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T Eremenko

Publications and source records attributed to T Eremenko.

At least 19 recordsLinked to original sources
PubMed1998

Cell membrane lipid molecular dynamics in a solenoid versus a magnetically shielded room.

The generalized polarization function of the fluorescent probe 2-dimethylamino-6-lauroylnaphthalene has been used to evaluate the lipid dynamics in Friend erythroleukemia cell membrane. The values of this function varied during the culture growth cycle, showing decreased lipid dynamics 24-48 h from the cell seeding. When the cycle occurred in a solenoid producing a magnetic field of 70 microT at 50 Hz in addition to the 45 microT DC of the earth (short-term 4-day exposure), the membrane lipid dynamics during this same time-period decreased by about 10% (P < .04). After long-term (184 days) or extremely long-term (395 days) exposure of the cells to the magnetic field, little additional variation in the membrane lipid dynamics was observed, suggesting an adaptation phenomenon. A variation of membrane lipid dynamics was also observed due to in vitro cell differentiation (P < .02). Nevertheless, the exposure of both undifferentiating and differentiating cells to a highly attenuated magnetic field in a magnetically shielded room (20 nT DC plus 2.5 pT AC) did not induce any modification of membrane lipid dynamics.

Animals↗
PubMed1998

Antiviral effect of trimeric 2',5'-oligoadenylic acid and some of its analogues.

The antiviral effect of 2',5'-trioligoadenylate (2',5'-A3) and some of its analogues was studied using several model cell culture systems and viruses: mice L929 fibroblast cells inoculated with vaccine virus, testicular piglet cells inoculated with Aueszki disease virus (strain BUK-628), and the same culture inoculated with a reference strain of transmissible gastroenteritis virus, strain Purdue-115. Our results suggest that both 2',5'-trioligoadenylate and its analogues are promising antiviral substances against DNA- and RNA-containing viruses.

Adenine Nucleotides↗
PubMed1998

The effect of trimeric 2',5'-oligoadenylic acid and its epoxy-derivative on human immunodeficiency virus (HIV-1) reproduction and retroviruses reverse transcriptase activity.

The effect of trimeric 2',5'-oligoadenylic acid (2',5' A3) and its epoxy-derivative (2',5'-A2 (RAA) on human immunodeficiency virus (HIV-1) reproduction was studied. An HIV-1 infectivity titer decrease was shown on the model of limphoblastoid cells when the substances under study were used. The interferonogenic effect of both substances was discovered. 2',5'-A2 (RAA) inhibited the activity of retrovirus reverse transcriptase (a C-type).

Adenine Nucleotides↗
PubMed1998

A protein kinase inhibitor from A431 subline overexpressing TGF alpha possesses antimicrobial activity.

During the last decade the key role of antimicrobial peptides in innate immunity has been argued. They were found in plants and in different phylogenic groups of animals (insects, amphibia, and even in mammals). We report the production of a human peptide antibiotic that was previously characterized as an EGF receptor tyrosine kinase inhibitor in epidermoid carcinoma A431/1522 cell subline overexpressing TGF alpha. It is a 3 kDa hydrophobic cationic peptide cytotoxic for different species of Gr+ and Gr- bacteria in micromolar concentration range, and demonstrating slight fungicidal activity.

Anti-Bacterial Agents↗
PubMed1997

Cell-cycle kinetics of Friend erythroleukemia cells in a magnetically shielded room and in a low-frequency/low-intensity magnetic field.

