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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Kalibreringav mikrovågsinstrumentet HK1-Mc för ostarna Herrgård 17 % och Grevé 17 %

Harrysson, Louise January 2013 (has links)
Under föreliggande studie studerades vattenhalten och höjden hos hårdostsorterna Herrgård med en fetthalt på 17 % (H17 %) och Grevé med en fetthalt på 17 %(G17 %). Syftet med studien var att kalibrera mikrovågsinstrumentet HK1-Mc. Instrumentet använder produktens höjd och vattens dielektriska egenskaper, för att mäta vattenhalten hos ostarna. Arbetet inleddes med en enpunktskalibrering av instrumentet varpå erhållna mätdata jämfördes med analysvärden från ett FTIR-instrument, som användes som referensanalysmetod. Erhållna mätvärden från mikrovågsinstrumentet och IR-instrumentet matades in i ett kalkylprogram som rekommenderats av tillverkaren, (Harrer & Kassen), varpå lämpligt ”slope” och ”intercept” erhölls för mikrovågsinstrumentet. Enligt erhållna mätvärden på vattenhalt från HK1-Mc respektive FTIR-instrumentet förelåg en korrelation mellan instrumenten på 1,1 %. Enligt erhållna värden från instrumentet HK1-Mc, finns det ett samband mellan vattenhalten och höjden på ostarna, determinationskoefficient på 60,4 %, efter kalibrering. Resultatet kan ej anses rimligt vid kalibrering av instrumentet och enligt mätvärden erhållna från referensinstrumentet är sambandet betydligt svagare, determintationskoefficient på 3,5 %, mellan vattenhalt och höjd efter kalibrering. Detta värde kan anses rimligt vid kalibrering av instrumentet. Korrelationen mellan vattenhalt och höjd kan bero på en förändring i förhållande mellan bundet och fritt vatten i och med att höjden på ostarna förändras med tiden. Korrelationen kan även bero på att uttagna prover under pågående kalibrering inte haft en tillräckligt stor spridning, vilket kan leda till att lutningen hos kalibreringskurvan blir felaktig. I slutskedet av arbetet upptäcktes att samtliga tidigare kalibrerade kanaler i mikrovågsinstrumentet ger en korrelation mellan vattenhalt och höjd. Trenden hos samtliga kanaler gör att nuvarande pågående kalibrering är obrukbar. Det finns misstanke om att minnet eller höjdsensorn hos instrumentet på något sätt har förändrats eller påverkats. Flera andra tekniska orsaker kan ligga till grund för instruments beteende.Orsaken / orsakerna till de tekniska problemen är under utredning. / The present study investigated the water content and the height of the hard cheese varieties Herrgård with a fat content of 17% (H17%) and Grevé with a fat content of 17% (G17%). The aim of this study was to calibrate the microwave instrument HK1-Mc. The microwave instrument HK1-Mc uses the microwaves in combination with the product height and dielectric properties of water, to measure the water content in cheeses. The work began with a one-point calibration of the instrument, where obtained data were compared with assay values from an FTIR instrument, which was used as the reference method of analysis. The obtained measurement data from the microwave instrument and IR instrument where inserted into a spreadsheet program recommended by the manufacturer HK1-Mc, (Harrer & Kassen), from which the appropriate "slope" and "intercept" values were obtained for the microwave instrument. According to the measurements obtained on water from HK1-Mc respective FTIR instrument there is a correlation between the instruments of 1.1%.According to the measurements obtained from the instrument HK1-Mc, there is a correlation between water content and height of the cheeses, coefficient of determination of 60.4%, after calibration, this results can not be considered reasonable in the calibration of the instrument. According to measurements obtained from the reference instrument the relationship is significantly weaker, determintationskoefficient of 3.5% between water content and height after calibration, this value can be considered reasonable in the calibration of the instrument. The correlation between water content and height can be due to a change in the relationship between bound and free water because the height of the cheeses changes with time. The correlation may also be due to that the samples during calibration had a narrow distribution, which may have led to the “slope” of the calibration curve being incorrect. In the final stage of the work it was discovered that all of the previously calibrated channels in the microwave instrument provide a correlation between water content and height. The trend among all channels makes the current calibration unusable. There is a suspicion that the memory or height sensor of the instrument has been changed or influenced. Several other technical reasons can be the basis for the instrument's behavior. The cause / causes of the technical problems are under investigation.
2

