The role of heterogeneities and intercellular coupling in wave propagation in cardiac tissue

2006 ◽  
Vol 364 (1842) ◽  
pp. 1299-1311 ◽  
Author(s):  
Benjamin E Steinberg ◽  
Leon Glass ◽  
Alvin Shrier ◽  
Gil Bub
Keyword(s):  
Wave Propagation ◽  
Plane Wave ◽  
Cardiac Tissue ◽  
Dimensionless Parameter ◽  
Spiral Waves ◽  
Excitable Media ◽  
Intercellular Coupling ◽  
Pathological Conditions ◽  
Linear Decrease

Electrical heterogeneities play a role in the initiation of cardiac arrhythmias. In certain pathological conditions such as ischaemia, current sinks can develop in the diseased cardiac tissue. In this study, we investigate the effects of changing the amount of heterogeneity and intercellular coupling on wavefront stability in a cardiac cell culture system and a mathematical model of excitable media. In both systems, we observe three types of behaviour: plane wave propagation without breakup, plane wave breakup into spiral waves and plane wave block. In the theoretical model, we observe a linear decrease in propagation velocity as the number of heterogeneities is increased, followed by a rapid, nonlinear decrease to zero. The linear decrease results from the heterogeneities acting independently on the wavefront. A general scaling argument that considers the degree of system heterogeneity and the properties of the excitable medium is used to derive a dimensionless parameter that describes the interaction of the wavefront with the heterogeneities.

Identification of the FitzHugh–Nagumo Model Dynamics via Deterministic Learning

2015 ◽  
Vol 25 (12) ◽  
pp. 1550159 ◽  
Author(s):  
Xunde Dong ◽  
Cong Wang
Keyword(s):  
Neural Networks ◽  
Simple Model ◽  
Differential Equations ◽  
Numerical Experiments ◽  
Cardiac Tissue ◽  
Spiral Waves ◽  
Excitable Media ◽  
Deterministic Learning ◽  
Spatial Point ◽  
Model Dynamics

In this paper, a new method is proposed for the identification of the FitzHugh–Nagumo (FHN) model dynamics via deterministic learning. The FHN model is a classic and simple model for studying spiral waves in excitable media, such as the cardiac tissue, biological neural networks. Firstly, the FHN model described by partial differential equations (PDEs) is transformed into a set of ordinary differential equations (ODEs) by using finite difference method. Secondly, the dynamics of the ODEs is identified using the deterministic learning theory. It is shown that, for the spiral waves generated by the FHN model, the dynamics underlying the recurrent trajectory corresponding to any spatial point can be accurately identified by using the proposed approach. Numerical experiments are included to demonstrate the effectiveness of the proposed method.

MECHANISM OF ACOUSTIC WAVE PROPAGATION: A REAL ROLE OF VIRTUAL SOURCES

2001 ◽  
Vol 09 (03) ◽  
pp. 719-730 ◽  
Author(s):  
HENRYK LASOTA
Keyword(s):  
Wave Propagation ◽  
Acoustic Wave ◽  
Plane Wave ◽  
Formal Proof ◽  
Equal Weight ◽  
Acoustic Wave Propagation ◽  
Dirac Delta ◽  
Delta Distribution ◽  
Mechanical Waves

The Huygens problem of self-regeneration of the acoustic wave crossing a liquid medium is discussed in the paper. Equal weight of both elastic and kinetic aspects of mechanical waves in fluids is stressed. Two types of virtual surface sources are defined, reflecting local action of the pressure and particle velocity, respectively. They are applied by the author in calculations of secondary radiation from the wave front of the plane wave. The Dirac delta impulse has been used as a waveform, the wave thus being reduced to its own front. The results have been obtained analytically, thanks to some particularly "friendly" features of the operation of convolution with the delta distribution. The paper gives formal proof to Fresnel's intuitive explanation of the mechanism of the forward-only propagation of the wave with no backward effects.

SUPEREXCITABILITY INDUCED SPIRAL BREAKUP IN EXCITABLE SYSTEMS

1996 ◽  
Vol 06 (09) ◽  
pp. 1753-1759 ◽  
Author(s):  
A. GIAQUINTA ◽  
S. BOCCALETTI ◽  
F.T. ARECCHI
Keyword(s):  
Wave Propagation ◽  
Diffusion Mechanism ◽  
Reaction Diffusion ◽  
Cardiac Cells ◽  
Excitable Media ◽  
Threshold Dynamics ◽  
Cardiac Tissues ◽  
Breakup Mechanism ◽  
Excitable Systems

We introduce a 2D coupled map lattice model which, besides simulating the two variable FitzHugh–Nagumo reaction diffusion mechanism, accounts also for a superexcitable period. Superexcitability in the threshold dynamics of excitable media has been recently observed in experiments on cardiac tissues. By this model, we can reproduce the transition from normal cardiac behavior toward fibrillating processes in a 2D assembly of cardiac cells. The role of superexcitability results in producing two states of wave propagation and a spiral breakup mechanism in qualitative agreement with the experimental evidence of coarse and fine fibrillation in human hearts.

