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PubMed1999

Tolerance of acid-adapted and non-adapted Escherichia coli O157:H7 cells to reduced pH as affected by type of acidulant.

A study was carried out to determine if three strains of Escherichia coli O157:H7 grown (18 h) in Tryptic Soy Broth (TSB) and TSB supplemented with 1.25% glucose (TSBG), i.e. unadapted and acid-adapted cells, respectively, exhibited changes in tolerance to reduced pH when plated on Tryptic Soy Agar (TSA) acidified (pH 3.9, 4.2, 4.5, 4.8, 5.1 and 5.4) with acetic, citric or malic acids. All test strains grew well on TSA acidified with acetic acid at pH > or = 5.4 or malic acid at pH > or = 4.5; two strains grew on TSA acidified with citric acid at pH > or = 4.5, while the third strain grew at pH > or = 4.8. Acid-adapted and control (unadapted) cells differed little in their ability to form visible colonies on TSA containing the same acid at the same pH. However, on plates not showing visible colonies, acid-adapted cells retained higher viability than unadapted cells when plated on acidified TSA. Growth of acid-adapted and control cells of E. coli O157:H7 inoculated into TSB containing acetic acid (pH 5.4 and 5.7) and citric or malic acids (pH 4.2 and 4.5) was also studied. There was essentially no difference in growth characteristics of the two types of cells in TSB acidified at the same pH with a given acid. Tolerance of acid-adapted and control cells on subsequent exposure to low pH is influenced by the type of acidulant. The order of sensitivity at a given pH is acetic > citric > malic acid. When performing acid challenge studies to determine survival and growth characteristics of E. coli O157:H7 in foods, consideration should be given to the type of acid to which cells have been exposed previously, the procedure used to achieve acidic environments and possible differences in response among strains. The use of strains less affected by pH than type of acidulant or vice versa could result in an underestimation of the potential for survival and growth of E. coli O157:H7 in acid foods.

Acids, Acyclic↗
PubMed2001

Development of a new calcium phosphate cement that contains sodium calcium phosphate.

A cement powder consisting of sodium calcium phosphate, Na3Ca6(PO4)5, in addition to tetracalcium phosphate and beta-tricalcium phosphate was prepared by pulverizing blocks of 4 wt% sodium-, 11 wt% carbonate-containing apatite samples that were heated at 1700 degrees C for 5 h. When mixed with 30 wt% malic acid or citric acid at a powder liquid ratio of 3:1, the cement set in 3 or 7 min at room temperature with compressive strength being around 52 or 27 MPa. In HeLa-cell cultures, the cement mixed with malic acid was less cytotoxic than the cement mixed with citric acid, which was far less cytotoxic than a commercial carboxylate cement used as a negative control, suggesting malic acid to be superior to citric acid as a liquid in this regard. Similar findings were also obtained with osteoclasts, of which culture experiments clearly suggested that the number of osteoclasts on the cement mixed with malic acid was significantly greater than that on the cement mixed with citric acid. Since osteoclastic response to substrates could be used as a maker in evaluating their bioresorbability associated with osteoclasts, the above finding may suggest that the cement that is to be mixed with malic acid would be more useful as bone substitutes.

Animals↗
PubMed1986

[Organic acids of various kinds of vegetables. IV. Changes in the acids and sugar in tomatoes, sweet peppers and cucumbers during development and ripening].

Concentrations of organic acids and sugars in tomatoes and sweet peppers change notably during ripening. The concentration of malic acid decreases while that of citric acid increases considerably and in redripe fruits clearly exceeds the content of malic acid. Several maxima and minima in acid concentrations occur during development. Both species show constant proportions of citric and isocitric acid (200:1 and 30:1 respectively). In sweet pepper, quinic and ascorbic acid can be found in noticeably higher amounts than in tomatoes. Additionally, succinic acid was detected in tomatoes and fumaric and shikimic acid in sweet pepper. Glucose and fructose, in approximately equal amounts, are the main sugar components; their concentrations are increased during ripening, especially in sweet peppers. The leaves of tomatoes and sweet pepper contain more malic acid and less citric acid than redripe fruits, though here as well citric acid predominates. There is considerably less glucose and fructose present in the leaves of sweet pepper than in the fruits while sucrose is increased. Sucrose is the main sugar component in the leaves. Compared to tomatoes and sweet peppers, egg-plants contain more amounts. - Potatoes contain citric, malic, quinic, succinic, fumaric, and soluble oxalic acid (in order of decreasing amounts). - In cucumbers malic acid notably exceeds citric acid. Both acids hardly change in concentration during ripening. Sugar content decreases during ripening.

