Organ-distribution of the metabolite 2-aminothiazoline-4-carboxylic acid in a rat model following cyanide exposure

The reaction of cyanide (CN(-)) with cystine to produce 2-aminothiazoline-4-carboxylic acid (ATCA) is one of the independent detoxification pathways of cyanide in biological systems. In this report, in vivo production of ATCA and its distributions in plasma and organs were studied after a subcutaneous sublethal dose of 4?mg/kg body weight potassium cyanide (KCN) administration to rats. At this sublethal dose of KCN, ATCA concentration was not significantly increased in the plasma samples, however, it was found significantly increased in liver samples. These results suggested that ATCA might not be a good diagnostic biomarker in plasma for sublethal cyanide exposure; however, liver could serve as the right organ for the detection of ATCA in post-mortem examinations involving cyanide exposure in military, firefighting, industrial and forensic settings.     

Determination of the cyanide metabolite 2-aminothiazoline-4-carboxylic acid in urine and plasma by gas chromatography-mass spectrometry

The cyanide metabolite 2-aminothiazoline-4-carboxylic acid (ATCA) is a promising biomarker for cyanide exposure because of its stability and the limitations of direct determination of cyanide and more abundant cyanide metabolites. A simple, sensitive, and specific method based on derivatization and subsequent gas chromatography-mass spectrometry (GC-MS) analysis was developed for the identification and quantification of ATCA in synthetic urine and swine plasma. The urine and plasma samples were spiked with an internal standard (ATCA-d(2)), diluted, and acidified. The resulting solution was subjected to solid phase extraction on a mixed-mode cation exchange column. After elution and evaporation of the solvent, a silylating agent was used to derivatize the ATCA. Quantification of the derivatized ATCA was accomplished on a gas chromatograph with a mass selective detector. The current method produced a coefficient of variation of less than 6% (intra- and interassay) for two sets of quality control (QC) standards and a detection limit of 25 ng/ml. The applicability of the method was evaluated by determination of elevated levels of ATCA in human urine of smokers in relation to non-smokers for both males and females.     

Species Differences in the Selective Inhibition of Monoamine Oxidase (1-methyl-2-phenylethyl)hydrazine and its Potentiation by Cyanide

The potentiating effects of cyanide on the inhibition of rat liver mitochondrial monoamine oxidase-A & B and of ox liver mitochondrial MAO-B by pheniprazine [(1-methyl-2-phenylethyl)hydrazine] has been studied. Pheniprazine was shown to behave as a mechanism-based MAO inhibitor. For rat liver MAO-B, the initial non-covalent step was characterized by dissociation constant (K _i) of 2450 nM and the first-order rate constant (k ₊₂) for the covalent adduct formation was 0.16 min⁻¹. As a reversible inhibitor it was selective towards rat liver MAO-A (K _i = 420 nM) but the rate of irreversible inhibition of that enzyme was considerably slower (k ₊₂ = 0.06 min⁻¹). MAO-B from ox liver more closely resembled MAO-A from the rat in sensitivity to reversible inhibition by pheniprazine (K _i = 450 nm) but it was closer to rat liver MAO-B in rate of irreversible inhibition (k ₊₂ = 0.29 min⁻¹). The K _i values were significantly decreased in the presence of KCN but there was little effect on the k ₊₂ values. However, sensitivities of the different enzymes to KCN varied widely and considerably higher concentrations of KCN were required for this effect to be apparent with the rat liver mitochondrial MAO-A than with MAO-B from rat and ox liver. The kinetic behaviour of cyanide activation was consistent with partial (non-essential) competitive activation in all cases. Special issue dedicated to Dr. Moussa Youdim.     

Biochemical effects of sublethal doses of cypermethrin on the sixth-instar larvae of Tribolium castaneum (Herbst.)

Effects of sublethal doses ie, 2, 4, 10, and 20 ppm of cypermethrin, were studied on the sixth-instar larvae of Tribolium castaneum (Herbst.). Of all the biochemical parameters tested, the free amino acids and cholesterol content and the activity of amylase were found to be the most sensitive components. Glutamate pyruvate transaminase activity was elevated at all doses except 2 ppm. The activities of alkaline phosphatase and glutamate oxaloacetate transaminase and glucose content were raised significantly at doses of 10 and 20 ppm. Acid phosphatase activity and the soluble protein content increased at a dose of 20 ppm. Total lipid and triglycerides, however, decreased significantly at this sublethal dose. Other biochemical parameters, such as cholinesterase and lactate dehydrogenase activities and the total protein, urea, glycogen, DNA, and RNA contents, were not significantly affected by exposure to different doses of cypermethrin.     

