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Dissertations / Theses on the topic 'Tissues'
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Moreau, Jodie E. "Stimulation of bone marrow stromal cells in the development of tissue engineered ligaments /." Thesis, Connect to Dissertations & Theses @ Tufts University, 2005.
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Thesis (Ph.D.)--Tufts University, 2005.Adviser: Gregory H. Altman. Submitted to the Dept. of Biology--Biotechnology. Includes bibliographical references (leaves 183-192). Access restricted to members of the Tufts University community. Also available via the World Wide Web;
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Deiuliis, Jeffrey Alan. "The metabolic and molecular regulation of adipose triglyceride lipase." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1185546165.
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Craddock, Russell. "Structural characterisation of aggrecan in cartilaginous tissues and tissue engineered constructs." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/structural-characterisation-of-aggrecan-in-cartilaginous-tissues-and-tissue-engineered-constructs(d1e72d1e-b0ac-4485-9a05-030a5faf8351).html.
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Collagen II and the proteoglycan aggrecan are key extracellular matrix (ECM) proteins in cartilaginous tissues such as the intervertebral disc (IVD). Given the functional role that these structural and functional proteins have in the IVD, ECM in tissue engineered intervertebral disc (TE IVD) constructs needs to recapitulate native tissue. As such, there is a need to understand the structure and mechanical function of these molecules in native tissue to inform TE strategies. The aims here were to characterise aggrecan and collagen II using atomic force microscopy (AFM), size-exclusion chromatography multi angle light scattering (SEC-MALS), histology, quantitative PCR, nanomechanical and computational modelling in: (i) skeletally immature and mature bovine articular cartilage (AC) and nucleus pulposus (NP), (ii) TE IVD constructs cultured in hypoxia or treated with transforming growth factor beta [TGFÎ23] or growth differentiation factor [GDF6]), and (iii) porcine AC and NP tissue. No variation in collagen II structure was observed although the proportion of organised fibrillar collagen varied between tissues. Both intact (containing all three globular domains) and non-intact (fragmented) aggrecan monomers were isolated from both AC and IVD and TE IVD constructs. Mature intact native NP aggrecan was ~60 nm shorter (core protein length) compared to AC. In skeletally mature bovine NP and AC tissue, most aggrecan monomers were fragmented (99% and 95%, respectively) with fragments smaller and more structurally heterogeneous in NP. Similar fragmentation was observed in skeletally immature bovine AC (99.5%), indicating fragmentation occurs developmentally at an early age. Fragmentation was not a result of enhanced gelatinase activity. Aggrecan monomers isolated from notochordal cell rich porcine NP were also highly fragmented, similar to bovine NP. Application of a computational packing model suggested fragmentation may affect porosity and nutrient transfer. The reduced modulus was greater in AC than NP (497 kPa and 76.7 kPa, respectively) with the difference likely due to the organisation and abundance of ECM molecules, rather than individual structure. Growth factors (GDF6 and TGFÎ23), and not oxygen tension treated TE IVD constructs were structurally (with >95% fragmented monomers), histologically and mechanically (GDF6: 60.2 kPa; TGFÎ23; 69.9 kPa) similar to native NP tissue (76.7 kPa) and there was evidence of gelatinase activity. To conclude, these results show that the ultrastructure of intact aggrecan was tissue and cell dependent, and could be modified by manipulation of cell culture conditions, specifically GDF6 which may play a role in aggrecan glycosylation.
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Li, Zhaohui. "Monitoring biological functions of cultured tissues using microdialysis." Thesis, University of Oxford, 2007. http://ora.ox.ac.uk/objects/uuid:f8b478fa-881e-4299-9ee5-b8ee29f37fe9.
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Continuous monitoring during tissue culture is important for the success of engineered tissue development. It is also challenging due to lack of suitable established monitoring techniques. In this study, microdialysis, a sampling technique for measuring the unbound solute concentrations in the tissues and organs of the living body, was adopted to monitor functional tissue growth in a bioreactor with explanted bovine caudal intervertebral discs (IVD) as the test tissue. Apart from cell metabolic activities, cell and tissue biological functions were investigated for the development of microdialysis for monitoring purposes. Methodologies of microdialysis with large pore size membrane probes for sampling macromolecular bio-functional markers were established. The effects of pumping methods, including 'push', 'pull' or 'push-and-pull', and the effect of the resulting transmembrane pressure on the fluid balance, and the relative recovery of small molecules and of macromolecules (proteins) were experimentally studied. The validity of the internal reference in-situ calibration was examined in detail. It was concluded that a push-and-pull system was the only effective method to eliminate fluid loss or gain. The relative recovery of small solutes was hardly affected by the applied pumping methods; however the relative recovery of macromolecules was significantly influenced by them. The in situ calibration technique using Phenol Red can provide reliable results for small molecules including glucose and lactic acid. Using lOkDa and 70kDa fluorescent dextrans as the internal standard for in situ calibration of large molecules of similar size, it was found that the pull pump system did not work well but that the push-and-pull pumping method did work well. A novel bioreactor system for in vitro IVD culture with static load and microdialysis monitoring was developed. Explanted IVDs were cultured under three different loads for up to 7 days. A single microdialysis probe with 3000 kDa membrane was inserted into each of the IVDs at a defined location. The in situ calibration technique was proved valid in the experiments and membrane fouling was not significant. The tissue metabolism and extracellular matrix turnover during 7 day culture were continuously monitored to investigate the effect of different loads. Microdialysis proved to be a feasible and efficient method for multi-parameter monitoring of tissue culture. Substantial effort was directed towards the identification of functional macromolecular markers in conjunction with microdialysis sampling. Amongst several proteins sampled, chitinase-3-like protein 1 (CHI3L1), a major soluble protein secreted by cultured IVD cells in alginate beads and by cultured IVD explants was identified following its successful isolation. Then it was established as a suitable functional marker. The effect of physico-chemical and mechanical stimuli (e.g. osmolarity, pH, oxygen tension and mechanical load) on secretion of CHI3L1 by cultured IVD cells and chondrocytes in alginate beads and by cultured IVD explant were investigated. CHI3L1 release was sensitive to physico-chemical stimulation. The production of CHI3L1 was directly correlated with the cell metabolism and this could be readily monitored with microdialysis.
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Kalcioglu, Zeynep Ilke. "Mechanical behavior of tissue simulants and soft tissues under extreme loading conditions." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/79558.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 157-168).
Recent developments in computer-integrated surgery and in tissue-engineered constructs necessitate advances in experimental and analytical techniques in characterizing properties of mechanically compliant materials such as gels and soft tissues, particularly for small sample volumes. One goal of such developments is to quantitatively predict and mimic tissue deformation due to high rate impact events typical of industrial accidents and ballistic insults. This aim requires advances in mechanical characterization to establish tools and design principles for tissue simulant materials that can recapitulate the mechanical responses of hydrated soft tissues under dynamic contact-loading conditions. Given this motivation, this thesis studies the mechanical properties of compliant synthetic materials developed for tissue scaffold applications and of soft tissues, via modifying an established contact based technique for accurate, small scale characterization under fully hydrated conditions, and addresses some of the challenges in the implementation of this method. Two different engineered material systems composed of physically associating block copolymer gels, and chemically crosslinked networks including a solvent are presented as potential tissue simulants for ballistic applications, and compared directly to soft tissues from murine heart and liver. In addition to conventional quasistatic and dynamic bulk mechanical techniques that study macroscale elastic and viscoelastic properties, new methodologies are developed to study the small scale mechanical response of the aforementioned material systems to concentrated impact loading. The resistance to penetration and the energy dissipative constants are quantified in order to compare the deformation of soft tissues and mechanically optimized simulants, and to identify the underlying mechanisms by which the mechanical response of these tissue simulant candidates are modulated. Finally, given that soft tissues are biphasic in nature, atomic force microscopy enabled load relaxation experiments are utilized to develop approaches to distinguish between poroelastic and viscoelastic regimes, and to study how the anisotropy of the tissue structure affects elastic and transport properties, in order to inform the future design of tissue simulant gels that would mimic soft tissue response.
by Zeynep Ilke Kalcioglu.
Ph.D.
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Carlson, Grady E. "Dynamic Biochemical Tissue Analysis of L-selectin Ligands on Colon Cancer Tissues." Ohio University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1343932605.
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Ueda, Yuichiro. "Application of Tissue Engineering with Xenogenic Cells and Tissues for Regenerative Medicine." 京都大学 (Kyoto University), 2004. http://hdl.handle.net/2433/147657.
