Endomorphin 1 (10, 30, 100 nmol/kg) administered intravenously (i.v.) to urethane-anesthetized rats consistently and dose-dependently lowered heart rate (HR) and mean arterial pressure (MAP); the decrease in blood pressure recovered faster as compared to the HR. The effects of endomorphin 2 were qualitatively similar. Naloxone (2 mg/kg, i.v.) completely antagonized the bradycardia and hypotension caused by endomorphin 1. Pretreatment of the rats with atropine methylnitrate, atropine sulfate (2 mg/kg, i.v.) or bilateral vagotomy nearly abolished the bradycardia and attenuated the hypotensive effect of endomorphin 1. Our studies suggest that the bradycardia effect following systemic administration of the new opioid peptide may be explained by activation of vagal afferents and the hypotensive effect may be secondary to a reduction of cardiac output and/or a direct vasodilation.

Amylin, or islet amyloid polypeptide is a 37-amino acid member of the calcitonin peptide family. Amylin role in the brainstem and its function in regulating heart rates is unknown. The diving reflex is a powerful autonomic reflex, however no neuropeptides have been described to modulate its function. In this thesis study, amylin expression in the brainstem involving pathways between the trigeminal ganglion and the nucleus ambiguus was visualized and characterized using immunohistochemistry. Its functional role in slowing heart rate and also its involvement in the diving reflex were elucidated using stereotaxic microinjection, whole-cel patch-clamp, and a rat diving model. Immunohistochemical and tract tracing studies in rats revealed amylin expression in trigeminal ganglion cells, which also contained vesicular glutamate transporter 2 positive. With respect to the brainstem, amylin containing fibers were discovered in spinal trigeminal tracts. These fibers curved dorsally toward choline acetyltransferase immunoreactive neurons of the nucleus ambiguus, suggesting that amylin may synapse to parasympathetic preganglionic neurons in the nucleus ambiguus. Microinjection of fluorogold to the nucleus ambiguus retrogradely labeled a population of trigeminal ganglion neurons; some of which also contained amylin. In urethane-anesthetized rats, stereotaxic microinjections of amylin to the nucleus ambiguus caused a dose-dependent bradycardia that was reversibly attenuated by microinjections of the selective amylin receptor antagonist, salmon calcitonin (8-32) (sCT (8-32)) or AC187, and abolished by bilateral vagotomy. In an anesthetized rat diving model, diving bradycardia was attenuated by glutamate receptor antagonists CNQX and AP5, and was further suppressed by AC187. Whole-cel patch-clamp recordings from cardiac preganglionic vagal neurons revealed that amylin depolarizes neurons while decreasing conductance. Amylin also resulted in a reduction in whole cell currents, consistent with the decrease in conductance. Amylin is also found to increase excitability of neurons. In the presence of TTX, spontaneous currents in cardiac preganglionic vagal neurons were observed to decrease in frequency in response to amylin while amplitude remained constant, signifying that amylin reduces presynaptic activity at cardiac preganglionic vagal neurons. Finally, evoked synaptic currents revealed that amylin decreases evoked currents, further demonstrating that amylin depolarization and increase in excitability of cardiac preganglionic vagal neurons is also associated with simultaneous inhibition of presynaptic transmission. Our study has demonstrated for the first time that the bradycardia elicited by the diving reflex is mediated by amylin from trigeminal ganglion cells projecting to cardiac preganglionic neurons in the nucleus ambiguus. Additionally, amylin results in the depolarization and increased excitability of cardiac preganglionic vagal neurons while inhibiting presynaptic transmission. / Pharmacology

INTRODUÇÃO: A estimulação cardíaca artificial convencional em ponta do ventrículo direito é o tratamento de eleição para os quadros de bradicardia severa, contudo, apesar de excelente para corrigir a frequência cardíaca, favorece o surgimento de dissincronia ventricular mecânica, podendo agravar ou originar insuficiência cardíaca. Neste contexto, desde a década de 90 são utilizadas no Instituto Dante Pazzanese as estimulações septal (ou para-Hissiana) e bifocal de ventrículo direito (septal e apical). Postula-se que a estimulação em posição septal teria melhores resultados tanto em termos clínicos quanto às medidas elétricas e ecocardiográficas de função sistólica quando comparada à posição apical. Esta nova estimulação ainda não foi amplamente testada frente à estimulação convencional com as novas tecnologias de avaliação da sincronia cardíaca. MÉTODOS: Pacientes portadores de fibrilação