L’Urotensine II (UII) est un peptide cyclique de 11 acides aminés initialement isolé à partir de l’urophyse de gobie. Cette hormone est impliquée dans l'homéostasie cardiovasculaire et exerce la majorité de ses effets par l'intermédiaire du récepteur de l'urotensine (UT). Le récepteur UT est couplé préférentiellement à la protéine G hétérotrimérique G?q et les propriétés fonctionnelles de ce récepteur ont principalement été étudiées pour sa capacité à induire la production d'inositol phosphate ainsi que la mobilisation de Ca[indice supérieur 2+] intracellulaire. Il a été rapporté que UT peut également coupler à d'autres protéines G hétérotrimériques G?i/o et qu’il peut activer plusieurs voies indépendantes de la protéine G, tels que la voie des MAP Kinase et de la beta-arrestine. Notre hypothèse stipule que différents ligands d’UT peuvent induire ou stabiliser différentes conformations du récepteur, chacune conduisant à une signalisation spécifique, ce concept est connu sous le nom de sélectivité fonctionnelle ou signalisation biaisée. Nous avons sélectionné 6 analogues de UII qui diffèrent dans leur structure chimique et nous avons évalué leur capacité à activer plusieurs voies de signalisation: G?q G?i, G?13, ERK, NF?B et le recrutement de la ?-arrestine. Par ailleurs, la technologie de transfert d’énergie bioluminescente par résonnance (BRET) fut utilisée pour évaluer l’activation spécifique des protéines G?q, G?i, G?13 ainsi que le recrutement de la ?-arrestine-2. Nous avons montré que la substitution de la lysine en huitième position de UII affecte la propriété du peptide à activer certaines voies de signalisation. De plus, l’analogue Nle8-UII agit comme agoniste complet sur la voie G?q mais active faiblement le recrutement de la ?-arrestine-2 ainsi que la voie NF?B. Cette étude a permis d’identifier des ligands sélectifs pour certaines voies de signalisation d’UT et pourrait permettre la conception de ligands sélectifs pour UT dans diverses pathologies associées à ce récepteur. [symboles non conformes]

Le récepteur relié au récepteur à l'estrogène alpha (ERR?) est un récepteur orphelin de la superfamille des récepteurs nucléaires impliqué dans la régulation du métabolisme énergétique. II cause l'expression de gènes impliqués dans les différentes voies métaboliques et peut ainsi augmenter le potentiel de production d'énergie des cellules. Fidèle à son état d'orphelin, l'activité de ERR? ne semble pas être régulée via la liaison d'un ligand, mais plutôt via la présence des corégulateurs. Les corégulateurs sont des protéines ayant pour fonction d'assister ou de nuire à l'action des récepteurs nucléaires et autres facteurs de transcription dans l'expression de leurs gènes cibles. L'étude de l'interaction entre ERR? et ses corégulateurs s'avère donc être incontournable pour la compréhension de son rôle dans les divers processus où il est impliqué et dans les pathologies auxquelles il est associé comme le cancer qui est un dérèglement cellulaire causé par des altérations génétiques, et est caractérisé par une prolifération incontrôlée de cellules au sein d'un organisme. Pour qu'une cellule devienne cancéreuse, elle doit acquérir des mutations précises au niveau du génome causant des modifications dans la régulation de différents processus. Un de ces processus est le métabolisme énergétique. Le but de ma maîtrise était d'identifier et d'étudier les corégulateurs de ERR? (PGC-1?, PGC-1? et PRC) et leur modulation de gènes cibles de ERR? dans le contexte du métabolisme énergétique du cancer. L'expression de ERR? et des trois membres de la famille PGC-1 a été mesurée par qPCR sur des tissus colorectaux sains et cancéreux appropriés. L'expression de ERR? ne semble pas significativement différente suivant l'apparition de la pathologie, alors que l'expression des coactivateurs PGC1-? et PGC-1? s'avère moins élevée dans les tissus cancéreux par rapport aux tissus sains. L'expression de PRC est plus grande dans le cancer colorectal. Ces résultats suggèrent que PRC pourrait posséder un rôle, exclusif à sa famille, dans le carcinome colorectal. Afin de trouver de nouveaux corégulateurs de ERR?, nous avons procédé à une expérience de double hybride sur levure qui a permis d'identifier 6 nouveaux partenaires d'interactions du récepteur : La leucine aminopeptidase 3 (LAP3), le synaptic nuclear envelope protein 1 (SYNE1 /nesprinl ), le proteasome macropain 26S subunit ATPase (PSMC5), la DEAD box polypeptide 1 (DDXI), le ring finger protein 2 (RNF2/Ring2) et l'interferon-related developmental regulator IFRD1. Leurs fonctions connues peuvent toutes être associées à l'action de ERR?, soit en régulant sa dégradation ou son activité. En particulier, nos résultats pour 1FRD1 montrent que son expression est supérieure dans la presque totalité des cancers colorectaux étudiés par rapport aux tissus sains adjacents. On peut ainsi supposer que cette protéine possède une fonction encourageant la carcinogenèse. De plus, des essais luciférases ont montré qu'IFRD1 augmente l'activité du récepteur nucléaire ERR?. Le partenariat entre ERR? et IFRD I pourrait donc être pertinent lors de la carcinogenèse colorectale. ERR?, PGC-1, PRC, IFRD1.

