2000 Fiscal Year Final Research Report Summary
Cell differentiation and secretory products of hypophyseal pars tuberalis
| Project/Area Number |
11670018
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
General anatomy (including Histology/Embryology)
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| Research Institution | KITASATO UNIVERSITY |
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Principal Investigator |
KAMEDA Yoko Kitasato Univ.School of Medicine, Prof., 医学部, 教授 (10032898)
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| Co-Investigator(Kenkyū-buntansha) |
MIURA Masaaki Kitasato Univ.School of Medicine, Research Associate, 医学部, 助手 (60276053)
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| Project Period (FY) |
1999 – 2000
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| Keywords | Hypophyseal pars tuberalis / Alpha-subunit of glycoproteins / Alpha-subunit mRNA / Immunoelectron microscopy / In situ hybridization / Ontogeny / Circadian rhythm / Pinealectomy |
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| Research Abstract |
The hypophyseal pars tuberalis surrounding the median eminence and infundibular stalk is composed of specific secretory cells and sustentacular or follicular cells. The pars tuberalis (PT)-specific cells are immunoreactive for α-subunit of glycoprotein hormones and express α-subunit mRNA.In chick embryos, the α-subunit mRNA and protein began to appear in the Rathke's pouch at embryonic day (E) 3.5. At E6, gonadotrophs immunoreactive for LH were first detected in the pars distalis. At E8, the pars tuberalis primordium located close to the median eminence was formed at the lateral apical end of the par distalis. The primordium expressed intense signal for α-subunit mRNA and protein. Thus, both primordia of the pars distalis and pars tuberalis expressed α-subunit. This subunit may play a role in the cytodifferentiation of the adenohypophyses. In addition, α-subunit mRNA level in the pars tuberalis was changed depending on photoperiods. In chicks exposed to continuous light for 30 days, the PT-specific cells were filled with enlarged secretory granules, showing the reduction of secretory activity and α-subunit mRNA level in the pars tuberalis markedly decreased. On the other hand, in chicks exposed to continuous darkness for 30 days, the PT-specific cells displayed enlarged cytoplasmic and nuclear areas and exocytotic features of secretory granules were more frequent. Alpha-subunit mRNA level was increased under continuous darkness. These data indicate that the PT-specific cells are responsive to photoperiodic changes. After pinealectomy, α-subunit mRNA level in the pars tuberalis was increased. However, in chicks under continuous light or darkness after pinealectomy, the cell activity and α-subunit mRNA level in the pars tuberalis were similar in changes to those of unoperated animals.
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