atrial permanente, sem possibilidade de estimulação atrial, com disfunção sistólica leve ou moderada e bradicardia com indicação de marca-passo definitivo foram submetidos à implante de marca-passo bifocal de ventrículo direito com eletrodos em posição septal e apical em todos os casos. Os pacientes foram randomizados para estimulação unifocal por dois meses e a seguir submetidos à crossover no ponto de estimulação cardíaca. Após cada período de estimulação eram realizados eletrocardiograma e ecocardiograma transtorácico bidimensional com avaliação de parâmetros de sincronia do miocárdio ventricular. RESULTADOS: Foram incluídos 25 pacientes em cada grupo de estimulação na análise final do estudo. A estimulação em posição septal demonstrou uma menor duração do QRS estimulado (153 ± 12 ms vs. 174 ± 16 ms, p < 0,001) e melhor fração de ejeção do ventrículo esquerdo (44 ± 9% vs. 40 ± 8%, p < 0,001) quando comparada com a posição apical. A classe funcional (NYHA) também foi menor com a estimulação septal (1,8 ± 0,6 vs. 2,2 ± 0,7, p < 0,001). A avaliação da sincronia cardíaca evidenciou menos dissincronia interventricular (p < 0,001) e intraventricular com a estimulação septal (Septal to posterior delay: 33,1 ± 28,7 vs. 80,7 ± 46,2 ms, p < 0,001; Índice de Yu: 33,4 ± 8,6 ms vs. 50,2 ± 14,0 ms, p < 0,001; Strain radial: 78,8 ± 57,1 ms vs. 137,2 ± 50,2 ms, p < 0,001). CONCLUSÃO: A avaliação intrapaciente mostrou que, em comparação com a estimulação apical convencional, a estimulação em posição septal esteve associada à menor dissincronia cardíaca medida pela ecocardiografia, o que pode estar relacionado à melhor função sistólica do ventrículo esquerdo e consequentemente melhores resultados clínicos observados. / INTRODUCTION: Conventional artificial cardiac pacing in the right ventricle apex is the treatment of choice for severe bradycardia. Although it is excellent for correcting heart rate, it favors the onset of electromechanical ventricular dyssynchrony, which may aggravate or even lead to heart failure. In this context, the Septal (or para-Hissian) and bifocal (septal and apical) stimulation were used since the 90\'s in the Dante Pazzanese Institute. It was observed that the septal stimulation could have better results both in clinical terms and in the electrical and echocardiographic measurements of systolic function when compared to the apical stimulation. This new stimulation has not been yet extensively tested against conventional one with the new technologies of cardiac synchrony evaluation. METHODS: Patients with permanent atrial fibrillation, without possibility of atrial stimulation, with mild or moderate systolic dysfunction and bradycardia with indication of pacemaker were submitted to implantation of bifocal pacemaker in the right ventricle with electrodes in a septal and apical position in all cases. The patients were randomized to unifocal stimulation for two months and then underwent crossover, changing the point of cardiac stimulation. After each stimulation period, electrocardiogram and two-dimensional transthoracic echocardiography were performed with evaluation of ventricular myocardial synchrony parameters. RESULTS: Twenty-five patients were included in each stimulation group in the final analysis of the study. Septal pacing demonstrated a shorter duration of the QRS (153 ± 12 ms vs. 174 ± 16 ms, p < 0.001) and a better left ventricular ejection fraction (44 ± 9% vs. 40 ± 8%, p < 0.001) when compared to the apical position. NYHA functional class was also lower with septal pacing (1.8 ± 0.6 vs. 2.2 ± 0.7, p < 0.001). The cardiac synchrony evaluation showed less interventricular (p < 0.001) and intraventricular dyssynchrony with septal pacing (Septal to posterior delay: 33.1 ± 28.7 vs. 80.7 ± 46.2 ms, p < 0.001; Yu index: 33.4 ± 8.6 ms vs. 50.2 ± 14.0 ms, p < 0.001; Radial strain: 78.8 ± 57.1 ms vs. 137.2 ± 50.2 ms, p < 0.001). CONCLUSION: The intrapatient comparision showed that, compared to the apical conventional stimulation, the septal pacing was associated with lower cardiac dyssynchrony measured by echocardiography, which may be related to the better left ventricular systolic function and consequently better clinical results observed.

