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N A Liapunova

Publications and source records attributed to N A Liapunova.

At least 19 recordsLinked to original sources
PubMed1998

[Cytogenetic of nucleolar organizer regions (NOR) of human chromosomes: identification of four morphofunctional variants of NOR, their inter-individual and inter-chromosomal distribution].

Cytogenetic characters of the nucleolus organizer regions (NORs) located on the short arms of five acrocentric chromosomes were studied in chromosome preparations obtained from cultured blood cells of 17 donors. In situ hybridization to a 3H-labeled probe was used to estimate the relative copy number of ribosomal genes (RGs) in all NORs of chromosomes identified by G-banding in each sample. The relative amount of potentially active RGs (0 to 4 arbitrary units) in each NOR was estimated from the size of AgNOR selectively stained with silver nitrate. Linear regression analysis revealed clusters of silent RGs (CSRGs) in 24 out of 170 NORs (14%). Based on the presence or absence of active and inactive RG clusters, NORs of human chromosomes were classified into four morphological functional variants (MFVs): (1) Ag-/CSRG-, (2) Ag-/CSRG+, (3) Ag+/CSRG-, and (4) Ag+/CSRG+. These variants were observed in 7.65%, 2.35%, 11.8%, and 78.2% of 170 analyzed NORs, respectively. NORs with CSRGs (MFV 2 and 3) were absent in 5 out of 17 donors. One, two, and three NORs with CSRGs were observed in four donors each. Analysis of the chromosome distribution of NOR MFVs showed that their frequencies remained almost the same in group-D and group-G acrocentric chromosomes. Although the tested samples were small (34 chromosomes for each pair), two observations were made with regard to individual chromosomes. First, almost half MFV-1 NORs (6 out of 13) were detected on chromosome 15. Second, the frequency of CSRGs was higher in chromosome 21 (29%) than in the other chromosomes (10%).

Adult↗
PubMed1994

[Localization of the CD4 receptor gene in the chromosomes of clone cells of the monocytoid line U-937 characterized by different sensitivities to HIV].

Karyotypes of two clones of U-937 line, with high and low sensitivity to HIV-1, were studied. The CD4-receptor gene-cellular receptor of HIV-1 was mapped. CD4-receptor gene was located according to in situ hybridization method, in locus 12 p11-p12, both in cells of high-sensitive clone U-937/16, and in cells of low-sensitive clone U-937/4. It is determined that in both the clones chromosomes 12 are presented in two copies and are not affected by rearrangements. That allows to conclude that the sensitivity of cells U-937 to HIV-1 does not depend on the dose of this gene, or on its transference in chromosomes.

CD4 Antigens↗
PubMed1994

[Analysis of chromosome aberrations and nucleolar organizer regions of chromosomes in workers producing pyromellitic dianhydride: the possibility of the adaptive role of Ag-NOR variants].

To assess the mutagenic danger of pyromellitic dianhydride (PMDA) production, the frequency of chromosome aberrations in peripheral blood lymphocytes from 56 workers and 37 control donors from Ufa was determined. A significant increase in the frequency of metaphases with aberrant chromosomes was found in the industrial group (5.3%) as compared with the control (2.9%). The effect of toxic factors on the functional state of acrocentric NORs was analyzed. No significant differences between PMDA-exposed workers and the control group in cumulative functional activity of 10 NORs (silver staining) was revealed. At the same time, a decreased proportion of cells with associations was found (76% in workers and 82% in donors), which may be a consequence of changes in immune status and in compensatory activation of cell proliferation, which leads to accumulation of young circulating lymphocytes with low associative capacity of acrocentrics. In addition, a significantly increased proportion of individuals carrying extreme Ag-NOR variants (grades 3.5-4.0) was observed in the industrial group (up to 37% vs 6% in the control), which may be due either to genotype selection at the number of active rRNA gene copies or to compensatory activation of repressed copies of ribosomal genes in some NORs.

Adult↗
PubMed1993

[Interconnection of the functional activity of nucleolar organizer regions of chromosomes with human reproductive pathologies].

Comparative analysis of transcriptional activity of human nucleolus organizer regions (NOR) of the chromosomes in the group of the control phenotypically healthy individuals (I) and in the spouses with repeated spontaneous abortions (II) was conducted in an attempt to verify the hypothesis: whether elimination of zygotes having received a very large or very small number of the copies of active rRNA genes may serve as a factor decreasing the fecundity of some spouses? It has been shown that the groups I and II have no differences in total activity of 10 NOR (Ag staining, rating estimation). At the same time, the II group is characterized by higher, in comparison with the I, heterogeneity of Ag-NOR variants in homologues of 5 nucleolus-organizing chromosomes. As a result, in the individuals of the group II the gametes are formed which are more heterogenous than in the group I for the Ag-NOR pattern variants. The imitation computer experiments revealed that in the group II elimination of zygotes as a consequence of inherited Ag-NOR variants combination should occur more frequently (in 22.2% cases) than in the group I (15.9%), p < 0.05. Thus, the hypothesis under test was substantiated in the present study.

