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 667 records · Page 37Linked to original sources
PubMed2004

Coordination features of ditopic oxa-azamacrocycles toward Ni(II) and Co(II). Dioxygen uptake by their dinuclear Co(II) complexes.

The coordination properties of the ditopic oxa-aza macrocycles L1-L3 toward Ni(II) and Co(II) have been investigated by means of potentiometric and UV-vis spectrophotometric measurements. L1-L3 contain two triamine and/or tetraamine chains separated by two dioxa chains and form both mono- and dinuclear complexes in aqueous solution. In the [ML]2+ complexes, the metal ion is coordinated by one of the two polyamine moieties, while the other does not participate in the coordination. In the dinuclear complexes each metal ion is coordinated, almost independently, to a single polyamine moiety. Under aerobic conditions the binuclear Co(II) complexes of the ligands L1-L3 are able to bind molecular oxygen, with a bridging coordination of O2 between the two metals.

Aza Compounds↗
PubMed1991

O2-. release by activated Kupffer cells upon hypoxia-reoxygenation.

Primary cultures of rat liver Kupffer cells generated large amounts of superoxide anion radical (O2-.) when subjected to reoxygenation after a hypoxic period of at least 2 h. O2-. formation reached its maximum rate of approximately 25 nmol/10(6) cells within 1 h after reoxygenation. Two to four hours after reoxygenation, the number of injured cells began to increase and after 10 h approximately 60% of the cells were dead. During the period of O2-. release no significant difference in cell viability was observed between reoxygenated and hypoxically incubated cells, indicating a distinct time lag between O2-. release and onset of cell damage. Addition of diphenyliodonium, a specific inhibitor of the neutrophilic NADPH oxidase, to the Kupffer cells just before reoxygenation diminished both O2-. formation and cell injury up to 70%. Reoxygenation injury was completely prevented when superoxide dismutase and catalase were added immediately before reoxygenation. The results indicate that Kupffer cells subjected to hypoxia-reoxygenation generate a burst of reactive oxygen species and that this kind of "activation," probably by activating the NADPH oxidase, contributes to the self-destruction of the cells.

Animals↗
PubMed1996

[Effects of efonidipine hydrochloride, a calcium antagonist derived from dihydropyridine, on acute myocardial ischemia in anesthetized open-chest dogs].

Effects of efonidipine hydrochloride (NZ-105), a dihydropyridine calcium antagonist, on the cardiovascular system were studied in dogs, in which the left anterior descending coronary artery (LAD) was ligated for 50 min. NZ-105 (10 or 30 micrograms/kg), nifedipine (NIF, 1 or 3 micrograms/kg) or nisoldipine (NIS, 1 or 3 micrograms/kg) was injected i.v. before LAD ligation. NZ-105, NIS or NIF decreased the total peripheral resistance (TPR) and blood pressure (BP) and increased the cardiac output (CO) and regional myocardial blood flow (RBF) dose-dependently. LAD ligation decreased RBF and produced segmental bulging in the ischemic area, decreased BP and CO, and did not change TPR. NZ-105, NIF or NIS attenuated the LAD ligation-induced regional myocardial changes. During LAD ligation, in the presence of NZ-105 (30 micrograms/kg), the values of heart rate (HR), BP, and TPR were lower, and that of CO was higher than those in the absence of the drug. Similar results were obtained with NIS (3 micrograms/kg) except that the value of HR in the presence of NIS was not lower. During ischemia, the presence of NIF (3 micrograms/kg), did not significantly change the values of the systemic circulation from those observed in the absence of NIF. In conclusion, NZ-105 may exert a cardioprotective effect by decreasing the oxygen demand of the ischemic heart.

Animals↗
PubMed1976

A new oxygenase, 2-nitropropane dioxygenase of Hansenula mrakii. Enzymologic and spectrophotometric properties.

