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PubMed1979

Effect of Ethylene and Oxygen on the Development of Cyanide-resistant Respiration in Whole Plant Mitochondria.

Mitochondria from whole potatoes (Solanum tuberosum) ordinarily fail to oxidize respiratory substrates and to consume molecular O(2) in the presence of cyanide. Mitochondrial preparations obtained from tubers previously held for 24 hours in ethylene (10 microliters per liter) in air are only partially inhibited by cyanide. Application of ethylene in 100% O(2) led to an additional increase in the resistance of the mitochondrial respiration to cyanide. The resistance to cyanide was accompanied by a decrease in the respiratory control but no change in oxidative phosphorylation as shown by the measurement of ATP synthesis.The development of resistance to cyanide following the application of ethylene appears to require whole tubers and may represent an inductive process.

Journal Article↗
PubMed1979

Factors Influencing the Development of Cyanide-resistant Respiration in Potato Tissue.

Ethylene, cyanide gas, and volatalized ethanol, acetaldehyde, and acetic acid were applied in a continuous flow to whole potato tubers. Freshly cut slices were obtained periodically during the treatment, and showed a progressive development of a cyanide-resistant respiration. The application of the employed volatiles in 100% O(2) accelerated the onset and the magnitude of the cyanide-resistant respiration.These results show that, similar to ethylene and cyanide, the application of ethanol, acetaldehyde, or acetic acid can also lead to the development of cyanide-resistant respiration in whole potato tubers, and that this type of respiration is retained in freshly cut slices.

Journal Article↗
PubMed1979

Cyanide-insensitive Respiration in Pea Cotyledons.

Mitochondria isolated by a zonal procedure from the cotyledons of germinating peas possessed a cyanide-resistant respiration. This respiration was virtually absent in mitochondria isolated during the first 24 hours of germination but thereafter increased gradually until the 6th or 7th day of seedling development. At this time between 15 and 20% of the succinate oxidation was not inhibited by cyanide. The activity of the cyanide-resistant respiration was also determined in the absence of cyanide. Relationships among mitochondrial structure, cyanide-resistant respiration, and seedling development are discussed.

Journal Article↗
PubMed1982

Malate Oxidation and Cyanide-Insensitive Respiration in Avocado Mitochondria during the Climacteric Cycle.

After preparation on self-generated Percoll gradients, avocado (Persea americana Mill, var. Fuerte and Hass) mitochondria retain a high proportion of cyanide-insensitive respiration, especially with alpha-ketoglutarate and malate as substrates. Whereas alpha-ketoglutarate oxidation remains unchanged, the rate of malate oxidation increases as ripening advances through the climacteric. An enhancement of mitochondrial malic enzyme activity, measured by the accumulation of pyruvate, closely parallels the increase of malate oxidation. The capacity for cyanide-insensitive respiration is also considerably enhanced while respiratory control decreases (from 3.3 to 1.7), leading to high state 4 rates.Both malate dehydrogenase and malic enzyme are functional in state 3, but malic enzyme appears to predominate before the addition of ADP and after its depletion. In the presence of cyanide, a membrane potential is generated when the alterntive pathway is operating. Cyanide-insensitive malate oxidation can be either coupled to the first phosphorylation site, sensitive to rotenone, or by-pass this site. In the absence of phosphate acceptor, malate oxidation is mainly carried out via malic enzyme and the alternative pathway. Experimental modification of the external mitochondrial environment in vitro (pH, NAD(+), glutamade) results in changes in malate dehydrogenase and malic enzyme activities, which also modify cyanide resistance. It appears that a functional connection exists between malic enzyme and the alternative pathway via a rotenone-insensitive NADH dehydrogenase and that this pathway is responsible, in part, for nonphosphorylating respiratory activity during the climacteric.

Journal Article↗
PubMed1989

Sulfide-Resistant Respiration in Leaves of Elodea canadensis Michx: Comparison with Cyanide-Resistant Respiration.

