| Budget Amount *help |
¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1989: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1988: ¥1,400,000 (Direct Cost: ¥1,400,000)
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| Research Abstract |
Animals maintain their interior environment on the selective permeability of the cell membrane of the epithelial cells and on the presence of impermeable junctions, septate junction of invertebrates and tight junction of vertebrates, which close the intercellular space between these cells. The impermeable junctions, however, not just prevent molecules from passing by the intercellular space, but could open-and-close in response to environmental conditions.
In this study, we investigated the phenomenon of physiological closing and opening of the septate junction of the body wall epithelium of the starfish larvae and analyzed its mechanism.
We will list up below the results and knowledge which we have obtained during the course of this study.
1) Conditions causing the septate junction to open: Treating the larvae for 15 min with i) sea water made hypertonic with various ions and small inorganic molecules such as NaCl, KCl, urea, glycine, arabinose etc.: 0.3 M), ii) sea water lacking in diva
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lent cation or one added with 0.11 M of sodium citrate, iii) chilled sea water (0ﾟC), or iv) let the larvae starve for ATP by keeping them under the influence of DNP, CCCP, KCN or sodium azide for 10 to 30 min, v) let intracellular cAMP rise by treating the larvae with 10 mM theophilin for 10 to 30 min, or vi) let down the electric potential of the cell membrane of the epithelial cells by adding 0.1 M KC1 or 0.2 M uabain.
2) Ultrastructure of the septate junction when it is opened: Although the septa, which bind the cell membrane of the opposing cells, intercellular space of this region does not enlarge.
3) Mechanism of opening-and-closing of the junction: i) Septate junction is actively closed in the normal conditions, consuming some energy. ii) Divalent cations are necessary to maintain the closed state. iii) Opening-and-closing of the junction is regulated mainly through the membrane potential. iv) There is a possibility that the concentration of intercellular cAMP take some part in this regulation. v) Participation of the cytoskeletal system is unlikely.
4) Applied technique: Taking advantage of the "opened state" of the junction, various macromolecules, such as enzymes and antibodies specifically recognizing the blastocoelic ECM components, were introduced into the blastocoels of living starfish larvae. This method opens a way for studying the roles of ECM components and mesenchyme cells in embryogenesis, as well as the interaction of the two as they take roles in the embryogenesis. Less
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