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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
621

Dysfonction diastolique, rigidité artérielle aortique et hypertension : facteurs anthropométriques et métaboliques associés et prise en charge en population générale / Diastolic dysfunction, aortic stiffness and hypertension : anthropometric and metabolic risk factors and management in general population

Chau, Kénora 10 December 2018 (has links)
L’augmentation de l’obésité durant les dernières décennies expose la population à un risque accru de problèmes métaboliques et des maladies cardiovasculaires. Ce travail étudiait, d’une part, l’association de l’obésité avec la dysfonction diastolique et la rigidité artérielle aortique vingt ans plus tard chez des adultes initialement en bonne santé. Cette étude montrait que l’obésité générale mesurée par l’indice de masse corporelle et l’adiposité abdominale mesurée par le tour de taille étaient associées positivement à la dysfonction diastolique. Mais elles semblaient jouer un rôle protecteur sur la rigidité artérielle. Le ratio “tour de taille/indice de masse corporelle” semblait mieux isoler l’adiposité abdominale/viscérale de l’obésité générale, et était associé positivement à la rigidité artérielle. Il permettrait de montrer un rôle néfaste à long terme de l’adiposité abdominale/viscérale sur la rigidité artérielle même quand le poids est normal. La présence combinée de l’obésité abdominale (mesurée par le tour de taille) et d’un taux plus élevé de triglycérides était associée à un risque élevé de dysfonction diastolique. Dans la deuxième partie, nous nous sommes intéressés aux individus ayant déjà une hypertension artérielle. Ce travail montrait que, parmi les sujets ayant une hypertension, ceux ayant une hypertension non-diagnostiquée avaient un profil spécifique (plus souvent de sexe masculin, un tour de taille moins élevé, et moins souvent de maladies cardiovasculaires/diabète, antécédents familiaux d’hypertension et consultations de soins primaires moins fréquents). La présence concomitante d’un nombre élevé de ces critères renforçait fortement l’absence de primo-diagnostic. Nos résultats peuvent aider dans l’identification précoce des sujets à risque, la prévention et le management thérapeutique / Worldwide increasing obesity over the last decades expose the population to an increased risk of metabolic perturbations and cardiovascular diseases. This research investigated first the association of obesity with diastolic dysfunction and aortic stiffness observed 20 years later in initially healthy adults. General obesity measured with body mass index and abdominal adiposity measured with waist circumference were positively associated with diastolic dysfunction. But, these anthropometric parameters played a protective role in aortic stiffness. The ratio “waist circumference / body mass index” appeared to better isolate abdominal adiposity from general obesity and was then positively associated with aortic stiffness. It allowed to evidence a harmful role of abdominal adiposity in aortic stiffness, even in subjects with normal body weight. The presence of abdominal adiposity (measured with waist circumference) combined with an elevated level of triglycerides was associated with a higher risk of diastolic dysfunction. In the second part, our research focused on hypertensive individuals. It showed that among hypertensive subjects, those having undiagnosed-hypertension had specific features (being more often male, having less elevated waist circumference, and having fewer cardiovascular diseases/diabetes, familial hypertension history, and primary care uses). The concomitant presence of a higher number of these criteria appeared to strongly reinforce the absence of diagnosis. Our findings may help to early identify subjects at risk, and to establish prevention and therapeutic management
622

Controle neurovascular de corredores amadores hipertensos / Neurovascular control of hypertensive amateur runners.