The rate of dark O(2) uptake of Elodea canadensis leaves was titrated with either cyanide or sulfide in the presence and in the absence of 5 millimolar salicylhydroxamic acid (SHAM), an inhibitor of the alternative oxidase. The inhibition of O(2) uptake by SHAM alone was very small (3-6%), suggesting that actual respiration mainly occurred through the cytochrome pathway. O(2) uptake was slightly stimulated by cyanide at concentrations of 50 micromolar or higher, but in the presence of SHAM respiration was strongly suppressed. The effects of sulfide on O(2) uptake were similar to those of cyanide, except that the percent stimulation of O(2) uptake by sulfide alone was somewhat higher than that of cyanide. However, the estimates of the capacity of the alternative pathway were similar with both inhibitors. Another difference is that maximal inhibition of respiration in the presence of SHAM was observed with lower concentrations of sulfide (50 micromolar) than cyanide (250 micromolar). The results suggest that sulfide can be used as a suitable inhibitor of cytochrome c oxidase in studies with intact plant tissues, and that sulfide does not apparently inhibit the alternative oxidase.

Journal Article↗
PubMed1989

[Direct potentiometric determination of the level of cyanide in plasma following an infusion of sodium nitroprusside].

Plasma cyanide concentrations were measured potentiometrically in 12 patients before and after infusion of sodium nitroprusside (SNP). A close correlation was found between the increase in plasma cyanide level and the total dose of SNP and between the increase and the mean rate of SNP infusion. After a total dose of 3.1 mumol SNP/kg (0.924 mg/kg) the maximum plasma cyanide concentration amounted to 2.2 mumol/1 (57 micrograms/l) which is lower than the recommended upper limit of 3 mumol/l plasma (78 micrograms/l); but indicates the importance of the recommended maximum dose of 5 mumol SNP/kg (1.5 mg/kg) and the control of plasma cyanide levels under SNP treatment. The direct potentiometric evaluation of the plasma cyanide level using the indicator method seems to be useful for such a control because it is more sensitive and faster than spectroscopic methods. The time needed for performing one measurement is about 35 minutes.

Adult↗
PubMed1987

Proton NMR study of the cyanide metmyoglobin reconstituted with meso-tetraalkylhemins. Dynamic free rotation of the synthetic hemins in the heme pocket.

Incorporation of the three synthetic hemins, Fe(III) meso-tetraalkylporphyrins with the methyl, ethyl, or n-propyl groups, into apomyoglobin was followed by spectrophotometry, and the stoichiometric complex formation was confirmed. The reconstituted myoglobins bind with an equimolar amount of cyanide to exhibit visible absorption peaks at 419, 570, and 608 nm. The spectral feature was independent of the cyanide concentrations. Proton NMR spectra of the cyanide complexes resolved the pyrrole-proton signals of the hemins in a -5 to -15-ppm region, which is comparable with that of the corresponding signals of deuterohemin-containing low-spin methemoproteins. These spectral observations indicate the presence of the NC-Fe-N(His-F8) structure in the presently reconstituted cyanide metmyoglobins. The pyrrole-proton NMR signals of the hemins in cyanide metmyoglobins appeared as a singlet, doublet, or quartet for the methyl, ethyl, or n-propyl hemin complexes, respectively. The systematic NMR spectral changes suggest the dynamic free rotation of the alkylhemins about the Fe-N(His-F8) bond. Temperature-dependent NMR spectral transition of the meso-tetraethylhemin-reconstituted myoglobin was consistent with thermally regulated dynamic free rotation of the hemin in the myoglobin heme pocket.

Apoproteins↗
PubMed1987

Mechanism of the cyanide-catalyzed oxidation of alpha-ketoaldehydes and alpha-ketoalcohols.

Cyanide catalyzes the reduction of dioxygen or of ferricytochrome c by dihydroxyacetone phosphate. The rapid initial phase of these reactions, but not the subsequent slow phase, was augmented by incubating the triose phosphate aerobically or anaerobically at pH 9.0 prior to adding the cyanide. The aerobic incubation, which was most effective, was associated with a decline in enediol, whereas the less effective anaerobic incubation was accompanied by an increase in enediol content. This suggested that the alpha-ketoaldehyde product of autoxidation of the enediol, rather than the enediol itself, was responsible for the rapid phase reaction which followed addition of cyanide. This was confirmed by exploring the cyanide-catalyzed oxidation of the alpha-ketoaldehyde, phenylglyoxal. The inhibitory effect of the manganese-containing superoxide dismutase indicated that O2- was a kinetically important intermediate of the rapid phase reaction. A reaction mechanism is proposed which is consistent with the results presented.

Catalase↗
PubMed1988

Unexpected stimulation of mitochondrial ADP-ribosylation by cyanide.

