Via Yahoo! News:
Researchers at Cornell University have created mice whose heart muscles are genetically engineered to fluoresce when the muscles contract. Junichi Nakai of the RIKEN Brain Science Institute in Wako-shi, Japan, developed the fluorescent molecule by modifying a green fluorescent protein (derived from bioluminescent jellyfish) and making it glow brightly enough to be observed in the working heart. The sensor molecule turns on and off like a switch in the presence of calcium; calcium concentrations in the muscle increase with each muscle contraction.Technorati Tags: mice, cardiology