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1
Moonens, Sofie. "Mirror Neurons : The human mirror neuron system." Thesis, Högskolan i Skövde, Institutionen för kommunikation och information, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:his:diva-6103.
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This literature review explores human mirror neurons from several angles. First it retells mirror neuron history, from the initial discovery in the macaque monkey research through to the experiments determining if there is a human brain homologue. Then the merits of two opposing evolutionary views – mirror neurons as an adaptation or an association, here referring to an adaptation’s byproduct – are discussed. Lastly the autistic mirror neuron dysfunction hypothesis – stating that a faulty mirror neuron system is at the basis of autistic behavioral patterns – is examined for its validity but ultimately found lacking and in need of further development.
2
Steinbush, H. W. M. "Het neuron als bruggenbouwer "bridging disciplines by neurons" /." Maastricht : Maastricht : Instituut hersenen en gedrag ; University Library, Universiteit Maastricht [host], 1999. http://arno.unimaas.nl/show.cgi?fid=12984.
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3
Moubarak, Estelle. "Constraints imposed by morphological and biophysical properties of axon and dendrites on the electrical behaviour of rat substantia nigra pars compacta dopaminergic neurons." Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0746.
Full textAbstract:
L’activité électrique des neurones est déterminée par des interactions complexes entre leurs propriétés morphologiques et biophysiques. Les neurones dopaminergiques (DA) de la substance noire compacte (SNc) présentent une caractéristique morphologique peu commune parmi les neurones de mammifères: leur axone émerge fréquemment d’une dendrite à une distance très variable du soma. Malgré cette importante variabilité dans la localisation de l’axone, peu d’articles ont étudié un lien potentiel entre morphologie neuronale et activité électrique dans ces cellules. Dans un premier article, nous avons exploré l’importante variabilité observée dans les neurones DA en caractérisant de nombreux paramètres morphologiques et biophysiques. Nos résultats suggèrent que la géométrie de l’AIS n’affecte pas significativement la forme du potentiel d’action ni l’activité pacemaker. En revanche, l’activité électrique est influencée par la morphologie et les conductances somatodendritiques. Dans une seconde étude, nous avons caractérisé le développement morphologique des neurones DA au cours des trois premières semaines post-natales. Nous avons observé une croissance asymétrique de l’arbre dendritique: la dendrite portant l’axone semble se complexifier plus que les autres dendrites. Cette asymétrie est associée à une contribution différente de la dendrite portant l’axone et des dendrites ne portant pas l’axone à la forme du potentiel d’action. Ces résultats suggèrent que les neurones DA de la SNc sont robustes aux variations morphologiques de l’axone et que les particularités morphologiques et biophysiques de leur arbre dendritique minimisent l’influence de l’AIS sur leur activité électrique<br>Neuronal output is defined by the complex interplay between the biophysical and morphological properties of neurons. Dopaminergic (DA) neurons of the substantia nigra pars compacta (SNc) are spontaneously active and generate a regular pacemaking activity. While most mammalian neurons have an axon emerging from the soma, the axon of DA neurons often arises from a dendrite at highly variable distances from the soma. Despite this large cell-to-cell variation in axon location, few studies have tried to unravel the potential link between neuronal morphology and electrical behaviour in this cell type. In a first article, we explored the high degree of cell-to-cell variability found in DA neurons by characterising several morphological and biophysical parameters. While AIS geometry did not seem to significantly affect action potential shape or pacemaking activity, we found that the electrical behaviour of DA neurons was particularly sensitive to somatodendritic morphology and conductances. In a second study, we characterised the morphological development of DA neurons during the first three post-natal weeks. We observed an asymmetric development of the dendritic tree, favouring the elongation and complexity of the axon-bearing dendrite. This asymmetry is associated with different contributions of the axon-bearing and non-axon bearing dendrites to action potential shape. Overall, the two studies suggest that DA neurons of the SNc are highly robust to cell-to-cell variations in axonal morphology. The peculiar morphological and biophysical profile of the dendritic arborization attenuates the role of the AIS in shaping electrical behaviour in this neuronal type
4
Serrat, Reñé Román. "Papel de Alex3 en la vía de señalización de Wnt y en la dinámica mitocondrial." Doctoral thesis, Universitat de Barcelona, 2012. http://hdl.handle.net/10803/83338.
Full textAbstract:
La proteína Alex3 forma parte de la familia de genes exclusiva de los mamíferos euterios Armcx, caracterizada por presentar una alta expresión en el SNC, por encontrarse localizada en clúster en el cromosoma X y porque se originaron a partir de la retrotransposición del gen Armc10 y una rápida duplicación en tándem en una evolución temprana de los mamíferos euterios. Las proteínas Armcx/Armc10 poseen primariamente una localización subcelular bimodal, encontrándose asociadas a la membrana externa mitocondrial y en el núcleo celular, localización que concuerda con sus secuencias proteicas que poseen putativos dominios de localización en estos compartimentos.
La sobreexpresión de las proteínas Armcx/Armc10 produce una profunda alteración de la red mitocondrial, demostrando que esta familia de proteínas juega un papel importante en la regulación de la dinámica y agregación mitocondrial y al menos, la sobreexpresión de la proteína Alex3, no induce cambios en los parámetros bio-energéticos mitocondriales, tales como el consumo de oxígeno, el potencial de membrana, el contenido de DNA mitocondrial, la actividad de la citocromo c oxidasa o la recaptación de Ca2+, ni alteran el balance de fisión/fusión mitocondrial.
Tanto la sobreexpresión como el silenciamiento de las proteínas Alex3 y Armc10 en neuronas hipocampales se ha visto alteran la distribución y transporte mitocondrial. Las proteínas Alex3 y Armc10 interaccionan con el complejo Kinesina/Miro/Trak2, regulador del transporte mitocondrial, lo cual sugiere que esta familia de proteínas regularían el transporte y dinámica mitocondrial a través de este complejo de proteínas. La interacción de Alex3 con este complejo también se ha visto es dependiente de los niveles de Ca2+, reduciéndose la interacción de estas proteínas cuando los niveles de Ca2+ son elevados.
Por otra parte, la vía de señalización asociada a proteínas Wnt se ha visto induce la degradación de la proteína Alex3 por un proceso independiente del proteosoma. Esta degradación no depende de los componentes de la vía canónica Dishevelled, GSK3-β y β-catenina ni de los componentes no canónicos JNK, CAMKII y calcineurina, habiéndose demostrado que la PKC y la CK2 juegan un papel principal en el control y degradación de los niveles de la proteína Alex3 de forma dependiente e independiente de las vías de señalización de Wnt. De manera similar, la depleción de los niveles intracelulares de Ca2+ también reproduce la degradación de Alex3. Además, la degradación de Alex3 a través de las vías de señalización asociadas a las proteínas Wnt revierte los fenotipos de agregación mitocondrial inducidos por la sobreexpresión de Alex3 y es evitado por la activación de la PKC, lo que sugiere que las proteínas Wnt podrían jugar un papel en el control de la dinámica mitocondrial mediante la regulación de las proteínas Armcx.<br>Alex3 protein belongs to the eutherian specific family of genes Armcx, characterized by a high expression on the CNS, to be localized in a cluster on the X chromosome and to be originated by retrotransposition of Armc10 gene in a fast duplication in tandem. The Armcx/Armc10 proteins have a primary bimodal localization, both in nucleus and mitochondria as indicate their putative domains.
Overexpression of Armcx/Armc10 proteins causes a profound alteration on the mitochondrial net showing that this family of proteins plays an important role in the regulation of the mitochondrial dynamics and at least, the overexpression of Alex3 protein neither change the bioenergetic parameters of mitochondria such as respiration, mitochondrial DNA content or calcium uptake nor alters the mitochondrial fusion/fission rate.
Both the overexpression and knock-down of Alex3 and Armc10 proteins in hippocampal neurons alters the mitochondrial distribution and transport. Alex3 and Armc10 interact with the Kinesin/Miro/Trak2 mitochondrial transport regulator complex, suggesting that the Armcx protein family regulates mitochondrial dynamics through this complex. Moreover the interaction of Alex3 with this complex is dependent of calcium levels, diminishing the interaction when calcium levels are high.
On the other hand, the Wnt signalling pathway induces the degradation of Alex3 protein in a proteosome independent process. This degradation is independent of the Wnt canonical and non-canonical members Dishevelled, GSK3β, β-catenin, JNK, calcineurin and CAMKII, but showing that the PKC and CKII members play a principal role in the control and degradation of Alex3 protein levels dependently and independently of Wnt pathways. Moreover, Alex3 degradation through Wnt signalling pathways, reverts the mitochondrial aggregation phenotypes and is avoided by PKC activation, suggesting that Wnt proteins can play a role in the control of mitochondrial dynamics through the regulation of Armcx proteins.
5
Wilson, Jennifer M. M. "Mechanisms of neuronal integration in adrenomedullary sympathetic preganglionic neurons." Thesis, University of Ottawa (Canada), 2002. http://hdl.handle.net/10393/6334.
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Sympathetic preganglionic neurons innervating the adrenal medulla (AD-SPN) regulate the release of adrenal catecholamines into the bloodstream. This research was undertaken to investigate the intrinsic properties and synaptic pathways characteristic of AD-SPN in neonatal rat spinal cord slice preparation. The presence of Lucifer Yellow from the patch pipette and Rhodamine-Dextran-Lysine from the adrenal medulla in the same neuron post recording identified AD-SPN. Active intrinsic properties revealed and characterised include: a potassium-mediated transient outward rectification present in 96% of AD-SPN and separable into a short 4-aminopyridine- and a long barium-sensitive component; a potassium-mediated sustained outward rectification revealed in TTx, activated positive to -50mV and blocked with quinine. These conductances contribute to the repolarising phase of the action potential. 89% of AD-SPN possessed potassium-mediated anomalous inward rectification. All AD-SPN displayed a high voltage-activated calcium spike that prolongs the action potential. The addition of internal caesium (140mM) revealed a low threshold spike mediated by T-type calcium channels that serve to facilitate burst firing. 75% of AD-SPN exhibited evidence of electrotonic coupling, indicated by characteristic oscillations in membrane potential and confirmed with dual recordings from electrotonically coupled AD-SPN. Electrotonic coupling promoted synchronous activity. An enhanced afterhyperpolarising potential facilitated transient termination of action potential firing forming bursts of activity. A role for calcium in the regulation of neuronal activity via action on electrotonic coupling was suggested by caffeine (10mM) decreasing, BAPTA-AM (15muM) and calcium free aCSF increasing the junctional conductance. Electrical stimulation of the descending fibres in both the ipsi- and contralateral funiculi evoked fast EPSPs in all AD-SPN that were mediated by both NMDA and non-NMDA receptors. A subpopulation of AD-SPN received fast IPSPs mediated by GABA acting via GABAA receptors. A train of stimuli (4 x 10Hz) in ipsi- and contralateral funiculi also evoked a slow IPSP mediated by noradrenaline acting via alpha 2-adrenergic receptors to increase a potassium conductance. The results provide insight into central mechanisms that contribute to the regulation of adrenomedullary catecholamine secretion.
6
Ganguly, Karunesh. "Activity-dependent regulation of neuronal excitability in hippocampal neurons /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2002. http://wwwlib.umi.com/cr/ucsd/fullcit?p3059903.
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7
Avó, Freixo Francisco Duque Projecto. "Novel roles for the mitotic kinase Nek7 in hippocampal neurons." Doctoral thesis, Universitat de Barcelona, 2016. http://hdl.handle.net/10803/399540.
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The microtubule cytoskeleton plays essential roles during cell division, migration, differentiation, defining cell morphology and organizing intracellular transport. The properties of microtubules, such as their stability, polarity and dynamics, are spatially and temporally regulated by several factors, including post-translational modifications, stabilizing/destabilizing MAPs, motors, kinases, phosphatases, etc.
Many of these factors were identified in cycling cells and particularly during mitosis. Nevertheless, some bona-fide mitotic microtubule regulators are also expressed in differentiated cells such as neurons. In a neuron, the microtubule cytoskeleton is organized differently in axons and dendrites, to guarantee a unidirectional transmission of the signal in a neuronal network. In axons, microtubules are generally more stable and are oriented with their plus-ends growing towards the axon cone, while in dendrites microtubules have mixed polarity.
In the work described in this thesis, we performed an RNAi screen in neurons with a short list of mitotic/microtubule — related genes that were found upregulated or constantly expressed in a microarray during hippocampal neuron differentiation in vitro.
In this screen, we found that the mitotic kinase Nek7 regulated axon length in immature neurons (5/6DIV). Nek7 depletion generates longer axons, and interestingly depletion/absence of Nek6, a kinase that works together with Nek7 in mitosis to phosphorylate the kinesin Eg5, generated the same phenotype. Eg5 pharmacological inhibition also increased axon length, as described by others, suggesting that these kinases are regulating axon length through Eg5. However, depletion of Nek9, another kinase form the same mitotic module, gave rise to shorter axons, indicating that the whole module is not conserved in neurons.
