|Medical Dictionary - Dictionary of Medicine and Human Biology|
Hydrogen ion, the proton.
Any of various antigens associated with the flagella of motile bacteria and used in serological identification of various bacteria — also called flagellar antigen.
A relatively pale band in the middle of the A band of striated muscle.
A diffusible substance that is thought to be released in the allergic reaction of skin and in the responses of tissue to inflammation and that is held to be similar to histamine or possibly to be histamine itself.
A narrow and less dense zone of myosin filaments bisecting the A band in striated muscle. H-Y antigen
Amale histocompatibility antigen determined by genes on the Y chromosome.
Symbol for hydrogen-1.
Symbol for hydrogen-2.
Symbol for hydrogen-3.
Parent compound of 2-acetylaminofluorene; occurs in coal tar.
Abbreviation for hepatitis-associated antigen.
Otto, Swiss ophthalmologist, 1850–1931.
See under rule.
habena, pl .habenae (ha-be′na, -be′ne)
1. A frenum or restricting fibrous band. 2. A restraining bandage. 3. SYN: habenula (2) . [L. strap]
habenal, habenar (hab′e-nal, ha-be′nar)
Relating to a habena.
habenula, pl .habenulae (ha-ben′u-la, -le)
Relating to a habenula, especially the stalk of the pineal body.
Henry, British dermatologist, 1900–1962. See H. syndrome.
R., German dermatologist, 1884–1941. See Mucha-H. disease.
1. An act, behavioral response, practice, or custom established in one's repertoire by frequent repetition of the same act. SEE ALSO: addiction. 2. A basic variable in the study of conditioning and learning used to designate a new response learned either by association or by being followed by a reward or reinforced event. See conditioning, learning. [L. habeo, pp. habitus, to have]
1. The process of forming a habit, referring generally to psychological dependence on the continued use of a drug to maintain a sense of well-being, which can result in drug addiction. 2. The method by which the nervous system reduces or inhibits responsiveness during repeated stimulation.
The physical characteristics of a person. [L. habit] fetal h. relationship of one fetal part to another. SYN: fetal attitude. gracile h. small stature, frail, underweight appearance.
A chopping stroke made with the edge of the hand in massage.
Geoffrey, British physician, 1889–1968. See Clarke-H. syndrome.
A genus of scorpions found in the southwestern U.S., characterized by numerous setae on the stinger; the commonest species is H. arizonensis, the olive hairy scorpion. SEE ALSO: Scorpionida. [G. hadros, thick, stout, + ouro, tail]
Ernst H.P.A., German naturalist, 1834–1919. See H. gastrea theory, H. law.
Haemadipsa ceylonica (he-ma-dip′sa sa-lon′i-ka)
A species of land leech found in Sri Lanka; it attaches itself to the skin of animals or humans. Its bite is painful, and numerous bites may cause anemia. [G. haima, blood, + dipsa, thirst]
Old term for ameboid protozoa now classified in the suborder Haemosporina, blood parasites that include the genus Plasmodium. [G. haima, blood, + amoibe, change]
An important genus of sucking lice (family Haematopinidae) affecting swine and other domestic and wild animals; it is normally nonpathogenic. H. asini affects horses, mules, and asses; H. eurysternus and H. quadripertusus, cattle; and H. suis, swine. [G. haima, blood, + L. pinus, pine tree]
Old name for Plasmodium species. [G. haima, blood, + kokkos, berry]
Haemodipsus ventricosus (he-mo-dip′sus ven-tri-ko′sus)
The rabbit louse, a transmitter of Francisella tularensis. [G. haima, blood, + dipsos, thirst; L. venter (ventr-), belly]
A sporozoan coccidian genus (order Eucoccidiida, family Haemogregarinidae) that parasitizes the blood cells of cold-blooded animals and the digestive system of invertebrate primary hosts in an obligatory two-host cycle. [G. haima, blood, + L. grex, a flock]
An economically important genus of nematode parasites (family Trichostrongylidae) occurring in the abomasum of ruminant animals and causing severe anemia, especially in younger or previously unexposed animals. Some significant species are Haemonchus placei (in cattle, sheep, and goats), Haemonchus similis (in cattle and sheep), and Haemonchus contortus, the stomach, barberpole, or twisted wire worm of cattle, sheep, goats, and other ruminants, of which a few cases have been reported from humans; accidental parasite of humans. [G. haima, blood, + onchos, spear]
A genus of sporozoa (suborder Haemosporina) parasitic in birds and reptiles, combined with Leucocytozoon, Hepatocystis, and other genera in the family Haemoproteidae. Schizogony occurs in endothelial cells of blood vessels, especially in the lungs of the host, while halter-shaped gametocytes are found in the red blood cells. Infection is transmitted by pupiparous Diptera, such as louse flies (Hippoboscidae) and by bloodsucking midges (Culicoides) [G. haima, blood, + Proteus, a sea god who had the power of assuming different shapes]
A suborder of coccidia (class Sporozoea) that lack syzygy, with separate development of macrogamete and microgamont, the latter producing eight flagellated microgametes; heteroxenous with merogany in vertebrates and sporogony in bloodsucking insects; includes the genera Haemoproteus, Leucocytozoon, and Plasmodium. [G. haima, blood, + sporos, seed]
William M., U.S. epidemiologist/statistician, 1910–1998. See Mantel-H. test.
