refers to a variety of conditionsmyloidosisA+
andinsolublebecomeproteinswherein normally soluble
ofextracellular spaceare deposited in the
The, disrupting normal function.tissuesororgansvarious
insoluble fibrous protein aggregates that develop in
. They result from aamyloidsown asamyloidosis are kn
, which causessecondary structurechange in the protein's
otein to take on a particular aggregated insolublethe pr
.pleated sheet-betaform, similar to the
+Amyloid is a starch like substance which stains brown/
blue/ black with iodine. Dog and horse are often
affected naturally than other animals.
+ Organs affected:
• Liver, kidney and spleen are frequently
• In progressive form all organs can be affected.
occurring as a
of some other
Native cells have two different methods of making+
different proteins. Some proteins cells make the whole
protein in one piece; for other proteins, cells make only
protein fragments, and the fragments come and join
ch a protein cantogether to form the whole protein. But su
sometimes fall apart into the original protein fragments.
This process of "flip flopping" happens frequently for
certain protein types, especially the ones that cause
+The fragments or actual proteins are at risk of mis-
folding as they are synthesized, to make a bad protein.
This causes proteolysis, which is the directed degradation
of proteins by cellular enzymes called proteases or by
intramolecular digestion; proteases come and digest the
mis-folded fragments and proteins. The problem occurs
when the proteins do not dissolve in proteolysis. This
happens because the mis-folded proteins sometimes
become robust enough that they are not dissolved by
normal proteolysis. When the fragments do not dissolve,
they get spit out of proteolysis and they aggregate to
form oligomers. The reason they aggregate is that the
parts of the protein that do not dissolve in proteolysis are
the β-pleated sheets, which are extremely hydrophobic.
They are usually sequestered in the middle of the protein,
while parts of the protein that are more soluble are found
near the outside. When they are exposed to water, these
hydrophobic pieces tend to aggregate with other
hydrophobic pieces. This ball of fragments gets stabilized
by GAG's (glycosaminoglycans) and SAP (serum amyloid
P), a component found in amyloid aggregations that is
thought to stabilize them and prevent proteolytic cleavage.
The stabilized balls of protein fragments are
called oligomers. The oligomers can aggregate together
and further stabilize to make amyloid fibrils.
Both the oligomers and amyloid fibrils can cause cell
toxicity and organ dysfunction.
-Grossly the liver cut surface
pale,waxy corresponding to the
abundant amorphous, light
esinophilic amyloid deposits.
- The deposits may cause moderate to
marked hepatomegaly, fraible and
may be end by rupture
Amyloid appears first in the space of Disse
and then progressively encroaches on
adjacent hepatic parenchymal cells and
sinusoids. In time, deformity, pressure
atrophy, and disappearance of
hepatocytes occur, causing total
replacement of large areas of liver
Macroscopic pale and shrunken because of
ischemia caused by vascular
narrowing induced by the deposition
of amyloid within capillaries wall.
Microscopic the amyloid is deposited primarily in
the glomeruli, but the interstitial
peritubular capillaries are also