La communication entre les neurones est fondée sur leur capacité à changer leur patron de décharge pour l’encodage de différents messages. Pour plusieurs fonctions vitales, comme la respiration et la mastication, les neurones doivent pouvoir générer des patrons d’activité répétitifs, et les groupes de neurones responsables de ces décharges rythmiques sont des générateurs de patron central (GPC). En dépit de recherches soutenues, les mécanismes précis qui sous-tendent la rythmogénèse dans les GPCs ne sont pas bien définis. Le plus souvent, la potentielle contribution des astrocytes demeure grandement inexplorée, même si ces cellules sont aujourd’hui connues pour leur implication dans la modulation synaptique neuronale. Pour nos travaux, le noyau sensoriel principal du trijumeau (NVsnpr) a été pris comme modèle à cause de son rôle central dans les mouvements rythmiques de la mastication. Dans ce noyau, des travaux antérieurs ont montré que la décharge en bouffées rythmiques est déclenchée dans les neurones lorsque la concentration de calcium extracellulaire ([Ca2+]e) est artificiellement baissée. Nous fondant sur cette observation, notre première hypothèse a postulé que la baisse de la [Ca2+]e pouvait survenir de façon physiologique en lien avec des stimulations sensorielles pertinentes. Deuxièmement, parce que les astrocytes ont été impliqués dans le tamponnage et l’homéostasie d’ions extracellulaires comme le K+, nous avons postulé que ces cellules pouvaient jouer un rôle équivalent dans le contrôle de la [Ca2+]e. Nos résultats montrent que les astrocytes peuvent réguler la [Ca2+]e et ainsi contrôler la capacité des neurones à changer leur patron de décharge. Premièrement, en stimulant les afférences sensorielles au NVsnpr, nous avons montré que des baisses physiologiques de la [Ca2+]e sont observées en parallèle à l’apparition de bouffées rythmiques neuronales. Deuxièmement, nous avons démontré que les astrocytes répondent aux mêmes stimuli qui induisent l’activité rythmique neuronale, et que leur blocage avec un chélateur de Ca2+ empêche les neurones de générer un patron de décharge en bouffées rythmiques. Cette habilité est rétablie en rajoutant la S100β, une protéine astrocytaire liant le Ca2+, dans le milieu extracellulaire, alors que l’anticorps anti-S100β empêche l’activité rythmique. Ces résultats indiquent que les astrocytes régulent une propriété neuronale fondamentale : la capacité à changer de patron de décharge. Ainsi, les GPCs dépendraient des fonctions intégrées des astrocytes et des neurones. Ces découvertes pourraient avoir des implications transposables à plusieurs autres circuits neuronaux dont la fonction dépend de l’induction d’activité rythmique. / Communication between neurons rests on their capacity to change their firing pattern to encode different messages. For several vital functions, such as respiration and mastication, neurons need to generate a repetitive firing pattern, and the groups of neurons responsible for these rhythmic discharges are called central pattern generator (CPG). Despite intense research in this field, the exact mechanisms underlying rhythmogenesis in CPGs are not completely defined. In most instances, the potential contribution of astrocytes is largely unexplored, even though these cells are now well known to be involved in neuronal synaptic modulation. In our work, the trigeminal main sensory nucleus (NVsnpr) was used as a model owing to its central role in the rhythmic movement of mastication. Previous work have shown that rhythmic bursting discharge is triggered in NVsnpr neurons when extracellular calcium concentration ([Ca2+]e) is artificially decreased. Based on this observation, our first hypothesis postulated that the reduction of [Ca2+]e could also happen physiologically in relation to relevant sensory stimulation. Secondly, because astrocytes have been involved in the buffering and the homeostasis of extracellular ions like potassium, we have postulated that these cells could also play a role in the control of [Ca2+]e. The results presented in this thesis show that astrocytes can regulate [Ca2+]e and thus control the ability of neurons to change their firing pattern. First, we showed that stimulation of sensory afferent fibers to the NVsnpr induced neuronal rhythmic bursting and in parallel reduction of [Ca2+]e . Secondly, we have demonstrated that astrocytes respond to the same sensory stimuli that induce neuronal rhythmic activity, and their blockade with a Ca2+ chelator prevents generation of neuronal rhythmic bursting. This ability is restored by adding S100β, an astrocytic Ca2+-binding protein, to the extracellular space, while the application of an anti- S100β antibody prevents generation of rhythmic activity. These results indicate that astrocytes regulate a fundamental neuronal property: that is the capacity to change their firing pattern. Thus, CPG functions result from integrated neuronal and glial activities. These findings may have broad implications for many other neural networks whose functions depend on the generation of rhythmic activity.