In mature neurons (14DIV) Nek7 depletion decreased the total length and branching of dendrites and affected dendritic spines, in a kinase-dependent way. Nek6 and Nek9 had no effect on these morphological parameters, but Eg5 inhibition also decreased dendrite length and branching, and spine density. Indeed, co-expression of an Eg5 S1033D phosphomimetic but not of a S1033A phosphor-null mutant, rescued the effects of Nek7 depletion. Furthermore, Nek7 controls Eg5 accumulation in dendrites, in a S1033 phosphorylation-dependent way. To explore the mechanisms behind these dendritic phenotypes, we analyzed microtubule polarity and stability in these dendrites, and observed that Nek7 depletion/Eg5 inhibition increases the percentage of retrograde microtubule EB3 comets in the distal parts of the dendrite. Additionally, Eg5 inhibition with STLC also increased EB3 comet density and decreased tubulin acetylation in dendrites. Ectopic generation of excess of microtubules and of minus-end distal microtubules in the distal regions of the dendrites by expression of the CM1 domain of CDK5Rap2 also gave rise to similar dendritic phenotypes, suggesting that these observations are correlated.
I also observed that Eg5 inhibition with STLC can counteract the effects of KIF23 depletion in terms of dendritic microtubule polarity, a motor kinesin that is involved in establishing the mixed polarity microtubule array in dendrites. Furthermore, this depends on Eg5 binding to microtubules and on its motor function, since FCPT treatment did not rescue KIF23 —depletion phenotypes.
We suggest a model where Nek7 phosphorylates Eg5 S1033 in dendrites, thus mediating Eg5 transport by dynein and accumulation in dendritic microtubules via TPX2, by analogy with mechanisms existent during mitosis. As expected, I observed that depletion of TPX2 also decreased total dendrite length. In dendrites, immobile Eg5 likely crosslinks and stabilizes microtubules in parallel bundles, and mobile Eg5 may also help to guide and sort microtubules into parallel bundles, and to mediates sliding of antiparallel microtubules. It is also possible that Eg5 can regulate the rate of short microtubule transport in dendrites, as demonstrated by others in axons. Altogether, these functions would promote dendritic growth and branching and correct spine formation.<br>Los microtúbulos son una componente importante del citoesqueleto, esenciales en la división celular, migración, transporte intracelular y diferenciación. La polaridad, estabilidad y dinámica de los microtúbulos son reguladas por muchos factores, como MAPs (proteínas asociadas a microtúbulos), quinesinas, dineínas, quinasas, fosfatasas, entre otros.
Muchos de estos reguladores fueron descubiertos y caracterizados por su función durante la mitosis, pero algunos también están presentes en células diferenciadas, como por ejemplo neuronas. Las neuronas dependen mucho de la organización de los microtúbulos para su función. En una neurona, el axón tiene microtúbulos de polaridad uniforme, mientras que en las dendritas la polaridad es mixta, y esto es esencial para la transmisión unidireccional de la señal nerviosa. El sistema de diferenciación de neuronas hipocampales in vitro se utiliza para estudiar la morfología neuronal y funciones del citoesqueleto. En mi trabajo de tesis doctoral, he caracterizado la función de una quinasa mitótica, Nek7, como reguladora de la diferenciación de neuronas hipocampales. He observado que Nek7, junto con Nek6, regula el crecimiento axonal en neuronas inmaduras (5/6DIV). En ausencia de Nek7 o Nek6 los axones son más largos, mientras que la depleción de Nek9, otra quinasa que funciona en conjunto con Nek6/7 en mitosis, genera axones más cortos.
En neuronas maduras (14DIV), Nek7 controla la morfología de dendritas y espinas a través de la regulación de la quinesina Eg5, que también es su substrato en mitosis. Los defectos generados por la depleción de Nek7 se rescatan con un mutante fosfo-mimético de Eg5 (S1033D) pero no con un mutante no fosforilable (S1033A). Además, Nek7 controla el reclutamiento y acumulación de Eg5 en la parte distal de las dendritas, a través de esta fosforilación. En la base de estos fenotipos encontramos problemas en la estabilidad y polaridad de microtúbulos en las dendritas. Tanto la depleción de Nek7 como la inactivación de Eg5 aumentan el porcentaje de microtúbulos de polaridad reversa en la parte distal de la dendrita, y disminuyen la acetilación de microtúbulos, un indicador de estabilidad. Finalmente se presenta un modelo en lo cual Eg5 regula la estabilidad, polaridad y deslizamiento de los microtúbulos dendríticos para favorecer el crecimiento dendrítico.
8
Stanke, Jennifer J. "Beyond Neuronal Replacement: Embryonic Retinal Cells Protect Mature Retinal Neurons." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1250820277.
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9
Bonifazi, Paolo. "Information processing in dissociated neuronal cultures of rat hippocampal neurons." Doctoral thesis, SISSA, 2005. http://hdl.handle.net/20.500.11767/4080.
Full textAbstract:
One of the major aims of Systems Neuroscience is to understand how the nervous system
transforms sensory inputs into appropriate motor reactions. In very simple cases sensory neurons
are immediately coupled to motoneurons and the entire transformation becomes a simple reflex, in
which a noxious signal is immediately transformed into an escape reaction. However, in the most complex behaviours, the nervous system seems to analyse in detail the sensory inputs and is performing some kind of information processing (IP). IP takes place at many different levels of the nervous system: from the peripheral nervous system, where sensory stimuli are detected and converted into electrical pulses, to the central nervous system, where features of sensory stimuli are extracted, perception takes place and actions and motions are coordinated. Moreover, understanding the basic computational properties of the nervous system, besides being at the core of Neuroscience,
also arouses great interest even in the field of Neuroengineering and in the field of Computer
Science. In fact, being able to decode the neural activity can lead to the development of a new
generation of neuroprosthetic devices aimed, for example, at restoring motor functions in severely
paralysed patients (Chapin, 2004). On the other side, the development of Artificial Neural Networks (ANNs) (Marr, 1982; Rumelhart & McClelland, 1988; Herz et al., 1981; Hopfield, 1982; Minsky & Papert, 1988) has already proved that the study of biological neural networks may lead to the development and to the design of new computing algorithms and devices. All nervous systems are based on the same elements, the neurons, which are computing devices which, compared to silicon components, are much slower and much less reliable. How are nervous systems of all living species able to survive being based on slow and poorly reliable components? This obvious and naïve question is equivalent to characterizing IP in a more quantitative way.
In order to study IP and to capture the basic computational properties of the nervous system,
two major questions seem to arise. Firstly, which is the fundamental unit of information processing:
2 single neurons or neuronal ensembles? Secondly, how is information encoded in the neuronal firing? These questions - in my view - summarize the problem of the neural code.
The subject of my PhD research was to study information processing in dissociated neuronal
cultures of rat hippocampal neurons. These cultures, with random connections, provide a more general view of neuronal networks and assemblies, not depending on the circuitry of a neuronal network in vivo, and allow a more detailed and careful experimental investigation. In order to record the activity of a large ensemble of neurons, these neurons were cultured on multielectrode arrays (MEAs) and multi-site stimulation was used to activate different neurons and pathways of the
network. In this way, it was possible to vary the properties of the stimulus applied under a
controlled extracellular environment. Given this experimental system, my investigation had two
major approaches. On one side, I focused my studies on the problem of the neural code, where I studied in particular information processing at the single neuron level and at an ensemble level,
investigating also putative neural coding mechanisms. On the other side, I tried to explore the possibility of using biological neurons as computing elements in a task commonly solved by conventional silicon devices: image processing and pattern recognition. The results reported in the first two chapters of my thesis have been published in two
separate articles. The third chapter of my thesis represents an article in preparation.
10
Albrecht, David. "Efectos de la proteína SPARC sobre la maduración de las sinapsis autápticas colinérgicas." Doctoral thesis, Universitat de Barcelona, 2012. http://hdl.handle.net/10803/107673.
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Las sinapsis son un elemento clave para el funcionamiento del sistema nervioso y la formación de las sinapsis es un proceso decisivo a lo largo de la vida. El establecimiento de los contactos sinápticos ocurre tanto en el sistema nervioso en desarrollo como en el cerebro adulto. Durante todo este proceso las neuronas y las células gliales se encuentran íntimamente acopladas por todo el sistema nervioso. Las investigaciones de las últimas décadas han evidenciado que las células gliales poseen un rol que va más allá del clásicamente atribuido, demostrando que la glía posee una función relevante en la formación y en el funcionamiento de las sinapsis mediante la secreción de diversas moléculas, las cuales han sido caracterizadas principalmente desde un punto de vista postsináptico. Para el estudio de la interacción neurona-glía, el laboratorio de Neurobiología ha implementado microcultivos de neuronas aisladas del ganglio cervical superior, sistema en el cual una neurona individual crece sobre una gota de colágeno haciendo contacto consigo misma. Los microcultivos establecidos rutinariamente en el laboratorio, consisten en una sola neurona que crece en ausencia de otros tipos celulares, denominados SCM; y una sola neurona que crece en presencia de células gliales o GM. Con este sistema, estudios previos realizados en el laboratorio demostraron que las células gliales incrementan la frecuencia de la neurotransmisión espontánea y modifica la plasticidad a corto plazo. Durante el desarrollo de esta tesis doctoral, se estableció que la glía periférica inmadura in vitro e in vivo secretan la proteína matricelular SPARC, proteína que se expresa ampliamente en el sistema nervioso en desarrollo y en áreas sinaptogénicas, a pesar de lo cual se desconoce la función que tiene en el desarrollo y en la plasticidad. En este trabajo se caracterizan las funciones de SPARC sobre la neurotransmisión y la maduración de las sinapsis colinérgicas autápticas, observándose que concentraciones nanomolares de SPARC durante el desarrollo sináptico aumentan la frecuencia de la neurotransmisión espontánea e incrementan la depresión a corto plazo. La secreción local de SPARC sobre neuronas maduras durante 24-36 horas, incrementa solamente la depresión a corto plazo. Finalmente, mediante electrofisiológica y microscopía electrónica correlativa, demostramos que los terminales presinápticos desarrollados en presencia de concentraciones nanomolares de SPARC, presentan dos a tres veces menos vesículas sinápticas totales y vesículas sinápticas ancladas a las zonas activas. Las evidencias experimentales obtenidas en este trabajo señalan que la proteína matricelular SPARC retiene las sinapsis autápticas colinérgicas en un estado inmaduro.<br>The synapses are a key element for the Nervous system functions. They are established mainly during the nervous system development, but they can be formed in the adult nervous system as well. Neurons and glial cells are intimately coupled during all these processes. During the last decade it has been described that glial cells participate in the synapses establishment and information processing, they do so secreting factors. To study the neuron-glía interaction, our laboratory has set up neuronal microcultures, where a single neuron grows in a drop of collagen, a permissive substracte, surrounded by agarose, a non permissive substrate, forcing the neuron to develop inside the collagen drop, forcing it to have contact only with itself. These kind of synapses are called autapses. During this PhD thesis, we found that immature glial cells secrete SPARC in vitro and in vivo. We proved that SPARC has an effect over the neurotransmission and the presynaptic terminal maturations in cholinergic autapses; nanomolar concentration of SPARC applied during the neuronal development enhances the spontaneous neurotransmission and the short-term plasticity. We have also characterized that nanomolar concentration of SPARC decreases the total vesicular number and the docked vesicles number in presynaptic terminal. These experimental results obtained during the thesis lead us to propose that SPARC arrest the synapses in an immature stage.
11
Kuebler, Eric Stephen. "Harnessing the Variability of Neuronal Activity: From Single Neurons to Networks." Thesis, Université d'Ottawa / University of Ottawa, 2018. http://hdl.handle.net/10393/37855.
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Neurons and networks of the brain may use various strategies of computation to provide the neural substrate for sensation, perception, or cognition. To simplify the scenario, two of the most commonly cited neural codes are firing rate and temporal coding, whereby firing rates are typically measured over a longer duration of time (i.e., seconds or minutes), and temporal codes use shorter time windows (i.e., 1 to 100 ms). However, it is possible that neurons may use other strategies. Here, we highlight three methods of computation that neurons, or networks, of the brain may use to encode and/or decode incoming activity. First, we explain how single neurons of the brain can utilize a neuronal oscillation, specifically by employing a ‘spike-phase’ code wherein responses to stimuli have greater reliability, in turn increasing the ability to discriminate between stimuli. Our focus was to explore the limitations of spike-phase coding, including the assumptions of low firing rates and precise timing of action potentials. Second, we examined the ability of single neurons to track the onset of network bursting activity, namely ‘burst predictors’. In addition, we show that burst predictors were less susceptible to an in vitro model of neuronal stroke (i.e., excitotoxicity). Third, we discuss the possibility of distributed processing with neuronal networks of the brain. Specifically, we show experimental and computational evidence supporting the possibility that the population activity of cortical networks may be useful to downstream classification. Furthermore, we show that when network activity is highly variable across time, there is an increase in the ability to linearly separate the spiking activity of various networks. Overall, we use the results of both experimental and computational methods to highlight three strategies of computation that neurons and networks of the brain may employ.
12
Matteoni, Cosetta. "Studies of neuronal nicotinic receptors of autonomic neurons: expression and function." Doctoral thesis, SISSA, 2007. http://hdl.handle.net/20.500.11767/4726.
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Neuronal nicotin~c receptors (nAChRs) are important membrane proteins to signal
intercellular communication in health and disease. Against a large body of data
related to brain or muscle nAChRs, there is comparatively less information
concerning such receptors on autonomic sensory neurons. The present investigation
was focused on characterizing the expression and function of nAChRs in chromaffin
cells of the rat adrenal medulla, on exploring how novel synthetic compounds could
modulate acutely or clu·onically nAChRs by using SH-SY5Y cells which are tumorderived
cells of chromaffin cell lineage, and how long-term application of nicotinic
agents could alter the function of such receptors.
