L’encéphalopathie hépatique (EH) est un syndrome neuropsychiatrique découlant des complications de l'insuffisance hépatique. Les patients souffrant d'une insuffisance hépatique chronique (IHC) présentent fréquemment une EH minimale (EHM) caractérisée par des dysfonctions cognitives subtiles qui affectent leur qualité de vie. L'insuffisance hépatique entraîne une hyperammoniémie, le facteur central dans la pathogenèse de l'EH. Pourtant, les taux d'ammoniaque sérique ne sont pas corrélés avec la sévérité de l'EH lors d'une IHC, suggérant que d'autres facteurs y contribuent. L'oedème cérébral est une caractéristique neuropathologique décrite chez les patients souffrant d'une EHM et plusieurs facteurs dont le stress oxydatif, les altérations du métabolisme énergétique et l'augmentation de la glutamine cérébrale pourraient contribuer à la pathogenèse de l'oedème cérébral lors d'une EHM induite par une IHC. Les mécanismes sous-jacents exacts ainsi que les relations entre ces facteurs et l'ammoniaque ne sont pas connus. Présentement, le seul traitement efficace de l'IHC est la transplantation hépatique, une option thérapeutique très limitée. Le but de cette thèse est de contribuer à l'avancement des connaissances sur les mécanismes sous-jacents liés au rôle du stress oxydatif, de la glutamine et du lactate dans la pathogenèse de l'oedème cérébral lors d'une EHM induite par une IHC afin d'envisager de nouvelles options thérapeutiques. Les objectifs précis étaient: 1. Établir le rôle de l’ammoniaque et sa relation avec le stress oxydatif dans la pathogenèse de l'oedème cérébral lors d'une EHM induite par une IHC. 2. Établir le rôle du stress oxydatif dans la pathogenèse de l'oedème cérébral, sa relation avec l'ammoniaque et l'effet du traitement avec des antioxydants. 3. Confirmer l'effet synergique entre l'ammoniaque et le stress oxydatif dans la pathogenèse de l'oedème cérébral. 4. Établir le rôle du lactate et de la glutamine dans la pathogenèse de l'oedème cérébral et leur relation avec l’ammoniaque. Pour atteindre ces objectifs, 2 modèles animaux d'EHM obtenus par microchirurgie chez le rat ont été utilisés: 1) la ligature de voie biliaire, un modèle d'IHC et 2) l'anastomose porto-cave, un modèle d'hyperammoniémie induite par la dérivation portosystémique. Nos résultats démontrent que l'ammoniaque et le stress oxydatif indépendamment n'induisent pas l'oedème cérébral lors d'une EHM. Pourtant, lorsque les 2 facteurs agissent ensemble ils présentent ii un effet synergique qui entraîne le développement de l'oedème cérébral, le stress oxydatif étant une première insulte, qui est suivie par l'hyperammoniémie comme deuxième insulte. En plus, le stress oxydatif a été mis en évidence seulement au niveau systémique, et non au niveau central dans notre modèle d'IHC en association avec l'oedème cérébral, suggérant que le stress oxydatif systémique est une conséquence de la dysfonction hépatique et que l'hyperammoniémie n’induit pas le stress oxydatif ni systémique ni central. Nous avons démontré qu’une augmentation du lactate cérébral est une conséquence directe de l'hyperammoniémie et joue un rôle important dans la pathogenèse de l'oedème cérébral lors d'une EHM induite par une IHC, tandis qu’une augmentation de la glutamine au niveau cérébral n'est pas un facteur clé. La compréhension de ces mécanismes a entraîné la proposition de 3 nouvelles stratégies thérapeutiques potentielles pour l'EHM. Elles ciblent la diminution de l'ammoniaque sérique, la réduction du stress oxydatif et l'inhibition de la synthèse du lactate. / Hepatic encephalopathy (HE) is a metabolic neuropsychiatric syndrome which occurs as a complication of liver failure/disease. Patients with chronic liver disease (CLD) present often with minimal HE (MHE) characterized by subtle cognitive dysfunction which impairs their quality of life. Impaired liver function leads to hyperammonemia which is a central factor in the pathogenesis of HE. However, ammonia alone is poorly correlated with the severity of HE during CLD, strongly suggesting other factors may contribute. Brain edema is a neuropathological feature described in MHE patients and several factors such as oxidative stress, energy metabolism alterations and an increase in glutamine may to contribute to the pathogenesis of brain edema during HE related to CLD. However the exact underlying mechanisms and the relationships between these factors and ammonia are poorly understood. To date, the only effective treatment of CLD remains liver transplantation, a limited therapeutic option. The aim of this thesis is to advance the knowledge into the mechanisms underlying the role of oxidative stress, glutamine and lactate in the pathogenesis of brain edema during MHE associated with CLD in order to uncover new therapeutic options. The study objectives were: 1. Define the role of ammonia and its relationship with oxidative stress in the pathogenesis of brain edema in CLD. 2. Define the role of oxidative stress in the pathogenesis of brain edema, its relationship with ammonia as well as the effect of antioxidant treatment. 