Suivi à long terme des effets d’un entrainement de la mémoire de travail (Cogmed) auprès d’enfants présentant un TDA/H

Essai doctoral présenté à la Faculté des études supérieures en vue de l’obtention du grade de Docteur en psychologie (D.Psy.), option neuropsychologie cliniqueLe trouble déficitaire de l’attention avec ou sans hyperactivité (TDA/H) est fréquemment associé à un déficit de la mémoire de travail. De nouvelles interventions ciblant spécifiquement cette fonction ont ainsi été développées, dont le programme Cogmed. Or, les effets à long terme de ce type d’intervention demeurent peu étudiés et peu d’études tiennent compte de la présence de médication ou de troubles associés. Cette étude, en continuité avec Dentz et al. (soumis), vise à évaluer les effets à long terme du programme Cogmed comme adjuvant à la médication auprès de jeunes présentant un TDA/H mixte avec comorbidité(s) sous traitement pharmacologique. Trente-et-un participants âgés de 7 à 13 ans présentant un TDA/H associé à un trouble d’apprentissage, un trouble d’opposition avec provocation ou un syndrome de la Tourette ont pris part à une évaluation six mois post-intervention. Un design en double aveugle et un groupe contrôle actif ont été utilisés. Les résultats montrent que le programme Cogmed ne permet pas d’améliorer davantage la mémoire de travail du groupe expérimental, comparativement au groupe contrôle actif. Aucun effet de transfert différé n’est observé sur le fonctionnement cognitif de même que sur le rendement scolaire et les symptômes liés au TDA/H. La présente étude ne permet pas de démontrer l’efficacité, ni de recommander le programme Cogmed comme approche complémentaire à la médication auprès de la population ciblée. L’article qui découle de cette étude s’inscrit dans le cadre d’un projet d’essai doctoral et sera donc précédé d’un contexte théorique général sur le TDA/H et l’entrainement cognitif et suivi d’une conclusion présentant certaines pistes de réflexion

Determination of the distribution of rare earth elements La and Gd in <i>Daphnia magna</i> via micro and nano-SXRF imaging

While our awareness of the toxicity of rare earth elements to aquatic organisms increases, our understanding of their direct interaction and accumulation remains limited. This study describes the acute toxicity of lanthanum (La) and gadolinium (Gd) in Daphnia magna neonates and discusses potential modes of action on the basis of the respective patterns of biodistribution. Ecotoxicological bioassays for acute toxicity were conducted and dissolved metal concentrations at the end of the tests were determined. The results showed a significant difference in nominal EC50 (immobility) between La (>30 mg L−1) and Gd (13.93 (10.92 to 17.38) mg L−1). Daphnids that were then exposed to a concentration close to the determined EC50 of Gd (15 mg L−1, nominal concentration) for 48 h and 72 h were studied by synchrotron micro and nano-X-ray fluorescence to evaluate the biodistribution of potentially accumulated metals. X-ray fluorescence analyses showed that La was mainly found in the intestinal track and appeared to accumulate in the hindgut. This accumulation might be explained by the ingestion of solid La precipitates formed in the media. In contrast, Gd could only be detected in a small amount, if at all, in the intestinal tract, but was present at a much higher concentration in the tissues and became more pronounced with longer exposure time. The solubility of Gd is higher in the media used, leading to higher dissolved concentrations and uptake into tissue in ionic form via common metal transporting proteins. By studying La and Gd biodistribution in D. magna after an acute exposure, the present study has demonstrated that different uptake pathways of solid and dissolved metal species may lead to different accumulation patterns and toxicity.PeerReviewe

A combined Fourier transform infrared and Cr K-edge X-ray absorption near-edge structure spectroscopy study of the substitution and diffusion of H in Cr-doped forsterite