Reverse transcription-polymerase chain reaction analysis indicated the presence of
a2, a3, a4, a5, a7, ~2 and P4 transcripts (a6 and P3 could not be detected) in rat
chromaffin cells. Immunocytochernistry and western blot analysis did not confirm
the expression of the a7 subunit. Inward currents elicited by nicotine pulses were
insensitive to a-bungarotoxin and low doses of methyllycaconitine, demonstrating
lack of functional a7 receptors. Partial block of nicotine currents was observed with
either AuIB a-conotoxin (selective against a3P4 receptors) or MII a-conotoxin
(selective against a3P2 receptors). Antagonism by dihydro-p-erythroidine (selective
at low doses against a4P2 receptors) summated nonlinearly with AuIB and MU
inhibition, confirming heterogeneity of neuronal nicotinic acetylcholine receptor
populations. These results suggest that the most frequently encountered receptors of
rat chromaffin cells should comprise a3p'4, a3P2 with the addition of a5 subunits,
and much less commonly a2p4, without excluding other subunit combinations.
Using SH-SY5Y cells, more stable in culture and therefore suitable for chronic
treatment, we investigated the effect of the novel cytisine dimer 1,2-bisNcytisinylethane
(CC4). On nAChRs CC4 lacked the agonist properties of cytisine
and was actually a potent antagonist (IC50 = 220 nM). Chronic treatment of SH-SYSY cells with 1 mM CC4 for 48 h significantly increased nicotine-evoked
currents with augmented sensitivity to the blockers a-conotoxin MII or
methyllycaconitine, indicating a relative increase of functional nicotinic receptors
comprising Beta2 and alpha7 subunits on the cell membrane.
Chronically treating SH-SYSY cells with nicotine showed that, despite
desensitization, they preserved a degree of responsiveness to nicotine pulses, and
that they rapidly recovered on washout to generate larger responses without changes
in kinetics or pharmacology.
In summary, these data have demonstrated the subunit expression and function of
nAChRs on peripheral autonomic cells, and have identified new properties like their
sustained ability to preserve function even in the presence of chronic agonist
application and their compensatory up-regulation. The present study, thus, sheds
new light on the plasticity of nAChRs and outlines new strategies for their
pharmacological modulation. Because of the role of nAChRs in the control of
chromaffin cell function in regulating blood pressure, it is suggested that changes in
nAChR activity might influence the mechanisms responsible for changes in blood
pressure in health and disease.
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Hoch, Thomas. "Aspects of information processing by individual neurons and populations of neurons." [S.l.] : [s.n.], 2007. http://opus.kobv.de/tuberlin/volltexte/2007/1566.
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Gutiérrez, Fernández Sara. "Funció del factor d'elongació eEF1A2 en plasticitat sinàptica." Doctoral thesis, Universitat de Barcelona, 2018. http://hdl.handle.net/10803/565534.
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La plasticitat sinàptica és la capacitat que té el sistema nerviós de canviar la seva estructura i funcionament al llarg del desenvolupament. En processos d’aprenentatge, es formen noves espines dendrítiques que permetran fer noves sinapsis, aquest procés rep el nom de plasticitat estructural, també s’ha descrit que es produeix un augment en la síntesi local de proteïnes a les espines. Els mRNAs que es transcriuen en el nucli viatgen silenciats en grànuls de mRNAs fins a arribar a les espines on es produeix una traducció local a les sinapsis. Tot i que la majoria dels estudis sobre el control de la traducció analitzen el paper regulador dels factors d’inici, actualment, hi han estudis que indiquen que els factors d’elongació també poden ser importants en la regulació de la traducció en neurones.
El nostre treball s’ha centrat en el factor d’elongació eEF1A, aquest factor presenta dues isoformes que són pràcticament idèntiques i que tenen expressió diferent en funció del teixit. La isoforma eEF1A1 s’expressa en tots els teixits de l’organisme exceptuant el cervell, cor i múscul esquelètic, on és reemplaçada totalment per la isoforma eEF1A2. Aquest factor a part de ser un regulador de la traducció també presenta altres funcions, una de les més estudiades ha estat la capacitat d’interacció amb el citoesquelet d’actina.
Aquesta tesi ha tingut com a objectiu general estudiar la relació entre la plasticitat estructural, on l’actina és un factor clau, i la traducció local en el context de la sinapsis. Concretament, ens hem centrat en la determinació de la rellevància funcional de la fosforilació del factor eEF1A2 en plasticitat sinàptica.<br>Synaptic plasticity is the ability the nervous system has to modify its structure and behavior throughout development. In learning processes, it is formed new dendritic spines that let do new synapses, this process is called structural plasticity, it is also described that there is an increment in protein local synthesis in the spines. mRNAs transcribed at the nuclei travel being silent in mRNAs granules until they arrive at the dendritic spines where it is produced local translation of these mRNAs in the synapsis. Despite the main local translation control studies examining the role of the initiaton factor, nowadays, there are studies that show that elongation factors can be also important in translational regulation in neurons.
Our work is focused on the elongation factor eEF1A, this factor has two isoforms that are virtually identical and that have tissue dependent expression. eEF1A1 isoform is expressed in all the tissues but the brain, heart and skeletal muscle, where it is replaced by isoform eEF1A2. This factor apart from being a translational regulator it has other functions as well, one of the most studied has been the ability to interact with the actin cytoskeleton.
The general objective of this thesis is to study the relationship between structural plasticity, where actin is a key factor, and local translation in the synaptic context. Specifically, we have focused on determining the functional relevance of EF1A2 phosphorylation in synaptic plasticity.
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Amer, Rebecca K. "Hepoxilins and neuronal repair, effects on SCG neurons after in vitro injury." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0021/MQ54161.pdf.
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Moreau, David. "Infrared stimulation of neurons." Thesis, Limoges, 2017. http://www.theses.fr/2017LIMO0050/document.
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L’exposition aux radiations laser infrarouge peut être utilisée afin de dépolariser des neurones et stimuler l’activité neuronale. Le mécanisme sous-jacent d’une telle stimulation est supposé résulter d’une interaction photothermique. En effet, l’absorption de la radiation infrarouge par le tissu biologique cible, et l’eau qu’il contient, induit une augmentation de température de manière localisée, qui soit influencerait directement les propriétés membranaires de la cellule soit agirait par le biais de l’activation de canaux ioniques thermo-sensibles. Dans la plupart des cas, l’activité électrique des neurones est mesurée électriquement à l’aide de microélectrodes, mais elle peut également être sondée par le biais de la microscopie de fluorescence faisant intervenir des indicateurs calciques. Dans ce travail, l’impact de l’exposition à la radiation infrarouge sur les signaux calciques de neurones a été étudié dans le but d’éclaircir et de préciser le mécanisme résultant de l’interaction photothermique. Des neurones HT22, issus d’hippocampe de souris, et des cellules U87, issues d’un glioblastome humain, ont été utilisés en tant qu’exemples de cellules électriquement excitables et non excitables respectivement. Afin de mesurer la température et les signaux calciques au niveau cellulaire, les fluorophores Rhodamine B et Fluo-4 ont été employés. Le montage, par conséquent tout optique, pour étudier l’influence de l’exposition infrarouge sur l’activité neurale est donc présenté, ainsi que la démarche scientifique menant à l’identification de l’implication de l’activité de la phospholipase C dans le mécanisme étudié. La possibilité de stimuler l’activité neurale in vivo, dans le cerveau d’une souris, avec une mesure simultanée des signaux calciques, est également démontrée à l’aide de souris transgéniques exprimant le GCaMP6S<br>Infrared laser light radiation may be used to depolarize neurons and to stimulate neural activity. The underlying mechanism of such stimulation is believed to happen due to a photothermal interaction. The absorption of the infrared radiation by the targeted biological tissue inducing a local temperature increase which either directly influence membrane properties or act via temperature sensitive ion channels. Action potentials are typically measured electrically in neurons with microelectrodes, but they can also be observed using fluorescence microscopy techniques that use synthetic or genetically encoded calcium indicators. In this work, we studied the impact of infrared laser light on neuronal calcium signals to address the mechanism of these thermal effects. HT22 mouse hippocampal neurons and U87 human glioblastoma cells were used loaded with the fluorescent calcium dye Fluo-4 and with the temperature sensitive fluorophore Rhodamine B to measure calcium signals and temperature changes at the cellular level. Here we present our all-optical strategy for studying the influence of infrared laser light on neural activity, and the scientific approach leading to conclusion of the involvement of Phospholipase C activity during infrared neural stimulation. The ability of infrared exposure to trigger neural activity in mice brain in vivo is also investigated with the use of GCaMP6s transgenic mice
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Ching, Shim. "Synaptogenesis between identified neurons." Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=55449.
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Serotonergic Retzius (R) neurons of the leech Hirudo medicinalis in culture reform inhibitory synapses with pressure sensitive (P) neurons while selectively reducing an extrasynaptic, depolarizing response to serotonin (5-HT) in the P neuron. We have examined if the selection of 5-HT responses is restricted to sites of contact between processes and growth cones of these cells. As measured by intracellular recording at the soma, focal application of 5-HT depolarized uncontacted P cell bodies, neurites and growth cones but not processes contacted by R cells. In patch clamp recordings of the depolarizing channels, application of 5-HT modulated channel activity in uncontacted but not in contacted growth cones. The selection of transmitter responses during synaptogenesis is therefore localized to discrete sites of contact specifically between synaptic partners.<br>Prior experiments have shown that tyrosine kinases play a crucial part in the selection of responses to 5-HT that occurs in the P cell (Catarsi and Drapeau, 1993). To further examine the mechanism responsible for this change in transmitter responses, we have utilized a monoclonal antibody against phosphotyrosine to determine if tyrosine phosphorylation could be detected in P and R cell pairs placed in contact. Our results revealed bright, punctate cytoplasmic staining in P cells paired with R cells.<br>Embryonic leeches were used to examine how R to P synaptogenesis proceeds in vivo. By filling the R and P neurons with different fluorescent dyes (Lucifer Yellow and Rhodamine-Dextran), confocal microscopy established that putative contact between neuropilar processes were made as early as 11 days of development. Spontaneous, chloride-dependent synaptic potentials in embryonic P cells similar to those seen in adult P cells were observed as early as day 10 of development.
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Wills, Sebastian Alexander. "Computation with spiking neurons." Thesis, University of Cambridge, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.616274.
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Kuang, Xutao. "Adaptation in multisensory neurons." Thesis, University of Southampton, 2008. https://eprints.soton.ac.uk/65419/.
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The most studied region in the mammalian brain for multisensory integration is the deep superior colliculus (DSC). Neurophysiological experiments have revealed many response properties of DSC neurons, such as cross-modal enhancement (CME) and sub-additive/additive/super-additive op- erational modes. CME occurs when the response of a multisensory neuron to stimulation in one sensory modality is enhanced, often non-linearly, by temporally and spatially coincident stimulation of a second sensory modality. Response enhancement is frequently larger for weaker input stimuli than for stronger stimuli, a phenomenon known as inverse e®ectiveness. It is believed that a non-linear, saturating response function may underlie CME associated with inverse effectiveness. We explore this idea in more detail, showing that apart from CME, many other response properties of DSC neurons, including the different dynamic ranges of responses to unimodal and multimodal stimuli and the diverse operational modes, also emerge as a direct consequence of a saturating response function such as a sigmoidal function. We then consider the question of how the exact form of a candidate, saturating sigmoidal function could be determined in a DSC neuron. In particular, we suggest that adaptation may determine its exact form. Adaptation to input statistics is a ubiquitous property of sensory neurons. Defining the operating point as the output probability density function, we argue that a neuron maintains an invariant operating point by adapting to the lowest-order moments of the input probability distribution. Based on this notion, we propose a novel adaptation rule that permits unisensory neurons to adapt to the lowest-order statistics of their inputs, and then extend this rule to allow adaptation in multisensory neurons, of which DSC neurons are an example. Adaptation in DSC neurons is expected to change the responses of a neuron to a fixed, probe or test stimulus. Such a neuron would therefore exhibit different CME when presented with the same stimulus drawn from different statistical ensembles. We demonstrate that, for suitable selections of test stimuli, adaptation to an increase in the mean, the variance or the correlation coefficient induce consistent changes in CME. By virtue of the robustness of the results, the underlying adaptation notion can be tested in neurophysiological experiments. Finally, it is known that descending cortical projections from the anterior ectosylvian sulcus and the rostral aspect of the lateral suprasylvian sulcus are indispensable for DSC neurons to exhibit CME. The structure of our proposed adaptation rule for multisensory neurons therefore permits us to speculate that the descending cortical inputs to multisensory DSC neurons facilitate the computation of the correlation coefficient between different sensory channels' activities.
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Boatin, William. "Characterization of neuron models." Thesis, Available online, Georgia Institute of Technology, 2005, 2005. http://etd.gatech.edu/theses/available/etd-04182005-181732/.
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Thesis (M. S.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2006.<br>Dr. Robert H. Lee, Committee Member ; Dr. Kurt Wiesenfeld, Committee Member ; Dr Robert J. Butera, Committee Member.
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Zagmutt, Caroca Sebastián. "Analysis of the in vivo effect of carnitine palmitoyltransferase 1A deletion in AgRP neurons." Doctoral thesis, Universitat de Barcelona, 2020. http://hdl.handle.net/10803/671758.
