Investigation de l'activité photochimique de la photosynthèse et son utilisation dans l'évaluation des effets toxiques de xénobiotiques

Dans cette thèse, le projet de recherche concerne l'investigation des effets toxiques des xénobiotiques sur le fonctionnement de l'appareil photosynthétique et l'état physiologique d'un système cellulaire ou d'un organisme multicellulaire. Le changement du rendement et des spectres de la cinétique de la fluorescence chlorophyllienne a été utilisé pour interpréter les mécanismes moléculaires de la photosynthèse lorsque la plante a été exposée à différents xénobiotiques. Les effets des xénobiotiques sur le changement des différents paramètres de fluorescence indiquant le rendement photochimique, la dissipation d'énergie via le transport d'électrons ou via les voies non photochimiques ont été utilisés pour déterminer des biomarqueurs qui sont indicateurs de toxicité. Dans notre recherche, nous avons utilisé l'algue unicellulaire Scenedesmus obliquus et des plantes supérieures (Lemna sp. et Hordeum vulgare) comme matériel pour les expériences. Des méthodes fluorométriques et spectroscopiques ont été utilisées pour étudier la réaction photochimique primaire et le transport des électrons photosynthétiques. Pour l'étude des réactions photochimiques du photosystème II in vitro, les fragments membranaires des thylacoïdes ont été utilisés. L'induction du stress oxydatif a été analysée par l'investigation de l'activité enzymatique de la catalase, l'ascorbate peroxydase, la glutathion réductase et la glutathion S-transférase. Dans la partie concernant l'étude des mécanismes de toxicité des xénobiotiques, nous avons démontré chez Lemna gibba que le méthanol inhibe le rendement photochimique et la dissipation d'énergie sous forme non photochimique. Lorsque les concentrations de méthanol étaient au-dessous de 0,5 %, un effet stimulant a été montré sur la formation de la biomasse. Nous avons interprété cet effet comme un mécanisme d'acclimatation de la photosynthèse envers la toxicité du méthanol et ses produits de dégradation. Dans l'étude de la toxicité de l'oxyfluorfène chez l'algue Scenedesmus obliquus, nous avons démontré que ce xénobiotique inhibe la synthèse de la chlorophylle et détériore le transfert d'énergie entre les antennes collectrices et le centre réactionnel du photosystème II. L'augmentation de l'activité des enzymes antioxydantes catalase et glutathion S-transférase a été interprétée comme une indication du stress oxydatif induit par l'oxyfluorfène. L'induction du stress oxydatif a également été démontrée comme une conséquence de l'effet toxique du fludioxonyl. Cet effet oxydatif a été indiqué par l'activité des enzymes catalase, ascorbate peroxydase et glutathion S-transférase. Il apparaissait que les effets du fludioxonyl sur la photosynthèse étaient négligeables. Cependant, chez la même espèce d'algue, l'inhibition du transport linéaire des électrons du photosystème II a été une conséquence directe des effets toxiques de l'isoproturon. Le changement des paramètres de fluorescence comme l'efficacité opérationnelle du photosystème II, le « quenching » photochimique et le ratio entre les antennes collectrices et le centre réactionnel, a montré une forte corrélation avec l'inhibition de la division cellulaire. L'étude des effets toxiques des ions cuivre a montré une forte inhibition de l'activité photochimique du PSII, une augmentation de la dissipation d'énergie sous forme non photochimique et une diminution de la proportion des antennes collectrices par centre réactionnel. L'induction d'un stress oxydatif a aussi été démontrée par le changement de l'activité de la catalase. Dans la deuxième partie de l'étude, nous avons investigué les effets toxiques des xénobiotiques sur le changement des paramètres de fluorescence utilisés comme des biomarqueurs de toxicité sur la photosynthèse et l'état physiologique d'un système algal unicellulaire et de l'organisme entier d'une plante. Pour le méthanol, l'atrazine, l'isoproturon, les ions cuivre, l'oxyfluorfène et fludioxonyl, nous avons montré que les paramètres de fluorescence indiquant le rendement photochimique du photosystème II, la dissipation d'énergie via le transport d'électrons ou les voies non photochimiques ont été les plus sensibles et fiables indicateurs de leurs effets toxiques sur la photosynthèse et sur l'état physiologique de l'organisme entier. Nous avons également déterminé que les paramètres de fluorescence peuvent montrer un changement structurel qui est induit par les différents xénobiotiques. Pour les xénobiotiques étudiés, nous avons démontré que le ratio entre les antennes collectrices et le centre réactionnel du photosystème II représente un biomarqueur sensible et fiable de leur toxicité. En conclusion, nous avons réussi à déterminer les paramètres les plus sensibles et fiables pouvant être employés comme des biomarqueurs dans les bioessais de toxicité

The availability and use of diagnostic tests for the management of acute childhood infections in Europe: the protocol for a cross-sectional survey of paediatricians.

