Dissertations / Theses on the topic 'Aortic tissue'
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Nowell, Justin L. "Anticoagulation Following Tissue Aortic Valve Replacement." Thesis, St George's, University of London, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.517184.
Full textLiu, Janet. "Design of a Novel Tissue Culture System to Subject Aortic Tissue to Multidirectional Bicuspid Aortic Valve Wall Shear Stress." Wright State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=wright1527077368757049.
Full textSmuts, Adriaan Nicolaas. "Design of tissue leaflets for a percutaneous aortic valve." Thesis, Stellenbosch : University of Stellenbosch, 2009. http://hdl.handle.net/10019.1/1625.
Full textThesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2009.
In this project the shape and attachment method of tissue leaflets for a percutaneous aortic valve is designed and tested as a first prototype. Bovine and kangaroo pericardium was tested and compared with natural human valve tissue by using the Fung elastic constitutive model for skin. Biaxial tests were conducted to determine the material parameters for each material. The constitutive model was implemented using finite element analysis (FEA) by applying a user-specified subroutine. The FEA implementation was validated by simulating the biaxial tests and comparing it with the experimental data. Concepts for different valve geometries were developed by incorporating valve design and performance parameters, along with stent constraints. Attachment techniques and tools were developed for valve manufacturing. FEA was used to evaluate two concepts. The influence of effects such as different leaflet material, material orientation and abnormal valve dilation on the valve function was investigated. The stress distribution across the valve leaflet was examined to determine the appropriate fibre direction for the leaflet. The simulated attachment forces were compared with suture tearing tests performed on the pericardium to evaluate suture density. In vitro tests were conducted to evaluate the valve function. Satisfactory testing results for the prototype valves were found which indicates the possibility for further development and refinement.
Kermani, Golriz. "Characterization of Rate Dependency and Inhomogeneity of Aortic Tissue." Diss., Temple University Libraries, 2016. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/412554.
Full textPh.D.
Traumatic aortic rupture (TAR) is one of the leading causes of morbidity and mortality in motor-vehicle accidents with the majority of injuries occurring in the peri-isthmus region. To date, the mechanisms of aorta injury are poorly understood as this injury cannot be replicated reliably in cadaver crash tests. Due to inconclusiveness of the experimental tests, finite element (FE) modeling is often used to gain a better insight into the mechanisms of TAR. However, the FE models are also hindered by many unknowns particularly the soft tissues biomechanical responses. A crucial step to improve the FE models of blunt chest trauma is to advance our understanding of the local mechanical properties of aortic tissue subject to high loading rates associated with TAR. The objective of this dissertation was to investigate the effects of tissue rate dependency and inhomogeneity in the modeling of loading conditions that lead to TAR. The material properties of human aorta in large deformations and high loading rates were characterized based on oscillatory biaxial tests. It was shown that a quasilinear viscoelastic (QLV) model with the instantaneous elastic response of the second order and the reduced relaxation function with one exponentially decaying term could describe the experimental results between 20 Hz and 130 Hz. The obtained decay rates (in the range of 70 to 550 s-1) were 10 to 100 folds higher than previously reported values and showed significant rate dependence within 10 ms after the loading. It was shown that the rate dependent properties, similar to the elastic properties, were anisotropic with generally higher decay rate and stiffness observed in the circumferential direction compared to the longitudinal direction. The inhomogeneity of porcine descending thoracic aorta was characterized in three dimensions using a nano-indentation technique and QLV modeling approach. The tests were conducted in the axial, circumferential, and radial orientations with about 100 micrometer spatial resolution. Aortic tissue was divided into 10 regions across the thickness, 4 quadrants in the circumferential direction, and 3 sections in the longitudinal direction. While across the thickness, the results in different orientations were significantly different, four distinct layers were identified that were matched with the anatomical features. In the axial direction, the medial quadrant, and in all directions, the proximal DTA had the lowest stiffness. The results predict that under equal stresses, the inner layers of the medial quadrant in upper DTA would undergo more strains and will be therefore more prone to failure. This prediction is in agreement with clinical observations. The inhomogeneity and rate dependency of aorta were implemented in the Global Human Body Models Consortium full-body FE model. It was demonstrated that in a simulation of blunt chest impact, both features significantly affected the tissue strain levels particularly in the isthmus, arch, and ascending aorta. Accurate quantifications of these features are essential to assess the risk of aortic injury based on FE models.
Temple University--Theses
Korossis, Sotirios Anastasios. "Biomechanics and hydrodynamics of decellularised aortic valves for tissue engineering." Thesis, University of Leeds, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.270873.
Full textRastgar, Agah Mobin. "Material Characterization of Aortic Tissue for Traumatic Injury and Buckling." Diss., Temple University Libraries, 2015. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/324268.
Full textPh.D.
While traumatic aortic injury (TAI) and rupture (TAR) continue to be a major cause of morbidity and mortality in motor vehicle accidents, its underlying mechanisms are still not well understood. Different mechanisms such as increase in intraluminal pressure, relative movement of aorta with respect to mediastinal structures, direct impact to bony structures have been proposed as contributing factors to TAI/TAR. At the tissue level, TAI is assumed to be the result of a complex state of supra-physiological, high rate, and multi-axial loading. A major step to gain insight into the mechanisms of TAI is a characterization of the aortic tissue mechanical and failure properties under loading conditions that resemble traumatic events. While the mechanical behavior of arteries in physiological conditions have been investigated by many researchers, this dissertation was motivated by the scarcity of reported data on supra-physiological and high rate loading conditions of aorta. Material properties of the porcine aortic tissue were characterized and a Fung-type constitutive model was developed based on ex-vivo inflation-extension of aortic segments with intraluminal pressures covering a range from physiological to supra-physiological (70 kPa). The convexity of the material constitutive model was preserved to ensure numerical stability. The increase in ë_è from physiological pressure (13 kPa) to 70 kPa was 13% at the outer wall and 22% at the inner wall while in this pressure range, the longitudinal stretch ratio ë_z increased 20%. A significant nonlinearity in the material behavior was observed as in the same pressure range, the circumferential and longitudinal Cauchy stresses at the inner wall were increased 16 and 18 times respectively. The effect of strain-rate on the mechanical behavior and failure properties of the tissue was characterized using uniaxial extension experiments in circumferential and longitudinal directions at nominal strain rates of 0.3, 3, 30 and 400 s-1. Two distinct states of failure initiation (FI) and ultimate tensile strength (UTS) were identified at both directions. Explicit direct relationships were derived between FI and UTS stresses and strain rate. On the other hand, FI and UTS strains were rate independent and therefore strain was proposed as the main mechanism of failure. On average, engineering strain at FI was 0.85±0.03 for circumferential direction and 0.58±0.02 for longitudinal direction. The engineering strain at UTS was not different between the two directions and reached 0.89±0.03 on average. Tissue pre-failure linear moduli showed an average of 60% increase over the range of strain rates. Using the developed material model, mechanical stability of aorta was studied by varying the loading parameters for two boundary conditions, namely pinned-pinned boundary condition (PPBC) and clamped-clamped boundary condition (CCBC). The critical pressure for CCBC was three times higher than PPBC. It was shown that the relatively free segment of aorta at the isthmus region may become unstable before reaching the peak intraluminal pressures that occur during a trauma. The mechanical instability mechanism was proposed as a contributing factor to TAI, where elevations in tissue stresses and strains due to buckling may increase the risk of injury.