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Food intake and whole-body energy balance are regulated by the brain through a sophisticated neuronal network located mostly in the hypothalamus. In particular, the hypothalamic arcuate nucleus (ARC) is a fundamental sensor for the hormones and nutrients that inform about the energy state of the organism.
The ARC contains two populations of neurons with opposite functions: anorexigenic proopiomelanocortin (POMC)-expressing neurons and orexigenic Agouti-related protein (AgRP)- expressing neurons. Activation of AgRP neurons leads to an increase in food intake and a decrease in energy expenditure. It has been suggested that lipid metabolism in the ARC plays an important role in the central control of whole-body energy balance. Yet it is unclear whether lipid metabolism regulates the activity of AgRP neurons specifically. To answer this question, we studied mutant mice lacking carnitine palmitoyltransferase 1A (CPT1A) specifically in AgRP neurons (Cpt1aAgRP(-/-) mice). CPT1A regulates the rate-limiting step in the mitochondrial oxidation of fatty acids (FAs) and therefore plays a central role in the metabolism of lipids.
The results presented here demonstrated that the deletion of Cpt1a in AgRP neurons induces sex- based differences on the energy metabolism. Although male and female Cpt1aAgRP(-/-) mice showed a reduction of the body weight gain, both genders afford this reduction in different way. Male Cpt1aAgRP(-/-) mice showed a reduction of food intake with no changes in the energy expenditure, while female Cpt1aAgRP(-/-) mice increased the energy expenditure with no changes in food intake. Despite these results, the AgRP neuronal activation in fasting condition or by high levels of ghrelin were impaired in both genders. At a peripheral level, the deletion of Cpt1a in AgRP had an impact on different adipose tissues. On the one hand, the lack of Cpt1a in AgRP neurons activated the brown adipose tissue (BAT) activity, on the other hand, induced a substantial reduction of white adipose tissues, specially inguinal and gonadal fat pads.
Although AgRP neurons have been associated with solid food consumption, here we also reported that AgRP neurons could be involved in water homeostasis. Mice lacking CPT1A in AgRP neurons showed reduced levels of AV/ADH hormone and had impaired activation of center related with thirst. Finally, our results reveal that AgRP neurons requires Cpt1a to maintain a normal morphology and physiology. The deletion of Cpt1a in AgRP neurons does not affect the neuronal viability. However, interfered in the number of dendritic spines altering their morphology and normal state of the synapses.
Altogether, our results suggest that CPT1A and FAs oxidation in AgRP neurons impact peripheral energy balance highlighting this pathway as a possible target for therapeutic strategies to decrease body weight. We also provide evidence that AgRP could be involved in the regulation of water homeostasis.
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Tanaka, Yasuhiro. "Local connections of excitatory neurons to corticothalamic neurons in the rat barrel cortex." Kyoto University, 2012. http://hdl.handle.net/2433/157432.
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Woolley, David. "The actions of a soft coral derived natural product on neurones." Thesis, Available from the University of Aberdeen Library and Historic Collections Digital Resources, 2008. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?application=DIGITOOL-3&owner=resourcediscovery&custom_att_2=simple_viewer&pid=24801.
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Carvalho, Milena Menezes. "Structural, functional and dynamical properties of a lognormal network of bursting neurons." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/76/76131/tde-25052017-110738/.
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In hippocampal CA1 and CA3 regions, various properties of neuronal activity follow skewed, lognormal-like distributions, including average firing rates, rate and magnitude of spike bursts, magnitude of population synchrony, and correlations between pre- and postsynaptic spikes. In recent studies, the lognormal features of hippocampal activities were well replicated by a multi-timescale adaptive threshold (MAT) neuron network of lognormally distributed excitatory-to-excitatory synaptic weights, though it remains unknown whether and how other neuronal and network properties can be replicated in this model. Here we implement two additional studies of the same network: first, we further analyze its burstiness properties by identifying and clustering neurons with exceptionally bursty features, once again demonstrating the importance of the lognormal synaptic weight distribution. Second, we characterize dynamical patterns of activity termed neuronal avalanches in in vivo CA3 recordings of behaving rats and in the model network, revealing the similarities and differences between experimental and model avalanche size distributions across the sleep-wake cycle. These results show the comparison between the MAT neuron network and hippocampal readings in a different approach than shown before, providing more insight into the mechanisms behind activity in hippocampal subregions.<br>Nas regiões CA1 e CA3 do hipocampo, várias propriedades da atividade neuronal seguem distribuições assimétricas com características lognormais, incluindo frequência de disparo média, frequência e magnitude de rajadas de disparo (bursts), magnitude da sincronia populacional e correlações entre disparos pré- e pós-sinápticos. Em estudos recentes, as características lognormais das atividades hipocampais foram bem reproduzidas por uma rede de neurônios de limiar adaptativo (multi-timescale adaptive threshold, MAT) com pesos sinápticos entre neurônios excitatórios seguindo uma distribuição lognormal, embora ainda não se saiba se e como outras propriedades neuronais e da rede podem ser replicadas nesse modelo. Nesse trabalho implementamos dois estudos adicionais da mesma rede: primeiramente, analisamos mais a fundo as propriedades dos bursts identificando e agrupando neurônios com capacidade de burst excepcional, mostrando mais uma vez a importância da distribuição lognormal de pesos sinápticos. Em seguida, caracterizamos padrões dinâmicos de atividade chamados avalanches neuronais no modelo e em aquisições in vivo do CA3 de roedores em atividades comportamentais, revelando as semelhanças e diferenças entre as distribuições de tamanho de avalanche através do ciclo sono-vigília. Esses resultados mostram a comparação entre a rede de neurônios MAT e medições hipocampais em uma abordagem diferente da apresentada anteriormente, fornecendo mais percepção acerca dos mecanismos por trás da atividade em subregiões hipocampais.
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Raffaelli, Marco. "Le déclin de TRF2 dans l'hippocampe au cours du vieillissement cause une déficience de la mémoire dépendante de ATM." Electronic Thesis or Diss., Université Côte d'Azur, 2024. http://www.theses.fr/2024COAZ6001.
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Le vieillissement est la cause principale de la grande majorité des pathologies, allant de l'athérosclérose aux tumeurs et à la démence. Il est donc incontestable que l'amélioration de la connaissance de ce phénomène au niveau cellulaire et moléculaire sera d'une valeur inestimable pour le traitement et la prévention d'un large éventail de pathologies humaines. Un facteur bien établi du vieillissement des cellules mitotiques est l'érosion des télomères médiée par la division cellulaire, un processus qui ne se produit pas dans les cellules post mitotiques telles que les neurones. En effet, on ne sait pas si les facteurs télomériques jouent un rôle dans le processus de vieillissement des neurones matures. Il a été récemment démontré que dans les myofibres post-mitotiques (cellules musculaires), l'expression du Telomere repeat-binding factor 2 (TRF2 - codé par le gène Terf2), un composant essentiel du complexe Shelterin de protection des télomères, diminue considérablement au cours du vieillissement, ce qui suggère que les modifications télomériques sont également impliquées dans le vieillissement des cellules post mitotiques. Nous avons donc décidé d'étudier si le même phénomène se produisait dans le neurone, un autre type de cellule post mitotique. De manière intéressante, notre groupe a montré que TRF2 possède des sites de liaison extra télomériques à proximité ou à l'intérieur de gènes impliqués dans les fonctions neuronales, ce qui suggère qu'il pourrait influencer leur expression. Ainsi, le but de notre projet est d'étudier les implications éventuelles de TRF2 dans le vieillissement neuronal. Pour cela, nous avons d'abord évalué l'expression de Terf2 dans l'hippocampe murin au cours du vieillissement, en montrant qu'elle diminue avec le temps. Ensuite, nous avons étudié l'effet de la régulation négative de Terf2 dans l'hippocampe murin sur la mémoire, un phénomène dépendant de l'hippocampe et notoirement altéré par le vieillissement. De manière remarquable, nous avons constaté que la régulation à la baisse de Terf2 entraîne un phénotype cognitif altéré affectant la mémoire épisodique et contextuelle. De plus, étant donné le rôle canonique de protection de l'ADN par les télomères de TRF2 dans les cellules en division, nous avons évalué l'effet de sa régulation négative dans l'hippocampe sur l'apparition de lésions de l'ADN, en montrant que la région de l'hippocampe Cornu ammonis 1 et 3 (CA1 et CA3) et le Gyrus denté (DG) présentent une réponse accrue aux lésions de l'ADN (DDR), en particulier au niveau des télomères. En outre, nous avons évalué si l'inhibition de la DDR (inhibition du capteur de dommages à l'ADN ATM par le médicament spécifique KU60019) pouvait sauver le phénotype cognitif observé. En effet, nous avons pu montrer que l'inhibition de la DDR permettait de remédier au déficit cognitif. Enfin, nous avons évalué l'effet de la surexpression de TRF2 chez les souris âgées. De manière assez impressionnante, nous avons constaté que cette surexpression permettait de sauver complètement la mémoire épisodique et contextuelle. De manière assez frappante, nous avons pu montrer qu'au niveau cellulaire, la régulation à la baisse de Terf2 entrave le transport axonal des vésicules (vésicules VAMP2) dans les cultures primaires de neurones hippocampiques et corticaux. De plus, l'analyse protéomique a révélé que la régulation négative de Terf2 dans l'hippocampe affecte l'expression de plusieurs gènes ayant des fonctions neuronales essentielles, notamment la plasticité synaptique. Dans l'ensemble, ces résultats jettent une lumière nouvelle sur la dynamique intracellulaire du vieillissement neuronal, avec un rôle sans précédent pour une protéine télomérique et sa cible canonique, ATM. Ces connaissances nouvellement acquises constitueront un terrain fertile pour de futures recherches visant à prévenir, arrêter ou même inverser la perte de mémoire liée à l'âge<br>Aging is the leading cause of the vast majority of all pathologies, ranging from atherosclerosis to tumors and dementia. It is therefore undisputable that improving the knowledge of this phenomenon at the cellular and molecular level will be of inestimable value for the sake of treating and preventing a broad spectrum of human conditions.A well-established driver of mitotic cell aging is cell division-mediated telomere erosion, a process that does not occur in postmitotic cells such as neurons. Indeed, it is not known whether telomeric factors play a role in the aging process of mature neurons. It was recently shown that in postmitotic myofibers (muscle cells) the expression of Telomeric repeat-binding factor 2 (TRF2 - encoded by the Terf2 gene), a pivotal component of the telomere-capping Shelterin complex, decreases dramatically during aging, suggesting that telomeric modifications are also involved in postmitotic cell aging. Therefore, we decided to investigate whether the same occurs in the neuron, another type of postmitotic cell. Interestingly, our group had shown that TRF2 has extratelomeric binding sites in the proximity or inside of genes involved in neuronal functions, suggesting that it might influence their expression. Thus, the aim of our project is to study eventual TRF2 implications in neuronal aging. For this purpose, we initially assessed Terf2 expression in the murine hippocampus during aging, showing that this decreases over time. Afterwards, we investigated the effect of Terf2 downregulation in the murine hippocampus on memory, a hippocampus-dependent phenomenon notoriously impaired by aging. Remarkably, we found that downregulating Terf2 leads to an impaired cognitive phenotype affecting episodic and contextual memory. Moreover, given the canonical telomeric-DNA protection role of TRF2 in dividing cells, we assessed the effect of its hippocampal downregulation on DNA damage occurrence, showing that the region of the hippocampus Cornu ammonis 1 and 3 (CA1 and CA3) and the Dentate gyrus (DG) present increased DNA damage response (DDR), specifically at the telomeric level. Furthermore, we assessed whether inhibiting the DDR (inhibition of the DNA damage sensor ATM by the specific KU60019 drug) could rescue the observed cognitive phenotype. Indeed, we could show a rescue of the cognitive deficit upon DDR inhibition. Finally, we assessed the effect of TRF2 overexpression in old mice. Impressively enough, we found that this completely rescues episodic and contextual memory. Quite strikingly, we could show that at the cellular level Terf2 downregulation impairs vesicle axonal transport (VAMP2 vesicles) in primary cultures of both hippocampal and cortical neurons. Moreover, proteomic analysis revealed that hippocampal Terf2 downregulation modulates the expression of several genes with pivotal neuronal functions, notably synaptic plasticity.All in all, these findings shed new light on the intracellular dynamics of neuronal aging, with a stunning unprecedented role for a telomeric protein and its canonical target, ATM. This newly acquired knowledge shall provide fertile ground for future investigations with the goal to prevent, stop or even revert age-dependent memory loss
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Jerregård, Helena. "Factors influencing nerve growth in situ and in vitro /." Linköping : Univ, 2001. http://www.bibl.liu.se/liupubl/disp/disp2001/med693s.pdf.
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Huynh, Cong Evelyne. "Le rôle émergeant des microtubules dans la physiopathologie des podocytopathies héréditaires." Thesis, Sorbonne Paris Cité, 2015. http://www.theses.fr/2015PA05T028.
