119 research outputs found
Nonadditivity of Polymeric and Charged Surface Interactions: Consequences for Doped Lamellar Phases
We explore theoretically the modifications to the interactions between
charged surfaces across an ionic solution caused by the presence of dielectric
polymers. Although the chains are neutral, the polymer physics and the
electrostatics are coupled; the intra-surface electric fields polarise any low
permittivity species (e.g., polymer) dissolved in a high permittivity solvent
(e.g., water). This coupling enhances the polymer depletion from the surfaces
and increases the screening of electrostatic interactions with respect to a
model which treats polymeric and electrostatic effects as independent. As a
result, the range of the ionic contribution to the osmotic interaction between
surfaces is decreased, while that of the polymeric contribution is increased.
These changes modify the total interaction in a nonadditive manner. Building on
the results for parallel surfaces, we investigate the effect of this coupling
on the phase behaviour of polymer-doped smectics.Comment: 29 pages, 11 figures, v2: minor corrections added, published version
available at http://dx.doi.org/10.1021/la050173
Impact des aménagements sur la migration anadrome du saumon atlantique (Salmo salar L.) sur le gave de Pau (France)
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Aspirin-Trigge red-Resolvin D1 reduces mucosal inflammation and promotes resolution in a murine model of acute lung injury
Acute Lung Injury (ALI) is a severe illness with excess mortality and no specific therapy. Protective actions were recently uncovered for docosahexaenoic acid -derived mediators, including D-series resolvins. Here, we used a murine self-limited model of hydrochloric acid-induced ALI to determine the effects of aspirin-triggered resolvin D1 (AT-RvD1) on mucosal injury. RvD1 and its receptor ALX/FPR2 were identified in murine lung after ALI. AT-RvD1 (~0.5 – 5 μg/kg) decreased peak inflammation, including bronchoalveolar lavage fluid (BALF) neutrophils by ~75%. Animals treated with AT-RvD1 had improved epithelial and endothelial barrier integrity and decreased airway resistance concomitant with increased BALF epinephrine levels. AT-RvD1 inhibited neutrophil-platelet heterotypic interactions by down-regulating both P-selectin and its ligand CD24. AT-RvD1 also significantly decreased levels of BALF pro-inflammatory cytokines, including IL-1β, IL-6, KC and TNF-α, and decreased NF-κB phosphorylated p65 nuclear translocation. Together, these findings indicate that AT-RvD1 displays potent mucosal protection and promotes catabasis after ALI
Sheared bioconvection in a horizontal tube
The recent interest in using microorganisms for biofuels is motivation enough
to study bioconvection and cell dispersion in tubes subject to imposed flow. To
optimize light and nutrient uptake, many microorganisms swim in directions
biased by environmental cues (e.g. phototaxis in algae and chemotaxis in
bacteria). Such taxes inevitably lead to accumulations of cells, which, as many
microorganisms have a density different to the fluid, can induce hydrodynamic
instabilites. The large-scale fluid flow and spectacular patterns that arise
are termed bioconvection. However, the extent to which bioconvection is
affected or suppressed by an imposed fluid flow, and how bioconvection
influences the mean flow profile and cell transport are open questions. This
experimental study is the first to address these issues by quantifying the
patterns due to suspensions of the gravitactic and gyrotactic green
biflagellate alga Chlamydomonas in horizontal tubes subject to an imposed flow.
With no flow, the dependence of the dominant pattern wavelength at pattern
onset on cell concentration is established for three different tube diameters.
For small imposed flows, the vertical plumes of cells are observed merely to
bow in the direction of flow. For sufficiently high flow rates, the plumes
progressively fragment into piecewise linear diagonal plumes, unexpectedly
inclined at constant angles and translating at fixed speeds. The pattern
wavelength generally grows with flow rate, with transitions at critical rates
that depend on concentration. Even at high imposed flow rates, bioconvection is
not wholly suppressed and perturbs the flow field.Comment: 19 pages, 9 figures, published version available at
http://iopscience.iop.org/1478-3975/7/4/04600
Panton–Valentine leukocidin is expressed at toxic levels in human skin abscesses
AbstractPus samples were prospectively collected from patients with Staphylococcus aureus skin infections and tested for Panton–Valentine leukocidin (PVL). PVL was detected at concentrations that were toxic for rabbit skin in all specimens from patients infected with strains harbouring PVL genes
Induced Pluripotent Stem Cell-Derived Retinal Pigmented Epithelium: A Comparative Study Between Cell Lines and Differentiation Methods
PurposeThe application of induced pluripotent stem cell-derived retinal pigmented epithelium (iPSC-RPE) in patients with retinal degenerative disease is making headway toward the clinic, with clinical trials already underway. Multiple groups have developed methods for RPE differentiation from pluripotent cells, but previous studies have shown variability in iPSC propensity to differentiate into RPE.MethodsThis study provides a comparison between 2 different methods for RPE differentiation: (1) a commonly used spontaneous continuously adherent culture (SCAC) protocol and (2) a more rapid, directed differentiation using growth factors. Integration-free iPSC lines were differentiated to RPE, which were characterized with respect to global gene expression, expression of RPE markers, and cellular function.ResultsWe found that all 5 iPSC lines (iPSC-1, iPSC-2, iPSC-3, iPSC-4, and iPSC-12) generated RPE using the directed differentiation protocol; however, 2 of the 5 iPSC lines (iPSC-4 and iPSC-12) did not yield RPE using the SCAC method. Both methods can yield bona fide RPE that expresses signature RPE genes and carry out RPE functions, and are similar, but not identical to fetal RPE. No differences between methods were detected in transcript levels, protein localization, or functional analyses between iPSC-1-RPE, iPSC-2-RPE, and iPSC-3-RPE. Directed iPSC-3-RPE showed enhanced transcript levels of RPE65 compared to directed iPSC-2-RPE and increased BEST1 expression and pigment epithelium-derived factor (PEDF) secretion compared to directed iPSC-1-RPE. In addition, SCAC iPSC-3-RPE secreted more PEDF than SCAC iPSC-1-RPE.ConclusionsThe directed protocol is a more reliable method for differentiating RPE from various pluripotent sources and some iPSC lines are more amenable to RPE differentiation
Low incidence of SARS-CoV-2, risk factors of mortality and the course of illness in the French national cohort of dialysis patients
Pragmatic management of Panton–Valentine leukocidin-associated staphylococcal diseases
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