| Project/Area Number |
01570012
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
General anatomy (including Histology/Embryology)
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| Research Institution | Kagawa Medical School |
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Principal Investigator |
HATAE Tanenori Kagawa Medical School, Anatomy, Professor, 医学部, 教授 (40037388)
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| Co-Investigator(Kenkyū-buntansha) |
KAWAI Yoshinori Kagawa Medical School, Anatomy, Assistant, 医学部, 助手 (80211861)
FUJITA Mamoru Kagawa Medical School, Anatomy, Associate Professor, 医学部, 助教授 (60037471)
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| Project Period (FY) |
1989 – 1990
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| Project Status |
Completed (Fiscal Year 1990)
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| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1990: ¥200,000 (Direct Cost: ¥200,000)
Fiscal Year 1989: ¥1,800,000 (Direct Cost: ¥1,800,000)
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| Keywords | Absorptive epithelia / Apical tubule / Cytochemistry / Ultrastructure / Electron Microscopy / Endocytosis / Endosome / 免疫細胞化学 |
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| Research Abstract |
1. Many, membranous tubules were observed in the apical cytoplasmic region of active-absorptive epithelia (kidney proximal tubule, ductuli efferentes and visceral yolk sac). These tubules frequently connected with endosomes forming an apical tubule-endosome complex. A tracer experiment showed that the apical tubules were formed by budding off from the endosomes and play a role in membrane recycling.
2. Specific helical structure was discovered in the apical tubules by using a fixative containing both aldehydes and osmium tetroxide. The helical structure was a left-handed quadruple helix, each strand of which consisted of helically wounded parallel rows (ca. 11 nm in diameter) in close proximity to the limiting membrane of the apical tubule cylinder (ca. 80 nm in diameter). Eleven particles constituted one full turn of each helix with a pitch of 60 nm. These particles surrounded an electron-lucent cylinder (ca. 38 nm in diameter), containing at its center another set of a single row of small particles (ca. 9 nm in diameter).
3. Computer aided three-dimensional reconstruction of the apical tubule-endosome complex based on tracing of serial thin sections showed that 20-40% of the membrane reside in the tubule portion in contrast to 5-10% of the volume. This result suggests the high efficiency of the apical tubules in the membrane recycling.
4. An analysis of the chemical nature of the apical tubules at electron microscopic levels demonstrated that the apical tubules contain a high concentration of carbohydrates and the material which forms the luminal specializations is composed of proteins, which are readily digested by a proteolytic enzyme. A further investigation using several lectins showed that the apical tubules contain N-acetylglucoseamine or sialic acid as a carbohydrate component.
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