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PubMed1988

Reaction plane approach for estimating the effects of buffers on the dissolution rate of acidic drugs.

A mass transfer model was developed to describe the dissolution and reaction of an acidic drug, naproxen [(+)-6-methoxy-alpha-methyl-2-naphthaleneacetic acid], from a rotating disk in buffered solutions. Dissolution in 0.0010 to 0.030 M acetate, citrate, and phosphate buffer solutions, with 0.1 M KCl added, over a pH range of 2 to 8 at 25 degrees C, was investigated. Features of the mass transfer model include: treatment of the mass transfer as a convective diffusion process; use of the buffer reactions and the acid ionization as a single flux boundary condition; the capacity to make accurate a priori predictions without fitting film thicknesses or diffusion coefficients; and the option of considering two limiting cases for the maximal increase in dissolution that could be expected in a reactive buffer and the increase in dissolution in a buffer at maximum buffer capacity.

Buffers↗
PubMed1995

Influence of pH, temperature, and buffers on the kinetics of ceftazidime degradation in aqueous solutions.

First-order rate constants (k) were determined for the hydrolysis of ceftazidime in the pH range of 0.5 to 8.5 at 45, 55, and 65 degrees C by a stability-indicating HPLC assay. In the absence of buffer effects, the pH-rate expression was k = kH1f1(aH+) + kH2f2(aH+) + kH3f3(aH+) + kSf3 + kOHf3(aOH-), where KH and KOH are the catalytic rate constants for the activity of hydrogen (aH+) and hydroxyl (aOH-) ions, respectively, and kS is the rate constant for spontaneous hydrolysis. The fractions of ceftazidime in various stages of dissociation (f1, f2, and f3) were calculated from kinetically determined apparent Ka values of 2.03 x 10(-2) and 4.85 x 10(-5). Catalytic constants (kcat) were calculated for formate, acetate, phosphate, and borate buffers, which accelerated hydrolysis. Each of the rate constants (kH1, kH2, kH3, kS, kOH, and kcat) were described as a function of temperature with calculated A and E values in the Arrhenius equation, kT = Ae-E/RT. Ceftazidime hydrolysis rate constants (k) were calculated as a function of pH, temperature, and buffer by combining the pH-rate expression with the buffer contributions calculated from kcat values and the temperature dependencies. These equations and their parameter values successfully calculated 95 of 104 experimentally determined rate constants with errors of < 10%. Maximum stability was observed in the relatively pH-independent region from 4.5 to 6.5. Hydrolysis rate constants at 30 degrees C were predicted and experimentally verified for four ceftazidime solutions, three of which (pH 4.4 acetate buffer and pH 5.5 and 6.5 phosphate buffers) maintained 90% of their initial concentration for approximately 1.5 days.

Buffers↗
PubMed2001

A comparison of different lysis buffers to assess allele dropout from single cells for preimplantation genetic diagnosis.

Single cell polymerase chain reaction (PCR) for preimplantation genetic diagnosis (PGD) requires high efficiency and accuracy. Allele dropout (ADO), the random amplification failure of one of the two parental alleles, remains the most significant problem in PCR-based PGD testing since it can result in serious misdiagnosis for compound heterozygous or autosomal dominant conditions. A number of different strategies (including the use of lysis buffers to break down the cell and make the DNA accessible) have been employed to combat ADO with varying degrees of success, yet there is still no consensus among PGD centres over which lysis buffer should be used (ESHRE PGD Consortium, 1999). To address this issue, PCR amplification of three genes (CFTR, LAMA3 and PKP1) at different chromosomal loci was investigated. Single lymphocytes from individuals heterozygous for mutations within each of the three genes were collected and lysed in either alkaline lysis buffer (ALB) or proteinase K/SDS lysis buffer (PK). PCR amplification efficiencies were comparable between alkaline lysis and proteinase K lysis for PCR products spanning each of the three mutated loci (DeltaF508 in CFTR 90% vs 88%; R650X in LAMA3 82% vs 78%; and Y71X in PKP1 91% vs 87%). While there was no appreciable difference between ADO rates between the two lysis buffers for the LAMA3 PCR product (25% vs 26%), there were significant differences in ADO rates between ALB and PK for the CFTR PCR product (0% vs 23%) and the PKP1 PCR product (8% vs 56%). Based on these results, we are currently using ALB in preference to PK/SDS buffer for the lysis of cells in clinical PGD.

