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PubMed1993

The effect of antibodies to subunit V of cytochrome oxidase on cyanide inhibition of electron transfer.

Binding of antibodies raised against subunit V of mammalian cytochrome oxidase to the intact membranous enzyme is redox-sensitive, suggesting the existence of 'open' and 'closed' protein conformers (Freedman, J.A., Cooper, C.E., Leece, B., Nicholls, P. and Chan, S.H.P. (1988) Biochem. Cell Biol. 66, 1210-1217). Similar open and closed states for the oxygen-reacting site have been proposed to explain cyanide binding kinetics (Jensen, P., Wilson, M.T., Aasa, R. and Malmström, B.G. (1984) Biochem. J. 224, 829-837). We therefore examined cyanide inhibition of oxidase activity polarographically and spectrophotometrically using soluble oxidase preincubated with and without anti-subunit V or non-immune rabbit gamma-globulin. The subunit-specific antibody decreased the cyanide 'on' rate and essentially eliminated the rapid phase of cyanide binding. We conclude that (i), bound antibody blocks HCN binding; (ii), antibody and HCN probably bind to the same conformation of the oxidase and (iii), the 'open'-'closed' conformation change that modulates binding of HCN may be similar to that which modulates antibody binding. The results are consistent with some reciprocating models of electron transfer and energy transduction by the oxidase (cf., Wikström, M.K.F., Krab, K. and Saraste, M. (1981) Cytochrome Oxidase: A Synthesis).

Animals↗

PubMed1994

Cyanide dissociation from the hemoglobin of Parascaris equorum.

The reduction of cyanomethemoglobin by dithionite leads to the appearance of an intermediate, the complex of cyanide with ferrous hemoglobin, whose dissociation is easily followed in a stopped flow apparatus. This reaction was studied in the hemoglobin from the parasitic nematode Parascaris equorum, whose extremely high oxygen affinity is due to a very low dissociation rate. The rate of cyanide dissociation from ferrous Parascaris hemoglobin is not so dramatically different from that of other hemoglobins and myoglobins. Other features of the reaction are: (i) the rate constant of cyanide release is pH independent, an observation which is agreement with the possible absence of the distal histidine, given the mechanism suggested in a previous study (Bellelli, A., Antonini, G., Brunori, M, Springer, B.A. and Sligar, S.G. (1990) J. Biol. Chem. 265, 18898-18901), and (ii) the time-course shows no kinetic cooperativity. The structural basis of the extremely high oxygen affinity of Parascaris hemoglobin cannot be explained on the basis of the results here reported. This study also confirms that, even though cyanide binding to ferrous hemoglobins is controlled by distal interactions, the functional behaviour of this ligand is characteristic and differs from the behaviour of oxygen.

Allosteric Regulation↗

PubMed1995

A hypothesis for cyanide-induced tonic seizures with supporting evidence.

A possible relationship among cyanide-induced convulsions, calmodulin, nitric oxide and protein kinase C was investigated in mice. The ED50 value of cyanide as measured by induction of tonic seizures was significantly increased in a dose-dependent manner when mercuric chloride (0.5 or 5.0 nmol/body), gangliosides (GGS) (90 nmol/body), a protein kinase C inhibitor or trifluoperazine (TFP) (45 or 90 nmol/body), a calmodulin inhibitor were preinjected intracerebroventricularly (i.v.t.) and NG-nitro-L-arginine (NNA) (300 mg/kg), a nitric oxide (NO) synthase inhibitor was preinjected intraperitoneally (i.p.) in mice. These results suggest that protein kinase C, calmodulin, and NO dependent cyclic guanosine monophosphate (GMP) dependent enzymes may contribute to the induction of convulsions. In contrast, 2,4-dinitrophenol (DNP) (50 nmol/body, intracerebroventricularly (i.v.t.), an uncoupler of oxidative phosphorylation significantly decreased the ED50 value of cyanide. In addition, DNP (100 nmol/body, i.v.t.) produced a severe tonic seizure in all of the treated mice. These indicate that adenosine triphosphate (ATP) depletion may also contribute in part to the development of cyanide-induced convulsions.