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L’étude des formes familiales de syndrome néphrotique (SN) ou de protéinurie glomérulaire avec lésions histologiques de hyalinose segmentaire et focale (HSF) a permis d’incriminer plus d’une vingtaine de gènes, majoritairement exprimés par le podocyte, cellule principale de la barrière de filtration glomérulaire (BFG). Parmi ces gènes, près d’une dizaine code des régulateurs du cytosquelette d’actine démontrant ainsi le rôle central de la plasticité et de l’architecture du podocyte dans le fonctionnement du filtre glomérulaire. L’ensemble de ces travaux a permis de définir une nouvelle catégorie de maladies nommées podocytopathies héréditaires. Mon projet de thèse a porté sur la caractérisation de plusieurs gènes (TTC21B, WDR73, TRIM3), dont nous avons identifié des mutations dans des cas de podocytopathies héréditaires isolées ou syndromiques. Les résultats du premier volet de ma thèse ont montré que la mutation faux sens p.P209L dans le gène TTC21B induit à l’état homozygote une nouvelle entité clinique associant à la fois une atteinte glomérulaire et une atteinte tubulaire. TTC21B code l’IFT139 (intraflagellar transport protein 139), une protéine impliquée dans le transport protéique antérograde dans le cil primaire, un organite présent à la surface de la plupart des cellules épithéliales. Ces résultats étaient inattendus car l’identification de mutations dans un gène codant une protéine ciliaire n’avait jamais été démontrée auparavant dans des cas de podocytopathies héréditaires, et surtout, il ne semblait pas exister de cil primaire à la surface des podocytes matures. Effectivement, nous avons montré que le cil primaire est présent dans les podocytes humains indifférenciés, mais disparait au cours de la différenciation. Nos résultats ont permis de comprendre l’apparente contradiction entre la survenue d’une pathologie glomérulaire relativement tardive (protéinurie et SN à l’adolescence) et l’absence de cil dans le podocyte mature. En effet, nous avons montré que la mutation p.P209L est une mutation hypomorphe qui induit des défauts mineurs dans la fonction ciliaire, alors qu’elle provoque, dans le podocyte différencié, une déstructuration importante du réseau d’actine et de microtubules du podocyte. Cette étude montre que la protéine ciliaire IFT139, par sa fonction extra-ciliaire, permet de réguler la dynamique des microtubules. Dans le deuxième volet de mon projet, en collaboration avec l’équipe de D Bonneau (Angers), nous avons identifié des mutations tronquantes dans le gène WDR73, dans deux familles non apparentées présentant un syndrome de Galloway-Mowat (SGM), pathologie de transmission autosomique récessive, très hétérogène cliniquement, associant SN et microcéphalie. Ces travaux ont permis d’identifier le premier gène impliqué dans le SGM, dans un sous-groupe de patients présentant un phénotype neurologique très homogène (microcéphalie post-natale, atrophie corticale avec atrophie cérébelleuse majeure, déficience intellectuelle très sévère), alors que l’atteinte glomérulaire est très variable. Ce gène code WDR73, une protéine à motifs WD40. Nos travaux ont montré que la protéine est exprimée dans les neurones du système nerveux central, en particulier dans les cellules de Purkinje du cervelet et dans les podocytes. Des études fonctionnelles nous ont permis de montrer que WDR73 est impliquée dans la survie cellulaire, puisqu’en son absence, une apoptose accrue est observée dans les fibroblastes de patients. De plus, elle est également nécessaire au maintien de la dynamique des microtubules dans les fibroblastes et dans les podocytes différenciés, alors qu’elle ne semble pas avoir de rôle dans la régulation de l’actine. (...)<br>The genetic study of familial forms of nephrotic syndrome or proteinuria with focal segmental glomerulosclerosis has permitted the identification of 30 causal genes, mainly expressed in the podocyte, which is the principal actor of the glomerular filtration barrier (GFB). Among those genes, approximately ten encode actin cytoskeleton regulators and components, thus highlighting the dramatic role of the podocyte architecture and plasticity in the function of the GFB. During the last decade, all the accumulating results, has made a new category of disease called hereditary podocytopathies. The aim of my thesis project was to characterize the effect of mutations in three candidate genes (TTC21B, WDR73, WDR73), identified by whole exome sequencing in isolated or syndromic podocytopathies. In the first part of my project, we found a homozygous missense mutation (p.P209L) in TTC21B, which encodes a ciliary gene named Intraflagellar transport protein IFT139. This protein ensures the trafficking of components from the tip to the base of the primary cilium, which is an organelle present on most mammalian epithelial cells. These results were unexpected because until now, the existence of the primary cilium was unknown. Our work demonstrates the presence of the primary cilium in the human immature podocyte that disappears once podocytes have differentiated. We also showed that IFT139 localized at the basal body and then relocalized along the complex microtubule network of differenciated cells. We showed that the hypomorphic mutation p.P209L causes minor ciliary defects in undifferentiated cells that are not responsible for the glomerular phenotype. Indeed, the glomerular lesions are rather due to drastic damage in actin and, microtubular dysregulation, found in differentiated podocytes. The second part of my thesis aimed to characterize the effects of truncating mutations identified in the WDR73 gene, found in two families. WDR73 is the first gene identified in Galloway Mowat syndrome by whole exome sequencing combined with homozygous mapping. This rare disease is defined by the association of microcephaly with nephrotic syndrome. In this study, the phenotypes of patients with WDR73 mutations are homogenous concerning neurological features, and are heterogeneous with regards to the renal defects. Thus, WDR73 mutations are responsible for a subset of particular patients affected with Galloway-Mowat syndrome. The WDR73 gene encodes WDR73, a WD-40 containing protein of unknown function. Our studies demonstrated that this protein is expressed in both neurons and podocytes in human tissues. We demonstrated that in undifferentiated cells, WDR73 is weakly expressed in the cytosol, while strong expression and relocalization to the spindle pole, microtubule asters and in the cleavage furrow occur during mitosis. Patient fibroblasts and WDR73-depleted podocytes displayed defects in nuclear morphology, which was associated with a decrease in cell survival in patient fibroblasts. Furthermore, we showed that patient fibroblasts and differentiated WDR73-depleted podocytes harbored an atypical morphology associated with a disorganized microtubule network, suggesting microtubule polymerization defects. Our functional studies demonstrated that WDR73 is crucial in both cell survival and microtubule polymerization in neurons and podocytes. The final part of my PhD work focused on the characterization of a missense mutation in the TRIM3 gene R28W identified by whole exome sequencing in a non consanguineous family with autosomal dominant focal segmental glomerulosclerosis. TRIM3 encodes TRIM3, an E3 ubiquitin-ligase that plays a role in transferrin endosomal recycling, and in microtubule trafficking via KIF21B, one of its known partners. Interestingly, the polymorphism V801M in ACTN4 co-segrates with the disease. Furthermore, mutations in this gene were already incriminated in autosomal dominant cases of HSF. (...)
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Fedorow, Heidi School of Medical Science UNSW. "Neuromelanin in human dopamine neurons." Awarded by:University of New South Wales. School of Medical Science, 2005. http://handle.unsw.edu.au/1959.4/32717.
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Neuromelanin (NM) is a dark polymer pigment present in specific populations of catecholaminergic neurons in the brain. Interest in this pigment has rekindled in recent years because of a hypothesised link between NM and the especial vulnerability of NM-containing neurons to cell death in Parkinson???s disease (PD). Many aspects of the biology of NM are yet to be characterised. It is not known if NM like the similar melanin of the skin is synthesised via an enzymatic pathway or solely through autoxidation as has traditionally been thought. Examination of the ultrastructure of NM granules showed that in contrast to peripheral melanosomes, an electron-lucent lipid component was present that represented 30% of pigment volume. The identity of the lipid component of NM has remained unclear since it was first suggested that NM contained lipid in the 1960???s. NM lipid was biochemically isolated from the substantia nigra of 32 human brains. Using reversed-phase high performance liquid chromatography, atmospheric pressure chemical ionisation mass spectrometry and 1H- and 13C NMR techniques, it was shown for the first time that the NM lipid is the polyisoprenoid dolichol. The age-related development and regulation of NM has not previously been described. Optical density and area measurements of unstained NM in ventral substantia nigra neurons spanning the ages of 24 weeks to 95 years old demonstrated three developmental phases. NM was not present at birth and initiation of pigmentation began at approximately 3 years of age, followed by a period of increasing pigment granule number and colouration until age 20. In PD brain, the ultrastructure of NM demonstrated that the amount of lipid did not change. However, filipin staining showed a reduction of cholesterol in PD NM containing neurons. In addition, immunogold staining of ??-synuclein demonstrated that this protein redistributed to the NM lipid in PD brain. The finding of phases in the development of NM, and the identification of lipid species in NM suggest that NM biology is regulated. This thesis has also demonstrated changes in the lipid and associated proteins in PD, suggesting NM???s chemical composition alters which may have functional consequences that contribute to PD.
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Oliet, Stéphane H. R. "Osmoreception in rat supraoptic neurons." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=28874.
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The osmotic control of neurohypophysial hormone release is mediated by central and peripheral osmoreceptors which perceive changes in fluid osmolality. The mechanism underlying signal transduction in these structures, however, has remained obscure. Supraoptic neurons, which synthesize and secrete the neurohypophysial hormones, are themselves recognized to be osmoreceptors. Combined electrophysiological and micromorphometric measurements were therefore obtained in acutely isolated rat supraoptic neurons to determine the cellular basis for signal transduction in osmoreception. Osmotically-evoked changes in cell volume and a gadolinium-sensitive cationic conductance were found to be temporally and proportionally related. In agreement, cell-attached patch-clamp recordings revealed the presence of gadolinium-sensitive cationic channels modulated in response to osmotic stimuli. The mean closed time of these channels was found to increase as a function of changes in membrane tension mediated either by external osmotic perturbation, or by application of pressure inside the patch pipette. The ionic selectivity, density, mechanosensitivity, and pharmacological properties of these channels are consistent with an involvement in the mechanism underlying osmosreception in supraoptic neurons.
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Johnson, Richard James Ramsay. "Plasticity in adult automatic neurons." Thesis, University College London (University of London), 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299940.
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Qiu, Xiaoliang. "Kiss1 Neurons and Metabolic Sensing." University of Toledo Health Science Campus / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=mco1373034912.
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Starodub, Alexander N. "Ionic channels in intestinal neurons /." The Ohio State University, 2000. http://rave.ohiolink.edu/etdc/view?acc_num=osu1488192119264469.
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Yelhekar, Tushar. "Chloride Homeostasis in Central Neurons." Doctoral thesis, Umeå universitet, Institutionen för integrativ medicinsk biologi (IMB), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-127655.
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The overall aim of the present thesis is to clarify the control of intracellular chloride homeostasis in central neurons, because of the critical role of chloride ions (Cl–) for neuronal function. Normal function of the central nervous system (CNS) depends on a delicate balance between neuronal excitation and inhibition. Inhibition is, in the adult brain, most often mediated by the neurotransmitter γ-aminobutyric acid (GABA). GABA may, however, in some cases cause excitation. GABA acts by activating GABA type A receptors (GABAARs), which are ion channels largely permeable to Cl–. The effect of GABAAR-mediated neuronal signaling - inhibitory or excitatory - is therefore mainly determined by the Cl– gradient across the membrane. This gradient varies with neuronal activity and may be altered in pathological conditions. Thus, understanding Cl– regulation is important to comprehend neuronal function. This thesis is an attempt to clarify several unknown aspects of neuronal Cl– regulation. For such clarification, a sufficiently sensitive method for measuring the intracellular Cl– concentration, [Cl–]i, is necessary. In the first study of this thesis, we examined two electrophysiological methods commonly used to estimate [Cl–]i. Both methods, here called the interpolation and the voltage-ramp method, depend on an estimate of the Cl– equilibrium potential from the current-voltage relation of GABA- or glycine-evoked Cl– currents. Both methods also provide an estimate of the membrane Cl– conductance, gCl. With a combination of computational and electrophysiological techniques, we showed that the most common (interpolation) method failed to detect changes in [Cl–]i and gCl during prolonged GABA application, whereas the voltage-ramp method accurately detected such changes. Our analysis also provided an explanation as to why the two methods differ. In a second study, we clarified the role of the extracellular matrix (ECM) for the distribution of Cl– across the cell membrane of neurons from rat brain. It was recently proposed that immobile charges located within the ECM, rather than as previously thought cation-chloride transporter proteins, determine the low [Cl–]i which is critical to GABAAR-mediated inhibition. By using electrophysiological techniques to measure [Cl–]i, we showed that digestion of the ECM decreases the expression and function of the neuron-specific K+ Cl– cotransporter 2 (KCC2), which normally extrudes Cl- from the neuron, thus causing an increase in resting [Cl–]i. As a result of ECM degradation, the action of GABA may be transformed from inhibitory to excitatory. In a third study, we developed a method for quantifying the largely unknown resting Cl– (leak) conductance, gCl, and examined the role of gCl for the neuronal Cl– homeostasis. In isolated preoptic neurons from rat, resting gCl was about 6 % of total resting conductance, to a major part due to spontaneously open GABAARs and played an important role for recovery after a high Cl– load. We also showed that spontaneous, impulse-independent GABA release can significantly enhance recovery when the GABA responses are potentiated by the neurosteroid allopregnanolone. In a final commentary, we formulated the mathematical relation between Cl– conductance, KCC2-mediated Cl– extrusion capacity and steady-state [Cl–]i. In summary, the present thesis (i) clarifies how well common electrophysiological methods describe [Cl–]i and gCl, (ii) provides a novel method for quantifying gCl in cell membranes and (iii) clarifies the roles of the ECM, ion channels and ion transporters in the control of [Cl–]i homeostasis and GABAAR-mediated signaling in central neurons.
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Maimaiti, Shaniya. "INSULIN ACTIONS ON HIPPOCAMPAL NEURONS." UKnowledge, 2017. http://uknowledge.uky.edu/pharmacol_etds/20.
