A atividade do complexo 1 da proteína alvo mecanístico da rapamicina (mTORC1), importante regulador da adiposidade e do metabolismo de lipídeos, está aumentada no tecido adiposo de camundongos obesos. A inibição completa de mTORC1 reduz a adiposidade, enquanto que sua inibição parcial potencializa a obesidade induzida por dieta. Assim, hipotetizamos que um nível ótimo de ativação de mTORC1 é necessário para promover aumento da adiposidade, de forma que sua superativação é tão inibitória para a deposição de gordura quanto sua inibição completa. Para testar esta hipótese, investigamos os efeitos da ativação constitutiva de mTORC1, induzida pela deleção de Tsc1, especificamente em adipócitos na adiposidade in vivo. A deleção de Tsc1 reduziu a massa do tecido adiposo visceral, mas não do subcutâneo, que foi associado ao aumento da lipólise e browning. Além disso, aumentou em ambos tecidos adiposos a massa e atividade oxidativa mitocondrial. Esses dados apoiam nossa hipótese de que é necessário um nível ótimo de ativação de mTORC1 para promover aumento da adiposidade. / The activity of mechanistic target of rapamycin complex 1 (mTORC1), an important regulator of adiposity and lipid metabolism, is increased in adipose tissue of obese mice. Complete mTORC1 inhibition reduces adiposity, whereas partial mTORC1 inhibition enhances diet-induced obesity. Therefore, we hypothesized that an optimal level of mTORC1 activity is required to increase adiposity, in such a manner that mTORC1 overactivation is as inhibitory to fat deposition as its complete inhibition. To test this hypothesis, we investigated the effects of constitutive mTORC1 activation, induced by Tsc1 deletion, specifically in adipocytes on adiposity in vivo. Tsc1 deletion reduced visceral, but not subcutaneous, fat mass, which was associated with increased lipolysis and browning. Moreover, it enhanced mitochondrial mass and oxidative activity in both visceral and subcutaneous fat. These data support our hypothesis that an optimal level of mTORC1 activation is necessary to increase adiposity.

Exposure to radiation has toxic effects and for this reason research on food or drugs with positive radiomodifying action (protective) is of outmost interest to Public Health and Consumer Protection. Thus, the aim of this study was testing the prospect grape juice (Vitis labrusca) as a positive radiomodifier of biological effects that characterize the Acute Radiation Syndrome (ARS). Sixteen male Wistar rats divided into four groups were used, where two groups are acutelly whole body X-irradiated and two were sham X-irradiated with a 200 kV X-rays machine specially designed for biological samples at the University of Leon, Spain. The rats received 10 ml of grape juice or placebo (isocaloric solution of glucose and fructose) to be consumed ad libitum one week before and two weeks after 6 Gy Xirradiation, when they were euthanasiated. Physiopathological, biomolecular and biochemical indications of ARS (anorexia, body weight and major organs, hematological parameters, and indicators of oxidative metabolism) were evaluated and compared with respect to the gastrointestinal system (liver). Results were in agreement with our hypotesis about a potential positive radiomodifier effect of grape juice intake against ARS. / A exposição à radiação ionizante possui efeitos tóxicos indesejáveis e por este motivo investigações sobre alimentos ou fármacos com ação radiomodificadora positiva (protetora) é de grande interesse para a Saúde e Defesa Pública Nacional. Neste sentido, esta tese tem como perspectiva testar o suco de uva organicamente produzido (Vitis labrusca) como um radiomodificador positivo dos efeitos biológicos que caracterizam a Síndrome Aguda da Radiação (SAR). Para tanto foram utilizados 16 ratos Wistar machos divididos em quatro grupos, onde dois grupos foram irradiados de corpo inteiro de forma aguda com raios-X utilizando um irradiador de 200 kV especialmente concebido para amostras biológicas instalado na Universidad de León, Espanha. Os ratos receberam diariamente 10 ml de suco de uva ou placebo (solução isocalórica de glicose e frutose) para serem ingeridos ad libitum uma semana antes e duas depois da irradiação com 6 Gy de dose absorvida, quando foram eutanasiados. Foram avaliados e comparados parâmetros morfológicos, fisiológicos, biomoleculares e bioquímicos indicativos da SAR (anorexia, peso corporal e dos principais órgãos, parâmetros hematológicos, e indicadores do metabolismo oxidativo) no sistema gastrointestinal (fígado). Os resultados corroboram a hipótese de que a ingestão ad libitum crônica do suco de uva exerce efeito radiomodificador positivo contra a SAR.

