Search

The article titled "Bioelectricity in multicellular aggregates of non-excitable cells: biophysical models" explores the interrelation between bioelectric and biochemical signals in the processes of organization and regeneration in multicellular aggregates. Biophysical models and experiments with model biosystems suggest that bioelectric signals, such as membrane potential, are involved in the organization of these aggregates. Additionally, it discusses how proteins inserted in the cell membrane, such as ion channels and intercellular junctions, influence bioelectric patterns and gene expression. The article proposes a biophysical model that focuses on the collective coupling between bioelectricity and gene transcription. The importance of identifying instructive multicellular patterns and studying the correction of aberrant morphologies through actions on channel conductances and junctions is raised. It also mentions the possibility of influencing epigenetic barriers through intercellular coupling and interventions based on endogenous bioelectric magnitudes. [Extracted from the article]

Copyright of Revista Argentina de Cardiología is the property of Sociedad Argentina de Cardiologia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the context of the current COVID-19 epidemic, numerous are the manifestations of the infected patients, including the alterations in the 12-lead electrocardiogram, where the presence of a J-wave can be found, secondary to the generation of a transmural voltage gradient, caused by the overexpression of the channels for transient outward potassium current (Ito), in the context of a severe infection with extensive myocardial injury. In this article is presented the case of an 83-year-old patient with a positive diagnosis of COVID-19, who progressed to septic shock, with mixed acidosis and mild hyperkalemia. The electrocardiogram showed the presence of a Jwave, probably secondary to the effect of pro-inflammatory cytokines on potassium channels and extensive areas of myocardial injury. [ABSTRACT FROM AUTHOR]

Copyright of Revista Facultad de Medicina de la Universidad Nacional de Colombia is the property of Universidad Nacional de Colombia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

CaCCs are proteins forming pores located in the cell membrane. The CaCCs allow exchange of ions through the membrane, which is key for an adequate cellular function and for the development of some diseases. The purpose of this work is to provide a review of the physio-pathological role of the CaCC. We reviewed literature from the US National Library of Medicine-PubMed.gov. Our results indicate that in spite of the fundamental role of CaCCs for developing chronic diseases, in our country little research and dissemination is done in the field. [ABSTRACT FROM AUTHOR]

Copyright of Revista Argentina de Cardiología is the property of Sociedad Argentina de Cardiologia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Revista de la Academia Colombiana de Ciencias Exactas, Físicas y Naturales is the property of Academia Colombiana de Ciencias Exactas, Fisicas y Naturales and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Hodgkin and Huxley's works were the starting point to generating mathematical models for explain, reproduce the experimental results and predict the behavior of voltage-sensitive ion channels in the axon. The high costs of these experiments avoid its implementation in teaching degree. An educational alternative is virtual experiments using computer simulations. In this work the development of a simulator that reproduces step by step the classic experiments of Hodgkin and Huxley on the conductance of voltage-dependent channels in squid giant axon is presented. The simulator was developed in Visual Basic language, ver 5.0 for Windows environment. It consists of four modules: (1) ionic currents simulation; (2) classical Hodgkin and Huxley's experiments; (3) current version model; (4) action potentials. It comprises connecting interface screens that allow simulate and compute the values of the variables associated with the channel conductance. The user can perform an unlimited number of virtual experiments that will facilitate the understanding of the subject. [ABSTRACT FROM AUTHOR]

Copyright of Medicina (Buenos Aires) is the property of Medicina (Buenos Aires) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The Andersen-Tawil syndrome is a cardiac ion channel disease that is inherited in an autosomal dominant way and is classified as type 7 of the congenital long QT syndromes. Affected gene is KCNJ2, which forms the inward rectifier potassium channel designated Kir2.1. This protein is involved in stabilizing the resting membrane potential and controls the duration of the action potential in skeletal muscle and heart. It also participates in the terminal repolarization phase of the action potential in ventricular myocytes and is a major component responsible for the correction in the potassium current during phase 3 of the action potential repolarization. Kir 2.1 channel has a predominant role in skeletal muscle, heart and brain. Alterations in this channel produce flaccid paralysis, arrhythmias, impaired skeletal development primarily in extremities and facial area. In this review we address the disease from the point of view of clinical and molecular diagnosis with emphasis on cardiac manifestations. [ABSTRACT FROM AUTHOR]

