[Endogenous DNases as a tool for isolation of nuclear matrix: critical parameters of nucleolysis]. / Endogennye DNKazy kak instrument polucheniia preparatov iadernogo matriksa: kriticheskie parametry nukleoliza.

Degree of nucleolysis has critical significance for isolation of nuclear matrix (NM) specifically enriched in transcribed DNA sequences as demonstrated at the example of inactive (c-fos, c-myc, and Ck) and active (p53, albumin, and 28S rRNA) genes in resting hepatocytes. Optimal degree of nucleolysis features degradation of loop domains of chromatin with preserved relatively uniform molecular weight distribution of DNA. Deviation from these parameters leads to nonspecific fragmentation of chromatin in various gene loci and isolation of NM samples nonspecifically enriched or depleted of transcribed DNA sequences. Under optimal hydrolytic conditions, the transcribed chromatin is more resistant to endogenous DNase attack, which allows selective conservation of its association with the nuclear matrix.

[Markers of the metabolic changes arising as a result of ionizing radiation exposure]. / Markery metabolicheskikh izmenenii, voznikaiushchikh vsledstvie vozdeistviia ioniziruiushchei radiatsii.

Time-related changes have been studied in the content of extracellular DNA, Fe(3+)-transferrin (TF), and Cu(2+)-ceruloplasmin (CP) in the blood plasma and the activity of ribonucleotide reductase (RR) in the tumor cells and spleen of mice during the development of acute lympholeukosis P-388 and after ionizing irradiation. At the initial stages of leucosis P-388, the content of extracellular DNA increases, the TF and CP pools in the blood plasma enlarge, and the RR activity in the tumor cells and spleen of tumoral mice markedly increases. A dose-dependent increase in RR activity was also recorded in the spleen of 5-day-old rats within 15-30 min after irradiation. The causes of these changes and the possibility for these indices to be used in estimating leucosis risk are discussed. Radiation-induced increases in RR activity are discussed in relation to the SOS-response to DNA damage; an increased pool of deoxyribonucleotides is necessary for repair of DNA. The mean contents of extracellular DNA, TF and CP in the blood plasma were obtained from children of different ages degrees of radioactive contamination suffering the consequences of the accident at the Chernobyl' Nuclear Power Station (n = 155). Groups of children have been isolated with increased, sharply decreased, and close to normal levels of extracellular DNA, TF, and CP. The lowered TF pool was observed in children with thyroid glands damaged by incorporated radioactive iodine with the degree of suppression determined by the dose. For most children subject to general irradiation, the TF and CP pools in the blood were higher than in the control, suggesting an adaptive response to irradiation.

[Change in the level of sphingosine in rat liver nuclei and cells during oncogene superexpression induced by cycloheximide]. / Izmenenie urovnia sfingozina v iadrakh i kletkakh pecheni krys pri indutsirovannoi superékspressii onkogenov tsiklogeksimidom.

Changes in the sphingosine content in rat liver cells and nuclei have been studied with reference to the level of nuclear oncogene expression, induced by cycloheximide (0.1, 0.5 and 3.0 mg/kg). It has been found that only the sublethal (3 mg/kg) dose of cycloheximide which induces the superexpression of c-fos and c-myc oncogenes can promote sphingosine accumulation in the cell. At the moment of enhanced expression of nuclear oncogenes, the maximum content of free sphingosine exceeds the control level 1.5- and 3-fold in the cell and in the nuclei, respectively. The difference in the sphingosine accumulation patterns in the cell and in the nuclei testifies to the fact that sphingomyelin metabolism is more active in the nuclei than in the cell. Sphingosine accumulation in the nuclei is characterized by coordination of sphingomyelinase activity and changes in the sphingomyelin content. A comparative analysis of activities of enzymes of sphingomyelin (sphingomyelinase) and phosphatidyl inositol (phosphatidyl inositol kinase) cycles indicates that in the nuclei the activation of the sphingomyelin cycle forestalls the cycloheximide-induced activation of the phosphatidyl inositol cycle and the maximal accumulation of nuclear oncogene mRNAs. A model of activation of oncogene expression with participation of sphingosine inhibiting protein kinase C and activating casein kinase II, the key enzymes of the signal transduction system of cell proliferation and differentiation, is proposed.

[Structural changes of chromatin during proto-oncogene activation by cycloheximide: dose-effect]. / Strukturnye izmeneniia khromatina v protsesse aktivatsii protonkogenov tsklogeksimidom: doza-éffekt.

The level of expression of cellular proto-oncogens c-myc and c-fos in rat liver has been studied as a function of protein synthesis rate (cycloheximide dose). Activation of proto-oncogens has been established to be initiated by 50% inhibition of nuclear protein synthesis. This promotes a certain level in chromatin structural rearrangements which is manifested, in particular, in decreasing activity of chromatin cleavage by Ca2+, Mg(2+)-DNAase and increasing degree of chromatin condensation. A role of topoisomerase II in chromatin structural rearrangements during proto-oncogen activation is postulated.

[Expression of oncogenes in the rat liver under conditions of template biosynthesis uncoupling by sublethal doses of cycloheximide]. / Ekspressiia onkogenov v pecheni krys v usloviiakh razobshcheniia matrichnykh biosintezov subletal'nymi dozami tsiklogeksimida.

