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E E Egorov

Publications and source records attributed to E E Egorov.

At least 19 recordsLinked to original sources
PubMed1997

[Azidothymidine, blocking telomerase functioning, shortens telomeric repeats in transformed human cells].

The long-term action of azidothymidine, reverse transcriptase inhibitor, on cultivated U-937 (human promyelocyte leukemia) and MeWo (human melanoma) cells led to the concentration-dependent decrease in the length of telomeric chromosomal repeats. Telomere shortening was accompanied by temporary retardation of cell proliferation. Combined with the data obtained previously, these results suggest that azidothymidine inhibits telomerase functioning in cultivated cells.

Cell Division↗
PubMedDate not supplied

[Telomerase].

Explore the source record for details and available documents.

Biotechnology↗
PubMedDate not supplied

[Effect of azidothymidine on reactivation of DNA synthesis in macrophage nuclei contained in heterokaryons].

EIn heterokaryons, DNA synthesis is reactivated in macrophage nuclei only in the case of fusion with immortal cells. Assuming that telomerase is responsible for reactivation, the effect of its inhibitor azidothymidine (AZT) was studied in heterokaryons of mouse resident peritoneal macrophages and immortal 3T3 Swiss cells. AZT suppressed reactivation of DNA synthesis in macrophage nuclei and had no effect on DNA synthesis in 3T3 Swiss cell nuclei, suggesting an altered telomere structure in normal mouse macrophages.

3T3 Cells↗
PubMedDate not supplied

[Proliferative senescence of embryo fibroblasts of Japanese senescence accelerated mice (SAM) is accompanied by parallel decreasing of response to various growth factors].

The Japanese senescence accelerated mice (SAM) are a group of the low-longevity mouse lines and represent a new convenient model for studying the senescence process. We studied the proliferation of embryo fibroblasts of SAMP1 and SAMR1 mouse lines. It was shown that fibroblasts of the shortest longevity line SAMP1 have a markedly decreased proliferative potential of the mean 8.7 population doublings, whereas fibroblasts of a relatively high-longevity line SAMR1 have an average proliferative potential of 12.3 doublings. The fibroblast senescence in both lines is accompanied by a simultaneous lowering of the cell proliferative response to the blood serum, epidermal, fibroblast, and platelet-derived growth factors. At initial stages of the cell culture growth, lines SAMP1 and SAMR1 exhibit the same reactions to growth factors, but already beginning from the fifth doubling, the SAMP1 cell response is sharply decreased as compared with SAMR1. Lowering the proliferative reaction is accompanied by a decreased phosphorylation of tyrosine in the cell proteins responsible for mitogenic reaction. Thus, the parallel decrease of proliferative response to different growth factors during fibroblast senescence is most likely due the emergence of a regulatory block at common stages of the mitogenic signal transduction.

Animals↗
PubMedDate not supplied

[Telomerization as a method of obtaining immortal human cells preserving normal properties].

Most human somatic cells have no telomerase activity. This leads to terminal underreplication of chromosomes and, hence, proliferative ageing of cells. We studied the consequences of introduction of the gene of the catalytic component of human telomerase hTERT in the normal fibroblasts of adult human skin. The expression of this gene led to the appearance of telomerase activity in the fibroblasts, elongation of telomeres (to the size characteristic of the embryonic cells), and immortalization. The cells retained their normal karyotype. The activity of ribosomal genes remained unchanged: the degree of their methylation, abundance, and transcriptional activity (two clones were studied). The cells did not undergo significant changes after transition over the Hayflick's limit, retained the constant rate of proliferation (one of the clones was followed to the level of 200 duplications of the population), and resembled, in appearance, young diploid human fibroblasts. The initial cells and cells transfected by an empty vector could pass through no more than 68 duplications, their proliferation slowed down and they acquired the morphology characteristic for the ageing cells. The telomerized cells retained the normal capacity of entering the proliferative rest as a result of serum starvation. Telomerization did not eliminate the contact inhibition of proliferation but led to an increased saturating density of cells, which reached the levels characteristic for the early embryonic cells. The long-term suppression of the telomerase function by azidothymidine led to a shortening of telomeres and significantly slowed down cell proliferation. The cells that did not divided for a long time were enlarged, preserved their viability, and resembled, in appearance, the ageing cells. In the test on heterokaryons (index of telomerase activity on the chromosomes inside the cell), the telomerized cells behaved as other immortal cells. All these data suggest that the telomerized cells preserved the normal mechanisms of regulation of cell proliferation.

Cell Culture Techniques↗
PubMedDate not supplied

[Stem cells: properties and perspectives of therapeutic use].

