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PubMed1986

Epoxidation of (+/-)-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene during (bi)sulfite autoxidation: activation of a procarcinogen by a cocarcinogen.

The (bi)sulfite ion undergoes extensive autoxidation in neutral aqueous media with the formation of sulfur trioxide radical anion that is detected by ESR. The radical anion subsequently reacts with molecular oxygen to form a peroxyl radical. We find that when (+/-)-trans-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene (BP-7,8-diol) is included in this autoxidation system, BP-7,8-diol is converted to diolepoxides, ultimate carcinogenic derivatives of benzo[a]pyrene. This epoxidation occurs with a stereoselectivity consistent with either a peroxyl radical or a peracid as the epoxidizing agent. The epoxidation is dependent on the concentration of both (bi)sulfite and oxygen. In the presence of 10 microM butylated hydroxyanisole, which abolishes (bi)sulfite autoxidation, no (bi)sulfite-dependent epoxidation occurs. These results are discussed in regard to the mechanism of (bi)sulfite autoxidation, and in relationship to the cocarcinogenicity of sulfur dioxide [anhydrous (bi)sulfite] for benzo[a]pyrene-induced pulmonary neoplasia.

Carcinogens↗
PubMed1991

Impact of chronic phosalone toxicity on erythropoietic activity of fish, Oreochromis mossambicus.

Effect of multiple sublethal concentrations of Phosalone on whole animal and kidney oxygen consumption, haematological indices and serum enzymes of freshwater fish, Oreochromis mossambicus, were carried out over a 90 day exposure period. Significant changes were observed which have been indicating that the presence of hypoxic condition in the biosystem, gradual increase in the rate of synthesis of haemoglobin and disruption of liver function during the toxicity of phosalone.

Animals↗
PubMed2006

Characterization of the structure and reactivity of monocopper-oxygen complexes supported by beta-diketiminate and anilido-imine ligands.

Copper-oxygen complexes supported by beta-diketiminate and anilido-imine ligands have recently been reported (Aboelella et al., J Am Chem Soc 2004, 126, 16896; Reynolds et al., Inorg Chem 2005, 44, 6989) as potential biomimetic models for dopamine beta-monooxygenase (DbetaM) and peptidylglycine alpha-hydroxylating monooxygenase (PHM). However, in contrast to the enzymatic systems, these complexes fail to exhibit C--H hydroxylation activity (Reynolds et al., Chem Commun 2005, 2014). Quantum chemical characterization of the 1:1 Cu-O(2) model adducts and related species (Cu(III)-hydroperoxide, Cu(III)-oxo, and Cu(III)-hydroxide) indicates that the 1:1 Cu-O(2) adducts are unreactive toward substrates because of the weakness of the O--H bond that would be formed upon hydrogen-atom abstraction. This in turn is ascribed to the 1:1 adducts having both low reduction potentials and basicities. Cu(III)-oxo species on the other hand, determined to be intermediate between Cu(III)-oxo and Cu(II)-oxyl in character, are shown to be far more reactive toward substrates. Based on these results, design strategies for new DbetaM and PHM biomimetic ligands are proposed: new ligands should be made less electron rich so as to favor end-on dioxygen coordination in the 1:1 Cu-O(2) adducts. Comparison of the relative reactivities of the various copper-oxygen complexes as hydroxylating agents provides support for a Cu(II)-superoxide species as the intermediate responsible for substrate hydroxylation in DbetaM and PHM, and suggests that a Cu(III)-oxo intermediate would be competent in this process as well.

Binding Sites↗
PubMed2004

Direct proline-catalyzed asymmetric alpha-aminoxylation of aldehydes and ketones.

The direct proline-catalyzed asymmetric alpha-aminoxylation of aldehydes and ketones has been developed using nitrosobenzene as an oxygen source, affording alpha-anilinoxy-aldehydes and -ketones with excellent enantioselectivity. Reaction conditions have been optimized, and low temperature (-20 degrees C) was found to be a key for the successful alpha-aminoxylation of aldehydes, while slow addition of nitrosobenzene is essential for that of ketones. The scope of the reaction is presented.

Aldehydes↗
PubMed1990

Effect of Altoside (ZR-515) on oxygen consumption, carbon dioxide out put and carbohydrate content of organophosphorus resistant strain of Musca domestica.

