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Biomedical subjects

S Kozubek

Publications and source records attributed to S Kozubek.

At least 55 records · Page 3Linked to original sources
PubMed1990

Lambda-prophage induction in repair-deficient and wild type E. coli strains by gamma-rays and heavy ions.

Lambda-prophage induction in repair-deficient and wild-type E. coli strains by heavy ions and gamma-rays has been investigated. The dose dependence of the fraction of induced cells has been measured and its initial slope (lambda-induction potency) determined. The induction by gamma-rays was found to be more efficient in a polA-repair-deficient strain; the value of lambda-induction potency is zero in lexA- and recA- strains. The lambda-induction potency increased with LET for wild-type cells but remained constant in the case of polA- mutant cells. It is suggested that the DNA damage triggering the lambda-prophage induction in the case of ionizing radiation could be a type of DNA single-strand break with complex structure which cannot be repaired by fast repair processes, and which requires a substantial level of energy deposition for induction in a DNA molecule.

Bacteriophage lambda↗
PubMed1989

Induction of the SOS response in Escherichia coli by heavy ions.

The effectiveness of heavy ions in inducing the SOS response in E. coli cells has been measured by means of the SOS-chromotest. The SOS induction potency of ionizing radiation increases with increasing LET, to 40-60 keV/microns, reaches a maximum and then decreases at greater LET values. We conclude that the SOS-inducing damages in the case of ionizing radiation could be DNA injuries of a 'complex' type, e.g., DNA double-strand breaks or some kind of heavily damaged single-strand lesions.

Alkaline Phosphatase↗
PubMed1989

Mutagenic action of heavy ions on Escherichia coli cells.

Induction of direct mutations in the lactose operon of E. coli cells by gamma-radiation and accelerated heavy ions with different LET was studied. The experiments were performed with the wild-type PolA and LexA strains. A quadratic dependence of the mutation rate on the dose of different radiations for the wild-type strain and the PolA mutant was observed. However, different types of radiation showed different relative genetic effectivenesses (RGE). The dependence of RGE on LET for the wild-type and PolA strain has a maximum. A LexA strain showed much reduced mutation rates and a linear dose response. The RGE decreased with increasing LET of ionizing radiation.

Bacterial Proteins↗
PubMed1987

Mathematical model of Ehrlich ascites tumor growth from in vitro treated cells.

A mathematical model is proposed describing the dependence of lethality and average life-span in mice on the number of Ehrlich ascites tumor (EAT) cells inoculated both intact or treated in vitro with various agents. Particularly, the effect of ionizing radiation is discussed, and the effect of combined action of two agents is also considered.

Animals↗
PubMed1987

Lethal effect of glucose load on malignant cells.

Ehrlich ascites tumor (EAT) cells were treated by glucose load under anoxic conditions (for 15 or 60 min) and/or by gamma-radiation (20 Gy). The efficiency of the treatment was judged from the tumorigenic activity of EAT cell inocula. The markedly increased efficiency of the combined treatment of EAT cells by glucose load in anoxia and by gamma-radiation is due to the additive action of both agents. The glucose load in anoxia leads to extensive desintegration of tumor cells. Further, the lethal effect of various pH values on EAT cells was investigated. Different pH values were obtained by means of both glucose load and phosphate buffers. The effect was investigated by determining the tumorigenic activity of EAT cells tested in vivo in mice and by determining the radiosensitivity of treated EAT cells. The results allowed us to conclude that the same values of pH lead to the same effect on EAT cells independently of the way by which the given pH value was reached.

Animals↗
PubMed1986

[Does diabetes affect the probability of cure and prolongation of life of oncological patients?].

The authors present an analysis of the results of therapy of 236 breast cancer patients, 212 patients with cancer of the uterine body, 269 patients with bladder cancer and 386 lung cancer patients. The frequency of diabetes mellitus is compared among cancer patients of different age groups. Cancer patients with diabetes mellitus were, on an average, more advanced in age than patients without it. A possible metabolic effect of glucose and acidification of tumors on the patients' cure is discussed.

Aged↗
PubMed1986

An iso-effect table for radiation tolerance of the human thoracic spinal cord. A new approach on the basis of the DFT conception.

