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Background:When subjected to time-dependent blood pressure, human arteries undergo large deformations, exhibiting mainly nonlinear hyperelastic type of response. The mechanical response of arteries depends on the health of tissues that comprise the artery walls. Typically, healthy arteries exhibit convex strain hardening under tensile loads, atherosclerotic parts exhibit stiffer response, and aneurysmatic parts exhibit softening response. In reality, arterial dynamics is the dynamics of a propagating pulse, originating in heart ventricle, propagating along aorta, bifurcating,etc. Artery as a whole cannot be simulated as a lump ring, however its cross section can be simulated as a vibrating ring having a phase lag with respect to the other sections, creating a running pressure wave. A full mathematical model would require fluid-solid interaction modeling continuity of blood flow in a compliant vessel and a momentum equation. On the other hand, laboratory testing often uses small-length arteries, the response of which is covered by the present work. In this way, material properties that change along the artery length can be investigated.Objective:The effect of strain hardening on the local dynamic response of human arteries (excluding the full fluid-structure interaction) is examined through appropriate hyperelastic models related to the health condition of the blood vessel. Furthermore, this work aims at constituting a basis for further investigation of the dynamic response of arteries accounting for viscosity.Method:The governing equation of motion is formulated for three different hyperelastic material behaviors, based on the constitutive law proposed by Skalaket al., Hariton, and Mooney-Rivlin, associated with the hardening behavior of healthy, atherosclerotic, and aneurysmatic arteries, respectively. The differences between these modelling implementations are caused by physiology, since aneurysmatic arteries are softer and often sclerotic arteries are stiffer than healthy arteries. The response is investigated by proper normalization of the involved material parameters of the arterial walls, geometry of the arteries, load histories, time effects, and pre-stressing. The effect of each problem parameter on the arterial response has been studied. The peak response of the artery segment is calculated in terms of radial displacements, principal elongations, principal stresses, and strain-energy density. The validity of the proposed analytical models is demonstrated through comparison with previous studies that investigate the dynamic response of arterial models.Results:Important metrics that can be useful to vascular surgery are the radial deformation and the maximum strain-energy density along with the radial resonance frequencies. These metrics are found to be influenced heavily by the nonlinear strain-hardening characteristics of the model and the longitudinal pre-stressing.Conclusion:The proposed formulation permits a systematic and generalizable investigation, which, together with the low computational cost of analysis, makes it a valuable tool for calculating the response of healthy, atherosclerotic, and aneurysmatic arteries. The radial resonance frequencies can explain certain murmures developed in stenotic arteries.

Apolipoprotein A-I (ApoA-I), a primary protein component of high-density lipoprotein (HDL), plays an important role in cholesterol metabolism mediating the formation of HDL and the efflux of cellular cholesterol from macrophage foam cells in arterial walls. Lipidation of ApoA-I is mediated by adenosine triphosphate (ATP) binding cassette A1 (ABCA1). Insufficient ABCA1 activity may lead to increased risk of atherosclerosis due to reduced HDL formation and cholesterol efflux. The standard radioactive assay for measuring cholesterol transport to ApoA-I has low throughput and poor dynamic range, and it fails to measure phospholipid transfer. We describe the development of two sensitive, nonradioactive high-throughput assays that report on the lipidation of ApoA-I: a homogeneous assay based on time-resolved fluorescence resonance energy transfer (TR-FRET) and a discontinuous assay that uses the label-free Epic platform. The TR-FRET assay employs HiLyte Fluor 647-labeled ApoA-I with N-terminal biotin bound to streptavidin-terbium. When fluorescent ApoA-I was incorporated into HDL, TR-FRET decreased proportionally to the increase in the ratio of lipids to ApoA-I, demonstrating that the assay was sensitive to the amount of lipid bound to ApoA-I. In the Epic assay, biotinylated ApoA-I was captured on a streptavidin-coated biosensor. Measured resonant wavelength shift was proportional to the amount of lipids associated with ApoA-I, indicating that the assay senses ApoA-I lipidation. © 2012 Society for Laboratory Automation and Screening.

