The Antiarrhythmic Action of the Na/Ca Exchanger Inhibitor SEA0400 on Drug-Induced Long QT Syndrome Depends on the Severity of Proarrhythmic Conditions in Anesthetized Atrioventricular Block Rabbits.

To clarify the pharmacological properties of the Na/Ca exchanger (NCX) inhibitor SEA0400 as an antiarrhythmic agent, we assessed its effects on rapid component of delayed rectifier K current (I) blocker-induced torsade de pointes (TdP) in isoflurane-anesthetized rabbits. Atrioventricular block was induced in rabbits using a catheter ablation technique, and the monophasic action potential (MAP) of the right ventricle was measured under electrical pacing at 60 beats/min. In non-treated control animals, intravenous administration of low-dose (0.

Role of cardiac α-adrenoreceptors for the torsadogenic action of I blocker nifekalant in the anesthetized atrioventricular block rabbit.

We analyzed role of cardiac α-adrenoreceptors for the torsadogenic action of I blocker nifekalant in isoflurane-anesthetized atrioventricular block rabbits. Bradycardia was induced by atrioventricular node ablation, and the ventricle was electrically driven at a constant rate of 60 beats/min throughout the experiments to prevent rate-dependent modification by the I blocker in ventricular repolarization phase. Nifekalant (3 mg/kg per 10 min, n = 5) prolonged the duration of monophasic action potential (MAP) by +178 ± 43 ms, increased the short-term variability of repolarization (STV) to 4.

The anaesthetized rabbit with acute atrioventricular block provides a new model for detecting drug-induced Torsade de Pointes.

Background And Purpose: Several rabbit proarrhythmia models have been developed using genetic or pharmacological methods to suppress the slow component of delayed rectifier K currents in the ventricle, leading to reduction of the repolarization reserve. Here we have characterized a novel rabbit in vivo proarrhythmia model with severe bradycardia caused by acute atrioventricular block (AVB).

Experimental Approach: Bradycardia was induced in isoflurane-anaesthetized rabbits by inducing AVB with catheter ablation, and the ventricle was electrically driven at 60 beats min throughout the experiment except when extrasystoles appeared.

Quantitative Mass Density Image Reconstructed from the Complex X-Ray Refractive Index.

We demonstrate a new analytical X-ray computed tomography technique for visualizing and quantifying the mass density of materials comprised of low atomic number elements with unknown atomic ratios. The mass density was obtained from the experimentally observed ratio of the imaginary and real parts of the complex X-ray refractive index. An empirical linear relationship between the X-ray mass attenuation coefficient of the materials and X-ray energy was found for X-ray energies between 8 keV and 30 keV.

Scanning hard x-ray differential phase contrast imaging with a double wedge absorber.

Two-directional differential phase contrast images were measured using an x-ray microbeam and a double wedge absorber. The wedge absorber converts the displacement of an x-ray beam that is refracted by an object into change of x-ray intensity. The double wedge absorber made it possible to detect values of two-directional refraction angle with microrad sensitivity simultaneously.

In situ observation of water distribution and behaviour in a polymer electrolyte fuel cell by synchrotron X-ray imaging.

In situ visualization of the distribution and behaviour of water in a polymer electrolyte fuel cell during power generation has been demonstrated using a synchrotron X-ray imaging technique. Images were recorded using a CCD detector combined with a scintillator (Gd(2)O(2)S:Tb) and relay lens system, which were placed at 2.0 m or 2.

Three-dimensional visualization of the inner structure of single crystals by step-scanning white X-ray section topography.

Visualization of the three-dimensional distribution of the crystal defects of large single crystals of calcium fluoride has been demonstrated by white X-ray section topography using sheet-like X-rays (BL28B2 at SPring-8). An image of the three-dimensional distribution of the crystal defects was reconstructed by stacking section topographs, which expressed the images of cross sections of the sample. The section topographs were recorded using a CMOS flat-panel imager or a CCD detector combined with scintillator (Gd(2)O(2)S:Tb) and relay lens system.

Silica films with a single-crystalline mesoporous structure.

Films of mesoporous materials attract broad interest because of their wide applicability in the fields of optics and electronics. Although many of these films have a regular local porous structure, the structural regularity has not been used practically yet because of difficulties in its control on macroscopic scales. Here, we demonstrate the preparation of mesoporous silica films whose porous structure can be described as a single crystal, that is, a long-range order of cage-like pores is maintained over centimetre scales.