. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. Reference : Biol Bull, 138 : 326-333. (June, 1970). INACTIVATION OF «-ECDYSONE AND CYASTERONE BY LARVAE OF THE FLESHFLY, SARCOPHAGA PEREGRIN A, AND PUPAE OF THE SILKWORM, SAMIA CYNTHIA 1 TETSUYA OHTAKI - AND CARROLL M. WILLIAMS The Biological Laboratories, Harvard University, Cambridge, Massachusetts 02138 Certain weeds, ferns, and evergreen trees contain complicated sterols closely resembling the insect hormones, a- and /?-ecdysones (Fig. 1). When injected into insects, many of these so called "phytoecdysones" hav
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. Reference : Biol Bull, 138 : 326-333. (June, 1970). INACTIVATION OF «-ECDYSONE AND CYASTERONE BY LARVAE OF THE FLESHFLY, SARCOPHAGA PEREGRIN A, AND PUPAE OF THE SILKWORM, SAMIA CYNTHIA 1 TETSUYA OHTAKI - AND CARROLL M. WILLIAMS The Biological Laboratories, Harvard University, Cambridge, Massachusetts 02138 Certain weeds, ferns, and evergreen trees contain complicated sterols closely resembling the insect hormones, a- and /?-ecdysones (Fig. 1). When injected into insects, many of these so called "phytoecdysones" have proved to be more active than the insects' own hormones. A case-in-point is cyasterone, a phytoecdysone which Takemoto, Hikino, Nomoto and Hikino (1967) isolated from the roots of Cyathula capitata (Ama- ranthaceae). As shown in Figure 1, cyasterone is characterized by the presence of a lactone ring at the end of its side-chain. When assayed on mature larvae of the flesh fly, Sarcophaga peregrina, cyasterone was twice as active as a-ecdysone (Ohtaki, Milkman and Williams, 1967). In assays on the bee, Nomia melanderi, it was 10 times as active (Hsiao and Hsiao, 1969). In assays on pupae of the silkworm, Sauiia cynthia, it was 20 times as active as a-ecdysone and 40 times as active as /3-ecdysone (Williams, 1968).. a-Ecdysone /3-Ecdysone Cyasterone FIGURE 1. Structural formulae of the authentic hormones, a- and /3-ecdysones, and the phytoecdysone, cyasterone. The stereochemistry of the side-chain is known only for a-ecdy- sone. The greater potency of the hormonal analogue is a phenomenon well known to students of mammalian endocrinology. Especially in the case of the sterol hor- mones of the gonads and adrenal cortex, amplification of activity has frequently been achieved by chemical modifications of the authentic hormones. The enhanced activity can often be accounted for in terms of the greater resistance of the ana- logues to enzymes attacking the native hormone (Steelman an
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