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Dr. Kennedy's Vocabulary Course: -G-
(View Course for 11/18/2013)
(A B C D E F G H I J K L M)
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Ron Kennedy, M.D.
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- G -
(A B C D E F G H I J K L M)
G - The meanings of the letter "G" in medicine:  (1) stands for guanine, one member of the base pair G-C (guanine-cytosine) in DNA. (The other base pair in the DNA is A-T [adenine-thymine].) (2) Abbreviation on a medication that stands for "glaucoma" and indicates the medication can cause problems for a person with this eye disorder. Further, a person with glaucoma might see the generic "C" code on a prescription bottle or vial if the medication might raise the pressure within the eye. These types of special caution codes are intended to be warnings for patients with specific medical conditions. (3)A small g is a symbol for gram, a unit of measurement of weight and mass in the metric system. In weight, a gram is equal to 1/1000 of a kilogram. In mass, a gram is equal to 1/1000 of a liter (one cubic centimeter) of water at 4 degrees centigrade.
G protein:  These molecules have been described as "biological traffic lights." Located inside the cell, G proteins are able respond to signals outside the cell -- light, smell, hormones -- and translate (transduce) these signals into action within the cell.
G-CSF (Granulocyte colony-stimulating factor):  A colony-stimulating factor that stimulates the production of neutrophils (a type of white blood cell). G-CSF is a cytokine that belongs to the family of drugs called hematopoietic (blood-forming) agents. Also called filgrastim. It is used in diseased states which suppress the production of white cells or use up white cells at an accelerated rate.
G6PD deficiency:  Deficiency of the enzyme glucose-6-phosphate dehydrogenase (G6PD), the most common enzyme defect of medical importance. About 10 percent of American black males have G6PD deficiency, as do a lesser percent of black females. G6PD deficiency is also increased in frequency in people of Mediterranean origin (including Italians, Greeks, Arabs, and Jews). The gene encoding G6PD is on the X chromosome. Males with this enzyme deficiency may develop anemia due to the breakup of their red blood cells when they are exposed to oxidant drugs, naphthalene moth balls, or fava beans. The offending drugs include the antimalarial primaquine, salicylates, sulfonamide antibiotics, nitrofurans, phenacetin, and some vitamin K derivatives. Fever, viral and bacterial infections, and diabetic acidosis can also precipitate a hemolytic crisis (when the red blood cells break up), resulting in anemia and jaundice. Large IV doses of vitamin C should also be avoided in these people. The concentration of G6PD deficiency in certain populations is believed to reflect a protective effect it afforded (much like sickle cell trait) against malaria.
Gage, Phineas:  The most famous patient to have survived severe damage to the brain and the first from whom something was learned about the relation between personality and the function of the front parts (the frontal lobes) of the brain. During work on a railroad in 1848, an unplanned explosion propelled a rod through Gage's head. Against all expectation, Gage survived. Once capable and responsible, Gage became profane, fitful, and obstinate - a man who was "no longer Gage.
Gain-of-function mutation:  A mutation that confers new or enhanced activity on a protein. (Loss-of-function mutations, which are more common, result in reduced or abolished protein function.)
Gait:  The manner of walking. Observation of the gait can provide clues to a number of diagnoses including Parkinson disease, cerebral palsy, congenital dislocation of the hip, and stroke.
Galactorrhea:  The spontaneous flow of milk from the nipple at any time other than during nursing. Galactorrhea can be due to "normal" factors such as an unrecognized pregnancy, trauma, surgery, overexercise or from a number of drugs (including amphetamine, cimetidine, female hormone replacement therapy, hydroxyzine, methyldopa, nicotine, narcotics, reserpine, antidepressants of the so-called tricyclic type, or verapamil). Galactorrhea can also be due to "abnormal" factors of a pathologic nature such as cirrhosis of the liver, a false pregnancy (pseudocyesis), kidney failure, disorders of the spinal cord, or a prolactinoma (a benign pituitary tumor that secretes the hormone prolactin which stimulates milk production). Galactorrhea is also sometimes called witch's milk.
Galactose:  A sugar contained in milk which makes up half of the sugar called lactose that is found in milk. Lactose is called a disaccharide, di meaning 2, since lactose is made up of two sugars, galactose and glucose, bound together.
Galactosemia:  A genetic metabolic disease in which there is a defect in the body's ability to use the sugar galactose. In classic galactosemia, the basic defect is a deficiency of the enzyme known as GALT (galactose-1-phosphate uridyl transferase). This causes an accumulation of galactose 1-phosphate which damages the liver, eye, brain and kidney. Galactosemia is one of the diseases in many newborn screening panels. The disease can be fatal, if undetected. If detected, it can be treated by avoiding galactose in the diet. The symptoms of galactosemia include jaundice (yellowish discoloration of the skin and the whites of the eyes), vomiting, poor feeding, poor weight gain, lethargy, irritability, convulsions, and opacities in the lenses of the eyes. The signs detected include hepatomegaly (enlarged liver), hypoglycemia (low blood sugar), aminoaciduria (amino acids are present in the urine), cirrhosis, ascites (fluid collected within the abdomen), cataracts and mental retardation.
Galastic syncope (laughter-induced syncope):  A sustained Valsalva pressure from uncontrolled laughing can temporarily stop blood flow through the brain and cause fainting (syncope). This is called "galastic syncope" or "laughter-induced syncope." Unless there is another complicating disorder, it is self-correcting as blood flow is restored after the syncopal episode stops the laughing and the attendant Valsalva pressure and blood flow to the brain is restored. It can present a danger if the "victim" is driving a car or operating other machinery which does not mix well with temporary loss of consciousness.
Galen:  Greek physician and philosopher (born about 129 AD, died about 210 AD) known among other things for his discovery of blood in human arteries and for his dissection of the human cranial nerves, the nerves that supply key areas of the head, face, and upper chest. Galen performed surgical dismantling (dissection) of animals and humans and described what he saw (not always the practice of the day). He identified the majority (seven of the twelve) of the cranial nerves. He also did experiments such as severing a nerve and observing the effects. He is thus regarded as "the founder of experimental physiology." Galen was the first to determine that arteries carried blood and not air! (For over 400 years the Alexandrian school of medicine had taught that arteries are full of air). Galen's theories about the blood circulation, however, were well off the mark and it was not until the 17th century that the great English physician William Harvey would challenge Galen's ideas in this regard. With Hippocrates who preceded him by some 500 years, Galen was preeminent among the most distinguished physicians of antiquity. He knew all of the medical knowledge of his day, gathered it together, and wrote voluminously (and well) about it. Galen summed up the medicine of antiquity. His writing were a blessing to the ancient world. But they became a curse when, for more than a millennium, they were held to be the unassailable authority on medicine and this paralyzed the progress of medicine, something Galen would have greatly deplored.
Galeophobia:  An abnormally large and persistent fear of sharks. Sufferers from this phobia experience anxiety even though they may be safe on a boat or in an aquarium or on a beach. Hollywood films depicting sharks as calculating, vengeful diabolical monsters have no doubt enkindled the fear of sharks in many persons. So have validated reports of sharks venturing into rivers and lakes. "Galeophobia" is derived from the Greek words "galeos" (shark with markings resembling those on a weasel) and "phobos" (fear).
Gallbladder:  A pear-shaped organ just below the liver that stores the bile secreted by the liver. During a fatty meal, the gallbladder contracts, delivering the bile through the bile ducts into the intestines to help with digestion. Abnormal composition of bile leads to formation of gallstones, a process termed cholelithiasis. The gallstones cause cholecystitis, inflammation of the gallbladder.
Gallbladder agenesis:  This is a condition in which the gallbladder fails to develop. This happens in approximately one out of every 1,000 people. Gallbladder agenesis is an isolated finding in more than two-thirds (70%) of people affected. The person with isolated gallbladder agenesis is healthy and no treatment is needed - and the prognosis is excellent. Gallbladder agenesis occurs in association with additional abnormalities in the remaining (30%) of cases which fall into two groups: one (9%) with atresia (failure of opening) of the bile ducts, and the other (21%) with normal bile ducts but distant abnormalities such as ventricular septal defect (a hole between the ventricles of the heart), imperforate anus (blind rectum with no anus), malrotation of the gut (failure of the intestines to rotate normally during embryonic development), renal agenesis (absence of a kidney), and syndactyly (fusion of fingers).
Gallium:  A rare metal with the atomic weight of 69. There are several isotopic forms of gallium that differ from it in atomic weight. One is gallium-68 which is produced by cyclotrons and emits gamma rays. The citrate form of gallium-68 is used as a radiotracer in a "gallium MRI" to locate sites of inflammation and tumor tissue within the body.
Gallop rhythm:  A heart rhythm that when listened to reminds one of the galloping of a horse.
Gallstone pancreatitis:  Gallstone-induced pancreatitis. See below.
Gallstones:  Stones that form when substances in the bile harden. Gallstones can be as small as a grain of sand or as large as a golf ball. There can be just one large stone, hundreds of tiny stones, or any combination. Gallstones can block the normal flow of bile if they lodge in any of the ducts that carry bile from the liver to the small intestine. That includes the hepatic ducts, which carry bile out of the liver; the cystic duct, which takes bile to and from the gallbladder; and the common bile duct, which takes bile from the cystic and hepatic ducts to the small intestine. Bile trapped in these ducts can cause inflammation in the gallbladder, the ducts, or, rarely, the liver. Other ducts which open into the common bile duct, in some people (and some not, due to anatomic variation) including the pancreatic duct, which carries digestive enzymes out of the pancreas. If a gallstone blocks the opening to that duct, digestive enzymes can become trapped in the pancreas and cause an extremely painful inflammation called gallstone pancreatitis. If any of these ducts remain blocked for a significant period of time, severe damage or infections can occur, affecting the gallbladder (cholecystitis), liver (hepatitis), or pancreas (pancreatitis). Gallstone attacks often occur after eating a meal, especially a fatty one. Symptoms can include pain for up to several hours in the upper back, or under the right shoulder together with nausea, vomiting, abdominal bloating or indigestion. These symptoms can mimic those of other problems, including heart attack, so accurate diagnosis is important. There are two types of gallstones - cholesterol stones and pigment stones. Cholesterol stones account for about 80 percent of gallstones in North America and Europe. Pigment stones have a high content of bilirubin (a colored pigment) and account for over 90 percent of gallstones in Asia. Gallstones are more common among women, Native Americans, Mexican Americans, and people who are overweight. Laparoscopic surgery to remove the gallbladder is the most common treatment. The surgery is called cholecystectomy. Open surgery is done if there are obstacles to laparoscopy. The gallbladder is a dispensable organ. Without it, the bile flows directly into the small intestine, instead of being stored in the gallbladder.
GALT:  The enzyme (galactose-1-phosphate uridyl transferase) lack of which causes the genetic metabolic disease called galactosemia. GALT is also the symbol for the gene that encodes the enzyme.
Galton, Sir Francis:  English advocate of eugenics, the idea of improving the physical and mental makeup of the human species by selective parenthood. Galton coined the word "eugenics" to denote scientific endeavors to increase the proportion of persons with better than average genetic endowment through selective mating of marriage partners. In his book "Hereditary Genius" (1869), Galton used the word "genius" to denote "an ability that was exceptionally high and at the same time inborn." The idea that mental capacities might be inherited was a novel proposition at the time. Born in 1822, Galton was knighted in 1909 and died in 1911. A eugenics chair was established at the University of London under the terms of his will. His ideas about Eugenics along with Darwin's ideas about "survival of the fitest" were used by the Nazis to justify their genocide before and during World War II.
Gamete:  The generic term for the germ cells, i.e. sperm or egg. Each human gamete normally has 23 chromosomes, the haploid number of chromosomes, half the number of chromosomes contained in most types of cells in the body. Thus when egg and sperm combine the result in the diploid number of chromosomes (36).
Gametogenesis:  The development and production of the male and female germ cells required to form a new individual.
Gametophobia:  An abnormal and persistent fear of being married. Sufferers of gametophobia experience undue anxiety even though they may rationally realize that the married state itself poses no threat to them. They may fear the challenge of living with another person and the responsibility of rearing a family. Or they may worry about failing as a sexual partner.
Gamma globulin:  A major class of immunoglobulins found in the blood, including many of the most common antibodies circulating in the blood. Also called immunoglobulin G (IgG).
Gamma hydroxybutyrate (GHB):  Known in Europe as Gamma-OH, gamma hydroxybutyrate is a colorless and odorless drug used illicitly for "recreational" purposes and for "date rape." GBH is a central nervous system depressant. It tends therefore to increase sociability and function as something of a transient antidepressant.
Gamma knife:  A type of radiosurgery (radiation therapy) machine that acts by focusing low-dosage gamma radiation from many sources on a precise target. Areas adjacent to the target receive only slight doses of radiation, while the target gets the full intensity. The gamma knife may be used to treat brain tumors, metastatic tumors in the brain (from sites such as the breast, lung, and skin), vascular malformations of the brain, acoustic neuromas (a tumor of the hearing nerve); meningiomas (tumors on the protective layers of the brain); trigeminal neuralgia causing severe facial pain; and temporal lobe epilepsy.
Gamma-linolenic acid:  Abbreviated GLA, an essential polyunsaturated fatty acid contained in some plant seed oils including evening primrose oil, black currant oil, and borage oil. GLA has been used for a number of different disorders.
Ganglion:  Refers to an aggregation of nerve cell bodies and also a tendon cyst that most commonly pops up near the wrist. The celebrated 2nd century Greek physician Galen (c. 130-201 A.D.) who lived and worked in Rome first used the word ganglion to denote a nerve complex.
Gangrene:  The death of body tissue due to the loss of blood supply to that tissue, sometimes permitting bacteria to invade it and accelerate its decay. Gas gangrene involves the invasion of a deep penetrating wound (in which the blood supply is compromised) by anaerobic bacteria (bacteria that can survive with little or no oxygen) such as members of Clostridium family of bacteria. The bacteria generate gas and pus. Gas gangrene is an acute, painful, dangerous condition. Dry gangrene is the death of tissue due to vascular insufficiency without bacterial invasion. The tissue simply dries up and shrivels.
Gap junction:  An organized collections of protein channels in cell membranes that allows ions and small molecules to pass between adjacent cells. The protein channels that make up gap junctions consist of two connexons. One connexon resides in the membrane of one cell. It aligns and joins the connexon of the neighboring cell, forming a continuous aqueous pathway by which ions and small molecules can freely pass from one cell to the other. Each connexon consist of six subunits called connexins. Gap junctions exist in almost all cell types with some exceptions such as skeletal muscle, red blood cells and circulating blood lymphocytes.
