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  3. Part Ⅱ Reading Comprehension (Skimming and Scanning)Directions: In this part yo

Part Ⅱ Reading Comprehension (Skimming and Scanning)Directions: In this part yo

游客2024-05-31  10
问题 Part Ⅱ Reading Comprehension (Skimming and Scanning)
Directions: In this part you will have 15 minutes to go over the passage quickly and answer the questions on Answer Sheet 1. For questions 1-7, choose the best answer from the four choices marked A ), B) , C) and D ). For questions 8-10, complete the sentences with the information given in the passage.
                                    How to Solve Three Puzzles
      New knowledge and sophisticated diagnostic techniques are helping doctors recognize early signs of autism (孤独症), Alzheimer’s disease(痴呆症) and heart problems in women. Harvard experts report on the advances that are giving patients hope.
     Detecting Autism
     Early diagnosis (诊断)of autism is critical because educational programs that build upon a child’s strengths and improve social skills may help sculpt the developing brain, minimizing the impact of the illness later in life. But spotting the disorder is hard since there is no test for it, although scientists are slowly uncovering gene abnormalities that make children vulnerable to autism. Last week The New England Journal of Medicine reported that a specific location on chromosome(染色体) 16 was the site of mutations responsible for so me cases of autism.
     For now, diagnosis depends on observing a child’s behavior. It’s a complex process, since no two cases are alike and signs range from mild to severe, landed, even though signs of autism may be apparent before their first birthday, most children aren’t diagnosed until the age of 3. That makes parents, who are so intimately familiar with their child’s behavior, perhaps the most effective diagnostic” tools. "The American Academy of Pediatrics recently issued screening guidelines recommending that pediatricians engage parents in evaluating infants for autism. Even babies developing typically, the guidelines say, should be screened at set intervals, such as during the 9-, 18- and 24-month visits.
      Healthy infants as young as 6 or 8 months do communicate and respond nonverbally to social cues. Most lo ok up or turn at the sound of their name. By 12 months they typically babble and point at objects. By 16 months they say single words; by 24 months, two-word phrases. In contrast, children with autism seldom make meaningful eye contact or respond to familiar voices. They may never speak. Their play is often repetitive and characterized by limited imagination (neatly arranging crayons instead of coloring with them). Others may simply flap their hands in excitement or disappointment.
     On their own, none of these signs means that a child has autism or another developmental disorder. Nevertheless, if’ your child has any of these signs, he or she merits evaluation. Although no treatments are curative, they can help children learn the skills they need to cope in a normal environment, achieve greater independence and have brighter futures.
    The Alzheimer’s Mystery
    Alzheimer’s disease, which begins years, even decades, before it causes symptoms, is a quietly ticking time bomb. But until recently doctors had no diagnostic test that could "hear" the ticking. Unfortunately, it didn’t matter much that Alzheimer’s couldn’t be spotted early at a stage called mild cognitive impairment, or MCI-since there were no treatments. Today, however, there are new diagnostic tests that can detect Alzheimer’s at an early stage, and several disease-modifying drugs are in advanced clinical trials.
   The brain shrinkage(萎缩) caused by Alzheimer’s can now be measured with volumetric magnetic resonance imaging (MR1). This technique takes a series of MRI brain scans and then uses sophisticated mathematical models to analyze the results. Most important, volumetric MRI enables researchers to identify subtle shrinkage in bra in areas first affected by Alzheimer’s, such as the hippocampus, which is involved in memory.
   Another technology in limited clinical use is fluoro-deoxy-glucose positron emission tomography (FDG PET). Images produced by FDG-PET reveal patterns of glucose metabolism (葡萄糖新陈代谢)in the cerebral cortex, the site of abstract thought, reasoning and learning. Because active neurons guzzle glucose for energy, diminished uptake in a specific pattern can denote Alzheimer’s. In the research setting, scientists have even used FDG-PET to identify people who do not yet have Alzheimer’s but are at risk for developing it, or f or developing mild cognitive impairment.
