sentence: Pituitary cells were dispersed as described previously [ 25 ] and cultured as mixed cells in medium 199 containing Earle 's salts ( Invitrogen , Carlsbad , CA ) , sodium bicarbonate , 10 % heatinactivated horse serum ( Invitrogen ) , penicillin ( 100 U / ml ) and streptomycin ( 100 µ g / ml ) .