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about OG阅读1中的一个句子疑问?

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楼主
发表于 2005-7-30 10:40:00 | 只看该作者

about OG阅读1中的一个句子疑问?

Therefore, prolonged periods at the elevated concentrations, as might be brought about


by a phosphodiesterase inhibitor, could lead to a greater amount of neuron firing and, consequently, to behavioral stimulation.



as might be brought about by a phosphodiesterase inhibitor是插入语还是非限定性定语从句?为什么不用WHICH引导而用了AS呢?谢谢


还有就是这篇文章不看翻译前意识不到behavioral stimulation就是中的stimulation就是中文中所讲的兴奋作用?因为小时候背stimulation是就是背的刺激这个意思,所以感觉理解不透文章意思。大家说我这是怎么会事,能不能有什么改进的地方呢?大家给哥们提提建议吧!



付文:


Caffeine, the stimulant in coffee, has been called


“the most widely used psychoactive substance on Earth .”


Synder, Daly and Bruns have recently proposed that


caffeine affects behavior by countering the activity in


(5) the human brain of a naturally occurring chemical called


adenosine. Adenosine normally depresses neuron firing


in many areas of the brain. It apparently does this by


inhibiting the release of neurotransmitters, chemicals


that carry nerve impulses from one neuron to the next.


(10) Like many other agents that affect neuron firing,


adenosine must first bind to specific receptors on


neuronal membranes. There are at least two classes


of these receptors, which have been designated A1 and


A2. Snyder et al propose that caffeine, which is struc-


(15) turally similar to adenosine, is able to bind to both types


of receptors, which prevents adenosine from attaching


there and allows the neurons to fire more readily than


they otherwise would.


For many years, caffeine’s effects have been attri-


(20) buted to its inhibition of the production of phosphodi-


esterase, an enzyme that breaks down the chemical


called cyclic AMP.A number of neurotransmitters exert


their effects by first increasing cyclic AMP concentra-


tions in target neurons. Therefore, prolonged periods at


(25) the elevated concentrations, as might be brought about


by a phosphodiesterase inhibitor, could lead to a greater


amount of neuron firing and, consequently, to behav-


ioral stimulation. But Snyder et al point out that the


caffeine concentrations needed to inhibit the production


(30) of phosphodiesterase in the brain are much higher than


those that produce stimulation. Moreover, other com-


pounds that block phosphodiesterase’s activity are not


stimulants.


To buttress their case that caffeine acts instead by pre-


(35) venting adenosine binding, Snyder et al compared the


stimulatory effects of a series of caffeine derivatives with


their ability to dislodge adenosine from its receptors in


the brains of mice. “In general,” they reported, “the


ability of the compounds to compete at the receptors


(40) correlates with their ability to stimulate locomotion in


the mouse; i.e., the higher their capacity to bind at the


receptors, the higher their ability to stimulate locomo-


tion.” Theophylline, a close structural relative of caffeine


and the major stimulant in tea, was one of the most


(45) effective compounds in both regards.


There were some apparent exceptions to the general


correlation observed between adenosine-receptor binding


and stimulation. One of these was a compound called


3-isobuty1-1-methylxanthine(IBMX), which bound very


(50) well but actually depressed mouse locomotion. Snyder


et al suggest that this is not a major stumbling block to


their hypothesis. The problem is that the compound has


mixed effects in the brain, a not unusual occurrence with


psychoactive drugs. Even caffeine, which is generally


(55) known only for its stimulatory effects, displays this


property, depressing mouse locomotion at very low


concentrations and stimulating it at higher ones.


沙发
 楼主| 发表于 2005-7-30 11:36:00 | 只看该作者

而且第一题的解释中


The first paragraph presents a recent hypothesis about how caffeine affects behavior. The


second paragraph describes an earlier and widely accepted hypothesis about how caffeine affects


behavior, and then presents evidence that is not consistent with that hypothesis. The third and


fourth paragraphs return to the newer hypothesis introduced in the first paragraph and provide


“evidence and arguments” that support this alternative hypothesis.



其中的


second paragraph describes an earlier and widely accepted hypothesis about how caffeine affects


behavior, and then presents evidence that is not consistent with that hypothesis   


文中哪里then presents evidence that is not consistent with that hypothesis   了?NN能不能给指出来啊?


板凳
发表于 2005-8-1 09:54:00 | 只看该作者

文中哪里then presents evidence that is not consistent with that hypothesis   了 ?


是 不 是 那 一 段 的 最 后 那两 句 话 ? But Snyder et al point out that the


caffeine concentrations needed to inhibit the production


(30) of phosphodiesterase in the brain are much higher than


those that produce stimulation. Moreover, other com-


pounds that block phosphodiesterase’s activity are not


stimulants.


还 有  as might be brought about by a phosphodiesterase inhibitor是插入语吧 。



不 好 意 思 , 很 菜 。 有 位 斑 竹 说 了 , 帮 助 别 人 就 是 在 帮 自 己 呵 呵 。


地板
 楼主| 发表于 2005-8-1 15:03:00 | 只看该作者

3q  大家谁还有什么高见呢?

5#
 楼主| 发表于 2005-8-2 10:30:00 | 只看该作者





3q  大家谁还有什么高见呢?

6#
 楼主| 发表于 2005-8-3 15:24:00 | 只看该作者

3q  大家谁还有什么高见呢?

7#
 楼主| 发表于 2005-8-5 18:13:00 | 只看该作者

3q  大家谁还有什么高见呢?

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