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Biological Trace Element Research Feb 2021Dules auriga, a native Brazilian teleost, was applied as a sentinel species regarding metal contamination at Ilha Grande Bay, previously considered a reference site in...
Dules auriga, a native Brazilian teleost, was applied as a sentinel species regarding metal contamination at Ilha Grande Bay, previously considered a reference site in Southeastern Brazil. Cytosolic (S50) and metallothionein-bound (HTS50) hepatic iron (Fe), zinc (Zn), copper (Cu), manganese (Mn), cadmium (Cd), and silver (Ag) were determined by inductively coupled plasma optical emission spectrometry (ICP-OES), while metallothionein (MT) concentrations were determined by polarography. Ag concentrations in both cytosolic fractions were below the limit of detection. All other HTS50 metal contents were significantly lower than S50 contents. No significant associations were found for MT. Fe and Mn S50 were positively and moderately correlated to total length, as well as HTS50 Mn, while total weight was correlated to both Mn fractions, suggesting that environmental Mn and Fe concentrations may influence fish growth. A moderate correlation between the condition factor and the S50 Cu fraction was observed, also indicating that Cu may affect fish growth. Inter-element correlations were observed, including between Cd, a toxic element, and Mn and Zn, both essential elements. Calculated molar ratios indicate that both Mn and Zn are in molar excesses compared with Cd, corroborating literature assessments regarding protective Mn and Zn effects against Cd. Lack of MT correlations suggests that metal concentrations may not be high enough to reach an MT induction threshold and that MT variability is probably linked to environmental metal concentrations. Therefore, the increased environmental contaminant levels observed in the study area indicate the need for biomonitoring efforts aiming at the application of efficient mitigation measures.
Topics: Animals; Brazil; Cadmium; Copper; Metallothionein; Metals; Metals, Heavy; Water Pollutants, Chemical; Zinc
PubMed: 32447576
DOI: 10.1007/s12011-020-02195-8 -
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 -
Journal of Analytical Methods in... 2020products have been used for the control of diabetes (type 2) across the world. Experimental and clinical evaluations of galegine substance produced by a medicinal plant...
products have been used for the control of diabetes (type 2) across the world. Experimental and clinical evaluations of galegine substance produced by a medicinal plant () provided the pharmacological and chemical basis for metformin discovery which was confirmed for diabetes therapy. In this paper, the molecularly imprinted polymer (MIP) was synthesized for galegine, using galegine as a template molecule, methacrylic acid (MAA) as a functional monomer, ethylene glycol dimethacrylate (EGDMA) as a cross-linker, azobisisobutyronitrile (AIBN) as a reaction initiator, and acetonitrile as a solvent. The assisted functional groups, morphology, topographic image of surface, and crystalline structure of synthesized MIP were characterized by FT-IR spectroscopy, field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM) images, and XRD diffraction pattern techniques, respectively. Also, the performance of the mentioned electrode was quantified and qualified by the differential pulse voltammetry technique (DPV). The galegine amount was determined with the polarographic technique. In this research, the galegine extraction conditions were optimized and graphene nanoparticles were used to increase the adsorption. In addition, different parameters affecting extraction were investigated such as MIP adsorbent amount, pH of solution, effect of the surfactant, and ionic compound to achieve high recovery percent. The recovery percent, limit of detection (LOD), limit of quantification (LOQ), and relative standard deviation (RSD %) were 4.101 g·mL, 12.427 g·mL, and 1.199% ( = 3), respectively. The results show that the prepared MIP can be used as an effective and inexpensive adsorbent for preconcentration and galegine extraction from a natural sample. It is noteworthy that this developed method was used successfully to determine galegine extracted from .
