The combinations of inducers of the coumarin hydroxylase-locus help investigate their mode of action.
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Amitrole↗
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Some problems associated with measuring monoamine oxidase activity in the presence of sodium azide.
The colourimetric assay of monoamine oxidase activity, as hydrogen peroxide production, normally requires the use of sodium azide to inhibit breakdown of hydrogen peroxide by catalase. Sodium azide was shown to act as an uncompetitive inhibitor of benzylamine deamination with an inhibitor constant of 1.5 mM. Catalase activity of isolated rat liver mitochondria could be eliminated with the irreversible inhibitor of catalase, 3-amino-1,2,4-triazole. The treatment did not affect benzylamine deaminating activity. The catalase-free preparation could be used to assay monoamine oxidase activity colourimetrically, as hydrogen peroxide production, in the absence of sodium azide.
Amitrole↗
Electron-microscopic cytochemical localization of diamine and polyamine oxidases in pea and maize tissues.
An electron-microscopic cytochemical method was used to localize diamine oxidase (DAO) in pea and polyamine oxidase (PAO) in maize (Zea mays L.). The method, based on the precipitation of amine-oxidase-generated H2O2 by CeCl3, was shown to be specific for DAO and PAO and permitted their localization in plant tissues with a high degree of resolution. Both enzymes are localized exclusively in the cell wall. Both DAO- and PAO-activity staining is most intense in the middle lamellar region of the wall and in cells exhibiting highly lignified walls. The oxidases could provide H2O2 for peroxidase-mediated cross-linking reactions in the cell wall and may, in this capacity, play a role in the regulation of plant growth.
Amine Oxidase (Copper-Containing)↗
On the role of peroxisomes in the metabolism of lipids--evidence from studies on mammalian tissues in vivo.
Recent investigations into the role of peroxisomes in mammalian lipid metabolism have employed double isotope methodologies to examine the influence of peroxisomal agents on lipid turnover in the liver and extra hepatic tissues of the living animal. The action of these agents, all of which caused extensive changes in the flux of lipid metabolism in the treated animals, may best be viewed in relation to their effects on the common pathway of fatty acid oxidation in peroxisomes. Clofibrate, for example, acts through induction of peroxisomal oxidases and catalase; glycolate and ethanol through activation of this pathway; and aminotriazole and allylisopropylacetamide through inhibition of the catalase step in the sequence. The data from these studies provide support for the concept of an important contributory and regulatory role of peroxisomes in relation to the overall balance of lipid metabolism, and emphasize that these organelles play a significant role in the oxidation of common fatty acids, as well as a potential for the elimination of fatty acids that are poorly oxidized by mitochondria. Additionally, the data raise intriguing questions on the extension of peroxisomal influence to include phospholipid metabolism and the substantial degree of inter-tissue communication which is involved in the balance of lipid metabolism in the whole animal.
Adipose Tissue↗
Endogenous peroxidase in the lacrimal gland of the rat and its differentiation against injected catalase and horseradish-peroxidase.
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Amitrole↗
Fetal uptake and embryogenetic effects of aminotriazole in mice.
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Administration, Oral↗
Allelism of SNQ1 and ATR1, genes of the yeast Saccharomyces cerevisiae required for controlling sensitivity to 4-nitroquinoline-N-oxide and aminotriazole.
SNQ1 gene function is required for the expression of resistance to 4NQO in wild-type yeast. The sequence of a 3.7 kb yeast DNA containing the gene SNQ1 was determined. The SNQ1 gene consists of an open reading frame of 1641 bp and encodes, according to the hydrophobicity analysis of the putative protein, a transmembrane protein of 547 amino acids. Homology searches in yeast genome databanks revealed a 100% sequence homology with gene ATR1 which controls resistance to aminotriazole in S. cerevisiae. Pre-treatment of wild-type yeast, but not of snq1-0::LEU2 disruption mutants, with sublethal doses of aminotriazole induced hyper-resistance to 4-nitroquinoline-N-oxide. Partial deletion of the nucleotide sequence coding for a putative ATP-binding site has no, or little, influence on resistance to 4NQO whereas total deletion of the region coding for this ATP-binding domain leads to 4NQO-sensitive null-mutants.
4-Nitroquinoline-1-oxide↗
Hydrogen peroxide mediates reperfusion injury in the isolated rat heart.