3. Confirm a synergistic role of ammonia and oxidative stress in the pathogenesis of brain edema. 4. Define the role of lactate and glutamine in the pathogenesis of brain edema and their relationship with ammonia. To achieve these objectives, we used 2 microsurgical rat models: 1) bile-duct ligation, a cirrhosis model and 2) portacaval anastomosis, a hyperammonemia model following portal-systemic shunting. Our findings demonstrate that ammonia and systemic oxidative stress independently do not induce brain edema in MHE related to CLD. However, when both factors are present, they exert a synergistic effect leading to the development of brain edema with oxidative stress presenting as a “first hit”, followed by hyperammonemia as a “second hit”. Moreover, solely systemic and not central oxidative stress was observed in our CLD rat model in relation to brain edema implying that systemic oxidative stress is a consequence of liver dysfunction and that central oxidative stress is not a direct iv effect of hyperammonemia in the setting of CLD. Moreover, we revealed that increased cerebral lactate is a direct consequence of hyperammonemia and also plays an important role in the pathogenesis of brain edema, while increased cerebral glutamine does not. The understanding of these mechanisms led to the proposal of three different strategies as potential HE therapies. These are directed towards lowering ammonia, reducing oxidative stress and inhibiting lactate synthesis.

Introdução: A maioria dos pacientes acometidos pela neoplasia que envolve a confluência biliopancreática é diagnosticada em fase avançada. A Colangiopancreatografia Retrógrada Endoscópica (CPRE) é o método de escolha para a drenagem da via biliar obstruída. Todavia, existe um índice de insucesso em torno de 10%. Nesses casos, técnicas alternativas serão aplicadas, como drenagem percutânea trans-hepática e drenagens cirúrgicas. Objetivo: Avaliar o sucesso técnico, clínico, qualidade de vida e sobrevida da drenagem biliar pela cirurgia convencional e técnica endoscópica ecoguiada em pacientes portadores de neoplasia maligna da confluência biliopancreática. Método: No período de abril de 2010 a setembro de 2013, foram estudados 32 pacientes portadores de neoplasia maligna da confluência biliopancreática. Todos os que foram incluídos nesse estudo apresentaram falha na drenagem biliar por CPRE. Três deles foram excluídos por insucesso técnico (falha na confecção da anastomose hepaticojejunal e da formação da fístula coledocoduodenal ecoguiada). O Grupo I foi formado por 15 pacientes submetidos à Hepaticojejunostomia (HJT) em \"Y\" de Roux e derivação gastrojejunal. O Grupo II foi formado por 14 pacientes submetidos à coledocoduodenostomia ecoguiada (CDT). O sucesso clínico foi avaliado pela queda da bilirrubina sérica total em mais de 50% nos sete primeiros dias após o procedimento. A qualidade de vida foi avaliada pelo questionário SF-36 e a sobrevida pela curva de Kaplan-Meier. Resultados: O sucesso técnico foi de 93,75% (15/16) no Grupo I e de 87,5% (14/16) no Grupo II (p = 0,598). O sucesso clínico ocorreu em 14 (93,33%) pacientes pertencentes ao Grupo I e em 10 (71,43%) do Grupo II. Não houve diferença estatisticamente significativa (p = 0,169). O comportamento médio dos escores de qualidade de vida foi estatisticamente igual entre as técnicas ao longo do seguimento (p > 0,05 Técnica * Momento). Houve alteração média estatisticamente significativa ao longo do seguimento nos escores de capacidade funcional, saúde física, dor, aspectos sociais, aspectos emocionais e saúde mental em ambas as técnicas (p < 0,05). O escore de saúde mental foi, em média, estatisticamente maior nos do Grupo II (CDT) em todos os momentos (p = 0,035). O tempo médio de sobrevida daqueles pertencentes ao Grupo I foi de 82,27 dias e os do Grupo II, de 82,36 dias. Sessenta por cento dos pertencentes ao Grupo I faleceram até 90 dias após o procedimento cirúrgico. Por outro lado, 42,9% dos submetidos à CDT faleceram no mesmo