University of Paris

About: University of Paris is a education organization based out in Paris, France. It is known for research contribution in the topics: Population & Transplantation. The organization has 102426 authors who have published 174180 publications receiving 5041753 citations. The organization is also known as: Sorbonne.

Risk bounds for model selection via penalization

Abstract: Performance bounds for criteria for model selection are devel- oped using recent theory for sieves. The model selection criteria are based on an empirical loss or contrast function with an added penalty term moti- vated by empirical process theory and roughly proportional to the number of parameters needed to describe the model divided by the number of ob- servations. Most of our examples involve density or regression estimation settings and we focus on the problem of estimating the unknown density or regression function. We show that the quadratic risk of the minimum penal- ized empirical contrast estimatoris bounded by an index of the accuracy of the sieve. This accuracy index quanties the trade-off among the candidate models between the approximation error and parameter dimension relative to sample size. If we choose a list of models which exhibit good approximation prop- erties with respect to different classes of smoothness, the estimator can be simultaneously minimax rate optimal in each of those classes. This is what is usually called adaptation. The type of classes of smoothness in which one gets adaptation depends heavily on the list of models. If too many models are involved in order to get accurate approximation of many wide classes of functions simultaneously, it may happen that the estimator is only approx-

Management of bleeding and coagulopathy following major trauma: an updated European guideline

Abstract: Introduction: Evidence-based recommendations are needed to guide the acute management of the bleeding trauma patient. When these recommendations are implemented patient outcomes may be improved. Methods: The multidisciplinary Task Force for Advanced Bleeding Care in Trauma was formed in 2005 with the aim of developing a guideline for the management of bleeding following severe injury. This document represents an updated version of the guideline published by the group in 2007 and updated in 2010. Recommendations were formulated using a nominal group process, the Grading of Recommendations Assessment, Development and Evaluation (GRADE) hierarchy of evidence and based on a systematic review of published literature. Results: Key changes encompassed in this version of the guideline include new recommendations on the appropriate use of vasopressors and inotropic agents, and reflect an awareness of the growing number of patients in the population at large treated with antiplatelet agents and/or oral anticoagulants. The current guideline also includes recommendations and a discussion of thromboprophylactic strategies for all patients following traumatic injury. The most significant addition is a new section that discusses the need for every institution to develop, implement and adhere to an evidence-based clinical protocol to manage traumatically injured patients. The remaining recommendations have been re-evaluated and graded based on literature published since the last edition of the guideline. Consideration was also given to changes in clinical practice that have taken place during this time period as a result of both new evidence and changes in the general availability of relevant agents and technologies. Conclusions: A comprehensive, multidisciplinary approach to trauma care and mechanisms with which to ensure that established protocols are consistently implemented will ensure a uniform and high standard of care across Europe and beyond.

Force mapping in epithelial cell migration

Abstract: We measure dynamic traction forces exerted by epithelial cells on a substrate. The force sensor is a high-density array of elastomeric microfabricated pillars that support the cells. Traction forces induced by cell migration are deduced from the measurement of the bending of these pillars and are correlated with actin localization by fluorescence microscopy. We use a multiple-particle tracking method to estimate the mechanical activity of cells in real time with a high-spatial resolution (down to 2 μm) imposed by the periodicity of the post array. For these experiments, we use differentiated Madin-Darby canine kidney (MDCK) epithelial cells. Our data provide definite information on mechanical forces exerted by a cellular assembly. The maximum intensity of the forces is localized on the edge of the epithelia. Hepatocyte growth factor promotes cell motility and induces strong scattering activity of MDCK cells. Thus, we compare forces generated by MDCK cells in subconfluent epithelia versus isolated cells after hepatocyte growth factor treatment. Maximal-traction stresses at the edge of a monolayer correspond to higher values than those measured for a single cell and may be due to a collective behavior.

Intercontinental emergence of Escherichia coli clone O25:H4-ST131 producing CTX-M-15

Abstract: BACKGROUND: Concomitant with the recent emergence of CTX-M-type extended-spectrum beta-lactamases (ESBLs), Escherichia coli has become the enterobacterial species most affected by ESBLs. Multiple locales are encountering CTX-M-positive E. coli, including specifically CTX-M-15. To gain insights into the mechanism underlying this phenomenon, we assessed clonality and diversity of virulence profiles within an international collection of CTX-M-15-positive E. coli. METHODS: Forty-one ESBL-positive E. coli isolates from eight countries and three continents (Europe, Asia and North America) were selected for study based on suspected clonality. Phylogenetic group, ERIC2 PCR profile, O H serotype, AmpC variant and antibiotic susceptibility were determined. Multilocus sequence typing (MLST) and PFGE provided additional discrimination. Virulence potential was inferred by detection of 46 virulence factor (VF) genes. RESULTS: Thirty-six (88%) of the 41 E. coli isolates exhibited the same set of core characteristics: phylogenetic group B2, ERIC2 PCR profile 1, serotype O25:H4, AmpC EC6, ciprofloxacin resistance and MLST profile ST131. By PFGE, the 36 isolates constituted one large cluster at the 68% similarity level; this comprised 17 PFGE groups (defined at 85% similarity), some of which included strains from different countries. The 36 isolates exhibited highly (91% to 100%) similar VF profiles. CONCLUSIONS: We describe a broadly disseminated, CTX-M-15-positive and virulent E. coli clonal group with highly homogeneous virulence genotypes and subgroups exhibiting highly similar PFGE profiles, suggesting recent emergence. Understanding how this clone has emerged and successfully disseminated within the hospital and community, including across national boundaries, should be a public health priority.

Ageing and vision: structure, stability and function of lens crystallins

Abstract: The alpha-, beta- and gamma-crystallins are the major protein components of the vertebrate eye lens, alpha-crystallin as a molecular chaperone as well as a structural protein, beta- and gamma-crystallins as structural proteins. For the lens to be able to retain life-long transparency in the absence of protein turnover, the crystallins must meet not only the requirement of solubility associated with high cellular concentration but that of longevity as well. For proteins, longevity is commonly assumed to be correlated with long-term retention of native structure, which in turn can be due to inherent thermodynamic stability, efficient capture and refolding of non-native protein by chaperones, or a combination of both. Understanding how the specific interactions that confer intrinsic stability of the protein fold are combined with the stabilizing effect of protein assembly, and how the non-specific interactions and associations of the assemblies enable the generation of highly concentrated solutions, is thus of importance to understand the loss of transparency of the lens with age. Post-translational modification can have a major effect on protein stability but an emerging theme of the few studies of the effect of post-translational modification of the crystallins is one of solubility and assembly. Here we review the structure, assembly, interactions, stability and post-translational modifications of the crystallins, not only in isolation but also as part of a multi-component system. The available data are discussed in the context of the establishment, the maintenance and finally, with age, the loss of transparency of the lens. Understanding the structural basis of protein stability and interactions in the healthy eye lens is the route to solve the enormous medical and economical problem of cataract.