Animal experiments could become obsolete with the development of a transgenic mouse by Maria Sacco of Italian Institute of Advanced Biomedical Technologies in Milan, Italy. The mouse, sensitive to tiny amounts of toxic chemicals, could slash the number of rodents sacrificed during drug development. Companies test compounds on these animals for their toxic effects by exposing over 200 rodents to the chemical for as long as 13 weeks. Sacco monitored the activity of a gene linked to a heat-shock promoter that turns on nearby genes when a cell undergoes environmental stress. After inserting the hybrid gene into a mouse chromosome, Sacco found that small quantities of toxic chemicals could activate the promoter making the detection method sensitive enough to react to amounts of the chemical too low to make the animal ill (New Scientist , Vol 156, No 2112).