Book 2 Listening (1108796), страница 18
Текст из файла (страница 18)
Dr Goodman's analysis shows that it does, but in a way that is not translated intoany obvious evolutionary advantage. Reducing family size certainly creates what look, on theface of things, like more competitive descendants. Children, grandchildren and greatgrandchildren alike get better marks at school, are more likely to go to university and havehigher incomes as adults. What these competitive individuals do not do, though, is go on tocompete in the one arena which matters in a Darwinian sense: reproduction. If anything, thetendency towards smaller, more socially successful families tends to feed back on itself overthe generations, and the contribution of the K-selected to the gene pool therefore shrinks.To biologists, this is all very puzzling.
If K-type behaviour is not delivering the goodsthen it should never have come about in the first place. But there may be an explanation: thatthe psychological make-up which encourages K-type behavior worked in the past but is notappropriate to modern circumstances. This does seem plausible. In large parts of the world,better hygiene, nutrition and medicine have almost abolished child mortality, meaning theadvantage of K over R is diminished.
Education is available free to all. And harem-formation,which would have been an option in the past for many K-selected males, is frowned on thesedays. In other words, the disadvantages of being r-selected have disappeared.The upshot is that the demographic transition may be the result of a mismatch betweenancient psychology and the modern world.
In that, it would be like the epidemic of obesitywhich results from stoneage appetites meeting capitalist abundance. Unlike obesity, though,small families do no harm to the individuals involved. In fact this particular mismatch mayactually be all that stands between humanity and ecological disaster. (From The Economist,September 1, 2012)67Unit 12. AlcoholScript 34. Allergy to wine.The oenophile's lamentAn explanation for a most unfortunate conditionOne of life's sadder statistics is that about 8% of people get sneezy and stuffy-headedafter drinking wine. This mild allergic reaction is often blamed on preservative chemicalscalled sulphites, but they are responsible for only an eighth of cases. The reason for the restis obscure.
Giuseppe Palmisano of the University of Southern Denmark, however, thinks heknows the answer.As he and his colleagues report in the Journal of Proteome Research, the culprits areglycoproteins - compounds composed, as their name suggests, of sugar and protein. That isnot a complete surprise.
Glycoproteins are implicated in several other allergies. But DrPalmisano thinks he has identified the ones specific to wine.To do so he started with a cheeky little chardonnay, treated it with ice-coldtrichloroacetic acid and ethanol to precipitate any glycoproteins, then digested thoseglycoproteins into smaller molecules called peptides that can be analysed by massspectroscopy. He screened the results against a database of known allergenic proteins.Three stood out. One is similar to allergenic proteins found in latex and pears. Another lookslike a second latex protein and an olive protein, both known allergens.
The third resemblesone of the most rampant allergens of them all, a ragweed protein that causes hay fever.Whether winemakers will be able to act on this knowledge is moot. But it might bepossible to tweak the production process to reduce the presence of the allergens. In anycase, you can now blame that stuffy feeling that comes after drinking on glycoproteins, notalcohol. Honest. (From The Economist, November 27, 2010)Script 35. Brewing.Heady DiscoveriesThe yeast that gave rise to lager is tracked down to South AmericaIn the 15th century a schism opened in the world of beer.
Brewers in Bavaria alightedon a new version of that age-old drink - one that liked to be fermented in the cold and couldthus be brewed in winter. The lager revolution had begun.The difference between lagers and more traditional ales lies in the yeast. Ales are madewith baker's yeast, Saccharomyces cerevisiae.
Lagers use a hybrid, half cerevisiae and halfsomething else. The interloper, though, has never been found - until now.After a worldwide search, a team of geneticists has pinned it down to South America.Chris Todd Bittinger of the University of Wisconsin-Madison and Diego Libkind of theArgentine National Council for Scientific and Technical Research, found their quarry over11,000 km (7,000 miles) from Bavaria, in the cool alpine forests of Patagonia.
As they explainin a paper in the Proceedings of the National Academy of Sciences, the newly describedspecies, named Saccharomyces eubayanus, lives in galls that infect beech trees there.These sugary galls often ferment on the forest floor, and locals have been known to make analcoholic beverage from them. Genetic sequencing confirmed that the yeast in the galls is99.5% identical with the non-ale half of the lager-yeast genome.That solves one mystery but creates another.
