[Transcripts of satellite DNA in blood plasma: probable markers of tumor growth].

A recent study of human normal and tumor tissues revealed a high transcriptional activity of pericentromeric satellite DNA repeats (they produce half of all transcripts in tumor cells that is many times higher than in normal ones). It was found also that the two subtypes of satellite DNA (HSATII and GSATII) are transcribed reciprocally, i.e.

[Mutation scanning of short amplicons: optimization of DNA melting conditions].

High resolution melting analysis (HRMA) using special "saturating" fluorescent dyes is a new and very effective approach to genotyping and mutation scanning. HRMA, which is carried out usually just after PCR without any intermediate manipulations (the "closed tube" format), is simple and high-throughput method excluding sample cross-contaminations. The "closed tube" format makes, however, HRMA dependent on PCR mixes and, as such, limits its capability.

[Detection of genetic mutations in clinical specimens from cancer patients: comparison of NIRCA and SSCP scanning methods].

Specimens of tumor with K-RAS mutations were used to compare SSCP and NIRCA efficiencies in screening long target regions for dispersed point mutations. K-RAS mutations were detected in 5 out of 10 tumor tissue samples from colorectal cancer patients (in codon 12-4 and codon 13-1). Mutant alleles occurred most frequently in adenocarcinoma of the ascending colon and rectum.

[Genetic defects as markers of tumor development].

Carcinogenesis is long-term multistep accumulation of defects of genes responsible for cell division, DNA repair, and apoptosis. The functions of these genes are known both for norm and for pathologies caused by their damage and resulting in "asocial" cell behavior. Owing to the recent progress in studying the mechanisms of carcinogenesis, some genetic defects may be considered from the applied point of view (as tumor markers rather than as pathogenetic factors) and employed in diagnostics.

[Analysis of DNA excreted from the body as an approach to diagnosis and monitoring tumor growth].

Proceeding from their early data showing that some portion of DNA originating from apoptotic cells can enter the blood stream and pass through the renal barrier by preserving its template capabilities, the authors analyzed urine DNA from 29 patients with colorectal cancer. PCR was used to compare DNA samples from the normal mucosa surrounding the tumor and from the urine collected just prior to surgery. Six microsatellite loci were studied with oligonucleotide primers.

[Metabolic and structural properties of extrachromosomal DNA in mammalian cells].

Discrete bands of free DNAs of approximately 25 kbp were detected in human cell cultures. According to electrophoretic shifts induced by single and double strand breaks, they from topological isoforms (supercoiled, open, and linear). Long-term labeling (24 h) of growing and quiescent cultured cells by [3H]thymidine indicates differences of free versus chromosomal DNAs including (i) significantly lower specific radioactivity in growing cells, (ii) higher specific radioactivity in quiescent cells, and (iii) resistance to fluorodeoxyuridine labeling.

[Analysis of the genome compartmentalization phenomenon in normal and neoplastic cells].

Intact cell nuclei (or whole cell lysates) were immobilized on Celite and extracted gradually with gradients of NaCl, LiCl-urea and temperature. Contrary to the notion of DNA integrity and continuity within chromosomes, a heterogeneous spectrum of DNA fragments of large size was obtained, adhesion of which to the nuclear interior widely varied. Similar chromatographic patterns of DNA were observed in analysis of various origin cells both in normal animal tissues and in malignant cells (Djungarian hamster fibroblasts transformed by SV40).

[Patterns in the degradation of individual genes of thymocytes in irradiated rats].

Degradation of genes of actin, albumin, histones, heat shock protein, and ribosomal RNA within DNA of irradiated animal thymocytes has been investigated. It has been shown that single strand enzymatic breaks occurred in thymocyte DNA 2 h following irradiation are localized in linker sites of nucleosomes. All the transcribed genes under study degrade to fragments that correspond by their length to DNA of nucleosomes and their oligomers.

[Changes in gene expression in the brain of rats with Zajdela's ascitic hepatoma].

Expression of some genes in the brain of ascitic hepatoma of Zajdela bearing rats was compared with that of control animals using Northern blot hybridization technique. The differences revealed were: an increased expression of actin gene and decreased expression of hsp70 gene in the brain of tumor-bearing animals.

[Comparative analysis of subdomain fragments of chromatin].

Nuclei isolated from Djungarian hamster fibroblasts transformed by SV40 were treated with restriction endonuclease Bsp RI, fixed on Celite columns and underwent successive gradients of dissociating agents, such as NaCl, LiCl-urea, and temperature. This procedure leads to fractionation of DNA fragments in accordance with the tightness of DNA-protein bonds in situ. The fractions obtained were analysed by agarose gel electrophoresis and dot-hybridization technique with the use of various DNA probes.

[Identification of the stable DNA-matrix complex (type II) as a site of replication fork].

The two types of DNA-matrix complexes (the weak and tight ones, or type I and type II, respectively) identified in our previous work were studied with respect to their involvement in DNA replication. Nuclei isolated from human fibrosarcoma HT1080 cell line were treated with either restriction endonucleases or ultrasonic desintegrator and afterwards subjected to the triple-gradient Nucleoprotein--Celite chromatography. This permitted fractionation of nuclear DNA into fragments not attached, weakly attached, and tightly attached to the nuclear matrix (DNA 0, DNA I, and DNA II, respectively).

[Radioactive labeling of DNA with 3H-thymidine: effect of the internal irradiation on cell growth, chromatin structure and gene activity].

The growth of djungarian hamster fibroblasts 4/21 is inhibited by 3H-thymidine present in a culture medium in concentrations from 18.5 to 740 KBq/ml. As judged from the gradient elution of DNA from isolated nuclei (the nucleoprotein-celite chromatography), DNA fragmentation increases together with the increase in 3H-thymidine concentration and the decrease in the cell growth rate.

[A new method of DNA and RNA transfer onto nitrocellulose filters during blot hybridization].

A quick (1-2 hour) method of DNA and RNA transfer onto nitrocellulose filters for subsequent blot-hybridization was elaborated. The main features of the method proposed are, firstly, almost complete exclusion of the mechanical impact on the gel and, secondly, addition to the transfer medium (20 X SSC) of a chaotropic agent, 0.5 M NaClO4.