scholarly journals Optical mapping of the electrical activity of isolated adult zebrafish hearts: acute effects of temperature

2014 ◽  
Vol 306 (11) ◽  
pp. R823-R836 ◽  
Author(s):  
Eric Lin ◽  
Amanda Ribeiro ◽  
Weiguang Ding ◽  
Leif Hove-Madsen ◽  
Marinko V. Sarunic ◽  
...  
Keyword(s):  
Action Potential ◽  
Electrical Activity ◽  
Cardiac Electrophysiology ◽  
Optical Mapping ◽  
Cooling System ◽  
Effect Of Temperature ◽  
Adult Zebrafish ◽  
Depth Analysis ◽  
Zebrafish Heart ◽  
Av Delay

The zebrafish ( Danio rerio) has emerged as an important model for developmental cardiovascular (CV) biology; however, little is known about the cardiac function of the adult zebrafish enabling it to be used as a model of teleost CV biology. Here, we describe electrophysiological parameters, such as heart rate (HR), action potential duration (APD), and atrioventricular (AV) delay, in the zebrafish heart over a range of physiological temperatures (18–28°C). Hearts were isolated and incubated in a potentiometric dye, RH-237, enabling electrical activity assessment in several distinct regions of the heart simultaneously. Integration of a rapid thermoelectric cooling system facilitated the investigation of acute changes in temperature on critical electrophysiological parameters in the zebrafish heart. While intrinsic HR varied considerably between fish, the ex vivo preparation exhibited impressively stable HRs and sinus rhythm for more than 5 h, with a mean HR of 158 ± 9 bpm (means ± SE; n = 20) at 28°C. Atrial and ventricular APDs at 50% repolarization (APD50) were 33 ± 1 ms and 98 ± 2 ms, respectively. Excitation originated in the atrium, and there was an AV delay of 61 ± 3 ms prior to activation of the ventricle at 28°C. APD and AV delay varied between hearts beating at unique HRs; however, APD and AV delay did not appear to be statistically dependent on intrinsic basal HR, likely due to the innate beat-to-beat variability within each heart. As hearts were cooled to 18°C (by 1°C increments), HR decreased by ∼40%, and atrial and ventricular APD50 increased by a factor of ∼3 and 2, respectively. The increase in APD with cooling was disproportionate at different levels of repolarization, indicating unique temperature sensitivities for ion currents at different phases of the action potential. The effect of temperature was more apparent at lower levels of repolarization and, as a whole, the atrial APD was the cardiac parameter most affected by acute temperature change. In conclusion, this study describes a preparation enabling the in-depth analysis of transmembrane potential dynamics in whole zebrafish hearts. Because the zebrafish offers some critical advantages over the murine model for cardiac electrophysiology, optical mapping studies utilizing zebrafish offer insightful information into the understanding and treatment of human cardiac arrhythmias, as well as serving as a model for other teleosts.

scholarly journals Stop the beat to see the rhythm: excitation-contraction uncoupling in cardiac research

2021 ◽  
Author(s):  
Luther M. Swift ◽  
Matthew W. Kay ◽  
Crystal M. Ripplinger ◽  
Nikki Gillum Posnack
Keyword(s):  
Electrical Activity ◽  
Cardiac Electrophysiology ◽  
Cardiac Tissue ◽  
Optical Mapping ◽  
Myocardial Contraction ◽  
Motion Artifacts ◽  
Secondary Effects ◽  
Metabolic Demand ◽  
Cardiovascular Research ◽  
Fluorescent Indicators

