Effects of 2-deoxy-D-glucose on DNA repair and mutagenesis in UV-irradiated yeast

Modification of low dose radiation induced radioresistance by 2-deoxy-D-glucose in Saccharomyces cerevisiae: mechanistic aspects

Use of 2-deoxy-D-glucose (2-DG) in combination with radiotherapy to radio-sensitize the tumor tissue is undergoing clinical trials. The present study was designed to investigate the effect of 2-DG on radiation induced radioresistance (RIR) in normal cells. The sub-lethal radiation dose to the normal cells at the periphery of target tumor tissue is likely to induce radioresistance and protect the cells from lethal radiation dose. 2-DG, since, enters both normal and tumor cells, this study have clinical relevance. A diploid respiratory proficient strain D7 of S. cerevisiae was chosen as the model system. In comparison to non-pre-irradiated cultures, the cultures that were pre-exposed to low doses of UVC (254 nm) or (60)Co-gamma-radiation, then maintained in phosphate buffer (pH 6.0, 67 mM), containing 10 mM glucose (PBG), for 2-5 h, showed 18-35% higher survivors (CFUs) after subsequent exposure to corresponding radiation at lethal doses suggesting the radiation induced radioresistance (RIR). The RIR, in the absence of 2-DG, was associated with reduced mutagenesis, decreased DNA damage, and enhanced recombinogenesis. Presence of 2-DG in PBG countered the low dose induced increase in survivors and protection to DNA damage. It also increased mutagenesis, altered the recombinogenesis and the expression of rad50 gene. The changes differed quantitatively with the type of radiation and the absorbed dose. These results, since, imply the side effects of 2-DG, it is suggested that new approaches are needed to minimize the retention of 2-DG in normal cells at the time of radiation exposure.

Thermoluminescence of terbium sensitised by samarium in CaF2

Thermoluminescence (TL) in sintered CaF2 doped with Tb4O7 has been studied for UV and X-ray irradiation. Three TL glow peaks for the Tb4O7 doped sample appeared in the temperature regions of about (1) 347-353 K, (2) 378-383 K and (3) 453-458 K, when heated at a rate of 20 K min(-1) after UV or X-ray irradiation at room temperature. It has been found that the 378 K peak intensity of the samples co-doped with Tb4O7 and Sm2O3 became stronger when compared with those doped with only terbium or samarium ions, and the TL peaks of (1) 347-353 K and (3) 453-458 K were not observed. The intensity of the 378 K peak of the co-doped sample was 12.9 times that of the sample doped only with Tb4O7. From the TL spectra and the excitation and emission spectra of photoluminescence for the CaF2 doped activators, it is concluded that the TL of Tb3+ ions is sensitised by the existence of Sm3+ ions. The 378 K TL peak may also be suitable for UV radiation dosimetry.

Thermoluminescence in sintered CaF2:Tb

In order to observe and estimate the dose of ultraviolet (UV) radiation, the thermoluminescence (TL) of sintered CaF2 doped with Tb4O7 and Sm2O3 was studied. A several kind of lanthanides elements are doped in pure CaF2 powder crystals and properties of the TL to UV radiation were observed. The TL intensity from CaF2:Tb was the highest among the samples doped other lanthanide elements. The TL emission may be due to the recombination reaction; Tb2+ + hole-->Tb3+*-->Tb3+ + hv. The TL peaks are observed at about 353 K, 378 K and 458 K. It was found that the 378 K TL peak intensity of CaF2:Tb became strong by addition of Sm2O3. The 378 K TL peak may also be suitable for use as a dosimeter.

An in vitro approach to study chromosomal DNA damage

In this study a simple electrophoresis approach has been proposed for assessing DNA damage per chromosome in vitro. Novel procedures of gel casting, sample loading, electrophoresis and quantification of damage have been suggested. Sets of Saccharomyces cerevisiae chromosomes subjected to DNA damage by Bleomycin, Co60-gamma-radiation alone and in combination with Hoechst were studied in detail. Statistical analyses showed that damage induced by Bleomycin bore linear positive correlation with %GA (r = 0.97) and %GT (r = 0.61) contents of chromosomes. Samples pre-treated with Hoechst showed much less damage by Co60-gamma-irradiation as compared to samples not treated with Hoechst but exposed to Co60-gamma-irradiation. The 'protective effect of Hoechst' bore linear positive correlation (r = 0.8) with %TAT content of chromosomes.