Increase In Hydrogen Ion Concentration Research Articles

Graft Copolymerization of Methacrylamide onto Guar Gum Using a Potassium Chromate/Malonic Acid Redox Pair

The effect of reaction conditions on the grafting parameters during the grafting of methacrylamide (MAM) onto guar-gum (GOH) using potassium chromate/ malonic acid redox pair was studied under ni sphere at different temperatures. On increasing the chromate ion concentration (from 3.5 × 10 -3 mol.dm -3 to 20.0 × 10 -3 mol.dm -3 ) grafting parameters were found to increase. Grafting ratio, efficiency, and add on were found to increase with the increase in malonic acid concentration from 3.5 × 10 -3 mol.dm -3 to 10.0 × 10 -3 mol dm -3 . It was observed that maximum efficiency was obtained when the monomer concentration was 20.0 × 10 -3 mol.dm -3 . With increasing hydrogen ion concentration, grafting parameters were found to increase. Homopolymer concentration, however, was found to decrease with increasing hydrogen ion concentration. Optimum tempera time for grafting of MAM onto guar gum were found to be 35°C and 120 min respectively. The graft copolymer was characterized by IR spectroscopy and thermogravimetric analysis.

Continuous-flow/stopped-flow system incorporating a rotating bioreactor for the determination of penicillins in pharmaceutical products

A rotating enzyme-immobilized reactor and a flat pH electrode have been incorporated into a sealed cell for use under continuous-flow/stopped-flow operation. The system has been used for rapid determination of penicillins G and V in pharmaceutical tablets and injectables. Detections based on the increase of hydrogen ion concentration due to enzymatic hydrolysis of the penicillins by the enzyme penicillinase [EC 3.5.2.6] immobilized on controlled-pore glass. Selective determination of the analyte in the 0.001–0.50 mM concentration range can be accomplished at the rate of 30 samples h −1.

Natural acidity or anthropogenic acidification in the spring flood of northern Sweden?

Episodic pH decline associated with spring flood runoff in a typical headwater stream in the boreal forest of northern Sweden is driven almost exclusively by natural processes. Despite a drastic decline in acid neutralisation capacity (ANC), a 75-fold increase in hydrogen ion concentration and an associated increase in inorganic monomeric aluminium fractions, anthropogenic deposition (the strong acids SO 4 2− and NO 3 − associated with anthropogenic deposition) made only a minor contribution (5–8%) to the ANC and pH decline during the spring flood of 1997. Instead the ANC decline from 60 μeq. l −1 during winter baseflow to −26 μeq. l −1 at peak flow, as well as the associated pH decline from approximately 6.4–4.6 was, according to an episodic acidification model, driven almost exclusively by organic acids originating from the soil and dilution by low ionic strength snowmelt water. The natural component of ANC and pH decline during spring flood, such as that reported here, has important implications for the aquatic ecology of the boreal zone in general, and for the Swedish liming program in particular, since government subsidies are used to keep pH above 6.0 throughout spring flood, in the belief that this is the natural pH level prior to the appearance of acid rain in Europe.

Kinetic studies on the complexation of aqua chromium (III) with DL-leucine in aqueous acidic media

Kinetics of formation of 1:2 complex between chromium (III) and DL-leucine was studied spectrophotometrically at h,,,=540 nm. The reaction was found to be first order in both reactants. Increasing hydrogen ion concentration from 2.5~10 a 103 mol.dm4 decreased the reaction rate: k,,,=a+b[~+]~'. Activation parameters were evaluated to be 38 kJ.mol-' and -159 JK-'.mol, for the enthalpy and entropy of activation respectively. A value of log K=2.9 at 42°C was obtained for the formation constant of the complexe ().

