Influence of irrigation water intake on local increase of radiocesium activity concentration in rice plants near a water inlet

To identify the cause of the phenomenon that rice plants close to the water inlet contain relatively higher radiocesium within a paddy field plot, we conducted a field experiment by establishing experimental channel using polypropylene corrugated sheets, and sampling surface water, paddy soil and rice plants according to the distance from the water inlet in 2014 and 2015. It was found that the ¹³⁷Cs activity concentrations in both dissolved and particulate forms in paddy surface water presented a declining trend from the water inlet towards the outlet. The ¹³⁷Cs activity concentration in paddy soil in the harvesting season and those of brown rice and rice straws were highest at 1-2 m from the water inlet. Balance calculation suggests that destination of the lost ¹³⁷Cs from the surface water was likely to be adsorption of the dissolved form and sedimentation of particulate form onto the soil. The concentration of exchangeable potassium ion in paddy soil was below the recommended standard of 250 mg kg^-1 (as K₂O in dry soil) near the water inlet at the harvesting period both years．These findings suggested that the possible crucial factors to induce rice plant uptake of radiocesium near the water inlet were either (1) direct absorption of dissolved ¹³⁷Cs in surface water by rice plants, (2) absorption of ¹³⁷Cs, which was originally retained in particulate matter and released by ion exchange and/or by organic matter decomposition in combination with (3) loss of soil exchangeable potassium caused due partly to transportation of soil particles with exchangeable potassium by the rapid water flow near the water inlet and/or leaching by ion exchange onto the soil of other cations such as calcium ion flowing into the paddy field. These findings will contribute to providing possible measures for producing safe rice in highly contaminated areas in which agricultural production will resume in the near future. We propose providing a non-planting zone for the area closer than about 5 m from the water intake to avoid the occurrence of high ¹³⁷Cs concentrations in rice crops.

Deposition of fission and activation products after the Fukushima Dai-ichi nuclear power plant accident

The Great Eastern Japan Earthquake on March 11, 2011, damaged reactor cooling systems at Fukushima Dai-ichi nuclear power plant. The subsequent venting operation and hydrogen explosion resulted in a large radioactive nuclide emission from reactor containers into the environment. Here, we collected environmental samples such as soil, plant species, and water on April 10, 2011, in front of the power plant main gate as well as 35 km away in Iitate village, and observed gamma-rays with a Ge(Li) semiconductor detector. We observed activation products ((239)Np and (59)Fe) and fission products ((131)I, (134)Cs ((133)Cs), (137)Cs, (110m)Ag ((109)Ag), (132)Te, (132)I, (140)Ba, (140)La, (91)Sr, (91)Y, (95)Zr, and (95)Nb). (239)Np is the parent nuclide of (239)Pu; (59)Fe are presumably activation products of (58)Fe obtained by corrosion of cooling pipes. The results show that these activation and fission products, diffused within a month of the accident.

Nickel-63 production in copper samples exposed to the Hiroshima atomic bomb: estimation based on an excitation function obtained by neutron irradiation experiments

The upper and lower limits of the excitation function of the (63)Cu(n,p)(63)Ni reaction were experimentally determined, and the number of (63)Ni nuclei produced in copper samples exposed to atomic bomb neutrons in Hiroshima was estimated by using the experimental excitation functions and the neutron fluences given in the DS02 dosimetry system. The estimated number of (63)Ni nuclei was compared with that measured and with that calculated using the DS02 dosimetry system and the corresponding ENDF/B-VI cross section. In comparison with DS02, there is about a 60% maximum difference in (63)Ni production at the hypocenter when the experimental upper cross section values are used. The difference becomes smaller at greater distances from the hypocenter and decreases, for example, to less than 30 and 5% when using the upper and lower experimental cross sections at 1,000 m, respectively.

