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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Inertial microfluidic vortex cell sorter

Wang, Xiao 27 May 2016 (has links)
No description available.
32

Fluid Dynamics and Inertial Focusing in Spiral Microchannels for Cell Sorting

Nivedita, Nivedita 03 June 2016 (has links)
No description available.
33

Cellular Sorting of the Dictyostelium discoideum Slug

Flowerday, Erin 07 August 2024 (has links) (PDF)
Dictyostelium discoideum (Dd) cells are amoeba cells that feed on soil or plant leaf matter bacteria. They divide freely in the presence of food. When starved, cell division is ended, and cells transition from unicellular to multicellular organisms initiated by a chemoattractant, cyclic adenosine monophosphate (cAMP). This study intricately examines cellular sorting within the Dd slug, focusing on individual cell dynamics. Represented as oriented ellipsoids, these cells maintain constant volume through a viscoelastic structure. Applying force to specific semi-axes reveals predictable deformations, highlighting the relationship between force and deformation rate. Manipulating damping coefficients and spring constants uncovers insights into cell viscosity and stiffness. Exploring the effects of a cell's active force and cone angle revealed that a cone angle less than 10 degrees or greater than 30 degrees and an active force less than 2N or greater than 6N of the prestalk cells led to unsatisfactory conditions, resulting in insufficiently directed cell movement, and an inability to achieve the desired cell sorting patterns within the slug. This work guides exploring diverse cellular behaviors, advancing the understanding of complex biological phenomena within a concise framework.
34

Purification of human iPSC-derived cells at large scale using microRNA switch and magnetic-activated cell sorting / マイクロRNAスイッチと磁気活性化セルソーティングを利用したヒトiPS細胞由来心筋細胞の大量純化法

Tsujisaka, Yuta 25 March 2024 (has links)
京都大学 / 新制・課程博士 / 博士(医学) / 甲第25177号 / 医博第5063号 / 新制||医||1071(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 川口 義弥, 教授 山中 伸弥, 教授 湊谷 謙司 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM
35

Conception et modélisation pour le contrôle de trajectoire dans les puces microfluidiques : Application au tri cellulaire par diélectrophorèse / Design and modeling for trajectory control in microfluidic chips : Application to cell sorting by dielectrophoresis

Gauthier, Vladimir 18 December 2018 (has links)
Cette thèse propose d'intégrer les principes de la micro-robotique dans un laboratoire sur puce afin d'améliorer les performances du tri cellulaire par diélectrophorèse. Contrôler la trajectoire des cellules dans une puce fluidique en temps réel nécessite de reconcevoir la puce, la modéliser et développer des lois de commande dédiées au contrôle en temps réel. Concernant la conception, cette thèse s’intéresse au compromis existant entre la vitesse de tri et les problématiques de suivi des cellules en temps réel. Une architecture originale basée sur deux plans d’électrodes, sur les faces supérieures et inférieures des canaux, est proposée. Des procédés de fabrication dédiés à cette architecture sont développés. En particulier, la fabrication d'électrodes transparentes et l'assemblage des deux réseaux d'électrodes parallèles sont étudiés. Concernant la modélisation, une formulation analytique du champ électrique découplant variables de commande, termes dépendant de la position de l’objet et termes dépendant uniquement de la géométrie de la puce est proposée afin de calculer rapidement et précisément la force de diélectrophorèse. Une analyse de l'anisotropie des forces de frottement présentes à proximité des électrodes vient compléter la modélisation dynamique du comportement des microparticules, et donne lieu à un modèle compatible avec la commande temps réel, validé expérimentalement sur des objets artificiels. Enfin, un contrôleur basé sur des techniques d’optimisation ainsi qu’un planificateur de trajectoires sont proposés pour le tri de cellules. Un simulateur est développé et met en avant les bonnes performances de tri d’un tel système. L’ensemble de ces méthodes permettront de contrôler la trajectoire de cellules biologiques dans des puces de tri afin d’en améliorer la sélectivité et la rapidité. / This thesis proposes to integrate the principles of micro-robotics in a lab-on-a-chip in order to improve the performance of cell sorting by dielectrophoresis. Controlling the trajectory of cells in a fluidic chip in real time requires redesigning the chip, modeling it and developing control laws dedicated to real-time control. Concerning the design, this thesis is interested in the compromise existing between the speed of sorting and the problems of cell tracking in real time. An original architecture based on two electrode planes, on the upper and lower faces of the channels, is proposed. Manufacturing processes dedicated to this architecture are developed. In particular, the manufacture of transparent electrodes and the assembly of the two parallel electrode arrays are studied. Concerning the modeling, an analytical formulation of the electric field uncoupling control variables, terms depending on the position of the object and terms depending solely on the geometry of the chip is proposed in order to quickly and accurately calculate the dielectrophoresis force. An analysis of the anisotropy of the friction forces present near the electrodes completes the dynamic modeling of the behavior of the microparticles, and gives rise to a model compatible with real-time control, validated experimentally on artificial objects. Finally, a controller based on optimization techniques and a trajectory planner are proposed for cell sorting. A simulator is developed and highlights the good sorting performance of such a system. All of these methods will control the trajectory of biological cells in sorting chips to improve selectivity and speed.
36

