Évaluation et caractérisation des enzymes de métabolisme de la superfamille des CYP450 dans l’intestin grêle humain

L’administration orale des médicaments est la voie la plus simple et sécuritaire pour le traitement des patients. Cependant, celle-ci est associée avec une importante variabilité interindividuelle pouvant être attribuée à la génétique, l’environnement, les pathologies, etc. L’effet de premier passage hépatique a longtemps été considéré en tant que la cause majeure de variabilité des concentrations plasmatiques des médicaments administrés oralement. Il est maintenant reconnu que les organes extra-hépatiques, en particulier l’intestin, peuvent avoir un effet significatif au niveau du métabolisme pré-systémique des médicaments. En effet, ces composés doivent passer dans les entérocytes avant d’accéder à la circulation sanguine, les exposant à des enzymes de métabolisme telles que les Cytochromes P450 (CYP450). Les CYP450 catalysent le métabolisme de phase 1 et sont impliqués dans le métabolisme de 75% des médicaments utilisés en clinique. Notre hypothèse est que la distribution régionale des CYP450 dans l’intestin grêle peut partiellement expliquer la variabilité interindividuelle dans les concentrations plasmatiques et la réponse aux médicaments. Nos objectifs sont d’y caractériser l’expression relative d’ARN messager et l’activité in vitro des CYP450 majeurs. Puisque le transport des médicaments peut affecter l’absorption des xénobiotiques dans l’intestin, notre objectif secondaire est d’évaluer l’expression d’ARNm des transporteurs de médicaments. Nous avons observé une grande variabilité interindividuelle dans l’expression d’ARNm et l’activité des CYP450 dans l’intestin grêle, ainsi qu’une activité catalytique significative pour les CYP3A4, CYP2J2 et CYP2C9. Nos résultats permettront l’élaboration de meilleurs modèles pharmacocinétiques et amélioreront la prédiction de la variabilité des concentrations plasmatiques pour les médicaments administrés oralement.Oral administration of drugs has proven to be the easiest and safest way to treat patients. However, it is associated with great interindividual variability that could be attributed to genetics, environment, pathologies, etc. Hepatic first-pass metabolism was long considered as a major cause for variability in drug plasma concentrations. It is now recognized that extrahepatic organs, especially the small intestine, can have a significant effect in pre-systemic metabolism for orally administrated drugs. Indeed, those compounds must go through the enterocytes before reaching the blood circulation, exposing them to drug-metabolizing enzymes, such as Cytochromes P450s (CYP450s). CYP450s mediate phase I metabolism reactions and are involved in the metabolism of 75% of clinically used drugs. Our hypothesis is that regional CYP450 distribution in the small intestine can partly explain the observed interindividual variability in drug plasma levels and drug response for orally administered drugs. Therefore, our objectives are to characterize relative mRNA expression levels and in vitro activities of major CYP450 isoenzymes in human small intestine. Since drug transport can affect xenobiotic absorption in the small intestine, our secondary objective is to assess mRNA expression levels for membrane drug transporters. We showed high interindividual variability in CYP450 mRNA expression and activity along the small intestine, as well as significant activity for CYP3A4, CYP2J2 and CYP2C9. Our results will lead to better pharmacokinetic models and will improve variability prediction in plasma concentrations for orally administered drugs

Using graphical tools in a phased activity for enhancing dialogical skills: An example with Digalo

ICT tools have been developed to facilitate web-based learning through and learning about argumentation. In this paper we will present an example of a learning activity mediated by Digalo-software for knowledge sharing through visually supported discussion-developed in a university setting. Our aim is to examine, in particular, socio-cognitive construction of knowledge and argumentation by students debating a controversial question in history. We propose a descriptive approach of understanding and meaning-making processes based on two levels of analysis: (1) a topic meaning-making process oriented level and (2) an argumentation oriented level. We focus our studies on how the participants-small groups of students-develop understanding of the topic, their arguments and their interactions through the use of different functionalities of this software. Our results show that interactive and argumentative processes are themselves objects of learning and develop through collective activity. Development of the understanding of the topic through argumentation is discussed and linked to the design of the activity and the affordances of the Digalo softwar

CTX-M β-Lactamases in Escherichia coli from Community-acquired Urinary Tract Infections, Cambodia

The prevalence of CTX-M β-lactamases has reached a critical level, which highlights the need for study of their spread in developing countries

Artificial Intelligence to Detect Papilledema from Ocular Fundus Photographs.