Anàlisi de l'obra narrativa de Ferrater Mora des de la seva filosofia

Bardera Poch, Damià 06 March 2015 (has links)
In this thesis we offer a philosophical reading of Josep Ferrater Mora’s narrative work, starting from Ferrater Mora’s philosophical thought. Thus, this is an intraferraterian doctoral thesis, which aims at proving that Ferrater Mora’s narrative work literarily reflects some of the key concepts and proposals of his thought: integrationism, the dispositions of being and meaning, some aspects of applied ethics, his philosophical anthropology and the importance of death. Regarding the secondary objectives ––all of which derivate from the main objective–– we aim at: i) proving how the author’s narrative work complements and nuances his philosophical work, for it contains aspects and issues hardly dealt with in his thought ––such as modern literary utopia and utopia in general; ii) seeing how the existence of Ferrater Mora’s narrative work is not an «accident» in his intellectual production, but the complete opposite; iii) making clear that Ferrater Mora’s thought and method are not only useful to analyze his narrative, but they also succeed in analyzing other aspects that are not directly related to Ferrater Mora or his narrative. / Aquesta tesi proposa una lectura filosòfica de l’obra narrativa de Josep Ferrater Mora a partir del pensament (i des del pensament) del propi autor. Es tracta, doncs, d’una tesi doctoral intraferrateriana, l’objectiu principal de la qual és demostrar que l’obra narrativa de Ferrater Mora reflecteix, literàriament, alguns dels conceptes i propostes claus del seu pensament: l’integracionisme, les disposicions ésser i sentit, algunes qüestions d’ètica aplicada, la seva antropologia filosòfica i la importància de la mort. Quant als objectius secundaris del treball, ens en proposem tres, tots ells derivats de l’objectiu principal: i) mostrar com l’obra narrativa de l’autor complementa i matisa la seva obra filosòfica, ja que conté aspectes i qüestions molt poc tractats en el seu pensament, com ara qüestions relacionades amb la utopia literària moderna i amb la utopia en general; ii) veure com l’existència de l’obra narrativa de Ferrater Mora no és un «accident» en el conjunt de la seva producció intel•lectual, ans al contrari; iii) fer evident que el pensament i mètode de Ferrater Mora no només serveixen per analitzar la seva narrativa, sinó que es revelen reeixits a l’hora d’analitzar altres aspectes no relacionats directament ni amb ell ni amb la seva narrativa.
3

Caratteristiche biologiche e potenziale applicativo delle cellule staminali derivate da membrane fetali / Biological characteristics and potential applications of fetal membranes derived stem cells