La libération des composés d'arôme détermine la qualité aromatique des produits alimentaires, et contribue ainsi aux choix et préférences des consommateurs. Dans ce contexte, la compréhension et la modélisation de la cinétique de libération est un défi scientifique et un enjeu de santé afin de pouvoir formuler des produits en intégrant des critères nutritionnels et sensoriels. Ce travail de thèse a permis d'étudier et de modéliser les mécanismes en bouche responsables de la dynamique de libération des stimuli olfactifs lors de consommation d'un aliment liquide ou solide chez l'homme.<br />• Dans un premier temps, un modèle mécanistique décrivant la libération des composés d'arôme au cours de la consommation d'un aliment liquide ou semi-liquide a été développé. Ces produits ont un temps de résidence en bouche très court et ne nécessitent pas de manipulation intra-orale complexe. Le modèle a été construit sur la base de bilans de matière prenant en compte des mécanismes de transfert entre certains sous-compartiments du système, ainsi que les conditions spécifiques aux différentes étapes de la consommation. Une comparaison du modèle avec des données de libération in vivo lors de la consommation de fluides newtnoniens aromatisés avec du diacétyle et de l'hexanoate d'éthyle a été effectuée. Cette étude nous a permis de comprendre le rôle du résidu post-pharyngé et de la viscosité sur la libération des composés d'arôme : • l'épaisseur du bol tapissant les muqueuses a pu être estimée à environ 15µm; • contrairement à l'hypothèse initiale, il a été mis en évidence que les propriétés pertinentes à prendre en considération pour la libération des composés d'arôme à partir d'un fluide newtonien sont celles d'un mélange de produit hautement dilué par la salive. • Dans un second temps, le modèle a été adapté à des produits nécessitant une mastication. Pour en rendre compte, de nouveaux mécanismes ont été intégrés: phénomènes de transfert de matière et de dissolution du produit dans la salive, génération d'une surface d'échange produit/fraction liquide du bol et l'ouverture vélopharyngienne lors de la mastication du produit. Le modèle a ensuite été confronté avec les données de libération du propanoate d'éthyle in vivo lors de la consommation de matrices fromagères modèles. Le modèle a pu être ajusté de façon satisfaisante à l'ensemble des données expérimentales et les deux paramètres inconnus de notre modèle (la vitesse d'incorporation moyenne de salive dans le bol au cours de la consommation et la fréquence d'ouverture du vélopharynx) ont pu être estimés. Cette étude nous a permis de comprendre le rôle de la mastication sur la libération des composés d'arôme lors de la consommation d'aliments solides. De plus, l'étude de la libération de la 2-nonanone a permis de mettre en évidence un phénomène d'adsorption sur les muqueuses pour cette molécule. • Enfin, il ressort de la comparaison des deux modèles que les paramèters clés gouvernant la libération des composés d'arôme ne sont pas les mêmes selon la catégorie de produit (liquide ou solide) considérée: • lors de la consommation d'aliments liquides ou semi-liquides, le coefficient de transfert de matière dans le bol, la fréquence respiratoire de l'individu et l'épaisseur du résidu post-pharyngé sont les trois facteurs clés gouvernant la libération des composés d'arôme; • en revanche, lors de la consommation de produits solides mastiqués, ce sont la vitesse d'incorporation moyenne de salive dans le bol, la fréquence d'ouverture du vélopharynx et la durée de mastication qui sont les trois paramètres ayant un effet majeur sur les cinétiques de libération. La démarche de modélisation nous a permis de mieux comprendre les parts relatives du produit, de l'individu, et de l'interaction produit-individu sur la libération des composés d'arôme au cours de la consommation d'un aliment. / Delivery of aroma compounds to olfactory receptors determines the aromatic quality of food products and contributes to consumer choices and preferences. Therefore, understanding and modelling the release kinetic is a scientific challenge and a health issue in order to formulate products of both high nutritional and sensory quality. This thesis studied in-mouth mechanisms responsible of the dynamics of olfactory stimuli release during food consumption. • First, a mechanistic model describing the aroma compounds release during consumption of a liquid or semi-liquid food has been developed. These products have a very short in-mouth residence time and do not require complex intra-oral manipulation. The model takes into account mass balances, transfer mechanisms occurring between some sub-compartments of the system, and the specific conditions at the different stages of consumption. A comparison of