Effects of aniracetam on extracellular levels of transmitter amino acids in the hippocampus of the conscious gerbils: an intracranial microdialysis study

The effects of aniracetam on extracellular amino acid levels in the hippocampus of conscious gerbils, with or without transient cerebral ischemia/reperfusion, were measured by microdialysis and reverse phase-high performance liquid chromatography. Increased extracellular levels of aspartate and glutamate that were observed in the hippocampus of conscious gerbils during transient global forebrain ischemia were reversed by aniracetam. In contrast, the level of extracellular gamma-aminobutyric acid was increased, while taurine was maintained at a higher level than other amino acids by administration of aniracetam (100 mg/kg, p.o.) 60 min before ischemia. Further, in contrast to ischemic animals, administration of aniracetam (100 mg/kg, p.o.) enhanced the release of glutamate and aspartate in the normal gerbil hippocampus. The results suggest that these effects might be due to a partial calcium agonist activity of aniracetam, and that the effects of aniracetam on amino acid levels might be a mechanism of protection against delayed neuronal death in the ischemic hippocampus, thereby improving memory dysfunction induced by ischemia/reperfusion. (C) 2003 Elsevier Science Ireland Ltd. All rights reserved.

人工湿地生态系统服务价值评价研究

阐述了人工湿地生态系统服务的定义、分类、项目及其评价方法。介绍了生态系统服务价值评价在国内外的研究现状,指出了当前研究工作的局限性,对将来的发展方向作出了研究展望。论述了人工湿地所具有的服务功能,结合前人的研究初步提出对其进行价值评价的方法及计算公式。

菖蒲对不同程度富营养化水体的适应性研究

对5种不同程度富营养化水体中的菖蒲(Acorus calamusL.)在静态培养过程中的叶片长度变化、叶片数目变化进行了观测,比较了培养后各水体中菖蒲根长、根数、鲜重、根活力、叶绿素含量、叶片可溶性总糖含量、鲜重增量和根系活力的差异。研究发现,菖蒲在5种不同程度富营养化水体中均能正常生长。在非极度富营养化的水体组中,水体富营养化程度越高,菖蒲生长越好。但在极度富营养水体中,菖蒲根系生长受到抑制,其根短且须根多,且叶片生长对此水体有一段适应期,试验前8 d,其中菖蒲叶片长度增长明显小于重度富营养,8 d后,

The vibrations of bubbles and balloons

Bubbles and balloons are two examples of structures that feature a pressure difference across the skin, a thin, tensioned membrane, and a doubly curved interface surface. While mathematical models have been formulated for bubble vibrations, no such model exists for balloon vibrations. This paper reviews a model of bubble vibrations, and compares its predicted natural frequencies and modeshapes to those of a rubber balloon. It is shown that the bubble model consistently underpredicts the balloon's natural frequencies, and it is concluded that the nonlinear elasticity present in the balloon skin accounts for this result.

月湖底栖动物的空间格局及其对水草可恢复区的指示

底质适宜是富营养湖泊恢复沉水植物(水草)的重要前提。大型底栖动物可综合指示底质的污染程度,于2002~2003年在武汉月湖开展了底栖动物水平分布对水草可恢复区指示作用的研究。首先通过月湖底栖动物与环境的相关分析,选择颤蚓科寡毛类作为底质营养状况的指示类群,然后利用同类湖泊群颤蚓与水草数据分析阈值,初步确定颤蚓密度≤100 ind/m2的底质适合水草生长,最后绘制月湖颤蚓分布的水平等值线,显示水草恢复的合适区域。在此基础上构建了应用底栖动物空间格局指示水草恢复区的技术原理框架。

汉江中下游春季浮游甲壳动物群落结构的空间差异

2002年4月,在汉江中下游从丹江口坝上至其河口沿途设17个采样点,共采集到浮游甲壳动物10科26属33种,其中桡足类4科10属11种,枝角类6科16属22种。根据各采样点的种类组成和数量分布,采用Shannon Wiener指数、Simpson指数和Pielou均匀度指数分析了不同江段浮游甲壳动物的群落多样性特征,并运用SOM人工神经网络方法对其群落结构的空间差异进行了比较。结果表明,汉江中下游江段浮游甲壳动物的密度分布呈现出中游高于下游的特征,而物种丰度和群落多样性指数则是下游高于中游;中游上段的属于