Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “CITRIC ACID”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,747 records · Page 97Linked to original sources
PubMed1998

Involvement of tachykinin NK3 receptors in citric acid-induced cough and bronchial responses in guinea pigs.

Aerosolized citric acid induces several pulmonary effects including bronchoconstriction, airway inflammation, and cough. Evidence from the use of tachykinin NK1 and NK2 receptor antagonists, as well as chronic treatment with high doses of capsaicin, have suggested that these effects are mediated through the release of tachykinins from sensory nerve endings. In the present study, we have investigated the effects of a tachykinin NK3 receptor antagonist, SR 142801 (osanetant), on cough, bronchoconstriction, and bronchial hyperresponsiveness induced by aerosolized citric acid (0.4 M) in guinea pigs. SR 142801, at 0.3 and 1 mg . kg-1 by intraperitoneal route, significantly inhibited cough in conscious guinea pigs by 57 +/- 3 and 62 +/- 10% (n = 8), respectively. In anaesthetized guinea pigs, it failed to inhibit the bronchoconstriction induced by citric acid when given alone but abolished it when combined with the tachykinin NK2 receptor antagonist, SR 48968 (saredutant). In guinea pigs pretreated with thiorphan (1 mg . kg-1), aerosolized citric acid (0.4 M, 1 h) induced airway hyperresponsiveness 24 h later, displayed by an exaggerated response to the bronchoconstrictor effect of acetylcholine. A microvascular leakage hypersensitivity also occurred and was demonstrated by a potentiation of the plasma protein extravasation from bronchial vessels induced by histamine. When given once intraperitoneally at 1 mg . kg-1 30 min before the citric acid exposure, SR 142801 inhibited both hyperresponsiveness to acetylcholine and the potentiation of histamine-induced increase in microvascular permeability. The results suggest that tachykinin NK3 receptors are involved in citric acid-induced effects on airways.

Animals↗
PubMed1990

Effects of medium-chain triglyceride feeding on energy balance in adult humans.

In recent years, the metabolism of triglycerides has attracted much attention. Oxidation of fatty acids is an essential energy supply, especially when glucose supply is limited. In the present study, the effect of a 3-day high medium-chain triglyceride (MCT; 51% of calories), low carbohydrate intake on plasma glucose and amino acid, and urinary organic acid levels, including dicarboxylic and tricarboxylic acid cycle intermediates, was determined in eight normal adult volunteer subjects. Urine was collected at baseline and at 48 to 72 hours for amino acid and organic acid levels, and plasma collected at 0 and 72 hours for glucose and amino acid concentration. The MCT diet increased urinary levels of dicarboxylic acids (adipic 8-, suberic 65-, sebacic 284-fold) and keto acids (acetoacetate and beta-hydroxybutyrate, 67.5-fold); alanine and lactate were decreased 2.5- and 4-fold, respectively, while pyruvate, other amino acids and citric acid intermediates remained unchanged. Plasma amino acid levels were unchanged, while the plasma glucose levels decreased by 8% from baseline. The loss of calories as urinary dicarboxylic acids and keto acids, although increased during the MCT diet, was less than 1% of the daily caloric intake. The data suggest MCT sustain energy expenditure through medium-chain fatty acid (MCFA) oxidation with no decrease in citric acid cycle intermediates, while sparing protein oxidation.

Adult↗
PubMed2001

Citric acid-enhanced Helicobacter pylori urease activity in vivo is unrelated to gastric emptying.