Les études d’imagerie par résonance magnétique fonctionnelle (IRMf) ont pour prémisse générale l’idée que le signal BOLD peut être utilisé comme un succédané direct de l’activation neurale. Les études portant sur le vieillissement cognitif souvent comparent directement l’amplitude et l’étendue du signal BOLD entre des groupes de personnes jeunes et âgés. Ces études comportent donc un a priori additionnel selon lequel la relation entre l’activité neurale et la réponse hémodynamique à laquelle cette activité donne lieu restent inchangée par le vieillissement. Cependant, le signal BOLD provient d’une combinaison ambiguë de changements de métabolisme oxydatif, de flux et de volume sanguin. De plus, certaines études ont démontré que plusieurs des facteurs influençant les propriétés du signal BOLD subissent des changements lors du vieillissement. L’acquisition d’information physiologiquement spécifique comme le flux sanguin cérébral et le métabolisme oxydatif permettrait de mieux comprendre les changements qui sous-tendent le contraste BOLD, ainsi que les altérations physiologiques et cognitives propres au vieillissement. Le travail présenté ici démontre l’application de nouvelles techniques permettant de mesurer le métabolisme oxydatif au repos, ainsi que pendant l’exécution d’une tâche. Ces techniques représentent des extensions de méthodes d’IRMf calibrée existantes. La première méthode présentée est une généralisation des modèles existants pour l’estimation du métabolisme oxydatif évoqué par une tâche, permettant de prendre en compte tant des changements arbitraires en flux sanguin que des changements en concentrations sanguine d’O2. Des améliorations en terme de robustesse et de précisions sont démontrées dans la matière grise et le cortex visuel lorsque cette méthode est combinée à une manipulation respiratoire incluant une composante d’hypercapnie et d’hyperoxie. Le seconde technique présentée ici est une extension de la première et utilise une combinaison de manipulations respiratoires incluant l’hypercapnie, l’hyperoxie et l’administration simultanée des deux afin d’obtenir des valeurs expérimentales de la fraction d’extraction d’oxygène et du métabolisme oxydatif au repos. Dans la deuxième partie de cette thèse, les changements vasculaires et métaboliques liés à l’âge sont explorés dans un groupe de jeunes et aînés, grâce au cadre conceptuel de l’IRMf calibrée, combiné à une manipulation respiratoire d’hypercapnie et une tâche modifiée de Stroop. Des changements de flux sanguin au repos, de réactivité vasculaire au CO2 et de paramètre de calibration M ont été identifiés chez les aînés. Les biais affectant les mesures de signal BOLD obtenues chez les participants âgés découlant de ces changements physiologiques sont de plus discutés. Finalement, la relation entre ces changements cérébraux et la performance dans la tâche de Stroop, la santé vasculaire centrale et la condition cardiovasculaire est explorée. Les résultats présentés ici sont en accord avec l’hypothèse selon laquelle une meilleure condition cardiovasculaire est associée à une meilleure fonction vasculaire centrale, contribuant ainsi à l’amélioration de la santé vasculaire cérébrale et cognitive. / Functional MRI (fMRI) studies using the BOLD signal are done under the general assumption that the BOLD signal can be used as a direct index of neuronal activation. Studies of cognitive aging often compare BOLD signal amplitude and extent directly between younger and older groups, with the additional assumption that the relationship between neuronal activity and the hemodynamic response is unchanged across the lifespan. However, BOLD signal arises from an ambiguous mixture of changes in oxidative metabolism, blood flow and blood volume. Furthermore, previous studies have shown that several BOLD signal components may be changed during aging. More physiologically-specific information on blood flow and oxidative metabolism would allow a better understanding of these signal changes and of the physiological and cognitive changes seen with aging. The work presented here demonstrates techniques to estimate oxidative metabolism at rest and during performance of a task. These techniques are extensions of previous calibrated fMRI methods and the first method presented is based on a generalization of previous models to take into account both arbitrary changes in blood flow and blood O2 content. The improved robustness and accuracy of this method, when used with a combined hypercapnia and hyperoxia breathing manipulation, is demonstrated in visual cortex and grey matter. The second technique presented builds on the generalization of the model and uses a combination of breathing manipulations including hypercapnia, hyperoxia and both simultaneously, to obtain experimentally-determined values of resting oxygen extraction fraction and oxidative metabolism. In the second part of this thesis, age-related vascular and metabolic changes are explored in a group of younger and older adults using a calibrated fMRI framework with a hypercapnia breathing manipulation and a modified Stroop task. Changes in baseline blood flow, vascular reactivity to the CO2 challenge and calibration parameter M were identified in the older participants. Potential biases in BOLD signal measurements in older adults arising from these physiological changes are discussed. Finally, the relationship between these cerebral changes and performance on the modified Stroop task, central vascular health and cardiovascular fitness are explored. The results of this thesis support the hypothesis that greater cardiovascular fitness is associated with improvements in central vascular function, contributing in turn to improved brain vascular health and cognition.

