To maintain normal blood flow, pressure overload in both arteries and veins requires a structural adaptation of the vessel wall (remodelling) that involves smooth muscle cell (SMC) hypertrophy and/or hyperplasia. Due to its potent vasoconstrictor and growth-promoting effects, endothelin-1 (ET-1) is a likely candidate to initiate and/or promote remodelling in ...

BACKGROUND: The cardiovascular effects of sildenafil (Viagra), a selective inhibitor of phosphodiesterase type 5 (PDE5), have been extensively studied. However, its effect on human retinal arteries and veins has not yet been investigated. The effect of a single dose administration of sildenafil on the retinal vessel diameters of healthy subjects ...

Hypertension is associated with altered structure of the resistance vessels, a process known as remodeling. This review summarizes current concepts concerning the structure of a subgroup of the resistance vessels, the small arteries, and the modes of remodeling, some of the determinants of remodeling, and some signaling pathways for remodeling. ...

PURPOSE: To determine how the adaptation of extranidal cerebral vessels affects feeding artery pressure, draining vein pressure, and regional hypotension due to the presence of brain arteriovenous malformations (BAVMs). CONCEPT: BAVMs cause high flows in feeding arteries and draining veins and can induce profound hypotension in the neighboring vasculature. Despite ...

During the development of hypertension, hypertrophy of smooth muscle cells and deposition of extracellular matrix thicken the walls of large arteries without reducing the size of the lumen. The small arteries and arterioles remodel inwardly through a eutrophic process of rearrangement of the same smooth muscle cells around a smaller ...

The aim of this study is to examine the interaction between two mild atherosclerotic proliferations spaced apart by a distance S by analyzing their influence on flow structure, pressure drop and stress field in an arterial vessel under pulsatile flow conditions. This has been achieved numerically by employing a time ...

The hypothesis was tested that chronic vasoconstriction is followed by a structural reduction in lumen diameter, measured at full dilation. An in vitro model of pressurized rat skeletal muscle arterioles was used. During a 3-day experimental period, constriction of active vessels was achieved with fetal calf serum or endothelin-1 (ET-1). ...

Laboratory observations have noted that during normocapnia and intact vascular tone, changes in the intracranial pressure (ICP) and arterial blood pressure (ABP) recordings are not similar. The purpose of the present study was to determine whether: 1) the diameter of cerebral pial arterioles synchronously increases during positive pressure inhalation and ...

OBJECTIVE: The effect of vessels and their size on radiofrequency lesion creation in the liver was evaluated with respect to potential for vascular injury and perfusion-mediated "heat sink" effect. SUBJECTS AND METHODS: Radiofrequency lesions targeted to tissue adjacent to a variety of vessels were created in vivo in the liver ...

We compared the shortening velocity of smooth muscle in arterioles that had low or high levels of myogenic tone or norepinephrine (NE)-induced tone. We hypothesized that enhanced myogenic tone of arterioles reflects an enhanced maximum velocity of shortening of arteriolar smooth muscle in a way that is different from that ...

Blood vessels are capable of dynamic structural adaptation in which their diameters and wall thicknesses change in response to chronic changes in hemodynamic conditions. Such structural changes can have large effects on vascular resistance to blood flow. Structural responses to hemodynamic stresses, i.e., wall shear stress resulting from blood flow ...

In this study we have explored the potential of PUVB (8-MOP + UVB) therapy for the reduction of luminal narrowing after arterial injury. In 15 rabbits, balloon dilation of iliac arteries was performed. In 20 arteries, dilation was combined with the delivery of pulsed ultraviolet light B (UVB) irradiation with ...

OBJECTIVE: Biosynthesis of eicosanoid metabolites in blood vessels regulates vascular tone and platelet function. We investigated whether intraluminal pressure modulates gene and protein expression of key eicosanoid enzymes in intact human conduit vessels and/or release of their vasoactive metabolites. METHODS: Paired segments of human umbilical veins were perfused under laminar ...

Hypertension, a disease with a high incidence in the population, affects all parts of the cardiovascular system. Studying the alteration of vasomotor responses of microvessels of hypertensive animals or responses of vessels following short-term increases in hemodynamic forces helps us to better understand the underlying cellular signaling events responsible for ...

BACKGROUND: The clinical implication of the tortuosity of white matter medullary arterioles has never been clarified precisely. We quantitatively investigated the relationship between such vascular tortuosity and the severity of hypertension (HT), which was graded according to the WHO classification. METHODS: Forty-seven autopsied brains with age-adjusted stages of HT were ...

Ground studies indicate that spaceflight may diminish vascular contraction. To examine that possibility, vascular function was measured in spontaneously hypertensive rats immediately after an 18-day shuttle flight. Isolated mesenteric resistance arterial responses to cumulative additions of norepinephrine, acetylcholine, and sodium nitroprusside were measured using wire myography within 17 h of ...

The purpose of this study was to examine the relationship between proposed correlation indices of cerebrovascular reserve and corresponding changes of cerebrovascular reserve as measured by changes of pial arteriolar diameter. Mild and severe physiologic challenge was produced in piglets by appropriate ventilation with foreign gas mixture and altered alveolar ...

