Dissertations / Theses: 'Dendrid'

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Tylich, Ondřej. "Elektromigrace tavidlových zbytků na povrchu DPS." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2016. http://www.nusl.cz/ntk/nusl-242134.

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Diploma thesis introduces the problems of electromigration, fluxes and flux residues. It includes a proposal for methods of measuring surface insulation resistance, information about selected types of fluxes and conformal coatings. It focuses on the influence of temperature, humidity. There are applied conductometric method and method of measuring SIR by IPC-25-B. The thesis describes the practical measurement of SIR and ionic contamination of PCB covered with flux and influence of RH, temperature and applied voltage is evaluated and discussed.

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Schippling, Susanne. "Funktionelle Analyse von Dendrin zellbiologische Untersuchungen und Inaktivierung des Dendrin-Gens der Maus /." [S.l.] : [s.n.], 2000. http://deposit.ddb.de/cgi-bin/dokserv?idn=961678046.

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Manubens-Gil, Linus 1989. "Computationl and modeling approaches to multi-scale anatomical description of neuronal circuitry." Doctoral thesis, Universitat Pompeu Fabra, 2018. http://hdl.handle.net/10803/664511.

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During the last century the nervous system has been mainly studied from a reductionistic approach, based on the hypothesis that understanding in depth single neurons or limited neuronal populations would lead to general conclusions on brain function. However, to what extent anatomical details of single neurons can affect the wiring of the networks they form is a largely overlooked question. Intellectual disability provides an excellent opportunity to explore the relevance of fine structural details, because many disorders show specific architectural alterations that correlate with cognitive performance. In this Thesis, I aimed to study how the network topology of neuronal circuits is affected by dendritic architectural features in a mouse model of intellectual disability, namely Down's syndrome, and upon the rewiring effect of pro-cognitive treatment. I did so from three points of view: 1. The exploration of a 2D minimal computational model of cortical layer II/III parameterized by experimental data on dendritic tree architecture of healthy mice and two Down syndrome mouse models 2. The study of within-region morphological variations of hippocampal CA1 pyramidal neurons and their dependency of spatial embedding and cellularity in healthy mice and a Down syndrome mouse model. 3. The development of an experimental and computational framework for whole brain multiscale assessment and reconstruction. My work revealed that the dendritic tree architecture and the distribution of synaptic contacts have significant implications on how optimal single neurons are for information processing efficiency and storage capacity, and that those single-neuron features permeate to the network level, determining the computational capacities of neural ensembles. Also, I found position-dependent neuromorphological inhomogeneities in CA1 pyramids along with variations of neuronal cell density, suggesting that intrinsic properties of CA1 can vary across its extension. Those inhomogeneities were different in healthy and TgDyrk1A mice, possibly affecting emergent functional aspects. In my Thesis I faced challenges to bridge structure and function and to study morphological inhomogeneities at different scale (single cell and cell population). To solve xii those challenges, I developed computational methods for 3D mapping cellular population and dendritic density and assessed their validity. I also developed a computational modeling framework that allows the instantiation of multi-scale biologically realistic networks. Finally, I optimized the CLARITY whole-brain clearing technique and developed a pipeline to apply our population-based analysis and multi-scale modeling methods to the structural interrogation of whole brains, and to study the implications of the neuronal morphospace on the topology of neuronal circuitry.
Durant l’últim segle, el sistema nerviós s’ha estudiat des d’un punt de vista reduccionista, basant-se en la hipòtesi que entendre en profunditat neurones individuals o fraccions petites de poblacions neuronals portaria a conclusions generals sobre la funció del cervell. De totes maneres, fins a quin punt detalls anatòmics de neurones individuals poden afectar la connectivitat de les xarxes que formen, és una qüestió que en gran part s’ha passat per alt. Les discapacitats intel·lectuals proporcionen una oportunitat excel·lent per explorar la rellevància de detalls estructurals, perquè molts trastorns cognitius mostren alteracions arquitectòniques específiques que correlacionen amb habilitats cognitives. En aquesta Tesi, pretenia estudiar com la topologia dels circuits neuronals és afectada per característiques arquitectòniques en un model murí de discapacitat intel·lectual, en concret de síndrome de Down, i per tractaments pro-cognitius amb efectes de remodel·lació de la xarxa. Ho he fet des de tres punts de vista: 1. L’exploració d’un model computacional 2D mínim de la capa cortical II/III parametritzat amb dades experimentals d’arquitectura dendrítica ens els nostres models de síndrome de Down. 2. L’estudi de neurones individuals, la seva diversitat i propietats morfològiques d’escala mesoscòpica en el model murí TgDyrk1A de síndrome de Down. 3. El desenvolupament d’un marc experimental i computacional per a l’estudi del problema des d’una perspectiva multi-escala. La meva feina ha mostrat que l’arquitectura dendrítica i la distribució de contactes sinàptics tenen implicacions significatives en l’optimalitat de neurones individuals per a l’eficiència en el processat d’informació i per a la capacitat d’emmagatzemar memòries, i que aquestes dues quantitats permeen al nivell de xarxa, determinant les capacitats computacionals de conjunts de neurones. També, he trobat variacions neuromorfològiques a CA1 dependents de la posició en neurones piramidals, acompanyades per variacions en densitat cel·lular, apuntat que propietats intrínseques de CA1 poden variar al llarg de la seva extensió. Aquestes inhomogeneitats eren diferents en ratolins sans i TgDyrk1A, possiblement tenint efectes en aspectes funcionals emergents concrets. xiv En la meva Tesi he afrontat reptes en lligar estructura i funció i en l’estudi de les inhomogeneïtats morfològiques en múltiples escales (de cèl·lula individual i de poblacions). Per a assolir aquests reptes, he desenvolupat mètodes computacionals per al mapejat 3D de poblacions cel·lulars i de densitats dendrítiques i he avaluat la seva validesa. També he desenvolupat un marc de modelització que permet l’instanciació multi-escala de xarxes neuronals biològicament realistes. Finalment, he optimitzat la tècnica de clarejat de cervell sencer CLARITY i he desenvolupat un pipeline per a aplicar les nostres eines d’anàlisi de poblacions i els mètodes multi-escala de model·lizatió per a l’anàlisi estructural de cervells sencers, i per a l’estudi de les implicacions del morfoespai neuronal en la topologia de la circuiteria neuronal.

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Bjørnstad, Pedersen Lars. "An analysis of a shared mating in V2." Thesis, Umeå universitet, Institutionen för fysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-96855.

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In this master thesis we investigate, from a topological point of view and without applying Thurston´s Theorem, why the mating of the so called basilica polynomial $f_{-1}(z)=z^{2}-1$ and the dendrite $f_{i}(z)=z^{2}+i$ is shared with the mating of $f_{-1}$ and the dendrite $f_{-i}(z)=z^{2}-i$ . Both these matings equal the rational map $R_{3}(z)=\frac{3}{z^{2}+2z}$ . Defined in the thesis are for both matings homeomorphic changes of coordinates $\psi_{-1}^{\pm}$ from the set $L=\overset{\circ}{K}\left(f_{-1} \right)\cup\left(\cup_{n=0}^{\infty}f_{-1}^{\circ(-n)}(z_{\alpha})\right)$ to the Fatou and Julia set of $R_{3}$ . Here $K\left(f_{-1} \right)$ is the filled Julia set of $f_{-1}$ and $z_{\alpha}$ is the $\alpha$ -fixed point of $K\left(f_{-1} \right)$ .
I detta examensarbete undersöker vi, från en topologisk synvinkel och utan applicering av Thurstons teorem, varför matchningen av det så kallade basilikapolynomet $f_{-1}(z)=z^{2}-1$ och dendriten $f_{i}(z)=z^{2}+i$ är delad med matchningen av $f_{-1}$ och dendriten $f_{-i}(z)=z^{2}-i$ . Båda dessa matchningar är lika med den rationella avbildningen $R_{3}(z)=\frac{3}{z^{2}+2z}$ . Definierat i examensarbetet är för båda matchningarna homoemorfa koordinatbyten $\psi_{-1}^{\pm}$ från mängden $L=\overset{\circ}{K}\left(f_{-1} \right)\cup\left(\cup_{n=0}^{\infty}f_{-1}^{\circ(-n)}(z_{\alpha})\right)$ till Fatou- och Juliamängden av $R_{3}$ . Här är $K\left(f_{-1} \right)$ den ifyllda Juliamängden av avbildningen $f_{-1}$ och $z_{\alpha}$ är den $\alpha$ -fixerade punkten i $K\left(f_{-1} \right)$ .

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Gräler, Markus. "Der G-Protein-gekoppelte Rezeptor EDG6." [S.l. : s.n.], 2000. http://www.diss.fu-berlin.de/2001/6/index.html.

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Evers, Jan Felix. "The role of dendritic filopodia in postembryonic remodelling of dendritic architecture." [S.l. : s.n.], 2005. http://www.diss.fu-berlin.de/2005/153/index.html.

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Saunders, Kate Marie. "Silurian dendroid graptolites : taxonomy, palaeoecology and biostratigraphy." Thesis, University of Portsmouth, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343388.

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8

Arendt, Oliver. "Untersuchungen zur diffusiblen Mobilität kalziumbindender Proteine in Dendriten von Nervenzellen." Leipzig Leipziger Univ.-Verl, 2009. http://d-nb.info/998768014/04.

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9

Sunseri, Erin Hannah. "Dendrite orientation in aluminum magnesium alloys." [Ames, Iowa : Iowa State University], 2009.

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Hilscher, Markus Michael. "Synchronization by Distal Dendrite-targeting Interneurons." PROGRAMA DE P?S-GRADUA??O EM NEUROCI?NCIAS, 2016. https://repositorio.ufrn.br/jspui/handle/123456789/24680.

