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PubMed2004

Reducing agent and tunicamycin-responsive protein (RTP) mRNA expression in the placentae of normal and pre-eclamptic women.

Recently, the gene encoding a new stress-induced protein termed reducing agent and tunicamycin-responsive protein (RTP) was identified. The function of RTP is unknown, however, the strong upregulation of RTP during cellular differentiation, and exposure to stress conditions including hypoxia suggests a specific role for RTP in these processes. In pre-eclampsia, impaired spiral artery remodelling and reduced perfusion may reduce oxygen tension in the placenta and thereby alter trophoblast differentiation and function. We therefore hypothesized that the expression of RTP mRNA is altered in the placentae of women with pre-eclampsia. The aims of this study were to determine the regional distribution and cellular localization of RTP mRNA expression and compare mRNA abundance in different regions of normotensive control and pre-eclamptic placentae. In normal and pre-eclamptic placentae, RTP mRNA was expressed in the syncytiotrophoblasts and in the intermediate trophoblasts of the basal plate. In early onset pre-eclampsia, RTP mRNA was more abundant in the chorionic villi regions. A further increase was localized to the syncytial knots and to the trophoblasts in the peri-infarct regions. The increased RTP expression may reflect lower oxygen tension and/or other stress stimuli in the placenta in pre-eclampsia.

Adult↗
PubMed1986

Influence of oxidizing or reducing agents on gastrointestinal absorption of U, Pu, Am, Cm and Pm by rats.

Absorption of 233U, 238Pu, 241Am, and 244Cm from the gastrointestinal (GI) tract was measured in rats, fed ad libitum or fasted, that were gavaged with solutions containing ferric iron, ferrous iron, iron powder, quinhydrone or ascorbic acid. Absorption and retention of all of these actinides was increased substantially by fasting and by the addition of mild oxidizing agents, ferric iron and quinhydrone. In contrast, absorption and retention were decreased to below the fasted level by all the reducing agents except ascorbic acid, which caused diarrhea and an increase in absorption. Absorption of the lanthanide element 147Pm from the intestine of fasted rats was also increased by ferric iron. Some of these actinide elements are polyvalent and are, in some cases, known to be absorbed from the GI tract more readily in their higher oxidation states. This suggested an oxidation-reduction mechanism for the effect of fasting and the action of the chemical agents used. However, the improbability that either 241Am(III) 244Cm(III) or 147Pm is converted to a different oxidation state under these conditions makes that mechanism unlikely. Other explanations are suggested.

Actinoid Series Elements↗
PubMedDate not supplied

Study of nuclear decondensation of the rat spermatozoa by reducing agents during epididymal transit.

Chromatin packing, mostly due to disulfide bond formation, is one important step in epididymal sperm maturation. In this study the in vitro effect of a reducing agent such as thioglycolate (Tg) was tested. Thioglycolate was assayed on rat sperm obtained from caput, corpus and cauda epididymides. Changes were verified via light microscopy (and area measurements) and both transmission and scanning electron microscopy using standard techniques. Due to the low molecular weight of Tg, it does not require detergent to enter sperm. The nuclear decondensation elicited by Tg and its effect on sperm surface, differ from caput to cauda, although the final nuclear area is not significantly different. The pattern of sperm nuclear decondensation suggests that it starts at the caudal segment of the head, perhaps due to the abundance of nuclear pores in this region. Under the experimental conditions described below the perforatorium was not affected. Thus, the nature and role in the rat sperm of the perforatorium deserves more detailed analysis.

Animals↗
PubMed2003

Prevention of patulin toxicity on rumen microbial fermentation by SH-containing reducing agents.

Patulin, a toxic fungal metabolite, negatively affects rumen fermentation. This mycotoxin has also been associated with intoxication cases in cattle. This study investigates the use of SH-containing reducing compounds to prevent patulin's negative effects on the rumen microbial ecosystem. The effect of 50 microg/mL patulin on the fermentation of alfalfa hay was measured in batch cultures with and without reducing agents. Sulfhydryl-containing cysteine and glutathione prevented the negative effects of the toxin on dry matter degradation, gas, and volatile fatty acid production (P < 0.01). However, non-sulfhydryl-containing ascorbic and ferulic acids did not protect against patulin's toxicity (P > 0.01). Patulin was unstable in buffered rumen fluid as the concentration decreased by half after 4 h of incubation. In the presence of sulfhydryl groups, the toxin disappeared rapidly and was not detected after 1 h of incubation. The utilization of sulfhydryl-containing compounds such as cysteine to avert patulin toxicity could have practical implications in ruminant nutrition.

