Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: T03G11 .9
 340,653 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Etoposide, a highly active and widely used antineoplastic agent, is O-demethylated to its active catechol metabolite. A high-performance liquid chromatographic assay method for the simultaneous quantitation of etoposide and etoposide catechol in human plasma was established. Etoposide and etoposide catechol were extracted from plasma using chloroform and methanol followed by phase separation, evaporation of the organic phase, and reconstitution of the residue. Chromatography was accomplished using a reversed-phase phenyl analytical column (390 mm x 3.9 mm I.D.) with a mobile phase of 76.6% 25 mM citric acid-50 mM sodium phosphate (pH 2.4)-23.4% acetonitrile pumped isocratically at 1 ml/min with electrochemical detection. The limit of detection for etoposide was 1.2 nM and for etoposide catechol was 0.2 nM. The precision (CV) for etoposide ranged from 0.7 to 3% and for the catechol metabolite from 1 to 6%; accuracy of predicted values ranged from 97 to 106% and 94 to 103%, respectively. The assay was linear from 0.1 to 10 microM for etoposide and from 0.005 to 0.5 microM for etoposide catechol in plasma. Recovery of etoposide and etoposide catechol ranged from 93 to 95% and 90 to 98%, respectively. Stability of etoposide and etoposide catechol in human plasma containing ascorbic acid stored at -70 degrees C for one year was demonstrated. This assay procedure is suitable for evaluation of etoposide and etoposide catechol pharmacokinetics in plasma following etoposide administration.
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PMID:Simultaneous quantitation of etoposide and its catechol metabolite in human plasma using high-performance liquid chromatography with electrochemical detection. 1040 9

The ratio of the stable isotopes of oxygen (18O/16O) has been measured in the sugar, citric acid and water from authentic single strength orange juices, originating from a number of different countries. The sugars and citric acid were recovered from the juices and their 18O/16O ratios were determined by pyrolysis/continuous flow-isotope ratio mass spectrometry (Py/CF-IRMS). The 18O/16O ratio of the fruit juice water was determined by the carbon dioxide/water equilibration method. The delta 18O/1000 values of 45 different sugars ranged from +29.1 to +38.8/1000 and 15 citric acids ranged from +18.9 to +25.4/1000. The delta 18O/1000 value of the water present in the same samples ranged from -2.1 to +7.8/1000. A correlation was evident between the delta 18O/1000 values of the sugar, citric acid and water from the juices. This information can be used to improve the assessment of the authenticity of commercial 'freshly squeezed' orange juices. The detection of the presence of reconstituted orange juice concentrate in 'freshly squeezed' orange juices was improved by 37% using regression analysis of the combined water and sugar delta 18O/1000 ratios when compared to the use of delta 18O/1000 ratios of fruit juice water alone.
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PMID:Determination of the oxygen-18/oxygen-16 isotope ratios of sugar, citric acid and water from single strength orange juice. 1040 8

Root surface demineralization is widely used as an adjunct to periodontal treatment. To clarify the influence of citric acid root conditioning on periodontal wound healing, the effects of citric acid and associated extracellular acidosis on the viability (MTT assay), attachment and protein synthesis ([3H]-proline incorporation into trichloroacetic acid-precipitated proteins) of human gingival fibroblasts (GF) were investigated. A concentration of 47.6 mmol/L of citric acid (pH 2.3) in water led to total cell death within three minutes of incubation. Media containing 23.8 mmol/L and 47.6 mmol/L of citric acid exerted strong cytotoxicity (47 to 90 per cent of cell death) and inhibited protein synthesis (IC50 = 0.28 per cent) of GF within three hours of incubation. Incubation of cells in a medium containing 11.9 mmol/L of citric acid also suppressed the attachment and spreading of fibroblasts on culture plates and Type I collagen, with 58 per cent and 22 per cent of inhibition, respectively. Culture medium supplemented with 11.9, 23.8 and 47.6 mmol/L of citric acid also led to extracellular acidosis by decreasing the pH value from 7.5 to 6.3, 5.2 and 3.8, respectively. In addition, it was confirmed that the toxic effect of media containing citric acid was due to their acidity rather than the citrate content. Most of the citric acid-induced cell death could be prevented by adjusting the pH value of the culture medium to pH 7.5. Sodium citrate, at a concentration of 47.6 mmol/L, also exerted little cytotoxicity. The results suggested that toxicity of citric acid in specific stages of the healing process must be considered prior to its clinical application. Careful management of citric acid in order to avoid contact with tissue or the development of other demineralizing agents is important in enhancing periodontal wound healing.
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PMID:The effects of extracellular citric acid acidosis on the viability, cellular adhesion capacity and protein synthesis of cultured human gingival fibroblasts. 1045 69

