Thèses : « Dendrites »

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Croydon, David Alexander. « Random fractal dendrites ». Thesis, University of Oxford, 2006. http://ora.ox.ac.uk/objects/uuid:4e17aebc-456d-4891-8527-692331ebff05.

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Dendrites are tree-like topological spaces, and in this thesis, the physical characteristics of various random fractal versions of this type of set are investigated. This work will contribute to the development of analysis on fractals, an area which has grown considerably over the last twenty years. First, a collection of random self-similar dendrites is constructed, and their Hausdorff dimension is calculated. Previous results determining this quantity for random self-similar structures have often relied on the scaling factors being bounded uniformly away from zero. However, using a percolative argument, and taking advantage of the tree-like structure of the sets considered here, it is shown that this condition is not necessary; a simple condition on the tail of the distribution of the scaling factors at zero is all that is assumed. The scaling factors of these recursively defined structures form what is known as a multiplicative cascade, and results about the height of this random object are also obtained. With important physical and probabilistic applications, the heat equation has justifiably received a substantial amount of attention in a variety of settings. For certain types of fractals, it has become clear that a key factor in estimating the heat kernel is the volume growth with respect to the resistance metric on the space. In particular, uniform polynomial volume growth, which occurs for many deterministic self-similar fractals, immediately implies uniform (on-diagonal) heat kernel behaviour. However, in the random fractal setting, this is frequently not the case, and volume fluctuations are often observed. Motivated by this, an analysis of how volume fluctuations lead to corresponding heat kernel fluctuations for measure-metric spaces equipped with a resistance form is conducted here. These results apply to the aforementioned random self-similar dendrites, amongst other examples. The continuum random tree (CRT) of Aldous is an important random example of a measure-metric space, and fits naturally into the framework of the previous paragraph. In this thesis, quenched (almost-sure) volume growth asymptotics for the CRT are deduced, which show that the behaviour in almost-every realisation is not uniform. Applying the results introduced above, these yield heat kernel bounds for the CRT, demonstrating that heat kernel fluctuations occur almost-surely. Finally, a new representation of the CRT as a random self-similar dendrite is presented.

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Svensson, Carl-Magnus. « Dynamics of spatially extended dendrites ». Thesis, University of Nottingham, 2009. http://eprints.nottingham.ac.uk/10788/.

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Dendrites are the most visually striking parts of neurons. Even so many neuron models are of point type and have no representation of space. In this thesis we will look at a range of neuronal models with the common property that we always include spatially extended dendrites. First we generalise Abbott’s “sum-over-trips” framework to include resonant currents. We also look at piece-wise linear (PWL) models and extend them to incorporate spatial structure in the form of dendrites. We look at the analytical construction of orbits for PWL models. By using both analytical and numerical Lyapunov exponent methods we explore phase space and in particular we look at mode-locked solutions. We will then construct the phase response curve (PRC) for a PWL system with compartmentally modelled dendrites. This sets us up so we can look at the effect of multiple PWL systems that are weakly coupled through gap junctions. We also attach a continuous dendrite to a PWL soma and investigate how the position of the gap junction influences network properties. After this we will present a short overview of neuronal plasticity with a special focus on the spatial effects. We also discuss attenuation of distal synaptic input and how this can be countered by dendritic democracy as this will become an integral part of our learning mechanisms. We will examine a number of different learning approaches including the tempotron and spike-time dependent plasticity. Here we will consider Poisson’s equation around a neural membrane. The membrane we focus on has Hodgkin-Huxley dynamics so we can study action potential propagation on the membrane. We present the Green’s function for the case of a one-dimensional membrane in a two-dimensional space. This will allow us to examine the action potential initiation and propagation in a multi-dimensional axon.

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Gudgel, Katherine Ann. « Growth of ammonium chloride dendrites ». Diss., The University of Arizona, 2001. http://hdl.handle.net/10150/289878.

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The ammonium chloride-water system has been used extensively as a transparent metal analog to model solidification in binary metal alloys. In this work, the growth rate and morphology of NH₄Cl dendrites grown from aqueous solutions were studied. Since an accurate knowledge of the materials parameters is essential to predicting the growth behavior, the equilibrium segregation coefficient was measured and a detailed analysis of the other NH₄Cl-H₂O materials properties cited in the literature was conducted. Isothermal experiments on bulk NH₄Cl-H₂O samples confirmed that the previously reported discontinuity in the growth rate as function of undercooling and associated transition from <100> oriented slowly growing dendrites to rapidly growing <111> dendrites are not artifacts of the sample geometry. Directional solidification experiments conducted to study the dendrite growth morphology revealed oscillations in both the growth rate and orientation. Results from these studies show that both the undercooling at which the <100> to <111> transition occurs and the peak velocity vary with composition. However, the observed shifts toward smaller apparent undercoolings and the narrowing of the oscillations at higher drive velocities result from changes in the local composition caused by the velocity and orientation dependencies of the partition coefficient. The oscillatory behavior of the <111> dendrites can be predicted using the residual <100> compositional field and the applied temperature gradient. By using an anisotropic segregation coefficient, the slow and fast growth rates can be separately modeled as a function of undercooling using the standard dendrite growth equations. While the transition to the <111> morphology can be attributed to the anisotropy in the k-value, several modifications need to be made to the existing dendritic growth models in order to describe the critical transition. Due to the complex relationships between the non-equilibrium segregation coefficient, composition, and growth rate, some of these modeling efforts have been left to future researchers. In addition to the inclusion of the overall anisotropy, our experiments indicate that the long-range compositional and thermal field effects must be incorporated into the dendrite growth models to explain the difference in growth rates of <111> Primary branches when <111> or <100> side-branches are present.

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Förstner, Friedrich. « The morphological identity of insect dendrites ». Diss., lmu, 2011. http://nbn-resolving.de/urn:nbn:de:bvb:19-129497.

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Jin, Xiaoming. « Dendritic development of GABAergic cortical interneurons revealed by biolistic transfection with GFP ». Morgantown, W. Va. : [West Virginia University Libraries], 2002. http://etd.wvu.edu/templates/showETD.cfm?recnum=2626.

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Thesis (Ph. D.)--West Virginia University, 2002.
Title from document title page. Document formatted into pages; contains vii, 218 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references.

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Nilson, James E. « Compartmental distribution of two cation chloride cotransporter types along starburst amacrine cell dendrites underlies the directional properties of these dendrites ». Thesis, Boston University, 2005. https://hdl.handle.net/2144/37167.

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Thesis (Ph.D.)--Boston University
PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you.
A fundamental aspect of vision is the ability to detect motion and to define its direction. In the retina, directionally selective ganglion cells respond to stimulus motion in a 'preferred' direction but respond little to stimulus motion in the opposite or 'null' direction. However despite nearly forty years of investigation, the precise cellular locus and underlying mechanisms of direction selective encoding have remained largely elusive. Recently, starburst amacrine cells, that are presynaptic to directionally selective ganglion cells, have been shown to provide direction specific inhibitory output to these ganglion cells. Therefore defining the biophysical properties specific to starburst amacrine cell dendrites will provide significant insight into the ability of visual systems to encode the direction of objects moving through an animal's visual field. Using a combination of intracellular filling of starburst amacrine cells and immunohistochemical localization of biophysically relevant molecules, we have examined how individual dendrites compute such motion. In order to define the relative degree and pattern of colocalization of these markers on filled dendrites we developed a new set of image acquisition and data analysis procedures that have allowed us to define the biophysical signature intrinsic to different portions of starburst amacrine cell dendrites. We have found that sodium-potassium-chloride cotransporter (NKCC2) and potassium-chloride cotransporter (KCC2) are expressed and differentially distributed on the proximal and distal dendritic compartments of starburst amacrine cells, respectively. The functional relevance of the anatomical distribution pattern of these cation-chloride-cotransporter types has been confirmed by others using physiological techniques. In summary, our studies provide a fundamental mechanism through which starburst amacrine cells define motion direction and transmit this information to directionally selective ganglions cells. In addition, our illumination of the basic concept of segregation of functional components to different dendritic compartments will likely prove to be an important theme of neuronal function throughout the nervous system.
2031-01-01

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Karam, Philippe Chucri. « Modeling passive and active mechanisms in motoneuron dendrites ». Thesis, Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/13713.

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George, Suma. « Simulink modeling and implementation of cmos dendrites using fpaa ». Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/44915.