International audienceSingle crystals of synthetic Cr-doped forsterite (Cr:Mg2SiO4) containing both Cr3+ and Cr4+ were partially hydroxylated in piston-cylinder apparatuses at 750-1300 degrees C and pressures from 0.5 to 2.5 GPa, with P(H2O) approximate to P-total. The oxygen fugacity (fO(2)) was buffered by graphite-water, Ni-NiO, Re-ReO2, Fe2O3-Fe3O4 or Ag-Ag2O, and the silica activity (a SiO2) was buffered by powdered forsterite plus either enstatite (Mg2Si2O6), periclase (MgO) or zircon-baddeleyite (ZrSiO4-ZrO2). Profiles of OH content versus distance from the crystal edge were determined using Fourier transform infrared (FTIR) spectroscopy, and profiles of the oxidation state and coordination geometry of Cr were obtained, at the same positions, using K-edge X-ray absorption near-edge structure (XANES) spectroscopy. The techniques are complementary - FTIR spectroscopy images the concentration and nature of O-H bonds, where Cr K-edge XANES spectroscopy shows the effect of the added H on the speciation of Cr already present in the lattice. Profiles of defect-specific absorbance derived from FTIR spectra were fitted to solutions of Fick's second law to derive diffusion coefficients, which yield the Arrhenius relationship for H diffusion in forsterite: log(10)(D) over tilde ([001]) = -2.5 +/- 0.6 + -(224 +/- 12 + 4.0 +/- 2.0 P)/2.303 RT , where (D) over tilde is the measured diffusion coefficient in m(2) s(-1), valid for diffusion parallel to [001] and calibrated between 1000 and 750 degrees C, P and T are in GPa and K, and R is 0.008314 kJK(-1) mol(-1). Diffusivity parallel to [100] is around 1 order of magnitude lower. This is consistent with previous determinations of H diffusion associated with M-site vacancies. The FTIR spectra represent a variety of Cr-bearing hydrous defects, along with defects associated with the pure Mg-Si-O-H system. It is proposed that all of the defects can form by interaction between the dry lattice, including Cr3+ and Cr4+, and fully hydroxylated M-site vacancies. The initial diffusive wave of hydroxylation is associated with neither reduction nor oxidation of Cr but with Cr4+ changing from tetrahedral to octahedral coordination. Superimposed on the H diffusion and concomitant change in Cr4+ site occupancy, but at a slower rate, producing shorter profiles, is reduction of Cr4+ to Cr3+ and potentially of Cr4+ and Cr3+ to Cr2+. In addition, by comparing FTIR data to trace element contents measured by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), constraints can be placed on absorption coefficients used for converting absorbance to H2O contents - our data support either wavenumber- or defect-dependent values of absorption coefficients. We estimate absorption coefficients of between 60 200 and 68 200 L mol(-1) cm(-1) for OH- associated with octahedral Cr3+ and an M-site vacancy and 18 700 to 24 900 L mol(-1) cm(-1) for two OH- associated with octahedrally coordinated Cr4+ and a Si vacancy (i.e. a clinohumite-type point defect)

Bifeo3 Harmonic Nanoparticle (Bfo-Hnps) Use for the Stem Cell Tracking: Labeling Investigation by Non Linear Microscopy and X-Ray Fluorescence

Duchenne Muscular Dystrophy is the most common form of degenerative muscle disease; currently, there is no effective treatment. In 2011, our group showed that an adult stem cell population (MuStem) isolated from healthy dog skeletal muscle induces long-term muscle repair and striking clinical efficacy after its systemic delivery in clinically relevant dystrophic dog. During last years, our group isolated the human counterparts (hMuStem) [1]. To achieve the full therapeutic potential of the hMuStem cells, their homing process, survival and engraftment post-transplantation must be clearly understood. BiFeO3 harmonic nanoparticles (BFO-HNPs) were used as probes for the hMuStem cell tracking [2]. We demonstrate the possibility of identifying <100 nm BFO-HNPs in depth of muscle tissue at more than 1 mm from the surface by multiphoton microscopy. Based on this successful assessment, we monitor over 14 days any modification on proliferation and morphology features of the hMuStem cells upon exposure to BFO-HNPs revealing their high biocompatibility. To complete these studies, the stability of BFO-HNPs was followed in the labeled hMuStem cells by investigation of Bi and Fe X-ray fluorescence mapping on both Nanoscopium (Soleil, Gif-sur-Yvette, France) and ID16B (ESRF, Grenoble, France) beamlines. In this work, correlation between non-linear microscopy and X-Ray fluorescence was done. Bi and Fe X-Ray fluorescence allowed us to localize with high resolution the BFO-HNPs in the labeled hMuStem cells and the variation of Bi/Fe ratio was analyzed to detect possible dissociation of the nanoparticles in the labeled cells

Microspectroscopy reveals dust-derived apatite grains in acidic, highly-weathered Hawaiian soils

