Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Oxygen Compounds”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 505 records · Page 28Linked to original sources
PubMed1989

Radiosensitisation and radioprotection by BSO and WR-2721: the role of oxygenation.

Endogenous and exogenous thiols are thought to influence cellular radiosensitivity directly by radical scavenging and/or hydrogen donation processes, and indirectly, by regulating the amount of oxygen (or other electron affinic radiosensitiser) able to reach the radiosensitive targets of the cell. The relative importance of these two mechanisms was evaluated in multicell spheroids treated with two agents currently undergoing clinical testing, the thiophosphate WR-2721 and the glutathione synthesis inhibitor BSO. Fluorescence-activated cell sorting techniques were used to recover cells selectively from different depths (different oxygenation status) within the spheroids. The radiosensitivity of cell populations recovered from different regions suggested that both agents acted primarily by affecting the oxygenation status of the spheroid. Similarly, the binding of a fluorescent marker for hypoxic cells, the nitrofuran AF-2, was markedly enhanced by WR-2721 addition, and decreased by BSO-induced thiol depletion. We conclude that the major radiobiological consequence of thiol manipulation in multicell systems is to increase or decrease the availability of oxygen.

Amifostine↗
PubMed2004

Evaluation of the anti-inflammatory activity of zhankuic acids isolated from the fruiting bodies of Antrodia camphorata.

We have previously shown that a concentrated ethanol extract of the fruiting bodies of Antrodia camphorata exhibited immunomodulating effects in human leukocytes and fourteen compounds including zhankuic acids A, B, C, and antcin K were identified in the extract. In this study, an acute cellular model in isolated peripheral human neutrophils was established to elucidate the anti-inflammatory effects of these compounds. Reactive oxygen species (ROS) production and firm adhesion by neutrophils display two important responses during inflammation. To evaluate whether these compounds could prevent inflammatory responses by neutrophils, their effects on N-formyl-methionyl-leucyl-phenylalanine (fMLP) or phorbol 12-myristate-13-acetate (PMA)-activated peripheral human neutrophils were examined. Pretreatment with 1 - 25 microM of zhankuic acids A, B, C, or antcin K concentration-dependently diminished fMLP- or PMA-induced ROS production, as measured by a lucigenin-amplified chemiluminescence, with IC (50) (microM) around 5 - 20 microM. Zhankuic acids A, B, C, or antcin K also effectively inhibited the fMLP- or PMA-induced firm adhesion without interfering with the up-expression of surface Mac-1 (CD11b/CD18), a beta2 integrin mediating the firm adhesion of neutrophils to endothelium. The anti-inflammatory actions of these drugs were not due to cytotoxic effects because no significant difference in cell viability was observed compared to vehicle control. These data suggest that inhibition of both ROS production and firm adhesion by neutrophils has no significant cytotoxic effect that could give these drugs the potential to be anti-inflammatory agents for the clinical treatment.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1990

Generation of radical anions of nifurtimox and related nitrofuran compounds by ascorbate.

Nifurtimox analogues bearing triazol-4-yl, benzimidazol-1-yl, triazin-4-yl or related groups as counterpart of the (5-nitro-2-furfurylidene) amino group were reduced to their nitro anion radicals by ascorbate in anaerobic solutions at high pH. The ESR spectra of the radical anions showed hyperfine spin couplings restricted to the nitrofuran moiety. With these compounds, the spin density at the nitro group was greater than with nifurtimox, nitrofurazone and nitrofurantoin. At neutral pH, solutions containing ascorbate and nitrofuran derivatives consumed oxygen, the compounds bearing unsaturated nitrogen heterocycles being the most effective. Superoxide dismutase and catalase decreased the rate of oxygen consumption, thus demonstrating the production of superoxide and hydrogen peroxide, respectively. NMR spectra of the triazol-4-yl and triazin-4-yl nitrofuran derivatives showed a deshielding effect for the azomethine proton, which was undetectable with nifurtimox and nitrofurazone.

Ascorbic Acid↗
PubMedDate not supplied

Radioprotection of mouse skin by WR-2721: the critical influence of oxygen tension.

The epidermal clone assay has been used to study the radioprotective effect of WR-2721 on mouse skin under different conditions of oxygenation and under anoxia. The skin has shown a progressive decrease in sensitivity as the inspired gas was changed from 100% oxygen towards 0% oxygen. Compared with mice breathing 100% oxygen, those breathing air are partially protected. The inspired oxygen concentration to given half the full oxygen effect is 10--12%. The radioprotection observed with 400 mg/kg WR-2721 is markedly dependent on the ambient oxygen concentration. The protection factor is 1.1 or less in mice breathing 5%, 1% of 0% oxygen. Protection is maximal (1.95) in air and in 50% oxygen and diminishes to 1.6 at higher oxygen tensions.

