This seems to be the main paper.
Feeding acetyl-L-carnitine and lipoic acid to old rats significantly improves metabolic function while decreasing oxidative stress
http://www.pnas.org/content/99/4/1870.full.pdf
Dr. Ames founded a company based on the ALA/ALC age reversal finding - juvenon
http://www.juvenon.com/about-us/the-science/
This paper has microscope photos of the differences in brain cells (scroll down)
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2790425/
Another paper by Ames on ALC/ALA w/r Cognition
http://www.pnas.org/content/99/4/2356.full.pdf
Another Ames paper
http://www.juvenon.com/pdfs/489car_vs_alcar.pdf
Non Ames paper that confirms the findings.
http://paperity.org/p/21857377/r-a-lipoic-acid-and-acetyl-l-carnitine-complementarily-promote-mitochondrial-biogenesis
Life Extension® Interview with Dr. Bruce Ames
http://www.lef.org/magazine/2011/8/interview-with-dr-bruce-ames/page-01