During pregnancy the walls of decidual spiral arteries (SAs) undergo clinically important structural modifications crucial for embryo survival/growth and maternal health. However, the mechanisms of SA remodeling (SAR) are poorly understood. Although an important prerequisite to this understanding is knowledge about the phenotype of SA muscular wall prior to and during the beginning of mouse SAR, this remains largely unexplored and was the main aim of this work. Using histological and immunohistochemical techniques, this study shows for the first time that during early mouse gestation, from embryonic day 7.5 (E7.5) to E10.5, the decidual SA muscular coat is not a homogeneous structure, but consists of two concentric layers. The first is a largely one cell-thick sub-endothelial layer of contractile mural cells (positive for α-smooth muscle actin, calponin and SM22α) with pericyte characteristics (NG2 positive). The second layer is thicker, and evidence is presented that it may be of the synthetic/proliferative smooth muscle phenotype, based on absence (α-smooth muscle actin and calponin) or weak (SM22α) expression of contractile mural cell markers, and presence of synthetic smooth muscle characteristics (expression of non-muscle Myosin heavy chain-IIA and of the cell proliferation marker PCNA). Importantly, immunohistochemistry and morphometrics showed that the contractile mural cell layer although prominent at E7.5-E8.5, becomes drastically reduced by E10.5 and is undetectable by E12.5. In conclusion, this study reveals novel aspects of the decidual SA muscular coat phenotype prior to and during early SAR that may have important implications for understanding the mechanisms of SAR. © 2011 Elsevier Inc. 416 211 216 Cited By :8

Within the context of finite deformation elasticity theory the problem of deforming an open sector of a thick-walled circular cylindrical tube into a complete circular cylindrical tube is analyzed. The analysis provides a means of estimating the radial and circumferential residual stress present in an intact tube, which is a problem of particular concern in dealing with the mechanical response of arteries. The initial sector is assumed to be unstressed and the stress distribution resulting from the closure of the sector is then calculated in the absence of loads on the cylindrical surfaces. Conditions on the form of the elastic strain-energy function required for existence and uniqueness of the deformed configuration are then examined. Finally, stability of the resulting finite deformation is analyzed using the theory of incremental deformations superimposed on the finite deformation, implemented in terms of the Stroh formulation. The main results are that convexity of the strain energy as a function of a certain deformation variable ensures existence and uniqueness of the residually-stressed intact tube, and that bifurcation can occur in the closing of thick, widely opened sectors, depending on the values of geometrical and physical parameters. The results are illustrated for particular choices of these parameters, based on data available in the biomechanics literature. Science Foundation Ireland [Grant No. SFI 08/W.1/B2580] peer-reviewed

