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ABSTRACT: The ability of eight species of plants to assimilate 2,4,6-trinitrotoluene (TNT) was investigated. Glycine max (soybean), in particular, demonstrated rapid assimilation of high concentrations of this explosive. Penetration and localization of [1-(14)C]-TNT in plant root cells and leaves were studied via electron microscopic autoradiography. TNT was shown to be localized primarily on membrane structures involved in the transportation of nicotinamide coenzymes (membranes of endoplasmic reticulum, mitochondria, plastids). [1-(14)C]-TNT in roots was incorporated mainly in low-molecular-weight metabolites; however, in stems and leaves, the radiocarbon was incorporated in biopolymers. Enzymatic transformation of TNT in roots was studied, and it was found that degradation involved mainly nitroreductase acting on the TNT nitro groups. The process was intensified in the presence of electron donors--NADH and NADPH. Nitroreductase activity was revealed in root cell cytosol and expression was strongly induced by plant cultivation on TNT-containing media. Oxidation of [C(3)H(3)]TNT by peroxidase and phenoloxidase was also studied. In contrast to the strongly induced nitroreductase, levels of these enzymes changed very little with TNT addition. This suggests that the main pathway of TNT transformation in plant cells is nitro group reduction. A plant's nitroreductase activity and its ability to incorporate TNT from aqueous solutions were correlated in four plants that were studied. The results suggest that plant nitroreductase activity may serve as a good biochemical indicator of plants that can be used for phytoremediation of soils contaminated with TNT.
Ecotoxicology and Environmental Safety 07/2006; 64(2):136-45. · 2.29 Impact Factor
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ABSTRACT: Electron microscopic radioautography demonstrated the penetration of [1-6(14)C]nitrobenzene in maize and soybean root tip cells: radioactive label was detected in cell wall, plasmalemma, nuclei, and cytoplasm. Among cytoplasmic organelles, the highest label was found in mitochondria and plastids. [1-6(14)C]nitrobenzene and/or products of its transformation accumulated in vacuoles. Study of the action of different concentrations of nitrobenzene on cell ultrastructural organization revealed the following picture. Nitrobenzene concentration up to 0.015 mM was harmless for plant cells. Increase of nitrobenzene concentration from 0.015 to 1.5 mM induced several pathological changes, up to the complete destruction of cells. The most damaged organelles were nuclei, mitochondria, and plastids. In the presence of 0.15 mM nitrobenzene the intensification of contacts among cell organelles, especially between endoplasmic reticulum and mitochondria/plastids, was observed. The data indicate some coordination between detoxication activity and energy metabolism during cell reaction to xenobiotic toxicity.
Ecotoxicology and Environmental Safety 08/2002; 52(3):190-7. · 2.29 Impact Factor
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ABSTRACT: The conversion of exogenous monatomic phenols (O-[1-(14)C]nitrophenol, 2,4-[1-14C]dinitrophenol, and alpha-[1-14C]naphthol) in pea seedlings has been investigated. It has been found that in the pea seedlings glycosylation of these phenols does not occur, but the main pathway of their detoxication is conjugation with the low-molecular-weight peptides. Approximately 80% of phenols absorbed by seedlings form phenol-peptide conjugates. The part of exogenous monatomic phenols is irreversibly bound to proteins via quinone-protein interaction. The amino acid content of the peptides involved in the conjugation process has been established. Penetration into the plant of monatomic exogenous phenols with a high dissociation constant leads to the stimulation of peptide formation.
