129 résultats pour "disease"
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Chromosome.
chromosome breaks off and attaches to another chromosome. A translocation involving chromosomes 9 and 22 is linked to a type of leukemia called chronic myelogenicleukemia. On the sex chromosomes, problems arise in men when an abnormal gene is present on the X chromosome. With no healthy gene found on the Y chromosometo override the abnormal gene, disease may result. For example, men who inherit a mutated gene that causes hemophilia from their mother on the X chromosome willdevelop this bleeding...
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Circulatory System.
C Additional Functions In addition to oxygen, the circulatory system also transports nutrients derived from digested food to the body. These nutrients enter the bloodstream by passingthrough the walls of the intestine. The nutrients are absorbed through a network of capillaries and veins that drain the intestines, called the hepatic portal circulation.The hepatic portal circulation carries the nutrients to the liver for further metabolic processing. The liver stores a variety of substances, suc...
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Giant Panda - biology.
In 2007 conservationists announced that a parasitic roundworm was responsible for a significant number of the panda deaths reported in the wild since 1990. Theparasite Baylisascaris schroederi causes the disease visceral larval migrans, which results in bleeding in the lungs, the liver, and the intestines, and can also affect the brain. It is not known if other recent pandas deaths were caused by the same parasite or by a different contagious disease. Loss of habitat from deforestation is forc...
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Multiple Sclerosis.
slow the progress of the disease. It has become increasingly clear that early treatment is crucial to prevent or delay further damage to the nervous system. There are also treatments for specific symptoms, including corticosteroids (often taken intravenously), that can shorten the duration of an MS attack. Several drugs canrelieve spasticity, fatigue, and bladder problems. People with MS often find that nondrug treatments, such as regular exercise and adequate rest, can help them tomaintain more...
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Malaria.
last long and is unlikely to be fatal. Infants and children are especially vulnerable to malaria because they have not yet built up immunity to the parasite. Some peoplehave genetic traits that help them resist malaria. Sickle-cell anemia and thalassemia, for example, are inherited blood disorders linked to malaria resistance. Travelers who lack immunity to malaria should take precautionary measures when visiting areas where the disease is prevalent. Such measures include using insectrepellents,...
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Vitamin.
Vitamin B 1, or thiamine, promotes the metabolism of carbohydrates, enabling these nutrients to release their energy. Thiamine also plays a role in the functioning of the nervous system, muscles, and heart. The body does not store thiamine and people who are malnourished may develop thiamine deficiency. Mild thiamine deficiency cancause fatigue, muscle weakness, and loss of appetite. Severe thiamine deficiency causes beriberi, a disease characterized by muscle weakness, swelling of the heart,and...
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Cat.
I
INTRODUCTION
Cat, small, mainly carnivorous animal, Felis silvestris catus, member of
D Coat Colors The domestic cat's original coat color was probably grayish-brown with darker tabby stripes, a color that provides excellent camouflage in a variety of environments. Allother coat colors and patterns are the result of genetic mutations; for example, solid coat colors such as black and blue are the result of a gene that suppresses tabbystripes; an orange coat is the result of a gene that transforms black pigment to orange; and a solid white coat is the result of a gene that complet...
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Cat - biology.
D Coat Colors The domestic cat's original coat color was probably grayish-brown with darker tabby stripes, a color that provides excellent camouflage in a variety of environments. Allother coat colors and patterns are the result of genetic mutations; for example, solid coat colors such as black and blue are the result of a gene that suppresses tabbystripes; an orange coat is the result of a gene that transforms black pigment to orange; and a solid white coat is the result of a gene that complet...
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Fruit - biology.
from a flower with several pistils. The ovary may have a single compartment, or carpel, which houses the ovule or ovules. Or the ovary may consist of two or morecarpels, each of which may contain one or more ovules. A drupe develops from an ovary with a single carpel and is characterized by an edible exocarp and mesocarp and an inedible, hard endocarp, or pit that encloses asingle seed. Cherries, peaches, apricots, and plums are examples of drupes. Almonds also are classified as drupes, but in a...
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Mental Illness.
note that under this definition, political dissidents could be considered mentally ill for refusing to accept the dictates of their government. VI PREVALENCE Mental illness affects people of all ages, races, cultures, and socioeconomic classes. The prevalence of mental illness refers to how many people experience a mentalillness during a specified time period. A United States and Worldwide In the United States, researchers estimate that about 24 percent of people 18 or older, or about 44 mill...
