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In vitro blood flow in a rectangular PDMS microchannel: experimental observations using a confocal micro-PIV system

Lima, R.; Wada, Shigeo; Tanaka, S.; Takeda, Motohiro; Ishikawa, Takuji; Tsubota, Ken-ichi; Imai, Yohsuke; Yamaguchi, Takami
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
ENG; ENG
Relevância na Pesquisa
66.07%
Progress in microfabricated technologies has attracted the attention of researchers in several areas, including microcirculation. Microfluidic devices are expected to provide powerful tools not only to better understand the biophysical behavior of blood flow in microvessels, but also for disease diagnosis. Such microfluidic devices for biomedical applications must be compatible with state-of-the-art flow measuring techniques, such as confocal microparticle image velocimetry (PIV). This confocal system has the ability to not only quantify flow patterns inside microchannels with high spatial and temporal resolution, but can also be used to obtain velocity measurements for several optically sectioned images along the depth of the microchannel. In this study, we investigated the ability to obtain velocity measurements using physiological saline (PS) and in vitro blood in a rectangular polydimethysiloxane (PDMS) microchannel (300 μm wide, 45 μm deep) using a confocal micro-PIV system. Applying this combination, measurements of trace particles seeded in the flow were performed for both fluids at a constant flow rate (Re = 0.02). Velocity profiles were acquired by successive measurements at different depth positions to obtain three-dimensional (3-D) information on the behavior of both fluid flows. Generally...

Analysis of the blood flow behavior through microchannels by a confocal micro-PIV/PTV system

Lima, R.
Fonte: Tohoku University Publicador: Tohoku University
Tipo: Tese de Doutorado
ENG
Relevância na Pesquisa
66.18%
Over the years, various experimental methods have been applied in an effort to understand the blood flow behavior in microcirculation. Most of our current knowledge in microcirculation is based on macroscopic flow phenomena such as Fahraeus effect and Fahraeus-Linqvist effect. The development of optical experimental techniques has contributed to obtain explanations on the way the blood flows through microvessels. Although the past results have been encouraging, detailed studies on the flow properties of blood in the microcirculation has been limited by several technical factors such as poor spatial resolution and difficulty to obtain quantitative detailed measurements at such small scales. Therefore, there is still a lack of knowledge on the microscale flow behavior of blood cells through microvessels. In recent years, due to advances in computers, optics, and digital image processing techniques, it has become possible to combine a particle image velocimetry (PIV) system with a conventional microscope. As a result, this combination, known as a micro-PIV, has greatly increased the resolution of the conventional PIV. Although the conventional micro-PIV technique has proven to be useful in measuring the flow behavior in microfluidics devices...

A particle method computer simulation: applications to the study of blood flow

Lima, R.; Kitagawa, Y.; Kamada, H.; Tsubota, Ken-ichi; Wada, Shigeo; Yamaguchi, Takami
Fonte: Sociedade Portuguesa de Biomecânica Publicador: Sociedade Portuguesa de Biomecânica
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
66.08%
The need to analyse the microscopic mechanical behaviour of blood flow was one of the main reasons to develop a new computer simulation using a particle method. This new mesh free method is based on a moving-particle semi-implicit (MPS) method, which has been developed to simulate incompressible fluids based on the Navier-Stokes equations. The simulation region was discretized by particles that moves in Lagrangian coordinates, where the plasma and platelets were modelled as fluid particles, red blood cells (RBC) as elastic particles and vessel wall as rigid particles. In this paper, some applications of the MPS method to study the blood flow are briefly analysed, such as the motion and deformation of red blood cells (RBC) in plasma flow and the platelet aggregation process in blood flow. Some preliminary studies suggest that there is evidence that the proposed method enables the analysis of the RBC motion and deformation in the plasma flow and also the initial thrombogenesis, growth and destruction of thrombus.