Temple University--Theses
Treibel, Thomas Alexander. "Aortic stenosis : a myocardial disease : insights from myocardial tissue characterisation." Thesis, University College London (University of London), 2017. http://discovery.ucl.ac.uk/1574742/.
Full textLuo, Yuanming. "Local properties and rupture characteristics of thoracic aortic aneurysm tissue." Diss., University of Iowa, 2018. https://ir.uiowa.edu/etd/6186.
Full textJoda, Akram Abdelazim Osman. "Fluid-structure interaction of the aortic valve for tissue engineering applications." Thesis, University of Leeds, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.550815.
Full textFraser, Katharine H. "Computational estimation of haemodynamics and tissue stresses in abdominal aortic aneurysms." Thesis, University of Edinburgh, 2007. http://hdl.handle.net/1842/24588.
Full textChu, Boby. "Characterization of aortic tissue fracture toughness and stiffness under cyclical fatigue loading." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=86772.
Full textThis present work incorporates the temporal aspect by examining the effects of fatigue on aortic wall properties, and adopts an energetics approach to evaluating the aorta's resistance to rupture. Tissue samples from porcine aortas were fatigued and were subjected to both biaxial and guillotine tests to assess stiffness and fracture toughness. The experiments indicate that both properties decreased according to a power function. After 1 000 000 loading cycles, the final/initial stiffness ratio dropped to 0.85, while its toughness counterpart fell to 0.80.
This work constitutes the first tentative steps towards the development of a clinical tool that can evaluate the fracture toughness of aneurismal aortic tissues and predict the temporal likelihood of aneurismal rupture.
L'anévrisme de l'aorte ascendante est une maladie asymptomatique. Sans traitement, un anévrisme peut se rompre, ce qui est fatal. Les pratiques cliniques actuelles reposent d'abord sur l'observation de la croissance de la taille de l'anévrisme qui est suivie de la résection chirurgicale de l'aorte lorsque son diamètre atteint 5 à 5,5 cm. Malheureusement, cette méthode est peu précise comme indicateur de risque de rupture et ne s'appuie que sur les observations cliniques pour justifier son application. Plusieurs outils de prédiction plus sophistiqués sont en voie de développement, mais les efforts récents se concentrent surtout sur la distribution des tensions au sein des parois anévrysmales, mais les résultats ne donnent aucune prédiction sur le délai avant que la résection soit nécessaire.
Ce travail incorpore l'aspect temporel en examinant l'effet de la fatigue sur les propriétés mécaniques des parois aortiques, tout en adoptant l'approche énergétique pour évaluer la résistance à la rupture du vaisseau. À cette fin, des échantillons de tissus d'aortes porcines sont étirés cycliquement. Leur rigidité et leur résistance à la rupture sont ensuite mesurées grâce aux tests biaxiaux et aux tests à la guillotine. Les résultats expérimentaux montrent une décroissance selon une loi de puissance. Après un million de cycles de tension, le rapport rigidité finale/rigidité initiale a baissé à 0,85, et celui de la résistance à la rupture a chuté jusqu'à 0,80.
Ce travail est une première étape dans le développement d'un outil clinique pour mesurer la résistance à la rupture des tissus aortiques anévrysmaux afin de prédire la probabilité d'une rupture sur une échelle de temps.
Bevis, Paul Michael. "Abdominal aortic aneurysms and the association with a systemic connective tissue disorder." Thesis, University of Bristol, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.544428.
Full textHan, Richard I.-Ming. "Early calcification patterns of bioprosthetic aortic tissue : a comparison of amino versus carboxyl group and combination cross-linked tissue." Master's thesis, University of Cape Town, 2003. http://hdl.handle.net/11427/2780.
Full textWeston, Matthew W. "Characterization of the shear stress on the aortic valve leaflet surface and its effects on cellular biosynthetic activity." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/9369.
Full textXing, Yun. "Effects of Mechanical Forces on the Biological Properties of Porcine Aortic Valve Leaflets." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/6828.
Full textDahal, Shataakshi. "Stem Cells Based Elastic Matrix Regeneration for Small Abdominal Aortic Aneurysms (AAAs) Repair." Cleveland State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=csu1599137475237285.
Full textDahal, Shataakshi. "Stem Cells Based Elastic Matrix Regeneration for Small Abdominal Aortic Aneurysms (AAAs) Repair." Cleveland State University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=csu1599137475237285.
Full textZemánek, Miroslav. "Influence of Geometrical Parameters on Rupture Risk of Abdominal Aortic Aneurysm." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2010. http://www.nusl.cz/ntk/nusl-233934.
Full textGarst, Christopher, Makenie Fulmer, Doug Thewke, and Stacy D. Brown. "Optimized Extraction of 2-Arachidonyl Glycerol and Anandamide from Aortic Tissue and Plasma for Quantification by LC-MS/MS." Digital Commons @ East Tennessee State University, 2016. https://dc.etsu.edu/etsu-works/5304.
Full textNejjar, Ibtissam. "Etude morphologique et biochimique du tissu elastique de l'aorte thoracique humaine lors du vieillissement et de l'atherosclerose." Toulouse 3, 1988. http://www.theses.fr/1988TOU30154.
Full textKumar, Vivek Ashok. "Design and evaluation of scaffolds for arterial grafts using extracellular matrix based materials." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/45869.
Full textSadeghi, Malvajerdi Neda. "Preliminary Analysis of an Internal Annuloplasty Ring for the Aortic Valve." Thesis, Université d'Ottawa / University of Ottawa, 2017. http://hdl.handle.net/10393/36142.