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Smoking.
causes about 20 times the number of deaths in the United States than all other addictive drugs combined. Smoking cessation methods are plentiful, and many books and products are available to help an individual stop smoking. Many smokers turn to group help because ofthe support and understanding provided by other former smokers or people trying to quit. Most successful group-help techniques involve a challenge and rewardsystem that also bolsters the self-discipline of the former smoker. A number...
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Obesity.
of a day, contributing to the development of obesity. V TREATMENTS FOR OBESITY Obesity can become a chronic lifelong condition caused by overeating, physical inactivity, and even genetic makeup. No matter what the cause, however, obesity can beprevented or managed with a combination of diet, exercise, behavior modification, and in severe cases, weight-loss medications and surgery. A Diets The most common and conservative treatment for obesity utilizes a nutritionally balanced, low calorie diet...
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Rice - biology.
V HISTORY According to the most widely accepted theory, rice cultivation originated as early as 10,000 BC in Asia. Archaeological evidence shows that rice was grown in Thailand as early as 4000 BC, and over the centuries spread to China, Japan, and Indonesia. By 400 BC rice was cultivated in the Middle East and Africa. The invading armies of Alexander the Great probably introduced rice to Greece and nearby Mediterranean countries around 330 BC. Rice was brought to the American colonies in t...
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Koala - biology.
V REPRODUCTION Female koalas become sexually mature around 18 to 24 months of age. They can produce one offspring a year until they reach about 13 years of age. Males begin toproduce sperm around age 2 and, in the absence of older, stronger males, they may breed at that young age. More often, however, a male must grow big enough tocompete with other males for females, and mating generally begins for males at about 4 years of age. The breeding season for koalas is from October to May, during the...
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Hawaii (state) - geography.
limestone along the coast. The volcanoes of the Hawaiian Islands are all so-called shield volcanoes, or lava domes. Unlike the volcanoes of Alaska and South America, those of Hawaii were notcreated by very explosive eruptions. Formed mostly by lava flows, they are great rounded mountain masses, rather than steep-sided cones. Mauna Kea, dormant forcenturies, is the highest mountain in the state. It rises to 4,205 m (13,796 ft) above sea level, and its summit is dotted with cinder cones formed by...
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Hawaii (state) - USA History.
limestone along the coast. The volcanoes of the Hawaiian Islands are all so-called shield volcanoes, or lava domes. Unlike the volcanoes of Alaska and South America, those of Hawaii were notcreated by very explosive eruptions. Formed mostly by lava flows, they are great rounded mountain masses, rather than steep-sided cones. Mauna Kea, dormant forcenturies, is the highest mountain in the state. It rises to 4,205 m (13,796 ft) above sea level, and its summit is dotted with cinder cones formed by...
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Deoxyribonucleic Acid - biology.
bacterium Escherichia coli . In 1998 scientists achieved the milestone of sequencing the complete genome of a multicellular organism—a roundworm identified as Caenorhabditis elegans . The Human Genome Project, an international research collaboration, was established to determine the sequence of all of the 3 billion nucleotide base pairs that make up thehuman genetic material. In 2003 scientists completed the sequencing of the human genome. The project identified nearly all of the estimated 20...
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Schizophrenia.
alcohol than other people. The use of alcohol and drugs often worsens the symptoms of schizophrenia, resulting in relapses and hospitalizations. IV CAUSES Schizophrenia appears to result not from a single cause, but from a variety of factors. Most scientists believe that schizophrenia is a biological disease caused by geneticfactors, an imbalance of chemicals in the brain, structural brain abnormalities, or abnormalities in the prenatal environment. In addition, stressful life events maycontri...
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Slavery in Africa.
The spread of Islam from Arabia into Africa after the religion’s founding in the 7th century AD affected the practice of slavery and slave trading in West, Central, and East Africa. Arabs had practiced slave raiding and trading in Arabia for centuries prior to the founding of Islam, and slavery became a component of Islamic traditions.Both the Qur'an (Koran) (the sacred scripture of Islam) and Islamic religious law served to codify and justify the existence of slavery. As Muslim Arabs conquered...
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Tiger - biology.
have a simple digestive system designed to process meat so that the nutrients can be readily absorbed into the bloodstream. With the exception of white tigers, which have blue eyes, all tigers have yellow eyes. Tigers mainly use vision to find prey. Although tigers see about as well as humansduring the day, their large eye openings gather more light than do human eyes, making tiger night vision far superior to that of humans. In addition, a special structurein the tiger’s eye, called the tapetu...
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Louis Pasteur.
