[资料]thesearchfortheanti-·agingpill成分剖析

READING PASSAGE 30
Y ou should spend about 20 minutes on Questions 28—40, which are based on Reading Passage 30
The Search for the Anti-·aging Pill0
In government laboratories and elsewhere, scientists are seeking a drug able to prolong life and youthful vigor．Studies of caloric restriction are showing the way.0
As researchers主on aging noted谓recently,（no treatment主on the market today has been proved to谓slow human aging-补）宾从the build-up of molecular and cellular damage that increases vulnerability to infirmity 定从as we grow older．But (one intervention，consumption of a low-calorie*yet nutritionally balanced diet主)．W orks谓incredibly well in a broad range of animals，状(increasing longevity and prolonging good health)．伴随状语Those findings主suggest谓(that caloric restriction could delay aging and increase longevity in humans,too宾从)．0
Unfortunately, for maximum benefit，状people主would probably have to reduce谓their caloric intake宾（by roughly thirty per cent，equivalent to dropping from 2,500 calories a day to l,750．宾补）Few mortals主could stick to 谓that harsh a regimen，宾（especially for years on end．状）But what if someone主could create谓 a pill宾that 定从mimicked the physiological effects of eating less without actually forcing people to eat less?Could such a‘caloric-restriction mimetic’，主as we call it，enable谓people 宾to stay healthy longer, postponing age-related disorders宾补(such as diabetes，
arteriosclerosis，heart disease and cancer)until very late in life? Scientists 主first posed 谓this question宾in the mid-1990s．状（after引导时间状语从句researchers came upon a chemical agent that in rodents seemed to reproduce many of caloric restriction's benefits．）No compound主that would safely achieve the same feat in people定从has been found谓yet，but the search主has been informative and has fanned 谓hope宾that caloric-restriction (CR) mimetics can indeed be developed eventually．定从00
The benefits of caloric restriction0
The hunt for CR mimetics主grew out 谓of a desire to better understand caloric restriction's many effects on the body．状Scientists主first recognized 谓the value of 宾the practice more than 60 years ago，状（when they found that rats fed a low-calorie diet lived longer on average than free-feeding rats and also had a reduced incidence of conditions that become increasingly common in old age．状语从句）What is more，some of the treated animals主survived谓longer than the oldest—living animals in the control group，补which定从means that the maximum lifespan(the oldest attainable age)，not merely the normal lifespan，increased．V arious interventions，主(such as infection-fighting drugs，插入语_)can Increase 谓a population's average survival time，宾but only approaches 主（that slow the body's rate of aging定从）will increase谓the maximum lifespan．宾00
The rat findings主have been replicated谓many times and extended并列谓语to creatures补ranging from yeast to fruit flies，worms，fish，spiders，mice and hamsters．分词作伴随状语Until fairly recently,状the studies主were limited谓to short-lived creatures 补
genetically distant from humans．But caloric．restriction projects主（underway in two species more closely related to humans-rhesus and squirrel monkeys后置定语）-(have made 谓scientists宾optimistic that CR mimetics could help people．宾补)00
The monkey projects主demonstrate谓that, compared with过去分词作状语control animals that eat normally, （caloric-restricted monkeys have lower body temperatures and levels of the pancreatic hormone insulin，and they retain more youthful levels of certain hormones that tend to fall with age宾从）．00
The caloric-restricted animals 主also look系better 表on indicators of risk for age-related diseases．For example，they主have谓lower blood pressure and triglyceride levels宾(signifying a decreased likelihood of heart disease)，and they 主have谓more normal blood glucose levels宾(pointing to a reduced risk for diabetes，which is marked by unusually high blood glucose levels)．Further, it has recently been shown that rhesus monkeys kept on caloric—restricted diets for an extended time(nearly 15 years)have less chronic disease．宾从）They and the other monkeys主must be followed 情态动词＋过去分词still longer, however, to know whether low-calorie intake can increase both average and maximum lifespans in monkeys．目的状语Unlike the multitude of elixirs being touted as the latest anti-aging cure，状语CR mimetics主would alter谓fundamental processes宾(that underlie aging．定从) W e 主aim to谓develop 补compounds (that fool cells into activating maintenance and repair．定从) 0
