Organ cultures were performed using Dulbecco’s minimal essential medium (Gibco BRL, Invitrogen, Cergy Pontoise, France) containing antibiotics (100 U ⁄ ml penicillin and 100 lg ⁄ ml streptomycin; Gibco BRL), 200 lg ⁄ ml l-glutamine (Gibco BRL), bovine pituitary extract, growth factors and foetal calf serum (Gibco BRL)