Office
of Biological and Environmental Research
DOE
Lowdose Radiation Program Workshop IV
2003
Abstract
Title:
Detection
of genomic instability in a-irradiated and bystander
human fibroblasts.
Authors:
Brian
Ponnaiya, Gloria Jenkins-Baker, Alan Bigelow, Stephen Marino
and Charles R. Geard
Institutions:
Center for Radiological Research, Columbia University, New
York.
We
have previously demonstrated the presence of a radiation induced
bystander effect using novel co-culturing techniques where
irradiated and bystander cells were cultured on two surfaces
of mylar separated by media. Here we present data from experiments
designed to investigate the induction of chromosomal aberrations
in irradiated and bystander fibroblasts using these co-culturing
techniques. Immortalized human fibroblasts ((BJ1-tert) were
cultured on both mylar surfaces and cells on one side were
irradiated with 0.1 or 1 Gy a-particles (an average
of 1 and 10 particles per cell nucleus respectively), the
two sides were separated 1 hour post irradiation and either
analyzed for chromosomal aberrations using standard Giemsa
staining at either immediate or delayed time points.
At
24-30 hours post irradiation, frequencies of chromosomal aberrations
in the irradiated populations were increased in a dose dependent
manner as would be expected. Populations that received 0.1
and 1 Gy had 0.3 and 1.3 aberrations per cell; these aberrations
were almost exclusively chromosome type aberrations. In contrast,
at these times bystander populations had elevated yields of
chromatid-type aberrations. Frequencies in the irradiated
populations ranged from 0.07 to 0.09 aberrations per cell
at 15 doublings, and 0.09-0.14 per cell at 20 doublings, with
no apparent dose response. Aberration frequencies in the bystander
populations were between 0.08-0.14 per cell at the delayed
time points assayed. Interestingly, the chromatid-type aberrations
observed immediately post irradiation in the bystander cells,
and at later times in both the irradiated and bystander populations
were qualitatively similar to those previously observed at
delayed times in neutron irradiated epithelial cells. Furthermore,
there was a similar lack of a dose response in those studies
as well.
Currently
experiments are ongoing to examine irradiated and bystander
cells at immediate and delayed times for the presence of chromosomal
aberrations that are not detectable by standard Giemsa staining
(e.g. translocations) using mFISH analyses. This study was
supported by CA49062, CA75061, DOE FG02-98 and RR11623.
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