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Biomedical subjects

D M Spitkovskiĭ

Publications and source records attributed to D M Spitkovskiĭ.

At least 19 recordsLinked to original sources
PubMed1993

[The effect of the environment on the repair of DNA damage in human lymphocytes].

The dependence of UV-induced unscheduled DNA synthesis (UDS) in the unstimulated lymphocytes of human peripheral blood on the ionic strength (mu) of the culture medium has been shown. In the level of mu lower or higher than the physiological (mu ph) one, UDS significantly decreases. The effect of modification of mu due to the changes of ionic strength is absent in the lymphocytes of the classic form of xeroderma pigmentosum. The phenomenon may become useful in the development of a new test for revealing cells with a genetically or physiologically changed system of UV-induced DNA repair. The mechanisms of investigated phenomenon, particularly their dependence on the structure of chromatin, as well as the influence of ionic strength on binding of the repair enzymes with DNA are discussed.

Cells, Cultured↗
PubMed1992

[The dependence of DNA repair induced by genetically hazardous exposures on the ionic strength of the medium containing the cells].

The dependence of UV-induced unscheduled DNA synthesis (UDS) in non-stimulated lymphocytes of human peripheral blood on the ionic strength (mu) of the culture medium has been shown. With the level of mu lower or higher than physiological (mu ph) the UDS significantly decreases. The effect of modification of mu due to changes in ionic strength is absent in the lymphocytes of patients with the classic form of xeroderma pigmentosum. This phenomenon may become useful for development of a new test revealing cells with genetically or physiologically changed system of UV-induced DNA repair. Mechanisms of investigated phenomenon, particularly their dependence on the chromatin structure, as well as the influence of ionic strength on binding the repair enzymes with DNA are discussed.

Adult↗
PubMed1986

[Detection of post-repair DNA damage and heterogeneity of its distribution in fractions of metaphase chromosomes of various sizes].

The distribution of single-strand DNA breaks induced by various N-methyl-N-nitrosourea concentrations in S-phase of the cell cycle has been studied in Djungarian hamster fibroblast culture in the isolated samples of fractions of metaphase chromosomes of varying size. For the first time, a dose-effect relationship between the molecular mass of single-stranded DNA fragments isolated in an alkaline sucrose gradient from small chromosomes and the lack of the effect on DNA in large chromosomes has been established. The phenomenon detected is being discussed in terms of structural heterogeneity of interphase nuclear chromatin, i.e. irregular distribution of eu- and heterochromatin in small and large chromosomes. Another possible explanation is the storage of various damaged chromosome fragments in small chromosomes. The data obtained, apart from their significance for chromatin structure analysis, can serve as an experimental basis for the detection of, otherwise undetectable, postreparative molecular DNA damages.

Animals↗
PubMed1985

[Electrophoretic analysis of the characteristics of the protein composition of leukocytes from Down's syndrome patients].

Protein with a molecular mass of 53000 daltons undetectable in healthy persons was identified by electrophoresis in peripheral blood leukocytes of patients with Down's syndrome. The protein was completely extracted with 0.4 N HCl from leukocyte homogenates and was found to be identical, as regards electrophoretic mobility, to protein detected in two patients with chronic myeloblastic leukemia. The causes of discrepancy between theoretically expected and electrophoresis-revealed differences in protein composition of normal and trisomal cells.

Adolescent↗
PubMed1981

[Histone competition for DNA and its possible role in the self-assembly of eu- and heterochromatin].

Electrophoretic analysis of histones bound to DNA and remaining free in the mixtures of DNA with the total histone of chromatin in a medium of physiological ionic strength has shown that even the minimal weight excess of the total histone with reference to DNA (1.1:1) leads to the formation of nucleohistone impoverished in HI fraction because of histone competition for DNA. Within the histone/DNA ratio equal to 1.4, H3, H4, H2A and H2B are bound to DNA without competition, i.e. at a ratio in which they are added to DNA. Provided the histone/DNA ratio is higher in the mixture, there form nucleohistones enriched with H3 and H4 fractions. The role of histone competition for DNA in eu- and heterochromatin assembly is discussed.

Animals↗
PubMed1981

[Changes in the protein composition of chromatin in the presence of supplementary total histone].

Relationships have been studied between call thymus chromatin isolated in a medium of low ionic strength (0.7 mM Na-phosphate buffer, pH 7) and total histone which was added in different amounts (up to a 40-fold excess) with respect to chromatin DNA. The maximum protein/DNA ratio in chromatin-histone complexes being formed was 3.27. It has been demonstrated for the first time that with an elevation in the amount of supplementary total histone there took place a release of natural histones of chromatin, first of HI and then of H2A and H2B. It is concluded that supplementary histone interacts with DNA, modifying its interplay and chromatin protein even though the dissociation is not fixed yet.

Chemical Phenomena↗
PubMed1980

[Dissociation and decompactization of chromatin by heparin in a medium of "physiologic" ionic strength].

It has been shown for the first time that heparin, one of the natural polyanions, is capable of dissociating the histones H1, H2A and H2B from chromatin in a medium of "physiological" ionic strength: 0.15 M NaCl + 0.7 mM Na-phosphate buffer, pH 7.0. Under the same conditions heparin produces chromatin fractionation, leading to the appearance of slow-sedimenting DNA, augments viscosity and reduces turbidity of chromatin suspension. This evidences the decompactization of deoxyribonucleoprotein fibrils.

Animals↗
PubMed1979

[Blood serum as a factor of chromatin condensation in trisomy-21 (Down's syndrome)].

The influence of blood sera from patients with Down's syndrome and healthy ones, and different serum fractions on the structure of the deoxyribonucleoprotein systems (DNP-system) has been studied. It was demonstrated that non-fractionated sera of the patients produce a condensation effect on the DNP-system in contradistinction to the sera from healthy people. The analysis of the action of single serum fractions showed that different condensation effect results from the activity of high molecular nondialysable thermosensitive components whose action disappears at gel-filtration of serum proteins. A possibility of the humoral control over chromatin structural organization in vivo is discussed in terms of the evidence on the similarity of serum proteins and chromosomal nonhistone proteins.

Chemical Fractionation↗
PubMed1978

[Geometric complementarity of the primary structures of histone molecules H2A, H2B, H3, H4 and several possible consequences of this phenomenon].

The paper treats of the correlations between the position geometry of the extended successions of the residue of basic amino acids and those nonbearing any positive charge along the polypeptide chains of the histone H2A, H2B, H3, H4 molecules forming nucleosomes protein frame. The number of histone packing variants in the tetramere conforming to the conditions of the revealed complementarity reached the value of 10(4), and in respect to histone octamere--10(8). A hypothesis was put forward on structural heterogeneity of nucleosomes (of functional significance) the choice of whose protein frame packing variant could be realized by the mechanisms of allosteric regulation of the primary structure of DNA molecule section serving as the nucleosome element.

Chromosomes↗