In vitro blood flow in circular PDMS microchannels: effect of the flow rate and hematocrit

Garcia, Valdemar; Dias, Ricardo P.; Correia, Teresa Montenegro; Lima, R.; Pinheiro, Elisa; Pinho, Diana; Rodrigues, Pedro
Fonte: Instituto Politécnico de Bragança Publicador: Instituto Politécnico de Bragança
Tipo: Conferência ou Objeto de Conferência
ENG
Relevância na Pesquisa
66.07%
Alocar também a:Teresa Montenegro Correia- ESA; Recently, Lima et al. (1) has performed confocal micro-PIV measurements on the blood flow through straight PDMS microchannel. In the study they have observed that the formation of the cell free layer is enhanced as the cross section ratio increases. However, the cross section ratio is not the only parameter that contributes for the creation of the cell-free layer. Hence, several other physical and hemorheological factors (such as flow rate, hematocrit, viscosity and cell deformability) need to be investigated in order to make use on the physics of microfluidics to either develop new lab-on-chip devices or to optimize the design of the existent microfluidic chips. The main aim of the present study is to show the effect of both flow rate and hematocrit on the blood flow and cell behavior. The circular polydimethylsiloxane (PDMS) microchannels were fabricated by using wire casting technique and the experiments were carried out by using dextran 40 containing different fractions of red blood cells (RBCs). The in vitro blood flow was measured by means of video microscopy and image analysis. Additionally, the pressure drop was also measured.

In vitro blood flow behaviour in microchannels with simple and complex geometries

Garcia, Valdemar; Dias, Ricardo P.; Lima, R.
Fonte: InTech Publicador: InTech
Tipo: Parte de Livro
ENG
Relevância na Pesquisa
66.11%
Over the years, various experimental methods have been applied in an effort to understand the blood flow behaviour in microcirculation. The development of optical experimental techniques has contributed to obtain possible explanations on the way the blood flows through microvessels. In recent years, due to advances in computers, optics, and digital image processing techniques, it has become possible to combine a conventional particle image velocimetry (PIV) system with an inverted microscope and consequently improve both spatial and temporal resolution. The present review outlines our most relevant studies on the flow properties of blood at a microscale level by using current micro-PIV and confocal micro-PIV techniques. In this chapter, our recent studies about in vitro blood flow behaviour in microchannels both in straight and with complex geometries are presented. In straight microchannels we present some phenomena such as Fahraeus effect and Fahraeus-Lindqvist effect, the flow of particles and red blood cells (RBCs) in diluted suspensions, the flow of RBCs in concentrated suspensions, the cell-free layer and sedimentations effects. The most recent studies in blood flow through complex geometries such as bifurcations, confluences and stenosis are also reviewed. By using a chromatographic method...

Endothelial and non-endothelial coronary blood flow reserve and left ventricular dysfunction in systemic hypertension

ROCHA, Aloísio Marchi; SALEMI, Vera Maria Cury; LEMOS NETO, Pedro Alves; MATSUMOTO, Afonso Yoshikiro; PEREIRA, Valéria Fontenelle Angelim; FERNANDES, Fábio; NASTARI, Luciano; MADY, Charles
Fonte: Faculdade de Medicina / USP Publicador: Faculdade de Medicina / USP
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
66.13%
OBJECTIVES: We evaluated the impairment of endothelium-dependent and endothelium-independent coronary blood flow reserve after administration of intracoronary acetylcholine and adenosine, and its association with hypertensive cardiac disease. INTRODUCTION: Coronary blood flow reserve reduction has been proposed as a mechanism for the progression of compensated left ventricular hypertrophy to ventricular dysfunction. METHODS: Eighteen hypertensive patients with normal epicardial coronary arteries on angiography were divided into two groups according to left ventricular fractional shortening (FS). Group 1 (FS >0.25): n=8, FS=0.29 ± 0.03; Group 2 (FS <0.25): n=10, FS= 0.17 ± 0.03. RESULTS: Baseline coronary blood flow was similar in both groups (Group 1: 80.15 ± 26.41 mL/min, Group 2: 100.09 ± 21.51 mL/min, p=NS). In response to adenosine, coronary blood flow increased to 265.1 ± 100.2 mL/min in Group 1 and to 300.8 ± 113.6 mL/min (p <0.05) in Group 2. Endothelium-independent coronary blood flow reserve was similar in both groups (Group 1: 3.31 ± 0.68 and Group 2: 2.97 ± 0.80, p=NS). In response to acetylcholine, coronary blood flow increased to 156.08 ± 36.79 mL/min in Group 1 and to 177.8 ± 83.6 mL/min in Group 2 (p <0.05). Endothelium-dependent coronary blood flow reserve was similar in the two groups (Group 1: 2.08 ± 0.74 and group Group 2: 1.76 ± 0.61...

