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 649 records · Page 36Linked to original sources
PubMed2003

Aluminum-induced oxidative stress in rat brain: response to combined administration of citric acid and HEDTA.

Aluminum, a known neurotoxic substance, has been suggested as a contributing factor in the pathogenesis of Alzheimer's disease. Therapeutic efficacy of combined administration of citric acid (CA) and N-(2-hydroxyethyl) ethylenediaminetriacetic acid (HEDTA) was evaluated in decreasing blood and brain aluminum concentration and parameters indicative of hematological disorders and brain oxidative stress. Adult male wistar rats were exposed to drinking water containing 0.2% aluminum nitrate for 8 months and treated once daily for 5 consecutive days with CA (50 mg/kg, orally) or HEDTA (50 mg/kg, intraperitoneally) either individually or in combination. Aluminum exposure significantly inhibited blood delta-aminolevulinic acid dehydratase while increased zinc protoporphyrin confirming changed heme biosynthesis. Significant decrease in the level of glutathione S-transferase in various brain regions and an increase in whole brain thiobarbituric acid reactive substance, and oxidized glutathione (GSSG) levels were also observed. Glutathione peroxidase activity showed a significant increase in cerebellum of aluminum exposed rats. Most of the above parameters responded moderately to the individual treatment with CA and HEDTA, but significantly reduced blood and brain aluminum burden. However, more pronounced beneficial effects on some of the above described parameters were observed when CA and HEDTA were administered concomitantly. Blood and brain aluminum concentration however, showed no further decline on combined treatment over the individual effect with HEDTA or CA. We conclude that in order to achieve an optimum effect of chelation, combined administration of CA and HEDTA might be preferred. However, further work is needed before a final recommendation could be made.

Aluminum↗
PubMed2003

Enamel dissolution in citric acid as a function of calcium and phosphate concentrations and degree of saturation with respect to hydroxyapatite.

The aim of this study was to investigate enamel dissolution in citric acid solutions as a function of solution calcium and phosphate concentrations and degree of saturation with respect to hydroxyapatite (DSHA). The primary relevance of the study is the development of soft drinks with reduced erosive potential. Nanoindentation was used to investigate changes in the hardness of polished human enamel surfaces after 120 s and 300 s exposure to solutions with pH 3.30 and a range of calcium and phosphate concentrations. All solutions were undersaturated with respect to hydroxyapatite, with 0.000 < or = DSHA < or = 0.295. A complex dependence of enamel softening on calcium concentration was observed. Substantial enamel softening occurred in solutions with calcium concentrations equal to or less than 120 mm (DSHA approximately 0.104), but there was little or no statistically significant softening of the enamel for calcium concentrations over 120 mm. This condition may be applicable to soft drink formulation. Furthermore, solutions with DSHA = 0.101 and different calcium/phosphate ratios resulted in different degrees of softening of the enamel. Hence, contrary to assumptions made in many models, enamel dissolution is not simply a function of DSHA, and individual calcium and phosphate concentrations are critical.

Calcium↗
PubMed2000

Properties of Aspergillus niger citrate synthase and effects of citA overexpression on citric acid production.

Using a combination of dye adsorption and affinity elution we purified Aspergillus niger citrate synthase to homogeneity using a single column and characterised the enzyme. An A. niger citrate synthase cDNA was isolated by immunological screening and used to clone the corresponding citA gene. The deduced amino acid sequence showed high similarity to other fungal citrate synthases. After processing upon mitochondrial import, the calculated M(r) of A. niger citrate synthase is 48501, which agrees well with the estimated molecular mass of the purified protein (48 kDa). In addition to an N-terminal mitochondrial import signal, a peroxisomal target sequence (AKL) was found at the C-terminus of the protein. Whether both signals are functional in vivo is not clear. Strains overexpressing citA were made by transformation and cultured under citric acid-producing conditions. Up to 11-fold overproduction of citrate synthase did not increase the rate of citric acid production by the fungus, suggesting that citrate synthase contributes little to flux control in the pathway involved in citric acid biosynthesis by a non-commercial strain.

Acetyl Coenzyme A↗
PubMed1964

PRELIMINARY REPORT ON AN IRON-SORBITOL-CITRIC ACID COMPLEX (JECTOFER), A NEW INTRAMUSCULAR IRON PREPARATION.

