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PubMed1998

The pH buffering capacity of hippocampal slices from young adult and aged rats.

We examined the hypothesis that aging alters the capacity of brain tissue to buffer intracellular pH changes. Intracellular buffering power was determined in hippocampal slices from young adult and aged rats by raising the partial pressure of CO2. Changes in intracellular and extracellular pH in response to increases and decreases in CO2 were measured simultaneously with spectrophotometry and pH-sensitive microelectrodes. The intrinsic buffering power did not differ between young adult (25.6 +/- 11.1 mM) and aged (28.2 +/- 8.6 mM) slices. However, the bicarbonate buffering power was higher in young adult slices (72.52 +/- 5.07 mM) compared with aged slices (58.67 +/- 5.78 mM) since the resting intracellular pH was about 0.1 unit lower in aged slices. This decreased bicarbonate buffering capacity may contribute to the increased vulnerability of the aged brain to metabolic stress.

Aging↗
PubMed1986

Buffering capacity of human semen.

The buffering capacity of 270 semen samples derived from 196 men of infertile couples was determined from titration curves. The average buffering capacity in the physiologic range (pH 7.0 to 6.0) was 41.1 slyke (standard deviation [SD], 9.9), which is significantly higher (P less than 0.01) than that in serum (23.3 slyke; SD, 7.5; n = 42). When the buffering capacity of several semen samples of one man in the course of time was measured, the variation between these samples was larger than the determination error. No correlation was found between the buffering capacity of serum and semen of the same man, nor between the buffering capacity of semen and the fertility grade determined by physical and morphologic analysis of the samples.

Buffers↗
PubMed2002

Study of flow profile distortions and efficiency in counter pressure moderated partial filling micellar electrokinetic chromatography in relation to the relative buffer zone lengths.

The influence of the relative buffer zone lengths on the efficiency was investigated in partial filling micellar electrokinetic chromatography using sodium dodecyl sulfate as separation additive. Varying relative zone lengths were obtained by applying identical initial separation zone lengths but different total lengths of the capillaries. Plate numbers of a homologous series of omega-phenylalcohols were measured to indicate the effect of both a changing relative zone length during the run and a counter pressure applied on the cathodic buffer reservoir. The magnitude and the course of these plate numbers are discussed on the basis of models for flow profile superposition and flow profile deformation which are caused by an intersegmental pressure arising at the boundary between the two buffer zones with different electroosmotic flow velocities. Calculation of the intersegmental pressure and of the resulting laminar flow components in the buffer zones on the basis of some equations for electroosmotic and hydrodynamic flow supported the interpretation that a long background buffer zone should be avoided

Buffers↗
PubMed2003

Ammonium hydrogencarbonate, an excellent buffer for the analysis of basic drugs by liquid chromatography-mass spectrometry at high pH.

Ammonium hydrogencarbonate buffer has been found to be especially useful for high-pH HPLC analysis of samples from both combinatorial and medicinal chemistry sources. Satisfactory results were obtained by the standard diode array, evaporative light-scattering, and MS detection by using this buffer at a concentration of 10 mM. From a practical standpoint, ammonium hydrogencarbonate is an ideal buffer for chromatographers since it provides excellent chromatographic behaviour and reproducible separation. In addition to this, its volatility makes it an essential tool for rapid LC-MS product identification. Ammonium hydrogencarbonate was tested for a number of drug-like compounds analysed as mixtures, and data obtained were compared to those from the classical and MS-friendly buffers widely used by chromatographers: trifluoroacetic and formic acids. The results of this study revealed the suitability of this buffer for routine HPLC application in research laboratories.

Buffers↗
PubMed1997

Adhesion of Lactobacillus species in urine and phosphate buffer to silicone rubber and glass under flow.

Coating uroepithelial cells or catheter materials with lactobacilli has been shown to retard the development of a uropathogenic biofilm, with biosurfactant production and strong adhesion being two prerequisite properties of the Lactobacillus strains to be employed. In this paper, adhesion of six selected Lactobacillus strains to silicone rubber and glass in urine and in a phosphate buffer was studied using a parallel plate flow chamber. In addition, adhesive cell surface properties of the lactobacilli, i.e. the pH dependences of their zeta potentials and their hydrophobicities by water contact angles, were determined. L. acidophilus ATCC 4356 and L. fermentum B54 were the only strains showing significant adhesion to both hydrophobic silicone rubber and hydrophilic glass, possibly by virtue of their high cell surface hydrophobicities (water contact angles of 68 and 75 degrees, respectively) and small zeta potentials (-10.0 and -8.1 mV in buffer, respectively). Both hydrophobic Lactobacillus strains adhered less well in urine than in buffer. The remaining Lactobacillus strains studied were hydrophilic, with water contact angles between 25 and 36 degrees, and had highly negative zeta potentials, reaching -37.7 mV in buffer. Adhesion of these highly negatively charged, hydrophilic strains in buffer was essentially absent, while for some of these strains minor adhesion in urine was observed. This study demonstrates that the adhesion of lactobacilli to substrata differs with strain hydrophobicity and charge, and that urinary components can affect the ability of hydrophilic Lactobacillus strains to adhere to substrata.

