Alzheimer's Disease Causes, Stages, and Symptoms Glossary of Terms with Definitions on MedicineNet.com

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Alzheimer's Disease Glossary of Terms

The following are health and medical definitions of terms that appear in the Alzheimer's Disease article.

Acetylcholine: A key chemical in neurons (nerve cells) that acts as a neurotransmitter and carries information across the synaptic cleft, the space between two nerve cells. Abbreviated ACh.

Acute: Of abrupt onset, in reference to a disease. Acute often also connotes an illness that is of short duration, rapidly progressive, and in need of urgent care.
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Aging: The process of becoming older, a process that is genetically determined and environmentally modulated.
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Alcohol abuse: Use of alcoholic beverages to excess, either on individual occasions ("binge drinking") or as a regular practice. For some individuals-children or pregnant women, for example-almost any amount of alcohol use may be legally considered "alcohol abuse," depending on local laws. Heavy alcohol abuse can cause physical damage and death.

Alzheimer's disease: A progressive neurologic disease of the brain that leads to the irreversible loss of neurons and dementia. The clinical hallmarks of Alzheimer's disease are progressive impairment in memory, judgment, decision making, orientation to physical surroundings, and language. A working diagnosis of Alzheimer disease is usually made on the basis of the neurologic examination. A definitive diagnosis can be made only at autopsy. On a cellular level, Alzheimer's disease is characterized by unusual helical protein filaments in nerve cells (neurons) of the brain. These odd twisted filaments are called neurofibrillary tangles. On a functional level, there is degeneration of the cortical regions, especially the frontal and temporal lobes, of the brain.
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Amyloid: Any of a number of complex proteins that are deposited in tissues and that share selected laboratory features such as a change in the fluorescence intensity of certain aromatic dyes like Congo Red.
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Antidepressant: Anything, and especially a drug, used to prevent or treat depression.
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Antidepressants: Anything, and especially a drug, used to prevent or treat depression.
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Antipsychotic: A medication (or another measure) that is believed to be effective in the treatment of psychosis. For example, aripiprazole (Abilify) is an antipsychotic medication used to treat schizophrenia.

Anxiety: A feeling of apprehension and fear characterized by physical symptoms such as palpitations, sweating, and feelings of stress. Anxiety disorders are serious medical illnesses that affect approximately 19 million American adults. These disorders fill people's lives with overwhelming anxiety and fear. Unlike the relatively mild, brief anxiety caused by a stressful event such as a business presentation or a first date, anxiety disorders are chronic, relentless, and can grow progressively worse if not treated.
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ApoE: Abbreviation for apolipoprotein E, a gene that codes for a protein component of lipoproteins (complexes of fat + protein) that are normal constituents of blood plasma -- namely, chylomicrons, HDL (high density lipoprotein), LDL (low density lipoprotein), and VLDL (very low density lipoprotein).
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Apolipoprotein E: A type of lipoprotein (a protein connected to a fat). Apolipoprotein E is abbreviated ApoE and the gene that encodes it is known as APOE. APOE is located on chromosome 19 in band 19q13.2.
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Artery: A vessel that carries blood high in oxygen content away from the heart to the farthest reaches of the body. Since blood in arteries is usually full of oxygen, the hemoglobin in the red blood cells is oxygenated. The resultant form of hemoglobin (oxyhemoglobin) is what makes arterial blood look bright red.
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Atypical: Not typical, not usual, not normal, abnormal. Atypical is often used to refer to the appearance of precancerous or cancerous cells.

Baseline: 1. Information gathered at the beginning of a study from which variations found in the study are measured.
2. A known value or quantity with which an unknown is compared when measured or assessed.
3. The initial time point in a clinical trial, just before a participant starts to receive the experimental treatment which is being tested. At this reference point, measurable values such as CD4 count are recorded. Safety and efficacy of a drug are often determined by monitoring changes from the baseline values.

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Benzodiazepines: A class of drugs that act as tranquilizers and are commonly used in the treatment of anxiety. Benzodiazepines can cause drowsiness.

