Sensitivity of Drosophila melanogaster to low concentrations of gaseous mutagens. IV. Mutations in embryonic spermatogonia
Kale, P.G.; Baum, J.W.
Mutation Research 113(2): 135-143
1983
ISSN/ISBN: 0027-5107 PMID: 6403851 Document Number: 209956
Drosophila embryos were treated with gaseous ethylene dibromide at concentrations ranging from 0.26-200 ppm, thereby exposing a homogeneous and non-dividing population of primordial spermatogonia. Mutations were induced at exposures as low as 1 ppm for 3 h indicating the sensitivity of spermatogonia and the usefulness of this life-cycle stage for detection of mutagens. Other advantages of using embryos are also discussed. The relations between exposure vs. percentage of mutations per chromosome tested and vs. percentage of positive males were linear at low exposures, indicating the possibility of extrapolation of the data to very low doses and lack of a threshold. For some males 50% of the progeny carried a mutation, and mutations continued to appear in all tested broods providing evidence of damage to stem cells undergoing quasi-dichotomous divisions. Damage to the stem cells is important in terms of total effects on the gene pool and may contribute more mutations than that due to damage in the more sensitive spermatocytes and spermatids. Spermatogonial stages should also be considered in mutagen screening and risk-benefit analyses.