Optical mapping is an imaging technique that is extensively used in cardiovascular research, wherein parameter-sensitive fluorescent indicators are used to study the electrophysiology and excitation-contraction coupling of cardiac tissues. Despite the many benefits of optical mapping, eliminating motion artifacts within the optical signals is a major challenge, as myocardial contraction interferes with the faithful acquisition of action potentials and intracellular calcium transients. As such, excitation-contraction uncoupling agents are frequently used to reduce signal distortion by suppressing contraction. Compared to other uncoupling agents, blebbistatin is the most frequently used as it offers increased potency with minimal direct effects on cardiac electrophysiology. Nevertheless, blebbistatin may exert secondary effects on electrical activity, metabolism, and coronary flow, and the incorrect administration of blebbistatin to cardiac tissue can prove detrimental, resulting in erroneous interpretation of optical mapping results. In this "Getting It Right" perspective, we briefly review the literature regarding the use of blebbistatin in cardiac optical mapping experiments, highlight potential secondary effects of blebbistatin on cardiac electrical activity and metabolic demand, and conclude with the consensus of the authors on best practices for effectively using blebbistatin in optical mapping studies of cardiac tissue.

scholarly journals Processing and analysis of cardiac optical mapping data obtained with potentiometric dyes

2012 ◽  
Vol 303 (7) ◽  
pp. H753-H765 ◽  
Author(s):  
Jacob I. Laughner ◽  
Fu Siong Ng ◽  
Matthew S. Sulkin ◽  
R. Martin Arthur ◽  
Igor R. Efimov
Keyword(s):  
Action Potential ◽  
Optical Imaging ◽  
Cardiac Electrophysiology ◽  
Optical Mapping ◽  
Dominant Frequency ◽  
Imaging Data ◽  
Mapping Data ◽  
Baseline Drift ◽  
Cardiac Fibrillation ◽  
Mapping Techniques

Optical mapping has become an increasingly important tool to study cardiac electrophysiology in the past 20 years. Multiple methods are used to process and analyze cardiac optical mapping data, and no consensus currently exists regarding the optimum methods. The specific methods chosen to process optical mapping data are important because inappropriate data processing can affect the content of the data and thus alter the conclusions of the studies. Details of the different steps in processing optical imaging data, including image segmentation, spatial filtering, temporal filtering, and baseline drift removal, are provided in this review. We also provide descriptions of the common analyses performed on data obtained from cardiac optical imaging, including activation mapping, action potential duration mapping, repolarization mapping, conduction velocity measurements, and optical action potential upstroke analysis. Optical mapping is often used to study complex arrhythmias, and we also discuss dominant frequency analysis and phase mapping techniques used for the analysis of cardiac fibrillation.

scholarly journals Adult zebrafish ventricular electrical gradients as tissue mechanisms of ECG patterns under baseline vs. oxidative stress

2020 ◽  
Author(s):  
Yali Zhao ◽  
Nicholas A James ◽  
Ashraf R Beshay ◽  
Eileen E Chang ◽  
Andrew Lin ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Cardiac Electrophysiology ◽  
Ex Vivo ◽  
Mechanical Efficiency ◽  
Adult Zebrafish ◽  
Qrs Complex ◽  
Electrical Stability ◽  
T Wave ◽  
Zebrafish Heart

Abstract Aims In mammalian ventricles, electrical gradients establish electrical heterogeneities as essential tissue mechanisms to optimize mechanical efficiency and safeguard electrical stability. Electrical gradients shape mammalian electrocardiographic patterns; disturbance of electrical gradients is proarrhythmic. The zebrafish heart is a popular surrogate model for human cardiac electrophysiology thanks to its remarkable recapitulation of human electrocardiogram and ventricular action potential features. Yet, zebrafish ventricular electrical gradients are largely unexplored. The goal of this study is to define the zebrafish ventricular electrical gradients that shape the QRS complex and T wave patterns at baseline and under oxidative stress. Methods and results We performed in vivo electrocardiography and ex vivo voltage-sensitive fluorescent epicardial and transmural optical mapping of adult zebrafish hearts at baseline and during acute H2O2 exposure. At baseline, apicobasal activation and basoapical repolarization gradients accounted for the polarity concordance between the QRS complex and T wave. During H2O2 exposure, differential regional impairment of activation and repolarization at the apex and base disrupted prior to baseline electrical gradients, resulting in either reversal or loss of polarity concordance between the QRS complex and T wave. KN-93, a specific calcium/calmodulin-dependent protein kinase II inhibitor (CaMKII), protected zebrafish hearts from H2O2 disruption of electrical gradients. The protection was complete if administered prior to oxidative stress exposure. Conclusions Despite remarkable apparent similarities, zebrafish and human ventricular electrocardiographic patterns are mirror images supported by opposite electrical gradients. Like mammalian ventricles, zebrafish ventricles are also susceptible to H2O2 proarrhythmic perturbation via CaMKII activation. Our findings suggest that the adult zebrafish heart may constitute a clinically relevant model to investigate ventricular arrhythmias induced by oxidative stress. However, the fundamental ventricular activation and repolarization differences between the two species that we demonstrated in this study highlight the potential limitations when extrapolating results from zebrafish experiments to human cardiac electrophysiology, arrhythmias, and drug toxicities.