Effect of graft reperfusion on haemodynamics and gas exchange during liver transplantation

We have documented the changes in gas exchange, haemodynamic state and associated physiological variables which occurred after graft reperfusion in 20 patients undergoing uncomplicated orthotopic liver transplantation. Gas exchange was measured during constant ventilation using a metabolic monitor. After reperfusion, there were increases in VO2 (mean increase 57 (SD 25) ml min-1) (P < 0.001), VCO2 (mean increase 38 (17) ml min-1) (P < 0.001) and PaCO2 (mean increase 0.88 (0.56) kPa) (P < 0.001). These were associated with increases in cardiac output (1.2 (1.0) litre min-1 m-2) (P < 0.001) and mean pulmonary artery pressure (9 (6) mm Hg) (P < 0.001). There was a decrease in standard bicarbonate concentration (0.96 (1.6) mmol litre-1) (P < 0.02) and increase in hydrogen ion concentration (8.15 (5.9) mmol litre-1) (P < 0.001) consistent with the release of an acid load from the graft and previously ischaemic tissues. The increases in PaCO2 and hydrogen ion concentration were significantly larger in patients in whom venovenous bypass was used during the anhepatic period compared with the "piggyback" surgical technique. We found correlations between the changes in PaCO2 and VCO2 (r2 = 0.25, P < 0.02), cardiac output and VCO2 (r2 = 0.34, P < 0.01), and cardiac output and VO2 (r2 = 0.34, P < 0.01). We conclude that major alterations in gas exchange occur after reperfusion which result from alterations in metabolic rate and haemodynamic changes. These may be clinically relevant, particularly in patients at risk of cerebral oedema.

Kinetics and mechanism of the complexation between hydroxopentaaquochromium(III) and octacyanomolybdate(IV) ions in acidic medium

The reaction between hydroxopentaaquochromium(III) and octacyanomolybdate(IV) was investigated spectrophotometrically and obeyed a 2:1 reactant stoichiometry with respect to formation of the [Cr(H2O)4OH]2 Mo(CN)8 complex. Kinetic studies reveal that the reaction is first order with respect to hydroxopentaaquochromium(III) in the presence of an excess of octacyanomolybdate(IV). The reaction rate increased with an increase in the ionic strength and temperature, and decreased with an increase in hydrogen ion concentration. A mechanism has been proposed based upon ion-pair formation. The results are best accounted for by the Eigen-Tamm mechanism. Anation of [Cr(H2O)5OH]2+ is discussed in terms of an associative interchange (Ia) where bond breaking and bond making are equally important. The activation parameters were calculated using Arrhenius's equation.

Calcitonin gene-related peptide modulates acid-mediated regulation of somatostatin and gastrin release from rat antrum

Background & Aims : Acid has been shown to stimulate calcitonin gene-related peptide (CGRP) release from peripheral sensory afferent nerve endings in the stomach. The aim of this study was to determine whether endogenous CGRP was involved, by a neurocrine mechanism, in acid-mediated stimulation of somatostatin and inhibition of gastrin release. Methods : A two-compartment sleeve of antral mucosal/submucosal tissue was perfused to determine sensory nerve and endocrine cell responses to luminal acid. CGRP receptor antagonist, CGRP 8–37, was used to inhibit the actions of endogenously released CGRP. Results : Perfusion of the antral sleeve lumen with media of increasing hydrogen ion concentration caused pH-dependent increases in CGRP and somatostatin release and decrease in gastrin release. CGRP 8–37 inhibited significantly basal somatostatin (−36%) and stimulated basal gastrin (+65%) release ( P < 0.02). Furthermore, CGRP 8–37 administration prevented luminal acid-mediated inhibition of gastrin release and stimulation of somatostatin release. These results indicate that CGRP 8–37 prevented acid-mediated feedback inhibition of gastrin release and acid-induced feedforward somatostatin release. Conclusions : These results suggest that CGRP plays an important role in the response of antral D and G cells to luminal acid and that local effector action of endogenous CGRP participates in regulation of antral regulatory peptide secretion.

Nitrogen additions (NaNO 3 and NH 4NO 3) at Aber forest, Wales: I. Response of throughfall and soil water chemistry

