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Cerebral Cortex (New York, N.Y. : 1991) Jan 2016The human default mode network (DMN) shows decreased blood oxygen level dependent (BOLD) signals in response to a wide range of attention-demanding tasks. Our...
The human default mode network (DMN) shows decreased blood oxygen level dependent (BOLD) signals in response to a wide range of attention-demanding tasks. Our understanding of the specifics regarding the neural activity underlying these "task-negative" BOLD responses remains incomplete. We paired oxygen polarography, an electrode-based oxygen measurement technique, with standard electrophysiological recording to assess the relationship of oxygen and neural activity in task-negative posterior cingulate cortex (PCC), a hub of the DMN, and visually responsive task-positive area V3 in the awake macaque. In response to engaging visual stimulation, oxygen, LFP power, and multi-unit activity in PCC showed transient activation followed by sustained suppression. In V3, oxygen, LFP power, and multi-unit activity showed an initial phasic response to the stimulus followed by sustained activation. Oxygen responses were correlated with LFP power in both areas, although the apparent hemodynamic coupling between oxygen level and electrophysiology differed across areas. Our results suggest that oxygen responses reflect changes in LFP power and multi-unit activity and that either the coupling of neural activity to blood flow and metabolism differs between PCC and V3 or computing a linear transformation from a single LFP band to oxygen level does not capture the true physiological process.
Topics: Action Potentials; Animals; Attention; Brain Mapping; Evoked Potentials, Visual; Image Processing, Computer-Assisted; Macaca; Magnetic Resonance Imaging; Neurons; Oxygen; Photic Stimulation; Visual Cortex; Visual Perception
PubMed: 25385710
DOI: 10.1093/cercor/bhu260 -
The Journal of Surgical Research Nov 2013Work on human and mouse skeletal muscle by our group and others has demonstrated that aging and age-related degenerative diseases are associated with mitochondrial... (Comparative Study)
Comparative Study
INTRODUCTION
Work on human and mouse skeletal muscle by our group and others has demonstrated that aging and age-related degenerative diseases are associated with mitochondrial dysfunction, which may be more prevalent in males. There have been, however, no studies that specifically examine the influence of male or female sex on human skeletal muscle mitochondrial respiration. The purpose of this study was to compare mitochondrial respiration in the gastrocnemius of adult men and women.
METHODS
Gastrocnemius muscle was obtained from male (n = 19) and female (n = 11) human subjects with healthy lower-extremity musculoskeletal and arterial systems and normal ambulatory function. All patients were undergoing operations for the treatment of varicose veins in their legs. Mitochondrial respiration was determined with a Clark electrode in an oxygraph cell containing saponin-skinned muscle bundles. Complex I-, II-, III-, and IV-dependent respiration was measured individually and normalized to muscle weight, total protein content, and citrate synthase (CS, index of mitochondrial content).
RESULTS
Male and female patients had no evidence of musculoskeletal or arterial disease and did not differ with regard to age, race, body mass index, or other clinical characteristics. Complex I-, II-, III-, and IV-dependent respiration normalized to muscle weight, total protein content, and CS did not statistically differ for males compared with females.
CONCLUSIONS
Our study evaluates, for the first time, gastrocnemius mitochondrial respiration of adult men and women who have healthy musculoskeletal and arterial systems and normal ambulatory function. Our data demonstrate there are no differences in the respiration of gastrocnemius mitochondria between men and women.
