问题 问答题 简答题

简述细胞因子测定的意义和复杂性。

答案

参考答案:

细胞因子的测定在免疫学、细胞和分子生物学的基础研究,揭示某些疾病的发生发展机制,以及某些疾病的诊断及治疗指导上具有重要的应用价值。其测定方法可根据针对的细胞因子表达分泌的阶段的表型测定及分泌后的功能测定而分为分子生物学测定方法、免疫测定方法和生物学测定方法三大类。三种方法之间相互关联,互为补充,但不能完全替代。细胞因子的种类较多,在体内表现为一个高度复杂的细胞因子网络,相互作用以使机体免疫系统得到控制和维持。故而一种细胞因子常具有功能多样性,不同细胞因子的功能相互之间可能会有重叠。因此,对于特定的细胞因子的测定,单纯依靠功能测定特异性较差,常需要采用上述多种方法综合分析。

单项选择题

Scholars of human migration speak of two main factors that influence an individual’s decision to move from one place to another-push and pull factors. Push factors are associated with the place of origin. A push factor can be as simple and mild a matter as difficulty in finding a suitable job, or as traumatic as religious persecution, war, or severe famine Obviously, refugees who leave their homes with guns pointed at their heads or with hate-filled mobs at their heels are motivated almost entirely by push factors (although pull factors do influence their choice of destination).

Pull factors are those associated with the place of destination. Most of these are economic, such as better job opportunities or the availability of good land to farm. The latter was an important factor in attracting settlers to the United States during the nineteenth century. In general, pull factors add up to an apparently better chance for a good life and material well-being than is offered by the place of origin.

Besides push and pull factors, there are what the sociologists call " intervening obstacles " . Even if push and/or pull factors are very p, they still may be outweighed by intervening obstacles, such as the distance of the move, the trouble and cost of moving, the difficulty of entering the new country, and the problems likely to be encountered on arrival.

The decision to move is also influenced by " personal factors " of the potential migrant. The same push-pull factors and obstacles operate differently on different people, sometimes because they are at different stages of their lives, or just because of their varied abilities and personalities. The prospect of pulling up stakes and moving to a new and perhaps very strange environment may appear interesting and challenging to a young, footloose man and appallingly difficult to a slightly older man with a wife and young children. Similarly, the need to learn a new language and customs may intrigue one person and frighten another.

Regardless of why people move, migration of large numbers of people causes friction. The United States and other " receiving countries " (the term used for countries that welcome large numbers of migrants) have experienced adjustment problems with each new wave of immigrants. The newest arrivals are usually given the lowest-paying jobs and are resented by natives who may have to compete with them for those jobs. It has usually taken several decades for each group to gain acceptance in the mainstream of society in the receiving country.

The author implies that personal factors()

A. attract people to move

B. are obstacles to migration

C. may affect migration

D. may confuse those potential migrants

填空题