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Search Results: 1 - 10 of 542123 matches for " Cécile Mérigoux "
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Characterization of Monomeric Intermediates during VSV Glycoprotein Structural Transition
Aurélie A. Albertini,Cécile Mérigoux,Sonia Libersou,Karine Madiona,Stéphane Bressanelli,Stéphane Roche,Jean Lepault,Ronald Melki,Patrice Vachette,Yves Gaudin
PLOS Pathogens , 2012, DOI: 10.1371/journal.ppat.1002556
Abstract: Entry of enveloped viruses requires fusion of viral and cellular membranes, driven by conformational changes of viral glycoproteins. Crystal structures provide static pictures of pre- and post-fusion conformations of these proteins but the transition pathway remains elusive. Here, using several biophysical techniques, including analytical ultracentrifugation, circular dichro?sm, electron microscopy and small angle X-ray scattering, we have characterized the low-pH-induced fusogenic structural transition of a soluble form of vesicular stomatitis virus (VSV) glycoprotein G ectodomain (Gth, aa residues 1–422, the fragment that was previously crystallized). While the post-fusion trimer is the major species detected at low pH, the pre-fusion trimer is not detected in solution. Rather, at high pH, Gth is a flexible monomer that explores a large conformational space. The monomeric population exhibits a marked pH-dependence and adopts more elongated conformations when pH decreases. Furthermore, large relative movements of domains are detected in absence of significant secondary structure modification. Solution studies are complemented by electron micrographs of negatively stained viral particles in which monomeric ectodomains of G are observed at the viral surface at both pH 7.5 and pH 6.7. We propose that the monomers are intermediates during the conformational change and thus that VSV G trimers dissociate at the viral surface during the structural transition.
Households Credits, Financial Intermediation and Monetary Policies  [PDF]
Cécile Bastidon
Modern Economy (ME) , 2014, DOI: 10.4236/me.2014.510093
Abstract: This paper develops a theoretical model of financial intermediation with three original characteristics. Firstly, all sectors are taken into account within total outstanding credits, including households. Secondly, in periods of high financial strains, the relationship between prices and funding supply volumes may be non-monotonic. Finally, the occurrence of interbank credit rationing results in other sectors’ funding rationing in credit and securities markets. The central bank conducts a non-standard type monetary policy. We show that the characteristics of financial intermediation then determine the magnitude of transmission of a shock on households financing costs and the content of the resulting monetary policy.
Radiation and breast cancer: a review of current evidence
Cécile M Ronckers, Christine A Erdmann, Charles E Land
Breast Cancer Research , 2004, DOI: 10.1186/bcr970
Abstract: The mammary gland is very sensitive to radiation-associated carcinogenesis, especially after exposures at young ages. Many aspects of the association between radiation and breast cancer have been elucidated in the past decades. This review is intended to summarize widely recognized features of radiation-associated breast cancer and to add a more detailed overview of relevant recent findings, especially focusing on factors that modify the radiation-related risk.In 2000, breast cancer was the most common malignant disease in women worldwide, with an estimated 1.05 million cases. Owing to high levels of screening in developed countries and the relatively favorable prognosis of early-stage disease, it is also the most prevalent malignancy in women, with almost 4 million women alive who have had breast cancer in the past 5 years [1]. In the USA, it is estimated that about 216,000 women will be diagnosed with breast cancer in 2004 and that 40,000 will die from the disease [2]. Male breast cancer is a rare disease, with an incidence about 1/100 of that for female breast cancer [2].Breast cancer is very rare before age 30 years, after which incidence rises steeply with advancing age up to about age 50 years. Thereafter, incidence still increases with age, but more slowly [3]. The strong dependence on age, as seen for many other adult-type cancers, is probably related to accumulating genetic damage that occurs during a human lifespan. The apparent change in slope of the age–incidence curve at about age 50 years is unique for breast cancer, and this is presumably related to hormonal changes associated with menopause, which is accompanied by a decrease in circulating estrogen levels [3]. Estrogens and other hormones are thought to affect the progression of initiated mammary gland cells in the path to malignancy. This has been shown clearly in early rodent studies, where chemical-associated or radiation-associated mammary tumors were most abundant after additional hormonal stim
Root Starch Reserves Are Necessary for Vigorous Re-Growth following Cutting Back in Lotus japonicus
Cécile Vriet, Alison M. Smith, Trevor L. Wang
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0087333
Abstract: Perenniality and vegetative re-growth vigour represent key agronomic traits in forage legume (Fabaceae) species. The known determinants of perenniality include the conservation of the vegetative meristem during and after the flowering phase, and the separation of flowering from senescence. The ability of the plants to store nutrient resources in perennial organs and remobilize them may also play an important role in the perennial growth habit, and in determining the capacity of the plant to re-grow following grazing or from one season to the next. To examine the importance of stored starch, we examined the vegetative re-growth vigour following cutting back of a unique collection of Lotus japonicus mutants impaired in their ability to synthesize or degrade starch. Our results establish that starch stored in the roots is important for re-growth vigour in Lotus japonicus. We extended this analysis to a collection of Lotus (trefoil) species and two ecotypes of Lotus japonicus displaying a large variation in their carbohydrate resource allocation. There was a positive correlation between root starch content and re-growth vigour in these natural variants, and a good general correlation between high re-growth vigour and the perennial life-form. We discuss the relationship between perenniality and the availability of root carbohydrates for re-growth.