Nitrogen was sprayed weekly onto the forest floor of a Sitka spruce stand for 2.5 years in a replicated block design experiment to investigate the impacts of chronic atmospheric nitrogen deposition, in both oxidised and reduced form, on these ecosystems. The nitrogen was applied as sodium nitrate at 35 or 75 kg N ha −1 year −1 and as ammonium nitrate at 35 kg N ha −1 year −1, and the response of the throughfall and soil water chemistry determined. The response to increased water availability was also determined in a zero-N treatment. Increased water availability resulted in decreased concentrations of ammonium and phosphate and increased hydrogen ion concentration in the throughfall above the height of the spray, indicating tree growth is limited by water at this site. No effect of increased nitrogen availability on throughfall or stemflow chemistry above that of the water response was observed. Ambient nitrogen inputs in throughfall plus stemflow were 17 kg N ha −1 year −1 of which 11 kg N ha −1 year −1 was leached. Retention capacity of additional nitrogen applied to the forest floor was found to differ for nitrate-N and ammonium-N. There was no retention capacity for incoming nitrate-N but 100% retention capacity for applied ammonium-N. Nitrate leaching losses increased in parallel with nitrate inputs and were independent of ammonium addition. There was no apparent transformation of ammonium to nitrate in the ammonium nitrate treatment. Total dissolved nitrogen losses were therefore lower in the ammonium nitrate 35 kg N ha −1 year −1 treatment relative to the sodium nitrate 35 kg N ha −1 year −1. As the soil exchange complex is dominated by aluminium, the increase in salt loading and lack of nitrate retention in both treatments was associated with increased soil water aluminium concentrations due to ion exchange between the incoming sodium or ammonium ions and aluminium on the soil exchange complex. No increase in soil water concentrations of any other cation, with exception of sodium in the sodium nitrate treatments, was observed. These findings suggest that any increase in nitrate deposition will result in increased nitrate and aluminium leaching at this site which can perhaps best be described as ‘nitrate saturated’. Elevated ammonium deposition will also result in increased aluminium leaching if accompanied by a mobile anion. More long term monitoring is required to evaluate these changes in soil water chemistry on tree vitality and the internal nitrogen cycle.

Hydrolysis and polycondensation of ethyl silicates. 2. Hydrolysis and polycondensation of ETS40 (ethyl silicate 40)

The effects of catalysts, pH and reaction conditions on the course of the hydrolysis and condensation of ETS40 (ethyl silicate 40), and on the composition of the reaction products were studied with the aid of gas and gel chromatography, potentiometry and gelation tests. Strong acids (HCl, HClO 4, HNO 3, H 2SO 4, p-toluenesulphonic acid), weak acids (Cl 3, CCOOH, ClCH 2COOH, (COOH) 2, CH 3COOH and HCOOH) and bases (LiOH, NH 4,OH) were used as catalysts. The hydrolysis rate increased with increasing temperature, catalyst concentration, initial water concentration and initial ethyl silicate concentration, whereas it decreased with increasing number of Si atoms in the ethyl silicate molecules. At pH 0–7 the hydrolysis was acid catalysed, but at pH above 7.0 it was base catalysed. Simultaneously with the hydrolysis, condensation occurred at a rate which increased with increasing temperature, catalyst concentration, ETS40 concentration and, above all, with increasing initial water concentration. The condensation rate depended on the pH. The condensation was at its slowest for pH around 2.0. For pH below 2.0, the condensation increased with increasing hydrogen ion concentration; for pH above 2.0 the condensation increased with decreasing hydrogen ion concentration. Phosphoric acid and hydrofluoric acid increased the rate of condensation considerably. The reaction of ETS40 with water at pH around 2.0 gave rise during the hydrolysis to solutions of ethoxyhydroxysiloxanes with an average of 14–20 Si atoms in a molecule, which displayed long-term stability.

Kinetics and Mechanism of Oxidation of Tin(II) by Hexachloroiridate(IV) in Aqueous Perchlorate Solutions

The kinetics of hexachloroiridate(IV) oxidation of tin(II) in aqueous perchlorate media at a constant ionic strength of 2.0 mol dm-3 have been studied spectrophotometrically. The reaction was found to follow second-order overall kinetics and first order with respect to each of the reactants. The results showed hydrogen ion dependence where the reaction rate increased with increasing hydrogen ion concentration. The activation parameters were evaluated and a tentative reaction mechanism has been discussed.

Effect of external pH on ethanol oxidation byCandida utilis

The external pH affects both ethanol and oxygen uptake rates by nongrowing cells of Candida utilis suspended either in distilled water or in phthalate buffer. The buffering properties of organic acids control the maximum rates of exogenous respiration and ethanol uptake. The substrate limitation of ethanol uptake rate and endogenous respiration rate increase proportionally with increasing hydrogen ion concentration in the medium.

