大閱讀1-73篇大閱讀-15_W

1、微信公眾號：醫(yī)學(xué)博士英語南京醫(yī)科大學(xué)小白老師大閱讀第 15 天 小白老師醫(yī)學(xué)考博英語網(wǎng)絡(luò)課程Penicillin changes the behaviour of young miceTHE symbiosis between human beings and the bacteria dwelling in their guts isa delicate thing. When it works well, both sides benefit. The bugs get a comfy home.The hosts get help with their digestion, making

2、 more food available than otherwisewould be. If relations are upset, though, bad consequences may flow. Both obesityand malnutrition can be exacerbated by the wrong gut bacteria. Illnesses such asasthma and eczema are linked to a lack of certain bugs from an infants intestines.And there is evidence,

3、 from experiments on mice, that an absence of gut flora affectsthe development of the brain. Such absence weakens the blood-brain barrier, whichnormally helps to keep foreign material out of that organ. It also seems to makeanimals less sociable than would otherwise be expected.The experiments which

4、 show these brain and behavioural changes have, though,either been done on mice raised in sterile conditions or on ones that have had theiralimentary bacterial ecosystems “nuked” with antibiotics in high dosefar higher,pro rata, than would be administered to a human for medical reasons. The next sta

5、geis to test whether anything similar happens to mice fed more realistic doses ofantibiotics. And this is what Sophie Leclercq of McMaster University, in Hamilton,Ontario, has now done.Dr Leclercq and her colleagues, who have just published their results in NatureCommunications, laced the drinking w

6、ater of some pregnant female mice withmedically appropriate levels of penicillin, starting a week before those females weredue to give birth, and carrying on three weeks after birth, to the point where theiroffspring were weaned (penicillin is known to be transferred from mother to pup inmilk). One

7、group of mothers-to-be had only the antibiotic added to their water. Asecond had a bacterium called Lactobacillus rhamnosus, a so-called probiotic thathas been demonstrated experimentally to be good for the intestinal health of mice,added as well. A third group of expectant mothers were given their

8、drinking water微信公眾號：醫(yī)學(xué)博士英語南京醫(yī)科大學(xué)小白老師unadulterated. Twenty-five pups were born to mothers in the first group, 19 to thesecond and 28 to the third.Six weeks post partum, the researchers tested the sociability of the variousoffspring by putting them, one at a time, for ten minutes, into a small, Y-shap

9、edtunnel with two chambers at the ends. One chamber contained another mouse, ofthe same sex as the experimental animal, held in a small wire cage. The secondcontained an empty cage.The team found that, when released into this apparatus, the offspring ofmothers exposed only to penicillin preferred to

10、 be alone. They spent more time inthe empty chamber (four and a half minutes, on average) than in the chambercontaining another mouse (three and three-quarter minutes). Those born of mothersexposed neither to penicillin nor to Lactobacillus showed the reverse pattern,averaging only three and a half

11、minutes in the empty chamber and almost five in thechamber that gave them company. Those mice born of mothers given both penicillinand Lactobacillus fell between these extremes, averaging a bit under four and a halfminutes in the chamber that gave them company, and three and three-quarters inthe emp

12、ty one. In all cases there was no significant difference between the sexes.Dr Leclercq got similar results when she tested the preferences of her mice forsocial novelty. She did this by letting them choose, in the tunnel, between a newmouse and the one they had already met. She found those exposed t

13、o penicillinalone less interested in the new mouse than those exposed to both penicillin andLactobacillus, or to neither.She also found that exposure to penicillin alone made male mice moreaggressive. She arranged for males in the experiment to be threatened by anunfamiliar male belonging to a strai

14、n known for being big and hostile. Males born ofmothers given unadulterated drinking water all quickly assumed a submissiveposture when confronted with such a stranger. Half of the males born of motherstreated with the antibiotic did not, however, submit. Indeed, they fought back eventhough they wer

15、e clearly outmatchedas did a fifth of the males whose mothershad been treated simultaneously with the antibiotic and Lactobacillus.微信公眾號：醫(yī)學(xué)博士英語南京醫(yī)科大學(xué)小白老師All these results are in line with the hypothesis that low doses of antibioticaffect behaviour similarly to high doses. So, when Dr Leclercq and he

16、r colleagueskilled and examined their animals shortly after the behavioural tests, they expectedto see permeable blood-brain barriers in the mice exposed to penicillin. But they didnot. They actually saw the reverse: the blood-brain barriers of mice exposed solely topenicillin were far less permeabl

17、e than those of the other two groups.What is going onand, in particular, what relationship (if any) exists betweenthe effects of gut flora on the blood-brain barrier and on behaviourremains to beseen. But Dr Leclercq and her colleagues have demonstrated that medically relevantdoses of penicillin, even when administered via the mother rather than directly, canhave palpable effects on young mice. Whether the same applies to young people,just before or after birth, is surely a matter wor