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PubMed1991

[Homeorrhetic modifications produced by a beta-agonist in the muscle and adipose tissues of the rat].

A repartitioning effect was observed in young rats after a chronic treatment with a nonselective beta-agonist administered subcutaneously. An increase in carcass protein (P less than 0.05) accompanied by a reduction in fat stores (P less than 0.01) and an increase in back fat oxygen consumption (P less than 0.05) were found in treated animals. The muscle mass accretion should be attributed to a reduction in muscle protein degradation, based on lower activity of the proteolytic enzyme cathepsin A in treated rats, rather than to changes in protein synthesis, assessed by an amino-acid incorporation technique. The anabolic actions of this compound apparently involve changes in muscle prostaglandin E2 and reduction-oxidation state.

Adipose Tissue↗
PubMed1990

Repartitioning effect of a mixed beta-agonist on body composition.

Subcutaneous administration of a mixed beta-agonist to young rats induced no changes in animal growth and food conversion efficiency. However, a repartitioning effect was found with increases in lean tissue and decreases in body fat. The enhancement of muscle protein deposition was attributed to a fall in protein breakdown as muscular cathepsin A activity was lower in treated rats. A reduction of muscle reduction-oxidation state is associated to those changes in protein metabolism.

Adrenergic beta-Agonists↗
PubMed1975

Redox metabolism of glutathione in the red blood cell.

A theoretical study of the biochemical and clinical aspects of the reduction-oxidation metabolism of glutathione in the mature red blood cell is presented. A summarizing survey of the literature data has led to the formulation of a mathematical model which comprises the kinetic properties of the enzymes partaking in the hexose monophosphate pathway (HMP) and the oxidation of NADPH and GSH. The model takes the form of a system of differential equations describing the motion of metabolites in one cell. The interactions between metabolites ane enzymes, in particular between glutathione and the SH-dependent enzymes of glucose phosphorylation and HMP have been included into the model...

Disulfides↗
PubMed1989

[Changes in the redox potential of serum samples following in vitro irradiation--an indicator of malignant tumor growth].

In serum samples of healthy persons and patients with malignant neoplasia the reduction-oxidation-potentials were determined. Measurements were made in untreated sera and after irradiation with different doses. Sera of healthy persons showed a decrease that of tumor patients an increase of redox-potential values. With this method malignant tumor growth can be demonstrated. It does not yet permit any statements on tumor localisation. On the other hand conclusions seem to be possible on growth speed of neoplasia. To our hitherto existing experiences estimations of redox-potential are applicable to the diagnosis of fast growing recurrences and metastases in tumor after-care, but can also support the therapeutic procedure decisively in defined differential diagnostic problems and in tumors of dignity in question.

Blood↗
PubMed1983

The importance of the intramolecular disulfide bridges in porcine somatotropin for its biological activity.

The dependance of the porcine somatotropin activity on the entireness of the intrachain disulfide bridges is investigated in three biological systems: bioassay in vivo, radioimmuno assay and receptor assay with rat liver membranes. Cleavage of the disulfide bridges is accomplished by reduction, oxidation and sulfitolysis, respectively. In no case is the hormone activity completely abolished with regard to measurements in the bioassay and radioimmuno assay. In the radioligand assay with rat liver membranes neither native porcine somatotropin nor the treated hormone preparations are bound by the receptors.

Amino Acids↗
PubMed1995

Changes of corneal redox state in diabetic animal models.

Metabolic and biochemical changes of the corneal epithelium and endothelium were studied in experimental diabetic animal models. Ocular redox fluorometry was used to noninvasively determine tissue reduction-oxidation (redox) changes in organ cultured rabbit corneas incubated in high glucose concentration media, alloxan-induced diabetic rabbits, and nonobese diabetic mice. The ratio of autofluorescence from reduced pyridine nucleotide to oxidized flavoproteins (PN/Fp) was used as the indicator of the redox state. Chemical assays for NADH and NAD+ were performed on in vitro materials. Analysis of corneal endothelial morphology using specular microscopy was performed to study possible correlations with metabolic changes. Both the PN/Fp and NADH/NAD+ ratios increased in the corneal endothelium under all experimental conditions. Changes in redox state were not observed in the corneal epithelium in any of the models. Morphologic analysis of the corneal endothelium revealed no significant changes. These results indicate that redox changes occur in the diabetic corneal endothelium, but not the corneal epithelium. Ocular redox fluorometry is capable of detecting changes in the corneal endothelial redox state noninvasively.