PubMed: 32190402
DOI: 10.1155/2020/3646712 -
Journal of Biological Inorganic... Mar 2020Oxygen affinity is an important property of metalloproteins that helps elucidate their reactivity profile and mechanism. Heretofore, oxygen affinity values were... (Review)
Review
Oxygen affinity is an important property of metalloproteins that helps elucidate their reactivity profile and mechanism. Heretofore, oxygen affinity values were determined either using flash photolysis and polarography techniques that require expensive instrumentation, or using oxygen titration methods which are erroneous at low nanomolar and at high millimolar oxygen concentrations. Here, we describe an inexpensive, easy-to-setup, and a one-pot method for oxygen affinity measurements that uses the enzyme chlorite dismutase (Cld) as a precise in situ oxygen source. Using this method, we measure thermodynamic and kinetic oxygen affinities (K and K) of different classes of heme and non-heme metalloproteins involved in oxygen transport, sensing, and catalysis. The method enables oxygen affinity measurements over a wide concentration range from 10 nM to 5 mM which is unattainable by simply diluting oxygen-saturated buffers. In turn, we were able to precisely measure oxygen affinities of a model set of eight different metalloproteins with affinities ranging from 48 ± 3 nM to 1.18 ± 0.03 mM. Overall, the Cld method is easy and inexpensive to set up, requires significantly lower quantities of protein, enables precise oxygen affinity measurements, and is applicable for proteins exhibiting nanomolar-to-millimolar affinity values.
Topics: Kinetics; Models, Molecular; Oxidoreductases; Oxygen; Thermodynamics
PubMed: 31897725
DOI: 10.1007/s00775-019-01750-6 -
Nature Communications Dec 2019In the brain, increased neural activity is correlated with increases of cerebral blood flow and tissue oxygenation. However, how cerebral oxygen dynamics are controlled...
In the brain, increased neural activity is correlated with increases of cerebral blood flow and tissue oxygenation. However, how cerebral oxygen dynamics are controlled in the behaving animal remains unclear. We investigated to what extent cerebral oxygenation varies during locomotion. We measured oxygen levels in the cortex of awake, head-fixed mice during locomotion using polarography, spectroscopy, and two-photon phosphorescence lifetime measurements of oxygen sensors. We find that locomotion significantly and globally increases cerebral oxygenation, specifically in areas involved in locomotion, as well as in the frontal cortex and the olfactory bulb. The oxygenation increase persists when neural activity and functional hyperemia are blocked, occurred both in the tissue and in arteries feeding the brain, and is tightly correlated with respiration rate and the phase of respiration cycle. Thus, breathing rate is a key modulator of cerebral oxygenation and should be monitored during hemodynamic imaging, such as in BOLD fMRI.
Topics: Animals; Brain; Cerebrovascular Circulation; Female; Hemodynamics; Humans; Locomotion; Magnetic Resonance Imaging; Male; Mice, Inbred C57BL; Olfactory Bulb; Oxygen; Respiration; Wakefulness
PubMed: 31797933
DOI: 10.1038/s41467-019-13523-5 -
Biosensors Nov 2019The benzodiazepine class of drugs are characterised by a readily electrochemically reducible azomethine group. A number are also substituted by other electrochemically... (Review)
Review
The benzodiazepine class of drugs are characterised by a readily electrochemically reducible azomethine group. A number are also substituted by other electrochemically active nitro, N-oxide, and carbonyl groups, making them readily accessible to electrochemical determination. Techniques such as polarography, voltammetry, and potentiometry have been employed for pharmaceutical and biomedical samples, requiring little sample preparation. This review describes current developments in the design and applications of electrochemical-based approaches for the determination of the benzodiazepine class of drugs form their introduction in the early 1960s to 2019. Throughout this period, state-of-the-art electroanalytical techniques have been reported for their determination. Polarography was first employed focused on mechanistic investigations. Subsequent studies showed the adsorption of many the benzodiazepines at Hg electrodes allowed for the highly sensitive technique of adsorptive stripping voltammetry to be employed. The development and introduction of other working electrode materials such as carbon led to techniques such as voltammetry to become commonly reported, and the modification of these electrodes has now become the most commonly employed approach using molecularly imprinting and nanotechnology.
Topics: Adsorption; Benzodiazepines; Biosensing Techniques; Electrochemical Techniques; Electrodes; Mercury; Molecular Structure; Surface Properties
PubMed: 31684040
DOI: 10.3390/bios9040130 -
Bulletin of Experimental Biology and... Sep 2019Activity of the energy production systems in rabbit liver and kidney under conditions of unfavorable vibration exposure was studied by the polarography method using a...
