Sustained decreases of the Blood Oxygenation Level Dependent (BOLD) signal have been observed in unstimulated areas of the cortex and sub-cortex in response to certain stimuli. However, the physiological basis of these task-based negative BOLD responses or NBRs is not as well understood as that of the more common positive BOLD response (PBR) employed for mapping functional brain activity. Low signal-to-noise ratio (SNR), high variability, and methodological discrepancies have led to competing results, and to this date, the NBR’s physiological and neuronal bases are still debated. The inherently low SNR of the functional Magnetic Resonance Imaging (fMRI) techniques employed to measure related functional changes of cerebral blood flow (CBF), cerebral blood volume (CBV) and cerebral metabolic rate of oxygen consumption (CMRO2) is also further reduced in regions of NBR and hampers a comprehensive, non-invasive investigation of its underlying physiology. To this effect, the dissertation attempts to bring about a better understanding of the NBR by enhancing the fidelity and sensitivity of techniques measuring the associated changes in CBF and CBV. Vascular contributions to surround NBR of likely neuronal origin in the human visual cortex have hence been investigated in relation to those of a simultaneously occurring, spatially adjacent PBR. Variants of Arterial Spin Labeling (ASL) and VAscular Space Occupancy (VASO) known for their higher sensitivity of detecting functional changes in CBF and CBV, respectively, at 3 T, were carefully optimized and employed in conjunction with a multi-echo center-out Echo Planar Imaging (EPI) readout called ME-DEPICTING. The functional sensitivities of the CBF and CBV signals measured concurrently with PBR in this manner were first compared with those of a standard ME-EPI, the current workhorse for fMRI measurements. The much shorter echo times of ME-DEPICTING were found to substantially reduce BOLD contaminations and improve the sensitivity of the respective CBF and CBV measurements while providing concurrent BOLD measurements of sensitivity equivalent to that of ME-EPI. The more sensitive and reliable ME-DEPICTING data were then employed for a thorough investigation of the functional changes in CBF and CBV (and to a smaller extent, CMRO2) occurring in regions of both PBR and NBR. The improvement in SNR allowed for a much better characterization of the CBF and CBV signals than previously accomplished. The findings confirm the undeniable role of vasoconstriction in the NBR and provide a clearer understanding of the shapes of the vascular signals and their coupling ratios, indicating a more arterial and deeper laminar origin of the NBR compared to PBR. Moreover, the study sheds light on the controversial vascular contribution to the post-stimulus undershoot in PBR. Lastly, the application of a neuronal flow-metabolism model suggests intriguing differences in the concentration of inhibitory neurons and/or their control of CBF in regions of NBR. These significant findings contribute to the current understanding of the vascular physiology of the BOLD responses and open up many exciting possibilities for further research.

Cerebrovascular diseases are by far the largest causes of death in the UK, as well as one of the leading causes of adult disability. The brain's healthy function depends on a steady supply of oxygen, delivered through the microvasculature. Cerebrovascular diseases, such as stroke and dementia, can interrupt the transport of blood (and hence oxygen) rapidly, or over a prolonged period of time. An interruption in flow can lead to ischaemia, with prolonged interruptions leading to tissue death and eventual brain damage. The microvasculature plays a key role in the transport of oxygen and nutrients to brain tissue; however, its role in diseases such as dementia is poorly understood, primarily due to the inability of current clinical imaging techniques to resolve microvessels, and due to the complexity of the underlying microvasculature. Therefore, in order to understand cerebrovascular diseases, it is necessary to be able to resolve and understand the microvasculature. In particular, generating large-scale models of the human microvasculature that can be linked back to contemporary clinical imaging is important in helping plug the current imaging gap that exists. A novel statistical model is proposed here that generates such large-scale models efficiently. Homogenization theory is used to generate a porous continuum capillary bed (characterised by its permeability) that allows for the efficient scaling up of the microvasculature. A novel order-based density-filling algorithm is then developed which generates morphologically accurate penetrating arterioles and venules, also demonstrating that the topology of the vessels only has a minor influence on CBF compared to diameter. Finally, the capillary bed and penetrating vessels are coupled into a large voxel-sized model of the microvasculature from which pressure and flux variations through the voxel can be analysed. A decoupling of the pressure and flux, as well as a layering of flow, was observed within the voxel, driven by the topology of the penetrating vessels. Micro-infarctions were also simulated, demonstrating the large local effects they have on the pressure and flux, whilst only causing a minor drop in CBF within the voxel.

