Search results for "intracellular ph"

A secondary mode of action of the herbicide lenacil: Modification of K+ permeability of Acer pseudoplatanus cells

1984

Abstract The action of lenacil on plasmalemma permeability to K+, transmembrane electric potential difference (PD) calculated from the tetraphenylphosphonium distribution, proton extrusion and intracellular pH of Acer pseudoplatanus cells calculated from the 5,5-dimethyloxazolidine,4-dione distribution, was studied and compared with the action of fusicoccin (FC) and diethylstilbestrol (DES). The three compounds temporarily stimulated the rate of 86Rb+ uptake with a half-maximum effect at 5.0 μM for 3-cyclohexyl-6, 7-dihdro-1H-cyclopentapyrimidine-2,4(3H,5H)-dione (lenacil). Lenacil and FC had no action on transmembrane electric potential difference, whereas DES decreased it. Lenacil inhibit…

2019

The effects of ionotropic γ-aminobutyric acid receptor (GABA-A, GABAA) activation depends critically on the Cl−-gradient across neuronal membranes. Previous studies demonstrated that the intracellular Cl−-concentration ([Cl−]i) is not stable but shows a considerable amount of activity-dependent plasticity. To characterize how membrane properties and different molecules that are directly or indirectly involved in GABAergic synaptic transmission affect GABA-induced [Cl−]i changes, we performed compartmental modeling in the NEURON environment. These simulations demonstrate that GABA-induced [Cl−]i changes decrease at higher membrane resistance, revealing a sigmoidal dependency between both par…

Proton Pump Inhibitors Display Antitumor Effects in Barrett's Adenocarcinoma Cells

2016

Recent evidence has reported that proton pump inhibitors (PPIs) can exert antineoplastic effects through the disruption of pH homeostasis by inhibiting vacuolar ATPase (H+-VATPase), a proton pump overexpressed in several tumor cells, but this aspect has not been deeply investigated in EAC yet. In the present study, the expression of H+-VATPase was assessed through the metaplasia-dysplasia-adenocarcinoma sequence in Barrett’s esophagus (BE) and the antineoplastic effects of PPIs and cellular mechanisms involved were evaluated in vitro. H+-VATPase expression was assessed by immunohistochemistry in paraffined-embedded samples or by immunofluorescence in cultured BE and EAC cell lines. Cells we…

Role of the tumor microenvironment in the activity and expression of the p-glycoprotein in human colon carcinoma cells.

2006

The metabolic microenvironment of solid tumors is characterized by an oxygen deficiency and increased anaerobic glycolysis leading to extracellular acidosis and ATP depletion, which in turn may affect other energy-dependent cellular pathways. Since many tumors overexpress active drug transporters (e.g. the p-glycoprotein) leading to a multidrug-resistant phenotype, this study analyzes the impact of the different aspects of the extracellular microenvironment (hypoxia and acidosis) on the activity and expression of the p-glycoprotein (pGP) in the human colon carcinoma cell line LS513. For up to 24 h cells were exposed to hypoxia (pO2<0.5 mmHg), an acidic extracellular environment (pH 6.6), or…

SCD5-induced oleic acid production reduces melanoma malignancy by intracellular retention of SPARC and cathepsin B

2015

A proper balance between saturated and unsaturated fatty acids (FAs) is required for maintaining cell homeostasis. The increased demand of FAs to assemble the plasma membranes of continuously dividing cancer cells might unbalance this ratio and critically affect tumour outgrowth. We unveiled the role of the stearoyl-CoA desaturase SCD5 in converting saturated FAs into mono-unsaturated FAs during melanoma progression. SCD5 is down-regulated in advanced melanoma and its restored expression significantly reduced melanoma malignancy, both in vitro and in vivo, through a mechanism governing the secretion of extracellular matrix proteins, such as secreted protein acidic and rich in cysteine (SPAR…

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…

Effects of Zizyphus lotus L. (Desf.) polyphenols on Jurkat cell signaling and proliferation.

2013

We assessed the effects of Zizyphus lotus L. (Desf.) polyphenols (ZLP) on T-cell signaling and proliferation. Our results showed that ZLP exerted no effect on the increases in intracellular free calcium concentrations, [Ca(2+)]i, in human Jurkat T-cells. However, ZLP modulated the thapsigargin-induced increases in [Ca(2+)]i in these cells. ZLP treatment was found to decrease the phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2). In addition, ZLP induced a rapid (t1/2=33s) and dose-dependent decrease in intracellular pH (pHi) in human Jurkat T-cells. Furthermore, ZLP significantly curtailed T-cell proliferation by diminishing their progression from S to G2/M phase of cell…

Intracellular pH-dependent efflux of the fluorescent probe pyranine in the yeast Yarrowia lipolytica.

2001

International audience; 8-Hydroxypyrene-1,3,6-trisulfonic acid (pyranine) can be used as a vital intracellular pH (pH(i)) indicator. In the yeast Yarrowia lipolytica, a partial efflux of the probe was detected by using the pH-independent wavelength of 415 nm. A simplified correction of the fluorescent signals was applied, enabling to show for this species a good near-neutral pH(i) maintenance capacity in a pH 3.9 medium. Octanoic acid, which is known to have toxic effects on yeast, decreased the pH(i) and increased the 260-nm-absorbing compounds leakage. However, this acid inhibited the fluorescent probe efflux linearly with its concentration suggesting a pH(i)-dependent efflux of pyranine …

Effect of intracellular P content on phosphate removal in Scenedesmus sp. Experimental study and kinetic expression

2014

The present work determines the effect of phosphorus content on phosphate uptake rate in a mixed culture of Chlorophyceae in which the genus Scenedesmus dominates. Phosphate uptake rate was determined in eighteen laboratory batch experiments, with samples taken from a progressively more P-starved culture in which a minimum P content of 0.11% (w/w) was achieved. The results obtained showed that the higher the internal biomass P content, the lower the phosphate removal rate. The highest specific phosphate removal rate was 6.5 mgPO4 P gTSS -1 h -1 . Microalgae with a P content around 1% (w/w) attained 10% of this highest removal rate, whereas those with a P content of 0.6% (w/w) presented 50% …

Chloride, carboxylate and carbonate transport by ortho-phenylenediamine-based bisureas

2013

Highly potent but structurally simple transmembrane anion transporters are reported that function at receptor to lipid ratios as low as 1 : 1 000 000. The compounds, based on the simple ortho-phenylenediamine-based bisurea scaffold, have been studied for their ability to facilitate chloride/nitrate and chloride/bicarbonate antiport, and HCl symport processes using a combination of ion selective electrode and fluorescence techniques. In addition, the transmembrane transport of dicarboxylate anions (maleate and fumarate) by the compounds was examined. Molecular dynamics simulations showed that these compounds permeate the membrane more easily than other promising receptors corroborating the e…