Alleles↗
PubMed2005

Amphoteric, buffering chromatographic beads for proteome prefractionation. I: theoretical model.

The possibility is reported here of fractionating proteins on amphoteric, buffering resins via ion-exchange chromatography. A given protein's adsorption to a particular amphoteric buffering resin is characterized by a bell-shaped curve in which the maximum protein binding capacity is observed at an optimum pH value lying approximately midway between the isoelectric point values (pI) of the resin and the protein. On either side of this maximum the protein binding capacity declines steadily, reaching zero at the pI of either the protein or exchanger. For instance, on beads of pI equal to 8, four proteins, two acidic (bovine albumin and ovalbumin) and two basic (cytochrome c and lysozyme), exhibit binding curves reaching zero values for the whole set when the exchanger is conditioned at pH 8.0. Away from the pI, and on both sides of the pH scale, the bell-shaped adsorption curves reach a maximum, for each protein, at a pH located at the midpoint between the pI values of each protein and that of the exchanger, and decline steadily to reach zero at the pI value of each protein species. Separation of model proteins using different amphoteric buffering resins of various pI was possible at different pH values according to both the pI of the proteins and of the exchangers. It was also demonstrated, using surface enhanced laser desorption/ionization mass spectrometry and two dimensional electrophoretic mapping, that separation of an Escherichia coli cell lysate on columns packed with amphoteric buffering resins of different pI and titrated to a particular pH value, delivered two distinctly different fractions, i.e. characteristically composed of, on the one hand, proteins having a pI below the buffer pH (the 'adsorbed' fraction), and on the other, of alkaline proteins possessing a pI above the pH of the buffer (the 'unadsorbed' fraction). This approach represents an attractive addition and/or alternative to the armory of protein pre-fractionation techniques currently employed in proteomics.

Albumins↗
PubMed1999

Role of intracellular buffering power on the mitochondria-cytosol pH gradient in the rat liver perfused at 4 degrees C.

The factors regulating the amplitude and the pH gradient between cytosol and mitochondria (DeltapHmito-cyt) were investigated in the isolated rat liver perfused at 4 degrees C. Liver ATP content, pH, and buffering power of cytosolic and mitochondrial compartments were evaluated in situ using phosphorus-31 nuclear magnetic resonance spectroscopy. No DeltapHmito-cyt was detected in the liver perfused without bicarbonate. Permeant weak acid in the perfusate (H2CO3, 25 mM, or isobutyric acid, 25, 50, or 100 mM) acidified both cytosol and mitochondria and revealed a DeltapHmito-cyt from 0.06 to 0.31 pH unit. Nevertheless, the manipulations of the DeltapHmito-cyt were more effective under bicarbonate-free conditions, due to the absence of buffering by H2CO3/HCO-3. In the absence of bicarbonate, the intracellular buffering power was threefold higher in the mitochondria (110 mmol/pH unit at pHmito 7.16) than in the cytosol (44 mmol/pH unit at pHcyt 7.30) and dependent on the matrix and cytosol pH, respectively. These buffering powers were almost double in the presence of bicarbonate. In the bicarbonate-free perfused liver, the respiratory activity was 0.08 +/- 0.02 micromol O2/min. g liver wet weight and the ATP turnover was only 40 +/- 7 nmol/min. g liver wet weight, indicating the weak activity of liver mitochondria when DeltapHmito-cyt was <0.05 pH unit. The ATP turnover during a 50 mM isobutyric acid load was 35 +/- 4 nmol/min. g liver wet weight whereas DeltapHmito-cyt rose to 0.26 +/- 0.02 pH unit and pHmito remained alkaline. Hence, although DeltapHmito-cyt was increased the ATP turnover remained unchanged. This work is the first evaluation of the mitochondrial buffering power in the isolated liver. The DeltapHmito-cyt observed within various acid loads reflected the differential titration of cytosol and mitochondria containing proteins and H2CO3/HCO-3 buffering systems. Moreover, no direct relationship between DeltapHmito-cyt and ATP turnover could be shown.