2-Nitropropane dioxygenase, purified to homogeneity from Hansenula mrakii (IFO 0895), has a molecular weight of approximately 62,000 and consists of two subunits nonidentical in molecular weight (39,000 and 25,000). Stoichiometrical studies and the results obtained with 18O2 showed that 2 atoms of molecular oxygen are incorporated into 2 molecules of acetone formed from 2-nitropropane. In addition to 2-nitropropane, nitroethane, 3-nitro-2-pentanol, and 1-nitropropane are oxidatively dentrified. The enzyme, which exhibits absorption maxima at 274, 370, 415, and 440 nm and a shoulder at 470 nm, contains 1 mol of FAD and 1 g atom of non-heme iron per mol of enzyme. The enzyme-bound FAD is reduced by 2-nitropropane under anaerogic conditions, but the enzyme-bound Fe3+ is not affected. The introduction of oxygen to the reduced form of enzyme causes reoxidation of the enzyme. The bound FAD and Fe3+ are reduced by the addition of nitromethane, which is not a substrate, under anaerobic conditions. The aerobic dialysis of the enzyme treated with nitromethane causes reoxidation of only the Fe2+. Sodium dithionite also reduces both the enzyme-bound FAD and Fe3+ under anaerobic conditions. When the enzyme is dialyzed against 10 mM potassium phosphate buffer (pH 7.0) immediately after reduction by dithionite, the absorption spectrum similar to that of the native enzyme appeared with concomitant restoration of approximately 80% of the activity. The enzyme activity is significantly inhibited by pyrocatechol-3,5-disulfonate disodium salt, 8-hydroxyquinoline, reducing agents such as 2-mercaptoethanol, and HgCl2. The Michaelis constants are as follows: 2-nitropropane (2.13 X 10(-2) M), nitroethane (2.43 X 10(-2) M), 3-nitro-2-pentanol (6.8 X 10(-3) M), 1-nitropropane (2.56 X 10(-2) M), and oxygen (3.03 X 10(-4) M, with 2-nitropropane).

Amino Acids↗
PubMed1994

Nematicidal activities of two phytoalexins from Taverniera abyssinica.

The traditional analgesic and antipyretic Ethiopian drug "Dingetegna" is made of dried root material of Taverniera abyssinica A. Rich (Leguminosae). In a screening for nematicidal natural products, "Dingetegna" extracts showed strong nematicidal activities towards C. elegans. In the following, medicarpin and 4-hydroxymedicarpin were isolated as nematicidal constituents from the extracts. In a microwell plate assay for nematicidal activity, both compounds exhibited an LD50 of 25 micrograms/ml towards C. elegans. Beside these nematicidal effects, weak cytotoxic and antimicrobial activities were observed. In addition, both compounds inhibited oxygen consumption of axenically grown C. elegans, L 1210 cells, and filamentous fungi. Respiration in sensitive bacteria was not affected. In L 1210 cells, the incorporation of precursors into macromolecules was affected in the presence of glucose, indicating that inhibition of respiration is not the only target site of the compounds.

Animals↗
PubMed2003

Solvent polarity and hydrogen-bonding effects on the nitrogen NMR shieldings of N-nitrosamines and DFT calculations of the shieldings of C-, N-, and O-nitroso systems.

High-precision nitrogen NMR shieldings, bulk susceptibility corrected, are reported for dimethyl-N-nitrosamine (I) and diethyl-N-nitrosamine (II) in a variety of solvents which represent a wide range of solvent properties from the point of view of polarity as well as hydrogen bond donor and acceptor strength. The observed range of solvent-induced nitrogen shielding variations of (I) and (II) is significant for the amino-type nitrogens, up to about 16 ppm, and originates essentially from the deshielding effect of the increasing polarity of solvent. On the other side, the nitroso nitrogen shieldings reveal an even stronger response to solvent effects, within about 20 ppm, but in this case the increasing polarity and hydrogen bond donor strength of solvent produce enhanced shielding. DFT quantum-mechanical calculations using the GIAO/B3PW91/6-311++G** approach and geometry optimizations employing the same basis set and hybrid density functionals show an excellent correlation with the experimental data on C-, N-, and O-nitroso moieties and reproduce not only major changes but also most of the subtle variations in the experimental nitrogen shieldings of the nitroso systems as a whole. A combination of the calculations involving the corresponding N and O-protonated species and the trends observed in the solvent-induced nitrogen shielding variations shows clearly that the prime acceptor site for hydrogen bonding is the nitroso oxygen atom.

Algorithms↗
PubMed1982

Radioprotection of mouse skin by WR-2721 in single and fractionated treatments.

The radioprotective action of WR-2721 on mouse skin has been studied using single doses, two and five fractions. Significant radioprotection was observed with 200-500 mg/kg, in animals breathing air or oxygen at the time of irradiation. The degree of radioprotection increased with increasing dose, and was significantly greater in air than in oxygen, especially at low drug doses. Cumulative drug toxicity limited the fractionated treatments to lower drug doses, but the protection observed was similar to that seen with single doses at the same drug levels. The protection factors observed are lower than many published values for skin, and we conclude that a single protection factor cannot yet be stated for any dose of WR-2721. Local tissue oxygenation may account for some of the discrepancies in different studies.