Indiana University-Purdue University Indianapolis (IUPUI) / Regulation of coronary blood flow is a highly dynamic process that maintains the delicate balance between oxygen delivery and metabolism in order to preserve cardiac function. Evidence to date support the finding that Kv and Cav1.2 channels are critical end-effectors in modulating vasomotor tone and blood flow. Yet the role for these channels in the coronary circulation in addition to their interdependent relationship remains largely unknown. Importantly, there is a growing body of evidence that suggests obesity and its pathologic components, i.e. metabolic syndrome (MetS), may alter coronary ion channel function. Accordingly, the overall goal of this investigation was to examine the contribution coronary Kv and Cav1.2 channels to the control of coronary blood flow in response to various physiologic conditions. Findings from this study also evaluated the potential for interaction between these channels, i.e. electromechanical coupling, and the impact obesity/MetS has on this mechanism. Using a highly integrative experimental approach, results from this investigation indicate Kv and Cav1.2 channels significantly contribute to the control of coronary blood flow in response to alterations in coronary perfusion pressure, cardiac ischemia, and during increases in myocardial metabolism. In addition, we have identified that impaired functional expression and electromechanical coupling of Kv and Cav1.2 channels represents a critical mechanism underlying coronary dysfunction in the metabolic syndrome. Thus, findings from this investigation provide novel mechanistic insight into the patho-physiologic regulation of Kv and Cav1.2 channels and significantly improve our understanding of obesity-related cardiovascular disease.

Tikslas: Išanalizuoti kvėpavimo sulaikymo įtaka blauzdos raumenų arterinei kraujotakai. Uždaviniai: 1. Nustatyti sportuojančių ir nesportuojančių merginų blauzdos raumenų arterinės kraujotakos kaitą sulaikius kvėpavimą iki negalėjimo. 2. Nustatyti arterinio kraujo spaudimo dažnių rodiklių kaita sulaikius kvėpavimą. Tyrimo metodai: Arterinio kraujo spaudimo (AKS) matavimai Korotkovo metodu ir arterinės kraujotakos registracija – veninės okliuzinės pletizmografijos metodu. Tyrimo organizavimas: Tyrime dalyvavo dešimt sportuojančių (adaptuotų greitumo – jėgos fiziniams krūviams) ir aštuoniolika nesportuojančių merginų. Arterinė kraujotaka blauzdos raumenyse ir AKS buvo registruojami po 20 min adaptacijos ramybės būsenoje, bei sulaikius kvėpavimą ir atsigavimo metu. Buvo atliekami du kvėpavimo sulaikymai iki negalėjimo. Rezultatai. Pirmojo kvėpavimo sulaikymo metu sportuojančių merginų kraujotaka mažėjo ir pabaigoje ji sumažėjo iki 1,5±0,3ml/100 ml/min. Atsigavimo metu kraujotakos intensyvumas pirmąją minutę didėjo ir prieš antrąjį sulaikymą beveik pasiekė pradinį lygį. Arterinės kraujotakos intensyvumas antrojo kvėpavimo sulaikymo metu didėjo, tačiau praėjus 45sek pradėjo nežymiai mažėti. Atsigavimo metu kraujotakos intensyvumas sumažėjo analogiškai, kaip ir po pirmo sulaikymo. Atsigavimo pabaigoje pradėjo didėti link pradinio lygio. Nesportuojančių merginų pirmojo kvėpavimo sulaikymo metu kraujotaka mažėjo ir pabaigoje ji sumažėjo iki 1,6±0,38ml/100 ml/min (p<0.05)... [toliau žr. visą tekstą] / Research aim - is to assess influence of arterial blood flow changes in the calf muscles during breathing stop. Research tasks – 1. Establish changes in the calf muscle blood flow before, during and after breathing stop for athletic and non-athletic girls. 2. Establish changes in arterial blood pressure before, during and after breathing stop for athletic and non-athletic girls. Research methods – arterial blood flow changes using venous occlusive plethysmography method, arterial blood pressure using Korotkoff sounds method. Research organization – The study involved 10 athletic (adapted to speed - strength exercise) and 18 non-athletic girls. The examinations were conducted at a room temperature of 18–20O C with the patient in a sitting position. Each girl was introduced with instruction of the research and explained to them, how everything will work. Arterial blood flow in the calf muscle and arterial blood pressure was recorded after 20 min of adaptation at rest, during breathing stop and at recovery time. Research was made of two breathing stop. Recovery from breathing stop was recorded 5min. The blood flow in the calf was determined by venous occlusion plethysmography. Research results – Athletic girls arterial blood flow during first breathing going down and in the end of first breathing stop was stop 1,5±0,3ml/100 ml/min. For non-athletic girls it was similar 1,6±0,38ml/100 ml/min. But during second breathing stop for athletic girls arterial blood flow was 2,4±0,7... [to full text]

