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PubMed1983

Diamide mediated deaggregation of activated blood platelets is not caused by changes in adenine nucleotide pattern.

Studies on the effect of diamide (azodicarboxyl-bis-dimethylamide), a glutathione oxidizing agent, on platelet functions revealed an initial acceleration of aggregation followed by a pronounced deaggregation. The whole pattern of adenine nucleotides was followed up during both, arachidonic acid and arachidonic acid + diamide induced aggregation to prove whether the diamide mediated deaggregation is caused by changes in one of the parameters of the energy metabolism, i. e. ATP level, adenylate energy charge or ATP/ADP ratio.

Adenine Nucleotides↗
PubMed1975

The effect of diamide and glutathione on the uptake of alpha-methyl-D-glucoside by slices of rat kidney cortex.

The uptake of alpha-methyl-D-glucoside was stimulated in slices of rat kidney cortex by pretreatment with reduced glutathione. Diamide, an oxidizind agent with high specificity for GSH, caused an inhibition of alpha-methyl-D-glucoside uptake. These effects appeared to be related specifically to GSH, since dithiothreitol and mercaptoethanol did not increase alpha-methyl-D-glucoside uptake, and were not as effective as GSH in reversing the effects of diamide. GSH and diamide had no effect on the uptake of another sugar analog, 3-O-methylglucose, which is not actively transported. Kinetic studies indicated that GSH increased the apparent V without affecting K-m. The results are discussed in terms of the possible role of GSH in the process of sugar transport.

Amides↗
PubMed1995

Biosynthesis of porphyrins and related macrocycles, Part 43. Isolation and characterization of intermediates of coenzyme B12 biosynthesis, a cobyrinic acid triamide, the a,c-diamide and their Co-(5'-deoxy-5'-adenosyl) derivatives, from Propionibacterium shermanii.

BACKGROUND: Vitamin B12 is synthesized by many different organisms, for example Pseudomonas denitrificans (aerobic) and Propionibacterium shermanii ('microaerophilic', or essentially anaerobic). The biosynthetic pathways in these two organisms show strong similarities but also some differences. There have been conflicting reports on where differences between these two organisms lie in the stages beyond the formation of the corrin macrocycle. Characterization of intermediates in the pathway will help resolve these conflicts. RESULTS: A single cobyrinic acid diamide and a single triamide have been isolated from Pr. shermanii. The diamide was shown to be the a,c-isomer. The triamide is not the a,c,g-isomer but it is indistinguishable from the single triamide isolated by other workers from Ps. denitrificans. The Co-(5'-deoxy-5'-adenosyl) derivative of the a,c-diamide was also isolated and fully characterized and the deoxyadenosyl derivative of the foregoing triamide has been shown to be present in the cells. CONCLUSIONS: Our results support a unique pathway in Pr. shermanii proceeding from cobyrinic acid towards coenzyme B12, at least as far as the adenosylated triamide intermediate. No evidence was found for multiple alternative pathways. The order of amidations of the carboxyl side-chains of cobyrinic acid up to the triamide stage is the same in Pr. shermanii and Ps. denitrificans.

Chromatography, High Pressure Liquid↗
PubMed2006

Multiple bicyclic diamide-lutetium complexes in solution: chemometric analysis of deep-UV Raman spectroscopic data.

The investigation of complex formation between a bicyclic diamide, a novel chelating agent for lanthanides and actinides, and lutetium in an acetonitrile solution is reported. A free ligand and its lutetium complexes showed weak, noncharacteristic near-UV absorption and no fluorescence, which limited the application of absorption and fluorescence spectroscopies for studying this system. Deep-UV Raman spectroscopy combined with chemometric analysis was shown to be a powerful tool for quantitative characterization of multiple equilibria between lutetium and a bicyclic diamide. Several chemometric methods were utilized for a comparative analysis of Raman spectroscopic data. It was found that a recently developed stepwise maximum angle calculation algorithm followed by alternative least squares (ALS) was more efficient than the commonly used combination of evolving factor analysis and ALS methods, especially when little or no information about the system composition and the spectra of individual components was available. A free ligand and 1:1, 1:2, and 1:3 metal-ligand complexes were distinguished in a bicyclic diamide-lutetium solution. The composition evolution of the solution during the course of titration with lutetium was described, and the stepwise stability constants of complex formation, K(1):K(2) = 0.80 +/- 0.15 (K(1,2) > 10(8) M(-1)) and K(3) = (5.5 +/- 1) x 10(3) M(-1), were estimated.