Amifostine↗
PubMed1990

Effect of cambendazole and haloxon on the carbohydrate metabolism of Ascaridia galli and Heterakis gallinae (Nematoda).

Cambendazole 10(-4) M significantly reduced the level of glycogen in both the parasites. Lactic acid level was found enhanced. Oxygen consumption was suppressed by 63 and 94% in A. galli and H. gallinae, respectively, by 10(-4) M cambendazole. Haloxon did not cause any significant change in glycogen and lactic acid level in either parasite, but reduced oxygen consumption by 23 and 31% in Ascaridia galli and Heterakis gallinae, respectively.

Animals↗
PubMed2005

Organic environments on Saturn's moon, Titan: simulating chemical reactions and analyzing products by FT-ICR and ion-trap mass spectrometry.

Laboratory simulations have been carried out to model chemical reactions that possibly take place in the stratosphere of Saturn's moon, Titan. The aerosol products of these reactions (tholin samples) have been systematically analyzed by mass spectrometry using electrospray ionization (ESI) and laser desorption (LD). A wide variety of ions with a general formula C(x)H(y)N(z) detected by ultrahigh resolution and accurate mass measurements in a Fourier transform/ion cyclotron resonance (FT-ICR) cell reflect the complexity of these polymeric products, both in chemical compositions and isomeric distributions. As a common feature, however, tandem mass spectral (MS/MS) data and H/D exchange products in the solution phase support the presence of amino and nitrile functionalities in these (highly unsaturated) "tholin" compounds. The present work demonstrates that ESI-MS coupled with FT-ICR is a suitable and "intact" method to analyze tholin components formed under anaerobic conditions; only species with C(x)H(y)N(z) are detected for freshly prepared and harvested samples. However, when intentionally exposed to water, oxygen-containing compounds are unambiguously detected.

Journal Article↗
PubMed1992

Photodynamic effects of chloroaluminum phthalocyanine tetrasulfonate are mediated by singlet oxygen: in vivo and in vitro studies utilizing hepatic microsomes as a model membrane source.

Chloroaluminum phthalocyanine tetrasulfonate (AlPcTS) is a promising photosensitizer for the photodynamic therapy (PDT) of cancer. In this study, we investigated the in vivo and in vitro photodestruction of hepatic microsomal membranes by AlPcTS and studied the role of reactive oxygen species in this process. Irradiation of hepatic microsomes prepared from AlPcTS-pretreated SENCAR mice to approximately 675 nm light resulted in rapid destruction of cytochrome P450 and associated monooxygenase activities, and enhancement of lipid peroxidation in a light-dose-dependent manner. The specificity of AlPcTS and light dependency on photodestruction of microsomal membranes was confirmed by Western blot analysis. Similar results were obtained when AlPcTS was added in vitro to a suspension of hepatic microsomes prepared from control animals followed by irradiation to approximately 675 nm light. Among the quenchers of singlet oxygen, superoxide anion, hydrogen peroxide, and hydroxyl radical, only the quenchers of singlet oxygen such as sodium azide, histidine, and 2,5-dimethyl furan afforded substantial protection in a dose-dependent manner against AlPcTS-mediated photodestruction of cytochrome P450 and associated monooxygenase activities, and photoenhancement of lipid peroxidation under both in vivo and in vitro conditions. These results suggest that lipid-rich microsomal membranes may be the potential targets of cell injury by AlPcTS-based PDT and that this process is mediated by singlet oxygen.

Animals↗
PubMed1992

Photosensitized formation of ascorbate radicals by chloroaluminum phthalocyanine tetrasulfonate: an electron spin resonance study.

The chloroaluminum phthalocyanine tetrasulfonate sensitized photooxidation of ascorbic acid to ascorbate radical (A.-) was followed by electron spin resonance (ESR) spectroscopy. In air saturated aqueous media, steady-state amounts of A.- are rapidly established upon irradiation. The ESR signal disappears within a few seconds after the light is extinguished--more slowly under constant irradiation as oxygen is depleted. No photooxidation was observed in deaerated media. The effect of added superoxide dismutase, catalase, desferrioxamine, and singlet oxygen scavengers (NaN3 and tryptophan) was studied, as was replacement of water by D2O and saturation with O2. The results are indicative of free radical production by direct reaction between ascorbate ion and sensitized phthalocyanine (a Type I mechanism) in competition with the (Type II) reaction of HA- with singlet oxygen, a reaction which does not produce ascorbate radical intermediates.

Ascorbic Acid↗
PubMed2001

Formation of nanomolar concentrations of S-nitroso-albumin in human plasma by nitric oxide.