Made available in DSpace on 2015-05-14T12:59:38Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 2427284 bytes, checksum: d24742c1a3622f9b0122565e2537caa8 (MD5) Previous issue date: 2012-08-03 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Previous studies have shown that the 2-nitrate-1,3-dibuthoxypropan (NDBP), an organic nitrate synthesized from glycerin, induced vasorelaxation in mesenteric artery of rats through activation of the NO-cGMP-PKG pathway and K+ channels, in addition, caused hypotension and bradycardia in normotensive conscious rats. The current research aimed to investigate the effects of the NDBP on cardiovascular system in rats, evaluating the NO release in rat smooth muscle cell culture, the ability of NDBP to induce tolerance to vasodilatation and the effect of the acute administration of the compound on autonomic control of blood pressure and heart rate of normotensive and hypertensive rats, using in vitro and in vivo approaches. For biochemical determination aortic rat smooth muscle cell culture (ARSMC) was used and the pharmacological experiments were developed using Wistar rats or spontaneously hypertensive (SHR) and normotensive Wistar Kyoto (WKY) rats. The NDBP caused concentration-dependent increases in NO levels in ARSMC. In addition, NDBP produced no change in the vasorelaxation induced by the NDBP when the rings were pre-incubated with the NDBP (10 &#956;M or 100 &#956;M), suggesting that the NDBP did not induce tolerance. In vivo experiments, SHR rats were significantly hypertensive compared with WKY rats. The acute administration of the NDBP (1, 5, 10, 15 and 20 mg/kg, i.v.) caused a biphasic response: hypotension and bradycardia followed by hypertension and tachycardia in WKY and SHR rats. The blockade of muscarinic receptors with atropine (2 mg/kg) blunted the bradycardia induced by NDBP (15 mg/kg) and reduced the hypotension in WKY and SHR. However, the pressor response to the compound was potentiated. Furthermore, vagotomy almost abolished the bradycardia in WKY and SHR. Moreover, hexamethonium (30 mg/kg), a nicotinic ganglionic blocker, reduced both bradycardia and pressor response in WKY and SHR. The administration of methylene blue (4 mg/kg), a soluble guanylyl cyclase (sGC) blocker, attenuated the hypotension and bradycardia induced by the NDBP (15 mg/kg) in WKY. Similar event occurred in SHR animals. In conclusion, the NDBP releases NO in ARSMC, and was unable to induce tolerance to its vasorelaxant effect, however, the cardiovascular effects of NDBP are mainly mediated by the central action of the compound, resulting in changes on autonomic function of spontaneously hypertensive and normotensive rats. / Relatos prévios demonstraram que o 2-nitrato-1,3-dibutoxipropano (NDBP), um nitrato orgânico sintetizado a partir da glicerina, induziu vasodilatação em anéis de artéria mesentérica cranial isolada de rato mediante a ativação da via NO-GMPc- PKG, bem como dos canais para K+ e, adicionalmente, causou hipotensão e bradicardia em ratos normotensos não-anestesiados. O estudo atual teve como objetivo investigar os efeitos do NDBP sobre o sistema cardiovascular em ratos, avaliando a liberação de NO eliciada pelo NDBP em células musculares lisas vasculares, a capacidade do NDBP induzir tolerância ao vasorrelaxamento e o efeito da administração aguda do composto sobre o controle autonômico de animais normotensos e hipertensos, por meio de abordagens in vitro e in vivo. Nos experimentos bioquímicos foi utilizada a cultura de células musculares lisas de aorta de rato (CMLAR) e, nos experimentos farmacológicos foram utilizados ratos Wistar ou ratos espontaneamente hipertensos (SHR) e normotensos Wistar Kyoto (WKY). Foi observado que o NDBP causou um aumento concentração-dependente nos níveis de NO em CMLAR. Além disso, não houve alteração no efeito vasodilatador do NDBP quando os anéis de artéria mesentérica foram previamente expostos ao NDBP, nas concentrações de 10 &#956;M ou 100 &#956;M, sugerindo que o nitrato orgânico em estudo não induziu tolerância. Nos experimentos in vivo, foi constatado que a pressão média basal dos animais espontaneamente hipertensos foi significantemente maior que a do grupo normotenso. A administração aguda do NDBP (1, 5, 10, 15 e 20 mg/kg, i.v.) induziu uma resposta bifásica: hipotensão e bradicardia seguidas de hipertensão e taquicardia, em ratos SHR e WKY. O bloqueio dos receptores muscarínicos pela atropina (2 mg/kg) atenuou a bradicardia induzida pelo NDBP (15 mg/kg), reduzindo também a hipotensão em WKY e SHR. Entretanto, a resposta pressora ao composto foi potencializada. A secção bilateral do nervo vago praticamente aboliu a bradicardia em WKY e SHR. Adicionalmente o hexametônio (30 mg/kg), um bloqueador nicotínico ganglionar, reduziu tanto a bradicardia quanto a resposta pressora em ambos os grupos. A administração do azul de metileno (4 mg/kg), um bloqueador da ciclase de guanilil solúvel (CGs), atenuou as repostas hipotensora e bradicárdica induzida pelo NDBP (15 mg/kg) em ratos WKY. Evento similar aconteceu nos animais SHR. Esses resultados sugerem que o NDBP libera NO em CMLAR, sendo incapaz de induzir tolerância ao seu efeito vasorrelaxante, entretanto, os efeitos cardiovasculares do NDBP são mediados, principalmente, pela ação central do composto, resultando em alterações na função autonômica de ratos normotensos e espontaneamente hipertensos.

