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PubMed2003

Helicobacter pylori strain ATCC700392 encodes a methyl-accepting chemotaxis receptor protein (MCP) for arginine and sodium bicarbonate.

Helicobacter pylori ATCC43504 responds chemotactically to aspartic acid and serine, but not to arginine, nor to sodium bicarbonate. In contrast, H. pylori ATCC700392 (strain 26695) shows chemotaxis to all four attractants. Open reading frame HP0099 from H. pylori 26695 is predicted to encode one of three methyl-accepting chemotaxis receptor proteins (MCPs). When Escherichia coli is transformed with a plasmid carrying HP0099 from strain 26695, the recombinants acquire chemotaxis to arginine, bicarbonate, and urea. In H. pylori 43504, the HP0099 gene is interrupted with a mini-IS605 insertion, which accounts for its inability to recognize arginine and bicarbonate as attractants. Together, these results argue that the H. pylori HP0099 gene encodes an MCP for arginine and bicarbonate.

Arginine↗
PubMed2000

Calorimetry a method to be used to characterise pyrolytically decarboxylated bicarbonate and assess its stability at elevated humidities.

Microcalorimetry was used to characterise bicarbonate after treatment at high temperatures. By measuring the heat flow from a sample of bicarbonate at 100% relative humidity, the net exothermic contribution could be used to estimate the fraction of pyrolytically formed Na(2)CO(3). The enthalpy value corresponding to the heat of solution of Na(2)CO(3) was also applicable to a physical mixture of NaHCO(3)/Na(2)CO(3). However, from the characteristic peaks of the heat flow versus time curve, pyrolytically formed Na(2)CO(3) could be distinguished from that present in the physical mixture. The different bicarbonate batches of varying degree of pyrolytic decarboxylation were also observed at an elevated relative humidity of 54%. From these measurements it could be inferred that a decarboxylation of up to 4.5% could be allowed without any significant effect on the stability of bicarbonate at 54%.

Calorimetry↗
PubMed1977

Bacteriostasis of Escherichia coli by milk. II. Effect of bicarbonate and transferrin on the activity of infant feeds.

Fresh human and bovine milk are bacteriostatic in vitro for only some (milk-sensitive) strains of E. coli. The addition of bicarbonate to the test system potentiates the bacteriostasis so that otherwise milk-resistant strains are inhibited. By titration of the bicarbonate in the milk, it is possible to determine the minimum concentration that will activate milk aganinst a milk resistant strain but be ineffective in boiled milk, i.e. it potentiates a heat-labile system in milk and does not merely exert a direct toxic effect. This concentration is lower for human milk than for cow's milk and can be reduced even further by the addition of more iron-binding protein. Lactoferrin and bicarbonate may be present in the gut of the newborn. In an attempt to imitate conditions in the infant gut, we therefore reinvestigated, in vitro and in the presence of added bicarbonate and transferrin, the bacteriostatic activity against E. coli of fresh breast-milk, commercial bottle-milk, and mixtures of these as fed to infants in the study. The results, and information about events in vivo deduced from the ratio of milk-sensitive to milk-resistant strains of E. coli isolated from babies' stool suggest that neonatal intestinal secretions may contribute to the bacteriostatic activity of their feeds so that (1) in fully breastfed babies all strains of E. coli are inhibited to the same extent; there is no selection on the basis of milk sensitivity and equal numbers of strains resistant and sensitive to milk are found in the stools; (2) in fully bottle-fed babies E. coli is not inhibited since the milk is non-bacteriostatic and again there is no selection; (3) in babies fed at the breast but bottle-milk supplemented, only milk-sensitive strains are inhibited; milk-resistant strains are not, and preferentially colonize the large intestines.

Animals↗
PubMed2003

Influence of backbone conformations of human carbonic anhydrase II on carbon dioxide hydration: hydration pathways and binding of bicarbonate.

