Search Results
Results 401 - 450 of 1587
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Armentano Ricardo L - - 2006
Damping is the conversion of mechanical energy of a structure into thermal energy, and it is related to the material viscous behavior. To evaluate the role of damping in the common carotid artery (CCA) wall in human hypertension and the possible improvement of angiotensin-converting enzyme (ACE) inhibition, we used noninvasive ...
Maneen Matthew J - - 2006
BACKGROUND AND PURPOSE: This study investigated the effect of peroxynitrite (ONOO-) on pressure-induced myogenic activity and vascular smooth muscle (VSM) actin of isolated posterior cerebral arteries (PCAs). METHODS: Histochemical staining of nitrotyrosine (NT) was used to demonstrate the presence of ONOO- in the cerebrovasculature after 1 hour of middle cerebral ...
Razus Domnina - - 2006
An experimental study on pressure evolution during closed vessel explosions of several gaseous fuel-air mixtures was performed, at various initial pressures within 0.3-1.2 bar and ambient initial temperature. Explosion pressures and explosion times are reported for methane-, n-pentane-, n-hexane-, propene-, butene-, butadiene-, cyclohexane- and benzene-air mixtures. The explosion pressures measured ...
Xiao Daliao - - 2006
The mechanisms of adaptation of uterine artery vascular tone to pregnancy are not fully understood. The present study tested the hypothesis that pregnancy decreases the PKC-mediated Ca(2+) sensitivity of the contractile process and attenuates myogenic tone in resistance-sized uterine arteries. In pressurized uterine arteries from nonpregnant (NPUA) and near-term pregnant ...
Smith Ronald D - - 2006
The VIOS (Vascular Improvement with Olmesartan medoxomil Study) study is a randomized, parallel study to determine the relative effects of suppressing the renin-angiotensin system (RAS) with the angiotensin receptor antagonist olmesartan medoxomil versus suppressing sympathetic drive with the beta-adrenoceptor antagonist atenolol on remodeling of the subcutaneous small resistance vessel. Remodeling ...
Triboulet Jean J Univ. of Montpellier II. - - 2006
This paper deals with the influence of the echographic probe pressure on the measurement of arterial diameter. It is common sense that arterial diameter measurements are affected by the pressure exerted on the B-mode ultrasound probe but we found no report in the current literature analyzing and quantifying this effect. ...
Heerkens Egidius H J - - 2006
Human essential hypertension is characterized by eutrophic remodeling of small arteries, with little evidence of hypertrophy. Likewise, vessels of young hypertensive TGR(mRen2)27 animals have undergone similar structural alterations. The role of integrins in resistance arteries of TGR(mRen2)27 during the eutrophic-remodeling process was examined as blood pressure rose. Initially, 8 alpha ...
Risler Norma R - - 2005
The basic hemodynamic abnormality in hypertension is an increased peripheral resistance that is due mainly to a decreased vascular lumen derived from structural changes in the small arteries wall, named (as a whole) vascular remodeling. The vascular wall is an active, flexible, and integrated organ made up of cellular (endothelial ...
Gleason Rudolph L RL - - 2005
Soft tissue growth and remodelling (G&R) are achieved through highly complex, temporally regulated mechanisms that lead to the adaptation of structurally significant cells and extracellular matrix proteins. Herein we present a constrained mixture model to describe vascular adaptations in response to large perturbations in luminal flow rate, transmural pressure and ...
Goto Hirohisa - - 2005
A general formula (Oka and Azuma's equation) has been rigorously derived for the circumferential wall tension in a hollow cylindrical tube in equilibrium. To evaluate the validity and usefulness of Oka and Azuma's equation, T = P(1) x r(1) - P(2) x r(2) (T, circumferential wall tension; P(1) and P(2), ...
Auer Roland N - - 2005
We here review the pathophysiology of primary intracerebral hemorrhage to compare and contrast bleeds due to hypertension and congophilic angiopathy. Hypertension is characterized by early proliferation of arteriolar smooth muscle, followed later by apoptotic smooth muscle cell death and collagen deposition. Eventually excess or deficient collagen deposition can lead respectively ...
Sato Yoshinobu - - 2005
Scale-up of wet granulation in a vertical high shear mixer was conducted. Pharmaceutical excipient mixtures composed of lactose, cornstarch and micro-crystalline cellulose, and hydroxypropylecellulose as a binder were mixed together and then granulated with purified water under various operating conditions and vessel scales. Torque of agitator shaft was continuously measured ...
