Dissertations / Theses on the topic 'Active tissue'
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Huang, Boyang. "Electro-active scaffolds for bone tissue engineering." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/electroactive-scaffolds-for-bone-tissue-engineering(e4374a7f-47fe-418f-a515-fe5a37668aa8).html.
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Bone is a highly hierarchical tissue which is able to heal and remodel in case of small defects and damage. For critical-size defects, the most commonly used approach requires the use of synthetic grafts. These grafts, also known as scaffolds, are physical substrates designed for cell attachment, proliferation and differentiation. Scaffolds for bone applications must be biocompatible, biodegradable, and highly porous, presenting mechanical properties similar to bone and surface characteristics that promote cell-scaffold interactions. The final properties of a scaffold strongly depend on both material compositions and process conditions. This research project investigates different aspects related to the design fabrication and characterization of bioactive electro-active scaffolds. Scaffolds were produced using an extrusion-based additive manufacturing system and different material compositions based on Poly (ε-caprolactone) (PCL) mixed with hydroxyapatite (HA), β-tri-calcium phosphate (TCP) and multi-wall carbon nanotubes (MWCNTs) were investigated. HA and TCP are biocompatible and degradable ceramics related to improve the bioactivity of the scaffolds and MWCNTs were selected to improve mechanical properties and due to their excellent electrical conductivity characteristics, to promote both cell-cell and cell-substrate communication. Experimental work was conducted to characterize both pre-processed materials and produced scaffolds evaluating the rheological, mechanical, thermal, chemical and biological properties. Rheological tests show that printability strongly depends on the concentration of the inorganic fillers (MWCNTs, HA and TCP) and processing parameters such as temperature, screw rotational velocity and deposition velocity. The addition of MWCNTs, HA and TCP can enhance the compressive modulus of PCL scaffolds from 48 MPa to 75 MPa in the case of PCL/HA, or 88 MPa in the case of PCL/TCP and PCL/MWCNTs. Biological results show that all scaffolds containing MWCNTs, HA and TCP are biocompatible (more than 80% cell viability), bioactive (40% increase for TCP, 60% increase for HA and 86% increase for MWCNTs) and osteoconductive (significant increase of ALP activity). Results also show that the addition of MWCNTs improves the osteoinductive properties and the presence of nano-sized HA improves the mineralization process. This research shows that PCL/HA/MWCNTs can be viable scaffolds for bone tissue engineering, providing a promising way for bone tissue regeneration.
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Bowyer, Stuart. "Active constraints for robotic surgery in deforming tissue." Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/51553.
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Active constraints are collaborative human-robot control algorithms which have a well-established history of use within robot assisted surgery research. This control strategy anisotropically regulates the motion of a human user in such a way that it effectively combines the competencies of surgeons and robots, allowing for improved clinical outcomes and surgeon experience. The significant majority of research previously presented for active constraints focuses on their application to static procedures, where the surgical environment is assumed to be rigid throughout. In this thesis, several research contributions are presented which assist with applying active constraints in surgical procedures within deforming soft tissue. The primary contribution is the formulation of a novel haptic control algorithm, based on friction, which can effectively guide a surgeon in both positioning and orienting a surgical instrument, while guaranteeing that the haptic interaction is energetically dissipative. The proven dissipative formulation of these 'dynamic frictional constraints' ensures that the surgeon always has overall control of a procedure and makes the system resilient to limitations and errors in the robot's comprehension of the surgical environment. To apply active constraints within deforming tissue, it is necessary to compute the geometric relationship between the surgical instruments and the constrained anatomy. A novel bounding volume is proposed which, when used in a hierarchy, exploits the limits of soft tissue deformations to increase the resolution of constraint geometries that can be used at stable control rates. The experimental validation of these research contributions in a clinically realistic nerve dissection simulation and in non-clinical dynamic path-following tasks, shows significant benefits to the user in several metrics characterising surgical accuracy and precision. These results demonstrate that the proposed enhancements of active constraints could lead to increased surgeon performance, fewer complications and improved clinical outcomes in soft tissue surgical procedures.
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Andersson, Jonas. "Adipose tissue as an active organ : blood flow regulation and tissue-specific glucocorticoid metabolism." Doctoral thesis, Umeå universitet, Medicin, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-48415.
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Background: Despite advances in the treatment of atherosclerosis, cardiovascular disease is the leading cause of death worldwide. With the population getting older and more obese, the burden of cardiovascular disease may further increase. Premenopausal women are relatively protected against cardiovascular disease compared to men, but the reasons for this sex difference are partly unknown. Redistribution of body fat from peripheral to central depots may be a contributing factor. Central fat is associated with hyperlipidemia, hyperglycemia, hypertension, and insulin resistance. Two possible mediators of these metabolic disturbances are tissue-specific production of the stress hormone cortisol and adipose tissue blood flow (ATBF). The aim of this thesis was to determine the adipose tissue production of cortisol by the enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) and to investigate the regulation of ATBF. Materials and Methods: Cortisol release was estimated by labeled cortisol infusions and tissue-specific catheterizations of subcutaneous and visceral adipose tissue (VAT) in men. We investigated ATBF by 133Xe-washout and its relation to autonomic activity, endothelial function, adipose tissue distribution, and adipokines in different groups of women. We further investigated the effect of two diets and of weight loss on ATBF in women. Results: We demonstrated significant cortisol release from subcutaneous adipose tissue in humans. Splanchnic cortisol release was accounted for entirely by the liver. Cortisol release from VAT (to the portal vein) was not detected. ATBF decreased according to increasing weight and postmenopausal status, and the level of blood flow was associated with nitric oxide (NO) activity and autonomic activity. ATBF was also highly associated with leptin levels and both subcutaneous adipose tissue and VAT areas. After 6 months of diet and weight reduction, a significant difference in ATBF was observed between diet groups. Conclusions: Our data for the first time demonstrate the contributions of cortisol generated from subcutaneous adipose tissue, visceral tissues, and liver by 11β-HSD1. ATBF is linked to autonomic activity, NO activity, and the amount of adipose tissue (independent of fat depot). Postmenopausal overweight women exhibited a loss of ATBF flexibility, which may contribute to the metabolic dysfunction seen in this group. Weight loss in a diet program could not increase the ATBF, although there were ATBF differences between diet groups. The results will increase understanding of adipose tissue biology and contribute to the development of treatment strategies targeting obesity and obesity-related disorders.
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Kamper, Marina. "Active contraction of the left ventricle with cardiac tissue modelled as a micromorphic medium." Master's thesis, Faculty of Engineering and the Built Environment, 2019. http://hdl.handle.net/11427/31132.
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The myocardium is composed of interconnected cardiac fibres which are responsible for contraction of the heart chambers. There are several challenges related to computational modelling of cardiac muscle tissue. This is due in part to the anisotropic, non-linear and time-dependent behaviour as well as the complex hierarchical material structure of biological tissues. In general, cardiac tissue is treated as a non-linear elastic and incompressible material. Most computational studies employ the theories of classical continuum mechanics to model the passive response of the myocardium and typically assume the myocardium to be either a transversely isotropic material or an orthotropic material. In this study, instead of a classical continuum formulation, we utilise a micromorphic continuum description for cardiac tissue. The use of a micromorphic model is motivated by the complex microstructure and deformations experienced by cardiac fibres during a heartbeat. The micromorphic theory may be viewed as an extension of the classical continuum theory. Within a micromorphic continuum, continuum particles are endowed with extra degrees of freedom by attaching additional vectors, referred to as directors, to the particles. In this study the directors are chosen such that they represent the deformation experienced by the cardiac fibres. In addition to the passive stresses, the myocardium experiences active stresses as a result of the active tension generated by cardiac fibres. The active tension in the heart is taken to be a function of the sarcomere length, intracellular calcium concentration and the time after the onset of contraction. Experimental studies show that the active behaviour of the myocardium is highly dependent on the tissue arrangement in the heart wall. With a classical continuum description, the sarcomere length is usually defined as a function of the stretch in the initial fibre direction. To allow for a more realistic description of the active behaviour, we define the sarcomere orientation, and consequently also the sarcomere stretch, as a function of the director field. Furthermore, we use the director field to describe the direction in which contraction takes place. The intent of this study is to use a micromorphic continuum formulation and an active-stress model to investigate the behaviour of the left ventricular myocardium during a heartbeat. The simulated results presented here correspond well with typical ventricular mechanics observed in clinical experiments. This work demonstrates the potential of a micromorphic formulation for analysing and better understanding ventricular mechanics.
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Behbahani, Homira. "Immune dysregulation in HIV-1 infected lymphoid tissue /." Stockholm, 2002. http://diss.kib.ki.se/2002/91-7349-193-4.
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Booth, Andrew. "Controlled release of active compounds from a magnetic nanoparticle-vesicle aggregate nanomaterial." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/controlled-release-of-active-compounds-from-a-magnetic-nanoparticlevesicle-aggregate-nanomaterial(5c87df99-8ab3-4965-bdc2-081333be1ef9).html.
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Non-invasive and controlled release of bioactive compounds is an important goal in the development of drug delivery systems and novel biomaterials for tissue engineering. This project aims to exert spatio-temporal control over the release of bioactive compounds from phospholipid vesicle carriers by crosslinking them with superparamagnetic iron oxide nanoparticles to form a magnetic release nanostructure. The magnetic properties of the nanoparticles allow release to be triggered by an alternating magnetic field (AMF), which induces localised heating and “melts” the vesicle membranes. The aggregates can also be manipulated in space by a static magnetic field to create patterned materials. Incorporation of these aggregates into hydrogels has created novel responsive biomaterials. Controlled release of ascorbic acid-2-phosphate has been used to induce collagen production by chondrocytes, demonstrating an AMF triggered cellular response in vitro. The existing system has been redesigned after detailed characterisation and assessment of the performance of each component. Magnetic release has been extensively assessed using fluorescence techniques to quantify release, and optimised through the development of new silica-derived nanoparticle coatings and aggregate formulations informed by quantitative characterisation of nanoparticle functionalisation. The replacement of calcium alginate hydrogels as a 3D cell culture matrix with hyaluronic acid- based hydrogels was found to eliminate gel-induced leakage of vesicle contents and also improves the compatibility of the system with a greater range of cell types. Recently the effective encapsulation and AMF-triggered release of proteins including enzymes has been demonstrated and released enzymes have been demonstrated to retain their activity. Released trypsin was shown to retain proteolytic activity while hyaluronidase released into hyaluronan-derived hydrogels has been demonstrated to influence the rheological properties of the gel. A galactose-terminated lipid has been synthesised that enables specific targeting of the asialoglycoprotein (ASGPR) cell surface receptor receptor found in human hepatocytes, demonstrating the potential for customisation of the MNPV system to particular requirements.
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Degache, Amelie. "Electrical impedance spectroscopy applied to the chronic monitoring of the fibrosis induced by cardiac active implants." Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0432.