Immune responses of the insect Manduca sexta towards the bacterium Photorhabdus luminescens

Millichap, Peter January 2008 (has links)
The Gram-negative bacterium Photorhabdus luminescens is a pathogen of insects. It is able to secrete a variety of toxins and effectors against its host in order to escape its immune defences. The model insect Manduca sexta is able to mount a variety of humoral and cellular responses against pathogen attack. Ultimately these prove ineffective against P. luminescens. The pre-treatment of M. sexta with Escherichia coli provides protection against the pathogenesis of P. luminescens. Here, I use RNA interference and Fluorescence-assisted cell sorting techniques to investigate interactions between pathogen and host to further elucidate the roles of various host factors in mounting the immune response. I also investigate the nutrient requirements of the bacteria for pathogenesis. I show data that peptidoglycan recognition protein (PGRP) is essential for the up-regulation of antimicrobial peptides, an important immune defence. I also show that P. luminescens has a requirement for two types of iron during pathogenesis of M. sexta. And lastly I show that P. luminescens is able to avoid phagocytosis, another important immune defence.
37

A flourescence activated cell sorting strategy for enrichment of adult neural progenitor cells

January 2012 (has links)
The discovery of neural stem cells (NSC) within the adult mammalian brain continues to fuel optimism regarding the ability of potential regenerative medicine applications to provide enhanced functional recovery from brain injuries. The adult NSC population is maintained within a complex microenvironment, referred to as the niche, where a unique cellular and extracellular environment maintains and regulates the NSC population and their progeny, enabling ongoing neurogenesis throughout adulthood. Characterization of how NSC interact with the extracellular environment and other cell subpopulations is an active area of research that will generate fundamental design parameters for biomaterial and tissue engineering strategies for neural tissue repair. A major obstacle to further progress is the lack of access to purified populations of primary NSC, a challenge which became the focus of this thesis. To address this obstacle, experimental methods were developed and optimized for isolating neural stem and progenitor cells (NSPC) from the adult NSC niche with fluorescence activated cell sorting (FACS). These methods were enhanced by the incorporation of a fluorescent reporter mouse driven by the gene Sox2, a neural stem cell associated transcription factor, which allowed NSPC enrichment within the Sox2+ population. The FACS based research approach was further developed to include additional surface antigens allowing isolation of NSPC at over 34% purity. The highly enriched population of NSPC was subjected to vital dye cell cycle analysis leading to the observation that an active and quiescent fraction exists within the NSPC pool that is delineated by β1-integrin expression. Access to enriched primary adult NSPC will lead to more a more accurate understanding of NSC dynamics with implications in fundamental biological research as well as biomaterials and tissue engineering.
38

THE ROLE OF STEM CELL ANTIGEN-1(Sca-1) IN MUSCLE AGING

Richards-Malcolm, Sonia Angela 01 January 2008 (has links)
Muscle aging is associated with a decrease in the number of satellite cells and their progeny, muscle progenitor cells (MPCs) that are available for muscle repair and regeneration. However, there is an increase in non-immuno-hematopoietic cells (CD45 negative) in regenerating muscle from aged mice characterized by high stem cell antigen -1(Sca-1) expression. In aged regenerating muscle, 14.2% of cells are CD45neg Sca-1pos while 7.2% of cells are CD45neg Sca-1pos in young adult muscle. In vitro, CD45neg Sca-1pos cells over express genes associated with fibrosis, potentially controlled by Wnt2. These cells are proliferative, non-myogenic and non-adipogenic, and arise in clonally-derived MPCs cultures from aged mice. Both in vitro and in vivo studies suggest that CD45neg Sca-1pos cells from aged muscle are more susceptible to apoptosis than their MPCs, which may contribute to depletion of the satellite cell pool. Therefore, with age, a subset of MPCs takes on an altered phenotype, which is marked by high Sca-1 expression. This altered phenotype prevents these cells from participating in muscle regeneration or replenishing the satellite cell pool, and instead may contribute to fibrosis in aged muscle.
39

Developing Microfluidic Volume Sensors for Cell Sorting and Cell Growth Monitoring