Made available in DSpace on 2016-06-02T19:22:59Z (GMT). No. of bitstreams: 1 5375.pdf: 1850581 bytes, checksum: 822cefb40c25ca3fd51f51b23edfe47b (MD5) Previous issue date: 2013-06-14 / Universidade Federal de Sao Carlos / Hypoxic bradycardia is a reflex response to hypoxia observed in most fish species studied so far. This reflex is initiated by the stimulation of O2 chemoreceptors and induced by an increase in the inhibitory vagal tonus. Despite of being well described and characterized, the hypothesis that hypoxic bradycardia improves the O2 transference from the ventilatory water to the gills still remain to be proved. The utilization of different methods to inhibit hypoxic bradycardia (vagotomy and atropinization) may have contributed to generate different cardiorespiratory responses, making this issue even more controversial. In this study the cardiorespiratory variables (heart frequency fH, metabolic rate - V&#61478;&#61472;O2 , O2 extraction from the ventilatory current EO2, gill ventilation - V&#61478;&#61472;G , breathing frequency fR, and ventilatory requirement - V&#61478;&#61472;G / V&#61478;&#61472;O2 ) were measured in the tambaqui, Colossoma macropomum, under normoxia and after 40 min of exposure to severe hypoxia (20 mmHg) and the 3 subsequent hours of recovery. Each fish was subjected to this protocol before (Control group), after atropine administration (A group) and after vagotomy (V group). Under hypoxia the fish of control group displayed the characteristic hypoxic bradycardia (reduction of 56% in fH) with hyperventilation (increases of 96% in fR and 650% in V&#61478;&#61472;G ). This hyperventilation was probably responsible by the decrease in EO2 (65%) and, consequently, in the V&#61478;&#61472;O2 (62%), resulting in an increase of 1800% in the V&#61478;&#61472;G / V&#61478;&#61472;O2 . The beginning of the recovery period was characterized by an elevated V&#61478;&#61472;O2 (~200% above the normoxic values) accompanied by tachycardia (50.6 bpm) and gradual recovery of EO2, fR, VT and V&#61478;&#61472;G . Atropine and vagotomy elevated the fH in normoxia (from 32.0 ± 1.7 to 77.8 ± 4.1 and 80.6 ± 5.8 bpm), indicating a high basal vagal tone. In these two groups the fH remained constant during the experimental time course. This evidenced that the post-hypoxia tachycardia probably occurred as a consequence of a reduction in the cholinergic tonus. The groups control, atropinized and vagotomized did not show significant differences in EO2, V&#61478;&#61472;O2 and the other respiratory variables analyzed in any protocol. This results point out that hypoxic bradycardia does not improve the O2 transference to the gills, independently of the method employed to abolish the bradycardic reflex. Therefore, other hypotheses on the hypoxic bradycardia must be investigated in this species. / A bradicardia hipóxica é uma resposta reflexa à hipóxia presente na maioria dos teleósteos. Este reflexo é induzido por um aumento no tônus vagal inibitório e iniciado pela estimulação de quimiorreceptores de oxigênio (O2). Apesar de muito descrita e bem caracterizada, a hipótese de que esta redução na frequência cardíaca (fH) melhore a transferência de O2 pelas brânquias ainda não foi comprovada. A utilização de diferentes métodos para inibir a bradicardia hipóxica (vagotomia e atropinização) pode ter contribuído para gerar respostas cardiorrespiratórias diversas e tornar esta questão ainda mais controversa. Neste trabalho foram avaliadas as variáveis cardiorrespiratórias (fH; taxa metabólica V&#61478;&#61472;O2 ; extração de O2 da corrente ventilatória EO2; ventilação branquial V&#61478;&#61472;G ; frequência respiratória fR; volume ventilatório VT e necessidade ventilatória V&#61478;&#61472;G / V&#61478;&#61472;O2 ) do tambaqui, Colossoma macropomum, em normóxia, após 40 min de hipóxia severa (20 mmHg) e durante 3 h de recuperação subsequente. Cada animal foi submetido a este protocolo antes (Ctr), após administração de atropina (A) e após vagotomia (V). Em hipóxia os animais Ctr apresentaram a característica bradicardia hipóxica (redução de 56% na fH) com aumentos na fR (~96 %) e VT (~275 %) elevando muito a VG (~650 %). Esta alta V&#61478;&#61472;G , provavelmente foi responsável pela queda significativa na EO2 (65%), consequentemente reduzindo a V&#61478;&#61472;O2 (62 %) e aumentando muito a VG / V&#61478;&#61472;O2 (1800 %) em hipóxia. O início do período de recuperação do grupo Ctr foi caracterizado por elevada V&#61478;&#61472;O2 (~200 % acima dos valores de normóxia), acompanhada de taquicardia (50,6 bpm) e recuperação gradual da EO2, fR, VT e V&#61478;&#61472;G . A atropina e a vagotomia elevaram a fH em normóxia (de 32,0 ± 1,7 para 77,8 ± 4,1 e 80,6 ± 5,8 bpm) indicando um alto tônus vagal de repouso, sendo que nestes dois grupos a fH permaneceu constante em todos os tempos experimentais evidenciando que a taquicardia póshipóxia foi, provavelmente, consequência de uma redução no tônus colinérgico. Na EO2, V&#61478;&#61472;O2 e demais parâmetros respiratórios analisados não houve diferenças entre os grupos Ctr, A e V, em nenhum momento do protocolo. Estes resultados demonstram que a bradicardia hipóxica, possivelmente, não melhora a transferência de O2 pelas brânquias de tambaqui independente do método de abolição do reflexo bradicárdico. Portanto, outras hipóteses sobre a função da bradicardia hipóxica, como na proteção do miocárdio, devem ser investigadas nesta espécie.