In 1885, a young boy and his mother arrived at Pasteur’s laboratory; the boy had been bitten badly by a rabid dog, and Pasteur was urged to treat him with his newmethod. At the end of the treatment, which lasted ten days, the boy was being inoculated with the most potent rabies virus known; he recovered and remainedhealthy. Since that time, thousands of people have been saved from rabies by this treatment. Pasteur’s research on rabies resulted, in 1888, in the founding of a special institute in...
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Nervous System.
of paralysis and other neurologic complications. Some diseases exhibit peculiar geographic and age distribution. In temperate zones, multiple sclerosis is a commondegenerative disease of the nervous system, but it is rare in the Tropics. The nervous system is subject to infection by a great variety of bacteria, parasites, and viruses. For example, meningitis, or infection of the meninges investing thebrain and spinal cord, can be caused by many different agents. On the other hand, one specific v...
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Fungus - biology.
Many fungi can reproduce by the fragmentation of their hyphae. Each fragment develops into a new individual. Yeast, a small, single-celled fungus, reproduces bybudding, in which a bump forms on the yeast cell, eventually partitioning from the cell and growing into a new yeast cell. V CLASSIFICATION OF FUNGI Scientists have long disagreed about how to classify fungi, and the classification systems are still developing. The first description of fungi was published in 1729 byItalian botanist Pier...
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Drug.
I
INTRODUCTION
Drug, substance that affects the function of living cells, used
normalizing chemical activity in the emotional centers of the brain. Antianxiety drugs, also referred to as tranquilizers, treat anxiety by decreasing the activity in theanxiety centers of the brain. Sedative-hypnotic drugs are used both as sedatives to reduce anxiety and as hypnotics to induce sleep. Sedative-hypnotic drugs act by reducing brain-cell activity.Stimulant drugs, on the other hand, increase neuronal (nerve cell) activity and reduce fatigue and appetite. Analgesic drugs reduce pain...
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Cancer (medicine).
unable to repair the DNA damage, p53 instructs the cell to undergo programmed cell death, or apoptosis , putting a stop to runaway cell division before it starts. Programmed cell death is a normal part of cell life and is tightly controlled by many genes, primarily p53. In a cancerous cell, one or more mutations prevent these genes from doing their jobs. When mutated, p53 allows a cell to continue to divide, even with damaged DNA.This can lead to additional mutations in proto-oncogenes or tumor...
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Prokaryote - biology.
earliest organisms to evolve, an estimated 3.4 billion to 3.5 billion years ago. The environment of the early Earth lacked oxygen, and cyanobacteria probably usedfermentation (a chemical process performed without the presence of oxygen) to produce the energy molecule adenosine triphosphate (ATP). Cyanobacteria introduced oxygen into the atmosphere through the process of photosynthesis. As the oxygen content in the atmosphere increased over the centuries, bacteria evolved that usedthis oxygen in...
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Respiratory System.
rapidly, or laughs while swallowing, the swallowing reflex may not work, and food or fluid can enter the larynx. Food, fluid, or other substances in the larynx initiate acough reflex as the body attempts to clear the larynx of the obstruction. If the cough reflex does not work, a person can choke, a life-threatening situation. TheHeimlich maneuver is a technique used to clear a blocked larynx ( see First Aid). A surgical procedure called a tracheotomy is used to bypass the larynx and get air to...
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Race - biology.
distributed as a cline, generally varying along a north-south line. Skin color is lightest in northern Europeans, especially in those who live around the Baltic Sea, andbecomes gradually darker as one moves toward southern Europe, the Mediterranean, the Middle East, and into northern Africa and northern subtropical Africa. Skin isdarkest in people who live in the tropical regions of Africa. The lack of clear-cut discontinuities makes any racial boundary based on skin color totally arbitrary. Sim...
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Honey Bee - biology.
B Reproduction and Development The queen controls the sex of her offspring. When an egg passes from her ovary to her oviduct, the queen determines whether the egg is fertilized with sperm from thespermatheca. A fertilized egg develops into a female honey bee, either worker or queen, and an unfertilized egg becomes a male honey bee, or drone. The queen lays the eggs that will develop into more queens in specially constructed downward-pointing, peanut-shaped cells, in which the egg adheres to the...
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Medical Ethics.
medical profession. In recent years, however, the field of medical ethics has struggled to keep pace with the many complex issues raised by new technologies for creating and sustaininglife. Artificial-respiration devices, kidney dialysis, and other machines can keep patients alive who previously would have succumbed to their illnesses or injuries.Advances in organ transplantation have brought new hope to those afflicted with diseased organs. New techniques have enabled prospective parents to con...
