optical-mapping-action-potentials-calcium-transients-mouse

Optical Mapping of Action Potentials and Calcium Transients in the Mouse Heart

The mouse heart is a popular model for cardiovascular studies due to the existence of low cost technology for genetic engineering in this species. ...

high-resolution-optical-mapping-of-the-mouse-sino-atrial-node

High-resolution Optical Mapping of the Mouse Sino-atrial Node

Sino-atrial node (SAN) dysfunctions and associated complications constitute important causes of morbidity in patients with cardiac diseases. The ...

Insulin stimulates glucose uptake into adipocytes by mobilizing intracellular membrane vesicles containing GLUT4 proteins to the plasma membrane. Here we applied time-lapse total internal reflection fluorescence microscopy to study moving parameters and characters of exogenously expressed GLUT4 vesicles in basal, insulin and nocodazole treated primary rat adipocytes. Our results showed that microtubules were essential for long-range transport of GLUT4 vesicles but not obligatory for GLUT4 distribution in rat adipocytes. Insulin reduced the mobility of the vesicles, made them tethered/docked to the PM and finally had constitutive exocytosis. Moreover, long-range bi-directional movements of GLUT4 vesicles were visualized for the first time by TIRFM. It is likely that there are interactions between insulin signaling and microtubules, to regulating GLUT4 translocation in rat adipocytes.

Bi-directional transport of GLUT4 vesicles near the plasma membrane of primary rat adipocytes.

Insulin stimuliert die Glukoseaufnahme in Adipozyten durch die Mobilisierung der intrazellul&auml;ren Membran Vesikel mit den GLUT4 Proteine an der Plasmamembran. Hier wir angewendet Zeitraffer Totalreflexion Fluoreszenzmikroskopie bewegten Parameter zu studieren und Zeichen des exogen exprimierten den GLUT4 Bl&auml;schen in basale, Insulin und Nocodazole behandelt prim&auml;re Ratte Adipozyten. Unsere Ergebnisse zeigten, dass Mikrotubuli f&uuml;r Langstrecken-Transport von den GLUT4 Bl&auml;schen, aber nicht obligatorisch f&uuml;r den GLUT4 Verteilung in Ratte Adipozyten waren. Insulin reduziert die Mobilit&auml;t von Vesikeln, machte sie angebunden/angedockt an der PM und hatte schlie&szlig;lich konstitutive Exozytose. Dar&uuml;ber hinaus wurden weitr&auml;umige bidirektionale Bewegungen von den GLUT4 Bl&auml;schen zum ersten Mal durch TIRFM visualisiert. Es ist wahrscheinlich, dass es Wechselwirkungen zwischen Insulin Signalisierung und Mikrotubuli, zur Regulierung den GLUT4-Translokation in Ratte Adipozyten gibt.

Bi-direktionale Transport den GLUT4 Vesikeln nahe der Plasmamembran der prim&auml;ren Ratte Adipozyten.

Proline-rich tyrosine kinase 2 (Pyk2) is a nonreceptor protein kinase regulated by intracellular Ca(2+), CaMK, and PKC and can be activated by different stress signals involved in heart failure. However, Pyk2 has not been investigated in the human heart, and the functional role of Pyk2 signaling at the whole heart level has not been elucidated. We hypothesize that Ca(2+)-dependent activation of Pyk2 is involved in cardiac electrophysiology. We examined the expression of Pyk2 in nonfailing versus ischemic and nonischemic failing human hearts (n = 6 hearts/group). To investigate Pyk2 function, we optically mapped perfused hearts from wild-type (WT; n = 7) and knockout (Pyk2(-/-); n = 8) mice during autonomic stimulation. Experiments were done in control mice and after 1 wk of transverse aortic constriction. We used the Illumina beadarray approach for transcriptional profiling of WT and Pyk2(-/-) mouse ventricles. Western blot analysis revealed a doubling of Pyk2 activation in nonischemic failing versus nonfailing human hearts. In mouse hearts, we observed a much higher probability of ventricular tachyarrhythmia during ACh perfusion in Pyk2(-/-) versus WT mice. Parasympathetic stimulation resulted in a dose-dependent decrease of atrial action potential duration (APD) in both WT and Pyk2(-/-) mice, whereas in ventricles it induced APD shortening in Pyk2(-/-) mice but not in WT mice. Deficiency of Pyk2 abolished ACh-induced prolongation of atrioventricular delay in Pyk2(-/-) mouse hearts but did not affect heart rate. Lower mRNA and protein levels of sarco(endo)plasmic reticulum Ca(2+)-ATPase 2 and higher mRNA levels of Na(+)/Ca(2+) exchanger 1 were detected in Pyk2(-/-) hearts compared with WT hearts. The transverse aortic constriction protocol did not change the phenotype. In conclusion, our results indicate a protective role of Pyk2 with respect to ventricular tachyarrhythmia during parasympathetic stimulation by regulation of gene expression related to Ca(2+) handling. We hypothesize that activation of Pyk2 in the human heart during heart failure may contribute to protection against arrhythmia.

