AN ALLATOSTATIC FACTOR AND JUVENILE-HORMONE SYNTHESIS BY CORPORA ALLATA IN LOCUSTA-MIGRATORIA

The hemolymph juvenile hormone (JH) titer in sexually immature female adults of Locusta migratoria (Ibaraki strain, Japan) was lower than in sexually mature females; nevertheless, JH synthetic activity by the c orpora allata (CA) In vitro was considerably higher in immature female s than in sexually mature females (Okuda et al., 1996). We carried out experiments to explain this contradiction, The CA activity of sexuall y immature female adults was very low when the CA were incubated as a complex together with the corpora cardiaca (CC) and brain, when the sa me complex was assayed after cutting the nerve cord connecting the CC and CA (NCA1), JH synthesis by the CA was enhanced tenfold. When this pair of CA Was incubated in fresh medium without the CC and brain, JH synthesis was further increased. Therefore, the higher in-vitro JH pro duction by CA from immature female adults was the result of isolation of the CA from the brain and CC, A methanolic extract of brain-CC comp lexes contained a factor that inhibited JH synthetic activity by CA in vitro in both immature and mature insects, and this inhibition was re versible, The factor was heat-resistant but lost allatostatic activity after pronase digestion, These results indicate that the allatostatic factor is probably a heat-stable peptide. (C) 1997 Elsevier Science L td.