Optical measurements reveal nature of intercellular coupling across ventricular wall

2005 ◽  
Vol 289 (4) ◽  
pp. H1428-H1435 ◽  
Author(s):  
Steven Poelzing ◽  
Bradley J. Roth ◽  
David S. Rosenbaum
Keyword(s):  
Gap Junctions ◽  
Cardiac Tissue ◽  
Optical Mapping ◽  
Three Dimensional ◽  
Optical Measurements ◽  
Ventricular Wall ◽  
Three Dimensional Model ◽  
Intercellular Coupling ◽  
Disease States ◽  
Heterogeneous Expression

Previously, we showed that intercellular uncoupling through gap junctions is an important mechanism for maintaining transmural heterogeneities of repolarization that are responsible for ventricular arrhythmias in disease states such as heart failure. However, rotational anisotropy between transmural muscle layers also may influence coupling. To determine the effect of rotational anisotropy on transmural coupling, we developed a numerical three-dimensional model of passive cardiac tissue in which rotational anisotropy was varied in a controlled fashion. Simulations of optical mapping demonstrated that spatial averaging produced a voltage decay in space best fit by a single decaying exponential compared with the theoretically predicted decay. As fiber orientation varied by 90° with respect to the transmural surface, the effective transmural space constant (λTM) changed by only 0.31% in simulations. In contrast, reducing intercellular conductivity by 24% decreased λTM by 7.7%. In the canine wedge preparation ( n = 5), λ measured by optical mapping of the epicardial and subepicardial surface was similar transverse (λTV = 0.73 ± 0.10 mm) and transmural (λTM = 0.70 ± 0.08 mm) to subepicardial fibers. We confirmed previous findings that λTM in subepicardial layers was significantly reduced by 14 ± 2% compared with deeper layers of myocardium, providing evidence for transmural uncoupling in the epicardial-midmyocardial interface. These data establish the theoretical and experimental basis for measuring intercellular coupling between muscle layers spanning the ventricular wall with optical mapping techniques. Furthermore, this study demonstrates that transmural uncoupling at the epicardial-midmyocardial interface may be attributable to heterogeneous expression of cardiac gap junctions and not rotational anisotropy.

Nonlinear Incompressible Finite Element for Simulating Loading of Cardiac Tissue—Part II: Three Dimensional Formulation for Thick Ventricular Wall Segments

1988 ◽  
Vol 110 (1) ◽  
pp. 62-68 ◽  
Author(s):  
A. Horowitz ◽  
I. Sheinman ◽  
Y. Lanir
Keyword(s):  
Finite Element ◽  
Cardiac Tissue ◽  
Large Deformations ◽  
Three Dimensional ◽  
Shear Stiffness ◽  
Cardiac Mechanics ◽  
Nonlinear Finite Element ◽  
Constitutive Law ◽  
Ventricular Wall ◽  
Collagenous Matrix

A three dimensional incompressible and geometrically as well as materially nonlinear finite element is formulated for future implementation in models of cardiac mechanics. The stress-strain relations in the finite element are derived from a recently proposed constitutive law which is based on the histological composition of the myocardium. The finite element is formulated for large deformations and considers incompressibility by introducing the hydrostatic pressure as an additional variable. The results of passive loading cases simulated by this element allow to analyze the mechanical properties of ventricular wall segments, the main of which are that the circumferential direction is stiffer than the longitudinal one, that its shear stiffness is considerably lower than its tensile and compressive stiffness, and that, due to its mechanically prominent role, the collagenous matrix may affect the myocardial perfusion.

DYNAMICS OF VENTRICULAR FIBRILLATION: A MODEL AND EXPERIMENTAL STUDY

1999 ◽  
Vol 07 (04) ◽  
pp. 513-527 ◽  
Author(s):  
E. VIGMOND ◽  
F. X. WITKOWSKI ◽  
L. J. LEON
Keyword(s):  
Correlation Function ◽  
Ventricular Fibrillation ◽  
Cross Correlation ◽  
Cardiac Tissue ◽  
Three Dimensional ◽  
Cross Correlation Function ◽  
Three Dimensional Model ◽  
Potential Mapping ◽  
Acute Form ◽  
Electrical Induction