Introduction: Fever is a frequent reason of consultation in children, but correctly identifying the few febrile children with potentially severe bacterial infections is difficult. This encourages clinicians to prescribe empirical antibiotics and subject children to extensive and sometimes invasive testing. Rapid point of care tests (POCTs) are recommended internationally to reduce the use of antibiotics and medical resources. The extent of the availability and use of POCTs by paediatricians in Europe is unclear, but appears to vary widely across countries. The aim of this study is to document the availability and use of rapid POCTs for the clinical management of acute childhood infections and to identify factors associated with the variability of their adoption across Europe. Methods and analysis: The study is an online cross-sectional survey of paediatricians working in primary care and hospitals in more than 24 European countries. Participants were recruited through several European research and clinical networks Descriptive statistics will be used to describe the availability of rapid POCTs to paediatricians and the use of rapid POCTs in a clinical scenario of an infant with undifferentiated fever. Weighted regression analyses will identify factors of the availability and use of rapid POCTs across the included countries. Ethics and dissemination: Participating to this anonymous survey does not carry any risk. Ethical approval was obtained from the London School of Hygiene and Tropical Medicine Ethics Committee. The results of the survey will be presented at European paediatrics conferences and submitted for publication in peer-reviewed medical journals. This study will contribute to understanding the reasons for the variability in the adoption of rapid POCTs across different countries. The findings from this study will be useful for clinicians, health services and the industry developing and implementing rapid POCTs, particularly for the clinical management of febrile children

Biochemical alterations in duckweed and algae induced by carrier solvents: Selection of an appropriate solvent in toxicity testing

Carrier solvents are often used in aquatic toxicity testing for test chemicals with hydrophobic properties. However, the knowledge of solvent effects on test organisms remains limited. This study aimed to understand biochemical effects of the four common solvents ((methanol, ethanol, acetone and dimethylsulfoxide (DMSO)) on two test species Lemna minor and Raphidocelis subcapitata by applying Fourier transform infrared spectroscopy (FTIR) coupled with multivariate analysis in order to select appropriate solvents in the toxicity testing. The results showed biochemical variations associated with solvent treatments at different doses on test species. From the obtained infrared spectra, the structures of lipid membrane and protein phosphorylation in the test species were found sensitive to the solvents. Methanol and ethanol mainly affected the protein secondary structure, while acetone and DMSO primarily induced the alterations of carbohydrate and proteins in the test species. The FTIR results demonstrated that methanol and ethanol showed higher biochemical alterations in the test species than acetone and DMSO, especially at the high doses (0.1% and 1% v/v). Based on the growth inhibition and FTIR spectroscopy, acetone and DMSO can be used as carrier solvent in the toxicity testing when their doses are lower than 0.1% v/v. This article is protected by copyright. All rights reserve

Phylogenomic analysis of the Chlamydomonas genome unmasks proteins potentially involved in photosynthetic function and regulation

Chlamydomonas reinhardtii, a unicellular green alga, has been exploited as a reference organism for identifying proteins and activities associated with the photosynthetic apparatus and the functioning of chloroplasts. Recently, the full genome sequence of Chlamydomonas was generated and a set of gene models, representing all genes on the genome, was developed. Using these gene models, and gene models developed for the genomes of other organisms, a phylogenomic, comparative analysis was performed to identify proteins encoded on the Chlamydomonas genome which were likely involved in chloroplast functions (or specifically associated with the green algal lineage); this set of proteins has been designated the GreenCut. Further analyses of those GreenCut proteins with uncharacterized functions and the generation of mutant strains aberrant for these proteins are beginning to unmask new layers of functionality/regulation that are integrated into the workings of the photosynthetic apparatus

