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Query: UMLS:C0847097 (acidity)
 15,165 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Phosphoenolpyruvate when heated in acidic solution exchanges its phosphoryl and carboxyl oxygens rapidly and its enolic oxygen much more slowly with oxygens from water. The incorporation of 18O into phosphoenolpyruvate was measured by gas chromatography-mass spectrometry and phosphorus-31 nuclear magnetic resonance after heating in H218O at 98 degrees C. The rates of exchange of all six oxygens of phosphoenolpyruvate with water increase with increasing acidity, and the phosphoryl oxygens exchange more rapidly than the carboxyl oxygens. The rate of exchange of each oxygen of the phosphoryl group is 16-fold greater than the hydrolysis rate at 1 N HCl. This provides a simple and useful method for the synthesis of [18O]phosphoenolpyruvate highly enriched in its phosphoryl-group oxygens. An enrichment of 89% was obtained with a 50% yield. The [18O]-phosphoenolpyruvate showed a binomial distribution of 18O in the phosphoryl-group oxygens. The exchange may be explained by the reversible formation of a transient cyclic phosphate and, for exchange of the enolic oxygen, a transient acyl phosphate. Preparation of [18O]phosphoenolypyruvate from [18O]Pi by a chemical synthesis from beta-chlorolactate was not satisfactory because of drastic loss of 18O during the procedures used. Some loss of 18O also occurred during an enzymic synthesis with KCNO, [18O]Pi, carbamate kinase, and pyruvate kinase.
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PMID:Facile oxygen exchanges of phosphoenolpyruvate and preparation of [18O]phosphoenolpyruvate. 683 16

The renal effects of dopamine have been studied in preterm infants with RDS. Dopamine has been given in doses of 0.5-2.0 microgram/kg/min as a continuous intravenous infusion in cases of peripheral circulatory disturbances. As a result, the circulation became stable and some renal parameters improved. There was a + 106% increase of urine output as well as a + 73%, + 140%, + 21% increase in Na-excretion, FeNa, creatinine clearance respectively. In accordance with the marked increase in phosphorus excretion the titratable acidity was also increased. There was a significant decrease in the renal urea excretion and free water clearance. These alterations were probably caused by an intrarenal hemodynamic redistribution. The possible mechanism of the renal changes are also discussed. The observations demonstrate the functional maturity of renal dopaminergic receptors in the preterm infants.
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PMID:Effects of dopamine on renal functions in premature neonates with respiratory distress syndrome. 685 36

A study of the effect of feeding a high protein diet on bone metabolism was conducted using adult rats deep-labeled with 45Ca. A control diet (15% soy protein plus 0.2% methionine) and a high protein diet (control plus 20% lactalbumin) were fed for 10 months. Rats fed the high protein diet exhibited increases in urinary Ca, 45Ca, sulfate and volume. Total 45Ca excretion, urine calcium specific activity and urine phosphorus initially were depressed indicating an increase in the intestinal absorption of calcium, then were not significantly different from control values. After 10 months, analysis of the femur, tibia and mandible revealed no differences in wet weight, dry fat-free or ash weight, calcium, phosphorus, magnesium, or residual 45Ca content. Specific gravity and ash density also were unaffected by protein intake, as were femur length and midshaft cortical thickness. No changes in bone composition were found which would indicate that high protein diets promote bone loss in this species. The adult rat appears to be capable of compensating for the increased urinary loss of Ca associated with an increment in acid load (whether derived from an increase in diet acidity or in metabolic acid production) by reducing the fractional loss of endogenous Ca in the feces.
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PMID:Effect of chronic high protein feeding on bone composition in the adult rat. 745 69

Forty-five patients with recurrent renal stone were examined for distal renal tubular acidosis (dRTA) defects by acid challenge test (150 mg ammonium chloride/kg body weight). Their 24-h urine samples were analysed for creatinine, calcium, oxalic acid, inorganic phosphorus, uric acid, magnesium and citric acid. One-hour urine samples before acid load and hourly samples for the 7 h following acid challenge test were collected and analysed for creatinine, calcium, citric acid, inorganic phosphorus, titratable acidity, and ammonium. The incidence of distal RTA defect was 22.2% in the patients examined. The major biochemical characteristics in RTA patients compared with patients without RTA were: (a) significantly higher urinary pH, (b) significantly lower excretion of citric acid, (c) no significant difference in calcium excretion and (d) a tendency toward lower titratable acidity and ammonium excretion.
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PMID:A study of recurrent stone formers with special reference to renal tubular acidosis. 748 48