Full textPekar, Tonya M. "Phosphoproteomic studies of smooth muscle contraction investigation of differential phosphorylation in relaxed/contracted rat aortic smooth muscle tissue using MALDI-TOF MS /." Huntington, WV : [Marshall University Libraries], 2003. http://www.marshall.edu/etd/descript.asp?ref=370.
Full textTitle from document title page. Document formatted into pages; contains xv, 148 p. including illustrations. Includes bibliographical references (p. 131-148).
Konduri, Suchitra. "The Influence of normal physiological forces on porcine aortic heart valves in a sterile ex-vivo pulsatile organ culture system." Thesis, Available online, Georgia Institute of Technology, 2005, 2005. http://etd.gatech.edu/theses/available/etd-03042005-135623/unrestricted/konduri%5Fsuchitra%5F200505%5Fmast.pdf.
Full textDr. Athanassios Sambanis, Committee Member ; Dr. Timothy M. Wick, Committee Member ; Dr. Ajit P.Yoganathan, Committee Chair. Includes bibliographical references.
Williams, Alex. "The Oscillatory Shear Index: Quantifications for Valve Tissue Engineering and a Novel Interpretation for Calcification." FIU Digital Commons, 2018. https://digitalcommons.fiu.edu/etd/3784.
Full textArbesu, Y. Miar Anais. "Cellule interstitielle de valve et sténose aortique : impact de la voie du facteur tissulaire." Thesis, Lille 2, 2015. http://www.theses.fr/2015LIL2S062/document.
Full textDefined as the narrowing of the aortic valve, aortic stenosis (AS) is the third cardiovascular pathology in industrialized countries. Affecting mainly people aged over 65 years, AS represents a major public health problem because of the aging of the population. After initially been considered as a passive degenerative process, it is now established that AS is an "atherosclerosis-like " disease characterized by the processes of inflammation, fibrosis, neo-angiogenesis and calcification. Some proteins of the coagulation pathway such as tissue factor (TF) are known to have a pro-fibrotic role and actively participate in the development of atherosclerotic lesions. Their implication in AS seems, therefore, probable and remain to be identified.Prevalent cellular component of the aortic valve, VICs have five distinct subpopulations: embryonic progenitor cells (EPCs), progenitor cells (pVICs) quiescent (qVICs), activated (aVICs) and osteoblastic (obVICs). During the valvulogenesis, EPCs allow the cellularization of the valve, differentiating into qVICs. These cells maintain the valvular homeostasis and, in case of damage, are activated (aVICs) to effectively repair the valve tissue. The valvular inflammation and VICs activation initiate the secretion of pro-calcifying proteins inducing the differentiation of aVICs into obVICs. Finally, pVICs, naturally present within the valve (called resident) or from the blood circulation (called hematopoietic), seem to promote cell renewal and may be involved in the angiogenic and osteoblastic processes.Although described, these subpopulations have never been studied longitudinally, in respect to their behavior in vitro. Our first objective was to perform this investigation. Our second objective was to study the potential role of TF pathway in the deleterious mechanisms of AS.As part of the longitudinal follow-up of VICs from control and pathological human aortic valves to the in vitro culture performed on plastic and collagen, we first showed that different subpopulations were present in these valves with different locations and proportions according to the pathophysiological state of the tissue. After enzymatic digestion, all subpopulations are found but, in culture, hematopoietic pVICs disappeared, whichever the support. Thus, we validated the primary culture model of VICs while highlighting its limitations: lack of hematopoietic pVICs, spontaneous osteoblastic differentiation and activation of VICs in culture.As part of the study the involvement of FT in the AS development, we showed its colocalization with thrombin and calcifications of pathological valves. We showed that the expression and activity of TF were constitutively more important in VICs from fibrocalcified valves than control ones and that IL-1β for pathological VICs and that its expression could be induced by IL1 beta. In addition, TF activation in the by its ligand FVII, induced, directly and via the PAR-2 receptor, different signaling pathways involved in cell proliferation and the processes of fibrosis and calcification. Thus, our findings suggest that the FT expressed by VICs mediates fibrocalcific processes of aortic stenosis
Junior, Antonio Aurelio de Paiva Fagundes. "Estudo do fluxo sanguíneo regional e dos marcadores de perfusão tecidual em pacientes com insuficiência cardíaca em uso de balão intra-aórtico." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/5/5131/tde-10122013-102948/.
Full textBACKGROUND: The intra-aortic balloon (IAB) represents the mechanism of ventricular assist more often used in patients with heart failure (HF) in our midst. OBJECTIVE: In this study, we evaluated the action of the IAB on the carotid and brachial blood flow, in addition to its effect on markers of tissue perfusion and the brain natriuretic peptide (BNP). METHODS: Between July 2006 and May 2009, 33 patients were evaluated, 10 were excluded. Patients were initially maintained with the IAB in 1:1 mode with maximum insufflation, for the initial phase of the study (condition 1). Held collection of arterial and central venous blood gases, and BNP (condition EXA1). Vascular ultrasonography was performed in high definition, to capture images of the curves of blood flow velocity, and measurement of systolic and diastolic arterial diameters (condition MD1). Then we evaluated the vascular responses to reactive hyperemia (condition HR1). Conducted the study in condition 1, the IAB was changed to 1:3 with minimal insufflation (condition 2) and all laboratory tests (condition EXA 2) and ultrasound (condition MD2 and HR2) were repeated. After the second condition, the IAB was again modified to 1:1, with maximum insufflation (condition 3). Similarly to the previous conditions, laboratory tests (condition EXA 3) and ultrasound (condition MD3 and HR3) were performed. Statistical evaluation was performed by analysis of variance for repeated measures and the use of Friedman nonparametric test. RESULTS: The mean age of the selected patients was 49.7 +- 13 years, 17 (74%) males and 6 (26%) were females. Concerning etiology, 9 (39%) patients had ischemic cardiomyopathy, 8 (34%), idiopathic dilated cardiomyopathy, 4 (17%) had Chagas disease and 2 were (8%) related to valvulopathy. Ejection fraction estimated by echocardiography ranged from 14 to 40%, with a mean of 22 +- 8%. Nine patients (39%) were in line for a heart transplant at the time of inclusion in the protocol and mortality during hospitalization was 60.8%. Analyzed laboratory data, among the three measurements, there was not statistically significant difference in the values of arterial bicarbonate (BIC) and base excess (BE). We also did not detect changes in central venous oxygen saturation (SCVO2) or in serum BNP level and venoarterial carbon dioxide gradient (DeltaPCO2). The results of the analysis of carotid flow velocity, index of carotid flow and velocity time integral in condition MD1, MD2 and MD3 revealed no statistically significant difference. Examined the brachial territory, there was no difference between the condition MD1 and MD2 and between MD1 and MD3 considering the flow velocity. However, there was difference between conditions MD2 and MD3 (p = 0.01). We found no significant difference between the three conditions considering the brachial flow index and velocity time integral. The flow-mediated dilation of the brachial artery (FMD) found itself changed from the initial moment, but the protocol does not reveal changes between HR1, HR2 and HR3. CONCLUSION: In heart failure patients, assistance with the BIA did not alter regional blood flow in brain and skeletal muscle territory assessed by flow carotid and brachial artery, respectively. Likewise, there was no change in tissue perfusion and cardiac function assessed by markers of oxidative metabolism and fluid overload used. Endothelial function evaluated on condition of dual pulse brachial artery flow provided by BIA circulatory support showed up changed with decreased vascular reactivity
Cheheltani, Rabee. "Development of infrared spectroscopic methods for assessment of extracellular matrix changes in cardiovascular diseases." Thesis, Temple University, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3623127.
