ISSN:
0362-2525
Keywords:
Life and Medical Sciences
;
Cell & Developmental Biology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Biology
,
Medicine
Notes:
The behavior of the nuclei of pharyngeal outer epithelial cells was observed by electron microscopy during regeneration of head fragments of planaria transected at the prepharyngeal region. On the fourth day of regeneration, the surface cells of the pharyngeal rudiment show some evidence of differentiation: septate desmosomes and immature rod-shaped bodies. These cells then develop many cilia and a few microvilli on their free surfaces, and the electron-density of their karyoplasm and cytoplasm increases. The basal cytoplasmic processes of the surface cells protrude into the intercellular spaces between underlying cells. Each elongated nucleus goes down into one of these processes. Two types of nuclear descent are observed. The first type occurs when the basal lamina has not yet formed under the epithelial cells. The second type occurs when the basal lamina has already developed under the epithelial cells. Many microtubules are seen running along the long axis of the cells with descending nuclei. Fine fibrous bodies are frequently observed in the descending nuclei of the epithelial cells. Intercellular substances with moderate electron-density are observed sporadically in the spaces between descending cytoplasmic processes and surrounding cells. Glycogen granules accumulate in large numbers in the basal cytoplasm in the vicinity of the descended nucleus. The mechanism of the descent of the perikarya of the pharyngeal outer epithelial cells is discussed in terms of these results.
Additional Material:
14 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jmor.1052060308
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