[en] We exposed ICR mice to low-dose (0.2 Gy) and low-dose-rate (0.7 mGy/h) -radiation (¹³⁷Cs) in the Low-dose-rate Irradiation Facility at the Radiation Health Research Institute to evaluate systemic effects of low-dose radiation. We compared the body and organ weights, number of blood cells (white and red blood cells and platelets), levels of biochemical markers in serum, and frequency of micronuclei in polychromatic erythrocytes between low-dose irradiated and nonirradiated control mice. The ICR mice irradiated with total doses of 0.2 and 2 Gy showed no changes in body and organ weights, number of blood cells (white and red blood cells), or frequency of micronuclei in the polychromatic erythrocytes of peripheral blood. However, the number of platelets (P = 0.002) and the liver weight (P < 0.01) were significantly increased in mice exposed to 0.2 and 2 Gy, respectively. These results suggest that a low-dose-rate of 0.7 mGy/h does not induce systemic damage. This dose promotes hematopoiesis in the bone marrow microenvironment and the proliferation of liver cells. In the future, the molecular biological effects of lower doses and dose rates need to be evaluated

[en] This study evaluated the effects of low dose radiation on spermatogenic cells using the morphological characteristics of sperm in the caudal epididymis of ICR mice. In this study, six abnormal sperm shapes (amorphous heads, blunt hooks, excessive hooks, two heads and tails, folded tails and short tails) were observed at eight days after γ-irradiation (¹³⁷Cs, 0, 0.2, 0.5, 1, 2 or 4 Gy) with both a high-dose-rate (0.8 Gy/min) and a low-dose-rate (0.7 mGy/hr). Fewer abnormal forms of sperm were observed in low-dose-rate irradiated mice than in mice that received a high-dose-rate irradiation (P=0.002). The ratio of the dose rate effect among low-dose-rate irradiated mice to high-dose-rate irradiated mice was approximately 0.6. In addition, sperm with blunt hooks and two heads and tails significantly increased in number after irradiation, potentially providing an endpoint marker for estimating the effects of radiation. This study suggests that low-dose-rate (0.7 mGy/hr) radiation does not damage stem spermatogonia and probably stimulates repair in damaged spermatogonial stem cells in male mice. (author)

[en] To understand how environmental effects of radiation and radionuclides from radiation facilities relate to human beings, the development of an unmanned monitoring system is required. For the reasons of that, the International Atomic Energy Agency (IAEA) suggests a method to evaluate the effects of radiation emitted from radiation facilities on marine water, freshwater, and habitats for land animals and plants on its Technical Report Series 190, 288, and 332. Recently, International Commission on Radiological Protection (ICRP) Publication No. 91 (2003) was consecutively published to protect non-human animals and plants from environmental radiation and radioactive materials. This study examined the potential usefulness of dark-striped field mice as a biological indicator of enviro-radiation and radionuclides around nuclear power plants and radioactive waste storage facilities. For the purpose, dark-striped mice were collected in regions of Korea where there are no radiation facilities. Their external morphological characters and isoenzyme patterns were observed. As a result, the most dark-striped mice scattered in Korea are Apodemus agrarius coreae

[en] It has been well known that high dose or high-dose-rate of ionizing radiation could impair DNA repair and induce cancer or genetical disorders. However, the effect of low-dose radiation is not well identified, and a number of studies are currently under way using in-vitro and in-vivo systems. this study was designed to explore whether low-dose-rate (LDR) (0.07 cGy/hr) total body irradiation could be suppress the development of thymic lymphoma in AKR/J mice. In addition, radio-sensitive genes among high- and low-dose-rate radiation exposed mice were analysis using methodology of whole genome microarray. The data from this study demonstrates that a strong reduction effect of LDR irradiation (0.07 cGy/hr) in thymic lymphoma incidence contributed to elongate life-span. The commonly expressed apoptosis (Cd5l, Fcgr3, and pycard) and immune (pycard, Lilrb3, Igh-6, Fcgr2b, and MGC60843) related genes will be a potential radio-sensitizer for ionizing radiation. F rom these experimental studies it is evident that LDR whole body irradiation could be used in the planning of cancer treatment, and other measures such could be added to further promote the efficacy of cancer radiotherapy.

[en] While a high-dose of ionizing radiation is generally harmful and causes damage to living organisms, a low-dose of radiation has been shown to be beneficial in a variety of animal models. To understand the basis for the effect of low-dose radiation in vivo, we examined the cellular and immunological changes evoked in mice exposed to low-dose radiation at very low (0.7 mGy/h) and low (3.95 mGy/h) dose rate for the total dose of 0.2 and 2 Gy, respectively. Mice exposed to low-dose radiation, either at very low- or low-dose rate, demonstrated normal range of body weight and complete blood counts. Likewise, the number and percentage of peripheral lymphocyte populations, CD4⁺ T, CD8⁺ T, B, or NK cells, stayed unchanged following irradiation. Nonetheless, the sera from these mice exhibited elevated levels of IL-3, IL-4, leptin, MCP-1, MCP-5, MIP-1α, thrombopoietin, and VEGF along with slight reduction of IL-12p70, IL-13, IL-17, and IFN-γ. This pattern of cytokine release suggests the stimulation of innate immunity facilitating myeloid differentiation and activation while suppressing pro-inflammatory responses and promoting differentiation of naive T cells into T-helper 2, not T-helper 1, types. Collectively, our data highlight the subtle changes of cytokine milieu by chronic low-dose γ-radiation, which may be associated with the functional benefits observed in various experimental models.