Amyloid Flashcards
(25 cards)
What is amyloid?
a class of insoluble abnormal protein deposits in tissue
What is amyloidosis?
disease condition where amyloid is deposited locally or systemically
Name the 2 classifications of amyloidosis
- systemic - involves more than one organ
2. localized - restricted to a single organ or tissue
How is amyloid identified grossly?
iodine-sulfuric acid method to stain amyloid deposits in tissue at necropsy
How is amyloid identified microscopically?
H&E stain
Congo red stain
Thioflavin S or T
What is the structure/composition of amyloid?
- fibrils
- protein secondary structure beta-pleated sheets
What is the significance of replacement of functional tissue with amyloid?
- physical compression of normal tissues resulting in atrophy
- disruption of normal structures and impaired function
Nomenclature of amyloid
“A” (for amyloid) followed by abbreviation for protein precursor (ex: AA, AL, etc.)
What is the significance of cytotoxic amyloid oligomers and/or fibrils?
- induce cell stress responses and apoptosis
Pathogenesis of amyloidosis
- increased production of precursor protein
- mutation in precursor protein resulting in more amyloidogenic form
- abnormal processing of precursor protein to form amyloidogenic polypeptides
Characteristics of AA (secondary/reactive) amyloidosis
- most serious systemic form in mammals and birds
- occurs secondary to recurrent or chronic disease
- increased hepatic synthesis of SAA
- macrophage degradation of SAA to amyloidogenic fragment
Clinical signs of systemic AA amyloidosis
- renal glomerulus problems
- marked proteinuria and renal failure
- hepatic failure may develop with severe liver involvement
Which gene mutation has recently been linked to Shar Pei AA amyloidosis?
HAS2 gene
What is the second form of canine amyloidosis?
- pulmonary vascular amyloid (most common systemic form)
- found in large proportion of aged dogs
- derived from apolipoprotein A1
what is the third form of canine amyloidosis?
- beta-protein derived (Alzheimer’s-like) cerebral amyloid
- associated with cognitive dysfunction
What is the first form of feline amyloidosis?
- systemic AA amyloidosis
- uncommon except in Abyssinian, Siamese, and Oriental short hair cats
- can cause hepatic failure and rupture
What is the second form of feline amyloidosis?
- islet amyloidosis
- long-standing insulin resistance results in increased production of IAPP
What form of diabetic cats have islet amyloidosis?
type 2 diabetics
What is the form of bovine amyloidosis?
- systemic AA amyloidosis
- involves renal (proteinuria) and/or GI tract (severe diarrhea)
- often associated with food abscesses and necrotizing pododermatitis
What are the two forms of equine amyloidosis?
- systemic AA amyloidosis (liver or GI involvement)
- localized AL form (nodular skin form or multinodular nasopharyngeal form)
Systemic AA amyloidosis can occur in which exotic wildlife species?
cheetahs
gazelles
black-footed cats
black-footed ferrets
What is the form of avian amyloidosis?
systemic AA amyloidosis (high incidence in waterfowl)
Features of AA amyloidosis in spleen
- multifocal white spots (involvement of white pulp)
- generalized enlargement of spleen (involvement of red pulp)
Features of AA amyloidosis in liver
hepatomegaly pale/yellow heavy friable atrophy of hepatic cords
