評論
打印
Science and Technology
科技
Bacteria and behaviour
細菌和行為學
Gut instinct
腸道反應
Tantalising evidence that intestinal bacteria can influence mood
誘人的證據表明，腸道細菌可以影響人的情緒
A GOOD way to make yourself unpopular at dinner parties is to point out that a typical person is, from a microbiologist's perspective, a walking, talking Petri dish.
一個讓你自己在晚宴上不受歡迎的好方式就是，從微生物學家的角度指出，一位有代表性的人就是一個會走動并會說話的皮氏培養皿。
An extraordinary profusion of microscopic critters inhabit every crack and crevice of the typical human, so many that they probably outnumber the cells of the body upon and within which they dwell.
每位有代表性的人的裂紋和縫隙里生活著無數的微小生物，它們的數目如此之多可能超過它們所依靠并棲息的人體細胞。
Happily, these microbes are mostly harmless.
幸運地是，這些微生物大部分都是無害的。
Some of them, particularly those that live in the gut, are positively beneficial, helping with digestion and keeping the intestines in good working order.
其中一些，特別是那些生活在消化道里的微生物，實際上是有益的，不僅有助于消化還保持腸道良好的工作秩序。
That is no surprise—bacteria as much as people have an interest in keeping their homes in sound condition.
這毫不奇怪——細菌和人一樣也喜歡保持家園狀態完好。
What is surprising is the small but growing body of evidence which suggests that bacteria dwelling in the gut can affect the brain, too, and thereby influence an individual's mood and behaviour.
奇怪的是，雖然數量不多，但越來越多的證據表明，生活在腸道的細菌也可能影響大腦，繼而影響個人的情緒和行為。
The most recent paper on the topic, published this week in the Proceedings of the National Academy of Sciences, reports (like much of the research in this field) on results in mice.
本周有關該主題的論文刊登在《美國國家科學院院刊》上的一篇文章報道（像這個領域的許多研究一樣）了應用小鼠的實驗結果。
The researchers, led by Javier Bravo of University College, Cork, split their rodent subjects into two groups.
科克大學學院的哈維爾?布拉沃（Javier Bravo）帶領下的研究人員將這些嚙齒目動物分成兩組。
One lot were fed a special broth containing Lactobacillus rhamnosus, a gut-dwelling bacterium often found in yogurt and other dairy products.
一組以一種在酸奶和其它乳制品中經常發現的含乳酸桿菌屬鼠李糖乳桿菌（學名為Lactobacillus rhamnosus）的特別液體培養基喂食。
The others were fed an ordinary diet, not fortified with microbes.
另一組則以不用微生物強化的一般食物喂食。
The team then subjected the mice to a battery of tests that are used routinely to measure the emotional states of rodents.
然后，研究組人員對小鼠進行了一套測試。這套測試經常用于衡量嚙齒類動物的情感狀態。
Most (though not all) of these tests showed significant differences between the two groups of animals.
大部分（雖然不是所有的）測試表明，兩組動物之間有著顯著的不同。
One test featured a maze that had both enclosed and open tunnels.
一個測試是以封閉和敞開的隧道迷宮為特點。
The researchers found that the bacterially boosted mice ventured out into the open twice as often as the control mice,
研究人員發現，喂食了李糖乳桿菌的小鼠更經常冒險進入敞開的隧道，而且次數是對照小鼠的兩倍之多。
which they interpreted to mean that these rodents were more confident and less anxious than those not fed Lactobacillus.
他們的解釋意味著這些嚙齒類動物比那些沒有喂食李糖乳桿菌的小鼠更有信心而且焦慮更少。
In another test the animals were made to swim in a container from which they could not escape.
在另一組測試中，研究人員讓這些動物在一個無法逃脫的容器內游泳。
Bacteria-fed mice attempted to swim for longer than the others before they gave up and had to be rescued.
在這些小鼠放棄游泳并不得不被救出之前，李糖乳桿菌喂養的小鼠試圖游泳的時間比其它小鼠更長。
Such persistence is usually interpreted by students of rodent behaviour as evidence of a more positive mood.
這種持久性經常被研究嚙齒類動物行為的學生解釋為更積極情緒的證據。
Direct measurements of the animals' brains supported the behavioural results.
對這些動物大腦的多次直接測量結果支持了行為學方面的效果。
Levels of corticosterone, a stress hormone, were markedly lower in the bacteria-fed mice than they were in the control group when both groups were exposed to stressful situations.
當兩組小鼠進行應激實驗時，喂食李糖乳桿菌的小鼠體內的應激激素皮質甾酮含量比那些對照組的小鼠體內要明顯低地多。
The number of receptors for gamma-aminobutyric acid, a natural chemical messenger that helps dampen the activity of certain nerve cells, varied in statistically significant ways between the brains of the two groups, with more in some parts of the treated animals' brains and fewer in others.
γ-氨基丁酸是有助于抑制特定神經細胞活動的自然化學信使。兩組小鼠的大腦中γ-氨基丁酸感受器的數目以統計學上顯著的方式改變。γ-氨基丁酸感受器在處理過的小鼠大腦的一些部分出現較多些，而在沒有處理過的小鼠大腦內則少些。
Most intriguing of all, when Dr Bravo cut the animals' vagus nerves-which transmit signals between the gut and the brain-the differences between the groups vanished.
最引人注目的是，當布拉沃博士（Dr Bravo）切斷這些動物的迷走神經---傳輸腸道和大腦之間的信號---兩組小鼠間的差異突然消失了。
The idea that gut-dwelling microbes can affect an animal's state of mind may strike some people as outlandish, and there are certainly loose ends still to be tied up.
這個想法---生活在腸道里的微生物能夠影響動物的精神狀態---可能給一些人留下稀奇古怪的印象，而且肯定還有一些零星問題有待解決。
Beyond their evidence that the vagus nerve is crucial to the relationship, for example, Dr Bravo and his colleagues do not yet know the precise mechanisms at work.
他們手頭的證據無法證明迷走神經對動物之間的關系至關重要，比如，布拉沃博士和其同事至今還不知道其起作用的明確機制。
There is also an obvious follow-up question: whether a similar thing is going on in people.
況且還有一個明顯的后續問題：人類是否也有類似的情況。
A few previous studies have hinted at the possibility.
以前的幾個研究已經暗示這種可能性。
For example, bacterial treatments may help with the mental symptoms of illnesses such as irritable-bowel syndrome.
例如，細菌的治療方法可能有助于改善諸如腸易激綜合癥疾病的精神癥狀。
All this is forcing a reassessment of people's relationship with the bacteria that live on and in them, which have long been regarded mainly as a potential source of infections.
所有這一切正在迫使人類重新評估自身與這些棲居于人體而且人類依靠它們維持生命的細菌之間的關系。
An editorial in this week's Nature raises the possibility that the widespread prescription of antibiotics-which kill useful bacteria as effectively as hostile ones-might be one factor behind rising rates of asthma, diabetes and irritable-bowel syndrome.
長期以來，這些細菌主要被認為是潛在的感染源。本周《自然雜志》的社論提出了一種可能性，廣泛使用的抗生素處方---抗生素殺死有益菌的有效性就像殺死不利的細菌一樣---可能是哮喘，糖尿病和腸易激綜合癥比例上升的真正因素之一。
If Dr Bravo's results apply to people, too, then mood disorders may end up being added to this list.
假如布拉沃博士（Dr Bravo）的結果也應用于人類，那么情感障礙可能最終被添加到這個目錄上。
