. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. HOLOTHUROID CUVIERIAN TUBULE REGENERATION 39 secondary lysosomes (1 to fj,m in diameter) also occur in the apical cytoplasm. The basal part of the cell, which is thin and elongated, traverses the undifferentiated cell layers be- fore contacting the basal lamina through a hemidesmosome- like structure. Undifferentiated cells are cube-shaped and have a high nuclear-cytoplasmic ratio (Fig. 3). However, although reduced, the perinuclear cytoplasm encloses a well-developed Golgi apparatus and RER, many mitochon- dria and free
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. HOLOTHUROID CUVIERIAN TUBULE REGENERATION 39 secondary lysosomes (1 to fj,m in diameter) also occur in the apical cytoplasm. The basal part of the cell, which is thin and elongated, traverses the undifferentiated cell layers be- fore contacting the basal lamina through a hemidesmosome- like structure. Undifferentiated cells are cube-shaped and have a high nuclear-cytoplasmic ratio (Fig. 3). However, although reduced, the perinuclear cytoplasm encloses a well-developed Golgi apparatus and RER, many mitochon- dria and free ribosomes, lipid granules, and numerous sec- ondary lysosomes (Fig. 3). Undifferentiated cells are con- nected to the basal lamina through hemidesmosome-like structures, but they are neither bound together nor bound to the peritoneocytes. Stage 2. At the end of this stage, the regenerating struc- ture already has the three tissue layers characteristic of a non-regenerating Cuvierian tubule, , a mesothelium. a connective tissue layer, and an inner epithelium (Figs. 4, 10). The general organization of the mesothelium is similar to the one observed in stage 1 except that some myocytes occur among the undifferentiated cells (Figs. 5. 10). Myo- cytes are cube-shaped. They have a large nucleus and en- close one bundle of myofilaments in their cytoplasm (Fig. 5). which also contains a well-developed RER and numer- ous mitochondria. No junction connecting the myocytes to the other mesothelial cells was observed. However, each myocyte is anchored to the basal lamina by a hemidesmo- some-like structure. A discrete nerve plexus is associated with the mesothelium of stage 2 regenerating tubules. It consists of nerve processes, preferentially located close to the myocytes (Figs. 5. 10). MV. Figure 10. Holothuria forskali. Reconstruction of a longitudinal sec- tion through the wall of a stage 2 regenerating Cuvierian tubule (not to scale). BL. basal lamina; C, cilium; CL, connective tis
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
