Activity-dependent Decay of Early LTP Revealed by Dual EPSP Recording in Hippocampal Slices from Young Rats

The early maintenance of long-term potentiation (LTP) was studied in the CA1 region of hippocampal slices from 12- to 18-day-old rats in a low-magnesium solution (0.1 mM). The α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) and N-methyl-D-aspartate (NMDA) receptor-mediated components of the field excitatory postsynaptic potential were estimated in parallel using early and late measurements of the composite potential. At the normal test stimulus frequency of 0.1 Hz, LTP was seen initially as a predominant increase in the AMPA component, but converted, via a substantial decay of this component and a gradual growth of the NMDA component, into nearly equal changes of the two components. Interrupting the test stimulation for 10 min, changing the test stimulus frequency to 1/60 Hz after LTP induction, or using a test stimulus frequency of 1/60 Hz during the entire experiment significantly reduced the decay of the potentiation of the AMPA component while enhancing the potentiation of the NMDA one. The ratio between the magnitudes of the two excitatory postsynaptic potential (EPSP) components showed a decaying time course that was independent of the manipulations used. Application of the NMDA antagonist D(-)-2-amino-5-phosphonopentanoic acid (50μM) after LTP induction stabilized the LTP of the AMPA component until washout was started. On the other hand, the phosphatase inhibitor okadaic acid (1 μM) resulted in decay of the potentiation of both EPSP components back to around baseline and altered the time course of the ratio between the components. Our results show that the early maintenance of LTP is controlled in an activity-dependent and NMDA-dependent manner. This process accelerates the decay of LTP of both AMPA and NMDA components in parallel, suggesting that it is similar to homosynaptic long-term depression, although it operates at the normal test stimulus frequency. The data support a scenario in which LTP ensues as a selective AMPA receptor modification and subsequently converts to another modification, possibly a presynaptic one.     

系统性红斑狼疮的肺胸膜损害

分析了系统性红斑狼疮并肺、胸膜损害30例,胸膜改变占首位,共19例,(63.3％),其中胸膜积液16例,合并心包积液3例。其次为SLE肺炎5例(16.7％),尿毒症肺水肿3例(10％),弥漫性肺间质纤维化2例(6.7％),肺不张1例(3.35％)。对临床表现、诊断、治疗和预后进行了讨论。     

神经活素对Pc12细胞作用的初步观察

从胎脑、颌下腺、肌肉组织中制备神经活素。其性能同脑活素一样：可促进Ｐｃ１２细胞的突起生长，提高其胞浆内乳酸脱氢酶活性，电泳显示二者有相同的三条带。提示：神经活素有可能替代脑活素应用于临床。     

荧光分光光度法测定水产品中烷烃类、芳烃类污染物

目的：对使用荧光分光光度法测定水产品中烷烃类、芳烃类污染物的方法进行验证,并检测三类样品。方法：通过氢氧化钠-乙醇皂化处理,用正已烷萃取,用石油醚溶解,测量萃取物荧光强度值进行定量。结果：测得标准油在0.00～12.0μg/ml范围内线性关系良好,相关系数0.9999,检出限为0.2 mg/kg,平均回收率90.2%,RSD5.4%。结论：本法准确度、灵敏度高,检出限低,操作稳定性好。     

涎腺恶性肿瘤的回顾性研究

本文对52例涎腺恶性肿瘤进行了回顾性研究。52例中发生于腮腺者27例(51.9％);病理类型以腺样囊性癌和粘液表皮样癌最多见;随访2～8年,死亡19例,病死率最高者为腺癌(5/8)和鳞癌(3/5)。作者对腺样囊性癌的病理分型提出了不同看法。     

用脱脂奶粉代替小牛胸腺DNA进行核酸分子杂交

本文应用脱脂奶粉代替小牛胸腺DNA等大分子物质配制预杂交液和杂交液进行核酸分子杂交,同时用经典的含小牛胸腺DNA等大分子物质的预杂交液和杂交液作为对照。结果表明,用脱脂奶粉可以代替小牛胸腺DNA等大分子物质进行核酸分子杂交,此法经济,配制简便,实际可用。     

阻断大脑中动脉建立大鼠局灶性脑梗塞模型的观察

通过经颅阻断大鼠大脑中动脉制成局灶性脑缺血动物模型。大脑中动脉阻塞后大鼠均出现各种神经病学征象。氯化三苯基四氮唑染色发现梗塞区位于皮质及基底节。光镜和电镜观察大脑中动脉阻塞后脑组织的病理改变,发现梗塞区不同程度的细胞和间质变性坏死。结果表明该模型是比较理想的局灶性脑缺血模型.     

顺丁烯二酸水溶液的热反应动力学

研究了不同温度、浓度条件下，顺丁烯二酸（顺酸）非催化反应网络，即顺酸可生成反丁烯二酸（反酸）和苹果酸，反酸与苹果酸存在可逆反应。建立了该反应网络的动力学模型。测定了不同反应条件下顺酸、反酸和苹果酸浓度随时间变化的规律，据此，动力学参数进行了估值。     

三种泻心汤及其类方不同配伍对正常大鼠胃粘液成分的影响

目的:探讨半夏泻心汤及其类方不同配伍对正常大鼠粘液含量的影响.方法:用均匀设计法对半夏泻心汤及其类方进行组方药量变化,以胃粘液含量为药理学指标,对所得的药理实验数据进行逐步回归分析.结果:与胃粘液含量关联度最大的为黄连,可以显著降低其含量,其次对半夏、大枣和甘草的交互项,可增加胃粘液含量.药物之间存在复杂的交互作用.结论:均匀设计为研究类方配伍提供了一种可供参考的试验设计方法.     

Rapid chemical kinetic techniques for investigations of neurotransmitter receptors expressed in Xenopus oocytes

Xenopus laevis oocytes have been used extensively during the past decade to express and study neurotransmitter receptors of various origins and subunit composition and also to express and study receptors altered by site-specific mutations. Interpretations of the effects of structural differences on receptor mechanisms were, however, hampered by a lack of rapid chemical reaction techniques suitable for use with oocytes. Here we describe flow and photolysis techniques, with 2-ms and 100-μs time resolution, respectively, for studying neurotransmitter receptors in giant (≈20-μm diameter) patches of oocyte membranes, using muscle and neuronal acetylcholine receptors as examples. With these techniques, we find that the muscle receptor in BC₃H1 cells and the same receptor expressed in oocytes have comparable kinetic properties. This finding is in contrast to previous studies and raises questions regarding the interpretations of the many studies of receptors expressed in oocytes in which an insufficient time resolution was available. The results obtained indicate that the rapid reaction techniques described here, in conjunction with the oocyte expression system, will be useful in answering many outstanding questions regarding the structure and function of diverse neurotransmitter receptors.