Turbulent blood flow plays an essential localizing role in the development of atherosclerotic lesions in experimentally induced hypercholesterolaemia in rats

PRADO, Cibele M.; RAMOS, Simone G.; ELIAS JR., Jorge; ROSSI, Marcos A.
Fonte: BLACKWELL PUBLISHING Publicador: BLACKWELL PUBLISHING
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
66.07%
Taking into account that atherosclerosis is a focal disease and high levels of plasma cholesterol are closely correlated with its pathogenesis, it is a challenge to explain how equal concentrations of cholesterol bathing the endothelium can produce local, rather than global, effects on arteries. The focal distribution of atherosclerotic lesions has been considered to be dependent, at least in part, on hydrodynamic factors. The present study was carried out to further test the hypothesis that these forces are an important localizing factor in rats feeding a hypercholesterolaemic diet and submitted to infra-diaphragmatic aortic constriction. These animals develop a normotensive prestenotic region with laminar blood flow that serves as control for a normotensive poststenotic region with turbulent blood flow. Our findings clearly demonstrated that the combination of turbulent blood flow and low wall shear stress (WSS) in the presence of hypercholesterolaemia and oxidative stress creates conditions to the formation of focally distributed incipient atherosclerotic lesions observed in the poststenotic segment. In contrast, only diffuse fatty streaks could be observed in the normotensive prestenotic segment with laminar blood flow and normal WSS in the presence of hypercholesterolaemia and oxidative stress. Although haemodynamic forces are not by themselves responsible for the pathogenesis of atherosclerosis...

Estudo do fluxo sanguíneo regional e dos marcadores de perfusão tecidual em pacientes com insuficiência cardíaca em uso de balão intra-aórtico; Study of regional blood flow and markers of tissue perfusion in patients with heart failure using an intra-aortic balloon

Fagundes Junior, Antonio Aurelio de Paiva
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 16/09/2013 PT
Relevância na Pesquisa
66.09%
INTRODUÇÃO: O balão intra-aórtico (BIA) representa o mecanismo de assistência ventricular mais frequentemente utilizado em pacientes com insuficiência cardíaca (IC), no Brasil. OBJETIVO: Neste trabalho, avaliamos a ação do BIA sobre o fluxo sanguíneo carotídeo e braquial, além do seu efeito sobre os marcadores de perfusão tecidual e sobre o peptídeo natriurético cerebral (BNP). MÉTODOS: Entre julho de 2006 e maio de 2009, 33 pacientes foram avaliados, sendo 10 excluídos. Os pacientes foram inicialmente mantidos com o BIA em modo 1:1, com insuflação máxima, para a fase inicial do estudo (condição 1). Realizou-se coleta de gasometria arterial, venosa central e BNP (condição EXA1). Foi realizada ultrassonografia vascular de alta definição, para captação de imagens das curvas de velocidade de fluxo sanguíneo, e medida dos diâmetros arteriais sistólico e diastólico (condição MD1). Em seguida, foi avaliada a resposta vascular frente à hiperemia reativa (condição HR1). Realizado o estudo na condição 1, o BIA foi modificado para 1:3 com insuflação mínima (condição 2) e todos os exames laboratoriais (condição EXA 2) e ultrassonográficos (condição MD2 e condição HR2) foram repetidos. Após a condição 2...

