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Biomedical subjects

A V Timofeev

Publications and source records attributed to A V Timofeev.

At least 37 records · Page 2Linked to original sources
PubMed1991

Use of protamine sulphate for elimination of substrate DNA in poliovaccines produced on continuous cell lines.

Cell substrate DNA was shown to be an abundant contaminant in the clarified preparations of the Sabin type 1, 2 and 3 poliovaccines produced on a continuous cell line (4647). The size of the DNA, as evaluated for the Sabin type 1 poliovaccine, was highly heterogeneous, ranging from 100 to 20,000 base pairs. In view of potential oncogenicity of this DNA a simple and efficient procedure for its elimination is proposed. The method is based on use of protamine sulphate which at the concentration of 2.0 mg ml-1 precipitated cell DNA almost completely without affecting the virus titres.

Animals↗
PubMed1991

[Effects of synthetic cholecystokinin analog on hormone secretion in fetal human pancreatic tissue culture].

We have investigated the effects of Pro-Met-Asp-Phe-NH2 (PMAP) on insulin and glucagon release from human fetal pancreatic microfragments in vitro. Four batches of precultured microfragments were incubated for 24 hrs in medium containing 5.5 mM glucose, 17 mM glucose, 1 microM PMAP or 1 microM PMAP plus 17 mM glucose. PMAP significantly enhanced both basal and glucose-stimulated insulin release (2.2- and 4.1-fold, respectively). Glucagon secretion was markedly inhibited by glucose (17 mM). PMAP neither affected the basal glucagon release nor potentiated the inhibitory action of glucose on glucagon release. Hence, PMAR selectively regulates insulin production in human fetal islet tissue without affecting glucagon production. Our results suggest that the substances similar or related to PMAP may prove to be of clinical value in drug correction of diabetes mellitus.

Fetus↗
PubMed1990

[Effects of serum and glucose on the proliferation of different types of cells of the human embryonic pancreas in primary culture].

We have utilized primary cultures of free-floating clusters obtained from pancreata of human cadaveric fetuses. Clusters have been incubated for 10 days in RPMI-1640 medium with 3H-thymidine and various concentrations of fetal calf serum and glucose. Viability of clusters was assessed by insulin radioimmunoassay. Cell reproduction was investigated by radioautography. We have revealed 2 populations of proliferating epithelial cells in clusters: the minor population of cells of duct-like structures and the major population of other epithelial cells. Rate of accumulation of labelled cells in both populations in clusters of 17-18-week-old fetuses was significantly higher than in clusters of 23-24-week-old fetuses. Proliferation of cells of duct-like structures was regulated by serum but not by glucose, whereas proliferation of other epithelial cells depended on both serum and glucose concentrations.

Autoradiography↗
PubMed1989

[Comparison of the specificity of polyclonal antibodies to the tick-borne encephalitis virus in immunoenzyme analysis and immunoblotting].

The present study deals with the optimization of the conditions of immunoblotting (IB) and the enzyme-linked immunosorbent assay (ELISA) with the use of mouse polyclonal immunoglobulins to tick-borne encephalitis virus. In contrast to ELISA, the results of IB depended, to a great extent, on the composition and pH of blocking buffer mixtures. In some cases IB permitted the detection of a heretofore unknown virus-specific polypeptide with a molecular weight of 58-60 KD. The results of the study lead to the conclusion on the impossibility of the direct transfer of data concerning the specificity of individual preparations of immunoglobulins in ELISA or IB due to differences in information.

Animals↗
PubMed1987

[Use of direct solid-phase immunoenzyme analysis for assessing the immunological activity of a vaccine against tick-borne encephalitis].

A high correlation between the current index of the effectiveness of tick-borne encephalitis vaccine, its protective activity in mice, and the results of the direct solid-phase enzyme-immunoassay has been established, which permits the use of this assay as an auxiliary method for the immunological evaluation of newly prepared commercial purified tick-borne-encephalitis vaccine.

Animals↗
PubMed1983

[Cell kinetics in the mouse esophageal epithelium in relation to the time of day].