Costa, Roberta <1983> 08 May 2013 (has links)
La ricerca sulle cellule staminali apre nuove prospettive per approcci di terapia cellulare. Molta attenzione è concentrata sulle cellule staminali isolate da membrane fetali, per la facilità di recupero del materiale di partenza, le limitate implicazioni etiche e le caratteristiche delle popolazioni di cellule staminali residenti. In particolare a livello dell’epitelio amniotico si concentra una popolazione di cellule (hAECs) con interessanti caratteristiche di staminalità, pluripotenza e immunomodulazione. Restano però una serie di limiti prima di arrivare ad un’applicazione clinica: l’uso di siero di origine animale nei terreni di coltura e le limitate conoscenze legate alla reazione immunitaria in vivo. La prima parte di questo lavoro è focalizzata sulle caratteristiche delle hAECs coltivate in un terreno privo di siero, in confronto a un terreno di coltura classico. Lo studio è concentrato sull’analisi delle caratteristiche biologiche, immunomodulatorie e differenziative delle hAECs. L’interesse verso le caratteristiche immunomodulatorie è legato alla possibilità che l’uso di un terreno serum free riduca il rischio di rigetto dopo trapianto in vivo. La maggior parte degli studi in vivo con cellule isolate da membrane fetali sono stati realizzati con cellule di derivazione umana in trapianti xenogenici, ma poco si sa circa la sopravvivenza di queste cellule in trapianti allogenici, come nel caso di trapianti di cellule di derivazione murina in modelli di topo. La seconda parte dello studio è focalizzata sulla caratterizzazione delle cellule derivate da membrane fetali di topo (mFMSC). Le caratteristiche biologiche, differenziative e immunomodulatorie in vitro e in vivo delle mFMSC sono state confrontate con i fibroblasti embrionali di topo. In particolare è stata analizzata la risposta immunitaria a trapianti di mFMSC nel sistema nervoso centrale (CNS) in modelli murini immunocompetenti. / The stem cell research opens new perspectives for cell therapy approaches. Much attention has been focused on stem cells isolated from fetal membranes, for the easy recovery of these tissues, the limited ethical implications and the characteristics of resident stem cells. In particular from the amniotic epithelium it is possible to isolate a population of cells (hAECs) with interesting characteristics of stemness, pluripotency and immunomodulation. However, before going to clinic there are some limitations to overcome: the use of culture media supplemented with animal serum and the limited knowledge related to immune reactions in vivo. The first part of this work is focused on the characterization of hAECs cultured in a serum-free medium, in comparison to a classical culture medium. The study is concerned with the biological, immunomodulatory and differentiation properties of hAECs. The interest towards immunomodulatory characteristics is related to the possibility that using a serum free medium could reduce the risk of grafts rejection after transplantation in vivo. The majority of in vivo studies with cells isolated from fetal membranes were carried out with human-derived cells in xenogeneic transplantation, but little is known about the survival of these cells in allogeneic settings, as for transplantation of murine cells in mouse models. The second part of this study is focused on the characterization of cells derived from murine fetal membranes (mFMSC). Biological characteristics, differentiation potential, in vitro and in vivo immunomodulatory properties of mFMSC has been compared with mouse embryonic fibroblasts. In particular we analyzed the immune response towards mFMSC grafted in the central nervous system (CNS) of immunocompetent mice.
4

Ricerca di polimorfismi genetici e di marcatori molecolari associati al carcinoma del colon-retto a scopo diagnostico e prognostico / Search for genetic polymorphisms and molecular markers associated with colorectal cancer for diagnostic and prognostic purposes

Rodia, Maria Teresa <1986> 19 April 2016 (has links)
Il carcinoma del colon-retto (CCR) comprende tutte le neoplasie con sede tra il cieco ed il retto. E’ il tumore più frequente nella popolazione italiana. Tra le cause che ne influenzano il rischio sono noti sia fattori esogeni che endogeni. La componente genetica riveste un ruolo chiave, infatti le cellule tumorali presentano mutazioni ereditate o acquisite a carico di numerosi geni coinvolti nelle principali vie di segnalazione, replicazione e riparazione. I nostri studi si sono rivolti all’identificazione di modificazioni nell’ambito degli acidi nucleici, mediante analisi di un semplice campione di sangue periferico. Abbiamo voluto indagare sia sul rischio genetico di contrarre la malattia e dunque sulla predittività, che sul riscontro della patologia e dunque sulla diagnosi e sulla prognosi. Studi molecolari hanno difatti evidenziato che alcuni polimorfismi a carico di determinati geni possono contribuire allo sviluppo di patologie tumorali. Il mio lavoro ha mirato, da una parte, a verificare se alcune varianti alleliche dei geni CDH1, MDR1 (ABCB1), ROCK1 e ROCK2 potessero essere considerate fattori di suscettibilità alla patologia, per un possibile impiego in qualità di marcatori predittivi e, dall'altra, ad identificare mRNA marcatori specifici, selezionati tramite un programma bioinformatico utilizzando, per la validazione, campioni di sangue provenienti da pazienti affetti da cancro del colon-retto e controlli sani. L’indagine condotta sui polimorfismi scelti per i geni indagati, ha evidenziato, per alcuni, un’associazione significativa, che mi ha permesso di raccogliere dati interessanti sull’eziologia del CCR. Lo studio di mRNA candidati marcatori, mi ha permesso di identificare TSPAN8, LGALS4 e COL1A2 quali promettenti strumenti di diagnosi e prognosi per il carcinoma del colon-retto. Ulteriori studi saranno necessari per testare i candidati biomarcatori in test di predittività, screening e di follow-up. / The colorectal cancer (CCR) includes all cancers located between the caecum and the rectum. It is the most common cancer in the Italian population. Among the causes that influence the risk they are known both exogenous and endogenous factors. The genetic component plays a key role, in fact, cancer cells have inherited or acquired mutations of many genes involved in major signaling, replication and repair pathways. Our studies were directed to the identification of modifications in the context of nucleic acids, by analyzing a simple peripheral blood sample. We investigated both the genetic risk of contracting the disease and thus the prediction, and on the detection of the disease and thus on diagnosis and prognosis. Molecular studies have indeed shown that some polymorphisms of certain genes may contribute to the development of cancer. My work has focused, on the one hand, to see if some allelic variants of CDH1, MDR1 (ABCB1), ROCK1 and ROCK2 genes could be regarded as factors of susceptibility to disease, for possible use as predictive markers and, on the other hand, to identify specific mRNA markers, selected through a bioinformatics program using, for the validation, blood samples from patients with colorectal cancer and healthy controls. The investigation conducted on polymorphisms chosen for the investigated genes, showed, for some of them, a significant association, which allowed me to gather interesting data on the etiology of the CRC. The study of candidated mRNA markers, allowed me to identify TSPAN8, LGALS4 and COL1A2 such promising diagnostic and prognosis tools for colorectal cancer. Further studies will be needed to test the candidated biomarkers for predictive testing, screening and follow-up.
5

