Our sisters the plants? notes from phylogenetics and botany on plant kinship blindness.

Before the upheaval brought about by phylogenetic classification, classical taxonomy separated living beings into two distinct kingdoms, animals and plants. Rooted in 'naturalist' cosmology, Western science has built its theoretical apparatus on this dichotomy mostly based on ancient Aristotelian ideas. Nowadays, despite the adoption of the Darwinian paradigm that unifies living organisms as a kinship, the concept of the "scale of beings" continues to structure our analysis and understanding of living species.

Differential effectiveness of pharmacological strategies to reveal dormant pulmonary vein conduction: a clinical-experimental correlation.

Background: Atrial fibrillation recurs in ∼30%-40% of patients after pulmonary vein (PV) isolation (PVI) procedures, often because of restored PV-left atrial (LA) conduction. Adenosine or isoproterenol are used clinically to reveal dormant PV conduction and guide additional ablation.

Objective: The purpose of this study was to assess the differential efficacy of adenosine and/or isoproterenol in revealing dormant PV conduction.

Arrhythmogenic left atrial cellular electrophysiology in a murine genetic long QT syndrome model.

Aims: Increasing evidence indicates that congenital long QT syndromes (LQTSs) promote atrial fibrillation. The atrial action potential (AP) has a short plateau, and whether LQTS atrial cardiomyocytes generate triggered activity via early afterdepolarizations (EADs) is unclear. Atrial cellular arrhythmia mechanisms have not been defined in congenital LQTS.

Mechanisms of atrial tachyarrhythmias associated with coronary artery occlusion in a chronic canine model.

Background: Coronary artery disease predisposes to atrial fibrillation (AF), but the effects of chronic atrial ischemia/infarction on AF-related substrates are unknown.

Methods And Results: Regional right atrial myocardial infarction (MI) was created in 40 dogs by ligating an artery that supplies the right atrial free wall and not the ventricles; 35 sham dogs with the same artery isolated but not ligated were controls. Dogs were observed 8 days after MI and subjected to open-chest study, in vitro optical mapping, and/or cell isolation for patch-clamp and Ca(2+) imaging on day 8.

Role of constitutively active acetylcholine-mediated potassium current in atrial contractile dysfunction caused by atrial tachycardia remodelling.

Aims: Atrial fibrillation (AF)-induced contractile dysfunction contributes importantly to thrombo-embolic stroke, the most serious AF complication. Atrial cardiomyocytes have a constitutively active acetylcholine-regulated K(+)-current (I(KAChc)) that is enhanced by atrial tachycardia (AT). I(KAChc) contributes to action potential duration (APD) shortening in AT-remodelled atrial cardiomyocytes; APD regulates contractility by controlling Ca(2+)-loading and systolic Ca(2+)-release.

Mechanisms by which adenosine restores conduction in dormant canine pulmonary veins.

Background: Adenosine acutely reconnects pulmonary veins (PVs) after radiofrequency application, revealing "dormant conduction" and identifying PVs at risk of reconnection, but the underlying mechanisms are unknown.

Methods And Results: Canine PV and left-atrial (LA) action potentials were recorded with standard microelectrodes and ionic currents with whole-cell patch clamp before and after adenosine perfusion. PVs were isolated with radiofrequency current application in coronary-perfused LA-PV preparations.

The calcium/calmodulin/kinase system and arrhythmogenic afterdepolarizations in bradycardia-related acquired long-QT syndrome.

Background: Sustained bradycardia is associated with long-QT syndrome in human beings and causes spontaneous torsades de pointes in rabbits with chronic atrioventricular block (CAVB), at least partly by downregulating delayed-rectifier K(+)-current to cause action potential (AP) prolongation. We addressed the importance of altered Ca(2+) handling, studying underlying mechanisms and consequences.

Methods And Results: We measured ventricular cardiomyocyte [Ca(2+)](i) (Indo1-AM), L-type Ca(2+)-current (I(CaL)) and APs (whole-cell perforated-patch), and Ca(2+)-handling protein expression (immunoblot).

