Thesis (Ph.D.)--McMaster University (Canada), 1992. / Source: Dissertation Abstracts International, Volume: 54-02, Section: B, page: 0826.

All four monosubstituted halobenzenes Sa-d have been converted to the corresponding cis-arenediols by a microbial oxidation with the bacterium Pseudomonas putida strain 39- D. Enantiomerically pure cis-diols were obtained from chloro- and bromobenzene. The acetonides of these two diols have been utilized as useful synthons in the preparation of several natural products, like conduritols E 1 and F 2, aminoconduritol A-1 3 and lycoricidine 4. The optical purity of bromocyclohexadienediol, was determined by its conversion to three different natural products ((+)-conduritol E 1, (-)-conduritol F 2, and (+)- aminoconduritol A-1 3), and compared with their optical rotation. Several dienophiles were added to the protected cis-arenediols to study the regio- and stereochemistry of the cycloaddition. The addition of dienophiles to the acetonide of the diols was anti in every case. When ethyl propiolate was used, two regioisomers 7 and 8 were obtained. In contrast, the addition of nitroso dienophiles, derived in situ from the oxidation of hydroxamic acids, to protected halocyclohexadienediols provided chiral bicyclic oxazines of type 9, as single isomers. These compounds were converted by reductive cleavage to 1,4-hydroxy amides. The anti-addition to the acetonide and the stereospecific formation of the two new chiral centers adjacent to the acetonide was exploited in an approach to a more complex phenanthrene natural product lycoricidine 4. / Ph. D.

The aim of this diploma thesis was to develop a miniaturized extraction method for a fast screening of non-volatile nitroso compounds using gas chromatography with a nitroso specific chemiluminescence detection. According to a final methodology, the samples were prepared by extraction of grinded malt using a mixture of pyridine and acetonitrile in ratio 60:40 (v/v). To enhance volatility of the determined analytes, the two-step derivatization using hexamethyldisalazane and N,O-bis(trimethyl)-trifluoroacetamide was used. The total volume of the sample was 200 l and the preparation time after optimization was in total 80 min. The extraction method was connected to a classification method, which can divide chromatographic peaks into the groups of N-nitroso and C-nitroso compounds, and interfering substances. After application of the methods mentioned above to real malt samples, the specific chromatographic peaks of C-nitroso and N-nitroso compounds were selected. Description of their properties and structure suggestion will be a subject of the following study. Keywords Nitroso compounds, malt, extraction, derivatization, gas chromatography, chemiluminescence detector

No description available.

INTRODUÇÃO: A esteatose é a doença hepática crônica mais frequente na população. Seus efeitos lesivos hepáticos podem adicionar-se aos efeitos da isquemia e reperfusão (I/R) nos transplantes de fígado e cirurgias hepáticas. Em ambos, o estresse oxidativo e o dano na microcirculação são importantes fatores na gênese da lesão hepática. Vários antioxidantes já foram testados em modelos experimentais de esteatose e I/R e mostraram benefício, entre eles a N-acetilcisteína (NAC). O óxido nítrico (NO) tem efeito controverso sobre a lesão de I/R, entretanto em baixas doses pode ser benéfico à microcirculação hepática. A S-nitroso-Nacetilcisteína (SNAC) fornece a NAC e também NO. Esta droga foi testada mostrando benefício em modelos experimentais de esteatose e I/R de músculo esquelético. Contudo, ainda não foi testada na lesão de I/R em fígados esteatáticos. MÉTODOS: Foram estudados 34 ratos machos Wistar divididos em 4 grupos: grupo I (n=8) - sem esteatose tratados com solução salina; grupo II (n=8) - sem esteatose tratados com SNAC; grupo III (n=9) - com