Ionizing radiation biological actions

Chemical and biological effects of ionizing radiation are thought to occur through two main mechanisms direct interaction of the radiation with food components and living cells in materials exposed to it, and indirect action from radiolytic products, such as the radicals formed from water molecules (see Chap. 12). 

A more reliable means of providing a reference of -OH in a biological system maybe by means of irradiation with ionizing radiation (von Sonntag et al. 2000). The action of ionizing radiation on an aqueous medium gives rise to OH whose yield/dose relationship (G value) is known (Chap. 2). Apart from this, since biological media are concentrated solutions the formation of the indicator product, e.g., a phenol (ArOH), via the direct effect [expressions (69) and (70)] must in principle be taken into account as well. It can be shown that with k4i [probe]/ k42 [cellular components] above 10 4 the direct effect contributes less than 10%... 

Because of their extreme reactivity, the existence of free radicals in biological systems was generally not considered possible until Gerschman and associates (G3) hypothesized that oxygen poisoning and X-irradiation have a common basis of action. Here, they reported the homolytic dissociation of water by ionizing radiation. 

The purpose of this article is to provide the pharmaceutical industry with an overview of the physical, chemical, and biological actions of ionizing radiation on molecules of interest to the industry, as well as to provide a current perspective on the prospects of the... 

Dartinger, H., and Jung, H. (1970), Molecular Radiation Biology The Action of Ionizing Radiation on Elementary Biological Objects, Springer-Verlag, New York. 

Comprehending corrosion as failure of materials under the action of the environment, it would be justified to relate this term to fracture of polymer materials under the action of ambient factors, including elevated temperatures, ionizing radiation, UV radiation, ozone, mechanical loads, chemical and biological matter. 

Ionizing radiation must exert its effects either directly on molecules or molecular aggregates that constitute protoplasm or indirectly through its action on the universal protoplasmic solvent, water. The free-radical concept and its potential importance in biological systems has recently been adequately reviewed (9). 

Studies of the biological action of ionizing radiation on cells and tissues are of interest for applications in radiotherapy as well as radiation protection. In general, the biological response to ion beam irradiation considerably differs from that to conventional photon beam irradiation. This difference for example constitutes one of the major rationales for the application of ion beams in tumor therapy. 

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