Increase in carotid artery intima-media thickness (IMT) is an early sign of atherosclerosis. Slow coronary flow (SCF) is characterized by delay of opacification of coronary arteries in coronary angiography in the absence of any evident obstructive lesion, but its etiopathogenesis remains unclear. Genes that regulate the renin angiotensin system also play a role in developing cardiovascular system disorders. The presence of deletion (D) allele in angiotensin converting enzyme (ACE) gene polymorphism is associated with coronary artery disease. The aim of this study was to investigate the carotid artery IMT measurement, as an early sign of atherosclerosis, in patients with SCF and without SCF and also to assess the effect of the renin-angiotensin gene system on carotid IMT. Forty-four patients with angiographically proven SCF and 44 cases with normal coronary flow (NCF) pattern with similar risk profile were enrolled in the study. Coronary flow patterns of the cases were determined by thrombolysis in myocardial infarction (TIMI) frame count method. Intima-media thickness was measured by recording ultrasonographic images of both the left and right common carotid artery with a 12-MHz linear array transducer. ACE I/D polymorphism and Angiotensin II tip 1 receptor (AT1R) A/C gene polymorphism were determined by polymerase chain reaction (PCR) amplification. Demographic characteristics and coronary artery disease risk factors of SCF and NCF groups were similar. Mean TIMI frame count and carotid IMT (mm) were significantly higher in the SCF group than controls (45.9 ± 12 vs 23.3 ± 3.7, P = 0.0001; 0.75 ± 0.08 vs 0.69 ± 0.06, P = 0.0001, respectively). Mean TIMI frame count was positively correlated with IMT of carotid artery in correlation analysis (r = 0.45, P = 0.0001). When analyzed in regard to ACE genotype in all subjects, IMT values were statistically different (0.78 ± 0.06 for DD genotype, 0.72 ± 0.05 for ID genotype, and 0.64 ± 0.06 for II genotype, P = 0.0001). This difference remained significant in subgroup analyses for each genotype. No association could be observed between the AT1R A/C1166 polymorphism and IMT of carotid artery measurement (P > 0.05). Lack of association was still observed with analysis carried out when genotype effect was assumed to be inherited as additive (CC versus AA versus AC) or dominant (AA versus AC+CC). Increased IMT in patients with SCF shows that subclinical atherosclerosis may play role in this phenomenon. This increase was most marked in the presence of D allele of ACE genotype, which is associated with vascular hypertrophy. © Springer-Verlag Tokyo 2007.

Over past few years, we are developing a system for facilitating large scale screening of patients for cardiovascular risk-arterial stiffness evaluation for noninvasive screening (ARTSENS). ARTSENS is an image-free device that uses a single element ultrasound transducer to obtain noninvasive measurements of arterial stiffness (AS) in a fully automated manner. AS is directly proportional to end-diastolic lumen diameter (Dd). Multilayered structure of the arterial walls and indistinct characteristics of intima-lumen interface (ILI) makes it quite difficult to accurately estimate Dd in A-mode radiofrequency (RF) frames obtained from ARTSENS. In this paper, we propose a few methods based on fitting simple mathematical models to the echoes from arterial walls, followed by a novel method to fuse the information from curve fitting error and distension curve to arrive at an accurate measure of Dd. To bring down the curve fitting time and facilitate processing on low-end processors, a novel approach using the autocorrelation of echoes from opposite walls of the artery has been discussed. The methods were analyzed for their comparative accuracy against reference Dd obtained from 85 human volunteers using Hitachi-Aloka eTRACKING system. Dd from all reported methods show strong and statistically significant positive correlation with eTRACKING and mean error of less than 7% could be achieved. As expected, Dd from all methods show significant positive correlation with age. � VC 2015 by ASME.

The objective of this study was to investigate differences in intima-media thickness (IMT) and diameter (D) measurements of the common carotid artery (CCA) in ultrasound imaging in normal subjects and renal failure disease (RFD) patients. Manual measurements by two experts and automated segmentation measurements (based on snakes and active contour models (ACM)) were carried out on 73 normal subjects, and 80 RFD patients. Statistical analysis was carried out using the Wilcoxon rank-sum test at p

The cerebral vasculature ensures proper cerebral function by transporting oxygen, nutrients, and other substances to the brain. Distribution of oxygenated blood throughout the neuroaxis takes place at the level of the circle of Willis (CW). While morphologic and functional alterations in CW arteries and its main branches have been reported in cerebrovascular and neurodegenerative diseases, accompanying changes in protein expression profiles remain largely uncharacterized. In this study, we performed proteomics to compile a novel list of proteins present in mouse CW arteries and its ramifications. Circle of Willis arteries were surgically removed from 6-month-old wild-type mice, proteins extracted and analyzed by two proteomics approaches, gel-free nanoLC-mass spectrometry (MS)/MS and gel-based GelLC-MS/MS, using nanoAcquity UPLC coupled with ESI-LTQ Orbitrap XL. The two approaches helped maximize arterial proteome coverage. Six biologic and two technical replicates were performed. In all, 2,188 proteins with at least 2 unique high-scoring peptides were identified (6,630 proteins total). Proteins were classified according to vasoactivity, blood-brain barrier specificity, tight junction and adhesion molecules, membrane transporters/channels, and extracellular matrix/basal lamina proteins. Furthermore, we compared the identified CW arterial proteome with the published brain microvascular proteome. Our database provides a vital resource for the study of CW cerebral arterial protein expression profiles in health and disease. © 2014 ISCBFM All rights reserved.