Animals↗
PubMed1996

Dichotomy in the post-ischemic metabolic and functional recovery profiles of isolated blood-versus buffer-perfused heart.

There is evidence that buffer- and blood-perfused hearts differ in their postischemic functional recoveries. The present study was designed to: (i) compare ischemia-induced contracture and post-ischemic functional recovery, and (ii) investigate whether the recovery profiles were related to either the release of purines and norepinephrine or high-energy phosphate content. Rat hearts (n = 8/group) were perfused at 37 degrees C with buffer (60 mmHg) or blood (60 mmHg from a support rat), made globally ischemic (15 min) and reperfused (15 min). The onset and severity of ischemic contracture were identical in both models [left ventricular end-diastolic pressure (LVEDP) at the end of 15 min ischemia was 30 +/- 5 and 27 +/- 4 mmHg respectively; P = N.S.]. However, the rate and extent of post-ischemic left ventricular developed pressure (LVDP) differed considerably. Blood-perfused hearts exhibited an initial rapid and complete recovery of LVDP followed by a steady decline to approximately 60% of pre-ischemic values. Buffer-perfused hearts recovered to only 80% after 5 min reperfusion and remained at this level for the duration of reperfusion LVEDP was higher in buffer-perfused than in blood-perfused hearts during the first 5 min of reperfusion; thereafter, LVEDP fell in buffer-perfused hearts to a level than was not significantly different from the observed in blood-perfused hearts. In buffer-perfused hearts, coronary flow recovered to 90% within 5 min and then remained constant; in blood-perfused hearts flow recovered to 100% by 1 min and continued to rise to a maximum by 7 min (201 +/- 15%). This increase appeared to mirror the secondary decline in LVDP. During the first 4 min of reperfusion, in both preparations, venous norepinephrine increased to six- to nine-fold of pre-ischemic values and then fell rapidly to near control levels by 6-9 min. Total purine release was high in early reperfusion in both groups. At the end of 15 min reperfusion, the tissue adenylate pool was similar in both groups. This study demonstrates that the nature of the perfusate used for an isolated rat heart preparation: (i) does not appear to influence the severity of ischemic injury as assessed by ischemic contracture, but (ii) does influence the qualitative and quantitative characteristics of the temporal profile that describes the recovery of systolic and diastolic function during the first 15 min of reperfusion: and (iii) it has no effect upon the changes seen in a number of metabolic indices that are often used for the assessment of injury and protection.

Animals↗
PubMed1985

Ultrasonic absorption studies of protein-buffer interactions. Determination of equilibrium parameters of titratable groups.

The acoustic absorption of protein solutions in the presence of phosphate and other buffering ions has been studied in the physiological pH range. Buffers containing hydroxyl residues as titratable groups cause a pronounced increase of protein sound absorption, which is attributed to relaxation processes of proton transfer reactions between buffer ions and accessible imidazole and alpha-amino groups of the protein surface. Amino group based buffers like Good's buffers do not induce additional sound absorption. Measurement of the ultrasonic absorption as a function of pH and of buffer concentration, and corresponding parameter fitting of the equation describing proton transfer relaxation processes has been used to evaluate equilibrium parameters. For the imidazole group of the amino acid histidine a pK value of 6.22 and for the imidazole group of the protein lysozyme a pK value of 5.71 have been determined. In hemoglobin the ligand-linked pK changes have been monitored by recording ultrasonic titration curves.

Buffers↗
PubMed1992

The influence of buffers during fixation on the appearance of smooth endoplasmic reticulum and glycogen in hepatocytes of normal and glycogen-depleted rats.

