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Shelley SP, James RS, Tallis J. The effects of muscle starting length on work loop power output of isolated mouse soleus and extensor digitorum longus muscle. J Exp Biol 2024; 227:jeb247158. [PMID: 38584504 DOI: 10.1242/jeb.247158] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2023] [Accepted: 03/27/2024] [Indexed: 04/09/2024]
Abstract
Force-length relationships derived from isometric activations may not directly apply to muscle force production during dynamic contractions. As such, different muscle starting lengths between isometric and dynamic conditions could be required to achieve maximal force and power. Therefore, this study examined the effects of starting length [±5-10% of length corresponding to maximal twitch force (L0)] on work loop (WL) power output (PO), across a range of cycle frequencies, of the soleus (SOL) and extensor digitorum longus muscle (EDL; N=8-10) isolated from ∼8 week old C57 mice. Furthermore, passive work was examined at a fixed cycle frequency to determine the association of passive work and active net work. Starting length affected maximal WL PO of the SOL and EDL across evaluated cycle frequencies (P<0.030, ηp2>0.494). For the SOL, PO produced at -5% L0 was greater than that at most starting lengths (P<0.015, Cohen's d>0.6), except -10% L0 (P=0.135, d<0.4). However, PO produced at -10% L0 versus L0 did not differ (P=0.138, d=0.35-0.49), indicating -5% L0 is optimal for maximal SOL WL PO. For the EDL, WL PO produced at -10% L0 was lower than that at most starting lengths (P<0.032, d>1.08), except versus -5% L0 (P=0.124, d<0.97). PO produced at other starting lengths did not differ (P>0.163, d<1.04). For the SOL, higher passive work was associated with reduced PO (Spearman's r=0.709, P<0.001), but no relationship was observed between passive work and PO of the EDL (Pearson's r=0.191, r2=0.04, P=0.184). This study suggests that starting length should be optimised for both static and dynamic contractions and confirms that the force-length curve during dynamic contractions is muscle specific.
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Affiliation(s)
- Sharn P Shelley
- Research Centre for Physical Activity, Sport and Exercise Science, Coventry University, Coventry, CV1 5FB, UK
| | - Rob S James
- Faculty of Life Sciences, University of Bradford, Bradford, BD7 1DP, UK
| | - Jason Tallis
- Research Centre for Physical Activity, Sport and Exercise Science, Coventry University, Coventry, CV1 5FB, UK
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Tran P, Linekar A, Dandekar U, Barker T, Balasubramanian S, Bhaskara-Pillai J, Shelley S, Maddock H, Banerjee P. Profiling the Biomechanical Responses to Workload on the Human Myocyte to Explore the Concept of Myocardial Fatigue and Reversibility: Rationale and Design of the POWER Heart Failure Study. J Cardiovasc Transl Res 2024; 17:275-286. [PMID: 37126208 PMCID: PMC10150683 DOI: 10.1007/s12265-023-10391-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/24/2022] [Accepted: 04/20/2023] [Indexed: 05/02/2023]
Abstract
It remains unclear why some patients develop heart failure without evidence of structural damage. One theory relates to impaired myocardial energetics and ventricular-arterial decoupling as the heart works against adverse mechanical load. In this original study, we propose the novel concept of myocardial fatigue to capture this phenomenon and aim to investigate this using human cardiomyocytes subjected to a modern work-loop contractility model that closely mimics in vivo cardiac cycles. This proof-of-concept study (NCT04899635) will use human myocardial tissue samples from patients undergoing cardiac surgery to develop a reproducible protocol to isolate robust calcium-tolerant cardiomyocytes. Thereafter, work-loop contractility experiments will be performed over a range of preload, afterload and cycle frequency as a function of time to elicit any reversible reduction in contractile performance (i.e. fatigue). This will provide novel insight into mechanisms behind heart failure and myocardial recovery and serve as a valuable research platform in translational cardiovascular research.
