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1-6 of 6
John F. McGregor
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Journal Articles
Journal:
Radiation Research
Radiation Research (1975) 61 (3): 519–525.
Published: 01 March 1975
Abstract
Exposure of sperm of the rainbow trout to ionizing radiation causes, in addition to major eye anomalies, gross malformations of the bodies of embryos. At the lower doses the observed yields of body malformations exceed those for the unirradiated controls but the difference falls short of statistical significance. At the higher doses the radiation effect is large and highly significant. Unlike the eye malformations, which increase in frequency in direct proportion with the radiation dose, the body malformations exhibit a disproportionate increase with increasing dose. Some of the malformations of fish embryos affect more than one part of the body, and in this respect resemble the multiple malformations and syndromes of human infants.
Journal Articles
Journal:
Radiation Research
Radiation Research (1972) 52 (3): 536–544.
Published: 01 December 1972
Abstract
Decreased mortality has been observed among embryos of rainbow trout as a result of exposure of the sperm to 25 and 50 rad of gamma rays, whereas higher doses of 200 and 400 rad result in increased mortality. The "beneficial" effect of the lower doses is more apparent during the early and intermediate stages of embryo development and the harmful effect of the higher doses is expressed mainly during the intermediate and later stages. Both effects appear to be due to hereditary changes since they each persist over many cell generations. The findings are of theoretical interest in relation to the shape of the lower end of the dose-effect curve for genetic changes, and of practical importance bearing on estimates of radiation-induced prenatal mortality in man.
Journal Articles
Journal:
Radiation Research
Radiation Research (1972) 51 (2): 402–409.
Published: 01 August 1972
Abstract
An observed "beneficial" effect from low doses of radiation is described. When mature sperm of rainbow trout were exposed to 25 and 50 rad, the ratios of eggs with embryos to eggs without embryos were significantly increased by approximately 35 and 40%, respectively, as compared with the control. With the higher dose of 400 rad to the sperm the effect was unconditionally "harmful" and the yield of embryos was greatly reduced. It is suggested that the beneficial effect may be due to changes in the protein of the sperm and the harmful effect to changes in the DNA.
Journal Articles
Journal:
Radiation Research
Radiation Research (1972) 49 (1): 155–169.
Published: 01 January 1972
Abstract
Low doses of ionizing radiation in the range 25-400 rad to mature trout sperm have resulted in major eye malformations in the immediate off-spring, with frequencies which fit a linear regression curve. A weighted mean of the responses per unit dose indicates that approximately 54 rad would be required to double the rate of malformations observed in the controls. It is believed that the major eye malformations observed in the present work are due predominantly to chromosome aberrations induced in the mature sperm. The reasons for the interpretation and the relevance of the observed linearity to the problem of protecting man against radiation-induced genetic injury are discussed.
Journal Articles
Journal:
Radiation Research
Radiation Research (1971) 47 (2): 450–460.
Published: 01 August 1971
Abstract
Studies to assess the importance of radiation-induced genetic damage, of kinds that persist following the cessation of repeated ancestral irradiations, imply that the obviously harmful expressions occur only prior to weaning and are not detected in young adults. Reductions in fertile matings and litter size, and an increase in postnatal mortality up to the time of weaning, were observed in a population of rats after 13 generations of parental irradiation and a 14th generation without irradiation. These findings indicate the persistence of induced genetic changes despite a substantial rate of elimination in each generation. Among young adult rats, however, the only observed effect was a small but significant decrease in the body weights of the males. This change is not believed to be indicative of any detriment to the adult animals because the opposite effect was found in adults of the preceding generation. It seems unlikely that both kinds of change, at least to this degree, would be harmful. It is concluded that eliminations of induced genetic changes in mammals take place through deaths that occur mainly during the early part of the life of the organism.
Journal Articles
Journal:
Radiation Research
Radiation Research (1968) 35 (2): 282–300.
Published: 01 August 1968
Abstract
Frequencies of major malformations of the eyes and the bodies of trout embryos were studied following exposures of embryos to 10, 100, and 1000 rads of x-rays at early cleavage, late cleavage, blastula, and germ ring stages. A sham-irradiated control was carried out for each stage of irradiation. Contrary to evidence from mammalian studies, embryos of trout developed a high incidence of major malformations when irradiated prior to active organogenesis, there being a peak effect of 40% eye malformations and 35% body malformations at late cleavage. The apparent lack of quantitatively similar responses in mammals must be due to loss of potentially malformed individuals to study through selective failures to implant or through postimplantation deaths. A curious finding was that the various kinds of malformations were apparently identical to those previously observed as a consequence of irradiations of sperm and eggs. Thus, the same vulnerable processes must be upset in similar ways both by exposures of the embryos to external agents such as radiations and by influences that are essentially internal to the embryos such as the altered hereditary material transmitted from irradiated sperm or eggs.