Induction of Oocyte-Nurse Cell Differentiation in the Ovary by the Brain during the Initial Stage of Oogenesis in the Silkworm, Bombyx mori(Lepidoptera:Bombycidae)

Co-culture of ovarian cells in young larvae with brain induced meiosis and endomitosis of the silkworm, Bombyx mori. This suggests that a substance secreted by the brain controls meiosis and endomitosis. When preparations from Bombyx heads were tested for meiosisinducing activity, both the crude and highly purified preparations of bombyxin induced meiosis in vitro, but the crude preparation of prothoracicotropic hormone (PTTH) showed much lower activity. This indicates that bombyxin is the brain substance that induces meiosis. 20-Hydroxyecdysone also induced meiosis, but only at a low concentration.