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Characterization of Agricultural Runoff Associated with ProAgri™ Treatment of Poultry Litter Added to SoilsHarris, Cl 05 1900 (has links)
One of the greatest problems facing crop producers, who utilize poultry litter as a fertilizer for their fields, is phosphorus (P) runoff. Although phosphorus is a necessary element for optimal crop production, it can also have an adverse reaction when introduced into the aquatic environment. This problem is thought to have been helped by a new litter treatment product, ProAgri™ that became available for use in the poultry houses, which allegedly binds up the excess P. The purpose of this study was to examine the effect of the ProAgri™ on water quality of runoff. Four different treatments which included a control with no poultry litter, untreated poultry litter, ProAgri™ treated poultry litter, and ProAgri™ plus Activator treated poultry litter were applied at the rate of 2 tons per acre. Natural and simulated rainfall events produced runoff that was analyzed for water quality.
No statistical differences (p>0.05) were found in soluble phosphorus, total suspended solids, turbidity, conductivity, dissolved oxygen, alkalinity, hardness, and pH in runoff water between treatments.
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PTEN Gene Delivery Induced Regression of Orthotopic Hepatoma in Syngenic RatsYeh, Bi-wen 17 August 2005 (has links)
Hepatocellular carcinoma (HCC) is one of the most common cancerous diseases worldwide. The annual occurrences exceed one million peoples affected. Currently, the treatment modalities for HCC include surgical resection, trans-arterial embolization (TAE) and chemotherapy. However, these modalities are not completely effective, underscoring the need for development of novel therapeutic approaches.
PTEN, a tumor suppressor that antagonizes the PI3K pathway, is frequently mutated or deleted in various human cancers. Loss of PTEN occurs in 40-50% of surgical resected HCC samples and predicts poor prognosis for HCC patients, suggesting PTEN restoration may constitute
a treatment alternative for HCC. Since PTEN increased ethanol-induced cytotoxicity in hepatoma cells, PTEN gene delivery may serve as an adjuvant therapy in conjunction with ethanol TAE for HCC. In the present study, we evaluated the efficacy of PTEN gene therapy and its combination with ethanol in a syngenic Novikoff hepatoma model by implantation of N1-S1 cells into livers of Sprague Dawley rats. Adenovirus encoding PTEN (Ad-PTEN) or green fluorescent protein (Ad-GFP) was generated for gene delivery studies. The optimal condition for adenovirus vectors to infect N1-S1 cells was determined at multiplicity of infection (MOI) of 100-200. Infection of N1-S1 cells with Ad-PTEN, but not Ad-GFP, increased PTEN levels and led to 40-50% inhibition of cell proliferation via cell cycle arrest. Besides, the half maximal -inhibitory concentration (IC50) for ethanol in N1-S1 cells was determined at 6%. Combination with PTEN gene delivery further augmented the cytotoxicity of ethanol in N1-S1 cells from 40% to 70% inhibition. To evaluate the prevention efficacy of PTEN gene delivery, N1-S1 cells were infected with adenovirus vectors then implanted into livers of Sprague-Dawley rats to induce Novikoff hepatoma. Injection of PBS- or Ad-GFP-treated N1-S1 cells led to large hepatoma (with an average size of 3-4 cm) with tumor incidence of 80-90%. In contrast, injection of Ad-PTEN-infected N1-S1 cells only induced one hepatoma (with size of 0.1 cm) in six rats, suggesting that pretreatment with PTEN gene delivery effectively abolished the tumorigenic potential of N1-S1 hepatoma cells in vivo. In summary, these results validate the feasibility of PTEN gene delivery as a new promising therapeutic strategy for the treatment of orthotopic hepatoma in immune-competent rats.
