Brain cancer: Happy families, hidden dangers 
　　IT IS well known that many sorts of cancer run in families; in other words you get them (or, at least, a genetic predisposition towards them) from your parents. The idea that you can get cancer from your brothers and sisters is more surprising. But that is the conclusion of a study conducted by Andrea Altieri and his colleagues at the German Cancer Research Centre, in Heidelberg.
　　Dr Altieri was looking for evidence to support the idea that at least some brain cancers are triggered by viruses and that children in large families are therefore at greater risk, because they are more likely to be exposed to childhood viral infections. This is not a new suggestion, but brain cancer is rare, and its rarity makes it hard to study systematically. In any field of science, small samples lead to spurious results. To find reliable answers to questions about something as infrequent as brain cancer, a whole country’s worth of data is needed.
　　Fortunately, at least one country can provide those data: Sweden. And in the current issue of Neurology, Dr Altieri describes what he discovered when he analysed the records of the Swedish Family Cancer Database. This includes everyone born in Sweden since 1931, together with their parents even if born before that date.
　　More than 13,600 Swedes have developed brain tumours in the intervening decades. In small families there was no relationship between an individual’s risk of brain cancer and the number of siblings he had. However, children in families with five or more offspring had twice the average chance of developing brain cancer over the course of their lives compared with those who had no brothers and sisters at all. Digging deeper, Dr Altieri found a more startling result. When he looked at those people who had had their cancer as children or young teenagers he found the rate was even higher—and that it was particularly high for those with many younger siblings. Under-15s with three or more younger siblings were 3.7 times more likely than only children to develop a common type of brain cancer called a meningioma, and at significantly higher risk of every other form of the disease that the researchers considered.
　　This finding, added to evidence linking viruses to a broad mixture of different cancers, has led Dr Altieri and his team to propose that bugs caught during childhood from younger siblings, may, indeed, lead to brain tumours. The initial premise of the argument, that the more children there are to bite, spit, climb and cuddle together, the more infections they pick up, has been demonstrated in studies on nursery schools. But the mechanisms by which younger siblings have more influence than elder ones are speculative. Experience suggests that snotty-nosed toddlers pass their infections on to family members more frequently than older children do. So it could simply be the frequency of infection that is important. An eldest child will be exposed to all of his siblings’ infections when they are at the snotty�瞡osed toddler stage; a second child will be exposed to one fewer; and so on.
