12 w old C57BL-6J & C57BL-6J-LepOb (obesity gene) exposed to either intermittent hypoxia (oxygen level drop 20.9% to 5%) over a 30 sec period and reoxygenized to 20% levels over a 30 sec period) or intermittent room air for 16 hours a day during 5 days. Lot batch =