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Les arythmies cardiaques représentent environ 50% des maladies cardiovasculaires qui sont la première cause de mortalité dans le monde. Les implants médicaux jouent un rôle majeur dans le traitement de ces arythmies. En France c’est environ 250 000 patients qui sont équipés d’un implant cardiaque et qui nécessitent un suivi régulier. Ces implants utilisent les dernières technologies de micro-nano électronique et possèdent un boitier de stimulation qui est placé en sous-cutané, connecté aux électrodes via une sonde intraveineuse. Un des principaux points faibles de tout implant réside dans l’interface électrode-tissu, en raison d’une réaction inflammatoire soutenue appelée la fibrose. Ce phénomène compromet la biocompatibilité de l’implant, encapsulant la sonde avec un tissu « isolant ». Cela crée des adhérences le long de la sonde et au niveau de l’électrode, ce qui entraine souvent une hausse des seuils de stimulation au cours du temps et une diminution des durées de vie des batteries. Cette réponse est connue et peut être minimisée lors de l’implantation grâce à des sondes à élution de stéroïdes mais la fibrose reste tout de même un obstacle pour les implants, justifiant notre intérêt d’étude sur le long terme de la biocompatibilité des implants cardiaques.La compréhension des mécanismes de la fibrose est primordiale pour ce travail. La fibrose est due à une activation et différentiation de certaines cellules cardiaques sous une contrainte mécanique, et le tissu cardiaque se retrouve modifié localement. Pour caractériser cette modification, on utilise la mesure d’impédance qui consiste à envoyer un courant électrique sinusoïdal I et recueillir la tension résultante U dans le tissu, l’impédance Z est le ratio U/I. en fonction de la fréquence de mesure, on peut explorer le tissu à une échelle microscopique ou macroscopique. Comme les patients sont déjà équipés de sondes cardiaques reliées à un circuit de stimulation qui peut aussi enregistrer l’activité cardiaque, l’idée principale de ce travail est d’examiner l’utilisation d’une mesure électrique qui pourrait caractériser l’encapsulation fibrotique de la sonde, avec pour objectif final d’embarquer cette méthode de caractérisation dans le circuit implanté. Cela nous amène à la problématique de ce projet : est-ce que la fibrose qui se développe autour des sondes cardiaques a une signature électrique ?Mon travail de thèse s’organise en trois axes. Deux axes expérimentaux sont conduits aux niveaux cellulaire et tissulaire. On envisage en plus un axe discutant la faisabilité de mesures d’impédance embarquées pour des conditions proches de l’in vivo. La partie tissulaire ou ex vivo présente la caractérisation de différentes natures de tissu, sain ou collagéneux, et a été développée à l’IHU LIRYC, sur des ventricules de cochons ou de brebis avec des sondes cardiaques implantées chez l’homme. Les spectres d’impédance obtenus sont analysés avec des modèles électriques connus et dont les paramètres sont extraits pour chaque type de tissus. Une analyse statistique montre que les deux natures de tissu sont caractérisées par des paramètres significativement différents. La partie cellulaire ou in vitro présente la caractérisation électrique, par mesure d’impédance, et biologique, par marquages immunocytochimiques, d’un modèle cellulaire de fibrose. Ce modèle est développé en cultivant des cellules cardiaques humaines, activées ou non par un facteur de croissance. Après une analyse statistique, les valeurs d’impédance des cultures activées montrent une différence significative par rapport aux cultures non activées, tandis que la caractérisation biologique montre une augmentation du nombre des cellules activées au cours du temps. Le dernier axe présente des résultats préliminaires sur de mesure d’impédance embarquée en vue d’une utilisation ultérieure in vivoCardiac arrhythmias represent about 50% of the cardiovascular diseases which are the first cause of mortality in the world. Implantable medical devices play a major role for treating these cardiac arrhythmias. In France, about 250.000 patients are equipped with an implanted device for arrhythmia treatment and need a regular monitoring. These devices use the latest technology of micro-nano-electronics and integrate a subcutaneous pulse generator connected to electrodes placed into the heart via intravenous leads. One of the main weaknesses of every implantable device lies in the electrode-tissue interface due to a sustained inflammatory response called fibrosis. This phenomenon jeopardizes the device biocompatibility, because it encapsulates the stimulation lead with an “insulating” tissue, creating adherences along the lead and often leading to an increase of the stimulation threshold over time and a larger electrical consumption. This response is well-known and minimized during the implantation surgery thanks the use of steroid-elution electrodes, however fibrosis still remains an impediment even for the most recent devices, enhancing the interest of studying long-term biocompatibility of cardiac implanted devices.The understanding of fibrosis mechanisms is essential for this work. It consists in some cardiac cells activation and differentiation under a mechanical stress, inducing fibrosis initiation and modifying locally the active cardiac tissue. To characterize this modification, we use electrical impedance measurements, consisting in sending a sinusoidal electrical current I and then measuring the resulting voltage U in the tissue; the impedance Z is the U/I ratio. Depending on the frequency of the measurement signal, we can explore the tissue from the microscopic to the macroscopic scales. As a patient is already equipped with cardiac leads connected to a stimulation device which can also record the cardiac electrical activity, the main idea of this work is to investigate the use of an electrical measurement that could characterize the fibrotic lead encapsulation, with the final objective to embed this characterization method in the implanted circuit. This brings us to the main question of our project: does the fibrosis developing around the cardiac leads have an electrical signature?My thesis work is organized along three axes. Two experimental axes are conducted at cellular and tissue levels, on in vitro or ex vivo models. In addition, an axis studying the feasibility of embedded impedance measurement for in vivo mimicking conditions is also discussed. The ex vivo part presents the characterization of tissue of different natures, healthy or collagenous, it was developed with the IHU LIRYC laboratory, on porcine or ovine cardiac tissue (ventricles mainly), with stimulation electrodes used on patients The impedance spectra are analyzed using a known electrical model from which characteristic parameters of the two tissue types are extracted. After statistical analysis, these parameters are found to be significantly different allowing us to distinguish both tissue types. The in vitro part presents the electrical characterization, using impedance measurements, in parallel to the biological characterization, using immunocytochemistry, of a cellular fibrosis model. It consists in culturing human cardiac cells, activated or not by a growth factor. After a statistical analysis, the impedance values show a significantly different signature for cultures with growth factor, with respect to sham cultures, while the biological characterization confirmed the presence of more activated and differentiated cells over time. The last axis gives preliminary results of embedded impedance measurements in custom circuits
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Izumi, Hideki. "Tissue factor pathway inhibitor-2 suppresses the production of active matrix metalloproteinase-2 and is down-regulated in cells harboring activated ras oncogenes." Kyoto University, 2001. http://hdl.handle.net/2433/151452.
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Abbott, Eric Justin. "Cutting trees with lasers : isolation of high quality RNA, enzymatically active protein and metabolites from individual tissue types of white spruce stems obtained using laser microdissection." Thesis, University of British Columbia, 2010. http://hdl.handle.net/2429/24249.
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Laser-assisted microdissection has been established for isolation of individual tissue types from herbaceous plants. However, there are few reports of cell- and tissue-specific analysis in woody perennials. While microdissected tissues are commonly analyzed for gene expression, reports of protein, enzyme activity and metabolite analysis are limited due in part to an inability to amplify these molecules. Conifer stem tissues are organized in a regular pattern with xylem, phloem and cortex development controlled by the activity of the cambial zone (CZ). Defense responses of conifer stems against insects and pathogens involve increased accumulation of terpenoids in cortical resin ducts (CRDs) and de novo formation of traumatic resin ducts from CZ initials. Woody plants are difficult to study at the level of individual tissues or cell-types and are thus good candidates for application of LMD. This thesis describes robust methods for isolation of individual tissue-types from white spruce (Picea glauca) stems for analysis of RNA, enzyme activity and metabolites. A tangential cryosectioning approach was important for obtaining large quantities of CRD and CZ tissues using LMD. Differential expression is reported for genes involved in terpenoid metabolism between CRD and CZ tissues and in response to treatment with methyl jasmonate (MeJA). Transcript levels of β-pinene synthase and levopimaradiene/abietadiene synthase were constitutively higher in CRDs, but induction was stronger in CZ in response to MeJA. 3-Carene synthase was more strongly induced in CRDs compared to CZ. A differential induction pattern was observed for 1-deoxyxyulose-5-phosphate synthase, which was up-regulated in CRDs and down-regulated in CZ. We identified terpene synthase enzyme activity in CZ protein extracts and terpenoid metabolites in both CRD and CZ tissues. Combined analysis of transcripts, proteins and metabolites of individual tissues will facilitate future characterization of complex processes of woody plant development, including periodic stem growth and dormancy, cell specialization, and defense and may be applied widely to other plant species.
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Ranft, Jonas M. "Mechanics of Growing Tissues: A Continuum Description Approach." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-105479.
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During development, higher organisms grow from a single fertilized egg cell to the adult animal. The many processes that lead to the eventual shape of the developed organism are subsumed as morphogenesis, which notably involves the growth of tissues by repeated rounds of cell division. Whereas coordinated tissue growth is a prerequisite for animal development, excessive cell division in adult animals is the key ingredient to cancer. In this thesis, we investigate the collective organization of cells by cell division and cell death. The multicellular dynamics of growing tissues is influenced by mechanical conditions and can give rise to cell rearrangements and movements. We develop a continuum description of tissue dynamics, which describes the stress distribution and the cell flow field on large scales. Cell division and apoptosis introduce stress sources that, in general, are anisotropic. By combining cell number balance with dynamic equations for the stress source, we show that the tissue effectively behaves as a viscoelastic fluid with a relaxation time set by the rates of division and apoptosis. If the tissue is confined in a fixed volume, it reaches a homeostatic state in which division and apoptosis balance. In this state, cells undergo a diffusive random motion driven by the stochasticity of division and apoptosis. We calculate the effective diffusion coefficient as a function of the tissue parameters and compare our results concerning both diffusion and viscosity to simulations of multicellular systems. Introducing a second material component that accounts for the extracellular fluid, we show that a finite permeability of the tissue gives rise to additional mechanical effects. In the limit of long times, the mechanical response of the tissue to external perturbations is confined to a region of which the size depends on the ratio of tissue viscosity and cell-fluid friction. The two-component description furthermore allows to clearly distinguish the different contributions to the isotropic part of the mechanical stress, i.e., the fluid pressure and the stress exerted by cells. Last but not least, we study the propagation of an interface between two different cell populations within a tissue driven by differences in the mechanical control of the rates of cell division and apoptosis. Combining simple analytical limits and numerical simulations, we distinguish two different modes of propagation of the more proliferative population: a diffusive regime in which relative fluxes dominate the expansion, and a propulsive regime in which the proliferation gives rise to dominating convective flowsDie Entwicklung höherer Organismen beginnt mit einer einzelnen befruchteten Eizelle und endet beim erwachsenen Tier. Die vielen Prozesse, die zur endgültigen Form des entwickelten Organismus führen, werden als Morphogenese zusammengefasst; diese umfasst insbesondere das Wachstum von Geweben durch wiederholte Zellteilungszyklen. Während koordiniertes Gewebewachstum eine Voraussetzung normaler Entwicklung ist, führt übermäßige, unkontrollierte Zellteilung letztlich zu Krebs. In dieser Arbeit untersuchen wir den Einfluss von Zellteilung und Zelltod auf die Organisation von Zellen in Geweben. Die Dynamik wachsender Gewebe wird durch mechanische Bedingungen beeinflusst, die u.a.