File:The Biological bulletin (19755382264).jpg

Title: The Biological bulletin
Identifier: biologicalbullet178mari (find matches)
Year: [1] (s)
Authors: Marine Biological Laboratory (Woods Hole, Mass. ); Marine Biological Laboratory (Woods Hole, Mass. ). Annual report 1907/08-1952; Lillie, Frank Rattray, 1870-1947; Moore, Carl Richard, 1892-; Redfield, Alfred Clarence, 1890-1983
Subjects: Biology; Zoology; Biology; Marine Biology
Publisher: Woods Hole, Mass. : Marine Biological Laboratory
Contributing Library: MBLWHOI Library
Digitizing Sponsor: MBLWHOI Library

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NEURAL DIFFERENTIATION 19
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Figure 18. Golgi region of a "neural" endodermal interstitial cell in a 48 h planula. Several mitochon- dria and microtubules are seen in close proximity to the Golgi. x37,400. Figure 19. Electron-dense droplets (arrows) in the Golgi region of a developing endodermal ganglionic cell. Such droplets are characteristic of neural differentiation. X20.400. mid-region of the planula. Interstitial cells destined to form ganglionic cells migrate out from all regions of the central endoderm and are evenly distributed along the planular anterior-posterior axis in the ectoderm. Since the interstitial cells and their progeny exhibit a rather precise positioning within the ectoderm, some mecha- nism of directed migration may be operating in the plan- ula. The FMRFamide findings support the notion of di- rected migration. FMRFamide-positive endodermal in- terstitial cells and FMRFamide-positive ectodermal Figure 14. Endodermal interstitial cell in the anterior region of a 48-h planula. This undifferentiated cell contains a centrally located nucleus (N), a few segments of rough endoplasmic reticulum (arrow), a few mitochondria, and numerous free ribosomes. Although not visible in this plane of section, the intersti- tial cell also contains a prominent nucleolus. This interstitial cell has migrated from its site of origin in the central endoderm to the outer endoderm (E) and is in close proximity to the mesoglea (M). x 14.400. Figure 15. Developing nematoblast in theanteriorendodermofa48-h planula. Interstitial cells travers- ing the nematocyte differentiation pathway are characterized by the appearance of large amounts of rough endoplasmic reticulum (arrow) and by the formation of a nematocyst capsule (C). Such cells eventually emigrate to the ectoderm. N, nucleus. X 10,800. Figure 16. Interstitial cell traversing the neural differentiation pathway in the anterior endoderm of a 48-h planula. Such interstitial cells committed to the ganglionic pathway form small electron-dense drop- lets (arrows) and dense cored vesicles (see Fig. 17), develop a Golgi (see Fig. 18), and accumulate microtu- bules in their cytoplasm (see Fig. 18). These cells do not develop neurites in the endoderm. N, nucleus. X9.600. Figure 17. Developing ganglionic cell in the endoderm of a 48-h planula. The cytoplasm of the differ- entiating interstitial cell becomes filled with electron-dense droplets (single arrow) and dense cored vesicles (double arrows). Similar droplets and vesicles are abundant in the cell bodies and the neurites of ectodermal ganglionic cells (see Fig. 4). N. nucleus. X21,600.

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