Perlingeiro, Patricia de Sá 28 November 2014 (has links)
INTRODUÇÃO: Alterações neurovasculares presentes na hipertensão arterial são minimizadas pelo treinamento físico em hipertensos previamente sedentários. Entretanto, é desconhecido se atletas hipertensos apresentam alterações neurovasculares ou se o treinamento físico previne tais danos. Este estudo avaliou o controle neurovascular de corredores hipertensos, durante o treinamento competitivo, assim como o efeito de 4 meses de treinamento de intensidade moderada nesta população. MÉTODOS: 37 corredores, homens (20 normotensos, 43 +-1 anos e 17 hipertensos, 42+-1 anos), foram avaliados no treinamento competitivo e posteriormente divididos em 4 subgrupos: normotensos que mantiveram treinamento competitivo (n=10); normotensos que realizaram treinamento de intensidade moderada (n=10); hipertensos que mantiveram treinamento competitivo (n=8); hipertensos que realizaram treinamento de intensidade moderada (n=8). Após 4 meses de intervenção, todos os corredores foram novamente avaliados. Atividade nervosa simpática muscular (ANSM) (microneurografia), propriedades arteriais (velocidade da onda de pulso (VOP) e sistema echo-tracking de alta resolução), controle barorreflexo da frequência cardíaca (FC) e da ANSM (infusão de drogas vasoativas) foram avaliados. RESULTADOS: Corredores hipertensos apresentaram maior pressão arterial sistólica (P < 0,001), diastólica (PAD) (P < 0,001) e média (PAM) (P < 0,001) que corredores normotensos. A ANSM foi maior no grupo hipertenso (disparos/min.; P=0,02 e disparos/100 batimentos; P=0,004) em relação ao grupo normotenso. Não houve diferença na VOP (P=0,71) e nas variáveis da carótida: espessura intima-média (P=0,18), diâmetro (P=0,09) e distensão (P=0,79) entre os grupos. A equação sigmoidal para controle barorreflexo da FC, mostrou menor ganho barorreflexo nos corredores hipertensos em relação aos normotensos (resetting) (P=0,002). O controle barorreflexo da FC, avaliado pela análise de regressão linear, não foi diferente entre os grupos, para aumento (slope P=0,41; intercepto P=0,31) e queda (slope P=0,16; intercepto P=0,73) da PAM. Similarmente, o controle barorreflexo da ANSM foi semelhante entre corredores normotensos e hipertensos, para aumento (slope P=0,65; intercepto P=0,51) e queda (slope P=0,91; intercepto P=0,80) da PAM. Após 4 meses, os dois subgrupos de corredores hipertensos apresentaram maior delta de queda da PAD (P < 0,02) e PAM (P < 0,02), quando comparados com os dois subgrupos de corredores normotensos. O treinamento de intensidade moderada ocasionou diminuição no delta da ANSM (P=0,015) no subgrupo de corredores hipertensos, assim como melhorou o controle barorreflexo da ANSM para aumento da PAM (slope P=0,03) nos subgrupos de normotensos e hipertensos, quando comparados com os subgrupos que mantiveram o treinamento competitivo. A manutenção do treinamento competitivo, em ambos os subgrupos de normotensos e hipertensos, ocasionou mudança no delta do intercepto do controle barorreflexo da FC, para aumento da PAM (P=0,04), quando avaliado pela regressão linear. Em relação às propriedades arteriais, ambos os treinamentos não ocasionaram modificações (P > 0,05). CONCLUSÕES: Corredores hipertensos apresentam ANSM elevada, mas manutenção das propriedades elásticas arteriais e do controle barorreflexo da FC e da ANSM, sugerindo um efeito positivo parcial do treinamento físico competitivo. Por outro lado, o treinamento de intensidade moderada é capaz de diminuir a ANSM dos corredores hipertensos e de melhorar o controle barorreflexo da ANSM, tanto em corredores hipertensos, quanto em corredores normotensos / INTRODUCTION: Neurovascular alterations presented in hypertension are minimized by physical training in previously sedentary hypertensive. However it is unknown if hypertensive athletes present neurovascular alterations or if physical training prevents these damages. This study evaluated the neurovascular control of hypertensive runners during competitive training as well as the effect of 4 months of moderate intensity training in this population. METHODS: 37 runners, male (20 normotensive, 43+-1 years old and 17 hypertensive, 42+-1 years old), were evaluated during competitive training and after that were divided in 4 subgroups: normotensive who maintained competitive training (n=10); normotensive who performed moderate intensity training (n=10); hypertensive who maintained competitive training (n=8); hypertensive who performed moderate intensity training (n=8). After 4 months of intervention, all the runners were evaluated again. Muscle sympathetic nerve activity (MSNA) (microneurography), arterial properties (pulse wave velocity (PWV) and high-resolution echo-tracking system), baroreflex control of heart rate (HR) and MSNA (infusion of vasoactive drugs) were evaluated. RESULTS: Hypertensive runners had higher systolic (P < 0.001), diastolic (DAP) (P < 0.001) and mean (MAP) (P < 0.001) arterial pressure than normotensive runners. MSNA was higher in hypertensive group (bursts/min.; P=0.02 and bursts/100 heart beats; P=0.004) than in normotensive group. There was no difference in PWV (P=0.71) and carotid variables: intima-media thickness (P=0.18), diameter (P=0.09) and distension (P=0.79) between groups. The gain of baroreflex control of HR, evaluated by sigmoidal logistic equation was lower in hypertensive runners than normotensive runners (resetting) (P=0.002). Baroreflex controf of HR, evaluated by linear equation analysis, was not different between groups during increase (slope P=0.41; intercept P=0.31) and decrease (slope P=0.16; intercept P=0.73) of MAP. Similarly, there was no difference between normotensive and hypertensive runners for baroreflex control of MSNA during increase (slope P=0.65; intercept P=0.51) and decrease (slope P=0.91; intercept P=0.80) of MAP. After 4 months, both hypertensive subgroups presented higher delta of decrease in DAP (P < 0.02) and MAP (P < 0.02), when compared to both normotensive subgroups. Moderate intensity training decreased MSNA (P=0.015) in hypertensive subgroup and improved baroreflex control of MSNA (slope P=0.03) in both normotensive and hypertensive subgroups when compared to competitive training subgroups. The intercept delta for baroreflex control of HR, in both normotensive and hypertensive competitive training subgroups, was changed during increase of MAP (P=0.04), when evaluated by linear equation. Arterial properties were not modified by competitive or moderate intensity training (P > 0.05). CONCLUSIONS: Hypertensive runners show high MSNA but preserved arterial elastic properties and baroreflex control of HR and MSNA, suggesting a positive partial effect of competitive physical training. On the other hand, the moderate intensity training is able to decrease MSNA in hypertensive runners and improves baroreflex control of MSNA in hypertensive as well in normotensive runners
623

