IN VITRO DEVELOPMENT OF INSECT TISSUES. II. THE ROLE OF ECDYSONE IN THE SPERMATOGENESIS OF SILKWORMS

¹ The Biological Laboratories, Harvard University, Cambridge, Massachusetts 02138

1. Germinal cysts, when removed from the testes and cultured in direct contact With the medium, undergo meiosis and spermatogenesis provided that a "macromolecular factor" (MF) is present.

2. By contrast, spermatogenesis within intact testes derived from either normal or injured pupae requires the presence, not only of MF, but also of ecdysone. The same is true for spermatogenesis in vivo.

3. The critical effects on the testes were exerted by concentrations of -ecdysone as low as 2 x 10^-7 M. The effects were shown to be specific for -ecdysone, -ecdysone, and phytoecdysones known to be highly active in vivo.

4. When MF and ecdysone were administered sequentially to cultures of intact testes, spermatogenesis took place only when the exposure to ecdysone preceded the exposure to MF.

5. The ecdysone requirement can be satisfied by the simultaneous culture of a pair of living, activated prothoracic glands. The glands were ineffective when homogenized or killed by sonication.

6. Prothoracic glands known to be inactive in vivo were also inactive in vitro. However, they could be "turned on" in vitro by the addition to the cultures of pupal brains known to be competent to secrete brain hormone.

7. These results strongly support the view that the prothoracic glands are activated by brain hormone to synthesize and secrete one or more materials with ecdysone activity.

8. Present indications are that ecdysone plays a permissive role in spermatogenesis and that its sole function is to alter the penetrability of the testis walls and thereby facilitate the entry of MF and perhaps other blood-borne molecules into contact with the germinal cysts.

9. Consideration is given to the possibility that the permissive role of ecdysone may not be an exclusive property of the testicular system.

This article has been cited by other articles:

				H. Chino, S. Sakurai, T. Ohtaki, N. Ikekawa, H. Miyazaki, M. Ishibashi, and H. Abuki Biosynthesis of agr-Ecdysone by Prothoracic Glands in vitro Science, February 8, 1974; 183(4124): 529 - 530. [Abstract] [PDF]