EFFECTS OF STROPHANTHIDIN ON THE SLOW INWARD CURRENT IN GUINEA-PIG ISOLATED VENTRICULAR MYOCYTES

1. The effect of strophanthidin on the slow inward current (Isi) and on contractile force were studied in guinea-pig isolated ventricular myocytes and intact papillary muscles, respectively. In myocytes, both low (10 nmol/L) and high (1-10 mumols/L) concentrations had small or no effects in either direction on Isi whereas norepinephrine (10-100 nmol/L) increased it. To determine whether the same results are obtained after decreasing or increasing intracellular calcium or sodium, the same concentrations of strophanthidin were tested in different procedures that are known to (i) increase [Ca]i and decrease [Na]i (high [Ca]o, 3.6-5.4 mmol/L; low [Na]o, 112 mmol/L; (ii) decrease [Ca]i and increase [Na]i (low [Ca]o, 0.45-1 mmol/L; Sr, 1 mmol/L; (iii) decrease [Ca]i and [Na]i (Cd, 0.1-0.2 mmol/L); and (iv) increase [Ca]i and [Na]i (veratridine, 0.2 mumol/L). High [Ca]o and veratridine increased whereas low [Ca]o and Cd decreased Isi. In contrast, during these various procedures, strophanthidin had small and inconsistent effects at a low or high concentration. In intact papillary muscles, low strophanthidin decreased whereas high strophanthidin increased contractile force. It is concluded that strophanthidin has little direct or indirect effect on Isi and that the decrease in force by low and increase in force by high concentrations in intact muscle are probably related to demonstrated decrease and increase, respectively, in intracellular sodium activity.     

多发性脑梗塞痴呆动物模型评价

多发性脑梗塞痴呆模型大鼠可出现行为学、病理生理学、生化代谢、神经递质、血液流变学、基因表达等多方面改变，且病理形态学表现与临床上多发性脑梗塞痴呆相似，可以用作血管性痴呆的实验研究。但复习以往有关文献研究发现，该模型仍有待于进一步完善，以期更好地应用于基础研究，保证对药物抗血管性痴呆作用评价及作用机制诠释的准确性。     

医学院校教师对课题责任人负责制认知的调查分析

目的通过6所医学院校的教师对PI制认知的调查，探讨医学院校实行课题责任人负责制的可行性及管理模式的运行机制。方法采取抽样调查法以无记名方式随机发放调查问卷表，运用SAS软件进行数据统计处理。结果教师对课题责任人负责制知晓度较高，认为利大于弊，对学校科研工作的发展有重要作用。结论实行课题责任人负责制需加大科研投入，搭建公共服务技术平台，建立合理的科研目标和考核指标，形成与中国高校实际相适应的科研管理体制，使课题责任人拥有更多的自主权和宽松的学术环境。     

新形势下中学与大学学生党建衔接工作的思考

在青年学生中吸收优秀分子已成为高校党组织发展工作的重要组成部分,最近几年来,高中党建工作也不断发展。了解青年学生党建现状,更好地利用中学党建工作成果,提出了做好衔接工作的现实意义及对策措施。     

电力电缆的预防性试验

主要叙述了电缆做预防性试验及其试验项目、方法和要求，以及需注意的问题。     

Effect of nilvadipine on the voltage-dependent Ca channels in rat hippocampal CA1 pyramidal neurons

Effects of nilvadipine on the low- and high-voltage activated Ca²⁺ currents (LVA and HVA I_Ca, respectively) were compared with other organic Ca²⁺ antagonists in acutely dissociated rat hippocampal CA1 pyramidal neurons. The inhibitory effects of nilvadipine, amlodipine and flunarizine on LVA I_Ca were concentration- and use-dependent. The apparent half-maximum inhibitory concentrations (IC₅₀s) at every 1- and 30-s stimulation were 6.3×10⁻⁷ M and 1.8×10⁻⁶ M for flunarizine, 1.9×10⁻⁶ M and 7.6×10⁻⁶ M for nilvadipine, and 4.0×10⁻⁶ M and 8.0×10⁻⁶ M for amlodipine, respectively. Thus, the strength of the use-dependence was in the sequence of nilvadipine>flunarizine>amlodipine. Nilvadipine also inhibited the HVA I_Ca in a concentration-dependent manner with an IC₅₀ of 1.5×10⁻⁷ M. The hippocampal CA1 neurons were observed to have five pharmacologically distinct HVA Ca²⁺ channel subtypes consisting of L-, N-, P-, Q- and R-types. Nilvadipine selectively inhibited the L-type Ca²⁺ channel current which comprised 34% of the total HVA I_Ca. On the other hand, amlodipine non-selectively inhibited the HVA Ca²⁺ channel subtypes. These results suggest that the inhibitory effect of nilvadipine on the neuronal Ca²⁺ influx through both LVA and HVA L-type Ca²⁺ channels, in combination with the cerebral vasodilatory action, may prevent neuronal damage during ischemia.     

