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【简答题】

When people lose legs after accidents or illnesses, emergency care and artificial limbs(假肢)often allow them to walk again. Newts (蝾螈) in the same situation, on the other hand, can grow limbs back on their own! Scientists have known for a long time that certain animals can re-grow limbs, but they haven’t quite figured out how these creatures do it. Researchers have now come up with some new ideas. Their work may give people the ability to re-grow lost limbs. The researchers started with two experiments:when you cut a newt’s leg at the ankle, only the foot grows back;when you cut off a leg at the very end, the whole leg grows back. In both cases, the re-growth begins with stem cells. Stem cells can develop into nearly any type of cell in the body. How do a newt’s stem cells know when to grow only a foot and when to re-grow a whole leg? This question relates to another mystery. In newt’s, a cut-off leg will grow back only if the nerve bundle(神经束)in it also grows back , but if something prs the nerve bundle from growing, the stem cells at the wound won’t re-grow a new leg. In its study, a British team focused on a protein called n-AG. When the team pred nerves in a limb from growing, but added the n-AG protein to stem cells in the limb, the limb still re-grew. That protein seems to guide limb re-growth. People have proteins that are similar to n-AG. Further research into these materials may someday help human limbs recover by themselves. 40. In the experiments, the researchers cut off a newt’s foot or leg to find out _____. A. what stem cells were B. whether they would grow back C. how long it would take to re-grow D. how they would re-grow 41. A newt will re-grow its leg if _____. A. its ankle was cut off but the nerve bundle was good B. its leg was cut off and the nerve bundle stopped growing C. its leg was cut off and the nerve bundle could grow back D. its ankle and the nerve bundle were cut off 42. What do the underlined words “these materials” refer to? A. Nerve bundles and proteins. B. Proteins similar to n-AG. C. Stem cells and proteins. D. Stem cells and nerve bundles. 43. The first sentence of the passage _____. A. acts as a lead–in B. shows where researchers got their new ideas C. states the author’s opinion D. describes the result of researchers’ studies

题目标签:蝾螈神经束
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刷刷题刷刷变学霸
举一反三

【单选题】两栖动物:蝾螈

A.
蜥蜴:爬行动物
B.
脊椎动物:壁虎
C.
鱼类:娃娃鱼
D.
哺乳动物:鸵鸟

【单选题】臂丛神经束支损伤时可出现

A.
前锯肌功能丧失,双手推墙时出现翼状肩胛
B.
伸腕、伸指功能丧失,出现腕下垂
C.
两者均有
D.
两者均无

【单选题】对于蛙、蝾螈等两栖动物的“两栖”,我们可以理解为[ ]

A.
皮肤裸露有花纹的动物
B.
成体既可以在水中生活,也可以在陆地上生活
C.
幼体在水中发育,成体营水陆两栖
D.
具有变态发育的动物

【单选题】桡侧血管神经束

A.
近侧1/3血管与神经合并
B.
远侧1/3血管与神经合并
C.
中1/3血管与神经合并
D.
近侧和远侧1/3血管与神经分开,中1/3血管与神经合并
E.
近侧和远侧1/3血管与神经合并,中1/3血管与神经分开

【单选题】Regeneration of Limbs Most people would agree that it would be wonderful if humans could regenerate limbs. Those who have lost their arms or legs would be complete again. The day is still far off when...

A.
Scientists have lately found that a lizard will grow a new tail if the old one is broken off.
B.
Regeneration is a process discovered centuries ago.
C.
How severe a wound is determines the strength of the current flowing around it.
D.
The lizard, unlike man, is a less-developed animal.

【单选题】恶性蝾螈瘤是指()。

A.
伴有软骨分化的恶性周围神经鞘膜瘤
B.
伴有腺样分化的恶性周围神经鞘膜瘤
C.
伴有横纹肌肉瘤分化的恶性周围神经鞘膜瘤
D.
伴有神经内分泌分化的恶性周围神经鞘膜瘤
E.
伴有血管肉瘤分化的恶性周围神经鞘膜瘤

【单选题】Regeneration of Limbs Most people would agree that it would be wonderful if humans could regenerate limbs.These who have lost their arms or legs would be complete again.The day is still far off when t...

A.
humans can never regenerate limbs.
B.
humans might be able to regenerate limbs in the future.
C.
human limbs may be regenerated on some animals first.
D.
regeneration of human limbs will soon become a reality.