~Anlass zu Zellbewegungen sein können. Wir entwickeln eine Kontinuumsbeschreibung der Gewebedynamik, die die mechanischen Spannungen und das Zellströmungsfeld auf großen Skalen beschreibt. Zellteilung und Apoptose wirken als Spannungsquellen, die in der Regel anisotrop sind. Indem wir die Erhaltungsgleichung für die Zellanzahldichte mit dynamischen Gleichungen für die Spannungsquellen kombinieren, zeigen wir, dass sich das Gewebe effektiv wie eine viskoelastische Flüssigkeit verhält, deren Relaxationszeit von Zellteilungs- und Apoptose-Raten abhängt. Wenn das Gewebe in einem gegebenen Volumen eingeschlossen ist, erreicht es einen homöostatischen Zustand, in dem Zellteilung und der Apoptose im Gleichgewicht sind. In diesem Zustand unterliegen die Zellen einer diffusiven Bewegung aufgrund der Stochastizität von Zellteilung und Apoptose. Wir berechnen den effektiven Diffusionskoeffizienten als Funktion der Gewebeparameter und vergleichen unsere Ergebnisse sowohl hinsichtlich der Diffusion und als auch der Viskosität mit numerischen Simulationen solcher vielzelliger Systeme. Die Berücksichtigung der extrazellulären Flüssigkeit als einer zweiten Materialkomponente erlaubt uns zu zeigen, dass eine endliche Permeabilität des Gewebes zusätzliche mechanische Effekte bedingt. Auf langer Zeitskalen bleibt die mechanische Reaktion des Gewebes auf externe Störungen auf einen Bereich beschränkt, dessen Größe vom Verhältnis der Gewebeviskosität zum Permeabilitätskoeffizienten abhängt. Die Zweikomponenten-Beschreibung erlaubt darüber hinaus eine klare Unterscheidung der verschiedenen Beiträge zum isotropen Teil der mechanischen Spannung, d.h., des hydrodynamischen und des von Zellen ausgeübten Drucks. Zuletzt untersuchen wir die Dynamik einer Grenzfläche zwischen zwei verschiedenen Zellpopulationen innerhalb eines Gewebes, die durch Unterschiede in der mechanischen Kontrolle der effektiven Zellteilungsraten angetrieben wird. Mithilfe der Kombination einfacher analytischer Grenzfälle und numerischer Simulationen zeigen wir, dass zwei unterschiedliche Ausbreitungsmodi unterschieden werden können: ein diffusives Regime, in dem relative Flüsse die Expansion der stärker wachsenden Zellpopulation dominieren, sowie ein Regime, in dem die Grenzfläche durch konvektive Strömungen angetrieben wird
Les organismes supérieurs se développent à partir d\'une seule cellule fécondée jusqu\'à l\'animal adulte. Les nombreux processus qui conduisent à la forme finale de l\'organisme sont connus sous le nom de morphogenèse, qui comprend notamment la croissance des tissus par des cycles répétés de division cellulaire. Alors que la croissance coordonnée des tissus est une condition nécessaire au développement des animaux, la division cellulaire excessive chez les animaux adultes est l\'ingrédient clé du cancer. Dans cette thèse, nous étudions l\'organisation collective des cellules par division et mort cellulaire. La dynamique multicellulaire des tissus en croissance est influencée par des conditions mécaniques et peut donner lieu à des réarrangements ainsi qu\'à des mouvements cellulaires. Nous élaborons une description continue de la dynamique des tissus qui décrit la distribution des contraintes et le champ d\'écoulement des cellules sur de grandes échelles. La division cellulaire et l\'apoptose introduisent des sources de contraintes qui, en général, sont anisotropes. En combinant l\'équation de conservation du nombre de cellules avec des équations dynamiques des sources de contraintes, nous montrons que le tissu se comporte de manière effective comme un fluide viscoélastique avec un temps de relaxation fixé par les taux de division et d\'apoptose. Si le tissu est confiné dans un volume donné, il atteint un état homéostatique dans lequel division et apoptose s\'équilibrent. Dans cet état, les cellules subissent un mouvement diffusif aléatoire dû à la stochasticité de la division et de l\'apoptose. Nous calculons le coefficient de diffusion effectif en fonction des paramètres du tissu et comparons nos résultats concernant à la fois la diffusion et la viscosité à des simulations numériques de tels systèmes multicellulaires. En introduisant un deuxième composant qui représente le liquide extracellulaire, nous montrons qu\'une perméabilité finie du tissu donne lieu à des effets mécaniques supplémentaires. Dans la limite des temps longs, la réponse mécanique du tissu à des perturbations extérieures est confinée à une région dont la taille dépend du rapport entre la viscosité tissulaire et le coefficient de frottement entre les cellules et le liquide extracellulaire. La description à deux composants permet en outre de distinguer clairement les différentes contributions à la partie isotrope de la contrainte mécanique, c\'est-à-dire la pression du fluide et la contrainte exercée par les cellules. Finalement, nous étudions la propagation d\'une interface entre deux populations de cellules différentes, due à des différences dans le contrôle mécanique des taux de division et de mort cellulaire. En combinant de simples limites analytiques et des simulations numériques, nous distinguons deux modes de propagation différents de la population cellulaire la plus proliférante : un régime diffusif dans lequel les flux relatifs dominent l\'expansion, et un régime de propulsion dans lequel la prolifération domine et entraine des flux convectifs
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Kankavi, Orhan. "Surfactant proteins in epithelial tissues emphasising skin /." [St. Lucia, Qld.], 2001. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16893.pdf.
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Mikulka, Jan. "Segmentační metody ve zpracování biomedicínských obrazů." Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2011. http://www.nusl.cz/ntk/nusl-233529.
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The PhD thesis deals with modern methods of image processing, especially image segmentation, classification and evaluation of parameters. It is focused primarily on processing medical images of soft tissues obtained by magnetic resonance tomography (MR) and microscopic images of tissues. It is easy to describe edges of the sought objects using of segmented images. The edges found can be useful for further processing of monitored object such as calculating the perimeter, surface and volume evaluation or even three-dimensional shape reconstruction. The proposed solutions can be used for the classification of healthy/unhealthy tissues in MR or other imaging. Application examples of the proposed segmentation methods are shown in this thesis. Research in the area of image segmentation is focused on methods based on solving partial differential equations. This is a modern method for image processing, often called the active contour method. It is of great advantage in the segmentation of real images degraded by noise with fuzzy edges and transitions between objects. The results of the thesis are methods proposed for automatic image segmentation and classification.
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Brown, Andrew. "Development of an autonomous parallel action tissue grasper to minimise tissue trauma." Thesis, University of Dundee, 2014. https://discovery.dundee.ac.uk/en/studentTheses/8151b394-f604-4d5f-98c5-dc8516ac0c42.
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Trauma caused by grasping during laparoscopic surgery is something which will never be fully eradicated however efforts should be taken to reduce the potential to cause trauma by grasping. Tissue is often grasped with excessive forces for long periods of time during surgeries such as cholecystectomies and colectomies. This along with failed grasping actions and the occurrence of slip has been shown to damage the tissue. Design features often employed within graspers such as profiling and the occlusion mechanism of the instrument cause areas of high, uneven distribution of pressures on the tissue which can result in perforation or tissue tearing. By investigating these contributing factors, development of graspers with a low risk to cause damage this combined with actuating the grasping force should reduce the incidence of grasping trauma, currently at estimated at one incidence per procedure. These trauma events can lead to conversion to open surgery, peritonitis and even death. Development of an autonomous grasping instrument to detect and prevent slip by actuating the grasping force is reported. Piezoelectric sensors are used to detect incipient slip and slip events. A closed loop control system then reacts to these perceived slip events to prevent slip occurring by actuating the applied force by small increments to increase or decrease grasping force. This leads to a system in which only the required amount of force necessary to overcome pull force is applied to the tissue. Other areas of investigation to reduce tissue trauma are presented. In chapter 3 design features such as surface profiling and fenestrations are evaluated to determine the potential to cause damage. A variety of profiles and fenestrations are studied and each is reported by representing the applied force to retention force ratio which indicates how good the profile is at retaining tissue against a pull force. The aim of this study was to develop surface profiling which had a high retention force but a reduced number of high stress areas which can lead to tissue damage. Three new parallel action grasping designs are presented and evaluated using finite element analysis. Parallel action grasping is important in reducing tissue trauma as it distributes pressure evenly across the active grasping area as opposed to more conventional pivot style graspers which have high stress concentration areas in the proximal opening. Each area of study within the thesis addresses areas of concern which have been shown to cause tissue trauma and postulates viable solutions to reduce the incidences of tissue trauma during laparoscopic surgery with the ultimate aim of developing a deployable and autonomous grasping device which will detect and prevent slip.
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Cheret, Daniel. "Elaboration et caractérisation d'un tissu de carbone active." Mulhouse, 1996. http://www.theses.fr/1996MULH0433.
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L'objectif de ce travail est l'élaboration d'un tissu de carbone active préparé selon un nouveau concept de fil. En effet, ce fil, ou plutôt multifil, est une association de deux composants: une âme et une couverture. L'âme assure la résistance mécanique du multifil et est constitué de monofilaments de haute ténacité. Disposés autour de cette âme résistante mécaniquement, des fibres à vocation adsorbante constituent la couverture. Ainsi préparé le multifil allie deux propriétés a priori difficilement compatibles, la résistance mécanique et l'adsorption. Dans un premier temps l'étude a porté sur la préparation et la caractérisation de précurseurs de couverture (4 viscose, une polyimide, une polyphénolique et une polyaramide) par carbonisation et activation au Co2 à 900°C ; la caractérisation poreuse ayant été effectuée par adsorption de gaz. A l'issue de cette étude, deux précurseurs intéressants ont été retenus: une viscose et une polyimide. L'effet d'une activation par la vapeur d'eau a également été étudiée. Un effet catalytique des sels de sodium en surface de la fibre viscose a ainsi pu être mis en évidence au cours de l'activation Co2. Ensuite, une étude de six multifils a été effectuée tant sur le plan de la texture poreuse que sur la résistance mécanique à la rupture. Un support textile a ensuite été confectionné et ses propriétés d'adsorption dynamique de molécule organique testées avec la molécule d'ypérite. Une corrélation entre la quantité de matière adsorbante, le taux d'activation, le volume microporeux, l'existence de pores de diamètre supérieur à celui de la molécule cible et l'efficacité de la filtration a été montré. Finalement le concept du multifil à la fois poreux et mécaniquement résistant a ainsi été validé
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Willemin, Anne-Sophie. "Stratégies cellulaires et environnementales pour le développement d’un substitut osseux prévascularisé." Thesis, Université de Lorraine, 2018. http://www.theses.fr/2018LORR0191.
