PubMed · 4251559
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
M Roland. 1970. Culdoscopy and laparoscopy: competitive or complementary technics?. https://doi.org/10.1016/s0015-0282(16)37456-8
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
Elevations from the Mars Orbiter Laser Altimeter (MOLA) have been used to construct a precise topographic map of the martian north polar region. The northern ice cap has a maximum elevation of 3 kilometers above its surroundings but lies within a 5-kilometer-deep hemispheric depression that is contiguous with the area into which most outflow channels emptied. Polar cap topography displays evidence of modification by ablation, flow, and wind and is consistent with a primarily H2O composition. Correlation of topography with images suggests that the cap was more spatially extensive in the past. The cap volume of 1.2 x 10(6) to 1.7 x 10(6) cubic kilometers is about half that of the Greenland ice cap. Clouds observed over the polar cap are likely composed of CO2 that condensed out of the atmosphere during northern hemisphere winter. Many clouds exhibit dynamical structure likely caused by the interaction of propagating wave fronts with surface topography.
PURPOSE: Methylene blue (MB) can be used as an intracellular electron acceptor. The purpose of this study was to demonstrate the usefulness of MB for the determination of total bioreductive capacity of cell suspensions. METHODS AND MATERIALS: We measured oxygen consumption by Clark electrode and pentose cycle activity by release of 14CO2 from 1-14C-glucose. RESULTS: Methylene blue catalyzes the reaction of intracellular reductants NADPH, NADH, and reduced glutathione (GSH) with oxygen, causing the production of hydrogen peroxide. The reaction rate correlates with the negative charge of molecule (NADPH(-4) > NADH(-2) > GSH(-1)), suggesting that reaction with positively charged oxidized MB is the limiting step of the reaction. In a cellular system MB causes the electron flow from cellular endogenous substrates to oxygen. It is activated by the disruption of the NADP+/NADPH ratio due to several processes. These are direct oxidation of NADPH and GSH, the GSH peroxidase catalyzed reaction of GSH with H2O2, followed by NADPH oxidation by oxidized glutathione (GSSG). This results in increased cellular oxygen consumption and stimulation of the oxidative limb of pentose cycle (PC) in the presence of MB. The cellular effect of MB differs from other electron accepting drugs. Diamide and tert-butylhydroperoxide act as direct oxidants, while MB is an electron carrier to oxygen. Accordingly, MB shows the highest effect on PC activation and oxygen consumption. CONCLUSIONS: Our results indicate that MB may be used for the determination of the total bioreductive capacity of the cells, measured by oxygen consumption and PC activation.
Nitration of tyrosine residues of proteins has been suggested as a marker of peroxynitrite-mediated tissue injury in inflammatory conditions. The nitration reaction has been extensively studied in vitro by bolus addition of authentic peroxynitrite, an experimental approach hardly reflecting in vivo situations in which the occurrence of peroxynitrite is thought to result from continuous generation of .NO and O-2 at physiological pH. In the present study, we measured the nitration of free tyrosine by .NO and O-2 generated at well defined rates from the donor compound (Z)-1-[N-[3-aminopropyl]-N-[4-(3-aminopropylammonio)butyl]-amino]- dia zen-1-ium-1,2-diolate] (spermine NONOate) and the xanthine oxidase reaction, respectively. The results were compared with the established nitration reaction triggered by authentic peroxynitrite. Bolus addition of peroxynitrite (1 mM) to tyrosine (1 mM) at pH 7.4 yielded 36.77 +/- 1.67 microM 3-nitrotyrosine, corresponding to a recovery of about 4%. However, peroxynitrite formed from .NO and O-2, which were generated at equal rates ( approximately 5 microM x min-1) from 1 mM spermine NONOate, 28 milliunits/ml xanthine oxidase, and 1 mM hypoxanthine was much less efficient (0.67 +/- 0.01 microM; approximately 0.07% of total product flow). At O-2 fluxes exceeding the .NO release rates, 3-nitrotyrosine formation was below the detection limit of the high performance liquid chromatography method (<0.06 microM). Nitration was most efficient (approximately 0.3%) with the .NO donor alone, i.e. without concomitant generation of O-2. Nitration by .NO had a pH optimum of 8.2, increased progressively with increasing tyrosine concentrations (0.1-2 mM), and was not enhanced by NaHCO3 (up to 20 mM), indicating that it was mediated by .NO2 rather than peroxynitrite. Our results argue against peroxynitrite produced from .NO and O-2 as a mediator of tyrosine nitration in vivo.