How a prototype caloric—restriction mimetic works00
The best-studied candidate主for a caloric-restriction mimetic，2DG 同位语
(2-deoxy-D-glucose)，works谓by interfering with the way状cells process glucose．定从It 主has proved谓toxic at some doses in animals and so cannot be used 并列谓语in humans．But it 主has demonstrated 谓that chemicals can replicate the effects of caloric restriction宾从；the trick 主is finding 谓the right one．宾00
Cells主use谓the glucose宾from food to generate A TP宾补(adenosine triphosphate)，the molecule that powers many activities in the body定从．By limiting food intake状，caloric restriction主minimizes谓the amount of glucose entering cells and decreases A TP generation．宾When 2DG is administered to animals that eat normally，时间状语从句glucose主reaches谓cells宾in abundance but the drug 主prevents谓most of it 宾from being processed 宾补and thus reduces并列谓语A TP synthesis宾．Researchers主have proposed 谓several explanations 宾for why interruption of glucose processing and A TP production might retard aging．原因状语One possibility 主relates to谓the ATP-making machinery’s emission of free radicals,宾(which are thought to contribute to aging and to such age-related diseases as cancer by damaging cells．非限制定从)Reduced operation 主of the machinery should limit 谓their production宾and thereby constrain并列谓语the damage．宾Another hypothesis 主suggests谓that decreased processing of glucose主could indicate to谓cells宾that food is scarce(even if it isn’t)and i nduce并列谓语them宾to shift into an anti-aging mode宾补( that emphasizes preservation of the organism over such‘luxuries’as growth and reproduction．宾从)0
Ant Intelligence00
(When we think of intelligent members the animal kingdom, 时间状语从句)the creatures 主that spring immediately to mind定从are系apes and monkeys.表But in fact the social lives主of some members of the insect kingdom are系sufficiently complex to 表suggest more than a hint of intelligence.表补Among these,状the world of the ant 主has come in 谓for considerable scrutiny 补lately,and the idea主that ants demonstrate sparks of cognition 定从has certainly not been rejected谓by those involved in these investigations.
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Ants主store谓food．宾repel attackers and use chemical signals to contact one another in case of attack．宾补Such chemical communication 主can be compared to谓the human use 宾of visual and auditory channels(as in religious chants，advertising images and jingles，political slogans and martial music)to arouse and propagate moods and attitudes．宾补The biologist Lewis Thomas 主wrote，谓（（Ants are so much like human beings as to be an embarrassment．They farm fungi, raise aphids*as livestock,1aunch armies to war, use chemical sprays to alarm and confuse enemies，capture slaves，engage in child labour, exchange information ceaselessly．They do everything but watch television．’宾从））00
However, in ants 状there is no cultural transmission主-everything must be encoded 谓in the genes-whereas in humans the opposite is true. Only basic instincts主are carried谓in the genes of a newborn baby,状other skills主being learned from谓others宾in the community as the child grows up. It may seem系that this cultural continuity gives us a
huge advantage over ants.表从They have never mastered fire nor progressed. Their fungus farming and aphid herding crafts主are系sophisticated表（when compared to the agricultural skills of humans five thousand years ago时间状从）but have been totally overtaken 谓by modern human agribusiness.00
Or have they? The farming methods of ants主are 系at least sustainable表．They 主do not ruin谓environment s宾or use谓enormous amounts of energy宾．Moreover, recent evidence主suggests 谓（that the crop farming of ants may be more sophisticated and adaptable than was thought.宾从）00
Ants 主were系farmers表fifty million years before humans were状．Ants主c an’t digest 谓the cellulose宾in leaves-but some fungi并列主语can．谓The ants 主therefore cultivate 谓these fungi宾in their nests，（bringing them leaves to feed on,现在分词作伴随状语）and then use 并列谓语them宾as a source of food．Farmer ants主secrete谓antibiotics宾( to control other fungi 状that might act as‘weeds’，and spread waste tofertilise the crop.定从)00
It was once thought that宾从the fungus that ants cultivate定从was a single type( that they had propagated．Essentially unchanged from the distant past．定从)Not so. Ulrich Mueller of Maryland and his colleagues主genetically screened 谓862 different types of fungi宾taken from ants’nests.分词作后置定语These 主turned out 谓to be highly diverse：表it seems系that ants are continually domesticating new species．表从Even more impressively, DNA analysis主of the fungi suggests谓（that the ants improve or modify