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En cas de pertes de substances osseuses de grande étendue, la capacité naturelle de réparation du tissu osseux n’est pas suffisante et nécessite d’être assistée. La greffe d’os autologue constitue actuellement la référence. Cependant, cette thérapeutique présente tout de même des inconvénients qui ont entrainé le développement de substituts osseux. Mais, aucun matériau à ce jour ne peut remplacer totalement l’os autologue, en raison notamment de la difficulté à recréer un système vasculaire fonctionnel au niveau du site lésé. Depuis quelques années, les espoirs se tournent vers la création d’un substitut osseux prévascularisé afin de pallier la principale limite des alternatives actuelles : l’établissement d’un réseau vasculaire au sein de ce biomatériau. Notre projet vise à évaluer l’effet stimulateur d’un composé naturel, les principes actifs de la nacre solubles dans l’éthanol (appelé Ethanol Soluble Matrix, ESM), à la fois sur les capacités angiogéniques de cellules de la lignée endothéliale et sur la différenciation ostéogénique de cellules souches mésenchymateuses (CSM) avec comme objectif le développement d’un substitut osseux prévascularisé. Dans un premier temps, nous avons montré que l’ESM stimulait les capacités angiogéniques des cellules de la lignée endothéliale : cellules endothéliales matures (HUVECs, cellules endothéliales issues de la veine ombilicale humaine) et cellules progénitrices endothéliales (CPEs) issues de sang de cordon. L'ESM, utilisé à la concentration de 200µg/mL, a permis de dépasser les résultats obtenus (expression génique et test fonctionnel) avec le milieu de culture de référence des CPEs : l’EGM-2 (Endothelial Growth Medium). Nous avons ensuite mis en évidence que l’ESM exerçait un effet stimulateur également sur les CSMs en augmentant l’expression de marqueurs spécifiques des chondrocytes et des chondrocytes hypertrophiques, suggérant une orientation de ces cellules vers une ossification endochondrale. En parallèle de ces travaux, nous avons étudié l’effet paracrine des CSMs sur les cellules de la lignée endothéliale, HUVECs et CPEs. Les vésicules extracellulaires de taille nanométrique (nEVs) ont montré leur capacité à induire une stimulation in vitro de la formation de réseaux vasculaires et de l’expression de gènes endothéliaux. Ces résultats encourageants soulignent la faisabilité de l’utilisation de l’ESM en tant que stimulus à la fois de l’angiogenèse des CPEs et de l’ostéogenèse des CSMs. Ce stimulus pourrait être associé aux nEVs issues de CSMs et aux CPEs au sein d’une matrice tridimensionnelle pour développer un substitut osseux prévasculariséIn case of critical-sized defects, the bone tissue ability of natural healing is not sufficient and needs to be assisted. The autologous bone graft is currently the gold standard. However, this solution has drawbacks that have led to the development of bone substitutes. Nowadays, no substitute is able to supply autogenous bone, due to the difficulties to mimic the vascular system. In recent years, the hopes are focusing on the creation of a prevascularized bone substitute to overcome the main limitation of current alternatives: the creation of a functional vascular network inside the substitute. Our project aims to evaluate the stimulating effect of a natural compound, the nacre extracts called Ethanol Soluble Matrix (ESM), both on the angiogenic abilities of endothelial cell lineage and on the osteogenic differentiation of mesenchymal stem cells (MSCs) to develop a pre-vascularized bone substitute. First, we showed that ESM stimulates the angiogenic potential of two types of endothelial cells: mature endothelial cells (HUVECs, human umbilical vein endothelial cells) and endothelial progenitor cells (EPCs) from cord blood. The ESM, used at the concentration of 200µg/mL, exceeded results obtained with the reference culture medium of EPCs: the EGM-2 (Endothelial Growth Medium). Then, we demonstrated that ESM also exerted a stimulating effect on MSC by increasing the expression of chondrocyte and hypertrophic chondrocyte specific markers, suggesting an orientation of these cells towards endochondral ossification. In line with this work, we studied the paracrine effect of MSCs on endothelial cell lineage, HUVECs and EPCs. Nanoscale extracellular vesicles (nEVs) have been shown to induce an in vitro stimulation of the vascular network formation and of the endothelial gene expression. These encouraging results highlight the feasibility of using ESM as a stimulus for both angiogenesis of EPCs and osteogenesis of MSCs. This stimulus could be associated with MSC-derived nEVs and EPCs within a three-dimensional matrix to develop a pre-vascularized bone substitute
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Assayag, Osnath. "Méthodes optiques passive et active pour l’étude des tissus biologiques." Paris 6, 2013. http://www.theses.fr/2013PA066762.
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Deux aspects de l'exploration des tissus biologiques par la lumière sont étudiés : l'imagerie et la photoactivation. La méthode d'imagerie est la Tomographie par Cohérence Optique Plein Champ (FF-OCT) qui image les photons balistiques par interférométrie en lumière faiblement cohérente. L’intérêt de la FF-OCT est de fournir des images "en face", de grande taille en un temps court ayant une résolution de l'ordre de 1µm3 et dont le contraste ne dépend que des propriétés de rétrodiffusion des structures du tissu. Deux études de caractérisation des tissus mammaires et cérébraux pour le diagnostic des tumeurs sont présentées. L'aspect morphologique des structures de base du tissu ainsi que sa modification en cas de lésion a été mis en évidence. Une procédure de classification des tissus fondée sur des critères spécifiques aux images FF-OCT a permis de reconnaitre les tissus malins des tissus bénins ou sains. La méthode de photoactivation étudiée est l'holographie monophoton pour des applications en optogénétique. Deux limites actuelles de la technique sont dépassées : 1) La non uniformité de l’intensité lumineuse des hologrammes dans le champ d’excitation est modifiée en corrigeant l’efficacité de diffraction du SLM utilisé pour le calcul holographique 2) La difficulté de contrôler le niveau d'expression des protéines photosensibles dans les cellules est surmontée en stimulant les cellules de manière inversement proportionnelle à leur niveau d'expression, entrainant ainsi des réponses identiques de cellules ayant la même fonction dans le réseau neuronalTwo different aspects of biological tissue exploration using light are presented in this work : Imaging and Photoactivation. For the imaging part, we are interested in Optical Coherence Tomography (OCT), a technique that selects ballistic photons using low coherence interferometry in order to virtually slice inside the tissue, and in particular to the so called Full Field Optical Coherence Tomogaphy variant. FF-OCT captures en face slices of tissue samples at 1 μm resolution in 3D, in a limited time (1 cm2 specimen processed in about 7 min), requiring no contrast agent injection. Two preclinical studies are performed on breast and cerebral tissue. In both cases, major architectural features and structures of benign or normal tissue were characterized. Subsequently, features resulting from pathological modification were assessed resulting in the development of a diagnosis decision tree and a classification procedure based on FF-OCT images only is proposed to distinguish malignant from benign or normal tissue. The second part of the work focuses on the use of single photon holography for optogenetics applications and proposes to exceed two current limitations of the technique for neuronal connectivity studies. First, the computed generation of holograms requires the use of a device called Spatial Light Modulator (SLM ) whose intrinsic characteristics impose a non-uniform distribution of light intensity over the field of excitation. By modifying the algorithm responsible for holograms generation we show that it is possible to correct the diffraction efficiency of the SLM. Secondly, the use of optogenetic tools can be limited by the difficulty of controlling the level of expression of optogenetic proteins in cells. This difficulty is overcome here by showing that it is possible to photoactivate cells in an inverse proportion to their expression level hence causing same physiological responses from cells having the same function
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Hu, Jing. "Isolation, tissue localization and physiological action of corticostatic peptides." Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=41284.
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Two rabbit and three guinea pig corticostatic (anti-adrenocorticotrophic) peptides were isolated from bone marrow cells and identified. The third guinea pig peptide proved to be a novel 13-member anti-parallel dimer. Removal of the two C-terminal arginines from rabbit corticostatin 1 lowered the biologic activity but removal of the two N-terminal arginines from the guinea pig peptides was without effect. Immunocytochemical localization of rabbit corticostatin 1 in the rabbit indicated that it was localized in immune tissues such as spleen and bone marrow but also in non-immune tissues such as lung, placenta, adrenal, anterior pituitary and various parts of the brain, Rabbit corticostatin 1 was measured in maternal and fetal tissues and in blood at 24, 27 and 30 days of pregnancy in the rabbit and marked changes were noted with increasing gestation, Rabbit corticostatin 1 did not inhibit the action of angiotensin II or Atrial Natriuretic Peptide but it did inhibit $ alpha$-Melanotrophic Stimulating Hormone binding to specific zona glomerulosa receptors.
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Israel, David Alan 1953. "The propagation of the action potential in cardiac tissue." Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/34033.
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Brasquet, Catherine. "Procédés d'adsorption sur tissus de carbone active, application au traitement des eaux." Pau, 1998. http://www.theses.fr/1998PAUU3016.
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Ce travail a pour objet l'etude des procedes d'adsorption d'un materiau recent, les tissus de carbone active, et son application au traitement de l'eau. Une caracterisation physico-chimique de tissus de carbone active ex-rayonne montre que ce sont des materiaux microporeux et de surfaces specifiques elevees, la porosite finale etant fonction des conditions d'activation. Par rapport a un charbon actif en grains, ils developpent d'importantes surfaces externes auxquelles sont directement connectes les micropores. Ces deux specificites permettent d'obtenir des vitesses initiales d'adsorption de micropolluants organiques 2 a 20 fois plus importantes que celles d'un charbon actif en grains, du fait d'une importante surface de contact fluide-solide et d'une diminution de la resistance au transfert intraparticulaire des polluants. Les differences entre les capacites d'adsorption des deux formes d'adsorbant sont moins marquees, meme si l'important reseau microporeux des fibres permet d'obtenir des capacites d'adsorption de l'ordre de 500 mg g#-#1. Une analyse qualitative de ces donnees, appuyee par une relation quantitative entre l'adsorption et la topologie moleculaire des adsorbants, montre que l'adsorption doit avoir lieu entre les plans de base des fibres de carbone active, par des interactions donneur-accepteur d'electrons entre la surface des fibres et le solute. Des composes aromatiques, ou hydrophobes, semblent favorises. L'etude des performances hydro-aerauliques des tissus montre l'influence sur les pertes de charge de caracteristiques specifiques aux structures tissees (armure, nombre d'interstices, etc. ), qui rendent difficiles d'utilisation des modeles classiques d'ecoulement du type ergun. L'application du modele de comiti permet de supposer que l'ecoulement a lieu a l'interieur des fils du tissu. Les capacites d'adsorption obtenues en reacteur continu sont elevees, comprises entre 50 et 250 mg g#-#1 selon le solute, avec un faible front d'adsorption, de l'ordre de 3,2 mm. Les deux comportements dynamiques, ecoulement et adsorption, sont chacun modelises avec succes au moyen d'un reseau neuronal prenant en compte les parametres influencant les processus (respectivement caracteristiques specifiques aux tissus et diffusion intraparticulaire).
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Heesom, Kate J. "The regulation of acetyl-CoA carboxylase by insulin in adipose tissue." Thesis, University of Bristol, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294552.
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Troike, Katie M. "White Adipose Tissue Beiging in Mice With Increased Growth Hormone Action." Ohio University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1497354961246326.
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Owera-Atepo, J. B. "The vagal nerve as a model for drug action on 5-hydroxytryptamine receptors." Thesis, University of Bradford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379818.
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Alert, Zenón Ricard. "Forces and flows in cells and tissues. Blebs, active gels, and collective cell migration." Doctoral thesis, Universitat de Barcelona, 2018. http://hdl.handle.net/10803/461383.
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In this thesis, we have studied mechanical aspects of some biological processes in cells and tissues, which we addressed by developing theoretical models based on the physics of soft active matter. The thesis contains three parts that focus on different biological systems.
In Part I, we study the adhesion between the plasma membrane and the actin cortex of eukaryotic cells. We propose a continuum model for membrane-cortex adhesion that couples the mechanics and hydrodynamics of the membrane to the force-dependent binding kinetics of the linker proteins. We predict the critical pressure difference that causes membrane-cortex detachment, and we discuss how cortical tension can be inferred from micropipette suction experiments. Then, we study the fluctuations of an adhered membrane, and suggest ways in which our predictions could allow probing membrane-cortex adhesion in fluctuation spectroscopy experiments.
Then, we employ the proposed model to study the nucleation of blebs, which are balloon-like membrane protrusions arising from a local membrane-cortex detachment. We show that bleb nucleation is governed by membrane peeling, the fracture propagation process whereby adjacent membrane-cortex bonds break sequentially. Through this mechanism, bleb nucleation is not determined by the energy of a local detachment like in the classical nucleation picture, but rather by the kinetics of membrane-cortex linkers. We predict the critical radius for bleb nucleation through membrane peeling and the corresponding effective energy barrier. Finally, we simulate a fluctuating adhered membrane to obtain the probability distribution of bleb nucleation times.
In Part II, we study the dynamics of active polar gels, which are soft materials, usually transiently-crosslinked polymeric networks, that are maintained out of equilibrium by internal processes that continuously transduce energy. We derive the constitutive equations of an active polar gel from a mesoscopic model for the dynamics of the molecules that crosslink the polar elements of the system. This way, we establish a connection between the molecular properties and the macroscopic behaviour of active polar gels. Specifically, we explicitly obtain the transport coefficients in terms of molecular parameters, showing that all transport coefficients have an active contribution that stems from breaking detailed balance for the crosslinker binding kinetics.
