J Doucet

Université Paris-Sud 11, Orsay, Île-de-France, France

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Publications (67)349.92 Total impact

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    ABSTRACT: Although major concerns exist regarding the potential consequences of human exposure to nanoparticles (NP), no human toxicological data is currently available. To address this issue, we took welders, who present various adverse respiratory outcomes, as a model population of occupational exposure to NP.The aim of this study was to evaluate if welding fume-issued NP could be responsible, at least partially, in the lung alterations observed in welders.
    Particle and Fibre Toxicology 05/2014; 11(1):23. DOI:10.1186/1743-8977-11-23 · 6.99 Impact Factor
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    ABSTRACT: When exceptionally preserved, hairs, wools, the skin stratum corneum and avian feathers can provide a wealth of archaeological and paleontological information. Long-term preservation of their information potential lies in the taphonomy (long-term behaviour laws) of keratin-based fibres and films. Here, we study the microscopic properties of archaeological hairs from the mediaeval burial of Marie de Bretagne (15th c., Orléans, France) preserved in a temperate environment, using complementary laboratory and synchrotron-based analytical instruments. We show that (a) the fibrillar keratin content of hair is exceptionally well preserved yet with limited degradation of the hair outer cortex in some hair strands, (b) exceptional preservation is attributed to the diffusion of copper and lead in the hair, (c) a posteriori examination led to the discovery of fragments of copper-based artefacts. We propose a possible scenario that led to the preservation of these tissues and discuss the archaeological interpretation of the microtaphonomy of these bioarchaeological remains.
    Journal of Archaeological Science 02/2014; 42:487-499. DOI:10.1016/j.jas.2013.11.028 · 2.14 Impact Factor
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    ABSTRACT: Mechanics is now recognized as crucial in cell function. To date, the mechanical properties of cells have been inferred from experiments which investigate the roles of actin and microtubules ignoring the intermediate filaments (IFs) contribution. Here, we analyse myoblasts behaviour in the context of myofibrillar myopathy resulting from p.D399Y desmin mutation which disorganizes the desmin IF network in muscle cells. We compare the response of myoblasts expressing either mutated or wild-type desmin to cyclic stretch. Cells are cultivated on supports submitted to periodic uniaxial stretch of 20% elongation amplitude and 0.3 Hz frequency. We show that during stretching cycles, cells expressing mutated desmin reduce their mean amplitude both for the elongation and spreading area compared to those expressing wild-type desmin. Even more unexpected, the reorientation angles are altered in the presence of p.D399Y desmin. Yet, at rest, the whole set of those parameters are similar for the two cell populations. Thus, we demonstrate that IFs affect the mechanical properties and the dynamics of cell reorientation. Since these processes are known due to actin cytoskeleton, these results suggest the IFs implication in mechanics signal transduction. Further studies may lead to better understanding of their contribution to this process.
    Physical Biology 12/2012; 10(1):016001. DOI:10.1088/1478-3975/10/1/016001 · 3.14 Impact Factor
  • 08/2012; 16(5):698. DOI:10.4267/10608/1714
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    ABSTRACT: IPANEMA, a research platform devoted to ancient and historical materials (archaeology, cultural heritage, palaeontology and past environments), is currently being set up at the synchrotron facility SOLEIL (Saint-Aubin, France; SOLEIL opened to users in January 2008). The new platform is open to French, European and international users. The activities of the platform are centred on two main fields: increased support to synchrotron projects on ancient materials and methodological research. The IPANEMA team currently occupies temporary premises at SOLEIL, but the platform comprises construction of a new building that will comply with conservation and environmental standards and of a hard X-ray imaging beamline today in its conceptual design phase, named PUMA. Since 2008, the team has supported synchrotron works at SOLEIL and at European synchrotron facilities on a range of topics including pigment degradation in paintings, composition of musical instrument varnishes, and provenancing of medieval archaeological ferrous artefacts. Once the platform is fully operational, user support will primarily take place within medium-term research projects for `hosted' scientists, PhDs and post-docs. IPANEMA methodological research is focused on advanced two-dimensional/three-dimensional imaging and spectroscopy and statistical image analysis, both optimized for ancient materials.
    Journal of Synchrotron Radiation 09/2011; 18(Pt 5):765-72. DOI:10.1107/S090904951102334X · 2.19 Impact Factor
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    ABSTRACT: Amyloidoses are increasingly recognized as a major public health concern in Western countries. All amyloidoses share common morphological, structural, and tinctorial properties. These consist of staining by specific dyes, a fibrillar aspect in electron microscopy and a typical cross-β folding in x-ray diffraction patterns. Most studies that aim at deciphering the amyloid structure rely on fibers generated in vitro or extracted from tissues using protocols that may modify their intrinsic structure. Therefore, the fine details of the in situ architecture of the deposits remain unknown. Here, we present to our knowledge the first data obtained on ex vivo human renal tissue sections using x-ray microdiffraction. The typical cross-β features from fixed paraffin-embedded samples are similar to those formed in vitro or extracted from tissues. Moreover, the fiber orientation maps obtained across glomerular sections reveal an intrinsic texture that is correlated with the glomerulus morphology. These results are of the highest importance to understanding the formation of amyloid deposits and are thus expected to trigger new incentives for tissue investigation. Moreover, the access to intrinsic structural parameters such as fiber size and orientation using synchrotron x-ray microdiffraction, could provide valuable information concerning in situ mechanisms and deposit formation with potential benefits for diagnostic and therapeutic purposes.
