Differential effects of the serotonin receptors on cultured rat cerebral cortical neurons

Effects of serotonin (5-HT) on cerebral cortical neurons were examined by patch clamp techniques. 5-HT produced a variety of responses such as outward (19/73 patches/neurons), slow inward (15/73 patches/neurons), fast inward (8/73 patches/neurons), and mixed currents (initially fast inward deflection followed by an outward response: 2/73 patches/neurons), with a latency of 12 sec, 15 sec, 0 sec, and 0 sec respectively, at a holding potential of −60 mV in whole-cell patches. The fast inward currents were again evoked by a selective 5-HT3 receptor agonist, 1-(m-chlorophenyl)-biguanide hydrochloride (CPBG). In the cell-attached patch clamp configuration, 5-HT inside the patch pipette elicited single channel currents with slope conductances of 42 pS and 132 pS (4/42 patches/neurons). CPBG inside the patch pipette evoked inward single channel currents with a lower slope conductance of 41 pS (3/23 patches/neurons). In contrast, application of 5-HT or a 5-HT₂ receptor agonist, α-methyl-5-hydroxytryptamine-maleate, outside the patch pipette induced outward single channel currents with a major slope conductance of 140 pS (8/30 patches/neurons) or 135 pS (6/20 patches/neurons), respectively. These results indicate that the outward and fast inward currents may be mediated respectively by the 5-HT₂ receptor, which is coupled to a G-protein, and by the 5-HT₃ receptor, which contains the non-selective cation channel, and that the mixed type may be caused by both the 5-HT₂ and 5-HT₃ receptors. Received 27 September 1996; received after revision 4 November 1996; accepted 7 November 1996     

Effect of hydrogen peroxide on the binding of Merocyanine 540 to human erythrocytes

The fluorescent dye Merocyanine 540 (MC540) is often used as a probe to monitor the molecular packing of phospholipids in the outer leaflet of biomembranes. In a previous study we showed that the increased staining of erythrocytes with a perturbed membrane structure was mainly due to an increase in the fluorescence yield of cell-bound MC540, rather than to an increase of the number of bound molecules. Erythrocytes and ghosts exposed to continuous fluxes of H₂O₂ exhibited pronounced lipid peroxidation. Further, red blood cells subjected to this form of oxidative stress also showed increased staining with MC540. It appeared that this was caused by a strong increase in binding of MC540, together with a slight red shift of the fluorescence emission maximum and a small increase in the fluorescence yield of bound MC540. The changed MC540 binding characteristics were not observed when lipid peroxidation was suppressed by the presence of the antioxidant BHT in the incubation medium. However, open ghosts exposed to H₂O₂ showed no increase of MC540 binding, excluding a direct involvement of lipid peroxidation. Measurement of fluorescence emission spectra and gel filtration studies showed that MC540 can bind to H₂O₂-exposed hemoglobin. Experiments with erythrocytes lysed in hypotonic medium after exposure to H₂O₂ revealed that peroxidation of lipids with H₂O₂ induced a non-specific permeabilization of the plasma membrane to MC540, thereby allowing MC540 to bind to the oxidatively denatured, more hydrophobic hemoglobin. These results indicate that conclusions about packing of phospholipids in the outer leaflet of the membrane based on increased MC540-staining should be drawn with care. Received 27 September 1996; received after revision 5 November 1996; accepted 27 November 1996     

平台用钢微观组织对其分层面上解理断裂应力的影响

利用专门设计的厚度方向缺口四点弯曲试样，结合相应的弹塑性有限元计算结果，在液氮温度下测取了一种海洋平台用钢的６种微观组织分层面上的解理断裂应力σ＊ｆ．结果显示，均匀细小的铁素体＋贝氏体组织具有比铁素体＋带状珠光体为高的σ＊ｆ值．对于同一终轧温度，轧后冷速愈高，其得到的微观组织之σ＊ｆ值愈高．而对于同一轧后冷却制度，则终轧于Ａｒ３与再结晶停止温度之间者其得到的微观组织具有最高的σ＊ｆ值．讨论了各微观组织组成相的作用     

幂律流体不稳定径向流的数值解法

对微可压缩非牛顿幂律流体在均质多孔介质中的非稳定径向渗流方程进行了回顾和对比，用有限差分方法建立了微分方程的数值解法．研究了时间步长、空间步长对数值解精度和稳定性的影响，并结合算例绘出了不同流性指数的瞬时压力曲线．该研究结果可用于非牛顿流体渗流机理研究及试井分析．     

随机冰载作用下海上固定平台管节点的疲劳寿命估算

根据冰激振动理论，分析了海冰对海上钻井平台的不同破坏形式．为了解决海洋石油钢结构在低温冰载作用下的疲劳性能问题，进行了室温与低温下随机冰载作用对钢结构疲劳裂纹扩展的试验研究．根据试验结果，计算了平台管节点的疲劳累积损伤和随机冰载的等效应力，提出了综合计算等效应力幅的新方法，给出了管节点的疲劳寿命曲线及其计算参数．这种新的计算方法，考虑了冰载相对时间和相对冰厚的随机性，能提高寿命估算的精确度     

用聚砜和磺化聚砜超滤膜处理含油污水的研究

在实验室中自行合成磺化聚砜（ＳＰＳ），刮制成板式、管式超滤膜，进行处理含油污水的实验室小试及现场中试，并与聚砜（ＰＳ）超滤膜对比．自制ＳＰＳ超滤膜的透水速度随离子交换当量（ＩＥＣ）的增大而增大．选用ＩＥＣ值在０．１～０．２ｍｏｌ／ｇ的ＳＰＳ作为膜材料．在处理含石油类（１０～８０ｍｇ／Ｌ）的含油污水时，与ＰＳ膜对比，ＳＰＳ膜的通量下降率较小，能维持较高的水通量；二者的截留率都在９０％以上，透过液中含油量、悬浮物、细菌等都基本达到国家排放标准及油田回注水水质标准．因此，从膜性能角度考虑，以ＳＰＳ膜代替ＰＳ膜在一定条件下能维持较高通量，有一定的优越性．