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A V Gudkov

Publications and source records attributed to A V Gudkov.

At least 73 records · Page 4Linked to original sources
PubMed1987

[Detection of tissue-specific gene expression using an in situ hybridization method of histoblotting].

A version of in situ hybridization on the histological sections that is used for screening specific mRNA in tissues in proposed. Sections of the frozen tissue samples are prepared on the cryostatic microtome, placed on nitrocellulose filters and hybridized with labelled DNA-probes under the conditions of RNA blot hybridization. The proposed method ("histoblotting") was used to study the distribution of actin and alpha-phetoprotein mRNA genes in tissues of 15 and 21-day rat embryos. The possibility of studying mRNA (by hibridizations) and protein (by immunoenzyme staining) and making histological analysis simultaneously by histoblotting is demonstrated.

Animals↗
PubMed1987

[Endogenous proretroviruses and other autonomous retroposons: traces of viral origin or decay?].

Origin of viruses is considered to be a fundamental trend in biology. In 1970 H. Temin proposed that some of them (namely, retroviruses) could originate from preexisting transcriptional units of cell genome. This "protovirus hypothesis" was supported recently by new findings. It is clear now that eukaryotic genomes contain sequences related to retroviral genes and long terminal repeats. Some endogenous retrovirus-related sequences can be considered to be interstitial stages in retrovirus origin. We suppose that not only retroviruses but all the autonomous retroposons could arise from cellular sequences.

DNA Transposable Elements↗
PubMed1987

[Multiple drug resistance of tumor cells: manifestations, genetic basis, clinical aspects].

Data are reviewed concerning the results of study of multidrug-resistant (MDR) tumor cells. MDR often develops in the course of chemotherapy or in vitro selection of tumor cells by vincristine, adriamycin, actinomycin D, colchicine, etc. MDR cells are resistant to all these drugs though their targets and mechanisms of toxic action are quite different. Resistance is due to the decreased accumulation by MDR cells of these compounds. The genetic basis for MDR is amplification of a large genomic region that contains a number of genes coding for products and functions that are under extensive study. Specific karyotype and amplified DNA alterations occur during the development of MDR imitating the processes of appearance and variability of multigene families. The obtained data demonstrate the ways of overcoming of tumor multidrug resistance in clinic.

Animals↗
PubMed1987

[Pattern of evolution of amplicons during the development of multiple drug resistance in Djungarian hamster cells].

Six cloned DNA fragments representing different portions of the genomic region amplified in multidrug resistant Djungarian hamster cells were used to study amplicon variations in a large number of the resistant cell lines. Expressed correlation exists between the degree of 3 cloned sequences amplification and the level of multidrug resistance. Three other cloned regions amplify coordinately with the latter ones at the initial steps of selection. Later their amplification halts and they mao even eliminate from amplicons of highly resistant cells. The rates and order of elimination of these sequences vary among different independently derived series of multidrug resistant cell lines.

Animals↗
PubMed1987

[Cloning and characteristics of DNA sequences amplified in Djungarian hamster cells with multidrug resistance].

A number of DNA clones containing the amplified DNA sequences were isolated from the genomic library of multidrug-resistant (MDR) Djungarian hamster cells using the DNAC0t 10-250 hybridization probe. Five independent nonoverlapping clones were obtained that covered more than 100 kb of the amplified genomic region. These clones were used as hybridization probes in blot-hybridization with DNA from 7 independently derived MDR Djungarian hamster cell lines selected for the resistance to colchicine or actinomycin D. Some clones contained the DNA sequences amplified in all of the cell lines tested while the others contained the cell line specific amplified sequences. Hybridization in situ was used to localize the amplified DNA in metaphase chromosomes of a MDR cell line that contained about 140 copies of these sequences. The approximate size of an amplicon calculated on the basis of the obtained data is about 1-2 X 10(3) kb.

Animals↗
PubMed1987

[Gene amplification in murine leukemia cells with multiple drug resistance acquired in vivo].

