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The Biochemical Journal Aug 1993The Michaelis constant of tyrosinase for oxygen in the presence of monophenols and o-diphenols, which generate a cyclizable o-quinone, has been studied. This constant...
The Michaelis constant of tyrosinase for oxygen in the presence of monophenols and o-diphenols, which generate a cyclizable o-quinone, has been studied. This constant depends on the nature of the monophenol and o-diphenol and is always lower in the presence of the former than of the latter. From the mechanism proposed for tyrosinase and from its kinetic analysis [Rodríguez-López, J. N., Tudela, J., Varón, R., García-Carmona, F. and García-Cánovas, F. (1992) J. Biol. Chem. 267, 3801-3810] a quantitative ratio has been established between the Michaelis constants for oxygen in the presence of monophenols and their o-diphenols. This ratio is used for the determination of the Michaelis constant for oxygen with monophenols when its value cannot be calculated experimentally.
Topics: Basidiomycota; Indolequinones; Indoles; Kinetics; Models, Chemical; Monophenol Monooxygenase; Oxygen; Polarography; Quinones; Spectrophotometry, Infrared
PubMed: 8352753
DOI: 10.1042/bj2930859 -
The Journal of Cell Biology Nov 1963Two methods of preparing a mitochondrial fraction from beef brain cortex are described. Data are presented on the rate of oxidation of substrates, P/O and respiratory...
Two methods of preparing a mitochondrial fraction from beef brain cortex are described. Data are presented on the rate of oxidation of substrates, P/O and respiratory control ratios, cholinesterase activity, and DNA content. Electron micrographs of isolated mitochondria and mitochondria in situ are shown. Comparisons are drawn between these preparations and mitochondria prepared in 0.25 M sucrose. The data on enzymic properties and contamination by non-mitochondrial material indicate that mitochondrial fractions which compare favorably with those from other tissues can be prepared from brain tissue.
Topics: Adenine Nucleotides; Animals; Antimetabolites; Brain; Cattle; Cerebral Cortex; Cholinesterases; Electrons; Glycerophosphates; Metabolism; Microscopy; Microscopy, Electron; Mitochondria; Oxidation-Reduction; Pharmacology; Polarography; Pyruvates; Research; Succinates
PubMed: 14090748
DOI: 10.1083/jcb.19.2.293 -
PloS One Aug 2009Complex I dysfunction is a common, heterogeneous cause of human mitochondrial disease having poorly understood pathogenesis. The extensive conservation of complex I...
Complex I dysfunction is a common, heterogeneous cause of human mitochondrial disease having poorly understood pathogenesis. The extensive conservation of complex I composition between humans and Caenorhabditis elegans permits analysis of individual subunit contribution to mitochondrial functions at both the whole animal and mitochondrial levels. We provide the first experimentally-verified compilation of complex I composition in C. elegans, demonstrating 84% conservation with human complex I. Individual subunit contribution to mitochondrial respiratory capacity, holocomplex I assembly, and animal anesthetic behavior was studied in C. elegans by RNA interference-generated knockdown of nuclear genes encoding 28 complex I structural subunits and 2 assembly factors. Not all complex I subunits directly impact respiratory capacity. Subcomplex Ilambda subunits along the electron transfer pathway specifically control whole animal anesthetic sensitivity and complex II upregulation, proportionate to their relative impairment of complex I-dependent oxidative capacity. Translational analysis of complex I dysfunction facilitates mechanistic understanding of individual gene contribution to mitochondrial disease. We demonstrate that functional consequences of complex I deficiency vary with the particular subunit that is defective.
Topics: Animals; Caenorhabditis elegans; Electron Transport Complex I; Electrophoresis, Polyacrylamide Gel; Gene Knockdown Techniques; Mass Spectrometry; Mitochondria; Oxidative Phosphorylation; Polarography; Polymerase Chain Reaction; RNA Interference
PubMed: 19672299
DOI: 10.1371/journal.pone.0006607 -
The Journal of Biological Chemistry Nov 1961
Topics: Polarography; Thiosulfate Sulfurtransferase; Transferases
PubMed: 13901419
DOI: No ID Found -
The Biochemical Journal Mar 2010Kidney function declines with advancing age and mitochondria have been implicated. In the present study we have examined the integrated function of mitochondria isolated...