Liver tissue of normal and glycogen depleted rats was prepared for transmission electron microscopy by perfusion fixation and subsequent osmication in the presence of various buffers, dehydration in aethanol and embedding in epon. The use of Na/K-phosphate or Na-cacodylate to buffer glutaraldehyde led to similar appearance and distribution of SER. When Na-cacodylate was used during osmication, more SER membranes were retained but less accumulations of glycogen were found than after osmication in the presence of Na/K-phosphate. Fixation with s-collidine buffered osmium led to an easily recognisable network of SER comprising wide tubules whereas glycogen was hindered to be stained. Veronal acetate or Na-cacodylate supplemented with sucrose resulted in marked dilation and disintegration of SER. A similar effect was obtained when Na/K-phosphate or Na-cacodylate was used in hyposmolar concentration as buffer for glutaraldehyde. Liver of fasted rats or glucagon-treated rats after perfusion with Na/K-phosphate buffered glutaraldehyde and osmication in the presence of Na/K-phosphate or Na-cacodylate comprised glycogen-depleted hepatocytes which contained abundant SER membranes occupying the entire space between other organelles even in samples harvested 3 h after glucagon administration. The diversity in appearance and distribution of SER and glycogen granules, which depends to a large extend on the buffer used, suggests that SER membranes may not be sufficiently stabilized during aldehyde fixation and osmication. We thus consider it likely that large accumulations of glycogen granules are the consequence of disintegration of SER membranes during processing rather than they represent the morphologic substrate of physiological degradation of SER membranes in the course of glycogen synthesis and deposition.

Animals↗
PubMed1977

Influence of fixation and buffer treatment on the release of enzymes from the plasma membrane.

1. Pretreatment of frozon cryostat sections with formaldehyde or calcium ions inhibits diffusion of the plasma membrane enzymes 5' nucleotidase, ATP-ase and alkaline phosphatase during incubation. 2. Treatment of fixed sections with different kinds of buffer at 37 degrees C induces diffusion of enzyme activity from the plasma membrane to other sites of the section and into the incubation medium. This buffer influence depends on temperature: at 4 degrees C only a slight diffusion occurs. Addition of phospholipase C, digitonin or taurocholate to the buffer opposes the buffer effect. 3. Pretreatment of frozen cryostat sections with a mixture of equal parts of chloroform and acetone give a good fixation of the plasma membrane enzymes 5'-nucleotidase, ATP-ase, alkaline phosphate and leucyl-beta-naphthylamidase. During this treatment the different kinds of lipids present in the membrane are ex-racted equally. After this fixation buffer treatment does not cause a visible diffusion of enzyme activity in the section. Only a slight diffusion (1 till 7 percent) into the buffer solution takes place. 4. The mentioned treatments open up possibilities to get insight into the membrane anchorage of plasma membrane enzymes.

Adenosine Triphosphatases↗
PubMed1986

The influence of extracellular buffer concentration and propionate on lactate efflux from frog muscle.

Lactate efflux from frog sartorius muscles was measured following a lactate load of about 18 mumol X g-1 induced by a 4-min period of stimulation. Lactate efflux rate was buffer concentration dependent. The initial efflux rate increased from about 150 nmol X g-1 X min-1 in 1 mM MOPS buffer to 400 nmol X g-1 X min-1 in 25 mM MOPS buffer. The addition of 20 mM propionate reduced mean intracellular pH by about 0.2 units and increased lactate efflux rate by 70% at the highest buffer concentration and 400% at the lowest buffer concentration. The observed results are in reasonable agreement with predictions based on a model in which net efflux is limited by diffusion of both buffer and lactate in the extracellular space. Transmembrane lactate efflux appears to consist of two components, one of which is proton linked and carried either by undissociated lactic acid or coupled proton-lactate transport, the other being carried by independent lactate ions.

Animals↗
PubMed1985

Potentiation of Na+-dependent uptake of gamma-aminobutyric acid in mouse brain particles by buffer-mediated proton removal.

