Joop,
I am not convinced that methylation has anything to do with the BBB theory that I have outlined. I have pointed out that levodopa can pass the BBB, whilst dopamine can't, and no methyl group is involved.
" How do you explain by methylation that whilst levodopa can pass a healthy BBB, dopamine can't. There is no methyl group involved here. The only difference is a molecule of carbon dioxide. The difference between the two compounds is very small, yet one can pass, the other can't."
You replied, "The difference between l-dopa and dopamine is a carboxyl-group (COOH)." However this is just repeating what I said, with no reference to methylation. There is no methyl group involved, levodopa is converted to dopamine by decarboxylation, ie losing a molecule of carbon dioxide, and this simple act is enough to convert the levodopa into a molecule, (dopamine), incapable of crossing the BBB.
I agree metals can be methylated, but have you references to show this enables them to cross the BBB. If when methylated, they can be proved to increase the permeability of the BBB, as well as exacerbating the symptoms of PD, then this will be relevant to what I am proposing. They can be added to the list of things which do this, eg pesticides, carbon monoxide, organophosphates, old age and stress.
It would be helpful if you if you could show your Dutch researcher this complete thread, and get his opinion on the possible correlation between BBB permeability and PD. Also, thanks again for your input, it is only by questioning an idea that we can progress.
Rick,
Thanks for your input also. There is a link with inflammation, and our favourite supplement(s) eg curcumin are also anti inflammatory in addition to reducing BBB permeability.
Most of the common supplements main function is as antioxidants, curcumin, alpha lipoic acid, glutathione etc., and I wondered by what mechanism they could be beneficial in reducing BBB permeability.
Then I read that the BBB is composed of molecules high in unsaturation and therefore susceptible to oxidation. The antioxidant supplements therefore probably protect the membrane from oxidation, since oxidation of the BBB increases its permeability. It all fits in.
I then found this paper.
http://www.msrc.co.uk/index.cfm?fuse...TOKEN=33116710

Experiments with animals have shown that there are three related chemicals, anthocyanosides, proanthocyanidins and procyanidolic oligomers, which strengthen the [Blood-Brain Barrier] BBB (Robert et al., 1977; Detre et al., 1986). These chemicals are found in blueberries, cherries, blackberries, grapes and the bark and needles of certain pine trees. They are currently available as encapsulated supplements called bilberry, grape seed extract and pycnogenol.

These supplements and/or substantial quantities of the above fruits should be ingested daily to help strengthen the BBB. The anthocyanosides and proanthocyanidins act as very powerful anti-oxidants, block enzyme actions and bind with the BBB and it is these properties which likely result in their beneficial effect on the BBB (see Stout essay for details).

The 3 related chemicals mentioned, anthocyanosides, proanthocyanidins and procyanidolic oligomers, are all strong antioxidants.
Ron