Concentrations Of KCN Research Articles

Potential of indigenous bacteria to remove cyanide with variations of contact time and temperature

The research on environmental biotechnology has been done in aims to study the ability of mixed culture indigenous bacteria to remove cyanide (KCN-) concentration which is determined by environment conditions of temperature and contact time. The research has been done using the artificial pollutants that contains 500 ppm of KCN- which is exposed to the SMSS (Stone Mineral Salt solution) as a growth media for mixed culture bacteria TBS and CTS. The effect of different environment conditions including temperature and contact time were studied on cyanide removal. Gas Chromatography - Mass Spectrophotometer (GC - MS) method is used to analysed the concentrations of KCN-. Initial condition of research operation is determined to be pH 7 and contact time of 48 hours. The removal of 500 ppm KCN- increases to 71% at incubation temperature 35°C and contact time of 36 hours. This research showed that indigenous bacteria TB1 and CS2 can remove 500 ppm KCN- on all temperature variations between (°C) 25 to 45 and the highest removal occur when contact time is 36 hours.

Responses of free amino acids in rice seedlings during cyanide metabolism

Responses of free amino acids to botanical assimilation of free cyanide were investigated. Young rice seedlings (Oryza sativa L. cv. XZX 45) were grown in nutrient solution amended with free cyanide (KCN). Cyanide was analyzed in solution as well as in plant materials to estimate the phyto-assimilation potential. Free amino acids in different parts of plants were also measured to determine metabolic responses to KCN exposure. Phyto-assimilation of KCN was obvious, and the rates were positively correlated to the concentration supplied. Although changes in total amino acid content in plant materials were negligible during KCN metabolism (p > 0.05), responses of different amino acids to KCN treatments were quite different. All treatments with KCN increased the content of proline (Pro) and isoleucine (Ile) in roots significantly compared with control (p < 0.05), while changes of aspartic acid, lysine, and histidine in roots were more evident at higher KCN treatments (p < 0.05). Results indicate that the content of Pro, Ile, and tyrosine showed pronounced increase in shoots of rice seedlings exposed to KCN at 1.44mg CN/L or higher (p < 0.05). Other amino acids slightly changed in all plant materials exposed to KCN (p > 0.05). Results indicate that specific amino acids in rice seedlings showed positive response to non-toxic concentrations of exogenous KCN. These findings could provide additional insights into the inducible mechanisms underlying the involvement of amino acids in KCN metabolism.

Microfluidic Device with Chemical Gradient for Single-Cell Cytotoxicity Assays

Here, we report the fabrication of a chemical gradient microfluidic device for single-cell cytotoxicity assays. This device consists of a microfluidic chemical gradient generator and a microcavity array that enables entrapment of cells with high efficiency at 88 ± 6% of the loaded cells. A 2-fold logarithmic chemical gradient generator that is capable of generating a serial 2-fold gradient was designed and then integrated with the microcavity array. High density single-cell entrapment was demonstrated in the device without cell damage, which was performed in 30 s. Finally, we validated the feasibility of this device to perform cytotoxicity assays by exposing cells to potassium cyanide (0-100 μM KCN). The device captured images of 4000 single cells affected by 6 concentrations of KCN and determined cell viability by counting the effected cells. Image scanning of the microcavity array was completed within 10 min using a 10× objective lens and a motorized stage. Aligning cells on the microcavity array eases cell counting, observation, imaging, and evaluation of singular cells. Thus, this platform was able to determine the cytotoxicity of chemicals at a single-cell level, as well as trace the cytotoxicity over time. This device and method will be useful for cytotoxicity analysis and basic biomedical research.