the fungi by regularly swapping and sharing strains with neighbouring ant colonies.宾从）00
Whereas prehistoric man主had 谓no exposure 宾to Urban lifestyles宾补-the forcing house of intelligence—the evidence主suggests谓(that ants have lived in urban settings for close on a hundred million years，developing and maintaining underground cities of speciaiised chambers and tunnels.宾从)00
(When we survey Mexico City, Tokyo，Los Angeles．时间从句)we主are amazed at 谓what has been accomplished by humans宾．Y et HoeIldobler and Wilson’s magnificent work 主for ant lovers, The Ants,同位语describes谓 a supercolony of the ant宾Formica yessensis on the Ishikari Coast of Hokkaido．This‘megalopolis’主was reported 谓to be composed of 360 million workers and a million queens living in 4,500 Interconnected nests across 谓补a territory of 2.7 square kilometres．0
Such enduring and intricately meshed levels主of technical achievement outstrip 谓by far anything宾achieved by our distant ancestors.过去分词作后置定语We 主hail谓as masterpieces the cave Paintings宾jn southern France and elsewhere，dating back some 20，000 years.现在分词作状语Ant societies主existed谓in something地点状语like their present form 同位语more than seventy million years ago．Beside this, prehistoric man主looks系technologically primitive.表Is this then some kind of intelligence，albeit of a different kind?补00
Research conducted主at Oxford，Sussex and Zurich Universities状has shown 谓（that
when desert ants return from a foraging trip, they navigate by integrating bearings and distances，宾从）( which they continuously update in their heads．非限制定语从句)They 主combine谓the evidence宾of visual landmarks with a mental library宾of local directions, all (within a framework状Which is consulted and updated.定从)So ants主can learn谓too．00
And in a twelve-year Programme of work，Ryabko and Reznikova主have found谓evidence宾that ants can transmit very complex messages.同位语从句Scouts主who had Iocated food in a maze定从returned 谓to mobilise their foraging teams，They主engaged in 谓contact sessions，宾（at the end of which the scout was removed in order to observe what her team might do.定从）Often the foragers 主proceeded谓to the exact spot宾in the maze where the food had been定从．Elaborate precautions主were taken 谓to prevent the foraging team using odour clues．谓补Discussion主now centres on 谓（whether the route through the maze is communicated as a‘left-right’sequence of turns or as a ‘compass bearing and distance’ message．宾从）00
During the course of this exhaustive study, Reznikova 主has grown系so attached to 表her laboratory ants that she feels She knows them as individuals同位语从句-even without the paint spots used to mark them．伴随状语It’s no surprise that｛｛Edward Wilson，主in his essay,‘In the company of ants’, advises谓readers宾（who ask what to do with the ants in their kitchen宾从）to：‘W atc h宾补where you step．Be careful of little lives’.表从｝｝00
volcanoes-earth-shattering news0
When Mount Pinatubo suddenly erupted on 9 June 1991，the power of volcanoes past and present again hit the headlines00
A V olcanoes主are系the ultimate earth-moving machinery．表A violent eruption主can blow谓the top few kilometres off a mountain宾，scatter并列谓语fine ash 宾practically all over the globe and hurl 并列谓语rock fragments 宾into the stratosphere to darken the skies 宾补a continent away.00
But the classic eruption主-（cone-shaped mountain，big bang，mushroom cloud and surges of molten lava同位语）-is 系only a tiny part of a global story表．Vulcanism,主（the name given to volcanic processes，同位语）really has shaped谓the world. 宾Eruptions主have rifted 谓continents,宾raised 谓mountain宾chains，constructed 谓islands宾and shaped谓the topography宾of the earth. The entire ocean floor 主has 谓a basement of volcanic宾basalt．00
V olcanoes 主have not only made谓the continents，宾t hey主are also thought to谓have made谓补the world’s first stable atmosphere and provided all the water for the oceans, rivers and ice-caps．There are now about 600 active volcanoes. Every year they 主add
谓two or three cubic kilometres of rock宾to the continents．Imagine a similar number of volcanoes smoking 现在分词作伴随状语away for the last 3,500million years. That主is系enough rock表to explain表补the continental crust．0