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A sincroniza??o neuronal surge de uma intera??o cooperativa de v?rios tipos celulares atrav?s de excita??o e inibi??o. Os mecanismos por tr?s desse tipo de coordena??o neuronal s?o, provavelmente, os mais din?micos entre as fun??es cerebrais, dificultando sua compreens?o. Entre os fatores que dificultam o estudo da sincronia, pode-se citar: o vasto n?mero de tipos de celulares, a diversidade de processos sin?pticos, a contribui??o de uma multiplicidade de canais e correntes i?nicas, entre outros. Essa tese tem como objetivo entender o papel de interneur?nios que especificamente inervam o dom?nio distal dos dendritos de c?lulas piramidais do hipocampo e neoc?rtex, na sincroniza??o de neur?nios em suas respectivas redes. A distribui??o de canais i?nicos e receptors sin?pticos em dendritos de c?lulas piramidais ? extremamente anisotr?pica. Assim, interneur?nios que inervam dom?nios proximais e distais dos dendritos causam efeitos distintos na c?lula alvo quando ativados. Por exemplo, por??es distais dos dendritos cont?m em abund?ncia um dos principais canais marcapassos em neur?nios: o canal regulado por nucleot?deo c?clico ativado por hiperpolariza??o. Esses canais produzem uma corrente cati?nica despolarizante (Ih) e tem um papel importante na regula??o da excitabilidade neuronal alterando dramaticamente as propriedades de disparo de neur?nios. Usando modelagem computacional, essa tese mostra como a amplitude de Ih em certos tipos celulares muda a taxa de disparo de um neur?nio, sua sincronia al?m da energia espectral e frequ?ncia de oscila??es. Al?m disso, como a express?o de Ih difere entre regi?es cerebrais, localiza??o e tipos celulares, essa tese, fazendo o uso de patch clamp, explora como Ih difere ao longo do eixo dorsoventral do hipocampo em c?lulas oriens-lacunosum moleculare (OLM), que s?o os principais interneur?nios que inervam dendritos distais dessa regi?o. Ademais, estudou-se aqui as c?lulas Martinotti, interneur?nios que inervam os dendritos distais do neoc?rtex. Nesse estudo, mostrou-se como uma popula??o definida de interneur?nios pode ser manipulada com o objetivo de controlar e coordenar o disparo de c?lulas piramidais. Ao fornecer inibi??o com energia e frequ?ncia adequada, as c?lulas Martinotti afetam especificamente um ?nico tipo de c?lula piramidal. Usando optogen?tica para ativar/desativar popula??es de c?lulas Martinotti, ? poss?vel gerar potenciais de a??o rebote em c?lulas piramidais quando alinhadas temporalmente. Os potenciais de a??o rebote, por sua vez, s?o resultado de uma forte inibi??o produzida pelas c?lulas Martinotti, o que faz com que esses esses interneur?nios possam resetar o disparo de c?lulas piramidais. De forma geral, c?lulas Martinotti e c?lulas OLM mostram similaridades surpreendentes em propriedades morfol?gicas, neuroqu?micas e eletrofisiol?gicas. Especialmente, suas longas proje??es axonais para camadas superiores assim como seus modos de disparo lentos, com baixos limiares e acomodativos tornam esses neur?nios singulares em suas capacidades de sincronizar os circuitos nos quais est?o inseridos.
Synchronization among neurons arises from the cooperative interaction of various cell types through excitation and inhibition. The mechanisms behind this type of neuronal orchestration are as versatile as almost no other coordination task in the brain, making its comprehension heavily challenging. Among many others, the high number of involved cell types, the diversity of synaptic processes as well as the contribution of a multitude of ion channels and currents span the plurality of neuronal synchronization mechanisms in our brains. Focusing on two brain areas, the hippocampus and the neocortex, this thesis aims to understand the role of distal dendritetargeting interneurons in shaping pyramidal cell activity and the timing of their action potentials. The distribution of ion channels and synaptic receptors in pyramidal cell dendrites is extremely anisotropic. Thus, interneurons innervating the proximal or distal areas of the dendrites cause different effects in the target cell when activated. For example, the distal portions of the pyramidal cell dendrites contain one of the most prominent pacemaker channels: the hyperpolarizationactivated cyclic nucleotide-gated channels. These channels produce a cationic depolarizing current (Ih) and play an essential role in the regulation of neuronal excitability. Using computational modeling, this thesis shows how the amount of Ih in certain cell types determines their spike rate, synchrony as well as power and frequency of ongoing network oscillations. Moreover, since Ih differs between brain regions as well as cell types and location, this thesis electrophysiologically explores how Ih differs along the dorsoventral axis of hippocampus in oriens-lacunosum moleculare (OLM) cells, the main distal dendrite-targeting interneurons of that region. Utilizing the main distal dendrite-targeting interneuron of the neocortex, the Martinotti cell, this thesis also shows how a defined population of interneurons can be manipulated in order to control and align pyramidal cell firing. By providing the right amount and frequency of inhibition, Martinotti cells are able to synchronize trains of subtype-specific pyramidal cells. Using optogenetic approaches to activate/inactivate populations of Martinotti cells, these dendrite-targeting interneurons are shown to trigger rebound action potentials in pyramidal cells when temporally aligned. The rebound action potentials in turn are the result of strong inhibition by Martinotti cells, giving these distal dendrite-targeting interneurons the power to reset pyramidal cell firing. Overall, Martinotti cells and OLM cells show quite striking similarities in morphological, neurochemical and electrophysiological properties. Especially, their long axonal projections to upper layers as well as their low-threshold, slow spiking fashion and the accommodating firing make these distal dendrite-targeting interneurons so special for neuronal synchronization.

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Le, Roux Peter David. "Neuron-glial interactions in dendrite growth." Doctoral thesis, University of Cape Town, 1995. http://hdl.handle.net/11427/27039.

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Interactions between neurons and glia occupy a central role in many aspects of development, maintenance, and function of the central nervous system (CNS). A fundamental event in CNS development is the elaboration of two distinct neuronal processes, axons and dendrites. The overall aim of this research was to characterize the interactions between central nervous system neurons and astroglial cells that regulate dendrite growth from cerebral cortical neurons. Embryonic (E18) mouse cerebral cortical neurons were cocultured with early postnatal (P4) rat astroglia derived from cerebral cortex, retina, olfactory bulb, mesencephalon, striatum and spinal cord. Axon and dendrite outgrowth from isolated neurons was quantified using morphological and double-labeling immunohistochemical techniques at 18 hours and 1, 3 and 5 days in vitro. Neurons initially extended the same number of neurites, regardless of the source of glial monolayer; however, astroglial cells differed in their ability to maintain primary dendrites. Homotypic cortical astroglia maintained the greatest number of primary dendrites. Astroglia derived from the olfactory bulb and retina maintained intermediate numbers of dendrites, whereas only a small number of primary dendrites were maintained by astroglia derived from striatum, spinal cord or mesencephalon. Initially longer axons were observed from neurons grown on astroglia that did not maintain dendrite number. After 5 days in vitro, axon growth was similar on the various monolayers, total primary dendrite outgrowth, however, was nearly threefold greater on astroglia derived from the cortex, retina and olfactory bulb than on astroglia derived from mesencephalon, striatum or spinal cord. This effect was principally on the number of primary dendrites rather than the elongation of individual dendrites and was independent of neuron survival. Similar morphological differences were observed after 5 days in vitro when cortical neurons were grown on polylysine in either a noncontact coculture system where astroglia continuously conditioned the culture medium or in astroglial conditioned medium. Preliminary biochemical analysis of the medium conditioned by cortical astroglia using heat and trypsin degradation, ultracentrifugation, dialysis, and heparin affinity chromatography suggested that a heparin binding protein with a molecular weight between 10 and 100kDa may be responsible for astroglial mediated dendrite growth. Neurons that were grown in medium conditioned by either mesencephalic or cortical astroglia for the first 24 hours followed by culture medium from astroglia of the alternate source for 4 days in vitro, confirmed that astroglia maintained, rather than initiated, the outgrowth of the primary dendritic arbor. In the next series of experiments, E18 mouse cortical neurons were cocultured with neonatal (P4) or mature (P12) rat astroglia derived from cortex and mesencephalon or astroglia derived from P4 and P12 lesioned cortex. After 5 days in vitro, the maturational age of astroglia did not appear to alter the extent of primary dendrite growth; instead dendrite growth reflected the region of the CNS from which the astroglia were derived. By contrast, a reduced ability to support axon growth from mouse cortical neurons in culture was observed on astroglia derived from mature rat cortex or mesencephalon. Reactive astroglia demonstrated similar neurite supporting characteristics to mature astroglia and were able to maintain dendrite growth, principally primary dendrite number. Axon elongation, however, was reduced on both neonatal and mature reactive astroglia. Neuron survival did not correlate with the ability of the various astroglia to support process outgrowth. Collectively these results indicate: 1) neuron-glial interactions are critical for the regulation of process outgrowth from embryonic cortical neurons in vitro, 2) axon and dendrite growth appear to be differently controlled by astroglia, 3) CNS astroglia demonstrate regional differences in maintaining, but not initiating growth of the primary dendritic arbor, 4) this effect may be due, in part, to release of a diffusible heparin binding protein factor, and 5) mature and reactive astroglia support primary dendrite, but limited axon growth. We propose therefore that the local astroglial environment maintains primary dendrite growth from neurons until synaptic contacts can be established. A mechanism that maintains the primary dendritic arbor and allows separate regulation of axon and dendrite growth, prior to the arrival of afferents, may be critical for establishing appropriate and specific synaptic connections. These findings have important implications in understanding development and function of the mammalian central nervous system and may lead to novel strategies for intervention in acute and chronic neurological disorders.