Bladder: Any pouch or other flexible enclosure that can hold liquids or gases but usually refers to the hollow organ in the lower abdomen that stores urine -- the urinary bladder. The kidneys filter waste from the blood and produce urine, which enters the bladder through two tubes called ureters. Urine leaves the bladder through another tube, the urethra. In women, the urethra is a short tube that opens just in front of the vagina. In men, it is longer, passing through the prostate gland and then the penis. Infection of the bladder is called cystitis.

Blood clots: Blood that has been converted from a liquid to a solid state. Also called a thrombus.
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Blood pressure: The blood pressure is the pressure of the blood within the arteries. It is produced primarily by the contraction of the heart muscle. It's measurement is recorded by two numbers. The first (systolic pressure) is measured after the heart contracts and is highest. The second (diastolic pressure) is measured before the heart contracts and lowest. A blood pressure cuff is used to measure the pressure. Elevation of blood pressure is called "hypertension".

Bowel: Another name for the intestine. The small bowel and the large bowel are the small intestine and large intestine, respectively.
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Brain: That part of the central nervous system that is located within the cranium (skull). The brain functions as the primary receiver, organizer and distributor of information for the body. It has two (right and left) halves called "hemispheres."

Carbon monoxide poisoning: Poisoning with carbon monoxide, a tasteless odorless gas that is a byproduct of combustion. Carbon monoxide acts as a poison by competing with oxygen for binding sites on hemoglobin, the molecule in red blood cells that carries oxygen from the lungs to the more remote tissues of the body and returns carbon dioxide from the tissues to the lungs. On inhalation, carbon monoxide binds to hemoglobin with a binding affinity 200--270 times greater than that of oxygen.
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Cascade: A sequence of successive activation reactions involving enzymes (enzyme cascade) or hormones (hormone cascade) characterized by a series of amplifications of an initial stimulus. In blood coagulation, for example, each enzyme activates the next until the final product, the fibrin clot, is reached.

Cell: The basic structural and functional unit in people and all living things. Each cell is a small container of chemicals and water wrapped in a membrane.
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Cerebrovascular: Pertaining to the blood vessels and, especially, the arteries that supply the brain. As in cerebrovascular accident or cerebrovascular disease.

Cerebrovascular disease: Disease of the blood vessels and, especially, the arteries that supply the brain. Cerebrovascular disease is usually caused by atherosclerosis and can lead to a stroke. See also atherosclerosis, stroke.

Chest: The area of the body located between the neck and the abdomen. The chest contains the lungs, the heart and part of the aorta. The walls of the chest are supported by the dorsal vertebrae, the ribs, and the sternum.
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Cholesterol: The most common type of steroid in the body, cholesterol has gotten something of a bad name. However, cholesterol is a critically important molecule.
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Chromosome: A visible carrier of the genetic information.
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Chronic: This important term in medicine comes from the Greek chronos, time and means lasting a long time.
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Clinical research trials: Trials to evaluate the effectiveness and safety of medications or medical devices by monitoring their effects on large groups of people.
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Clinical trials: Trials to evaluate the effectiveness and safety of medications or medical devices by monitoring their effects on large groups of people.
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Cognition: The process of knowing and, more precisely, the process of being aware, knowing, thinking, learning and judging. The study of cognition touches on the fields of psychology, linguistics, computer science, neuroscience, mathematics, ethology and philosophy.
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Cognitive: Pertaining to cognition, the process of knowing and, more precisely, the process of being aware, knowing, thinking, learning and judging. The study of cognition touches on the fields of psychology, linguistics, computer science, neuroscience, mathematics, ethology and philosophy.
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Contrast: Short for "contrast media." Contrast media are X-ray dyes used to provide contrast, for example, between blood vessels and other tissue.

