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  3. Modern offices may scorn the stuff, but paper has found a new use in the laboratory — as the basis for 3D models of tumours and

Modern offices may scorn the stuff, but paper has found a new use in the laboratory — as the basis for 3D models of tumours and

admin2012-06-20  33
问题     Modern offices may scorn the stuff, but paper has found a new use in the laboratory — as the basis for 3D models of tumours and damaged hearts.
    Chemist George Whitesides and his colleagues at Harvard University reckon that the balls of cells they have grown at the centre of stacked paper could help us better understand how tumours and damaged hearts respond to drugs, and even to select therapies most suited to individuals.
    Cells tend to be grown on flat plates in the lab, which isn’t representative of the 3D structure of cells in the body. "It’s nothing like human tissue," says Whitesides. In our bodies, cells are exposed to natural concentration gradients: the further away they are from major blood vessels, the less oxygen and nutrients they get. But in 2D cell cultures, such gradients aren’t present. "We need to move away from those boring flatlands that cell culture dishes represent," says cell biologist Emmanuel Reynaud who was not involved in the research.
    Although techniques for growing cells in 3D exist, many are time-consuming and far from perfect. For example, once the cells have grown, the cultures need to be sliced with a knife to be analysed. "Not only does this kill some cells, it’s extremely difficult to do," Whitesides says. His group has now developed a cheap alternative.
    The team start by spraying a gel containing their cells onto small sheets of sterile chromatography paper (无菌色谱纸). The cells they used included human lung cancer cells, human fibroblasts (纤维原细胞), which make up connective tissue, and mouse immune cells. "I tried everything I could get my hands on," says Whitesides.
    The cells seeped through the paper "like coffee through a napkin (餐巾)", he says. When the researchers stacked up eight sheets of cell-infused paper and suspended them in an oxygen and nutrient-rich broth (液体培养基), they found that the cells grew into a ball.
    To analyse how these cells behaved, the researchers simply peeled off the layers one at a time and analysed them individually. It seemed that the outer cells closer to the medium were nourished while the cells on the inside showed signs of being starved, which is what you would expect to happen to a tumour inside the body.
What can we know about the cells in our body from the third paragraph?
选项 A、They are less effective in treating tumors than those grown in the lab.
B、They are the same as the cells grown on the flat plate in the laboratory.
C、The closer they are to the main blood vessels, the less oxygen and nutrients they get.
D、Their distance from the main blood vessels determines the amount of oxygen and nutrients they gain.
答案D
解析 第三段第三句提到体内的细胞面临着自然的浓度差：即它们离主血管越远，获得的氧气和营养越少，由此可知[C]与文意相反，可排除。[D](他们离主血管的距离决定着它们获得氧气和营养的数量)与文意表达一致，故为答案。另外两项与文意不符。
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