La navigation des axones sur de longues distances est jalonnée de zones de choix, entraînant des changements de direction pour suivre des trajectoires hautement stéréotypées. Dans ce modèle de guidage séquentiel, chaque étape est vue comme essentielle à la suivante. De façon intrigante, quelques exemples suggèrent que le suivi strict de la trajectoire puisse être dispensable pour que les axones atteignent leur destination finale. Nous nous sommes intéressés à cette capacité trajectoire indépendante des axones à localiser leur cible. Pour ce faire, nous avons utilisé deux populations neuronales de la moelle épinière ayant des cibles diamétralement opposées dans l'organisme : les interneurones dorsaux, qui projettent dans le système nerveux central, et les motoneurones ventraux, qui ciblent les muscles en périphérie. Après avoir été déplacés chirurgicalement dans des embryons de poulet, ces deux populations de neurones envoient des axones vers leurs territoires cibles qu'ils atteignent par des trajectoires inédites. Ces observations suggèrent l'existence d'un système de guidage global délivrant aux axones des informations spatiales à large échelle. Outre les signaux moléculaires de guidage bien connus, les signaux bioélectriques sont également des candidats intéressants pour remplir cette fonction. Des champs électriques (CE) ont été détectés dans les embryons en développement et sont connus pour être des vecteurs d'information spatiale. Nous avons testé sur des neurones en culture si des CE comparables à ceux mesurés pendant le développement embryonnaire pourraient guider l'élongation des axones moteurs et d'interneurones dorsaux de poulet. Nous avons trouvé que les deux types d'axones s'orientent en direction de la cathode (-) dans un CE. Cependant, ils présentent des sensibilités significativement différentes aux CE, qui pourraient contribuer à des choix de trajectoires différents in vivo. Ensuite, nous avons observé un effet inhibiteur de la Concanavaline A (ConA) sur la réponse des axones aux champs, indiquant un rôle des récepteurs membranaires connus pour lier la ConA. Nous avons donc réalisé un screen pharmacologique sur des pompes et des canaux ioniques qui se lient à la ConA, conduisant à l'identification des pompes Na+/K+ ATPases comme des candidats prometteurs. Des expériences préliminaires d'invalidation des sous-unités de ces pompes suggèrent qu'elles contribuent à la réponse aux CE et à la navigation axonale in vitro et in vivo. Finalement, nos résultats apportent une vision nouvelle des mécanismes assurant la fidélité et la résilience du guidage axonal, et révèlent la contribution méconnue des signaux bioélectriques et des pompes Na+/K+ ATPases au développement neuronal / Long distance navigation of axons is marked by choice points, instructing highly stereotyped directional changes of axon trajectories. In this stepwise model, each step is thought to be essential for the next one, but intriguingly, examples suggest that pathway experience can be dispensable for axons to reach their final destination. We investigated pathway-independent ability of axons to locate their target, using two populations of spinal cord neurons having drastically different target location in the organism: the dorsal interneurons, which target the central nervous system and ventral motoneurons, which target muscles. After grafting these neurons at ectopic positions in the chicken embryo, both neuron-types were observed to form axons which, remarkably, oriented towards and reached appropriate targets. This suggests that, in the embryo, an overall guidance information might exist that enables the axons to locate positions over large scales. Beside well-studied chemical cues, bioelectric signals are attractive candidates for this function. Electric Fields (EF) were detected in the embryo and reported to encode spatial information. Thus, using in vitro set-ups, we investigated whether EFs in the range of the ones measured in the embryo could influence the navigation of chick motor and dorsal interneuron axons. We found that both axon subsets orient parallel to EFs. Yet, they significantly exhibited different sensitivities, which could contribute to elicit different trajectory choices in vivo. Next, we found that Concanavalin A (ConA) could block axon response to EF, supporting a role of cell surface receptors known to bind to ConA. Thus, we performed a pharmacological screening on ion channels and pumps that bind ConA and identified Na+/K+ ATPases as promising candidates. Preliminary knock-down experiments targeting Na+/K+ ATPases subunits suggest their contribution to CE response and axon navigation in vitro and in vivo. Collectively, our findings should provide novel insights into the mechanisms ensuring axon guidance fidelity and resilience and reveal unknown contributions of bioelectric signals and Na+/K+ ATPases during neuronal development

Obesity is nowadays one of the very topics discussed as a highly serious health problem. This thesis is concerned with the percentage of body fat have student teachers for 1st Primary Schools Faculty of Education, University of South Bohemia in Czech Budejovice and the results are compared with the survey in 2005. Research underwent 114 students, of which 8 were men and 106 women. Measurements were carried out in the months of May to October of 2011. For measuring device was used OMRON BF 300, which uses the method of bioelectrical impedance of the upper limbs. The results show that, compared with research in 2005 there was a slight increase in percent body fat in women and men.

