684 research outputs found
Rapid and MR-Independent IK1 activation by aldosterone during ischemia-reperfusion
In ST elevation myocardial infarction (STEMI) context, clinical studies have shown the deleterious
effect of high aldosterone levels on ventricular arrhythmia occurrence and cardiac
mortality. Previous in vitro reports showed that during ischemia-reperfusion, aldosterone
modulates K+ currents involved in the holding of the resting membrane potential (RMP).
The aim of this study was to assess the electrophysiological impact of aldosterone on IK1
current during myocardial ischemia-reperfusion. We used an in vitro model of “border zone”
using right rabbit ventricle and standard microelectrode technique followed by cell-attached
recordings from freshly isolated rabbit ventricular cardiomyocytes. In microelectrode experiments,
aldosterone (10 and 100 nmol/L, n=7 respectively) increased the action potential
duration (APD) dispersion at 90% between ischemic and normoxic zones (from 95±4ms to
116±6 ms and 127±5 ms respectively, P<0.05) and reperfusion-induced sustained premature
ventricular contractions occurrence (from 2/12 to 5/7 preparations, P<0.05). Conversely,
potassium canrenoate 100 nmol/L and RU 28318 1 ÎĽmol/l alone did not affect AP
parameters and premature ventricular contractions occurrence (except Vmax which was
decreased by potassium canrenoate during simulated-ischemia). Furthermore, aldosterone
induced a RMP hyperpolarization, evoking an implication of a K+ current involved in the
holding of the RMP. Cell-attached recordings showed that aldosterone 10 nmol/L quickly
activated (within 6.2±0.4 min) a 30 pS K+-selective current, inward rectifier, with pharmacological
and biophysical properties consistent with the IK1 current (NPo =1.9±0.4 in control vs
NPo=3.0±0.4, n=10, P<0.05). These deleterious effects persisted in presence of RU 28318,
a specific MR antagonist, and were successfully prevented by potassium canrenoate, a non
specific MR antagonist, in both microelectrode and patch-clamp recordings, thus indicating
a MR-independent IK1 activation. In this ischemia-reperfusion context, aldosterone induced
rapid and MR-independent deleterious effects including an arrhythmia substrate (increased
APD90 dispersion) and triggered activities (increased premature ventricular contractions
occurrence on reperfusion) possibly related to direct IK1 activation
Formation of fractal structure in many-body systems with attractive power-law potentials
We study the formation of fractal structure in one-dimensional many-body
systems with attractive power-law potentials. Numerical analysis shows that the
range of the index of the power for which fractal structure emerges is limited.
Dependence of the growth rate on wavenumber and power-index is obtained by
linear analysis of the collisionless Boltzmann equation, which supports the
numerical results.Comment: accepted by PR
Autonomous Extraction of Millimeter-scale Deformation in InSAR Time Series Using Deep Learning
Systematic characterization of slip behaviours on active faults is key to
unraveling the physics of tectonic faulting and the interplay between slow and
fast earthquakes. Interferometric Synthetic Aperture Radar (InSAR), by enabling
measurement of ground deformation at a global scale every few days, may hold
the key to those interactions. However, atmospheric propagation delays often
exceed ground deformation of interest despite state-of-the art processing, and
thus InSAR analysis requires expert interpretation and a priori knowledge of
fault systems, precluding global investigations of deformation dynamics. Here
we show that a deep auto-encoder architecture tailored to untangle ground
deformation from noise in InSAR time series autonomously extracts deformation
signals, without prior knowledge of a fault's location or slip behaviour.
Applied to InSAR data over the North Anatolian Fault, our method reaches 2 mm
detection, revealing a slow earthquake twice as extensive as previously
recognized. We further explore the generalization of our approach to
inflation/deflation-induced deformation, applying the same methodology to the
geothermal field of Coso, California
L-Grassf: A New Model for Simulating the Genetic Environment Interactions on the Reproductive Phenology of Grasses
Predicting the reproductive phenology in perennial grasses is a major concern because it determines the quantity and quality of forage. It varies a lot depending on site, year and cultivar. Projections of future climates suggest significant changes in seasonal temperature pattern, with new combinations of temperature and photoperiod, whose consequences on the floral induction of perennial grasses are unknown. L-GrassF is a new Functional Structural Plant Model simulating genetic variability of the phenology of perennial ryegrass in order to better understand the perenniality of grasslands and better anticipate the effects of climate change. L-GrassF stems from a previous model (L-Grass) and now simulates the reproductive stages by integrating the interactions between vegetative growth, floral induction and reproductive organ development. The sensitivity analysis of a set of parameters was studied in the range of oceanic temperate climate conditions, on several European cultivars. It was further calibrated and validated on two independent datasets from the French Variety and Seed Study and Control Group (GEVES), which include the observations of heading dates for seven cultivars of Lolium perenne grown in six French locations between 2001 and 2017
Electron-impact ionization of atomic hydrogen at 2 eV above threshold
The convergent close-coupling method is applied to the calculation of fully
differential cross sections for ionization of atomic hydrogen by 15.6 eV
electrons. We find that even at this low energy the method is able to yield
predictive results with small uncertainty. As a consequence we suspect that the
experimental normalization at this energy is approximately a factor of two too
high.Comment: 10 page
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