Bioaccumulation du Cd et du Zn chez les plants de tomates (Lycopersicon esculentum L.)

This work aims at evaluating the accumulation of cadmium (Cd) and zinc (Zn) (trace elements) in the organs of young tomato plants (Lycopersicon esculentum L. var. Rio Grande) and their effects on the rate of chlorophyll and enzyme activities involved in the antioxidant system: catalase (CAT), glutathion-S-transferase (GST) and peroxysase ascorbate (APX). Plants previously grown on a basic nutrient solution were undergoing treatment for 7 days, either by increasing concentrations of CdCl₂ or ZnSO₄ (0, 50, 100, 250, 500 μM) or by the combined concentrations of Cd and Zn (100/50, 100/100, 100/250, 100/500 μM). The results concerning the determination of metals in the various compartments of tomato plants as a function of increasing concentrations of Cd or Zn, suggest a greater accumulation of Cd and Zn in the roots compared to leaves. The combined treatment (Cd/Zn) interferes with the absorption of the two elements according to their concentrations in the culture medium. The presence of Zn at low concentrations (50 μM of Zn/100 μM Cd) has little influence on the accumulation of Cd in the roots and leaves, while the absorption of these two elements in the leaves increases and decreases in roots when their concentrations are equivalent (100/100 μM) compared to treatment alone. When the concentration of Zn is higher than that of Cd (500 μM of Zn/100 μM Cd) absorption of the latter is inhibited in the roots while increasing their translocation to the leaves. Meanwhile, the dosage of chlorophylls shows that they tend to decrease in a dose-dependent for both treatments (Cd or Cd/Zn), however, treatment with low concentrations of Zn (50 and 100 μM) stimulates chlorophyll synthesis. However, treatment with different concentrations of Cd seems to induce the activity of the enzymes studied (CAT, APX, GST). It is the same for treatment with different concentrations of Zn and this particularly for the highest concentrations. Finally, the combined treatment (Zn/Cd) also appears to cause enzyme inductions: CAT, APX and GST.     

The lectin concanavalin-A signals MT1-MMP catalytic independent induction of COX-2 through an IKKγ/NF-κB-dependent pathway

The lectin from Canavalia ensiformis (Concanavalin-A, ConA), one of the most abundant lectins known, enables one to mimic biological lectin/carbohydrate interactions that regulate extracellular matrix protein recognition. As such, ConA is known to induce membrane type-1 matrix metalloproteinase (MT1-MMP) which expression is increased in brain cancer. Given that MT1-MMP correlated to high expression of cyclooxygenase (COX)-2 in gliomas with increasing histological grade, we specifically assessed the early proinflammatory cellular signaling processes triggered by ConA in the regulation of COX-2. We found that treatment with ConA or direct overexpression of a recombinant MT1-MMP resulted in the induction of COX-2 expression. This increase in COX-2 was correlated with a concomitant decrease in phosphorylated AKT suggestive of cell death induction, and was independent of MT1-MMP’s catalytic function. ConA- and MT1-MMP-mediated intracellular signaling of COX-2 was also confirmed in wild-type and in Nuclear Factor-kappaB (NF-κB) p65^−/− mutant mouse embryonic fibroblasts (MEF), but was abrogated in NF-κB1 (p50)^−/− and in I kappaB kinase (IKK) γ^−/− mutant MEF cells. Collectively, our results highlight an IKK/NF-κB-dependent pathway linking MT1-MMP-mediated intracellular signaling to the induction of COX-2. That signaling pathway could account for the inflammatory balance responsible for the therapy resistance phenotype of glioblastoma cells, and prompts for the design of new therapeutic strategies that target cell surface carbohydrate structures and MT1-MMP-mediated signaling. Concise summary Concanavalin-A (ConA) mimics biological lectin/carbohydrate interactions that regulate the proinflammatory phenotype of cancer cells through yet undefined signaling. Here we highlight an IKK/NF-κB-dependent pathway linking MT1-MMP-mediated intracellular signaling to the induction of cyclooxygenase-2, and that could be responsible for the therapy resistance phenotype of glioblastoma cells.     