Acids↗
PubMed2002

Subulatin, an antioxidic caffeic acid derivative isolated from the in vitro cultured liverworts, Jungermannia subulata, Lophocolea heterophylla, and Scapania parvitexta.

The new caffeic acid derivative, subulatin (1), was isolated from in vitro cultured liverworts, Jungermannia subulata, Lophocolea heterophylla, and Scapania parvitexta. The structure of 1 involved two caffeic acids, D-glucose, and 2-carboxy-6-(1,2-dihydroxy-ethyl)-4,5-dihydroxy-5,6-dihydro-4H-pyran. The connectivity of those and the absolute stereochemistry of 1 were elucidated on the basis of spectroscopic evidence. The antioxidative activity of 1 was comparable to that of alpha-tocopherol. (2'R)-Phaselic acid (2a) and (-)-9,2''-epiphylloyl-L-malic acid (4) were also isolated from J. subulata and L. heterophylla, respectively. A chiral HPLC analysis of the p-bromobenzoyl-malic acids derived from 2a showed that 2a from J. subulata was unusual (+)-trans-caffeoyl-D-malic acid.

Antioxidants↗
PubMed2003

Crassulacean acid metabolism photosynthesis: ;working the night shift'.

Crassulacean acid metabolism (CAM) can be traced from Roman times through persons who noted a morning acid taste of some common house plants. From India in 1815, Benjamin-Heyne described a 'daily acid taste cycle' with some succulent garden plants. Recent work has shown that the nocturnally formed acid is decarboxylated during the day to become the CO(2) for photosynthesis. Thus, CAM photosynthesis extends over a 24-hour day using several daily interlocking cycles. To understand CAM photosynthesis, several landmark discoveries were made at the following times: daily reciprocal acid and carbohydrate cycles were found during 1870 to 1887; their precise identification, as malic acid and starch, and accurate quantification occurred from 1940 to 1954; diffusive gas resistance methods were introduced in the early 1960s that led to understanding the powerful stomatal control of daily gas exchanges; C(4) photosynthesis in two different types of cells was discovered from 1965 to approximately 1974 and the resultant information was used to elucidate the day and night portions of CAM photosynthesis in one cell; and exceptionally high internal green tissue CO(2) levels, 0.2 to 2.5%, upon the daytime decarboxylation of malic acid, were discovered in 1979. These discoveries then were combined with related information from C(3) and C(4) photosynthesis, carbon biochemistry, cellular anatomy, and ecological physiology. Therefore by approximately 1980, CAM photosynthesis finally was rigorously outlined. In a nutshell, 24-hour CAM occurs by phosphoenol pyruvate (PEP) carboxylase fixing CO(2)(HCO(3) (-)) over the night to form malic acid that is stored in plant cell vacuoles. While stomata are tightly closed the following day, malic acid is decarboxylated releasing CO(2) for C(3) photosynthesis via ribulose bisphosphate carboxylase oxygenase (Rubisco). The CO(2) acceptor, PEP, is formed via glycolysis at night from starch or other stored carbohydrates and after decarboxylation the three carbons are restored each day. In mid to late afternoon the stomata can open and mostly C(3) photosynthesis occurs until darkness. CAM photo-synthesis can be both inducible and constitutive and is known in 33 families with an estimated 15 to 20 000 species. CAM plants express the most plastic and tenacious photosynthesis known in that they can switch photosynthesis pathways and they can live and conduct photosynthesis for years even in the virtual absence of external H(2)O and CO(2), i.e., CAM tenaciously protects its photosynthesis from both H(2)O and CO(2) stresses.

Journal Article↗
PubMed1999

Oxaloacetate decarboxylase from Pseudomonas stutzeri: purification and characterization.