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In this thesis, I have studied CMOS dendrites, implemented them on a reconfigurable analog platform and modeled them using MATLAB Simulink. The dendrite model was further used to build a computational model. I implemented a Hidden Markov Model (HMM) classifier to build a simple YES/NO wordspotter. I also discussed the inter-relation between neural systems, CMOS transistors and HMM networks. The physical principles behind the operation of silicon devices and biological structures are similar. Hence silicon devices can be used to emulate biological structures like dendrites. Dendrites are a branched, conductive medium which connect a neurons synapses to its soma. Dendrites were previously believed to be like wires in neural networks. However, recent research suggests that they have computational power. We can emulate dendrites using transistors in the Field Programmable Analog Array (FPAA). Our lab has built the Reconfigurable Analog Signal Processor (RASP) family of FPAAs which was used for the experiments. I analytically compared the mathematical model of dendrites to our model in silicon. The mathematical model based on the device physics of the silicon devices was then used to simulate dendrites in Simulink. An automated tool, sim2spice was then used to convert the Simulink model into a SPICE netlist, such that it can be implemented on a FPAA. This is an easier tool to use for DSP and Neuromorphic engineers who's primary areas of expertise isn't circuit design.

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Ou, Yimiao. « Molecular mechanisms controlling the arborization of dendrites in «Drosophila» ». Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=96940.

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The assembly and function of neural circuits depend on the patterned outgrowth, guidance and targeting of dendrites into appropriate territories during development. As a hallmark of any neuron, cell type-specific dendrite morphology has a crucial role in determining the sensory or synaptic input a neuron receives. Despite recent advances in exploring the molecular and cellular mechanisms that define dendritic architecture, our understanding of dendrite development is still far from complete. In this thesis research, I have taken a genetic screen approach and a candidate molecule approach to discover novel genes and mechanisms that are involved in dendrite morphogenesis, using Drosophila dendritic arborization (da) neurons as a model system. In three independent but related studies, my research led me to focus on 1) the nuclear receptor for the steroid hormone ecdysone (EcR), 2) the transcription factor Longitudinals Lacking (Lola) and 3) the cell surface recognition molecule Turtle (Tutl). I have found that these three different factors each regulate distinct aspects of dendritic arborization including dendrite branching, distribution and self-avoidance. Through their identification, expression patterns, and a characterization of their effects in loss-of-function and gain-of-function experiments, my findings provide novel insight into the regulatory networks that control dendrite morphogenesis.
L'élaboration et le fonctionnement harmonieux des circuits nerveux dépendent de la croissance des dendrites et de leur guidage et ciblage vers les territoires appropriés au cours du développement. La morphologie des dendrites sert de signe distinctif pour chaque neurone, et ainsi, joue un rôle crucial dans la détermination des différents influx (synaptiques ou sensoriels) que reçoit un neurone. Malgré de récentes avancées dans la compréhension des mécanismes moléculaires et cellulaires qui contrôlent l'architecture dendritique, notre connaissance du développement des dendrites reste encore incomplète. Mes travaux de recherche se sont attachés à découvrir de nouveaux gènes et mécanismes impliqués dans la morphogenèse dendritique. Dans ce but, j'ai choisi au cours de ma thèse deux méthodes d'étude: une approche par crible génétique et une approche par gènes candidats, que j'ai appliquées aux neurones appelés dendritic arborization (da) de la drosophile, mon modèle d'étude. Mes recherches m'ont permis de me concentrer sur trois molécules: 1) le récepteur nucléaire de l'hormone stéroïde ecdysone (EcR), 2) le facteur de transcription Longitudinals Lacking (Lola) et enfin, 3) la molécule de surface Turtle (Tutl). J'ai pu montrer que chacun de ces facteurs est implique dans des aspects distincts du processus de morphogenèse dendritique incluant le branchement, la distribution et l'auto-répulsion dendritiques. L'identification de ces molécules, la description de leurs patrons d'expression et la caractérisation des phénotypes associés à leurs pertes ou gains de fonctions, m'ont permis d'apporter de nouvelles connaissances des réseaux de régulation contrôlant la morphogenèse dendritique.

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Coutts, Emma Jayne. « The effect of noise in models of spiny dendrites ». Thesis, Heriot-Watt University, 2010. http://hdl.handle.net/10399/2352.

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The dendritic tree provides the surface area for synaptic connections between the 100 billion neurons in the brain. 90% of excitatory synapses are made onto dendritic spines which are constantly changing shape and strength. This adaptation is believed to be an important factor in learning, memory and computations within the dendritic tree. The environment in which the neuron sits is inherently noisy due to the activity in nearby neurons and the stochastic nature of synaptic gating. Therefore the effects of noise is a very important aspect in any realistic model. This work provides a comprehensive study of two spiny dendrite models driven by different forms of noise in the spine dynamics or in the membrane voltage. We investigate the effect of the noise on signal propagation along the dendrite and how any correlation in the noise may affect this behaviour. We discover a difference in the results of the two models which suggests that the form of spine connectivity is important. We also show that both models have the capacity to act as a robust filter and that a branched structure can perform logic computations.

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Heintz, Tristan Georges Paul. « Regional differences of integrin function in dendrites and axons ». Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.648195.

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Sorensen, Staci A. « Afferent input regulates dendritic structure in nucleus laminaris / ». Thesis, Connect to this title online ; UW restricted, 2006. http://hdl.handle.net/1773/10668.

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Hasel, Philip. « Investigation into the destructive and adaptive responses of neural cells to stress ». Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/23547.

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Homeostasis within the neuro-glial unit is essential to the longevity of neurons. Conversely, loss of homeostasis, particularly of Ca2+ levels, of redox balance and of ATP, contribute to neuronal loss and dysfunction in many neurodegenerative and neurological disorders. This thesis is centred on better understanding the vulnerability of neurons to stress, as well as adaptive responses to these stresses. Since neurodegenerative conditions associated with Ca2+, redox and bioenergetic dyshomeostasis are often characterised by early dendritic pathology, I first studied dendritic vs. somatic responses of primary cortical neurons to these types of challenges in real-time. Using a wide range of genetically-encoded probes to measure Ca2+, ATP, NADH, glutathione and glutamate, I show that dendrites are selectively vulnerable to oxidative stress, excitotoxicity as well as to metabolic demand induced by action potential (AP) burst activity. However, I provide evidence that neurons undergoing energetically demanding AP burst activity can adjust their metabolic output by increasing mitochondrial NADH production in a manner dependent on the mitochondrial calcium uniporter (MCU), as well as increase their capacity to buffer their intracellular redox balance. Finally, I have studied transcriptional programs in astrocytes triggered by neurons and neuronal activity to better understand adaptive signaling between different cell types in the neuro-glial unit. I developed a novel system combining neurons and astrocytes from closely-related species, followed by RNA-seq and in silico read sorting. I uncovered a program of neuron-induced astrocytic gene expression which drives and maintains astrocytic maturity and neurotransmitter uptake function. In addition I identified a novel form of synapse-to-nucleus signaling, mediated by glutamatergic activity and acutely regulating diverse astrocytic genes involved in astrocyte-neuron metabolic coupling. Of note, neuronal activity co-ordinately induced astrocytic genes involved in astrocyte-to-neuron thyroid hormone signaling, extracellular antioxidant defences, and the astrocyte-neuron lactate shuttle, suggesting that this non cell-autonomous signaling may form part of the homeostatic machinery within the neuro-glial unit.

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Mauss, Alex Stefan. « Development and patterning of motorneuron dendrites in the Drosophila embryo ». Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.611196.

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Kunka, Mark David. « Nonlinear evolution of small peclet number dendrites with surface tension / ». The Ohio State University, 1995. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487868114110492.

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Janzakova, Kamila. « Développement de dendrites polymères organiques en 3D comme dispositif neuromorphique ». Electronic Thesis or Diss., Université de Lille (2022-....), 2023. http://www.theses.fr/2023ULILN017.