Labeling Mitochondria with Fluorescent Dyes for Imaging

INTRODUCTIONThe eukaryotic cell has evolved to compartmentalize its functions and transport various metabolites among cellular compartments. Therefore, it is important to study cellular organization and structure/function relationships. The mitochondrion is a double-membraned organelle that is important in various metabolic processes, including oxidative phosphorylation, electron transport, the Krebs cycle, β-oxidation of fatty acids, and part of the urea cycle. This protocol presents methods for labeling mitochondria in both live and fixed cells using several different fluorescent molecules. Rhodamine 123, tetramethylrhodamine ethyl ester (TMRE), and tetramethylrhodamine methyl ester (TMRM) are membrane-potential-sensitive, cationic fluorophores. Therefore, the mitochondrion must be functioning and generating a membrane potential in order to attract and maintain the dyes in the mitochondrion. These dyes are also used as sensitive indicators of the mitochondrial membrane potential. Rhodamine 123 is specific for the mitochondrion. In contrast, TMRM, TMRE, and the carbocyanine dyes can also label the endoplasmic reticulum to some degree. Mito Tracker CMTMRos has the added feature of chemical reactivity so that, once incorporated in the mitochondrion, it can chemically link to thiol groups and will not leave the mitochondrion when the membrane potential decreases as a result of fixation and/or cell death. Hence, it can be used to locate mitochondria in specimens that will subsequently be fixed. The effect of submicromolar concentrations of mitochondrial inhibitors, for example, KCN, rotenone, antimycin α, and uncouplers of oxidative phosphorylation, such as carbonylcyanide-m-chlorophenyl hydrazone (CCCP) and the related carbonylcyanide-p-trifluoromethoxyphenyl hydrazone (FCCP), can be examined on isolated mitochondria or mitochondria in intact cells.

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.

Nitric oxide increases oxidative phosphorylation efficiency

We have studied the effect of nitric oxide (NO) and potassium cyanide (KCN) on oxidative phosphorylation efficiency. Concentrations of NO or KCN that decrease resting oxygen consumption by 10-20% increased oxidative phosphorylation efficiency in mitochondria oxidizing succinate or palmitoyl-L-carnitine, but not in mitochondria oxidizing malate plus glutamate. When compared to malate plus glutamate, succinate or palmitoyl-L-carnitine reduced the redox state of cytochrome oxidase. The relationship between membrane potential and oxygen consumption rates was measured at different degrees of ATP synthesis. The use of malate plus glutamate instead of succinate (that changes the H(+)/2e(-) stoichiometry of the respiratory chain) affected the relationship, whereas a change in membrane permeability did not affect it. NO or KCN also affected the relationship, suggesting that they change the H(+)/2e(-) stoichiometry of the respiratory chain. We propose that NO may be a natural short-term regulator of mitochondrial physiology that increases oxidative phosphorylation efficiency in a redox-sensitive manner by decreasing the slipping in the proton pumps.

Comparative Measurement of Cyanide and Paraquat Mitochondrial Toxicity Using Two Different Mitochondrial Toxicity Assays

ABSTRACTCyanide (KCN) and paraquat (PQ) are very toxic to mitochondria. In this study the toxicity of KCN and PQ in the isolated rat liver mitochondria was determined using the MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay and JG-B (Janus green B) assay by multiwell scanning spectrophotometry. JG-B was used not only for the vital staining of mitochondria, but also for the mitochondrial viability assay and was compared to the MTT assay.The rat liver mitochondria were first isolated by centrifuge in a mixture of 0.25 M saccharose solution and 0.05 M Tris buffer. Various concentrations of paraquat (0.001 to 100 mM) and KCN (0.0001 to 100 M) on the mitochondria isolated from the liver were investigated. The 50% lethal concentration of toxins were found for PQ (4.45 ± 0.02, 4.96 ± 0.01) and KCN (0.22 ± 0.02, 0.49 ± 0.02), as determined by these assays ( JG-B and MTT, respectively ). Significant correlations were also observed among the two methods with a 95% coefficient interval (r2 = 0.84, p < 0.001; r2 = 0.91, p < 0.001; PQ and KCN, respectively). These results suggest that both methods are reliable and are comparable for determining the mitochondrial assay. It is concluded that the JG-B assay may be preferable to the MTT assay because of its simplicity, low cost, sensitivity, and objectivity; in addition, this method is not time dependent.