Bergh Niklas - - 2005
The vascular endothelium transduces physical stimuli within the circulation into physiological responses, which influence vascular remodelling and tissue homeostasis. Therefore, a new computerized biomechanical ex vivo perfusion system was developed, in which small intact vessels can be perfused under well-defined biomechanical forces. The system enables monitoring and regulation of vessel ...
Shi Ying - - 2006
Nonselective inhibition of nitric oxide (NO) synthase (NOS) augments myogenic autoregulation, an action that implies enhancement of pressure-induced constriction and dilatation. This pattern is not explained solely by interaction with a vasoconstrictor pathway. To test involvement of the Rho-Rho kinase pathway in modulation of autoregulation by NO, the selective Rho ...
Bagatto Brian - - 2006
There has been considerable recent interest in the development of the circulation in the zebrafish. Optical techniques typically used to visualize changes in heart size allow measurement of stroke volume during early vertebrate development, but this approach is complicated in zebrafish larvae because of the heart's irregular shape and its ...
Tangney Paul - - 2005
We used simulations with a classical force field to study the transformation under hydrostatic pressure of isolated single-walled nanotubes (SWNT) from a circular to a collapsed cross section. Small-diameter SWNTs deform continuously under pressure, whereas larger-diameter SWNTs display hysteresis and undergo a first-order-like transformation. The different behavior is due to ...
Li Yang - - 2005
We investigated the effect of relaxin on vasodilation, myogenic reactivity, and compliance of small mesenteric arteries and veins. In acute experiments, small (second order) mesenteric arteries and veins from female rats were mounted in a pressure myograph, perfused intraluminally with relaxin, and exposed to incremental increases in intraluminal pressure (20-120 ...
Gu Hai - - 2006
The slit arteriotomy for end-to-side arterial microanastomosis is a technique used to revascularize free flaps in reconstructive surgery. Does a slit open to a width sufficient for blood supply? How is the slit opening affected by factors, such as arterial wall thickness and material stiffness? To answer these questions we ...
Botet Xavier - - 2005
A new technique for ligating vessels and similar structures that offers more security is described. The aim of the study was to test whether this hypothesis was correct. Six different types of knots, including the one described in this article were compared by a strength-testing study. The knots were tied ...
Pries Axel R - - 2005
Vascular functions, including tissue perfusion and peripheral resistance, reflect continuous structural adaptation (remodeling) of blood vessels in response to several stimuli. Here, a theoretical model is presented that relates the structural and functional properties of microvascular networks to the adaptive responses of individual segments to hemodynamic and metabolic stimuli. All ...
Han Hai-Chao HC Department of Mechanical Engineering, University of Texas at San Antonio, San Antonio, TX 78249, USA. haichao.han@utsa.edu - - 2006
To study the effect of pressure changes on the opening angle of arteries in organ culture, tubular segments of porcine common carotid arteries were cultured with pulsatile flow perfusion under hypertensive (150+/-20 mmHg), normotensive (100+/-20 mmHg), or hypotensive (30+/-10 mmHg) pressure while maintaining the arteris at a physiological wall shear ...
Inoguchi Hiroyuki - - 2006
To design a "mechano-active" small-diameter artificial vascular graft, a tubular scaffold made of elastomeric poly(L-lactide-co-epsilon-caprolactone) fabrics at different wall thicknesses was fabricated using an electrospinning (ELSP) technique. The wall thickness of the fabricated tube (inner diameter; approximately 2.3-2.5 mm and wall thickness; 50-340 microm) increased proportionally with ELSP time. The ...
Patton Niall - - 2005
PURPOSE: To explore the association between axial length and retinal vascular network geometry (arteriovenous diameter ratio [AVR], arteriolar branching angles, and junctional exponents). DESIGN: Prospective, cross-sectional study. METHODS: Patients were recruited from a pseudophakic population that had preexisting axial length measurements. Mean arterial blood pressure and previous medical history were ...
Anschütz Stephanie - - 2005
The hypothesis that the amplitude of the myogenic response is modulated by factors released from nerve endings was tested in rat tail small arteries. A pressure myograph in conjunction with direct stimulation of nerve endings by electrical field stimulation (EFS) was used to determine rat small artery contractile reactions. Vessel ...
