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PubMed1992

Healing of the intrabony periodontal lesion following root conditioning with citric acid and wound closure including an expanded PTFE membrane.

The effect of citric acid conditioning of the root surface in conjunction with gingival flap surgery including barrier membranes (expanded polytetrafluoroethylene) was clinically evaluated in 26 intrabony periodontal defects in 23 patients. Control treatment included gingival flap surgery with barrier membranes alone. Twelve defects were treated with the experimental and 14 with the control protocol. Healing was evaluated 12 months after surgery. Initial probing depths approximated 6.9 mm and defect depths measured during surgery exceeded 4 mm. The patients exhibited good oral hygiene over the study interval as substantiated by low plaque and bleeding scores. Acid conditioning of the root surface did not enhance periodontal healing in this study, similar amounts of defect resolution were observed following either treatment protocol. Probing depth reduction generally approximated 1.8 mm; gain of clinical attachment, 0.8 mm; and defect bone fill, 1.2 mm. Under the prevailing conditions, the barrier membrane procedure apparently gave a healing result beyond which further improvement could not be achieved by root surface conditioning.

Adult↗
PubMed2006

The viability of a nonenzymatic reductive citric acid cycle--kinetics and thermochemistry.

The likelihood of a functioning nonenzymatic reductive citric acid cycle, recently proposed as the precursor to biosynthesis on early Earth, is examined on the basis of the kinetics and thermochemistry of the acetate --> pyruvate --> oxaloacetate --> malate sequence. Using data derived from studies of the Pd-catalyzed phosphinate reduction of carbonyl functions it is shown that the rate of conversion of pyruvate to malate with that system would have been much too slow to have played a role in the early chemistry of life, while naturally occurring reduction systems such as the fayalite-magnetite-quartz and pyrrhotite-pyrite-magnetite mineral assemblages would have provided even slower conversions. It is also shown that the production of pyruvate from acetate is too highly endoergic to be driven by a naturally occurring energy source such as pyrophosphate. It is thus highly doubtful that the cycle can operate at suitable rates without enzymes, and most unlikely that it could have participated in the chemistry leading to life.

Citric Acid Cycle↗
PubMed1987

Evolutionary roots of the citric acid cycle in prokaryotes.

Advances in biochemistry, microbiology, and molecular biology suggest new approaches for exploring the early evolution of bioenergetic systems. These approaches, still in their infancy, are necessarily directed to detection of 'molecular fossils' in diverse extant prokaryotes. Since the Earth was devoid of atmospheric oxygen during early cellular evolution, it is likely that 'precursor fragments' of the classical citric acid cycle are to be found in contemporary anaerobic bacteria. Accumulating evidence indicates that such fragments originally served biosynthetic roles of one kind or another, before they were recruited for assembly of the energy-yielding aerobic cycle. The extraordinary versatility of citric acid cycle intermediates and reactions for multiple uses raises the possibility that origination of the aerobic cycle, viewed as an evolutionary event, occurred more than once.

Bacteria↗
PubMed1983

Healing responses of human intraosseous lesions following the use of debridement, grafting and citric acid root treatment. II. Clinical and histologic observations: one year postsurgery.

This report details histologic healing responses at intrabony sites within two patients about 1 year after surgery. Treatment consisted of open flat debridement of the lesions. At specific sites, augmenting procedures such as autogenous grafts, allografts, synthetic grafts and citric acid root treatment were utilized. In addition, notches were made through calculus prior to root planing at specific root surfaces. These notches were placed at varying distances from the base of the lesion. Patients were followed postsurgically with frequent maintenance visits. Block sections were removed at the end of the experimental period. Clinical reduction in pocket depth was noted at all treated sites. This reduction consisted of limited pocket closure, marginal gingival recession and repocketing. Histologically, all specimens showed evidence of repair. The most mature repair appeared at sites treated with debridement and autogenous grafts. "Regeneration" of lost periodontal attachment was demonstrated by evidence of cementogenesis, osteogenesis and the presence of functionally oriented ligaments. However, the coronal regeneration appeared spatially limited. Allografts showed a similar, but less mature healing response. Synthetic graft material acted essentially as a "filler" within the defect. Citric acid root treatment did not demonstrate clear evidence of augmentation of the repair process. Of particular note in these human specimens was further histologic demonstration that "regeneration" potential apparently can only take place in close proximity to histologically viable periodontal ligament cells which may act as "donor sites" for coronal "regeneration" of lost periodontal attachment. This histologic response was observed regardless of treatment modalities used.

Adult↗
PubMed2002

Reactive oxygen species in sustained airway constriction induced by citric acid aerosol inhalation.

