Distinct modes of death in human neural stem and glioblastoma cells irradiated with carbon-ion radiation and gamma-rays.

Purpose: Accumulated damage in neural stem cells (NSCs) during brain tumor radiotherapy causes cognitive dysfunction to the patients. Carbon-ion radiotherapy can reduce undesired irradiation of normal tissues more efficiently than conventional photon radiotherapy. This study elucidates the responses of NSCs to carbon-ion radiation.Methods: Human NSCs and glioblastoma A-172 cells were irradiated with carbon-ion radiation and γ-rays, which have different linear-energy-transfer (LET) values of 108 and 0.2 keV/µm, respectively. After irradiation, growth rates were measured, apoptotic cells were detected by flow cytometry, and DNA synthesizing cells were immunocytochemically visualized.Results: Growth rates of NSCs and A-172 cells were decreased after irradiation. The percentages of apoptotic cells were remarkably increased in NSCs but not in A-172 cells. In contrast, the fractions of DNA synthesizing A-172 cells were decreased in a dose-dependent manner. These results indicate that apoptosis induction and DNA synthesis inhibition contribute to the growth inhibition of NSCs and glioblastoma cells, respectively. In addition, high-LET carbon ions induced more profound effects than low-LET γ-rays.Conclusions: Apoptosis is an important clinical target to protect NSCs during brain tumor radiotherapy using carbon-ion radiation as well as conventional X-rays.

Impact of pretilachlor herbicide and pyridaphenthion insecticide on aquatic organisms in model streams.

To detect the impact of pesticides on aquatic organisms, model streams (3m wide, 20 m long) were established in paddy field in Japan. More than 100 species of aquatic organisms were generated in the model streams. Field tests with pretilachlor herbicide and pyridaphenthion insecticide were carried out in the streams for 3 yr (2001-2003). Exposure of pretilachlor (max. 0.382 mg/L) showed little density changes in algae with a Bray-Curtis percent similarity in the range 81.6-93.3% for algae. Exposure to high concentrations (>0.1mg/L) of pyridaphenthion produced visible density reductions in Cladocera zooplankton species. Reduction of individual aquatic insects in the model streams by pyridaphenthion caused an increase of chlorophyll a greater than that of the control streams. The pesticides used showed no substantial differences in the ecosystems of model streams exposed to maximum environmental concentrations (e.g., 0.01 mg/L) detected in real rivers.

Effects of polymerization and hydrolysis degrees of poly(vinyl alcohol) (PVA) on the efficiency of the PVA-solid substrate for room-temperature phosphorimetry.

Several kinds of poly(vinyl alcohols) (PVAs) having different degrees of polymerization and hydrolysis were tested as a material of a solid substrate for room-temperature phosphorimetry (RTP). Effects of these differences on the efficiency of the solid substrate were investigated. Completely hydrolyzed PVAs acquired a luminescence property in the grinding process of substrate preparation, but partially hydrolyzed PVAs did not acquire this property. When the completely hydrolyzed PVA substrates were prepared by drying their aqueous solutions, their luminescence property almost disappeared. However, very weak background emission remained on the surface of a completely dried substrate which had been treated with an analyte aqueous solution. This residual background affected the spectrum of the analyte, especially at low concentrations. Stability of the phosphorescence intensity with the passage of time was superior on the partially hydrolyzed PVAs than on the completely hydrolyzed PVAs. On the other hand, the RTP intensity and reproducibility were superior on the completely hydrolyzed PVAs. Practically, partially hydrolyzed PVAs were more suitable as a material of the substrate because of the stability of its RTP intensity and the weakness of its background emission. The linear dynamic range of the analytical curve for p-aminobenzoic acid on the substrate of partially hydrolyzed PVA having a degree of polymerization of 3,500 was 5-2,000 pmol/spot (20 microL) and its correlation coefficient was 0.963 for 30 data points.