Radiobiology Unit 2

Cells in all phases of the cell cycle useful for in vivo studies

Cells grouped in specific stages of the cell cycle useful for in vitro studies

Conducted cell survival studies for radiosensitivity using HeLa cells. Investigated reproductive failure from radiation

Division delay, interphase death (apoptosis), reproductive failure

When the mitotic index is altered because of exposure to ionizing radiation. The division is delayed, leading to a false surge in division once it resumes; can occur at doses of 0.1Gy, 0.5Gy for human kidney cells

Ratio of the number of cells in mitosis at a given time to total number of cells in the population

When a percentage of the cell population in mitosis is artificially increased (due to a division delay)

Apoptosis, nonmitotic death, nondivision death cell death before the cell divides; doses of 0.5Gy lymphocytes, mouse spermatogonia at 0.25Gy., parotid cells at 9Gy

The inability of the cell to undergo repeated division after irradiation. Cells do not have to be dead, just unable to reproduce repeatedly

Graphically represent radiation effects X axis: dose of radiation Y axis: percentage of cells surviving

Graphically represent radiation effects X axis: dose of radiation Y axis: response of population to radiation

Represents the dose of radiation that is required to destroy all except 37% of the cell population

If the curve has a shoulder portion, the point where the curve becomes linear. Here, cellular damage becomes proportional to the radiation dose.

If the curve has a shoulder, the linear portion of the curve until it intersects the Y axis. Represents the number of key targets in the cells that must be struck by the radiation to produce the response the curve demonstrates. Varies between 2-10

1. Lethal single-hit killing 2. Interaction of a sufficient number of sublethal lesions to cause death