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Aging is the main risk factor for cognitive decline. The hippocampus, a brain region critical for learning and memory formation, is especially vulnerable to normal and pathological age-related cognitive decline. Dysregulation of both insulin and intracellular Ca2+ signaling appear to coexist and their compromised actions may synergistically contribute to neuronal dysfunction with aging. This dissertation focused on the interaction between insulin, Ca2+ dysregulation, and cognition in hippocampal neurons by examining the contributions of insulin to Ca2+ signaling events that influence memory formation. I tested the hypothesis that insulin would increase cognition in aged animals by altering Ca2+-dependent physiological mechanisms involved in learning. The possible effects of insulin on learning and memory in young and aged rats were studied. In addition, the effects of insulin on the Ca2+-dependent afterhyperpolarization in CA1 pyramidal hippocampal neurons from young and aged animals were compared. Further, primary hippocampal cultures were used to examine the possible effects of insulin on voltage-gated Ca2+ channel activity and Ca2+-induced Ca2+-release; mechanisms known to influence the AHP.
We found that intranasal insulin improved memory in aged F344 rats. Young and aged F344 rats were treated with Humalog®, a short-acting insulin analog, or Levemir®, a long-acting insulin analog. The aged rats performed similar to young rats in the Morris Water Maze, a hippocampal dependent spatial learning and memory task. Electrophysiological recordings from CA1 hippocampal neurons revealed that insulin reduced the age-related increase in the Ca2+-dependent afterhyperpolarization, a prominent biomarker of brain aging that is associated with cognitive decline. Patch clamping recording from hippocampal cultured neurons showed that insulin reduced Ca2+ channel currents. Intracellular Ca2+ levels were also monitored using Fura-2 in response to cellular depolarization. Results indicated that a reduction in Ca2+-induced Ca2+-release from intracellular stores occurred in the presence of insulin.
These results suggest that increasing brain insulin levels in aged rats may have improved memory by reducing the AHP and intracellular Ca2+concentrations. This study indicates a possible mechanism responsible for the beneficial effects of intranasal insulin on cognitive function absorbed in selective Alzheimer’s patients. Thus, insulin therapy may reduce or prevent age-related compromises to Ca2+ regulatory pathways typically associated with cognitive decline.
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DE, SANCTIS Claudia. "MicroRNAs profiling in Dopaminergic neurons." Doctoral thesis, Università degli studi del Molise, 2018. http://hdl.handle.net/11695/83499.
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Lo sviluppo dei neuroni dopaminergici mesencefalici (mDA) è un fenomeno complesso e non ancora pienamente compreso. Molti studi hanno focalizzato la loro attenzione sul ruolo svolto da diversi fattori di trascrizione specifici e ben noti. L'obiettivo della mia tesi di dottorato è focalizzato su una classe relativamente nuova di regolatori post-trascrizionali denominati microRNA (miRNAs), in grado di regolare l'espressione genica legando le sequenze parzialmente complementari nelle regioni 3' non tradotte (UTR) degli mRNAs target.
Per studiare il ruolo svolto dai miRNAs durante la differenziazione dei neuroni mDA, abbiamo scelto di analizzare il profilo di espressione dei miRNA usando piattaforme di Array. A tale scopo, abbiamo utilizzato un protocollo ottimizzato da cellule staminali di epiblasto di topo (epiSC) differenziate in neuroni mDA (Jeager et al.,2011).
Dall'analisi bioinformatica dei dati dell'array, ottenuti dalle epiSC differenziate in neuroni mDA, abbiamo identificato alcuni candidati molto probabilmente implicati nella differenziazione e nella funzione dei neuroni DA. I miRNA candidati sono stati sottoposti a screening per la loro capacità di indurre il fenotipo DA. A questo scopo, ho generato vettori lentivirali inducibili per ciascun miRNAs e ho infettato colture primarie mesencefaliche di topo allo stadio E12.5. Tra tutti i miRNA candidati, miR-218 e miR-34b/c aumentano il numero di cellule TH + positive, suggerendo il loro possibile contributo nei neuroni mDA. Inoltre, miR-218 e miR-34b/c, risultano arricchiti sia nel mesencefalo dei topi (E13.5) che nelle cellule GFP + sortate al FACS, isolate da embrioni E13.5 Pitx3-GFP di topo, rispetto al controllo.
I dati ottenuti dal saggio di Luciferasi e dal saggio di reporter a doppia fluorescenza suggeriscono che miR-34b/c legano e sopprimono la 3'UTR di Wnt1 e viene espresso durante la differenziazione dei neuroni mDA.
Tramite analisi di ibridazione in situ e dati d’ immunoistochimica ho potuto verificare che miR-218 è espresso in particolare nel mesencefalo di topo allo stadio E14, dove co-localizza rostralmente con Isl-1 (marcatore di motoneuroni) e caudalmente con TH, Pitx3, Lmx1a (marcatori dopaminergico). Questi dati suggeriscono che miR-218 è espresso anche nei motoneuroni craniali, come descritto in altri recenti studi (Thiebes, K.P. et al., 2014; Amin, N.D et al., 2015).
Per comprendere ulteriormente il ruolo di miR-218 nello sviluppo e nella funzione dei neuroni dopaminergici ho generato topi knock-out condizionali (cKO) per miR-218-2. Accoppiando miR-218-2 flox / flox con topi En1Cre /+ che esprimono Cre sotto il controllo del promotore di Engrailed 1 (En1, marker pro-dopaminergico), sarò in grado di comprendere il contributo di miR-218 nel sistema dopaminergico. I topi miR-218-2 flox / flox En1Cre /+ da osservazioni preliminari, hanno mostrato un fenotipo con danno motorio, ma per confermare questi dati sto attualmente effettuando test comportamentali e analisi in vivo. Attraverso il profilo di espressione di miRNAs, siamo in grado di comprendere il meccanismo e la funzione del sistema dopaminergico, poiché i miRNAs sono regolatori chiave nelle reti di espressione genica, possono influenzare molti processi biologici e in futuro potrebbero essere utilizzati come biomarkers per diagnosticare patologie legate al sistema nervoso.<br>Midbrain dopaminergic neurons (mDA) development is a complex and still not fully understood phenomenon. Many studies till now concentrated their attention on the roles played by several, specific and well-known transcription factors. The aim of my PhD thesis is focus on a relatively new class of post-transcriptional regulators named microRNAs (miRNAs) able to regulate gene expression by targeting partially complementary sequences in the 3’untranslated regions (UTRs) of the target mRNAs.
To investigate the role played by miRNAs during mDA differentiation, we choose to analyze miRNAs expression profile by using miRNA Array platforms. To this purpose we used an optimized protocol from mouse Epiblast stem cells (epiSC) differentiated into DA neurons (Jeager et al. 2011).
By bioinformatics analysis of the array data, obtained from epiSC differentiated into mDA neurons, we identified few candidates most likely implicated in the DA neurons differentiation and function. The candidate miRNAs were screened for their ability to induce DA phenotype. To this purpose, I generated inducible lentiviral vectors for each miRNA and I have infected mesencephalic primary cultures from mice at stage E12.5. Among all candidate miRNAs, miR-218 and miR-34b/c increase the number of TH+ positive cells, showing their possible contribution in the mDA neurons. Moreover, miR-218 and miR-34b/c, were enriched both in midbrain of mice (E13.5) and in FACS sorted GFP+ cells isolated from E13.5 Pitx3-GFP mice embryos when compared with control.
Data obtained from Luciferase Assay and Dual Fluorescence Reporter Assay suggest that miR-34b/c target and suppress Wnt1 3’UTR and it is expressed during DA neurons differentiation.
By performing In situ hybridization analysis and immunohistochemistry, I was able to detect miR-218 in particular in the mouse midbrain at stage E14, where co-localize rostrally with Isl-1 (motor neuron marker) and caudally with TH, Pitx3, Lmx1a (dopaminergic marker). This data suggests that miR-218 is expressed also in cranial motor neurons, as described in others recent studies (Thiebes, K.P. et al. 2014; Amin, N.D et al. 2015). To further understand the role of miR-218 in development and function of dopaminergic neurons I have generated the conditional knock-out (cKO) mice for miR-218-2. By mating miR-218-2 flox/flox with En1Cre/+ mice expressing the Cre under Engrailed 1 promoter (En1 is a pro-dopaminergic marker) I will be able to investigate the contribution of miR-218 in dopaminergic system. Preliminary observations on miR-218-2 flox/flox En1Cre/+ mice shown motor impairment phenotype, but to confirm this data I’m currently performing behavior tests and in vivo analysis. Through miRNA expression profiling we be able understand mechanism and function of dopaminergic system, because miRNAs are as key regulators in gene expression networks, can influence many biological processes and have also shown promise as biomarkers for neuro-disorders.
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Arosio, Daniele. "Imaging Chloride Homeostasis in Neurons." Doctoral thesis, Università degli studi di Trento, 2017. https://hdl.handle.net/11572/368512.
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Intracellular chloride and pH are fundamental regulators of neuronal excitability and they are often co-modulated during excitation-inhibition activity. The study of their homeostasis requires simultaneous measurements in vivo in multiple neurons. Combining random mutagenesis screening, protein engineering and two-photon-imaging this thesis work led to the discovery of new chloride-sensitive GFP mutants and to the establishment of ratiometric imaging procedures for the quantitative combined imaging of intraneuronal pH and chloride. These achievements have been demonstrated in vivo in the mouse cortex, in real-time monitoring the dynamic changes of ions concentrations during epileptic-like discharges, and in glioblastoma primary cells, measuring osmotic swelling responses to various drugs treatment.
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Arosio, Daniele. "Imaging Chloride Homeostasis in Neurons." Doctoral thesis, University of Trento, 2017. http://eprints-phd.biblio.unitn.it/1937/2/DECLARATORIA_ENG_signed.pdf.
Full textAbstract:
Intracellular chloride and pH are fundamental regulators of neuronal excitability and they are often co-modulated during excitation-inhibition activity. The study of their homeostasis requires simultaneous measurements in vivo in multiple neurons. Combining random mutagenesis screening, protein engineering and two-photon-imaging this thesis work led to the discovery of new chloride-sensitive GFP mutants and to the establishment of ratiometric imaging procedures for the quantitative combined imaging of intraneuronal pH and chloride. These achievements have been demonstrated in vivo in the mouse cortex, in real-time monitoring the dynamic changes of ions concentrations during epileptic-like discharges, and in glioblastoma primary cells, measuring osmotic swelling responses to various drugs treatment.
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Erasmus, Louwrence Daniel. "The formulation and evaluation of a neuron model based on biological neurons / Louwrence Daniël Erasmus." Thesis, North-West University, 2007. http://hdl.handle.net/10394/2307.
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This thesis formulates and evaluates a mathematical model from an engineer's point of view based on the currently-known information-processing processes and structures of biological neurons. The specification and evaluation of the RealNeuron model form a baseline for current use in engineering solutions and future developments.
The RealNeuron is a carefully-reduced model that retains the essential features of more complex models. A systems engineering approach is used to formulate it, i.e. the model is described as using multiple resolution levels with configurable modular elements at each resolution level and is then implemented, verified and validated in a bottom-up method. It is computationally efficient and only adds or subtracts ion concentrations based on the states at the membrane structure's level. The results are integrated at the lower levels of resolution. The RealNeuron's simple calculations make simulations on personal computers possible by using standard spreadsheet software for a seven-neuron classical-conditioning neural circuit. All the simulated states at the highest level of resolution (i.e. pumps, channels, etc.), the intermediate levels of resolution (i.e. membrane potentials, neurotransmitters in the synapse, etc.) and the lowest level of resolution (i.e. conditioning signal, conditioned signal, conditioned reaction, etc.) are available on a spreadsheet.
The RealNeuron is verified in a bottom-up manner. The pumps, channels and receptors are verified first. These components are then integrated into the different membrane types (post-synaptic membrane, main membrane, axonal membrane) and verified while the membrane components are validated simultaneously. This process is repeated until individual neurons have been built up and RealNeuron networks have finally been constructed. The RealNeuron is verified and validated in configurations for AND, NAND, OR, NOR, NOT and XOR logic functions. It is also verified and validated by the implementation of classical conditioning.
In a noisy environment, the RealNeuron's performance is dependent on the pump's parameters in the main membrane of the sensor neurons.
This thesis proposes that a grade of machine intelligence is used to distinguish between the different synthesis requirements for intelligent machines.
An engineering synthesis of a RealNeuron network, based on classical conditioning, demonstrates how to implement a RealNeuron network that can be used in machines built to the grade of machine intelligence requirement which is classical-conditioning learning implemented with neural networks that can change learned associations in a dynamic environment.<br>This thesis formulates and evaluates a mathematical model from an engineer's point of view based on the currently-known information-processing processes and structures of biological neurons. The specification and evaluation of the RealNeuron model form a baseline for current use in engineering solutions and future developments.
The RealNeuron is a carefully-reduced model that retains the essential features of more complex models. A systems engineering approach is used to formulate it, i.e. the model is described as using multiple resolution levels with configurable modular elements at each resolution level and is then implemented, verified and validated in a bottom-up method. It is computationally efficient and only adds or subtracts ion concentrations based on the states at the membrane structure's level. The results are integrated at the lower levels of resolution. The RealNeuron's simple calculations make simulations on personal computers possible by using standard spreadsheet software for a seven-neuron classical-conditioning neural circuit. All the simulated states at the highest level of resolution (i.e. pumps, channels, etc.), the intermediate levels of resolution (i.e. membrane potentials, neurotransmitters in the synapse, etc.) and the lowest level of resolution (i.e. conditioning signal, conditioned signal, conditioned reaction, etc.) are available on a spreadsheet.