Animals↗
PubMed1991

Effect of selenium and reducing agents on in vitro immunoglobulin M synthesis by bovine lymphocytes.

A series of experiments was conducted to evaluate the effects of inorganic and organic forms of Se with or without reducing agents on in vitro IgM production by bovine lymphocytes. Peripheral mononuclear cells were isolated from nonlactating Jersey cows fed a diet with adequate Se. Cells were stimulated with pokeweed mitogen and, in addition, were cultured with various Se compounds at a concentration of 100 ng Se/ml. Mercaptoethanol (50 microM) and glutathione (1 mM) were included in cultures of cells stimulated by pokeweed mitogen with and without inorganic Se. Sodium selenite was less effective than selenomethionine and selenocystine in augmenting pokeweed mitogen-induced Ig synthesis. The addition of mercaptoethanol to pokeweed mitogen-stimulated control cultures enhanced in vitro IgM production, whereas the addition of glutathione had a negligible effect, but addition of either in combination with sodium selenite dramatically depressed IgM production. These results suggest that Se in inorganic or organic forms enhances B-cell function in vitro.

Animals↗
PubMed2005

Rhodium-catalyzed reductive coupling of disulfides and diselenides with alkyl halides, using hydrogen as a reducing agent.

[reaction: see text] We have established that RhCl(PPh3)3 catalyzes a reductive coupling of disulfides and diselenides with alkyl halides in the presence of triethylamine using hydrogen as a reducing agent. This reaction serves as a convenient new method to produce unsymmetrical sulfides and selenides from disulfides and diselenides instead of unstable and odoriferous thiols and selenols.

Journal Article↗
PubMed1991

Comparative study of the anti-HIV activities of ascorbate and thiol-containing reducing agents in chronically HIV-infected cells.

To elucidate the action of vitamin C on pathogenic human retroviruses, we investigated and compared the effects of noncytoxic concentrations of ascorbic acid (AA), its calcium salt (Ca-ascorbate), and two thiol-based reducing agents [glutathione (GSH) and N-acetyl-L-cysteine (NAC)] against human immunodeficiency virus (HIV)-1 replication in chronically infected T lymphocytes. Ca-ascorbate reduced extracellular HIV reverse transcriptase (RT) activity by about the same magnitude as the equivalent dose of AA. Long-term experiments showed that continuous presence of ascorbate was necessary for HIV suppression. NAC (10 mmol/L) caused less than twofold inhibition of HIV RT and conferred a synergistic effect (approximately eightfold inhibition) when tested simultaneously with AA (0.426 mmol/L). In contrast, nonesterified GSH (less than or equal to 1.838 mmol/L) had no effect on RT concentrations and did not potentiate the anti-HIV effect of AA. These results further support the potent antiviral activity of ascorbate and suggest its therapeutic value in controlling HIV infection in combination with thiols.

Acetylcysteine↗
PubMed1992

Lymphocyte transformation and thiol compounds; the role of ADF/thioredoxin as an endogenous reducing agent.

ADF (adult T-cell leukemia-derived factor), an inducer of IL-2R with growth promoting activity, is a homologue of thioredoxin which is involved in many thiol-dependent reducing reactions. ADF is constitutively produced and released by human lymphoid cell lines transformed by lymphocyte-tropic viruses, such as human T-lymphotropic virus type I (HTLV-I) and Epstein-Barr virus (EBV). We found that the viability and growth of these ADF high-producer cell lines (ATL-2, HUT102, MT-2, 3B6 and RPM18866) were highly dependent on L-cystine in the culture. In contrast to the relative cystine independency of ADF low-producer cells (Jurkat, Jijoye, U937 and K562), the growth of ADF high-producer cells was almost completely suppressed in L-cystine-free condition. Their viability and growth in L-cystine-free medium were markedly improved by 5 x 10(-5) M L-cysteine, 5 x 10(-5) M 2-ME or 10(-3) M GSH and partially by 10(-3) M DTT. The results demonstrate the requirement of reducing condition involving thiol compounds for the optimal growth of the virally transformed lymphoid cells. Furthermore, recombinant ADF (rADF) and suboptimal dose of 2-ME additively enhanced the growth of ATL-2 cells in L-cystine-free medium, implying the possible involvement of endogenous reducing agents such as ADF/thioredoxin homologue in the process of lymphocyte transformation/activation.