No description available.

No description available.

The purpose of the study was to investigate a possible connection between alpha-l-antitrypsin (A1AT) deficiency and familial epilepsy and mental retardation of possible congenital or genetic origin.The individuals were genotyped by using a two dimensional cross-electrophoretic procedure. The electrophoretic procedure involved isoelectric focusing on an acid-starch gel followed by immunoelectrophoresis. The control and experimental groups were then statistically compared to population norms by using the chi-square test. The 0.05 level of significance was established as the critical probability level for the nonacceptance of a connection.ResultsOf the 49 individuals in the control group, 46 had, a protease inhibitor (Pi) genotype of PiMM 1 , and there was 1 each of the Pi MF, Pi MS, and Pi Mz genotypes. Of the 50individuals in the familial epilepsy experimental group, 43 were genotyped as PiMM, 2 as PiMS, and 5 as PIMF. Of the 16 individuals in the mental retardation experimental group, 14 were genotyped as PiMM, 1 as PiMS, and 1 as PiMF.The probability of reoccurrence for the various groups were: control - 0.3 to 0.5; familial epilepsy - 0.3 to 0.5; and mental retardation - 0.7 to 0.8.Conclusions1. The applicability of starch gel electrophoresis in a clinical setting is questionable because of cost, length of time required, and difficulty in handling.2. The control group demonstrated no statistical variation in the 1AT frequency from general population norms.3. The familial epilepsy experimental group showed no statistical evidence linking it to abnormal A1AT genotypes.4. The mental retardation experimental group demonstrated no statistical evidence linking it to abnormal A.1 AT genotypes.

Over the past decade, advances in ethylene oligomerization have witnessed explosive growth of interest from both commercial and academic standpoint, with chromium metal invariably being the metal of preference. A common feature in this literature was the extended long debate regarding the mechanism, metal oxidation states responsible for selectivity and the role of the ligand. This thesis work embarked on the isolation and characterization of new active intermediates called “single component catalysts” (or self activating) to address two important questions: (1) how the catalyst precursors re-arrange upon activation and (2) the real oxidation state of the activated species. Four different ligands systems have been examined for this purpose. The first part is a study on the NPIIIN ligand which can be described as a dynamic and non-spectator ligand. Upon aluminum alkyl activation, a series of single component chromium catalysts for selective ethylene oligomerization and polymerization have been isolated, fully characterized and tested. New selective single component chromium(I) catalysts have also been isolated and tested positively for ethylene trimerization. The second part includes a new series of chromium complexes based on the NPVN ligand. This ligands enabled to obtain the first polymer-free extremely active catalytic system. In both NPN ligand systems, a new activation pathway was discovered by using vinyl Grignard reagent [(CH2=CH)MgCl] as activator and/or reducing agent. The third part explores new modified pyrrole-chromium complexes which were found to be highly active and selective ethylene trimerization catalysts. This part was a continuation of previous work from our lab to complete the mechanistic picture of this highly successful pyrrole-chromium catalyst independently commercialized by Phillips-Chevron and Mitsubishi. Interestingly upon aluminum alkyl treatment, the first example of a Schrock-type chromium ethylidene complex has been isolated and characterized and found to be a potent catalyst for selective ethylene trimerization. Finally, the other ligands introduced in this thesis are new systems called pyridine-SNS and Si-SNS that introduce some modification to the known commercial SNS catalyst (Sasol technology). The introduction of a pyridine ring or a silyl unit in the ligand scaffold has allowed to understand the mechanism of action of this remarkable system.

Single image matting refers to the problem of accurately estimating the foreground object given only one input image. It is a fundamental technique in many image editing applications and has been extensively studied in the literature. Various matting techniques and systems have been proposed and impressive advances have been achieved in efficiently extracting high quality mattes. However, existing matting methods usually perform well for relatively uniform and smooth images only but generate noisy alpha mattes for complex images. The main motivation of this thesis is to develop a new matting approach that can handle complex images. We examine the color sampling and alpha propagation techniques in detail, which are two popular techniques employed by many state-of-the-art matting methods, to understand the reasons why the performance of these methods degrade significantly for complex images. The main contribution of this thesis is the development of two novel matting algorithms that can handle images with complex texture patterns. The first proposed matting method is aimed at complex images with homogeneous texture pattern background. A novel texture synthesis scheme is developed to utilize the known texture information to infer the texture information in the unknown region and thus alleviate the problems introduced by textured background. The second proposed matting algorithm is for complex images with heterogeneous texture patterns. A new foreground and background pixels identification algorithm is used to identify the pure foreground and background pixels in the unknown region and thus effectively handle the challenges of large color variation introduced by complex images. Our experimental results, both qualitative and quantitative, show that the proposed matting methods can effectively handle images with complex background and generate cleaner alpha mattes than existing matting methods.

