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O M Platonov

Publications and source records attributed to O M Platonov.

At least 19 recordsLinked to original sources
PubMed1991

[Cycle dependent expression of the gene coding for B2mRNA].

The relative contents of individual tissue specific RNA B2mRNAx was studied in the population of nuclear and poly(A)+ cytoplasmic RNA from the livers of intact, falsely operated and having suffered the partial liver resection rats. Dot-hybridization technique was used to study this transcript containing the transcribed copy of the B2 repetitive genetic element of rats. The expression of the gene coding for B2mRNAx takes place at the lower level in the liver induced to proliferation as compared with the one in the liver of intact animals. It is changed reproducibly in antiphase with the c-fos RNA and with major inclinations at the moments of cellular phases switch.

Animals↗
PubMed1984

[Transcription peculiarities of nuclear genome in different stages of liver regeneration. Activity of cytosol protein factor on the activation of different forms of nuclear DNA-dependent RNA-polymerases].

Subfraction P containing a "regeneration factor" which controls the activity of three forms of DNA-dependent RNA-polymerase was isolated from rat liver hepatocyte cytosol one hour after partial hepatectomy. The factor exerts differentiated effects towards purified enzyme: it increases the activity of RNA-polymerase I and inhibits that of RNA polymerases II and III in a system with the enzyme from resting liver. In a heterologous system, the effect of the factor is nonspecific.

Animals↗
PubMed1983

[Peculiarities of nuclear genome transcription in the early stages of liver regeneration. Complex nature of the activating effect of the cytoplasmic regenerating factor on transcription in isolated rat liver nuclei].

The cytosol fractions from resting rat liver and from the liver 1 hour after partial hepatectomy which were not adsorbed on DEAE-cellulose were subjected to gel filtration with a view of elucidating the mechanism of its activating effect on the RNA-synthesizing ability of isolated nuclei of resting liver. The activating effect of this fraction is a complex one and includes both specific and non-specific factors. A subfraction typical for regenerating liver was detected, which activates RNA elongation in a synthesizing system with isolated nuclei of resting liver.

Animals↗
PubMed1982

[Features of nuclear genome transcription at early steps of liver regeneration: expression of DNA fractions with different repeating sequence frequencies].

The mode of hybridization of dRNA fraction from normal and regenerating rat liver with purified fractions of repeating and unique sequences of DNA was studied. In order to repress the reassociation of DNA the nucleic acids were annealed in a solution of 2 x SSC--80% formamide at 48 degrees. The differential hybridization curves suggest that the amount of transcripts with a high DNA sequence frequency increases, while the complexity of transcripts of unique DNA sequences decreases 3 hrs after partial hepatectomy. Simultaneously the amount of RNA transcribed from the unique and moderately repeating DNA fractions remains practically unchanged.

Animals↗
PubMed1981

[Peculiarities of nuclear genome transcription at early stages of liver regeneration. Possible role of mitochondrial translation in activation of nuclear RNA biosynthesis].

During the first hour following partial hepatectomy the mitochondria came in proximity with the nucleus and were concentrated around the electron-dense zones of euchromatin shifted towards the peripheral parts of the nucleus. After 1.5 hrs following the surgery the specific radioactivity of nuclear RNA was increased due to activation of nucleolar RNA biosynthesis. The activation of endogenous template activity of isolated nuclei by cytosol obtained 1 hr after the surgery was due to mobilization of "free", i. e. non-bound to the template, form of nuclear RNA polymerase. A preliminary administration of chloramphenicol completely blocked the mitochondrial tropism towards the nucleus and the activation of nuclear RNA biosynthesis. It was assumed that the activation of nuclear genome transcription at early stages of liver regeneration is mediated by mitochondrial translation. A possible mechanism of coordination of nuclear and mitochondrial genome activity based on identicity of mitochondrial RNA-polymerase and one of the subunits of nuclear RNA-polymerase I is discussed.

Animals↗
PubMed1980

[Some features of nuclear genome transcription at early stages of liver regeneration. Nuclear DNA-like RNAs, complementary to uniquie and repeating sequences of DNA].

Transcription of unique and repeating sequences of DNA at early stages of liver regeneration after partial hepatectomy was studied. The total nuclear dRNA (tdRNA) and its two fractions (dRNA63O and dRNA85O) from the control and regenerating liver were subjected to hybridization with the excess of DNA. One hour after partial hepatectomy the kinetics of tdRNA hybridization did not differ from the controls; 3 hrs after operation the rate of unique transcripts hybridization was decreased. The rate of dRNA63O hybridization was shown to be considerably decreased 3 hrs after partial hepatectomy, while the kinetics of hybridization of dRNA85O remained unchanged. It was assumed that the changes of dRNA hybridization during the first few hours after partial hepatectomy are due to a significant increase in the amount of copies of some unique transcripts.