Adult↗
PubMed1996

Some commonly overlooked properties of calcium buffer systems: a simple method for detecting and correcting stoichiometric imbalance in CaEGTA stock solutions.

When the two-solution approach is used to make CaEGTA buffers, the most critical requirement is that the CaEGTA stock solution contain equimolar quantities of calcium and chelator. The impact on [Ca2+] of errors in the molar ratio is magnified at high buffer ratios, so stoichiometric imbalance is most readily detected there. In this paper we examine some of the properties of calcium buffer systems that illustrate these principles, and describe a simple and sensitive method for detecting and correcting stoichiometric imbalance in the CaEGTA stock solution. The method derives its high sensitivity from the fact that the CaEGTA stock solution itself represents a calcium buffer system with a very high buffer ratio.

Buffers↗
PubMed1990

Bicarbonate-buffered lidocaine-epinephrine-hyaluronidase for eyelid anesthesia.

A double-masked, randomized clinical trial was conducted to determine if subcutaneous eyelid injections of a bicarbonate-buffered lidocaine-epinephrine-hyaluronidase mixture were less painful than unbuffered injections. Twenty-one patients received both buffered (pH = 7.4) and unbuffered (pH = 4.6) injections. After each injection, patients recorded pain on a scale of 0, "no pain," to 10, "severe pain." Mean pain score for buffered injections was 2.0 versus 4.1 for unbuffered injections (P = 0.0003). Seventeen (81%) of 21 patients ranked the buffered injection less painful. Use of a bicarbonate-buffered lidocaine-epinephrine-hyaluronidase mixture is effective in making ophthalmic anesthesia less painful.

Adult↗
PubMed2000

Regulation of exocytosis in neuroendocrine cells: spatial organization of channels and vesicles, stimulus-secretion coupling, calcium buffers and modulation.

Neuroendocrine cells display a similar calcium dependence of release as synapses but a strongly different organization of channels and vesicles. Biophysical and biochemical properties of large dense core vesicle release in neuroendocrine cells suggest that vesicles and channels are dissociated by a distance of 100-300 nm. This distinctive organization relates to the sensitivity of the release process to mobile calcium buffers, the resulting relationship between calcium influx and release and the modulatory mechanisms regulating the efficiency of excitation-release coupling. At distances of 100-300 nm, calcium buffers determine the calcium concentration close to the vesicle. Notably, the concentration and diffusion rate of mobile buffers affect the efficacy of release, but local saturation of buffers, possibly enhanced by diffusion barriers, may limit their effects. Buffer conditions may result in a linear relationship between calcium influx and exocytosis, in spite of the third or fourth power relation between intracellular calcium concentration and release. Modulation of excitation-secretion coupling not only concerns the calcium channels, but also the secretory process. Transmitter regulation mediated by cAMP and PKA, as well as use-dependent regulation involving calcium, primarily stimulates filling of the releasable pool. In addition, direct effects of cAMP on the probability of release have been reported. One mechanism to achieve increased release probability is to decrease the distance between channels and vesicles. GTP may stimulate release independently from calcium. Thus, while in most cases primary inputs triggering these pathways await identification, it is evident that large dense core vesicle release is a highly controlled and flexible process.

Animals↗
PubMed1993

Buffered versus plain lidocaine for digital nerve blocks.