Inhibition of specific electron transport pathways leads to oxidative stress and decreased Candida albicans proliferation

Candida parapsilosis mitochondria contain three respiratory chains: the classical respiratory chain (CRC), a secondary parallel chain (PAR) and an "alternative" oxidative pathway (AOX). We report here the existence of similar pathways in C. albicans. To observe the capacity of each pathway to sustain yeast growth, C. albicans cells were cultured in the presence of inhibitors of these pathways. Antimycin A and KCN totally abrogated yeast growth, while rotenone did not prevent proliferation. Furthermore, rotenone promoted only partial respiratory inhibition. Lower concentrations of KCN that promote partial inhibition of respiration did not inhibit yeast growth, while partial inhibition of respiration with antimycin A did. Similarly, AOX inhibitor BHAM decreased O(2) consumption slightly but completely stunted cell growth. Reactive oxygen species production and oxidized glutathione levels were enhanced in cells treated with antimycin A or BHAM, but not rotenone or KCN. These findings suggest that oxidative stress prevents C. albicans growth.

The Effect Of Some Respiratory Inhibitors On The Lipase Activity Of Germinating Peanuts (&lt;i&gt;Arachis hypogea&lt;/i&gt;)

Peanut (Arachis hypogea) seeds were treated with varying concentrations of KCN, KNO3) and Urea (0.01 M and 0.05 M) prior to germination. Lipase activities of germinating seeds were affected by chemical treatment. The effect induced by the chemicals is explained on the basis of interfering effect with the function of the organelles. The lipase activity of all the seeds had maximum activity on the 6th day of germination. Key Words: Peanut, lipase, chemical treatment. Bio-Research Vol.2(2) 2004: 34-36

Photobiomodulation Directly Benefits Primary Neurons Functionally Inactivated by Toxins: ROLE OF CYTOCHROME c OXIDASE

Far red and near infrared (NIR) light promotes wound healing, but the mechanism is poorly understood. Our previous studies using 670 nm light-emitting diode (LED) arrays suggest that cytochrome c oxidase, a photoacceptor in the NIR range, plays an important role in therapeutic photobiomodulation. If this is true, then an irreversible inhibitor of cytochrome c oxidase, potassium cyanide (KCN), should compete with LED and reduce its beneficial effects. This hypothesis was tested on primary cultured neurons. LED treatment partially restored enzyme activity blocked by 10-100 microm KCN. It significantly reduced neuronal cell death induced by 300 microm KCN from 83.6 to 43.5%. However, at 1-100 mm KCN, the protective effects of LED decreased, and neuronal deaths increased. LED significantly restored neuronal ATP content only at 10 microm KCN but not at higher concentrations of KCN tested. Pretreatment with LED enhanced efficacy of LED during exposure to 10 or 100 microm KCN but did not restore enzyme activity to control levels. In contrast, LED was able to completely reverse the detrimental effect of tetrodotoxin, which only indirectly down-regulated enzyme levels. Among the wavelengths tested (670, 728, 770, 830, and 880 nm), the most effective ones (830 nm, 670 nm) paralleled the NIR absorption spectrum of oxidized cytochrome c oxidase, whereas the least effective wavelength, 728 nm, did not. The results are consistent with our hypothesis that the mechanism of photobiomodulation involves the up-regulation of cytochrome c oxidase, leading to increased energy metabolism in neurons functionally inactivated by toxins.

The membrane-bound respiratory chain of Pseudomonas pseudoalcaligenes KF707 cells grown in the presence or absence of potassium tellurite.

