生物医学工程类英中对照格式

The biologically determined duration of human life should beyond doubt be at least 110 years; some data suggest it should be 150 years. In reality though, the mean duration of human life does not reach even the middle of this span. Whether there has ever been that “golden age” of humankind when, as told by the Biblical sources, people did reach that age – it is hard to tell. The 80-year mark is not reached by 65% of people, 90% do not reach 90 years, and only a few live beyond their centenary. Even if human beings avoid illness and injury in their whole life, they still inevitably die because of “old age”. But why, in some cases, this “old age” takes 60-year-olds, while in other cases, it spares 90-year-olds? What is the basis of ageing?

Many authors addressing these questions only point at life-long contamination of the body, its self-intoxication as it were. But what are the mechanisms of the subsequent disorders? What does the immune system do – our principal guardian of Health that is closely linked to the quality of life?

Indeed, ageing is accompanied by certain changes in the immune system among others. They affect all of its components: stem cells, Т- and B-lymphocytes, macrophages. Since early childhood, the “thymic clock” starts to gradually slow down, which is observed as the lower proliferative activity of Т-cells; their worsening effector and helper functions make one susceptible to infections and malignancies (their rates are known to be age-related). An old person is indeed increasingly vulnerable to infections, which become to be among the principal direct causes of death. Respiratory infections and pyelonephritis are particularly frequent. With advancing age, higher rates are seen also for a number of other diseases, such as cardiovascular pathology, tumours, diabetes, and dementia. These changes taking place in the body are often called “age-related” or “normal for this age”.

Immunodeficiency implies a less strict control of abnormal mitoses, cell divisions and formation of tumour cells. They occur in the body on a constant basis and quite frequently at that; however, possessing a foreign antigenic structure, they immediately are “spotted” by the immune guardians and exterminated on the spot. If these guardians “miss” them the moment they appear and fail to exterminate them on time, their antigenic structure is recognized as “own” not before long, and, according to fundamental biological principles, the production of these antibodies is blocked. The outcome of this body-tumour fighting becomes predetermined.