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PubMed1978

The use of short-term tests to measure the preventive action of reducing agents on formation and activation of carcinogenic nitroso compounds.

The effect of reducing agents on the nitrosation of methylguanidine (MG) and on the in vitro activation of dimethylnitrosamine (DMN) was examined by measuring DNA-repair synthesis (unscheduled incorporation of [3h]TdR), shifts in alkaline sucrose gradients, frequency of chromosome aberrations, and clone-forming capacity of cultured human fibroblasts. The reducing agents examined were sodium ascorbate, cysteine, cysteamine, and propyl gallate. Since the short-term bioassays used can be quantitated, it has become relatively easy to detect the inhibitory action of reducing compounds on the nitrosation reaction of MG and metabolic activation (with S-9 preparation) of the precarcinogen DMN, to measure their effective dose range, and to establish the most effective ratios between inhibitory agent and reactant. The results indicate that DNA-repair synthesis is a suitable short-term test for studying the numerous combinations and premutations between several carcinogenic or non-carcinogenic agents, and for estimating the capacity of inhibitory agents to affect formation and activation of chemical carcinogens.

Adolescent↗

PubMed2002

Effect of reducing agents on the acidification capacity and the proton motive force of Lactococcus lactis ssp. cremoris resting cells.

Reducing agents are potential inhibitors of the microbial growth. We have shown recently that dithiothreitol (DTT), NaBH(4) and H(2) can modify the proton motive force of resting cells of Escherichia coli by increasing the membrane protons permeability [Eur. J. Biochem. 262 (1999) 595]. In the present work, the effect of reducing agents on the resting cells of Lactococcus lactis ssp. cremoris, a species widely employed in dairy processes was investigated. DTT did not affect the acidification nor the DeltapH, in contrast to the effect previously reported on E. coli. The DeltaPsi was slightly increased (30 mV) at low pH (pH 4) in the presence of 31 mM DTT or 2.6 mM NaBH(4). In the case of Na(2)S(2)O(4), small amounts (0.9 mM) drastically decreased the acidification range and this product was shown to abolish the DeltapH. These results are discussed in terms of the diversity of action of the chemical reagents and strain sensitivity.

Borohydrides↗

PubMed1996

Red cell vitamin E and oxidative damage: a dual role of reducing agents.

The purpose of this study was to determine the role of reducing agents in maintaining the integrity of vitamin E-deficient red cells. Three groups of one-month-old male Wistar rats were fed a basal vitamin E-deficient diet supplemented with either 0, 10 or 100 mg d, 1-alpha-tocopheryl acetate per kg diet for up to 12 weeks. Washed red blood cells (5%) were resuspended in saline-phosphate buffer, pH 7.4, and were incubated at 37 degrees C with or without containing 12.5 mM 2, 2'-azobis (2amino- propane) dihydrochloride (AAPH), 2.8 mM glucose, 1 mM ascorbic acid, 10 mM hydrogen peroxide (H2O2), 250 microM dimethylsulfoxide (DMSO) or 2.8 mM deoxyribose (DR) for up to 20 hours. Addition of either glucose, AAPH, ascorbic acid or H2O2 markedly accelerated the rates of hemolysis and lipid peroxidation in the red cells of vitamin E-deficient rats. On the contrary, both glucose and ascorbic acid were protective against oxidative damage to the red cells of vitamin E-supplemented rats in a dose-dependent manner. Also, vitamin E-supplemented red cells were more resistant to AAPH and H2O2 than the deficient cells. DMSO or. DR had no significant effects on the rates of hemolysis or lipid peroxidation. Glucose, but not others, maintained or slowed down the loss of glutathione (GSH) during incubation. The results obtained suggest a dual role of ascorbic acid and GSH in the function of vitamin E in maintaining red cell integrity: these reducing agents may exert antioxidant function by participating in vitamin E regeneration when certain levels of vitamin E is maintained, but promote oxidative damage by enhancing free radical generation when vitamin E is low or depleted.