Kidney function declines with advancing age and mitochondria have been implicated. In the present study we have examined the integrated function of mitochondria isolated from kidneys of 6- and 24-month-old Fischer 344 rats. OXPHOS (oxidative phosphorylation) of intact mitochondria and cytochrome c oxidase activity in permeabilized mitochondria were determined with polarographic assays. The activities of the ETC (electron transport chain) complexes and the cytochrome content in solubilized mitochondria were measured using spectrophotometric methods. The respiratory complexes were evaluated with blue native gel electrophoresis. Mitochondrial preparations were evaluated by immunoblotting for cytochrome c, Smac/Diablo and VDAC (voltage-dependent anion channel). Mitochondrial morphology was examined by electron microscopy. OXPHOS of mitochondria isolated from 24-month-old animals was decreased 15-25% with complexes I, II, III and IV, and fatty acid substrates. The electron microscopic appearance of mitochondria, the activity of the ETC complexes and the protein abundance of individual complexes and supercomplexes were unchanged. The content of cytochrome c was decreased by 37% in aged mitochondria, as determined by spectrophotometric methods and confirmed with immunoblotting. Polarographic determination of cytochrome c oxidase activity with endogenous cytochrome c demonstrated a 23% reduction in aged mitochondria, which was corrected with the addition of exogenous cytochrome c. Renal mitochondrial OXPHOS decreased with aging in the Fischer 344 rat. Decreased mitochondrial cytochrome c content is a major factor contributing to the OXPHOS defect of mitochondria isolated from kidneys of elderly animals.
Topics: Aging; Animals; Citrate (si)-Synthase; Electron Transport Complex IV; Immunoblotting; Kidney; Male; Mitochondria; Oxidation-Reduction; Oxidative Phosphorylation; Polarography; Rats; Rats, Inbred F344
PubMed: 20100174
DOI: 10.1042/BJ20091373 -
Journal of Bacteriology Sep 1966Iglewski, W. J. (The Pennsylvania State University, University Park), and E. H. Ludwig. Respiration of mengovirus-infected L-929 cells. J. Bacteriol. 92:733-738....
Iglewski, W. J. (The Pennsylvania State University, University Park), and E. H. Ludwig. Respiration of mengovirus-infected L-929 cells. J. Bacteriol. 92:733-738. 1966.-Polarographic techniques were employed to study the oxidative metabolism of L-929 cells during a one-step mengovirus growth cycle. Virus maturation began 3.5 hr after infection and was complete with 7 hr. Virus maturation was accompanied by a decreased rate of endogenous respiration and an increased rate of oxidation of succinate and alpha-glycerophosphate by L-929 cells. The rate of glucose uptake was the same for mengovirus-infected and control L-929 cells. However, there was a decreased oxidation of glucose to carbon dioxide and a decreased production of lactic acid by L cells infected with mengovirus under aerobic conditions. Mengovirus was produced equally well under aerobic and anaerobic conditions. The implications of the alterations in metabolism with respect to virus synthesis are discussed.
Topics: Carbon Isotopes; Enterovirus; Enterovirus Infections; Glucose; Glycerophosphates; Lactates; Polarography; Radiometry; Succinates; Virus Cultivation
PubMed: 4288496
DOI: 10.1128/jb.92.3.733-738.1966 -
Brazilian Dental Journal 2003Copper/aluminum alloys are largely utilized in odontological restorations because they are less expensive than gold or platinum. However, tarnishing and important...
Copper/aluminum alloys are largely utilized in odontological restorations because they are less expensive than gold or platinum. However, tarnishing and important corrosion in intrabuccal prostheses made with copper/aluminum alloys after 28 days of use have been reported. Several kinds of food and beverage may attack and corrode these alloys. Copper is an essential component of several important enzymes directly involved in mitochondrial respiratory metabolism. Aluminum, in contrast, is very toxic and, when absorbed, plasma values as small as 1.65 to 21.55 microg/dl can cause severe lesions to the nervous system, kidneys, and bone marrow. Because mitochondria are extremely sensitive to minimal variation of cellular physiology, the direct relationship between the mitocondrial respiratory chain and cell lesions has been used as a sensitive parameter to evaluate cellular aggression by external agents. This work consisted in the polarographic study of mitochondrial respiratory metabolism of livers and kidneys of rabbits with femoral implants of titanium or copper/aluminum alloy screws. The experimental results obtained did not show physiological modifications of hepatic or renal mitochondria isolated from animals of the three experimental groups, which indicate good biocompatibility of copper/ aluminum alloys and suggest their odontological use.