Excitation function for 63Cu(n,p)63Ni reaction in neutron energy range up to 15 MeV

The excitation function for the (63)Cu(n,p)(63)Ni reaction has been measured by activation method using the 4.5 MV Dynamitron accelerator of the Fast Neutron Laboratory of Tohoku University. Copper plates and hollow spherical copper shells were irradiated by neutrons of various energy up to 14.9 MeV produced by the T(p,n), D(d,n), and T(d,n) reactions. The (63)Ni produced in the irradiated copper target was chemically separated. The beta-rays emitted from the extracted (63)Ni were measured by a liquid scintillation method. The cross sections obtained were compared with the evaluated data files of JENDL-3.3, ENDF/B-VI and FENDL/A-2.0. Consequently, it is found that FENDL/A-2.0 is consistent with our experimental data in the energy range studied in this work. The effect of proton shell appeared in the excitation function obtained is also discussed.

Effect of long-term hormone replacement therapy on angiotensin-converting enzyme activity and bradykinin in postmenopausal women with essential hypertension and normotensive postmenopausal women

OBJECTIVE

Hormone replacement therapy (HRT) reduces the incidence of cardiovascular disease in postmenopausal women. Three-month short-term HRT in postmenopausal women with essential hypertension increased the plasma concentrations ofbradykinin with decreased serum angiotensin-converting enzyme (ACE) activity, which may be partially responsible for the cardioprotective effects of HRT. The objective was to determine whether 12-month long-term HRT in postmenopausal women with essential hypertension would maintain the decreased ACE activity and increased bradykinin levels and whether long-term HRT would increase the plasma bradykinin concentrations of normotensive postmenopausal women who had shown no significant changes in the 3-month HRT study, despite their decreased serum ACE activity.

DESIGN

Twenty hypertensive and 15 normotensive postmenopausal women were treated with conjugated estrogens (0.625 mg/day) and medroxyprogesterone (2.5 mg/day) for 12 months. Twenty hypertensive and 15 normotensive postmenopausal women were used as controls. The controls were not treated with HRT. Serum ACE activity and plasma bradykinin concentrations were measured at baseline and at 12 months.

RESULTS

Long-term HRT in both hypertensive and normotensive postmenopausal women significantly decreased serum ACE activity from 15.5+/-0.7 IU/L and 16.0+/-0.9 IU/L, respectively, at baseline to 13.3+/-0.5 IU/L and 14.2+/-0.9 IU/L, respectively, 12 months after the start of HRT (p < 0.05 and p < 0.05, respectively). Long-term HRT in both hypertensive and normotensive postmenopausal women also significantly increased plasma bradykinin concentrations from 22.1+/-4.4 pg/mL and 19.2+/-3.0 pg/mL, respectively, at baseline to 86.7+/-21.2 pg/mL and 73.5+/-23.0 pg/mL, respectively, 12 months after the start of HRT (p < 0.01 and p < 0.05, respectively). No significant changes in serum ACE activity or plasma bradykinin concentrations were observed in the control groups.

CONCLUSIONS

Long-term HRT in hypertensive and normotensive postmenopausal women decreases their serum ACE activity and increases their plasma bradykinin concentrations. Thus, maintenance of elevated bradykinin with decreased serum ACE activity by HRT may be useful in reducing the risk of cardiovascular disease in both hypertensive and normotensive postmenopausal women.

A sub-boiling distillation method for the preparation of low carbon content water from urine samples for tritium measurement by liquid scintillation counting

A new preparation method was developed for obtaining low carbon content water from urine samples for the measurement of tritium by a liquid scintillation counter. The method uses a simple and convenient subboiling distillation bottle. Many urine samples have been purified by this method and the change of tritium level in a tritium-handling radiation-worker was observed.