Coronary artery disease: A major cause of illness and death, coronary artery disease (CAD) begins when hard cholesterol substances (plaques) are deposited within a coronary artery.
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CT scan: Computerized tomography scan. Pictures of structures within the body created by a computer that takes the data from multiple X-ray images and turns them into pictures on a screen. CT stands for computerized tomography.
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Cure: 1. To heal, to make well, to restore to good health. Cures are easy to claim and, all too often, difficult to confirm.
2. A time without recurrence of a disease so that the risk of recurrence is small, as in the 5-year cure rate for malignant melanoma.
3. Particularly in the past, a course of treatment. For example, take a cure at a spa.
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Dementia: Significant loss of intellectual abilities such as memory capacity, severe enough to interfere with social or occupational functioning.
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Depression: An illness that involves the body, mood, and thoughts, that affects the way a person eats and sleeps, the way one feels about oneself, and the way one thinks about things. A depressive disorder is not the same as a passing blue mood. It is not a sign of personal weakness or a condition that can be wished away. People with a depressive disease cannot merely "pull themselves together" and get better. Without treatment, symptoms can last for weeks, months, or years. Appropriate treatment, however, can help most people with depression.
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Diabetes: Refers to diabetes mellitus or, less often, to diabetes insipidus. Diabetes mellitus and diabetes insipidus share the name "diabetes" because they are both conditions characterized by excessive urination (polyuria).
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Diagnosis: 1 The nature of a disease; the identification of an illness. 2 A conclusion or decision reached by diagnosis. The diagnosis is rabies. 3 The identification of any problem. The diagnosis was a plugged IV.
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Diarrhea: A familiar phenomenon with unusually frequent or unusually liquid bowel movements, excessive watery evacuations of fecal material. The opposite of constipation. The word "diarrhea" with its odd spelling is a near steal from the Greek "diarrhoia" meaning "a flowing through." Plato and Aristotle may have had diarrhoia while today we have diarrhea. There are myriad infectious and noninfectious causes of diarrhea.
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Down syndrome: A common chromosome disorder due to an extra chromosome number 21 (trisomy 21). Down syndrome causes mental retardation, a characteristic face, and multiple malformations. Down syndrome is a relatively common birth defect. The chromosome abnormality affects both the physical and intellectual development of the individual.
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Drain: A device for removing fluid from a cavity or wound. A drain is typically a tube or wick. As a verb, to allow fluid to be released from a confined area.

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Durable power of attorney: This is a type of advance medical directive in which legal documents provide the power of attorney to another person in the case of an incapacitating medical condition.
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Dysfunction: Difficult function or abnormal function.
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Encephalopathy: Disease, damage, or malfunction of the brain. In general, encephalopathy is manifested by an altered mental state that is sometimes accompanied by physical changes. Although numerous causes of encephalopathy are known, the majority of cases arise from infection, liver damage, anoxia, or kidney failure. The term encephalopathy is very broad and, in most cases, is preceded by various terms that describe the reason, cause, or special conditions of the patient that leads to brain malfunction. For example, anoxic encephalopathy means brain damage due to lack of oxygen, and hepatic encephalopathy means brain malfunction due to liver disease. Depending upon the cause and severity of the condition, symptoms may range from mild alterations in mental status to severe and potentially fatal manifestations such as dementia, seizures, and coma.

Essential: 1. Something that cannot be done without.
2. Required in the diet, because the body cannot make it. As in an essential amino acid or an essential fatty acid.
3. Idiopathic. As in essential hypertension. "Essential" is a hallowed term meaning "We don't know the cause."

Estrogen: Estrogen is a female hormone produced by the ovaries. Estrogen deficiency can lead to osteoporosis.
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Expiration date: The date for a drug estimated for its shelf life with proper storage in sealed containers away from harmful and variable factors like heat and humidity.
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Fahrenheit: Thermometer scale in which the freezing point of water is 32°F and the boiling point of water 212°F.
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FDA: The Food and Drug Administration, an agency within the U.S. Public Health Service, which is a part of the Department of Health and Human Services.
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fMRI: Functional magnetic resonance imaging.

Fungal: Pertaining to a fungus. For example, a fungal skin infection.

Gastrointestinal: Adjective referring collectively to the stomach and small and large intestines.
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Gene: The basic biological unit of heredity. A segment of deoxyribonucleic acid (DNA) needed to contribute to a function.
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Genes: The basic biological units of heredity. Segments of deoxyribonucleic acid (DNA) needed to contribute to a function.
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Genetic: Having to do with genes and genetic information.

Genetic testing: Tests done for clinical genetic purposes. Genetic tests may be done for diverse purposes pertaining to clinical genetics, including the diagnosis of genetic disease in children and adults; the identification of future disease risks; the prediction of drug responses; and the detection of risks of disease to future children.