What comes out of volcanic craters主从is系mostly gas．表More than 90％of this gas 主is 系water vapour表from the deep earth：（enough to explain, over 3,500 million years, the water in the oceans.补）The rest of the gas主is 系（nitrogen，carbon dioxide，sulphur dioxide，methane，ammonia and hydrogen.表）The quntity of these gases,主（again multiplied over 3,500 million years，插入语）js系enough to explain the mass of the world’s atmosphere．表W e 主are系alive 表（because volcanoes provided the soil，air and water we need．原因状语从句）0
B Geologists 主consider谓the earth宾（as having a molten core，surrounded by a semi-molten mantle and a brittle，outer skin，宾补）lt主helps谓to（think of a soft-boiled egg with a runny yolk，a firm but squishy white and a hard shell．谓补）（If the shell is even slightly cracked during boiling，条件状语从句）the white material 主bubbles out and sets谓（like a tiny mountain chain over the crack-like an archipelago of volcanic islands such as the Hawaiian Islands．谓补）But the earth主is系so much bigger表and the mantle并列状语below is 系so much hotter,表00
（Even though the mantle rocks are kept solid by overlying pressure，让步状语从句）they主can still slowly‘flow谓’like thick”treacle. The flow主,thought to be in the form of convection currents，is 系powerful enough表（to fracture the‘eggshell’of the crust into
plates，and keep them bumping and grinding against each other, or even overlapping ，表补）at the rate of a few centimetres a year. These fracture zones, 主where the collisions occur,定从are系where earthquakes happen．表And，very often，volcanoes．00
C T hese zones主are 系lines of weakness, or hot spots.表Every eruption 主is系different,表but put at its simplest, 过去分词作定语（where there are weaknesses, rocks deep in the mantle, heated to 1,350。

C,定从）will start to谓expand and rise. 谓补As they do so,状语the pressure主drops,谓and they主expand and become 谓liquid and rise谓more swiftly.0
Sometimes it主is系slow表：（vast bubbles of magma-molten-rock from the mantle-inch towards the surface，cooling slowly, to show through as granite extrusions Lason Skye，or the Great Whin Sill, the lava dyke squeezed out like toothpaste that carries part of Hadrian’s W all in northern Ehgland补）．Sometimes-(as in Northern Ireland，W ales and the Karoo in South Africa状从)-the magma主rose谓faster, and then flowed out并列谓语horizontally on to the surface in vast thick sheets．in the Deccan plateau in western India，there are more than two million cubic kilometres of lava, some of it 2,400 metres thick，formed 过去分词作后置定语over 500,000 years of slurping eruption.
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Sometimes the magma主moves谓very swiftly indeed. It does not have time to cool宾补as it surges upwards．状从The gases主trapped inside the boiling rock过去分词作后置定语expand 谓suddenly, the lava主glows谓with heat，it begins to谓froth谓补，and it 主explodes谓with tremendous force.伴随状语Then the slightly cooler lava 主following 现在
分词作定语it begins 谓to flow over谓补the lip of the crater. It 主happens谓on Mars,状it happened on the moon, it even happens on some of the moons of Jupiter and Uranus．By studying the evidence，状语vulcanologists 主can read 谓the force宾of the great blasts of the past．1s the pumice light and full of holes?The explosion主was系tremendous表．Are系the rocks主heavy,表with huge crystalline basalt shapes，伴随语like the Giant’s Causeway in Northern Ireland? It主was系a slow ,gentle定eruption.表0 0
The biggest eruptions主are系deep表on the mid-ocean floor，状（where new lava ls forcing the continents apart and widening the Atlantic by perhaps five centimeters a year．定从）Look at maps of volcanoes，earthquakes and island chains like the Philippines and Japan，祈使句and you can see the rough outlines of what are called tectonic plates-the plates（which make up the earth’s crust and mantle．The most dramatic of these is the Pacific’ring of fire’定从）where there have been the most violenlt explosions-地点状语从句（Mount Pinatubo near Manila，Mount St Helen's in the Rockies and EI Chichon in Mexico about a decade ago，not to mention world-shaking blasts like Krakatoa in the Sunda Straits in 1883．补语）00
D But volcanoes主are 系not very predictable．表That主is系（because geological time is not like human time．原因状语从句）During quiet periods，volcanoes主cap 谓themselves with their own lava伴随语（by forming a powerful cone from the molten rocks slopping over the rim of the crater；方式状语）later the lava主cools谓slowly into a huge，hard，stable plug which blocks any further eruption 谓补until the pressure below becomes
irresistible.状In the case of Mount Pinatubo，this 主took 谓600 years.00。