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Paolucci, Clara. "Role of nitric oxide in the maturation process of human dendric cells." Thesis, Open University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.273309.

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Fetter, Ingmar. "Der Einfluß von Botulinumneurotoxin A auf Wachstum und Differenzierung primär dissoziierter hippocampaler Zellkulturen." Doctoral thesis, Humboldt-Universität zu Berlin, Medizinische Fakultät - Universitätsklinikum Charité, 1999. http://dx.doi.org/10.18452/14488.

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Obwohl die Struktur und das Ausmaß dendritischer Verzweigungen eine wichtige Rolle bei der Informationsübertragung neuronaler Zellen spielen, ist bislang wenig über die Bausteine und Molekularmechanismen des Dendritenwachstums bekannt. Unter der Verwendung primär dissoziierter hippocampaler Zellkulturen embryonaler Mäuse untersuchte ich frühe Stadien des Zellfortsatzwachstums. Dabei konnte ich SNAP-25 (synaptosomal associated protein of 25 kDA), ein Schlüsselprotein der regulierten Exozytose, nicht nur in Axonen und terminalen Axonendigungen, sondern auch anhand von Doppelimmunmarkierungen mit den dendritischen Markern Transferrin-Rezeptor und MAP-2 in Dendriten lokalisieren. Die spezifische Inaktivierung von SNAP-25 durch Botulinumneurotoxin A (BoNT/A) führte zur Hemmung des Axonwachstums und des Vesikelrecyclings in terminalen Axonendigungen. Darüberhinaus wurde auch das Wachstum dendritischer Fortsätze von Körner- und Pyramidenzellen durch BoNT/A signifikant gehemmt. Daraus läßt sich schließen, daß SNAP-25, im Gegensatz zu Synaptobrevin, an konstitutiven Prozessen in den Axonen und Dendriten hippocampaler Neurone beteiligt ist.
Structure and dimension of the dendritic arbor are important determinants of information processing by the nerve cell, but mechanisms and molecules involved in dendritic growth are essentially unknown. I investigated early mechanisms of dendritic growth using mouse fetal hippocampal neurons in primary culture, which form processes during the first week in vitro. I detected a key component of regulated exocytosis, SNAP-25 (synaptosomal associated protein of 25 kDa)., in axons and axonal terminals as well as in dendrites identified by the occurrence of the dendritic markers transferrin receptor and MAP2. Selective inactivation of SNAP-25 by botulinum neurotoxin A (BoNTA) resulted in inhibition of axonal growth and of vesicle recycling in axonal terminals. In addition, dendritic growth of hippocampal pyramidal and granule neurons was significantly inhibited by BoNTA. These observations indicate that SNAP-25, but not synaptobrevin, is involved in constitutive axonal growth and dendrite formation by hippocampal neurons.

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Jäckle, Markus [Verfasser]. "Microscopic factors influencing dendrite growth / Markus Jäckle." Ulm : Universität Ulm, 2020. http://d-nb.info/1222595966/34.

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Vestberg, Robert. "Dendron decorated chromophores for optical power limiting applications." Doctoral thesis, Stockholm, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-78.

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Evans, Rowan. "Reproduction of the unitary, larviparous ascidian Dendroda grossularia." Thesis, University of Liverpool, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260360.

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Harry, Katherine Joann. "Lithium dendrite growth through solid polymer electrolyte membranes." Thesis, University of California, Berkeley, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10150902.

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The next generation of rechargeable batteries must have significantly improved gravimetric and volumetric energy densities while maintaining a long cycle life and a low risk of catastrophic failure. Replacing the conventional graphite anode in a lithium ion battery with lithium foil increases the theoretical energy density of the battery by more than 40%. Furthermore, there is significant interest within the scientific community on new cathode chemistries, like sulfur and air, that presume the use of a lithium metal anode to achieve theoretical energy densities as high as 5217 W˙h/kg. However, lithium metal is highly unstable toward traditional liquid electrolytes like ethylene carbonate and dimethyl carbonate. The solid electrolyte interphase that forms between lithium metal and these liquid electrolytes is brittle which causes a highly irregular current distribution at the anode, resulting in the formation of lithium metal protrusions. Ionic current concentrates at these protrusions leading to the formation of lithium dendrites that propagate through the electrolyte as the battery is charged, causing it to fail by short-circuit. The rapid release of energy during this short-circuit event can result in catastrophic cell failure.

Polymer electrolytes are promising alternatives to traditional liquid electrolytes because they form a stable, elastomeric interface with lithium metal. Additionally, polymer electrolytes are significantly less flammable than their liquid electrolyte counterparts. The prototypical polymer electrolyte is poly(ethylene oxide). Unfortunately, when lithium anodes are used with a poly(ethylene oxide) electrolyte, lithium dendrites still form and cause premature battery failure. Theoretically, an electrolyte with a shear modulus twice that of lithium metal could eliminate the formation of lithium dendrites entirely. While a shear modulus of this magnitude is difficult to achieve with polymer electrolytes, we can greatly enhance the modulus of our electrolytes by covalently bonding the rubbery poly(ethylene oxide) to a glassy polystyrene chain. The block copolymer phase separates into a lamellar morphology yielding co-continuous nanoscale domains of poly(ethylene oxide), for ionic conduction, and polystyrene, for mechanical rigidity. On the macroscale, the electrolyte membrane is a tough free-standing film, while on the nanoscale, ions are transported through the liquid-like poly(ethylene oxide) domains.

Little is known about the formation of lithium dendrites from stiff polymer electrolyte membranes given the experimental challenges associated with imaging lithium metal. The objective of this dissertation is to strengthen our understanding of the influence of the electrolyte modulus on the formation and growth of lithium dendrites from lithium metal anodes. This understanding will help us design electrolytes that have the potential to more fully suppress the formation of dendrites yielding high energy density batteries that operate safely and have a long cycle life.

Synchrotron hard X-ray microtomography was used to non-destructively image the interior of lithium-polymer-lithium symmetric cells cycled to various stages of life. These experiments showed that in the early stages of lithium dendrite development, the bulk of the dendritic structure was inside of the lithium electrode. Furthermore, impurity particles were found at the base of the lithium dendrites. The portion of the lithium dendrite protruding into the electrolyte increased as the cell approached the end of life. This imaging technique allowed for the first glimpse at the portion of lithium dendrites that resides inside of the lithium electrode.

After finding a robust technique to study the formation and growth of lithium dendrites, a series of experiments were performed to elucidate the influence of the electrolyte’s modulus on the formation of lithium dendrites. Typically, electrochemical cells using a polystyrene – block¬ – poly(ethylene oxide) copolymer electrolyte are operated at 90 °C which is above the melting point of poly(ethylene oxide) and below the glass transition temperature of polystyrene. In these experiments, the formation of dendrites in cells operated at temperatures ranging from 90 °C to 120 °C were compared. The glass transition temperature of polystyrene (107 °C) is included in this range resulting in a large change in electrolyte modulus over a relatively small temperature window. The X-ray microtomography experiments showed that as the polymer electrolyte shifted from a glassy state to a rubbery state, the portion of the lithium dendrite buried inside of the lithium metal electrode decreased. These images coupled with electrochemical characterization and rheological measurements shed light on the factors that influence dendrite growth through electrolytes with viscoelastic mechanical properties. (Abstract shortened by ProQuest.)

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McLachlan, Ian Gordon. "Genetic control of dendrite morphogenesis in C. elegans." Thesis, Harvard University, 2016. http://nrs.harvard.edu/urn-3:HUL.InstRepos:33493511.

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The shapes and attachments of cells determine the machinery of organs; for example, the shapes and attachments of neurons and glia establish the wiring of the brain. To understand how neuronal dendrites obtain their morphologies and make the appropriate connections, we used C. elegans sense organs as models. Previous work identified a requirement for the extracellular matrix protein DYF-7 in dendrite extension: DYF-7 anchors dendrites dendrite endings at the embryonic nose while neuronal cell bodies migrate away, and in its absence, dendrites fail to extend. Here, we show that these dendrites are part of a sensory epithelium composed of glial cells and neurons. The dendrites are ensheathed by glial cells, form adherens junctions onto glia, and are stabilized at their apical surfaces by the extracellular matrix protein DYF-7. In dyf-7 mutants, the pulling force of cell migration causes this sensory epithelium to rupture along the glia:glia junctions. By comparison, dendrites of the URX and BAG neurons are intimately connected to the external surface of glial cells but are not known to form adherens junctions and are not affected in dyf-7 mutants. To identify factors required for URX and BAG dendrite extension, we performed forward genetic screens for dendrite extension defects in these cells and identified mutations in the cytoplasmic protein GRDN-1/Girdin and the adhesion molecule SAX-7/L1CAM. We show that in wild-type embryos, URX and BAG dendrites also extend by attaching to the nose and then stretching during embryo elongation but, in grdn-1 embryos, they fail to remain attached. GRDN-1 can promote dendrite attachment by acting in glia—it localizes to glial endings and causes localized accumulation of SAX-7, creating an adhesive compartment where dendrites attach. Thus, GRDN-1 and SAX-7 determine dendrite length by positioning a neuron-glia attachment site that couples dendrite extension to embryonic growth. Finally, we identified several other mutants with URX dendrite morphogenesis defects, including overgrowth of the URX dendrite; some have been mapped to genes associated with the cytoskeleton. Together, these studies define genetic mechanisms that control morphogenesis of distinct classes of sensory dendrites through specific adhesive interactions with their glial neighbors.
Medical Sciences

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Shirata, Naritoshi. "Glomerulosclerosis Induced by Deficiency of Membrane-Associated Guanylate Kinase Inverted 2 in Kidney Podocytes." Kyoto University, 2018. http://hdl.handle.net/2433/232451.