The P388rm and P388rx cell lines resistant to antracycline antibiotics were obtained as a result of chemotherapy of mice bearing P388 leukemia, by means of increasing dosages of rubomycin and ruboxyl, respectively. These cell lines possessed cross-resistance to vinblastine, vincristine, colchicine, actinomycin D and some other drugs. Multidrug resistance (MDR) of P388rm and P388rx is due to decreased uptake of different cytotoxic compounds by the cells. Development of resistance to rubomycin and ruboxyl was accompanied by the appearance of additional chromosomal structures--long homogeneously staining regions (HSRs), double minute chromosomes and others usually containing amplified DNA sequences. Southern blot-hybridization with cloned DNA fragments amplified in Djungarian and Chinese hamster cell lines having MDR has revealed in P388rm and P388rx cells approximately 50-fold amplification of mdr and pC52 genes. Thus, in mouse leukemia cells which acquired MDR in vivo, as a result of chemotherapy, amplification is observed of the same genes that undergo amplification during selection of cell cultures for MDR in vitro.

Animals↗
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↗
PubMed1986

Genetic structure of the endogenous proviruses and expression of the gag gene in Brown Leghorn chickens.

Seven loci of endogenous proviruses were detected in the genome of Brown Leghorn chickens. Sets of endogenous proviruses in DNA of the chicken embryos examined were identified by blot hybridization with 32P-labelled DNA of RSV and EcoRI restriction endonuclease digestion. Comparison of the results showed that only one locus (A) of endogeneous provirus was associated with a gs+ phenotype as determined by the immunoperoxidase reaction and antibodies against gag gene products of RSV. Restriction endonuclease analysis with HindIII, BamHI and SacI revealed that proviruses A and F in Brown Leghorn chickens correspond to loci ev-3 and ev-6, respectively, in White Leghorn chickens. Other loci (B, C, D, E, and X) were designated ev-22, ev-23, ev-24, ev-25, ev-26, respectively. None of these loci expressed infectious virions. The structure of most of the endogenous proviruses examined is considerably different from the genome of the endogenous chicken virus RAV-O. The difference in structure may be one possible cause of the absence of endogenous provirus expression.

Animals↗
PubMed1986

Methylation of endogenous proviruses of Brown Leghorn chickens.

Among the 7 endogenous proviruses we have detected in Brown Leghorn chickens none encodes the production of virions and only one, ev-3, expresses the gag gene. To study the possible role of DNA methylation in the inhibition of provirus expression, we performed blot hybridization and restriction endonuclease analysis with EcoRI and SmaI, is sensitive to methylation. Of the six endogenous proviral loci examined (ev-3, ev-6,, ev-22, ev-23, ev-24, ev-25), two loci, ev-23 and ev-24, were methylated at all SmaI restriction sites, in both the DNA from erythrocytes of adult chickens and the DNA from 10-day embryos. Since both these viruses are closely related to the genome of RAV-O, DNA methylation might be the cause of the absence of gene expression.

Animals↗
PubMed1985

Gene amplification in Djungarian hamster cell lines possessing decreased plasma membrane permeability for colchicine and some other drugs.

By multistep selection a set of clones and sublines possessing different levels of resistance to colchicine or adriablastin was obtained from the SV40-transformed Djungarian hamster cell lines, DM-15 and DMcap. Resistance to both colchicine and adriablastin is associated with an alteration of plasma membrane permeability leading to a decreased uptake of various drugs (3H-colchicine, 3H-cytochalasin B, 3H-actinomycin D, 3H-puromycin, 3H-vinblastine, 14C-chloramphenicol). The DNA of cells highly resistant to cholchicine can transmit resistance only to low dosages of the drug. Comparison of DNAs from wild-type and resistant cells digested by restriction endonucleases revealed new classes of repeated DNA sequences in resistant cell lines. The degree of DNA repetition was correlated with the level of drug resistance. The repeated DNA sequences evidently represent parts of the genome that are amplified in resistant cells. The size of the amplified sequences is 200-250 kilobase pairs (kb). Cell lines highly resistant to colchicine contain amplified DNA, which like mitochondrial DNA replicate asynchronously with the main portion of the cellular DNA and related but not identical DNA sequences are amplified in independent cell lines selected for resistance to colchicine, adriablastin, and actinomycin D. These cell lines display similar patterns of alterations of plasma membrane permeability. The amplified DNA sequences may contain a gene or genes the overexpression of which leads to change in plasma membrane permeability and a development of resistance to various drugs.

