The long-term effects of the R-irradiation of D. melanogaster at the 1-hour egg stage with the dosages of 0.25, 0.50, 0.75, 1.0, 2.0 and 4.0 Gy were investigated. DNA samples were isolated from whole 5-6-days adult males. The aliquots of DNA were digested by S1-nuclease. Preimaginal stage lethality increased with irradiation dose increasing. At the same time, decrease in imaginal LS (life span) was observed after irradiation with the greatest dose (4 Gy) only. Moreover, hormesis by LS has revealed: in males irradiation with 0.25, 0.75 and 1 Gy increased the mean LS, and with 0.25 and 0.5 Gy caused the maximum LS; in females exposures with 0.25, 0.75 and 2 Gy increased the maximum LS. The densitometric assay of DNA electrophoregrams showed decrease by 39.2% of the part of high-molecular-weight DNA in control as a result of S1-nuclease action. Samples of DNA from the irradiated flies were more stable to enzyme action. The higher stability of DNA originated from the irradiated flies could be the result of reparation system activation. Ultrastructural changes induced at the egg stage by irradiation at the dose of 0.75 Gy testify the increased transcriptional activity of the brain cells.
Adaptation, Physiological Animals