Showing papers on "Cyanide published in 1990"

Are the kinetics of technetium-99m methoxyisobutyl isonitrile affected by cell metabolism and viability?

Abstract: To investigate the role of cell viability and metabolism on the myocardial kinetics of a new tracer, technetium-99m-methoxyisobutyl isonitrile (Tc-99m-MIBI), 250 microCi/l Tc-99m-MIBI was infused in isolated rat hearts under constant flow conditions. The hearts were studied after inducing irreversible damage by cytochrome c oxidase inhibitor sodium cyanide (n = 8) or sarcolemmal membrane detergent Triton X-100 (n = 8). The control hearts (n = 6) received no toxins. Mean Tc-99m-MIBI peak accumulation activity was significantly reduced after cyanide (51.1 +/- 44.2% of control, p less than 0.01) and Triton (13.8 +/- 2.7% of control, p less than 0.001) administration. Kinetic studies also showed marked reduction in accumulation rates and marked increase in clearance rates for cyanide (p less than 0.01) and Triton (p less than 0.01) groups compared with controls. Potential changes in regional flow distribution were assessed using microspheres. When peak accumulation activity was corrected for these changes, there remained significant differences between the groups. In the cyanide and Triton groups, irreversible cell injury was confirmed by creatine kinase and lactate dehydrogenase release, triphenyl tetrazolium chloride staining, and electron microscopy. All the cells were viable in the control group. We conclude that the accumulation and clearance kinetics of Tc-99m-MIBI are significantly affected by cell viability. Tc-99m-MIBI kinetics appear to be dependent on sarcolemmal integrity and to a lesser extent on aerobic metabolism.

Cyanide detection using a substrate-regenerating peroxidase-based biosensor

Abstract: An enzyme-based, dual working electrode system is described for the sensing of cyanide. Horseradish peroxidase (HRP) is incorporated as the sensing element. A continuous monitoring of oxidative activity by the enzyme results through the generation and regeneration of substrates at the electrode surfaces. Thus, HRP is oxidized by hydrogen peroxide generated from dissolved oxygen, at the primary electrode, and then reduced through the secondary electrode by mediated electron transfer using ferrocene as a carrier. Ferrocene regeneration at this electrode is proportional to the intrinsic activity of HRP. The dynamics of the system are investigated by using a rotating ring-disk electrode. The enzyme is immobilized to provide better control over its catalytic activity and to increase the lifetime of the biosensor. Cyanide inhibition of current can be modeled by reversible binding kinetics. Detection of cyanide is possible in submicromolar (ppb) concentrations, with a half maximal response at 2 microM. The response time for detection of introduced cyanide is within 1 s. The sensor can be operated between 5 and 40 degrees C, and cyanide inhibition is unaffected by pH changes between 5 and 8. The sensor is reproducible for cyanide determination and is stable for over 6 months.

The relationship between phosphate status and cyanide-resistant respiration in bean roots.

Abstract: Bean (Phaseolus vulgaris L.) seedlings were cultured on complete or phosphate-deficient nutrient medium. After 14 days of culture on phosphate-deficient medium the visible symptoms of P(i) deficiency were observed only in the shoot, the fresh and dry weights of the roots were slightly higher than in control plants. The decreased P(i) content in the roots had little effect on total respiration rate but had an effect on the level of inhibition of respiration by cyanide. The high resistance of respiration to cyanide observed in P(i) -deficient roots was the result of the suppression of cytochrome path activity and an increased participation of the alternative, cyanide-resistant pathway. The cytochrome pathway activity increased when inorganic phosphate was supplied to P(i) -deficient roots for 1 or 3.5 h. It is speculated that the suppression of cytochrome pathway in P(i) -deficient roots may result from restriction of the phosphorylating capacity or a partial inhibition of cytochrome oxidase activity.

Degradation of the metal-cyano complex tetracyanonickelate(II) by cyanide-utilizing bacterial isolates.