Topics: Aging; Cell Respiration; Electron Transport; Female; Healthy Volunteers; Humans; Linear Models; Male; Middle Aged; Mitochondria; Muscle, Skeletal; Myofibrils; Oxygen Consumption; Polarography; Sex Characteristics
PubMed: 23768768
DOI: 10.1016/j.jss.2013.05.054 -
Biochimica Et Biophysica Acta Apr 2004Photosystem II (PSII) produces dioxygen from water in a four-stepped process, which is driven by four quanta of light and catalysed by a Mn-cluster and tyrosine Z.... (Review)
Review
Photosystem II (PSII) produces dioxygen from water in a four-stepped process, which is driven by four quanta of light and catalysed by a Mn-cluster and tyrosine Z. Oxygen is liberated during one step, coined S(3)=>S(0). Chemical intermediates on the way from reversibly bound water to dioxygen have not yet been tracked, however, a break in the Arrhenius plot of the oxygen-evolving step has been taken as evidence for its existence. We scrutinised the temperature dependence of (i) UV-absorption transients attributable to the reduction of the Mn-cluster and tyrosine Z by water, and (ii) polarographic transients attributable to the release of dioxygen. Using a centrifugatable and kinetically competent Pt-electrode, we observed no deviation from a linear Arrhenius plot of oxygen release in the temperature range from -2 to 32 degrees C, and hence no evidence, by this approach, for a sufficiently long-lived chemical intermediate. The half-rise times of oxygen release differed between Synechocystis WT* (at 20 degrees C: 1.35 ms) and a point mutant (D1-D61N: 13.1 ms), and the activation energies differed between species (Spinacia oleracea, 30 kJ/mol versus Synechocystis, 41 kJ/mol) and preparations (PSII membranes, 41 kJ/mol versus core complexes, 33 kJ/mol, Synechocystis). Correction for polarographic artefacts revealed, for the first time, a temperature-dependent lag-phase of the polarographic transient (duration at 20 degrees C: 0.45 ms, activation energy: 31 kJ/mol), which was indicative of a short-lived intermediate. It was, however, not apparent in the UV-transients. Thus the "intermediate" was probably newly formed and transiently bound oxygen.
Topics: Cyanobacteria; Electron Transport; Kinetics; Manganese; Mutation; Oxidation-Reduction; Oxygen; Photosystem II Protein Complex; Polarography; Spectrophotometry, Ultraviolet; Temperature; Thermodynamics
PubMed: 15100031
DOI: 10.1016/j.bbabio.2003.06.001 -
Physiologia Plantarum Feb 2021The Mn CaO cluster of photosystem II (PSII) advances sequentially through five oxidation states (S to S ). Under the enzyme cycle, two water molecules are oxidized, O is...
The Mn CaO cluster of photosystem II (PSII) advances sequentially through five oxidation states (S to S ). Under the enzyme cycle, two water molecules are oxidized, O is generated and four protons are released into the lumen. Umena et al. (2011) have proposed that, with other charged amino acids, the R323 residue of the D1 protein could contribute to regulate a proton egress pathway from the Mn CaO cluster and Tyr via a proton channel identified from the 3D structure. To test this suggestion, a PsbA3/R323E site-directed mutant has been constructed and the properties of its PSII have been compared to those of the PsbA3-PSII by using EPR spectroscopy, polarography, thermoluminescence and time-resolved UV-visible absorption spectroscopy. Neither the oscillations with a period four nor the kinetics and S-state-dependent stoichiometry of the proton release were affected. However, several differences have been found: (1) the P decay in the hundreds of ns time domain was much slower in the mutant, (2) the S Q /DCMU and S Q /DCMU radiative charge recombination occurred at higher temperatures and (3) the S Tyr , S Tyr , S Tyr split EPR signals induced at 4.2 K by visible light from the S Tyr , S Tyr , S Tyr , respectively, and the (S Tyr )' induced by NIR illumination at 4.2 K of the S Tyr state differed. It is proposed that the R323 residue of the D1 protein interacts with Tyr likely via the H-bond network previously proposed to be a proton channel. Therefore, rather than participating in the egress of protons to the lumen, this channel could be involved in the relaxations of the H-bonds around Tyr by interacting with the bulk, thus tuning the driving force required for Tyr oxidation.
Topics: Arginine; Electron Spin Resonance Spectroscopy; Oxidation-Reduction; Photosystem II Protein Complex; Protons
PubMed: 32359083
DOI: 10.1111/ppl.13115 -
Research in Microbiology 2016(51)V NMR spectroscopy was used for detection and identification of cell-associated vanadate (V(5+)) species after exposure of Phycomyces blakesleeanus mycelium, in...