Role of Pyk2 in cardiac arrhythmogenesis.

Prolin-reiche Tyrosinkinase 2 (Pyk2) ist eine Nonreceptor-Proteinkinase, die durch intrazellul&auml;re Ca(2+), CaMK und PKC geregelt und kann durch verschiedene Stress-Signale, die Herzinsuffizienz beteiligt aktiviert werden. Jedoch Pyk2 nicht in das menschliche Herz wurde untersucht und die funktionelle Rolle Pyk2 zu signalisieren, auf der das ganze Herz-Ebene ist nicht gekl&auml;rt. Wir vermuten, dass die kardiale Elektrophysiologie Ca(2+)-abh&auml;ngige Aktivierung des Pyk2 beteiligt ist. Wir untersuchten den Ausdruck des Pyk2 in Nonfailing versus isch&auml;mischen und nonischemic menschliche Herzen versagt (n = 6 Herzen/Gruppe). Um Pyk2-Funktion zu untersuchen, wir optisch zugeordnet PERFUNDIERTE Herzen von Wildtyp (WT; n = 7) und Ko (Pyk2(-/-); n = 8) M&auml;use w&auml;hrend der vegetativen Stimulation. Experimente wurden im Steuerelement M&auml;use und nach 1 Woche von quer Aorten Verengung geschlossen. Wir haben den Illumina Beadarray Ansatz f&uuml;r transkriptionelle Profilierung der WT und Pyk2(-/-) Maus Ventrikel. Western-Blot-Analyse ergab eine Verdoppelung der Pyk2 Aktivierung in Nonischemic gegen nonfailing menschlichen Herzen versagt. In den beobachteten wir eine viel h&ouml;here Wahrscheinlichkeit ventrikul&auml;re atriale w&auml;hrend ACh Perfusion in Pyk2(-/-) gegen WT-M&auml;use. Parasympathische Stimulation f&uuml;hrte eine dosisabh&auml;ngige R&uuml;ckgang von Vorhofflimmern Aktionspotential Dauer (APD) WT und Pyk2(-/-) M&auml;use, w&auml;hrend im Ventrikel es APD Verk&uuml;rzung bei Pyk2(-/-) M&auml;usen, aber nicht in WT-M&auml;use induziert. Ein Mangel an Pyk2 ACh-induzierte Verl&auml;ngerung der atrioventrikul&auml;re Verz&ouml;gerung in den Pyk2(-/-) abgeschafft, sondern hatte keine Auswirkungen auf die Herzfrequenz. Und unteren mRNA und Protein-Ebene von Sarco (Endo) plasmic Retikulum Ca(2+)-ATPase 2 und h&ouml;here mRNA Na(+)/Ca(2+) W&auml;rmetauscher 1 wurden in Pyk2(-/-) Herzen verglichen mit WT Herzen entdeckt. Das Transversale Aorten Verengung-Protokoll &auml;nderte nicht den Ph&auml;notyp. Unsere Ergebnisse zeigen abschlie&szlig;end eine sch&uuml;tzende Rolle der Pyk2 in Bezug auf ventrikul&auml;re atriale w&auml;hrend der parasympathische Stimulation durch Regulierung der Genexpression betreffend ihre Ca(2+). Wir theoretisieren, Aktivierung des Pyk2 in das menschliche Herz bei Herzinsuffizienz zum Schutz gegen Herzrhythmusst&ouml;rungen beitragen kann.

Die Rolle der Pyk2 in Herz Arrhythmogenesis.

Sinoatrial node is responsible for the origin of the wave of excitation, which spreads throughout the heart and orchestrates cardiac contraction via calcium-mediated excitation-contraction coupling. P wave represents the spread of excitation in the atria. It is well known that the autonomic nervous system controls the heart rate by dynamically altering both cellular ionic fluxes and the anatomical location of the leading pacemaker. In this study, we used isolated rabbit right atria and mathematical model of the pacemaker region of the rabbit heart. Application of isoproterenol resulted in dose-dependent acceleration of the heart rate and superior shift of the leading pacemaker. In the mathematical model, such behavior could be reproduced by a gradient of expression in Î²1-adrenergic receptors along the superior-inferior axis. Application of acetylcholine resulted in preferentially inferior shift of pacemaker and slowing of the heart rate. The mathematical model reproduced this behavior with imposing a gradient of expression of acetylcholine-sensitive potassium channel. We conclude that anatomical shift of the leading pacemaker in the rabbit heart could be achieved through gradient of expression of Î²1-adrenergic receptors and I(K,ACh).