We tested if there is a direct relationship between reactive oxygen species and citric acid-induced airway constriction. Guinea pigs were divided into two groups: control and dimethylthiourea (a hydroxyl radical scavenger). The animals in each group were further separated into four subgroups: baseline, recovery 2-3 min, recovery 10 min, and recovery 20 min. Each animal was anesthetized, cannulated, paralyzed, and artificially ventilated. Citric acid aerosol inhalation caused the following significant changes in the control group during the recovery period: airway constriction for at least 20 min, increases in luminol-amplified t-butyl hydroperoxide-initiated chemiluminescence counts in the bronchoalveolar lavage samples at 2-3 and 20 min, an increase in bronchoalveolar lavage fluid substance P level at 2-3 min, and elevations in the bronchoalveolar lavage fluid total cell and neutrophil numbers at 20 min. All citric acid-induced alterations were prevented by dimethylthiourea pretreatment. These results suggest that citric acid inhalation induces the initial release of reactive oxygen species and tachykinins, which causes further cellular infiltration and sustained airway constriction.

Administration, Inhalation↗
PubMed1997

Survival of heated Bacillus coagulans spores in a medium acidified with lactic or citric acid.

The influence of the intensity of heat treatments on the capacity of citric or lactic acid to prevent growth of survivors of Bacillus coagulans spores after 10 days storage at 35 degrees C was studied. In most cases, the number of survivors during storage decreased. The extent of this spore inactivation depended on the intensity of previous heat treatment and the pH of the medium and the acidulant used. The inactivating effect of storage was pronounced even at pH values less acidic than those used by the canning industry. Citric acid was more effective than lactic acid on spores given only low heat treatments, but lactic was more effective against those given more severe heat treatments. The severity of heat treatment required for lactic to be more effective than citric acid increased with pH of the medium. Heat treatment also required increased pH for heated spores to grow. pH 4.6, regardless of acidulant used, was unable to prevent growth of unheated spores but a less acidic pH (pH 5.2) did prevent growth even when spores had been given only mild heat treatments (10 s at 100 degrees C).

Bacillus↗
PubMed2006

Changes in primary metabolism leading to citric acid overflow in Aspergillus niger.

For citric acid-accumulating Aspergillus niger cells, the enhancement of anaplerotic reactions replenishing tricarboxylic acid cycle intermediates predisposes the cells to form the product. However, there is no increased citrate level in germinating spores and a complex sequence of developmental events is needed to change the metabolism in a way that leads to an increased level of tricarboxylic acid cycle intermediates in mycelia. A review of physiological events that cause such intracellular conditions, with the special emphasis on the discussion of hexose transport into the cells and regulation of primary metabolism, predominantly of glycolytic flux during the process, is presented.

Aspergillus niger↗
PubMed1987

Effect of citric acid conditioning on fibroblast cell density in periodontal wounds.

The present experiment was undertaken to study the repopulation of curetted root surfaces by fibroblast-like cells in experimental periodontal wounds. 6 beagle dogs were used. After reflecting mucoperiosteal flaps, fenestration wounds were made through the buccal cortical plate exposing roots of maxillary canines in 6 beagle dogs. Exposed root surfaces were curetted to remove cementum and periodontal ligament. On 1 side, the exposed root surface was conditioned with citric acid (pH 1) for 3 min while the contralateral root was treated with distilled water. Millipore filters were placed over the wounds to prevent flap connective tissues from contacting the exposed root surface. Histometric analysis was made 10 days after wounding. Fibroblast-like cells were seen migrating into the fenestration space and were primarily aligned along the root surface. Cell densities measured at the borders and central part of the wound showed significantly lower values (p less than 0.01 and p less than 0.05) in acid-conditioned wounds compared to controls. No significant difference in cell density was noted between the borders and central part of the wound in the acid-conditioned group. In the controls, the cell density at the borders was significantly greater than at the center, suggesting active cell migration from the borders. The present findings suggest that citric acid conditioning of root dentin may result in a low cell density during the early stages of healing in experimental periodontal wounds.

Alveolar Process↗
PubMed1986

Effect of dithiocarbamates on citric acid production by Aspergillus niger.

Dithiocarbamates were found to enhance the production of citric acid under solid-state fermentation conditions by Aspergillus niger. Maximum increase was observed with tetramethylthiuram disulfide (TMTD). Percent increases observed were 74.2% with 2.5 micrograms/mL of TMTD, 19.6% with 2.5 micrograms/mL of sodium dimethyldithiocarbamate and 33.1% with 0.6 micrograms/mL of zinc dimethyldithiocarbamate.

Aspergillus niger↗
PubMed1973

Developmental block in citric acid cycle mutants of Bacillus subtilis.

