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PrefaceEcdysone is an outsider among steroid hormones. It is a latecomer to the steroid family, having been isolated in 1954 and identified as a steroid in 1963. However, it is the most widespread steroid hormone in nature. Surprisingly, textbooks of endocrinology often ignore ecdysone, although studies on ecdysone have contributed significantly to scientific progress, e.g. by the development of the "Faltmolekiil-Methode" for the X-ray analysis of complex molecules of Walter Hoppe and Robert Huber. Another example are the experiments by Ul-rich Clever and Peter Karlson with Chironomus larvae. They showed the way to the understanding of the mode of action of steroid hormones and other lipophilic signal substances in general. Compared to the vertebrate-type steroids, however, there is still a grievous lack of knowledge about many aspects of ecdysone endocrinology.This book appears in the hope that this information gap can be filled. In order to catch up a litde with the sister steroids, a truly international team of 77 "ecdysonists" from five continents has tried here to provide an up-to-date summary of our knowledge of ecdysone. As can be seen from the diverse and often colorful reviews, the authors have quite different points of view, reflecting their individual personalities and approaches to the topic. I thank them for their excellent manuscripts, and for their diligence and patience during the preparation of the book.The chapters cover different fields of research on ecdysteroids, including chemistry, analytics, biochemistry, molecular biology, genetics, and endocrinology, as well as biology. The reader will be able to use the book as an up-to-date (1988/1989) reference of structures and literature, as well as a source of information on his or her special interests.In 1978, a group of authors proposed a generic term for ecdysone and ecdysone-like compounds: "ecdysteroids" were defined as "all compounds structurally related to ecdysone". In their article on phytoecdysteroids (chapter 4, page 39), René Lafont and Dennis Horn introduce a more precise definition based on chemical criteria. They distinguish between "true ecdysteroids" and "ecdysteroid-related compounds". True ecdysteroids are defined as "compounds where the steroid nucleus bears a cw-fused A/B ring junction, a 7-ene-6-one chromophore and a 14a-OH (irrespective of a molting hormone assay)". Ecdysteroid-related compounds "do not fulfill all the above criteria". We will see whether this new definition will be accepted by the community of ecdysonists.The idea for this book was born during preparation of the Vlllth Ecdysone Workshop 1987 in Marburg, FRG, which was held to honor Peter Karison on the occasion of his retirement. I gratefully acknowledge that Jules Hoffmann contributed significantly to the final decision to proceed with this project. He was successful with the help of two bottles of remarkable Gewiirztraminer which we enjoyed in Andlau. Alsace. Especially, 1 would like to thank Gerd Käuser, who not only helped to conceive the book but also took part in all aspects of its realization. His contribution was flavored with a characteristic but always constructive criticism. With pleasure 1 acknowledge the generous support of the project by the Thieme Verlag.Finally, it is with considerable regret that 1 have to report the untimely death of our respected colleague and coauthor Tetsuiji Kame-tani.Jan Koolman