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Affiliation(s)
- Patrick Tran
- Centre for Sport, Exercise & Life Sciences, Faculty of Health & Life Sciences, Coventry University, Coventry, UK.
- Cardiology Department, University Hospitals Coventry and Warwickshire NHS Trust, Clifford Bridge Road, Coventry, UK.
| | - Adam Linekar
- Centre for Sport, Exercise & Life Sciences, Faculty of Health & Life Sciences, Coventry University, Coventry, UK
- InoCardia Ltd, TechnoCentre, Puma Way, Coventry, UK
| | - Uday Dandekar
- Cardiology Department, University Hospitals Coventry and Warwickshire NHS Trust, Clifford Bridge Road, Coventry, UK
- Warwick Medical School, University of Warwick, Coventry, UK
| | - Thomas Barker
- Centre for Sport, Exercise & Life Sciences, Faculty of Health & Life Sciences, Coventry University, Coventry, UK
- Cardiology Department, University Hospitals Coventry and Warwickshire NHS Trust, Clifford Bridge Road, Coventry, UK
- Warwick Medical School, University of Warwick, Coventry, UK
| | - Sendhil Balasubramanian
- Cardiology Department, University Hospitals Coventry and Warwickshire NHS Trust, Clifford Bridge Road, Coventry, UK
- Warwick Medical School, University of Warwick, Coventry, UK
| | - Jain Bhaskara-Pillai
- Cardiology Department, University Hospitals Coventry and Warwickshire NHS Trust, Clifford Bridge Road, Coventry, UK
- Warwick Medical School, University of Warwick, Coventry, UK
| | - Sharn Shelley
- Centre for Sport, Exercise & Life Sciences, Faculty of Health & Life Sciences, Coventry University, Coventry, UK
- InoCardia Ltd, TechnoCentre, Puma Way, Coventry, UK
| | - Helen Maddock
- Centre for Sport, Exercise & Life Sciences, Faculty of Health & Life Sciences, Coventry University, Coventry, UK
- InoCardia Ltd, TechnoCentre, Puma Way, Coventry, UK
| | - Prithwish Banerjee
- Centre for Sport, Exercise & Life Sciences, Faculty of Health & Life Sciences, Coventry University, Coventry, UK
- Cardiology Department, University Hospitals Coventry and Warwickshire NHS Trust, Clifford Bridge Road, Coventry, UK
- Warwick Medical School, University of Warwick, Coventry, UK
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Garrett AS, Dowrick J, Taberner AJ, Han JC. Isolated cardiac muscle contracting against a real-time model of systemic and pulmonary cardiovascular loads. Am J Physiol Heart Circ Physiol 2023; 325:H1223-H1234. [PMID: 37712924 PMCID: PMC10907072 DOI: 10.1152/ajpheart.00272.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/10/2023] [Revised: 09/01/2023] [Accepted: 09/08/2023] [Indexed: 09/16/2023]
Abstract
Isolated cardiac tissues allow a direct assessment of cardiac muscle function and enable precise control of experimental loading conditions. However, current experimental methods do not expose isolated tissues to the same contraction pattern and cardiovascular loads naturally experienced by the heart. In this study, we implement a computational model of systemic-pulmonary impedance that is solved in real time and imposed on contracting isolated rat muscle tissues. This systemic-pulmonary model represents the cardiovascular system as a lumped-parameter, closed-loop circuit. The tissues performed force-length work-loop contractions where the model output informed both the shortening and restretch phases of each work-loop. We compared the muscle mechanics and energetics associated with work-loops driven by the systemic-pulmonary model with that of a model-based loading method that only accounts for shortening. We obtained results that show simultaneous changes of afterload and preload or end-diastolic length of the muscle, as compared with the static, user-defined preload as in the conventional loading method. This feature allows assessment of muscle work output, heat output, and efficiency of contraction as functions of end-diastolic length. The results reveal the behavior of cardiac muscle as a pump source to achieve load-dependent work and efficiency outputs over a wider range of loads. This study offers potential applications of the model to investigate cardiac muscle response to hemodynamic coupling between systemic and pulmonary circulations in an in vitro setting.NEW & NOTEWORTHY We present the use of a "closed-loop" model of systemic and pulmonary circulations to apply, for the first time, real-time model-calculated preload and afterload to isolated cardiac muscle preparations. This method extends current experimental protocols where only afterload has been considered. The extension to include preload provides the opportunity to investigate ventricular muscle response to hemodynamic coupling and as a pump source across a wider range of cardiovascular loads.
