ACTIVATORY MECHANISMS OF THE PROTHORACIC GLANDS OF MONEMA FLAVESCENS (LEPIDOPTERA) WITH SPECIAL REFERENCE TO THE SECRETION OF ECDYSONE

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Abstract
The problem of hormonal secretion with special reference to the synthesis of ecdysone in the prothoracic glands of M. flavescens was investigated. Initial secretory activity of the prothoracic glands is characterized by increased cell and nuclear volume and extensive nuclear folding. Cholesterol molecules are incorporated into the cytoplasm. They are transferred from the agranular-ER [endoplasmic reticulum] to the mitochondria and incorporated into the secretory granules of the mitochondria. In the course of transfer, cholesterol molecules are elaborated into ecdysone precursor. After breaking the mitochondrial sheath, the secretory material breaks down in the cytoplasm and is released through microvilli to the hemolymph. At that time, the precursor of ecdysone is elaborated to .alpha.-ecdysone and is then secreted into the hemolymph where .alpha.-ecdysone is converted to the .beta.-form. The prothoracic glands synthesize ecdysones from cholesterol and secrete them in vitro and in vivo.