Cyanide as a feeding stimulant for the southern army worm, Spodoptera eridania

ABSTRACT.

• 1 All instars of Spodoptera eridania larvae grow as well or better when cyanide is present in their diet as when it is absent. Concentrations up to 0.05% stimulate feeding in first to fourth instar larvae. Concentrations from 0.1% to 1.0% stimulate feeding in fifth and sixth instar larvae.
• 2 Three-day-old sixth instar larvae pre-exposed to cyanide are completely resistant to its acutely toxic effects, but previously unexposed larvae suffer reversible symptoms of poisoning when feeding on a diet containing 1.0% KCN.
• 3 A 1.0% dietary KCN exposure during the sixth instar reduces ecdysis to 17% adult emergence and completely inhibits oviposition.
• 4 Cyanide concentrations from 0.5% to 1.0% in the diet, although effecting increased growth rates, induce necrotic lesions in larval mid-gut epithelial cells.
• 5 Thiocyanate, one of the in vivo cyanide metabolites, at 0.5% in the diet reduces pupation to 23%, delays and reduces adult emergence to 20% and inhibits oviposition.
• 6 The preferred host plant of S.eridania is the lima bean, Phaseolus lunatus, probably due to its content of the cyanogenic glycoside linamarin. Dietary valine has no effect on the southern armyworm feeding and growth behaviour (Long & Brattsten, 1982) but dietary cyanide does. The lima bean is known to contain up to 31 ppm cyanide in some varieties.

     

Nitrogen supply and cyanide concentration influence the enrichment of nitrogen from cyanide in wheat (Triticum aestivum L.) and sorghum (Sorghum bicolor L.)

Cyanide assimilation by the β‐cyanoalanine pathway produces asparagine, aspartate and ammonium, allowing cyanide to serve as alternate or supplemental source of nitrogen. Experiments with wheat and sorghum examined the enrichment of ¹⁵N from cyanide as a function of external cyanide concentration in the presence or absence of nitrate and/or ammonium. Cyanogenic nitrogen became enriched in plant tissues following exposure to ¹⁵N‐cyanide concentrations from 5 to 200 µm , but when exposure occurred in the absence of nitrate and ammonium, ¹⁵N enrichment increased significantly in sorghum shoots at solution cyanide concentrations of ≥50 µm and in wheat roots at 200 µm cyanide. In an experiment with sorghum using ¹³C¹⁵N, there was also a significant difference in the tissue ¹³C:¹⁵N ratio, suggestive of differential metabolism and transport of carbon and nitrogen under nitrogen‐free conditions. A reciprocal ¹⁵N labelling study using KC¹⁵N and ¹⁵NH₄⁺ and wheat demonstrated an interaction between cyanide and ammonium in roots in which increasing solution ammonium concentrations decreased the enrichment from 100 µm cyanide. In contrast, with increasing solution cyanide concentrations there was an increase in the enrichment from ammonium. The results suggest increased transport and assimilation of cyanide in response to decreased nitrogen supply and perhaps to ammonium supply.     

Dose and Time‐Dependent Effects of Cyanide on Thiosulfate Sulfurtransferase, 3‐Mercaptopyruvate Sulfurtransferase,and Cystathionine λ‐Lyase Activities

We assessed the dose‐dependent effect of potassium cyanide (KCN) on thiosulfate sulfurtransferase (TST), 3‐mercaptopyruvate sulfurtransferase (3‐MPST), and cystathionine λ‐lyase (CST) activities in mice. The time‐dependent effect of 0.5 LD50 KCN on cyanide level and cytochrome c oxidase (CCO), TST, 3‐MPST, and CST activities was also examined. Furthermore, TST, 3‐MPST, and CST activities were measured in stored mice cadavers. Hepatic and renal TST activity increased by 0.5 LD50 KCN but diminished by ≥2.0 LD50. After 0.5 LD50 KCN, the elevated hepatic cyanide level was accompanied by increased TST, 3‐MPST, and CST activities, and CCO inhibition. Elevated renal cyanide level was only accompanied by increased 3‐MPST activity. No appreciable change in enzyme activities was observed in mice cadavers. The study concludes that high doses of cyanide exert saturating effects on its detoxification enzymes, indicating their exogenous use during cyanide poisoning. Also, these enzymes are not reliable markers of cyanide poisoning in autopsied samples.     