Cyanide, the classical inhibitor of the mitochondrial respiratory chain at site III, stimulates ADP-ribosylation of a number of mitochondrial proteins, the major protein being the 50-55 kDa band. Sodium azide, sharing the same inhibitory site, does not have the same effect. Rotenone or antimycin A have no influence on mitochondrial ADP-ribosylation. Data suggest that no apparent correlation exists between oxidoreductase function and protein ADP-ribosylation. Purified nuclear poly(ADP-ribose) polymerase activity was not affected by cyanide. The cyanide effect on mitochondrial ADP-ribosylation seems intriguing and may be attributed to NAD+-CN complex formation, since NAD reacts with cyanide at pH greater than 8 with N-substituted nicotinamide which may prevent inhibition of ADP-ribosylation.

Adenosine Diphosphate Ribose↗
PubMed1983

Kinetic analysis of anaerobic metabolism in rats during acute cyanide poisoning.

In order to investigate the changes in energy metabolism during acute anoxia, blood levels of various metabolites were analysed in cyanide-poisoned rats. After intraperitoneal injection of a sublethal dose of potassium cyanide (5 mg/kg), blood samples were obtained by cervical dislocation at intervals of 5 min until 30 min. Lactate and lactate/pyruvate ratio (L/P) in plasma concomitantly changed with cyanide; increased rapidly at 5 min, remained fairly constant until 20 min and then began to decrease at 25 min. In contrast, the products of ATP degradation, oxypurines and inorganic phosphate (Pi), increased gradually until 25 min and then began to decrease at 30 min. Allantoin in plasma scarcely increased throughout the experiments. The results indicate that the rapid activation of anaerobic ATP formation by glycolysis was followed by the increase in ATP degradation in cyanide-poisoned rats, Thus, increase in plasma oxypurines could be regarded as an indicator for severe anoxic states in tissues with massive ATP degradation.

Allantoin↗
PubMed1985

Antagonism of cyanide poisoning by chlorpromazine and sodium thiosulfate.

Anti-cyanide action by sodium thiosulfate (ST) was enhanced by prior administration of chlorpromazine (CPZ). However, CPZ (alone) provided no protection against cyanide lethality. To investigate the possibility that CPZ enhances thiocyanate formation in ST-pretreated mice, the effects of CPZ on rhodanese activity and the time course of plasma thiocyanate concentrations were investigated. CPZ did not alter hepatic rhodanese kinetics nor did it enhance plasma thiocyanate concentrations in ST-pretreated mice. The effect of CPZ and ST on the time course of cytochrome oxidase inhibition and recovery, in vivo, was also investigated. At 4 mg KCN/kg, maximal inhibition of brain (40%) and heart (60%) cytochrome oxidase occurred 10 to 20 min post-challenge in control and CPZ-pretreated mice, while no inhibition occurred in ST- and CPZ/ST-pretreated mice. Twenty milligrams KCN/kg caused 100% lethality in control and CPZ-pretreated mice and 6/25 and 4/20 deaths were observed in ST- and CPZ/ST-pretreated mice, respectively. No significant inhibition of brain, heart, and liver cytochrome oxidase activities was observed in surviving ST- and CPZ/ST-pretreated mice challenged with 20 mg KCN/kg. Control and CPZ-pretreated mice died within 5 min of KCN challenge and had almost the same degree of inhibition of brain (35 and 29%, respectively) and heart (60 and 55%, respectively) cytochrome oxidase as did similarly pretreated mice 5 min after challenge with a nonlethal cyanide dose (4 mg/kg). Our results suggest that CPZ does not enhance the formation of thiocyanate in ST-pretreated mice. In addition, the similar degree of cytochrome oxidase inhibition noted after both lethal and nonlethal KCN treatments raises questions as to the ultimate target in cyanide-induced lethality.

Analysis of Variance↗
PubMed1986

Stereospecific effect of naloxone hydrochloride on cyanide intoxication.