La detenzione amministrativa degli stranieri. Nuove frontiere in materia di liberta' personale / Immigration detention and legal safeguards against arbitrary detention

Cancellaro, Francesca <1984> January 1900 (has links)
La detenzione amministrativa degli stranieri, pur condividendo il carattere tipicamente afflittivo e stigmatizzante delle pene, non si fonda sulla commissione di un reato e non gode delle medesime garanzie previste dal sistema della giustizia penale. Nel nostro ordinamento l’inadeguatezza della legislazione, l’ampio margine di discrezionalità rimesso all’autorità di pubblica sicurezza, nonché il debole potere di sindacato giurisdizionale rimesso all’autorità giudiziaria, raggiungono il loro apice problematico nell’ambito delle pratiche di privazione della libertà personale che hanno per destinatari gli stranieri maggiormente vulnerabili, ossia quelli appena giunti sul territorio e il cui status giuridico non è ancora stato accertato (c.d. situazione di pre-admittance). E’ proprio sulla loro condizione che il presente lavoro si focalizza maggiormente. Le detenzioni de facto degli stranieri in condizione di pre-admittance sono analizzate, nel primo capitolo, a partire dal “caso Lampedusa”, descritto alla luce dell’indagine sul campo condotta dall’Autrice. Nel secondo capitolo viene ricostruito lo statuto della libertà personale dello straniero sulla base dei principi costituzionali e, nel terzo capitolo, sono analizzati i principi che informano il diritto alla libertà personale nell’ambito delle fonti sovranazionali, con particolare riferimento al diritto dell’Unione Europea e al sistema della Convenzione Europea dei Diritti dell’Uomo. Sulla scorta dei principi indagati, nel quarto capitolo è tracciata l’evoluzione legislativa in materia di detenzione amministrativa dello straniero in Italia e, nel quinto capitolo, è approfondito il tema dei Centri dell’immigrazione e delle regole che li disciplinano. Nelle conclusioni, infine, sono tirate le fila del percorso tracciato, attraverso la valutazione degli strumenti di tutela in grado di prevenire le pratiche di privazione della libertà informali e di garantire uno standard minimo nella tutela della libertà individuale, anche nelle zone di frontiera del nostro ordinamento. / This thesis focuses on the issue of the legality of migrants’ detention immediately following disembarkation on EU shores. Under Italian practice, this phase is one of those where access to justice and legal advice are poorly protected, so that under the justification of necessity and urgency, cases of unlawful deprivation of liberty frequently take place without any legal basis and judicial review. This has been the case at the Immigration Centre located on Lampedusa Island in recent years, where under the label of ‘reception’ in reality migrants have been subjected to unlawful detention. As personally observed by the author, who carried out some fieldwork research within this Centre, the above situation has represented a case of arbitrary detention in breach of the principles established in the Italian Constitution and in International Conventions, in primis in the case law under the European Convention of Human Rights. This thesis builds on the Lampedusa case study with the aim of suggesting better ways to protect migrants’ personal liberty. Starting from the evaluation of the general legal safeguards available in the field of immigration detention in Italy, this thesis criticizes the habeas corpus system, specifically addressed to those who are in limbo’ between the arrival at the border of Europe and the determination of their individual legal status. It concludes that in Italy a migrant’s right to personal liberty is undermined by the lack of legal remedies in the Italian system.
6

