Worm Breeder's Gazette 9(1): 38

These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.

Effects of Heavy Ion Irradiation on C. elegans

G. Nelson and R. Hammen

We have been investigating the effects of heavy ion irradiation on C.
elegans using the Lawrence Berkeley Laboratory's Bevalac accelerator 
as a source of ions of various charge, energy and fluence.  To date, 
ions of C, Ne, Ar, Fe and La have been used to irradiate N2 and JP10 (
eT1 balanced over dpy-18 and unc-46, of Rosenbluth, et. al., Genetics 
109: 493) in order to characterize: 1)  lethal mutation rates and 
structures vs. fluence and LET (linear energy transfer), and 2)  
fertility and gonad development vs. fluence, LET and target size (cell 
number in gonad primordia).  The goals are to understand how heavy ion 
mechanisms of mutagenesis and cell killing are related to their LET, 
charge, velocity and tract structure and to compare these mechanisms 
to those for gamma & X-rays, which deposit energy in a more uniform 
fashion.  For example, with respect to forward lethal mutation rate, 
495 MeV/amu Fe ions at a fluence of 3x10+E7/cm^2 (three to four hits 
per gonad nucleus)  are roughly equivalent to 2x10+E10 Co-60 gamma 
photons (2400 hits per gonad nucleus or 1000 rads).
A brief summary of our findings to date is:  (1)  Mutation rate in 
the eT1 balanced region of LG III and LG V (strain JP10) is strongly 
dependent on LET below 100 KeV/ m and at three hits per cell reaches 
8% of F1's at LET = 1100 KeV/ m.  (2)  At LET = 198 KeV/ m the lethal 
mutation rate in JP10 in the dose range 32 to 1600 'rad equivalents' (
Note that rads is a misleading unit for heavy ion radiation as it 
takes no account of track structure) is linear and equal to 
approximately 0.6% of F1's per 'rad'.  (3)  A large fraction of ion-
induced lethals have altered segregation patterns.  (4)  Fertility in 
N2 irradiated as larvae is strongly dependent on LET and gonad size.  
The LET effect is maximum at about 100 KeV/ m and gonads with 
approximately 30-50 cells are most sensitive.  Larvae with gonads of 
greater than 100 cells produce many males indicating survival of cells 
with sublethal damage to LG X.
HELP!  We are trying to find ways of immobilizing worms for extended 
periods of time (e.g., one week) in order to correlate particle tracks 
with worms and worm parts.  The best we can do is to keep dauers in 3% 
agarose at 11 C, but we want to hold worms at 20-22 C.  Suggestions 
would be most welcome-call GN @ (818) 354-4401.