(51)V NMR spectroscopy was used for detection and identification of cell-associated vanadate (V(5+)) species after exposure of Phycomyces blakesleeanus mycelium, in exponential phase of growth, to sodium orthovanadate. Complete disappearance of monomer and dimer signals and decreased intensity of the tetramer signal were observed about 40 min after treatment. Simultaneously, a signal at -532 ppm, with increasing intensity, was detected in spectra. The time-dependent rise in this signal was connected to a decrease in the extracellular monomer signal, indicating its transport into the cell. The signal at -532 ppm did not belong to any known simple oxido-vanadate species, nor to a complex with any of the components of experimental medium. This signal was the only one present in spectrum of the mycelium washed 35 min after treatment, and the only one observed in mycelium cultivated on vanadate-contained medium. Therefore, its appearance can be attributed to intracellular complexation, and may represent an important detoxification mechanism of the cell exposed to a physiologically relevant concentration of vanadate. Experiments ((51)V NMR and polarography) performed with Cd-pretreated mycelium (inhibitor of an enzyme responsible for V(5+) reduction) and ferricyanide-preincubated mycelium excluded the possibility of V(5+) tetramer's entry into the cell.
Topics: Inactivation, Metabolic; Magnetic Resonance Spectroscopy; Mycelium; Phycomyces; Vanadates
PubMed: 27164550
DOI: 10.1016/j.resmic.2016.04.012 -
Analytical Sciences : the International... Aug 2003A selective, sensitive, rapid and simple-handling analytical method for the determination of cyanide at low detection limits in surface and underground water, soil and...
A selective, sensitive, rapid and simple-handling analytical method for the determination of cyanide at low detection limits in surface and underground water, soil and industrial waste samples was developed. The method is based on a reaction, proposed by Guilbault and Kramer, where free cyanide reacts with p-nitrobenzaldehyde to form an intermediate cyanohydrin, which reacts with o-dinitrobenzene to give a highly colored purple compound. The original procedure was modified for application in a small device containing a gas-permeable membrane. The cyanide is converted in the volatile hydrogen cyanide, which permeates through a PTFE membrane, reaching colorimetric reagents. In order to obtain semi-quantitative results, printed color scales were built. The method allows rapid, accurate, selective, low-cost and simple-handling determinations of free cyanide, even in complex samples. About 150 real samples were analyzed. Less than 10 ng of free cyanide per ml (10 microg l(-1)) can be easily detected. For more concentrated solutions, the results had been compared to those obtained using differential pulse polarography. The standard addition method was used for more diluted solutions.
PubMed: 12945666
DOI: 10.2116/analsci.19.1139 -
Acta Crystallographica. Section E,... Dec 2016The lattice of 5,7,12,14-tetra-hydro-5,14:7,12-bis-([1,2]benzeno)-penta-cene-6,13-dione, CHO, at 173 K has triclinic (-1) symmetry and crystallizes with four...
The lattice of 5,7,12,14-tetra-hydro-5,14:7,12-bis-([1,2]benzeno)-penta-cene-6,13-dione, CHO, at 173 K has triclinic (-1) symmetry and crystallizes with four independent half-mol-ecules in the asymmetric unit. Each mol-ecule is generated from a CHO substructure through an inversion center at the centroid of the central quinone ring, generating a wide H-shaped mol-ecule, with a dihedral angle between the mean planes of the terminal benzene rings in each of the two symmetry-related pairs over the four mol-ecules of 68.6 (1) (), 65.5 (4) (), 62.3 (9) (), and 65.8 (8)° (), an average of 65.6 (1)°. This compound has applications in gas-separation membranes constructed from polymers of intrinsic microporosity (PIM). The title compound is a product of a double Diels-Alder reaction between anthracene and -benzo-quinone followed by de-hydrogenation. It has also been characterized by cyclic voltammetry and rotating disc electrode polarography, FT-IR, high resolution mass spectrometry, elemental analysis, and H NMR.