período. Não houve diferença estatisticamente significativa no tempo de sobrevida entre os Grupos (p = 0,389). Conclusão: Os dados relacionados aos sucessos técnico, clínico, qualidade de vida e sobrevida foram semelhantes em ambos os grupos, não se verificando diferença estatisticamente significativa / Introduction: Most patients with neoplasm in the biliopancreatic junction are diagnosed at an advanced stage. Endoscopic retrograde cholangiopancreatography (ERCP) is the method of choice for drainage of obstructed biliary tract. However, there is a failure rate of about 10%. In such cases, alternative techniques, such as, percutaneous transhepatic drainage and surgical drainage are applied. Aim: To evaluate the technical and clinical success, quality of life and patient survival of biliary drainage by conventional surgery and endosonography-guided technique in patients with malignant neoplasm of the biliopancreatic junction. Methodology: From April 2010 to September 2013, 32 patients with malignant neoplasm of the biliopancreatic junction were studied. All patients included in this study had failed biliary drainage by ERCP. Three patients were excluded due to technical failure (failure in the construction of hepatico-jejuno anastomosis and formation of endosonography-guided choledochoduodenal fistula). Group I comprised of 15 patients who underwent Roux-en-Y hepaticojejunostomy (HJT) and gastrojejunal bypass. Group II consisted of 14 patients who underwent endosonography-guided choledochoduodenostomy (CDT). Clinical success was assessed by the decrease of more than 50% in total serum bilirubin in the first seven days after the procedure. Quality of life was assessed by SF-36 questionnaire and survival by Kaplan-Meier curve. Results: Technical success rate was 93.75% (15/16) in group I and 87.5% (14/16) in group II (p = 0.598). Clinical success occurred in 14 (93.33%) patients in group I and 10 (71.43%) patients in group II. There was no significant statistically difference (p = 0.169). The average quality of life score were statistically equal between the techniques during follow-up (p > 0.05 * Technical Moment). There were statistically significant mean changes during follow-up of functional capacity score, physical health, pain, social functioning, emotional and mental health aspects in both techniques (p < 0.05). The mental health score was, on average, statistically higher in group II (CDT) at all times (p = 0.035). The median survival time of patients in group I was 82.27 days and Group II patients was 82.36 days. Sixty percent of patients in group I died within 90 days after the surgical procedure. On the other hand, 42.9% of the patients who underwent CDT died in the same period. There was no statistically significant difference in survival time between the groups (p = 0.389). Conclusion: Data relating to technical and clinical success, quality of life and survival were similar in both groups and there were no statistically significant differences

L’œdème cérébral est une complication associée à l’encéphalopathie hépatique (EH) lors d’une insuffisance hépatique chronique (cirrhose du foie). Présentement, l’origine de sa pathogenèse, vasogénique (rupture de la barrière hémato-encéphalique (BHE)) ou cytotoxique (prise anormale d’ions), n’a pas encore été déterminée. Il a été démontré que le co-transporteur Na-K-Cl (NKCC1) du côté luminal des microvaisseaux sanguins cérébraux (CMV) joue un rôle dans le développement de l’œdème cérébral dans des modèles d’ischémie où la bumetanide, un inhibiteur de NKCC, atténue l’œdème cérébral. Deux modèles d’EH ont été utilisés pour cette étude i) la ligature de la voie biliaire (BDL) qui présente l’hyperammoniémie chronique, l’œdème cérébral et le stress oxydatif systémique ; ii) l’anastomose portocave (PCA) qui présente de l’hyperammoniémie chronique seulement. Les buts du projet étaient de: i) définir l’origine du développement de l’œdème chez les rats BDL en étudiant l’extravasation de macromolécules, les jonctions serrées et l’activation des métalloprotéinases matricielles de la BHE; ii) observer les effets de l’hyperammoniémie chronique indépendamment sur la BHE chez les rats PCA; iii) évaluer le rôle de l’hyperammoniémie et du stress oxydatif et iv) étudier le rôle du NKCC1 dans les CMV dans la pathogenèse de l’œdème cérébral. Les résultats du projet démontrent que l’œdème est d’origine cytotoxique chez les rats BDL et que l’intégrité de la BHE est conservée chez les rats PCA malgré l’hyperammoniémie. L’expression génique du NKCC1 