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Glutamate: A form of glutamic acid. See: Glutamic acid.

Grief: The normal process of reacting to a loss. The loss may be physical (such as a death), social (such as divorce), or occupational (such as a job). Emotional reactions of grief can include anger, guilt, anxiety, sadness, and despair. Physical reactions of grief can include sleeping problems, changes in appetite, physical problems, or illness.
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Hearing aid: An instrument to help in hearing. There are four common styles of hearing aids.
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Heart: The muscle that pumps blood received from veins into arteries throughout the body. It is positioned in the chest behind the sternum (breastbone; in front of the trachea, esophagus, and aorta; and above the diaphragm muscle that separates the chest and abdominal cavities. The normal heart is about the size of a closed fist, and weighs about 10.5 ounces. It is cone-shaped, with the point of the cone pointing down to the left. Two-thirds of the heart lies in the left side of the chest with the balance in the right chest.
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Heart disease: Any disorder that affects the heart. Sometimes the term "heart disease" is used narrowly and incorrectly as a synonym for coronary artery disease. Heart disease is synonymous with cardiac disease but not with cardiovascular disease which is any disease of the heart or blood vessels. Among the many types of heart disease, see, for example: Angina; Arrhythmia; Congenital heart disease; Coronary artery disease (CAD); Dilated cardiomyopathy; Heart attack (myocardial infarction); Heart failure; Hypertrophic cardiomyopathy; Mitral regurgitation; Mitral valve prolapse; and Pulmonary stenosis.

Heimlich maneuver: An emergency treatment for obstruction of the airway in adults. It may be needed when someone chokes on a piece of food that has "gone down the wrong way."
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High blood pressure: Also known as hypertension, high blood pressure is, by definition, a repeatedly elevated blood pressure exceeding 140 over 90 mmHg -- a systolic pressure above 140 with a diastolic pressure above 90.
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HIV: Acronym for the Human Immunodeficiency Virus, the cause of AIDS (acquired immunodeficiency syndrome). HIV has also been called the human lymphotropic virus type III, the lymphadenopathy-associated virus and the lymphadenopathy virus. No matter what name is applied, it is a retrovirus. (A retrovirus has an RNA genome and a reverse transcriptase enzyme. Using the reverse transcriptase, the virus uses its RNA as a template for making complementary DNA which can integrate into the DNA of the host organism).
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Hygiene: The science of preventive medicine and the preservation of health. From the name of Hygeia, the daughter of Asklepios, the Greek god of medicine (whose staff with entwined snake is the symbol of medicine). Asklepios (known to the Romans as Aesculapius) had a number of children including not only Hygeia but also Panaceia, the patroness of clinical medicine. Hygeia also followed her father into medicine. As the patroness of health, Hygeia was charged with providing a healthy environment to prevent illness. In Greek, "hygieia" means health.

Hypertension: High blood pressure, defined as a repeatedly elevated blood pressure exceeding 140 over 90 mmHg -- a systolic pressure above 140 with a diastolic pressure above 90.
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Incontinence: Inability to control excretions. Urinary incontinence is inability to keep urine in the bladder. Fecal incontinence is inability to retain feces in the rectum.

Injury: Harm or hurt. The term "injury" may be applied in medicine to damage inflicted upon oneself as in a hamstring injury or by an external agent on as in a cold injury. The injury may be accidental or deliberate, as with a needlestick injury. The term "injury" may be synonymous (depending on the context) with a wound or with trauma.

Insomnia: The perception or complaint of inadequate or poor-quality sleep because of one or more of the following: difficulty falling asleep; waking up frequently during the night with difficulty returning to sleep; waking up too early in the morning; or unrefreshing sleep. Insomnia is not defined by the number of hours of sleep a person gets or how long it takes to fall asleep. Individuals vary normally in their need for, and their satisfaction with, sleep. Insomnia may cause problems during the day, such as tiredness, a lack of energy, difficulty concentrating, and irritability.
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Ipecac: A naturally occurring substance with multiple properties including the ability to cause vomiting (emesis). Ipecac is derived from dried roots of a bush called Uragoga ipecacuanha that is native to Brazil. In the past, a sizable proportion of poison exposures in the U.S. were treated with ipecac. This practice has dropped off and some experts recommend that it should be abandoned, except in rare instances.