2,4-Dinitrophenol↗

PubMed1991

Cyanide induces Ca(2+)-dependent and -independent release of glutamate from mouse brain slices.

The effect of cyanide-induced histotoxic hypoxia on endogenous glutamate release from mouse cortical, cerebellar and hippocampal slices was studied. Incubation of slices with cyanide over a 30 min period resulted in extracellular accumulation of glutamate which was decreased in the absence of Ca2+ in the incubation media. When glutamate release was continuously monitored by fluorometry, cyanide initiated a rapid release of glutamate. This initial release was found to be independent of extracellular calcium. Depolarizing concentrations of potassium chloride produced a predominantly Ca(2+)-dependent release. It is concluded that cyanide exposure induced a rapid release of endogenous glutamate mediated by both Ca(2+)-dependent and Ca(2+)-independent mechanisms.

Animals↗

PubMed1990

Cyanide intoxication--III. On the analogous and different effects provoked by non-lethal and lethal challenged doses.

1. The effect of acute cyanide administration to mice in a lethal and a non-lethal dose and the anti-cyanide effect of S-adenosyl-L-methionine (SAM) and thiosulphate were investigated. 2. The poisoning action was determined by measuring cytochrome oxidase, rhodanese and delta-aminolevulinic acid dehydratase (ALA-D) activity. 3. The toxic metabolizing degree was investigated by measuring plasma and urine thiocyanate levels. 4. The state of the sulfane sulfur pool was investigated by determining cyanide labile-sulfur levels. 5. These results support the belief that rhodanese plays a fundamental role in the detoxification process only when high levels of cyanide are administered.

Animals↗

PubMed1991

In vitro effect of cyanide, thiosulphate and S-adenosyl-L-methionine on the activity of rhodanese and other enzymes.

1. Some in vitro studies were performed to elucidate the action of S-adenosyl-L-methionine (SAM) and thiosulphate on liver rhodanese, delta-amino-levulinic acid dehydratase (Al A-D) and cytochrome oxidase affected by cyanide in the experimental conditions. 2. SAM was unable to interact with the sulfur substituted rhodanese complex suggesting that SAM would blockade the thiosulphate binding sites on rhodanese. 3. Cyanide and thiosulphate inhibited ALA-D activity when both compounds were present in the incubation or the preincubation mixture. Cyanide binding on the enzyme was irreversible. 4. Cyanide inhibited cytochrome oxidase activity and the reversible nature of the binding was demonstrated by gel filtration. 5. SAM had no effect on either ALA-D or cytochrome oxidase activities.

Animals↗

PubMed1988

Effects of carbonyl cyanide m-chlorophenylhydrazone on quantal transmitter release and ultrastructure of frog motor nerve terminals.

The quantal acetylcholine release and the ultrastructural effects of the metabolic inhibitor carbonyl cyanide m-chlorophenylhydrazone have been examined at frog neuromuscular junctions. Carbonyl cyanide m-chlorophenylhydrazone (2 microM) caused a temperature-dependent block of evoked quantal transmitter release accompanied by an increase in the rate of spontaneous quantal release. The carbonyl cyanide m-chlorophenylhydrazone-induced increase in miniature endplate potential frequency was neither antagonized nor prevented by tetrodotoxin. It also occurred in a Ca2+-free medium and after replacement of Ca2+ by Sr2+, indicating that it does not depend upon a Na+ or Ca2+ influx from the external medium but may act by releasing Ca2+ from intraterminal stores. Spontaneous quantal transmitter release was exhausted irreversibly within 4 h of carbonyl cyanide m-chlorophenylhydrazone (2 microM) action, during which time an average of 4.7 x 10(5) acetylcholine quanta were released per junction. The morphologic analysis revealed a significant temperature and time-dependent reduction in the number of synaptic vesicles with swelling and dispersion of mitochondria within the motor nerve terminals. Changes in synaptic vesicle number appear to be directly related to the intensity of transmitter release. The good correlation observed between the number of quanta secreted and the number of vesicles lost by nerve terminals in the absence of vesicle recycling provides an estimate of the initial store of transmitter quanta.

