Rodrigue Closset

University of Liège, Luik, Walloon Region, Belgium

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Publications (14)37.26 Total impact

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    ABSTRACT: The bio-inertness of titanium and its alloys attracts their use as bone implants. However a bioactive coating is usually necessary for improving the bone bonding of such implants. In this study, electrophoretic deposition(EPD) of hydroxyapatite (HA) powder on titanium plate was performed using butanol as solvent under direct current (DC) and alternating current (AC) fields. The zeta potential of the suspensions was measured to understand their stability and the charge on the particles. Coating thickness was varied by adjusting the voltage and time of deposition. Surface morphology and cross section thickness were studied using scanning electron microscopy and image analysis software. Surface crack density was calculated from the micrographs. The results showed that the samples of similar thickness have higher grain density when coated using AC as compared to DC EPD. This facile but novel test proves the capability of AC-EPD to attain denser and uniform HA coatings from non-aqueous medium.
    Journal of the European Ceramic Society. 06/2013; 33(s 13–14).
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    ABSTRACT: The optimization of the photocatalytic activity and hydrophilic conversion of TiO2 is an active research area in the field of self-cleaning materials and energy storage/conversion. One major focus is the crystalline phase of TiO2, known to be the most efficient of the anatase structures. Another issue is the decoration of TiO2 with noble metals, which act as charge carrier traps for electrons. The latter hinders or reduces the electron–hole recombination rate and often leads to a more efficient photocatalytic activity.In this paper, we describe how an interlayer consisting of 3–4 nm silver nanoparticles (Ag-NPs) promotes TiO2 anatase crystallisation and has a positive effect on the photoinduced catalytic and hydrophylic properties of TiO2 thin films. Ag-NPs and TiO2 were deposited by magnetron sputtering in the same reactor in a two-step process: a) condensation of Ag-NPs produced in the gas phase thanks to a high-pressure discharge, and b) conventional TiO2 magnetron deposition in oxide mode. Four temperatures from RT to 288 °C were investigated and film thickness was 80 nm.Particle size and film structure were determined by TEM, HRTEM and XRD. Photocatalytic activities of the samples were tracked by the evaluation of the surface hydrophilicity after UV illumination and 24 hours post-illumination, and by UV-induced palmitic acid degradation.Research Highlights► Silver nanoparticles were deposited on glass by magnetron sputtering. ► 80 nm TiO2 layers were post-deposited in-situ at T° from RT to 288 °C. ► Silver nanoparticles promote anatase crystallisation and do not diffuse to the surface. ► Water contact angle is reduced from 15° (Glass/TiO2) to ≈ 5° (Glass/Ag/TiO2). ► Palmitic acid degradation is improved by one order of magnitude.
    Surface and Coatings Technology 01/2011; 205:3774-3778. · 1.94 Impact Factor
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    ABSTRACT: The respiratory tract is continuously exposed to both innocuous airborne antigens and immunostimulatory molecules of microbial origin, such as LPS. At low concentrations, airborne LPS can induce a lung DC-driven Th2 cell response to harmless inhaled antigens, thereby promoting allergic asthma. However, only a small fraction of people exposed to environmental LPS develop allergic asthma. What prevents most people from mounting a lung DC-driven Th2 response upon exposure to LPS is not understood. Here we have shown that lung interstitial macrophages (IMs), a cell population with no previously described in vivo function, prevent induction of a Th2 response in mice challenged with LPS and an experimental harmless airborne antigen. IMs, but not alveolar macrophages, were found to produce high levels of IL-10 and to inhibit LPS-induced maturation and migration of DCs loaded with the experimental harmless airborne antigen in an IL-10-dependent manner. We further demonstrated that specific in vivo elimination of IMs led to overt asthmatic reactions to innocuous airborne antigens inhaled with low doses of LPS. This study has revealed a crucial role for IMs in maintaining immune homeostasis in the respiratory tract and provides an explanation for the paradox that although airborne LPS has the ability to promote the induction of Th2 responses by lung DCs, it does not provoke airway allergy under normal conditions.
    The Journal of clinical investigation 11/2009; 119(12):3723-38. · 15.39 Impact Factor
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    ABSTRACT: Microarrays have become an important research tool for life science researchers. Expression microarrays are capable of profiling the gene expression pattern of tens of thousands of genes in a single experiment. It appears to be the platform of choice for parallel gene expression profiling. Various equine-specific gene expression microarrays have been generated and used. However, homologous microarrays are not yet commercially available for the horse. An alternative is the use of heterologous microarrays, mainly microarrays specific for mice or humans. Although the use of microarrays in equine research is still in its infancy, gene expression microarrays have shown their potential in equine research. This review presents the previous, current and potential use of expression microarrays in equine research.