Cutaneous melanoma remains the deadliest form of skin cancer, with a diagnosis of metastasis indicating a median survival rate of less than a year. Solar ultraviolet (UV) radiation, especially childhood sun exposure, is an important etiological risk factor of melanoma. Previous studies determined that mice selectively lacking the nuclear hormone receptor Retinoid X Receptor α in epidermal keratinocytes (RXRα[superscript ep-/-]) developed a higher number of aggressive melanocytic tumors compared to wild type mice after two-step chemical carcinogenesis, suggesting a novel role of keratinocytic nuclear receptor signalling during melanoma progression. We then discovered a progressive loss of RXRα expression in epidermal keratinocytes during melanoma progression in humans. We also investigated the contributions of CDK4[superscript R24C/R24C] and keratinocytic RXRα to influence metastatic progression in a mouse model by generating RXRα[superscript ep-/-]/CDK4[superscript R24C/R24C] bigenic mice containing an activated cyclin dependent kinase 4 (CDK4), besides lacking RXRα in epidermal keratinocytes. Those bigenic mice developed malignant melanomas that metastasized to regional lymph nodes after carcinogen exposure. Expression of several keratinocyte-derived growth factors implicated in melanomagenesis were upregulated in the skin of bigenic mice, and recruitment of RXRα was shown on the promoters of endothelin-1 (Edn1) and hepatocyte growth factor (Hgf). We then confirmed a downregulation of factors (FAS, E-cadherin and PTEN) implicated in apoptosis, invasion and survival within the melanocytic tumors. To further evaluate the paracrine role that EDN1 has on melanocyte activation, we utilized a transgenic mouse model where the gene encoding Edn1 was selectively ablated from epidermal keratinocytes using the Cre-LoxP strategy to create the EDN1[superscript ep-/-] knockout mouse line. We discovered a direct in vivo transcriptional regulation of keratinocytic Edn1 by the tumor-suppressor p53 in epidermal keratinocytes in response to UV irradiation. We also demonstrate that in vivo disruption of keratinocyte-derived EDN1 signaling alters melanocyte proliferation and decreases epidermal and dermal melanocyte populations in both normal and UV exposed mouse skin. EDN1 also has a protective role against UVR-induced DNA damage and apoptosis and similar effects on UV-induced melanocyte proliferation and DNA damage are observed in p53-null mice. Inhibition of EDN1 signaling by topical application of an EDNRB antagonist BQ788 on mouse skin also recapitulates epidermal EDN1 ablation. Furthermore, treatment of primary murine melanocytes with BQ788 abrogates signaling downstream of this receptor. Taken together, these studies demonstrate the contribution of RXRα regulated keratinocytic paracrine signaling during the cellular transformation and malignant conversion of melanocytes. Also, they establish an essential role of EDN1 in epidermal keratinocytes to mediate UV-induced melanocyte homeostasis in vivo. / Graduation date: 2013

Human centromeres contain large arrays of α-satellite DNA that are thought to provide centromere function. These arrays show size and sequence variations. However, the lower limit of the sizes of these DNA arrays in normal centromeres is unknown. Using a set of chromosome-specific α-satellite probes for each of the human chromosomes, interphase Fluorescence In Situ Hybridisation (FISH) was performed in a population screening study. This study demonstrated that extreme reduction of chromosome-specific α-satellite is unusually common in chromosome 21 (screened with the αRI probe), with a prevalence of 3.70%, compared to <=.12 % for each of chromosomes 13 and 17, and 0 % for the other chromosomes. No analphoid centromere was identified in over 17,000 morphologically normal chromosomes studied. All the low-alphoid centromeres are fully functional as indicated by their mitotic stability and binding to centromere proteins including CENtromere Protein-A (CENP-A), CENtromere Protein-B (CENP-B), CENtromere Protein-C (CENP-C), and CENtromere Protein-E (CENP-E). Sensitive metaphase FISH analysis of the low-alphoid chromosome 21 centromeres established the presence of residual αRI as well as other non-αRI α-satellite DNA suggesting that centromere function may be provided by (i) the residual αRI DNA, (ii) other non-αRI a-satellite sequences, (iii) a combination of i and ii, or (iv) an activated neocentromere DNA. (For complete abstract open document)

Thèse (M.Sc.)--Université Laval, 2007. / Bibliogr.: f. [105]-118. Publié aussi en version électronique dans la Collection Mémoires et thèses électroniques.