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1
Green, J., D. T. Yamaguchi, C. R. Kleeman, and S. Muallem. "Cytosolic pH regulation in osteoblasts. Regulation of anion exchange by intracellular pH and Ca2+ ions." Journal of General Physiology 95, no. 1 (1990): 121–45. http://dx.doi.org/10.1085/jgp.95.1.121.
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Measurements of cytosolic pH (pHi) 36Cl fluxes and free cytosolic Ca2+ concentration ([Ca2+]i) were performed in the clonal osteosarcoma cell line UMR-106 to characterize the kinetic properties of Cl-/HCO3- (OH-) exchange and its regulation by pHi and [Ca2+]i. Suspending cells in Cl(-)-free medium resulted in rapid cytosolic alkalinization from pHi 7.05 to approximately 7.42. Subsequently, the cytosol acidified to pHi 7.31. Extracellular HCO3- increased the rate and extent of cytosolic alkalinization and prevented the secondary acidification. Suspending alkalinized and Cl(-)-depleted cells in Cl(-)-containing solutions resulted in cytosolic acidification. All these pHi changes were inhibited by 4',4',-diisothiocyano-2,2'-stilbene disulfonic acid (DIDS) and H2DIDS, and were not affected by manipulation of the membrane potential. The pattern of extracellular Cl- dependency of the exchange process suggests that Cl- ions interact with a single saturable external site and HCO3- (OH-) complete with Cl- for binding to this site. The dependencies of both net anion exchange and Cl- self-exchange fluxes on pHi did not follow simple saturation kinetics. These findings suggest that the anion exchanger is regulated by intracellular HCO3- (OH-). A rise in [Ca2+]i, whether induced by stimulation of protein kinase C-activated Ca2+ channels, Ca2+ ionophore, or depolarization of the plasma membrane, resulted in cytosolic acidification with subsequent recovery from acidification. The Ca2+-activated acidification required the presence of Cl- in the medium, could be blocked by DIDS, and H2DIDS and was independent of the membrane potential. The subsequent recovery from acidification was absolutely dependent on the initial acidification, required the presence of Na+ in the medium, and was blocked by amiloride. Activation of protein kinase C without a change in [Ca2+]i did not alter pHi. Likewise, in H2DIDS-treated cells and in the absence of Cl-, an increase in [Ca2+]i did not activate the Na+/H+ exchanger in UMR-106 cells. These findings indicate that an increase in [Ca2+]i was sufficient to activate the Cl-/HCO3- exchanger, which results in the acidification of the cytosol. The accumulated H+ in the cytosol activated the Na+/H+ exchanger. Kinetic analysis of the anion exchange showed that at saturating intracellular OH-, a [Ca2+]i increase did not modify the properties of the extracellular site. A rise in [Ca2+]i increased the apparent affinity for intracellular OH- (or HCO3-) of both net anion and Cl- self exchange. These results indicate that [Ca2+]i modifies the interaction of intracellular OH- (or HCO3-) with the proposed regulatory site of the anion exchanger in UMR-106 cells.
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Feitkenhauer, H., and U. Meyer. "A new method for the fast determination of kinetic parameters in anaerobic digestion processes and application to textile wet processing wastewater." Water Science and Technology 48, no. 8 (2003): 203–10. http://dx.doi.org/10.2166/wst.2003.0470.
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A new method for the fast and efficient determination of the anaerobic degradability and for the calculation of kinetic parameters is proposed. It is based on the idea that monitoring of the acidification step in the anaerobic degradation cascade is sufficient, as the subsequent steps (acetogenesis, methanogenesis) are well known processes dependent on the intermediate concentrations and not on the original substrate used. The investigation of the acidification is subdivided into two steps. In the first step, biomass is adapted to the new substrate in a continuously operated bioreactor. The second step, the only step monitored, is the acidification of the substrate (or wastewater) in a batch experiment. Three different methods to monitor the acidification were tested: gas chromatography (offline), on-line titration and monitoring of the base consumption (direct titration). The results of these methods were compared to ÒtraditionalÓ batch tests. It is shown that the simplest method (direct titration) revealed the most important information. The investigated substrates were selected pollutants of textile wet processing wastewater.
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Sullivan, R., JD Griffin, J. Wright, et al. "Effects of recombinant human granulocyte-macrophage colony-stimulating factor on intracellular pH in mature granulocytes." Blood 72, no. 5 (1988): 1665–73. http://dx.doi.org/10.1182/blood.v72.5.1665.1665.
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Abstract We studied the effects of recombinant human granulocyte-macrophage colony-stimulating factor (GM-CSFrh) on the internal pH of granulocytes using the fluorescent probe BCECF. GM-CSFrh did not directly alter the resting pH of granulocytes isolated from the peripheral blood; however, when the cells were preincubated for 90 minutes with the growth factor and then activated with the chemotactic peptide N-formyl met leu phe (fMLP), they exhibited both an acceleration in the initial rate of acidification and a marked delay in realkalinization. The kinetic changes both in initial acidification and in subsequent realkalinization induced by GM-CSFrh priming were not prevented by protein synthesis inhibitors and were observed in granulocytes harvested from patients with both sex-linked and autosomal recessive chronic granulomatous disease (CGD). By directly quantitating H+ ion secretion, by monitoring the effects of sodium repletion on intracellular pH, and through use of the sodium channel inhibitors amiloride and dimethyl amiloride and the Na+/K+-ATPase inhibitor ouabain, we showed that the altered kinetics of intracellular acidification and alkalinization following fMLP stimulation of GM-CSFrh- primed granulocytes could not be accounted for by changes in transmembrane proton exportation regulated by the Na+/H+ antiport channel. Although the initial acidification following fMLP was abrogated by 2-deoxy-D-glucose in both GM-CSFrh-pretreated and GM-CSFrh- untreated granulocytes, retardation of the subsequent phase of alkalinization was observed in GM-CSFrh-primed cells even after inhibition of both glycolytic and mitochondrial metabolism. Our data indicate that the increased cytosolic acidification following fMLP stimulation in granulocytes “primed” with GM-CSFrh does not result from disordered proton excretion but instead from increased release of intracellular free acid which is only partially coupled to glucose catabolism or to the generation of superoxide anion (O2-).
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Sullivan, R., JD Griffin, J. Wright, et al. "Effects of recombinant human granulocyte-macrophage colony-stimulating factor on intracellular pH in mature granulocytes." Blood 72, no. 5 (1988): 1665–73. http://dx.doi.org/10.1182/blood.v72.5.1665.bloodjournal7251665.
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We studied the effects of recombinant human granulocyte-macrophage colony-stimulating factor (GM-CSFrh) on the internal pH of granulocytes using the fluorescent probe BCECF. GM-CSFrh did not directly alter the resting pH of granulocytes isolated from the peripheral blood; however, when the cells were preincubated for 90 minutes with the growth factor and then activated with the chemotactic peptide N-formyl met leu phe (fMLP), they exhibited both an acceleration in the initial rate of acidification and a marked delay in realkalinization. The kinetic changes both in initial acidification and in subsequent realkalinization induced by GM-CSFrh priming were not prevented by protein synthesis inhibitors and were observed in granulocytes harvested from patients with both sex-linked and autosomal recessive chronic granulomatous disease (CGD). By directly quantitating H+ ion secretion, by monitoring the effects of sodium repletion on intracellular pH, and through use of the sodium channel inhibitors amiloride and dimethyl amiloride and the Na+/K+-ATPase inhibitor ouabain, we showed that the altered kinetics of intracellular acidification and alkalinization following fMLP stimulation of GM-CSFrh- primed granulocytes could not be accounted for by changes in transmembrane proton exportation regulated by the Na+/H+ antiport channel. Although the initial acidification following fMLP was abrogated by 2-deoxy-D-glucose in both GM-CSFrh-pretreated and GM-CSFrh- untreated granulocytes, retardation of the subsequent phase of alkalinization was observed in GM-CSFrh-primed cells even after inhibition of both glycolytic and mitochondrial metabolism. Our data indicate that the increased cytosolic acidification following fMLP stimulation in granulocytes “primed” with GM-CSFrh does not result from disordered proton excretion but instead from increased release of intracellular free acid which is only partially coupled to glucose catabolism or to the generation of superoxide anion (O2-).
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Hoffmann, G., Y. Ko, A. Sachinidis, et al. "Kinetics of Na+/H+ exchange in vascular smooth muscle cells from WKY and SHR: effects of phorbol ester." American Journal of Physiology-Cell Physiology 268, no. 1 (1995): C14—C20. http://dx.doi.org/10.1152/ajpcell.1995.268.1.c14.