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Les technologies neuromorphiques constituent une voie prometteuse pour le développement d'une informatique plus avancée et plus économe en énergie. Elles visent à reproduire les caractéristiques attrayantes du cerveau, telles qu'une grande efficacité de calcul et une faible consommation d'énergie au niveau des logiciels et du matériel. À l'heure actuelle, les implémentations logicielles inspirées du cerveau (telles que ANN et SNN) ont déjà démontré leur efficacité dans différents types de tâches (reconnaissance d'images et de la parole). Toutefois, pour tirer un meilleur parti des algorithmes inspirés du cerveau, il est possible de les combiner avec une implémentation materielle appropriée qui s'appuierait également sur une architecture et des processus inspirés du cerveau. L'ingénierie neuromorphique s'est principalement appuyée sur les technologies conventionnelles (CMOS circuits, memristor) pour le développement de circuits inspirés du cerveau. Néanmoins, ces implémentations sont fabriquées suivant une approche top-down. En revanche, l'informatique cérébrale repose sur des processus bottom-up tels que l'interconnectivité entre les cellules et la formation de voies de communication neuronales.À la lumière de ce qui précède, ce travail de thèse porte sur le développement de dispositifs neuromorphiques organiques programmables en 3D qui, contrairement à la plupart des technologies neuromorphiques actuelles, peuvent être créés de manière bottom-up. Cela permet de rapprocher les technologies neuromorphiques du niveau de programmation du cerveau, où les chemins neuronaux nécessaires sont établis uniquement en fonction des besoins.Tout d'abord, nous avons découvert que les interconnexions 3D à base de PEDOT:PSS peuvent être formées au moyen d'électropolymérisation bipolaire en courant alternatif, permettant d'imiter la croissance des cellules neuronales. En réglant individuellement les paramètres de la forme d'onde (tension d'amplitude de crête - VP, fréquence - f, duty cycle- dc et tension de décalage - Voff), une large gamme de structures semblables à des dendrites a été observée avec différents degrés de ramification, volumes, surfaces, asymétries et dynamiques de croissance.Ensuite, nous avons montré que les morphologies dendritiques obtenues à différentes fréquences sont conductrices. De plus, chaque structure présente une valeur de conductance qui peut être interprétée comme un poids synaptique. Plus important encore, la capacité des dendrites à fonctionner comme OECT a été révélée. Différentes morphologies de dendrites ont présenté des performances différentes en tant qu'OECT. De plus, la capacité des dendrites en PEDOT:PSS à modifier leur conductivité en réponse à la tension de grille a été utilisée pour imiter les fonctions de mémoire du cerveau (plasticité à court terme -STP et plasticité à long terme -LTP). Les réponses à la STP varient en fonction de la structure dendritique. En outre, l'émulation de la LTP a été démontrée non seulement au moyen d'un fil de grille Ag/AgCl, mais aussi au moyen d'une grille dendritique en polymère développée par électropolymérisation.Enfin, la plasticité structurelle a été démontrée par la croissance dendritique, où le poids de la connexion finale est régi par les règles d'apprentissage de type Hebbien (plasticité dépendante du moment de l'impulsion - STDP et plasticité dépendante du rythme de l'impulsion - SRDP). En utilisant les deux approches, une variété de topologies dendritiques avec des états de conductance programmables (c'est-à-dire le poids synaptique) et diverses dynamiques de croissance ont été observées. Finalement, en utilisant la même plasticité structurelle dendritique, des caractéristiques cérébrales plus complexes telles que l'apprentissage associatif et les tâches de classification ont été émulées.En outre, les perspectives futures de ces technologies basées sur des objets dendritiques polymères ont été discutées
Neuromorphic technologies is a promising direction for development of more advanced and energy-efficient computing. They aim to replicate attractive brain features such as high computational efficiency at low power consumption on a software and hardware level. At the moment, brain-inspired software implementations (such as ANN and SNN) have already shown their successful application for different types of tasks (image and speech recognition). However, to benefit more from the brain-like algorithms, one may combine them with appropriate hardware that would also rely on brain-like architecture and processes and thus complement them. Neuromorphic engineering has already shown the utilization of solid-state electronics (CMOS circuits, memristor) for the development of brain-inspired devices. Nevertheless, these implementations are fabricated through top-down methods. In contrast, brain computing relies on bottom-up processes such as interconnectivity between cells and the formation of neural communication pathways.In the light of mentioned above, this work reports on the development of programmable 3D organic neuromorphic devices, which, unlike most current neuromorphic technologies, can be created in a bottom-up manner. This allows bringing neuromorphic technologies closer to the level of brain programming, where necessary neural paths are established only on the need.First, we found out that PEDOT:PSS based 3D interconnections can be formed by means of AC-bipolar electropolymerization and that they are capable of mimicking the growth of neural cells. By tuning individually the parameters of the waveform (peak amplitude voltage -VP, frequency - f, duty cycle - dc and offset voltage - Voff), a wide range of dendrite-like structures was observed with various branching degrees, volumes, surface areas, asymmetry of formation, and even growth dynamics.Next, it was discovered that dendritic morphologies obtained at various frequencies are conductive. Moreover, each structure exhibits an individual conductance value that can be interpreted as synaptic weight. More importantly, the ability of dendrites to function as OECT was revealed. Different dendrites exhibited different performances as OECT. Further, the ability of PEDOT:PSS dendrites to change their conductivity in response to gate voltage was used to mimic brain memory functions (short-term plasticity -STP and long-term plasticity -LTP). STP responses varied depending on the dendritic structure. Moreover, emulation of LTP was demonstrated not only by means of an Ag/AgCl gate wire but as well by means of a self-developed polymer dendritic gate.Finally, structural plasticity was demonstrated through dendritic growth, where the weight of the final connection is governed according to Hebbian learning rules (spike-timing-dependent plasticity - STDP and spike-rate-dependent plasticity - SRDP). Using both approaches, a variety of dendritic topologies with programmable conductance states (i.e., synaptic weight) and various dynamics of growth have been observed. Eventually, using the same dendritic structural plasticity, more complex brain features such as associative learning and classification tasks were emulated.Additionally, future perspectives of such technologies based on self-propagating polymer dendritic objects were discussed

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Oakley, John Christopher. « The role of calcium spikes in neocortical pyramidal cell dendrites : implications for the transduction of dendritic current into spike output / ». Thesis, Connect to this title online ; UW restricted, 1999. http://hdl.handle.net/1773/10525.

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Naim, Magda Mohamed. « Primary afferent input to neurons in laminae III and IV of the rat spinal cord which possess the neurokinin-1 (NK-1) receptor ». Thesis, University of Glasgow, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298697.

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Glenn, L. Lee, et Jeff Knisley. « Transients in Branching Multipolar Neurons With Tapering Dendrites and Sodium Channels ». Digital Commons @ East Tennessee State University, 2005. https://dc.etsu.edu/etsu-works/7523.

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Book Summary: Computational models of neural networks have proven insufficient to accurately model brain function, mainly as a result of simplifications that ignore the physical reality of neuronal structure in favor of mathematically tractable algorithms and rules. Even the more biologically based "integrate and fire" and "compartmental" styles of modeling suffer from oversimplification in the former case and excessive discretization in the second. This book introduces an integrative approach to modeling neurons and neuronal circuits that retains the integrity of the biological units at all hierarchical levels. With contributions from more than 40 renowned experts, Modeling in the Neurosciences, Second Edition is essential for those interested in constructing more structured and integrative models with greater biological insight. Focusing on new mathematical and computer models, techniques, and methods, this book represents a cohesive and comprehensive treatment of various aspects of the neurosciences from the molecular to the network level. Many state-of-the-art examples illustrate how mathematical and computer modeling can contribute to the understanding of mechanisms and systems in the neurosciences. Each chapter also includes suggestions of possible refinements for future modeling in this rapidly changing and expanding field. This book will benefit and inspire the advanced modeler, and will give the beginner sufficient confidence to model a wide selection of neuronal systems at the molecular, cellular, and network levels.

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Wefelmeyer, Winnie. « Calcium and chloride dynamics in immature neurons and their role in dendritic growth ». Thesis, University of Oxford, 2010. http://ora.ox.ac.uk/objects/uuid:5b67b345-8469-4370-8e3f-68bef6a629e9.

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Activity-dependent dendritic development is an important process in the maturation of neuronal circuits. The precise morphology of a neuron’s dendritic tree dictates which other cells it is able to interact with and how it will receive and process synaptic information. The aim of this Thesis was to investigate the mechanisms by which dendrites grow and, in particular, how changes in intracellular ion concentrations contribute to these mechanisms. One important activity-dependent signal is calcium as it can translate neuronal activity into morphological changes. Despite this, very little is known about calcium signalling during the period of dendritic development. Using single-cell electroporation of immature CA1 hippocampal pyramidal neurons, I characterised the spatial and temporal properties of local calcium transients in growing dendrites. This revealed a high frequency of transients at shaft filopodia and stable branchpoints, but an almost complete absence from the tips of dendritic branches. Another important factor during development is the intracellular chloride concentration because this regulates neuronal excitability. Prematurely lowering intracellular chloride by expressing the chloride co-transporter KCC2 led to less stable dendritic filopodia and stunted dendritic growth. These effects were independent of local calcium signalling and suggested that chloride regulation itself may be fundamental to normal dendritic growth. To examine this further I developed imaging techniques to measure the spatial and temporal dynamics of chloride in growing dendrites. This work revealed a somatodendritic gradient of increasing intracellular chloride, whereby the highest concentrations were found at sites of growth. Further analysis suggested a close link between local chloride regulation and morphological changes. The dendritic tips that exhibited high intracellular chloride levels and the potential to rapidly modulate these levels, also exhibited the greatest morphological dynamics. These findings have important implications for understanding the mechanisms of dendritic growth and establish the spatiotemporal regulation of chloride as a key parameter.

