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下列哪项防治措施不适宜降低心脏病孕产妇的死亡率
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下列哪项是以医源性传播为主的肝炎
There are faults which age releases us from, and there are virtues which turn to vices with the lapse of years. The worst of these is thrift, which in early and middle life is wisdom and duty to practice for a provision against destitution. As time goes on this virtue is apt to turn into the ugliest, cruelest, shabbiest of the vices. Then the victim of it finds himself storing past all probable need of saying for himself or those next him, m the deprivation of the remoter kin of the race; In the earlier time when gain was symbolized by gold or silver, the miser had a sensual joy in the touch of his riches, in hearing the coins clink in their fall through his fingers, and in gloating upon their increase sensible m the hand and eye. Then the miser had his place among the great figures of misdoing; he was of a dramatic effect, like a murderer or a robber; and something of this bad distinction clung to him even when his coins had changed to paper currency, the clean, white notes of the only English bank, or the greenbacks of our innumerable banks of issue; but when the sense of riches had been transmuted to the balance in his favor at his banker’s, or the bonds in his drawer at the safety-deposit vault, all splendor had gone out of his vice. His bad eminence was gone, but he clung to the lust of gain which had ranked him with the picturesque wrong-doers, and which only ruin from without could save him from, unless he gave his remnant of strength to saving himself from it. Most aging men are sensible of all this, but few have the frankness of that aging man who once said that he who died rich died disgraced, and died the other day in the comparative poverty of fifty millions. The words "in the comparative poverty of fifty millions" at the end of the passage suggests a notion that ______.
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.\ The problem that has been annoying cancer researchers for years is the difficulty in telling ______.
决定孕早期合并心脏病患者是否能继续妊娠的重要依据是
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