Amidines↗

PubMed1988

Synergistic actions of disulfide-reducing agents on 1-methyladenine-induced oocyte maturation in starfish.

Several disulfide-reducing agents, such as dithiothreitol, 2,3-dimercapto-1-propanol, cysteine ethyl ester, and cysteine methyl ester enhanced the effectiveness of 1-methyladenine (1-MeAde) to induce oocyte maturation in the starfish Asterina pectinifera. This enhancement occurred at relatively low concentrations at which these agents by themselves were ineffective in inducing oocyte maturation. The agents caused a marked (about twofold) increase in specific [1-3H]MeAde binding. The binding increased directly in relation to the potency of the agents in enhancing 1-MeAde action. Scatchard analysis indicated that dithiothreitol increased the Bmax without affecting the affinity of 1-MeAde binding. These results strongly suggest that disulfide-reducing agents enhance the maturational action of 1-MeAde by increasing the number of 1-MeAde binding sites in oocyte cortices.

Adenine↗

PubMed1990

Lightening of dark radiographs with a superproportional reducing agent.

Copper sulfate reducer is useful for lightening and improving the diagnostic quality of dark radiographs. The solution consists of copper sulfate, sodium chloride, and sulfuric acid. The radiograph is immersed and bleached in the solution until it turns white, redeveloped in weak developer, and fixed. Reduction is superproportional; that is, the percentage of reduction is greater in darker areas than it is in lighter areas. The degree of reduction increases with increased density. The degree of reduction decreases with increased redevelopment time. The reduced radiograph may have a gray, brown, or black image. Resolution is increased on the reduced radiograph.

Copper↗

PubMed2002

Application of the effects of ionic strength reducing agents in the purification and crystallization of chitinase A.

The effects of ionic strength reducing agents may find a large number of applications. Based on these effects, we have redesigned the purification scheme of Chitinase A (ChiA) from Serratia marcescen. This scheme led to reproducibly crystallizable enzyme in both salting-in and salting-out conditions, which are presented here. Herein, we demonstrate some experimental applications of the ionic strength reducing agents theory and, in parallel, provide further evidence of the theory's correctness. Finally, we report a new crystal form produced recently in salting-in crystallization experiments. This form may allow the co-crystallization of ChiA mutants with longer substrates.

Ammonium Sulfate↗

PubMed1998

Changes in gene expression during the growth arrest of HepG2 hepatoma cells induced by reducing agents or TGFbeta1.

The growth of hepatoma cells can be inhibited by treatment with TGFbeta1 or with exogenous reducing agents. To gain information on the molecular mechanisms underlying growth arrest, we visualized and compared gene expression profiles of proliferating versus non proliferating HepG2 cells by computer-assisted gene fishing, an improved technique of RNA fingerprinting that allows the selective amplification of coding regions within transcripts. While many transcripts are selectively regulated by either treatment, a set of bands appear to be coordinately regulated by 2ME and TGFbeta1, suggesting their possible involvement in the mechanisms of growth arrest. Display tags corresponding to 18 differentially expressed genes were cloned and, in most cases, identified as known genes or, more frequently, as their homospecific/cross-specific homologues. A novel member of the kinesin superfamily was identified amongst the genes induced by both 2ME and TGFbeta1. This gene, KIF3C, is upregulated in several cell lines undergoing growth arrest. Taken together, our findings show that computer-assisted gene fishing is a powerful tool for the identification and cloning of genes involved in the control of cell proliferation and indicate that extracellular reducing agents can regulate cell growth through modulation of gene expression.

Carcinoma, Hepatocellular↗

PubMed1977

Evaluation of formamidine sulfinic acid and other reducing agents for use in the preparation of Tc-99m labeled radiopharmaceuticals.

