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Biomedical subjects

V N Letov

Publications and source records attributed to V N Letov.

At least 19 recordsLinked to original sources
PubMed1989

[Evolution of subpopulations of cells of transplantable tumors following x-ray irradiation].

The paper is devoted to a study of the structure of subpopulations of 3 experimental tumors (ascitic Ehrlich carcinoma, melanoma B-16 and Lewis lung adenocarcinoma) in their progression and following single local X-radiation. At the same time some functional indices of cell viability were investigated over time: intracellular pH, intensity of respiration, the level of cell protein, the level of lipid peroxidation (according to the content of one of its end-products--malonic dialdehyde). Considerable differences of subpopulations within one tumor and between different tumor types were established. The relationship of functional differences of these subpopulations with the clonogenicity of forming cells was shown. X-radiation caused inhomogeneous changes in the structure of subpopulations, the above indices changed. The authors have analyzed the regularity of these changes, their relationship with radiosensitivity or radioresistance of tumor cell subpopulations.

Adenocarcinoma↗
PubMed1988

[Dynamic changes in the pH and potassium concentration in a suspension of ascitic tumor cells under glucose load].

A single addition of glucose to 10% (6 v/v) suspension of the Ehrlich ascite tumor cells results in biphasic changes of pH and potassium ion concentration in the extracellular medium during 120 minutes. Phases of pH and potassium changing do not coincide. Increasing glucose amount from 100 to 400 mumol/10 ml suspension causes no marked modification of ion dynamics. Possible mechanisms of the above phenomena and their relation to cell power are discussed.

Animals↗
PubMed1988

[Fractionated irradiation of Ehrlich carcinoma using fast neutrons].

Ehrlich's carcinoma growth inhibition was studied under the conditions of fractionated irradiation with fast neutrons and x-rays. Fast neutrons were obtained from a reaction of 13.6 MeV alpha----Be on the Y-120 cyclotron. Neutron beam irradiation doses were within 2-17 Gy, x-ray doses from 7.5 to 72 Gy. Tumors were subjected to local irradiation with 1-8 fractions at a 3-4 day interval. The results showed that an increase in the total duration of a course of irradiation and a decrease in a dose per fraction resulted in a reduced effect of carcinoma growth inhibition. At the same time, an increase in the fast neutron RBE under these conditions from 3.4 (in single irradiation) to 5.4 (in 8-fold irradiation) indicated more pronounced inhibition of reparation and/or repopulation in a tumor in neutron beam irradiation.

Animals↗
PubMed1987

[Principle of neutron teletherapy with the Soviet U-120 cyclotron].

The authors present the results of their clinical developments on fast neutron irradiation of malignant tumors on the low-flow cyclotron U-120. The technique involved design of complexes provided with the sources of fast neutrons based on beryllium, gas deuterium and beryllium-deuterium targets. The spectrometry and dosimetry measurements of collimated bunches of fast neutrons have shown that the mean energies of neutrons from beryllium and gas deuterium targets are 6.0 and 11.5 MeV, while the absorbed doses are 0.8 and 0.5 sGy/min X microA. The increase of the local power of the biological dose inside the phantom irradiated by the collimated bunch of fast neutrons is shown to be due to intermediate energy neutrons, the contribution of which to the spectrum of fast neutrons increases with the decrease of their mean energy. The problems of selection of the sources of fast neutrons for neutron therapy are discussed.

Equipment Design↗
PubMed1987

[Experience with neutron teletherapy of malignant tumors].

A medico-biological complex for fast neutron therapy of cancer and research in physics and radiobiology was developed at the Siberian Branch of the Center within the framework of Cyclotron Department of Research Institute of Nuclear Physics (Polytechnical Institute, Tomsk). Certain problems of forming a fast neutron beam from the Y-120 type cyclotron are discussed. Baseline data of dosimetric and radiobiologic studies are presented. The first experience of Soviet researchers with fast neutron treatment of head and neck cancer is described. Favorable preliminary results suggest further clinical application of the said procedure.

Animals↗
PubMed1986

[Comparative effectiveness of metronidazole, hyperglycemia and hyperthermia in irradiation of Ehrlich carcinoma with fast neutrons].

A study was made of a possibility of the modification of the effects of fast neutrons (with the mean energy of about 6 MeV.) by local hyperthermia (HT), short-term induced hyperglycemia (STIH) and metronidazole (MZ). The study was conducted in vivo on intramuscularly transplantable ascitic mouse Ehrlich's carcinoma. The dose-effect relationship built up in different time after the day of irradiation, was considered in parallel with the time course of tumor growth; regression curves were obtained using computer. Using the value of 50% tumor growth inhibition and the ratio of areas under the model dose-effect curves as criteria of a degree of modification the authors have come to a conclusion that HT possesses the most noticeable intensifying effect.

Animals↗