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Biomedical subjects

W A Pryor

Publications and source records attributed to W A Pryor.

At least 163 records · Page 9Linked to original sources
PubMed1976

Autoxidation of polyunsaturated fatty acids: II. A suggested mechanism for the formation of TBA-reactive materials from prostaglandin-like endoperoxides.

The nature and mechanism of formation of the thiobarbituric acid (TBA)-reaction material produced in the autoxidation of polyunsaturated fatty acids (PUFA) or their esters has been studied. On the basis of chemical studies and spectroscopic evidence, it is concluded that the TBA test detects malonaldehyde which arises at least in part from the acid-catalyzed or thermal decomposition or endoperoxides (2,3-dioxanorbornane compounds). These endoperosides have structures related to those of the endoperoxides produced in the biosynthetic sequence leading to prostaglandins. A mechanism is proposed in which these endoperoxides are formed in a free radical cyclization process operating in competition with hydroperoxide formation during the autoxidation of PUFA or their esters containing three or more double bonds. When 20:3 or 20:4 PUFA undergo autoxidation, some of the natural, physiologically active prostaglandins would be produced, although in very low yield, along with many other stereo- and positional isomers. Thus, it is possible that some of the complex symptoms of lipid peroxidation in vivo could be due to nonenzymatically produced prostaglandins or their steroisomers.

Chemical Phenomena↗
PubMed1976

Electron spin resonance (ESR) study of cigarette smoke by use of spin trapping techniques.

The technique of spin trapping has been applied to the gas phase of cigarette smoke to identify and quantify the radicals present. It was found that radicals could be trapped only if the smoke was filtered. Three spin traps were used: N-tert-butyl-alpha-phenyl nitrone (PBN). 5,5-dimethyl-delta1-pyrroline-1-oxide (DMPO) and alpha-[3,5-di-tert-butyl-4-hydroxyphenyl)-N-tert-butyl nitrone (OHPBN). From the electron spin resonance (ESR) splitting constants of the radicals produced by the reaction of smoke radicals with the spin traps and also from the effec of varying the path length between the cigarette and the spin trap solution, it is concluded that three types of signals are observed. Type I signals indicate the presence of oxygenated radicals which appear to be a mixture of alkoxy radicals (RO) and aroyloxy (ArCO2-) radicals. Our data do not allow conclusions about the nature of the R or Ar groups in these two oxy radicals; however, considerations based on lifetimes suggest that the R group probably is tertiary. Type II and III signals are not typical spectra of spin adducts. Instead, we believe they result from reaction of smoke (and probably radicals in smoke) with the PBN spin trap and indicate that smoke has the ability to effect one-electron oxidations. Only type I signals are observed with DMPO and OHPBN. A quantitative study shows that 4 x 10(14) spins/puff are present in the smoke, in contrast with the result of a recent study which used a very different method for determining the radical content of smoke. A discussion of the nature of the radicals in smoke and some tentative conclusions are presented.

Computers↗
PubMedDate not supplied

The smoke produced from the oxidative pyrolysis of perfluoro polymers: an ESR spin-trapping study.

Spin adducts are observed when the unfiltered smoke produced during the aerobic pyrolysis of perfluoro polymers (PFP) is bubbled through a solution of the ESR spin trap alpha-phenyl-N-tert-butylnitrone (PBN). The spin adducts include those from an oxy radical and the fluorine atom, and in addition the spin trap is oxidized to PBNOx. The spin adduct of a chlorine atom also is observed, presumably because of chlorine-containing impurities in the polymers. Tetrafluoroethylene is produced during the pyrolysis of PFP; therefore, we subjected tetrafluoroethylene to the same pyrolysis as was used for PFP, and we observe the same series of spin adducts. We suggest that the spin adducts formed from the whole, unfiltered smoke from PFP smoke may result both from free radicals that form during the pyrolysis of PFP and from the oligomerization of the tetrafluoroethylene produced during the pyrolysis. These spin-trapping results support the theory that reactive free radicals are present in PFP smoke and may contribute to PFP smoke toxicity.