Mutants deficient in different enzymes of the citric acid cycle can be subdivided into two groups according to the frequency at which they produce heat-resistant spores in nutrient sporulation medium. However, the majority of cells can develop in this medium only to the axial filament stage I of sporulation; aconitase and isocitrate dehydrogenase mutants need the addition of glutamate to reach this stage.

Aconitate Hydratase↗
PubMed1980

A surgical procedure for the treatment of localized gingival recession in conjunction with root surface citric acid conditioning.

A total of 9 teeth were treated with a free gingival graft followed by a coronally positioned flap in conjunction with conditioning of the root surface with citric acid. The grafting procedure was done 2 weeks after the subjects could perform adequate plaque control. Thirty days after grafting, a mucoperiosteal flap was raised. The root surface was thoroughly planed and conditioned with citric acid at pH 1.0, and the flap was then positioned coronally. Clinical measurements of the amount of recession, sulcus depth, and keratinized gingiva were taken preoperatively, and at 30 and 60 days after surgery. Recession was reduced by a mean of 3.24 +/- 2.08 mm. Width of keratinized gingiva was increased to a mean of 4.99 +/- 1.23 mm. Both of these findings were highly significant. Sulcus depth was not significantly changed.

Acid Etching, Dental↗
PubMed2003

Preventing blockage of long-term indwelling catheters in adults: are citric acid solutions effective?

Community health practitioners are frequently faced with the problem of indwelling catheters failing to drain. This mini-review examines the evidence regarding the effectiveness of citric acid-based bladder washout solutions (solution G, solution R), compared with saline for preventing blockage of long-term catheters in older adults. Although there is some evidence on the effect of citric acid solutions in laboratory conditions, the search yielded no evidence measuring catheter patency in humans. Only one randomized controlled trial addressing the use of citric acid solutions with human subjects was found. This provided some confirmation that solution G had immediate effect but gave no evidence of long-term benefit. No difference was apparent on examination of catheter tips. As the evidence is weak, practitioners should consider the use of citric acid maintenance solution as non-routine and only following formal evaluation in a one-off trial on appropriate patients.

Adult↗
PubMed2006

Enhanced malachite green removal from aqueous solution by citric acid modified rice straw.

In this paper, rice straw was thermochemically modified with citric acid (CA) as esterifying agent. Two introduced free carboxyl groups of esterified rice straw were further loaded with sodium ion to yield potentially biodegradable cationic sorbent. In order to investigate the effect of chemical modification on the cationic dye sorption of rice straw, the removal capacities of native and modified rice straw sorbing a cationic dye (malachite green) from aqueous solution were compared. The effects of various experimental parameters (e.g. initial pH, sorbent dose, dye concentration, contact time) were investigated. For modified rice straw (MRS), the malachite green (MG) removal percentage came up to the maximum value beyond pH 4. For the 250 mg/l of MG solution, the 1.5 g/l or up of MRS could almost completely remove the dye from aqueous solution. Under the condition of 2.0 g/l sorbent used, the percentage of MG sorbed on MRS kept above 93% over a range from 100 to 500 mg/l of MG concentration. The sorption isotherms fitted the Langmuir or Freundlich models. The sorption equilibriums were reached at about 10 h. The sorption processes followed the pseudo-first-order rate kinetics. After chemical modification, the intraparticle diffusion rate constant (k(id)) was obviously increased. The results in this study indicated that MRS was an excellent sorbent for removal of MG from aqueous solution.

Adsorption↗
PubMed1999

Citric acid fermentation by magnetic drum contactor: use of methanol and ethanol for higher production.

Use of methanol or ethanol in the magneto-biotechnological technique was found to be enhance citric acid production in a magnetic drum contactor operation with Aspergillus niger AJ 117173. Continuous and repeated-batch fermentations were conducted with the addition of 2% ethanol. Continuous fermentation for 50 d gave a better citric acid yield (85%) and average productivity (3.8 g.l(-1).d(-1)) than repeated-batch fermentation over 60 d (65%, 2.3 g.l(-1).d(-1)).

Journal Article↗
PubMed1989

[In vivo study of bacterial invasion in root planed and citric acid treated radicular surfaces of periodontally involved human teeth].

