Americans Robert Lefkowitz and Brian Kobilka have won the 2012 Nobel Prize in chemistry for studies of proteins that let body cells respond to signals from the outside.

Scientists from Britain and Japan shared a Nobel prize yesterday for the discovery that adult cells can be transformed back into embryo-like stem cells that may one day regrow tissue in damaged brains, hearts or other organs.

British researcher John Gurdon and Shinya Yamanaka of Japan have won this year’s Nobel Prize in medicine or physiology.