Experiments under way in several labs aim to create beneficial types of genetically modified (GM) foods, including starchier potatoes and caffeine-free coffee beans. Genetic engineers are even trying to transfer genes from a cold-winter fish to make a frost-resistant tomato.
A low-sugar GM strawberry now in the works might one day allow people with health problems such as diabetes to enjoy the little delicious red fruits again. GM beans and grains supercharged with protein might help people at risk of developing kwashiorkor. Kwashiorkor, a disease caused by severe lack of protein, is common in parts of the world where there are severe food shortages.
Commenting on GM foods, Jonathon Jones, a British researcher, said: "The future benefits will be enormous, and the best is yet to come".
To some people, GM foods are no different from unmodified foods. "A tomato is a tomato," said Brian Sansoni, an American food manufacturer.
Critics of GM foods challenge Sansoni's opinion. They worry about the harm that GM crops might do to people, other animals, and plants.
In a recent lab study conducted at Cornell University, scientists tested pollen made by Bt corn, which makes up one-fourth of the U.S. corn crop. The scientist sprinkled the pollen onto milkweed, a plant that makes a milky juice and is the only known food source of the monarch butterfly caterpillar. Within four days of munching on the milkweed leaves, almost half of a test group of caterpillars had died. "Monarchs are considered to be a flagship species for conservation." said Cornell researcher Linda Raynor. "This is a warning bell."
Some insects that are not killed by GM foods might find themselves made stronger. How so? The insecticides used to protect most of today's crops are sprayed on the crops when needed and decay quickly in the environment. But GM plants produce a continuous level of insecticide. Insect species feeding on those crops may develop resistance to the plants and could do so in a hurry, say the critics. Insects may also develop a resistance to the insecticide Bt.
At the forum on GM food held last year in Canada. GM crops that have been made resistant to the herbicide might crossbreed with wild plants, creating "superweeds" that could take over whole fields.
So where do you stand? Should GM food be banned in the United States, as they are in parts of Europe? Or do their benefits outweigh any of the risks they might carry?
1. Paragraphs 1,2&3 tries to give the idea that
A) GM foods may bring about great benefits to humans.
B) We cannot recognize the benefits of GM foods too early.
C) GM foods may have both benefits and harm.
D) GM foods are particularly good to the kwashiorkor patients.
2. Why is the case of the pollen-sprayed milkweed citied in Paragraph 6?
A) It is cited to show GM foods can kill insects effectively.
B) It is cited to show GM foods contain more protein.
C) It is cited to show GM foods also have a dark side.
D) It is cited to show GM foods may harm crops.
3. What happens to those insects when not killed by the spray of insecticide?
A) They may lose their ability to produce offspring.
B) They may have a higher ability to adapt to the environment.
C) They move to other fields free from insecticide.
D) They never eat again those plants containing insecticide.
4. Which of the following statements concerning banning GM foods is true according to the passage?
A) Underdeveloped countries have banned GM foods.
B) Both Europe and the U.S. have banned GM foods.
C) Most European countries have not banned GM foods.
D) The United States has not banned GM foods.
5. What is the writer's attitude to GM foods?
A) We cannot tell from the passage.
B) He thinks their benefits outweigh their risks.
C) He thinks their risks outweigh their benefits.
D) He thinks their benefits and risks are balanced.
Most of the food we eat is turned into glucose for our bodies to use for energy. The pancreas, an organ near the stomach, makes a hormone called insulin to help glucose get into your body cells. When you have diabetes, your body either doesn't make enough insulin or can't use its own insulin well. This problem causes glucose to build up in your blood.
You may recall having some of these signs before you found out you had diabetes.
*Being very thirsty.
*Urinating a lot - often at night
*Having unclear vision from time to time.
*Felling very tired much of the time.
*Losing weight without trying.
*Having very dry skin.
*Having sores that are slow to heal.
*Getting more infections than usual.
Two main types of diabetes are Type 1 and Type 2. Another type of diabetes appears during pregnancy in some women. It's called gestational diabetes.
One out of ten people with diabetes' has Type 1 diabetes. These people usually find out they have diabetes when they are children or young adults. The pancreas of a person with Type 1 makes little or no insulin. People with Type 1 diabetes must inject insulin every day to live.
Most people with diabetes have Type 2 diabetes. The pancreas of people with such diabetes keeps making insulin for some time, but the body can't use it well. Most people with Type 2 find out about their diabetes after age 30 or 40.
Some risk factors which make people more likely to get Type 2 diabetes are:
* A family history of diabetes.
* Lack of exercise.
* Weighing too much.
Diabetes can hurt your eyes, your kidneys, and your nerves. It can lead to problems with the blood circulation in your body. Even your teeth and gums can be harmed. And diabetes in pregnancy can cause special problems.
1. This writing is meant to tell people
A) how to avoid getting diabetes.
B) what to pay attention to when they have diabetes.
C) what diabetes is.
D) about the least development in curing diabetes.
2. A person with diabetes may have had all the following signs EXCEPT
A) becoming fatter and fatter.
B) becoming thinner and thinner.
C) having to get out of bed at night and night.
D) feeling like to drink a lot of water very often.
3. Which of the following statements is TRUE?
A) Most persons with Type 1 or Type 2 diabetes are women in pregnancy.
B) Most women in pregnancy may have the danger of getting diabetes.
C) We find more persons with Type 2 diabetes among children than older persons.
D) We find more persons with Type 2 diabetes among older persons than children.
4. When you have Type 2 diabetes, it is sometimes possible to find that
A) your son has diabetes too.
B) your father has diabetes too.
C) your father-in-law is too fat.
D) your brother does not like sports.
5. People get diabetes because
A) their stomachs are not able to produce enough insulin.
