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Biomedical subjects

S Kozubek

Publications and source records attributed to S Kozubek.

At least 73 records · Page 4Linked to original sources
PubMed1981

A new concept of cumulative biological effect.

The basis of the NSD concept is systematically reviewed and compared with that used in derivation of a new factor describing a cumulative biological effect (CBE) at the end of a fractionated irradiation. It is shown that some basic assumptions used in derivation of NSD and TDF factors cannot be fulfilled. The new CBE factor is free of this deficiency; it can be useful especially for studying biological effects of different irradiation beams.

Humans↗
PubMed1979

NSD and cell survival.

The relation between the NSD concept and cell survival in fractionated irradiation is established; the slope of Strandquist's lines is related to the shape of survival curves for the given type of cells and radiation. A new parameter, CBE, derived from TDF for determining cumulative biological effect is proposed.

Cell Survival↗
PubMedDate not supplied

[The effect of glycerine on gamma-induced mutagenesis in Salmonella typhimurium cells].

A study was made of the modifying effect of glycerol on the survival rate and gamma radiation-induced mutagenesis of Salmonella typhimurium cells TA98, TA100 and TA102. The DMF value, with respect to the survival rate, was 2.05-0.20. The dependence of the yield of gamma radiation-induced mutants on radiation dose was described by the curve with a maximum; the mutation frequency M(D) was well described by a gradual function M(D) = kDx. DMF values of the induced mutagenesis amounted to 2 for strains TA100 and TA102, and 1.5 for strain TA98.

Dose-Response Relationship, Radiation↗
PubMedDate not supplied

[The effect of genotype on the induction of prophage lambda in E. coli cells by ionizing radiation of various LET].

A study was made of the influence of the repair genotype on lambda prophage induction by ionizing radiation of different LET in lysogenic E. coli cells. Bacterial strains W3110, P3478, GC244, and 30SO were exposed to gamma-rays and helium ions of 22 keV/microns. Induction of the prophage in GC244 and 30SO strains deficient by lexA and recA genes was either inhibited (GC244) or lacking (30SO). Inducibility of P3478 carrying polA mutation was 12 and 5 times as high as that of the wild type strain after exposure to gamma-radiation and helium ions, respectively.

Bacteriophage lambda↗
PubMedDate not supplied

[The mutagenic effect of accelerated heavy ions on E. coli cells].

In studying E. coli mutation rate as a function of dose of different types of ionizing radiation it was found that mutagenic efficiency of helium ions (LET-22, 54 and 72 keV/microns) was higher than that of gamma-rays. As LET increased the mutagenic efficiency decreased. The mutation rate for all types of radiation under study was both a power function and a linear-quadratic function of dose.

Carbon↗
PubMedDate not supplied

[The effect of pre-irradiation conditions of cultivation on the induction of mutations in E. coli bacteria by gamma radiation].

The influence of preirradiation cultivation conditions on the survival rate and mutation frequency in gamma-irradiated E. coli AB 1,157 and Hfr has been investigated. Radiosensitivity of cells and mutagenesis have been shown to vary depending on the growth medium. These differences are related to different efficiency of gene expression regulating the inducible SOS-response of cells.

Cell Survival↗
PubMedDate not supplied

[Induction of prophage lambda during the irradiation of E. coli cells exposed to radiations of various LET].

Induction of lambda prophage in lysogenic E. coli cells exposed to ionizing radiation of different LET was studied as a function of dose I(D). Activities of pleiotropic RecA protein were shown to contribute to the shape of the I(D) curve. The experimental data were fitted by the function I(D) = alpha D(1-exp(-D0-1.D]exp(-beta D). Inducibility alpha increased with increasing LET which was related to the increased incidence of DNA lesions being a SOS-system call.

Bacteriophage lambda↗
PubMedDate not supplied

[Lethal action of accelerated heavy ions on mammalian cells as affected by inhibitors of DNA synthesis. Results of experimental research].

Radiosensitivity of Chinese hamster cells exposed to 137Cs-gamma-radiation and accelerated heavy ions of 4He (L = 22 and 60 keV/micron), 12C (L = 231 keV/micron), and 20Ne (L = 690 keV/micron) was studied in standard conditions and in the presence of arabinosylcytosine and hydroxyurea. These agents were shown to exert a radiosensitizing effect in the case of gamma-radiation. The effect was less pronounced with 4He ion-radiation and was absent upon irradiation with 12C and 20Ne ions. The radiosensitivity was maximum upon irradiation with 4He ions at L = 60 keV/micron. The RBE coefficients of heavy ions under study decreased in the presence of DNA synthesis inhibitors.

Animals↗
PubMedDate not supplied

[Lethal action of accelerated heavy ions on mammalian cells as affected by inhibitors of DNA synthesis. A theoretical analysis].

Günter-Schulz's model and the authors' own model were used to study the dependence of radiosensitivity (D0(-1)) of Chinese hamster cells on linear energy transfer (LET) upon irradiation in standard conditions and in the presence of DNA synthesis inhibitors, arabinosylcytosine and hydroxyurea. A better agreement of the experimental and theoretical results was obtained using Kozubek-Krasavin's model than the model of Günter and Schulz.

Animals↗
PubMedDate not supplied

[Effect of alpha-irradiation on sensitive and super resistant mutants of Escherichia coli].

A study was made of the sensitivity of E. coli (the wild type, rec A13 and Gamr 444 mutants) to gamma- and alpha-radiation. The most pronounced differences in radiosensitivity of the strains under study were noted with gamma-radiation. The sensitivity of the studied strains to alpha-radiation was levelled. The authors discuss the mechanisms of the effects observed in various E. coli strains exposed to ionizing radiation of different LET.

Alpha Particles↗
PubMedDate not supplied

[Biological effectiveness of ionizing radiations of various quality in Escherichia coli bacteria (a theoretical analysis). A cell inactivation model].

The dependence of the radiosensitivity of bacteria (the wild type, superresistant and rec-mutants) on linear energy transfer (LET) is considered. A nonformal model of inactivation of different bacterial mutants has been developed on the basis of the experimental data available. The concept of "metastable siles" (MS) is introduced. MS are peculliar DNA lesions arising from the occurrence of large nucleolytic gaps on both strands of DNA. Different mechanisms responsible for MS formation are considered. The kinetic equations of the model are solved and the parameters determined for both sensitive and resistant mutants.

DNA Repair↗
PubMedDate not supplied

[Biological effectiveness of ionizing radiations of various quality in Escherichia coli bacteria (a theoretical analysis). The induction of single- and double-stranded DNA breaks].

Peculiarities of induction of single- and double-strand DNA breaks (SSR and DSB) in E. coli cells by ionizing radiation of different LET are discussed. On the basis of the model proposed the dependence of the yield of SSR and different types of DSB upon LET was calculated. It was shown that enzymatic DSB were mainly induced by gamma-radiation. As LET increased the yield of enzymatic DSB decreased and that of direct DSR increased.

DNA↗
PubMedDate not supplied

[Biological effectiveness of ionizing radiations of various quality in Escherichia coli bacteria (a theoretical analysis). Cell radiosensitivity and DNA repair].

On the basis of the ideas reported earlier a study was made of the dependence of radiosensitivity (D0-1) of isogenic mutations of E. coli upon LET. This dependence was shown to be conditioned not only by the physical parameters of radiation but also by the ability of cells to repair definite types of DNA lesions. The influence of the balance in the activity of repair enzymes in E. coli on the shape of D0-1 (LET) curve is discussed.

DNA↗