No abstract available

No abstract available

[en] The biosynthetic mechanism of silk fibroin in silkworms, Bombyx mori, is unique because this fibrous protein composed mainly of glycine, alanine and serine is produced very rapidly in large quantity in the posterior silk glands. It is very meaningful to investigate into the biosynthesis of silk protein under nondestructive condition by in vivo NMR and C-13 labeling techniques. The sugar metabolism related to the production of silk fibroin was analyzed by monitoring the change in the C-13 labeled peaks in the NMR spectra for silkworms. In this paper, the monitoring of the 2-(C-13) glycine metabolism in Bombyx mori by the C-13 NMR in vivo is reported. In particular, the in vivo transport of glycine from the midgut to the posterior silk gland was measured, and the rate constants were determined with the course of the peak intensity in the C-13 NMR spectra. It is possible to discuss quantitatively the in vivo production of silk fibroin with these rate constants. The experiment and the results are reported. The in vivo C-13 NMR spectra of a 5 day old, 5th instar larva of Bombyx mori after the oral administration of 2-(C-13) glycine are shown. The significant increase of the peak intensity occurred. (K.I.)

No abstract available

No abstract available

[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)