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Search Results: 1 - 10 of 24291 matches for " Jean-Denis Docquier "
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Major Enzymatic Factors Involved in Bacterial Penicillin Resistance in Burkina Faso
Boukare Zeba,Martin Kiendrebeogo,Aline Lamien,Jean-Denis Docquier
Pakistan Journal of Biological Sciences , 2007,
Abstract: Many clinical species of bacteria were isolated from biological samples such as urines, blood and wound in Saint Camille medical centre of Ouagadougou. Among the concerned species, the most important members were Escherichia coli and Klebsiella pneumoniae. These β-lactamases producing isolates were directly screened by PCR to identify the nature of the amplified genes responsible for penicillin destroying activity. Therefore specific TEM and SHV primers were used. The PCR products were sequenced. The sequencing results indicated that the parental forms blaTEM-1 and blaSHV-1 were the most common determinants of β-lactamase found, respectively in Escherichia species and Klebsiella pneumoniae. The bacterial susceptibility analysis by MICs measurement clearly correlated the presence of concerned β-lactamase determinants and their resistance patterns. This study is part of a set of investigations carried out by our laboratory to assess the β-lactamase incidence in the failure of β-lactam therapy. In particular, the purpose of this study was to determine the precise nature of β-lactamase supporting the low susceptibility of host bacteria towards penicillins.
Resistencia a carbapenemes en aislamientos de Pseudomonas aeruginosa: un ejemplo de interacción entre distintos mecanismos
Santella,Gisela; Pollini,Simona; Docquier,Jean-Denis; Almuzara,Marisa; Gutkind,Gabriel; Rossolini,Gian Maria; Radice,Marcela;
Revista Panamericana de Salud Pública , 2011, DOI: 10.1590/S1020-49892011001200008
Abstract: objective: to identify the outer membrane protein absent in the resistant isolates and to determine both the causes of its absence in the membrane and the presence of other mechanisms of carbapenem resistance in clinical isolates of pseudomonas aeruginosa. methods: twenty isolates from an outbreak of p. aeruginosa previously characterized as metallo-beta-lactamase imp-13 producers were studied. all the isolates exhibited equal expression of the imp-13 enzyme, but only five of them were carbapenem-resistant. it was found that the five resistant isolates lacked a outer membrane protein. the oprd and ampc genes were sequenced; the outer membrane proteins were identified using matrix-assisted laser desorption/ionization time-of-flight (maldi-tof) mass spectrometry; the oprd and ampc expressions, as well as the mex efflux system, were assessed by real-time polymerase chain reaction; and finally, the contribution of reduced oprd to carbapenem resistance was determined. results: the absent outer membrane protein in group r was identified as oprd-ts; however, no variations in its expression were observed. the oprd gene presented mutations in the five resistant isolates. the production of ampc pdc-5-type enzyme and the mexab-oprm efflux system was the same in both carbapenem-sensitive and ?resistant isolates. the contribution of the combined presence of imp-13 and reduced oprd to increased resistance was examined. conclusions: different mechanisms contribute to carbapenem resistance in imp-13-producing isolates. the possibility that these imp-13-producing isolates could go undetected poses a latent risk when selecting mutants with added resistance mechanisms in order to enhance carbapenem resistance.
L'humérus de chien magdalenién de Erralla (Gipuzkoa, Espagne) et la domestication tardiglaciaire du loup en Europe
Jean-Denis Vigne
Munibe Antropologia-Arkeologia , 2005,
Abstract: Retomando los argumentos morfológicos y crono-estratigráficos de Altuna y al. (1985), el autor confirma que, en efecto, el humero del cánido del nivel V de la cueva de Erralla resulta ser el de un perro que data del magdaleniense, incluso con toda probalbilidad del magdaleniense antiguo cantábrico (Dryas I, aprox. 16000 BP [17500-17000 antes J.C.]), sin que se pueda excluir del todo una contaminación porcedente del Magdaleniense Terminal (Allerod, aprox. 12500 BP). Las dimensiones de esta pieza son parecidas a las del húmero del perro de Pont d'Ambon (Dordogna, Azilien, aprox. 10700 BP). Aún sabiendo que constituyen dos de las nueve indicaciones de perro tardiglaciar en Europa, los hallazgos de Erralla y de Pont d'Ambon, que nos remiten a estos perros de tama o muy similar, han sido a menudo ignorados en los trabajos de síntesis sobre domesticaciones pre-holoceno del lobo.
