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PubMed1988

Effect of citric acid treatment on the migration of epithelium on root surfaces in vitro.

Explants of bovine gingival mucosa were cultured for four days on scaled and citric acid-conditioned root surfaces. Demineralization of the hard tissue with citric acid exposed the collagenous matrix of the root. Undemineralized islands were frequently seen among the collagen fibers of the treated roots. When cultured on scaled, control root surfaces, the epithelium migrated inwards between the connective tissue of the explant and the root surface. On citric acid-treated roots, epithelial migration in this direction was rare although it was possible. Citric acid treatment of the substratum directed the epithelium to migrate outwards from the explant. Only a few of the controls showed epithelial migration to the outward direction. The findings indicate that demineralization of the root surface has an influence on the direction in which the epithelium initially starts to migrate. An induced delay of epithelial migration between the gingival connective tissue and the hard tissue may be favorable for connective tissue attachment to the root surface.

Animals↗
PubMed1999

Scale-up of citric acid fermentation by redox potential control

To obtain high citric acid productivity in Aspergillus niger fermentation on beet molasses substrate, a certain redox potential profile with two maxima (260 and 280 mV) and two minima (180 and 80 mV) must be maintained. The most effective regulation of redox potential is by regulation of aeration and agitation. It has been shown that control of redox potential by aeration and agitation is a most successful method for scale-up from 10-L laboratory scale to the 100- and 1000-L pilot-plant scale, even in geometrically dissimilar stirred-tank reactors. Copyright 1999 John Wiley & Sons, Inc.

Journal Article↗
PubMed2005

Nucleation of calcium carbonate in presence of citric acid, DTPA, EDTA and pyromellitic acid.

The influence of four calcium complexing additives, i.e., citric acid (CIT), diethylenetriaminepentaacetic acid (DTPA), ethylenediaminetetraacetic acid (EDTA) and pyromellitic acid (PMA), and their concentration on the induction time of calcium carbonate nucleation has been studied. The experiments were performed by rapidly mixing a sodium carbonate solution and a calcium chloride solution of various concentrations. The induction time was obtained by recording the white light absorption of the solution. Chemical speciation was used to estimate the initial thermodynamic driving force of each experiment. The induction time was found to increase with additive concentration. The effect varies from one additive to another. CIT causes the greatest increase in induction time and PMA the least. Using classical nucleation theory the experimental data were evaluated in terms of the interfacial energy. In pure water a value of 37.8 mJ m(-2) was obtained, showing good agreement with other works. CIT, DTPA and EDTA caused a notable increase of the interfacial energy at a concentration of 0.5 mmol l(-1). PMA does not appear to have any effect at all on the interfacial energy. Different mechanisms for the influence of the additives on the measured induction time and on the estimated interfacial energy are discussed.

Journal Article↗
PubMed1999

Ultrastructural changes of the tooth root surface by Nd:YAG laser irradiation followed by citric acid and tetracycline.

The neodymium:yttrium-aluminum-garnet (Nd:YAG) laser has been used for treatment of dentinal hypersensitivity, eradicating periodontal pathogens, and facilitating calculus removal. However, Nd:YAG laser irradiation exerts potentially harmful effects on the tooth root surface. The purpose of this study was to examine the ultrastructural changes of the tooth root surface caused by Nd:YAG laser irradiation, and to determine whether chemical and mechanical preparations can correct these ultrastructural changes. Eighteen tooth specimens (3 x 3 x 0.5 mm) with healthy root surfaces were prepared and irradiated with an Nd:YAG laser at various power densities. Root surfaces were irradiated at 100 mJ at 20 pulses per second (pps) for 2 seconds followed by the application of citric acid (pH 1.2) or tetracycline solution (100 mg/mL) for 3 and 5 minutes, respectively, or ultrasonic scaling for 5 strokes of 3 seconds per stroke. As observed with low-vacuum scanning electron microscopy, (Wet-SEM), Nd:YAG laser irradiation at 70 to 100 mJ, 20 pps for 2 seconds caused surface cratering, areas of porosity, pitting, fissures, and lava-like structures in an area 140 to 280 microns in diameter. Irradiation of 50 mJ, 20 pps for 2 seconds, led to only mild surface charring. No evidence of morphologic changes was found when root surfaces were irradiated with the Nd:YAG laser at 20 mJ, 20 pps for 2 seconds or at 50 mJ, 10 pps for 8 seconds. The laser-induced lava-like structures were partially detached by citric acid (pH 1.2) etching and ultrasonic scaling, but not by tetracycline (100 mg/mL). These results indicate that chemical and mechanical preparations can be used effectively in conjunction with Nd:YAG laser irradiation for root surface preparation during both nonsurgical and surgical periodontal treatments.