La mesure et le contrôle du pouls et du flux sanguin en continu sont d'importants paramètres pour l'évaluation de signes essentiels physiologiques sur la condition de santé d'un individu. Les dispositifs commerciaux existants, ainsi que les méthodes de recherche ou utilisées dans le milieu médical exigent un bon contact électrique ou optique pour obtenir cette mesure en continu. Pendant ces travaux de recherche, une méthode originale non invasive de mesure du rythme cardiaque fondée sur la perturbation localisée d'un champ magnétique au passage du flux sanguin a été développée, permettant l'acquisition des signaux à travers les vêtements, la transpiration, les salissures ou autres polluants dans l'environnement proche du capteur. Cette méthode est appelée la Signature Sanguine par Modulation Magnétique (MMSB) et les mesures ont été accomplies sur de multiples individus. Le système a été modélisé mathématiquement et simulé dans un environnement multiphysique, puis validé par l'utilisation des données expérimentales. Les résultats de mesure, en utilisant la méthode MMSB, pour le pouls et le flux sanguin ont été comparés et se trouvent bien corrélés, avec les résultats obtenus grâce à d'autres instruments. De plus, deux dispositifs ont été développés et sont en cours de commercialisation, pour des applications de vie quotidienne / Continuous pulse rate, blood pressure and blood flow monitoring are important for the assessment of physiological vital signs as these are able to provide continuous feedback on the health condition of an individual. Existing commercial, medical and research methods to continuously acquire such these physiological vital signs require good electrical or optical contact. During this research, a magnetic based sensing method, at room temperature, for blood pulse, flow and pressure is developed to achieve data acquisition through fabric, environmental contaminants and body-fluids. This method is named Modulated Magnetic Signature of Blood (MMSB) and physical measurements were conducted on multiple subjects, mathematically modelled and simulated in a multi-physics environment with verification through use of measurement data. Measurement results, using MMSB, for blood pressure and blood flow were compared, and found to be well correlated, with lifestyle device and medical research instruments respectively. In addition, two devices are developed, and are in the midst of commercialization, to support lifestyle applications

Name of the thesis Reactive oxygen species and their neurophysiological role Aim of the thesis Aim of the theoretical part is to provide overview of reactive oxygen species (ROS) and show their place in organism - posstive and necessary effects for the organism on the one hand and source of serious diseases on the other hand. Futhermore, the theoretical part deals with the restoration balance between the production of free radicals and antioxidants protection. Theoretical part also deals with substance FeTTPS. Aim of the experimental part is to determinate whether the application of FeTTPS affects cerebral blood flow during trancallosal stimulation with increasing frequency. Futhermore, to determinate whether the applicatication of this substance affects the slope of the curve and threshold of evoked potencials and number and duration of afterdischargers. Research method The research took place at the premises of Onstitue of Physiology, Academy of Sciences, Czech Republic. Experiments were carried out on laboratory albine Wistar rats. General anesthesia was performed to rats, stimulating and sensing electrodes were implated in epidural area of sensorimotoor cortex and Laser Doppler flow probe was implated into the contralateral hemisphere. In the first part of experiment included 11 animals. We...

