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Medical Dictionary


β or B
The second letter of the Greek alphabet.

3-Aminopropionic acid or β-aminopropionic acid;a decarboxylation production of aspartic acid. Found in brain, in carnosine, and in coenzyme A.

β-alanine-pyruvate aminotransferase
An enzyme that reversibly transfers the amino group of β-alanine to pyruvate, thus producing l-alanine and malonate semialdehyde. A deficiency of this enzyme is believed to be the cause of hyper-β-alaninemia.

The 20β isomer of α-allocortol and 5α enantiomer of β-cortol; a metabolite of hydrocortisone found in urine.

The 20β isomer of α-allocortolone and 5α enantiomer of β-cortolone; a metabolite of hydrocortisone found in urine.

The 5α-pregnane-3β,20α(and β)-diols; both are metabolites of progesterone and adrenocortical hormones; found in urine.

β-aminoisobutyrate:pyruvate aminotransferase
β-Aminosiobutyrate:pyruvate transaminase;an enzyme that catalyzes the reversible transfer of an amino group from β-aminoisobutyrate to pyruvate, producing l-alanine and methylmalonate semialdehyde; a step in valine degradation. A deficiency of this enzyme results in hyper-β-aminoisobutyric aciduria.

β-aminoisobutyric acid
3-Amino-2-methylpropionic acid;an end product of thymine catabolism; high urinary levels (200–300 mg/day) have been noted in some individuals, either from some disease process or following a genetic pattern.

A glucanohydrolase yielding β-maltose units from the nonreducing ends of 1,4-α-glucans. An exoamylase. SYN: glycogenase, saccharogen amylase.

β-aspartyl(acetylglucosamine) (as-par′til-as′e-til-gloo′ko-sa-men)
Misnomer for 1-(β-asparagino)-N-acetylglucosamine or 1-(β-aspartamido)-N-acetylglucosamine, or, formally, 1-(β-l-aspartamido)-N-2-acetamido-1,2-dideoxy-β-d-glucose; a compound of N-acetylglucosamine and asparagine, linked via the amide nitrogen of the latter and carbon-1 of the former. An important structural linkage in many glycoproteins. Elevated levels are found in certain cases of progressive mental retardation.

1. Second letter of the Greek alphabet, beta. 2. In chemistry, denotes the second in a series, the second carbon from a functional ( e.g., carboxylic) group, or the direction of a chemical bond toward the viewer. For terms having this prefix, see the specific term.

Symbol for electron.

Symbol for positron.

Abbr: bacillus.

Abbr: barometric.

Abbr: Baumé scale.

Abbr: bel.

Abbr: bicuspid.

One of the four ABO blood groups characterized by the presence of antigens designated by the letter B and by the presence of antibodies against the antigens present in the A blood group.

1. Symbol for boron; for aspartic acid or asparagine when it is unclear which of the two amino acids is present; for bromouridine; second substrate in a multisubstrate enzyme-catalyzed reaction. 2. As a subscript, refers to barometric pressure.

Ba or BA
Symbol for barium.

Isaac, U.S. inventor, 1799–1862. See B. metal.

Stephen Moulton, American chemist, 1843–1931. During his career Babcock provided agriculture with a number of inventions and procedures, the Babcock test being the foremost. The introduction of this test, devised in 1890, discouraged the watering down of milk, resulted in a scale for milk prices based on quality, and provided a new impetus for the improvement of dairy herds. Babcock also invented an improved viscometer, which is used for measuring the viscosity of milk and other liquids, and did research on the nutritional value of various feeds, thereby providing groundwork for the discovery of vitamin A. See also B. tube.

Babcock test
A test for determining the fat content of milk and milk products.

Victor, Roumanian bacteriologist, 1854–1926. See Babesia, B. nodes, under node. In 1888 Babès made two important discoveries. With the German pathologist Paul Ernst he discovered and described the metachromatic granules seen in the protoplasm of bacteria. These granules stain deeply with aniline dyes and are now known as Babes-Ernst granules or bodies. He also discovered a group of small protozoan parasites that invade the blood of various animals and are now placed in the genus Babesia, named after him.

Babes-Ernst granule, also called Babes-Ernst body
A metachromatic granule in protoplasm.