One hundred and twenty-eight patients with iron deficiency anemia were treated with a new intramuscular iron preparation, iron-sorbitol-citric acid. One group of 10 patients received a total of 1000 mg. each of elemental iron intramuscularly. All obtained a rise in hemoglobin of over 2.1 g. %, an elevation of serum iron, and a reticulocyte response over 6%. A second larger group of subjects consisted of 113 prenatal and five gynecologic patients; these received an average total dose of 1050 mg. and 1020 mg., respectively, and the average increase in hemoglobin ranged from 1.6 g. % to 2.5 g. %.None of the patients developed significant side effects after injection or permanent staining at the site of injection. Three patients experienced a transient ache at the injection site, and three developed local urticaria-like reactions lasting 24 hours.This new preparation appears to be a safe and clinically effective therapeutic agent in situations in which parenteral iron is indicated.

Anemia↗
PubMed1996

Noninvasive probing of citric acid cycle intermediates in primate liver with phenylacetylglutamine.

In human and primate liver, phenylacetate and glutamine form phenylacetylglutamine, which is excreted in urine. Probing noninvasively the labeling pattern of liver citric acid cycle intermediates with phenylacetylglutamine assumes that the labeling pattern of its glutamine moiety reflects that of liver alpha-ketoglutarate. To validate this probe, we infused monkeys with [U-13C3]lactate, [3-13C]lactate, [1, 2-13C2]acetate, [2-13C]acetate, [U-13C3]glycerol, or 2-[3-13C]ketoisocaproate and compared the labeling patterns of urinary phenylacetyl-glutamine with those of glutamate and glutamine in liver, plasma, muscle, and kidney and liver alpha-ketoglutarate. Only with [U-13C3]lactate or [3-13C]lactate does the labeling pattern of phenylacetylglutamine reflect patterns of liver alpha-ketoglutarate and glutamate. With [13C]acetate, muscle and kidney glutamate are more labeled than liver metabolites. This confirms that with [13C]acetate, the labeling pattern of liver metabolites is influenced by 13CO2 and [13C]glutamine made in peripheral tissues. Our data validate the use of phenylacetylglutamine labeled from [3-13C]lactate or [3-13C]pyruvate to probe noninvasively the pyruvate carboxylase-to-pyruvate dehydrogenase flux ratio in human subjects.

Animals↗
PubMed2000

Mitochondrial dysfunction during hypoxia/reoxygenation and its correction by anaerobic metabolism of citric acid cycle intermediates.

Kidney proximal tubule cells developed severe energy deficits during hypoxia/reoxygenation not attributable to cellular disruption, lack of purine precursors, the mitochondrial permeability transition, or loss of cytochrome c. Reoxygenated cells showed decreased respiration with complex I substrates, but minimal or no impairment with electron donors at complexes II and IV. This was accompanied by diminished mitochondrial membrane potential (DeltaPsi(m)). The energy deficit, respiratory inhibition, and loss of DeltaPsi(m) were strongly ameliorated by provision of alpha-ketoglutarate plus aspartate (alphaKG/ASP) supplements during either hypoxia or only during reoxygenation. Measurements of (13)C-labeled metabolites in [3-(13)C]aspartate-treated cells indicated the operation of anaerobic pathways of alphaKG/ASP metabolism to generate ATP, yielding succinate as end product. Anaerobic metabolism of alphaKG/ASP also mitigated the loss of DeltaPsi(m) that occurred during hypoxia before reoxygenation. Rotenone, but not antimycin or oligomycin, prevented this effect, indicating that electron transport in complex I, rather than F(1)F(0)-ATPase activity, had been responsible for maintenance of DeltaPsi(m) by the substrates. Thus, tubule cells subjected to hypoxia/reoxygenation can have persistent energy deficits associated with complex I dysfunction for substantial periods of time before onset of the mitochondrial permeability transition and/or loss of cytochrome c. The lesion can be prevented or reversed by citric acid cycle metabolites that anaerobically generate ATP by intramitochondrial substrate-level phosphorylation and maintain DeltaPsi(m) via electron transport in complex I. Utilization of these anaerobic pathways of mitochondrial energy metabolism known to be present in other mammalian tissues may provide strategies to limit mitochondrial dysfunction and allow cellular repair before the onset of irreversible injury by ischemia or hypoxia.

Adenosine Triphosphate↗
PubMed1994

Effects of different pH values of citric acid solutions on the calcium and phosphorus contents of human root dentin.