Ecotoxicology and Environmental Safety 03/2002; 51(2):85-9. · 2.29 Impact Factor
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ABSTRACT: Organic xenobiotics absorbed by roots and leaves of higher plants are translocated by different physiological mechanisms. The following pathways of xenobiotic detoxication have been observed in higher plants: conjugation with such endogenous compounds as peptides, sugars, amino acids, and organic acids; oxidative degradation and consequent oxidation of xenobiotics with the final participation of their carbon atoms in regular cell metabolism. The small parts of xenobiotics are excreted maintaining their original structure and configuration. Enzymes catalyze oxidative degradation of xenobiotics from the initial hydroxylation to their deep oxidation. The wide intracellular distribution and inductive nature of oxidative enzymes lead to the high detoxication ability. With plant aging, transformation of the monooxygenase system into peroxidase takes place. Once in the cells, xenobiotics are incorporated into different cell organelles. All xenobiotics examined are characterized by a negative effect on cell ultrastructure. The penetration of high doses of xenobiotics into plant cells leads to significant deviations from the norm and, in some cases, even to the complete cell destruction and plant death.
Ecotoxicology and Environmental Safety 10/2000; 47(1):1-26. · 2.29 Impact Factor
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ABSTRACT: Transformation of phenol (14C6H5OH) penetrating through the roots of mung bean (Phaseolus aureus) and wheat (Triticum vulgare) sterile seedlings has been studied. Phenol was coupled to low-molecular-weight peptides, producing phenol-peptide conjugates. Hydrolytic cleavage of the conjugates liberated initial labeled phenol and some unlabeled amino acids. Phenol- glutathione and phenol-homoglutathione were not found among the peptide conjugates. It is suggested that the conjugation is carried out via the hydroxyl group of phenol and functional groups of peptides. Conjugation with low-molecular-weight peptides is considered to be the main pathway for phenol detoxication, since about 60% of phenol absorbed by plants conjugates with peptides. In the plants treated with phenol, the amount of low-molecular-weight peptides is increased. The increase in peptide synthesis in plants seems to be induced by the penetration of toxic phenol molecules into the cell. The small amount of phenol molecules assimilated through roots is transformed via aromatic ring cleavage and bibasic carbonic acid formation.
Ecotoxicology and Environmental Safety 03/1999; 42(2):119-24. · 2.29 Impact Factor
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ABSTRACT: The effects of aliphatic hydrocarbons--methane, ethane, propane, butane, and their mixture--on the photosynthetic apparatus of maize (Zea mays) and raygrass (Arrhenetherum elatius) leaves have been studied. The pathology of subcellular organelles as well as of the whole architectonics of the cell was observed. An especially destructive action of alkanes is expressed on the granalamellae system of chloroplasts. This action is more profound in the upper part of the leaf.
Ecotoxicology and Environmental Safety 11/1997; 38(1):36-44. · 2.29 Impact Factor
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ABSTRACT: The [1-6(14)C]benzene and [1-(14)C]toluene vapors penetrate into hypostomatous leaves of Acer campestre, Malus domestica, and Vitis vinifera from both sides, whereas hydrocarbons are more intensively absorbed by the stomatiferous side and more actively taken up by young leaves. Benzene and toluene conversion in leaves occurs with the aromatic ring cleavage and their carbon atoms are mainly incorporated into nonvolatile organic acids, while their incorporation into amino acids is less intensive. Intact spinach chloroplasts oxidize benzene, and this process is strongly stimulated in light. Oxidation of benzene by spinach chloroplasts or by enzyme preparation from spinach leaves is almost completely inhibited by 8-oxyquinoline or sodium diethyldithiocarbamate, and slightly affected by alpha, alpha'-dipyridyl. Benzene oxidation by enzyme preparation is significantly stimulated by NADH and NADPH; in their presence, the benzene hydroxylation product, phenol, is formed in a determinable amount. It is supposed that the enzyme performing the first step of oxidative transformation of benzene in plant leaves contains copper as the prosthetic group.
Ecotoxicology and Environmental Safety 07/1997; 37(1):24-9. · 2.29 Impact Factor
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ABSTRACT: The induction of individual components of the plant microsomal monooxygenase system have been studied. Quantitative distribution of NADPH reducible equivalents at monooxygenase and oxidase reactions and rereduction of coenzyme have been exhibited when there is deficiency of oxygen. Xenobiotic oxidation specificity in NADPH and NADH synergism with NADPH have been detected. The dependence of hydroxylation rate on the degree of hydrophobicity of xenobiotic molecules has been established. The possibility of cytochrome P-450 switching over from biosynthetic into detoxication pathway and transformation of monooxigenase mechanism of oxidation into peroxidase according to plant age have been demonstrated.