Animals↗
PubMed1996

Use of near-infrared spectroscopy to monitor tissue oxygenation.

Near-infrared spectroscopy (NIRS) is a relatively new tool that allows continuous noninvasive monitoring of in vivo oxygenation in selected tissues such as muscle and brain. Since hemoglobin, myoglobin, and cytochrome c oxidase are the only biological compounds to exhibit variable absorption of near-infrared (NIR) light in response to changes in oxygen availability, NIRS can determine changes in tissue oxygenation. NIRS can measure regional blood volume, local oxyhemoglobin and deoxyhemoglobin contents, and reduction-oxidation state of cellular mitochondrial cytochrome a, a3. As a comprehensive monitor of regional oxygen metabolism, NIRS has been applied in certain clinical and research settings. Despite technical limitations and the lack of definite "gold standards" to allow validation of results, NIRS remains a promising technology with applications in both the critical care environment and the research laboratory studying mechanisms of oxygen metabolism.

Blood Volume↗
PubMed2000

Regulation of sodium currents through oxidation and reduction of thiol residues.

Changes in redox state are involved in several physiological and pathophysiological processes. Previous experiments have demonstrated that nitric oxide can function as a reactive oxygen species, inhibiting neuronal sodium currents by nitrosylation of thiol residues. We hypothesized that nitric oxide and thiol oxidizers similarly modulate voltage-dependent sodium currents. Voltage-dependent sodium currents were studied with the whole-cell patch-clamp technique in NB41A3 neuroblastoma cells. The nitric oxide donor 3-(2-hydroxy-2-nitroso-1-propylhydrazino)-1-propanamine did not affect sodium currents. In contrast, the thiol oxidizers thimerosal and 4,4'-dithiopyridine significantly inhibited sodium currents. The effect of thimerosal persisted after washout, but could be fully reversed by the reducing agent dithiothreitol. Reduced glutathione did not restore the sodium current amplitude when given extracellularly, while intracellular glutathione prevented the inhibitory effect of thimerosal. Pretreatment with the alkylating agent N-ethylmaleimide blocked the inhibitory action of thimerosal. Thiol oxidation caused a shift in the voltage dependence of fast and slow inactivation to more hyperpolarized potentials without concomitant effects on the voltage dependence of activation. Mercaptoethanol and reduced glutathione enhanced sodium currents by shifting the voltage dependence of inactivation to depolarized potentials. These results demonstrate that the oxidation and reduction of thiol residues alters the properties of voltage-sensitive sodium channels and may play an important role in the regulation of membrane excitability.

Animals↗
PubMed2006

Effects of sulfur dioxide and nitric oxide on mercury oxidation and reduction under homogeneous conditions.

This paper is particularly related to elemental mercury (Hg0) oxidation and divalent mercury (Hg2+) reduction under simulated flue gas conditions in the presence of nitric oxide (NO) and sulfur dioxide (SO2). As a powerful oxidant and chlorinating reagent, Cl2 has the potential for Hg oxidation. However, the detailed mechanism for the interactions, especially among chlorine (Cl)-containing species, SO2, NO, as well as H2O, remains ambiguous. Research described in this paper therefore focused on the impacts of SO2 and NO on Hg0 oxidation and Hg2+ reduction with the intent of unraveling unrecognized interactions among Cl species, SO2, and NO most importantly in the presence of H2O. The experimental results demonstrated that SO2 and NO had pronounced inhibitory effects on Hg0 oxidation at high temperatures when H2O was also present in the gas blend. Such a demonstration was further confirmed by the reduction of Hg2+ back into its elemental form. Data revealed that SO2 and NO were capable of promoting homogeneous reduction of Hg2+ to Hg0 with H2O being present. However, the above inhibition or promotion disappeared under homogeneous conditions when H2O was removed from the gas blend.

Air Pollutants↗
PubMed1991

Oxidation and reduction of exogenous cytochrome c by the activity of the respiratory chain.