The respiratory chain of Pseudomonas pseudoalcaligenes KF707 in membranes isolated from cells grown in the presence or absence of the toxic oxyanion tellurite (TeO3(2-)) was examined. Aerobic growth in the absence of tellurite shows an NADH-dependent respiration which is 80% catalysed by the cytochrome (cyt) bc1-containing pathway leading to two terminal membrane-bound cyt c oxidases inhibited by different concentrations of KCN (IC50 0.2 and 1 microM). A third oxidase, catalysing the remaining 20% of the cyanide-resistant respiration and fully inhibited by 2-3 mM KCN, is also present; this latter pathway accounts for 60-70% of the total NADH-dependent respiration in membranes from cells grown in LB medium supplemented with potassium tellurite (35 microg x ml(-1)). Two high-potential b-type haems (E(m,7) +395 and 318 mV) are redox centres of a membrane-bound cyt c oxidase (possibly of the cbb3 type) which shows a 50% decrease of its activity in parallel with a similar decrease of the c-type haem content (mostly soluble cyt c) in membranes from tellurite-grown cells; the latter type of cells specifically contain a cyt b type at +203 mV (pH 9.0) which is likely to be involved in cyanide-resistant respiration. Comparison of the growth curve of KF707 cells in parallel with tellurite uptake showed that intracellular accumulation of tellurium (Te(0)) crystallites starts from the mid-exponential growth phase, whereas tellurite-induced changes of the respiratory chain are already evident during the early stages of growth. These data were interpreted as showing that reduction of tellurite to tellurium and tellurite-dependent modifications of the respiratory chain are unrelated processes in P. pseudoalcaligenes KF707.

Heme oxygenase-2 interaction with metalloporphyrins: function of heme regulatory motifs.

Heme oxygenase-2 (HO-2) degrades heme [Fe-protoporphyrin IX (Fe-PP)] to CO and bilirubin. The enzyme is a hemoprotein and interacts with nitric oxide. HO-2 has two copies of heme regulatory motif (HRM) with a conserved core of Cys264-Pro265 and Cys281-Pro282. We examined interaction of HO-2 HRMs with Fe-PP, Zn-protoporphyrin IX (Zn-PP; HO-2 inhibitor), and protoporphyrin IX (PP IX). Spectral analyses, using 1:4 or 1:1 molar ratio of the heme to 10-residue peptides, corresponding to HRM containing HO-2 sequences, revealed specific interactions as indicated by a shift in the absorption spectrum of heme. Five residue peptides qualitatively produced similar results. Substitution of cysteine with alanine in either peptide eliminated interactions, and substitution of proline with alanine reduced the peptides' affinity for heme. Neither Zn-PP nor PP IX absorption spectrum was affected by HRM peptides. The circular dichroism spectra confirmed heme-HRM peptides interactions. An astounding 4,000-6,000-fold higher concentrations of KCN were required at pH 7.5 to displace HRM peptides from heme. Data suggest (a) each HRM can contribute to HO-2-heme interaction, (b) heme iron interacts with cysteine thiol, (c) charged residues upstream of Cys264-Pro265 result in its high-affinity heme binding, and (d) inhibition of HO-2 activity by synthetic metalloporphyrins does not involve HRMs. We suggest that heme bound to HRMs may serve as a binding site/reservoir for gaseous signal molecules.

Flavohemoglobin Hmp Affords Inducible Protection for Escherichia coli Respiration, Catalyzed by Cytochromesbo′ or bd, from Nitric Oxide

Respiration of Escherichia coli catalyzed either by cytochrome bo' or bd is sensitive to micromolar extracellular NO; extensive, transient inhibition of respiration increases as dissolved oxygen tension in the medium decreases. At low oxygen concentrations (25-33 microm), the duration of inhibition of respiration by 9 microm NO is increased by mutation of either oxidase. Respiration of an hmp mutant defective in flavohemoglobin (Hmp) synthesis is extremely NO-sensitive (I(50) about 0.8 microm); conversely, cells pre-grown with sodium nitroprusside or overexpressing plasmid-borne hmp(+) are insensitive to 60 microm NO and have elevated levels of immunologically detectable Hmp. Purified Hmp consumes O(2) at a rate that is instantaneously and extensively (>10-fold) stimulated by NO due to NO oxygenase activity but, in the absence of NO, Hmp does not contribute measurably to cell oxygen consumption. Cyanide binds to Hmp (K(d) 3 microm). Concentrations of KCN (100 microm) that do not significantly inhibit cell respiration markedly suppress the protection of respiration from NO afforded by Hmp and abolish NO oxygenase activity of purified Hmp. The results demonstrate the role of Hmp in protecting respiration from NO stress and are discussed in relation to the energy metabolism of E. coli in natural O(2)-depleted environments.

