托福阅读：挑战TIME第16期

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托福阅读：挑战TIME 第16 期
托福阅读复习了很久，却不知道自己的水平如何？快来看看前程百利小编为您整理的挑战
TIME系列，大家可以通过这一系列的托福阅读训练，来了解自己目前的水平，快来挑战吧。

Why Banked Blood Goes Bad

【Introduction】

输送血液可以称为生命的礼物。然而，从每年5百万输血病人的大部分情况来看，实际上，
输血弊大于利。

【Section One】Article

It's a problem that doctors have been wrestling with for several years, as study
after study shows a disturbing spike in heart disease and death in patients receiving
transfusions. The trend affects almost every group of critically ill patients — from
trauma sufferers in the ER to heart attack victims, patients with anemia and those
undergoing chemotherapy. This increase in death and heart disease, doctors say, is
unrelated to infectious blood-borne diseases or allergic reactions that often follow
transfusions. "After you control for sickness and all sorts of things, patients who
receive transfusions still have more heart attacks. It makes no sense," says Dr.
Jonathan Stamler, a professor of medicine at Duke University Medical Center.

Logically, and medically, patients who need transfusions — those with low blood
counts — should benefit immediately from a transfusion of new oxygen-laden red blood
cells. Yet many get sicker. Puzzled by the paradox, Stamler and his colleagues decided
to look more closely at banked blood — to figure out whether it underwent certain changes
that turned it from life-saving in the donor to potentially deadly in the bag.

Their finding, reported this week in the Proceedings of the National Academy of
Sciences: nitric oxide (NO). A workhorse of the blood, the gas helps red blood cells
ferry oxygen to tissues and props open tiny vessels to allow freer blood flow. It turns
out that within hours of leaving the body, levels of nitric oxide in the blood begin
to drop, until, by the time donated blood expires after 42 days, the gas is almost
nonexistent. "The reality is that we are giving blood that cannot deliver oxygen
properly," says Stamler, lead author of the study. "Many patients who are getting blood
are being put at incre ased risk."

Previous trials have shown that heart disease patients, for example, who receive
a blood transfusion to help restore oxygen to deprived tissues, have a 25% chance of
having a heart attack and an 8% chance of dying within 30 days; similar patients who