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PubMed1984

[Mutagenic action of tritium on the germ cells of male mice. I. The induction of dominant lethal mutations by tritium oxide and an assessment of its relative biological effectiveness].

The frequency of dominant lethal mutations (DLM) in the germ cells of male mice exposed to either THO- or gamma-irradiation of 137Cs at the dose of 0.5-3.7 Gr was studied. The distribution of the number of dead embryos in females from the control group as well as that at a dose of irradiation less than 1 Gr, corresponds to the Poisson rule. Spermatids appeared to be more radiosensitive than spermatocytes and spermatozoa. The rate of the effect caused by irradiation of both spermatocytes and spermatids did not depend on the dose rate of gamma-irradiation ranging from 1.10(-3) to 1.7 Gr per min. The linear quadratic formula of aD+bD2 describes the relation of the DLM frequency to the doses of either beta- or gamma-irradiation. The THO RBE increases with the decrease of the dose reaching 2.5 at the D less than 0.1 Gr.

Animals↗
PubMed1981

[Genetic effects of the breakdown of tritium incorporated into Saccharomyces cerevisiae yeast cells. IV. The lethal and mutagenic effects and the nature of the mutations induced by tritium breakdown in the 5th position of cytosine].

We have studied in lethal and mutagenic effects and the nature of mutations induced by 3H decays in the 5-th position of cytosine (5-3H-C). The lethal efficiency was determined as alpha 1 = (10.3 +/- 6.7) x 10(-3) decay-1 or alpha 1 = (12.9 +/- 9.4) x 10(-5) rad-1 and the mutagen efficiency for ade1, ade2 genes -- as alpha m = (4.3 +/- 2.3) x 10(-7) decay-1 or alpha m = (5.4 +/- 2.9) x 10(-9) rad-1. For ade2 gene the spectrum of mutations induced by 5-3H-C was as follows: 1% of frameshifts and 99% of base pair substitutions -- 9% of transversions, 3% of AT leads to GC transitions and 87% of GC leads to AT transitions. Our results establish the 5-3H-C as one of the most effective and specific mutagens reported so far for yeast. According to the scheme of Krasin with coworkers, the final product of 3H decay in the 5-th position of cytosine is uracil. Our calculations show that more than 90% of uracil residues are removed from the yeast genome by cell repair systems.

Cytosine↗