Full textExtracellular matrix (ECM) is a key component and regulator of many biological tissues. Several cardiovascular pathologies are associated with significant changes in the composition of the matrix. Better understanding of these pathologies and the physiological phenomenon behind their development depends on reliable methods that can measure and characterize ECM content and structure. In this dissertation, infrared spectroscopic methodologies are developed to study the changes in extracellular matrix of cardiovascular tissue in two cardiovascular pathologies; myocardial infarction and abdominal aortic aneurysm.
The specific aims of this dissertation were: 1. To develop a Fourier transform infrared imaging spectroscopy (FT-IRIS) methodology for creating distribution maps of collagen in remodeled cardiac tissue sections after myocardial infarction, and to quantitatively compare maps created by FT-IRIS with conventional staining techniques. 2. To develop an FT-IRIS method to assess elastin and collagen composition in the aortic wall. This will be accomplished using ex vivo animal aorta samples, where the primary ECM components of the wall will be systematically enzymatically degraded. 3. To apply the newly developed FTIR imaging methodology to evaluate changes in the primary ECM components (collagen and elastin) in the wall of human AAA tissues. The infrared absorbance band centered at 1338 cm-1, was used to map collagen deposition across heart tissue sections of a rat model of myocardial infarction, and was correlated strongly in the size of the scar (R=0.93) and local intensity of collagen deposition (R=0.86).
In enzymatically degraded pig aorta samples, as a model of ECM degradation in abdominal aortic aneurysm (AAA), partial least squares (PLS) models were created to predict collagen and elastin content in aorta based on collected FTIR spectra and biochemically measured values. PLS models based on FT-IRIS spectra were able to predict elastin and collagen content of the samples with strong correlations (R2=0.90 and 0.70 respectively). Elastin content prediction from IFOP spectra was successful through a PLS regression model with high correlation (R2=0.81).
The PLS regression coefficient from the FT-IRIS models were used to map collagen and elastin human AAA biopsy tissue sections, creating a similar map of each component compared to histologically stained images. The mean value of collagen deposition in each tissue was calculated for 13 pairs of AAA samples where stress had been calculated using finite element modeling. In most pairs with stress values higher than 5 N/m2, collagen content was lower in the sample with higher stress value. Collagen maturity had a weak negative correlation (R=-0.35) with collagen content in these samples.
These results confirm that infrared spectroscopy is a powerful tool that can be applied to replace or complement conventional methods such as histology and biochemical analysis to characterize ECM components in cardiovascular tissues. Furthermore, infrared spectroscopy has the potential for translation to a clinical environment to examine ECM changes in aorta in a minimally invasive fashion using fiber optic technology.
Simmers, Phillip Charles. "Benefits of Nitric Oxide Cues to Matrix Synthesis by Healthy and Aneurysmal Human Smooth Muscle Cells within 3D Cocultures." Cleveland State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=csu1399977973.
Full textTremblay, Dominique. "Mechanical and structural characterization of ascending aortic tissues and graft materials used in the aortic arch reconstruction." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=86901.
Full textLes mécanismes impliqués dans le développement des maladies aortiques telles que les anévrismes de l'aorte ascendante (AA) humaine sont inconnus. On pense que la capacité de remodelage des cellules endothéliales (CE) et musculaires lisses (CML) combinées avec une distribution non uniforme des contraintes à la surface et dans le tissu aortique dû à une hémodynamie perturbée produit par une valve aortique malade jouent un rôle important dans la progression de la maladie. Dans cette thèse, on fait l'hypothèse qu'il existe un remodelage aortique local dans les tissus aortiques dilatés et que ce remodelage dépendent du type valve. Cependant, très peu de données sont disponibles sur les propriétés mécaniques et structurelles de l'AA saine et dilatée. Une description détaillée de ce tissu fournira des indices essentiels pour mieux comprendre la progression de la maladie et aidera à identifier les mécanismes impliqués. L'analyse régionale a révélé une variation circonférentielle de la rigidité, de l'épaisseur et du contenu en collagène dans les tissus sain et BAV-T1 dilatés mais non présents dans les tissus TAV dilatés. En moyenne, on a montré des différences d'épaisseur et du contenu en collagène entre les tissus dilatés TAV et BAV-T1. On a également trouvé des variations régionales de la densité et de l'orientation des CML dans l'AA porcine. La grande courbure montre une densité plus élevée de CML orientées dans la direction axiale. Bien que l'activation des CML à la phenylephrine ait eu un effet significatif sur la rigidité de l'AA, aucunes variations circonférentielles ou directionelles de cet effet ont été trouvées. On observe la présence de remodelage local, suite à une reconstruction de l'arche aortique, causé par la différence de compliance entre l'aorte native et le greffon de remplacement. Aucune étude n'avait essayé de quantifier cette différence dans l'aorte reconstruite. Nous avons trouvé des$
Bode, M. (Michaela). "Characterization of type I and type III collagens in human tissues." Doctoral thesis, Oulun yliopisto, 2000. http://urn.fi/urn:isbn:9514255534.
Full textMohand, Kaci Faïza. "Bioingénierie des cellules souches mésenchymateuses médullaires cultivées en 3D : application au traitement de l’anévrysme de l’aorte abdominale." Thesis, Paris Est, 2012. http://www.theses.fr/2012PEST0079.