Coronary vessels are squeezed by the surrounding myocardium during systole, impeding blood flow specifically in the subendocardium. To study the myocardial compression effect, we applied pulsatile transvascular pressure to isolated, cannulated subendocardial (Endo) and subepicardial (Epi) resistance arteries. Pressure pulsation at 0.5 to 2.5 Hz between 20 and 100 mmHg ...

Structural reductions in vessel luminal diameters in response to elevated pressure may play a role in the elevation of peripheral resistance generally observed in hypertension. In the present study, a theoretical model is used to simulate the effect of increased driving pressure on flow resistance in microvascular networks. The angioarchitecture ...

To study pulmonary arteriolar vasomotion in control conditions and in the transition to hydraulic edema, changes in subpleural pulmonary arteriolar diameter and perivascular interstitial volume were evaluated in anesthetized spontaneously breathing rabbits. Images of subpleural pulmonary microvessels were recorded in control conditions and for up to 180 min during a ...

The first part of this paper focuses on unusual aspects of the cerebral circulation. Cerebral vessels have less smooth muscle and adventitia than other vessels, and the endothelial blood-brain barrier is unique. Because the wall of the arteries is thin, one might expect that the vessels are especially vulnerable to ...

Pressure-flow relationships at the entrance of the coronary circulation in the diastolic myocardium exhibit a zero-flow pressure intercept (P(int)). We tested whether this intercept is the same throughout the vascular bed. Microvascular pressure-flow relationships were therefore measured in vessels of various sizes of the maximally dilated vasculature of perfused unstimulated ...

The authors have designed a mathematical model to investigate the influences of the physical and chemical properties of the cerebral blood vessel resistance on vessel diameter. The model is based on the way the total tension within the blood vessel walls varies due to specific ions interacting and affecting the ...

RATIONALE AND OBJECTIVES: To assess the influence of gadolinium-containing magnetic resonance contrast agents on contractility of the arterial vessel wall. METHODS: Bilateral segments of rabbit carotid arteries were mounted in flow chambers, surrounded by aerated (95% O2, 5% CO2) Krebs' solution, and perfused at a constant rate by separated and ...

Myogenic tone is an important determinant of vascular tone and blood flow in small resistance arteries of certain vascular beds. The role of the endothelium in myogenic responses is unclear. We hypothesized that endothelium-derived NO release modulates myogenic constriction in small resistance arteries and that mesenteric small arteries from mice ...

Remodeling of large and small arteries contributes to the development and complications of hypertension. The focus of this review is some of the mechanisms involved in the remodeling of small arteries in hypertension. In hypertension, changes in small artery structure are basically of 2 kinds: (1) inward eutrophic remodeling, in ...

Advancements in laparoscopic surgery are often dictated by the limitations of technical instrumentation. Energy sources other than electrosurgery have become popular with the promise of quick and effective vascular control. With their success surgeons have begun using these on structures other than blood vessels with little or no data establishing ...

Terminal vascular beds continually adapt to changing demands. A theoretical model is used to simulate structural diameter changes in response to hemodynamic and metabolic stimuli in microvascular networks. Increased wall shear stress and decreased intravascular pressure are assumed to stimulate diameter increase. Intravascular partial pressure of oxygen (PO(2)) is estimated ...

1. Self-referencing ion-selective (SERIS) electrodes were used to measure the temperature and pressure dependence of Cl(-) efflux, during myogenic contraction of pressurized rat cerebral resistance arteries. 2. At room temperature (18-21 degrees C), a small, pressure-independent Cl(-) efflux was measured. On warming to 37 degrees C, arteries developed pressure-dependent myogenic ...

We studied a possible link between the melatonin-induced increase in cerebral arteriolar tone and the melatonin-induced shift in cerebral blood flow (CBF) autoregulation to a lower pressure level. Using the cranial window technique, we showed that intravenous infusion of melatonin constricted pial arterioles (-5.1 +/- 1.3 and -5.4 +/- 0.7 ...

AIMS: To investigate the peripheral vascular effects and pharmacokinetics of dihydroergotamine (DHE) 0.5 mg after a single subcutaneous administration in humans. METHODS: A double-blind, placebo-controlled cross-over study was performed in 10 healthy male subjects. A wash-out period of 2 weeks separated the two study periods. During each period, just before ...

Under real or simulated microgravity conditions the control of arterial vascular tone is greatly disturbed. The low arterial vessel reactivity to sympathetic influences may be the cause of an increase in flow in hind limb skeletal muscles in tail-suspended (TS) rats. Our previous experiments with constant pressure perfusion of rat ...

When carbonic anhydrase activity decreases, the regional blood flow (rBF) in organs increases as hypercapnia develops. However, the effects of acetazolamide (AZ)-induced vasodilation have not been estimated with respect to vessel size and organs. The aim of this study was to determine the diameter of the capillaries in various organs ...

