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At least 1,171 records · Page 65Linked to original sources
PubMed2003

Mode of anti-fungal activity of 1,10-phenanthroline and its Cu(II), Mn(II) and Ag(I) complexes.

The mode of action of the anti-fungal compounds, 1,10-phenanthroline (phen), [Cu(phen)2(mal)] x 2H2O, [Mn(phen)2(mal)] x 2H2O and [Ag2(phen)3(mal)] x 2H2O (malH2 = malonic acid), was examined using the pathogenic yeast Candida albicans. The compounds have minimum inhibitory concentrations (MIC's) in the range 1.25-5.0 microg cm(-3) and at a concentration of 10 microg cm(-3) display some fungicidal activity. Yeast cells exposed to these drugs show a diminished ability to reduce 2,3,5-triphenyltetrazolium chloride (TTC), indicating a reduction in respiratory function. Treating exponential and stationary phase yeast cells with phen and the Cu(II) and Mn(II) complexes causes a dramatic increase in oxygen consumption. All of the drugs promote reductions in the levels of cytochromes b and c in the cells, whilst the Ag(I) complex also lowers the amount of cytochrome aa3. Cells treated with phen and the Cu(II) and Ag(I) species show reduced levels of ergosterol whilst the Mn(II) complex induces an increase in the sterol concentration. The general conclusion is that the drugs damage mitochondrial function and uncouple respiration. That the drugs are not uniformly active suggests their bioactivity has a degree of metal-ion dependency. Phen and metal-phen complexes represent a novel set of highly active anti-fungal agents whose mode of action is significantly different to that of the polyene and azole prescription drugs.

Antifungal Agents↗
PubMed1992

Oxidized glutathione causes sensitization of calcium release to inositol 1,4,5-trisphosphate in permeabilized hepatocytes.

The effects of GSSG on Ca2+ mobilization by Ins(1,4,5)P3 were studied in permeabilized rat hepatocytes. Incubation with GSSG (2 mM) increased the sensitivity to Ins(1,4,5)P3 for Ca2+ release, with no effect on the size of the Ca2+ pool that could be released with maximal concentrations of Ins(1,4,5)P3. GSSG decreased the EC50 for Ins(1,4,5)P3 from a control value of 578 +/- 23 nM to 137 +/- 21 nM. GSSG had no effect on the metabolism of Ins(1,4,5)P3 in permeabilized cells, and sensitization of Ca2+ release was still observed when the poorly metabolizable analogue inositol 1,4,5-trisphosphorothioate was used. GSSG did not affect the ATP-dependent Ca2+ pump or the extent of loading of intracellular Ca2+ pools. In addition, the enhancement of Ins(1,4,5)P3-sensitivity by GSSG occurred under conditions where the Ca2+ pumps were blocked with thapsigargin or by chelation of medium Ca2+ just before Ins(1,4,5)P3 addition. The effect of GSSG was time- and dose-dependent, maximal effects being observed after 5 min incubation with 2 mM-GSSG. Cystine mimicked the GSSG-induced increase in Ins(1,4,5)P3-sensitivity, and the effects could be reversed by dithiothreitol (DTT). DTT, GSH glutathione and cysteine had no effect when added alone. Other agents known to react with protein thiols, including N-ethylmaleimide, p-chloromercuribenzoic acid and Ag+, did not affect the sensitivity to Ins(1,4,5)P3, but were inhibitors of ATP-dependent Ca2+ uptake. The data suggest that the sensitivity of the intracellular Ca2+ pools to release by Ins(1,4,5)P3 can be modulated by the formation of mixed disulphides with GSSG or other oxidized thiols.

Animals↗
PubMed2007

Synthesis of 1,2,4-triazole C-nucleosides from hydrazonyl chlorides and nitriles.

A series of 1,3-diaryl-5-(2,3,5-tri-O-benzoyl-beta-D-ribofuranosyl)-1H-1,2,4-triazole nucleosides (3a-f) were synthesized via the intermolecular cyclization of hydrazonyl chlorides with peracylated ribofuranosyl cyanide catalyzed by Yb(OTf)3 or AgNO3, respectively. Similarly, the 1,2,4-triazole of glucopyranosyl C-nucleosides 5a,b were prepared from the hydrazonyl chlorides and the nitrile 4. Alternatively, the 1,2,4-triazole N-nucleoside 8 was obtained from cyclization of the unsymmetrical bis[alpha-(4-methoxyphenyl)aminobenzylidene]-hydrazine with peracylated 1-amino-D-manno-pentitol.