Journal Article↗
PubMed1975

Studies of the mechanisms of radiosensitization of bacterial and mammalian cells by Diamide.

Diamide sensitizes bacterial and mammalian cells to radiation by at least two mechanisms. Sensitization of V79-GL1 Chinese Hamster cells is due mainly to a reduction of a reduction of the survival-curve shoulder, is observed both in oxygen and in hypoxia,and is additive to the sensitization of hypoxic cells by some nitroimidazoles. In contrast, sensitization of the radioresistant organism, Micrococcus sodonensis, which has apronounced shoulder, is entirely dose-modifying. In a rapid-mix study using Serratia marcescens, two mechanisms of sensitization have been identified. After 4 to 40 msec preirradiation contact with Daimide, the enhancement ratio is constant at 1.6; after 10min contact, it is 2.5. With V79-GL1 cells, no sensitization occurs in the short-time-range; likewise non is seen when Diamide is added to bacteria or mammalian cells 4 msec after irradiation. It is concluded that Diamide sensitizes by at least two mechanisms, one of which resembles that of the electron-affinic type.

Animals↗
PubMed1988

Abnormal proteins as the trigger for the induction of stress responses: heat, diamide, and sodium arsenite.

Thermotolerance and synthesis of heat shock proteins are induced in cells in response to a variety of environmental stresses. We examined the suggestion of Hightower (1980) that modifications of intracellular proteins may be the triggering event that induces heat shock protein synthesis and thermotolerance. We did so by modifying cellular proteins, using diamide, a sulfhydryl oxidizing agent, and dithio-bis (succinimidyl propionate), an agent that cross-links bifunctional amino groups. Both of these agents induced heat shock proteins and thermotolerance in CHO (HA-1) cells. Furthermore, we observed cross-resistance and self-tolerance with three seemingly unrelated stimuli (diamide, heat, and sodium arsenite). This observation suggests that the induction of protective responses to these stimuli is mediated by a common mechanism. The results support the hypothesis that production of abnormal proteins by various stresses induces the stress responses as well as tolerance.

Animals↗
PubMed1991

Heme oxygenase induction by CoCl2, Co-protoporphyrin IX, phenylhydrazine, and diamide: evidence for oxidative stress involvement.

The induction of heme oxygenase in rat liver by cobaltous chloride (CoCl2) and Co-protoporphyrin IX is entirely prevented by the administration of alpha-tocopherol and allopurinol. CoCl2 was converted in the liver into Co-protoporphyrin IX before it induced heme oxygenase activity. Actinomycin and cycloheximide affected to a similar degree the induction of heme oxygenase by both CoCl2 and Co-protoporphyrin IX. Administration of either CoCl2 or Co-protoporphyrin strongly decreased the intrahepatic GSH pool, a decrease which was completely prevented by the administration of either alpha-tocopherol or allopurinol. The latter compounds prevented heme oxygenase induction as well as the decrease in hepatic GSH when administered 2 h before, together with, or 2 h after CoCl2. However, when given 5 h after administration of CoCl2, alpha-tocopherol and allopurinol showed no preventive effect. Similar results were obtained when Co-protoporphyrin IX was used, with the difference that when alpha-tocopherol and allopurinol were given 2 h after administration of the inducer, they showed no protective effect. Phenylhydrazine and diamide also induced heme oxygenase activity in rat liver. This inductive effect was preceded by a decrease in the intrahepatic GSH pool, which took place several hours before induction of the oxygenase. Administration of alpha-tocopherol and allopurinol prevented induction of the oxygenase but had no effect on the decrease in GSH levels. These results suggest that the induction of heme oxygenase by phenylhydrazine and the diamide is preceded by an oxidative stress which very likely originates in the depletion of GSH. The induction of heme oxygenase by hemin was not prevented by administration of alpha-tocopherol or allopurinol. Coprotoporphyrin IX did not affect the pattern of the molecular forms of hepatic biliverdin reductase, at variance with CoCl2, which is known to convert molecular form 1 of the enzyme into molecular form 3.