Abstract: Ten bacterial isolates capable of growth on tetracyanonickelate(II) [K2[Ni(CN)4]] (TCN) as the sole nitrogen source were isolated from soil, freshwater, and sewage sludge enrichments. Seven of the 10 were identified as pseudomonads, while the remaining 3 were classified as Klebsiella species. A detailed investigation of one isolate, Pseudomonas putida BCN3, revealed a rapid growth rate on TCN (generation time, 2 h), with substrate removal and growth occurring in parallel. In addition to TCN, all isolates were able to utilize KCN, although the latter was significantly more toxic; MICs ranged from 0.2 to 0.8 mM for KCN and greater than or equal to 50 mM for TCN. While growth occurred over a wide range of TCN concentrations (0.25 to 16 mM), degradation was most substantial under growth-limiting conditions and did not occur when ammonia was present. In addition, cells grown on TCN were found to accumulate nickel cyanide [Ni(CN)2] as a major biodegradation product. The results show that bacteria capable of growth on TCN can readily be isolated and that degradation (i) appears to parallel the capacity for growth on KCN, (ii) does not occur in the presence of ammonia, and (iii) proceeds via the formation of Ni(CN)2 as a biological metabolite.

Photographic emulsions containing internally modified silver halide grains

Abstract: Photographic emulsions are disclosed comprised of radiation sensitive silver bromide grains optionally containing iodide. The grains exhibit a face centered cubic crystal lattice structure and are formed in the presence of a hexacoordination complex of rhenium, ruthenium, or osmium with at least four cyanide ligands.

The effects of metabolic inhibition on uterine metabolism and intracellular pH in the rat.

Abstract: 1. Uterine metabolism was studied in pregnant and non-pregnant rats by measuring high energy phosphates and intracellular pH (with 31-phosphorus nuclear magnetic resonance (31P NMR) spectroscopy) and lactic acid efflux. Isolated, superfused uteri were investigated during control conditions (30 degrees C) and in the presence of metabolic inhibitors and high [K+]. 2. In control conditions the ratio of phosphocreatine and ATP concentrations ([PCr]/[ATP]) was higher in the pregnant (0.88 +/- 0.09) than the non-pregnant uterus (0.52 +/- 0.04). When oxidative phosphorylation was inhibited by cyanide, there was a significant (P less than 0.01) decrease in [PCr] and [ATP] and an increase in the concentration of inorganic phosphate ([Pi]). These changes were greater in the non-pregnant than the pregnant uterus. 3. There was no difference in the mean value of resting pHi found in pregnant and non-pregnant uterus (7.19 +/- 0.04 and 7.17 +/- 0.03, external pH 7.4, n = 10 and 12 respectively). There was a significant intracellular acidification in both pregnant (0.31 +/- 0.04 pH unit) and non-pregnant (0.27 +/- 0.02 pH unit) uterine tissue in the presence of cyanide. These effects of cyanide on metabolites and pHi were fully reversed upon return to control solutions. 4. When both aerobic and anaerobic glycolysis were blocked by iodoacetate, there was a rapid disappearance of high energy phosphates from the 31P NMR spectrum and a large increase in the phosphomonoester spectral region, where sugar phosphate intermediates of glycolysis resonate. These changes were seen in both pregnant and non-pregnant uteri and were irreversible. 5. Lactate production was detected, in the presence of oxygen, in both pregnant and non-pregnant preparations (0.43 +/- 0.07 and 0.25 +/- 0.09 mumols g-1 min-1, respectively). In both preparations the rate of lactate production was markedly increased in the presence of cyanide. The increase was much more marked in non-pregnant (approximately 10-fold) than pregnant (approximately 5-fold) uteri, resulting in a very similar rate of lactate efflux in cyanide. 6. When lactate efflux in non-pregnant uteri was blocked by alpha-cyano-4-hydroxycinnamate, there was a significant acidification (0.21 +/- 0.04 pH unit, n = 6). The addition of cyanide produced a more pronounced acidification (0.34 +/- 0.04 pH unit) than that seen with either cyanide or alpha-cyano-4-hydroxycinnamate alone.(ABSTRACT TRUNCATED AT 400 WORDS)

Recovery of double metal cyanide complex catalyst from a polymer

Abstract: A process for recovering double metal cyanide complex catalyst from a polymer such as polypropylene glycol in a form suitable for use as a polymerization catalyst is described. The process comprises the steps of (a) combining the polymer with a non-polar solvent to precipitate the catalyst and (b) filtering the resulting mixture in the presence of a filter aid to separate the polymer from the precipitated catalyst. In contrast to the prior art methods of catalyst removal, the process of the invention yields polymer uniformly low in color as well as recovered catalyst which may be reused in subsequent polymerizations.