Title: Qualitative diagnostics in fitness center. The aim of the diploma thesis: The aim of the theoretical part of the diploma thesis is to summarize the knowledge about the diagnostic entrance test for motion assumptions in fitness and afterwards to help as a study material for people who are interested in being educated in this department. The aim of the practical part of the diploma thesis is to perform the model situation of the diagnostic entrance test in the fitness center carried out in the presence of 10 certificated personal trainers with many years of experience and then with help of semi-structured dialogs and the overall analysis of the concept of the diagnostic, together with an analysis of their experience with diagnostic entrance test in fitness as a whole. Subsequently these data are compared with the theoretical part of this thesis. Objectives: There was used the method of analyzing specialist literature and qualitative research. The qualitative research was done in the fitness center. Results: The outcome of the project supported the theory that the diagnostic entrance test is still not common part of the work of fitness trainer and commonly implemented diagnostics in fitness does not match the theoretical principles of diagnostics, but it is sufficient for the purposes of...

Made available in DSpace on 2014-12-17T15:14:45Z (GMT). No. of bitstreams: 1 ClaudiaPTC.pdf: 3289641 bytes, checksum: e41c19b786c3a7976dfecbc61abd2ca4 (MD5) Previous issue date: 2007-10-05 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / In the 20th century, the acupuncture has spread on occident as a complementary practice of heath care. This fact has motivated the international scientific community to invest in research that seek to understand why acupuncture works. In this work we compare statistically volt age fluctuation of bioelectric signals caught on the skin at an acupuncture point (IG 4) another nearby on acupuncture point. The acquisition of these signals was performed utilizing an electronic interface with a computer, which was based on an instrumentation amplifier designed with adequate specifications to this end. On the collected signals from a sample of 30 volunteers we have calculated major statistics and submitted them to pairing t-test with significance leveI a = O, 05. We have estimated to bioelectric signals the following parameters: standard deviation, asymmetry and curtose. Moreover, we have calculated the self-correlation function matched by on exponential curve we have observed that the signal decays more rapidly from a non-acupoint then from an acupoint. This fact is an indicative of the existence of information in the acupoint / Ao longo do s?culo XX o uso da acupuntura passou a se disseminar no mundo Ocidental como pr?tica complementar de sa?de. Este fato tem motivado a comunidade cient?fica internacional a investir em pesquisas que buscam compreender por que a acupuntura funciona. Nesta disserta??o comparamos estatisticamente a flutua??o de voltagem de sinais bioel?tricos captados sobre a pele em um ponto de acupuntura (IG 4) e outro ponto pr?ximo de n?o-acupuntura. A aquisi??o desses sinais foi realizada utilizando uma interface eletr?nica com um computador, a qual foi baseada em um amplificador de instrumenta??o projetado com as especifica??es adequadas a este fim. Sobre os sinais coletados de uma amostra de 30 volunt?rios calculamos as estat?sticas relevantes e as submetemos ao teste t-pareado com n?vel de signific?ncia a = 0,05. Estimamos para o sinal bioel?trico as seguintes grandezas: desvio padr?o, assimetria e curtose. Al?m disso, calculamos a fun??o de auto-correla??o que foi ajustada por uma curva exponencial. Observamos que o sinal decai mais rapidamente no n?o-acuponto do que no acuponto. Tal fato ? um indicativo da presen?a de informa??o no acuponto

