Increased PARP-1 levels in nuclear matrix isolated from heat shock treated rat liver.

Poly(ADP-ribose) polymerase-1 (PARP-1), a chromatin-associated enzyme that catalyzes the NAD+-dependent addition of ADP-ribose polymers onto a variety of nuclear proteins, has been shown to be associated with the nuclear matrix. PARP-1 levels in the nuclear matrix vary depending on the matrix isolation method used. The nuclear matrix appears to be the most thermosensitive nuclear structure during heat shock. Here we provide evidence for the extensive translocation of PARP-1 from chromatin to the nuclear matrix during heat shock. This translocation is accompanied by inhibition of PARP activity in the nucleus and elevation of PARP activity in the nuclear matrix. Our data suggest that thermal destabilization of the nuclear matrix is less likely to contribute to the translocation of PARP-1 to the nuclear matrix.

[Ultrastructural study of TNT effect on the callus cells and the cells of intact plants of Yucca gloriosa L].

Intracellular distribution of assimilated 2,4,6-trinitrotoluene (TNT) in callus cells, flower buds and leaves of intact Yucca gloriosa L. plants using electron microscope radioautography. The radiotracer was detected in vacuoles, plastids, mitochondrion, endoplasmic reticulum and cytoplasm. It was found that in dedifferentiated callus cells TNT was incorporated in the vacuoles in greater quantities in comparison with the cells of intact plant. Correspondingly the ultrastructural integrity of the dedifferentiated cells is less damaged.

Absorption, distribution, and transformation of TNT in higher plants.

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.

Benzoic acid transformation via conjugation with peptides and final fate of conjugates in higher plants.

Transformation of [1(14)C]- and [7(14)C] benzoic acids in sterile seedlings of maize (Zea mays) and pea (Pisum sativum) was studied. The tested labeled compounds were supplied in plants through roots as water solutions. The larger part of the assimilated benzoic acid forms conjugates with low-molecular-weight plant peptides. As a result of hydrolytic cleavage of the conjugation products, initial labeled benzoic acid molecules and unlabeled amino acids are released. It is supposed that conjugation takes place between the benzoic acid carboxyl group and the peptide functional groups. The amino acid composition of the conjugate peptides was determined. After removal of the plants from the labeled benzoic-acids-containing medium, the amount of conjugation products gradually decreases and the process is accompanied by the emission of labeled carbon dioxide, indicating that the conjugation products are degraded and that their radioactive component carbon atoms are then oxidized to carbon dioxide. Parallel to the conjugation reaction, a smaller part of the benzoic acid that entered the plant is transformed via oxidation, as a result of which an aromatic ring is cleaved and the resulting aliphatic fragment is incorporated into regular cell metabolism. The smallest part of the assimilated benzoic acid radiolabel is incorporated into a cell biopolymer fraction. Benzoic acid, of which the radioactive label is detected in the plant subcellular organelles and finally deposited in the vacuoles, affects the cell ultrastructural organization and the activities of the main metabolic enzymes. Intensification of catabolic processes takes place, indicating an energy demand needed for xenobiotic detoxification.

[ADP-ribosylation intensifies cleavage of DNA loops in the nuclear matrix].

Using DNA pulse field electrophoresis it has been shown that ADP-ribosylation in the nucleoids of human mononuclear leukocytes and rat brain cortex neurons stimulates cleavage of DNA loops at their attachmant sites to the nuclear matrix. The conclusion has been drawn suggesting possible participation of ADP-ribosylation in DNA-topoisomerase II activity modulation in the nuclear matrix of eukaryotic cells.

Electron microscopic investigation of nitrobenzene distribution and effect on plant root tip cells ultrastructure.

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.

[Plant potential for detoxification (review)]. / Detoksikatsionnyi potentsial rastenii (obzor).

Data on the uptake, excretion, and biodegradation of organic xenobiotics by plants are reviewed. Detoxification pathways operating in plants and their role in remediation of biosphere are described. Structure-, concentration, and time-dependent effects of xenobiotics on the ultrastructural organization of cells are analyzed.

Organic toxicants and plants.

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.