Anodic dissolution of gold in cyanide solutions containing ions of thallium(I)

The potential dependence of the gold dissolution rate in alkali-cyanide solutions with and without 1.5 × 10-5 M T1NO3 is studied using the technique of the electrode surface renewal prior to taking measurements. The thallium ions accelerate the gold dissolution at potentials below 0.2 V and inhibit it at more positive potentials. The effect depends on the time the electrode is in contact with solution before the measurements, the potential scan rate, and concentrations of KCN and KOH. Possible approaches to interpreting the discovered phenomena are suggested.

The role of the alternative oxidase in stabilizing the in vivo reduction state of the ubiquinone pool and the activation state of the alternative oxidase

A possible function for the alternative (nonphosphorylating) pathway is to stabilize the reduction state of the ubiquinone pool (Qr/Qt), thereby avoiding an increase in free radical production. If the Qr/Qt were stabilized by the alternative pathway, then Qr/Qt should be less stable when the alternative pathway is blocked. Qr/Qt increased when we exposed roots of Poa annua (L.) to increasing concentrations of KCN (an inhibitor of the cytochrome pathway). However, when salicylhydroxamic acid, an inhibitor of the alternative pathway, was added at the same time, Qr/Qt increased significantly more. Therefore, we conclude that the alternative pathway stabilizes Qr/Qt. Salicylhydroxamic acid increasingly inhibited respiration with increasing concentrations of KCN. In the experiments described here the alternative oxidase protein was invariably in its reduced (high-activity) state. Therefore, changes in the reduction state of the alternative oxidase cannot account for an increase in activity of the alternative pathway upon titration with KCN. The pyruvate concentration in intact roots increased only after the alternative pathway was blocked or the cytochrome pathway was severely inhibited. The significance of the pyruvate concentration and Qr/Qt on the activity of the alternative pathway in intact roots is discussed.

11 beta-hydroxysteroid dehydrogenase is an exclusive 11 beta- reductase in primary cultures of rat hepatocytes: effect of physicochemical and hormonal manipulations.

11 beta-Hydroxysteroid dehydrogenase (11 beta HSD) catalyzes the conversion of corticosterone to inert 11-dehydrocorticosterone, thus regulating glucocorticoid access to intracellular receptors. This type 1 isoform (11 beta HSD-1) is a bidirectional NADPH(H)-dependent enzyme in vitro and is highly expressed in liver, where it is regulated by glucocorticoids, thyroid hormones, estrogen, and GH in vivo. In humans in vivo, enzyme inhibition alters glucose homeostasis, an effect thought to be mediated in the liver. However, detailed investigation of the biology of 11 beta HSD-1 in liver, its function, regulation, and indeed even reaction direction, has been hampered by the lack of clonal hepatic cell lines that express 11 beta HSR-1. Studies of nonhepatic cell lines have suggested that 11 beta HSD-1 is directly regulated by hormones, and transfection of nonhepatic cell lines has sown that reaction direction varies between cell types, possibly reflecting intracellular cosubstrate (NADP+/NADPH) ratios or PH. To investigate reaction direction and gene regulation of 11 beta HSD-1 in hepatocytes, we defined conditions for primary culture of adult rat hepatocytes that maintain high 11 beta HSR-1 messenger RNA expression. In intact primary hepatocytes over a wide range of steroid concentrations (2.5-250 nM), 11 beta-reduction was the predominant reaction direction [33.5 +/- 0.5% conversion of 11-dehydrocorticosterone (25 nM) to corticosterone after 30 min], with undetectable 11 beta-dehydrogenation. However, homogenates of hepatocyte cultures showed plentiful 11 beta-dehydrogenase activity. Treatment of hepatocyte cultures with the metabolic inhibitors sodium azide (5 nM) and KCN (1 nM) altered cellular NADP+/NADPH ratios from 0.244 +/- 0.042 in controls to 0.020 +/- 0.001 and 0.152 +/- 0.009, respectively, but had no effect on 11 beta-reductase or 11 beta- dehydrogenase activity. High concentrations of KCN (10 mM) modestly increased 11 beta-reductase activity (32.4 +/- 1.7% to 48.8 +/- 0.5%, whereas 11 beta-dehydrogenation remained at the limit of detection. Manipulation of culture medium pH (6.2-8.0) had no effect on enzyme activity. Dexamethasone (10-7 M) induced hepatocyte 11 beta-reductase activity from 23.4 +/- 0.7% to only weakly affects reaction direction. Glucocorticoid and insulin regulation of hepatic 11 beta HSD-1 is directly mediated, but other hormonal controls are either lost in culture or mediated indirectly. This primary hepatocyte culture system will allow investigation of the control of 11 beta-reductase activity and its implications for glucocorticoid-regulated hepatic functions.