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Guinaudeau, Ophélie. « Neurone abstrait : une formalisation de l’intégration dendritique et ses propriétés algébriques ». Thesis, Université Côte d'Azur (ComUE), 2019. http://www.theses.fr/2019AZUR4001/document.

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Les neurones biologiques communiquent par le biais d’impulsions électriques, appelées spikes, et les fonctions cérébrales émergent notamment de la coordination entre les réceptions et émissions de ces spikes. Par ailleurs, il est largement admis que la fonction de chaque neurone dépend de sa morphologie. Les dendrites conditionnent l’intégration spatio-temporelle des spikes reçus et influent sur les temps d’occurrence des spikes émis. Elles sont donc fondamentales pour l’étude in silico des mécanismes de coordination, et en particulier pour l’étude des assemblées de neurones. Les modèles de neurones existants prenant en compte les dendrites, sont généralement des modèles mathématiques détaillés, souvent à base d’équations différentielles, dont la simulation nécessite des ressources de calculs importantes. De plus, leur complexité intrinsèque rend difficile l’analyse et les preuves sur ces modèles. Dans cette thèse, nous proposons un modèle de neurone intégrant des dendrites d’une manière abstraite. Dans l’objectif d’ouvrir la porte aux méthodes formelles, nous établissons une définition rigoureuse du cadre de modélisation et mettons en évidence des propriétés algébriques remarquables de l’intégration dendritique. Nous avons notamment démontré qu’il est possible de réduire la structure d’un neurone en préservant sa fonction d’entrée/sortie. Nous avons ainsi révélé des classes d’équivalence dont nous savons déterminer un représentant canonique. En s’appuyant sur la théorie des catégories et par des morphismes de neurones judicieusement définis, nous avons ensuite analysé plus finement ces classes d’équivalence. Un résultat surprenant découle de ces propriétés : un simple ajout de délais dans les modèles informatiques de neurones permet de prendre en compte une intégration dendritique abstraite, sans représenter explicitement la structure arborescente des dendrites. À la racine de l’arborescence dendritique, la modélisation du soma contient inévitablement une équation différentielle lorsque l’on souhaite préserver l’essence du fonctionnement biologique. Ceci impose de combiner une vision analytique avec la vision algébrique. Néanmoins, grâce à une étape préalable de discrétisation temporelle, nous avons également implémenté un neurone complet en Lustre qui est un langage formel autorisant des preuves par model checking. Globalement, nous apportons dans cette thèse un premier pas encourageant vers une formalisation complète des neurones, avec des propriétés remarquables sur l’intégration dendritique
Biological neurons communicate by means of electrical impulses, called spikes. Brain functions emerge notably from reception and emission coordination between those spikes. Furthermore, it is widely accepted that the function of each neuron depends on its morphology. In particular, dendrites perform the spatio-temporal integration of received spikes and affect the occurrence of emitted spikes. Dendrites are therefore fundamental for in silico studies of coordination mechanisms, and especially for the study of so-called neuron assemblies. Most of existing neuron models taking into account dendrites are detailed mathematical models, usually based on differential equations, whose simulations require significant computing resources. Moreover, their intrinsic complexity makes difficult the analysis and proofs on such models. In this thesis, we propose an abstract neuron model integrating dendrites. In order to pave the way to formal methods, we establish a rigorous definition of the modeling framework and highlight remarkable algebraic properties of dendritic integration. In particular, we have demonstrated that it is possible to reduce a neuron structure while preserving its input/output function. We have thus revealed equivalence classes with a canonical representative. Based on category theory and thanks to properly defined neuron morphisms, we then analyzed these equivalence classes in more details. A surprising result derives from these properties: simply adding delays in neuron computational models is sufficient to represent an abstract dendritic integration, without explicit tree structure representation of dendrites. At the root of the dendritic tree, soma modeling inevitably contains a differential equation in order to preserve the biological functioning essence. This requires combining an analytical vision with the algebraic vision. Nevertheless, thanks to a preliminary step of temporal discretization, we have also implemented a complete neuron in Lustre which is a formal language allowing proofs by model checking. All in all, we bring in this thesis an encouraging first step towards a complete neuron formalization, with remarkable properties on dendritic integration

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Palavalli, Amrutha Ravindranath. « Etude de la dynamique du développement des dendrites dans les neurones sensoriels de la Drosophile ». Thesis, Aix-Marseille, 2019. http://theses.univ-amu.fr.lama.univ-amu.fr/191213_PALAVALLI_199shz503gjpdt117oxkoxb397dogzc_TH%20(1).pdf.

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Les dendrites des neurones présentent une grande diversité dans leur morphologie qui s’avère être cruciale pour l’intégration des informations qu’elles reçoivent. Bien que plusieurs molécules et voies de signalisation sont connues pour gouverner le développement des dendrites, comment ces molécules instruisent l’architecture complexe et stéréotypée des arborisations dendritiques reste mal connu. Deux mécanismes de morphogenèse ramifiée ont émergé de l’étude de systèmes ramifiés pour lesquels une description de leur développement était rendue possible. Les systèmes déterministes ont des points de branchements stéréotypés et prédictibles, souvent contrôlés par des signaux développementaux externes et préétablies. Les systèmes auto-organisés sont plus variables mais les ramifications suivent des règles statistiques qui finissent par produire des morphologies similaires. Nous avons étudié les neurones multi-dendritiques chez la Drosophile, qui constituent un système de choix pour comprendre les règles qui gouvernent la morphologie des dendrites. Premièrement, nous avons d’abord découvert qu’une grande partie de la morphogenèse ramifiée des dendrites est établie au cours de l’embryogenèse, après quoi le système déjà structuré s’adapte seulement à l’échelle au cours de la croissance larvaire. Nous avons ensuite développé un nouveau protocole pour observer le développement embryonnaire des dendrites in vivo qui suggère que la croissance de dendrite primaire est déterministe alors que celle des dendrites secondaires est plutôt auto-organisée. Nous avons de plus montré que les dendrites secondaires sont contrôlées au moins en partie par la répulsion au soi orchestrée par dscam1
Neurons have very specific dendrite morphologies crucial for the correct integration of inputs that they receive. Dendrite morphology is likely shaped by both internal and external inputs that are tightly controlled in space and time. Although several molecules and pathways involved in dendrite patterning are known, how these molecules instruct neurons to achieve their type-specific morphology remains unclear. This is mainly due to a lack of precise descriptions during dendrite development as in vivo live imaging of neuronal systems has several technical challenges. However, two mechanisms of branching morphogenesis emerge from studying branched systems in which such precise descriptions during development have been possible. Deterministic systems have stereotyped, predictable branch points often controlled by extrinsically patterned developmental cues. Self-Organized systems are variable but branching features follow conserved statistical rules that ultimately result in similar morphologies. Our study therefore aimed to understand whether neuronal morphogenesis was deterministic or self-organized. We used the Drosophila multi-dendritic neurons that been a favored system for studying dendrite morphology. We first established that a majority dendrite patterning occurs during embryogenesis after which the dendrite pattern nearly scales with larval growth. We then developed a protocol to observe embryonic development of the dendrite, which suggested that the primary branches grow deterministically and that secondary branches might be self-organized. We further show that secondary branches are patterned at least partly by self-repulsion via dscam1

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Baudouin, Stéphane Boudin Hélène. « Le développement neuronal rôle de la protéine adaptatrice CD3zeta et mécanismes régulant la fonction du récepteur de chimiokine CXCR4 / ». [S.l.] : [s.n.], 2009. http://castore.univ-nantes.fr/castore/GetOAIRef?idDoc=53986.

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Schoen, Alan. « A linear compartmental model that simulates resonance and signal-transfer in dendrites ». Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=107661.