A total of 228 crossbred weanling pigs (average age of 25 d and BW of 6.44 kg) were used in two trials to evaluate the responses to sex, diet acidity, protein level, and source of calcium on the performance, gastrointestinal digesta measurements, bone measurements, and carcass composition. Diet acidity was manipulated by varying the sources of supplemental phosphorus in the diets. Trial 1 (5 wk) was conducted as a 2 x 3 x 2 factorial to evaluate sex (gilts and barrows), diet acidity (pH 5.9 and .90% P, pH 6.1 and .63% P, and pH 6.9 and .63% P), and level of protein (16 and 22% CP). In Trial 2 (6 wk), diet acidity (pH 5.5, 5.9, and 6.8, all with .7% P) and Ca sources (CaCO3 and CaSO4) were used with gilts and barrows. The sex x diet acidity interactions were significant for ADG in both trials. Barrows seemed to respond to both the more acidic diets and the buffered phosphate diets even though the pH was less acidic than that of the unbuffered diets. Gilts responded only to the more acidic diets. In Trial 1, gilts ate more and grew faster (P < .05) than barrows, but no sex effects on performance were observed in Trial 2. Pigs fed 22% CP diets grew faster (P < .001) and more efficiently (P < .001) than did pigs fed 16% CP diets, but protein level x diet acidity and protein level x sex interactions were not significant. Stomach digesta DM, pH, and titration value were not consistently influenced by sex and diet acidity in Trials 1 and 2, by protein level in Trial 1, and by calcium source in Trial 2. Only the sex x diet acidity interaction for stomach DM tended to be significant in both trials; gilts fed the less acidic diets had the lowest DM, whereas barrows fed the more acidic diets had the lowest DM values. Although not significant in every case in both trials, bone (average of metacarpal and metatarsal) volume was lower and specific gravity and shear stress values were higher for gilts than for barrows. Pigs fed 16% CP diets had higher specific gravity (P < .05) and stress (P < .06) values than pigs fed 22% CP diets. A protein level x diet acidity interaction (P < .03) for stress suggested that pigs fed 22% CP diets were unaffected by diet acidity, whereas pigs fed 16% CP had the highest stress values when fed the more acidic diet and the lower P level.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effects of diet acidity and protein level or source of calcium on the performance, gastrointestinal content measurements, bone measurements, and carcass composition of gilt and barrow weanling pigs. 788 26

An analytical method to measure malondialdehyde (MDA) was developed. MDA was derivatized with N-methylhydrazine (NMH) to 1-methylpyrazole (1-MP). 1-MP was extracted and analyzed by capillary gas chromatography with nitrogen-phosphorus detection. Analyte concentration, pH, and matrix effects of 1-MP-spiked samples were investigated to determine optimal recovery conditions. Efficiencies for solid-phase extraction ranged from 95.6 +/- 0.9 to 81.6 +/- 3.5% compared to 75.0 +/- 6.4 to 67.5 +/- 9.6% for liquid-liquid extraction for 20 to 1 nmol/ml 1-MP-spiked samples, respectively. Solid-phase extraction of 1-MP was more effective than liquid-liquid extraction over a range of pH 2-8.5 and in various aqueous matrices. Addition of methanol to the matrix decreased the solid-phase extraction efficiency. Reaction yield at pH 2-8.5 showed full conversion of MDA to 1-MP following reaction with NMH. Recovery of bound MDA was investigated by incubating bovine serum albumin (BSA) spiked with MDA at 37 degrees C for 18 h and separating the free MDA and MDA-bound protein. The recovery of bound MDA from BSA increased by increasing the acidity and temperature. Specific applications of this method for biological samples are given for the analysis of endogenous MDA in the plasma and red blood cells of mice and the formation of MDA in ultraviolet-irradiated cells in culture.
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PMID:Analysis of malondialdehyde in biological samples by capillary gas chromatography. 797 60