In this study, the hydration of carbon dioxide and the formation of bicarbonate in human carbonic anhydrase II have been examined. From semiempirical QM/MM molecular dynamics studies, dominant conformations of the protein backbone, possibly contributing to the catalytic activity, have been isolated and further examined by means of density functional QM/MM methods. In agreement with experimental observations, a binding site for cyanate, which acts as an inhibitor, has been located, whereas for carbon dioxide, depending on the conformation of the protein environment, either a different binding site or no binding site has been found. In the latter case, carbon dioxide diffuses barrierless to the zinc-bound oxygen, and then a weakly bound bicarbonate complex is formed. The formed complex is characterized by a long C-O bond to the zinc-bound hydroxide. The nature of the calculated stationary points was verified by determination of vibrational frequencies. Finally, the dissociation of the formed bicarbonate from zinc has been considered. Therefore, a water molecule was included in the QM zone of the QM/MM hybrid potential, and minimization yielded a pentacoordinated intermediate. From a potential energy scan, an activation energy of 6.2 kcal/mol for dissociation of bicarbonate from Zn has been found.

Bicarbonates↗
PubMed2000

[Standard bicarbonate and base excess--obsolete parameters!].

The various techniques of interpretation of acid-base disorders are reviewed with special reference to the in vitro generated parameters 'standard bicarbonate' and 'base excess' on one hand and to the application of in vivo physiological data on the different acid-base disturbances on the other hand. The pivotal assumption that in vitro titration of PCO2 in whole blood (needed for estimation of standard bicarbonate and base excess) is representative for the in vivo behavior of the intact organism lacks any supportive evidence. The more serious pitfalls of interpretating acid-base problems by use of standard bicarbonate and base excess can be: 1. Inaccurate identification of the severity of an underlying acid-base disturbance, 2. Inadequate estimation of the time course of adaptation to an acid-base disorder (acute versus chronic) and 3. Failure to identify mixed acid-base disorders. Therefore, it is strongly recommended to use the traditional parameters (pH, PCO2, bicarbonate) in the light of the wealth of physiological in vivo data that form a sound basis for accurate clinical diagnosis.

Acid-Base Imbalance↗
PubMed1980

Localization of parathyroid-hormone-independent sodium bicarbonate inhibition of tubular phosphate reabsorption.

We investigated phosphate transport along superficial nephrons in two groups of acutely parathyroidectomized (APTX) rats. Animals of group 1 were infused with 0.5 M sodium chloride; and those of group 2, with 0.5 M sodium bicarbonate at the same rates. Compared to the sodium chloride infusion, the sodium bicarbonate infusion was associated with a significant increase in urinary excretion of phosphate: the fractional phosphate excretion was 2.3 +/- (SD) 1.3% in the sodium chloride group and 14.4 +/- 3.2% in the sodium bicarbonate group, P less than 0.01, whereas the fractional sodium excretion was identical, 7.4 +/- 0.60% and 7.5 +/- 0.50%. Micropuncture studies performed at the late accessible proximal and early accessible distal sites of the same superficial nephrons indicate that the reabsorptive capacity for phosphate (absolute reabsorption/absolute delivered phosphate per nephron segment) is decreased during sodium bicarbonate infusion in the convoluted proximal tubule as well as in the loop (segment located between late proximal and early distal accessible convolutions) and the terminal nephron. Such an effect is independent of both parathyroid hormone secretion and extracellular fluid volume expansion.

Animals↗
PubMed1985

Effects of acetate and bicarbonate dialysate in stable chronic dialysis patients.

The effects of acetate and bicarbonate dialysate on the biochemical and clinical parameters of 16 stable chronic hemodialysis patients were investigated in a double-blind crossover study. A central delivery system was used for both types of dialysates with identical sodium concentrations (138 mEq/liter) and osmolality in a single-pass dialysate flow. The results indicate that dialysis with bicarbonate leads to significantly less hypoxemia (P less than or equal to 0.001) and hypotensive episodes (P less than or equal to 0.002) than with acetate. Pre- to post-dialysis blood pressure changes were also more marked during acetate dialysis. Older patients with recurrent hypotension on acetate benefit most from bicarbonate dialysate. This group of patients appears to metabolize acetate more slowly and has a significantly lower post-dialysis bicarbonate concentration (P less than or equal to 0.005) than asymptomatic patients during dialysis with acetate dialysate.

Acetates↗
PubMed1995

Bicarbonate transport in collecting duct segments during chloride-depletion alkalosis.