Oxaloacetate decarboxylase (OXAD), the enzyme that catalyzes the decarboxylation of oxaloacetate to pyruvic acid and carbon dioxide, was purified 245-fold to homogeneity from Pseudomonas stutzeri. The three-step purification procedure comprised anion-exchange chromatography, metal-chelate affinity chromatography, and biomimetic-dye affinity chromatography. Estimates of molecular mass from sodium dodecyl sulfate-polyacrylamide gel electrophoresis and native high-performance gel-filtration liquid chromatography were, respectively, 63 and 64 kDa, suggesting a monomeric protein. OXAD required for maximum activity divalent metal cations such as Mn2+ and Mg2+ but not monovalent cations. The enzyme is not inhibited by avidin, but is competitively inhibited by adenosine 5'-diphosphate, acetic acid, phosphoenolpyruvate, malic acid, and oxalic acid. Initial velocity, product inhibition, and dead-end inhibition studies suggested a rapid-equilibrium ordered kinetic mechanism with Mn2+ being added to the enzyme first followed by oxaloacetate, and carbon dioxide is released first followed by pyruvate. Inhibition data as well as pH-dependence profiles and kinetic parameters are reported and discussed in terms of the mechanism operating for oxaloacetate decarboxylation.

Bicarbonates↗
PubMed1995

Hydrolysis of succinic acid dimethyl ester in rat pancreatic islets.

The hydrolysis of the dimethyl ester of [1,4-14C]succinic acid and/or [2,3-14C]succinic acid was measured in homogenates of rat pancreatic islets, liver, jejunum, brain, BC3H1 mouse myocytes, NG108-19 mouse neuroblastoma x rat glioma hybrid cells, and Caco-2 human colon adenocarcinoma cells. The specific activity of the enzyme was much higher in liver, jejunum, and Caco-2 cells than in the other cell types. The affinity of the enzyme for succinic acid dimethyl ester (SAD) was also much higher in liver than in islet homogenates. In the latter case, both particulate and cytosolic activity were observed upon subcellular fractionation. The activity found in islet homogenates was commensurate with the rate of SAD hydrolysis in intact cells. While the intracellular pool of acidic metabolites generated from SAD remained fairly stable over a 15- to 120-min incubation and was mainly located in the cytosolic compartment, the amount of acidic metabolites released in the extracellular milieu progressively increased with the length of incubation. Such metabolites included both monocarboxylic and dicarboxylic acids, the latter consisting mainly of succinic acid and, to a much lesser extent, of fumaric acid and malic acid. However, at variance with SAD, succinic acid failed to be taken up by intact islets. There was no close parallelism between the specific activity of the SAD esterase and the extent of SAD utilization in distinct cell types.

Animals↗
PubMed1987

Relative efficacy of chelating agents as antidotes for acute gallium nitrate intoxication.

Twelve chelating agents were administered to mice by IP injection to compare their relative effectiveness in preventing death after a single IP injection of gallium nitrate. Na2Ca-ethylenediaminetetraacetate (EDTA), Na3Ca-diethylenetriaminepentaacetate (DTPA), dimercaptosuccinic acid (DMSA), 4,5-dihydroxy-1,3-benzene-disulfonic acid (Tiron), sodium diethyldithiocarbamate (DDC), L-cysteine and sodium salicylate were not effective for acute gallium nitrate intoxication. The therapeutic indices of the effective chelators were: 25.4 (deferoxamine mesylate), 35.7 (citric acid), 42.3 (succinic acid), 52.2 (malic acid) and 111.1 (oxalic acid).

Animals↗
PubMed2006

Molecular cloning and characterization of a novel lactate dehydrogenase gene from Clonorchis sinensis.