In an isolated, normothermic rat heart model (Langendorff, 37 degrees C), dimethylthiourea (DMTU) infusion only during reperfusion reduced both injury and measurable hydrogen peroxide (H2O2) concentrations after global ischemia. Cardiac function was assessed by measurement of ventricular developed pressure (DP). H2O2 was assessed using H2O2 dependent aminotriazole inactivation of myocardial catalase. Depletion of xanthine oxidase by two methods (tungsten or allopurinol inhibition) also improved recovery of function and H2O2 production. The results indicate that XO derived H2O2 contributes to myocardial reperfusion injury.
Amitrole↗
The intramitochondrial location of cytochrome c peroxidase in wild-type and petite Saccharomyces cerevisiae.
Cytochemical and ultrastructural analysis of wild-type cells of Saccharomyces cerevisiae, grown aerobically in a glucose-limited chemostat, shows that cytochrome c peroxidase is localized between the membranes of the cristae, that is, in the intracristal space. This enzyme is thus positioned appropriately within the organelle to act as an alternate terminal oxidase for the respiratory chain. The proximity of the peroxidase to major sites of generation of its two substrates may account for the small leakage of hydrogen peroxide from yeast mitochondria, as compared with the larger outflow from mammalian mitochondria. In the cytoplasmic petite mutant, gross distortion of promitochondrial membrane arrangement is evident. Nevertheless, cytochrome c perioxidase activity is present in the same amounts as is found in wild-type cells, and is localized predominantly within annuli of membrane which constitute the promitochondria in these cells. No unequivocal evidence was obtained for the localization of catalase in microbodies or other organelles in either wild-type or petite cells.
Amitrole↗
[On the endogenous peroxidase in the spleen of swine (author's transl)].
We studied the distribution of endogenous peroxidase in the spleen of swine by modifications of the Graham and Karnovsky diaminobenzidine procedure. There is a peroxidatic activity in the majority of the ellipsoid cells (cells of the sheathed capillaries of Schweigger-Seidel), which is localized in the endoplasmic reticulum and the perinuclear cisterna. This staining is inhibited completely by aminotriazole and is rapidly destroyed even by low concentratoins of glutaraldehyde. Furthermore, the reaction is abolished after boiling of tissue sections or in the absence of H2O2. The macrophages of the red pulp and a minority of the ellipsoid cells are peroxidase negative. Our results are discussed in respect to some recent studies on the system of mononuclear phagocytes. It is suggested, that the enzyme active ellipsoid cells represent a special form of macrophages, enzyme histochemically related to Kupffer cells and resident peritoneal macrophages. The enzyme negative cells of the ellipsoids are probably fibroblasts.
3,3'-Diaminobenzidine↗
Ultrastructural electron probe X-ray microanalytical reaction product identification of three different enzymes in the same mouse resident peritoneal macrophage.
Simultaneous cytochemical enzyme localization procedures for peroxidase (PO) plus acid phosphatase (AcP-ase) and/or aryl sulphatase (AS) have been investigated at the ultrastructural (EM) level. Electron probe X-ray microanalysis (EPMA) will identify and differentiate the reaction products. Dual reaction product localization of PO plus AcP-ase or alternatively PO plus AS have been obtained in the same mouse resident peritoneal macrophage. This has been acquired by first performing a PO-reaction followed by AcP-ase or followed by AS. In both cases PO-related reaction products (PODAB/Os or PODAB/Pt) were localized in nuclear envelope (NE) and rough endoplasmic reticulum (RER). Cells were identified by this reaction product as resident macrophages. Reaction products from the AcP-ase related cerium (AcP-aseCe), localized in lysosomes have been identified and differentiated from the PO-related osmium containing products. Similarly AS related barium (ASBa), localized in lysosomal structures and (R)ER was identified and differentiated. Triple reaction product localization of PO followed by AcP-ase plus AS could also be obtained. In this case, PO-related platinum containing reaction products (PODAB/Pt or PODAB/Os) in NE and RER has been identified and differentiated from the AcP-ase related lysosomal cerium (AcP-aseCe) and the AS related barium localized in lysosomal and (R)ER structures. Reversing the sequences in both dual cytochemical procedures: AcP-aseCe or ASBa followed by PODAB/Os (or PODAB/Pt) resulted in AcP-aseCe or ASBa activity related reaction products only. Reversing the sequence in the triple reaction procedures (ASBa followed by AcP-aseCe) resulted in the absence of the barium containing reaction products. By application of OsO4 postfixation with aminotriazole (ATR) additives the detrimental effects upon the various precipitates have been confirmed. In LM studies, using rat intestine and non-metal identification reactions for two of the enzymes (pararosaniline for AcP-ase, DAB for peroxidase), the influences of the metal ions used in EM were tested on the appearance of the coloured reaction products. Cerium ions used in EM for detection of AcP-aseCe activity have been shown to influence the PODAB visibility in LM and EM experiments. From the AS reaction media components neither barium ions nor p-nitro catachol sulphate influenced the LM visibility of the PO reaction.
