(A)
In discovering the genes responsible for storing fat in cells, scientists at the Albert Einstein College of Medicine of Yeshiva University have answered one of biology’s most fundamental questions.
Scientists had previously identified the genes responsible for synthesizing fat within cells. But the genes governing the next step—packaging the fat inside a layer of phospholipids and proteins to form lipid droplets—have long been sought, and for good reason.
“Storing fat in lipid droplets appears crucially important for enabling cells to use fat as an energy source,”says Dr. David Silver, assistant professor of biochemistry at Einstein. He and his colleagues identified two genes that are crucial for packaging fat into lipid droplets. They called the genes FIT1 and FIT2 (for Fat-Inducing Transcripts 1 and 2). Both genes code for proteins that are more than 200 amino acids in length, and the two genes are 50 percent similar to each other. The amino acid sequences of the FIT proteins do not resemble any other known proteins found in any species, indicating that the FIT genes comprise a novel gene family.
The researchers conducted several different experiments to confirm the roles of FIT1 and FIT2 in fat storage. In one experiment, they overexpressed both FIT1 and FIT2 genes in human cells. While the rate of fat synthesis stayed the same in both “overexpressed” and control cells, the number of lipid droplets in the “overexpressed” cells increased dramatically, between four- and six -fold.
Using a different tactic to evaluate FIT function, the researchers next “knocked down” FIT2 in mouse fat cells. Their reasoning: If FIT2 is indeed essential for lipid droplet formation, then suppressing FIT2 expression should abolish lipid-droplet accumulation. Examination of these fat cells for lipid droplets revealed that ceils with suppressed FIT2 expression had a drastic reduction in lipid droplets.
Finally, the researchers carded out a similar FIT2 “knock down” experiment in a whole animal—the zebrafish. Zebrafish eggs were injected with a segment of DNA designed to interfere with FIT2 expression. Then, to induce lipid droplet formation in zebrafish larvae, free-swimming six-day-old larvae were fed a high-fat diet for six hours. Although the larvae had exhibited normal feeding behavior, examination of their livers and intestines revealed a near-absence of lipid droplets.
“These lines of evidence supported our conclusion that FIT’ genes are necessary for the accumulation of lipid droplets in cells,” says Dr. Silver. “Now that we’ve identified the genes and the proteins they code for, it should be possible to develop drugs that can regulate their expression or activity. Such drugs could prove extremely valuable, not only for treating obesity, but for alleviating the serious disorders that arise from obesity including type 2 diabetes and heart disease.”
What is the passage mainly concerned with?
Early Education
It is increasingly common to hear people referring to “the nanotechnology industry”, just like the software or mobile phone industries, but will such a thing ever exist? Many of the companies working with nanotechnology are simply applying our knowledge of the nanoscale to existing industries, whether it is improving drug delivery mechanisms for the pharmaceutical industry, or producing nanoclay particles for the plastics industry. In fact nanotechnology is an enabling technology rather than an industry in its own right. No one would ever describe Microsoft or Oracle as being part of the electricity industry, even though without electricity the software industry could not exist. Rather, nanotechnology is a fundamental understanding of how nature works at the atomic scale. New industries will be generated as a result of this understanding, just as the understanding of how electrons can be moved in a conductor by applying a potential difference led to electric lighting, the telephone, computing, the internet and many other industries, all of which would not have been possible without it. While it is possible to buy a packet of nanotechnology, a gram of nanotubes for example, it would have zero intrinsic value. The real value of the nanotubes would be in their application, whether within existing industry, or to enable the creation of a whole new one.
What the present change will turn out to be will depend on______.
What Peter Cochrane says chiefly means that________.
It is implied in the second paragraph that_________.
In terms of the scale of change, the author considers the present change_____.
(B)
Futurologists have not been very precise about how, and how much, digital media will change our lives. Most comment has focused on the expectation that consumers will soon be able to use their TV or PC to shop, bank and order movies from their armchair. Commentators envisage more dramatic changes to everyday life. Nicholas Negroponte, director of MIT’ s Media Lab, believes that a key development over the next five years will be the “personalization” of the computer, with wearable devices such as a wrist-mounted TV, computer and telephone. Peter Cochrane, head of research at British Telecom, looks further ahead, asking us to “imagine a virtual reality interface, with your visual cortex flooded by information from spectacle-mounted or contact lenses augmented by directional audio input, tactile gloves and prosthetic arms and fingers that will give you the sensation of touch, resistance and weight”.
Historically, enthusiasts for new technologies have usually been overoptimistic about the speed of change. Most new technologies take longer to be adopted by the general public than these enthusiasts expect, although there have been exceptions: once they had reached critical mass, VCRs and mobile phones took off faster than most experts predicted. Arguably, everyday life in the advanced economies changed more between the 1880s and the 1930s than in the last fifty years or, possibly, the next. Nevertheless, it is valid to talk about a digital “revolution”, since the extent of change is dramatic by any standards and digital technology is its biggest single driving force. Even if the enthusiasts overstate how quickly things will change, they may turn out to be right about the scale of that change.
Which of the following statements best describes the conclusion of the severaldifferent experiments?
What is the one of the implications of the discovery of FIT genes?
What can be said about FIT1 and FIT2 according to the passage?
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2005年初级经济师考试《邮电经济专
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