In Part III, we study cell colonies and tissues, focusing in collective cell migration and tissue morphology. First, we propose a particle-based description of cell colonies to study how the different organizations of cells in tissues emerge from intercellular interactions. The model intends to capture generic cellular behaviours such as cell migration, adhesion, and cell-cell overlapping. In addition, it models the so-called contact inhibition of locomotion (CIL), which repolarizes cell migration away from cell-cell contacts, as a torque on the migration direction. We show how CIL yields an effective repulsion between cells, which allows to predict transitions between non-cohesive, cohesive, and 3D tissues. We conclude that, at low cell-cell adhesion, CIL hinders the formation of cohesive tissues. Yet, in continuous cell monolayers, CIL gives rise to self-organized collective motion, ensures tensile stresses in the monolayer, and opposes cell extrusion, thereby hindering the collapse of the monolayer into a 3D aggregate.
Then, we focus on the spreading of epithelial monolayers, which we address by means of a continuum model based on the theory of active polar gels. First, we concentrate on the wetting transition of epithelial tissues, which separates monolayer spreading from retraction towards a 3D aggregate — namely the equivalent of a fluid droplet. We show that a critical radius exists for the wetting transition, which does not exist in the classical wetting picture. Thus, we show how the wetting properties of tissues emerge from active cellular forces, evidencing that the wetting transition has an active nature.
Finally, we study the morphological stability of the front of a spreading monolayer. The model predicts that traction forces cause a long-wavelength instability of the monolayer front, whereas tissue contractility has a stabilizing effect. The predicted instability can explain the formation of finger-like multicellular protrusions observed during epithelial spreading. It can also explain the symmetry breaking of tissue shape observed during monolayer dewetting. By fitting the predictions to experimental data, we infer the monolayer viscosity and the noise intensity of tissue shape fluctuations, which we suggest to have an active origin.En aquesta tesi hem estudiat aspectes mecànics d'alguns processos biològics en cèl·lules i teixits, que hem abordat desenvolupant models teòrics basats en la física de la matèria tova activa. La tesi té tres parts centrades en sistemes biològics diferents. En la primera part s'estudia l'adhesió entre la membrana plasmàtica i el còrtex d'actina de les cèl·lules eucariotes. Proposem un model continu per l'adhesió membrana-còrtex que acobla la mecànica i la hidrodinàmica de la membrana amb la cinètica de les proteïnes que ancoren la membrana al còrtex. Prediem la pressió crítica pel desenganxament i estudiem les fluctuacions de la membrana adherida. Després, ens centrem en la nucleació de butllofes cel·lulars, que són protrusions degudes a desenganxaments locals de la membrana. Mostrem que la nucleació de butllofes cel·lulars està governada pel procés de pelat de la membrana, pel qual proteïnes connectores adjacents es desenganxen seqüencialment. Per aquest mecanisme, la nucleació de butllofes no està determinada per l'energia com en l'escenari clàssic sinó per la cinètica dels connectors. A la segona part es deriven les equacions constitutives d'un gel polar actiu a partir d'un model mesoscòpic per la dinàmica de les molècules entrellaçadores. Així, prediem explícitament els coeficients de transport dels gels polars actius en termes de paràmetres moleculars. Tots els coeficients de transport tenen una contribució activa, provinent del trencament de balanç detallat per la cinètica dels entrellaçadors. A la tercera part estudiem colònies cel·lulars i teixits. Primer, proposem un model de partícules per estudiar com les diferents organitzacions dels teixits emergeixen de les interaccions intercel·lulars. El model captura comportaments cel·lulars genèrics i, en particular, la inhibició de la motilitat per contacte. Es mostra com aquesta interacció dóna una repulsió efectiva entre cèl·lules. Després, s'estudia l'escampament de monocapes epitelials en base a un model continu basat en la teoria dels gels polars actius. Primer es mostra que, a diferència del que passa en l'escenari clàssic, la transició de mullat d'un teixit té un radi crític determinat per les forces cel·lulars actives. Finalment, es prediu que, a causa de les forces de tracció, el front d'una monocapa en expansió, fet que explica observacions experimentals.
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PIGNON, METIVIER HELENE. "Procedes de traitement d'eau par adsorption sur tissus de carbone active couplage ultrafiltration - adsorption." Nantes, 2001. http://www.theses.fr/2001NANT2038.
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L'etude presentee porte sur les procedes d'adsorption en milieu aqueux mettant en uvre des materiaux recents : les tissus de carbone active. Le couplage de ces derniers avec l'ultrafiltration est envisage pour le traitement d'effluents complexes. Dans un premier temps, l'adsorption de pesticides et de colorants sur tissu de carbone active est etudiee en reacteur discontinu, par le biais de cinetiques et d'equilibres d'adsorption en systeme mono- et multicompose. Les vitesses et capacites d'adsorption des pesticides sont d'autant plus importantes que la solubilite du micropolluant est faible. En melange, la competition est surtout marquee dans le domaine des fortes concentrations. Enfin, la presence d'une matrice organique naturelle se revele etre sans influence sur l'adsorption de l'atrazine. Dans le cas des colorants, une approche par le biais de relations quantitatives structure - activite impliquant des indices topologiques montre que l'adsorption est d'autant plus rapide que le colorant est de petite taille et de geometrie plane. L'etude menee sur des melanges binaires met en evidence l'influence de l'affinite de l'adsorptif pour l'adsorbant et celle des vitesses d'adsorption des differents co-adsorptifs sur les phenomenes de competition. Dans un second temps, l'adsorption sur tissu de carbone active est couplee a l'ultrafiltration. Les performances de ce procede sont evaluees pour le traitement d'une eau de surface dopee en atrazine, puis pour des rejets colores, un effluent modele de type industrie textile et des encres pour cartouches de stylos. L'ultrafiltration pourvoit a l'elimination de la turbidite, ainsi qu'a celle des composes de forte masse molaire. L'adsorption sur tissu de carbone active vise quant a elle les composes de faible masse molaire. Quel que soit l'effluent etudie, le couplage ultrafiltration - adsorption sur tissu de carbone active se presente comme un procede performant pour le traitement de milieux aqueux complexes.
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Breschet, Gilbert. "Recherches sur les hydropisies actives en général et sur l'hydropisie active du tissu cellulaire en particulier présentées à la Faculté de médecine de Paris le 31 août 1812 /." Paris : BIUM, 2003. http://www.bium.univ-paris5.fr/histmed/medica/cote?TPAR1812x173.
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Brownson, Kathleen. "INVESTIGATION OF CARDIAC ELECTROPHYSIOLOGY IN HUMAN VENTRICULAR TISSUE." UKnowledge, 2014. http://uknowledge.uky.edu/cbme_etds/16.
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Individuals with cardiomyopathy are at higher risk to die from sudden cardiac arrest than those with non-failing (NF) hearts. This study examined the differences in electrical properties of failing and NF human hearts in terms of cardiac memory through explicit control of diastolic intervals in a sinusoidal fashion, restitution of action potential duration (APD) through standard and dynamic pacing protocols, maximum rate of depolarization and APD alternans. Recordings of transmembrane potentials were made in tissues extracted from patients with heart failure and one donor NF heart. Computational simulations were performed using the O’Hara Rudy model for generating surrogates of control data. Significant differences were seen between left ventricular (LV) tissue and NF LV tissue in tilt, and measures of memory in terms of area and thickness during the sinusoidal 400ms protocol. Minimum delay was also significantly higher in the failing LV during the sinusoidal 150ms protocol. Failing tissues showed a higher restitution slope and prolonged AP which is consistent with previous studies and is hypothesized to contribute to the increased susceptibility to unstable alternans. This study further explored how disease alters the electrical functioning of the heart and why these patients are at a higher risk of ventricular arrhythmia.
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Srivastava, Vaibhav. "Active oxygen involvement in developmental processes in Populus : with emphasis on HipI-superoxide dismutase /." Umeå : Swedish University of Agricultural Sciences, 2009. http://epsilon.slu.se/200921.pdf.
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Masson, Sylvain. "Étude de l'adsorption de micropolluants émergents sur des tissus de carbone activé." Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAA030/document.
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Face au problème des micropolluants émergents trouvés dans l’eau, l’utilisation de carbones activés est un moyen de réduire cette pollution à la source. Le but de ce travail est de mieux comprendre les mécanismes d’adsorption de certains micropolluants sur des tissus et feutres de carbones activés.Neuf molécules ont été étudiées dont des médicaments : la carbamazépine (CBZ), le diclofénac (DFN), l’ibuprofène (IBP) et l’ofloxacine (OFX), un produit anticorrosion : le benzotriazole (BZT), un perturbateur endocrinien : le bisphénol-A (BPA), deux herbicides : le mécoprop (MCP) et le pentachlorophénol (PCP) et une molécule utilisée comme indicateur de pollution des eaux usées : la caféine (CAF). Les adsorbants ultramicroporeux (tissu KIP1200 et feutre CSV4) et l’adsorbant mésoporeux (tissu BBV 800) (fournis par Dacarb, France) ont été caractérisés par adsorption d'azote à 77K et de CO2 à 273K, titrages acido-basiques (méthode de Boehm), mesure du pHpzc (point isoélectrique). Les cinétiques et isothermes d'adsorption ont été étudiées à 25°C à pH=7,5 dans un tampon phosphate NaHPO4/KH2PO4 (à 0,04M). La concentration résiduelle est analysée par HPLC.Les cinétiques d'adsorption ont été étudiées pour les 9 molécules à différentes concentrations initiales. Le temps pour atteindre l’équilibre d’adsorption dépend du volume des molécules ainsi que de leur affinité avec l’adsorbant. La quantité maximale adsorbable dépend du volume microporeux ainsi que de la surface spécifique de l’adsorbant, la quantité adsorbable est donc plus importante sur le tissu KIP 1200 que sur le feutre CSV 4. La vitesse de diffusion est la plus lente pour les adsorbants possédant un volume microporeux important, le tissu mésoporeux BBV 800 permet donc une adsorption rapide grâce à de plus larges pores qui permettent un accès plus rapide à la porosité.Des analyses en mélanges binaires et multi composés ont alors été réalisées pour connaître les paramètres clés gouvernant les cinétiques d’adsorption. Une compétition existe entre molécules dans certains cas (BZT et MCP par exemple) avec une première phase gouvernée par la cinétique d’adsorption liée à la diffusion dans les pores et la deuxième phase gouvernée par des phénomènes thermodynamiques entre le système soluté/solvant/carbone.Les isothermes d'adsorption ont été réalisés à 3 températures différentes et modélisées par des équations de Langmuir-Freundlich pour tous les micropolluants. Des paramètres thermodynamiques (enthalpie d’adsorption et enthalpie libre) ont alors été calculés et corrélés aux propriétés physico-chimiques des molécules. Une corrélation est mise en évidence entre l’enthalpie libre et la polarisabilité des molécules ainsi que les forces de Van der Waals déterminées avec le logiciel COSMO-RS mettant en évidence l’importance des forces non polaires dans le phénomène d’adsorption. Des mesures par calorimétrie d’adsorption à très faibles quantités adsorbées ont permis de mettre en évidence que l’entropie est le paramètre thermodynamique qui contrôle l’adsorption de molécules (BZT, PCP, CAF et OFX) sur le tissu KIP 1200. De fortes énergies d’interaction ont été mis en évidence entre les molécules (BZT, CAF et OFX) et les sites d’adsorption.Une étude d’adsorption-désorption de N2 et de CO2 sur des tissus KIP 1200 chargés en PCP, BZT, CAF et OFX a permis de mieux localiser le lieu de l’adsorption dans la porosité montrant une adsorption prioritairement dans les ultramicropores puis dans les supermicropores. Il a été montré également par cette méthode et par des mesures thermiques que l’eau est fortement adsorbée dans la porositéA lot of studies have revealed that some organic molecules such as pharmaceutical molecules, solvents, pesticides, etc.. are frequently found in water, at concentrations below µg/L, even after treatment at the exhaust of wastewater treatment plants. These molecules are highly toxic when accumulated in environment. One of the possibility for removing these micropollutants is the adsorption on activated carbons. Thus the aim of this work is to better understand the adsorption mechanism of some micropollutants onto activated carbon (ACs) in felt or fabric form.Nine micropollutants were studied, such as some pharmaceuticals: Carbamazepine (CBZ), Diclofenac (DFN), Ibuprofen (IBP), and Ofloxacin (OFX); one anti-corrosion compound : Benzotriazol (BZT); two herbicides : Mecoprop (MCP) and Pentachlorophenol (PCP) and an endocrine disruptor : Bisphenol A (BPA). Adsorption of Caffeine (CAF) which is an anthropic indicator of pollution in waste water, was also studied. The ACs (microporous KIP1200 fabric and CSV4 felt and mesoporous BBV 800 fabric, from Dacarb, France) were characterized by N2 adsorption-desorption at 77 K and CO2 adsorption at 273 K, pHpzc (point of zero charge) measurements and acido-basic titrations (Boehm method). The adsorption kinetics and isotherms were studied at pH 7.4 at 25°C in NaHPO4/KH2PO4 buffered solutions (about 0.04 M) using UV spectrometry and HPLC for the analysis of organic molecules in the remaining solution.Kinetics have been studied for 9 molecules at different initial concentrations. Time to reach adsorption equilibrium depends of the volume of the molecule and its affinity with the activated carbon. The maximum adsorbed quantity depends of the microporous volume and the specific area of the adsorbent, the adsorbed quantity is then bigger for KIP 1200 fabric than for CSV 4 felt. The speed of diffusion is slower for the adsorbent with high microporous volume, the mesoporous BBV 800 fabric gives place to a quick adsorption kinetics thanks to its large pores that gives an easy access to porosity.Binary and multi components kinetics have been done in order to understand key processes that drive kinetics adsorption. Competition between molecules have been shown (for BZT and MCP for example). Adsorption kinetics can be divided into two phases: the first one is driven by pore diffusion and the second one by thermodynamic phenomenon between the solute, the solvent and the AC.The adsorption isotherms of the molecules were studied at 13, 25 and 40°C; and the thermodynamic parameters (isoteric enthalpies and entropies Gibbs free energies) were determined. A correlation between Gibbs free energy and polarizability of molecules as well as Van der Waals energy calculated with Cosmotherm software shows the importance of non polar forces on adsorption phenomenon. Adsorption calorimetry experiments showed that entropy is the thermodynamic parameter that drives adsorption of molecules (BZT, PCP, CAF and OFX) onto KIP 1200 fabric.The pore size distributions of the carbons loaded with micropollutants were determined by DFT simulation from CO2 and N2 adsorption isotherms, to investigate the porosity accessible to the adsorbate. The accessible pore are firstly the ultramicropores and then supermicropores. With this technique and thermal experiments, it has been shown that water is highly bonded inside the porosity
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Le, Leuch Louis-Marie. "Procédés de transfert-réaction de composés odorants sur tissus de carbone activé." Nantes, 2004. http://www.theses.fr/2004NANT2042.