Acetylcholine↗

PubMed1984

Cyanide loss from tissue baths in the presence and absence of tissue.

Loss of cyanide from Krebs-Henseleit solution (KHS) was studied in aerated tissue baths at 38 degrees C in the presence and in the absence of tissue. The rate of cyanide loss was greater from 300-microM than from 30-microM solutions and still greater from 300-microM solutions in the presence of vascular tissue. Initial cyanide loss was much greater from the tissue-containing bath, and the half-time was shorter in the presence of tissue (54 min) than in its absence (98 min) in baths containing the same initial cyanide concentration (300 microM).

Animals↗

PubMed1991

Toxicokinetic aspects of chronic cyanide exposure in the rat.

Rats received 40, 80 and 160 mg KCN/kg body wt./24 h in the drinking water for 13 weeks. Fairly constant dose-related cyanide and thiocyanate levels were measured in blood, plasma and urine during the exposure. Blood cyanide concentrations were in the range of 16.0-25.5 nmol CN-/ml blood, thiocyanate concentrations in the range of 341-877 nmol SCN-/ml plasma following continuous administration of the maximum tolerated dose-level of 160 mg/kg body wt/24 h. The results suggest that continuous 13-week maximum tolerated cyanide exposure does not lead to saturation of cyanide detoxification pathways.

Administration, Oral↗

PubMed1992

High-performance liquid chromatographic determination of cyanide in human red blood cells by pre-column fluorescence derivatization.

A method for the determination of cyanide in human red cells has been developed. Cyanide was extracted from red cells by adding water and methanol, and then derivatized with 2,3-naphthalene-dialdehyde and taurine to give a fluorescent product, which was determined by reversed-phase high-performance liquid chromatography with fluorescence detection. The recovery of cyanide from red cells was ca. 83%, and the limit of detection was 100 pmol/ml. The mean concentrations of red cell cyanide from ten smokers and from ten non-smokers were 705 and 466 pmol/ml, respectively. The method was also applicable to whole blood.

Chromatography, High Pressure Liquid↗

PubMed1996

Determination of cyanide and thiocyanate in blood by gas chromatography and gas chromatography-mass spectrometry.

We devised a sensitive and simple method for determining cyanide and its major metabolite, thiocyanate, in blood using an extractive alkylation technique. Pentafluorobenzyl bromide was used as the alkylating agent, and tetradecyldimethylbenzylammonium chloride was used as the phase-transfer catalyst. The derivatives obtained were analyzed qualitatively by gas chromatography-mass spectrometry and quantitatively by gas chromatography with an electron-capture detection. The detection limits of cyanide and thiocyanate were 0.01 and 0.003 mumol/ml, respectively, while the gross recovery of both compounds was 80%. The calibration curve was linear over the concentration range from 0.02 to 1.0 mumol/ml for cyanide and from 0.01 to 1.0 mumol/ml for thiocyanate. The accuracy and precision of the method were evaluated, and the coefficients of variation were found to be within 10%. Using the method, the blood levels of two victims who had died from cyanide poisoning were determined.

Chromatography, Gas↗

PubMed1991

Cyanide toxicity from acetonitrile-containing false nail remover.

A patient presented without symptoms 30 minutes after ingesting acetonitrile, also known as methylacyanide. He had prompt gastric lavage and activated charcoal administration. Hours later, the onset of clinical toxicity was heralded by mental status abnormalities and vomiting prior to a generalized seizure. Following administration of sodium thiosulfate, the patient made an uneventful recovery. A blood cyanide level drawn shortly after presentation, but reported after the patient had been discharged, documented significant exposure. During hospitalization, cyanide toxicity was inferred from the history of ingestion of acetonitrile, plus a significant absence of venous blood hemoglobin desaturation. Because even small amounts can be harmful and toxicity is delayed, all acetonitrile ingestions should be presumed dangerous. Patients should be observed and repeatedly evaluated for at least 24 hours. In the absence of cyanide level determinations, lethargy, vomiting, seizures, and the lack of normal venous blood hemoglobin desaturation are clues to cyanide toxicity.

