Wikipedia

Alzheimer's disease

progressive, neurodegenerative disease characterized by memory loss

Alzheimer's Disease (AD) is a brain disease that slowly destroys brain cells. As of now, there is no cure for Alzheimer's disease. With time, the different symptoms of the disease become more marked. Many people die because of Alzheimer's disease. The disease affects different parts of the brain but has its worst effects on the areas of the brain that control memory, language, and thinking skills. Alzheimer's Disease is the most common form of senile dementia accounting for up to 70% of cases.

Alzheimer's disease
Other namesAlzheimer disease, Alzheimer's
Drawing comparing a normal aged brain (left) and the brain of a person with Alzheimer's (right). Characteristics that separate the two are pointed out.
Pronunciation
  • ˈaltshʌɪməz
Medical specialtyNeurology
SymptomsDifficulty in remembering recent events, problems with language, disorientation, mood swings
Usual onsetOver 65 years old
DurationLong term
CausesPoorly understood
Risk factorsGenetics, head injuries, depression, hypertension[1]
Diagnostic methodBased on symptoms and cognitive testing after ruling out other possible causes
Differential diagnosisNormal aging
MedicationAcetylcholinesterase inhibitors, NMDA receptor antagonists (small benefit)[2]
PrognosisLife expectancy 3–9 years
Frequency29.8 million (2015)
DeathsFor all dementias 1.9 million (2015)

The clinical symptoms of AD usually occurs after age 65, but changes in the brain which do not cause symptoms and are caused by Alzheimer's, may begin years or in some cases decades before. Although the symptoms of AD begin in older people it is not a normal part of aging.

At this time there is no cure for Alzheimer's, but there are treatments that can help some patients with the signs and symptoms so they do not affect them as badly. There are also treatments which slow down the disease so the damage to the brain does not happen as quickly. There are also certain personal habits that people can learn which may help to delay the onset of the disease.

While it is not yet known exactly what causes Alzheimer's disease, there are a number of risk factors which may make a person more likely to get it. Some of these risk factors are genetic; changes to four different genes have been found which increase the risk.

The current lifetime risk for a 65-year-old person to get Alzheimer's disease is estimated to be at 10.5%. It is the sixth leading cause of death in the United States causing about 83,500 deaths a year. In 2007, there were over 26.6 million people throughout the world who were affected by AD.[3]

Alzheimer's disease was named after Alois Alzheimer, a German psychiatrist and neuropathologist who first described the disease after studying the case of a middle-aged woman, Auguste Deter, who was a patient at a hospital in Frankfurt, Germany in 1906.[4] The disease was named Alzheimer's disease in 1910 by Dr. Emil Kraepilin a co-worker of Alzheimer.

Tangles and plaques

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The vesicles, which contain neurotransmitters, are brought to the end of the microtubule inside the neuron's (brain cell) axon to the synapse, to send a signal to the dendrite of the next neuron.
 
Tangles
The tau proteins holding the microtubules together undergo a chemical change called hyperphosphorylation. They now no longer hold the microtubule together.
 
The two strands 'walking' down the microtubule is a motor protein called kinesin. The kinesin is carrying a vesicle on top, with the neurotransmitters inside. It cannot finish its job because the microtubule has fallen apart. The pieces of hyperphosphorylated tau form tangles inside the neuron. The neuron eventually dies and the tangle is all that remains.
 
Plaque
Formation of 'plaque'. The beta-amyloid which extends out from the neuron is snipped and the pieces float in the spaces between the neurons and clump together to form a bundle of plaque. 

Two of the main features found in the brains of people with of Alzheimer's disease, are neurobrillary tangles ('tangles' for short), which are made up of a protein called tau, and senile plaques (which are made mostly from another protein called beta-amyloid, they are also sometimes called beta-amyloid bundles or 'bundles' for short). The tau proteins that form the tangles previously held together a structure inside the neurons called a microtubule which is an important part of the neuron; it forms part of the cytoskeleton (cell skeleton) which is what maintains a cell's shape, and microtubules plays a part in cell communication.[5]

Both tangles and plaques may be caused by other diseases, such as Herpes simplex virus Type 1 which is being investigated as a possible cause or contributor in developing Alzheimer's. It is not known for sure if tangles and plaques are part of what causes Alzheimer's, or if they are the results.