Topics: Alloys; Aluminum; Animals; Biocompatible Materials; Bone Screws; Copper; Corrosion; Dental Materials; Femur; Kidney; Male; Mitochondria; Mitochondria, Liver; Oxygen Consumption; Polarography; Rabbits; Statistics as Topic; Subcellular Fractions; Surface Properties; Titanium
PubMed: 12656462
DOI: 10.1590/s0103-64402003000100006 -
Biophysical Journal May 1973Polyadenylic acid (poly A) was studied under various conditions using both DC polarography and phase sensitive AC polarography and by measuring the time-course of the...
Polyadenylic acid (poly A) was studied under various conditions using both DC polarography and phase sensitive AC polarography and by measuring the time-course of the current during the lifetime of a single drop of the dropping mercury electrode. Under certain conditions the current at potentials of the limiting portion of the DC polarographic wave does not reach its limiting value and in extreme situations peak-shaped curves are observed. This phenomenon is explained in terms of desorption and repulsion from the electrode of neutral poly A due to its polyanionic character. Consequently, the suppression of the current can be enhanced by increasing negative potential of the electrode and by exposing the negative charges of phosphate groups, e.g., by increasing pH and temperature and by decreasing ionic strength and buffer capacity; vice versa, the current suppression can be at least partially eliminated by reversing these conditions. Polyamines which seem to shield the phosphate groups through specific interactions are very effective in eliminating the current suppression. The effectiveness of a polyamine is determined by its chain length and by the density of its amino groups and the geometry of their distribution.
Topics: Adenine Nucleotides; Buffers; Electric Conductivity; Hydrogen-Ion Concentration; Kinetics; Mathematics; Osmolar Concentration; Polarography; Polyamines; Polynucleotides; Sodium Chloride; Temperature
PubMed: 4704485
DOI: 10.1016/s0006-3495(73)85998-3 -
Proceedings of the National Academy of... May 2015The mechanism underlying temporal correlations among blood oxygen level-dependent signals is unclear. We used oxygen polarography to better characterize oxygen...
The mechanism underlying temporal correlations among blood oxygen level-dependent signals is unclear. We used oxygen polarography to better characterize oxygen fluctuations and their correlation and to gain insight into the driving mechanism. The power spectrum of local oxygen fluctuations is inversely proportional to frequency raised to a power (1/f) raised to the beta, with an additional positive band-limited component centered at 0.06 Hz. In contrast, the power of the correlated oxygen signal is band limited from ∼ 0.01 Hz to 0.4 Hz with a peak at 0.06 Hz. These results suggest that there is a band-limited mechanism (or mechanisms) driving interregional oxygen correlation that is distinct from the mechanism(s) driving local (1/f) oxygen fluctuations. Candidates for driving interregional oxygen correlation include rhythmic or pseudo-oscillatory mechanisms.
Topics: Algorithms; Animals; Arrhythmias, Cardiac; Brain; Brain Mapping; Electrodes; Heart Rate; Learning; Macaca; Magnetic Resonance Imaging; Neural Pathways; Normal Distribution; Oscillometry; Oxygen; Polarography; Rest; Signal Processing, Computer-Assisted
PubMed: 25918427
DOI: 10.1073/pnas.1419837112 -
Annals of Botany Sep 2005Claims that submerged roots of alder and other wetland trees are aerated by pressurized gas flow generated in the stem by a light-induced thermo-osmosis have seemed...
BACKGROUND AND AIMS
Claims that submerged roots of alder and other wetland trees are aerated by pressurized gas flow generated in the stem by a light-induced thermo-osmosis have seemed inconsistent with root anatomy. Our aim was to seek a verification using physical root-stem models, stem segments with or without artificial roots, and rooted saplings.
METHODS
Radial O2 loss (ROL) from roots was monitored polarographically as the gas space system of the models, and stems were pressurized artificially. ROL and internal pressurization were also measured when stems were irradiated and the xylem stream was either CO2 enriched or not. Stem photosynthesis and respiration were measured polarographically. Stem and root anatomy were examined by light and fluorescence microscopy.
KEY RESULTS
Pressurizing the models and stems to
CONCLUSIONS
Pressurized gas flow to submerged roots does not occur to any significant degree in alder, but stem photosynthesis, using internally sourced CO2 from respiration and the transpiration stream, may play an important role in root aeration in young trees and measurably affect the overall carbon balance of this and other species.
Topics: Alnus; Carbon Dioxide; Light; Oxygen; Photosynthesis; Plant Roots; Plant Stems; Polarography; Water
PubMed: 16093272
DOI: 10.1093/aob/mci213