Animals↗
PubMed1980

[some features of nuclear genome transcription at early stages of liver regeneration. RNA-polymerase activity of isolated nuclei].

The RNA-polymerase activity of isolated nuclei after 1, 3, 6, 12 and 24 hrs following partial hepatectomy was studied. The enzyme activity showed almost a 2-fold decrease after the first post-operative hour, followed by an increase of activity which reached its maximum after 6 hrs. A decrease of nuclear hepatocyte RNA-polymerase sensitivity to alpha-amanitine after 1 and 3 hrs following the surgery was found. After 6 hrs the enzyme was activated by alpha-amanitine. Using selective incorporation of four labelled ribonucleoside triphosphates, it was shown that alpha-amanitine causes a shift in the nucleotide composition of RNA synthesized in the regenerating liver towards the AU-type RNA.

Amanitins↗
PubMed1980

[Some features of nuclear genome transcription at early stages of liver regeneration. Effect of cytoplasmic factors on the RNA-polymerase activity of isolated nuclei].

Cytosol from the regenerating liver significantly activates the RNA-polymerase activity of isolated nuclei in normal liver. This activation occurs immediately after partial hepatectomy, reaches its maximum after the 1st post-operative hour and is practically eliminated after 1,5 hrs. The effect is thermolabile and is completely blocked by a preliminary administration of cycloheximide. Fractionation of cytosol on DEAE-cellulose reveals significant chromatographic differences of the activating factor as compared to that described in literature, which is present both in normal and regenerating liver. An important role of this factor in reprogramming of the genome from the hepatocytes at the preproliferation stage is postulated.

Animals↗
PubMed1980

[Reassociation of rat DNA fractions].

A method for direct registration of the first derivative of DNA reassociation kinetics in spectrophotometric cuvettes is proposed. Using this method, the rat liver DNA obtained by chromatography on hydroxyapatite was studied. The differential curves of reassociation and changes in hyperchromic spectra revealed the presence in the rat genome of 4 types of repeating sequences differing in their GC-content. A scheme of preparative separation of DNA with respect to the reassociation rate was developed. Three types of sequences repeating 3.10(5), 600 and 1 times in the genomes with the GC-content of 50, 42, and 33%, respectively, were obtained in a homogeneous state. The advantages of the differential method of registration of the kinetic curves for the study of DNA structure and calculation of fractionation schemes are discussed.

Animals↗
PubMedDate not supplied

[Intracellular distribution of newly formed hepatocyte RNA in the 1st hours following partial hepatectomy].

Two periods in the activity of cell are distinguished during the first three hours after partial hepatectomy. The first period (about 0.5 h) is characterized by the activation of RNA synthesis in all the compartments of the cell, including mitochondria, and by approach of the latter to the nucleus, which is probably induced by the demand of a great quantity of energy for both the present and subsequent intranuclear synthesis. These data have permitted referring the response of hepatocytes in the first period to nonspecific ones. The second period (0.5-3 h) is distinguished by the differentiated response of hepatocytes to the proliferative stimulus.

Animals↗
PubMedDate not supplied

[Effect of cytosol on RNA-synthesizing ability of isolated nuclei of rat hepatocytes].

The addition of cytozol to isolated nuclei of the liver is accompanied by a rise in the amount of a new synthetizing RNA and changes in its nucleotide composition. An increase in the intensity of [3H] ATP incorporation at the end of incubation evidences for polyadenylation of the reaction product. Under the effect of cytozol 30-32% of RNA synthetized de novo is released. Heating of cytozol (50 degrees C, 15 min) leads to a loss of its ability to activate RNA synthesis by isolated nuclei.

Adenosine Triphosphate↗
PubMedDate not supplied

[Autoradiographic study of RNA synthesis and secretion into the cytoplasm during the early stages of liver regeneration].

Autoradiographic experiments with regeneration of rat liver showed that RNA transport from nucleus to cytoplasm occurs more quickly in 3h following partial hepatectomy while the total RNA synthesis increases insignificantly. Nucleolar RNA synthesis at this time grows in some hepatocytes and decreases in others though it does not differ on the average from the control one. By the 6th h after partial hepatectomy total RNA synthesis significantly increases simultaneously with the acceleration of RNA transport to cytoplasm. Nucleolar RNA synthesis intensifies in all hepatocytes.

Animals↗