ACTIVITY CONCENTRATIONS OF RADIOCAESIUM, 90SR AND 129I IN AGRICULTURAL CROPS COLLECTED FROM FUKUSHIMA AND REFERENCE AREAS IN JAPAN, AND INTERNAL RADIATION DOSES.

Significant quantities of radionuclides were released into the environment due to the 2011 TEPCO's FDNPS accident. Radiocaesium is the most important radionuclide for assessment of radiation dose, and small amounts of 90Sr and very long-lived radionuclide of 129I were also released into the environment. Spinach, potato and brown rice were collected from Fukushima, neighboring prefectures and reference areas of negligible deposition in 2018 and 2019. The activity concentration of 137Cs in crops in Hamadori (coastal side) was relatively higher than other areas. The activity concentration of 90Sr in the crops showed a similar range among four areas in Fukushima, and they were similar level of those collected throughout Japan. The activity concentration of 129I in the crops collected from Hamadori was higher than other Fukushima areas. However, the activity ratio of 129I/137Cs was lower by five to seven orders of magnitude. Internal radiation doses of radiocaesium for adult males from ingestion of local crops collected from Hamadori were 0.0046 mSv, and that of 129I were 0.00000045 mSv in 2019.

EFFECT ON MICROBIAL PRODUCTS ON CAESIUM ELUTION BEHAVIOUR FROM CLAY MINERALS.

Some microorganisms in the environment make siderophores, which are low molecular chelators, to take up minerals from soil. Eleven bacteria were separated from the root of white clover by chlome azrol S (CAS) assay. Each bacterium was incubated in casamino acid (CAA) culture, and siderophores in CAA culture were purified. These extractions were applied to biotite or vermiculite spiked with Cs. From each clay mineral, 57.1-72.8% (5100 ppm), 55.6-63.8% (920 ppm) and 48.6-54.3% (2300 ppm), 31.6-34.4% (520 ppm) was eluted, respectively. To understand elution behaviour, Cs desorption ratio of each clay was measured every 30 min. The results indicate Cs elution was occurred quickly.

Application of a CZT detector to in situ environmental radioactivity measurement in the Fukushima area.

Instead of conventional Ge semiconductor detectors and NaI(Tl) scintillation spectrometers, an application of a CdZnTe semiconductor (CZT) whose crystal has the dimension of 1 cm cubic to the in situ environmental radioactivity measurement was attempted in deeply affected areas in Fukushima region. Results of deposition density on soil for (134)Cs/(137)Cs obtained seemed consistent, comparing obtained results with those measured by the Japanese government.

Isotopic investigations for the origin of relic from the Matsusaki site, Japan.

We measured the environmental radioactivity and isotope ratio, (87)Sr/(86)Sr ratio, (234)U/(238)U, delta(13)C, and (228)Ra/(226)Ra activity ratio, of adhesion that adhered to a wooden tubing vessel obtained from the Matsusaki site, one of the salt-production sites where Moshio is manufactured, in Aichi Prefecture, Japan. The environmental radioactivity and isotope ratio verified that the adhesion originated from the seaweed and/or sea grass.

Spatial distribution of soil contamination by 137Cs and 239,240Pu in the village of Dolon near the Semipalatinsk nuclear test site: new information on traces of the radioactive plume from the 29 August 1949 nuclear test.

