Heavy-Ion Effects on Yeast: Survival and Recovery in Vegetative Cells of Different Sensitivity

Cellular and Subcellular Effects of Very Heavy Ions

“…Initial investigations with very heavy ions showed a linear relationship between the inactivation cross section and Z* 2 // 2 which was confirmed later by more extensive studies (Weber et al 1985). This is at variance with the findings on cell killing in the same system (see above, Sch6pfer et al 1982). One has to take into account, however, that much higher doses are necessary for r-RNA synthesis inhibition than for the loss of colony forming ability: the D o values for X-rays are 1960 and 160 Gy, respectively.…”

“…There was even a sensitization if two heavy ion exposures were separated by a 4-6 h interval (Wulf 1983), an effect already noted by Ngo et al (1980) and Bianchi et al (1980). In diploid yeast, on the other hand, recovery from potentially lethal damage was found even with uranium, but only with higher energies, which points again to the importance of 'penumbra inactivation' (Sch6pfer et al 1982).…”

“…values Kiefer 1976, Lyman andHaynes 1967) while it is lost with mammalian cells (Todd 1967, Skarsgard et al 1967, Barendsen 1968, Wulf 1983. Also, recovery from potentially lethal damage is demonstrable in diploid yeast after heavy ion exposure (Lyman and Haynes 1967, Schneider and Kiefer 1976, Sch6pfer et al 1982, but not in mammalian cells (Raju et al 1977, Bertsche et al 1981, Wulf 1983). It appears that the proximity of primary lesions impedes their repariability in mammalian cells but not in yeast.…”

“…It is obvious that l.e.t. is no Colony-forming ability Sch6pfer et al (1980Sch6pfer et al ( , 1982Sch6pfer et al ( , 1984 Kuchinka et al , 1985 t Estimated radius of the sensitive site. This list is not comprehensive and more references can be found in the text.…”

Radiation quality and the shape of dose–effect curves at low doses of ionizing radiation for eukaryotic cells

“…It means that the RBE of densely ionizing radiation for such the cases is strongly dependent on the survival level chosen for comparison, RBE being very large (10)(11)(12)(13)(14)(15) for low doses approaches ratio of slopes of exponential parts of survival curves (3)(4)(5) as level of the survival fraction decreases. Conversely, for diploid yeast cells which have a double set of chromosomes like mammalian cells the shape of survival curves is sigmoid independently of radiation quality [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27]. We have quoted here a lot works performed with yeast and mammalian cells irradiated with low-and high-LET radiation to emphasize that the observed differences in the responses of these cells are not random and systematically obtained by different researchers.…”