Basic Radiation Biology

Throughout almost 4 billion years, life on Earth has been shaped by interactions of the organisms with their environment and by numerous adaptive responses to environmental stressors. Among those stressors, radiations, both of terrestrial and of cosmic origin, are a persistent stress factor that life has to cope with. Radiation interacts with matter primarily through the ionization and excitation of electrons in atoms and molecules. These matter-energy-interactions have been decisively involved in the creation and maintenance of living systems on Earth. Because it is a strong mutagen, radiation is considered a powerful promoter of biological evolution on the one hand, and an account of deleterious consequences to individual cells and organisms, e.g., by causing inactivation or mutation induction, on the other. In response to the harmful effects of environmental radiation, life has developed a variety of defense mechanisms, including the increase in the production of stress proteins, the activation of the immune defense system, and a variety of efficient repair systems for radiation-induced DNA injury.

There are two alternative ways of radiation damage to the biological key substances, such as proteins, RNA, and DNA: either by direct energy absorption (direct radiation effect), or via interactions with radicals, e.g., produced by radiolysis of cellular water molecules (indirect radiation effect) (Figure 7-05).

Figure 7-05. Radiobiological chain of events within a biological cell with the two alternative pathways of radiation damage, resulting in either direct or indirect radiation effects.
0 0

Post a comment