Biomedical subjects

S Kozubek

Publications and source records attributed to S Kozubek.

At least 37 records · Page 2Linked to original sources

PubMed1997

Adenine-induced arrest of mammalian cells in early S-phase is related to the prevention of DNA synthesis inhibition caused by gamma-irradiation.

Adenine prevents the down-regulation of DNA synthesis in gamma-irradiated EAT and HL60 cells. This protective effect is related to the initiation of DNA replication. The effectiveness of this protection increases with the concentration of adenine in both cell lines. The maximum protective effect of adenine induced in EAT cells occurs at about 10 times lower concentration as compared with HL60 cells; however, the level of this effect is almost the same in both cell lines. The results indicate that the prevention of the down-regulation of DNA synthesis in gamma-irradiated EAT and HL60 cells is conditioned mainly by the arrest of the cells in the early S-phase. It is evident that DNA synthesis in cells beyond G1/S boundary is insensitive to gamma-radiation.

Adenine↗

PubMed1997

A biosensor for environmental genotoxin screening based on an SOS lux assay in recombinant Escherichia coli cells.

A genetically controlled luminescent bacterial reporter assay, the SOS lux test, was developed for rapid detection of environmental genotoxins. The bioassay is based on the recombinant plasmid pPLS-1, which was constructed as a derivative of pBR322, carrying the promoterless luxCDABFE genes of Photobacterium leiognathi downstream of a truncated cda gene from ColD with a strong SOS promoter. E. coli recA+ strains containing this construction are inducible to high levels of light production in the presence of substances or agents that cause damage to the DNA of the cells. The light signal, reflecting the SOS-inducing potency, is recorded from the growing culture within 1 s, and the test results are available within 1 to 2 h. Induction of bioluminescence was demonstrated by treatment of E. coli C600(pPLS-1) with 6 genotoxic chemicals (mitomycin C, N-methyl-N'-nitro-N-nitrosoguanidine, nalidixic acid, dimethylsulfate, hydrogen peroxide, and formaldehyde) and with UV and gamma radiation. A clear dose-response relationship was established for all eight genotoxins. The sensitivity of the SOS lux test is similar to that of other bioassays for genotoxicity or mutagenicity, such as the SOS chromotest, umu test, and Ames mutatest. These results indicate that the SOS lux test is potentially useful for the in situ and continuous detection of genotoxins.

Base Sequence↗

PubMed1997

The influence of microgravity on repair of radiation-induced DNA damage in bacteria and human fibroblasts.

The influence of the space flight environment, above all microgravity, on the repair of radiation-induced DNA damage was examined during the Spacelab mission IML-2 as (1) rejoining of DNA strand breaks induced by X irradiation in cells of Escherichia coli B/r (120 Gy) and (2) in human fibroblasts (5 and 10 Gy); (3) induction of the SOS response after gamma irradiation (300 Gy) of cells of Escherichia coli PQ37; and (4) survival of spores of Bacillus subtilis HA 101 after UV irradiation (up to 340 J m(-2)). Cells were irradiated prior to the space mission and were kept frozen (E. coli and fibroblasts) until incubation for defined periods (up to 4.5 h) in orbit; thereafter they were frozen again for laboratory analysis. Germination and growth of spores of B. subtilis on membrane filters was initiated by humidification in orbit. Controls were performed in-flight (1g reference centrifuge) and on the ground (1g and 1.4g). We found no significant differences between the microgravity samples and the corresponding controls in the kinetics of DNA strand break rejoining and of the induction of the SOS response as well as in the survival curves (as proven by Student's t test, P < or = 0.1). These observations provide evidence that in the microgravity environment cells are able to repair radiation-induced DNA damage almost normally. The results suggest that a disturbance of cellular repair processes in the microgravity environment might not be the explanation for the reported synergism of radiation and microgravity.

Adult↗

PubMed1997

Protective effect of adenine on DNA synthesis in irradiated Ehrlich ascites tumor cells.

Ehrlich ascites tumor cells were cultured in the presence of adenine for several hours before gamma irradiation. The inhibition of DNA synthesis that is normally observed when these cells are irradiated was prevented. More detailed analysis using the velocity sedimentation technique provided evidence that this protective effect occurred at the level of initiation of DNA replication. This conclusion is supported by the fact that adenine failed to prevent the inhibition of DNA synthesis induced by hydroxyurea. The ability of adenine to suppress the gamma-ray-induced inhibition of DNA synthesis was dependent on both its concentration and the exposure time. This suppression was already pronounced by about 4 h after exposure of the cells to adenine, and the maximum effect was observed within 6-20 h. The optimum concentration of adenine was about 0.1 mM. Among other purines tested, a similar effect was caused only by guanine.