Activity of the energy production systems in rabbit liver and kidney under conditions of unfavorable vibration exposure was studied by the polarography method using a galvanic-type closed oxygen sensor. The rate of oxidation of endogenous substrates by mitochondria was determined by the tissue and was 5.2±0.6 and 8.13±1.4 (ng-atom O)×min×mg protein for liver and kidney of intact animals, respectively. After 21 vibration sessions against the background of inhibition of NAD-dependent substrate oxidation in liver mitochondria, the rate metabolism of exogenous succinic acid increased by 44% and then decreased with prolongation of the effect, which indicated impaired function of the respiratory chain. Similar fluctuations of the parameters were revealed in kidney mitochondria, though their amplitude was lower. The study of bioenergetic mechanisms of hypoxia in various tissues makes it possible to determine the targets for the pharmacological action of antihypoxic drugs.
Topics: 2,4-Dinitrophenol; Animals; Electron Transport; Flavin-Adenine Dinucleotide; Hypoxia; Kidney; Liver; Male; Mitochondria; NAD; Organ Specificity; Oxidative Phosphorylation; Rabbits; Succinic Acid; Vibration
PubMed: 31606807
DOI: 10.1007/s10517-019-04583-0 -
Molecular Medicine Reports Nov 2019Volatile anesthetics may protect the heart against ischemia‑reperfusion injury via the direct action on mitochondrial complexes and by regulating the production of...
Volatile anesthetics may protect the heart against ischemia‑reperfusion injury via the direct action on mitochondrial complexes and by regulating the production of reactive oxygen species (ROS). Recently, we reported that isoflurane induced the attenuation of mitochondrial respiration caused by complex I substrates. This process was not associated with endogenous production of mitochondrial nitric oxide (NO). In the present study, we investigated the effects of isoflurane on mitochondrial respiration and ROS production using complex II substrates. The detailed mechanism of these effects was explored with regards to NO production and the expression of mitochondrial ATP‑dependent K+ (mKATP) channels. Mitochondria were isolated from the heart of Sprague‑Dawley rats. The respiratory rates of mitochondria (0.5 mg/ml) were measured via polarography at 28˚C with computer‑controlled Clark‑type O2 electrodes. The complex II substrate succinate (5 mM) was used; 0.25 mM of isoflurane was administered prior to ADP‑initiated state 3 respiration. The mitochondrial membrane potential (ΔΨm) was measured under treatment with the substrate succinate, or succinate in the presence of the complex I inhibitor rotenone. The detection was achieved in a cuvette‑based spectrophotometer operating at wavelengths of 503 nm (excitation) 527 nm (emission) in the presence of 50 nM of the fluorescent dye rhodamine 123. The H2O2 release rates in the mitochondria were measured spectrophotometrically with succinate, or succinate and rotenone using the fluorescent dye Amplex red (12.5‑25 µM). The results indicated that isoflurane increased the state 3 and 4 respiration rates caused by succinate, which were higher than those noted in the control group in the presence of succinate alone. The NOS inhibitor L‑NIO or the NO‑sensitive guanylyl cyclase 1H‑[1,2,4]oxadiazolo[4,3‑a]quinoxalin‑1‑one did not inhibit the increase in the respiration rate (state 3) induced by isoflurane. The ROS scavengers SPBN and manganese (III) tetrakis (4‑benzoic acid) porphyrin chloride inhibited the increase in the respiration rate (state 3 and 4) induced by isoflurane. This effect was not noted for the putative KATP channel blockers 5‑hydroxydecanoic acid and glibenclamide. Isoflurane caused a greater decrease in the concentration of H2O2 during ADP‑initiated state 3 respiration, and L‑N5‑(1‑Iminoethyl)‑ornithine did not inhibit this effect. In conclusion, isoflurane was determined to modulate mitochondrial respiration and ROS production caused by the complex II substrate succinate. These effects were independent of endogenous mitochondrial NO generation and mitochondrial KATP channel opening.