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Merkel, Matthias. "From cells to tissues." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-156597.
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An essential prerequisite for the existence of multi-cellular life is the organization of cells into tissues. In this thesis, we theoretically study how large-scale tissue properties can emerge from the collective behavior of individual cells. To this end, we focus on the properties of epithelial tissue, which is one of the major tissue types in animals. We study how rheological properties of epithelia emerge from cellular processes, and we develop a physical description for the dynamics of an epithelial cell polarity. We apply our theoretical studies to observations in the developing wing of the fruit fly, Drosophila melanogaster. In order to study epithelial mechanics, we first develop a geometrical framework that rigorously describes the deformation of two-dimensional cellular networks. Our framework decomposes large-scale deformation into cellular contributions. For instance, we show how large-scale tissue shear decomposes into contributions by cell shape changes and into contributions by different kinds of topological transitions. We apply this framework in order to quantify the time-dependent deformation of the fruit fly wing, and to decompose it into cellular contributions. We also use this framework as a basis to study large-scale rheological properties of epithelia and their dependence on cellular fluctuations. To this end, we represent epithelial tissues by a vertex model, which describes cells as elastic polygons. We extend the vertex model by introducing fluctuations on the cellular scale, and we develop a method to perform perpetual simple shear simulations. Analyzing the steady state of such simple shear simulations, we find that the rheological behavior of vertex model tissue depends on the fluctuation amplitude. For small fluctuation amplitude, it behaves like a plastic material, and for high fluctuation amplitude, it behaves like a visco-elastic fluid. In addition to analyzing mechanical properties, we study the reorientation of an epithelial cell polarity. To this end, we develop a simple hydrodynamic description for polarity reorientation. In particular, we account for polarity reorientation by tissue shear, by another polarity field, and by local polarity alignment. Furthermore, we develop methods to quantify polarity patterns based on microscopical images of the fly wing. We find that our hydrodynamic description does not only account for polarity reorientation in wild type fly wings. Moreover, it is for the first time possible to also account for the observed polarity patterns in a number of genetically altered fliesEine wesentliche Voraussetzung für die Existenz mehrzelligen Lebens ist, dass sich einzelne Zellen sinnvoll zu Geweben ergänzen können. In dieser Dissertation untersuchen wir, wie großskalige Eigenschaften von Geweben aus dem kollektiven Verhalten einzelner Zellen hervorgehen. Dazu konzentrieren wir uns auf Epitheliengewebe, welches eine der Grundgewebearten in Tieren darstellt. Wir stellen theoretische Untersuchungen zu rheologischen Eigenschaften und zu zellulärer Polarität von Epithelien an. Diese theoretischen Untersuchungen vergleichen wir mit experimentellen Beobachtungen am sich entwickelnden Flügel der schwarzbäuchigen Taufliege (Drosophila melanogaster). Um die Mechanik von Epithelien zu untersuchen, entwickeln wir zunächst eine geometrische Beschreibung für die Verformung von zweidimensionalen zellulären Netzwerken. Unsere Beschreibung zerlegt die mittlere Verformung des gesamten Netzwerks in zelluläre Beitrage. Zum Beispiel wird eine Scherverformung des gesamten Netzwerks auf der zellulären Ebene exakt repräsentiert: einerseits durch die Verformung einzelner Zellen und andererseits durch topologische Veränderungen des zellulären Netzwerks. Mit Hilfe dieser Beschreibung quantifizieren wir die Verformung des Fliegenflügels während des Puppenstadiums. Des Weiteren führen wir die Verformung des Flügels auf ihre zellulären Beiträge zurück. Wir nutzen diese Beschreibung auch als Ausgangspunkt, um effektive rheologische Eigenschaften von Epithelien in Abhängigkeit von zellulären Fluktuationen zu untersuchen. Dazu simulieren wir Epithelgewebe mittels eines Vertex Modells, welches einzelne Zellen als elastische Polygone abstrahiert. Wir erweitern dieses Vertex Modell um zelluläre Fluktuationen und um die Möglichkeit, Schersimulationen beliebiger Dauer durchzuführen. Die Analyse des stationären Zustands dieser Simulationen ergibt plastisches Verhalten bei kleiner Fluktuationsamplitude und visko-elastisches Verhalten bei großer Fluktuationsamplitude. Neben mechanischen Eigenschaften untersuchen wir auch die Umorientierung einer Zellpolarität in Epithelien. Dazu entwickeln wir eine einfache hydrodynamische Beschreibung für die Umorientierung eines Polaritätsfeldes. Wir berücksichtigen dabei insbesondere Effekte durch Scherung, durch ein anderes Polaritätsfeld und durch einen lokalen Gleichrichtungseffekt. Um unsere theoretische Beschreibung mit experimentellen Daten zu vergleichen, entwickeln wir Methoden um Polaritätsmuster im Fliegenflügel zu quantifizieren. Schließlich stellen wir fest, dass unsere hydrodynamische Beschreibung in der Tat beobachtete Polaritätsmuster reproduziert. Das gilt nicht nur im Wildtypen, sondern auch in genetisch veränderten Tieren
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Musson, David. "Adrenomedullin in dental tissues." Thesis, University of Birmingham, 2010. http://etheses.bham.ac.uk//id/eprint/794/.
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Tooth development is complex and dependent on epithelial-mesenchymal interactions involving key molecular signalling pathways. Preliminary data indicate that the pleiotropic growth factor adrenomedullin (ADM) is expressed during tooth development. Furthermore, in osteoblasts, cells which share structural and functional similarities to odontoblasts, ADM increases proliferation in vitro and can promote mineralised bone volume and strength in vivo. Immunohistochemical analysis of ADM demonstrated expression during key stages in tooth development in particular in cells responsible for signalling odontoblast differentiation and subsequently in secretory odontoblasts. Similarities with the temporo-spatial expression profile of TGF-β1 were also observed. In vitro analysis using the developmentally derived dental cell lines, MDPC-23 and OD-21, demonstrated ADM stimulated a biphasic response in dental cell numbers with peak stimulation at 10-11M and that it stimulated mineral deposition at levels comparable to that of the known mineralising agent dexamethasone. Analysis of tooth tissue volume and key mandibular measurements in Swiss mice systemically treated with ADM using techniques including micro-Computer Tomography did not identify significant differences in craniofacial mineralised tissue structures compared to sham treated controls. The data presented here along with the known pleiotropic properties of ADM indicate it may be an important regulator of tooth development particularly in the processes of cell proliferation, differentiation and mineralisation. However, in adult animals systemic ADM supplementation appears to have limited affect on mandibular bone and dentine synthesis.
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Rosahl, Agnes Lioba. "How tissues tell time." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2015. http://dx.doi.org/10.18452/17113.
