Leptin levels in human and rodent: measurement of plasma leptin and ob RNA in obese and weight-reduced subject. - Maffei,M.; Halaas,J.; Ravussin,E.; Pratley,R.E.; Lee,G.H.; Zhang,Y.; Fei,H.; Kim,S.; Lallone,R.; Ranganathan,S. (Nature Med, 1995)