【文章內(nèi)容簡介】 pears. Space travel can be so delightful but at the same time invisibly dangerous. For instance, astronauts lose bone mass. That’ s why exercise is considered so vital that National Aeronautics and Space Administration (NASA) puts it right on the workday schedule. The focus on fitness is as much about science and the future as it is about keeping any individual astronauts return home, and, more importantly, how to maintain strength and fitness for the two and a half years or more that it would take to make a roundtrip to Mars. is the major challenge to astronauts when they sleep in space? A. Seeking a way to fall asleep quickly B. Choosing a fortable sleeping bag C. Deciding on a proper sleep position D. Finding a right time to go to sleep. astronauts will suffer from a carbondioxide headache when _____. A. the y circle around on their bikes B. they use microputers without a stop C. they watch a movie while pedaling D. they exercise in one place for a long time astronauts feel sick on the station during the first few days because _____. A. their senses stop working B. their brains receive contradictory (矛盾的） messages. C. they float out of their seats unexpectedly have to stand up straight of the NASA’ s major concerns about astronauts is _____. A. how much exercise they do on the station B. how they can remain healthy for long in space C. whether they can recover after returning home D. whether they are able to go back to the station[來源 :學(xué) ,科 ,網(wǎng) Z,X,X,K] D For centuries, medical pioneers have refined a variety of methods and medicines to treat sickness, injury, and disability, enabling people to live longer and healthier lives. “ A salamander (a small lizardlike animal) can grow back its leg. Why can39。t a human do the same?” asked Peruvianborn surgeon Dr. Anthony Atala in a recent interview. The question, a reference to work aiming to grow new limbs for wounded soldiers, captures the inventive spirit of regenerative medicine. This innovative field seeks to provide patients with replacement body parts. These parts are not made of steel。 they are the real things living cells, tissue, and even medicine is still mostly experimental, with clinical applications limited to procedures such as growing sheets of skin on burns and wounds. One of its most significant advances took place in 1999， when a research group at North Carolina ’ s Wake Forest Institute for Regenerative Medicine conducted a successful an replacement with a laboratorygrown bladder. Since then, the team, led by Dr. Atala, has continued to generate a variety of other tissues and ans 一 from kidneys to ears. The field of regenerative medicine builds on work conducted in the early twentieth century with the first successful transplants of donated human soft tissue and bone. However, donor ans are not always the best option. First of all, they are in short supply, and many people die while waiting for an available an。 in the United States alone, more than 100,000 people are waiting for an transplants. Secondly, a patient’ s body may ultimately reject the transplanted donor an. An advantage of regenerative medicine is that the tissues are grown from a patient’ s own cells and will not be rejected by the body’ s immune system. Today, several labs are working to create bioartificial body parts. Scie ntists at Columbia and Yale Universities have grown a jawbone and a lung. At the University of Minnesota, Doris Taylor has created a beating bioartificial rat heart. Dr. Atala’ s medical team has reported longterm success with bioengineered bladders implanted into young patients with spina bifida (a birth defect that involves the inplete development of the spinal cord). And at the University of Michigan, H. David Humes has created an artificial kidney. So far, the kidney procedure has only been used successfully with sheep, but there is hope that one day similar kidney will be implantable in a human patient. The continuing research of scientists such as these may eventually make donor ans unnecessary and, as a result, significantly increase individuals’ chances of survival. 32. In the latest field of regenerative medicine, what are replacement parts made of? A. Donated cells, tissues and ans. B. Rejected cells, tissues and ans. C. Cells, tissues and ans of one’ s own. D. Cells, tissues and ans made of steel. 33. What have scientists experimented successfully on for a bioartificial kidney? A. Patients. B