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West Virginia - geography.
Forests, mostly of hardwood varieties, cover 79 percent of West Virginia. The principal commercial species are the oak, yellow poplar, maple, birch, beech, black walnut,hickory, and gum. Softwoods include pines and hemlock firs. Flowering trees include the wild crab apple, dogwood, hawthorn, and redbud. Among the many floweringbushes and plants are the rhododendron, which is the state flower, the laurel, blueberry, hepatica, wild geranium, and black-eyed Susan. Insects and disease, mostly introd...
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West Virginia - USA History.
Forests, mostly of hardwood varieties, cover 79 percent of West Virginia. The principal commercial species are the oak, yellow poplar, maple, birch, beech, black walnut,hickory, and gum. Softwoods include pines and hemlock firs. Flowering trees include the wild crab apple, dogwood, hawthorn, and redbud. Among the many floweringbushes and plants are the rhododendron, which is the state flower, the laurel, blueberry, hepatica, wild geranium, and black-eyed Susan. Insects and disease, mostly introd...
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Antibiotics.
In some species of bacteria the cell wall consists primarily of a thick layer of peptidoglycan. Other species have a much thinner layer of peptidoglycan and an outer aswell as an inner membrane. When bacteria are subjected to Gram's stain, these differences in structure affect the differential staining of the bacteria with a dye calledgentian violet. The differences in staining coloration (gram-positive bacteria appear purple and gram-negative bacteria appear colorless or reddish, depending on t...
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Forest.
suffocation; nutritional excesses or deficiencies; winter injury; and injury from smoke, gases, and fumes. See articles on individual trees. See also Conservation; Diseases of Plants; Forestry. Contributed By:David L. AdamsMicrosoft ® Encarta ® 2009. © 1993-2008 Microsoft Corporation. All rights reserved.
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Evolution - biology.
genetic diversity to extinction. Sexual reproduction ensures that the genes in a population are rearranged in each generation, a process termed recombination. Although the combinations of genes inindividuals change with each new generation, the gene frequency, or ratio of different alleles in the entire population, remains relatively constant if no evolutionaryforces act on the population. One such force is the introduction of new genes into the genetic material of the population, or gene pool...
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History of Colonial America - U.
Despite the lack of settlement, New France prospered as a vast fur-trading enterprise. French explorers traveled deep into the North American continent seeking newsupplies of deerskins and beaver pelts. In 1673 French missionary Jacques Marquette reached the Mississippi River in present-day Wisconsin. In 1681 explorer René-Robert Cavelier, Sieur de La Salle, traveled down the majestic Mississippi to the Gulf of Mexico. He honored the reign of King Louis XIV (1643-1715) by creating the newcolony...
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Democratic Republic of the Congo - country.
Except in the high elevations, the country’s climate is very hot and humid. The average annual temperature in the low central area is about 27°C (about 80°F).Temperatures are considerably higher in February, the hottest month. At altitudes above about 1,500 m (about 5,000 ft) the average annual temperature is about 19°C(about 66°F). Average annual rainfall is about 1,500 mm (about 60 in) in the north and about 1,300 mm (about 50 in) in the south. Frequent heavy rains occur fromApril to November...
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Federal Republic of Germany - country.
B Rivers and Lakes Rivers have played a major role in Germany’s economic development. The Rhine River flows in a northwesterly direction from Switzerland through much of westernGermany and The Netherlands into the North Sea. It is a major European waterway and a pillar of commerce and trade. Its primary German tributaries include theMain, Mosel, Neckar, and Ruhr rivers. The Oder (Odra) River, along the border between Poland and Germany, runs northward and empties into the Baltic; it provides an...
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Air Pollution.
Several pollutants attack the ozone layer. Chief among them is the class of chemicals known as chlorofluorocarbons (CFCs), formerly used as refrigerants (notably in airconditioners), as agents in several manufacturing processes, and as propellants in spray cans. CFC molecules are virtually indestructible until they reach thestratosphere. Here, intense ultraviolet radiation breaks the CFC molecules apart, releasing the chlorine atoms they contain. These chlorine atoms begin reacting withozone, br...
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Conservation.
cancers, Hodgkin’s disease and leukemia. Unfortunately, human activities have greatly reduced biodiversity around the world. The 20th century encompasses one of the greatest waves of extinction, orelimination of species, to occur on the planet. The greatest threat to biodiversity is loss of habitat as humans develop land for agriculture, grazing livestock, industry,and habitation. The most drastic damage has occurred in the tropical rain forests, which cover less than seven percent of the Earth’...
