NO介质在大鼠红藻氨酸诱导癫痫发作中的作用

目的：进一步探讨脑内一氧化氮(NO)介质(NO或NO衍生物)在复杂部分性及全身强直阵挛性癫痫发作中的作用。方法：采用红藻氨酸(KA)诱导大鼠癫痫发作,以NO合酶抑制剂L-硝基精氨酸(L-NNA)或NO前体L-精氨酸(L-Arg)予以预处理,观察其癫痫发作行为及海马结构内NO含量(NO2^-/NO3^-)的变化。结果：给予大鼠惊厥剂量KA(10mg/kg),15min时出现湿狗样抖动(WDS),1～3h出现全身痉挛;经L-NNA(50mg/kg)或L-Arg(40mg/kg)预处理的大鼠,注射相同剂量的KA后,其癫痫行为发生明显变化,L-NNA预处理的大鼠癫痫发作行为明显加重,表现为全身痉挛的潜伏期缩短、时间延长、死亡率提高;L-Arg预处理的大鼠癫痫发作行为减弱,WDS和全身痉挛的潜伏期均延长,发作程度减轻、时间缩短,观察时间内无一例死亡。KA给药后30min海马结构内的NO2^-/NO3^-含量迅速增多,7d时仍持续增高;与NS预处理组相比,经L-Arg预处理的动物,KA给药后3h及3d,其NO2^-/NO3^-浓度升高明显。结论：兴奋诱导性癫痫发作过程中内源性NO介质的变化可能具有重要的抗发作作用。     

血循环障碍在高原冻伤中的形态计量观测

本文对高原冻伤中血液循环障碍作形态计量,旨在探讨血循环障碍在冻伤过程中的变化及高原冻伤发病机理中所起的作用。实验选用Ｗｉｓｔａｒ雄性大鼠４０只,随机分为平原冻伤组、急性低氧冻伤组和低氧习服冻伤组。习服组动物于低压舱内模拟海拔６０００ｍ缺氧每日４ｈ,连续两周。其余动物常规饲养。习服期满次日习服组与低氧组一同进入舱内模拟海拔６０００ｍ低氧４ｈ,再行冷冻。冻后继续低氧４ｈ。冻后４８ｈ取材。对各组动物冻后４８ｈ冻肢皮下血管的病变作图象分析。结果发现,平原组血管淤滞、血栓绝对数及其百分比均为最低,习服组最高,低氧组居中。但低氧组与平原组的血栓／淤滞百分比无明显差别。骨骼肌坏死的面积百分比习服组显著高于低氧组与平原组,而后两组间无差别。血栓／淤滞百分比与骨骼肌坏死面积百分比之间的有高度相关关系。冻融是直接引起血管内皮损伤的原发因素,局部血液循环障碍是造成严重的继发损伤的主要原因。     

炎症和氧化应激对内皮祖细胞动员及其功能的影响

内皮祖细胞对于维持血管内皮完整性和血管稳态具有重要作用.增强EPC的数量和功能可使心血管疾病患者获益.炎症、氧化应激对内皮祖细胞动员及其功能发挥具有重要影响,本文着重综述炎症和氧化应激对内皮祖细胞动员的调控,并探讨增进内皮祖细胞数量和功能的相关治疗策略.     

植物体内的钙信使系绕

Ca对植物不仅仅是一种大量营养元素,更重要的是作为偶连胞外信号与胞内生理生化反应的第二信使,作为植物代谢和发育的主要调控者。本文介绍了Ca在植物细胞中的分布及其体内平衡机制,以及Ca2+信使系统调控的植物生理生化过程,讨论了外界信号通过Ca2+信使系统的传递和表达过程,Ca2+信使系统对基因表达的可能影响,以及Ca2+信使系统的作用机制,并提出了今后的研究方向。     