Garlic:  A perennial herb of the lily family cultivated for its pungent, edible bulbs. Garlic has been used with the intention of lowering blood pressure and cholesterol. Garlic may decrease normal blood clotting and should be used with caution in patients taking medications to prevent blood clotting (anticoagulants) such as warfarin /Coumadin
Gas chromatography (GC):  A type of automated chromatography (a technique used to separate mixtures of substances) in which the mixture to be analyzed is vaporized and carried by an inert gas through a special column and thence to a detection device. The special column can contain an inert porous solid (in gas-solid chromatography) or a liquid coated on a solid support (in gas-liquid chromatography). The basic aim with GC is to separate each component that was in the mixture so that it produces a different peak in the detection device output which is graphed on a chart recorder. GC is a valuable tool in biochemistry (and other fields of chemistry, as in the analysis of perfumes).
Gastrectomy:  Surgery to remove part of all of the stomach.
Gastric:  Having to do with the stomach.
Gastric atrophy:  A condition in which the stomach muscles shrink and become weak. It results in a lack of digestive juices.
Gastric banding:  A surgically implanted device used to help a person lose weight. In a surgical procedure, a band is placed around the upper part of the stomach, creating a small pouch that can hold only a small amount of food. The narrowed opening between the stomach pouch and the rest of the stomach controls how quickly food passes from the pouch to the lower part of the stomach. The system helps the patient eat less by limiting the amount of food that can be eaten at one time and increasing the time it takes for food to be digested.
Gastric cancer:  Cancer of the stomach. Stomach cancer is the second most frequent cancer and the second leading cause of death from cancer. It can develop in any part of the stomach and spread to other organs. Infection with a bacterium called Helicobacter pylori is associated with gastric cancer. In one study, gastric cancer developed in about 3% of the infected patients and none of the uninfected patients. Eradication of the bacterium prevents or delays the development of gastric cancer. The risk of gastric cancer is also increased in Down syndrome (aka Trisomy X). Symptoms of stomach cancer are often vague, such as loss of appetite and weight, so diagnosis is often delayed. The cancer is diagnosed definitively with a biopsy of stomach tissue. Cancer of the stomach is difficult to cure unless it is found early. Treatment may include surgery, chemotherapy and radiotherapy. Surgery is the most common treatment. It involves removal of part (subtotal or partial gastrectomy) or all (total gastrectomy) of the stomach.
Gastric emptying study:  A gastric emptying study evaluates the emptying of food from the stomach. For a gastric emptying study, a patient eats a meal in which the solid food, liquid food or both are mixed with a small amount of radioactive material. A scanner (acting like a Geiger counter) is placed over the stomach to monitor the amount of radioactivity in the stomach for several hours after the test meal. In patients with abnormal emptying of the stomach, the food and radioactive material stay in the stomach longer than normal (usually hours) before emptying into the small intestine.
Gastric MALT lymphoma:  A low-grade malignant lymphoma of the stomach associated with chronic infection by the bacterium Heliobacter pylori. Three-quarters of gastric MALT lymphomas regress after the eradication of H. pylori with antibiotics. The one-quarter that are unresponsive to antibiotics carry a characteristic chromosomal translocation or are at an advanced stage.
Gastric outlet:  The exit from the stomach through the pyloric valve into the duodenum.
Gastric outlet obstruction:  Any disease that mechanically impedes gastric emptying, the normal emptying of the stomach. There is obstruction of the channel of the pylorus and duodenum through which the stomach empties. The cause of the obstruction may be a benign or malignant disease. The most common malignancy that produces gastric outflow obstruction is pancreatic cancer. The benign causes of gastric outflow obstruction include pyloric ulcer and gastric polyps in adults, pyloric stenosis and congenital duodenal webs in children, and the ingestion of caustic substances in all age ranges.
Gastric stapling:  A surgical procedure that converts the upper part of the stomach into a very small pouch by stapling portions of the stomach together, forcing an obese person to eat only tiny portions yet still feel full. It is normally done only in severe cases, and in combination with diet and exercise. A similar operation is called gastric banding.
Gastric ulcer:  A hole in the lining of the stomach corroded by the acidic digestive juices which are secreted by the stomach cells. Ulcer formation is related to Heliobacter pylori bacteria in the stomach, anti-inflammatory medications, and smoking cigarettes. Ulcer pain may not correlate with the presence or severity of ulceration. Diagnosis is made with barium x-ray or with the use of a viewing tube slipped through the throat to the stomach (endoscopy).
Gastritis:  Inflammation of the stomach.
Gastroenteritis:  Inflammation of the stomach and the intestines. Can cause nausea and vomiting and/or diarrhea. Gastroenteritis has numerous causes: including infectious organisms (viruses, bacteria, etc.), food poisoning, and stress.
Gastroenterologist:  A physician who specializes in the diagnosis and treatment of disorders of the gastrointestinal tract, including the esophagus, stomach, small intestine, large intestine, pancreas, liver, gallbladder, and biliary system.
Gastroenterology:  The medical specialty devoted to the study, diagnosis and treatment of disorders of the digestive system. These disorders may affect the esophagus (swallowing tube), stomach, small intestine, large intestine (colon), rectum, liver, gallbladder, or pancreas.
Gastroesophageal:  Pertaining to both the stomach and the esophagus, as in the gastroesophageal junction, the place where the esophagus connects to the stomach.
Gastroesophageal junction:  The junction between the stomach and the esophagus; the place where the esophagus connects to the stomach.
Gastroesophageal reflux:  The return of stomach contents back up into the esophagus This frequently causes heartburn because of irritation of the esophagus by stomach acid, commonly called gastroesophageal reflux disease or GERD.
Gastrointestinal:  Adjective referring collectively to the stomach and small and large intestines.
Gastrointestinal stromal tumor:  GIST. A type of tumor that usually begins in cells in the wall of the gastrointestinal tract. It can be benign or malignant. Malignant GISTs can occur from the esophagus to the rectum, but occur most commonly in the stomach and small intestine. Treatment for GIST includes STI571 (Gleevec), the first approved drug to directly turn off the signal of a protein known to cause a cancer.
Gastrointestinal tract:  The tube that extends from the mouth to the anus in which the movement of muscles and release of hormones and enzymes digest food. The gastrointestinal tract starts with the mouth and proceeds to the esophagus, stomach, duodenum, small intestine, large intestine (colon), rectum and, finally, the anus. Also called the alimentary canal, digestive tract and, perhaps most often in conversation, the GI tract.
Gastroparesis:  Gastroparesis is a disease of either the stomach muscle itself or the nerves controlling the muscle. As a consequence, food and secretions do not empty normally from the stomach, and there is nausea and vomiting. Abdominal bloating and pain can result. Gastroparesis may be associated with paralysis of other parts of the gastrointestinal tract (the small intestine and colon). The most common cause of gastroparesis is diabetes mellitus. (So often is gastroparesis due to diabetes that there is a term, gastroparesis diabeticorum, that refers exclusively to it). A nuclear medicine test (gastric emptying study) designed to study gastric emptying is the most common means of diagnosis of gastroparesis. Gastroparesis is treated with medications to increase the contractions of the stomach muscle, occasionally with surgery, and experimentally with electrical pacing. The word "gastroparesis" is compounded from "gastro", pertaining to the stomach + "paresis", a loss of strength = a loss of strength of the stomach = stomach paralysis.
Gastropathy:  Disease of the stomach.
Gastroschisis:  A birth defect in which there is a separation in the abdominal wall. Through this opening protrudes part of the intestines which are not covered by peritoneum (the membrane that normally lines the inside of the abdomen). The opening in the abdominal wall in gastroschisis is never at the site of the umbilicus (the navel or belly button). Rather, the umbilicus is characteristically to the left of the gastroschisis and is separated from it by a bridge of skin.
Gastroscope:  A flexible, lighted instrument that is put through the mouth and down the esophagus to view the stomach. Tissue from the stomach can also be removed through the gastroscope.
Gastrostomy:  A surgical opening into the stomach. This opening may be used for feeding usually via a feeding tube called a gastrostomy tube. This can also be done by percutaneous endoscopic gastrostomy (PEG). PEG is a surgical procedure for placing a feeding tube but does not necessitate doing an open laparotomy (operation on the abdomen). The aim of PEG (as with any gastrostomy) is to feed those who cannot swallow.
Gaucher disease:  A series of 5 diseases due to deficient activity of the enzyme glucocerebrosidase, leading to accumulation of glucocerebroside in tissues of the body. The 5 types of Gaucher disease encompass a continuum of clinical findings from a lethal form before or just after birth to a form so mild that it may not be diagnosed until old age. All 5 types of Gaucher disease are inherited in an autosomal recessive manner.
Gaucher disease, type 1:  The most common and best known form of Gaucher disease. It affects the spleen, liver, and bone marrow and spares the brain. The symptoms include enlargement of the spleen (usually the first sign), anemia, low blood platelets, increased skin pigmentation, and a yellow fatty spot on the white of the eye (a pinguecula). Severe bone involvement can lead to pain and collapse of the bone of the hips, shoulders, and spine. This type of Gaucher disease is the most common genetic disease among Jews in North America.
Gaucher disease, types 2-5:  A series of disease due to glucocerebrosidase deficiency and accumulation of glucocerebroside in cells. By comparison with type 1 Gaucher disease, these are far less frequent forms of Gaucher disease. Types 2 and 3 Gaucher disease are characterized by primary neurologic disease including profound involvement of the brain. The onset of symptoms is before age 2 in both types 2 and 3 with death by age 2 to 4 in type 2 and a more slowly progressive course with survival into the third or fourth decade in type 3. Types 2 and 3 are collectively known as infantile cerebral Gaucher disease. Type 4 Gaucher disease is lethal in the perinatal period and is marked by collodion skin and hydrops fetalis. Type 5 is the cardiovascular form of Gaucher disease with calcification of the aortic and mitral valves, mild spleen enlargement, and eye involvement.
Gay suicide risk:  High rates of suicide have consistently been reported among homosexuals, particularly among adolescents and young adults. A 1989 report concluded that "gay youth are 2 to 3 times more likely to attempt suicide than other young people. They may comprise up to 30% of completed youth suicides annually."
GB virus C:  A virus first identified in 1995 that is genetically related to the hepatitis C virus but which does not cause hepatitis and, in fact, is not known to be responsible for any disease. Infection with GB virus C (GBV-C) is beneficial to HIV-infected patients. They enjoy longer survival if they are coinfected with this virus and HIV than if they have HIV alone. Having two viruses is better than one here. GB virus C (GBV-C) is also called hepatitis G. However, the designation GB virus C (GBV-C) is preferred because the virus is not a cause of hepatitis.
Gefitinib:  A drug that attaches to the epidermal growth factor receptor (EGFR) on the surfaces of cells. The drug was designed to treat non-small-cell lung cancer. Marketed under the brand name Iressa.
Gel electrophoresis:   The process in which molecules (such as proteins, DNA, or RNA fragments) can be separated according to size and electrical charge by applying an electric current to them while they are in a gel. The current forces the molecules through pores in a thin layer of gel, a firm jelly-like substance. The gel can be made so that its pores are just the right dimensions for separating molecules within a specific range of sizes and shapes. Smaller fragments usually travel further than large ones.
Gene:  The basic biological unit of heredity. A segment of deoxyribonucleic acid (DNA) needed to contribute to a function
Gene amplification:  Making multiple copies of a gene. Repeated copying of a gene. Gene amplification plays a role in cancer cells. A tumor cell amplifies, or copies, DNA segments as a result of cell signals and sometimes environmental events.
Gene array analysis:   A way of analyzing the differential expression of thousands of species of mRNA (messenger RNA) at the same time in two different samples (as, for example, in normal vs. tumor tissue, or at different developmental stages). Gene array analysis involves synthesizing labeled cDNA (complementary DNA) from 2 or more sources, and hybridizing them to identical gene arrays. This procedure can be done in standard molecular biology laboratories with basic instrumentation. Gene array analysis is an extraordinarily powerful tool in molecular biology today and is expected to shape the molecular medicine of tomorrow. Many diseases will be defined in a "customized" fashion according to the array of genes in the particular patient affected. Not only diseases, but also optimal treatments, will be put into discrete categories according to the diagnostic gene array of the person being evaluated. Medicine will not be practiced in the same way in 2050 as it was in 2000, thanks in part to gene array analysis.
Gene deletion:  The total loss (or absence) of a gene. Gene deletion plays a role in birth defects and in the development of cancer.
Gene duplication:  An extra copy of a gene. Gene duplication is a key mechanism in evolution. Once a gene is duplicated, the identical genes can undergo changes and diverge to create two different genes.
Gene expression:  The translation of information encoded in a gene into protein or RNA. Expressed genes include genes that are transcribed into messenger RNA (mRNA) and then translated into protein, as well as genes that are transcribed into types of RNA such as transfer RNA (tRNA) and ribosomal RNA (rRNA) that are not translated into protein. Gene expression is a highly specific process in which a gene is switched on at a certain time and "speaks out."
Gene family:  A group of genes related in structure and often in function. The genes belonging to a gene family are descended from an ancestral gene.
Gene mapping:  The process of determining the relative positions of genes on a chromosome (or another piece of DNA) and the distances between the genes in linkage units or in physical units.
Gene markers:  Detectable genetic traits or distinctive segments of DNA that serve as landmarks for a target gene. Markers are on the same chromosome as the target gene. They must be near enough to the target gene to be genetically linked to it: to be inherited usually together with that gene, and so serve as signposts to it.
Gene pool:  The sum total of genes, with all their variations, possessed by a particular species at a particular time.
Gene product:  The RNA or protein that results from the expression of a gene. The amount of gene product is a measure of the degree of gene activity.
Gene silencing:  A mechanism by which cells shut down large sections of chromosomal DNA. Gene silencing is done by incorporating the DNA to be silenced into a form of DNA called heterochromatin that is already silent.
Gene testing:  Testing a sample of blood (or another fluid or tissue) for evidence of a gene. The evidence can be biochemical, chromosomal, or genetic. The aim is to learn whether a gene for a disease is present or absent.
Gene transfer:  The insertion of unrelated genetic information in the form of DNA into cells.
Gene-expression profilin:  A genomic technique that based on the fact that only a fraction of the genes encoded in the genome of a cell are expressed by being transcribed into messenger RNA (mRNA). The complement of mRNAs in a cell largely dictates its complement of proteins. Consequently, gene expression is a major determinant of the biology of both normal and malignant cells.
General paresis:  Progressive dementia and generalized paralysis due to chronic inflammation of the covering and substance of the brain (meningoencephalitis). General paresis is a part of late (tertiary) syphilis, occurring a decade or more after the initial infection.
Generalized anxiety disorder (GAD):  A condition characterized by 6 months or more of chronic, exaggerated worry and tension that is unfounded or much more severe than the normal anxiety most people experience. People with GAD usually expect the worst. They worry excessively about money, health, family, or work, even when there are no signs of trouble. They are unable to relax and often suffer from insomnia.
Generic:  1. The chemical name of a drug. 2. A term referring to the chemical makeup of a drug rather than to the advertised brand name under which the drug may be sold. 3.A term referring to any drug marketed under its chemical name without advertising.
Genesis:  A suffix referring to the beginning, development, or production of something. For example, gametogenesis is the development and production of the male and female germ cells (the gametes) required to form a new individual. Osteogenesis is the production of bone. Pathogenesis is the development of a disease, the sequence of events leading up to that disease.