In a group of mandibular incisors, the calcium and phosphorus contents of the cervical, middle, and apical thirds of the roots were determined using an electron microprobe analyzer, before and after treatment with citric acid solutions of different concentrations. The treated surfaces were examined using a scanning electron microscope. The relative calcium and phosphorus loss values obtained from the samples treated with pH 0.8, 1.1, 1.3, 1.5, and 1.7 solutions were significantly different from those obtained in the control group. The demineralizing effect of the pH 0.8 and pH 1.3 solutions was the same, with both of these being less effective than the pH 1.1 solution.

Acid Etching, Dental↗
PubMed1977

Bronchial secretion from normal human airways after inhalation of prostaglandin F2alpha, acetylcholine, histamine, and citric acid.

Sputum produced by normal subjects after inhalation of prostaglandin F2alpha, acetylcholine, histamine, and citric acid has been analysed. Prostaglandin F2alpha was the most effective of the drugs in promoting sputum production. The material expectorated after inhalation of prostaglandin F2alpha shows the characteristics of mucoid sputum from patients with chronic bronchitis. The apparent viscosity and the concentration of marker substances for bronchial glycoprotein was in the lower part of the range found in mucoid chronic bronchitic sputum. The concentration of marker substances for serum glycoproteins and tissue fluid transudate were below the range found in chronic bronchitis, indicating that, in disease states, in addition to bronchial mucus there is a marked tissue fluid transudate component. Sputum produced after inhalation of acetylcholine and histamine contained relatively more tissue fluid transudate than sputum produced after inhalation of prostaglandin F2alpha, Sputum produced after inhalation of prostaglandin F2alpha, is of special value in indicating the nature of secretion from normal airways.

Acetylcholine↗
PubMed2003

Influence of enteric citric acid on the release profile of 4-aminopyridine from HPMC matrix tablets.

A weakly basic experimental drug, 4-aminopyridine (4-AP), was taken as a model to study the influence of enteric citric acid (ECA) on the release profile from hydroxypropyl methylcellulose (HPMC) matrices, to set up a system bringing about gradual release of the drug. For this purpose, powder mixtures were wet granulated with water and compressed with a hydraulic press at 55 MPa. Dissolution studies were made using first 900 ml HCl 0.1 N, and then phosphate buffer pH 7.4. Dissolution curves were described by M(t)/M(inf)=kt(n). As physically expected, increasing proportions (2-9%) of the in acid insoluble ECA decreased the release rate. In an acid medium, ECA acts as a physical barrier obstructing the diffusion path, dissolving after the pH change to 7.4. Both circumstances flattening the release profile. Apparent zero order release was observed at ECA concentrations of about 10%. The presence of ECA compensates the effect of decreased solubility of 4-AP at pH 7.4. Unexpectedly, higher ECA proportions (10-50%) act increasing the dissolution rate. This is attributed to a void space formation around the insoluble ECA, after HPMC hydration, which percolates after a critical ECA proportion of approximately 10%. Moreover, decreasing release constant values (k) show a logarithmic relationship with increasing values of the exponent (n). This indicates that an apparent zero-order release can be obtained at a given release constant.

4-Aminopyridine↗
PubMed2003

Pyruvate and citric acid cycle carbon requirements in isolated skeletal muscle mitochondria.

Carbohydrate depletion precipitates fatigue in skeletal muscle, but, because pyruvate provides both acetyl-CoA for mainline oxidation and anaplerotic carbon to the citric acid cycle (CAC), the mechanism remains obscure. Thus pyruvate and CAC kinetic parameters were independently quantified in mitochondria isolated from rat mixed skeletal muscle. Mitochondrial oxygen consumption rate (Jo) was measured polarographically while either pyruvate or malate was added stepwise in the presence of a saturating concentration of the other substrate. These substrate titrations were carried out across a physiological range of fixed extramitochondrial ATP free energy states (DeltaGP), established with a creatine kinase energy clamp, and also at saturating [ADP]. The apparent Km,malate for mitochondrial Jo ranged from 21 to 32 microM, and the apparent Km,pyruvate ranged from 12 to 26 microM, with both substrate Km values increasing as DeltaGP declined. Vmax for both substrates also increased as DeltaGP fell, reflecting thermodynamic control of Jo. Reported in vivo skeletal muscle [malate] are >10-fold greater than the Km,malate determined in this study. In marked contrast, the K(m,pyruvate) determined is near the [pyruvate] reported in muscle approaching exhaustion associated with glycogen depletion. When data were evaluated in the context of a linear thermodynamic force-flow (DeltaGP-Jo) relationship, the DeltaGP-Jo slope was essentially insensitive to changes in [malate] in the range observed in vivo but decreased markedly with declining [pyruvate] across the physiological range. Mitochondrial respiration is particularly sensitive to variations in [pyruvate] in the physiological range. In contrast, physiological [malate] exerts very little, if any, influence on mitochondrial pyruvate oxidation measured in vitro.

