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HUMAN DISEASES (Part 2 of 7)   Leave a comment

What Happens When Immunity Backfires

Paradoxically, a person’s immunity system can backfire and develop auto-antibodies against his own body tissue. In many diseases of unknown cause, doctors have found many unusual antibodies in the blood serum of patients.

Rheumatoid arthritis (RA), chronic disease of the connective tissue, causing painful sensations in joints and muscles.

Doctors think the patients become sensitive to something made by their own bodies. Only a slight change in certain proteins in normal body tissue is necessary for them to become antigens. Most diseases marked by the production of auto-antibodies cannot be traced to infection or drug allergy. In rheumatoid arthritis, for example, the rheumatoid factor is the presence of auto-antibodies in the victim’s blood. These auto-antibodies may stick to the membranes lining the bone joints and cause a reaction that destroys tissue in the joints. In other disorders associated with reversed immunity, auto-antibodies strike red blood cells, tissues surrounding small blood vessels, or other target areas. Ulcerative colitis, a disorder marked by an inflamed portion of the intestine, often with ulcers, is also believed to be an autoimmune disease.

In some cases, lymphocyte defects or discrepancies in antibody production lead to an immune deficiency. The victim is then helpless against recurring infections. A simple head cold can soon become pneumonia. Antibiotics or serums with antibody-rich gamma globulin offer temporary relief in such cases.

1796: Inoculation against disease. The simple medical procedure known as vaccination first came into use in about 1713 as a means of preventing smallpox. Such inoculation sometimes proved dangerous, because individuals sometimes caught a severe case of the disease instead of a mild one. This problem was solved by Edward Jenner, a British physician, in 1796. He realized that individuals inoculated with the much milder cowpox virus became immune to smallpox. Jenner tested his theory in May 1796.

This kind of inoculation earned the name vaccine, from the Latin word vaccinus, meaning “from cows.” Since Jenner’s day vaccines have been developed to fight polio, diphtheria, whooping cough, measles, typhoid fever, cholera, tetanus, and other diseases.

1928: Penicillin. In 1928 the Scottish bacteriologist Alexander Fleming was doing research on the Staphyloccus bacteria when he noticed that a growth of mould Penicillium notatium was contaminating the culture. There was no bacteria where the mould was present. Following up on this fact, Fleming found there was something in the mould that prevented bacterial growth. He named this substance penicillin.

By continued experiment Fleming learned that penicillin is capable of killing many common disease-causing bacteria. His discovery proved to be one of the first and most useful antibiotics used in medicine today. By 1940 penicillin had been turned into an injectable medicine. Its use grew dramatically during World War II as an infection-preventing agent.

HOW DRUGS FIGHT DISEASE

With the advent of drug therapy in the 20th century, doctors began to use lifesaving drugs to fight disease. The clinical use of sulphanilamide, the predecessor of sulphur drugs, in the 1930s and the mass production of penicillin, the first antibiotic, in the 1940s gave physicians extremely powerful tools with which to fight infection. A disease-fighting drug never acts by itself. It always works in conjunction with the body’s immunity system. Vaccines have also become available for the prevention of certain diseases.

How Certain Drugs Quell Infection

Such antibiotics as penicillin, streptomycin, and tetracycline are very effective against bacterial infections. The name “antibiotic” comes from antibiosis, or the use of substances made by one living thing to kill another. Antibiotics are made by bacteria and moulds that are specially cultured in commercial drug laboratories.

Antibiotics kill bacteria and other disease organisms in various ways. Some destroy the cell walls of bacteria. Others interfere with bacterial multiplication or fatally alter the way bacteria make vital proteins. Still others mix up the genetic blueprints of the bacteria.

Ordinarily, an antibiotic tricks bacteria into using the antibiotic’s chemicals instead of closely related ones that the organisms really need for making the key enzymes required for their growth and reproduction. With the antibiotic assimilated into their systems instead of the vital chemicals, an essential activity or structure of the pathogens is lacking and they die.

Sulphur drugs act in a somewhat similar but less effective way. Weakened but not killed by the sulphur drugs, the pathogens fall easy prey to the body’s scavenger cells. Drugs are also available against parasitic worms, infectious amoeba, and other pathogenic organisms.

