首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
Seven years ago, an Environmental Protection Agency statistician stunned researchers studying the effects of air pollution on he
Seven years ago, an Environmental Protection Agency statistician stunned researchers studying the effects of air pollution on he
admin
2010-02-20
39
问题
Seven years ago, an Environmental Protection Agency statistician stunned researchers studying the effects of air pollution on health when he reported analyses indicating that as many as 60,000 U. S. residents die each year from breathing federally allowed concentrations of airborne dust. This and subsequent studies figured prominently in EPA’s decision last year to ratchet down the permitted concentration of breathable particles in urban air -- and in human airways.
At the time, many industrialists argued that they shouldn’t have to pay for better pollution control because science had yet to suggest a plausible biological mechanism by which breathing low concentrations of urban dust might sicken or kill people. Now, scientists at the University of Texas Houston Health Science Center describe how they uncovered what they think may be one of the basic elements of that toxicity.
On the alert for foreign debris, a community of white blood cells known as alveolar macrophages patrols small airways of the lung. When these cells encounter suspicious material, they identify it and send out a chemical clarion call to rally the immune system cells best suited to disabling and disposing of such matter.
The trick is to recruit only as many troops as are needed. If they call in too many, the lung can sustain inflammatory damage from friendly fire. Alongside the small troop of macrophages that stimulates defense measures, a larger squadron of macrophages halts immune activity when it threatens the host.
Andrij Holian and his coworkers in Houston have found that people with healthy lungs normally have 10 times as many suppressor macrophages as stimulatory ones. In people with asthma and other chronic lung diseases -- who face an in- creased risk of respiratory disease from inhaling urban dust -- that ratio may be only 3 to 1. The reason for the difference is not known.
In a report to be published in the March Environmental Health Perspectives, Holian’s team describes test-tube studies of human alveolar macrophages. The macrophages showed no response to ask collected from the Mount St. Helen’s eruption. However, when exposed to airborne dust from St. Louis and Washington, D.C. , most of the suppressor macrophages underwent apoptosis, or cellular suicide, while the stimulatory ones survived unaffected. Ash from burned residual oil, a viscous boiler fuel, proved even more potent at triggering suppressor cell suicides.
It this test-tube system models what’s actually happening in the human lung, Holian told Science News, the different responses of the two classes of lung macrophages could result in an overly aggressive immune response to normal triggering events. Indeed, he says, it would be the first step in a cascade that can end in inflammatory lung injury. "We may one day be able to target this upstream event and prevent that injury."
"This is, I think, an important contribution to the overall story," says Daniel L. Costa of EPA’s pulmonary toxicology branch in Research Triangle Park, N.C.
Studies by EPA suggest that certain metals -- especially iron, vanadium, nickel, and copper -- in smoke from combustion of fossil fuels trigger particularly aggressive inflammatory responses by lung cells. Costa says these metals play a "preeminent" role in the toxicity of airborne particulates. When EPA researchers removed the metals, they also removed the toxicity, he says. Moreover, he notes, these metals tend to reside on the smallest water-soluble particles in urban air -- the fraction targeted for more aggressive controls under the new rules.
John Vandenberg, assistant director of EPA’s National Health and Environmental Effects Research Laboratory in Re- search Triangle Park, says Holian’s results are "a nice complement to our studies."
This passage is mainly about _____.
选项
A、how inhaled dust harms the lungs
B、the function of Environmental Protection Agency
C、the function of human alveolar macrophages
D、studies by Environmental Protection Agency
答案
A
解析
该题问:本方要介绍的是什么?本文通篇谈的是breathable particles in urban air and in human airways 和 hung diseases之间的因果关系。所以,选项A的how inhaled dust harms the lungs正确,应为正确答案。本文虽然反复提到Environmental Protection Agency(环保局),涉及到环保局的function及所进行的studies,但都只是次要意思,所以选项B和D都不是答案;虽然本文多次提到选项C的the function of human alveolar macrophages(人肺泡中的巨噬细胞的功能)中的human alveolar macrophages,但也仅是分析lung diseases时所涉及的次要意思而已。所以,选项C不是答案。
转载请注明原文地址:https://kaotiyun.com/show/FsqO777K
0
专业英语八级
相关试题推荐
A、Hisjobpaidalot.B、Hehasgotanotherjob.C、Hedidnotspendsomuchmoneyashehadbefore.D、Hesoldhiscar.C
A、Howtallareyou?B、Youhavebecomeverytall.C、Youhavetogrowsomemore.D、Howdidyoumeasuretheheight?B
Noonecanbeagreatthinkerwhodoesnotrealizethatasathinkeritishisfirstdutytofollowhisintellecttowhateverco
Racket,dinclamor,noise,whateveryouwanttocallit,unwantedsoundisAmerica’smostwidespreadnuisance.Butnoiseismore
Studentsshouldbehelpedbyacoursethatconsidersthecomputer’svariousimpactsoncommerce,economy,science,technology,c
ThefoundersoftheRepublicviewedtheirrevolutionprimarilyinpoliticalratherthaneconomicorsocialterms.Andtheytalke
A、Hecanworkbetterwithoutacomputer.B、Heisworkingwithanewcomputer.C、Hehasneverusedacomputerinhiswork.D、Hen
IusedtoboastthatBritainwasarelativelyuncorruptsociety.LookatFrance,Iwouldsay,whereahighproportionofrecent
EmployeesintheUSarepaidfortheirtime.Thismeansthattheyaresupposedto
TheAmericanTaxSystemGovernmentsraiserevenuesthroughtaxation.Ataxisa【1】_______paymenttogovernment.I
随机试题
A.风门B.丰隆C.阴谷、关元D.气海肾气虚所致的哮喘除选主穴外还可配用
患者,男,58岁。因结核性心包积液来院。患者2天来发热,呼吸困难明显加重,不能平卧,下肢水肿。查体:半卧位,喘息状,血压82/70mmHg,脉搏112次/分,呼吸22次/分,口唇轻绀,颈静脉明显怒张,心脏向两侧扩大,心音遥远,可触及奇脉,肝肋下4.0cm,
设备监造与施工监理的不同点包括()。
适筋梁正截面受力分析中,正常使用极限状态变形和裂缝宽度的计算在第( )阶段。
2017年4月,位于某市某镇某村的村委会经镇政府同意,在本村荒山开办一采矿场,随后承包给了村民沈某、孔某经营。因二人不交纳第二年的承包费,村委会在请镇政府出面协调未果的情况下,请该县矿产局进行干预。县矿产局调查后认为,该采矿场未依法办理采矿许可证,村委会不
对会议主持人的语言要求不包括()。
简述生产力对教育的制约作用。
在人类社会的发展史上,经历了三次科技革命,其标志为()。
(2013年真题)常言道:“不知者,不为罪。”请结合我国刑法学中的认识错误理论加以辨析。
据某地区统计,今年中小学生中肥胖学生约占10%,而且肥胖学生人数正在以8%的速度增长。假设近年中小学生的总量变化不大,据此我们可以推算出,明年该地区中小学生中肥胖学生的比例约为(28)。
最新回复
(
0
)