Objective: its demostrate, through theoretical analysis, that the physiological concept principle "all or none" that applies to excitable cells, is inadequate and contradictory phrase, because it lends itself to misinterpretation and electrostatic phenomenon blurs the channels underlying of voltage-gated Na+ (Nav). Discussion: The segments voltage sensors S4 of Na+ channels present arginine residues with positive charge, which interact with the internal environment and generate electric repulsion caused by the pore opening of the channel through which enters the sodium ions and depolarize membrane. As above occurs only when the membrane reaches a threshold level, then, the phrase "all or nothing" principle, in physiology classic texts and indexed journals is contradictory and meaningless. Conclusion: Since it is a purely electrical phenomenon which is triggered when the excitable cell membrane reaches a fair variation of voltage (threshold level), we propose that rather than continue to use the traditional phrase "all or nothing" principle, is used the phrase "electrostatic effect", to be more consistent with the molecular and electrical events that actually occur in the excitable membrane. [ABSTRACT FROM AUTHOR]

Mitochondria play an important role in energy metabolism within the cell. Also are known to be intimately involved in the processes that lead to cell death following reperfusion, in both necrotic and apoptotic forms of cell death, and so are potential targets for protective interventions. In this review, we consider several aspect of mitochondrial function that we believe to be possible targets for myocardial protection; namely, roles of the mitochondrial ion channels in the heart with particular emphasis on cardioprotection against ischemia/reperfusion injury, mitochondrial Ca2+ transport, the permeability transition pore, and improved mitochondrial substrate supply. These protective processes are activated by signaling pathways, which converge on mitochondria; these pathways can also be stimulated by pharmacological treatments like some anesthetics with cardioprotective effects. Finally, we describe how improved understanding of the aspects of mitochondrial function may lead to better protective strategies in the future. [ABSTRACT FROM AUTHOR]

Our objective is the calculation of the plasma electrical charge in major burn patients, by means of a computer programme focussed on predicting patient mortality. The PICAL computer software (own development) starts off with the objective of calculating the plasmatic charge and the influence of ions and proteins applied to 143 patients in the Major Burn Patient Unit in the Unfallkrankenhaus Hospital in Berlin (Germany). A statistical study is carried out to define patient mortality once the previous calculations have been performed, considering: 1) their biochemical parameters in the first 48 hours, 2) their clinical factors: age, total burned surface area, depth of the burn, presence of inhalation syndrome, etc. A logistic regression analysis was made using these data calculating the mortality predictive function, which was validated by a group of 35 new patients. The importance of each plasmatic ion and proteins was calculated in the electrical balance of the patients with major burns. Age, burned surface area, pH and [Mg2+] were introduced for the study of mortality in these patients via statistical analysis. From the study it was confirmed that anions [HCO3-] and [Cl ], together with cation [Na+] are the ions with most influence on the plasmatic balance of major burn patients. Protein concentration has a lower incidence on this balance: a loss of 50% in albumin concentration during the first 48 hours is equivalent to a loss of 1 mmol/l in the [HCO3-] concentration. It can also be stated that the use of parameters pH and [Mg2+] can improve mortality prediction in these patients. [ABSTRACT FROM AUTHOR]

Copyright of Médicas UIS is the property of Universidad Industrial de Santander and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Estrogen exerts pleiotropic functions on the cardiovascular system through binding to estrogen receptors (ERs). Traditionally, ERs have been recognized as transcription factors regulating the expression of target genes. In the past decades, however, numerous studies have revealed rapid actions of estrogen in different systems, especially in non-reproductive tissues such as the cardiovascular system. At this level, estrogen triggers rapid vasodilatation, exerts anti-inflammatory effects, regulates vascular cell growth and migration, and confers protection to cardiomyocytes. These so-called 'extranuclear actions' do not require gene expression or protein synthesis and are independent of the nuclear localization of ERs. Indeed, some of these actions are elicited by ERs residing at or near the plasma membrane. Through complex interactions with membrane-associated signaling molecules such as ion channels, G proteins and the tyrosine kinase c-Src, liganded extra-nuclear ERs lead to the activation of downstream cascades such as mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3-OH kinase (PI3K). These cascades are responsible for important cardiovascular actions of estrogen, for instance, the activation of nitric oxide synthesis or the remodeling of the endothelial actin cytoskeleton. Moreover, these cascades play crucial roles in regulating the expression of target proteins implicated in cell proliferation, apoptosis, differentiation, movement and homeostasis. Recent advancements in the characterization of the molecular basis of the extranuclear signaling of estrogen help us to understand the biological functions of estrogen and would be beneficial in elucidating current controversies on estrogen's clinical efficacy in the cardiovascular system. [ABSTRACT FROM AUTHOR]