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THE AVIAN REOVIRUS TRICISTRONIC S1 mRNA: NEW INSIGHTS INTO CONTROL OF TRANSLATION INITIATIONRacine, Trina 17 May 2010 (has links)
The S1 genome segment of avian reovirus is functionally tricistronic, encoding three independent protein products (named p10, p17 and ?C) from three sequential, partially overlapping open reading frames (ORFs). The dogma of translation initiation, the cap-dependent scanning model, suggests that ribosomes would normally only translate the 5?-proximal ORF. Four alternate mechanisms of translation initiation could account for translation of the downstream ?C ORF; an IRES element, reinitiation, ribosome shunting, and leaky scanning. The objective of my doctoral research was to investigate the translation initiation mechanisms that are operative on the S1 mRNA.
Translation of the p10 and p17 ORFs was revealed to be coordinated via standard leaky scanning, while none of the known mechanisms of translation initiation could account for expression of the ?C ORF. Further investigation determined that two alternate cap-dependent mechanisms contribute to translation initiation at the ?C AUG codon. The first mechanism involves a modified version of enhanced leaky scanning. Although insertion of upstream elements known to impede scanning ribosomal subunits dramatically inhibited translation of the downstream ORF in the context of other mRNAs, the same elements only marginally reduced ?C translation. Specific features of the S1 mRNA therefore function to promote leaky scanning and translation of the ?C ORF. The inability to eliminate ?C expression beyond a threshold retention level of ~20-30%, despite the presence of eight upstream start codons that should eliminate leaky scanning, strongly suggests that ribosomes must also utilize a scanning-independent means to access the internal ?C start site. This mechanism for ?C translation initiation, which I termed ribosome handoff, allows ribosomes to bypass upstream elements, and requires a sequence-dependent translation enhancer element present within S1 nucleotides 366-392 that may function to mediate handoff via complementarity with 18S ribosomal RNA.
Translation initiation at the ?C start site is therefore made possible by two alternative mechanisms, enhanced leaky scanning and ribosome handoff from the 5?-cap. The novelty of these two mechanisms highlights the complexity of the translation initiation process and the potential heterogeneity of cellular ribosomes, which raises the possibility that internal initiation may be far more common than currently appreciated.
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Chargement cumulé au bas du dos : effet de l'expérience en manutention et comparaison de méthodes simplifiées pour l'estimerCorriveau, Josianne January 2013 (has links)
Il y a plusieurs facteurs de risque reconnus de lombalgies. Les tâches de manutention ainsi que les chargements cumulés au dos font partis de ces facteurs de risque. Cette étude vise à déterminer si l’expertise à un impact sur le chargement cumulé sur L5/S1 lors de deux tâches de manutention. Il est supposé que les travailleurs expérimentés ont un chargement cumulé moindre que les travailleurs novices. Elle vise également à vérifier l’impact du chargement cumulé sur L5/S1 d'une cadence imposée lors de la première tâche et de la configuration du lieu de travail lors de la 2e tâche. Pour ces objectifs, il est supposé que la cadence imposée apportera un chargement cumulé moins élevé que la cadence libre et qu'il n'y aura pas de différence entre les configurations. Finalement, le dernier objectif est de déterminer le nombre de cycles de manutention minimal nécessaire pour faire une extrapolation des chargements cumulés qui n'aura pas de différence significative lorsque comparé au nombre total de cycles effectués. Il est supposé que l’utilisation d'un nombre restreint de cycles de manutention devrait permettre d'extrapoler les données avec un faible taux d’erreur, mais qu’il en faudra plus de quatre étant donné la variabilité des tâches à accomplir. Quinze manutentionnaires expérimentés et 15 novices ont participé à l’étude. Les participants devaient effectuer deux tâches. La première était une tâche de palettisation où les participants devaient faire des aller-retour à cadences libre et imposée de 24 boîtes d'une palette, vers une autre, pour un total de 96 boîtes considérées. La deuxième tâche était un transfert