The effect of applying JHA ZR-515 at a concentration of 50 microliter/liter water in the larval rearing medium from the first larval instar on oxygen consumption, carbon dioxide out put and total carbohydrates was studied. The oxygen consumed by the pupae previously treated as larvae with ZR-515 was decreased and no adult could emerge. The carbon dioxide out put seems to follow a more or less the pattern of oxygen consumption. The concentration of total carbohydrate content in one day old pupae previously treated as larvae was significantly lower than normals. In three days old there was a marked significant increase and in five days old, the carbohydrate content was significantly higher than controls.

Animals↗
PubMed1980

The effect of glucagon on hepatic cellular energetics during a low flow state.

An investigation of the effect of glucagon on liver high energy phosphate concentration during a low flow state is presented. Two groups of dogs were subjected to a 120-minute period of hemorrhagic hypotension followed by reinfusion of shed blood plus additional normal saline to restore the central venous pressure to 10 cm H2O. One group received glucagon intravenously in addition. Despite a significant increase in portal flow and oxygen delivery and a significant increase in liver glucose associated with glucagon administration, there was significant impairment in the ability of the liver to regenerate adenosine triphosphate (ATP). Evidence is presented to show the decreased ATP concentration was not related to hepatic blood flow, but was presumably due to increased catabolism.

Adenosine Triphosphate↗
PubMed1996

The relationship between partial pressure of oxygen and perfusion in two murine tumors after X-ray irradiation: a combined gadopentetate dimeglumine dynamic magnetic resonance imaging and in vivo electron paramagnetic resonance oximetry study.

Changes of partial pressure of oxygen (pO2) and blood perfusion were studied in MTG-B and RIF-1 tumors (n = 5 each) before and after a single 20-Gy dose of X-ray irradiation. Using electron paramagnetic resonance oximetry, we have observed an initial fast decrease of pO2 after irradiation, followed by a slow increase. The time course of these changes was faster in the MTG-B tumors than in the RIF-1 tumors. Gadopentetate dimeglumine (Gd-DTPA) dynamic magnetic resonance imaging studies showed a reduction in uptake of Gd-DTPA at the time of minimum pO2 and a recovery at the time of maximum pO2 in each tumor. Previous work indicates that there is microscopic heterogeneity in tumors, with well-vascularized "capillary regions" being closer to capillaries than poorly vascularized "noncapillary regions." We propose a two-component (slow and fast) model of Gd-DTPA uptake that is designed to quantify the kinetics of these two compartments by analyzing the total tumor uptake kinetics without having to identify specific regions of interest. Total perfusion in the tumors was greatly reduced at the time of minimum oxygenation, and the volume of the slow component increased after irradiation. We conclude that a decrease in blood perfusion is one of the main causes of the decline in pO2 observed after irradiation.

Animals↗
PubMed2005

Responses of the surface membrane and excretory system of Schistosoma mansoni to damage and to treatment with praziquantel and other biomolecules.

Damage to the surface membrane of adult Schistosoma mansoni, and the activity of the excretory system, as shown by resorufin fluorescence, was observed following treatment with praziquantel and incubation with other molecules. Praziquantel treatment induced damage to the surface membrane as measured by the use of a variety of fluorescent compounds. The excretory system of the male worm was inhibited immediately after praziquantel treatment, but fully recovered after culture for 2 h following removal of praziquantel. The excretory system of the female, observed to be minimally active in untreated worm pairs, was often greatly activated in paired females, as shown by intense resorufin labelling, after praziquantel treatment, and this continued during recovery of the male excretory system. In experiments with normal worm pairs, the female could be activated by inhibiting the metabolic rate of the pair by a cooling procedure. The effects on the excretory system of changes in culture conditions (such as changes in pH, concentrations of bacterial lipopolysaccharide, cytokines, reactive oxygen species, compounds which remove cholesterol, such as beta-methyl cyclodextrin, and damaging basic poly-L-lysine) were also assessed. It is concluded that the extensive excretory system of the adult worm is responsive to drug treatment and to certain changes in environmental conditions. Its activity seems to be strongly linked to the integrity of the surface membrane.

