Untitled - D Ank Unlimited

amphiregulin 38 amyloid P component
nervous system disease characterized by progressive muscle
rigidity and painful spasms. Amphiphysin is a 125- to
128-kDa cytoplasmic, synaptic, vesicle-associated protein
expressed in neurons, certain types of endocrine cells, and
spermatocytes. Its biological function may involve synaptic
vesicle endocytosis. Autoantibodies to glutamic acid decarboxylase
(GAD) are detected in 60% of SMS. Amphiphysin
autoantibodies are present in SMS patients negative for
GAD autoantibody, all of whom are female breast cancer
patients. The amphiphysin autoepitope is present in the C
terminal region of the protein. Small-cell lung carcinoma
patients who present with paraneoplastic encephalomyelitis
have been reported to manifest immunoglobulin G (IgG)
autoantibodies against amphiphysin.
amphiregulin
A glycoprotein member of the epidermal growth factor
(EGF) family of proteins. The carboxyl terminal amino
acid residues of amphiregulin positions 46 to 84 share much
sequence homology with the EGF family. The actions of
amphiregulin are wide ranging and include the stimulation
of proliferation of certain tumor cell lines, fibroblasts,
and various other normal cells. These actions are mediated
by binding to EGF receptors possessing intrinsic tyrosine
kinase activity.
Amyloid
Medullary carcinoma of thyroid with amyloid deposits.
Amyloid fibril
composed of
paired pilaments
β-Pleated sheet
Amyloid.
Binding sites for
Congo red dye
amyloid
An extracellular, homogeneous eosinophilic material deposited
in various tissues in disease states designated as primary
and secondary amyloidosis. It is composed chiefly of protein
and shows a green birefringence when stained with Congo
red and observed by polarizing light microscopy. By electron
microscopy, the fibrillary appearance is characteristic.
Neoplastic cells
X-ray crystallography reveals a β-pleated sheet structure
arranged in an antiparallel fashion that gives the protein its
optical and staining properties. The amino termini of the
individual chains face opposite directions, and the chains are
bound by hydroxyl bonds. Amyloid consists of two principal
and several minor biochemical varieties. Pathogenetic
mechanisms for its deposition differ, although the deposited
protein appears similar from one form to another. Amyloid is
composed of nonbranching fibrils 7.5 to 10 nm wide and of
indefinite length. It also has a P component that is nonfibrillary,
is pentagonal in structure, and constitutes a minor
component. Chemically, amyloid falls into two principal
classes: AL, consisting of amyloid light chains, and AA
(amyloid-associated), comprising a nonimmunoglobulin protein
called AA. These molecules are antigenically different
and have dissimilar deposition patterns based on the clinical
situation. AL amyloid is comprised of whole immunoglobulin
light chains, their N terminal fragments, or a combination
of the two. Λ Light chains rather than κ are usually found in
AL. Proliferating immunoglobulin-producing B cells, as in
B cell dyscrasias, produce AL amyloid protein. AA amyloid
fibroprotein is not an immunoglobulin and has a molecular
weight of 8.5 kDa. Serum amyloid-associated (SAA) protein
is the serum precursor of AA amyloid. It constitutes the
protein constituent of a high density lipoprotein and acts
as an acute phase reactant. Thus, its level rises remarkably
within hours of an acute inflammatory response. AA protein
is the principal type of amyloid deposited in the tissues during
chronic inflammatory diseases. Several other distinct
amyloid proteins also exist.
amyloid fibrillosis
Every amyloid has a β-pleated sheet structure that accounts
for the ability of Congo red to stain it and the ability of
proteolytic enzymes to digest it. Refer also to amyloid and
amyloidosis.
amyloid P component
The P component has a molecular weight of 180 kDa. It
migrates in electrophoresis with the α globulin fraction,
and by electron microscopy reveals a pentagonal shape,
suggesting that it consists of subunits linked by hydrogen
bonds. It is a minor component of all amyloid deposits and
is nonfibrillar. It is a normal a 1 glycoprotein and has close
structural homology with the C-reactive protein. It has an
affinity for amyloid fibrils and accounts for their PAS positive
staining quality.
Amyloidosis: amyloid fibrils.