| Budget Amount *help |
¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1990: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1989: ¥500,000 (Direct Cost: ¥500,000)
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| Research Abstract |
Most of the cells of the neural gland in Halocynthia roretzi are binucleate and the binucleate cells seem to proliferate in the limited area of the dorsal epithelium.
In ll species of solitary ascidians observed, the binucleate cells were observed in the neural glands of Halocynthia and. H. aurantium. In H. hilgendorfi f. Cnemidocarpa and verrucosa, somo cells have two nuclei. No binucleate cells were found in other species. The occurrence of binucleate cells may be associated with adaptation to a cold, sea-water environment.
From the immunohistochemical observations, the positive reaction for mammalian LHRH was observed in the neural ganglion but no reaction in the neural gland. In contrast, positive reaction for only silver-carp GTH was observed in the neural gland. These positive reactions were confirmed with reabsorption test. The results suggest that the neural ganglion and gland of ascidians may be the homologue of the vertebrate hypothalamus and pituitary. Other antibodies to pitu
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itary hormones; GH, PRL, LH, FSH, ACTH and MSH gave no reaction in either the neural ganglion or the neural gland. Moreover, insulin, glucagon and secretin were not observed in both the neural ganglion and gland. This is contradictory to the results of pestarino (1984 and 1985), and this requires further study. Antibody to beta-endorphin gave positive reaction in either the neural gland or the dorsal strand. Met-enkephalin was observed in either the ganglion or the dorsal strand. Immunoreactivity both in the ganglion and gland was obtained with antibody to substance P. The significance of the existence of these substances requires further examination. Immunoreaction positive for amphibian PRL was obtained in the neural ganglion. However, the presence of PRL can not detected biochemically using the immunoreaction for anti-amphibian PRL by western blot method after development with SDS polyacrylamide gel electrophoresis. It seems to be very small contents of it in the sample from the neural ganglion.
According to the re-examinations of ultra-structural studies on the neural complex, the dense secretory granules were observed both in the neural cells and their saxons. Moreover, the cells of dorsal strand also have many dense granules. No secretory granules were observed in the binucleate cells of the neural gland, but they have many vacuoles. Therefore, these cells may have a secretory function.
Thus, the neural gland of ascidian still remains the possibility to be homologue of the vertebrate pituitary. Less
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