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Nikolaos Stergiopoulos

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Publications associées (238)

On the in-series and in-parallel contribution of elastin assessed by a structure-based biomechanical model of the arterial wall

Nikolaos Stergiopoulos, Sylvain Roy, Gilles Prod'Hom, Alkiviadis Tsamis

Earlier experimental work on decellularized arteries revealed the existence of significant residual stresses within the arterial wall, which are released upon chemical removal of vascular smooth muscle in normal arteries causing substantial radial expansio ...

2008

A new implantable device for telemetric control of pulmonary blood flow

Nikolaos Stergiopoulos

The main problem encountered in pulmonary artery banding is the difficulty in determining the optimal perimeter of the band, and sometime repeated surgical operations are required to adjust the band perimeter in order to control the pulmonary blood flow. T ...

2007

Effect of elastin degradation on carotid wall mechanics as assessed by a constituent-based biomechanical model

Nikolaos Stergiopoulos, Luca Augsburger, Sylvain Roy, Edouard Fonck, Gilles Prod'Hom

Arteries display a nonlinear anisotropic behavior dictated by the elastic properties and structural arrangement of its main constituents, elastin, collagen, and vascular smooth muscle. Elastin provides for structural integrity and for the compliance of the ...

2007

Transcriptional and post-transcriptional regulation of preproendothelin-1 by plaque-prone hemodynamics

Nikolaos Stergiopoulos, Paolo Silacci, Rafaela Fernandes Da Silva

Plaque-prone areas are exposed to a particular hemodynamic environment characterized by a low mean shear stress value and a cyclic reversal flow. This mechanical environment, also termed oscillatory shear stress (OSS), induces the expression of several pro ...

2007

Oscillatory shear stress and reduced compliance impair vascular functions

Nikolaos Stergiopoulos, Veronica Gambillara, Paolo Silacci, Tyler Nerton Thacher, Rafaela Fernandes Da Silva

Shear stress has been shown to influence endothelial cell gene expression and morphology. In particular, low and bi-directional shear stress, mimicking conditions at plaque-prone areas, down-regulates the expression of several atheroprotective genes, and u ...

2007

Effects of an aging vascular model on healthy and diseased hearts

Nikolaos Stergiopoulos, David Jegger, Patrick Segers, Rafaela Fernandes Da Silva

The vitamin D(3) and nicotine (VDN) model is a model of isolated systolic hypertension (ISH) due to arterial calcification raising arterial stiffness and vascular impedance similar to an aged and stiffened arterial tree. We therefore analyzed the impact of ...

2007

RGD-Functionalized polymer brushes as substrates for the integrin specific adhesion of human umbilical vein endothelial cells

Nikolaos Stergiopoulos, Paolo Silacci, Harm-Anton Klok, Stefano Tugulu

This report demonstrates the feasibility of surface-initiated atom transfer radical polymerization to prepare thin polymer layers ("brushes") that can be functionalized with short peptide ligands and which may be of use as coatings to promote endothelializ ...

2007

Role of arginase pathway in response to shear stress: new potential therapeutic targets for atherosclerosis?

Nikolaos Stergiopoulos, Veronica Gambillara, Rafaela Fernandes Da Silva

Introduction: Alterations of wall shear stress can predispose the endothelium to the development of atherosclerotic plaques. Ample evidence indicates that arginase expression and/or activity correlates with several risk factors for cardiovascular disease i ...

2007

Arterial remodeling in response to hypertension using a constituent-based model

Nikolaos Stergiopoulos, Alkiviadis Tsamis

Hypertension-induced arterial remodeling has been previously modeled using stress-driven remodeling rate equations in terms of global geometrical adaptation (Rachev A, Stergiopulos N, Meister JJ. Theoretical study of dynamics of arterial wall remodeling in ...

2007

Structural strain energy function applied to the ageing of the human aorta

Nikolaos Stergiopoulos, Martin Zulliger

Stiffening of the aorta with progressing age leads to decrease of aortic compliance and thus to an increase of pulse pressure amplitude. Using a strain energy function (SEF) which takes into account the composition of the arterial wall, we have studied the ...

2007

Shear stress and cyclic circumferential stretch, but not pressure, alter connexin43 expression in endothelial cells

Nikolaos Stergiopoulos, Paolo Silacci

Hemodynamic forces play a critical role in atherogenesis, as evidenced by the focal pattern of development of atherosclerotic lesions. Whereas disturbed flow in the branches and curved regions of large arteries is proatherogenic, laminar flow in the straig ...

2006

Arterial pressure transfer characteristics: effects of travel time

Nikolaos Stergiopoulos, Nico Westerhof

We investigated the quantitative contribution of all local conduit arterial, blood, and distal load properties to the pressure transfer function from brachial artery to aorta. The model was based on anatomical data, Young's modulus, wall viscosity, blood v ...

2006

The effect of a myocardial infarction on the normalized time-varying elastance curve

Nikolaos Stergiopoulos, David Jegger, Rafaela Fernandes Da Silva

It has been suggested that the shape of the normalized time-varying elastance curve [E(n)(t(n))] is conserved in different cardiac pathologies. We hypothesize, however, that the E(n)(t(n)) differs quantitatively after myocardial infarction (MI). Sprague-Da ...

2006

Plaque-prone hemodynamics impair endothelial function in pig carotid arteries

Nikolaos Stergiopoulos, Veronica Gambillara, Paolo Silacci, Sylvain Roy

Hemodynamic forces play an active role in vascular pathologies, particularly in relation to the localization of atherosclerotic lesions. It has been established that low shear stress combined with cyclic reversal of flow direction (oscillatory shear stress ...

2006

Nonlinear isochrones in murine left ventricular pressure-volume loops: how well does the time-varying elastance concept hold?

Nikolaos Stergiopoulos, Nico Westerhof, Patrick Segers

The linear time-varying elastance theory is frequently used to describe the change in ventricular stiffness during the cardiac cycle. The concept assumes that all isochrones (i.e., curves that connect pressure-volume data occurring at the same time) are li ...

2005

Arterial wall response to ex vivo exposure to oscillatory shear stress

Nikolaos Stergiopoulos, Veronica Gambillara, Paolo Silacci

The aim of this study was to analyze the arterial wall response to plaque-prone hemodynamic environments, known to occur mainly in areas of arterial trees such as bifurcations and branching points. In these areas, the vasculature is exposed to cyclically r ...

2005

Biomechanical properties of decellularized porcine common carotid arteries

Nikolaos Stergiopoulos, Paolo Silacci, Sylvain Roy

To analyze the effects of decellularization on the biomechanical properties of porcine common carotid arteries, decellularization was performed by a detergent-enzymatic procedure that preserves extracellular matrix scaffold. Internal diameter, external dia ...

2005

Noninvasive Doppler-derived myocardial performance index in rats with myocardial infarction: validation and correlation by conductance catheter

Nikolaos Stergiopoulos, David Jegger, Patrick Segers

The rodent model of myocardial infarction (MI) is extensively used in heart failure studies. However, long-term follow-up of echocardiographic left ventricular (LV) function parameters such as the myocardial performance index (MPI) and its ratio with the f ...

2005

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