Validation of transit-time flowmetry for chronic measurements of regional blood flow in resting and exercising rats

Fonte: Associação Brasileira de Divulgação Científica Publicador: Associação Brasileira de Divulgação Científica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/07/1997 EN
Relevância na Pesquisa
66.09%
The objective of the present study was to validate the transit-time technique for long-term measurements of iliac and renal blood flow in rats. Flow measured with ultrasonic probes was confirmed ex vivo using excised arteries perfused at varying flow rates. An implanted 1-mm probe reproduced with accuracy different patterns of flow relative to pressure in freely moving rats and accurately quantitated the resting iliac flow value (on average 10.43 ± 0.99 ml/min or 2.78 ± 0.3 ml min-1 100 g body weight-1). The measurements were stable over an experimental period of one week but were affected by probe size (resting flows were underestimated by 57% with a 2-mm probe when compared with a 1-mm probe) and by anesthesia (in the same rats, iliac flow was reduced by 50-60% when compared to the conscious state). Instantaneous changes of iliac and renal flow during exercise and recovery were accurately measured by the transit-time technique. Iliac flow increased instantaneously at the beginning of mild exercise (from 12.03 ± 1.06 to 25.55 ± 3.89 ml/min at 15 s) and showed a smaller increase when exercise intensity increased further, reaching a plateau of 38.43 ± 1.92 ml/min at the 4th min of moderate exercise intensity. In contrast, exercise-induced reduction of renal flow was smaller and slower...

Blood flow measurements in rats using four color microspheres during blockade of different vasopressor systems

De Angelis,K.; Gama,V.M.; Farah,V.A.M.; Irigoyen,M.C.
Fonte: Associação Brasileira de Divulgação Científica Publicador: Associação Brasileira de Divulgação Científica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2005 EN
Relevância na Pesquisa
66.13%
The use of colored microspheres to adequately evaluate blood flow changes under different circumstances in the same rat has been validated with a maximum of three different colors due to methodological limitations. The aim of the present study was to validate the use of four different colors measuring four repeated blood flow changes in the same rat to assess the role of vasopressor systems in controlling arterial pressure (AP). Red (150,000), white (200,000), yellow (150,000), and blue (200,000) colored microspheres were infused into the left ventricle of 6 male Wistar rats 1) at rest and 2) after vasopressin (aAVP, 10 µg/kg, iv), 3) renin-angiotensin (losartan, 10 mg/kg, iv), and 4) sympathetic system blockade (hexamethonium, 20 mg/kg, iv) to determine blood flow changes. AP was recorded and processed with a data acquisition system (1-kHz sampling frequency). Blood flow changes were quantified by spectrophotometry absorption peaks for colored microsphere components in the tissues evaluated. Administration of aAVP and losartan slightly reduced the AP (-5.7 ± 0.5 and -7.8 ± 1.2 mmHg, respectively), while hexamethonium induced a 52 ± 3 mmHg fall in AP. The aAVP injection increased blood flow in lungs (78%), liver (117%) and skeletal muscle (>150%)...

Endothelial and non-endothelial coronary blood flow reserve and left ventricular dysfunction in systemic hypertension