aller-retour de quatre boîtes d'un convoyeur vers un diable. Soixante-quatre transferts sont faits dans chacune des deux configurations, soit 90° et 180°, pour un total de 128 boîtes déplacées. Un système optoélectronique, une plate-forme de force et un modèle de dynamique inverse ont été utilisés pour estimer les moments de force résultants et asymétriques en L5/S1. L'intégrale des moments a servi à déterminer le chargement cumulé. Des analyses de variance à mesures répétées ont été effectuées afin de déterminer s’il y a des effets d'expertise, de cadence et de configuration. Des tests T ont été effectuées pour comparer les méthodes simplifiées aux standards de comparaison. Un seuil alpha de 0,05 a été utilisé pour tous les tests statistiques. Il n’y a pas d'effet d'expertise sur les moments de force résultants, et ce, pour les deux tâches effectuées, mais les manutentionnaires expérimentés ont des moments de force asymétriques cumulés significativement moins élevés que les manutentionnaires novices lors de la première tâche. La cadence est un facteur déterminant dans le calcul du chargement cumulé. Les moments de force résultants et asymétriques sont moins élevés lors de la cadence imposée plus rapidement que lors de la cadence libre, et ce peu importe l’expertise des manutentionnaires. Aussi, le fait de déplacer des boîtes à 90° donnent des chargements cumulés plus petits qu’à 180°. Les estimations des méthodes simplifiées varient en fonction des différentes conditions observées (cadence, configuration, expertise). Toutefois, les coefficients de variation (COV) de presque toutes les méthodes étudiés sont inférieurs à 10%, ce qui signifie que les résultats seraient semblables à ceux obtenus dans cette étude si la même expérimentation était refaite dans les mêmes conditions. En conclusion, l’expertise ne semble pas être une facteur déterminant qui influence le chargement cumulé, mais la cadence de travail, la configuration de l’espace de travail et le type de transferts effectués semblent en être. Il s'agit de la première étude biomécanique considérant un si grand nombre de transferts de boîtes pour déterminer le nombre minimal de cycles de manutention nécessaire à une extrapolation fiable des chargements cumulés. Pour le moment, la meilleure solution demeure de considérer tous les transferts dans le calcul des chargements cumulés. De plus, le fait de ne pas considérer les périodes où aucune charge n’est supportée par le manutentionnaire, c'est-à-dire les moments où le manutentionnaire n'a pas de boîte dans les mains, sous-estiment de près de 20% les chargements cumulés.
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Segmentação automática para classificação digital de sinais de fonocardiograma / Automatic segmentation for signal classification of digital phonocardiogramAguiar, Nelson Augusto Oliveira de 10 August 2016 (has links)
Com o avanço tecnológico surgem novas ferramentas que auxiliam os médicos no diagnóstico de diversas doenças. Na área cardiovascular, após permanecer por um longo período em segundo plano, a ausculta cardíaca voltou a ser muito utilizada devido ao surgimento, no mercado, de estetoscópios digitais. Tais aparelhos contam com novos recursos tecnológicos que permitem a captação e a análise de dados de forma automática, oferecendo mais informações ao profissional da área. Levando em conta essa nova ascensão da área de Fonocardiografia,o presente trabalho se dedicou à separação das bulhas S1 e S2 por meio de ferramentas computacionais, com o propósito de auxiliar médicos não especialistas em Cardiologia a verificar a existência de possíveis anormalidades no som cardíaco. Acreditando na possibilidade de este procedimento vir a ser utilizado posteriormente para auxiliar no reconhecimento de padrões dos sons cardíacos, este trabalho se propôs a criar um algoritmo para detecção automática de anormalidades que afetam as bulhas S1 e S2. Assim, aplicou-se a técnica de Wavelet sobre uma base de dados de sons cardíacos constituída de 1209 bulhas, auditada pelo Real Hospital Português e também pelo Instituto Dante Pazzanese de Cardiologia. Os melhores resultados obtidos na separação das bulhas foram, nos sons normais, de 96,96% de acurácia para a S1 e de 97,92% para a S2. Já nos sons cardíacos com sopro, obteve-se a acurácia de 87,46% para a separação da S1 e de 89,26% para a S2. Juntos, os resultados dos sons normais e dos sons com sopro totalizaram uma acurácia de 94,02% para a separação