Renal correction of chloride-depletion alkalosis (CDA) by chloride replacement results in bicarbonate secretion in the cortical collecting duct (CD) and urinary bicarbonate excretion. To assess the participation of the more distal segments of the CD, we determined net total CO2 transport in the outer medullary (OMCD), initial (IMCDi) and terminal (IMCDt) inner medullary CD segments obtained from Sprague-Dawley rats with normal acid-base balance (NML) or with CDA produced by peritoneal dialysis. Tubules were bathed and perfused with isotonic solutions containing Cl 110 mM and HCO, 25 mM. Net total CO2 transport was decreased in all segments: OMCD 22.1 +/- 4.2 to 9.2 +/- 2.0; IMCDi 38.1 +/- 4.6 to 9.3 +/- 1.7; IMCDt 6.7 +/- 1.2 to -0.5 +/- 0.4 pmol/min/mm tubule length. Perfusion rates, tubule lengths, and transepithelial voltages did not differ between groups in any segment. These data show that all CD segments beyond the cortical segment decrease bicarbonate reabsorption during CDA. This permits the bicarbonate secreted by the cortical CD to be excreted, and is likely an important mechanism for the correction of CDA.

Acid-Base Equilibrium↗
PubMed2004

Bicarbonate activation of adenylyl cyclase via promotion of catalytic active site closure and metal recruitment.

In an evolutionarily conserved signaling pathway, 'soluble' adenylyl cyclases (sACs) synthesize the ubiquitous second messenger cyclic adenosine 3',5'-monophosphate (cAMP) in response to bicarbonate and calcium signals. Here, we present crystal structures of a cyanobacterial sAC enzyme in complex with ATP analogs, calcium and bicarbonate, which represent distinct catalytic states of the enzyme. The structures reveal that calcium occupies the first ion-binding site and directly mediates nucleotide binding. The single ion-occupied, nucleotide-bound state defines a novel, open adenylyl cyclase state. In contrast, bicarbonate increases the catalytic rate by inducing marked active site closure and recruiting a second, catalytic ion. The phosphates of the bound substrate analogs are rearranged, which would facilitate product formation and release. The mechanisms of calcium and bicarbonate sensing define a reaction pathway involving active site closure and metal recruitment that may be universal for class III cyclases.

Adenosine Triphosphate↗
PubMed1979

Mechanism of the stimulation of serine and alanine transport into isolated rat liver cells by bicarbonate ions.

1. Bicarbonate ions stimulate the transport of serine and alanine into isolated hepatocytes. 2. The effect of bicarbonate is to increase the Vmax. of the transport process without changing the apparent Km. 3. The intracellular pH was estimated from the distribution of the weak base methylamine and the weak acid 5,5'-dimethyloxazolidine-2,4-dione (DMO) across the plasma membrane. 4. The addition of bicarbonate to a cell suspension caused the internal pH to become more acid. 5. The initial rate of serine, alanine and glycine transport was a linear function of the initial difference in pH across the membrane. 6. It is concluded that bicarbonate activates the transport of these amino acids primarily by increasing the pH difference across the plasma membrane. 7. It is suggested that the uptake of serine together with Na+ ions occurs in exchange for H+ ions, which are translocated outwards on the same carrier system. Some preliminary evidence consistent with this model is presented.

Alanine↗
PubMed2002

Acetazolamide inhibits stimulated feline liver and gallbladder bicarbonate secretion.

Bile acidification is a key factor in preventing calcium carbonate precipitation and gallstone formation. Carbonic anhydrase II (CA II), that is inhibited by acetazolamide, plays a role in regulation of the acid-base balance in many tissues. This study examines the effect of acetazolamide on secretin- and vasoactive intestinal peptide (VIP)-stimulated gallbladder mucosal bicarbonate and acid secretion. Gallbladders in anaesthetized cats were perfused with a bicarbonate buffer bubbled with CO2 in air. In 20 experiments VIP (10 microg kg(-1) h(-1)) and in 10 experiments secretin (4 microg kg(-1) h(-1)) were infused continuously intravenous (i.v.). Hepatic bile and samples from the buffer before and after perfusion of the gallbladder were collected for calculation of ion and fluid transport. During basal conditions a continuous secretion of H+ by the gallbladder mucosa was seen. Intravenous infusion of vasoactive intestinal peptide (VIP) and secretin caused a secretion of bicarbonate from the gallbladder mucosa (P < 0.01). This secretion was reduced by intraluminal (i.l.) acetazolamide (P < 0.01). Bile flow was enhanced by infusion of VIP and secretin (P < 0.01) but this stimulated outflow was not affected by i.v. acetazolamide. The presence of CA II in the gallbladder was demonstrated by immunoblotting. Biliary CA activity has an important function in the regulation of VIP- and secretin-stimulated bicarbonate secretion across the gallbladder mucosa.

