ISSN:
1432-0878
Keywords:
Pigmented retina
;
Cytochalasin B
;
Clonal culture
;
Electron microscopy
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary Three-week-old clones of pigmented retinal cells can be divided into four morphologically distinct regions: an outer zone of flattened cells, the squamous zone; a ring of rounded to spindle shaped cells which pile up and secrete large amounts of mucopolysaccharide, the stratified zone; a region of lightly pigmented cells, the intermediate zone; and the center consisting of a single layer of heavily pigmented cuboidal cells, the pigmented cuboidal zone. The ultrastructure of the cells in the pigmented cuboidal zone and the epithelial cells of eleven-day-old embryonic pigmented retina is similar. Both cell types are cuboidal in profile, rest on a typical basal lamina, interdigitate with adjoining cells at their bases, and have apical surface protrusions. The embryonic epithelial cells and cells of the two innermost zones of the clones have a web of thin filaments (40–70 Å in diameter), just beneath the apical protrusions. Skeins of these filaments are often interconnected by discrete dense bodies. Near the zonulae adhaerentes bundles of filaments are embedded in peripheral dense material and extend around the periphery of the cell. After treatment with low concentrations (1 μg/ml) of cytochalasin B (CCB) the retiform layer of filaments beneath the apical protrusions is dispersed, but the peripheral filaments remain intact. Cells treated in this manner retain their polygonal shape but their surfaces are altered. Higher concentrations of CCB (10 μg/ml) disperse the filaments and disrupt the junctional complexes. The cells lose their surface protrusions and become more spherical. Thick filaments and microtubules are unaffected by CCB. Time-lapse cinematography reveals active movements of apical protrusions and focal contractions of cells of the intermediate zone. These movements are blocked by CCB. We infer that the apical filaments are implicated in the activity of the apical protrusions and at least partially responsible for the maintenance of the polygonal shape. Contraction of these arrays of filaments may be responsible for the focal contractions.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00306953
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