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Earthquake.
III CAUSES Most earthquakes are caused by the sudden slip along geologic faults. The faults slip because of movement of the Earth’s tectonic plates. This concept is called theelastic rebound theory. The rocky tectonic plates move very slowly, floating on top of a weaker rocky layer. As the plates collide with each other or slide past eachother, pressure builds up within the rocky crust. Earthquakes occur when pressure within the crust increases slowly over hundreds of years and finally exceeds...
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Muhammad Ali.
In 1984 Ali was first diagnosed with Parkinson syndrome, a medical condition closely related to Parkinson disease. Symptoms include body tremors, slurred or difficultspeech, rigid limbs, facial immobilization, and other neurological problems. The disorder sometimes develops in boxers, because of the repeated blows to the head theysuffer over a long career. As the former champion coped with the condition, he became a strong advocate for more research money for Parkinson disease and relatedconditi...
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Muhammad Ali
I
INTRODUCTION
Muhammad Ali, born in 1942, American boxer, one of the greatest fighters in the history of the sport.
In 1984 Ali was first diagnosed with Parkinson syndrome, a medical condition closely related to Parkinson disease. Symptoms include body tremors, slurred or difficultspeech, rigid limbs, facial immobilization, and other neurological problems. The disorder sometimes develops in boxers, because of the repeated blows to the head theysuffer over a long career. As the former champion coped with the condition, he became a strong advocate for more research money for Parkinson disease and relatedconditi...
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Woman in white chapter 5
didn't answer but he smiled. Then the next day the count and his wife were gone to London. Then Percival lied to Laura and said that Marian left the house and was in Cumberland. But that was not true, Percival said that was the only way to make Laura go to Cumberland. Then Eliza left the house. The cook's narrative When Laura arrived at London a Doctor examined and and said that a serious case of heart disease. She won't live much longer. And the next day she died. Then the cook answered tw...
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Owl - biology.
Among the largest species of typical owls are the eagle owls. They have tufts of feathers on their heads that are called “ears.” The great horned owl is the only eagleowl found in the Americas. It is about 60 cm (25 in) in length with a wingspan of 1.4 m (60 in). Numerous species of eagle owls inhabit Europe, Africa, and Asia. Mostwidely distributed is the northern eagle owl, found from Scandinavia and Spain to Japan. It is about 71 cm (28 in) long with a wingspan of about 2m (72 in). Nearly asl...
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Jakarta - geography.
voluntary movement of families to Indonesia's less populated islands). Jakarta is a magnet for migrants from other areas of Indonesia; during the late 1980s an estimated 250 migrants arrived daily. Most were between the ages of 15 and39 years, many with six years of education or less. There is also a significant number of commuters and seasonal migrants who work in government, manufacturing,and services. In addition, many of these temporary residents are engaged in informal employment as drivers...
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Depression (psychology).
IV CAUSES Some depressions seem to come out of the blue, even when things are going well. Others seem to have an obvious cause: a marital conflict, financial difficulty, or somepersonal failure. Yet many people with these problems do not become deeply depressed. Most psychologists believe depression results from an interaction betweenstressful life events and a person’s biological and psychological vulnerabilities. A Biological Factors Depression runs in families. By studying twins, researche...
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Extinction (biology) - biology.
III ROLE OF MASS EXTINCTION IN EVOLUTION Historically biologists—most famous among them British naturalist Charles Darwin—assumed that extinction is the natural outcome of competition between newlyevolved, adaptively superior species and their older, more primitive ancestors. These scientists believed that newer, more highly evolved species simply drove less well-adapted species to extinction. That is, historically, extinction was thought to result from evolution. It was also thought that this...
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Native American Religions.
In the worldview of most of the indigenous peoples of North America, there were also spiritual beings to be avoided. Native Americans of the Southwest in particular,such as the Navajo and Apache, dreaded contact with ghosts, who were believed to resent the living. These peoples disposed of the bodies of deceased relativesimmediately and attempted to distance themselves from the spirits of the dead, avoiding their burial sites, never mentioning their names, and even abandoning thedwellings in whi...
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Panama Canal - Geography.
The size of ships using the Panama Canal has steadily increased. About 27 percent of the vessels that use the canal are built to the maximum dimensions that can passthrough it (a category called “Panamax”). This has prompted further widening of Gaillard Cut, so that the larger Panamax vessels may transit safely. However, some ofthe world’s commercial and military ships are too large for the canal. Since the 1940s, new U.S. battleships and aircraft carriers have been built exceeding the canal’sdi...