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Query: UMLS:C0847097 (acidity)
 15,165 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A method is described to study the effect of successively changing incubation conditions on the release of rapidly labeled RNA from isolated nuclei. Nuclear columns containing immobilized rat liver nuclei isolated after in vivo application of labeled orotic acid are perfused with different non-radioactive media. Within the course of one perfusion, the rate of RNA release can be repeatedly altered by variation of temperature, acidity and concentrations of nucleoside triphosphates, complexing agents, sodium chloride and manganese chloride. RNA release can be started and stopped, indicating that the reaction does not result from damage to nuclei. During 60 min perfusion the same product, labeled ribonucleoprotein (sigma = 1.43 g/cm3 in CsCl), is released. High release rates depend on the ratio of nucleoside triphosphate to divalent cation concentration, not on the concentration of the agents per se. Ribonucleoside and deoxyribonucleoside triphosphates exert the same effect as ATP. The SH reagents iodoacetamide and iodoacetate only slightly affect the ATP-induced reaction. In contrast, p-chloromercuribenzoate, after an initial stimulation, causes inhibition of RNA release.
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PMID:Studies on ribonucleic acid metabolism using nuclear columns. Release of rapidly labeled RNA from rat liver nuclei. 1 Feb 44

The intact heart of a young rat was excised rapidly and cooled to 0 degree C; its energy-rich compounds were examined by 31P Fourier Transform nuclear magnetic resonance. The heart showed the characteristic spectrum of sugar phosphates, inorganic phosphate, phosphocreatine, and magniesium phates, inorganic phosphate, phosphocreatine, and magnesium ATP, characteristics of the energizing state of the nonbeating tissue. Warming to 30 degrees C imposes an energy load upon the heart consistent with short-term resumption of beating, concomitant intracellular acidosis, and decomposition of all detectable energy-rich compounds. The intracellular acidity causes a shift from pH 7.0 to 6.0. The effects of possible interferences with this pH measurement are considered. The method appears to have wide usefulness in cardiac infarct models for detecting the fraction of the total volume occupied by the infarct and for studying the effect of various proposed therapies upon this infarcted volume.
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PMID:Phosphorus nuclear magnetic resonance studies on normoxic and ischemic cardiac tissue. 1 7

Liver and kidney slices prepared 30min after intravenous injections of formaldehyde-treated 125I-labelled bovine serum albumin into mice degrade approx. 25-40% of the protein to a trichloroacetic acid-soluble form during 60min incubation at 37 degrees C. The presence of bicarbonate in Krebs-Ringer phosphate medium inhibited intracellular proteolysis, and similar results were obtained at pH5 or pH7 in kidney or liver slices. Cellular integrity was required to obtain substantial rates of proteolysis. This intralysosomal intracellular degradation of an exogenous protein was partially inhibited by inhibitors of oxidative ATP formation, such as cyanide, azide, 2,4-dinitrophenol and absence of oxygen. Arsenite and iodoacetamide were also effective inhibitors, but the effects of fluoride were variable. These results suggest that an energy requirement exists for intralysosomal proteolysis in intact cells and are consistent with the hypothesis that energy may be required to maintain intralysosomal acidity.
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PMID:An energy requirement for the degradation of intravenously injected 125I-labeled albumin in mouse liver and kidney slices. 66 41

The uptake of Ca2+ by liver mitochondria, when phosphate movement is inhibited, occurs when Co2 is present and not in its absence. Uptake of Ca2+ to form CaCO3 yields 2H+/Ca2+. Heart mitochondria, when phosphate movement is inhibited, will take up Ca2+ with the exact equivalent of hydroxybutyrate, lactate or acetate. By providing a carrier for Cl- with tributyltin, a stoicheiometric uptake of Cl- with the Ca2+ takes place. The uptakes appear to occur without significant pH change; there appears to be no CO2-dependent uptake into heart mitochondria. Oxygenation of anaerobic heart mitochondria, in the presence of an inhibitor of phosphate movement and of generation of phosphate from internal ATP, does not yield significant change of external acidity in relation to the amount of O2 added. Use of Bromothymol Blue as an indicator of the distribution of a weak acid anion confirms that the transient nature of the response of the dye distribution to Ca2+ is connected with movement of endogenous phosphate. Bromothymol Blue accumulated in response to Ca2+ is discharged when entry of the Ca2+ (in the presence of mersalyl) is mediated with nigericin. It is concluded that Ca2+ uptakes will occur alternatively with the equivalent of anions or in exchange for endogenous K+ and that proton production is connected with the changes of ionization of phosphate (unless phosphate movement is inhibited) and in liver mitochondria with the hydration of CO2.
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PMID:Anion/calcium ion ratios and proton production in some mitochondrial calcium ion uptakes. 74 66