Cyanide intoxication in mice can be antagonized by the opiate antagonist, (-)naloxone HCl, alone or in combination with sodium thiosulfate and/or sodium nitrite. Potency ratios, derived from LD50 values, were compared in groups of mice pretreated with sodium nitrite (sc, 100 mg/kg), sodium thiosulfate (ip, 1 g/kg), and (-)naloxone HCl (sc, 10 mg/kg) either alone or in various combinations. These results indicate that naloxone HCl provides a significant protection against the lethal effects of potassium cyanide. The protective effect of sodium thiosulfate, but not sodium nitrite, was enhanced with (-)naloxone HCl. The combined administration of sodium nitrite and sodium thiosulfate was further enhanced with (-)naloxone HCl. This protective effect of naloxone HCl against the lethal effect of cyanide appears to be restricted to the (-)stereoisomer, as the (+)stereoisomer, the inactive opiate antagonist, is also inactive in protecting against the lethal effects of cyanide. The mechanism of antagonism is discussed.

Animals↗
PubMed1992

A possible mechanism for the increase in brain tyrosine levels induced by cyanide in mice.

Subcutaneous administration of cyanide significantly increased blood tyrosine levels of mice in a dose dependent manner. Tyrosine aminotransferase activity in liver of mice was significantly decreased in the presence of cyanide (8, 10, 20, 40, 50, 65, 80 and 100 microM), also in a concentration-dependent manner, with a positive correlation between the percentage increase of blood tyrosine levels and the percentage decrease of hepatic tyrosine aminotransferase activity. These results suggest that the increased tyrosine levels induced in blood by cyanide may be related to its inhibition of tyrosine aminotransferase activity in the liver. Cyanide decreased hepatic ATP content and increased blood ammonia levels and brain tyrosine in a dose-dependent manner. As it is known that hyperammonaemia increases the uptake of neutral amino acids such as tyrosine into the brain from blood, the mechanism by which tyrosine levels increase in the brain may be based on increases of both tyrosine and ammonia levels in blood.

Adenosine Triphosphate↗
PubMed1989

Cyanide and arsenic poisoning by intravenous injection.

A 29-year-old man was found unresponsive a few minutes after self-injecting undetermined amounts of potassium cyanide and sodium arsenite intravenously in a suicide attempt. Treatment with the Lilly Cyanide Antidote kit rapidly resolved the initial coma, despite a whole blood cyanide level of 4.4 micrograms/mL. A 12-hour urine arsenic collection begun on admission showed 10,065 micrograms arsenic/12 hr. The patient received intramuscular BAL initially, which was followed by two ten-day courses of oral D-penicillamine. Complications included upper gastrointestinal tract bleeding requiring transfusion, transient elevations of liver function tests, self-limited complaints of decreased vision with conjunctival hyperemia and photophobia, and an abscess at the injection site. Although specific antidote therapy completely resolved the cyanide toxicity, early and prolonged arsenic chelation did not prevent a mild sensory peripheral neuropathy from developing with onset about 17 days after self-injection.

Adult↗
PubMed1987

Magnetic resonance studies on the copper site of dopamine beta-monooxygenase in the presence of cyanide and azide anions.

In order to elucidate the coordination state of water molecules in the Cu(II) site of dopamine [( 3,4-dihydroxyphenyl)ethylamine] beta-monooxygenase, measurements of the paramagnetic 1H nuclear magnetic relaxation rate of solvent water in the enzyme solution containing cyanide or azide as an exogenous ligand were carried out to obtain the values of intrinsic paramagnetic relaxation rate decrements Rp1 and Rp2 for the ligand-enzyme 1:1 and 2:1 complexes, respectively. Rp1 (percent) values were 53 (pH 5.5) and 52 (pH 7.0) for cyanide and 38 (pH 5.5) and 32 (pH 7.0) for azide, while Rp2 (percent) values were 98 (pH 5.5) and 96 (pH 7.0) for azide. Although no Rp2 values for cyanide were obtained because of its reducing power at the Cu(II) site, the Rp1 and Rp2 values obtained above prove that the Cu(II) center has two coordinated water molecules that are exchangeable for exogenous ligands at either pH. Supporting evidence was provided by electron paramagnetic resonance (EPR) titration, in which the enzyme solution containing cyanide-enzyme (1:1) complex in an equal proportion to uncomplexed enzyme gave an observed paramagnetic relaxation rate decrement, Rp, of 23%. Another characteristic of the Rp1 and Rp2 values was their invariability with respect to pH, indicating that the three-dimensional structure of the Cu(II) site is pH-invariant within the range examined. Binding constants of ligand to enzyme Kb1 and Kb2 for 1:1 and 2:1 complex formation, respectively, were also determined through an analysis of the Rp values; it was found that Kb1 was larger than Kb2 irrespective of pH. (ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Medulla↗
PubMed1976

Mechanism of inhibition by carbonyl cyanide m-chlorophenylhydrazone and sodium deoxycholate of cytochrome P-450-catalysed hepatic microsomal drug metabolism.

