Nikolaos Stergiopoulos

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We determined total arterial compliance from pressure and flow in the ascending aorta of seven anesthetized dogs using the pulse pressure method (PPM) and the decay time method (DTM). Compliance was determined under control and during occlusion of the aorta at four different locations (iliac, renal, diaphragm, and proximal descending thoracic aorta). Compliance of PPM gave consistently lower values (0.893 +/- 0.015) compared with the compliance of DTM (means +/- SE; r = 0.989). The lower compliance estimate

Background: An increased fibrosis of the corpora cavernosa is a prevalent process that underlies most cases of erectile dysfunction. Apelin, an endogenous circulating peptide, has been documented as an important effector on cardiovascular homeostasis, cont ...

Auto-antibodies to apolipoprotein A-1 (anti-apoA-1 IgG) were shown to promote inflammation and atherogenesis, possibly through innate immune receptors signalling. Here, we aimed at investigating the role of Toll-like receptors (TLR) 2 and 4 on anti-apoA-1 ...

Central aortic diastolic pressure decay time constant ( ) is according to the two-element Windkessel model equal to the product of total peripheral resistance (R) times total arterial compliance (C ). As such, it is related to arterial stiffness, which has ...

AIM: To propose a method for obtaining non-invasive highly accurate measurements of arterial diameter, thickness and pressure at a single location on a peripheral arm artery, and use this data to estimate the status of the arterial wall. METHODS: Diameter and thickness were measured with an A-mode ultrasonic echo-tracking device, with a precision of close to 1 micron. Pressure was measured with a photoplethysmograph at the finger level. A simple hemodynamic model was used to estimate, from the measured pres

Aging affects elastin, a key component of the arterial wall integrity and functionality. Elastin degradation in cerebral vessels is associated with cerebrovascular disease. The goal of this study is to assess the biomechanical properties of human cerebral ...

Objectives: To investigate the effect of general anesthesia on aortic compliance and other cardiovascular hemodynamics in chronically instrumented pigs with compliant and noncompliant (stiff) aortas. Design: Experimental study. Setting: University animal l ...

Objectives: We quantified the dysfunction of the aortic wall, determined structural and elastic properties, and provided histological data of the thoracic aortas of apolipoprotein E (apoE)-deficient mice which are used as model of atherosclerosis. Methods: ...

PURPOSE. The purpose of our study is to develop and validate a methodology to measure the compliance of the vascular network in the eye using biomechanical parameters, namely arterial pressure, intraocular pressure (IOP), and ocular compliance of the eyeball (OC).

We propose a new variational framework for the problem of reconstructing flow fields from noisy measurements. The formalism is based on regularizers penalizing the singular values of the Jacobian of the field. Specifically, we rely on the nuclear norm. Our ...

Monitoring of cardiac output (CO) is a mainstay of hemodynamic management in the acutely or critically ill patient. Invasive determination of CO using thermodilution, albeit regarded as the gold standard, is cumbersome and bears risks inherent to catheteri ...

With progressing age, large arteries diminish their longitudinal stretch, which in extreme cases results in tortuosity. Increased age is also associated with loss of vessel distensibility. We measured pressure-diameter curves from muscular porcine carotid arteries ex vivo at different longitudinal stretch ratios (lambda(z) = 1.4 and 1.8) and under different vascular smooth muscle (VSM) conditions (fully relaxed, normal VSM tone, and maximally contracted). Distensibility was found to be halved by decreasing

Vascular remodeling is an adaptive response to variations in the hemodynamic environment acting on the arterial wall. Remodeling translates into changes of structure, geometry and mechanical properties of the artery. Our aim was to study the remodeling response of pig right common carotid arteries in vitro.

In this study a numerical solution for the problem of pulsating flow in rigid tubes is described. The method applies to the case of known flow rate waveform, as opposed to Womersley solution where the pressure gradient was the known quantity. The solution provides the pressure gradient and wall shear stress waveforms as well as the instantaneous velocity profiles. Results show that the method can be used to study the blood flow characteristics in large arteries.

Background: The renin-angiotensin system (RAS) plays an important role in erectile function. The RAS contains 2 major axes: one deleterious, composed of ACE-Ang II-AT1 receptor, and another protective, composed of ACE2-Ang-(1-7)-Mas receptor. While aging i ...

Neutrophilic inflammation might have a pathophysiological role in both carotid plaque rupture and ischemic stroke injury. Here, we investigated the potential benefits of the CXC chemokine-binding protein Evasin-3, which potently inhibits chemokine bioactiv ...

Intimal hyperplasia (IH) is a vascular remodeling process which often leads to failure of arterial bypass or hemodialysis access. Experimental and clinical work have provided insight in IH development; however, further studies under precise controlled conditions are required to improve therapeutic strategies to inhibit IH development. Ex vivo perfusion of human vessel segments under standardized hemodynamic conditions may provide an adequate experimental approach for this purpose. Therefore, chronically per

In-vivo assessment of aortic characteristic impedance (Zao) and total arterial compliance (CT) has been hampered by the need for either invasive or inconvenient and expensive methods to access simultaneous recordings of aortic pressure and flow, wall thick ...

Systems and methods are provided for treating a sexual disorder such as erectile dysfunction (ED) or female sexual arousal disorder (FSAD). An electrical stimulation system may include an implantable stimulation unit, an external patient controller, and an ...

The objective of this study was to investigate whether reduction of cyclic circumferential stretch will impair endothelial function and elevate basal levels of oxidative stress, both known risk factors linked to cardiovascular disease. ...

Nikolaos Stergiopoulos

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Use of pulse pressure method for estimating total arterial compliance in vivo

Apelin-13 Protects Corpus Cavernosum Against Fibrosis Induced by High-Fat Diet in an MMP-Dependent Mechanism

Anti-apoA-1 auto-antibodies increase mouse atherosclerotic plaque vulnerability, myocardial necrosis and mortality triggering TLR2 and TLR4

Novel theory and potential applications of central diastolic pressure decay time constant

Non-invasive method for the assessment of non-linear elastic properties and stress of forearm arteries in vivo

Effect of aging on elastin functionality in human cerebral arteries

Effects of Isoflurane Anesthesia on Aortic Compliance and Systemic Hemodynamics in Compliant and Noncompliant Aortas

Wall properties of the apolipoprotein E-deficient mouse aorta

Eye Vessel Compliance as a Function of Intraocular and Arterial Pressure and Eye Compliance

Improved Variational Denoising of Flow Fields with Application to Phase-Contrast MRI Data

Machine learning-enabled estimation of cardiac output from peripheral waveforms is independent of blood pressure measurement location in an in silico population

Effects of longitudinal stretch on VSM tone and distensibility of muscular conduit arteries

Functional, mechanical and geometrical adaptation of the arterial wall of a non-axisymmetric artery in vitro

The inverse Womersley problem for pulsatile flow in straight rigid tubes

Characterization of the Renin-Angiotensin System in Aged Cavernosal Tissue and its Role in Penile Fibrosis

Treatment with Evasin-3 reduces atherosclerotic vulnerability for ischemic stroke, but not brain injury in mice

Comparative assessment of intimal hyperplasia development after 14 days in two different experimental settings: tissue culture versus ex vivo continuous perfusion of human saphenous vein

Determination of Aortic Characteristic Impedance and Total Arterial Compliance From Regional Pulse Wave Velocities Using Machine Learning: An in-silico Study

Systems and methods for treating sexual disorders using electro-stimulation

Reduced cyclic stretch, endothelial dysfunction, and oxidative stress: an ex vivo model