Cyclic N-Oxides↗
PubMedDate not supplied

An electron spin resonance study of the particles produced in the pyrolysis of perfluoro polymers.

Electron spin resonance (ESR) analysis at room temperature of the particles produced during the aerobic pyrolysis of perfluoro polymers (PFP) shows the presence of end-chain peroxyl radicals. These radicals, which would normally have lifetimes of several seconds at most, are stabilized by being immobilized in the particles and decay at a rate of about 20%/day. Normally, radicals with this stability would not be expected to be reactive; however, these peroxyl radicals react with 3-chloropropene, with iodine in benzene, with methyl linoleate in methanol, and with aqueous liposomes from soy phosphatidylcholine. Also, stable radicals of this sort would not be expected to give spin adducts; however, when the particles are suspended in a benzene solution containing alpha-phenyl-N-tert-butylnitrone (PBN), they react to give the same series of spin adducts that are detected when the unfiltered smoke from the oxidative pyrolysis of perfluoro polymers is bubbled directly into PBN solutions. This appears to be the first report of the reaction of radicals entrapped in a solid with a spin trap. The nitroxide species produced by the PBN-particle reaction include a fluorine atom spin adduct, an oxy radical adduct, and benzoyl tert-butyl nitroxide (PBNOx), the oxidation product of the spin trap; all of these appear to arise from reaction of the particle-bound peroxyl radicals with the spin trap. Because the particles are in the highly respirable range (down to 0.01 micron), these entrapped peroxyl radicals may be carried deep within the lung when fumes from PFP pyrolysis are inhaled and would be expected to place an oxidative burden on the lung.(ABSTRACT TRUNCATED AT 250 WORDS)

Electron Spin Resonance Spectroscopy↗
PubMedDate not supplied

1H NMR studies on mutagenic nitrofluoranthenes and exposure risk assessment.

The 1H NMR spectra of the nitrofluoranthene isomers are presented to allow gas chromatographic analysis of environmental samples suspected of containing nitrofluoranthenes. The mutagenic isomers 1-, 2-, 3-, 7-, and 8-nitrofluoranthene and 1,2- and 1,3-dinitrofluoranthene and a nonmutagenic analogue, 1-phenyl-4-nitronaphthalene, have been studied by using nuclear Overhauser effects and 2D shift-correlated 1H NMR spectroscopy. The X-ray crystal structure of 1-phenyl-4-nitronaphthalene is also reported. Reduction potentials and coplanarity of the nitro group have been used to correlate the mutagenicity of nitrated polycyclic aromatic hydrocarbons (nitro-PAH) measured by the Ames assay, but our data suggest that these parameters are not sufficient for the prediction of mutagenic potency in the nitrofluoranthene series.

Carcinogens↗
PubMedDate not supplied

Chemical, physical, and toxicological characterization of fumes produced by heating tetrafluoroethene homopolymer and its copolymers with hexafluoropropene and perfluoro(propyl vinyl ether).

Submicrometer solid-particle (fume) aerosols with up to about 10(8) particles/cm3 are formed when dilute vapors of low molecular weight (MW) (ca. 5000-10,000) perfluoro polymers condense in air. The aerosol (e.g., 0.2 mg/m3) formed from these vapors is highly toxic to laboratory rats by inhalation (30-min exposure) when fresh but loses toxicity in minutes, apparently owing to coagulation. These fumes may result from (a) pyrolysis of tetrafluoroethene homopolymer or tetrafluoroethene-hexafluoropropene copolymer or (b) evaporation, at 200-320 degrees C, of isolated low MW polymer or low MW polymer present in perfluoro polymer resins. Some perfluoro polymer fume aerosols contain reactive functional groups, but others without detectable reactive groups are at least as toxic.

Animals↗
PubMedDate not supplied

The ozonation of unsaturated fatty acids: aldehydes and hydrogen peroxide as products and possible mediators of ozone toxicity.