esteatose tratados com solução salina; grupo IV (n=9) - com esteatose tratados com SNAC. A indução da esteatose foi realizada com dieta aproteica. Os animais foram submetidos a isquemia hepática parcial (70%) por um período de 1 hora e um período de reperfusão de 4 horas. A droga foi administrada por via intraperitoneal. Foram avaliados histologia, respiração mitocondrial e estresse oxidativo (MDA) hepáticos, transaminases séricas e mieloperoxidase e extravasamento do corante azul de Evans pulmonares. RESULTADOS: Não houve diferença entre os grupos I e II em todas as variáveis avaliadas (histologia, função mitocondrial (RCR e ADP/O), transaminases (AST e ALT), azul de Evans e mieloperoxidase pulmonares), encontrando-se apenas uma tendência a menor estresse oxidativo (MDA) (p = 0,07) no fígado isquêmico do grupo tratado (grupo II). A comparação entre os grupos III e IV não encontrou diferença nas transaminases (AST e ALT), e no azul de Evans e mieloperoxidase pulmonares. O grupo IV (esteatose e SNAC) apresentou no fígado isquêmico menor hemorragia intraparenquimatosa (p = 0,02), melhor função mitocondrial (RCR) (p = 0,01) (ADP/O) (p = 0,01), e menor estresse oxidativo (MDA) (p = 0,007) quando comparado com o grupo não tratado (grupo III). CONCLUSÕES: Neste modelo, o tratamento com SNAC não melhora a lesão de I/R em ratos sem esteatose. No entanto, a SNAC melhora a lesão hepática pós I/R em ratos com fígado esteatótico. / Steatosis is the most frequent chronic liver disease in general population. Steatosis can make ischemia/reperfusion (I/R) lesions worse in liver transplants and hepatic surgeries. Oxidative stress and hepatic microcirculatory damage are related to generation of steatosis and I/R lesions. Several antioxidant drugs, for example the N-acetylcysteine (NAC), have been already used in steatotic and I/R experimental models, and showed better outcome in treated groups. The nitric oxide (NO) has controversial effects on I/R, however, in low doses it can improve hepatic microcirculation. The S-nitroso-N-acetylcysteine (SNAC) releases NAC and NO. It ameliorated oxidative stress in experimental models of steatosis and skeletal muscle I/R. In contrast, this drug has never been used in steatotic liver I/R. METHODS: thirty four male Wistar rats were studied and divided in four groups: group I (n=8) - without steatosis and treated with saline solution; group II (n=8) - without steatosis and treated with SNAC; group III (n=9) - with steatosis and treated with saline solution; group IV (n=9) - with steatosis treated with SNAC. Aproteic diet was used for steatosis induction. The animals underwent a partial hepatic ischemia (70%) for 1 hour and reperfusion for 4 hours. The drug was administrated intraperitoneally. The parameters evaluated were hepatic histology, mitochondrial respiration and oxidative stress (MDA), seric transaminasis and pulmonary mieloperoxidasis and Evans blue extravasation. RESULTS: There were not any difference between groups I and II in all parameters evaluated (histology, mithocondrial function (RCR and ADP/O), transaminasis (AST and ALT), pulmonary Evans blue extravasation and mieloperoxidasis), and it showed only tendency of less oxidative stress (MDA) (p=0,07) in ischemic liver of treated group (group II). The comparison between groups III and IV didn\'t show any difference in transaminasis (AST and ALT), pulmonary Evans blue and mieloperoxidasis. Group IV (steatosis and SNAC) showed in the ischemic liver lower intraparenchymatous hemorrhage (p=0,02), better mitochondrial function (RCR) (p=0,01) and (ADP/O) (p=0,01), and less oxidative stress (MDA) (p=0,007) when compared with untreated group (group III). CONCLUSIONS: Based on this experimental model, SNAC treatment shows no benefit in non steatotic I/R lesion, however, in steatotic rats, SNAC ameliorates hepatic lesions post I/R.

