Influence of dose rate on the induction of simple and complex chromosome exchanges by gamma rays

Bradford Loucas, Richard Eberle, Susan M. Bailey, Michael Cornforth

Research output: Contribution to journalArticle

39 Citations (Scopus)

Abstract

Single-color painting of whole chromosomes, or protocols in which only a few chromosomes are distinctively painted, will always fail to detect a proportion of complex exchanges because they frequently produce pseudosimple painting patterns that are indistinguishable from those produced by bona fide simple exchanges. When 24-color multi-fluor FISH (mFISH) was employed for the purpose of distinguishing (truly) simple from pseudosimple exchanges, it was confirmed that the acute low-LET radiation dose-response relationship for simple exchanges lacked significant upward curvature. This result has been interpreted to indicate that the formation of simple exchanges requires only one chromosome locus be damaged (e.g. broken) by radiation to initiate an exchange-not two, as classical cytogenetic theory maintains. Because a one-lesion mechanism implies single-track action, it follows that the production of simple exchanges should not be influenced by changes in dose rate. To examine this prediction, we irradiated noncycling primary human fibroblasts with graded doses of 137Cs γ rays at an acute dose rate of 1.10 Gy/min and compared, using mFISH, the yield of simple exchanges to that observed after exposure to the same radiation delivered at a chronic dose rate of 0.08 cGy/min. The shape of the dose response was found to be quasi-linear for both dose rates, but, counter to providing support for a one-lesion mechanism, the yield of simple aberrations was greatly reduced by protracted exposure. Although chronic doses were delivered at rates low enough to produce damage exclusively by single-track action, this did not altogether eliminate the formation of complex aberrations, an analysis of which leads to the conclusion that a single track of low-LET radiation is capable of inducing complex exchanges requiring up to four proximate breaks for their formation. For acute exposures, the ratio of simple reciprocal translocations to simple dicentrics was near unity.

Original languageEnglish (US)
Pages (from-to)339-349
Number of pages11
JournalRadiation Research
Volume162
Issue number4
DOIs
StatePublished - Oct 2004

Fingerprint

chromosomes
Gamma Rays
gamma radiation
Linear Energy Transfer
induction
Chromosomes
gamma rays
Radiation
dosage
Radiation Dose-Response Relationship
Color
Chromosome Painting
Paintings
Cytogenetics
lesions (animal)
dose response
radiation
Fibroblasts
lesions
reciprocal translocation

ASJC Scopus subject areas

  • Agricultural and Biological Sciences (miscellaneous)
  • Radiology Nuclear Medicine and imaging
  • Biophysics
  • Radiation

Cite this

Influence of dose rate on the induction of simple and complex chromosome exchanges by gamma rays. / Loucas, Bradford; Eberle, Richard; Bailey, Susan M.; Cornforth, Michael.

In: Radiation Research, Vol. 162, No. 4, 10.2004, p. 339-349.

Research output: Contribution to journalArticle

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