INTRODUÇÃO: A estimulação cardíaca artificial convencional em ponta do ventrículo direito é o tratamento de eleição para os quadros de bradicardia severa, contudo, apesar de excelente para corrigir a frequência cardíaca, favorece o surgimento de dissincronia ventricular mecânica, podendo agravar ou originar insuficiência cardíaca. Neste contexto, desde a década de 90 são utilizadas no Instituto Dante Pazzanese as estimulações septal (ou para-Hissiana) e bifocal de ventrículo direito (septal e apical). Postula-se que a estimulação em posição septal teria melhores resultados tanto em termos clínicos quanto às medidas elétricas e ecocardiográficas de função sistólica quando comparada à posição apical. Esta nova estimulação ainda não foi amplamente testada frente à estimulação convencional com as novas tecnologias de avaliação da sincronia cardíaca. MÉTODOS: Pacientes portadores de fibrilação atrial permanente, sem possibilidade de estimulação atrial, com disfunção sistólica leve ou moderada e bradicardia com indicação de marca-passo definitivo foram submetidos à implante de marca-passo bifocal de ventrículo direito com eletrodos em posição septal e apical em todos os casos. Os pacientes foram randomizados para estimulação unifocal por dois meses e a seguir submetidos à crossover no ponto de estimulação cardíaca. Após cada período de estimulação eram realizados eletrocardiograma e ecocardiograma transtorácico bidimensional com avaliação de parâmetros de sincronia do miocárdio ventricular. RESULTADOS: Foram incluídos 25 pacientes em cada grupo de estimulação na análise final do estudo. A estimulação em posição septal demonstrou uma menor duração do QRS estimulado (153 ± 12 ms vs. 174 ± 16 ms, p < 0,001) e melhor fração de ejeção do ventrículo esquerdo (44 ± 9% vs. 40 ± 8%, p < 0,001) quando comparada com a posição apical. A classe funcional (NYHA) também foi menor com a estimulação septal (1,8 ± 0,6 vs. 2,2 ± 0,7, p < 0,001). A avaliação da sincronia cardíaca evidenciou menos dissincronia interventricular (p < 0,001) e intraventricular com a estimulação septal (Septal to posterior delay: 33,1 ± 28,7 vs. 80,7 ± 46,2 ms, p < 0,001; Índice de Yu: 33,4 ± 8,6 ms vs. 50,2 ± 14,0 ms, p < 0,001; Strain radial: 78,8 ± 57,1 ms vs. 137,2 ± 50,2 ms, p < 0,001). CONCLUSÃO: A avaliação intrapaciente mostrou que, em comparação com a estimulação apical convencional, a estimulação em posição septal esteve associada à menor dissincronia cardíaca medida pela ecocardiografia, o que pode estar relacionado à melhor função sistólica do ventrículo esquerdo e consequentemente melhores resultados clínicos observados. / INTRODUCTION: Conventional artificial cardiac pacing in the right ventricle apex is the treatment of choice for severe bradycardia. Although it is excellent for correcting heart rate, it favors the onset of electromechanical ventricular dyssynchrony, which may aggravate or even lead to heart failure. In this context, the Septal (or para-Hissian) and bifocal (septal and apical) stimulation were used since the 90\'s in the Dante Pazzanese Institute. It was observed that the septal stimulation could have better results both in clinical terms and in the electrical and echocardiographic measurements of systolic function when compared to the apical stimulation. This new stimulation has not been yet extensively tested against conventional one with the new technologies of cardiac synchrony evaluation. METHODS: Patients with permanent atrial fibrillation, without possibility of atrial stimulation, with mild or moderate systolic dysfunction and bradycardia with indication of pacemaker were submitted to implantation of bifocal pacemaker in the right ventricle with electrodes in a septal and apical position in all cases. The patients were randomized to unifocal stimulation for two months and then underwent crossover, changing the point of cardiac stimulation. After each stimulation period, electrocardiogram and two-dimensional transthoracic echocardiography were performed with evaluation of ventricular myocardial synchrony parameters. RESULTS: Twenty-five patients were included in each stimulation group in the final analysis of the study. Septal pacing demonstrated a shorter duration of the QRS (153 ± 12 ms vs. 174 ± 16 ms, p < 0.001) and a better left ventricular ejection fraction (44 ± 9% vs. 40 ± 8%, p < 0.001) when compared to the apical position. NYHA functional class was also lower with septal pacing (1.8 ± 0.6 vs. 2.2 ± 0.7, p < 0.001). The cardiac synchrony evaluation showed less interventricular (p < 0.001) and intraventricular dyssynchrony with septal pacing (Septal to posterior delay: 33.1 ± 28.7 vs. 80.7 ± 46.2 ms, p < 0.001; Yu index: 33.4 ± 8.6 ms vs. 50.2 ± 14.0 ms, p < 0.001; Radial strain: 78.8 ± 57.1 ms vs. 137.2 ± 50.2 ms, p < 0.001). CONCLUSION: The intrapatient comparision showed that, compared to the apical conventional stimulation, the septal pacing was associated with lower cardiac dyssynchrony measured by echocardiography, which may be related to the better left ventricular systolic function and consequently better clinical results observed.