Cell Line↗
PubMed1977

Cytotoxicity of ascorbate and other reducing agents towards cultured fibroblasts as a result of hydrogen peroxide formation.

Several types of cultured fibroblasts, including chick embryo, human and mouse, were killed by the addition of sodium ascorbate at final concentrations of 0.05-0.25 mM to cultures at the time of inoculation or to attached cells. Ascorbate did not affect the attachment of cells to the substratum. The effect on chick embryo fibroblasts was visible by four hours and by six hours almost all cells had swelled and were becoming detached. By 24 hours detached cells had either lysed or become crenated in appearance. Other end-diol reducing agents and also glutathione and cysteine were effective while gulonolactone, a non-reducing analogue of ascorbate, was ineffective. Preincubation of medium containing ascorbate but no cells, conditions which result in degradation of the vitamin, led to loss of toxicity, indicating that a degradation product was not the lethal agent and that a component of the medium was not converted to a lethal substance. The lethal effect of both ascorbate and glutathione was prevented by the addition of catalase to the medium suggesting that H2O2 formed by intracellular reactions and then excreted into the medium was the cytotoxic agent. This conclusion was supported by the findings that 0.05 mM H2O2 added to chick embryo fibroblasts was lethal and that the effect of this compound on cellular morphology was almost identical to that of ascorbate.

Ascorbic Acid↗
PubMed1992

Improvement of flow through arterial stenoses by drag reducing agents.

The potential of drag reducing polymers (DRP) to selectively improve blood flow through clinically significant arterial stenoses was investigated. An artificial stenosis of the left common iliac artery in dogs decreased left femoral artery pressure by 25%. High-molecular-weight polyacrylamide (PA) or polyethylene oxide (PEO) were infused at a slow constant rate while we measured left and right common iliac artery blood flows and left and right femoral artery and vein pressures. As DRP were infused, left iliac artery flow (QL) increased early and then decreased to baseline values as flow began to increase in the right iliac artery. The peak increase in QL was 24 +/- 9% for PA and 46 +/- 19% for PEO and occurred before right iliac artery flow (QR) increased. As additional polymer was infused, QR increased to a maximum of 41 +/- 12 and 131 +/- 40% with PA and PEO, respectively. Femoral artery pressures and hindlimb resistances tended to decrease in both limbs but the only significant differences occurred in the right (nonstenosed) side when QR was elevated. This study provides the first evidence that low concentrations of DRP might be capable of improving blood flow through stenotic blood vessels without altering flow in normal vessels. Although DRP might represent a new class of compounds that could be utilized in the treatment of cardiovascular diseases, the degree of variation in individual responses is a concern, the exact mechanism of action is unclear, and information on pharmacodynamics is lacking.

Acrylic Resins↗
PubMed2004

Reductive dechlorination of alpha-, beta-, delta-, and gamma-hexachlorocyclohexane isomers by hydroxocobalamin in the presence of either dithiothreitol or titanium(III) citrate as reducing agents.

