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At least 19 recordsLinked to original sources
PubMed1978

[The determination of salivary pH by contact pH meter in individuals receiving psychotropic therapy. Study of pH on the tongue and at the orifice of Wharton's and Stenon's ducts (author's transl)].

The authors studied salivary pH at different sites in 172 patients receiving psychotropic therapy in hospital. For statistical purposes, the study was limited to individuals receiving a "moderate" dose of: --a benzodiazepine derivative --a neuroleptic and benzodiazepine --antidepressant, neuroleptic and benzodiazepine. Regardless of the type of psychotropic therapy and of the site of measurement, acidification of salivary pH which was statistically significant in comparison with values found in healthy subjects was noted. This acidification was particularly marked with regard to "lingual" pH. In addition, regardless of the site of measurement, a higher degree of acidification of salivary pH was seen in individuals receiving a combination of psychotropic agents. This acidification was particularly striking with regard to salivary pH in patients given a combination of antidepressant, neuroleptic and a benzodiazepine derivative. The cause of this acidification is not definitely known. A number of hypotheses may be put forward: decrease in salivary volume (Laudenbach, 6, and Vermeil, 7), excretion of acid metabolites by the salivary glands, effect of psychotropic agents upon the action itself of the salivary glands.

Antidepressive Agents↗
PubMed1977

Contribution of pH-sensitive metabolic processes to pH homeostasis in isolated rat kidney tubules.

The metabolism of isolated rat kidney tubules suspended in calcium-free physiological saline buffered with phosphate was found to be sensitive to changes in the pH of the suspending medium. Lowering the pH from 7.8 to 6.4 brought about increases in the rates of oxidation of added succinate, glutamate or glutamine as well as in the production of glucose from lactate, glutamine, succinate and fructose. The cellular ATP level was also higher in tubules incubated at pH 6.4 In contrast, the utilization of added glucose was greater at pH 7.8 than at pH 6.4, a substantial amount of lactate being produced at the higher pH. When glucose and either lactate or glutamine were provided as co-substrates glucose was the preferred fuel at pH 7.8 but the alternative substrate was the more readily utilized at pH 6.4. As a consequence of the metabolic activities of the tubules the pH of the suspending medium changed, utilization of lactate, glutamate or glutamine causing a rise in pH while conversion of glucose to lactate caused a fall in pH. In cases where two substrates were metabolized concurrently over a period of 3 h the extracellular pH tended towards a plateau level of approximately pH 7.4. It is proposed that pH-sensitive metabolism in isolated kidney tubules contributes to pH homeostasis in the cellular environment.

Adenosine Triphosphate↗
PubMed1977

Light-induced pH changes and changes in absorbance of pH indicators in Rhodospirillum rubrum chromatophores.

1. The light-induced pH change of chromatophore suspensions from Rhodospirillum rubrum was stimulated significantly and similarly by KCl, NaCl, LiCl, RbCl, CsCl, MgCl2, MnCl2, and CaCl2. In the dark, the pH of chromatophore suspensions decreased immediately and markedly on adding these salts. 2. The light-induced pH change stimulated by KCl plus valinomycin was inhibited by LiCl and NaCl, but not by RbCl. 3. The optimum pH values for light-induced pH change and photosynthetic ATP formation were around 5 and 8, respectively. The amount of chromatophore-bound ubiquinone-10 reduced in the light was independent of pH from 5 to 9. At pH 8, the number of protons incorporated into chromatophores in the light was one-half of the number of ubiquinone-10 molecules reduced in the light. 4. Among several pH indicators tested, bromothymol blue (BTB) and neutral red (NR) showed absorbance changes on illumination of chromatophores. Although the pH change indicated by the absorbance change was opposite to the light-induced pH change of the medium, the effect of KCl on the absorbance changes of BTB and NR, and the effect of valinomycin on that of NR, but not on that of BTB, were similar to those on the light-induced pH change. 5. The light-induced absorbance change of BTB was significantly inhibited by NR, whereas that of NR was hardly influenced by BTB. 6. Oligomycin stimulated the light-induced absorbance change of BTB under either non-phosphorylating or phosphorylating conditions. On the other hand, that of NR under phosphorylating conditions was 50% of that under non-phosphorylating conditions, and was increased by oligomycin.

Bacterial Chromatophores↗
PubMed1975

Intracellular pH of isolated rat diaphragm muscle with metabolic and respiratory changes of extracellular pH.