　　考研詞匯：
　　trigger[ˈtrigə]
　　vt.引發(fā)，引起，觸發(fā);n.扳機(jī)
　　[真題例句] The explanation for insensitivity to smell seems to be that the brain finds it (14：inefficient) to keep all smell receptors working all the time but can (15：create) new receptors if necessary.[2005年完形]
　　(15) [A] introduce[B] summon
　　[C] trigger[D] create
　　[例句精譯] 對(duì)氣味不敏感的解釋或許是，大腦似乎覺得讓所有的嗅覺接收器每時(shí)每刻都工作效率太低，只在必要時(shí)激活一些新的嗅覺接收器。
　　(15) [A] 介紹，傳入[B] 召喚，召集
　　[C] 引發(fā)，引起[D] 創(chuàng)造，創(chuàng)作
　　spurious[ˈspjuəriəs]
　　a.偽造的, 假造的, 欺騙的
　　intervene[ˌintəˈvi:n]
　　v.①(in)干涉，干預(yù);②插入，介入
　　initial[iˈniʃəl]
　　a.①最初的，開頭的;②詞首的;n.詞首大寫字母

　　[真題例句] Despite a spell of initial (a.①) optimism in the 1960s and 1970s when it appeared that transistor circuits and microprocessors might be able to copy the action of the human brain by the year 2010, researchers lately have begun to extend that forecast by decades if not centuries.[2002年閱讀2]
　　[例句精譯] 雖然一開始在20世紀(jì)60年代和70年代有過(guò)一段樂(lè)觀的時(shí)期——那時(shí)候仿佛晶體管電路和微處理器的發(fā)展將使他們?cè)?010年能夠模仿人類大腦的活動(dòng)——但是最近研究人員已經(jīng)開始將這個(gè)預(yù)測(cè)延后數(shù)十年，甚至數(shù)百年。
　　speculative[5spekjulEtiv]
　　a.投機(jī)的，猜測(cè)的，深思熟慮的
　　[真題例句] Two other explanations are more speculative.[1998年閱讀2]
　　[例句精譯] 其他兩種解釋帶有很大的猜測(cè)性。
　　sibling[5sibliN]
　　n.兄弟, 姐妹, 同胞, 同屬
　　背景常識(shí)介紹：
　　腦癌又稱顱內(nèi)腫瘤或腦腫瘤，它包括腦實(shí)質(zhì)或其鄰近組織(血管、脈絡(luò)體、垂體、松果體等)原發(fā)的腫瘤。
　　研究發(fā)現(xiàn)排行大的人容易患腦癌。《神經(jīng)學(xué)》報(bào)道，有3個(gè)或3個(gè)以上弟妹的人最容易在15歲之前患上腦癌。德國(guó)的科學(xué)家通過(guò)對(duì)1300多名腦癌患者的跟蹤調(diào)查發(fā)現(xiàn)，腦癌的患癌率與其擁有弟弟妹妹的數(shù)量有關(guān)，而與其擁有哥哥姐姐的數(shù)量并無(wú)聯(lián)系。這或許和其在成長(zhǎng)過(guò)程中神經(jīng)系統(tǒng)受感染和反復(fù)感染的機(jī)會(huì)的多寡有關(guān)。
　　參考譯文：
　　腦癌：幸福家庭，危機(jī)暗伏
　　癌癥會(huì)在家族中蔓延是大家熟知的;換句話說(shuō)，你是從父母那里得到癌癥的(或至少是易患癌癥的傾向)。而你會(huì)從兄弟姐妹那里得到癌癥的說(shuō)法卻更讓人吃驚。但是位于海德堡的德國(guó)癌癥研究中心的安德里亞·阿爾提耶里與同事們經(jīng)過(guò)研究得出的結(jié)論。
　　阿爾提耶里博士本來(lái)是在尋找證據(jù)來(lái)支持這個(gè)觀點(diǎn)，即至少部分腦癌是由病毒感染引起的，這讓大家庭中的孩子面臨更大危險(xiǎn)，因?yàn)樗麄兏�容易暴露在兒童時(shí)期的病毒感染中。這個(gè)提議并不新鮮，但腦癌是罕見的，這使做系統(tǒng)研究變得很難。在任何科學(xué)領(lǐng)域，少量的樣本會(huì)帶來(lái)不可靠的結(jié)果。要給腦癌這樣罕見的疾病找到可靠結(jié)論就需要整個(gè)國(guó)家的統(tǒng)計(jì)數(shù)據(jù)。
　　幸運(yùn)的是至少有一個(gè)國(guó)家可以提供這樣的數(shù)據(jù)：瑞典。在本期的《神經(jīng)病學(xué)》上，阿爾提耶里博士描述了他在分析瑞典家庭癌癥數(shù)據(jù)庫(kù)中的記錄之后的發(fā)現(xiàn)。其中包含1931年以來(lái)在瑞典出生的所有人，甚至還有他們?cè)诖饲俺錾�的父母�?
　　在這之間的幾十年中超過(guò)13，600瑞典人得了腦癌。在小家庭里一個(gè)人得腦癌的風(fēng)險(xiǎn)與他的兄弟姐妹數(shù)目沒(méi)有關(guān)聯(lián)性。然而在有5個(gè)以上的孩子的家庭里，這些孩子在他們生命中得腦癌的平均風(fēng)險(xiǎn)是那些沒(méi)有兄弟姐妹的人的兩倍。隨著更深入的研究，阿爾提耶里博士有了更為驚人的發(fā)現(xiàn)。當(dāng)他研究那些在兒童時(shí)期或青少年時(shí)期得腦癌的人時(shí)，他發(fā)現(xiàn)得病的幾率更高——尤其是那些擁有許多弟弟妹妹的人。在15歲以下的擁有3個(gè)或更多弟弟妹妹的人比獨(dú)生子得腦膜瘤的機(jī)會(huì)高3.7倍，并且研究人員認(rèn)為他們得其他癌癥的機(jī)會(huì)也明顯更大。
　　這個(gè)發(fā)現(xiàn)為病毒和各種各樣的癌癥之間的聯(lián)系補(bǔ)充了證據(jù)，也使阿爾提耶里博士和他的團(tuán)隊(duì)提出在童年時(shí)從弟弟妹妹那里傳染來(lái)的病菌會(huì)導(dǎo)致腦癌。最初的假設(shè)是越多孩子在一起嬉鬧，越多的身體、唾液和口的接觸，感染的機(jī)會(huì)就越多。這已經(jīng)在托兒所里證實(shí)了。但弟弟妹妹們比年長(zhǎng)的兄弟姐妹更有影響力現(xiàn)在還只是猜測(cè)。根據(jù)經(jīng)驗(yàn)來(lái)說(shuō)掛著鼻涕的學(xué)步頑童比大一些的孩子更容易把疾病傳染給家里其他人。所以可能重要的只是感染疾病的次數(shù)。最大的孩子要經(jīng)歷所有弟弟妹妹們的幼年階段;第二個(gè)孩子將少經(jīng)歷一個(gè);以此類推。