A laserterapia tem sido muito utilizada como tratamento alternativo em pacientes com dores crônicas relacionadas às disfunções temporomandibulares. Isso se deve aos efeitos: analgésico, antiinflamatório, miorrelaxante, de redução da fadiga durante as contrações tetânicas, aumento da força de mordida e diminuição da dor orofacial. Embora sejam observados resultados clínicos, ainda não é bem compreendido o seu efeito em nível celular. Assim, este estudo tem como objetivo analisar os efeitos das diferentes densidades (doses) de irradiação do laser de baixa intensidade (LLLI), em nível celular, sobre o músculo masseter de ratos Wistar. Os animais foram alocados aleatoriamente em 6 grupos (n=10), receberam 10 irradiações do laser (GaAlAs,780nm, 5mW e spot 0,04cm²) sobre o músculo masseter esquerdo variando a densidade de energia (I. 0; II. 0,5; III. 1,0; IV. 2,5; V. 5,0 e VI. 20 J/cm²). Após as 10 irradiações os músculos masseteres foram obtidos dos animais sob anestesia para análises: 1. Histoenzimológicas para atividade da nicotinamida adenina dinucleotídeo diaforase(NADH), succinato desidrogenase (SDH) e adenosina trifosfatase (ATPase), 2. Microscopia de luz (HE), 3. Microscopia eletrônica de transmissão e 4. Imunohistoquímica para fator de crescimento do endotélio vascular (VEGF) e o receptor 2 para VEGF (VEGFR-2). A atividade do NADH nos grupos IV, V e VI (30±1,26; 33,47±2,15; 31,67±1,77 - fibras intermediárias) apresentou um aumento significativo (p>0,05) no metabolismo oxidativo em relação aos demais grupos. Na atividade do SDH, o aumento foi discreto, com aumento significativo (p>0,05), apenas no grupo V (32,2±1,61 fibras intermediárias), com o padrão de aumento metabólico muito parecido nas reações de NADH e SDH. A atividade da ATPase não revelou diferenças entre os grupos tanto em meio ácido como no alcalino. A microscopia de luz revelou fibras musculares arredondadas e núcleos periféricos achatados, os quais tornaram mais arredondados com as densidades maiores de energia. Ultraestruturalmente as irradiações com as maiores densidades de energia revelaram mitocôndrias de tamanhos e formas variadas e cisternas do retículo sarcoplasmático dilatadas entre as miofibrilas. As análises qualitativas mostraram um padrão de aumento a expressão do VEGF e VEGFR-2 proporcionais à densidade de energia do laser usada. Conclui-se que o laser com densidades maiores foi capaz de aumentar o metabolismo oxidativo, sem alterar a capacidade contrátil, aumentar o volume do núcleo, modificar a ultraestrutura das fibras musculares e as expressões do VEGF e VEGFR-2. / The laser therapy has been widely used as an alternative treatment in patients with chronic pain related to temporomandibular disorders. This is due to the effects: analgesic, anti inflammatory, muscle relaxant, reducing fatigue during tetanic contractions, increased bite strength and decrease in orofacial pain. Although clinical results are observed, is not well understood its effect on the cellular level. This study aims to analyze the effects of different densities (doses) irradiation of low level laser therapy (LLLI) on cellular level, on the masseter muscle of rats. The animals were randomly assigned to 6 groups (n=10), received 10 laser irradiation (GaAlAs, 780nm, 5mW spot and 0.04 cm²) on the left masseter muscle by varying the energy density (I. 0; II. 0.5; III. 1.0; IV. 2.5; V. 5.0 and VI. 20 J/cm²). After 10 irradiations the masseter muscles were obtained from animals under anesthesia for analysis: 1. Histoenzimologic for nicotinamide adenine dinucleotide (NADH), succinate dehydrogenase (SDH) and adenosine triphosphatase (ATPase), 2. Light microscopy (HE), 3. Transmission electron microscopy and 4. Immunohistochemistry for vascular endothelial growth factor (VEGF) and receptor 2 for VEGF (VEGFR-2). The activity of NADH in groups IV, V and VI (30±1,26; 33,47±2,15; 31,67±1,77 - intermediate fiber) increased significantly (p> 0.05) in oxidative metabolism in relation to other