Impact of infection on proteome-wide glycosylation revealed by distinct signatures for bacterial and viral pathogens

Mechanisms of infection and pathogenesis have predominantly been studied based on differential gene or protein expression. Less is known about posttranslational modifications, which are essential for protein functional diversity. We applied an innovative glycoproteomics method to study the systemic proteome-wide glycosylation in response to infection. The protein site-specific glycosylation was characterized in plasma derived from well-defined controls and patients. We found 3862 unique features, of which we identified 463 distinct intact glycopeptides, that could be mapped to more than 30 different proteins. Statistical analyses were used to derive a glycopeptide signature that enabled significant differentiation between patients with a bacterial or viral infection. Furthermore, supported by a machine learning algorithm, we demonstrated the ability to identify the causative pathogens based on the distinctive host blood plasma glycopeptide signatures. These results illustrate that glycoproteomics holds enormous potential as an innovative approach to improve the interpretation of relevant biological changes in response to infection

Genomic investigations of unexplained acute hepatitis in children

Since its first identification in Scotland, over 1,000 cases of unexplained paediatric hepatitis in children have been reported worldwide, including 278 cases in the UK1. Here we report an investigation of 38 cases, 66 age-matched immunocompetent controls and 21 immunocompromised comparator participants, using a combination of genomic, transcriptomic, proteomic and immunohistochemical methods. We detected high levels of adeno-associated virus 2 (AAV2) DNA in the liver, blood, plasma or stool from 27 of 28 cases. We found low levels of adenovirus (HAdV) and human herpesvirus 6B (HHV-6B) in 23 of 31 and 16 of 23, respectively, of the cases tested. By contrast, AAV2 was infrequently detected and at low titre in the blood or the liver from control children with HAdV, even when profoundly immunosuppressed. AAV2, HAdV and HHV-6 phylogeny excluded the emergence of novel strains in cases. Histological analyses of explanted livers showed enrichment for T cells and B lineage cells. Proteomic comparison of liver tissue from cases and healthy controls identified increased expression of HLA class 2, immunoglobulin variable regions and complement proteins. HAdV and AAV2 proteins were not detected in the livers. Instead, we identified AAV2 DNA complexes reflecting both HAdV-mediated and HHV-6B-mediated replication. We hypothesize that high levels of abnormal AAV2 replication products aided by HAdV and, in severe cases, HHV-6B may have triggered immune-mediated hepatic disease in genetically and immunologically predisposed children

Relationship between molecular pathogen detection and clinical disease in febrile children across Europe: a multicentre, prospective observational study

BackgroundThe PERFORM study aimed to understand causes of febrile childhood illness by comparing molecular pathogen detection with current clinical practice.MethodsFebrile children and controls were recruited on presentation to hospital in 9 European countries 2016-2020. Each child was assigned a standardized diagnostic category based on retrospective review of local clinical and microbiological data. Subsequently, centralised molecular tests (CMTs) for 19 respiratory and 27 blood pathogens were performed.FindingsOf 4611 febrile children, 643 (14%) were classified as definite bacterial infection (DB), 491 (11%) as definite viral infection (DV), and 3477 (75%) had uncertain aetiology. 1061 controls without infection were recruited. CMTs detected blood bacteria more frequently in DB than DV cases for N. meningitidis (OR: 3.37, 95% CI: 1.92-5.99), S. pneumoniae (OR: 3.89, 95% CI: 2.07-7.59), Group A streptococcus (OR 2.73, 95% CI 1.13-6.09) and E. coli (OR 2.7, 95% CI 1.02-6.71). Respiratory viruses were more common in febrile children than controls, but only influenza A (OR 0.24, 95% CI 0.11-0.46), influenza B (OR 0.12, 95% CI 0.02-0.37) and RSV (OR 0.16, 95% CI: 0.06-0.36) were less common in DB than DV cases. Of 16 blood viruses, enterovirus (OR 0.43, 95% CI 0.23-0.72) and EBV (OR 0.71, 95% CI 0.56-0.90) were detected less often in DB than DV cases. Combined local diagnostics and CMTs respectively detected blood viruses and respiratory viruses in 360 (56%) and 161 (25%) of DB cases, and virus detection ruled-out bacterial infection poorly, with predictive values of 0.64 and 0.68 respectively.InterpretationMost febrile children cannot be conclusively defined as having bacterial or viral infection when molecular tests supplement conventional approaches. Viruses are detected in most patients with bacterial infections, and the clinical value of individual pathogen detection in determining treatment is low. New approaches are needed to help determine which febrile children require antibiotics.FundingEU Horizon 2020 grant 668303