From a Clonorchis sinensis adult worm cDNA library, we isolated a cDNA clone encoding a novel lactate dehydrogenase (LDH) gene which encoded a putative protein with a predicted molecular weight of 35.6 kDa. The optimum pH and temperature for the enzyme were 7.5 and 50 degrees C in the pyruvate reduction while 11 and 80 degrees C in the lactate oxidation reaction, respectively. CsLDH showed no substrate inhibition by high lactate and NAD(+) concentration, and the optimal pyruvate and optimal NADH concentrations were 10 and 0.5 mmol/l, respectively. The relative activities of these 2-oxocarboxylic acids were pyruvic acid>2-ketobutyrate>oxalacetic acid>alpha-ketoglutaric acid>phenylpyruvate. The cofactor 3-acetylpyridine adenine dinucleotide was much more effective than NAD(+). The cofactor analogs in which the nicotinamide ring is replaced by 3-pyridinealdehyde were lower activity cofactors, while the nicotinamide ring is replaced by nicotinic acid or thionicotinamide which is not a cofactor to CsLDH. The succinic acid and malic acid are not substrates of CsLDH. Cu(2+), Fe(2+), and Zn(2+) greatly inhibited the CsLDH activity both in the direction of pyruvate reduction and in the direction of lactate oxidation. The inhibition of CsLDH by gossypol may make gossypol a potential therapy drug or a lead compound for C. sinensis. Accordingly, the CsLDH may be a novel potential drug target.

Amino Acid Sequence↗
PubMed1987

Organic aciduria in rats fed high amounts of xylitol or sorbitol.

The acidification of urine during polyol feeding was investigated with 27 Long-Evans male rats (aged 12 weeks) which were fed a xylitol diet (X), a sorbitol diet (S), or a basal diet for 4 weeks. The amount of polyols in the diet was increased from 5% to the final 20% level within 3 weeks. The polyol-fed animals showed reduced weight gain, lowered urine pH (from 6.5 to 5.6), and a 4-fold increase in the titratable acid excretion. X and S increased the daily urine volumes by 49 and 63%, respectively, but did not affect the wet weight or the pH values of the feces. as chromatographic-mass spectrometric analyses of organic acids revealed highly increased amounts of methylmalonic acid (13- to 20-fold) and 2-oxoglutaric acid (4- to 5-fold) in the urine of polyol-fed rats. The urinary excretion of citric acid and malic acid was also increased significantly (2- to 4-fold). The acidity of urine was not reflected in the blood acid-base balance of the animals. The increases in the levels of urinary organic acids in the polyol-fed rats were explained in terms of impaired mitochondrial oxidation of these acids and of impaired conversion of methylmalonic acid to succinic acid.

Animals↗
PubMed2000

Ammonium, bicarbonate and calcium effects on tomato plants grown under saline conditions.

Tomato plants (70 days old) were grown in hydroponic culture into a greenhouse, where supply of inorganic carbon, ammonium and calcium to saline nutrient solution, was investigated in order to reduce the negative effect of salinity. After 70 days, an ameliorating effect upon the decrease in growth observed under salinity was only observed with the treatments NaCl+Ca(2+) and NaCl+HCO(3)(-)+NH(4)(+)+Ca(2+). A large reduction of hydraulic conductance (L(0)) and stomatal conductance (G(s)) was observed with all treatments, compared with the control. However, the reductions were less when NaCl and Ca(2+) were added together. Organic acids (mainly malic acid) in the xylem were decreased with all treatments except with NaCl+NH(4)(+) and with all single treatments added together (NaCl+HCO(3)(-)+NH(4)(+)+Ca(2+)). Amino acid concentrations in the xylem (mainly asparagine and glutamine) decreased when plants were treated with NaCl and NaCl+Ca(2+), but there was a large increase in the plants treated with NaCl+NH(4)(+) or with all treatments together. As HCO(3)(-) is an important source of carbon for NH(4)(+) assimilation, the increase in the concentration of amino acids and organic acids caused by the treatments that contained NH(4)(+), support the idea that fixation of dissolved inorganic carbon was occurring and that the products were transported via the xylem to the shoot. The ameliorating effect of Ca(2+) on root hydraulic conductivity plus the increase of NH(4)(+) incorporation into the amino acid synthesis pathway possibly due to dissolved inorganic carbon fixation, could reduce the negative effect of salinity on tomato plants.

Journal Article↗
PubMed2002

Elimination of aluminum adjuvants.