Genetic:  Having to do with genes and genetic information.
Genetic anticipation:  A remarkable phenomenon in which a genetic disease appears earlier appearance and with increased from with each succeeding generation. Anticipation was once thought not to exist in genetics. It was chalked off as a meaningless statistical artifact. However, anticipation has now been proven to occur in a large number of important genetic disorders, including Huntington disease and myotonic dystrophy. In molecular terms, anticipation is due to the expansion of a trinucleotide repeat sequence in the DNA. This phenomenon also occurs in the fragile X syndrome, the most common inherited form of mental retardation.
Genetic code:  The instructions in a gene that tell the cell how to make a specific protein. A, T, G, and C are the "letters" of the DNA code. They stand for the chemicals adenine, thymine, guanine, and cytosine, respectively, that make up the nucleotide bases of DNA. Each gene's code combines the four chemicals in various ways to spell out 3-letter "words" that specify which amino acid is needed at every step in making a protein.
Genetic Counseling:  An educational counseling process for individuals and families who have a genetic disease or who are at risk for such a disease. Genetic counseling is designed to provide patients and their families with information about their condition and help them make informed decisions.
Genetic disease:  A disease caused by an abnormality in an individual's genome. There are a number of different types of genetic inheritance. Single gene inheritance, aka Mendelian or monogenic inheritance, is caused by changes or mutations that occur in the DNA sequence of a single gene. There are more than 6,000 known single-gene disorders, which occur in about 1 out of every 200 births. Some examples are cystic fibrosis, sickle cell anemia, Marfan's syndrome, Huntington's disease, and hemochromatosis. Single-gene disorders are inherited in recognizable patterns: autosomal dominant, autosomal recessive, and X-linked. Multifactorial inheritance, aka complex or polygenic inheritance, is caused by a combination of environmental factors and mutations in multiple genes. For example, different genes that influence breast cancer susceptibility have been found on chromosomes 6, 11, 13, 14, 15, 17, and 22. Some common chronic diseases are multifactorial disorders. Examples include heart disease, high blood pressure, Alzheimer disease, arthritis, diabetes, cancer, and obesity. Multifactorial inheritance also is associated with heritable traits such as fingerprint patterns, height, eye color, and skin color. Chromosome abnormalities, can cause disease, for example, Down syndrome or trisomy 21 is a common disorder that occurs when a person has three copies of chromosome 21. There are many other chromosome abnormalities including Turner syndrome (45,X), Klinefelter syndrome (47, XXY), the cat cry syndrome (46, XX or XY, 5p-), and so on. Mitochondrial inheritance is caused by mutations in the nonchromosomal DNA of mitochondria. Mitochondria are small round or rod-like organelles that are involved in cellular respiration and found in the cytoplasm of plant and animal cells. Each mitochondrion may contain 5 to 10 circular pieces of DNA. Examples of mitochondrial disease include an eye disease called Leber's hereditary optic atrophy; a type of epilepsy called MERRF which stands for Myoclonus Epilepsy with Ragged Red Fibers; and a form of dementia called MELAS for Mitochondrial Encephalopathy, Lactic Acidosis and Stroke-like episodes. Mitochondrial ineritance comes exclusively from the mother because only the mother's mitochondria are passed on to the child.
Genetic infantile agranulocytosis:  Children born with this condition lack neutrophils (a type of white blood cell that is important in fighting infection). They children suffer frequent infections from bacteria which in the past led to death in three-quarters of cases before 3 years of age. This disease is also known as severe congenital neutropenia (SCN). Children with SCN have no special problems with viral or fungal infections. They do have an increased risk of developing acute myelogenous leukemia or myelodysplasia, a bone marrow disorder. The bone marrow and blood show a number of other abnormalities (including maturational arrest of neutrophil precursors at the promyelocyte stage, absolute monocytosis, eosinophilia and thrombocytosis). The gamma globulin level in blood is low. The inheritance of the disease is autosomal recessive. Both seemingly-normal parents carry an SCN gene while each of their children, boys and girls alike, has a 1 in 4 (25%) risk of receiving both SCN genes and having the disease: severe congenital neutropenia (SCN). SCN was first clearly described by Kostmann in 1956. It is now known to be caused by a defect in a gene on chromosome 1 (in 1p35-p34.3) that codes for what is called the granulocyte colony-stimulating factor receptor (GCSFR). Treatment with recombinant human granulocyte colony-stimulating factor (GCSF) elevates the granulocyte counts, helps resolve preexisting infections, diminishes the number of new infections and results in significant improvements in survival and quality of life. Some patients have developed leukemia or myelodysplastic syndrome following treatment with GCSF. Congenital neutropenia is due to diverse causes. Not all patients with congenital neutropenia have mutations in the GCSFR gene. Alternative names for infantile genetic agranulocytosis include Kostmann disease or syndrome, and severe congenital neutropenia (SCN).
Genetic meltdown:  A genomic crisis due to an extraordinarily high rate of mutation, a phenomenon known to occur in viruses and perhaps in other organisms. For example, the antiviral agent Ribavirin acts by inducing genomic meltdown. The drug accelerates the already-high mutation rate of RNA viruses, creates a genomic crisis, and destroys the infectivity of the virus. There is a limit to how much variation a genome can tolerate without irretrievably degrading its genetic information. If a population of viruses is replicating at the brink, just a bit of extra pressure from a mutagen, such as ribavirin, can nudge it into the abyss of genetic meltdown, resulting in an inability for it to replicate and survive.
Genetic screening:  Testing a population to identify individuals at risk for a genetic disease or for transmitting it. Newborns may be screened for PKU (phenylketonuria), Jews for the gene for Tay-Sachs disease, Blacks for the sickle cell gene, etc.
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. Now, for example, genetic testing is available to determine which nutritional supplements a person actually needs thus taking guessword out of the equaation.
Genetic transformation:  A process by which the genetic material carried by an individual cell is altered by the incorporation of foreign (exogenous) DNA into its genome.
Genetic transport disease:  Within the body, many molecules are able to pass across the membranes that surround cells. These molecules can accomplish this feat due to specific transport systems. These systems include special receptors on the membrane of the cell and special carrier proteins. The receptor recognizes the molecule and receives it on the cell membrane. Then the molecule hitches a ride through the cell membrane on the back of a carrier protein. With such remarkable specificity, it is little wonder that sometimes there are defects in transport systems. Several dozen different diseases are now known to be due to transport defects. An example of a transport disease is cystinuria, the most common defect known in the transport of an amino acid (namely, cystine) and a significant cause of kidney stones. Like cystinuria, all transport defects are genetic (inherited).
Genetic transposition:  The ability of genes to change position on chromosomes, a process in which a transposable element is removed from one site and inserted into a second site in the DNA. Genetic transposition was the first type of genetic instability to be discovered.
Genetics:  The scientific study of heredity. Genetics pertains to humans and all other organisms. So, for example, there is human genetics, mouse genetics, fruitfly genetics, various plant genetics etc.
Genital:  Pertaining to the external and internal organs of reproduction.
Genital herpes:  A viral infection transmitted through intimate contact with the moist mucous linings of the genitals. This contact can involve the mouth, the vagina or the genital skin. The herpes simplex type 2 (HSV-2) enters the mucous membranes through microscopic tears. Once inside the body, HSV-2 travels to nerve roots near the spinal cord and settles there permanently. When an infected person has a herpes outbreak, the virus travels down the nerve fibers to the site of the original infection and when it reaches the skin, the classic redness and blisters occur. Outbreaks of genital herpes are closely related to the functioning of the immune system. Women who have suppressed immune systems, either through stress, disease, or medications, have more frequent and longer-lasting outbreaks.
Genital wart:  A wart in the moist skin of the genitals or around the anus. Genital warts are due to a human papillomavirus (HPV). The HPVs, including those that cause genital warts, are transmitted through sexual contact. HPV can also be transmitted from mother to baby during childbirth. Most people infected with HPV have no symptoms, but these viruses increase a woman's risk for cancer of the cervix. HPV infection is the most common sexually transmitted disease in the US. It is also the leading cause of abnormal PAP smears and pre-cancerous changes of the cervix in women. There is no cure for HPV infection, although anti-viral medications can reduce outbreaks and topical preparations can speed healing. Once contracted, the virus can stay with a person for life. Also called condyloma acuminatum, condylomata. There is now a controversial vaccine against HPV.
Genitalia:  The male and female reproductive organs. The genitalia include internal structures such as the ovary, and external structures such as the penis.
Genitourinary (GU):  Pertaining to the genital and urinary systems, more commonly termed urogenital.
Genome:  All of the genetic information, the entire genetic complement, all of the hereditary material possessed by an organism. Humans and many other higher animals actually have two genomes, which together make up the total genome: A chromosomal genome -- inside the nucleus of the cell in the familiar form of chromosomes; and a mitochondrial genome -- outside the nucleus in the cytoplasm of the cell, usually in the form of one round chromosome (the mitochondrial chromosome).
Genome annotation:  The process of identifying the locations of genes and all of the coding regions in a genome and determining what those genes do. An annotation (irrespective of the context) is a note added by way of explanation or commentary. Once a genome is sequenced, it needs to be annotated to make sense of it.
Genome Database:  The official central repository for genomic mapping data resulting from the Human Genome Initiative. It was established at Johns Hopkins University in Baltimore, Maryland, USA in 1990. In 1999, the Bioinformatics Supercomputing Centre (BiSC) at The Hospital for Sick Children in Toronto, Ontario, Canada, assumed the management of GDB.
Genomic:  Pertaining to the genome, all of the genetic information possessed by any organism.
Genomic imprinting:  The phenomenon of parent-of-origin gene expression. The expression of a gene depends upon the parent who passed on the gene. For instance, two different disorders - Prader-Willi syndrome and Angelman syndrome -- are due to deletion of the same part of chromosome 15. When the deletion involves the chromosome 15 that came from the father, the child has Prader-Willi syndrome, but when the deletion involves the chromosome 15 that came from the mother, the child has Angelman syndrome. Genomic imprinting plays a critical role in fetal growth and development. Imprinting is regulated by DNA methylation and chromatin structure.
Genomic library:  A collection of clones made from a set of randomly generated overlapping DNA fragments representing the entire genome of an organism.
Genoplasty:   A technology that uses the repair mechanisms normally present in cells to repair gene defects.
Genotoxin:  A poisonous substance which damages DNA. A genotoxin can cause mutations in DNA (and so be a mutagen), it can trigger cancer (and so be a carcinogen), or it can cause a birth defect (and so be a teratogen).
Genotype:  The genetic constitution (the genome) of a cell, an individual or an organism. The genotype is distinct from its expressed features, or phenotype. The phenotype results from the interaction between the genotype and the environment. It is the composite of the characteristics shown by the cell, individual or organism under a particular set of environmental conditions.
Genu:  The Latin word for the knee. When the knee is referred o in medicine, it is just called the knee. However, the word "genu" is also used in medicine as in: genu recurvatum (hyperextension of the knee), genu valgum (knock knee) and genu varum (bowleg).
Gephyrophobia:  (G. gephyra [bridge]) An abnormal and persistent fear of crossing bridges. Sufferers of this phobia experience undue anxiety even though they realize their fear is irrational. Their fear may result partly from the fear of enclosure (claustrophobia) or the fear of heights (acrophobia). High bridges over waterways and gorges can be especially intimidating, as can be very long or very narrow bridges. Fear of bridges is a relatively common phobia.
Gerascophobia:  (G. geras [old age]) An abnormal and persistent fear of growing old. Sufferers of this fear experience undue anxiety about aging even though they may be in good health -- physically, economically and otherwise. They may worry about the loss of their looks, their independence, inactivity after retirement, impaired mobility, the onset of disease, and confinement in a nursing home. Modern society's preoccupation with youthful beauty does nothing to alleviate their fears.
GERD:  Stands for Gastroesophageal Reflux Disease, a disorder in which there is recurrent return of stomach contents back up into the esophagus, frequently causing heartburn, a symptom of irritation of the esophagus by stomach acid. This can lead to scarring and stricture of the esophagus, which can require stretching (dilating). 10% of patients with GERD develop Barrett's esophagus which increases the risk of cancer of the esophagus. 80% of patients with GERD have a hiatal hernia, a breakdown in the integrity of the passageway of the esophagus through the diaphragm.
GERD surgery (fundoplication):  A surgical technique that strengthens the barrier to acid reflux when the lower esophageal sphincter does not work normally and there is gastro-esophageal reflux.
Geriatric medicine:  (G. geron = old man + iatreia = treatment of disease) The branch of medicine concerned with the diagnosis, treatment and prevention of disease in older people and the problems specific to aging. Also called geriatrics.
Germ:  1. A cell or group of cells (a primordium) capable of developing into an organ, a part or an organism in the entire organism. Eggs and sperms are germ cells. 2. A pathogenic a microorganism. A microbe capable of causing disease. The germ theory of disease held, correctly, that these minute bodies can cause disease.
Germ cell:  The eggs and sperms are the germ cells: the reproductive cells. Each mature germ cell is haploid in that it has a single set of 23 chromosomes containing half the usual amount of DNA (the diploid number) and half the usual number of genes. Except for the eggs and sperm, each cell in the human body -- there are 100 trillion cells in each of us (a number which may soon be equal to the U.S. national debt) -- contains the entire human genome, all the genetic information necessary to build a human being, and this information is encoded within the cell nucleus in 6 billion base pairs, subunits of DNA, packaged in 23 pairs of chromosomes, one chromosome in each pair coming from each parent. The germs cells -- the eggs and sperms -- are thus notable exceptions to the usual rules governing chromosomes, genes, and DNA.
Germ cell tumor:  A tumor that arise from a germ cell. These tumors may arise within the gonads -- the ovary and testis. Most testicular tumors are, in fact, germ cell tumors. Germ cell tumors also occur in sites outside the gonads, reflecting the fact that germ cells travel to diverse areas of the body, such as the chest, abdomen, and brain during fetal development.
Germ line:  1. The sequence of cells which develop into eggs and sperm. 2. Inherited material that comes from the eggs or sperm and is passed on to offspring.
German disease:  Syphilis. Depending upon someone's thoughts as to where the disease came from, syphilis was also known as the French, Italian, Spanish and Polish disease.
German measles (rubella):  In 1941 N. M. Gregg, an Australian ophthalmologist, recognized that infection of the mother with German measles (rubella) during early pregnancy could cause a characteristic syndrome of congenital malformations. The first feature noticed was cataracts. Gregg published his pioneering observations in 1942. Rapid progress in understanding rubella was not possible until the rubella virus could be grown and demonstrated in tissue culture. This was reported in 1962. It was then learned that if a pregnant woman acquires rubella, the virus persists throughout her pregnancy, is present at birth, and continues to be shed by her infected child for many months after birth. Even if the child born with rubella looks normal, the child can be contagious and infect nurses, doctors, medical students, and others caring for it. The standard MMR vaccine is given to prevent measles, mumps and rubella. The MMR vaccine is now given in two dosages. The first at 12-15 months of age. The second at 4-6 years. Most children receive MMR vaccinations. Exceptions may include children born with an inability to fight off infection, some children with cancer, on treatment with radiation or drugs for cancer, on long term steroids (cortisone). People with severe allergic reactions to eggs or the drug neomycin should probably avoid the MMR vaccine. Pregnant women should wait until after delivery before being immunized with MMR. Measles, mumps, and rubella vaccines may be administered as individual shots, if necessary, or as a measles- rubella combination. Some parents object to vaccines in general and they have the right to refuse the administration of vaccines to their children.