scholarly journals Construction and use of a zebrafish heart voltage and calcium optical mapping system, with integrated electrocardiogram and programmable electrical stimulation

2015 ◽  
Vol 308 (9) ◽  
pp. R755-R768 ◽  
Author(s):  
Eric Lin ◽  
Calvin Craig ◽  
Marcel Lamothe ◽  
Marinko V. Sarunic ◽  
Mirza Faisal Beg ◽  
...  
Keyword(s):  
Action Potential ◽  
Action Potential Duration ◽  
Large Scale ◽  
Optical Mapping ◽  
Rate Dependence ◽  
P Wave ◽  
Calcium Dynamics ◽  
Mapping System ◽  
Electrical Stimulator ◽  
Zebrafish Heart

Zebrafish are increasingly being used as a model of vertebrate cardiology due to mammalian-like cardiac properties in many respects. The size and fecundity of zebrafish make them suitable for large-scale genetic and pharmacological screening. In larger mammalian hearts, optical mapping is often used to investigate the interplay between voltage and calcium dynamics and to investigate their respective roles in arrhythmogenesis. This report outlines the construction of an optical mapping system for use with zebrafish hearts, using the voltage-sensitive dye RH 237 and the calcium indicator dye Rhod-2 using two industrial-level CCD cameras. With the use of economical cameras and a common 532-nm diode laser for excitation, the rate dependence of voltage and calcium dynamics within the atrial and ventricular compartments can be simultaneously determined. At 140 beats/min, the atrial action potential duration was 36 ms and the transient duration was 53 ms. With the use of a programmable electrical stimulator, a shallow rate dependence of 3 and 4 ms per 100 beats/min was observed, respectively. In the ventricle the action potential duration was 109 ms and the transient duration was 124 ms, with a steeper rate dependence of 12 and 16 ms per 100 beats/min. Synchronous electrocardiograms and optical mapping recordings were recorded, in which the P-wave aligns with the atrial voltage peak and R-wave aligns with the ventricular peak. A simple optical pathway and imaging chamber are detailed along with schematics for the in-house construction of the electrocardiogram amplifier and electrical stimulator. Laboratory procedures necessary for zebrafish heart isolation, cannulation, and loading are also presented.

scholarly journals Machine-readable Yin–Yang imbalance: traditional Chinese medicine syndrome computer modeling based on three-dimensional noninvasive cardiac electrophysiology imaging

2019 ◽  
Vol 47 (4) ◽  
pp. 1580-1591 ◽  
Author(s):  
Wei Cen ◽  
Ralph Hoppe ◽  
Aiwu Sun ◽  
Hongyan Ding ◽  
Ning Gu
Keyword(s):  
Chinese Medicine ◽  
Traditional Chinese Medicine ◽  
Electrical Activity ◽  
Computer Modeling ◽  
Cardiac Electrophysiology ◽  
Three Dimensional ◽  
Mathematical Physics ◽  
Syndrome Differentiation ◽  
Physics Model ◽  
Machine Readable