Dynamic behaviour of dowel-type connections under in-service vibration

Reynolds, Thomas Peter Shillito January 2013 (has links)
This study investigated the vibration serviceability of timber structures with dowel-type connections. It addressed the use of such connections in cutting-edge timber structures such as multi-storey buildings and long-span bridges, in which the light weight and flexibility of the structure make it possible that vibration induced by dynamic forces such as wind or footfall may cause discomfort to occupants or users of the structure, or otherwise impair its intended use. The nature of the oscillating force imposed on connections by this form of vibration was defined based on literature review and the use of established mathematical models. This allowed the appropriate cyclic load to be applied in experimental work on the most basic component of a dowel-type connection: a steel dowel embedding into a block of timber. A model for the stiffness of the timber in embedment under this cyclic load was developed based on an elastic stress function, which could then be used as the basis of a model for a complete connector. Nonlinear and time-dependent behaviour was also observed in embedment, and a simple rheological model incorporating elastic, viscoelastic and plastic elements was fitted to the measured response to cyclic load. Observations of the embedment response of the timber were then used to explain features of the behaviour of complete single- and multiple-dowel connections under cyclic load representative of in-service vibration. Complete portal frames and cantilever beams were tested under cyclic load, and a design method was derived for predicting the stiffness of such structures, using analytical equations based on the model for embedment behaviour. In each cyclic load test the energy dissipation in the specimen, which contributes to the damping in a complete structure, was measured. The analytical model was used to predict frictional energy dissipation in embedment, which was shown to make a significant contribution to damping in single-dowel connections. Based on the experimental results and analysis, several defining aspects of the dynamic response of the complete structures, such as a reduction of natural frequency with increased amplitude of applied load, were related to the observed and modelled embedment behaviour of the connections.
624

