scholarly journals Wavelength and temperature-dependent apparent quantum yields for photochemical formation of hydrogen peroxide in seawater

2014 ◽  
Vol 16 (4) ◽  
pp. 777-791 ◽  
Author(s):  
David J. Kieber ◽  
Gary W. Miller ◽  
Patrick J. Neale ◽  
Kenneth Mopper
Keyword(s):  
Hydrogen Peroxide ◽  
Light Dose ◽  
Quantum Yields ◽  
Temperature Dependent ◽  
Marine Waters ◽  
Photochemical Formation ◽  
Dose Dependent

Wavelength, temperature and light-dose dependent hydrogen peroxide photoproduction quantum yields were determined in subtropical, temperate and polar marine waters.

Gentamicin enhanced production of hydrogen peroxide by renal cortical mitochondria

1987 ◽  
Vol 253 (4) ◽  
pp. C495-C499 ◽  
Author(s):  
P. D. Walker ◽  
S. V. Shah
Keyword(s):  
Hydrogen Peroxide ◽  
Mitochondrial Respiration ◽  
Critical Role ◽  
Reactive Oxygen ◽  
Reactive Oxygen Metabolites ◽  
Enhanced Production ◽  
Production Of Hydrogen ◽  
Hydrogen Peroxide Generation ◽  
Dose Dependent ◽  
Oxygen Metabolites

Agents that affect mitochondrial respiration have been shown to enhance the generation of reactive oxygen metabolites. On the basis of the well-demonstrated ability of gentamicin to alter mitochondrial respiration (stimulation of state 4 and inhibition of state 3), it was postulated that gentamicin may enhance the generation of reactive oxygen metabolites by renal cortical mitochondria. The aim of this study was to examine the effect of gentamicin on the production of hydrogen peroxide (measured as the decrease in scopoletin fluorescence) in rat renal cortical mitochondria. The hydrogen peroxide generation by mitochondria was enhanced from 0.17 +/- 0.02 nmol . mg-1 . min-1 (n = 14) in the absence of gentamicin to 6.21 +/- 0.67 nmol . mg-1 . min-1 (n = 14) in the presence of 4 mM gentamicin. This response was dose dependent with a significant increase observed at even the lowest concentration of gentamicin tested, 0.01 mM. Production of hydrogen peroxide was not increased when gentamicin was added to incubation media in which mitochondria or substrate was omitted or heat-inactivated mitochondria were used. The gentamicin-induced change in fluorescence was completely inhibited by catalase (but not by heat-inactivated catalase), indicating that the decrease in fluorescence was due to hydrogen peroxide. Thus this study demonstrates that gentamicin enhances the production of hydrogen peroxide by mitochondria. Because of their well-documented cytotoxicity, reactive oxygen metabolites may play a critical role in gentamicin nephrotoxicity.

Light Dose-Dependent Thickness Control of Photoacid Generator-Bearing Hydrogel

2015 ◽  
Vol 358 (1) ◽  
pp. 52-58 ◽  
Author(s):  
Taku Satoh ◽  
Kimio Sumaru ◽  
Toshiyuki Takagi ◽  
Toshiyuki Kanamori
Keyword(s):  
Light Dose ◽  
Thickness Control ◽  
Dose Dependent ◽  
Photoacid Generator

Quantum Yields for the Photodegradation of Pollutants in Dilute Aqueous Solution: Phenol, 4-Chlorophenol and N-Nitrosodimethylamine

1996 ◽  
Vol 1 (2) ◽  
Author(s):  
Te-Fu L. Ho ◽  
James R. Bolton ◽  
Ewa Lipczynska-Kochany
Keyword(s):  
Aqueous Solution ◽  
Hydrogen Peroxide ◽  
Quantum Yield ◽  
High Performance ◽  
Flash Photolysis ◽  
Quantum Yields ◽  
Visible Absorption ◽  
Dilute Aqueous Solution ◽  
Uv Visible ◽  
Photolysis Of Phenol

