BIOL123 - L6

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  • Created by: Katherine
  • Created on: 02-06-16 11:12
What are prion diesases?
Spongiform encephalopathies
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What are they?
A family of rare, progressive neurodegenerative disorders that affect humans and animals. Distinguished by long incubation periods, characteristic spongiform changes associated with neuronal loss, and a failure to induce inflammatory response.
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What do these changes result in?
Loss of motor control, dementia, paralysis, death.
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What is a prion?
A proteinaceous infective particle. They have physical properties unlike any other biological agent. No virus has been casually associated with prions.
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What is the edidence for the infectious agent being a protein?
It is radiation resistant extreme resistance to UV), Very heat stable (denatured by 134'C), It is nuclease resistant (resistant to DNAse and RNAse - these degrate nucelic acids) it is sensitive to protein modification agents (SDS)
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What is the prion protein?
PrPc
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Prion diseases show the cnversion of a helix rich normal prion protein into a misfolded B sheet rich protein, which is this important?
Folded = increased detergent insolubility, aggregation of proteins into stable, proteinase - resistant to plaques and fibrils, Neuronal cell death and spongiform changes in the brain.
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WHat is the main issue associated with prion diseases?
Protein misfolding and protein aggregation.
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What are the 2 mechanisms of prion mediated neuronal degeneration that are not fully understood?
Loss of function, PrPc functions as a Cu binding protein and protects synapses from oxidative damage. Gain of function - prion mediated neuronal degeneration caused by increase PrPsc neurotoxicity.
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What do PrP knockout mcie show?
Relatively little phenotypic effect - toher than inabiltiy to propagate prions
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What are the subtle abnormalities of these mice?
Altered circadians rhythms and olfaction, abnormal neural transmission and electrial activity, defective proliferaiton and differentiation of neural precursor cells. Increased sensitivity to hypoxia, ischemia and seizures. Enhanced resistance to infe
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What are the 4 types of prion diseases?
Sporadic, familial or inherited, latrogenic, transmissible.
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Give an exmaple of a prion disease?
GSS - It is a rate neurodegenerative disease that affects patients rangiing from 20 - 60. The disease is characterised by adult onset of memory loss, dementia, ataxia and pathologic deposition of amyloid like plaques in the brain.
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What is the mutation that causes GSS?
P102L. Pathogentic mutations enhance the rate of spontaneous conversion of PrPc to PrPsc Mutations disrupt the secondary structure of the molecule. Mutations davour switch.
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What is Latrogenic CJD spread by?
Surgical equipment. Or pituitary growth hormones extracted from human corpses that had CJD.
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What is TSE?
Transmissible spongiform Encephalopahy
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What is TSE?
A slow developing virus (long incubation period). Caused by tribal cannibalism.
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The BSE evidemic effected over ... cattle?
180,000
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The cost of BSE epidemic in UL was over...
£4 billion.
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How is variant CJD caused?
By consuming meat from cows infected with bovine spongidorm encephalopathy also known as mad cow disease.
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How long is the incubation period of vCJD?
Very long, could be over 10 years. It can be tranmitted by blood transfusions.
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What is CWD?
Chronic wasting disease
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What are the hosts of this disease?
Mule deer, white tailed deer, elk and moose. It was an endemic in colorado.
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How is CWD transmitted?
By intra-cerebral injection to mice, ferrets, mink, squirrel monkeys and goats. It is in humans who have eaten the deer.
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Is CDJ contageous?
Latrogenically, e.g. cannibalism of VCJD. But there is no evidence that it can be spread through day to day contact.
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Species barrier to transmission .
The is efficeint transmission from hamster to hamster to other hamsters or to a transgenic mous with hamster PrP genes.
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Can it be infectious?
Most studies involve injecting tissue directly into the brain, but oral exposure is less effective.
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Why is oral exposure difficulat?
Injected prions need to travel from the gut to the brain. Specialised epithelial cells (M cells) capture antigen from gut lumen - transport it to mucosal lymphoid tisue. Prions are phagotysed by lymphoic cells. Travle to lymph nodes and spleen.
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What is SCID?
Sevvere combined immunodeficieny - genetically deficient immune system - lack both T and B lymphocytes.
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What are SCID mice resistant to?
Peripheral prion challenege, this explains the importancce of the lymphoid system in the spread of prion dieases.
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SDIC mice can be infected by direct injection of prions into the brain, this condims...
That the immune system plays no role in generation of disease. Additionally, there is no inflammation around encephalophath lesions = not an autoimmun disease.
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The magnitude of the VCJD problem in the UK will depend on?
Magnitude of species barrier, average infectious does. Incubation period.
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What is the prevalence f VCJD infection in UK?
1:4000
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Asymptomatic individuals with VCDJ prion infections pose risk to others via blood transfusion, blood products, organ or
tissues graphs.
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How can prion diease be foun?
There is a new blood based assay developed to detect prion infections.
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What are they?

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A family of rare, progressive neurodegenerative disorders that affect humans and animals. Distinguished by long incubation periods, characteristic spongiform changes associated with neuronal loss, and a failure to induce inflammatory response.

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What do these changes result in?

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Card 4

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What is a prion?

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Card 5

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What is the edidence for the infectious agent being a protein?

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