Human transport is the only way thefungus could have travelled from Patagonia to Europe, but exploration of the New World didnot begin until the end of the 15th century, and Patagonia was not reached until the 16th. Yetthere are records of cold-fermented beer being made in Munich as early as 1420.Dr Bittinger suspects lagering in its basic form - lengthy and cool fermentation - didprecede the arrival of eubayanus, but that these early lagers were poor. Then, in one batch,eubayanus drifted in and could thrive at the low temperatures which cerevisiae disliked.Brewers favoured that batch, and the yeast spread.
Indeed, the historical record provides a68hint that something was afoot around this time. In 1553 Bavaria outlawed summer-made beerbecause wintertime brews had outstripped them in quality.Eventually, the two yeast strains hybridised to form Saccharomyces pastorianus, theyeast used by lager brewers today.
Those brewers will cheer the discovery of eubayanus, asit opens a trove of genes that did not make the transition to pastorianus but which might helpthe process of cold brewing. One South American beer company is already discussing usingpure eubayanus, as well as lab-created hybrids, in a test brew. Whether that will improve thelager's flavour is another matter. As Dr Bittinger points out, natural selection has done apretty tasty job already.
(From The Economist, August 27, 2011)Script 36. Combating addictionCan a vaccine stop drug abuse?It may be possible to vaccinate people against addictive drugsThe idea of vaccinating drug addicts against their affliction is an intriguing one. Inprinciple, it should not be too hard. The immune system works, in part, by making antibodiesthat are specific to particular sorts of hostile molecule. Such antibodies recognise and attachthemselves to these molecules, rendering them harmless. Vaccines work by presenting theimmune system with novel targets, so that it can learn to react to them if it comes acrossthem again.The problem is that the molecules antibodies recognise and react to are the big ones,such as proteins, that are characteristic of bacteria, viruses and other infectious agents.Small molecules, such as drugs, go unnoticed.
But not for much longer, if Kim Janda of theScripps Research Institute in San Diego has his way. In a paper just published in the Joumalof the American Chemical Society, Dr Janda and his colleagues suggest how a vaccineagainst methamphetamine, a popular street drug, might be made. If their method works, itwould open the possibility of vaccinating people against other drugs, too.The idea of a methamphetamine vaccine is not new.
The problem is getting the immunesystem to pay attention to a molecule that is such a small target. The way that has been triedin the past is to build the vaccine from several components.First, there is a large carrier protein that forms a platform for the target. Then there isthe target itself, a set of smaller molecules called haptens that are attached to the carrier.These may either be the drug in question or some analogue of it that, for one reason oranother, is reckoned to have a better chance of training the immune system.
Finally, there isa chemical cocktail called an adjuvant that helps get the immune system to pay attention tothe carrier protein and the haptens.Dr Janda noticed that past experiments on methamphetamine vaccines had all revolvedaround tweaking either the carrier protein or the adjuvant, rather than tinkering with thehaptens. He thought he might be able to change that, on the basis of work he had carried outpreviously, trying to design a vaccine against nicotine. In particular, nicotine is a highlyflexible molecule. That makes it hard for the immune system to recognise.
To overcome this,his team on the nicotine project had to work out how to fix their haptens to the carrier proteinin a way that rendered them less capable of twisting and turning, and thus made them easierfor the immune system to identify.In the new study, Dr Janda and his colleagues report that they have performed a similartrick with methamphetamine haptens. They used computer models to visualise the haptens inthree dimensions and thus work out how the molecules could be rearranged such that theycould not spring, twist or turn when being examined by the immune system. In light of thisinformation they designed six new methamphetamine-like haptens.Once built, they attached the new hapten molecules to carrier proteins, mixed them withadjuvant, injected the results into mice and waited.
After several weeks they tested the miceto see if the animals' blood contained antibodies to methamphetamine. Of the six newhaptens, three successfully provoked the mice to make such antibodies. As a bonus, one ofthose three also stimulated the production of antibodies against another widely used drug,amphetamine.69That is still a long way from providing a working vaccine, but it is an important stepforward. And if human immune systems react in the same way to the new vaccines as murineones do, the day when a drug addict might be offered vaccination rather than opprobrium willhave come a little closer. (From The Economist, May 19, 2011)Script 37. Oral healthWine gumsOne of the components of red wine protects against tooth decayWithout regular brushing and flossing, teeth accumulate bacterial films that secrete acidand cause cavities.
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