Objectives The principal diagnostic methods of traditional Chinese medicine (TCM) are inspection, auscultation and olfaction, inquiry, and pulse-taking. Treatment by syndrome differentiation is likely to be subjective. This study was designed to provide a basic theory for TCM diagnosis and establish an objective means of evaluating the correctness of syndrome differentiation. Methods We herein provide the basic theory of TCM syndrome computer modeling based on a noninvasive cardiac electrophysiology imaging technique. Noninvasive cardiac electrophysiology imaging records the heart’s electrical activity from hundreds of electrodes on the patient’s torso surface and therefore provides much more information than 12-lead electrocardiography. Through mathematical reconstruction algorithm calculations, the reconstructed heart model is a machine-readable description of the underlying mathematical physics model that reveals the detailed three-dimensional (3D) electrophysiological activity of the heart. Results From part of the simulation results, the imaged 3D cardiac electrical source provides dynamic information regarding the heart’s electrical activity at any given location within the 3D myocardium. Conclusions This noninvasive cardiac electrophysiology imaging method is suitable for translating TCM syndromes into a computable format of the underlying mathematical physics model to offer TCM diagnosis evidence-based standards for ensuring correct evaluation and rigorous, scientific data for demonstrating its efficacy.

scholarly journals Inhibition of let-7c Regulates Cardiac Regeneration after Cryoinjury in Adult Zebrafish

2019 ◽  
Vol 6 (2) ◽  
pp. 16 ◽  
Author(s):  
Suneeta Narumanchi ◽  
Karri Kalervo ◽  
Sanni Perttunen ◽  
Hong Wang ◽  
Katariina Immonen ◽  
...  
Keyword(s):  
Cardiac Function ◽  
Cardiac Regeneration ◽  
Nuclear Antigen ◽  
Heart Regeneration ◽  
Adult Zebrafish ◽  
Tissue Samples ◽  
Micro Rnas ◽  
Proliferating Cell ◽  
Zebrafish Heart

The let-7c family of micro-RNAs (miRNAs) is expressed during embryonic development and plays an important role in cell differentiation. We have investigated the role of let-7c in heart regeneration after injury in adult zebrafish. let-7c antagomir or scramble injections were given at one day after cryoinjury (1 dpi). Tissue samples were collected at 7 dpi, 14 dpi and 28 dpi and cardiac function was assessed before cryoinjury, 1 dpi, 7 dpi, 14 dpi and 28 dpi. Inhibition of let-7c increased the rate of fibrinolysis, increased the number of proliferating cell nuclear antigen (PCNA) positive cardiomyocytes at 7 dpi and increased the expression of the epicardial marker raldh2 at 7 dpi. Additionally, cardiac function measured with echocardiography recovered slightly more rapidly after inhibition of let-7c. These results reveal a beneficial role of let-7c inhibition in adult zebrafish heart regeneration.

scholarly journals Contribution of two-pore K+ channels to cardiac ventricular action potential revealed using human iPSC-derived cardiomyocytes

2017 ◽  
Vol 312 (6) ◽  
pp. H1144-H1153 ◽  
Author(s):  
Sam Chai ◽  
Xiaoping Wan ◽  
Drew M. Nassal ◽  
Haiyan Liu ◽  
Christine S. Moravec ◽  
...  
Keyword(s):  
Action Potential ◽  
Expression Profile ◽  
Cardiac Electrophysiology ◽  
Human Heart ◽  
Induced Pluripotent Stem Cell ◽  
Heart Tissue ◽  
Induced Pluripotent ◽  
Interfering Rna ◽  
Human Ipsc ◽  
Physiological Systems

