[en] The activities of seven kinds of apples produced in Aomori prefecture were measured with a high pure Ge detector set in a 15 cm-thick lead shield. The activities of ⁴⁰K were detected in all samples, but an artificial radioactive nuclide was not detected. The slices of an apple were contacted to an imaging plate for 15 days in a 15 cm-thick lead shield and cross sectional activity distributions were measured. By using the distribution map, the activities of skin, flesh and lead portion of an apple 'Ohrin' were calculated to 0.041, 0.032 and 0.046 Bq/g, respectively. This measuring system will be used for the activity estimations of the farm products, specially apples, because of that many atomic institutions are in operation and in the planning stage on Aomori prefecture. (author)

[en] Radiation-induced intestinal injury is a common complication in radiotherapy for the cancer located in abdomen or pelvis. However, there is no effective treatment for radiation-induced intestinal injury now. It is therefore important to develop new treatments for radiation-induced intestinal injury. In this study, we investigated whether embryonic stem (ES) cells could be transplanted directly into the radiation-damaged intestine and could colonize and differentiate into the intestinal epithelial cells. The intestines of female nude mice (ICR nu/nu) were irradiated at a single dose of 30 Gy, and were immediately transplanted with male 129/Sv-derived ES cells into the wall of the irradiated intestine by direct injection. The intestine was removed on days 13 to 27 after transplantation. The Y-chromosome DNA of transplanted ES cells in the irradiated intestine was determined by polymerase chain reaction. Colonization and differentiation of transplanted ES cells in the irradiated intestine were analyzed by histological and immunohistochemical methods with antibodies against stage-specific embryonic antigen-1, α-smooth muscle actin and cytokeratin AE1/AE3. The cells of donor origin were identified in the intestine of irradiated mice, and intestinal crypt-like structures were observed on day 13 after transplantation. Importantly, we observed that ES cells could differentiate into epithelial cells in the submucosa of irradiated intestine on day 13 and 27 after transplantation. These results suggest that transplanted ES cells could colonize and differentiate in the intestinal intestine. Such a new approach for damaged intestine with transplanted stem cells would be promising. (author)

[en] Tumor hypoxia and angiogenesis associated with malignant progression have been studied widely. The efficacy of angiogenesis inhibition combined with radiotherapy has been demonstrated in cancer treatment. Here, we studied the effect of hypoxia and angiogenesis inhibition on radiation-induced late rectal injury. The rectum of C57BL/6N mice was irradiated locally with a single dose of 25 Gy. Radiation-induced histological changes were examined at 90 days after irradiation by hematoxylin-eosin (H.E.) staining and azan staining. Pimonidazole was administered and its distribution was assayed by immunohistochemistry staining. Expression of transforming growth factor β1 (TGF-β1), hypoxia-inducible factor-1α (HIF-1α) and vascular endothelial growth factor (VEGF) was assessed on the fibrotic region using realtime polymerase chain reaction (PCR) and immunohistochemistry. In addition, the effects of TGF-β, VEGF and HIF-1α on radiation-induced injury were investigated by the administration of neutralizing antibody of TGF-β, antibody of VEGF or YC-1 (3-(5'-hydroxymethyl-2'-furyl)-1-benzylindazole) which was developed as an agent for inhibiting HIF-1 expression after irradiation respectively. Fibrosis and uptake of pimonidazole were found 90 days after irradiation. The expression of TGF-β1, HIF-1α and VEGF significantly increased with the formation of fibrosis induced by irradiation compared with unirradiated controls. In addition, treatment of neutralizing antibody of TGF-β, antibody of VEGF or YC-1 reduced the development of radiation-induced injury. Our results suggested that radiation-induced hypoxia may play an important role in late rectal injury. Although the inhibition of HIF-1α and VEGF reduced the radiation induced late injury, the precise mechanism is still unclear. (author)

[en] Irradiation before tooth extraction delays wound healing in the alveolar socket. This study examined the influences of local and whole body irradiation before tooth extraction on appearance of osteoblasts in the alveolar bone of rat maxillary first molars because bone formation is observed at the initial phase of wound healing. Several osteoblasts were generated 3 days after tooth extraction, and the number of cells increased day by day. Morphological studies showed there were little differences between local irradiation and non-irradiated controls. In contrast, the extraction wound in the whole body irradiation group showed delayed healing, and there was poor granulation tissue and very few osteoblasts at the bottom of the socket. An ultrastructural study showed that the osteoblasts in the extraction socket of whole body irradiation rats were smaller, and had poorly developed organelles. Injection of bone marrow cells to whole body-irradiated animals immediately after tooth extraction partially restored the number of osteoblasts. New periosteal bone formations outside of sockets showed little delay in the whole body irradiation group. These findings suggest that bone formation in the wound healing of extraction socket requires bone marrow cells from hematopoietic organs such as the bone marrow as well as local sources around the alveolar socket, during the initial phase of wound healing. (author)

