1996 Fiscal Year Final Research Report Summary
Neurosecretory cells found along the dorsal strand of ascidians
| Project/Area Number |
06804052
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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 |
生物形態・構造
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| Research Institution | Saitama University |
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Principal Investigator |
TERAKADO Kiyoshi Saitama University, Department of Regulation Biology, Associate Professor, 理学部, 助教授 (40008834)
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| Project Period (FY) |
1994 – 1996
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| Keywords | Protochordate / ascidian / neural complex / dorsal strand / GnRH neuron / pituitary hormone / hypophysis / immunocytochemistry |
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| Research Abstract |
Hypophysis, which functions to maintain the homeostasis in all vertebrate species, appears suddenly in its complete form in lower vertebrates. That is, the hypophysis is the organ unique for vertebrates and is absent in invertebrates. From a phylogenetic point of view, the possibility that any structure homologous to the vertebrate adenohypophysis may exist in protochordates has long been pointed out. In ascidians, the neural gland was considered to be homologous to the vertebrate adenohypophysis because of its morphological similarity. However, despite of recent extensive studies using various methods, the evidence that indicates its homology is very scarce.
In this research project, we obtained some important cytochemical and developmental evidences revealing the homology of asacidian dorsal strand to the vertebrate adenohypophysis. They are : (1) presence of prolactin (PRL) -immunoreactive cells along the doesal strand. The localization of the immunoreactive material in the secretory granules of these cells has been ascertained by immunoelectron microscopy. (2) presence of gonadotropin (GTH) -immunoreactive cells. (3) presence of adrenocorticotropin (ACTH) -and POMC-related beta-endorphin immunoreactive cells. In adition, numerous gonadotropin-releasing hormone (GnRH) -producing neurons are localized in the vicinity of the dorsal strand. These structures in ascidians may correspond to the hypothalamus-pituitary system of vertebrate.
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