. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. ECDYSONE AND SPERMATOGENESIS 549 Cherbas, 1970), can obviously account for the long-lasting effects of even brief exposure to ecdysone (Table II). However, at the present time we are unable to state where this binding takes place in relation to the numerous cellular and mem- branous components of the testis walls. There is also insufficient information to decide whether the changes in penetrability involve the active or facilitated transport of MF, or the opening of channels for passive diffusion between cells. In the absenc
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. ECDYSONE AND SPERMATOGENESIS 549 Cherbas, 1970), can obviously account for the long-lasting effects of even brief exposure to ecdysone (Table II). However, at the present time we are unable to state where this binding takes place in relation to the numerous cellular and mem- branous components of the testis walls. There is also insufficient information to decide whether the changes in penetrability involve the active or facilitated transport of MF, or the opening of channels for passive diffusion between cells. In the absence of added ecdysone, the required level of ecdysone activity can be generated in vitro by the simultaneous culture of living, endocrinologically com- petent prothoracic glands (Tables V and VI). Since this activity failed to appear in the absence of activated prothoracic glands, these findings strongly support the view that the prothoracic glands synthesize and secrete one or more materials with ecdysone activity. The only reasonable alternative is that the prothoracic glands secrete an ecdysone precursor which can be converted into active hormone by the plasma or the reacting tissues—in this case the testis itself. We have observed that active prothoracic glands were ineffective when sonicated or homogenized. This implies that the synthesis and secretion of ecdysone are synchronized and that little hormone is stored within the prothoracic glands. On the basis of the calibration of the in vitro system (Table III) the "stored" ecdysone in a pair of active prothoracic glands can be equated to less than /*g a-ecdysone. As summarized in Tables V and VI, prothoracic glands which were known to be inactive in vivo were also inactive in vitro. However a most noteworthy finding was that inactive glands could be "turned on" by the addition to the culture of a living, endocrinologically competent brain. Our interpretation of the experiments reported here as wel
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