A dileucine motif targets MCAM-l cell adhesion molecule to the basolateral membrane in MDCK cells

Melanoma cell adhesion molecule (MCAM), an adhesion molecule belonging to the Ig superfamily, is an endothelial marker and is expressed in different epithelia. MCAM is expressed as two isoforms differing by their cytoplasmic domain: MCAM-l and MCAM-s (long and short). In order to identify the respective role of each MCAM isoform, we analyzed MCAM isoform targeting in polarized epithelial Madin-Darby canine kidney (MDCK) cells using MCAM-GFP chimeras. Confocal microscopy revealed that MCAM-s and MCAM-l were addressed to the apical and basolateral membranes, respectively. Transfection of MCAM-l mutants established that a single dileucine motif (41-42) of the cytoplasmic domain was required for MCAM-l basolateral targeting in MDCK cells. Although double labelling experiments showed that MCAM-l is not a component of adherens junctions and focal adhesions, its expression on basolateral membranes suggests that MCAM-l is involved in epithelium insuring.     

Probing the infiltrating character of brain tumors: inhibition of RhoA/ROK-mediated CD44 cell surface shedding from glioma cells by the green tea catechin EGCg

Glioma cell-surface binding to hyaluronan (HA), a major constituent of the brain extracellular matrix (ECM) environment, is regulated through a complex membrane type-1 matrix metalloproteinase (MT1-MMP)/CD44/caveolin interaction that takes place at the leading edges of invading cells. In the present study, intracellular transduction pathways required for the HA-mediated recognition by infiltrating glioma cells in brain was investigated. We show that the overexpression of the GTPase RhoA up-regulated MT1-MMP expression and triggered CD44 shedding from the U-87 glioma cell surface. This potential implication in cerebral metastatic processes was also observed in cells overexpressing the full-length recombinant MT1-MMP, while the overexpression of a cytoplasmic domain truncated from of MT1-MMP failed to do so. This suggests that the cytoplasmic domain of MT1-MMP transduces intracellular signaling leading to RhoA-mediated CD44 shedding. Treatment of glioma cells with the Rho-kinase (ROK) inhibitor Y27632, or with EGCg, a green tea catechin with anti-MMP and anti-angiogenesis activities, antagonized both RhoA- and MT1-MMP-induced CD44 shedding. Conversely, overexpression of recombinant ROK stimulated CD44 release. Taken together, our results suggest that RhoA/ROK intracellular signaling regulates MT1-MMP-mediated CD44 recognition of HA. These molecular processes may partly explain the diffuse brain-infiltrating character of glioma cells within the surrounding parenchyma and thus be a target for new approaches to anti-tumor therapy.     

The impact of flucycloxuron on eggs weight kinetic and hematological parameters of chicken (Gallus domesticus)

The struggle against the harmful bugs of culture is intensified, and several products are appeared every year without the knowledge how to control their effects on environment and especially on being life. The introduced chemical products in nature are generally, the synthesis products witch are the pesticides. Our study consist the impact mechanism of a pesticides (FCX) on other biological model than harmful bugs, this biological model is a vertebrate model witch is the domestic chicken eggs (Gaollus domesticus). The toxicity of Flucycloxuron reviewed across the eggs weight kinetic accompanied with embryonic hematological parameters, in ovo and after hatching. The tested concentrations of pesticide are 1, 10 and 20 microg/egg injected at first day of incubation. Eggs treatment by three concentrations of pesticides, disturbs the studied parameters, where we observe that the pesticide inhibit the nutriment transformation, translated by eggs decreased weight kinetic according to the control, also the FCX affect the shell weight and cause the alteration of shell integrity. Hematological parameters show a clear impact of the pesticide at the lowest concentration (1 microg/egg). The obtained results confirm that the chosen biological model is good bio-indicator for eventual pollution and they are not far from pesticides toxicity.     

