Radiobiology and the Classification of Biological Effects

Types of cell damage

  • Types 1
  • Types 2
  • Types 3
  • Types 4
  • Types 5
  • Types 6
  • Types 7
  • Types 8
cell damage

There are different types of cell damage:

  • Molecular - Damage to enzymes, RNA and DNA, and interference with metabolic pathways.
  • Sub-cellular - Damage to cell membranes, nucleus, chromosomes, mitochondria and lysosomes.
  • Cellular - Inhibition of cell division, cell death, transformation to a malignant state.
    Tissue /Organ Disruption / life-shortening / cancer.
  • Person / Population - Death / life-shortening / genetic damage due to gene and chromosome mutation.

 

Radiobiology is the study of the effects of radiation on living tissues.

 

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cell damage

The cell cycle consists of the G, S and M phases.

  • Interphase:
    • G1 - First Gap
    • S - Synthesis
    • G2 - Second Gap
  • M Phase

Checkpoint genes are active in the G2 phase and if damage is detected, the replication process is delayed until repair occurs.

 

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cell damage

When the cell divides (at mitosis) it is at its most radiosensitive phase. Chromosomal aberrations (changes) due to radiation treatment will inhibit cellular replication and proliferation.

 

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cell damage

A simple radiobiological experiment can demonstrate the different radiosensitivities of the cell cycle. Chinese Hamster cells can be used to show the response of cells at different stages of the cell cycle can respond to doses of 6.6Gy.

 

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stochastic effects

Direct Action of Radiation

When γ rays are absorbed in biological matter, some of t When γ rays are absorbed in biological matter, some of the energy is converted to fast electrons, which can interact directly with the critical targets of the cell - DNA γ rays are already electrons and may also react directly.

 

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stochastic effects

Indirect Action of Radiation

The radiation may interact with other atoms or molecules in the cell to produce free radicals that are able to reach and damage the critical target - DNA may interact with other atoms or molecules in the cell to produce free radicals that are able to reach and damage the critical target - DNA.

 

 

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stochastic effects

The images on the left show replication due to Chromosonal Abberations:

 

 

 

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To watch a video on the different types of cell damage, click the play button (white triangle) below (contains audio).

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