1. Determine the relative contributions of nuclear hits, cytoplasmic hits and media hits to the biological outcome from controlled radiation exposure.
2. Evaluate a variety of biological endpoints such as micronuclei, cell cycle effects, and changes in gene expression to better understand the role that direct energy deposition has on their production.
3. Determine how such changes impact risk.
   

Experimental Approach:

Cells will be grown in culture and exposed to radiation using the micro-beam. This protocol makes it possible to expose known numbers of cells and parts of cells to defined numbers and energy of alpha particles. After exposure each individual cell will be followed as a function of time after exposure to determine the fate of the exposed and non-exposed cells. Alternatively, cells can be labeled with 2 vital dyes then plated in known proportions. The microbeam can then irradiate cells of only one color. Following irradiation the "hit" cells can be discriminated from the bystander cells by color, and selected endpoints can be measured.

Expected Outcomes:

1. Determine the role of media, cell type, the fraction of the cells exposed and cell organelle exposure on biological alterations.
2. Measure the impact of alpha particle traversals on biological responses in both "hit" and non-hit cells.
3. Define the role of "bystander" effects on risk from development of disease, using small numbers of alpha particles.