Spatiotemporal control of heart rate in a rabbit heart.

Sinoatrial Knoten ist verantwortlich f&uuml;r die Entstehung der Welle der Erregung, die breitet sich im ganzen Herzen und orchestriert kardiale Kontraktion &uuml;ber Kalzium-vermittelte Erregung-Kontraktion-Kupplung. P-Welle stellt die Ausbreitung der Erregung in den Atrien. Es ist bekannt, dass das autonome Nervensystem die Herzfrequenz steuert, indem dynamisch ver&auml;ndern zellul&auml;re Ionische Flussmittel und der anatomischen Lage der f&uuml;hrenden Schrittmacher. In dieser Studie haben wir isoliert Kaninchen richtig Vorh&ouml;fe und mathematisches Modell des Gebietes Schrittmacher des Herzens Kaninchen verwendet. Anwendung von Isoproterenol f&uuml;hrte dosisabh&auml;ngig Beschleunigung der Herzfrequenz und &uuml;berlegene Verschiebung der f&uuml;hrenden Herzschrittmachers. Im mathematischen Modell kann ein solches Verhalten durch einen Verlauf des Ausdrucks &beta;1-adrenerge Rezeptoren entlang der Achse Superior-minderwertigen nachgeahmt werden. Anwendung von Acetylcholin f&uuml;hrte bevorzugt minderwertig Verlagerung des Herzschrittmachers und Verlangsamung der Herzfrequenz. Das mathematische Modell reproduziert dieses Verhalten mit eine Steigung von Ausdruck der Acetylcholin-Sensitive Kaliumkanal imposanten. Wir schlie&szlig;en diese anatomische Verlagerung von der f&uuml;hrenden Schrittmacher in der Hase Herz durch Farbverlauf des Ausdrucks von &beta;1-adrenerge Rezeptoren und I(K,ACh) erreicht werden k&ouml;nnte.

Raumzeitliche Kontrolle der Herzfrequenz in ein Kaninchen-Herz.

Cardiac dysfunction is a primary cause of patient mortality in Duchenne muscular dystrophy, potentially related to elevated cytosolic calcium. However, the regional versus global functional consequences of cellular calcium mishandling have not been defined in the whole heart. Here we sought for the first time to elucidate potential regional dependencies between calcium mishandling and myocardial fiber/sheet function as a manifestation of dystrophin-deficient (mdx) cardiomyopathy. Isolated-perfused hearts from 16-mo-old mdx (N = 10) and wild-type (WT; N = 10) were arrested sequentially in diastole and systole for diffusion tensor MRI quantification of myocardial sheet architecture and function. When compared with WT hearts, mdx hearts exhibited normal systolic sheet architecture but a lower diastolic sheet angle magnitude (|β|) in the basal region. The regional diastolic sheet dysfunction was normalized by reducing perfusate calcium concentrations. Optical mapping of calcium transients in isolated hearts (3 mdx and 4 WT) revealed a stretch-inducible regional defect of intracellular calcium reuptake, reflected by a 25% increase of decay times (T(50)) and decay constants, at the base of mdx hearts. The basal region of mdx hearts also exhibited greater fibrosis than did the apex, which matched the regional sheet dysfunction. We conclude that myocardial diastolic sheet dysfunction is observed initially in basal segments along with calcium mishandling, ultimately culminating in increased fibrosis. The preservation of relatively normal calcium reuptake and diastolic/systolic sheet mechanics throughout the rest of the heart, together with the rapid reversibility of functional defects by reducing cytosolic calcium, points to the significance of regional mechanical factors in the progression of the disease.

Focal but reversible diastolic sheet dysfunction reflects regional calcium mishandling in dystrophic mdx mouse hearts.

