Dai J D, Gilbert L I
Department of Biology, University of North Carolina, Chapel Hill 27599-3280, USA.
Cell Tissue Res. 1999 Aug;297(2):319-27. doi: 10.1007/s004410051360.
The prothoracic glands of the tobacco hornworm, Manduca sexta, secrete the precursor of the insect molting hormone and normally undergo programmed cell death (PCD) during pupal-adult metamorphosis, between days 5 and 6 after pupation. This phenomenon can be elicited prematurely in vitro by the addition of 20-hydroxyecdysone (20E) to the gland cultures. To induce nuclear condensation in vitro in the glands from day-1 pupae, the effective dose range of 20E is 0.7-7 micrograms/ml and the minimum exposure period is 24 h. Prothoracic glands from different stages of pupal-adult development express different responsiveness to exogenous ecdysteroids. By utilizing terminal deoxynucleotidyl-transferase-mediated dUTP nick-end-labeling (TUNEL) and the apoptotic DNA laddering method together with transmission electron microscopy, it has been demonstrated that the ecdysteroid-induced cell death of the prothoracic glands occurs via not only apoptosis but also autophagy, i.e., the induced dying cells show both severe nuclear fragmentation and autophagic vacuole formation, characteristics typical of apoptotic and autophagic cell death. The composite data indicate that ecdysteroids regulate directly both apoptotic and autophagic mechanisms of PCD of the prothoracic glands.
烟草天蛾（烟草天蛾，即烟草夜蛾）的前胸腺分泌昆虫蜕皮激素的前体，并且通常在化蛹后第5至6天的蛹 - 成虫变态期间经历程序性细胞死亡（PCD）。通过在腺体培养物中添加20 - 羟基蜕皮激素（20E），这种现象可以在体外提前引发。为了在体外诱导1日龄蛹的腺体出现核浓缩，20E的有效剂量范围是0.7 - 7微克/毫升，最短暴露时间是24小时。蛹 - 成虫发育不同阶段的前胸腺对外源蜕皮甾体表现出不同的反应性。通过联合使用末端脱氧核苷酸转移酶介导的dUTP缺口末端标记（TUNEL）和凋亡DNA梯状条带法以及透射电子显微镜，已证明蜕皮甾体诱导的前胸腺细胞死亡不仅通过凋亡发生，还通过自噬发生，即诱导的死亡细胞表现出严重的核碎片化和自噬泡形成，这是凋亡和自噬性细胞死亡的典型特征。综合数据表明，蜕皮甾体直接调节前胸腺PCD的凋亡和自噬机制。