Various reducing agents have been evaluated for their potential usefulness in the preparation of 99mTc labeled radiopharmaceuticals for use in nuclear medicine. Adequate labeling of various radiopharmaceuticals was accomplished using formamidine sulfinic acid. Nitrogen-purging of solutions is not required, which is an advantage for in-house preparation. Tagging requires heating, however, so heat-labile material cannot be used. Various compounds that could not be labeled when stannous chloride was used, could be tagged with 99mTc when formanidine sulfinic acid was used as the reducing agent.

Amidines↗

PubMed2005

Silver nanoparticle formation in microemulsions acting both as template and reducing agent.

A novel method of making silver nanoparticles in water-in-oil microemulsions using the surfactants as both the reducing agent and as the structure-directing agent is presented. Since no external strong reducing agent is used the kinetics of the formation is slow, which makes it possible to study the silver nanoparticle formation in situ. The microemulsions used were based on either the nonionic surfactant Brij30 (C12E4), which reduces the silver ion to metallic silver and is thereby partly oxidized, or mixtures of Brij30 and AOT (sodium bis(2-ethylhexyl) sulfosuccinate, where the latter does not reduce the silver ions. The influences of silver ion and nonionic surfactant concentrations on the formation kinetics of the nanoparticles were followed in situ using UV-vis spectroscopy, and both parameters were found to have a big influence. The microemulsion droplet's size, size distribution, and shape were examined by small-angle X-ray scattering (SAXS), and the formed silver nanoparticles were studied using both transmission electron microscopy and SAXS. The SAXS measurements showed that the presence of silver nitrate does not affect the microemulsion systems noticeably and that the droplet's size and shape are retained during the particle formation. It is shown that the size and morphology of the particles do not directly follow the shape and size of the microemulsion droplets even though there is a relation between the droplet size and the radii of the formed particles.

Journal Article↗

PubMed2005

Use of acid-reducing agents in protease inhibitor-based HAART and the potential for negative treatment outcomes.

A number of protease inhibitors (PIs) are dependent on an acidic gastric pH for optimal drug dissolution and absorption. As a result, the potential for negative drug interactions with acid-reducing agents exists and could lead to subtnerapeutic drug concentrations, viral breakthrough, and development of drug resistance. Pharmacokinetic evaluations of a number of PIs given with acid-reducing agents have been performed and show varying degrees of effect. Given the possibility of decreases in PI exposures, clinicians should be aware of the potential for a negative interaction when selecting PI-based HAART for patients taking acid-reducing agents.

Acids↗

PubMed2002

Metalloenzyme-like activity of Alzheimer's disease beta-amyloid. Cu-dependent catalytic conversion of dopamine, cholesterol, and biological reducing agents to neurotoxic H(2)O(2).

Beta-amyloid (Abeta) 1-42, implicated in the pathogenesis of Alzheimer's disease, forms an oligomeric complex that binds copper at a CuZn superoxide dismutase-like binding site. Abeta.Cu complexes generate neurotoxic H(2)O(2) from O(2) through Cu(2+) reduction, but the reaction mechanism has been unclear. We now report that Abeta1-42, when binding up to 2 eq of Cu(2+), generates the H(2)O(2) catalytically by recruiting biological reducing agents as substrates under conditions where the Cu(2+) or reducing agents will not form H(2)O(2) themselves. Cholesterol is an important substrate for this activity, as are vitamin C, L-DOPA, and dopamine (V(max) for dopamine = 34.5 nm/min, K(m) = 8.9 microm). The activity was inhibited by anti-Abeta antibodies, Cu(2+) chelators, and Zn(2+). Toxicity of Abeta in neuronal culture was consistent with catalytic H(2)O(2) production. Abeta was not toxic in cell cultures in the absence of Cu(2+), and dopamine (5 microm) markedly exaggerated the neurotoxicity of 200 nm Abeta1-42.Cu. Therefore, microregional catalytic H(2)O(2) production, combined with the exhaustion of reducing agents, may mediate the neurotoxicity of Abeta in Alzheimer's disease, and inhibitors of this novel activity may be of therapeutic value.

