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A
Not, without, -less; equivalent to L. in- and E. un-.
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A (adenine)
A (adenine): In genetics, A stands for
adenine, one
member of the A-T (adenine-thymine) base pair in DNA. The other base
pair in DNA is G-C (guanine-cytosine).
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A bands
the dark-staining anisotropic cross striations in the myofibrils of muscle fibers, comprising regions of overlapping thick (myosin) and thin (actin) filaments.
Alternate names: A discs, anisotropic discs, Q bands1, Q discs
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A bile
bile from the common duct.
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A cells
alpha cells of pancreas or of anterior lobe of hypophysis.
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A chain
the shorter polypeptide component of insulin containing 21 amino acyl residues, beginning with a glycyl residue (NH2-terminus); insulin consists of an A chain linked to a B chain by two disulfide bonds; the amino-acid composition of the A chain is a function of species;
in general, one of the polypeptides in a multiprotein complex.
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A fibers
myelinated nerve fibers in somatic nerves, measuring 1–22 mcm in diameter, conducting nerve impulses at a rate of 6–120 meters per second.
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A wave
the initial negative deflection in the electroretinogram, presumably reflecting retinal photoreceptor activity;
an atrial deflection in an electrogram recorded from within the atrium of the heart;
the first positive deflection of the atrial and venous pulses due to atrial systole.
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A−
Symbol for anion.
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a-
Not, without, -less; equivalent to L. in- and E. un-.
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A- (prefix)
A- (prefix): Prefix much employed in the
health
sciences indicating �not, without, -less� as, for example, in alexia
(not read),
aphagia (not eat), aphonia (not voice, voiceless). The �a-� usually
becomes �an-� before a vowel as, for example, in anemia
(without blood), anotia (no ear), anoxia (no oxygen). The prefix
�a-� comes from the Greek meaning �not.�
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a-c interval
the interval between the onset of the a wave and that of the c wave of the jugular pulse.
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A-DNA
a form of DNA in which the helix is right handed and the overall appearance is short and broad.
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A-E amputation
acronym for above-the-elbow amputation.
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A-K amputation
acronym for above-the-knee amputation.
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A-mode
In diagnostic ultrasound, a one-dimensional presentation of a reflected sound wave in which echo amplitude (A) is displayed along the vertical axis and echo delay (depth) along the horizontal axis; the echo information derives from tissue interfaces along a single line in the direction of the sound beam.
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A-P-C
Abbreviation for adenoidal-pharyngeal-conjunctival; antigen-presenting cells, under cell.
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A-pattern esotropia
convergent strabismus greater in upward than in downward gaze.
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A-pattern exotropia
divergent strabismus greater in downward than in upward gaze.
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A-strabismus
strabismus in which esotropia is more marked in looking upward than downward;
strabismus in which exotropia is more marked on looking downward than upward.
Alternate names: A-pattern strabismus
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A-V shunt
arteriovenous shunt.
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A-V strabismus syndrome
strabismus in which the angle of deviation is more marked on looking upward or downward.
See Also: A-pattern esotropia, V-pattern esotropia, A-pattern exotropia, V-pattern exotropia
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A-V valves
abbreviation for the cardiac atrioventricular valves; the mitral and tricuspid valves.
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A.B.C. process
purification of water or deodorization of sewage by a mixture of alum, blood, and charcoal.
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a.c.
Abbreviation for L. ante cibum, before a meal or ante cibos, before meals.
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A.D.
Abbreviation for auris dextra [L.], right ear.
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A.S.
Abbreviation for auris sinistra [L.], left ear.
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A.U.
Abbreviation for auris utraque [L.], each ear or both ears.
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A/T cloning
cloning of fragments in which the only overhanging (or uncomplemented) ends are the A or T bases; occurs often in use of specific enzymes to cut or make DNA fragments.
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A2 thalassemia
β thalassemia, heterozygous state.
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