Effects of polymethylmethacrylate nanoplastics on the swimming behaviour and gut microbiome of the freshwater amphipod Gammarus pulex.

Plastic pollution has posed a significant environmental concern being widely spread in terrestrial and aquatic ecosystems. Nanoplastic particles (NPs: <1000 nm) have been drawing attention for their potential toxicological implications on organisms. Aquatic animals are increasingly exposed to NPs but their effects on many aquatic invertebrates remain inadequately known.

Cardiac arrhythmias in fish induced by natural and anthropogenic changes in environmental conditions.

A regular heartbeat is essential for maintaining the homeostasis of the vertebrate body. However, environmental pollutants, oxygen deficiency and extreme temperatures can impair heart function in fish. In this Review, we provide an integrative view of the molecular origins of cardiac arrhythmias and their functional consequences, from the level of ion channels to cardiac electrical activity in living fish.

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.

Three steps down: Metabolic depression in winter-acclimatized crucian carp (Carassius carassius L.).

Acclimatization of certain ectothermic vertebrates to winter conditions is associated with reduced energy consumption (winter dormancy). Principally, this may be achieved by reducing movement activity, depression of basal cellular functions, or by switching from aerobic to anaerobic energy production to sustain low energy consumption during anoxia. Therefore, we determined standard (SMR), routine (RMR) and anoxic (AMR) metabolic rates in summer- (SumA; 20 °C) and winter-acclimatized (WinA; 2 °C) crucian carp (Carassius carassius), an anoxia-tolerant teleost fish.

Dual effect of metals on branchial and renal Na,K-ATPase activity in thermally acclimated crucian carp (Carassius carassius) and rainbow trout (Oncorhynchus mykiss).

Heavy metals are harmful to aquatic animals by disrupting their ionic balance. Here, we compare the effects of three metals, zinc (Zn), nickel (Ni) and manganese (Mn) on Na,K-ATPase activity in gills and kidneys in fish species with different ecophysiological characteristics. Crucian carp (Carassius carassius), a cold-dormant species, and rainbow trout (Oncorhynchus mykiss), a cold-active species, were acclimated to 2 °C and 18 °C, and branchial and renal Na,K-ATPase activities were measure in the presence of Zn, Ni and Mn.

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.

Cardiac Toxicity of Cadmium Involves Complex Interactions Among Multiple Ion Currents in Rainbow Trout (Oncorhynchus mykiss) Ventricular Myocytes.

Cadmium (Cd ) is cardiotoxic to fish, but its effect on the electrical excitability of cardiac myocytes is largely unknown. To this end, we used the whole-cell patch-clamp method to investigate the effects of Cd on ventricular action potentials (APs) and major ion currents in rainbow trout (Oncorhynchus mykiss) ventricular myocytes. Trout were acclimated to +4 °C, and APs were measured at the acclimated temperature and elevated temperature (+18 °C).

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.

Reduced ventricular excitability causes atrioventricular block and depression of heart rate in fish at critically high temperatures.

At critically high temperature, cardiac output in fish collapses as a result of depression of heart rate (bradycardia). However, the cause of bradycardia remains unresolved. To investigate this, rainbow trout (; acclimated at 12°C) were exposed to acute warming while electrocardiograms were recorded.

Polycyclic Aromatic Hydrocarbons Phenanthrene and Retene Modify the Action Potential via Multiple Ion Currents in Rainbow Trout Oncorhynchus mykiss Cardiac Myocytes.

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous contaminants in aqueous environments. They affect cardiovascular development and function in fishes. The 3-ring PAH phenanthrene has recently been shown to impair cardiac excitation-contraction coupling by inhibiting Ca and K currents in marine warm-water scombrid fishes.

Temperature and external K dependence of electrical excitation in ventricular myocytes of cod-like fishes.

Electrical excitability (EE) is vital for cardiac function and strongly modulated by temperature and external K concentration ([K]), as formulated in the hypothesis of temperature-dependent deterioration of electrical excitability (TDEE). As little is known about EE of arctic stenothermic fishes, we tested the TDEE hypothesis on ventricular myocytes of polar cod () and navaga () of the Arctic Ocean and those of temperate freshwater burbot (). Ventricular action potentials (APs) were elicited in current-clamp experiments at 3, 9 and 15°C, and AP characteristics and the current needed to elicit APs were examined.

