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Biomedical subjects

I B Zbarsky

Publications and source records attributed to I B Zbarsky.

17 recordsLinked to original sources
PubMed1998

Phosphorylation and biosynthesis of high molecular weight proteins of tumor nuclear matrix.

Our previous studies showed a predominance of high molecular weight protein group in tumor nuclear matrices. Contrary to normal cells, proteins of this group are preferentially phosphorylated. Phosphoproteins of hepatoma nuclear matrix are selectively subjected to rapid proteolysis. By alkali treatment and a monoclonal antibody against phosphotyrosyl residue the presence of two high molecular weight bands of phosphotyrosyl-containing proteins was detected in nuclear matrices of tumor but not of normal liver cells. High molecular weight protein group of tumor nuclear matrices revealed also a rapid turnover and preferential incorporation of labeled amino acids selectively inhibited by chloramphenicol.

Animals↗
PubMed1987

An unusual NAD(P)H-dependent O2-.-enerating redox system in hepatoma 22a nuclei.

Nuclear membranes from many tumors contain an unusual redox chain discovered originally in the Hepatoma 22a nuclear membranes which catalyzes superoxide dismutase-sensitive adrenaline oxidation to adrenochrome in the presence of either NADPH or NADH as electron donor, the reaction being inhibited by cyanide and azide. This redox chain can reduce anthracycline antitumor antibiotics adriamycin and carminomycin to their free radical states under anaerobic conditions. Evidence has been obtained for a higher stability of the carminomycin radical as compared to that of adriamycin. Operation of the nuclear membrane-bound redox chain can be a source of oxygen radical-mediated single strand breaks in DNA. The role of the nuclear membrane-associated electron transfer chain in augmenting the anticancer action of the anthracycline antibiotics is discussed.

Animals↗
PubMed1985

DNAaseI-hypersensitive minichromosomes of SV40 possess an elastic torsional strain in DNA.

Previously, we have shown that DNA in a small fraction (2-5%) of SV40 minichromosomes was torsionally strained and could be relaxed by treating minichromosomes with topoisomerase I. This fraction was enriched with endogeneous RNA polymerase II (Luchnik et al., 1982, EMBO J., 1, 1353). Here we show that one and the same fraction of SV40 minichromosomes is hypersensitive to DNAase I and is relaxable by topoisomerase I. Moreover, this fraction completely loses its hypersensitivity to DNAase I upon relaxation. The possibility that this fraction of minichromosomes can be represented by naked DNA is ruled out by the results of studying the kinetics of minichromosome digestion by DNAase I in comparison to digestion of pure SV40 DNA and by measuring the buoyant density of SV40 chromatin in equilibrium CsCl gradient. Our data obtained with SV40 minichromosomes may be relevant to the mechanism responsible for DNAase I hypersensitivity in the loops or domains of cellular chromatin.

Animals↗
PubMed1984

Protein patterns of the nuclear matrix in differently proliferating and malignant cells.

SDS-polyacrylamide gel electrophoresis of the nuclear matrix proteins showed a predominance of high molecular weight and low molecular weight polypeptides in the nuclear matrices of hepatomas and cultured Chinese hamster fibroblasts as compared to quiescent and regenerating rat liver. These features were more prominent in solid hepatoma 27 than in Zajdela ascites hepatoma or in cultured cells. In proliferating cells (tumors, regenerating liver, log phase cell culture) a polypeptide band of 150 kD and lamin B were conspicuous at the expense of lamins A and C.

Animals↗
PubMed1984

Visualization of reactive oxygen species formation by phagocytizing macrophages.

Activated peritoneal macrophages exhibiting phagocytosing capacity produced an electron-dense precipitate of formazan in contact sites of macrophage plasmalemma and phagocytosed yeast cells. No production of formazan occurred, when non-opsonized latex particles were ingested by macrophages. Formazan precipitation could be prevented by anaerobiosis but not by addition of cyanide.

Anaerobiosis↗
PubMed1984

Superoxide dismutase-sensitive, NAD(P)H-dependent reduction of oxygen by the membrane-bound redox chains of liver microsomes and hepatoma nuclei in the presence of adrenaline.

Evidence has been obtained that the NAD(P)H-dependent "generation of superoxide radicals" by various types of membrane bound redox chains, as studied by the adrenaline method, does not occur in the absence of adrenaline. Studies of the oxygen uptake associated with the NAD(P)H-dependent adrenaline co-oxidation confirm the presence of an unusual cyanide-sensitive electron transfer system in the nuclear membranes from Hepatoma 22a. This redox chain contains a b-type cytochrome which resembles cytochrome b5.

Animals↗
PubMed1982

Elastic torsional strain in DNA within a fraction of SV40 minichromosomes: relation to transcriptionally active chromatin.

After treatment of SV40 minichromosomes with DNA topoisomerase I, the superhelicity in the bulk of the DNA extracted from minichromosomes is known to remain unchanged. However, we found that the DNA extracted from a small fraction of SV40 minichromosomes (2-5%), was almost completely relaxed, and covalently closed as shown by agarose gel electrophoresis. Thus, the DNA in these 2-5% of SV40 minichromosomes was probably torsionally strained (TS). The proportion of such TS minichromosomes is close to the estimated proportion of transcriptionally active minichromosomes. The distribution of the TS minichromosomes in sucrose gradient coincided with the distribution of transcriptionally active complexes. Both sedimented faster than the majority of minichromosomes. Furthermore, after treatment with topoisomerase I the relaxed minichromosomes could be quantitatively separated from the bulk of material by recentrifugation in a sucrose gradient. A major part of the endogenous RNA polymerase activity was recovered in the relaxed fraction. These data suggest that TS-minichromosomes correspond to transcriptionally active chromatin. After relaxation with topoisomerase I the TS minichromosomes lacked histones.