Regulating Valvular Interstitial Cell Phenotype by Boundary Stiffness

Kural, Mehmet Hamdi 01 June 2014 (has links)
"A quantitative understanding of the complex interactions between cells, soluble factors, and the biological and mechanical properties of biomaterials is required to guide cell remodeling towards regeneration of healthy tissue rather than fibrocontractive tissue. The goal of this thesis was to elucidate the interactions between the boundary stiffness of three-dimensional (3D) matrix and soluble factors on valvular interstitial cell (VIC) phenotype with a quantitative approach. The first part of the work presented in this thesis was to characterize the combined effects of boundary stiffness and transforming growth factor-β1 (TGF-β1) on cell-generated forces and collagen accumulation. We first generated a quantitative map of cell-generated tension in response to these factors by culturing VICs within micro-scale fibrin gels between compliant posts (0.15-1.05 nN/nm) in chemically-defined media with TGF-β1 (0-5 ng/mL). The VICs generated 100 to 3000 nN/cell after one week of culture, and multiple regression modeling demonstrated, for the first time, quantitative interaction (synergy) between these factors in a 3D culture system. We then isolated passive and active components of tension within the micro-tissues and found that cells cultured with high levels of stiffness and TGF-β1 expressed myofibroblast markers and generated substantial residual tension in the matrix yet, surprisingly, were not able to generate additional tension in response to membrane depolarization signifying a state of continual maximal contraction. In contrast, negligible residual tension was stored in the low stiffness and TGF-β1 groups indicating a lower potential for shrinkage upon release. We then studied if ECM could be generated under the low tension environment and found that TGF-β1, but not EGF, increased de novo collagen accumulation in both low and high tension environments roughly equally. Combined, these findings suggest that isometric cell force, passive retraction, and collagen production can be tuned by independently altering boundary stiffness and TGF-β1 concentration. In the second part, by using the quantitative information obtained from the first part, we investigated the effects of dynamic changes in stiffness on cell phenotype in a 3D protein matrix, quantitatively. Our novel method utilizing magnetic force to constrain the motion of one of two flexible posts between which VIC-populated micro-tissues were cultured effectively doubled the boundary stiffness and resulted in a significant increase in cell-generated forces. When the magnetic force was removed, the effective boundary stiffness was halved and the tissue tension dropped to 65-87% of the peak value. Surprisingly, following release the cell-generated forces continued to increase for the next two days rather than reducing down to the homeostatic tension level of the control group with identical (but constant) boundary stiffness. The rapid release of tension with the return to baseline boundary stiffness did not result in a decrease in number of cells with α-SMA positive stress fibers or an increase in apoptosis. When samples were entirely released from the boundaries and cultured free floating (where tension is minimal but cannot be measured), the proportion of apoptotic cells in middle region of the micro-tissues increased more than five-fold to 31%. Together, these data indicate that modest temporary changes in boundary stiffness can have lasting effects on myofibroblast activation and persistence in 3D matrices, and that a large decrease in the ability of the cells to generate tension is required to trigger de-differentiation and apoptosis. "
625

Finite Element Analysis for Fixture Stiffness

Zheng, Yi 05 May 2005 (has links)
With growing demands on improved product quality and shorter time to market, there is need for rigorous but practical tools to support the fixture design and analysis process. Computer-aided fixture design (CAFD), with predictable fixture stiffness, becomes a means to provide an appropriate solution in fixture design. The effectiveness of previous CAFD systems is not fully satisfactory partially because analysis of fixture stiffness has not kept pace with the development of CAFD. The dissertation research provides a model of fixture unit stiffness analysis and an experimental method of identifying contact stiffness parameters. The model and the method offer the potential for a more realistic analysis of fixture stiffness properties of a fixture-workpiece system, based on a fixture unit description. An FEA model of fixture unit stiffness is developed with contact elements for solving contact problems encountered in the study of fixture unit stiffness. The penalty function method is used to model the contact conditions in the energy equation of the general FEA and to describe the nonlinearity of connection shown in previous experiments. The contact and friction conditions are represented mathematically in the FEA model. The FEA model and the analysis procedure are validated by numerical simulation. An experimental study on contact parameters is carried out to identify contact stiffness, including normal contact stiffness and tangential contact stiffness, by both static and dynamic approaches. For normal contact stiffness, a static identification procedure is developed to estimate the contact parameters, using experimental data. Four factors - testing environment, contact area, surface finish of the specimen, and normal loads, - are examined to see how they affect the behavior of the contact interface. A dynamic method is also used to identify normal contact stiffness. A scheme of eigenvalue analysis is developed to test the contact structure to estimate contact stiffness. The dynamic test results are compared with the results of static test under the same experimental condition and a reliable correspondence is presented. Similar to methods devised to identify normal contact stiffness, a frequency-domain identification system is developed to estimate tangential contact stiffness, using FEA and experimental data. A simulation study on vibration data from tangential contact model is presented in this study. The experimental study is carried out and tangential contact stiffness is estimated based on numerical simulation and experimental data. This research establishes the finite element model of fixture unit stiffness and develops the experimental approaches to identify contact stiffness. Based on this study, the database of fixture stiffness can be built up, and further used in CAFD
626