Evidence for a Causative Role of Cyanide, Derived from Ethylene Biosynthesis, in the Herbicidal Mode of Action of Quinclorac in Barnyard Grass

Root application of the quinolinecarboxylic acid herbicide quinclorac to barnyard grass ((Echinochloa crus-galli (L.) P. Beauv.) caused inhibition of shoot growth accompanied by chlorosis and necrosis. After 1 day of exposure, cyanide levels in the shoot tissue increased according to the concentration of the herbicide and the time of its application and closely correlated with the reduction in shoot fresh weight. Four days after the application of 10 and 100 μM quinclorac, the respective cyanide levels in the shoot tissue were approximately two and three times higher than controls and reached a maximum of 40 μM. Increases in β-cyanoalanine synthase activity, the main HCN detoxifying enzyme, ethylene production, and in the endogenous levels of 1-aminocyclopropane-1-carboxylic acid (ACC) preceded cyanide accumulation, When ACC was exogenously supplied to detached shoots of barnyard grass via the vascular system, its accumulation within the tissue coincided with increases in ethylene formation and cyanide content. Both metabolites of ACC appeared to be formed in stoichiometrically equivalent amounts. Root treatment of intact plants with KCN caused concentration-dependent increases in the levels of cyanide found in the shoot tissue which inversely correlated with the changes in fresh weight. The concentrations of quinclorac or KCN applied via the roots which led to twofold increases in the cyanide levels of the shoots had similar effects on the shoot fresh weight, causing reductions of nearly 30%. The phytotoxic symptoms, chlorosis and necrosis, were also similar. In contrast, phytotoxic tissue sensitivity to ethylene released by applied 2-chloroethylphosphonic acid (ethephon) was only very low. It is concluded that cyanide, derived ultimately from quinchlorac-stimulated ACC synthesis, is a causative factor in the herbicidal effects observed in the shoots of barnyard grass.

5424271 Strains of Drechslera spp., weed control compositions containing the same and methods for controlling weeds using the same: Yamaguchi Kenich; Arita Masanobu; Gohbara Masatosh; Shinmi Tatsuo; Fukui Keiko; Tohyama Emi Mobara, Japan Assigned to Mitsui Toatsu Chemicals Inc