est associée à l’œdème mais pas son expression protéique et sa phosphorylation. Enfin, l’étude démontre que l’hyperammoniémie et le stress oxydatif indépendant ne jouent pas un rôle dans la pathogenèse de l’œdème mais suggère qu’ils y aient un effet synergique. / Brain edema is a complication associated with hepatic encephalopathy (HE) due to chronic liver failure (cirrhosis). It is unclear whether brain edema is of vasogenic (blood brain barrier (BBB) breakdown) or cytotoxic (abnormal cellular uptake of ions) origin. It has been demonstrated that the Na-K-Cl cotransporter (NKCC1) located on the luminal side of the cerebral microvessels (CMV) is implicated in the pathogenesis of brain edema in animal models of ischemia and that the administration of bumetanide, an inhibitor of NKCC, attenuates brain water increase. Two distinct animal models of chronic liver failure and HE are used in the present study; 1) bile duct ligation (BDL) where brain edema, chronic hyperammonemia and systemic oxidative stress are observed; 2) portacaval anastomosis (PCA) where only chronic hyperammonemia is observed. The aims of the study were to: i) determine the origin of brain edema in BDL rats measuring brain extravasation, tight junctions expression and matrix metalloproteinase activation; ii) observe the effects of chronic hyperammonemia on the BBB in PCA rats; iii) study the role of oxidative stress and hyperammonemia; iv) evaluate the role of NKCC in CMV in the pathogenesis of brain edema. The results of the study determined that brain edema in BDL rats is of cytotoxic origin and chronic hyperammonemia independently has no effect on the BBB. An increase of NKCC1 mRNA is associated with brain edema but protein expression and phosphorylation are not. Furthermore, hyperammonemia and oxidative stress independently are not implicated in the development of brain edema however a synergistic effect between the two pathogenic factors in BDL rats remains a possibility.

Introdução: A maioria dos pacientes acometidos pela neoplasia que envolve a confluência biliopancreática é diagnosticada em fase avançada. A Colangiopancreatografia Retrógrada Endoscópica (CPRE) é o método de escolha para a drenagem da via biliar obstruída. Todavia, existe um índice de insucesso em torno de 10%. Nesses casos, técnicas alternativas serão aplicadas, como drenagem percutânea trans-hepática e drenagens cirúrgicas. Objetivo: Avaliar o sucesso técnico, clínico, qualidade de vida e sobrevida da drenagem biliar pela cirurgia convencional e técnica endoscópica ecoguiada em pacientes portadores de neoplasia maligna da confluência biliopancreática. Método: No período de abril de 2010 a setembro de 2013, foram estudados 32 pacientes portadores de neoplasia maligna da confluência biliopancreática. Todos os que foram incluídos nesse estudo apresentaram falha na drenagem biliar por CPRE. Três deles foram excluídos por insucesso técnico (falha na confecção da anastomose hepaticojejunal e da formação da fístula coledocoduodenal ecoguiada). O Grupo I foi formado por 15 pacientes submetidos à Hepaticojejunostomia (HJT) em \"Y\" de Roux e derivação gastrojejunal. O Grupo II foi formado por 14 pacientes submetidos à coledocoduodenostomia ecoguiada (CDT). O sucesso clínico foi avaliado pela queda da bilirrubina sérica total em mais de 50% nos sete primeiros dias após o procedimento. A qualidade de vida foi avaliada pelo questionário SF-36 e a sobrevida pela curva de Kaplan-Meier. Resultados: O sucesso técnico foi de 93,75% (15/16) no Grupo I e de 87,5% (14/16) no Grupo II (p = 0,598). O sucesso clínico ocorreu em 14 (93,33%) pacientes pertencentes ao Grupo I e em 10 (71,43%) do Grupo II. Não houve diferença estatisticamente significativa (p = 0,169). O comportamento médio dos escores de qualidade de vida foi estatisticamente igual entre as técnicas ao longo do seguimento (p > 0,05 Técnica * Momento). Houve alteração média estatisticamente significativa ao longo do seguimento nos escores de capacidade funcional, saúde física, dor, aspectos sociais, aspectos emocionais e saúde mental em ambas as técnicas (p < 0,05). O escore de saúde mental foi, em média, estatisticamente maior nos do Grupo II (CDT) em todos os momentos (p = 0,035). O tempo médio de sobrevida daqueles pertencentes ao Grupo I foi de 82,27 dias e os do Grupo II, de 82,36 dias. Sessenta por cento dos pertencentes ao Grupo I faleceram até 90 dias após o procedimento cirúrgico. Por outro lado, 42,9% dos submetidos à CDT faleceram no mesmo período. Não houve diferença estatisticamente