| featuring updated 4:55 p.m. ET April 21, 2008 in Keith Srakocic / APAs the Pennsylvania primary nears, Democratic rivals are doing a lot of talking — both in person and in a crescendo of TV ads.  David Friedman / msnbc.comMainstream M.D.s who once shunned the snake oil of the anti-aging movement are now buying in. Though short on science to back it, the anti-aging business is booming.  Other vehicle sales struggling.  CategoriesBrowseMarketplacevia MSN ShoppingEntrepreneur.comvia PerfectMatch.comvia HomePages.com $7 online stock trades via Monster via MSN Autos Shortcuts You don't appear to have javascript enabled. Some parts of msnbc.com may not display correctly. Javascript allows for features such as personalization and a customized layout based on your interests. . ExploreOther top stories  | Only on msnbc.comTODAY Mary Ann Chastain / AP Top video stories Video  Video Video Video TODAYVideo Video Video Slide showsMary Ann Chastain / APMiramaxSlide show Tony Gutierrez / APSlide show Bernadette Tuazon / APSlide show Matt Cardy / Getty ImagesSlide show Julie Jacobson / APSlide show FoxSlide show Steve Helber / AP...