Inductive and synergistic interactions between plant allelochemical flavone and Bt toxin Cry1Ac in Helicoverpa armigera

Genetically engineered crops simultaneously produce defensive allelochemicals and Bacillus thuringiensis (Bt) toxin proteins to kill some of the world's most devastating insect pests. How the two types of toxins, when ingested sequentially or simultaneously, interact at both lethal and sublethal doses in these pests remains underexplored. Here, we examined the toxicological interactions between the Bt toxin Cry1Ac and the flavonoid allelochemical flavone in Helicoverpa armigera. Simultaneous exposure of H. armigera neonates to lethal doses (LC₂₅) of Cry1Ac and flavone caused a mortality significantly higher than that of either toxin alone and their expected additive mortality. Preexposure for 24 h to a sublethal dose (LC₁₀) of Cry1Ac followed by 6-d simultaneous exposure to the same dose of Cry1Ac plus a lethal dose (1.6 mg/g diets, LC₅₀) of flavone resulted in a mortality significantly higher than that of the LC₅₀ dose of flavone alone and the expected additive mortality of the LC₅₀ dose of flavone plus the LC₁₀ dose of Cry1Ac. One-day preexposure to the sublethal dose (LC₁₀) of flavone followed by 6-d simultaneous exposure to the LC₅₀ dose (6 ng/cm²) of Cry1Ac plus the LC₁₀ dose of flavone yielded a mortality significantly higher than that of the LC₅₀ dose of Cry1Ac but similar to the expected additive mortality of the LC₅₀ dose of Cry1Ac plus the LC₁₀ dose of flavone. The results suggest that Cry1Ac induces and synergizes the toxicity of flavone against H. armigera larvae.     

Physiologically based pharmacokinetic modeling of hydrogen cyanide in humans following the oral administration of potassium cyanide and cyanogenic glycosides from food

Abstract

Cyanogenic glycosides (CGs) are commonly found in some edible plants and seeds. After ingestion, CGs can release toxic hydrogen cyanide (HCN) in humans. At present, unfortunately, there is no tool capable of predicting the cyanide concentration in human blood and organs following oral administration of CG-containing food. The aim of this study was to develop a physiologically based pharmacokinetic (PBPK) model of cyanide following the ingestion of CG-containing food in humans. To develop this model, pharmacokinetic data concerning cyanide concentration levels in humans exposed to potassium cyanide (KCN) and CG-containing foods (persipan paste, linseed, cassava, and bitter apricot kernels) were obtained from published data. This study created a model structure consisting of four organ compartments including the lungs, kidneys, liver, and slowly perfused tissues by employing Berkeley Madonna software to extract three unknown parameters including the maximum velocity of rhodanese, the absorption rate constant, and the bioavailability for oral administration of KCN and the four CG-containing foods (equivalent a 6.8?mg dose of cyanide). The model was then validated by comparing the simulated results for the concentration-time courses of cyanide levels in venous blood with data from two clinical studies covering the oral administration of KCN and linseed at three other doses.     

Zinc uptake by isolated rat hepatocytes

Isolated rat hepatocytes were used to investigate the uptake of zinc at early exposure times. Hepatocytes were incubated with ⁶⁵Zn (1–500 μM) and samples were withdrawn at times ranging from 25 s to 60 min. A biphasic pattern of uptake was observed with a rapid first phase of uptake followed by a slower second phase. The relationship between velocity of uptake and substrate concentration for the first phase was nonlinear, while that of the second phase was linear. The presence of 10 μM cadmium produced a decrease in the velocity of uptake of only the first phase. This suggests that the first phase is at least partly carrier mediated, while there is no indication of involvement of a carrier in the second phase. KCN (1 mM) and carbonyl cyanide m-chlorophenylhydrazone (2 μM), did not cause any change in the uptake of ⁶⁵Zn (1 μM), which suggests that there is no active component in the uptake of zinc.     