Arterial stiffness and endothelial function in obstructive sleep apnoea : the effect of Continuous Positive Airway Pressure (CPAP) therapy

Jones, Anne January 2016 (has links)
Introduction: Obstructive sleep apnoea (OSA) is common and is caused by repetitive obstruction of the upper airway during sleep. OSA is associated with increased cardiovascular morbidity and mortality and is an independent risk factor for hypertension. The immediate physiological effects of OSA include intermittent hypoxia, repeated arousal from sleep and intra-thoracic pressure swings. The resulting activation of the sympathetic nervous system, systemic inflammation and oxidative stress may result in increased arterial stiffness and endothelial dysfunction, potentially explaining any causal link between OSA and cardiovascular disease (CVD). Continuous positive airway pressure (CPAP) therapy improves excessive daytime sleepiness (EDS) and in non-randomised studies, reduces cardiovascular mortality. Prior to starting this study, there was a limited amount of evidence suggesting that CPAP therapy improved arterial stiffness and endothelial function, but the effects in subjects without pre-existing CVD were unclear. Aims: i) to determine whether CPAP therapy has an effect upon measures of arterial stiffness and endothelial function in patients with OSA, in the absence of known CVD. ii) To compare arterial stiffness and endothelial function in a subset of patients with OSAHS (defined as OSA and EDS), with a group of well-matched control subjects. Methods: Fifty three patients with OSA, defined as an apnoea/hypopnoea index of ≥15, and without known CVD, entered a double-blind placebo-controlled crossover trial of 12 weeks CPAP therapy, of whom forty three completed the study protocol. Sham CPAP was used in the placebo arm of the study and vascular assessments were made at baseline and after each arm of the study. Arterial stiffness was determined by measuring aortic distensibility using cardiovascular magnetic resonance imaging and by measuring the augmentation index (AIx) and aortic pulse wave velocity (PWV) by applanation tonometry. Endothelial function was assessed non-invasively by measuring vascular reactivity after administration of salbutamol and glyceryl trinitrate. In a subset of twenty patients with OSAHS, arterial stiffness and endothelial function at baseline were compared to readings obtained from healthy control subjects, matched on a one-to-one basis for age, sex and BMI. Results: Patients with OSAHS (n=20) had increased arterial stiffness [AIx 19.3(10.9) vs. 12.6(10.2) %; p=0.017] and impaired endothelial function, measured as the change in AIx following salbutamol [-4.3(3.2) vs. -8.0(4.9) %; p=0.02] compared to controls. Twelve weeks of CPAP therapy had no significant effect upon any measure of arterial stiffness or endothelial function in patients with OSA (n=43). A trend towards a reduction in AIx following CPAP therapy was seen, but this was non-significant. There was a reduction in systolic blood pressure following CPAP therapy [126(12) vs. 129(14) mmHg]. Sub group analysis showed CPAP to have no effect on arterial stiffness or endothelial function in patients with EDS or in patients using CPAP for ≥4 hours per night. Conclusions: This study demonstrates that even in the absence of known CVD, patients with OSAHS have evidence of increased arterial stiffness and impaired endothelial function. However, in patients with OSA, free from CVD, CPAP therapy did not lead to an improvement in any measure of arterial stiffness or endothelial function after 12 weeks.
627

Análise das propriedades acústicas de contrapisos produzidos com materiais reciclados