    Biophysical Journal 07/2011; 101(2):486-93. DOI:10.1016/j.bpj.2011.05.055 · 3.83 Impact Factor
  • American Thoracic Society 2011 International Conference, May 13-18, 2011 • Denver Colorado; 05/2011
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    ABSTRACT: A characteristic feature of the dense phases formed by fiber-shaped molecules is their organization into parallel rods packed in a hexagonal or pseudo-hexagonal lateral network. This is typically the case for the collagen triple helices inside fibrils, as confirmed by recent X-ray diffraction experiments carried out on highly crystallized fibers obtained by immersing the freshly extracted fibers in a salt-controlled medium. However such diffraction patterns also generally exhibit additional features in the form of diffuse scattering, which is a clear signature of a low degree of lateral ordering. Only few studies have analyzed and modeled the lateral packing of collagen triple helices when the structure is disordered. Some authors have used the concept of short-range order but this approach does not contain any echo of a hexagonal order. In this study, we use an analytical expression derived from the paracrystal model which retains the hexagonal symmetry information and leads to a good agreement with the experimental data in the medium-angle region. This method is quite sensitive to the degree of disorder and to the inter-object distance. One clear result is that the shift in peak positions, generally attributed to variations in intermolecular distances, can also arise from a change in the degree of ordering without any significant modification of the distances. This underlines the importance of evaluating the degree of ordering before attributing a shift in peak position to a change in the unit-cell. This method is generic and can be applied to any system composed of rod-shaped molecules.
    Journal of Structural Biology 02/2011; 173(2):197-201. DOI:10.1016/j.jsb.2010.11.018 · 3.37 Impact Factor
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    ABSTRACT: The purpose of this study was to characterize the effect of TIEG1 on the molecular structure of collagen within tail tendon fibers using 3-mo-old female C57BL/6 wild-type (WT) and TIEG1 KO mice. Synchrotron X-ray microdiffraction experiments were carried out on single tendon fibers extracted from the WT and TIEG1 KO dorsal tail tendon. The fibers were scanned in the radial direction, and X-ray patterns were obtained. From these patterns, the meridional direction was analyzed through X-ray intensity profile. In addition, collagen content was investigated using hydroxyproline assays, and qualitative real-time PCR experiments were performed on RNA isolated from fibroblasts to examine specific gene expression changes. The results showed different X-ray diffraction patterns between WT and TIEG1 KO tendon fibers, indicating a disorganization of the collagen structure for the TIEG1 KO compared with WT mice. Furthermore, the analyses of the X-ray intensity profiles exhibited a higher (23 A) period of collagen for the TIEG1 KO compared with the WT mice. The results of the hydroxyproline assays revealed a significant decrease in the TIEG1 KO compared with WT mice, leading to a decrease in the total amount of collagen present within the TIEG1 KO tendons. Moreover, qualitative real-time PCR results showed differences in the expression profiles of specific genes known to play important roles in tendon fiber development. These data further elucidate the role of TIEG1 on tendon structure and could explain the previous defects in the structure-function relationship found for TIEG1 KO tendon fibers.
    Journal of Applied Physiology 04/2010; 108(6):1706-10. DOI:10.1152/japplphysiol.00356.2010 · 3.43 Impact Factor
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    ABSTRACT: X-rays interact strongly with biological organisms. Synchrotron radiation sources deliver very intense X-ray photon fluxes within micro- or submicro cross-section beams, resulting in doses larger than the MGy. The relevance of synchrotron radiation analyses of biological materials is therefore questionable since such doses, million times higher than the ones used in radiotherapy, can cause huge damages in tissues, with regard to not only DNA, but also proteic and lipid organizations. Very few data concerning the effect of very high X-ray doses in tissues are available in the literature. We present here an analysis of the structural phenomena which occur when the model tissue of human hair is irradiated by a synchrotron X-ray micro-beam. The choice of hair is supported by its hierarchical and partially ordered keratin structure which can be analysed inside the tissue by X-ray diffraction. To assess the damages caused by hard X-ray micro-beams (1 microm(2) cross-section), short exposure time scattering SAXS/WAXS patterns have been recorded at beamline ID13 (ESRF) after various irradiation times. Various modifications of the scattering patterns are observed, they provide fine insight of the radiation damages at various hierarchical levels and also unexpectedly provide information about the stability of the various hierarchical structural levels. It appears that the molecular level, i.e. the alpha helices which are stabilized by hydrogen bonds and the alpha-helical coiled coils which are stabilized by hydrophobic interactions, is more sensitive to radiation than the supramolecular architecture of the keratin filament and the filament packing within the keratin associated proteins matrix, which is stabilized by disulphide bonds.