da S1 e de 94,54% para a S2. / New technological tools are often created in the medical field to assist doctors in the clinical diagnosis of many diseases. After being forgotten for many years in the cardiovascular area, cardiac auscultation is now back in the spotlight, as soon as digital stethoscope became available in the market. New digital stethoscope records patient\'s heart sounds, which can be automatically analyzed or also sent to another device for further more detailed investigation. This feature helps physicians in the study of auscultation results. Taking into account the new rise of cardiac auscultation, the present paper attempted to provide the separation of S1 and S2 heart sounds by computer tools, in order to support non-specialist physicians in finding heart sound abnormalities. Heart sound separation can thus be employed for the creation of pattern recognition algorithms, which are able to identify abnormalities automatically. This paper proposed the development of a S1 and S2 heart sound separation algorithm by using Wavelet technique, who was applied upon a database containing 1209 individual heart sounds. The referred database was audited by Royal Portuguese Hospital and Dante Pazzanese Institute of Cardiology medical staff. The best obtained results for S1 and S2 separation in regular heart sounds were a 96.96% accuracy rate for S1 and a 97.92% accuracy rate for S2. In murmur heart sounds were obtained an 87.46% accuracy rate for S1 and an 89.26% accuracy rate for S2. Overall results achieved a 94.02% accuracy rate for S1 and a 94.54% accuracy rate for S2.
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Μικροπαλαιοντολογική μελέτη του πυρήνα Ζ1 απο το Ιόνιο. Παλαιοκλιματολογικά- παλαιοοικολογικά συμπεράσματα / Micropaleodological study of core z1 from ionian sea. Paleoclimatological- paleooicological conclusionsΜυλωνά, Γεωργία 17 May 2007 (has links)
Στα ιζήματα του πυρήνα Ζ1, που συλλέχθηκε στο Ιόνιο πέλαγος, πραγματοποιήθηκαν μικροπαλαιοντολογικές (πλαγκτονικά τρηματοφόρα) και ισοτοπικές (δP18PΟ) αναλύσεις. Τα προκαταρκτικά αποτελέσματα της μελέτης οδήγησαν στον εντοπισμό τριών κύριων κλιματικών περιόδων: την τελευταία παγετώδη περίοδο, την μεταβατική περίοδο και το Ολόκαινο. Οι θερμότερες κλιματικές συνθήκες εντοπίζονται κατά τη διάρκεια σχηματισμού του σαπροπηλού S1. Ο σχηματισμός του S1 αποδίδεται στην επικράτηση θερμών και ταυτόχρονα χαμηλής αλατότητας επιφανειακών νερών που είχε ως αποτέλεσμα τη μείωση του ρυθμού κυκλοφορίας στην υδάτινη στήλη και την ανάπτυξη ανοξικών συνθηκών στα νερά του πυθμένα. Επιπλέον, εντοπίστηκαν τέσσερα ψυχρά γεγονότα σύντομης διάρκειας: Το πρώτο κατά τη μεταβατική περίοδο από την τελευταία παγετώδη περίοδο στο Ολόκαινο και πιθανώς πρόκειται για το γεγονός Younger Dryas. Τα άλλα τρία εντοπίζονται κατά τη διάρκεια του Ολοκαίνου εκ των οποίων το πρώτο συμπίπτει με τη λήξη του S1 και το δεύτερο εντοπίζεται κατά τη διάρκεια απόθεσης του S1, χωρίς όμως να προκαλεί (στα μέχρι σήμερα αποτελέσματα) σαφή διακοπή στην ιζηματογένεσή του, όπως έχει εντοπιστεί σε αντίστοιχες περιπτώσεις πυρήνων από την Ανατολική Μεσόγειο. / The preliminary results based on the abundances of planktonic foraminifera and oxygen isotopes at the sediments of the core Z1, selected from the Ionian Sea (Otranto Basin) revealed three main climatic periods: Last Glacial, Late Glacial and Holocene. The warmest conditions of the studied interval prevailed during the formation of sapropel S1. Four stadials occurred during Late Glacial and Holocene. The older corresponds to Younger Dryas event, while the other three occurred during Holocene. The establishment of warm and low salinity surficial waters seems that caused the reduction of water mass circulation and thus the formation of the sapropel S1. Although the presence of a stadial around the middle of the S1, no distinct interruption of the sapropelic sedimentation have been occurred. The younger stadial coincides with the end of the sapropel S1. The evolution of the planktonic assemblages seems to be similar with that of the Central Mediterranean for the studied interval. Therefore, almost all the biozones and ecozones of the Central Mediterranean have been recognized at the sediments of Z1. The application of the factor analysis revealed four factors. The first two correspond to the variation of SST, while the other two are related to the development of high fertility waters during cold periods and during the formation of S1.
