Category Archives: Biochemistry

Effects of Acid Rain

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Effects of Acid Rain

The acids in acid rain react chemically with any object they contact. Acids are corrosive chemicals that react with other chemicals by giving up hydrogen atoms. The acidity of a substance comes from the abundance of free hydrogen atoms when the substance is dissolved in water. Acidity is measured using a pH scale with units from 0 to 14. Acidic substances have pH numbers from 1 to 6—the lower the pH number, the stronger, or more corrosive, the substance. Some non-acidic substances, called bases or alkalis, are like acids in reverse—they readily accept the hydrogen atoms that the acids offer. Bases have pH numbers from 8 to 14, with the higher values indicating increased alkalinity. Pure water has a neutral pH of 7—it is not acidic or basic. Rain, snow, or fog with a pH below 5.6 is considered acid rain.

When bases mix with acids, the bases lessen the strength of an acid. This buffering action regularly occurs in nature. Rain, snow, and fog formed in regions free of acid pollutants are slightly acidic, having a pH near 5.6. Alkaline chemicals in the environment, found in rocks, soils, lakes, and streams, regularly neutralize this precipitation. But when precipitation is highly acidic, with a pH below 5.6, naturally occurring acid buffers become depleted over time, and nature’s ability to neutralize the acids is impaired. Acid rain has been linked to widespread environmental damage, including soil and plant degradation, depleted life in lakes and streams, and erosion of human-made structures.

 

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Effects of Aging on the Human Body

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Several general changes take place in the human body as it ages: hearing and vision decline, muscle strength lessens, soft tissues such as skin and blood vessels become less flexible, and there is an overall decline in body tone.

Most of the body’s organs perform less efficiently with advancing age. For example, the average amount of blood pumped by the heart drops from about 6.9 liters (7.3 quarts) per minute at age 20 to only 3.5 liters (3.7 quarts) pumped per minute at age 85. For this same age range, the average amount of blood flowing through the kidneys drops from approximately 0.6 liters (0.6 quarts) per minute to 0.3 liters (0.3 quarts). Not all people experience decreased organ function to the same degree—some individuals have healthier hearts and kidneys at age 85 than others do at age 50.

The immune system also changes with age. A healthy immune system protects the body against bacteria, viruses, and other harmful agents by producing disease-fighting proteins known as antibodies. A healthy immune system also prevents the growth of abnormal cells, which can become cancerous. With advancing age, the ability of the immune system to carry out these protective functions is diminished—the rate of antibody production may drop by as much as 80 percent between age 20 and age 85. This less-effective immune system explains why a bout of influenza, which may make a young adult sick for a few days, can be fatal for an elderly person. Thus, it is as important for an older person to be vaccinated against the flu and pneumonia as it is for young people to be vaccinated against childhood diseases.

Most of the glands of the endocrine system, the organs that secrete hormones regulating such functions as metabolism, temperature, and blood sugar levels, retain their ability to function into advanced age. However, these glands often become less sensitive to the triggers that direct hormone secretion. In the aging pancreas, for example, higher blood sugar levels are required to stimulate the release of insulin, a hormone that helps the muscles convert blood sugar to energy.

The ovaries and the testes, the endocrine glands that regulate many aspects of sexual reproduction, alter during the aging process. As a man ages, the testes produce less of the male sex hormone, testosterone. A woman’s ovaries undergo marked changes from about age 45 to age 55 during a process known as menopause. The ovaries no longer release egg cells, and they no longer generate the hormones that stimulate monthly menstrual cycles. After women have gone through menopause, they are no longer capable of having children without the aid of reproductive technology. The physical changes associated with aging do not have a significant impact on sexual activity—most healthy people maintain an interest in sex all of their lives.

 

Effects of Acid Rain on Human Health

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Effects of Acid Rain on Human Health

The acidification of surface waters causes little direct harm to people. It is safe to swim in even the most acidified lakes. However, toxic substances leached from soil can pollute local water supplies. In Sweden, as many as 10,000 lakes have been polluted by mercury released from soils damaged by acid rain, and residents have been warned to avoid eating fish caught in these lakes. In the air, acids join with other chemicals to produce urban smog, which can irritate the lungs and make breathing difficult, especially for people who already have asthma, bronchitis, or other respiratory diseases. Solid particles of sulfates, a class of minerals derived from sulfur dioxide, are thought to be especially damaging to the lungs.

 

 

Biochemistry in 1989: Genetic Engineering (Engineered Virus)

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Researchers at Cornell University in Ithaca, N.Y., began the first open-air test of a genetically engineered virus in July. They sprayed the virus, one of a family of insect parasites called baculoviruses, on a cabbage field at Cornell’s experimental station in Geneva, N.Y., in an attempt to protect the plants from the cabbage looper caterpillar.

The researchers hope eventually to make a more potent form of the virus that will kill the caterpillars quickly, but they fear that such a potent virus could be harmful to the environment. As a first step, therefore, molecular biologist H. Alan Wood and colleagues removed from the virus a gene responsible for producing a protein that prevents the virus from being damaged by sunlight and weather. In the absence of the gene, Wood said, the virus would die out over a period of about two years. If the baculovirus does, in fact, die out, scientists will then assume that they can safely engineer it to make it more potent.