Root application of the quinolinecarboxylic acid herbicide quinclorac to barnyard grass ((Echinochloa crus-galli (L.) P. Beauv.) caused inhibition of shoot growth accompanied by chlorosis and necrosis. After 1 day of exposure, cyanide levels in the shoot tissue increased according to the concentration of the herbicide and the time of its application and closely correlated with the reduction in shoot fresh weight. Four days after the application of 10 and 100 μM quinclorac, the respective cyanide levels in the shoot tissue were approximately two and three times higher than controls and reached a maximum of 40 μM. Increases in β-cyanoalanine synthase activity, the main HCN detoxifying enzyme, ethylene production, and in the endogenous levels of 1-aminocyclopropane-1-carboxylic acid (ACC) preceded cyanide accumulation, When ACC was exogenously supplied to detached shoots of barnyard grass via the vascular system, its accumulation within the tissue coincided with increases in ethylene formation and cyanide content. Both metabolites of ACC appeared to be formed in stoichiometrically equivalent amounts. Root treatment of intact plants with KCN caused concentration-dependent increases in the levels of cyanide found in the shoot tissue which inversely correlated with the changes in fresh weight. The concentrations of quinclorac or KCN applied via the roots which led to twofold increases in the cyanide levels of the shoots had similar effects on the shoot fresh weight, causing reductions of nearly 30%. The phytotoxic symptoms, chlorosis and necrosis, were also similar. In contrast, phytotoxic tissue sensitivity to ethylene released by applied 2-chloroethylphosphonic acid (ethephon) was only very low. It is concluded that cyanide, derived ultimately from quinchlorac-stimulated ACC synthesis, is a causative factor in the herbicidal effects observed in the shoots of barnyard grass.

Aging, cytochrome oxidase activity, and hydrogen peroxide release by mitochondria

The objective of this study was to explore the possible cause(s) underlying the previously observed, age-related increase in the rate of mitochondrial H 2O 2 release in the housefly. The hypothesis that an imbalance between different respiratory complexes may be a causal factor was tested. Cytochrome c oxidase activity was found to sharply decline in the latter part of the life span of the flies. Effects of different substrates and respiratory inhibitors were determined in order to ascertain if a decrease in cytochrome c oxidase activity could be responsible for the increased H 2O 2 release. H 2O 2 was measured spectrofluorometrically using horseradish peroxidase and p-hydrophenylacetate as an indicator. Neither NADH-linked substrates nor succinate caused a stimulation of H 2O 2 production. H 2O 2 release by mitochondria, inhibited with rotenone and antimycin A, was greatly increased upon supplementation with α-glycerophosphate; however, the further addition of KCN or myxothiazol, to such preparations, caused a depression of H 2O 2 generation. In contrast, relatively low concentrations of KCN or myxothiazol were found to stimulate H 2O 2 release in insect mitochondria supplemented with α-glycerophosphate and exposed to rotenone, but not antimycin A. Results are interpreted to suggest that partial inhibition of cytochrome c oxidase activity can lead to the stimulation of mictochondrial H 2O 2 production in the housefly at site(s) other than NADH dehydrogenase and ubisemiquinone/ cytochrome b region; a possible source may be glycerophosphate dehydrogenase.

Calcium mediation of cyanide-induced catecholamine release: Implications for neurotoxicity

Exposure of rat pheochromocytoma (PC12) cells to KCN (1.0-10 mM) over a 30-min period stimulated secretion of dopamine (DA) and decreased intracellular DA content. Addition of KCN (10 mM) to rat frontal cortex slices preloaded with 1-[7-3H]norepinephrine ([3H]NE) increased secretion of NE over a 10- to 30-min incubation period. In PC12 cells release of DA by KCN was nearly abolished in calcium-free media or by prior addition of diltiazem, a calcium channel antagonist. Release of [3H]NE from rat cortical slices by cyanide was only partly inhibited by diltiazem suggesting that intracellular calcium may be involved in this response. In PC12 cells KCN also produced a dose-related release of the DA precursor dihydroxyphenylalanine, without altering intracellular stores. Levels of the DA metabolite 3,4-dihydroxyphenylacetic acid (DOPAC) were enhanced at lower concentrations of KCN. These observations indicate cyanide elicits exocytotic release of neurotransmitters in a calcium-dependent manner and also show that cyanide alters catecholamine metabolism. These actions of cyanide may be important in CNS symptoms of intoxication.