Dual effect of polyaromatic hydrocarbons on sarco(endo)plasmic reticulum calcium ATPase (SERCA) activity of a teleost fish (Oncorhynchus mykiss).

Polycyclic aromatic hydrocarbons (PAHs) are embryo- and cardiotoxic to fish that might be associated with improper intracellular Ca management. Since sarco(endo)plasmic reticulum Ca-ATPase (SERCA) is a major regulator of intracellular Ca, the SERCA activity and the contractile properties of rainbow trout (Oncorhynchus mykiss) ventricle were measured in the presence of 3- and 4-cyclic PAHs. In unfractionated ventricular homogenates, acute exposure of SERCA to 0.

Spatial uniformity of action potentials indicates base-to-apex depolarization and repolarization of rainbow trout (Oncorhynchus mykiss) ventricle.

The spatial pattern of electrical activation is crucial for a full understanding of fish heart function. However, it remains unclear whether there is regional variation in action potential (AP) morphologies and underlying ion currents. Because the direction of depolarization and spatial differences in the durations of ventricular APs set limits to potential patterns of ventricular repolarization, we determined AP morphologies, underlying ion currents and ion channel expression in four different ventricular regions (spongy myocardium; and apex, base and middle of the compact myocardium), and correlated them with in vivo electrocardiograms (ECGs) in rainbow trout (Oncorhynchus mykiss).

Effect of Channel Assembly (KCNQ1 or KCNQ1 + KCNE1) on the Response of Zebrafish IKs Current to IKs Inhibitors and Activators.

In cardiac myocytes, the slow component of the delayed rectifier K+ current (IKs) ensures repolarization of action potential during beta-adrenergic activation or when other repolarizing K+ currents fail. As a key factor of cardiac repolarization, IKs should be present in model species used for cardiovascular drug screening, preferably with pharmacological characteristics similar to those of the human IKs. To this end, we investigated the effects of inhibitors and activators of the IKs on KCNQ1 and KCNQ1 + KCNE1 channels of the zebrafish, an important model species, in Chinese hamster ovary cells.

Effects of Na+ channel isoforms and cellular environment on temperature tolerance of cardiac Na+ current in zebrafish (Danio rerio) and rainbow trout (Oncorhynchus mykiss).

Heat tolerance of heart rate in fish is suggested to be limited by impaired electrical excitation of the ventricle due to the antagonistic effects of high temperature on Na+ (INa) and K+ (IK1) ion currents (INa is depressed at high temperatures while IK1 is resistant to them). To examine the role of Na+ channel proteins in heat tolerance of INa, we compared temperature dependencies of zebrafish (Danio rerio, warm-dwelling subtropical species) and rainbow trout (Oncorhynchus mykiss, cold-active temperate species) ventricular INa, and INa generated by the cloned zebrafish and rainbow trout NaV1.4 and NaV1.

Ionic basis of atrioventricular conduction: ion channel expression and sarcolemmal ion currents of the atrioventricular canal of the rainbow trout (Oncorhynchus mykiss) heart.

Atrioventricular (AV) nodal tissue synchronizes activities of atria and ventricles of the vertebrate heart and is also a potential site of cardiac arrhythmia, e.g., under acute heat stress.

Transcript expression of inward rectifier potassium channels of Kir2 subfamily in Arctic marine and freshwater fish species.

Inward rectifier K (Kir2) channels are critical for electrical excitability of cardiac myocytes. Here, we examine expression of Kir2 channels in the heart of three Gadiformes species, polar cod (Boreogadus saida) and navaga (Eleginus nawaga) of the Arctic Ocean and burbot (Lota lota) of the temperate lakes to find out the role of Kir2 channels in cardiac adaptation to cold. Five boreal freshwater species: brown trout (Salmo trutta fario), arctic char (Salvelinus alpinus), roach (Rutilus rutilus), perch (Perca fluviatilis) and pike (Esox lucius), and zebrafish (Danio rerio), were included for comparison.

Transcripts of Kv7.1 and MinK channels and slow delayed rectifier K current (I) are expressed in zebrafish (Danio rerio) heart.