Release of dopamine and chemoreceptor discharge induced by low pH and high PCO2 stimulation of the cat carotid body.

1. Cat carotid bodies were incubated with the precursor [3H]tyrosine to label the catecholamine deposits and then mounted in a superfusion chamber which allowed simultaneous collection of the released [3H]dopamine (DA) and recording of action potentials from the carotid sinus nerve. 2. Low pH (7.2-6.6) superfusion of the carotid bodies for periods of 10 min produced a parallel increase in the release of [3H]DA and chemoreceptor discharge. 3. Carotid sinus nerve denervation of the carotid body 12-15 days prior to the experiments did not modify the release of [3H]DA elicited by low pH. 4. Superfusion of the carotid bodies with Ca(2+)-free, high-Mg2+ (1.6 mM) media reduced basal release of [3H]DA and chemoreceptor discharge by about 30%. Release evoked by low pH was reduced by 82%. Peak and average chemoreceptor discharge recorded in response to low pH were reduced by 28%. 5. Solutions containing weak acids (sodium acetate, 10 mM), adjusted at pH 7.4, elicited release of [3H]DA and increased chemoreceptor discharge. 6. With HCO3-CO2-buffered superfusion media, a reduction of bicarbonate to 5.6 mM (pH 6.8), an increase in CO2 to 20% (pH 6.8), or a simultaneous increase in CO2 to 20% and bicarbonate to 90 mM (pH 7.4), resulted in all cases in a corresponding increase in [3H]DA release and chemoreceptor discharge. The most effective stimulus was 20% CO2-pH 6.8 and the least effective 5% CO2-5.6 mM-HCO3-pH 6.8. 7. Inhibition of carbonic anhydrase with acetazolamide while perfusing the carotid bodies with a 20% CO2-equilibrated (pH 7.4) solution resulted in comparable reductions in the release of [3H]DA and chemoreceptor discharge. 8. It is concluded that the effective acidic stimulus at the carotid body chemoreceptors is an increase in hydrogen ion concentration in type I cells. It is also concluded that DA plays a critical role in the genesis of carotid sinus nerve discharges.

Anaerobic ATP provision, glycogenolysis and glycolysis in rat slow-twitch muscle during tetanic contractions

Rat soleus muscles were tetanically stimulated in situ with an occluded circulation to examine anaerobic adenosine triphosphate (ATP) provision and the regulation of glycolytic ATP production. Soleus muscles were stimulated for 30-60 s at 1 Hz with 100-200 ms trains (40-80 Hz). Muscles were sampled pre- and post-stimulation for measurements of pH, high energy phosphates and glycolytic intermediates. Total ATP provision by the slow oxidative fibres was 65-121 mumol/g dry muscle and 27-35% of the amount produced by fast glycolytic fibres. Contributions to total ATP provision in the initial 30 contractions were: phosphocreatine, 71%; glycolysis, 28%; and endogenous ATP, 1%. Following 60 contractions the contributions were 45-54%, 44-51% and 2-4%, respectively. During the initial 30 contractions, glycogenolysis (phosphorylase activity) and glycolysis [phosphofructokinase (PFK) activity] were similar as glucose-6-phosphate (G-6-P) and fructose-6-phosphate (F-6-P) did not accumulate. Small accumulations of PFK deinhibitors inorganic phosphate, adenosine diphosphate, adenosine monophosphate and fructose-1,6-diphosphate appeared to account for the PFK activity. In the final 30 contractions, phosphorylase activity increased above PFK as G-6-P and F-6-P accumulated. PFK activity and glycolytic ATP production also increased despite increasing hydrogen ion concentration [H+]. During intense tetanic stimulation of soleus muscle, glycolytic ATP production is initially limited by a low glycogen phosphorylase activity. The activity of PFK increases during in situ contraction through the accumulation of deinhibitors, despite increasing [H+].