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Ce travail a pour objet l'étude de procédés de traitement d'air chargé en molécules odorantes par transfert - réaction sur tissus de carbone activé. Couramment rencontrés en traitement d'odeurs, le sulfure d'hydrogène, l'ammoniac et l'acide acétique ont été choisis comme molécules modèles. Une caractérisation physico-chimique des tissus de carbone activé (TCA) montre une structure microporeuse permettant de développer une surface spécifique importante. De plus la surface de ces matériaux présente des propriétés chimiques particulières (pH de surface, groupements oxygénés) pouvant être le siège de réactions d'oxydation catalytique. Des données cinétiques et d'équilibres sont générées en réacteur discontinu. Différents paramètre tels que le taux d'humidité, les propriétés structurales et chimiques de surface des adsorbants ont été étudiés. Les données générées montrent que l'H2S adsorbé subit une réaction d'oxydation à la surface du matériau. La quantification des sous-produits de réaction a permis d'identifier les mécanismes mis en jeu, et a révélé un taux de conversion élevé en soufre élémentaire. De plus, le rôle auto-catalytique du soufre formé par la réaction d'oxydation d'H2S a été mis en évidence. Les capacités d'élimination ont été augmentées par imprégnation des tissus par des catalyseurs métalliques. Deux voies d'imprégnation ont été explorées : l'imprégnation par voie humide et l'électrodéposition. Dans les deux cas, de meilleurs résultats en terme de capacités de traitement sont obtenus. Néanmoins, ils dépendent de la nature du métal utilisé, de la quantité imprégnée et de l'activation thermique. L'étude en système dynamique a été réalisée en configuration plane au travers de mesures de pertes de charge et de capacités de traitement. Ces données ont mis en évidence les faibles épaisseurs critiques des tissus comparées à celle des grains. De plus, ces résultats ont permis de concevoir et dimensionner des mises en œuvre plus complexes, sous forme de filtres cylindriques enroulés et plissés, ainsi qu'une configuration de type tangentielle. L'ensemble de ces résultats montre d'intéressantes possibilités d'utilisations des tissus de carbone activé dans lr traitement d'effluents odorantsThis work deals with odorous air treatments by transfer reaction onto activated carbon fiber cloth. Frequently met in odor treatment, hydrogen sulfide, ammonia and acetic acid were used as odorous-type molecules. A physicochemical characterization of activated carbon fabrics shows a microporous structure making it to develop an important specific surface. Moreover, surface of these materials presents particular chemical properties (pH of surface, oxygenated groups) being able to develop catalytic oxidation reactions. Kinetic data and isotherms curves are generated out of discontinuous batch reactor. Different parameters such as the water content, structural and chemical properties of the adsorbents surface were studied. The experimental data show that adsorbed H2S is oxidized at the material surface. The quantification of the reaction by-products made it possible to identify the oxidation mechanisms and reveals a high rate of conversion of H2S into elemental sulfur. Moreover the autocatalytic role of the sulfur formed by the oxidation reaction was highlighted. Thus, the elimination capacities are increased by metal catalysts. Two impregnation ways are explored: the incipient wetness impregnation and the electrodeposition. In both case, best results in terms of treatment capacities were obtained. Nevertheless, they depend on the metal catalyst nature, the impregnation rate and the thermal activation. The study in dynamic system was performed in plane configuration by the way of pressure drops and treatments capacities measurements. These data highlight the low thickness of fabric to be used compared to granular activated carbon. Moreover, these results made it possible to conceive and dimension more complex settings, in the form of rolled up and folded cylindrical filters, as well as a tangential filter configuration. These data show that the activated carbon fiber cloth is very promising for odors molecules treatments
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CARVALHO, CLAUDIO RIBEIRO. "A FINITE ELEMENT ANALYSIS OF THE SKIN UNDER ACTION OF AXISYMMETRIC TISSUE EXPANDERS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1999. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=1272@1.
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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIORHoje em dia, é crescente a utilização de expansores de pele, visando criar um excesso de pele localizado, com o qual pode-se corrigir imperfeições encontradas na pele de um paciente. Este processo, envolve um implante de uma bolsa de silicone sob a pele, sendo enchida vagarosamente, através da injeção de uma solução fluida salina. Obviamente, a pele se expande no mesmo formato da forma da bolsa implantada. Em estudos prévios já realizados, as propriedades viscoelásticas da pele expandida foram ignoradas. O objetivo deste trabalho, é modelar a pele expandida por um expansor axissimétrico e inicializar os estudos para expansores sem simetria, como um material viscoelástico, isotrópico e homogêneo. Para este fim, é utilizado o método dos elementos finitos. Na análise de elementos finitos, é usado um modelo viscoelástico linear, com três diferentes tipos de elementos, casca, membrana e elementos sólidos, procurando o melhor elemento para descrever o modelo. É realizado também, um estudo paramétrico, variando a espessura dos elementos e comparando seus resultados. Para a análise por elementos finitos, é utilizado o programa ABAQUS, sendo o método validado através de resultados numéricos já obtidos. No futuro, nossa intenção é modelar expansores de forma não axissimétricas e aplicar nosso trabalho em experimentos in- vivo.
Nowadays, soft tissue expanders are being increasingly, used to create local skin flaps which can cover relatively large tissue defects. This involves inserting a silicon-rubber balloon (prosthesis) in its collapsed state under the subcutaneous tissue of the patient, closing the incision, and then inflating the balloon slowly with a saline fluid through a one way valve. The valve is part of the balloon prosthesis. Obviously, the skin expands in the form of a dome in unison with the balloon underneath it. In preliminary studies designed to evaluate the behavior of skin created by soft tissue expansion, the viscoelastic proprieties of skin were ignored. The objective of the present work is model skin as an isotropic homogeneous viscoelastic material using the finite element method for large deformation in axisymmetric expanders. In finite element analysis we are using a linear viscoelastic model with three different kinds of elements, solid, shell and membrane, looking for the best element to describe the model. We are also making a parametric study, varying the thickness of the elements and comparing the results. To develop this finite element analysis, we are using the ABAQUS program . The methods have been validated using results from previous experimental works . In the future, we intend to model non-axisymmetric expanders and apply this work to in-vivo experiments.
En la actualidad, la utilización de expansores de piel está en franco crecimiento. El objetivo de esta utilización es crear un exceso de piel localizado, con el cual se pueden corregir imperfecciones encontradas en la piel de un paciente. Este proceso consiste en el implante de una bolsa de silicone bajo la piel, a través de la injección de una solución fluida salina. Obviamente, la piel se expande en el mismo formato de la forma de la bolsa implantada. En estudios previos, se ignoraron las propriedades viscoelásticas de la piel expandida. El objetivo de este trabajo es modelar la piel expandida por un expansor axisimétrico e inicializar los estudios para expansores sin simetría, como un material viscoelástico, isotrópico y homogéneo. Para este fin, se utiliza el método de los elementos finitos. En el análisis de elementos finitos, se utiliza un modelo viscoelástico lineal, con tres tipos diferentes de elementos, casca, membrana y elementos sólidos, buscando el mejor elemento para descrivir el modelo. Se realiza también un estudo paronétrico, variando la espesura de los elementos y comparando sus resultados. Para el análisis por elementos finitos, se utiliza el programa ABAQUS, y el método es evaluado a través de resultados numéricos obtenidos con anterioridad. En el futuro, nuestra intención es modelar expansores de forma no axisimétricas y aplicar nuestro trabajo en experimentos in- vivo.
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Labit, Elodie. "Le tissu adipeux : tissu modèle pour étudier le lien entre organisation et fonction ainsi que la régénération tissulaire." Thesis, Toulouse 3, 2016. http://www.theses.fr/2016TOU30101/document.