The kinetics of mouse esophageal epithelial cells was investigated throughout 90 h after a single injection of 3H-thymidine at 01 or at 13 h--the times of the peak and minimal magnitudes of the radioisotope index in the circadian rhythm of proliferation. The mitotic cycle parameters in the cells varied but insignificantly. For cells treated with 3H-thymidine at 01 h, T = 24.3 h, ts = 6 h, tG2 min = 1.5 h, tG2+ 1/2 M = 2.9 h and tG1+/2 M = 15.4 h; for those treated with 3H-thymidine at 13 h, T = 25.6 h, ts = 8.4 h, tG2 min = 1 h, tG2+ 1/2 M = 2.2 h, tG1+ 1/2 M = 15 h. Cells labeled at 01 h proliferated more actively for a long period of time as compared to those labeled at 13 h. The synchronism in undergoing several successive mitotic cycles was greater for cells labeled at the peak radioisotope index. The data obtained also suggest that the majority of cells enter the G0 phase after the completion of the first cycle. The duration of the G0 phase varies in different cell populations.

Animals↗
PubMed1983

[Participation of different cell populations in the mouse esophageal epithelium in the formation of a circadian rhythm of proliferation].

Investigation of the variations in the index of labeled mitoses throughout 90 hours after a single injection to mice of 3H-thymidine at 01 or at 13 o'clock (the periods of the maximal and minimal labeling index in the circadian rhythm of cell proliferation) showed that the cell population which had completed synchronously the mitotic cycle during the first day of experiment also plays the main role in the formation of the peak rhythms in the mitotic index in the following days. The capability of a part of the synchronous population cells to preserve high proliferation rate during several days may be accounted for by the fact that the duration of the mitotic cycle of these cells is comparable with the duration of the rhythm period. The contribution of the asynchronous population into the formation of the peak rhythms in the mitotic activity is insignificant. However, this population proliferates actively enough during the periods of the decreased mitotic index.

Animals↗
PubMed1982

Nonuniform distribution of enzymes in fish eggs.

The distribution of enzymes in the blastoderm and the yolk was investigated in the eggs of the bony fish, Misgurnus fossilis. The total activities of lactate dehydrogenase (LDH), glucose-6-phosphate dehydrogenase (G-6-PD), and aldolase (ALD) did not change during early development. However, the enzymes were redistributed in the egg: at the blastula stage the blastoderm contains about 60% of the total ALD activity and 80% of the total LDH and G-6-PD activities. The "free cytoplasm" volume, in which the enzymic proteins can be solubilized, is greater in the yolk than in the blastoderm. Low levels of homologous enzymes from other species injected into the egg are distributed between the blastoderm and the yolk in the same way as are the native enzymes; they are primarily localized in the blastoderm. Injected exogenous enzyme concentrates preferentially in the yolk, apparently being distributed proportionately with respect to the "free cytoplasm" volumes. The ratio of these "free cytoplasmic" volumes, determined by distribution of the injected enzyme (LDH), in the yolk and in the blastoderm is 6.8. On the basis of our results we propose that many egg enzymes are noncovalently bound to blastoderm structures, and that the "nonbound" fraction of the enzymes in the cytosol is distributed proportionally to the "free cytoplasm" volumes in the blastoderm and in the yolk. Fractionation of the subcellular constituents of blastoderm extracts by ultracentrifugation or by gel filtration on Sepharose in the presence of an excess of LDH reveals the high-molecular weight LDH-containing complexes. These complexes are absent in the yolk and in the unfertilized eggs. These results are consistent with the hypothesis that the binding of the enzyme to subcellular structures in the blastoderm is an important mechanism in ooplasmic segregation.

Animals↗
PubMed1981

[Cell population kinetics and the cell population mechanism of circadian rhythm in the proliferative activity in the esophageal epithelium of mice maintained under constant illumination].

3H-thymidine was injected to male mice maintained either on a 12 hour light-dark cycle or on a prolonged continuous light (LL-group) at the peak of DNA synthetic activity of the esophagus epithelium (1a. m). The parameters of the diurnal rhythm of cell division and mitotic cycle of the basal layer were studied. In the LL-group of animals, an expressive asynchronization of diurnal rhythm of mitotic index was found. At the same time the labelled cell population revealed a slight degree of asynchronization. The data suggest that the process of asynchronization of the overall kinetics in the tissue throughout the whole day is associated with differences in the state of separate cell populations entering mitotic cycle at the various time of the day. The mitotic cycle duration in both groups of animals is almost alike and equal to 24-27 hours, i. e. is close to that of the diurnal rhythm.

Animals↗