Ecotoxicology and Environmental Safety 04/1997; 36(2):118-22. · 2.29 Impact Factor
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ABSTRACT: L-Methionine sulfoximine (MSO) at concentration 1.25 mM in vivo causes the inhibition of glutamine synthetase (GS) in both roots and leaves of young seedlings of kidney bean following the accumulation of high levels of ammonia and decrease in amounts of free amino acids that is more pronounced in leaves. The inhibition of GS by MSO in leaves in the case of externally supplied 5 mM (15NH4)2SO4 assimilation leads to ammonia accumulation and the decrease in the amounts of glutamine and glutamic acid and the intensity of the incorporation of 15N into them. In roots the inhibition of GS is not followed by the decrease of 15N content into glutamate. It is concluded that the pathway of ammonia primary assimilation in leaves is via GS and glutamate synthase (GOGAT), while in roots glutamate dehydrogenase also plays an important role in this process.
Ecotoxicology and Environmental Safety 07/1996; 34(1):70-5. · 2.29 Impact Factor
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ABSTRACT: The action of different concentrations of 1,2-benzanthracene and 3,4-benzpyrene on maize root cell ultrastructural organization was studied. It has been shown that low concentrations of xenobiotics (1,2-benzanthracene 20–100 μg/ml; 3,4-benzpyrene 2.6 × 10−9–2.6 × 10−8 μg/ml) do not cause noticeable changes on ultrastructural level due to the cell's ability to assimilate and metabolize them. At the same time, these low concentrations of 3,4-benzpyrene inhibit DNA synthesis in nuclei. Higher concentrations of 1,2-benzanthracene (200 μg/ml) and 3,4-benzpyrene (2.6 × 10−7–2.6 × 10−5 μg/ml) lead to significant ultrastructural changes up to the complete destruction of the cell.
International Biodeterioration & Biodegradation.
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ABSTRACT: The effect of various benzidine concentrations on the ultrastructural organization of maize root tip cells was investigated. Data showed that benzidine at concentration of 2.2×10−7– did not cause noticeable changes of the ultrastructure. When benzidine concentration was increased up to several pathological changes occurred ending in the complete destruction of the cell. Radioautographic investigation to follow the penetration and facts of [1–1214C]benzidine into cells showed that the radioactive label reached the nucleus chromatine within 10 min. Then the label was detected in the nucleolus and the cytoplasmic organelles followed by excretion into vacuoles (60 min). Benzidine at 2.2×10−4, inhibited DNA synthesis in the nuclei. Cytochemical investigation showed that exposure to of benzidine for 24 h caused an inhibition of Ca2+–ATPase and an increase of the concentration of free calcium in the cytoplasm resulting from the release of calcium from the membrane system. Data suggest that ultrastructural changes are caused by disturbance of cell calcium homeostasis, resulting in a deregulation of the Ca2+ dependent metabolic processes.
International Biodeterioration & Biodegradation.
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ABSTRACT: Data obtained in this work shows that the transformation of plant cytochrome P-450 to P-420 under the action of oxygen and oxidative substrates is associated to substitution of monooxygenase activity by peroxidase. Under these conditions the oxygenase reductase component and the cytochrome b5 change their function to play a role in the respiratory chain. Thus, electrons are transferred from NADPH to the bc1-complex of a mitochondrial respiratory chain via the reductase and the cytochrome b5. In the presence of xenobiotics the reductase and cytochrome b5 switch from their energetic to their detoxification function, supplying cytochrome P-450 with NADPH reducing equivalents. Furthermore, evidence was obtained suggesting that when NADPH is deficient, electrons are transferred from complex II and III of the mitochondrial respiratory chain to cytochrome P-450.
International Biodeterioration & Biodegradation.