Antibiotics are not very effective against viruses because the drugs cannot get into the body cells where viruses hide and multiply. However, the body produces a protein called interferon that inhibits viral reproduction.

A drug is sometimes recognized by the body’s immunity system as an antigen. It then triggers a severe reaction. In some cases, a person can suffer anaphylaxis, or extreme sensitivity, to penicillin after repeated injections. Without quick medical aid, severe cases of anaphylactic shock can be fatal.

How Bacteria Become Drug Resistant

Once in every several hundred million cell divisions a mutation makes a bacterium immune to an antibiotic drug. The mutation alters the bacterium’s genetic code and thus its ability to use certain chemicals for its life activities. Mutations can be caused by the radiations from outer space that stream into the Earth’s atmosphere, as well as by some atmospheric chemicals. As a result of the mutation, all bacteria that stem from the immune germ will be resistant to the drug unless any of them undergoes a mutation that makes the strain susceptible again. Hence, whenever a new antibiotic is developed, there will be a chance that bacteria will develop an immunity against it. But because mutations are fairly rare, doctors have a good chance of fighting a bacterial disease with the new drug before future strains become resistant.

Some members of a bacterial strain are resistant to certain drugs naturally. In the course of time they can eventually become selected through evolutionary forces to become the dominant drug-resistant forms of a pathogenic strain.

More importantly, some bacteria can pass on their drug resistance to bacteria of another strain by “infection.” Since the passing of resistance factors does not depend upon the lengthy process of mutation, it poses a much greater problem of drug immunity. As a consequence, doctors often must prescribe more than one antibiotic to fight certain diseases in the hope that this will slow bacterial resistance.

Use of Vaccines and Hormones

A person can become artificially immune to some diseases by means of a vaccine. Vaccines contain antigens that stimulate the production of protective antibodies. Immunity to smallpox, polio, measles, rabies, and certain other diseases, is induced by injecting a person with vaccines containing living but attenuated, or weakened, disease organisms.

A vaccine containing only dead organisms protects against typhoid fever and whooping cough, as well as against measles and polio. Vaccines containing toxins, or poisons, are used to prevent diphtheria and tetanus. When injected into a person, they trigger the production of special antibodies called antitoxins.

Some body disorders are caused by too much or too little hormone production. Hormones are body chemicals that influence many vital biochemical reactions. When someone suffers a hormone deficiency, a doctor usually can treat the deficiency with hormone shots.

1347: Black Death. The plague is one of the most devastating diseases that has ever afflicted mankind. It is a highly contagious fever caused by the bacillus Yersinia pestis, which is carried by fleas that infest rats.

The plague, commonly called bubonic plague or the Black Death, has been known since ancient times, but the best documented instance was its deadly appearance in Europe in 1347. It raged throughout all of Europe, killing at least one-fourth of the population probably 25 million people. Without understanding how it is spread, people had no defence against the disease. Poor sanitary conditions and the disruption of war only worsened the epidemic.

In Europe the epidemic started in Sicily and was spread by shipboard rats to other Mediterranean ports. It moved to North Africa, Italy, Spain, England, and France. By 1349 it made its way to Austria, Germany, Switzerland, and the Low Countries. By 1350 it reached Scandinavia and the Baltic states.

In general, the population of Europe did not recover to its size before the plague until the 16th century, and some towns never recovered. The immediate results of the plague a general collapse of economies, a breakdown of class relationships, and a halt to wartime hostilities forced a massive restructuring of society. It has had a lasting impact on art, literature, and religious thought.

INFECTIOUS DISEASES

Infectious diseases can be transmitted in many ways. They can be spread in droplets through the air when infected persons sneeze or cough. Whoever inhales the droplets can then become infected. Some diseases can be passed through contaminated eating or drinking utensils. Some can be spread through sexual activity. Others can even be spread in the course of medical or surgical treatment, or through the use of dirty injection equipment, especially by drug abusers.

Cold (also called common cold, or coryza), illness, acute inflammation of upper respiratory tract.

Once an infectious organism gains a foothold in the body, it begins to thrive and multiply. Its success is slow or fast, depending upon the nature of the pathogen. The symptoms of the common cold, for example, appear within a few days of infection. However, the symptoms of kuru, an uncommon disease of the nervous system, often appear three years or longer after infection.

