進化千萬年 人類爲什麼如此怕蛇
The human brain is wired to react fearfully to snakes, including in people without a conscious fear of snakes, says a study in this month's issue of Biological Psychology.
《華爾街日報》―發表於《生物心理學》(Biological Psychology)二月刊的研究論文稱，人類大腦對蛇天生的反應就是畏懼，沒意識到自己怕蛇的人也包括在內。The study suggests the brain evolved to pay greater attention to the presence of snakes than other creatures, because snakes were among the earliest human predators and posed a daily threat.
該研究指出，比較其他生物，大腦在進化過程中變得更能注意到蛇的存在，因爲蛇是人類最早的掠食者之一，每天都帶來威脅。This heightened awareness of snakes is embedded in the brain's circuitry, even though snakes are no longer a danger to most people, researchers said. Fear of spiders, while also common, has no evolutionary associations, as spiders weren't predatory, they said.
研究人員稱，即便蛇對大多數人來說不再危險，但這種對蛇的高度戒備卻深深印入了人腦的神經迴路中。他們還指出，雖然人類對蜘蛛的畏懼也很常見，但這與進化沒有關聯，因爲蜘蛛不是人類的掠食者。
The study involved 24 non-phobic Norwegian women, 18 to 31 years old. The women viewed two sets of color photos while an EEG measured activity in their brain. In the first set, 600 pictures each of snakes, spiders and small birds were randomly displayed on a computer at a rate of three per second. This test assessed which creature attracted the subjects' instant -- but unconscious -- attention. They then viewed 30 pictures of each species at a slower speed to assess the brain's continuous neural response.
該研究的受試者爲24名年齡在18至31歲、無恐懼症的挪威女性。她們觀看了兩組彩色照片，同時腦電圖(EEG)會檢測她們大腦的活動。在第一組實驗中，各600張蛇、蜘蛛和小鳥的照片以每秒三張的速度在電腦上隨機展示。該測試評估的是哪種生物會引起受試者迅速但無意識的關注。隨後她們還觀看了以更慢的速度展示的各物種的30張照片，目的是評估她們大腦的持續性神經反應。Before the tests, the subjects rated their fear on a scale from 0 (none) to 45 (very high). The average scores for snakes, spiders and birds were 16, 12 and 4, respectively. Compared with the spider and bird pictures, the speedy display of snake images evoked a significantly stronger brain response that was most pronounced in the brain's occipital or visual processing region, researchers said.
在實驗之前，受試者按照從0（毫不害怕）到45分（非常害怕）的量級給她們的恐懼評分。對蛇、蜘蛛和小鳥的平均恐懼分數分別爲16分、12分和4分。研究者稱，與蜘蛛和小鳥的照片相比，蛇照片的快速展示引發了明顯更強烈的大腦反應，該反應在大腦的枕骨葉即視覺處理區表現得最顯著。The response to the spider pictures was closely associated with the subjects' self-reported fear. Spider fear is learned and stems from disgust rather than fear of physical harm, the study suggests.
受試者對蜘蛛圖片的反應與她們自己所陳述的恐懼密切相關。研究顯示，對蜘蛛的畏懼是後天的，它源自厭惡而非對身體傷害的恐懼。In the second test, the brain responses to spiders and snakes weren't significantly different, but were stronger than for birds.
在第二個實驗中，大腦對蜘蛛和蛇的反應並無明顯區別，但要強於對小鳥圖片的反應。Caveat: The study was small and only involved women.
警告：該研究規模較小，而且受試者只有女性。Breast-milk benefit: A specialized antibody in breast milk may play an important role in a newborn's susceptibility to intestinal infections and inflammatory bowel diseases as they mature, suggests a study published online in the Proceedings of the National Academy of Sciences.
母乳的好處：發表於《美國國家科學院學報》(Proceedings of the National Academy of Sciences)網絡版的一項研究顯示，母乳中的一種特殊抗體或許對新生兒逐漸長大時是否易於患上腸道感染和炎症性腸病有很大的影響。Breast milk contains an antibody called secretory immunoglobin A (SIgA), which protects against infection and helps infants develop a healthy mix of gastrointestinal bacteria. When breast-feeding stops, other mucus-secreting organs, such as the nose, throat and eyes, start to produce SIgA, but it wasn't known if the initial exposure to SIgA through breast milk had long-term benefits, researchers said.
母乳含有一種名爲分泌型免疫球蛋白A(SIgA)的抗體，它可以抵禦感染，有助於嬰兒的胃腸菌羣實現健康的混合比例。研究人員稱，在停止母乳餵養後，嬰兒其他分泌黏液的器官，如鼻子、喉嚨和眼睛就會開始生成SIgA，不過一開始通過母乳接觸SIgA是否有長遠益處還不明確。A purified form of SIgA might be a potential treatment for intestinal infections and inflammation, particularly in formula-fed infants or older children and adults who don't produce enough of the antibody, they said.
研究人員還指出，純正的SIgA或許是治療腸道感染和炎症的潛在療方，特別是對用配方奶餵養的嬰兒或年紀較大的兒童以及生成的抗體不足的成年人而言。Experiments at the University of Washington in Seattle were conducted on the offspring of mice that produced breast milk with SIgA and mice bred to produce milk without the antibody. Analysis of fecal samples showed SIgA was present only in offspring that received the antibody and fell to low levels after weaning. Within a week, the weaned mice began to produce SIgA through other tissues, while SIgA wasn't detected at any time in mice that didn't receive the antibody. Mice lacking SIgA had significantly different gut bacteria than mice with the antibody, including Ochrobactrum anthropi, a bacterium linked to hospital-acquired infections.
