Search results for "Hydrogen-ion concentration"
showing 10 items of 769 documents
Polysialic acid can mediate membrane interactions by interacting with phospholipids
2009
Polysialic acid (polySia) is expressed on the surface of neural cells, neuroinvasive bacterial cells and several tumor cells. PolySia chains attached to NCAM can influence both trans interactions between membranes of two cells and cis interactions. Here, we report on the involvement of phospholipids in regulation of membrane interactions by polySia. The pH at the surface of liposomes, specific molecular area of phosphatidylcholine molecules, phase transition of DPPC bilayers, cyclic voltammograms of BLMs, and electron micrographs of phosphatidylcholine vesicles were studied after addition of polysialic acid free in solution. The results indicate that polySia chains can associate with phosph…
Modeling the isothermal inactivation curves of Listeria innocua CECT 910 in a vegetable beverage under low-temperature treatments and different pH le…
2015
Thermal inactivation kinetics of Listeria innocua CECT 910 inoculated in a vegetable beverage at three pH conditions (4.25, 4.75, and 5.20), four levels of temperature (50, 55, 60, 65℃), and different treatment times (0–75 min) were obtained. Survival curves did not follow a log-linear relationship and consequently were fitted to various mathematical models: Weibull, Geeraerd, Cerf with shoulder, and the modified Gompertz equation. Results indicated that the best model for the treatment conditions was the modified Gompertz equation, which provides the best goodness-of-fit and the lowest Akaike information criterion value. Sensitivity analysis indicated that the most influential factors affe…
Is the acidity of ascitic fluid a reliable index in making the presumptive diagnosis of spontaneous bacterial peritonitis?
1986
Ascitic fluid pH and arterial-ascitic fluid pH gradient were compared to ascitic fluid polymorphonuclear cell count in 84 patients with cirrhotic ascites and in 12 with malignant ascites to assess their role as diagnostic tests for spontaneous bacterial peritonitis and to clarify the relationship between ascitic fluid pH and lactate. Ascitic fluid pH was significantly lower (pH 7.30) in spontaneous bacterial peritonitis (n = 18) and probable spontaneous bacterial peritonitis (n = 12) than in sterileascites (pH 7.41; n = 54). Since blood pH levels were not different in the presence of infection, arterial-ascitic fluid pH gradient was significantly higher in spontaneous bacterial peritonitis …
Mixed complexes of alkaline earth uranyl cabonates: A laser-induced time-resolved fluorescence spectroscopic study
2008
The interaction of the alkaline earth ions Mg2+, Sr2+ and Ba2+ with the uranyl tricarbonate complex has been studied by time resolved laser-induced fluorescence spectroscopy. In contrast to the non-luminescent uranyl tricarbonate complex the formed products show slight luminescence properties. These have been used to determine the stoichiometry and complex stabilities of the formed compounds. As the alkaline earth elements are located in an outer shell of the complex the influence of the type of the alkaline earth element on the stability constant is not very drastic. Therefore all obtained data were averaged in order to derive an common stability constant for the described complexes. These…
Photoinduced chemiluminescence of pharmaceuticals
2005
Abstract A screening test for the forward development of chemiluminescence systems able to determine pharmaceutical compounds is reported. The test is based on the on-line photodegradation of the drugs by using a photoreactor consisting of 697 cm × 0.5 mm PTFE tubing helically coiled around an 8 W low-pressure mercury lamp. Photodegraded pharmaceuticals are detected by direct chemiluminescence of the resulting photofragments and their subsequent reaction with potassium permanganate in sulphuric acid medium as oxidant. The screening comprised 97 compounds with different molecular structures and relevant members of the most important families of pharmaceuticals are tested (amino acids, carbox…
Acid Dnase Activities In Peripheral, Mononuclear Blood Cells: A Possible Parameter To Detect Proliferating Cell Populations
1992
After electrophoresis in DNA -containing polyacrylamide gels, two acid DNase activities can be detected in peripheral, mononuclear cells of the human blood. One of these acid DNase activities correlates with cell proliferation; its isoelectrical point is at pI 7.4. By means of this DNase activity, a quantity of less than 1% leukemic cells can be detected. The increased acid DNase activity can indicate the proliferation of malignant cell populations and possibly the proliferation of cell populations during immunological reactions
A chimera carrying the functional domain of the orphan protein SLC7A14 in the backbone of SLC7A2 mediates trans-stimulated arginine transport.
2012
In human skin fibroblasts, a lysosomal transport system specific for cationic amino acids has been described and named system c. We asked if SLC7A14 (solute carrier family 7 member A14), an orphan protein assigned to the SLC7 subfamily of cationic amino acid transporters (CATs) due to sequence homology, may represent system c. Fusion proteins between SLC7A14 and enhanced GFP localized to intracellular vesicles, co-staining with the lysosomal marker LysoTracker(®). To perform transport studies, we first tried to redirect SLC7A14 to the plasma membrane (by mutating putative lysosomal targeting motifs) but without success. We then created a chimera carrying the backbone of human (h) CAT-2 and …
Acidosis induces multi-drug resistance in rat prostate cancer cells (AT1) in vitro and in vivo by increasing the activity of the p-glycoprotein via a…
2008
Because solid growing tumors often show hypoxia and pronounced extracellular acidosis, the aim of this study was to analyze the impact of an acidotic environment on the activity of the p-glycoprotein (pGP) and on the cellular content and cytotoxicity of the chemotherapeutic drug daunorubicin in the AT1 R-3327 Dunning prostate carcinoma cell line cultured in vitro and in vivo. In vitro, extracellular acidosis (pH 6.6) activated p38 and ERK1/2 and thereby induced daunorubicin resistance via a pronounced activation of pGP. De-novo protein synthesis was not necessary and analysis of transport kinetics indicated a fast and persistent pGP activation at pH 6.6 (when compared with 7.4). Intracellul…
Effect of reducing agents on the acidification capacity and the proton motive force of Lactococcus lactis ssp. cremoris resting cells.
2002
International audience; Reducing agents are potential inhibitors of the microbial growth. We have shown recently that dithiothreitol (DTT), NaBH(4) and H(2) can modify the proton motive force of resting cells of Escherichia coli by increasing the membrane protons permeability [Eur. J. Biochem. 262 (1999) 595]. In the present work, the effect of reducing agents on the resting cells of Lactococcus lactis ssp. cremoris, a species widely employed in dairy processes was investigated. DTT did not affect the acidification nor the DeltapH, in contrast to the effect previously reported on E. coli. The DeltaPsi was slightly increased (30 mV) at low pH (pH 4) in the presence of 31 mM DTT or 2.6 mM NaB…
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 + -…