Perturbations in polyamines and related enzymes following chlordecone-potentiated bromotrichloromethane hepatotoxicity

The mechanism by which chlordecone (CD) amplifies the hepatotoxicity of halomethanes such as CCl₄, CHCl₃, and BrCCl₃ has been a subject of intense study. Recent work has shown that suppression of hepatocellular regeneration leads to accelerated progression of liver injury leading to complete hepatic failure due to an unusual interaction between individually nontoxic low-dose combination of CD and CCl₄. Since polyamines are involved in cell division, their levels reflect the extent to which there is suppression of hepatocellular regeneration during CD and CCl₄ interaction. The present studies were designed to investigate the polyamine levels and associated enzymes in livers of rats treated with BrCCl₃ alone or CD and BrCCl₃ low-dose combination in order to confirm whether the sequence of events of hepatotoxicity is similar to that seen in CCl₄ toxicity or that seen during CD and CCl₄ interaction. The extent of liver toxicity in rats fed 10 ppm chlordecone (CD) for 15 days prior to the injection of a single low dose of BrCCl₃ (15 μL/kg body weight) or after exposure to a high dose of BrCCl₃ (80 μL/kg body weight) without CD pretreatment, was similar 6 and 24 hr later as assessed by plasma transaminase levels. There was also an increase in transaminase levels, in rats exposed to a single low dose of BrCCl₃ alone (15 μL/kg body weight) but this increase was far below the high-dose exposure alone or the combination treatment. Hepatic levels of ornithine decarboxylase, S-adeno-sylmethionine decarboxylase, N¹-acetylputrescine, N¹-acetylspermidine, putrescine, spermidine, and spermine at the end of 24 hr increased after exposure to a low dose of BrCCl₃ alone as compared to exposure to a high dose alone or the low-dose combination of CD and BrCCl₃. Liver spermidine N¹-acetyltrans-ferase was elevated at 2, 6, and 24 hr after exposure to a high dose of BrCCl₃ alone as compared to treatment with a low-dose combination of CD and BrCCl₃ suggesting decreased synthesis of this enzyme, in spite of a greater need as seen from liver transaminase levels. In general, it was observed that there is significant elevation in some polyamines and related enzymes during toxicity of a low dose of BrCCl₃ which seemed to stabilize within 24 hr. This was not observed with the other two groups of rats exposed either to BrCCl₃ high dose alone or the low-dose combination of CD and BrCCl₃. Results indicate that CD and BrCCl₃ low-dose combination treatment causes increased liver toxicity resulting in compromised polyamine metabolism which is coincidental with suppressed hepatocellular regeneration leading to accelerated progressive phase of liver injury culminating in complete hepatic failure. These findings point to the possibility that the mechanism of potenti-ation of BrCCl₃ hepatotoxicity by CD is similar to that seen for CD and CCl₄ interaction.     

High-dose ascorbic acid decreases detoxification of cyanide derived from amygdalin (laetrile): studies in guinea pigs

Cysteine, a sulphur-containing amino acid, is required to metabolize ascorbic acid (as ascorbate sulphate) and detoxify cyanide (to thiocyanate). In guinea pigs, conjoint use of laetrile (a cyanogenic glycoside) and ascorbic acid (in large doses) decreases the detoxification of cyanide derived from laetrile through diminishing the availability of cysteine, but not impairing hepatic rhodanese activity, which is involved in the detoxification of cyanide to thiocyanate. These results agree with the symptoms of a sublethal dose of KCN toxicity manifested by the animals. The studies, therefore, indicate that individuals taking megadoses of ascorbic acid concurrently with laetrile may be subject to self-poisoning.     