Acid Phosphatase↗
Role of cellular defense against hydrogen peroxide-induced inhibition of myocyte respiration.
Hydrogen peroxide (H2O2) serves as a precursor for highly reactive oxygen intermediates. However, the respiratory function of myocytes is relatively resistant to exogenously administered H2O2. In this study, we examined whether or not the reduction of cellular defense increases the toxicity of H2O2. Rat heart myocytes were isolated by collagenase digestion. Respiratory rates of myocytes, suspended in a medium containing sucrose, 3-N-morpholino-propanesulfonic acid, EGTA and bovine serum albumin, were determined polarographically in the presence of pyruvate and malate with or without 2,4-dinitrophenol (DNP). Mitochondrial membrane potentials were measured by using [3H]triphenylmethylphosphonium+. Cellular defense was attenuated by i) inhibiting the catalase activity by 3-amino-1,2,4-triazole (AT), ii) reducing the glutathione concentration by diethyl maleate (DEM) or ethacrinic acid (EA), and iii) permeabilizing the sarcolemmal membrane by saponin. The dose-response relationship between H2O2 (0.1-5 mM) and mitochondrial membrane potential was not greatly affected by these experimental conditions. Myocyte respiration was inhibited by 5 mM H2O2, particularly that measured in the presence of DNP (48% of control). DEM treatment did not significantly affect the respiratory inhibition by H2O2, whereas the degree of inhibition was somewhat greater following EA or AT treatment. By contrast, the sensitivity of cellular respiration to H2O2 was potentiated approximately two orders of magnitude by the permeabilization of sarcolemmal membrane; thus, 100 microM H2O2 inhibited both DNP-stimulated and unstimulated respiration to 17% and 35% of control, respectively. The results indicate that factors existing in the sarcolemma and/or in the cytosol, which become ineffective and/or are diluted, respectively, following permeabilization with saponin, are important cellular defense mechanisms in alleviating the toxic effect of exogenous H2O2 on the respiration of mitochondria in situ in myocytes.
Amitrole↗
Human phagocytic cells as oxygen metabolite scavengers.
Human neutrophils or monocytes decreased hydrogen peroxide (H2O2) concentrations in vitro. Neutrophils or monocytes decreased H2O2 concentrations as well as human erythrocytes. Treatment with aminotriazole or azide decreased both phagocyte and erythrocyte catalase activity and the ability of each cell to decrease H2O2 concentrations in vitro. Prestimulation of phagocytic cells with phorbol myristate acetate (PMA) or opsonized zymosan decreased neither their catalase activity nor their ability to decrease H2O2 concentrations. The results suggest that unstimulated or stimulated phagocytic cells can scavenge H2O2 and may potentially decrease H2O2-mediated tissue injury. The H2O2 scavenging potential of phagocytic cells is due at least partially to their catalase activity.
Amitrole↗
Nitro blue tetrazolium staining: a morphological demonstration of superoxide in the rat retina.
Nitro blue tetrazolium (NBT) is an artificial electron acceptor which has been suggested to be a useful tool in studies of free radicals. To establish whether NBT could be useful in morphological demonstration of free radicals in the retina, the staining pattern was examined in normal rat retina and after incubation with the free radical scavenger superoxide dismutase or with inhibitors of free radical protective enzymes, such as potassium cyanide, dicoumarol, and aminotriazole. After 60 min incubation in 1 mM NBT, staining was observed in photoreceptors, in some cells in the inner nuclear and ganglion cell layers, and in glial cells. Staining also appeared in the plexiform layers and occasionally in small blood vessels. Addition of superoxide dismutase caused a decreased staining of the inner parts of the retina. The inhibitors of free radical scavengers caused a dose-dependent increase in staining of the inner parts of the retina and, at high concentrations of potassium cyanide, of the photoreceptors. Thus, NBT seems indeed to be useful in morphological studies of free radicals in the retina.
Amitrole↗
Endogenous peroxidase in mast cells localized with a semipermeable membrane technique.
Hamster mast cells have been found to give strong peroxidatic reactions at pH 5, 7.5 and 10 when sections of skeletal muscle are incubated for 2.5 h in the dark at room temperature on semipermeable membranes covering a gelled incubation medium consisting of 0.01% hydrogen peroxide, 5.5mM diaminobenzidine and 1.36% agar dissolved in Universal buffer. The technique is very efficient: with it, all mast cells react in marked contrast to the negative reaction they usually give with conventional techniques. The peroxidatic reactions are abolished if tissues are perfused beforehand with either aminotriazole or KCN but not if these inhibitors are incorporated in the gelled incubation medium. This and other evidence suggests that the mast cell reactions are not due to either catalase or haemoglobin adsorbed onto mast cell granules from lysed red blood cells. Skeletal muscle fibres do not exhibit any visible peroxidase activity with the membrane technique.