The purpose of this study was to investigate whether plaque bacteria invade the exposed radicular dentin after root planing or chemical root treatment in vivo. Eighteen caries-free human periodontally involved teeth with hopeless prognoses were studied. Fourteen teeth were scaled and root planed with hand curette type scalers. The proximal surface of each treated tooth was designated as the RP surface. The remaining half of the proximal surface was treated with citric acid (pH 1.0) for 3 minutes and was designated as the CA surface. Four untreated teeth served as controls. After 4 weeks, the teeth were extracted, and were processed for light microscopy and for scanning electron microscopy concerning bacterial invasion into the supragingival radicular dentin. The following results were obtained. 1. Radicular cementum was present on most untreated tooth surfaces. However, bacteria were never seen in the dentinal tubules. 2. Bacterial invasion into the dentinal tubules was observed in five of the 10 proximal surfaces (50% of the RP surfaces) and in nine of the 10 proximal surfaces (90% of the CA surfaces). 3. The depth (9.5 +/- 24.1 microns vs 84.6 +/- 136.3 microns) and percentage (0.8 +/- 2.1% vs 20.3 +/- 17.3%) of bacterial invasion in the dentinal tubules of the RP surfaces was lower than that of the CA surfaces. 4. Cocci and short rods were present in the supragingival dentinal tubules. 5. Since CA surfaces may accelerate bacterial invasion the citric acid treatment might be harmful in patients with inadequate plaque control.

Citrates↗
PubMed1983

Mathematical analysis of isotope labeling in the citric acid cycle with applications to 13C NMR studies in perfused rat hearts.

Rat hearts have been perfused in vitro with 5 mM glucose and either 5 mM acetate or 1 mM pyruvate to achieve steady state conditions, followed by replacement of the acetate with 90% enriched [2-13C]acetate or pyruvate with 90% enriched [3-13C]pyruvate. The hearts were frozen different times after addition of 13C-substrate and neutralized perchloric acid extracts from three pooled hearts per time point were used to obtain high resolution proton-decoupled 13C NMR spectra at 90.55 MHz. The 13C fractional enrichment of individual carbons of different metabolites was calculated from the area of the resolved resonances after correction for nuclear Overhauser enhancement and saturation effects. A mathematical flux model of the citric acid cycle and ancillary transamination reactions was constructed with the FACSIMILE program, and used to solve unknown flux parameters with constant pool sizes by nonlinear least squares analysis of the approximately 200 simultaneous differential equations required to describe the reactions. With [2-13C] acetate as substrate, resonances and line splittings due to 13C-13C spin coupling of the C-2, C-3, and C-4 carbons of glutamate were well resolved. The half-times to reach maximum 13C enrichment were 2.6 min for glutamate C-4 and 8 min for glutamate C-2 and C-3. From these data, a well determined citric acid cycle flux of 8.3 mumol/g dry weight X min was calculated for an observed oxygen consumption of 31 mumol/g dry weight X min. With [3-13C]pyruvate as substrate, resonances of aspartate C-2 and C-3 and of alanine C-3 were well resolved in addition to those of glutamate C-2, C-3, and C-4. Nonlinear least squares fitting of these data to the model gave nonrandomly distributed residuals for the 13C fractional enrichments of glutamate C-4, suggesting an incomplete model, but a well determined cycle flux of 11.9 mumol/g dry weight X min for an oxygen uptake of 35 mumol/g dry weight X min. Our studies demonstrate the practicality of 13C NMR, used in conjunction with mathematical modeling, for the measurement of metabolic flux parameters in living systems.

Animals↗
PubMed1984

Cerebral metabolic and circulatory effects of 1,1,1-trichloroethane, a neurotoxic industrial solvent. 2. Tissue concentrations of labile phosphates, glycolytic metabolites, citric acid cycle intermediates, amino acids, and cyclic nucleotides.

In order to obtain information on the mechanisms of neurotoxicity of 1,1,1-trichloroethane, rats maintained artificially ventilated on N2O:O2 (70:30) were exposed to a concentration of 1,1,1-trichloroethane of 8000 ppm, 43.7 mg L-1, that induces moderate ataxia in awake, spontaneously breathing animals. After 5 and 60 min of exposure, as well as after a 60-min recovery period following 60 min of exposure, the brain was frozen in situ and cortical tissue was assayed for phosphocreatine (PCr), + ATP, ADP, AMP, glycogen, glucose, pyruvate, lactate, citric acid cycle intermediates, associated amino acids, and cyclic nucleotides; in addition, purine nucleotides, nucleosides, and bases were assayed by HPLC techniques. Exposure of animals to 1,1,1-trichloroethane failed to alter blood glucose, lactate, and pyruvate concentrations. However, the solvent induced highly significant increases in tissue lactate and pyruvate concentrations that were also reflected in cisternal CSF. Associated with these changes were increases in all citric acid cycle intermediates except succinate, an increase in alanine concentration, and a rise in the glutamate/aspartate ratio. After 5 min, a small decrease in glycogen concentration also occurred. All these changes were reversed when the exposure was terminated. No changes were observed in tissue concentrations of purine nucleotides, nucleosides, and bases except for a small reduction of ATP concentration after 60 min of exposure, still noticeable after 60 min of recovery. Apart from a small reduction in cAMP concentration after 5 min of exposure, cyclic nucleotide concentrations did not change.

Animals↗