Adenine↗

PubMed1996

DNA repair in microgravity: studies on bacteria and mammalian cells in the experiments REPAIR and KINETICS.

The impact of microgravity on cellular repair processes was tested in the space experiments REPAIR and KINETICS, which were performed during the IML-2 mission in the Biorack of ESA: (a) survival of spores of Bacillus subtilis HA101 after UV-irradiation (up to 340 J m-2) in the experiment REPAIR; (b) in the experiment KINETICS the kinetics of DNA repair in three different test systems: rejoining of X-ray-induced DNA strand breaks (B1) in cells of Escherichia coli B/r (120 Gy) and (B2) in human fibroblasts (5 and 10 Gy) as well as (B3) induction of the SOS response after gamma-irradiation (300 Gy) of cells of Escherichia coli PQ37. Cells were irradiated prior to the space mission and were kept in a non-metabolic state (metabolically inactive spores of B. subtilis on membrane filters, frozen cells of E. coli and human fibroblasts) until incubation in orbit. Germination and growth of B. subtilis were initiated by humidification, E. coli and fibroblasts were thawed up and incubated at 37 degrees C for defined repair periods (up to 4.5 h), thereafter they were frozen again for laboratory analysis. Relevant controls were performed in-flight (1 x g reference centrifuge) and on ground (1 x g and 1.4 x g) The results show no significant differences between the microgravity samples and the corresponding controls neither in the survival curves nor in the kinetics of DNA strand break rejoining and induction of the SOS response (proven by Student's t-test, 2 P = 0.05). These observations provide evidence that in the microgravity environment cells are able to repair radiation-induced DNA damage close to normality. The results suggest that a disturbance of cellular repair processes in the microgravity environment might not be the explanation for the reported synergism of radiation and microgravity.

Bacillus subtilis↗

PubMed1996

Complex repair kinetics of DNA strand breaks induced by gamma-rays of UV radiation in Ehrlich ascites tumour cells.

Fluorometric analysis of DNA unwinding (FADU)-a sensitive technique for the detection of strand breaks in DNA-has been modified and used for the detailed investigation of repair kinetics of DNA-strand breaks arising under different conditions in Ehrlich ascites tumour (EAT) cells irradiated by gamma-rays or ultraviolet (UV) radiation. The repair kinetics of DNA-strand breaks induced in EAT cells by gamma-radiation was measured at radiation doses of 8, 20 and 50 Gy. We found complex repair curves in all cases, probably reflecting the combined processes of break rejoining and break generation during repair. In order to affect the above-mentioned processes, we have used different conditions of repair and different types of radiation. Lowering of the temperature of incubation and treating the cells by 5-fluoro-2'-deoxyuridine (FUdR) lead to complex changes of the repair curve with a reduced "wave" pattern. In order to change the type of damage to DNA, we used UV radiation (254 nm, 10 and 20 J/m2). Detailed studies of the repair kinetics showed that the repair curve for 10 J/m2 had a second maximum within 70 min after irradiation.

Animals↗

PubMed1996

The response of mouse lymphosarcoma cells to continuous gamma irradiation.

Long-lasting survival of LS/BL tumor cells under continuous exposure in vivo to 60Co irradiation at an exposure rate of 10 cGy/h was observed. While LS/BL tumor cells tolerated the irradiation for more than 150 weeks, the number of hematopoietic stem cells decreased to less than 1% of control values within 7 days of irradiation. The liver colony method was used to develop sublines from nonirradiated and continuously (110 weeks) irradiated LS/BL cells for the analysis of karyotypes of the resulting clones of lymphosarcoma cells. The appearance of new structural abnormalities t(12:9) in one of the sublines tested correlated with its faster host killing when compared to the parent line.

Animals↗

PubMed1995

Interpretation of mutation induction by accelerated heavy ions in bacteria.