西雅圖華盛頓大學 (University of Washington in Seattle)對老鼠的後代展開了實驗，其中一些老鼠分泌含SIgA的乳汁，另一些因餵食方法分泌的是不含該抗體的乳汁。對排泄物採樣的分析表明，SIgA只在喂有含該抗體的乳汁的幼鼠中出現，但抗體水平在斷奶後降至低位。在一週之內，斷奶幼鼠的其他器官組織便開始生成SIgA，而未被餵食含SIgA乳汁的幼鼠從未被檢測出該抗體。缺乏SIgA的老鼠與含該抗體的老鼠的腸道細菌大爲不同，其中包括與醫院獲得性感染有關的人蒼白桿菌。The addition of a chemical used to induce colitis in laboratory mice caused significantly greater tissue damage in the mice that didn't receive SIgA. Intestinal gene patterns also differed significantly between the two groups.
研究人員添加了一種化學物在實驗鼠身上誘發結腸炎，結果是不含SIgA的老鼠的器官組織遭到了明顯更嚴重的損害。此外，這兩組老鼠的腸基因模式也截然不同。Caveat: It's possible that maternal differences in gut microbes at the time of delivery contributed to the genetic changes in offspring independently of SIgA in breast milk, researchers said. The research was conducted on rodents and hasn't been tested in human studies.
警告：研究人員稱，母鼠在分娩時的腸道微生物的差異有可能引發了與乳汁中SIgA無關的幼鼠基因的改變。該研究在老鼠身上展開，尚未對人類進行實驗。Reducing salt consumption by half a teaspoon a day significantly improved blood-vessel function in overweight and obese individuals with normal blood pressure, potentially lowering their risk of cardiovascular disease, according to a report in the March issue of Atherosclerosis.
《動脈硬化》(Atherosclerosis) 雜誌三月刊的一項報告指出，將每日的鹽攝入量減少半匙可改善超重人羣及血壓正常的肥胖人士的血管功能，有可能降低他們患上心血管疾病的風險。The magnitude of the blood-vessel changes recorded in the study could shift a person from a high-risk category to a low-risk one for heart attack and stroke, which are associated with a high-salt diet, researchers said.
研究人員稱，該研究記錄到的血管變化的量值，顯示一個人從心臟病及中風高危人羣轉爲低危人羣。這兩種疾病與高鹽飲食有關。The Centers for Disease Control and Prevention recommends consuming no more 6 grams (2,300 milligrams of sodium), or one teaspoon of salt a day. For African-Americans, diabetics and people older than 51 or with high blood pressure, the CDC recommends consumption be limited to two-thirds of a teaspoon (about 4 grams of salt or 1,500 milligrams of sodium). Most Americans consume an average of 9 grams of salt (3,450 milligrams of sodium) a day, according to the CDC.
美國疾病控制與預防中心(Centers for Disease Control and Prevention，簡稱“CDC”)建議每日的食鹽量不要超過六克（2,300毫克鈉），也就是一天一茶匙鹽。對於非裔美國人、糖尿病患者以及51歲以上的人羣或高血壓患者，CDC的建議把攝入量控制在三分之二茶匙（約爲四克鹽或1,500毫克鈉）。根據該中心的數據，美國人每日的鹽攝入量平均爲九克（3,450毫克鈉）。Researchers at the University of South Australia recruited 25 men and women ages 40 to 70 for the 12-week study. The subjects followed a diet containing 9 grams of salt a day for six weeks and a reduced salt diet of 6 grams a day for six weeks. Flow-mediated dilatation, an ultrasound technique used to assess blood-vessel elasticity, was measured at the start of the study and after two, six and 12 weeks.
南澳大學(University of South Australia)的研究人員徵集了25名年齡在40歲至70歲的男女受試者參加爲期12周的實驗。受試者前六週的飲食遵照的是每天九克的鹽攝入量，在接下來的六週中將攝入量減至每天六克。與此同時，研究人員分別在研究一開始、兩週後、六週後以及12周後檢測採用血流介導的血管舒張功能，這是一種用於評估血管擴張度的超聲波技術。Blood-vessel function significantly increased on the reduced salt diet after two days compared with the higher salt diet, and by 45% over six weeks. Levels of endothelin-1, proteins that constrict blood vessels and raise blood pressure, decreased by 14%.
與鹽攝入量較高時期相比，受試者的血管功能在減少鹽攝入量兩天後便大幅提高，在六週中提高了45%。內皮素-1的水平則降低了14%，該類蛋白質會使血管收縮、血壓升高。The subjects' blood pressure and weight remained the same, indicating the reduced-salt diet had an independent effect on vascular health, researchers said.
研究人員稱，受試者的血壓與體重在實驗期保持不變，這表明少鹽飲食對血管健康的作用是獨立的。Caveat: The study was small and lacked a control group of normal-weight people.
警告：該研究規模較小，缺乏一個由正常體重人羣組成的控制組。