Babesia (ba-be′ze-a)
The economically most important genus of the protozoan family Babesiidae; characterized by multiplication in host red blood cells to form pairs and tetrads; it causes babesiosis (piroplasmosis) in most types of domestic animals, and two species cause disease in splenectomized or normal people; vectors are ixodid or argasid ticks. [V. Babès]
  • B. divergens: the cause of bovine babesiosis in western and central Europe; vector tick is Ixodes ricinus; it has caused human babesiosis in splenectomized individuals in Europe; also found in reindeer.
  • B. microti: a malarialike protozoan naturally parasitizing certain rodents (Peromyscus and Microtus spp.) in North America; a number of human cases have been reported in the U.S. The local tick vector is Ixodes scapularis, whose numbers and infection levels have greatly increased in recent years with the increase in the deer population, which serves as an abundant blood source for I. scapularis. SEE ALSO: Borrelia burgdorferi.

Babesiella (ba-be-ze-el′a)
See Babesia.

Babesiidae (ba′be-zi′i-de, -ze′i-de)
A family of protozoan parasites (class Sporozoea, order Piroplasmida) occurring in the red blood cells of various mammals. The organisms are piriform, round, or oval and reproduce by schizogony to form tetrads or by binary fission to form pairs in the red blood cells; transmission is effected by ticks. The family includes the genera Babesia, Echinozoon, and Entopolypoides; Aegyptianella, formerly included, is now thought to be a rickettsia. SEE ALSO: Theileriidae.

babesiosis (ba-be′ze-o′sis)
A disease caused by infection with a species of the protozoan Babesia, transmitted by ticks. In animals, the disease is characterized by fever, malaise, listlessness, severe anemia, and hemoglobulinuria; the death rate frequently is higher in adult than in young animals. SYN: piroplasmosis. human b. a rare human disease caused by infection with Babesia species (most frequently B. divergens in Europe and B. microti in the U.S.) that has been fatal in some splenectomized individuals.

Joseph F., French neurologist, 1857–1932. See B. phenomenon, B. sign, B. reflex, B. syndrome.

baby (ba′be)
An infant; a newborn child.
  • blue b. a child born cyanotic because of a congenital cardiac or pulmonary defect causing incomplete oxygenation of the blood.
  • blueberry muffin b. an infant with purple skin lesions the appearance of which has been compared to that of a blueberry muffin. Lesions are caused by dermal erythropoiesis and are seen in congenital infections such as cytomegalovirus infection, toxoplasmosis, or rubella. The infection interferes with the normal production of blood cells in the bone marrow.
  • collodion b. [MIM*146600] a newborn child with lamellar ichthyosis; at birth, the skin is bright red, shiny, translucent, and drawn tight, giving a distorted appearance (as if having been painted with collodion) of immobilization of the face; contraction of the skin causes ectropion, a pressed down appearance of the nose, and a gaping of the mouth and the labia; autosomal dominant inheritance.
  • test-tube b. popular term for a b. born after uterine implantation of a maternal ovum fertilized in vitro.

bacampicillin hydrochloride (bak′am-pi-sil′in)
A semisynthetic penicillin with the same activity and uses as ampicillin, but better absorbed on oral administration.

baccate (bak′at)
Pulpy throughout like a berry. [L. bacca, berry]

Guido, Italian physician, 1832–1916. See B. sign.

bacciform (bak′si-form)
Berry-shaped. [L. bacca, berry]

George W., U.S. parasitologist, *1890. See B.-Pettit test.

See Rivinus.

Jean George, U.S. physiologist, 1877–1959. See B. bundle.

Bacillaceae (ba-si-la′se-e)
A family of aerobic or facultatively anaerobic, sporeforming, ordinarily motile bacteria (order Eubacteriales) containing Gram-positive rods. These organisms are chemoheterotrophic. Some species are pathogenic. Ordinarily two genera, Bacillus and Clostridium, are included. The type genus is Bacillus.

bacillar, bacillary (bas′i-lar, bas′i-la-re)
Shaped like a rod; consisting of rods or rodlike elements.

bacille Calmette-Guérin (BCG) (bah-sel′)
An attenuated strain of Mycobacterium bovis used in the preparation of BCG vaccine that is used for immunization against tuberculosis and in cancer chemotherapy. SYN: Calmette-Guérin bacillus. [Fr.]

bacillemia (bas-i-le′me-a)
The presence of bacilli in the circulating blood. [bacillus + G. haima, blood]

bacilli (ba-sil′i)
Plural of bacillus.

bacilliform (ba-sil′i-form)
Rod-shaped. [L. bacillus, a rod, + forma, form]

bacillin (ba-sil′in)
An antibiotic substance produced by Bacillus subtilis.