This work was undertaken to compare the behavior of Friend erythroleukemia cells in a solenoid, where the magnetic field was 70 microT at 50 Hz (plus 45 microT DC of Earth) with that of the same cells in a magnetically shielded room, where the magnetic field was attenuated to 20 nT DC and 2.5 pT AC. The control laboratory magnetic field corresponded to 45 microT DC and a stray 50 Hz field below 0.2 microT. The culture growth cycle of cells maintained inside the solenoid was slightly accelerated compared with that of cells maintained outside the solenoid (P < .05). This stimulation probably depended on sensitivity of cell cycle to a magnetic field, because, inside the solenoid, the percentage of G1 cells slightly increased during the culture growth cycle, whereas that of S cells slightly decreased. Acceleration of growth was detected soon after exposure of the cultures to the solenoid field, and growth did not change further if the action of this field continued for a long time, accounting for adaptation. The solenoid field also caused a small increase of cell survival without influencing cell volume. By contrast, the culture growth cycle of cells maintained inside the magnetically shielded room was slightly decelerated compared with that of cells maintained outside the room (P < .05). The essential absence of any field inside the magnetically shielded room also caused a small increase of cell volume, whereas, during the culture growth cycle, the percentage of G1 cells decreased, and that of S cells increased. The majority of these events did not change in cells induced to differentiate hemoglobin through dimethylsulfoxide.

Animals↗
PubMed1993

5-Methylcytosine in genes with methylation-dependent regulation.

An asymmetric distribution of deoxy-5-methylcytidylic acid-inhibiting restriction sites (dcm-sites) takes place in ten human genes regulated by 5-methylcytosine. These genes are dcm-site enriched upstream and dcm-site poor downstream. Along them, there is a scattering of hypermethylatable introns and hypomethylatable exons with a common code: the 5mCpG dinucleotides characterize promoters; Gp5mCs characterize introns; Tp5mCs and Cp5mCs are in small concentrations in exons. Housekeeping genes contain more dcm-sites when compared with tissue-specific genes. This depends on the higher number of dcm-sites in their promoters and introns. In exons, the relatively lower number of dcm-sites is almost the same in both housekeeping and tissue-specific genes. Going from 5' to 3', the average frequency of occurrence of these sites per nucleotide units decreases in introns and increases in exons. This difference is highly discriminated for tissue-specific and less discriminated for housekeeping genes.

5-Methylcytosine↗
PubMed1987

DNA methylases separated through the HeLa cell cycle methodology show allosteric properties.

Two DNA methylases (DNAmets) can be separated through the cell cycle. The first appears as a minor peak in G1, the second as a major peak in S. Both enzymes protect from HpaII a plasmid (H31), constructed with the pBR322 vector (4.3 kbp) and the inverted A gamma fragment of the human globin gene (3.5 kbp), inserted at its HindIII site (the vector carries several HpaII sites, the insert only one HpaII site). DNAmets G1 and S show distinct Km values and different kinetics vs the ionic strength of the medium, while their Michaelis-Menten and Lineweaver-Burk plots are sigmoidal and hyperbolical curves, respectively. This is the first suggestion about the allosteric nature of the eukaryotic DNAmet system.

Allosteric Regulation↗
PubMed1985

Hypomethylation of repair patches in HeLa cells.

In HeLa cells, under conditions where normal semiconservative synthesis is suppressed by hydroxyurea, the excision repair process after irradiation by UV results in a small amount of incorporation of nucleotides into nonreplicated DNA. By labelling the cytosine moieties of these repair patches, and measuring the ratio between cytosine and 5-methylcytosine, we have found that the level of methylation of cytosine in repair patches five hours after UV-irradiation of the cells is about half of that observed in normal semiconservatively synthesized DNA.

5-Methylcytosine↗
PubMed1985

Cell-cycle dependence and properties of the HeLa cell DNA polymerase system.