groups. The activity of SDH showed a slight increase, only the group V (32,2±1,61 intermediate fiber) increased significantly (p> 0.05), but the pattern of metabolic increase was very similar in both reactions. The ATPase activity showed no differences between groups nor in acid or alkaline. The qualitative analysis showed a pattern of increased expression of VEGF and VEGFR-2 directly proportional to the energy density of laser. Light microscopy showed rounded muscle fibers and peripheral flattened nuclei, which become more rounded with the highest energy densities. Ultrastructurally the irradiation with higher energy densities showed mitochondria of different sizes and shapes and dilated cisterns of sarcoplasmic reticulum between the myofibrils. It is concluded that higher densities of laser was able to increase the oxidative metabolism without altering the contractile capacity, increasing nuclei volume, modify ultrastructure of muscle fibers and the expressions of VEGF and VEGFR-2.

Les études d’imagerie par résonance magnétique fonctionnelle (IRMf) ont pour prémisse générale l’idée que le signal BOLD peut être utilisé comme un succédané direct de l’activation neurale. Les études portant sur le vieillissement cognitif souvent comparent directement l’amplitude et l’étendue du signal BOLD entre des groupes de personnes jeunes et âgés. Ces études comportent donc un a priori additionnel selon lequel la relation entre l’activité neurale et la réponse hémodynamique à laquelle cette activité donne lieu restent inchangée par le vieillissement. Cependant, le signal BOLD provient d’une combinaison ambiguë de changements de métabolisme oxydatif, de flux et de volume sanguin. De plus, certaines études ont démontré que plusieurs des facteurs influençant les propriétés du signal BOLD subissent des changements lors du vieillissement. L’acquisition d’information physiologiquement spécifique comme le flux sanguin cérébral et le métabolisme oxydatif permettrait de mieux comprendre les changements qui sous-tendent le contraste BOLD, ainsi que les altérations physiologiques et cognitives propres au vieillissement. Le travail présenté ici démontre l’application de nouvelles techniques permettant de mesurer le métabolisme oxydatif au repos, ainsi que pendant l’exécution d’une tâche. Ces techniques représentent des extensions de méthodes d’IRMf calibrée existantes. La première méthode présentée est une généralisation des modèles existants pour l’estimation du métabolisme oxydatif évoqué par une tâche, permettant de prendre en compte tant des changements arbitraires en flux sanguin que des changements en concentrations sanguine d’O2. Des améliorations en terme de robustesse et de précisions sont démontrées dans la matière grise et le cortex visuel lorsque cette méthode est combinée à une manipulation respiratoire incluant une composante d’hypercapnie et d’hyperoxie. Le seconde technique présentée ici est une extension de la première et utilise une combinaison de manipulations respiratoires incluant l’hypercapnie, l’hyperoxie et l’administration simultanée des deux afin d’obtenir des valeurs expérimentales de la fraction d’extraction d’oxygène et du métabolisme oxydatif au repos. Dans la deuxième partie de cette thèse, les changements vasculaires et métaboliques liés à l’âge sont explorés dans un groupe de jeunes et aînés, grâce au cadre conceptuel de l’IRMf calibrée, combiné à une manipulation respiratoire d’hypercapnie et une tâche modifiée de Stroop. Des changements de flux sanguin au repos, de réactivité vasculaire au CO2 et de paramètre de calibration M ont été identifiés chez les aînés. Les biais affectant les mesures de signal BOLD obtenues chez les participants âgés découlant de ces changements physiologiques sont de plus discutés. Finalement, la relation entre ces changements cérébraux et la performance dans la tâche de Stroop, la santé vasculaire centrale et la condition cardiovasculaire est explorée. Les résultats présentés ici sont en