Iron: An essential mineral. Iron is necessary for the transport of oxygen (via hemoglobin in red blood cells) and for oxidation by cells (via cytochrome). Deficiency of iron is a common cause of anemia. Food sources of iron include meat, poultry, eggs, vegetables and cereals (especially those fortified with iron). According to the National Academy of Sciences, the Recommended Dietary Allowances of iron are 15 milligrams per day for women and 10 milligrams per day for men. Iron overload can damage the heart, liver, gonads and other organs. Iron overload is a particular risk in people who may have certain genetic conditions (hemochromatosis) sometimes without knowing it and also in people receiving recurrent blood transfusions. Iron supplements meant for adults (such as pregnant women) are a major cause of poisoning in children.

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Memory: 1. The ability to recover information about past events or knowledge. 2. The process of recovering information about past events or knowledge. 3. Cognitive reconstruction. The brain engages in a remarkable reshuffling process in an attempt to extract what is general and what is particular about each passing moment.
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Meningitis: Inflammation of the meninges, usually due to a bacterial infection but sometimes from viral, protozoan, or other causes (in some cases the cause cannot be determined).
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Metabolic: Relating to metabolism, the whole range of biochemical processes that occur within us (or any living organism). Metabolism consists of anabolism (the buildup of substances) and catabolism (the breakdown of substances).
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Mild cognitive impairment: Abbreviated MCI. A brain disorder in which thinking abilities are mildly impaired. Individuals with mild cognitive impairment are able to function in everyday activities but have difficulty with memory -- trouble remembering the names of people they met recently, remembering the flow of a conversation, and a tendency to misplace things. The individual may be aware of these difficulties and compensate with increased reliance on notes and calendars. The diagnosis of MCI relies on the fact that the individual is able to perform all their usual activities successfully, without more assistance from others than they previously needed. In this regard, MCI is different from dementia. In dementia, memory loss has progressed to such a point that normal independent function is impossible and the individual can no longer successfully manage their finances or provide for their own basic needs. Most (but not all) patients with MCI develop a progressive decline in their thinking abilities over time, and Alzheimer's disease is usually the underlying cause.

Motor: In medicine, having to do with the movement of a part of the body. Something that produces motion or refers to motion. For example, a motor neuron is a nerve cell that conveys an impulse to a muscle causing it to contract. The term "motor" today is also applied to a nerve that signals a gland to secrete. Motor is as opposed to sensory.

MRI: Abbreviation and nickname for magnetic resonance imaging. For more information, see: Magnetic Resonance Imaging; Paul C. Lauterbur; Peter Mansfield.

Multiple sclerosis: Abbreviated MS. A disease of the central nervous system (CNS) marked by numbness, weakness, loss of muscle coordination, and problems with vision, speech, and bladder control. MS is an autoimmune disease in which the body's immune system attacks myelin, a key substance that serves as a nerve insulator and helps in the transmission of nerve signals. The progress, severity and specific symptoms in MS are unpredictable. One never knows when attacks will occur, how long they will last, or how severe they will be. Most people with MS are between the ages of 20 and 40 at the time of diagnosis. The term "multiple" refers to the multiple places in the CNS that are affected and to the multiple relapses and remissions characteristic of MS.
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Mutation: A permanent change, a structural alteration, in the DNA or RNA. In humans and many other organisms, mutations occur in DNA. However, in retroviruses like HIV, mutations occur in RNA which is the genetic material of retroviruses.
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Nausea: Nausea, is the urge to vomit. It can be brought by many causes including, systemic illnesses, such as influenza, medications, pain, and inner ear disease. When nausea and/or vomiting are persistent, or when they are accompanied by other severe symptoms such as abdominal pain, jaundice, fever, or bleeding, a physician should be consulted.

Nerve: A bundle of fibers that uses chemical and electrical signals to transmit sensory and motor information from one body part to another. See: Nervous system.

Nerve cell: See: Neuron.

