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nucleic acids are not the only structural components of active viruses. Certain viral particles have recently been shown to contain lipids as part of their essential structures. High-magnification electron micrographs will reveal furthermore that some of them possess a distinct membrane. If we examined the structure of some of bacteria under highmagnification electron microscope we should see that they possess a distinct membrane. What are Bacteria? Bacteria rule the world. Man is dependent upon them from the day of his birth until the hour of his death. They are man's most useful servants and his most destructive masters. One is prone to ask: What are bacteria? Where do they occur? What are their functions? Bacteria are minute single-celled living beings devoid of roots, leaves and stems. They are so small that they can be seen only with the aid of a powerful microscope; They are often spoken of as microorganisms. This term includes not only bacteria but all forms of life so small that you should require the microscope in their study. They are often referred to as germs or microbes. The early investigators considered them animals and would refer to them as «animalcules». If we examined the bacteria we should find that they have many of the characteristics of animals. Some have the power of independent motion. All are devoid of green colouring matter, chlorophyll; most of them are compelled to live upon complex foods as do the animals. Their general structure, their methods of growth, their formation of threads and spores, and their simplicity in some of the lower forms of plant life, have caused the biologist to class them as plants. However, it is impossible to make a clear-cut1 distinction between some microscopical plants and some microscopical animals. The important thing to remember is that bacteria are the simplest forms of life, and partake of the characteristics of both plants and animals. For this reason, and for convenience, scientists agree to consider the bacteria with the plants. Where do bacteria occur? Bacteria are widely distributed, occurring nearly everywhere. They are found in all natural soils, the number varying with the kind of soil, quantity of plant and animal debris present, moisture and treatment. They decrease in number with depth. Although they occur in air, it is not their natural home as under ordinary conditions they cannot grow and multiply in it. The number and variety found in air vary. The atmosphere of some high mountains and the air over the ocean far from shore may be free from bacteria. City and country air also differ from each other in the number and kind of bac- teria which they contain. There is a great variation in the air of buildings. Bacteria are especially numerous where dust is plentiful. Most natural waters contain many bacteria. In sewage and polluted waters2 they are especially numerous. If measures against pollution and contamination of water were not taken in time there would be much danger to people's health. They occur only in small numbers or not at all in deep wells3 and springs.4 A turbid stream, which contains the drainage of many cities, has a great variety and number of bacteria in opposition to the clear, rapid flowing water of uninhabited mountainous regions. The intestines, owing to their alkaline reaction and the partly digested condition of their contents, are a great reservoir of bacteria. In the upper part there are few, but in the descending colon billions of bacteria are present. Sometimes they constitute one third of the total dry contents of the intestine. The health of the individual is determined by the number and kind of bacteria. The normal tissues and the blood of animals are usually free from bacteria. If ordinary saprophytic bacteria entered the animal's body they would be ingested and destroyed by leukocytes. Microorganisms are rarely found on certain healthy mucous membranes, such as those of the kidneys, bladder and lungs. Occasionally they pass through the skin or the mucous membranes of the digestive tract after which they may be found for a short time in the blood. In certain diseased conditions the blood and tissues of man and lower animals become filled with bacteria. Functions of Bacteria. The real significance of bacteria comes in the fact that we are living in a world filled with them. They cannot be kept out of the alimentary tract. Considerable attention should be given to the favouring of the beneficial bacteria in man. The great Russian bacteriologist Mechnikov claimed that the rate with which man ages would be determined not by the years he has lived, but by the bacteria, which inhabit his digestive system. Acute Osteomyelitis 1. In this text we shall discuss the signs and symptoms of acute osteomyelitis, an infectious suppurative disease affecting bones. Osteomyelitis is generally caused by Staphylococcus, which reaches the bones via the blood stream from a distant focus, often a throat infection. Its rise was especially sharp during World War II, particulary in 1942-46 when the lack of due antibiotics made the disease uncured. 