Method for purifying a polyoxyalkylene alcohol

Abstract: A method for purifying a polyoxyalkylene alcohol, which comprises treating with a treating agent consisting essentially of a pH buffer, a polyoxyalkylene alcohol containing a double metal cyanide complex catalyst, synthesized by ring-opening polymerization of an alkylene oxide in the presence of said catalyst, and then removing the catalyst and the treating agent from the polyoxyalkylene alcohol.

Electrocatalysis of Anodic Oxygen Transfer Reactions: Oxidation of Cyanide at Electrodeposited Copper Oxide Electrodes in Alkaline Media

Abstract: Films of copper oxide were readily deposited electrochemically on conductive surfaces from alkaline solutions containing copper (I, II) cyanide. The resulting electrodes showed catalytic activity for the anodic oxidation of CN− to CNO− in alkaline media. The half‐wave potential was pH dependent, indicating the involvement of OH− in the reaction mechanism. Electrocatalysis was concluded to occur by oxygen transfer mediation facilitated by formation of CuIIIsites in the surface. The deposited films were only loosely adherent to the substrates and were susceptible to chemical dissolution in the presence of excessively high CN− concentrations over a long time period (ca. 30 min).

Recovery of precious metals

Abstract: Recovery of precious metals such as gold and silver from aqueous cyanide solutions thereof, by contact with a reagent containing a guanidine functionality The guanidine reagent extracts the precious metal from the aqueous solution which is subsequently stripped from the guanidine reagent and recovered by conventional methods Certain novel guanidine compounds suitable for extracting gold and silver are disclosed

Synthetic methods and reactions. 144. Regiospecific and chemoselective ring opening of epoxides with trimethylsilyl cyanide-potassium cyanide/18-crown-6 complex

Abstract: Trimethylsilyl cyanide with catalytic potassium cyanide/18-crown-6 complex opens epoxides regiospecifically to give 3-((trimethylsilyl)oxy) nitriles. The addition of cyanide occurs at the least substituted carbon. The reaction is chemoselective for monosubstituted epoxides due the participation of a pentavalent silicon species

Ethyl carbamate formation in grain‐based spirits: part iii. the primary source

Abstract: Low concentrations of ethyl carbamate, which may occur in distilled spirits are shown to originate from traces of cyanide, produced in distillates by thermal decomposition of the cyanohydrin of isobutyraldehyde (IBAC) which is present in fermented wash. This compound arises during fermentation by the hydrolytic action of yeast beta-glucosidase on a naturally-occurring cyanogenic glycoside, identified as epiheterodendrin (EPH). EPH, which is a heat-stable precursor of IBAC is located in the acrospires of malted barley and is readily transferred to worts during mashing. Although many barley varieties display the ability to produce volatile cyanide, some low-yielders have been identified. EPH is absent from unmalted barley and its development is strongly influenced by malting conditions. Conversion of measurable cyanide (MC) into ethyl carbamate takes place during- or after distillation but, apparently, not before.

Effect of 2,4-Dichlorophenoxyacetic Acid on Endogenous Cyanide, β-Cyanoalanine Synthase Activity, and Ethylene Evolution in Seedlings of Soybean and Barley