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The kinetic properties of Na+/H+ exchange were investigated in vascular smooth muscle cells (VSMC) in culture from normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR). Antiport activity was measured in 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein-loaded cells after nigericin-induced cytosolic acidification. Studies were performed without (control) and with pretreatment of the cells with phorbol 12-myristate 13-acetate (PMA; 200 nM). Na+/H+ exchange markedly differed between the two strains with lower Hill coefficients [1.56 +/- 0.17 (SE) vs. 2.62 +/- 0.36] and higher maximal activity (Vmax) values (55.85 +/- 5.24 vs. 31.11 +/- 2.38 mmol H+.l-1.min-1) in SHR compared with WKY cell lines. PMA markedly altered the antiport kinetics in WKY VSMC with a decrease in the Hill coefficient (1.75 +/- 0.14) without affecting Vmax (31.88 +/- 1.55 mmol H+.l-1.min-1). In VSMC from SHR, PMA had no effect on the kinetic variables investigated. Thus two kinetic abnormalities are present with respect to Na+/H+ antiport activity in VSMC from SHR compared with WKY, i.e., increased Vmax and decreased Hill coefficient. The observation that PMA does not affect the kinetics of the Na+/H+ antiport in VSMC from SHR suggests a marked degree of antiporter prestimulation in this animal model of genetic hypertension.
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Morano, K. A., and D. J. Klionsky. "Differential effects of compartment deacidification on the targeting of membrane and soluble proteins to the vacuole in yeast." Journal of Cell Science 107, no. 10 (1994): 2813–24. http://dx.doi.org/10.1242/jcs.107.10.2813.
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Lysosomal/vacuolar protein targeting is dependent on compartment acidification. In yeast, sorting of soluble vacuolar proteins such as carboxypeptidase Y is sensitive to acute changes in vacuolar pH. In contrast, the vacuolar membrane protein alkaline phosphatase is missorted only under conditions of chronic deacidification. We have undertaken a temporal analysis to define further the relationship between compartment acidification and sorting of soluble and membrane vacuolar proteins. Depletion of either the Vma3p or Vma4p subunits of the yeast vacuolar ATPase over time resulted in loss of vacuolar ATPase activity and vacuolar acidification. A kinetic delay in processing of carboxypeptidase Y occurred concomitant with these physiological changes while transport of alkaline phosphatase remained unaffected. Carboxypeptidase S, another vacuolar hydrolase that transits through the secretory pathway as an integral membrane protein, displayed a pH sensitivity similar to that of soluble vacuolar proteins. These results indicate that compartment acidification is tightly coupled to efficient targeting of proteins to the vacuole and that there may be multiple distinct mechanisms for targeting of vacuolar membrane proteins.
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Mikeš, Vladimír. "A Kinetic Method for Determination of the Biosynthetic Activity of Glutamine Synthetase." Collection of Czechoslovak Chemical Communications 57, no. 10 (1992): 2174–80. http://dx.doi.org/10.1135/cccc19922174.
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In the present paper a rapid and simple kinetic method for determination of the biosynthetic activity of glutamine synthetase is described based upon the decomposition of ATP, accompanied with acidification of the slightly buffered medium which can be measured by means of a pH indicator. The method can be used for determination of the enzyme activity in whole permeabilized cells, crude cell extracts, as well as for kinetic studies and studies of the effects of inhibitors on the purified glutamine synthetase.
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Sun, Xiu Yun, Can Chen, Wei Wang, Jin You Shen, Jian Sheng Li, and Lian Jun Wang. "Acidification of Waste Activated Sludge during Mesophilic Phase in Two Phases Anaerobic Digestion System." Advanced Materials Research 610-613 (December 2012): 2416–20. http://dx.doi.org/10.4028/www.scientific.net/amr.610-613.2416.
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Waste activated sludge is always used to product methane by two phases anaerobic digestion, but fermenting to accumulate VFAs has seldom reported. This paper deals with the effects of pH value, adding ratio and hydraulic retention time (HRT) on WAS acidification during mesophilic phase in two phases anaerobic digestion (TPAD) system through batch experiments. In order to gain the most amount of VFAs for providing more carbon source, the optimal conditions for WAS mesophilic anaerobic digestion observed in this study are pH=7, adding ratio=12.5%, HRT=4d and TC/TNb value=1.7~2.0. Finally, we analyzed acid production kinetic under the optimal conditions. It can be inferred that the performance of WAS acidification is sensitive to operating conditions.
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Porzionato, Natalia, Mariangeles Mellota, Roberto Candal, and Gustavo Curutchet. "Acid Drainage and Metal Bioleaching by Redox Potencial Changes in Heavy Polluted Fluvial Sediments." Advanced Materials Research 825 (October 2013): 496–99. http://dx.doi.org/10.4028/www.scientific.net/amr.825.496.
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Sediments from polluted urban streams act as a sink of contaminants. The high content of organic matter and sulphides makes the system appropriate for binding heavy metals. However, changes in the redox potential leads to processes in which sediments acts like a low sulphidic ore in an oxidizing environment, and could generate acid drainages. Human and not human disturbances of the sediments could derive in its oxidation catalyzed by sulphur oxidizing bacteria (SOB). This process leads to acidification and metal release. In this study we analyze the acidification potential of anaerobic sediments of polluted streams near Buenos Aires with static and kinetic methods. The results remark the necessity to consider this process before any sediment management action.
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Ma, Jingwei, Shanbiao Xie, Liang Yu, et al. "pH shaped kinetic characteristics and microbial community of food waste hydrolysis and acidification." Biochemical Engineering Journal 146 (June 2019): 52–59. http://dx.doi.org/10.1016/j.bej.2019.03.004.
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Saucedo-Casta�eda, G., and J. G�mez. "The effect of glucose and ammonium sulfate on kinetic acidification by heterogeneous mixed culture." Biotechnology Letters 11, no. 2 (1989): 121–24. http://dx.doi.org/10.1007/bf01192187.
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Trost, N., and W. Metzler. "A kinetic model for soil acidification in its context with the associated equilibrium model." Applied Mathematical Modelling 12, no. 3 (1988): 256–61. http://dx.doi.org/10.1016/0307-904x(88)90031-5.
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Hendriks, I. E., Y. S. Olsen, L. Ramajo, et al. "Photosynthetic activity buffers ocean acidification in seagrass meadows." Biogeosciences 11, no. 2 (2014): 333–46. http://dx.doi.org/10.5194/bg-11-333-2014.
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Abstract. Macrophytes growing in shallow coastal zones characterised by intense metabolic activity have the capacity to modify pH within their canopy and beyond. We observed diel pH changes in shallow (5–12 m) seagrass (Posidonia oceanica) meadows spanning 0.06 pH units in September to 0.24 units in June. The carbonate system (pH, DIC, and aragonite saturation state (ΩAr)) and O2 within the meadows displayed strong diel variability driven by primary productivity, and changes in chemistry were related to structural parameters of the meadow, in particular, the leaf surface area available for photosynthesis (LAI). LAI was positively correlated to mean, max and range pHNBS and max and range ΩAr. In June, vertical mixing (as Turbulent Kinetic Energy) influenced max and min ΩAr, while in September there was no effect of hydrodynamics on the carbonate system within the canopy. Max and range ΩAr within the meadow showed a positive trend with the calcium carbonate load of the leaves, pointing to a possible link between structural parameters, ΩAr and carbonate deposition. Calcifying organisms, e.g. epiphytes with carbonate skeletons, may benefit from the modification of the carbonate system by the meadow. There is, however, concern for the ability of seagrasses to provide modifications of similar importance in the future. The predicted decline of seagrass meadows may alter the scope for alteration of pH within a seagrass meadow and in the water column above the meadow, particularly if shoot density and biomass decline, on which LAI is based. Organisms associated with seagrass communities may therefore suffer from the loss of pH buffering capacity in degraded meadows.
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Du, Juan, Yuning He, Pingli Liu, Yigang Liu, Xianghai Meng, and Liqiang Zhao. "Corrosion inhibition of N80 steel in 10% HCl + 8% HBF4solution." Anti-Corrosion Methods and Materials 66, no. 1 (2019): 1–10. http://dx.doi.org/10.1108/acmm-01-2018-1883.
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PurposeThis paper aims to analyze the corrosion and corrosion inhibition of N80 in 10 per cent HCl + 8 per cent fluoroboric acid (HBF4) solution for acidizing operation.Design/methodology/approachThe corrosion rate, kinetic parameters (Ea, A) and thermodynamic parameters (ΔH, ΔS) of N80 steel in fresh acid and spent acid, 10 per cent HCl + 8 per cent HBF4, 10 per cent HCl and 8 per cent HBF4solutions were calculated through immersion tests. The corrosion and inhibition properties were studied through X-ray diffraction and electrochemical measurements. The corrosion morphology of the corrosion product was examined by scanning electron microscopy (SEM).FindingsThe results demonstrated that the spent acid was the main cause of acidification corrosion, and the HBF4would cause serious corrosion to N80 steel. The results showed that the N80 steel was more seriously corroded in the spent acid than in fresh acid, and the hydrolysis of HBF4accelerates the dissolution process of N80 steel anode to control the corrosion reaction. The results showed that the acidification will definitely cause serious corrosion to the oil tube; therefore, necessary anti-corrosion measures must be taken in the acidification process.Originality/valueThe results showed that acidizing the formation with 10 per cent HCl + 8 per cent HBF4will definitely cause serious corrosion to the oil tube, especially when the spent acid flows back. Therefore, necessary anti-corrosion measures must be taken in the acidification process, especially in the spent acid flowback stage.
