PubMed Health⌕ Search

Biomedical subjects

Iu A Neĭfakh

Publications and source records attributed to Iu A Neĭfakh.

8 recordsLinked to original sources
PubMed1986

[Relation between the toxic killing of mouse small intestine enterocytes and the interval between the administration of the S-specific agent hydroxyurea].

The dependence of small intestinal lesions on the interval between repeated regular injections of hydroxyurea was studied. The doses of 1 g/kg and 0.2 g/kg were used. To activate the enterocyte proliferation the mice were pre-irradiated at 2 Gy. 3-4 hours after the last hydroxyurea injection the two distinct minimum points of epithelial lesions were observed at interinjection intervals of 9 and 16.5 hours. The result was dose-independent.

Animals↗
PubMed1986

[Resonance nature of the relation of mouse survival to the interval between administrations of the S-specific agent--hydroxyurea].

The dependence of murine survival on the intervals between periodic hydroxyurea (HU) injections was studied. The single dose of HU comprised 250 mg per kg. Intervals between injections varied from 5 to 19 hours while their number changed from 6 to 9 in different experiments. A resonant increase in the survival was observed under HU administered every 8-9 or 16 1/2 hours.

Animals↗
PubMedDate not supplied

[Dynamics of proliferating cell populations during exposure to periodic phase-specific factors].

Dynamics of the numbers of population of proliferating cells under periodic phase-specific cytotoxic effect with and without blocking action was studied on the basis of a mathematical model. It has been shown that at real values of the model parameters after the beginning of the effects the population number exponentially depends of time. Dependence of the population number dynamics on integral parameters of the cell cycle and the exposure regime was studied. It has been shown that at certain periods a resonance decrease of the damage of the population cells must be observed. The values of the periods corresponding to the resonance decrease of the damage are determined mainly by the mean duration of the cell cycle and the time of blocking action, at small duration of the blocking action they are approximately multiple to the average time of the cell cycle. The theoretical predictions are proved experimentally in the experiments on determining the relationship between the damage of small intestine epithelium and mouse survival and the period of repeated periodic injections of S-phase-specific cytotoxic agent hydroxyurea. A distinct resonance increase of mouse survival and decreased damage of the epithelium were observed under the injections of oxyurea with the periods near to the mean and doubled mean time of the cell cycle of crypt enterocytes. The results obtained not only support the correctness of theoretical predictions, but make it possible to estimate the parameters of the stem cell cycle of mouse small intestine epithelium. They also show that this approach can be used for reducing aftereffects of chemotherapy by means of phase-specific agents.

Animals↗
PubMedDate not supplied

[Classical and non-classical DNA conformations].

All possible right and left double helical structures which may exist in short fragments as well in polymeric DNA have been obtained on the basis of a developed rigorous and accurate method of conformational analysis of DNA. In polymeric DNA only right regular double helices are possible with preference of B-form that is the main biological form of DNA. In contrast, for short fragments the left and right helices have practically the same energies providing some physical ground for side-by-side form, which biologically is possible as a recombination form and maybe as a replication form.

DNA↗
PubMedDate not supplied

[Optimization of the exposure of normal and transformed cell populations to phase-specific agents].

Dynamic behavior of stem cells population of the "critical" tissue (normal population) and tumor cell population under periodic treatment with a phase-specific cytotoxic agent was considered. The results were used for optimization of anticancer chemotherapy. The schedules of treatment were found which provide a maximum rate of tumor-cell elimination for any given rate of the normal population size decrease. If the mean generation times of normal and tumor populations differ (which was stated for many tumors), usage of the optimal period markedly increases the selectivity of therapy, while application of other periods can result in selective elimination of the normal population. Problems concerned with practical realization of the proposed regimes are discussed.

Animals↗
PubMedDate not supplied

[Possible DNA conformations].

The complete analysis of possible DNA structures has been undertaken in the space of dihedral angles. The structural sets obtained join energetically and geometrically possible conformations. Thus, the necessary condtions of existence are fulfilled for these structural forms. The half of our structural families includes all structures and structural sets proposed by other authors [10, 24]. Other six families have not been presented elsewhere. The results of the energy optimization suggest the left handed forms are unfavourable energetically, because main chain torsional term and the energy of nucleotide moiety. At the same time there is a great number of various lefthanded forms.

DNA↗
PubMedDate not supplied

[Denaturation temperature of collagen as a linear function of its amino acid composition].

TD of collagen have been constructed as linear function of fractions of each from 18 amino acids using experimental data for 29 proteins. For coefficient estimation the least squire method have been used. As a result the TD of any collagen may be calculated by using of the function obtained. 14 amino acids strongly influence on TD. The suggestion arises that poly(Gly-Ile-Lys) may produce collagen like structure.

Amino Acids↗