INTRODUÇÃO: O infarto agudo do miocárdio está associado à hiperativação simpática e diminuição do fluxo sanguíneo muscular (FSM). Por outro lado, tem sido documentado que o treinamento físico promove importantes adaptações autonômicas e vasculares no indivíduo. O objetivo deste estudo foi testar a hipótese de que o treinamento físico diminuiria a atividade nervosa simpática muscular (ANSM) e aumentaria o FSM em repouso e durante o exercício físico em pacientes com Síndrome Isquêmica Miocárdica Instável (SIMI). MÉTODOS: Foram incluídos no estudo, 63 pacientes internados na Unidade Clínica de Coronariopatia Aguda diagnosticados com SIMI. Um mês após o evento isquêmico, 51 pacientes continuaram o seguimento e foram alocados, consecutivamente, em 2 grupos: treinamento físico (SIMI-TF, n=25, 54±1 anos), e sedentário (SIMI-Sed, n=26, 52±2 anos). Ao final do estudo, 14 pacientes do grupo SIMI-TF e 20 pacientes do grupo SIMI-Sed finalizaram o protocolo experimental. Esses pacientes foram comparados a um grupo controle saudável (n=13, 49±1anos). A ANSM foi medida pela técnica de microneurografia. O FSM foi avaliado por pletismografia de oclusão venosa, a pressão arterial (PA) foi medida pelo método oscilométrico indireto e a frequência cardíaca pelo eletrocardiograma. Todas as avaliações foram realizadas no basal, durante a fase de internação hospitalar e, no basal e durante 3 minutos de exercício físico de preensão de mãos (30% da contração voluntária máxima) no período de seguimento do estudo (1º., 3º.e 7º. mês após o evento isquêmico). O treinamento físico foi realizado em cicloergômetro, 3 vezes por semana, durante 6 meses. RESULTADOS: Durante a fase de internação hospitalar, a ANSM basal foi significativamente maior (65±2 vs. 32±2 disparos/100batimentos, p<0,001) e a condutância vascular no antebraço (CVA= FSM/PAmédia) foi significativamente menor (1,91±0,1 vs. 2,99±0,38 unidades, p<0,001) no grupo SIMI em relação ao grupo Controle. Comportamento semelhante foi observado 1 mês após o evento isquêmico, a ANSM continuou aumentada (64±3 vs. 62±4 vs. 32±2 disparos/100batimentos, p<0,001, respectivamente) e a CVA diminuída (1,73±0,1 vs. 1,72±0,1 vs. 2,99±0,4 unidades, p<0,001, respectivamente) nos grupos SIMI-Sed e SIMI-TF em relação ao grupo Controle. Durante o exercício de preensão de mãos, os níveis de ANSM foram maiores (71±4 e 69±4 vs. 43±3 disparos/100batimentos, p<0,001, respectivamente) e a CVA foi menor (1,60±0,1 e 1,59±0,2 vs. 3,53±0,47 unidades, p<0,001, respectivamente), nos grupos SIMI-Sed e SIMI-TF em relação ao grupo Controle. Após o treinamento físico, a ANSM basal diminuiu no grupo SIMITF (62±4 vs. 40±3 disparos/100batimentos, p=0,02), atingindo níveis semelhantes ao grupo Controle (40±3 vs. 32±2 disparos/100batimentos, p=0,24, respectivamente). Durante o exercício físico, a ANSM diminuiu no grupo SIMI-TF (72±5 vs. 60±5 disparos/100batimentos, p<0,001). Porém, a CVA não foi significativamente modificada tanto no basal como durante o exercício no grupo SIMI-TF. Nenhuma alteração significativa foi observada na ANSM e CVA do grupo SIMI-Sed, tanto em repouso como durante o exercício. CONCLUSÕES: Em pacientes com SIMI, o treinamento físico normalizou a ANSM basal e diminuiu seus níveis durante o exercício, porém, não modificou o FSM. Como a ativação simpática está relacionada com pior prognóstico, nossos resultados ressaltam a importância clínica do treinamento físico em pacientes após SIMI / Introduction: The myocardial infarction is associated with sympathetic hiperactivation and reduced forearm blood flow (FBF). On the other hand, the exercise training leads to important autonomic and vascular adaptations. The purpose of this study was to test the hypothesis that exercise training would decrease the muscle sympathetic nerve activity (MSNA) and would increase the FBF at rest and during exercise in patients with acute coronary syndrome (ACS). Methods: Sixty-three patients admitted to the coronary intensive care unit with ACS were studied. One month after ischemic event, 51 patients continued the follow-up study and were allocated consecutively in two groups: exercise training (ACS-ET, n=25, 54±1 years) and sedentary (ACSSed, n=26, 52±2 years). At the end of the study, 14 patients in the group ACS-ET and 20 patients in the group ACS-Sed concluded the experimental protocol. These patients were compared to a control group of healthy subjects (n=13, 49±1 years). The MSNA was measured by microneurography technique. The FBF was measured by venous occlusion plethysmography, the blood pressure (BP) was measured by indirect oscillometric method and the heart rate