吗啡受体拮抗剂翻转电针镇痛的程度决定于电针刺激的频率

电针镇痛能被吗啡受体拮抗剂所对抗,被认为是内源性吗啡样物质参与针刺镇痛的有力证据。给大鼠皮下注射吗啡受体拮抗剂纳洛酮或纳曲酮 1mg/kg, 可以对抗低频和中频(2和15Hz)电针的镇痛效应,但不能对抗高频(100Hz)电针镇痛效应。增加纳洛酮剂量至20mg/kg才能部分对抗 100Hz电针镇痛。根据不同剂量纳洛酮(0.25—20mg/kg)对抗不同频率电针镇痛的剂量效应曲线,求得对2,15和100Hz电针镇痛产生50％翻转作用的纳洛酮剂量分别为 0.53,1.02和 24mg/kg。2—15Hz变频电针的镇痛作用也需用大剂量纳洛酮(20mg/kg)才能阻断。实验表明,在三种频率下,改变电针刺激强度(1,2,3V)并不影响纳洛酮翻转电针镇痛的百分数。以上结果表明,纳洛酮翻转电针镇痛的程度决定于电针的频率,不同频率的电针刺激可能在中枢神经系统中释放出不同的内源性吗啡样物质而发挥镇痛作用。     

A DESEEDED AVENA TEST METHOD FOR SMALL AMOUNTS OF AUXIN AND AUXIN PRECURSORS

The main results presented in this article may be summarized as follows: 1. A test method with deseeded Avena seedlings for small concentrations of auxin and precursors of auxin has been described. 2. This method makes possible quantitative determinations of about ten times as low concentrations of hormone as can be obtained with the standard method, (a) Through an increase in the time of the test, so that nearly all the hormone applied can be utilized. (b) Through an increase in sensitivity of deseeded plants to unilaterally applied small concentrations of hormone. 3. The effect of deseeding in relation to curvature growth is primarily the prevention of auxin regeneration through the removal of the material for auxin synthesis, and in addition the prevention of physiological aging. 4. The mechanism of auxin synthesis in the tip of the coleoptile and the mechanism of auxin regeneration in the new physiological tip have been shown to be identical. 5. The application of the deseeded method is illustrated by determinations of auxin in primary leaves and coleoptile sections of Avena seedlings. 6. The deseeded method has been used as a test method for precursors of auxin obtainable from the coleoptile and from other sources. The method further makes possible a distinction between auxins and these substances which may become activated by the plant. 7. Evidence for the existence of a precursor of auxin in the plant is given (a) indirectly by determinations of the decrease in auxin synthesis in deseeded plants. (b) Directly by its isolation from the plant. 8. Precursors of hetero-auxin are demonstrated; their chemical nature and activation are briefly considered.     

Tb~(3+)作为荧光探针研究钙调蛋白与拮抗药物的相互作用

本文报导以Tb~(3+)作为荧光探针,研究钙调蛋白(CaM)与其拮抗药物分子间相互作用的机制.所用方法简便、快速、灵敏.CaM的内源荧光研究表明,Tb~(3+)类似于Ca~(2+),也能诱导CaM分子构象发生改化,由于CaM分子中Ca~(2+)的第Ⅲ、Ⅳ结合位点上各有一个Tyr线基,如(?)280nm激发,则发生从Tyr向Tb~(3+)的能量转移,从而导致Tb~(3+)在490和545nm处的特征荧光发射大大加强.本文检测了药物分子与Tb~(3+)-CaM结合对该荧光发射的影响.实验表明,TFP与CaM的高亲和位点处于CaM分子C-末端部位,即含第Ⅲ、Ⅳ结构域的半分子上:丙拮抗药物酸枣仁皂甙A则优先结合在含第Ⅰ、Ⅱ的结构域的另一半分子(?).     

THE CHANGING CONCEPT OF AUXIN

Kefford , N. P., and P. L. Goldacre . (Division of Plant Industry, C.S.I.R.O., Canberra, Australia.) The changing concept of auxin. Amer. Jour. Bot. 48(7): 643–650. Illus. 1961.—Recent findings in auxin research are interpreted as follows: The concept of auxin as only a cell-enlargement regulator can no longer accommodate the variety of growth phenomena controlled by auxin. In isolated tissues, auxin interacts with gibberellin in the control of cell enlargement, and auxin and kinin interact in initiating cell division. Some evidence suggests a single site of auxin action for both processes. It is proposed that auxin is not a determining agent but a predisposing agent, causing the production of something in limiting amount which is required in both processes —in the presence of kinin, cell division is activated; in the presence of gibberellin, cell enlargement is activated. In the presence of limiting amounts of auxin, there could be competition between the 2 processes, the outcome depending on the balance of kinin and gibberellin. The possibility of competition in the presence of supraoptimal auxin concentrations is also suggested. Difficulties arise in the application of this concept to observations on intact plants, where cause and effect relationships are not readily established; the use of excised plant parts shows the relationships more clearly. The role of auxin in cell and organ differentiation is also discussed. The primary auxin reaction is not yet known. The biological assay for auxins is discussed with reference to this and to natural auxins. The function of auxin in the correlation of tissue and organ growth through the auxin transport system is stressed, and it is pointed out that if transport is a necessary requirement of a native auxin, indole-3-acetic acid is at present the only substance known to qualify.     

AUXIN DESTRUCTION BY MARASMIUS PERNICIOSUS

Attempts were made to determine whether Marasmius perniciosus Stahel., causal agent of the witches' broom disease of cacao, produces substances that could elicit on the host some of the symptoms which are characteristic of the disease. In vitro the fungos did not produce significant amounts of cytokinins or auxins. However, culture filtrates destroyed indole-3-acetic acid (IAA) rapidly because of two different IAA-oxidizing enzymes: (1) a peroxidase (IAA oxidase) characterized by (a) dependence on Mn⁺⁺ and 2,4-dichlorophenol (DCP), (b) pH. optimum of 3.0, (c) inactivation at 85 C for 5 min, (d) stimulation of oxidative activity by addition of 0.3 μmole/ml H₂O₂; and (2) a laccase characterized by (a) no dependence on Mn⁺⁺ and DCP, (b) pH optimum of 6.0, (c) inactivation at 95 C for 5 min, (d) ability to oxidize IAA and phenolic substrates in the absence of H₂O₂. The peroxidase was completely inhibited by scopoletin (0.0002 m ) ; the laccase was inhibited by thiourea (0.1 m ). The laccase could be separated from the peroxidase by elution through a column of Sephadex G-100. It is suggested that the main pathogenic effect of the fungus may be associated with these auxin-inactivating systems.