Rocha,Aloísio Marchi; Salemi,Vera Maria Cury; Lemos Neto,Pedro Alves; Matsumoto,Afonso Yoshikiro; Pereira,Valéria Fontenelle Angelim; Fernandes,Fábio; Nastari,Luciano; Mady,Charles
Fonte: Faculdade de Medicina / USP Publicador: Faculdade de Medicina / USP
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2009 EN
Relevância na Pesquisa
66.13%
OBJECTIVES: We evaluated the impairment of endothelium-dependent and endothelium-independent coronary blood flow reserve after administration of intracoronary acetylcholine and adenosine, and its association with hypertensive cardiac disease. INTRODUCTION: Coronary blood flow reserve reduction has been proposed as a mechanism for the progression of compensated left ventricular hypertrophy to ventricular dysfunction. METHODS: Eighteen hypertensive patients with normal epicardial coronary arteries on angiography were divided into two groups according to left ventricular fractional shortening (FS). Group 1 (FS >0.25): n=8, FS=0.29 ± 0.03; Group 2 (FS <0.25): n=10, FS= 0.17 ± 0.03. RESULTS: Baseline coronary blood flow was similar in both groups (Group 1: 80.15 ± 26.41 mL/min, Group 2: 100.09 ± 21.51 mL/min, p=NS). In response to adenosine, coronary blood flow increased to 265.1 ± 100.2 mL/min in Group 1 and to 300.8 ± 113.6 mL/min (p <0.05) in Group 2. Endothelium-independent coronary blood flow reserve was similar in both groups (Group 1: 3.31 ± 0.68 and Group 2: 2.97 ± 0.80, p=NS). In response to acetylcholine, coronary blood flow increased to 156.08 ± 36.79 mL/min in Group 1 and to 177.8 ± 83.6 mL/min in Group 2 (p <0.05). Endothelium-dependent coronary blood flow reserve was similar in the two groups (Group 1: 2.08 ± 0.74 and group Group 2: 1.76 ± 0.61...

ATP as a mediator of erythrocyte-dependent regulation of skeletal muscle blood flow and oxygen delivery in humans

González-Alonso, José
Fonte: Blackwell Science Inc Publicador: Blackwell Science Inc
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
66.09%
In healthy human beings, blood flow to dynamically contracting skeletal muscle is regulated primarily to match oxygen (O2) delivery closely with utilisation. This occurs across a wide range of exercise intensities, as well as when exercise is combined with conditions that modify blood O2 content. The red blood cells (RBCs), the primary O2 carriers in the blood, contribute to the regulation of the local processes matching O2 supply and demand. This is made possible by the ability of RBCs to release the vasoactive substance adenosine triphosphate (ATP) in response to reductions in erythrocyte and plasma O2, as well as to other adjuvant metabolic and mechanical stimuli. The regulatory role of RBCs in human beings is supported by the observations that, i) exercising skeletal muscle blood flow responds primarily to changes in the amount of O2 bound to the erythrocyte haemoglobin molecules, rather than the amount of O2 in plasma, and ii) exercising muscle blood flow can almost double (from 260 to 460 ml min−1 100 g−1) with alterations in blood O2 content, such that O2 delivery and are kept constant. Besides falling blood O2 content, RBCs release ATP when exposed to increased temperature, reduced pH, hypercapnia, elevated shear stress and augmented mechanical deformation...

Concentrated Ambient Particles Alter Myocardial Blood Flow During Acute Ischemia in Conscious Canines

Bartoli, Carlo R.; Wellenius, Gregory A.; Akiyama, Ichiro; Okabe, Kazunori; Coull, Brent Andrew; Diaz, Edgar; Lawrence, Joy E.; Verrier, Richard Leonard; Godleski, John Joseph
Fonte: National Institute of Environmental Health Sciences Publicador: National Institute of Environmental Health Sciences
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
66.08%
Background: Experimental and observational studies have demonstrated that short-term exposure to ambient particulate matter (PM) exacerbates myocardial ischemia. Objectives: We conducted this study to investigate the effects of concentrated ambient particles (CAPs) on myocardial blood flow during myocardial ischemia in chronically instrumented conscious canines. Methods: Eleven canines were instrumented with a balloon occluder around the left anterior descending coronary artery and catheters for determination of myocardial blood flow using fluorescent microspheres. Telemetric electrocardiographic and blood pressure monitoring was available for four of these animals. After recovery, we exposed animals by inhalation to 5 hr of either filtered air or CAPs (mean concentration ± SD, 349.0 ± 282.6 μg/m(^{3})) in a crossover protocol. We determined myocardial blood flow during a 5-min coronary artery occlusion immediately after each exposure. Data were analyzed using mixed models for repeated measures. The primary analysis was based on four canines that completed the protocol. Results: CAPs exposure decreased total myocardial blood flow during coronary artery occlusion by 0.12 mL/min/g (p < 0.001) and was accompanied by a 13% (p < 0.001) increase in coronary vascular resistance. Rate–pressure product...