Antiviral Agents↗
PubMed2004

MOS dosemeter using bismuth oxide (Bi2O3) and copper phthalocyanine (CuPc) polymer thick film.

A metal-oxide-silicon (MOS)-capacitor having an Ag/Bi2O3/CuPc/Ag and an MOS-transistor with Ag (gate)-Bi2O3 (gate insulator)-CuPc (semiconductor)-CdO (drain and source) structure were fabricated using screen-printing polymer thick film. The effects of gamma irradiation on the characteristics of both MOS-capacitor and MOS-transistor were investigated. The flat band voltage (VFB) of the MOS-capacitor showed a shift towards the negative gate voltage when exposed to gamma rays. The IDS-VGS characteristics displayed enhancement mode transistor for such devices. The threshold voltage was found to be 4.25 V, which displayed a linear and gradual decrease in DeltaVT = 0.5 V at VDS = 0 V and DeltaVT = 1.0 V at VDS = 2 V when exposed to gamma rays of dose step of 60 Gy.

Bismuth↗
PubMed2002

Polymeric (3-amino-2-chloropyridine)nitratosilver(I).

In the title compound [alternative name: poly[silver(I)-micro-(3-amino-2-chloropyridine)-micro-nitrato]], [Ag(NO(3))(C(5)H(5)ClN(2))](n) the Ag(I) atom is in an irregular AgN(2)O(3) geometry, surrounded by one pyridyl N atom [Ag-N 2.283 (5) A], one amine N atom [Ag-N 2.364 (6) A] and three O atoms from different nitrate ions [Ag-O 2.510 (6)-2.707 (6) A]. The Ag ions are bridged by the 3-amino-2-chloropyridine ligands into helical chains. Adjacent uniform chiral chains are further interlinked through the NO(3) bridges into an interesting two-dimensional coordination network in the solid.

Journal Article↗
PubMed1992

Sulphydryl reagents trigger Ca2+ release from the sarcoplasmic reticulum of skinned rabbit psoas fibres.

1. By analogy with studies on sarcoplasmic reticulum (SR) vesicles, Ca2+ release induced by heavy metals and mercaptans (e.g. cysteine) was investigated in rabbit skinned psoas fibres through measurements of isometric tension. 2. Heavy metals (at 2-5 microM) elicited phasic contractions by triggering Ca2+ release from the SR and had the following order of potency: Hg2+ > Cu2+ > Cd2+ > Ag+ > Ni2+. Higher concentrations produced tonic contractions due to maintained high Ca2+ permeability of SR membranes. 3. Contractions induced by heavy metals required a functional and Ca(2+)-loaded SR, were dependent on [Ca2+]free, blocked by Ruthenium Red (RR), inhibited by free Mg2+ and reduced glutathione (GSH) but not by oxidized glutathione (GSSG). Such contractions were not elicited through direct interaction(s) of heavy metals with the myofilaments. 4. In the presence of catalytic concentrations of Hg2+ or Cu2+ (2-5 microM), additions of cysteine (25-100 microM) elicited rapid twitches, producing 70% of maximal force with a time to half-peak of 2 s. Contractions induced by cysteine plus a catalyst required a functional SR network, were dependent on free [Mg2+] and were blocked by RR or GSH but not by GSSG. 5. In the presence of Hg2+ (2-5 microM), low concentrations of cysteine (10 microM) elicited tonic contractures, but subsequent or higher additions of cysteine (50-100 microM) caused further SR Ca2+ release and tension, followed by rapid and full relaxation. 6. High cysteine (200-250 microM, without Cu2+ or Hg2+) blocked contractions elicited by Cl- induced depolarization of sealed T-tubules. High cysteine probably acted as a sulphydryl reducing agent which promoted rapid relaxation of the fibres through the closure of Ca(2+)-release channels and ATP-dependent re-uptake of Ca2+ by the SR. 7. In some batches of skinned fibres (approximately 10%), cysteine (5-50 microM) alone (without Hg2+ or Cu2+ catalyst) produced rapid twitches. This implied that the catalyst(s) necessary to promote the sulphydryl oxidation reaction with exogenously added cysteine may be present in intact fibres but is usually lost by the skinning procedure. 8. The data demonstrate that skeletal fibres contain a highly reactive and accessible sulphydryl site on an SR protein which can be reversibly oxidized and reduced to respectively, open and close SR Ca(2+)-release channels. A model of sulphydryl-gated excitation-contraction coupling is proposed where the voltage sensor on the T-tubule membrane directly oxidizes sulphydryl sites on SR Ca(2+)-release channels.

