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.
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1 September 1968
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September 01 1968
STUDIES ON THE POSTERIOR SILK GLAND OF THE SILKWORM, BOMBYX MORI : III. Ultrastructural Changes of Posterior Silk Gland Cells in the Fourth Larval Instar
Takashi Morimoto,
Takashi Morimoto
From the Department of Physiology, the Kansai Medical School, Moriguchi, Osaka, Japan
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Shiro Matsuura,
Shiro Matsuura
From the Department of Physiology, the Kansai Medical School, Moriguchi, Osaka, Japan
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Sunao Nagata,
Sunao Nagata
From the Department of Physiology, the Kansai Medical School, Moriguchi, Osaka, Japan
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Yutaka Tashiro
Yutaka Tashiro
From the Department of Physiology, the Kansai Medical School, Moriguchi, Osaka, Japan
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Takashi Morimoto
From the Department of Physiology, the Kansai Medical School, Moriguchi, Osaka, Japan
Shiro Matsuura
From the Department of Physiology, the Kansai Medical School, Moriguchi, Osaka, Japan
Sunao Nagata
From the Department of Physiology, the Kansai Medical School, Moriguchi, Osaka, Japan
Yutaka Tashiro
From the Department of Physiology, the Kansai Medical School, Moriguchi, Osaka, Japan
Received:
November 28 1967
Revision Received:
May 06 1968
Online ISSN: 1540-8140
Print ISSN: 0021-9525
Copyright © 1968 by The Rockefeller University Press.
1968
J Cell Biol (1968) 38 (3): 604–614.
Article history
Received:
November 28 1967
Revision Received:
May 06 1968
Citation
Takashi Morimoto, Shiro Matsuura, Sunao Nagata, Yutaka Tashiro; STUDIES ON THE POSTERIOR SILK GLAND OF THE SILKWORM, BOMBYX MORI : III. Ultrastructural Changes of Posterior Silk Gland Cells in the Fourth Larval Instar . J Cell Biol 1 September 1968; 38 (3): 604–614. doi: https://doi.org/10.1083/jcb.38.3.604
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