No abstract

SUMMARYPhotosynthesis of Phaseolus vulgaris L. leaves was measured after treatment with microcystm-LR (MC-LR), a potent cyanobacterial toxin and inhibitor of protein phosphatases 1 and 2A. The net photosynthetic rate fell by over 50 °o within 8 h of dipping leaves in MC-LR solution. This inhibitory effect was observed when leaves were treated once with concentrations above 10"^ mol m"^. At 10"^ mol m^^, the inhibition caused by MC-LR was transient, and net photosynthesis rates essentially recovered after 5 d, whereas at 10"' mol m"', the net photosynthesis rate in treated leaves was still 42% of controls after 8 d. Necrosis was observed at the higher concentration, but not usually below 10"' mol m~^. Analysis of net photosynthetic rate as a function of internal COj concentration and photosynthetically active photon flux density indicated that both the CO.,-saturated rate of photosynthesis and the carboxylation efficiency were lo\yered when MC-LR-treated leaves were exposed to photosynthetically-saturating light. When the leaves were exposed to 2-0 x 10"* mol m"^ MC-LR solution repeatedly, the photosynthetic rate was significantly reduced after 7 d, suggesting that intermittent exposure of P. vulgaris leaves to low concentrations of MC-LR brings about an effect on photosynthesis more inhibitory than that of a single exposure to high concentrations of MC-LR. These results indicate that relatively low concentrations of MC-LR cause damage to the photosynthetic apparatus o( P. vulgaris in situ. We discuss the significance of these findings in relation to current spray irrigation practice for crop plants involving the use 6f water containing cyanobacterial blooms and microcystins.

Pulse discharge sintering (PDS) technique was employed to synthesize the ternary compound Ti 3 SiC 2 from four starting powder mixtures. The experimental results demonstrated that when the starting material of 3Ti/Si/2C or 3Ti/SiC/C was used high content of the secondary phase, TiC, higher than 30 mass%, was found in the sintered material. When TiC powder as starting material was used (Ti/Si/2TiC) in the same stoichiometric composition, however, the final sintered product contained low TiC content of a few percent. Further adjusting the composition to the off-stoichiometric of 2Ti/2Si/3TiC, the content of the secondary phase TiC was further controlled to be around 1 mass%. In the materials sintered from Ti/Si/2TiC and 2Ti/2Si/3TiC an optimum sintering temperature exists at 1573 K, at which the highest Ti 3 SiC 2 phase purity was achieved. When sintered at the optimum temperature a density of higher than 99% was obtained. At the optimum sintering temperature, both the phase purity and the density of the material sintered from 2Ti/2Si/3TiC showed very little dependence on the sintering time ranging from a few minutes to four hours, indicating the phase stability at this temperature.

Serum levels of group II phospholipase A2 (PLA2) have been reported to be associated with stage of disease in cancer patients. These levels are also related to the malignant potential in tissues, and are an important prognostic factor. We radioimmunoassayed group II PLA2 levels in pleural and peritoneal effusions from patients with various cancers. We also investigated the production of group II PLA2 in cells in effusions from cancer patients by Northern blotting, immunocytochemistry and in situ hybridization. Immunoreactive group II PLA2 levels were significantly higher in effusions from 47 patients with various cancers, compared with those in sera and cirrhotic ascites. There was no significant correlation between group II PLA2 levels in effusions and those in sera. Group II PLA2 mRNA was expressed at a high level in cells from effusions, by Northern blot analysis, but not in those cells from blood. The localization of group II PLA2 protein and mRNA was intense in carcinoma cells and CD68-positive macrophages, determined by immunocytochemistry and in situ hybridization. In addition, IL-6 and IL-8 levels were significantly higher in effusions, in comparison with those in sera from patients, suggesting that cancer cells and macrophages produce group II PLA2 by IL-6. These group II PLA2 levels are apparently significantly increased in effusions, and the carcinoma cells and macrophages produce group II PLA2, as noted in effusions from patients with various cancers. Int.