Analysis of the properties of the DNA polymerase (pol) system as a function of fundamental factors of the assay environment allowed a rather accurate estimation of its dependence on the HeLa cell cycle. For pol alpha, the temperature and pH optima were 38.1 degrees C and 8.0, respectively; for pol beta, these optima were 36.2 degrees C and pH 7.4. Pol gamma showed a pH optimum at 7.7. Optimum activity for both the alpha and beta enzymes was observed at 60 mM Tris. The maximal activity at 36.2 degrees C and pH 7.4 was associated with resistance to N-ethylmaleimide (MalNEt), whereas that at 38.1 degrees C and pH 8.0 was sensitive to MalNEt. Incorporation of [3H]dTTP was maximal after 1 hr of incubation for the former activity and after 4 hr, for the latter. In extracts from cells in early S phase, the pol activity decreased after 1 hr of incubation, was MalNEt-resistant, and was characterized by temperature and pH optima at 36.2 degrees C and 7.4, respectively. In extracts of late S-phase cells, the pol-catalyzed incorporation of [3H]dTTP continued after 4 hr of incubation, was MalNEt-sensitive, and was characterized by temperature and pH optima at 38.1 degrees C and 8.0, respectively. Thus, a pol beta-type activity appeared in early S phase, whereas a pol alpha-type activity appeared in late S. During the G1, M, and G2 phases, a background level of pol activity was observed that showed intermediate kinetic properties.

Cell Cycle↗
PubMed1984

In vitro methylation of total and foldback DNAs in normal and virus-transformed cells.

The levels of the in vitro methylation of total and palindromic DNAs in nuclei isolated from normal and virus-transformed cells are compared. The methylation rate of total DNA in normal rat kidney cells is much higher than that detected in normal mouse fibroblasts. However, for both cell species, while the maximal rate of DNA methylation is observed in the mid-logarithmic phase of the cell culture growth, palindromes are always found to be more heavily methylated than total DNA. The 5-methylcytosine content of DNA, especially of palindromes, is higher in virus-transformed cells than in untransformed cells.

Animals↗
PubMed1984

Virus genome integration as a function of the host cell genome replicative cycle.

Mouse 3T3 cells were grown and synchronized in monolayer with the double thymidine block. Their infection with SV40 took place continuously during the cellular cycle. However, integration of viral DNA into host cell DNA occurred preferentially during the S phase. Phase G1 appeared to be necessary for virus-cell DNA recombination in S phase. Phase G2 did not alter the stability of the integrated viral genome.

Animals↗
PubMed1981

Electron spin resonance of growing normal and virus-transformed cells.

A g = 2.003 ESR signal, attributed to a free radical localized in HeLa cell nuclei and mitochondria but absent in membranes and cytoplasm, has been studied as a function of the culture growth cycle in normal (NRK and 3T3) and virus transformed (NRK/RSV and 3T3/SV40) cells. For both these cell pairs, the signal is higher during the "lag" stage and lower during the "growth" stage. The average specific intensity of the signal in normal cells is about twice that in virus-transformed cells. However, the maximal point of resonance during the lag state is higher in transformed cells than in normal ones. The lag stage in NRK and NRK/RSV cells is much longer than in 3T3 and 3T3/SV40 cells, while the maximal value of the g = 2.003 ESR signal occurs, early in the lag stage of 3T3 and 3T3/SV40 cells and late in the lag stage of NRK and NRK/RSV cells.

Animals↗
PubMed1980

Organization, replication and modification of the human genome: synthesis and methylation of palindromic, repeated and unique HeLa nDNA sequences during the S-phase.

At least five supermethylated nDNA families have been found in HeLa cells. The concentration of 5-methylcytosine increases on palindromes from 1 to 5 hours during the nDNA duplicative phase, decreasing again at the 6th hour of S. The early S-phase involves the accumulation of 5-methylcytosines on the nDNA sequences reassociating near a Cot = 3 x 10(-1). Late S involves increment of this base on the sequences which reassociate near a Cot = 9 x 10(-1) and Cot = 7 x 10(1). The unique sequences show a moderate methylation from 3 to 6 hours of S. This information shows that genes are methylated with an order during the S-phase in a system in which nDNA organization, modification and replication appear to be severely subordinated one to another. The possible role of methylation of foldback nDNA in regulation of transcription during the eukaryotic cell life cycle is discussed.

5-Methylcytosine↗
PubMed1979

Organization, replication and modification of the human genome: temporal order of synthesis and methylation of two classes of HeLa nDNA separated in Ag+--Cs2-SO4 gradients.