Chromosomes, Human↗
PubMed1991

[Effects of cycloheximide on protein, RNA and DNA synthesis in cultures of CHO cells and human diploid fibroblasts].

In CHO cell line and primary human diploid fibroblasts culture an incorporation of protein, RNA and DNA biosyntheses precursors was investigated under different conditions of inhibition of translation by cycloheximide (CHM). Both CHO and human fibroblasts transitory treatment by CHM in the serumfree medium resulted in inhibition of protein and DNA syntheses during S-period while RNA synthesis increased up to 130% (CHM concentration from 0.003 to 2 Mg/ml), as well as in Go--an incorporation of 3H-U increased to 200% (CHM concentration-100 Mg/ml). Long-term treatment (48 hours) in the serum-free medium resulted in decreased uptake of 3H-T and 3H-L during first 6 hours of experiment, while incorporation of 3H-U increased to 160%. By 16-th hour of treatment characters of protein, RNA and DNA syntheses came back to control levels.

Animals↗
PubMed1989

[The effect of bleomycin on DNA synthesis in human cells: evidence for grouping of initiation of replicons in the S-period].

The effect of bleomycin (Blm) on DNA synthesis has been studied in a synchronous culture of human embryonic lung cells. The data obtained suggest that in the Blm presence in a medium (20 micrograms/ml) DNA synthesis initiation in new replicons is suppressed. The Blm action at different S-phase intervals has been shown to inhibit DNA synthesis unequally. Four discrete time intervals have been singled out in the course of the 10-hr S-phase in which a grouped initiation of replicon portions can be supposed. Together with the data on DNA replication in large-size replicon units (50-500 microns), the obtained results account well for the uneven DNA synthesis in S-phase, manifested by 3 or 4 peaks of [3H]-thymidine incorporation in pulse-labelled cells.

Bleomycin↗
PubMed1989

[Expression of ribosomal genes under the action of 5-azacytidine in the African green monkey RAMT cell line].

The use of cytosine analogue--5-Azacytidine(5AzaC), derepression of ribosomal genes has been studied in one of organising chromosomes in the African green monkey RAMT cell line in which the nucleolar organizer region (NOR) in parental cells was active. The effect of 5AzaC on the functional state of NOR was assessed by the length of the secondary constriction in this chromosome and by the intensity of Ag-staining of NOR. 5AzaC was added to the cell culture at concentrations 2-16 M, either immediately after the cell passage or at the 24th h from the beginning of cell cultivation for the following 17-34 hours. As a control the cells cultivated in the absence of 5AzaC were used. Comparison of control cells with those treated with 5AzaC showed: 1) increase of the length of the second constriction in the chromosome with the initial inactive NOR in the 5AzaC--treated cells; 2) a marked increase of the intensity of NOR's Ag-staining in the same chromosome after incorporation of 5-AzaC into DNA. The conclusion about the methylation of cytosine bases in the DNA of ribosomal genes in one NOR organising chromosomes in RAMT cell line was made.

Animals↗
PubMed1989

[Effect of methylnitronitrosoguanidine on DNA synthesis in animal cells: decrease in the rate of replication fork movement].

The effect of methylnitronitrosoguanidine (MNNG) on the rate of DNA replication fork (RF) progress has been studied by DNA fiber autoradiography in asynchronous Microtus agrestis and Chinese hamster cells. The rate of RF progress has been shown to be decreased by 14% and 36% at MNNG concentrations of 50 and 100 microM in M. agrestis cells; the rate of DNA synthesis being reduced by 50 and 75% respectively. In Chinese hamster cells the MNNG concentration of 5 microM does not affect the rate of RF and that of 10 microM decreases the latter by 11%, the respective fall in the synthesis of DNA rate being 13 and 57%. It has been concluded that the decreased RF rate contributes only partially to the overall DNA synthesis inhibition following the MNNG administration. Inhibition of DNA synthesis at the MNNG concentrations reducing the DNA synthesis by less then 40-50% is mainly caused by the inhibition of the initiation points and, possibly, by the stopping of operating RF. Further DNA synthesis inhibition (at the MNNG concentrations leading to DNA synthesis decrease exceeding 50%) is mostly due to the reduced RF progress rate.

Animals↗
PubMed1989

[A new approach to cloning of tandem repetitive DNA sequences].

A new approach to screening of the repeated human DNA sequences tandemly arranged in the genome is described. Efficiency of the developed approach for search of tandemly arranged DNA sequences is corroborated by the obtained experimental data.

Cloning, Molecular↗
PubMed1988

[Relation between the intensity of transcription and the rRNA gene content of individual nucleolar-forming regions of human chromosomes].

A comparison has been carried out of satellite strand lengths, Ag-staining intensity and labelling intensity in in situ hybridization of 3H-thymidine-labelled 28S-rRNA gene fragment in nucleolar-forming regions (NFR's) of individual acrocentric chromosomes from blood lymphocytes of 2 karyotypically normal individuals. To identify chromosomes modified R-staining was performed (5-bromdesoxy-pyridine + Höchst fluorochrome 33258 + Giemsa dye). The data obtained demonstrate, firstly, the variability between 10 acrocentric human chromosomes both in the content of ribosome genes and in silvering intensity and NFR satellite strand length and, secondly, a positive correlation between three studied characteristics of individual chromosomes. In one case an exception has been noted in one homologue of chromosome 21 of an individual A: high intensity of hybridization labelling was accompanied by weak Ag-staining and short satellite strand. It was concluded that the variability of transcription activity of individual NFR's detected by Ag-staining is, as a rule, based on the variability in the content of ribosome gene DNA in them and, in some cases, the presence of rRNA gene copies in inactive state.