Microtubules  

Microtubules are made of a protein called tubulin. The tubulin is polymerized, which is when molecules form the same shapes over and over again that are linked together in groups, and these groups are linked together. They can form long chains or other shapes; in this case the polymerized tubulin forms microtubules. The microtubules are rigid tubes like microscopic straws which are hollow inside. Microtubules help keep the shape of the neuron, and are inolved in passing signals through the neuron.[6]

Tau  

Tau is a protein that is found mostly in the neurons of the central nervous system. They help hold together the microtubules within the neurons. and when changes happen in the way the tau proteins are supposed to work the microtubules break apart. The tau proteins which are no longer holding the microtubules together form strands called fibrils, which then clump together inside the neuron to make what are called neurofibrillary tangles . These clumps, also known as 'tau tangles', are all that remain after a neuron has died.[7]

Braak Staging of Alzheimer's disease-related neurofibrillary changes.
This is currently used only for research purposes[8]
Stage Neurofibrillary tangles in: Symptoms
I/II
Transentorhinal stage
 Transentorhinal region and entorhinal region No symptoms
III/IV

Limbic stage
 Hippocampal formation and parts of the limbic system and the amygdala Beginning Alzheimer's disease
Cognitive impairments: memory problems, spatial cognition
V/VI
Isocortical stage
 Throughout the cerebral cortex Dementia: fully developed Alzheimer's disease

Beta-amyloid  

Beta-amyloid(Aβ) (also called 'amyloid beta') plaques start with a protein called amyloid precursor protein (APP). APP is one of the proteins that make up a cell's membrane or outer covering, that protects the cell. In this case a neuron.. As it is made inside the cell, APP sticks out through the membrane of the cell.

 
The arterial wall has three layers. In cerebral amyloid angiopathy, beta-amyloid accumulates in the middle layer, the tunica media, and the outer layer, the tunica externa.
 
MRI scan showing Cerebral amyloid angiopathy. The beta-amyloid deposits show up as black 'dots' spread throughout the brain's outer layer, the cerebral cortex.

In different parts of the of cell including the outermost part of the cell membrane, chemicals called enzymes snip the APP into small pieces. These enzymes that do the snipping are alpha-secretase, beta-secretase, and gamma-secretase. Depending on which enzyme is doing the snipping and what parts of the APP are snipped, two different things can happen. One that is helpful and one that causes the formation of beta-amyloid plaques.

The plaques are formed when beta-secretase snips the APP molecule at one end of the beta-amyloid peptide, releasing sAPPβ from the cell. Gamma-secretase then cuts the pieces of APP that is left and, still sticking out of the neuron’s membrane, at the other end of the beta-amyloid peptide. After this snipping the beta-amyloid peptide is released into the space outside the neuron and begins to stick to other beta-amyloid peptides. These pieces stick together to form oligomers. Different oligomers of various sizes are now floating around in the spaces between the neurons, which may be responsible for reacting with receptors on neighboring cells and synapses, affecting their ability to function.

Some of these oligomers are cleared from the brain. Those that are not cleared out clump together with more pieces of beta-amyloid. As more pieces clump togther the oligomers get bigger larger, and the next size up are called protofibrils and the next size after that are called fibrils. After a while, these fibrils clump together with other protein molecules, neurons and non-nerve cells floating around in the space between the cells and form what are called plaques.

Cerebral amyloid angiopathy (CAA)

Deposits of beta-amyloid also form in the walls (in the tunica media, the middle layer, and tunica adventitia or tunica externa, the outer layer) of small and mid-sized arteries (and sometimes veins) in the cerebral cortex and the leptomeninges (the leptomeninges are the two inner layers - pia mater and arachnoid - of the meninges, a protective 3-layer membrane covering the brain.)

CAA is found in 30% of people over the age of 60 years who do not have any dementia but is found in 90%-96% of people with Alzheimer disease and is severe in one third to two thirds of these cases.[9]

Stages

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The first area of the brain to be affected by Alzheimer's is the "transentorhinal region"[10] which is part of the medial temporal lobe located deep within the brain. Neurons start dying in this area first. It then spreads into the adjacent entorhinal cortex (EC) which acts as a central hub, for a widespread network that handles signals for memory and movement[11](like a main train station with train tracks going to different areas).

