Abstract
Theories of mammalian cellular radiosensitivity that exclude metabolic modification of radiation damage are untenable (Nagasawa et al., 1980). Evidence supporting that conclusion has been obtained from experiments with a radiosensitive, proliferating cell, the S/S variant of the L5178Y murine leukaemic lymphoblast, and a radioresistant, nondividing cell, the retinal photoreceptor (rod) of the rabbit. When S/S cells (mid-) G1 + 8 h in the cycle, at the peak of radioresistance, were X-irradiated at 37 degrees C and then treated hyperthermically (12 h, 38.7-40.3 degrees C), the survival curve, which has a shoulder at 37 degrees C, changed progressively to the simple exponential obtained for G1 cells. Under conditions where Ne ions (LET = 35 keV microns-1) have a relative biological effectiveness (RBE) of approximately 2 for normally radioresistant cells in vitro and in situ, the RBE for G1 S/S cells was approximately 1. Neon ions (1-50 Gy) caused similar amounts of DNA damage in S/S cells and photoreceptors, but the cellular responses were very different. After 5 Gy, the surviving fraction of asynchronous S/S cells was 10(-5), DNA structures were not restored and by 8 h post-irradiation extensive DNA degradation was evident; in the retina, however, the photoreceptor complement was unchanged for greater than 1 year, DNA structures appeared to be restored and remained so (many months) until late DNA degradation began. These phenomena can be explained satisfactorily only if temporal processes play a significant role in cellular radiosensitivity.
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Selected References
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- Blakely E. A., Tobias C. A., Yang T. C., Smith K. C., Lyman J. T. Inactivation of human kidney cells by high-energy monoenergetic heavy-ion beams. Radiat Res. 1979 Oct;80(1):122–160. [PubMed] [Google Scholar]
- Cox A. B., Keng P. C., Glass N. L., Lett J. T. Effects of heavy ions on rabbit tissues: alopecia. Int J Radiat Biol Relat Stud Phys Chem Med. 1981 Dec;40(6):645–657. doi: 10.1080/09553008114551631. [DOI] [PubMed] [Google Scholar]
- Cox A. B., Keng P. C., Lee A. C., Lett J. T. Effects of heavy ions on rabbit tissues: damage to the forebrain. Int J Radiat Biol Relat Stud Phys Chem Med. 1982 Oct;42(4):355–367. doi: 10.1080/09553008214551291. [DOI] [PubMed] [Google Scholar]
- Goldin E. M., Cox A. B., Lett J. T. Correlation of survival with the restoration of DNA structure in X-irradiated L5178Y S/S cells. Radiat Res. 1980 Sep;83(3):668–676. [PubMed] [Google Scholar]
- Keng P. C., Bergtold D. S., Lett J. T. Effects of heavy ions on rabbit tissues: analysis of low levels of DNA damage in retinal photoreceptor cells. Int J Radiat Biol Relat Stud Phys Chem Med. 1983 Mar;43(3):219–229. doi: 10.1080/09553008314550281. [DOI] [PubMed] [Google Scholar]
- Keng P. C., Lee A. C., Cox A. B., Bergtold D. S., Lett J. T. Effects of heavy ions on rabbit tissues: cataractogenesis. Int J Radiat Biol Relat Stud Phys Chem Med. 1982 Feb;41(2):127–137. doi: 10.1080/09553008214550141. [DOI] [PubMed] [Google Scholar]
- LETT J. T., PARKINS G., ALEXANDER P., ORMEROD M. G. MECHANISMS OF SENSITIZATION TO X-RAYS OF MAMMALIAN CELLS BY 5-BROMODEOXYURIDINE. Nature. 1964 Aug 8;203:593–596. doi: 10.1038/203593a0. [DOI] [PubMed] [Google Scholar]
- Lett J. T., Caldwell I., Dean C. J., Alexander P. Rejoining of x-ray induced breaks in the DNA of leukaemia cells. Nature. 1967 May 20;214(5090):790–792. doi: 10.1038/214790a0. [DOI] [PubMed] [Google Scholar]
- Wheeler K. T., Lett J. T. On the possibility that DNA repair is related to age in non-dividing cells. Proc Natl Acad Sci U S A. 1974 May;71(5):1862–1865. doi: 10.1073/pnas.71.5.1862. [DOI] [PMC free article] [PubMed] [Google Scholar]