Neurological: Having to do with the nerves or the nervous system.

Neurology: The medical specialty concerned with the diagnosis and treatment of disorders of the nervous system -- the brain, the spinal cord, and the nerves.
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Neurotransmitter: A chemical that is released from a nerve cell which thereby transmits an impulse from a nerve cell to another nerve, muscle, organ, or other tissue. A neurotransmitter is a messenger of neurologic information from one cell to another.

NIH: The National Institutes of Health. The NIH is an important U.S. health agency. It is devoted to medical research. Administratively under the Department of Health and Human Services (HHS), the NIH consists of 20-some separate Institutes and Centers. NIH's program activities are represented by these Institutes and Centers.
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Nurse: 1) A person trained, licensed, or skilled in nursing. 2) To feed an infant at the breast.

Nursing: 1) Profession concerned with the provision of services essential to the maintenance and restoration of health by attending the needs of sick persons. 2) Feeding a infant at the breast.

Nursing home: A residential facility for persons with chronic illness or disability, particularly older people who have mobility and eating problems. Also called a convalescent home, long-term care facility.

Onset: In medicine, the first appearance of the signs or symptoms of an illness as, for example, the onset of rheumatoid arthritis. There is always an onset to a disease but never to the return to good health. The default setting is good health.
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Pain: An unpleasant sensation that can range from mild, localized discomfort to agony. Pain has both physical and emotional components. The physical part of pain results from nerve stimulation. Pain may be contained to a discrete area, as in an injury, or it can be more diffuse, as in disorders like fibromyalgia. Pain is mediated by specific nerve fibers that carry the pain impulses to the brain where their conscious appreciation may be modified by many factors.
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Parkinson's disease: See: Parkinson disease.

Pneumonia: Inflammation of one or both lungs with consolidation. Pneumonia is frequently but not always due to infection. The infection may be bacterial, viral, fungal or parasitic. Symptoms may include fever, chills, cough with sputum production, chest pain, and shortness of breath.

Poison: Any substance that can cause severe distress or death if ingested, breathed in, or absorbed through the skin. Many substances that normally cause no problems, including water and most vitamins, can be poisonous if taken in too large of a quantity. Poison treatment depends on the substance: if there are treatment instructions on the substance's container and you are sure it contained no other item, follow those directions immediately. Always contact your nearest Poison Control Center if you are concerned about possible poison ingestion.

Poison Control Center: Special information centers set up to inform Americans about how to respond to potential poisoning. These centers maintain a database of poisons and appropriate emergency treatment. The Poison Control Center in your area should be listed with other community service numbers in the front of your telephone book, and can also be reached immediately through any telephone operator.
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Poisoning: Taking a substance that is injurious to health or can cause death. Poisoning is still a major hazard to children, despite child-resistant (and sometimes adult-resistant) packaging and dose-limits per container.
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Post-menopausal: See: Postmenopausal.

Prescription: A physician's order for the preparation and administration of a drug or device for a patient. A prescription has several parts. They include the superscription or heading with the symbol "R" or "Rx", which stands for the word recipe (meaning, in Latin, to take); the inscription, which contains the names and quantities of the ingredients; the subscription or directions for compounding the drug; and the signature which is often preceded by the sign "s" standing for signa (Latin for mark), giving the directions to be marked on the container.

Prognosis: 1. The expected course of a disease.
2. The patient's chance of recovery.
The prognosis predicts the outcome of a disease and therefore the future for the patient. His prognosis is grim, for example, while hers is good.
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Progressive: Increasing in scope or severity. Advancing. Going forward. In medicine, a disease that is progressive is going from bad to worse.

Protein: A large molecule composed of one or more chains of amino acids in a specific order determined by the base sequence of nucleotides in the DNA coding for the protein.
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Pseudodementia: A severe form of depression resulting from a progressive brain disorder in which cognitive changes mimic those of dementia.

Psychiatric: Pertaining to or within the purview of psychiatry, the medical specialty concerned with the prevention, diagnosis, and treatment of mental illness.
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Quality of life: An important consideration in medical care, quality of life refers to the patient's ability to enjoy normal life activities. Some medical treatments can seriously impair quality of life without providing appreciable benefit, while others greatly enhance quality of life.

