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T1 - A hypothesis on prion disorders

T1 - Prion hypothesis

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Prion diseases in animals and man

Until recently, support for the hypothesis that the tertiary structure of PrPSc enciphers strain-specific information () was minimal, exceptfor the DY strain isolated from mink with transmissible encephalopathy(). PrPSc in DY prions showed diminished resistance to proteinase K digestionand greater truncation of the NH2-terminus. The DY strain presenteda puzzling anomaly because other prion strains exhibiting similarincubation times did not show this aberrant behavior of PrPSc (). Also notable was the generation of new strains duringpassage of prions through animals with different PrP genes (,).

A hypothesis on the etiopathogenesis of prion diseases

Determining how early in the incubation period PrPSc can be detected by immunological methods is complicated by the lack ofa reliable, sensitive, and relatively rapid bioassay. Mice inoculatedintracerebrally with BSE brain extracts require more than a yearto develop disease (). The number of inoculated animals developingdisease can vary over a wide range, depending on the titer ofthe inoculum, the structures of PrPC and PrPSc, and the structure of protein X (Table ). Some investigatorshave stated that transmission of BSE to mice is quite variable,with incubation periods exceeding 1 year (), while othersreport a low prion titer of 102.7 ID50 units per milliliter of 10% BSE brain homogenate ()compared with 107 to 109 ID50 units per milliliter in rodent brain (). Such problemswith the measurement of bovine prions demonstrate the urgent needfor Tg mice that are highly susceptible to bovine prions.

Prion hypothesis - Wikibooks, open books for an …

Table 1. The prion diseases.

Prusiner's pioneering work has opened new avenues for understanding thepathogenesis of more common dementia-type illnesses. For example, thereare indications that Alzheimer's disease is caused when certain, non-prion,proteins undergo a conformational change that leads to the formation ofharmful deposits or plaques in the brain. Prusiner's work has also establisheda theoretical basis for the treatment of prion diseases. It may be possibleto develop pharmacological agents that prevent the conversion of harmlessnormal prion proteins to the disease-causing prion conformation.

Without exception, all known prion diseases lead to the death of thoseaffected. There are, however, great variations in pre-symptomatic incubationtimes and how aggressively the disease progresses.

Prion Hypothesis: The end of the Controversy?

N2 - Prion diseases include a group of either sporadic, inherited or infectious disorders characterized by spongiform neurodegeneration and reactive glyosis in several brain regions. Whatever the origin, the neuropathological hallmark of prion diseases is the presence of brain aggregates containing an altered isoform of a cellular protein, named prion protein. Recent findings show the potential toxicity of the normal cellular prion protein, which occurs when its physiological metabolism is altered. In particular, several studies demonstrate that accumulation of the prion protein in the cytosol can be a consequence of an increased amount of misfolded prion proteins, a derangement of the correct protein trafficking or a reduced activity of the ubiquitin-proteasome system. The same effects can be a consequence of a mutation in the gene coding for the prion protein. In all these conditions, one assists to accumulation and self-replication of insoluble prion proteins which leads to a severe disease resembling what observed following typical "prion infections". This article provides an opinion aimed at reconciling the classic Prusiner's theory concerning the "prion concepts" with the present knowledge arising from experimental studies on neurodegenerative disorders, suggesting a few overlapping steps in the pathogenesis of these diseases.

Prion diseases include a group of either sporadic, inherited or infectious disorders characterized by spongiform neurodegeneration and reactive glyosis in several brain regions. Whatever the origin, the neuropathological hallmark of prion diseases is the presence of brain aggregates containing an altered isoform of a cellular protein, named prion protein. Recent findings show the potential toxicity of the normal cellular prion protein, which occurs when its physiological metabolism is altered. In particular, several studies demonstrate that accumulation of the prion protein in the cytosol can be a consequence of an increased amount of misfolded prion proteins, a derangement of the correct protein trafficking or a reduced activity of the ubiquitin-proteasome system. The same effects can be a consequence of a mutation in the gene coding for the prion protein. In all these conditions, one assists to accumulation and self-replication of insoluble prion proteins which leads to a severe disease resembling what observed following typical "prion infections". This article provides an opinion aimed at reconciling the classic Prusiner's theory concerning the "prion concepts" with the present knowledge arising from experimental studies on neurodegenerative disorders, suggesting a few overlapping steps in the pathogenesis of these diseases.

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  • The prion hypothesis in Parkinson's disease: Braak …

    Prion - Wikipedia

  • Prion hypothesis: the end of the controversy? - …

    Prion hypothesis: the end of the controversy?: …

  • The Prion Hypothesis of Parkinson’s Disease | …

    A timeline representation of the major milestones in the prion hypothesis

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Prion hypothesis proved? - The Lancet Neurology

Infectious particles possessing nucleic acid are dependent upon it to direct their continued replication. Prions however, are infectious by their effect on normal versions of the protein. Therefore, sterilizing prions involves the denaturation of the protein to a state where the molecule is no longer able to induce the abnormal folding of normal proteins. However, prions are generally quite resistant to denaturation by proteases, heat, radiation, and formalin treatments,[34] although their infectivity can be reduced by such treatments.

Prion Propagation - microbewiki

Bovine spongiform encephalopathy (BSE) and human Creutzfeldt-Jakob disease (CJD) are among the most notable central nervoussystem degenerative disorders caused by prions. CJD may presentas a sporadic, genetic, or infectious illness. Prions are transmissibleparticles that are devoid of nucleic acid and seem to be composedexclusively of a modified protein (PrPSc). The normal, cellular prion protein (PrPC) is converted into PrPSc through a posttranslational process during which it acquiresa high -sheet content. It is thought that BSE is a result ofcannibalism in which faulty industrial practices produced prion-contaminatedfeed for cattle. There is now considerable concern that bovineprions may have been passed to humans, resulting in a new formof CJD.

Prion Diseases and the BSE Crisis - Science | AAAS

Specific mutations within the prion gene give rise to structurally variantdisease-causing prion proteins. These structural prion variants accumulatein different regions of the brain. Dependent upon the region of the brainthat becomes infected, different symptoms, typical for the particular typeof disease are evident. When the cerebellum is infected the ability to coordinatebody movements declines. Memory and mental acuity are affected if the cerebralcortex is infected. Thalamus specific prions disturb sleep leading to insomnia,and prions infecting the brain stem primarily affect body movement.

15/11/2011 · Prion Diseases and the BSE Crisis ..

Kuru among the Fore-people in New Guinea was studied by CarletonGajdusek (recipient of the the 1976 Nobel Prize in Physiology or Medicine).Kuru was shown to be transmitted in connection with certain cannibalisticrituals and was thought to be due to an unidentified "slow virus".The infectious agent has now been identified as a prion. Duration of illnessfrom first symptoms to death: 3 to 12 months.

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