Jacobsen Anna L - - 2005
Possible mechanical and hydraulic costs to increased cavitation resistance were examined among six co-occurring species of chaparral shrubs in southern California. We measured cavitation resistance (xylem pressure at 50% loss of hydraulic conductivity), seasonal low pressure potential (P(min)), xylem conductive efficiency (specific conductivity), mechanical strength of stems (modulus of elasticity ...
Viol Anthony W - - 2005
BACKGROUND: Loss of vascular tone in resistance arterioles has been implicated as the cause of hypotension in septic shock. It is believed that the overproduction of nitric oxide (NO) by the inducible isoform of nitric oxide synthase (iNOS) results in the vasodilatation seen in septic shock. However, we have shown ...
Liddell Robert P - - 2005
PURPOSE: Current animal hindlimb ischemia models involve surgical ligation of the femoral artery and delivery of therapeutic angiogenic agents into the adductor compartment. The authors hypothesize that an endovascular model of hindlimb ischemia would be a more appropriate platform, closely resembling atherosclerosis by occluding the vessel from within, causing less ...
Bagi Zsolt - - 2005
OBJECTIVE: Type 2 diabetes mellitus (T2-DM) is frequently associated with vascular dysfunction and elevated blood pressure, yet the underlying mechanisms are not completely understood. We hypothesized that in T2-DM, the regulation of peripheral vascular resistance is altered because of changes in local vasomotor mechanisms. METHODS AND RESULTS: In mice with ...
Takagi Kentaro - - 2005
The effects of electroacupuncture stimulation (EAS) of the hind paw and the back on the mesenteric microhemodynamics in anesthetized rats were investigated using an intravital microscope system. Red blood cell (RBC) velocity in the mesenteric arterioles was measured by the dual-sensor method developed by the authors. Electrical stimulation was applied ...
Petersen K A - - 2005
Calcitonin gene-related peptide (CGRP) and related peptides may be involved in migraine pathogenesis. To understand their vasomotor role in the cerebral circulation, we performed two studies, a pressurized arteriography study of the middle cerebral artery (MCA) and a genuine closed cranial window (gCCW) in vivo study. Using the pressurized arteriography ...
Hendlin Kari - - 2005
BACKGROUND AND PURPOSE: The dynamics of ureteral balloon expansion may differ with increasing extrinsic compressive forces and inflation pressures. This study compared the ability of ureteral balloons to expand under different conditions. MATERIALS AND METHODS: The balloons tested were the Cook Accent, Ascend, Ascend AQ, and Pursuit; the Bard 195503 ...
Roy Sylvain - - 2005
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 diameter, and wall thickness were measured by optical microscopy on neighboring histological sections before and after decellularization. Rupture tests were ...
Cheng Allen - - 2005
In an attempt to provide a better understanding of our finding that regions with contracting left ventricular myofibers need not develop a significant transmural systolic wall thickening gradient, the analytic approach of Costa et al. was applied to the four-dimensional dynamic data obtained 1 and 8 wk after surgical implantation ...
Jean-Louis Seendy - - 2005
PURPOSE: Several studies have investigated the changes in retinal vessel diameter during physiological stress or pathologic conditions. These studies were principally based on individual fundus photographs and as such did not allow the evaluation of vessel dynamics over time. The research objective was to detail the time course and amplitude ...
Karam Gebran N - - 2005
BACKGROUND AND AIMS: The xylem, or water transport system, in vascular plants adopts different morphologies that appear sequentially during growth phases. This paper proposes an explanation of these morphologies based on engineering design principles. METHODS: Using microscopic observations of the different growth stages, an engineering analysis of the xylem vessels ...
Stålhand J - - 2005
It was shown in a previous study by Stålhand et al. (2004) that both material and residual strain parameters for an artery can be identified noninvasively from an in vivo clinical pressure-diameter measurement. The only constraints placed on the model parameters in this previous study was a set of simple ...
Coats Paul - - 2005
Atherosclerosis in a major leg artery leads to impaired blood supply, which normally progresses to critical limb ischemia. Atherosclerosis produces substantial alterations of structure and endothelial function in the large conduit arteries. Pressure unloading and ischemia in the distal vasculature bring about alterations in microvascular function. Resistance arteries undergo significant ...
