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A prion / ˈ p r iː ɒ n / ⓘ is a misfolded protein that induces misfolding in normal variants of the same protein, leading to cellular death.Prions are responsible for prion diseases, known as transmissible spongiform encephalopathy (TSEs), which are fatal and transmissible neurodegenerative diseases affecting both humans and animals.
PMCA was originally developed to, in vitro, mimic prion replication with a similar efficiency to the in vivo process, but with accelerated kinetics. [1] PMCA is conceptually analogous to the polymerase chain reaction - in both systems a template grows at the expense of a substrate in a cyclic reaction, combining growing and multiplication of the template units.
Prions multiply by causing normally folded proteins of the same type to take on their abnormal shape, which then go on to do the same, in a kind of chain reaction. These abnormal proteins are gradually accumulated in the body, especially in nerve cells, which subsequently die.
How viruses do this depends mainly on the type of nucleic acid DNA or RNA they contain, which is either one or the other but never both. Viruses cannot function or reproduce outside a cell, and are totally dependent on a host cell to survive. Most viruses are species specific, and related viruses typically only infect a narrow range of plants ...
When infected, the host cell is forced to rapidly produce thousands of identical copies of the original virus. Unlike most living things, viruses do not have cells that divide; new viruses assemble in the infected host cell. But unlike simpler infectious agents like prions, they contain genes, which allow them to mutate and evolve.
The subsequent demonstration that human prion diseases were transmissible reinforced the importance of spongiform change as a diagnostic feature, reflected in the use of the term "spongiform encephalopathy" for this group of disorders. Prions appear to be most infectious when in direct contact with affected tissues.
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A human pathogen is a pathogen (microbe or microorganism such as a virus, bacterium, prion, or fungus) that causes disease in humans. The human physiological defense against common pathogens (such as Pneumocystis) is mainly the responsibility of the immune system with help by some of the body's normal microbiota.