    Veterinary Immunology and Immunopathology 11/2008; 127(3-4):197-202. · 1.88 Impact Factor
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    ABSTRACT: Environmental causes of heaves are well described, but the molecular mechanisms of the disease remain unclear. Previous studies have highlighted the implications of variations in gene expression, most using reverse transcription polymerase chain reaction (RT-PCR). This well-known technique limits the number of genes that can be studied in a single assay. Microarray appears to be a valuable tool to by-pass this limitation, but so far there has been no equine-specific microarray available on the market. The present study was performed to determine whether a human microarray could be used to study gene expression in nucleated cells originating from peripheral blood and bronchoalveolar lavage fluid (BALF) in heaves-affected horses. With a four-fold cut-off, a total of 46 candidates were identified with differentially regulated genes between heaves-affected horses and controls. A real-time quantitative RT-PCR (RT-QPCR) conducted on a selection of genes, determined on the basis of previous publications, was used to validate the microarray results. The microarray failed to detect the presence of interleukin (IL)-1beta and IL-8 mRNA in the nucleated cells from BALF otherwise confirmed by real-time RT-QPCR. Although some candidate genes have been identified using this method, a complete expression profile of genes related to heaves could not be obtained with the use of the human microarray.
    The Veterinary Journal 09/2008; 177(2):216-21. · 2.42 Impact Factor
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    ABSTRACT: The aim of this paper was to describe, and when possible compare, the multivariate methods used by the participants in the EADGENE WP1.4 workshop. The first approach was for class discovery and class prediction using evidence from the data at hand. Several teams used hierarchical clustering (HC) or principal component analysis (PCA) to identify groups of differentially expressed genes with a similar expression pattern over time points and infective agent (E. coli or S. aureus). The main result from these analyses was that HC and PCA were able to separate tissue samples taken at 24 h following E. coli infection from the other samples. The second approach identified groups of differentially co-expressed genes, by identifying clusters of genes highly correlated when animals were infected with E. coli but not correlated more than expected by chance when the infective pathogen was S. aureus. The third approach looked at differential expression of predefined gene sets. Gene sets were defined based on information retrieved from biological databases such as Gene Ontology. Based on these annotation sources the teams used either the GlobalTest or the Fisher exact test to identify differentially expressed gene sets. The main result from these analyses was that gene sets involved in immune defence responses were differentially expressed.
    Genetics Selection Evolution 11/2007; 39(6):651-68. · 3.49 Impact Factor
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    ABSTRACT: We sought to determine whether prolactin (PRL) could influence the neutrophilic inflammation that characterizes chronic mastitis. Most of the genes encoding inflammatory proteins depend on the nuclear factor kappaB (NF-kappaB) for their expression. We addressed the hypothesis that immunomodulatory activities of PRL might arise from an increase in NF-kappaB activity. MAC-T cells, a bovine mammary epithelial cell line, were stimulated with increasing concentrations of bovine PRL (1, 5, 25, 125, and 1,000 ng/mL). Level of NF-kappaB binding activity was measured and mRNA was evaluated for IL-1beta, IL-6, IL-8, granulocyte-macrophage colony-stimulating factor (GMCSF), IFN-gamma, and tumor necrosis factor (TNF)-alpha, cytokines known to require NF-kappaB for their maximal transcription. Prolactin activated NF-kappaB; maximal NF-kappaB activation was weaker with PRL than with TNF-alpha at 30 or 180 min poststimulation. In addition, PRL significantly amplified, in a dose-dependent manner, mRNA expression of IL-1beta, IL-6, IL-8, GMCSF, and TNF-alpha. We measured PRL concentrations in blood and milk from healthy and chronic mastitis-infected cows, and studied the relationship between the PRL concentration and the degree of inflammation in the mammary gland as indirectly assessed by somatic cell counts (SCC). Plasma PRL did not differ significantly between healthy and chronic mastitis-affected cows (63.7 and 67.5 ng/mL, respectively). Milk PRL concentration was significantly increased in chronic mastitis-affected quarters with the highest SCC, and had a positive significant correlation between SCC, as well as between the number of neutrophils present in milk samples. The present findings show that PRL promotes an inflammatory response in bovine mammary epithelial cells via NF-kappaB activation, and suggest a role for PRL in the pathogenesis of chronic mastitis.