Full textAbdominal aortic aneurysm (AAA) is a degenarative disease of the arterial wall, which is usually treated with a conventional surgery or an andovascular stent. Due to its high morbidity and mortality, the AAA constitutes a major public health concern. The aim of this thesis is to evaluate the imapct of OD culture of mesenchymal stem cells (MSC), in particular on their phenotype, their multipotency, their ability to repair aneurysms in vivo and to acquire a phenotype suitable to the nechanical stress they support in vitro. Optmal culture conditions in a 3D hydrogel of hyaluronic acid preserving the multipotency of MSC in vitro have been established. Under mechanical effects, reproducing those supported by the aortic wall in vivo, 2D and 3D CSM seem to preserve their multipotency. However, under such dynamic conditions, the viability of 3D CSM increases unlike that of 2D CSM. By using a rat xenograft model, the results also show that injection of 2D or 3D CSM, stabilizes the AAA and improves the mechanical strenght of the aneurysmal vessel wall. The study in rat was supplemented by an evaluation of a therapeutic cell-based approach using 3D CSM in the case of chronic false aneurysms of the isthlus in pigs. This step allowed the characterization of 3D CSM and the development of an experimental model in pigs, which allows to consider cell therapy in this model. More genrally, this work contributes to a better understanding of CSM biology and to an improvement of the approaches used in cell therapy and regenerative medicine
Choudhury, Nusrat Zabeen. "Characterization of healthy and diseased human ascending aorta tissue." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=83857.
Full textEriksen, H. (Heidi). "Carboxyterminal telopeptide structures of type I collagen in various human tissues." Doctoral thesis, University of Oulu, 2010. http://urn.fi/urn:isbn:9789514262449.
Full textSabia, Paulo Henrique Brossi. "Projeto e construção de um equipamento biaxial para a caracterização mecânica de tecidos biológicos tubulares." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/3/3152/tde-16112015-154649/.
Full textThe evolution of Medicine has enabled humans to live longer. With that, the incidence of abdominal aortic aneurysms (AAAs) has grown, especially among males. The lack of detailed knowledge on the mechanical behavior of the abdominal aortic tissue is the main bottleneck in the improvement of the criterion for recommending corrective surgery. Therefore, many patients still die from the rupture of those aneurysms. Better understanding of the tissues mechanical behavior will allow the refinement of todays criterion, thus saving more lives. This understanding can be obtained from Continuum Mechanics, using mechanical test experimental data to evaluate and describe the behavior of the material. The data has to come from tests performed in two independet axes. This Masters thesis presents the project, manufacturing and calibration of an apparatus for the test of cylindrical biological tissues in two directions, longitudinal and circumferential. Aspects of pre-existent tests and methods and their positive and negative sides were taken into account. The specimens will come from cadavers, and it will be possible to pre-condition them, as well as to test them to the rupture. Latex tubes were used in the calibration of the apparatus, whose utilization is expected to improve the knowledge on AAA rupture probability, as well as to improve the comprehension of the penile urethral tissues behavior.
Syvannarath, Varouna. "Rôle du CD31 dans l'issu des lésions tissulaires cardiovasculaire aigues." Thesis, Sorbonne Paris Cité, 2019. https://theses.md.univ-paris-diderot.fr/SYVANNARATH_Varouna_va2.pdf.
Full textCD31 also called PECAM-1 (Platelet Endothelial Cell Adhesion Molecule-1) is a 130-kDa single pass transmembrane glycoprotein composed of 6 extracellular Ig-like domains and a cytoplasmic tail with two ITIMs motifs (Immunoreceptor Tyrosine based Inhibitory Motifs). The CD31 trans-homophilic receptor is exclusively and constitutively expressed by endothelial cells, platelets and all leukocytes and play a crucial role in cells regulation at blood-vessel interface.Upon sequential phosphorylation, the two ITIMs of CD31 promote phosphatase-dependent pathway while tyrosine/inositol-dependent pathway is uncoupled. Thus, activator or inhibitor CD31 effect depends on cell type. CD31 engagement drives mutual cell-cell detachment signals and raises the activation threshold of CD31+ cells, globally acting as a negative co-signaling receptor on platelet and leukocytes. The case is different for the endothelial cells, which adhere on their basal membrane and establish permanent CD31-CD31 interactions at their lateral borders. Indeed, the permanent trans-homophilic interaction of CD31 molecules engaged at the cell-cell junctions of the adherent endothelial cells and their basal serine phosphorylation may account for the prevalent positive effect on endothelial cell survival and physiologic functions. Regulation of endothelial, platelet and leukocyte interactions by CD31 may be particularly important during biological responses that develop following cardiovascular injury.To evaluate this hypothesis, I studied during my thesis the role of CD31 in the outcome of aortic dissection and myocardial ischemia reperfusion, two clinical conditions related to acute and high life-threatening lesions not only immediately but also in the long term, if tissue remodeling is not appropriate. My work has shown that the function of CD31 is important in the outcome of acute cardiovascular lesions: it promotes the return to homeostasis in the microcirculation to ensure perfusion of the injured tissue but it also actively contributes to the tissue repair, in particular favoring the acquisition of a repair phenotype by the leucocytes infiltrated at the lesion sites. In the case of aortic dissection, our results show that the function of CD31 is crucial to allow rapid resorption of the hematoma and the formation of a collagen-rich scar in the arterial lesion thus preventing aneurysmal evolution and the risk of rupture of the aorta. In the case of myocardial infarction, the effectiveness of recanalization procedures depends on the restoration of microvascular circulation. Indeed, the survival of each heart muscle fiber will depend on its own capillary. In CD31 KO mice, we found that the response of platelets, leukocytes, and endothelium within the microcirculation in the infarct area is inappropriate. Thus, in the absence of CD31, dysfunction of the blood cells interacting with the endothelium in microcirculation prevents tissus reperfusion. This phenomenon, also known as "no-reflow", corresponds to an absence of microvascular reperfusion despite the re-opening of the occluded artery and results in an enlargement of necrosis zone.Thus, the regulatory functions of CD31 seem to play a particularly determining role in the outcome of acute lesions of the cardiovascular system, where hemodynamic stresses make the tissue repair even more difficult and urgent
Scott-Emuakpor, D. "Human aorta tissue matrix constituents : Changes with age and in disease." Thesis, Lancaster University, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355489.
Full textSpear, Rafaëlle. "Analyse transcriptomique des cellules vasculaires isolées du tissu anévrysmal de l'aorte abdominale sous-rénale chez l'homme." Thesis, Lille 2, 2014. http://www.theses.fr/2014LIL2S050/document.
