美国科学60秒 SSS 2015-05-29_在线英语听力室_免费在线英语听力学习网站

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Some 70 million American adults have high blood pressure. Three quarters of them rely on medication to keep the condition in check. But you've got to remember to actually take the daily dose. Now researchers have devised a longer-lasting alternative: a vaccine¹ to lower blood pressure...for rats, at least.

Scientists jabbed hypertensive rates with three doses of the formulation. It's a DNA² vaccine, containing DNA fragments from angiotensin II—a hormone³ that boosts blood pressure as well as fragments from hepatitis B, to guarantee the immune system's attention. Cells suck up the vaccine's DNA and start pumping out the proteins the DNA codes for. When the host's defenses get a whiff (a smell that is only smelled briefly⁴ or faintly) from the proteins, it reacts. It really revs⁵ up (make or become active or energetic) against the hepatitis B fragments, and while it's at it, it starts taking out some angiotensin II as well.

The result is a reduction of angiotensin II's usual blood raising effect, similar to what blood pressure meds like Benicar do. Less angiotensin II means more relaxed blood vessels⁶ and a drop in pressure. That effect lasted six months in the vaccinated⁷ rats, and lengthened⁸ their lifespan by eight weeks. Necropsies on the vaccinated rats revealed healthier heart tissue than normally found with high blood pressure, and no damage to the kidneys or livers. The results are in the journey Hypertension.

Other blood pressure vaccines⁹ have been tried, unsuccessfully, but this naval¹⁰ DNA-based vaccine could induce (bring about or give rise to) longer-lasting effect, and the hope of twice yearly shot instead of daily pills.

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1 vaccine
n.牛痘苗，疫苗；adj.牛痘的，疫苗的
参考例句：
The polio vaccine has saved millions of lives.脊髓灰质炎疫苗挽救了数以百万计的生命。 She takes a vaccine against influenza every fall.她每年秋季接种流感疫苗。

2 DNA
(缩)deoxyribonucleic acid 脱氧核糖核酸
参考例句：
DNA is stored in the nucleus of a cell.脱氧核糖核酸储存于细胞的细胞核里。 Gene mutations are alterations in the DNA code.基因突变是指DNA密码的改变。

3 hormone
n.荷尔蒙，激素，内分泌
参考例句：
Hormone implants are used as growth boosters.激素植入物被用作生长辅助剂。 This hormone interacts closely with other hormones in the body.这种荷尔蒙与体內其他荷尔蒙紧密地相互作用。

4 briefly
adv.简单地，简短地
参考例句：
I want to touch briefly on another aspect of the problem.我想简单地谈一下这个问题的另一方面。 He was kidnapped and briefly detained by a terrorist group.他被一个恐怖组织绑架并短暂拘禁。

5 revs
abbr.revolutions （复数）旋转，回转，转数n.发动机的旋转( rev的名词复数 )v.（使）加速( rev的第三人称单数 )；（数量、活动等）激增；（使发动机）快速旋转；（使）活跃起来
参考例句：
The engine was doing 6000 revs. 引擎转速为6000。来自互联网 Shared primary objectives included the highest possible torque and fast response from low revs. 共同的主要目标包括尽可能高转矩和响应速度快的低转速。来自互联网

6 vessels
n.血管( vessel的名词复数 )；船；容器；（具有特殊品质或接受特殊品质的）人
参考例句：
The river is navigable by vessels of up to 90 tons. 90 吨以下的船只可以从这条河通过。来自《简明英汉词典》 All modern vessels of any size are fitted with radar installations. 所有现代化船只都有雷达装置。来自《现代汉英综合大词典》

7 vaccinated
[医]已接种的，种痘的，接种过疫菌的
参考例句：
I was vaccinated against tetanus. 我接种了破伤风疫苗。 Were you vaccinated against smallpox as a child? 你小时候打过天花疫苗吗？

8 lengthened
（时间或空间）延长，伸长( lengthen的过去式和过去分词 )
参考例句：
The afternoon shadows lengthened. 下午影子渐渐变长了。 He wanted to have his coat lengthened a bit. 他要把上衣放长一些。

9 vaccines
疫苗，痘苗( vaccine的名词复数 )
参考例句：
His team are at the forefront of scientific research into vaccines. 他的小组处于疫苗科研的最前沿。 The vaccines were kept cool in refrigerators. 疫苗放在冰箱中冷藏。

10 naval
adj.海军的，军舰的，船的
参考例句：
He took part in a great naval battle.他参加了一次大海战。 The harbour is an important naval base.该港是一个重要的海军基地。