To characterize honey types, a citric acid determination may be useful. A citric acid determination on honey was carried out with previous polyvinylpolypyrrolidone (PVPP) clarification followed by the Boehringer-Mannheim GmbH enzymatic test. The sample solution was prepared from 2 g of honey in 100 mL of Milli-Q water. A volume of 10 mL of this sample was clarified with PVPP stirring for 1 min and filtered. The enzymatic determination was measured spectrophotometrically at 340 nm, using citrate lyase, L-malate dehydrogenase, and L-lactate dehydrogenase. With these conditions, there were no observed interference effects. The proposed method improves precision [coefficient of variation (CV) between 0.26% and 1.60%] and recovery (between 98.0% and 100.9%) on the direct enzymatic analysis (% CV between 1.02 and 2.66 and recovery between 84.0% and 115.6%). Furthermore, the cost was reduced 70% using a microtest. The method was applied to 20 honeys of Galicia (northwestern Spain), and the results ranged between 44.2 and 827.0 mg of citric acid/kg of honey (mean = 192.9 mg/kg).
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PMID:Enzymatic Determination of Citric Acid in Honey by Using Polyvinylpolypyrrolidone Clarification. 1055 9

The flux of carbon into lactic acid, diacetyl and acetoin during the co-metabolism of glucose and citrate by Lactococcus lactis subsp. lactis biovar. diacetylactis has been determined using natural abundance isotopic ratio analysis. During fermentation in the conditions used (glucose, 27.8 mM; citric acid, 13.9 mM; initial pH 6.2-6.4, anaerobic) it is shown that approximately 65% of the carbon source used for the aroma compounds is derived from the carbohydrate. Equally, citrate contributes approximately 30% of the carbon recovered in lactic acid. Thus, there is no evidence for a metabolic separation of the catabolism of these two carbon sources.
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PMID:Metabolic flux in glucose/citrate co-fermentation by lactic acid bacteria as measured by isotopic ratio analysis. 1062 Jun 67

This study was carried out to identify the suitable buffer for cryopreservation of buffalo semen. Semen was collected with artificial vagina (42 degrees C) from four buffalo bulls. Split pooled ejaculates (n=5), possessing more than 60% visual sperm motility, were extended at 37 degrees C either in tri-sodium citrate (CITRATE), Tris-citric acid (TCA), Tris-Tes (TEST) or Tris-Hepes (HEPEST). Semen was cooled to 4 degrees C in 2 h, equilibrated at 4 degrees C for 4 h, filled in 0.5 ml straws and frozen in a programmable cell freezer before plunging into liquid nitrogen. Thawing of frozen semen was performed after 24 h at 37 degrees C for 15 s. Sperm motion characteristics, plasma membrane integrity, and acrosome morphology of each semen sample were assessed by using computer-assisted semen analyzer (CASA), hypo-osmotic swelling (HOS) assay, and phase-contrast microscope, respectively. Analysis of variance revealed that percent post-thaw visual motility tended (P=0.07) to be higher in HEPEST (61.0+/-2.9) and lowest in CITRATE (48.0+/-2.5). Computerized motility did not vary due to buffering system. Percent post-thaw linear motility tended (P=0.09) to be higher in TCA (78.2+/-5.5) and lower in TEST (52.0+/-6.9). Circular motility (%) was significantly lower (P<0.05) in TCA (11.6+/-2.8) and higher in TEST (29.8+/-5.6). Curvilinear velocity (microm s(-1)) was lower (P<0.05) in TCA (69.4+/-2.0) than in CITRATE (79.0+/-5.8), TEST (87. 2+/-1.6) and HEPEST (82.6+/-3.0). Lateral head displacement (microm) was lowest (P<0.05) in TCA (1.7+/-0.2) and highest in TEST (3.7+/-0. 6). Plasma membrane integrity and normal acrosomes of buffalo spermatozoa did not differ due to buffering system and averaged 40. 0+/-2.7% and 61.4+/-4.6%, respectively. Based upon lower circular motility, curvilinear velocity, and lateral head displacement, it is concluded that post-thaw quality of buffalo semen can be improved using the Tris-TCA buffering system.
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PMID:Effect of buffering systems on post-thaw motion characteristics, plasma membrane integrity, and acrosome morphology of buffalo spermatozoa. 1080 74

