scholarly journals Intimal and medial contributions to the hydraulic resistance of the arterial wall at different pressures: a combined computational and experimental study

2016 ◽  
Vol 13 (119) ◽  
pp. 20160234 ◽  
Author(s):  
K. Y. Chooi ◽  
A. Comerford ◽  
S. J. Sherwin ◽  
P. D. Weinberg
Keyword(s):  
Hydraulic Resistance ◽  
Arterial Wall ◽  
Ex Vivo ◽  
Water Flux ◽  
Applied Pressure ◽  
Volumetric Strain ◽  
Transport Processes ◽  
Constitutive Law ◽  
Hydraulic Permeability ◽  
The Media

The hydraulic resistances of the intima and media determine water flux and the advection of macromolecules into and across the arterial wall. Despite several experimental and computational studies, these transport processes and their dependence on transmural pressure remain incompletely understood. Here, we use a combination of experimental and computational methods to ascertain how the hydraulic permeability of the rat abdominal aorta depends on these two layers and how it is affected by structural rearrangement of the media under pressure. Ex vivo experiments determined the conductance of the whole wall, the thickness of the media and the geometry of medial smooth muscle cells (SMCs) and extracellular matrix (ECM). Numerical methods were used to compute water flux through the media. Intimal values were obtained by subtraction. A mechanism was identified that modulates pressure-induced changes in medial transport properties: compaction of the ECM leading to spatial reorganization of SMCs. This is summarized in an empirical constitutive law for permeability and volumetric strain. It led to the physiologically interesting observation that, as a consequence of the changes in medial microstructure, the relative contributions of the intima and media to the hydraulic resistance of the wall depend on the applied pressure; medial resistance dominated at pressures above approximately 93 mmHg in this vessel.

Intimal Tissue Factor Activity Is Released from the Arterial Wall after Injury

2000 ◽  
Vol 83 (04) ◽  
pp. 622-628 ◽  
Author(s):  
Peter Giesen ◽  
Billie Fyfe ◽  
John Fallon ◽  
Merce Roque ◽  
Milton Mendlowitz ◽  
...  
Keyword(s):  
Tissue Factor ◽  
Arterial Wall ◽  
Ex Vivo ◽  
Factor Xa ◽  
Arterial Injury ◽  
Flow Chamber ◽  
Luminal Surface ◽  
Activity Factor ◽  
Large Platelet ◽  
The Media

SummaryTissue factor (TF), the initiator of coagulation, has been implicated as a critical mediator of arterial thrombosis. Previous studies have demonstrated that TF is rapidly induced in the normal rodent arterial wall by balloon injury, but is not associated with fibrin deposition. A second injury, however, performed 10–14 days after the first, is followed by small platelet-fibrin microthrombi. This study was undertaken to better localize active TF in balloon-injured rat arteries and to explore possible mechanisms underlying the apparent discrepancy between injury-induced TF expression and the lack of large platelet-fibrin thrombi. By immunohistochemistry, TF antigen was first detected in the media 24 h after injury to rat aortas, and subsequently accumulated in the neointima. Using an ex vivo flow chamber, no TF activity (Factor Xa generation) was found on the luminal surface of normal or injured aortas. Wiping the luminal surface with a cotton swab exposed TF activity in all vessels; levels were increased ≈3-fold in arteries containing a neointima. The exposed TF activity was rapidly washed into the perfusate, rendering the luminal surface inactive. The loss of luminal TF into the circulation may attenuate thrombosis at sites of arterial injury.

Stress Distribution in a Bilayer Elastic Model of a Coronary Artery

2013 ◽  
Vol 80 (4) ◽  
Author(s):  
Keiichi Takamizawa ◽  
Yasuhide Nakayama
Keyword(s):  
Blood Pressure ◽  
Residual Stress ◽  
Stress Distribution ◽  
Residual Strain ◽  
Arterial Wall ◽  
Circumferential Stress ◽  
Outer Region ◽  
Constitutive Law ◽  
Elastic Model ◽  
The Media

In earlier studies on stress distribution in arteries, a monolayer wall model was often used. An arterial wall consists of three layers, the intima, the media, and the adventitia. The intima is mechanically negligible as a stress supporting layer against the blood pressure in young healthy vessels, although it is important as an interface between blood and arterial wall. The media and adventitia layers are considered to support blood pressure. Recently, residual strain and a constitutive law for porcine coronary arteries have been investigated in separated media and adventitia. Using the data obtained through these investigations, a stress analysis considering residual stress (strain) in each layer was performed in this study, and residual strain and stress were computed for a bilayer model. The circumferential residual stress was compressive in the inner region, tensile in the outer region, and had discontinuity at the boundary between the media and adventitia. A peak circumferential stress occurred in the media at the boundary between the media and adventitia under a physiological condition, and an almost flat distribution was obtained in the adventitia. This pattern does not change under a hypertensive condition. These results suggest that a remodeling with hypertension occurs in the media.