Niflumic acid-induced increase in potassium currents in frog motor nerve terminals: effects on transmitter release

The actions of the nonsteroidal antiinflammatory drug niflumic acid were studied on frog neuromuscular preparations by conventional electrophysiological techniques. Niflumic acid reduced the amplitude and increased the latency of endplate potentials in a concentration-dependent manner. Neuromuscular junctions pretreated with niflumic acid (0.05–0.5 mM) showed much less depression than control when they were stimulated with trains of impulses. Inhibition of acetylcholine release was reverted by raising the extracellular Ca²⁺ concentration but not by simply washing out the preparations with niflumic acid-free solutions. Pretreatment with indomethacin (0.1 mM), another nonsteroidal antiinflamatory drug, did not affect the niflumic acid-induced inhibition of evoked responses. Niflumic acid (0.1 mM) did not change the amplitude of miniature endplate potentials and had a dual action on the frequency of miniatures: it decreased their frequency at 0.1 mM whereas it produced an enormous increase in the rate of spontaneous discharge at 0.5 mM. Niflumic acid (0.1–1 mM) reversibly increased the amplitude and affected the kinetics of presynaptic voltage-activated K⁺ current and Ca²⁺-activated K⁺ current in a concentration-dependent manner. Niflumic acid (0.1–1 mM) irreversibly decreased the amplitude and reversibly affected the kinetics of the nodal Na⁺ current. Indomethacin (0.1 mM) had no effect on presynaptic currents. In conclusion, niflumic acid reduces acetylcholine release by increasing presynaptic K⁺ currents. This may shorten the depolarizing phase of the presynaptic action potential and may reduce the entry of Ca²⁺ with each impulse.     

A prospective study of psychosocial background factors associated with congenital malformations

Women's life situation and experiences during pregnancy were prospectively studied in relationship to the development of congenital malformations (CMs) in their offspring, within samples of 84 offspring of pregnant index women with a history of nonorganic psychosis and 100 offspring of pregnant control women. Within both samples, offspring CMs were related to more problematic maternal life situations during pregnancy, the common denominator in these problems across samples being difficulties associated with the husband. Little relationship was found between CMs and the woman's own attitude toward the pregnancy or her mental condition during pregnancy. In both groups, total life situational problems and distress were more strongly related to the development of very minor CMs (termed "variants") than to the major, classical CMs.     

企业职工社会心理调查的方法学研究

作者自行设计一种问卷对某企业职工进行社会心理调查。问卷由 A、B两表构成。A 表列出42个问题,包含可能影响该企业职工社会心理的三大类11项因素,要求从该企业中随机抽取的被调查者针对问题回答“是”或“否”。其后附开放式问题一个,被调查者可自由作答,以补封闭式提问的不足。B 表按心理投射机制设计,以解除被调查者的疑虑。测试结果表明,此问卷的信度和效度令人满意。     

Transient outward current (I A) in clonal anterior pituitary cells: blockade by aminopyridine analogs

Summary Whole cell voltage-clamp recordings from GH₃ cells, a clonal cell line derived from a rat anterior pituitary tumor, demonstrated a rapidly activating and inactivating (transient) voltage-dependent outward current. This current, referred to as I _A, was elicited by step depolarization from holding potentials negative to –50 mV, showed strong outward rectification at potentials positive to –30 mV, and exhibited steady state inactivation with V _1/2 near –64 mV. The current rose to a peak within < 10–20 ms following depolarization and decayed in two exponential phases, I _Af and IA _AS with time constants of 30–50 and 500–700 ms, respectively. Both I _A components exhibited similar voltage dependencies for activation and inactivation. Aminopyridines (2 mol/l – –5 mmol/l) produced a dose dependent, reversible blockade of I _A (70% inhibition at 0.5 to 2 mmol/l) with the following rank order of potencies: 4-aminopyridine > 3,4-diaminopyridine = 3-aminopyridine > 2-aminopyridine. These drugs reduced the peak conductance of I _A, and produced complex effects on its time-dependent decay. With submaximal degrees of block, there was an increase in the inactivation rate, suggesting that open channels are preferentially blocked by the drugs. It is concluded that GH₃ pituitary cells possess an aminopyridine-sensitive transient outward current comparable to the A-current in neural cells. However, this cell line is unusual in that it expresses both rapidly and slowly decaying A-current components.Abbreviations n-AP n-aminopyridine - 3,4-DAP 3,4-diaminopyridine - TEA tetraethylammonium - EGTA ethylene glycol bis(-aminoethyl ether)N,N-tetraacetic acid - HEPES 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid Send offprint requests to M. A. Rogawski at the above address