| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1992: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1991: ¥1,400,000 (Direct Cost: ¥1,400,000)
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| Research Abstract |
The caudal neurosecretory system (CNS) synthesizes and releases at least two peptide hormones, urotensins I and II (UI and UII). While these neuropeptides have been shown to have a wide variety of biological activities, a clear picture of their coordinated functions in fish has not yet emerged. The sequencing of these peptides by us and others has broadened our thinking about their possible functions since UI and UII have been found to have sequence homology to corticotropin-releasing factor (CRF) and somatostatin, respectively. Taking the possible hypophysiotropic functions of UI and UII into consideration, we carried out histochemical and molecular biological studies to elucidate the physiological functions of the CNS.
First, we synthesized UI and UII, and developed radioimmunoassays for both peptides. This enables us to measure contents of UI and UII in the CNS and other tissues. Second, we established an in situ hybridization (ISH) histochemistry for UI and UII, which has the advantage of great specificity in terms of both the genetic information expressed and identification of the cells in which that information is expressed. We demonstrated that UI and UII are expressed in almost all identifiable caudal neurosecretory neurons. Further, we found that UI is expressed in the hypotalamic nuclei, the locations of which differ from those of CRF-producing neurons. This strongly suggests that UI has a hypophysiotropic function. Third, we also established a method for identification of UI transcripts and UI peptides in the same neurons by combined ISH and immunohistochemistry. This provides information on the dynamic aspects of gene expression, and synthesis and release of hormones.
Using the methods mentioned above, we are now investigating changes in the gene expressions and contents of UI and UII in various tissues in normal and hypophysectomized fish subjected to various environments and conditions to elucidate the hypophysiotropic functions of UI and UII.
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