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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Development, Organization and Plasticity of the Zebrafish Olfactory System

Braubach, Oliver Robert 10 March 2011 (has links)
Olfaction is vitally important to animals in all environments and is used to identify food, habitat, conspecifics and predators. Some odors, like pheromones or the pungent smell of spoiled foods, can trigger pre-existing behavioral responses that appear to require no learning. Most odors, however, are only attended to as a result of prior experience. It is believed that different types of odors are processed in different olfactory pathways in the forebrain. This thesis examines the relationship between innate and learned olfactory behaviors and the anatomy of the neural pathways that underlie them, using the zebrafish olfactory system as a model. I first characterized an appetitive olfactory behavior, which is displayed promptly by zebrafish when they encounter amino acid odors. A similar appetitive behavior can also be learned by the fish for another, initially neutral odorant, if it is repeatedly paired with food rewards. Zebrafish can therefore respond to, and learn to respond to certain odors. I then conducted an in-depth anatomical analysis of the structure and distribution of glomeruli in the zebrafish olfactory system. Glomeruli are spheroidal synaptic aggregates that organize and shape olfactory information that arrives in the brain. Throughout the development of zebrafish, I identified two distinct populations of glomeruli. One population consisted of 25 individually identifiable, anatomically stereotypic glomeruli that closely resembled specialized glomeruli in mammals and insects. These glomeruli were already formed during embryonic development and persisted in remarkably stable configurations throughout later developmental stages. I hypothesize that the 25 individually identifiable glomeruli constitute stable olfactory pathways (i.e., for innate olfactory behaviors). Most glomeruli, however, were anatomically variable and displayed different distributions within coarsely circumscribed regions in the zebrafish olfactory bulbs. The development of these glomeruli could be modified by sensory experience, suggesting that they may comprise plastic olfactory pathways that subserve the establishment of learned olfactory behaviors. Collectively my results show that innate and learned olfactory behaviors may indeed be represented in different olfactory pathways, and that these types of pathways may be located in both main and accessory olfactory systems.
2

Synaptic Connectivity After Methimazole-Induced Injury

Lance, Lea N., Chapman, Rudy T., Rodriguez-Gil, Diego J. 05 May 2020 (has links)
Olfactory sensory neurons in the olfactory epithelium are responsible for detecting the odors we smell and are constantly dying. However, in order for the sense of smell to be maintained, the olfactory system has the unique ability to generate new neurons. After an olfactory sensory neuron is born in the olfactory epithelium, it must extend an axon towards the olfactory bulb in the central nervous system. Within the olfactory bulb, these axons make specific synaptic contacts with the dendritic processes of mitral cells, which are the main projection neurons from the olfactory bulbs into higher cortical areas in the brain. In addition to regeneration due to normal turnover, the olfactory system is also capable of recovery after an injury. The olfactory system’s ability to recover is remarkable because it is capable of regeneration after a mild injury (a portion of olfactory epithelium is removed) or a severe injury (in which the entire olfactory epithelium is removed.) A well-established model for producing a severe type of injury in the olfactory epithelium is by inducing a chemical ablation by a single injection of the drug methimazole. A specific interest in the regenerative process after injury is reestablishment of synaptic connections. We hypothesized that expression of synaptic markers will allow for establishing a timeline of functional recovery of the olfactory system after injury. Our lab has studied three synaptic vesicle associated proteins, vesicular glutamate transporter -1 (VGlut-1), vesicular glutamate transporter-2 (VGlut-2), and synaptophysin, as well as one activity-regulated protein, tyrosine hydroxylase. These studies found specific temporal expression profiles at 2, 7 and 14 days post injury. Our initial data show that VGlut-1 and VGlut-2 are decreased after injury, indicative of a reduction in synaptic connectivity in both olfactory sensory neuron axons and in dendrites of mitral cell neurons. These changes in synaptic connectivity help in understanding functional connectivity after an injury and can further be used to correlate histological axonal tracing with behavioral studies.
3

The Recently University Graduated Employees' Experience with the Starbucks Brand in Thailand