Peripheral arterial elastic properties are greatly affected by cardiovascular as well as other pathologies, and their assessment can provide useful diagnostic indicators. The photoplethysmographic technique can provide finger blood volume and pressure waveforms non-invasively, which can then be processed statically or beat-to-beat to characterize parameters of the vessel wall mechanics. We employ an occlusion-deflation protocol in 48 healthy volunteers to study peripheral artery compliance-related indices over positive and negative transmural pressure values as well as under the influence of a valid vasoconstrictor (cigarette smoking). We calculate beat-to-beat indices (compliance index CI, distensibility index DI, three viscoelastic model parameters (compliance C, viscosity R and inertia L), pressure-volume loop areas A and damping factor DF as well as symmetrical (C(max)) and asymmetrical (C(A)(max)) static compliance estimates, and their distributions over transmural pressure. All distributions are bell-shaped and centred on negative transmural pressure values. Distribution heights were significantly lower in the smoking group (w.r.t. the non-smoking group) for C, CI, DI and significantly higher in R and DF. The estimated volume signal time lag was also significantly lower in the smoking group. Left and right distribution widths were significantly different in all parameters/groups but DI (both groups), C(A)(max), A (smoking group) and L (non-smoking group), and positions of maxima/minima were significantly altered in C(A)(max), R and DF. C, DF and CI are seen to be most sensitive under this protocol, while C(max) and C(A)(max) are seen to be insensitive. These quantities provide complementary, time- and transmural pressure-dependent information about arterial wall mechanics, and the choice of index should depend on the physiological conditions at hand as well as relevant time resolution and transmural pressure range.

Objective : To determine the relationship of serum total homocysteine (tHcy), serum folate and 5,10-methylenetetrahydrofolate reductase (MTHFR) 677C→T genotype with ultrasonic arterial wall measurements associated with subclinical atherosclerosis. Study design : Cross-sectional analysis of 767 participants in an ongoing prospective study. Intima-media thickness (IMT) of the common carotid (IMTcc), IMT of the internal carotid including plaque when present (IMTmax) and the sum of the thickest plaques present in both carotid and both common femoral bifurcations (total plaque thickness (TPT)) were measured using ultrasound. Results : People in the upper homocysteine quartile were more likely to have clinical cardiovascular disease (CVD) than those in the lowest three quartiles. They were also more likely to have plaques. The MTHFR 677C→T genotype was not associated with any of the measures of subclinical atherosclerosis in either men or women but was the most important determinant of total homocysteine levels in men under 60 years of age. Conclusions : Increased homocysteine levels but not MTHFR 677C→T genotype, are associated with subclinical atherosclerosis and the presence of plaques. Our results indicate that measurements of blood levels of homocysteine and folate in people at intermediate risk for atherosclerotic CVD before symptoms occur, might improve risk stratification and facilitate the decision to provide folate/B vitamin intervention in primary prevention. © 2009 Informa UK Ltd. All rights reserved. 13 1 11 Cited By :11