Zebrafish are increasingly used as a model for human cardiac electrophysiology, arrhythmias, and drug screening. However, K ion channels of the zebrafish heart, which determine the rate of repolarization and duration of cardiac action potential (AP) are still incompletely known and characterized. Here, we provide the first evidence for the presence of the slow component of the delayed rectifier Kchannels in the zebrafish heart and characterize electrophysiological properties of the slow component of the delayed rectifier Kcurrent, I.

Expression of calcium channel transcripts in the zebrafish heart: dominance of T-type channels.

Calcium channels are necessary for cardiac excitation-contraction (E-C) coupling, but Ca channel composition of fish hearts is still largely unknown. To this end, we determined transcript expression of Ca channels in the heart of zebrafish (), a popular model species. Altogether, 18 Ca channel α-subunit genes were expressed in both atrium and ventricle.

Cardiac voltage-gated sodium channel expression and electrophysiological characterization of the sodium current in the zebrafish (Danio rerio) ventricle.

Na channel α-subunit composition of the zebrafish heart and electrophysiological properties of Na current (I) of zebrafish ventricular myocytes were examined. Eight Na channel α-subunits were expressed in both atrium and ventricle of the zebrafish heart. Na1.

Small functional current in sinoatrial pacemaker cells of the brown trout () heart despite strong expression of HCN channel transcripts.

Funny current (), formed by hyperpolarization-activated cyclic nucleotide-gated channels (HCN channels), is supposed to be crucial for the membrane clock regulating the cardiac pacemaker mechanism. We examined the presence and activity of HCN channels in the brown trout () sinoatrial (SA) pacemaker cells and their putative role in heart rate () regulation. Six HCN transcripts (HCN1, HCN2a, HCN2ba, HCN2bb, HCN3, and HCN4) were expressed in the brown trout heart.

Effects of seasonal acclimatization on action potentials and sarcolemmal K currents in roach (Rutilus rutilus) cardiac myocytes.

Temperature sensitivity of electrical excitability is a potential limiting factor for high temperature tolerance of ectotherms. The present study examines whether heat resistance of electrical excitability of cardiac myocytes is modified by seasonal thermal acclimatization in roach (Rutilus rutilus), a eurythermal teleost species. To this end, temperature dependencies of ventricular action potentials (APs), and atrial and ventricular K currents were measured from winter-acclimatized (WiR) and summer-acclimatized (SuR) roach.

Effects of prolonged anoxia on electrical activity of the heart in crucian carp (Carassius carassius).

The effects of sustained anoxia on cardiac electrical excitability were examined in the anoxia-tolerant crucian carp (Carassius carassius). The electrocardiogram (ECG) and expression of excitation-contraction coupling genes were studied in fish acclimatised to normoxia in summer (+18°C) or winter (+2°C), and in winter fish after 1, 3 and 6 weeks of anoxia. Anoxia induced a sustained bradycardia from a heart rate of 10.

Zebrafish heart as a model for human cardiac electrophysiology.

The zebrafish (Danio rerio) has become a popular model for human cardiac diseases and pharmacology including cardiac arrhythmias and its electrophysiological basis. Notably, the phenotype of zebrafish cardiac action potential is similar to the human cardiac action potential in that both have a long plateau phase. Also the major inward and outward current systems are qualitatively similar in zebrafish and human hearts.

Molecular basis and drug sensitivity of the delayed rectifier (IKr) in the fish heart.

Fishes are increasingly used as models for human cardiac diseases, creating a need for a better understanding of the molecular basis of fish cardiac ion currents. To this end we cloned KCNH6 channel of the crucian carp (Carassius carassius) that produces the rapid component of the delayed rectifier K(+) current (IKr), the main repolarising current of the fish heart. KCNH6 (ccErg2) was the main isoform of the Kv11 potassium channel family with relative transcript levels of 98.

Process Development of Adenoviral Vector Production in Fixed Bed Bioreactor: From Bench to Commercial Scale.

Large-scale vector manufacturing for phase III and beyond has proven to be challenging. Upscaling the process with suspension cells is increasingly feasible, but many viral production applications are still applicable only in adherent settings. Scaling up the adherent system has proven to be troublesome.

Inward rectifier potassium current (I K1) and Kir2 composition of the zebrafish (Danio rerio) heart.