Thanasupanuvech, Jaruwan January 2010 (has links)
<p><strong>Strategic Question:</strong> How Starbucks should improve coffee business in order to reach more the recently university graduated employees in Thailand?</p><p><strong>Research Question:</strong> How the positive and negative experience of the recently university graduated employees with Starbucks brand in term of total perceived quality and sensory system?</p><p><strong>Purpose:</strong> The purpose of this research is to study the recently university graduated employees’ experience in Thailand by using total perceived quality and sensory system as the criteria to measure.</p><p><strong>Method:</strong> This research is mainly based on qualitative approach using interview method as primary data. The interview questions were designed and distributed to people in three channels; Starbucks Facebook, Skype, and Pantip FriendFlock, whereas, secondary data came from company website, literature books, and university database.</p><p><strong>Conclusion:</strong> Most of the recently university graduated employees who are Starbucks consumers are coffee-oriented which means that their experiences based on the physical and emotional elements. Starbucks uses the strong elements to create and improve its products and services, for example; quality of raw materials which its consumers can touch by tasting, healthy products and modern packaging can perceive by using their vision. Luxury atmosphere, good service mind, and aroma therapy in the store can, furthermore, imply to consumers’ emotion.</p>
4

The Recently University Graduated Employees' Experience with the Starbucks Brand in Thailand

Thanasupanuvech, Jaruwan January 2010 (has links)
Strategic Question: How Starbucks should improve coffee business in order to reach more the recently university graduated employees in Thailand? Research Question: How the positive and negative experience of the recently university graduated employees with Starbucks brand in term of total perceived quality and sensory system? Purpose: The purpose of this research is to study the recently university graduated employees’ experience in Thailand by using total perceived quality and sensory system as the criteria to measure. Method: This research is mainly based on qualitative approach using interview method as primary data. The interview questions were designed and distributed to people in three channels; Starbucks Facebook, Skype, and Pantip FriendFlock, whereas, secondary data came from company website, literature books, and university database. Conclusion: Most of the recently university graduated employees who are Starbucks consumers are coffee-oriented which means that their experiences based on the physical and emotional elements. Starbucks uses the strong elements to create and improve its products and services, for example; quality of raw materials which its consumers can touch by tasting, healthy products and modern packaging can perceive by using their vision. Luxury atmosphere, good service mind, and aroma therapy in the store can, furthermore, imply to consumers’ emotion.
5

Evolution of the G protein-coupled receptor signaling system : Genomic and phylogenetic analyses

Krishnan, Arunkumar January 2015 (has links)
Signal transduction pathways mediated by G protein-coupled receptors (GPCRs) and their intracellular coupling partners, the heterotrimeric G proteins, are crucial for several physiological functions in eukaryotes, including humans. This thesis describes a broad genomic survey and extensive comparative phylogenetic analysis of GPCR and G protein families from a wide selection of eukaryotes. A robust mining of GPCR families in fungal genomes (Paper I) provides the first evidence that homologs of the mammalian families of GPCRs, including Rhodopsin, Adhesion, Glutamate and Frizzled are present in Fungi. These findings further support the hypothesis that all main GPCR families share a common origin. Moreover, we clarified the evolutionary hierarchy by showing for the first time that Rhodopsin family members are found outside metazoan lineages. We also characterized the GPCR superfamily in two important model organisms (Amphimedon queenslandica and Saccoglossus kowalevskii) that belong to different metazoan phyla and which differ greatly in morphological characteristics. Curation of the GPCR superfamily (Paper II) in Amphimedon queenslandica (an important model to understand evolution of animal multicellularity) reveals the presence of four of the five GRAFS families and several other GPCR gene families. However, we find that the sponge GPCR subset is divergent from GPCRs in other studied bilaterian and eumetazoan lineages. Mapping of the GPCR superfamily (Paper III) in a hemichordate Saccoglossus kowalevskii (an essential model to understand the evolution of the chordate body plan) revealed the presence of all major GPCR GRAFS families. We find that S. kowalevskii encodes local expansions of peptide and somatostatin- like GPCRs. Furthermore, we delineate the overall evolutionary hierarchy of vertebrate-like G protein families (Paper IV) and provide a comparative perspective with GPCR repertoires. The study also maps the individual gene gain/loss events of G proteins across holozoans with more expanded invertebrate taxon sampling than earlier reports. In addition, Paper V describes a broad survey of nematode chemosensory GPCR families and provides insights into the evolutionary events that shaped the GPCR mediated chemosensory system in protostomes. Overall, our findings further illustrate the evolutionary hierarchy and the diversity of the major components of the G protein-coupled receptor signaling system in eukaryotes.
6