Passive elastic behavior of arterial wall remains difficult to model. Although phenomenological and structural models exist, the question of how the three-dimensional network structure of the collagen in the artery determines its mechanical properties is still open. A model is presented that incorporates a collagen network as well as the noncollagenous material that comprise the artery. The collagen architecture is represented as a network of interconnected fibers, and a neo-Hookean constitutive equation is used to describe the contribution of the noncollagenous matrix. The model is multiscale in that volume-averaging theory is applied to the collagen network, and it is structural in that parameters of the microstructure of the collagen network were considered instead of a macroscopic constitutive law. The computational results provided a good fit to published experimental data for decellularized porcine carotid arteries. The model predicted increased circumferential compliance for increased axial stretch, consistent with previously published reports, and a relatively small sensitivity to open angle. Even at large extensions, the model predicted that the noncollagenous matrix would be in compression, preventing collapse of the collagen network. The incorporation of fiber-fiber interactions led to an accurate model of artery wall behavior with relatively few parameters. The counterintuitive result that the noncollagenous component is in compression during extension and inflation of the tissue suggests that the collagen is important even at small strains, with the noncollagenous components supporting the network, but not resisting the load directly. More accurate representation of the microstructure of the artery wall is needed to explore this issue further. Copyright © 2007 by ASME. 129 611 618 611-618

Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-27T11:21:03Z No. of bitstreams: 0Bitstream added on 2014-05-27T14:28:33Z : No. of bitstreams: 1 2-s2.0-33645505156.pdf: 537666 bytes, checksum: a70f3d6285bf6019040d38c0aa00763c (MD5) Made available in DSpace on 2014-05-27T11:21:03Z (GMT). No. of bitstreams: 0 Previous issue date: 2004-04-01 In the renal and femoral arteries of rabbit was verified that both vessels had walls structured by myostromal components, despite of their different distributive of blood, being the renal artery a visceral blood vessel and the femoral artery a parietal vessel. This wall pattern in these vessels concerned to presence of connective stromal elements (collagen and elastic fibres and lamellae) and smooth muscle cells coexisting with some equilibrium in the wall structure of the renal and femoral arteries, mainly in the medial layer architecture. An intimal folding pattern was verified around the vascular lumen, possibly related to capacitance of the both arteries regarding to variability of pressure levels in cardiac cycle. Furthermore, myostromal relations of connective elements and smooth muscle cells verified in the medial layer and the network formed by connective elements in the adventitial layer of these arteries contributed to maintenance of wall viscoelasticity properties of the vessels. Programa de Pós-graduação em Anatomia dos Animais Domésticos e Silvestres FMVZ Universidade de São Paulo, São Paulo, São Paulo Departamento de Anatomia Universidade Estadual Paulista, Botucatu, São Paulo Programa de Pós-graduação em Biologia Celular e Estrutural Unicamp, Campinas, São Paulo Departamento de Ciências Morfofisiológicas Universidade Estadual de Maringá, Maringá, Paraná , Distrito de Rubiao Junior, s/n, 18618-000, Botucatu, São Paulo Departamento de Anatomia Universidade Estadual Paulista, Botucatu, São Paulo

The limited biocompatibility of decellularized scaffolds is an ongoing challenge in tissue engineering. Here, we demonstrate the residual immunogenicity of an extensively decellularized equine carotid artery (dEAC intens) and identify the involved immunogenic components. EAC were submitted to an elaborated intensified decellularization protocol with SDS/sodium desoxycholate for 72 h using increased processing volumes (dEAC intens), and compared to dEACord prepared by an ordinary protocol (40 h, normal volumes). Matrix integrity was checked via correlative volumetric visualization which revealed only minor structural changes in the arterial wall. In dEACintens, a substantial depletion of cellular components was obvious for smooth muscle actin (100%), MHC I complexes (97.8%), alphaGal epitops (98.4% and 91.3%) and for DNA (final concentration of 0.34±0.16 ng/mg tissue). However, dEACintens still evoked antibody formation in mice after immunization with dEACintens extracts, although to a lower extent than dEACord. Mouse plasma antibodies recognized a 140 kDa band which was revealed to contain collagen VI alpha1 and alpha2 chains via mass spectrometry of both 2D electrophoretically separated and immunoprecipitated proteins. Thus, even the complete removal of cellular proteins did not yield non-immunogenic dEAC as the extracellular matrix still conferred immunogenicity by collagen VI. However, as lower antibody levels were achieved by the intensified decellularization protocol, this seems to be a promising basis for further development.