Relationships between intracellular and extracellular pH isolated rat diaphragms were determined both during respiratory and metabolic changes of extracellular pH. Metabolic changes of extracellular pH were produced by varying bicarbonate concentration of the suspending Krebs-Ringer solution and respiratory changes were produced by varying PCO2 of the suspending medium. At any defined extracellular pH, the bicarbonate concentration ratios between intracellular and extracellular space were the same during both metabolic and respiratory changes of extracellular pH. However, when extracellular pH varied within 7.15 and 7.4 intracellular pH remained essentially constant. In order to maintain the intracellular pH constant during extracellular pH changes, a bicarbonate efflux during metabolic changes from the intracellular compartment, and a bicarbonate influx during respiratory changes to the intracellular compartment must occur. The maintenance of identical intracellular/extracellular bicarbonate concentration ratios regardless of the mechanisms of extracellular pH changes (metabolic or respiratory) suggests an active mechanism for the transport of bicarbonate or H-+ ions.

Acid-Base Equilibrium↗
PubMed1979

Characterization of the pH-dependent dimer-to-protomer transformation of cytochrome C oxidase at alkaline pH.

The pH-induced dissociation of cytochrome c oxidase from dimer to protomer has been studied in the pH range 7 to 11. Findings are as follows: The heme A:copper ratio is 1.0 at both pH 7.4 and 10.6. The relative enzymatic activity is preserved at all pH values at which the dimer or protomer are found. The fraction of protomer, determined from sedimentation velocity profiles, increases from 0 to 1 as the pH is raised. The absorption and circular dichroism spectra in the Soret region change in ways indicating that the contributions of cytochrome a in typical cytochrome aa3 spectral patterns are progressively lost as pH increases. At pH values more alkaline than the above, denaturation occurs. The fraction of protomer, and certain parameters defined to quantitate the changes in spectral form, exhibit similar pH profiles for a given preparation; but these concerted changes occur over different pH ranges for different preparations. Nevertheless the optical parameters are linearly correlated with the fraction of protomer for each preparation. It is concluded that the spectral properties of the dimer and the protomer are intrinsic attributes of each species and are not directly affected by changes in ambient pH.

Animals↗
PubMed1978

The effect of fibrin deposition on the sensitivity of the continuous monitoring pH electrode and on the recorded pH value: an in vitro study.

One of the problems concerning the continuous pH-monitoring technique is whether the relationship between pH measured by the electrode and pH in central and/or capillary fetal blood is constant. To test to what extent a fibrin clot deposited on the pH-electrode influenced the recorded value and the sensitivity of the electrode, the following in vitro study was performed. Fibrin was deposited on the pH-electrode by means of thromboplastin and fibrinogen, or by thromboplastin and whole blood. The deposition of a clot was verified by inspection of the electrode in a microscope. The time for stabilization of the recorded pH-value and the recorded pH-value was measured in standard calibration solutions before and after deposition of the fibrin clot and after decomposition of the fibrin clot by plasmin. FDP was measured in the decomposition solution. From the study it was obvious that the stabilization time of the electrode was considerably influenced by deposition of an "unphysiological" fibrin clot, less so if the clot was deposited by means of whole blood. The recorded pH-value was not influenced.

Electrodes↗
PubMed1976

pH-sensitive glass microelectrodes and intracellular pH measurements.

1. Some properties of the open-tipped, uninsulated, pH-sensitive glass microelectrode were examined in several electrical experiments. 2. Based on these observations, technical and theoretical problems were considered for application to the pH measurement in small cells. 3. The intracellular pH, (pH)i, of the epithelial cell in rat duodenum measured was approximately 7.0. A reduction in (pH)i was apparent (about 0.3) with the addition of 20 mM-glucose to the bathing fluid. 4. It was concluded that with certain limitations such uninsulated, open-tipped microelectrodes may be successfully utilized for intracellular pH measurements.

Animals↗
PubMed1975

[Validity of pH measurements by means of micro pH combination electrodes in blood and other biological fluids (author's transl)].

pH measurements in blood or in media containing either proteins or polypeptides and performed by means of micro pH combination electrodes type N 58 (Schott & Gen., Mainz) yield in a systematic error according to the regression line y = 1.135 chi - 0.842, in the range between pH 5.3 and 8.3. This deviation from the real pH value is independent of the protein concentration and amounts to 0.1-0.2 pH units in the physiological range. The error does not occur if the pH measurements are performed in media which are free of proteins and polypeptides, respectively. If the electrolyte solution within the reference electrode is replaced (NaCl solution instead of KCl solution) the error is distinctly reduced. For this reason, this deviation should be caused by the variation of the diffusion potential across the platinum junctions.

