醫(yī)學(xué)英語(yǔ)綜合教程課文和翻譯新整理

1、Unit2. Cells and AgingAging is a normal process accompanied by a progressive alteration of the body s homeostatic adaptive responses; the specialized branch of medicine that deals with the medical problems and care of elderly person is called geriatrics.衰老是一種正常的生理過(guò)程，伴有機(jī)體內(nèi)環(huán)境穩(wěn)定適應(yīng)性應(yīng)答的進(jìn)行性改變。研究老年人的健康問(wèn)題和保

2、健的一門特殊醫(yī)學(xué)分支被稱作老年病學(xué)The obvious characteristics of aging are well known; graying and loss of hair, loss of teeth, wrinkling of skin, decreased muscle mass, and increased fat deposits. The physiological signs of aging are gradual deterioration in function and capacity to maintain a constant internal env

3、ironment (homeostasis) in response to changes in temperature, diet, and oxygen supply. These sings of aging are related to a net decrease in the number of cells in the body and to the dysfunctioning of the cells that remain.衰老的明顯特征眾所周知：頭發(fā)花白和脫落，牙齒脫落，皮膚起皺，肌肉減少，脂肪積存增加。衰老的生理征兆是機(jī)體對(duì)環(huán)境刺激反應(yīng)的功能和能力的逐漸退化如 同維持機(jī)

4、體內(nèi)環(huán)境穩(wěn)定來(lái)應(yīng)對(duì)溫度，飲食和氧氣供應(yīng)改變的能力減退一樣，機(jī)體新陳代謝也減慢了。衰老的這些跡象與機(jī)體中細(xì)胞數(shù)目的凈減少以及存余細(xì)胞的功能 紊亂有關(guān)。The extracellular components of tissues also change with age.Collagen fibers, responsible for the strength in tendons, increase in number and change in quality with aging.These changes in the collagenof arterial walls are as m

5、uch responsible for their loss ofextensibility as are the deposits associated with atherosclerosis, thedeposition of fatty materials in the arterial walls.Elastin, anotherextracellular component, is responsible for the elasticity of bloodvessels and skin. It thickens, fragments, and acquires a great

6、er affinity for calcium with age changes that may also be associatedwith the development of atherosclerosis.組織的細(xì)胞外成分也隨著年齡的變化而變化。負(fù)責(zé)肌腱力量的膠原纖維的數(shù)量增加，而質(zhì)量卻隨著衰老降低。 動(dòng)脈壁上的膠原質(zhì)的變化與動(dòng)脈壁伸展性喪失有關(guān)，正如動(dòng)脈粥樣硬化，即動(dòng)脈壁脂肪物質(zhì)堆積造成動(dòng)脈壁伸展性缺失一樣。彈性蛋白是另一種細(xì)胞外成分，與血管和皮膚的彈性有關(guān)， 隨著年齡的變化，它變粗，易斷裂并且與鈣有很大的親和力，這些變化可能也與動(dòng)脈粥樣硬化的發(fā)生有關(guān)。Glucose, the m

7、ost abundant sugar in the body, may also play a role in the aging process. According to one hypothesis, glucose is added, haphazardly, to proteins inside and outside cells, forming irreversibleAs a person ages, morecross-links between adjacent protein molecules.cross-links are formed, and this proba

8、bly contributes to the stiffening and loss of elasticity in aging tissues.葡萄糖是機(jī)體中含量最多的糖類，它在衰老的過(guò)程中可能也起作用。根據(jù)一個(gè)假說(shuō)，隨機(jī)地在細(xì)胞內(nèi)外蛋白質(zhì)上添加葡萄糖，結(jié)果會(huì)在相鄰蛋白質(zhì)分子之間形成不可逆的交聯(lián)。 隨著人的衰老，會(huì)形成更多的交聯(lián)，這很可能就是造成衰老的組織僵硬及彈性喪失的原因。Although many millions of new cells normally are produced each minute, several kinds of cells- heart cells,

