Транспорт органических анионов в клетках корня и его роль в процессах клеточной сигнализации у высших растений

The organic anion balance is critical for metabolic, bioenergetic, and electrochemical processes in plant cells, controlling the quality and quantity of yield and plant stress resistance. Nevertheless, the redistribution and membrane transport of these substances in plant tissues have not been investigated in detail. The mechanism of passive anion efflux from a plant cell through the ion channels has not been established so far. Here, using the patch-clamp technique, we have characterized the ion channel-mediated conductances of ascorbate, malate, gluconate, citrate, fumarate, and pronionate in the root cells of Arabidopsis thaliana, Triticum aestivum, and Helianthus annuus. These conductances showed high permeability to ascorbate, malate, and citrate, as well as low permeability to fumarate, propionate, and gluconate. Anion channel conductances of root cells showed rapid activation kinetics and low potential dependence. They were also inhibited by 9-anthracenecarboxylic acid, suggesting that they belong to the ALMT family of anion channels found only in higher plants. Aequorin chemilu minometry was used to test the effect of organic anions on the Ca2+ signaling in root cells. Among four organic anions tested, only ascorbate induced a significant increase in the cytosolic Ca2+ activity at physiological levels (1 and 10 mM). This effect may underlie the previously unknown functions of exogenous ascorbate related to short- and long-distance signaling in higher plants.Обмен органических анионов имеет большое значение для метаболических, биоэнергетических и электрохимических процессов в растительной клетке, напрямую влияя на качественные и количественные показатели продуктивности, а также реакции стрессоустойчивости у высших растений. Тем не менее, процессы перераспределения и мембранного транспорта данных веществ в тканях растений пока исследованы крайне недостаточно, в частности, до сих пор не установлены механизмы выхода анионов из клетки так называемым пассивным путем, т. е. посредством ионных каналов. В настоящей работе с использованием метода локальной фиксации потенциала (Patch-Clamp) впервые выявлены и детально охарактеризованы анионные каналы клеток корня Arabidоpsis thaliаna, Triticum aestivum, Helianthus annuus, опосредующие выходящий поток важнейших органических анионов, таких как аскорбат, малат, глюконат, цитрат, фумарат и пропионат. Установлено, что данные транспортные системы обладают высокой проницаемостью для аскорбата, малата и цитрата, одновременно демонстрируя низкую проницаемость для фумарата, пропионата и глюконата. Анионные каналы клеток корня имеют быструю кинетику активации и низкую потенциал-зависимость, они также ингибируются 9-антраценкарбоновой кислотой, что указывает на их возможную принадлежность к семейству ионных каналов ALMT, которое существует только у высших растений. С использованием эквориновой хемилюминометрии протестировано воздействие органических анионов на процессы Са2+- сигнализации в корне, в результате чего показано, что аскорбат способен индуцировать повышение уровня цитоплазматической активности Са2+. Данный эффект может лежать в основе ранее неизвестных функций экзогенного аскорбата, связанных с обеспечением реакций ближней и дальней сигнализации у высших растений

Machine Learning Techniques for the Detection of Shockable Rhythms in Automated External Defibrillators

Early recognition of ventricular fibrillation (VF) and electrical therapy are key for the survivalof out-of-hospital cardiac arrest (OHCA) patients treated with automated external defibrilla-tors (AED). AED algorithms for VF-detection are customarily assessed using Holter record-ings from public electrocardiogram (ECG) databases, which may be different from the ECGseen during OHCA events. This study evaluates VF-detection using data from both OHCApatients and public Holter recordings. ECG-segments of 4-s and 8-s duration were ana-lyzed. For each segment 30 features were computed and fed to state of the art machinelearning (ML) algorithms. ML-algorithms with built-in feature selection capabilities wereused to determine the optimal feature subsets for both databases. Patient-wise bootstraptechniques were used to evaluate algorithm performance in terms of sensitivity (Se), speci-ficity (Sp) and balanced error rate (BER). Performance was significantly better for publicdata with a mean Se of 96.6%, Sp of 98.8% and BER 2.2% compared to a mean Se of94.7%, Sp of 96.5% and BER 4.4% for OHCA data. OHCA data required two times morefeatures than the data from public databases for an accurate detection (6 vs 3). No signifi-cant differences in performance were found for different segment lengths, the BER differ-ences were below 0.5-points in all cases. Our results show that VF-detection is morechallenging for OHCA data than for data from public databases, and that accurate VF-detection is possible with segments as short as 4-s

Systematic computation of nonlinear cellular and molecular dynamics with low-power cytomimetic circuits: a simulation study

This paper presents a novel method for the systematic implementation of low-power microelectronic circuits aimed at computing nonlinear cellular and molecular dynamics. The method proposed is based on the Nonlinear Bernoulli Cell Formalism (NBCF), an advanced mathematical framework stemming from the Bernoulli Cell Formalism (BCF) originally exploited for the modular synthesis and analysis of linear, time-invariant, high dynamic range, logarithmic filters. Our approach identifies and exploits the striking similarities existing between the NBCF and coupled nonlinear ordinary differential equations (ODEs) typically appearing in models of naturally encountered biochemical systems. The resulting continuous-time, continuous-value, low-power CytoMimetic electronic circuits succeed in simulating fast and with good accuracy cellular and molecular dynamics. The application of the method is illustrated by synthesising for the first time microelectronic CytoMimetic topologies which simulate successfully: 1) a nonlinear intracellular calcium oscillations model for several Hill coefficient values and 2) a gene-protein regulatory system model. The dynamic behaviours generated by the proposed CytoMimetic circuits are compared and found to be in very good agreement with their biological counterparts. The circuits exploit the exponential law codifying the low-power subthreshold operation regime and have been simulated with realistic parameters from a commercially available CMOS process. They occupy an area of a fraction of a square-millimetre, while consuming between 1 and 12 microwatts of power. Simulations of fabrication-related variability results are also presente