bacillomyxin (ba-sil-o-mik′sin)
An antibiotic active against certain pathogenic fungi obtained from cultures of Bacillus subtilis. [Bacillus + G. mykes, fungus, + -in]

bacillosis (bas-i-lo′sis)
A general infection with bacilli.

bacilluria (bas-i-loo′re-a)
The presence of bacilli in the urine. [bacillus + G. ouron, urine]

Bacillus (ba-sil′us)
A genus of aerobic or facultatively anaerobic, sporeforming, ordinarily motile bacteria (family Bacillaceae) containing Gram-positive rods. Motile cells are peritrichous; spores are thick-walled and stain poorly with Gram stain; these organisms are chemoheterotrophic and are found primarily in soil. A few species are animal pathogens; some species evoke antibody production. The type species is B. subtilis. [L. dim. of baculus, rod, staff] B. anthracis a bacterial species that causes anthrax in humans, cattle, swine, sheep, rabbits, guinea pigs, and mice; contains virulence plasmids associated with capsule and toxin production. B. brevis a bacterial species found in soil, air, dust, milk, and cheese; some strains produce the antibiotic gramicidin or tyrocidin. B. cereus a bacterial species that causes an emetic type and a diarrheal type of food poisoning in humans, and can cause infections in humans and other mammals. It can cause a highly destructive infection of the traumatized eye. B. circulans a bacterial species found in soil that has been incriminated in human infections including septicemia, mixed abscess infections, and wound infections. B. hemolyticus former name for Clostridium haemolyticum. B. histolyticus former name for Clostridium histolyticum. B. megaterium a saprophytic bacterial species of experimental interest; strains produce bacteriocins (megacins). B. polymyxa a bacterial species found in soil, water, milk, feces, and decaying vegetables; some strains produce the antibiotic polymyxin. B. pumilis a usually saprophytic species of bacteria that has been associated with food poisoning and rarely with abscess or bowel fistula formation. B. sphaericus a bacterial species that is an insect pathogen and that has been associated with occasional human and other mammalian infections, especially in immunocompromised hosts; human infections have included meningitis, endocarditis, and food poisoning. B. subtilis a bacterial species found in soil and decomposing organic matter; some strains produce the antibiotic subtilin, subtenolin, or bacillomycin; it has been associated with human infections primarily of immunocompromised patients, and with food poisoning. It is the type species of the genus B.. SYN: grass b., hay b.. B. thuringiensis a bacterial species that is an insect pathogen used for vector control that has been implicated in human and mammalian infections. In the laboratory it may be misdiagnosed as a strain of B. cereus.

bacillus, pl .bacilli (ba-sil′us, -i)
1. A vernacular term used to refer to any member of the bacterial genus B.. 2. Term used to refer to any rod-shaped bacterium. [L. dim. of baculus, a rod, staff] abortus b. SYN: Brucella abortus. Battey b. SYN: Mycobacterium intracellulare. [Battey hospital in Rome, GA] blue pus b. SYN: Pseudomonas aeruginosa. Bordet-Gengou b. SYN: Bordetella pertussis. Calmette-Guérin b. SYN: bacille Calmette-Guérin. cholera b. SYN: Vibrio cholerae. coliform bacilli (ko′li-form, kol′i-form) common name for Escherichia coli that is used as an indicator of fecal contamination of water, measured in terms of coliform count; occasionally used to refer to all lactose-fermenting enteric bacteria. colon b. SYN: Escherichia coli. comma b. SYN: Vibrio cholerae. Döderlein b. a large, Gram-positive bacterium occurring in normal vaginal secretions; although thought by some to be identical with Lactobacillus acidophilus, the identity of Döderlein b. is still doubtful. Ducrey b. SYN: Haemophilus ducreyi. dysentery b. an organism of the genus Shigella which causes dysentery. Eberth b. SYN: Salmonella typhi. Flexner b. SYN: Shigella flexneri. Friedländer b. SYN: Klebsiella pneumoniae. gas b. SYN: Clostridium perfringens. grass b. SYN: B. subtilis. Hansen b. SYN: Mycobacterium leprae. hay b. SYN: B. subtilis. Hofmann b. SYN: Corynebacterium pseudodiphtheriticum. influenza b. SYN: Haemophilus influenzae. Kitasato b. SYN: Yersinia pestis. Klebs-Loeffler b. SYN: Corynebacterium diphtheriae. Koch b. SYN: Mycobacterium tuberculosis. Koch-Weeks b. SYN: Haemophilus aegyptius. lactic acid b. a member of the genus Lactobacillus. leprosy b. SYN: Mycobacterium leprae. Loeffler b. SYN: Corynebacterium diphtheriae. Moeller grass b. SYN: Mycobacterium phlei. Morgan b. SYN: Morganella morganii. Much b. an alleged non–acid-fast granular form of the tubercle b.; not demonstrable by the Ziehl stain, but takes a modified Gram stain; it is said to be the form present in the tuberculous skin lesion. necrosis b. SYN: Fusobacterium necrophorum. paracolon b. any one of a number of diverse enteric bacteria that fail to ferment lactose promptly. paradysentery b. SYN: Shigella flexneri. paratyphoid b. one of the three organisms causing the three forms, A, B, and C, of paratyphoid fever. SEE ALSO: paratyphoid fever. plague b. SYN: Yersinia pestis. Shiga b. SYN: Shigella dysenteriae. Shiga-Kruse b. SYN: Shigella dysenteriae. tubercle b. 1. SYN: Mycobacterium tuberculosis. 2. SYN: Mycobacterium bovis. typhoid b. SYN: Salmonella typhi. Vincent b. probably Fusobacterium nucleatum. Weeks b. SYN: Haemophilus influenzae. Welch b. SYN: Clostridium perfringens. Whitmore b. SYN: Pseudomonas pseudomallei.