Wiggers initially described that after electrical induction of ventricular fibrillation (VF) the rhythm so induced progresses in complexity [14]. Previously Witkowski et al. [15] have described two distinct phases of perfused VF. The acute form was characterized by relatively well organized activity and was observed in the first few minutes after induction. The chronic form developed after this initial reentry and was more disorganized in nature. In this paper we describe computer simulations carried out using a complex three-dimensional model of cardiac tissue. Depending on the time constant of the dynamics of the calcium current, activity ranged from organized scroll waves, to highly disorganized chaotic activity in which it was possible to identify up to 10 different vortex filaments which continually drifted and split. The model data was compared to experimental measurements via the maximum cross-correlation function described previously by Witkowski et al. [15]. We found that the max cross-correlation function for a single scroll wave ranged between 0.6 and 0.9, and is similar to what was experimentally observed from optical transmembrane potential mapping during early VF. For the highly disorganized activity the maximum cross-correlation function was in the range of 0.2, which similarly was in same range reported experimentally for fully developed VF.

scholarly journals Afterdepolarizations Promote the Transition From Ventricular Tachycardia to Fibrillation in a Three-Dimensional Model of Cardiac Tissue

2002 ◽  
Vol 66 (5) ◽  
pp. 505-505 ◽  
Author(s):  
Takashi Ashihara ◽  
Takenori Yao ◽  
Tsunetoyo Namba ◽  
Ayaka Kawase ◽  
Takanori Ikeda ◽  
...  
Keyword(s):  
Ventricular Tachycardia ◽  
Cardiac Tissue ◽  
Three Dimensional ◽  
Dimensional Model ◽  
Three Dimensional Model

Three-Dimensional Model for Virtual Surgical Simulation, during Complex Skull Base Surgery and Aneurysm Surgery

Skull Base ◽  
2008 ◽  
Vol 18 (S 01) ◽  
Author(s):  
Akio Morita ◽  
Toshikazu Kimura ◽  
Shigeo Sora ◽  
Kengo Nishimura ◽  
Hisayuki Sugiyama ◽  
...  
Keyword(s):  
Skull Base ◽  
Surgical Simulation ◽  
Skull Base Surgery ◽  
Three Dimensional ◽  
Aneurysm Surgery ◽  
Dimensional Model ◽  
Three Dimensional Model

Digitalization system of ancient architecture decoration art based on neural network and image features

2020 ◽  
pp. 1-12
Author(s):  
Wu Xin ◽  
Qiu Daping
Keyword(s):  
Neural Network ◽  
Construction Industry ◽  
Three Dimensional ◽  
Performance Testing ◽  
Image Features ◽  
Three Dimensional Model ◽  
Performance Effect ◽  
Data Process ◽  
And Performance ◽  
Construction Mode

The inheritance and innovation of ancient architecture decoration art is an important way for the development of the construction industry. The data process of traditional ancient architecture decoration art is relatively backward, which leads to the obvious distortion of the digitalization of ancient architecture decoration art. In order to improve the digital effect of ancient architecture decoration art, based on neural network, this paper combines the image features to construct a neural network-based ancient architecture decoration art data system model, and graphically expresses the static construction mode and dynamic construction process of the architecture group. Based on this, three-dimensional model reconstruction and scene simulation experiments of architecture groups are realized. In order to verify the performance effect of the system proposed in this paper, it is verified through simulation and performance testing, and data visualization is performed through statistical methods. The result of the study shows that the digitalization effect of the ancient architecture decoration art proposed in this paper is good.

Phonetic iconicity in the evaluative morphology of a sample of Indo-European, Niger-Congo and Austronesian languages

2010 ◽  
Vol 3 (2) ◽  
pp. 156-180 ◽  
Author(s):  
Renáta Gregová ◽  
Lívia Körtvélyessy ◽  
Július Zimmermann
Keyword(s):  
Three Dimensional ◽  
Sound Symbolism ◽  
Three Dimensional Model ◽  
Austronesian Languages ◽  
Place Of Articulation ◽  
European Languages ◽  
Phonetic Symbolism ◽  
The Individual ◽  
Core Vocabulary

Universals Archive (Universal #1926) indicates a universal tendency for sound symbolism in reference to the expression of diminutives and augmentatives. The research ( Štekauer et al. 2009 ) carried out on European languages has not proved the tendency at all. Therefore, our research was extended to cover three language families – Indo-European, Niger-Congo and Austronesian. A three-step analysis examining different aspects of phonetic symbolism was carried out on a core vocabulary of 35 lexical items. A research sample was selected out of 60 languages. The evaluative markers were analyzed according to both phonetic classification of vowels and consonants and Ultan's and Niewenhuis' conclusions on the dominance of palatal and post-alveolar consonants in diminutive markers. Finally, the data obtained in our sample languages was evaluated by means of a three-dimensional model illustrating the place of articulation of the individual segments.

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