accord avec l’hypothèse selon laquelle une meilleure condition cardiovasculaire est associée à une meilleure fonction vasculaire centrale, contribuant ainsi à l’amélioration de la santé vasculaire cérébrale et cognitive. / Functional MRI (fMRI) studies using the BOLD signal are done under the general assumption that the BOLD signal can be used as a direct index of neuronal activation. Studies of cognitive aging often compare BOLD signal amplitude and extent directly between younger and older groups, with the additional assumption that the relationship between neuronal activity and the hemodynamic response is unchanged across the lifespan. However, BOLD signal arises from an ambiguous mixture of changes in oxidative metabolism, blood flow and blood volume. Furthermore, previous studies have shown that several BOLD signal components may be changed during aging. More physiologically-specific information on blood flow and oxidative metabolism would allow a better understanding of these signal changes and of the physiological and cognitive changes seen with aging. The work presented here demonstrates techniques to estimate oxidative metabolism at rest and during performance of a task. These techniques are extensions of previous calibrated fMRI methods and the first method presented is based on a generalization of previous models to take into account both arbitrary changes in blood flow and blood O2 content. The improved robustness and accuracy of this method, when used with a combined hypercapnia and hyperoxia breathing manipulation, is demonstrated in visual cortex and grey matter. The second technique presented builds on the generalization of the model and uses a combination of breathing manipulations including hypercapnia, hyperoxia and both simultaneously, to obtain experimentally-determined values of resting oxygen extraction fraction and oxidative metabolism. In the second part of this thesis, age-related vascular and metabolic changes are explored in a group of younger and older adults using a calibrated fMRI framework with a hypercapnia breathing manipulation and a modified Stroop task. Changes in baseline blood flow, vascular reactivity to the CO2 challenge and calibration parameter M were identified in the older participants. Potential biases in BOLD signal measurements in older adults arising from these physiological changes are discussed. Finally, the relationship between these cerebral changes and performance on the modified Stroop task, central vascular health and cardiovascular fitness are explored. The results of this thesis support the hypothesis that greater cardiovascular fitness is associated with improvements in central vascular function, contributing in turn to improved brain vascular health and cognition.

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Pesquisa do Estado de Minas Gerais (FAPEMIG) / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico (CNPq) / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / O excesso de gordura corporal caracter?stico da obesidade est? relacionado a diversas altera??es metab?licas, que incluem a resist?ncia ? insulina. Dentre as medidas n?o farmacol?gicas empregadas para a melhora da sensibilidade ? insulina est? o treinamento f?sico aer?bio, como o treinamento intervalado de alta intensidade (HIIT, do ingl?s high intensity interval training). Sendo assim, esse estudo avaliou os efeitos do HIIT em componentes bioqu?micos, celulares e moleculares relacionados ? resist?ncia ? insulina em obesos. Indiv?duos obesos sens?veis (n=9) e resistentes ? insulina (n=8) foram submetidos a 8 semanas de HIIT, em cicloerg?metro, realizado 3 vezes por semana, com intensidade e volume progressivos (8 a 12 est?mulos; 80 a 110% da pot?ncia m?xima). Amostras de sangue venoso e do m?sculo vasto lateral foram obtidas antes e ap?s o programa de HIIT. Ap?s o programa de treinamento houve aumento da sensibilidade ? insulina nos obesos resistentes ? insulina, mas n?o houve redu??o da massa de gordura. A concentra??o de citocinas no soro, o estresse oxidativo sist?mico e frequ?ncia das c?lulas imunes n?o foram modificadas ap?s o treinamento. No m?sculo esquel?tico, o HIIT promoveu aumento da fosforila??o do substrato do receptor de insulina (IRS) (Tyr612), da Akt (Ser473) e da prote?na quinase dependente de c?lcio/calmodulina (CAMKII) (Thr286), e aumento do conte?do da ?