Evidence for a physical component to the radiation-induced bystander effect?
OBJECTIVE
The nature of the transferrable factor which goes from irradiated objects to bystander objects remains undefined. Most agree that a chemical entity is the likely 'factor' although some authors have produced in vitro evidence for the involvement of a physical component or a very potent volatile capable of traveling through air distances. In this paper we test the hypothesis that the communicated signal may be physical at least in part.


METHODS
The in vivo fish model was used to allow signal production and response to occur in organisms in vivo without any shared blood or central nervous system (CNS) connections. A reporter assay and calcium flux measurements were used to detect signal production when irradiated fish were separated from unirradiated fish by (a) a plastic container, and (b) a foil-wrapped plastic container.


RESULTS
The unirradiated fish showed bystander effects in both cases. The use of foil excludes the possibility of a light signal and although a highly active volatile could travel from one tank to another, the arrangement of sham and irradiated tanks makes it highly unlikely that this could explain our result.


CONCLUSIONS
We conclude that there must be a physical component in the mechanism such as a weak acoustic or electromagnetic signal.
Department of Medical Physics and Applied Radiation Sciences, McMaster University, Hamilton, Ontario, Canada. mothers@mcmaster.ca
Carmel
C
Mothersill
Richard W
RW
Smith
Jennifer
J
Fazzari
Fiona
F
McNeill
William
W
Prestwich
Colin B
CB
Seymour
D000162:Acoustics; D000818:Animals; D024201:Bystander Effect / Q000528:radiation effects*; D002118:Calcium / Q000378:metabolism; D002470:Cell Survival / Q000528:radiation effects; D055590:Electromagnetic Phenomena; D005260:Female; D042541:Intracellular Space / Q000378:metabolism / Q000528:radiation effects; D008297:Male; D008954:Models, Biological; D055585:Physical Phenomena; D015027:Zebrafish / Q000378:metabolism
D002118:Calcium