Diagnostic Errors↗
PubMed1978

Fluorescence probe measurement of the intralysosomal pH in living cells and the perturbation of pH by various agents.

A quantitative method is described for the measurement of intralysosomal pH in living cells. Fluorescein isothiocyanate-labeled dextran (FD) is endocytized and accumulates in lysosomes where it remains without apparent degradation. The fluorescence spectrum of this compound changes with pH in the range 4-7 and is not seriously affected by FD concentration, ionic strength, or protein concentration. Living cells on coverslips are mounted in a spectrofluorometer cell and can be perfused with various media. The normal pH inside macrophage lysosomes seems to be 4.7-4.8, although it can drop transiently as low as 4.5. Exposure of the cells to various weak bases and to acidic potassium ionophores causes the pH to increase. The changes in pH are much more rapid than is the intralysosomal accumulation of the weak bases. Inhibitors of glycolysis (2-deoxyglucose) and of oxidative phosphorylation (cyanide or azide) added together, but not separately, cause the intralysosomal pH to increase. These results provide evidence for the existence of an active proton accumulation mechanism in the lysosomal membrane and support the theory of lysosomal accumulation of weak bases by proton trapping.

Animals↗
PubMed1978

Electrostatic interactions at charged lipid membranes. Measurement of surface pH with fluorescent lipoid pH indicators.

The 5-dimethylaminonapthalene-1-sulfonyl (dansyl) chromophore attached to the polar head groups of lipids has been used as a fluorescent lipoid pH indicator to evaluate the interfacial pH in lipid-water lamellar systems prepared from negatively charged lipids. The pH in the vicinity of the charged lipid bilayers is different from the pH of the bulk aqueous phase and the difference is a function of the electrolyte concentration in the aqueous phase and of the lipid packing in the bilayer. At a fixed electrolyte concentration in the aqueous phase, the observed interfacial pH is 0.6 to 0.7 pH units lower above the thermal phase transition of the lipid than it is below this temperature. A quantitative interpretation of the results is given on the basis of the Gouy-Chapman theory. The results indicate that the dansyl chromophore is located in front of the charged surface and its distance from this surface increases with a decrease in lipid packing.

Chemical Phenomena↗
PubMed1976

The pH dependence of quantitative ristocetin-induced platelet aggregation: theoretical and practical implications-a new device for maintenance of platelet-rich plasma pH.

Quantitative ristocetin-induced platelet aggregation of normal platelet-rich plasma (PRP) decreased with time after PRP preparation. An increase in p H of the PRP with time proved to be responsible for this finding. Diffusion of CO2from the plasma is the prime determinant of the change in pH. Since a complex combination of factors influences CO2 diffusion (surface area-to-volume relationship, capping, mixing, etc.) The change in pH is variable with time. Thus, quantitative ristocetin aggregation should be pH controlled. A simple device for maintaining PRP pH constant by control of the ambient pCO2 was designed and found effective in keeping both pH and quantitative ristocetin aggregation constant over a prolonged period of time. It can be adapted for use in platelet aggregation studies employing other reagents. The pH dependence of ristocetin-induced platelet aggregation is consistent with other data supporting an elctrostatic interaction between the platelet, von Willebrand factor, and ristocetin. We favor a model wherein ristocetin neutralizes some of the platelet's negative change and permits the von Willebrand factor to bridge sites on separate platelets to induce agglutination.

Blood Coagulation Tests↗
PubMed1978

Pyranine as a sensitive pH probe for liposome interiors and surfaces. pH gradients across phospholipid vesicles.

Pyranine is shown to be a convenient and sensitive probe for reporting pH values, pHi, at the interior of anionic and at the outer surface of cationic liposomes. It is well shielded from the phospholipid headgroups by water molecules in the interior of anionic liposomes, but it is bound to the surface of cationic liposomes. Hydrogen ion concentrations outside the liposomes, 'bulk pH values', pHo, were measured by a combination electrode. While pHi = pHo for neutral, pHi less than pHo for anionic and pHi greater than pHo for cationic liposomes prepared in 5.0 . 10(-3) M phosphate buffers. pKa values for the ionization of pyranine were 7.22 +/- 0.04 and 6.00 +/- 0.05 in water and at the external surface of cationic liposomes. The surface potential for cationic liposomes containing dipalmitoyl-DL-alpha-phosphatidylcholine, cholesterol and octadecylamine in the molar ratio of 1.00 : 0.634 : 1.01, were calcuated to be +72.2 mV. Proton permeabilities were measured for single and multicompartment anionic liposomes. Transfer of anionic liposomes prepared at a given pH to a solution of different pH resulted in a pH gradient if sodium phosphate or borate were used as buffers. In the presence of sodium acetate proton equilibration is promptly established.

