Meningitic Escherichia coli K1 Penetration and Neutrophil Transmigration Across the Blood–Brain Barrier are Modulated by Alpha7 Nicotinic Receptor

Alpha7 nicotinic acetylcholine receptor (nAChR), an essential regulator of inflammation, is abundantly expressed in hippocampal neurons, which are vulnerable to bacterial meningitis. However, it is unknown whether α7 nAChR contributes to the regulation of these events. In this report, an aggravating role of α7 nAChR in host defense against meningitic E. coli infection was demonstrated by using α7-deficient (α7-/-) mouse brain microvascular endothelial cells (BMEC) and animal model systems. As shown in our in vitro and in vivo studies, E. coli K1 invasion and polymorphonuclear neutrophil (PMN) transmigration across the blood-brain barrier (BBB) were significantly reduced in α7-/- BMEC and α7-/- mice. Stimulation by nicotine was abolished in the α7-/- cells and animals. The same blocking effect was achieved by methyllycaconitine (α7 antagonist). The tight junction molecules occludin and ZO-1 were significantly reduced in the brain cortex of wildtype mice infected with E. coli and treated with nicotine, compared to α7-/- cells and animals. Decreased neuronal injury in the hippocampal dentate gyrus was observed in α7-/- mice with meningitis. Proinflammatory cytokines (IL-1β, IL-6, TNFα, MCP-1, MIP-1alpha, and RANTES) and adhesion molecules (CD44 and ICAM-1) were significantly reduced in the cerebrospinal fluids of the α7-/- mice with E. coli meningitis. Furthermore, α7 nAChR is the major calcium channel for nicotine- and E. coli K1-increased intracellular calcium concentrations of mouse BMEC. Taken together, our data suggest that α7 nAChR plays a detrimental role in the host defense against meningitic infection by modulation of pathogen invasion, PMN recruitment, calcium signaling and neuronal inflammation

Micropropagation and rejuvenation of Sequoia sempervirens (Lamb) Endl: a review

International audienc

Micropropagation and rejuvenation of Sequoia sempervirens (Lamb) Endl: a review

This article describes the botanical, biological and forest-tree characteristics of Sequoia sempervirens, the reasons for interest in its in vitro vegetative multiplication, the difficulty in achieving this from old and remarkable trees, and reviews means of overcoming this limitation. Among such means are the repeated culture of stem fragments on media containing appropriate hormonal combinations, the micrografting of buds originating from old trees onto juvenile rootstocks, and regeneration of buds from previously rejuvenated material. The value and limitations of these protocols and of morphological, physiological and biochemical markers of rejuvenation are discussed. The experimental conditions required for the formation of somatic embryos are described. Increased knowledge of in vitro micropropagation will be essential to enhance the use of clonal selection and offer practical outlets to studies concerning somatic hybridization and somatic embryogenesis.Micropropagation et rajeunissement du Sequoia sempervirens (Lamb) Endl : revue. Cet article présente les principales caractéristiques botaniques, biologiques et forestières du Sequoia sempervirens. Il analyse l'intérêt de la multiplication végétative réalisée in vitro soit par micropropagation sensu stricto (figs 1, 2 et 3), soit par régénération (figs 6, 7 et 9); il discute les raisons de la difficulté à la réaliser à partir d'arbres âgés et remarquables ainsi que les moyens de la contourner. Parmi ces moyens figurent la réitération des cultures de fragments de tige sur des milieux contenant un équilibre hormonal adéquat (tableaux I et II), le microgreffage de bourgeons appartenant à des plantes âgées sur des porte-greffes juvéniles (figs 4 et 5), la régénération de bourgeons à partir de matériel préalablement rajeuni selon l'un des protocoles précédents (figs 10 et 11). L'intérêt et les limites de ces protocoles sont discutés, en considérant les marqueurs morphologiques (figs 12 et 13), physiologiques et biochimiques du rajeunissement. Les conditions d'obtention de l'embryogenèse somatique chez cet arbre sont décrites (fig 8). Finalement, l'accroissement de nos connaissances en micropropagation in vitro apparaît essentiel pour augmenter la qualité de la sélection clonale et offrir des débouchés pratiques aux travaux concernant l'hybridation somatique et l'embryogenèse somatique. L'acquisition de telles connaissances de base devrait permettre une meilleure utilisation de cet arbre

Réflexion sur les modalités d'appréciation du rajeunissement in vitro chez le Sequoia sempervirens

International audienc

Réflexion sur les modalités d'appréciation du rajeunissement in vitro chez le Sequoia sempervirens

International audienc

Auxin metabolism and rooting in young and mature clones of Sequoia sempervirens

International audienc

Influence of the surface roughness on CIGS-based solar cell parameters

International audienc

Influence of the surface roughness on CIGS-based solar cell parameters

International audienc