As a subscript, refers to blood.
Abbreviation for bis [L.], twice; barn.
bile from the gallbladder.
β cell of pancreas or of anterior lobe of hypophysis;
Alternate names: B lymphocyte
B cell receptors
a complex comprising a membrane-bound immunoglobulin molecule and two associated signal-transducing α and β chains.
B cells: A type of white blood cell and,
more particularly, a key kind of lymphocyte. Many B cells mature into
plasma cells, which produce antibodies (proteins) necessary to fight
off infections (bacteria, viruses, etc.), while other B cells mature
into memory B cells. All
of the plasma cells
descended from a single B cell produce the same antibody which is
directed against the antigen that stimulated it to mature. The same
principle holds with memory B cells. Thus, all of the plasma cells
and memory cells "remember" the stimulus that led to their formation.
maturation of B cells in birds takes place in an organ called the
bursa of Fabricus. Hence, the B (from bursa). B cells in mammals,
including humans, mature largely in the bone marrow. So the B is
the longer polypeptide component of insulin containing 30 amino acyl residues, beginning with a phenylalanyl residue (NH2-terminus); insulin consists of a B chain linked to an A chain by two disulfide bonds; the amino acid composition of the B chain is a function of species;
the light chain of an immunoglobulin.
myelinated fibers autonomic nerves, with a diameter of 2 mcm or less, conducting at a rate of 3–15 meters per second.
an immunologically important lymphocyte that is not thymus dependent, is short-lived, and resembles the bursa-derived lymphocyte of birds in that it is responsible for the production of immunoglobulins; it is the precursor of the plasma cell and expresses surface immunoglobulins (SIGS) but does not release them. It does not play a direct role in cell-mediated immunity. B lymphocyte can be characterized immunophenotypically by CD19 surface markers.
Alternate names: B cell2
See Also: T lymphocyte
B variant GM2-gangliosidosis
B variant GM2-gangliosidosis:
This disorder known as Tay-Sachs disease (TSD) is concisely
defined by OMIM (Online Mendelian Inheritance in Man) 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. � �Autosomal� points to the gene
for TSD residing on a nonsex (autosomal) chromosome
(namely, chromosome15q23-q24). �Recessive� indicates a
person with 2 copies of the gene has TSD whereas someone
with 1 copy is a carrier in normal health. TSD worsens,
with time, as the central nervous system progressively
deteriorates. The �classic� (�textbook�) type of TSD has
its 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.
�Fatal by age 2 or 3 years� today would be modified to
�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. TSD is due to deficiency of an
enzyme (a protein needed to catalyze a specific chemical
reaction within the body). Lack of the enzyme which
results in failure to process a lipid (a fat) which
accumulates and is deposited in the brain and other
tissues, to their detriment. The enzyme is called
hexosaminidase-A (hex-A) and the lipid that is deposited is
called GM2-ganglioside. 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.
(Other Jewish genetic diseases include Gaucher disease,
Niemann-Pick disease, Bloom syndrome, and factor XI
defiency). 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. Alternative names
for TSD itself are amaurotic familial idiocy (outdated),
hexosaminidase A deficiency, hex-A deficiency. TSD is named
for the English physician Waren Tay (1843-1927) and the New
York neurologist Bernard (Barney) Sachs (1858-1944). Tay in
1881 studied an infant with progressive neurological
impairment and described �symmetrical changes in the yellow
spot in each eye�, the �cherry-red spots� characteristic of
TSD. Sachs saw a child In 1887 and the child�s sister in
1898 with the cherry-red spots and �arrested cerebral
development� and in 1910 he demonstrated the presence of
accumulated lipid in the brain and retina.
the initial positive deflection in the electroretinogram, possibly arising from the inner nuclear layer of the retina.
Bárány caloric test
a test for vestibular function, made by irrigating the external auditory canal with cool and warm water; this thermal stimulation of the vestibular apparatus results in nystagmus and past-pointing; in vestibular disease, the response may be reduced or absent.
Alternate names: caloric test, nystagmus test
in cases of ear disease, in which the vestibule is healthy, injection into the external auditory canal of water below the body temperature will cause rotatory nystagmus toward the opposite side; when the injected fluid is above the body temperature the nystagmus will be toward the injected side; if the labyrinth is diseased or nonfunctional there may be diminished or absent nystagmus.
a hernia through the opening for the saphenous vein.
area bounded by the posterior border of the hyoglossus muscle, the posterior belly of the digastric, and the greater horn of the hyoid bone.
an automatic audiometer in which the test tone sweeps the frequency range while the patient controls intensity by pressing a button when the tone is heard and releases when tone cannot be heard; may be operated either at a fixed frequency or at steadily changing frequencies.
Alternate names: automatic audiometer
audiometry in which the subject controls increases and decreases in intensity at a fixed frequency or, more unusually, as the frequency of the stimulus is gradually changed so that the subject traces back and forth across the threshold of hearing.
Alternate names: automatic audiometry
an arteriovenous aneurysm in the tissues outside the injured vein.
a small fold in the interior of the lacrimal sac at its junction with the lacrimal duct.
Alternate names: Krause valve
premolar aplasia, hyperhidrosis, and premature canities; autosomal dominant trait.
a modification of the DMF caries index.
a condition characterized by mental deficiency, epilepsy, hypogonadism, hypometabolism, obesity, large ears, and narrow palpebral fissures; X-linked recessive inheritance.
cells of the basilar membrane of the cochlea.
small crystals observed microscopically in prostatic fluid that is treated with a drop or two of 1% solution of ammonium phosphate.
ganglion on the cochlear nerve in the internal acoustic meatus.
a cell-free extract of yeast, such as was prepared by Eduard and Hans Büchner who observed it to catalyze alcoholic fermentation; this observation essentially eliminated “vitalism” as being responsible for biologic chemical reactions and initiated the beginnings of modern biochemistry (enzymology).
a porcelain funnel that contains a perforated porcelain plate upon which filter paper can be laid.
obsolete term for idiopathic hyperlipemia.
a wedge of skin and subcutaneous fat excised, usually at the end of a closed wound and created by flap transfer or advancement, so that a smooth repair can be obtained.
a complex of three proteins associated with the B-cell receptor (CR2, CD19, and TAPA-1).
B-cell differentiation/growth factors
various substances, usually obtained from the supernatant of T-cell cultures, such as interleukins-4, -5, and -6. These substances are necessary for B-cell growth, maturation, and differentiation into plasma cells or B-memory cells.