[en] Tumor hypoxia and angiogenesis have been studied extensively. However, the relation between normal tissue injury and hypoxia is still unclear. In this study, we investigated the effect of hypoxia on radiation-induced late rectal injury in mice. The rectum of C57BL/6N mice was irradiated locally with a single dose of 25 Gy and the following experiments were performed including hematoxylin-eosin (H.E.) staining, azan staining, real-time polymerase chain reaction (PCR), immunohistochemistry and immunofluorescence. Radiation-induced fibrotic changes were observed from 14 days and reached the peak 30 days after irradiation. The expression of transforming growth factor β1 (TGF-β1), hypoxia-inducible factor-1α (HIF-1α), vascular endothelial growth factor (VEGF) and endothelial cell marker CD31 increased significantly with the formation of fibrosis induced by irradiation compared with unirradiated control. In addition, the maximum expression of TGF-β1, HIF-1α and VEGF was found at 14, 30 and 90 days after irradiation, respectively. The temporal changes of cytokines were consistent with the dynamic change of fibrosis. Our data suggests that late normal tissue injury involved various cytokines including hypoxia-induced angiogenic cytokines. These results may have important implications in the understanding of radiation-induced late normal tissue injury. (author)

[en] To determine the feasibility of generating electric power from X-rays and gamma rays emitted by nuclear waste, an electric power generation module was first designed and tested with a diagnostic X-ray tube. This module consisted of an ultrahigh-speed and extremely thick intensifying screen and an amorphous silicon photovoltaic cell. Then, the circuit current and the load voltage induced by X-rays were simultaneously measured by a variable-load method. A maximum power of 2.7 mW was obtained at a tube voltage of 120 kV, a tube current of 400 mA, and an irradiation time of 0.2 s with a distance of 0.33 m between the focal point of the X-ray tube and the power generation module. An analysis of the absorbed energy determined that the efficiency of energy conversion was 1.4%. Next, these results were extrapolated in order to determine the amount of power generated for a case in which the radioactive source is either spent nuclear fuel or high-level waste. Such a system can continuously generate 38 W of electric power. The potential of this new method that enables electricity generation by X-rays and gamma rays is significant considering the vast amounts of spent nuclear fuel and high-level waste in storage around the world. (author)

[en] The effective treatments of radiation-induced intestinal injury are currently unavailable. Developing new treatments for radiation-induced intestinal injury is thus important. The present study investigated whether transplantation of mesenchymal stem cells (MSCs) is able to prevent radiation-induced intestinal injury. Intestines of female nude mice (ICR nu/nu) were irradiated at a single dose of 30 Gy. Transplantation of male MSCs (C57BL/6) was then immediately performed into the walls of irradiated intestine by direct injection for the irradiation+MSCs group. Mice were weighed daily and survival was recorded for 13 days after irradiation. From 13 to 27 days after irradiation, intestines of mice were obtained in order to assay histological changes by staining with hematoxylin-eosin and Masson trichrome. Mean body weight of the irradiation+MSC group was significantly higher than that of the irradiation-only group from 8 days after irradiation. In addition, survival rates were significantly higher in the irradiation+MSC group than for the irradiation-only group from 5 days after irradiation. Histological observation revealed that intestines of irradiation+MSC-transplanted mice were thick in the submucosal and muscle layers, and had almost fully recovered from radiation-induced intestinal injury at day 27. Specifically, ulcerated areas in the intestines of the irradiation+MSC-transplanted mice were smaller by 13 days after irradiation and were fewer in numbers at 27 days when compared with the irradiation-only group. Our results suggest that transplanted MSCs may play an important role in preventing radiation-induced injury and may offer a novel method to treat radiation-induced intestinal injury. (author)

[en] The current limits for radioactive materials (sum of ¹³⁴Cs and ¹³⁷Cs) in food were set taking into account the radiation dose from ¹³⁴Cs, ¹³⁷Cs, ⁹⁰Sr, ¹⁰⁶Ru and Pu. Although the limits were based on the concentration ratio of radionuclides in soil etc., it was assumed that radiation doses from radioactive caesium (¹³⁴Cs+¹³⁷Cs) were equal to that from other radionuclides in regard to sea foods. In this study, we evaluate the contribution to the radiation dose from ¹³⁴Cs+¹³⁷Cs and others. The contribution of radionuclides other than radioactive caesium was less than that assumed when the limits were set. (author)

[en] Most radiation protection items made from modern lead contain ²¹⁰Pb. This study estimated the impact on eye lens of radiation derived from the ²¹⁰Pb in three types of radiation protection glasses. The counts from the glasses were measured using a Geiger-Mueller survey meter. The net count rate was 92 ± 1 cpm at a distance of 0.5 cm for one type of glasses. Additionally, we conducted a qualitative γ-ray spectrum analysis using a high-purity germanium semiconductor detector. The absorbed dose in the eye lens was related to ²¹⁰Pb and its daughter radionuclide, ²¹⁰Bi; this dose was calculated by applying dose conversion coefficients provided by the International Commission on Radiological Protection. The absorbed dose rate in eye lens was conservatively calculated to be on the order of 10 nGy/h for the type of glasses containing the most ²¹⁰Pb. The dose from β-rays accounted for >99%. In addition, we investigated the dose-reduction effect using a thin acrylic plate. The count rate approximately decreased to background level by inserting a plate with a thickness of 1 mm. We conclude that the impact of ²¹⁰Pb contained in radiation protection glasses is negligibly small, particularly considering the usefulness of the significant external exposure reduction. (authors)