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Segmentação automática para classificação digital de sinais de fonocardiograma / Automatic segmentation for signal classification of digital phonocardiogramNelson Augusto Oliveira de Aguiar 10 August 2016 (has links)
Com o avanço tecnológico surgem novas ferramentas que auxiliam os médicos no diagnóstico de diversas doenças. Na área cardiovascular, após permanecer por um longo período em segundo plano, a ausculta cardíaca voltou a ser muito utilizada devido ao surgimento, no mercado, de estetoscópios digitais. Tais aparelhos contam com novos recursos tecnológicos que permitem a captação e a análise de dados de forma automática, oferecendo mais informações ao profissional da área. Levando em conta essa nova ascensão da área de Fonocardiografia,o presente trabalho se dedicou à separação das bulhas S1 e S2 por meio de ferramentas computacionais, com o propósito de auxiliar médicos não especialistas em Cardiologia a verificar a existência de possíveis anormalidades no som cardíaco. Acreditando na possibilidade de este procedimento vir a ser utilizado posteriormente para auxiliar no reconhecimento de padrões dos sons cardíacos, este trabalho se propôs a criar um algoritmo para detecção automática de anormalidades que afetam as bulhas S1 e S2. Assim, aplicou-se a técnica de Wavelet sobre uma base de dados de sons cardíacos constituída de 1209 bulhas, auditada pelo Real Hospital Português e também pelo Instituto Dante Pazzanese de Cardiologia. Os melhores resultados obtidos na separação das bulhas foram, nos sons normais, de 96,96% de acurácia para a S1 e de 97,92% para a S2. Já nos sons cardíacos com sopro, obteve-se a acurácia de 87,46% para a separação da S1 e de 89,26% para a S2. Juntos, os resultados dos sons normais e dos sons com sopro totalizaram uma acurácia de 94,02% para a separação da S1 e de 94,54% para a S2. / New technological tools are often created in the medical field to assist doctors in the clinical diagnosis of many diseases. After being forgotten for many years in the cardiovascular area, cardiac auscultation is now back in the spotlight, as soon as digital stethoscope became available in the market. New digital stethoscope records patient\'s heart sounds, which can be automatically analyzed or also sent to another device for further more detailed investigation. This feature helps physicians in the study of auscultation results. Taking into account the new rise of cardiac auscultation, the present paper attempted to provide the separation of S1 and S2 heart sounds by computer tools, in order to support non-specialist physicians in finding heart sound abnormalities. Heart sound separation can thus be employed for the creation of pattern recognition algorithms, which are able to identify abnormalities automatically. This paper proposed the development of a S1 and S2 heart sound separation algorithm by using Wavelet technique, who was applied upon a database containing 1209 individual heart sounds. The referred database was audited by Royal Portuguese Hospital and Dante Pazzanese Institute of Cardiology medical staff. The best obtained results for S1 and S2 separation in regular heart sounds were a 96.96% accuracy rate for S1 and a 97.92% accuracy rate for S2. In murmur heart sounds were obtained an 87.46% accuracy rate for S1 and an 89.26% accuracy rate for S2. Overall results achieved a 94.02% accuracy rate for S1 and a 94.54% accuracy rate for S2.
