Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0220723 (PCA)
 4,687 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

BL-5255, 2-(2-n-propoxyphenyl)-5-(5-1 H-tetrazolyl)pyrimidin-4 (3H)-one, effectively inhibited allergic reactions in sensitized rats or guinea pigs when administered by oral or intravenous routes as the water-soluble sodium or ethanolamine monohydrate salts. In the IgE-mediated rat PCA, BL-5255 was 50 times more potent than disodium cromoglycate by intravenous administration. When administered orally in this model, BL-5255 inhibited the PCA reaction by 50% at 0.1 mg/kg. At less than 0.1 mg/kg p.o., the compound protected conscious actively sensitized guinea pigs from aerosolized antigen-induced collapse. In N. brasiliensis-sensitized rats, BL-5255 administered at 0.1--10 mg/kg p.o. inhibited antigen-induced airway constriction in a dose-related manner. BL-5255 is not a histamine or serotonin antagonist but appears to exert its antiallergic effect by inhibiting the release of mediators.
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PMID:BL-5255, a tetrazolylpyrimidinone with potent oral antiallergy activity in animals. 9 59

Water-soluble spin labels were used to study dimyristoyllecithin (DML) phospholipid multilayers. Previous studies report that there is a "bound" water region associated with dimyristoyllecithin containing about 10 molecules of water per phospholipid, a "trapped" water region located between the lamellae containing approximately 11 molecules per phospholipid, and a "ftion show that certain water-soluble spin-label mol-cules have their motional properties differentially modified by these three water environements. Furthermore, the labels also reveal the onset of lipid-phase transitions even though they have high water solubility. A phosphate-containing spin label demonstrated strong an isotropic motion in the lipid-water system above the phase transition but not below. The addition of cholesterol to the DML-water system removed the anisotropic motion of 2,2,6,6-tetramehtyl-4-phosphopiperidine-N-oxyl (Tempophosphate) and obscured the detection bound, trapped, and free water. In addition to the change-charge interactions between Tempophosphate and DML, two other spin labels were used both in the charged and uncharged states. 2,2,6,6-Tetramethyl-4-aminopiperidine-N-oxyl (Tempamine) in the charged state showed extremely strong anisotropic motion, presumably due to the interaction between the charged amine and the phosphate group of DML. When only partially charged, Tempamine showed much less anisotropic motion. PCA was analyzed at pH values where the carboxyl group was protonated and unprotonated. The resulting interaction was different at the two pH values. These water-soluble spin labels mimic ionic or nonionic solutes. Upon freezing, the spin labels are shown to be expelled from the ice regions into the remaining aqueous regions. The usefulness of this approach in studying solute behavior when freezing occurs and potential studies involving aqueous regions of cytoplasm are considered.
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PMID:Spin-label studies on the aqueous regions of phospholipid multilayers. 18 8

Yeast sterol mutants were subjected to ESR analysis in an attempt to elucidate how altered sterol composition correlates with membrane permeability. The technique requires spin labeling the intact yeast cells with a small, water-soluble nitroxide probe (2,2,5,5 tetramethyl-3-pyrrolin-1-oxyl-3-carboxylic acid, PCA), suspending cells in a NiCl2 solution, and measuring the extent of Ni2+ entry through the membrane by its magnetic dipolar line broadening effect on the PCA signal. The wild type, A184D, was found to be impermeable to Ni2+ during all growth phases while the sterol mutant erg 6/2 was readily permeable to Ni2+. Other sources of line broadening such as increased rotational correlation time and cell nonviability are shown to be neglibible. Internal Ni2+ concentrations for erg 6/2 and kinetics of Ni2+ entry were determined.
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PMID:ESR determinations of membrane permeability in a yeast sterol mutant. 22 96