BACKGROUND: In a previous study, the use of a citric acid test meal produced a rapid dose-dependent increase in urease activity that was significantly greater than that resulting from a pudding meal, ascorbic acid or sodium citrate. The mechanism was hypothesized to be related to the ability of citric acid to delay gastric emptying and possibly to enhance intragastric distribution of the urea. OBJECTIVE: To compare the effects of sodium citrate, two doses of citric acid and a pudding meal on gastric motor function. METHOD: Eleven normal healthy volunteers were investigated using non-invasive techniques to measure gastric emptying and gastric motility. We evaluated gastric emptying using the Meretek 13Ceebiscuit solid phase gastric emptying breath test, which employs a 340-calorie biscuit containing 200 mg of the edible 13C-blue-green alga Spirulina platensis, after the administration of test meals of pudding, 2 g and 4 g of citric acid and 2 g of sodium citrate. Electrogastrograms (Digitrapper EGG) were also recorded for 30 min before and 180 min after the test meal. RESULTS: Gastric emptying, as assessed by the half-time (T1/2), was delayed similarly with the pudding (136.8 +/- 9 min) and with 4 g of citric acid (144.5 +/- 7 min) (P > 0.7). Sodium citrate (108.7 +/- 6 min) and 2 g of citric acid (110.1 +/- 6 min) had similar effects on gastric emptying (P=0.986), and were significantly less effective in delaying gastric emptying (P < 0.01) compared to pudding or 4 g of citric acid. The electrogastrograms remained normal and there were no differences among meals and no relation with the gastric emptying results. CONCLUSIONS: The increased intragastric urea hydrolysis associated with citric acid test meals cannot be attributed to delayed gastric emptying. Changes in the intragastric distribution of urea or a direct effect of citric acid on the bacteria (e.g. via the cytoplasmic protein, UreI) are more likely to be responsible.

Adolescent↗
PubMed1989

[Influence of tannic acid on physical and chemical properties of alpha-tricalcium phosphate-citric acid-tannic acid complex].

A mixture of alpha-tricalcium phosphate [alpha-Ca3(PO4)2; alpha-TCP] with a citric acid solution produces a hardened alpha-TCP-citric acid complex. The influence of tannic acid as an additive in the solution on the physical and chemical properties of the obtained complex was examined as a basic study for new calcium phosphate materials incorporating alpha-TCP. alpha-TCP was mixed with mixing liquids containing citric and tannic acids at various ratios [total acid = 45% (w/w)] at a powder/liquid = 2.2/1.0 (g/g). Compressive strength, setting time, and solubility & disintegration of the resulting complexes were measured by the methods specified by ADAS No. 61. After immersing the plates of the complexes in distilled water for 1 and 7 days, the surface structure of the plates was examined by using X-ray diffraction, scanning electron microscopy and IR spectroscopy. The substances solubilized and disintegrated in the water for 1 day were also examined by measuring quantitative Ca and P concentration. When the ratio of tannic acid to total acids (T/A) was higher than 30% (w/w), both setting time and solubility & disintegration increased remarkably. In the case of the complex at T/A = 30%, both setting time and solubility & disintegration showed the minimum value (6.25 min and 1.70%). For compressive strength, the maximum value (139 MPa) was obtained at T/A = 10%. Although the strength decreased markedly with increasing T/A beyond 10%, that of the complex at T/A = 30% was still a high level (103 MPa). The products on the surfaces before and after immersing the plates in distilled water were also discussed.

Calcium Phosphates↗
PubMed1983

Importance of calcium in citric acid-induced airway constriction.

In previous studies, a 5-min inhalational challenge with 10% citric acid aerosol (0.52 M) elicited bronchoconstriction in Basenji-Greyhound (BG) dogs with hyperreactive airways but not in mongrel dogs. This response was independent of vagal reflexes because it was not attenuated by atropine. Citric acid might elicit bronchoconstriction because of acidity, calcium chelation, or some other effect of the citrate molecule. To assess these factors, barbiturate-anesthetized BG dogs were challenged (5 min) with aerosols of 10% acetic acid or a citric acid (0.48 M)/Na3citrate (0.04 M) mixture of equivalent pH, 6% Na2-ethylenediaminetetraacetic acid (EDTA), or 6% CaNa2EDTA. Each challenge was delivered in a separate week. The acidity alone was not an adequate stimulus, since pulmonary resistance (RL) was unaltered by 10% acetic acid, although markedly increased by the citric acid-Na3citrate mixture [2.2 +/- 0.4 (SE) cmH2O X l-1 X s prechallenge, 10.0 +/- 2.2 postchallenge]. Aerosols of Na2EDTA provoked a similar increase in RL (2.1 +/- 0.4 cmH2O X l-1 X s prechallenge, 9.0 +/- 1.8 postchallenge). Neither effect was attenuated by intravenous atropine (0.2 mg/kg). CaNa2EDTA caused no changes in RL. We conclude that it is the calcium chelating action of citric acid rather than its acidity that is responsible for bronchoconstriction in BG dogs with hyperreactive airways.