In the present work, we review the properties of some stem cell types, namely embryonic, hematopoietic and mesenchymal stem cells, which present the most significant interest for use in medicine. Stem cells are undifferentiated cells capable of both self-maintenance and differentiation into mature specialized cells. According to their origin, stem cells can be classified as embryonic and somatic ones. The first ones can be indefinitely maintained in culture, and possess the ability to differentiate into all cells of the adult organism. The second ones possess the limited capacity to differentiate and, probably, a limited proliferative potential. For therapeutic use, important but hotly debated is the plasticity of somatic stem cells, i.e. context-dependent differentiation into "non-related" cell types. It is assumed that the differentiation of the majority of stem cell types proceeds according to the principle of stepwise hierarchical maturation through the stage of intermediate rapidly proliferating progenitor cells. The use of stem cells in medicine is mostly at the preclinical stage now. Despite the fact that embryonic stem cells are highly promising as therapeutic agents, a number of circumstances substantially limits their therapeutic use in the near future. At the same time, approaches involving autotransplantation of hematopoietic or mesenchymal stem cells are beginning to be applied successfully in the clinical trials for treatment of limb ischaemia and myocardial infarction. It is clear that despite a large number of problems and unsolved questions, the use of stem cells in medicine promises a dramatic progress in the treatment of many severe diseases.

Cell Differentiation↗
PubMedDate not supplied

[Role of telomerase in reactivation of macrophage nuclei in heterokaryons].

It was shown that the duration of stay of macrophages in the peritoneal cavity of mice and method of their isolation did not affect markedly their capacity for resumption of DNA synthesis in heterokaryons. This means that mouse macrophage undergo such changes during differentiation that reactivation of DNA synthesis in their nuclei is only possible after interaction of telomeres with telomerase, since it was already shown that telomerase was involved in reactivation of DNA synthesis in the macrophage nuclei. The results of experiments did not reveal differences in the length of telomeres in mouse macrophages and other somatic cells. This could depend on the significant length of mouse telomeres and, as a result, their shortening, sufficient for the inhibition of proliferation, is beyond the limits of sensitivity of the current methods. It is also possible that changes in DNA properties in the macrophages occurring during their differentiation depend on changes in the conformation of the telomere complex in these cells. Testing of this suggestion is relevant with respect to recent data that cell hybridization, specifically in the form of heterokaryons, may be essential in realization of the therapeutic effect caused by the introduction of cells during cell therapy.

Animals↗
PubMedDate not supplied

[Positive and negative regulation of replication in hybrid cells].

DNA replication blockage in various differentiated cells was investigated on the model of heterokaryons. Two distinct types of DNA synthesis regulation in heterokaryons "differentiated cell + proliferating cell" were revealed: I. Neutrophils and nucleated erythrocytes efficiently prevented the entry of non-malignant proliferating cells nuclei into the S-period but usually failed to substantially inhibit the replication in malignant cells nuclei. Both "mortal" and immortalized proliferating cells activated the DNA synthesis in neutrophil and chicken erythrocyte nuclei. II. Macrophages did not influence the DNA synthesis in the nuclei of non-malignant cells in heterokaryons but drastically inhibited that in the nuclei of malignant cells. Only immortalized cells reactivated DNA synthesis in the nuclei of macrophages. These data show that the mechanisms maintaining differentiated cells in non-proliferating state are not uniform. Nucleated erythrocytes were shown to suppress the duplication of centrioles in partner cells. The possibility of the blockage of DNA replication upon the fusion of two proliferating cells (fibroblast + leukemia cell) was demonstrated for the first time in the present work. The influence of various oncogenes upon the regulation of DNA synthesis in heterokaryons was investigated in detail. New modifications of the methods of cell fusion, enucleation and heterokaryon identification were proposed.

Animals↗
PubMedDate not supplied

[The nature of a proliferation block in differentiated cells with heterokaryons as a model: various types of absence of proliferation in cells in terminal differentiation].

Heterokaryons obtained by fusion of proliferating and terminally differentiated cells were studied. The data obtained suggest that mechanisms of proliferation arrest are different in macrophages on one hand and nucleate erythrocytes and polymorph leukocytes on the other. Macrophages appeared to be devoid of factors preventing replication in nontransformed and spontaneously immortalized cells. Inhibition of proliferation was probably due to certain modifications of macrophage genome which arise during differentiation and can be compensated by the effect of "immortalizing" oncogenes. On the contrary, nucleate erythrocytes and polymorphs evidently contain some factors mediating negative control of proliferation. For reactivation of DNA synthesis in these cell types after fusion with other cells the latter did not have to be immortalized. After cell fusion macrophages specifically inhibit DNA synthesis in cells containing active oncogenes.

Animals↗
PubMedDate not supplied

[Activity of c-myc protein is necessary in the first 6 hours of the prereplicative period for 3T3 Swiss cells].

It was shown what microinjection of polyclonal antibodies to the myc protein specifically inhibits DNA synthesis in serum-stimulated 3T3 Swiss cells during the first 6 h of the prereplicative period. The effect depends on the concentration of antibodies. Microinjections of polyclonal antibodies against the whole protein were more effective when microinjections of antibodies against parts of the protein. Microinjections of five kinds of monoclonal antibodies and their mixture were in effective. It was also shown what induction of expression of the antisense myc sequence in 3T3 Swiss cells leads to potent inhibition of DNA synthesis during the first 6 h of the prereplicative period. Thus it is clear what the myc protein participates in the early stages of preparation to replication, i.e., transition of cells from G0 to G1.

3T3 Cells↗