In this report, a quantitative interpretation of mutation induction cross sections by heavy charged particles in bacterial cells is presented. The approach is based on the calculation of the fraction of energy deposited by indirect hits in the sensitive structure. In these events the particle does not pass through the sensitive volume, but this region is hit by delta rays. Four track structure models, developed by Katz (in Quantitative Mathematical Models in Radiation Biology, pp. 57-83, Springer-Verlag, 1988). Chatterjee et al. (Radiat. Res. 54, 479-494, 1973), Kiefer and Straaten (Phys. Med. Biol. 31, 1201-1209, 1982) and Kudryashov et al. (Proceedings of the First Soviet Congress on Microdosimetry, Atomizdat, Moscow, 1973), respectively, were used for the calculations. With the latter two models, very good agreement of the calculations with experimental results on mutagenesis in bacteria was obtained. Depending on the linear energy transfer (LET infinity) of the particles, two different modes of mutagenic action of heavy ions are distinguished: "delta-ray mutagenesis," which is related to those radiation qualities that preferentially kill the cells in direct hits (LET infinity > or = 100 keV/microns), and "track core mutagenesis," which arises from direct hits and is observed for lighter ions or ions with high energy (LET infinity < or = 100 keV/microns).

Bacillus subtilis↗

PubMed1994

Mutation induction by accelerated heavy ions in bacteria.

Induction of lacI- forward mutations in Escherichia coli Ymcl and his(-)-->his+ reversions in Salmonella typhimurium TA102 was investigated after irradiation with heavy ions in the range of Z = 1-36. Particle specific energies (E) were in the range of 1-600 MeV/u. A strong dependence of the mutation induction cross-section (sigma m) on both particle energy and LETinfinity was observed. The results suggest that two different ranges of LETinfinity can be distinguished. In the range of high LETinfinity (> 100 keV/micron) sigma m increases with increasing specific particle energy if LETinfinity is kept constant (Fe ions as compared with carbon ions or alpha-particles). In the range of low LETinfinity (< 100 keV/micron) sigma m decreases with increasing energy (Ne ions as compared with He ions).

Deuterium↗

PubMed1994

Cell inactivation, mutation and DNA strand-break induction by gamma-rays at very low temperatures.

Cell inactivation, mutation and DNA strand-break induction by gamma-radiation have been investigated at very low temperatures (-78 degrees C, -196 degrees C, and -268 degrees C). In Escherichia coli Ymel, lacI+-->lacI- and Salmonella typhimurium TA102, his--->his+ dose-modifying factors determined for low radiation doses are similar for both mutation induction and cell inactivation. The sensitivity of repair-deficient strains E. coli polA- and E. coli recA- was also reduced at low temperature to a comparable extent. This suggests that the lesions which are responsible for cell inactivation and mutagenesis could be strongly mutually related and/or that different types of lesions which are responsible for cell inactivation and mutation induction in bacteria are reduced at low temperature to the same or similar extent. Likewise, a lower yield of DNA strand breaks in plasmids irradiated at low temperature was observed.

DNA↗

PubMed1994

Double strand breaks in the DNA of Bacillus subtilis cells irradiated by heavy ions.

Cells of Bacillus subtilis strain TKJ 8431 in stationary phase were irradiated with X-rays (150 kV at DLR) or heavy ions (Ne, Ar, Pb with residual energies between 3 and 15 MeV/u at GSI). The action cross section for the formation of double strand breaks in the DNA of the irradiated cells follows a similar dependence on mass and energy of the ions as has been found for various biological endpoints, e.g. inactivation, mutagenesis and repair efficacy.

Argon↗

PubMed1994

Mutagenic effects of heavy ions in bacteria.

Various mutagenic effects by heavy ions were studied in bacteria, irradiated at accelerators in Dubna, Prague, Berkeley or Darmstadt. Endpoints investigated are histidine reversion (B. subtilis, S. typhimurium), azide resistance (B. subtilis), mutation in the lactose operon (E. coli), SOS chromotest (E. coli) and lambda-prophage induction (E. coli). It was found that the cross sections of the different endpoints show a similar dependence on energy. For light ions (Z < or = 4) the cross section decreases with increasing energy. For ions of Z = 10, it is nearly independent of energy. For heavier ions (Z > or = 26) it increases with energy up to a maximum or saturation. The increment becomes steeper with increasing Z. This dependence on energy suggests a "mutagenic belt" inside the track that is restricted to an area where the density of departed energy is low enough not to kill the cell, but high enough to induce mutations.

Azides↗

PubMed1992

Induction of SOS repair by ionizing radiation. Results from experiments at accelerators.

beta-galactosidase and alkaline phosphatase activities of Escherichia coli strain PQ37 carrying the fusion gene of sulA and lacZ treated with different types of ionizing radiation were examined. The induction factor (ratio of beta-galactosidase to alkaline phosphatase activity), reflecting the SOS-induction potency, increases significantly with radiation dose. Maximum effectiveness to induce SOS-response has been found for deuterium and helium ions in comparison to gamma-rays, carbon or krypton ions. Increased energy of helium ions leads to greater SOS-induction potency of radiation.