Allopurinol↗
PubMed1981

Aggregation of intramembrane particles in erythrocyte membranes treated with diamide.

Treatment of erythrocytes with diamide (diazene dicarboxylic acid bis-(N,N-dimethylamide)) results in oxidation of sulfhydryl groups of the membrane, and cross-linking of membrane proteins into high molecular weight complexes. Concomitant freeze-etching studies show aggregation of intramembrane particles on the protoplasmic fracture face of erythrocyte ghost membranes treated with the oxidant. Furthermore, after a 3 h incubation of erythrocytes with 10 mM diamide at 37 degrees C, cellular energy levels declined to about 70% of control values. The data suggest that disulfide cross-linking of the major membrane proteins releases the apparent physical occlusion of the band 3 proteins within the interstices of the cytoskeletal shell. This results in the translational mobility of band 3 proteins which is reflected ultra-structurally in the freeze-etch images.

Adenosine Triphosphate↗
PubMed1983

Formation of aqueous pores in the human erythrocyte membrane after oxidative cross-linking of spectrin by diamide.

Oxidation of erythrocyte membrane SH-groups by diamide and tetrathionate induces cross-linking of spectrin (Haest, C.W.M., Kamp, D., Plasa, G. and Deuticke, B. (1977) Biochim. Biophys. Acta 469, 226-230). This cross-linking was now shown to go along with a concentration- and time-dependent enhancement of membrane permeability for hydrophilic nonelectrolytes and ions. The enhancement is specific for oxidative SH-group modifications, is reversible by reduction of the induced disulfides, can be suppressed by a very brief pre-treatment of the cells with low concentrations of N-ethylmaleimide and is strongly temperature-dependent. The pathway of the induced permeability discriminates nonelectrolytes on the basis of molecular size and exhibits a very low activation energy (Ea 3-8 kcal/mol). These findings are reconcilable with the formation of a somewhat inhomogeneous population of aqueous pores with radii probably less than or equal to 0.65 nm. Estimated pore numbers vary with the size of the probe molecule. Assuming a diffusion coefficient as in bulk water within the pore, at least 20 pores per cell have to be postulated; more realistic lower diffusion coefficients increase that number. Alterations of the lipid domain by changes of cholesterol contents and insertion of hexanol or nonionic detergents alter the number or size of the pores. Since aggregation of skeletal and intrinsic membrane proteins also occurs after the SH-oxidation, in parallel to the formation of membrane leaks, one may consider (a) defects in the disturbed bilayer interface, (b) a mismatch between lipid and intrinsic proteins or (c) channels in between aggregated intrinsic proteins as structures forming the pores induced by diamide treatment.

Azo Compounds↗
PubMed1985

Effects of diamide and dibucaine on platelet glycoprotein Ib, actin-binding protein and cytoskeleton.

During extraction of platelets by 1% Triton X-100, the actin-binding protein (platelet filamin) and a 230 kDa protein are degraded by a calcium-activated thiol protease. Occurrence of degradation products of Mr 190 000 (HF-1) and 90 000 (HF-2) is a sensitive indicator of this proteolysis, and can be used to decide whether reduced amounts of the actin-binding protein in extracts are due to proteolysis or to incorporation in the Triton-insoluble (cytoskeletal) fraction. Diamide, which is a sulfhydryl-oxidizing protein cross-linker, inhibits the calcium-activated protease, polymerizes the actin-binding protein and the 230 kDa protein, increases the incorporation of glycoprotein Ib into the cytoskeletal fraction, and inhibits platelet agglutination induced by bovine von Willebrand factor. Inhibition of platelet agglutination by pretreatment with diamide is partly reversed by dibucaine which activates the calcium-activated protease. These observations are in accordance with a working hypothesis that interactions of glycoprotein Ib with cytoskeleton affect, and possibly regulate, its receptor function in the intact platelet.