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Dendrites carry signals between synapses and the soma and they play a central role in neural computation. Although dendrites contain many nonlinear ion channels, they are linear under some experimental conditions. In signal-transfer experiments with continuous-time inputs, a simple two-port linear model provides a near-perfect fit to the dendrite-to-soma input/output relationship. I extended this model by converting it to a membrane impedance framework which I applied to reconstructed neuron models. The membrane impedance model preserves the accuracy of the two-port model with minimal computational complexity. Using this approach, I demonstrate two membrane impedance profiles that reproduced the experimentally-observed two-port results. The impedance profiles show that the two-port results are compatible with different computational schemes. They also show that linear-resonance can be used to minimize the effect of location on signal-transfer. My model provides a novel computational view of neurons, where dendrites function as linear resonant filters which carry signals between computational units.
Les dendrites transportent des signaux entre les synapses et le soma et jouent un rôle central dans computation neuronales. Même si les dendrites contiennent plusieurs canaux à ions non-linéaire, ceux-ci peuvent être linéaires sous certaines conditions expérimentales. Lors d'une expérience de transfert de signaux avec des entrées continues dans le temps, un simple model linéaire à deux-ports peut approximer presque parfaitement la relation dendrite-soma entrée-sortie. J'ai étendu ce modèle en le convertissant à un contexte d'impédance de membrane que j'ai utilisé pour reconstruire les modèles de neurones. Le modèle d'impédance de membrane conserve la précision du modèle deux-ports avec une complexité computationnelle minimale. En utilisant cette approche, je démontrons le profile de l'impédance de deux membranes qui reproduisent les résultats deux-ports observés expérimentalement. Les profiles de l'impédance montrent que les résultats deux-ports sont compatibles avec différentes approches computationnelles. Aussi, nos modèles suggèrent une résonnance linéaire qui peut être utilisée pour minimiser l'effet de l'emplacement sur le signal-transfert. Mon modèle fournit une nouvelle approche computationnelle pour les neurones, où les dendrites fonctionnent comme filtre résonant linéaire transportant les signaux entrent les unités computationnelles.

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Ma, Dan. « Protein synthetic organelles and mRNAs in the dendrites of hypothalamic magnocellular neurons ». Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325153.

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Glenn, L. Lee, et Jeffrey R. Knisley. « Voltage Transients in Branching Multipolar Neurons With Tapering Dendrites and Sodium Channels ». Digital Commons @ East Tennessee State University, 2005. https://dc.etsu.edu/etsu-works/7537.

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Book Summary: With contributions from more than 40 renowned experts, Modeling in the Neurosciences: From Ionic Channels to Neural Networks is essential for those interested in neuronal modeling and quantitative neiroscience. Focusing on new mathematical and computer models, techniques and methods, this monograph represents a cohesive and comprehensive treatment of various aspects of the neurosciences from the biophysical, cellular and netwrok levels. Many state-of-the-art examples are presented as to how mathematical and computer modeling can contribute to the understanding of mechanisms and systems in the neurosciences. Each chapter also includes suggestions of possible refinements for future modeling in this rapidly changing and expanding field. This book will benefit and inspire the advanced modeler, and give the beginner sufficient confidence to model a wide selection of neuronal systems at the biophysical, cellular and network levels.

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Chakrabarty, Arnab. « Role of sensory input in structural plasticity of dendrites in adult neuronal networks ». Diss., lmu, 2013. http://nbn-resolving.de/urn:nbn:de:bvb:19-155241.

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Chapot, Camille [Verfasser], et Thomas [Akademischer Betreuer] Euler. « Local signal processing in mouse horizontal cell dendrites / Camille Chapot ; Betreuer : Thomas Euler ». Tübingen : Universitätsbibliothek Tübingen, 2017. http://d-nb.info/1167311256/34.

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Mukanowa, Janina. « Activity-dependent changes in neuronal architecture : dendrites, axon and the axon initial segment ». Thesis, King's College London (University of London), 2014. https://kclpure.kcl.ac.uk/portal/en/theses/activitydependent-changes-in-neuronal-architecture(e665f67d-850e-4329-8677-6662323a3781).html.

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The assembly of the brain during embryonic development was thought to be largely independent of its electrical activity. It was believed that activity, broadly defined as spontaneous or evoked changes in membrane potential, is important only in later stages of development, after a basic template of the nervous system has already been established. Recent data, however, suggests that activity plays a crucial role in all stages of neural development, from cell proliferation and migration to establishment and maturation of synaptic connections. In this thesis, I explore the role of activity on early development of axons, dendrites and the axon initial segments of hippocampal neurons in vitro. Activity was modulated by either elevated levels of KCl or optogenetic stimulation of ChR2-expressing neurons. Elevated activity had only a modest effect on the morphology of dendritic and axonal compartments, however it strongly affected the structure of the axon initial segment (AIS). Chronic depolarisation of developing hippocampal neurons led to reversible, cell-death independent, AIS disassembly in a subset of susceptible neurons. This effect required Ca2+ influx though L-type voltage-gated Ca2+ channels and was observed mostly in young (4-7 DIV) neurons, suggesting the existence of a developmental window for this type of activity-induced change. Electrophysiological recordings and Ca2+ imaging experiments showed that cells without an AIS have markedly decreased Na+ currents and are unable to initiate repetitive firing. The AISs that were not disassembled in response to elevated activity had significantly altered structural properties, in terms of their length and position along the axon. The exact nature of these changes depended on the specific developmental stage at which the neurons were depolarised. The susceptibility of the AIS to alterations in neuronal activity may suggest the existence of a novel form of plasticity in immature neurons, which may be important for stabilisation of neuronal activity in developing hippocampal circuits.

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Marchenko, Olena O., Sulagna Das, Ji Yu, Igor L. Novak, Vladimir I. Rodionov, Nadia Efimova, Tatyana Svitkina, Charles W. Wolgemuth et Leslie M. Loew. « A minimal actomyosin-based model predicts the dynamics of filopodia on neuronal dendrites ». AMER SOC CELL BIOLOGY, 2017. http://hdl.handle.net/10150/624039.

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Dendritic filopodia are actin-filled dynamic subcellular structures that sprout on neuronal dendrites during neurogenesis. The exploratory motion of the filopodia is crucial for synaptogenesis, but the underlying mechanisms are poorly understood. To study filopodial motility, we collected and analyzed image data on filopodia in cultured rat hippocampal neurons. We hypothesized that mechanical feedback among the actin retrograde flow, myosin activity, and substrate adhesion gives rise to various filopodial behaviors. We formulated a minimal one-dimensional partial differential equation model that reproduced the range of observed motility. To validate our model, we systematically manipulated experimental correlates of parameters in the model: substrate adhesion strength, actin polymerization rate, myosin contractility, and the integrity of the putative microtubule-based barrier at the filopodium base. The model predicts the response of the system to each of these experimental perturbations, supporting the hypothesis that our actomyosin-driven mechanism controls dendritic filopodia dynamics.

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Jullié, Damien. « Les endosomes de recyclage fusionnent transitoirement avec la membrane plasmique des dendrites neuronales ». Thesis, Bordeaux 2, 2012. http://www.theses.fr/2012BOR21942/document.

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Le trafic membranaire est essentiel dans les neurones pour la morphogénèse, le recyclage des vésicules synaptiques et des récepteurs. L’exocytose des récepteurs AMPA contenus dans les endosomes de recyclage (ER) est nécessaire pour l’expression de la plasticité synaptique à long terme (PLT). Pour étudier ce mécanisme, nous avons visualisé l’exocytose par microscopie de fluorescence sur des neurones en culture transfectés avec le récepteur de la transferrine (TfR), un marqueur des ER, fusionné à la phluorine. Un examen systématique des événements d'exocytose a révélé des différences de comportement. Dans la plupart des cas, les récepteurs diffusent rapidement dans la membrane plasmique après exocytose (discharge), mais dans environ 25% des cas, les récepteurs restent concentrés (display). L’utilisation de changements rapides de pH extracellulaire autour de la cellule montre que l’exocytose est transitoire : après quelques secondes (médiane 2.6s) les récepteurs sont réinternalisés. Ce mécanisme a pu être étendu aux récepteurs AMPA et β2-adrenergique, pour lesquels l’exocytose de type display avait déjà été décrite. L’imagerie deux couleurs montre que Rab11, un marqueur des ER, est enrichie au site d’exocytose. L’expression d’un dominant négatif de Rab11 connu pour inhiber la PLT provoque une diminution spécifique de la fréquence des évènements discharge. Dans nos recherches sur le mécanisme de l’exocytose, nous avons testé l’implication des protéines SNARE dans la fusion membranaire. Ainsi VAMP4 est enrichie avec le TfR dans les ER qui sont exocytés à une fréquence équivalente. De plus, elle est requise pour le recyclage du TfR
Membrane trafficking is essential for neuronal function: from growth of neurons and synapse formation to recycling of synaptic vesicles and receptors, questions concerning exocytosis and endocytosis are stimulating neurobiology research. In particular, trafficking of glutamate receptors present in recycling endosomes (REs) is necessary for the expression of long term potentiation (LTP). To investigate the mechanism of exocytosis in dendrites, we have imaged cultured rat hippocampal neurons transfected with transferrin receptor, a classical marker of REs, tagged with phluorin. As for AMPA receptors or β2-adrenegric receptors, single exocytic events has revealed two main behaviors: in most cases, receptors diffuse quickly in the plasma membrane after exocytosis (discharge events), but receptors can also remain clustered (display events). Using fast extracellular pH changes around the recorded cell, we show that for display events exocytosis is transient: after a few seconds (median 2.6 s) receptors are internalized. Moreover, using two color imaging of single exocytosis events with markers of neuronal compartments, we found that Rab11 is enriched at the exocytosis site, confirming the endosomal origin of the vesicles. Overexpression of a dominant negative form of Rab11 known to impair LTP decreases selectively the frequency of discharge events. As SNARE proteins are involved in virtually all membrane fusion processes, we investigated the role of Vamp proteins in somatodendritic exocytosis events. We found that Vamp4, unlike Vamp2 or Vamp7, is enriched in TfR containing compartments and can undergo exocytosis at high frequency and is required for TfR exocytosis

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Macia, Mario Luis. « A study of dendritic precipitation, grain boundary serration formation and discontinuous precipitation in nickel base superalloys ». Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/19645.