Airway Resistance↗
PubMed2004

Removal of metals from industrial sludge by extraction with different acids.

This study addresses the feasibility of removing Cu and Ni from sludges of printed circuit board (PCB) plants by acidic extraction. Citric acid, acetic acid, hydrochloric acid, nitric acid, and sulfuric acid at various concentrations were experimentally examined to determine preferred conditions for removing Cu and Ni. Experimental results indicate that the removal ratios of Cu were 57% (citric acid), 79% (acetic acid), 81% (hydrochloric acid), 91% (nitric acid), and 92% (sulfuric acid), and that of Ni was 74% (citric acid), 70% (acetic acid), 75% (hydrochloric acid), 92% (nitric acid), and 93% (sulfuric acid), using 1 N extractants. The removal ratios obtained using sulfuric acid or nitric acid at a particular concentration were in the order Pb> Ni> Cu> Zn. The kinetic extraction results revealed that the extraction of Cu and Ni by nitric acid and sulfuric acid exhibited a lagphase after 60min and the removal ratio was then around 90%. The kinetic results also revealed that the extraction rate constants of Cu and Ni increased with the concentration of the acid. The extraction rate constants of Cu and Ni followed the order sulfuric acid > nitric acid > acetic acid, and it also showed that Ni was more easily extracted than Cu from PCB sludge. The total percentages of Cu extracted by 1 N acetic acid, nitric acid, and sulfuric acid, determined in three replicate extractions were 78, 94, and 94%, and those of Ni were 89, 94, and 98%, respectively. The residue sludge, following three replicate extractions using 1 N acetic acid, nitric acid, and sulfuric acid, was further tested by toxicity characteristic leaching procedures (TCLP), and more than 15 mg/L of Cu was leached, exceeding the legal concentration in Taiwan. This observation reveals that the residue sludge following three replicate extractions by acids remained hazardous waste. Further treatment, such as solidification, must be performed before the sludge is disposed of.

Acids↗
PubMed2000

Critical factors in chitin production by fermentation of shrimp biowaste.

Factors affecting Lactobacillus fermentation of shrimp waste for chitin and protein liquor production were determined. The objective of the fermentation is medium conditioning by Lactobacillus through production of proteases and lowering of the pH. The efficiency was tested by conducting fermentation of biowaste in 1-1 beakers with or without pH adjustment using different acids. Addition of 5% glucose to the biowaste supported the growth of lactic acid bacteria and led to better fermentation. Among four acids tested to control pH at the start and during fermentation, acetic acid and citric acid proved to be the most effective. In biowaste fermented with 6.7% L. plantarum inoculum, 5% glucose, and pH 6.0 adjusted with acetic acid, 75% deproteination and 86% demineralization was achieved. Replacement of acetic acid by citric acid gave 88% deproteination and 90% demineralization. The fermentation carried out in the presence of acetic acid resulted in a protein fraction that smelled good and a clean chitin fraction.

Acetic Acid↗
PubMed2004

Effect of a micronutrient fortificant mixture and 2 amounts of calcium on iron and zinc absorption from a processed food supplement.

BACKGROUND: Iron, zinc, and calcium can interact with each other in a way that inhibits their respective absorption. On the other hand, mineral fortification has been used to improve simultaneous iron and zinc absorption from food supplements. OBJECTIVE: We evaluated the effect of a novel fortificant mixture consisting of NaFeEDTA, zinc methionine, ascorbic acid, and citric acid on iron and zinc absorption from a dry food supplement designed for preschool children. DESIGN: The standard food supplement contained cereal and legume flour, dried milk, and a mixture of micronutrients including ferrous sulfate and zinc sulfate as sources of supplemental iron and zinc, respectively. Standard and novel food products were prepared as porridge with or without the addition of 200 mg Ca as calcium phosphate. Iron absorption and zinc absorption from the food products were evaluated simultaneously in 13 nonpregnant, adult women by extrinsically labeling the products with radioisotopes of iron and zinc and carrying out whole-body counting 7 d after the food products were consumed in random order. RESULTS: The absorption of iron from the NaFeEDTA-containing (novel) food product was 1.7 times that from the ferrous sulfate-containing (standard) product (P = 0.015). There was no significant effect of dietary calcium on iron absorption. Zinc absorption was not associated with the form of zinc consumed, but higher dietary calcium was marginally associated with lower zinc absorption (P = 0.071). CONCLUSIONS: A mixture of fortificants containing NaFeEDTA, zinc sulfate or zinc methionine, ascorbic acid, and citric acid, but without calcium, can improve iron and zinc absorption from food products. A cost-benefit analysis of the novel fortificant mixture needs to be performed.