 
The transentorhinal region, a narrow area of the medial temporal lobe is first affected by Alzheimer's disease, it then spreads to the area next to it in the temporal lobe; the entorhinal region (or entorhinal cortex).[8]

The EC is the main area for communication between the hippocampus, and the neocortex - which is the outer portion of the brain responsible for higher functioning such as how the brain perceives information from the five senses; (smell, sight, taste, touch and hearing; Ex. seeing a person's face and recognizing them,) generating motor commands (Ex, moving and arm or leg, walking, running) spatial reasoning, conscious thought and language.

The disease then spreads into the hippocampus which is part of the limbic system. The hippocampus is the part of the brain that is involved in forming new memories, organizing them, and storing them for later recall. It is also where emotions and senses, such as smell and sound are attached to specific memories. Example 1.: A memory might make you happy or sad. Example 2.: A smell might bring up a certain memory.

The hippocampus then sends memories to the different parts of the cerebral hemisphere where they are placed in long-term storage and it helps retrieve them when necessary. Example: An adult trying to remember the name of a classmate from kindergarten.

In addition to handling memory the hippocampus is also involved in emotional responses, navigation (getting around) and spatial orientation (knowing your sense of place as you move around Example: Knowing your way around your bedroom even with the lights off).

There are actually two parts of the hippocampus which is shaped like a horseshoe with one in the left part of the brain and the other in the right part of the brain.

Diagnosis

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This PiB-PET scan shows a lot of amyloid beta (Aβ) in the brain of a person with Alzheimer's. Pib stands for Pittsburgh compound B (PiB) which is a type of dye that is injected into a person before the scan is done. The amyloid beta absorbs the PiB; when the PET scan is done the areas where there is Pib fluoresces (glows) PiB-PET scans are now being used in research to detect amyloid beta (Aβ) in the preclinical phase (before there are any symptoms).

Preclinical

Red Blue Green Purple Orange
Purple Orange Green Blue Red

Blue Orange Purple Green Red
Purple Green Red Blue Orange

The Stroop Color–Word Test

This is a short example of the test. The test is used to measure different cognitive functions such as selective attention.

Naming the colors of the first set of words is easier and quicker than the second, because in the first set, the colors match the words, in the second set they do not. So a person has to pay more attention.

People having problems with attention as may happen in early-stage Alzheimer's tend to do poorly on this test.[12][13]

With current research using advances in neuroimaging such as FDG-PET and PIB-PET scans, and cerebrospinal fluid (CSF) assays, it is now possible to detect the beginning processes of Alzheimer's disease that occur before symptoms begin. The research suggests that clinically normal older people (no symptoms at all) have biomarker evidence of amyloid beta (Aβ) build-up in the brain. This amyloid beta (Aβ) is linked to changes in the structure of the brain and how it works that is the similar to what is seen in people with mild cognitive impairment (MCI) - which may lead to Alzheimer's - and people with Alzheimer's.

These small preclinical changes (no symptoms) in the brain may occur many years, to even a few decades before a person is diagnosed with Alzheimer's. With a stage where there is some memory loss, or mild cognitive impairment. These changes put a person at risk of developing the clinical symptoms of full-blown Alzheimer's but not everyone who has these changes will get the disease. Even though there is no cure for Alzheimer's, there are new treatments which are being developed which would work better in the very first stages of the disease.[14]

At this time exactly what makes up the preclinical phase of Alzheimer's is still being researched, such as why some people with go on to develop Alzheimer's and others do not. So the term preclinical phase is being used for research only. There is a worldwide effort in various countries doing research in this area known as the World Wide Alzheimer's Disease Neuroimaging Initiative (WW-ADNI) which is the umbrella organization for neuroimaging studies being carried out through the North American ADNI, European ADNI (E-ADNI), Japan ADNI, Australian ADNI (AIBL), Taiwan ADNI, Korea ADNI, China ADNI and Argentina ADNI.[15]

Beginning stages

"Misdiagnosis in very early stages of Alzheimer's is a significant problem, as there are more than 100 conditions that can mimic the disease. In people with mild memory complaints, our accuracy is barely better than chance," according to study researcher P. Murali Doraiswamy, MBBS, professor of psychiatry and medicine at Duke Medicine, "Given that the definitive gold standard for diagnosing Alzheimer's is autopsy, we need a better way to look into the brain."