The effect of the reducing potential on the reductive dehalogenation of the different HCH (hexachlorocyclohexane) isomers has not yet been studied. In the present study, the potential for dehalogenation of (alpha-, beta-, delta-, and gamma-HCH isomers by the dithiothreitol (DTT) and titanium(III) citrate (reducing potential at pH 7, -0.33 and -0.48 V, respectively), with and without the addition of hydroxocobalamin was investigated. In the presence of DTT without catalyst, there was no disappearance of any of the HCH isomers studied after 1 h of treatment. However, disappearance of the gamma- and alpha-HCH isomers was observed during the same time period when titanium(III) citrate was used as the reductant in the absence of catalyst (62.9 and 16.6% disappearance, respectively). Addition of the hydroxocobalamin to the DTT system favored mainly the disappearance of gamma- and alpha-HCH (92.9 and 30.8% disappearance after 1 h, respectively); disappearance of delta-HCH and beta-HCH was small (11.9%) or negligible, respectively. Addition of the hydroxocobalamin to the titanium(III) citrate system favored the degradation of all HCH isomers under study: beta- and alpha-HCH completely disappeared to undetectable levels (<0.1%) after 1 and 2 min, respectively; degradation of delta-HCH and beta-HCH was slower than that of the other two isomers, although they had almost completely disappeared (99.9 and 99.6% disappearance, respectively) after 10 and 60 min, respectively. The order of disappearance, gamma-HCH > alpha-HCH > delta-HCH > beta-HCH, coincided with a decreasing order of the axially positioned Cl atoms of these isomers (considering their thermodynamically most stable configuration). This study is the first description of the rapid degradation of delta- and beta-HCH under abiotic conditions, and the results demonstrate the effect of the reducing potential on the reductive dehalogenation of HCH isomers.

Citric Acid↗
PubMedDate not supplied

N-(4-chlorophenyl)-N-hydroxy-N'-(3-chlorophenyl)urea, a general reducing agent for 5-, 12-, and 15-lipoxygenases and a substrate for their pseudoperoxidase activities.

Lipoxygenases contain a nonheme iron that undergoes oxidation and reduction during the catalytic cycle. The conversion from the Fe3+ enzyme form to the Fe2+ form can be achieved using reducing inhibitors, a reaction that can be reversed with lipid hydroperoxides. The present study describes the properties of N-(4-chlorophenyl)-N-hydroxy-N'-(3-chlorophenyl)urea (CPHU), which functions as a reducing agent for various lipoxygenases and stimulates the degradation of lipid hydroperoxide catalyzed by these enzymes (pseudoperoxidase activity). CPHU was a substrate for the pseudoperoxidase reaction of purified soybean lipoxygenase-1 with apparent Km values for CPHU and 13-hydroperoxy-9,11-octadecadienoic acid (13-HpODE) of 14 and 15 microM, respectively. CPHU was converted during the pseudoperoxidase reaction to a mixture of products that can be resolved by reverse-phase high pressure liquid chromatography. By comparison with the chemical reaction of CPHU and potassium nitrosodisulfonate, the major enzymatic reaction product was tentatively identified as a one-electron oxidation product of CPHU. At low concentrations (50 microM), dithiothreitol completely protected against the degradation of hydroxyurea without inhibiting the pseudoperoxidase reaction. Under these conditions, the rate of the pseudoperoxidase reaction with CPHU as a substrate can be quantitated by the change in absorbance at 234 nm owing to the consumption of 13-HpODE. In addition to soybean lipoxygenase-1, CPHU was found to be a substrate for the pseudoperoxidase activities of purified recombinant human 5-lipoxygenase and porcine leukocyte 12-lipoxygenase. The results are consistent with CPHU reacting with lipoxygenase by a one-electron oxidation to generate the ferrous enzyme form and the nitroxide radical, which could be reduced back to CPHU by DTT.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1982

Reversal of copper-induced inhibition of vasopressin responsiveness by reducing agents.

Copper inhibits the hydro-osmotic response to vasopressin in the urinary bladder of Bufo marinus at a site proximal to cyclic AMP production. This effect is not reversed by washing in Cu2+ -free Ringer's solution but is overcome by serosal addition of reducing agents, suggesting that vasopressin responsiveness in this tissue is modulated by either the redox potential or the sulfhydryl content of the serosal membrane.

Animals↗
PubMed2005

In situ infrared spectroscopic studies on the mechanism of the selective catalytic reduction of NO by C3H8 over Ga2O3/Al2O3: high efficiency of the reducing agent.