-hidroxiacil-CoA desidrogenase (?-HAD) e citocromo C oxidase (COX-IV). Houve ainda, redu??o da fosforila??o da quinase regulada por sinal extracelular (ERK1/2) nos obesos resistentes ? insulina. Conclu?mos que 8 semanas de HIIT promoveram melhora da sensibilidade ? insulina, modificou componentes da via de sinaliza??o da insulina e do metabolismo oxidativo no m?sculo esquel?tico. Essas altera??es ocorreram independentes de mudan?as na gordura corporal total e de par?metros inflamat?rios sist?micos. / Tese (Doutorado) ? Programa Multic?ntrico de P?s-Gradua??o em Ci?ncias Fisiol?gicas, Universidade Federal dos Vales do Jequitinhonha e Mucuri, 2016. / Obesity is characterized by excess of body fat, and its development can lead to a variety of metabolic disorders, including insulin resistance. Exercise is recognized as a non-pharmacological approach to increasing skeletal muscle insulin sensitivity, although the mechanisms are not elucidated. Additionally, the understanding of high intensity interval training (HIIT, high intensity interval training) treat insulin resistance is less understood. Therefore, this study evaluated the effects of HIIT on biochemical, molecular, and cellular markers related to insulin resistance in sedentary obese individuals. Sensitive (n=9) and insulin resistant (n=8) obese individuals (body mass index ? 30 kg/m-2) were engaged in 8 weeks of HIIT using a cycle ergometer. The HIIT was performed 3 times a week, and its intensity and volume progressively increased throughout the training period (from 8 to 12 stimuli; from 80 to 110% of the maximum power). Venous blood and the vastus lateralis muscle samples were obtained before and after the HIIT. HIIT enhanced insulin sensitivity in insulin-resistant obese individuals without changing body fat mass. Cytokine concentration in serum, blood oxidative stress, and frequency of some immune cells were not altered by HIIT. In skeletal muscle, HIIT increased the phosphorylation of insulin receptor substrate (IRS) (Tyr612), Akt (Ser473), and protein kinase dependent calcium/calmodulin (CaMKII) (Thr286). HIIT also increased the expression of ?-hydroxyacyl-CoA dehydrogenase (?-HAD) and cytochrome C oxidase (COX-IV). A reduction of the kinase phosphorylation of extracellular signal-regulated (ERK1/2) was only seen in obese insulin resistant individuals. The results show that 8 weeks of HIIT enhanced insulin sensitivity, modified components of the insulin-signaling pathway, and improved skeletal muscle oxidative metabolism. These changes were independent of alterations in body fat and inflammatory parameters.

A laserterapia tem sido muito utilizada como tratamento alternativo em pacientes com dores crônicas relacionadas às disfunções temporomandibulares. Isso se deve aos efeitos: analgésico, antiinflamatório, miorrelaxante, de redução da fadiga durante as contrações tetânicas, aumento da força de mordida e diminuição da dor orofacial. Embora sejam observados resultados clínicos, ainda não é bem compreendido o seu efeito em nível celular. Assim, este estudo tem como objetivo analisar os efeitos das diferentes densidades (doses) de irradiação do laser de baixa intensidade (LLLI), em nível celular, sobre o músculo masseter de ratos Wistar. Os animais foram alocados aleatoriamente em 6 grupos (n=10), receberam 10 irradiações do laser (GaAlAs,780nm, 5mW e spot 0,04cm²) sobre o músculo masseter esquerdo variando a densidade de energia (I. 0; II. 0,5; III. 1,0; IV. 2,5; V. 5,0 e VI. 20 J/cm²). Após as 10 irradiações os músculos masseteres foram obtidos dos animais sob anestesia para análises: 