Prothoracic glands of tobacco hornworm larvae cultured
in vitro
secrete into the culture medium a substance which was active in ecdysone bioassays and determined to be ecdysone-like by radioimmunoassay. The prothoracic glands appear to be the sole source of this substance. The material was identified as α-ecdysone by thin-layer, gas-liquid, and high-resolution liquid chromatography and mass spectrometry. No other active moulting principles were present in the medium. It appears that the prothoracic gland secretes a prohormone, α-ecdysone, which is subsequently converted into the active moulting hormone, β-ecdysone, in other insect tissues.
The median neurosecretory cells of the pars intercerebralis of Iphita limbata seem to release two demonstrable components, probably representing allatotropin to the corpus allatum and myotropin to the aortic neurohemal site.
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