Animals↗
PubMed2006

Four free cysteine residues found in human IgG1 of healthy donors.

Modifications with different thiol reagents demonstrated that 28 of 32 cysteine residues of human IgG1 are involved in the formation of disulfide bonds, and four cysteines remain free. So IgG1 is a protein possessing both free SH-groups and disulfide bonds. Only one of the four SH-groups is accessible for silver or mercury ions and hydrophobic reagents, whereas the remaining three SH-groups are masked and can be revealed only after deep denaturation of the protein. Detection of the masked cysteine residues was shown to depend on the kinetics of intramolecular changes occurring during denaturation of the protein and on the method of the assay of the SH-groups.

Cysteine↗
PubMed1990

Sulfhydryls on frog skeletal muscle membrane participate in contraction.

To examine the molecular mechanism underlying contractile activation, we studied effects of a sulfhydryl reagent, N-(7-dimethylamino-4-methylcoumarinyl)maleimide (DACM), on twitch, Ag(+)-induced contraction, and K+ and caffeine contractures in single toe muscle fibers of frog. DACM suppressed twitch and Ag(+)-induced contraction, dose dependently, but not caffeine contracture. K+ contracture also was decreased appreciably by exposure to 40 microM DACM for 10 min. DACM elicited no shift of the mechanical threshold or inhibition of resting potential but slightly inhibited action potential. Increase of the fluorescence intensity produced by binding of 10 microM DACM to sulfhydryl groups was depressed by brief pretreatment with 100 microM Ag+. When exposed to 1 mM dithiothreitol (DTT) within 5 s of the rising phase of 5 microM Ag(+)-induced contraction, the fiber rapidly decreased the tension to the resting level. In this case, reapplication of 5 microM Ag+ after washing out DTT elicited a new contraction similar to the first Ag(+)-induced contraction. The second contraction amplitude depended on the time between the onset of the first Ag(+)-induced contraction and DTT application. If DTT was applied after more than 16 s, tension no longer developed on the second exposure to Ag+ or K+. The experiments provide evidence that crucial sulfhydryl groups participate in muscle activation. The possible role of the sulfhydryl group on the transverse tubular membrane in tension development is discussed.

Animals↗
PubMed1993

In situ fluorescent visualization of nucleolar organizer region-associated proteins with a thiol reagent.

Nucleolar organizer regions (NORs) are nucleolus-forming rDNA loops associated with argyrophil proteins, the amount of which varies according to the proliferative state of the cell. It has been presumed that the nucleolar protein-related thiol groups may have a role in selective silver staining. We investigated the nuclear thiol distribution with a fluorescent thiol reagent, coumarinyl-phenyl-maleimide (CPM) in human K-562 myeloblast cultures and found that SH group-related fluorescence was brightest in the area of nucleoli, which became highly selective after RNAse digestion. A remarkable co-localization of AgNOR silver reaction and CPM fluorescence was observed, although occupation of the SH groups by CPM did not prevent the silver staining. We applied the stain to dual-parameter flow cytometry in combination with DNA content measurements, which provide further information on nucleolar function and changes in experimental and pathological specimens.

Adenocarcinoma↗
PubMed1994

Studies on the preparation of bioactive lignans by oxidative coupling reaction. II. Oxidative coupling reaction of methyl(E)-3-(4,5-dihydroxy-2-methoxyphenyl)propenoate and lipid peroxidation inhibitory effects of the produced lignans.

The oxidative coupling reaction of methyl (E)-3-4(4,5-dihydroxy-2-methoxyphenyl)propenoate (10), obtainable from esculetin, has been studied using silver oxide and potassium hexacyanoferrate(III). The products were separated, after acetylation, by silica gel column chromatography. 1-Aryl-1,2-dihydronaphthalene derivative 12 was obtained as a major product, accompanied by the benzo[kl]xanthene derivative 13. In the oxidation with silver oxide, a benzodioxane compound 14a was produced additionally in a minor amount. Thus, the course of the reaction differed notably from those of ferulic or caffeic acid derivatives. The compounds 11, 12, 13 and 14a were tested for their inhibitory effects on lipid peroxidation in rat brain homogenate and rat liver microsomes. They showed activities more effective than that of idebenone in rat brain homogenate, and were found to be more potent than benzofuran lignans 4 and 5, and much more potent than (+/-)-alpha-tocopherol in rat liver microsomes.

