Ventricular Action Potential Adaptation to Regular Exercise: Role of β-adrenergic and K\u3csub\u3eATP\u3c/sub\u3e Channel Function

Regular exercise training is known to affect the action potential duration (APD) and improve heart function, but involvement of β-adrenergic receptor (β-AR) subtypes and/or the ATP-sensitive K+ (KATP) channel is unknown. To address this, female and male Sprague-Dawley rats were randomly assigned to voluntary wheel-running or control groups; they were anesthetized after 6–8 wk of training, and myocytes were isolated. Exercise training significantly increased APD of apex and base myocytes at 1 Hz and decreased APD at 10 Hz. Ca2+ transient durations reflected the changes in APD, while Ca2+ transient amplitudes were unaffected by wheel running. The nonselective β-AR agonist isoproterenol shortened the myocyte APD, an effect reduced by wheel running. The isoproterenol-induced shortening of APD was largely reversed by the selective β1-AR blocker atenolol, but not the β2-AR blocker ICI 118,551, providing evidence that wheel running reduced the sensitivity of the β1-AR. At 10 Hz, the KATP channel inhibitor glibenclamide prolonged the myocyte APD more in exercise-trained than control rats, implicating a role for this channel in the exercise-induced APD shortening at 10 Hz. A novel finding of this work was the dual importance of altered β1-AR responsiveness and KATP channel function in the training-induced regulation of APD. Of physiological importance to the beating heart, the reduced response to adrenergic agonists would enhance cardiac contractility at resting rates, where sympathetic drive is low, by prolonging APD and Ca2+ influx; during exercise, an increase in KATP channel activity would shorten APD and, thus, protect the heart against Ca2+ overload or inadequate filling

Ventricular Action Potential Adaptation to Regular Exercise: Role of β-adrenergic and K\u3csub\u3eATP\u3c/sub\u3e Channel Function

Regular exercise training is known to affect the action potential duration (APD) and improve heart function, but involvement of β-adrenergic receptor (β-AR) subtypes and/or the ATP-sensitive K+ (KATP) channel is unknown. To address this, female and male Sprague-Dawley rats were randomly assigned to voluntary wheel-running or control groups; they were anesthetized after 6–8 wk of training, and myocytes were isolated. Exercise training significantly increased APD of apex and base myocytes at 1 Hz and decreased APD at 10 Hz. Ca2+ transient durations reflected the changes in APD, while Ca2+ transient amplitudes were unaffected by wheel running. The nonselective β-AR agonist isoproterenol shortened the myocyte APD, an effect reduced by wheel running. The isoproterenol-induced shortening of APD was largely reversed by the selective β1-AR blocker atenolol, but not the β2-AR blocker ICI 118,551, providing evidence that wheel running reduced the sensitivity of the β1-AR. At 10 Hz, the KATP channel inhibitor glibenclamide prolonged the myocyte APD more in exercise-trained than control rats, implicating a role for this channel in the exercise-induced APD shortening at 10 Hz. A novel finding of this work was the dual importance of altered β1-AR responsiveness and KATP channel function in the training-induced regulation of APD. Of physiological importance to the beating heart, the reduced response to adrenergic agonists would enhance cardiac contractility at resting rates, where sympathetic drive is low, by prolonging APD and Ca2+ influx; during exercise, an increase in KATP channel activity would shorten APD and, thus, protect the heart against Ca2+ overload or inadequate filling

How Leadership Improves Intercultural Negotiation

With the gradual deepening of economic integration, trade cooperation around the world has become more extensive, and the influence of cultural differences in international trade cooperation has become increasingly obvious. It is becoming important to recognize cultural differences, recognize cultural conflicts arising from different cultural backgrounds, and strengthen intercultural coordination and management of collaborators from different cultural backgrounds. This can facilitate the smooth development of intercultural negotiations despite being a challenging task. This paper uses the case study method to study the Rumaila oilfield project of Jichai and BP, and it uses intercultural leadership theory to analyze and summarize the business negotiations of the Rumaila project and the existence of cultural differences. The problems that arise during the negotiation and cooperation process are clarified and the methods for solving the problems are found. It is hoped that through the research in this article, it can have a positive impact on intercultural negotiations and generate some useful enlightenment for future intercultural negotiations. By examining this case study, I hope to delve into an analysis

Electrical and Biomechanical Properties of Rat Ventricular Myocytes: Effect of Exercise-Training & Beta-Adrenergic Regulation