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a cardiac channelopathy characterized by altered intracellular calcium handling resulting in ventricular arrhythmias and high risk of cardiac sudden death in young cases with normal structural hearts. Patients present with exertional syncope and the trademark dysrhythmia is polymorphic and/or bidirectional ventricular tachycardia during exercise or adrenergic stimulation. Early detection of CPVT is crucial because opportune medical intervention prevents sudden cardiac death. Mutations in the ryanodine receptor RYR2 explain nearly 70% of the CPVT cases and cause the autosomic dominant form of the disease. Mutations in calsequestrin 2 causes a recessive form and explain less than 5% of all cases. Genetic screening in CPVT , besides providing early detection of asymptomatic carriers at risk, has provided important insights in the mechanism underlying the disease. Mutational analysis of RYR2 has been a challenge due to the large size of the gene, 105 exons encoded for 4 967 amino-acids. In this review we analyze general concepts of the disease, differential diagnosis and strategies for genetic screening. [ABSTRACT FROM AUTHOR]

We use brownian dynamics to simulate the ion permeation through Gramicidin A channel and to compute the current through the channel as a function of the applied voltage and the ionic concentration in the media. A new method ia proposed to mantain the ionic concentrations in the intracellular and extracellular media. The current obtained by using a smoothed version of the most recently reported potential mean force profile and a singlefile force proportional to 1/r9 are much smaller than the experimental ones. By using an hypothetical potential mean force profile with one-half the potential barrier reported in the literature we obtained a conductance that differs just in 4.9% of the experimental one, but the channel saturation with concentration increases, observed in experiments, is lost. These difficulties are the same ones that are confronted by all simulations in this area, and they are topic of research at the present time. [ABSTRACT FROM AUTHOR]

We review basic concepts of Markov processes as they are discrete state models with stochastic transitions. We emphasize how to calculate transition probabilities between states and their random variables. Through this paper we discuss how this concepts could be applied to support a mathematical modelling of ionic channels. Channels have several conformational states and they skip from one to another in a non-deterministic fashion, so these techniques may be useful to understand channel behavior. Finally, we detail the mathematical analysis for a two-state model and include some simulations obtained from it. The unitary currents simulated are important since they can be added to obtain the whole-cell macroscopic current, found in excitable cells. [ABSTRACT FROM AUTHOR]

The cell membrane, due to its structure and the diffusion processes between the interior and the exterior of the cell, generates some electrochemical gradients, as certain flows, in certain well-known regions as the ionic channels; many of these particles are ions, that is to say, particles with electric charge. These channels can be interpreted as electric conductors with specific electromagnetic properties. This structure of ionic channels and the two-layered phospholipids, allows us to represent the cell membrane as an RC circuit, the resistance would be referred to the ionic channels, and the condenser to the two-layered phospholipids. We also show the problems of interpretation and analysis that arise when looking at this particular system from the optics of electromagnetism and of the historical processes in the development of the theory of membranes, as an element that brings in itself a new representation and a change in the language used, which generates problems in its understanding and interpretation. [ABSTRACT FROM AUTHOR]

The Gramicidin A is the most studied ion channel, both by theory and experiments. There are many reports in the literature on the potential mean force (PMF) that a cation experiences through the channel. Despite of that, it has not been possible to reproduce correctly the experimental curves of the current as a function of the applied voltage and as a function of the ionic concentration; a difficulty we also confronted in a previous work (C. Aponte et al. (2006) Rev. Col. Fís., 38(4): 1639-1642). Hereby, we explore the possibility of a reduction of the energy barrier at the middle of the channel due to the polarization of the surrounding dielectric media. Our brownian dynamics simulations show a significative increment of the ionic currents, up to the experimental reports, but the saturation in the current with increasing ionic concentrations is still undecided. [ABSTRACT FROM AUTHOR]