S-Nitrosothiols are potentially important mediators of biological processes including vascular function, apoptosis, and thrombosis. Recent studies indicate that the concentrations of S-nitrosothiols in the plasma from healthy individuals are lower than previously reported and in the range of 30-120 nM. The mechanisms of formation and metabolism of these low nM concentrations, capable of exerting biological effects, remain unknown. An important issue that remains unresolved is the significance of the reactions of low fluxes of nitric oxide (NO) with oxygen to form S-nitrosothiols in a complex biological medium such as plasma, and the impact of red blood cells on the formation of S-nitrosothiols in blood. These issues were addressed by exposing plasma to varying fluxes of NO and measuring the net formation of S-nitrosothiols. In the presence of oxygen and physiological fluxes of NO, the predominant S-nitrosothiol formed is S-nitroso-albumin at concentrations in the high nM range (approximately 400-1000 nM). Although the formation of S-nitrosothiols by NO was attenuated in whole blood, presumably by erythrocytic hemoglobin, significant amounts of S-nitrosothiols within the physiological range of S-nitrosothiol concentrations (approximately 80 nM) were still formed at physiological fluxes of NO. Little is known about the stability of S-nitroso-albumin in plasma, and this is central to our understanding of the biological effectiveness of S-nitrosothiols. Low molecular weight thiols decreased the half-life of S-nitroso-albumin in plasma, and the stability of S-nitroso-albumin is enhanced by the alkylation of free thiols. Our data suggests that physiologically relevant concentrations of S-nitrosothiols can be formed in blood through the reaction of NO with oxygen and proteins, despite the low rates of reaction of oxygen with NO and the presence of erythrocytes.

Chromatography, Affinity↗
PubMed2002

Novel fluorescent oxygen indicator for intracellular oxygen measurements.

Intracellular oxygen concentration is of primary importance in determining numerous physiological and pathological processes in biological systems. In this paper, we describe the application of the oxygen sensing indicator, ruthenium dibipyridine 4-(1"-pyrenyl)-2,2'-bipyridine chloride [Ru(bpy-pyr)(bpy)(2)], for molecular oxygen measurement in J774 murine macrophages. Ru(bpy-pyr)(bpy)(2) exhibits strong visible absorption, efficient fluorescence, long excited state lifetime, large Stokes shift, and high photo- and chemical stability. The fluorescence of Ru(bpy-pyr)(bpy)2 is efficiently quenched by molecular oxygen. It is 13 fold higher in a nitrogenated solution than in an oxygenated one. The dye passively permeates into cells and maintains its oxygen sensitivity for at least 5 h when the cells are stored in a phosphate buffered saline solution at pH 7.4. The oxygen sensitivity, photostability, and chemical stability of the indicator and the effect of hypoxia and hyperoxia on the intracellular oxygen level in single macrophages are discussed.

Animals↗
PubMed1997

Pharmacokinetic analysis of octa-alpha-butyloxy-zinc phthalocyanine in mice bearing Lewis lung carcinoma.

OBJECTIVE: In this study, the pharmacokinetics of octa-alpha-butyloxy-zinc phthalocyanine (8-alpha-bo-ZnPc) was studied with regard to Lewis lung carcinoma in mice after intravenous administration of 7.8 mumole/kg body weight at different incubation intervals. SUMMARY BACKGROUND DATA: The newly synthesized potential photosensitizer 8-alpha-bo-ZnPc is characterized by a high absorption coefficient at the far red wavelength (735 nm) with a good singlet oxygen quantum yield. METHODS: After intravenous administration of 7.8 mumole/kg body weight in mice bearing Lewis lung carcinoma, the accumulated photosensitizer was chemically extracted (at incubation intervals of 2, 6, 12, 24, 48, and 168 hours) from selected tissues, and the concentrations were measured by absorption spectroscopy. RESULTS: The parenchymatous organs, liver, and spleen showed maximum 8-alpha-bo-ZnPc concentrations after 6 hours of incubation. An extensive uptake was detected in lung extracts taken at 6, 12, 24, and 48 hours. The malignant tissue did not accumulate high 8-alpha-bo-ZnPc during the entire investigation period. The photosensitizer extracted from muscle, representing normal tumor-surrounding tissue and skin, was even lower. CONCLUSIONS: Because of the extremely low accumulation rate of the tumor, 8-alpha-bo-ZnPc is suggested to be administered topically or in combination with a suitable carrier system in order to increase the photosensitizer concentration in the target tissue, as well as to decrease the loss of dye to other tissues.

Animals↗