Particle Deposition in Arteries Ex Vivo: Effects of Pressure, Flow, and Waveform

2003 ◽  
Vol 125 (3) ◽  
pp. 389-394 ◽  
Author(s):  
Naomi C. Chesler ◽  
Omyekachi C. Enyinna
Keyword(s):  
Particle Deposition ◽  
Carotid Arteries ◽  
Ex Vivo ◽  
Confocal Laser ◽  
Hydraulic Permeability ◽  
Perfusion System ◽  
Pressure Flow ◽  
Arterial Tissue ◽  
The Media ◽  
Microscopy Images

The goal of this study was to quantify the effect of hemodynamic pressure, flow and waveform perturbations on the deposition of protein-sized particles in porcine carotid arteries ex vivo. An ex vivo perfusion system was used to control the pressure and flow environment for excised arterial tissue. Confocal laser microscopy images revealed that 200 nm particles were deposited intimally and that more spheres were evident along vessels perfused under oscillatory waveform conditions than all others. Under all pressure, flow and waveform conditions, particles were excluded from the media and adventitia of the vessel wall. The steady flow data support the use of Darcy’s Law with pressure-dependent hydraulic permeability to model arterial tissue.

Fibrinolytic Activity of the Arterial Wall

1969 ◽  
Vol 21 (01) ◽  
pp. 001-011 ◽  
Author(s):  
K Onoyama ◽  
K Tanaka
Keyword(s):  
Carotid Artery ◽  
Fibrinolytic Activity ◽  
Arterial Wall ◽  
Aortic Wall ◽  
Internal Carotid ◽  
Atheromatous Plaque ◽  
Human Fibrinogen ◽  
The Media ◽  
The Common ◽  
Almost All

SummaryThe tissue fibrinolysis was studied in 550 specimens of 7 kinds of arteries from 80 fresh cadavers, using Astrup’s biochemical method and Todd’s histochemical method with human fibrinogen.In the microscopically normal aortic wall, almost all specimens had the fibrinolytic activity which was the strongest in the adventitia and the weakest in the media.The fibrinolytic activity seemed to be localized in the endothelium.The stronger activity lay in the adventitia of the aorta and the pulmonary artery and all layers of the cerebral artery.The activity of the intima and media of the macroscopically normal areas seemed to be stronger in the internal carotid artery than in the common carotid artery.Mean fibrinolytic activity of the macroscopically normal areas seemed to decrease with age in the intima and the media of the thoracic aorta and seemed to be low in the cases with a high atherosclerotic index.The fibrinolytic activities of all three layers of the fibrous thickened aorta seemed to decrease, and those of the media and the adventitia of the atheromatous plaque to increase.The fibrinolytic activity of the arterial wall might play some role in the progress of atherosclerosis.

Age-related changes in endothelial permeability and distribution volume of albumin in rat aorta

1993 ◽  
Vol 264 (3) ◽  
pp. H679-H685 ◽  
Author(s):  
J. Belmin ◽  
B. Corman ◽  
R. Merval ◽  
A. Tedgui
Keyword(s):  
Arterial Wall ◽  
Relative Concentration ◽  
Endothelial Permeability ◽  
Distribution Volume ◽  
Albumin Concentration ◽  
Macromolecular Transport ◽  
Age Related ◽  
The Media ◽  
Old Rats ◽  
Age Related Changes

Age-related changes in macromolecular transport across the arterial wall were investigated in 10-, 20-, and 30-mo-old WAG/Rij rats. Animals were injected with 125I- and 131I-labeled albumin, 90 and 5 min before they were killed, respectively. The transmural distribution of relative concentration of tracers in the aortic wall was obtained using en face serial sectioning technique. The apparent endothelial permeability to albumin calculated from the distribution of 5-min 131I-labeled albumin concentrations was significantly enhanced in 20- and 30-mo-old rats compared with 10-mo-old rats. The apparent distribution volume of albumin within the media, estimated as the mean medial 125I-labeled albumin concentration, was not significantly changed in 20-mo-old rats but was significantly decreased in the 30-mo-old animals. These age-related changes in the macromolecular transport suggest that the entry of plasma macromolecules in the aged arterial wall might be enhanced, whereas the efflux through the media may be impeded, possibly contributing to their trapping in the subendothelium.

scholarly journals Basolateral transport of tetraethylammonium by a clone of LLC-PK1 cells.