Amifostine↗
PubMed1999

Probing the "active site" of diamine oxidase: structure-activity relations for histamine potentiation by O-alkylhydroxylamines on colonic epithelium.

The responses of the canine colonic epithelium to histamine are potentiated by O-alkylhydroxylamines. A study of a series of such compounds suggested that active compounds had the structure R-O-NH2, substitution of a nitrogen led to total loss of activity. The locus of the potentiation effect was traced to the inhibition of diamine oxidase. A new series of aliphatic and aromatic O-alkylhydroxylamines were synthesized to explore further the structure-activity relations of this effect. The potentiating effects of these compounds were determined by examining the changes in short circuit current (Isc) produced by histamine and from the activity of a soluble preparation of diamine oxidase. We found that 1) branched compounds are less active than their straight chain counterparts, 2) greater steric bulk of the aliphatic substituent decreased activity, 3) the presence of a double bond had no significant effect though a triple bond reduced activity, 4) longer straight chain compounds were less active than the shorter chain derivatives and 5) all benzylic compounds were less active than the straight chain aliphatics. O-1-benzyl was inactive however the meta or para oxygen substituted compounds as well as the O-(1-E-Cinnamyl) derivative were active. A current model for the action of diamine oxidase proposes a crucial role for a trihydroxyphenylalanine quinone cofactor as part of the active site together with a copper atom. Using molecular modeling based on our inhibition data we are able to define the region of space that is just beyond the reactive carbonyl of the trihydroxyphenylalanine residue at the active site of diamine oxidase. We suggest that a negatively charged species, such as an aspartate or a glutamate, resides in a trough about 7 to 8 A from the trihydroxyphenylalanine carbonyl carbon and this species aids in the strong selective binding of substrates such as putrescine and histamine.

Amine Oxidase (Copper-Containing)↗
PubMed1983

Radioprotection by WR-2721 in vitro at low oxygen tensions: implications for its mechanisms of action.

Radioprotection of spheroids of Chinese hamster V79 cells by WR-2721 was found to be a function of spheroid size, with the greatest dose-modifying effect by the protector observed for spheroids almost large enough to contain radioresistant "anoxic" cells. The nature of the response suggested that most of the protective effect was due to the presence of an increased hypoxic fraction in the drug-treated spheroids. Similarly, when single-cell suspensions were irradiated at various oxygen tensions, one component of radioprotection by WR-2721 was found to be highly dependent upon the available oxygen. Two mechanisms of radioprotection of V79 cells by WR-2721 were thus demonstrated: a modest, oxygen-independent effect, presumably due to hydrogen donation, and an oxygen-depleting effect, which is of maximal significance for cells or tissues which would otherwise be partially sensitized by low levels of oxygen.

Amifostine↗
PubMed1983

Further study discounts role for singlet oxygen in fungal degradation of lignin model compounds.

This study reexamined our contention that singlet oxygen (1O2) plays a role in the fungal degradation of lignin (BBRC 102(1981)484). Cultures of Phanerochaete chrysosporium and a photochemical 1O2-generating system (riboflavin/light/O2) cleaved a lignin substructure model compound, 1,2-bis(4-methoxyphenyl)propane-1,3-diol (I), by indistinguishable mechanisms. However, the rate of cleavage of I in D2O was the same as in H2O in the photochemical 1O2-generating system, indicating that 1O2 was not involved. Furthermore, products formed from I in a chemical system for generating 1O2 (H2O2 + NaOCl) differed from those produced by cultures or the photochemical system. It is concluded that 1O2 is not responsible for cleavage of I or related compounds in the fungal cultures or in the photochemical system.

Chemical Phenomena↗
PubMed2002

Chemical polymorphism of the cuticular lipids of the cabbage white Pieris rapae.

The epicuticular composition of different body parts of the Cabbage White, Pieris rapae L., was investigated using GC and GC/MS. The major group of components, hydrocarbons, occurs in two distinct classes, which show different distributions on the cuticle of the insects. Unbranched shorter chain compounds (C21 to C31, linear group) dominate on body, head and wings, while longer chain, polymethyl-branched compounds (C35 to C39, branched group) are predominantly found on the antennae. Several other components like 1,3-pentacosadiene and oxygenated aliphatic compounds occur in minor amounts on the cuticle. The reason for this polymorphism is discussed.

Animals↗
PubMed1988

Stimulation of the activity of horseradish peroxidase by nitrogenous compounds.

