Effects of population density on the sediment mixing induced by the gallery-diffusor Hediste (Nereis) diversicolor O.F. Müller, 1776

The aim of this work was to quantify the intensity of sediment mixing induced by the gallery-diffusor (functional bioturbation group) Hediste diversicolor as a function of density, using particles tracers (luminophores). In order to assess the impact of density on sediment reworking, a 1-D model was used to obtain sediment reworking coefficients such as Db (biodiffusion-like) and r (biotransport). Densities used in this experiment corresponded to population densities observed in the sampling area (Saint-Antoine Canal, Gulf of Fos, France): 144, 288, 577, 1153 indiv/m2. At first, results showed that neither luminophore maximum burying depth nor the more marked tracer accumulation areas were influenced by density. Thus density did not seem to have any influence on size of galleries or complexity of structure. Then, density-dependent relations with Db (biodiffusion-like mixing) and r (biotransport) were highlighted with an observed process intensity rate twice as high at highest worm density. On the other hand, Db and r per capita coefficients were negatively influenced by density. Db and r per capita at highest density were equal to ∼20% of individual Db and r obtained at the lowest density. Finally, this study showed the importance of density which appears to be a key parameter in the functioning of the sedimentary ecosystem

Benthic macrofauna and sediment reworking quantification in contrasted environments in the Thau Lagoon

As part of the Microbent-PNEC Program: ‘‘Biogeochemical processes at the wateresediment interface in eutrophicated environment’’, the aim of this work was to specifically investigate and quantify the relationships between macrobenthos and sediment reworking in the Thau Lagoon in order to provide information on the potential contaminant distribution and movements at the wateresediment interface. In order to achieve this, three cores were sampled at two stations (in the central part of the Thau Lagoon and near the shellfish farming zone) in the Thau Lagoon, in December 2001, April 2002, August 2002, January 2003 and May 2003. On the basis of quantification of macrobenthos and sediment reworking, evidence is provided of: (1) similar sediment mixing intensities for different species composition at the two stations; (2) the major role of functional bioturbation groups (e.g., biodiffusors and gallery-diffusors) modulated by seasonal variability on sediment mixing; (3) an increase of intensity in summer suggesting potentially different patterns of redistribution, bioaccumulation and chemical fate (e.g., speciation) of deposited contaminants

CD133, CD15/SSEA-1, CD34 or side populations do not resume tumor-initiating properties of long-term cultured cancer stem cells from human malignant glio-neuronal tumors

<p>Abstract</p> <p>Background</p> <p>Tumor initiating cells (TICs) provide a new paradigm for developing original therapeutic strategies.</p> <p>Methods</p> <p>We screened for TICs in 47 human adult brain malignant tumors. Cells forming floating spheres in culture, and endowed with all of the features expected from tumor cells with stem-like properties were obtained from glioblastomas, medulloblastoma but not oligodendrogliomas.</p> <p>Results</p> <p>A long-term self-renewal capacity was particularly observed for cells of malignant glio-neuronal tumors (MGNTs). Cell sorting, karyotyping and proteomic analysis demonstrated cell stability throughout prolonged passages. Xenografts of fewer than 500 cells in Nude mouse brains induced a progressively growing tumor. CD133, CD15/LeX/Ssea-1, CD34 expressions, or exclusion of Hoechst dye occurred in subsets of cells forming spheres, but was not predictive of their capacity to form secondary spheres or tumors, or to resist high doses of temozolomide.</p> <p>Conclusions</p> <p>Our results further highlight the specificity of a subset of high-grade gliomas, MGNT. TICs derived from these tumors represent a new tool to screen for innovative therapies.</p

Suivi a long terme après succès primaire d'ablation par radiofréquence du flutter auriculaire commun (recherche des facteurs prédictifs de récidive, étude rétrospective chez 185 patients)

DIJON-BU Médecine Pharmacie (212312103) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

Titularización : una nueva visión para el desarrollo del país

El objetivo de este trabajo es analizar el proceso de titularización como mecanismo alterno de financiación haciendo énfasis en el sector público en Colombia. Para ello se realizó un estudio de mercado de valores en Colombia, y su poca utilización. Se realizó igualmente un análisis histórico de la titularización en los principales países de mundo, para posteriormente enfocarse en el génesis y desarrollo de la titularización en Colombia. Se examinó el proceso de titularización en sí mismo, identificando los sujetos que interactúan en el proceso, las vías jurídicas para llevar al cabo con éxito la titularización, los activos susceptibles de titularización y en general, todos los aspectos relacionados con el correcto desarrollo de éste mecanismo de financiación.Abogado (a)Pregrad

Control of Enterotoxin Gene Expression in Bacillus cereus F4430/73 Involves the Redox-Sensitive ResDE Signal Transduction System

In contrast to Bacillus subtilis, the role of the two-component regulatory system ResDE has not yet been investigated in the facultative anaerobe Bacillus cereus. We examined the role of ResDE in the food-borne pathogen B. cereus F4430/73 by constructing resDE and resE mutants. Growth performances, glucose metabolism, and expression of hemolysin BL (Hbl) and nonhemolytic enterotoxin (Nhe) were analyzed in the three strains under distinct oxygenation and extracellular oxidoreduction potential (ORP) conditions. We show that growth and glucose metabolism were only moderately perturbed in both resDE and resE mutants under aerobiosis, microaerobiosis, and anaerobiosis generated under N(2) atmosphere (initial ORP = +45 mV). The major effects of resDE and resE mutations were observed under low-ORP anaerobic conditions generated under hydrogen atmosphere (iORP = −148 mV). These conditions normally favor enterotoxin production in the wild type. The resE mutation was more deleterious to the cells than the resDE mutation, causing growth limitation and strong deregulation of key catabolic genes. More importantly, the resE mutation abolished the production of enterotoxins under all of the conditions examined. The resDE mutation only decreased enterotoxin expression under anaerobiosis, with a more pronounced effect under low-ORP conditions. Thus, the ResDE system was found to exert major control on both fermentative growth and enterotoxin expression, and it is concluded that the ResDE system of B. cereus should be considered an anaerobic redox regulator. The data presented also provide evidence that the ResDE-dependent regulation of enterotoxins might function at least partially independently of the pleiotropic virulence gene regulator PlcR