1992 ◽  
Vol 2 (10) ◽  
pp. 1507-1515
Author(s):  
T D McKinney ◽  
M B Scheller ◽  
M Hosford ◽  
M E Lesniak ◽  
T S Haseley
Keyword(s):  
Organic Cation ◽  
Basolateral Membrane ◽  
Transport Processes ◽  
Proton Exchange ◽  
Metabolic Inhibitors ◽  
Organic Cations ◽  
Dependent Manner ◽  
Electrogenic Transport ◽  
The Media ◽  
Uptake Medium

In these studies, a clone of cells derived from the porcine renal epithelial line LLC-PK1 grown on porous filters was used to evaluate basolateral uptake of the organic cation tetraethylammonium (TEA). (3H) TEA (1 microM) entered cells in a saturable and time-dependent manner achieving a steady-state value at 2 to 2.5 h. Uptake was reduced by hypothermia and the metabolic inhibitors sodium azide and iodoacetate. Several other organic cations in 1 mM concentrations inhibited the majority of TEA uptake. In lower concentrations, the inhibitory potency of these was: verapamil greater than cimetidine approximately amiloride approximately quinidine greater than procainamide approximately N1-methylnicotinamide. When sodium was replaced with potassium in the uptake medium, TEA uptake was also reduced consistent with electrogenic transport. However, uptake was reduced further by 1 mM cimetidine in the presence of both NaCl and KCl buffers. TEA uptake was not significantly different when the media pH was varied from 6.0 to 8.0. In addition, results of experiments in which intracellular pH was altered with NH4Cl were not consistent with the presence of organic cation/proton exchange. TEA/TEA exchange could not be demonstrated in experiments in which cells were preloaded with 1 mM nonradioactive TEA and uptake of (3H)TEA was measured or in which nonradioactive TEA in the external medium failed to enhance efflux from cells preloaded with (3H)TEA. These results indicate that the basolateral membrane of LLC-PKc10 cells has one or more transport processes for the mediated uptake of organic cations. However, the precise mechanism(s) involved in this transport remains to be elucidated.

Modelling coating cohesion effect on soil mechanical stability and permeability of the biopore - matrix interface pore region

2021 ◽  
Author(s):  
Luis Alfredo Pires Barbosa ◽  
Horst H. Gerke
Keyword(s):  
Axial Compression ◽  
Mechanical Stability ◽  
Transport Processes ◽  
Spherical Particles ◽  
External Loading ◽  
Hydraulic Permeability ◽  
Matrix Interface ◽  
Pore Region ◽  
Soil Matrix ◽  
Soil Stiffness

<p>Biopore surface is often characterized by finer particles and increased concentration of polysaccharides from root and earthworm exudates, presenting physico-chemical properties different from those of the soil matrix. Such exudates controls not only the wettability or sorption properties but also the adhesive forces of the surrounding soil particles. Thus, increased mechanical stability may be expected on biopore-matrix interface affecting preferential flow and transport processes, as well.</p> <p>However, it is still unknown (i) to what extent the particle cohesion in the coated region is able to increase the resilience of the biopore to an external loading and (ii) how it affects the permeability of the biopore-matrix pore region.</p> <p>We created a discrete element model (DEM) model of a hollow cylindrical soil sample with a coated biopore in the center (i.e., 1 cm height, 1 cm outer and 0.6 cm inner diameter). The spherical particles in the model presented diameter of 0.13 mm for the coated material and 0.22 mm for the soil matrix. The cohesion among particles in the soil matrix was set to a constant value of 10.9 MPa while the cohesion among particles in the coated region varied between 10.9 and 50.9 MPa. The sample was subjected to axial compression and the force and cracks recorded. The permeability in the radial direction from the biopore to soil matrix was calculated using ImageJ and a 3D stokes solver (FDMMS).</p> <p>The increment in the coating cohesion increased the overall soil stiffness in terms of the Young’s modulus. Before axial compression, the calculated hydraulic permeability for the interface coating and matrix was 182 μm<sup>2</sup>. After compression, although the lower coating cohesion resulted in a larger number of cracks, permeability increased with coating cohesion. This suggests that with increasing soil stiffness, the cracks decrease in number but increase in length (i.e. improved connectivity).</p>

Culture Medium With Blood Analog Mechanical Properties

2007 ◽  
Author(s):  
Chantal N. van den Broek ◽  
Marcel C. M. Rutten ◽  
Ole Frøbert ◽  
Frans N. van de Vosse
Keyword(s):  
Culture Medium ◽  
Arterial Wall ◽  
Ex Vivo ◽  
Shear Stresses ◽  
Fluid Viscosity ◽  
Endothelial Phenotype ◽  
Physiological Fluid ◽  
Wall Shear ◽  
Medium Viscosity

Culture of arteries has become increasingly important in studying atherosclerosis and the effect of clinical interventions [1]. Ideally, arterial culturing should imitate in vivo conditions within an ex vivo environment. Physiological wall shear stresses are important as they induce an atheroprotective endothelial phenotype [2], which is relevant for maintaining arterial wall integrity. The arteries in such ex vivo studies, however, are perfused with culture medium, which has a viscosity lower than blood. Previously, the culture medium has been supplemented with dextran to obtain physiological fluid viscosity and wall shear stresses. However, several researchers [3,4] reported side effects of dextran on the cells in the arterial wall independent of its effect on medium viscosity. Also, dextran increases medium osmolality to supraphysiological levels [5]. This suggests that dextran may not be the optimal substance to increase medium viscosity.

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