Borges, Joice Giuliani Krás 27 November 2015 (has links)
Submitted by Silvana Teresinha Dornelles Studzinski (sstudzinski) on 2016-02-18T12:09:06Z No. of bitstreams: 1 Joice Giuliani Krás Borges_.pdf: 2287182 bytes, checksum: 91bf17f3aaf35b6e94a1a9a7d0ca42c3 (MD5) / Made available in DSpace on 2016-02-18T12:09:06Z (GMT). No. of bitstreams: 1 Joice Giuliani Krás Borges_.pdf: 2287182 bytes, checksum: 91bf17f3aaf35b6e94a1a9a7d0ca42c3 (MD5) Previous issue date: 2015-11-27 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / FAPERGS - Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul / Em meio às mudanças que o setor da construção civil está passando, encontra-se a necessidade de buscar soluções que não agridam o meio ambiente, visto que o setor é grande responsável pela escassez de recursos naturais e pelo aumento da poluição ambiental. Uma alternativa precursora é a inserção de produtos mais sustentáveis, com a utilização de resíduos que podem ser usados como matéria prima em substituição aos agregados naturais. Diante disso, o desafio é a comprovação do desempenho dos produtos e dos sistemas construtivos, principalmente após a nova versão da NBR 15575 (ABNT, 2013) - Desempenho das edificações. A norma estabelece parâmetros de desempenho e requisitos de conforto ao usuário, entre os quais está o acústico. Neste contexto o objetivo do trabalho foi investigar o potencial acústico de compósitos de argamassa com substituição parcial da areia por resíduos: da agroindústria (casca de arroz), da indústria de calçados (EVA) e da construção civil (resíduo de madeira, serragem). Foram investigados os teores de substituição de 25%, 50% e 75%. A medição de isolamento acústico foi efetuada através do ruído de impacto, em placas de 1 m², nas espessuras 3 e 5cm, e ensaio de rigidez dinâmica em placas de 20x20 cm, nas espessuras 3 e 5 cm. Os resultados mostraram que a redução dos níveis de ruído de impacto é maior na medida em que se aumenta a espessura e o teor de resíduos das amostras, especialmente nas bandas de frequências acima de 500 Hz. Em relação aos níveis de pressão sonora padronizado ponderado (L’nT,W), o EVA se destacou entre os resíduos, seguido da casca de arroz. As amostras confeccionadas com 75% de EVA apresentaram um forte decaimento nas bandas de frequência acima de 500 Hz. As amostras confeccionadas com 50% de casca de arroz apresentaram reduções de 1 dB para as espessuras de 3 cm e de 3 dB nas amostras com espessuras de 5 cm em relação às amostras de referência. / Bearing in mind the evolution of construction industry, it’s needed to find solutions that do not harm the environment, considering that the sector is largely responsible for the lack of natural resources and increased environmental pollution. A precursor alternative is increase the use of more sustainable products, such as residues to replace natural aggregates. Thus, the challenge is to prove the performance of products and construction systems, especially after the new version of NBR 15575 (ABNT, 2013) - Performance of buildings. The standard establishes performance and comfort requirements for the users, among which is the acoustic. In this context, the aim of this study was to investigate the acoustic potential of grout composites with partial replacement of sand by residues of agro-industry (rice husk), the shoe industry (EVA) and civil construction (wood waste, sawdust). The substitution levels of 25%, 50% and 75% were investigated. The sound insulation measurement was performed through the impact noise in 1 m² plates, in thicknesses 3 and 5 cm, and the dynamic stiffness test, in plates of 20x20 cm, with thicknesses of 3 and 5 cm. The results showed that the reduction of the impact noise level is higher as it increases the thickness and the residues of the samples, especially in bands above 500 Hz frequency. Regarding the sound pressure levels of weighted standard impact (L'nT,W), EVA stood out among the residues, followed by rice husk. The samples made with 75% EVA showed strong decay in the frequency bands above 500 Hz. The samples made with 50% of rice husk showed reductions of 1 dB for the thickness of 3 cm, and 3 dB in samples with thickness of 5 cm, in comparison with the reference samples.
628

La migration des cellules et leur sensibilité aux propriétés physiques de la matrice extracellulaire : rôle d'ICAP-1, un régulateur des intégrines et de la contractilité / About cell migration and cellular response to the physical properties of the extracellular matrix : iCAP-1 regulates integrins and cell contractility.