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Dupere, Jonathan R. B. « An electrophysiological and pharmacological characterization of a Ca'2'+ channel currents in the soma and dendrites of adult rat cerebellar Purkinje cells ». Thesis, University of Bristol, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388018.

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Ikpegbu, Ekele. « Effects of FGF-2 on E11-mediated osteocytogenesis in skeletal health and disease ». Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/31361.

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Fibroblast growth factor 2 (FGF-2) is known to be released from cartilage upon injury and is able to influence chondrocyte gene expression in vitro. In cartilage, FGF-2 regulates E11/podoplanin expression in murine joints following surgical destabilisation (DMM model of osteoarthritis (OA)), and in cartilage explant injury models. In bone, E11 is critical for the early stages of osteocytogenesis and is responsible for the acquisition of the osteocyte dendritic phenotype. This dendritic phenotype is dysregulated in OA and given the known role of the osteocyte in controlling bone remodelling, this may contribute to the subchondral bone thickening observed in OA. Hence, the aim of this study was to elucidate the nature of FGF-2- mediated E11 expression and osteocytogenesis in skeletal health and disease. This thesis has shown that FGF-2 dose-dependently increased E11 mRNA expression in MC3T3 cells, primary osteoblasts and in primary calvaria organ cultures, which was confirmed by E11 protein western blotting data. The FGF-2 induced changes in E11 expression were accompanied by significant increases in the mRNA expression of the osteocyte markers Phex and Dmp1, and significant decreases in the mRNA expression of the osteoblast markers Col1a1, Postn, Bglap and Alpl expression. This thus supports the hypothesis that FGF-2 drives osteocytogenesis. The acquisition of osteocyte phenotype involves the re-organisation of the cytoskeleton, such as F-actin. This step is important for the transition of cuboidal-shaped osteoblasts to the stellate-shaped osteocyte phenotype. FGF-2 stimulation of MC3T3 cells and primary osteoblasts revealed more numerous and longer dendrites, as visualised by phalloidin staining for F-actin and indicative of the acquisition of the osteocyte phenotype. In contrast, control cells had a typical rounded morphology with fewer and shorter dendrites. Furthermore, immunofluorescence labelling for E11 in control cells revealed uniform distribution throughout the cytoplasm, especially in the perinuclear region. In contrast, FGF-2 treated cells showed a modified distribution where E11 was negligible in the cytoplasm, but concentrated in the dendrites. The use of siRNA knockdown of E11 achieved a 70% reduction of basal E11 mRNA expression. This knockdown also effectively abrogated FGF-2-related changes in E11 expression and dendrite formation as disclosed by mRNA and protein expression, immunofluorescence and F-actin staining with phalloidin. Despite these FGF-2 driven increases in E11 and osteocyte dendrite formation in vitro, immunohistochemical labelling revealed no differences in E11 expression in subchondral, trabecular and cortical osteocytes from naïve Fgf-2 deficient mice in comparison to wild-type mice. Similar results were observed upon sclerostin immunolabelling. FGF-2 stimulation of MC3T3 cells elicited activation of ERK1/2, Akt and p38 MAPK. However, inhibition of the aforementioned pathways failed to reduce FGF-2- mediated E11 expression and as such, the specific signalling pathway responsible remains unclear. Upstream, the expression of Fgfr1 was increased (>10-fold) over 24 h time point, while a reduction was seen in Fgfr2/3 expression over same time point especially in the FGF-2 treated cultures. This suggests that increased E11 expression and the acquisition of the osteocyte phenotype may be speculatively though upregulation of Fgfr1. The expression of E11 and sclerostin in OA pathology in mice, human and dogs were investigated. Initially sequence homology using the Clustal Omega alignment program showed both proteins to be homologous in the domestic animals under study. A comparative study using canine subchondral bone osteocytes revealed increased E11 expression in the OA samples relative to the control. This feature may be related to newly embedded osteocytes during sclerosis. However, E11 and sclerostin were unchanged in both murine (DMM) and human OA subchondral bone osteocytes in comparison to controls. In mice, this may be due to limited OA development; whilst in humans the sample size, age, stage of the disease and sourcing from same diseased joint may be important in the interpretation of the results. The expression of E11 and sclerostin during OA pathology was also investigated in Fgf-2 deficient mice in which OA was induced using the DMM model. There was no difference in E11 expression between the OA and control (sham-operated) samples, suggesting that compensation of E11 expression may be mediated by growth factors from the FGF family. Surprisingly, increased E11 expression was observed in the control Fgf-2 deficient mice, in comparison to the wild-type control mice. This suggests a potential adjustment to loading by the contralateral knee, as this was not observed in naïve mice from both groups. Together, these data show that FGF-2 promotes the osteocyte phenotype, and that this is mediated by increased E11 expression. These results may help explain (1) the altered osteocyte phenotype and (2) increased subchondral bone thickening observed in OA. This knowledge will be of interest in the search for disease modifying therapeutics for skeletal health, including OA and osteoporosis.

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Angibaud, Julie. « Rôle de la molécule immune CD3dzëta dans le développement neuronal et les fonctions cérébrales ». Nantes, 2010. http://archive.bu.univ-nantes.fr/pollux/show.action?id=0592173b-3ec8-4c03-a093-0435991aa821.

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Le développement neuronal se construit selon une succession d’étapes aboutissant à la formation d’un réseau fonctionnel. Des données récentes montrent que des molécules bien décrites dans le système immunitaire (SI) possèdent également un rôle non immun dans certaines étapes du développement cérébral. Nous avons cherché à identifier la fonction de la protéine CD3dzëta, constituant majeur du complexe CD3 des lymphocytes T, au cours de la neuritogenèse et de la différenciation dendritique. Au cours du développement neuronal précoce, nos analyses immunohistochimiques sur des neurones différenciés à partir de cellules souches neurales montrent que le CD3dzëta est présent dès la naissance des neurones et est impliqué dans l’émergence des premiers prolongements neuronaux. Des approches combinées de perte et de gain de fonction révèlent qu’au cours de la formation des neurites, le CD3dzëta joue un rôle inhibiteur sur la formation des neurites, en stabilisant l’émergence fines structures immatures, appelées filopodes, via la protéine Rho GEF Vav2. De façon intéressante, cette action inhibitrice de CD3dzëta est conservée à des stades de développement plus tardifs lors de la dendritogenèse. A ce stade, CD3dzëta régule négativement la croissance dendritique. Notre étude a permis d’identifier un rôle inédit de la protéine CD3dzëta dans le système nerveux central. Nous avons montré que CD3dzëta agit comme un frein moléculaire dans l’élaboration des prolongements neuronaux. Ces résultats sont particulièrement importants pour appréhender les effets potentiels neuropathologiques sur le système nerveux central lors de thérapies ciblant le SI
Neuronal development is achieved by a complex process leading to the formation of a functional network. Recent data showed that well-known molecules previously characterized in the immune system have also non immune functions in critical stages of cerebral development. The aim of our study was to identify the function of CD3dzëta, a major component of the CD3 complex in T lymphocytes, during neuritogenesis and dendrite differentiation. Upon neuronal differentiation from neural stem cells, immunohistochemical studies showed that CD3dzëta was expressed as soon as neuronal birth, and was involved in the emergence of the first neurites. A combination of loss- and gain-of-function experiments revealed that CD3dzëta played an inhibitory role on neurite formation by stabilizing the emergence of thin immature structures, called filopodia, through a Rho GEF VAV2-dependant mechanism. Interestingly, this inhibitory action was conserved at latter stages of neuronal development, during neuritogenesis. At this stage, CD3dzëta negatively regulated dendritic outgrowth. Our study revealed an unexpected role of CD3dzëta in the central nervous system. We showed that CD3dzëta acts as a molecular brake in the establishment of neuronal extension. Moreover, our results point out of potential neuropathological consequences on cerebral functions of therapies targeted the immune system

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Zhang, Yun [Verfasser]. « Augmin complex components control branching of sensory neuron dendrites in Drosophila larvae. / Yun Zhang ». Bonn : Universitäts- und Landesbibliothek Bonn, 2016. http://d-nb.info/1107184355/34.