Referral: The recommendation of a medical or paramedical professional. If you get a referral to ophthalmology, for example, you are being sent to the eye doctor. In HMOs and other managed care schemes, a referral is usually necessary to see any practitioner or specialist other than your primary care physician (PCP), if you want the service to be covered. The referral is obtained from your PCP, who may require a telephone or office consultation first.
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Rehabilitation: The process of restoration of skills by a person who has had an illness or injury so as to regain maximum self-sufficiency and function in a normal or as near normal manner as possible. For example, rehabilitation after a stroke may help the patient walk again and speak clearly again.
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Reuptake: The reabsorption of a secreted substance by the cell that originally produced and secreted it. The process of reuptake, for example, affects serotonin.
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Risk factor: Something that increases a person's chances of developing a disease.

Rule out: A term much used in medicine, meaning to eliminate or exclude something from consideration. The ACB (albumin cobalt binding) test helps rule out a heart attack in the differential diagnosis of severe chest pain.

Scan: As a noun, the data or image obtained from the examination of organs or regions of the body by gathering information with a sensing device.
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Sclerosis: Localized hardening of skin.

Sensation: In medicine and physiology, sensation refers to the registration of an incoming (afferent) nerve impulse in that part of the brain called the sensorium, which is capable of such perception. Therefore, the awareness of a stimulus as a result of its perception by sensory receptors. (Sensory is here synonymous with sensation.)
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Sensitivity: 1. In psychology, the quality of being sensitive. As, for example, sensitivity training, training in small groups to develop a sensitive awareness and understanding of oneself and of ones relationships with others. 2. In disease epidemiology, the ability of a system to detect epidemics and other changes in disease occurrence. 3. In screening for a disease, the proportion of persons with the disease who are correctly identified by a screening test. 4. In the definition of a disease, the proportion of persons with the disease who are correctly identified by defined criteria.

Sensory: Relating to sensation, to the perception of a stimulus and the voyage made by incoming (afferent) nerve impulses from the sense organs to the nerve centers.
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Serotonin: A hormone, also called 5-hydroxytryptamine, in the pineal gland, blood platelets, the digestive tract, and the brain. Serotonin acts both as a chemical messenger that transmits nerve signals between nerve cells and that causes blood vessels to narrow.
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Short-term memory: A system for temporarily storing and managing information required to carry out complex cognitive tasks such as learning, reasoning, and comprehension. Short-term memory is involved in the selection, initiation, and termination of information-processing functions such as encoding, storing, and retrieving data.
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Sleep: The body's rest cycle.
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SPECT: An acronym that stands for Single Photon Emission Computed Tomography, a nuclear medicine procedure in which a gamma camera rotates around the patient and takes pictures from many angles, which a computer then uses to form a tomographic (cross-sectional) image.
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Sporadic: Occurring upon occasion or in a scattered, isolated or seemingly random way.
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Steroid: A general class of chemical substances that are structurally related to one another and share the same chemical skeleton (a tetracyclic cyclopenta[a]phenanthrene skeleton).
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Stomach: 1. The sac-shaped digestive organ that is located in the upper abdomen, under the ribs. The upper part of the stomach connects to the esophagus, and the lower part leads into the small intestine.
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Stool: The solid matter discharged in a bowel movement.

Stress: Forces from the outside world impinging on the individual. Stress is a normal part of life that can help us learn and grow. Conversely, stress can cause us significant problems.
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Stroke: The sudden death of some brain cells due to a lack of oxygen when the blood flow to the brain is impaired by blockage or rupture of an artery to the brain. A stroke is also called a cerebrovascular accident or, for short, a CVA.
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Subdural: Below the dura, the outermost, toughest, and most fibrous of the three membranes (meninges) covering the brain and the spinal cord. An subdural hematoma is a collection of blood beneath the dura.

Substance: 1. Material with particular features, as a pressor substance.
2. The material that makes up an organ or structure. Also known in medicine as the substantia.
3. A psychoactive drug as, for example, in substance abuse.