Reajustes posturais em individuos neurologicamente normais e em portadores da Sindrome de Down na gangorra : efeito da manipulação sensorial / Postural adjustaments during balance on seesaw : the effect of sensorial stimulation

Carvalho, Regiane Luz 20 February 2006 (has links)
Orientador: Gil Lucio Almeida / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-08T18:24:05Z (GMT). No. of bitstreams: 1 Carvalho_RegianeLuz_D.pdf: 2608751 bytes, checksum: ce9d54702e5b3dae42169737d4eb3c81 (MD5) Previous issue date: 2006 / Resumo: O objetivo deste estudo foi investigar o papel e a integração das informações sensoriais em indivíduos neurologicamente normais e portadores da síndrome de Down durante a manutenção do equilíbrio em condição de grande instabilidade. Métodos: Participaram deste estudo 8 sujeitos portadores da síndrome de Down (SD) pareados por sexo e idade com o grupo controle que balançaram em uma gangorra de 60cm de raio com combinação de 3 alturas (7,12 e 17cm). As informações sensoriais foram manipuladas pela oclusão da visão, aplicação da estimulação galvânica nos processos mastóideos e vibração no tendão de Aquiles. Os ângulos das articulações do quadril, joelho e tornozelo e a atividade eletromiográfica de alguns músculos da perna e do tronco foram registrados. Resultados: Na ausência de manipulação sensorial os dois grupos analisados mantiveram o equilíbrio na gangorra utilizando principalmente o deslocamento e contração dos músculos do tornozelo. Os indivíduos controle adotaram um padrão alternado de ativação muscular, sendo que a magnitude da resposta postural foi modulada com a altura da gangorra. Em contrapartida os indivíduos portadores da SD apresentaram um padrão generalizado de cocontração e não foram de capazes de modular sua resposta com a demanda mecânica da tarefa. No grupo controle a estimulação galvânica reduziu a magnitude da resposta muscular, mas não alterou o padrão alternado de contração. Já a vibração alterou este padrão de ativação, tornando-o de certa forma semelhante ao observado nos indivíduos portadores da SD. Nos indivíduos portadores da SD a estimulação galvânica reduziu significantemente a habilidade de manutenção do equilíbrio na gangorra, ao passo que a vibração não alterou nem o equilíbrio nem a estratégia postural. Discussão. Os indivíduos controle se adaptaram a redução de uma modalidade sensorial. A perda da modulação do padrão alternado com a vibração indicou a grande importância da propriocepção na elaboração de respostas coordenadas ao nível do tornozelo. Por outro lado, os indivíduos portadores da SD apresentaram déficits na elaboração das respostas posturais. A perda do equilíbrio com a estimulação galvânica e a falta de efeito da vibração nos permite sugerir que, devido a déficits proprioceptivos a importância destas informações é reduzida acarretando em um aumento da importância das informações vestibulares durante o balanço na gangorra / Abstract: Introduction: The main of this study was investigates the sensory integration and function in neurological (CG) and Down syndrome (DS) subjects during balance on unstable seesaw. Methods: Eight individuals with DS and eight CG were studied. Six balancing conditions were collected combining 3 seesaw heights and two manipulations: Galvanic Vestibular Stimulation (GVS) and Achilles tendon vibration. The angles and EMG activities of the some leg and trunk muscles were collected. Results: The CG adopted an alternated pattern of ankle muscle activation during balance and modulated the balance with the seesaw height. The individuals with DS showed the co-contraction muscle pattern during balance and were not able to modulate the muscle answer with the seesaw height. The GVS did not affect CG pattern of muscle contraction although the muscle activation has been partially inhibit. However the detriment of reciprocal pattern was observed due to vibration and under this perceptual condition the control subjects adopted a muscle pattern that remember the ones used by individuals with DS. On the other hand, individuals with DS lack the ability to keep balance during the vestibular manipulation and were no affected by vibration. Discussion: The CNS of CG rapidly assess and re-weigh available sensory inputs, assuring the balance success. On the other hand, individuals with DS showed a deficit in the mechanism responsible to elicit an appropriate postural response. They increased the postural response with GVS and decreased with vibration. This fact may indicate that because of proprioceptive dysfunctions the individuals with DS re-weigh the organization of sensory systems increasing the importance of vestibular system and decreasing the proprioceptive importance / Doutorado / Fisiologia / Mestre em Biologia Funcional e Molecular
7

