Pseudomonas oleovorans as a tool in bioconversions of hydrocarbons: growth,morphology and conversion characteristics in different two-phase systems

The bioconversion of hydrocarbons by Pseudomonas oleovorans has been studied in two-phase systems. In these systems, the hydrocarbon substrate is present in sufficient amounts to form the bulk apolar phase. High cell densities (up to 20 mg dry mass per ml water phase) are reached when the apolar phase consists of n-octane, 1-octene or 1-decene. There is considerable cell damage after incubation for 50–70 h. Loss of cell viability and membrane damage as observed by freeze-fracture electron microscopy correlate with a loss of hydrocarbon oxidation, measured as the conversion of 1-octene to 1,2-epoxyoctane. The final yield of oxidized hydrocarbon in the apolar substrate phase can be increased substantially by replacing the damaged cells with freshly grown cells. Yields up to 150 mg 1,2-epoxyoctane per ml 1-octene and up to 20–25 mg 1,2-epoxyoctane per ml culture were obtained with four cycles of the cell renewal procedure. Several other substrates in addition to octene were tested in the optimized two-phase system. Of these, 1-decene was converted into (R)-1,2-epoxydecane with an optical purity of 60%, while allylbenzene was converted into chiral 1,2-epoxy-3-phenylpropane. Some of the future applications of the conversion products are discussed.     

Cell adhesion and integrin expression are modulated by oxidative stress in EA.hy 926 cells

The effects of oxidative stress on integrin-mediated cell adhesion to the extracellular matrix (ECM) and related apoptosis were investigated using the EA.hy926 endothelial cells treated (or not) with two oxidants: the hypoxanthine/xanthine oxidase system (HX/XO) or the tert-butyl hydroperoxide (t-BHP) which both increased cell apoptosis. Cell adhesion onto vitronectin (Vn) and fibronectin (Fn) was increased at low concentrations of HX/XO (up to 5 mU/ml) or t-BHP (up to 125 μM) and prevented ROS-induced apoptosis. Flow cytometry analysis of integrin expression showed that the expression of integrin αv and α5 subunits was, respectively, increased and decreased. Cell adhesion inhibition experiments using function-blocking monoclonal antibodies against integrin subunits indicated that αvβ1 and αvβ3 integrins were involved in adhesion of cells to Vn, and αvβ3 integrin played a major role in oxidant-treated cells. For adhesion to Fn, α5β1 and αvβ1 integrins were required for oxidant-treated cells. Taken together, the results suggest that reactive oxygen species (ROS) produced either by HX/XO or t-BHP could affect expression and/or activation of specific integrins in the interaction of EA.hy926 cells with ECM.     

Effects of management works on the interstitial fauna of floodplain aquatic systems (River Rhône, France)

Long-term changes in composition, structure and biodiversity (i.e. taxonomic richness, diversity index, species traits and habitat-affinity) of interstitial assemblages were studied in two floodplain systems: a restored backwater and an artificial drainage canal. Before restoration, the backwater, affected by both terrestrialisation and eutrophication, was weakly populated by a low diversified fauna dominated by walkers, macrofauna, detritivores, and stygoxenes (i.e. taxa that occur incidentally in ground waters) that reproduce biparentally and lack parental care. This backwater displayed an upstream–downstream gradient in response to restoration works. Upstream, the dredging of fine organic sediments favoured inputs of nutrient-poor groundwater and exchanges between groundwater and surface water that induced an increase in taxonomic richness (in both herbivores and stygoxenes). Downstream the deposition of fine sediment that was suspended in the water column by restoration work enhanced colmation that induced a decrease in herbivore and swimming taxa, and an increase in mesofaunal taxa, whilst phreatobites (i.e. taxa specialized to interstitial life) remained absent from the system. The drainage canal that was artificially hollowed-out to lower the surrounding water table, harbors mixed assemblages of epigean (i.e. taxa of surface-water habitats) and hypogean (i.e. taxa of groundwater habitats) taxa. The upstream part, which is weakly influenced by surface waters, was colonized by phreatobites as oligotrophic conditions increased. The intermediate part, which is fed by surface water and where mesotrophic conditions occurred as habitats progressively matured and diversified, showed diversification of its fauna. The downstream part of the drainage canal displayed the reverse dynamic – this suggests a reduction in groundwater supply due to the clogging of sediment interstices fine sediments, the deposition of which is linked to the Rossillon backwater restoration works.     