Increased dispersion of repolarization has been suggested to underlie increased arrhythmogenesis in human heart failure (HF). However, no detailed repolarization mapping data were available to support the presence of increased dispersion of repolarization in failing human heart. In the present study, we aimed to determine the existence of enhanced repolarization dispersion in the right ventricular (RV) endocardium from failing human heart and examine its association with arrhythmia inducibility. RV free wall preparations were dissected from five failing and five nonfailing human hearts, cannulated and coronary perfused. RV endocardium was optically mapped from an ∼6.3 × 6.3 cm(2) field of view. Action potential duration (APD), dispersion of APD, and conduction velocity (CV) were quantified for basic cycle lengths (BCL) ranging from 2,000 ms to the functional refractory period. We found that RV APD was significantly prolonged within the failing group compared with the nonfailing group (560 ± 44 vs. 448 ± 39 ms, at BCL = 2,000 ms, P < 0.05). Dispersion of APD was increased in three failing hearts (161 ± 5 vs. 86 ± 19 ms, at BCL = 2,000 ms). APD alternans were induced by rapid pacing in these same three failing hearts. CV was significantly reduced in the failing group compared with the nonfailing group (81 ± 11 vs. 98 ± 8 cm/s, at BCL = 2,000 ms). Arrhythmias could be induced in two failing hearts exhibiting an abnormally steep CV restitution and increased dispersion of repolarization due to APD alternans. Dispersion of repolarization is enhanced across the RV endocardium in the failing human heart. This dispersion, together with APD alternans and abnormal CV restitution, could be responsible for the arrhythmia susceptibility in human HF.

Right ventricular arrhythmogenesis in failing human heart: the role of conduction and repolarization remodeling.

Diabetes increases oxidant stress and doubles the risk of dying after myocardial infarction, but the mechanisms underlying increased mortality are unknown. Mice with streptozotocin-induced diabetes developed profound heart rate slowing and doubled mortality compared with controls after myocardial infarction. Oxidized Ca(2+)/calmodulin-dependent protein kinase II (ox-CaMKII) was significantly increased in pacemaker tissues from diabetic patients compared with that in nondiabetic patients after myocardial infarction. Streptozotocin-treated mice had increased pacemaker cell ox-CaMKII and apoptosis, which were further enhanced by myocardial infarction. We developed a knockin mouse model of oxidation-resistant CaMKIIδ (MM-VV), the isoform associated with cardiovascular disease. Streptozotocin-treated MM-VV mice and WT mice infused with MitoTEMPO, a mitochondrial targeted antioxidant, expressed significantly less ox-CaMKII, exhibited increased pacemaker cell survival, maintained normal heart rates, and were resistant to diabetes-attributable mortality after myocardial infarction. Our findings suggest that activation of a mitochondrial/ox-CaMKII pathway contributes to increased sudden death in diabetic patients after myocardial infarction.

Diabetes increases mortality after myocardial infarction by oxidizing CaMKII.

The goal of this study was to develop a low-energy, implantable device-based multistage electrotherapy (MSE) to terminate atrial fibrillation (AF).

Multistage electrotherapy delivered through chronically-implanted leads terminates atrial fibrillation with lower energy than a single biphasic shock.

Visible light photocatalytic H2-production from aqueous solutions is of great importance for its potential application in converting solar energy into chemical energy. In this study, a series of CdS nanostructures with different contents of wurtzite (WZ) and zinc blende (ZB) phases were successfully synthesized by a simple solvothermal route in an ethylenediamine and ethylene glycol mixed solution. The solvent volume ratio of ethylenediamine in the mixed solution (R) exhibited an obvious influence on the crystalline phase and morphology of the resulting CdS products. With increasing R, the percentage of wurtzite first increased and then decreased, whilst the morphology changed from nanoparticles to multi-armed nanorods, and finally to long rods and sheets. The prepared multi-armed CdS nanorod samples showed especially high and stable photocatalytic H2-production activity with Pt (0.25 wt%) as a co-catalyst and lactic acid aqueous solution as a sacrificial reagent under visible light irradiation. The optimized CdS nanorods with the highest percentage (64%) of the WZ phase exhibited a high H2-production rate of 231.4 μmol h(-1) (about 16.6 times higher than that of CdS nanoparticles with a low percentage (38.4%) of WZ CdS) and with a quantum efficiency (QE) of 28% at 420 nm. This high photocatalytic H2-production activity could be attributed to the results of the positive synergistic effects of the hexagonal WZ phase and morphology of multi-armed nanorods.

Effects of crystalline phase and morphology on the visible light photocatalytic H₂-production activity of CdS nanocrystals.

Intracellular Ca(2+) concentration ([Ca(2+)]i) is regulated and signals differently in various subcellular microdomains, which greatly enhances its second messenger versatility. In the heart, sarcoplasmic reticulum Ca(2+) release and signaling are controlled by local [Ca(2+)]i in the junctional cleft ([Ca(2+)]Cleft), the small space between sarcolemma and junctional sarcoplasmic reticulum. However, methods to measure [Ca(2+)]Cleft directly are needed.

