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(hĭs-tăm″ĭ-nē′mĕ-ă) [histamine + Gr. haima, blood] Histamine in the blood.

histamine test

1. Injection of histamine subcutaneously to stimulate gastric secretion of hydrochloric acid. 2. A test for vasomotor headache; a histamine injection precipitates the onset of a headache in persons with this disease.


(hĭs′tĭ-dās) Histidine ammonia-lyase.


(hĭs′tĭ-dĭn, -dēn) An essential amino acid, C6H9N3O2, that is, one that must be consumed in the diet.

h. ammonia-lyase A liver enzyme that catalyzes L-histidine with the resultant formation of urocanic acid and ammonia. Deficiency of this enzyme causes histidinemia.


(hĭs″tĭ-dĭ-nē′mē-ă) A hereditary metabolic disease caused by lack of the enzyme histidine ammonialyase, which is normally present in the urine.

histio-, histi-

[Gr. histion, web, cloth, sail] Prefixes meaning tissue. SEE: histo-.


(hĭs′tē-ō-sīt″) [Gr. histion, little web, kytos, cell] A monocyte that enters and remains within a particular tissue. SYN: histocyte; macrophage.


(hĭs″tē-ō-sī-tō′mă) [″ + ″ + oma, tumor] A tumor containing histiocytes.


(his″tē-ō-sī-tō′sĭs) [histiocyte + -osis] An abnormal number of histiocytes in the blood.

Langerhans cell h. Any of a number of clinical conditions, most commonly seen in infants and children, caused by disease of Langerhans cell histiocytes. These cells, which are characteristic of all of the variants of the disease, cause granulomas. The great variation in the signs and symptoms produced depends upon their location and how widely spread they are. Almost any organ system including the skeleton may be involved. These diseases were previously given names such as histiocytosis X, Hand-Schüller-Christian disease, Letterer-Siwe disease, and eosinophilic granuloma. Treatment may consist of surgical removal of bone lesions and radiation therapy for lesions threatening vital functions such as sight and hearing. Corticosteroids or cytotoxic agents are useful in controlling soft-tissue disease and multiple skeletal lesions. Bone marrow transplantation has been used in recurrent and progressive Langer-hans cell histiocytosis.

histo-, hist-

[Gr. histos, mast, beam (of a ship)] Prefixes meaning tissue. SEE: histio-.


(hĭs″tō-blăst) [″ + blastos, germ] A tissue-forming cell.


(hĭs″tō-kĕm′ĭs-trē) The study of chemistry of the cells and tissues. It involves use of both light and electron microscopy and special chemical tests and stains.


(hĭs″tō-kŏm-păt″ĭ-bĭl′ĭ-tē) Cell-mediated immunological similarity or compatibility.


(hĭs′tō-sīt) [″ + kytos,...

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