首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
考研
There’s a human liver sitting in a lab dish in Madison, Wis. Also a heart, a brain and every bone in the human body even though
There’s a human liver sitting in a lab dish in Madison, Wis. Also a heart, a brain and every bone in the human body even though
admin
2011-02-25
78
问题
There’s a human liver sitting in a lab dish in Madison, Wis. Also a heart, a brain and every bone in the human body even though the contents of the dish are a few cells too small to be seen without a microscope. But these are stem cells, the most immature human cells ever discovered, taken from embryos before they had decided upon their career path in the body. (46)
If scientists could only figure out how to give them just the right kick in just the right direction, each could become a liver, a heart, a brain or a bone.
(47)
When a team from the University of Wisconsin announced their discovery, doctors around the world looked forward to a new era of medicine one without organ-donor shortages or the tissues-rejection problems that bedevil transplant patients today.
Doctors also saw obstacles, though. One of them was a U. S. Congress skittish about research on stem cells taken from unwanted human embryos and aborted fetuses. Indeed, 70 lawmakers asked in a firmly worded letter that the Federal Government ban all such work.
Yet the era of "grow your own" organs is already upon us, as researchers have sidestepped the stem cell controversy by making clever use of ordinary cells. Today a machinist in Massachusetts is using his own cells to grow a new thumb after he lost part of his chest wall in an accident. A teenager born without half of his chest wall is growing a new cage of bone and cartilage within his chest cavity. Scientists announced that bladders, grown from bladder cells in a lab, have been implanted in dogs and are working. Meanwhile, patches of skin, the first "tissue-engineered" organ to be approved by the U. S. Food and Drug Administration, are healing sores and skin ulcers on hundreds of patients across the U. S.
How have scientists managed to do all this without those protean stem cells? Part of the answer is smart engineering. (48)
Using materials such as polymers with pores no wider than a toothbrush bristle, researchers have learned to sculpt scaffolds in shapes into which cells can settle.
The other part of the answer is just plain cell biology. (49)
Scientists have discovered that they don’t have to teach old cells new tricks; given the right framework and the right nutrients, cells will organize themselves into real tissues as the scaffolds dissolve.
"I’m a great believer in the cells. They’re not just lying there, looking stupidly at each other," says Francois Auger, an infectious disease specialist and builder of artificial blood vessels at Laval University in Quebec City. "They will do the work for you if you treat them right."
Replacement hearts—or even replacement heart parts—are at least a decade off, estimates Kiki Hellman, who monitors tissue-engineering efforts for the FDA. "Any problem that requires lots of cell types ’talking’ to one another is really hard," she notes. Bone and cartilage efforts are much closer to fruition, and could be ready for human trials within two years. (50)
And what of those magical stem cells that can grow into any organ you happen to need—if the law and biologists’ knowledge permit?
"Using them," says Sefton, "is really the Holy Grail."
选项
答案
科学家们发现,他们无需告诉老细胞怎样去执行新的功能;只要有适当的模型和营养,细胞就能自行发育成真正的人体组织,而模型会慢慢消失。
解析
句子的框架是Scientists have discovered that they don’t have to…;given the right framework and the right nutrients,cells will organize themselves into…as the scaffolds dissolve。分号连接一个并列宾语从句,前句that引导的句子作discover的宾语,分号后面given…是if they are given…的省略,主句又跟有as引导的时间状语从句。
转载请注明原文地址:https://kaotiyun.com/show/Szp4777K
0
考研英语一
相关试题推荐
WhichofthefollowingisNOTtrue?______OwingtotheeffortsoftheoriginatorsoftheWelfareState______
Shynessisthecauseofmuchunhappinessforagreatmanypeople.Shypeopleare(1)_____andserf-conscious;thatis,theyare
Whatdoestheauthorbelieveaccordingtothepassage?______Whydoesthedrop-outrateofcollegestudentsseemtogoup?_____
Einstein’sconnectionwiththepoliticsofthenuclearbombiswellknown:hesignedthefamouslettertoPresidentFranklinRoo
Threeweeksagoyoubookedatwo-weekholidaytoSanyawithFly-by-NightTravel.Youarenothappywiththeholiday—theflightw
Itisacuriousparadoxthatwethinkofthephysicalsciencesas"hard",thesocialsciencesas"soft",andthebiologicalscie
YourforeignfriendClarehasjustgraduatedfromBeifangUniversityinChinaandplanstogobacktotheUnitedStatessoon.Wr
SometimebetweendigestingChristmasdinnerandputtingyourheadbackdowntowork,spareathoughtortwoforthecranberry.
China’sentryintotheWTOactuallyrepresentstheresultofathree-sidedwin-winsituation-China,theUnitedStatesandthe
TomanypeopletheBermudaTriangleisreallyamysterybecause______.Itismentionedinthepassagethat______
随机试题
某地区有居民20000户,现在采用简单随机抽样的方法,进行一次居民家庭月收入的抽样调查。根据以往的调查数据,知道该地居民月收入的标准差为2000元,调查要求把握程度为95%,允许误差为100元,为达到调查要求至少应抽取多少户作为样本?
轮状病毒肠炎患儿的大便性状是
患儿,7岁。右上中切牙冠折后半小时内到医院就诊。检查:穿髓孔较大,探疼明显,叩诊不适。应选治疗方法
A.升麻B.柴胡C.葛根D.蔓荆子E.桑叶
血液中脂肪酶主要来自胃肠黏膜,少量来自胰腺。()
在进行寿命期不同的互斥方案选择时,可采用的方法是()。
下列围护结构类型中,高压旋喷桩挡墙属于()。
红字更正法通常适用的情况有()。
光纤通信作为一门新兴技术,其近年来发展速度之快、应用面之广是通信史上罕见的,也是世界新技术革命的重要标志和未来信息社会中各种信息的主要传送工具。下列对光纤通信优点的描述中,说法不正确的是()。
8个56Kb/s的信道通过统计时分复用到一条主干线路,如果该线路的利用率为90%,则其带宽应该是(26)Kb/s。
最新回复
(
0
)