Junctional cleft [Ca²⁺]i measurements using novel cleft-targeted Ca²⁺ sensors.

Arrhythmia is the major cause of death in patients with heart failure, for which β-adrenergic receptor blockers are a mainstay therapy. But the role of β-adrenergic signaling in electrophysiology and arrhythmias has never been studied in human ventricles.

Arrhythmogenic remodeling of β2 versus β1 adrenergic signaling in the human failing heart.

Graphene-based ternary composite photocatalysts with genuine heterostructure constituents have attracted extensive attention in photocatalytic hydrogen evolution. Here we report a new graphene-based ternary composite consisting of CdS nanorods grown on hierarchical layered WS2 /graphene hybrid (WG) as a high-performance photocatalyst for hydrogen evolution under visible light irradiation. The optimal content of layered WG as a co-catalyst in the ternary CdS/WS2 /graphene composites was found to be 4.2 wt %, giving a visible light photocatalytic H2 -production rate of 1842 μmol h(-1)  g(-1) with an apparent quantum eﬃciency of 21.2 % at 420 nm. This high photocatalytic H2 -production activity is due to the deposition of CdS nanorods on layered WS2 /graphene sheets, which can efficiently suppress charge recombination, improve interfacial charge transfer, and provide reduction active sites. The proposed mechanism for the enhanced photocatalytic activity of CdS nanorods modified with hierarchical layered WG was further confirmed by transient photocurrent response. This work shows that a noble-metal-free hierarchical layered WS2 /graphene nanosheets hybrid can be used as an effective co-catalyst for photocatalytic water splitting.

Hierarchical Layered WS2 /Graphene-Modified CdS Nanorods for Efficient Photocatalytic Hydrogen Evolution.

To look for previously unrecognized cardiac structural abnormalities and address the genetic cause for sudden unexplained nocturnal death syndrome (SUNDS).

Does Sudden Unexplained Nocturnal Death Syndrome Remain the Autopsy-Negative Disorder: A Gross, Microscopic, and Molecular Autopsy Investigation in Southern China.

ArticleTotal : 2	Year
Publication title Cited by 69	2011
Publication title Cited by 17	2016

Article	Year
Bi-directional transport of GLUT4 vesicles near the plasma membrane of primary rat adipocytes. Biochemical and biophysical research communications\| PubMed ID: 17532293	2007
Role of Pyk2 in cardiac arrhythmogenesis. American journal of physiology. Heart and circulatory physiology\| PubMed ID: 21666110	2011
Spatiotemporal control of heart rate in a rabbit heart. Journal of electrocardiology\| PubMed ID: 21937057	2011
Focal but reversible diastolic sheet dysfunction reflects regional calcium mishandling in dystrophic mdx mouse hearts. American journal of physiology. Heart and circulatory physiology\| PubMed ID: 22777417	2012
Right ventricular arrhythmogenesis in failing human heart: the role of conduction and repolarization remodeling. American journal of physiology. Heart and circulatory physiology\| PubMed ID: 23042951	2012
Diabetes increases mortality after myocardial infarction by oxidizing CaMKII. The Journal of clinical investigation\| PubMed ID: 23426181	2013
Multistage electrotherapy delivered through chronically-implanted leads terminates atrial fibrillation with lower energy than a single biphasic shock. Journal of the American College of Cardiology\| PubMed ID: 24076284	2014
Effects of crystalline phase and morphology on the visible light photocatalytic H₂-production activity of CdS nanocrystals. Dalton transactions (Cambridge, England : 2003)\| PubMed ID: 24683600	2014
Junctional cleft [Ca²⁺]i measurements using novel cleft-targeted Ca²⁺ sensors. Circulation research\| PubMed ID: 24871564	2014
Arrhythmogenic remodeling of β2 versus β1 adrenergic signaling in the human failing heart. Circulation. Arrhythmia and electrophysiology\| PubMed ID: 25673629	2015
Hierarchical Layered WS2 /Graphene-Modified CdS Nanorods for Efficient Photocatalytic Hydrogen Evolution. ChemSusChem\| PubMed ID: 27059296	2016
Does Sudden Unexplained Nocturnal Death Syndrome Remain the Autopsy-Negative Disorder: A Gross, Microscopic, and Molecular Autopsy Investigation in Southern China. Mayo Clinic proceedings\| PubMed ID: 27707468	2016

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