Branched respiratory chain in aerobically grown Staphylococcus aureus —oxidation of ethanol by cells and protoplasts

Addition of ethanol and some other primary alcohols, except methanol, to cells and protoplasts (but not membrane particles) considerably stimulated the rate of oxygen consumption. This additional respiration was strongly inhibited by 0.1 mM KCN. The cyanide inhibition curve of endogenous substrate oxidation was slightly biphasic while in the presence of ethanol it became clearly biphasic having K _i values of approx. 0.1 and 0.5 mM. Based on the steady-state cytochrome spectra in the presence of 0.1 mM KCN, we attributed the lower K _i to cytochrome a ₆₀₂. Proteolysis of protoplasts external membrane proteins did not change the rate of endogeneous substrate oxidation but prevented the inhibition of this respiration by low concentrations of KCN and stimulation of oxygen consumption by ethanol. The activity of NAD⁺-dependent ethanol dehydrogenase in the cytoplasm was found to be 520 nmol NADH-x min^–1 x mg^–1 protein. Proteolysis of external membrane proteins apparently inhibits the operation of the cytochrome a ₆₀₂-containing electron transport branch inducing the suppression of electron flow from NADH to oxygen.     

Nitrite-induced methemoglobinemia in Nile tilapia, Oreochromis niloticus

Exposure of Nile tilapia, Oreochromis niloticus (mean weight, 55.72 ± 4.30 g), to two sublethal NO₂–N concentrations was studied for 24 and 48 h in a static test. In nitrite exposure tests, the percentages of methemoglobin, external nitrite, plasma nitrite, hemoglobin and hematocrit were assessed. Nitrite exposure in the range of 0.50 and 1.38 mg l⁻¹ NO₂–N caused an increase in methemoglobin levels; however, methemoglobin percentages ranging from 16% to 42% represented a mild methemoglobinemia. Levels of methemoglobin were unrelated to environmental and plasmatic nitrite concentrations. The nitrite concentration in the blood did not seem to be linked to time of exposure. Nitrite exposure in Nile tilapia was associated with a marked reduction in hemoglobin and hematocrit.     

Cyanide toxicity and interference with diet selection in quail (Coturnix coturnix)

Cyanide is a ubiquitous substance in the environment. Most of the cyanide absorbed by an animal is detoxified by enzymatic combination with sulfur, thus the detoxification process imposes a nutritional cost. In mammals, interactions among nutrients and toxics may influence the composition of the diet and food intake, as a function of positive or negative post-ingestive feedback. The present work aimed to describe the toxic effects of cyanide, and to determine whether cyanide interferes with diet selection in quail (Coturnix coturnix). A toxicological study was performed with 27 female quails that were assigned to three groups that received by gavage 0, 1.0 or 3.0 mg of KCN/kg/day, for 7 consecutive days. The diet selection trial was conducted with 20 female quails, that had access to two separate rations: a conventional quail ration and the same ration supplemented with 1% NaSO₄. During the toxicological study, clinical signs of poisoning and death occurred in a quail treated with cyanide. Histological changes were found only in animals dosed with cyanide, and these consisted of mild hepatic periportal vacuolation, an increased number of vacuoles in the colloid of the thyroid glands, and spongiosis in the mesencephalon. No clinical signs were found in any quail throughout the diet selection trial. There were no significant differences in food consumption or ration preference. In conclusion, exposure to cyanide promotes damage to the liver and central nervous system in quails. In contrast, the ingestion of sulfur by quail was not affected by exposure to cyanide.     

Effect of alpha-ketoglutarate on neurobehavioral, neurochemical and oxidative changes caused by sub-chronic cyanide poisoning in rats

Recent studies revealed that alpha-ketoglutarate (A-KG) alone or with sodium thiosulfate (STS) provide significant protection against acute and sub-acute cyanide poisoning in rodents. This study addresses the protective effect of A-KG and/or STS in sub-chronic (90 days) cyanide poisoning. Wistar rats were divided into seven groups (n = 10): Control animals, potassium cyanide (KCN) A-KG, STS, KCN + A-KG, KCN + STS and KCN + A-KG + STS. Spontaneous motor activity and motor coordination were recorded every 15th day. Lipid peroxidation (LPO), reduced glutathione (GSH), glutathione peroxidase (GPx), superoxide dismutase (SOD) and catalase (CAT) in blood, brain, liver and kidney, and glutamate, aspartate and dopamine in discrete regions of brain were measured following 90 days exposure. Cyanide significantly decreased motor coordination, accompanied by increase in LPO (blood, brain and liver) and dopamine (corpus striatum and cerebral cortex) levels, and depletion in GSH (blood, brain and liver), GPx (brain and liver), SOD (brain and liver), and CAT (blood and brain) levels. Although treatment of A-KG and STS alone significantly blunted the toxicity of KCN, concomitant use of both afforded the maximum protection. This study shows a promising role of A-KG and STS as treatment regime for long term cyanide exposure.     