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Spinnler, Henry E., and Georges Corrieu. "Automatic method to quantify starter activity based on pH measurement." Journal of Dairy Research 56, no. 5 (1989): 755–64. http://dx.doi.org/10.1017/s0022029900029332.
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SummaryA new method for measuring the activity of mesophilic and thermophilic lactic acid bacteria is proposed based on measuring the pH of cultures at extremely short intervals (30–90 s) during growth and calculating several kinetic parameters, i.e. the maximum acidification rate (Vm), the time and pH at which Vm occurred, the time or pH range during which the observed rates were greater than Vm/2. These were easily calculated by coupling the pH meter to a microcomputer.
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Liu, Xin Yuan, Jing Jing Wang, Jia Min Nie, Nan Wu, Fang Yang, and Ren Jie Yang. "Biogas production of Chicken Manure by Two-stage fermentation process." E3S Web of Conferences 38 (2018): 01048. http://dx.doi.org/10.1051/e3sconf/20183801048.
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This paper performs a batch experiment for pre-acidification treatment and methane production from chicken manure by the two-stage anaerobic fermentation process. Results shows that the acetate was the main component in volatile fatty acids produced at the end of pre-acidification stage, accounting for 68% of the total amount. The daily biogas production experienced three peak period in methane production stage, and the methane content reached 60% in the second period and then slowly reduced to 44.5% in the third period. The cumulative methane production was fitted by modified Gompertz equation, and the kinetic parameters of the methane production potential, the maximum methane production rate and lag phase time were 345.2 ml, 0.948 ml/h and 343.5 h, respectively. The methane yield of 183 ml-CH4/g-VSremoved during the methane production stage and VS removal efficiency of 52.7% for the whole fermentation process were achieved.
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Hendriks, I. E., Y. S. Olsen, L. Ramajo, et al. "Photosynthetic activity buffers ocean acidification in seagrass meadows." Biogeosciences Discussions 10, no. 7 (2013): 12313–46. http://dx.doi.org/10.5194/bgd-10-12313-2013.
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Abstract. Macrophytes growing in shallow coastal zones characterized by intense metabolic activity have the capacity to modify pH within their canopy and beyond. We observed diel pH ranges is in shallow (5–12 m) seagrass (Posidonia oceanica) meadows from 0.06 pH units in September to 0.24 units in June. The carbonate system (pH, DIC, and aragonite saturation state (ΩAr) and O2 within the meadows displayed strong diel variability driven by primary productivity, and changes in chemistry were related to structural parameters of the meadow, in particular, the leaf surface area available for photosynthesis (LAI). LAI was positively correlated to mean and max pHNBS and max ΩAr. Oxygen production positively influenced the range and maximum pHNBS and the range of ΩAr. In June, vertical mixing (as Turbulent Kinetic Energy) influenced ΩAr, while in September there was no effect of hydrodynamics on the carbonate system within the canopy. ΩAr was positively correlated with the calcium carbonate load of the leaves, demonstrating a direct link between structural parameters, ΩAr and carbonate deposition. There was a direct relationship between ΩAr, influenced directly by meadow LAI, and CaCO3 content of the leaves. Therefore, calcifying organisms, e.g. epiphytes with carbonate skeletons, might benefit from the modification of the carbonate system by the meadow. The meadow might be capable of providing refugia for calcifiers by increasing pH and ΩAr through metabolic activity. There is, however, concern for the ability of seagrasses to provide this refugia function in the future. The predicted decline of seagrass meadows may alter the scope for alteration of pH within a seagrass meadow and in the water column above the meadow, particularly if shoot density and biomass decline, both strongly linked to LAI. Organisms associated with seagrass communities may therefore suffer from the loss of pH buffering capacity in degraded meadows.
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Husted, R. F., and J. L. Fischer. "Selectivity of basolateral anion exchange in the acidification pathway of turtle bladder." American Journal of Physiology-Renal Physiology 252, no. 6 (1987): F1022—F1027. http://dx.doi.org/10.1152/ajprenal.1987.252.6.f1022.
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The turtle urinary bladder in vitro acidifies the solution bathing its luminal surface. Protons are actively extruded across the apical membrane by an H+-ATPase. Bicarbonate ion exits the cell across the basolateral membrane via a stilbene-sensitive, anion exchange for chloride. Chloride then exits the cell via a conductive pathway. The present studies were undertaken to define the specificity of the basolateral anion exchange mechanism for chloride. Turtle bladders were mounted on chambers in vitro, short-circuited, and treated with ouabain. The current remaining after inhibition of sodium transport was used to measure the acidification rate. Ion replacement studies with bromide, isethionate, sulfate, and nitrate indicated that only bromide supported acidification at rates comparable to chloride. In separate experiments, kinetic analysis of anion interaction with the exchanger indicates that maximal acidification rates decrease in the order: Cl greater than Br greater than SO4 greater than methyl sulfate = gluconate. The affinity of the exchanger decreases in the order: Cl greater than SO4 greater than Br greater than HCO3 greater than methylsulfate greater than gluconate. These selectivity sequences indicate "strong" interaction of the anions with the selectivity site. The differences in position of the polyatomic anions in the two sequences indicates that the "binding" site is accessible but that transport is limited by steric factors.
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Regenberg, A., B. Schneider, and R. Gangstø. "Sensitivity of pelagic CaCO<sub>3</sub> dissolution to ocean acidification in an ocean biogeochemical model." Biogeosciences Discussions 10, no. 7 (2013): 11343–73. http://dx.doi.org/10.5194/bgd-10-11343-2013.
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Abstract. In ocean biogeochemical models pelagic CaCO3 dissolution is usually calculated as R = k * Sn, where k is the dissolution rate constant transforming S, the degree of (under-) saturation of seawater with respect to CaCO3, into a time dependent rate R, and n is the reaction rate order. Generally, there are two ways to define the saturation state of seawater with respect to CaCO3: (1) Δ[CO32−], which reflects the difference between the in-situ carbonate ion concentration and the saturation concentration, and (2) Ω, which is approximated by the ratio of in-situ carbonate ion concentration over the saturation concentration. Although describing the same phenomenon, the deviation from equilibrium, both expressions are not equally applicable for the calculation of CaCO3 dissolution in the ocean across pressure gradients, as they differ in their sensitivity to ocean acidification (change of [CO32−]) over depth. In the present study we use a marine biogeochemical model to test the sensitivity of pelagic CaCO3 dissolution to ocean acidification (1–4 × CO2 + stabilization), exploring the possible parameter space for CaCO3 dissolution kinetics as given in the literature. We find that at the millennial time scale there is a wide range of CaCO3 particle flux attenuation into the ocean interior (e.g. a reduction of −55 to −85% at 1000 m depth), which means that there are significant differences in the impact on particle ballasting, depending on the kinetic expression applied.
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Hofmann, A. F., E. T. Peltzer, and P. G. Brewer. "Kinetic bottlenecks to chemical exchange rates for deep-sea animals – Part 2: Carbon Dioxide." Biogeosciences 10, no. 4 (2013): 2409–25. http://dx.doi.org/10.5194/bg-10-2409-2013.
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Abstract. Increased ocean acidification from fossil fuel CO2 invasion, from temperature-driven changes in respiration, and from possible leakage from sub-seabed geologic CO2 disposal has aroused concern over the impacts of elevated CO2 concentrations on marine life. Discussion of these impacts has so far focused only on changes in the oceanic bulk fluid properties (ΔpH, Δ[∑ CO2], etc.) as the critical variable and with a major focus on carbonate shell formation. Here we describe the rate problem for animals that must export CO2 at about the same rate at which O2 is consumed. We analyse the basic properties controlling CO2 export within the diffusive boundary layer around marine animals in an ocean changing in temperature (T) and CO2 concentration in order to compare the challenges posed by O2 uptake under stress with the equivalent problem of CO2 expulsion. The problem is more complex than that for a non-reactive gas, since with CO2 the influence of the seawater carbonate acid-base system needs to be considered. These reactions significantly facilitate CO2 efflux compared to O2 intake at equal temperature, pressure and fluid flow rate under typical oceanic concentrations. The effect of these reactions can be described by an enhancement factor, similar to that widely used for CO2 invasion at the sea surface. While organisms do need to actively regulate flow over their surface to thin the boundary layer to take up enough O2, this seems to be not necessary to facilitate CO2 efflux. Instead, the main impacts of rising oceanic CO2 will most likely be those associated with classical ocean acidification science. Regionally, as with O2, the combination of T, P and pH/pCO2 creates a zone of maximum CO2 stress at around 1000 m depth.