The partial oxidation of propane and the mechanism of selective catalytic reduction (SCR) of NO by propane over Ga2O3/Al2O3 in excess of O2 have been investigated using in situ Fourier transform infrared spectroscopy. An optimized Ga2O3/Al2O3 catalyst shows high activity and efficiency of the reducing agent propane (100% conversion of NO at 623 K, GHSV: 10,000 h(-1)). One molecule of propane converts more than 4 NO molecules to N2. The reaction starts with the partial oxidation of C3H8 by O2 and carboxylates (acetate, formate) are formed on the catalyst surface above 573 K. This oxidation represents the rate-determining step of the SCR reaction. These surface carboxylates represent a dominating intermediate and (easily) react with (adsorbed) NO forming nitrogen-containing organic species. The latter are proposed to react with NO to form N2. Total oxidation of propane was enhanced at temperatures above 773 K leading to decreased reductant efficiency. Surface nitrite and nitrate species can also be observed, but they were found to be spectators only. This could be concluded from the electron balance (conversion of propane relative to NO) and from the relative rates of the single reaction steps. On the basis of these investigations and stoichiometric calculations, a conclusive reaction mechanism is proposed.

Journal Article↗
PubMed1994

Selective retention of secretory proteins in the yeast endoplasmic reticulum by treatment of cells with a reducing agent.

We have used four glycoproteins as markers to study how disulfide bond formation and protein folding effect the intracellular transport of proteins in yeast. Under normal conditions, the vacuolar enzyme carboxypeptidase Y (CPY) and the secretory stress-protein hsp150 acquired disulfide bonds in the endoplasmic reticulum (ER). Treatment of living cells with the reducing agent dithiothreitol (DTT) prevented disulfide formation of newly synthesized CPY and hsp150, resulting in retention of the proteins in the ER. When DTT was removed, the sulfhydryls were reoxidized, and the transport of the proteins to their correct destinations was resumed. Even mature CPY, located in the vacuole, could be reduced with DTT, and reoxidized after removal of the drug. DTT treatment blocked intracellular transport of hsp150 only when present during the synthesis and translocation of the protein. Reduction of folded hsp150, accumulated in the ER due to a sec block prior to DTT treatment, did not inhibit its secretion. The Kar2p/BiP protein, a component of the ER lumen, was found to be associated with fully translocated reduced hsp150, but not with native hsp150, suggesting that Kar2p/BiP may be involved in the putative retention mechanism. The cysteine-free pro-alpha-factor, and invertase which was shown to have free sulfhydryls, were secreted and modified similarly in the presence and absence of DTT, showing that the secretory pathway of yeast functioned under reducing conditions.

Biological Transport↗
PubMed1975

Electron spin resonance study of melanin treated with reducing agents.

The electron spin resonances (ESR) of several native and modified melanins have been determined. Melanins isolated from black wool and synthesized from 3,4-dihydroxyl-L-phenylalanine (L-DOPA) and tyrosine all show similar ESR signals. Modification of the isolated melanins by treatment with reducing agents causes some lightening in color and slight changes in the ESR spectra. Lithium and liquid ammonia (Birch) reduction applied to melanins from wool and L-DOPA gave very different results, as reflected by ESR spectra, but in both cases the changes were much greater than those produced by other treatments. In general, reductive treatments in nonaqueous media in the presence of metals increase the free radical content and line width, whereas treatment in aqueous media resulted in decreased free radical content. These observations are consistent with a melanin pigment which is an irregular polymer and has unpaired electrons localized on different but similar monomer units.

Ammonia↗
PubMed1981

Sodium hypophosphite as reducing agent for determination of submicrogram quantities of mercury in animal feeds and manures.

The reduction of mercury in samples of dairy cattle and chicken feed rations and manures prepared by acid digestion for determination by flameless atomic absorption is rapidly, smoothly, and quantitatively effected by sodium hypophosphite. The reducing agent is air-stable, is effective over a wide range of mercury concentrations, and is useful in the presence of many mineral acids commonly used for wet digestion of these matrices. The accuracy and precision obtained in determinations with this reagent are equivalent to those obtained using stannous chloride at the same conditions. Recovery efficiencies for the total analytical procedure were studied using cattle manure and feed rations spiked to 0.6 ppm Hg as phenylmercuric nitrate; the range of recoveries varied from 93 to 102% (97% average). The absolute detection limit of the method is 10 ng Hg, and the precision varies in the range of 2.2-6% for samples containing 3 ppt-10 ppm Hg. The advantages of sodium hypophosphite lie in the elimination of premature reduction of mercury caused by traces of stannous chloride adhering to the walls of the reaction vessel, the elimination of several wash steps in the determination, and the long shelf life of the reagent.

Animal Feed↗