Title: Comparison of individual methods of basal metabolism determination Objectives: The aim of the work is to compare the individual methods of basal metabolism. These values were measured by indirect calorimetry, plethysmography, bioelectric impedance and predictive equations. Methods: The research was attended by 31 people, including eight men and twenty-three women. All participants of my research were aged 21-30 years. None of the participants was a professional athlete, they were all healthy and none of the women were pregnant or had menstruation. The indirect calorimetry, bioelectronics impedance device Tanita MC - 980 and BOD POD were used to collect the data. Basal metabolic rates were calculated from the prediction equations by Harris & Benedict, Fleisch's equation and Schofield's equation using measured anthropometric values. Results: The results of the methods that have been used for this group of people vary, but the difference is not significant. If we choose as a reference method indirect calorimetry, we can't replace it by any other method. The results for other methods are not significantly different, so we can replace one method with another, except indirect calorimetry. From calculations, we also found out that fat free mass greatly influences the results of basal metabolic rate...

Biofuel production via fermentation is produced primarily by fermentation of simple sugars. Besides the sugar fermentation route, there exists a promising alternative process that uses syngas (CO, H2, CO2) produced from biomass as building blocks for biofuels. Although syngas fermentation has many benefits, there are several challenges that still need to be addressed in order for syngas fermentation to become a viable process for producing biofuels on a large scale. One challenge is mass transfer limitations due to low solubilities of syngas species. The hollow fiber reactor (HFR) is one type of reactor that has the potential for achieving high mass transfer rates for biofuels production. However, a better understanding of mass transfer limitations in HFRs is still needed. In addition there have been relatively few studies performing actual fermentations in an HFR to assess whether high mass transfer rates equate to better fermentation results. Besides mass transfer, one other difficulty with syngas fermentation is understanding the role that CO and H2 play as electron donors and how different CO and H2 ratios effect syngas fermentation. In addition to electrons from CO and H2, electrodes can also be used to augment the supply of electrons or provide the only source of electrons for syngas fermentation. This work performed an in depth reactor comparison that compared mass transfer rates and fermentation abilities. The HFR achieved the highest oxygen mass transfer coefficient (1062 h-1) compared to other reactors. In fermentations, the HFR showed very high production rates (5.3 mMc/hr) and ethanol to acetic acid ratios (13) compared to other common reactors. This work also analyzed the use of electrons from H2 and CO by C. ragsdalei and to study the effects of these two different electron sources on product formation and cell growth. This study showed that cell growth is not largely effected by CO composition although there must be at least some minimum amount of CO present (between 5-20%). Interestingly, H2 composition has no effect on cell growth. Also, more electron equivalents will lead to higher product formation rates. Following Acetyl-CoA formation, H2 is only used for product formation but not cell growth. In addition to these studies on electrons from H2 and CO, this work also assessed the redox states of methyl viologen (MV) for use as an artificial electron carrier in applications such as syngas fermentation. A validated thermodynamic model was presented in order to illustrate the most likely redox state of MV depending on the system setup. Variable MV extinction coefficients and standard redox potentials reported in literature were assessed to provide recommended values for modeling and analysis. Model results showed that there are narrow potential ranges in which MV can change from one redox state to another, thus affecting the potential use as an artificial electron carrier.