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Gul, Latife Betul, Ahmet Hilmi Con, and Osman Gul. "Storage stability and sourdough acidification kinetic of freeze-dried Lactobacillus curvatus N19 under optimized cryoprotectant formulation." Cryobiology 96 (October 2020): 122–29. http://dx.doi.org/10.1016/j.cryobiol.2020.07.007.
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Matangue, Mario Tauzene Afonso, and Claudio Milton Montenegro Campos. "Determination of kinetic parameters of an upflow anaerobic sludge blanket reactor (uasb), treating swine wastewater." Ciência e Agrotecnologia 35, no. 6 (2011): 1204–10. http://dx.doi.org/10.1590/s1413-70542011000600022.
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This research aimed to estimate the kinetic parameters of a UASB reactor treating swine wastewater from farming. The system consisted of: a degritter with a triangular-notch weir in order to measure the flow; a static sieve; an acidification/equalization tank (AET); ABR and UASB reactors; a settling tank; two infiltration ponds and a greenhouse for fertirrigation. The hydraulic retention times (HRT) adopted for the UASB reactor, were: 8.0; 9.6; 8.4; 6.0 and 4.8 hours. The operational temperature was 23.4º C±1.5º C. The analyzed physical-chemical parameters were temperature COD (total and filtered), BOD (total and filtered), total volatile solids (affluent, effluent and of the reactor's profile sludge), flow rate and nutrients (N and P). The kinetic coefficients estimated were: growth coefficient Y=0.091 mg tCOD mg TVS-1.d-1, decay coefficient Kd=0.01 d-1; concentration of limiting substrate Ks=282.5 tCOD mg L-1 and maximum growth rate µmax= 0.051 d-1. For data validation, simple linear regression models were applied and their interaction verified with a "t" test. The results matched with the those found in other references for the same type of kinetic studies.
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Waldbusser, George G., Burke Hales, and Brian A. Haley. "Calcium carbonate saturation state: on myths and this or that stories." ICES Journal of Marine Science 73, no. 3 (2015): 563–68. http://dx.doi.org/10.1093/icesjms/fsv174.
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Abstract In a recent opinion article titled “The Omega Myth”, Cyronak et al. provide a series of arguments as to why saturation state should not matter to marine calcifiers. In sections of their article, they highlight several aspects of our published work, and unfortunately appear to misinterpret the foundation for the kinetic–energetic hypothesis we have laid out previously. While we are in full agreement that omega sensitivity is not a substrate limitation issue, we more clearly detail below what a kinetic limitation means and why it is different from a substrate limitation. The kinetic argument we have previously presented highlights how the energetic cost of calcification increases with a decreasing saturation state (or omega). We then highlight several issues with a bicarbonate/proton flux model applied to newly developing marine bivalve larvae, and discuss how a bicarbonate/proton flux and omega-based sensitivity model do not have to be mutually exclusive. Our intent with this comment is to clarify the points raised by Cyronak et al. about our work, and help to move the thinking past dialectic debate towards a more synthetic view on ocean acidification impacts on marine calcifiers.
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WOLOSKER, Herman, Joao B. T. ROCHA, Simone ENGELENDER, Rogerio PANIZZUTTI, Joari De MIRANDA, and Leopoldo de MEIS. "Sarco/endoplasmic reticulum Ca2+-ATPase isoforms: diverse responses to acidosis." Biochemical Journal 321, no. 2 (1997): 545–50. http://dx.doi.org/10.1042/bj3210545.
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The effects of acidic pH on the kinetics of Ca2+-ATPase isoforms from intracellular membranes of skeletal muscle, cardiac muscle, cerebellum and blood platelets were studied. At neutral pH, all four Ca2+-ATPase isoforms exhibited similar Ca2+-concentration requirements for half-maximal rates of Ca2+ uptake and ATP hydrolysis. A decrease in the pH from 7.0 to 6.0 promoted a decrease in both the apparent affinity for Ca2+ [increasing half-maximal activation (K0.5)] and the maximal velocity (Vmax) of Ca2+ uptake. With skeletal muscle vesicles these effects were 5 to 10 times smaller than those observed with all the other isoforms. Acidification of the medium from pH 7.0 to 6.5 caused the release of Ca2+ from loaded vesicles and a decrease in the amount of Ca2+ retained by the vesicles at the steady state. With the vesicles derived from skeletal muscle these effects were smaller than for vesicles derived from other tissues. The rate of passive Ca2+ efflux from skeletal and cardiac muscle vesicles, loaded with Ca2+ and diluted in a medium containing none of the ligands of Ca2+-ATPase, was the same at pH 7.0 and 6.0. In contrast, the rate of Ca2+ efflux from cerebellar and platelet vesicles increased 2-fold after acidification of the medium. The effects of DMSO, Mg2+ with Pi and arsenate on the rate of Ca2+ efflux varied among the different preparations tested. The differences became more pronounced when the pH of the medium was decreased from 7.0 to 6.0. It is proposed that the kinetic differences among the Ca2+-ATPase isoforms may reflect different adaptations to cellular acidosis, such as that which occurs during ischaemia.
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Vallega, G. A., M. L. Canessa, B. C. Berk, T. A. Brock, and R. W. Alexander. "Vascular smooth muscle Na+-H+ exchanger kinetics and its activation by angiotensin II." American Journal of Physiology-Cell Physiology 254, no. 6 (1988): C751—C758. http://dx.doi.org/10.1152/ajpcell.1988.254.6.c751.
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We have studied the kinetic properties of basal and angiotensin II (ANG II)-stimulated Na+-H+ exchange in cultured rat aortic smooth muscle cells. Initial rates of 22Na+ influx were measured in the presence of ouabain (1 mM) and bumetanide (0.1 mM) with and without amiloride after intracellular acidification by preincubation in Na-free media. The kinetics of amiloride (100 microM)-sensitive Na+ influx were studied under the following conditions: 1) constant intracellular pH (pHi; 6.8) and varying external Na+ (Na+o), which gave a Km of 23.6 +/- 2.0 (SD, n = 3) mM and a maximum velocity (Vmax) of 25 nmol.mg protein-1.min-1 (varying the amiloride concentration gave a Ki of 22 microM for inhibition under these conditions); and 2) constant Na+o (100 mM) and varying pHi (from 7.4 to 6.2), which indicated that amiloride-sensitive Na+ influx was stimulated by cell acidification when an outward H+ gradient was imposed. ANG II-stimulated amiloride-sensitive Na+ influx for up to 30 min with a half-maximal activation 10(-8) M. The pHi dependence from cell pH (pHi 7.2-6.2) of amiloride-sensitive Na+ influx stimulated by ANG II was similar to that of the basal values, a finding indicating that ANG II did not change the affinity of Na+-H+ exchange for intracellular H+. However, at pHi 6.8, ANG II increased the Vmax of amiloride-sensitive Na+ influx from 25 to 33 nmol.mg protein-1.min-1 and markedly decreased the Km for Na+o from 23.6 +/- 7.4 to 3.7 (SD, n = 4; P less than 0.005) mM.(ABSTRACT TRUNCATED AT 250 WORDS)
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Vargas-Uscategui, Ramiro, Anthony Arenas-Clavijo, and Juan Sebastian Ramírez-Navas. "Efecto del proceso de acidificación sobre el color de queso cottage." Agronomía Mesoamericana 28, no. 3 (2017): 677. http://dx.doi.org/10.15517/ma.v28i3.22876.
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The objective of this study was to evaluate the color change of cottage cheese made with different processes of acidification (enzymatic and chemical) over time. The research was conducted at Universidad del Valle (Cali, Colombia) laboratories, between 2014 and 2015. Microbial rennet and lactic culture (CC) were used for enzymatic coagulation method (control cheese), and solutions of citric acid (CA) and phosphoric acid (PA) were used for the chemical method. The physicochemical properties were determined, and color behavior was analyzed over nine days of storage. Significant differences in acidity and moisture for the three coagulants were found. In the color plane, it was observed that the final and initial points of the coordinates a * and b * are close together; changes in color were mostly due to changes in brightness. The speed at which brightness decreased in the three cheeses matches kinetics order to zero and one. The first order kinetics displayed in higher values of linear correlation coefficients (R), AC: 0.8410 ± 0.0533; AF: 0.8390 ± 0.0847, and CC: 0.8717 ± 0.0256. The kinetics of change in color also adjusted correctly to zero and the first order kinetic model; that is, no significant difference (p <0.05) between these results. However, the speed of color change for the three cheeses had a slightly higher setting for zero order kinetics, as evidenced by the linear correlation coefficient (R) results, AC: 0.8800 ± 0.0205; AF: 0.8543 ± 0.0099, and CC: 0.7982 ± 0.0605.
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Viollier, Patrick H., Wolfgang Minas, Glenn E. Dale, Marc Folcher, and Charles J. Thompson. "Role of Acid Metabolism in Streptomyces coelicolor Morphological Differentiation and Antibiotic Biosynthesis." Journal of Bacteriology 183, no. 10 (2001): 3184–92. http://dx.doi.org/10.1128/jb.183.10.3184-3192.2001.