Adult↗
PubMed2001

Effect of acetate on glycogen replenishment in liver and skeletal muscles after exhaustive swimming in rats.

Immediately after exhaustive swimming, rats were given one of the following orally: distilled water (W), glucose (G); acetic acid (A); citric acid (C); glucose and acetic acid (GA); and glucose and citric acid (GC), and they were killed 2 h after ingestion (each trial: n=4). Exhaustive exercise resulted in a significant reduction of the glycogen store in the gastrocnemius muscle. The glycogen stores in the liver were significantly higher following ingestion in groups GA and GC, in the gastrocnemius in groups G, GA and GC, and in the soleus in group GC, than immediately post exercise. These results suggest that oral acetic acid with glucose can facilitate liver glycogen restoration during the early period of recovery, and that acetate has about the same physiological effects as citrate on glycogen replenishment.

Acetic Acid↗
PubMed2000

Role of substance P and tachykinin receptor antagonists in citric acid-induced cough in pigs.

The purpose of this work was to investigate the role of tachykinins in cough induced by citric acid (0.8 M) in pigs. With this object, we have studied the effect of citric acid on substance P content in the tracheo-bronchial tree and the effects of substance P and of tachykinin receptor antagonists on citric acid-induced cough. Citric acid exposure significantly increased substance P concentration in both broncho-alveolar and tracheal lavage fluids, while it decreased significantly the substance P content in tracheal mucosa. Substance P did not elicit cough, but significantly potentiated the citric acid-induced cough frequency. Tachykinin NK(1), NK(2) or NK(3) receptor antagonists, SR 140333 (nolpitantium), SR 48968 (saredutant) and SR 142801 (osanetant), respectively, significantly inhibited citric acid-induced cough. The same inhibitory effect of tachykinin receptor antagonists was observed, when substance P was nebulised before citric acid challenge. We conclude that citric acid induces in pigs a release of substance P in the tracheo-bronchial tree, which plays a sensitising role on the cough reflex. The involvement of tachykinin NK(1), NK(2), NK(3) receptors are also demonstrated in this reflex.

Animals↗
PubMed2004

Browning and decomposed products of model orange juice.

A model solution of orange juice containing sugars, ascorbic acid, and citric acid was prepared and its browning during storage was examined. The solution gradually turned brown. Ascorbic acid (AsA) most contributed to the browning. Citric acid and such amino acids as Arg and Pro promoted the browning. DTPA, a strong chelator, inhibited the browning. 3-Hydroxy-2-pyrone (3OH2P), 5-hydroxymethylfurfural (HMF), furfural, 5-hydroxymaltol, and 2-furoic acid were identified as decomposed products in the stored solution. When 3OH2P was stored, the solution turned slightly brown. Furfural solution added with amino acids turned yellow. 3OH2P showed a positive relation with the browning of retail orange juice during storage.

Amino Acids↗
PubMed2001

Binding citrate/DNA in presence of divalent cations. Potential mimicry of acidic peptides/DNA interactions.

Citric acid whose structure is comparable to that of small acidic peptides, can bind to DNA in the presence of divalent cations (Cu2+, Fe2+, Zn2+, Mg2+). Citrate-DNA interaction occurs also in a cell homogenate and in this experimental model too requires the presence of natural divalent cations. In fact the addition of 2 mM EDTA to cell homogenate strongly decreases the DNA-citrate binding. The results demonstrate that divalent cations can act as bridges between two acidic molecules and that citric acid can mimic the structure of acidic peptides.

Animals↗
PubMed2001

Effects of rotary instrumentation and different etchants on removal of smear layer on human dentin.