Animals↗
PubMed2004

In vivo measurement and imaging of tumor oxygenation using coembedded paramagnetic particulates.

Tumor tissue oxygenation is an important parameter that is positively correlated to the chemo- or radiation treatment outcome of certain tumors. Hence, methods to accurately and noninvasively determine the concentration of oxygen (pO2) in tumors will be valuable. In this study, electron paramagnetic resonance (EPR) spectroscopy, utilizing microcrystalline particulates of lithium phthalocyanine (LiPc), was used to perform repeated measurements of pO2 as a function of tumor growth. We permanently embedded the particulates in the tumor by coimplanting them with RIF-1 tumor cells during inoculation in mice. This procedure enabled repeated measurements of oxygen concentration in the tumor to be obtained for >2 weeks during its growth phase. The particulates were stable and nontoxic to the tumor cells. Both an in vitro clonogenic assay and an in vivo tumor growth rate examination in C3H mice showed no apparent effect on cell proliferation or tumor growth rate. The measurements indicated that the pO2 of the tumor decreased exponentially with tumor growth and reached hypoxic levels ( approximately 4 mmHg) within 4 days after inoculation of the tumor cells. Spatial EPR imaging revealed a nonuniform distribution of the embedded particulates, which were localized mainly in the middle of the tumor volume. Oxygen mapping of the tumor, obtained by spectroscopic EPR imaging, showed significant variation of pO2 within the tumor. In summary, EPR spectroscopy and imaging with an embedded oximetry probe enabled accurate and repeated measurements of pO2 to be obtained in growing tumors under nonperturbing conditions.

Analysis of Variance↗
PubMed2002

Sublethal actions of copper in abalone (Haliotis rufescens) as characterized by in vivo 31P NMR.

The sublethal biochemical actions of copper in live, intact red abalone (Haliotis rufescens) were characterized by in vivo 31P nuclear magnetic resonance spectroscopy (NMR). This non-invasive technique is ideal for examining cellular respiration since critical metabolite concentrations, including phosphoarginine ([PA]), inorganic phosphate ([P(i)]) and [ATP], and the arginine kinase (AK) rate constant, can be monitored in real time. Both metabolite concentrations and enzyme rate constants were measured in abalone during 8-h exposures to 66 microg l(-1) (1.04 microM) and 126 microg l(-1) (1.98 microM) copper (as CuCl2). Significant decreases in [PA] and corresponding increases in [P(i)] resulted, while [ATP] remained constant. In controls [PA], [P(i)] and [ATP] all remained unchanged. Furthermore, both copper concentrations induced a significant elevation in the forward AK rate constant over the basal value of 0.020 +/- 0.002 s(-1). Metabolite levels and enzyme rate constants were also measured during 8-h 66 microg l(-1) copper exposures both before and after a 2-week subchronic exposure to 36 microg l(-1) (0.57 microM) copper. Unlike before the subchronic exposure, no significant changes in [PA], [P(i)] or [ATP] were observed after the 36 microg l(-1) copper treatment, compared with controls. This induced tolerance was also evident from the forward AK rate constant data. Finally, copper accumulation was determined in gill, digestive gland and foot muscle samples. Whereas acute exposure only led to significant accumulation in the gill, copper levels in subchronically exposed abalone were significantly elevated in both the gill and digestive gland, and marginally so in foot muscle. Overall, the gill appears to be the primary site of copper accumulation and toxicity, while the foot and adductor muscles maybe secondarily impacted. The observed metabolic changes may result from insufficient oxygen delivery to the muscles, resulting from mucus accumulation or cytological damage at the gill. In conclusion, abalone acutely exposed to copper pollution may develop asphyxial hypoxia. Since their survival is dependent on adherence to rock surfaces, such a reduction of muscle function could ultimately prove fatal.

Adenosine Triphosphate↗
PubMed2004

Identification of specific nonbridging phosphate oxygens important for DNA cleavage by human topoisomerase I.