Abstract: Treatment of etiolated seedlings of barley (Hordeum vulgare) and soybean (Glycine max) with 1 millimolar 2,4-dichlorophenoxyacetic acid (2,4-D) resulted in a 14-fold and greater than 100-fold increase in ethylene production, respectively. Simultaneous monitoring of endogenous cyanide and beta-cyanoalanine synthase (beta-CAS) (EC 4.4. 1.9) activity was also performed. Endogenous levels of cyanide did not change in barley. In soybean, endogenous cyanide increased within 3 hours, increased again 6 hours after exposure to 2,4-D, and continued to increase throughout the experimental period. The activity of beta-CAS increased in both barley and soybean 9 hours after herbicide treatment. The increase in cyanide preceded the increase in beta-CAS activity by 3 to 6 hours in soybean. The steady-state concentration of endogenous cyanide in soybean was 1 micromolar, based on rates of ethylene production and cyanide metabolism by beta-CAS. This agreed with the determination of endogenous cyanide by both distillation and isotope dilution. Given the apparent compartmentalization of beta-CAS in mitochondria and the localization of ethylene/HCN production at the plasmalemma and/or tonoplast, our results suggest that extra-mitochondrial accumulation of cyanide in the cytoplasm may occur. If so, the activity of cyanide-sensitive cytoplasmic enzymes could be adversely affected, thus possibly contributing to the toxicity of 2,4-D.

Mechanistic and kinetic aspects of silver dissolution in cyanide solutions

Abstract: The factors influencing the dissolution kinetics of pure silver in cyanide solution have been analysed in terms of an electrochemical mechanism. A kinetic model is presented which incorporates coupled diffusion and charge transfer for the anodic branch, and combined diffusion, adsorption and charge transfer for the cathodic branch. The anodic oxidation of silver has been investigated using a silver rotating-disc electrode for concentrations between 10−3 and 10−1m NaCN. Oxygen reduction on silver has been studied at oxygen partial pressures between 0.104 and 1.00 atm. Mechanistic aspects of the oxygen discharge reaction are considered in explaining the kinetic differences between gold and silver dissolution in cyanide solution. It is shown that under conditions typical of conventional cyanidation gold dissolves measurably faster than silver.

Diastereomer-dependent substrate reduction properties of a dinitrogenase containing 1-fluorohomocitrate in the iron-molybdenum cofactor.

Abstract: In vitro synthesis of the iron-molybdenum cofactor (FeMo-co) of dinitrogenase using homocitrate and its analogs allows the formation of modified forms of FeMo-co that show altered substrate specificities (N2, acetylene, cyanide, or proton reduction) of nitrogenase [reduced ferredoxin:dinitrogen oxidoreductase (ATP-hydrolyzing), EC 1.18.6.1]. The (1R,2S)-threo- and (1S,2S)-erythro-fluorinated diastereomers of homocitrate have been incorporated in vitro into dinitrogenase in place of homocitrate. Dinitrogenase activated with FeMo-co synthesized using threo-fluorohomocitrate reduces protons, cyanide, and acetylene but cannot reduce N2. In addition, proton reduction is inhibited by carbon monoxide (CO), a characteristic of dinitrogenase from NifV- mutants. Dinitrogenase activated with FeMo-co synthesized using erythro-fluorohomocitrate reduces protons, cyanide, acetylene, and N2. In this case proton reduction is not inhibited by CO, a characteristic of the wild-type enzyme. Cyanide reduction properties of dinitrogenase activated with FeMo-co containing either fluorohomocitrate diastereomer are similar, and CO strongly inhibits cyanide reduction. Dinitrogenases activated with FeMo-co containing homocitrate analogs with a hydroxyl group on the C-1 position are much less susceptible to CO inhibition of cyanide reduction. However, proton and cyanide reduction by dinitrogenase containing FeMo-co activated with (1R,2S) threo-isocitrate is only one-third that of dinitrogenase activated with the racemic mixture of -isocitrate and shows strong CO inhibition of substrate reduction. These results suggest that CO inhibition of proton and cyanide reduction occurs when the hydroxyl group on the C-1 position of analogs is "trans" to the C-2 carboxyl group (i.e., in the threo conformation). When racemic mixtures of these analogs are used in the system, it seems that the erythro form is preferentially incorporated into dinitrogenase. Finally, carbonyl sulfide inhibition of substrate reduction by dinitrogenase is dependent on the homocitrate analog incorporated into FeMo-co.

Immunohistochemical localization of rhodanese.