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Affiliation(s)
- Amy S Garrett
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
| | - Jarrah Dowrick
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
| | - Andrew J Taberner
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
- Department of Engineering Science and Biomedical Engineering, The University of Auckland, Auckland, New Zealand
| | - June-Chiew Han
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
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Safety pharmacology during the COVID pandemic. J Pharmacol Toxicol Methods 2021; 111:107089. [PMID: 34182120 PMCID: PMC8233455 DOI: 10.1016/j.vascn.2021.107089] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Accepted: 06/18/2021] [Indexed: 11/22/2022]
Abstract
This editorial summarizes the content of the current themed issue of J Pharmacol Toxicol Methods derived from the 2020 Annual Safety Pharmacology Society (SPS) meeting that was held virtually September 14–17, 2020 due to the ongoing COVID-19 global pandemic. A selection of articles arising from the virtual meeting is summarized. Like previous years they continue to reflect current areas of innovation in SP including new methodologies to predict human safety, best practices for IKr current measurement, and best practice considerations for the conduct of in vivo nonclinical QT studies. The meeting included scientific content from 94 abstracts (reproduced in the current volume of J Pharmacol Toxicol Methods). This continued innovation reflects a rubric in SP that identifies problems, seeks solutions and, importantly, validates the solutions.
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Yang PC, Giles WR, Belardinelli L, Clancy CE. Mechanisms of flecainide induced negative inotropy: An in silico study. J Mol Cell Cardiol 2021; 158:26-37. [PMID: 34004185 PMCID: PMC8772296 DOI: 10.1016/j.yjmcc.2021.05.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/17/2021] [Revised: 05/11/2021] [Accepted: 05/12/2021] [Indexed: 11/27/2022]
Abstract
It is imperative to develop better approaches to predict how antiarrhythmic drugs with multiple interactions and targets may alter the overall electrical and/or mechanical function of the heart. Safety Pharmacology studies have provided new insights into the multi-target effects of many different classes of drugs and have been aided by the addition of robust new in vitro and in silico technology. The primary focus of Safety Pharmacology studies has been to determine the risk profile of drugs and drug candidates by assessing their effects on repolarization of the cardiac action potential. However, for decades experimental and clinical studies have described substantial and potentially detrimental effects of Na+ channel blockers in addition to their well-known conduction slowing effects. One such side effect, associated with administration of some Na+ channel blocking drugs is negative inotropy. This reduces the pumping function of the heart, thereby resulting in hypotension. Flecainide is a well-known example of a Na+ channel blocking drug, that exhibits strong rate-dependent block of INa and may cause negative cardiac inotropy. While the phenomenon of Na+ channel suppression and resulting negative inotropy is well described, the mechanism(s) underlying this effect are not. Here, we set out to use a modeling and simulation approach to reveal plausible mechanisms that could explain the negative inotropic effect of flecainide. We utilized the Grandi-Bers model [1] of the cardiac ventricular myocyte because of its robust descriptions of ion homeostasis in order to characterize and resolve the relative effects of QRS widening, flecainide off-target effects and changes in intracellular Ca2+ and Na+ homeostasis. The results of our investigations and predictions reconcile multiple data sets and illustrate how multiple mechanisms may play a contributing role in the flecainide induced negative cardiac inotropic effect.
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Affiliation(s)
- Pei-Chi Yang
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, United States of America
| | - Wayne R Giles
- Department of Physiology & Pharmacology, University of Calgary, Canada
| | | | - Colleen E Clancy
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, United States of America.
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