A method to detect low-level 63Ni activity for estimating fast neutron fluence from the Hiroshima atomic bomb

The Hiroshima and Nagasaki atomic bombs resulted in the worst reported exposure of radiation to the human body. The data of survivors have provided the basis for the risk estimation for ionizing radiation, and thus are widely used as the basis of radiation safety. In this report we have studied a new method to detect the low-level 63Ni activity in copper samples in order to estimate the fast neutron fluence from the Hiroshima atomic bomb. Only 0.8 x 10(-3) Bq g(-1) of 63Ni is expected to be produced by the atomic bomb in a copper sample with the 63Cu(n, p)63Ni reaction at a distance of 500 m from the hypocenter. Our method has the required level of sensitivity for determination of the fast neutron fluence out to distances of at least 500 m, and perhaps as far as 1,000 m. We have already investigated and collected some bomb-irradiated copper samples for further study.

[Solid scintillator "Ready Cap" for measurement with a liquid scintillation counter--spectra and counting efficiencies for 15 different radionuclides]

"Ready Cap", a small plastic container coated with solid scintillator has recently been introduced (Beckman Instruments, Inc.). Pulse height spectra and counting efficiencies obtained with a liquid scintillator and Ready Cap using a liquid scintillator counter were compared for 15 different radionuclides. For radionuclides emitting low-energy beta-rays or characteristic X-rays, the spectra for Ready Cap shifted toward the higher energy side compared with the spectra for the liquid scintillator. This tendency was reversed for the nuclides emitting higher-energy beta-radiations (36Cl and 32P). Generally, counting efficiencies both in Ready Cap and in liquid scintillator increased with increase in the energy of beta- or X-rays. For some nuclides, Ready Cap gave higher counting efficiencies and for others it gave lower values than in the liquid scintillator. However, the differences were not large within each nuclide. The use of Ready Cap is recommended for measurements of radionuclides when liquid scintillation cocktails have no means of waste disposal under the present Japanese radioisotope regulation.

Detection and properties of A-factor-binding protein from Streptomyces griseus

The optically active form of tritium-labeled A-factor (2-isocapryloyl-3R-hydroxymethyl-gamma-butyrolactone), a pleiotropic autoregulator responsible for streptomycin production, streptomycin resistance, and sporulation in Streptomyces griseus, was chemically synthesized. By using the radioactive A-factor, a binding protein for A-factor was detected in the cytoplasmic fraction of this organism. The binding protein had an apparent molecular weight of approximately 26,000, as determined by gel filtration. Scatchard analysis suggested that A-factor bound the protein in the molar ratio of 1:1 with a binding constant, Kd, of 0.7 nM. The number of the binding protein was roughly estimated to be 37 per genome. The "inducing material" virginiae butanolide C (VB-C), which has a structure very similar to that of A-factor and is essential for virginiamycin production in Streptomyces virginiae, did not inhibit binding. In addition, no protein capable of specifically binding 3H-labeled VB-C was found in S. griseus. Together with the observation that VB-C had almost no biological activity on the restoration of streptomycin production or sporulation in an A-factor-deficient mutant of S. griseus, these results indicated that the binding protein had a strict ligand specificity. Examination for an A-factor-binding protein in Streptomyces coelicolor A3(2) and Streptomyces lividans showed the absence of any specifically binding protein.

Distribution of tritiated tetrodotoxin administered intraperitoneally to pufferfish

Tetrodotoxin was recoil-tritiated by the 3He(n,p)3H reaction and purified by gel filtration. The [3H]tetrodotoxin gave only one spot in both cellulose acetate strip electrophoresis and thin layer chromatography. The specific toxicity of tetrodotoxin did not decrease during the recoil tritiation and the [3H]tetrodotoxin showed a specific radioactivity of 25 x 10(-6) Ci/mmole. In spite of the low specific radioactivity, the [3H]tetrodotoxin was able to be used to investigate the anatomical distribution of tetrodotoxin in pufferfish. When intraperitoneally injected into 'torafugu' puffer, [3H]tetrodotoxin accumulated in most tissues, the level being highest in the skin, followed by the liver, intestines and muscle. With time, the [3H]tetrodotoxin radioactivity level in the injected pufferfish decreased in most tissues, except for skin and gallbladder. Based on these results, the metabolism of tetrodotoxin in pufferfish is discussed.