Germanium:  A nonessential trace element that has caused nephrotoxicity (kidney injury) and death when used chronically by humans, even at recommended levels of use. The U.S. FDA warns that products containing germanium have been "labeled for drug use (e.g., with claims that they are intended for use in the diagnosis, cure, mitigation, treatment, or prevention of diseases such as AIDS or cancer), although there are no approved new drug applications or current investigational new drug applications on file. Germanium-containing products also have been offered for entry as food products such as dietary supplements." Germanium has been offered for sale under a variety of names including Germanium Sesquioxide, GE-132, GE-OXY-132, Vitamin O, Pro-Oxygen, Nutrigel 132, Immune Multiple, and Germax. The FDA recommends that such products containing germanium for human usage be labeled "poisonous and deleterious." However, there are legitimate uses for germanium in the semiconductor industry.
Germinoma:  A type of germ cell tumor. Recall that a germ cell is wither an egg or sperms, i.e. the reproductive cells are germ cells.
Germline mutation:  A heritable change in the DNA that occurred in a germ cell (a cell destined to become an egg or in the sperm) or the zygote (the conceptus) at the single-cell stage. When transmitted to a child, a germline mutation is incorporated in every cell of their body. Germline mutations play a key role in genetic diseases. They play a role, too, in certain types of cancer as, for example, the eye tumor retinoblastoma and Wilms tumor, a childhood malignancy of the kidney. A germline mutation is in contrast to a somatic mutation which is acquired in a single body cell.
Gerstmann-Sträussler-Scheinker syndrome (GSS):  A rare familial form of progressive dementia inherited in an autosomal dominant manner due to a mutant prion gene on chromosome 20pter-p12. Degeneration of the nervous system usually starts in the fourth or fifth decade of life with slowly developing dysarthria (difficulty speaking) and cerebellar ataxia (wobbliness) and later the progressive dementia become evident. Death usually occurs within 10 years of the onset of symptoms. First described in 1936 by the Austrian neurologists Josef Gerstmann (1887-1969), Ernst Sträussler (1872-1959), and I. Scheinker. The syndrome is now known to be a form of transmissible spongiform encephalopathy (TSE), a prion disease. Also called cerebral amyloidosis with spongiform encephalopathy, cerebellar ataxia with progressive dementia, subacute spongiform encephalopathy, and prion dementia.
Gestalt therapy:  A psychotherapeutic concept that stresses understanding mental processes as holistic entities (gestalts) rather than as discrete steps. Gestalt therapy often uses group therapy techniques to help patients gain this type of insight.
Gestation:  The period of time from conception to birth.
Gestational diabetes:  A form of diabetes mellitus that appears during pregnancy (gestation) in a woman who previously did not have diabetes and usually goes away after the baby is born.
Gestational hypertension:  High blood pressure that develops during pregnancy and may subside after delivery. Women who have experienced gestational hypertension are more likely to develop hypertension and suffer a stroke later in life.
GFAP (Glial Fibrillary Acidic Protein):  The degenerative brain condition called Alexander disease is caused by mutation in GFAP (glial fibrillary acidic protein).
GHB:  Known in Europe as Gamma-OH, this is gamma hydroxybutyrate, a colorless and odorless drug used illicitly for "recreational" purposes and for "date rape." GBH is a central nervous system depressant. It tends therefore to increase sociability and function as something of a transient antidepressant. It is also used as a soporitic for insomnia under the brand name Xyrem.
Giant cell arteritis:  A serious disease characterized by inflammation of the walls of the blood vessels (vasculitis). The vessels affected by the inflammation are the arteries (hence the name "arteritis"). The age of affected patients is usually over 50 years of age. Giant cell arteritis can lead to blindness and/or stroke. It is detected by a biopsy of an artery. Giant cell arteritis is treated with high dose cortisone-related medications. Also called temporal arteritis, cranial arteritis, and cerebral vasculitis.
Giant cell pneumonia::  Also known as Hecht's pneumonia, this is a deadly but fortunately rare complication of measles. It tends to strike children who are immuno-deficient as from leukemia or HIV/AIDS. The autopsy shows multinucleated giant cells lining the alveoli (air sacs) of the lungs. Named for the early 20th-century Austrian pathologist Victor Hecht.
Giant cell tumor of bone:  A tumor of bone characterized by massive destruction of the end of a long bone. The sites most commonly struck by this tumor are the the distal end of the femur and the proximal end of the tibia (therefore at the knee). The tumor is often coated by new bony growth. It causes pain, restricts movement, and is usually cancerous. Treatment is by surgery, usually followed by chemotherapy. There is no evidence that the tumor cells themselves are capable of bone destruction; instead, the tumor cells stimulate the formation of cells that function like osteoclasts and resorb bone. The term "giant cell" reflects the fact that osteoclasts are large multinucleate cells (cells with more than one nucleus) that appear very large when viewed magnified through a microscope. Giant cell tumor of bone is also often called osteoclastoma, reflecting the long-held incorrect view that the tumor cells are themselves osteoclasts.
Giant hypertrophic gastritis:  This is a premalignant disorder of the stomach characterized by overgrowth of the stomach lining (the gastric mucosa) and hypoalbuminemia (low blood serum level of albumin) due to loss of albumin by the stomach. The abnormalities of the stomach are highly characteristic with giant folds, excess mucus secretion by the lining of the stomach, and hypochlorhydria (decreased acid secretion by the stomach). The disease tends to lead to stomach cancer. Symptoms include nausea, vomiting, pain in the abdomen, swelling, poor appetite, and weight loss. The cause of the disease is not known, although infections with cytomegalovirus and Helicobacter pylori have been suspected to play a role. In some families, siblings have had the disease, due possibly to autosomal recessive inheritance. The overgrowth of the stomach lining (gastric hypertrophy) appears to be due to activation of the receptor for epidermal growth factor in the stomach. Treatment of severe disease can involve partial or complete removal of the stomach. Treatment with a monoclonal antibody against the epidermal growth factor receptor has been reported to result in marked reduction in the frequency of nausea and vomiting, an increase in the serum albumin concentration, and improvement in the abnormalities of the stomach. The disease is also known by a confusing number of other names including giant hypertrophy of gastric mucosa, hypertropic gastritis, hypertrophic hypoproteinemic gastropathy, hypoproteinemic hypertrophic gastropathy, Menetrier disease, Menetrier disease, and Menetrier's disease (after the French physician Pierre E, Menetrier (1859-1935) who first described it in 1888).
Giant intestinal fluke:  Fasciolopsis buski. (See: Fasciolopsis.)
Giant platelet syndrome:  This condition is a primary problem of platelets in which the platelets lack the ability to stick adequately to injured blood vessel walls and as a result of this problem there is abnormal bleeding. The giant platelet syndrome usually presents in the newborn period, infancy, or early childhood with bruises, nose bleeds (epistaxis), and/or gum (gingival) bleeding. Later problems can occur with anything which can induce bleeding such as menstruation, trauma, surgery, or stomach ulcers.
Giardia lamblia:  A parasite responsible for a contagious form of diarrhea termed giardiasis.
Giardiasis:  Caused by a parasite (Giardia lamblia) responsible for a contagious form of diarrhea. The parasite is most commonly transmitted through direct contact with infected feces or by eating food or drinking water contaminated by feces. Giardia is one of the most common intestinal parasites in the world. The disease is most prevalent in developing countries, where infections are associated with poor sanitary conditions, poor water quality control, and overcrowding.
GIFT:  The acronym GIFT stands for Gamete Intrafallopian Transfer. A technique in which the male and female cells required to begin reproduction are injected into the fallopian tubes of the female for fertilization. This technique is one of the methods doctors use to overcome infertility, the inability of couples to produce offspring on their own. This GIFTis not gift; it is very expensive.
Gigantism:  Excessive growth both in height and specific body parts. Gigantism with extreme height may be associated with disorders of pituitary gland, which may oversecrete human growth hormone (somatotrophin) during childhood before the bones fuse. Excessive growth of specific body parts is also a feature of a number of disorders such as the Wiedemann-Beckwith syndrome in which there is macroglossia (an abnormally large tongue).
Gilbert syndrome:  A common, harmless genetic condition in which a liver enzyme essential to the disposal of bilirubin (the chemical that results from the normal breakdown of hemoglobin from red blood cells) is abnormal. The abnormality is caused by a mutation the UDP-glucuronosyltransferase gene. This enzyme abnormality results in mild elevations of bilirubin pigment in the blood, and the elevated bilirubin pigment can sometimes cause mild yellowing (jaundice) of the eyes. Gilbert's syndrome is a frequent finding in people in North America and Europe. The condition is usually detected serendipitously (purely by accident) in the course of routine blood screening. People with Gilbert syndrome are otherwise entirely normal with no other signs or symptoms and their liver enzyme levels in blood serum are also entirely normal. Treatment is not necessary. The condition has also been referred to as constitutional hepatic dysfunction and familial nonhemolytic jaundice.
Ginger:  A perennial tropical herb that has been used as a treatment for nausea and bowel spasms. Ginger may lead to blood thinning. It is therefore best not taken with medications that prevent blood clotting (anticoagulants) such as warfarin (Coumadin).
Gingivitis:  Gingiva: The gum. Gum disease with inflammation of the gums. On inspection, the gums will appear red and puffy, and will usually bleed during tooth-brushing or dental examination. Treatment is by improved cleaning, with more-frequent and longer brushing and flossing, and/or the use of electronic tooth-cleaning equipment. Antiseptic mouthwashes may also be recommended. There are more serious forms of gingivitis including acute necrotizing u;cerative, acute membranous, fusospirillary, fusospirochetal, phagadenic, ulcerative, and Vincent's.
Gingko biloba:  An herb that is very popular as a treatment for dementia (a progressive brain dysfunction) and to improve thinking. Gingko can cause mild stomach upset and headache. Gingko seems also to have blood thinning properties. Therefore, it is not recommended to be taken with aspirin, nonsteroidal anti-inflammatory drugs (such as ibuprofen/Advil, Motrin or naproxen/Aleve), or medications to prevent blood clotting (anticoagulants) such as warfarin/Coumadin. Gingko should be avoided in patients with epilepsy taking seizure medicines, such as phenytoin /Dilantin, carbamazepine /Tegretol, and phenobarbital.
Ginseng:  An herb that has been used to stimulate the adrenal gland and thereby increase energy. It also may have some beneficial effect on reducing blood sugar in patients with diabetes mellitus. Ginseng can cause elevation in blood pressure, headache, vomiting, insomnia, and nose bleeding. Ginseng can also cause falsely abnormal blood tests for digoxin level in persons taking the drug for heart disease. It is unclear whether ginseng may affect female hormones. Its use in pregnancy is not recommended. Ginseng may affect the action of the normal blood clotting element (platelets). It should be avoided in patients taking aspirin, nonsteroidal antiinflammatory drugs (such as ibuprofen/Advil, Motrin or naproxen/Aleve), or medications to prevent blood clotting (anticoagulants) such as warfarin/Coumadin. Ginseng may also cause headaches, tremors, nervousness, and sleeplessness. It should be avoided in persons with manic disorder and psychosis.
GJB2:  A gene that provides instructions to make a protein called gap junction beta 2. Mutations in the GJB2 gene are responsible for autosomal dominant and autosomal recessive forms of nonsyndromic deafness (hearing loss without related signs and symptoms affecting other parts of the body) as well as some other genetic disorders. The GJB2 gene is a member of the gap junction or connexin family. This family of genes produces protein subunits for channels (gap junctions) that connect neighboring cells. The channels (which are made from several protein subunits) permit the movement of nutrients, charged atoms (ions), and communication signals between cells. Gap junction beta 2 protein is found in cells throughout the body, particularly in the inner ear and the skin. Because of its presence in the inner ear, especially the snail-shaped structure called the cochlea, researchers have focused on the role of this protein in hearing. Hearing requires the conversion of sound waves to electrical nerve impulses. This conversion involves many processes, including maintaining the proper level of potassium ions in the inner ear. Some studies indicate that channels made with gap junction beta 2 protein help to maintain the correct level of potassium ions. Other research suggests that the GJB2 gene is required for the maturation of certain cells in the cochlea. The GJB2 gene also plays a role in the growth and maturation of the outermost layer of skin (epidermis). Mutations in the GJB2 gene cause a number of diseases.
Glabella:  1. The area between the eyebrows, just above the nose. 2. The corresponding area on the frontal bone between the eyebrow ridges.
Gland:  1. A group of cells that secrete a substance for use in the body. For example, the thyroid gland. 2. A group of cells that removes materials from the circulation. For example, a lymph gland.
Glanders:  A bacterial infection that causes a chronic debilitating disease of equids (horses, mules, and donkeys) as well as some members of the cat family and is transmissible to people. The bacterium responsible for glanders is Burkholderia mallei (formerly called Pseudomonas mallei). Glanders attacks the mucous membranes of the nostrils, producing increased secretion and discharge of mucus, and enlargement and induration of the lymph glands of the lower jaw. Hence, the name glanders (from the French glandres meaning glands). Glanders occurs in central and southeast Asia, the Middle East, parts of Africa, and possibly South America. It usually is acquired through direct skin or mucous membrane contact with infected animal tissues. The incubation period is 1 to 14 days. The clinical presentation varies; skin inoculation can result in localized infection with nodule formation and swollen glands. The disease often manifests as pneumonia, bronchopneumonia, or lobar pneumonia, with or without bacteremia (bacterial blood stream infection). There may be liver and spleen involvement. Antibiotics such as sulfadiazine have been used to treat humans. The mortality from this infection was approximately 95% before the use of antimicrobial agents; however, except when bacteremia develops, better diagnosis and more appropriate therapy have lowered mortality. No vaccine against this infection is available. The General Accounting Office, the investigative arm of the US Congress, in a 1999 report considered glanders to be a "potential" biologic threat for terrorism, but noted it is difficult to acquire seed stock of the agent (Burkholderia mallei) and moderately difficult to process and disseminate it. The agent is very stable. Its lethal effects were deemed to be "moderate to high."
Glandular fever (infectious mononucleosis):   "Mono" and "kissing disease" are popular terms for this very common illness caused by the Epstein-Barr virus (EBV). By the time most people reach adulthood, an antibody against EBV can be detected in their blood meaning they have been infected with EBV. The illness is less severe in young children. The infection can be spread by saliva. The incubation period for "mono" is 4 to 8 weeks. Symptoms include fever, fatigue, sore throat, and swollen lymph glands. "Mono" can cause liver inflammation (hepatitis) and spleen enlargement (splenomegaly) and Vigorous contact sports should be avoided to prevent rupture of the spleen> rupture.