History

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"I have lost myself, so to speak" .
This was how Auguste Deter, described what was happening to her. She was the first person to be diagnosed with what is now called Alzheimer's disease.
 
Alois Alzheimer

He conducted interviews with Auguste Deter at the hospital in Frankfurt when she was alive. And performed microscopic studies of her brain after she died.
 
"Irrenschloss"
(Castle of the Insane)
It was here at the City Asylum for the Insane and Epileptic, in Frankfurt am Main, Germany, where Auguste Deter was committed at age 51, only eight months after her symptoms began. She was the first person to be diagnosed, with what is now known as Alzheimer's disease, in her case the early-onset type.

In 1901, a 51-year-old woman named Auguste Deter, was committed to the City Asylum for the Insane and Epileptic, (Städtischen Anstalt für Irre und Epileptische) in Frankfurt am Main, Germany which had the nickname "Irrenschloss" (Castle of the Insane). She was married and had a normal life until eight months prior to her commitment, when she started having psychological and neurological problems, such as problems with memory and language, paranoia, becoming disorientated and having hallucinations.

She was studied by a doctor on staff named Alois Alzheimer (1864–1915). Alzheimer became interested in her case because of her age; while the effects of senile dementia were known at the time, they usually did not start until a person was in their early to mid-sixties. Her case was also notable because of the rapid onset of dementia, only eight months, from the first reported symptoms, until she was committed.

While conducting one of his examinations of Ms. Deter, he asked her to perform a series of simple writing tasks. Unable to do what was asked such as write her name, she said "I have lost myself, so to speak" ("Ich habe mich sozusagen selbst verloren").

Alzheimer left the hospital in Franfkurt in 1902 to begin working with Emil Kraepelin at the Psychiatric University Hospital in Heidelberg-Bergheim, and in 1903 both he and Kraepelin began working at Ludwig Maximilian University in Munich.

When Ms. Deter died of septicemia on 8 April 1906, Alzheimer was informed and her brain was sent to Munich for him to study. Studying samples of her brain under a microscope he noticed neurofibriallry tangles and bundles made up of beta-amyloid plaque, which are two of the main features of the disease. On 3 November 1906, Alzheimer presented the results of his findings in Auguste's case at the Conference of South-West German Psychiatrists in Tübingen, and he published his findings in the case in 1907.

In 1910, Emil Kraepelin named the disease 'Alzheimer's disease'. Alzheimer's disease usually beigins affecting people between ages 60–65, in Ms. Deter's case - who was 55-years-old when she died - she had a form of what is now known as Early-onset Alzhiemer's disease.[16]

Famous cases

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Ronald Reagan suffered from Alzheimer's for 10 years

Anyone can get Alzheimer's disease, rich people or poor famous people and unfamous people. Some of the famous people who have gotten Alzheimer's disease are former United States President Ronald Reagan and Irish writer Iris Murdoch, both of whom were the subjects of scientific articles examining how their cognitive capacities got worse with the disease.[17][18][19]

Other cases include the retired footballer Ferenc Puskás,[20] the former Prime Ministers Harold Wilson (United Kingdom) and Adolfo Suárez (Spain),[21][22] the actress Rita Hayworth,[23] the Nobel Prize-winner Raymond Davis, Jr.,[24] the actors Charlton Heston and Gene Wilder,[25][26] the novelist Terry Pratchett, politician and activist Sargent Shriver,[27][28] the Blues musician B.B. King,[29] director Jacques Rivette,[30] Indian politician George Fernandes,[31] and the 2009 Nobel Prize in Physics recipient Charles K. Kao.[32] In 2012, Nobel Prize writer Gabriel García Márquez was diagnosed with the disease.[33] Former Finnish President Mauno Koivisto died of the disease in May 2017.[34] Country singer Glen Campbell died of the disease in August 2017.[35]