Incubation period, length of time before the symptoms of a disease appear.

Every infectious disease has an incubation period. This is the length of time between the pathogen’s gaining a foothold in the body and the appearance of the first symptoms of the disease.

Several factors also determine whether a person will become the victim of a disease after being infected. The number of invading germs the dose of the infection influences the outbreak of disease. So does the virulence of the pathogens; that is, their power to do harm. In addition, the condition of the body’s immunological defences also affects the probability of catching a disease.

Contagious Disease

A great many infectious diseases are contagious; that is, they can easily be passed between people. To acquire certain contagious diseases someone need only be in the presence of someone with it, or come in contact with an infected part of the body, or eat or drink from contaminated utensils.

Someone can be a carrier of a contagious disease in several ways. He can be an asymptomatic carrier, or have a disease without ever developing its symptoms. He can be an incubationary carrier and pass on the pathogens at any time during the “silent” incubation period. He can be a convalescent carrier and transmit some of the infectious organisms remaining in the body even after recovery. Of course, anyone suffering the frank symptoms of a contagious disease can pass it on to others while the disease is running its course.

HEART AND BLOOD SYSTEM DISEASES

Disease of the heart or of the blood vessels, called cardiovascular disease, is the leading cause of death in the United States and Canada. It claims more than a million lives each year in the United States; more than 70,000 each year in Canada.

The heart is a muscular pump. When its own tissue or blood vessels become diseased, serious and sometimes fatal harm can follow.

Coronary Artery Disease

Disease of the coronary arteries that supply oxygen and nutrients to the heart is the most common heart ailment. Coronary artery disease accounts for more than a third of all deaths among males in the United States between the ages of 35 and 55. It also strikes many women past the age of 50. Hypertension (high blood pressure), overweight, cigarette smoking, diabetes mellitus, excess cholesterol, triglycerides and other fats in the blood, and probably lack of regular exercise contribute to the chance of getting coronary artery disease.

Coronary artery disease is characterized by an atheroma, a fatty deposit of cholesterol beneath the inner lining of the artery. The atheroma obstructs the passage of blood, thereby reducing the flow of nourishing blood to the heart muscle. It also sets up conditions for a blood clot in the coronary artery. Atheroma formation seems to run in families. Eating foods rich in saturated animal fat and cholesterol is also thought to contribute to atheroma formation.

Many persons with coronary artery disease do not experience symptoms. If the obstruction is bad enough, however, it may cause angina pectoris, myocardial infarction, or heart enlargement and failure.

Angina pectoris, brief paroxysm of severe chest pain with feeling of suffocation.

Angina pectoris is a chest pain that feels like something is squeezing or pressing the chest during periods of physical exertion. It takes place when the heart’s oxygen needs cannot be met because of a blocked coronary artery. Rest will relieve the pain. Some persons have angina pectoris for years and still live active lives.

Myocardial infarction is commonly called heart attack. Tissue death that results from a lack of blood is called infarction. When the coronary artery becomes so obstructed that the myocardium, or heart muscle, does not receive oxygen, it dies.

Heart attack (also called myocardial infarction, or coronary occlusion), an acute episode of heart disease.

Once, it was believed that a blood clot occluded the coronary artery and caused the infarction. This is why a heart attack is sometimes called a coronary occlusion. However, it now appears that most clots form in the artery after the infarction.

The first few hours after a heart attack are the most critical because abnormal heart rhythms may develop. Ventricular fibrillation is the most dangerous. The ventricles of the heart contract so fast that the pumping action is baulked Death follows in three or four minutes. Heart attack patients are usually treated in the coronary care unit of a hospital for a few days to enable electronic monitoring of the heart rate and rhythm.

Heart failure, condition that develops when repeated heart attacks occur.

Heart failure can occur when repeated heart attacks put too much strain on the remaining healthy heart muscle. As attacks destroy more and more heart muscle, the remaining muscle hypertrophies, or enlarges, to maintain effective pumping. Pressure builds up in a weakened heart, however, and causes fluid backup in the lungs. As a result, the heart output cannot keep pace with the body’s oxygen demands.