Glans:  The glans penis, the rounded head of the penis. 2) The rounded head of the clitoris.
Glass eye:  1. A globe of glass that looks like and is intended to replace the eyeball. 2. By extension, a real eye that looks glassy and as lifeless as a poorly crafted glass eye. The first glass eye was made in 1832 by the glassblower Ludwig Muller-Uri in Lauscha, Germany. Although artificial eyes can be manufactured from plastic today, no other material is said to be equal to a glass eye created from a special blend of Cryolite glass.
Glaucoma:  A common eye condition in which the fluid pressure inside the eyes rises because of slowed fluid drainage from the eye. If untreated, it may damage the optic nerve and other parts of the eye, causing the loss of vision or even blindness. The elderly, African-Americans, and people with family histories of the disease are at greatest risk. There are no symptoms in the early stage of glaucoma. Glaucoma is often called "the sneak thief of sight." Often, by the time the patient notices vision loss, glaucoma can only be halted, not reversed. There are several different types of glaucoma, including open-angle glaucoma and acute angle-closure glaucoma, Open-angle glaucoma is the common adult-onset type of glaucoma. Acute angle-closure glaucoma is a less common form of glaucoma but one that can rapidly impair vision.
Gleason score:  A grading system for prostate carcinoma devised by Dr. Donald Gleason in 1977 as a method for predicting the behavior of prostate cancer. Tumors with a low Gleason score are less likely to show aggressive behavior and therefore are less likely to have spread outside of the gland to lymph nodes (metastases). Gleason's original data showed a progressive increase in death due to the cancer with an increasing Gleason score. Gleason described five distinct patterns of prostate cancer growth which were based on the pattern that the tumor glands made (as viewed through the microscope on stained tissue sections). These are commonly referred to now as Gleason patterns 1 through 5, with pattern 1 being the most well differentiated and therefore the most favorable. Most, if not all tumors, have a mixture of patterns.
Glenn shunt:  A surgical operation for children born with cyanotic heart disease ("blue babies"), in which a large vein (the superior vena cava) is anastomosed (connected) to the right pulmonary artery so that blood bypasses the malformed right chambers of the heart and is shunted directly into the lungs to be oxygenated. The operation was created by William W. L. Glenn (1914-2003), then chief of cardiovascular surgery at Yale University.
Glenoid labrum:  A ring of fibrocartilage that runs around the cavity of the scapula (wingbone) in which the head of the humerus (the bone in the upper arm) fits. The labrum deepens this cavity (the glenoid cavity) and effectively increases the surface of the shoulder joint.
Gliadin:  A glycoprotein (a carbohydrate plus a protein) within gluten. Gliadin is found in wheat and some other grains, including oats, rye, barley, and millet. People with celiac disease, Crohn's disease, and other conditions may be sensitive to gliadin in the diet. In these conditions, antibodies to gliadin can often be detected in the blood.
Glial cell:  A supportive cell in the central nervous system -- the brain and spinal cord. Glial cells do not conduct electrical impulses (as opposed to neurons, which do). The glial cells surround neurons and provide support for them and insulation between them. Glial cells are capable of extensive signaling in response to a diversity of stimuli. Bidirectional communication exists between glial cells and neurons, and between glial cells and vascular cells. Glial cells are the most abundant cell types in the central nervous system. There are three types of glial cells: astrocytes, oligodendrocytes, and microglia. Astrocytes are concerned with neurotransmission and neuronal metabolism. Oligodendrocytes are involved in the production of myelin, the insulating material around neurons.. And microglia are part of the immune system.
Glioblastoma multiforme:  A type of tumor that forms from glial (supportive) tissue in the brain. It is highly malignant, grows very quickly, and has cells that look quite different from normal glial cells. Early symptoms may include sleepiness, headache, and vomiting. Also called a grade IV astrocytoma.
Glioma:  A brain tumor that begins in a glial, or supportive, cell, in the brain or spinal cord. Malignant gliomas are the most common primary tumors of the central nervous system (the brain and spinal cord). They are often resistant to treatment and carry a poor prognosis. Edward Kennedy developed such a tumor.
Gliosis:  A process leading to scars in the central nervous system that involves the production of a dense fibrous network of neuroglia (supporting cells) in areas of damage. Gliosis is a prominent feature of many diseases of the central nervous system, including multiple sclerosis and stroke. After a stroke, neurons die and disappear with replacement gliosis.
Glisson's capsule:  The capsule encasing the liver, a layer of connective tissue surrounding the liver and ensheathing the hepatic artery, portal vein, and bile ducts within the liver. Named for the British physician, anatomist, physiologist, and pathologist Francis Glisson (1597-1677).
Globus:  A word straight from the Latin, meaning (not unexpectedly) a globe or sphere. The word "globus" is used in a number of different contexts in medicine. For example, the globus major is the head of the epididymis, the structure just behind the testis. The globus minor is the lower end of the epididymis. Globus hystericus, sometimes just called globus, is the sensation of having a lump in the throat. This is a symptom of hysterical neurosis (conversion hysteria) as well as of diseases such as reflux laryngitis. The globus pallidus is a pale-appearing spherical area in the brain.
Glomerulus:  1.In the kidney, a tiny ball-shaped structure composed of capillary blood vessels actively involved in the filtration of the blood to form urine. The glomerulus is one of the key structures that make up the nephron, the functional unit of the kidney. 2. In the olfactory bulb, an anatomically discrete module receiving input from an olfactory sensory neuron. The glomerulus in the kidney was so named by the Italian anatomist Marcello Malpighi (1628-1694). The structure was once called a Malphigian corpuscle. "Glomerulus" is the diminutive of the Latin "glomus" meaning "ball of yarn." It is literally a "little ball of yarn." Plural: glomeruli.
Glossal:   Of or pertaining to the tongue. Contained in words lik hypoglossal nerve and thyroglossal cyst. From the Greek glossa meaning tongue.
Glossitis:  Inflammation of the tongue.
Glossolalia:  Nonsensical sounds that mimic the rhythms and inflections of actual speech. Glossolalia may be seen in deep sleep or in trance states. It is also the scientific term for the trance-induced religious phenomena known as "speaking in tongues."
Glossopharyngeal nerve:  The glossopharyngeal nerve is the ninth cranial nerve. The 12 cranial nerves, the glossopharyngeal nerve included, emerge from or enter the skull (the cranium), as opposed to the spinal nerves which emerge from the vertebral column. The glossopharyngeal nerve supplies the tongue, throat, and one of the salivary glands (the parotid gland). Problems with the glossopharyngeal nerve result in trouble taste and swallowing.
Glottis:  The middle part of the larynx (the "voice box"), the area where the vocal cords are located.
Glucocerebrosidase deficiency:  Causes type 1 Gaucher disease, a progressive genetic disease due to an enzyme defect. The enzyme, glucocerebrosidase, is needed to break down the chemical glucocerebroside. The enzyme defect leads to the progressive accumulation of glucocerebroside in the spleen, liver, and lymph nodes. Gaucher disease is the most common genetic disease in Ashkenazi Jews (European Jews) and in American and Canadian Jews. A common early sign of the disease is enlargement of the spleen (located in the upper left abdomen). Other common signs include anemia, a decrease in blood platelets, increased pigmentation of the skin, and a yellow fatty spot on the white of the eye (a pinguecula). Severe bone involvement can lead to pain and collapse of the bone of the hips, shoulders, and spine. The risk for the parents having a child with the disease is 1 in 4 with each pregnancy.
Glucocorticoid:  A hormone that predominantly affects the metabolism of carbohydrates and, to a lesser extent, fats and proteins. Glucocorticoids are made in the outside portion (the cortex) of the adrenal gland and are classed as steroids. Cortisol is the major natural glucocorticoid.
Glucosamine:  A molecule derived from the sugar glucose by the addition of an amino (NH2) group. Glucosamine is a component of a number of structures including the blood group substances and cartilage. Glucosamine cam be purchased as a nutritional supplement and may improve symptoms of pain and stiffness in some patients with osteoarthritis, according to research studies. Glucosamine has not been evaluated for rheumatoid arthritis. Glucosamine has been marketed as a "cartilage rebuilder." This is in part under the assumption that, because glucosamine is a component of normal cartilage, consuming it will assist in the rebuilding of damaged cartilage. There is no strong evidence that glucosamine alone, or in combination with chondroitin, is of value in rebuilding cartilage that is damaged by osteoarthritis. It has also received acclaim as a "cure" for arthritis - for which there is no evidence. Nevertheless, most people with arthritis benefit, some greatly, from supplementation with glucosamine.
Glucose:  This simple sugar (monosaccharide) serves as the chief source of immediate energy in the body. Glucose is the principal sugar the body makes (in the liver). The body makes glucose from proteins, fats and, in largest part, more complex carbohydrates. Glucose is carried to each cell through the bloodstream. Cells, however, cannot use glucose without the help of insulin which allows glucose to enter the cells. Glucose is also known as dextrose. Glucose may be consumed orally or given IV to increase the level of blood glucose when the level falls too low (hypoglycemia). In hypoglycemia, cells cannot function normally, and symptoms develop such as nervousness, cool skin, headache, confusion, convulsions or coma. Ingested glucose is absorbed directly into the blood from the intestine and results in a rapid increase in the blood glucose. IV glucose acts even more rapidly to relieve hypoglycemia.
Glucose tolerance test:  A blood test done to make the diagnosis of diabetes mellitus and other conditions (see below). The test was designed originally to determines the tolerance for the sugar glucose. "Tolerance" refers to the body's ability to handle (tolerate) glucose. However, the test is not that simple. The test depends on a number of factors including the ability of the intestine to absorb glucose, the power of the liver to take up and store glucose, the capacity of the pancreas to produce insulin, the amount of "active" insulin it produces, and the sensitivity of the cells in the body to the action of insulin. For the test, the subject fasts overnight and is then given a specific amount (100 grams) of glucose by mouth and then blood glucose levels are monitored for 3 to 6 hours. Normally, blood glucose should return to normal within 2 to 2½ hours. Since the dose of glucose is taken by mouth, the test is sometimes called an oral glucose tolerance test. The outcome of the test may indicate any of the following:

Depressed glucose tolerance -- in which the blood glucose peaks sharply before declining slower then usual to normal levels -- as in:

  • Diabetes mellitus
  • Hemochromatosis (iron overload disease)
  • Cushing syndrome (too much of the hormone cortisol)
  • Pheochromocytoma (adrenaline-producing tumor)
  • Central nervous system lesions

Increased glucose tolerance -- in which the blood glucose levels peak at lower than normal levels -- as in:

  • Malabsorption syndrome
  • Insulinoma (an insulin-producing tumor)
  • Addison disease (adrenocortical insufficiency)
  • Hypopituitarism (underactivity of the pituitary gland)
  • Hypothyroidism (underactivity of the thyroid gland)
Glucose-6-phosphate dehydrogenase (G6PD):  Deficiency of G6PD is the commonest disease-causing enzyme defect in humans affecting an estimated 400 million people. The G6PD gene is on the X chromosome. Males with the enzyme deficiency develop anemia due to breakup of their red blood cells when they are exposed to oxidant drugs such as the antimalarial primaquine, the sulfonamide antibiotics or sulfones, naphthalene moth balls, or fava beans.
Glutamic acid:  An amino acid, one of the 20 building blocks of protein. It is a nonessential amino acid (i.e. it is made in the body). Glutamic acid is present in many animal and plant proteins. It is involved in ammonia metabolism and serves as a neurotransmitter. Glutamic acid was isolated from wheat gluten in 1866 and first synthesized in 1890. Symbol: Glu.
Glutamine:  An amino acid, one of the 20 building blocks of protein. Glutamine is present in plant and animal proteins and can be synthesized by the body. It is therefore not "essential" to the diet. Glutamine serves as an important carrier of ammonia and contributes it to the formation of urea and purines which are essential to make DNA and RNA. Glutamine is broken down in the kidney. It was isolated in 1833 from beet juice but not synthesized until 1933.
Glutathione S-transferase:  A family of enzymes that utilize glutathione in reactions contributing to the transformation of a wide range of compounds, including carcinogens, therapeutic drugs, and products of oxidative stress. These enzymes play a key role in the detoxification of such substances. The glutathione S-transferases act by catalyzing the reaction of glutathione with an acceptor molecule to form an Sulfur substituted glutathione.
Glutathione S-transferase omega-1:  An enzyme that remarkably influences the age of onset of symptoms of two common degenerative brain disorders, Alzheimer's disease and Parkinson's disease.
Gluteal:  Pertaining to the buttock region formed by the gluteal muscles (the gluteus maximus, gluteus medius, and gluteus minimus). The gluteal muscles extend the thighs and help support the body in standing. The gluteal muscles also serve in hip abduction (spreading the legs).
Gluten:  A protein found in wheat or related grains and many foods that we eat. Gluten can be found in a large variety of foods including soups, salad dressings, processed foods and natural flavorings. Unidentified starch, binders and fillers in medications or vitamins can be unsuspected sources of gluten.
Gluten enteropathy:  A condition, also called celiac sprue, in which the absorption of food nutrients through the small intestine is impaired by an immune (allergic) reaction to gluten, a protein found in wheat or related grains and many other foods. Frequent diarrhea and weight loss can be symptoms. A skin condition called dermatitis herpetiformis can be associated with celiac sprue. The most accurate test for the condition is a biopsy of the involved small bowel. Treatment is avoidance of gluten in the diet. For stubborn sprue, medications can be used.
Gluteus maximus:  The greatest gluteal muscle and the biggest muscle in the human body. The gluteus maximus forms the bulk of the buttocks. It acts to extend the upper leg, spread it, and turn it outward. There are two other gluteal muscles called the gluteus medius and gluteus minimus, all together termed the "glueteals." They are the muscle you sit on, and the ones you show off, maybe, at the beach.
Glycemic index:  An indicator of the ability of different types of foods that contain carbohydrate to raise the blood glucose levels within 2 hours. Foods containing carbohydrates that break down most quickly during digestion have the highest glycemic index. Also called the dietary glycemic index.
Glycine:  An amino acid, one of the 20 building blocks of protein. A nonessential amino acid, glycine is part of many proteins, participates in purine synthesis, and is a neurotransmitter. Symbol: Gly.
Glycobiology:  The study of molecules that contain carbohydrates, their structure and function, and the roles they play in biology. This involves the extracellular matrix (connective tissue) which was long believed to merely be a static support with only limited influence on important decisions by the cell in growth and differentiation. In the 1970s, it was found that the extracellular matrix is dynamic, turning over at points of growth and morphogenesis. Supplements in this area of medicine are called glyconutrients.
Glycogen storage disease:  Any one of the 14 recognized diseases that interfere with the storage of carbohydrates as glycogen in the body, aka McArdle's disease.