There is an increase in the prevalence of obesity among people with schizophrenia thought to be due in part to the weight enhancing side-effects of medications commonly used to treat the symptoms of schizophrenia. Despite the deleterious health effects associated with obesity and its impact on quality of life and medication compliance, little is known about body composition and energy expenditure in this clinical group. The primary purpose of this thesis was to enhance understanding of body composition and energy expenditure, particularly resting energy expenditure in men with schizophrenia who take atypical antipsychotic medications. Unique to this investigation is the evaluation of clinical tools used to predict body composition and energy expenditure against reference methodologies in men with schizophrenia. Further, given the known links between obesity and physical activity, an additional but less comprehensive component of the thesis was a consideration of total and activity energy expenditure in addition to the interaction between psychiatric symptoms, side-effects of antipsychotic medications and physical activity also occurred as part of this thesis. Collectively, the goals of this thesis were addressed through a series of studies – the first two studies were related to the measurement and characteristics of body composition in men with schizophrenia, while the third and fourth studies were related to the measurement and characteristics of resting energy expenditure in men with schizophrenia. The fifth and sixth studies the utilised doubly labelled water technique to quantify activity and total energy expenditure in a small group of men with schizophrenia and explored the use of accelerometry in this cohort. The final study briefly considered the impact of psychiatric symptoms and self-reported medication side-effects on objectively measured physical activity. In the first study, thirty-one male adults previously diagnosed with schizophrenia and sixteen healthy male controls were recruited. Estimates of body composition derived from an anthropometry-based equation and from bioelectric impedance analysis (BIA) using deuterium dilution as the reference methodology to determine total body water were compared. The study also determined the validity of equations commonly used to predict body composition from BIA in the men with schizophrenia. A further aim was to determine the superiority of either BIA or body mass index (BMI) as an indicator of obesity in this cohort. The inclusion of the control group, closely matched for age, body size and body composition demonstrated that there was no difference in the ability of body composition prediction methods to distinguish between fat and fat-free mass (FFM) in controls and men with schizophrenia when both groups had similar body composition. However this study indicated that an anthropometry-based equation previously used in people with schizophrenia was a poor predictor of body composition in this cohort, as evidenced by wide limits of agreement (25%) and systematic variation of the bias. In comparison, the best predictor of percentage body fat (%BF) in this group was gained when impedance values were used to predict percentage body fat via the equation published by Lukaski et al (1986). Although percentage body fat was underpredicted using the Lukaski et al. (1986) equation, the mean magnitude was relatively small (1.3%), with the limits of agreement approximately 13%. Linear regression analysis revealed that %BF predicted using the Lukaski et al. (1986) equation explained 25% more of the variance in percentage body fat than BMI. Further, this study also indicated that BIA was more sensitive than BMI in distinguishing between overweight and obesity in this cohort of men with schizophrenia. Because of the almost exclusive use of BMI as an indicator of obesity in people with schizophrenia, the level of excess body fat may be in excess of that previously indicated. The second study extended the examination of body composition in men with schizophrenia. In this study, the thirty-one participants with schizophrenia (age, 34.2 ± 5.7 years; BMI, 30.2 ± 5.7 kg/m2) were individually matched with sedentary controls by age, weight and BMI. Deuterium dilution was used to distinguish between FFM and fat mass. The previous study had indicated that while BIA was a suitable group measure for obesity, on an individual level the technique lacked the precision required for investigating body composition in men with schizophrenia. Waist circumference was used as an indicator of body fat distribution. The findings of this study indicated that in comparison with healthy sedentary controls of similar body size and age, men with schizophrenia had higher levels of body fat which was more centrally distributed. Percentage body fat was on average 4% higher and waist circumference, on average 5 cm greater in men with schizophrenia than the sedentary controls of the same age and BMI. Further, this study indicates that the use of BMI to predict body fat in men with schizophrenia will result in greater bias than when it is used to predict body fat in other sedentary men. Commonly used regression equations to predict energy requirements at rest are based on the relationships between weight and resting energy expenditure (REE) and in such equations, weight acts as a surrogate measure of FFM. The objectives of study three were to measure REE in a small group of men with schizophrenia who were taking the antipsychotic medication clozapine and to determine whether REE can be predicted with sufficient accuracy to substitute for the measurement of REE in the clinical and/or research settings. Body composition was determined using deuterium dilution and REE was measured using a Deltatrac Metabolic Cart via a ventilated hood. The male participants, (aged 28.0 ± 6.7 yrs, BMI 29.8 ± 6.8 kg/m2) were weight stable at the time of the study and had been taking clozapine for 20.5 ± 12.8 months, with doses of 450 ± 140 mg/day. Of the six prediction equations evaluated, the equation of Mifflin et al. (1990) with no systematic bias, the lowest bias and the lowest limits of agreement proved to be the most suitable equation to predict REE in this cohort. The overestimation of REE can be corrected for by deducting 160 kcal/day from the predicted REE value when using the Mifflin et al. (1990) equations. However, the magnitude of the error associated with the prediction of REE for an individual is 370 kcal/day. The findings of this study indicate that REE cannot be predicted with sufficient individual accuracy in men with schizophrenia, therefore it was necessary to measure rather than predict REE in subsequent studies. In the fourth study, indirect calorimetry (Deltatrac Metabolic Cart via ventilated hood) and deuterium dilution were used to accurately determine REE, respiratory quotient (RQ) and FFM in 31 men with schizophrenia and healthy sedentary controls individually matched for age and BMI. Data from this study indicated that gross REE was lower in men with schizophrenia than in healthy sedentary controls of a similar age and body size. However, there was no difference between the groups in REE when REE was adjusted for FFM using the mathematically correct method (analysis of covariance with FFM as the covariate). There was however a statistically and clinically significant difference in resting, fasted RQ between men with schizophrenia and controls, suggesting that RQ rather than REE may be an important correlate worthy of further investigation in men with schizophrenia who take antipsychotic medications. Studies five and six involved the application of the doubly labelled water (DLW) technique to accurately determine total energy expenditure (TEE) and activity energy expenditure (AEE) in a small group of men with schizophrenia who had been taking the atypical antipsychotic medication clozapine. The participants were those who took part in study three. The purpose of these studies was to assess the validity of a commercially available tri-axial accelerometer (RT3) for predicting free-living AEE and to investigate TEE and AEE in men with schizophrenia. There was poor agreement between AEE measured using DLW and AEE predicted using the RT3. However, using the RT3 to measure inactivity explained over two-thirds of the variance in AEE. This study found that the relationship between current AEE per kilogram of body weight and change from baseline weight in men taking clozapine was strong although not significant. The sedentary nature of the group of participants in this study was reflected in physical activity levels, (PAL, 1.39 ± 0.27), AEE (435 ±352 kcal/day) and TEE (2511 ± 606 kcal/day) that fell well short of values recommended by WHO (2000) for optimal health and to prevent weight gain. Given the increasing recognition of the importance of sedentary behaviour to weight gain in the general community, further examination of the unique contributing factors such as medication side effects and symptoms of mental illness to activity levels in this clinical group is warranted. The final study used accelerometry (RT3) to objectively measure activity in a group of 31 men with schizophrenia who had been taking atypical antipsychotic medications for more than four months. The purpose of this study was to explore the relationships between psychiatric symptomatology, side-effects of medication and physical activity. Accelerometry output was analysed to provide a measure of inactivity and moderate intensity activity (MIA). The well-validated and reliable standardised clinical interview, the Positive and Negative Syndrome Scale (PANSS) was used as a measure of psychiatric symptoms. Perceived side-effects of medication were assessed using the Liverpool University Neuroleptic Rating Side-Effects Scale (LUNSER). Surprisingly, there was no relationship reported between any measures of negative symptoms and physical inactivity. However, self-reported measures of medication side-effects relating to fatigue, sleepiness during the day and extrapyramidal symptoms explained 40% of the variance in inactivity. This study found significant relationships between some negative symptoms and moderate intensity activity. Despite the expectation that as symptoms of mental illness reduce, inactivity may diminish and moderate intensity activity will increase, it may not be surprising that in practice this is an overly simplistic view. It may be that measures of social functioning and possibly therefore cognition may be better predictors of physical activity than psychiatric symptomatology per se.