Alzheimer Disease↗

PubMed1983

Hydroxylation of the C-8 position of deoxyguanosine by reducing agents in the presence of oxygen.

The C-8 position of deoxyguanosine was hydroxylated by various reducing agents in the presence of oxygen in 0.1 M phosphate buffer (pH 6.8) at 37 degrees C. As reducing agents, ascorbic acid, hydroxylamine, hydrazine, sodium bisulfite and dihydroxymaleic acid were used. Metal powder (Fe, Ni) or metalethylenediaminetetraacetic acid (EDTA) complex (FeII-EDTA, TiIII-EDTA) was also effective for the hydroxylation reaction in the presence of oxygen. Guanine residues in calf thymus DNA were also modified by these reagents. The possible biological significance of the hydroxylation of guanine residue in DNA in relation to mutagenesis and carcinogenesis is discussed.

Ascorbic Acid↗

PubMed2004

Conformational regulation of alpha 4 beta 1-integrin affinity by reducing agents. "Inside-out" signaling is independent of and additive to reduction-regulated integrin activation.

The alpha(4)beta(1)-integrin (very late antigen-4 (VLA-4), CD49d/CD29) is an adhesion receptor involved in the interaction of lymphocytes, dendritic cells, and stem cells with the extracellular matrix and endothelial cells. This and other integrins have the ability to regulate their affinity for ligands through a process termed "inside-out" signaling that affects cell adhesion avidity. Several mechanisms are known to regulate integrin affinity and conformation: conformational changes induced by separation of the C-terminal tails, divalent ions, and reducing agents. Recently, we described a fluorescent LDV-containing small molecule that was used to monitor VLA-4 affinity changes in live cells (Chigaev, A., Blenc, A. M., Braaten, J. V., Kumaraswamy, N., Kepley, C. L., Andrews, R. P., Oliver, J. M., Edwards, B. S., Prossnitz, E. R., Larson, R. S., and Sklar, L. A. (2001) J. Biol. Chem. 276, 48670-48678). Using the same molecule, we also developed a fluorescence resonance energy transfer-based assay to probe the "switchblade-like" opening of VLA-4 upon activation. Here, we investigated the effect of reducing agents on the affinity and conformational state of the VLA-4 integrin simultaneously with cell activation initiated by inside-out signaling through G protein-coupled receptors or Mn(2+) in live cells in real time. We found that reducing agents (dithiothreitol and 2,3-dimercapto-1-propanesulfonic acid) induced multiple states of high affinity of VLA-4, where the affinity change was accompanied by an extension of the integrin molecule. Bacitracin, an inhibitor of the reductive function of the plasma membrane, diminished the effect of dithiothreitol, but had no effect on inside-out signaling. Based on this result and differences in the kinetics of integrin activation, we conclude that conformational activation of VLA-4 by inside-out signaling is independent of and additive to reduction-regulated integrin activation.

Anti-Bacterial Agents↗

PubMed1989

Sulfhydryl reducing agents promote neutrophil adherence without increasing surface expression of CD11b/CD18 (Mac-1, Mo1).

The disulfide reducing agents dithioerythreitol and dithiothreitol, but not oxidized dithiothreitol, induced polymorphonuclear neutrophils to adhere to endothelial cells or to plastic. Adherence was inhibited by monoclonal antibodies 60.1 and 60.3, which are directed to functional epitopes on the CD11b and CD18 polypeptides of the neutrophil membrane adhesion complex (Mac-1, Mo1). The increased adherence induced by the sulfhydryl reducing agents was not accompanied by increased expression of CD11b/CD18. These studies demonstrate that a qualitative alteration in CD11b/CD18 is sufficient to promote neutrophil adherence.