2. The disease generally affects the upper end of tibia or lower end of femur. The infection is followed by intense reaction, with pus formation in the marrow spaces. From there the suppuration spreads along the marrow cavity and also through the cortex, to erupt on the surface and form a subperiosteal abscess. In some cases the marrow cavity is widely involved; in others, on the contrary, there is a large subperiosteal abscess, but little or no pus within the bone. 3. Almost always part of bone becomes necrotic, due to the toxic effect of pus under tension and to obliteration by the subperiosteal abscess of the periosteal vessels supplying the bone cortex. The main nutrient artery itself may be thrombosed, leading to necrosis of the major part of the bone. 4. Acute osteomyelitis generally affects children, especially if in poor health, after an infectious fever. Sometimes there is a history of minor injury to the part a few days before the onset of acute symptoms. 5. In a typical case the onset is sudden. Then pain and inflammation of the bone are accompanied by marked toxaemia. The temperature rises, often to 103? or 104? F, the face is flushed and the tongue is furred. The leucocyte count rises to 20.000 or more. Delirium is frequent. The pain is severe. The limb is held immobile. The skin over the inflamed region is hot and red, and dilated veins may be evident. Slight superficial edema appears early. Localising signs develop early in the case of a superficial bone such as the tibia, later if the bone is deeply placed. 6. Acute osteomyelitis is a dangerous disease, especially when it affects a deep-seated bone, such as the upper end of the femur, pelvis or vertebrae. In those who survive the acute phase the disease often persists as chronic osteomyelitis. Eventually complete restoration of functions and general health will be expected in most cases, when appropriate treatment is applied. Fractures A fracture is a broken bone. There may be different types of fractures. A closed or simple fracture results from an injury which breaks a bone without causing any external wound at the site of the break. In case of an open or compound fracture there is a wound of the skin at the site of the fracture, and this will allow communication between the outside air and the broken bone, therefore it is «open». When the sharp ends of a broken bone damage an internal organ such as the brain or lungs, this is known as «complicated fracture». In compound fractures early and prompt healing with good function will be obtained only by early repositions in correct position. This is necessary not only to restore the bone structures, but to place the soft parts in relationship for correct function as well. All compound fracture patients must be protected against movement, muscle spasm, and loss of position. This is accomplished by fixation of fracture fragments in plaster of Paris casts1 or in any other way. Frequent dressing of wounds in compound fractures is unnecessary. What are the symptoms and signs of a fracture? Shock is always present in some degree with any fracture. Sometimes it may be severe. Pain and tenderness at the site of fracture is quickly followed by bruising and swelling. Bleeding is frequent in case of an open fracture. Irregularity on the surface of the bone may also be seen, e.g. on the collar-bone or the bone of an arm. In an open fracture the ends of the broken bone may be sticking out of the wound. A person's leg which was broken may be turned underneath him with the foot turned round the wrong way. The bones of the leg may be bent in a place where there is no joint, e.g. between the knee and the ankle if both bones of the leg are broken. First-aid treatment of fracture. Lay the patient down. This will lessen shock. If there is a fracture of the skull raise the patient's head and shoulders a little and support them. Stop bleeding if the fracture is open, and apply a dressing. In all open fractures there is some bleeding, but it can generally be stopped by putting on a dressing. If bleeding continues, it is necessary to use indirect pressure, especially if the bleeding is from an artery. Fix the damaged part so that any movement by the patient cannot cause the broken bone to move, as this will increase the deformity, cause great pain and make shock worse. Coronary Heart Disease 1. The coronary blood vessels surrounding the heart have derived their name from the fact that they encircle the heart like a crown, or corona. These vessels transport almost a half pint of blood every minute over the surface of the heart. Any sudden blockage of one of the coronary arteries deprives that section of the heart of its blood supply. Cardiac cells die, heart contractions may cease, and circulation may come to a standstill. If a coronary artery is completely plugged, the condition is called a coronary occlusion or heart attack. The vascular pathologic disorder itself has been very variable. If the obstruction is only partial or in one of the smaller coronary tributaries, prompt treatment often leads to the individual's recovery. An occlusion in main coronary arteries is very serious and may cause sudden death. Other causes of the coronary disease include heavy physical exercise, aging, dietary habits, obesity, smoking, or hypertension. 