Riordon, Jason A. 28 April 2014 (has links)
Microfluidics has seen an explosion in growth in the past few years, providing researchers with new and exciting lab-on-chip platforms with which to perform a wide variety of biological and biochemical experiments. In this work, a volume quantification tool is developed, demonstrating the ability to measure the volume of individual cells at high resolution and while enabling microfluidic sample manipulations. Care is taken to maximise measurement sensitivity, range and accuracy, though novel use of buoyancy and dynamically tunable microchannels. This first demonstration of a microfluidic tunable volume sensor meant volume sensing over a much wider range, enabling the detection of ̴ 1 µm3 E.coli that would otherwise go undetected. Software was written that enables pressure-driven flow control on the scale of individual cells, which is used to great success in (a) sorting cells based on size measurement and (b) monitoring the growth of cells. While there are a number of macroscopic techniques capable of sorting cells, microscopic lab-on-chip equivalents have only recently started to emerge. In this work, a label-free, volume sensor operating at high resolution is used in conjunction with pressure-driven flow control to actively extract particle/cell subpopulations. Next, a microfluidic growth monitoring device is demonstrated, whereby a cell is flowed back and forth through a volume sensor. The integration of sieve valves allows cell media to be quickly exchanged. The combination of dynamic trapping and rapid media exchange is an important technological contribution to the field, one that opens the door to studies focusing on cell volumetric response to drugs and environmental stimuli. This technology was designed and fabricated in-house using soft lithography techniques readily available in most biotechnology labs. The main thesis body contains four scientific articles that detail this work (Chapters 2-5), all published in peer-reviewed scientific journals. These are preceded by an introductory chapter which provides an overview to the theory underlying this work, in particular the non-intuitive physics at the microscale and the Coulter principle.
40

Role of EphB receptors in intestinal epithelial cell positioning and colorectal cancer progression

Cortina Duran, Carme 10 September 2009 (has links)
In the intestinal epithelium, Wnt signaling drives the expression of the genes encoding tyrosine kinase receptors EphB2 and EphB3 and represses the expression of their membrane-tethered ligands, ephrin-Bs. Eph-ephrin interactions result in cellular repulsion and are involved in boundary formation. The project of this thesis is to understand the mechanism by which EphB−ephrin-B signals restrict cell positioning of cell types (cell sorting) in the normal intestinal epithelium and suppress colorectal cancer (CRC) progression beyond the earliest stages. We have demonstrated that at the onset of CRC EphB receptors impair the expansion of tumor cells through a mechanism dependent on E-cadherin–mediated adhesion. We show that EphB-mediated compartmentalization restricts the spreading of EphB+ tumor cells into ephrin-B1+ territories in vitro and in vivo. Our results indicate that CRC cells must silence EphB expression to avoid repulsive interactions imposed by normal ephrin-B1+ intestinal cells at the onset of tumorigenesis. We have discovered that cell sorting is the outcome of two integrated mechanisms: cell contraction/repulsion and differential cell adhesion. The latter is the driving force to induce EphB/ephrin-B−mediated cell compartmentalization. We have developed in vitro models to analyze the mechanisms that induce E-cadherin remodeling upon EphB activation. We found RhoA, p120-catenin and the metalloproteinase ADAM10 as downstream effectors of EphB signaling involved in the control of cell sorting in CRC cells. / A l'epiteli intestinal, la ruta de senyalització Wnt indueix l'expressió dels gens que codifiquen per als receptors tirosina kinasa EphB2 i EphB3 i reprimeixen la dels seus lligands transmembrana, efrines de tipus B. Les interaccions Eph-efrina causen repulsió cel·lular i estan implicades en la formació de fronteres entre compartiments. La finalitat d'aquesta tesi és entendre el mecanisme pel qual la senyalització per EphB−efrina-B restringeix el posicionament dels diferents tipus cel·lulars a l'epiteli intestinal normal i suprimeix la progressió del càncer colorectal (CRC) en els primer estadis. Hem demostrat que, a l’inici del CRC, els receptors EphB restringeixen l'expansió de les cèl·lules tumorals a través d'un mecanisme depenent d'adhesió intercel·lular a través d’E-cadherina. En aquest treball es mostra in vitro i in vivo que la compartimentalització mitjançada per la senyalització dels receptors EphB restringeix l’invasió de les cèl·lules tumorals EphB+ als territoris efrina-B+. Aquests resultats indiquen que les cèl·lules de CRC han de silenciar l’expressió d'EphB per evitar les interaccions repulsives imposades per les cèl·lules intestinals normals efrina-B+ circumdants al començament del procés de tumorigènesi. Hem pogut discernir que el reordenament cel·lular per senyals EphB−efrina-B és el resultat de dos mecanismes integrats: la contracció/repulsió intercel·lular i l’adhesió diferencial entre diferents poblacions cel·lulars. Aquesta última és la força principal que condueix a la compartimentalització cel·lular mitjançada per EphB−efrina-B. Hem desenvolupat models in vitro per analitzar els mecanismes que provoquen el remodelament de la E-cadherina sota la senyalització per EphB. Presentem RhoA, p120-catenina i ADAM10 com a efectors de la senyalització de la ruta EphB implicats en el control de la compartimentalització cel·lular en el CRC.

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