The products of the reactions of ozone with aqueous emulsions of unsaturated fatty acids and with liposomes made from phosphatidylcholine esters were characterized. Ozonolysis of emulsions of methyl oleate yields approximately 1 mol of hydrogen peroxide and 2 mol of aldehydes per mole of ozone used and fatty acid reacted. That is, the net equation that occurs is RCH = CHR' + O3 + H2O----RCHO + R'CHO + H2O2 . Ozonolysis of emulsions of oleic, linoleic, linolenic, and arachidonic acids gives 1 mol of hydrogen peroxide per mole of ozone used. Only very low yields (less than 5%) of reducible materials other than hydrogen peroxide are observed, suggesting that the yields of organic peroxidic materials, including Criegee ozonides and lipid hydroperoxides, are small. Ozonolysis of rat erythrocyte ghost membranes and rat bronchoalveolar lavage also gives significant yields (about 50%) of hydrogen peroxide based on the moles of ozone consumed. Reactions of ozone with bovine serum albumin, glutathione, and glucose do not produce hydrogen peroxide, implying that the hydrogen peroxide formed during the ozonation of biological materials arises almost exclusively from ozone/olefin reactions. Hydrogen peroxide and aldehydes are suggested to be important mediators of the modifications observed in both the lung and extrapulmonary tissues when ozone is inhaled.

Air Pollutants↗
PubMedDate not supplied

Release of iron from ferritin by aqueous extracts of cigarette smoke.

This study demonstrates the ability of aqueous extracts of cigarette smoke to reduce iron and cause its release from ferritin. Superoxide dismutase (SOD) increases the rates of iron release with the less filtered smoke extracts, but has no effect on the rate of iron release caused by aqueous extracts of well-filtered gas-phase cigarette smoke. Faster rates of iron release are observed under anaerobic conditions, and the reducing power of the cigarette smoke extracts is prolonged when incubated in argon. Hydroquinone and catechol, two of the major polyhydroxybenzenes in cigarette smoke, increase in concentration in the smoke extracts as these are subjected to less filtration, and higher concentrations of polyhydroxybenzenes correlate with higher rates of iron release from ferritin. Concomitant with iron release, depletions of amino acids in ferritin are observed. Depletion of histidine is partially prevented by bathophenanthrolinedisulfonate and mannitol, while lysine and arginine depletions remain unaffected. These observations suggest that cigarette smoke components react directly with these amino acid residues in ferritin. Cigarette smoke induced release of iron could alter iron metabolism in the lungs of chronic smokers and contribute to the increase in the total oxidative burden on the lungs of smokers.

Aerobiosis↗
PubMedDate not supplied

Inactivation of alpha 1-proteinase inhibitor by peroxynitrite.

We here report the reactions of peroxynitrite (O=NOO-) with alpha 1-proteinase inhibitor (alpha 1PI) and with a synthetic decapeptide (MER10) containing the sequence of amino acids found in the active site of alpha 1PI (Pro-Met-Ser-Ile-Pro-Pro-Glu-Val-Lys-Phe). Peroxynitrite inactivates alpha 1PI at both pH 7.4 and 12.0. Thiourea and methionine protect alpha 1PI against inactivation by peroxynitrite, while mannitol and benzoate fail to afford effective protection. The major product isolated from the reaction between peroxynitrite and MER10 was analyzed by NMR, mass spectrometry, and amino acid analysis. These analyses indicate that peroxynitrite primarily oxidizes the methionine residue in the peptide. We detect neither smaller molecular weight peptides, which would indicate cleavage of MER10, nor hydroxylation or nitration of the phenylalanine residue. Our results suggest that peroxynitrite is capable of oxidizing methionine residues in proteins without the involvement of the hydroxyl radical or nitrogen dioxide. The implications of these observations on lung diseases attributed to cigarette smoke are discussed.

Amino Acid Sequence↗