was measured by electrocardiogram. All measurements were done at rest condition during inpatient phase and at rest condition and during 3 minutes of handgrip exercise (30% of maximum voluntary contraction) during outpatient follow-up (1st, 3rd and 7th months after the ischemic event). The exercise training was performed on a cycle ergometer 3 times per week for 6 months. RESULTS: During inpatient phase, the MSNA at rest was significantly higher (65±2 vs. 32±2 bursts/100heart beats, p<0.001) and forearm vascular conductance (FVC=FBF/mean BP) was significantly lower (1.91±0.1 vs. 2.99±0.38 units, p<0.001) in ACS group when compared to control group. One month after the ischemic event, the MSNA remained significantly higher (64±3 vs. 62±4 vs. 32±2 bursts/100 heart beats, p<0,001) and the FVC continue significantly lower (1.73±0.1 vs. 1.72±0.1 vs. 2.99±0.4 units, p<0,001) in the ACS-Sed and ACS-ET groups when compared to the control group. During handgrip exercise, the MSNA levels were significantly higher (71±4 and 69±4 vs. 43±3 bursts/100heart beats, p <0.001, respectively) and FVC levels were significantly lower (1.60±0.1 and 1.59± 0.2 vs. 3.53 ± 0.47 units, p <0.001, respectively) in the ACS-Sed and ACS-ET groups when compared to the control group, respectively. After exercise training, the MSNA at rest decreased significantly in the group ACS-ET (62±4 vs. 40±3 bursts/100 heart beats, p=0.02), reaching similar levels to those found in the control group (40±3. vs. 32±2 burts/100 heart beats, p= 0.24, respectively). During handgrip exercise the MSNA decreased significantly in ACS-ET group (72±5 vs. 60±5 bursts/100 heart beats, p <0.001). However, the FVC was not significantly changed at rest and during exercise in ACS-ET group. No significant change was observed in MSNA and FVC in ACS-Sed group at rest and during exercise. CONCLUSIONS: In patients with ACS, the exercise training normalized the MSNA at rest and decreased their levels during exercise, but no change was observed in the FVC. Since sympathetic activation is related to poor prognosis, our results highlight the clinical importance of ET in patients with ACS

Imagem por ressonância magnética tem sido um dos principais métodos para a aquisição de imagens para diagnósticos na medicina, em especial para a obtenção de medidas do cérebro. Apesar de se mostrar muito eficiente, o método atualmente utilizado para a realização da ressonância em hospitais e centros de diagnósticos, em alguns casos, necessita da aplicação de um contraste de gadolínio intravenoso. Essa injeção do contraste pode mostrar-se um tanto quanto invasivo, podendo em alguns casos resultar em algumas reações indesejadas nos pacientes. Em vista disso, um método que tem sido bastante estudado recentemente e muito promissor é o de Arterial Spin Labeling (ASL). Este método tem como sua principal vantagem o fato de não ser invasivo e de possibilitar a quantificação da perfusão sanguínea cerebral (CBF). No presente trabalho, foi feita uma otimização do contraste na aquisição das fases mais tardias da metodologia de ASL em múltiplas fases. Isso foi feito através de uma modulação do angulo de flip e é particularmente importante para a análise das imagens de pacientes com problemas neurovasculares, principalmente aqueles associados ao retardo nos tempos de trânsito do sangue arterial. Também, foi realizada toda a obtenção e processamento de dados para a avaliação da perfusão sanguínea cerebral utilizando o método proposto. / Magnetic resonance imaging has been one of the major methods to acquire images for medical diagnoses, specially, for obtaining brain images. Although the major method using magnetic resonance used today has high efficiency, in some cases it needs an injection of intravascular contrast agent, like gadolinium. This contrast agent application can be a lot invasive for the patient, in extremes cases resulting to allergic reactions the patient. Therefore, a method that has been studied recently and is very promising is the Arterial Spin Labeling (ASL). This method has the major advantage the feature that it is completely non invasive for the patient and it allows to quantify the perfusion value. In this work, it was implemented an optimization of the contrast in the late phases of ASL multiphase acquisition. It was made using a modulation of the flip angle and it is critical to analyze images from patients with some neurovascular disease, especially those associated with arterial blood transit time delay. Besides that, it was made all data acquisition and data processing for the brain perfusion evaluation using the proposed method.