A number of buffers showed a remarkable facilitatory effect on the uptake of GABA into a mouse brain microsomal subfraction (P3) at 0 degrees C and pH 7.3 in the presence of 80 mM NaCl. Complete dose-response curves were obtained for 21 buffers, ranging in pKa values from 6.2 to 9.9. The data are consistent with the interpretation that the unprotonated forms of the buffers are responsible for the enhancement of GABA uptake by P3 particles and that this is a result of the removal of protons from a membrane site (or sites) in such a manner as to allow the GABA transporter to function. However, the enhancing effects of the buffers could not solely be attributable to unhindered interaction of protonated membrane sites with unprotonated forms of the buffer. Additional factors related to structures of the buffers and membrane properties which might be importantly operative in the enhancement are discussed.

Animals↗
PubMed1987

pH-dependent electrical properties and buffer permeability of the Necturus renal proximal tubule cell.

Necturus kidneys were perfused with Tris-buffered solutions at three different pH values, i.e. 7.5, 6.0 and 9.0. A significant drop in fluid absorption occurred at pH 6.0, whereas pH 9.0 did not increase volume flow significantly. When acute unilateral, i.e. either in the lumen or the peritubular capillaries, and bilateral pH changes were elicited in both directions from 7.5 to 9.0 at a constant Tris-butyrate buffer concentration, both peritubular membrane potential difference V1 and transepithelial potential difference V3 hyperpolarized, independently of the side where the change in pH was brought about. Acid perfusions at pH 6.0 caused a similar response but of opposite sign. Analysis of the potential changes shows that pH influences not only the electromotive force and resistance of the homolateral membrane, but also the electrical properties of the paracellular path. Interference of pH with Na, Cl or K conductance was assessed. Any appreciable role for sodium or chloride was excluded, whereas the potassium transference number (tK) of the peritubular membrane increased 16% in alkaline pH. However, this increase accounts only for 19 to 36% of the observed hyperpolarization. Since changes in Tris-butyrate buffer concentration at constant pH do not affect V1 or V3 considerably, the hyperpolarization in pH 9 cannot be explained by an elevation in internal pH only, or by a Tris-H+ ion diffusion potential only. The role of the permeability of the buffers: bicarbonate, butyrate and phosphate, in determining electrical membrane parameters was evaluated. Transport numbers of the buffer anions ranked as follows: tHCO3 greater than tbutyrate greater than tphosphate. It is concluded that modulation of membrane potential by extracellular pH is mediated primarily by a change in peritubular cell membrane tK and additionally by membrane currents carried by buffer anions.

Animals↗
PubMed1999

The use of different buffers during continuous hemofiltration in critically ill patients with acute renal failure.

OBJECTIVE: To determine the impact of different hemofiltration (HF) replacement fluids on the acid-base status and cardiovascular hemodynamics in patients with acute renal failure (ARF) and continuous veno-venous hemofiltration (CVVH). DESIGN: Prospective, cohort study. SETTING: Intensive Care Unit of the Heinrich Heine University Hospital, Düsseldorf, Germany. SUBJECT AND METHODS: One hundred and thirty-two critically ill patients with acute renal failure and continuous veno-venous HF were studied. Fifty-two patients were subjected to lactate-based (group 1), and 32 to acetate-based hemofiltration (group 2) while 48 (group 3) were treated with bicarbonate-based buffer hemofiltration fluid. Fifty-seven had a septic, and 75 a cardiovascular, origin of the ARF. Creatinine, blood urea nitrogen (BUN), serum bicarbonate, arterial pH, lactate and Apache II scores were noted daily. MAIN RESULTS: The mean CVVH duration was 9.8 +/- 8.1 days, mortality was 65%. No difference was present between the groups under investigation with regard to the main clinical parameters. Lactate- and bicarbonate-based hemofiltration led to significantly higher serum bicarbonate and arterial pH values as compared to the acetate-based hemofiltration. Serum bicarbonate values at 48 h after the initiation of CVVH treatment were 25.7 +/- 3.8 mmol/l (p < 0.001) in group 1, 20.6 +/- 3.1 mmol/l in group 2 and 23.3 +/- 3.9 mmol/l (p < 0.001) in group 3. While a lack of increase in serum bicarbonate and arterial pH was correlated to poor prognosis in lactate- and bicarbonate-based hemofiltration, no such observation was made in acetate-based hemofiltration. Cardiovascular hemodynamics were superior in patients treated with lactate- and bicarbonate-based buffer solution as compared to those treated with acetate-based buffer solution. CONCLUSIONS: The degree of correction of acidosis during hemofiltration was determined by patient outcome in patients treated with lactate- and bicarbonate-based buffer solutions, but not in patients receiving acetate-buffered solution. Bicarbonate and lactate-based buffer solutions were found to be superior to acetate-based replacement fluid.

