[Eutrophication and pollution level of microcystin in Dianshan Lake].

A survey was conducted in Dianshan Lake to study the eutrophication indexes including total phosphorus (TP), total nitrogen (TN), pH, temperature, diaphaneity and chlorophyll-a level and dominant algae in seasons. The impacts of temperature, light, nitrogen and phosphorus on growth of and microcystin LR production by Microcystis aeraginosa strain under laboratory conditions were studied. Relationship between algal cell density and concentration of microcystin LR were studied. Results suggest that water in Dianshan Lake was eutrophicated. The suitable seasons for algae growth are the end of spring and summer. The annual average of TP and TN were 1.93 mg/L and 0.18 mg/L respectively. And 93.5 and 92.2 percent of TP and TN were higher than the criteria for the third class water body. Significant impact from agriculture was indicated since the peak of algae laged one month after the maxium use of fertilizer. The dominant algae in Dianshan Lake were cyanobacteria, bacillariophyta, cryptophyta and euglenophyta. Microcystis, anabaena and synedra, which excrete toxins and indicate water pollution, and are dominant algae species in summer. M. aeraginosa strain had a biggest growth rate at temperature of 25 degrees C and light intensity of 3 0001x, while microcystin LR production contents reached maximum at 20 degrees C and 5000lx respectively. The optimum TP and TN concentrations for growth of and toxin production by M. aeraginosa were found to be 650 micromol/L and 6.5 micromol/L respectively. TP is suspected to be the limiting factor for the growth of algae both in field and laboratory conditions. Positive correlations between total microcystin LR concentrations and algae cell density or M. aeraginosa cell densities are found. The algae cell density can be used to predict the level of algal toxins in water.

[The immediate early genes expression in the PC12 cells activated by anatoxin-a].

OBJECTIVE: To explore the regulative action of IEGs when the nicotinic acetylcholine receptors (nAChRs) of PC12 cells were activated by anatoxin-a. METHODS: Using the reverse transcription polymerase chain reaction (RT-PCR) method, the mRNA gene expression of c-fos, c-jun, NGFI-A and NGFI-B were measured while PC12 cells were activated by anatoxin-a. RESULTS: As 10(-9), 10(-8) and 10(-7) mol/L anatoxin-a activated PC12 cells for an hour, or 10(-7) mol/ L anatoxin-a activated PC12 cells for 30 min, 60 min, 120 min, the intracellular gene expression of c-fos and NGFI-A increased significantly than the control group (P < 0.05), it was 2-6 times than the control group. And the gene expression of c-fos presented dose-response and time-effect relation. However, under the same condition, the gene expression of c-jun and NGFI-B did not show any remarkable changes. CONCLUSION: c-fos and NGFI-A might be involved to modulation the action of anatoxin-a activating the nAChRs of PC12 cells.

[Effects of microcystins on cell cycle and expressions of c-fos and c-jun].

OBJECTIVES: To investigate the effects of microcystins on cell cycle and expressions of c-fos and c-jun, and explore the potential carcinogenic mechanisms of Microcystins. METHODS: Microcystic cyanobacteria extraction (MCE) purified by Sep-Pak C(18) cartridge was added into the media and co-incubated with SHE cell for various periods. Immunohistochemistry assay was applied to detect the expressions of c-fos and c-jun at 1, 3, 6 hr time point, and cell cycle at 6, 12, 24 hr point were analyzed by flow cytometry respectively. RESULTS: Sustained up-regulated expression of c-fos and c-jun were induced by MCE during the experimental period, and 5 - 6 folds increased expression were observed at 6 hour point after treatment. As much as 44.8 per cent of cells were induced to entry S-phase from resting G(0)/G(1). CONCLUSION: Up-regulating the expression of transcript factor such as c-fos and c-jun thus to induce cell abnormal proliferation may be the potential carcinogenic mechanisms of microcystins.