BACKGROUND: Nonophthalmologist physicians do not confidently perform direct ophthalmoscopy. The use of artificial intelligence to detect papilledema and other optic-disk abnormalities from fundus photographs has not been well studied. METHODS: We trained, validated, and externally tested a deep-learning system to classify optic disks as being normal or having papilledema or other abnormalities from 15,846 retrospectively collected ocular fundus photographs that had been obtained with pharmacologic pupillary dilation and various digital cameras in persons from multiple ethnic populations. Of these photographs, 14,341 from 19 sites in 11 countries were used for training and validation, and 1505 photographs from 5 other sites were used for external testing. Performance at classifying the optic-disk appearance was evaluated by calculating the area under the receiver-operating-characteristic curve (AUC), sensitivity, and specificity, as compared with a reference standard of clinical diagnoses by neuro-ophthalmologists. RESULTS: The training and validation data sets from 6779 patients included 14,341 photographs: 9156 of normal disks, 2148 of disks with papilledema, and 3037 of disks with other abnormalities. The percentage classified as being normal ranged across sites from 9.8 to 100%; the percentage classified as having papilledema ranged across sites from zero to 59.5%. In the validation set, the system discriminated disks with papilledema from normal disks and disks with nonpapilledema abnormalities with an AUC of 0.99 (95% confidence interval [CI], 0.98 to 0.99) and normal from abnormal disks with an AUC of 0.99 (95% CI, 0.99 to 0.99). In the external-testing data set of 1505 photographs, the system had an AUC for the detection of papilledema of 0.96 (95% CI, 0.95 to 0.97), a sensitivity of 96.4% (95% CI, 93.9 to 98.3), and a specificity of 84.7% (95% CI, 82.3 to 87.1). CONCLUSIONS: A deep-learning system using fundus photographs with pharmacologically dilated pupils differentiated among optic disks with papilledema, normal disks, and disks with nonpapilledema abnormalities. (Funded by the Singapore National Medical Research Council and the SingHealth Duke-NUS Ophthalmology and Visual Sciences Academic Clinical Program.)

Organised Genome Dynamics in the Escherichia coli Species Results in Highly Diverse Adaptive Paths

The Escherichia coli species represents one of the best-studied model organisms, but also encompasses a variety of commensal and pathogenic strains that diversify by high rates of genetic change. We uniformly (re-) annotated the genomes of 20 commensal and pathogenic E. coli strains and one strain of E. fergusonii (the closest E. coli related species), including seven that we sequenced to completion. Within the ∼18,000 families of orthologous genes, we found ∼2,000 common to all strains. Although recombination rates are much higher than mutation rates, we show, both theoretically and using phylogenetic inference, that this does not obscure the phylogenetic signal, which places the B2 phylogenetic group and one group D strain at the basal position. Based on this phylogeny, we inferred past evolutionary events of gain and loss of genes, identifying functional classes under opposite selection pressures. We found an important adaptive role for metabolism diversification within group B2 and Shigella strains, but identified few or no extraintestinal virulence-specific genes, which could render difficult the development of a vaccine against extraintestinal infections. Genome flux in E. coli is confined to a small number of conserved positions in the chromosome, which most often are not associated with integrases or tRNA genes. Core genes flanking some of these regions show higher rates of recombination, suggesting that a gene, once acquired by a strain, spreads within the species by homologous recombination at the flanking genes. Finally, the genome's long-scale structure of recombination indicates lower recombination rates, but not higher mutation rates, at the terminus of replication. The ensuing effect of background selection and biased gene conversion may thus explain why this region is A+T-rich and shows high sequence divergence but low sequence polymorphism. Overall, despite a very high gene flow, genes co-exist in an organised genome