AbstractA broadband method has been applied to determine the quantum yields for the photochemical removal of three common pollutants: phenol, 4-chlorophenol and N-nitrosodimethylamine (NDMA) in dilute aqueous solution. Flash photolysis (xenon flash lamps) was used to cause a significant amount of photolysis without photolyzing intermediates. The analysis of reactant depletion following a single flash was carried out by high- performance liquid chromatography (HPLC) or UV/visible absorption spectroscopy. The method for determining quantum-yields employed p-benzoquinone as an actinometer and was validated by determining the average (200-400 nm) quantum yield for the generation of hydroxyl radicals from the photolysis of hydrogen peroxide (0.90 ± 0.10) and the quantum yields for the photolysis of phenol (0.13 ± 0.02) and 4-chlorophenol (0.24 ± 0.04). The values determined agree very well with the literature ones obtained with monochromatic radiation. The quantum yield for the direct photolysis of NDMA was found to be 0.11 ± 0.03 at neutral pH and 0.27 ± 0.02 at pH 2-4. Under conditions where hydrogen peroxide is the principal absorber, the NDMA quantum yield is 0.32 ± 0.04, independent of pH in the range 2-8.

scholarly journals Differential effect of culture epimastigotes and blood-form Trypamastigotes on normal mouse splenocyte responsiveness to mitogens

1986 ◽  
Vol 81 (2) ◽  
pp. 207-213 ◽  
Author(s):  
L. E. Serrano ◽  
J. A. O'Daly
Keyword(s):  
Normal Mouse ◽  
Potential Role ◽  
Parasite Growth ◽  
Active Living ◽  
Strong Inhibition ◽  
Temperature Dependent ◽  
Blastogenic Response ◽  
Dose Dependent ◽  
Mouse Lymphocytes

Blood form trypomastigotes of the Y strain of T. cruzi, produced a strong inhibition of the blastogenic response to T and B cell mitogens, of the C3H/He, C57BLand BALB/cJ strains of mice, while culture epimastigotes of the Y strain kept in a medium that allows parasite growth at 26°. 30° and 37°C produced a strong stimulatory effect that was even higher than the effect of the mitogens alone. Both the inhibitory or the stimulatory effects were dose-dependent. The stimulatory effect of epimastigotes was also temperature-dependent producing increasedstimulation indexes as the temperature of parasite cultures was raised. Metabolically active,living parasites seemed to be necessary for an improved lymphocyte stimulation suggesting a potential role of secreted metabolites as polyclonal activators of mouse lymphocytes.

Gentamicin-induced mobilization of iron from renal cortical mitochondria

1993 ◽  
Vol 265 (3) ◽  
pp. F435-F439 ◽  
Author(s):  
N. Ueda ◽  
B. Guidet ◽  
S. V. Shah
Keyword(s):  
Hydrogen Peroxide ◽  
Hydroxyl Radical ◽  
Tissue Injury ◽  
Iron Chelator ◽  
Iron Release ◽  
Radical Scavengers ◽  
Iron Mobilization ◽  
No Formation ◽  
Hydroxyl Radical Scavengers ◽  
Dose Dependent

Iron, presumably by participating in generation of hydroxyl radical or other oxidant species or initiation of lipid peroxidation, has been shown to play an important role in several models of tissue injury, including acute renal failure induced by the antibiotic gentamicin. However, the sources of iron remain unknown. Rat renal mitochondria incubated at 37 degrees C with gentamicin resulted in a time- (15-60 min) and a dose-dependent (0.01-5 mM) iron release as measured by formation of iron-bathophenanthroline sulfonate complex FeII-(BPS)3 [at 60 min, control: 1.2 +/- 0.1 nmol/mg protein, n = 7; gentamicin (5 mM): 5.1 +/- 0.4 nmol/mg protein, n = 7]. No formation of FeII(BPS)3 complex was detected in the absence of mitochondria or when incubations were carried out at 0 degrees C. Similar results were obtained when 2,2'-dipyridyl, another iron chelator, was used for measurement of iron release. On the basis on our previous study that gentamicin enhances generation of hydrogen peroxide by renal cortical mitochondria, we examined whether effect of gentamicin on iron release is mediated by hydrogen peroxide. Catalase (which decomposes hydrogen peroxide), but not heat-inactivated catalase, as well as pyruvate, a potent scavenger of hydrogen peroxide, prevented gentamicin-induced iron mobilization. Superoxide dismutase, a scavenger of superoxide anion, or hydroxyl radical scavengers (dimethylthiourea or sodium benzoate) had no effect. Taken together, the data with scavengers indicate that gentamicin-induced iron mobilization from mitochondria is mediated by hydrogen peroxide.