Forty-four cases of well documented progressive radiation myelopathy of thoracic spinal cord were analyzed in terms of the new DFT conception (Dose-Fraction-Time). The DFT conception is a new radiobiological cell tissue kinetic model comprising explicitly repopulation. The conception has been previously tested against many animal experimental data. Good agreement could be demonstrated. The comparison with clinical data enabled us to establish human thoracic spinal cord tolerance DFT value of DFT = 70. For all cases of thoracic progressive spinal cord radiation myelopathy where the radiation fields were up to 20 cm of the cord length the value of the DFT has been found above the proposed value. Tolerance irradiation doses of various regular irradiation schemes were calculated from the DFT = 70 for practical use. Our predictions are in agreement with tolerance irradiation regimes recommended by various authors on the basis of their clinical experience. Moreover, such an approach enabled to establish safe tolerance doses in cases where currently used NSD or ED conceptions could lead to dangerous consequences--mainly for shorter irradiation schedules. This is the first attempt to utilize the DFT conception in the clinical practice.

Dose-Response Relationship, Radiation↗
PubMed1984

Cell sensitivity to irradiation and DNA repair processes. I. DNA damage and its repair in Escherichia coli.

Basic types of DNA damage produced by gamma-radiation in cells are reviewed. Different DNA injuries are related to various levels of DNA repair processes, established in the case of Escherichia coli cells. The role of the balance of repair enzyme activities is considered in connection with the induction of enzymatic DNA double-strand breaks (DSBs). The concept of "metastable sites" has been introduced. "Metastable sites" are formed from great nucleolytic gaps. They are measured as DSBs although they can be repaired as single-strand breaks (SSBs). A simple mathematical model of the inactivation of different mutants of E. coli cells has been constructed on the basis of available experimental data. Kinetic equations of the model have been solved and some parameters estimated for both sensitive and resistant mutants.

DNA↗
PubMed1984

Cell sensitivity to irradiation and DNA repair processes. II. The cell sensitivity to ionizing radiation of different LETs.

A new model of DNA single-strand break (SSB) and double-strand break (DSB) induction by radiations of different LET has been developed. Utilizing quadratic dependence of the dose that delta-electrons depart in the track of heavy particles the fraction of heavy particle energy deposited in the target of DNA dimensions has been calculated. SSBs arise from energy depositions in one strand of DNA, direct DSBs arise from two SSBs on opposite strands of DNA in the track of one particle. It is concluded that DSBs induced by gamma-radiation are mostly of enzymatic origin, meanwhile DSBs induced by high-LET radiation are direct DSBs. The dependence of the radiosensitivity D0-1 on LET (L) for isogenic mutants of E. coli with different sensitivity to gamma-radiation has been determined on the bases of the model and considering microscopic energy fluctuations. The shape of D0-1 (L) function is formed both by physical characteristics of radiation and by the ability of cells to repair some types of DNA damage. The model provides a basis for further investigation.

DNA↗
PubMed1984

Late effects of fractionated irradiation of normal tissue.

The formulae derived in previous papers for cell tissue kinetics have been fitted to further animal data on late reactions. Equations for some human tissue late reactions after X-rays and neutrons have been derived and discussed. The presented analyses of clinical data have preliminary character and the suggested formulae should be further checked and precised before using in clinical radiotherapy.

Animals↗
PubMed1983

Cumulative effect of nonstandard radiation.

Experimental data on cumulative effect of nonstandard beams are evaluated and analyzed in terms of cell kinetic model. The dependence of RBE on the dose per fraction is derived. The repopulation is shown to diminish RBE. The ratio of RBEs for late and acute injury is discussed. The "neutron TDF" proposed for clinical purposes is criticized.

Animals↗
PubMed1982

A simple radiobiological model for fractionated radiation therapy.

A new cell tissue kinetic model has been tested against rat skin data. A two parameter survival curve formula was used for cellular lethality and two or three further parameters correspond to simple relations for repopulation. The model does not depend on the level of tissue reaction, thus enabling us to predict the degree of reaction. Further improvements can be made by including changes in cell survival curve during irradiation, because of cell cycle effects. The model describes rat skin data much better than other methods having been proposed by various authors.

Animals↗
PubMed1982

Survival curve description for fractionated radiation therapy.

The methods of survival curve description are evaluated. New method of fitation of survival curve data is described. Representations of survival curve are compared and the shapes of different survival curve formula are shown. New simple formula is suggested for practical purposes.

Animals↗
PubMed1981

Radiation damage to the rat spinal cord. A radiologic model.

A new kinetic model for evaluation of the cumulative biologic effect of fractionated irradiation was described previously. Survival curves were calculated from two parametric Huggett formulae in agreement with the connection to NSD. The model has been further developed and now consists of 4 simple parameters based on radiation biologic considerations.

Animals↗