In vitro dissolution experiments although perhaps not at typical body concentrations and temperatures demonstrated that the alpha-hydroxycarboxylic acids present in interstitial fluid (citric acid, lactic acid, and malic acid) are capable of dissolving aluminum-containing adjuvants. Amorphous aluminum phosphate adjuvant dissolved more rapidly than crystalline aluminum hydroxide adjuvant. Intramuscular administration in New Zealand White rabbits of aluminum phosphate and aluminum hydroxide adjuvants, which were labelled with 26Al, revealed that 26Al was present in the first blood sample (1 h) for both adjuvants. The area under the blood level curve for 28 days indicated that three times more aluminum was absorbed from aluminum phosphate adjuvant than aluminum hydroxide adjuvant. In vivo studies using 26Al-labelled adjuvants are relatively safe because accelerator mass spectrometry (AMS) can quantify quantities of 26Al as small as 10(-17) g. A similar study in humans would require a whole-body exposure of 0.7 microSv per year compared to the natural background exposure of 3000 microSv per year. The in vitro dissolution and in vivo absorption studies indicate that aluminum-containing adjuvants which are administered intramuscularly are dissolved by alpha-hydroxycarboxylic acids in interstitial fluid, absorbed into the blood, distributed to tissues, and eliminated in the urine.

Adjuvants, Immunologic↗
PubMed1983

Ischemic change of organic acids in kidney.

Organic acids in rabbit renal tissue biopsy were analyzed by capillary column gas chromatography--mas s spectrometry. The change of these organic acids under ischemic conditions was determined over 60 min after clamping the renal artery and vein. The results showed that lactic acid, glycolic acid, 2-hydroxybutyric acid, 3-hydroxypropionic acid, 2-methyl-glyceric acid, glyceric acid and malic acid increased at 4 and 6 min after clamping, but then decreased at 15 min. Glycerol increased 2 min after clamping and then decreased. However, 3-deoxyaldonic acids of 3-deoxytetronic acid, 3-deoxy-2-C-hydroxymethyltetronic acid and 3-deoxypentonic acid decreased in the renal tissue biopsy from 2 min after clamping.

Animals↗
PubMed2005

Separation of membranes from acid-solubilized fish muscle proteins with the aid of calcium ions and organic acids.

Calcium chloride, and to a lesser extent MgCl2, aided in the separation of membranes by centrifugation from cod (Gadus morhua) muscle homogenates solubilized at pH 3 in the presence of citric acid or malic acid but not lactic acid. Adding citric acid and Ca2+ before solubilizing the cod muscle homogenates was needed for the effect. At 1 mM citric acid, 70-80% of the phospholipid and 25-30% of the protein were removed at 10 mM Ca2+. At 8 mM Ca2+, citric acid showed an optimal effect on phospholipid removal at 5 mM with 90% of the phospholipid and 35% of the protein removed. The treatment with citric acid and Ca2+ was also effective in separating the membrane from solubilized herring (Clupea harengus) muscle homogenate. Ca2+ and citric acid might exert their influence by disconnecting linkages between membranes and cytoskeletal proteins.

Animals↗
PubMed2003

Photosynthetic flexibility in Pedilanthus tithymaloides poit, a CAM plant.

The induction of CAM in Pedilanthus tithymaloides (Euphorbiaceae) under water-limited conditions was evaluated by following diurnal oscillations of CO2 fixation, titratable acidity and malic acid content in the leaf extracts. CAM induction was assessed by measuring the activities of phosphoenolpyruvate carboxylase (PEPC), NADH-malate dehydrogenase (MDH) and phosphoenolpyruvate caroxykinase (PEPCK) in the leaves as well. Drought resulted in large increases in the nocturnal acid accumulation and rates of CO2 uptake in the leaves of P. tithymaloides. The drought-induced CAM activity tended to be reversible after re-watering. Nevertheless, under well-watered conditions, plants of P. tithymaloides showed day time CO2 uptake patterns with less pronounced diurnal oscillations of organic acids. Our data indicate that although P. tithymaloides is a CAM plant, environmental variables like drought induce photosynthetic flexibility in this species. This type of plasticity in CAM and metabolic versatility in P. tithymaloides should be an adaptation for prolonged survival under natural adverse edaphic and microclimate situations.

Carbon Dioxide↗
PubMed1990

Effect of calcium citrate-malate on skeletal development in young, growing rats.

