Oxygene dissous et saturation dans un milieu de forte production organique (Etang de Berre). Role d'une halocline sur leur distribution et sur les rapports oxygene-phosphate. Notion de bilan

Résumé L'évolution des structures de distribution de l'oxygène (concentration et saturation) a été suivie, dans les eaux de l'Etang de Berre, durant plusieurs années. A l'existence d'une pycnocline (halocline) à gradient très exprimé, correspond celle d'une oxycline aboutissant à l'anoxie dans certain cas. L'analyse des relations entre oxygène et phosphore minéral, en conditions de pénurie d'oxygène, montre que l'existence d'anomalies dans ces relations tient au fonctionnement du système consommation-production-régénération. Un concept de bilan théorique d'oxygène dans un bassin saumâtre est proposé.

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The evolution of oxygen distribution parameters (concentration and saturation) has been monitored in brackish waters of lake Etang de Berre during several years. In relation with the occurrence of a well-defined pycnocline (halocline) an oxycline is shown to be present, leading to anoxic conditions in some cases. The relationships between oxygen and nutrients under conditions of oxygen depletion are examined and it is shown that anomalies are due to the dynamic aspects of the consumption-production-regeneration system. A concept of theoretical oxygen budget in a brackish water basin is proposed.

     

Induction of several acute-phase protein genes by heavy metals: a new class of metal-responsive genes.

Acute-phase reactants, metallothioneins, and heat-shock proteins are the products of three families of genes that respond to glucocorticoids and cytokines. Metallothioneins and heat-shock proteins, however, are also stimulated by heavy metals, whereas very little is known about the effect of heavy metals on acute-phase-reactant genes. We have studied the effect of heavy metals (Hg, Cd, Pb, Cu, Ni, and Zn) and Mg on the acute-phase reactants alpha 1-acid glycoprotein, C-reactive protein, alpha 1-antitrypsin and alpha 1-antichymotrypsin. alpha 1-Acid glycoprotein and C-reactive protein mRNA levels were increased severalfold in livers of heavy-metal-treated Balb/c mice. The strongest induction was mediated by Hg, followed in order of response by Cd greater than Pb greater than Cu greater than Ni greater than Zn greater than Mg. None of the metals affected the mRNA levels of albumin, alpha 1-antitrypsin, and alpha 1-antichymotrypsin. Furthermore, failure to repress albumin, a negative acute-phase reactant, indicated that the induction of these genes was not due to a metal-mediated inflammatory response. The metals also induced alpha 1-acid glycoprotein and C-reactive protein in adrenalectomized animals, indicating that induction by the heavy metals is not mediated by the glucocorticoid induction pathway. Sequence analysis has revealed a region of homology to metal-responsive elements in the alpha 1-acid glycoprotein and C-reactive protein promoters. Additionally, an alpha 1-acid glycoprotein expression vector, pAGP(-595)CAT, responded to Hg and Cd when transfected into human HepG2 cells.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ezrin Binds to DEAD-Box RNA Helicase DDX3 and Regulates Its Function and Protein Level

Ezrin is a key regulator of cancer metastasis that links the extracellular matrix to the actin cytoskeleton and regulates cell morphology and motility. We discovered a small-molecule inhibitor, NSC305787, that directly binds to ezrin and inhibits its function. In this study, we used a nano-liquid chromatography-tandem mass spectrometry (nano-LC–MS-MS)-based proteomic approach to identify ezrin-interacting proteins that are competed away by NSC305787. A large number of the proteins that interact with ezrin were implicated in protein translation and stress granule dynamics. We validated direct interaction between ezrin and the RNA helicase DDX3, and NSC305787 blocked this interaction. Downregulation or long-term pharmacological inhibition of ezrin led to reduced DDX3 protein levels without changes in DDX3 mRNA. Ectopic overexpression of ezrin in low-ezrin-expressing osteosarcoma cells caused a notable increase in DDX3 protein levels. Ezrin inhibited the RNA helicase activity of DDX3 but increased its ATPase activity. Our data suggest that ezrin controls the translation of mRNAs preferentially with a structured 5′ untranslated region, at least in part, by sustaining the protein level of DDX3 and/or regulating its function. Therefore, our findings suggest a novel function for ezrin in regulation of gene translation that is distinct from its canonical role as a cytoskeletal scaffold at the cell membrane.     

A Further Investigation on the Primary Productivity in the Divergence Zone Near the French Mediterranean Coast

The present investigation re-examines hydrological features, the inorganic phosphate distribution and primary productivity near the “Hyères” Islands in the French Mediterranean in the early summer divergence zone as previously studied by MINAS and BLANC (1970). In addition, concentrations of particulate nitrogen, Chl-a and nitrate have been determined. Uptake rates of ¹⁵N-labelled nitrate (“new production”) and the oxygen consumption (ETS-activity) by the phytoplankton population have been estimated.     

