Application of classical models of chirality to surface second harmonic generation

International audienceTwo classical models (Kuhn and Kauzmann) are extended to calculate the second-order nonlinear response of an isotropic layer of chiral molecules. Calculation of the various nonlinear susceptibilities (electric dipolar, magnetic dipolar, and electric quadrupolar) is performed and applied to the derivation of the second harmonic field radiated by the molecules. It is shown that the two models give strikingly different results about the origin of the chiral response in such experiments. Previously published results are analyzed in view of this calculation which allows to understand the different interpretations proposed. This calculation emphasizes the interest of surface second harmonic generation to access information about the microscopic origin of optical activity in chiral molecules. © 2001 American Institute of Physics

Homeostatic Eosinophils: Characteristics and Functions

Eosinophils are typically considered to be specialized effector cells that are recruited to the tissues as a result of T helper type 2 (Th2) cell responses associated with helminth infections or allergic diseases such as asthma. Once at the site of injury, eosinophils release their cytotoxic granule proteins as well as preformed cytokines and lipid mediators, contributing to parasite destruction but also to exacerbation of inflammation and tissue damage. Accumulating evidence indicates that, besides their roles in Th2 responses, eosinophils also regulate homeostatic processes at steady state, thereby challenging the exclusive paradigm of the eosinophil as a destructive and inflammatory cell. Indeed, under baseline conditions, eosinophils rapidly leave the bloodstream to enter tissues, mainly the gastrointestinal tract, lungs, adipose tissue, thymus, uterus, and mammary glands, where they regulate a variety of important biological functions, such as immunoregulation, control of glucose homeostasis, protection against obesity, regulation of mammary gland development, and preparation of the uterus for pregnancy. This article provides an overview of the characteristics and functions of these homeostatic eosinophils

Wavelength dependence of nonlinear circular dichroism in a chiral ruthenium-tris(bipyridyl) solution

International audienceNonlinear circular dichroism is studied in a solution of ruthenium-tris(bipyridyl) salt in one-beam and pump-probe experiments by tuning the laser wavelength across the circular dichroism structure. The dispersion of the nonlinear circular dichroism is measured. This wavelength dependence is well accounted for by a model calculation where nonlocality is included in the optical response of a two-coupled-oscillator system. This calculation also allows us to address the question of the contribution of electric quadrupolarization to the nonlinear optical activity of an isotropic liquid of chiral molecules. © 2002 The American Physical Societ

Resident CD11b(+)Ly6C(-) Lung Dendritic Cells Are Responsible for Allergic Airway Sensitization to House Dust Mite in Mice.

peer reviewedConventional dendritic cells (DCs) are considered to be the prime initiators of airway allergy. Yet, it remains unclear whether specific DC subsets are preferentially involved in allergic airway sensitization. Here, we systematically assessed the respective pro-allergic potential of individually sorted lung DC subsets isolated from house dust mite antigen (HDM)-treated donor mice, following transfer to naive recipients. Transfer of lung CD11c(+)CD11b(+) DCs, but not CD11c(+)CD11b(-)CD103(+) DCs, was sufficient to prime airway allergy. The CD11c(+)CD11b(+) DC subpopulation was composed of CD11c(+)CD11b(+)Ly6C(+) inflammatory monocyte-derived cells, whose numbers increase in the lungs following HDM exposure, and of CD11c(+)CD11b(+)Ly6C(-) DCs, which remain stable. Counterintuitively, only CD11c(+)CD11b(+)Ly6C(-) DCs, and not CD11c(+)CD11b(+)Ly6C(+) DCs, were able to convey antigen to the lymph nodes and induce adaptive T cell responses and subsequent airway allergy. Our results thus support that lung resident non-inflammatory CD11c(+)CD11b(+)Ly6C(-) DCs are the essential inducers of allergic airway sensitization to the common aeroallergen HDM in mice

