has been significant progress in the development of new technologies and methodologies to characterize gene expression. The fluorescent-based real-time reverse transcription (RT) polymerase chain reaction (PCR) is an important tool used for clinical and molecular research, biotechnology and as a diagnostic test. Insulin-like growth factors (IGF-1 and IGF-2) and insulin are ubiquitously expressed and play important roles in the regulation of cell growth, differentiation and the maintenance of cell differentiation in mammals. The IGF system (IGF-1, IGF-2, IGF -1 receptor, IGF-2 receptor and six IGF-binding proteins) and insulin are consequently essential to most aspects of male and female reproduction. IGF-1 is produced in multiple tissues but predominately in the liver, from where it enters the circulation. Insulin is secreted by β-cells of the pancreas’ islets of Langerhans. Both IGF-1 and insulin polypeptides bind to specific cell surface receptors. These receptors are members of the superfamily known as tyrosine protein kinases, and are composed of two α and two β subunits linked by disulfide bonds to form an αβ–αβ heterotetramer. The α subunits include ligand binding sites, whereas the β subunits contain tyrosine kinase activity. The aim of this project was to develop real-time RT-PCR assays for quantification of equine insulin-like growth factor-1 receptor (IGF-1R) and insulin receptor (INS-R) mRNA. The assays were developed using stallion testicular tissue samples, obtained by excisional biopsy, from three horse breeds (Friesan, Thoroughbred and Warmblood). The assays developed were efficient, sensitive and had a broad linear range of detection (seven logs for IGF-1R and six logs for INS-R). The assays worked well in our hands and were both sensitive and specific for the detection of equine IGF-1R and INS-R mRNA in a variety of equine tissues. / Dissertation (MMedVet)--University of Pretoria, 2011. / Production Animal Studies / Unrestricted

L'enjeu des travaux effectués au cours de cette thèse est l'extraction in silico de molécules potentiellement intéressantes dans le processus d'inhibition du récepteur tyrosine kinase c-Met. La faculté de cette protéine à interagir dans les phénomènes d'embryogenèse et de réparation tissulaires rendent son inhibition cruciale dans les traitements contre les développements tumoraux où c-Met se trouve impliquée. Pour cela, la stratégie employée implique l'utilisation de méthodes in silico de conception rationnelle de médicaments. Nous avons utilisé comme support les multiples structures cristallographiques publiées sur la ProteinData Base. Un travail de modélisation par homologie fut tout d'abord nécessaire pour combler les lacunes des structures cristallographiques collectées. Afin d'échantillonner au mieux l'espace conformationnel de la kinase c-Met et de caractériser sa flexibilité, une longue campagne de simulation de Dynamique Moléculaire fut menée. Pour compléter ces simulations, nous avons également utilisé la méthode des modes normaux de vibration. De ces 2 approches, nous avons extrait un ensemble de 10 conformères considérés comme les plus représentatifs de l'espace conformationnel simulé pour la kinase c-Met et avons proposé un mode de fonctionnement de ce récepteur. Utilisant les conformations représentatives, nous avons ensuite mené une importante campagne de criblage virtuel sur plusieurs chimiothèques constituant environ 70.000 composés. L'analyse des résultats de l'arrimage moléculaire nous a conduits à la sélection de composés intéressants possédant théoriquement une bonne affinité pour la kinase c-Met. Ces molécules ont été soumises aux tests expérimentaux. / The challenge of this PhD work is the in silico identification of potentially interesting molecules concerning the inhibitory process of tyrosine kinase receptor c-Met. The faculty of this protein to interact in embryogenesis and tissue repair phenomena makes its inhibition crucial for treatments against tumor development in which c-Met is involved. For that purpose, the employed strategy involves the use of several in silico methods for rational drug design. As the basement of this work, we used the multiple crystal structures published in the ProteinData Base (PDB). A preliminary homology modeling work was needed to fill gaps in the crystal structures. To sample at best the c-Met kinase conformational space and to characterize its flexibility, a long Molecular Dynamics (MD) simulation campaign was carried out both on apo and holo forms of available crystal structures. To complete these simulations, part of this work consisted to use normal modes of vibration (NM) method. From these two approaches (DM and NM), we extracted a set of 10 conformers considered as the most representative of the kinase simulated conformational space and we suggested a mode of operation of this kinase. Using extracted conformations from the conformational sampling has enabled us to conduct an extensive campaign on several virtual screening libraries constituting a total of approximately 70,000 compounds. Analysis of the molecular docking results has led us to the selection of several theoretically interesting molecules with good potential affinity for c-Met kinase. These molecules were submitted to experimental tests performed by the biologist team associated to our work.