Dust deposition is an important source of phosphorus (P) to many ecosystems. However, there is little evidence of dust-derived P-containing minerals in soils. Here we studied P forms along a well-described climatic gradient on Hawaii, which is also a dust deposition gradient. Soil mineralogy and soil P forms from six sites along the climatic gradient were analyzed with bulk (X-ray diffraction and P K-edge X-ray absorption near edge structure) and microscale (X-ray fluorescence, P K-edge X-ray absorption near edge structure, and Raman) analysis methods. In the wettest soils, apatite grains ranging from 5 to 30 µm in size were co-located at the micro-scale with quartz, a known continental dust indicator suggesting recent atmospheric deposition. In addition to co-location with quartz, further evidence of dust-derived P included backward trajectory modeling indicating that dust particles could be brought to Hawaii from the major global dust-loading areas in central Asia and northern Africa. Although it is not certain whether the individual observed apatite grains were derived from long-distance transport of dust, or from local dust sources such as volcanic ash or windblown fertilizer, these observations offer direct evidence that P-containing minerals have reached surface layers of highly-weathered grassland soils through atmospheric deposition

Contribution in the study of the stability of Callvo-Oxfordian clay rock minerals in the presence of iron at 90° C

Dans le contexte de stockage des déchets radioactifs en profondeur, des interactions entre le fer métal d’une part et la roche du Callovo-Oxfordien (COx), sa fraction argileuse purifiée (SCOx) ou des phases argileuses pures (kaolinite, illite, smectites) d’autre part, sont réalisées à 90°C sous atmosphère anoxique en solution chlorurée-salée. Le rôle des minéraux non argileux du COx est également étudié. L'oxydation rapide du fer métal entraine une libération d’ions fer en solution, une augmentation du pH et une diminution du Eh (réducteur). Une dissolution partielle des phases argileuses ainsi que la précipitation de serpentines ferrifères (odinite ou berthiérine, principalement) et de magnétite en faible quantité sont alors observées. En cas d’apport d'O2 au système, les serpentines ferrifères sont déstabilisées. L'exsolution du fer permet la formation d'oxydes et d’hydroxydes de fer et des particules argileuses proches des phases initiales précipitent. Lorsque du quartz est ajouté à SCOx, la dissolution partielle de ce minéral est responsable de la modification des chemins réactionnels. La formation de magnétite est alors limitée et les serpentines ferrifères sont enrichies en silice. Dans le cas de la kaolinite, DRX, MET, XPS et analyses texturales mettent en évidence la croissance des serpentines ferrifères (berthierines majoritairement) sur la surface basale des kaolinites, formant des particules kaolinite-serpentines-Fe démixées. Les techniques spectroscopiques (Mössbauer, XAS et STXM) permettent de déterminer les rapports Fe2+/Fe3+ et AlIV/AlVI jusqu'au niveau des particules élémentaires et de proposer des formules structurales pour ces serpentines ferrifèresIn the context of underground disposal of high-level radioactive waste, interactions between metallic iron and Callovo-Oxfordian rock (COx), its purified clay fraction (SCOx) or pure clay phases (kaolinite, illite, smectites) were investigated at 90°C under anoxic atmosphere in chlorine solution. Role of COx non clay minerals in these reactions was also studied. Rapid metallic iron oxidation conducts to iron cations release in solution, pH increase (8-10) and Eh decrease (reducive conditions). The partial dissolution of initial clay phases and the crystallization of Fe-serpentines (odinite or berthierine mainly) and of low amount of magnetite were observed. The introduction of O2 into the system leads to Fe-serpentines destabilisation. Iron exsolution conducts to iron oxides and hydroxides formation and clay particles with composition close to the initial ones precipitate. Addition of quartz into the system leads to the partial dissolution of this mineral and to the modification of reaction pathways. Precipitation of magnetite is reduiced and Fe-serpentines are silica enriched. In the case of kaolinite-metallic iron interaction, combinated used of XRD, MET, XPS and textural analyses evidences the growth of berthierine on the basal face of kaolinites, resulting in Fe-serpentine-kaolinite demixed particles. Through the used of spectroscopic analyses (Mössbauer, XAS and STXM), we were able to determine Fe2+/Fe3+ and AlIV/AlVI ratio in elementary particles, which allows proposing structural formulae for the Fe-serpentine

Contribution à l'étude de la stabilité des minéraux constitutifs de l'argilité du Callovo-Oxfordien en présence de fer à 90° C