the model predictions with in vivo release data during the consumption of Newtnonien fluids flavored with diacetyl and ethyl hexanoate was performed. This study highlighted the role of post-pharyngeal residue and viscosity on the aroma compounds release: • the thickness of bolus covering the mucous membranes has been estimated at about 15μm; • it was found that the relevant properties to be considered for the release of aroma compounds from a Newtonian fluid are those of a mixture highly diluted by saliva. • Second, the model previously developed was adapted for products requiring chewing. It takes into account the phenomena of mass transfer and dissolution of the product in the saliva during chewing. The generation of a product/liquid contact surface as well as the velopharyngial opening that occurs during the mastication of the product were also integrated into the model. The model was then confronted with in vivo release data for ethyl propanoate during consumption of four cheese matrices. All simulations have been satisfactorily fitted to experimental data and the two unknown parameters of our model (the average rate of saliva incorporation into the bolus and the frequency of velopharyngial opening) could be estimated. This study has enabled us to understand the role of mastication on the release of aroma compounds during consumption of solid food: • the opening of velopharynx during intra-oral manipulation of the product produces a continuous supply of aroma compounds in the nose; • the residence time of solid product in the mouth are much longer than for the consumption of liquid and semi-liquid foods, allowing the secretion of significant volumes of saliva. In addition, the study of the release of 2-nonanone highlighted an adsorption phenomenon on the mucous membranes for this molecule. • Finally, sensitivity analysis of the two release models indicates that: • when eating a liquid or semi-liquid food, the mass transfer coefficient in the bolus, the breath rate and the thickness of post-pharyngeal residue are the three key factors governing the release of aroma compounds; • however, when eating a solid food product, it is the average rate of saliva incorporation into the bolus during consumption, the frequency and duration of velopharyngeal opening, and the mastication time which are the three parameters that have major effects on the kinetics of release. The modeling approach allowed us to better understand the relative effects of the product, the individual, and individual-product interaction on the release of aroma compounds during food consumption. The results of this work indicated that the most important parameters depend on the category of product (liquid or solid) under consideration.

Considerando-se a relevância da influência da musculatura na funcionalidade do sistema estomatognático, buscou-se com este trabalho realizar avaliação do comportamento e atuação da musculatura mastigatória em indivíduo diabético, tipo 2. Este estudo teve como objetivo comparar a atividade eletromiográfica, a espessura dos músculos masseter e temporal e a força de mordida entre indivíduos portadores de diabetes (GD) e um grupo controle (GC), saudáveis. A atividade eletromiográfica foi avaliada utilizando o eletromiógrafo Myosystem BR-1 nas condições posturais da mandíbula e na mastigação não-habitual de Parafilme M&reg; e habitual de uvas passas e amendoins. Para a análise da espessura muscular foram adquiridas imagens dos músculos masseter e temporal no repouso e na contração voluntária máxima utilizando o aparelho de ultrassom SonoSite Titan. A força de mordida molar máxima direita e esquerda foi obtida por meio do dinamômetro digital Kratos. Os dados coletados foram submetidos ao tratamento estatístico utilizando testes de comparação (teste t de Student), considerando o intervalo de confiança de 95% (SPSS 20.0). Os resultados obtidos nesta pesquisa revelaram que os indivíduos com diabetes apresentaram na atividade eletromiográfica diferença estatisticamente significante apenas na condição de mastigação de Parafilme M&reg;para os músculos temporais esquerdo e direito (p<0,05). Na análise ultrassonográfica verificou-se maior espessura muscular para os masseteres e menor espessura para os temporais no grupo diabético quando comparado ao grupo controle, estatísticamente significante. Com relação à força de mordida, observou-se que nos indivíduos diabéticos, a força de mordida foi menor, sem significância estatística. Concluiu-se que, os músculos masseteres e temporais dos diabéticos, tipo 2, sofreram alterações eletromiográficas e em suas espessuras, o que requer do cirurgião-dentista oferecer tratamentos odontológicos que reabilitem com maior eficiência seus pacientes diabéticos. / Considering the importance