References

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  1. ↑ Ballard C, Gauthier S, Corbett A, Brayne C, Aarsland D, Jones E (March 2011). "Alzheimer's disease". Lancet. 377 (9770): 1019–31. doi:10.1016/S0140-6736(10)61349-9. PMID 21371747. S2CID 20893019.
  2. ↑ Commission de la transparence (June 2012). "Drugs for Alzheimer's disease: best avoided. No therapeutic advantage" [Drugs for Alzheimer's disease: best avoided. No therapeutic advantage]. Prescrire International. 21 (128): 150. PMID 22822592.
  3. ↑ Brookmeyer R, Johnson E, Ziegler-Graha K, Arrighi HM. Forecasting the global burden of Alzheimer’s disease. Alzheimers Archived 2023-06-01 at the Wayback Machine Dementia. 2007;3:186–191. PMID 19595937
  4. ↑ "Alzheimer's Disease Fast Facts". CNN.com. August 23, 2013. Archived from the original on March 7, 2014. Retrieved February 5, 2014.
  5. ↑ Roger M. Nitsch. Neurodegenerative Diseases: Neurobiology, Pathogenesis and Therapeutics. Eds. by M. Flint Beal, Anthony E. Lang, Albert C. Ludolph Cambridge University Press; 1 edition (2005) pp.452-453. ISBN 052181166X
  6. ↑ Cooper GM: The Cell: A Molecular Approach. 2nd edition. Sunderland (MA): Sinauer Associates; 2000.[1] Archived 2019-10-29 at the Wayback Machine
  7. ↑ David Ames, Alistair Burns, John O'Brien: Dementia 3Ed ,(Hodder Arnold Publication), CRC Press; 3 edition (2005) pp.408-410. ISBN 0340812036
  8. ↑ 8.0 8.1 Braak H, Braak E. Staging of Alzheimer's disease-related neurofibrillary changes. Neurobiol Aging. 1995 May-Jun;16(3):271-8; discussion 278-84. PMID 7566337
  9. ↑ Weller RO, Preston SD, Subash M, Carare RO. Cerebral amyloid angiopathy in the aetiology and immunotherapy of Alzheimer Archived 2023-06-01 at the Wayback Machine disease. Alzheimers Res Ther. 2009 Oct 12;1(2):6. doi: 10.1186/alzrt6. PMID 19822028
  10. ↑ Taylor KI, Probst A. Anatomic localization of the transentorhinal region of the perirhinal cortex. Aging. 2008 Oct;29(10):1591-6. Epub 2007 May 2. PMID 17478012 [2] Archived 2011-03-31 at the Wayback Machine
  11. ↑ Mathias Jucke: Alzheimer: 100 Years and Beyond (Research and Perspectives in Alzheimer's Disease Archived 2023-06-01 at the Wayback Machine) Springer; 1 edition (November 16, 2006) p. 98; ISBN 3540376518
  12. ↑ G Binetti, E Magni, A Padovani et al. Executive dysfunction in early Alzheimer's disease. J Neurol Neurosurg Psychiatry. 1996 January; 60(1): 91–93. PMCID PMC486198 [3] Archived 2022-03-23 at the Wayback Machine
  13. ↑ Cognitive Neuropsychology Of Alzheimer's Disease. Eds. Robin G. Morris, James T. Becker. Oxford University Press, USA; 2 edition (2005) pp-109-110 ISBN 0198508301
  14. ↑ Sperling RA, Aisen PS, Beckett LA, et al. Toward defining the preclinical stages of Alzheimer's disease: recommendations from the National Institute on Aging-Alzheimer's Association workgroups on diagnostic guidelines for Alzheimer's disease. Dement. 2011 May;7(3):280-92. doi: 10.1016/j.jalz.2011.03.003. Epub 2011 Apr 21. PMID 21514248
  15. ↑ "World Wide Alzheimer's Disease Neuroimaging Initiative (WW-ADNI)". Archived from the original on 2016-07-01. Retrieved 2013-03-18.
  16. ↑ Shelley J. Allen: Neurobiology of Alzheimer's Disease (Molecular and Cellular Neurobiology) Oxford University Press, USA; 3 edition (2007) p.1 ISBN 0198566611