STUDY OBJECTIVES: To test whether buffered lidocaine is less painful to administer as a digital nerve block than plain lidocaine. DESIGN: Randomized, double-blind, prospective clinical trial. SETTING: University hospital emergency department. PARTICIPANTS: Adults not allergic to lidocaine requiring a digital nerve block. INTERVENTIONS: Subjects received digital nerve blocks by injection of buffered lidocaine on one side and plain lidocaine on the other in a predetermined, randomized order. Pain of infiltration was assessed. Scores were compared using a two-tailed t-test. Standard 1% lidocaine was used if additional anesthetic was required. MEASUREMENTS AND MAIN RESULTS: Thirty-one patients were enrolled. Buffered lidocaine was significantly less painful to administer than plain lidocaine (P < .001; t = 4.21). Supplemental anesthesia was required less often for buffered lidocaine (two times) compared with plain lidocaine (six times), although this difference was not statistically significant. CONCLUSION: Because it causes less pain and is equally efficacious, buffered lidocaine is preferable to plain lidocaine for digital nerve blocks in adults.

Adolescent↗
PubMed1995

Comparison of plain, warmed, and buffered lidocaine for anesthesia of traumatic wounds.

STUDY OBJECTIVE: To compare pain on infiltration, need for additional anesthesia, and pain on suturing in patients given plain, warm, and buffered lidocaine preparations before the suturing of traumatic wounds in the emergency department. DESIGN: Randomized, prospective, single-blinded convenience sample. SETTING: University hospital ED. PARTICIPANTS: Patients with traumatic lacerations. Patients allergic to lidocaine and patients with abnormal mental status or altered pain sensorium were excluded. INTERVENTIONS: All wounds were anesthetized by use of a standard injection technique. Wound margins were anesthetized with plain, buffered, or warm lidocaine in a randomized fashion. Pain of infiltration was recorded for each margin by means of a previously validated visual-analogue pain scale. RESULTS: The main outcome parameter was pain of infiltration. Need for additional anesthesia and pain on suturing were secondary outcome parameters. We evaluated 45 patients. Pain on injection varied by the type of lidocaine (mean pain scores: plain, 8.2; buffered, 4.7 [P < .05 versus plain]; warm, 4.9 [P < .05 versus plain]). There was no significant difference between the mean pain scores of the groups given warm and buffered lidocaine (P = NS). Need for additional anesthesia and pain on suturing did not vary by the type of anesthesia. The order of injection was not found to influence results. Mean pain scores were not different for margins 1 and 2 in any of the groups (P = NS). CONCLUSION: Both buffered and warmed lidocaine were as efficacious as plain lidocaine, and they had significantly less pain associated with infiltration than did plain lidocaine. In EDs with fluid warmers, warmed lidocaine may be the most convenient, well-tolerated, efficacious lidocaine preparation for anesthesia of traumatic wounds.

Adolescent↗
PubMed1995

A randomized, controlled trial of oral midazolam and buffered lidocaine for suturing lacerations in children (the SLIC Trial).

STUDY OBJECTIVE: To evaluate the efficacy of oral midazolam (0.3 mg/kg) and buffered lidocaine in reducing the anxiety associated with the repair of childhood lacerations. DESIGN: Prospective, randomized, double-blind, placebo-controlled trial. SETTING: Community-based emergency department. PARTICIPANTS: Children younger than 10 years. INTERVENTIONS: Each subject was randomized into one of four treatment groups: A, midazolam and buffered lidocaine (n = 25); B, placebo and buffered lidocaine (n = 27); C, midazolam and plain lidocaine (n = 32); and D, placebo and plain lidocaine (n = 23). RESULTS: Anxiety level was scored on a scale of 1 to 4 on the basis of predetermined behavior criteria before and during repair. Parents independently rated the child's distress using a visual analog scale. Vital signs were measured on admission and at discharge. There were no significant differences among the treatment groups for age, location and length of laceration, or initial anxiety scores. Midazolam decreased the number of children with anxiety levels 3 and 4 by 24% (95% CI, 7.5% to 41.3%). There was a 33% reduction of the parents' distress rating with midazolam (P < .01). Buffered lidocaine had no effect on anxiety level. CONCLUSION: Oral midazolam (0.3 mg/kg) is a safe and effective treatment for reducing anxiety during the suturing of lacerations in children less than 10 years of age. In this study, buffered lidocaine had no effect on anxiety level.

Administration, Oral↗
PubMed1998

Pain of local anesthetics: rate of administration and buffering.