The village of Dolon located about 60 km northeast from the border of the Semipalatinsk Nuclear Test Site in Kazakhstan is one of the most affected inhabited settlements as a result of nuclear tests by the former USSR. Radioactive contamination in Dolon was mainly caused by the first USSR nuclear test on 29 August 1949. As part of the efforts to reconstruct the radiation dose in Dolon, Cs and Pu in soil samples collected from 26 locations in the vicinity of and within the village were measured to determine the width and position of the center-axis of the radioactive plume that passed over the village from the 29 August 1949 nuclear test. Measured soil inventories of Cs and Pu were plotted as a function of the distance from the supposed center-axis of the plume. A clear shape similar to a Gaussian function was observed in their spatial distributions with each maximum around a center-axis. It was suggested that the plume width that contaminated Dolon was at most 10 km and the real center-axis of the radioactive plume passed 0.7-0.9 km north of the supposed centerline. A peak-like shape with the maximum near the center-axis was also observed in the spatial distribution of the Pu/Cs activity ratio, which may reflect the fractionation effect between Pu and Cs during the deposition process. These results support the recently reported results. The data obtained here will provide useful information on the efforts to estimate radiation dose in Dolon as reliably as possible. Health Phys. 94(4):328-337; 2008.

A preliminary study on the use of (10)Be in forensic radioecology of nuclear explosion sites.

Cosmogenic (10)Be, known for use in dating studies, unexpectedly is also produced in nuclear explosions with an atom yield almost comparable to (e.g.) (137)Cs. There are major production routes via (13)C(n, alpha)(10)Be, from carbon dioxide in the air and the organic explosives, possibly from other bomb components and to a minor extent from the direct fission reaction. Although the detailed bomb components are speculative, carbon was certainly present in the explosives and an order of magnitude calculation is possible. The (n, alpha) cross-section was determined by irradiating graphite in a nuclear reactor, and the resulting (10)Be estimated by Accelerator Mass Spectrometry (AMS) giving a cross-section of 34.5+/-0.7mb (6-9.3MeV), within error of previous work. (10)Be should have applications in forensic radioecology. Historical environmental samples from Hiroshima, and Semipalatinsk (Kazakhstan) showed two to threefold (10)Be excesses compared with the background cosmogenic levels. A sample from Lake Chagan (a Soviet nuclear cratering experiment) contained more (10)Be than previously reported soils. (10)Be may be useful for measuring the fast neutron dose near the Hiroshima bomb hypocenter at neutron energies double those previously available.

Deposition of tritiated water vapour to water surface in an outdoor field.

Deposition of tritiated water vapour in the atmosphere to a water surface was studied in an outdoor field, where elevated concentrations of tritiated water vapour existed in the atmosphere over twelve days. Exchange velocities of tritiated water vapour between air and water were evaluated from tritium concentrations in air and water obtained in the field experiment. It was found that the average of outdoor exchange velocities was about three times greater than that observed in a nuclear reactor room previously. Relationships between the outdoor exchange velocities and meteorological conditions were analysed to derive a multiple correlation equation. The wind speed was strongly correlated with the exchange velocity and the air temperature appeared to have an enhancing effect on the velocity. These observations were supported by a follow-up experiment conducted on a laboratory scale.

Mineralized nodule formation by cultures of human dental pulp-derived fibroblasts.

Pulp fibroblasts were isolated from human deciduous and supernumerary teeth and cultured in vitro. With continued culture in normal tissue-culture medium, six pulp fibroblast strains formed cell nodules after 10-15 days. By electron microscopy the nodules had matrix vesicles, and needle-shaped crystals associated with a dense network of collagen fibrils. The crystalline material exhibited a pattern consistent with hydroxyapatite when nodules were examined by X-ray diffractometry. Furthermore, the cells showed high levels of alkaline phosphatase activity, which could be increased more than seven-fold by the addition of 1,25(OH)2D3 (5 x 10(-9)-5 x 10(-8) M). In addition to the production of type I collagen, these cells also synthesized fibronectin and osteonectin. The formation of mineralized tissue nodules by pulp cells in vitro provides a useful system for study of the pathological calcification of pulp tissues.

Characterization of leukocyte chemotactic activity of bacteriocin from Streptococcus mutans Rm-10.