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Biochemistry in 1989: Genetic Engineering (Experimental AIDS Vaccines)

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Almost two years of testing showed that a genetically engineered AIDS vaccine is safe in humans, the vaccine’s maker, MicroGeneSys, Inc., of West Haven, Conn., said in June. The continuing trial involved more than 120 gay and bisexual men who tested negative for infection with HIV, the virus that causes AIDS, when the tests were begun in 1987. Aside from the mild side effects normally seen with vaccines, the AIDS vaccine, which contains proteins found on the surface of HIV, produced no toxic effects. The initial testing was to determine whether the vaccine was safe; trials to determine whether the vaccine can actually prevent AIDS were begun shortly after the vaccine’s safety was assured.

In a separate development, Jonas Salk of the Salk Institute for Biological Sciences in San Diego announced at the Fifth International Conference on AIDS in Montreal in June that three chimpanzees injected with a potential AIDS vaccine developed strong immune responses. Instead of HIV surface proteins, Salk’s preparation uses whole killed viruses, an approach he followed in developing his famous polio vaccine. The potential AIDS vaccine caused no adverse effects when tested for safety in 19 human volunteers.

Biochemistry in 1989: Genetic Engineering (Erythropoietin for Anemia)

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In June the U.S. Food and Drug Administration (FDA) approved the marketing of a genetically engineered form of erythropoietin (EPO) for use in treating anemia in patients with severe kidney disease. EPO is a hormone produced in the kidney that stimulates the growth of red blood cells. The new drug, epoetin alfa (sold under the name Epogen), was expected to benefit many of the more than 90,000 people in the United States who regularly undergo dialysis to remove toxic chemicals from their blood because their kidneys have failed. Dialysis destroys red blood cells, making the patients anemic. Also, many dialysis patients require frequent transfusions, which lead to a toxic buildup of iron (from destroyed red cells) in their blood; EPO should ease that problem.

Later in June the FDA gave limited approval for another use of EPO. The drug was authorized as an ‘investigational new drug for treatment,’ for use in people with AIDS who suffer from anemia, either from the virus that causes the disease or because they are taking zidovudine (previously called AZT) to control the disease’s progression. Zidovudine kills red blood cells, and EPO helps to replace them.

 

Biochemistry in 1989: Genetic Defects (Diabetes)

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Researchers from the University Of Pittsburgh School Of Medicine have developed a genetic test that can detect susceptibility to Type I diabetes, the most serious form of diabetes and one that is normally controlled by insulin injections. By studying DNA in white blood cells, Massimo Trucco and colleagues reported in June, they can identify children who are susceptible to the disease, which scientists believe develops after an encounter with a triggering agent, such as certain viral infections.

Trucco noted that physicians now have no way to prevent the development of Type I diabetes, but experiments in animals suggest that such treatments may be possible in the future. For the meantime, he added, the test will allow parents to monitor their children for initial signs of the disease, which often resemble influenza. Many children are first diagnosed in emergency rooms, where they have been taken in a diabetic coma because early symptoms were not recognized.

 

Biochemistry in 1989: Genetic Defects (Retinitis Pigmentosa)

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By studying more than 100 members of an Irish family with a high incidence of retinitis pigmentosa (RP) — a hereditary condition that causes degeneration of the eye’s retina and subsequent blindness and afflicts more than 100,000 Americans and 1.5 million people worldwide — researchers from Ireland and the United States found the location of the gene that causes one form of it. The discovery is particularly important because researchers have no idea how the disease develops and no therapy is available for it.

Geneticists Stephen Daiger of the University of Texas Health Sciences Center in Houston and Peter Humphries of Trinity College in Dublin announced in July that the gene for a form of RP called autosomal dominant RP is located in a small region of chromosome 3. In autosomal dominant RP, when one parent has the disease, a child has a 50 percent chance of inheriting it. Discovery of the gene’s location makes possible prenatal screening for the defect and should lead to new information about how the disease occurs.

 

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Biochemistry in 1989: Genetic Defects (Prenatal Screening)

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It may eventually be possible to conduct prenatal screening for certain genetic defects, such as sickle-cell anemia, cystic fibrosis, and phenylketonuria, using only blood from the mother, thereby eliminating the small risk of miscarriage associated with amniocentesis, according to Diana Bianchi of Children’s Hospital in Boston.

A pregnant woman‘s blood contains a small number of red blood cells from the fetus, perhaps one such fetal cell in a billion of the mother’s cells. Bianchi reported in July that it is possible to isolate these fetal cells using antibodies that bind only to them. Unlike adult red blood cells, fetal cells contain a nucleus, with chromosomes, which can be tested for the presence of genetic defects. But the process is ‘really at the limits of technology,’ Bianchi said, and probably could not be used routinely for several years.

Biochemistry in 1989: Genetic Defects (Pygmies)

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Scientists have long wondered why African Pygmies rarely grow beyond the height of 4 feet 10 inches, even though they appear to have normal quantities of human growth hormone in their blood. Now, researchers from the Northwestern University Medical School and the University of Florida may have found the answer. They reported in June that Pygmies seem to have low levels of growth hormone receptors, the cellular proteins to which growth hormone must bind so that it can signal tissues to continue their growth.

In a separate study, also reported in June, endocrinologists at the University of Oklahoma Health Sciences Center in Oklahoma City studied a group of American teenagers who were short even though they too apparently produced normal amounts of human growth hormone. This group also had a shortage of the growth hormone receptor. The researchers speculated that it might be possible to increase stature in such children by administering a protein that is normally produced in cells as a result of the hormone binding to the receptor.

 

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