Glycohemoglobin:  Also known as glycosylated hemoglobin, hemoglobin to which glucose is bound, a measure of the long-term control of diabetes mellitus. The level of glycohemoglobin is increased in red blood cells of persons with poorly controlled diabetes mellitus. Since the glucose stays attached to hemoglobin for the life of the red blood cell (normally about 120 days), the level of glycohemoglobin reflects the average blood glucose level over the past 3 months. The normal level for glycohemoglobin is less than 7%. Diabetics rarely achieve such levels, but tight control aims to come close to it. Levels above 9% show poor control, and levels above 12% show very poor control. It is commonly recommended that glycohemoglobin be measured every 3 to 6 months in diabetes.
Glycopeptide:  A short chain of amino acids that has sugar molecules attached to it. A glycoprotein is similar in structure to a glycopeptide but has a longer chain of amino acids.
Glycoprotein:  A molecule that consists of a carbohydrate plus a protein. Glycoproteins play essential roles in the body. For instance, in the immune system almost all of the key molecules involved in the immune response are glycoproteins. A glycopeptide is similar in structure to a glycoprotein but has a shorter chain of amino acids.
Glycosylated hemoglobin:  Hemoglobin to which glucose is bound. Glycosylated hemoglobin is tested to monitor the long-term control of diabetes mellitus. The level of glycosylated hemoglobin is increased in the red blood cells of persons with poorly controlled diabetes mellitus. Since the glucose stays attached to hemoglobin for the life of the red blood cell (normally about 120 days), the level of glycosylated hemoglobin reflects the average blood glucose level over the past 3 months. The normal level for glycosylated hemoglobin is less than 7%. Diabetics rarely achieve such levels, but tight control aims to come close to it. Levels above 9% show poor control, and levels above 12% show very poor control. It is commonly recommended that glycosylated hemoglobin be measured every 3 to 6 months in diabetes.
GM1 gangliosidosis (Landing disease):  A genetic lipid storage disorder that is similar in certain respects to Hurler syndrome and Tay-Sachs disease but which affects both the brain and the viscera (the internal organs). GM1 gangliosidosis causes skeletal deformities and exerts severe effects on the brain and internal organs. Death usually occurs by the age of 2. GM1 gangliosidosis is one of the classic lipid storage diseases. The gene responsible for it maps to chromosome 3. There is no treatment for the disease. It is also known as familial neurovisceral lipidosis and Landing disease (after the pioneering pediatric pathologist Ben Landing).
GM2-gangliosidosis, B variant (Tay-Sachs disease):  Defined as "an autosomal recessive, progressive neurodegenerative disorder, which in the classic infantile form, is usually fatal by age 2 or 3 years, results from deficiency of the enzyme hexosaminidase A. " TSD is a model of a fatal metabolic disease that occurs primarily within a well-defined subpopulation. It is one of several genetic diseases found more often in persons of Jewish origin. The frequency of TSD is much higher in Ashkenazi Jews (of European origin) than in other groups of Jews. (In the U.S., 95% of Jews are Ashkenazi and are at risk for TSD). TSD occurs more rarely, in non-Jews. Knowledge of the biochemical basis TSD has permitted screening programs for carrier detection and prenatal diagnosis of TSD. There are forms of TSD with somewhat more hex-A and hence later onset, termed juvenile TSD and adult TSH. TSD is named for the English physician Waren Tay (1843-1927) and the New York neurologist Bernard (Barney) Sachs (1858-1944). TSD worsens, with time, as the central nervous system progressively deteriorates. "Classic" TSD has an insidious onset in infancy. The child with TSD usually develops normally for the first few months of life. An exaggerated startle reaction may first be noted. Head control is lost by 6-8 months of age. The infant cannot roll over or sit up. Spasticity and rigidity develop. Excessive drooling and convulsions become evident. Blindness and head enlargement set in by the second year. With current treatment, it is fatal by age 5. After age 2, total constant nursing care is needed. Death is due usually to cachexia (wasting away) or aspiration pneumonia initiated by food going down "the wrong way" into the lungs.
Gnashing:  Grinding the teeth. More formally called "bruxism." Gnashing, or bruxism, is due to clenching of the teeth other than in chewing and is associated with forceful lateral or protrusive jaw movements. This results in grinding or rubbing the teeth together. Gnashing usually occurs during sleep. It is sometimes so excessive that it damages the occlusal surfaces of the teeth, particularly the molar teeth, and may contribute to the temporomandibular joint (TMJ) syndrome.
Gnathostomiasis:  A disease due to the migration of an immature roundworm called Gnathostoma. Migration just under the skin causes migratory, painful, itchy swellings. Migration to other tissues can result in cough, blood in the urine, eye involvement and, most seriously, meningitis and encephalitis. People become infected by eating undercooked fish or poultry or drinking water containing the worm's larvae. Once mainly in Asia, this worm has emerged as an important parasite in Mexico. Removal and identification of the worm is both diagnostic and therapeutic. Treatment is surgical removal and use of the antiparasitic drug albendazole.
Goiter:  A thyroid gland that is bigger than usual. A goiter is not cancerous. A goiter can be associated with levels of thyroid hormone that are normal (euthyroid), too high (hyperthyroid) or too low (hypothyroid).
Goiter, diffuse toxic (DTG) (Graves disease):  The most common cause of hyperthyroidism (overactivity of the thyroid gland), with generalized diffuse overactivity ("toxicity") of the entire thyroid gland which becomes enlarged into a goiter. There are three clinical components to Graves disease: (1) hyperthyroidism (the presence of too much thyroid hormone), (2) ophthalmopathy specifically involving exophthalmos (protrusion of the eyeballs), and (3) dermopathy with skin lesions. The ophthalmopathy can cause sensitivity to light and a feeling of "sand in the eyes." With further protrusion of the eyes, double vision and vision loss may occur. The ophthalmopathy tends to worsen with smoking. The dermopathy of Graves disease is a rare, painless, reddish lumpy skin rash that is an autoimmune process. DTG is caused by production of thyroid-stimulating (TSH) antibodies which bind to and activate the thyrotropin receptor on thyroid cells. Genes make only a moderate contribution to the susceptibility to Graves disease. No single gene is known to cause the disease or to be necessary for its development. Factors that can trigger the onset of Graves disease include stress, smoking, radiation to the neck, medications (such as interleukin-2 and interferon-alpha), and infectious organisms such as viruses. The diagnosis of Graves disease is made by a characteristic thyroid scan (showing diffusely increase uptake), the characteristic triad of ophthalmopathy, dermopathy, and hyperthyroidism, or blood testing for TSI (thyroid stimulating immunoglobulin) the level of which is abnormally high.
Goiter, iodide:  As too little iodine can cause thyroid disease, so may prolonged intake of too much iodine also lead to the development of goiter (swelling of the thyroid gland) and hypothyroidism (abnormally low thyroid activity). Certain foods and medications contain large amounts of iodine. Examples include seaweed; iodine-rich expectorants (such as SSKI and Lugol's solution) used in the treatment of cough, asthma, chronic pulmonary disease; and amiodarone (Cordarone), an iodine-rich medication used in the control of abnormal heart rhythms (cardiac arrhythmias).
Goiter, toxic multinodular:  Condition in which the thyroid gland contains multiple lumps (nodules) that are overactive and produce excess thyroid hormones, aka Parry's disease or Plummer's disease.
Goitrogenic foods:  Goitrogenic are foods that can affect thyroid function by inhibiting synthesis of thyroid hormones, resulting in enlargement of the gland (goiter). Goitrogenic foods include Brussel sprouts, rutabaga, radishes, cabbage, kale, kohlrabi, turnips, and cauliflower.
Golfer's cramp:  A dystonia that affects the muscles of the hand and sometimes the forearm and only occurs when playing golf. Similar focal dystonias have also been called typist's cramp, pianist's cramp, musician's cramp, and writer's cramp. Golfer's cramp provides a reason to switch to, say, tennis and get tennis elbow.
Gonad:  A reproductive gland (ovary or testis) that produces germ cells (gametes). In embryonic life, the gonad in males and females is initially identical and in this condition is said to be "indifferent" before it differentiates into a definitive testis or ovary. An indifferent gonad becomes a testis if the embryo has a Y chromosome, but if the embryo has no Y chromosome, the indifferent gonad becomes an ovary. Thus, an XY chromosome complement leads to testes while an XX chromosome complement leads to ovaries. Some jave just one X chromosome and no Y. They become female and have Turner syndrome, a condition of infertility. The absence of a Y chromosome permits the indifferent gonad to become an ovary. However, two X chromosomes are needed for the ovary to function normally. The male gonad is the testicle (or testis), located behind the penis in a pouch of skin (the scrotum). The testicles produce and store sperm, and they are also the body's main source of male hormones (testosterone). These hormones control the development of the reproductive organs and other male characteristics, such as body and facial hair, low voice, and wide shoulders. The word "testis" is Latin for "witness." In ancient times, a person providing testimony might validate it by holding the scrotum, his or another man's. "And the servant put his hand under the thigh of Abraham his master, and swore to him concerning the matter." (Genesis 24:9)
Gonadotropin:  Hormones that are secreted by the pituitary gland, and that affect the function of the male or female gonads. The are FSH (follicle-stimulating hormone and HCG (human chorionic gonadotropin).
Gonarthritis:  Inflammation of the knee joint.
Gonorrhea:  A sexually transmitted infection (STI) caused by the bacterium Neisseria gonorrhoea. Although gonorrhea is known primarily as a sexually transmitted infection (STI), it is not exclusively so, but can also be transmitted to the newborn during the birthing process.
Goodman syndrome:  A genetic syndrome characterized by acrocephalosyndactyly - birth defects involving the head and face and the fingers. The craniofacial features are essentially those of acrocephaly while the finger abnormalities include polydactyly (extra fingers), syndactyly (fusion of the fingers), clinodactyly, and ulnar deviation (with the fingers deviated laterally, toward the ulnar bone). The syndrome is inherited as an autosomal recessive trait (unlike most forms of acrocephalosyndactyly which are autosomal dominant traits). The syndrome was described in 1979 by the medical geneticist Richard M. Goodman and his colleagues who called it acrocephalopolysyndactyly IV (ACPS IV). Today it is sometimes called Goodman syndrome.
Goodpasture syndrome:  An autoimmune disease characterized by a combination of lung and kidney disease - specifically, pulmonary hemorrhage (bleeding in the lungs) and glomerulonephritis (inflammation of the glomerulus) - due to severe inflammation in the basement membranes of the alveolus of the lung and the glomerulus in the kidney with the formation of antibodies to components of the basement membrane at both sites. Symptoms include cough with bloody sputum, bloody urine, decreased urine output, fatigue (weakness) and weight loss. Hypertension and swelling (edema) are also common findings on physical examination. The syndrome is named for the pioneering American pathologist Ernest William Goodpasture (1886 - 1960) who discovered it during the influenza pandemic of 1918.The syndrome has also been named anti-glomerular basement membrane antibody disease.
Gorham disease:  Also called disappearing bone disease. Extensive loss of calcium from a single bone so that it cannot be seen on x-ray. Any bone can be involved but the upper arm, shoulder, and jaw are most frequent. This type of selective decalcification is sometimes associated with the presence of an hemangioma, a knot of distended blood vessels. The synonyms for this condition include invisible bone disease, vanishing bone disease, phantom bone disease and massive osteolysis.
Gorlin syndrome:  The nevoid basal cell carcinoma syndrome, a genetic disorder inherited in an autosomal dominant manner and characterized by a broad face, rib malformations, and an extraordinary predisposition to basal cell carcinoma, a type of skin cancer.
Gottron sign:  A scaly, patchy redness over the knuckles seen in patients with dermatomyositis, an inflammatory muscle disorder.
Gout:  Condition characterized by abnormally elevated levels of uric acid in the blood, recurring attacks of joint inflammation (arthritis), deposits of hard lumps of uric acid in and around the joints, and decreased kidney function and kidney stones. Uric acid is a breakdown product of purines, that are part of many foods we eat. The tendency to develop gout and elevated blood uric acid level (hyperuricemia) is often inherited and can be promoted by obesity, weight gain, alcohol intake, high blood pressure, abnormal kidney function, and drugs. The most reliable diagnostic test for gout is the identification of crystals in joints, body fluids and tissues. Doctors initially look for elevated serum uric acid.
Gout, tophaceous:  A form of chronic gout whereby nodular masses of uric acid crystals (tophi) are deposited in different soft tissue areas of the body. Even though tophi are most commonly found as hard nodules around the fingers, at the tips of the elbows, and around the big toe, tophi nodules can appear anywhere in the body. They have been reported in unexpected areas such as in the ears, vocal cords, or against the spinal cord.
Gouty arthritis:  An attack that is usually extremely painful of joint inflammation due to deposits of uric acid crystals in the joint fluid (synovial fluid) and joint lining (synovial lining). Intense joint inflammation occurs as white blood cells engulf the uric acid crystals, causing pain, heat, and redness of the joint tissues. The term "gout" commonly is used to refer to these painful arthritis attacks but gouty arthritis is only one manifestation of gout.
Gower syndrome (situational syncope):  The temporary loss of consciousness in particular kinds of situations. (Syncope is temporary loss of consciousness or, in plain English, fainting). The situations that trigger this reaction are diverse and include having blood drawn, straining while urinating or defecating or coughing. The reaction also can be due to the emotional stress of fear or pain. With Gower syndrome, people often become pale and feel nauseated, sweaty, and weak just before they lose consciousness. Gower syndrome is caused by a reflex of the involuntary nervous system called the vasovagal reaction. The vasovagal reaction leads the heart to slow down (bradycardia) and, at the same time, it leads the nerves to the blood vessels in the legs to permit those vessels to dilate (widen). The result is that the heart puts out less blood, the blood pressure drops, and what blood is circulating tends to go into the legs rather than to the head. The brain is deprived of oxygen and the fainting episode occurs. A vasovagal reaction is also called a vasovagal attack. Gower syndrome is synonymous with situational syncope, vasovagal syncope, and vasodepressor syncope. Sir William Richard Gower (1845-1915) was an English neurologist.
Graft:  Healthy skin, bone, or other tissue taken from one part of the body to replace diseased or injured tissue removed from another part of the body. For example, skin grafts can be used to cover areas of skin that have been burned or surgically removed.
Graft-versus-host disease (GVHD):  A complication of bone marrow transplants in which T cells in the donor bone marrow graft go on the offensive and attack the host's tissues. GVHD is seen most often in cases where the blood marrow donor is unrelated to the patient or when the donor is related to the patient but not a perfect match. There are two forms of GVHD: an early form called acute GVHD that occurs soon after the transplant when the white cells are on the rise and a late form called chronic GVHD. Acute GVHD typically occurs within the first three months after a transplant and can affect the skin, liver, stomach, and/or intestines. The earliest sign is usually a rash on the hand, feet, and face which may spread and look like a sunburn. Severe problems with acute GVHD may include blisters on the skin, watery or bloody diarrhea with cramping, and jaundice (yellowing of the skin and eyes) reflecting liver involvement. Chronic GVHD typically occurs 2-3 months after the transplant and causes symptoms similar to those of autoimmune disorders such as lupus and scleroderma. Patients develop a dry, itchy rash which is raised like alligator skin. There also may be hair loss, decrease in sweating in the skin, and premature greying of the hair. Mouth dryness is a common symptom. It may progress to food sensitivity and spicy and acid food may sting. The eyes may also be involved with dryness and feel irritated and become red. Almost any organ can be affected by chronic GVHD. Prevention of severe GVHD includes elutriation (T-cell depletion), a technique in which the donor bone marrow is largely depleted of the T-cells that cause GVHD. Most patients also receive immunosuppressive drugs such as cyclosporine and methotrexate. Significant GVHD is usually treated with steroids and sometimes a drug called anti-thymocyte globulin.