Dose-Response Relationship, Radiation↗

PubMed1992

The effect of the anoxic radiosensitizing agent TAN on induction of revertants by gamma-rays and helium ions in Salmonella tester strains.

The modification effect of the anoxic radiosensitizer TAN on the mutagenesis in various Salmonella tester strains after gamma-ray and helium ion irradiation was studied. The oxygen enhancement ratios (OER) for all 3 strains on the lethal assay after gamma-irradiation are approximately equal to 2. The induction of reversions in TA98 and TA100 does not modify under anoxia. The value of OER on the mutagenic assay in TA102 equals 1.6. The OER after helium ion irradiation on the lethal and mutagenic assays was less than after gamma-irradiation. The mutagenesis in 3 strains after irradiation under anoxia is enhanced by TAN. The value of the TAN modification effect after gamma-irradiation increases from 2.1 +/- 0.2 for TA102 to 5.2 +/- 0.4 for TA100. However, the TAN influence on mutagenesis in TA100 after helium ion irradiation decreases to 3.1 +/- 0.3. We conclude that peculiarities of mutagenesis in various tester strains under anoxia with TAN can be explained by considering the nature of premutational DNA damages.

Anaerobiosis↗

PubMed1992

Radioprotective action of glycerol and cysteamine on inactivation and mutagenesis in Salmonella tester strains after gamma- and heavy ion irradiation.

Inactivation and mutagenesis were studied in Salmonella tester strains after gamma-irradiation and after heavy ion irradiation in the presence of glycerol and cysteamine. Ions from deuteron to carbon with residual energies of 2-9 MeV/n were used. Cell sensitivity slightly increased with LET before decreasing. In the presence of glycerol the maximum was shifted to higher values of LET. The radioprotective effect of glycerol for cell killing diminished gradually with increasing LET from 2.0 for gamma-radiation to 1.1 for carbon ions. Mutagenic effectiveness increased slightly for deuterium and helium ions. The protective effect of glycerol decreased with LET but could still be detected for helium ions. The radioprotective effect of cysteamine on mutagenesis was found to be very small in the case of gamma-radiation for the three strains examined.

Cesium Radioisotopes↗

PubMed1992

Mutagenic effects of heavy ions in bacteria.

The peculiarities and mechanisms of the mutagenic action of gamma-rays and heavy ions on bacterial cells have been investigated. Direct mutations in the lac-operon of E. coli in wild type cells and repair deficient strains have been detected. Furthermore, the induction of revertants in Salmonella tester strains was measured. It was found that the mutation rate was a linear-quadratic function of dose in the case of both gamma-rays and heavy ions with LET up to 200 keV/micrometer. The relative biological effectiveness (RBE) increased with LET up to 20 keV/micrometer. Low mutation rates were observed in repair deficient mutants with a block of SOS-induction. The induction of SOS-repair by ionizing radiation has been investigated by means of the "SOS-chromotest" and lambda-prophage induction. It was shown that the intensity of the SOS-induction in E. coli increased with increasing LET up to 40-60 keV/micrometer.

Alpha Particles↗

PubMed1992

Induction of lacI- mutations in Escherichia coli cells after single and split-dose irradiation.

In the lacI system of Escherichia coli, X-ray mutagenesis follows a linear-quadratic curve with suppression; the survival curve is exponential. Dose fractionation leads to nearly complete repair of premutational lesions during an incubation interval of 3.5 h. Repair starts with a delay of 1.5-2 h, suggesting the involvement of an inducible repair/mutation fixation system. The dose-dependence of mutagenesis is described by a simple model assuming two hits being required. A probable explanation might be that the premutagenic lesions consist of two closely spaced lesions on the opposite strands of the DNA molecule.

Dose-Response Relationship, Radiation↗

PubMed1990

Investigation of the SOS response of Escherichia coli after gamma-irradiation by means of the SOS chromotest.

The kinetics of SOS system induction in Escherichia coli PQ37 cells by gamma-irradiation has been studied by the SOS chromotest technique. It was shown that the synthesis of constitutive alkaline phosphatase is not immediately stopped in cells that suffered lethal damages from gamma-irradiation. The production of DNA damages inducing the SOS system was 0.021/Gy per genome. The SOS system was switched off approximately 200 min after gamma-irradiation. A correction is proposed to the calculation of the SOS system induction factor.

Alkaline Phosphatase↗