STUDY OBJECTIVE: To determine the impact of administration rate and buffering on the pain associated with subcutaneous infiltration of lidocaine. METHODS: Forty-two adult volunteers employed at a tertiary care center participated in this prospective, single-blinded study. Each subject received four lidocaine injections prepared and administered as follows: slow, buffered (SB); slow, unbuffered (SU); rapid, buffered (RB); rapid, unbuffered (RU). Buffering was accomplished by mixing 1% lidocaine with 8.4% sodium bicarbonate in a 9:1 ratio. Slow administration was 30 seconds and rapid was 5 seconds. Needle size (27-gauge), injection depth (.25 inch), lidocaine volume (1.0 mL), and temperature (room) were the same for each of the four injections. In all four conditions, the needle remained in the forearm for 30 seconds, to ensure blinding. The main outcome measure was the mean pain score for each condition, as recorded on a 10-cm visual analog scale. RESULTS: The lowest pain scores (mean +/- SE) were recorded for the SU and SB conditions at 1.49 +/- 29 and 1.48 +/- 26, respectively, and they were significantly lower than the scores for RB (2.34 +/- 28; P < .01) or RU (3.11 +/- 33; P < .001). Each of the slow conditions was reported to be the "least painful" of the four significantly more often than either rapid condition. CONCLUSION: This is the largest blinded study to assess administration rate and the pain of a local anesthetic. We found that administration rate had a greater impact on the perceived pain of lidocaine infiltration than did buffering.

Adult↗
PubMed2002

Buffer administration during CPR promotes cerebral reperfusion after return of spontaneous circulation and mitigates post-resuscitation cerebral acidosis.

To explore the effects of alkaline buffers on cerebral perfusion and cerebral acidosis during and after cardiopulmonary resuscitation (CPR), 45 anaesthetized piglets were studied. The animals were subjected to 5 min non-interventional circulatory arrest followed by 7 min closed chest CPR and received either 1 mmol/kg of sodium bicarbonate, 1 mmol/kg of tris buffer mixture, or the same volume of saline (n=15 in all groups), adrenaline (epinephrine) boluses and finally external defibrillatory shocks. Systemic haemodynamic variables, cerebral cortical blood flow, arterial, mixed venous, and internal jugular bulb blood acid-base status and blood gases as well as cerebral tissue pH and PCO(2) were monitored. Cerebral tissue acidosis was recorded much earlier than arterial acidaemia. After restoration of spontaneous circulation, during and after temporary arterial hypotension, pH in internal jugular bulb blood and in cerebral tissue as well as cerebral cortical blood flow was lower after saline than in animals receiving alkaline buffer. Buffer administration during CPR promoted cerebral cortical reperfusion and mitigated subsequent post-resuscitation cerebral acidosis during lower blood pressure and flow in the reperfusion phase. The arterial alkalosis often noticed during CPR after the administration of alkaline buffers was caused by low systemic blood flow, which also results in poor outcome.

Acidosis↗
PubMed1998

Alkaline buffers for correction of metabolic acidosis during cardiopulmonary resuscitation with focus on Tribonat--a review.

A combined hypercarbic and metabolic acidosis develops during the low flow state of cardiac arrest treated with cardiopulmonary resuscitation. Several negative consequences of the acidosis have been demonstrated, two of the most important being reduced contractility of the ischaemic but still beating myocardium and impaired resuscitability of the arrested heart. Even though interventions to re-establish a spontaneous circulation should be the number one priority during cardiopulmonary resuscitation, attempts to treat the acidosis are often carried out in order to avoid the reported negative inotropic effect. Different alkaline buffers have been used, but it has been demonstrated over the years that such treatment may aggravate the situation due to a variety of deleterious side-effects of the buffers. A mixture of THAM, acetate, sodium bicarbonate and phosphate registered as Tribonat has been suggested as a suitable alternative to conventional buffer substances. The problems preceding the designation of Tribonat as well as studies evaluating its effects are reviewed in this article. Tribonat seems to offer a more well-balanced buffering without any major disadvantages compared with previously used alkaline buffers, even though improved survival has not been reported.

Acidosis↗
PubMed1990

Cardiac effects of carbon dioxide-consuming and carbon dioxide-generating buffers during cardiopulmonary resuscitation.