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Durch ihren Einfluß auf die Genexpression reguliert die zirkadiane Uhr physiologische Funktionen vieler Organe. Obwohl der zugrundeliegende allgemeine Uhrmechanismus gut untersucht ist, bestehen noch viele Unklarheiten über die gewebespezifische Regulation zirkadianer Gene. Neben ihrer gemeinsamen 24-h-Periode im Expressionsmuster unterscheiden diese sich darin, zu welcher Tageszeit sie am höchsten exprimiert sind und in welchem Gewebe sie oszillieren. Mittels Überrepräsentationsanalyse lassen sich Bindungsstellen von Transkriptionsfaktoren identifizieren, die an der Regulation ähnlich exprimierter Gene beteiligt sind. Um diese Methode auf zirkadiane Gene anzuwenden, ist es nötig, Untergruppen ähnlich exprimierter Gene genau zu definieren und Vergleichsgene passend auszuwählen. Eine hierarchische Methode zur Kontrolle der FDR hilft, aus der daraus entstehenden Menge vieler Untergruppenvergleiche signifikante Ergebnisse zu filtern. Basierend auf mit Microarrays gemessenen Zeitreihen wurde durch Promotoranalyse die gewebespezifische Regulation von zirkadianen Genen zweier Zelltypen in Mäusen untersucht. Bindungsstellen der Transkriptionsfaktoren CLOCK:BMAL1, NF-Y und CREB fanden sich in beiden überrepräsentiert. Diesen verwandte Transkriptionsfaktoren mit spezifischen Komplexierungsdomänen binden mit unterschiedlicher Stärke an Motivvarianten und arrangieren dabei Interaktionen mit gewebespezifischeren Regulatoren (z.B. HOX, GATA, FORKHEAD, REL, IRF, ETS Regulatoren und nukleare Rezeptoren). Vermutlich beeinflußt dies den Zeitablauf der Komplexbildung am Promotor zum Transkriptionsstart und daher auch gewebespezifische Transkriptionsmuster. In dieser Hinsicht sind der Gehalt an Guanin (G) und Cytosin (C) sowie deren CpG-Dinukleotiden wichtige Promotoreigenschaften, welche die Interaktionswahrscheinlichkeit von Transkriptionsfaktoren steuern. Grund ist, daß die Affinitäten, mit denen Regulatoren zu Promotoren hingezogen werden, von diesen Sequenzeigenschaften abhängen.A circadian clock in peripheral tissues regulates physiological functions through gene expression timing. However, despite the common and well studied core clock mechanism, understanding of tissue-specific regulation of circadian genes is marginal. Overrepresentation analysis is a tool to detect transcription factor binding sites that might play a role in the regulation of co-expressed genes. To apply it to circadian genes that do share a period of about 24 hours, but differ otherwise in peak phase timing and tissue-specificity of their oscillation, clear definition of co-expressed gene subgroups as well as the appropriate choice of background genes are important prerequisites. In this setting of multiple subgroup comparisons, a hierarchical method for false discovery control reveals significant findings. Based on two microarray time series in mouse macrophages and liver cells, tissue-specific regulation of circadian genes in these cell types is investigated by promoter analysis. Binding sites for CLOCK:BMAL1, NF-Y and CREB transcription factors are among the common top candidates of overrepresented motifs. Related transcription factors of BHLH and BZIP families with specific complexation domains bind to motif variants with differing strengths, thereby arranging interactions with more tissue-specific regulators (e.g. HOX, GATA, FORKHEAD, REL, IRF, ETS regulators and nuclear receptors). Presumably, this influences the timing of pre-initiation complexes and hence tissue-specific transcription patterns. In this respect, the content of guanine (G) and cytosine (C) bases as well as CpG dinucleotides are important promoter properties directing the interaction probability of regulators, because affinities with which transcription factors are attracted to promoters depend on these sequence characteristics.
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Cristea, Anca. "Ultrasound tissue characterization using speckle statistics." Thesis, Lyon 1, 2015. http://www.theses.fr/2015LYO10329.
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L'objectif de la caractérisation des tissus par ultrasons ou ‘Quantitative Ultrasound (QUS)’ est de différencier les tissus pathologiques en associant les paramètres d’un modèle aux caractéristiques physiques du tissu. L'usage exclusif des ultrasons pour obtenir un diagnostic peut garantir que le patient ne subira pas une procédure invasive (e.g. une biopsie), utilisant des rayonnements ionisants (e.g. la tomographie) ou même inconfortable et coûteuse (e.g. IRM). Les méthodes de QUS extraient des informations sur la microstructure du tissu à partir du contenu spectral ou temporel des signaux ultrasonores. Le signal temporel radiofréquence (RF) et son enveloppe sont d'intérêt à cause du speckle crée par l’interférence des ondes, qui peut être modélisé par des distributions statistiques. Ce travail propose d'explorer la possibilité d'obtenir des estimations QUS fiables en utilisant des distributions statistiques comme modèles pour le speckle ultrasonore. Les estimations sont constituées des paramètres des distributions respectives et dépendent de la densité de diffuseurs dans le milieu. L’évaluation s’effectue sur des images simulées, des fantômes de particules et des biofantômes. Dans la première partie, la distribution Gaussienne Généralisée est utilisée pour modéliser le signal RF, et la distribution de Nakagami est utilisée pour modéliser son enveloppe. Les deux distributions sont limitées à discriminer les milieux avec une faible densité de diffuseurs, parce que les valeurs de leurs paramètres de forme saturent pour un speckle pleinement développé. Par conséquent, puisque la formation du speckle pleinement développé dépend de la résolution du système d'imagerie, la caractérisation peut se faire seulement à de très hautes résolutions, correspondant à des hautes fréquences qui ne sont pas communes en échographie clinique. Une application du modèle de Nakagami sur l’image crée par la seconde harmonique montre le potentiel du paramètre de forme de Nakagami en tant que mesure de la nonlinéarité du milieu. Dans la deuxième partie, l'enveloppe a été modélisée en utilisant la distribution K-Homodyne. Le paramètre de regroupement des diffuseurs α permet de discriminer entre les milieux denses jusqu’à une limite supérieure à celle du paramètre de Nakagami. Pourtant, cette limite est difficile à estimer avec précision, parce que les valeurs caractéristiques pour le speckle pleinement développé sont affectées par un biais et une variance élevés. Le biais et la variance peuvent être améliorés en augmentant la quantité de données utilisée pour l’estimation. Dans la dernière partie, une technique de déconvolution spécialement conçue pour la caractérisation des tissus a été évaluée. Des essais exhaustifs ont montré qu’elle n’est pas suffisamment robuste pour une application clinique, puisque les images déconvoluées ne sont pas fidèles à la réflectivité originale du milieuThe purpose of ultrasound tissue characterization or Quantitative Ultrasound (QUS) is to differentiate between tissue pathologies by associating model parameters to physical tissue features. The exclusive use of ultrasound for diagnosis would guarantee that the patient does not undergo a procedure that is invasive (e.g. a biopsy), using ionizing radiation (e.g. tomography) or simply uncomfortable and expensive (e.g. MRI). QUS methods extract information on the tissue microstructure from the temporal or spectral content of the acquired ultrasound signals. The temporal radiofrequency (RF) signal and its envelope are of interest because of the speckle patterns created by wave interference, which can be modeled by statistical distributions. The present work proposes to explore the possibility of obtaining reliable QUS estimates by using statistical distributions as models for ultrasound speckle. The estimates consist in the parameters of the respective distributions and are indicators of the scatterer density in the medium. The evaluation is conducted on simulated images, particle phantoms and biophantoms. In the first part, the Generalized Gaussian distribution is used to model the RF signal, and the Nakagami distribution is used to model its envelope. The two distributions show limitations in discriminating media with high scatterer densities, as the values of their shape parameters saturate in the fully developed speckle regime. Therefore, since the formation of fully developed speckle depends on the resolution of the imaging system, characterization can be done only at very high resolutions, corresponding to high frequencies that are not common in clinical ultrasound. An application of the Nakagami model on the second harmonic image shows the potential of the Nakagami shape parameter as a measure of the nonlinearity of the medium. In the second part, the echo envelope was modeled using the Homodyned-K distribution. The scatterer clustering parameter α allows the discrimination of dense media up to a concentration that is higher than the one that limits the Nakagami distribution. However, this limit is difficult to estimate precisely, because the values of α that are characteristic for fully developed speckle suffer from large estimation bias and variance. The bias and the variance can be improved by performing the estimation on a very large amount of data. In the final part, a deconvolution technique designed specifically for ultrasound tissue characterization has been analyzed. Extensive testing has shown it to not be sufficiently robust for clinical applications, since the deconvolved images are not reliable in terms of fidelity to the original reflectivity of the medium
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Lipworth, Wendy. "Reconfiguring tissue banking consent through enrichment of a restricted debate." Connect to full text, 2005. http://hdl.handle.net/2123/683.
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Thesis (M. Sc.)--University of Sydney, 2005.Title from title screen (viewed 21 May 2008). Submitted in fulfilment of the requirements for the degree of Master of Science to the Unit for the History and Philosophy of Science and Centre for Values, Ethics and Law in Medicine. Includes bibliographical references. Also available in print form.
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Wijanto, Florent. "Multiscale mechanics of soft tissues." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLX093.
