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A MODIFIED MATHEMATICAL MODEL OF HUMAN VENTRICULAR CARDIOMYOCYTE INCORPORATING SEPARATE T-TUBULAR AND SURFACE DYADS AND SUBMEMBRANE SPACES
Pásek, Michal ; Bébarová, M. ; Christé, G.
Intracellular Ca2+ load and Ca2+ transient are considerably dependent on distribution of sarcolemmal Ca2+ pump and Na+-Ca2+ exchanger between the t-tubular and surface membranes in the presence of separate dyadic and subsarcolemmal spaces in rat ventricular cell model. To explore analogical phenomenon in human, we modified our previously published model of human ventricular myocyte. When the t-tubular fractions of Na+-Ca2+ exchanger and of sarcolemmal Ca2+ pump were increased to the newly proposed value of 0.95 in the modified model, the following changes were observed at 1 Hz steady-state stimulation: a shortening of the action potential duration at 90% repolarisation by 6% and an increase of the cytosolic Ca2+ transient by 22%. Further analysis revealed a critical role of Ca2+ concentration changes in the subsarcolemmal spaces and consequent change in cellular Ca2+ cycling in this effect.
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Sensitivity of action potential to changes of inward rectifier potassium current IK1 is different in recent models of human ventricular cardiomyocytes
Pásek, Michal ; Šimurda, J. ; Christé, G.
The inwardly rectifying potassium current IK1 is one of the principle ionic currents responsible for repolarization phase of mammalian action potentials (APs). To estimate the impact of individual ionic currents on AP configuration, mathematical models have been widely used. In this study, we compared the effects of alcohol-induced changes of IK1 on AP duration (APD) as simulated in four recently published computer models of human ventricular cells. As expected, increasing or decreasing IK1 conductance by 20% respectively caused a shortening or a lengthening of APD. However, the effect was largely model-dependent, ranging from 1% to about 15% change of APD. Given the conflicting available experimental data on the features of IK1 in human ventricular myocytes there is a need for a set of well-established end-point constraints for a reliable human ventricular myocyte model to be generated.
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Physiological consequences of ion concentration changes in transverse-axial tubular system in a model of human ventricular cardiomyocyte
Ohlidalova, D. ; Pásek, Michal ; Šimurda, J. ; Christé, G.
A mathematical model of human ventricular cell incorporating the transverse axial tubular system (TATS) was designed and used to explore the role of TATS in human ventricular cell electrophysiological activity. The model is based on the latest quantitative description of guinea pig ventricular cell electrophysiology and modified to respect the published data obtained from human cardiac preparations. Computer simulations suggest that significant transient depletions of Ca2+ ions and accumulation of K+ ions may occur in the human TATS. The preliminary analysis of the effects of tubular Ca2+depletions on the activity of the model cell indicates their role in limitation of intracellular Ca2+ overload at higher frequencies of stimulation.
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Inženýrská mechanika
Fuis, Vladimír ; Pásek, Michal
Cílem v pořadí již 14. konference je získat přehled současného stavu rozvoje mechaniky těles, mechaniky tekutin a termodynamiky, zejména ve vztahu k projektům řešeným v České republice.
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