significativa no tempo de sobrevida entre os Grupos (p = 0,389). Conclusão: Os dados relacionados aos sucessos técnico, clínico, qualidade de vida e sobrevida foram semelhantes em ambos os grupos, não se verificando diferença estatisticamente significativa / Introduction: Most patients with neoplasm in the biliopancreatic junction are diagnosed at an advanced stage. Endoscopic retrograde cholangiopancreatography (ERCP) is the method of choice for drainage of obstructed biliary tract. However, there is a failure rate of about 10%. In such cases, alternative techniques, such as, percutaneous transhepatic drainage and surgical drainage are applied. Aim: To evaluate the technical and clinical success, quality of life and patient survival of biliary drainage by conventional surgery and endosonography-guided technique in patients with malignant neoplasm of the biliopancreatic junction. Methodology: From April 2010 to September 2013, 32 patients with malignant neoplasm of the biliopancreatic junction were studied. All patients included in this study had failed biliary drainage by ERCP. Three patients were excluded due to technical failure (failure in the construction of hepatico-jejuno anastomosis and formation of endosonography-guided choledochoduodenal fistula). Group I comprised of 15 patients who underwent Roux-en-Y hepaticojejunostomy (HJT) and gastrojejunal bypass. Group II consisted of 14 patients who underwent endosonography-guided choledochoduodenostomy (CDT). Clinical success was assessed by the decrease of more than 50% in total serum bilirubin in the first seven days after the procedure. Quality of life was assessed by SF-36 questionnaire and survival by Kaplan-Meier curve. Results: Technical success rate was 93.75% (15/16) in group I and 87.5% (14/16) in group II (p = 0.598). Clinical success occurred in 14 (93.33%) patients in group I and 10 (71.43%) patients in group II. There was no significant statistically difference (p = 0.169). The average quality of life score were statistically equal between the techniques during follow-up (p > 0.05 * Technical Moment). There were statistically significant mean changes during follow-up of functional capacity score, physical health, pain, social functioning, emotional and mental health aspects in both techniques (p < 0.05). The mental health score was, on average, statistically higher in group II (CDT) at all times (p = 0.035). The median survival time of patients in group I was 82.27 days and Group II patients was 82.36 days. Sixty percent of patients in group I died within 90 days after the surgical procedure. On the other hand, 42.9% of the patients who underwent CDT died in the same period. There was no statistically significant difference in survival time between the groups (p = 0.389). Conclusion: Data relating to technical and clinical success, quality of life and survival were similar in both groups and there were no statistically significant differences

<p>The main goal of this thesis research is to expand the range of unique properties of phase transforming cellular materials (PXCMs), a new class of architected materials, and to extend their applicability both in the engineering disciplines and in the medical field. A novel aspect of PXCMs is their unique energy dissipation during loading via a snapping mechanism associated with a geometric transition between one stable configuration to another stable configuration at the unit cell level. Phase transformation is analogous to displacive transformations, such as martensitic transformations in shape memory alloys, with no change in configurational entropy. To accomplish this goal, three problem areas are addressed with the first exploring the effects of length scale as added structural hierarchy on material properties and energy dissipation, the second providing an analysis of the durability of architected materials via a novel additive manufacturing method, and the third, an extension into the medical field. Two examples are provided that demonstrate the effects of length scale as added structural hierarchy on material properties, and a machine learning approach for the feasible design of materials with additional levels of structural hierarchy is presented. A simple design approach coupled with a novel additive manufacturing method is discussed for the design of architected materials with high durability. Lastly, a concept for de-clogging bile stents via a temperature driven, shape-memory mechanism inspired by peristaltic locomotion in the human esophagus is presented.</p>