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Les réseaux de fibre sont une structure omniprésente dans les tissus biologiques, aussi bien au niveau macroscopique, où ils sont l'ingrédient principal des tissus mous, qu'au niveau microscopique, en tant que constituants des structures collagèniques ou du cytosquelette. L'objectif de ce travail de thèse est de proposer un modèle basé sur la microstructure physique des réseaux de fibres afin d'obtenir une compréhension du comportement mécanique des réseaux de fibres biologiques. Le modèle est basé sur une description de fibres glissant les unes par rapport aux autres et interagissant via des ponts qui se comportent comme des ressorts. Ces ponts peuvent s'attacher et se détacher de manière stochastique avec un taux de détachement qui dépend de la force subie. Comparé aux modélisations existantes, notre travail met en jeu une configuration en glissement dynamique des fibres, ainsi que des sites d'attachement discrets ne permettant l'attachement qu'à des endroits localisés de la fibre. Le détachement des ponts est basé sur la diffusion thermique hors d'un puit de potentiel suivant la théorie de Kramers. Cette théorie donne un contexte physique à la dynamique du détachement ainsi qu'une dépendance naturelle du détachement au chargement via l'inclinaison du paysage énergétique par la force de chargement. Le modèle donne deux modes de contrôle du système : un contrôle à vitesse imposée, appelé système dur, et un contrôle à force imposée, appelé système mou. Notre travail permet également de visualiser le comportement du système à travers une simulation stochastique. Les simulations offrent deux algorithmes, chacun adapté à la méthode de contrôle du système, en système dur ou mou et respectant la causalité dans chacun des modes. Les résultats de la simulation sont explorés via la visualisation des données sortantes de la simulation, qui servent de support pour l'investigation paramétrique du comportement du modèle et ancrent l'interprétation physique des résultats. En particulier, l'influence de l'espacement des sites d'attachement du système, un point caractéristique du modèle, est examiné. De même, nous explorons l'effet de chargements complexes (transitoires, cycliques, etc.) qui représentent les chargements physiologiques des tissus fibreuxFibre networks are ubiquitous structures in biological tissues, both at the macroscopic level being the main ingredient in soft tissues and at the microscopic level, as constituents of collagen structures or the cytoskeleton. The goal of this work is to propose a model based on the physical microstructure of fibre networks in order to provide an understanding of the mechanical behaviour of biological fibre networks. The current model starts from fibres sliding with respect to one another and interacting via spring-like cross-bridges. These cross-bridges can attach and detach stochastically with a load-dependent detachment rate. Compared to existing modelling approaches, this work features a dynamic sliding configuration for the interacting fibres and discrete binding sites which permit attachment on localised spaces of the fibre. The detachment of cross-bridges is based on thermal diffusion out of an energy well, following the Kramers rate theory. This theory provides a physical background to the detachment dynamics as well as a natural load dependency in the tilting of the energy landscape by the load force. The model provides two modes by which the depicted system may be driven: an imposed velocity driving, called a hard device and an imposed load driving, called a soft device. The work also provides a way of visualising the behaviour of the model by performing a stochastic simulation. The simulations provided present two algorithms, each tailored to represent the driving of the system, whether in hard or soft device, respecting the causality in each of the driving mode. Simulation results are explored via data visualisation of simulation output. These visualisation serve as an entry point into parametric investigation of the model behaviour and anchor the interpretation of the results into physical systems. In particular, the influence of binding site spacing, one of the key features of the model, is investigated. We also investigate the effects of complex loading paths (transitory, cyclic, etc.) which can be associated to the physiological loadings fibrous tissues
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Yuan, Tai-Yi. "Innovative Methods to Determine Material Properties of Cartilaginous Tissues and Application for Tissue Engineering." Scholarly Repository, 2011. http://scholarlyrepository.miami.edu/oa_dissertations/607.
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Low back pain is one of the major health concerns in the US. It affects up to 80% of the population at some time during their lives. It not only causes discomfort to patients and affects their physical ability but also has a huge economic impact on society. Although the cause of low back pain is still poorly understood, it is implicated that degeneration of the intervertebral disc is the primary factor. Currently, researchers are trying to use tissue engineering approaches to develop new treatments capable of removing the degenerated disk and replacing it with a biological substitute. However, to create such a biological substitute, we need to first understand the structure-function relationship of the tissue. Only when we understand the function of the tissue, can we begin creating biological substitutes. While culturing a biological substitute, we also need methods to determine how the substitute responds to its environment. At present, there are many different types of bioreactors developed for cartilaginous tissues. However, there is a lack of a system that can detect the chemical, electrical and mechanical response noninvasively with control feedback in real-time. It is hard to provide the optimal culture environment to the substitute without knowing its response in real-time. The objective of this dissertation is to develop new methods to investigate the transport property, oxygen consumption rate and mechano-electrochemical and mechanical properties of the tissue. Because cells are responsible for the tissue health, it is necessary to understand how they can obtain nutrients under different environments, e.g. under different loading condition. In addition, with the use of a bioreactor with the capability of detecting the real-time response combined with a feedback control system, we can provide the most favorable conditions for tissue or biological substitutes to grow. The new measurement methods developed in this dissertation can contribute to further understanding the function of the tissue. The methods outlined in this dissertation can also provide new tools for future tissue engineering applications. Moreover, the findings in this dissertation can provide information for developing a more comprehensive theoretical model to elucidate the etiology of disc degeneration.
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Ralfs, Julie D. "The influence of freezing and tissue porosity on the material properties of vegetable tissues." Thesis, University of Reading, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251279.
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Swain, Robin. "Non-invasive biochemical analysis of cells, tissues and tissue constructs with Raman micro-spectroscopy." Thesis, Imperial College London, 2008. http://hdl.handle.net/10044/1/11327.
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Bittig, Thomas. "Morphogenetic signaling in growing tissues." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2008. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1222339699038-97723.
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During the development of multicellular organisms, organs grow to well-defined shapes and sizes. The proper size and patterning of tissues are ensured by signaling molecules as e.g. morphogens. Secreted from a restricted source, morphogens spread into the adjacent target tissue where they form a graded concentration profile. Upon binding of the morphogens to receptors on the cell surfaces, the morphogenetic signal is transduced inside the cell via the phosphorylation of transcription factors, which subsequently regulate the expression of different target genes. Thus, cell fates are determined by the local concentration of such morphogens. In this work, we investigate three key aspects of morphogenetic signaling processes in growing tissues. First, we study the mechanics of tissue growth via cell division and cell death. We examine the rearrangements of cells on large scales and times by developing a continuum theory which describes the growing tissue as an active complex fluid. In our description we include anisotropic stresses generated by oriented cell division, and we show that average cellular trajectories exhibit anisotropic scaling behaviors. Our description is used to study experimentally measured shape changes of the developing wing disk of the fruit fly Drosophila melanogaster. Second, we focus on the spreading of morphogens in growing tissues. We show that the flow field of cell movements due to oriented cell division and cell death causes a drift term in the morphogen transport equation, which captures the stretching and dilution of the concentration profile. Comparing our theoretical results to recent experiments in the Drosophila wing disk, we find that the transport of the morphogen Dpp is mainly intracellular. We moreover show that the decay length of the Dpp gradient increases during development as a result of changing degradation rate and diffusion coefficient, whereas the drift of molecules due to growth is negligible. Thus growth does not affect the decay length of the gradient, but the decay length of the gradient might affect the tissue growth rate as discussed in this work. Finally, we develop a microscopic theoretical description of the intracellular transduction machinery of morphogenetic signals within an individual cell. Our description captures the kinetics of the trafficking of proteins between different cellular compartments in response to receptor-bound signaling molecules. Analyzing experimental data at the Drosophila neuromuscular junction, we show that the morphogenetic signaling is modulated by synaptic signaling via neuronal action potentials.
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Lee, Douglas P. "Glycerolipid metabolism in mammalian tissues." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2002. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/NQ62649.pdf.
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Jang, Lee Jihye. "Glycomic analysis of biological tissues." Thesis, Imperial College London, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.441384.
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Movasaghi, Zanyar. "Spectroscopic Investigation of Cancerous Tissues." Thesis, Queen Mary, University of London, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.509600.
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Lawrence, C. E. "The regeneration of articular tissues." Thesis, Anglia Ruskin University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.380722.