Anti-Bacterial Agents↗
PubMed2005

The effect of chemical stimulation of esophageal mucosa on citric acid induced cough and specific airway resistance in guinea pig.

BACKGROUND: Gastroesophageal reflux disease is one of the most common causes of chronic cough. The mechanism of the cough initiation in these patients remains unresolved. OBJECTIVES: This study was designed to investigate the effect of intraesophageal (IE) administration of capsaicin on cough and specific airway resistance (Saw) in guinea pigs. METHODS: Male TRIK strain guinea pigs were used. In the first experiment 12 controls received IE saline, 9 animals (group 1) received IE capsaicin (400 microM, 0.2 ml) and 12 guinea pigs (group 2) received IE capsaicin (400 microM, 0.2 ml) 24 hours after IE administration of hydrochloric acid (3 M, 0.2 ml). Cough induced by inhalation of citric acid (CA) and Saw was determined after IE administration of saline in controls and capsaicin in groups 1 a 2. In the second experiment, CA induced cough was determined in guinea pigs (n=13) in the beginning of the study (control response), after NaOH (1 M, 0.2 ml) was administered IE. One week later in conditions of corrosive esophagitis CA induced cough was determined after IE administration of capsaicin (cough during esophageal stimulation). RESULTS: There was no difference in CA induced cough between controls, group 1 and 2 (p=0.98). Saw was hot affected by IE capsaicin stimulation and CA inhalation in group 1 and group 2. There was no difference found between control cough response and those induced after IE capsaicin in animals with corrosive esophagitis (p=0.75). CONCLUSION: Esophageal stimulation with capsaicin did not trigger and/or modulate CA induced cough and Saw in guinea pigs models. (Fig. 5, Ref. 22.)

Airway Resistance↗
PubMed2004

Regulation of pyruvate dehydrogenase activity and citric acid cycle intermediates during high cardiac power generation.

A high rate of cardiac work increases citric acid cycle (CAC) turnover and flux through pyruvate dehydrogenase (PDH); however, the mechanisms for these effects are poorly understood. We tested the hypotheses that an increase in cardiac energy expenditure: (1) activates PDH and reduces the product/substrate ratios ([NADH]/[NAD(+)] and [acetyl-CoA]/[CoA-SH]); and (2) increases the content of CAC intermediates. Measurements were made in anaesthetized pigs under control conditions and during 15 min of a high cardiac workload induced by dobutamine (Dob). A third group was made hyperglycaemic (14 mm) to stimulate flux through PDH during the high work state (Dob + Glu). Glucose and fatty acid oxidation were measured with (14)C-glucose and (3)H-oleate. Compared with control, the high workload groups had a similar increase in myocardial oxygen consumption ( and cardiac power. Dob increased PDH activity and glucose oxidation above control, but did not reduce the [NADH]/[NAD(+)] and [acetyl-CoA]/[CoA-SH] ratios, and there were no differences between the Dob and Dob + Glu groups. An additional group was treated with Dob + Glu and oxfenicine (Oxf) to inhibit fatty acid oxidation: this increased [CoA-SH] and glucose oxidation compared with Dob; however, there was no further activation of PDH or decrease in the [NADH]/[NAD(+)] ratio. Content of the 4-carbon CAC intermediates succinate, fumarate and malate increased 3-fold with Dob, but there was no change in citrate content, and the Dob + Glu and Dob + Glu + Oxf groups were not different from Dob. In conclusion, compared with normal conditions, at high myocardial energy expenditure (1) the increase in flux through PDH is regulated by activation of the enzyme complex and continues to be partially controlled through inhibition by fatty acid oxidation, and (2) there is expansion of the CAC pool size at the level of 4-carbon intermediates that is largely independent of myocardial fatty acid oxidation.