Electromyogram (EMG) activity of the posterior cricoarytenoid (PCA muscles were active, but was otherwise closed. Larynx closure may contribute to the end-inspiratory pauses often observed in the intact animal. During inhalation of an asphyxiant test gas in place of room air, PCA and diaphragm activity generally increased; and increases in anesthesia decreased the EMG activity of both muscles. Water on the larynx transiently abolished both PCA and diaphragm discharge; but EMG activity returned to the PCA muscles before the diaphragm. Further, reactivation of the diaphragm was not always accompanied by a synchronized burst of PCA activity. Therefore, it is possible under some conditions to dissociate the motor outputs from the PCA muscles and diaphragm in this immature mammal.
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PMID:Laryngeal effects and respiration in the suckling opossum. 74 Nov 2

When Rhodopseudomonas spheroides cells grown aerobically in the dark were incubated in medium containing tritiated water (THO), incorporation of T into the bacterial cell materials occurred under growth and no-growth conditions. The overall T incorporation under no-growth conditions was stimulated by vigorous aeration and was suppressed strongly in the presence of either 10(-3) M KCN or 0.3% HgCl2, indicating that the bulk of the incorporation might depend upon bacterial cell metabolism or respiration. 10 mug/ml chloramphenicol and 20 mug/ml rifamipicin slightly suppressed the T incorporation. The extent of T incorporation was proportional to the concentration of T in the medium. Accordingly, regardless of differences in the concentration of T in the medium, the maximum ratio of T content per hydrogen atom in the cell materials to that of THO in the medium was approximately 0.2 in non-growing cells and 0.5 in growing cells, whereas the value was 0.02-0.03 in cells incubated in medium containing KCN or HgCl2. The non-growing cells aerated in THO medium were lyophilized and fractionated by the modified method of Schneider. More than 40% of the total T incorporated into the cell materials was recovered in the cold PCA-soluble fraction, whereas the distribution of T into fractions solbule in ether-ethanol, hot PCA and alkali was 10 to 20% each. More than 75% of the T extracted in the cold PCA-soluble fraction was volatile. While the amounts of RNA and protein in the non-growing cells decreased on adding chloramphenicol or rifampicin, the distribution of T in these fractions did not change much. Our results on T incorporation into non-growing cells indicate that the major T incorporation into bacterial cell materials is independent of biosynthetic reactions using labeled precursors produced by the assimilation of T into metabolites, but presumably depends on energy-linked conformational changes of macromolecules.
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PMID:Incorporation of tritium into cell materials of Rhodopseudomonas spheroides from tritiated water in the medium under aerobic conditions. 108 4

Mechanism of the antiallergic action of 6-methyl-N-(1H-tetrazol-5-yl)-2-pyridinecarboxamide (TA-5707F) was studied using the water-soluble sodium salt (TA-5707). 1) TA-5707 administered p.o. at the dose ca. 3 times the ID50 for the PCA reaction did not inhibit capillary dye leakage induced on the rat skin by intracutaneous injection of histamine, serotonin, bradykinin and leukotriene D4 (LTD4). 2) TA-5707, at concentrations above 10(-7) M, inhibited antigen-induced histamine release and dye leakage in the rat peritoneal cavity (passive peritoneal anaphylaxis). 3) TA-5707 inhibited both anaphylactic and compound 48/80-induced histamine release from the rat peritoneal mast cells, the IC50 being ca. 10(-5) M in both cases. It was concluded that TA-5707F exerts its antiallergic action by inhibiting the release of chemical mediators from sensitized cells.
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PMID:Studies on a new antiallergic pyridinecarboxamide TA-5707F and its sodium salt (TA-5707). II. Mechanism of antiallergic action of TA-5707. 244 38

