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译者 zjgjasoncool
Platelets can quickly stanch the bleeding from a cut in your finger, but the hemorrhaging caused by a car crash or a battlefield injury might overwhelm the blood-clotting abilities of these cell fragments. Now, researchers report that they have designed a potential helper for such situations, a synthetic platelet that they show can curtail blood loss in animals.
血小板可以使手指的伤口迅速止血，但面对车祸或是战场上的大出血，这些细胞碎片的凝血功能是不够的。日前，研究人员报告说他们发明了一种应对这种情况的潜在帮手，一种已经能在动物身上抑制流血的人造血小板。
After an injury, platelets stick to the walls of damaged vessels, to each other, and to clotting proteins, forming a plug. Platelet transfusions can boost clotting in trauma patients, wounded soldiers, and people with low platelet counts because of disease or cancer treatment. But platelets obtained from donated blood have several drawbacks, including a shelf life of only 5 days--versus 6 weeks for red blood cells--and a risk of bacterial infections.
受伤以后，血小板粘在破损血管壁上，并且互相粘结，从而使蛋白质凝固，形成血栓。输血小板可以帮助创伤患者、受伤的士兵和因治疗疾病或癌症而导致血小板过低的人凝血。但从捐献的血液中提取的血小板有一些缺陷，其保存期只有5天（红血球为6周），并且有受细菌感染的风险。
Researchers have devised replacement platelets, such as red blood cells outfitted with a three-amino-acid sequence called RGD that natural platelets latch on to, thus potentially inducing a clot. So far, none of these alternatives has reached the emergency room. "If there was a suitable platelet substitute, that would be a tremendous achievement for clinical medicine," says hematologist Marcel Levi of the University of Amsterdam in the Netherlands.
研究人员已经发明了一些血小板的替代品，例如带有被称之为RGD的三胺酸序列的红血球，天然血小板就吸附这种红血球上，从而导致凝血。到目前为止，这些替代品均未在急救室使用。荷兰阿姆斯特丹大学的血液学家Marcel Levi说："如果出现一种合适的血小板替代品，那会是临床医疗领域的巨大成就。"
Six years ago, James Bertram, then a graduate student at Yale University, and colleagues started developing a substitute. Their design involves spheres about one-tenth the diameter of a platelet and made of the same biodegradable polyester used in absorbable sutures. The spheres carry molecules of polyethylene glycol--an ingredient in everything from laxatives to Dr Pepper--tipped with RGD or a slightly longer string of amino acids. The idea is that the spheres will adhere to platelets and help them congregate into a clot.
6年前，当时还是研究生的James Bertram和他的同僚开始开发血小板的替代品。他们的设计为直径约为天然血小板十分之一的球体，材料与可吸收缝合线使用的生物可降解聚合物一样。这些球体带有聚乙二醇原子（很多商品，如通便剂、胡椒博士饮料，都有这种成分），顶端是RGD序列或稍长一些的氨基酸串。其创意在与这些球体粘在血小板上，并且帮助血小板聚集凝血。
The researchers tested the spheres in rats with a cut in the femoral artery, the large vessel that carries blood into the hind leg. These wounds sealed themselves in about 4 minutes, but an intravenous injection of the synthetic platelets, given just after the cut, reduced the bleeding time by 23%, the researchers report today in Science Translational Medicine. The spheres crammed into the clot that formed at the site of the cut, the team found, suggesting that they help the animals' own platelets coalesce.
研究人员在大鼠的股动脉（向后腿送血的大血管）伤口上测试了这些球体。研究人员在《科学转化医学》杂志今天的报道中说，这些伤口约4分钟自愈，但是如果在伤口出现后即静脉注射人造血小板，出血时间可以减少23%。该团对发现，伤口处的血块中塞满了这种球体，这就意味着球体促进了动物自身血小板的结合。
"It's one of the first times that we have been able to stop bleeding intravenously" rather than with measures like bandages and sutures, says senior author Erin Lavik, a biomedical engineer at Case Western Reserve University in Cleveland, Ohio. She notes that the U.S. Food and Drug Administration has already okayed the materials in the artificial platelets for other medical uses, which might make it easier to get the product approved. Lavik says that the team now wants to gauge the platelets' clotting capability in larger animals, such as pigs, that are more similar to humans.
俄亥俄州克利夫兰市Case Western Reserve大学的生物医药工程师兼资深作家Erin Lavik说，这是人类首次以静脉注射的方式成功止血，而不是用绷带或缝合线。他强调说美国食品药品监督管理局已经同意这种制造人造血小板材料用于其它医疗领域，这或许可以使人造血小板的审批容易一些。Lavik说该团队希望在更接近人的大动物身上（例如猪）进行实验人造血小板的凝血能力。
Some experts call the results promising. "They have some potentially exciting, preliminary work," says hematologist Paul Ness of the Johns Hopkins Medical Institutions in Baltimore, Maryland. "I was quite impressed with the science," adds hematologist Morris Blajchman of McMaster University in Hamilton, Canada.
一些专家宣称人造血小板的前途一片光明。马里兰州巴尔的摩市约翰霍普金斯医疗研究所的血液学家Paul Ness说："他们做了一些令人激动的基础工作，很有潜力。"加拿大Hamilton市McMaster大学的血液学家Morris Biajchman说："这项科技给我留下了深深的印象。"
But John Hess, a hematologist at the University of Maryland School of Medicine in Baltimore and the former head of the U.S. Army's blood product development program, isn't sanguine. Patients suffering from severe bleeding are losing large amounts of platelets, so an approach that relies on recruiting platelets might not work, says Hess. "You might run out of platelets before you can control the hemorrhage."
但前美军陆军血液制品开发项目的主任兼巴尔的摩市马里兰医学院的血液学家John Hess并不抱乐观的态度。严重出血的病人会同时流失大量的血小板，所以来吸引血小板的方法可能并不管用。Hess说："在控制住大出血之前，人的血小板可能已经流光了。"
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