Animals↗
PubMed1982

Granules 25-30 nm in diameter: basic constituent of the nuclear matrix, chromosome scaffold, and nuclear envelope.

Rat liver nuclear matrix and similar structures derived from isolated Chironomus polytene chromosomes, nuclear envelopes, and intranuclear bodies of frog late oocytes (the karyospheres) were studied by electron microscopy with platinum shadowing and negative staining. We have shown that the treatment of whole nuclei, nuclear envelopes, polytene chromosomes, or karyospheres with nonionic detergent, high salt, and RNase and DNase followed by dilute alkali or hyaluronidase digestion reveals numerous rather uniform granules 25-30 nm in diameter. With omission of the nucleases the granules appear to be associated with DNA strands mostly organized in loops. Many granules form clusters and are arranged in linear or arch-like aggregates or cycles resembling the pore complexes. We suppose that these spherical bodies constitute a basic component of the nuclear matrix, chromosome scaffold, and nuclear envelope and are bound together by hyaluronic acid or some similar glycosaminoglycan.

Animals↗
PubMed1981

Some features of nucleo-cytoplasmic RNA transport from isolated nuclei.

Messenger RNA is released preferentially from isolated rat liver nuclei in the presence of the ATP-generating system and cytosol. The release is suppressed by spermidine, while cytoplasmic RNase inhibitor was ineffective and PCMB like some other thiol-blocking agents inhibitory. Cytoplasmic SOD added to the system strongly suppressed RNA release. A similar effect could be obtained by anaerobiosis due to addition of SMP. In both cases the inhibition is reversed by cyanide. In contrast to normal liver where the generation of superoxide radicals takes place almost exclusively in microsomes and is coupled with the oxidation of NADPH, in mouse ascites hepatoma 22a the generation of superoxide radicals occurs mainly in the nuclear envelope and is coupled wih the oxidation of both NADPH and NADH and inhibited by cyanide.

Animals↗
PubMed1981

Nuclear skeleton structures in some normal and tumor cells.

Nuclear protein fractions, described earlier, were identified as constituents of the nuclear sap (the 'globulin fraction'), that of the nucleoli and ribonucleoprotein network (the 'acidic protein'), and of the nuclear envelope (the 'residual protein'). The latter two fractions compose the protein skeleton of the cell nucleus. An essential difference between electrophoretic profiles of nuclear skeleton structures in experimental tumors and those of normal tissues was revealed. Tumor preparations contained more high molecular weight polypeptides and, in earlier stages of growth, low molecular weight components as well. Fractionation of the nuclear matrix proteins showed that the bulk of them are soluble in diluted alkali. The alkali-insoluble fraction retains the shape of the nucleus and appears in the electron microscope as a spongy nuclear skeleton. A finely dispersed fraction sedimenting from the alkaline suspension is enriched with the pore complexes. The fractions obtained differ in protein composition and probably contain protein components which are similar in molecular weights but non-identical.

Animals↗
PubMed1981

Proteins tightly bound to DNA in the regions of DNA attachment to the skeletal structures of interphase nuclei and metaphase chromosomes.

Proteins tightly bound to the DNA of mouse L cells were examined both in the regions of DNA attachment to the protein skeleton and in the DNA loops. The interphase nuclear matrix and the metaphase chromosomal scaffold, containing from 2 to 15% of the original DNA, as well as the material released from the skeleton were isolated by mild nuclease treatment. At least six proteins resistant to sarcosyl-Cs2SO4 treatment are associated exclusively with skeleton-attached DNA both in interphase nuclei and metaphase chromosomes. Two (p52 and p60) can be dissociated from the complex by mercapto-ethanol-sarcosyl treatment. Both skeleton-attached and released DNA fractions contain a group of tightly bound low molecular weight polypeptides consisting of a major p18 band and one or two minor bands. They seem to be randomly distributed throughout the whole DNA loop. Some of the specific proteins that are tightly associated with DNA at the site of its interaction with the skeleton may directly be responsible for DNA attachment to the skeleton.

Animals↗
PubMed1975

Elementary particles in isolated rat liver and spleen nuclear membranes.

Elementary spherical particles similar to those described in the mitochondria are found in isolated rat liver and spleen nuclear membranes. The particles are characterized by electron microscopy of sections and preparations negatively stained with phosphotungstic acid or with the ATPase histochemical reaction product. The particles exhibit adenosine triphosphatase activity and have a mushroom-like shape with a sphere about 85-90 angstrom in diameter attached to inner face of the inner nuclear membrane by a stalk about 50 angstrom in length and 35 angstrom in diameter. It is supposed that these particles, just as analogous particles localized at the inner mitochondrial membrane, are involved in the coupling of oxidation and phosphorylation in the nuclear envelope.

Adenosine Triphosphatases↗