Heat induced liver cell proliferation in the livebearing fish Poeciliopsis

Synopsis Liver regeneration is induced by heat stress in the small viviparous fish, Poeciliopsis. Acute exposure to sublethal temperatures, one to two degrees below their killing temperature, damages tissue and initiates liver cell proliferation in P. lucida, P. monacha, and P. monacha-lucida hybrid clones, SYN-4 and SYN-5. Regeneration of liver cells began within 1–2 days following heat stress and proceeded over 5 days. Peak cell proliferation occurred 2–3 days after treatment in fish of all four genotypes. Cell proliferation was induced in the two all-female clones, SYN-4 and SYN-5, by exposure to 40.5° C for 60 minutes. This treatment imposed mortalities of 17.9% and 16.7%, respectively, whereas reduction of the temperature to 39.5°C and reduction of the time to 30 minutes resulted in no mortalities without significantly lowering the level of cell proliferation (p > 0.05). Liver cell proliferation induced by both heat treatments was significantly higher (p < 0.05) in the SYN-5 hybrids than in SYN-4. The induction of liver cell proliferation with sublethal temperature exposures is discussed as it may relate to chemical carcinogenesis in both feral and laboratory fish. Acute heat exposure may be used experimentally in fish as an independent stimulus for liver cell proliferation in carcinogenesis studies. In poikilothermic animals-heat exposure offers an alternative to surgical removal of approximately two-thirds of the liver, the method most frequently used in rodents to study the process of liver regeneration.     

Oxidative Stress and Hepatocellular Injury Induced by Oral Administration of Cr3+ in Chicken

This study aims to investigate the oxidative stress and hepatocellular injury induced by Cr³⁺ in chicken. Different doses of CrCl₃ solutions (50% LD₅₀, 25% LD₅₀, and 12.5% LD₅₀) and equivalent water were orally administered to chicken. Chicken liver samples were measured for the activities of antioxidant enzymes, the contents of glutathione, total antioxidant capacity (T‐AOC), malondialdehyde (MDA), and hydrogen peroxide to indirectly evaluate the oxidative stress in chicken liver. Results indicated that the oral administration of Cr³⁺ at high dose significantly increased (P < 0.05) the MDA levels after 28 days of exposure, with decreased T‐AOC, glutathione, and antioxidant enzymes activities. Low and medium doses groups show that T‐AOC, glutathione, and antioxidant enzymes activities increased after 14 days, then decreased gradually, but low and medium groups higher than control group, only high group lower than control group finally. These statistics and histopathological analysis suggest that high dose and long‐term exposure of Cr³⁺ induce oxidative stress and hepatocellular injury.     

The respiratory responses to cyanide of a cyanide-resistant Klebsiella oxytoca bacterial strain

The respiratory system of a cyanide-resistant Klebsiella oxytoca was analyzed by monitoring the changes in the cytochrome contents in response to various inhibitors in the presence of various concentrations of cyanide. The cells grown in the medium without cyanide (KCN) have two terminal oxidases, cytochrome d (Ki = 10(-5) M KCN) and o (Ki = 10(-3) M KCN). When cells were grown on medium with 1 mM KCN, the expression of both b-type cytochrome and cytochrome d in the plasma membranes of the cell decreased by more than 50%, while cytochrome o increased by 70%, as compared with the cells grown in the absence of KCN. Two terminal oxidases with Ki values of about 10(-3) M and 1.7 x 10(-2) M KCN were observed in the plasma membrane fractions of the cells growing on KCN enriched medium. 2-n-Heptyl-4-hydroxyquinoline-N-oxide markedly inhibited the oxidation of NADH by the plasma membranes from the cells grown in the medium without KCN, but not in those plasma membranes from KCN-grown cells. The NADH oxidases in plasma membranes of K. oxytoca grown with and without KCN were equally sensitive to UV irradiation. Adding freshly isolated quinone to the UV-damaged plasma membranes restored the NADH oxidase activity from both types of plasma membranes. From these results, we propose the presence of a non-heme type of terminal oxidase to account for the KCN resistance in K. oxytoca.