The RealNeuron is verified in a bottom-up manner. The pumps, channels and receptors are verified first. These components are then integrated into the different membrane types (post-synaptic membrane, main membrane, axonal membrane) and verified while the membrane components are validated simultaneously. This process is repeated until individual neurons have been built up and RealNeuron networks have finally been constructed. The RealNeuron is verified and validated in configurations for AND, NAND, OR, NOR, NOT and XOR logic functions. It is also verified and validated by the implementation of classical conditioning.
In a noisy environment, the RealNeuron's performance is dependent on the pump's parameters in the main membrane of the sensor neurons.
This thesis proposes that a grade of machine intelligence is used to distinguish between the different synthesis requirements for intelligent machines.
An engineering synthesis of a RealNeuron network, based on classical conditioning, demonstrates how to implement a RealNeuron network that can be used in machines built to the grade of machine intelligence requirement which is classical-conditioning learning implemented with neural networks that can change learned associations in a dynamic environment.<br>Thesis (Ph.D. (Electrical and Electronic Engineering))--North-West University, Potchefstroom Campus, 2008.
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Mahoney, Sally-Ann. "A role for tissue transglutaminase in neuron / glial interaction and development of cerebellar granule neurons." Thesis, University of Bristol, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361111.
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Adams, Van L. "Seasonal plasticity of A15 dopaminergic neurons in the ewe." Morgantown, W. Va. : [West Virginia University Libraries], 2001. http://etd.wvu.edu/templates/showETD.cfm?recnum=2096.
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Thesis (M.S.)--West Virginia University, 2001.<br>Title from document title page. Document formatted into pages; contains vii, 79 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 70-78).
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Vázquez, de la Torre Cervera Aurelio. "Estudio de la apoptosis inducida por la inhibición de la vía de la PI3K/AKT." Doctoral thesis, Universitat de Barcelona, 2013. http://hdl.handle.net/10803/110926.
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Una de las vías que se postula que tienen una mayor importancia en las enfermedades neurodegenerativas es la de los inositoles fosfato. Para el estudio de esta vía se ha utilizado un inhibidor farmacológico de la fosfoinositol 3 cinasa (PI3K), el LY294002, en un modelo in vitro de células granulares de cerebelo de rata (CGC). Al tratar las CGC con una dosis de 30μM de LY294002 se produce una muerte celular por apoptosis que es independiente de calpaínas y dependiente de caspasas, además no se observa la fragmentación de p35 ni de α espectrina que se da por activación de las calpaínas. Los ensayos de actividad caspasa nos muestran un incremento significativo de la actividad de las caspasas 6 y 9 pero no de la 3 como sucede en otros modelos de apoptosis como la deprivación de S/K+.
Nuestros estudios muestran que aunque existen algunas similitudes entre los modelos de inhibición de la PI3K y la deprivación de S/K+ también existen importantes diferencias. En ambos se produce una desfosforilación de AKT en Ser476 y consecuentemente una desfosforilación de GSK3β en Ser9, lo que indica la activación de GSK3β. Respecto a la proteína Rb en ambos modelos se observa un incremento de su fosforilación, si bien su papel es distinto ya que en la deprivación de S/K+ conduce a la liberación del E2F y a la transcripción de proteínas relacionadas con el ciclo celular. Además, se observó un incremento de la síntesis de DNA. Por el contrario el tratamiento con LY294002, pese a provocar un incremento en la fosforilación del Rb, no lleva a la expresión de ciclinas, CDKs ni un aumento de la síntesis de DNA.. Sin embargo el uso de inhibidores de CDK como flavopiridol y roscovitina muestran una protección significativa frente a la apoptosis inducida por LY294002, nuestros estudios muestran por vez primera que, no solo flavopiridol sino también otros inhibidores de CDK como la roscovitina tienen capacidad para inhibir la actividad GSK3β.
Rb puede ser fosforilado por p38, un miembro de la vía de las MAPK las cuales son inhibidas por AKT. Nuestros resultados indican que LY294002 produce un incremento de la actividad de p38, pero no de JNK. Además, los cultivos Knockout de JNK3 no muestran una protección frente al tratamiento con LY294002, lo que refuerza la idea de que JNK no juega un papel central en este modelo. El incremento de actividad de p38 fue revertido con SB203580, un inhibidor de p38, así como por SP600125, inhibidor de JNK. Ambos fármacos mostraron una protección significativa frente a la apoptosis inducida por LY294002 y una reducción de la fosforilación del factor de transcripción c‐Jun, implicado en la apoptosis. La activación de c‐Jun conduce a la expresión de genes proapoptóticos como dp5 relacionados con la vía intrínseca, la inhibición de p38 previno del aumento de expresión de dp5. Por el contrario otras proteínas implicadas en la vía como Bim no están reguladas por c‐Jun ya que la inhibición de esta vía no reduce su activación.
En nuestro estudio podemos concluir que, LY294002 produce una apoptosis dependiente de caspasas 6 y 9, sin implicación ni de calpaínas ni de proteínas del ciclo celular. La inhibición de AKT lleva a la activación de GSK3β y de p38. Además, p38 es capaz de fosforilar c‐Jun que regula la expresión de genes relacionados con la apoptosis por la vía intrínseca.<br>The inositol pathway has been reported that plays a key role in neurodegenerative diseases We study the mechansims involved in the apoptosis induced by inhibiting the phosphoinositol 3 kinase (PI3K) using a pharmacological inhibitor named LY294002 in an in vitro model of rat cerebellar granule cells (CGC). LY294002 induced apoptotic cell death through calpain independent and caspase dependent. Furthermore, we could not observed neither fragmentation of of p35 or α espectrin which is caused by calpains. The caspase activity assays showed a significant increase in caspase 6 and 9 but not in caspasa 3, in contrast with other apoptotic models such as de S/K+ deprivation.
Our studies show that although exist several common points between inhibition of PI3K and S/K+ deprivation, also exist important differences between them. In both cases it has been observed AKT dephosphorylation at Ser476 and consequently GSK3β dephosphorylation at Ser9, which indicates GSK3β activation. On the other side, it was observed an increase of Rb phosphorylation in both models. However, it seems that the role played by this protein is different since in the de S/K+ deprivation leads to E2F released which participates in the transcription of proteins related to cell cycle. Moreover, the BrdU assay showed an increase in DNA synthesis. On the contrary, the LY294002 treatment, in spite of the fact that induced an increase of Rb phosphorylation, it did not induce any change of the levels neither cell cycle proteins or However, CDK inhibitors such as flavopiridol and roscovitine protected from the apoptosis induced by LY294002, our studies showed for the first time, that not only flavopiridol, but also other CDK inhibitors such as roscovitine could inhibit the GSK3β activity. Furthermore Rb can be phosphorylated by p38, which is a protein of MAPK pathway that is down‐regulated by AKT. Our results showed that LY294002 produced an increase of p38 activity, but not of JNK. Moreover, JNK3 Knockout cultures were not significantly protected from LY294002 treatment, this reinforces the idea that JNK is not the main target involved in this model. The increase of p38 activity was prevented with SB203580, a specific p38 inhibitor, and either with SP600125, a JNK inhibitor. Both drugs shown a significant protection from the apoptosis induced by LY294002 and prevented from c‐Jun phosphorylation, a transcription factor implied in apoptosis. The activation of c‐Jun triggered the expression of proapoptotic genes such as dp5 which is related to the intrinsic pathway, p38 inhibition prevented from the increase in dp5 expression. On the contrary, other proapoptotic proteins related to this pathway such as Bim was not regulated by c‐Jun since the inhibition of p38 pathway did not reduce its expression.
In our study we can conclude that LY294002 induced apoptosis mediated by caspasas 6 and 9. Neither calpains nor cell cycle proteins were involved in this apoptotic model. The inhibition of AKT leaded to GSK3β and p38 activation. Moreover, p38 was able to phosphorylate c‐Jun that triggers the expression of proapoptotic genes implied in the apoptotic intrinsic pathway.
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Tang, Ping. "Simulation du traitement effectué par certaines cellules étoilées du noyau cochléaire antéroventral et analyse de leur comportement en terme de modulation d'amplitude /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 1995. http://theses.uqac.ca.
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Teller, Amado Sara. "Functional organization and networ resilience in self-organizing clustered neuronal cultures." Doctoral thesis, Universitat de Barcelona, 2016. http://hdl.handle.net/10803/396114.
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Major dynamical traits of a neuronal network are shaped by its underlying circuitry. In several neurological disorders, the deterioration of brain's functionality and cognition has been ascribed to changes in the topological properties of the brain's circuits. To deepen in the understanding of the activity-connectivity relationship, neuronal cultures have emerged as remarkable systems given their accessibility and easy manipulation. A particularly appealing configuration of these in vitro systems consists in an assembly of interconnected aggregates of neurons termed 'clustered neuronal networks'.
These networks exhibit a complex dynamics in which clusters fire in small groups, shaping communities with rich spatiotemporal properties. The detailed characterization of this dynamics, as well as its resilience to perturbations, has been the main objective of this thesis. In our experiments we monitored spontaneous activity using calcium fluorescence imaging, which allows the detection of neuronal firing events with both high temporal and spatial resolution. The detailed analysis of the recorded activity, in the context of network theory and community analysis, allowed for the quantification of important properties, including the effective connectivity map and its major topological descriptors.
As major results, we observed that these clustered networks present hierarchical modularity, assortative mixing and the presence of a rich club core, a series of features that have also been observed at the scale of the brain. All these characteristic topological traits are associated with a robust architecture that reinforces and stabilizes network activity. To verify the existence of such robustness in our cultures, we studied their resilience upon chemical and physical damage. We concluded that, indeed, clustered networks present higher resilience compared to other configurations. Moreover, these clustered networks exhibited recovery mechanisms that can be linked to the balance between integration and segregation in the network, which ultimately tend to preserve network activity upon damage. Thus, these in vitro preparations offer a unique scenario to explore vulnerability in networks with topological properties similar to the brain. Moreover, the combination of all these approaches can help to develop models to quantify damage upon network degradation, with promising applications for the study of neurological disorders in vitro.<br>Desvelar la relación entre la red de conexiones anatómica y su emergente dinámica es uno de los grandes desafíos de la neurociencia actual. En este sentido, los cultivos neuronales han tomado un papel muy importante para entender esta cuestión, ya que fenomenologías fundamentales pueden ser estudiadas a escalas más tratables. Los cultivos neuronales se obtienen típicamente a base de disociar tejido neuronal de una parte específica del cerebro, corteza cerebral de rata en nuestro caso, y su cultivo en un medio adecuado. Neuronas en cultivo constituyen en 1-2 semanas una red nueva con una actividad espontánea rica.
Una de las preparaciones in vitro que ofrece mayor potencial es las 'redes clusterizadas'. Estas redes se auto-organizan de forma natural, formando grupos de neuronas (clústeres) interconectados a través de axones. La caracterización de la dinámica de estas redes clusterizadas, así como su sensibilidad a perturbaciones, ha sido el objetivo principal de esta tesis.
Así, hemos caracterizado la red funcional del cultivo a partir de su dinámica espontánea, desarrollando para ello un novedoso modelo fisicomatemático. Hemos observado que las redes tienen una conectividad modular, donde clústeres tienden a conectarse fuertemente en pequeños grupos, los cuales a su vez se conectan entre ellos. Además, las redes funcionales muestran propiedades topológicas clave, en especial asortatividad (interconexión preferente de clústeres con número similar de conexiones) y la existencia de un 'rich club' (grupo de clústeres con una interconectividad tan destacada que forman el núcleo fundamental de la red). Estas propiedades confieren una gran robustez y flexibilidad a la red. Por esta razón, en la tesis hemos investigado diferentes perturbaciones físicas y bioquímicas, demostrando que las redes clusterizadas son mucho más resistentes a daño que otras configuraciones, lo que refuerza la relación entre las propiedades topológicas descritas y resistencia al daño. Además, observamos que las redes presentaron diferentes mecanismos de reforzamiento entre conexiones para preservar la actividad de la red. Por ello, las redes clusterizadas constituyen una plataforma ideal para estudiar resistencia en redes o como sistema modelo aplicado a estudios de enfermedades neurodegenerativas, como por ejemplo Alzheimer.
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Creyssels, Sophie. "Comprendre les mécanismes cellulaires déficients dans la MPS VII par l'utilisation de neurones humains dérivés d'iPSC." Thesis, Montpellier, 2015. http://www.theses.fr/2015MONTT009.