Substance abuse: The excessive use of a substance, especially alcohol or a drug. (There is no universally accepted definition of substance abuse.)
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Symptom: Any subjective evidence of disease. Anxiety, lower back pain, and fatigue are all symptoms. They are sensations only the patient can perceive. In contrast, a sign is objective evidence of disease. A bloody nose is a sign. It is evident to the patient, doctor, nurse and other observers.

Syndrome: A set of signs and symptoms that tend to occur together and which reflect the presence of a particular disease or an increased chance of developing a particular disease.
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Syphilis: A sexually transmitted disease caused by Treponema pallidum, a microscopic organism called a spirochete. This worm-like, spiral-shaped organism infects people by burrowing into the moist mucous membranes of the mouth or genitals. From there, the spirochete produces a non-painful ulcer known as a chancre. There are three stages of syphilis:
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Taste: Taste belongs to our chemical sensing system, or the chemosenses. The complicated process of tasting begins when molecules released by the substances stimulate special cells in the mouth or throat. These special sensory cells transmit messages through nerves to the brain where specific tastes are identified.
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Therapeutic: Relating to therapeutics, that part of medicine concerned specifically with the treatment of disease. The therapeutic dose of a drug is the amount needed to treat a disease.
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Thermometer: A device used to measure the temperature of gaseous, liquid or solid matter or of a chemical reaction such as fire. Temperature measurement is important to a wide range of activities, including industry, scientific research, and health care. In health care, thermometers are used to measure the temperature of the human body. They include the following types:
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Thiamine: Vitamin B1. Thiamine (vitamin B1) acts as a coenzyme in the metabolism of the body. Deficiency of thiamine leads to beriberi, a syndrome characterized by inflammation of multiple nerves (polyneuritis), heart disease (cardiopathy), and edema (swelling).

Thyroid: 1. The thyroid gland. Also, pertaining to the thyroid gland. 2. A preparation of the thyroid gland used to treat hypothyroidism. 3. Shaped like a shield. (The thyroid gland was so-named by Thomas Wharton in 1656 because it was shaped like an ancient Greek shield.)
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Traction: In medicine, a procedure for manually pulling a part of the body to a beneficial effect.
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Trauma: Any injury, whether physically or emotionally inflicted. "Trauma" has both a medical and a psychiatric definition. Medically, "trauma" refers to a serious or critical bodily injury, wound, or shock. This definition is often associated with trauma medicine practiced in emergency rooms and represents a popular view of the term. In psychiatry, "trauma" has assumed a different meaning and refers to an experience that is emotionally painful, distressful, or shocking, which often results in lasting mental and physical effects.
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Tumor: An abnormal mass of tissue. Tumors are a classic sign of inflammation, and can be benign or malignant (cancerous). There are dozens of different types of tumors. Their names usually reflect the kind of tissue they arise in, and may also tell you something about their shape or how they grow. For example, a medulloblastoma is a tumor that arises from embryonic cells (a blastoma) in the inner part of the brain (the medulla). Diagnosis depends on the type and location of the tumor. Tumor marker tests and imaging may be used; some tumors can be seen (for example, tumors on the exterior of the skin) or felt (palpated with the hands).
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Vascular: Relating to the blood vessels of the body. The blood vessels of the body, as a group, are referred to as the vascular system.
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Vascular dementia: A common form of dementia in older persons that is due to cerebrovascular disease, usually with stepwise deterioration from a series of small strokes and a patchy distribution of neurologic deficits affecting some functions and not others. Risk factors include high blood pressure, an unsteady way of walking, and advanced age. Symptoms include confusion, problems with recent memory, wandering or getting lost in familiar places, loss of bladder or bowel control (incontinence), emotional problems such as laughing or crying inappropriately, difficulty following instructions, and problems handling money. The damage is typically so slight that the change is noticeable only as a series of small steps. However, over time, as more small blood vessels in the brain are blocked, there is noticeable gradual mental decline. Vascular dementia commonly begins between the ages of 60 and 75 and affects men more often than women. Also known as multi-infarct dementia. See also CADASIL.

Vitamin B12: A vitamin important for the normal formation of red blood cells and the health of the nerve tissues. Undetected and untreated vitamin B12 deficiency can lead to anemia and permanent nerve and brain damage.
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