Energy conversion in an internally illuminated annular‐plate airlift photobioreactor

Algal‐derived therapeutics, bioactive molecules, and fuels produced in photobioreactors (PBRs) are of great scientific and economic interest, but the high cost of production still prevents their widespread use. Specifically, the cost of the energy inputs and the control of the photonic inputs that enable production optimization continue to be problematic. To this end, a novel 55‐L annular‐plate airlift PBR (APAPBR) with internal illumination was designed and characterized for the batch production of algal biomass. The APAPBR was able to convert mixing and photonic energy inputs into Chlorella pituita SG1 biomass at an efficiency of 0.064 (J biomass [J input]^?1), or 0.27 g dry cell weight (DW) W^?1 d^?1. Thanks to a high degree of photon capture and the airlift effect that provided energy‐efficient mixing and mass transfer, this energy conversion is 54% of the theoretical maximum as determined in previous studies. Under these efficiency conditions, C. pituita SG1 was able to grow photoautotrophically to 3.9 ± 0.2 gDW L^?1. Additionally, a mathematical approach was used to predict the mean light intensity with the highest biomass yield per unit of photonic input and the maximum biomass concentration achievable under the given process conditions. These predictions were validated in our system by the experimental cultivation data. This APAPBR represents a simple, innovative, and energy‐efficient PBR configuration that could decrease the cost of phototrophic bioprocesses and enable novel bioprocesses that require a high degree of control over the photonic input.     

Toxicity of the ammonium nitrate NH4NO3 on the respiratory metabolism of three biological models: parameciums, mosses and lichens

The inopportune throws out of diverse substances in the atmosphere, constitutes without any doubt the obvious of environmental pollution by man. Among these substances, we are interested in the ammonium nitrate NH4NO3, nitrate fertilizers widely used in farming in our region - Annaba located in the eastern part of Algeria - and manufactured in the same region. In fact, the excessive fertilization, the intensive spreading of animal faeces and the industrial pollution are the accumulation sources of nitrate in vegetables, drilling and the underground waters. The goal of this study is to show the obviousness of a possible toxic effect of NH4NO3 on paramecium an inferior plants resed as biological models. The tests of toxicity were achieved on samples of the area of culture of parameciums. Four concentrations were chosen: 10, 20, 30 and 40 mM, and added before and after appearance of the parameciums in the area. The prepared solutions with the same concentrations of NH4NO3, were used for the dampening of the samples of mosses and lichens. The use of an original technique the polarography allowed us to measure the quantity of oxygen consumed by the organisms in presence of the polluent. The results show that: (i): The treatment by NH4NO3 stimulates the respiratory metabolism of paramecium, (ii): with mosses as well as the measure of the consumption of the oxygen shous the abviousness contrasted with a dampening of respiration but also of the photosynthesis. The perturbation of the respiration and photosynthesis of mousses and lichens can explain the degradation of the plant material and the disappearance of certain species from our ecosystem.     

Investigation of the sorption mechanisms of metal-complexed dye onto Posidonia oceanica (L.) fibres through kinetic modelling analysis

This research deals with the exploitation of highly available and renewable marine biomass, Posidonia oceanica (L.) fibres as low cost biosorbent for the removal of metal-complexed textile dyestuff from aqueous medium, and the investigation of the probably involved physiochemical mechanisms. Experiments were carried out in batch reactor. Firstly, the adsorption process was studied as a function of initial solution pH and contact time under different initial dye concentration. The results showed that the highest dye adsorption capacity was found at pH 2 under a constant temperature of 30 °C, and the equilibrium state was reached within 48 h of exposure time. Secondly, several adsorption kinetic models were applied to fit the experimental data, namely Lagergren irreversible first-order, Reversible first-order, Pseudo-second-order, Elovich, Ritchie and intraparticle diffusion models. The proposed explanations were deduced from the theoretical assumptions behind the most appropriate model(s), which could satisfactorily describe the present biosorption phenomenon. The interpretation of the related results have shown that, with R² of about 99%, the pseudo-second order model is the most suitable dynamic theory describing the biosorption of metal complex dye onto P. oceanica fibres, predicting therefore a chemisorption process.