La spécialisation des techniques agricoles que nous connaissons ces dernières décennies, particulièrement dans les régions rurales, est à l’origine de l’abus de fertilisants. Ces derniers sont actuellement reconnus comme étant les causes principales de la contamination de l’eau souterraine par les nitrates. Suite à leur ingestion via l’eau potable, les nitrates sont transformés en nitrites par la flore buccale. Une fois dans l’estomac les nitrites réagissent avec certaines amines provenant de l’alimentation pour générer des nitrosamines cancérogènes. L’objectif de notre étude était d’estimer quantitativement l’excès de risque de cancer (ER) pour les populations de sept régions rurales du Québec qui consomme l’eau potable provenant de réseaux municipaux alimentés en eau souterraine. Le territoire à l’étude était caractérisé par une agriculture intensive d’élevage. Les médianes (et 95e centiles) régionales des concentrations de nitrates mesurées dans les réseaux de ces régions étaient de : 0,18 (2,74); 0,48 (10,35); 0,15 (1,28); 0,32 (11); 0,05 (0,76); 0,10 (4,69); 0,09 (2,13) mg N-NO3-/l. Nous avons envisagé un scénario de transformation complète des nitrites et de certaines amines (diméthylamine, diéthylamine, n-butylamine, méthyléthylamine) en nitrosamines spécifiques : N-diméthylnitrosamine (NDMA), N-diéthylnitrosamine (NDEA), N-n-dibutylnitrosamine (NDBA) et N-méthyléthylnitrosamine (NMEA). Pour estimer la concentration de nitrites formés dans l’estomac, nous avons considéré une consommation définie d’eau potable, le volume de l’estomac et un taux de transformation des nitrates en nitrites. Supposant les quantités de nitrites et de chaque amine constantes pendant 1h, nous avons considéré la constante de nitrosation spécifique à chaque amine pour évaluer la dose d’exposition journalière à chaque nitrosamine équivalente formée. Par la suite, la combinaison de cette dose à un estimateur de potentiel cancérogène qhumain spécifique à chaque nitrosamine, nous a permis d’évaluer l’ER associé à chacune d’elles. Globalement l’analyse a démontré que les ER les plus élevés, estimés pour le NDBA, étaient de l’ordre de 10-6, ne contribuant pas de façon significative à une augmentation du risque de cancer pour ces populations. / Specialization of agricultural practices in rural regions over the past few decades has led to overuse of fertilizers which are main causes of groundwater contamination by nitrates. After their ingestion through drinking water, nitrates are transformed into nitrites by the oral flora. Once in the stomach, nitrites react with some amines from food supply to form nitrosamines with some being probably carcinogenic to humans. The aim of this study was to quantitatively estimate the possible excess cancer risk (ER) for populations of seven rural regions in Quebec that consume water from public drinking water systems using groundwater. The studied regions practice extensive breeding agriculture. The regional medians (and 95th percentile) of nitrate levels in water from those seven regions were: 0.18 (2.74); 0.48 (10.35); 0.15 (1.28); 0.32 (11); 0.05 (0.76); 0.10 (4.69) and 0.09 (2.13) mg N-NO3-/l, respectively. Indeed, we first considered a scenario of complete transformation of nitrites and some amines (dimethylamine, diethylamine, n-butylamine and methylethylamine) into specific nitrosamines: N-dimethylnitrosamine (NDMA), N-diethylnitrosamine (NDEA), N-nitrosodi-n-butylamine (NDBA) and N-nitrosomethylethylamine (NMEA). Gastric nitrite concentrations were estimated on the basis of defined drinking water intake, stomach volume, and the transformation rate of nitrates into nitrites. Considering that levels of nitrites and each amine were kept constant for 1 hour, and taking in account the nitrosatability rate constant specific to each amine, we then estimated the daily doses of the corresponding endogenously formed nitrosamines. Furthermore combination of dose with the human cancer potency factor qhuman specific to each nitrosamine, allowed the estimation of excess cancer risk. The highest ER estimated for NDBA was in the order of 10-6, thus not contributing to a significant increase in the risk of cancer for that population.

