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Scientists have known for more than two decades that cancer is a disease of the genes. Something scrambles the DNA inside a nucleus, and suddenly, instead of dividing in a measured fashion, a cell begins to copy itself furiously. Unlike an ordinary cell, it never, stops. But describing the process isn’t the same as figuring it out. Cancer cells are so radically different from normal ones that it’s almost impossible to untangle the sequence of events that made them that way. So for years researchers have been attacking the problem by taking normal cells and trying to determine what changes will turn them cancerous - always Without success. According to a report in the current issue of Nature, a team of scientists based at M. I .T.’s Whitehead Institute for Biomedical Research has finally managed to make human ceils malignant -a feat they accomplished with two different cell types by inserting just three altered genes into their DNA. While these manipulations were done only in lab dishes and won’t lead to any immediate treatment, they appear to be a crucial step in understanding the disease. This is a "landmark paper," wrote Jonathan Weitzman and Moshe Yaniv of the Pasteur Institute in Paris, in an accompanying commentary. The dramatic new result traces back to a breakthrough in 1983, when the Whitehead’s Robert Weinberg and colleagues showed that mouse cells would become cancerous when subjected to two altered genes. But when they tried such alterations on human cells, they didn’t work. Since then, scientists have learned that mouse cells differ from human cells in an important respect: they have higher levels of an enzyme called telomerase. That enzyme keeps caplike structures called telomeres on the ends of chromosomes from getting shorter with each round of cell division. Such shortening is part of a cell’s aging process, and since cancer cells keep dividing forever, the Whitehead group reasoned that making human cells more mouselike might also make them cancerous. The strategy worked. The scientists took connective-tissue and kidney cells and introduce three altered genes—one that makes cells divide rapidly; another that disables two substances meant to rein in excessive division; and a third that promotes the production of telomerase, which made the cells essentially immortal. They’d created a tumor in a test tube. "Some people believed that telomerase wasn’t that important," says the Whitehead’s William Hahn, the study’s lead author. "This allows us to say with some certainty that it is.\ One key factor in creating tumor with human cells is ______.
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药物中的特殊杂质 盐酸普鲁卡因注射液
王某携全家老小赴深圳经商，于是将几件不易携带但又较为贵重的家具交给邻居周某保管，其中包括价值4000元的全自动洗衣机一台。与此同时，周某委托王某将自己一个祖传的手镯带到深圳去卖掉，价格以市场价为准。王某到达深圳后，经调查，该手镯的市场价为1万元，正当王某准备拿到市场上卖掉时，其好友秦某前来探望，并发现了该手镯。王某告知了该手镯的情况，秦某表示特别喜欢该手镯，请王某以5000元的价格卖给他，并许以好处。王某考虑再三，答应了秦某的要求。周某后来得知了此事，遂要求王某赔偿损失，但王某坚称5000元即是市场价格，拒绝赔偿。周某一气之下将王某的洗衣机以自己的名义卖给了不知情的谭某，谭某支付了价款并实际占有了该洗衣机。问题： 本案中共存在哪几个法律关系？
When Lewis Ziska wanted to see how a warmer wood with more carbon dioxide in the air would affect certain plants, he didn’t set up his experiment in a greenhouse or boot up a computer model. He headed for Baltimore. Cities are typically 7 degrees warmer than the countryside, as well as big sources of CO2. So Ziska, a plant physiologist at the U.S. Department of Agriculture, compa,ed ragweed growing in vacant lots in Baltimore with ragweed in rural fields—and discovered the dark side of sunny claims that global warming will produce a "greening of planet Earth". Urban ragweed grows three to five times bigger than rural ragweed, starts spewing allergenic pollen weeks earlier each spring and produces 10 times more pollen. In as few as 20 years the whole world will have CO2 levels at least as high as some cities do now. As climate changes due to the greenhouse effect, hayfever sufferers would do well to lay in copious supplies of Kleenex. From mosquitoes that carry tropical diseases such as malaria, to plants that produce allergenic pollen, scientists are finding that a warmer, CO2-rich world will be very, very. good for plants, insects and microbes that make us sick. Although the most obvious threat to human health is more frequent and more intense heat weaves, such as the one that killed thousands of people in Europe in 2003, that is only the beginning. In the case of plants, it’s not just that they grow faster and shed pollen earlier as the woad warms. The carbon-enriched air also alters their physiology. In a six-year study at a pine forest managed by Duke University, where pipes and fans adjust the CO2 concentration and the air, scientists found that elevated CO2 increases the growth rate of poison ivy. More surprising, by increasing the air’s ration of carbon to nitrogen, elevated CO2 also increases the toxicity of urushiol, the rash-causing oil. "Poison ivy will become not just more abundant in the future," says Ziska. "It will also be more toxic. " Plants interpret warmth and abundant CO2as: what a great climate for reproduction. Monitoring stations in Europe are recording higher pollen counts for allergenic grasses and trees, led by birch and hazel, notes a 2005 study by the Center for Health and the Global Environment at Harvard Medical School. Those counts are rising earlier each year: the warming already underway is shifting the pollen season by almost one day per year. By 2017, you’ll be reaching for tissues nine days sooner than you do now. More good news: in a greenhouse world po]len will be not only more abundant but more allergenic, he and Ziska find. Since cities already have the high CO2 levels that the rest of the world can soon expect, "’there is no question these climate-related changes have already begun," says Arlington, Texas, Mayo," Dr. Robert Cluck. "Every summner we’re seeing West Nile virus earlier and earlier, and the higher levels of ozone that come with higher temperatures are increasing the rates of asthma and causing heart and lung damage comparable to living with a cigarette smoker. " In a greenhouse world, tropical diseases will expand their range and their prevalence. For instance, alternating floods and droughts—the pattern that comes with climate change—provide perfect conditions for mosquitoes that carry malaria, West Nile and dengue fever. Warming makes mosquitoes bit more. They’ll face fewer predators, too. The frequent droughts expected in a greenhouse world are murder on damselflies and dragonflies. As dengue fever, yellow fever and malaria extend their range to higher elevations and higher latitudes, those diseases could appear in the developed woad, too. The southern tier of western and eastern Europe, as well as the southern United States, are most at risk, says Harvard’s Epstein. Dengue fever has already popped up on the Mexican side of the U.S. border, a worrisome expansion of its current range. Say this for the climate contrarians who insist that a warmer world will he a better, more productive world: if they’re referring to allergens and pathogens, they’re dead right. What is the author’s main purpose in writing this article
患者，女，25岁，因停经50天感心慌，胸闷诊为“先天性心脏病合并早孕”来院咨询是否可继续妊娠。查体：口唇、甲床轻度发绀，血压正常，心率80次/分，律整，胸骨左缘第3～4肋间可闻Ⅰ～Ⅱ级收缩期杂音，肺动脉瓣第二心音亢进，双肺呼吸音清，超声诊断：室间隔缺损伴肺动脉高压，下列处理措施哪项是正确的
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