Il volto europeo del reato di negazionismo tra richieste di incriminazione UE e principi fondamentali CEDU / The crime of denialism in Europe: EU requests of criminalization vis-à-vis ECHR principles on free speech

Lobba, Paolo <1983> 14 June 2013 (has links)
La presente indagine mira ad esaminare, in chiave innovativa, i rapporti tra l’Europa ed un reato prettamente europeo: il negazionismo. Sviluppatosi in maniera assolutamente predominante nel nostro continente, le ragioni della sua diffusione sono molteplici. Al di là della lotta a razzismo ed antisemitismo, il motivo principale va identificato nel ruolo “fondativo” che riveste la memoria dell’Olocausto in Europa, collocata nel cuore dell’universo valoriale su cui si reggono i due principali attori europei, ovverosia l’Unione europea e la Corte europea dei diritti dell’uomo. La ricerca, dunque, ruota attorno a due poli tematici. Da un lato, sono state esaminate le politiche normative dell’Unione europea in materia di razzismo e xenofobia, entro cui spicca la promozione dell’incriminazione del negazionismo “allargato”, cioè esteso alle condotte di negazione non solo dell’Olocausto, ma anche degli altri crimini internazionali. Dall’altro lato, l’analisi della trentennale giurisprudenza della Corte di Strasburgo in materia ha evidenziato come, con riguardo alle manifestazioni negazioniste, sia stato elaborato uno “statuto speciale”, che si risolve nel perentorio diniego di tutela per questa categoria di opinioni, sottratte a monte all’ordinario giudizio di bilanciamento in quanto giudicate incompatibili con i valori sottesi alla CEDU. Lo scopo di questo lavoro riposa nel tentativo di individuare le interazioni tra questi due sistemi istituzionali, per interpretare una tendenza che converge con nettezza verso un incremento della repressione penale della parola. Da questo complesso intreccio di norme e principi, di hard law e soft law, sarà possibile enucleare la natura giuridica ed il contenuto delle richieste di incriminazione rivolte agli Stati membri. Una volta appurato che agli Stati è concesso di restringere il campo di applicazione del reato di negazionismo, adottando degli indici di pericolosità delle condotte, sarà analizzata la tenuta di questi “elementi opzionali del reato” alla luce dei principi penalistici di tassatività, materialità, offensività e laicità. / The present study aims to analyse the legal treatment of the crime of denialism by the two main European actors, namely the European Union (‘EU’) and the European Court of Human Rights (‘ECtHR’). These two systems find themselves in a delicate position that raises a need for deep investigation. They have to cherish and protect the memory of a historical event that is central to their own identity, whereas at the same time promoting the respect of fundamental rights such as freedom of speech. The first section seeks to identify the obligations stemming from the EU legal system, the institutional mandate of which is to harmonise criminal legislation of Member States by setting some basic common elements. Notably, the impact on domestic systems of the Framework Decision 2008/913/JHA on racism and xenophobia shall be assessed. The second part of the present research shall turn to the jurisprudence of the ECtHR to examine the relationship between Holocaust denial as a crime and the right to freedom of expression, with a view to deducing the principles with which States have to comply in the criminalisation of this kind of utterance. The overall goals shall be to identify: a) the interactions between these two systems; b) whether their policies on denialism may be better portrayed in terms of contrast or mutual support; c) the legal nature and content of the obligations originating for the Member States; d) whether a Europe-wide criminal prohibition on denialism appears likely to occur, whether it would be desirable and, if so, under which conditions.
7

Three Jacobean Spenserians : William Browne, George Wither and Christopher Brooke

O'Callaghan, Michelle Francis January 1993 (has links)
No description available.
8