INTRODUÇÃO: A esteatose é a doença hepática crônica mais frequente na população. Seus efeitos lesivos hepáticos podem adicionar-se aos efeitos da isquemia e reperfusão (I/R) nos transplantes de fígado e cirurgias hepáticas. Em ambos, o estresse oxidativo e o dano na microcirculação são importantes fatores na gênese da lesão hepática. Vários antioxidantes já foram testados em modelos experimentais de esteatose e I/R e mostraram benefício, entre eles a N-acetilcisteína (NAC). O óxido nítrico (NO) tem efeito controverso sobre a lesão de I/R, entretanto em baixas doses pode ser benéfico à microcirculação hepática. A S-nitroso-Nacetilcisteína (SNAC) fornece a NAC e também NO. Esta droga foi testada mostrando benefício em modelos experimentais de esteatose e I/R de músculo esquelético. Contudo, ainda não foi testada na lesão de I/R em fígados esteatáticos. MÉTODOS: Foram estudados 34 ratos machos Wistar divididos em 4 grupos: grupo I (n=8) - sem esteatose tratados com solução salina; grupo II (n=8) - sem esteatose tratados com SNAC; grupo III (n=9) - com esteatose tratados com solução salina; grupo IV (n=9) - com esteatose tratados com SNAC. A indução da esteatose foi realizada com dieta aproteica. Os animais foram submetidos a isquemia hepática parcial (70%) por um período de 1 hora e um período de reperfusão de 4 horas. A droga foi administrada por via intraperitoneal. Foram avaliados histologia, respiração mitocondrial e estresse oxidativo (MDA) hepáticos, transaminases séricas e mieloperoxidase e extravasamento do corante azul de Evans pulmonares. RESULTADOS: Não houve diferença entre os grupos I e II em todas as variáveis avaliadas (histologia, função mitocondrial (RCR e ADP/O), transaminases (AST e ALT), azul de Evans e mieloperoxidase pulmonares), encontrando-se apenas uma tendência a menor estresse oxidativo (MDA) (p = 0,07) no fígado isquêmico do grupo tratado (grupo II). A comparação entre os grupos III e IV não encontrou diferença nas transaminases (AST e ALT), e no azul de Evans e mieloperoxidase pulmonares. O grupo IV (esteatose e SNAC) apresentou no fígado isquêmico menor hemorragia intraparenquimatosa (p = 0,02), melhor função mitocondrial (RCR) (p = 0,01) (ADP/O) (p = 0,01), e menor estresse oxidativo (MDA) (p = 0,007) quando comparado com o grupo não tratado (grupo III). CONCLUSÕES: Neste modelo, o tratamento com SNAC não melhora a lesão de I/R em ratos sem esteatose. No entanto, a SNAC melhora a lesão hepática pós I/R em ratos com fígado esteatótico. / Steatosis is the most frequent chronic liver disease in general population. Steatosis can make ischemia/reperfusion (I/R) lesions worse in liver transplants and hepatic surgeries. Oxidative stress and hepatic microcirculatory damage are related to generation of steatosis and I/R lesions. Several antioxidant drugs, for example the N-acetylcysteine (NAC), have been already used in steatotic and I/R experimental models, and showed better outcome in treated groups. The nitric oxide (NO) has controversial effects on I/R, however, in low doses it can improve hepatic microcirculation. The S-nitroso-N-acetylcysteine (SNAC) releases NAC and NO. It ameliorated oxidative stress in experimental models of steatosis and skeletal muscle I/R. In contrast, this drug has never been used in steatotic liver I/R. METHODS: thirty four male Wistar rats were studied and divided in four groups: group I (n=8) - without steatosis and treated with saline solution; group II (n=8) - without steatosis and treated with SNAC; group III (n=9) - with steatosis and treated with saline solution; group IV (n=9) - with steatosis treated with SNAC. Aproteic diet was used for steatosis induction. The animals underwent a partial hepatic ischemia (70%) for 1 hour and reperfusion for 4 hours. The drug was administrated intraperitoneally. The parameters evaluated were hepatic histology, mitochondrial respiration and oxidative stress (MDA), seric transaminasis and pulmonary mieloperoxidasis and Evans blue extravasation. RESULTS: There were not any difference between groups I and II in all parameters evaluated (histology, mithocondrial function (RCR and ADP/O), transaminasis (AST and ALT), pulmonary Evans blue extravasation and mieloperoxidasis), and it showed only tendency of less oxidative stress (MDA) (p=0,07) in ischemic liver of treated group (group II). The comparison between groups III and IV didn\'t show any difference in transaminasis (AST and ALT), pulmonary Evans blue and mieloperoxidasis. Group IV (steatosis and SNAC) showed in the ischemic liver lower intraparenchymatous hemorrhage (p=0,02), better mitochondrial function (RCR) (p=0,01) and (ADP/O) (p=0,01), and less oxidative stress (MDA) (p=0,007) when compared with untreated group (group III). CONCLUSIONS: Based on this experimental model, SNAC treatment shows no benefit in non steatotic I/R lesion, however, in steatotic rats, SNAC ameliorates hepatic lesions post I/R.