1. Treatment of liver microsomal fraction with 0.03-0.12% sodium deoxycholate and 0.005-0.06 mM carbonyl cyanide m-chlorophenylhydrazone decreases phospholipid-dependent hydrophobicity of the microsomal membrane, assayed by the kinetics of 8-anilinonaphthalene-1-sulphonate binding and ethyl isocyanide difference spectra. 2. Sodium deoxycholate at a concentration of 0.01% lacks its detergent properties, but competitively inhibits aminopyrine binding and activates the initial rate of NADPH-cytochrome P-450 reductase. In the presence of 0.03-0.09% sodium deoxycholate the rate-limiting factor in p-hydroxylation of aniline is the content of cytochrome P-450. and that for N-demethylation of aminopyrine is the activity of NADPH-cytochrome P-450 reductase. 3. Carbonyl cyanide m-chlorophenylhydrazone has no effect on the binding and metabolism of aniline; investigation of its inhibiting effect on aminopyrine N-demethylase established that the rate-limiting reaction is the dissociation of the enzyme-substrate complex in the microsomal preparations. 4. In the mechanism of action of carbonyl cyanide m-chlorophenylhydrazone the key step may be the electrostatic interaction of its protonated form and one of the forms of activated oxygen at the catalytic centre of cytochrome P-450. 5. at least two different phospholipid-dependent hydrophobic zones are assumed to exist in the microsomal membrane, both coupled with cytochrome P-450. One of them reveals selective sensitivity to the protonation action of carbonyl cyanide m-chlorophenylhydrazone and contains the 'binding protein' for type I substrates and NADPH-cytochrome P-450 reductase; the other contains the cytochrome P-450 haem group and binding sites for type II substrates.

Aminopyrine↗
PubMed1980

Non-classical inhibition of uricase by cyanide.

The interactions of Aspergillus flavus uricase with the substrates O2 and urate and the inhibitors xanthine, cyanide, periodate and hydroxylamine were investigated. Under equilibrium conditions O2 does not bind directly to the enzyme, and the absence of O2 had no effect on either the binding stoicheiometry or binding constant for xanthine, as measured by equilibrium dialysis and microcalorimetry. Cyanide, periodate and hydroxylamine inhibit uricase in a non-classical manner. A decrease in initial velocity to a steady-state inhibited velocity can be observed on a time scale of minutes. The time-dependence, which is unaltered by prior incubation with the inhibitors, is consistent with a first-order transition. Rate constants for induction of inhibition are linearly dependent on inhibitor concentration, but independent of urate and O2 concentrations. Radioactively labelled urate forms a stable but reversible complex with uricase in the presence of cyanide and O2. These results were used to deduce the nature of enzyme-bound intermediates and thus for the proposal of a novel mechanism for cyanide inhibition.

Aspergillus flavus↗
PubMed1999

Bioactivation of cyanide to cyanate in sulfur amino acid deficiency: relevance to neurological disease in humans subsisting on cassava.

Neurological disorders have been reported from parts of Africa with protein-deficient populations and attributed to cyanide (CN-) exposure from prolonged dietary use of cassava, a cyanophoric plant. Cyanide is normally metabolized to thiocyanate (SCN-) by the sulfur-dependent enzyme rhodanese. However, in protein-deficient subjects where sulfur amino acids (SAA) are low, CN may conceivably be converted to cyanate (OCN-), which is known to cause neurodegenerative disease in humans and animals. This study investigates the fate of potassium cyanide administered orally to rats maintained for up to 4 weeks on either a balanced diet (BD) or a diet lacking the SAAs, L-cystine and L-methionine. In both groups, there was a time-dependent increase in plasma cyanate, with exponential OCN- increases in SAA-deficient rats. A strongly positive linear relationship between blood CN- and plasma OCN- concentrations was observed in these animals. These data are consistent with the hypothesis that cyanate is an important mediator of chronic cyanide neurotoxicity during protein-calorie deficiency. The potential role of thiocyanate in cassava-associated konzo is discussed in relationship to the etiology of the comparable pattern of motor-system disease (spastic paraparesis) seen in lathyrism.

Animals↗