Ultrastructural changes of Drosophila larval and prepupal salivary glands cultured in vitro with ecdysone |
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Authors: | Robert Farka? Gabriela ?u?áková |
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Institution: | (1) Institute of Experimental Endocrinology, Slovak Academy of Sciences, Vlárska 3, 833 06 Bratislava;(2) Dept. of Developmental Genetics, German Cancer Research Center, Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany;(3) Institute of Experimental Phytopathology and Entomology, Slovak Academy of Sciences, Nádražná 52, 900 28 Ivanka pri Dunaji, Slovakia |
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Abstract: | Summary Alterations in the ultrastructure of in vitro cultured larval salivary glands of Drosophila melanogaster in response to the steroid hormone ecdysone were studied in relation to complex changes in puffing patterns. We found that
the changes in the fine structure of cultured glands reflected progression of the puffing pattern, and they paralleled those
seen in vivo. We observed that glue secretion by exocytosis, the main function of salivary glands, took place between puff stage 5 (PS5)
and PS7. Glue could not be expectorated under culture conditions but was slowly released from the lumen through a duct into
the medium. After the cultured glands reached PS13/PS14, further progress of puffing and fine structural alterations required
that the ecdysteroid titer be transiently extremely low or absent. Under in vitro conditions we did not observe the putative new secretory program(s) described for glands in vivo after PS12. However, ultrastructural changes which unambiguously indicated that an autohistolytic process had begun in vitro started to appear after PS17. Many salivary gland cells developed numerous features of progressive self-degradation between
PS18 and PS21. Actual degradation of salivary glands in vivo seemed to be rapid, but in vitro degradation was never completed, probably due to a lack of exogenous factors from the hemolymph. Manipulations of ecdysone
titer in vitro in the culture medium, known during the larval puffing cycle to cause premature induction of developmentally specific puffing
patterns, did not affect the normal development of ultrastructural features of the cytoplasm and nucleus. |
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Keywords: | ecdysone metamorphosis Drosophila salivary glands electron microscopy |
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