Morimoto T, Matsuura S, Nagata S, Tashiro Y
J Cell Biol. 1968 Sep;38(3):604-14. doi: 10.1083/jcb.38.3.604.
The development of the cells in the posterior silk gland of the silkworm, Bombyx mori, during the fourth larval instar has been studied. In the early stages of this instar, the wet weight of the gland and the amounts of RNA, DNA, and protein per animal increase logarithmically until they reach a stationary state at about 72 hr. At around 96 hr of the fourth instar, the larvae enter the molting state, which lasts for about 24 hr until the fourth ecdysis. Towards the end of the molt stage, the growth of the silk gland is resumed. Electron microscopical observation shows that in the early intermolt stage the cytoplasm is filled with free ribosomes and with rough endoplasmic reticulum (ER), first of the lamellar type (0-6 hr) and then of the vesicular or tubular type. The Golgi apparatus also is well developed. At the beginning of the molt stage (90-96 hr), however, most of the ER becomes lamellar in type, concentric lamellar structures being occasionally observed, and the Golgi vacuoles disappear. Autophagosomes and lysosomes increase markedly and the apical portion of the cytoplasm becomes extensively vacuolated; this suggests that the secretory activities are completely depressed, and pronounced degenerative changes appear during the molt stage. Towards the end of the molt stage, large lamellar ER elements are fragmented into smaller lamellae and there is a pronounced increase in the number of free ribosomes.
对家蚕（Bombyx mori）四龄幼虫期后部丝腺细胞的发育进行了研究。在此龄期早期，腺体的湿重以及每只动物的RNA、DNA和蛋白质含量呈对数增加，直至约72小时达到稳定状态。在四龄幼虫约96小时时，幼虫进入蜕皮状态，持续约24小时直至第四次蜕皮。接近蜕皮阶段末期时，丝腺恢复生长。电子显微镜观察显示，在蜕皮间期早期，细胞质中充满游离核糖体和粗面内质网（ER），最初是板层状（0 - 6小时），然后是泡状或管状。高尔基体也发育良好。然而，在蜕皮阶段开始时（90 - 96小时），大部分内质网变为板层状，偶尔可见同心板层结构，高尔基体泡消失。自噬体和溶酶体显著增加，细胞质顶端部分出现广泛空泡化；这表明分泌活动完全受到抑制，并且在蜕皮阶段出现明显的退行性变化。接近蜕皮阶段末期时，大的板层内质网成分破碎成较小的板层，游离核糖体数量明显增加。
