凝血因子（blood clotting factors)

From the fourth paragraph we learn that ______.

A．heart attacks are more likely caused by alcohol than stroke

B．moderate drinking discourage blood platelets from clotting

C．boosting the levels of good cholesterol can lead to heart attacks

D．moderate drinking protect people by making the blood cell clump

From the fourth paragraph we learn that ______.

A．heart attacks are more likely caused by alcohol than stroke

B．moderate drinking discourages blood platelets from clotting

C．boosting the levels of good cholesterol can lead to heart attacks

D．moderate drinking protects people by making the blood cell clump

HIV and Its Transmission

Research has revealed a great deal of valuable medical, scientific, and public health information about the human immunodeficiency virus (HIV) and acquired immunodeficiency syndrome (AIDS). The ways in which HIV can be transmitted have been clearly identified. Unfortunately, false information or statements that are not supported by scientific findings continue to be shared widely through the Internet or popular press. Therefore, the Centers for Disease Control and Prevention (CDC) has prepared this fact sheet to correct a few misperceptions about HIV.

How HIV Is Transmitted

HIV is spread by sexual contact with an infected person, by sharing needles (primarily for drug injection) with someone who is infected, or, less commonly, through transfusions of infected blood or blood clotting factors (凝血因子). Babies born to HIV-infected women may become infected before or during birth or through breast-feeding after birth.

Some people fear that HIV might be transmitted in other ways; however, no scientific evidence supporting any of these fears has been found. If HIV were being transmitted through other routes (such as through air, water, or insects), the pattern of reported AIDS cases would be much different from what has been observed. For example, if mosquitoes could transmit HIV infection, many more young children and preadolescents would have been diagnosed with AIDS.

All reported cases suggesting new or potentially unknown routes of transmission are thoroughly investigated by state and local health departments with the assistance, guidance, and laboratory support from CDC. No additional routes of transmission have been recorded, despite a national sentinel (监测) system designed to detect just such an occurrence.

The following paragraphs specifically address some of the common misperceptions about HIV transmission.

HIV in the Environment

Scientists and medical authorities agree that HIV does not survive well in the environment, making the possibility of environmental transmission remote. HIV is found in varying concentrations or amounts in blood, semen (精液), vaginal (阴道的) fluid, breast milk, saliva (唾液), and tears. To obtain data on the survival of HIV, laboratory studies have required the use of artificially high concentrations of laboratory-grown virus. Since the HIV concentrations used in laboratory studies are much higher than those actually found in blood or other specimens, drying of HIV-infected human blood or other body fluids reduces the theoretical risk of environmental transmission to that which has been observed—essentially zero. Incorrect interpretation of conclusions drawn from laboratory studies has unnecessarily alarmed some people.

Results from laboratory studies should not be used to assess specific personal risk of infection because: (1) The amount of virus studied is not found in human specimens or elsewhere in nature, and (2) no one has been identified as infected with HIV due to contact with an environmental surface. Additionally, HIV is unable to reproduce outside its living host except under laboratory conditions. Therefore, it does not spread or maintain infectiousness outside its host.

Households

Although HIV has been transmitted between family members in a household setting, this type of transmission is very rare. These transmissions are believed to have resulted from contact between skin or mucous membranes (黏膜) and infected blood. To prevent even such rare occurrences, precautions should be taken in all settings "including the home" to prevent exposure to the blood of persons who are HIV infected, at risk for HIV infection, or whose infection and risk status are unknown, For example.

Gloves should be worn during contact with blood or other body fluids that could possibly contain vis

A．Y

B．N

C．NG

A、promoting the effect of antithrombin III.

B、complexation of Ca2+ in the plasma.

C、inhibiting the activity of thrombin.

D、neutralizing the acidic clotting factors

A、全血凝固时间(clotting time，CT)

B、激活全血凝固时间(activated coagulation time，ACT)

C、白陶土部分凝血活酶时间(kaolin partial thromoplastin time，KPTT)

D、血块收缩时间(clot retraction time，CRT)

E、凝血酶原时间(prothrombin time，PT)

章原有位置，以恢复文章原貌。请将答案涂在答题卡相应的位置。 Vitamins

Vitamins are organic compounds which are present in certain foods and are essential to the health of men and other animals. __46__. Without these substances, the breakdown and absorption of foods could not occur. Certain vitamins participate in the formation of blood cells, hormones, nervous system chemicals, and genetic materials. __47__.Fat-soluble vitamins include vitamins A,D,E and K. The water-soluble vitamins include vitamin C and the B-vitamin complex.