Recent studies have demonstrated an increase in carbon dioxide (CO2) tension (PCO2) in both mixed venous and coronary vein blood early in the course of cardiac arrest and cardiopulmonary resuscitation. Because increased PCO2 in the myocardium correlates with both ischemic injury and depression of contractile function, the effects of hypertonic solutions of either the CO2-"generating" sodium bicarbonate (NaHCO3) buffer, a mixture of sodium carbonate (Na2CO3) and sodium bicarbonate (carbicarb) acting as a CO2-"consuming" buffer, or saline placebo (NaCl) were compared during cardiopulmonary resuscitation in 25 healthy minipigs. Both buffer agents significantly increased the pH and HCO3- of arterial, mixed venous and coronary vein blood. Bicarbonate increased whereas carbicarb reduced blood PCO2 in the systemic circuit as anticipated. However, neither the PCO2 nor the lactate content of coronary vein blood was favorably altered by buffer therapy. Four of eight animals treated with bicarbonate, five of eight treated with carbicarb and six of nine placebo-treated animals were successfully resuscitated and had a comparable 24 h survival rate. Coronary perfusion pressure during precordial compression, a critical determinant of resuscitability, was transiently decreased by each of the hypertonic solutions. Accordingly, neither CO2-generating nor CO2-consuming buffers mitigated increases in coronary vein PCO2 or improved the outcome of cardiopulmonary resuscitation under these experimental conditions.

Acid-Base Equilibrium↗
PubMed2003

Impedance characterization of a piezoelectric immunosensor. Part I: antibody coating and buffer solution.

This study investigated the impedance characteristics of a 5 MHz quartz crystal resonator oscillating in a thickness-shear mode for utilization as a biosensor. An impedance analyzer measured the impedance of the quartz crystal, which determined all mechanical properties of the oscillating quartz and its immediate environment. In this study, the impedance behavior of the oscillating crystal was characterized in air, in potassium phosphate buffer solution, and with immobilization of antibodies using protein-A. The potassium phosphate buffer behaved like a Newtonian liquid. The series resonance frequency shifted down about 900 Hz on contact with the buffer. An immobilized-antibody layer on the quartz surface behaved like a rigid mass when immersed in the buffer solution. The impedance curve following immobilization of antibodies was shifted down in frequency by about 200 Hz compared with its value when the bare crystal was immersed in the buffer solution.

Antibodies↗
PubMed2005

Quantitative predictions to conditions of zwitterionic stacking by transient moving chemical reaction boundary created with weak electrolyte buffers in capillary electrophoresis.

This paper develops a novel procedure of quantitative predictions for the on-column stacking conditions of a zwitterionic analyte by a moving chemical reaction boundary (MCRB) in capillary electrophoresis (CE). The procedure concerns the choice of the weak acidic running and alkaline sample buffers and the velocity design of MCRB created with the two buffers. Based on the theory of MCRB, the theoretical computations are performed. From the computations, the following two predictions are refined for the stacking conditions of zwitterion. (1) The zwitterion velocity in the acidic buffer should be greater than that of MCRB moving toward the cathode, or the zwitterion cannot be well stacked by the MCRB. (2) The gap between pH values of the acidic and alkaline sample buffers ought to comprise the isoelectric point (pI) of zwitterion to be stacked; namely, there exists the relation of pH (acidic buffer) < pI < pH (sample). The predictions are quantitatively proved by the experiments of zwitterionic stacking with two kinds of MCRBs. In addition, the experiments also show the tightly stacked peak of zwitterion existing in the process of MCRB, but not after the MCRB. The theoretical and experimental results hold obvious significances to other zwitterion (such as peptide and protein) on-column stacking in CE.

Buffers↗
PubMed1985

Release of exchangeably bound guanine nucleotides from tubulin in a magnesium-free buffer.

The number of moles of guanine nucleotides (denoted GXP), either guanosine 5'-triphosphate (GTP) or guanosine 5'-diphosphate (GDP), bound to a mole of phosphocellulose-purified tubulin after gel filtration into a variety of nucleotide-free buffers has been measured (H. B. Croom, J. J. Correia, and R. C. Williams, Jr., unpublished results). All buffers we have studied that promote reduction of the number of bound nucleotides to fewer than two per tubulin dimer also eventually cause irreversible loss of activity of the protein. However, in 0.1 M 1,4-piperazinediethanesulfonic acid (pH 6.9) and 2 mM dithioerythritol (with no Mg2+), tubulin rapidly releases approximately 0.4 mol of bound nucleotides during two successive gel filtrations requiring less than 0.5 h and regains the ability to polymerize when magnesium and GTP are immediately added to the buffer. No change in conformation detectable by circular dichroism or sedimentation velocity accompanies this reversible process. (Upon prolonged incubation in the buffer, however, tubulin undergoes irreversible changes according to apparent first-order kinetics with a half-life of approximately 8 h. These changes include the irreversible release of nucleotide, a loss of the ability to polymerize, and a decrease in molar ellipticity between 210 and 240 nm.) The nucleotide which is reversibly released in this buffer comes from that population which exchanges readily with [3H]GTP in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