On the nature of damage involved in liquid-holding recovery in diploid yeast after gamma- and alpha-irradiation.

Cells surviving after liquid-holding recovery following gamma- and alpha-irradiations are found to be slightly more sensitive to a second series of radiation doses. Further, the shoulder on the gamma survival curve of the pre-irradiated and liquid-held cells disappears. The shoulder and sensitivity are restored only when these cells are grown in broth before the second series of doses. In addition to this, liquid-holding recovery reduces progressively if the cells after irradiation are incubated in broth for different periods of time before holding. These observations suggest that: (1) the so-called potentially lethal damage may consitute that part of the sub-lethal damage which interact with one another to form lethal damage; (2) during liquid-holding, the interaction among sub-lethal damage transforming them to the status of lethal damage is inhibited; (3) the 'recovered' cells are saturated with sub-lethal damage, the repair of which will be completed only when the cells are placed in a nutrient medium. The inhibitory process is not a passive one, but requires energy metabolism.