It has been previously demonstrated that calcium from calcium citrate-malate (CCM), a mixture of calcium, citric acid and malic acid, is better-absorbed than calcium from calcium carbonate (CaCO3) in humans and in rats. It was of interest to determine if this differential in absorption would result in differences in bone development under chronic feeding conditions. The present study was designed to compare CCM with CaCO3 for effects on bone development in weanling female C/D rats fed either CCM or CaCO3 at 0.3 or 0.6% dietary Ca for 4 or 12 wk. There was a nonsignificant trend for rats fed CCM to weigh more and have larger bones than rats fed CaCO3. Histologic evaluation of cortical and trabecular bone revealed normal bone formation in all rats. Trabecular bone was significantly affected by calcium level and source. The 0.3% Ca diets (either source) resulted in reduced trabecular bone volumes in tibias. After 4 wk, rats fed CCM had 23-25% more trabecular bone than rats fed CaCO3. By 12 wk, the difference was even greater; rats fed CCM had 44-47% more trabecular bone than rats fed CaCO3. Dietary calcium source did not affect cortical bone. It is concluded that because of its positive effects on bone, CCM is a more bioavailable calcium source than CaCO3.

Animals↗
PubMed1981

Metal Complexation in Xylem Fluid : II. THEORETICAL EQUILIBRIUM MODEL AND COMPUTATIONAL COMPUTER PROGRAM.

Theoretical considerations of metal complex formation in aqueous solutions were used to develop a computer program (CHELATE) to calculate all equilibrium species (free metal ions, metal complexes, etc.) in any user-defined system, such as xylem fluid. Mass-balance equations were established to describe each free metal ion and each free ligand concentration as a function of solution pH, total metal or total ligand, hydrogen-association constants, and the stability constants of known metal complexes. A default data base can be altered by the user to define any desired system covered by the stored equilibrium data. The program can currently handle nine metal ions, 35 ligands, and 500 complex species. The validity of the program was confirmed by using experimental test systems in which free-metal ion activity measurements were made with ion-selective electrodes.Program CHELATE was used to calculate the distribution of six metals in 0- to 1-hour exudate from soybean (Glycine max L. Merr.) and tomato (Lycopersicon esculentum Mill.) plants grown in normal and Zn-phytotoxic nutrient solutions. The results indicated that Fe is bound by citric acid, and Cu is bound by several amino acids in the normal-Zn exudate. Most of the Cu in soybean exudate is bound to asparagine and histidine. In tomato, Cu is bound to histidine, glutamine, and asparagine. Zinc, Mn, Ca, and Mg are bound primarily by citric acid and malic acid in both species; the per cent bound for these metals is lower than that for Fe and Cu. Zinc phytotoxicity caused equilibrium concentration shifts and resulted in the formation of several additional metal complexes not found in the normal-Zn exudate.

Journal Article↗
PubMed1992

Expression of maize phosphoenolpyruvate carboxylase in transgenic tobacco : effects on biochemistry and physiology.

The expression of maize (Zea mays) phophoenolpyruvate carboxylase (PPC) gene constructions was studied in transgenic tobacco plants (Nicotiana tabacum). Where transcription was under the control of a maize PPC gene promoter, a low level of aberrantly large PPC transcript was detected. Analysis of this PPC transcript indicated that transcription initiation occurs upstream of the normal site. Despite the aberrant transcription initiation, expression of the PPC transcript was still light-regulated. Higher levels of maize PPC transcript of the correct size were obtained with a chimeric gene construction containing a tobacco (Nicotiana plumbaginifolia) chlorophyll a/b binding protein gene promoter. The PPC activities in the leaves of these transgenic plants were up to twofold higher than those of nontransformed plants. Two forms of PPC with different kinetic properties were identified in leaf extracts of the transgenic plants: one form with a high apparent K(m) for phosphoenolpyruvate (maize isozyme), and a second form exhibiting a low apparent K(m) (tobacco isozyme). Biochemical analyses of these plants indicated that the transgenic plants had significantly elevated levels of titratable acidity and malic acid. These biochemical differences did not produce any significant physiological changes with respect to photosynthetic rate or CO(2) compensation point.

Journal Article↗