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Vessel Size (vessel + size)
Selected AbstractsThe effects of acute and chronic exercise on the vasculatureACTA PHYSIOLOGICA, Issue 4 2010J. J. Whyte Abstract Regular physical activity (endurance training, ET) has a strong positive link with cardiovascular health. The aim of this review is to draw together the current knowledge on gene expression in different cell types comprising the vessels of the circulatory system, with special emphasis on the endothelium, and how these gene products interact to influence vascular health. The effect beneficial effects of ET on the endothelium are believed to result from increased vascular shear stress during ET bouts. A number of mechanosensory mechanisms have been elucidated that may contribute to the effects of ET on vascular function, but there are questions regarding interactions among molecular pathways. For instance, increases in flow brought on by ET can reduce circulating levels of viscosity and haemostatic and inflammatory variables that may interact with increased shear stress, releasing vasoactive substances such as nitric oxide and prostacyclin, decreasing permeability to plasma lipoproteins as well as the adhesion of leucocytes. At this time the optimal rate-of-flow and rate-of-change in flow for determining whether anti-atherogenic or pro-atherogenic processes proceed remain unknown. In addition, the impact of haemodynamic variables differs with vessel size and tissue type in which arteries are located. While the hurdles to understanding the mechanism responsible for ET-induced alterations in vascular cell gene expression are significant, they in no way undermine the established benefits of regular physical activity to the cardiovascular system and to general overall health. This review summarizes current understanding of control of vascular cell gene expression by exercise and how these processes lead to improved cardiovascular health. [source] Variable-Pulse Nd:YAG Laser in the Treatment of Facial TelangiectasiasDERMATOLOGIC SURGERY, Issue 1 2006AVERY A. BEVIN MD BACKGROUND Variable-pulse 1,064 nm wavelength lasers have been used with good effectiveness on leg telangiectasias and reticular veins and have shown promising results on facial telangiectasias as well. OBJECTIVE To investigate the effectiveness of a variable-pulse neodymium:yttrium-aluminum-garnet (Nd:YAG) laser using a small spot size in the treatment of facial telangi-ectasias. METHODS Eight male patients (mean age 75 years) underwent a single treatment session using a variable-pulse 1.5 mm spot size Nd:YAG laser with epidermal cooling. Telangiectasia diameters were 0.3 to 2.0 mm. Test sites were performed using three pulse widths (3, 20, and 60 ms), with fluences varying depending on vessel size and response. Full treatments were per-formed using test parameters giving the best response. Thirteen weeks later, the patients returned for final evaluation and satisfaction rating. RESULTS Fluences ranged from 226 to 425 J/cm2, with smaller vessels requiring larger energies. Pulse duration was equally divided between the 20 and 60 ms settings. The shortest pulse width (3 ms) was inferior in all patients. Longer pulse durations achieved superior vessel elimination with minimal immediate purpura and no postinammatory hyperpigmentation. The average mean vessel clearance was 26 to 50% in half of the patients and 51 to 75% in the other half as evaluated by three unbiased dermatologists with extensive laser experience. CONCLUSION A small,spot size Nd:YAG laser using a pulse width of 20 ms or higher appears to be effective in clearing a significant percentage of facial telangectasias with a single pass. The side effects were minimal. [source] Integrating remote sensing in fisheries controlFISHERIES MANAGEMENT & ECOLOGY, Issue 5 2005N. KOURTI Abstract, To complement existing fishery control measures, in particular the Vessel Monitoring System (VMS), a pilot operational system to find fishing vessels in satellite images was set up. Radar is the mainstay of the system, which furthermore includes fully automated image processing and communication protocols with the authorities. Different image types are used to match different fisheries , oceanic, shelf and coastal. Vessel detection rates were 75,100% depending on image type and vessel size. Output of the system, in the form of an overview of vessel positions in the area highlighting any discrepancies with otherwise reported positions, can be at the authorities within 30 min of the satellite image being taken , fast enough to task airborne inspection for follow up. [source] Patterns and consequences of differential vascular sectoriality in 18 temperate tree and shrub speciesFUNCTIONAL ECOLOGY, Issue 2 2006A. E. ZANNE Summary 1Resource delivery within plants depends on supply pathways. Some species have relatively constrained (sectored) vascular connections, while others have relatively unconstrained (integrated) vascular connections. 