of the influence of the muscles in the functionality of the stomatognathic system, we sought to carry out this work evaluation of the behavior and performance of the masticatory muscles in diabetic subjects, type 2. This study aimed to compare the electromyographic activity, the thickness of masseter and temporalis muscles and bite force among individuals with diabetes (GD) and healthy control group (GC). The electromyographic activity was assessed using electromyography Myosystem BR-1 in postural conditions of the jaw and non-habitual chewing Parafilm M&reg;and habitual chewing of raisins and peanuts. For the analysis of muscle thickness were acquired images of the masseter and temporal muscles at rest and at maximum voluntary contraction using the SonoSite Titan ultrasound machine. The maximum bite force, right and left molar, was obtained through digital dynamometer Kratos. The data collected were subjected to statistical analysis using comparison tests (Student\'s t test) , considering a confidence interval of 95 % (SPSS 20.0). The results obtained in this study revealed that individuals with diabetes showed the statistically significant difference electromyographic activity only on condition chewing Parafilm M&reg; for left and right in temporal muscles (p< 0.05). On ultrasound examination, there was greater muscle thickness for the masseter and temporal thickness less for the diabetic group compared to controls, statistically significant difference. With respect to bite force, it was observed that in diabetic patients, the bite force was lower without statistical significance. It was concluded that the masseter and temporal muscles of diabetics, type 2, suffered electromyographic changes and their thicknesses, which requires the dentist to provide dental treatments that more effectively rehabilitate their diabetic patients.

Made available in DSpace on 2016-08-10T10:38:42Z (GMT). No. of bitstreams: 1 CELINA KASSUMI KUNIEDA SUZUKI.pdf: 2013145 bytes, checksum: c807ebe49c872194bb7af7cd6bb5d17f (MD5) Previous issue date: 2012-06-29 / The increased prevalence of childhood obesity in recent years suggests the existence of a genetic predisposition or susceptibility to conditioning factors for obesity which act on the environmental factors related to lifestyle involving diet and physical activity. Food education programs and physical activities have been developed in order to reverse this situation. The chewing is considered one of the early stages of the digestive process and therefore primordial important because performing correctly promotes natural hunger satiety as well as a healthy digestion. The aim of this study is to investigate the polymorphism of the TNF-&#945; and DRD2 genes and the influence of masticatory profile in childhood obesity to enable the preparation of proposals for more effective interventions to control weight gain. For this purpose the study has been divided into two articles. ARTICLE 1: This study evaluated the profile of the obese child chewing through survey and evaluation of clinical history miofunctional from the protocols of MgBr and AMIOFE-A (attached) in 11 normal children representing the control population (Group I) and 16 obese children (Group B) participating in the CAIS Group of Obesity in Goiânia Municipal and School of Clinical Speech Therapy PUC Goiás aged between 6 and 13 years for both sexes. According to the findings obtained in the research, it is concluded that obese group (OB) presents an incision chewing food made with the central and lateral incisors with the majority labial sealing with or without excessive movement, unilateral pattern, with higher presence of altered behaviors in chewing and shorter chewing time. ARTICLE 2: This study evaluated the genetic polymorphism of TNF-&#945; gene (G308A) and DRD2 (Taq1&#945; - C32806T) in 27 patients with childhood obesity (16) and controls (11) using the method ARMS-PCR and PCR-RFLP, respectively, in peripheral blood samples. The results suggest that the genetic polymorphism of Taq1&#945; (C32806T) in the DRD2 gene was associated with the increase of obesity in the childhood. Still genetic variants of the SNP G308A TNF-&#945; gene is not possible to confirm it s influence on children s weight gain. Understanding how genetic variations affect the tendency to become or remain obese is an important step to comprehend the mechanisms that lead to obesity. / O aumento da prevalência da obesidade infantil nestes últimos anos sugere a existência de predisposição ou suscetibilidade genética como fatores condicionantes para a obesidade, sobre a qual atuam fatores ambientais relacionados ao estilo de vida, que envolvem hábitos alimentares e atividade física. Programas de educação alimentar e de atividades físicas