Paradoxical Increase in Arterial Hydrogen Ion Concentration in Patients with Hepatorenal Failure Given Lactate-Based Fluids

We have investigated lactate intolerance in nine patients with acute hepatorenal failure during 21 machine haemofiltration treatments using a lactate based replacement solution. In all cases hyperlactataemia occurred, the mean arterial lactate increased from 1 +/- 0.2 mmol/l (mean +/- SEM) prior to treatment to 3.2 +/- 0.3 mmol/l at 1 h (P less than 0.01), 4.2 +/- 0.4 mmol/l at 2 h (P less than 0.01), 4.2 +/- 0.4 mmol/l at 3 h (P less than 0.01) and 3.9 +/- 0.4 mmol/l (P less than 0.01) post-treatment. There were correlations between the maximum increase in blood lactate and both the change in arterial hydrogen ion concentration (r = 0.71, P = 0.001) and the mean arterial blood pressure prior to starting treatment (r = -0.57, P = 0.007). During eight of the treatments (38%), the arterial hydrogen ion concentration increased. This group showed increased lactate intolerance in association with a lesser pretreatment mean arterial pressure. The administration of exogenous lactate to patients with hepatorenal failure who are at, or near to, the threshold of their own endogenous lactate metabolism can result in an increase in hydrogen ion concentration rather than the expected decrease, and therefore lactate-based dialysate solutions are best avoided.

Celiprolol, a Compound Which Attenuates Myocardial Acidosis and Improves Regional Segmental Function following Ischemia in Dogs: a Comparison with Propranolol

Celiprolol, propranolol or saline were administered to separate groups (n = 5-6) of anesthetized dogs in which a critical stenosis was applied to the circumflex coronary artery for 90 min and then reperfused for 30 min. Test drugs were administered at 30 min poststenosis and the effects on pH, regional function and endocardiogram were monitored. A reduction in coronary flow of 54 +/- 2% (n = 27) yielded marked increases in hydrogen ion concentration (H+) of 17 +/- 2 X 10(-8) and ischemic endocardial ST segment of 6 +/- 1 mV while ischemic segmental shortening decreased 75 +/- 9%. Heart rate, arterial pressure and normal regional function were not altered. Celiprolol 0.1 and 1 mg/kg, i.v., reversed the alterations in H+ and ischemic ST segment to prestenosis values while improving ischemic segmental shortening 20 and 38%, respectively, and not affecting heart rate. Propranolol 0.1 and 1 mg/kg, i.v., reversed the alterations in H+ and ischemic ST segment to prestenosis values while further decreasing ischemic segmental shortening 66 and 30%, respectively. Upon reperfusion, ischemic segmental shortening returned to prestenosis values in the group treated with celiprolol 1 mg/kg, i.v., while the propranolol- and saline-treated groups further decreased. It is concluded that celiprolol is efficacious in normalizing myocardial function and ischemia-induced electrophysiological changes following coronary artery stenosis.

The mechanism of pH-dependent hydrogen peroxide cytotoxicity in vitro

The present paper is concerned with the influence of hydrogen ion concentration and composition of the medium on clonogenic survival of epithelial cells exposed to hydrogen peroxide in vitro. The survival of cells incubated with H2O2 in phosphate-buffered saline at pH 6.5 was 1 x 10(-2) and increased abruptly to 9 x 10(-2) at pH 7.0. The pH dependence of the cytocidal effect was particularly conspicuous when Eagle's minimum essential medium (SFMEM) was used for cell exposure to H2O2: the survival was characterized by exponential pH dependence and varied from 1 x 10(-1) to 9 x 10(-1) for pH 6.5 and 7.5, respectively, with a superimposed sharp peak value of 9 x 10(-1) at pH 7.0. The enhanced pH dependence of the H2O2 cytotoxicity in SFMEM was found to result from the additive action of glucose and histidine present in this medium. Glucose alone protected the cells with the efficiency decreasing with increasing hydrogen ion concentration. Histidine was responsible for the intermediate maximum in the pH-dependent survival spectrum. In addition, the changes in cell survival were accompanied by pH-dependent release of GSSG from the exposed cells. The GSSG efflux was inhibited by glucose in the medium. The influence of glucose on both the pattern of cell survival and the associated GSSG release indicate that the glutathione peroxidase activity supported by the pentose phosphate pathway is crucial in cell protection against extracellular H2O2 toxicity.

Effects of acidification on mercury methylation, demethylation, and volatilization in sediments from an acid-susceptible lake.