O uso indiscriminado de recursos ergogênicos como os esteróides anabolizantes vêm se tornando um problema crescente em diversos segmentos da população, além do meio atlético, tendo como finalidade a obtenção de melhor desempenho físico ou simplesmente melhor aparência física, porém muitas vezes sem a preocupação com os riscos dos efeitos colaterais promovidos por esta prática. No presente trabalho estudamos os efeitos da associação do uso de doses suprafisiológicas de esteróides anabolizantes e do treinamento físico aeróbio de natação sobre o fluxo sangüíneo coronário de ratos normotensos, verificando a participação da adenosina como um dos possíveis mecanismos de regulação deste fluxo, além de alterações estruturais cardíacas que poderiam influenciar na perfusão sangüínea cardíaca. Ao observarmos somente o efeito do treinamento físico, verificamos que o mesmo foi eficaz em promover adaptações benéficas ao sistema cardiovascular, como a presença de hipertrofia cardíaca fisiológica e melhora no fluxo sangüíneo coronário em repouso, provavelmente mediado por uma maior formação de adenosina circulante e cardíaca. O uso de esteróides anabolizantes associado ao treinamento físico atenuou os efeitos benéficos promovidos pelo treinamento, observando-se a presença de hipertrofia cardíaca acompanhada por redução de débito cardíaco e fluxo sangüíneo coronário, mediado por menor produção de adenosina circulante, além de prejuízo na resposta vasodilatadora à acetilcolina, demonstrando uma provável disfunção endotelial e redução na densidade capilar cardíaca, caracterizando desta forma, um quadro patológico / The abusive use of ergogenic resources as the anabolic steroid became an increasing problem in several segments of the population, beyond the athletical way, searching for better performance or physical appearance, without being worried about the risks of the collateral effects promoted by this practice. In the present work we studied the effects of the use of supraphysiological doses of anabolic steroids associated with aerobic swimming training on the coronary blood flow of normotensive rats, investigating the participation of adenosine as one of the possible mechanisms of blood flow regulation, besides the cardiac structural alterations that could influence the coronary blood perfusion. The effect of the physical training was efficient to promote beneficial adaptations of the cardiovascular system, as the presence of physiological cardiac hypertrophy and improves the coronary blood flow at rest, probably mediated by a higher circulating and cardiac adenosine production. The use of anabolic steroids associated with the swimming training attenuated the beneficial effect promoted by training, being observed the presence of cardiac hypertrophy, followed by reduction of cardiac output and coronary blood flow, mediated by lower circulating adenosine production, besides the impairment of the vasodilator response to the acetylcholine, demonstrating a probable endothelial dysfunction and reduction of the cardiac capillary density, characterizing in this way, a pathological state

Orientador: Fernando Gomes Romeiro / Resumo: Aminoácidos de cadeia ramificada aumentam a perfusão cerebral de pacientes com encefalopatia hepática (EH), mas o aminoácido responsável por esse aumento e os mecanismos envolvidos ainda não são conhecidos. Este estudo comparou a perfusão cerebral e a melhora clínica durante a suplementação de leucina ou isoleucina. Após a randomização, 27 indivíduos com cirrose e EH receberam suplementos de leucina ou isoleucina por um ano. Exames de tomografia computadorizada por emissão de fóton único (SPECT) e cintilografia cerebral dinâmica (DBS) foram realizados antes do estudo e após 1, 8 e 12 meses de suplementação. Apenas o grupo que recebeu isoleucina teve aumento da perfusão cerebral aos 8 meses de tratamento pelo exame de SPECT e pela cintilografia (p<0,001 e p = 0,05, respectivamente), também observado pelo SPECT aos 12 meses de suplementação (p < 0,05). O aumento do fluxo cerebral foi associado a melhora da EH aos 8 e 12 meses de suplementação (p=0,008 e 0,004, respectivamente), porém essa melhora não foi observada no grupo que recebeu leucina (p=0,313 e 0,055, respectivamente). A suplementação com isoleucina obteve melhor impacto na restauração da perfusão cerebral em pacientes com EH. / Abstract: Branched-chain amino acids increase the brain perfusion of patients with hepatic encephalopathy (HE), but the amino acid and the mechanisms involved are still unknown. This study compared brain perfusion and clinical improvement during leucine or isoleucine supplementation. After randomization, 27 subjects with cirrhosis and HE received leucine or isoleucine supplements for one year. Brain single photon emission computed tomography (SPECT) and dynamic brain scintigraphy (DBS) were performed pretreatment and at 1, 8 and 12 months of supplementation. Brain perfusion was increased only in the isoleucine group at 8 months of treatment by both SPECT and DBS (p<0.001 and p = 0.05, respectively) and by SPECT at the 12th month (p < 0.05). This was associated with hepatic encephalopathy improvement at 8 and 12 months (p=0.008 and 0.004, respectively), which was not observed in the leucine group (p=0.313 and 0.055, respectively). Isoleucine supplementation achieved a better impact on brain perfusion restoration in HE. / Doutor