Adenosine Diphosphate↗
PubMed1987

Regulation of citric acid cycle genes in facultative bacteria.

In a facultative anaerobe such as Escherichia coli the citric acid cycle is an inducible pathway rather than a constitutive pathway. In spite of intensive study at the enzymological and molecular biological levels many aspects of the cycle, including its regulation during the aerobic/anaerobic switch, are not fully understood.

Citric Acid Cycle↗
PubMed1993

Glycolysis-citric acid cycle interrelation: a new approach and some insights in cellular and subcellular compartmentation.

In the development of an integrated approach to study metabolic compartmentation and regulation in brain, we have emphasized the importance, versatility, and need to exploit the recent methodological advances in (1) NMR spectroscopy, (2) primary cultures of neurons and glial cells, and (3) subcellular fractionation (especially brain mitochondrial isolation). The integrated approach has the advantage of being able to draw data and inferences based on some combination of results derived from in vivo, cellular, and subcellular studies. For example, some in vivo NMR data may suggest that an enzymatic step may be rate-limiting in a particular pathway. This information may be used to frame testable hypotheses and questions that can be investigated in experiments involving primary cultures of neural cells and subcellular fractions. Subsequently, the data from such in vitro studies could serve as the bases for constructing the hypothetical framework for predicting the regulatory role, in vivo, of the enzyme in the pathway. We have discussed the known as well as the as yet ill-defined facets of the cellular and subcellular aspects of the glycolysis-citric acid cycle interrelation and have attempted to illustrate how such an integrated approach could be applied to generate testable hypotheses for investigating the mechanisms concerned with metabolic compartmentation and regulation in brain. In the process of the illustration, we discuss some of the evidence in support of the general hypothesis that the transfer of reducing equivalents across the inner mitochondrial membrane plays a major role in mediating the coupling of the glycolytic flux to that of the citric acid cycle. We have given some indications as to how this hypothesis could be further investigated employing our approach. Moreover, we hope that other workers will find this integrated approach useful in designing multidisciplinary studies to investigate mechanistic issues related to this important theme.

Animals↗
PubMed1979

[On the contamination of the citric acid fermentation. II. Sodium 5-nitrofurylacrylate as an antiseptic against representatives of the Enterobacteriaceae (author's transl)].

In context with the first communication which deals with the characterization of the so-called brown contamination called forth by Enterobacteriaceae in the citric acid fermentation of molasses, the present paper describes the screening of antiseptic substances able to suppress the contamination mentioned without damaging the normal growth of the producing mould Aspergillus niger and its ability of producing citric acid. Among the substances tested the sodium salt of 5-nitrofurylacrylic acid (5-NFA) excelled partly because of its antiseptic effect in relatively small concentrations and partly because the mould tolerates appreciable amounts of this antiseptic. Therefore there may be applied, in the presence of a heavy contamination, relatively high concentrations of the antiseptic without fear of damaging the producing mould. Usually a dose of 10 to 15 mg 5-NFA in 11 of medium was sufficient to suppress the brown contamination.

Acrylates↗
PubMed2005

Differential effects of heptanoate and hexanoate on myocardial citric acid cycle intermediates following ischemia-reperfusion.

In the normal heart, there is loss of citric acid cycle (CAC) intermediates that is matched by the entry of intermediates from outside the cycle, a process termed anaplerosis. Previous in vitro studies suggest that supplementation with anaplerotic substrates improves cardiac function during myocardial ischemia and/or reperfusion. The present investigation assessed whether treatment with the anaplerotic medium-chain fatty acid heptanoate improves contractile function during ischemia and reperfusion. The left anterior descending coronary artery of anesthetized pigs was subjected to 60 min of 60% flow reduction and 30 min of reperfusion. Three treatment groups were studied: saline control, heptanoate (0.4 mM), or hexanoate as a negative control (0.4 mM). Treatment was initiated after 30 min of ischemia and continued through reperfusion. Myocardial CAC intermediate content was not affected by ischemia-reperfusion; however, treatment with heptanoate resulted in a more than twofold increase in fumarate and malate, with no change in citrate and succinate, while treatment with hexanoate did not increase fumarate or malate but increased succinate by 1.8-fold. There were no differences among groups in lactate exchange, glucose oxidation, oxygen consumption, and contractile power. In conclusion, despite a significant increase in the content of carbon-4 CAC intermediates, treatment with heptanoate did not result in improved mechanical function of the heart in this model of reversible ischemia-reperfusion. This suggests that reduced anaplerosis and CAC dysfunction do not play a major role in contractile and metabolic derangements observed with a 60% decrease in coronary flow followed by reperfusion.