Animals↗
PubMed1985

Regular pattern of karyotypic alterations accompanying gene amplification in Djungarian hamster cells: study of colchicine, adriablastin, and methotrexate resistance.

Chromosomal analysis of 26 Djungarian hamster cell lines obtained from 11 independent clones and possessing different levels of resistance to colchicine or adriablastin as a consequence of gene amplification revealed regular patterns in the karyotypic changes that accompanied the development of drug resistance. Usually the sequence of karyotypic changes was as follows: first an additional chromosome 4 appeared: then single unpaired small chromatin bodies (SCBs) arose; later in the middle part of the long arm of one of three chromosomes 4 long homogeneously staining regions (HSRs) and double minute chromosomes (DMs) were formed; and finally in the most resistant variants large clusters of SCBs appeared. The emergence of the clusters of the SCBs correlated well with the occurrence of autonomously replicating, amplified DNA sequences. In contrast to DNA of the HSRs the DNA of the SCBs could replicate outside the S-phase of the cell cycle. When kept in a non-selective medium, the cells gradually lost their resistance to colchicine: 1%-4% of the cells lost the capacity to form colonies in the selective medium independently of the pattern of location in them of amplified genes (in chromosomal HSRs. SCBs, or DMs). Loss of drug resistance was accompanied by disappearance of the chromosomal HSRs, SCBs, and DMs. Chromosomal analysis of the set of methotrexate-resistant Djungarian hamster cell lines indicated the following karyotypic evolution: first the additional material on the distal part of one of two chromosomes 3 appeared; then the light HSRs were formed on the distal part of one of two chromosomes 4; later clusters of SCBs and HSRs arose on the distal part of the short arm of chromosome 3. Probably the amplification of different genes is characterized by specific patterns of karyotypic alterations.

Animals↗
PubMed1984

Variations of endogenous chicken proviruses: characterization of new loci of endogenous proviruses in the genome of Italian partridge chickens.

The composition and structure of endogenous proviruses present in the genome of Italian Partridge chickens were studied by the method of blot hybridization using RAV-2 [32P]DNA or LTR of RSV as hybridization probes. The genomes of 5 out of 39 chickens analyzed did not contain endogenous proviruses related to RAV-2. Different sets of five so far undescribed endogenous proviruses, differing in the structure and location, were detected in the DNA of other IP chickens. None of them is identical in its structure to the DNA of the endogenous chicken virus RAV-0, all five loci of endogenous proviruses of IP chickens were defective. The origin, the patterns of genetic variation and the function of endogenous proviruses are discussed.

Animals↗
PubMed1983

Localization of provirus DNA of Rous sarcoma virus in the DNA of infected, transformed and tumour cells of chickens.

The integration of the RSV provirus genome into chicken cell DNA was studied by restriction analysis at various times after infection with RSV. One to two copies of provirus DNA per cell genome are integrated and integration occurs at different sites of DNA without apparent specificity, independently of the stage of infection and transformation of cells. The exogenous virus DNA is integrated into cell genome independently of the endogenous proviruses. The number of integrated proviruses does not correlate with the number of non-integrated proviruses in infected cells. No changes in structure and location of endogenous proviruses were found in spontaneous chicken tumours.

Animals↗
PubMed1983

[Amplification of portions of the genome in mammalian somatic cells resistant to colchicine. VI. Restriction analysis of the amplified DNA sequences].

Fragments specific for the amplified regions in DNA of Djungarian hamster colchicine-resistant cells were studied after restriction endonuclease digestion. We used three different methods of detection of these fragments: a) comparison of the wild type and resistant cell DNA electroforegramms stained by ethidium bromide; b) blotting of DNA from sensitive and resistant variants onto nitrocellulose filters and their hybridization with nick-translated DNA from resistant cells, in the presence of the excess of unlabelled DNA from the wild type cells (competitive hybridization); c) investigation of autonomously replicating DNA from sensitive and colchicine-resistant sublines. The highest resolution was found using the third method. However, the competitive hybridization is evidently a more universal approach to restriction analysis of DNA amplified sequences, because it gives quite high resolution and may be used for studying both autonomously and non-autonomously replicating sequences.

Animals↗