Gram:  A unit of measurement of weight and mass in the metric system. In weight, a gram is equal to a thousandth of a kilogram. In mass, a gram is equal to a thousandth of a liter (one cubic centimeter) of water at 4 degrees centigrade. The abbreviation for gram is gm. Its symbol is g.
Gram Calorie:  Another word for "calorie"; a unit of food energy. In nutrition terms, the word calorie is used instead of the more precise scientific term kilocalorie which represents the amount of energy required to raise the temperature of a liter of water one degree centigrade at sea level. The common usage of the word calorie of food energy is understood to refer to kilocalorie and actually represents, therefore, 1000 true calories of energy. A gram calorie is also known as a calorie, cal, or small calorie.
Gram stain:  The Danish bacteriologist J.M.C. Gram (1853-1938) devised a method of staining bacteria using a dye called crystal (gentian) violet. Gram's method helps distinguish between different types of bacteria. The gram-staining characteristics of bacteria are denoted as positive or negative, depending upon whether the bacteria take up and retain the crystal violet stain or not. Gram-positive bacteria retain the color of the crystal violet stain in the Gram stain. This is characteristic of bacteria that have a cell wall composed of a thick layer of a particular substance (specifically, peptidologlycan containing teichoic and lipoteichoic acid complexed to the peptidoglycan). The Gram-positive bacteria include staphylococci ("staph"), streptococci ("strep"), pneumococci, and the bacterium responsible for diphtheria (Cornynebacterium diphtheriae) and anthrax (Bacillus anthracis). Gram-negative bacteria lose the crystal violet stain (and take the color of the red counterstain) in Gram's method of staining. This is characteristic of bacteria that have a cell wall composed of a thin layer of a particular substance (specifically, peptidoglycan covered by an outer membrane of lipoprotein and lipopolysaccharide containing endotoxin). The Gram-negative bacteria include most of the bacteria normally found in the gastrointestinal tract that can be responsible for disease as well as gonococci (venereal disease) and meningococci (bacterial meningitis). The organisms responsible for cholera and bubonic plague are Gram-negative.
Granary weevil:  A true weevil that is among the most destructive of all insects in stored grain and that is the culprit responsible for a disease called miller's lung. The weevil larvae develop inside kernels of whole grain in storage, making an infestation difficult to remove in the milling process. Therefore, the granary weevil is largely a pest of stored wheat, corn and barley, especially in elevators, mills and bulk storages. The adult cannot fly, and field infestations do not occur. The granary weevil is also known as the wheat weevil or Sitophilus granarius.
Grand mal epilepsy (aka "grand mal"):  A form of epilepsy characterized by tonic-clonic seizures. involving two phases -- the tonic phase in which the body becomes rigid, and clonic phase in which there is uncontrolled jerking. Tonic-clonic seizures may or may not be preceded by an aura, and are often followed by headache, confusion, and sleep. They may last for mere seconds, or continue for several minutes. If a tonic-clonic seizure does not resolve or if such seizures follow each other in rapid succession, emergency help should be sought immediately. The person could be in a life-threatening state known as status epilepticus. Insuring an open airway is critically important. Treatment is with antiseizure medications.
Grand multipara:  The term "multipara" applies to any woman who has given birth 2 or more times. A woman who has given birth 5 or more times is called a grand multipara. For a pregnancy to count as a "birth", it must go to at least 20 weeks of gestation (the mid-point of a full-term pregnancy) or yield an infant that weighs at least 500 grams, irrespective of whether the infant is liveborn or not.
Grand rounds:  A formal meeting at which physicians discuss the clinical case of one or more patients. Grand rounds originated as part of residency training wherein new information was taught and clinical reasoning skills were enhanced. Grand rounds today are an integral component of medical education. They present clinical problems in medicine by focusing on current or interesting cases.
Granny cam:  A camcorder (a video camera and video recorder in one unit) that displays a live feed of elderly people, as in a nursing home, to keep an eye on them and the care they receive. The issue of the granny cams has a matter for debate between the nursing home industry, which opposes them as an invasion of privacy, and advocates who favor such surveillance as a means of discouraging elder abuse. Also known as a granny-cam or grannycam.
Granular leukocyte:  A type of white blood cell filled with microscopic granules (tiny sacs) containing enzymes that digest microorganisms. Granular leukocytes - they are better known as granulocytes - are part of the innate immune system and have somewhat non specific, broad-based activity. They do not respond exclusively to specific antigens, as do B-cells and T-cells.
Granulation:  That part of the healing process in which rough, pink tissue containing new connective tissue and capillaries forms around the edges of a wound. Granulation of a wound is normal and desirable.
Granulocyte colony-stimulating factor (G-CSF):  A colony-stimulating factor that stimulates the production of neutrophils (a type of white blood cell). G-CSF is a cytokine that belongs to the family of drugs called hematopoietic (blood-forming) agents. Also called filgrastim.
Granulocytopenia:  A marked decrease in the number of granulocytes (white blood cell filled with microscopic granules (tiny sacs) containing enzymes that digest microorganisms).
Granuloma:  A granuloma is one of a number of forms of localized nodular inflammation found in tissues. The fact that a granuloma is localized is important. So is its nodularity. Granulomas have a typical pattern when examined under a microscope. Granulomas can be caused by a variety of biologic, chemical and physical irritants of tissue. A calcified granuloma is a granuloma containing calcium deposits. Since it usually takes some time for calcium to be deposited in a granuloma, it is generally assumed that a calcified granuloma is an old granuloma. For example, a calcified granuloma in the lung may be due to tuberculosis contracted years earlier that is now dormant.
Granulomatosis, allergic:  A disease (also more commonly called the Churg-Straus syndrome) characterized by inflammation of the blood vessels in persons with a history of asthma or allergy. The symptoms of the Churg-Strauss syndrome include fatigue, weight loss, inflammation of the nasal passages, numbness, and weakness. The ultimate test for the diagnosis of Churg-Straus syndrome is a biopsy of involved tissue. Treatment of Churg-Strauss syndrome involves stopping inflammation and suppressing the immune system. The Churg-Straus syndrome is named for the American pathologists Jacob Churg and Lotte Straus.
Granulomatosis, Wegener's:  An inflammatory disease of small arteries and veins (vasculitis) that classically involves vessels supplying the tissues of the lungs, nasal passages (sinuses), and kidneys. Symptoms include fatigue, weight loss, fevers, shortness of breath, bloody sputum, joint pains, and sinus inflammation, sometimes with nasal ulcerations and bloody nasal discharge. Wegener's granulomatosis most commonly affects young or middle-aged adults. The diagnosis of Wegener's granulomatosis is confirmed by finding evidence of vasculitis and abnormal cellular formations called granulomas on biopsy of tissue involved by the inflammatory process. Wegener's granulomatosis is a serious disease. Without treatment, it can be fatal within months. Treatment is directed toward stopping the inflammation process by suppressing the immune system.
Granulomatous colitis:  Crohn's disease of the colon (the large intestine). Crohn's disease is a chronic inflammatory disorder, primarily involving the small and large intestine, but which can affect other parts of the digestive system as well. It is named for the doctor who first described the disease in 1932. The disease is usually diagnosed in persons in their teens or twenties, but can occur at any point in life. Crohn's disease can be a chronic, recurrent condition or can cause minimal symptoms with or even without medical treatment.
Grapefruit diet:  The Grapefruit diet is a weight loss plan that incorporates eating half a grapefruit with each meal and following a severely restrictive low-calorie diet. Like many other "fad" diets, rumors have circulated that this diet is associated with a major medical center, but this is untrue. The grapefruit diet has not been recommended by medical professionals as a weight loss plan and is not considered to be a healthy way to lose weight. Rather, it is an example of an unhealthy, "fad" diet that may contribute to the cycle of weight loss and gain known as "yo-yo" dieting.
Graves disease (aka diffuse toxic goiter):  Generalized diffuse overactivity ("toxicity") of the entire thyroid gland which becomes enlarged into a goiter. Graves disease is the most common cause of hyperthyroidism. There are three components to Graves disease: Hyperthyroidism (the presence of too much thyroid hormone), ophthalmopathy specifically involving exophthalmos (protrusion of the eyeballs), and dermopathy with skin lesions. The ophthalmopathy can cause sensitivity to light and a feeling of "sand in the eyes." With further protrusion of the eyes, double vision and vision loss may occur. The ophthalmopathy tends to worsen with smoking. The dermopathy of Graves disease is a rare, painless, reddish lumpy skin rash which is an autoimmune process. It is caused by thyroid-stimulating antibodies which bind to and activate the thyrotropin receptor on thyroid cells. Graves disease can run in families. The rate of concordance for Graves disease is about 20% among monozygotic (identical) twins, and the rate is much lower among dizygotic (nonidentical) twins, indicating that genes make only a moderate contribution to the susceptibility to Graves disease. No single gene is known to cause the disease or to be necessary for its development. Factors that can trigger the onset of Graves disease include stress, smoking, radiation to the neck, medications (such as interleukin-2 and interferon-alpha), and infectious organisms such as viruses. The diagnosis of Graves disease is made by a characteristic thyroid scan (showing diffusely increase uptake), the characteristic triad of ophthalmopathy, dermopathy, and hyperthyroidism, or blood testing for TSI (thyroid stimulating immunoglobulin) the level of which is abnormally high. Current treatments for the hyperthyroidism of Graves disease consist of antithyroid drugs, radioactive iodine, and surgery. There is regional variation in which of these measures tends to be used - for example, radioactive iodine is favored in North America and antithyroid drugs nearly everywhere else. The surgery, subtotal thyroidectomy, is designed to remove the majority of the overactive thyroid gland. The disease is named for Robert Graves who in 1835 first identified the association of goiter, palpitations, and exophthalmos. Graves disease is also commonly known as diffuse toxic goiter.
Gravid:  Pregnant. For example, the term "prima gravida" denotes a first pregnancy.
Gray:  A unit of absorbed radiation equal to the dose of one joule of energy absorbed per kilogram of matter, or 100 rad. The unit is named for the British physician L. Harold Gray (1905-1965), an authority on the use of radiation in the treatment of cancer. The abbreviation for a gray is Gy.
Gray baby syndrome:  A syndrome due to toxicity of the antibiotic chloramphenicol in the newborn, especially the premature newborn, because of lack the necessary liver enzymes to metabolize this drug. Chloramphenicol accumulates in the baby, causing hypotension (low blood pressure), cyanosis (blue coloring of lips, nail beds, and skin from lack of oxygen in the blood), and often death. Chloramphenicol is therefore usually not given to newborns or premature babies.
Gray matter:  The cortex of the brain which contains nerve cell bodies. The gray matter is in contrast to the white matter, the part of the brain that contains myelinated nerve fibers (the "wiring" of the brain). The gray matter is so named because it in fact appears gray. The white matter is white because that is the color of myelin, the insulation covering the nerve fibers. It is this insulation which is damaged by mercury toxicity.
Gray's Anatomy:  A book entitled "Anatomy Descriptive and Surgical" by Henry Gray appeared in 1858. It is the best known of all medical books. Gray's Anatomy is a scientific and artistic masterpiece. Gray let the natural beauty and grace of the body's interconnected systems and structures shine forth. The illustrations are superb. The text is clear (and, some might say, dull). It is one of the great reference works of all time, used by physicians, students, artists, and anyone interested in human anatomy. Gray's Anatomy is a scientific and artistic masterpiece. Gray let the natural beauty and grace of the body's interconnected systems and structures shine forth. The illustrations are superb. The text is clear (and, some might say, dull). It is one of the great reference works of all time, used by physicians, students, artists, and anyone interested in human anatomy.
Great Plague:  The "Great Plague" that swept London in 1665 was probably not really the plague but rather typhus. The plague was a highly contagious, infectious, virulent, devastating disease due to a bacteria called Yersinia pestis which mainly infects rats and other rodents that serve as the prime reservoir for the bacteria. Fleas function as the prime vectors carrying the bacteria from one species to another. The fleas bite the rodents infected with Yersinia pestis and then they bite people and so transmit the disease. Transmission of the plague to people can also occur from eating infected animals such as squirrels (e.g., in the southeastern U.S.) Once someone has the plague, they can transmit it to another person via aerosol droplets by coughing.
Great pox:  Syphilis. An old name to distinguish it from the smallpox.
Great saphenous vein (aka large saphenous vein):  The larger of the two saphenous veins, the principal veins that run up the leg superficially (near the surface). The great saphenous vein runs from the foot all the way up to the saphenous opening, an oval aperture in the broad fascia of the thigh, a fibrous membrane through which the vein passes and then joins the femoral vein which drains blood from the entire lower extremity. (The other saphenous vein, termed the small saphenous vein, runs behind the outer malleolus (the protuberance on the outside of the ankle joint), comes up the back of the leg and joins the popliteal vein in the space behind the knee (the popliteal space).
Greek medicine:  The foundations of much of modern Western medicine lie in classical Greece, from about 800 B.C. to about 200 A.D. During this period, Greek medicine departed from the divine and mystical and moved toward observation and logical reasoning. These ideas spread throughout the Mediterranean world and as far east as India, and their influence has remained strong in the West to this day. After the fall of the Roman Empire in the 5th century, most works of the Greek physicians were lost to Western Europe. In the 14th and 15th centuries, however, Western Europeans began to rediscover Greek scientific and medical texts. This was due in part to the discovery of Arab repositories of learning in Spain and elsewhere during the Crusades as well as the immigration to Italy of Byzantine scholars at the fall of Constantinople in 1453. At first Greek theories, prescriptions, and procedures were accepted as medical dogma about human anatomy, physiology, and treatment. Later, however, the Greeks' entreaties to their readers to observe the human body and the world around them won out, and scholars began to perform their own research, leading to much of the medicine practiced in the West today.
Green fluorescent protein (GFP):  A protein that glows green under fluorescent light. Found naturally in the jellyfish Aequorea victoria, GFP fluoresces green when exposed to blue light. It has a sequence of three amino acids (serine-tyrosine-glycine) which is responsible for its fluorescence. GFP has been much used in molecular and cell biology research as a reporter of gene expression - The expression of a gene can be monitored in cells by linking the control sequences for a gene to the GFP structural gene, which serves as a reporter and also as a protein tag - The GFP structural gene is fused to another gene, producing a fusion protein that is tagged by GFP. The location of this tagged gene can be seen within living cells. Thus, the fluorescence produced by GFP can serve to reveal where a particular protein is expressed and to monitor protein-protein interactions.