The puzzle of the prayer : a study of John 17

Diehl, Judith A. January 2007 (has links)
This thesis is an investigation into the literary features of the prayer in John 17. Often called the “High Priestly Prayer of Jesus,” this traditional title for John 17 does not adequately cover the depth of significance and meaning realized in the prayer. The main chapters of the investigation include characterization, structure and setting, style and imagery, the genre of the Farewell Discourses and the form of the prayer itself. The prayer is used by the Gospel author to summarize and emphasize key themes and motifs for the benefit of the author’s intended readers. The author intentionally broke from the narrative story and included extensive discourse material, including this prayer, to encourage and inform the community of Christfollowers to whom he wrote. In a dramatic way, the prayer reflects the fulfillment of redemptive prophecies from the past and guarantees a new relationship between God and his people, sealed in the person and the work of Jesus. The prayer promises the benefits of “eternal life” to the people who receive the words of Jesus. Chapter 17 is a critical literary “hinge” that informs the reader in two directions, past and future. John 17 is a promise and a hope, positioned as a rhetorical, epideictic conclusion, for the encouragement of the Gospel readers past, present and future.
9

Niveles de IL-6, IL-10, IL-17, IL21 y TGF-B1 asociados a la periodontitis crónica :Financiado por proyecto FONDECYT 1090046

Rivas Mayorga, Catalina Andrea January 2011 (has links)
Trabajo de Investigación Requisito para optar al Título de Cirujano Dentista / Autor no autoriza el acceso a texto completo de su documento / INTRODUCCIÓN: La periodontitis crónica es una enfermedad de origen infeccioso caracterizada por la interacción entre bacterias patógenas y mecanismos de defensa del hospedero. Se ha demostrado que las citoquinas IL-6, IL-21, y TGF-β participan en la diferenciación de células Th17, mientras que TGF-β , en ausencia de las otras mencionadas, induce la diferenciación de células Treg. Esto indica una fuerte relación entre células Th17 y Treg: si se favorece la producción de las primeras se fomenta la destrucción tisular, mientras que las Treg, se asocian a una respuesta protectora para los tejidos. El objetivo de este trabajo fue identificar a IL-21 y cuantificar los niveles de IL-21, IL-17, IL-6, IL-10 y TGF-β en fluido gingival crevicular (FGC) de sujetos con periodontitis crónica e individuos periodontalmente sanos. METODOLOGÍA: Se seleccionaron 20 sujetos sin periodontitis y 20 con diagnóstico de periodontitis crónica según criterios de inclusión y exclusión. Se obtuvieron muestras de FGC usando tiras de papel en sacos ≥ 5mm en enfermos, y en sitios sin signos clínicos de inflamación ni destrucción periodontal en el grupo control. La presencia de las citoquinas se determinó mediante Western-blot, y la cuantificación se realizó mediante test de ELISA. Los valores obtenidos fueron analizados con los test estadísticos correspondientes (Shapiro-Wilk y MannWhitney), considerando un p<0,05 como estadísticamente significativo. RESULTADOS: Al realizar el Western-blot fue posible identificar todos los mediadores inflamatorios mencionados. Los niveles detectados de IL-6 (1,27(1,70) pg/mL v/s 7,66(7,66) pg/mL), IL-21 (16,16(13,75) pg/mL v/s 11,38(3,21) pg/mL) e IL-10 (48,0(55,33) pg/mL v/s 4,67(7,33) pg/mL) fueron mayores en muestras de sujetos con periodontitis crónica, con una diferencia estadísticamente significativa respecto a los sanos. IL-17 (156,52(164,35) pg/mL) y TGF-β (6,92(9,63) pg/mL) fueron medibles en FGC de enfermos, pero indetectables en el de sujetos sanos. CONCLUSIÓN: Los resultados obtenidos indican que existe un desbalance entre las citoquinas relacionadas con Treg y Th17 en el FGC de individuos enfermos, con respecto a sujetos periodontalmente sanos. Esto podría ser un indicio del posible desequilibrio de estas células en periodontitis crónica, con una t endencia a la diferenciación de Th17 y, por ende, a la inflamación y destrucción tisular característica de esta patología.
10

Biosynthesis, role(s) and regulation of the PI-2b pilus in the hypervirulent ST-17 clone of Streptococcus agalactiae / Biosynthèse, rôle(s) et régulation du pilus PI-2b dans le clone hypervirulent ST-17 de Streptococcus agalactiae