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Le tissu adipeux (TA) est connu pour sa plasticité puisqu'il est capable de s'hypertrophier ou de s'atrophier, en fonction de la situation métabolique de l'individu. Cette plasticité est liée au fait que le TA joue un double rôle dans le maintien de la balance énergétique : il est à la fois i) réserve d'énergie mobilisable (adipocytes blancs) mais également ii) consommateur d'énergie via la thermogénèse (adipocytes bruns, adipocytes beiges). En raison de l'évolution croissante des maladies métaboliques dites de surcharge dans lesquelles ce TA va s'hypertrophier, la majorité des études abordent cette notion de plasticité à l'échelle cellulaire, et se focalise ainsi sur les adipocytes (prolifération, différenciation, activité) et les autres populations cellulaires résidant dans le TA, capables d'interagir avec eux. En revanche, il y a très peu d'études sur cette plasticité à l'échelle tissulaire. Au cours de ma thèse, je me suis intéressée i) à l'organisation tissulaire d'un dépôt de TA blanc (dépôt sous-cutané inguinal) et ii) les conséquences d'une ablation massive du TA blanc. L'ensemble de ce travail a été réalisé chez la souris.A l'aide de l'imagerie 3D sur tissu entier, nous montrons que ce dépôt est hétérogène : il est composé d'une partie dans laquelle il est possible de segmenter des entités fonctionnelles (lobules ?), située au cœur du dépôt, et d'une partie non segmentable, située à la périphérie du dépôt. Cette hétérogénéité structurale est associée à une hétérogénéité fonctionnelle : les deux régions se distinguent en termes de morphologie adipocytaire et de pattern d'expression génique. De plus, seule la partie segmentable répond à la mise au froid des animaux par une up-régulation du niveau d'expression d'Ucp1 et d'autres gènes marqueurs du " brunissement ". Parallèlement à cela, nous montrons que selon la souche de souris (C57bl6 et MRL), la réponse du TA inguinal à une ablation partielle n'est pas la même : chez la souris MRL (rare mammifère capable de régénération), ce dépôt adipeux est capable de régénérer, ce qui n'est pas le cas chez la souris C57Bl/6. La régénération est inhibée chez la souris MRL par un traitement avec un agoniste des récepteurs aux opioïdes (tramadol) alors qu'elle peut être induite chez la souris C57Bl/6 par un antagoniste de ces récepteurs (naloxone). Cette régénération est dépendante d'une forte et intense production d'espèces actives de l'oxygène par les granulocytes. L'utilisation de souris invalidées pour le récepteur mu démontre l'implication de cette sous-famille de récepteurs. Enfin, cet effet des opioïdes est majoritairement le fait des cellules immunitaires, et plus particulièrement les granulocytes. Ces données mettent en exergue une nouvelle vision du TA blanc sous - cutané, qui ne doit pas être considéré comme un tissu inerte mais bel et bien comme un tissu hétérogène complexe (structurellement et fonctionnellement) pouvant être capable de régénérationAdipose tissue (AT) is very plastic tissue. During metabolic disease, it would be overdeveloped or atrophy. It is due to the fact that AT is i) energy storage thanks to white adipocyte and ii) energy consumer thanks to brown or brite adipocyte. The cellular composition is very well studied (adipocytes activity, proliferation, differenciation, link between AT stromal cells / adipocytes) but the tissue organization of AT is not known. During my thesis work, we study the i) tissular organization of white AT and ii) AT response after massive removal of white AT. Mice are used for this work. In the first step, our 3 dimensional imaging of white AT shows that AT is heterogeneous tissue: AT has 2 components: segmentable area, in the AT core and non-segmentable area, in the AT periphery. This structural heterogeneity is correlated with functional heterogeneity because segementable area differs to non-segmentable area from adipocyte shape and pattern genic expression. Furthermore, only segmentable area can be respond to cold exposure by Ucp1 up-regulation and browning genes markers. In the second step, massive ablation of subcutaneous white AT is performed on two mice strains: C57Bl/6 and MRL (known to be able to regenerate). MRL mice inguinal AT regenerate, unlike inguinal AT of C57Bl/6 mice. The use of antagonist of opioid receptor (naloxone) treatment leads regeneration AT in C57Bl/6. In opposite, opioid receptor agonist (tramadol) treatment in MRL mice inhibits AT regeneration. AT regeneration is dependant of burst oxydatif production by granulocytes. The use of the receptor knock down mice highlights that is the only receptor is involved in AT regeneration. More precisely, opioids effects are mediated by receptor on granulocyte immune cells
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Suliman, Shameela Haroon. "The soft-tissue profile preferences of a group of lay persons and professionals." Thesis, University of the Western Cape, 2008. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_8182_1267657357.
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"
Although facial aesthetics has always been a part of orthodontic diagnosis and treatment planning, the criteria for facial evaluation have been somewhat arbitrary. They are often based on parameters from the field of art or from evaluating faces chosen by orthodontists or other professionals. The aims and objectives of the study were to determine the soft-tissue profile preference of a group of lay persons and professionals
to compare the preferences of the male and female assessors (lay persons group) with regard to the preferred profiles for the maleand female patient respectively
to test similarities and differences in the professional's perceptions of the various profiles. This qualitative study was undertaken at the orthodontic clinic at UWC using post-treatment soft tissue profile photographs of patients who had attended the orthodontic clinic..."
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Kopanska, Katarzyna. "Mechanism of action of silicon : extracellular matrix synthesis and stabilisation." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610697.
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Subrenat, Albert. "Procedes de traitement d'air charge en c. O. V. Par adsorption-desorption sur tissu de carbone active." Nantes, 1999. http://www.theses.fr/1999NANT2028.
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Ce travail a pour objet l'etude de procedes de traitement d'air charge en composes organiques volatils par adsorption-desorption sur des materiaux recents, les tissus de carbone active. Une caracterisation physique des tissus de carbone active montre que ce sont des materiaux essentiellement microporeux dont les surfaces specifiques sont elevees. Le comportement electrique de ces tissus est comparable a celui des conducteurs ohmiques classiques. Ainsi, leur chauffage par effet joule direct est envisageable comme mode de regeneration. La valeur de la resistivite electrique depend des parametres d'activation et de l'orientation du tissu. L'echauffement de ces materiaux est en general tres homogene, la distribution des temperature observee par camera infrarouge etant liee a l'heterogeneite du degre d'activation. Des donnees cinetiques et d'equilibre sont generees en reacteur discontinu. Les resultats montrent que les vitesses de transfert gaz-solide sont tres elevees, et les capacites d'adsorption importantes. La faisabilite des cycles adsorption-desorption pour des temperatures de regeneration peu elevees est demontree. La presentation sous forme de tissu permet de concevoir des adsorbeurs originaux. Ainsi des modules cylindriques plisses sont dimensionnes et utilises dans une unite pilote. L'aerodynamique de ces systemes est etudiee par la mesure des pertes de charge. Un outil de simulation numerique de l'ecoulement au travers de tels systemes est utilise pour predire les pertes de charge dans des configurations complexes et permet d'acceder au champ des pressions statiques et des vitesses. Les bonnes performances en adsorption et en desorption de ces reacteurs sont etudiees en fonction des conditions operatoires. Quelques exemples d'utilisation des tissus de carbone active dans des applications industrielles de traitement d'air sont presentees, et montrent la faisabilite du developpement industriel de tels procedes.
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Blalock, Timothy Daniel. "Biochemical characterization and action of connective tissue growth factor and its receptor in corneal scarring." [Gainesville, Fla.] : University of Florida, 2003. http://purl.fcla.edu/fcla/etd/UFE0001161.
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Porri, Aimone [Verfasser], and George [Akademischer Betreuer] Coupland. "Tissue specific action of Gibberellin in Arabidopsis flowering and development / Aimone Porri. Gutachter: George Coupland." Köln : Universitäts- und Stadtbibliothek Köln, 2013. http://d-nb.info/1044073543/34.
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Tan, Garry D. "Adipose tissue function in humans : in vivo studies of PPARγ action and of regional adiposity." Thesis, University of Oxford, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.425030.
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Bassi, Anita Kaur. "The use of phosphorous containing polymers to mimic the action of bisphosphonate drugs in bone repair." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/the-use-of-phosphorous-containing-polymers-to-mimic-the-action-of-bisphosphonate-drugs-in-bone-repair(a94df78f-96f1-4279-a99c-72b8636b57bc).html.
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Bone has the capacity to regenerate itself, however for challenging defects such as non-uniform factures, repair can be problematic. A similar challenge is presented in the repair of osteoporotic bone. Osteoporotic bone becomes increasingly porous and brittle and the risk of fracture is greatly increased. A drug mimic, poly(vinyl phosphonic acid – co – acrylic acid)(PVPA), has been incorporated into FDA approved poly(ε-caprolactone)(PCL), and aims to mimic the action of bisphosphonates to reduce the activity of osteoclasts. The PVPA polymer contains pendant phosphonic acid groups which are hypothesised to mimic the P-C-P backbone found in bisphosphonates. The PCL/PVPA scaffold has been found to have sufficient mechanical strength in order to be used as a bone void filler as well as providing a hydrophilic surface for superior cell attachment. The substrate has been found to significantly enhance the deposition of collagen, alkaline phosphatase activity and the expression of osteocalcin. Alizarin red staining revealed an increase in the rate of mineralisation in the presence of the drug mimic. The PCL/PVPA substrates have been suggested to induce osteoblast cells from a proliferative phase to a mineralisation stage. This is believed to be due to the presence of phosphorous within the scaffold which could lead to the critical concentration required for the initiation of mineralisation being reached more rapidly and effectively. The PVPA polymer has been found to mimic the action of bisphosphonates by inducing osteoclast apoptosis in vitro, and its actions of osteoclast apoptosis are comparable to that of Alendronate, a commonly administered bisphosphonate. A critical size defect model has demonstrated that the PVPA polymer has the ability to heal critical size defects; the healing potential was two fold greater than the control PCL substrate. Initial in vivo studies using a subcutaneous model demonstrated an improvement in mineralisation in the presence of PVPA. Untreated PCL/PVPA substrates displayed a high level of branched blood vessel formation, essential for healthy bone formation. However PVPA samples pre-treated with VEGF, hindered blood vessel formation and the infiltration of cells. This suggests that the PVPA alone is capable of inducing neovascularisation without the addition of VEGF. The findings suggest that the PCL/PVPA system could be used to treat challenging bone defects such as non-unions and osteoporotic fractures.
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Chen, Cailin. "Control of the formation and the action of androgens in peripheral tissues." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1996. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq25226.pdf.
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Thyagarajan, Sridevi. "ADRENERGIC STIMULATION IN ACUTE HYPERGLYCEMIA: EFFECTS ON CELLULAR AND TISSUE LEVEL MURINE CARDIAC ELECTROPHYSIOLOGY." UKnowledge, 2018. https://uknowledge.uky.edu/cbme_etds/49.
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Cardiovascular complications associated with elevated levels of glucose in the blood (Hyperglycemia, HG) is a growing health concern. HG is known to be associated with a variety of cardiovascular morbidities including higher incidence of electrical disturbances. Although effects of chronic HG have been widely investigated, electrophysiological effects of acute hyperglycemia are relatively less known. Further, hyperglycemic effects on adrenergic response is not widely investigated. We used excised ventricular tissues from mice to record trans-membrane potentials during a variety of pacing protocols to investigate cellular/tissue level electrophysiological effects of acute hyperglycemia and adrenergic stimulation (1µM Isoproterenol, a β-adrenergic agonist). A custom program was used to compute action potential durations (APD), maximal rates of depolarization (dv/dtmax), and action potential amplitudes (APA) from the recorded trans-membrane potentials. From these computed measures, electrical restitution and alternans threshold were quantified. Restitution was quantified using the Standard Protocol (SP; basic cycle length BCL= 200ms), Dynamic Protocol (DP; 200-40ms or until blockade) and a novel diastolic interval (DI) control protocol with Sinusoidal Changes in DI. Results from 6 mice show that acute hyperglycemia causes prolongation of the APD. Effects of adrenergic stimulation during acute hyperglycemia were partially blunted compared with non-hyperglycemic state, i.e. hyperglycemia minimized the decrease in APD that was produced by adrenergic stimulation. Similar, but less consistent (across animals) effects were seen in other electrophysiological parameters such as alternans threshold. These results show that acute hyperglycemia may itself alter cellular level electrophysiology of myocytes and importantly, modify adrenergic response. These results suggest that in addition to long term re-modeling that occurs in diabetes, acute changes in glucose levels also affect electrical function and further may contribute to systemically observed changes in diabetes by blunting adrenergic response. Therefore, further investigation into the electrophysiological effects of acute changes in glucose levels are warranted.
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Rankin, A. C. "Ionic basis of the negative chronotropic action of adenyl compounds : Radioisotope studies with cardiac pacemaker tissue." Thesis, University of Glasgow, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379302.