An acidified sodium chlorite (ASC) solution was investigated for its antimicrobial effects on broiler carcasses processed under conditions similar to those used in U.S. commercial poultry facilities. Of particular interest was the ability of the ASC solution to reduce natural bioburden in a prechill procedure. A number of parameters such as pretreatment washing of carcasses with water (no wash versus water wash), ASC concentration (500, 850, and 1,200 ppm), method of application (spray versus dip), and method of acid activation (phosphoric acid versus citric acid) were explored to evaluate disinfection conditions. ASC dip solutions (18.9 liters) were freshly prepared for groups of five prechill eviscerated carcasses per treatment (n = 10 carcasses). ASC treatment was shown to be an effective method for significantly reducing naturally occurring microbial contamination on carcasses. Reductions following immersion dipping were demonstrated at all disinfectant concentrations for total aerobes (82.9 to 90.7%), Escherichia coli (99.4 to 99.6%), and total coliforms (86.1 to 98.5%). Additionally, testing showed that ASC solutions maintained stable pH and minimal chlorite ion concentration deviations throughout each treatment. The results of the parameter evaluations indicated that maximal antimicrobial activity was achieved in carcasses that were prewashed and then exposed to a 5-s dip in a solution containing phosphoric acid- or citric acid-activated ASC. At 1,200 ppm ASC, a mild but transitory whitening of the skin was noted on dipped carcasses. The results support the methods currently approved by the U.S. Department of Agriculture for the use of ASC solutions as a prechill antimicrobial intervention in U.S. poultry processing plants.
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PMID:Acidified sodium chlorite antimicrobial treatment of broiler carcasses. 1094 85

The forms of Al for uptake by the roots and translocation from the root to the shoot were investigated in a buckwheat (Fagopyrum esculentum Moench, cv. Jianxi) that accumulates Al in its leaves. The Al concentration in the xylem sap was 15-fold higher in the plants exposed to AlCl3 than in those exposed to an Al-oxalate (1:3) complex, suggesting that the roots take up Al in the ionic form. The Al concentration in the xylem sap was 4-fold higher than that in the external solution after a 1-h exposure to AICl3 solution and 10-fold higher after a 2-h exposure. The Al concentration in the xylem sap increased with increasing Al concentration in the external solution. The Al uptake was not affected by a respiratory inhibitor, hydroxylamine, but significantly inhibited by the addition of La. These results suggest that Al uptake by the root is a passive process, and La3+ competes for the binding sites for Al3+ on the plasma membrane. The form of Al in the xylem sap was identified by 27Al-nuclear magnetic resonance analysis. The chemical shift of 27Al in the xylem sap was around 10.9 ppm, which is consistent with that of the Al-citrate complex. Furthermore, the dominant organic acid in the xylem sap was citric acid, indicating that Al was translocated in the form of Al-citrate complex. Because Al is present as Al-oxalate (1:3) in the root, the present data show that ligand exchange from oxalate to citrate occurs before Al is released to xylem.
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PMID:Form of aluminium for uptake and translocation in buckwheat (Fagopyrum esculentum Moench). 1098 53

