Functional and structural changes in Drosophila salivary gland cells triggered by ecdysterone |
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| Authors: | C L Poels A de Loof H D Berendes |
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| Affiliation: | 1. Centre for Exploration Targeting, Australian Research Council Centre of Excellence for Core to Crust Fluid Systems (CCFS), School of Earth and Environment, University of Western Australia, Crawley, WA 6009, Australia;2. Australian Research Council Centre of Excellence for Core to Crust Fluid Systems, The Institute for Geoscience Research, Department of Applied Geology, Curtin University, GPO Box U1987, Perth, WA 6845, Australia;3. Western Australian Argon Isotope Facility, Department of Applied Geology and JdL-CMS, Curtin University, Perth, Australia;4. Mineral Deposit Research Unit, Department of Earth and Ocean Sciences, University of British Columbia, Vancouver V6T 1Z4, Canada;5. Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, PR China;1. Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta, T6G 2E3, Canada;2. National Research Center for Geoanalysis, Chinese Academy of Geological Sciences, Beijing 100037, PR China;3. Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, PR China;4. State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, PR China;1. Group of Mutagenesis, Department of Genetics and Microbiology, Faculty of Biosciences, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, Barcelona, Spain;2. Zoology Department, Faculty of Sciences, Sohag University, 82524 Sohag, Egypt;3. Facultad de Recursos Naturales Renovables, Universidad Arturo Prat, Iquique, Chile |
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| Abstract: | In normal development a complex pattern of changes in the submicroscopic structure of Drosophila hydei salivary gland cells occurs in relation to the onset of secretory activity of these cells prior to puparium formation. The major changes involved in this structural reorganization of cytoplasmic components are as follows. The mucopolysaccharide secretory product present in the form of globules which are randomly distributed over the cytoplasm in the course of the third instar migrate to, and accumulate at, the cell apex. The arrangement and number of microvilli undergo drastic changes involving elongation and increase in number of the villi. The RER, which is originally distributed randomly, is reorganized into whorls and vesicles. These major changes can be experimentally reproduced by administration of the steroid moulting hormone derivative ecdysterone to larvae in the middle of the third instar.Administration of ecdysterone to early third instar larvae, in which salivary glands are still inactive with respect to mucopolysaccharide synthesis, results in only a partial reproduction of the features displayed by middle third instar glands. The changes in the arrangement and number of microvilli do not occur in the early third instar glands.The changes observed in the early third instar salivary gland cells indicate that the onset of mucopolysaccharide synthesis is inhibited by the steroid treatment. Support for this assumption is provided by studies on the features of the RER and Golgi systems in middle third instar salivary gland cells.On the basis of this investigation it may be suggested that the steroid ecdysterone is an effective trigger of mechanisms active in cytodifferentiation. It seems that not only secretion of mucopolysaccharides is initiated by the steroid, but also the synthesis of this substance inhibited. |
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