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M F Lyon

Publications and source records attributed to M F Lyon.

At least 127 records · Page 7Linked to original sources
PubMed1976

Dose-response data for X-ray induced translocations in spermatogonia of Rhesus monkeys.

The yields of translocations in spermatocytes after irradiation of spermatogonia of Rhesus monkeys with doses of 100, 200 or 300 rad X-rays were low, and consistent with a humped dose-response curve with a peak at about 200 rad. Such a curve would agree well with earlier results on the marmoset and man, but the yields at any dose in the Rhesus monkey were lower.

Animals↗
PubMed1975

The induction by X-rays of chromosome aberrations in male guinea-pigs, golden hamsters and rabbits. II. Properties of translocations induced in post-meiotic stages.

Translocations induced by X-rays in post-meiotic germ cells of male guinea-pigs, golden hamsters and rabbits were studied cytologically in the F1 sons of the irradiated males. The percentage of spermatocytes displaying multivalent configurations varied with the translocation, but the average percentage appeared to depend on the species: fewer quadrivalents were observed in hamster than in guinea-pig heterozygotes and most were recorded for rabbit heterozygotes. Chain quadrivalents were more abundant than ring quadrivalents at meiosis for the guinea-pig and hamster, in contrast to the mouse. Too few translocation heterozygotes were examined to determine which meiotic configuration was the more prevalent in the rabbit. In all three species, as in the mouse, translocations were found which caused male sterility, due to partial or complete failure of spermatogenesis, although most translocations caused semi-sterility. For these semi-sterile males both the frequency and time of embryonic death in the progeny appeared to be the same as in the mouse. It is concluded that similar types of chromosome aberrations are induced by X-rays in post-meiotic germ cells of male guinea-pigs, rabbits, golden hamsters and mice.

Animals↗
PubMed1975

The induction by X-rays of chromosome aberrations in male Guinea-pigs, rabbits and golden hamsters. III. Dose-response relationship after single doses of X-rays to spermatogonia.

The induction by X-rays of translocations in spermatogonia was studied by cytological means in spermatocytes derived from them. In the rabbit and guinea-pig hump shaped dose-response curves were obtained, with a linear relationship at the low doses. The shapes of the curves were similar to those reported for the mouse, except that the maximum occurred at 600-700 rad in the mouse as opposed to 300 rad in the guinea-pig and rabbit. Unlike the guinea-pig and rabbit, the golden hamster showed a hump dose-response curve without a definite peak value and with little decrease in yield at high radiation doses. Over the low dose range 100-300 rad, the slopes of the curves of translocation yield were in the order:mouse (highest), rabbit, guinea-pig and hamster. Data on sterile periods suggested that the amount of spermatogonial killing in the rabbit and guinea-pig was as great or greater than in the mouse, and that in the golden hamster it was most severe. It is suggested that the differing shapes of the dose-response curves can be explained by a lower sensitivity to translocation induction in the test species and, also especially in the golden hamster, a greater sensitivity to cell killing. The possibility of extrapolating from these data to other species is discussed.

Animals↗
PubMed1975

X-ray induced dominant lethal mutations in mature and immature oocytes of guinea-pigs and golden hamsters.

The induction of dominant lethal mutations by doses of 100-400 rad X-rays in oocytes of the guinea-pig and golden hamster was studied using criteria of embryonic mortality. For both species higher yields were obtained from mature than from immature oocytes, in contrast to results for the mouse. Data on fertility indicated that in the golden hamster, as in the mouse, immature oocytes were more sensitive to killing by X-rays than mature oocytes but that the converse was true in the guinea-pig. The dose-response relationship for mutation to dominant lethals in pre-ovulatory oocytes of guinea-pig and golden hamsters was linear, both when based on pre- and post-implantation loss and when on post-implantation loss only. The rate per unit dose was higher for the golden hamster, and the old golden hamsters were possibly slightly more sensitive than young ones. The mutation rate data for mature oocytes of the mouse, using post-implantation loss alone, also fitted a linear dose-response relationship, except that the rate per unit dose was lower than for the other two species.

Animals↗
PubMed1975

The induction by X-rays of chromosome aberrations in male Guinea-pigs and golden hamsters. IV. Dose response for spermatogonia treated with fractionated doses.

The effect of dose fractionation on the induction of translocations by 400 and 600 rad X-rays in spermatogonia of guinea-pigs and hamsters was investigated cytologically. Three types of fractionation were used, dividing the dose into (a) two equal fractions 24 h apart, (b) two equal fractions 8 weeks apart, and (c) eight or twelve equal fractions of 50 rad, at intervals of one week. The two species responded similarly throughout, but gave lower translocation yields than the mouse. The effects of the first and third types of fractionation were similar to those described previously in the mouse, and suggested that a first radiation dose modifies the spermatogonial population so that its sensitivity to a dose 24 h later is altered, and that repeated radiation doses result in development of resistance to translocation induction. After 8-week fractionation the results suggested that in guinea-pigs and hamsters the spermatogonial population had not returned to normal by 8 weeks after the first dose, whereas in the mouse normal sensitivity had returned by this time. The results, reported previously, of single doses of X-rays suggest that the spermatogonial population consists of fractionated doses in the mouse suggest that the sensitive and resistant types represent different phases of the same cell type rather than two distinct types of cell. In the guinea-pig and hamster this question remains open.

Animals↗
PubMed1975

Specific locus mutation rates after repeated small radiation doses to mouse oocytes.

When female mice were given a dose of 20 X 20 rad X-rays, the specific locus mutation rate among offspring conceived up to 7 weeks after the end of treatment was 1/39887 or 0.18-10(-7)/rad/locus, whereas when the same total dose of 200 rad was given in a single exposure the mutation rate was 9/34813 or 1.85-10(-7)/rad/locus. The lower mutation rate after the 20 X 10 rad dose was obtained whether the total or 200 rad was given over a period of 5 days or 4 weeks, and if only young conceived in the first 20 days, rather than 7 weeks, were considered. It is suggested that each 10 rad fraction had the same small effect, and hence that these results confirm and extend RUSSELL's previous finding that the dose-response relationship for specific locus muations in females is curved.

Animals↗