Increasing evidence suggests that cyclooxygenase-2 (COX-2) is involved in synaptic transmission and plasticity, and prostaglandin E2 (PGE2) is a key molecule in COX-2-meduated synaptic modification. However, the precise mechanisms, in particular, which subtypes of PGE2 receptors (EPs) mediate the PGE2-induced synaptic response, are not clear. Recently, we demonstrated that EPs are expressed heterogeneously in the hippocampus, and EP2/4 are mainly expressed in presynaptic terminals. Here, we report that PGE2 increased synaptic stimulus-evoked amplitudes of EPSPs in hippocampal slices and frequency of miniature EPSCs (mEPSCs) in hippocampal neurons in culture. These actions were mimicked by an EP2 agonist and attenuated by protein kinase A inhibitors. Decrease of EP2 expression through silencing the EP2 gene eliminated PGE2-induced increase of the frequency of mEPSCs. COX-2 and microsomal PGE synthase-1 (mPGES-1) andmPGES-2are present in postsynaptic dendritic spines, because they are colocalized with PSD-95 (postsynaptic density-95), a postsynaptic marker. In addition, the frequency of mEPSCs was enhanced in neurons pretreated with interleukin-1 or lipopolysaccharide, which elevated expression of COX-2 and mPGES-1 and produced PGE2, and this enhancement was inhibited by a COX-2 inhibitor that inhibited production of PGE2. Our results suggest that PGE2 synthesized by postsynaptically localized COX-2 functions as a retrograde messenger in hippocampal synaptic signaling via a presynaptic EP2 receptor.

通过对太原市不同季节、不同监测位点大气二氧化硫（SO2）浓度的监测，分析了太原市SO2污染状况，指出在太原市对SO2排放企业的治理和管理工作势在必行。

The genotoxicity of municipal landfill leachate was studied using the Vicia faba root-tip cytogenetic bioassay. Results show that landfill leachates collected in different seasons decreased the mitotic index (MI) and caused significant increases of micronucleus (MN) frequencies and anaphase aberration (AA) frequencies in a concentration-dependent manner (concentration expressed as 'chemical oxygen demand' measured by the method of potassium dichromate oxidation (CODCr)). In addition,a seasonal difference in genotoxicity induced by leachate was observed. The results confirm that leachate is a genotoxic agent in plant cells and imply that exposure to leachate in the aquatic environment may pose a potential genotoxic risk to organisms. The results also show that the V. faba cytogenetic bioassay is efficient, simple and reproducible in enotoxicity studies of leachate, and that there is a correlation between the genotoxicity and the chemical measurement (CODCr) of leachate.

The induction of micronuclei (MN) in polychromatic erythrocytes (PCE) of mouse bone marrow by municipal landfill leachate was studied in vivo. Results showed that mouse exposure via drinking water containing various concentrations of leachate caused asignificant increase of MN frequencies in a concentration (Chemical oxygen demand measured with potassium dichromate oxidation, CODCr)-ependent manner. MN induction in female and male mice was different at higher concentrations. This implies that leachate is a genotoxic agent in mammalian cells and that exposure to leachate in an aquatic environment may pose a potential genotoxic risk to human beings.

BACKGROUND: Sulfur dioxide(SO2) and its derivatives are recognized as the factors responsible for cellular chromosome cleavage and genotoxicity and capable of inducing oxidative injury and changes in enzyme activity. The toxicity of S02 and its' derivatives, from the perspective of cell membrane injuries and neurotoxic effects in particular, remains currently unclear. OBJECTIVE: To study the characteristics of depolarization-activated potassium current in rat hippocampal neurons, and observe the changes in the current in response to cell treatment with SO2 and its derivatives.