    Journal of Dairy Science 02/2007; 90(1):155-64. · 2.57 Impact Factor
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    ABSTRACT: Microarray analyses have become an important tool in animal genomics. While their use is becoming widespread, there is still a lot of ongoing research regarding the analysis of microarray data. In the context of a European Network of Excellence, 31 researchers representing 14 research groups from 10 countries performed and discussed the statistical analyses of real and simulated 2-colour microarray data that were distributed among participants. The real data consisted of 48 microarrays from a disease challenge experiment in dairy cattle, while the simulated data consisted of 10 microarrays from a direct comparison of two treatments (dye-balanced). While there was broader agreement with regards to methods of microarray normalisation and significance testing, there were major differences with regards to quality control. The quality control approaches varied from none, through using statistical weights, to omitting a large number of spots or omitting entire slides. Surprisingly, these very different approaches gave quite similar results when applied to the simulated data, although not all participating groups analysed both real and simulated data. The workshop was very successful in facilitating interaction between scientists with a diverse background but a common interest in microarray analyses.
    Genetics Selection Evolution 01/2007; 39(6):621-31. · 3.49 Impact Factor
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    ABSTRACT: A large variety of methods has been proposed in the literature for microarray data analysis. The aim of this paper was to present techniques used by the EADGENE (European Animal Disease Genomics Network of Excellence) WP1.4 participants for data quality control, normalisation and statistical methods for the detection of differentially expressed genes in order to provide some more general data analysis guidelines. All the workshop participants were given a real data set obtained in an EADGENE funded microarray study looking at the gene expression changes following artificial infection with two different mastitis causing bacteria: Escherichia coli and Staphylococcus aureus. It was reassuring to see that most of the teams found the same main biological results. In fact, most of the differentially expressed genes were found for infection by E. coli between uninfected and 24 h challenged udder quarters. Very little transcriptional variation was observed for the bacteria S. aureus. Lists of differentially expressed genes found by the different research teams were, however, quite dependent on the method used, especially concerning the data quality control step. These analyses also emphasised a biological problem of cross-talk between infected and uninfected quarters which will have to be dealt with for further microarray studies.
    Genetics Selection Evolution 01/2007; 39(6):633-50. · 3.49 Impact Factor
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    Thomas A, Closset R, Bureau F, Lekeux P
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    ABSTRACT: RESUME : Le microdamier est un outil technologique miniaturisé potentiellement applicable à l'étude et l'analyse de multiples composés moléculaires, tels que des protéines, lipides, hydrates de carbone ou acides nucléiques. C'est avec les acides nucléiques que les microdamiers attirent, depuis une quin-zaine d'années, l'attention de la communauté scientifique du fait de son immense potentiel en matière de recherche scientifique, de diagnostic clinique, et de développement de nouveaux médicaments. Seuls les microdamiers à ADN sont investigués dans cet article. Nés du mariage de la microélectroni-que, de la biochimie, de la biologie moléculaire, de l'informatique et de l'analyse d'image, les micro-damiers permettent d'analyser simultanément plusieurs milliers d'informations génétiques différentes. Grâce à ce nouvel outil, il est possible en parallèle d'identifier, voire de doser, un nombre considérable de séquences d'acides nucléiques contenues dans un échantillon biologique (sang, biopsie, mais aussi eau, aliments...). Cet article propose, après s'être penché sur le mode de fonctionnement des microdamiers, d'en comprendre les critères de qualité ainsi que les avantages et inconvénients. Les deux parties suivantes sont consacrées à la place qu'occupent les microdamiers dans le recherche scientifique et dans l'établissement d'un diagnostic clinique. Enfin la dernière partie évalue les pers-pectives qu'offrent les microdamiers dans les sciences vétérinaires.