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Changes in the structural organization of cartilage and synovial tissue, or in the macromolecules produced by their cells, alter the properties of the tissues. Elucidation of the changes under controlled experimental conditions could make a significant contribution to the understanding of the pathogenesis of arthritis. To this end a model system has been developed to study proteoglycan and collagen regeneration in porcine articular cartilage and synovial tissue: partially depleted of matrix by exogenous enzyme(s), the tissues were maintained in organ culture, the medium consisting of Dulbecco's modification of Eagle's medium and 15% rabbit serum, and the responses of the chondrocytes and synoviocytes studied biochemically and histologically. Cleavage of proteoglycan core protein in cartilage explants by trypsin, equivalent to the disruption occurring in joint inflammation, induced glycosaminoglycan synthesis. The chondrocytes, particularly of the mid and hypertrophic zones, acquiring a basophilic territorial matrix and eventually an interterritorial matrix, which replaced the ex vivo material. Further damage to collagen by bacterial collagenase induced collagen synthesis, and enhanced glycosaminoglycan synthesis, but hyaluronic acid disruption proved partially inhibitory to recovery, the interterritorial matrix being less basophilic than comparable trypsinized explants. ³⁵SO₄ uptake by depleted explants showed a similar but sustained rate of glycosaminoglycan synthesis compared with untreated explants. The effects of corticosteroids, currently used for the temporary palliation of joint inflammation, on the regeneration processes were studied. The hydrolytic potential of the cultures and the frequency of medium changes had a profound effect on biologically active cortisol levels when cortisol succinate was present. Lower than physiological levels of cortisol (≤2.76 x 10^-7M) promoted glycosaminoglycan synthesis in all disrupted explants except those with cleaved hyaluronic acid chains. During the later stages of culture, in the presence of cortisol, (≤2.76 x 10-7M), the interterritorial glycosaminoglycan concentration increased. Whether collagen fibres were disrupted or not, collagen synthesis was evident, although with pharmacological concentrations of steroid (≤2.76 x 10^-6 M) all synthetic processes were increasingly inhibited. Exogenous trypsin induced extensive resorption of collagen fibres in minced synovial tissue, probably by activation of synovial collagenase. The destruction was partially reduced with trypsin inhibitor or cortisol. In areas of degradation macrophage-like cells accumulated but with early removal of trypsin, despite loss of collagen, fibroblast-like cells accumulated at the base of the explants with synthesized pericellular collagen evident. Collagen release into the medium was measured by an improved hydroxyproline assay designed to reduce interference from serum proteins. Although physiological doses of cortisol (≤2.76 x 10-7 M) enhanced collagen synthesis by, and the development of, the fibroblastic cells, extensive tissue repair was not observed, merely the formation of a cell population in the Millipore membrane. This model of tissue regeneration, remodelling and repair leads to the conclusion that within the arthritic joint the chondrocyte has the potential to rapidly attempt to repair damaged matrix, the extent of synthesis being proportional to the extent and type of matrix disruption. The chondrocyte responds by synthesizing glycosaminoglycans, that aggregate within the matrix, and collagen, with cortisol, at below physiological concentrations, enhancing this regeneration. Synovial tissue did not recover from disruption although the synoviocytes, on reversion to fibroblast-like cells, accumulated new collagen.
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Bromley, M. "Histochemical studies in rheumatoid tissues." Thesis, University of Manchester, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370401.
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Farzaneh, Ali. "Computational morphogenesis of city tissues." Thesis, Open University, 2017. http://oro.open.ac.uk/49302/.
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Scientific discoveries of the 20th century had a profound impact not only on the study of the natural sciences but disciplines worldwide. The studies were rooted in understanding the complex process of organisation, development and evolution in natural systems before attempting to emulate the behaviours in artificial systems, leading to the emergence of new disciplines such as systems theory, complexity science, genetics, developmental and evolutionary biology. The discoveries had a profound impact in understanding the nature of cities as they develop over time. Once considered top-down models in equilibrium, the dynamic qualities of cities could be explained through the study of dynamic complex systems, exhibiting non-deterministic characteristics that over time emerge as organised structures. These characteristics are not exclusive to cities alone; they are inherent to all complex systems. The understanding of cities as complex systems has stimulated a body of research through mathematical and scientific modelling in understanding the behaviour of cities over time. The studies have been strongly focused on the analytical performance of city morphologies and less on the relational qualities of how systems interact to produce functioning spatial configurations. With the rapid rate of urbanisation and the emergence of new cities around the world, the approach to the design of cities remains rooted in static, top-down models. The implications of such models have led to high energy consumption, lack of integration and poor performance. It is a contradiction to consider cities as complex systems but design them as simple systems. The thesis explores principles of complex systems through the study of biological morphogenesis (the formation and development of organisms over time) for their implementation in formalising a design model for the formation, development and evolution of cities. The central contribution of the thesis lies in the computational modelling of cities in three main areas. The first is the co-evolution of networks and block systems towards the generation of differentiated spatial morphologies. Network systems are generated by coupling multi-agent systems and branching systems from the mathematics of natural systems, and the block systems are generated through procedural subdivision and volumetric modelling. The process involves substantial computational coding and the integration of knowledge from outside disciplines including biology, genetics, complexity theory and mathematics. The second is the development of a unified computational model combining morphological, topological and analytical modelling. The integration of the models is contingent on the writing of classes including graph theory, centrality measures and environmental calculations - all classes were written in C#. The third area is the evolutionary modelling of urban systems. The process utilised the open-source evolutionary solver Octopus in evolving solutions. The advantage lay in the populace-based nature of the model in generating differentiated phenotypes - or geometries - as a response to multiple-objectives. The model has been designed to enable the integration of systems of different types. Analytical data can be used as input to influence the model on the types of decisions it can make. The model has also been designed to enable the exploration of multiple design objectives at varying spatial and time scales. A significant part of the design model takes advantage of open source software including the open source language C#. The software have been extensively modified by hard coding. The model is mutable so that others may add new classes and procedures in the future.
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Dudko, Olga K., and George H. Weiss. "Photon diffusion in biological tissues." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-196826.
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The use of laser-based optical techniques for medical imaging is an attractive alternative to other methods that utilize ionizing radiation. Beside being non-carcinogenic, it is non-invasive, the equipment is transportable, and the methodology can be used to examine properties of soft tissue. However, unlike x-ray photons, optical photons generated in the near-infrared suffer significant amounts of scattering by heterogeneous bodies (e.g., organelles) found in biological tissue. Thus, theory is required to interpret experimental data which appear in the form o spatially or temporally varying light patterns on the skin surface. There is a wide range of parameters over which either diffusion theory or the theory of lattice random walks can be called on to translate optical data into medically significant information embodied in optical parameters of the tissue. We discuss several problems in diffusion theory arising in the analysis of optical measurements, for tissues modeled by a semi-infinite or slab geometry, having either isotropic or anisotropic optical parameters. The measured quantities are related to the
intensity of light re-emitted on the tissue surface. A brief discussion is given related to the telegrapher’s equation, which has been suggested as a simple way of incorporating the effects of forward scattering. Mention is made of calculations related to layered media which frequently occur in tissues such as skull and esophagus. Finally, we briefly discuss discrete random walk models for photon migration. These have
recently been used to provide parameters conveying information related to the region interrogated by photons constrained to reappear on skin surface.
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Dudko, Olga K., and George H. Weiss. "Photon diffusion in biological tissues." Diffusion fundamentals 2 (2005) 114, S. 1-21, 2005. https://ul.qucosa.de/id/qucosa%3A14453.
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The use of laser-based optical techniques for medical imaging is an attractive alternative to other methods that utilize ionizing radiation. Beside being non-carcinogenic, it is non-invasive, the equipment is transportable, and the methodology can be used to examine properties of soft tissue. However, unlike x-ray photons, optical photons generated in the near-infrared suffer significant amounts of scattering by heterogeneous bodies (e.g., organelles) found in biological tissue. Thus, theory is required to interpret experimental data which appear in the form o spatially or temporally varying light patterns on the skin surface. There is a wide range of parameters over which either diffusion theory or the theory of lattice random walks can be called on to translate optical data into medically significant information embodied in optical parameters of the tissue. We discuss several problems in diffusion theory arising in the analysis of optical measurements, for tissues modeled by a semi-infinite or slab geometry, having either isotropic or anisotropic optical parameters. The measured quantities are related to the
intensity of light re-emitted on the tissue surface. A brief discussion is given related to the telegrapher’s equation, which has been suggested as a simple way of incorporating the effects of forward scattering. Mention is made of calculations related to layered media which frequently occur in tissues such as skull and esophagus. Finally, we briefly discuss discrete random walk models for photon migration. These have
recently been used to provide parameters conveying information related to the region interrogated by photons constrained to reappear on skin surface.
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Valet, Manon. "Transport properties in biomimetic tissues." Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS397.