The effect of altered cerebral blood flow on the cerebral kinetics of thiopental and propofol in sheep

Upton, R.; Ludbrook, G.; Grant, C.; Doolette, D.
Fonte: Lippincott Williams & Wilkins Publicador: Lippincott Williams & Wilkins
Tipo: Artigo de Revista Científica
Publicado em //2000 EN
Relevância na Pesquisa
66.1%
BACKGROUND: Thiopental and propofol are highly lipid-soluble, and their entry into the brain often is assumed to be limited by cerebral blood flow rather than by a diffusion barrier. However, there is little direct experimental evidence for this assumption. METHODS: The cerebral kinetics of thiopental and propofol were examined over a range of cerebral blood flows using five and six chronically instrumented sheep, respectively. Using anesthesia (2.0% halothane), three steady state levels of cerebral blood flow (low, medium, and high) were achieved in random order by altering arterial carbon dioxide tension. For each flow state, 250 mg thiopental or 100 mg propofol was infused intravenously over 2 min. To quantify cerebral kinetics, arterial and sagittal sinus blood was sampled rapidly for 20 min from the start of the infusion, and 1.5 h was allowed between consecutive infusions. Various models of cerebral kinetics were examined for their ability to account for the data. RESULTS: The mean baseline cerebral blood flows for the "high" flow state were over threefold greater than those for the low. For the high-flow state the normalized arteriovenous concentration difference across the brain was smaller than for the low-flow state, for both drugs. The data were better described by a model with partial membrane limitation than those with only flow limitation or dispersion. CONCLUSIONS: The cerebral kinetics of thiopental and propofol after bolus injection were dependent on cerebral blood flow...

Sex-Specific Differences in Peripheral Microvascular Blood Flow in Preterm Infants

Stark, M.; Clifton, V.; Wright, I.
Fonte: Int Pediatric Research Foundation Inc Publicador: Int Pediatric Research Foundation Inc
Tipo: Artigo de Revista Científica
Publicado em //2008 EN
Relevância na Pesquisa
66.08%
Microvascular blood flow is related to physiologic instability in newborn preterm infants. We investigated sex-specific differences in basal microvascular blood flow and the ability of the microvasculature to respond to vasoactive stimuli following preterm birth. Ninety-six infants in two gestational age groups (24-28 and 29-36 wk) were studied on days 1-5 of life. Laser Doppler flowmetry was used to measure baseline microvascular blood flow and vasodilatation in response to acetylcholine and local warming. A significant interaction of gestational age and sex was observed for baseline flow at 24 h of age. In the 24-28 wk group, male infants had higher baseline flow than females. Male, but not female, infants born at 24-28 wk exhibited a significant relationship between baseline flow and vasodilatory response to acetylcholine at 24 h of age. By 120 h of age, both sexes exhibited similar responses. Infants born at 24-28 wk exhibited greater vasodilatation in response to local warming than those born at 29-36 wk at 24, 72, and 120 h of age. Sex-specific differences in microvascular blood flow and vasodilatory capacity in the immediate newborn period may affect the transitional circulation, contributing to excess of morbidity and mortality in preterm males.; Michal J. Stark...