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ABSTRACT Studies of citrate synthase (CitA) were carried out to investigate its role in morphological development and biosynthesis of antibiotics in Streptomyces coelicolor. Purification of CitA, the major vegetative enzyme activity, allowed characterization of its kinetic properties. The apparent K m values of CitA for acetyl coenzyme A (acetyl-CoA) (32 μM) and oxaloacetate (17 μM) were similar to those of citrate synthases from other gram-positive bacteria and eukaryotes. CitA was not strongly inhibited by various allosteric feedback inhibitors (NAD+, NADH, ATP, ADP, isocitrate, or α-ketoglutarate). The corresponding gene (citA) was cloned and sequenced, allowing construction of a citA mutant (BZ2). BZ2 was a glutamate auxotroph, indicating that citA encoded the major citrate synthase allowing flow of acetyl-CoA into the tricarboxylic acid (TCA) cycle. Interruption of aerobic TCA cycle-based metabolism resulted in acidification of the medium and defects in morphological differentiation and antibiotic biosynthesis. These developmental defects of the citA mutant were in part due to a glucose-dependent medium acidification that was also exhibited by some other bald mutants. Unlike other acidogenic bald strains,citA and bldJ mutants were able to produce aerial mycelia and pigments when the medium was buffered sufficiently to maintain neutrality. Extracellular complementation studies suggested that citA defines a new stage of theStreptomyces developmental cascade.
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Bendayan, R., B. Lo, and M. Silverman. "Characterization of cimetidine transport in LLCPK1 cells." Journal of the American Society of Nephrology 5, no. 1 (1994): 75–84. http://dx.doi.org/10.1681/asn.v5175.
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In this study, cimetidine uptake and its regulation by LLCPK1 monolayers were investigated. Uptake was temperature dependent with kinetic and specificity characteristics typical of a carrier-mediated mechanism. With cimetidine uptake in the presence of an excess concentration of the potent inhibitor quinidine as a measure of nonspecific transport, the estimated kinetic parameters for cimetidine uptake at 37 degrees C under steady-state conditions are Km = 32.3 +/- 6.4 microM and Vmax = 20.2 +/- 2.1 pmol/mg per minute. Amiloride, quinidine, and quinine inhibited cimetidine uptake, whereas N1-methylnicotinamide, tetraethylammonium, and guanidine did not. The uptake of cimetidine was increased in the presence of a cell-->lumen H+ gradient, consistent with the behavior of a cimetidine-H+ antiport system. Furthermore, the activity of both the Na(+)-H+ exchanger and H(+)-ATPase acted to dissipate the cell-->lumen H+ gradient, thereby decreasing net cimetidine transport. These results suggest that there is a cimetidine-H+ exchange system in LLCPK1 cells and that the net secretion of organic base in vivo may be regulated by luminal acidification mechanisms.
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Verri, T., M. Maffia, A. Danieli, et al. "Characterisation of the H(+)/peptide cotransporter of eel intestinal brush-border membranes." Journal of Experimental Biology 203, no. 19 (2000): 2991–3001. http://dx.doi.org/10.1242/jeb.203.19.2991.
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H(+)/peptide cotransport in brush-border membrane vesicles (BBMVs) from eel (Anguilla anguilla) intestine was studied by measuring d-[(3)H]-phenylalanyl-l-alanine uptake and by monitoring peptide-dependent intravesicular acidification using the pH-sensitive dye Acridine Orange. d-[(3)H]-phenylalanyl-l-alanine influx was greatly stimulated by an inside-negative membrane potential and enhanced by an inwardly directed H(+) gradient. In parallel, vesicular H(+) influx was significantly increased in the presence of extravesicular d-phenylalanyl-l-alanine or a series of glycyl and l-prolyl peptides. H(+)/peptide cotransport displayed saturable kinetics involving a single carrier system with apparent substrate affinities of 0.9-2.6 mmol l(−1) depending on the particular peptide. All substrates tested competed with this system. Pre-incubation of BBMVs with dipeptides prevented diethylpyrocarbonate inhibition of transport activity, suggesting that the substrates mask histidine residues involved in the catalytic function of the transporter. Using human PepT1-specific primers, a reverse transcription-polymerase chain reaction (RT-PCR) signal was detected in eel intestine. Our results suggest that, in eel intestine, a brush-border membrane ‘low-affinity’-type H(+)/peptide cotransport system is present that shares kinetic features with the mammalian intestinal PepT1-type transporters.
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Le Feunteun, Steven, and François Mariette. "Effects of Acidification with and without Rennet on a Concentrated Casein System: A Kinetic NMR Probe Diffusion Study." Macromolecules 41, no. 6 (2008): 2079–86. http://dx.doi.org/10.1021/ma702248z.
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Mestres, C., T. C. Nguyen, L. Adinsi, J. Hounhouigan, G. Fliedel, and G. Loiseau. "The interaction between starch hydrolysis and acidification kinetic determines the quality of a malted and fermented sorghum beverage." Journal of Cereal Science 63 (May 2015): 8–13. http://dx.doi.org/10.1016/j.jcs.2015.02.004.
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TANAKA, Takuji, and Rickey Y. YADA. "Expression of soluble cloned porcine pepsinogen A in Escherichia coli." Biochemical Journal 315, no. 2 (1996): 443–46. http://dx.doi.org/10.1042/bj3150443.
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A system for the production of soluble porcine pepsinogen A (EC 3.4.23.1) was developed by fusing the pepsinogen and thioredoxin genes and then expressing the fused product (Trx-PG) in Escherichia coli. The expressed fusion protein was purified using a combination of ion-exchange and hydrophobic chromatography. Trypsin digestion of the fusion protein yielded pepsinogen which was one residue longer than the intrinsic length. Acidification of either the fusion protein or pepsinogen (tryptic digestion of Trx-PG) yielded recombinant pepsin A (r-pepsin). When compared with commercial porcine pepsin A, r-pepsin had similar milk-clotting and proteolytic activities, kinetic parameters and pH dependency. The above results indicate that an expression system was developed which yielded fully active soluble pepsin(ogen) from Escherichia coli.
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Artavanis-Tsakonas, Katerina, Pia V. Kasperkovitz, Eliseo Papa, et al. "The Tetraspanin CD82 Is Specifically Recruited to Fungal and Bacterial Phagosomes prior to Acidification." Infection and Immunity 79, no. 3 (2010): 1098–106. http://dx.doi.org/10.1128/iai.01135-10.
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ABSTRACTCD82 is a member of the tetraspanin superfamily, whose physiological role is best described in the context of cancer metastasis. However, CD82 also associates with components of the class II major histocompatibility complex (MHC) antigen presentation pathway, including class II MHC molecules and the peptide-loading machinery, as well as CD63, another tetraspanin, suggesting a role for CD82 in antigen presentation. Here, we observe the dynamic rearrangement of CD82 after pathogen uptake by imaging CD82-mRFP1 expressed in primary living dendritic cells. CD82 showed rapid and specific recruitment toCryptococcus neoformans-containing phagosomes compared to polystyrene-containing phagosomes, similar to CD63. CD82 was also actively recruited to phagosomes containing other pathogenic fungi, includingCandida albicansandAspergillus fumigatus. Recruitment of CD82 to fungal phagosomes occurred independently of Toll-like receptor (TLR) signaling. Recruitment was not limited to fungi, as bacterial organisms, includingEscherichia coliandStaphylococcus aureus, also induced CD82 recruitment to the phagosome. CD82 intersected the endocytic pathway used by lipopolysaccharide (LPS), implicating CD82 in trafficking of small, pathogen-associated molecules. Despite its partial overlap with lysosomal compartments, CD82 recruitment toC. neoformans-containing phagosomes occurred independently of phagosome acidification. Kinetic analysis of fluorescence imaging revealed that CD82 and class II MHC simultaneously appear in the phagosome, indicating that the two proteins may be associated. Together, these data show that the CD82 tetraspanin is specifically recruited to pathogen-containing phagosomes prior to fusion with lysosomes.
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BROOKS, STEPHEN P. J., and KENNETH B. STOREY. "Influence of Hormones, Second Messengers and pH on the Expression of Metabolic Responses to Anoxia in a Marine Whelk." Journal of Experimental Biology 145, no. 1 (1989): 31–43. http://dx.doi.org/10.1242/jeb.145.1.31.