Two-pore K+ (K2p) channels have been described in modulating background conductance as leak channels in different physiological systems. In the heart, the expression of K2p channels is heterogeneous with equivocation regarding their functional role. Our objective was to determine the K2p expression profile and their physiological and pathophysiological contribution to cardiac electrophysiology. Induced pluripotent stem cells (iPSCs) generated from humans were differentiated into cardiomyocytes (iPSC-CMs). mRNA was isolated from these cells, commercial iPSC-CM (iCells), control human heart ventricular tissue (cHVT), and ischemic (iHF) and nonischemic heart failure tissues (niHF). We detected 10 K2p channels in the heart. Comparing quantitative PCR expression of K2p channels between human heart tissue and iPSC-CMs revealed K2p1.1, K2p2.1, K2p5.1, and K2p17.1 to be higher expressed in cHVT, whereas K2p3.1 and K2p13.1 were higher in iPSC-CMs. Notably, K2p17.1 was significantly lower in niHF tissues compared with cHVT. Action potential recordings in iCells after K2p small interfering RNA knockdown revealed prolongations in action potential depolarization at 90% repolarization for K2p2.1, K2p3.1, K2p6.1, and K2p17.1. Here, we report the expression level of 10 human K2p channels in iPSC-CMs and how they compared with cHVT. Importantly, our functional electrophysiological data in human iPSC-CMs revealed a prominent role in cardiac ventricular repolarization for four of these channels. Finally, we also identified K2p17.1 as significantly reduced in niHF tissues and K2p4.1 as reduced in niHF compared with iHF. Thus, we advance the notion that K2p channels are emerging as novel players in cardiac ventricular electrophysiology that could also be remodeled in cardiac pathology and therefore contribute to arrhythmias. NEW & NOTEWORTHY Two-pore K+ (K2p) channels are traditionally regarded as merely background leak channels in myriad physiological systems. Here, we describe the expression profile of K2p channels in human-induced pluripotent stem cell-derived cardiomyocytes and outline a salient role in cardiac repolarization and pathology for multiple K2p channels.

Abstract P309: Particulate Matter Increases Oxidative Stress And Shortens The Action Potential In IPS-derived Cardiomyocytes

2021 ◽  
Vol 129 (Suppl_1) ◽  
Author(s):  
Mariana Argenziano ◽  
jiajia yang ◽  
Mariana Burgos Angulo ◽  
Thomas V McDonald
Keyword(s):  
Oxidative Stress ◽  
Particulate Matter ◽  
Action Potential ◽  
Cardiac Electrophysiology ◽  
Structural Changes ◽  
Hospital Admissions ◽  
Induced Pluripotent Stem Cell ◽  
Toxic Substances ◽  
Direct Role ◽  
Atp Production

Introduction: Air particulate matter (PM) represents one of the most critical environmental issues worldwide, causing more than 3 million deaths a year. In the US, hospital admissions due to heart failure (HF) increase by 0.8% for every 10 μg/m3 elevation in PM. However, the biological mechanisms behind the effects of PM on cardiovascular disease (CVD) remain poorly defined. Recent studies showed that PM 2.5 can translocate into the circulation, causing cumulative toxicity. With air pollution increasing due to human activity and the growing prevalence of HF, there is a critical need to understand PM's contributions to CVD to develop preventive treatments and novel therapeutic approaches. Hypothesis: We hypothesize that PM can exert its toxic effect by increasing oxidative stress and apoptosis and affecting cardiac electrophysiology. Methods: Three independent induced pluripotent stem cell lines (IPSC) were differentiated into cardiomyocytes (iCMs) and cultured for 30 days before treatment with 100 μg/ml of PM 2.5 for 48h. Experiments including immunostaining, qPCR, RNAseq and Multielectrode Array (MEA) were performed in control (CT) and PM-treated iCMs (PM). Results: Treatment with PM increased ROS and decreased ATP production (CT 9.9±1.2pmol vs PM 6.6±0.8pmol, p<0.01, n=20). Immunostaining showed mitochondrial fragmentation and increased expression of cleaved caspase3 without structural changes. Moreover, PM caused upregulation of the apoptotic markers P53 , PARP1 and CASP3, oxidative stress markers CYP1A1, CYP1B1 and MT2A, and cardiac markers CACNA1C together with downregulation of GJA1 . RNAseq analysis showed upregulation of Gene Ontology terms related to detoxification, response to toxic substances and oxidative stress. Upregulated KEGG pathways included oxidative phosphorylation, hypertrophic cardiomyopathy and dilated cardiomyopathy. MEA experiments revealed a decrease in the spike amplitude and conduction velocity, along with shortening of the action potential (APD90: CT 577±20ms vs. PM 489±16ms, p<0.05, n=20) and increased beat period irregularity (CT 3.2±0.7% vs. PM 13.1±1.6%, p<0.001, n=20). These electrophysiological changes were reversed by treatment with the antioxidant N-acetylcysteine. Conclusions: We conclude that PM plays a direct role in the development of CVD, causing an increase in oxidative stress and affecting the electrophysiology of the heart. Further functional studies in iCMs from HF patients will provide evidence of the effects of these changes on the phenotype of the disease.

