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Biomedical subjects

S P Rad'ko

Publications and source records attributed to S P Rad'ko.

9 recordsLinked to original sources
PubMed1987

[Structural heterogeneity of chromatin preparations at the level of DNA topology].

The structural heterogeneity of calf thymus chromatin preparations was studied at the level of DNA topology by analysing the influence of ethidium bromide on the chromatin viscosity in deproteinizing medium. In 0.7 M NaCl the chromatin was separated into the fractions with linear DNA (3--36% in various preparations) and with supercoiled circular DNA (scc DNA), which differ from each other in their adhesive properties. Reduction of disulfide bonds in residual chromatin protein with 5% mercaptoethanol linearized scc DNA, present in chromatin preparations as nuclear matrix subunits containing some loops of scc DNA on the protein globule.

Animals↗
PubMed1986

[Dynamic and static chromatin].

It was found that the dependence of the viscosity of calf thymus chromatin dispersions and human leukocytes on ethidium bromide concentration had two peaks indicative of domains with circular supercoiled DNA and varying resistance to ultrasound in the cells and isolated chromatin. The hypothesis of V. D. Paponov and P. S. Gromov (Bull. Exp. Biol. Med., N5, 590, 1985) on the transformation of static relations of nucleosome DNA-containing nuclei into dynamic, after chromatin exposure to ultrasound due to DNA linearization in chromatin domains possessing circular supercoiled DNA, has been confirmed.

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PubMedDate not supplied

[The formation and repair of DNA breaks in subpopulations of irradiated rat bone marrow cells].

Using the method of viscosimetry of alkaline lysates it was shown that the saturable DNA repair system was present in rat bone marrow cells which was described by a complex kinetics. Isokinetic fractionation in a sucrose and dextran gradient permitted to isolate three fractions differing in the ratio between differentiated cells and cells capable of division. The estimation of the postirradiation DNA repair kinetics in these cells revealed a comparatively high level of repair in normocytes which confirmed the presence of the relationship between the level of DNA repair in cells and their proliferative potency.

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PubMedDate not supplied

[The rate factor in DNA sedimentation studies].

Zimm theory was used to study the effect of the rate of centrifugation on the coefficient and the profile of sedimentation of a polydispersed single-stranded DNA. There was a good agreement between the calculated and experimental DNA sedimentograms in alkaline lysates of irradiated rat bone marrow cells. This approach permited to take the rate factor into consideration on the basis of the parameters necessary for the work of the rotor and the gradient. Simple formulae were obtained connecting the molecular mass of DNA with the rate and the time necessary for its centrifugation. Possible consequences of not taking the rate factor into account in centrifuging the polymer DNA molecules are discussed.

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PubMedDate not supplied

[Induction of double-strand DNA breaks in rat bone marrow cells by X-radiation].

The method of sedimentation in a neutral sucrose gradient was used to study double-stranded DNA in a total population of rat bone marrow cells. As a result of cell lysis in neutral conditions the fragments of double--stranded DNA were formed having the molecular mass of (3 +/- 0.3) X 10(9)D. A study was made of the dynamics of accumulation of DNA double-strand breaks after irradiation of a cell suspension. It was shown that the yield of double-strand breaks and the ratio between single- and double--strand breaks in bone marrow cells were similar to those of cultured L5178Y cells.

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