Chromosomes, Human↗
PubMed1988

[Interindividual and intercellular differences in the total activity of ribosomal genes detectable by the Ag staining of nucleolus organizer regions in human acrocentric chromosomes].

Selectively Ag-stained nucleolar organizing regions (NORs) of human chromosomes were analysed using four size categories: 0, 1, 2 or 3 grades. A criterion of NORs' total activity has been proposed as a sum of grades (sigma (+]. On this basis, interindividual polymorphism was defined in 60 healthy individuals with normal karyotypes. The reaction norm of sigma (+) was determined (from 16 to 22 grades). In the cells of the patients with two nucleolar organizing chromosomes involved in Robertsonian translocations the sigma (+) was within the reaction norm (16-19). The total NORs activity was determined in a patient having both normal karyotype cells and two cell clones with one or two small bisatellited chromosomes: sigma (+) in three cell clones amounted to 20.5, 23.0 and 26.3. In the clones with additional NORs, the silver staining intensity for 10 NORs of the main set did not change, which leads to a suggestion that no compensatory change in the number of rRNA gene copies working takes place in man. The data obtained allow to suppose that zygotic selection operates in man, which ensures maintainance of the number of the ribosomal gene's copies necessary for viability of an individual.

Chromosome Banding↗
PubMed1985

[The effect of methylnitronitrosoguanidine on DNA synthesis in human and animal cells. Inhibition of DNA synthesis in asynchronous and synchronous cultured cells].

Methylnitronitrosoguanidine (MNNG) is reported to inhibit DNA synthesis in intact human cells, in the cells from patients with ataxia telangiectasia (AT) or the cells from two rodent species. DNA synthesis in different cell lines exhibits varying sensitivity to MNNG inhibitory effect. 4-5-fold higher concentrations of MNNG are required for 50% inhibition of DNA synthesis in AT cells or in field vole cells as compared with the concentration required for human cells or Chinese hamster. The different compactness of two chromatin fractions might possibly result in lower sensitivity of DNA synthesis in heterochromatin to MNNG-induced inhibition as compared with the sensitivity of euchromatin. The genetic expression of AT defect on the cellular level is supposed to be connected with changes in supramolecular packaging of chromatin in interphase nuclei.

Animals↗
PubMed1980

[Organization of mammalian genome replication: data on the high rate of DNA replication in replicons of structural heterochromatin].

By the autoradiography, the increase of the mean rate of replication fork movement in DNA was shown for human skin fibroblasts during S-period induced by reseeding the stationary culture; the portion of high-rate replicons growing parallel to the increase in numbers of cells, in which the constitutive heterochromatin was replicating. Furthermore, the heterogeneity of replicons was investigated in regard to the rate of DNA chain growth in asynchronous cell populations of human and three rodent species (Microtus agrestis, Tscherskia triton, Cricetulus griseus). A positive correlation was found between the portion of replicons, with a relatively high rate of replication (more than 60 micron/h), and the relative amounts of C-heterochromatin in genomes of these species. On the basis of these studies it has been assumed, that the replicons with the high rate of DNA chain growth belong to the constitutive heterochromatin.

Animals↗
PubMed1977

The units of DNA replication in the mammalian chromosomes: evidence for a large size of replication units.

The replication of chromosomal DNA in human and Chinese hamster cell populations has been studied by means of the DNA fiber autoradiography. It was found that the rate of DNA replication for one fork in human cells varies from 0.2 to 0.9 micron/min, the average being 0.6 micron/min. In the Chinese hamster cells the rate DNA replication is greater, varying from 0.3 to 1.2 micron/min, the average being 0.8 micron/min. There are no clusters containing a great number of replication units in human and Chinese hamster cells. Sequences consisting of two or three replicons which belong to single DNA molecule have been observed, but their frequency was relatively low. The distances between the initiation points in such sequences of replicons vary from 40 to 280 micron, the average value being 130 micron. This value represents the minimum size of the replication units which have completed the DNA synthesis within 3 h of the S-period. The DNA synthesis in most replication units fails to be accomplished within the three hours of labelling. The process can be completed only in the fragments of DNA molecules of 40 to 200 micron (the average value being 100 micron) in human cells, whereas in the Chinese hamster cells the fragments of 40 to 250 micron (the average being about 140 micron) are completely replicated. Provided that the replicaton is bidirectional the complete replicons are supposed to contain two such fragments. Consequently, the greater part of replication units in mammalian cells covers the pieces of a few hundred microns in DNA molecules. The relation between replication process at the DNA molecules level and that at the metaphase chromosome level is discussed.

Autoradiography↗