Creutzfeldt-Jakob Disease
What is Creutzfeldt-Jakob disease?
Creutzfeldt-Jacob disease is a rare yet fatal degenerative neurological disorder (brain disease). It is the most common form of ‘transmissible spongiform encephalopathy’ found in humans. Named after the two German neurologists, Hans Gerhard Creutzfeldt and Alfons Maria Jakob, who first described the disease in the 1920’s. After careful
observation the two neurologists realised that
the brains of patients who had died from the
disease had most of their nerve cells replaced
by fine fibres spotted with microscopic holes of that similar to of a sponge. 1, 2, 3
Symptoms and effects of CJD
There are many problems that arise when trying to correctly diagnose a person with CJD because firstly it has a very long incubation period, meaning a person may be infected with CJD for a long time before the disease kicks in or any of the tell-tale signs surface. The average incubation period for CJD is between 4 to 30 years; resulting in the possibility that many people are infected with the disease and are not aware of it. Another problem that arises is that the early signs of CJD are often misinterpreted for signs of mild depression as patients demonstrate mood swings and memory lapses, also they tend to lose interest in social activities and their ability to work becomes impaired. 3, 6
As the disease progresses however, they may lose sense of balance and become unsteady when trying to stand, there vision will deteriorate and speech patters will become slurred. This is because CJD attacks the nerve cells in brains and anything that is controlled by the brain meaning almost everything in the human body will cease to function correctly, such as eyesight, speech, movements etc. as predicted in the very late stages on the disease people tend to experience involuntary jerking limbs, tremors. They will also lose the ability to move or talk completely leaving them in a vegetated state. 3
So to sum up the symptoms:
-
Early stages – Mood wings, Memory lapses, Loss of interest in social activities, Impaired ability to work
-
Middle Stages – Loss of balance, Poor vision, Slurred speech
-
Late Stages – Loss of movement and speech completely, involuntary muscle contractions and jerking, Tremors
Cause of CJD
There were many speculations among neurologists of what is the actual cause of CJD until a U.S neurologist by the name of Stanley B. Prusiner proposed his theory on proteinaceous infectious particles (Shortened to Prions), the theory is that a prion is an infectious agent comprised purely of proteins. 7, 8, 9
Consuming beef infected wit the mad cow disease is believed to pass on the CJD into humans, it is actually believed that there are hereditary, infectious, and sporadic forms of the disease meaning that prions can arise by passing from generation to generation, it can be caught usually by consuming infected beef or it can appear randomly and suddenly for no reason in a perfectly healthy person.16
Structure of prions
Prions are compiled of purely proteins and the protein in question can be found throughout healthy human and animal bodies, it is called PrPC. however in prions the protein’s shape seems to have been altered, and is referred to as PrPSc. 9
Any protein is made up of various amino acids; there are 20 amino acids that occur naturally in proteins. The amino acids have a general structure of
These amino acids keep joining with other amino acids via condensation to form very long polypeptide chains, a protein is usually made up of 3 or 4 of these polypeptide chains. Each amino acid has a different side chain called the residual group, R. different interaction take place amongst these R groups causing the Chain to coil into either α-helices or β-pleated sheets, then finally to twist into a Three Dimensional Shape. 10
In PrPSc there seems to be more β-sheet’s replacing usual areas of α-helix that would
be found in the PrPC, resulting in the same protein however a completely different molecular structure.
What do prions do?
Prions convert PrPC proteins into complexes such as themselves PrPSc, these then convert further PrPC proteins resulting in a continuous and irreversible cycle. Eventually the continuous production of prions will result in cell death, this is because prions join up to create a form of plaque known as amyloids within the central nervous system. These plaque formations disrupt normal tissue structure this is expressed as holes in the tissue creating a sponge like architecture due to the destruction of neurones. 9
Methods to combat prions
Due to The very stable shape of the PrPSc molecule it is virtually indestructible; it is also resistant against proteases, an enzyme in the body whose job it is to break down proteins when the number of proteins becomes too great. This is because enzymes rely on a lock and key system to work, meaning they have particular shapes and attach themselves to the corresponding shape and break them down, as the prion has an abnormal shape the protease can not join itself to the prion. 16
The prion is also immune against ultraviolet radiation which is usually used to inactivate viruses by destroying their nucleic acid, but as the prion consists purely of protein the ultraviolet light is practically useless against it. 15
Research
Research led by John Collinge and Giovanna Mallucci of the MRC prion unit, University College London, UK, are breeding mutant mice that lack the prion protein. So far their results have shown that in mice that lack this protein, a similar disease to that of CJD ceases. Though the infected prion is still present in the mice, the mice seem to remain healthy while normal mice who carry the normal prion protein die the soon. 16
16
Further research is taking place in the area of blood and tonsils as they may act as an early warning sign of how many people are infected with CJD. This is because it is said that the tonsils of patients infected show symptoms of the disease before they die.
The research programme has begun collecting removed tonsils from the general public to gain an understanding of the extent of CJD.
Bovine Spongiform Encephalopathy
What is Bovine Spongiform Encephalopathy?