Chronic maternal hypertension characterized by renal dysfunction is associated with reduced placental blood flow during late gestation in rabbits

McArdle, A.; Roberts, C.; Maduwegedera, D.; Flower, R.; Denton, K.
Fonte: Amer Physiological Soc Publicador: Amer Physiological Soc
Tipo: Artigo de Revista Científica
Publicado em //2010 EN
Relevância na Pesquisa
66.1%
Maternal hypertension associated with renal disease is a common pregnancy complication. Previously, we have shown in a rabbit model of mild hypertension that offspring from hypertensive mothers have increased blood pressure as adults. In human pregnancy, hypertension has been associated with decreased utero-placental blood flow. The aim of this study was to determine placental blood flow (PBF) in mild (2-kidney-1-wrapped; 2K-1W) and moderate (2-kidney-2-wrapped; 2K-2W) rabbit models of maternal hypertension. We hypothesized that PBF would be inversely related to the severity of the hypertension. PBF and renal blood flow (RBF) were measured using microspheres on day 28 of a 32-day gestation, in normotensive (sham), 2K-1W, and 2K-2W hypertensive groups. Mean arterial pressure (MAP, approximately 7 mmHg, P < 0.05) was increased, and RBF ( approximately 35%, P < 0.05) was reduced in the 2K-1W and 2K-2W (MAP approximately 20 mmHg, P < 0.01; RBF approximately 53%, P < 0.05) groups compared with the sham group. In the 2K-1W group, PBF fell by approximately 12% (P = 0.08) and fetal-to-placental weight ratio increased by approximately 12% (P < 0.01) compared with the sham group, reflecting an increase in the functional capacity of the placenta to deliver nutrients to the fetus. In the 2K-2W group...

The effect of alcohol on pancreatic blood flow: an experimental study.

Benveniste, Glen L.
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2014
Relevância na Pesquisa
66.13%
The reference sample method using 15 micron diameter radionuclide labelled carbon microspheres was used to establish a rat model of pancreatic blood flow which was then used to follow up previously reported studies in dogs which showed that intravenously administered alcohol lead to a fall in pancreatic blood flow. In addition, the oral administration of alcohol alone and in combination with glucose was studied. The literature regarding pancreatic blood flow was reviewed with special emphasis on techniques of measurement and the effect of intravenously administered alcohol. While the rat model proved highly successful, it was not possible to use a dual injection technique as had been previously carried out in the larger experimental animal. This meant that instead of carrying out a control measurement on each animal it was necessary to have separate control and experiment groups. The major findings of the study were of difference in pancreatic blood flow between fasted (105 ± 9, mean ± s.e.) and non-fasted animals (134 ± 11) which was significant at the 0.025 level using the unpaired t test (t=2.14, df 18, p<0.025). No significant changes in pancreatic blood flow were observed with alcohol administered via intravenous or via gastric infusion compared to control groups. The major finding of the study was that a combination of alcohol and glucose administered via gastric infusion was found to produce a rise in pancreatic blood flow (161 ± 19) which was greater than that seen with either intravenous alcohol alone (111 ± 9) or glucose alone (90 ± 6). This change was highly significant (t=2.70...

Untersuchung über die Wertigkeit der Flussmessung mittels MRT in den Nierenarterien zur Beurteilung der seitengetrennten Nierendurchblutung bei Patienten mit Nierenarterienstenose. Ein Vergleich zur Nierenfunktionsszintigraphie; Evaluation of a new MRI-method for blood flow in renal artery stenosis. Comparisons with measurements of kidney function by clearance method and by scintigraphy