    Journal of Structural Biology 11/2009; 170(1):69-75. DOI:10.1016/j.jsb.2009.11.006 · 3.37 Impact Factor
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    ABSTRACT: X-ray fluorescence microscopy (microXRF) is applied for the first time to study macrophages exposed to unpurified and purified single-walled (SW) and multiwalled (MW) carbon nanotubes (CNT). Investigating chemical elemental distributions allows one to (i) image nanotube localization within a cell and (ii) detect chemical modification of the cell after CNT internalization. An excess of calcium is detected for cells exposed to unpurified SWCNT and MWCNT and related toxicological assays are discussed.
    Nano Letters 10/2008; 8(9):2659-63. DOI:10.1021/nl800914m · 12.94 Impact Factor
  • Metal07 Conf., 17th - 21st Sept. Amsterdam, The Netherlands; 01/2008
  • Computer Methods in Biomechanics and Biomedical Engineering 01/2008; 11:29-30. DOI:10.1080/10255840802296889 · 1.79 Impact Factor
  • L'Actualité chimique 10/2007; 312-313:105-111. · 0.09 Impact Factor
  • Loïc Bertrand, Jean Doucet
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    ABSTRACT: Starting January 2004, the SOLEIL synchrotron has set up a dedicated interface for cultural heritage (art and technology history, archaeology, conservation and restoration). The present contribution aims at summarising the activities of the interface for the period 2004-06. A first step consisted in a detailed survey of the current context of synchrotron usage for cultural heritage through strong interactions with actors of the field, an extensive review of the existing publications and the co-organisation of specific workshops and round tables. From this preliminary survey, the interest of a dedicated project involving European research infrastructures is clearly emphasised. Such a project should focus oil solving the major issues and limitations encountered by the heritage community in its use of advanced characterisations techniques.
    Il Nuovo Cimento C 01/2007; 30:35-40. DOI:10.1393/ncc/i2006-10034-x
  • Loïc Bertrand, Jean Doucet, Denis Raoux
    7th EC conference 'Safeguarded Cultural Heritage. Understanding and Viability for the Enlarged Europe' Prague, Czech Republic, 31 May - 3 June 2006; 01/2007
  • Acta Crystallographica Section A Foundations of Crystallography 08/2006; A62(S54). DOI:10.1107/S0108767306098916 · 2.07 Impact Factor
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    ABSTRACT: Several aspects of the intermediate filaments' molecular architecture remain mysterious despite decades of study. The growth process and the final architecture may depend on the physical, chemical, and biochemical environment. Aiming at clarifying this issue, we have revisited the structure of the human hair follicle by means of X-ray microdiffraction. We conclude that the histology-based growth zones along the follicle are correlated to the fine architecture of the filaments deduced from X-ray microdiffraction. Our analysis reveals the existence of two major polymorph intermediate filament architectures. Just above the bulb, the filaments are characterized by a diameter of 100 Angstroms and a low-density core. The following zone upwards is characterized by the lateral aggregation of the filaments into a compact network of filaments, by a contraction of their diameter (to 75 Angstroms) and by the setting up of a long-range longitudinal ordering. In the upper zone, the small structural change associated with the tissue hardening likely concerns the terminal domains. The architecture of the intermediate filament in the upper zones could be specific to hard alpha-keratin whilst the other architecture found in the lower zone could be representative for intermediate filaments in a different environment.
    Journal of Structural Biology 05/2006; 154(1):79-88. DOI:10.1016/j.jsb.2005.11.013 · 3.37 Impact Factor
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    ABSTRACT: The soluble protein Ure2p from the yeast Saccharomyces cerevisiae assembles in vitro into straight and insoluble protein fibrils, through subtle changes of conformation. Whereas the structure of soluble Ure2p has been revealed by X-ray crystallography, further characterization of the structure of insoluble Ure2p fibrils is needed. We performed X-ray absorption near-edge spectroscopy (XANES) at the sulfur K-edge to probe the state of Cys221 in the fibrillar form of Ure2pC221 and provide structural information on the structure of Ure2p within fibrils. Although the Ure2p dimer dissociation into its constituent monomers has proven to be a prerequisite for assembly into fibrils, we showed the ability of every Ure2pC221 monomer to establish disulfide bonds upon incubation of the fibrils under oxidizing conditions. Our result indicates either that the constituent unit of the fibrillar form of the protein is a dimeric Ure2p or that the fibrils are made of protofilaments assembled in such a way that the residue C221 from a Ure2p molecule in one protofilament is located in the vicinity of a C221 residue from another molecule belonging to a neighbor protofilament.
    Journal of Molecular Biology 04/2006; 356(4):843-9. DOI:10.1016/j.jmb.2005.12.011 · 3.96 Impact Factor
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    ABSTRACT: Without Abstract
    01/2006: pages 33-40;