The role of ecdysteroids in the determination of gut-purge timing in the saturniid, Samia cynthia ricini
The role of ecdysteroids in the determination of gut-purge timing in the saturniid, Samia cynthia ricini
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蜕皮类固醇在决定蓖麻毒素肠道清除时间中的作用
DOI：
10.1016/0022-1910(82)90113-5
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发表时间：
1982
影响因子：
2.2
通讯作者：
H. Ishizaki
中科院分区：
文献类型：
--
作者：
M. Fujishita;E. Ohnishi;H. Ishizaki
在12小时光照和12小时暗光周期下，蓖麻蛾末龄(5龄)幼虫的血淋巴蜕皮类固醇滴度在肠道清洗前的早期暗期开始上升，这标志着幼虫-预蛹的转变，在肠道清洗前4.5小时达到峰值，滴度为7.6 ng/毫升。蜕皮激素增加的这一曲线是相移的，与肠道排泄相移的同时，伴随着肠道排泄前暗相的相移，这表明蜕皮激素的释放受决定肠道排泄时间的昼夜时钟的控制。正常灌肠前18小时注射蜕皮酮和20-羟基蜕皮酮(10-20μg)，8小时后出现明显的性早熟排泄峰。早期注射可加速肠道排泄，但加速程度无法预测。这些结果表明，蜕皮激素的定时激增是肠道清洗门控发生的原因，肠道清洗幼虫在暴露于足够的蜕皮激素激增的情况下，在肠道清洗幼虫获得以门控方式进行肠道清洗的能力之前18小时。
Under a 12-hr light and 12-hr dark photoperiod, haemolymph ecdysteroid titre of the last(5th)-instar larva ofSamia cynthia ricinibegins to rise in the early scotophase preceding gut purge, which marks the larval-prepupal transition, to reach a peak titre of 7.6 ng/mlca.4.5 hr before gut purge. This profile of ecdysteroid increment is phase-shifted in response to phase shifts of the scotophase immediately before gut purge, in parallel with gut-purge phase shifts, suggesting that ecdysone release is under the control of a circadian clock dictating gut-purge timing. Ecdysone and 20-hydroxyecdysone (10–20 μg), injected no later than 18 hr before the normal gate of gut purge induced well-defined peaks of precocious gut purgeca.8 hr after injection. Earlier injections caused acceleration of gut purge but the degree of acceleration was unpredictable. These results suggest that the timed surge of ecdysteroids is responsible for the gated occurrence of gut purge and that 18 hr before gut purge larvae acquire the competence to undergo gut purge in a gated fashion provided that they are exposed to a sufficient surge of ecdysteroids.