问题 单项选择题

布美他尼利尿作用部位在()。

A.肾小球

B.集合管

C.远曲小管初段

D.髓袢升支粗段

E.远曲小管远端和集合管

答案

参考答案:D

解析:

本组题考查要点是“常用利尿药的作用部位”。呋塞米属于袢利尿剂。袢利尿剂又称Na+-K+-2Cl-同向转运子抑制剂。该类药的作用机制是通过特异性地与Cl-结合位点结合而抑制分布在髓袢升支管腔膜侧的Na+-K+-2Cl-同向转运子,从而抑制NaCl的重吸收,降低肾的稀释与浓缩功能,排出大量接近于等渗的尿液。袢利尿剂主要作用于髓袢升支粗段,利尿作用强,其代表药物是呋塞米。其他药物如布美他尼、依他尼酸、托拉塞米等的作用部位、机制以及对电解质的影响虽与呋塞米相似,但在利尿作用的效能和过敏反应发生率上,它们之间存在差别。留钾利尿剂为低效利尿剂,能够减少K+排出。它可分为两类,一类为醛固酮(盐皮质激素)受体阻断剂(如螺内酯),另一类为肾小管上皮细胞Na+通道抑制剂(如氨苯蝶啶、阿米洛利),它们均主要作用于远曲小管远端和集合管。氢氯噻嗪属于噻嗪类利尿剂。噻嗪类利尿剂作用于髓袢升支厚壁段皮质部和远曲小管初段,其作用机制是直接抑制远曲小管初段腔壁上的Na+-Cl-共转运子的功能,由此减少了肾小管上皮细胞对Na+、Cl-和水的排出。

问答题 简答题
单项选择题

Those of us hurrying to finish our taxes by tomorrow’s deadline will probably be subjected to thoughts of the I.R.S. (Internal Revenue Service) as an all-powerful bully. But the truth is, the government is not always a match for the tax advisors of wealthy people, so a lot of taxes will go unpaid at the top of the income scale.

Lawyers who represent high-income taxpayers earn more than 10 times what senior government lawyers do—an obvious disadvantage for the government agencies in attracting and retaining top talent. The lawyers who write our tax rules are overworked and sometimes inexperienced, so that they leave loopholes that are exploited by more experienced private lawyers. And the government always loses cases which it should win, and provides private lawyers with precedents.

As this vicious cycle shows, skimping (节约) on tax administration is a false economy. Instead, if we substantially increase government salaries and staffing levels, we can raise more revenue, with lower tax rates and less waste. Four reforms should be adopted immediately.

First, the government should focus on hiring talented young lawyers, since the pay disparity with the private sector is narrower for them. These efforts will be more effective if Congress helps new graduates repay student loans, which often are more than $100,000. A loan repayment program would be a powerful recruiting device.

Second, the government should tap another promising talent pool—recent retirees from private practice—to mentor young lawyers. The salary gap is less of an issue for retirees, and the opportunity to give back to the tax system can be quite appealing.

Third, the government should retain a small team of a dozen top tax lawyers at salaries closer to the market rate. They can serve as a rapid reaction force, deciding whether to shut down a new aggressive strategy immediately or to let it be evaluated through usual government channels.

Fourth, the government should retain private lawyers to help with high-priority projects. An important constraint is that lawyers who represent private clients may view it as a conflict to help the government. But this is not always true.

Through bar associations, private lawyers already volunteer to review proposed changes in the tax law and offer ways to improve them. Tax academics can also be a valuable and conflict-free source of expertise, since they ordinarily do not represent clients. And some tax litigators (诉讼律师) may view it as a prestigious opportunity and a patriotic service to represent the government in a tax case that could set an important precedent.

The tax system can be only as p as the people who run it, so the government has to recruit and retain the most promising talent. A tax system can be fair and efficient only when it is administered soundly.

Private lawyers can easily exploit advantages in current tax system mainly because ()

A. they earn more than the lawyers working for the government

B. they are more experienced and talented

C. the tax system only suits the poor

D. they want successful precedents to improve their career