Amines↗
PubMed1978

The change in the pH 4 and pH 6 forms of alpha-glucosidase in cultured amniotic fluid cells and its implication in prenatal diagnosis of Pompe's disease.

Activities of two major forms of alpha-glucosidase in cultured amniotic fluid cells have been measured by the 4-methylumbelliferyl-alpha-D-glucoside assay after 3, 6 and 9 weeks of culturing. Activity of the pH 4 forms of alpha-glucosidase, which is deficient in Pompe's disease, was low in early culture but increased rapidly as the culture time was increased. The cells harvested at 3 weeks had a low absolute activity of the pH 4 form as well as low ratio of the pH 4 to pH 6 enzyme. The pH 6 form is not affected in Pompe's disease. The results suggest cautions when attempting early diagnosis by use of microtechniques and re-emphasizes the need for differentiation of these two forms of alpha-glucosidases in prenatal diagnosis of Pompe's disease.

Amniotic Fluid↗
PubMed1977

Continuous subcutaneous pH measurement in human fetuses: correlations with scalp and umbilical blood pH.

The subcutaneous pH values of 42 fetuses has been measured continuously during labor with the use of the electrode designed by Stamm and associates. We have obtained 60 per cent good tracings. The results have confirmed the reliability of the subcutaneous pH measurement, if the electrode is correctly inserted, when compared with both capillary and umbilical artery blood pH measurements (r = 0.91, p less than 0.001 and 0.83, p less than 0.001, respectively). Technical improvements appear to be necessary prior to widespread clinical use of continuous pH measurement.

Electrodes↗
PubMed1977

Effect of the medium pH and the cell pH upon the kinetical parameters of phosphate uptake by yeast.

1. Both the maximum rate of phosphate uptake and the Km depend upon the pH of the medium in a complex way. 2. The effect of medium pH upon the maximum rate of uptake is mainly indirect and is correlated with changes in cell pH. 3. The Km is affected by the medium pH both directly via an apparent competitive inhibition by hydroxyl anions and indirectly in a similar way as the maximum rate of uptake.

Culture Media↗
PubMed1977

Energetics of the cooperative and noncooperative binding of nicotinamide adenine dinucleotide to yeast glyceraldehyde-3-phosphate dehydrogenase at pH 6.5 and pH 8.5. Equilibrium and calorimetric analysis over a range of temperature.

The binding of nicotinamide adenine dinucleotide (NAD+) to yeast glyceraldehyde-3-phosphate dehydrogenase (GPDH) has been studied at pH 6.5 and 8.5, at 5,25, and 40 degrees C, by calorimetry, fluorometry, spectrophotometry, equilibrium dialysis, and flow dialysis. As reported earlier for pH 7.3 (Velick S.F., Baggott, J.P., and Sturtevant, J.M. (1971), Biochemistry 10, 779), the binding is accompanied by enthalpy changes which become rapidly more negative as the temperature increases, with delta Cp = -500 to -750 cal deg-1 (mole of NAD+ bound)-1, and by entropy changes which also, as required by the large negative delta Cp, become rapidly more negative with increasing temperature. The binding data at pH 6.5 can be fitted on the basis of either four identical noninteracting sites, or of four sites showing a small degree of negative cooperativity. The data at pH 8.5, particularly at 40 degrees C, require the introduction of positive cooperativity, as was previously shown by Kirschner et al. (Kirschner, K., Eigen, M., Bittman, R., and Voigt, B. (1966), Proc. Natl. Acad. Sci. U.S.A. 56, 1661), and can be equally well fitted on the basis of a sequential model (Adair, G.S. (1925), J. Biol. Chem. 63, 529) or a concerted model (Monod, J., Wyman, J., and Changeux, J.P. (1965), J. Mol. Biol. 12, 88). It is proposed that the observed thermodynamic changes are largely the result of a hydrophobic effect due to a decrease in the exposure of nonpolar groups to the solvent, and of a tightening of the protein structure when the coenzyme is bound with concomitant decrease in the number of easily excitable internal degrees of freedom.

Binding Sites↗
PubMed1977

Measurement of the pH of frozen buffer solutions by using pH indicators.

A method was established to estimate the pH change of several buffers solutions on freezing by using a combination of pH indicators. Among more than 30 buffers solutions examined, almost half exhibited a pH change in the temperature range between freezing point and 220 degrees K; the results were tabulated. Glycerol was found to suppress the pH changes because of its "salt buffer" effect.

Buffers↗