Breath samples which were collected into Alcomille Breath Bags (Etzlinger Electronics, Geneve, Switzerland) were assessed for their acetaldehyde and ethanol levels by gas chromatography. Simultaneously, their levels in the venous blood were determined with the PCA method. A good correlation fit for acetaldehyde and ethanol levels was obtained in both blood and breath samples, respectively. The blood/breath partition ratio for acetaldehyde was 109 +/- 10 and that for ethanol was 2,300 +/- 100. The water/air, saline/air, and plasma/air partition ratios of acetaldehyde in vitro were 119, 120, and 155, respectively. Conversely, the water/air, saline/air, plasma/air, and blood/air partition ratios of ethanol were 2,160, 2,040, 1,920 and 1,720, respectively. The acetaldehyde in the bag was well preserved. In analyzing breath acetaldehyde, it is very important that only the end expiratory air is collected. Determination of acetaldehyde level with Alcomille Breath Bag is very useful to investigate alcohol metabolism, when some problems exist in the collection of blood samples and in the treatment for the analysis of blood acetaldehyde.
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PMID:Partition ratio of acetaldehyde between blood and breath after ethanol consumption. 262 69

Two nitroxide spin labels (NSL) were compared for in vitro relaxivity and in normal rats for efficiency of urographic enhancement. One of the NSL, PCA, a pyrrolidinyl agent, was ionic and one, NAT, was a non-ionic pyrrolidinyl NSL with multiple hydroxyl substituents for water solubility. Using both NSLs the renal medulla and papilla were noted to show greater contrast enhancement than the cortex, with a maximum enhancing effect between 5 and 15 minutes. Using doses of 1.0 and 2.5 mmol/kg, more than 100 per cent increases in spin echo intensities above the baseline were observed. The lowest tested dose of 0.1 mmol/kg showed an easily detectable enhancing effect for NAT. The good contrast enhancing properties of NAT, considered together with its better acute tolerance, justifies further investigation of this non-ionic compound.
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PMID:Comparison of ionic and non-ionic nitroxide spin labels for urographic enhancement in magnetic resonance imaging. 296 Mar 54

Pseudomonas testosteroni protocatechuate 4,5-dioxygenase catalyzes extradiol-type oxygenolytic cleavage of the aromatic ring of its substrate. The essential active site Fe2+ binds nitric oxide (NO) to produce an EPR active complex with an electronic spin of S = 3/2. Hyperfine broadening of the EPR resonances of the nitrosyl complex of the enzyme by protocatechuate (3,4-(OH)2-benzoate, PCA) enriched specifically with 17O (I = 5/2) in either the 3 or the 4 hydroxyl group shows that both groups can bind directly to the Fe2+ in the ternary complex. Analogous results are obtained for PCA binding to catechol 2,3-dioxygenase-NO complex suggesting that substrate binding by the Fe2+ may be a general property of extradiol dioxygenases. The protocatechuate 4,5-dioxygenase inhibitor, 4-17OH-benzoate binds directly to the Fe of the nitrosyl adduct of the enzyme through the OH group. Since previous studies have shown that water also is bound to the Fe in this ternary complex, but not in the ternary complex with PCA, the data strongly imply that there are 3 sites in the Fe coordination which can be occupied by exogenous ligands. 3-17OH-benzoate is an inhibitor of the enzyme but does not elicit detectable hyperfine broadening in the EPR spectrum of the nitrosyl adduct suggesting that it binds to the enzyme, but not to the Fe. The EPR spectra of ternary enzyme-NO complexes with PCA or 4-OH-benzoate labeled with 17O exclusively in the carboxylate substituent are not broadened, suggesting that this moiety does not bind to the Fe.
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PMID:Binding of 17O-labeled substrate and inhibitors to protocatechuate 4,5-dioxygenase-nitrosyl complex. Evidence for direct substrate binding to the active site Fe2+ of extradiol dioxygenases. 300 98

The productivity of three different plate count media were compared on unchlorinated drinking water samples. The R2A medium gave constantly higher counts than both Kings agar B and PCA, when incubated at 21 degrees C for 3 to 14 days. Spread plates were superior to pour plates for both R2A and Kings agar B, but for the R2A medium this difference diminished with time of incubation. It is suggested that this could partly be assigned to its content of sodium pyruvate as a H2O2 scavenger. Experiments with different strengths of the R2A medium showed that not only its complexity but also the low concentration of nutrients supplied is of significant importance to the productivity of the original formulation of this medium.
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PMID:Colony counts in drinking water bacteriology--importance of media and methods. 312 73


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