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Herdman, Anthony T. « Current source density analysis of current sinks in apical dendrites of CA1 pyramidal neurons ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/mq37548.pdf.

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Ghoudi, Hamza. « Propriétés statistiques des réseaux des applications couplées et récurrence des applications des dendrites locales ». Thesis, Toulon, 2019. http://www.theses.fr/2019TOUL0019.

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Cette thèse est divisée en deux grandes parties : la première est consacrée aux propriétés statistiques des systèmes dynamiques et l’autre porte sur des propriétés des systèmes dynamiques topologiques.Dans la première partie, d’abord nous rappelons quelques notions de base des systèmes dynamiques aléatoire et de la théorie des valeurs extrêmes. Ensuite, par l’application de cette théorie aux réseaux des applications couplées nous montrons que la probabilité de l’apparition de la synchronisation dans ces réseaux est liée à la distribution du maximum d’une certaine observable évaluée le long de presque toutes les orbites. De plus, nous montrons qu’une telle distribution appartient à la famille des lois des valeurs extrêmes, où le paramètre de cette distribution (indice extrémal) nous permet d’obtenir une description détaillée de la probabilité de synchronisation. Enfin, nous illustrerons les résultats théoriques par des calculs numériques robustes qui nous permettent d’aller au-delà du cadre théorique fourni.Dans la seconde partie, nous commençons par introduire quelques notions de base des systèmes dynamiques topologiques. Ensuite, nous étudions la relation entre les ensembles des points récurrents et périodiques d’une application continue de dendrites locales dans lui-même dans lequel l’ensemble des points d’extrémité est dénombrable
This thesis is divided into two parts the first is devoted to the study of the statistical properties of Dynamical systems and the other is about properties of topological dynamical systems.ln the first part, we recall the basic notions of random dynamical systems and the theory of extreme values. Then, by applying this theory to the cou pied map lattices, we show that the probability of the appearance of synchronization is related to the distribution of the maximum of a certain observable evaluated a long almost ail orbits. Moreover, we show that such a distribution belongs to the family of extreme value laws, where the parameter of this distribution (extremal index) allows us to obtain a detailed description of the probability of synchronization. Finally, we support the theoretical results by robust numerical computations that allow us to go beyond the theoretical framework. ln a second part, we give some basic notions of topological dynamical systems. Next, we study the relations between the sets of recurrent points and periodic points of a continuous self mapping of a local dendrite whose the endpoints set is countable

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Sondereker, Katelyn B. « EXPLORATION OF THE MORPHOLOGY, CONNECTIVITY, AND FUNCTION OF MELANOPSIN GANGLION CELL OUTER RETINAL DENDRITES ». University of Akron / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=akron1606144098442214.

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Krapivkina, Julia. « Identification de protéines SNARE de l'exocytose des endosomes de recyclage dans les dendrites neuronales ». Thesis, Bordeaux, 2016. http://www.theses.fr/2016BORD0343/document.

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Le trafic membranaire est un processus universel qui est essentiel pour la fonction neuronale dans un large spectre de fonctions. De la croissance neuronale et le développement morphologique à la libération des neurotransmetteurs et la plasticité synaptique, il prend en charge l'activité neuronale et donne d'innombrables questions qui animent la recherche sur la neurobiologie d'aujourd'hui. Notamment, l’exocytose des endosomes de recyclage (ER) dans les compartiments somatodendritiques participe à la transmission synaptique et à la potentialisation synaptique à long terme (PLT). Cependant la machine moléculaire sous-tendant l’exocytose des ER reste encore méconnue. Afin d’identifier les protéines SNAREs vésiculaires (v-SNARE) impliquées dans les différentes formes d’exocytose des ER postsynaptiques, nous avons d'abord imagé les protéines VAMP neuronales fusionnées avec la pHluorine, une GFP mutée sensible au pH dans les neurones de l’hippocampe en culture. Nous avons constaté que seulement VAMP2 et VAMP4, mais pas VAMP7, rapportaient des événements d’exocytose somatodendritique dans les neurones matures. Après avoir identifié ces deux protéines candidates, nous avons utilisé la combinaison de différentes techniques de régulation négative chronique ou aiguë pour désactiver leur fonction et observer les conséquences sur l’exocytose des ER, la transmission synaptique basale ou la PLT. Nos résultats suggèrent que VAMP2 est impliqué dans une forme d’exocytose régulée importante pour la PLT, mais pas l’exocytose constitutive des récepteurs AMPA, qui stabilise la transmission basale. VAMP4 est nécessaire pour l'exocytose constitutive d'une grande partie des endosomes, mais l'implication fonctionnelle de ces endosomes doit encore être explorée, car la régulation négative de VAMP4 ne modifie pas la transmission basale
Membrane trafficking is a universal process that is essential for neuronal function in a wide spectrum of applications. From neuronal growth and morphological development to neurotransmitter release and synaptic plasticity, it supports neuronal activity and gives countless questions that drive today’s neurobiology research. Notably, the trafficking of recycling endosomes (REs) in somatodendritic compartments participates in synaptic transmission and plasticity, such as long-term synaptic potentiation (LTP). However, the fusion machinery mediating RE exocytosis is still unclear. To identify the vesicular SNAREs (v-SNAREs) involved in different forms of postsynaptic RE exocytosis, we first imaged neuronal VAMP proteins fused with pH-sensitive pHluorin in cultured hippocampal neurons, and found that only VAMP2 and VAMP4, but not VAMP7, underwent somatodendritic exocytosis in mature neurons. After identifying these two candidate proteins, we used a combination of different downregulation techniques to chronically or acutely deactivate their function and observe consequences on REs exocytosis, basal synaptic transmission and LTP. Our results suggest that VAMP2 is involved in activity-regulated exocytosis important for LTP, but not constitutive postsynaptic AMPARs exocytosis, supporting basal transmission. VAMP4 is required for constitutive exocytosis of at least a large proportion of REs, but the functional implication of these endosomes still need to be explored, as VAMP4 downregulation did not alter basal synaptic transmission

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Moore, Carlene Drucilla. « The role of centaurin alpha-1 in the regulation of neuronal differentiation ». Thesis, Birmingham, Ala. : University of Alabama at Birmingham, 2008. https://www.mhsl.uab.edu/dt/2008d/moore.pdf.

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Monteiro, Olivia F. de S. « Mechanisms of dendritic peptide release ». Thesis, University of Edinburgh, 2010. http://hdl.handle.net/1842/4420.

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Magnocellular neurones (MCNs) are capable of secreting vasopressin and oxytocin from the somato-dendritic compartment, which can occur independently to secretion from nerve terminals. One hypothesis of the mechanism that regulates this differential release is that dendrites utilise different vesicle pools compared to those found in terminals. Little is known for the function of neuronal dendrites, especially the mechanism for peptide release. One theory is that vesicles stored in dendrites are non-released vesicles ready for recycling or degradation. Immunofluorescent labelling was performed on hypothalamic slices of the transgenic rat where enhanced green fluorescent protein (eGFP) was tagged to vasopressin. Lysosomes were detected by the lysosome-associated membrane protein LAMP1. Correlation analysis of LAMP1 labelling and VP-eGFP had shown that localisation of lysosomes in dendrites is positively correlated to loci of high vasopressin expression. This suggests active degradation of vesicles in dendrites. It is not known whether preferential release of peptides occurs along the profile of dendrites. Experiments were carried out using a temperature block to block exit of vesicles from the Golgi apparatus. Release of the temperature block triggered release of a wave of newly synthesised vesicles from the Golgi apparatus. Measurement of the fluorescent intensity of VP-eGFP showed that preferential release of peptides does not occur along the profile of dendrites. I have also utilised confocal live cell imaging to study the dynamics of dendritic vasopressin release using VP-eGFP slice explants. Experiments using high potassium stimulation showed significant increase in the release of vasopressin after priming with thapsigargin (intracellular calcium mobiliser), in accordance to in vitro release and microdialysis studies. These results demonstrate that live cell imaging can be achieved in magnocellular neurons, providing a robust model system in the study of dendritic peptide release. Large dense core vesicles (LDCVs) in other cell types such as bovine adrenal chromaffin cells were shown to segregate according to vesicle age, suggesting that vesicle age is an important factor in the regulation of peptide release. Whether vesicles of different age groups exist in magnocellular dendrites is not known. Thus, biolistic transfection with exogenous fluorescent proteins for expression under temporal control was carried out. However, low transfection rate in magnocellular neurones and the high background fluorescence caused by scattered gold particles used as bullets for transfection deemed this method inappropriate for the purpose of imaging vesicles. Hence, development of an adenoviral transduction system was employed. By using an inducible adenovirus gene construct coupled with a fluorescent reporter gene, it is possible to visualise vesicle pool segregation under different experimental conditions. Subcloning of a red fluorescent construct tagged to ppANF was tested on PC12 cells to show targeting of fluorescence expression to LDCVs. Successful production of an inducible adenoviral DNA with the red fluorescent construct insert was confirmed by PCR and DNA sequencing. Whilst the generation of viral particles is still to be achieved, successful production of the virus will be an invaluable system for inducible gene expression in neurones.