foram desenvolvidos visando reverter este quadro. A mastigação é considerada uma das fases iniciais do processo digestório e de primordial importância, pois quando realizada de forma correta, promove a saciedade natural da fome, bem como uma digestão saudável. O objetivo deste estudo foi investigar o polimorfismo dos genes TNF-&#945; e DRD2 e a influência da mastigação na obesidade infantil para possibilitar a elaboração de propostas de intervenções mais eficazes para o controle do ganho de peso Para esta finalidade, o estudo foi dividido em dois artigos. ARTIGO 1: Este estudo avaliou o perfil mastigatório da criança obesa, por meio de levantamento de histórico clínico e avaliação miofuncional orofacial a partir dos protocolos do MGBR e AMIOFE-A (anexos), em 11 crianças eutróficas representando a população controle (Grupo EU) e 16 crianças obesas (Grupo OB) participantes de Grupo de Obesidade dos CAIS Municipais da cidade de Goiânia e da Clínica- Escola de Fonoaudiologia da PUC Goiás, com idade entre 6 e 13 anos de ambos os sexos. Conforme os achados obtidos na pesquisa, conclui-se que o grupo obeso (OB) apresenta uma mastigação com incisão do alimento feito com os incisivos centrais e laterais, sendo a maioria com vedamento labial sem ou com movimentação excessiva, padrão unilateral, com maior presença de comportamentos alterados na mastigação e tempo de mastigação reduzido. ARTIGO 2: Este estudo avaliou o polimorfismo genético dos genes TNF-&#945; (G308A) e DRD2 (Taq1&#945; - C32806T) em 27 pacientes com obesidade infantil (16) e de controle (11), utilizando o método de ARMS-PCR e PCR-RFLP, respectivamente, em amostras do sangue periférico. Os resultados sugerem que o polimorfismo genético em Taq1&#945; (C32806T) no gene DRD2 apresentou associação com o incremento na obesidade infantil. Por outro lado, as variantes genéticas do SNP G308A do gene TNF-&#945; não permitiram confirmar sua participação no ganho de peso em crianças. Entender como variações genéticas afetam a obesidade consiste em um passo importante na compreensão dos mecanismos desencadeadores da obesidade.

Made available in DSpace on 2016-04-27T18:12:24Z (GMT). No. of bitstreams: 1 Carmen das Gracas Fernandes.pdf: 490932 bytes, checksum: aa212bdbaeabb7a658b87ee477190f47 (MD5) Previous issue date: 2007-10-10 / Clinical experience with patients which present chronic orofacial pain associated to muscular disturbances delimited the problem of this research once it provokes uncertainties generated by limitations that phenomenon of pain promotes in the evolution of the therapeutic phonoaudiologic processes. The objective of this study is to analyze the effects of the phonoaudiologic therapeutic listening of the psychic contents associated to chronic orofacial pain, presupposing the indissociability among body, language and psychism. This research has a clinical-qualitative and exploratory nature. It was developed by study of clinical cases of two female patients, being one 23 years old and other 32 years old; both refering to the beginning of the pain around the age 7. Clinical material was analysed based on phonoaudiologic and psychoanalytical theoretical references on the perspective of the articulation among body, psychism and language in order to understand the existing correlation between corporal structure and its vulnerabilities face to psychic factors. Concepts of pain, suffering, latent and manifest contents, clinical listening and transference have been considered. Clinical experience with these two patients revealed that pain affects the functions of stomatognathic system, especially mastication, and mobilizes conscious and unconscious psychic contents. The therapeutic phonoaudiologic process was favoured by simultaneous intervention as to both aspects, reducing the pain in both cases. Due to the complexity of symptoms associated to the chronic pain, it is necessary phonoaudiologic assistance, including in an interdisciplinary team work. The phonoaudiologic therapeutic listening, supported by Psychoanalysis theoretical references, contributes to effectiveness of phonoaudiologic treatment in both cases / A experiência clínica com pacientes que apresentam dor orofacial crônica associada a distúrbios musculares delimitou o problema dessa pesquisa ao provocar inquietações geradas pelas limitações que o fenômeno da dor promovem na evolução dos processos terapêuticos fonoaudiológicos. De acordo com o relato dos pacientes, há o envolvimento de conteúdos subjetivos, particularmente os psíquicos, provocando ansiedade e depressão. O objetivo desse estudo é analisar os efeitos da escuta terapêutica fonoaudiológica dos conteúdos psíquicos associados à dor orofacial crônica, pressupondo-se a indissociabilidade entre corpo, linguagem e psiquismo. Esta