Catálogo de publicaciones - libros

We used a newly developed technique that insolubilizes and visualizes K excreted from the gills to demonstrate that gill mitochondria-rich (MR) cells are responsible for K excretion in seawater-acclimated Mozambique tilapia. To achieve a better understanding of the molecular mechanism of K excretion from the gills, we identified the cDNA sequences of some candidate molecules that may be involved in K transport. Of these candidate molecules, only a renal outer medullary K channel (ROMK) exhibited markedly upregulated mRNA levels in response to a high external K concentration. We found that ROMK expressed in the apical opening of MR cells was the main molecular pathway responsible for K excretion. Using the insolubilization technique, we further demonstrated the excretion of Cs and Rb, which are known to be biochemical analogs of K, through the K transport pathway in the gills of seawater tilapia. The activation of ROMK in the gill MR cells induced by K supplementation could eliminate unnecessary biochemical analogs of K more rapidly, possibly serving as an effective countermeasure against radiocesium in aquaculture.

This study presents new findings related to radioactivity measurements in birds and other wild animals. High levels of radioactive contamination were found in the feathers of birds after the accident and most of this radioactivity was not washed out. However, there was little contamination in the new feathers produced by the same species after approximately 1 year. We discuss the possible effects of radioactivity, particularly cascade effects among wildlife in the Satoyama ecosystem. Satoyama consists of well-managed agricultural fields, grasslands, and several types of forests at a small-scale topography level. We describe our long-term monitoring approach.

Paddy soil freezes during winter in Iitate village. The frozen soil is as hard as asphalt, and local farmers can easily peel a plate of frozen soil using an agricultural machine. The radiation level in the ground surface was demonstrated to reduce from 1.28 to 0.16 μSv/h by stripping the frozen soil in field experiments. In this chapter, two remediation methods have been introduced and the collaboration between researchers, volunteers, and farmers in Iitate Village has been discussed.

We report the impact of radiocesium released by the Fukushima Daiichi nuclear power plant accident on fruit trees in the vicinity. Specifically, we discuss our findings related to the absorption and translocation of radiocesium in peach ( L. Batsch) trees because peaches are a major crop in Fukushima Prefecture.

At the time of the nuclear accident, the majority of deciduous fruit tree species had no foliage and had not entered the flowering stage. This was also the case for peach trees, although we confirmed at harvest time that radiocesium had migrated to new plant parts. One possible explanation for this is that the presence of radiocesium in the new leaves and fruits, which was not present at the time of the nuclear accident, was affected by direct radiocesium deposition on the existing above-­ground plant parts and this may have been absorbed by the tree. In the year of the accident, the root uptake of radiocesium deposited on the soil contributed very little to the overall contamination compared with absorption by the trees through the above-ground plant parts. The magnitude of radiocesium translocation from the old to new plant parts was significantly different between the year of the accident and the year after the accident. We report the findings since the Fukushima Daiichi nuclear power plant accident and speculate the pathways of radiocesium entry and release in peach trees.

High concentrations of radionuclide contamination of wild mushrooms occurred near the Fukushima Daiichi nuclear power plant and along the path of radioactive plumes. This is a serious problem for the forest ecosystem and commercial wild mushroom production. Radioactivity in wild mushrooms collected from low-level contamination forest areas throughout Japan was measured approximately 6 months after the accident. In general, the radioactivity in mushrooms did not exceed those in the neighboring forest litter. However, further accumulation of Cs is expected in mushrooms; therefore, continuous monitoring is necessary even in low-contamination areas. We also found that residual Cs radioactivity due to nuclear weapons tests, mainly in 1950s, besides fallout from the Fukushima nuclear accident still remained in soil and was accumulated by mushrooms.

A massive amount of radioactive substances, including cesium-137 (Cs), emitted from the disabled nuclear power plant has deposited on the forested areas in the northeastern region of Honshu Island, Japan after the Fukushima Daiichi nuclear power plant accident. Forests in these regions are particularly important not only for the forest products industry but also for source areas of drinking water and for residential environments. To clarify the mechanisms of diffusion and export of Cs deposited on the forested ecosystem, we initiated intensive field observations in a small catchment, including forest and farmlands, in the Kami-Oguni River catchment in the northern part of Fukushima Prefecture. The following expected major pathways of Cs diffusion and export were investigated: (1) transportation by water movement of dissolved and particulate or colloidal forms through hydrological processes and (2) diffusion through the food web in terrestrial and aquatic ecosystems of forests. Preliminary findings indicated the following: (1) most of the Cs was discharged as suspended matter, and particulate organic matter appeared to be the most important carrier of Cs. High water flow generated by storm accelerated the transportation of Cs from the forested catchments. Estimation of Cs export thus requires precise evaluation of the high flow acceleration during storm events. (2) Because litter and its detritus may form the biggest pool of Cs in the forested ecosystem, Cs diffusion occurs more rapidly through the detritus food chain than the grazing food chain. Most predators have already ingested Cs, particularly in aquatic environments. An urgent question is when and how Cs diffuses through grazing food chains and how rapidly this process occurs. To elucidate or predict these phenomena, the mechanisms of Cs release from litter and soil organic matter need to be clarified.

This study aimed to improve public knowledge on radiation risk and its management system by providing information for the consumers in order to assist in food purchase decision making. To develop the necessary information, we administered web-based questionnaires twice and conducted two rounds of focus group interviews (FGIs) involving five groups between each questionnaire. Attitude toward food from suffered areas, trust in the risk management sector, and change in the knowledge level with and without providing the information were examined in each questionnaire. FGIs were conducted to identify any insufficient or confusing point in the provided information on radiation risk. As a result, although the risk of radiocesium was not regarded as high compared with other risks in beef, the willingness to pay (WTP) for food from affected areas was lower even if the contamination was checked to be below the regulation level. Public knowledge on current radiocesium contamination in food, risk control measures such as the regulation level and inspection, and health effects of low-dose radiation exposure was limited. The developed information package is available on the website of the Research Center for Food Safety belonging to the University of Tokyo.