Oxidation of exogenous NADH by isolated rat liver mitochondria is generally accepted to be mediated by endogenous cytochrome c which shuttles electrons from the outer to the inner mitochondrial membrane. More recently it has been suggested that, in the presence of added cytochrome c, NADH oxidation is carried out exclusively by the cytochrome oxidase of broken or damaged mitochondria. Here we show that electrons can be transferred in and out of intact mitochondria. It is proposed that at the contact sites between the inner and the outer membrane, a "bi-trans-membrane" electron transport chain is present. The pathway, consisting of Complex III, NADH-b5 reductase, exogenous cytochrome c and cytochrome oxidase, can channel electrons from the external face of the outer membrane to the matrix face of the inner membrane and viceversa. The activity of the pathway is strictly dependent on both the activity of the respiratory chain and mitochondrion integrity.

Adenosine Diphosphate↗
PubMed2000

Tandem one-Pot palladium-catalyzed reductive and oxidative coupling of benzene and chlorobenzene

The in situ combination of oxidative coupling of benzene to biphenyl and reductive coupling of chlorobenzene (also to biphenyl) using palladium catalysts (Pd(2+)/Pd(0)) is described. In each cycle, the reductive process regenerates the catalyst for the oxidative process and vice versa. Kinetic investigations show that the reaction rate depends on [C(6)H(6)], [C(6)H(6)Cl], and catalyst loading, with E(a)() = 13 kcal mol(-)(1). The reduced palladium catalyst undergoes deactivation through aggregation and precipitation, but it is observed that during this deactivation process the Pd(0) becomes an active catalyst for the reductive coupling of chlorobenzene. Accordingly, while Pd(0)/C particles are inactive, Pd(0) colloids do catalyze the tandem reaction. Conversion is increased in the presence of a phase-transfer catalyst, presumably due to stabilization of the active Pd(0) clusters. The two halves of the catalytic cycle are examined in the light of previous research, regarding analogous oxidative and reductive coupling reactions, using stoichiometric amounts of PdCl(2) and Pd(0), respectively. The roles of homogeneous PdCl(2) and Pd(0) clusters are discussed.

Journal Article↗
PubMed2004

Self-stimulated NO reduction and CO oxidation by iron oxide clusters.

It is shown that a bare Fe2O3 cluster can oxidize CO to form CO2 and reduce NO to form N2 by undergoing compositional changes between Fe2O2 and Fe2O3 states. Investigations based on density functional theory reveal that the above reactions occur through an interesting sequence. An initial CO or NO adsorbed on the Fe2O3 weakens one of the O-Fe bonds to create a loosely attached O site. A subsequent CO gets oxidized by this O and transforms the cluster to a reduced Fe2O2 that now reduces NO via multiple oxidation and reduction steps that return the cluster to the oxidized Fe2O3 state. It is shown that the small size allows geometrical rearrangements that eliminate reaction barriers, allowing energetics and not barriers to be the primary motor for catalysis. Detailed reaction paths and the corresponding energetics are presented to illustrate the viability of the proposed mechanisms.

Adsorption↗
PubMed2003

Tissue angiotensin-converting-enzyme (ACE) deficiency leads to a reduction in oxidative stress and in atherosclerosis: studies in ACE-knockout mice type 2.

UNLABELLED: Background- Angiotensin II, produced by angiotensin-converting-enzyme (ACE), enhances oxidative stress and atherogenesis. In this study, we analyzed whether tissue ACE deficiency in ACE-knockout mice type-2 would affect their oxidative status. Moreover, by crossbreeding the ACE-knockout mice with atherosclerotic apolipoprotein E (apo E)-deficient (E0) mice, we questioned whether tissue ACE deficiency affects atherogenesis. METHODS AND RESULTS: ACE-deficient mice type-2 (ACE+/-) exhibited reduced serum lipid peroxidation compared with ACE+/+ mice. Peritoneal macrophages from ACE+/- mice demonstrated lower oxidative status, as exhibited by decreases of 47%, 33% 56%, and 51%, in their lipid peroxides, superoxide release, dichlorofluorescein fluorescence, and LDL oxidation, respectively, compared with ACE+/+ mice. ACE+/- mice crossbred with E0 mice, resulting in atherosclerotic mice heterozygous for ACE (ACE+/-/E0 mice), exhibited reduced lipid peroxidation, increased paraoxonase activity, and lower macrophage LDL oxidation compared with E0 and ACE+/+/E0 mice. ACE+/-/E0 mice also exhibited reduced NADPH-induced aortic superoxide ion production by 52% and a reduction of 43% in their atherosclerotic lesion size compared with E0 mice. Finally, 2 animals genotyped as homozygous-knockout for both ACE and APOE genes (ACE-/-/E0), exhibited a striking reduction of 86% in their atherosclerotic lesion area compared with E0 mice. CONCLUSIONS: Reduction of tissue ACE with the ACE-knockout mouse type-2 model inhibited oxidative stress and atherogenesis.