Topics: Animals; Cell Respiration; Electron Transport; Electron Transport Complex II; Hydrogen Peroxide; Isoflurane; Male; Membrane Potential, Mitochondrial; Mitochondria; Nitric Oxide; Oxygen Consumption; Potassium Channels; Rats; Reactive Oxygen Species
PubMed: 31545457
DOI: 10.3892/mmr.2019.10658 -
Bulletin of Environmental Contamination... Oct 2019The identification of estuarine sentinel species is of paramount importance. The potential of the species Dules auriga sampled from Guanabara Bay, Brazil regarding metal...
The identification of estuarine sentinel species is of paramount importance. The potential of the species Dules auriga sampled from Guanabara Bay, Brazil regarding metal contamination was assessed. Hepatic metallothionein (MT) and Fe, Zn, Cu, Mn, Cd and Ag concentrations were determined in cytosolic fractions (S50 and HT S50) by polarography and ICP-OES, respectively. HT S50 Fe, Mn and Zn were lower than in the S50 fraction, indicating MT-detoxification. MT was correlated to HT S50 Zn, indicating Zn homeostasis. Zn was negatively correlated to weight (TW) and length (TL), suggesting environmental Zn influence. A moderate negative correlation between HT S50 Cu and the condition factor (CF) was observed, indicating that increasing environmental Cu concentrations may decrease D. auriga CF. Several inter-elemental correlations were observed. No MT, TW and TL correlations were found. Thus, MT variability is probably linked to environmental metal concentrations. D. auriga fulfills most sentinel requisites, and MT may be an adequate metal contamination biomarker in this species.
Topics: Animals; Bays; Brazil; Cytosol; Environmental Monitoring; Estuaries; Fishes; Liver; Metallothionein; Metals, Heavy; Water Pollutants, Chemical
PubMed: 31214755
DOI: 10.1007/s00128-019-02654-6 -
American Journal of Physiology.... Aug 2019High energy expenditure is reported in cystic fibrosis (CF) animal models and patients. Alterations in skeletal muscle oxidative capacity, fuel utilization, and the...
High energy expenditure is reported in cystic fibrosis (CF) animal models and patients. Alterations in skeletal muscle oxidative capacity, fuel utilization, and the creatine kinase-phosphocreatine system suggest mitochondrial dysfunction. Studies were performed on congenic C57BL/6J and F508del () mice. Indirect calorimetry was used to measure gas exchange to evaluate aerobic capacity during treadmill exercise. The bioenergetic function of skeletal muscle subsarcolemmal (SSM) and interfibrillar mitochondria (IFM) was evaluated using an integrated approach combining measurement of the rate of oxidative phosphorylation by polarography and of electron transport chain activities by spectrophotometry. CF mice have reduced maximal aerobic capacity. In SSM of these mice, oxidative phosphorylation was impaired in the presence of complex I, II, III, and IV substrates except when glutamate was used as substrate. This impairment appeared to be caused by a defect in complex V activity, whereas the oxidative system of the electron transport chain was unchanged. In IFM, oxidative phosphorylation and electron transport chain activities were preserved, whereas complex V activity was reduced, in CF. Furthermore, creatine kinase activity was reduced in both SSM and IFM of CF skeletal muscle. The decreased complex V activity in SSM resulted in reduced oxidative phosphorylation, which could explain the reduced skeletal muscle response to exercise in CF mice. The decrease in mitochondrial creatine kinase activity also contributed to this poor exercise response.
Topics: Animals; Cystic Fibrosis; Cystic Fibrosis Transmembrane Conductance Regulator; Energy Metabolism; Female; Male; Mice; Mice, Inbred C57BL; Mice, Inbred CFTR; Mice, Transgenic; Mitochondria, Muscle; Muscle, Skeletal; Oxidative Phosphorylation; Oxidative Stress; Physical Conditioning, Animal; Sequence Deletion
PubMed: 31211618
DOI: 10.1152/ajpendo.00064.2019