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The roles of hormones, second messengers and pH in triggering or potentiating biochemical responses to anaerobiosis were evaluated using in vitro incubations of isolated muscle tissues (foot, radular retractor, ventricle) from the marine whelk Busycon canaliculatum (L.). Incubating tissues in vitro under anoxic conditions stimulated changes in muscle fmctose-2,6-bisphosphate levels and pyruvate kinase kinetics (Km values for phosphoenolpyruvate, I50 values for L-alanine) that were virtually equivalent to those that occur in vivo. Additions of hormones (epinephrine, norepinephrine, octopamine, serotonin, glucagon, insulin) or inhibitors of prostaglandin synthesis (dexamethasone, aspirin) had no effect on these metabolic responses to anoxia. The second messenger compounds, dibutyryl cyclic AMP and Ca2+ + ionophore A23187 + phorbol myristate acetate, produced isolated and tissue-specific responses in muscles incubated under aerobic conditions, but the magnitude and pattern of these responses differed from those seen in anoxia. Second messengers also had no effect on the development of biochemical responses in anoxic muscles. Tissue pH was artificially altered in order to evaluate the role of pH change (acidification occurs during anoxia in vivo) in the control of metabolic responses to anoxia. In all cases, the changes in the kinetic properties of pyruvate kinase (PK) correlated with the state of oxygenation of the tissue and not with the measured tissue pH value; higher tissue pH did not prevent anoxiainduced phosphorylation of PK and lower tissue pH did not alter the kinetic patterns of the aerobic enzyme. Overall, the study indicates that cells and tissues of the whelk respond individually to anoxia and that coordination of the action of protein kinases during anoxia is not mediated by pH or by common secondmessenger mechanisms.
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Fan, Z., Y. Tokuyama, and J. C. Makielski. "Modulation of ATP-sensitive K+ channels by internal acidification in insulin-secreting cells." American Journal of Physiology-Cell Physiology 267, no. 4 (1994): C1036—C1044. http://dx.doi.org/10.1152/ajpcell.1994.267.4.c1036.
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The effect of intracellular acidification (low pHi) on open probability of the ATP-sensitive K+ (KATP) channel was examined in insulin-secretion cells using an inside-out configuration of the patch-clamp technique. In an insulin-secreting cell line beta-TC3, KATP single-channel currents (IKATP) were readily recorded in the absence of internal ATP. ATP (50 microM and 0.5 mM) dramatically decreased the channel activity. A step decrease of intracellular pH (pHi) from 7.4 to 6.7 or 6.3 in the presence of ATP gradually increased the channel activity. In addition, low pHi in the presence of ATP could partially restore channel activity lost in a process called "rundown." Kinetic analysis revealed a change in channel gating at low pHi with ATP. The bursting durations of IKATP at pHi 6.3 in the presence of ATP were significantly longer than those at pHi 7.4 in the absence of ATP. These results suggest that the increased channel activity at low pHi might have resulted from a mechanism involving an alteration of channel conformation. We also observed an inhibitory effect of low pHi on channel activity. However, the inhibitory effect was much more apparent at pHi 5.7 and was only partially reversible. The activation effect of low pHi on IKATP in the presence of ATP was also observed in acutely isolated rat islet cells and in another insulin-secretion cell line RINm5F, although the effect was weaker and was variable among experiments. We conclude that, as in frog skeletal muscle and cardiac muscle, an increase in channel activity at low pHi is one of the mechanisms underlying proton modulation of IKATP in insulin-secreting cells.
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Campos, Cláudio Milton Montenegro, Bruno Botelho Saléh, and Fernanda Ribeiro do Carmo. "Determination of kinetic parameters of a lab-scale upflow anaerobic sludge blanket reator (uasb) removing organic loading from swine manure effluents." Ciência e Agrotecnologia 29, no. 5 (2005): 1045–51. http://dx.doi.org/10.1590/s1413-70542005000500020.
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The present work aimed at determining and evaluating the kinetic parameters from the UASB reactor treating swine manure effluent in a lab-scale experiment. The research was carried out in the Laboratory of Water Analysis at the Engineering Department (LAADEG) at the campus of Federal University of Lavras - UFLA. The system was assembled with an acidification and equalization tank (AET), an UASB reactor and an aerated facultative pond (AFP). The hydraulic retention time (HRT) adopted in the UASB reactor were: 55; 39; 34; 24; 17; and 16 hours. The operational average temperature in the UASB reactor was 25 ± 2ºC. The kinetic studies used the following parameters: Chemical Oxygen Demand (COD T), Total Volatile Solids (TVS), Temperature, Flowrate and Total Solids Profile (TVS P), in the reactor, and the number of analyses were: 72; 72; 250; 250; and 30, respectively. The frequency was twice a week for COD T, and TVS, and daily for temperature and flowrate. The kinetic parameters determined were: yield coefficient Y=0.3046 to 0.4231mg COD T mgTVS-1.d-1, decay coefficient Kd=0.0125 to 0.0173d-1, maximum growth rate coefficient ìmax=0.2835 to 0.03938d-1 and limiting substrate concentration coefficient Ks= 51.70 to 71.80mg COD T.L-1. The values found were within the range appointed in the specific literatures and were determined based on linear regression studies, giving in this way, a technical scientific support to the physical chemical operational data collected during the operational research period.
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Igarashi, P., M. I. Freed, M. B. Ganz, and R. F. Reilly. "Effects of chronic metabolic acidosis on Na(+)-H+ exchangers in LLC-PK1 renal epithelial cells." American Journal of Physiology-Renal Physiology 263, no. 1 (1992): F83—F88. http://dx.doi.org/10.1152/ajprenal.1992.263.1.f83.
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Porcine renal epithelial cells (LLC-PK1/clone 4) have Na(+)-H+ exchangers with different kinetic properties in their apical and basolateral membranes. cDNAs encoding the basolateral Na(+)-H+ exchanger were recently cloned. To determine whether expression of the basolateral Na(+)-H+ exchanger was affected by chronic metabolic acidosis, LLC-PK1/clone 4 cells were grown on permeant supports and incubated in control medium (pH 7.4) or acid medium (pH 6.9). After 48 h, Na(+)-H+ exchanger transport activity was measured as N-ethyl-N-isopropylamiloride (EIPA)-sensitive 22Na+ influx. Acidification caused an 84% stimulation of the transport activity of the basolateral Na(+)-H+ exchanger. The apical Na(+)-H+ exchanger was stimulated 72%, and there was no change in the EIPA-insensitive 22Na+ flux across either membrane. Stimulation of Na(+)-H+ exchange was not due to differences in intracellular pH at the time transport was assayed. To determine whether there were corresponding changes in transcript levels, poly(A)+ RNA was isolated from LLC-PK1 cells and hybridized with a cDNA encoding the basolateral Na(+)-H+ exchanger. Levels of transcripts encoding the basolateral Na(+)-H+ exchanger were increased 70% after 48 h of acidification, and there were no changes in transcripts encoding cytoskeletal gamma-actin or glyceraldehyde-3-phosphate dehydrogenase. We conclude that conditions simulating chronic metabolic acidosis coordinately increase the transport activity and transcript levels of the basolateral Na(+)-H+ exchanger in porcine renal epithelial cells.
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Klionsky, D. J., H. Nelson, N. Nelson, and D. S. Yaver. "Mutations in the yeast vacuolar ATPase result in the mislocalization of vacuolar proteins." Journal of Experimental Biology 172, no. 1 (1992): 83–92. http://dx.doi.org/10.1242/jeb.172.1.83.
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The vacuolar ATPase of the yeast Saccharomyces cerevisiae acidifies the vacuolar lumen and generates an electrochemical gradient across the vacuole membrane. We have investigated the role of compartment acidification of the vacuolar system in the sorting of vacuolar proteins. Strains with chromosomal disruptions of genes (delta vat) encoding the A (69 x 10(3) M(r)), B (57 x 10(3) M(r)) or c (16 x 10(3) M(r)) subunits of the vacuolar ATPase accumulate and secrete precursor forms of the soluble vacuolar hydrolases carboxypeptidase Y and proteinase A. A kinetic analysis suggests that these precursor proteins accumulate in, and are secreted from, the Golgi complex or post-Golgi vesicles. In addition, subcellular fractionation shows that vacuolar hydrolase-invertase hybrid proteins are inefficiently localized to the vacuole in delta vat strains. This result suggests that the vat mutations cause a steady-state defect in vacuolar protein sorting. The vat mutations also affect the sorting of vacuolar membrane proteins. Precursor forms of alkaline phosphatase are accumulated in vat mutant cells, but to a lesser extent than is seen for the soluble vacuolar hydrolases. This finding, coupled with the insensitivity of alkaline phosphatase to the ATPase inhibitor bafilomycin A1, suggests that vacuolar membrane protein sorting is less sensitive to changes in lumenal pH when compared with the targeting of soluble vacuolar proteins. These results indicate that acidification of the vacuolar system is important for efficient sorting of soluble proteins to the vacuole.
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Zerbini, G., A. Maestroni, R. Mangili, and G. Pozza. "Amiloride-insensitive Na+-H+ exchange: a candidate mediator of erythrocyte Na+-Li+ countertransport." Journal of the American Society of Nephrology 9, no. 12 (1998): 2203–11. http://dx.doi.org/10.1681/asn.v9122203.