Animals↗
PubMed1993

Release of protein 4.1-rich vesicles from diamide-treated erythrocytes under hydrostatic pressure.

The effect of cross-linking of membrane proteins on vesiculation under high pressure (2.0 kbar) of human erythrocytes was examined. To get the large molecular weight aggregates characterized by cross-linking of cytoskeletal proteins with integral ones, the erythrocytes were pretreated with diamide under pressure (1.0 kbar) where no vesiculation occurs. Vesicles released at 2.0 kbar from such erythrocytes contained protein 4.1 as major membrane protein. Upon reduction of cross-linking by dithiothreitol prior to vesiculation, the released vesicles contained membrane proteins similar to intact cells. On the other hand, in the erythrocyte pretreated with diamide at atmospheric pressure, no such large molecular weight aggregate was observed and the membrane protein composition of the vesicles released from the cells at 2.0 kbar was also similar to that of intact cells. These results suggest that the membrane protein composition of released vesicles is much affected by the properties of cross-linking of membrane proteins in erythrocytes.

Cytoskeletal Proteins↗
PubMed1985

Effect of diamide on proton translocation by the mitochondrial H+-ATPase.

Treatment of sonic submitochondrial particles with the bifunctional thiol reagent, diamide, results in an enhancement of proton conductivity and ATPase activity, which is reversed by the reducing agent dithiothreitol, is suppressed by Fo inhibitors like oligomycin and is absent in particles that are deprived of peripheral Fo polypeptides. The effect of diamide is apparently due to oxidation of dithiols to disulfides in peripheral polypeptide(s) of Fo.

Azo Compounds↗
PubMed1987

In vitro oxidation of alpha-tocopherol (vitamin E) in human platelets upon incubation with unsaturated fatty acids, diamide and superoxide.

Incubation of human blood platelets in vitro in Tyrode solution with unsaturated fatty acids, diamide or superoxide (generated in situ) resulted in the oxidation of tocopherol in the platelets. Arachidonate concentrations of (3-5).10(-4) M caused a 50% decrease in platelet alpha-tocopherol. The addition of saturated fatty acids or platelet-active substances such as ADP, dibutyryl cyclic AMP, and some prostaglandins, or peroxidizing agents such as hydrogen peroxide and tert-butylhydroperoxide to the incubation medium did not cause any change in platelet tocopherol content. During incubations of platelets with arachidonate, malonaldehyde as well as alpha-tocopherolquinone were produced. The latter was also produced during incubations with diamide or superoxide. The oxidation of tocopherol induced by unsaturated fatty acids may be one factor responsible for the well-known increase in dietary vitamin E requirements induced by polyunsaturated fatty acids. The oxidative consumption of tocopherol in the membranes could be expected to take place during localized release of oxidants such as superoxide and polyunsaturated fatty acids during normal biological function (e.g., phagocytosis) or pathological processes (e.g., ischemia). Tocopherol utilization is kept low probably by the regeneration of the compound by vitamin C and/or the preferential utilization of the other biological antioxidants.

Adenosine Diphosphate↗
PubMed1986

Radiosensitization by diamide analogs and arsenicals.

Several analogs of the glutathione (GSH) oxidizing reagent diamide [diazenedicarboxylic acid bis(N,N'-diethylamide)] were tested as radiosensitizers of aerobic cells. In general, radiosensitization correlates with the rate of reaction with cellular reducing agents and occurs only when the reductive capacity of the cell is exceeded. SR-4077, [diazenedicarboxylic acid bis(N,N-piperidide)], is particularly suitable for mechanistic studies, because it is less cytotoxic than diamide, but is equally reactive toward cellular GSH. SR-4077 sensitizes CHO cells to X rays under aerobic conditions, even when the drug is added after irradiation. Radiosensitization is expressed both as a change in the exponential slope of the radiation cell survival curve and as a decrease in the shoulder of the survival curve. Phenylarsine oxide, a dithiol-binding reagent, sensitizes aerobic CHO cells to X rays by modification of the shoulder of the survival curve. The results are consistent with the hypothesis that the shoulder-modifying effect of GSH oxidants is caused by the loss of protein thiols, which might be involved in the repair of X ray-induced DNA damage.