Homeostatic Eosinophils: Characteristics and Functions

Eosinophils are typically considered to be specialized effector cells that are recruited to the tissues as a result of T helper type 2 (Th2) cell responses associated with helminth infections or allergic diseases such as asthma. Once at the site of injury, eosinophils release their cytotoxic granule proteins as well as preformed cytokines and lipid mediators, contributing to parasite destruction but also to exacerbation of inflammation and tissue damage. Accumulating evidence indicates that, besides their roles in Th2 responses, eosinophils also regulate homeostatic processes at steady state, thereby challenging the exclusive paradigm of the eosinophil as a destructive and inflammatory cell. Indeed, under baseline conditions, eosinophils rapidly leave the bloodstream to enter tissues, mainly the gastrointestinal tract, lungs, adipose tissue, thymus, uterus, and mammary glands, where they regulate a variety of important biological functions, such as immunoregulation, control of glucose homeostasis, protection against obesity, regulation of mammary gland development, and preparation of the uterus for pregnancy. This article provides an overview of the characteristics and functions of these homeostatic eosinophils

Clinical signs and physiopathological mechanisms of the main chronic inflammatory airway diseases of the horse

The respiratory tract of the horse can be the seat of several chronic inflammatory diseases whose principal ones are the recurrent airway obstruction, the inflammatory airway disease, the summer pasture-associated obstructive pulmonary disease and the follicular pharyngitis. These diseases can have an important impact on horses’ health and on their sports performances. A good knowledge of their aetiologies and their physiopathological mechanisms would allow a better control of these affections. However, even if many studies were made on this subject, there are currently very few certainties as for the inflammatory mechanisms governing these diseases. This article aims to make an inventory of knowledge and deficiencies concerning these four chronic inflammatory diseasesLe tractus respiratoire du cheval peut être le siège de plusieurs maladies inflammatoires chroniques dont les principales sont la pousse, la maladie inflammatoire des voies respiratoires, le syndrome d’obstruction pulmonaire associé au pâturage en été et la pharyngite folliculaire. Ces maladies peuvent avoir un impact important sur la santé des chevaux mais aussi sur leurs performances sportives. Une meilleure connaissance de leurs étiologies et de leurs mécanismes physiopathologiques permettrait une meilleure maîtrise de ces affections. Cependant, même si de nombreuses études se sont penchées sur le sujet, il existe actuellement très peu de certitudes quant aux mécanismes inflammatoires régissant la plupart de ces maladies. Cet article vise à faire un état des lieux des connaissances et des lacunes concernant ces quatre maladies inflammatoires chronique

Valorisation d’un déchet polysaccharidique : la pulpe de betterave. Applications à l’élimination d’ions métalliques dans l’eau

International audienceThe fixation of metal ions on sugar beet pulp, a low-cost material, has been studied. After a simple treatment of the sorbent, the results have shown that the kinetics are fast (≤ 90 min), and the pulp presents different fixation capacities according to the metals sorbed (Ni2+ < Cu2+ << Pb2+) and comprised between 11 and 57 mg.g-1. The mode of fixation is attributed to ion exchange while a non negligible part of adsorption could sometimes occur.La pulpe de betterave, déchet de l’industrie sucrière est étudiée pour son utilisation dans l’élimination de cations métalliques présents dans les effluents aqueux. Les meilleures conditions opératoires (préparation du matériau, effet du pH…) sont définies. Les cinétiques d’élimination s’avèrent être relativement rapides (≤ 90 min), les capacités de fixation dépendent du métal utilisé (Ni2+ < Cu2+ << Pb2+) et s’échelonnent entre 11 et 57 mg.g-1. Une approche du mécanisme de fixation a révélé un échange d’ion majoritaire, complété parfois d’adsorption

Pannexin-1 in Human Lymphatic Endothelial Cells Regulates Lymphangiogenesis

International audienceThe molecular mechanisms governing the formation of lymphatic vasculature are notyet well understood. Pannexins are transmembrane proteins that form channels which allow fordiffusion of ions and small molecules (<1 kDa) between the extracellular space and the cytosol.The expression and function of pannexins in blood vessels have been studied in the last few decades.Meanwhile, no studies have been conducted to evaluate the role of pannexins during humanlymphatic vessel formation. Here we show, using primary human dermal lymphatic endothelial cells(HDLECs), pharmacological tools (probenecid, Brilliant Blue FCF, mimetic peptides [10Panx]) andsiRNA-mediated knockdown that Pannexin-1 is necessary for capillary tube formation on Matrigeland for VEGF-C-induced invasion. These results newly identify Pannexin-1 as a protein highlyexpressed in HDLECs and its requirement during in vitro lymphangiogenesis

Connexin43 mediates the invasive properties of human glioblastoma cells.

International audienc