bacitracin (bas-i-tra′sin)
An antibacterial antibiotic polypeptide of known chemical structure isolated from cultures of an aerobic, Gram-positive, spore-bearing bacillus (member of the Bacillus subtilis group); active against hemolytic streptococci, staphylococci, and several types of Gram-positive, aerobic, rod-shaped organisms; usually applied locally. Zinc b. is also available. [Bacillus + Margaret Tracy, source of orig. culture]

back (bak)
1. Posterior aspect of trunk, below neck and above buttocks; 2. Vertebral column with associated muscles (erector spinae and transversospinalis) and overlying integument. See dorsum. adolescent round b. SYN: Scheuermann disease. hollow b. SYN: lordosis. poker b. SYN: spondylitis deformans. saddle b. SYN: lordosis.

backache (bak′ak)
Nonspecific term used to describe back pain; generally refers to pain below the cervical level.

backbone (bak′bon)
SYN: vertebral column.

backcross (bak′kros)
1. Mating of an individual heterozygous at one or more loci to an individual homozygous at the same loci. 2. SYN: testcross.

The reversal of the normal flow of a fluid or current. SEE ALSO: regurgitation. pyelovenous b. retrograde movement of fluid (urine or injected contrast materials) from renal pelvis into renal venous system. This occurs under conditions of distal obstruction or injection of solutions into renal collecting system.

background (bak′grownd)
Instrument response in the absence of a sample.

backing (bak′ing)
In dentistry, a metal support which serves to attach a facing to a prosthesis.

back-knee (bak′ne′)
SYN: genu recurvatum.

backprojection (bak′pro-jek′shun)
In computed tomography or other imaging techniques requiring reconstruction from multiple projections, an algorithm for calculating the contribution of each voxel of the structure to the measured ray data, in order to generate an image; the oldest and simplest method of image reconstruction. Cf.:Fourier analysis. SYN: apical lordotic projection. Cf.:Fourier analysis.

backscatter (bak′skat-er)
Secondary radiation deflected more than 90° from the primary beam. See scattered radiation.

The backwards movement of RNA polymerase along the DNA template to a state more stable than that encountered when some base pairs disrupt the attachment of the 3′ end from the active transcription site.

baclofen (bak′lo-fen)
A muscle relaxant used in the symptomatic treatment of spinal cord injuries and multiple sclerosis; an agonist at GABAb receptors.

Harry E., U.S. proctologist, *1900. See B. anoscope.

bacteremia (bak-ter-e′me-a)
The presence of viable bacteria in the circulating blood; may be transient following trauma such as dental or other iatrogenic manipulation or may be persistent or recurrent as a result of infection. SYN: bacteriemia. [bacteria + G. haima, blood]

See bacterio-.

bacteria (bak-ter′e-a)
Plural of bacterium. blue-green b. Cyanobacteria. cell wall–defective b. b. with absent or damaged cell walls; morphologically, they may become spheroplasts, round structures with little or no cell wall, or they may develop filamentous forms, with or without bulbous, extruded portions. coryneform b. common name for nondiphtheria corynebacterium, usually a nonpathogenic component of skin and oropharyngeal flora in humans and animals can cause opportunistic infections in the immunocompromised host.

bacterial (bak-ter′e-al)
Relating to bacteria.

bactericholia (bak′ter-i-ko′le-a)
Bacteria in bile.


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