Full textAbdominal aortic aneurysm (AAA) is a public health problem, which mainly affects men older than 65 year. AAA are usually asymptomatic with a natural evolution towards rupture associated with a high mortality rate. Among non coding ribonucleic acids (RNAs), microRNAs are stable in tissue and biofluids and are interesting candidates for the search of biomarkers. Inflammation, extracellular matrix (ECM) degradation and media rarefaction are involved in AAA. Many inflammatory cells are involved in AAA. Anoikis is an apoptosis secondary to a cell detachment from ECM and is responsible for rarefaction of smooth muscle cells (SMC). Differential proteomic analysis of cultured SMC from AAA patients was performed in the laboratory and highlighted the overexpression of a disintegrin and metalloproteinase with thrombospondin motif of type 5 (ADAMTS 5) in SMC of AAA patients. Isolation of cells with laser microdissection allows to keep their phenotype and to find potential markers that may be masked by global tissue analysis.The aim of my PhD work was to perform a global miRNA screening of cells isolated from human aneurysmal wall and an analysis targeted on ADAMTS 5, a metalloprotease with an enzymatic activity on ECM proteins. The main objectives were a better understanding of AAA and the identification of new biomarkers.The distribution of cells in the aneurysmal wall was studied by immunohistochemistry in human aneurysmal and healthy aortic samples. Once located, the cells were isolated by laser microdissection and screened for miRNAs by microarrays. Differential expression of selected miRNAs was quantified by PCR in the cells isolated by laser microdissection and in whole aortas. They were then compared in plasma of AAA patients and atherosclerotic patients without AAA by quantitative PCR to identify potential biomarkers.In AAA, the M1 proinflammatory macrophages were located in the adventitia and the M2 antiinflammatory macrophages in the intraluminal thrombus; the type B lymphocytes were organized in tertiary lymphoid organs (ATLOs) in 11/20 of analysed samples. SMC were rare and restricted to the media. Among the 850 miRNAs tested on microarray, 205 miRNAs were detected in isolated cells. MiR-29b and let-7f were upregulated in plasma of AAA patients, and thus are potential biomarkers.The expression of ADAMTS 5 in aneurysmal SMC was evaluated by immunohistochemistry of healthy and aneurysmal aortic wall and quantified by Western blot in isolated SMC from healthy and aneurysmal wall.Two aneurysmal SMC morphotypes were identified: a rounded morphotype positive for caspase 3, an apoptotic marker, and a spindle-shaped morphotype similar to the healthy aortic SMC. The expression profile of ADAMTS 5 subunits was different in rounded SMC compared to aneurysmal and healthy spindle-shaped SMC. In vitro induction of apoptosis of SMC was established in order to study the mechanisms involved in ADAMTS 5 expression in AAA and their consequences on enzymatic actions.The global transcriptomic screening of aneurysmal cells isolated by laser microdissection has identified potential markers of AAA, miR-29b and let-7f. The targeted analysis suggested that ADAMTS 5 is involved in the evolution profile of SMC towards anoikis in AAA. Further investigations will allow a better understanding of AAA pathophysiology
Chung, Timothy Kwang-Joon. "Study of multi-axial failure properties of planar biological soft tissues." Diss., University of Iowa, 2017. https://ir.uiowa.edu/etd/5732.
Full textThomas, Vineet Sunny. "A Comparative Study for the Effect of Tissure Anisotropy on the Behavior of a Single Cardiac Pressure Cycle for a Symmetric Tri-Leaflet Valve." University of Akron / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=akron1284703306.
Full textLaville, Colin. "Caractérisation mécanique et modélisation numérique des tissus de valve aortique." Thesis, Paris Sciences et Lettres (ComUE), 2017. http://www.theses.fr/2017PSLEM069/document.
Full textThis PhD thesis aims to develop experimental and numerical tools for the mechanical characterization and the numerical modeling of natural or artificial aortic valve tissues. These tools are intended to be used for the development of new biomimetic polymeric implants. Nowadays, almost 300 000 prosthetic valves are implanted every year worldwide. Two families of prosthetic valves are currently available~: mechanical and biological prostheses. However, both solutions suffer from major drawbacks. In this context, polymeric prostheses represent a promising alternative but currently suffer from insufficient material properties to be suitable for a long--lasting implantation. In this work, an experimental protocol using biaxial tensile tests together with full--field surface measurement and confocal microscopy is proposed. Since numerical simulation is intended to assist the design phase of new implants by predicting their mechanical behavior, a structure and a fluid solver are developed and coupled. Using experimental results, implemented constitutive models are calibrated through an inverse analysis procedure
BARISEEL, HERVE. "Devenir tardif des protheses polyesters tissees en position aortique : recul de 76,2 mois." Nice, 1994. http://www.theses.fr/1994NICE6558.
Full textNeves, Karla Bianca. "Efeito da adipocina chemerin sobre a reatividade vascular: análise em aortas de rato." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/60/60138/tde-27092012-094715/.
Full textAlthough hypertrophy and hyperplasia of adipocytes as well as increased synthesis and release of adipokines are commonly observed in obesity, a condition associated with insulin resistance and endothelial dysfunction, it is extremely important to understand the biological effects of adipokines, or more specifically of the adipokine chemerin, in non-pathological conditions,. The mechanisms by which cytokines released by the adipose tissue may interfere with vascular function are not yet fully understood. Furthermore, the effects of the cytokine/adipokine chemerin on vascular function are not known. Considering that the chemerin receptor is expressed by vascular smooth muscle and endothelial cells, this study investigated the effects produced by this cytokine in vascular reactivity, as well as the mechanisms by which it modifies vascular function in non-obese animals. Our working hypothesis is that chemerin enhances vascular reactivity to constrictor stimuli, such as endothelin-1(ET-1) and phenylephrine (Phe), and decreases the vasodilation induced by acetylcholine (ACh) and sodium nitroprussiate (SNP). Our specific aims were to determine: 1) whether chemerin induces changes in vascular reactivity, 2) if the alterations of vascular reactivity induced by chemerin are mediated by changes in the function of endothelial cells or vascular smooth muscle cells, 3) which signaling pathways (focus on the MAPKs pathway) are being modified by chemerin and how they contribute to changes in vascular reactivity produced by this cytokine. Our study showed that the adipokine chemerin has biological and cellular activity in aortas from non-obese rats. Chemerin increased vascular responses to contractile stimuli (ET-1 and PhE), producing effects both in the endothelial and vascular smooth muscle cells. The increased contractile responses to ET-1 and PhE were mediated via activation of MEK-ERK1/2, COX-1 and COX-2 and increased expression of the ETA and ETB receptors. Furthermore, this adipokine reduced the vasodilation induced by ACh via eNOS uncoupling and oxidative stress, and by SNP, via effects in the enzyme guanylate cyclase. Our studies may contribute to a better understanding of the role of factors released by the visceral adipose tissue on vascular function and, consequently, on the vascular lesions in obesity and obesity-associated diseases.