Szili, Noémi Réka 07 June 2017 (has links)
Streptococcus agalactiae (Streptocoque du Groupe B, SGB) est une bactérie pathogène opportuniste à Gram-positif responsable principalement d’infections néonatales. Les études épidémiologiques ont montré que les souches appartenant au complexe clonal 17 (ST-17) sont responsables de 80% des cas de méningites tardives. La génomique comparative a permis de mettre en évidence des gènes codant pour des protéines de surface spécifiques au clone ST-17 comme les adhésines Srr2 et HvgA. On y trouve également un locus codant pour un pilus spécifique appelé PI-2b, qui constitua l’objet principal de cette thèse. Ce locus PI-2b est ubiquitaire dans les souches ST-17, mais on le retrouve également dans quelques souches humaines non-ST-17 comme la souche A909 ainsi que dans les souches bovines. Dans la première partie de ce travail, nous avons comparé l’expression du pilus PI-2b dans les souches ST-17 versus non-ST-17. L’expression du locus PI-2b, bien que variable au sein du complexe ST-17, est plus faible que dans les souches non-ST-17. Dans la souche représentative du ST-17 BM110, l’expression du gène spb1codant pour la piline majeure est 4-6 fois plus faible que dans la souche A909. Nous avons montré que cet effet est dû à la présence d’une séquence de 43 paires de base en amont du locus PI-2b, formant une structure de type tige-boucle, qui empêche la transcription provenant du locus situé en amont codant pour l’antigène B. Grâce à des expériences de fusion transcriptionnelle avec un gène rapporteur codant pour la GFP, nous avons montré qu’une région étendue du promoteur ainsi que des facteurs spécifiques à S. agalactiae sont nécessaires pour l’expression maximale du locus PI-2b. Le niveau maximal de transcription du pilus PI-2b est observé à 37 °C. L’ensemble de nos résultats suggère une régulation complexe de l’expression du locus PI-2b, dont l’expression plus faible dans les souches ST-17, pourrait conférer aux bactéries la capacité d’échapper au système immunitaire de l’hôte et de disséminer plus efficacement. La deuxième partie de ce travail a porté sur le rôle des gènes orf, lep et san1519 dont la fonction sur la biosynthèse du pilus n’était pas connue. Nous avons montré que les gènes orf et lep sont importants pour l’expression et la polymérisation du pilus PI-2b. Nous avons montré que lep code pour une signal peptidase fonctionnelle qui participe à la maturation de la piline majeure. Quant à orf, nos autres résultats ainsi le chevauchement traductionnel entre ce gène et lep, conservé dans d’autres espèces de streptocoques, suggèrent un rôle dans la stabilisation des ARNm / Streptococcus agalactiae (also known as Group B Streptococcus, GBS) is an opportunistic Gram-positive pathogen responsible for severe invasive infections, especially in neonates. GBS strains belonging to the ST-17 sequence type are responsible for 80% of late-onset neonatal meningitis. Genomic comparison of ST-17 strains to non-ST-17 GBS isolates revealed a few surface proteins that are characteristic of ST-17 clone, such as HvgA and Srr2, which contribute to colonization and dissemination. Similarly, the PI-2b type pilus is conserved in ST-17 strains and the main goal of this PhD project was to decipher the role of this pilus in the physiopathology of ST-17 strains. In the first part of this work, we compared the expression of the PI-2b pilus in our ST-17 representative strain BM110, and a non-ST-17 human clinical isolate, A909. We showed that PI-2b expression, although variable, was lower in ST-17 isolates as compared to non ST17 isolates. In the representative strain BM110, we demonstrated that the lower expression was be due to the presence of a 43-base pair (bp) hairpin-like structure in the upstream region of PI-2b, preventing read-through transcription from upstream antigen B (AgB) operon. Furthermore, gene reporter assays to characterize the Ppi-2b promoter region revealed the requirement of an extended 5’ region and of GBS-specific regulatory factors to drive PI-2b transcription. PI-2b transcription was shown to be maximal at 37 °C. Collectively our results suggest a complex regulation of PI-2b expression in ST-17 clinical isolates, that may confer a selective advantage in the human host either by reducing host immune responses and/or increasing their dissemination potential.In the second part of this work, we sought to investigate the role of the putative adhesin AP1-2b, and the two accessory genes lep and orf in the biosynthesis of PI-2b pilus. We showed that both orf and lep are important for PI-2b expression. Our results suggest that Lep is a functional signal peptidase involved in the optimal processing of the major PI-2b pilin. The role of orf remains to be uncovered

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