Lysosomes and Related Structures in the Posterior Silk Gland Cells of Bombyx mori. II. In Prepupal and Early Pupal Stadium

[摘要] References(11)Cited-By(11)Acid phosphatase activity measures in various stages of the posterior silk gland cells of Bombyx mori suggested that the lysosomal enzyme used for degenerative and cytolytic processes in the prepupal-pupal stadium was not synthesized in the prepupal-pupal stadium but in the feeding stage of the fifth larval instar. The specific activity of the lysosomal enzymes (activity per unit weight of the gland) was rather low in the spinning period but increased rapidly after spinning was completed. Electron microscopic cytochemical observations revealed that the number of acid phosphatase positive granules per unit area peaked at about 36 h of the prepupal stadium, decreased once and then increased markedly towards the end of the prepupal stadium. Ultra-structural changes in the prepupal-pupal stadium also appeared to be biphasic. In the spinning period (prepupa 0-72 h), focal degenerative changes by the autophagosomes-autolysosomes system appeared preferentially near or at the canal zone in the apical and perinuclear cytoplasm. After completion of spin-ning, cytolytic processes became evident everywhere; the apical and perinuclear cytoplasm were digested extensively by the same autophagic mechanisms, and at the same time the basal cytoplasm and nucleus were partitioned and packed by smooth membranes. Thus the silk gland was fragmented into a number of globules containing cytoplasmic and/or nuclear components.

[学科分类] 分子生物学，细胞生物学和基因