Se trouver, se perdre, se retrouver : innervation des organes sensoriels de la ligne latérale / About finding and loosing : establishment of connectivity in the lateral line system

Schuster, Kevin 25 March 2011 (has links)
Dans cette thèse, je me suis intéressé aux mécanismes qui permettent aux axones des neurones sensoriels de trouver leurs organes cibles à une grande distance. Dans le cas du système de la ligne latérale postérieure (LLP) du poisson-zèbre, des organes sensoriels sont déposés au cours de la migration d'un primordium. Des neurites sensoriels accompagnent le primordium au cours de cette migration et sont ainsi guidés vers leurs organes cibles. J'ai démontré que l'inactivation du signal «Glial cell line-Derived Neurotrophic Factor » (GDNF) rend les axones sensoriels incapables de suivre le primordium. GDNF est également utilisé comme signal de guidage lors de la régénération axonale après section du nerf et donc permet aux axones de retrouver leur cible. Ensuite j'ai démontré que le signal « Brain Derived Neurotrophic Factor » (BDNF) exerce un autre rôle dans le développement de la LLP puisqu'il est essentiel pour l'ancrage et la connexion des axones à leurs organes cibles. Dans une deuxième partie, nous avons montré que le développement de la LLP embryonnaire du Thon Rouge est fortement similaire à celui du Poisson-Zèbre, pourtant relativement basal. Cette similitude comprend le fait que les axones de la LLP suivent le primordium. / In this thesis, I address the question of how peripheral axons of sensory neurons find their distant target organs. In the case of the posterior lateral line (PLL) system of zebrafish, sensory organs are deposited by a migrating primordium and sensory neurites accompany this primordium during its migration. In this way, the neurites are guided to their prospective target organs. I show that the inactivation of «Glial cell line Derived Neurotrophic Factor » (GDNF) signaling leads to the inability of sensory axons to track the migrating primordium. GDNF signaling is also used as a guidance cue during axonal regeneration following nerve cut. I conclude that GDNF is a major determinant of directed neuritic growth and of target finding in this system, and propose that GDNF acts by promoting local neurite outgrowth. Further, I demonstrate that «Brain Derived Neurotrophic Factor » (BDNF) signaling exerts another role in PLL development as it is essent ial to anchor and properly connect axons to their targets organs.In another project, we could demonstrate that the development of the embryonic PLL of the atlantic blue-fin tuna shows striking similarities to that of the relatively basal zebrafish, including that PLL axons follow the migrating primordium.
8

Thalamic Afferents to Reorganized Auditory Cortices in Postnatally Deafened Cats

Corley, Sarah Beth 01 January 2007 (has links)
Deafness affects approximately 40 million people in the United States. However, little is known about how the brain reorganizes itself in response to this major loss of inputs. Preliminary studies of neonatally deafened cats reveals that the auditory cortical area, the auditory field of the anterior ectosylvian sulcus (FAES), is reorganized as a visual area and is involved in the control of visual orientation behaviors. The plastic changes in neuronal connectivity that underlie this cortical reorganization are not known, but it is our hypothesis that sensory driving via thalamocortical inputs must change from auditory to visual thalamic origins. The present study used neuroanatomical tracing techniques in two hearing adult cats and two adult cats deafened at birth to determine the thalamic origin of projections to the FAES. When tracer was injected into the FAES of hearing animals, MGm, MGv, Pom, and dorsal thalamic nuclei showed retrogradely labeled cell bodies indicative of their projection to the FAES. When tracer was injected into the FAES of the neonatally deafened animals, MGm, MGv, Sgl, Pom, and dorsal thalamic nuclei also showed retrogradely labeled cells. In the deafened animals, no retrogradely labeled neurons were identified in the primary visual thalamic areas. Because essentially the same thalamic regions project to the FAES but relay different sensory messages in hearing and deafened animals, it must be concluded that neuronal plasticity occurred prior to the thalamocorticals projection. Therefore, therapeutic efforts to ameliorate the effects of deafness might best address thalamic rather than cortical mechanisms of plasticity and neuronal reorganization.
9

