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("calcium wave*" OR "ca2+ wave*") AND ("heart" OR "cardiac")

Alexander V Maltsev, Sean P Parsons, Mary S Kim, Kenta Tsutsui, Michael D Stern, Edward G Lakatta, Victor A Maltsev, Oliver Monfredi
Local Ca2+ Releases (LCRs) are crucial events involved in cardiac pacemaker cell function. However, specific algorithms for automatic LCR detection and analysis have not been developed in live, spontaneously beating pacemaker cells. In the present study we measured LCRs using a high-speed 2D-camera in spontaneously contracting sinoatrial (SA) node cells isolated from rabbit and guinea pig and developed a new algorithm capable of detecting and analyzing the LCRs spatially in two-dimensions, and in time. Our algorithm tracks points along the midline of the contracting cell...
2017: PloS One
Bijay Limbu, Kushal Shah, Makarand Deo
The Cardiac Purkinje cells (PCs) exhibit distinct calcium (Ca2+) homeostasis than that in ventricular myocytes (VMs). Due to lack of t-tubules in PCs, the Ca2+ ions entering the cell have to diffuse through the cytoplasm to reach the sarcoplasmic reticulum (SR) before triggering Ca2+-induced-Ca2+-release (CICR). In recent experimental studies PCs have been shown to be more susceptible to action potential (AP) abnormalities than the VMs, however the exact mechanisms are poorly understood. In this study, we utilize morphologically realistic detailed biophysical mathematical model of a murine PC to systematically examine the role intracellular Ca2+ diffusion in the APs of PCs...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
Y X Li, V Gautam, A Brüstle, I A Cockburn, V R Daria, C Gillespie, K Gaus, C Alt, W M Lee
Commercial microscopy systems make use of tandem scanning i.e. either slow or fast scanning. We constructed, for the first time, an advanced control system capable of delivering a dynamic line scanning speed ranging from 2.7 kHz to 27 kHz and achieve variable frame rates from 5 Hz to 50 Hz (512 × 512). The dynamic scanning ability is digitally controlled by a new customized open-source software named PScan1.0. This permits manipulation of scanning rates either to gain higher fluorescence signal at slow frame rate without increasing laser power or increase frame rates to capture high speed events...
February 6, 2017: Journal of Biophotonics
Jianjun Wu, Xiangchong Wang, Ying Ying Chung, Cai Hong Koh, Zhenfeng Liu, Huicai Guo, Qiang Yuan, Chuan Wang, Suwen Su, Heming Wei
Aconitine (ACO) is well-known for causing lethal ventricular tachyarrhythmias. While cardiac Na+ channel opening during repolarization has long been documented in animal cardiac myocytes, the cellular effects and mechanism of ACO in human remain unexplored. This study aimed to assess the proarrhythmic effects of ACO in human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). ACO concentration-dependently (0.3 ~ 3.0 μM) shortened the action potentials (AP) durations (APD) in ventricular-like hiPSC-CMs by > 40% and induced delayed after-depolarization...
2017: PloS One
Yohannes Shiferaw
Spontaneous calcium (Ca) waves in cardiac myocytes are known to underlie a wide range of cardiac arrhythmias. However, it is not understood which physiological parameters determine the onset of waves. In this study, we explore the relationship between Ca signaling between ion channels and the nucleation of Ca waves. In particular, we apply a master equation approach to analyze the stochastic interaction between neighboring clusters of ryanodine receptor (RyR) channels. Using this analysis, we show that signaling between clusters can be described as a barrier hopping process with exponential sensitivity to system parameters...
September 2016: Physical Review. E
Julliane Vasconcelos Joviano-Santos, Artur Santos-Miranda, Humberto Cavalcante Joca, Jader Santos Cruz, Anderson José Ferreira
What is the central question of this study? Recently, there have been many studies exploring the biological effects of angiotensin-(1-7), which has been proved to have cardioprotective actions. However, the effects of this peptide on cardiac arrhythmias in vivo and details regarding its mechanism of action are still undetermined. What is the main finding and its importance? We investigated protective effects of angiotensin-(1-7) on cardiac arrhythmias in vivo, which were not properly explored in terms of cellular mechanisms...
December 1, 2016: Experimental Physiology
Jegan Iyyathurai, Bernard Himpens, Geert Bultynck, Catheleyne D'hondt
Intercellular communication is essential for the coordination and synchronization of cellular processes. Gap junction channels play an important role to communicate between cells and organs, including the brain, lung, liver, lens, retina, and heart. Gap junctions enable a direct route for ions like calcium and potassium, and low molecular weight compounds, such as inositol 1,4,5-trisphosphate, cyclic adenosine monophosphate, and various kinds of metabolites to pass between cells. Intercellular calcium wave propagation evoked by a local mechanical stimulus is one of the gap junction assays to study intercellular communication...