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Kennovin, Gordon D. "An investigation into the mechanism of action of nitroprusside on isolated cardiovascular tissues." Thesis, University of St Andrews, 1989. http://hdl.handle.net/10023/14900.
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The effect of photolysis of nitroprusside was investigated in both frog ventricular trabeculae and rabbit ear arterial strips. Unphotolysed nitroprusside failed to elicit any effect on frog ventricular twitch tension. However, upon photolysis it had a potent negative inotropic action. The extent of twitch depression was shown to depend on the degree of photolysis. It was postulated that these effects are due to a labile physiologically active photolytic product. This was positively identified as nitric oxide. Preliminary results of the negative inotropic action of thiols and synthesised nitrosothiols are also presented. In contrast to frog ventricle, intact nitroprusside does exert a relaxing effect on precontracted mammalian smooth muscle. This effect is markedly potentiated by photolysis. It is concluded that the mechanism of action of nitroprusside on both tissues involves the release of nitric oxide which is postulated to activate guanylate cyclase. This suggests that mammalian vascular smooth muscle has a mechanism for degrading nitroprusside which is absent in frog ventricle.
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Lundholm, Lovisa. "Molecular mechanisms of estrogen action in relation to metabolic disease /." Stockholm, 2007. http://diss.kib.ki.se/2007/978-91-7357-392-4/.
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Björnholm, Marie. "Molecular mechanisms of insulin action in human skeletal muscle and adipose tissue : implications for diabetes and obesity /." Stockholm, 2002. http://diss.kib.ki.se/2002/91-7349-245-0.
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Cerino, Cordova Felipe de Jesus. "Utilisation de tissu carbone activé biologiquement modifié par A. Ferrooxidans dans des procédés biologique et bioélectrochimique." Grenoble INPG, 2003. http://www.theses.fr/2003INPG0066.
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La faisabilité d'employer des Tissus de Carbone Activé (TCA, marque PICA) comme cathodes biologiquement modifiées dans un réacteur bioélectrochimique de récupération métallique (Cd2+) a été étudiée. La sorption de la bactérie Acidithiobacillus ferrooxidans (souches BRGM et DSM583) est régie par le modèle de Langmuir. Cette sorption biologique diminue les capacités de fixation du cadmium sur le tissu de carbone activé. Lors de réduction électrochimique, le meilleur taux de conversion (17 %) est obtenu en utilisant le tissu WKL20 modifié par 3,8 mg protéine (BRGM). G C-1, mais avec un rendement faradique faible. Les TCA possèdent une faible activité oxydante des ions ferreux, respectivement 17,71 et 35,41 mg Fe2+ oxydé. L-1. H-1 pour les tissus WKL20 et WWP3. La formation d'un biofilm stable sur les TCA composé de A. Ferrooxidans e t de jarosite augmente sensiblement l'oxydation des ions ferreux en ions ferrique 600 mg Fe2+ oxydé. L-1. H-1.
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Brooks, Nicole E. "Fibroblast Growth Factor 21 Expression in Mice with Altered Growth Hormone Action: Links to Obesity, Type 2 Diabetes Mellitus, and Increased Longevity." Ohio University Honors Tutorial College / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ouhonors1461161246.
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FERRY, ANTRAS JOCELYNE. "Regulation hormonale de l'expression des genes de structure, fibronectine et actine, et des genes lies a la differenciation terminale dans les adipocytes de la lignee 3t3-f442a." Paris 11, 1991. http://www.theses.fr/1991PA115007.
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Ketcha, Wanda Germain Jean Magloire. "Characterisation of oestrogenic properties of Isoflavones derived from Millettia griffoniana Baill.: - Molecular mode of action and tissue selectivity." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2006. http://nbn-resolving.de/urn:nbn:de:swb:14-1154000965292-60098.
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Six isoflavones derived from Millettia griffoniana namely, 4’-methoxy-7-O-[(E)-3-methyl-7hydroxymethyl-2,6 octadienyl]isoflavone (7-O-DHF), Griffonianone C (Griff C), 7-O-geranylformononetin (7-O-GF), 3’,4’-dihydroxy-7-O-[(E)-3,7-dimethyl-2,6-octadienyl]isoflavone (7-O-GISO), Griffonianone E (Griff E), 4’-O-geranylisoliquiritigenin (4-O-GIQ) were tested for potential oestrogenic activities in three different oestrogen receptor alpha (ERα) dependent assays, namely a recombinant yeast assay, a reporter gene assay based on stably transfected MCF-7 cells (MVLN cells) and the induction of alkaline phosphatase in Ishikawa cells. The oestrogenic activities of isoflavones from Millettia griffoniana could be completely suppressed by the pure oestrogen antagonist, fulvestrant. The expression of Ki-67, proliferating cell nuclear antigen (PCNA) and cyclin D1 (CD1) mRNA used as indicator of cell proliferation in MCF-7 cells was assayed. Based on these in vitro results, Griff C was further tested in vivo. The main objective of this part of the work was to study the mechanistic basis of the oestrogenicity Three different doses of Griff C (2, 10, or 20 mg/kg BW) of Griff C in ovariectomised Wistar rats. 17β-oestradiol (E2: 10 µg/kg BW) was used as positive control. They were treated daily for three consecutive days and sacrificed 24 hours after receiving the last dose. The whole uterus was removed and weight. Liver and vena cava fragments were also collected and stored together with uteri in liquid nitrogen for subsequent real-time PCR to evaluate the effects of Griff C on the regulation of some relevant oestrogen–responsive genes in the uterus, the liver and the vena cava. The role of Griff C in apoptosis or in cell survival, through mediation of the phosphatidylinositol 3 kinase-Akt (PI3K-Akt) signaling pathway, was also investigated. Western blot analysis revealed that Griff C slightly increased the phosphorylation of Akt at its serine 473 residue. In this work, oestrogenic properties of the isoflavones derived from Millettia griffoniana are described using reporter gene assays and the oestrogen-inducible alkaline phosphatase Ishikawa model for the first time. These in vitro data were verified in vivo showing the regulation of the expression of various relevant oestrogen-responsive genes by Griff C. The spectrum of its activity was clearly similar to that of 17β-oestradiol on uterine hepatic and vena cava tissues of ovariectomised rats except for the proliferative response. However Griff C remained 100 to 1000 times less effective than oestradiol. These findings confirmed that some of the biological effects attributed to Millettia griffoniana are closely related to oestrogen-mediated action.
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Chang, Eugene Tze-Yeng. "Towards understanding the electrogram : theaoretical & experimental multiscale modelling of factors affecting action potential propagation in cardiac tissue." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/12792.
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Conduction of electrical excitation in cardiac tissue is mediated by multiple physiological factors. Abnormal conduction may lead to onset of arrhythmia, and is correlated experimentally and clinically with electrogram fractionation. In-silico modelling studies seek to characterise and predict the biophysical phenomena underlying electrical excitation and conduction, and thus inform experiment design, and diagnostic and treatment strategies. Existing models assume syncytial or continuum behaviour, which may not be an accurate assumption in the disease setting. The aim of this thesis is to correlate simple theoretical and experimental models of abnormal cardiac conduction, and investigate the limits of validity of the theoretical models under critical parameter choices. An experimental model of 1D continuum conduction is established in guinea pig pap- illary muscle to examine the relationship between mean tissue resistivity and electrical conduction velocity (CV). The relationship is compared with a monodomain tissue model coupled with the Luo Rudy I (LR1) guinea pig ventricular action potential, which obeys classical cable theory of conduction under pharmacological modulation. An experimental model of 1D discrete conduction is created via development of a micro-patterned culture model of the HL-1 atrial myocyte cell line on micro-electrode arrays, which has a lower baseline conduction velocity compared to conventional cardiomyocyte models. A novel 1D bidomain model of conduction of discrete cells coupled by gap junctions is proposed and validated, based on existing analytical and numerical studies, and coupled to the LR1 model. Simulation of slow conduction under modulation of physiological parameters reveal difference in the excitation conduction between continuum and discrete models. Electro- gram fractionation is observed in the discrete model, which may be a more realistic model of conduction in diseased myocardium. This work highlights possibilities and challenges in comparing and validating theoretical models with data from experiments, and the im- portance of choosing the appropriate modelling assumptions for the specific physiological question.
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Mehra, Anupriya. "NMDA receptor of the blood brain barrier : mechanism of action and interaction with tPA." Thesis, Normandie, 2017. http://www.theses.fr/2017NORMC404/document.
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La neuroinflammation est un dénominateur commun de plusieurs troubles du système nerveux central. Les réactions inflammatoires sont souvent médiées par plusieurs voies de signalisation qui conduisent à l'ouverture de la barrière hémato-encéphalique. L'activateur tissulaire du plasminogène (tPA) est une serine protéase qui induit l'ouverture de la barrière hémato-encéphalique. Au cours des dernières années, il a également été montré que les récepteurs NMDA situés dans les cellules endothéliales peuvent jouer un rôle crucial dans la propagation de la réaction inflammatoire.Mon travail au cours de ma thèse a mis l'accent sur la découverte des mécanismes par lesquels le récepteur NMDA effectue une médiation de l'ouverture de la barrière hémato-encéphalique induite par le TPA. Dans notre première étude, nous montrons que les récepteurs NMDA endothéliaux sont des cibles thérapeutiques potentielles pour prévenir l'infiltration et l'inflammation des cellules immunitaires médiées par l'EAE. Nous montrons que l'anticorps monoclonal du récepteur NMDA spécifique à la souris, le Glunomab, pourrait protéger la barrière de la moelle épinière de dommages inflammatoires. Nous montrons également que les récepteurs NMDA sont exprimés en étroite association avec les protéines de jonction serrées dans les cellules endothéliales cérébrales. Dans notre deuxième étude, nous montrons pour la première fois que les récepteurs NMDA neuroendothéliaux peuvent présenter une action métabotropique lors de l'inflammation. Nous soulignons également que ces récepteurs sont en effet des récepteurs NMDA non conventionnels exprimant la sous unité GluN3A. En outre, nous rapportons que le tPA accélère l'ouverture de la barrière hémato-encéphalique en présence d'une agoniste rare de la glycine par un mécanisme dépendant de l'activation de RhoA. Les résultats de mon projet apportent une nouvelle vision du rôle des récepteurs NMDA métabotropiques dans les cellules endothéliales cérébrales. En outre, il fournit également des détails plus précis sur l'ouverture de la barrière hémato-encéphalique via l’activateur tissulaire du plasminogèneNeuroinflammation is a common denominator of several central nervous system disorders. Inflammatory reactions are often mediated by several signaling pathways which lead to the opening of the blood brain barrier. Tissue plasminogen activator (tPA) is a serine protease induces opening of the blood brain barrier. In recent years, it has also been shown that NMDA receptors located in endothelial cells can play a crucial role in propagation of inflammatory reaction. My doctoral study focused on the finding the underlying mechanisms of action(s) by which NMDA receptor mediates tPA induced opening of the blood brain barrier. In our first study we show that endothelial NMDA receptors are potential therapeutic targets to prevent EAE mediated immune cell infiltration and inflammation. We show that NMDA receptor specific mouse monoclonal antibody Glunomab could prevent the brain spinal cord barrier from inflammatory damage. We also show that NMDA receptors are expressed in close association of tight junction proteins in cerebral endothelial cells. In our second study, we show for the first time that, neuroendothelial NMDA receptors can exhibit metabotropic mode of action during inflammation. We also highlight that these receptors are indeed GluN3A expressing non-conventional NMDA receptors. In addition, we report that tPA accelerates the opening of blood brain barrier in presence of an uncommon agonist glycine by RhoA activation dependent mechanism.My project results provide a nouvelle insight for the role of metabotropic NMDA receptors in cerebral endothelial cells. In addition it also provides more precise details of blood brain barrier opening mediated by tissue plasminogen activator