pesquisa é de natureza clínico-qualitativa, exploratória, desenvolvida por meio de estudo de caso clínico de duas pacientes do sexo feminino, uma com 23 anos e a outra com 32 anos de idade. Ambas referem o início da dor aos sete anos. O material clínico foi analisado a partir dos referenciais teóricos psicanalítico e fonoaudiológico na perspectiva da articulação entre corpo, psiquismo e linguagem para tentar compreender a correlação existente entre a estrutura corporal e suas vulnerabilidades aos fatores psíquicos. Foram considerados os conceitos sobre dor, sofrimento, conteúdo manifesto e latente, escuta e transferência. O resultado da análise dos casos revela que o processo terapêutico fonoaudiológico foi favorecido pela intervenção simultânea quanto a ambos os aspectos, resultando na redução da dor em ambos os casos. Considera-se que devido à complexidade de sintomas associados à dor crônica, é necessário o trabalho fonoaudiológico em equipe interdisciplinar. Observa-se que a escuta terapêutica fonoaudiológica, sustentada pelo referencial teórico da psicanálise, contribuiu para a efetividade do tratamento fonoaudiológico nos dois casos clínicos estudados

Métodos convencionais para a confecção de próteses totais envolvem uma série de procedimentos técnicos complexos. No entanto, métodos simplificados podem ser tão efetivos quanto os convencionais, porém é importante que a mastigação não sofra influências deletérias. Assim, o objetivo deste estudo foi comparar um método simplificado de confecção de próteses totais a outro convencional, tendo como variáveis a performance e a habilidade mastigatórias. A amostra foi formada por pacientes desdentados solicitando tratamento com próteses totais duplas. Os participantes foram divididos aleatoriamente em dois grupos: Grupo S (n=17), que recebeu próteses confeccionadas por um método simplificado, e Grupo C (n=18), que recebeu próteses confeccionadas de forma convencional. Após 3 meses da instalação das próteses, a performance mastigatória foi avaliada por um método colorimétrico, utilizando duas biocápsulas como alimento teste, após 20 e 40 ciclos mastigatórios, e a habilidade mastigatória dos participantes foi avaliada por meio de questionário (Questionário HM) e escala visual analógica (EVA). Foi feita referência dos resultados a um grupo de participantes dentados, Grupo DN (n=17). Os três grupos foram comparados por meio de testes adequados à distribuição dos dados (&alpha;=5%). A performance mastigatória foi similar nos grupos C e S e representou 31% daquela encontrada no grupo DN. A habilidade mastigatória foi semelhante para S e C independente do método de análise, sendo que algumas questões do questionário HM, analisadas isoladamente, tiveram maior ocorrência de respostas favoráveis para o primeiro. Conclui-se que métodos simplificados de confecção de próteses totais são capazes de reabilitar a mastigação de maneira comparável ao método convencional, tanto fisiologicamente como segundo as percepções do paciente. / Complete denture fabrication involves a series of complex technical procedures. Nevertheless, simplified methods may be as effective as conventional ones and mastication should not be further impaired. Therefore, this study aimed to compare a simplified method and a conventional protocol for complete denture fabrication, in terms of masticatory performance and ability. A sample was formed by edentulous patients requesting treatment with maxillary and mandibular complete dentures. Participants were randomly allocated into two groups: Group S (n=17), which received dentures fabricated by a simplified method, and Group C (n=18), which received conventionally fabricated dentures. After 3 months following insertion, masticatory performance was evaluated by means of a colorimetric assay based on chewing two capsules as test food during 20 and 40 cycles. Masticatory ability was assessed by means of a questionnaire (HM) with dichotomous answers and a single question answered by means of a visual analogue scale (VAS). A third group (DN, n=17) formed by dentate volunteers served as an external comparator. Results for the three groups were compared by means of statistical tests suitable for the distribution of data (&alpha;=5%). Groups C and S presented similar masticatory performance which corresponded to 31% of group DN. Results for masticatory ability showed similarity between S and C, regardless of the assessment method, though some isolate items of the HM questionnaire showed more favorable results for the first group. It can be concluded that simplified methods for complete denture fabrication are able to restore masticatory function to a level comparable to the conventional protocol, physiologically and according to patient perceptions.