Ion channel subunit expression changes in cardiac Purkinje fibers: a potential role in conduction abnormalities associated with congestive heart failure.

Purkinje fibers (PFs) play key roles in cardiac conduction and arrhythmogenesis. Congestive heart failure (CHF) causes well-characterized atrial and ventricular ion channel subunit expression changes, but effects on PF ion channel subunits are unknown. This study assessed changes in PF ion channel subunit expression (real-time PCR, immunoblot, immunohistochemistry), action potential properties, and conduction in dogs with ventricular tachypacing-induced CHF.

Funny current downregulation and sinus node dysfunction associated with atrial tachyarrhythmia: a molecular basis for tachycardia-bradycardia syndrome.

Background: Sinoatrial node (SAN) dysfunction is frequently associated with atrial tachyarrhythmias (ATs). Abnormalities in SAN pacemaker function after termination of ATs can cause syncope and require pacemaker implantation, but underlying mechanisms remain poorly understood. This study examined the hypothesis that ATs impair SAN function by altering ion channel expression.

Calpain mediates cardiac troponin degradation and contractile dysfunction in atrial fibrillation.

The self-perpetuation of atrial fibrillation (AF) is associated with atrial remodeling, including the degradation of the myofibril structure (myolysis). Myolysis is related to AF-induced activation of cysteine proteases and underlies loss of contractile function. In this study, we investigated which proteases are involved in the degradation of myofibrillar proteins during AF and whether their inhibition leads to preservation of contractile function after AF.

Cellular signaling underlying atrial tachycardia remodeling of L-type calcium current.

Atrial tachycardia (AT) downregulates L-type Ca(2+) current (I(CaL)) and causes atrial fibrillation-promoting electric remodeling. This study assessed potential underlying signal transduction. Cultured adult canine atrial cardiomyocytes were paced at 0, 1, or 3 Hz (P0, P1, P3) for up to 24 hours.

Differential interactions of Na+ channel toxins with T-type Ca2+ channels.

Two types of voltage-dependent Ca(2+) channels have been identified in heart: high (I(CaL)) and low (I(CaT)) voltage-activated Ca(2+) channels. In guinea pig ventricular myocytes, low voltage-activated inward current consists of I(CaT) and a tetrodotoxin (TTX)-sensitive I(Ca) component (I(Ca(TTX))). In this study, we reexamined the nature of low-threshold I(Ca) in dog atrium, as well as whether it is affected by Na(+) channel toxins.

Calcium-handling abnormalities underlying atrial arrhythmogenesis and contractile dysfunction in dogs with congestive heart failure.

Background: Congestive heart failure (CHF) is a common cause of atrial fibrillation. Focal sources of unknown mechanism have been described in CHF-related atrial fibrillation. The authors hypothesized that abnormal calcium (Ca(2+)) handling contributes to the CHF-related atrial arrhythmogenic substrate.

Antiarrhythmic properties of a rapid delayed-rectifier current activator in rabbit models of acquired long QT syndrome.

Aims: Impaired repolarization in cardiac myocytes can lead to long QT syndrome (LQTS), with delayed repolarization and increased susceptibility to Torsades de Pointes (TdP) arrhythmias. Current pharmacological treatment of LQTS is often inadequate. This study sought to evaluate the antiarrhythmic effect of a novel compound (NS1643) that activates the rapid delayed-rectifier K+ current, I(Kr), in two rabbit models of acquired LQTS.

Pulmonary vein region ablation in experimental vagal atrial fibrillation: role of pulmonary veins versus autonomic ganglia.

Background: Pulmonary vein (PV) -encircling radiofrequency ablation frequently is effective in vagal atrial fibrillation (AF), and there is evidence that PVs may be particularly prone to cholinergically induced arrhythmia mechanisms. However, PV ablation procedures also can affect intracardiac autonomic ganglia. The present study examined the relative role of PVs versus peri-PV autonomic ganglia in an experimental vagal AF model.

Adrenergic control of a constitutively active acetylcholine-regulated potassium current in canine atrial cardiomyocytes.

