首页
登录
职称英语
Seven years ago, an Environmental Protection Agency statistician stunned rese
Seven years ago, an Environmental Protection Agency statistician stunned rese
游客
2023-12-20
10
管理
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." [br] Which of the following statements about human alveolar macrophage is TRUE?
选项
A、Airborne dust may trigger suppressor macrophage suicides.
B、Airborne dust may trigger stimulatory macrophage suicides.
C、The ratio of suppressor macrophages to stimulatory ones in people with lung diseases is much higher than that in people with healthy lungs.
D、Only stimulatory macrophages show responses to airborne dust.
答案
A
解析
该题问:下列哪一项关于人类肺泡中的巨噬细胞的陈述是正确的?见本文第七段第三句一.most of the suppressor macrophages underwent apoptosis,or cellular suicide,while the stimulatory ones survived unaffected.可知选项A正确。B项意思正好相反。从第六段可知,肺部健康的人的suppressor macrophages与stimulatory macro- phages的比例是10比1,有呼吸疾病的人则是3比1,C项意思相反。
转载请注明原文地址:https://www.tihaiku.com/zcyy/3288918.html
相关试题推荐
Seekingtomatchadesiretomakemoneywithhisenvironmentalinstincts,Lo
Seekingtomatchadesiretomakemoneywithhisenvironmentalinstincts,Lo
Seekingtomatchadesiretomakemoneywithhisenvironmentalinstincts,Lo
TheAgencyforInternationalDevelopmentisa______organization.[br]Accordin
1 Theword"environmentalist"hasbeenbandiedaboutsomuchthatapersoncan’
[originaltext]TheAmericanSpaceAgencyiscontinuingexperimentsthatwould
[originaltext]TheU.S.SpaceAgencyNASAsaysRussia’sorbitingMirspacest
Sevenyearsago,anEnvironmentalProtectionAgencystatisticianstunnedrese
Sevenyearsago,anEnvironmentalProtectionAgencystatisticianstunnedrese
[originaltext]TheU.S.SpaceAgencyNASAsaysRussia’sorbitingMirspacest
随机试题
当系统的工作压力大于2.4MPa时,应采用消防水泵串联或()分区供水形式。
肝硬化失代偿期的内分泌紊乱不包括()A.雌激素增加 B.糖皮质激素减少
A. B. C. D.
当某商品的期货价格过低而现货价格过高时,交易者通常会( ),从而会使两者价差趋
经营∶纳税A.借书∶归还 B.评比∶投票 C.球赛∶运动 D.注册∶登记
根据ICD-10的说法,精神病性症状包括()。多选A.显著的精神运动性兴奋
对于经税务机关认定为企业集团需每年定期报送企业集团及其成员单位税收调查数据的委托
电信市场准入管制的目标是()。A:保护电信企业的垄断地位 B:建立合理的市场结
起重吊装采用2个以上吊点起吊时,下列吊索与水平线夹角,宜选用的角度是()。201
现浇混凝土灌注桩,按成孔方法分为()。A、柱锤冲扩桩 B、泥浆护壁成孔灌注桩
最新回复
(
0
)