Document Detail

Targets for radiation-induced cell death: target replication during the cell cycle evaluated in cells exposed to X-rays or 125I decays.
MedLine Citation:
PMID:  8103545     Owner:  NLM     Status:  MEDLINE    
Chinese hamster ovary cells were labelled with 125I-iododeoxyuridine (1.15 x 10(3) Bq/ml) for 12 h, then synchronized by mitotic selection, plated for cell cycle traverse, and harvested during successive stages of the cell cycle for freezing and accumulation of 125I decays. Cell viability was evaluated by the colony-forming assay. Cells subjected to 125I decays during the G1 phase exhibited exponential survival curves with an N = 1 and a D0 = 38-41 decays/cell. A continuous increase in 125I resistance was observed as cells progressed through the S phase and cells in late-S/G2 yielded shouldered survival curves with a N = 2 and a D0 = 78-84 decays/cell. After mitosis, the radiation resistance of cells returned to G1 values. These findings suggest that the primary target for radiation-induced cell death is duplicated during S phase, with G1 cells containing one target and G2 cells two targets. Dual targets, although located within a single cell, act as independent entities as if already distributed between two separate daughter cells. Therefore, the colony-forming assay provides survival values representative of single cells/single targets only for cells irradiated during the G1 phase of the cell cycle. For cells irradiated in S or G2 phases, when intracellular target multiplicity > 1, the colony-forming assay systematically gives higher values of cell survival by up to 100% due to the target multiplicity. Experiments with external X-rays confirm these conclusions.
K G Hofer; N van Loon; M H Schneiderman; G V Dalrymple
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  International journal of radiation biology     Volume:  64     ISSN:  0955-3002     ISO Abbreviation:  Int. J. Radiat. Biol.     Publication Date:  1993 Aug 
Date Detail:
Created Date:  1993-10-06     Completed Date:  1993-10-06     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  8809243     Medline TA:  Int J Radiat Biol     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  205-16     Citation Subset:  IM; S    
Institute of Molecular Biophysics, Florida State University, Tallahassee 32306.
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MeSH Terms
CHO Cells
Cell Cycle / radiation effects*
Cell Death / radiation effects*
Colony-Forming Units Assay
Iodine Radioisotopes
Models, Biological
Radiation Dosage
S Phase / radiation effects
Grant Support
Reg. No./Substance:
0/Iodine Radioisotopes

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