Massive transfusion of cold blood causes hemodinamic disturbances because of its acidity, surplus of potassium and defiency of calcium. Negative influence also results from stronger viscosity of blood, from the change of the active substances of blood coagulation, change of the patient's coagulation system responding to the transfused blood, subclinical troubles in this system according to the degree of the shock, reduced ability of oxygen transport caused by viscous blood, poor microcirculation etcr. Arrythmia, bradycardia, fibrilation of heart ventricles, may occur. Vasoconstrictions, microembolism and other incidents may appear. The quality of preserved blood changes during the conservation is changed, potassium and ATP are the indicators for its quality. At massive transfusions blood has to be warmed, filtered through special filters, to the patient has to be given just the quality of blood he needs etcr. The transfusiologist can help the therapist with useful advices and informations for the patient's sake.
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PMID:[Serological and clinical aspects of mass transfusion]. 100 97

Total phosphorus was estimated after mineralization of a sample, containing organic phosphoesters and proteins; a method is based on the formation of phosphomolybdenovanadium complex at acid pH. The analyses for inorganic phosphorus were carried our together with estimation if some labile phosphoesters (glucose-I-phosphate, ADP, ATP), which was possible due to low acidity of the medium (0.24 N HC1O4), small concentrations of reagents (3.2 mg/ml of molybdate, 0.08 mg/ml vanadate), addition of sodium citrate to neutralize the excess of molybdenovanadium acid and extraction of the colored complex with butyl or isobutyl alcohol. Optical density was measured at two wave lengths (340 nm and 390 nm) which enabled to estimate from 0.5 to 80 microng of phosphrorus in a sample.
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PMID:[Determination of total and inorganic phosphorus in the presence of organic phosphoric acid esters and proteins]. 102 59

Saccharomyces cerevisiae, Schizosaccharomyces pombe, Endomyces magnussi, Lodderomyces elongisporus and Rhodotorula gracilis, yeast species ranging from a glycolytic type to a strictly aerobic one, were tested for the activity of their plasma membrane H(+)-ATPase and the effect of alkaline metal cations thereon. The ATP-hydrolyzing activity of membranes from glucose-activated cells ranged from 456 to 932 mumol inorganic phosphate released per min per 1 g membrane protein. The effect of 0.2 M Li+, Na+, K+, Rb+ and Cs+ never exceeded the statistical range of error. In contrast, acidification after glucose addition ranged from 0.15 (for R. gracilis) to 14.8 nmol H+ per min per mg dry weight (for S. cerevisiae) and it was markedly influenced by the presence of alkaline metal chlorides, the highest effect observed being a seven-fold increase by K+ in a S. cerevisiae suspension. The effects were additive to those observed without ions in solution and are ascribed to the operation of independent channels and/or exchange systems for H+ with a clear selectivity toward K+. The separate nature of the ion-triggered extracellular acidification is supported by a different ratio of titration to pH-derived acidity with and without K+.
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PMID:Role of alkaline metal ions in the H(+)-ATPase activity of various yeast species. 129 Apr 64