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Grillaud, Maxime. "Design and synthesis of multifunctional adamantane-based dendrons for biological applications." Thesis, Strasbourg, 2014. http://www.theses.fr/2014STRAF021.

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Les polymères synthétiques tels que les dendrons ou les dendrimères possèdent des propriétés structurales intéressantes. Leur monodispersité et leur synthèse étape par étape permet de contrôler et de caractériser totalement leur structure. De plus, la multivalence offre aux vecteurs une meilleure affinité d’interactions entre plusieurs copies d’un ligand lié au dendron/dendrimère et le récepteur désiré en comparaison au ligand seul. L’adamantane est une molécule rigide et stable dont plusieurs dérivés ont été commercialisés pour des applications thérapeutiques, principalement comme agents antiviraux. De plus, il est possible de le fonctionnaliser sur 4 positions symétriques via des synthèses organiques. Sa conformation 3D permet d’amoindrir les encombrements stériques entre les groupements fonctionnels. Nous avons alors choisi de combiner les propriétés de l’adamantane et des dendrons afin de construire de nouveaux vecteurs synthétiques. Leurs synthèses s’effectuent avec de hauts rendements et chaque nouveau composé a été totalement caractérisé par les différentes techniques d’analyses chimiques et structurales. Les dendrons à base d’adamantane polycationiques non cytotoxiques ont révélé une forte pénétration cellulaire permettant de mieux comprendre les mécanismes d’internalisation des dendrons. Ils ont également été évalués pour la formation de complexes avec un plasmide d’ADN. Des modifications sur leurs structures ont amélioré leur capacité à interagir avec l’acide nucléique grâce à la modification du point focal. Enfin, un peptide thérapeutique aux propriétés protectrices dans le lupus érythémateux disséminé, P140, a été couplé à un dendron à base d’adamantane à 3 branches et nous avons analysé les effets biologiques du trimère en comparaison avec le monomère
Dendrons (wedge-shaped dendrimer sections) have been investigated as ideal nanoscale carrier molecules for the delivery of bioactive materials into the cells. Molecular engineering of these hyperbranched, monodisperse, well-defined structures can be easily performed using simple organic synthesis. Multivalency constituted by the multiple surface groups at the periphery of a dendron promotes higher binding affinity for ligand/receptor interactions. Adamantane molecule is a rigid structure consisting of four cyclohexane rings fused in chair conformation. The well-defined 3D conformation, the hydrophobicity and the lipophilicity provide to adamantane-based compounds favorable properties for their transport through biological membranes. In this context, the first part of this work was focused on the design and the synthesis of a novel type of polycationic dendrons based on adamantane, which are able to penetrate into cells without triggering cytotoxic effects. The next study of this Thesis concerned the investigation of our polycationic adamantane-based dendrons for gene delivery. We evaluated the capacity of the dendrons to complex a plasmid DNA. Hydrophobic compounds (biotin and cholesterol) were covalently bound to the focal point of the dendrons via “click” chemistry and the effects of the dendron generation, the peripheral cationic groups, and the hydrophobic modifications on the formation and stability of the complexes were studied. Finally, the dendrons constituted of an adamantane core, a focal point and three arms, were synthetized starting from a multifunctional adamantane derivative. We have coupled P140, a therapeutic peptide with protective properties in systemic lupus erythematosus, to an adamantane-based dendron and we have analyzed the biological effects of the resulting trimer compared to the monomer

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Stainton, Neil McVean. "The preparation and properties of dendric and hyperbranched polyesters and their blends with PET." Thesis, Durham University, 1994. http://etheses.dur.ac.uk/1703/.

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Conroy, Devin Thomas. "Chemically reacting plumes, gas hydrate dissociation and dendrite solidification." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2008. http://wwwlib.umi.com/cr/ucsd/fullcit?p3291498.

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Thesis (Ph. D.)--University of California, San Diego, 2008.
Title from first page of PDF file (viewed March 17, 2008). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 199-205).

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Chilton, R. Anthony. "Experiental study and modelling of the cell-dendrite transition." Thesis, University of Oxford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249265.

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Huttunen, Tomi. "Imažinist Mariengof dendi, montaž, ciniki /." Helsinki : University of Helsinki, 2007. http://urn.fi/URN:ISBN:978-952-10-4432-8.

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25

Shi, Ri Yi. "Neuronal Survival After Dendrite Amputation: Investigation of Injury Current Blockage." Thesis, University of North Texas, 1988. https://digital.library.unt.edu/ark:/67531/metadc501278/.

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After dendrite transection, two primary injury current pathways may acount for cell death: (1) the lesion current at the site of injury and (2) the voltage sensitive calcium channels along the dendrite. Lesions were made with a laser microbeam in mouse spinal monolayer cell cultures. Polylysine was tried as a positively charged "molecular bandage" to block the lesion current. The calcium channel blockers, verapamil and nifedipine, were used to reduce the calcium channel current. Control toxicity curves were obtained for all three compounds. The results show that neither verapamil, nifedipine, nor polylysine (MW: 3,300) protect nerve cells after dendrite amputation 100 ptm from the soma. The data also indicate that these compounds do not slow the process of cell death after such physical trauma.

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Maraschky, Adam M. "Experimental and Modeling Studies of Dendrite Initiation during Lithium Electrodeposition." Case Western Reserve University School of Graduate Studies / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=case1590505470067127.

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Rajamure, Ravi Shanker. "Directional Solidification of Al - 7 WT % Si ALLOY RAVI SHANKER RAJAMURE Bachelor of Chemical Engineering Visvesvaraya Technological University April, 2005 Submitted in partial fulfillment of requirements for the degree MASTER OF SCIENCE IN CHEMICAL ENGI." Cleveland State University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=csu1292861453.

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Barreiro, Daniela Pacheco [UNESP]. "Coléteres dendróides em Alibertia sessilis (Vell.) K.Schum.(Rubiaceae)." Universidade Estadual Paulista (UNESP), 2006. http://hdl.handle.net/11449/88137.

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Made available in DSpace on 2014-06-11T19:23:08Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-02-24Bitstream added on 2014-06-13T18:50:24Z : No. of bitstreams: 1 barreiro_dp_me_botib.pdf: 1501640 bytes, checksum: aa250655ae3cef104579c8c1bda9f123 (MD5)
A presença de coléteres na superfície adaxial de órgãos jovens constitui uma característica relevante de Rubiaceae. Alibertia sessilis (Vell.) K. Schum., conhecida como marmelinho ou marmelo-do-cerrado, é uma espécie subarbustiva de Rubiaceae nativa de cerrado e tem grande importância alimentícia e medicinal neste bioma. Os ápices vegetativo e reprodutivo apresentam-se recobertos por uma secreção hialina, de aspecto vítreo e hidrofóbico produzida por coléteres. Neste trabalho foram investigados a distribuição, estrutura, histoquímica e o modo de secreção dos coléteres presentes em ápices vegetativos e reprodutivos desta espécie. Para estudos convencionais, as amostras foram preparadas segundo técnicas usuais em microscopia de luz e microscopia eletrônica de varredura (MEV) e transmissão (MET); técnica especial foi aplicada para dissolução da secreção e observação dos coléteres ao MEV. A técnica do ZIO foi empregada para maior visualização do sistema de endomembranas ao MET. Testes histoquímicos foram feitos em secções de material recém coletado. Coléteres nesta espécie são do tipo dendróide e ocorrem em abundância na face adaxial das estípulas, brácteas e sépalas; consistem de um eixo central multicelular e multisseriado revestido por numerosas células epidérmicas digitiformes ou pontiagudas, de tamanhos irregulares, unidas entre si somente na porção proximal e separadas umas das outras na porção distal. As células colunares são axialmente alongadas e possuem paredes espessas, núcleo conspícuo, citoplasma abundante e vacúolos desenvolvidos. As células epidérmicas possuem paredes delgadas, núcleo conspícuo, citoplasma abundante e vacuoma pouco desenvolvido. Os coléteres, de ambos os ápices, não possuem cutícula. Lipídeos, proteínas e polissacarídeos foram detectados nas células epidérmicas e colunares; compostos...
The presence of colleters in the adaxial surface of young organs constitutes a relevant characteristic of Rubiaceae. Alibertia sessilis (Vell.) K. Schum., known as marmelinho or marmelo-docerrado, is a subshrub native Rubiaceae species of cerrado and it has great nutritious and medicinal importance in this biome. The vegetative and reproductive apices present recovered for a hyaline secretion, of glass aspect and hydrophobic produced by colleters. In this work the distribution, structure, histochemistry and the way of secretion of the colleters present in vegetative and reproductive apices of this species were investigated. For conventional studies, the samples were prepared according to usual techniques in light microscopy and scanning (SEM) and transmission electron microscopy (TEM); special technique was applied for dissolution of the secretion and observation of the colleters to MEV. The technique of ZIO was used for larger visualization of the endomembranes system to MET. Histochemical assays were made in fresh material sections. Colleters in this species are of the dendroid type and occur abundantly in the adaxial surface of the stipules, bracts and sepals; they consist of a multicellular and multiseriate central axis recovered by numerous digitiform or sharp epidermal cells of irregular sizes, joined among themselves only in the proximal portion and separated from each other in the distal portion. The columnar cells are axially elongated and present thick walls, conspicuous nucleus, abundant cytoplasm and developed vacuoles. The epidermal cells present thin walls, conspicuous nucleus, abundant cytoplasm and a few developed vacuome. The coléteres, of both apices, don't present cuticle. Lipids, proteins and polysaccharides were detected in the epidermal and columnar cells; phenolic compounds were only detected in the columnar cells... (Complete abstract click electronic access below)

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29

Zhang, Ye. "The role of the secretory pathway in dendrite and axon development." Diss., Search in ProQuest Dissertations & Theses. UC Only, 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3390087.