Giersch, Jenny Yuhko
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
DE_DE
Relevância na Pesquisa
66.18%
Fragestellung. Es sollte untersucht werden, inwieweit die MR-Phasenkontrast-flussmessung ohne Kontrastmittel als nicht-invasive und nicht-nephrotoxische Methode zur Beurteilung der seitengetrennten Nierendurchblutung bei Nierenarterienstenose (NAS) und zur Detektion einer NAS im Vergleich zur Nierenfunktionsszintigraphie geeignet ist. Methoden. MR-Blutflussmessung in den Nierenarterien (nMR-Fluss) bei 13 Hypertonikern mit NAS (46-71 Jahre) und 6 Hypertonikern ohne Stenose (29-63 Jahre). Bei 12 Patienten mit NAS zusätzlich Bestimmung der Technetium-99m-MAG-3-Clearance jeder Niere durch Nierenfunktionsszintigraphie ohne Captopril und Berechnung des seitengetrennten effektiven renalen Blutflusses (ERB). Korrelation von nMR-Fluss, MAG3-Clearance und ERB. Prüfung auf signifikante Unterschiede zwischen NAS-Gruppe 1 (NAS = 0-29%, n = 21), NAS-Gruppe 2 (NAS = 30-69%, n = 8) und NAS-Gruppe 3 (NAS = 70-100%, n = 6) für alle Methoden. Bestimmung der Genauigkeit von nMR-Fluss, MAG3-Clearance und ERB zur Detektion einer NAS > / = 70% mit ROC-Kurve. Vergleich zwischen Ergebnissen von Patienten, die einen ACE-Hemmer und / oder AT2-Rezeptorantagonisten eingenommen hatten, und denen von übrigen Patienten. Vergleich zwischen Ergebnissen unter Einschluss aller Patienten und nach Ausschluss von chronischer Niereninsuffizienz (CN) (n = 6 Patienten). Bestimmung von weiteren klinischen Parametern: Alter...

Systemic blood flow relations in conscious South American rattlesnakes

Filogonio, Renato; Taylor, Edwin W.; Carreira, Laura B. T.; Leite, Gabrielle S. P. C.; Abe, Augusto S.; Leite, Cleo A. C.
Fonte: Soc Brasileira Herpetologia Publicador: Soc Brasileira Herpetologia
Tipo: Artigo de Revista Científica Formato: 171-176
ENG
Relevância na Pesquisa
66.12%
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Processo FAPESP: 2008/57712-4; Processo FAPESP: 2012/06938-8; Estimating total systemic blood flow based on measurements from a single aortic arch is common practice in cardiovascular studies on reptiles to avoid heavy instrumentation and consequent stress responses. This practice requires the validation of a specific correction factor that expresses the relationship between the measured blood flow and the blood flow to be estimated. Misleading estimations may occur when correction factors are used in different conditions from those they were originally measured. Despite recognized as a problem, such misleading estimations are common in physiology. In the present study, we derived values for correction factors to estimate systemic blood flow in the South American rattlesnake, Crotalus durissus, following recovery from anesthesia, using serial measurements of blood flow in the three main systemic arteries, left or distal right aortic arches and the carotid artery. Blood flow recorded in the left aortic arch provided the most reliable and less variable correction factors. Different from previously published...

Study of venous blood flow changes during laparoscopic surgery using a thermodilution technique

Marshall, N.; Bessell, J.; Maddern, G.
Fonte: Blackwell Science Asia Publicador: Blackwell Science Asia
Tipo: Artigo de Revista Científica
Publicado em //2000 EN
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66.07%
BACKGROUND: Many modalities exist to analyse those factors that contribute to venous stasis and deep venous thrombosis (DVT) during laparoscopic surgery. To the authors' knowledge intraoperative measurement of femoral venous blood flow has not yet been performed nor has the influence of sequential compression devices been assessed using this parameter. METHODS: The thermodilution technique similar to that employed in cardiac output measurement was used to determine changes in blood flow in the right femoral vein during laparoscopic cholecystectomy. Deep venous thrombosis prophylaxis involved perioperative use of sequential compression devices and subcutaneous heparin 5000 U. RESULTS: Pneumoperitoneum and the Trendelenburg position reduced femoral venous return in four of the six patients studied, but sequential compression devices failed to return blood flow to baseline in a predictable fashion. CONCLUSIONS: Although the measurement of blood flow using thermodilution is regarded as a reliable technique, during general anaesthesia the results may be susceptible to haemodynamic variations related to the anaesthetic agents as well as to the laparoscopic procedure. In addition sequential compression devices (when used alone) may not provide adequate prophylaxis against DVT because they do not predictably increase femoral blood flow.