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Les processus moléculaires mis en jeu lors de maladies de surcharge lysosomale (MSL) et qui conduisent à des dysfonctions neuronales sont peu connus. Afin de mieux comprendre comment s’opèrent ces dysfonctions neuronales associées à la mucopolysaccharidose de type VII (MPS VII), une MSL causée par la déficience en l’activité enzymatique de la ß-glucuronidase, nous avons généré des neurones humains MPS VII à partir cellules souches pluripotentes induites (iPSC). Grâce à la reprogrammation des fibroblastes de patients MPS VII, nous avons généré et caractérisé des neuroprécurseurs dérivés d’iPSC (NSC) et des neurones. Les iPSC MPS VII ont été positives pour les tests de pluripotence (activité de la phosphatase alcaline, expression des marqueurs de pluripotence SSEA3, TRA-2-49 et Nanog par immunofluorescence et expression des gènes de pluripotence SOX2, Oct4 et Lin28 par qRT-PCR, formation des corps embryonnaires et génération de cellules dérivées des trois feuillets embryonnaires in vivo par la formation de tératomes) et présentaient un caryotype normal. Les NSC dérivés d’iPSC exprimaient les marqueurs Nestin et SOX2, et ont été utilisés pour générer des neurones. Les neurones MPS VII exprimaient des marqueurs neuronaux comme MAP2, formaient des synapses et présentaient une activité calcium-dépendante.Afin d’identifier les dysfonctions moléculaires présentes dans la MPS VII, nous avons comparé les NSC et les neurones, avec ou sans milieu conditionné contenant l’enzyme recombinante humaine de la ß-glucuronidase (rhGUS), enzyme actuellement utilisée en phase 1/2, de chez Ultragenyx. Cette enzyme est internalisée par les cellules, rejoint leurs lysosomes et corrige les dysfonctions lysosomales de la MPS VII, restaurant ainsi un phénotype cellulaire physiologique (phénomène aussi appelé ‘enzyme replacement therapy’ (ERT)). Ces diverses conditions nous permettent d’éviter la variabilité clonale des iPSC, et de mieux identifier les déficiences neuronales, corrigées par l’ERT, qui sont associées à la MPS VII<br>The molecular pathways linking lysosomal storage diseases (LSD) to neuronal dysfunction are poorly understood. To better understand neuronal dysfunction associated with mucopolysaccharidosis type VII (MPS VII), a LSD due to deficiency in ß-glucuronidase activity, we generated human MPS VII neurons from induced pluripotent stem cells (iPSC). Starting from MPS VII patient fibroblasts, iPSC-derived neural stem cells (NSC) and neurons were generated and characterized. MPS VII iPSC were positive for pluripotency tests (alkaline phosphatase activity, expression of pluripotency markers SSEA3, TRA-2-49 and Nanog by immunostaining and pluripotency gene SOX2, Oct4 and Lin28 expression by qRT-PCR, embryonic bodies formation and generation of cells derivated from the three germ layers in vivo by teratoma formation) and had a normal karyotype. IPSC-derived NSC expressed the markers Nestin and SOX2, and were used to generate neurons. MPS VII neurons expressed mature neuronal markers as MAP2, formed synapses and displayed a calcium-dependent activity. To identify molecular defects in MPS VII, we compared NSC and neurons, with or without conditioned medium containing a recombinant human ß-glucuronidase (rhGUS), enzyme currently used in phase 1/2, from Ultragenyx. This enzyme is taken up by cells, reaches their lysosoms and corrects MPS VII lysosoms dysfunctions, restoring cells to healthy phenotype (phenomena also called enzyme replacement therapy (ERT)). Our assays allow us to circumvent clonal variability associated with iPSC, and to better identify neuronal defects, corrected by ERT, which are associated with MPS VII disease
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Nesbit, Matthew. "The development of an identified neuronal population within rat visual cortex : callosal projection neurons." Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361816.
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Petersson, Marcus. "Dendritic and axonal ion channels supporting neuronal integration : From pyramidal neurons to peripheral nociceptors." Doctoral thesis, KTH, Beräkningsbiologi, CB, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-102362.
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The nervous system, including the brain, is a complex network with billions of complex neurons. Ion channels mediate the electrical signals that neurons use to integrate input and produce appropriate output, and could thus be thought of as key instruments in the neuronal orchestra. In the field of neuroscience we are not only curious about how our brains work, but also strive to characterize and develop treatments for neural disorders, in which the neuronal harmony is distorted. By modulating ion channel activity (pharmacologically or otherwise) it might be possible to effectively restore neuronal harmony in patients with various types of neural (including channelopathic) disorders. However, this exciting strategy is impeded by the gaps in our understanding of ion channels and neurons, so more research is required. Thus, the aim of this thesis is to improve the understanding of how specific ion channel types contribute to shaping neuronal dynamics, and in particular, neuronal integration, excitability and memory. For this purpose I have used computational modeling, an approach which has recently emerged as an excellent tool for understanding dynamically complex neurophysiological phenomena. In the first of two projects leading to this thesis, I studied how neurons in the brain, and in particular their dendritic structures, are able to integrate synaptic inputs arriving at low frequencies, in a behaviorally relevant range of ~8 Hz. Based on recent experimental data on synaptic transient receptor potential channels (TRPC), metabotropic glutamate receptor (mGluR) dynamics and glutamate decay times, I developed a novel model of the ion channel current ITRPC, the importance of which is clear but largely neglected due to an insufficient understanding of its activation mechanisms. We found that ITRPC, which is activated both synaptically (via mGluR) and intrinsically (via Ca2+) and has a long decay time constant (τdecay), is better suited than the classical rapidly decaying currents (IAMPA and INMDA) in supporting low-frequency temporal summation. It was further concluded that τdecay varies with stimulus duration and frequency, is linearly dependent on the maximal glutamate concentration, and might require a pair-pulse protocol to be properly assessed. In a follow-up study I investigated small-amplitude (a few mV) long-lasting (a few seconds) depolarizations in pyramidal neurons of the hippocampal cortex, a brain region important for memory and spatial navigation. In addition to confirming a previous hypothesis that these depolarizations involve an interplay of ITRPC and voltage-gated calcium channels, I showed that they are generated in distal dendrites, are intrinsically stable to weak excitatory and inhibitory synaptic input, and require spatial and temporal summation to occur. I further concluded that the existence of multiple stable states cannot be ruled out, and that, in spite of their small somatic amplitudes, these depolarizations may strongly modulate the probability of action potential generation. In the second project I studied the axonal mechanisms of unmyelinated peripheral (cutaneous) pain-sensing neurons (referred to as C-fiber nociceptors), which are involved in chronic pain. To my knowledge, the C-fiber model we developed for this purpose is unique in at least three ways, since it is multicompartmental, tuned from human microneurography (in vivo) data, and since it includes several biologically realistic ion channels, Na+/K+ concentration dynamics, a Na-K-pump, morphology and temperature dependence. Based on simulations aimed at elucidating the mechanisms underlying two clinically relevant phenomena, activity-dependent slowing (ADS) and recovery cycles (RC), we found an unexpected support for the involvement of intracellular Na+ in ADS and extracellular K+ in RC. We also found that the two major Na+ channels (NaV1.7 and NaV1.8) have opposite effects on RC. Furthermore, I showed that the differences between mechano-sensitive and mechano-insensitive C-fiber types might reside in differing ion channel densities. To conclude, the work of this thesis provides key insights into neuronal mechanisms with relevance for memory, pain and neural disorders, and at the same time demonstrates the advantage of using computational modeling as a tool for understanding and discovering fundamental properties of central and peripheral neurons.<br><p>QC 20120914</p>
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Jayakar, Selwyn S. "Abl family kinases regulate neuronal nicotinic receptors and synapses in chick ciliary ganglion neurons." Connect to full text in OhioLINK ETD Center, 2009. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=mco1242668863.
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Dissertation (Ph.D.)--University of Toledo, 2009.<br>"In partial fulfillment of the requirements for the degree of Doctor of Philosophy in Biomedical Sciences." Title from title page of PDF document. Bibliography: p. 138-150.
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GIANSANTE, GIORGIA. "The paroxysmal disorder gene PRRT2 downregulates NaV channels and neuronal excitability in human neurons." Doctoral thesis, Università degli studi di Genova, 2018. http://hdl.handle.net/11567/929007.
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Proline-Rich Transmembrane Protein 2 (PRRT2) has been identified as the single causative gene for a group of paroxysmal syndromes, including benign familial infantile seizures, paroxysmal kinesigenic dyskinesia and migraine. Most of the mutations of this gene lead to a premature stop codon, generating an unstable form of mRNA or a truncated protein that is degraded, pointing out the loss of the PRRT2 function as pathogenic mechanism of action. In this thesis, we have used different approaches to investigate the pathophysiological function of PRRT2. An important role for PRRT2 in the neurotransmitter release machinery, brain development and synapse formation has been uncovered by a previous work performed in our laboratory by acute silencing of PRRT2 expression. Here, we analyzed the phenotype of primary hippocampal neurons obtained from mouse PRRT2 knockout (KO) embryos. Analysis of synaptic function in primary neurons obtained from PRRT2-KO showed a largely similar, albeit attenuated, synaptic phenotype with respect to acute PRRT2 silencing characterized by weakened spontaneous/evoked synaptic transmission and increased facilitation at excitatory synapses. These effects were accompanied by a strengthened inhibitory transmission that, however, displayed faster synaptic depression. At the network level, these synaptic phenotypes, resulted in a state of increased spontaneous and evoked neurotransmitter release with increased excitability of excitatory neurons. To better dissect the physiological role of PRRT2, we characterized the phenotypes of neurons differentiated from Induced Pluripotent Stem Cells (iPSCs) from patients homozygous for the PRRT2 c.649dupC mutation. Hence, we observed an increased Na+ current and firing activity in iPSCs rescued with the re-expression of the human wild-type form of PRRT2. By use of heterologous expression system, we demonstrate that PRRT2 interacts with NaV1.2/NaV1.6, but not with NaV1.1 channels, modulating their membrane exposure and decreasing their conductances. In brief, our findings highlighted that PRRT2 mutations might be a negative modulator of NaV1.2/NaV1.6 channels and point out the critical role of this protein in the regulation of the neuronal network functionality.
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Javalet, Charlotte. "Rôle des exosomes comme nouvelle voie de communication entre les neurones." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAV028/document.
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Les exosomes sont des vésicules d’origine endosomale sécrétées par les cellules dans leur environnement après fusion à la membrane plasmique des endosomes multivésiculés. Les exosomes représentent un nouveau mode de communication entre les cellules en permettant un transfert direct de protéines, de lipides et d’ARN. L’objectif de ma thèse était d’étudier le rôle des exosomes dans la communication entre les neurones. Précédemment, le laboratoire a montré que les neurones sécrètent des exosomes de manière régulée par l’activité synaptique. Nous avons observé que les exosomes neuronaux ne sont endocytés que par les neurones. Après avoir montré qu’ils ne contiennent que des ARN courts, nous avons réalisé un séquençage complet de leurs microARN et observé que ces microARN étaient sélectivement exportés dans les exosomes. Nos observations suggèrent que les microARN contenus dans les exosomes peuvent modifier la physiologie des neurones receveurs. Nos résultats renforcent l’hypothèse du rôle des exosomes dans la communication entre les neurones via le transfert de microARN<br>Exosomes are vesicles of endocytic origin released by cells into their environment following fusion of multivesicular endosomes with the plasma membrane. Exosomes represent a novel mechanism of cell communication allowing direct transfer of proteins, lipids and RNA. The goal of my PhD thesis was to study that exosomes represent a novel way of interneuronal communication. Our team has previously reported that neurons release exosomes in a way tightly regulated by synaptic activity. We observed that exosomes released by neurons are only endocytosed by neurons. We found that exosomes contain only small RNA and did a deep sequencing of all their microRNA. MicroRNA are selectively exported into exosomes. It seems that exosomal microRNA can modify the physiology of receiving neurons. Our results strengthen the hypothesis of the role of exosomes in the interneuronal communication by the way of microARN transfert
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Fame, Ryan Marie. "Molecular Controls over Developmental Acquisition of Diverse Callosal Projection Neuron Subtype Identities." Thesis, Harvard University, 2012. http://dissertations.umi.com/gsas.harvard:10591.
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The mammalian neocortex is an exquisite, highly organized brain structure composed of hundreds of subpopulations of neurons and glia, precisely connected to enable motor control, sensory perception, information integration, and planning. Unique molecular, structural, and anatomical neuronal properties underlie diverse functionality, endowing much of the neocortex’s complex processing power. Neocortical size correlates with information processing capacity, suggesting that increased neuronal number and diversity begets increased sophistication. One excitatory projection neuron type, callosal projection neurons (CPN), has disproportionately expanded with cortical size increase. CPN directly connect homotypic regions of the two neocortical hemispheres by sending axons via the largest white matter fiber tract in the brain, the corpus callosum (CC), allowing quick relay, integration, and comparison of information. In humans, the CC contains over 300,000 axons, CPN have been centrally implicated in autism spectrum disorders, and absence or surgical disruption of CPN connectivity in humans is associated with defects in abstract reasoning, problem solving, and generalization. Therefore, CPN are critical to complex brain functions, and their diversity likely contributes to these roles. Work presented in this dissertation addresses molecular controls over CPN development, specifically genes that are expressed by, and function in, particular subpopulations of CPN. While much progress has been made in identifying molecular controls over neocortical arealization, lamination, and broad subtype specification, CPN diversity has remained largely unaddressed. Therefore, this work begins by identifying genes more highly expressed in CPN than other closely related projection neuron populations, and uncovers molecular diversity within CPN. From this molecular diversity, functional analysis of three candidate molecular controls over CPN subtype diversity follows. Cited2 acts broadly in neocortical progenitor development and postnatally in refining somatosensory CPN identity. Caveolin1 identifies a population of CPN with dual axonal projections. Tmtc4 is mutated in human CC disease and can function in CPN axonal development. These analyses of CPN molecular diversity in mouse then expand to an investigation of which molecular subpopulations are conserved, expanded, or uncommon between rodent and primate, allowing both for comparative evolutionary theories of CPN function, and indicating which CPN populations critical for human brain function can be best studied in rodent models.