APACHE↗
PubMed2000

Modes of allosteric interactions with free and [3H]N-methylscopolamine-occupied muscarinic M2 receptors as deduced from buffer-dependent potency shifts.

Muscarinic M2 acetylcholine receptors contain an allosteric site that is probably located at the entrance of the ligand binding pocket above the orthosteric binding site. With the orthosteric area not occupied, allosteric agents might gain access to this site. The interaction of allosteric agents with orthoster-occupied receptors is known to depend on the buffer conditions in an alloster-specific fashion. Utilizing the buffer-dependent potency shift as an indicator, we aimed to find out for two rod-like shaped and flexible allosteric agents whether or not there is evidence for a switch in the site of attachment in free compared with [3H]N-methylscopolamine ([3H]NMS)-occupied porcine heart M2 receptors. These agents are the bispyridinium compounds WDuo3 (1,3-bis[4-(phthalimidomethoxyimino-methyl)-pyridinium-1-yl] propane dibromide) and Duo3 (4,4'-bis-[(2,6-dichloro-benzyloxy-imino)-methyl]-1,1'-propane-1,3-diyl-bis-pyridinium dibromide). The prototype allosteric agents gallamine and alcuronium were included. Inhibition of [3H]NMS association was taken to reflect alloster interaction with free receptors, inhibition of [3H]NMS dissociation indicated binding to [3H]NMS-occupied receptors. In Na,K,Pi buffer (4 mM Na2HPO4, 1 mM KH2PO4, pH 7.4 at 23 degrees C) compared with Mg,Tris,Cl,Pi buffer (45 mM Tris-HCl, 2.6 mM MgHPO4, pH 7.3 at 37 degrees C) WDuo3 underwent the same loss of potency for the interaction with either free or [3H]NMS-liganded receptors. The loss of potency was quantified by a potency ratio (PR), i.e. the ratio between the concentrations of the modulator leading to a half-maximal delay of [3H]NMS association or dissociation, respectively, in Mg,Tris,Cl,Pi compared with Na,K,Pi. For WDuo3 the ratios were PRass=27 and PRdiss=22, respectively. For Duo3, the interaction with free and [3H]NMS-occupied receptors only slightly depended on the composition of the incubation medium: PRass=1.3, PRdiss=2.8. In contrast to the other agents, the concentration-effect curves of which had slope factors nH not different from unity, the curves of Duo3 were steep (nH about -1.6). For alcuronium the shift factors amounted to PRass=29 and PRdiss=25, for gallamine to PRass=216 and PRdiss=159. In conclusion, there was a wide variation between the allosteric agents with regard to the respective buffer dependence of action. Yet, for a given allosteric agent, the interaction with either free or [3H]NMS-occupied receptors was always characterized by the same buffer-dependent shift. Thus, even the applied rod-shaped allosteric agents do not appear to switch to the orthosteric site in free compared with orthoster-occupied M2 receptors.

Alcuronium↗
PubMed2003

Bovine colostrum supplementation does not affect plasma buffer capacity or haemoglobin content in elite female rowers.