Little, Marie-Térèse E. "The ontogeny of acyl coenzyme A: cholesterol acyltransferase in rat liver, intestine, adipose tissue, and aorta." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/29416.
Full textMedicine, Faculty of
Medicine, Department of
Experimental Medicine, Division of
Graduate
Radomychelski, I., Анатолій Миколайович Романюк, Анатолий Николаевич Романюк, Anatolii Mykolaiovych Romaniuk, Артем Михайлович Піддубний, Артем Михайлович Поддубный, Artem Mykhailovych Piddubnyi, et al. "Investigation of the presence of neutrophils and macrophages in the tissues of calcified aorta affected by atherosclerosis." Thesis, Springer, 2020. https://essuir.sumdu.edu.ua/handle/123456789/81352.
Full textWalker, Rachel. "Perivascular adipose tissue and vascular function : the influence of nitric oxide, ageing and atherosclerosis." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/perivascular-adipose-tissue-and-vascular-function-the-influence-of-nitric-oxide-ageing-and-atherosclerosis(ea89f957-1a84-423a-b99b-5b180ea6874d).html.
Full textLa, Joie Elaine Naomi. "Tissue welding : studies of pulsed diode laser interaction with ICG stained porcine aorta and elastin-based biomaterial /." Full text open access at:, 1995. http://content.ohsu.edu/u?/etd,249.
Full textVieira-Damiani, Gislaine 1976. "Análise computacional de fibras elásticas e colágenas da aorta humana." [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/310249.
Full textTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas
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Resumo: A hipertensão arterial sistêmica (HAS) bem como o envelhecimento provoca mudanças na estrutura dos grandes vasos sanguíneos - aorta e seus ramos - propiciando o desenvolvimento de processos degenerativos que são a causa de diversas doenças. O uso de ferramentas fotônicas na aquisição de imagens, associado a recursos matemáticos para a interpretação delas representa um avanço para as análises histopatológicas, pois permitem a visualização e compreensão de pequenas estruturas que antes eram impossíveis de serem observadas. O objetivo desse trabalho foi associar estas duas tecnologias (ferramentas fotônicas e recursos matemáticos) e com isso criar uma metodologia para a análise simultânea de fibras elásticas e colágenas na aorta. Para tanto utilizamos aorta ascendente de 72 pacientes, sendo 22 normotensos, 38 portadores de HAS e 12 aortas de dissecção. As lâminas coradas com hematoxilina eosina foram examinadas no microscópio multifoton, com dois fótons: laser de argônio para fluorescência da eosina, corante de fibras elásticas e Ti:safira para SHG, sinal gerado por moléculas de colágeno. A distribuição e organização das fibras elásticas e colágenas foram analisadas pelas seguintes variáveis: morfometria geométrica, derivadas da matriz de co-ocorrência de Haralick, Transformada de Fourier e fluorescência ótica integrada. Usando estes descritores da textura associados a fractais, observamos que a geração do SHG é dependente não só da presença do colágeno como também do arranjo destas fibras. Observamos ainda que em indivíduos normotensos, quando comparados aos portadores de HAS, ocorre uma diminuição na distribuição do sinal SHG ao longo da espessura da camada média partindo da íntima em sentido à adventícia. Dessa maneira concluímos que os maiores distúrbios das fibras elásticas, nos indivíduos normais ocorrem na transição do terço interno para o médio, enquanto que nos portadores de HAS eles estão distribuídos em toda a espessura da aorta. Além disso, estes estudos nos permitiram verificar que a dissecção da aorta ocorre entre dois reforços de colágeno, uma vez que este fenômeno foi constatado entre dois picos de SHG
Abstract: The arterial hypertension as well as aging induces changes in the structure of large blood vessels - aorta and its branches - leading to development of degenerative processes which are the cause of many diseases. The use of photonics tools for image acquisition, associated to mathematical resources for interpretation of them represents an advance in histopathological analysis, because it allows the visualization and understanding of small structures that were impossible to be observed before. The main objective of this study was to associate both technologies (photonics tool and mathematical resources) to create a new methodology to evaluate, simultaneously, elastic and collagen fibers in aorta. For this we've used autopsies of ascending aortas from 72 patients, being 22 samples from normotensives individuals, 38 from HAS patients and 12 aortas from dissection. HE-stained paraffin sections from ascending aortas were analyzed by multifoton microscopy, with 2 types of photons: Two-photon excited fluorescence (TPEF) for elastin and Ti:safira for SHG to analyze collagen fibers. The distribution and organization of elastic and collagen fibers were analyzed by the following variables: geometric morphometric, derived from the co-occurrence matrix of Haralick, Fourier Transform and Fluorescence optics integrated. Using these texture descriptors associated to analysis of fractals, we've observed that SHG generation is not only dependent on the presence of collagen but on the arrangement of these fibers as well. We also observed that in normotensives individuals, if compared to HAS patients, occurs a decrease in the SHG intensity along the medial thickness from intimate in direction to adventitia. Thus we conclude that the major disorders of elastic fibers in normal subjects occur in the transition from the third layer to the middle, while in HAS individuals these disorders are distributed throughout the thickness of the aorta. Furthermore, this study has allowed us to verify that the aortic dissection has occurred between two peaks of SHG, since this phenomenon was observed between two ribs collagen
Doutorado
Biologia Estrutural, Celular, Molecular e do Desenvolvimento
Doutora em Fisiopatologia Médica
Loubser, Dirk Jacobus. "Nitric oxide and the endothelium : characterisation of in vitro nitric oxide detection techniques and an ex vivo method of measuring endothelial function." Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/86496.