Animals↗
PubMed1975

Reversible extinction of the morphogen in bone matrix by reduction and oxidation of disulfide bonds.

Beta-Mercaptoethanol (beta-ME) or dithiothreitol (DTT) reduction extinguishes the capacity of bone matrix gelatin to produce new bone following implantation in a muscle pouch. If the reducing solution is used in concentrations of 50 mmoles/l or less, the extinction can be partially reversed by bubbling of oxygen through the solution for one hour. Sulfhydryl group blocking reagents prevent reoxidation of reduced bone gelatin, and restoration of the bone morphogenetic property (BMP). Unspecific borohydride reduction at 37 degrees destroys bone yield irreversibly, but at 2 degrees reduction of free aldehyde groups in bone gelatin does not prevent beta-ME and DTT reversible extinction. These observations are interpreted to suggest that the disulphide linkage may be an essential part of the biologically active conformation of either a non-collagenous bone morphogenetic polypeptide firmly bound to collagen or a collagen by-product entrapped within a water insoluble gel matrix.

Animals↗
PubMed1976

A relation between (NAD+)/(NADH) potentials and glucose utilization in rat brain slices.

Changes in several parameters involved in the control of metabolism were correlated with changes in glucose utilization in rat brain slices incubated under conditions which reduced glucose oxidation by 40 to 70%. The parameters included: the concentrations of ATP, ADP, AMP, and the adenylate energy charge; the cytoplasmic oxidation-reduction state ([NAD+]/[NADH]), determined from the [pyruvate]/[lactate] equilibrium; the mitochondrial oxidation-reduction state, determined from the [NH4+] ]2-oxoglutarate]/[glutamate] Equilibrium; the cytoplasmic and mitochondrial oxidation-reduction potentials (in volts), calculated from the respective [NAD+]/ [NADH] ratios using the Nernst equation; and the difference between the cytoplasmic and mitochondrial [NAD+]/[NADH] potentials. The conversion of [3, 4-14C] glucose to 14CO2 and of [U-14C] glucose to acetylcholine and to lipids, proteins, and nucleic acids by the brain slices were also determined. The values obtained by subtracting the mitochondrial from the cytoplasmic [NAD+1/[NADH] potentials correlated more closely with glucose utilization than did other parameters, under the conditions studied. For the synthesis of acetylcholine, the correlation coefficient was 0.96, and for the production of 14CO2 from [3, 4-14C] glucose it was 0.82.

Adenine Nucleotides↗
PubMed1984

Oxidative and reductive reactions of sulphhaemoglobin with various reagents correlated with changes in quaternary structure of the protein.

The absorption maxima in the Soret region and near 620nm of sulphhaemoglobin shifted from 419.5nm to 423nm and from 623nm to 619nm respectively with a decrease in oxygen concentrations of the sulphhaemoglobin solution [101.3, 20.3 and 0 kPa (760, 152 and 0 mmHg) partial pressures]. The major changes in the positions of the absorption maxima occurred drastically at oxygen concentrations between 20.3 kPa and 0 kPa, suggesting that the quaternary structure of sulphhaemoglobin has changed from the R to the T state. Inositol hexaphosphate, a known allosteric effector of haemoglobin, enhanced the shift in peak location. This result supports the view that the shift of the absorption maxima reflects changes in the conformation of sulphhaemoglobin. To investigate the relationship between the conformation of sulphhaemoglobin and the reactivity of the protein with various reagents, we studied the oxidation and reduction reactions of the protein with ascorbic acid, ferricyanide and nitrite under aerobic and anaerobic conditions. The results showed that the rates of oxidation and reduction of ferrous and ferric sulphhaemoglobins with these compounds are associated with the conformation of the protein.

Ascorbic Acid↗