Acetazolamide↗
PubMed2000

Alkalinization of amide local anaesthetics by addition of 1% sodium bicarbonate solution.

A number of methods exist by which the pH of local anaesthetic solutions may be increased. Most commonly, these require the addition of differing amounts of sodium bicarbonate solution according to the local anaesthetic drugs. Sodium bicarbonate (1%) was titrated against pH in six commonly used local anaesthetic solutions. Titration curves of pH and volume of sodium bicarbonate solution added are shown for this group of local anaesthetics. This study demonstrates that 1 mL of 1% sodium bicarbonate solution may be used to alkalinize this range of local anaesthetics without the risk of precipitation. We also conclude that Ropivacaine (at concentration 0.75% and 1.0%), is unsuitable for alkalinization since it precipitates at a pH of 6.0.

Alkalies↗
PubMed2003

Enhancement of biocontrol activity of yeasts by adding sodium bicarbonate or ammonium molybdate to control postharvest disease of jujube fruits.

AIMS: To assess the potential of sodium bicarbonate and ammonium molybdate as additives in enhancing the biocontrol efficacy of Rhodotorula glutinis and Cryptococcus laurentii against blue mould in jujube fruits. METHODS AND RESULTS: Two yeasts at a concentration of 107 CFU ml-1, in combination with 238 mmol l-1 sodium bicarbonate or 15 mmol l-1 ammonium molybdate, showed a significant inhibition effect on blue mould of jujube fruits stored at 20 degrees C for 5 days. The colonizing ability of the yeasts in wounded sites was significantly decreased in the presence of ammonium molybdate. CONCLUSIONS: Combining R. glutinis or C. laurentii with sodium bicarbonate or ammonium molybdate provided a more effective control of postharvest disease than using the antagonistic yeasts or the chemicals alone. SIGNIFICANCE AND IMPACT OF THE STUDY: The addition of sodium bicarbonate or ammonium molybdate reduced the number of antagonists required to efficiently control disease of postharvest fruits, which could result in the reduction of costs.

Antibiosis↗
PubMed1998

Biocompatibility and buffers: effect of bicarbonate-buffered peritoneal dialysis fluids on peritoneal cell function.

BACKGROUND: Conventional peritoneal dialysis fluids (PDF) have been shown to compromise the function of both leukocytes and human peritoneal mesothelial cells (HPMC). Various in vitro studies have identified the low initial pH in combination with high lactate content, as well as the hyperosmolality and high glucose concentration present in currently used solutions as the primary determinants of their bioincompatibility. Bicarbonate buffered PDF (at neutral pH) display improved in vitro biocompatibility as compared to conventional, lactate buffered PDF. However, little information is currently available regarding the potential impact of PDF on the function of human peritoneal fibroblasts (HPFB), the major cell population present in peritoneal interstitium. METHODS: The current study compares the effect of bicarbonate and lactate buffered PDF in a model system of resting peritoneal mesothelial cells and fibroblasts cultured from human omentum. Interleukin-1 beta-stimulated IL-6 release from HPMC and HPFB was used as the cell functional parameter. RESULTS: While short (30 min) pre-exposure to lactate buffered PDF significantly reduced the IL-1 beta-stimulated IL-6 release from HPMC during a subsequent recovery period (24 hr), a significant decrease in HPMC IL-6 secretion with bicarbonate buffered PDF was only observed after prolonged (> or = 60 min) exposure. In contrast, no significant IL-6 inhibition was detected with HPFB pre-exposed to PDF for up to 90 minutes. A significant suppression of HPFB IL-6 secretion was only observed in coincubation experiments (24 hr) with dilutions of both types of PDF. CONCLUSIONS: These results indicate that (i) bicarbonate buffered PDF are less inhibitory to peritoneal cell function as compared to conventional, lactate buffered PDF; and (ii) HPFB may be more resistant than HPMC to bioincompatible PDF.