Animals↗
PubMed2002

Treatment of recalcitrant wastewater from ethanol and citric acid production using the microalga Chlorella vulgaris and the macrophyte Lemna minuscula.

Laboratory-scale experiments were performed to develop a procedure for biological treatment of recalcitrant anaerobic industrial effluent (from ethanol and citric acid production) using first the microalga Chlorella vulgaris followed by the macrophyte Lemna minuscula. This recalcitrant dark-colored wastewater, containing high levels of organic matter and low pH, prevents the growth of microalgae and macrophytes, and therefore, could not be treated by them. Therefore, the wastewater was diluted to 10% of the original concentration with wash water from the production line. Within 4 days of incubation in the wastewater, C. vulgaris population grew from 5 x 10(5) to 2 x 10(6) cells/mL. This culture reduced ammonium ion (71.6%), phosphorus (28%), and chemical oxygen demand (COD) (61%), and dissolved a floating microbial biofilm after 5 days of incubation. Consequently, L. minuscule was able to grow in the treated wastewater (from 7 to 14 g/bioreactor after 6 days), precipitated the microalgal cells (by shading the culture), and reduced other organic matter and color (up to 52%) after an additional 6 days of incubation. However, L. minuscula did not improve removal of nutrients. This study demonstrates the feasibility of combining microalgae and macrophytes for bioremediation of recalcitrant industrial wastewater.

Anaerobiosis↗
PubMed1998

[Kinetic assessment of salivary secretory response to citric acid. Differences with pilocarpine].

BACKGROUND: Induction of salivation is becoming increasingly popular in the assessment of salivary gland status. Various mechanical or pharmacological procedures are empirically used to produce salivation. Oral stimulation by citric acid (AC) is by far the most used sialagogue procedure. AIM: To characterize the salivary secretory response to AC solutions applied to the dorsolateral tongue surfaces. SUBJECTS AND METHODS: Young healthy women from the upper levels of a medical career (n = 19) participated as volunteers. Salivary volume and UV-absorbing organic material in saliva from single subjects were measured after various protocols of topical stimulation by AC. RESULTS: After a single stimulation by 1-8% AC the salivary flow rate peaked before 30 seconds and recovered the basal level earlier than 2 minutes. Repetitive stimulations at 30-sec intervals kept the flow rate at a maximum. After suspending these stimulations, basal flow rate was recovered before 2 minutes. Repetitive AC-stimulations at 8-min intervals produced a series of identical and independent secretory responses. The concentration of organic material in saliva remained unaltered after the various modes of stimulation. Thus, the profile of organic material secretion was always a direct expression of changes in salivary flow rate. In contrast to AC, the oral administration of the cholinergic agonist pilocarpine (PIL) produced a two-wave salivary response that as a whole lasted for about 30 minutes. In this case the volume and the amount of organic material were at least 10-fold the ones secreted in response to AC. CONCLUSIONS: AC provoked a rapid and short-lived salivary response that differs markedly from the one produced by other secretagogues, like pilocarpine.

Adult↗
PubMed1996

An oral sodium citrate-citric acid non-particulate buffer in humans.

We have investigated the effect on the pH of the gastric fluid of a single dose of sodium citrate 0.3 mol litre-1 (antacid) and a solution containing sodium citrate dehydrate (100 mg ml-1) with citric acid monohydrate (66 mg ml-1) (buffer). The dose for both solutions was 0.4 ml kg-1 via a nasogastric tube. Each group comprised 10 patients undergoing neurosurgical operations of 5-7 h duration. A control group of 10 patients received no gastric solution. The pH of the gastric aspirate was measured hourly using a Metrohm 632 digital pH meter (Synectics Medical, Sweden). Mean baseline gastric pH was 2.64 (SD 1.71). In the control group, pH increased to 4.4 (1.51) at 5 h, returning to baseline at 7 h. In the antacid group, pH increased to 6.11 (0.47) at 15 min and decreased to 3.70 (1.94) at 7 h (P < 0.01). In the buffer group, pH was stable at 3.80-3.95 (0.22) over 7 h (P > 0.01). Total mean gastric aspirate was 0.5 ml kg-1.

Acid-Base Equilibrium↗