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Avaliação Dos Desempenhos Hidráulico e Economico de Um Sistema de Irrigação Localizada Utilizando Programação LinearMarcuzzo, Francisco 02 1900 (has links)
A implantação de pomares cítricos irrigados, em diversas regiões do Estado de São Paulo, onde a variação da declividade é um fator limitante ao desempenho satisfatório da uniformidade de emissão d’água, impulsiona aos projetistas delinearem sistemas de irrigação visando a maior uniformidade de emissão, sem uma certeza sólida de que a mesma se reverterá em maior produção. Este fato acaba por penalizar o produtor irrigante de citros, devido ao alto custo inicial de implantação de um sistema de irrigação localizada, que é fixa e está distribuída em todo o espaço a ser irrigado.A existência de diferentes combinações de uniformidade de emissão na unidade operacional com a declividade do terreno favorece a ocorrência de várias possibilidades de configurações no sistema de irrigação, por conseguinte de diferentes custos de implantação e de posterior manejo do sistema. Desde que bem dimensionado, consegue-se verificar no sistema de irrigação localizada que a otimização do sistema através da programação linear é a melhor metodologia frente aos outros métodos propostos na pesquisa operacional, visto que se encontra a solução ótima global para as variáveis pré-estabelecidas no dimensionamento.Este trabalho teve por objetivo, através da programação linear, avaliar os desempenhos hidráulico e econômico (custos fixos e variáveis) de um sistema de irrigação localizada para a cultura da laranja; analisando se um melhor desempenho hidráulico, em diferentes condições de declividade, reverteria em uma maior receita liquida ao produtor.Os resultados obtidos permitem uma análise consistente dos parâmetros hidráulicos da uniformidade de emissão pré-estabelecida para a linha de derivação, influencia desta nas linhas laterais, produtividade, uniformidade de emissão real e receita liquida do produtor frente às distintas configurações hidráulicas e sob as declividades propostas. Verificou-se que nem sempre a melhor configuração hidráulica reverte em maior lucro ao irrigante para as condições de estudo indicadas. Obteve-se, em ordem decrescente, as lâminas de irrigação que resultaram em maior receita bruta para a laranja irrigada: 7,74; 11,61; 3,87 m3/árvore/ano e, que a 0 e 3% de declividade, os únicos valores de uniformidade de pressão real nas linhas laterais que estão acima dos valores calculados de uniformidade de emissão para a linha de derivação estão a 92%.
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Diversidade genética de amostras brasileiras do vírus da bronquite infecciosa determinada pelo seqüenciamento de nucleotídeos dos genes N e S1. / Genetic diversity of Brazilian isolates of infections bronchitis virus by the sequencing of N and S1 genes.Montassier, Maria de Fatima Silva 27 May 2008 (has links)
Foram submetidos à análise molecular, 15 isolados do vírus da bronquite infecciosa (VBI) obtidos durante o período de 1988 a 2000, de surtos à campo da Bronquite Infecciosa (BI), em aves de corte ou de postura das regiões Sul e Sudeste do Brasil. Os resultados obtidos da análise filogenética das sequências parciais dos genes da glicoproteína de espícula (S1) e da nucleoproteína (N) evidenciaram que a maior parte dos isolados estão distribuídos em dois grandes grupos; o primeiro deles mais estreitamente relacionado às estirpes do genótipo Massachusetts e o segundo constituído apenas por isolados brasileiros autóctones com uma grande diversidade em relação às estirpes ou isolados do grupo Massachusetts e de outros países ou continentes. Os sítios polimórficos mais importantes formaram-se em locais específicos e de maneira agrupada nas sequências dos genes S1 ou N e predominam em regiões codificadoras das cadeias polipeptídicas S1 e N que configuram sítios estruturais e antigênicos importantes envolvidos, na expressão de propriedades biológicas relevantes. / Fifteen Brazilian field isolates of infectious bronchitis virus (IBV); were recovered, between 1988 and 2000, from commercial broiler or layer flocks located in South and Southeast Brazilian regions. Molecular and phylogenetic analysis of partial sequences of 5\'-proximal of S1 gene and 3\'-terminus of N gene from these IBV isolates, identified two main groups; the Massachusetts group and a Brazilian indigenous group, which presenting a high diversity regarding the first group or other IBV strains from different countries and continents. The major polymorphic sites are arranged in clusters and predominate in the regions of S1 and N genes which code for relevant structural and antigenic sites responsible for the expression of important biological properties.