Methylphosphonate-bearing oligonucleotides are characterized by the replacement of one of the nonbridging oxygen atoms with a methyl group. While neutralizing the negative charge associated with the phosphodiester at the point of substitution, the methyl group also imparts chirality to the phosphorus atom. Herein we report the synthesis of a number of oligonucleotides containing isomerically pure S(p) and R(p) methylphosphonates at single positions for the purpose of investigating the hydrogen-bonding contacts necessary for human topoisomerase I function. It was possible to correlate these data to the recent X-ray crystal structure of a truncated form of the enzyme and demonstrate a severe decrease of cleavage efficiency when any of the nonbridging oxygen atoms upstream from the cleavage site was removed. Also observed was increased cleavage for oligonucleotides substituted with methylphosphonates downstream from the cleavage site. These effects were shown to be due primarily to alteration of the binding of the modified DNA substrates by human DNA topoisomerase I.

Base Pairing↗
PubMedDate not supplied

[Effect of dimephosphon on the blood circulation and oxygen tension in the brain of normal waking rabbits and in motion sickness].

By using methods of hydrogen clearance and polarography it was shown that rocking of conscious rabbits is followed by an increase of total cerebral blood flow, local blood flow and oxygen tension (pO2) in the frontal, occipital and temporal brain cortex during hypotension and a decrease of the heart rate. Dimephosphon causes a decrease of the cerebral blood flow both during the stationary position of animals and rocking, exerting a weak influence on pO2 in the cerebral cortex, arterial blood pressure and the heart work.

Animals↗
PubMed2004

Atmospheric-pressure Penning ionization mass spectrometry.

A preliminary study on the atmospheric-pressure Penning ionization (APP(e)I) of gaseous organic compounds with Ar* has been made. The metastable argon atoms (Ar*: 11.55 eV for (3)P(2) and 11.72 eV for (3)P(0)) were generated by the negative-mode corona discharge of atmospheric-pressure argon gas. By applying a high positive voltage (+500 to +1000 V) to the stainless steel capillary for the sample introduction (0.1 mm i.d., 0.3 mm o.d.), strong ion signals could be obtained. The ions formed were sampled through an orifice into the vacuum and mass-analyzed by an orthogonal time-of-flight mass spectrometer. The major ions formed by APP(e)I are found to be molecular-related ions for alkanes, aromatics, and oxygen-containing compounds. Because only the molecules with ionization energies less than the internal energy of Ar* are ionized, the present method will be a selective and highly sensitive interface for gas chromatography/mass spectrometry.

Argon↗
PubMed1987

Pulmonary hydroxyproline content and production following treatment of mice with O,S,S-trimethyl phosphorodithioate.

The systemic administration of O,S,S-trimethyl phosphorodithioate (OSS), a contaminant of various organophosphorus insecticides, induces delayed damage to rat and mouse lung tissue. The lesion, particularly in the rat, closely resembles that produced by butylated hydroxytoluene (BHT) in mice. Although the time course of cell damage and repair has been studied in both species, it is not clear whether excess collagen, indicative of fibrosis, is deposited. Changes in pulmonary hydroxyproline content and synthesis, indices of collagen metabolism, were analysed in mice treated with 45 mg/kg OSS. A significant increase in total lung hydroxyproline was evident 21 days after treatment compared to both pair-fed and ad libitum controls. This increase was not augmented by subsequent treatment with 35 mg/kg 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) or exposure to 70% oxygen for 7 days. The rate at which lung tissue synthesized hydroxyproline was increased 7-14 days after treatment with OSS. These data demonstrate that treatment of mice with OSS results in changes indicative of pulmonary fibrosis. However, in contrast to some other lung-toxic chemicals, this lesion was not enhanced by subsequent treatment with BCNU or hyperoxia.

Animals↗
PubMed2002

The functionally distinct hemoglobins of the Arctic spotted wolffish Anarhichas minor.