STATEMENT OF PROBLEM: Various methods of rotary preparation and conditioning of teeth affect surface topography and may affect the retention of dental restorations. PURPOSE: This study microscopically evaluated dentin surfaces prepared by different rotary instruments and etched using several types of acid etchants that have been deemed suitable dentin conditioners. MATERIAL AND METHODS: Occlusal surfaces of 35 extracted human molars were ground wet with 320-grit silicon carbide paper to the depth of the central groove and then prepared with diamond (n = 5) and finishing burs (n = 30). Five specimens from each group were used for SEM evaluation of mechanical preparation effects. Dentin specimens (n = 5) prepared with finishing burs were then etched with 1 of 5 etchants (25% polyacrylic acid, 10% phosphoric acid, 10% citric acid, 20% lactic acid, or 32% phosphoric acid) for 10 seconds. Specimens were critical-point dried and freeze fractured for SEM analysis. RESULTS: Diamond rotary instruments created more undulating surfaces than finishing burs. Fine grooves were observed running perpendicular to undulations and parallel to the direction of instrument rotation. Specimens prepared with finishing burs exhibited a smooth surface interrupted by only a slight granularity. The amorphous smear layer was partially removed after the application of 25% polyacrylic acid (pH 1.53), but all dentinal tubules contained plugs. The number of dentin tubules containing plug material and the amount of material in the tubules decreased noticeably with 10% phosphoric acid (pH 0.86), and the dentin surface had an appearance similar to the specimen etched with 10% citric acid (pH 1.70). The surfaces treated with 20% lactic acid (pH 1.40) produced a clearly etched surface with minimal demineralization. Etching of dentin with 32% phosphoric acid (pH 0.16) revealed significant changes in dentin with the evidence of increased tubule diameter. CONCLUSION: Differences related to the method of instrumentation were found in the surface characteristics of dentin. The degree of smear layer removal was related to the pH of the acid etchant.

Acid Etching, Dental↗
PubMed1996

The tachykinin NK2 receptor antagonist SR 48968 inhibits citric acid-induced airway hyperresponsiveness in guinea pigs.

Airway hyperresponsiveness is a main feature of asthma, and several lines of evidence suggest that tachykinins might be involved in the pathogenesis of airway hyperresponsiveness in rodents. We conducted a study designed to describe an original model of airway hyperresponsiveness induced by citric acid administered as aerosol to guinea pigs, and to investigate the effects of the nonpeptide neurokinin1 (NK1) and neurokinin2 (NK2)-receptor antagonists, SR 140333 and SR 48968, respectively, on the development of this airway hyperresponsiveness. Animals received thiorphan 1 mg/kg intraperitoneally and 30 min later were exposed to an aerosol of citric acid 0.4 M for 1 h. After 24 h, the animals were anesthetized and ventilated. Airway hyperresponsiveness was evidenced by significant shifts to the left of dose-response curves for intravenous acetylcholine (ACh) without a change in maximum responses to ACh. Exposure to citric acid induced an airway hyperresponsive that was abolished by chronic pretreatment with capsaicin (120 mg/kg, 5 d before citric acid exposure). SR 48968 1 mg/kg intraperitoneally, given once at 30 min before the citric acid exposure, inhibited airway hyperresponsiveness, whereas SR 140333 1 mg/kg or codeine 30 mg/kg given under similar conditions did not. The inhibition of airway hyperresponsiveness by SR 48968 did not result from functional antagonism, since SR 48968 did not affect ACh-induced bronchoconstriction, nor did it result from inhibition of tachykinin, which could have been released under the influence of ACh in hyperresponsive animals, since SR 48968 given after the exposure to aerosolized citric acid failed to inhibit airway hyperresponsiveness. In conclusion, these results show that inhaled citric acid can induce the development of an airway hyperresponsiveness in the guinea pig through a release of tachykinins, and also demonstrate that NK2-receptor stimulation plays a predominant role in the development of airway hyperresponsiveness.

Acetylcholine↗
PubMed2005

241Am, 137Cs, Sr and Pb uptake by tobacco as influenced by application of Fe chelators to soil.