Made available in DSpace on 2016-06-02T19:22:53Z (GMT). No. of bitstreams: 1 3162.pdf: 1363154 bytes, checksum: 725b7e9d57697bbcc0ab7a78df25145a (MD5) Previous issue date: 2010-06-25 / Financiadora de Estudos e Projetos / Air-breathing fish are classified as obligatory (when breathing obligatory atmospheric air independently of the water O2 tension) or facultative air-breather (using an air breathing organ ABO -, when theirs gills are not able to extract all O2 necessary to maintain the aerobic mechanisms under hypoxic conditions). The catfish, Clarias gariepinus, is airbreathing fish that shows modifications on the gill lamella, forming a ventilatory fan, and on the 2o e 4o gill arches, forming an arborescent organ. These structures form the ABO of this specie.The objectives of the present study were: 1. To determine if C. gariepinus is an obligatory or a facultative air breather. 2. To analyze the cardio-respiratory responses ( &#61478;VO2 - metabolic rate; &#61478;VG - gill ventilation; VT ventilatory volume; fR respiratory frequency; EO2 O2 extraction from the ventilatory current; fH- heart frequency) in response to progressive hypoxia. 3. To verify if the critical O2 tension (PcO2) of this specie is correlated with the O2 uptake from the atmospheric air.To classify the air-breathing mode of C. Gariepinus, the fish (Wt ~ 350 g; n = 7) were maintained in normoxia during 24 hours without access to air. The fR maintained constant during all the experiment and there was no mortality, indicating that C. gariepinus is a facultative air-breather. To analyze the cardio-respiratory responses to progressive hypoxia, &#61478;VO2 , EO2, fR, VT, &#61478;VG , EO2 and fH were recorded under the following water O2 tensions(PwO2): 100, 70, 50 e 30 mmHg. Fish maintained a constant &#61478;VO2 until the PcO2 (~ 55 mmHg), below which &#61478;VO2 decreased significantly. This decreasing was followed with the significant reduction of EO2 in PinspO2 of 62,7 ± 1,30 mmHg reaching values of 19,6 ± 1,9 % in severe hypoxia. The &#61478;VG and the VT increased progressively until PinspO2 of 28,0 ± 0,5 mmHg, reaching highest values of, respectively, 1545,7 ± 63,5 mLH2O.kg-1.min-1, 33,9 ± 0,8 mLH2O.Kg-1.resp-1 e 57,2 ± 1,4 resp.min-1. The fH reduced progressively from 43,4 ± 0,4 bpm, in normóxia, arriving significant values just above the PcO2 and reaching minimum values (19,2 ± 3,0 bpm) in severe hypoxia. Under progressive hypoxia (100, 70, 50, 30 e 20 mmHg) and with the access to the atmospheric air, C. gariepinus (Wt ~ 610 g; n = 9) presented a 5-fold increase in the air-breathing frequency (fRA). A bradycardia was observed just before the air breath and a tachycardia just after.Concluding, C. gariepinus is a continuous facultative air-breathing fish that regulate the 2 O V &#61478;&#61472;until the PcO2 of ~54 mmHg. Below this tension fish increase the &#61478;VG mainly due to a larger increase of VT (lower metabolic cost of &#61478;VG ). The hypoxic pre-air breath bradycardia is characteristic of aquatic breathers while the post-air breath tachycardia is typical of air respirators. The fRA increased proportionally with the progressive hypoxia, mainly just above the PcO2. These results show that C. gariepinus is adapted to survive at hypoxic habitats and that this species show a higher dependence of the atmospheric air than the others facultative air-breathing fishes. / Peixes de respiração aérea são classificados como respiradores aéreos obrigatórios (aqueles que respiram ar atmosférico independente das tensões de O2 da água) ou facultativos (aqueles que usam o órgão de respiração aérea ABO quando as brânquias não conseguem extrair a quantidade de O2 necessário para manter o metabolismo aeróbico em condições hipóxicas). O bagre-africano, Clarias gariepinus, é um peixe de respiração aérea que apresenta modificações na lamela branquial, formando um leque ventilatório, e, nos 2os e 4os arcos branquiais, os órgãos arborescentes. Estas últimas estruturas formam o ABO desta espécie.Os objetivos do presente estudo foram: 1. Determinar se C. gariepinus é um respirador aéreo facultativo ou obrigatório. 2. Analisar as respostas cardiorrespiratórias ( &#61478;VO2 - taxa metabólica; EO2 - extração de O2 da corrente ventilatória; &#61478;VG - ventilação branquial; VT - volume ventilatório; fR - frequência respiratória; fH- frequência cardíaca) em resposta a hipóxia gradual. 3. Verificar se a tensão crítica de O2 (PcO2) desta espécie está relacionada com a tomada de O2 do ar atmosférico.Para classificar a modalidade da respiração aérea de C. gariepinus, os peixes (Wt ~ 350 g; n = 7) foram mantidos em normóxia durante 24 h sem acesso ao ar atmosférico. A fR manteve-se constante durante todo o experimento e não houve mortalidade, indicando que C. gariepinus é um respirador aéreo facultativo. Para analisar as respostas cardiorrespiratórias em normóxia (controle) e hipóxia gradual, a &#61478;VO2 , EO2, fR, VT, &#61478;V G e fH foram registradas durante as seguintes tensões de O2 (PwO2): 100, 70, 50 e 30 mmHg. Os peixes mantiveram &#61478;VO2 constante até a PcO2 (~ 55 mmHg), abaixo da qual a &#61478;VO2 decresceu significativamente. Esta diminuição da &#61478;VO2 foi acompanhada da diminuição significativa da EO2 em PinspO2 de 62,7 ± 1,30 mmHg atingindo valores de 19,6 ± 1,9 %, em hipóxia severa. A &#61478;VG , VT e fR aumentaram progressivamente até a PinspO2 de 28,0 ± 0,5 mmHg, chegando a valores máximos de, respectivamente, 1545,7 ± 63,5 mLH2O.kg-1.min-1, 33,9 ± 0,8 mLH2O.Kg-1.resp-1 e 57,2 ± 1,4 resp.min-1. A fH diminui progressivamente de 43,4 ± 0,4 bpm, em normóxia, até alcançar valores significativos próximos a PcO2 e valores mínimos em hipóxia severa (19,2 ± 3,0 bpm). Em experimentos de hipóxia gradual (100, 70, 50, 30, 20 e 10 mmHg) com acesso ao ar atmosférico, C. gariepinus aumentou aproximadamente 5x a