Quantitative variations in ovarian follicles of female Sprague Dawley rats after exposure to low dose gamma radiation

In the present experiment, an attempt was made to assess the genetic risk of low dose radiations in mammals. For this purpose female Sprague Dawley rats, 11-12 weeks old, were irradiated with whole body Co 60 gamma rays in three fractionated doses of 0.10 Gy (cumulative dose 0.30 Gy) given at an interval of one month at two different dose-rates (0.00368 Gy/min. and 0.0589 Gy/min.). Ovaries were studied for quantitative evaluation of follicles at 1, 4, 12, 28 and 52 weeks after last fractionated exposure. Quantitation revealed lower number of ovarian follicles in irradiated animals than in controls. The follicular number decreased with the advancement of time after last exposure (i.e. 2 months) and reached a peak level on 28 weeks. After that the recovery was evident but the number remained below 25% of total follicles even at 52 weeks autopsy interval, which indicated an irreversible damage in ovarian tissue. Primary follicles were found to be the most radiosensitive among the various types of follicles. The highest loss in these follicles was noted at 12 weeks after exposure with the high dose-rate, where only 10.61% of them were scored. Dose-rate exhibited an inverse relationship with the number of surviving follicles. At the higher dose-rate (0.0589 Gy / min.), depletion in the total follicular number was significantly higher than at the low dose-rate (0.00368 Gy/min.) used.

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Biological Effects of Continuous Low-Dose-Rate Irradiation in Silkworms and Mice: Growth Promotion and Tumor Transplantability

Dose-Response ◽

10.1177/1559325818811753 ◽

2018 ◽

Vol 16 (4) ◽

pp. 155932581881175 ◽

Cited By ~ 4

Author(s):

Masahiro Nakashima ◽

Chikao Sugie ◽

Zhen Wang ◽

Takuhito Kondo ◽

Yoshihiko Manabe ◽

...

Keyword(s):

Body Weight ◽

Dose Rate ◽

Low Dose ◽

Growth Promotion ◽

High Dose Rate ◽

Whole Body ◽

High Dose ◽

Silkworm Larvae ◽

Low Dose Rate ◽

Emt6 Tumor

A previous study showed that continuous low-dose-rate irradiation promoted the growth of silkworm larvae. This study aimed to confirm that finding, determine the optimal dose rate for growth promotion, and compare low- and high-dose-rate irradiation in silkworms, while also investigating the effects of the radiation-emitting sheet on growth and tumor transplantability in mice. Silkworm eggs were placed on low-dose-emitting sheets with 4 different dose rates (γ-ray rate: 1.7 -22.4 μSv/hour) or on control sheets. The other groups of silkworm larvae received single whole-body X-irradiation (0.1-50 Gy), and subsequent body weight changes were monitored. Starting at 3 weeks old, Balb/c mice were bred on the same sheets, and body weight change was measured. Seven weeks later, the mice were used to investigate the transplantability of EMT6 tumor cells cultured in vitro. The silkworms bred on the 13.4- and 22.4-μSv/hour sheets became larger than the control. Single 50-Gy irradiation suppressed the growth of silkworms. An increase in the time to EMT6 tumor development was observed in low-dose-rate-irradiated mice. This study confirmed growth promotion of silkworms by continuous low-dose radiation and demonstrated growth suppression at a high dose rate. Growth promotion was not observed in mice; further studies using higher dose-rate sheets may be warranted.

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