2In this study, patterns of vascular hydraulic sectoriality, anatomy and ecological tolerance were examined for 18 Northern Hemisphere temperate woody species growing at Arnold Arboretum, Jamaica Plain, MA, USA. A hydraulic technique was used to measure axial and tangential conductivity on branch segments. From a ratio of these values, a sectoriality index was calculated. 3Species that were more hydraulically sectored had greater vessel size, variation in vessel area and tangential nearest-neighbour distance, as well as lower vessel density, than did integrated species. 4Ecologically, higher tolerance to drought and wind was correlated with being sectored, while higher tolerance to flood and shade was correlated with being integrated. 5These results suggest that sectored species should be especially prominent in xeric environments where sectoriality may reduce embolism spread by minimizing vessel-to-vessel contact and pitting, and integrated species should be especially prominent when resources are spatially patchy or heterogeneous. [source] Earlywood vessel size of oak as a potential proxy for spring precipitation in mesic sitesJOURNAL OF BIOGEOGRAPHY, Issue 12 2008Patrick Fonti Abstract Aim, In this study, we evaluate the importance of the mean earlywood vessel size of oaks as a potential proxy for climate in mesic areas. Location, The study was conducted in Switzerland at three forest sites dominated by oak (Quercus petraea and Q. pubescens). The three sites were in different climatic zones, varying mainly in terms of precipitation regime. Methods, Three 50-year-long site chronologies of mean earlywood vessel size and tree-ring widths were obtained at each site and related to monthly meteorological records in order to identify the main variables controlling growth. The responses of mean vessel size to climate were compared with those of the width variables to evaluate the potential climatic information recorded by the earlywood vessels. Results, The results show that the mean vessel size has a different and stronger response to climate than ring-width variables, although its common signal and year-to-year variability are lower. This response is better in particular at mesic sites, where it is linked to precipitation during spring, i.e. at the time of vessel formation, and is probably related to the occurrence of only a few processes controlling vessel growth, whereas radial increment is controlled by multiple and varying factors. Main conclusions, The mean earlywood vessel size of oak appears to be a promising proxy for future climate reconstructions of mesic sites, where radial growth is not controlled by a single limiting factor. [source] Comparison of 1- and 2-Marker Techniques for Calculating System Magnification Factor for Angiographic Measurement of Intracranial VesselsJOURNAL OF NEUROIMAGING, Issue 4 2005A. A. Divani PhD ABSTRACT Background and Purpose. Accurate estimation of an intracranial vessel size is crucial during a diagnostic or therapeutic angiography procedure. The use of 1 or 2 external markers of known size is previously proposed to manually estimate the magnification factor (MF) of an intracranial vessel. The authors evaluated the use of different external marker techniques commonly used during angiographic measurements. Methods. Forty-three intracranial vessels in 17 patients were measured using 1-and 2-marker techniques. To obtain the MF, 2 metallic markers were attached to the frontal-temporal regions. The MFs for the targeted vessels were obtained from the x-ray films by measuring the image sizes of the markers and their positions with respect to the target vessel. Results. Using a phantom, the errors resulted from (a) linear interpolation of MFs, (b) linear interpolation of inverse MFs, and (c) using the MFs of 1 marker, which were 1.23% to 2.23%, 0.8% to 1.55%, and 3.85% to 14.62%, respectively. A similar trend was observed for the measurement of cerebral arteries. Conclusion. The use of 2 markers can result in a more accurate estimation of the vessel size. The use of only 1 external marker can lead to substantial error based on the location of the target vessel. Optimizing image acquisition is also crucial for accurate determination of vessel size. [source] Vascular response to laser photothermolysis as a function of pulse duration, vessel type, and diameter: Implications for port wine stain laser therapyLASERS IN SURGERY AND MEDICINE, Issue 2 2002Sol Kimel PhD Abstract Background and Objective Treatment of port wine stains (PWS) by photothermolysis can be improved by optimizing laser parameters on an individual patient basis. We have studied the critical role of pulse duration (tp) on the treatment efficacy. Study Design/Materials and Methods The V-beam laser (Candela) allowed changing tp over user-specified discrete values between 1.5 and 40 milliseconds by delivering a series of 100 microsecond spikes. For the 1.5 and 3 millisecond pulses, three spikes were observed at intervals