Etude biochimique d'un cytochrome P450 de cerveau humain (le CYP2U1)

Parmi les 57 cytochromes P450 identifiés lors du séquençage complet du génome humain, on en dénombre environ 15 dont on ne connaît pratiquement rien de leurs rôles physiologiques, de leurs substrats, et de leurs structures, d où le nom de P450 orphelins . Le CYP2U1 est l un des cytochromes P450 les plus fortement exprimé au niveau du cerveau et du cervelet mais c est aussi l un des plus conservé parmi les différentes espèces du règne animal. Ce travail de thèse a tout d abord consisté à optimiser les conditions d expression du CYP2U1 sous une forme active. Un premier système d expression dans la levure Saccharomyces Cerevisiae a permis une production d un complexe CYP2U1-P450 réductase catalytiquement actif permettant des études de recherche de substrat. Un second système d expression dans Escherichia Coli devrait permettre d obtenir de plus grandes quantités d enzyme soluble destinée à des études structurales. Dans un second temps, une recherche de substrats a été effectuée à l aide d analyse d incubats par chromatographie liquide couplée à une détection par spectrométrie de masse. A ce jour, un screening dirigé de plus de soixante-dix molécules, substrats de P450s de la famille 2, a permis d identifier les premiers substrats exogènes du CYP2U1, les analogues de terfénadone et la débrisoquine. D autre part, une étude par modélisation moléculaire de la structure du CYP2U1 a été effectuée. Cette étude montre que le CYP2U1 diffère de tous les autres P450s par la présence d un insert très spécifique dans son domaine N-terminal. Des modèles par homologie basés sur les structures cristallographiques des P450s de la famille 2 ont été construits. Ces modèles ont été validés par dynamique moléculaire et ont permis de proposer un mode d interaction avec la membrane, d identifier la position des canaux d accès ainsi que de déterminer la topologie du site actif. Enfin, un docking des premiers substrats exogènes au sein du site actif du CYP2U1 a permis de confirmer la régioselectivité des hydroxylations catalysées par le CYP2U1.Among the 57 human cytochrome P450 genes that have been identified; substrates, structure and physiologic role of 15 of them is practically unknown. They are called orphan. One of them, CYP2U1 is one of the most expressed cytochrome P450 in the brain and in the cerebellum but also one of the most conserved isoform in the all animal kingdom. This manuscript first describes the optimization of the heterologous expression of an active form of CYP2U1. Expression in a eukaryotic host, yeast Saccharomyces Cerevisiae first allows the production of a catalytic active CYP2U1-P450 reductase complex needed for substrate screening. Another expression system in a prokaryote host Escherichia Coli will allow higher production rate of a truncated and soluble form of the protein which will permit structural studies. Then a directed substrate screening was performed with the liquid chromatography mass spectrometry analysis of CYP2U1 incubations. To date, 70 molecules, CYP2 family substrates, were tested that allow the identification of the two first exogenous CYP2U1 substrates: débrisoquine and terfenadone analogs. A structural study was achieved using a homology tridimensional model of the enzyme. We have found that CYP2U1 is longer than the other human CYPs, with an N-terminal 20 amino acids insertion, located after the helical membrane spanning domain. Structural models were built using six crystallized human CYP2s as templates. Molecular dynamics experiments in membrane suggested a specific interaction with the membrane. The active site topology and the access channels were also determined and a docking of the two first exogenous CYP2U1 substrates was performed in order to confirm the regioselective hydroxylation activities observed in vitro.PARIS5-Bibliotheque electronique (751069902) / SudocPARIS-BIUM-Bib. électronique (751069903) / SudocSudocFranceF

Uncovering the minor contribution of land-cover change in upland forests to the net carbon footprint of a boreal hydroelectric reservoir