Injection of sublethal doses of cycloheximide (CHI) to rats allowed to reveal three stages in the dynamics of protein synthesis: 1) suppression stage (0-6 hrs), 2) regeneration stage (6-12 hrs), 3) stimulation stage (6-12 hrs). RNA-polymerases are activated when protein synthesis is inhibited. The stimulation stage precedes the activation of DNA replication. This model of DNA replication induced by CHI is specified by the expression of various cell oncogenes (c-fos, c-mys, p53, c-Ha-ras, c-sis, c-src). The investigated oncogenes may be divided into 4 groups according to the character of their expression. 1. Oncogenes (c-fos, c-myc) are switched on step-by-step 1 hour after CHI injection, the superexpression of the oncogenes being comparatively short. Maximum expression of c-fos and c-myc oncogenes is registered after 2-3 hours, respectively. 2./p53 oncogene expression increases within a few hours' after CHI injection and manifests itself at all three stages of protein synthesis till DNA replication. 3. c-Ha-ras oncogene is expressed at a high level in control and experimental animals. 4. Expression of c-sis and c-src oncogenes are absent both before and after CHI injection. Sublethal doses of CHI have the same effect on oncogene expression as the lethal ones.

[Phase-specific protein synthesis in human fibroblasts after synchronization by a double thymidine block]. / Fazospetsificheskii sintez belkov v fibroblastakh cheloveka posle sinkhronizatsii dvoinym timidinovym blokom.

Kinetics of acid-insoluble non-histone protein synthesis during S and G2 cell cycle phases of diploid human fibroblasts and heteroploid transformed cells was investigated. Two distinct groups of protein with different kinetic pattern depending on the cell culture type were revealed. Export of one group of protein and turnover of the other group of acid-insoluble non-histone protein is arrested in heteroploid transformed cells.

[Correlation of the activity of the key enzymes of glycolysis and respiration in hepatomas with different growth rates]. / Sootnoshenie aktivnosti kliuchevykh fermentov glikoliza i dykhaniia v gepatomakh s razlichnoi skorost'iu rosta.

It is shown that an increase in the activity of glycolysis resulting from the rise of the hepatoma growth rate is accompanied by a decrease in the activity of the pentose-phosphate pathway and respiratory chain. It is supposed that variations in the activity both of different carbohydrate catabolism ways and the respiration with a rise of the hepatoma growth rate reflect changes in the relative content of cells at different phases of the cell cycle.

[Sequence of activation of template biosynthesis in normal and transformed human cells after synchronization by a double thymidine block]. / Posledovatel'nost' aktivatsii matrichnykh biosintezov v normal'nykh i transformirovannykh kletkakh cheloveka posle sinkhronizatsii dvoinym timidinovym blokom.

The sequence of matrix biosyntheses of DNA, RNA and various proteins in normal and transformed human fibroblasts in the first mitotic cycle after synchronization of cells by double thymidine block was studied. Two important regularities of synthesis of acid-soluble histone-like and acid-insoluble proteins in normal and transformed cells were established. In normal fibroblasts, the synthesis of both acid-soluble and acid-insoluble proteins is minimal before DNA replication and maximal in the G2-phase; that in transformed cells is maximal after removal of the thymidine block and decreased in the G2-phase. In normal fibroblasts, the synthesis of acid-insoluble proteins is maximal before, while that of acid-soluble ones--after the maximum of DNA synthesis. In transformed cells the situation is opposite. RNA synthesis in normal and transformed cells is stimulated at the end of the G2-phase. In normal cells, protein synthesis is coupled with the activation of RNA synthesis, whereas in transformed fibroblasts protein synthesis occurs, in all probability, in the next mitotic cycle. These differences are especially well-pronounced in the expression of some LMG proteins. It is concluded that in transformed cells the regulatory control over the coupling of matrix biosyntheses is impaired.

[Activation of nuclear polypeptide synthesis in rat liver cells after inhibition of template protein synthesis. The role of nuclear polypeptide synthesis in the changes of the chromatin structure]. / Aktivatsiia iadernogo polipeptidnogo sinteza v kletkakh pecheni krys pri tormozhenii matrichnogo sinteza belkov. Vklad iadernogo polipeptidnogo sinteza v izmenenie struktury khromatina.

The correlation between the rates of nuclear polypeptide synthesis (NPS) and matrix protein synthesis in rat liver cells was investigated. It was shown that NPS is activated under conditions of protein synthesis inhibition in the cytoplasm. Model experiments revealed that the NPS and ADP ribosylation systems compete for chromatin structure: ADP ribosylation induces condensation, while NPS--decondensation of chromatin.

[Paramagnetic metal complexes of iron in the regenerative processes of the liver]. / Paramagnitnye metallokompleksy zheleza v regeneratornykh protsessakh pecheni.

ESR study was carried out of the content of oxidized form of cytochrom P-450 at regenerative processes in the liver. It has been shown that after partial hepatectomia and the effect of cycloheximid in the liver of experimental animals regular gradual changes of the content of the paramagnetic form of cytochrom P-450 are observed, an inverse correlation between these changes and protein biosynthesis being noted.