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Erythrocyte Na+-Li+ countertransport shows an increased activity in essential hypertension and diabetic nephropathy, but its nature remains unknown. This amiloride-insensitive membrane transport may not be a mode of operation of the amiloride-sensitive NHE1, the only Na+-H+ exchange isoform found in human erythrocytes. Whether an independent, although unknown, amiloride-insensitive isoform mediates Na+-Li+ countertransport is unclear. Na+-H+ exchange activity was measured in acid-loaded erythrocytes. Dimethylamiloride, a specific inhibitor of Na+-H+ exchange and phloretin, a known inhibitor of Na+-Li+ countertransport, gave a reduction in H+-driven Na+ influx (by 31 and 37%, respectively). This effect was additive, and a 66% reduction in H+-driven Na+ influx was found in the presence of both inhibitors. Internal acidification, a stimulus for Na+-H+ exchange, enhanced Na+-Li+ countertransport activity (from 287 +/- 55 to 1213 +/- 165 micromol x Lcell(-1) h(-1), mean +/- SEM, P = 0.003). This transport remained sensitive to phloretin under both conditions. Conversely, external acidification decreased Na+-Li+ countertransport activity (as expected for a Na+-H+ exchanger). Competition between internal H+ and Li+ or Na+ for a common binding site was present. Finally, similar kinetic parameters for external Na+ characterized Na+-Li+ countertransport and the phloretin-sensitive component of H+-driven Na+ influx. These findings suggest that both Na+-Li+ countertransport and the amiloride-insensitive, phloretin-sensitive component of H+-driven Na+ influx can be mediated by a previously unrecognized novel amiloride-insensitive Na+-H+ exchange isoform in human erythrocytes.
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Ahearn, G. A., and L. P. Clay. "Kinetic analysis of electrogenic 2 Na+-1 H+ antiport in crustacean hepatopancreas." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 257, no. 3 (1989): R484—R493. http://dx.doi.org/10.1152/ajpregu.1989.257.3.r484.
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Na+ uptake by short-circuited brush-border membrane vesicles of the hepatopancreatic epithelium from the freshwater prawn Macrobrachium rosenbergii was Cl- independent, amiloride sensitive, and stimulated by a transmembrane proton gradient ([H+]i greater than [H+]o). Na+ influx (3-s uptake) was a sigmoidal function of [Na]o (2.5-150 mM), when pHi = 6.0, pHo = 8.0, and followed the Hill equation for binding cooperativity [maximal Na+ influx (Jm) = 140.6 nmol mg-1s-1; affinity constant (K') = 82.2 mM Na+; Hill coefficient (n) = 2.07]. Influx kinetic analyses at physiological conditions suggested two external cation-binding sites shared by Na+ and H+ (proton dissociation constant Pk1 = 5.7; Pk2 = 4.0) and a single internal cation site used only by H+ (Pk = 6.5). Amiloride was a competitive inhibitor of Na+ transport at both external binding sites (Ki1 = 50 microM; Ki2 = 1,520 microM). Electrogenic Na+-H+ exchange by these vesicles was demonstrated using an equilibrium-shift method of analysis and a transmembrane electrical potential difference as the only driving force for transport. In addition, electrogenic net Na+ influx (3-s uptake) was observed in vesicles loaded with 5 mM 22Na at pH 7.0 and exposed to media containing several 22Na or proton concentrations. Results suggest the following exchange model: low [Na]o, (1 Na+ and 1 H+)-1 H+; high [Na+]o, 2 Na+-1 H+. This antiport mechanism may account for two major functional operations of the gastrointestinal tract in these animals: 1) proton secretion against considerable concentration gradients leading to stomach luminal acidification, and 2) Na+ absorption from lumen to cytoplasm potentially making a significant contribution to organismic ion balance.
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KORZENIEWSKI, Bernard, and Jerzy A. ZOLADZ. "Influence of rapid changes in cytosolic pH on oxidative phosphorylation in skeletal muscle: theoretical studies." Biochemical Journal 365, no. 1 (2002): 249–58. http://dx.doi.org/10.1042/bj20020031.
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Cytosolic pH in skeletal muscle may vary significantly because of proton production/consumption by creatine kinase and/or proton production by anaerobic glycolysis. A computer model of oxidative phosphorylation in intact skeletal muscle developed previously was used to study the kinetic effect of these variations on the oxidative phosphorylation system. Two kinds of influence were analysed: (i) via the change in pH across the inner mitochondrial membrane and (ii) via the shift in the equilibrium of the creatine kinase-catalysed reaction. Our simulations suggest that cytosolic pH has essentially no impact on the steady-state fluxes and most metabolite concentrations. On the other hand, rapid acidification/alkalization of cytosol causes a transient decrease/increase in the respiration rate. Furthermore, changes in pH seem to affect significantly the kinetic properties of transition between resting state and active state. An increase in pH brought about by proton consumption by creatine kinase at the onset of exercise lengthens the transition time. At intensive exercise levels this pH increase could lead to loss of the stability of the system, if not compensated by glycolytic H+ production. Thus our theoretical results stress the importance of processes/mechanisms that buffer/compensate for changes in cytosolic proton concentration. In particular, we suggest that the second main role of anaerobic glycolysis, apart from additional ATP supply, may be maintaining the stability of the system at intensive exercise.
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Christodoulou, Christian, Chris Goodier, and Gareth Glass. "Towards arresting reinforced concrete corrosion – a review." MATEC Web of Conferences 199 (2018): 05001. http://dx.doi.org/10.1051/matecconf/201819905001.
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This work reviews developments in the understanding of chloride induced corrosion of steel in concrete from both a kinetic and thermodynamic perspective. Corrosion damage is at least in part attributed to the production of acid at sites of corrosion initiation. Solid phase inhibitors provide a reservoir of hydroxyl ions to inhibit damage. Pit re-alkalisation is identified as an important protective effect in electrochemical treatments used to arrest corrosion. A process like pit re-alkalisation is achieved more easily by impressing current from sacrificial anodes using a power supply which may then be followed by low maintenance galvanic protection to prevent local acidification. Methods for monitoring the steel corrosion rate in electrochemically treated reinforced concrete have been developed and used to assess corrosion risk. Some of these concepts have been adopted in the recent international standard on cathodic protection, ISO 12696:2016, some of the amendments of which are considered in the work presented here.
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Ramírez, Jorge, Oscar Ramírez, Carlos Saldaña, Roberto Coria, and Antonio Peña. "A Saccharomyces cerevisiae Mutant Lacking a K+/H+ Exchanger." Journal of Bacteriology 180, no. 22 (1998): 5860–65. http://dx.doi.org/10.1128/jb.180.22.5860-5865.1998.
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ABSTRACT The KHA1 gene corresponding to the open reading frame YJL094c (2.62 kb) encoding a putative K+/H+antiporter (873 amino acids) in Saccharomyces cerevisiaewas disrupted by homologous recombination. The core protein is similar to the putative Na+/H+ antiporters fromEnterococcus hirae (NAPA gene) andLactococcus lactis (LLUPP gene) and the putative K+/H+ exchanger from Escherichia coli (KEFC gene). Disruption of the KHA1gene resulted in an increased K+ accumulation and net influx without a significant difference in efflux, as well as an increased growth rate, smaller cells, and twice the cell yield per glucose used. Flow cytometry analysis showed an increase of the DNA duplication rate in the mutant. Kinetic studies of86Rb+ uptake showed the same saturable system for wild-type and disruptant strains. Mutant cells also produced a greater acidification of the medium coincident with an internal pH alkalinization and showed a higher oxygen consumption velocity. We speculate that higher K+ accumulation and increased osmotic pressure accelerate the cell cycle and metabolic activity.
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Zerbini, G., R. Mangili, D. Gabellini, and G. Pozza. "Modes of operation of an electroneutral Na+/Li+ countertransport in human skin fibroblasts." American Journal of Physiology-Cell Physiology 272, no. 4 (1997): C1373—C1379. http://dx.doi.org/10.1152/ajpcell.1997.272.4.c1373.
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An elevated activity of erythrocyte Na+/Li+ countertransport (SLC) is an intermediate phenotype of human essential hypertension, but cells other than erythrocytes have not been studied. Therefore, we have examined several transport modes of Na+/Li+ exchange in human skin fibroblasts. External Na+-stimulated Li+ efflux was 152 +/- 31 (SE) nmol x mg protein(-1) x min(-1) (n = 8). At intracellular pH 7.3, intracellular Na+-stimulated Li+ influx, intracellular Li+-stimulated Na+ influx, and external Li+-stimulated Na+ efflux were very similar, indicating the presence of a tightly coupled 1:1 SLC. This pathway was not affected by 5-(N,N-dimethyl)-amiloride and changes in the membrane potential, but phloretin and intracellular acidification (intracellular pH 6.8) were markedly inhibitory. Kinetic analyses of the external Na+ site also compared with SLC, although the internal site appeared to show a low affinity for Li+. We conclude that an SLC pathway similar to that in human erythrocytes is expressed in human skin fibroblasts.
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Santos Júnior, Luís Carlos Oliveira dos, Iuri Heberle, Ana Carolina Moura de Sena Aquino, et al. "High-pressure supercritical carbon dioxide uses to inactivate Escherichia coli in pumpkin puree." Research, Society and Development 10, no. 4 (2021): e6510413853. http://dx.doi.org/10.33448/rsd-v10i4.13853.