2016: Methods in Molecular Biology
Mani Sadredini, Tore Kristian Danielsen, Jan Magnus Aronsen, Ravinea Manotheepan, Karina Hougen, Ivar Sjaastad, Mathis Korseberg Stokke
Abnormal cellular Ca2+ handling contributes to both contractile dysfunction and arrhythmias in heart failure. Reduced Ca2+ transient amplitude due to decreased sarcoplasmic reticulum Ca2+ content is a common finding in heart failure models. However, heart failure models also show increased propensity for diastolic Ca2+ release events which occur when sarcoplasmic reticulum Ca2+ content exceeds a certain threshold level. Such Ca2+ release events can initiate arrhythmias. In this study we aimed to investigate if both of these aspects of altered Ca2+ homeostasis could be found in left ventricular cardiomyocytes from rats with different states of cardiac function six weeks after myocardial infarction when compared to sham-operated controls...
2016: PloS One
Pierre Bobin, Audrey Varin, Florence Lefebvre, Rodolphe Fischmeister, Grégoire Vandecasteele, Jérôme Leroy
AIMS: A major concern of using phosphodiesterase (PDE) inhibitors in heart failure is their potential to increase mortality by inducing arrhythmias. By diminishing cyclic adenosine monophosphate (cAMP) hydrolysis, they promote protein kinase A (PKA) activity under β-adrenergic receptor (β-AR) stimulation, hence enhancing Ca(2+) cycling and contraction. Yet, cAMP also activates CaMKII via PKA or the exchange protein Epac, but it remains unknown whether these pathways are involved in the pro-arrhythmic effect of PDE inhibitors...
May 1, 2016: Cardiovascular Research
Gonzalo Hernandez-Hernandez, Enric Alvarez-Lacalle, Yohannes Shiferaw
This corrects the article DOI: 10.1103/PhysRevE.92.052715.
December 2015: Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics
Gonzalo Hernandez-Hernandez, Enric Alvarez-Lacalle, Yohannes Shiferaw
Spontaneous calcium release (SCR) occurs when ion channel fluctuations lead to the nucleation of calcium waves in cardiac cells. This phenomenon is important since it has been implicated as a cause of various cardiac arrhythmias. However, to date, it is not understood what determines the timing and location of spontaneous calcium waves within cells. Here, we analyze a simplified model of SCR in which calcium release is modeled as a stochastic processes on a two-dimensional network of randomly distributed sites...
2015: Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics
Pecoraro Michela, Verrilli Velia, Pinto Aldo, Popolo Ada
Gap junctions (GJs) channels provide the basis for intercellular communication in the cardiovascular system for maintenance of the normal cardiac rhythm, regulation of vascular tone and endothelial function as well as metabolic interchange between the cells. They allow the transfer of small molecules and may enable slow calcium wave spreading, transfer of "death" or of "survival" signals. In the cardiomyocytes the most abundant isoform is Connexin 43 (Cx43). Alterations in Cx43 expression and distribution were observed in myocardium disease; i...
December 5, 2015: European Journal of Pharmacology
Markus B Sikkel, Sunil Kumar, Vincent Maioli, Christina Rowlands, Fabiana Gordon, Sian E Harding, Alexander R Lyon, Kenneth T MacLeod, Chris Dunsby
Oblique plane microscopy (OPM) is a form of light sheet microscopy that uses a single high numerical aperture microscope objective for both fluorescence excitation and collection. In this paper, measurements of the relative collection efficiency of OPM are presented. An OPM system incorporating two sCMOS cameras is then introduced that enables single isolated cardiac myocytes to be studied continuously for 22 seconds in two dimensions at 667 frames per second with 960 × 200 pixels and for 30 seconds with 960 × 200 × 20 voxels at 25 volumes per second...
March 2016: Journal of Biophotonics
Benjamin S Spearman, Alexander J Hodge, John L Porter, John G Hardy, Zenda D Davis, Teng Xu, Xinyu Zhang, Christine E Schmidt, Michael C Hamilton, Elizabeth A Lipke
UNLABELLED: Conductive and electroactive polymers have the potential to enhance engineered cardiac tissue function. In this study, an interpenetrating network of the electrically-conductive polymer polypyrrole (PPy) was grown within a matrix of flexible polycaprolactone (PCL) and evaluated as a platform for directing the formation of functional cardiac cell sheets. PCL films were either treated with sodium hydroxide to render them more hydrophilic and enhance cell adhesion or rendered electroactive with PPy grown via chemical polymerization yielding PPy-PCL that had a resistivity of 1...