Fat-soluble vitamins are usually absorbed with foods that contain fat. Excessive amounts of these vitamins are stored in the body's fat, the liver and kidneys. Because fat-soluble vitamins can be stored, they do not have to be consumed every day.

__48__. A deficiency of vitamin A leads to skin changes and night blindness, or failure of the eye to adapt to the dark. Vitamin A can be obtained directly from foods of animal origin such as milk, eggs, and liver.__49__.

Vitamin D acts muck like a hormone and regulates calcium and phosphorus absorption and metabolism. Some vitamin D is obtained from such foods as eggs, fish, liver, butter, and milk. But humans get most of their vitamin D from exposure of the skin to sunlight. A deficiency of vitamin D leads to bone problems.

The role of vitamin E in the human body has not been established. ­­__50__ Vitamin E is found in seed oil and wheat.

Vitamin K is necessary for the clotting of blood. It is produced in sufficient quantities by bacteria in the intestine, but is also provided by leafy green vegetables and eggs.

The water-soluble vitamins, C and B complex, cannot be stored and therefore need to be consumed daily to satisfy the body's needs. Vitamin C is important in the formation and maintenance of connective tissue. It protects gums, skin, and mucous membranes. It is mainly found in fruits like oranges.

B-complex vitamins serve a wide range of important metabolic functions and prevent some diseases. They are found mostly in the liver.

A. Vitamins are classified into two groups, that is, the fat-soluble(溶解脂肪的) and the water-soluble(溶解水的) vitamins.

B. Their functions are mainly to enhance the metabolism(新陈代谢) of proteins and fats.

C. It is necessary for a healthy life.

D. Vitamin A is essential for normal growth and for the health of epithelial cells.

E. It has been popularly advocated for a great variety of diseases, but no clear evidence exists that it eases any specific disease.

F. Vitamin A can also be obtained through eating green and yellow fruits and vegetables

第46题：请选择（46）处最佳答案。

lectual achievements of the 20th century. Born with an extremely rare and usually fatal disorder that left her without a functioning immune system (the "bubble-boy disease", named after an earlier victim who was kept alive for years in a sterile plastic tent), she was treated beginning in 1990 with a revolutionary new therapy that sought to correct the defect at its very source, in the genes of her white blood cells. It worked. Although her last gene-therapy treatment was in 1992, she is completely healthy with normal immune function, according to one of the doctors who treated her, W. French Anderson of the University of Southern California. Researchers have long dreamed of treating diseases from hemophilia to cancer by replacing mutant genes with normal ones. And the dreaming may continue for decades more. "There will be a gene-based treatment for essentially every disease," Anderson says, "within 50 years. "

It's not entirely clear why medicine has been so slow to build on Anderson' s early success. The National Institutes of Health budget office estimates it will spend $ 432 million on gene-therapy research in 2005, and there is no shortage of promising leads. The therapeutic genes are usually delivered through viruses that don' t cause human disease. "The virus is sort of like a Trojan horse," says Ronald Crystal of New York Presbyterian/Weill Cornell Medical College. "The cargo is the gene. "

At the University of Pennsylvania's Abramson Cancer Center, immunologist Carl June recently treated HIV pa tients with a gene intended to help their cells resist the infection. At Cornell University, researchers are pursuing gene-based therapies for Parkinson's disease and a rare hereditary disorder that destroys children' s brain cells. At Stanford University and the Children' s Hospital of Philadelphia, researchers are trying to figure out how to help patients with hemophilia who today must inject themselves with expensive clotting drugs for life. Animal experiments have shown great promise.

But somehow, things get lost in the translation from laboratory to patient. In human trials of the hemophilia treatment, patients show a response at first, but it fades over time. And the field has still not recovered from the setback it suffered in 1999, when Jesse Gelsinger, an 18-year-old with a rare metabolic disorder, died after receiving an experimental gene therapy at the University of Pennsylvania. Some experts worry that the field will be tarnished further if the next people to benefit are not patients but athletes seeking an edge. This summer, researchers at the Salk Institute in San Diego said they had created a "marathon mouse" by implanting a gene that enhances running ability; already, officials at the World Anti-Doping Agency are preparing to test athletes for signs of "gene doping". But the principle is the same, whether you're trying to help a healthy runner run faster or allow a muscular-dystro-phy patient to walk. "Everybody recognizes that gene therapy is a very good idea," says Crystal. "And eventually it's going to work. "

The case of Ashanthi Desilva is mentioned in the text to

A．show the promise of gene-therapy

B．give an example of modem treatment for fatal diseases

C．introduce the achievement of Anderson and his team

D．explain how gene-based treatment works