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30

Sardana, Juhi. "Differential modes of Eph signaling in olfactory dendrite targeting of Drosophila." Diss., Ludwig-Maximilians-Universität München, 2014. http://nbn-resolving.de/urn:nbn:de:bvb:19-180987.

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Schwenk, Benjamin. "The FTLD risk factor TMEM106B controls lysosomal trafficking and dendrite outgrowth." Diss., Ludwig-Maximilians-Universität München, 2015. http://nbn-resolving.de/urn:nbn:de:bvb:19-181956.

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Frontotemporal dementia is the second most common neurodegenerative disease in people younger than 65 years. Patients suffer from behavioral changes, language deficits and speech impairment. Unfortunately, there is no effective treatment available at the moment. Cytoplasmic inclusions of the DNA/RNA-binding protein TDP-43 are the pathological hallmark in the majority of FTLD cases, which are accordingly classified as FTLD-TDP. Mutations in GRN, the gene coding for the trophic factor progranulin, are responsible for the majority of familiar FTLD-TDP cases. The first genome-wide association study performed for FTLD-TDP led to the identification of risk variants in the so far uncharacterized gene TMEM106B. Initial cell culture studies revealed intracellular localization of TMEM106B protein in lysosomes but its neuronal function remained elusive. Based on these initial findings, I investigated the physiological function of TMEM106B in primary rat neurons during this thesis. I demonstrated that endogenous TMEM106B is localized to late endosomes and lysosomes in primary neurons, too. Notably, knockdown of the protein does neither impair general neuronal viability nor the protein level of FTLD associated proteins, such as GRN or TDP-43. However, shRNA-mediated knockdown of TMEM106B led to a pronounced withering of the dendritic arbor in developing and mature neurons. Moreover, the strong impairment of dendrite outgrowth and maintenance was accompanied by morphological changes and loss of dendritic spines. To gain mechanistic insight into the loss-of-function phenotypes, I searched for coimmunoprecipitating proteins by LC-MS/MS. I specifically identified the microtubule-binding protein MAP6 as interaction partner and was able to validate binding. Strikingly, overexpression of MAP6 in primary neurons phenocopied the TMEM106B knockdown effect on dendrites and loss of MAP6 restored dendritic branching in TMEM106B knockdown neurons, indicating functional interaction of the two proteins. The link between a lysosomal and a microtubule-binding protein made me study the microtubule dependent transport of dendritic lysosomes. Remarkably, live cell imaging studies revealed enhanced movement of dendritic lysosomes towards the soma in neurons devoid of TMEM106B. Again, MAP6 overexpression phenocopied and MAP6 knockdown rescued this effect, strengthening the functional link. The MAP6-independent rescue of dendrite outgrowth by enhancing anterograde lysosomal movement provided additional evidence that dendritic arborization is directly controlled by lysosomal trafficking. From these findings I suggest the following model: TMEM106B and MAP6 together act as a molecular brake for the retrograde transport of dendritic lysosomes. Knockdown of TMEM106B and (the presumably dominant negative) overexpression of MAP6 release this brake and enhance the retrograde movement of lysosomes. Subsequently, the higher protein turnover and the net loss of membranes in distal dendrites may cause the defect in dendrite outgrowth. The findings of this study suggest that lysosomal misrouting in TMEM106B risk allele carrier might further aggravate lysosomal dysfunction seen in patients harboring GRN mutations and thereby contribute to disease progression. Taken together, I discovered the first neuronal function for the FTLD-TDP risk factor TMEM106B: This lysosomal protein acts together with its novel, microtubule-associated binding partner MAP6 as molecular brake for the dendritic transport of lysosomes and thereby controls dendrite growth and maintenance.
Frontotemporale Demenz ist die zweithäufigste Form neurodegenerativer Erkrankungen bei Menschen unter 65 Jahren. Patienten leiden an Verhaltensauffälligkeiten und Sprach- sowie Artikulationsstörungen. Leider steht zurzeit keine wirksame medikamentöse Therapie zur Verfügung. Das pathologische Hauptmerkmal der meisten FTLD-Fälle sind zytoplasmatische Einschlüsse des DNA/RNA-bindenden Proteins TDP-43. Diese Fälle werden entsprechend als FTLD-TDP klassifiziert. Für einen Großteil der familiären FTLD-TDP Fälle sind Mutationen in GRN, dem für den Wachstumsfaktor Progranulin kodierenden Gen, verantwortlich. Die erste für FTLD-TDP durchgeführte genomweite Assoziationsstudie führte zur Entdeckung von genetischen Varianten im bis dato uncharakterisierten Gen TMEM106B. Diese Varianten sind mit einem erhöten Risiko an FTLD zu erkranken assoziiert. Initiale Studien in Zellkultur zeigten eine Lokalisierung des TMEM106B Proteins in Lysosomen, die Frage nach der neuronale Funktion des Proteins blieb allerdings bisher unbeantwortet. Auf diesen ersten Ergebnissen aufbauend untersuchte ich während meiner Dissertation die physiologische Funktion von TMEM106B in primären Ratten-neuronen. Ich konnte zeigen, dass endogenes TMEM106B auch in primären Neuronen in späten Endsosomen und Lysosomen lokalisiert ist. Beachtenswerterweise verminderte die Herunterregulierung (shRNA-vermittelter Gen-Knockdown) des Proteins weder das generelle Überleben der Neuronen noch die Level von anderen FTLD-assoziierten Proteinen, wie GRN oder TDP-43. Die Herunterregulierung von TMEM106B führte jedoch zu einem ausgeprägten Verlust von Dendriten in sich entwickelnden und ausgereiften Neuronen. Des Weiteren war die starke Beeinträchtigung dendritischen Wachstums und Aufrechterhaltung von einer morphologischen Veränderung und dem Verlust der Dornfortsätze begleitet. Um den Mechanismus dieser Phänotypen zu erklären, suchte ich nach TMEM106B coimmunopräzipitierenden Proteinen mittels Massenspektrometrie. Ich konnte das Mikrotubuli bindende Protein MAP6 als spezifischen Bindungspartner identifizieren und die Interaktion beider Proteine validieren. Hervorzuheben ist, dass die Überexpression von MAP6 in primären Neuronen den Effekt der Herunterregulation von TMEM106B auf die Dendriten kopierte und die Herunterregulation von MAP6 die dendritischen Verästelungen in TMEM106B depletierten Neuronen sogar wiederherstellen konnte. Diese Ergebnisse legen eine funktionelle Interaktion beider Proteine nahe. Die Verbindung zwischen einem lysosomalen und einem an die Mikrotubuli bindenden Protein brachte mich dazu, den Mikrotubuli abhängigen Transport von dendritischen Lysosomen zu untersuchen. Bemerkenswerterweise zeigten mittels Lebendzellmikroskopie erzeugte Aufnahmen eine erhöhte Bewegung dendritischer Lysosomen Richtung Zellsoma in TMEM106B depletierten Neuronen. Auch in diesem Kontext konnte die Überexpression von MAP6 den Effekt kopieren und die Herunterregulation von MAP6 den Effekt aufheben und somit die These einer funktionellen Interaktion festigen. Die MAP6 unabhängige Wiederherstellung des dendritischen Wachstums durch die Erhöhung des lysosomalen Transports in anterograder Richtung lieferte einen zusätzlichen Beweis dafür, dass das dendritische Wachstum direkt von lysosomalem Transport abhängt. Ausgehend von diesen Ergebnissen schlage ich folgendes Modell vor: TMEM106B und MAP6 wirken zusammen als molekulare Bremse für den retrograden Transport dendritischer Lysosomen. Die Herunterregulation von TMEM106B und die (wahrscheinlich dominant negative wirkende) Überexpression von MAP6 lösen diese Bremse und verstärken die retrograde Bewegung von Lysosomen. Daraufhin könnten der gestiegene Proteinumsatz und der Verlust von Plasmamembranbestandteilen zu einem Fehler im dendritischen Wachstum führen. Die Ergebnisse dieser Arbeit legen nahe, dass fehlerhafter, lysosomaler Transport in TMEM106B Risikoallelträgern zu einer Verstärkung der lysosomalen Fehlfunktion in Patienten mit GRN Mutation führt und dabei zur Krankheitsentwicklung beiträgt. Zusammengefasst habe ich die erste neuronale Funktion für den FTLD-TDP Risikofaktor TMEM106B entdeckt: Dieses lysosomale Protein wirkt zusammen mit seinem neuentdeckten, Mikrotubuli assoziierten Bindungspartner MAP6 als molekulare Bremse für den dendritischen Transport von Lysosomen und kontrolliert dadurch Wachstum und Aufrechterhaltung von Dendriten.

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Ribeiro, Suzie Jesus. "A study of DNA/Dendron nanoparticles for genetic immunisation against anthrax." Thesis, University College London (University of London), 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.439784.

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Schnepel, Philipp. "Non-linear integration in the apical dendrite of neocortical pyramidal neurons." [S.l. : s.n.], 2008. http://nbn-resolving.de/urn:nbn:de:bsz:25-opus-51023.

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Bryden, Francesca. "Synthesis of water-soluble porphyrin-dendron conjugates for targeted photodynamic therapy." Thesis, University of Hull, 2013. http://hydra.hull.ac.uk/resources/hull:17231.