Régent, Myriam 17 June 2011 (has links)
Les cellules sont organisées en tissus dont les propriétés physiques comme la rigidité et l'élasticité sont variables. La matrice extracellulaire (MEC) est produite et remodelée par les cellules qui s'adaptent en retour aux conditions physico-chimiques de cet environnement extracellulaire. Cela nécessite une communication bidirectionnelle entre la cellule et la matrice. Les intégrines sont des protéines transmembranaires impliquées dans l'adhérence, liant la MEC au cytosquelette d'actine via une plateforme protéique appelée adhérence focale, lieu d'une double signalisation (inside-out et outside-in). Des variations de tension intracellulaire imposées par l'environnement modifient la distribution et la taille de ces adhérences. Leur dynamique est aussi contrôlée par certaines protéines cytoplasmiques comme la protéine ICAP-1, partenaire de l'intégrine b1. En cherchant à comprendre le lien entre la tension interne et l'activation des intégrines, j'ai montré qu'ICAP-1 contrôle l'étalement, la contractilité interne et la migration cellulaire en présence comme en absence de l'intégrine b1, révélant un rôle ICAP-1 indépendant de son interaction avec l'intégrine b1. Ce contrôle semble passer par l'interaction ICAP-1/ROCK et a révélé un contrôle de l'intégrine b3 par l'intégrine b1. / The physical properties of cell tissues are variable and cells adapt their behaviour to the physical and chemical extracellular environment such as rigidity and composition of the extracellular matrix (ECM) which is produced and remodelled by cells. This implicates a bidirectionnal signalling between cells and the ECM. Integrins are transmembrane proteins involved in cell adhesion, linking the ECM to the actin cytoskeleton through adaptor proteins forming adhesion site called focal adhesion (FA) where take place an inside-out and an outside-in signallings. Intracellular tension can be controlled by extracellular cues, modifying the size and distribution of FA. FA dynamics is also regulated by cytoplasmic proteins such as ICAP-1 that interacts with b1 integrin. Looking for a better comprehension of the link between cell tension and integrin activation, I show that ICAP-1 controls cell spreading, cell contractility and cell migration both in presence or absence of b1 integrins meaning that ICAP-1 has an action without its interaction b1 integrin. This action seems to implicate the interaction between ICAP-1 and ROCK and revealed a control of b1 integrin on b3 integrin.
629

Avaliação do índice de rigidez arterial em pacientes transplantados de coração, hipertensos e não hipertensos / Arterial stiffness index assessment in heart transplanted patients, hypertensive and non-hypertensive

Souza Neto, João David de 02 October 2015 (has links)
A hipertensão arterial sistêmica (HAS) pós-transplante é frequente e está associada com aumento da morbimortalidade cardiovascular e subsequente disfunção do enxerto, sendo relatada como consequência ao uso de imunossupressores, especialmente os inibidores da calcineurina. Este estudo pretende avaliar o impacto da hipertensão arterial sobre a rigidez arterial calculada utilizando o índice ambulatorial de rigidez arterial (IARA) como desfecho substituto obtido pela monitorização ambulatorial da pressão arterial (MAPA) em pacientes transplantados de coração. Trata-se de um estudo prospectivo, observacional, analítico, com grupo controle, realizado no Hospital de Messejana Dr. Carlos Alberto Studart Gomes, hospital público do estado do Ceará, especializado em doenças cardiopulmonares e de referência em transplante de coração. Foram selecionados pacientes adultos transplantados do coração, os quais passaram por exames clínicos e complementares, e um grupo controle com pacientes não transplantados hipertensos. Todos foram submetidos a MAPA e obtenção do IARA com o objetivo de estimar o risco de rigidez arterial. Foram realizados testes estatísticos de significância e regressão logística para controle de confundimento. A média de idade dos transplantados foi de 55 anos, contra 48 dos não transplantados. A hipertensão prévia foi mais frequente em não transplantados, mas diabetes e doença arterial coronariana foram mais frequentes em transplantados. A média diastólica dos transplantados (82) é significativamente maior que a dos não transplantados (74) e o descenso sistólico é praticamente inexistente em pacientes transplantados (-0,18) que no grupo-controle (9,45). A condição de transplantado do paciente não é determinante de rigidez arterial, mas a hipertensão arterial sistólica na primeira avaliação, a média sistólica em 24h, a média diastólica em 24h, o descenso sistólico, o descenso diastólico e o IARA (parâmetros da MAPA) o são. Este estudo encontrou que num grupo de transplantados de coração adultos, a hipertensão arterial sistêmica está independentemente associada com a rigidez arterial estimada pelo IARA, que é um novo método, não invasivo, de fácil execução e de baixo custo. A evidência demonstrada por este estudo pode auxiliar no direcionamento de tratamento dos pacientes transplantados, contribuindo com melhoria do prognóstico / Hypertension post cardiac transplant is frequent and is associated with increased cardiovascular morbidity and mortality and graft dysfunction, being reported because of the use of immunosuppressant, especially the calcineurin inhibitors. This study aims to evaluate the impact of hypertension on the arterial stiffness calculated using the IARA as surrogate outcome obtained by the Home Blood Pressure Monitoring in heart transplanted patients. This is an observational study, analytical, with the control group, in Heart and Lung Messejana´s Hospital, a public institution in the State of Ceará, which is specialized in cardiopulmonary diseases and especially in heart transplant, with adult patients cardiac transplanted, which underwent clinical and complementary exams, from which were obtained the IARA. Statistical significance tests and logistic regression to control for confounding were performed. The average age of transplanted was 55 years, against 48 of the non-transplanted. Hypertension was more frequent in prior not transplanted, but diabetes and coronary artery disease were more frequent in transplanted. The average diastolic of transplanted (82) is significantly higher than the non-transplanted (74) and decrease systolic is virtually nonexistent in transplant patients (-0.18) than in the control group (9.45). The condition of the transplanted patient is not determinant of arterial stiffness (p = 0.105), but are the systolic hypertension in the first evaluation, the average systolic, diastolic average in 12:0 am 12:0 am, systolic, diastolic descent and the IARA (parameters of the HBPM). This study showed that in a group of adult cardiac transplanted, hypertension is independently associated with arterial stiffness estimated by IARA, which is a new method, non-invasive, easy to perform and inexpensive. The evidence demonstrated by this study may assist in treatment of transplanted patients, contributing to improving the prognosis
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Análise dinâmica não linear em torres de concreto armado submetidas ao vento sintético. / Dynamic nonlinear analysis of reinforced concrete towers submitted to the synthetic wind.