Acetonitriles↗

PubMedDate not supplied

Cyanide poisoning from propionitrile exposure.

A 55-year-old worker was exposed to propionitrile by both the inhalational and dermal routes. He rapidly lost consciousness and developed metabolic acidosis consistent with cyanide poisoning. Treatment with hydroxycobalamin and sodium thiosulfate produced complete symptom resolution within an hour. Serial blood cyanide and thiocyanate levels documented a rapid decrease in cyanide and concomitant increase in thiocyanate. Serious cyanide poisoning can occur from propionitrile exposure. Treatment with hydroxycobalamin and sodium thiosulfate can produce rapid clinical improvement.

Cyanides↗

PubMed1988

Carbamylation of hemoglobin in vivo with chronic sublethal dietary cyanide: implications for hemoglobin S.

Carbamylation of the hemoglobin in sickle cell anemia has been demonstrated to improve the status of this hemoglobinopathy. Using an animal model of West African human patterns of chronic sublethal dietary cyanide ingestion, 12 miniature swine consuming either 0, 0.4, 0.7, or 1.2 mg of cyanide/kg body weight/day were studied for 24 weeks to determine if this dietary regime could produce irreversible carbamylated hemoglobin. Throughout the study, the hematological status of all animals remained similar; however, the levels of carbamylated hemoglobin as measured by nanomoles of valine hydantoin varied proportionally to dietary sublethal cyanide intakes, indicating that these natural dietary levels could effect an important and presumably permanent modification of the hemoglobin's beta chain. Serum thiocyanate levels were also positively correlated with cyanide ingestion loads (r = 0.83, P less than 0.01). The implications of these findings in swine are important for the millions of humans with hemoglobin S who regularly consume similar levels of dietary cyanide and for our assessments of the biochemical and medical status of hemoglobin S under natural conditions.

Animals↗

PubMed1992

Cyanide selectively augments kainate- but not NMDA-induced release of glutamate and taurine.

The effect of cyanide on the kainate-, quisqualate- and N-methyl-D-aspartate (NMDA)-induced release of several amino acids from cerebellar granule neurons was studied. Cyanide, 100 microM, augmented the kainate- and quisqualate-induced release of glutamate and taurine in neurons but had no effect on the NMDA-induced release of these excitatory amino acids. In addition to the interaction with the above excitatory amino acids, cyanide had effects on several amino acids independent of excitatory amino acid stimulation; cyanide treatment resulted in a significant elevation over saline controls of arginine and taurine, but not alanine, aspartate+asparagine or glycine. With the exception of taurine, this pattern was not apparent in cells treated with any of the above excitatory amino acid.

Animals↗

PubMed2005

The concomitant expression and availability of conventional and alternative, cyanide-insensitive, respiratory pathways in Candida albicans.

The opportunistic oral pathogen Candida albicans expresses a cyanide-insensitive alternative oxidase (AOX) upon exposure to respiratory inhibitors that act downstream from coenzyme Q, and upon ageing of cells. To investigate whether the conventional pathway is retained when the alternative pathway is induced, cells were grown in the presence of sodium cyanide, a reversible inhibitor of cytochrome oxidase. AOX expression was monitored by Western blotting and the presence of cytochromes associated with complexes III and IV of the conventional pathway was monitored by recording spectra between 500 and 650 nm at 77K. The activities of complexes III and IV were determined in polarographic and enzyme-kinetic experiments using specific respiratory substrates and inhibitors. Results indicated that complexes III and IV are constitutively expressed and are functional in cells expressing AOX. Furthermore, the enzymatic activities of complexes III and IV were similar in mitochondrial preparations from cells grown with or without cyanide. We next investigated whether both pathways are simultaneously available for electron transfer from the Q pool to molecular oxygen. Respiration was virtually completely inhibited by the combination of cyanide and salicyl hydroxamic acid (SHAM) or antimycin A and SHAM, but only partly inhibited by either of these inhibitors alone. This indicates that electrons can in principle flow either through the conventional or the alternative respiratory pathway. The availability of two electron pathways in C. albicans and the potential use of either pathway endows this pleomorphic fungus with another level at which it can rapidly adjust to altered environmental conditions.