To determine the potential for phytoextraction of 241Am and other contaminants from soil, accumulation of 241Am, 137Cs, Sr, Fe, Al, Pb, and Mg by tobacco was determined for soil applications of two concentrations of ethylenediaminetetraacetic acid (EDTA), citric acid, and ascorbic acid. In tobacco receiving EDTA at 3.1 mmol/kg of soil, 241Am content of plants averaged 15 Bq/kg (ranging up to 26 Bq/kg) while Fe concentrations became constant at 4.5 mmol/kg. Soil treatment with 18.8 mmol/kg EDTA resulted in average 241Am concentrations of 29 Bq/kg (19 times higher than controls). Uptake of Pb was similar to 241Am. In these samples, Fe increased to a maximum of almost 18 mmol/kg and 241Am content increased linearly with both Fe and Al. Plants receiving ascorbic and citric acids took up smaller quantities of 241Am, Pb, and Fe, even though these reagents were able to elute about as much Fe from the soil as EDTA. Synchrotron microbeam X-ray fluorescence (SXRF) was used to determine radial distributions of elements in roots and stems with and without EDTA treatment. SXRF maps indicate differences in behavior between Fe and Pb that are consistent with the bulk plant observations and provide insight into changes in metal content of the roots in the presence of EDTA.

Americium↗
PubMed1990

A clinical scanning electron microscope study of tooth surface preparation and bonding.

This clinical study utilized cut dentine surfaces on which the Creation Bond System and Scotchbond were applied after various surface treatments. It was observed under the scanning electron microscope that preparation with a tungsten carbide bur left a smear layer on the dentine. When this surface was pumiced, the smear layer remained and the tubules were plugged with smear debris. Polyacrylic acid and citric acid removed the smear layer from the dentine surface. When the Creation Bond System was applied to the surface treated with polyacrylic acid, hollow depressions were produced. Application of the Creation Bond System to the surface treated with citric acid resulted in some resin tag formation into the dentinal tubules as well as hollow depressions on the resin surface. The presence of these irregularities in the resin indicated fluid from the dentinal tubules prevented contact of the bonding resin with the dentine surface. This degree of contamination was not observed when Scotchbond was applied to a pumiced dentine surface.

Acid Etching, Dental↗
PubMed1993

Inhibitory effects of capsazepine and SR 48968 on citric acid-induced bronchoconstriction in guinea-pigs.

We have examined the effects of capsazepine, a selective capsaicin antagonist, and SR 48968, a selective NK2 receptor antagonist, on citric acid inhalation-induced bronchoconstriction in guinea-pigs. Simultaneous inhalation of capsazepine (10 microM) significantly inhibited (by 85%) the bronchoconstriction induced by inhaled citric acid (0.4 M) but not that induced by histamine (2 mM). In capsaicin-pretreated (50 mg/kg s.c. 3 weeks earlier) guinea-pigs, citric acid failed to cause any bronchoconstriction, while the effect of histamine was uninfluenced. Furthermore, citric acid inhalation-induced bronchoconstriction was also markedly inhibited (by 65%) after pretreatment with SR 48968 (0.3 mg/kg i.v.). SR 48968 blocked the bronchoconstriction but not the hypotension evoked by neurokinin A. Therefore, these results suggest that inhalation of a low-pH solution such as citric acid can stimulate sensory neurons through a mechanism similar to that for capsaicin with regard to sensitivity to capsazepine. Tachykinins such as neurokinin A are then locally released from the terminals of sensory nerves and cause bronchoconstriction, mainly by NK2 receptor mechanisms.

Administration, Inhalation↗
PubMed2001

[Effect of organic acids on soil chemical behavior of lead and cadmium and their toxicity to plants].

The interaction between organic acids (citric and oxalic acids) and heavy metals was examined in this paper. Equilibrium dialysis showed that the extent organic acids bound metals depended on the metal involved, and their binding properties affected the adsorption of Pb and Cd by soil, which was increased in the presence of oxalic acid, and decreased in the presence of citric acid. The effect of citric acid on the behavior and toxicity of Pb and Cd to plants was also studied. The presence of citric acid could reduce the toxicity of Pb, and inhibit the uptake of Cd in shoots and roots. However, there was no significant effect on the apparent toxicity of Cd. The interaction between Pb and Cd was found to be complicated. The Pb content in rice was higher in the presence of Cd, while the content of Cd is lower in the presence of Pb.

Aconitic Acid↗