In the case of a work-loop contraction, the software achieves seamless transitions between phases of length control (isometric contraction, isometric relaxation, and restoration of resting muscle length) and force control (isotonic shortening). The area enclosed by the resulting force-length loop represents the work done by the trabecula. The change of enthalpy expended by the muscle is given by the sum of the work term and the associated amount of evolved heat. With these simultaneous measurements, we provide the first estimation of suprabasal, net mechanical efficiency (ratio of work to change of enthalpy) of mammalian cardiac trabeculae. The maximum efficiency is at the vicinity of 12%.work; heat; enthalpy; efficiency; microcalorimeter THE ADVANTAGE OF USING ISOLATED tissue preparations for the study of cardiac energetics arises from the ease of administration of ionic or pharmacological interventions. The disadvantage of their use is that it is difficult to achieve realistic approximations of the mechanics of the intact heart. In situ, the heart repetitively undergoes a pressure-volume-time trajectory consisting of sequential periods of isovolumic contraction, emptying, isovolumic relaxation, and passive refilling. Commonly, experiments consist entirely of unloaded, isometric or, more usually, fixed-end contractions. Such artificial mechanical events are rarely, if ever, encountered by the heart. To enhance our understanding of cardiac energetics, it is thus desirable to adopt contraction protocols that more closely resemble the repetitive pressure-volume-time behavior of the heart. Such approximations have been achieved previously using multicellular, isolated, cardiac preparations. Gibbs and colleagues (6, 22) routinely measured the heat and work output of papillary muscles undergoing afterloaded isotonic contractions, thereby generating characteristic enthalpy-load relations and allowing derivation of the load-dependence of mechanical efficiency. Peterson et al. (21) were the first to apply a computer-based "adaptive" approach to the control of muscle segment length to generate isotonic con...

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Controlled Auxotonic Twitch in Papillary Muscle: A New Computer-Based Control Approach

Cited by 10 publications

References 32 publications

Interventricular comparison of the energetics of contraction of trabeculae carneae isolated from the rat heart

Interventricular comparison of the energetics of contraction of trabeculae carneae isolated from the rat heart

Insights From Computational Modeling Into the Contribution of Mechano-Calcium Feedback on the Cardiac End-Systolic Force-Length Relationship

An innovative work-loop calorimeter for in vitro measurement of the mechanics and energetics of working cardiac trabeculae

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