Turbulent electrical activity at sharp-edged inexcitable obstacles in a model for human cardiac tissue

2014 ◽  
Vol 307 (7) ◽  
pp. H1024-H1035 ◽  
Author(s):  
Rupamanjari Majumder ◽  
Rahul Pandit ◽  
A. V. Panfilov
Keyword(s):  
Wave Propagation ◽  
Cardiac Tissue ◽  
Spiral Wave ◽  
Spiral Waves ◽  
Delayed Rectifier ◽  
High Frequency Stimulation ◽  
Secondary Importance ◽  
Ionic Model ◽  
Delayed Rectifier Current ◽  
Human Cardiac Tissue

Wave propagation around various geometric expansions, structures, and obstacles in cardiac tissue may result in the formation of unidirectional block of wave propagation and the onset of reentrant arrhythmias in the heart. Therefore, we investigated the conditions under which reentrant spiral waves can be generated by high-frequency stimulation at sharp-edged obstacles in the ten Tusscher-Noble-Noble-Panfilov (TNNP) ionic model for human cardiac tissue. We show that, in a large range of parameters that account for the conductance of major inward and outward ionic currents of the model [fast inward Na+ current ( INa), L—type slow inward Ca2+ current ( ICaL), slow delayed-rectifier current ( IKs), rapid delayed-rectifier current ( IKr), inward rectifier K+ current ( IK1)], the critical period necessary for spiral formation is close to the period of a spiral wave rotating in the same tissue. We also show that there is a minimal size of the obstacle for which formation of spirals is possible; this size is ∼2.5 cm and decreases with a decrease in the excitability of cardiac tissue. We show that other factors, such as the obstacle thickness and direction of wave propagation in relation to the obstacle, are of secondary importance and affect the conditions for spiral wave initiation only slightly. We also perform studies for obstacle shapes derived from experimental measurements of infarction scars and show that the formation of spiral waves there is facilitated by tissue remodeling around it. Overall, we demonstrate that the formation of reentrant sources around inexcitable obstacles is a potential mechanism for the onset of cardiac arrhythmias in the presence of a fast heart rate.

Hepatoprotective Role of Berberine on Doxorubicin Induced Hepatotoxicity - Involvement of Cyp

2020 ◽  
Vol 21 (7) ◽  
pp. 541-547
Author(s):  
Bao Sun ◽  
Yue Yang ◽  
Mengzi He ◽  
Yanan Jin ◽  
Xiaoyu Cao ◽  
...  
Keyword(s):  
Drug Metabolism ◽  
Cardiac Tissue ◽  
Liver Toxicity ◽  
Elevated Serum ◽  
Similar Response ◽  
Wide Range ◽  
Cytokine Levels ◽  
Major Organ ◽  
Anti Oxidant

Background: The liver is one of the major organ involved in drug metabolism. Cytochrome P450s are predominantly involved in drug metabolism. A wide range of CYPs have been reported in the liver which have been involved in its normal as well as in diseased conditions. Doxorubicin, one of the most potent chemotherapeutic drugs, although highly efficacious, also has adverse side effects, with its targets being liver and cardiac tissue. Objective: The study aims to evaluate the reversal potentials of berberine on Doxorubicin induced cyp conversion. Methodology: In the present study, the interplay between anti-oxidants, cytochrome and inflammatory markers in DOX induced liver toxicity and its possible reversal by berberine was ascertained. Results: DOX administration significantly elevated serum as well as tissue stress, which was reverted by berberine treatment. A similar response was observed in tissue inflammatory mediators as well as in serum cytokine levels. Most profound reduction in the cytochrome expression was found in Cyp 2B1, 2B2, and 2E1. However, 2C1, 2C6, and 3A1 although showed a decline, but it did not revert the expression back to control levels. Conclusion: It could be concluded that berberine may be an efficient anti-oxidant and immune modulator. It possesses low to moderate cytochrome modulatory potentials.

Dietary Carotenoids in Managing Metabolic Syndrome and Role of PPARs in the Process

2020 ◽  
Vol 16 (6) ◽  
pp. 846-853
Author(s):  
Raghunandan Purohith ◽  
Nagendra P.M. Nagalingaswamy ◽  
Nanjunda S. Shivananju
Keyword(s):  
Metabolic Syndrome ◽  
Dietary Intervention ◽  
Bioactive Constituents ◽  
Dietary Antioxidants ◽  
Predisposing Factor ◽  
Beneficial Effects ◽  
Pathological Conditions ◽  
Established Relationship ◽  
Comprehensive Study

Metabolic syndrome is a collective term that denotes disorder in metabolism, symptoms of which include hyperglycemia, hyperlipidemia, hypertension, and endothelial dysfunction. Diet is a major predisposing factor in the development of metabolic syndrome, and dietary intervention is necessary for both prevention and management. The bioactive constituents of food play a key role in this process. Micronutrients such as vitamins, carotenoids, amino acids, flavonoids, minerals, and aromatic pigment molecules found in fruits, vegetables, spices, and condiments are known to have beneficial effects in preventing and managing metabolic syndrome. There exists a well-established relationship between oxidative stress and major pathological conditions such as inflammation, metabolic syndrome, and cancer. Consequently, dietary antioxidants are implicated in the remediation of these complications. The mechanism of action and targets of dietary antioxidants as well as their effects on related pathways are being extensively studied and elucidated in recent times. This review attempts a comprehensive study of the role of dietary carotenoids in alleviating metabolic syndromewith an emphasis on molecular mechanism-in the light of recent advances.

The Role of Androgen Under Normal and Pathological Conditions in Sebaceous Glands: The Possibility of Target Therapy

2016 ◽  
Vol 9 (4) ◽  
pp. 311-319 ◽  
Author(s):  
Abdullah Azmahani ◽  
Yasuhiro Nakamura ◽  
Keely M. McNamara ◽  
Hironobu Sasano
Keyword(s):  
Target Therapy ◽  
Sebaceous Glands ◽  
Pathological Conditions
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