桂莪术化学成分的研究

从桂莪术(Curcuma kwangsiensis)中分得一个新的倍半萜内酯化合物,命名为桂莪术内酯(gweicurculactone)。另外还分得β-谷甾醇,吉玛酮胡萝卜甙,棕榈酸四种化合物的结晶。     

群勃龙及其人尿代谢物的GC/MSD分析

群勃龙(去甲雄三烯醇酮,trenbolone)在MsTFA,MBTFA,MO-MSTFA衍生化后形成的TMS醚式和TFA酯化产物,经GC/MSD分析,获得各自的特征图谱,讨论了有关的衍生化问题。群勃龙阳性尿样分析结果显示,其主要代谢产物是表群勃龙(epitrenbolone)和可能的羟基群勃龙(hydroxy-trenbolone),另有少量原型以及可能有去甲雄三烯二酮(triendione)存在。     

滨蒿中利胆成分的薄层光密度法测定

本文报告了用薄层光密度法测定滨蒿中三种主要利胆成分(绿原酸、对羟基苯乙酮和6,7-二甲氧基香豆素)。将浓缩的甲醇提取液点到含羧甲基纤维素钠的硅胶G板上,先后用氯仿一乙酸乙酯—甲酸(2:2:1)和环己烷—乙酸乙酯(1:1)进行分次展开,用薄层扫描仪双波长反射法直线扫描。采用外标两点法定量。三种成分的回收率为95.8～98.4%,方法的变异系数为1.83～4.48%。     

L-arginine via nitric oxide is an inhibitory feedback modulator of Aplysia feeding

An increase in L-arginine hemolymph concentration acts as a postingestion signal inhibiting Aplysia feeding. At physiological concentrations (a 10-μM increase over background), the inhibitory effect of L-arginine is too weak to block feeding in hungry animals. However, a 10-μM increase in L-arginine concentration acts along with another inhibitory stimulus, the sustained presence of food odor, to inhibit feeding after a period of access to food. A physiological concentration of L-arginine also blocked the excitatory effect of a stimulus enhancing feeding, pheromones secreted by mating conspecifics. High concentrations of L-arginine (2.5 mM) alone also inhibited ad libitum feeding. L-arginine is the substrate from which nitric oxide synthase (NOS) produces nitric oxide (NO). Both an NO donor and a 10-μM increase in L-arginine inhibited biting in response to a weak food stimulus. Treatment with NOS inhibitors initiated food-finding and biting in the absence of food, indicating that food initiates feeding against a background of tonic nitrergic inhibition. Increased feeding in response to blocking NOS is accompanied by firing of the metacerebral (MCC) neuron, a monitor of food arousal. The excitatory effect on the MCC of blocking NOS is indirect. The data suggest that L-arginine acts by amplifying NO synthesis, which acts as a background stimulus inhibiting feeding. Background modulation of neural activity and behavior by NO may also be present in other systems, but such modulation may be difficult to identify because its effects are evident only in the context of additional stimuli modulating behavior.