Staphylococcus xylosus est couramment utilisé comme ferment dans les produits carnés pour son rôle dans le développement de la flaveur et de la couleur. Beaucoup de propriétés technologiques ont été caractérisées in vitro. Cependant, les mécanismes moléculaires mis en place par cette bactérie pour s’adapter à une matrice carnée et aux composés nitrosés, fréquemment ajoutés dans ces produits, étaient méconnus. Pour identifier ces mécanismes, des approches de transcriptomique globale ont été mises en œuvre. S. xylosus survit dans un modèle viande en modulant l’expression de 55 % de ses gènes. Il surexprime des gènes codant des protéines impliqués dans le catabolisme du glucose et du gluconate et des gènes codant des peptidases. En parallèle, il sous exprime de nombreux gènes impliqués dans la synthèse des acides aminés probablement en raison de leur disponibilité dans le modèle viande. Le modèle viande est un milieu riche en divers substrats et la bactérie pourrait adapter sa physiologie via les régulateurs transcriptionnels CcpA et CodY. S. xylosus répond au sel ajouté au modèle viande en surexprimant des gènes impliqués dans des mécanismes d’osmoprotection, d’extrusion de Na + et de protons. S. xylosus répond aux composés nitrosés dans le modèle viande en modulant 24 % de son génome. Ces composés nitrosés génèrent un stress nitrosant et S. xylosus répond à ce stress par la surexpression de gènes impliqués dans l’homéostasie du fer via la dérépression du régulateur Fur. S. xylosus surexprime aussi des gènes codant des enzymes antioxydants via la dérépression du régulateur PerR. De plus, il surexprime des gènes impliqués dans la réparation de l’ADN et des protéines. La viande est un aliment riche en fer hémique et non hémique. Ainsi, S. xylosus est capable d’acquérir du fer à partir de ferritine, de transferrine et potentiellement des hémoprotéines. La ferritine est une source préférentielle de fer pour S. xylosus. Un opéron codant potentiellement un complexe membranaire impliqué dans des réactions d’oxydo-réduction a été identifié. Un mutant de délétion/insertion dans le premier gène de l’opéron confirme que ce système pourrait jouer un rôle dans l’acquisition du fer de la ferritine chez S. xylosus. Cette étude révèle un changement global dans l’expression des gènes de S. xylosus dans un modèle viande, elle souligne la capacité de S. xylosus à s’adapter à un stress osmotique ou nitrosant et elle caractérise pour la première fois la capacité d’un staphylocoque à utiliser du fer de la ferritine. / Staphylococcus xylosus is used as starter culture in meat product for its role in the development of flavor and color. S. xylosus is characterized for its technological properties in vitro. However, the molecular mechanisms for its adaptation in meat with or without nitrate and nitrite, frequently added in meat product, remained unknown. Global transcriptomic approaches were carried out to determine the molecular mechanisms. S. xylosus modulated the expression of 55 % of the genes to survive in a meat model. Many genes encoding proteins involved in glucose and gluconate catabolisms and peptidases were up expressed. In parallel, a lot of genes involved in amino acids synthesis were down regulated, probably due to their availability in the meat model. The meat model is a rich medium composed of various substrates and S. xylosus adapted its physiology through the transcriptional regulators CcpA and CodY. Finally, it responded to salt added in the meat model in overexpressing genes involved in mechanisms of osmoprotection, Na + and H + extrusion. S. xylosus modulated the expression of 24 % of the genes in presence of nitroso compounds in the meat model. These compounds generated a nitrosative stress. S. xylosus responded to this stress by over expressing genes involved in iron homeostasis through the derepression of the regulator Fur. It over expressed also genes encoding antioxidant enzymes through the derepression of the regulator PerR. Moreover, it over expressed genes involved in DNA and proteins repairs. Meat is rich in hemic and non-hemic iron. S. xylosus is able to grow in presence of ferritin, transferrin and potentially hemoproteins. Ferritin is one of preferential iron sources. An operon encoding potentially a membranous complex involved in oxydo-reduction reactions has been identified. A strain defective in the first gene of the operon confirmed that this complex could contribute to the iron acquisition from ferritin. This study revealed a global change in the gene expression of S. xylosus in the meat model; it highlighted ability of S. xylosus to mitigate nitrosative or osmotic stress, it characterised for the first time the capacity of a Staphylococcus to acquire ferritin-iron.