Toxicity of Superparamagnetic Iron Oxide Nanoparticles on Green Alga Chlorella vulgaris

Toxicity of superparamagnetic iron oxide nanoparticles (SPION) was investigated on Chlorella vulgaris cells exposed during 72 hours to Fe3O4 (SPION-1), Co0.2Zn0.8Fe2O4 (SPION-2), or Co0.5Zn0.5Fe2O4 (SPION-3) to a range of concentrations from 12.5 to 400 μg mL−1. Under these treatments, toxicity impact was indicated by the deterioration of photochemical activities of photosynthesis, the induction of oxidative stress, and the inhibition of cell division rate. In comparison to SPION-2 and -3, exposure to SPION-1 caused the highest toxic effects on cellular division due to a stronger production of reactive oxygen species and deterioration of photochemical activity of Photosystem II. This study showed the potential source of toxicity for three SPION suspensions, having different chemical compositions, estimated by the change of different biomarkers. In this toxicological investigation, algal model C. vulgaris demonstrated to be a valuable bioindicator of SPION toxicity

Secrets d'écrivains - Entretien entre Nausicaa Dewez et David Marten à propos d'une enquête sur les entretiens littéraires

Les écrivains ne font pas qu’écrire leurs livres : ils en parlent aussi, et cela de plus en plus. Au cours du 20e siècle, l’entretien littéraire s’est imposé comme un véritable genre et sa place dans le système littéraire est absolument cruciale : la critique littéraire prend de plus en plus la forme de l’entretien, les auteurs s’en servent pour dialoguer avec les lecteurs, le public y cherche ce qui se dérobe dans les livres. Le présent volume est une enquête sur cette pratique singulière, dont il prend aussi la forme : un livre d’interviews, donc, où toutes les questions portent sur les rapports des écrivains avec le genre de l’interview. Que représente l’entretien pour les écrivains ? Pour leurs intervieweurs ? De quelle façon les uns et les autres l’abordent-ils ? Comment s’y préparent-ils ? Quelle place les auteurs lui donnent-ils par rapport à leur œuvre ? D’Amélie Nothomb à Emmanuel Carrère, de François Bon à Michel Deguy, de Jacques Chancel à Jean-Philippe Toussaint : écrivains et professionnels du genre se penchent ici avec générosité sur la manière dont ils abordent l’exercice, tous médias confondus (presse écrite, radio, télévision, présentations en public, internet).status: publishe

Functionalized Glutathione on Chitosan-Genipin Cross-Linked Beads Used for the Removal of Trace Metals from Water

Functionalized glutathione on chitosan-genipin cross-linked beads (CS-GG) was synthesized and tested as an adsorbent for the removal of Fe(II) and Cu(II) from aqueous solution. The beads were characterized by several techniques, including Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), CNS elementary analysis, scanning electron microscopy (SEM), and atomic force microscopy (AFM). The effect of several parameters such as the pH, the temperature, and the contact time was tested to optimize the condition for the adsorption reaction. The beads were incubated in aqueous solutions contaminated with different concentrations of Fe(II) and Cu(II) (under the range concentration from 10 to 400 mg·L−1), and the adsorption capacity was evaluated by inductively coupled plasma optical emission spectrometry (ICP-OES). The adsorption equilibrium was reached after 120 min of incubation under optimal pH 5 for Fe(II) and after 180 min under optimal pH 6 for Cu(II). According to the Langmuir isotherm, the maximum adsorption capacities (qmax) for Fe(II) and Cu(II) were 208 mg·g−1 and 217 mg·g−1, respectively. Our results showed that the adsorption efficiency of both metals on CS-GG beads was correlated with the degree of temperature. In addition, the adsorption reaction was spontaneous and endothermic, indicated by the positive values of ΔG0 and ΔH0. Therefore, the present study demonstrated that the new synthesized CS-GG beads had a strong adsorption capacity for Fe(II) and Cu(II) and were efficient to remove these trace metals from aqueous solution