2. Pain which had been developed in the heart may be due to a bloodflow deficiency in the coronary vessels. This is referred to (actually felt in) the left arm and shoulder. Such pain from the heart has been called angina pectoris. Angina pectoris may not actually be noticed until the work load is too great in relation to the flow in the coronary vessels. People who had experienced it repeatedly often do not feel pain unless they experience strong emotion. Others experience it much of the time. 3. Fortunately, the great majority of coronary disease patients will have recovered and have been able to lead active, useful lives, when they receive proper treatment under good medical supervision. There are many preparations which have been effective and are under clinical investigation at the present time. Heart and artery diseases 4. Heart and artery diseases have been presently the number one health problem in the world. Cardiovascular ailments are by far the chief causes of illness, disability, and death among both middle-aged and elderly people. Among these, coronary heart disease, illness of the blood vessels supplying the heart, is responsible for the greatest number of deaths (over 50 per cent of all cardiovascular diseases). Causes of other cardiovascular disease deaths, in order of decreasing importance, are stroke and hypertension. These three diseases are responsible for more than 80 per cent of all cardiovascular disease deaths. 5. Like cancer and emphysema, heart diseases appear to be related to the extension of the average life span. Certain factors are definitely involved in the high incidence of heart disease - the stress, diets high in saturated fats, the tendency toward obesity with age, lack of sufficient physical exercise, and the incidence of smoking. These factors appear to relate to a higher incidence of heart desease than in societies lacking these characteristics. 6. The severity and danger of heart and artery diseases which we had previously described cannot be minimized; a disease in an arm or leg may cripple a person, but a disease of the heart may lead to his death. Hypertension Hypertension simply means high blood pressure. As a normal heart pumps blood through the body, a certain degree of pressure is excreted against the blood vessels. With each beat of the left ventricle, a wave ol pressure starts at the heart and travels along the arteries. This wave is called the pulse. The pulse can be felt on any arteries that are close to the surface of the body, such as on the wrist, the sides of the throat and the temple. The pulse results from the blood pressure. The blood pressure at the moment of contraction is the systolic pressure; it should normally be sufficient to displace about 120 mm. mercury in a glass tube. The blood pressure at the moment of relaxation of the heart is the diastolic pressure; it normally displaces about 80 mm. of mercury. Blood pressure readings, which are frequently taken during a general physical examination are presented as a ratio of the first figure over the second. Most physiologists consider the blood pressure reading of 150/90 as excessive. This can be considered a useful definition of high blood pressure. Hypertension is very common. It is believed that about one out of every five individuals suffers from it and that about 13 per cent of all deaths are a direct result of it. Recently hypertension has become more common with increasing age and now it affects men about twice as often as women. In about 90 per cent of the known cases, it has been described as essential hypertension, a hereditary condition. In other cases it may be due to the removal of a kidney, kidney disease, excessive narrowing of the arteries, hormone imbalance, or excessive salt in the diet. It has been known for many years that hypertension is damaging for two reasons: 1) it puts an excess work load on the heart and the left ventricle in particular; 2) the arteries may be damaged by excessive pressure. A hypertensive patient tends to develop cardiovascular ailments much sooner than a person who has not suffered from hypertension. This high blood pressure in the arteries causes a hardening (sclerosis) of blood vessels all over the body. The vessels become weakened; clots tend to form in them much more easily; some vessels rupture and haemorrhage. For centuries haemorrhage in the vessels of the brain (cerebral haemorrhage) and vessels of the kidneys has been known to be particularly destructive. Infections of the respiratory tract 1. While the slides were being prepared the lecturer announced the theme to be discussed. He said: «The respiratory tract is subject to infection more frequently than any other part of the body. Respiratory infections stand third as a cause of deaths; they lead all other causes between ages of fifteen and thirty-five. The upper portion of the respiratory tract, the nose, throat and trachea, are affected more often than the lower, the bronchi and lungs. The deeper the inflammation, the more serious are its consequences; pneumonia is frequently fatal. Inflammation of the deeper respiratory structures results from a downward extension of a comparatively harmless inflammation in the upper structures» 2. All the respiratory passages, except the deepest structures of the lungs, are covered with the mucous membrane; when this tissue becomes inflamed it is being swollen and there is a profuse flow of mucus. Pus resulting from bacterial action is mixing with the mucus, making it opaque and white or staining it yellow; the discharge is then said to be mucopurulent. Inflammation of the mucous membrane is of the so-called catarrhal type; the term «catarrh» indicates a chronic state of inflammation. Chronic Bronchitis 3. The inside of the bronchioles is lined with a highly specialized membrane. This membrane has a layer of mucus to trap the foreign matter that have entered the lungs. Millions of hairlike cilia are constantly sweeping the layer of mucus with its trapped foreign particles upward to the throat where it is being swallowed. 