In the context of underground disposal of high-level radioactive waste, interactions between metallic iron and Callovo-Oxfordian rock (COx), its purified clay fraction (SCOx) or pure clay phases (kaolinite, illite, smectites) were investigated at 90°C under anoxic atmosphere in chlorine solution. Role of COx non clay minerals in these reactions was also studied. Rapid metallic iron oxidation conducts to iron cations release in solution, pH increase (8-10) and Eh decrease (reducive conditions). The partial dissolution of initial clay phases and the crystallization of Fe-serpentines (odinite or berthierine mainly) and of low amount of magnetite were observed. The introduction of O2 into the system leads to Fe-serpentines destabilisation. Iron exsolution conducts to iron oxides and hydroxides formation and clay particles with composition close to the initial ones precipitate. Addition of quartz into the system leads to the partial dissolution of this mineral and to the modification of reaction pathways. Precipitation of magnetite is reduiced and Fe-serpentines are silica enriched. In the case of kaolinite-metallic iron interaction, combinated used of XRD, MET, XPS and textural analyses evidences the growth of berthierine on the basal face of kaolinites, resulting in Fe-serpentine-kaolinite demixed particles. Through the used of spectroscopic analyses (Mössbauer, XAS and STXM), we were able to determine Fe2+/Fe3+ and AlIV/AlVI ratio in elementary particles, which allows proposing structural formulae for the Fe-serpentinesDans le contexte de stockage des déchets radioactifs en profondeur, des interactions entre le fer métal d'une part et la roche du Callovo-Oxfordien (COx), sa fraction argileuse purifiée (SCOx) ou des phases argileuses pures (kaolinite, illite, smectites) d'autre part, sont réalisées à 90°C sous atmosphère anoxique en solution chlorurée-salée. Le rôle des minéraux non argileux du COx est également étudié. L'oxydation rapide du fer métal entraine une libération d'ions fer en solution, une augmentation du pH et une diminution du Eh (réducteur). Une dissolution partielle des phases argileuses ainsi que la précipitation de serpentines ferrifères (odinite ou berthiérine, principalement) et de magnétite en faible quantité sont alors observées. En cas d'apport d'O2 au système, les serpentines 'ferrifères sont déstabilisées. L'exsolution du fer permet la formation d'oxydes et d'hydroxydes de fer et des particules argileuses proches des phases initiales précipitent. Lorsque du quartz est ajouté à SCOx, la dissolution partielle de ce minéral est responsable de la modification des chemins réactionnels. La formation de magnétite est alors limitée et les serpentines ferrifères sont enrichies en silice. Dans le cas de la kaolinite, DRX, MET, XPS et analyses texturales mettent en évidence la croissance des serpentines ferrifères (berthierines majoritairement) sur la surface basale des kaolinites, formant des particules kaolinite-serpentines-Fe démixées. Les techniques spectroscopiques (Mössbauer, XAS et STXM) permettent de déterminer les rapports Fe2+/Fe3+ et AlIV/AlVI jusqu'au niveau des particules élémentaires et de proposer des formules structurales pour ces serpentines ferrifère

Cryo-laser scanning confocal microscopy of diffusible plant compounds

Background The in vivo observation of diffusible components, such as ions and small phenolic compounds, remains a challenge in turgid plant organs. The analytical techniques used to localize such components in water-rich tissue with a large field of view are lacking. It remains an issue to limit compound diffusion during sample preparation and observation processes. Results An experimental setup involving the infusion staining of plant tissue and the cryo-fixation and cryo-sectioning of tissue samples followed by fluorescence cryo-observation by laser scanning confocal microscopy (LSCM) was developed. This setup was successfully applied to investigate the structure of the apple fruit cortex and table grape berry and was shown to be relevant for localizing calcium, potassium and flavonoid compounds. Conclusion The cryo-approach was well adapted and opens new opportunities for imaging other diffusible components in hydrated tissues

Contribution à l'étude de la stabilité des minéraux constitutifs de l'argilité du Callovo-Oxfordien en présence de fer à 90 C

