Molecular and cellular aspects of radiation hormesis in Drosophila melanogaster

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 was increased with increasing irradiation dose. At the same time, decrease in imaginal LS 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 electrophoregramms 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.

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