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Coli ATCC 25922 inactivation was studied to determine the effect of high-pressure carbon dioxide (HPCD) process on pumpkin puree. Experiments were performed using a batch HPCD system at three conditions of pressure (7.5 MPa, 17.5 MPa and 27.5 MPa) at 32 °C. Afterwards, at the best experimental condition (27.5 MPa – 275 bar), a kinetic was performed to assess inactivation of microorganisms over time (from 1 to 8 h). The physicochemical characteristics (pH, total soluble solids – TSS, titratable acidity – TA, total carotenoids, total reducing sugars – TRS, moisture and optical microscopy) of the pumpkin puree were also evaluated. HPCD with acidification increases bacterial efficacy of treatments, as well as significant changes in physicochemical parameters. HPCD treatment reduced the microbial load moderately in all experiments, by a maximum of approximately 3.17 log cycles in 8 h of process at 27.5 MPa (275 bar). Optical microscopy showed no difference in cell wall, just in starch which was expected by cooking.
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Batlle, D., J. Redon, C. Gutterman, et al. "Acid-base status and intracellular pH regulation in lymphocytes from rats with genetic hypertension." Journal of the American Society of Nephrology 5, no. 5 (1994): S12. http://dx.doi.org/10.1681/asn.v55s12.
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This article reviews work from this laboratory dealing with acid-base status and intracellular pH (pHi) regulation in rat genetic models of hypertension. With freshly isolated thymic lymphocytes, pHi and its regulation were examined in the spontaneously hypertensive rat (SHR). In this rat model, pHi was found to be reduced as compared with that of lymphocytes from normotensive Wistar-Kyoto (WKY) rats. The activity of the Na+/H+ antiporter assessed after stimulation by acute cell acidification was similar in lymphocytes from SHR and WKY rats both in the nominal absence of HCO3- and in media containing HCO3- (22 mM). The kinetic properties of the Na+/H+ antiporter, examined as a function of pHi with the Hill kinetic model, revealed no significant differences between lymphocytes from SHR and WKY rats. The kinetic properties of the Na(+)-dependent and Na(+)-independent Cl(-)-HCO3- exchangers, examined as a function of external Cl-, were also virtually identical in lymphocytes from SHR and WKY rats. Unlike the Na(+)-H+ exchanger and the Na(+)-independent Cl(-)-HCO3- exchanger, which had their highest activities at extremes of pHi (low pHi, Na(+)-H+ exchanger; high pHi, Na(+)-independent Cl(-)-HCO3- exchanger), the Na(+)-dependent Cl(-)-HCO3- exchanger had its maximal activity near steady-state pHi. In Dahl/Rapp salt-sensitive rats with hypertension, the pHi of thymic lymphocytes was also reduced as compared with that of normotensive salt-resistant animals. In this model, renal net acid excretion in salt-sensitive rats was augmented as compared with that of salt-resistant rats. The increase in renal acid excretion was due to an increase in both ammonium and titratable acid excretion and was observed while animals were placed on high, normal and low salt diets. The findings of intracellular acidosis and enhanced renal acid excretion suggest that cellular acid overproduction is augmented in salt-sensitive hypertension.
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Elzenga, J. Theo M., Marten Staal, and Hidde B. A. Prins. "Modulation by phytochrome of the blue light-induced extracellular acidification by leaf epidermal cells of pea (Pisum sativum L.): a kinetic analysis." Plant Journal 22, no. 5 (2000): 377–89. http://dx.doi.org/10.1046/j.1365-313x.2000.00748.x.
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Witt, Susanne, Mahavir Singh, and Henryk M. Kalisz. "Structural and Kinetic Properties of Nonglycosylated Recombinant Penicillium amagasakienseGlucose Oxidase Expressed in Escherichia coli." Applied and Environmental Microbiology 64, no. 4 (1998): 1405–11. http://dx.doi.org/10.1128/aem.64.4.1405-1411.1998.
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ABSTRACT The gene coding for Penicillium amagasakiense glucose oxidase (GOX; β-d-glucose; oxygen 1-oxidoreductase [EC1.1.3.4 ]) has been cloned by PCR amplification with genomic DNA as template with oligonucleotide probes derived from amino acid sequences of N- and C-terminal peptide fragments of the enzyme. RecombinantEscherichia coli expression plasmids have been constructed from the heat-induced pCYTEXP1 expression vector containing the mature GOX coding sequence. When transformed into E. coli TG2, the plasmid directed the synthesis of 0.25 mg of protein in insoluble inclusion bodies per ml of E. coli culture containing more than 60% inactive GOX. Enzyme activity was reconstituted by treatment with 8 M urea and 30 mM dithiothreitol and subsequent 100-fold dilution to a final protein concentration of 0.05 to 0.1 mg ml−1 in a buffer containing reduced glutathione-oxidized glutathione, flavin adenine dinucleotide, and glycerol. Reactivation followed first-order kinetics and was optimal at 10°C. The reactivated recombinant GOX was purified to homogeneity by mild acidification and anion-exchange chromatography. Up to 12 mg of active GOX could be purified from a 1-liter E. coli culture. Circular dichroism demonstrated similar conformations for recombinant and native P. amagasakiense GOXs. The purified enzyme has a specific activity of 968 U mg−1 and exhibits kinetics of glucose oxidation similar to those of, but lower pH and thermal stabilities than, native GOX from P. amagasakiense. In contrast to the native enzyme, recombinant GOX is nonglycosylated and contains a single isoform of pI 4.5. This is the first reported expression of a fully active, nonglycosylated form of a eukaryotic, glycosylated GOX inE. coli.
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Benahmed Djilali, Adiba, Abdelouahab Benseddik, Halima Boughellout, Karim Allaf, and Mohamed Nabiev. "Biological and functional properties of vine leaves." North African Journal of Food and Nutrition Research 5, no. 11 (2021): 43–52. http://dx.doi.org/10.51745/najfnr.5.11.43-52.
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Aims: The main objective of the present research work was to evaluate the (phytochemical, biochemical, and antimicrobial) properties of Muscat of Alexandria leaf powder and develop new functional dairy product using the mixture lactic bacteria and vine leaf powder as prebiotic for health applications (gastric and cardiac problems, etc.). Material and Methods: Various nutritional parameters of the vine leaf powder namely: pH, acidity, water content, ashes, salts, fatty acids) were determined. Also, their bioactive substances (TPC, total flavonoids content, tannin content, soluble-water polysaccharides) were extracted and quantified using referenced methods. The evaluation of antimicrobial activity of these substances was carried out by disc method. Vine leaf powder and aqueous extract were used to improve acidification kinetic. Also, functional yogurt using the mixture (lactic bacteria and vine leaf powder as prebiotic) was prepared. Results: The main results demonstrate that, the vine leaf powder contains high-value components such as salts with a high k/Na ratio, fatty acids (palmitic, linolenic and oleic) and bioactives (polyphenols, tannins and polysaccharides). The antimicrobial activity of these bioactive metabolites varies depending on the resistance of the strains tested. On the other hand, vine leaf TPC and polysaccharides act as an antifungal against (C. albicans and A. niger) and increase the acidification rate and consequently the growth and activity of the lactic bacteria in the yogurt, which suggests a probable prebiotic effect. Conclusions: Through this study, we have demonstrated the high content of vine leaves in several bioactive compounds such as polyphenols, flavonoids, tannins and polysaccharides. These compounds display an interesting antimicrobial activity and an extensive effect on the activity of lactic bacteria, which suggests a prebiotic effect. Keywords: Bioactive substances, antimicrobial activity, prebiotic, vine leaves.
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Lauf, P. K., J. Bauer, N. C. Adragna, et al. "Erythrocyte K-Cl cotransport: properties and regulation." American Journal of Physiology-Cell Physiology 263, no. 5 (1992): C917—C932. http://dx.doi.org/10.1152/ajpcell.1992.263.5.c917.
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Erythrocytes possess a Cl-dependent, Na-independent K transport system cotransporting K and Cl in a 1:1 stoichiometry that is membrane potential independent. This K-Cl cotransporter is stimulated by cell swelling, acidification, Mg depletion, and thiol modification. Cell shrinkage, elevation of cellular divalent ions, thiol alkylation, phosphatase inhibitors, and derivatives of certain loop diuretics and stilbenes are inhibitory. Thus regulation of K-Cl cotransport at the membrane and cytoplasmic levels is highly complex. Basal K-Cl cotransport decreases with cellular maturation, whereas its modes of stimulation and inhibition are variable between species. The physiological inactivation appears to be prevented in low-K animal erythrocytes. In certain human hemoglobinopathies, K-Cl cotransport may be the cause of cellular dehydration and volume decrease. K-Cl cotransport occurs also in nonerythroid cells, such as in epithelial and liver cells of other species. At the threshold of molecular characterization, this comprehensive review places our present understanding of the mechanisms modulating K-Cl cotransport physiologically and pathophysiologically into kinetic and thermodynamic perspectives.