Search results for "MESH : Membrane Potential"
showing 7 items of 7 documents
Fluorescent probes to evaluate the physiological state and activity of microbial biocatalysts: A guide for prokaryotic and eukaryotic investigation
2008
International audience; Many fluorescent techniques are employed to evaluate the viability and activity of microbial cells used in biotechnology. These techniques are sometimes complex and the interpretation of results opened to misunderstanding. Moreover, new developments are constantly proposed especially concerning a more accurate evaluation of the state of the cells including eukaryotic microorganisms. This paper aims at presenting to biotechnologists unfamiliar with fluorescence the principles of these methods and the related possible pitfalls. It focuses on probes of the physical (integrity and fluidity) and energetical (intracellular pH and membrane potential) state of the cell membr…
Trefoil factor TFF1-induced protection of conjunctival cells from apoptosis at premitochondrial and postmitochondrial levels.
2008
PURPOSE. Goblet cells of the conjunctival epithelium synthesize and secrete TFF1 (Trefoil factor 1), a small protease-resistant peptide that, together with mucins, is responsible for the rheologic properties of the tear film. This study aimed to determine whether TFF1, whose synthesis increases in inflammatory conditions such as pterygium, could protect conjunctival cells from apoptosis. METHODS. Chang conjunctival cells, either wild-type or expressing TFF1 through stable transfection, were exposed to benzalkonium chloride (BAK) and ultraviolet (UV) irradiation to trigger apoptosis. The authors used cell fractionation to detect lipid raft‐associated proteins, coimmunoprecipitation to explor…
Influence of the drying processes of yeasts on their volatile phenol sorption capacity in model wine.
2009
International audience; Volatile phenols, such as 4-ethylphenol, are responsible for a "horsey" smell in wine. Thus, the study of volatile phenol sorption in yeasts, and their subsequent elimination from wine, helps to optimize eco-friendly wine curative processes. Here, we compared the influences of spray drying, lyophilization and evaporative drying at low water activity on yeast, for improving the 4-ethylphenol sorption capacity in a synthetic model wine. The changes that occur in the physico-chemical characteristics of the yeast surface (surface hydrophobicity, electron-donor character and zeta potential) during these drying processes were determined to assess if any correlation exists …
Mechanisms underlying the toxicity of lactone aroma compounds towards the producing yeast cells
2003
M. A G U E D O , L. B E N E Y , Y. W A C H EA N D J. - M. B E L I N. 2003. Aims: To study the fundamental mechanisms of toxicity of the fruity aroma compound c-decalactone, that lead to alterations in cell viability during its biotechnological production by yeast cells; Yarrowia lipolytica that is able to produce high amounts of this metabolite was used here as a model. Methods and Results: Lactone concentrations above 150 mg l )1 inhibited cell growth, depolarized the living cells and increased membrane fluidity. Infrared spectroscopic measurements revealed that the introduction of the lactone into model phospholipid bilayers, decreased the phase transition temperature. Moreover, the H + -…
FRET multiphoton spectral imaging microscopy of 7-ketocholesterol and Nile Red in U937 monocytic cells loaded with 7-ketocholesterol.
2004
To show the effect of 7-ketocholesterol (7KC) on cellular lipid content by means of flow cytometry and the interaction of 7KC with Nile Red (NR) via ultraviolet fluorescence resonance energy transfer (FRET) excitation of NR on U937 monocytic cells by means of 2-photon excitation confocal laser scanning microscopy (CLSM).Untreated and 7KC-treated U937 cells were stained with NR and analyzed by flow cytometry and CLSM. 3D sequences of images were obtained by spectral analysis in a 2-photon excitation CLSM and analyzed by the factor analysis of medical image sequences (FAMIS) algorithm, which provides factor curves and images. Factor images are the result of the FAMIS image processing method, …
Changes in the proton-motive force in Escherichia coli in response to external oxidoreduction potential.
1999
International audience; The pH homeostasis and proton-motive force (Deltap) of Escherichia coli are dependent on the surrounding oxidoreduction potential (ORP). Only the internal pH value and, thus, the membrane pH gradient (DeltapH) component of the Deltap is modified, while the membrane potential (DeltaPsi) does not change in a significant way. Under reducing conditions (Eh < 50 mV at pH 7.0), E. coli decreases its Deltap especially in acidic media (21% decrease at pH 7.0 and 48% at pH 5.0 for a 850-mV ORP decrease). Measurements of ATPase activity and membrane proton conductance (CH+m) depending on ORP and pH have shown that the internal pH decrease is due to an increase in membrane prot…
Effects of a high-fat diet on energy metabolism and ROS production in rat liver.
2011
International audience; BACKGROUND & AIMS: A high-fat diet affects liver metabolism, leading to steatosis, a complex disorder related to insulin resistance and mitochondrial alterations. Steatosis is still poorly understood since diverse effects have been reported, depending on the different experimental models used. METHODS: We hereby report the effects of an 8 week high-fat diet on liver energy metabolism in a rat model, investigated in both isolated mitochondria and hepatocytes. RESULTS: Liver mass was unchanged but lipid content and composition were markedly affected. State-3 mitochondrial oxidative phosphorylation was inhibited, contrasting with unaffected cytochrome content. Oxidative…