Hibernation enhances contractile responses of basilar artery in ground squirrels: The role of Rho-kinase and NO.

Hibernation is accompanied by dramatic decrease of blood flow in many organs due to the increase of their vascular resistances. We compared the responses of mesenteric, renal, and cerebral proximal resistance arteries in summer active (SA) and winter hibernating (WH) ground squirrels and studied the signaling pathways of Rho-kinase and NO. Wire myography and Western blotting were used to assess the arterial responses and protein abundances.

Functional Analysis of the Channelrhodopsin Genes from the Green Algae of the White Sea Basin.

Optogenetics, the method of light-controlled regulation of cellular processes is based on the use of the channelrhodopsins that directly generate photoinduced currents. Most of the channelrhodopsin genes have been identified in the green microalgae Chlorophyta, and the demand for increasing the number of functionally characterized channelrhodopsins and the diversity of their photochemical parameters keeps growing. We performed the expression analysis of cation channelrhodopsin (CCR) genes in natural isolates of microalgae of the genera and from the unique Arctic Circle region.

The metamorphosis of amphibian myocardium: moving to the heart of the matter.

Amphibians are a classical object for physiological studies, and they are of great value for developmental studies owing to their transition from an aquatic larval form to an adult form with a terrestrial lifestyle. Axolotls (Ambystoma mexicanum) are of special interest for such studies because of their neoteny and facultative pedomorphosis, as in these animals, metamorphosis can be induced and fully controlled in laboratory conditions. It has been suggested that their metamorphosis, associated with gross anatomical changes in the heart, also involves physiological and electrical remodeling of the myocardium.

A mutation in the cardiac KV7.1 channel possibly disrupts interaction with Yotiao protein.

Here, we characterized the p.Arg583His (R583H) Kv7.1 mutation, identified in two unrelated families suffered from LQT syndrome.

Novel Gain-of-Function Mutation in the Kv11.1 Channel Found in the Patient with Brugada Syndrome and Mild QTc Shortening.

Brugada syndrome (BrS) is an inherited disease characterized by right precordial ST-segment elevation in the right precordial leads on electrocardiograms (ECG), and high risk of life-threatening ventricular arrhythmia and sudden cardiac death (SCD). Mutations in the responsible genes have not been fully characterized in the BrS patients, except for the SCN5A gene. We identified a new genetic variant, c.

3-Methyl-phenanthrene (3-MP) disrupts the electrical and contractile activity of the heart of the polar fish, navaga cod (Eleginus nawaga).

Alkylated polycyclic aromatic hydrocarbons are abundant in crude oil and are enriched during petroleum refinement but knowledge of their cardiotoxicity remains limited. Polycyclic aromatic hydrocarbons (PAHs) are considered the main hazardous components in crude oil and the tricyclic PAH phenanthrene has been singled out for its direct effects on cardiac tissue in mammals and fish. Here we test the impact of the monomethylated phenanthrene, 3-methylphenanthrene (3-MP), on the contractile and electrical function of the atrium and ventricle of a polar fish, the navaga cod (Eleginus nawaga).

Characterization of hERG K channel inhibition by the new class III antiarrhythmic drug cavutilide.

Cavutilide (niferidil, refralon) is a new class III antiarrhythmic drug which effectively terminates persistent atrial fibrillation (AF; 84.6% of patients, mean AF duration 3 months) and demonstrates low risk of torsade de pointes (1.7%).

Global Air Pollutant Phenanthrene and Arrhythmic Outcomes in a Mouse Model.

Background: The three-ringed polycyclic aromatic hydrocarbon (PAH) phenanthrene (Phe) has been implicated in the cardiotoxicity of petroleum-based pollution in aquatic systems, where it disrupts the contractile and electrical function of the fish heart. Phe is also found adsorbed to particulate matter and in the gas phase of air pollution, but to date, no studies have investigated the impact of Phe on mammalian cardiac function.

Objectives: Our objectives were to determine the arrhythmogenic potential of acute Phe exposure on mammalian cardiac function and define the underlying mechanisms to provide insight into the toxicity risk to humans.

Tricyclic hydrocarbon fluorene attenuates ventricular ionic currents and pressure development in the navaga cod.

The release of polycyclic aromatic hydrocarbons (PAHs) into the environment due to oil and diesel fuel spills is a serious threat to Arctic fish populations. PAHs produce multiple toxic effects in fish, but disturbance of electrical and contractile activity of the heart seems to be the most negative effect. Our study focused on the effects of fluorene, a tricyclic PAH resembling the well-investigated tricyclic phenanthrene, on major ionic currents and action potential (AP) waveform in isolated ventricular myocytes and on contractile activity in isolated whole hearts of polar navaga cod (Eleginus nawaga).

Sodium current preserves electrical excitability in the heart of hibernating ground squirrel (Citellus undulatus).

Hibernating mammals are capable of maintaining normal cardiac function at low temperatures. Excitability of cardiac myocytes crucially depends on the fast sodium current (I), which is decreased in hypothermia due to both depolarization of resting membrane potential and direct negative effect of low temperature. Therefore, I in hibernating mammals should have specific features allowing to maintain excitability of myocardium at low temperatures.

The Dependence of the Electrophysiological Effects of Class III Antiarrhythmic Drug Refralon on the Frequency of Myocardium Activation.