Dans le contexte de stockage des déchets radioactifs en profondeur, des interactions entre le fer métal d une part et la roche du Callovo-Oxfordien (COx), sa fraction argileuse purifiée (SCOx) ou des phases argileuses pures (kaolinite, illite, smectites) d autre part, sont réalisées à 90C sous atmosphère anoxique en solution chlorurée-salée. Le rôle des minéraux non argileux du COx est également étudié. L'oxydation rapide du fer métal entraine une libération d ions fer en solution, une augmentation du pH et une diminution du Eh (réducteur). Une dissolution partielle des phases argileuses ainsi que la précipitation de serpentines ferrifères (odinite ou berthiérine, principalement) et de magnétite en faible quantité sont alors observées. En cas d apport d'O2 au système, les serpentines ferrifères sont déstabilisées. L'exsolution du fer permet la formation d'oxydes et d hydroxydes de fer et des particules argileuses proches des phases initiales précipitent. Lorsque du quartz est ajouté à SCOx, la dissolution partielle de ce minéral est responsable de la modification des chemins réactionnels. La formation de magnétite est alors limitée et les serpentines ferrifères sont enrichies en silice. Dans le cas de la kaolinite, DRX, MET, XPS et analyses texturales mettent en évidence la croissance des serpentines ferrifères (berthierines majoritairement) sur la surface basale des kaolinites, formant des particules kaolinite-serpentines-Fe démixées. Les techniques spectroscopiques (Mössbauer, XAS et STXM) permettent de déterminer les rapports Fe2+/Fe3+ et AlIV/AlVI jusqu'au niveau des particules élémentaires et de proposer des formules structurales pour ces serpentines ferrifèresIn the context of underground disposal of high-level radioactive waste, interactions between metallic iron and Callovo-Oxfordian rock (COx), its purified clay fraction (SCOx) or pure clay phases (kaolinite, illite, smectites) were investigated at 90C under anoxic atmosphere in chlorine solution. Role of COx non clay minerals in these reactions was also studied. Rapid metallic iron oxidation conducts to iron cations release in solution, pH increase (8-10) and Eh decrease (reducive conditions). The partial dissolution of initial clay phases and the crystallization of Fe-serpentines (odinite or berthierine mainly) and of low amount of magnetite were observed. The introduction of O2 into the system leads to Fe-serpentines destabilisation. Iron exsolution conducts to iron oxides and hydroxides formation and clay particles with composition close to the initial ones precipitate. Addition of quartz into the system leads to the partial dissolution of this mineral and to the modification of reaction pathways. Precipitation of magnetite is reduiced and Fe-serpentines are silica enriched. In the case of kaolinite-metallic iron interaction, combinated used of XRD, MET, XPS and textural analyses evidences the growth of berthierine on the basal face of kaolinites, resulting in Fe-serpentine-kaolinite demixed particles. Through the used of spectroscopic analyses (Mössbauer, XAS and STXM), we were able to determine Fe2+/Fe3+ and AlIV/AlVI ratio in elementary particles, which allows proposing structural formulae for the Fe-serpentinesNANCY-INPL-Bib. électronique (545479901) / SudocSudocFranceF

Evidence of the impact of substitutions in ferrihydrite on rare earth element adsorption

National audienceThe use of Rare Earth Elements (REE) in energy technology and other sectors has rapidly increased in the last few decades, and more REE are mined every year. This has led to concerns about their impact on the environment, and their designation as an emerging pollutant. One of the factors controlling the fate of REE in the environment is adsorption on metal hydroxides. In nature, ferrihydrite (Fh), amorphous iron hydroxide with a high adsorption capacity, is ubiquitous and known to commonly contain metal substitutions. Though REE adsorption on Fh has been studied for its pure form [1-3], there is no study on the influence of substitutions on this adsorption. For this purpose, a series of ferrihydrites were synthesized with varying contents (0 to 100%) of aluminium (Al, omnipresent and easily substituted into iron hydroxides) as substitutes. Total REE and pure cerium (Ce) and neodymium (Nd) adsorption experiments were then performed. The obtained REE patterns are all different. While the pure ferrihydrite is superimposable to the ones from previous studies [1-3], the aluminium substitution modify the pattern shape and the ferrihydrite sorption capacity: Al-substituted ferrihydrites adsorb less REE but show a strong increase in heavy REE enrichment as compared to pure ferrihydrite. We demonstrated that these modifications are due to modification of the ferrihydrite size and shape leading to modifications of the distribution of the binding sites. Furthermore, when looking at the redox of Ce adsorbed to ferrihydrites, Ce(III) and Ce(IV) are both present, but the Ce(III)/Ce(IV) ratio increases with the increasing aluminium substitution rate. These results contradict the usually assumed importance of Fe(III) redox reactivity as the main driver of Ce(III) oxidation, as oxidation is enhanced with higher redox-inert Al(III) content. With these results we show how strong the commonly naturally occurring Al-substitution can affect the reactivity of ferrihydrite towards REE.   References: Bau, M. (1999). Geochimica et Cosmochimica Acta, 63(1), 67-77. Ohta, A., & Kawabe, I. (2000). Geochemical Journal, 34(6), 439-454. Quinn, K. A., Byrne, R. H., & Schijf, J. (2006). Marine Chemistry, 99(1-4), 128-150