Bacteriocins have several biological activities in addition to their antibacterial effect. We investigated the chemotactic properties and mode of action of purified streptococcal bacteriocin. Bacteriocin purified from a culture supernatant of Streptococcus mutans (S. mutans) Rm-10 induced chemotaxis of human polymorphonuclear leukocytes and monocytes. Following purification, leukocyte migration appeared in one bacteriocin fraction, and this migration was dependent on the concentration gradient in dilution ranges from 1/960 to 1/15. Chemotactic activity of the bacteriocin was heat labile and trypsin sensitive. Moreover, preincubation of bacteriocin with varying dilutions of its antiserum prepared in rabbits resulted in a significant loss of the chemotactic activity.

[Some phenolic compounds stimulate the proliferation of human pulpal fibroblasts].

Phenolic compounds are widely used in dental clinics especially for the treatment of inflammatory responses of the dental pulp. However, the role of these agents in the repair of pulpal connective tissue is unclear. In the present study, an effect has been identified in several phenolic compounds that can stimulate active proliferation of pulpal fibroblasts. Human pulpal fibroblasts (HPF) were obtained from subcultures of between 5 and 15 passages. HPF in tissue culture plates were incubated in serum-free medium with several phenolic compounds at concentrations of 10(-8) M to 10(-4) M for 4 days. After incubation, cells were fixed, stained in culture plates and the number of nuclei counted. Phenol (10(-8) M to 10(-4) M) stimulated proliferation in a quiescent population of HPF, and the number of cells increased 27-41% compared with unstimulated cells. When HPF were incubated with p-chlorophenol, guaiacol, thymol or eugenol, there was a significant activation of cell proliferation (5 to 22%). Moreover, cell viability of the HPF was not influenced at all, except in the cases of p-chlorophenol and eugenol at concentrations of 10(-4) M. These observations may contribute to an understanding of the relationship between the stimulative effects of phenolic compounds and pulpal tissue repair.

[In vitro cultivation of human pulpal fibroblast strains--permanent and deciduous teeth].

We succeeded in separating and the cultivating stable monolayer cultures of dental pulp fibroblast strains derived from permanent and deciduous human teeth. Human permanent (n = 67) and deciduous teeth (n = 26) were extracted under acupuncture anaesthesia for the correction of malocclusion. After splitting the teeth, the pulp tissues were carefully removed, placed in tissue culture flasks, and grown in Dulbecco's modified Eagle medium supplemented with 10% fetal calf serum (FCS). The human pulpal fibroblasts (HPF) of permanent teeth and deciduous teeth (DHPF) were subcultured. Both the HPF and DHPF appeared to migrate from adherent tissues within 24 to 48 hr after explanation. They proliferated in the pulp explants, and lined up in parallel rows of cells closest to the explant tissue within 7 to 10 days in all of the experimental cases. The outgrowing cells were subcultured at 1.3 x 10(4) cells/cm2 in tissue culture flasks every 4-11 days. They showed vigorous proliferation. The average number of cells in the 6-7 day cultures of HPF were 5.6 x 10(4) cells/cm2 from 3 to 16 passages. It was 4.7 x 10(4) cells/cm2 from 3 to 10 passages with DHPF. However, no difference was observed between HPF and DHPF in the amount of synthesized protein in culture flasks. Furthermore, the growth rate of DHPF was more sensitive than that of HPF to the FCS percentages of the culture media.

Macrophage-produced oxygen radical generating activities for polymorphonuclear leukocytes.

Guinea pig peritoneal macrophages were stimulated in vitro by bacterial lipopolysaccharide. After incubation, the supernatants of macrophage cultures were collected and tested for O2- production on guinea pig peritoneal polymorphonuclear leukocytes. The supernatants of macrophage cultures stimulated by lipopolysaccharide had significantly higher levels of O2- -generating activities in polymorphonuclear leukocytes, and these activities appeared in the macrophage cultures within 2 h after stimulation by lipopolysaccharide. However, the supernatants obtained from the nonstimulated cultures could not produce these activities. These activities disappeared with heating or trypsin and were not produced in macrophage cultures by incubation with cycloheximide.