Full textENGLISH ABSTRACT: Introduction: Nitric oxide (NO) is an important chemical messenger in the cardiovascular system. Despite considerable progress in this field, there remains an on-going need for affordable and user-friendly NO measurement techniques. Therefore, in this study we aimed to develop and characterise NO-detection techniques not previously used in our laboratory, and, in addition, characterise an ex vivo method to measure the functional effects of the endothelium and NO production in the vasculature. Methods: Three different NO-detection techniques were compared: (i) Amperometric NO sensors. Here, NO-increasing effects of known NO synthase (NOS) activators were investigated (insulin, acetylcholine and biosynthetic human insulin). Three different NO sensors were evaluated on cultured endothelial cells and aortic tissue. Putative NOincreasing effects of shear stress were also investigated; (ii) Nitrite (NO2 -) + nitrate (NO3 -) sensors. Here, I aimed to measure NO release from cultured endothelial cells; (iii) Colorimetric NO2 - measurement assay with the Griess reagent. Here, NO2 - production by endothelial cells was measured with a plate reader. In the second part of the study an organ bath - isometric tension technique was established to measure endothelium-dependent function of aortic rings. Functional differences in aortic rings isolated from diet-induced obese rats compared to lean rats were investigated. Ring contraction was induced with phenylephrine and relaxation with acetylcholine. These investigations were further supported by western blot analyses of selected critical proteins. Lastly, the effects of perivascular adipose tissue (PVAT) on contraction and relaxation were investigated in endothelium-containing or denuded aortic ring segments. Results: Although some success was achieved with the amperometric sensors regarding calibration, any experimental results obtained were difficult to repeat due to instability of the sensors. With the NO2 -/NO3 - sensor we were not able to carry out any planned experiments due to failure to properly calibrate and standardise the sensors. Success was achieved with the Griess method. All the drugs used as positive controls (DEA/NO, fenofibrate, oleanolic acid and IL-1ß) proved to be potent inducers of NO2 - release from endothelial cells. Interestingly, the isometric tension studies showed a higher % relaxation in high fat (HF) diet aortic rings compared to those from lean animals. Western blot data showed downregulation of eNOS activation and iNOS expression in obese groups, which was suggestive of endothelial dysfunction. Interestingly, proteins associated with oxidative stress (p22phox and nitrotyrosine) were downregulated in obese groups. The presence of PVAT exerted anti-contractile effects on the rings from HF rats, however in denuded aortic rings, PVAT showed a significant pro-contractile response in both lean and HF groups. PVAT also exerted anti-relaxation effects in aortic rings from both lean and HF rats. Conclusion: We managed to successfully establish two new techniques for our laboratory (Griess method and the organ bath – isometric tension method) which can complement the more established techniques in our laboratory in order to aid us in future vascular research. Finally, the isometric tension technique used in the obese rat studies generated interesting data, which further assisted in characterising the dietinduced obesity rat model in our laboratory.
AFRIKAANSE OPSOMMING: Inleiding: Stikstofoksied (NO) is ‘n belangrike chemiese boodskapper in die kardiovaskulêre sisteem. Ondanks vordering in die veld, bestaan daar ‘n aangaande behoefte aan bekostigbare en gebruikersvriendelike NO-metingstegnieke. Gevolglik het ons in hierdie studie daarna gemik om NO-metingstegnieke wat nie vantevore in ons laboratorium beskikbaar was nie, te ontwikkel en karakteriseer. Verder het ons ten doel gehad om ‘n ex vivo model te karakteriseer om die funksionele effekte van vaskulêre endoteel en NO produksie te meet. Metodes: Drie verskillende NO-metingstegnieke was ondersoek: (i) Amperometriese NO sensors. Hier het ons die verhogende effekte op NO van bekende aktiveerders van NO sintetase (NOS) ondersoek (Insulien, asetielcholien en biosintetiese menslike insulien). Drie verskillende NO-sensors was ge-evalueer in gekultuurde endoteelselle en aortaweefsel. Die vermeende NO verhogende effekte van die wrywingskragte opgewek deur laminere vloei (“shear stress”) is ook ondersoek. (ii) Nitriet (NO2 -) + nitraat (NO3 -) sensors. Hier het ons beplan om NO-vrystelling deur gekultuurde endoteelselle te meet. (iii) Kolorimetriese meting van NO2 - met die Griess reagens. Hier het ons m.b.v. ‘n mikroplaat leser die NO2 - - vrystelling deur endoteelselle gemeet. In die tweede deel van die studie het ons ‘n orgaan bad–isometriese spanningstegniek opgestel om endoteelafhanklike funksie van aortaringe te meet. Funksionele verskille in aortaringe van vetsugtige rotte is vergelyk met kontrole rotte. Ringkontraksie is met fenielefrien geïnduseer en verslapping met asetielcholien. Hierdie ondersoeke is verder ondersteun deur Western blot analises van sleutelproteïene in die aortaweefsel. Laastens het ons die effekte van perivaskulêre vetweefsel (PVAT) op kontraksie en verslapping in aortaringe met of sonder intakte endoteel ondersoek. Resultate: Alhoewel ‘n mate van sukses behaal was met die kalibrasie van die amperometriese sensors, was eksperimentele resultate moeilik om te herhaal a.g.v. sensor-onstabiliteit. Geen eksperimente kon met die NO2 -/NO3 - sensors uitgevoer word nie weens ‘n onvermoë om ordentlike kalibrasie en standardisering uit te voer. Ons het egter wel sukses behaal met die Griess-metode. Al die middels wat as positiewe kontroles gebruik was (DEA/NO, fenofibraat, oleanoliese suur and IL-1ß) het geblyk kragtige induseerders van NO2 - produksie vanaf endoteelselle te wees. Die isometriese spanningsstudies het ‘n hoer % verslapping getoon in die hoë vet (HF) dieet aortaringe in vergelyking met die kontroles. Western blot data het ‘n afregulering van eNOS en iNOS getoon in die HF diere, wat aanduidend is van endoteel disfunksie, terwyl proteïene geassosieer met oksidatiewe stress (p22phox en nitrotirosien) afgereguleer was in die HF groep. Die aanwesigheid van PVAT het ‘n anti-kontraktiele effek gehad op die ringe van die HF groep. Toe die endoteel egter verwyder was, het PVAT in beide kontrole en HF ringe ‘n beduidende pro-kontraktiele effek gehad. Verder het PVAT ook anti-verslappingseffekte op aortaringe beide kontrole en HF rotte uitgeoefen. Gevolgtrekking: Ons het daarin geslaag om twee nuwe tegnieke vir ons laboratorium suksesvol te vestig (Griess metode en die orgaanbad-isometriese spanningstegniek) wat in die toekoms die meer gevestigde tegnieke in ons laboratorium kan komplementeer. Laastens het die isometriese spanningstegniek wat in die dieetstudies gebruik is, data opgelewer wat ons verder sal help om die vetsug model in ons laboratorium te karakteriseer.
Constantinidès-Mégret, Colette. "Etude de la structure physique de l'elastine par spectroscopies thermostimulees (aed, cts)." Toulouse 3, 1988. http://www.theses.fr/1988TOU30128.
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