The effect of space radiation on the induction of chromosome damage
K. George1, H. Wu2, V. Willingham1, F. A. Cucinotta3
1Wyle
Laboratories, Houston, TX
2Kelsey
Seybold, Houston, TX
3NASA, Johnson
Space Center, Houston, TX
kerry.a.george1@jsc.nasa.gov
To obtain information on the cytogenetic damage caused
by space radiation, chromosome exchanges in lymphocytes from crewmembers
of long-term MIR missions and a shorter duration shuttle mission, were
examined using fluorescence in situ hybridization. A significant increase
in chromosomal aberrations was observed after the long duration flights.
Biological doses calculated from ground-based dose-response curves of
preflight samples exposed to gamma rays were compared to individual TLD
values and the average RBE was slightly higher than quality factors
obtained from tissue-equivalent proportional counter readings. The ratio
of aberrations identified as complex was significantly higher post-flight
for some crewmembers, which is thought to be an indication of exposure to
heavy ions. Ground-based studies have shown that the frequency of
aberrations measured post-flight could be influenced by a mitotic delay in
cells damaged by high LET radiation and this effect could lower biological
dose estimates. To counteract this effect, prematurely condensed
chromosome (PCC) spreads were collected. Frequencies of aberrations in PCC
were compared with those in metaphase spreads. The effects of spacecraft
shielding were also tested by in vitro exposure of lymphocytes to
accelerated protons at three different dose rates (from 0.075 Gy/hr to 0.7
Gy/min). The effect of 15 g/cm2 aluminum shielding on the frequency of
total chromosome exchanges measured in PCC will be presented.