Production of Ethanol from d-Xylose by Using d-Xylose Isomerase and Yeasts

d-Xylulose, an intermediate of d-xylose catabolism, was observed to be fermentable to ethanol and carbon dioxide in a yield of greater than 80% by yeasts (including industrial bakers' yeast) under fermentative conditions. This conversion appears to be carried out by many yeasts known for d-glucose fermentation. In some yeasts, xylitol, in addition to ethanol, was produced from d-xylulose. Fermenting yeasts are also able to produce ethanol from d-xylose when d-xylose isomerizing enzyme is present. The results indicate that ethanol could be produced from d-xylose in a yield of greater than 80% by a two-step process. First, d-xylose is converted to d-xylulose by xylose isomerase. d-Xylulose is then fermented to ethanol by yeasts.     

The Role in Ozone Phytotoxicity of the Evolution of Ethylene upon Induction of 1-Aminocydopropane-1-carboxylic Acid Synthase by Ozone Fumigation in Tomato Plants

The rate of evolution of ethylene by tomato plants was rapidlyincreased by O₃ fumigation. The time course of the increasein 1-aminocyclopropane-1-carboxylic acid (ACC) synthase activitywas the same as that in the rate of evolution of ethylene, suggestingthat ACC synthase activity might be a rate-limiting step inthe evolution of ethylene that is caused by O₃ fumigation. Therate of the O₃-induced evolution of ethylene was increased bythe application of ACC to tomato plants, suggesting the involvementof ACC oxidase in the O₃-induced evolution of ethylene. Treatmentof plants with tiron inhibited the evolution of ethane, butnot of ethylene. These results indicated that evolution of ethylenein O₃-treated tomato plants might result from enzymatic reactionscatalyzed by both ACC synthase and ACC oxidase, but not fromstimulation by O₃ of the peroxidation of lipids mediated byfree radicals. Pretreatment of leaves with aminoethoxyvinylglycine (AVG), aninhibitor of ACC synthase, significantly inhibited the evolutionof ethylene that was induced by O₃ and concomitantly reducedthe extent of O₃-induced visible damage to leaves. Treatmentwith 2,5-norbonadiene, an inhibitor of the action of ethylene,strongly reduced the extent of visible damage caused by O₃,even though it did not suppress the evloution of ethylene. Theseresults indicate that ethylene acts on certain metabolic processesto cause visible damage. (Received September 7, 1995; Accepted December 18, 1995)     

Seasonal Trophic Niche Shift and Cascading Effect of a Generalist Predator Fish

Few studies have examined how foraging niche shift of a predator over time cascade down to local prey communities. Here we examine patterns of temporal foraging niche shifts of a generalist predator (yellow catfish, Pelteobagrus fulvidraco) and the abundance of prey communities in a subtropical lake. We predicted that the nature of these interactions would have implications for patterns in diet shifts and growth of the predator. Our results show significant decreases in planktivory and benthivory from late spring to summer and autumn, whereas piscivory increased significantly from mid-summer until late autumn and also increased steadily with predator body length. The temporal dynamics in predator/prey ratios indicate that the predation pressure on zooplankton and zoobenthos decreased when the predation pressure on the prey fish and shrimps was high. Yellow catfish adjusted their foraging strategies to temporal changes in food availability, which is in agreement with optimal foraging theory. Meanwhile the decrease in planktivory and benthivory of yellow catfish enabled primary consumers, such as zooplankton and benthic invertebrates, to develop under low grazing pressure via trophic cascading effects in the local food web. Thus, yellow catfish shifts its foraging niche to intermediate consumers in the food web to benefit the energetic demand on growth and reproduction during summer, which in turn indirectly facilitate the primary consumers. In complex food webs, trophic interactions are usually expected to reduce the strength and penetrance of trophic cascades. However, our study demonstrates strong associations between foraging niche of piscivorous fish and abundance of prey. This relationship appeared to be an important factor in producing top-down effects on both benthic and planktonic food webs.