Véronique Le Tilly - Academia.edu (original) (raw)

Papers by Véronique Le Tilly

HAL (Le Centre pour la Communication Scientifique Directe), May 21, 2012

La mesure de l'activité de mollusques bivalves est un moyen d'enregistrer le comportement de biva... more La mesure de l'activité de mollusques bivalves est un moyen d'enregistrer le comportement de bivalves in situ et donc d'évaluer des changements de la qualité de l'eau. Nous proposons une méthode statistique basée sur la théorie des valeurs extrêmes permettant d'estimer des changements globaux (pollution, changement de température) et ainsi d'aider à la surveillance de systèmes aquatiques. Mots-clés. Estimateur à noyau, Haute fréquence, Valeurs extrêmes Abstract. Measurement of mollusks bivalves activity is a way to record the animal behavior and so to evaluate possible changes in the water quality. We propose a statistical method based on the theory of extreme values to estimate global changes (pollution, change of temperature) and so to contribute to the survey of aquatic systems.

HAL (Le Centre pour la Communication Scientifique Directe), Jun 8, 2009

Etude comparative de récepteurs aux œstrogènes: Aspects moléculaire et cellulaire de la réponse a... more Etude comparative de récepteurs aux œstrogènes: Aspects moléculaire et cellulaire de la réponse aux œstrogènes et anti-œstrogènes impliqués dans les causes et thérapies du cancer du sein. présentée par

Food Packaging and Shelf Life, 2020

Food trays are often made from extruded polystyrene (XPS), and quantities of millimetre-sized par... more Food trays are often made from extruded polystyrene (XPS), and quantities of millimetre-sized particles of this material are trapped between the meat they contain and the sealing film. The purpose of this study is to identify the chemical nature of these particles and quantify them. Furthermore, the quantification of synthetic or organic fibres was also carried out. The results show that XPS microplastics (MP-XPS) contaminate food products at a level ranging from 4.0 to 18.7 MP-XPS/kg of packaged meat. Analysis shows that these microplastics are likely to come from the XPS trays. These particles are difficult to remove by mere rinsing and are probably cooked before being consumed. However, at this stage, it is not clear from the scientific literature whether there is a potential risk to humans associated with the ingestion of MP-XPS. In addition to these MP-XPS, it should also be pointed out that fibres can also contaminate meat.

Marine pollution bulletin, 2018

Elutriation is an efficient process for extracting microplastics. The development of a numerical ... more Elutriation is an efficient process for extracting microplastics. The development of a numerical model has shown the need for optimizing aspects of the design of the actual elutriation protocol as well as the dimensioning of the column to increase its efficiency. The study aims to propose new dimensioning data and protocol elements for designing an efficient column. Using a numerical model, the filling velocity was calculated as a function of the size and the density of the particles to prevent sand suspension. The sieving protocol was adapted to increase the density limit for the extraction of plastic particles from 1460 to >1800 kg·m. The durations of the elutriation and the column height were calculated to improve the control of the particle suspension. These results contribute to the development of the next generation of elutriation system and will accelerate the study of plasticome in the context of sandy sediments.

Marine Pollution Bulletin, 2017

This field study is intended to propose a global methodology to assess and monitor the water qual... more This field study is intended to propose a global methodology to assess and monitor the water quality of the gulf of Morbihan, a littoral ecosystem under increasing anthropic pressure. To this end, the Locmariaquer site, where Crassostrea gigas is extensively cultivated, was selected to perform a one-year follow-up of tissular glutathione Stransferase and acetylcholinesterase specific activities in this filter feeder organism. Calculation of an integrated index, corresponding to the ratio of the two enzymes activities, allowed to discriminate from the environmental noise, several clusters which could be representative environmental stress, potentially latent pollution. Moreover, the estrogenic activity was assessed in water samples collected at Locmariaquer and other strategic sites of the gulf. The results evidenced a low estrogenic-disrupting compound contamination of waters. Overall, this methodology produced an accurate outlook of a basal state for the gulf and could be developed in the context of a chronic monitoring of this site.

