Worm Breeder's Gazette 9(1): 38
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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.