Silva, Murilo Sasaki de Paula e 14 June 2017 (has links)
O tema está relacionado com o constante crescimento da necessidade em implantarnovas torres de telecomunicações devido ao crescimento acelerado da infraestrutura de telecomunicações no Brasil. Todos os dias, novos sistemas de transmissão e recepção de ondas eletromagnéticas estão sendo implantados no território brasileiro. O objetivo deste trabalho é propor um procedimento seguro e eficaz para a análise estrutural de torres de telecomunicações em concreto armado de grande esbeltez, com base em um modelo dinâmico não linear, submetendo à carga de vento. Estas cargas são simuladas pelo método do vento sintético proposto por Franco (1993). A análise do concreto armado será realizada de acordo com a NBR-6118 (ABNT, 2007). A fim de determinar com precisão os deslocamentos da estrutura submetida ao carregamento de vento, um método iterativo computacional será utilizado obter as respostas não lineares. Realiza-se uma análise linear e, a partir dos resultados de esforços solicitantes, as tensões e a porção fissurada de cada seção transversal é obtida e parte-se para a determinação dos deslocamentos de 2ª ordem da torre. Em cada iteração, um procedimento do tipo P-Delta será utilizado para levar em conta a não linearidade geométrica da estrutura. As condições de contorno do problema estão relacionadas com a restrição do nível de tensões, deslocamentos e frequências de vibração da estrutura. Ao fim, uma análise dinâmica em torno da configuração não linear será realizada, e o deslocamento total da torre será dado pela somatória da componente estática com a componente flutuante do vento. / The theme is related to the constant growth in the need to deploy new telecommunications towers due to the accelerated growth of telecommunications infrastructure in Brazil. Every day, new systems of transmission and reception of electromagnetic waves are being implanted in the Brazilian territory. The objective of this work is to propose a safe and efficient procedure for the structural analysis of telecommunication towers with high slenderness constructed in reinforced concrete, based on a dynamic nonlinear model, submitting it to the wind load. These loads are simulated by the synthetic wind method proposed by Franco (1993). The analysis of the reinforced concrete will be held according to NBR-6118 (ABNT, 2007). In order to determine accurately the displacements of the structure subjected to wind loading, an iterative computational method will be held to obtain non-linear responses. A linear analysis is carried out and, with the results of the forces, the tensions and the fissured portion of each cross section are obtained and then 2nd order displacements of the tower. In each iteration, a P-Delta type procedure will be held to take into account the geometric non-linearity of the structure. The boundary conditions of the problem are related to the restriction of the stress level, displacements and vibration frequencies of the structure. At the end, a dynamic analysis around the nonlinear configuration will be performed, and the total displacement of the tower will be given by the sum of the static component with the floating component of the wind.

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