Neurophysiological Effects of Sleep Deprivation in Healthy Adults,a Pilot Study

Total sleep deprivation (TSD) may induce fatigue, neurocognitive slowing and mood changes, which are partly compensated by stress regulating brain systems, resulting in altered dopamine and cortisol levels in order to stay awake if needed. These systems, however, have never been studied in concert. At baseline, after a regular night of sleep, and the next morning after TSD, 12 healthy subjects performed a semantic affective classification functional magnetic resonance imaging (fMRI) task, followed by a [¹¹C]raclopride positron emission tomography (PET) scan. Saliva cortisol levels were acquired at 7 time points during both days. Affective symptoms were measured using Beck Depression Inventory (BDI), Spielberger State Trait Anxiety Index (STAI) and visual analogue scales. After TSD, perceived energy levels, concentration, and speed of thought decreased significantly, whereas mood did not. During fMRI, response speed decreased for neutral words and positive targets, and accuracy decreased trendwise for neutral words and for positive targets with a negative distracter. Following TSD, processing of positive words was associated with increased left dorsolateral prefrontal activation. Processing of emotional words in general was associated with increased insular activity, whereas contrasting positive vs. negative words showed subthreshold increased activation in the (para)hippocampal area. Cortisol secretion was significantly lower after TSD. Decreased voxel-by-voxel [¹¹C]raclopride binding potential (BP_ND) was observed in left caudate. TSD induces widespread cognitive, neurophysiologic and endocrine changes in healthy adults, characterized by reduced cognitive functioning, despite increased regional brain activity. The blunted HPA-axis response together with altered [¹¹C]raclopride binding in the basal ganglia indicate that sustained wakefulness requires involvement of additional adaptive biological systems.     

Cytoprotective properties of alpha-tocopherol are related to gene regulation in cultured D-galactosamine-treated human hepatocytes

Vitamin E (alpha-tocopherol) has demonstrated antioxidant activity and gene-regulatory properties. d-Galactosamine (D-GalN)-induced cell death is mediated by nitric oxide in hepatocytes, and it is associated with hepatic steatosis. The beneficial properties of alpha-tocopherol and their relation to oxidative stress and gene regulation were assessed in D-GalN-induced cell death. Hepatocytes were isolated from human liver resections by a collagenase perfusion technique. alpha-Tocopherol (50 microM) was administered at the advanced stages (10 h) of D-GalN-induced cell death in cultured hepatocytes. Cell death, oxidative stress, alpha-tocopherol metabolism, and NF-kappaB-, pregnane X receptor (PXR)-, and peroxisome proliferator-activated receptor (PPAR-alpha)-associated gene regulation were estimated in the hepatocytes. D-GalN increased cell death and alpha-tocopherol metabolism. alpha-Tocopherol exerted a moderate beneficial effect against apoptosis and necrosis induced by D-GalN. Induction (rifampicin) or inhibition (ketoconazole) of alpha-tocopherol metabolism and overexpression of PXR showed that the increase in PXR-related CYP3A4 expression caused by alpha-tocopherol enhanced cell death in hepatocytes. Nevertheless, the reduction in NF-kappaB activation and inducible nitric oxide synthase expression and the enhancement of PPAR-alpha and carnitine palmitoyl transferase gene expression by alpha-tocopherol may be relevant for cell survival. In conclusion, the cytoprotective properties of alpha-tocopherol are mostly related to gene regulation rather than to antioxidant activity in toxin-induced cell death in hepatocytes.