La cristallisation est un phénomène dans lequel les atomes ou molécules s’arrangent de manière hautement ordonnée. Il s’agit d’une des plus anciennes méthodes de purification. De plus, la structure cristalline d’un matériau influence ses propriétés. En métallurgie, par exemple, plusieurs opérations sont effectuées sur le métal, chacune affectant la structure cristalline et par le fait même les propriétés du matériau. Une compréhension des facteurs affectant la structure cristalline serait désirable en chimie des matériaux. Par exemple, dans le développement de matériaux poreux, la structure permettrait de moduler la quantité de vide dans un cristal et d’ajuster ainsi sa porosité. Prévoir l’organisation moléculaire est aussi désirable dans les panneaux solaires afin de bien positionner les composantes actives. Pour les polymères, le taux de cristallinité affecte directement les propriétés mécaniques telles que la densité et la dureté. La cristallisation se fait par étape. Au début, quelques particules commencent par se lier intermoléculairement de manière réversible. À ce moment de la cristallisation, la perte d’entropie contrebalance les bénéfices enthalpiques et le processus n’est pas favorisé thermodynamiquement. Une fois qu’un certain nombre de particules se sont lié, un noyau ou germe de nucléation est formé et à ce moment la cristallisation devient favorisée thermodynamiquement. Cette étape critique s’appelle la nucléation. La structure et la forme du noyau de nucléation servent de gabarit pour la construction subséquente du cristal. Après la germination vient la croissance épitaxiale. Comprendre l’étape de germination permet donc de moduler l’organisation moléculaire au tout début de la formation du cristal. Le projet présenté dans ce mémoire vise à examiner le phénomène de la nucléation à l’aide de molécules organiques conçues pour porter plusieurs groupements pouvant se lier réversiblement de manière covalente. Le nombre critique de molécules pour construire un noyau de cristallisation et la nature de leur association peuvent être étudiés. Le cœur organique choisi pour ces molécules est celui de l’adamantane car ses dérivés cristallisent bien en général et peuvent être fonctionnalisés facilement. Le groupement choisi pour pouvoir se lier réversiblement est le nitroso, qui s’associe pour générer des liaisons azodioxy. L’objectif du projet fut donc la synthèse et l’étude du comportement du mono-, di-, tri- et tétranitrosoadamantane. / Crystallization is a phenomenon in which atoms or molecules arrange themselves in a highly ordered fashion. It is one of the oldest methods of purification. In addition, the structure of a crystalline substance influences its properties. In metallurgy, for example, many operations are applied to metals in an effort to change the crystal structure and thus the properties of the material. Acquiring a full comprehension of the factors affecting crystallization is therefore a desirable goal in materials chemistry. In the area of porous solids, for example, modifying the structure can be used to modulate the amount of free space inside the solid. Similarly, controlling the molecular organization of the components of solar panels is needed to optimize performance. For polymers, the degree of crystallinity directly affects mechanical properties such as density and hardness. Molecular crystallization is a stepwise process. At the start, a few molecules associate reversibly. At this point, the loss of entropy counterbalances stabilizing enthalpic effects, and the process is not favored thermodynamically. Once a certain number of molecules have assembled, a seed or germ of nucleation is formed. It is at this moment that crystallization becomes spontaneous. This critical step is called nucleation. The structure and shape of the seed serves as a template for subsequent construction of the crystal. After the seed is formed, the crystal then undergoes epitaxial growth. Understanding the seeding step allows modulation of the crystal at the very beginning of its formation. The project described in the present Master’s thesis aims to study the phenomenon of nucleation using specially designed organic molecules. The idea is to use molecules comprising multiple groups that can associate reversibly by forming weak covalent bonds. The critical number of molecules needed to obtain a crystal nucleus and their manner of association can be studied. The organic core chosen is that of adamantane because its derivatives tend to crystallize well and functionalization is straightforward. The functional group chosen to favor strong but reversible association is nitroso, because nitroso compounds typically exist in equilibrium with azodioxy dimers. The objective of work summarized in the memoir is to synthesis, characterize, and examine the associative properties of mono-, di-, tri-, and tetranitrosoadamantane.