Heart disease is one of the leading causes of morbidity and mortality in the western world, and programs of exercise-training have been shown to ameliorate cardiovascular risk factors and protect against heart diseases. The cellular/molecular mechanisms of regular exercise induced adaptations in the heart remains incomplete. To address this, female and male Sprague-Dawley rats were randomly assigned to exercise trained (TRN) or sedentary (SED) groups. After 6-8 weeks training, ventricular myocytes were isolated and studied.Exercise-training prolonged the action potential duration (APD) in myocytes isolated from apex and base regions at low stimulation rate (1Hz), while shortening the APD at high stimulation (10Hz). The exercise-induced effect on the Ca2+ transient duration reflected the changes observed in APD. Wheel running shifted the β-adrenergic receptor (β-AR) agonist dose-response curve rightward compared to SED by reducing β1-AR responsiveness. Wheel-running significantly increased myocyte shortening velocity and rate of intracellular Ca2+ rise with 1, 2 and 5 Hz stimulation, while the extent of shortening increased only at 5 Hz. At 1 & 2 Hz, β-AR agonist accelerated sarcomere shortening & relaxation velocity and rate of intracellular Ca2+ decline in TRN and SED, but increased sarcomere shortening only in TRN. The β-AR agonist effect was dose dependent in TRN but not SED.Pharmacological studies of myocytes showed higher ATP sensitive potassium channel (KATP) function in ventricular repolarization and larger KATP currents in TRN compared to SED. Exercise-training elevated the KATP channel pore forming protein subunit Kir6.2 content in apex and regulatory protein subunit SUR2A content in base regions of male and female rats. Rapidly activating delayed rectifier potassium channel (Ikr) contributes relatively little to ventricular repolarization compared to slowly activating delayed rectifier potassium channel IKs in both male and female rats, and higher IKs current was observed in apex compared to base region. Exercise-training decreased IKs current as well as the content of IKs channel protein subunits KCNQ1 and KCNE1. β-agonist significantly elevated IKs current density and exercise-training decreased IKs responsiveness to β-AR stimulation.The down-regulation of IKs provides a molecular basis for prolonged APD and Ca2+ transient observed in TRN rats with 1Hz stimulation, which contributes to enhanced cardiac contractility and efficiency at rest. The up-regulation of KATP channel in TRN rats largely explains the exercise-induced APD shortening at 10Hz, which helps reduce the energy consumption and maintain diastolic interval adequate for myocardial relaxation at high heart rates. A novel finding was that exercise-training elevated kinetics of sarcomere shortening/relaxation and its response to β-AR stimulation

Parallel computation using MEMS oscillator-based computing system

In recent years, parallel computing systems such as artificial neural networks (ANNs) have been of great interest. In these systems which emulate the behavior of human brains, the processing is carried out simultaneously. However, it is still a challenging engineering problem to design highly efficient hardware for parallel computing systems. We will study the properties of networks of Microelectromechanical System (MEMS) oscillators to explore their capabilities as parallel computing infrastructure. Furthermore, we simulate the time-variant states of MEMS oscillators network under various initial conditions and performance of certain tasks. Recent theoretical results show that networks of MEMS oscillators have some properties such as phase locking, frequency locking, and synchronization which make the parallel computation possible. We demonstrate how networks of MEMS oscillators can be used for parallel computing in pattern recognition tasks through a series of Jupyter notebooks. The simulations results show that MEMS oscillator networks are able to memorize and recognize multiple patterns as well as perform image convolution with a structure consisting of a multitude of 2-oscillator networks. Hence, MEMS oscillator network is a potential candidate for future embedded computing system to improve computational performance of problems

Mining the Impact of Investor Sentiment on Stock Market from WeChat

In this study, the CSI 300 Index in China mainland and original articles from authoritative stock WeChat public accounts are investigated regarding their relations. First, a sentence-level sentiment classification approach for analyzing investor sentiment polarities in text corpus is proposed by expanding synonyms. Then, the Granger causality test is utilized to examine the impact of sentiment index on the stock price and volume-values. It shows that the influence of overall investor sentiment on volume-values is more rapid than that on stock price and the impact of positive sentiment is found to be more lasting than the negative in both stock price and volume-values. Furthermore, it is worth noting that there is a dual-stage phenomenon in the impact of positive sentiment on volume-values, which indicates that some investors react to positive information immediately while others may choose to wait and follow the trend

Paradoxical constitutive law between donor O-H bond length and its stretching frequency in water dimer

The constitutive laws of hydrogen bonds (H-bonds) are central to understanding microphysical processes not precisely observed, especially in terms of structural properties. Previous experiences in water H-bonding revealed that as the intermolecular O...O distance shortens, the O-H stretching frequency redshifts; thus, an elongated O-H bond length can be empirically inferred, which is described as the constitutive law under the cooperative effect. Here, using the high-precision CCSD(T) method, we report a violation of the conventional constitutive law in water dimer. That is, when the variation in the O...O distance changes from stretching by 0.06 to contracting by -0.15 angstrom compared to the equilibrium position, the donor O-H bond length decreases from 0.9724 to 0.9717 angstrom, and the O-H stretching frequency redshifts from 3715 to 3708 cm-1. Our work highlights that the O-H bond length decreases simultaneously with its stretching frequency, which is clearly inconsistent with the previously recognized constitutive law.Comment: 10 pages, 2 figure