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Dans ce travail nous développons un modèle expérimental biomimétique de la communication cellule-cellule. Il s'agit de réseaux de gouttelettes aqueuses baignant dans l'huile et reliées par des bicouches lipidiques ornées de canaux ioniques. Pour produire ces réseaux de gouttelettes, nous développons d'abord une méthode d'impression originale basée sur l'extraction périodique à travers une interface huile/air d'un capillaire dans lequel la phase aqueuse est injectée. Nous incorporons ensuite aux bicouches un canal ionique – l’hémolysine - pour étudier la diffusion d'une sonde fluorescente dans des réseaux nanoporeux 1D par microscopie d’épifluorescence. Nous établissons que le temps de diffusion caractéristique dépend de façon non linéaire de la concentration introduite en nanopores. Nous montrons que nos résultats peuvent être compris par le biais d’une description théorique basée sur les temps de premier passage, dans laquelle les nanopores sont regroupés dans la membrane plutôt qu'isolés. Dans la dernière partie, nous utilisons des réactions cell-free pour exprimer directement dans les gouttelettes l'hémolysine précédemment utilisée ou le canal ionique mécanosensible MscL. Nous avons démontré dans ce cadre l'insertion et la fonctionnalité de l'hémolysine ainsi synthétisée par microscopie confocale et mesures électrophysiologiques. Ces résultats permettront d’entreprendre l'étude des propriétés de transport diffusives dans les réseaux mécanosensibles sous contrainte mécaniqueIn this thesis work, we develop an experimental model biomimetic of cell-cell communication. It consists in networks of aqueous droplets bathing in oil and connected by lipid bilayers decorated with ion channels. To produce these droplet networks, we first develop an original printing method based on the periodic extraction through an oil/air interface of a capillary in which the aqueous phase is injected. When the bilayers are decorated with the ion channel hemolysin, we then study the diffusion of a fluorescent probe in 1D nanoporous networks, using epifluorescence microscopy. We establish that the characteristic diffusion time depends non-linearly on the nanopores concentration. We show that our results are well captured within a first passage time theoretical description, in which nanopores are clustered rather than being independent. In the last part, we use cell-free reactions to express directly within the droplets the previously used hemolysin or the mechanosensitive ion channel MscL. We successfully demonstrate the insertion and functionality of synthesized hemolysin using both confocal microscopy and electrophysiological measurements. These results pave the way to the study of diffusive transport properties in mechanosensitive networks under mechanical stress
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He, Bai-sen. "Osmotic dehydration in plant tissues." Thesis, Aston University, 2005. http://publications.aston.ac.uk/12236/.
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The primary aim of the thesis is to provide a comprehensive investigation of the osmotic dehydration processes in plant tissue. Effort has been concentrated on the modelling for simulating the processes. Two mathematical models for simulating the mass transfer during osmotic dehydration processes in plant tissues are developed and verified using existing experimental data. Both models are based on the mechanism of diffusion and convection of any mobile material that can transport in plant tissues. The mass balance equation for the transport of each constituent is established separately for intracellular and extra-cellular volumes with taking into account the mass transfer across the cell membrane the intracellular and extra-cellular volumes and the shrinkage of the whole tissue. The contribution from turgor pressure is considered in both models. Model two uses Darcy’s law to build the relation between shrinkage velocity and hydrostatic pressure in each volume because the plant tissue can be considered as the porous medium. Moreover, it has been extended to solve the multi-dimensional problems. A lot of efforts have been made to the parameter study and the sensitivity analyses. The parameters investigated including the concentration of the osmotic solution, diffusion coefficient, permeability of the cell membrane, elastic modulus of the cell wall, critical cell volume etc. The models allow us to quantitatively simulate the time evolution of intracellular and extra-cellular volumes as well as the time evolution of concentrations in each cross-section.
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Casas, ferrer Laura. "Microfluidic flow of biomimetic tissues." Thesis, Université de Montpellier (2022-….), 2022. http://www.theses.fr/2022UMONS001.
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Nous avons conçu un prototissu biomimétique comme modèle de tissus cellulaires qui permet d'identifier le rôle individuel des différents constituants cellulaires qui jouent un rôle dans le comportement rhéologique des tissus. L'objectif final est de caractériser le comportement d'écoulement de ce prototissu sous confinement microfluidique. La première partie de la thèse se concentre sur la conception et la synthèse du prototissu à partir de l'assemblage de Vésicules Unilamellaires Géantes (GUVs). Le système ligand-récepteur que nous avons utilisé pour l'assemblage est la paire streptavidine-biotine. Nous avons démontré qu'en modifiant le rapport streptavidine-biotine, le nombre de vésicules en solution et la concentration de biotine dans la membrane des vésicules, il est possible de contrôler la taille des agrégats et la compacité du tissu. Nous avons également modifié la morphologie du tissu biomimétique en changeant la méthode d'incubation, passant ainsi de formes 3D à une structure monocouche 2D. Un autre système d'adhésion basé sur des complémentarités de séquences d’ADN a également été évalué. Il s'est avéré efficace pour contrôler l'adhésion entre les vésicules, et a permis de concevoir des prototissus avec un niveau élevé de compaction. Dans la deuxième partie de la thèse, la rhéologie de ce tissu biomimétique a été testée au moyen d'une configuration microfluidique. Plus précisément, une pression contrôlée a été appliquée et la déformation de l'agrégat lors de son écoulement à travers une constriction a été suivie. Le changement de taille et de forme de l'agrégat a été calculé pour les petits agrégats, ce qui a contribué à élucider la nature de leur comportement élastique. Pour les agrégats plus grands, le mouvement vers l'avant du front de l'agrégat dans une constriction microfluidique en fonction du temps a été mesuré. Il a été possible d'observer un comportement viscoélastique, que nous avons comparé à celui observé dans les tissus épithéliaux. Le modèle de prototissu et les outils que nous avons développés pour caractériser sa rhéologie peuvent être mis en oeuvre à présent pour étudier les propriétés mécaniques des tissus cellulaires en faisant varier ses propriétés clés : l'adhésion entre les cellules individuelles, les propriétés mécaniques du cytosquelette et l'activité cellulaireWe designed a biomimetic prototissue as a model for cellular tissues that allows to identify the individual role of the different cellular constituents that play a role in the rheological behavior of tissues. The final goal is to characterize the flow behavior of this prototissue under microfluidic confinement. The first part of the Thesis focuses on the design and synthesis of the prototissue from the assembly of Giant Unilamellar Vesicles (GUVs). The ligand-receptor system that we used to drive the assembly was provided by the streptavidin-biotin pair. We have demonstrated that by changing the streptavidin-to-biotin ratio, the number of vesicles in solution and the biotin concentration in the vesicle membrane it is possible to tune the size of the aggregates and the compactness of the tissue. We have also been capable of changing the morphology of the biomimetic tissue from 3D-shapes to a 2D-monolayer structure by changing the incubation method. An alternative adhesion system based on DNA tethers was also evaluated. It proved to be effective in tuning the adhesion between vesicles, and was found to allow the design of prototissue with a high level of compaction. In the second part of the Thesis, the rheology of this biomimetic tissue was tested by means of a microfluidic setup. Specifically, a controlled pressure was applied and the deformation of the aggregate as it flowed through a constriction was tracked. The change in the aggregate size and shape was calculated for small aggregates, which contributed to elucidate the nature of their elastic behavior. For larger aggregates, the forward motion of the aggregate front in a microfluidic constriction as a function of time was measured. It was possible to observe a viscoelastic behavior, that we compared to the one observed in soft epithelial tissues. Both the prototissue model and the tools we developed to characterize its rheology can be implemented in the future to investigate cellular tissues mechanical properties varying its key properties: the adhesion between individual cells, the mechanical properties of the cytoskeleton and the cellular activity
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Hossler, Fred E. "Ultrastructure Atlas of Human Tissues." Digital Commons @ East Tennessee State University, 2014. http://amzn.com/1118284534.
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Presents a variety of scanning and transmission electron microscope images of the major systems of the human body. This book looks at the structure and function of tissues at the subcellular and molecular level, an important perspective in understanding and combating diseases.https://dc.etsu.edu/etsu_books/1047/thumbnail.jpg
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Kilaru, Aruna. "Oil Biosynthesis in Nonseed Tissues." Digital Commons @ East Tennessee State University, 2016. https://dc.etsu.edu/etsu-works/4768.
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Lu, Jike Faculty of Medicine UNSW. "Transplantation of nasal olfactory tissues into transected spinal cord of adult rats." Awarded by:University of New South Wales, 2000. http://handle.unsw.edu.au/1959.4/17798.