During the HeLa S-phase, DNA was methylated, at 1-hr intervals in isolated nuclei and fractionated in Ag+-Cs2SO4 gradients providing a heavy GC-rich peak and a main light AT-rich peak. Both size and specific methylation of these peaks changed during the nDNA duplicative phase. Replication of the heavy GC-rich nDNA fraction, which contains genes for ribosomal RNA, occurred in early S; in contrast, replication of the main AT-rich nDNA fraction was maximal in late S. Concomitantly, specific methylation of the GC-rich nDNA was maximal in the first part of S, while that of the AT-rich nDNA was maximal in the second part of S. This suggested that genes are replicated and methylated with order during the S-phase.

Cell Cycle↗
PubMed1978

Organization, replication and modification of the human genome: differential methylation of two classes of HeLa nuclear DNA separated on Ag+--Cs2SO4 gradients.

HeLa nuclear DNA sediments as a single peak, in neutral CsCl, while it is separated in a heavier and a lighter components, in alkaline Ag+--Cs2SO4. The heavy fraction, on the average, represents about 20% of the total DNA. CsCl analytical ultracentrifugation shows that heavy DNA bands at 1.715 g/cm3 and contains 53% GC (10% of the total GC), whereas light DNA bands at 1.703 g/cm3 and contains 40% GC (32% of the total GC). Coherently, Tm values in 0.1 x SSC are 82.5 degrees C, for heavy DNA, and 72.5 degrees C, for light DNA. After treatment with [3H-methyl-S-adenosyl-L-methionine in isolated nuclei, the concentration of labelled 5-methylcytosine was found to be highest in the more dense regions of the heavy peak and in the less dense regions of the light peak. Exposure to ultrasound modifies the quantitative relationship of the two peaks and improves the separation of supermethylated AT- and GC-rich DNAs. Four possible triplets as sites for DNA-methylase recognition are discussed.

Cell Nucleus↗
PubMed1977

An electron paramagnetic resonance study of free radicals in cells.

An electron paramagnetic resonance study was performed on cell lines of the following strains: HeLa, 37RC, L, FLC, NRK/RSV, 3T3/SV40. Unsynchronized and synchronized HeLa cells were studied with particular attention paid to the relation between growth and free radical concentration. Free radical levels were shown to be a function of the growth stage and different phases of the cell cycle.

Cell Division↗
PubMed1975

Polysome translational state during the cell cycle.

HeLa cells were synchronized with a double thymidine block. Ribosomal subunits, monomers and polyribosomes have been quantitatively analysed at hourly intervals, during interphase, and every 15 min, during mitosis. This analysis was performed on linear 7-47% sucrose gradients. From the beginning of G1 up to the end of S phase, a certain equilibrium among ribosomal subunits, monomers and polyribosomes is maintained, while from the time of entering G2 to M the translation machinery appears to be mobilized in the sense of polysome formation. Under these conditions, the amount of polysomes per cell during the mitotic cycle is expressed by a bi-phasic pattern showing pre- and post-mitotic peaks with a falling-off during S. The G1 peak, meanwhile, is much lower than the G2 peak. The incorporation of [3H]leucine into nascent polypeptide chains on polysomes, as well as into bulk cell proteins and into nuclear and cytoplasmic proteins considered separately, is also represented by a bi-phasic curve which shows, however, a higher peak in G1 and a lower peak in G2, with two fallings-off during S and M, respectively. Since between the G1 and the G2 amino acid pools there are not strong differences of leucine concentration, the discrepancy between the amount of polysomes and the rate of labelling is discussed on the basis of the differences of polysome shape found at the different stages of the cycle. In young cells, in fact, there is an abundance of small polysomes, while in the old cell large polysomes predominate. It is suggested that, in the old cell, the rate of translation on large polysomes could be relatively lower or that among these heavy aggregates a given number of "frozen" polysomes could be present. The ribosome state is considered as a probable limiting-factor of translation, particularly in mitosis.

Cell Division↗