Several outbreaks of salmonellosis associated with alfalfa sprouts have been documented in the United States since 1995. This study was undertaken to evaluate various chemical treatments for their effectiveness in killing Salmonella on alfalfa seeds. Immersing inoculated seeds in solutions containing 20,000 ppm free chlorine (Ca[OCl]2), 5% Na3PO4, 8% H2O2, 1% Ca(OH)2, 1% calcinated calcium, 5% lactic acid, or 5% citric acid for 10 min resulted in reductions of 2.0 to 3.2 log10 CFU/ g. Treatment with 1,060 ppm Tsunami or Vortex, 1,200 ppm acidified NaClO2, or 5% acetic acid were less effective in reducing Salmonella populations. With the exceptions of 8% H2O2, 1% Ca(OH)2, and 1% calcinated calcium that reduced populations by 3.2, 2.8, and 2.9 log10 CFU/g, respectively, none of treatments reduced the number of Salmonella by more than 2.2 log10 CFU/g without significantly reducing the seed germination percentage. Treatment with 5% acetic, lactic, or citric acids substantially reduced the ability of seeds to germinate. Treatment with 1% Ca(OH)2 in combination with 1% Tween 80, a surfactant, enhanced inactivation by 1.3 log10 CFU/g compared to treatment with 1% Ca(OH)2 alone. Presoaking seeds in water, 0.1% EDTA, 1% Tween 80, or 1% Tween 80 plus 0.1% EDTA for 30 min before treatment with water, 2,000 ppm NaOCl, or 2% lactic acid had a minimal effect on reducing populations of Salmonella. Results indicate that, although several chemical treatments cause reductions in Salmonella populations of up to 3.2 log10 CFU/g initially on alfalfa seeds when analyzed by direct plating, no treatment eliminated the pathogen, as evidenced by detection in enriched samples.
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PMID:Comparison of aqueous chemical treatments to eliminate Salmonella on alfalfa seeds. 1107 86

Oxidation of malate to oxaloacetate in Escherichia coli can be catalyzed by two enzymes: the well-known NAD-dependent malate dehydrogenase (MDH; EC 1.1.1.37) and the membrane-associated malate:quinone-oxidoreductase (MQO; EC 1.1.99.16), encoded by the gene mqo (previously called yojH). Expression of the mqo gene and, consequently, MQO activity are regulated by carbon and energy source for growth. In batch cultures, MQO activity was highest during exponential growth and decreased sharply after onset of the stationary phase. Experiments with the beta-galactosidase reporter fused to the promoter of the mqo gene indicate that its transcription is regulated by the ArcA-ArcB two-component system. In contrast to earlier reports, MDH did not repress mqo expression. On the contrary, MQO and MDH are active at the same time in E. coli. For Corynebacterium glutamicum, it was found that MQO is the principal enzyme catalyzing the oxidation of malate to oxaloacetate. These observations justified a reinvestigation of the roles of MDH and MQO in the citric acid cycle of E. coli. In this organism, a defined deletion of the mdh gene led to severely decreased rates of growth on several substrates. Deletion of the mqo gene did not produce a distinguishable effect on the growth rate, nor did it affect the fitness of the organism in competition with the wild type. To investigate whether in an mqo mutant the conversion of malate to oxaloacetate could have been taken over by a bypass route via malic enzyme, phosphoenolpyruvate synthase, and phosphenolpyruvate carboxylase, deletion mutants of the malic enzyme genes sfcA and b2463 (coding for EC 1.1.1.38 and EC 1.1.1.40, respectively) and of the phosphoenolpyruvate synthase (EC 2.7.9.2) gene pps were created. They were introduced separately or together with the deletion of mqo. These studies did not reveal a significant role for MQO in malate oxidation in wild-type E. coli. However, comparing growth of the mdh single mutant to that of the double mutant containing mdh and mqo deletions did indicate that MQO partly takes over the function of MDH in an mdh mutant.
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PMID:Functions of the membrane-associated and cytoplasmic malate dehydrogenases in the citric acid cycle of Escherichia coli. 1109 47


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