Indiana University-Purdue University Indianapolis (IUPUI) / Non-invasive surface recording of bioelectric potentials continues to be an essential tool in a variety of research and medical diagnostic procedures. However, the integrity of these recordings, and hence the reliability of subsequent analysis, diagnosis, or recommendations based on the recordings, can be significantly compromised when various types of noise are allowed to penetrate the recording circuit and contaminate the signals. In particular, for bioelectric phenomena in which the amplitude of the biosignal is relatively low, such as muscle activity (typically on the order of millivolts) or neural traffic (microvolts), external noise may substantially contaminate or even completely overwhelm the signal. In such circumstances, the tissue-electrode interface is typically the primary point of signal contamination since its impedance is relatively high compared to the rest of the recording circuit. Therefore, in the recording of low-amplitude biological signals, it is of paramount importance to minimize the impedance of the tissue-electrode interface in order to consistently obtain low-noise recordings. The aims of the current work were (1) to complete the development of a set of tools for rapid, simple, and reliable full-spectrum characterization and analytical modeling of the complex impedance of the tissue-electrode interface, and (2) to characterize the interfacial impedance and signal-to-noise ratio (SNR) at the surface of the skin across a variety of preparation methods and determine a factor or set of factors that contribute most effectively to the reduction of tissue-electrode impedance and noise contamination during recording. Specifically, we desired to test an initial hypothesis that surface abrasion is the principal determining factor in skin preparation to achieve consistently low-impedance, low-noise recordings. During the course of this master’s study, (1) a system with portable, battery-powered hardware and robust acquisition/analysis software for broadband impedance characterization has been achieved, and (2) the effects of skin preparation methods on the impedance of the tissue-electrode interface and the SNR of surface electromyographic recordings have been systematically quantified and compared in human subjects. We found our hypothesis to be strongly supported by the results: the degree of surface abrasion was the only factor that could be correlated to significant differences in either the interfacial impedance or the SNR. Given these findings, we believe that abrasion holds the key to consistently obtaining a low-impedance contact interface and high-quality recordings and should thus be considered an essential component of proper skin preparation prior to attachment of electrodes for recording of small bioelectric surface potentials.

La fibrillation auriculaire (FA) est le type d’arythmie cardiaque le plus fréquent. Cependant, ses mécanismes sont encore mal compris et le développement de stratégies thérapeutiques efficaces reste un défi. Des recherches ont montré que les mécanismes de remodelage structurel, notamment la dissociation électrique endocardique-épicardique, jouent un rôle potentiellement important dans l'initiation, la complexité et le maintien de la FA. En ce sens, les potentiels extracellulaires sont des outils non invasifs largement utilisés dans le diagnostic et la compréhension de cette arythmie ainsi que dans le guidage des interventions par cathéter. L'objectif principal de cette thèse était de développer des modèles informatiques des oreillettes et d’étudier dans ces modèles comment les potentiels extracellulaires et les cartes d'activation à haute résolution peuvent être exploités pour caractériser les mécanismes de dissociation endocardique-épicardique en tant que substrat de la FA. Dans un premier temps, en utilisant un modèle de tissu auriculaire, nous avons montré que la dissociation endo-épicardique (délai endo-épicardique et couplage transmural) affecte l'asymétrie des électrogrammes unipolaires à travers l'orientation des sources de courant dipolaire dans le tissu auriculaire. Ce résultat a été par la suite confirmé par l’analyse morphologique des composantes de l’onde P dans un modèle anatomique des oreillettes. Nous avons en outre montré que l’épaisseur de la paroi auriculaire ainsi que le couplage transmural étaient des déterminants importants de ce délai, et que ce dernier peut induire des altérations significatives de la morphologie l’onde P même lorsque les cartes d’activation sont similaires et que les ondes P ont la même durée. Dans un second temps, nous avons exploré les effets tridimensionnels de la dissociation endo-épicardique et validé une technique de détection de percée d’ondes (breakthroughs) basée sur l’analyse