The Arctic fish Anarhichas minor, a benthic sedentary species, displays high hemoglobin multiplicity. The three major hemoglobins (Hb 1, Hb 2, and Hb 3) show important functional differences in pH and organophosphate regulation, subunit cooperativity, and response of oxygen binding to temperature. Hb 1 and Hb 2 display a low, effector-enhanced Bohr effect and no Root effect. In contrast, Hb 3 displays pronounced Bohr and Root effects, accompanied by strong organophosphate regulation. Hb 1 has the beta (beta(1)) chain in common with Hb 2; Hb 3 and Hb 2 share the alpha (alpha(2)) chain. The amino acid sequences have been established. Several substitutions in crucial positions were observed, such as Cys in place of C-terminal His in the beta(1) chain of Hb 1 and Hb 2. In Hb 3, Val E11 of the beta(2) chain is replaced by Ile. Homology modeling revealed an unusual structure of the Hb 3 binding site of inositol hexakisphoshate. Phylogenetic analysis indicated that only Hb 2 displays higher overall similarity with the major Antarctic hemoglobins. The oxygen transport system of A. minor differs remarkably from those of Antarctic Notothenioidei, indicating distinct evolutionary pathways in the regulatory mechanisms of the fish respiratory system in the two polar environments.

Adenosine Triphosphate↗
PubMed2007

Exceptional affinity of nanostructured organic-inorganic hybrid materials towards dioxygen: confinement effect of copper complexes.

We report the exceptional reactivity towards dioxygen of a nanostructured organic-inorganic hybrid material due to the confinement of copper cyclam within a silica matrix. The key step is the metalation reaction of the ligand, which can occur before or after xerogel formation through the sol-gel process. The incorporation of a Cu(II) center into the material after xerogel formation leads to a bridged Cu(I)/Cu(II) mixed-valence dinuclear species. This complex exhibits a very high affinity towards dioxygen, attributable to auto-organization of the active species in the solid. The remarkable properties of these copper complexes in the silica matrix demonstrate a high cooperative effect for O(2) adsorption; this is induced by close confinement of the two copper ions leading to end-on mu-eta(1):eta(1)-peroxodicopper(II) complexes. The anisotropic packing of the tetraazamacrocycle in a lamellar structure induces an exceptional reactivity of these copper complexes. We show for the first time that the organic-inorganic environment of copper complexes in a silica matrix fully model the protecting role of protein in metalloenzymes. For the first time an oxygenated dicopper(II) complex can be isolated in a stable form at room temperature, and the reduced Cu(2) (I,I) species can be regenerated after several adsorption-desorption cycles. These data also demonstrate that the coordination scheme and reactivity of the copper cyclams within the solid are quite different from that observed in solution.

Adsorption↗
PubMed2002

Cobalt cluster-containing carbonyl ylides for catalytic, three-component assembly of oxygen heterocycles.

[reaction: see text] A dicobalt hexacarbonyl (Co(2)(CO)(6)) cluster is essential for the unusually broad dipolarophile scope and for the sense and degree of diastereoselection in a catalytic, three-component synthesis of tetrahydrofurans and dihydrofurans. Likely involving a new class of carbonyl ylide, these cycloadditions are stereospecific with respect to the dipolarophile and exhibit high diastereoselectivity and regioselectivity in most cases. Differentiation of all four positions of the tetrahydrofuran can thus be accomplished in a triply convergent manner.

Biological Factors↗
PubMed1980

Selective inhibition of thermogenesis by tributyl S,S,S,-phosphorotrithioate (DEF).

1 Rats and mice given tributyl S,S,S,-phosphorotrithioate (DEF) showed large dose-related falls in body temperature which lasted several hours to several days at environmental temperatures below thermoneutrality (30 to 31 degrees C). 2 DEF produced only mild sedation and a remarkable degree of motor control was retained even when body temperatures fell below 30 degrees C. At the dose producing maximal hypothermia only 2% of rats died within the first 24 h, although prolonged hypothermia was usually lethal. 3 Hypothermia was associated with a complete block of cold-induced thermogenesis, with relatively little effect on basal metabolism at thermoneutrality. 4 Heat conservation mechanisms (peripheral vasoconstriction and piloerection) appeared to be unaffected by DEF and retained their usual temperature thresholds. 5 Adrenal catecholamine secretion in response to handling or acute cold exposure was normal in DEF-treated rats but the fall in body temperature could be markedly reduced by large intraperitoneal injections of noradrenaline, although not atropine. The increase in oxygen consumption produced by injected catecholamines was also unaffected by DEF treatment. 6 It is concluded that the block of cold-induced thermogenesis probably results from a lack of catecholamine release at the tissue level. That this is likely to be mediated at a peripheral site is suggested by the lack of effect of intracerebroventricular DEF.

Animals↗