PARENT SESSION
1:30 PM to 3:30 PM
Wednesday, April 24, 2002
Poster Session 30 Bystander Effects
Room: Nevada Exhibition Center
(P35-344) Modulation of Adaptive Response in Alpha Particle Induced Bystander Mutagenesis.
Zhou, Hongning*,1, Gerhard, Randers-Pehrson1, Hall, Eric1, Hei, Tom1, 1 Center for Radiological Research, Columbia University, New York, New York
ABSTRACT-
The risk of developing radiation-induced cancer has traditionally been estimated from cancer incidence among Japanese A-bomb survivors. These data provide the best estimate of cancer risk over the dose range from 20 to 250 cGy. The cancer risk at doses below 20cGy, however, remains uncertain and has been the subject of controversy for decades in the absence of definitive data. Although two conflicting phenomena, bystander effect and adaptive response, appear to be of important at low dose radiation and have potential to impact on the shape of the dose response relationship, there is very limited data available comparing the bystander effect versus adaptive response. In our present study, AL cells plated in the microbeam dishes two days before as described were exposed with a 0.1 Gy dose of 250 kV X-rays from a Westinghouse Coronado X-ray machine, operating at 10mA, with 0.2mm copper and 1mm aluminum filter, the absorbed dose rate was calculated to be 25.0 cGy/min. Four hours later, 10% of randomly selected cells were irradiated with exact number of alpha particles using Columbia precision particle microbeam. After alpha particle traversal, the cells were keeping in microbeam dishes for 2 days before replating in culture flasks. Determination of the mutant fraction was carried out as described before. Our preliminary data showed that the mutants yield from the population where 10% of randomly selected cells were irradiated with single alpha particle decreased significantly if the cells were pretreated with a low dose of X-ray. The results show that in the presence of low dose radiation stress, the bystander mutagenesis is modulated by the adaptive response. Though the mechanism(s) is unclear, it is likely that when cells are exposure to low doses X-ray, they initiate a series of self-preservation mechanisms that diminish their ability to respond to bystander signaling.
KEYWORDS: Bystander Effect, Adaptive Response, Mutagenesis, Alpha Particle