Nikolaos Stergiopoulos

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Recently a new method has been proposed as a tool to measure arterial pulse wave velocity (PWV), a measure of the stiffness of the large arteries and an emerging parameter used as indicator of clinical cardiovascular risk. The method is based on measuremen ...

Aims B cell functions in the process of atherogenesis have been investigated but several aspects remain to be clarified. ...

We investigated how parameters describing the heart and the arterial system contribute to the systolic and diastolic pressures (Ps and Pd, respectively) and stroke volume (SV). We have described the heart by the varying-elastance model with six parameters and the systemic arterial tree by the three-element windkessel model, leading to a total of nine parameters. Application of dimensional analysis led to a total of six dimensionless parameters describing dimensionless Ps and Pd, i.e., pressures with respect

The dynamics of arterial wall remodeling was studied on the basis of a phenomenological mathematical model. Sustained hypertension was simulated by a step increase in blood pressure. Remodeling rate equations were postulated for the evolution of the geometrical dimensions that characterize the zero stress state of the artery. The driving stimuli are the deviations of the extreme values of the circumferential stretch ratios and the average stress from their values at the normotensive state. Arterial wall was

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 ...

Accurate assessment of the left ventricular (LV) systolic function is indispensable in the clinic. However, estimation of a precise index of cardiac contractility, i.e., the end-systolic elastance (E-es), is invasive and cannot be established as clinical r ...

IntroductionHypercholesterolemia is a prevalent risk factor for the development of erectile dysfunction (ED), mostly due to an increase in oxidative stress and impaired nitric oxide (NO) bioavailability within the penis. Arginase is an enzyme that shares t ...

We developed a new method to determine the location and importance of reflection sites in the arterial system. The method is based on the decomposition of the aortic pressure wave into its forward and backward components, and it provides the reflection profile of the arterial system as a wave reflection site amplitude versus distance from the heart. The reflection profile can be seen as the response of the arterial system to a pressure delta pulse where reflections upstream from the measurement location hav

We designed block copolymer pro-amphiphiles and amphiphiles for providing very long-term release of nitric oxide (NO). A block copolymer of N-acryloylmorpholine (AM, as a hydrophile) and N-acryloyl-2,5-dimethylpiperazine (AZd, as a hydrophilic precursor) w ...

Shear stress is one of the major hemodynamic forces acting on the endothelium. However, it is not well known how endothelial cells (EC) respond mechanically to these stimuli in vivo. Here we investigated whether changes in biomechanics properties and shear ...

Vasomotion has been studied on segments of rat mesenteric and femoral arteries perfused in vitro. We have investigated 1) the effect of perfusion flow on the characteristics of vasomotion and 2) the nature and patterns of vasomotion. We have found that perfusion flow is not a control parameter that contributes to the genesis of vasomotion but that it affects, in most cases only slightly, the frequency and amplitude of vasomotion. We have found evidence that vasomotion is low-dimensional chaotic. The correla

Pharmacological treatments targeting CXC chemokines and the associated neutrophil activation and recruitment into atherosclerotic plaques hold promise for treating cardiovascular disorders. Therefore, we investigated whether FK866, a nicotinamide phosphori ...

The goal of the present study was to analyze the intercellular calcium communication between smooth muscle cells (SMCs) and endothelial cells (ECs) by simultaneously monitoring artery diameter and intracellular calcium concentration in a rat mesenteric arterial segment in vitro under physiological pressure (50 mmHg) and flow (50 microl/min) in a specially developed system. Intracellular calcium was expressed as the fura 2 ratio. The diameter was measured using a digital image acquisition system. Stimulation

Glaucoma results in an increase in the resistance of the aqueous humor outflow, which in turn leads to an increase of the intraocular pressure (IOP). Several treatments are proposed to reduce and stabilize the IOP that include medications, filtering surger ...

We propose a new, simple way of constructing elastic tubes which can be used to model the nonlinear elastic properties of large arteries. The tube models are constructed from a silicon elastomer (Sylgard 184, Dow Corning), which exhibits a nonlinear behavior with increased stiffness at high strains. Tests conducted on different tube models showed that, with the proper choice of geometric parameters, the elastic properties, in terms of area-pressure relation and compliance, can be similar to that of real art

Aim: The investigation of the association between total arterial compliance (C-T)-estimated by a novel technique-with left ventricular mass (LVM) and hypertrophy (LVH). Our hypothesis was that C-T may be better related to LVM compared to the gold-standard ...

Identification of a Strain Energy Function (SEF) is used when describing the complex mechanical properties of soft biological tissues such as the arterial wall. Classic SEFs, such as the one proposed by Chuong and Fung (J. Biomech. Eng. 105(3) (1983) 268), have been mostly phenomenological and neglect the particularities of the wall structure. A more structural model was proposed by Holzapfel et al. (J. Elasticity 61 (2000) 1-48.) when they included the characteristic angle at which the collagen fibers are

Diastolic dysfunction (DD) is a major component of heart failure with preserved ejection fraction (HFpEF). Accordingly. a profound understanding of the underlying biomechanical mechanisms involved in DD is needed to elucidate all aspects of HFpEF. In this ...

PURPOSE: To report the in vivo results of a continuously adjustable glaucoma drainage device (GDD) in glaucoma surgery with rabbits. METHODS: Under general anesthesia, the AGDD was implanted on 12 white New-Zealand rabbits for duration of 6 months. The adj ...

Background: Structural constitutive models of vascular wall integrate information on composition and structural arrangements of tissue. In blood vessels, collagen fibres are arranged in coiled and wavy bundles and the individual collagen fibres have a devi ...

Nikolaos Stergiopoulos

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Numerical validation of a new method to assess aortic pulse wave velocity from a single recording of a brachial artery waveform with an occluding cuff

Follicular regulatory helper T cells control the response of regulatory B cells to a high-cholesterol diet

Determinants of stroke volume and systolic and diastolic aortic pressure

Theoretical study of dynamics of arterial wall remodeling in response to changes in blood pressure

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

In vivo application and validation of a novel noninvasive method to estimate the end-systolic elastance

An Increased Arginase Activity Is Associated with Corpus Cavernosum Impairment Induced by Hypercholesterolemia

Method for determining distribution of reflection sites in the arterial system

Micelles for delivery of nitric oxide

Local Shear Stress and Dyslipidemia Interfere with Actin Cyto-Skeleton and Lysosomal Organization Contributing to Vascular Fragility

Arterial vasomotion: effect of flow and evidence of nonlinear dynamics

Nicotinamide phosphoribosyltransferase inhibition reduces intraplaque CXCL1 production and associated neutrophil infiltration in atherosclerotic mice

Simultaneous arterial calcium dynamics and diameter measurements: application to myoendothelial communication

3D simulation of the aqueous flow in the human eye

Modeling of the wave transmission properties of large arteries using nonlinear elastic tubes

Total arterial compliance, estimated by a novel method, is better related to left ventricular mass compared to aortic pulse wave velocity: The SAFAR study

A strain energy function for arteries accounting for wall composition and structure

Biomechanics of diastolic dysfunction: a one-dimensional computational modeling approach

Eyewatch, an Innovative Adjustable GDD for the Treatment of Glaucoma - in Vivo Results

A structural constitutive model considering angular dispersion and waviness of collagen fibres of rabbit facial veins