Antigens, CD↗

PubMed1990

A filter paper dye-binding assay for quantitative determination of protein without interference from reducing agents or detergents.

A method is described for quantitation of protein in the presence of reducing agents, detergents, and other substances which often interfere with assays of protein in solution. The proteins are applied to Whatman No. 1 filter paper, air-dried, washed with methanol, and then stained with Coomassie brilliant blue G. Following destaining, the paper is air-dried and the protein-bound dye is extracted. Sample absorbance measurements are made in a 96-well plate using an automated microplate reader (600-405 nm) or in a cuvette at 610 nm. This filter paper assay is useful for determining 100 ng to 20 micrograms of protein in the presence of ammonium sulfate, urea, thiol-reducing agents, amino acids, DNA, ionic and nonionic detergents, and acid or base.

Animals↗

PubMed2000

Reducing agents and light break an S-S bond activating rhodopsin in vivo in Chlamydomonas.

Light induces retinal synthesis via photoactivation of a small amount of Chlamydomonas rhodopsin pigment (Foster et al., Proc. Natl. Acad. Sci. USA 85, 6379-6383). A reducing agent [dithiothreitol (DDT) or mercaptoacetic acid (MAA)] also induces retinal synthesis in the dark via a rhodopsin with a chromophore. If the opsin is saturated with retinal and is bleached with light in the presence of a thiol trapping agent, the bleaching becomes irreversible. We conclude that the reducing agent as well as light break a disulfide bond resulting in activation of the rhodopsin and induction of carotenogenesis. Both the chemical and light induction is inhibited by GDPbetaS and pertussis toxin. Breaking the bridge between the 3rd and 5th helix may lead to increased proton accessibility of Asp134 leading to the rolling of the 3rd helix and MetaIIb formation.

Animals↗

PubMed1986

A mild method for the purification of guinea pig peritoneal macrophage Fc gamma receptors. Affinity chromatography and elution of the receptor with reducing agents.

A method for the purification of Fc gamma receptors from guinea pig peritoneal macrophages using mild conditions is described. The method is based on the observation that reduction and alkylation of IgG disulfide bonds partially or completely abrogate their binding to Fc gamma receptors. Cell lysates were directly applied to Sepharose-IgG or Sepharose-TNP-Ab(IgG) and the specifically bound Fc gamma receptor was eluted from adsorbents by incubation with reducing agents (2-mercaptoethanol or dithiothreitol). Alternatively, cell lysates were first treated with IgG and then applied to Protein A-Sepharose and the receptor was eluted with reducing agents. Yields of the purified Fc gamma receptor preparations and their activities were considerably higher than when the receptor was eluted from affinity chromatography gels with acetic acid or other acidic buffers or chaotropic agents. The best results were obtained when Fc gamma receptor-IgG complexes were applied to Protein A-Sepharose. No significant difference in the subunit structure was observed using SDS-PAGE when receptor preparations obtained by elution with reducing agents were compared with preparations obtained by elution with acidic buffers.

Animals↗

PubMed1952

The antistreptococcal property of milk. II. The effects of anaerobiosis, reducing agents, thiamine, and other chemicals on lactenin action.

Lactenin is reversibly inactivated by the exclusion of atmospheric oxygen. It is also inactivated by the sulfur-containing reducing agents cysteine, glutathione, thioglycollic acid, and BAL. Group A streptococci which have been acted upon by lactenin have been killed, and not merely prevented from multiplying, since they cannot be revived by inactivating lactenin through the addition of a reducing agent. Thiamine in great excess inactivates lactenin. The mechanism by which it accomplishes this has not been discovered, but it suggests that the mode of action of lactenin may be to deny thiamine to the lactenin-sensitive cell. Lactenin sensitivity is not, however, related to a requirement for exogenous thiamine, nor does lactenin appear to function by binding environmental thiamine in a form unavailable to the sensitive cell.

Anaerobiosis↗