Abstract: The role of rhodanese in the detoxication of acute cyanide exposure is controversial. The debate involves questions of the availability of rhodanese to cyanide in the peripheral circulation. Blood-borne cyanide will distribute to the brain and may induce lesions or even death. The present study addresses the dispute by determining the distribution of rhodanese in tissues considered to have the highest rhodanese activity and thought to serve as major detoxication sites. The results indicate that rhodanese levels are highest in (1) hepatocytes that are in close proximity to the blood supply of the liver (2) epithelial cells surrounding the bronchioles (a major entry route for gaseous cyanide) and (3) proximal tubule cells of the kidney (serving to facilitate cyanide detoxication and elimination as thiocyanate). Rhodanese activity in the brain is low compared with liver and kidney (Mimori et al., 1984; Drawbaugh & Marrs, 1987); the brain is not considered to be a major site of cyanide detoxication. The brain, however, is the target for cyanide toxicity. In this study our goal was also to differentiate the distribution of rhodanese in an area of the brain. We found that the enzyme level is highest in fibrous astrocytes of the white matter. Cyanide-induced brain lesions may thus occur in areas of the brain lacking sufficient sites for detoxication.

Photosensitized CN− oxidation over TiO2

Abstract: The oxidation of cyanide catalyzed by TiO2 under UV illumination is investigated. The study was performed by determining the yield of cyanide photo-oxidation using different initial cyanide concentrations, irradiation times, masses of semiconductor in suspension, light intensities, pH values and temperatures. It was observed that during the first minutes of irradiation CNO− was the main product of oxidation, but at long irradiation times all the cyanide was converted to CO32−. From the kinetic analysis performed by using the experimental data, it is deduced that the rate constant of the cyanide oxidation by photogenerated holes is 70% greater than the corresponding rate constant of the water oxidation. Finally, some experiments using a continuous flow photoreactor were carried out. With this system a good yield for the removal of cyanide, which could be maintained for at least 9 h, is reported.

Preparation of lactone polymers using double metal cyanide catalysts

Abstract: Lactone monomers are polymerized using double metal cyanide compounds as catalysts to yield useful lactone polymers. Block or random copolymers of lactones and epoxides may also be prepared.

The Chemistry of Cyanide-Metal Complexes in Relation to Hydrometallurgical Processes of Precious Metals

Abstract: Thermodynamic stability diagrams have been constructed for the cyanide-metal-sulphide/telluride/selenide systems. These were used to study the solution chemistry of the various metal-cyanide complexes in connection with cyanide leaching of gold and silver from complex sulphide, arsenosulphide, telluride and selenide ores. The results show that the formation of the metal-cyanide complexes and their stability relative to the metal oxides and sulphides depend critically on the total concentration of the cyanide and metal ions. At lower concentration ratios of Tc(CN)/Tc(Me), Ag, Cu, Ni and Zn all form insoluble metal cyanide precipitates. At higher concentration ratios, the precipitates are dissolved to form soluble cyano-metal complexes. The formation of gold and silver sulphides does not affect the stability region of aurocyanide and silver-cyanide complexes. Gold and silver telluride and selenide are stable in the presence of cyanide. These results suggest that direct leaching of gold and silver t...

Photodissociation/gas diffusion/ion chromatography system for determination of total and labile cyanide in waters

Abstract: An automated system for determination of total and labile cyanide in water samples has been developed. The stable metal-cyanide complexes such as Fe(CN){sub 6}{sup 3{minus}} are photodissociated in an acidic medium with an on-line pyrex glass reaction coil irradiated by an intense Hg lamp. The released cyanide (HCN) is separated from most interferences in the sample matrix and is collected in a dilute NaOH solution by gas diffusion using a hydrophobic porous membrane separator. The cyanide ion is then separated from remaining interferences such as sulfide by ion exchange chromatography and is detected by an amperometric detector. The characteristics of the automated system were studied with solutions of free cyanide and metal-cyanide complexes. The results of cyanide determination for a number of wastewater samples obtained with the new method were compared with those obtained with the standard method. The sample throughput of the system is eight samples per hour and the detection limit for total cyanide is 0.1 {mu}g/L.