Bicarbonates↗
PubMed2002

Effects of pH-neutral, bicarbonate-buffered dialysis fluid on peritoneal transport kinetics in children.

BACKGROUND: Due to their superior biocompatibility, pH-neutral solutions are beginning to replace acidic lactate-buffered peritoneal dialysis (PD) fluids. We hypothesized that pH-neutral and acidic solutions might differentially affect peritoneal transport in the early dwell phase, due to differences in ionic shifts and initial peritoneal vasodilation. Such differences may become clinically relevant in patients with frequent short cycles on automated PD (APD). METHODS: Twenty-five children were treated with a lactate-buffered (35 mmol/L, pH 5.5) or a bicarbonate-buffered PD solution (34 mmol/L, pH 7.4) in randomized order on two sequential days. Each day a four-hour Standardized Permeability Analysis (SPA) was performed, followed by overnight APD (7 cycles, fill volume 1000 mL/m2, dwell time 75 min). Functional peritoneal surface area was dynamically assessed using the three-pore model. RESULTS: While intraperitoneal pH was constant at 7.41 +/- 0.03 throughout the SPA with bicarbonate fluid, the dialysate remained acidic for more than one hour with lactate solution (pH 7.12 +/- 0.08 at 1 h). Total pore area was 60% higher during the first 30 minutes of the dwell than under steady-state conditions, without a difference between acidic and pH-neutral fluid. Net base gain, intraperitoneal volume kinetics, glucose absorption, ultrafiltration rate, effective lymphatic absorption and the transport of urea, potassium, beta2-microglobulin and albumin were similar with both fluids. However, phosphate and creatinine elimination were 10% lower with bicarbonate PD fluid, resulting in corresponding significant decreases in the 24-hour clearances of these solutes. CONCLUSION: The peritoneal surface area is not measurably influenced by pH-neutral PD fluid. Creatinine and phosphate elimination appears to be slightly reduced with bicarbonate fluid; this observation awaits clarification in extended therapeutical trials.

Adolescent↗
PubMed2002

Effect of acetate-free biofiltration and bicarbonate hemodialysis on neutrophil activation.

BACKGROUND: Activation of polymorphonuclear neutrophils (PMNs) and monocytes has been described during hemodialysis (HD), which results in the release of reactive oxygen species and cytokines. Acetate-free biofiltration (AFB) has been shown to cause less monocyte activation and cytokine release than bicarbonate HD (BHD). No data are available to date on the effect of AFB on PMN activation. METHODS: We studied ex vivo superoxide anion release by PMNs isolated from nine patients treated in random order with AFB or BHD (three sessions each). Plasma interleukin-1beta (IL-1beta) levels and the nitric oxide (NO) synthetic pathway also were evaluated. A polyacrylonitrile (AN69; Hospal, Bologna, Italy) dialyzer was used for both treatments. Fourteen healthy volunteers were used as controls. Blood samples were drawn predialysis and 5 and 15 minutes after starting dialysis to obtain plasma and PMNs. RESULTS: Neither ex vivo superoxide anion release nor blood PMN count was affected by AFB. Conversely, a peak in superoxide anion production associated with a decrease in PMN count was observed at 5 minutes during BHD. Results of superoxide anion production by control PMNs exposed in vitro to AFB or bicarbonate dialysis bath or Hank's balanced salt solution supplemented with bicarbonate or acetate indicated that BHD-induced PMN activation could be attributed to the amount of bicarbonate present in the dialysis bath. IL-1beta plasma levels did not change during dialysis with AFB and were numerically higher at 5 and 15 minutes with respect to predialysis values during BHD. Uremic plasma obtained during either AFB or BHD induced greater NO synthesis by human umbilical vein endothelial cells than control plasma. CONCLUSION: AFB, unlike BHD, does not cause PMN and monocyte activation, which could have a positive impact on dialysis-associated cardiovascular disease of dialyzed patients.

Aged↗
PubMed1994

Improved mineral balance and skeletal metabolism in postmenopausal women treated with potassium bicarbonate.