Condensation and symmetry-breaking in the zero-range process with weak site disorder
Cécile Mailler,Peter M?rters,Daniel Ueltschi
Mathematics , 2015,
Abstract: Condensation phenomena in particle systems typically occur as one of two distinct types: either as a spontaneous symmetry breaking in a homogeneous system, in which particle interactions enforce condensation in a randomly located site, or as an explicit symmetry breaking in a system with background disorder, in which particles condensate in the site of extremal disorder. In this paper we confirm a recent conjecture by Godr\`eche and Luck by showing, for a zero range process with weak site disorder, that there exists a phase where condensation occurs with an intermediate type of symmetry-breaking, in which particles condensate in a site randomly chosen from a range of sites favoured by disorder. We show that this type of condensation is characterised by the occurrence of a Gamma distribution in the law of the disorder at the condensation site. We further investigate fluctuations of the condensate size and confirm a phase diagram, again conjectured by Godr\`eche and Luck, showing the existence of phases with normal and anomalous fluctuations.
Postprandial morphological response of the intestinal epithelium of the Burmese python (Python molurus)
Jean-Hervé Lignot,Cécile Helmstetter,Stephen M Secor
Quantitative Biology , 2006, DOI: 10.1016/j.cbpb.2005.05.005
Abstract: The postprandial morphological changes of the intestinal epithelium of Burmese pythons were examined using fasting pythons and at eight time points after feeding. In fasting pythons, tightly packed enterocytes possess very short microvilli and are arranged in a pseudostratified fashion. Enterocyte width increases by 23% within 24 h postfeeding, inducing significant increases in villus length and intestinal mass. By 6 days postfeeding, enterocyte volume had peaked, following as much as an 80% increase. Contributing to enterocyte hypertrophy is the cellular accumulation of lipid droplets at the tips and edges of the villi of the proximal and middle small intestine, but which were absent in the distal small intestine. At 3 days postfeeding, conventional and environmental scanning electron microscopy revealed cracks and lipid extrusion along the narrow edges of the villi and at the villus tips. Transmission electron microscopy demonstrated the rapid postprandial lengthening of enterocyte microvilli, increasing 4.8-fold in length within 24 h, and the maintaining of that length through digestion. Beginning at 24 h postfeeding, spherical particles were found embedded apically within enterocytes of the proximal and middle small intestine. These particles possessed an annular-like construction and were stained with the calcium-stain Alizarine red S suggesting that they were bone in origin. Following the completion of digestion, many of the postprandial responses were reversed, as observed by the atrophy of enterocytes, the shortening of villi, and the retraction of the microvilli. Further exploration of the python intestine will reveal the underlying mechanisms of these trophic responses and the origin and fate of the engulfed particles.
The Western Africa Ebola virus disease epidemic exhibits both global exponential and local polynomial growth rates
Gerardo Chowell,Cécile Viboud,James M. Hyman,Lone Simonsen
Quantitative Biology , 2014,
Abstract: Background: While many infectious disease epidemics are initially characterized by an exponential growth in time, we show that district-level Ebola virus disease (EVD) outbreaks in West Africa follow slower polynomial-based growth kinetics over several generations of the disease. Methods: We analyzed epidemic growth patterns at three different spatial scales (regional, national, and subnational) of the Ebola virus disease epidemic in Guinea, Sierra Leone and Liberia by compiling publicly available weekly time series of reported EVD case numbers from the patient database available from the World Health Organization website for the period 05-Jan to 17-Dec 2014. Results: We found significant differences in the growth patterns of EVD cases at the scale of the country, district, and other subnational administrative divisions. The national cumulative curves of EVD cases in Guinea, Sierra Leone, and Liberia show periods of approximate exponential growth. In contrast, local epidemics are asynchronous and exhibit slow growth patterns during 3 or more EVD generations, which can be better approximated by a polynomial than an exponential. Conclusions: The slower than expected growth pattern of local EVD outbreaks could result from a variety of factors, including behavior changes, success of control interventions, or intrinsic features of the disease such as a high level of clustering. Quantifying the contribution of each of these factors could help refine estimates of final epidemic size and the relative impact of different mitigation efforts in current and future EVD outbreaks.