December 2015: Acta Biomaterialia
Gema Ruiz-Hurtado, Linwei Li, María Fernández-Velasco, Angélica Rueda, Florence Lefebvre, Yueyi Wang, Philippe Mateo, Cécile Cassan, Barnabas Gellen, Jean Pierre Benitah, Ana María Gómez
Abnormalities in cardiomyocyte Ca2+ handling contribute to impaired contractile function in heart failure (HF). Experiments on single ryanodine receptors (RyRs) incorporated into lipid bilayers have indicated that RyRs from failing hearts are more active than those from healthy hearts. Here, we analyzed spontaneous Ca2+ sparks (brief, localized increased in [Ca2+]i) to evaluate RyR cluster activity in situ in a mouse post-myocardial infarction (PMI) model of HF. The cardiac ejection fraction of PMI mice was reduced to ∼30% of that of sham-operated (sham) mice, and their cardiomyocytes were hypertrophied...
October 2015: Journal of General Physiology
Jingqun Zhang, Qiang Zhou, Chris D Smith, Haiyan Chen, Zhen Tan, Biyi Chen, Alma Nani, Guogen Wu, Long-Sheng Song, Michael Fill, Thomas G Back, S R Wayne Chen
Carvedilol is the current β-blocker of choice for suppressing ventricular tachyarrhythmia (VT). However, carvedilol's benefits are dose-limited, attributable to its potent β-blocking activity that can lead to bradycardia and hypotension. The clinically used carvedilol is a racemic mixture of β-blocking S-carvedilol and non-β-blocking R-carvedilol. We recently reported that novel non-β-blocking carvedilol analogues are effective in suppressing arrhythmogenic Ca(2+) waves and stress-induced VT without causing bradycardia...
September 1, 2015: Biochemical Journal
Lendert Gelens, Kerwyn Casey Huang, James E Ferrell
Theoretical studies have shown that a deterministic biochemical oscillator can become chaotic when operating over a sufficiently large volume and have suggested that the Xenopus laevis cell cycle oscillator operates close to such a chaotic regime. To experimentally test this hypothesis, we decreased the speed of the post-fertilization calcium wave, which had been predicted to generate chaos. However, cell divisions were found to develop normally, and eggs developed into normal tadpoles. Motivated by these experiments, we carried out modeling studies to understand the prerequisites for the predicted spatial chaos...
August 4, 2015: Cell Reports
Eleonora Savio-Galimberti, Björn C Knollmann
Flecainide blocks ryanodine receptor type 2 (RyR2) channels in the open state, suppresses arrhythmogenic Ca2+ waves and prevents catecholaminergic polymorphic ventricular tachycardia (CPVT) in mice and humans. We hypothesized that differences in RyR2 activity induced by CPVT mutations determines the potency of open-state RyR2 blockers like flecainide (FLEC) and R-propafenone (RPROP) against Ca2+ waves in cardiomyocytes. Using confocal microscopy, we studied Ca2+ sparks and waves in isolated saponin-permeabilized ventricular myocytes from two CPVT mouse models (Casq2-/-, RyR2-R4496C+/-), wild-type (c57bl/6, WT) mice, and WT rabbits (New Zealand white rabbits)...
2015: PloS One
Pavol Petrovič, Ivan Valent, Elena Cocherová, Jana Pavelková, Alexandra Zahradníková
The role of cardiac ryanodine receptor (RyR) gating in the initiation and propagation of calcium waves was investigated using a mathematical model comprising a stochastic description of RyR gating and a deterministic description of calcium diffusion and sequestration. We used a one-dimensional array of equidistantly spaced RyR clusters, representing the confocal scanning line, to simulate the formation of calcium sparks. Our model provided an excellent description of the calcium dependence of the frequency of diastolic calcium sparks and of the increased tendency for the production of calcium waves after a decrease in cytosolic calcium buffering...
June 2015: Journal of General Physiology
R Thul, K Rietdorf, M D Bootman, S Coombes
Atrial myocytes in a number of species lack transverse tubules. As a consequence the intracellular calcium signals occurring during each heartbeat exhibit complex spatio-temporal dynamics. These calcium patterns arise from saltatory calcium waves that propagate via successive rounds of diffusion and calcium-induced calcium release. The many parameters that impinge on calcium-induced calcium release and calcium signal propagation make it difficult to know a priori whether calcium waves will successfully travel, or be extinguished...
September 2015: Biochimica et Biophysica Acta
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