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.

Maximum heart rate in brown trout (Salmo trutta fario) is not limited by firing rate of pacemaker cells.

Temperature-induced changes in cardiac output (Q̇) in fish are largely dependent on thermal modulation of heart rate (f), and at high temperatures Q̇ collapses due to heat-dependent depression of f This study tests the hypothesis that firing rate of sinoatrial pacemaker cells sets the upper thermal limit of f in vivo. To this end, temperature dependence of action potential (AP) frequency of enzymatically isolated pacemaker cells (pacemaker rate, f), spontaneous beating rate of isolated sinoatrial preparations (f), and in vivo f of the cold-acclimated (4°C) brown trout (Salmo trutta fario) were compared under acute thermal challenges. With rising temperature, f steadily increased because of the acceleration of diastolic depolarization and shortening of AP duration up to the break point temperature (T) of 24.

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.

Glycogen dynamics of crucian carp (Carassius carassius) in prolonged anoxia.

Mobilization of glycogen stores was examined in the anoxic crucian carp (Carassius carassius Linnaeus). Winter-acclimatized fish were exposed to anoxia for 1, 3, or 6 weeks at 2 °C, and changes in the size of glycogen deposits were followed. After 1 week of anoxia, a major part of the glycogen stores was mobilized in liver (79.

Deltamethrin is toxic to the fish (crucian carp, Carassius carassius) heart.

Pyrethroids are extensively used for the control of insect pests and disease vectors. Pyrethroids are regarded safe due to their selective toxicity: they are effective against insects but relatively harmless to mammals and birds. Unfortunately, pyrethroids are very toxic to fishes.

Lowering Temperature is the Trigger for Glycogen Build-Up and Winter Fasting in Crucian Carp (Carassius carassius).

Seasonal changes in physiology of vertebrate animals are triggered by environmental cues including temperature, day-length and oxygen availability. Crucian carp (Carassius carassius) tolerate prolonged anoxia in winter by using several physiological adaptations that are seasonally activated. This study examines which environmental cues are required to trigger physiological adjustments for winter dormancy in crucian carp.

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.

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.

Electrical excitation of the heart in a basal vertebrate, the European river lamprey (Lampetra fluviatilis).

Hagfishes and lampreys (order Cyclostomata) are living representatives of an ancient group of jawless vertebrates (class Agnatha). Studies on cyclostome hearts may provide insights into the evolution of the vertebrate heart and thereby increase our understanding of cardiac function in higher vertebrates, including mammals. To this end, electrical excitability of the heart in a basal vertebrate, the European river lamprey (Lampetra fluviatilis), was examined.

Electrical excitability of the heart in a Chondrostei fish, the Siberian sturgeon (Acipenser baerii).

Sturgeon (family Acipenseridae) are regarded as living fossils due to their ancient origin and exceptionally slow evolution. To extend our knowledge of fish cardiac excitability to a Chondrostei fish, we examined electrophysiological phenotype of the Siberian sturgeon (Acipenser baerii) heart with recordings of epicardial ECG, intracellular action potentials (APs), and sarcolemmal ion currents. Epicardial ECG of A.

Effects of deltamethrin on excitability and contractility of the rainbow trout (Oncorhynchus mykiss) heart.

Pyrethroids are extensively used for the control of pest insects and disease vectors. Pyrethroid use is regarded safe due to their selective toxicity: they are effective against insects but relatively harmless to mammals and birds. Unfortunately, pyrethroids are very toxic to fishes.

Acute heat tolerance of cardiac excitation in the brown trout (Salmo trutta fario).

The upper thermal tolerance and mechanisms of heat-induced cardiac failure in the brown trout (Salmo trutta fario) was examined. The point above which ion channel function and sinoatrial contractility in vitro, and electrocardiogram (ECG) in vivo, started to fail (break point temperature, BPT) was determined by acute temperature increases. In general, electrical excitation of the heart was most sensitive to heat in the intact animal (electrocardiogram, ECG) and least sensitive in isolated cardiac myocytes (ion currents).