Clinical Impact of Targeting Inaccuracy Due to Distortion of the Leksell Stereotactic Frame  [PDF]
Cécile Renier, Nicolas Massager
Open Journal of Modern Neurosurgery (OJMN) , 2018, DOI: 10.4236/ojmn.2018.83026
Abstract: Background: Distortion of the Leksell stereotactic frame can occur during surgical and radiosurgical frame-based procedures. The targeting accuracies of surgical procedures such as DBS surgery or frame-based biopsy, or Gamma Knife radiosurgical procedures, are related to the stereotactic frame that is commonly referred to a non-deformable referential system. Objective: To evaluate the clinical impact of frame distortion on accuracy of targeting in various stereotactic procedures. Methods: We studied the influence of increasing levels of distortion of the Leksell frame both on surgical procedures using the stereotactic arch, and on radiosurgical procedures with the Gamma Knife. For surgical procedures we applied the Target Simulator of Elekta to a frame submitted to different levels of frame distortion, and we measured the modifications of accuracy of targeting. For radiosurgical procedures the Leksell frame was applied on an anthropomorphic phantom and modifications of target coordinates were measured by an imaging method using the stereotactic CBCT of the Gamma Knife ICON. Results: For surgical procedures, we found a linear relation between the amount of the frame distortion and the extent of the deviation from the stereotactic target using the stereotactic arch (R2 = 0.99709). The level of bending of the frame is also linearly related to the level of inaccuracy of stereotactic targeting based on acquisition of MRI and CTscan with the Elekta imaging boxes (R2 = 0.96825). The inaccuracy of targeting related to frame bending can be avoided by a systematic control at the end of frame placement and by the use of the CBCT of the Gamma Knife Icon. Conclusion: Distortion of the frame is a significant source of clinical inaccuracy of targeting for stereotactic procedures. Frame bending must be checked after each frame placement and corrected if needed to avoid targeting inaccuracy during stereotactic surgery and radio-surgery procedures.
Analysis of comparative data with hierarchical autocorrelation
Cécile Ané
Mathematics , 2008, DOI: 10.1214/08-AOAS173
Abstract: The asymptotic behavior of estimates and information criteria in linear models are studied in the context of hierarchically correlated sampling units. The work is motivated by biological data collected on species where autocorrelation is based on the species' genealogical tree. Hierarchical autocorrelation is also found in many other kinds of data, such as from microarray experiments or human languages. Similar correlation also arises in ANOVA models with nested effects. I show that the best linear unbiased estimators are almost surely convergent but may not be consistent for some parameters such as the intercept and lineage effects, in the context of Brownian motion evolution on the genealogical tree. For the purpose of model selection I show that the usual BIC does not provide an appropriate approximation to the posterior probability of a model. To correct for this, an effective sample size is introduced for parameters that are inconsistently estimated. For biological studies, this work implies that tree-aware sampling design is desirable; adding more sampling units may not help ancestral reconstruction and only strong lineage effects may be detected with high power.
Gene Expression Profiling of Dendritic Cells Reveals Important Mechanisms Associated with Predisposition to Staphylococcus Infections
Mehdi Toufeer, Cécile M. D. Bonnefont, Eliane Foulon, Cécile Caubet, Christian Tasca, Marie-Rose Aurel, Christèle Robert-Granié, Rachel Rupp, Gilles Foucras
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0022147
Abstract: Background Staphylococcus aureus is a major pathogen of humans and animals and emerging antibiotic-resistant strains have further increased the concern of this health issue. Host genetics influence susceptibility to S. aureus infections, and the genes determining the outcome of infections should be identified to find alternative therapies to treatment with antibiotics. Here, we used outbred animals from a divergent selection based on susceptibility towards Staphylococcus infection to explore host immunogenetics. Methodology/Principal Findings We investigated how dendritic cells respond to heat-inactivated S. aureus and whether dendritic cells from animals showing different degrees of susceptibility had distinct gene expression profiles. We measured gene expression levels of in vitro S. aureus-stimulated bone marrow-derived dendritic cells at three different time points (0, 3 and 8 hrs) by using 15 k ovine Agilent microarrays. Furthermore, differential expression of a selected number of genes was confirmed by RT-qPCR. Gene signatures of stimulated DCs were obtained and showed that genes involved in the inflammatory process and T helper cell polarization were highly up-regulated upon stimulation. Moreover, a set of 204 genes were statistically differentially expressed between susceptible and resistant animals, and grouped them according to their predisposition to staphylococcal infection. Interestingly, over-expression of the C1q and Ido1 genes was observed in the resistant line and suggested a role of classical pathway of complement and early regulation of inflammation pathways, respectively. On the contrary, over expression of genes involved in the IL1R pathway was observed in susceptible animals. Furthermore, the leucocyte extravasation pathway was also found to be dominant in the susceptible line. Conclusion/Significance We successfully obtained Staphylococcus aureus associated gene expression of ovine BM-DC in an 8-hour kinetics experiment. The distinct transcriptional profiles of dendritic cells obtained from resistant and susceptible animals may explain susceptibility towards S. aureus infections in a broader context.
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