222Rn and 226Ra Concentrations in Spring Water and Their Dose Assessment Due to Ingestion Intake.

222Rn and 226Ra concentrations of less than a few to several thousands of Bq L-1 have been observed in several underground bodies of water around the world. Although regulations for these concentrations in water have been implemented internationally, there are currently no regulations in place in Japan. However, concentrations that exceed these internationally recognized regulatory values have also been observed in Japan. In this study, concentrations in spring water in the northern part of Japan were measured and the effective dose from intake of the water was evaluated. 222Rn concentrations were measured using a liquid scintillation counter, and 226Ra concentrations were measured using a high purity germanium detector after chemical preparation. The measured 222Rn concentrations (=12.7 ± 6.1 Bq L-1) and 226Ra concentrations (<0.019-0.022 Bq L-1) did not exceed the reference values set by international and European/American organizations. A conservative estimate of the annual effective ingestion dose of 8 µSv for 222Rn and 226Ra obtained in this study is much smaller than the estimated overall annual effective dose of 2.2 mSv from natural radiation to the Japanese population. However, this dosage accounts for 8% of the WHO individual dosing criteria of 0.1 mSv/year for drinking water.

Recovery of human mesenchymal stem cells grown on novel microcarrier coated with thermoresponsive polymer.

The cultivation of cells on microcarriers (MCs) in stirred suspension system is useful method for the large-scale culture of human mesenchymal stem cells (hMSCs) for allogenic transplantation. To harvest hMSCs from MCs without using proteolytic enzyme treatment but by lowering temperature, polystyrene MCs coated with a copolymer called CAT having zwitterionic and thermoresponsive characteristics, which has a lower critical solution temperature (LCST) in the range of 28-32 â„ƒ, were developed and compared with those coated with poly(N-isopropylacrylamide) (PNIPAM), which has an LCST almost the same as that of the CAT copolymer. A preliminary study using polystyrene dishes coated with the CAT copolymer at various densities showed superior adhesion efficiency and cell growth compared with those coated with PNIPAM; however, the rate of cell recovery by lowering the temperature to 24 â„ƒ was only about 80% in both cases. Although cells grew on polystyrene MCs coated with PNIPAM (0.64-16 µg/cm2) and on those coated with CAT (0.0050-1.0 µg/cm2), the cell recovery rate at 24 â„ƒ was lower than 20%. The decrease in recovery temperature from 24 to 4 â„ƒ resulted in about 50% cell recovery from CAT-coated (0.010-0.10 µg/cm2) MC, whereas the rate of cell recovery from PNIPAM-coated MC remained at about 20%. CAT (0.20 µg/cm2) coating after treatment of polystyrene MCs with oxygen plasma discharge increased the cell recovery rate to 72% at 4 â„ƒ. Consequently, the combination of oxygen plasma discharge treatment and CAT coating of polystyrene MCs might provide not only adhesion efficiency and growth of MSCs comparable to those on polystyrene MCs without any treatment but also a high cell recover rate of more than 70%.