Antimycin A↗

PubMed2004

Prenatal toxicity of cyanide in goats--a model for teratological studies in ruminants.

Although exposure to cyanogenic plants or cyanide during pregnancy has adverse effects, no teratological study with cyanide has been conducted in goats or any other ruminant. The objective of the present study was to evaluate the effects of the maternal exposure to potassium cyanide (KCN) during pregnancy on both dams and offspring and furthermore, to develop a model for prenatal toxicological studies in ruminants. Twenty-six pregnant goats were allocated into four groups and given 0, 1.0, 2.0, or 3.0mg KCN/kg body weight per day orally (administered via twice-daily gavage) from Day 24 of pregnancy to term. However, one control dam and another from the 3.0mg KCN/kg per day group were sacrificed on Day 120. At birth, the kids were examined carefully for gross abnormalities. Three months after birth, the male kids and one dam from each group were sacrificed for histopathological study. Although clinical signs of poisoning were observed in dams, cyanide treatment did not alter the length of gestation or the number of live kids. Two prognata kids were born in the 3.0mg KCN/kg group, and one dam from the same group aborted two fetuses. There were histological lesions only in the KCN-treated dam (and its fetuses) sacrificed on Day 120; these consisted of an increased number of resorption vacuoles of thyroid follicular colloid, and status spongiosis of nervous white matter. This study proposes a new animal model for teratogenic trials that could be important to evaluate the effects of chemicals throughout pregnancy in goats and potentially other ruminants.

Abnormalities, Drug-Induced↗

PubMed1998

NADH fluorescence in isolated guinea-pig and rat cardiomyocytes exposed to low or high stimulation rates and effect of metabolic inhibition with cyanide.

In this study we investigated whether NADH fluorescence levels changed in response to low or high rates of electrical stimulation in single ventricular myocytes isolated from rat and guinea-pig hearts, either during a single contraction or upon sustained electrical stimulation of cells. NADH levels were determined from cell autofluorescence and cell length monitored using an edge-tracking device. NADH/NAD+ was obtained by addition of cyanide, 100% NADH, and carbonylcyanide-p-trifluoromethoxy phenylhydrazone (FCCP), 100% NAD+. Rat myocytes exhibited slightly higher resting fluorescence levels than guinea-pig cells; however, NADH/NAD+ was higher in rat than guinea-pig cells (P < 0.05), 24.3+/-4.3 (N = 17) vs 14.6+/-1.6 (N = 17), respectively. There was no change in NADH fluorescence during a single contraction when cells were stimulated at either low (0.2 Hz) or high (3 Hz) rates in either species. Furthermore, NADH levels did not change upon sustained stimulation at 3 Hz in either species. Metabolic blockade with cyanide induced a dose dependent rise in NADH fluorescence which was similar for both rat and guinea-pig myocytes and reached a maximum at > or = 1 mM of cyanide. Although a full recovery of NADH fluorescence was seen in both types of cells after brief exposure to cyanide, the rate of recovery was significantly slower in rat myocytes; times to 90% recovery were 110+/-29 sec, N = 6, and 264+/-50 sec, N = 6, for guinea-pig and rat cells, respectively. This work demonstrates that although rat and guinea-pig myocytes have different resting NADH/NAD+, their response to electrical stimulation is the same, whereas in response to metabolic inhibition subtle differences are seen.

Animals↗