Hydropower in boreal conditions is generally considered the energy source emitting the least greenhouse gas per kilowatt-hour during its life cycle. The purpose of this study was to assess the relative contribution of the land-use change on the modification of the carbon sinks and sources following the flooding of upland forested territories to create the Eastmain-1 hydroelectric reservoir in Quebec’s boreal forest using Carbon Budget Model of the Canadian Forest Sector. Results suggest a carbon sink loss after 100 yr of 300,000 ± 100,000 Mg CO2 equivalents (CO2e). A wildfire sensitivity analysis revealed that the ecosystem would have acted as a carbon sink as long as <75% of the territory had burned over the 100-yr-long period. Our long-term net carbon flux estimate resulted in emissions of 4 ± 2 g CO2e kWh−1 as a contribution to the carbon footprint calculation, one-eighth what was obtained in a recent study that used less precise and less sensitive estimates. Consequently, this study significantly reduces the reported net carbon footprint of this reservoir and reveals how negligible the relative contribution of the land-use change in upland forests to the total net carbon footprint of a hydroelectric reservoir in the boreal zone can be

Management of Esophageal Carcinoma Associated with Cirrhosis: A Retrospective Case-Control Analysis

Objectives. Esophageal carcinoma and cirrhosis have the overlapping etiologic factors. Methods. In a retrospective analysis conducted in 2 Breton institutions we wanted to asses the frequency of this association and the outcome of these patients in a case-control study where each case (cirrhosis and esophageal cancer) was paired with two controls (esophageal cancer). Results. In a 10-year period, we have treated 958 esophageal cancer patients; 26 (2.7%) had a cirrhosis. The same treatments were proposed to the 2 groups; cases received nonsignificantly different radiation and chemotherapy dose than controls. Severe toxicities and deaths were more frequent among the cases. At the end of the treatment 58% of the cases and 67% of the controls were in complete remission; median and 2-year survival were not different between the 2 groups. All 4 Child-Pugh B class patients experienced severe side effects and 2 died during the treatment. Conclusions. This association is surprisingly infrequent in our population! Child-Pugh B patients had a dismal prognosis and a bad tolerance to radiochemotherapy; Child-Pugh A patients have the same tolerance and the same prognosis as controls and the evidence of a well-compensated cirrhosis has not modified our medical options

Utility of Quantitative 99mTc-MAA SPECT/CT for 90yttrium-Labelled Microsphere Treatment Planning: Calculating Vascularized Hepatic Volume and Dosimetric Approach

Objectives. The aim of this study was to assess the effectiveness of SPECT/CT for volume measurements and to report a case illustrating the major impact of SPECT/CT in calculating the vascularized liver volume and dosimetry prior to injecting radiolabelled yttrium-90 microspheres (Therasphere). Materials and Methods. This was a phantom study, involving volume measurements carried out by two operators using SPECT and SPECT/CT images. The percentage of error for each method was calculated, and interobserver reproducibility was evaluated. A treatment using Therasphere was planned in a patient with three hepatic arteries, and the quantitative analysis of SPECT/CT for this patient is provided. Results. SPECT/CT volume measurements proved to be accurate (mean error <6% for volumes ≥16 cm3) and reproductive (interobserver agreement = 0.9). In the case report, 99mTc-MAA SPECT/CT identified a large liver volume, not previously identified with angiography, which was shown to be vascularized after selective MAA injection into an arterial branch, resulting in a large modification in the activity of Therasphere used. Conclusions. MAA SPECT/CT is accurate for vascularized liver volume measurements, providing a valuable contribution to the therapeutic planning of patients with complex hepatic vascularization

Enjeux et solutions pour la sylviculture intensive de plantations dans un contexte d'aménagement écosystémique