tp/2 and for tp,,,6 milliseconds, four spikes separated by tp/3. The ScleroPlus laser (Candela) has a smooth output over its fixed 1.5 milliseconds duration. Blood vessels in the chick chorioallantoic membrane (CAM) were irradiated at fixed wavelength (595 nm), spot size (7 mm), radiant exposure (15 Jcm,2), and at variable tp. The CAM contains an extensive microvascular network ranging from capillaries with diameter D,<,30 ,m to blood vessels of D,,,120 ,m. The CAM assay allows real-time video documentation, and observation of blood flow in pre-capillary arterioles (A) and post-capillary venules (V). Vessel injury was graded from recorded videotapes. Mathematical modeling was developed to interpret results of vessel injury when varying tp and D. A modified thermal relaxation time was introduced to calculate vessel wall temperature following laser exposure. Results Arterioles. For increasing tp, overall damage was found to decrease. For fixed tp, damage decreased with vessel size. Venules. For all D, damage was smaller than for corresponding arterioles. There was no dependence of damage on tp. For given tp, no variation of damage with D was observed. Photothermolysis due to spiked (V-beam) vs. smooth (Scleroplus) delivery of laser energy at fixed tp (1.5 milliseconds), showed similar vessel injuries for al values of D (P>0.05). Conclusions The difference between initial arteriole and venule damage could be explained by the threefold higher absorption coefficient at 595 nm in (oxygen-poor!) arterioles. In human patients, PWS consist of ectatic venules (characterized by higher absorption), so that these considerations favor the use of 595-nm irradiation for laser photothermolysis. For optimal treatment of PWS it is proposed that tp be between 0.1 and 1.5 milliseconds. This is based on a modified relaxation time ,d,, defined as the time required for heat conduction into the full thickness of the vessel wall, which is assumed to have a thickness ,D ,,0.1D. The corresponding ,d, will be a factor of about six smaller than given in the literature. For vessels with D between 30 and 300 ,m, ,d, ranges from 0.1 to 1.5 milliseconds. Lasers Surg. Med. 30:160,169, 2002. © 2002 Wiley-Liss, Inc. [source] Assessment of blood volume, vessel size, and the expression of angiogenic factors in two rat glioma models: a longitudinal in vivo and ex vivo studyNMR IN BIOMEDICINE, Issue 10 2008Samuel Valable Abstract Assessment of angiogenesis may help to determine tumor grade and therapy follow-up. In vivo imaging methods for non-invasively monitoring microvasculature evolution are therefore of major interest for tumor management. MRI evaluation of blood volume fraction (BVf) and vessel size index (VSI) was applied to assess the evolution of tumor microvasculature in two rat models of glioma (C6 and RG2). The results show that repeated MRI of BVf and VSI , which involves repeated injection of an iron-based MR contrast agent , does not affect either the physiological status of the animals or the accuracy of the MR estimates of the microvascular parameters. The MR measurements were found to correlate well with those obtained from histology. They indicate that microvascular evolution differs significantly between the two glioma models, in good agreement with expression of angiogenic factors (vascular endothelial growth factor, angiopoietin-2) and with activities of matrix metalloproteinases, also assessed in this study. These MRI methods thus provide considerable potential for assessing the response of gliomas to anti-angiogenic and anti-vascular agents, in preclinical studies as well as in the clinic. Furthermore, as differences between the fate of tumor microvasculature may underlie differences in therapeutic response, there is a need for preclinical study of several tumor models. Copyright © 2008 John Wiley & Sons, Ltd. [source] Clinical assessment of a new real time 3D quantitative coronary angiography system: Evaluation in stented vessel segmentsCATHETERIZATION AND CARDIOVASCULAR INTERVENTIONS, Issue 1 2006Rainer Gradaus MD Abstract Background: Foreshortening is a recognized problem that is present in angiography and results from views that are not perpendicular to coronary lesions. This limits visual coronary analysis as well as 2D quantitative coronary angiography systems (QCA). The CardiOp-B System® is a 3D image acquisition and processing software system designed as an add-on to conventional X-ray angiography system. CardiOp-B's features include real time and off line analysis with comprehensive 3D reconstruction integrating all of the available information of two 2D vessel angiographies into one 3D image. It was the aim of the study to analyze the accuracy of this new 3D QCA system. Methods: 3D QCA was performed in 50 patients (age 64 ± 10.9; 84% male; LV-EF 63 ± 16%) measuring 61 stents during high-pressure inflation (diameter: 2.25,4 mm; length: 8,32 mm). The obtained values (proximal and distal stent diameter, stent length) were correlated