A estase de secreção salivar e alimentos deglutidos na luz esofágica de pacientes com megaesôfago chagásico traz como consequências: (1) supercrescimento bacteriano na luz do órgão, (2) episódios de aspiração pulmonar e infecções respiratórias de repetição, (3) aumento do risco dos procedimentos terapêuticos cirúrgicos ou endoscópicos em caso de perfuração pela maior possibilidade de contaminação, (4) desenvolvimento de processos inflamatórios crônicos na mucosa esofágica, que podem predispor ao aparecimento de displasia e câncer. Apesar disto, a microbita esofágica no megaesôfago nunca foi estudado. Esse estudo teve o objetivo de analisar qualitativa e quantitativamente a microbiota presente no líquido de estase esofágico de pacientes portadores de megaesôfago chagásico, comparando-a com a existente em indivíduos sadios. Foram estudados prospectivamente 25 pacientes (10 homens e 15 mulheres) com idades variando de 24 a 74 anos ( &#61507; = 49,1a). Quinze pacientes eram portadores de esofagopatia chagásica, sendo 5 portadores de mega grau I (MG1), 5 portadores de mega grau II (MG2) e 5 portadores de mega grau III (MG3), segundo a classificação de Rezende; e 10 indivíduos sadios, agrupados no Grupo Controle (GC). Utilizou-se método de coleta que permitia aspiração de líquido através de sonda de Levine diretamente da luz esofágica, evitando-se a contaminação com microrganismos da orofaringe. Após análise microbiológica qualitativa e quantitativa, foi feita a descrição dos microrganismos encontrados nos vários grupos e sua classificação em aeróbios Gram positivos, aeróbios Gram negativos, anaeróbios e fungos. A análise estatística visou avaliar diferenças quantitativas entre os microrganismos nos diferentes grupos, sendo para tanto utilizado o teste não paramétrico de Kruskal-Wallis, com nível de rejeição menor 0,05 (5%). A positividade das culturas no Grupo Controle foi 40%, com predomínio do gênero Streptococcus sp, em concentrações que variaram de 101 a 102 ufc/ml. No Grupo Megaesôfago 93,3% da culturas foram positivas, com grande variedade de bactérias, mas predomínio de aeróbios Gram positivos (Streptococcus sp. foi o mais comum) e anaeróbios (Veillonella sp foi a mais freqüente) em concentrações que variaram de 101 a 105 ufc/ml. As concentrações foram geralmente mais elevadas em MG3, quando comparado com MG1, MG2 e GC (p<0,05). Concluiu-se que no megoesôfago, diferentemente dos indivíduos sadios, existe a presença de rica microflora bacteriana, constituída principalmente por aeróbios Gram positivos e anaeróbios, em concentrações tanto maiores quanto maior o seu grau de dilatação. Parte desta microbiota tem capacidade de metabolizar nitratos, etapa importante na formação de nitrosaminas. / The stasis of saliva and swallowed food in the esophageal lumen of patients with chagasic megaesophagus causes: (1) bacterial overgrowth in the esophageal lumen, (2) recurring pulmonary aspirations and respiratory infections, (3) increased risk of surgical or endoscopic procedures if perforation occurs by the major possibility of contamination, and (4) the development of chronic inflammatory process in esophageal mucosa, that can predispose to the development of dysplasia and cancer. In spite of this, esophageal microbiota in the megaesophagus has never been studied. The aim of this study was to analyze qualitatively and quantitatively the microbiota in chagasic megaesophagus in comparison to the normal esophagus. Twenty-five patients (10 men and 15 women) were prospectively studied, with ages varying from 24 to 74 years (&#61507;=49,1), from March to September 2000. Fifteen patients with chagasic megaesophagus (MG), were divided into three sub- groups according to the grade of esophageal dilation: MG1 – 5 patients with megaesophagus grade I; MG2- 5 patients with megaesophagus grade II; MG3- 5 patients with megaesophagus grade III. Another group of ten patients without any esophageal disease was constituted in the Control Group (CG). The sample collection was performed using a method specially developed to avoid contamination with microorganisms of the oral cavity and oropharynx. After qualitative and quantitative analysis, the microorganisms found were described and classified as Gram positive aerobes, Gram negative aerobes, anaerobes and fungus. Statistical analysis using Kruskal-Wallis non-parametric test was performed in order to find quantitative differences of microorganisms in the different groups. In CG 40% of the cultures were positive with predominance of the genus Streptococcus sp, in concentrations that varied from 101 to 102 cfu/ml. In MG, 93,3% of the cultures were positive, with great bacterial variability and predominance of a variety of aerobic Gram-positive (Streptococcus sp was the most common) and anaerobic bacteria (Veillonella sp was the most frequent), in concentrations that varied from 101 to 105 cfu/ml. The bacterial concentrations were generally more elevated in MG3 in comparison to MG1, MG2 and CG (p<0,05). It was concluded that patients with megaesophagus present a varied microbiota constituted mostly of aerobic Gram positive and anaerobic bacteria, in concentrations that vary with the megaesophagus dilatation degree. Some of the bacteria found in MG are able to metabolize nitrates intro nitrites, an important step in the formation of nitrosamines.