Animals↗
PubMed2005

Increased parathyroid hormone gene expression in secondary hyperparathyroidism of experimental uremia is reversed by calcimimetics: correlation with posttranslational modification of the trans acting factor AUF1.

Most patients with chronic kidney disease develop secondary hyperparathyroidism with disabling systemic complications. Calcimimetic agents are effective tools in the management of secondary hyperparathyroidism, acting through allosteric modification of the calcium-sensing receptor (CaR) on the parathyroid gland (PT) to decrease parathyroid hormone (PTH) secretion and PT cell proliferation. This study showed that rats that were fed an adenine high-phosphorus diet had increased serum PTH and PTH mRNA levels at 7 and 21 d. For studying the effect of activation of the CaR by the calcimimetics R-568 on PTH gene expression, R-568 was given by gavage to uremic rats for the last 4 d of a 7-d adenine high-phosphorus diet. R-568 decreased both PTH mRNA and serum PTH levels. The effect of the calcimimetic on PTH gene expression was posttranscriptional and correlated with differences in protein-RNA binding and posttranslational modifications of the trans acting factor AUF1 in the PT. The AUF1 modifications as a result of uremia were reversed by treatment with R-568 to those of normal rats. Therefore, uremia and activation of the CaR mediated by calcimimetics modify AUF1 posttranslationally. These modifications in AUF1 correlate with changes in protein-PTH mRNA binding and PTH mRNA levels.

Aniline Compounds↗
PubMed2006

Kinetic-spectrophotometric determination of trace amounts of silver using the oxidation of thionine with peroxodisulfate.

A simple, rapid and sensitive method has been developed for determination of traces of silver(I) (0.2 - 13 ng mL(-1)) based on its catalytic effect on the oxidation of thionine by peroxodisulfate in the presence of 1 - 10 phenanthroline as an activator. The reaction is monitored spectrophotometrically by measuring the decrease in absorbance of thionine at 600 nm by the fixed time method. The detection limit is 0.098 ng mL(-1) and the relative standard deviation for 0.5, 3.0, 5.0 and 10 ng ml(-1) Ag(I) are 4.1, 1.37, 1.06 and 0.64%, respectively. The method is free from most interferences and it was applied to determination of silver in photographic solutions and well-water samples.

Catalysis↗
PubMed2005

Effect of metal conditioner application on bond strength of luting cements to a noble metal.

The purpose of this study was to evaluate the adhesive performance of luting cements to a noble metal alloy treated with metal conditioners. Cast disk specimens made of a noble metal alloy were gritblasted with alumina followed by no treatment or priming with two different types of metal conditioner. A mold was placed on the metal surface and filled with luting cement. Ten samples per test group were stored in 37 degrees C distilled water for 24 hours, then shear tested at a cross-head speed of 1.0 mm/minute. ANOVA and Tukey's HSD tests (alpha=0.05) were done. The mean bond strength of resin-modified glass ionomer cement increased significantly with metal conditioner application compared to the controls, indicating the efficacy of the tested metal conditioners in improving bond strength. Based on the results of this study, it seemed to be a useful method to incorporate a functional monomer into resin cements so as to improve the bond strength to a noble metal alloy.

Composite Resins↗
PubMed1976

The role of prostaglandins in chemically induced inflammation.

Dye leakage in rats, produced by intracutaneous injections of irritants into the abdominal skin, was quantitated using the Evans blue technique of Harada et al. (1971). In control rats and in rats pretreated with indomethacin (an inhibitor of prostaglandin synthesis) concentration-response lines were obtained for 5-hydroxytryptamine, histamine, bradykinin and prostaglandin E1, bradykinin in the presence of prostaglandin E1 (10-6 M), adenosine-5'-triphosphate, compound 48/80, capsaicin and silver nitrate. In rats pretreated with indomethacin the dye leakage responses to histamine, prostaglandin E1, adenosine-5'-triphosphate and silver nitrate were significantly reduced, but no significant changes were observed in the responses to the other irritants. It is suggested that part of the action of histamine, adenosine-5'-triphosphate and prostagland in E1 is produced indirectly by releaseor stimulation of the synthesis of prostaglandins or their precursors. These results might have important implications in the understanding of the inflammatory response.

Adenosine Triphosphate↗