1. Histoenzimológicas para atividade da nicotinamida adenina dinucleotídeo diaforase(NADH), succinato desidrogenase (SDH) e adenosina trifosfatase (ATPase), 2. Microscopia de luz (HE), 3. Microscopia eletrônica de transmissão e 4. Imunohistoquímica para fator de crescimento do endotélio vascular (VEGF) e o receptor 2 para VEGF (VEGFR-2). A atividade do NADH nos grupos IV, V e VI (30±1,26; 33,47±2,15; 31,67±1,77 - fibras intermediárias) apresentou um aumento significativo (p>0,05) no metabolismo oxidativo em relação aos demais grupos. Na atividade do SDH, o aumento foi discreto, com aumento significativo (p>0,05), apenas no grupo V (32,2±1,61 fibras intermediárias), com o padrão de aumento metabólico muito parecido nas reações de NADH e SDH. A atividade da ATPase não revelou diferenças entre os grupos tanto em meio ácido como no alcalino. A microscopia de luz revelou fibras musculares arredondadas e núcleos periféricos achatados, os quais tornaram mais arredondados com as densidades maiores de energia. Ultraestruturalmente as irradiações com as maiores densidades de energia revelaram mitocôndrias de tamanhos e formas variadas e cisternas do retículo sarcoplasmático dilatadas entre as miofibrilas. As análises qualitativas mostraram um padrão de aumento a expressão do VEGF e VEGFR-2 proporcionais à densidade de energia do laser usada. Conclui-se que o laser com densidades maiores foi capaz de aumentar o metabolismo oxidativo, sem alterar a capacidade contrátil, aumentar o volume do núcleo, modificar a ultraestrutura das fibras musculares e as expressões do VEGF e VEGFR-2. / The laser therapy has been widely used as an alternative treatment in patients with chronic pain related to temporomandibular disorders. This is due to the effects: analgesic, anti inflammatory, muscle relaxant, reducing fatigue during tetanic contractions, increased bite strength and decrease in orofacial pain. Although clinical results are observed, is not well understood its effect on the cellular level. This study aims to analyze the effects of different densities (doses) irradiation of low level laser therapy (LLLI) on cellular level, on the masseter muscle of rats. The animals were randomly assigned to 6 groups (n=10), received 10 laser irradiation (GaAlAs, 780nm, 5mW spot and 0.04 cm²) on the left masseter muscle by varying the energy density (I. 0; II. 0.5; III. 1.0; IV. 2.5; V. 5.0 and VI. 20 J/cm²). After 10 irradiations the masseter muscles were obtained from animals under anesthesia for analysis: 1. Histoenzimologic for nicotinamide adenine dinucleotide (NADH), succinate dehydrogenase (SDH) and adenosine triphosphatase (ATPase), 2. Light microscopy (HE), 3. Transmission electron microscopy and 4. Immunohistochemistry for vascular endothelial growth factor (VEGF) and receptor 2 for VEGF (VEGFR-2). The activity of NADH in groups IV, V and VI (30±1,26; 33,47±2,15; 31,67±1,77 - intermediate fiber) increased significantly (p> 0.05) in oxidative metabolism in relation to other groups. The activity of SDH showed a slight increase, only the group V (32,2±1,61 intermediate fiber) increased significantly (p> 0.05), but the pattern of metabolic increase was very similar in both reactions. The ATPase activity showed no differences between groups nor in acid or alkaline. The qualitative analysis showed a pattern of increased expression of VEGF and VEGFR-2 directly proportional to the energy density of laser. Light microscopy showed rounded muscle fibers and peripheral flattened nuclei, which become more rounded with the highest energy densities. Ultrastructurally the irradiation with higher energy densities showed mitochondria of different sizes and shapes and dilated cisterns of sarcoplasmic reticulum between the myofibrils. It is concluded that higher densities of laser was able to increase the oxidative metabolism without altering the contractile capacity, increasing nuclei volume, modify ultrastructure of muscle fibers and the expressions of VEGF and VEGFR-2.