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The targeting of photosensitisers with tumour-associated biomolecules is widely used for improved photosensitiser tumour localisation during photodynamic therapy, allowing fewer side effects in comparison to conventional cancer treatments. In particular, conjugation to antibody fragments allows exploitation of their high affinity towards tumour-associated antigens; however current methods of conjugating porphyrins to antibody fragments represent a compromise between high binding ratios and good stoichiometric and site-specific control. The work presented herein addresses this problem through the synthesis of porphyrin-dendron conjugates and their attachment at the interchain disulfide bridge of antibody fragments, allowing improved binding ratios while maintaining good structural control. Synthesis of a range of click-functionalised porphyrins and dendrons bearing complimentary peripheral functionalities was carried out, followed by click conjugation of these structures under microwave irradiation to produce a range of lipophilic and hydrophilic porphyrin-dendron conjugates with between two and four peripheral porphyrins. Photophysical evaluation demonstrated retention of UV-vis and fluorescent character of porphyrins after conjugation, with some quenching of UV-vis absorption observed due to the close proximity of the porphyrins. Singlet oxygen quantum yields showed some quenching in all conjugates, with more sterically hindered systems showing the greatest reduction in SOQY in comparison to control porphyrins. Conjugation of porphyrins to a HER2-targeted Herceptin™ Fab fragment was carried out through pre-conjugation of an alkyne-dibromomaleimide heterobifunctional linker to the Fab fragment, with two examples of cationic porphyrins conjugated via a click chemistry strategy to yield conjugates with precise 1:1 stoichiometry. Preliminary cytotoxicity studies of the targeted photosensitisers showed that both conjugates exhibited limited dark toxicity, and excellent cell killing in the HER2+ BT-474 cell line. Successful focal-point deprotection and azide functionalisation was carried out on a single porphyrin-dendron conjugate, with a successful model click reaction to an alkyne-functionalised sugar displaying the possibility of bioconjugation of porphyrindendron conjugates via a click methodology.

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Aniejurengho, Orode Uche Venitia. "Dendron-based synthetic bacteriophages for the treatment of Proteus mirabilis infections." Thesis, University of Brighton, 2016. https://research.brighton.ac.uk/en/studentTheses/0aa0ac9f-6b96-416b-9556-bcbf9a540290.

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In the last two decades a surge in antibiotic resistance has limited antibiotic effectiveness increasing the risk of uncontrolled epidemics especially for biofilm-related infections. The National Institute of Health reports that 80 % of human infections are biofilm related. The Proteus mirabilis bacteria were focused on in this study as they are significant biofilm formers in chronic infections such as biofilm-related urinary tract infections for which there are currently no completely effective treatment strategies. As biofilms can increase antibiotic resistance by up to 1000-fold, there is an urgent need for the development of novel antimicrobials. Thus, bacteriophages which are viruses that target and kill bacteria have been proposed as suitable alternatives, but factors like storage stability and re-isolation pose limitations. Towards investigating the development of new antimicrobial strategies, the aims of this thesis were to assess: (i) the therapeutic potential of bacteriophages against Proteus mirabilis biofilms and (ii) the development of a novel antimicrobial strategy based on a synthetic biology approach for improvement of bacteriophage-based biofilm control. The work presented in this thesis led to or may lead to four areas of development, which have the potential to contribute to fields of biofilm research, bioengineering and materials science. Firstly, novel bacteriophages against clinical strains of Proteus mirabilis were isolated with physicochemical and genomic characterisation. Unlike other studies, the effect of temperature was included in the selection of favourable bacteriophages for anti-biofilm use. Secondly, towards improving bacteriophage-based treatment, dendrimeric nanoparticles known as dendron were posed as alternatives, these were synthesised and characterised, and demonstrated improved biofilm reduction and eradication by 35 % and 100 % respectively compared with the most effective bacteriophage. Thirdly, this study developed insight into the dendron’s mechanism of action, which was previously unreported, and was proposed to be through disruption of Proteus mirabilis DNA systems. Fourthly, in a unique approach, the dendron was bioengineered with bacteriophage DNA using electrostatic interactions. The results suggested that the dendron has potential to be used as a carrier for bacteriophage DNA, and presents the first attempt in published literature at combining the anti-biofilm properties of bacteriophages and dendrons towards futuristic development of synthetic bacteriophages. The results also provide a promising antimicrobial strategy for use of dendrons as therapeutic agents, alone or in combination with antibiotics and bacteriophages for treatment of biofilm-related infections.

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Rooney, Timothy M. "Genes Required for Wallerian Degeneration Also Govern Dendrite Degeneration: A Dissertation." eScholarship@UMMS, 2004. http://escholarship.umassmed.edu/gsbs_diss/775.

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Neurons comprise the main information processing cells of the nervous system. To integrate and transmit information, neurons elaborate dendritic structures to receive input and axons to relay that information to other cells. Due to their intricate structures, dendrites and axons are susceptible to damage whether by physical means or via disease mechanisms. Studying responses to axon injury, called Wallerian degeneration, in the neuronal processes of Drosophila melanogaster has allowed the identification of genes that are required for injury responses. Screens in Drosophila have identified dsarm and highwire as two genes required for axon degeneration; when these genes are mutated axons fail to degenerate after injury, even when completely cut off from the neuronal cell body. We found that these genes are also required for dendrite degeneration after injury in vivo. Further, we reveal differences between axon and dendrite injury responses using in vivo timelapse recordings and GCaMP indicators of intracellular and mitochondrial calcium transients. These data provide insights into the neuronal responses to injury, and better define novel targets for the treatment of neurodegenerative diseases.

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Hossain, Sharmin. "Morphological characterization of dynamic dendrite growth in the awake developing brain." Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/51505.

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Precise wiring between dendrites and axons during brain development is a critical requirement for forming proper neuronal connectivity, a prerequisite to generate correct brain function. Establishing this highly complex physical network entails forming precise patterns of dendritic and axonal arborization as well as correct targeting of these processes to appropriate brain regions. As compared to our current understanding of axonal development, relatively little is known regarding the structural organization and of dendritic arbor growth during dendritogenesis. Two major obstacles in studying dendritogenesis in vivo are technical challenges in observing the dynamic behavior of these structures in the developing brain, and post-imaging analyses of their complex growth patterns. Here, we used in vivo rapid time-lapse imaging in the intact and awake vertebrate brain to observe dynamic dendritogenesis and analyzed components of growing dendritic arbors of individual neurons to elucidate how short-term growth behaviors culminate to produce the dendritic arbor patterning of mature neurons. Of particular interest, this work establishes that dendritic growth cones exist on all growing dendrites, but due to their dynamic nature, they have been grossly under-reported in previous in vivo studies. In this study, I find that dendritic growth cone morphology correlates with branch behavior, report differences in two different dendritic filopodial populations in vivo, and describe how dendritic growth behavior changes over neuronal maturation. Further, we have developed a novel analysis tool called Dynamo to accurately track and analyze dendritic components. I have used this tool to screen three candidate guidance cue molecules, including ephrin-A1, ephrin-B1, and slit2, for their potential role in regulating dynamic behavior of growing dendrites, and found that slit2 exposure decreases branch motility and increases branchtip filopodial motility in vivo. I also find that neurons located in the caudomedial tectum project their dendrites in a biased rostral orientation to reach the tectal neuropil, and that interfering with the Slit receptor Robo3, prevents this biased dendrite growth. These findings provide novel insights into how dendrites develop in vivo in the awake vertebrate brain.
Medicine, Faculty of
Graduate

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Rooney, Timothy M. "Genes Required for Wallerian Degeneration Also Govern Dendrite Degeneration: A Dissertation." eScholarship@UMMS, 2015. https://escholarship.umassmed.edu/gsbs_diss/775.

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Neurons comprise the main information processing cells of the nervous system. To integrate and transmit information, neurons elaborate dendritic structures to receive input and axons to relay that information to other cells. Due to their intricate structures, dendrites and axons are susceptible to damage whether by physical means or via disease mechanisms. Studying responses to axon injury, called Wallerian degeneration, in the neuronal processes of Drosophila melanogaster has allowed the identification of genes that are required for injury responses. Screens in Drosophila have identified dsarm and highwire as two genes required for axon degeneration; when these genes are mutated axons fail to degenerate after injury, even when completely cut off from the neuronal cell body. We found that these genes are also required for dendrite degeneration after injury in vivo. Further, we reveal differences between axon and dendrite injury responses using in vivo timelapse recordings and GCaMP indicators of intracellular and mitochondrial calcium transients. These data provide insights into the neuronal responses to injury, and better define novel targets for the treatment of neurodegenerative diseases.

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39

Reeves, Alastair Ian. "Contaminant tracking through dendro-chemical analysis of tree-radii." Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=69688.

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The research used dendro-chemical analysis of ash tree rings and current year leaf litter to track Cd, Pb, Zn, Cu, Mn, Cr, and Sn spread and cycling from a closed garbage dump-toxic waste site. This technique allowed for determination of areal extent, contaminant levels and time period of initial contaminant contact. Only Zn, Sn, and Cu were found in elevated quantities in the xylem wood and Pb in the leaf litter. Elemental concentrations of Pb, Sn and Cd in xylem wood and leaves of ash were positively correlated. Tin was the only element to demonstrate a clear initial contact period and elemental accumulation with age. Significant levels of Cu accumulated in the heartwood while Zn revealed significant but inconsistent accumulated patterns. Expected attenuation zones associated with municipal solid waste landfill leachate dispersion were not found; thus the pathway for contaminant dispersion was likely through groundwater flow.
An elemental index was developed to facilitate the use of dendro-chemical analysis in periods of suppressed tree growth resulting from environmental pollution.