Asymptomatic Free Air: An Abnormal Presentation of Pneumatosis

Carey, Andrew J, Garner, Joseph, Guarderas, Mateo, MD, Vance, John, DO, Floresguerra, Carlos, MD 12 April 2019 (has links)
Pneumatosis intestinalis, air within the bowel wall, continues to have an elusive etiology due to its varied clinical presentation and associated disease processes. Pneumatosis may be an incidental finding on a routine CT Scan or it could present as peritonitis with intra-abdominal free air. The pathogenesis, therefore, is likely to be multifactorial rather than directly related to one particular, inciting pathology. Here we present a case of a 73-year-old male scheduled for a non-emergent incisional hernia repair who was found to have peritoneal free air without physical exam findings of peritonitis. This unusual case illustrates a rare presentation of small bowel, omental, and abdominal wall pneumatosis. The objective of this presentation is to broaden the clinician’s understanding of pneumatosis intestinalis, including a recommendation to discern the underlying illness as emergent or benign. Finally, we make the case for clinical intuition and the physical exam.
10

Molecular determinants of morphology and function of microvilliated sensory cells in zebrafish / Déterminants moléculaires de la morphologie et des fonctions des cellules sensorielles microvilliées chez le poisson zèbre

Desban, Laura 06 September 2018 (has links)
La détection des stimuli sensoriels est assurée par des cellules réceptrices spécialisées souvent grâce à des protrusions membranaires apicales telles que les microvillosités. La forme finale des extensions apicales microvilliées conditionne de nombreuses propriétés de la transduction sensorielle mais leur formation reste méconnue. Quels sont les facteurs moléculaires responsables de l’initiation et de l’élongation des filaments d’actine chez les cellules sensorielles microvilliées (CSMs) ? Peut-on décrire des éléments clés de la morphogenèse en commun ? Quel est le rôle structurel des microvillosités dans la fonction sensorielle ?J’ai étudié deux types sensoriels microvilliés : les neurones contactant le liquide cérébrospinal (NcLCS) et les cellules sensorielles des neuromastes (CSn). Mon projet visait à investiguer les mécanismes moléculaires sous-jacents à la morphogenèse des CSMs par l’étude des NcLCS. J’ai décrit les étapes critiques menant à la formation de l’extension apicale des NcLCS auxquelles j’ai pu associer des candidats potentiels grâce l’analyse transcriptomique des NcLCS. J’ai démontré le rôle critique de l’interaction entre Espin et Myo3b dans l’élongation de l’extension apicale des NcLCS et j’ai établi un lien direct entre structure et fonction en montrant que le raccourcissement de l’extension apicale aboutissait à la réduction de la réponse sensorielle.Mon travail a permis d’apporter des éléments de réponse quant à la formation de l’organe sensoriel des NcLCS. L’analyse transcriptomique des CSn a par ailleurs révélé des facteurs de morphogenèse communs avec les NcLCS, suggérant que toutes les CSMs partagent des propriétés de différenciation conservées. / Sensory systems use specialized receptor cells, many of which detect sensory cues through specialized apical membrane protrusions, such as microvilli. The final shape of the microvilliated apical extension requires specific molecular machinery and determines many of the properties of sensory transduction. The establishment of this structure remains however elusive. What molecular factors orchestrate the initiation and elongation of actin filaments in microvilliated sensory cells (MSCs)? Can we find key elements of morphogenesis common to MSCs? What is the precise role of microvilli structure in sensory function? I investigated two sensory cell types harboring microvilli: spinal cerebrospinal fluid-contacting neurons (CSF-cNs) and neuromast hair cells (nHCs). The primary goal was to unravel the molecular mechanisms underlying morphogenesis of MSCs by focusing on CSF-cNs. I was able to describe critical steps leading to the development of CSF-cN apical extension. My participation to the transcriptome analysis of CSF-cNs revealed candidate molecular factors associated with each of these steps. I demonstrated the importance of the interaction between Espin and Myo3b to ensure the proper lengthening of CSF-cN apical extension. In this system, I established a direct link between morphology and function by showing that shorter apical extensions lead to reduced sensory response. Altogether, my work shed light on the formation of CSF-cN sensory organelle and its functional role. In parallel, the establishment of the nHC transcriptome dataset revealed similar morphogenetic factors with CSF-cNs, supporting the idea that all MSCs share conserved features for their differentiation.

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