Objectives: Canine atrial cardiomyocytes display a constitutively active, acetylcholine-regulated, time-dependent K+ current (IKH) that contributes to atrial repolarization and atrial tachycardia-induced atrial-fibrillation promotion. Adrenergic stimulation favors atrial arrhythmogenesis but its effects on IKH are poorly understood.

Methods And Results: Adrenergic modulation of IKH was studied in isolated canine atrial cardiomyocytes with whole-cell patch-clamping, and action-potential consequences were assessed in multicellular preparations with fine-tipped microelectrodes.

Induction of heat shock response protects the heart against atrial fibrillation.

There is evidence suggesting that heat shock proteins (HSPs) may protect against clinical atrial fibrillation (AF). We evaluated the effect of HSP induction in an in vitro atrial cell line (HL-1) model of tachycardia remodeling and in tachypaced isolated canine atrial cardiomyocytes. We also evaluated the effect of HSP induction on in vivo AF promotion by atrial tachycardia-induced remodeling in dogs.

Comparison of Ca2+-handling properties of canine pulmonary vein and left atrial cardiomyocytes.

Cardiac tissue in the pulmonary vein sleeves plays an important role in clinical atrial fibrillation. Mechanisms leading to pulmonary vein activity in atrial fibrillation remain unclear. Indirect experimental evidence points to pulmonary vein Ca(2+) handling as a potential culprit, but there are no direct studies of pulmonary vein cardiomyocyte Ca(2+) handling in the literature.

Kir3-based inward rectifier potassium current: potential role in atrial tachycardia remodeling effects on atrial repolarization and arrhythmias.

Background: We previously characterized a novel K+ current (IKH) with properties of constitutively active acetylcholine-related current in dog atrium. I(KH) is sensitive to tertiapin-Q (IC50 approximately 10 nmol/L), a highly selective Kir3 current blocker. This study assessed the role of IKH in atrial tachycardia (AT)-remodeled canine left atrium (LA) with the use of tertiapin-Q as a probe.

Characterization of the in vivo and in vitro electrophysiological effects of the novel antiarrhythmic agent AZD7009 in atrial and ventricular tissue of the dog.

This study evaluated the effects of the novel antiarrhythmic agent AZD7009 on atrial and ventricular repolarization and on the Na+-current system, using Vmax as an index. Anesthetized dogs were infused with AZD7009 or azimilide to produce three pseudo steady-state plasma concentrations in vivo. Microelectrode techniques were used to record action potentials and effective refractory period (ERP) in vitro.

Atrial tachycardia remodeling of pulmonary vein cardiomyocytes: comparison with left atrium and potential relation to arrhythmogenesis.

Background: The pulmonary veins (PVs) are important in the pathophysiology of atrial fibrillation (AF), as is atrial tachycardia (AT) remodeling. The relative importance of AT remodeling in PVs versus other atrial sites is unknown. The present study assessed AT-induced cellular changes in PVs versus left atrium (LA) and their relationship to arrhythmogenesis.

Characterization of a hyperpolarization-activated time-dependent potassium current in canine cardiomyocytes from pulmonary vein myocardial sleeves and left atrium.

Cardiomyocytes from the pulmonary vein sleeves (PVs) are known to play an important role in atrial fibrillation. PVs have been shown to exhibit time-dependent hyperpolarization-induced inward currents of uncertain nature. We observed a time-dependent K(+) current upon hyperpolarization of PV and left atrial (LA) cardiomyocytes (I(KH)) and characterized its biophysical and pharmacological properties.

Cellular electrophysiology of canine pulmonary vein cardiomyocytes: action potential and ionic current properties.

Pulmonary vein (PV) cardiomyocytes play an important role in atrial fibrillation; however, little is known about their specific cellular electrophysiological properties. We applied standard microelectrode recording and whole-cell patch-clamp to evaluate action potentials and ionic currents in canine PVs and left atrium (LA) free wall. Resting membrane potential (RMP) averaged -66 +/- 1 mV in PVs and -74 +/- 1 mV in LA (P < 0.