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glial fibrillary acidic protein.


general fertility rate; glomerular filtration rate.


grapefruit seed extract.


growth hormone. SEE: under hormone.


In ophthalmology and optometry, a visual distortion in which the primary image is accompanied by a fainter copy of itself. ghost, n.

ghost riding, ghost riding the whip

Exiting an automobile while it is moving, either walking or dancing alongside it, or balancing on top of it. It is an activity that has been associated with serious and sometimes fatal trauma.


(grel′in) [Abbr. of growth hormone-releasing (peptide) + -in] A polypeptide secreted by the stomach. It has several effects including increasing appetite, participating in energy homeostasis, and regulating body weight.


growth hormone–releasing hormone. SEE: under hormone.


gastrointestinal; glycemic index.

Giannuzzi, Giuseppe

(jă-noot′sē) Italian anatomist, 1839–1876.


[Gr. gigas, giant] An individual or structure much larger than normal.


(jē-ăr′dē-ă) [Alfred Giard, Fr. biologist, 1846–1908] A genus of protozoa possessing flagella. They inhabit the small intestine of humans and other animals, are pear shaped, and have two nuclei and four pairs of flagella. They attach themselves to the cells of the intestinal mucosa, from which they absorb nourishment. Cysts can survive in water for up to 3 months. The concentration of chlorine routinely used in treating domestic water supplies does not kill Giardia cysts, but boiling water inactivates them.

G. lamblia A species of Giardia found in humans, transmitted by ingestion of cysts in fecally contaminated water or food. In current usage, the preferred name for G. lamblia is G. duodenalis. These organisms are found worldwide. The most common symptoms of G. duodenalis infection are diarrhea, fever, cramps, anorexia, nausea, weakness, weight loss, abdominal distention, flatulence, greasy stools, belching, and vomiting. Onset of symptoms begins about 2 weeks after exposure; the disease may persist for up to 2 to 3 months. There is no effective chemoprophylaxis for this disease. Metronidazole, quinacrine, or tinidazole are preferred treatments. SEE: water, emergency preparation of safe drinking.

 DIAGNOSIS: Cysts or trophozoites can be identified in feces. Three consecutive negative tests are required before the feces are considered to be negative. Duodenal contents also can be examined by aspiration or string test, in which an ordinary string is swallowed and allowed to remain in the duodenum long enough for the protozoa to attach. On removal, it is ...

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