    Annales de médecine vétérinaire 01/2005; 29(145):93-116. · 0.03 Impact Factor
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    ABSTRACT: Bovine subclinical mastitis can be defined as a moderated inflammatory disease characterized by a persistent accumulation of neutrophils in milk. As GMCSF-mediated delay of neutrophil apoptosis contributes to the accumulation of inflammatory cells at the site of inflammation in many human diseases, we sought to determine whether subclinical mastitis in cows is also associated with a GMCSF-dependent increase in milk-neutrophil survival. We first addressed the hypothesis that GMCSF delays bovine neutrophil apoptosis by activation of the signal transducer and activator of transcription (STAT) family members STAT3 and STAT5, which are critical regulators of the expression of various Bcl-2 family proteins. Granulocyte-macrophage colony-stimulating factor significantly delayed apoptosis of blood neutrophils obtained from healthy cows. In these cells, GMCSF activated STAT5, but not STAT3, and induced an increase in the mRNA of the antiapoptotic Bcl-2 member, Bcl-xL. Granulocyte-macrophage colony-stimulating factor-dependent STAT5 activation and up-regulation of Bcl-xL mRNA were blocked by the Jak inhibitor, AG-490. This inhibition was associated with abrogation of the prosurvival effect of GMCSF, demonstrating a key role for STAT5 in delayed neutrophil apoptosis. We further found that GMCSF expression was increased in milk cells from cows affected with subclinical mastitis. Neutrophils from these cows demonstrated a significant delay of apoptosis as compared with neutrophils obtained from healthy cows and were unresponsive to GMCSF. Active STAT5 complexes were detected in these neutrophils. Finally, in the presence of AG-490, apoptosis was induced and a time-dependent down-regulation of Bcl-xL mRNA was observed in milk neutrophils from mastitis-affected cows. These results indicate that neutrophil survival is enhanced in milk of subclinical mastitis-affected cows and suggest a role for a GMCSF-activated STAT5 signaling pathway in this phenomenon. This pathway could thus represent a target for the control of persistent accumulation of neutrophils in the bovine mammary gland.
    Journal of Dairy Science 01/2005; 87(12):4104-14. · 2.57 Impact Factor
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    ABSTRACT: The aim of this paper was to describe, and when possible compare, the multivariate methods used by the participants in the EADGENE WP1.4 workshop. The first approach was for class discovery and class prediction using evidence from the data at hand. Several teams used hierarchical clustering (HC) or principal component analysis (PCA) to identify groups of differentially expressed genes with a similar expression pattern over time points and infective agent (E. coli or S. aureus). The main result from these analyses was that HC and PCA were able to separate tissue samples taken at 24 h following E. coli infection from the other samples. The second approach identified groups of differentially co-expressed genes, by identifying clusters of genes highly correlated when animals were infected with E. coli but not correlated more than expected by chance when the infective pathogen was S. aureus. The third approach looked at differential expression of predefined gene sets. Gene sets were defined based on information retrieved from biological databases such as Gene Ontology. Based on these annotation sources the teams used either the GlobalTest or the Fisher exact test to identify differentially expressed gene sets. The main result from these analyses was that gene sets involved in immune defence responses were differentially expressed.
    Genetics, Selection, Evolution 39 (2007) 6.
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    [Show abstract] [Hide abstract]
    ABSTRACT: A large variety of methods has been proposed in the literature for microarray data analysis. The aim of this paper was to present techniques used by the EADGENE (European Animal Disease Genomics Network of Excellence) WP1.4 participants for data quality control, normalisation and statistical methods for the detection of differentially expressed genes in order to provide some more general data analysis guidelines. All the workshop participants were given a real data set obtained in an EADGENE funded microarray study looking at the gene expression changes following artificial infection with two different mastitis causing bacteria: Escherichia coli and Staphylococcus aureus. It was reassuring to see that most of the teams found the same main biological results. In fact, most of the differentially expressed genes were found for infection by E. coli between uninfected and 24 h challenged udder quarters. Very little transcriptional variation was observed for the bacteria S. aureus. Lists of differentially expressed genes found by the different research teams were, however, quite dependent on the method used, especially concerning the data quality control step. These analyses also emphasised a biological problem of cross-talk between infected and uninfected quarters which will have to be dealt with for further microarray studies
    Genetics, Selection, Evolution 39 (2007).
  • [Show abstract] [Hide abstract]
    ABSTRACT: Microarray analyses have become an important tool in animal genomics. While their use is becoming widespread, there is still a lot of ongoing research regarding the analysis of microarray data. In the context of a European Network of Excellence, 31 researchers representing 14 research groups from 10 countries performed and discussed the statistical analyses of real and simulated 2-colour microarray data that were distributed among participants. The real data consisted of 48 microarrays from a disease challenge experiment in dairy cattle, while the simulated data consisted of 10 microarrays from a direct comparison of two treatments (dye-balanced). While there was broader agreement with regards to methods of microarray normalisation and significance testing, there were major differences with regards to quality control. The quality control approaches varied from none, through using statistical weights, to omitting a large number of spots or omitting entire slides. Surprisingly, these very different approaches gave quite similar results when applied to the simulated data, although not all participating groups analysed both real and simulated data. The workshop was very successful in facilitating interaction between scientists with a diverse background but a common interest in microarray analyses.
    Genetics, Selection, Evolution 39 (2007) 6.