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T G Tsvetkova

Publications and source records attributed to T G Tsvetkova.

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

[C-polymorphism of chromosomes in female reproductive system disorders].

Frequencies of extreme C segments of chromosomes 1, 9, and 16 were studied in patients with isolated gonadotropin deficiency (I), gonadotropin resistant ovary (I), and polycystic ovarian disease (III). Increased chromosome 9 heterochromatin was revealed for all syndromes, and increased chromosome 1 heterochromatin was revealed for groups II and III. Identical changes in heterochromatic parts of chromosomes, linked with increased heterochromatin, probably suggest a lack of specificity for the syndromes studied.

Chromosomes, Human, Pair 1↗
PubMed1992

[Characterization of cloned alpha-satellite sequence from the extrachromosomal DNA of HeLa cell culture].

We have obtained the alphoid DNA clones, pK1 and pK2, from the extrachromosomal DNA of Hela cells treated by cycloheximide (30 micrograms/ml). Nucleotide sequences of the clones were aligned. The sides of the pK1 and pK2 are 390 and 184 bp, respectively. The marked RELP for the clones was not observed. The results of in situ hybridization have shown an approximately equal distribution of Ag-grains over major part of human chromosomes, with a slight preference for chromosomes 1, 5 and 19 (the 1-st group of alpha-satellite DNA). Therefore, the obtained alphoid sequences seem to be rather conservative and non-chromosome-specific. We suppose that increase of the alphoid DNA content in the fraction of the extrachromosomal DNA under the cycloheximide treatment is a result of the sporadic statistical processes rather then consequence of the specific excision.

Base Sequence↗
PubMed1989

[Specificity of the location of human chromosomes in the nucleus of a moving cell].

Data are presented on the distribution of centromeric heterochromatin of the human X-chromosome in the interphase nucleus of a moving cell. The in situ hybridization made it possible to obtain some results leading to the following conclusions: in moving fibroblasts centromeric heterochromatin of the X-chromosome is located in end regions of the interphase nucleus; there was no preferential localization noted of the centromeric region of the X-chromosome in the front or back areas of the nucleus as to the direction of the movement.

Cell Movement↗
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

Variability of human rRNA genes: inheritance and nonrandom chromosomal distribution of structural variants of nontranscribed spacer sequences.

Human rRNA genes contain variable regions, one of which is located in nontranscribed spacers (NTSs) closely downstream from the 3'-end of the transcribed region. This polymorphism may be detected by means of blot hybridization analysis as a set of distinct restriction fragments corresponding to this part of the rRNA genes. We have analyzed DNA of 51 individuals and found eight structural NTS variants of this region; two of these were common to all individuals analyzed, and six others were found in different combinations and with different frequencies. The copy number of each variant also differed but was not less than 10-20 copies per cell. The analysis of DNA isolated from leukocytes of the members of 11 families indicated that some of the structural variants (of the NTS region) are inherited as a single Mendelian locus. We propose that rRNA genes that belong to one particular structural variant form clusters on separate chromosomes. To test this proposition, we developed a combined method, including AgNO3-staining of chromosomes, in situ hybridization, and DNA analysis with methylation-sensitive restrictases, and used it for study of persons who had methylated rRNA genes located on AgNO3-negative nucleolar organizers. It was found that in three of four cases methylated genes really belonged to one structural variant. This approach may be used for detailed localization of separate classes of NTS structural variants of human rRNA genes.

Blotting, Southern↗
PubMed1986

[Molecular and cytogenetic approach to the mapping of methylated polymorphic restriction fragments of human rRNA genes].

Combined restriction with Bam H I and Sal I (or Hpa II) has revealed Bam H I fragment on a non-transcribed spacer of rRNA genes in one out of four individuals under study. Using Ag-staining and hybridization in situ, chromosome 13p+ enriched by inactive rRNA gene copies was found in the given individual. Since Sal I does not restrict methylated sequences and rRNA genes are repressed by methylation, it is concluded that methylated Banm I-restricted rRNA gene fragments of non-transcribed spacer are localized in chromosome 13p+ of the individual in question.

Chromosome Mapping↗
PubMed1983

[Q- and C-band polymorphism of the chromosomes in a group of patients with the Shereshevskiĭ-Turner syndrome].

Q- and C-band polymorphism of heterochromatic regions of chromosomes were studied in a group of patients with Turner's syndrome (30 girls with the karyotype 45, X) and in 105 normal individuals. No significant differences in the frequencies of Q-polymorphic variants for the most part of chromosomes studied (with the exception of chromosome 13 satellites) were obtained between patients with Turner's syndrome and the control. There were no differences in the mean number of Q-variants per individual in both groups investigated. An increase in the frequency of large C-segments of chromosome 9 was detected in patients with Turner's syndrome. An increase in the frequency of individuals carrying a combination of several extreme variants in the individual karyotype was found for patients with Turner's syndrome. The differences revealed are of non-specific character for a given form of developmental pathology.

Chromosome Banding↗
PubMed1979

[Human chromosome polymorphism and disordered reproductive function. I. Routine chromosome variants].

Routine polymorphic variants of chromosomes of 58 married couples with reproductive failure (two or more spontaneous abortions, stillbirths and malformed children) and 48 control couples, having two or more normal children and no spontaneous abortions and stillbirths, were investigated by conventional staining technique. Extreme variants of chromosomes 1, 9, 16, 17, 13--15, 21--22 and Y were found in 17.2% of subjects with reproductive loss and in 15.6% of control individuals. No significant differences in frequencies of scored routine variants were noted between married couples with reproductive failure and couples with normal reproduction.

Abortion, Habitual↗
PubMed1979

[Human chromosome polymorphism and disordered reproductive function. II. C-variant chromosomes].

C-stained polymorphic variants of chromosomes 1, 9, 13--16, 21, 22 and Y were studied in married couples with reproductive failure (200 individuals) and in control couples having normal children and no spontaneous abortions and stillbirths. Location of heterochromatic segments, their size and heteromorphism of homologues were estimated. The individuals with reproductive failure were carriers of variants of chromosomes 9 and acrocentrics with higher content of heterochromatic material as well as with heterochromatic chromosome 9 significantly more frequently as compared with control individuals.

Abortion, Habitual↗
PubMed1977

[Quantitative assessment of human chromosomal polymorphism with regard to paracentromeric heterochromatin].

The measurement of C-segment length in chromosomes 1, 9 and 16 of 7 individuals was carried out. The regression analysis was employed to study a change of the C-segment sizes in the process of mitotic chromosome condensation. Typical values of C-segment length for chromosomes 1, 9 and 16 are about 1.4, 1.1 and 0.8mu respectively. Among 7 individuals there was no two which had identical size of C-segments for all three chromosomes studied. In six individuals heteromorphysm of C-segments was revealed. It was found that visually detected heteromorphysm may be expressed quantitatively as ratio length of C-segments in homologous chromosomes.

Cells, Cultured↗
PubMed1976

Isochromosome X in man: different DNA replication patterns in the long arms.

An X isochromosome for the long arm was studied in 3 patients with Turner's syndrome using the BrdUrd-Hoechst 33258-Giemsa method and C-staining. In all 3 patients studied, the long arms of the i(Xq) were asymmetrical with respect to chronology of DNA synthesis. The most striking asynchrony of DNA replication was observed in large early replicating segments adjacent to the centromeric region. Two C bands of similar appearance were observed localized symmetrically in both arms. The data are interpreted in accordance with two possible origins of an abnormal X which is known as i(Xq).

DNA Replication↗