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coquina

Lets talk about the blood brain barrier

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What gets through?

Substances such as glucose, oxygen and certain ions.

Why?

Because they are small and necessary for the functioning of the brain. Substances such as cratinine, urea, chloride, insulin and sucrose pass through more slowly,

 

What doesn't get through?

Substances such as proteins and most antibiotics.

Why?

Because they are too large generally.

 

Capillaries in the brain are structurally different from those in other parts of the body. They are constructed of more densly packed endothelial cells than other capillaries and are surrounded by large numbers of neuroglia and a continuous basement membrane.

 

Substances that pass through are either very small, or have to be actively transported across the barrier by carrier molecules, except in the area of the hypothalamus and the roof of the fourth ventricle. In that area, the barrier either doesn't exist, or is less selective.

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I've been reading some articles about Alzheimer's Disease, there is some evidence that there is a problem with the blood-brain barrier.

 

http://www.alzheimersupport.com/library/showarticle.cfm/ID/2050/e/1/T/Alzheimers/

 

ST. LOUIS -- Alzheimer's disease may be caused by a problem transporting a certain protein across the blood brain barrier and out of the brain, according to new Saint Louis University research published in the October issue of Neuroscience.

 

The findings are important, says William A. Banks, M.D., a Saint Louis University professor and the lead author of the article, because they give us a new approach for treating Alzheimer's disease.

 

"It's going to be a big piece to solving the Alzheimer's disease puzzle," says Dr. Banks, a professor of geriatrics in the department of internal medicine and professor of pharmacological science at Saint Louis University School of Medicine. "If one could reverse the transport deficit problem, the system should be able to pump the protein out again. The impaired transporter problem may be an easier therapeutic target."

 

Normally, amyloid beta protein, the protein thought to cause Alzheimer's disease, leaves the brain and crosses the blood brain barrier, which is a wall of blood vessels that feed the brain and regulate the entry and exit of brain chemicals. But in persons with Alzheimer's disease, amyloid beta protein becomes blocked in the brain and can't make it across the blood brain barrier. The more amyloid beta protein accumulates, the tougher it is for the blood brain barrier to move it out, and the more disabled a person becomes.

 

Because the transport deficit causes the amyloid beta protein to

 

I gather that this amyloid beta protein is what causes the "plaques" found in the brains of A/D patients. Is this a protein that is normally able to cross into the brain? If so, the brain must use it for something, but you'd think it would undergo a chemical change and not come out the same as it went in.

 

I'm interested in knowing more about A/D because there seems to be a very strong genetic propensity for it in my dad's side of the family.

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I gather that this amyloid beta protein is what causes the "plaques" found in the brains of A/D patients. Is this a protein that is normally able to cross into the brain? If so, the brain must use it for something, but you'd think it would undergo a chemical change and not come out the same as it went in.

 

No. Beta-amyloid is formed when amyloid precursor protein (APP) which is a brain protein anyway, is abnormally broken down into shorter fragments. The problem comes when the amyloid can't be removed. It begins to build up and forms the plaques associated with AD.

 

There are literally hundreds of sites on the net, related to, if not devoted to Alzheimer's.

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I gather that this amyloid beta protein is what causes the "plaques" found in the brains of A/D patients.

 

amyloid beta is in plaques, but the primary component is a protein called Tau. There are lots of other proteins in the plaques too like ubiquitin and heat-shock proteins, but A-beta has gotten most of the attention in the past few years.

 

As for what crosses the BBB, dont forget anything that is lipid soluble will cross, they are just cells after all. The ones that come to mind are steroids, most ilicit drugs, alcohol and lots more.

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