scholarly journals Excited-State Relaxation in Luminescent Molybdenum(0) Complexes with Isocyanide Chelate Ligands

Inorganics ◽  
2020 ◽  
Vol 8 (2) ◽  
pp. 14
Author(s):  
Patrick Herr ◽  
Oliver S. Wenger
Keyword(s):  
Excited State ◽  
Excited States ◽  
Quantum Yields ◽  
Nonradiative Relaxation ◽  
Temperature Dependent ◽  
Tert Butyl ◽  
Thermally Activated ◽  
Ligand Charge Transfer ◽  
Order Of Magnitude ◽  
Electronic Ground

Diisocyanide ligands with a m-terphenyl backbone provide access to Mo0 complexes exhibiting the same type of metal-to-ligand charge transfer (MLCT) luminescence as the well-known class of isoelectronic RuII polypyridines. The luminescence quantum yields and lifetimes of the homoleptic tris(diisocyanide) Mo0 complexes depend strongly on whether methyl- or tert-butyl substituents are placed in α-position to the isocyanide groups. The bulkier tert-butyl substituents lead to a molecular structure in which the three individual diisocyanides ligated to one Mo0 center are interlocked more strongly into one another than the ligands with the sterically less demanding methyl substituents. This rigidification limits the distortion of the complex in the emissive excited-state, causing a decrease of the nonradiative relaxation rate by one order of magnitude. Compared to RuII polypyridines, the molecular distortions in the luminescent 3MLCT state relative to the electronic ground state seem to be smaller in the Mo0 complexes, presumably due to delocalization of the MLCT-excited electron over greater portions of the ligands. Temperature-dependent studies indicate that thermally activated nonradiative relaxation via metal-centered excited states is more significant in these homoleptic Mo0 tris(diisocyanide) complexes than in [Ru(2,2′-bipyridine)3]2+.

scholarly journals Protein phosphatase-type 2B is involved in the regulation of the acrosome reaction but not in the temperature-dependent flagellar movement of fowl spermatozoa

Reproduction ◽  
2004 ◽  
Vol 128 (6) ◽  
pp. 783-787 ◽  
Author(s):  
K Ashizawa ◽  
G J Wishart ◽  
A R A H Ranasinghe ◽  
S Katayama ◽  
Y Tsuzuki
Keyword(s):  
Protein Phosphatase ◽  
Acrosome Reaction ◽  
Molecular Mechanisms ◽  
Dependent Manner ◽  
Temperature Dependent ◽  
Acrosomal Exocytosis ◽  
Protein Dephosphorylation ◽  
Dose Dependent ◽  
Protein Phosphatase Type ◽  
Stimulation Of

The motility and acrosomal integrity of fowl spermatozoa in TES/NaCl buffer, with or without homogenized inner perivitelline layers (IPVL) prepared from laid fowl eggs, was almost negligible at 40 °C. However, motility became vigorous even at 40 °C when 2 mmol CaCl2/l was added, and the acrosome reaction was also stimulated in the presence, but not in the absence, of IPVL. The presence of deltamethrin or fenvalerate, specific inhibitors of protein phosphatase-type 2B (PP2B), did not permit the restoration of motility at 40 °C but, in the presence of IPVL, these compounds stimulated the acrosome reaction in a dose-dependent manner in the range of 1–1000 nmol/l. These results suggest that IPVL is necessary for the activation of the acrosome reaction in fowl spermatozoa and that Ca2+ plays an important role in the stimulation of motility and acrosomal exocytosis. Furthermore, it appears that the intracellular molecular mechanisms for the regulation of the acrosome reaction of fowl spermatozoa are different from those for the restoration of motility, i.e. protein dephosphorylation by PP2B in the former but not in the latter case.

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