Amitrole↗
Cellular membrane contrast and contrast differentiation with osmium triazole and tetrazole complexes.
Addition of heterocyclic nitrogen compounds to the classical osmium tetroxide postfixation medium, applied after glutaraldehyde fixation, results in enhanced membrane contrast in ultrathin sections of liver tissue. The addition of similar compounds to potassium osmate solutions, results in contrast differences in some cellular membranes. The membranes of the rough endoplasmic reticulum, the nuclear envelope and the plasma membrane acquire contrast, while the mitochondrial membranes do not. The apolar regions of membranes are contrasted when osmium tetroxide is combined with heterocyclic nitrogen compounds, whereas the polar regions are contrasted by combinations of potassium osmate with these compounds. This polar membrane contrast is probably due to the presence of an amino-group in the heterocyclic nitrogen compounds. Compounds without the amino-group do not contrast membranes, although the glycogen is contrasted. X-ray microanalysis served to establish the relative osmium content in contrasted glycogen, and showed that such nitrogen compounds play a role in complexation of cations in aldehyde-fixed tissues. Electron spectroscopy for chemical analysis (ESCA) measurements of isolated muscle glycogen show that after treatment with various osmium tetroxide or potassium osmate solutions, hexavalent and quadrivalent osmium species are present in the glycogen. The presence of (heterocyclic) nitrogen compounds in such solutions stabilizes certain osmium valency species, and this may account for the contrast observed.
Amitrole↗
A quantitative study of peroxidase activity in unfixed tissue sections of the guinea-pig thyroid gland.
A technique for the cytochemical demonstration of peroxidase activity in unfixed guinea-pig thyroid tissue is described in this paper. The substrate 3,3'-diaminobenzidine tetrahydrochloride (DAB) is oxidized by the peroxidase to form an insoluble reaction product. Optimal results were obtained after 20 min incubation at 37 degrees C in reaction medium containing 1.4 mM DAB (in 0.1 M Tris-HCl) and 0.15 mM hydrogen peroxide at pH 8.0. Peroxidase activity was seen in the thyroid follicle cells as a diffuse brown reaction product (which was more dense and granular in erythrocytes). The enzyme activity was quantified using a scanning-integrating microdensitometer, and the effects of two specific peroxidase inhibitors were evaluated. Both 3-amino-1,2,4-triazole and methimazole inhibited peroxidase activity in the follicle cells (enzyme activity was still seen in the erythrocytes), maximal inhibition occurring at 10 mM. Stimulation of peroxidase in the thyroid was observed in vivo (1 I.U. TSH administered every 8 h for two days), with the maximal stimulation occurring after 1 day.
3,3'-Diaminobenzidine↗
Ultraviolet action spectra for peroxide generation in human and pig epidermal keratinocytes loaded with dihydrorhodamine 123.
We developed a new and simple method for measuring peroxides in a single living cell, and the generation of peroxides upon ultraviolet (UV) irradiation was measured in human and pig epidermal keratinocytes. The method was based on the fact that the non-fluorescent dye, dihydrorhodamine 123, reacts in the presence of peroxides, such as H2O2, and changes into the fluorescent rhodamine 123, and hence the fluorescence intensity is proportional to the amount of reacted peroxide. The epidermal keratinocytes were loaded with the dihydrorhodamine under a fluorescence microscope and exposed to UV radiation. Taking C as the content of peroxides generated within the cell and I as the increase in fluence (radiation intensity x time = photons/cm2), the following empirical relationship was established: C = Cs (1-exp(-kI)), where Cs is the content of peroxides at the saturation state, and k is a kinetic parameter. The dependence of the two parameters on wavelength in the range 280-400 nm was studied. In human keratinocytes Cs had a peak at 310 nm and a small peak (shoulder) at 380 nm, while k increased gradually toward shorter wavelengths. In pig keratinocytes, on the other hand, k had a peak around 380 nm and a shoulder at 330 nm, while Cs remained unchanged. Aminotriazole, an inhibitor of catalase, and low temperatures increased the stationary levels of peroxide generation in pig keratinocytes upon UV irradiation, indicating that the reaction used for measuring intracellular peroxides is competitive with the intrinsic reactions in scavenging peroxides.
Amitrole↗