Fluorine Based Superhydrophobic Coatings
Jean-Denis Brassard,D.K. Sarkar,Jean Perron
Applied Sciences , 2012, DOI: 10.3390/app2020453
Abstract: Superhydrophobic coatings, inspired by nature, are an emerging technology. These water repellent coatings can be used as solutions for corrosion, biofouling and even water and air drag reduction applications. In this work, synthesis of monodispersive silica nanoparticles of ~120 nm diameter has been realized via St?ber process and further functionalized using fluoroalkylsilane (FAS-17) molecules to incorporate the fluorinated groups with the silica nanoparticles in an ethanolic solution. The synthesized fluorinated silica nanoparticles have been spin coated on flat aluminum alloy, silicon and glass substrates. Functionalization of silica nanoparticles with fluorinated groups has been confirmed by Fourier Transform Infrared spectroscopy (FTIR) by showing the presence of C-F and Si-O-Si bonds. The water contact angles and surface roughness increase with the number of spin-coated thin films layers. The critical size of ~119 nm renders aluminum surface superhydrophobic with three layers of coating using as-prepared nanoparticle suspended solution. On the other hand, seven layers are required for a 50 vol.% diluted solution to achieve superhydrophobicity. In both the cases, water contact angles were more than 150°, contact angle hysteresis was less than 2° having a critical roughness value of ~0.700 μm. The fluorinated silica nanoparticle coated surfaces are also transparent and can be used as paint additives to obtain transparent coatings.
Y-SNPs Do Not Indicate Hybridisation between European Aurochs and Domestic Cattle
Ruth Bollongino, Julia Elsner, Jean-Denis Vigne, Joachim Burger
PLOS ONE , 2008, DOI: 10.1371/journal.pone.0003418
Abstract: Background Previous genetic studies of modern and ancient mitochondrial DNA have confirmed the Near Eastern origin of early European domestic cattle. However, these studies were not able to test whether hybridisation with male aurochs occurred post-domestication. To address this issue, G?therstr?m and colleagues (2005) investigated the frequencies of two Y-chromosomal haplotypes in extant bulls. They found a significant influence of wild aurochs males on domestic populations thus challenging the common view on early domestication and Neolithic stock-rearing. To test their hypothesis, we applied these Y-markers on Neolithic bone specimens from various European archaeological sites. Methods and Findings Here, we have analysed the ancient DNA of 59 Neolithic skeletal samples. After initial molecular sexing, two segregating Y-SNPs were identified in 13 bulls. Strikingly, our results do not support the hypothesis that these markers distinguish European aurochs from domesticated cattle. Conclusions The model of a rapid introduction of domestic cattle into Central Europe without significant crossbreeding with local wild cattle remains unchallenged.
Development of a Chitosan-Based Biofoam: Application to the Processing of a Porous Ceramic Material
Jean-Denis Mathias,Nicolas Tessier-Doyen,Philippe Michaud
International Journal of Molecular Sciences , 2011, DOI: 10.3390/ijms12021175
Abstract: Developing biofoams constitutes a challenging issue for several applications. The present study focuses on the development of a chitosan-based biofoam. Solutions of chitosan in acetic acid were dried under vacuum to generate foams with high-order structures. Chitosan concentration influenced significantly the morphology of developed porosity and the organization of pores in the material. Physico-chemical characterizations were performed to investigate the effects of chitosan concentration on density and thermal conductivity of foams. Even if chitosan-based biofoams exhibit interesting insulating properties (typically around 0.06 W·m ?1·K ?1), it has been shown that their durabilities are limited when submitted to a wet media. So, a way of application consists to elaborate a ceramic material with open porosity from a slurry prepared with an organic solvent infiltrating the porous network of the foam.
Moment Approximation of Infection Dynamics in a Population of Moving Hosts
Bruno Bonté, Jean-Denis Mathias, Rapha?l Duboz
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0051760
Abstract: The modelling of contact processes between hosts is of key importance in epidemiology. Current studies have mainly focused on networks with stationary structures, although we know these structures to be dynamic with continuous appearance and disappearance of links over time. In the case of moving individuals, the contact network cannot be established. Individual-based models (IBMs) can simulate the individual behaviours involved in the contact process. However, with very large populations, they can be hard to simulate and study due to the computational costs. We use the moment approximation (MA) method to approximate a stochastic IBM with an aggregated deterministic model. We illustrate the method with an application in animal epidemiology: the spread of the highly pathogenic virus H5N1 of avian influenza in a poultry flock. The MA method is explained in a didactic way so that it can be reused and extended. We compare the simulation results of three models: 1. an IBM, 2. a MA, and 3. a mean-field (MF). The results show a close agreement between the MA model and the IBM. They highlight the importance for the models to capture the displacement behaviours and the contact processes in the study of disease spread. We also illustrate an original way of using different models of the same system to learn more about the system itself, and about the representation we build of it.