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40

Mahnke, Amanda Hope. "Alterations to Dendrite Morphology in Response to Antipsychotic Drug Treatment and Hypoglutamatergia." Thesis, Tulane University School of Science and Engineering, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3639160.

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Schizophrenia is a prevalent neurological disorder characterized by disrupted neuronal circuitry. Antipsychotic drugs (APDs) are capable of ameliorating the symptoms of schizophrenia with varying efficacy. Clozapine, the "gold-standard" for antipsychotic drug treatment, has been shown by this lab to induce the outgrowth of mediodorsal thalamic (MDT) dendritic arbor in rodents, a brain region which has altered function and decreased regional volume in schizophrenic patients. These studies further explored the ability of APD treatment to restructure dendrite arbor and the mechanisms of clozapine's ability to elaborate MDT arbor. Additionally, glutamate hypofunction is thought to contribute to the schizophrenic disease state. Using a novel model of perinatal glutamate hypofunction, we examined the long-term effects on dendritic architecture of developmental glutamate signaling disruption.

MDT dysfunction is hypothesized to contribute to cognitive symptoms of schizophrenia. Clozapine has increased efficacy in ameliorating these symptoms. To further understand clozapine's actions to remodel MDT dendritic architecture, we examined whether clozapine-induced morphological alterations are limited to the thalamus or if they also occur in additional regions associated with cognitive schizophrenic pathology, the hippocampus and striatum. We found that clozapine can induce dendritic remodeling in the hippocampus, but the not to the amplitude of remodeling seen in the thalamus, indicating that the MDT is uniquely altered by clozapine treatment and may be an important locus of clozapine's action.

The mechanisms of clozapine's remodeling of MDT arbor, we examined changes to mRNA and miRNA expression and calcium dynamics in the MDT in response to APD treatment. Clozapine-treatment altered the expression of genes involved in cytoskeletal remodeling, external membrane receptors, and calcium dynamics, as well as increased the rate of calcium influx into thalamic neurons.

Disruption to glutamate signaling has been hypothesized to contribute to schizophrenic pathology. Disruption to perinatal vesicular glutamate packaging along the corticolimbic axis has long term effects for neuronal morphology and function. Interestingly, we find that disruption along the corticolimbic axis also has downstream effects on MDT dendritic architecture.

These studies show that the MDT is an important locus of action for clozapine and is capable of remodeling dendritic architecture in response to afferent circuitry dysfunction.

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41

Chen, Jerry L. "Experience-dependent dendrite remodeling of GABAergic interneurons in the adult visual cortex." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/57993.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Biology, 2010.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 85-97).
An ever increasing amount of evidence is demonstrating that structural plasticity is a diverse and ongoing feature that contributes to plasticity in the adult brain. It was previously shown that dendritic arbors of inhibitory interneurons in superficial layer 2/3 can remodel in the adult cortex. Here, we investigated the role of these structural rearrangements during experience-dependent adult plasticity. Using in vivo two photon imaging, we monitored intemeuron dendritic branch tip remodeling in response to changes in visual experience in the adult mouse visual cortex. We find that branch tip dynamics are induced by novel experiences in a stimulus-specific manner. Visual deprivation produces rearrangements that are circuit-specific and are different for branch tips extending into LI or L2/3. The weakening of dendritic input onto these cells functions to reduce levels of inhibition in local cortical circuits. This reduced inhibitory tone provides more salience to remaining instructive input, allowing more structural and functional adaptations to occur. In order to better understand how synaptic plasticity accompanies these dendritic arbor rearrangements as well as other forms of structural plasticity, we developed a method to simultaneously monitor structural and synaptic dynamics in the mammalian brain using in vivo two-photon microscopy. Structural and synaptic components can be labeled in cortical neurons of mice in a cell type and laminar specific manner through co-injection of independent lentiviral vectors at a late embryonic or early postnatal age. We demonstrate that excitatory and inhibitory post-synaptic densities can be visualized by tagging fluorescent proteins to PSD95 and Gephyrin, respectively. Finally, we show that the fluorescent proteins, Teal and Venus, can be simultaneously excited and spectrally resolved through linear unmixing so that individual structural and synaptic components can be identified and followed over time. Through this approach, the relationship between synaptic and structural plasticity can be studied in the living brain.
by Jerry L. Chen.
Ph.D.

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42

Perugini, Valeria. "Poly-ɛ-lysine dendron aptamers as regulators of angiogenesis in tissue regeneration." Thesis, University of Brighton, 2013. https://research.brighton.ac.uk/en/studentTheses/937e14a0-921a-4004-af1d-bbd97f6cd425.

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The successful regeneration of damaged or injured tissues is strictly dependent upon the ability to control angiogenesis. The formation of new blood vessels from pre-existing ones is mainly regulated by the vascular endothelial growth factor (VEGF), a mitogen specific for endothelial cells. A number of therapeutic approaches are being pursued to control this process in pathological conditions, including the use of synthetic peptides which have shown their capacity to either promote or inhibit angiogenesis. However, their lack of stability and short half-lives have strictly limited their clinical applications. To address these limitations, here, both anti- and pro- angiogenic peptide sequences (WHLPFKC and YIGSR) were synthesised at the uppermost branching generation of poly-ɛ-lysine dendrons.

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43

Tie, Chenyang. "Conformation and Assembly Research on Dendron Derivatives: Azobenzene Oligomers and Dendritic Peptides." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1282077432.

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44

Krol, Alexandra. "Regulation of Neuronal Dendrite Development and Migration by the Atypical Cadherin Fat3." Thesis, Harvard University, 2015. http://nrs.harvard.edu/urn-3:HUL.InstRepos:17467479.

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Neuronal shape and position are critical to the formation and function of neuronal circuits. Although neurons develop axons and dendrites cell-autonomously in vitro, how extracellular cues in vivo direct neurite specification and placement remains poorly understood. The role of atypical cadherin Fat3 in amacrine cell development illustrates how the same extracellular cue can guide both dendrite formation and migration. In the mouse retina, amacrine cells have a bipolar morphology during their migration. Upon reaching the nascent inner plexiform layer (IPL), they elaborate one neurite into the IPL and retract the other. Loss of Fat3 leads amacrine cells to develop an extra dendrite outside the IPL as well as errors in migration. We found Fat3 protein is concentrated at the IPL throughout amacrine cell development, suggesting Fat3 detects a directional signal. Here we investigated the signaling pathways upstream and downstream of Fat3 that mediate its role in amacrine cell development. In Drosophila, Fat’s ligand is Dachsous. Fat and Dachsous binding is modulated by the kinase Four-jointed. Our analysis of mutant retinas determined that Fat3 and vertebrate Four-jointed genetically interacted. However knockout studies of vertebrate Dachsous homologues suggested they are not relevant Fat3 ligands in the retina. Instead, analysis of retinas missing retinal ganglion cells suggested Fat3-mediated homophilic adhesion between amacrine cells may be important. Sparse loss of Fat3 from amacrine cells also led to extraneous neurites, suggesting Fat3 acts cell autonomously. Ex vivo live imaging revealed both migration and neurite dynamics were less directed in Fat3 mutant amacrine cells. We hypothesized Fat3 acts to target asymmetric localization of cytoskeletal regulators to the leading neurite. To identify downstream Fat3 effectors, we performed a pulldown assay using the Fat3 intracellular domain. We identified several cytoskeletal regulators as candidate binding partners. We focused on the actin regulators Ena/VASP and demonstrated a direct interaction with the Fat3 intracellular domain. In the retina, Ena/VASP localized with Fat3 to the IPL, and loss of Fat3 changed Ena/VASP distribution. Furthermore, forcing uniform membrane recruitment of Ena/VASP in developing amacrine cells phenocopied loss of Fat3. Together these results suggest Fat3 polarizes the activity of cytoskeletal effectors to help direct amacrine cell migration and dendrite placement.
Medical Sciences

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45

Hattori, Yukako. "Subtype-specific postmitotic transcriptional programs controlling dendrite morphogenesis of Drosophila sensory neuron." 京都大学 (Kyoto University), 2014. http://hdl.handle.net/2433/188831.

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Yukako Hattori, Tadao Usui, Daisuke Satoh, Sanefumi Moriyama, Kohei Shimono, Takehiko Itoh, Katsuhiko Shirahige, Tadashi Uemura, Sensory-Neuron Subtype-Specific Transcriptional Programs Controlling Dendrite Morphogenesis: Genome-wide Analysis of Abrupt and Knot/Collier, Developmental Cell, Volume 27, Issue 5, 9 December 2013, Pages 530-544, ISSN 1534-5807
Kyoto University (京都大学)
0048
新制・課程博士
博士(生命科学)
甲第18418号
生博第298号
新制||生||39(附属図書館)
31276
京都大学大学院生命科学研究科統合生命科学専攻
(主査)教授上村匡, 教授西田栄介, 教授荒木崇
学位規則第4条第1項該当

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46

Walter, Aurélie. "Élaboration de nano-objets magnétiques dendronisés à vocation théranostic." Thesis, Strasbourg, 2014. http://www.theses.fr/2014STRAE020/document.

