Differential inactivation analysis of diploid yeast exposed to radiation of various LET. I. Computerized single-cell observation and preliminary application to X-ray-treated Saccharomyces cerevisiae.

This series of investigations was designed to observe growth and division of single, diploid yeast cells within the first four generations after irradiation with ionizing radiation. Evidence exists that cell reactions important for the final cell fate occur during this period, and therefore the analysis of cell kinetics and of stationary forms of inactivated cells can be performed. A large number of experiments is necessary to obtain statistically confirmed results of single-cell observation. An automatically steered microphotographic registration device has been developed to facilitate the collection of large numbers of observations. Optical data scanned by a TV camera and digitally stored in a computer are processed by pattern recognizing programs to achieve the correct correlation of newly built cells to existing ones and to deliver a pedigree over four generations of at least eight cells for every irradiated single cell. The pooled data of many pedigrees of this kind allow the analysis of the differential behavior of a total population. From the analysis of X-irradiated cells one can conclude that a single cell that produces at least a microcolony of five cells is eventually able to form a microcolony and thus can be considered a survivor. That means the division probability of cells to go from generation zero to three corresponds to the survival curve of the colony-forming ability test. Therefore this method is suitable for the differential description of the important phenomenological cell reactions after irradiation.