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Transplants of olfactory ensheathing cells (OECs) from olfactory bulbs have recently been shown to support regrowth and reinnervation of damaged spinal cord, which has led to improved functional recovery. Using complete transection in adult rat, the studies presented in this thesis examine the role of peripherally derived olfactory tissue in promoting axonal regeneration and functional recovery. Chapter One and Two provide the background to the area of spinal cord regeneration and the methods used in this thesis. Chapter Three shows that transplants of OECs from rat olfactory lamina propria (OLP) are able to support axon regrowth in the lesioned spinal cord. The BBB score was significantly higher in experimental rats (5.4???0.84) compared with control animals (1.9???0.33) (P<0.001). These dissociated OECs from OLP can promote axonal regrowth through the lesion. Histological assessment showed that: 1) axons labelled with Fluororuby grew into the injury site in OECs-transplanted rats, with occasional fibres extending into the rostral cord; 2) brainstem neurons in the raphe nucleus were retrogradely labeled with Fluororuby; and 3) serotonergic axons were detectable distal to the lesion in OECs-transplanted rats. No fibres grew into the injured region and no retrograde labeling or serotonergic fibres were seen in control animals. The role of regenerated serotonergic fibres in OECs-transplanted rats is discussed. Chapter Four demonstrates that solid pieces of OLP dissected from the nose can re-establish the continuity of the transected cord and supply the OECs that can migrate to the cord stumps to support the axon regeneration. Experimental rats which received OLP from olfactory mucosa showed significantly greater locomotive recovery (BBB scores: OLP, 5.0???1.9; control, 1.5???0.5, p<0.0001). In animals with OLP transplants, histological analysis indicated that nerve fibres, expressing neurofilament and serotonin were present at the transection site. Locomotive recovery of the hindlimbs occurred, similar to that seen after OECs transplantation. Retrograde labeling of medullary raphe neurons and gigantocellular reticular nucleus occurred following Fluororuby injection in the cord distal to the lesion, further supporting the supraspinal origin of the 5-HT innervation in the present studies. These results indicate that OLP is effective in promoting partial spinal cord repair. Chapter Five examines functional recovery of spinal reflex circuitry, ie., H-reflex excitability using paired stimuli, in OLP-transplanted rats compared with normal and respiratory lamina propria (RLP) transplanted animals. H-reflex amplitude of the conditioned response was significantly reduced in OLP transplanted rats compared to RLP transplanted animals (p< 0.05). Therefore, hindlimb reflex excitability can be modulated by OLP transplants after transection of the spinal cord in adult rats. Chapter Six examines whether functional recovery can occur if transplantation of OLP tissue is delayed by 1 month after the spinal cord transection. The BBB score was significantly higher in experimental rats (4.3???0.8 for OLP) compared with control animals (1.0???0.3, P< 0.001), but recovery was less than after acute transplantation. Asx before, histological assessment of OLP animals showed: a) serotonergic axons were present in the cord below the transection site; b) brainstem raphe nuclei was retrogradely labeled; c) bisbenzimide pre-labeled cells from OLP transplants migrated in host spinal cord. These changes were not seen in control animals. These results indicate that OLP has the ability to promote axonal regeneration in chronically injured cord of adult rats. Chapter Seven compares the results from these three types of intervention. In conclusion, these studies show that peripherally derived OECs or solid pieces of OLP can promote partial spinal cord repair in acute or chronic transection injuries. Such tissue might provide a potential source for autologous grafting in human paraplegia.
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Mukherjee, Indra Neil. "A rational design approach for the cryopreservation of natural and engineered tissues." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/22579.
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Thesis (Ph. D.)--Chemical and Biomolecular Engineering, Georgia Institute of Technology, 2008.Committee Chair: Sambanis, Athanassios; Committee Member: Long, Jr., Robert C.; Committee Member: Ludovice, Peter J.; Committee Member: Prausnitz, Mark R.; Committee Member: Song, Ying C.
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Chan, Kwok-Kwan. "Treatment of tissues by ultrasound hyperthermia and the surgical removal of tissues by ultrasonic vibrator/aspirator." Thesis, University of Aberdeen, 1986. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU367488.
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My thesis is composed of two parts. Ultrasound hyperthermia is emphasised in part i, and surgical removal of tissues by ultrasonic surgical aspirator is emphasized in part ii. A hyperthermia system making use of overlapping five divergent ultrasonic beams has been developed in my studies. The system is microcomputer controlled. Tissue temperatures are monitored every 30 seconds during treatment with thermocouple arrays, and then the computer adjusts the hyperthermia applicator's output to reach and maintain the therapeutic temperature level in the treated volume. One of the features of the hyperthermia applicator design is that not only divergent field pattern is produced by individual transducer, but also ultrasonic beams are pointed to a focal region by the geometry of the applicator. Computer simulations of the field patterns generated by the applicator in nonabsorbing water medium and simulations of temperature distributions in soft tissue model have been done. Both direct visualization of field patterns in ink-water medium by using Sarvazyan method and measurements with thermocouple probe scanning across and along the field in water are consistent with the computer simulations. In-vitro experiments with pieces of meat and computer simulations of temperature distributions show that the hyperthermia system may be useful in cancer therapy. In-vitro experiments have demonstrated that a large volume of tissue at a few centimetres below the surface can be heat up. Animal experiments have also been carried out and the results are described. Effective blood flows and ultrasonic intensity distributions in the treated region have been estimated by using simplified bio-heat transfer equation. Thermal doses to tissue in treatments are also estimated. In addition, adverse effects of ultrasound on normal blood vessel walls are discussed, and the results of scanning electron microscopy of blood vessel walls are presented. In part ii a theoretical model for tissue fragmentation with ultrasonic surgical aspirator has been suggested. The number of cycles of vibrations required for the CUSA to fragment ox-liver is estimated. The calculated value is consistent with the experimental finding in the order of magnitude. A motor-driven vibrator/ aspirator has been developed in my studies. Its rate of removing ox-liver is comparable to that of the CUSA. Advantages and disadvantages of these two probes are discussed.
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Skvortsova, Yulia Alexandrovna Geng M. Lei. "Simulation of tissues for biomedical applications." [Iowa City, Iowa] : University of Iowa, 2009. http://ir.uiowa.edu/etd/436.
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Priestman, David Andrew. "Prolinase and prolidase in human tissues." Thesis, University of Edinburgh, 1987. http://hdl.handle.net/1842/24235.
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Newton, Adam J. H. "Modelling adenosine dynamics in neural tissues." Thesis, University of Warwick, 2015. http://wrap.warwick.ac.uk/81484/.
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The neuromodulator adenosine is involved in both physiological and pathological activity, such as sleep, epilepsy and stroke. However, the complex processes underlying the release, transport and clearance of adenosine from the extracellular space and their interactions are still poorly quantified. In this thesis I develop the �rst detailed model of the dynamics of adenosine in neural tissue, including intracellular and extracellular metabolism, using parameters taken from an extensive search of the literature. This approach also identifies physiological and metabolic parameters that have yet to be experimentally measured. The model provides estimates of the range of influence of adenosine, the distance where the extracellular concentration is greater than that required for half of the maximum inhibition by the dominant type of adenosine receptors in the cortex, and suggests that under physiological conditions the adenosine signal will be highly localised. The model predicts that adenosine concentration profiles are primarily determined by diffusion and that neuronal transport and metabolism are the dominant clearance mechanisms. The model can be used with either experimental or endogenous sources of adenosine, and I apply it to the bath application of adenosine to a tissue slice, (a method used extensively to study the e�ect of adenosine on synaptic transmission). The model is used to predict the effective dose response curve of bath applied adenosine and to compare the effects of transporter blockers. I then turn to the modelling of biosensors, which are used extensively to measure the concentration of various analytes in tissue, including adenosine. Biosensors are often calibrated in a flow injection system with a known concentration of the analyte. Mathematical and computational models are used to compare the response characteristics of biosensors in this free environment with the tortuous environment in which they are used. An estimated correction factor is obtained together with the sensitivity of this factor to the characteristics of the biosensor. This work provides a framework to move from qualitative studies of changes of adenosine in the brain to quantitative analysis of the spatio-temporal dynamics of adenosine signalling and its in uence on networks of neurons.
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Yamamoto, Daniel L. "Adrenergic signaling in insulin-sensitive tissues." Doctoral thesis, Stockholm : Wenner-Gren Institute for Experimental Biology, Stockholm University, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-6668.
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Parker, Ines. "Adrenergic mechanisms in rabbit gingival tissues /." Title page, table of contents, summary and declaration only, 1985. http://web4.library.adelaide.edu.au/theses/09DM/09dmp239.pdf.