Ecotoxicology and Environmental Safety, 2016

Human activities require fossil fuels for transport and energy, a substantial part of which can a... more Human activities require fossil fuels for transport and energy, a substantial part of which can accidentally or voluntarily (oil spillage) flow to the marine environment and cause adverse effects in human and ecosystems' health. This experiment was designed to estimate the suitability of an original cellular biomarker to early quantify the biological risk associated to hydrocarbons pollutants in seawater. Oocytes and hepatopancreas cells, isolated from oyster (Crassostrea gigas), were tested for their capacity to regulate their volume following a hypo-osmotic challenge. Cell volumes were estimated from cell images recorded at regular time intervals during a 90 min-period. When exposed to diluted seawater (osmolalities from 895 to 712 mosm kg À 1), both cell types first swell and then undergo a shrinkage known as Regulatory Volume Decrease (RVD). This process is inversely proportional to the magnitude of the osmotic shock and is best fitted using a first-order exponential decay model. The Recovered Volume Factor (RVF) calculated from this model appears to be an accurate tool to compare cells responses. As shown by an about 50% decrease in RVF, the RVD process was significantly inhibited in cells sampled from oysters previously exposed to a low concentration of diesel oil (8.4 mg L À 1 during 24 h). This toxic effect was interpreted as a decreased permeability of the cell membranes resulting from an alteration of their lipidic structure by diesel oil compounds. In contrast, the previous contact of oysters with diesel did not induce any rise in the gills glutathione S-transferase specific activity. Therefore, this work demonstrates that the study of the RVD process of cells selected from sentinel animal species could be an alternative bioassay for the monitoring of hydrocarbons and probably, of various chemicals in the environment liable to alter the cellular regulations. Especially, given the high sensitivity of this biomarker compared with a proven one, it could become a relevant and accurate tool to estimate the biological hazards of micropollutants in the water.

Comptes Rendus Chimie, 2016

The present study aims to demonstrate the direct link between the microbial ecosystem of drinking... more The present study aims to demonstrate the direct link between the microbial ecosystem of drinking water distribution systems and animal health in pig breeding. Based on a survey over 18 months, a treatment using essential oils proved to be efficient in increasing piglet health and zootechnical performance. Water pipe biofilms were monitored by laser scanning confocal microscopy, while zootechnical performance and health cost data were collected from professional organisations. In two representative monitored herds, it was observed that the drinking water distribution pipes, initially fouled by fungi, were replaced by a bacterial film while both veterinary costs and the total feed conversion ratio decreased. Essential oils may thus provide an efficient and sustainable alternative to the massive use of antibiotics for transforming an initial detrimental ecosystem to a positive biofilm.

Industrial Crops and Products, 2016

Polyhydroxyalkanoates (PHA) are bacterial polyesters usually produced from costly sugars or volat... more Polyhydroxyalkanoates (PHA) are bacterial polyesters usually produced from costly sugars or volatile fatty acids (VFAs). In this work, two processing waters rich in vegetable proteins and reducing sugars, i.e. a mixture of saccharose and stachyose in Leguminous Processing Water (LPW) and a mixture of glucose and fructose in Fruit Processing Water (FPW), were tested as growth medium for PHA production in a two-stage fermentation with a unique marine bacterial species: Halomonas i4786. In preliminary shake flask experiments, it was shown that the two media can effectively support the bacterial growth and the accumulation of PHA (evaluated using Nile Red staining). In batch cultivation mode in a 5-L fermentor, PHA productivities of 1.6 g.L-1 and 1.8 g.L-1 were further achieved within 72h, in LPW and FPW respectively. Polymer characterization by Differential Scanning Calorimetry and Steric Exclusion Chromatography indicated that the two substrates led to the biosynthesis of polymers with different chain length, distribution and crystallinity. To summarize, these results show that by-products derived from local agri-food industry can be used as a user-adapted and cost-effective source to produce bio-sourced and biodegradable plastic materials.

World Journal of Microbiology and Biotechnology, 2015

The expansion of polyhydroxyalkanoates (PHAs) into the biodegradable polymers market is mainly pr... more The expansion of polyhydroxyalkanoates (PHAs) into the biodegradable polymers market is mainly prevented by their production process which is still complicated with a low efficiency, resulting in relatively expensive products. In this study, we developed a method that used the lipophilic fluorescent probe Nile Red (1 mg l(-1) solution in DMSO) directly into the culture broth to stain the PHA inclusions inside bacterial cells followed by detection of the emitted fluorescence by both microscopic and spectrometric techniques. Epifluorescence microscopy provides a rapid tool to distinguish producing from non-producing bacterial species and the relative fluorescence intensity (FI) determined at the maximum of emission spectra in the wavelength region of 560-710 nm (λex: 543 nm), allows a fast assessment of the cultural conditions that may enhance PHA production yield. During two-step cultivation in 500-ml flasks with glucose as the sole carbon source, the method aimed to select bacterial strains efficient for PHA synthesis among a marine collection. Subsequently, the NR assay was used to determine the C0/N0 ratio of the producing media that may improve the polymer yield as well as to follow the time course of fermentation. Characterization by GC-MS and DSC confirmed the production of the P(3-HB) homopolymer.

