What Peg had done, a retinal cell transplant, not a "stem cell transplant"! And what's this about mucuna pruriens "making dopamine naturally? Mucuna IS a crude mixture of L-dopa and it's transformation to dopamine is no more "natural" than the transformation of L-dopa in sinemet into dopamine. The dopa decarboxylase enzyme works on both substrates because they are the same molecule ! And I've said it before, mucuna is not as good as sinemet because it does not contain the ingredient that inhibits the transformation of dopa to dopamine outside of the brain. Before there were such "peripheral decarboxylase enzyme inhibitors", the drug was marketed as "Laradopa", which is just sinemet without the carbidopa PDE inhibitor. THis gave lots more side effects because dopamine is, like the closely related tyramine, a heart stimulant, and not to be present in high concentrations outside the brain.
I'm sure that most of us have heard about the "cheese effect", that is , when a person is given a monoamine-A oxidase inhibitor (the first kind of effective antidepressants) if they eat food high in tyrosine (an amino acid), peripheral decarboxylase enzymes produce too much tyramine, and a very unpleasant syndrome ensues. This is also why they warn us not to take more than 10mg of Selegiline or 2mg of Azilect/ day, because these drugs which are selective monoamine-B inhibitors (allow more dopamine from being broken down in the brain synapses where it is needed) into a monoamine -A inhibitor which can cause a "cheese effect" like result.
Getting off topic here, but my point is that retinal cells have been shown to become dopamine producers when transplanted to the substantia nigral area of the brainstem. Somehow these cells obey an "order" to morph into dopamine producers, but at this point we don't know how efficient they are at doing this. Real "stem cells" which can be bioengineered to be even closer to real nigral neurons, which are what we need. THis CAN BE DONE! This is what we are all waiting for. WHY DON"T THE LITTLE DOGGIES JUST GIT ALONG AND DO IT.
PLEASE, give us PWP a break and get on with the right surgical intervention experiments. cs