Animals↗
PubMed1997

Effect of diamide on force generation and axial stiffness of the cochlear outer hair cell.

We found that diamide, which affects spectrin, reduces the axial stiffness of the cochlear outer hair cell, the cylindrically shaped mechanoreceptor cell with a unique voltage-sensitive motility. This effect thus provides a means of examining the relationship between the stiffness and the motility of the cell. For measuring axial stiffness and force production, we used an experimental configuration in which an elastic probe was attached to the cell near the cuticular plate and the other end of the cell was held with a patch pipette in the whole-cell recording mode. Diamide at concentrations of up to 5 mM reduced the axial stiffness in a dose-dependent manner to 165 nN per unit strain from 502 nN for untreated cells. The isometric force elicited by voltage pulses under whole-cell voltage clamp was also reduced to 35 pN/mV from 105 pN/mV for untreated cells. Thus the isometric force was approximately proportional to the axial stiffness. Our observations suggest a series connection between the motor and cytoskeletal elements and can be explained by the area motor model previously proposed for the outer hair cell.

Animals↗
PubMed2001

In vitro phagocytosis of carrier mouse red blood cells is increased by Band 3 cross-linking or diamide treatment.

Chemical alteration of red blood cells (RBCs) can induce increased phagocytosis of modified cells by macrophages. In this study we have used different chemical treatments for the modification of the mouse red-blood-cell membrane surface, namely oxidant compounds, such as ascorbate/Fe(+2) and diamide [azodicarboxylic acid bis(dimethylamide)], or Band 3-cross-linking reagents. We monitored the phagocytosis of oxidized or Band 3-cross-linked mouse red blood cells by peritoneal macrophages. The extent of phagocytosis of RBCs is not affected by oxidation with ascorbate/Fe(3+), but it is increased (up to 10%) by oxidation with 2 mM diamide. Furthermore, phagocytosis is greatly increased (up to 40%) as a result of cross-linking with either of two Band 3 bifunctional reagents [bis(sulphosuccinimidyl) suberate (BS(3)) and 3,3'-dithiobis(sulphosuccinimidyl propionate) (DTSSP)]. To evaluate targeting towards macrophages of such modified RBCs for therapeutical purposes, we have determined the phagocytosis of Band 3 carrier RBCs loaded with carbonic anhydrase. In this case phagocytosis is high enough (25%) to deliver the enzyme into macrophages. We have also assayed the influence of serum components and IgG on the efficiency of phagocytosis and discuss the possible phagocytosis mechanisms. In the case of BS(3)-cross-linked carrier RBCs, phagocytosis is markedly enhanced (from 12% up to 25%) by serum components. This opens a way for therapeutic application of these carrier RBCs, with special relevance in short-term delivery to cells of the mononuclear phagocytic system.

Animals↗
PubMed1995

Arabidopsis thaliana NADPH oxidoreductase homologs confer tolerance of yeasts toward the thiol-oxidizing drug diamide.

To isolate new plant genes involved in the defense against oxidative stress, an Arabidopsis cDNA library in a yeast expression vector was transformed into a yeast strain deficient in the YAP1 gene, which encodes a b-Zip transcription factor and regulates general stress response in yeasts. Cells from approximately 10(5) primary transformants were subjected to a tolerance screen toward the thiol-oxidizing drug diamide, which depletes the reduced glutathione in the cell. Four types of Arabidopsis cDNAs were isolated. Three of these cDNAs (P1, P2, and P4) belong to a plant zeta-crystallin family and P3 is an Arabidopsis homolog of isoflavonoid reductases. As such, all four isolated cDNAs are homologous to NADPH oxidoreductases. P1, P2, and P3 steady-state mRNAs accumulated rapidly in Arabidopsis plants under various oxidative stress conditions, such as treatment with paraquat, t-butylhydroperoxide, diamide, and menadione. The data suggested that proteins encoded by the isolated cDNAs play a distinct role in plant antioxidant defense and are possibly involved in NAD(P)/NAD(P)H homeostasis.

Amino Acid Sequence↗