BUBONIC PLAGUE   Leave a comment

DEFINITION: a contagious disease, the most common form of plague, caused by a bacterium (Yersinia pestis ) transmitted by fleas from infected rats, and characterized by buboes, fever, prostration, and delirium.

Black Death a deadly disease, probably bubonic plague, which devastated Europe and Asia in the 14th cent.

1337: Hundred Years’ War begins. Two basic issues created the antagonism between England and France in the middle of the 14th century: the succession to the French throne and the extent of British possessions in France. In 1336 the flame that lit the fire was French king Philip VI halt of the thriving wool trade between England and France.

The resulting war which would be known as the Hundred Years’ War was not a continual struggle but an intermittent one that actually lasted more than a century. Charles V of France died in 1328 leaving no successor. There were two claimants to the throne: Edward III of England, who was also duke of Guyenne in France; and the count of Valois. A French assembly chose the count, who took the name Philip VI. This could have been the end of the matter, but the new king chose to confiscate Edward’s territory of Guyenne. Edward then asserted his claim to the throne of France by sending an army to Flanders in 1337.

Notable among the events of the war were: the battles of Crecy in 1346 and Agincourt in 1415, both were unexpected victories for the English; the interruption of fighting due to the spread of the bubonic plague in 1348; and the involvement of Joan of Arc inspiring the French to victory at Orleans in 1429. Eventually France won the war, but at great cost to the land and its people. England retained only the city of Calais, which it gave up in 1558.

This long war inspired much literature, including plays by William Shakespeare and George Bernard Shaw. Dramatic accounts of St. Joan have proved particularly appealing to audiences.

1347: Black Death. The plague is one of the most devastating diseases that has ever afflicted mankind. It is a highly contagious fever caused by the bacillus Yersinia pestis, which is carried by fleas that infest rats.

The plague, commonly called bubonic plague or the Black Death, has been known since ancient times, but the best documented instance was its deadly appearance in Europe in 1347. It raged throughout all of Europe, killing at least one-fourth of the population probably 25 million people. Without understanding how it is spread, people had no defence against the disease. Poor sanitary conditions and the disruption of war only worsened the epidemic.

In Europe the epidemic started in Sicily and was spread by shipboard rats to other Mediterranean ports. It moved to North Africa, Italy, Spain, England, and France. By 1349 it made its way to Austria, Germany, Switzerland, and the Low Countries. By 1350 it reached Scandinavia and the Baltic states.

In general, the population of Europe did not recover to its size before the plague until the 16th century, and some towns never recovered. The immediate results of the plague a general collapse of economies, a breakdown of class relationships, and a halt to wartime hostilities forced a massive restructuring of society. It has had a lasting impact on art, literature, and religious thought.

Caused by rod-shaped bacteria Yersinia pestis (Pasteurella pestis), bubonic plague is an acute and severe infection. Plague is initially spread by the bite of a flea from an infected rodent (rat, squirrel), and passed from person to person by mucus droplets spread from coughing. When infected by plague bacteria, a person becomes ill within a few hours to a few days. They spread through the body, causing high fever, swollen lymph nodes, rash, and changes in blood pressure. Other forms of plague are pneumonic, which causes severe pneumonia, and septicaemic All forms of plague are extremely dangerous.

The plague bacteria cause a massive infection that overwhelms the body’s defences When plague is untreated, many victims die within a few days. Treatment is with antibiotics such as tetracycline and streptomycin and is begun immediately when infection from plague is suspected. People are immunized against plague before they travel into areas where plague is endemic (always present). Control of plague requires the control of wild rodents. Insect repellents are used against flea bites.

During the 1300s nearly half the population of Europe was killed by an epidemic of plague. The disease was called the Black Death, which described the dark colour of many victims’ faces after death. Plague still occurs in most of the world, but epidemics such as those of earlier centuries are fortunately not seen. Public health departments of all countries do all they can to avert plague epidemics.

Recommended reading includes ‘The Outline of History’, by H.G. Wells, which was first published in 1920. Volume 2 of the revised edition (1971) of this famous work contains information related to this article. Also recommended is the current edition of ‘The Merck Manual’.

Assisted by Ann Giudici Fettner

Posted 2012/02/05 by Stelios in Education

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