Biochemistry, 2015

Among hormone-inducible transcription factors, estrogen receptors (ERs) play important roles in t... more Among hormone-inducible transcription factors, estrogen receptors (ERs) play important roles in tissue growth and differentiation, via either direct or indirect binding, in the nucleus, to specific DNA targets called estrogen responsive elements (EREs), or through nongenomic pathways. In humans, two estrogen receptor isoforms (hERs), designated hERα and hERβ, have been identified. These two hERs, encoded by genes located on distinct chromosomes, exhibit divergent tissue-specific functions and different subcellular distributions depending on their binding status, free or complexed to their cognate ligands. Because it is hypothesized that such distinct behaviors may arise from various conformational stabilities and flexibilities, the effect of salt concentration and temperature was studied on the free and estrogen-activated hERα and hERβ. Our results show that the conformational stability of hERβ is weakly modulated by salt concentration as opposed to hERα. In addition, we show that the estrogenbound hERs exhibit a more constrained structure than the unliganded ones and that their conformational flexibility is more affected by diethylstilbestrol binding than that of estradiol, 4-hydroxytamoxifen, or raloxifen. In line with these results, conformational analysis and computational docking were performed on hERα and hERβ, which confer molecular support of a diethylstilbestrol-induced restrained flexibility as compared to other ligands. We found that Trp383 in hERα and Trp335 in hERβ can closely interact with the NR-box motif of the H12 helix and act as a gatekeeper of the agonist-bound versus antagonist-bound conformations. Altogether, our study contributes to an improved knowledge of the diverse physicochemical properties of fulllength hERs, which will help in our understanding of their distinct cellular roles in various cellular contexts. E strogens, as primordial female steroid hormones, play important roles in the reproductive function via their action on organs such as breast, uterus, and prostate, and also in nonreproductive systems such as brain, bone, heart, and liver. 1 The physiological functions controlled by estrogens are partly mediated by the estrogen receptor (ER), a hormone-inducible transcription factor, localized in and/or out of the nuclear compartment. In the nuclear compartment, ER positively or negatively regulates the expression of genes involved in tissue growth and differentiation, 2,3 either by directly binding on specific DNA sequences located in the promoters of target genes or by interacting with other transcriptional factors in the nucleus. The extranuclear ER exerts rapid nongenomic actions that are usually associated with the activation of various protein kinase cascades. 4 A dysregulation of ER signaling is associated with breast cancer. The first human ER identified, designated hERα, was cloned from MCF-7 cells where it is overexpressed. 5 A few years later, a second ER, designated hERβ, was identified in different human organs. 6,7 In humans, separate genes located on distinct chromosomes encode these two subtypes. 8 These estrogen receptors exhibit specific tissue distributions, biological roles, 9,10 and ligand affinities for various endogenous estrogens. 11 The two hERs exhibit distinct subcellular distributions, while forming different protein transitory complexes and being involved in separate functional regulations mainly because they are involved in the regulation of a distinct set of genes. 12,13

Chemistry & biology, Jan 8, 2015

Cyclin-dependent kinase 5 (CDK5) is a multifunctional enzyme that plays numerous roles, notably i... more Cyclin-dependent kinase 5 (CDK5) is a multifunctional enzyme that plays numerous roles, notably in brain development. CDK5 is activated through its association with the activators, p35 and p39, rather than by cyclins. Proteolytic procession of the N-terminal part of its activators has been linked to Alzheimer's disease and various other neuropathies. The interaction with the proteolytic product p25 prolongs CDK5 activation and modifies the substrate specificity. In order to discover small-molecule inhibitors of the interaction between CDK5 and p25, we have used a bioluminescence resonance energy transfer (BRET)-based screening assay. Among the 1,760 compounds screened, the generic drug tamoxifen has been identified. The inhibition of the CDK5 activity by tamoxifen was notably validated by monitoring the phosphorylation state of tau protein. The study of the molecular mechanism of inhibition indicates that tamoxifen interacts with p25 to block the CDK5/p25 interaction and pave th...

MW 19.0 kDa, 2 ½ SS bridges involved in polymers Casein micelle MW ~ 10 6 kDa av. diam = 180 nm