The rates of change in intracellular pH during repeated exercise sessions with rest periods was determined by 31 phosphorus-nuclear magnetic resonance spectroscopy (31P-MRS). Five long-distance runners and six healthy male subjects as controls performed a 2-min femoral flexion at 20 kg.m.min-1 in a 2.1 T superconducting magnet with a 67-cm bore and repeated this exercise four times with 2-min rest periods intervening. In all cases during exercise the inorganic phosphate (Pi) peak split into two, the earlier increased rapidly (high-pH Pi) and the later (low-pH Pi) increased more slowly. The Pi peaks were separated by a fitting procedure using the least square mean method. The high-pH Pi area during exercise decreased as the number of repeated exercise periods increased, while the low-pH Pi area gradually increased. Although the total Pi area decreased exponentially during the recovery period, the high-pH Pi area decreased first and then the low-pH Pi area reduced gradually. The pH values were estimated from the chemical shift between the phosphocreatine peak and each split peak in the Pi. The high-pH in pooled data ranged from 6.6 to 7.0 during exercise and recovery, while the low pH decreased to 6.2 during exercise. As the number of exercise periods increased, each pH value gradually became less acidic, although there was a tendency to more acidity in the control subjects than in the long-distance runners.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Changes in intracellular pH during repeated exercise. 822 43

Thirteen different formulations of throat lozenges were examined for their acidity, demineralizing action on hydroxylapatite, and fermentability by human dental plaque micro-organisms. Their flavouring acids gave them low pH values in the range 2.6-3.7, leading to the dissolution of calcium and phosphorus from hydroxylapatite. The combination of antiseptics and flavouring acids in the lozenges inhibited microbial growth and metabolism. In the absence of any antiseptics and flavouring acids, the growth and metabolic activity of cultures of plaque micro-organisms were significantly greater on sucrose+glucose lozenges than on a new Lycasin formulation.
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PMID:Dental properties of antiseptic throat lozenges formulated with sugars or Lycasin. 855 89

We carried out a balance study to examine the effects of isomaltulose, lactose, isomalt, and isomaltulose-based oligomers (IBOs) on mineral (calcium, magnesium, phosphorus, and iron) absorption and retention. Four-week-old male Wistar rats were divided into five groups of six rats each and fed a basal diet or diet the containing either 5% isomaltulose, 5% lactose, 5% isomalts or isomaltulose-based oligomers (IBOs) ad libitum for 16 d. After 1 wk, the animals were subjected to a 5-d mineral (calcium, magnesium, phosphorus, and iron) balance study. The isomalt feeding, as well as the IBOs feeding, led to significantly elevated mineral absorption and retention. On the other hand, lactose feeding, widely known to enhance calcium absorption, increased only calcium absorption and isomaltulose feeding did not affect mineral absorption or retention. The organic acids in cecum contents were increased by IBOs or isomalt feeding. Succinic and acetic acids in cecum contents were significantly increased by IBOs feeding. Similarly, succinic, acetic, and i-valeric acids and total amount of organic acid in cecum content were significantly increased by isomalt feeding. Although the organic acids in cecum contents were increased by IBOs or isomalt feeding, the pH values and acidity in cecum contents were not changed by IBOs or isomalt feeding. The effect of addition of various organic acids to the mucosal fluid was examined with in vitro study using a hindgut segment. By the addition of acetic acid, and butyric acid, the mineral (calcium, magnesium, and phosphorus) uptake was increased.
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PMID:The effects of isomaltulose, isomalt, and isomaltulose-based oligomers on mineral absorption and retention. 890 97

Magnesium orthophosphates have lately been examined as catalysts for various organic processes. In this work, we studied many compounds of this type synthesized under widely variable conditions, particularly as regards the magnesium and phosphorus sources, precipitant, and gel treatment used. The structure, composition and surface properties of each solid were found to depend on the synthetic procedure used. Thus, freshly made gels consisted largely of MgHPO(4). 3H(2)O, Mg(3)(PO(4))(2). 8H(2)O, or Mg(3)(PO(4))(2). 22H(2)O. The latter two can be interconverted by using various treatments. Calcination of the most extensively hydrated gel produces catalysts of increased specific surface area, acidity, and basicity. Thermal treatment yields phases such as Mg(2)P(2)O(7), Mg(3)(PO(4))(2), and NaMg(4)(PO(4))(3). The activity and selectivity exhibited by these solids in the conversion of gaseous 2-hexanol vary enormously with the particular synthetic procedure. In addition to surface properties, the structure and composition of the catalysts-particularly their sodium content-appear to play essential roles in their catalytic behavior, which is seemingly determined by their previously suggested dehydrogenating ability (with formation of sodium-magnesium mixed phosphates). Copyright 1999 Academic Press.
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PMID:Synthesis and Characterization of Magnesium Phosphates and Their Catalytic Properties in the Conversion of 2-Hexanol. 1046 37


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