4. Repeated irritation of this ciliated mucous membrane can paralize the action of the cilia, eventually destroy them and stimulate an excessive production of mucus. This is the condition known as chronic bronchitis. Since the cilia can no longer clear the lungs of mucus, it accumulates until the flow of air through the bronchioles is obstructed. This obstruction then evokes coughing that helps to clear the lungs. Frequent coughing is the most important, prominent symptom of chronic bronchitis. Other symptoms may include shortness of breath1 and wheezing. 5. The main treatment of chronic bronchitis consists of eliminating the irritation that causes it. The source of irritation is often smoking tobacco. The so-called «smoker's cough» is in reality a symptom of chronic bronchitis. The first step in treating any lung disorder is to stop smoking. Coughing itself can contribute to the irritation of the bronchioles. If the source of irritation is an infection the disease will be receiving the treatment of a physician. Jaundice 1. Perhaps the most obvious symptom that may result from disease of the liver or biliary passages is jaundice, and the estimation of the level of bilirubin in the serum is to be therefore frequently carried out in the investigation of a case of liver disease. 2. The fact that sera from different cases of jaundice can give different types of reaction has been used as a basis for differentiating between different types of jaundice. Jaundice should be divided into three main types, viz.: obstructive jaundice, hepatocellular or «toxic» jaundice (with or without some degree of accompanying obstruction) and hemolytic jaundice. In uncomplicated obstructive jaundice, liver function is largely or wholly normal, so that the bile pigments are excreted normally into the bile passages; but owing to the presence of some obstruction (either a stone impacted in the common bile duct, or obliteration of the duct by a carcinoma of the head of the pancreas) the bile is unable to enter the duodenum and has instead to be re-absorbed into the circulation. In hepatocellular jaundice the function of the liver cells is changed so that they can not excrete the normal amount of bile pigment reach- ing them in the blood stream. In this case bilirubin level gradually rises. In hemolytic jaundice the excessive amounts of bile pigment (which are formed as a result of the excessive red cell destruction) are incompletely excreted by the liver cells and have been re-absorbed from the obstructive bile passages. In hepatocellular or obstructive jaundice the excess of circulating pigment has not passed through the liver cells. Peptic Ulcer Ulcer is a common condition. What causes ulcers? A peptic ulcer, as the name says, is an erosion in the lining of the digestive tract as a result of the action of the enzyme pepsin. An increase in the acid content of the gastric juice starts pepsin digesting the mucosa. Most of the symptoms are ascribed to the high degree of acidity of the juice. Not all persons with hyper-acidity must develop ulcers. The second, commonly recognized factor is emotional stress. Emotional stress produces conditions especially favourable to ulcer formation. Peptic ulcer disease can be called a psychosomatic disease; an actual bodily ailment, produced, or at least aggravated, by the mental and emotional state. There are two very distinctive varieties of peptic ulcer - gastric and duodenal. Although they are found in two different places-the stomach and the duodenum respectively - they look alike and cause similar distress. Gastric ulcer is caused by the hormone gastrin, secreted during the gastric phase of digestion. Distention of the stomach lining causes gastrin to be secreted from the antrum; gastrin in turn stimulates the gastric glands to work overtime. Gastric ulcers bleed into the stomach and may actually perforate the stomach wall. Duodenal ulcer, found in the first ten inches of the small intestine, is four times as common as gastric ulcer. This is the «ulcer of stress» mentioned earlier, though the psychic factor is also present in other forms. The patient usually complains of a pain and «heartburn» after meals (within the first hour in case of gastric ulcer, from three to four hours after meal in duodenal ulcer). Besides the pain which the patient is often unable to bear, he may also suffer from frequent vomiting. If the gastric juice shows an abnormal concentration of HCl1, the diagnosis is practically certain. Since the secretion of gastric juice is excessive in all forms of peptic ulcer, proper diet should be neccessary for the suppression of secretion. This means that the diet, instead of being appetizing, has to be monotonous, in order to suppress the appetite juice. Meat and alcohol are to be forbidden. |