Les plantations forestières représentent un outil sylvicole reconnu pour assurer un approvisionnement en matière ligneuse qui répond aux attentes de la société envers l'aménagement durable des forêts. Toutefois, elles font aussi partie du scénario sylvicole qui a le plus grand potentiel d'artificialisation de la forêt naturelle. Les objectifs de la sylviculture intensive de plantations peuvent alors paraître, de prime abord, en contradiction avec ceux de l'aménagement écosystémique. Nous décrivons le processus par lequel nous avons défini et documenté des enjeux associés aux plantations et proposé des pistes de solutions pour que la sylviculture intensive de plantations puisse s'intégrer à l'aménagement écosystémique. Nous avons identifié des enjeux relatifs à l'ampleur, à la localisation et à l'agencement spatial des plantations, aux attributs clés et à la résilience de la forêt naturelle, à l'acceptabilité sociale, ainsi qu’à la productivité et à la rentabilité des plantations. Nous avons également proposé des pistes de solutions qui permettraient de réaliser les plantations dans un contexte d'aménagement écosystémique, telles que la modulation des traitements sylvicoles pour augmenter la naturalité des plantations, la réalisation des traitements de manière à obtenir la production attendue, ainsi qu'un déploiement dans le paysage qui intègre les préoccupations des parties prenantes et qui considère la naturalité de la matrice forestière. Forest plantations are recognized as a silvicultural tool for ensuring a timber supply that meets public expectations regarding sustainable forest management. However, they are also part of the silvicultural scenario that shows the greatest potential for the artificialization of natural forests. From a firsthand perspective, intensive plantation silviculture objectives may appear antagonistic to those of ecosystem management. Here we describe the process through which we defined and documented plantation issues, then propose potential solutions to allow the integration of intensive plantation silviculture into ecosystem management. We identify issues related to the scale, localization and spatial arrangement of plantations, the key attributes and resilience of natural forests, social acceptability, and the productivity and profitability of plantations. We also propose potential solutions likely to help manage plantations within a context of ecosystem management. These include modulating silvicultural treatments to enhance the naturalness of plantations, conducting treatments to obtain expected production rates, and ensuring that plantations are deployed across the landscape in a manner that integrates stakeholder concerns and considers the naturalness of the forest matrix

Usefulness and pitfalls of MAA SPECT/CT in identifying digestive extrahepatic uptake when planning liver radioembolization

International audiencePURPOSE: Identifying gastroduodenal uptake of (99m)Tc-macroaggregated albumin (MAA), which is associated with an increased risk of ulcer disease, is a crucial part of the therapeutic management of patients undergoing radioembolization for liver tumours. Given this context, the use of MAA single photon emission computed tomography (SPECT)/CT may be essential, but the procedure has still not been thoroughly evaluated. The aim of this retrospective study was to determine the effectiveness of MAA SPECT/CT in identifying digestive extrahepatic uptake, while determining potential diagnostic pitfalls. METHODS: Overall, 139 MAA SPECT/CT scans were performed on 103 patients with different hepatic tumour types. Patients were followed up for at least 6 months according to standard requirements. RESULTS: Digestive, or digestive-like, uptake other than free pertechnetate was identified in 5.7% of cases using planar imaging and in 36.6% of cases using SPECT/CT. Uptake sites identified by SPECT/CT included the gastroduodenal region (3.6%), gall bladder (12.2%), portal vein thrombosis (6.5%), hepatic artery (6.5%), coil embolization site (2.1%) as well as falciform artery (5.0%). For 2.1% of explorations, a coregistration error between SPECT and CT imaging could have led to a false diagnosis by erroneously attributing an uptake site to the stomach or gall bladder, when the uptake actually occurred in the liver. CONCLUSION: SPECT/CT is more efficacious than planar imaging in identifying digestive extrahepatic uptake sites, with extrahepatic uptake observed in one third of scans using the former procedure. However, more than half of the uptake sites in our study were vascular in nature, without therapeutic implications. The risk of coregistration errors must also be kept in mind

Depressive symptoms and alcohol correlates among Brazilians aged 14 years and older: a cross-sectional study