We studied the frequency dependence of the effects of the novel Russian class III antiarrhythmic drug refralon on the duration of action potentials (AP) in rabbit ventricular myocardium. The absence of an inverse frequency dependence of AP prolongation was demonstrated: the effects of refralon at stimulation frequency of 1 Hz were stronger than at 0.1 Hz.

High temperature and hyperkalemia cause exit block of action potentials at the atrioventricular junction of rainbow trout (Oncorhynchus mykiss) heart.

At critically high temperatures, atrioventricular (AV) block causes ventricular bradycardia and collapse of cardiac output in fish. Here, the possible role of the AV canal in high temperature-induced heart failure was examined. To this end, optical mapping was used to measure action potential (AP) conduction in isolated AV junction preparations of the rainbow trout (Oncorhynchus mykiss) heart during acute warming/cooling in the presence of 4 or 8 mM external K concentration.

Disruption of a Conservative Motif in the C-Terminal Loop of the KCNQ1 Channel Causes LQT Syndrome.

We identified a single nucleotide variation (SNV) (c.1264A > G) in the KCNQ1 gene in a 5-year-old boy who presented with a prolonged QT interval. His elder brother and mother, but not sister and father, also had this mutation.

α1-adrenergic receptors accompanied by GATA4 expression are related to proarrhythmic conduction and automaticity in rat interatrial septum.

The development of interatrial septum (IAS) is a complicated process, which continues during postnatal life. The hypertrophic signals in developing heart are mediated among others by α-adrenergic pathways. These facts suggest the presence of specific electrophysiological features in developing IAS.

MicroRNA miR-133a-3p Facilitates Adrenergic Proarrhythmic Ectopy in Rat Pulmonary Vein Myocardium by Increasing cAMP Content.

Cardiac-specific microRNA miR-133a-3p modulates adrenergic signaling. Adrenergic receptors and their intracellular pathways are the key players in proarrhythmic ectopy derived from the myocardial sleeves of the pulmonary veins. We studied the effect of miR-133a-3p on ectopy induced by norepinephrine in myocardial tissue of rat pulmonary veins.

Variable Clinical Appearance of the Kir2.1 Rare Variants in Russian Patients with Long QT Syndrome.

Background: The gene encodes inward rectifier Kir2.1 channels, maintaining resting potential and cell excitability. Presumably, clinical phenotypes of mutation carriers correlate with ion permeability defects.

The role of activation of two different sGC binding sites by NO-dependent and NO-independent mechanisms in the regulation of SACs in rat ventricular cardiomyocytes.

The mechanoelectrical feedback (MEF) mechanism in the heart that plays a significant role in the occurrence of arrhythmias, involves cation flux through cation nonselective stretch-activated channels (SACs). It is well known that nitric oxide (NO) can act as a regulator of MEF. Here we addressed the possibility of SAC's regulation along NO-dependent and NO-independent pathways, as well as the possibility of S-nitrosylation of SACs.

Ionic currents underlying different patterns of electrical activity in working cardiac myocytes of mammals and non-mammalian vertebrates.

The orderly contraction of the vertebrate heart is determined by generation and propagation of cardiac action potentials (APs). APs are generated by the integrated activity of time- and voltage-dependent ionic channels which carry inward Na and Ca currents, and outward K currents. This review compares atrial and ventricular APs and underlying ion currents between different taxa of vertebrates.

Migraine-Associated Mutation in the Na,K-ATPase Leads to Disturbances in Cardiac Metabolism and Reduced Cardiac Function.

Background Mutations in gene encoding the Na,K-ATPase α isoform are associated with familial hemiplegic migraine type 2. Migraine with aura is a known risk factor for heart disease. The Na,K-ATPase is important for cardiac function, but its role for heart disease remains unknown.

Adrenergic prolongation of action potential duration in rainbow trout myocardium via inhibition of the delayed rectifier potassium current, I.

Catecholamines mediate the 'fight or flight' response in a wide variety of vertebrates. The endogenous catecholamine adrenaline increases heart rate and contractile strength to raise cardiac output. The increase in contractile force is driven in large part by an increase in myocyte Ca influx on the L-type Ca current (I) during the cardiac action potential (AP).

The role of M3 receptors in regulation of electrical activity deteriorates in the rat heart during ageing.

Ageing is a complex process which affects all systems of the organism and therefore changes the environment where the heart is working. In this study we demonstrate the ageing-related changes in the mechanisms of parasympathetic regulation of mammalian heart. Electrophysiological effects produced by selective activation of M3-cholinoreceptors were compared in isolated cardiac preparations from young adult (4 months), adult (1 year) and ageing (2 years) rats using sharp glass microelectrode technique.

The snake heart pacemaker is localized near the sinoatrial valve.

To provide the first description of the exact location of primary pacemaker of the squamate heart, we used sharp microelectrode impalements and optical mapping of isolated sinus venosus preparations from Burmese pythons. We located the dominant pacemaker site at the base of the right leaflet of the sinoatrial valve (SAV), but latent pacemakers were also identified in a circular region around the SAV. Acetylcholine (10-5 mol l-1) or noradrenaline (10-6 mol l-1) induced shifts of the leading pacemaker site to other points near the SAV.

Micro-RNA 133a-3p induces repolarization abnormalities in atrial myocardium and modulates ventricular electrophysiology affecting I and Ito currents.

Mir-133a-3p is the most abundant myocardial microRNA. The impact of mir-133a-3p on cardiac electrophysiology is poorly explored. In this study, we investigated the effects of mir-133a-3p on the main ionic currents critical for action potential (AP) generation and electrical activity of the heart.