Abstract
From the early 1990s there have been radical changes in our understanding of radiobiological effects and in methods of investigating them. Following earlier indications, it has now become clear that there is a range of non-(DNA)-targeted effects. They play a significant role in radiation responsiveness in relation to that of the classical, DNA-targeted effects. Recognition of these effects has coincided with and stimulated the development of a number of low-dose and targeted microirradiation techniques that have enabled these more newly recognized effects to be investigated in considerable detail. The key phenomena are bystander effects, genomic instability and adaptive responses and they are clearly interrelated and share some common pathways. Cell-to-cell communication is a dominant feature of these responses and the ability of new methods to target specifically, either with microbeams or with targeted radioisotopes, is helping to provide new insights into the mechanisms. Individual cells and subcellular targets can be selected within populations and the responses can often be registered by time-lapse imaging. Much of the emphasis has been to apply these methods to simple in vitro systems and the present challenge is to explore the role of non-targeted effects in 3-D and model tissue systems. The microbeam approach is of particular value in studies related to radiation risk. This is because it is possible to determine the actions of single particle tracks and thereby mimic in vitro the exposure conditions that generally apply at protection levels.