Abstract\ud \ud Background\ud The associations between depressive symptoms and alcohol-related disorders, drinking patterns and other characteristics of alcohol use are important public health issues worldwide. This study aims to study these associations in an upper middle-income country, Brazil, and search for related socio-demographic correlations in men and women.\ud \ud \ud Methods\ud A cross-sectional study was conducted between November 2005 and April 2006. The sample of 3,007 participants, selected using a multistage probabilistic sampling method, represents the Brazilian population aged 14 and older. Depressive symptoms were assessed using the Center for Epidemiologic Studies Depression Scale and alcohol dependence was assessed using the Composite International Diagnostic Interview. Associations assessed using bi-variate analysis were tested using Rao-Scott measures. Gender specific multinomial logistic regression models were developed.\ud \ud \ud Results\ud Among the participants with alcohol dependence, 46% had depressive symptoms (17.2% mild/moderate and 28.8% major/severe; p < 0.01); 35.8% (p = 0.08) of those with alcohol abuse and 23.9% (p < 0.01) of those with a binge-drinking pattern also had depressive symptoms. Alcohol abstainers and infrequent drinkers had the highest prevalence of major/severe depressive symptoms, whereas frequent heavy drinkers had the lowest prevalence of major/severe depressive symptoms. In women, alcohol dependence and the presence of one or more problems related to alcohol consumption were associated with higher risks of major/severe depressive symptoms. Among men, alcohol dependence and being ≥45 years old were associated with higher risks of major/severe depressive symptoms.\ud \ud \ud Conclusions\ud In Brazil, the prevalence of depressive symptoms is strongly related to alcohol dependence; the strongest association was between major/severe depressive symptoms and alcohol dependence in women. This survey supports the possible association of biopsychosocial distress, alcohol consumption and the prevalence of depressive symptoms in Brazil. Investing in education, social programs, and care for those with alcohol dependence and major/severe depressive symptoms, especially for such women, and the development of alcohol prevention policies may be components of a strategic plan to reduce the prevalence of depression and alcohol problems in Brazil. Such a plan may also promote the socio-economic development of Brazil and other middle-income countries.Brazilian National Secretariat on Drug Policies (SENAD) [grant number 017/2003]

TMT NFIRAOS: adaptive optics system for the Thirty Meter Telescope

NFIRAOS is the first-light adaptive optics system planned for the Thirty Meter Telescope, and is being designed at the National Research Council of Canada's Herzberg Institute of Astrophysics. NFIRAOS is a laser guide star multiconjugate adaptive optics system - a practical approach to providing diffraction limited image quality in the NIR over a 30" field of view, with high sky coverage. This will enable a wide range of TMT science that depends upon the large corrected field of view and high precision astrometry and photometry. We review recent progress developing the design and conducting performance estimates for NFIRAOS

Prevalence of Drug-Resistant HIV-1 Variants in Untreated Individuals in Europe: Implications for Clinical Management

BackgroundInfection with drug-resistant human immunodeficiency virus type 1 (HIV-1) can impair the response to combination therapy. Widespread transmission of drug-resistant variants has the disturbing potential of limiting future therapy options and affecting the efficacy of postexposure prophylaxis penta increase-spacing 1>MethodsWe determined the baseline rate of drug resistance in 2208 therapy-naive patients recently and chronically infected with HIV-1 from 19 European countries during 1996-2002 ResultsIn Europe, 1 of 10 antiretroviral-naive patients carried viruses with ⩾1 drug-resistance mutation. Recently infected patients harbored resistant variants more often than did chronically infected patients (13.5% vs. 8.7%; P=.006). Non-B viruses (30%) less frequently carried resistance mutations than did subtype B viruses (4.8% vs. 12.9%; P<.01). Baseline resistance increased over time in newly diagnosed cases of non-B infection: from 2.0% (1/49) in 1996-1998 to 8.2% (16/194) in 2000-2001 ConclusionsDrug-resistant variants are frequently present in both recently and chronically infected therapy-naive patients. Drug-resistant variants are most commonly seen in patients infected with subtype B virus, probably because of longer exposure of these viruses to drugs. However, an increase in baseline resistance in non-B viruses is observed. These data argue for testing all drug-naive patients and are of relevance when guidelines for management of postexposure prophylaxis and first-line therapy are update