frequência de respiração aérea (fRA). Em cada tensão hipóxica ocorreu uma bradicardia pré-RA seguido de taquicardia significativa pós-RA (típico de respiração aérea); a fR manteve-se praticamente constante (~ 32 resp.min-1) até as duas últimas PwO2 (20 e 10 mmHg), nas quais a fR diminuiu para 23,0 ± 1,18 resp.min-1.Finalmente, C. gariepinus é um peixe de respiração aérea facultativa contínua que regula a &#61478;VO2 até a PcO2 de ~ 55 mmHg. Abaixo desta tensão o animal aumenta a &#61478;VG devido principalmente a um pronunciado aumento na VT (diminuição do custo metabólico da &#61478;VG ). A bradicardia hipóxica pré-RA é uma característica de respiradores aquáticos, enquanto a taquicardia hipóxica pós-RA é típica de respiradores aéreos. A fRA aumentou proporcionalmente com a hipóxia gradual, principalmente próximo a PcO2. Tais resultados demonstram que C. gariepinus está adaptado a sobreviver em habitats hipóxicos e demonstra uma maior dependência do ar atmosférico do que outros respiradores bimodais facultativos.

L'apnée est une complication fréquente chez les nouveaux-nés prématurés. L'un des problèmes les plus fréquents est l'épisode d'apnée bradycardie dont la répétition influence de manière négative le développement de l'enfant. C'est pourquoi les enfants prématurés sont surveillés en continu par un système de monitoring. Depuis la mise en place de ce système, l'espérance de vie et le pronostic de vie des prématurés ont été considérablement améliorés et ainsi la mortalité réduite. En effet, les avancées technologiques en électronique, informatique et télécommunications ont conduit à l'élaboration de systèmes multivoies de monitoring néonatal de plus en plus performants. L'un des principaux signaux exploités dans ces systèmes est l'électrocardiogramme (ECG). Toutefois, même si l'analyse de l'ECG a évolué au fil des années, l'ensemble des informations qu'il fournit n'est pas encore totalement exploité dans les processus de décision, notamment en monitoring en Unité de Soins Intensifs en Néonatalogie (USIN). L'objectif principal de cette thèse est d'améliorer la prise en compte des dynamiques multi-dimensionnelles en proposant de nouvelles approches basées sur un formalisme bayésien, pour la détection précoce des apnées bradycardies chez le nouveau-né prématuré. Aussi, dans cette thèse, nous proposons deux approches bayésiennes, basées sur les caractéristiques de signaux biologiques en vue de la détection précoce de l'apnée bradycardie des nouveaux-nés prématurés. Tout d'abord avec l'approche de Markov caché, nous proposons deux extensions du Modèle de Markov Caché (MMC) classique. La première, qui s'appelle Modèle de Markov Caché Couplé (MMCC), créé une chaîne de Markov à chaque dimension de l'observation et établit un couplage entre les chaînes. La seconde, qui s'appelle Modèle Semi-Markov Caché Couplé (MSMCC), combine les caractéristiques du modèle de MSMC avec le mécanisme de couplage entre canaux. Pour les deux nouveaux modèles (MMCC et MSMCC), les algorithmes récursifs basées sur la version classique de Forward-Backward sont introduits pour résoudre les problèmes d'apprentissage et d'inférence dans le cas couplé. En plus des modèles de Markov, nous proposons deux approches passées sur les filtres de Kalman pour la détection d'apnée. La première utilise les modifications de la morphologie du complexe QRS et est inspirée du modèle générateur de McSharry, déjà utilisé en couplant avec un filtre de Kalman étendu dans le but de détecter des changements subtils de l'ECG, échantillon par échantillon. La deuxième utilise deux modèles AR (l'un pour le processus normal et l'autre pour le processus de bradycardie). Les modèles AR sont appliqués sur la série RR, alors que le filtre de Kalman suit l'évolution des paramètres du modèle AR et fournit une mesure de probabilité des deux processus concurrents. / Apnea-bradycardia episodes (breathing pauses associated with a significant fall in heart rate) are the most common disease in preterm infants. Consequences associated with apnea-bradycardia episodes involve a compromise in oxygenation and tissue perfusion, a poor neuromotor prognosis at childhood and a predisposing factor to sudden-death syndrome in preterm newborns. It is therefore important that these episodes are recognized (early detected or predicted if possible), to start an appropriate treatment and to prevent the associated risks. In this thesis, we propose two Bayesian Network (BN) approaches (Markovian and Switching Kalman Filter) for the early detection of apnea bradycardia events on preterm infants, using different features extracted from electrocardiographic (ECG) recordings. Concerning the Markovian approach, we propose new frameworks for two generalizations of the classical Hidden Markov Model (HMM). The first framework, Coupled Hidden Markov Model (CHMM), is accomplished by assigning a Markov chain (channel) to each dimension of observation and establishing a coupling among channels. The second framework, Coupled Hidden semi Markov Model (CHMM), combines the characteristics of Hidden semi Markov Model (HSMM) with the above-mentioned coupling concept. For each framework, we present appropriate recursions in order to use modified Forward-Backward (FB) algorithms to solve the learning and inference problems. The proposed learning algorithm is based on Maximum Likelihood (ML) criteria. Moreover, we propose two new switching Kalman Filter (SKF) based algorithms, called wave-based and R-based, to present an index for bradycardia detection from ECG. The wave-based algorithm is established based on McSarry's dynamical model for ECG beat generation which is used in an Extended Kalman filter algorithm in order to detect subtle changes in ECG sample by sample. We also propose a new SKF algorithm to model normal beats and those with bradycardia by two different AR processes.