Peptide histidine methionine (PHM) increases ileostomy output

The human vasoactive intestinal peptide (VIP) gene also encodes peptides histidine methionine (PHM) which has substantial sequence homology with VIP. Both are present in nerve fibers in the human ileum and circulate in greatly increased concentrations in patients with the watery diarrhoea syndrome. We have infused PHM (23 pmol/kg/min) into 5 patients with ileostomies to determine the effect of PHM on human ileal output. Plasma PHM levels rose from 22 +/- 6 to 6013 +/- 874 pM (mean +/- S.E.M.) during PHM infusions and ileal output rose from 16 +/- 3 to 177 +/- 27 g/30 min (P less than 0.0001). PHM infusions also produced a significant fall in the percentage of solid material and a rise in the concentration of chloride in the ileal effluent. Mean plasma PHM concentrations during PHM infusions were equal to the highest levels seen in patients with the watery diarrhoea syndrome, so PHM may contribute to diarrhoea in this condition. Neuronal PHM may exert physiological control over ileal transport of water and electrolytes.     

Distance-based differential analysis of gene curves

MOTIVATION: Time course gene expression experiments are performed to study time-varying changes in mRNA levels of thousands of genes. Statistical methods from functional data analysis (FDA) have recently gained popularity for modelling and exploring such time courses. Each temporal profile is treated as the realization of a smooth function of time, or curve, and the inferred curve becomes the basic unit of statistical analysis. The task of identifying genes with differential temporal profiles then consists of detecting statistically significant differences between curves, where such differences are commonly quantified by computing the area between the curves or the l? distance. RESULTS: We propose a general test statistic for detecting differences between gene curves, which only depends on a suitably chosen distance measure between them. The test makes use of a distance-based variance decomposition and generalizes traditional MANOVA tests commonly used for vectorial observations. We also introduce the visual l? distance, which is shown to capture shape-related differences in gene curves and is robust against time shifts, which would otherwise inflate the traditional l? distance. Other shape-related distances, such as the curvature, may carry biological significance. We have assessed the comparative performance of the test on realistically simulated datasets and applied it to human immune cell responses to bacterial infection over time.     

Exhaled breath condensate pH as a biomarker of COPD severity in ex-smokers

Endogenous airway acidification, as assessed by exhaled breath condensate (EBC) pH, is present in patients with stable COPD. The aim of this study was to measure EBC pH levels in a large cohort of COPD patients and to evaluate associations with functional parameters according to their smoking status.EBC was collected from 161 patients with stable COPD and 112 controls (current and ex-smokers). EBC pH was measured after Argon deaeration and all subjects underwent pulmonary function testing.EBC pH was lower in COPD patients compared to controls [7.21 (7.02, 7.44) vs. 7.50 (7.40, 7.66); p < 0.001] and ex-smokers with COPD had lower EBC pH compared to current smokers [7.16 (6.89, 7.36) vs 7.24 (7.09, 7.54), p = 0.03]. In ex-smokers with COPD, EBC pH was lower in patients with GOLD stage III and IV compared to patients with stage I disease (p = 0.026 and 0.004 respectively). No differences were observed among current smokers with different disease severity. EBC pH levels in ex-smokers were associated with static hyperinflation (as expressed by IC/TLC ratio), air trapping (as expressed by RV/TLC ratio) and diffusing capacity for carbon monoxide, whereas no associations were observed in current smokers.Endogenous airway acidification is related to disease severity and to parameters expressing hyperinflation and air trapping in ex-smokers with COPD. The possible role of EBC pH in COPD needs to be further evaluated in longitudinal studies.     

Optimization of a high-throughput CTAB-based protocol for the extraction of qPCR-grade DNA from rumen fluid, plant and bacterial pure cultures

The quality and yield of extracted DNA are critical for the majority of downstream applications in molecular biology. Moreover, molecular techniques such as quantitative real-time PCR (qPCR) are becoming increasingly widespread; thus, validation and cross-laboratory comparison of data require standardization of upstream experimental procedures. DNA extraction methods depend on the type and size of starting material(s) used. As such, the extraction of template DNA is arguably the most significant variable when cross-comparing data from different laboratories. Here, we describe a reliable, inexpensive and rapid method of DNA purification that is equally applicable to small or large scale or high-throughput purification of DNA. The protocol relies on a CTAB-based buffer for cell lysis and further purification of DNA with phenol : chloroform : isoamyl alcohol. The protocol has been used successfully for DNA purification from rumen fluid and plant cells. Moreover, after slight alterations, the same protocol was used for large-scale extraction of DNA from pure cultures of Gram-positive and Gram-negative bacteria. The yield of the DNA obtained with this method exceeded that from the same samples using commercial kits, and the quality was confirmed by successful qPCR applications.