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The human jaw, like all other articulated body parts, exhibits small oscillatory movements during isometric holding tasks. These movements, known as physiological tremor, arise as a consequence of the interaction of various factors. One of these factors is reflex feedback from peripheral receptors. In the human jaw, receptors that innervate the periodontium are able to transduce minute changes in force. This thesis examines the contribution of these periodontal mechanoreceptors (PMRs) to the genesis of physiological tremor of the human jaw. By using frequency domain analysis of time series recorded during isometric biting tasks, the character of physiological jaw tremor can be revealed. Physiological jaw tremor was observed in force recorded from between the teeth as well as from electromyograms recorded from the principal muscles of mastication. These recordings have shown us that jaw physiological tremor consists of a frequency invariant component between 6 and 10Hz. This frequency remains unaltered under various load conditions where the mechanical resonance of the jaw would be expected to vary greatly (Chapter 2). Such findings indicate a ‘neurogenic’ origin for this tremor. A possible candidate for this neurogenic component of physiological tremor in the jaw is the reflex feedback arising from the PMRs. Using local anaesthetisation, it has been shown in this thesis, that by blocking outflow from the PMRs, the amplitude of neurogenic physiological jaw tremor can be reduced dramatically. This procedure caused a dramatic reduction in not only the mechanical recordings of tremor but also in the coupling between masseteric muscles bilaterally (Chapter 3) and between single motor units recorded from within a homonymous muscle (Chapter 4). The obvious mechanism by which periodontal mechanoreceptor anaesthetisation could reduce the amplitude of physiological tremor in the jaw would be by reducing the amplitude of the oscillatory input to the motoneurones driving the tremor. This interpretation remains controversial however as physiological tremor in the jaw can be observed at force levels above which the PMRs are supposedly saturated in their response. In light of this knowledge, the saturating characteristics of these receptors in terms of reflex output were examined. To do this, a novel stimulation paradigm was devised whereby the incisal teeth were mechanically stimulated with identical stimulus waveforms superimposed upon increasing tooth preloads. This necessitated the use of a frequency response method to quantify the reflexes. An optimal frequency for stimulation was identified and used to confirm that the hyperbolic saturating response of PMRs observed previously, translated to a similar phenomenon in masticatory reflexes (Chapter 5). These data reinforced the idea that physiological tremor in the jaw was not just a consequence of rhythmic reflex input from PMRs, as the dynamic reflex response uncoupled from the input as the receptor-mediated reflex response saturated. An alternative hypothesis was then developed that suggested the effect of PMR suppression in physiological tremor was via tonic rather than rhythmic effects on the masseteric motoneurone pool. By utilising a novel contraction strategy to manipulate the mean firing rate of the motor neuron pool at a given level of force production, data contained in Chapter 6 shows that population motor unit firing statistics influence the expression of physiological tremor, and such manipulations mimic, to an extent, the changes in firing statistics and tremor amplitude seen during anaesthetisation of the PMRs. This thesis therefore posits a mechanism whereby periodontal input influences the firing rate of motoneurones in such a way as to promote tremulous activity (Chapter 5). However, as this proposed mechanism did not explain the full extent of tremor suppression seen during PMR anaesthetisation it can therefore only be considered a contributing factor in a multifactor process. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1297555 / Thesis (Ph.D.) -- University of Adelaide, School of Molecular and Biomedical Science, 2007

Le mouvement masticatoire est généré et coordonné par un générateur de patron central (GPC) situé au niveau du pont. Plusieurs résultats antérieurs de notre laboratoire soutiennent que le réseau de neurones à l’origine de la rythmogénèse est situé dans le noyau sensoriel principal du nerf trijumeau (NVsnpr). Ces mêmes expériences révèlent que des diminutions de la concentration calcique extracellulaire ([Ca2+]e) tiennent une place importante dans la génération des bouffées de décharges des neurones de cette région. Notre laboratoire tente de vérifier si la contribution des astrocytes à l’homéostasie de la concentration calcique extracellulaire est impliquée dans la genèse du rythme. Cette étude a pour but la caractérisation spatiale du syncytium astrocytaire au sein du NVsnpr dorsal et l’étude de l’effet de la [Ca2+]e sur les propriétés astrocytaires électrophysiologiques et de connectivité. Nous avons utilisés pour ce faire la technique d’enregistrement par patch-clamp sur une préparation en tranche de tronc cérébral de rat. Nous démontrons ici que la diminution de la [Ca2+]e n’affecte pas les propriétés électrophysiologiques astrocytaires, mais induit une augmentation de la taille du syncytium. De plus, nous établissons l’existence au sein du NVsnpr dorsal d’une organisation anatomofonctionnelle du réseau astrocytaire calquée sur l’organisation neuronale. / The masticatory movement is generated and coordinated by a central pattern generator (CPG) located in the pons. Previous results from our laboratory suggest that the neural network responsible for its rythmogenesis is located in the trigeminal main sensory nucleus (NVsnpr). Moreover, results indicate that in this region, decrease in extracellular calcium concentration ([Ca2+]e) plays an important role in genarating burst. One of our laboratory's goal is to assess if the contribution of astrocytes to the extracellular calcium concentration homeostasis is involved in the genesis of the mastication rhythm. With this study, we characterized the astrocyte syncytium within the NVsnpr and measured the effect of [Ca2+]e on the astrocytes electrophysiology and their networks. A patch-clamp recording technique in conjunction with a rat brain stem slice preparation was used. We demonstrate that a decrease in [Ca2+]e does not affect the electrophysiological properties of astrocytes but induces an increase in the size of the syncytium. We also report the existence, within the dorsal NVsnpr, of an anatomofunctional organization between neurons and astrocytes.

