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【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 this might happen. But in the last 10 years, doctors have reported regeneration in smaller parts of the body, most often fingers. Regeneration is not a newly-discovered process. For centuries, scientists have seen it work in some kinds of animals. Break off a lizards (蜥蜴的) tail, for example, and it will grow a new tail. Scientists now are looking for a way to turn on this exciting ability in more highly-developed animals, including humans. Their experiments show that nerves, cell chemistry and the natural electric currents in the body all seem to have a part in this process. The body of every animal contains general purpose cells that change into whatever kind of cells the body needs. Animals such as the lizard or salamander (蝾螈) use these cells to regenerate a new tail or leg when the old one is broken off. These cells collect around the wound. They form a mass called a blastema (胚基). The cells of the blastema begin to change. Some become bone cells, some muscle cells, some skin cells. Slowly, a new part re-grows from the body outward. When completed, the new part is just like the old one. More than 200 years ago, Italian scientist Luigi Spallanzani showed that younger animals have a greater ability to regenerate lost parts than older animals. So do animals lower on the ladder of evolutionary development. The major difference seems to be that less-developed animals have more nerves in their tails and legs than humans do in their arms and legs. Another helpful piece of information was discovered in the late 1800s. Scientists found that when a creature is injured, an electrical current flows around the wound. The strength of the current depends on how severe the wound is and on how much nerve tissue is present. In 1945, American scientist Meryl Rose tested another idea about regeneration. He thought a new limb might grow only from an open wound. Doctor Rose cut off the front legs of some frogs, below the knee. He kept the wounds wet with a strong salty liquid. This pred skin from growing over the wounds. The results were surprising. Frogs do not regenerate new legs naturally. But these frogs began to grow new limbs. About half of each cut-off leg grew back again. New bones and muscles developed. This research has led doctors to new ways of treating cut-off fingers. Doctors have observed, for example, that many children and some s will re-grow the top of a finger if the wound is left open. In Dr. Rose’s test, frogs with cut-off legs______.

A.
didn’t survive
B.
bled freely from their open wounds
C.
began to grow new limbs
D.
started to grow tails
题目标签:胚基蝾螈
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【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】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】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.
humans can never regenerate limbs
B.
human limbs may be regenerated on some animals first
C.
humans might be able to regenerate limbs in the future
D.
regeneration of human limbs will soon become a reality

【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.