Interpretation of UV-survival curves of Aspergillus conidiospores.
Semi-logarithmic dose-response curves for survival of UV-irradiated conidiospores of A. nidulans have an initial shoulder (at low doses) followed by a decline which becomes linear. To explain the initial shoulder and the resulting extrapolation number (log S intercept of the linear extrapolation line) a general model is presented, which includes multi-target (n) and multi-hit (h) effects and allows for the effect of initial repair and of a compound parameter k, which stands for inherent sensitivity of the spores and for dose received inside the spores. From experiments on (a) the modification of k (spore wall colour and shelter effects), (b) a repair-deficient strain (shoulderless) and (c) preincubation during which DNA-replication takes place, it is concluded that the shoulder is generated by initial repair rather than by a multi-hit nature of the cell-killing process. In experiments where k takes different values (sub a and c), notably the position of the point of intersection of the linear lines gives conclusive information. In general, the log S intercept of the linear extrapolation line cannot be used to estimate the target number.
Bos
C J
CJ
Department of Genetics, Agricultural University, Wageningen, The Netherlands.
Stam
P
P
van der Veen
J H
JH
D001233:Aspergillus nidulans / Q000235:genetics / Q000254:growth & development / Q000528:radiation effects*; D004260:DNA Repair; D004307:Dose-Response Relationship, Radiation; D009154:Mutation; D013045:Species Specificity; D014466:Ultraviolet Rays