Pakter Helena M - - 2005
BACKGROUND: The extent of arteriolar narrowing has been recognized as a major sign of end-organ damage in patients with hypertension, but most methods used for its evaluation are highly dependent on the observer. We describe a new semi-automated method to measuring arteriolar-to-venous (A/V) ratio in retinal photography and present its ...
Allahdadi Kyan J - - 2005
We reported previously that simulating sleep apnea in rats by exposing them 7 hours per day to intermittent hypoxia/hypercapnia (IH) elevates plasma endothelin-1 and causes hypertension, which is reversed by an endothelin-1 antagonist. We hypothesized that in this model of sleep apnea-induced hypertension, vascular sensitivity to endothelin-1 is increased in ...
Izzard Ashley S - - 2005
Hypertension is known to be associated with an increase in the wall/lumen ratio (W/L) of the resistance arteries. Growth, eutrophic remodelling and changes in arterial distensibility can all contribute to an increase W/L. Wall stress may stimulate growth, whereas remodelling and/or reduced distensibility may be the result of prolonged contraction. ...
Sun Lei - - 2005
High blood pressure (hypertension) is implicated in the development of atherosclerosis. Blood vessels are constantly subjected to stretch due to blood pressure and changes in stretch usually instigate adaptive vascular remodeling, including abnormal growth and proliferation of vascular smooth muscle cells (VSMCs) as well as extracellular matrix (ECM). In this ...
Mulvany Michael J - - 2005
The structure of the resistance vessels in patients with essential hypertension is altered, with reduction of the lumen diameter and increase in wall-to-lumen ratio without change in wall mass, known as eutrophic remodelling. The alteration appears to cause a reduction in the vascular reserve, in particular the coronary reserve (the ...
Kurbel Sven - - 2005
It is generally assumed that almost no pressure gradient exists in the aorta and large arteries. This holds truth in rest, but during heavy exercise, when the resistance of arterioles in active skeletal muscles is diminished, the remaining resistance of large and small arteries might become significant and limit the ...
Abe Kaoru - - 2005
To evaluate the ability of ultrasonically activated shears (USAS) to occlude lymphatic vessels, we investigated the bursting pressure of lymphatic vessels occluded with USAS and compared with pressures in an artery and a vein. The inguinal lymphatic vessels, testicular arteries, and testicular veins were removed from male pigs. The vessels ...
Morris Cassandra - - 2005
This study was designed to directly quantify the effect of localized static magnetic field (SMF) exposure on the diameter of microvessels in adult rat skeletal muscle in vivo. Microvascular networks in the exteriorized rat spinotrapezius microvasculature were exposed to a localized, uniform 70 mT SMF for 15 min. Arteriolar vessel ...
Ple┼čea I E - - 2005
AIMS: The study was performed in order to assess the alterations of extra-parenchymal and intraparenchymal vascular structures in 82 hypertensive patients suspected of primary intraparenchymal hematoma, which died and were autopsied in order to confirm the diagnosis. MATERIAL AND METHODS: The studied material consisted of nervous tissue situated near and ...
Pietrow Paul K - - 2005
BACKGROUND AND PURPOSE: Laparoscopic bipolar instruments are commonly employed to cauterize and divide tissue. A next-generation bipolar device has been developed that employs vapor pulse coagulation energy. We assessed the vessel-sealing capability of this device and quantified thermal spread during application. MATERIALS AND METHODS: Bilateral laparoscopic nephrectomy was performed on ...
Blum M - - 2005
PURPOSE: The effect of elevated blood glucose level on the myogenic response of human retinal arterioles to acute increases in blood pressure is investigated. METHODS: The vascular response to raised blood pressure (Bayliss effect) was measured in 12 healthy volunteers by use of the retinal vessel analyzer (RVA). For a ...
Petersen K A - - 2005
The genuine closed cranial window model, in which the thinned parietal bone constitutes the covering of the preparation, has contributed to a better understanding of the pathophysiological mechanisms in migraine. In its present form, only measurements of the middle meningeal artery (MMA) are performed. The aim of this study was, ...
Gokina Natalia I - - 2005
Several recent studies have implicated the RhoA-Rho kinase pathway in arterial myogenic behavior. The goal of this study was to determine the effects of Rho kinase inhibition (Y-27632) on cerebral artery calcium and diameter responses as a function of transmural pressure. Excised segments of rat posterior cerebral arteries (100-200 microm) ...
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