Studies were conducted on isolated rat gracilis muscle arterioles to examine the role of vascular heme oxygenase (HO)-derived carbon monoxide (CO) on myogenic constrictor responses to stepwise increments in intraluminal pressure. The arterioles express HO-2 but not HO-1 and manufacture CO. Both HO-2 protein expression and CO production are reduced ...

Correction of structural abnormalities in resistance arteries of patients with essential hypertension is a potential treatment goal, in addition to blood pressure reduction. However, available evidence from human as well as from animal studies indicates that antihypertensive therapy is not always accompanied by normalization of resistance vessel structure, despite normalization ...

Arterial vessels express one or more heme oxygenase (HO) isoenzymes that catalyze the metabolism of heme to carbon monoxide (CO) and biliverdin. Carbon monoxide promotes vasorelaxation through mechanisms that, depending on the vessels, involve activation of soluble guanylate cyclase, stimulation of calcium-activated potassium channels, or diminished synthesis of constrictor mediators, ...

PURPOSE: The purpose of this study was to assess the vasoconstrictor effect of the prostaglandin F2 alpha analog latanoprost in isolated porcine ciliary arteries. MATERIAL AND METHODS: With a myograph system to measure isometric forces, porcine ciliary arteries were exposed, in a cumulative manner, to increasing concentrations of latanoprost (0.1 ...

To demonstrate axial artery motion during the cardiac cycle, the common carotid arteries (CCA) of 10 pigs were exposed and equipped with piezoelectric crystals sutured onto the artery as axial position detectors. An echo-tracking system was used to simultaneously measure the CCA diameter. For each animal, data for pressure, length, ...

BACKGROUND: Exposure to high +Gz forces may induce arm pain, which has been hypothesized to be caused by pressure-induced overdistension of local blood vessels. The purpose of the present investigation was to study the pressure-distension relation of veins and arteries in the human arm and the relation between arm pain ...

Evolution of species has led to the appearance of circulatory systems including blood vessels and one or more pulsatile pumps, typically resulting in a low-pressurised open circulation in most invertebrates and a high-pressurised closed circulation in vertebrates. In both open and closed circulations, the large elastic arteries proximal to the ...

Vascular grafts can be twisted inadvertently during implantation. If twisted excessively, they may kink and obstruct flow. In this study, in vitro experiments were performed to identify the mechanical factors that determine graft kinking. These included graft material, graft length, graft diameter, graft wall thickness, perfusion pressure, and flow rate. ...

Xenon may increase cerebral blood flow and intracranial pressure (ICP). To evaluate the effects of xenon on brain circulation, we measured pial vessel diameter changes, CO(2) reactivity, and ICP during xenon inhalation in rabbits. Minimum alveolar anesthetic concentration (MAC) for xenon was established in rabbits (n = 6). By using ...

Information is sparse concerning the effect of oophorectomy (OOX) on bone vascularization and blood flow of possible significance for altered remodeling. Whether OOX affects functional characteristics of isolated bone resistance arteries was investigated. Ring preparations (diameter approximately 250 microm) of small femoral bone arteries from oophorectomized and sham-operated rabbits were ...

Experiments were conducted to delineate the vascular effector systems that contribute to setting mesenteric vascular tone in swine during the first postnatal month. Terminal mesenteric arteries (TMA), which function as resistance vessels, were studied in vitro with a microvascular perfusion system allowing independent pressure and flow manipulation. When pressure was ...

The aim of the present study was to investigate the association between ultrasound Doppler measurements of resistive index (RI) in the central retinal artery and retinal vascular resistance (R) assessed with laser Doppler velocimetry, vessel size measurement, and calculation of ocular perfusion pressure (PP) in healthy subjects. An increase in ...

AIMS: There is evidence that secondary hyperparathyroidism alters arterial vessel wall properties. However, it is unclear whether effects of parathyroid hormone (PTH) on the vascular wall are direct or permissive and related to hypertension and renal failure. To assess early direct effects of PTH on large artery wall properties isobaric ...

OBJECTIVE: In this study we have examined for the first time the signal transduction mechanisms involved in the generation of pressure-dependent myogenic tone in human small resistance arteries from the subcutaneous vascular bed. METHODS: Myogenic responses and the subcellular mechanisms involved in the generation of this response were studied on ...

OBJECTIVE: We examined the time course of arteriogenesis (collateral artery growth) after femoral artery ligation and the effect of monocyte chemoattractant protein-1 (MCP-1). METHODS: New Zealand White rabbits received MCP-1 or phosphate buffered saline (PBS) for a 1-week period, either directly or 3 weeks after femoral artery ligation (non-ischemic model). ...

BACKGROUND: Dystrophin has a key role in striated muscle mechanotransduction of physical forces. Although cytoskeletal elements play a major role in the mechanotransduction of pressure and flow in vascular cells, the role of dystrophin in vascular function has not yet been investigated. Thus, we studied endothelial and muscular responses of ...

An inward rectifier potassium current, Kir, has been identified in cerebral and coronary resistance vessels, where it is considered to be an important determinant of resting membrane potential (RMP) and to play a role in blood flow regulation. We investigated the functional role of Kir in the renal afferent arteriole ...