B) their pancreas are not able to produce enough glucose.
C) there is too much glucose in their blood.
D) there is too much insulin in their blood.
In 18th-century colonial America, those who wanted to become physicians either learned as personal students from established professionals or went abroad to study in the traditional schools of London, Paris, and Edinburgh. Medicine was first taught formally by specialists at the University of Pennsylvania, beginning in 1765, and in 1767 at King's College (now Columbia University), the first institution in the colonies to give the degree of doctor of medicine. Following the American Revolution, the Columbia medical faculty (formerly of King's College)was combined with the College of Physicians and Surgeons, chartered in 1809, which survives as a division of Columbia University.
In 1893 the Johns Hopkins Medical School required all applicants to have a college degree and was the first to afford its students the opportunity to further their training in an attached teaching hospital. The growth of medical schools attached with established institutions of learning went together with the development of proprietary schools of medicine run for personal profit, most of which had low standards and poor facilities. In 1910 Abraham Flexner, the American education reformer, wrote Medical Education in the United States and Canada, exposing the poor conditions of most proprietary schools. Subsequently, the American Medical Association and the Association of American Medical Colleges laid down standards for course content, qualifications of teachers, laboratory facilities, connection with teaching hospitals, and licensing of medical professionals that survive to this day.
By the late 1980s the U.S. and Canada had 142 4-year medical colleges recognized by the Liaison Committee on Medical Education to offer the M.D. degree; during the 1987-88 academic year, 47,262 men and 25,686 women entered these colleges and an estimated 11,752 men and 5,958 women were graduated. Graduates, after a year of internship, receive licenses to practice if they pass an examination given either by a state board or by the National Board of Medical Examiners.
1. In 18th-century America,
A) there was no higher institution of learning which taught medicine.
B) there were already a few higher institutions of learning which taught medicine.
C) those higher institutions of learning which taught medicine were better than those in Europe.
D) those higher institutions of learning did not give the degree of doctor of medicine.
2. In the 19th-century, all American medical schools
A) began to give their students chances for training in hospitals.
B) had good teachers and fine facilities
C) had large numbers of students.
D) None of the above is true.
3. The American Medical Association and the Association of American Medical Colleges were
A) to ban those proprietary schools of medicine.
B) to build up relations between medical schools and hospitals.
C) to ensure the quality of medical teaching and practice.
D) to prevent some medical schools from making too much profit.
4. In the present-day America, graduates from medical schools
A) have to work in hospitals for a year and pass an examination before they can be recognized as qualified doctors.
B) have to be licensed by the national Board of Medical Examiner before they can serve their internship in hospital.
C) have to pass an examination given by both a state board and the National Board of Medical Examiners.
D) None of the above is true.
5. This passage is largely about
A） how difficult it is to become a doctor in America.
B） how American medical education has developed in history
C） how nice the American medical education system is.
D) how to become a good doctor.
High Stress May Damage Memory
According to a report issued in May 1998, elderly people who have consistently high blood levels of cortisol don't score as well on memory tests as their peers with lower levels of the stress hormone. What's more, high levels of cortisol are also associated with shrinking of the hippocampus, a region of the brain that plays a key role in learning and memory.
The finding suggest that even cortisol levels in the normal, "healthy" range can actually accelerate brain aging.
The study results "now pride substantial evidence that long-term exposure to adrenal stress hormones may promote hippocampal aging in normal elderly humans, " write Nada Porter and Philip Landfield of the University of Kentucky in Lexington in their editorial. Cortisol is a hormone released in response to stress by the adrenal glands, which sit on top of the kidneys.
Over a 5 to 6-year period, Dr. Sonia Lupien and his colleagues measured 24-hour cortisol levels in 51 healthy volunteers, most of whom were in their 70s.
Despite wide variation in cortisol levels, the participants could be divided into three subgroups: those whose cortisol progressively increased over time and was currently high(increasing/high); those whose cortisol progressively increased over time and was currently moderate(increasing/moderate); and subjects whose cortisol decreased, but was currently moderate(decreasing/moderate).
The researchers tested the volunteers' memory on six people in the increasing/high category and five people in the decreasing/moderate group. The groups did not differ on tests of immediate memory, but the increasing/high cortisol group had other memory problems compared with those in the decreasing/moderate group.
The researchers also found that the total volume of the hippocampus in those in the increasing/high group was 14% lower than those in the decreasing/moderate group, although there were no differences in other brain regions.
The results suggest that "… brain again can be accelerated by levels of adrenal hormones that are not generally regarded as pathological and that variation within this normal range is related to variation in the rate of brain aging," write Porter and Landfield. "This further suggests that chronic stress may accelerate the worsening of hippocampus. "
1. The part of the brain important for a person's learning and memory is
A) the cortisol.
B) the adrenal glands.
C) the stress hormones.
D) the hippocampus.
2. When the levels of cortisol go higher, the hippocampus in the brain may
A) become larger.
B) become smaller.
C) be missing.
D) be totally damaged.
3. According to the article, when people feel too worried or nervous or when they overwork,
A) the adrenal glands will produce a stress hormone.
B) the kidneys will produce adrenal glands.
C) the hippocampus will produce high level of cortisol in the blood.
D) the cortisol will produce something that makes a poorer memory.
4. When the total volume of the hippocampus becomes smaller, other brain regions
A) become smaller too.
B) Become larger.
C) may remain the same in size.
D) may be damaged.
5. Porter and Landfield's research shows that
A) the change in the levels if adrenal hormones has nothing to do with the degree of brain aging.
B) the change in the levels of adrenal hormones has a lot to do with the degree of brain aging.
C) the long-term stress will gradually make the hippocampus worse.
D) None of the above is correct.