The distributions of 210Po and 210Pb in the intermediate layer (400–2000 m) of the northwestern North Pacific were determined to elucidate the export flux of
particulate matter. 210Po generally showed depletion relative to 210Pb in the intermediate layer, suggesting that 210Po was scavenged by particles. Because the removal rate constants of 210Po in the western region were higher than those in the eastern region and this trend coincided with that of the particle fluxes
in the surface layer, the export production in the surface layer was assumed to influence the particle flux in the intermediate
layer of the northwestern North Pacific.
Authors:T. Nakanishi, M. Kusakabe, T. Aono, and M. Yamada
A technique to determine concentrations of 32P, 33P and 7Be in dissolved and particulate forms, in the upper ocean was developed. By using a large volume in situ filtration and concentration
system (LV-FiCS), several tons of seawater at different depths were filtered concurrently through two kinds of filters. The
dissolved radionuclides were concentrated onto adsorbents in the LV-FiCS. The radionuclides obtained were further purified
by precipitation and ion-exchange chromatography, and quantified by gamma-spectrometry and ultra-low level liquid scintillation
counter measurements. The technique was used with good results in a coastal area of Ibaraki, Japan.
Authors:T. Sakai, M. Aoyama, T. Kusakabe, M. Tsuda, and H. Satake
Gonadotropin-releasing hormone (GnRH) is a ten-amino acid peptide hormone that plays pivotal roles in reproduction in vertebrates and octopus. Recently, six GnRH forms (t-GnRH-3-8) and four GnRH receptor subtypes (Ci-GnRHR-1-4) were identified in the protochordate,
. In this study, we show the functional modulation of Ci-GnRHR-1 via heterodimerization with the orphan receptor subtype, Ci-GnRHR-4. The dimerization between Ci-GnRHR-1 and R-4 was detected by co-immunoprecipitation and immunoblot analysis. Binding assays confirmed the binding of t-GnRHs to Ci-GnRHR-1 but not to R-4, and verified no alternation in ligand-binding affinity between Ci-GnRHR-1 homodimer and Ci-GnRHR1&4 heterodimer. The heterodimer was found to stimulate the elevation of intracellular calcium, time-extension of ERK phosphorylation, and up-regulation of cell proliferation, all in a ligand specific manner, compared with the Ci-GnRHR-1 homodimer. In combination, these results indicated that Ci-GnRHR-4 is not an inactive receptor, but a modulatory factor for Ci-GnRHR-1 in
Authors:J. Zheng, M. Yamada, T. Aono, and M. Kusakabe
From the viewpoint of environmental radioactivity monitoring, the determination of uranium and its isotope ratio is important
for identifying and assessing the environmental impact of any unexpected release from nuclear facilities. In this work, a
survey was conducted to determine 238U concentrations and 235U/238U atom ratios in coastal waters off Rokkasho Village, Aomori, Japan, where several uranium-related nuclear facilities have
been operating since 1992, and a newly constructed nuclear fuel reprocessing plant is scheduled to be commissioned in 2006.
Seawater samples were analyzed directly after a 10-fold dilution using isotope dilution sector-field ICP-MS. Based on the
results, we concluded that there is no observable uranium contamination in the investigated sites. In addition, for the first
time, a correlation between uranium concentration and salinity was established in coastal waters using the SF-ICP-MS technique.
Authors:A. Okubo, J. Zheng, M. Yamada, T. Aono, T. Nakanishi, H. Kaeriyama, and M. Kusakabe
An analytical method for the determination of 239Pu and 240Pu in marine particle samples by sector field high-resolution ICP-MS was developed. The method was applied for large and small
particle samples (particle diameter: >70 μm and 1–70 μm, respectively, collected with a large volume in situ filtration and
concentration system at different depths in the water column off Rokkaho, Japan, where the spent nuclear fuel reprocessing
plant of Japan Nuclear Fuel Ltd. has started test operation since March 2006.