with the predefined size of the stents at the used inflation pressure. Results: The linear correlation for the proximal stent diameter was Stentprox= 0.03 + 0.93 × real stent size (r2 = 0.85). The linear correlation for the distal stent diameter was Stentdistal= ,0.03 + 0.89 × real stent size (r2 = 0.81). The linear correlation for the stent length was Stentlength= ,0.61 + 1.02 × real stent length (r2 = 0.98). Conclusions: The CardiOp-B System® is a new 3D QCA system with a high linear correlation between the real vessel size and the obtained vessel dimension. It provides real time or off line accurate and comprehensive diagnostic information to the interventional cardiologist without changing the basic coronary angiography procedure. © 2006 Wiley-Liss, Inc. [source] LARGE-SCALE SIMULATION OF THE HUMAN ARTERIAL TREECLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 2 2009L Grinberg SUMMARY 1Full-scale simulations of the virtual physiological human (VPH) will require significant advances in modelling, multiscale mathematics, scientific computing and further advances in medical imaging. Herein, we review some of the main issues that need to be resolved in order to make three-dimensional (3D) simulations of blood flow in the human arterial tree feasible in the near future. 2A straightforward approach is computationally prohibitive even on the emerging petaflop supercomputers, so a three-level hierarchical approach based on vessel size is required, consisting of: (i) a macrovascular network (MaN); (ii) a mesovascular network (MeN); and (iii) a microvascular network (MiN). We present recent simulations of MaN obtained by solving the 3D Navier,Stokes equations on arterial networks with tens of arteries and bifurcations and accounting for the neglected dynamics through proper boundary conditions. 3A multiscale simulation coupling MaN,MeN,MiN and running on hundreds of thousands of processors on petaflop computers will require no more than a few CPU hours per cardiac cycle within the next 5 years. The rapidly growing capacity of supercomputing centres opens up the possibility of simulation studies of cardiovascular diseases, drug delivery, perfusion in the brain and other pathologies. [source] Mathematically Assessing the Consequences of Food Terrorism ScenariosJOURNAL OF FOOD SCIENCE, Issue 7 2008Y. Liu ABSTRACT:, We derive mathematical expressions for the mean number of casualties resulting from a deliberate release of a biological or chemical agent into a food supply chain. Our analysis first computes the amount of contaminated food as a function of the network topology and vessel sizes in the food processing plant. A probabilistic analysis, in which each potential consumer of contaminated food has his own random purchase time, infectious dose, and incubation period, determines the number of people who consume enough tainted food to get infected or poisoned before the attack is detected and food consumption is halted. These simple formulas can be used by the U.S. government and the food industry to develop a rough-cut prioritization of the threats from food terrorism, which would be a 1st step toward the allocation of appropriate prevention and mitigation resources. [source] A Separate Role for ICAM-1 and Fluid Shear in Regulating Leukocyte Interactions with Straight Regions of Venular Wall and Venular ConvergencesMICROCIRCULATION, Issue 6 2009RONEN SUMAGIN ABSTRACT Objective: Variation in expression of adhesion molecules plays a key role in regulating leukocyte behavior, but the contribution of fluid shear to these interactions cannot be ignored. Here, we dissected the effects of each of these factors on leukocyte behavior in different venular regions. Materials and Methods: Leukocyte behavior was quantified in blood-perfused microvascular networks in anesthetized mouse cremaster muscle, using intravital confocal microscopy. ICAM-1 expression and fluid shear rate were quantified by using ICAM-1 fluorescent labeling, fluorescent particle tracking, and computational fluid dynamics. Results: Tumor necrosis factor alpha induced an increase in ICAM-1 expression and abolished the differences observed among control venules of different sizes. Consequently, leukocyte adhesion was increased to a similar level across all vessel sizes [5.1±0.46 leukocytes/100 ,m vs. 2.1±0.47 (control)], but remained significantly higher in venular convergences (7.8±0.4). Leukocyte transmigration occurred primarily in the smallest venules and venular convergences (23.9±5.1 and 31.9±2.7 leukocytes/10,000 ,m2 tissue, respectively). In venular convergences, the two inlet vessels are predicted to create a region of low velocity, increasing leukocyte adhesion probability. Conclusions: In straight regions of different-sized venules, the variability in ICAM-1 expression accounts for the differences in leukocyte behavior; in converging regions, fluid shear potentially has a greater effect on leukocyte endothelial cell interactions. [source] | |||||||||||||