PubMed: 27980819
DOI: 10.1107/S2056989016017461 -
Frontiers in Chemistry 2014A great challenge in the area of heavy metal trace detection is the development of electrochemical techniques and devices which are user-friendly, robust, selective,... (Review)
Review
A great challenge in the area of heavy metal trace detection is the development of electrochemical techniques and devices which are user-friendly, robust, selective, with low detection limits and allowing fast analyses. This review presents the major contribution of the French scientific academic community in the field of electrochemical sensors and electroanalytical methods within the last 20 years. From the well-known polarography to the up-to-date generation of functionalized interfaces, the different strategies dedicated to analytical performances improvement are exposed: stripping voltammetry, solid mercury-free electrode, ion selective sensor, carbon based materials, chemically modified electrodes, nano-structured surfaces. The paper particularly emphasizes their advantages and limits face to the last Water Frame Directive devoted to the Environmental Quality Standards for heavy metals. Recent trends on trace metal speciation as well as on automatic "on line" monitoring devices are also evoked.
PubMed: 24818124
DOI: 10.3389/fchem.2014.00019 -
Reactive Oxygen Species (Apex, N.C.) Sep 2018In this work, we investigated the effects of graphene quantum dots (GQDs) on copper redox-mediated free radical generation and cell injury. Using electron paramagnetic...
In this work, we investigated the effects of graphene quantum dots (GQDs) on copper redox-mediated free radical generation and cell injury. Using electron paramagnetic resonance (EPR) spectrometry in conjunction with 5,5-dimethyl-1-pyrroline -oxide (DMPO) as a spin trap, we found that GQDs at a concentration as low as 1 μg/ml significantly inhibited Cu(II)/HO-mediated hydroxyl radical formation. GQDs also blocked Cu(II)-catalyzed nucleophilic addition of HO to DMPO to form a DMPO-OH adduct in the absence of HO, suggesting a potential for GQDs to inhibit copper redox activity. Indeed, we observed that the presence of GQDs prevented HO-mediated reduction of Cu(II) to Cu(I) though GQDs themselves also caused the reduction of Cu(II) to Cu(I). To further investigate the effects of GQDs on copper redox activity, we employed the Cu(II)/hydroquinone system in which copper redox activity plays an essential role in the oxidation of hydroquinone to semiquinone radicals with consequent oxygen consumption. Using oxygen polarography as well as EPR spectrometry, we demonstrated that the presence of GQDs drastically blocked the oxygen consumption and semiquinone radical formation resulting from the reaction of Cu(II) and hydroquinone. These results suggested that GQDs suppressed free radical formation via inhibiting copper redox activity. Lastly, using cultured human cardiomyocytes, we demonstrated that the presence of GQDs also protected against Cu(II)/HO-mediated cardiac cell injury as indicated by morphological changes (e.g., cell shrinkage and degeneration). In conclusion, our work shows, for the first time, the potential for using GQDs to counteract copper redox-mediated biological damage.
PubMed: 30177973
DOI: 10.20455/ros.2018.855 -
Current Protocols in Human Genetics Oct 2009The oxidative phosphorylation (OXPHOS) system consists of five multimeric complexes embedded in the mitochondrial inner membrane. They work in concert to drive the...
The oxidative phosphorylation (OXPHOS) system consists of five multimeric complexes embedded in the mitochondrial inner membrane. They work in concert to drive the aerobic synthesis of ATP. Mitochondrial and nuclear DNA mutations affecting the accumulation and function of these enzymes are the most common cause of mitochondrial diseases and have also been associated with neurodegeneration and aging. For this reason, several approaches for the assessment of the OXPHOS system enzymes have been developed. Based on the methods described elsewhere, the assays describe methods that form a biochemical characterization of the OXPHOS system in cells and mitochondria isolated from cultured cells or tissues.
Topics: Cell Respiration; Cells, Cultured; Humans; Mitochondria; Oxidative Phosphorylation; Polarography; Spectrophotometry
PubMed: 19806590
DOI: 10.1002/0471142905.hg1903s63