Upon interaction with liver cells, insulin is internalized along with its receptor into nonlysosomal endocytic structures termed endosomes. In this work, the biochemical evidence supporting the role of endosomal acidity in the degradation of internalized insulin and in the recycling of the internalized insulin receptor is described. Treatment of rats by chloroquine and/or quinacrine, two acidotropic drugs, increases by 5-10 fold the amount of endogenous insulin associated with endosomal fractions and, in rats injected by 125I-labeled or native insulin, the endosomal uptake of these ligands at late times after injection. With 125I-insulin, these drugs inhibit the degradation of internalized hormone as judged on physical, biological and immunological criteria. Chloroquine and quinacrine treatment also increases the insulin receptor content of endosomal fractions and, in rats injected by native insulin, the ligand-induced accumulation of receptors in endosomal fractions at late times after injection. Subfractionation of endosomal fractions on Percoll gradients shows that chloroquine treatment shifts the distribution of both insulin and the insulin receptor towards higher densities, the receptor shift being slightly more pronounced in insulin-injected rats. Incubation of isolated endosomes containing internalized insulin at 30-37 degrees C results in a rapid degradation of this ligand, with a maximal at pH 5-6. Addition of ATP, by decreasing the endosomal pH, stimulates insulin degradation above pH 7, whereas addition of chloroquine and quinacrine, by elevating endosomal pH, exerts opposite effects. These data indicate that endosomal acidity is required for optimum degradation of internalized insulin within endosomes and recycling of the internalized receptor.
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PMID:Role of acidic subcellular compartments in the degradation of internalized insulin and in the recycling of the internalized insulin receptor in liver cells: in vivo and in vitro studies. 156 42

In the amoeba, Dictyostelium discoideum, endocytic vacuoles are acidified by proton pumps which reside not in their membranes but in an associated organelle which we call the acidosome. These two organelles can be dissociated in vitro, and we now describe conditions for their functional reassociation. Fluorescein 5-isothiocyanate-dextran was fed to amoebae to report on the pH of their endocytic vacuoles. Following homogenization, the endocytic vacuoles were dissociated from acidosomes by removing Mg2+ and cytosol and purged of their native acidity by transient exposure to nigericin. The endocytic vacuoles could then be reacidified by ATP if first preincubated under these optimized conditions: 30 degrees C for 30 min in the presence of acidosomes, a 4-fold excess of cytosol, and 5 mM Mg2+ at pH 7.4. Reacidification was observed with early but not late endocytic compartments. Mn2+ and Ca2+ were poor substitutes for Mg2+; albumin did not substitute for cytosol. Neither Ca2+, ATP, nor adenosine 5'-O-(3-thiotriphosphate) affected reconstitution appreciably; guanosine 5'-O-(3-thiotriphosphate) inhibited reacidification by 50% when present during preincubation at 0.1 mM. Warming the cytosol to 50 degrees C or exposing it to protease abolished its activity but N-ethylmaleimide did not. Molecular sieving indicated that the cytosolic factor was a macromolecule. We conclude that the specific functional association of acidosomes and endocytic vacuoles can be reconstituted in vitro with soluble proteins plus Mg2+.
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PMID:Reconstitution of the association of endocytic vacuoles and acidosomes from Dictyostelium. 164 80

The endocytic compartment in the amoeba Dictyostelium discoideum was labeled by feeding fluorescein 5-isothiocyanate-dextran. In homogenates containing 2 mM Mg2+, the compartments so labeled copurified with all of the vacuolar H(+)-ATPase activity in a dense peak. The fluorescence properties of the probe showed that these dense vacuoles were inherently acidic. Furthermore, after purging their residual acidity, they could be re-acidified by the addition of ATP. These data suggest that the H(+)-ATPase was structurally and functionally coupled to the endocytic space. The association of the H(+)-ATPase and endocytic compartment was reversed by the removal of either Mg2+ or traces of the cytosol. Endocytic vacuoles prepared in this way were deficient in vacuolar H(+)-ATPase activity and were not acidified upon addition of MgATP. The missing proton pumps were recovered in large buoyant vacuoles that lacked ingested fluorescein 5-isothiocyanate-dextran, acid hydrolases, and residual acidity. These vacuoles were also less susceptible than endosomes to disruption by digitonin, suggesting that their bilayers were low in sterols. These results indicate that the endocytic circuit in Dictyostelium is acidified by a discrete and separable proton-pumping organelle.
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PMID:Endosomes are acidified by association with discrete proton-pumping vacuoles in Dictyostelium. 170 36


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