It has been reported that bovine colostrum (BC) supplementation improves buffer capacity (beta) during exercise, but whether the improvement results from changes in tissue and/or blood buffer systems has not been determined. The purpose of the present study was to examine the effect of supplementation with BC on blood buffer systems. Thirteen elite females rowers were supplemented with 60 g.day(-1) of either BC ( n=6) or whey protein (WP, n=7) during 9 weeks of pre-competition training in a randomised, double-blind, placebo-controlled, parallel design. All subjects undertook the study as a group and completed the same training program. Resting haemoglobin (Hb) concentration and plasma buffer capacity (pbeta) (determined by titration with HCl) were measured pre- and post-supplementation. There were no differences in macronutrient intakes ( P>0.56) or training volumes ( P>0.99) between BC and WP during the study period. There were no differences in Hb [BC 13.28 (0.28) mg.dl(-1), WP 13.70 (0.26) mg.dl(-1); P=0.45] or pbeta [BC 14.8 (1.1) nmol HCl.ml(-1).pH(-1), WP 14.8 (0.5) nmol HCl.ml(-1).pH(-1); P=0.68] between groups at week 0. pbeta increased in both groups during the study period ( P<0.001), but the increases were not significantly different between groups ( P=0.52). Hb did not change significantly in either group ( P=0.35). These data indicate that supplementation with BC does not affect pbeta or Hb. We therefore suggest that adaptations in tissue buffer systems are responsible for the previously reported increases in buffer capacity that result from BC supplementation.

Adaptation, Physiological↗
PubMed2004

Buffer capacity, pH, and flow rate in saliva of children aged 2-60 months with Down syndrome.

This study measured the flow rate, pH, and buffer capacity of saliva from children with Down syndrome aged 2-60 months. We compared 25 children with Down syndrome with 21 children without Down syndrome. The whole saliva was collected under slight suction and the pH and the buffer capacity were determined using a digital pHmeter. The buffer capacity was measured by titration with 0.01 N HCl. The Down syndrome group demonstrated higher buffer capacity than the control group in the pH ranges of 6.9-6.0, 5.9-5.0, and 4.9-4.0. The flow rate was low in the Down syndrome group. Boys from the Down syndrome group demonstrated higher buffer capacity in the pH ranges 6.9-6.0, 5.9-5.0, and 4.9-4.0 than controls, while girls from the Down syndrome group showed no difference compared with controls. Girls with Down syndrome demonstrated significant difference only in the range of pHi-pH 7.0. Conclusion. These data suggest that the Down syndrome persons present a better buffer capacity, supporting the results observed in several studies which found the low dental caries in persons with Down syndrome.

Buffers↗
PubMed1978

A simplified polyacrylamide gel electrophoresis apparatus for simultaneous application of multiple buffer systems or detergent combinations.

A previous design of an apparatus for the simultaneous fractionation by polyacrylamide gel electrophoresis in 10 different buffer systems (1) was replaced by a greatly simplified new design, employing small, cylindrical buffer partitions within the lower buffer reservoir and/or upper buffer reservoir of a conventional, temperature-regulated polyacrylamide gel electrophoresis apparatus for cylindrical gels. The apparatus was tested in application to the problem of simultaneous polyacrylamide gel electrophoresis in different buffer systems with the purpose of optimizing the operative pH for a particular fractionation problem. It was also applied to fractionations in a single buffer system to which various combinations of ionic and nonionic detergents were admixed.

Adenylyl Cyclases↗
PubMed1976

Effects of increased intracellular pH-buffering capacity on the light response of Limulus ventral photoreceptor.

Aspects of a possible involvement of hydrogen ions in the electrophysiological responses to light of Limulus ventral photoreceptors were investigated. A 1 M solution of either a zwitter-ionic pH buffer or a weakly-buffering control substance was pressure injected through a micropipette into a ventral photoreceptor cell. To estimate the amount injected, 35SO4 was included in the solution. Membrane currents induced by light flashes were measured by a voltage-clamp technique. The buffer-filled micropipette passed current and a 3M KCl filled micropipette monitored membrane voltage. The sensitivity (peak light-induced current/stimulus energy) was measured, after dark adaptation, before and after injection. Injections of buffers, pH 6.3-7.2, to intracellular concentrations of at least 40-200 mM produced only a small mean decrease in sensitivity, approximately equal to that caused by injections of control substances. Excitation, therefore, apparently is not mediated by a change in intracellular pH. Buffers with pH values 5.4-8.4 were also injected. The time to peak of the response depended on pH, being shortened by up to 20% at pH values below 7.7 and lengthened at higher pH values. The time to peak of the response appeared to be shortened by an increase in intracellular pH-buffering capacity even when there was no change in intracellular pH.

Animals↗