Les déterminants des performances scolaires des élèves marocains

Le Maroc fait partie des pays en développement dont le niveau des acquis des élèves reste relativement faible. En dépit des efforts engagés en vue d’améliorer en partie la qualité des apprentissages, les résultats des enquêtes internationales et nationales révèlent de faibles niveaux des acquis. Dès lors, l’objectif de cet article est de revenir sur les facteurs qui influencent les performances scolaires des élèves. Nous nous intéressons plus spécifiquement aux déterminants microéconomiques de la qualité de l’éducation à travers les performances des élèves. Les études sur les déterminants des performances scolaires sont riches d’enseignement. Les premières contributions se sont focalisées sur le rôle de l’environnement familial dans l’explication de la réussite des élèves (Coleman, 1966, par exemple). D’autres, plus récemment, ont abordé les facteurs liés à l’établissement scolaire. Pour autant, les contributions récentes mettent en avant l’importance à la fois de l’environnement familial et de l’école (Hanushek, 2003). Des travaux plus récents oulignent également l’influence des pairs sur les performances scolaires. Le présent travail s’inscrit dans cette logique. Son originalité se situe à un double niveau. La première réside dans la mise en évidence de l’ensemble des facteurs explicatifs des performances des élèves et des inégalités scolaires. Malgré l’existence d’une littérature abondante sur le sujet, cette question n’a pas été abordée, à notre connaissance, dans le cas marocain. La seconde cherche à corriger les problèmes d’endogénéité dans les modèles multiniveaux. Enfin, La technique d’imputation adoptée permet de traiter de façon pertinente les valeurs manquantes dans les bases de données. Cet article est structuré en trois parties. La première aborde la littérature empirique sur les déterminants de la réussite scolaire des élèves. La deuxième partie examine le modèle utilisé et décrit la base de données du Programme national d’évaluation des acquis (PNEA). Elle examine l’approche et la méthodologie utilisée. Enfin, la troisième partie traite des résultats obtenus et nous permet de formuler les principaux enseignements pouvant être tirés de nos résultats en matière de politiques publiques

Enzyme engineering of bovine trypsin

Bovine trypsin is a biocatalyst widely used to cleave recombinant proteins during the downstream processing of therapeutic proteins, and is used particularly for insulin bioprocessing. Evolution has produced a wealth of natural biocatalysts over billions of years, which are generally not optimised for specific industrial applications. Bovine trypsin has a relatively broad specificity towards cleavage at the C-terminal end of arginine or lysine residues. Consequently it has a tendency to cleave alternative sites in the insulin process leading to loss of yield and more complex downstream processing. This project describes efforts to alter the primary specificity of bovine trypsin. Trypsin variants were generated using two traditional random mutagenesis methods tailored to improve the chance of producing a useful mutant. These were focussed error prone PCR (fepPCR) and multiple-site saturation mutagenesis (MSSM). In order to select residues useful for MSSM, a study of the correlation between (1) mutations enhancing specificity or activity and (2) sequence entropy and distance of mutations from the active site was carried out based on past examples of directed and rational evolution. This analysis along with biochemical information for trypsin aided the selection of two specificity "hotspots" for random mutagenesis, each comprising four residues. These hotspots were regions in the trypsin gene close to or directly involved in substrate binding. Depending on the mutagenesis method used, the size of the mutant libraries differed considerably. For example, fepPCR of a 522 bp region of the trypsin gene required approximately 3,000 mutants to encompass all possibilities whereas the library size for MSSM was 160,000 for each of the selected four-residue regions. Two alternative library screening approaches, with different throughput capabilities, were tested to isolate mutants of interest. Automated colony screening was considered suitable for the smaller fepPCR library and consisted of the following steps: (1) transformation of a plasmid library into E. coli BL21-Gold(DE3) cells (2) fermentation of individual colonies in 384 square-well microplates (3) lysis of the cultures and (4) spectrophotometric activity measurement on a variety of substrates. The best mutant had a 2.54-fold improvement in arginine specificity. For the larger MSSM libraries, a nutritional selection method was developed using E. coli arg-auxotrophic strains. An alternative approach to generating trypsin variants was also explored based on the known ability of bovine trypsin to autolyse into "pseudo-trypsins". Since these pseudo-trypsins are variants of the native form of the enzyme, it was anticipated that they would have specificities different to that of the native enzyme. Efforts were made to separate the variants via novel chromatographic techniques and to characterise them with respect to molecular weight and specificity. Finally, the activity profile of bovine trypsin was comprehensively carried out on a range of novel substrates, and a comparison made between commercially available bovine trypsin and Eli Lilly's recombinant trypsin. Similar reaction profiles were returned by both enzymes on all substrates with the previously unreported finding that there was a preference for cleavage at the C-terminal end of two positively charged basic residues (i.e. KR or RR rather than GR)

Additional file 6: Figure S5. of 1H-pyrrole-2,5-dione-based small molecule-induced generation of mesenchymal stem cell-derived functional endothelial cells that facilitate rapid endothelialization after vascular injury

Lipid uptake assay using DiI-LDL. MSCs or iMDFECs were incubated with DiI-LDL (10 μg/ml) for 4 h. The cells were lysed in 0.1 N NaOH and 0.1 % SDS, and the amount of DiI-LDL was determined by fluorescence reading (excitation/emission at 530/580 nm). The fluorescence of DiI-LDL was normalized by the cell lysate protein concentrations. DiI-LDL 3,3′-dioctadecylindocarbocyanine-low density lipoprotein, iMDFEC induced mesenchymal stem cell-derived functional endothelial cell, MSC mesenchymal stem cell. (TIFF 33 kb

Additional file 7: Figure S6. of 1H-pyrrole-2,5-dione-based small molecule-induced generation of mesenchymal stem cell-derived functional endothelial cells that facilitate rapid endothelialization after vascular injury

Evaluation of amount of MSCs or iMDFECs incorporated by using SRY as a marker of incorporated male-origin transplanted cells. Total RNA was prepared from the common carotid artery harvested at day 21 after the balloon injury. Data represent the mean Âą standard deviation of three independent experiments. iMDFEC induced mesenchymal stem cell-derived functional endothelial cell, MSC mesenchymal stem cell. (TIFF 114 kb