BSE like Creutzfeldt-Jacob disease is a member of the Transmissible spongiform encephalopathies family. Commonly known as ‘mad cow disease’ it is a fatal, neurodegenerative disease that occurs in cattle. It is very similar to CJD. In the United Kingdom around 180, 000 cattle became infected with the disease. 17
Symptoms of BSE
Symptoms of BSE are that almost identical to those found in humans:
- Loss of balance
- Memory loss
- Mood swings
- Change of attitude and behaviour
- Weight loss
- Loss of movement
Other symptoms include reduced production of milk etc. 17, 18
Causes of BSE
The BSE epidemic in the UK is said to have been started by feeding cows, who are usually herbivores remains of other cattle and sheep infected with BSE (in the case of sheep it is called scrapie) in the form of meat and bone meal as a protein supply. It is believed that though BSE can occur randomly or even through heritance the infectious method is the most common. 17
Like other spongiform encephalopathies it is not a virus but the notorious prion agent that kills the cow, Working in the same method as it does in humans. 17
Tackling BSE
It is widely believed that the disease can be transmitted to humans through the consumption of infected carcasses, resulting in the CJD the human version of the disease. Resulting in the death of 163 people in the UK and 37 from various other countries, though no reports were ever discovered in the United States. To quickly tackle the BSE problem exports and imports out of countries ceased, while in the UK under the eradication programme 4.4 million livestock were slaughtered. 17
Amyloids – A hard waxy deposit consisting of protein and polysaccharides that
results from the degeneration of tissue
Degenerative – deterioration in the medical sense. Generally, it is the change from a higher to a lower form. More specifically, it is the change of tissue to a lower or less functionally active form.
Hereditary – Something that is passed on through generations genetically.
Infectious Agent – an agent capable of producing infection
Nucleic Acid – Any of a group of complex compounds found in all living cells and viruses, composed of purines, pyrimidines, carbohydrates, and phosphoric acid. Nucleic acids in the form of DNA and RNA control cellular function and heredity.
Proteases – Any of various enzymes, including the endopeptidases and exopeptidases, which catalyze the hydrolytic breakdown of proteins into peptides or amino acids.
PrPC – is a normal protein found on the membranes of cells.
PrPSc – The infectious isoform of PrPC, known as PrPSc,
Sporadic – Occurring at irregular intervals; having no pattern or order in time.
Transmissible Spongiform Encephalopathy – One of a number of progressive neurodegenerative disorders in animals and humans caused by similar uncharacterized agents that produce spongiform changes in the brain.
- http://en.wikipedia.org/wiki/Creutzfeldt-Jakob_disease
- http://en.wikipedia.org/wiki/Creutzfeldt-Jakob_disease#History
- http://www.irishhealth.com/index.html?level=4&con=225
- http://www.gva.be/dossiers/-b/bse/img/hans.jpg
- http://www.uke.uni-hamburg.de/institute/neuropathologie/images_content/institut-neuropathologie/JAKOB.jpg
- http://news.bbc.co.uk/2/hi/health/1235241.stm
- http://en.wikipedia.org/wiki/Prion
- http://www-tech.mit.edu/V117/N48/nobel.48w.html
- http://en.wikipedia.org/wiki/Prion#Discovery
- SNAB
- http://opm.phar.umich.edu/images/proteins/2irg.gif
- http://employees.csbsju.edu/hjakubowski/classes/ch331/protstructure/antiparallelpleatedsheet.jpg
- http://www.rsc.org/education/teachers/learnnet/cfb/enzymes.htm
- http://webs.wichita.edu/mschneegurt/biol103/lecture16/lecture16.html
-
prion. (2008). In Encyclopædia Britannica. Retrieved April 21, 2008, from Encyclopædia Britannica Online: http://search.eb.com/eb/article-9061428
- http://news.bbc.co.uk/1/low/sci/tech/3228549.stm 16
- http://en.wikipedia.org/wiki/Bovine_spongiform_encephalopathy
18. http://www.emedicinehealth.com/
home > topics a-z list > mad cow disease and variant creutzfeldt-jakob dis
article
Last Editorial Review: 9/12/2005
-News.bb.co.uk-
I am aware that this is a news website and was fully aware during my research that since it is a media based website the information it holds is very likely to be tainted or bias, however whatever information I chose to extract from the website I compared with research I found from other more trust worthy sites and science journals, it either fitted in or matched the information on these other sources, therefore I regarded the information I extracted to be of that of value and valid.
-en.wikipedia.org-
I regarded the online wikipedia with great caution when using it for my research as I was aware that unqualified, random users can alter, change add and withdraw information on wikipedia. However as before I compared findings with already gathered information and though I will not classify the whole of wikipedia as a valid source I declare that the few bits of information I extracted from it are trust worthy.
-Salter Nuffield Advance Biology, AS Student Book, Published 2005-
I considered this to be a very strong source of information as it a text book used to teach students as level biology, and is therefore exam board approved.
-www.irishhealth.com-
this website provided useful information on the CJD diseases, I deemed it a valid source as it is dedicated to health and diseases and as it is going out to the public I am confident in thinking it holds no invalid information, hence accepting it as a valid source.