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De, Koninck Paul. « Factors that affect the extension of dendrites and the expression of nicotinic acetylcholine receptors by rat peripheral neurons ». Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=29006.

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The establishment of neuronal polarity constitutes a central phase in neuronal development and synaptogenesis. In my thesis, I study factors that regulate the development of neuronal polarity and its relationship with neurotransmitter receptor expression. For my experiments, I have investigated the development of sensory neurons from neonatal rat nodose ganglia in culture. Sensory neurons have a pseudo-unipolar morphology, do not extend dendrites, and are devoid of synaptic connections on their somata. However, nodose neurons form synapses de novo in cultures, and I show that the neurons have retained the ability to extend dendrites. Extrinsic factors control dendrite extension by these neurons: the ganglionic satellite cells inhibit the growth of dendrites and induce the neurons to develop a unipolar morphology. In the absence of satellite cells, nodose neurons establish a new multipolar morphology and, in response to nerve growth factor (NGF), extend several dendrites. However, brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) do not induce the neurons to extend dendrites, but promote the expression of properties typical of nodose neurons in vivo.
As nodose neurons acquire a new dendrite-axonal polarity in the presence of NGF, they increase the density of functional neuronal nicotinic acetylcholine receptors (nAChRs) on their somato-dendritic domains. To learn more about the relationship between dendrites extension and nAChR gene expression, I have examined the changes in transcript levels of nAChR subunits in neonatal rat sympathetic neurons developing in culture. I show that the developmental pattern of nAChR subunit expression in the cultured neurons follows closely that of sympathetic neurons developing in vivo, with the exception of one specific subunit $ alpha sb7$. I show that the increase in $ alpha sb3$ mRNA levels correlates well with an increase in the density of functional nAChRs on the neurons. In addition, my results suggest that these increases are regulated by mechanisms intrinsic to neonatal sympathetic neurons. On the other hand, the changes in $ alpha sb7$ gene expression, which correlate with changes in $ alpha$-bungarotoxin binding, are activity-dependent and regulated by a calcium/calmodulin-dependent protein kinase pathway. The results presented in this thesis provide insights on how neurons are influenced in their extension of dendrites and how this extension affects neurotransmitter receptor expression.

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Chwalla, Barbara. « Genes and mechanisms underlying the development of dendrites in the central nervous system of the Drosophila embryo ». Thesis, University of Cambridge, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.608389.

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Baudouin, Stéphane. « Le développement neuronal : rôle de la protéine adaptatrice CD3zeta et mécanismes régulant la fonction du récepteur de chimiokine CXCR4 ». Nantes, 2009. http://archive.bu.univ-nantes.fr/pollux/show.action?id=e1c7ec15-2047-495f-a325-8bf974e8128c.

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Le développement neuronal est assuré par un ensemble de mécanismes complexes permettant à terme la formation d'un réseau fonctionnel. Des données récentes montrent que des molécules bien décrites dans le système immunitaire ont également un rôle non immun dans des étapes fondamentales du développement cérébral. C'est dans ce contexte que nous avons étudié la molécule adaptatrice CD3zeta et le récepteur de chimiokine CXCR4. A des stades précoces de développement de neurones en culture, nous avons montré que CD3zeta est sélectivement associé aux cônes de croissance et aux filopodes. Des approches combinées de perte et de gain de fonction ont montré un rôle inhibiteur de CD3zeta dans la régulation du développement dendritique. Nos résultats suggèrent une nouvelle fonction de CD3zeta dans le contrôle de la morphogénèse dendritique. La chimiokine SDF-1 et son récepteur CXCR4 ont un rôle crucial dans plusieurs aspects du développement neuronal. Au cours de la formation des prolongements neuronaux, il a été montré que SDF-1 régule spécifiquement la formation de l’axone sans affecter les autres neurites. Nous avons montré que la stimulation du récepteur CXCR4 par son ligand SDF-1 induit l’internalisation du récepteur dans les dendrites mais pas dans l’axone. Ce résultat suggère que l’absence d’internalisation de CXCR4 dans le domaine axonal pourrait être un mécanisme permettant une action sélective de SDF-1 sur la pousse axonale. Nos résultats révèlent un rôle inédit de CD3zeta dans le développement neuronal et un mécanisme de régulation original de CXCR4 pouvant favoriser l’action sélective de SDF-1 sur les axones
Neuronal development is achieved by a complex set of mechanisms leading ultimately to the formation of a functional network. Recent data show that well-known molecules of the immune system also have non immune functions in critical stages of cerebral development. In this context, we studied the adaptor molecule CD3zeta and the chemokine receptor CXCR4. At early stages of neuronal development in culture, we have shown that CD3zeta is selectively associated with growth cones and filopodia. A combination of loss- and gain-of-function experiments in cultured neurons showed an inhibitory function of CD3zeta in dendrite development. These findings reveal a novel role of CD3zeta in the control of dendrite morphogenesis. The chemokine SDF-1 and its receptor CXCR4 have a critical role in many aspects of neuronal development. During the formation of neuronal processes, it has been shown that SDF-1 selectively regulates axonal patterning and does not affect the other neurites. We found that the stimulation of CXCR4 by SDF-1 induces receptor internalization in the somatodendritic domain but not in axons. This result suggests that the lack of CXCR4 internalization in axons might be a mechanism used to allow a selective action of SDF-1 in axonal growth. Our results reveal a novel role of CD3zeta in neuronal development and an original regulatory mechanism for CXCR4 that could promote a selective action of SDF-1 on axons

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De, La Garza Richard. « Determination of neuronal morphology in spinal monolayer cultures ». Thesis, University of North Texas, 1989. https://digital.library.unt.edu/ark:/67531/metadc798395/.

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The objective of the completed research was to characterize the morphology of individual neurons within monolayer networks of fetal mouse spinal tissue via intraperikaryal injections of horseradish peroxidase (HRP). Thirty labelled neurons were reconstructed via camera lucida drawings and morphometrically analyzed.

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Nibhanupudi, Syam S. « Affect of pressurised solidification on the secondary dentritic arm spacing in lead-tin alloy ». abstract and full text PDF (free order & ; download UNR users only), 2008. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1453603.

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Kawabata, Kelly. « Functional Analysis of MTSS1 Regulation of Purkinje Cell Dendritic Development and Actin Dynamics ». Kyoto University, 2018. http://hdl.handle.net/2433/235121.

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Lebrun, Clément. « Identification des facteurs de transcription dont l'expression est régulée au cours de la maturation des cellules de Purkinje : rôle de Klf9 dans la survie cellulaire et le développement dendritique ». Paris 6, 2010. http://www.theses.fr/2010PA066203.

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Au cours des 10 premiers jours de vie postnatale (P0-P10), les cellules de Purkinje de souris passent par une période de mort développpementale et subissent une régression puis une croissance dendritique. Afin de sélectionner des candidats susceptibles de contrôler l’arrêt de la mort développementale ou la maturation dendritique, nous avons cherché les facteurs de transcription dont l’expression varie entre P0 et P10. L’analyse de transcriptomes de cortex cérébelleux à différents âges, puis la validation de l’expression des gènes candidats par différentes techniques, nous a permis de sélectionner 1 facteur de transcription dont l’expression augmente : Klf9 (Krüppel like facteur). En culture organotypique de cervelet, l’expression précoce de Klf9 par transduction lentivirale augmente la survie des cellules de Purkinje transduites, tandis que son inhibition par expression lentivirale de shARN la diminue. La diminution de cette survie peut être supprimée par ajout d’IGF1, un facteur trophique des cellules de Purkinje. Le nombre de cellules de Purkinje diminue également dans le cervelet de souris Klf9-/- mis en culture organotypique. Ainsi, l’expression de Klf9 est nécessaire et suffisante à la survie des cellules de Purkinje en culture organotypique, suggérant un rôle de ce facteur dans l’arrêt de la mort développementale de ces neurones. Notre étude a permis également de montrer l’induction de la rétraction des dendrites primaires et de la formation des épines des cellules de Purkinje suite à l’expression précoce de Klf9. Ainsi, ce facteur intervient également dans le développement dendritique et la formation des épines des cellules de Purkinje

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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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