The human jaw, like all other articulated body parts, exhibits small oscillatory movements during isometric holding tasks. These movements, known as physiological tremor, arise as a consequence of the interaction of various factors. One of these factors is reflex feedback from peripheral receptors. In the human jaw, receptors that innervate the periodontium are able to transduce minute changes in force. This thesis examines the contribution of these periodontal mechanoreceptors (PMRs) to the genesis of physiological tremor of the human jaw. By using frequency domain analysis of time series recorded during isometric biting tasks, the character of physiological jaw tremor can be revealed. Physiological jaw tremor was observed in force recorded from between the teeth as well as from electromyograms recorded from the principal muscles of mastication. These recordings have shown us that jaw physiological tremor consists of a frequency invariant component between 6 and 10Hz. This frequency remains unaltered under various load conditions where the mechanical resonance of the jaw would be expected to vary greatly (Chapter 2). Such findings indicate a ‘neurogenic’ origin for this tremor. A possible candidate for this neurogenic component of physiological tremor in the jaw is the reflex feedback arising from the PMRs. Using local anaesthetisation, it has been shown in this thesis, that by blocking outflow from the PMRs, the amplitude of neurogenic physiological jaw tremor can be reduced dramatically. This procedure caused a dramatic reduction in not only the mechanical recordings of tremor but also in the coupling between masseteric muscles bilaterally (Chapter 3) and between single motor units recorded from within a homonymous muscle (Chapter 4). The obvious mechanism by which periodontal mechanoreceptor anaesthetisation could reduce the amplitude of physiological tremor in the jaw would be by reducing the amplitude of the oscillatory input to the motoneurones driving the tremor. This interpretation remains controversial however as physiological tremor in the jaw can be observed at force levels above which the PMRs are supposedly saturated in their response. In light of this knowledge, the saturating characteristics of these receptors in terms of reflex output were examined. To do this, a novel stimulation paradigm was devised whereby the incisal teeth were mechanically stimulated with identical stimulus waveforms superimposed upon increasing tooth preloads. This necessitated the use of a frequency response method to quantify the reflexes. An optimal frequency for stimulation was identified and used to confirm that the hyperbolic saturating response of PMRs observed previously, translated to a similar phenomenon in masticatory reflexes (Chapter 5). These data reinforced the idea that physiological tremor in the jaw was not just a consequence of rhythmic reflex input from PMRs, as the dynamic reflex response uncoupled from the input as the receptor-mediated reflex response saturated. An alternative hypothesis was then developed that suggested the effect of PMR suppression in physiological tremor was via tonic rather than rhythmic effects on the masseteric motoneurone pool. By utilising a novel contraction strategy to manipulate the mean firing rate of the motor neuron pool at a given level of force production, data contained in Chapter 6 shows that population motor unit firing statistics influence the expression of physiological tremor, and such manipulations mimic, to an extent, the changes in firing statistics and tremor amplitude seen during anaesthetisation of the PMRs. This thesis therefore posits a mechanism whereby periodontal input influences the firing rate of motoneurones in such a way as to promote tremulous activity (Chapter 5). However, as this proposed mechanism did not explain the full extent of tremor suppression seen during PMR anaesthetisation it can therefore only be considered a contributing factor in a multifactor process. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1297555 / Thesis (Ph.D.) -- University of Adelaide, School of Molecular and Biomedical Science, 2007