    A different kind of PET-scan technology builds on recent discoveries about amyloidal plaques and tau tangles, the neuron-killing proteins that accumulate in the brains of Alzheimer’s patients. Researchers at the University of Pittsburgh have developed Pittsburgh Compound-B, or PIB. When injected into the blood, this com pound binds to amyloid plaques in the brain, allowing them to be detected on PET scans. PET scans with PIB clearly distinguish people with Alzheimer’s from healthy people. They may also help identify people with the progressive form of MCI.
     Taking a different approach, other researchers are identifying early changes in the levels of particular bring proteins in cerebrospinal fluid. (The clear spinal fluid constantly bathes the brain and spinal cord.) Spinal-fluid levels of the protein tau are typically elevated in Alzheimer’s, and an altered version of the tau protein, known as phosphorylated tau, can be detected early in Alzheimer’s. Lowered spinal-fluid concentrations of an altered version of beta-amyloid, called AB42, are typical in Alzheimer’s and can also help identify people with mild cognitive impairment who are most likely to progress to Alzheimer’s.
     Although all these new imaging and biochemical developments are individually promising, the combine ion of several different imaging tests and biochemical markers may yield the most accurate diagnosis. For example, scientists at the New York University School of Medicine have reported that combining volumetric MRI of the hippocampus with spinal-fluid measures of phosphorylated tau and isoprostane—a marker of oxidative stress--improved diagnostic accuracy in identifying people with mild cognitive impairment who are most likely to progress to Alzheimer’s.
     Heart Disease in Women
     When it comes to diagnosing the most common kind of heart disease, some cardiologists share Henry Higgins’s lament in "My Fair Lady": "Why can’t a woman be more like a man? That’s because many women don’t have the typical symptoms, like crushing chest pain and shortness of breath brought on by physical activity or stress. Instead, they have diffuse discomfort in the chest, unusual exhaustion or depression without an apparent reason. To make matters worse, the tests considered best at diagnosing coronary-artery disease generally don’t work as well for women as they do for men. As a result, an alarming number of women with heart disease go undiagnosed and untreated despite repeated visits to the doctor and the emergency room.
     Blood flows to heart muscle first through large arteries (the coronary arteries) and then through a branching network of smaller blood vessels. The symptoms of heart disease, in men or women, often result from cholesterol-filled plaques that can slow and completely block the flow of blood to the heart muscle. This type of heart disease, which has been recognized for a century, can be seen with tests such as coronary angiograms (or arteriogram) and, less well, with noninvasive tests such as special CT and MRI scans.
     In just the past decade, researchers have learned that many women with chest pain and other symptoms of heart disease have a condition called coronary microvascular disease, which affects the heart’s smallest arteries. This fundamentally different form of heart disease is as common and as costly as all female-specific cancers com bind, affecting as many as 3 million American women. It affects men, too, but not nearly as often.
     Many doctors have not yet heard about coronary micro-vascular disease. Currently, the most definitive test involves measuring coronary-artery flow reserve or coronary reactivity. It involves threading an ultra thin wire with blood-flow sensors at the tip deep into a coronary artery. Blood flow in the artery is then measured be fore and after injections of one or more medications that should cause the micro-vessels to dilate. An alternative, noninvasive way of detecting micro-vascular disease is with cardiac MRI. This scan measures the amount of blood fl owing into the heart muscle before and after the heart is infused with a drug that dilates the micro-vessels. As with the coronary-reactivity test, if blood flow does not increase, there is disease of the micro-vessels.
     If you are a woman with recurrent chest pain or discomfort, shortness of breath, unexplainable exhaustion and depression, you may need special evaluation even if you have clear arteries on an angiogram. If your doctor says there’s nothing wrong, ask for a second opinion at one of a growing number of women’s cardio vascular-care centers. You may have coronary micro-vascular disease.  [br] Those images produced by FDG-PET can reveal______.
选项 A、the number of glucose metabolism
B、the size of glucose metabolism
C、the pattern of glucose metabolism
D、the distribution of glucose metabolism
答案 C
解析 细节辨认题 。本题考查FDG-PET技术在诊断痴呆症方面的应用。从原文可知，通过 FDG3-PET获得的图像能反映在cerebral cortex处的葡萄糖新陈代谢的类型，而cerebral cortex正是大脑中思考、推理和学习的部位，所以答案为C项。
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