Waldemar M.W., Russian physician, 1860–1930. See H. vaccine.
Genus in the family Enterobacteriaceae; found in human feces, a rare cause of nosocomial infection; associated with diarrheal disease of undefined mechanism. There is a single species, H. alvei.
hafnium (Hf) (haf′ne-um)
A rare chemical element, atomic no. 72, atomic wt. 178.49. [L. Hafnia, Copenhagen]
Hans Christian, Danish physician, *1888. See NPH insulin.
Werner, German surgeon, 1831–1894. See H. needle.
Surname of person in whom deficiency of H. factor was first observed.
Treatment of the sick by contact with relics of the saints, visits to shrines, and other religious observances. [G. hagios, sacred]
S.E. Patrik, Swedish orthopedist, 1870–1937. See H. deformity, H. disease.
Christian F.S., German physician and founder of homeopathy, 1755–1843. See hahnemannian.
Relating to homeopathy as taught by Hahnemann.
Hahn oxine reagent
See under reagent.
Wilhelm von, Austrian mineralogist, 1795–1871. See H. brushes, under brush.
Hugh E., U.S. dermatologist, *1909. See H.-H. disease.
W. Howard, U.S. dermatologist, 1898–1967. See H.-H. disease.
hair (ˈha(ə)r, ˈhe(ə)r)
The bulbous expansion at the base of a hair from which the hair shaft develops.
hairpin ( har′pin)
1. The structure formed by a polynucleic acid by base-pairing between neighboring complementary sequences of a single strand of either DNA or RNA. 2. The structure seen in a prostaglandin where two segments of the molecule fold back on one another.
See Trichostrongylus, Gordius.
1. Of or resembling hair. 2. Covered with hair. SEE ALSO: hirsutism. SYN: pilar, pilary, pilose.
Blurring of the visual image by glare.
A chloramine used for the sterilization of drinking water.
William A., U.S. physician, *1915. See Stryker-H. syndrome.
Ludwig, German physician, 1876–1949. See H.-Prowazek bodies, under body.
John B.S., English biochemist and geneticist, 1892–1964. See H. relationship.
John S., Scottish physiologist at Oxford, 1860–1936. See H. apparatus, H. effect, H. transformation, H. tube, H.-Priestley sample.
Hale colloidal iron stain
See under stain.
Stephen, English physiologist, 1677–1761. See H. piesimeter.
A substance that elicits an antigen-antibody reaction, but no precipitation.
The period in which the radioactivity or number of atoms of a radioactive substance decreases by half; similarly applied to any substance, such as a drug in serum, whose quantity decreases exponentially with time. Cf.:half-time. biologic half-life the time required for one-half of an amount of a substance to be lost through biologic processes. effective half-life the time required for the body burden of an administered quantity of radioactivity to decrease by half through a combination of radioactive decay and biologic elimination. physical half-life the time required for half the atoms of a radionuclide to undergo disintegration.
SYN: lunule of nail. red half-moon irregular red discoloration of the usually pale demilune at the base of the fingernail; may be seen in congestive failure, malignant disease, or liver disease, but not specific for any of these.
The time, in a first-order chemical (or enzymic) reaction, for half of the substance (substrate) to be converted or to disappear. Cf.:half-life.
halfway house (haf′wa hows)
A facility for individuals who no longer require the complete facilities of a hospital or institution but are not yet prepared to return to independent living.
halibut liver oil (hal′i-but)
The fixed oil obtained from the fresh or suitably preserved livers of halibut species of the genus Hippoglossus (family Pleuronectidae); a supplementary source of vitamins A and D.
A salt of a halogen.
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