The effect of experimental acidification on mercury methylation, demethylation, and volatilization was examined in surficial sediment samples from a weakly buffered northern Wisconsin lake. All mercury transformations were measured with radioisotopic tracers. Acidification of sediment pH with H2SO4, HCl, or HNO3 significantly decreased 203Hg(II) methylation. Acidification of pH 6.1 (ambient) sediments to pH 4.5 with either H2SO4 or HCl inhibited methylation by over 65%. The decreased methylation was due to the increased hydrogen ion concentration because methylation was not affected by concentrations of Na2SO4 or NaCl equimolar to the amount of acid added. Inhibition of methylation was observed even after prolonged acidification of sediments to pH 5.0 for up to 74 days. Acidification of sediments to pH 5.5, 4.5, and 3.5 with HNO3 resulted in a near complete inhibition of methylation at each pH. Similarly, the addition of equimolar amounts of NaNO3 resulted in a near complete inhibition of methylation, indicating that the inhibition was due to the nitrate ion rather than to the acidity. Demethylation of methyl mercury was not affected by pHs between 8.0 and 4.4, but sharply decreased below pH 4.4. Volatilization of 203Hg(II) from surface sediments was less than 2% of methylation activity and was not significantly different from that in killed sediments. This study indicated that acidification of sediments inhibits mercury methylation and that the observed increase in the mercury burdens in fish from low pH lakes is not due to increased production of methylmercury in sediments.

The total ionic status of muscle during intense exercise.

During intense exercise, the high rate of glycolysis results in a large accumulation of intracellular lactate (La-) and increased hydrogen ion concentration (H+]) (Spriet et al., 1985). High intracellular [H+] during heavy exercise has often been implicated as a cause of muscle fatigue. A number of loci for fatigue have been suggested: excitation-contraction coupling (Fabiato and Fabiato, 1978), control of glycolytic flux at the level of Phosphorylase (Chasiotis et al., 1983) and phosphofructokinase (Trivedi and Danforth, 1966) and impairment of ionic pumps and exchanges on the sarcoplasmic reticulum and sarcolemma (Nakamura and Schwartz, 1972).

Rates and mechanisms of the reactions of octacyanomolybdate(V) anion with L-cysteine, penicillamine and thioglycolic acid in aqueous acidic solutions

The rates and mechanisms of the reactions of octacyanomolybdate(V) anion with L-cysteine, penicillamine and thioglycolic acid have been studied in aqueous acidic solution and constant ionic strength I = 1.00 mol dm −3 (NaClO 4) for cysteine and I = 0.10 mol dm −3 (NaClO 4) for penicillamine and thioglycolic acid respectively. The reactions show a second order substrate dependence and the rates are found to decrease with increasing hydrogen ion concentration [H +]. This is attributed to the deprotonation of the −SH and −CO 2H groups in these thiols prior to electron-transfer. No evidence was found for the formation of an intermediate complex of significant stability. The reactions are interpreted in terms of outer-sphere mechanism.

Effects of lactic acid on astrocytes in primary culture.

Excessive tissue lactic acidosis is considered to be detrimental to the central nervous system (CNS) and may adversely affect recovery from anoxia, ischemia, trauma and epilepsy. Since astrocytes are believed to play a role in pH regulation in the CNS, we studied the effect of this acid on primary astrocyte cultures. Cells exposed to lactic acid showed chromatin clumping, an increase of lipid and dense bodies, a loss of polyribosomal clusters, slightly increased cytoplasmic lucency, swollen mitochondria and tangled intermediate filaments. These alterations progressed with lower pH and longer exposure. Irreversible changes occurred one to two hours after exposure at pH 6; after 30 to 60 minutes (min) at pH 5.5 and after ten to 30 min at pH 5. Comparable results were obtained with the use of other weak acids indicating that the observed changes were due to increased hydrogen ion concentration rather than secondary to lactate per se. Additionally, various concentrations of lactic acid adjusted to identical pH produced similar morphologic alterations. Thus, while lactic acid caused marked and at times irreversible alterations in astrocytes, severe and prolonged acidosis was required to produce such injurious effects. This relative resistance of astrocytes to acidosis is in keeping with their potential role in pH regulation in brain.