Les canaux activés par l’hyperpolarisation et sensibles aux nucléotides cycliques (hy- perpolarization cyclic nucleotide-gated channel; HCN) ont un rôle dans la régulation du rythme cardiaque ainsi que dans la transmission des influx nerveux. De nombreuses pathologies sont causées par un disfonctionnement de ces canaux. A ce jour, Ivabradine représente la seule molécule utilisée comme médicament, mais malgré sa spécificité en- vers les canaux HCNs, elle n’est pas sélective entre les isoformes de la famille HCN. Dans le but d’identifier une molécule plus adéquate pour le traitement qu’Ivabradine, nous avons analysé l’interaction entre les canaux HCNs et 9 bloqueurs connus garce à l’arrimage moléculaire. Cette analyse nous a permis d’identifier les résidus nécessaires pour la liaison des ligands. On observe aussi qu’Ivabradine ne forme aucune liaison so- lide avec les canaux HCNs mais ne fait que bloquer le passage par sa présence tout comme ses dérivées Zatebradine et Cilobradine. Les ligands de plus petites tailles quant à eux, se logent dans une cavité hydrophobe et forme des liaisons stable avec les pro- téines. Nos résultats semblent suggérer que le blocage par Ivabradine est plus efficace, mais que les liaisons stables des petits ligands possèdent un potentiel plus grand vers une meilleure affinité. Par contre, les interactions observées suggèrent que la spécificité envers les isoformes proviendrait des cinétiques des canaux et des dépendances d’états des ligands plutôt que des interactions identifiées. Pour finir, l’arrimage des ligands sur la conformation fermé du canal HCN1 suggère qu’il existerait une conformation fermée- liée non connue puisqu’aucun ligand n’a pu accéder au pore. / HCN channels have a role in regulating heart rate as well as in the transmission of nerve impulses. Many pathologies are caused by a malfunction of these channels. To date, Ivabradine is the only molecule used as a drug, but despite its specificity for HCN chan- nels, it is not selective between the isoforms of the HCN family. In order to identify a molecule more suitable for the treatment than ivabradine, we analyzed the interaction between HCN family and 9 known blockers using docking. This analysis allowed us to identify the necessary residuals for ligand binding. It is also observed that ivabradine forms no solid bond with the HCN channels but only blocks the passage by its pres- ence, the same was observed for its derivatives Zatebradine and Cilobradine. Ligands of smaller size, for their part, are lodged in a hydrophobic cavity and form stable bonds with the proteins. Our results seem to suggest that blocking with Ivabradine is more effi- cient but that the stable bonds of small ligands have a greater potential for better affinity. However, the observed interactions suggest that the specificity towards isoforms would come from the kinetics of the channels and state dependencies of ligands rather than identified interactions. Finally, the binding of the ligands to the closed conformation of the HCN1 channel suggests that there would be a closed-bound conformation that is not known since no ligand has been able to access the pore.

This dissertation work describes design and construction of simulated aorta device intended to demonstrate performance of the intra-aortal balloon catheter (IAB), and to test reaction of the contra-pulsation pump during simulated cardiac output in conditions of tachycardia, bradycardia and arrhythmia. The major part of the device is transparent plastic tube. The pressure pulses (waves) are generated inside this plastic tube to simulate real cardiac output. These pressure pulses are generated by step motor with membrane. The step motor is controlled by programmable control system AMiNi-E. Individual pressure pulses simulate cardiac output in conditions of tachycardia, bradycardia and arrhythmia. Required simulated cardiac output is selected by control switches. Generated pressure pulses are read by pressure sensor and are transferred to the control system of the configuration computer. Read data can be displayed as graphs in program Microsoft Excel. The intra-aortal balloon catheter (IAB) is inserted inside the aorta and is connected with contra-pulsation pump which on pressure pulse is responding.