A convenient and nondestructive method using bio-impedance analysis to determine fish freshness during ice storage

Fish freshness can be assessed through K values, but this method has a number of limitations, including a complex procedure and destructive sampling. With the aim to develop a convenient method of assessing fish freshness, we measured the changes in K values (up to 40%) and bio-impedance (Z value; frequency 2, 5, 20, 50, 100 kHz) of ordinary muscle in fish of eight marine species, all caught in the East China Sea, during ice storage and examined their relationships. The results indicated that the K value in all fishes increased linearly with storage time, while their Z value decreased only after 24 h of storage. Moreover, after 24 h of storage and at K values of < 40%, impedance ratios at 2–100 kHz (C value, C?=?Z_{2 kHz}/Z_{100 kHz}) were significantly correlated (p ?<?0.05) with both storage time and K values in all fishes. These findings suggest that the bio-impedance ratio effectively reflects the change in ATP-related compounds of fish and that a convenient, nondestructive method using the C value can be used instead of the complicated K value measurement to assess the freshness of marine fishes after 24 h of ice storage.     

Glia-synapse interaction through Ca2+-permeable AMPA receptors in Bergmann glia

Glial cells express a variety of neurotransmitter receptors. Notably, Bergmann glial cells in the cerebellum have Ca2+-permeable alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-type glutamate receptors (AMPARs) assembled without the GluR2 subunit. To elucidate the role of these Ca2+-permeable AMPARs, we converted them into Ca2+-impermeable receptors by adenoviral-mediated delivery of the GluR2 gene. This conversion retracted the glial processes ensheathing synapses on Purkinje cell dendritic spines and retarded the removal of synaptically released glutamate. Furthermore, it caused multiple innervation of Purkinje cells by the climbing fibers. Thus, the glial Ca2+-permeable AMPARs are indispensable for proper structural and functional relations between Bergmann glia and glutamatergic synapses.     

Effect of the application of polluted wheat (Triticum aestivum L. Thell.) straw during plowing on the transfer of radiocesium from the soil to komatsuna (Brassica rapa L. var. perviridis)

Radioactive substances were released into the environment after the nuclear accident at the Fukushima Daiichi Nuclear Power Station; this led to the contamination of the soil at Fukushima Prefecture. Mixing of organic matter with soil during plowing is known to influence radiocesium (¹³⁴Cs and ¹³⁷Cs) absorption by crops. However, the effect of mixing organic matter polluted by radioactive substances during plowing on radiocesium absorption by plants is not yet known. The aim of this study was to investigate the effect on the radiocesium absorption by komatsuna (Brassica rapa L. var. perviridis) cultivated in a 45-L container containing Andosol (14,300 Bq kg^?1) or Gray Lowland soil (33,500 Bq kg^?1) mixed with polluted wheat (Triticum aestivum L. Thell.) straw (2080 Bq kg^?1). The radiocesium concentration of the plants and the soil and the amount of exchangeable radiocesium in the soil were determined using a germanium semiconductor. The transfer of radiocesium from the soil to plants decreased by 53 and 27% in Andosol and Gray Lowland soil, respectively, after the application of 10 t ha^?1 polluted wheat straw. This reduction in the level of radiocesium transfer might be attributed to potassium contained in the wheat straw, which might compete with cesium during membrane transport and thereby block the transport of cesium from the soil solution to the roots and from the roots to the shoots. Alternatively, the applied wheat straw probably absorbed radiocesium and decreased the amount of exchangeable radiocesium in the soil. Our findings suggest that the mixing of polluted wheat straw with contaminated soil might influence the absorption of radiocesium content by agricultural products. Further studies are warranted to determine the long-term effects of the application of polluted wheat straw on the rate of radiocesium transfer to crops.     

Numerical assessments of the impacts of climate change on regional groundwater systems in a paddy-dominated alluvial fan

Quantitative assessment of the impacts of climate change on groundwater levels is important for sustainable groundwater use. This study examined the Tedori River alluvial fan in Ishikawa Prefecture, Japan, where paddy fields occupy 45 % of the total area. A regional groundwater flow model simulated future groundwater levels in response to 38 climate change projections generated for each of three GCMs, using three GHG emission scenarios with the ELPIS-JP datasets. The numerical groundwater flow model consisted of a 1-D unsaturated water flow model (HYDRUS-1D) for estimating groundwater recharge and a 3-D groundwater flow model (MODFLOW). Variable parameters consisted of daily air temperature, precipitation, humidity, solar radiation, and wind speed, which influence groundwater through infiltration, evapotranspiration, snowfall, and snowmelt. Groundwater levels had both decreasing and increasing trends, depending on climate change. There were more decreasing than increasing trends, and the maximum groundwater drawdown during 2010–2090 was ~1 m. Groundwater level was most sensitive to change in rate of precipitation during the non-irrigation period. Variations of relatively low-intensity precipitation days, when daily precipitation was <10 mm, had an effect on groundwater level. These results contribute to development of adaptive and sustainable groundwater managements (e.g. land use management and pumping strategies) in the future.     

Assessment of long-term changes in nitrogen pollution load potential from sewage treatment water in the Tedori River Alluvial Fan Area, Japan

Long-term changes (1974–2007) in the nitrogen pollution load potential (NPLP) arising from sewage treatment water were assessed in the Tedori River Alluvial Fan Area of Japan. The total NPLP from sewage treatment systems (STS) during the 34 year period was 439 t (10³ kg) year⁻¹ from about 260,000 users in 1974 increasing to a peak of 793 t year⁻¹ in 1992 from about 363,000 users, and then decreasing to 676 t year⁻¹ from about 400,000 users in 2007. The NPLP outflow into the area increased from 356 t year⁻¹ in 1974 to a peak of 596 t year⁻¹ in 1985 followed by a rapid decrease to 98 t year⁻¹ in 2007. The NPLP outflow from the public STS to the Japan Sea began in 1979 and rapidly increased to 575 t year⁻¹ in 2007 from about 362,000 users. This represents 85.5% of the total NPLP. The NPLP from septic tanks in the area was 356 t year⁻¹ from about 107,000 users in 1974 gradually increasing to a peak of 587 t year⁻¹ from about 177,000 users in 1985 before rapidly decreasing to 60 t year⁻¹ from about 15,000 users in 2007. Although the current NPLP is about 98 t year⁻¹ in the study area, the average NPLP during 34 years was very different at 424 t year⁻¹. NPLP assessments affecting groundwater and closed water bodies should consider long-term processes of nitrogen pollution from STS over time periods compatible with the residence time of the receiving waters.