des cartes d'activation à haute résolution et le suivi des ondes, en utilisant un modèle électro-anatomique de découplage endo-épicardique local. Nous avons utilisé cet outil pour la caractérisation de la dissociation endo-épicardique. Un critère de validité en a été dérivé, ce qui faciliterait la comparaison des taux de percée avec les données cliniques et la validation des outils d'analyse des signaux cartographiques lors de la caractérisation de la dissociation endo-épicardique. Enfin, nous avons développé un outil d'optimisation multi-paramètre qui rend possible l’étude des limites des modèles continus homogénéisés dans l'étude des mécanismes de dissociation endo-épicardique et aide dans le choix des modèles (continu homogénéisé ou discret détaillé). L’outil permet d’estimer le profil régulier de conductivité qui reproduit le mieux les propriétés de conduction cardiaque d'un modèle discret donné. Les résultats ont montré l'efficacité de cet outil pour reproduire des cartes d'activation dans le modèle homogénéisé même en présence de fibrose sévère. Ultimement, ce travail pose les bases du développement de nouveaux modèles informatiques pouvant aider à l’interprétation des signaux électriques dans des tissus cardiaques remodelés où la présence de micro-hétérogénéités exhibe les limites des modèles homogénéisés. / Atrial fibrillation (AF) is the most common type of cardiac arrhythmia. However, its mechanisms are still poorly understood and the development of effective therapeutic strategies remains a challenge. Research studies have shown that the mechanisms of structural remodeling, including endocardial-epicardial electrical dissociation, play a potentially important role in the initiation, complexity, and maintenance of AF. In this sense, extracellular potentials are non-invasive tools widely used in the diagnosis and understanding of this arrhythmia as well as in the guidance of catheter interventions. The main objective of this thesis was to develop computer models of the atria and to study in these models how extracellular potentials and high resolution activation maps can be exploited to characterize the mechanisms of endocardial-epicardial dissociation as substrate of AF. First, using an atrial tissue model, we showed that endo-epicardial dissociation (endo-epicardial delay and transmural coupling) alters the asymmetry of unipolar electrograms through the orientation of dipolar current sources in the atrial tissue. This result was later confirmed by morphological analysis of the P-wave components in an anatomical model of the atria. We further showed that atrial wall thickness as well as transmural coupling were important determinants of this delay, and that the latter can induce significant alterations in P-wave morphology even when activation maps are similar and P-waves have the same duration. Secondly, we explored the three-dimensional effects of endo-epicardial dissociation and validated a breakthrough wave detection technique based on the analysis of high-resolution activation maps and wave tracking, using an electro-anatomical model of local endo-epicardial decoupling. We used this tool for the characterization of endo-epicardial dissociation. A validity criterion was derived, which would facilitate the comparison of breakthrough rates with clinical data and the validation of mapping signals analysis tools for characterizing endo-epicardial dissociation. Finally, we developed a multi-parameter optimization tool that makes it possible to study the limits of homogenized continuous models in the study of endo-epicardial dissociation mechanisms and to help in the choice of models (homogenized continuous or detailed discrete). The tool enabled the estimation of the regular conductivity profile that best reproduces the cardiac conduction properties of a given discrete model. The results showed the effectiveness of this tool in reproducing activation maps in the homogenized model even in the presence of severe fibrosis. Ultimately, this work lays the foundations for the development of new computer models that can help in the interpretation of electrical signals in remodeled heart tissues where the presence of micro-heterogeneities exhibits the limits of homogenized models.

The aim of this work is describe common methods of biological feedback therapy that is used to treat some psychosomatic diseases. Subsequently, the description is focused on minimal brain dysfunction treatment by the help of EEG biofeedback. Properties and technical requirements for this therapy are concretized. The last part of this thesis is dedicated to the design and realization of practical software tool for EEG biofeedback therapy which is made in LabView 7.1. The M535 acquisition unit and NI USB-6221 measuring device are used for hardware solution.