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Cette thèse présente la conception de nano-objets magnétiques dendronisés permettant à la fois le diagnostic par imagerie par IRM et la thérapie par hyperthermie magnétique (HM). La validation in vitro et in vivo des propriétés de ces nano-objets et la démonstration de leur efficacité pour le ciblage spécifique de tumeurs sont rapportées. Un état de l’art sur la synthèse des NPs d’oxydes métalliques, leur fonctionnalisation ainsi que leurs propriétés en IRM et en HM est présenté. L’influence de la méthode de fonctionnalisation de NPs d’oxyde de fer puis l’influence de l’architecture de la molécule greffée sur la stabilité colloïdale et la relaxivité ont été étudiées. Des NPs de différentes tailles, morphologies et composition ont ensuite été synthétisées et fonctionnalisées par une molécule dendron et leurs les propriétés en IRM et en HM ont été étudiées. Le ciblage spécifique de la mélanine au sein de mélanome a été montré
This thesis presents the design of dendronized magnetic nano- objects for both diagnostic imaging by MRI and magnetic hyperthermia therapy (HM). In vitro and in vivo validation of these nano-objects properties and the demonstrattion of their effectiveness for specific targeting of tumors are reported. A state of the art on the synthesis of metal oxide NPs, their functionalization and their properties in MRI and HM is presented. The influence of the NPs iron oxide functionalization method and the influence of the molecule architecture on the colloidal stability and relaxivity were studied. NPs of different sizes, morphologies and composition were then synthesized and functionalized with a dendron molecule and the MRI and HM properties were investigated. The specific targeting of melanin in melanoma was demonstrated

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Bull, Elizabeth Eleanor. "Geology and palaeontology of the Telychian (Silurian), Reservoir Formation of the North Esk inlier, near Edinburgh, Scotland." Thesis, Open University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.295571.

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48

Barreiro, Daniela Pacheco. "Coléteres dendróides em Alibertia sessilis (Vell.) K.Schum.(Rubiaceae) /." Botucatu : [s.n.], 2006. http://hdl.handle.net/11449/88137.

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Orientador: Silvia Rodrigues Machado
Banca: Rita de Cássia Sindronia Maimoni-Rodella
Banca: Joecildo Francisco Rocha
Resumo: A presença de coléteres na superfície adaxial de órgãos jovens constitui uma característica relevante de Rubiaceae. Alibertia sessilis (Vell.) K. Schum., conhecida como marmelinho ou marmelo-do-cerrado, é uma espécie subarbustiva de Rubiaceae nativa de cerrado e tem grande importância alimentícia e medicinal neste bioma. Os ápices vegetativo e reprodutivo apresentam-se recobertos por uma secreção hialina, de aspecto vítreo e hidrofóbico produzida por coléteres. Neste trabalho foram investigados a distribuição, estrutura, histoquímica e o modo de secreção dos coléteres presentes em ápices vegetativos e reprodutivos desta espécie. Para estudos convencionais, as amostras foram preparadas segundo técnicas usuais em microscopia de luz e microscopia eletrônica de varredura (MEV) e transmissão (MET); técnica especial foi aplicada para dissolução da secreção e observação dos coléteres ao MEV. A técnica do ZIO foi empregada para maior visualização do sistema de endomembranas ao MET. Testes histoquímicos foram feitos em secções de material recém coletado. Coléteres nesta espécie são do tipo dendróide e ocorrem em abundância na face adaxial das estípulas, brácteas e sépalas; consistem de um eixo central multicelular e multisseriado revestido por numerosas células epidérmicas digitiformes ou pontiagudas, de tamanhos irregulares, unidas entre si somente na porção proximal e separadas umas das outras na porção distal. As células colunares são axialmente alongadas e possuem paredes espessas, núcleo conspícuo, citoplasma abundante e vacúolos desenvolvidos. As células epidérmicas possuem paredes delgadas, núcleo conspícuo, citoplasma abundante e vacuoma pouco desenvolvido. Os coléteres, de ambos os ápices, não possuem cutícula. Lipídeos, proteínas e polissacarídeos foram detectados nas células epidérmicas e colunares; compostos... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The presence of colleters in the adaxial surface of young organs constitutes a relevant characteristic of Rubiaceae. Alibertia sessilis (Vell.) K. Schum., known as "marmelinho" or "marmelo-docerrado", is a subshrub native Rubiaceae species of cerrado and it has great nutritious and medicinal importance in this biome. The vegetative and reproductive apices present recovered for a hyaline secretion, of glass aspect and hydrophobic produced by colleters. In this work the distribution, structure, histochemistry and the way of secretion of the colleters present in vegetative and reproductive apices of this species were investigated. For conventional studies, the samples were prepared according to usual techniques in light microscopy and scanning (SEM) and transmission electron microscopy (TEM); special technique was applied for dissolution of the secretion and observation of the colleters to MEV. The technique of ZIO was used for larger visualization of the endomembranes system to MET. Histochemical assays were made in fresh material sections. Colleters in this species are of the dendroid type and occur abundantly in the adaxial surface of the stipules, bracts and sepals; they consist of a multicellular and multiseriate central axis recovered by numerous digitiform or sharp epidermal cells of irregular sizes, joined among themselves only in the proximal portion and separated from each other in the distal portion. The columnar cells are axially elongated and present thick walls, conspicuous nucleus, abundant cytoplasm and developed vacuoles. The epidermal cells present thin walls, conspicuous nucleus, abundant cytoplasm and a few developed vacuome. The coléteres, of both apices, don't present cuticle. Lipids, proteins and polysaccharides were detected in the epidermal and columnar cells; phenolic compounds were only detected in the columnar cells... (Complete abstract click electronic access below)
Mestre

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Baton, Franck. "Effets de la carbonisation oxygénée sur le signal isotopique (δ13C) du bois : vers une dendroclimatologie isotopique sur charbons archéologiques." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066236/document.

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Les charbons de bois trouvés en contexte archéologique permettent de reconstituer les couverts forestiers passés et les pratiques sylvicoles associées. Le δ13C de ces charbons a été utilisé pour des reconstructions paléoclimatiques, cependant ses variations peuvent aussi être dues à la carbonisation. Afin de mieux contraindre, à l’échelle du cerne, les variations du δ13C du bois dues à la carbonisation, des carbonisations ont été faites avec des échantillons de chêne cadicufoliés en conditions proches des foyers domestiques. Une diminution du δ13C après la carbonisation a été observée. Cet effet est très variable, notamment en fonction du compartiment du bois considéré (aubier, duramen, bois initial, bois final). Ces mesures de δ13C ont été complétées par celles du taux de carbone montrant qu’il ne varie pas parallèlement au δ13C. De ce fait l’utilisation, prônée par certains travaux, du taux de carbone pour évaluer les variations de d13C suite à la carbonisation n’est pas pertinente. Cependant, les variations cerne à cerne et intracerne du δ13C ne sont pas significativement affectées par la carbonisation, et des reconstructions climatiques à partir du δ13C de bois carbonisés paraissent donc envisageables. Afin de tester cette approche cerne à cerne, plusieurs charbons archéologiques issus du site Néolithique de Chalain, dont les paléoclimats étaient bien documentés, ont été échantillonnés. Cette approche a été couplée à des mesures dendro-anthracologiques (largeurs des cernes, proportion du bois final, rayon de courbure et proportion de vaisseaux avec des thylles) afin de mieux comprendre les variations de δ13C mesurées, et de tenter de les coupler aux pratiques sylvicoles. Les valeurs de δ13C sont en accord avec les paléoclimats déjà inférés et les variations intra-cerne, ou saisonnières, de δ13C révèlent que la période froide était caractérisée par des saisons plus contrastées. Les mesures dendro-anthracologiques ont permis, entre autres, de préciser les variations de δ13C entre les différents compartiments du bois et de proposer une interprétation concernant les variations des pratiques sylvicoles en lien avec le climat. En conclusion, la carbonisation oxygénée provoque un abaissement des valeurs de δ13C du bois mais n’empêche pas les reconstructions paléo-climatiques à partir de leurs variations, notamment saisonnières, mesurées sur des charbons archéologiques
Archeological charcoals are used for reconstructing past woodland vegetation and the related historical forest practices. Charcoals δ13C are used for paleoclimate reconstructions. To better constrain the use of δ13C, we investigated the effect of oxygenated carbonization on ring scale δ13C variations in oak wood. Results showed a significant decrease of δ13C values after carbonization. This effect, however, is highly variable according to the wood compartment considered: heartwood, sapwood, earlywood, or latewood. Carbon content measurements do not exhibit the same variations along oxygenated carbonization as observed with δ13C. Therefore, the use of carbon content for evaluating carbonization effects on δ13C, which is proposed by some authors, is not appropriate. Interannual and seasonal δ13C variations, however, are not significantly affected by oxygenated carbonization. Thus, paleoclimate reconstruction from charcoals δ13C appears possible. To test both ring scale variations, archeological charcoals were sampled from a climatically well documented Neolithic site of Chalain. Several dendro-anthracological parameters (latewood proportion, duraminization, charcoal-pith distance estimation) were characterized for a better understanding of δ13C variations, in order to integrate historical woodland practices and the climatic interpretations. Charcoal tree-rings exhibited width and δ13C significantly different between the two studied periods, in agreement with previously inferred climatic difference. Intra-ring δ13C suggested that the cool and moist climatic period also corresponded to higher seasonal contrast than the dryer climatic period. Dendro-anthracological parameters allow better understanding of δ13C variations between wood compartments and provide information on past woodland exploitations. To conclude, oxygenated carbonizations induce a decrease in wood δ13C values, but do not prevent the paleoclimate interpretations of δ13C variations in archeological charcoals

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Steiger, Jens [Verfasser], and O. [Akademischer Betreuer] Kraft. "Mechanisms of Dendrite Growth in Lithium Metal Batteries / Jens Steiger. Betreuer: O. Kraft." Karlsruhe : KIT-Bibliothek, 2015. http://d-nb.info/106673691X/34.

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Dissertations / Theses on the topic 'Dendrid'

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