Greenstick fracture:  A fracture in which one side of a bone is broken while the other is bent (like a green stick).
Grid, Amsler:  A grid pattern that resembles a checkerboard utilized for examination of the eye. The patient covers one eye and stares at a black dot in the center of the grid. While staring at the dot, the patient may notice that the straight lines in the pattern appear wavy. This kind of wavy pattern on viewing the Amsler grid is abnormal. It can be an important warning sign of what is called wet age-related macular degeneration. The macula is an area in the retina that is responsible for central (straight-ahead) vision. It deteriorates most often after age 60 resulting in age-related macular degeneration (AMD). An early sign of the dangerous "wet" type of AMD is the wavy appearance of the lines on the Amsler grid. The early diagnosis of wet AMD is critical since laser surgery is urgently needed to preserve sight.
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.
Grief therapy:  Therapy for people who have unusually serious grief reactions. The goal of grief therapy is to identify and solve problems the mourner may have in separating from the person who died. When separation difficulties occur, they may appear as physical or behavior problems, delayed or extreme mourning, conflicted or extended grief, or unexpected mourning.
Groin:  In anatomy, the area where the upper thigh meets the trunk. More precisely, the fold or depression marking the juncture of the lower abdomen and the inner part of the thigh. In sports medicine, "groin injuries" are well known in pages of the sports section of newspapers.
Gross anatomy:  The study of the form of structures that can be seen with the naked eye, as opposed to microscopic anatomy (or histology) which involves structures seen under the microscope. Traditionally, both gross and microscopic anatomy have been studied in the first year of medical school in the U.S. The most celebrated textbook of anatomy in the English-speaking world is Gray's Anatomy, still a useful reference book. The word "anatomy" comes from the Greek ana- meaning up or through + tome meaning a cutting. Anatomy was once a "cutting up" because the structure of the body was originally learned through dissecting it, cutting it up.
Gross hematuria:  Hematuria means blood in the urine and gross hematuria refers to hematuria that is so much that it is visible grossly with just the naked eye. Gross hematuria is in contrast to microhematuria in which the blood is visible only under a microscope. Hematuria, whether it be gross or microscopic, is abnormal and should be further investigated. It may or may not be accompanied by pain. Painful hematuria can be caused by a number of disorders, including infections and stones in the urinary tract. Painless hematuria can also be due to a large number of causes, including cancer.
Group A strep:  A type of streptococcus (strep) bacteria that can cause strep throat and common skin problems such as impetigo as well as rheumatic fever. Autoimmune reactions to strep have also been associated with a number of disorders, including guttate psoriasis (cradle cap), Sydenham's chorea (a movement disorder related to rheumatic fever), obsessive-compulsive disorder, Tourette syndrome, autism, and anorexia nervosa. Group A strep are also known popularly as flesh-eating bacteria.
Group B streptococcus infection:  A major cause of infections, including infections involving the pregnant woman and her newborn infant. Strep B can infect the mother's uterus, placenta, and urinary tract; in fact, they are present in the vagina of 10 to 25 percent of all pregnant women. Infections in the infant can be localized, or may involve the entire body. In babies, strep infections are divided into early-onset and late-onset disease. Early- onset disease presents within the first six days of life with breathing difficulty, shock, pneumonia, and occasionally infection of the spinal fluid and brain (meningitis). Late-onset disease presents between the seventh day and the third month of age with a bloodstream infection (bacteremia) or meningitis. The bacteria can also infect an area of bone; a joint, like the knee or hip; or the skin. Group B strep infection in the newborn is a serious and potentially life- threatening event, particularly because fever and warning signs are often minimal or absent, and because the newborn's immune system is not mature. Early signs of infection can be as subtle as poor feeding, lethargy, or poor temperature control. Women with vaginal group B strep can transmit it to their infant before birth, after the membranes are ruptured, or during the delivery. These babies have a .5 to 1 percent chance of contracting the early-onset type of infection. The risk rises with premature infants; infants born more than 18 hours after the amniotic membranes have ruptured; and infants whose mothers had fever, evidence of infection of the uterus lining, or infection of the urinary tract during labor and delivery. With many infants discharged less than 24 hours after birth today, there is growing pressure to culture all women during pregnancy for group B step. Antibiotic treatment can be considered for culture-positive women before delivery. A positive culture permits the infant's doctor to be especially alert to early signs of problems. Group B strep infection of the newborn is treated aggressively with antibiotics, usually in a neonatal intensive care unit, but the disease still carries a significant mortality rate. Prevention and early detection are critically important.
Group therapy:  There are two meanings: (1) A type of psychiatric care in which several patients meet with one or more therapists at the same time. The patients form a support group for each other as well as receiving expert care and advice. The group therapy model is particularly appropriate for psychiatric illnesses that are support-intensive, such as anxiety disorders, but is not well suited for treatment of some other psychiatric disorders. (2) A type of psychoanalysis in which patients analyze each other with the assistance of one or more psychotherapists, as in an "encounter group." See also gestalt therapy.
Growing pains:  Pains in growing children, usually in the legs. These pains are thought to occur during periods of rapid growth of the long bones of the legs - the femur, tibia, and fibula.
Growth hormone (aka somatotropin):  A hormone made in the pituitary gland that stimulates the release of another hormone called somatomedin by the liver, thereby causing growth. Growth hormone is produced by the anterior pituitary gland, the front section of the gland, and is a polypeptide that consists of 191 amino acids. Growth hormone is given to children with pituitary dwarfism (short stature due to underfunction of the anterior pituitary) to help them grow. Excessive growth hormone production in children can lead to gigantism, and in adults it can lead to acromegaly. In 2003 the FDA approved a new use for Humatrope, a biosynthesized brand of human growth hormone, for the long-term treatment of children with idiopathic (of unknown origin) short stature, also called non-growth hormone deficient short stature. "Short stature" has been defined by the American Association of Clinical Endocrinologists and the Growth Hormone Research Society as height more than 2 standard deviations (SD) below the mean for age and sex. This corresponds to the shortest 2.3% of children. This new indication restricts therapy to children who are even shorter, specifically more than 2.25 SD below the mean for age and sex, or the shortest 1.2% of children. For example, for 10-year old boys and girls, this would correspond to heights of less than 4' 1" inch. This would further correspond to heights of less than 5' 3" and 4' 11" in adult men and women, respectively. In clinical studies, the drug added several inches to the children's eventual height.
Guanine:  One of the four bases in DNA that make up the letters ATGC. Guanine is the "G". The others are adenine, cytosine, and thymine. Guanine always pairs with cytosine to form the base pair G-C (guanine-cytosine) in the DNA. The other base pair in the DNA is A-T (adenine-thymine). Each base pair forms a rung in the DNA ladder. Guanine is also one of the four bases in RNA.
Guided imagery:  An alternative medicine technique in which patients use their imagination to visualize improved health, or to "attack" a disease, such as a tumor. Some studies indicate that the positive thinking can have an effect on disease outcome, so this technique is now utilized as "complimentary medicine" in some oncology centers and other medical facilities.
Guillain-Barre syndrome:   A disorder characterized by progressive symmetrical paralysis and loss of reflexes, usually beginning in the legs. The paralysis characteristically involves more than one limb (most commonly the legs), is progressive, and is usually proceeds from the end of an extremity toward the torso. Areflexia (loss of reflexes) or hyporeflexia (diminution of reflexes) may occur in the legs and arms. Guillain-Barre syndrome is not associated with fever, an important fact in differentiating Guillain-Barre from other diseases. Guillain-Barre usually occurs after a respiratory infection, and it is apparently caused by a misdirected immune response that results in the direct destruction of the myelin sheath surrounding the peripheral nerves or of the axon of the nerve itself. The syndrome sometimes follows other triggering events, including vaccinations. Among the vaccines reportedly associated with Guillain-Barre syndrome are the 1976-1977 swine flu vaccine, oral poliovirus vaccine, and tetanus toxoid. Aside from vaccinations, infection with the bacteria Campylobacter jejuni and viral infections can trigger Guillain-Barre syndrome. There is presently no test to prove the diagnosis of Guillain-Barre syndrome. Other conditions such as polio that may mimic Guillain-Barre need to be ruled out before the diagnosis is made. Treatment includes plasmapheresis and intravenous gamma globulin (IVIG). In most cases of Guillain-Barre syndrome, the patient makes a complete or nearly complete recovery. President Franklin D. Roosevelt may not have had polio but rather the Guillain-Barre syndrome, according to a review of his clinical findings in 2003. FDR was diagnosed with polio at age 39 in 1921. As with most distant diagnoses, this is retrospective speculation.
Guinea worm disease:  A parasitic disease caused by infection with the guinea worm (Dracunculus medinensis), the largest parasite known to plague people. Guinea worm disease is also called Dracunculiasis and end-of-the-road disease because it is not seen in the big cities. Once it infects a person, the guinea worm migrates through the body. It eventually emerges from the body (through the feet in 90% of cases) causing intensely painful edema (swelling), a blister and then an ulcer. Perforation of the skin by the guinea worm, which can be 6 feet long, is accompanied by fever and nausea and vomiting. Infected persons may remain sick for some months. The disease is gotten by drinking water contaminated with the infected intermediate forms of the parasite, called cyclops. The full-grown guinea worm begins to migrate throughout the infected person's body within about a year after ingestion.
Gulf War syndrome:  A highly controversial syndrome involving a constellation of illnesses experienced by up to 80,000 American veterans who were in the Gulf War. Despite extensive (and expensive) research, no specific cause has been found for the Gulf War syndrome. Consequently, many physicians and scientists (but very few of the veterans with the syndrome) regard it as the result of psychological and social factors. A study reported in 2001 disclosed that the diagnosis depends upon who sees the patient and that mental health workers are more likely to believe that Gulf War illness is due to a physical factor such as a contagious or toxic agent, while general internal medicine physicians are more likely to think that the syndrome is a manifestation of mental illness. To hold that point of view, doctors have to believe a select population of people who were prone to mental illness, were, by some statistical impossibility, involved in the Gulf War. Otherwise, why was this syndrome not present in hundreds of thousands of people involved in other wars?
Gum disease:  Inflammation of the soft tissue (gingiva) around the teeth and abnormal loss of bone that surrounds the teeth and holds them in place. Gum disease is caused by toxins secreted by bacteria in "plaque" that accumulate over time along the gum line. This plaque is a mixture of food, saliva, and bacteria. Early symptoms of gum disease include gum bleeding without pain. Pain is a symptom of more advanced gum disease as the loss of bone around the teeth leads to the formation of gum pockets. Bacteria in these pockets cause gum infection, swelling, pain, and further bone destruction. Advanced gum disease can cause loss of otherwise healthy teeth.
Gun stock deformity (cubitus varus):  A deformity of the elbow resulting in a decreased carrying angle (so that, with the arm extended at the side and the palm facing forward, the forearm and hand are held at less than 5 degrees). There is deviation of the forearm toward the midline of the body. (Cubitus is the Latin word for elbow and varus means angled inward.)
Gustatory sweating:  Sweating on the forehead, face, scalp, and neck occurring soon after ingesting food. Some gustatory sweating is normal after eating hot, spicy foods. Otherwise, gustatory sweating is most commonly a result of damage to a nerve that goes to the parotid gland, the large salivary gland in the cheek. In this setting, referred to as Frey syndrome, the sweating is usually on one side of the head. Gustatory sweating is also a rare complication of diabetes mellitus. In this case sweating may occur on both sides of the head, with mild or substantial severity. This distressing problem can be difficult to treat. Treatments used include oxybutynin chloride, propantheline bromide, and clonidine (brand name: Catapres). Recently, some success has been reported using topical applications of glycopyrrolate: the lotion was applied to the skin of the forehead and face, sparing the eyes and mouth.
Guthrie test:  A simple screening blood test for phenylketonuria (PKU). The Guthrie test was the original impetus to newborn metabolic screening.
Guttate psoriasis:  A type of psoriasis characterized by red, scaly patches of inflamed skin on all parts of the body. It is associated with a lung infection in many cases.
GVHD:  Graft-versus-host disease.
Gymnophobia:  An abnormal and persistent fear of nudity. Sufferers of this phobia experience undue anxiety even though they realize their fear is irrational. They may worry about seeing others naked or being seen naked, or both. Their fear may stem from anxiety about sexuality in general, from a fear that their bodies are physically inferior, or from a fear that their nakedness leaves their bodies - and their personalities - exposed and unprotected. "Gymnophobia" is derived from the Greek "gymnos" (naked) and "phobos" (fear). The word "gymnasium" comes from the Greek "gymnasion" (a place for athletic exercises) and the Greek "gymnasein" (to train naked).
GYN:  Abbreviation for gynecology, the branch of medicine dealing with the disease specific to women.
Gynecoid:  Like a woman, womanly, female. The word gynecoid comes from the Greek gyno, gynaikos meaning woman. Gyneco-, gyno-, gyn-, and gyne- are combining forms meaning woman. For example: gynecoid obesity: Fat distribution in a female fashion and gynecoid pelvis: A pelvis that is shaped like a woman's.
Gynecoid pelvis:  The gynecoid pelvis is one that is generally characteristic of a woman in its bone structure and therefore its shape. Gynecoid means like a woman, womanly, female. The gynecoid pelvis is more delicate, wider and not as high as the male pelvis. The angle of the female pubic arch is wide and round. The female sacrum is wider than the male's and the iliac bone is flatter. The pelvic basin of the female is more spacious and less funnel-shaped. From a purely anatomic viewpoint, the female pelvis is better suited to accommodate the fetus during pregnancy and permit birth.
Gynecologic oncologist:  A physician who specializes in cancers of the female reproductive organs. The training to become a gynecologic oncologist is first that of an obstetrician/gynecologist, followed by 2-4 years of structured training in all effective forms of treatment of gynecologic cancers (surgery, radiation therapy, chemotherapy and experimental treatments) as well as in the biology and pathology of gynecologic cancers.
Gynecologist:  A doctor who specializes in treating diseases of the female reproductive organs. These days gynecologists do not address all of women's medicine but instead focus mainly on disorders of the female reproductive organs.
Gynecology:  The branch of medicine particularly concerned with the health of the female organs of reproduction and diseases thereof.
Gynecomastia:  Excessive development of the male breasts. Temporary enlargement of the breasts is not unusual or abnormal in boys during adolescence or during recovery from malnutrition. Gynecomastia may be abnormal as, for example, in Klinefelter's syndrome.
Gyrus:  A convolution on the surface of a cerebral hemisphere caused by the infolding of the cerebral cortex. The gyri are bounded by crevices in the cortex called sulci. Many gyri are constant enough in their occurrence as anatomic features that they have been given names as, for example, the cingulate gyrus, the dentate gyrus, and so on. From the Greek gyros = a circle.mThe functional purpose of this aspect of anatomy is to increase the surface area of the brain permitting more neurons to be present and presumably leading to a higher level of intelligence.

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