Vascular progenitors derived from murine bone marrow stromal cells are regulated by fibroblast growth factor and are avidly recruited by vascularizing tumors

Bone marrow-derived stromal cells (BMSC) possess a population of vascular progenitor cells that enable them to acquire a histology and immunophenotype coherent with endothelial cells (EC). Recent evidence indicates that a hypoxic environment such as that encountered in tumor masses regulates BMSC angiogenic properties by pathways that remain to be defined. It is also unclear as to what extent these marrow-derived precursor cells could contribute to the growth of endothelium-lined vessels at the vicinity of tumor masses. In this study, we found that BMSC exhibited the ability to generate three-dimensional capillary-like networks on Matrigel, and that this property was up-regulated by growth factors-enriched conditioned media isolated from several tumor-derived cell lines. In particular, basic fibroblast growth factor, a key mediator of angiogenesis, was found to be the most potent growth factor for inducing BMSC proliferation, migration, and tubulogenesis. The setup of a new two-dimensional in vitro co-culture assay further showed that BMSC were massively recruited when cultured in the presence of either cancerous or differentiated EC lines. In vivo, subcutaneous co-injection of BMSC with U-87 glioma cells in nude mice resulted in the formation of highly vascularized tumors, where BMSC differentiated into CD31-positive cells and localized at the lumen of vascular structures. Our data suggest that BMSC could be recruited at the sites of active tumor neovascularization through paracrine regulation of their angiogenic properties. These observations may have crucial implications in the development of novel therapies using BMSC engineered to secrete anti-cancerous agents and to antagonize tumor progression.     

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.     

Ultrastructural Distribution of Calcium in Cutaneous Electroreceptor Organs of Teleost Fish

The calcium distribution in the ampullary electroreceptor and the type B electrore-ceptor organ (gymnarchomast) of Gymnarchus niloticus (Gymnarchidae) and in the tuberous organ of Apteronotus leptorhynchus (gymnotidae) was studied. Endogenous calcium appeared as electron-dense precipitates when the cutaneous organs were pre-fixed with phosphate-buffered glutaraldehyde and postfixed with osmium tetroxide plus potassium bichromate. Calcium precipitates were localized in both intracellular compartments of sensory cells and afferent nerve fibers. In contrast to sensory cells, small amounts of calcium precipitates were found in the cytoplasm of accessory cells. In sensory cells, electron-dense deposits were apparent mainly in synaptic vesicles near synaptic ribbons, inside vacuoles of the endoplasmic reticulum, and between the layers of the nuclear membrane. Very few deposits were found in mitochondria. Precipitates were also observed within the axons of afferent nerves and between the layers of the myelin sheath. The synaptic cleft was devoid of calcium. Calcium deposits have a specific cellular distribution in electro-receptor organs of teleost fish.     

Medulloblastoma cell invasion is inhibited by green tea (-)epigallocatechin-3-gallate

Epigallocatechin-3-gallate (EGCG), the major green tea polyphenol, can reach the brain following oral intake and could thus act as an anti-tumoral agent targeting several key steps of brain cancer cells invasive activity. Because integrin-mediated extracellular matrix recognition is crucial during the cell adhesion processes involved in carcinogenesis, we have investigated the effects of EGCG on different cellular integrins of the pediatric brain tumor-derived medulloblastoma cell line DAOY. Using flow cytometry, we report the levels of expression of several cell surface integrins in DAOY. These include high expression of alpha2, alpha3, and beta1 integrins, as well as alphav and beta3 integrins. Moreover, we provide evidence that EGCG can antagonize DAOY cell migration specifically on collagen by increasing cell adhesive ability through specific gene and protein upregulation of the beta1 integrin subunit. Our results suggest that this naturally occurring green tea polyphenol may thus be used as a nutraceutical therapeutic agent in targeting the invasive character of medulloblastomas.