Animals↗
PubMed1984

Rabbit antiserum to a citric acid extract of human skeletal muscle staining thymomas from myasthenia gravis patients.

Rabbit antiserum to a citric acid extract of human skeletal muscle (CA) stained both the cell membrane and the cross-striational bands of skeletal muscle cells. The rabbit antiserum also stained the cell membrane of epithelial thymoma cells from myasthenia gravis (MG) patients. Normal and hyperplastic thymus tissue were not stained, apart from scattered myoid thymic cells. Absorption of the antiserum with CA abolished staining of the thymoma, indicating that human skeletal muscle and epithelial thymoma cells possess common antigens.

Absorption↗
PubMed1986

Organization of citric acid cycle enzymes into a multienzyme cluster.

The possibility that some of the enzymes of the citric acid cycle may be loosely associated into a multienzyme cluster has been investigated using extracts prepared by gentle disruption of cells. Gel filtration and sucrose density gradient centrifugation have shown that five sequential enzymes of the cycle specifically associate into a cluster: fumarase, malate dehydrogenase, citrate synthase, aconitase and isocitrate dehydrogenase. Ultrasonication destroys the abilities of the enzymes to associate. The cluster could catalyse the sequence of reactions leading from fumarate to oxoglutarate and has been found in extracts of several bacterial species as well as rat liver mitochondria.

Acinetobacter↗
PubMed1970

Citric acid cycle: gene-enzyme relationships in Bacillus subtilis.

The genetic location of mutations affecting the citric acid cycle and the properties of mutants of Bacillus subtilis possessing these mutations have been examined. Genes coding for the component enzymes of the cycle were found to be unlinked to each other and thus do not form an operon. The mutational defect in a mutant lacking fumarase mapped between thr-5 and cysB3. Mutations causing inability to produce isocitrate dehydrogenase and succinate dehydrogenase were found to map between argA11 and leu-1. The alpha-ketoglutarate dehydrogenase mutations were mapped at the terminal end of the B. subtilis chromosome through a weak linkage in phage PBS-1 transduction of one class of these mutations of ilvA2 and metB4. A second class of alpha-ketoglutarate dehydrogenase mutations mapped closer to ilvA2 and metB4 but still terminal with respect to these markers. Aconitaseless mutants possessed mutations that could not be linked to any of the known transducing segments of the chromosome. An effect of mutation conferring loss of one enzyme of the cycle on the specific activity of the other enzymes in the cycle was observed.

Autoradiography↗
PubMedDate not supplied

Citric acid cycle: a mainstream metabolic pathway influencing life span in Drosophila melanogaster?

The role of the citric acid cycle enzyme NADP-dependent isocitrate dehydrogenase (IDH-NADP) and its allele product variants in resisting the oxidative agent paraquat, was analyzed among descendants of reciprocal crosses between fast developmental time short-lived individuals (F-) and slow developmental time long-lived ones (S+), in Drosophila melanogaster. Taking preadult developmental time into account, the data suggested that IDH-NADP differences in enzymatic activity between electrophoretically fast and slow allele product variants could play an important role in paraquat resistance and longevity, because individuals with slow developmental time bearing the fast electrophoretic variant of IDH-NADP ("fast" allele) were the most resistant. The fast electrophoretic variant of this enzyme is known to be the most active one and its activity is related to increased reduction of NADP to NADPH. This process could be very important for an effective balance between several pathways that use NADPH as precursor molecules and the oxidative stress defense system that uses it as an oxygen free radical reductor. We also reported a strong maternal effect on these traits, because survivors of a paraquat bioassay carrying cytoplasm inherited from slow developmental long-lived females (S+ cytoplasm) showed the highest frequency of the fast electrophoretical variant of IDH-NADP.

Alleles↗