Influence of temperature and surfactants on the solubilization of hexachlorobutadiene and hexachloroethane

The solubilization of hexachlorobutadiene (HCBD) and hexachloroethane (HCA) in water as a function of temperature and in the presence of surfactants was investigated in order to predict their fate in groundwater and to increase their recovery. HCBD and HCA solubility data were experimentally determined at five temperatures in the range from (285.15 to 318.15) K. Thermodynamic parameters for dissolution (ΔsolG°, ΔsolH°, and ΔsolS°) have been calculated in order to propose a physical explanation of the minimum solubility observed between 293.15 and 298.15 K for both compounds. The solubilization process appeared to be influenced by the network of water molecules rather than by physical and chemical properties of HCBD or HCA, due to an opposite effect of temperature onto Brownian motion, which increases with temperature, and hydrogen-bond network, which collapses with temperature. Concerning the influence of surfactants, determination of the micelle–water partition coefficients (Kmw) and the molar solubilization ratio (MSR) has shown that the solubilization per micelle was more important for nonionic surfactants Triton X-100 and Tween 80 than for anionic SDBS. Also, the increase of solubility was 1 order of magnitude higher for liquid HCBD than for crystalline HCA irrespective of surfactant

Anthrax Edema Toxin Modulates PKA- and CREB-Dependent Signaling in Two Phases

Background: Anthrax edema toxin (EdTx) is an adenylate cyclase which operates in the perinuclear region of host cells. However, the action of EdTx is poorly understood, especially at molecular level. The ability of EdTx to modulate cAMPdependent signaling was studied in Jurkat T cells and was compared with that of other cAMP-rising agents: Bordetella pertussis adenylate cyclase toxin, cholera toxin and forskolin. Methodology/Principal Findings: EdTx caused a prolonged increase of the intracellular cAMP concentration. This led to nuclear translocation of the cAMP-dependent protein kinase (PKA) catalytic subunit, phosphorylation of cAMP response element binding protein (CREB) and expression of a reporter gene under control of the cAMP response element. Neither p90 ribosomal S6 kinase nor mitogen- and stress-activated kinase, which mediate CREB phosphorylation during T cell activation, were involved. The duration of phospho-CREB binding to chromatin correlated with the spatio-temporal rise of cAMP levels. Strikingly, EdTx pre-treated T cells were unresponsive to other stimuli involving CREB phosphorylation such as addition of forskolin or T cell receptor cross-linking. Conclusions/Significance: We concluded that, in a first intoxication phase, EdTx induces PKA-dependent signaling, which culminates in CREB phosphorylation and activation of gene transcription. Subsequently CREB phosphorylation is impaired and therefore T cells are not able to respond to cues involving CREB. The present data functionally link the perinuclea

Domestication et histoire évolutive des espèces fruitières : que pouvons-nous apprendre des études de génétique ? Exemples chez les Rosacées

Chapitre 5National audienc

PKA-dependent phosphorylation of CREB upon stimulation of Jurkat cells with EdTx, CT, CyaA, or forskolin.

<p>Cells were stimulated for the indicated times with EdTx (10 nM EF+40 nM PA), CT (3 nM), CyaA (5 nM), or forskolin (25 µM) in the presence or absence of 20 µM H-89 dihydrochloride, an inhibitor of PKA, lysed and processed for western blotting using an antibody against S133-pCREB. On each lane 10 µg of protein were loaded. Different loading was controlled by staining against actin. In separate experiments, RSK1/2 and MSK1, which mediate CREB phosphorylation during T cell activation, were found not to be activated following T cell stimulation with EdTx, CT, CyaA and forskolin (not shown). The experiment shown is representative of four performed.</p

Inhibition of CREB re-phosphorylation in cells pre-treated with EdTx, CT, CyaA or forskolin.

<p>Jurkat cells were incubated with EdTx (10 nM EF+40 nM PA), CT (3 nM), CyaA (5 nM), or forskolin (25 µM) and 16 or 24 h after this first treatment, CREB phosphorylation was re-stimulated by addition of forskolin (25 µM) or by α-CD3 antibody mediated cross-linking of the TCR for 30 min. Cells were then lysed and processed for western blotting with antibody against S133-pCREB. The intensity of each band was determined using the software Quantity One (Bio-Rad) and was corrected for different loadings using the corresponding value of actin as control. The value of untreated samples was set equal to 1. The blots show one representative experiment and the graphs give the mean and standard deviation of three independent experiments.</p

Time course of cAMP production by Jurkat cells stimulated with EdTx, CT, CyaA, or forskolin.

<p>Jurkat T cells were stimulated for the indicated times with EdTx (10 nM EF+40 nM PA), CT (3 nM), CyaA (5 nM), or forskolin (25 µM). At the end of the incubations, the samples, which contained 10⁵ cells, were lysed and immediately subjected to competition ELISA in order to determine the amount of cAMP present. Adefovir dipivoxil, a specific inhibitor of EdTx, abolished cAMP synthesis in EdTx-treated cells (not shown). Note the different cAMP scales in the four panels. Experiments were not normalized to percentage values to provide the actual levels of cAMP. Data are the mean and standard deviation of four independent experiments for EdTx and three for CT, CyaA and forskolin, performed in triplicates.</p

Activation and nuclear translocation of PKA catalytic subunit upon stimulation of Jurkat cells with EdTx, CT, CyaA, or forskolin.

<p>Cells were transiently transfected with a fluorescent probe coding for the PKA catalytic subunit fused to yellow fluorescent protein, stimulated with EdTx (10 nM EF+40 nM PA), CT (3 nM), CyaA (5 nM), or forskolin (25 µM), fixed and observed at the microscope. a) in resting cells, the catalytic subunit of PKA resides within the ring-shaped cytoplasm. b) 1.5 h after addition of EdTx, the majority of the PKA catalytic subunit is still present in the cytosol, whilst c) after 8 h it is inside the nucleus. The migration of PKA catalytic subunit induced by CT, CyaA, and forskolin after 1.5 h are shown in panels d), e) and f), respectively.</p