Electrophysiological properties and molecular background of the zebrafish (Danio rerio) cardiac inward rectifier current (IK1) were examined. Ventricular myocytes of zebrafish have a robust (-6.7 ± 1.

Seasonal acclimatization of the cardiac action potential in the Arctic navaga cod (Eleginus navaga, Gadidae).

Freshwater fishes of north-temperate latitudes adjust electrical excitability of the heart to seasonal temperature changes by changing expression levels of ion channel isoforms. However, little is known about thermal responses of action potential (AP) in the hearts of marine polar fishes. To this end, we examined cardiac AP in the atrial myocardium of the Arctic navaga cod (Eleginus navaga) from the White Sea (Russia) acclimatized to winter (March) and summer (September) seasons.

Tetrodotoxin sensitivity of the vertebrate cardiac Na+ current.

Evolutionary origin and physiological significance of the tetrodotoxin (TTX) resistance of the vertebrate cardiac Na(+) current (I(Na)) is still unresolved. To this end, TTX sensitivity of the cardiac I(Na) was examined in cardiac myocytes of a cyclostome (lamprey), three teleost fishes (crucian carp, burbot and rainbow trout), a clawed frog, a snake (viper) and a bird (quail). In lamprey, teleost fishes, frog and bird the cardiac I(Na) was highly TTX-sensitive with EC(50)-values between 1.

Thermal adaptation of the crucian carp (Carassius carassius) cardiac delayed rectifier current, IKs, by homomeric assembly of Kv7.1 subunits without MinK.

Ectothermic vertebrates experience acute and chronic temperature changes which affect cardiac excitability and may threaten electrical stability of the heart. Nevertheless, ectothermic hearts function over wide range of temperatures without cardiac arrhythmias, probably due to special molecular adaptations. We examine function and molecular basis of the slow delayed rectifier K(+) current (I(Ks)) in cardiac myocytes of a eurythermic fish (Carassius carassius L.

A novel inwardly rectifying K+ channel, Kir2.5, is upregulated under chronic cold stress in fish cardiac myocytes.

A new member of the inward-rectifier K(+) channel subfamily Kir2 was isolated and characterised from the crucian carp (Carassius carassius) heart. When expressed in COS-1 cells this 422 amino acid protein produced an inward-rectifying channel with distinct single-channel conductance, mean open time and open probability. Phylogenetic sequence comparisons indicate that it is not homologous to any known vertebrate Kir channel, yet belongs to the Kir2 subfamily.

BpMADS4 has a central role in inflorescence initiation in silver birch (Betula pendula).

Acceleration of flowering would be beneficial for breeding trees with a long juvenile phase; conversely, inhibition of flowering would prevent the spread of transgenes from the genetically modified trees. We have previously isolated and characterized several MADS genes from silver birch (Betula pendula Roth). In this study, we investigated the more detailed function of one of them, BpMADS4, a member of the APETALA1/FRUITFULL group of MADS genes.

Cloning and expression of cardiac Kir2.1 and Kir2.2 channels in thermally acclimated rainbow trout.

Potassium currents are plastic entities that modify electrical activity of the heart in various physiological conditions including chronic thermal stress. We examined the molecular basis of the inward rectifier K+ current (IK1) in rainbow trout acclimated to cold (4 degrees C, CA) and warm (18 degrees C, WA) temperature. Inward rectifier K+ channel (Kir)2.

Steady-state effects of temperature acclimation on the transcriptome of the rainbow trout heart.

Cold-acclimated (CA) phenotype of trout heart was induced by 4-wk acclimation at 4 degrees C and was characterized by 32.7% increase in relative heart mass and 49.8% increase in ventricular myocyte size compared with warm-acclimated (WA; 18 degrees C) fish (P < 0.

Functional characterization of SEPALLATA3 and AGAMOUS orthologues in silver birch.

The development of flowers is regulated by a complex network of transcriptional activators and repressors, many of which belong to the MADS box gene family. In this study, we describe two MADS box genes of silver birch (Betula pendula Roth), BpMADS1 and BpMADS6, which are similar to SEPALLATA3 and AGAMOUS in Arabidopsis thaliana, respectively. In situ hybridization showed that BpMADS1 was expressed in the inflorescence meristem at a very early stage, but not later.