A variety of nitrogenous compounds broaden the activity versus pH profile for the peroxidation of dianisidine catalyzed by horseradish peroxidase (HRP), but not by myeloperoxidase, chloroperoxidase, Escherichia coli hydroperoxidase I, methemoglobin, or microperoxidases. The peroxidation of dianisidine catalyzed by cytochrome c peroxidase was affected by the nitrogenous compounds, but to a lesser extent than was the action of HRP. The peroxidations of a variety of phenols by HRP exhibited broad activity versus pH profiles and were unaffected by the nitrogenous compounds. The energy of activation for the peroxidation of dianisidine by HRP was unaffected by changes of pH in the range 6.5-8.5 and was unchanged by the presence of the nitrogenous compounds. The nitrogenous compounds markedly increased Vm for the peroxidation of dianisidine by HRP, but did not change the slope of Lineweaver-Burk plots of kinetic data. These results are accommodated by a mechanism in which nitrogenous compounds hydrogen-bond to the distal histidine of HRP and in so doing raise its pK alpha. Since the acid form of the distal histidine is thought to facilitate peroxidations catalyzed by HRP by hydrogen bonding to the ferryl oxygen of compound II, raising its pK alpha broadens the activity versus pH profile for the peroxidation of anilino substrates, such as dianisidine. We propose that phenolic substrates hydrogen-bond directly to the ferryl oxygen, thus displacing the distal histidine and eliminating the possibility of being influenced by nitrogenous compounds.

Amines↗
PubMed1984

Effects of oxygen and sulphydryl-containing compounds on irradiated transforming DNA. II. Glutathione, cysteine and cysteamine.

This paper extends our earlier observations on the effects of the sulphydryl (SH)-containing compound dithiothreitol (DTT) on the radiation response of Bacillus subtilis transforming DNA to three other SH-containing compounds-cysteamine, cysteine and glutathione (GSH). In general, all four compounds protect transforming DNA in a manner which is dependent on gassing conditions. In O2, the protection is consistent with the scavenging of OH radicals by the SH compounds, but in N2 there is additional protection which may be due to hydrogen atom donation from the SH compound to radiation-induced DNA lesions, a process which is blocked by O2. This additional protection in N2 results in an increase in the ratio of inactivation in the absence and presence of oxygen with increasing SH concentration to a maximum followed by a decrease at high SH concentrations. The maximum value of the ratio and the SH concentration at which it occurs depend on the SH compound. In particular, GSH appears to be significantly less efficient in the hydrogen-donation repair reaction with transforming DNA than are the other three SH compounds. Furthermore, on the basis of our results, we postulate the existence of a damage fixation process which occurs in the absence of O2, in competition with damage repair by SH compounds, and that this anoxic damage fixation occurs at a rate not less than 300 s-1. We also demonstrate here that the damage fixing reaction of O2 with transforming DNA radicals proceeds 200-fold faster than the competing repair reaction by hydrogen-donation from DTT.

Bacillus subtilis↗
PubMed2006

Lone-pair activity in lead(II) complexes with unsymmetrical lariat ethers.

We have carried out a study about the structural effect of the lone-pair activity in lead(II) complexes with the unsymmetrical lariat ethers L(7), L(8), (L(8)-H)-, (L(9)-H)-, and (L(10)-H)-. All these ligands are octadentate and differ by the aromatic unit present in their backbones: pyridine, phenol, phenolate, thiophenolate, and pyrrolate, respectively. In these lead(II) complexes, the receptor may adopt two possible syn conformations, depending on the disposition of the pendant arms over the crown moiety fragment. The conformation where the pendant arm holding the imine group is placed above the macrocyclic chain containing two ether oxygen atoms has been denoted as I, whereas the term II refers to the conformation in which such pendant arm is placed above the macrocyclic chain containing the single oxygen atom. Compounds of formula [Pb(L(7))](ClO4)2 (1) and [Pb(L(8)-H)](ClO4) (2) were isolated and structurally characterized by X-ray diffraction analyses. The crystal structure of 1 adopts conformation I and shows the lead(II) ion bound to the eight available donor atoms of the bibracchial lariat ether in a holodirected geometry, whereas the geometry of 2 is best described as hemidirected, with the receptor adopting conformation II. The five systems [Pb(L(7))]2+, [Pb(L(8))]2+, [Pb(L(8)-H)]+, [Pb(L(9)-H)]+, and [Pb(L(10)-H)]+ were characterized by means of density functional theory calculations (DFT) performed by using the B3LYP model. An analysis of the natural bond orbitals (NBOs) indicates that the Pb(II) lone-pair orbital remains almost entirely s in character in the [Pb(L(7))]2+ complexes, whereas in [Pb(L(8)-H)]+, the Pb(II) lone pair is polarized by a certain 6p contribution. The reasons for the different roles of the Pb(II) lone pair in compounds 1 and 2 as well as in the related model compounds are discussed. Our results point to the presence of a charged donor atom in the ligand (such as a phenolate oxygen atom, pyrrolate nitrogen atom, or even thiophenolate sulfur atom) favoring hemidirected geometries.

Journal Article↗