scholarly journals The effect of temperature on spontaneous action potential discharge of the isolated sinus venosus from winter and summer plaice (Pleuronectes platessa)

1995 ◽  
Vol 198 (1) ◽  
pp. 137-140 ◽  
Author(s):  
A A Harper ◽  
I P Newton ◽  
P W Watt
Keyword(s):  
Action Potential ◽  
Discharge Rate ◽  
Cardiac Pacemaker ◽  
Intrinsic Rate ◽  
Effect Of Temperature ◽  
Pacemaker Activity ◽  
Duration Of Action ◽  
Diastolic Depolarization ◽  
Significant Difference

The spontaneous cardiac pacemaker activity and conformation were recorded in vitro, using intracellular recording methods, from heart tissue of summer- and winter-caught plaice. The effects of changing temperature on the pacemaker rate, duration of action potential and diastolic depolarization were investigated by altering the temperature of the superfusing medium. The resting intrinsic rate of discharge was significantly greater in pacemaker cells from winter plaice (P=0.05), but there was no significant difference between winter and summer fish in the apparent Arrhenius activation energies for this process. However, there was a significant difference in the estimated intercept, indicating a thermal shift in the processes underlying the spontaneous pacemaker rhythm. There was no significant difference in the diastolic depolarization duration recorded from winter and summer fish over the temperature range 4&shy;22 &deg;C. The major effect of previous environmental temperature was on the duration of the action potential (P&lt;0.02), indicating that the observed changes in pacemaker discharge rate were not influenced by the processes that determine the duration of the pacemaker diastolic depolarisation but were modulated by the channel events that give rise to the action potential.

scholarly journals Economic aspects and energy performance of the cooled polycrystalline solar photovoltaic technology

2016 ◽  
Vol 5 (1-2) ◽  
pp. 162-170
Author(s):  
Henrik Zsiborács ◽  
Béla Pályi ◽  
Gábor Pintér ◽  
Nóra Hegedűsné Baranyai ◽  
Péter Szabó ◽  
...  
Keyword(s):  
Cooling System ◽  
Energy Performance ◽  
Climatic Conditions ◽  
Green Energy ◽  
Effect Of Temperature ◽  
Economic Aspects ◽  
Solar Pv ◽  
Pv System ◽  
Economic Relations ◽  
Cooling Technology

In this paper the economic aspects of the water spraying cooling technology of polycrystalline solar modules with respect to the effect of temperature on performance was examined. The main purpose of this work was to explore the economic relations of the spraying cooling technology of solar modules. In the study 5 kW PV system for residential customers, 5 kW and 50 kW PV system for business customer were studied. In Hungarian climatic conditions, considering the inflation values used, the interest rate, the annual utilization of the cooling system, the expected profit and the maintenance costs show us that neither of the cooling solutions is capable of better payback time than the reference uncooled solar PV system. The further research goal is to determine the usability of the cooling system in such countries which have on the one hand more ideal climatic conditions, on the other hand more predictable green energy feed regulations.

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