  17. ↑ Garrard P; Maloney LM; Hodges JR; Patterson K (February 2005). "The Effects of Very Early Alzheimer's Disease on the Characteristics of Writing by a Renowned Author". Brain. 128 (Pt 2): 250–60. doi:10.1093/brain/awh341. PMID 15574466. Archived from the original on 2006-06-29. Retrieved 2014-02-05.
  18. ↑ Sherman FT (September 2004). "Did President Reagan Have Mild cognitive Impairment While in Office? Living Longer with Alzheimer's Disease". Geriatrics. 59 (9): 11, 15. PMID 15461232. Archived from the original on 2012-12-15. Retrieved 2014-02-05.
  19. ↑ Venneri A; Forbes-Mckay KE; Shanks MF (April 2005). "Impoverishment of Spontaneous Language and the Prediction of Alzheimer's Disease". Brain. 128 (Pt 4): E27. doi:10.1093/brain/awh419. PMID 15788549.
  20. ↑ "Hungary Legend Puskas Dies at 79". BBC News. 2006-11-17. Archived from the original on 2011-08-25. Retrieved 2008-01-25.
  21. ↑ "Prime Ministers in History: Harold Wilson". London: 10 Downing Street. Archived from the original on 2008-08-25. Retrieved 2008-08-18.
  22. ↑ "Mi padre no reconoció al Rey pero notó el cariño". El País. Madrid. 2008. Archived from the original on 2011-08-25. Retrieved 2008-10-01.
  23. ↑ "Chicago Rita Hayworth Gala". Alzheimer's Association. 2007. Archived from the original on 2009-12-23. Retrieved 2010-02-03.
  24. ↑ David B. Caruso (2 June 2006). "Raymond Davis, who detected elusive solar particles, dies at 91". The Boston Globe. Archived from the original on 2018-12-25. Retrieved 2007-10-10.
  25. ↑ "Charlton Heston has Alzheimer's Symptoms". CNN. 2002-08-09. Archived from the original on 1 February 2008. Retrieved 2008-01-25.
  26. ↑ "Gene Wilder, star of Willy Wonka and Mel Brooks comedies, dies aged 83". Guardian. August 30, 2016. Archived from the original on September 7, 2016. Retrieved August 30, 2016.
  27. ↑ McFadden, Robert D. (January 18, 2011). "R. Sargent Shriver, Peace Corps Leader, Dies at 95". The New York Times. Archived from the original on 2012-01-15. Retrieved 2015-08-18.
  28. ↑ Pauli Michelle (2007-12-12). "Pratchett Announces He Has Alzheimer's". London: Guardian News and Media. Archived from the original on 29 September 2008. Retrieved 2008-08-18.
  29. ↑ "B.B. King Coroner's Report: No Evidence of Poisoning". Rollingstone.com. 14 July 2015. Archived from the original on 15 July 2015. Retrieved July 15, 2015.
  30. ↑ "Jacques Rivette, Enigmatic French New Wave Director, Dies at 87". New York Times.com. January 29, 2016. Archived from the original on March 23, 2017. Retrieved January 30, 2016.
  31. ↑ "George Fernandes Being treated for Alzheimer's by Yoga Guru Ramdev". Daily News and Analysis. 2010-01-19. Archived from the original on 22 January 2010. Retrieved 2010-01-19.
  32. ↑ "Nobel Winner Kao Coping with Fame and Alzheimer's". China Daily. 2009-10-09. Archived from the original on 24 January 2011. Retrieved 2011-02-06.
  33. ↑ Alexander, Harriet (7 June 2012). "Gabriel Garcia Marquez suffering from dementia". The Telegraph. Archived from the original on 7 April 2018. Retrieved 1 April 2018.
  34. ↑ "Mauno Koiviston terveys heikentyi alkuvuodesta – kaatuminen vei hoitokotiin" (in Finnish). Ilta-Sanomat. 12 May 2017. Archived from the original on 13 May 2017. Retrieved 12 May 2017.
  35. ↑ Doyle, Patrick. "Glen Campbell, 'Rhinestone Cowboy' Singer Who Fused Country and Pop, Dead at 81". Rolling Stone. Archived from the original on 2017-08-08. Retrieved 2017-08-30.

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