9、skeletal muscle fibers,nerve cells - cannot be replaced, Experiments have shown that many other cell types have only a limited capability to divide. Cells grown outside the body divide only a certain number of times and then stop. The number of divisions correlates with the donor/s age and with the

10、normal lifespan of the different species from which the cells are obtained.Theseobservations provides strong evidence for the hypothesis that cessationof mitosis is a normal, genetically programmed event.According to thisview, an“aging ” gene is part of the genetic blueprint at birth, andit turns on

11、 at a preprogrammed time, slowing down or halting processes vital to life.雖然正常情況下，每分鐘會(huì)有好幾百萬(wàn)的新細(xì)胞產(chǎn)生，但有幾種細(xì)胞：心臟細(xì) 胞，骨骼肌纖維細(xì)胞，神經(jīng)細(xì)胞是無(wú)法替代的。實(shí)驗(yàn)顯示，許多種類的細(xì)胞分裂能力有限。在機(jī)體外生長(zhǎng)的細(xì)胞僅僅分裂幾代就停止了。細(xì)胞分裂數(shù)與捐獻(xiàn)者的年齡和這些細(xì)胞來(lái)自的不同物種的正常壽命有關(guān)。 這些發(fā)現(xiàn)為這種假說(shuō)提供了有力的證據(jù)，即（細(xì)胞的）有絲分裂的終止是正常的，是由基因決定的。 根據(jù)這個(gè)觀點(diǎn)，衰 老基因是出生時(shí)就存在的基因藍(lán)圖的一部分，在預(yù)定的時(shí)間里開(kāi)啟，減慢或停止對(duì) 生命至關(guān)重要的

12、生理過(guò)程。Another theory of aging is the free radical theory. Free radicals are electrically charged molecules that have an unpaired electron. Such molecules are unstable and highly active and can easily damage proteins. Some effects are wrinkled skin, stiff joints, and hardened arteries.Free radical may

13、 also damage DNA. Among the factors that produce free radicals are air pollution, radiation, and certain foods we eat. Other substances in the diet such as vitamin E, vitamin C, beta-carotene, and selenium are antioxidants and inhibit free radical formation. The free radical theory of aging is bolst

14、ered by two recent discoveries. Strains of fruitt flies bred for longevity produce larger-than-normal amouts of an enzyme called superoxide dismutase, which functions to neutralize free radicals. Also, injection of genes that lead to production of superoxide dismutase into fruit fly embryos prolongs

15、 their average lifetime.衰老的另一個(gè)理論即自由基理論，自由基是含有未配對(duì)電子的帶電荷分子。這種分子性質(zhì)不穩(wěn)定，具有高反應(yīng)活性，容易損害蛋白質(zhì)。自由基的影響有：皮膚起皺，關(guān)節(jié)僵直，動(dòng)脈硬化。自由基也可以損害 DNA產(chǎn)生自由基的因素有：空氣污染，放射線，以及我們吃的某些食物。飲食中的其他物質(zhì)如維生素E,維生素C,B -胡蘿卜素以及硒都是抗氧化劑，可以抑制自由基的形成。最近的兩個(gè)研究支持了衰老的自由基理論。孕育長(zhǎng)壽的果蠅株從而產(chǎn)生超正常量的酶：過(guò)氧化物歧化酶，它可以中和自由基。同樣，把產(chǎn)生過(guò)氧化物歧化酶生成的基因注入果蠅胚胎中會(huì)延長(zhǎng)其平均壽命。Whereas some the

16、ories of aging explain the process at the cellular lever, others concentrates on regulatory mechanisms operating within the entire organism. For example, the immune system, which manufactures antibodies against foreign invaders, may start to attack the body s owncells. This autoimmune response might be caused by changes in the surfaces of cells, causing antibodies to attach and mark the cell for destruction. As s