The BOLD contrast employed in functional MRI studies is an ambiguous signal composed of changes in blood flow, blood volume and oxidative metabolism. In situations where the vasculature and metabolism may have been affected, such as in aging and in certain diseases, the dissociation of the more physiologically-specific components from the BOLD signal becomes crucial. The latest generation of calibrated functional MRI methods allows the estimation of both resting blood flow and absolute oxygen metabolism. The work presented here is based on one such proof-of-concept approach, dubbed QUO2, whereby taking into account, within a generalized model, both arbitrary changes in blood flow and blood O2 content during a combination of hypercapnia and hyperoxia breathing manipulations, yields voxel-wise estimates of resting oxygen extraction fraction and oxidative metabolism. In the first part of this thesis, the QUO2 acquisition protocol and data analysis were revisited in order to enhance the temporal stability of individual blood flow and BOLD responses, consequently improving reliability of the model-derived estimates. Thereafter, an assessment of the within and between-subject variability of the optimized QUO2 measurements was performed on a group of healthy volunteers. In parallel, an analysis was performed of the sensitivity of the model to different sources of random and systematic errors, respectively due to errors in measurements and choice of assumed parameters values. Moreover, the various impacts of the oxygen concentration administered during the hyperoxia manipulation were evaluated through a simulation and experimentally, indicating that a mild hyperoxia was beneficial. Finally, the influence of Alzheimer’s disease in vascular and metabolic changes was explored for the first time by applying the QUO2 approach in a cohort of probable Alzheimer’s disease patients and age-matched control group. Voxel-wise and region-wise differences in resting blood flow, oxygen extraction fraction, oxidative metabolism, transverse relaxation rate constant R2* and R2* changes during hypercapnia were identified. A series of limitations along with recommended solutions was given with regards to the delayed transit time, the susceptibility artifacts and the challenge of performing a hypercapnia manipulation in cohorts of elderly and Alzheimer’s patients. / Le contraste BOLD employé dans les études d’imagerie par résonance magnétique fonctionnelle (IRMf) provient d’une combinaison ambigüe de changements du flux sanguin cérébral, du volume sanguin ainsi que du métabolisme oxydatif. Dans un contexte où les fonctions vasculaires ou métaboliques du cerveau ont pu être affectées, tel qu’avec l’âge ou certaines maladies, il est crucial d’effectuer une décomposition du signal BOLD en composantes physiologiquement plus spécifiques. La dernière génération de méthodes d’IRMf calibrée permet d’estimer à la fois le flux sanguin cérébral et le métabolisme oxydatif au repos. Le présent travail est basé sur une telle technique, appelée QUantitative O2 (QUO2), qui, via un model généralisé, prend en considération les changements du flux sanguin ainsi que ceux en concentrations sanguine d’O2 durant des périodes d’hypercapnie et d’hyperoxie, afin d’estimer, à chaque voxel, la fraction d’extraction d’oxygène et le métabolisme oxydatif au repos. Dans la première partie de cette thèse, le protocole d’acquisition ainsi que la stratégie d’analyse de l’approche QUO2 ont été revus afin d’améliorer la stabilité temporelle des réponses BOLD et du flux sanguin, conséquemment, afin d’accroître la fiabilité des paramètres estimés. Par la suite, une évaluation de la variabilité intra- et inter-sujet des différentes mesures QUO2 a été effectuée auprès d’un groupe de participants sains. En parallèle, une analyse de la sensibilité du model à différentes sources d’erreurs aléatoires (issues des mesures acquises) et systématiques (dues aux assomptions du model) a été réalisée. De plus, les impacts du niveau d’oxygène administré durant les périodes d’hyperoxie ont été évalués via une simulation puis expérimentalement, indiquant qu’une hyperoxie moyenne était bénéfique. Finalement, l’influence de la maladie d’Alzheimer sur les changements vasculaires et métaboliques a été explorée pour la première fois en appliquant le protocole QUO2 à une cohorte de patients Alzheimer et à un groupe témoin du même âge. Des différences en terme de flux sanguin, fraction d’oxygène extraite, métabolisme oxydatif, et taux de relaxation transverse R2* au repos comme en réponse à l’hypercapnie, ont été identifiées au niveau du voxel, ainsi qu’au niveau de régions cérébrales vulnérables à la maladie d’Alzheimer. Une liste de limitations accompagnées de recommandations a été dressée en ce qui a trait au temps de transit différé, aux artéfacts de susceptibilité magnétique, de même qu’au défi que représente l’hypercapnie chez les personnes âgées ou atteintes de la maladie d’Alzheimer.