Advances in Deoxynivalenol Toxicity Mechanisms: The Brain as a Target
Marion S. Bonnet,Julien Roux,Lourdes Mounien,Michel Dallaporta,Jean-Denis Troadec
Toxins , 2012, DOI: 10.3390/toxins4111120
Abstract: Deoxynivalenol (DON), mainly produced by Fusarium fungi, and also commonly called vomitoxin, is a trichothecene mycotoxin. It is one of the most abundant trichothecenes which contaminate cereals consumed by farm animals and humans. The extent of cereal contamination is strongly associated with rainfall and moisture at the time of flowering and with grain storage conditions. DON consumption may result in intoxication, the severity of which is dose-dependent and may lead to different symptoms including anorexia, vomiting, reduced weight gain, neuroendocrine changes, immunological effects, diarrhea, leukocytosis, hemorrhage or circulatory shock. During the last two decades, many studies have described DON toxicity using diverse animal species as a model. While the action of the toxin on peripheral organs and tissues is well documented, data illustrating its effect on the brain are significantly less abundant. Yet, DON is known to affect the central nervous system. Recent studies have provided new evidence and detail regarding the action of the toxin on the brain. The purpose of the present review is to summarize critical studies illustrating this central action of the toxin and to suggest research perspectives in this field.
NO INFLUENCE OF HYPOXIA ON COORDINATION BETWEEN RESPIRATORY AND LOCOMOTOR RHYTHMS DURING ROWING AT MODERATE INTENSITY
Nicolas Fabre,Stéphane Perrey,Philippe Passelergue,Jean-Denis Rouillon
Journal of Sports Science and Medicine , 2007,
Abstract: Besides neuro-mechanical constraints, chemical or metabolic stimuli have also been proposed to interfere with the coordination between respiratory and locomotor rhythms. In the light of the conflicting data observed in the literature, this study aimed to assess whether acute hypoxia modifies the degree of coordination between respiratory and locomotor rhythms during rowing exercises in order to investigate competitive interactions between neuro-mechanical (movement) and chemical (hypoxia) respiratory drives. Nine male healthy subjects performed one submaximal 6-min rowing exercise on a rowing ergometer in both normoxia (altitude: 304 m) and acute hypoxia (altitude: 2877 m). The exercise intensity was about 40 % and 35 % (for normoxia and hypoxia conditions, respectively) of the individual maximal power output measured during an incremental rowing test to volitional exhaustion carried out in normoxia. Metabolic rate and minute ventilation were continuously collected throughout exercise. Locomotor movement and breathing rhythms were continuously recorded and synchronized cycle-by-cycle. The degree of coordination was expressed as a percentage of breaths starting during the same phase of the locomotor cycle. For a same and a constant metabolic rate, acute hypoxia did not influence significantly the degree of coordination (mean ± SEM, normoxia: 20.0 ± 6.2 %, hypoxia: 21.3 ± 11.1 %, p > 0.05) while ventilation and breathing frequency were significantly greater in hypoxia. Our results may suggest that during rowing exercise at a moderate metabolic load, neuro-mechanical locomotion-linked respiratory stimuli appear "stronger" than peripheral chemoreceptors- linked respiratory stimuli induced by hypoxia, in the context of our study
Central nesfatin-1-expressing neurons are sensitive to peripheral inflammatory stimulus
Marion S Bonnet, Emilie Pecchi, Jér?me Trouslard, André Jean, Michel Dallaporta, Jean-Denis Troadec
Journal of Neuroinflammation , 2009, DOI: 10.1186/1742-2094-6-27
Abstract: During infection and inflammation, the immune, endocrine and nervous systems closely interact to coordinate a range of physiological and behavioral changes known as the acute phase reaction. The behavioral symptoms collectively referred to as "sickness behavior" include fever, anorexia, adipsia, lethargy and reduction in social interactions [1,2]. Cytokines peripherally released act on specific central nuclei involved in feeding and homeostatic regulation, which leads to the central component of the acute phase response. The complex neuronal circuitry involved in the coordinated response to inflammation, which includes notably the nucleus of the solitary tract (NTS), area postrema (AP), ventrolateral medulla, parabrachial nucleus, paraventricular hypothalamic nucleus (PVN), supraoptic nucleus (SON), arcuate nucleus (ARC) and central nucleus of the amygdala, has been identified mainly by quantification of the immediate-early gene c-fos [3,4]. The expression of the c-fos gene is widely considered to be a high resolution marker of neuronal activity, since a body of evidence demonstrates that Fos protein is expressed in neurons whose activity is strongly stimulated by synaptic input [5]. Used in combination with immunohistochemical determination of neuronal phenotype, this approach has led to the identification and location of neurons activated by inflammation and involved in the triggering of sickness behavior [6-8].Recently, Oh-I and co-authors reported the identification of a novel factor with anorexigenic properties, which they called nesfatin-1 [9]. Nesfatin-1 is reported to reduce food intake both after central (3rd ventricle) and peripheral administration [9,10]. Apart from adipose tissue, from which nesfatin-1 was first isolated, this protein is also expressed by gastric mucosa [11] and pancreatic β-cells [12]. This pattern of nesfatin-1 expression, as well as the presence of nesfatin-1 within the plasma of rodents and humans, strongly suggests that this compoun
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