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Staphylococcus aureus protein S1, an RNA chaperone involved in translation initiation and sRNA regulation / La protéine S1 chez Staphylococcus aureus, une protéine chaperonne de l’ARN impliquée dans l'initiation de la traduction et la régulation médiée par des ARN non codantsMarenna, Alessandra 29 September 2017 (has links)
Bien que l'initiation de la traduction soit un processus conservé entre les bactéries, nous avons montré que le mécanisme par lequel les ARNm structurés sont reconnus et adaptés sur le ribosome diffère chez Staphylococcus aureus, un micro-organisme avec un bas taux de G+C et chez Escherichia coli. Une particularité du ribosome de S. aureus est l'absence de la protéine ribosomale S1, qui non seulement est plus courte que celle de E. coli mais qui possède également une organisation distincte des domaines. Mes expériences suggèrent que la protéine S1 (SauS1) favorise spécifiquement l'initiation de la traduction de l'opéron α-psm 1-4 en liant son ARNm hautement structuré. En outre, il influence aussi l'expression et la production de facteurs de virulence comme les exotoxines (α-haemolysine, δ-hémolysine et γ- hémolysine) et les exoenzymes (protéases et lipases). En plus de son rôle dans la traduction, SauS1 pourrait être impliquée dans d'autres processus cellulaires tels que le métabolisme de l'ARN et la régulation par des ARN non-codants (ARNnc). Elle forme des complexes in vivo avec plusieurs ARNnc dont la stabilité serait affectée dans la souche délétée du gène rpsA codant S1. SauS1 a donc une activité chaperonne favorisant la cinétique d’appariement entre deux molécules d'ARN et au moins dans un cas, elle stimule la reconnaissance entre un ARNnc et son ARN cible. Ainsi, SauS1 appartient à une nouvelle classe de chaperons d'ARN qui jouent un rôle clé dans la régulation du virulon de S. aureus. / Even if translation initiation is a conserved process among bacteria, we have recently shown that low G+C content Gram-positive, such as Staphylococcus aureus, differ from E. coli on the mechanism by which structured mRNAs are recognized and adapted on the ribosome. One peculiarity of the S. aureus ribosome is the absence of ribosomal protein S1, which is shorter than E. coli S1 and has different domains organization. My work could demonstrate that S. aureus S1 (SauS1) specifically promotes translation initiation of the α-psm 1-4 operon by binding its highly structured mRNA. Moreover, it influences the expression and production of other exotoxins (α-haemolysin, δ-haemolysin and γ-haemolysins) and exoenzymes (proteases and lipases). Besides its role in translation, SauS1 could be implicated in other cellular processes such as RNA maturation/degradation and sRNA-mediated regulation. It forms in vivo complexes with several sRNAs whose level is affected in a strain deleted of rpsA gene, coding for S1. Preliminary results show that SauS1 has a chaperone activity promoting the kinetic of annealing of two model RNA molecules and at least in one case, we could demonstrate that it stimulates the recognition between a sRNA and its target RNA. Taken together, SauS1 belongs to a new class of RNA chaperones that play key roles in the regulation of S.aureus virulon.
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