BACKGROUND: In normal subjects, a low level of metabolic acidosis and positive acid balance (the production of more acid than is excreted) are typically present and correlate in degree with the amount of endogenous acid produced by the metabolism of foods in ordinary diets abundant in protein. Over a lifetime, the counteraction of retained endogenous acid by base mobilized from the skeleton may contribute to the decrease in bone mass that occurs normally with aging. METHODS: To test that possibility, we administered potassium bicarbonate to 18 postmenopausal women who were given a constant diet (652 mg [16 mmol] of calcium and 96 g of protein per 60 kg of body weight). The potassium bicarbonate was given orally for 18 days in doses (60 to 120 mmol per day) that nearly completely neutralized the endogenous acid. RESULTS: During the administration of potassium bicarbonate, the calcium and phosphorus balance became less negative or more positive--that is, less was excreted in comparison with the amount ingested (mean [+/- SD] change in calcium balance, +56 +/- 76 mg [1.4 +/- 1.9 mmol] per day per 60 kg; P = 0.009; change in phosphorus balance, +47 +/- 64 mg [1.5 +/- 2.1 mmol] per day per 60 kg; P = 0.007) because of reductions in urinary calcium and phosphorus excretion. The changes in calcium and phosphorus balance were positively correlated (P < 0.001). Serum osteocalcin concentrations increased from 5.5 +/- 2.8 to 6.1 +/- 2.8 ng per milliliter (P < 0.001), and urinary hydroxyproline excretion decreased from 28.9 +/- 12.3 to 26.7 +/- 10.8 mg per day (220 +/- 94 to 204 +/- 82 mumol per day; P = 0.05). Net renal acid excretion decreased from 70.9 +/- 10.1 to 12.8 +/- 21.8 mmol per day, indicating nearly complete neutralization of endogenous acid. CONCLUSIONS: In postmenopausal women, the oral administration of potassium bicarbonate at a dose sufficient to neutralize endogenous acid improves calcium and phosphorus balance, reduces bone resorption, and increases the rate of bone formation.

Aged↗
PubMed2001

The influence of pilocarpine and biperiden on pH value and calcium, phosphate, and bicarbonate concentrations in saliva during and after radiotherapy for head and neck cancer.

OBJECTIVE: The purpose of the present study was to investigate the influence of parasympathomimetic pilocarpine and anticholinergic biperiden on salivation, pH value, and calcium, phosphate, and bicarbonate concentrations in saliva in patients irradiated for malignant tumors of the head and neck region. STUDY DESIGN: Sixty-nine patients were randomly assigned into 3 groups. Group A consisted of patients receiving pilocarpine, group B of those who were receiving biperiden during radiotherapy and pilocarpine for 6 weeks after its completion, and group C comprised patients receiving neither of the mentioned drugs. The quantity of secreted unstimulated saliva, its pH value, as well as calcium, phosphate, and bicarbonate concentrations in saliva were measured before the beginning of radiotherapy, after 30 Gy of irradiation, at completed irradiation, and 3, 6, and 12 months after completion of radiotherapy. RESULTS: Saliva secretion was found to be the least affected in the group of patients receiving biperiden throughout the course of radiotherapy. One year after completion of therapy, the quantity of secreted saliva could only be measured in the patients receiving biperiden during radiotherapy; it amounted to 16% of the average initial quantity of saliva secreted before the beginning of irradiation. In all 3 groups of patients, mean pH value decreased during radiotherapy and started to increase again after completion of irradiation. In group B the decrease in pH value after radiotherapy was statistically significantly smaller than that in group C (P =.01). During and after irradiation, calcium concentration was increased in all 3 groups of patients. Phosphate concentration decreased during radiotherapy in all 3 groups. In group B it started to increase again 3 months after completion of radiotherapy. Bicarbonate concentration showed a slight increase during radiotherapy and started to decrease again after completion of irradiation. CONCLUSION: The results of our study indicate that the inhibition of saliva secretion during radiotherapy and its stimulation after completion of treatment can contribute not only to some preservation of the quantity of saliva but also to at least partial preservation of its quality in terms of pH value and calcium, phosphate, and bicarbonate concentrations.

Administration, Oral↗