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Chan, Yee-loi, and 陳以來. "Nano-mechanical characterization of dental tissues." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B44764480.
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Yang, Teo Heng Jimmy. "Structure-property relationships in biological tissues." Thesis, Heriot-Watt University, 2007. http://hdl.handle.net/10399/90.
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Berry, GearoÌid Paul. "Acoustic poroelasticity imaging of biological tissues." Thesis, Institute of Cancer Research (University Of London), 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.436325.
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Regini, Justyn Wiktor. "Order-disorder phenomena in polyelectrolyte tissues." Thesis, Open University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239688.
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Sandholzer, Michael. "Heat-induced alterations of dental tissues." Thesis, University of Birmingham, 2014. http://etheses.bham.ac.uk//id/eprint/5049/.
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In forensic investigations involving severely burned human remains, dental analysis stands alone as other means of identification are often destroyed. Therefore, the aim of the present work was to investigate the influence of duration of heat exposure and heating regimes regarding the macroscopic, compositional, structural and crystalline alterations of dental tissues. Experiments were carried out using 215 freshly extracted human teeth, exposed to temperatures of 400 to 1000°C. Shrinkage and shape preservation was analysed using micro-CT, whilst crystalline alterations were evaluated with synchrotron-based SAXS/WAXS experiments. The alterations of organic constituents were assessed using TGA and FTIR. Moreover, calibrated digital photographs were used to document and analyse colour alterations. Although dentinal shrinkage was found at 400°C, tooth morphology was well preserved even at 1000°C. Surface colour alterations were linked to the degradation of organic components, and were highly dependent upon the duration of heat exposure and the heating regime, whilst crystalline alterations were less influenced by these factors. The combination of novel analytical approaches enabled the documentation and quantification of heat-induced alterations of dental tissues, providing results that can be used in the forensic identification process and allow an improved estimation of the cremation temperature range based on human dental remains.
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Sebastian, Anil. "Recreating bone marrow tissues in vitro." Thesis, University of Manchester, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.528263.
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Baish, James W., and Rakesh Jain. "Diffusion in tumors and normal tissues." Diffsuion fundamentals 16 (2011) 4, S. 1, 2011. https://ul.qucosa.de/id/qucosa%3A13733.
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Troutman, Mr Eric Christopher. "Hypothermic Machine Perfusion of Composite Tissues." Thesis, Virginia Tech, 2017. http://hdl.handle.net/10919/81272.
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Organ perfusion systems have successfully been applied to solid organ preservation and subsequent transplantation. However, their use in limb preservation for Vascularized Composite Tissue Allotransplantation (VCA) has yet to be thoroughly investigated. This thesis explores the potential for hypothermic machine perfusion in prolonging limb graft viability in a swine forelimb amputation model. The experiment was designed with the right and left forelimbs from the same pig randomly assigned to the treatment and control groups. Eighteen (18) limbs were procured from a local abattoir, vessels cannulated, and an initial flush of a modified phosphate buffered saline (PBS) solution was performed. Half of those limbs, assigned to the treatment group, were then preserved with continuous hypothermic machine perfusion for 12 hours. The perfusate was a PBS solution supplemented with 5% w/v dextrose. The remaining nine limbs, assigned to the control group, were placed into a plastic bag and kept at room temperature (ca. 20oC) for the entire duration of the experiment. Methylene blue was used to verify perfusion throughout limbs. Histopathological analysis revealed the presence of significantly greater deterioration of the perfused limbs compared to control. I concluded that PBS solution is not suitable for extended limb preservation. Inadequate perfusate volume and lack of solution replenishment resulted in metabolic waste build up, accelerating total organ damage. Continued research is needed in order to develop clinically relevant hypothermic machine perfusion devices capable of prolonged limb preservation.Master of Science
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Basan, Markus. "Physics of cellular tissues and cancer." Paris 6, 2010. http://www.theses.fr/2010PA066115.
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Dans cette thèse, nous développons des descriptions théoriques des tissus cellulaires basées sur une modélisation continue ainsi que sur des simulations numériques. Nous formulons un modèle continu de croissance tumorale qui ne dépend que de quelques paramètres macroscopiques effectifs qui peuvent être déterminés expérimentalement. En particulier, nous proposons que chaque tissu se régule in vivo à une pression qui lui est propre - que nous avons appelée pression homéostatique – et que différentes valeurs de cette pression pour différents tissus prédise le résultat de leur compétition en espace confiné. Motivés par ce modèle, nous suggérons que la croissance des métastases soit un processus de nucléation. Cela pourrait expliquer l’inefficacité du processus métastatique, la croissance préférentielle des métastases sur les surfaces des tissus et les membranes, ainsi que la distribution des tailles de métastases observée in vivo. A l’échelle subcellulaire, nous proposons un modèle de réaction-diffusion pour comprendre le rôle des protéines cytoplasmiques -caténine et -caténine dans le processus d'inhibition de contact entre cellules épithéliales. Ce modèle relie des observations expérimentales indépendantes concernant le rôle joué par les proteins cadhérines et caténines dans le phénotype cellulaire épithélial et dans la tumorigenèse. Traitant l'épithélium comme un fluide visqueux, nous trouvons une nouvelle instabilité hydrodynamique qui conduit à la formation protubérances invasives dans le stroma sous-jacent. Nos résultats expliquent pourquoi cette instabilité est plus prononcée dans les tissus avec un plus haut degré de malignité et comment ce processus pourrait éventuellement jouer un rôle dans l'invasion. Finalement, nous étudions les tissus par des simulations de dynamique de particules dissipatives basées sur un modèle mécanistique simple. A l’aide de ces simulations, nous sommes en mesure non seulement de reproduire les résultats obtenus avec des modèles continus, mais nous mesurons également comment le comportement des cellules individuelles influence les propriétés des tissus à grande échelle
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Kolesky, David Barry. "3D Bioprinting of Vascularized Human Tissues." Thesis, Harvard University, 2016. http://nrs.harvard.edu/urn-3:HUL.InstRepos:33493427.
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The ability to manufacture human tissues that replicate the spatial, mechano-chemical, and temporal aspects of biological tissues would enable myriad applications, including drug screening, disease modeling, and tissue repair and regeneration. However, given the complexity of human tissues, this is a daunting challenge. Current biofabrication methods are unable to fully recapitulate the form and function of human tissues, which are composed of multiple cell types, extracellular matrices, and pervasive vasculature.
My Ph.D. thesis focuses on advancing the capabilities of human tissue fabrication. Specifically, we demonstrate a multimaterial bioprinting method capable of producing 1D, 2D, and 3D vascularized tissue constructs by co-printing ECM, cell-laden, and fugitive inks. After these heterogeneous tissue constructs are printed and infilled with ECM, they are cooled to 4˚C to remove the fugitive ink leaving behind a pervasive network that is subsequently lined with endothelial cells. These constructs are ~ 1 mm in thickness and can be sustained for up to 14 days via rocking-based flow through their vasculature. We then created a new extracellular matrix that enabled the fabrication of tissues that exceed 1 cm in thickness that are perfused on a microfluidic chip for long time periods (> 6 weeks). To demonstrate functionality, growth factors are perfused via the vasculature to differentiate stem cells toward an osteogenic lineage in situ. Finally, we created renal proximal tubules (a sub-unit of kidney tissue) by this approach. Specifically, we constructed 3D tubules circumscribed by renal proximal tubule epithelial cells (PTECs). The PTECs form confluent, leak-tight epithelial monolayers that exhibit primary cilia and expresses Na+/K+ ATPase, Aquaporin 1, and K-cadherin. The combination of 3D geometry and on-chip perfusable nature gives rise to enhanced, polarized PTEC phenotypes that develop an enhanced brush border, basement membrane protein deposition, basolateral interdigitations, enhanced cell height, megalin expression, and albumin uptake relative to 2D controls.
In summary, this multimaterial 3D bioprinting platform enables production of engineered human tissue constructs in which multiple cell types and vasculature are programmably placed within extracellular matrices. These 3D tissues may find potential applications in drug screening, disease models, and ultimately, tissue engineering and regenerative medicine.Engineering and Applied Sciences - Engineering Sciences
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Zijp, Jacob Rudolf. "Optical properties of dental hard tissues." [S.l. : [Groningen : s.n.] ; University Library Groningen] [Host], 2001. http://irs.ub.rug.nl/ppn/315857544.
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Baish, James W., and Rakesh Jain. "Diffusion in tumors and normal tissues." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-184556.
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