Metaplasia produced in cultures of chick ectoderm by high vitamin A / by Honor B. Fell and E. Mellanby.

  • Fell, Honor B.
Date:
[1953?]
Catalogue details

Licence: In copyright

Credit: Metaplasia produced in cultures of chick ectoderm by high vitamin A / by Honor B. Fell and E. Mellanby. Source: Wellcome Collection.

    6/24 (page 475)
    had become very compact and dense. The ‘ fluffy5 appearance of the epidermis was now very pronounced in some cultures and in others, though still regular, the epithelium was much thickened; there was still no sign of keratinization. A strange feature of this stage was the presence of a translucent, viscid envelope round the explants, which clung to the tissue during transplantation and could not be completely washed away with saline. This material was not composed of cell debris, although it contained some cellular remains, and until the explants were examined histologically its nature remained obscure. Histological examination of the + A cultures showed that keratinization was completely suppressed. The epidermis of the 7-day explants was three to four cells deep (PL 1, fig. 4). In places the superficial layer was flattened as in the controls, but elsewhere, especially near the periphery of the culture, the cells were cubical and the surface of the cytoplasm was coloured a deep vio]et with Delafield’s haematoxylin and chromotrop, and bright red with PAS (Periodic acid-Schiff reaction) or mucicarmine, so that in section the epithelium was bordered by a sharply defined purple or red line. This appearance was never seen in similarly stained controls of the same age. In the thickened epithelium near the periphery of the explant, scattered vacuolated cells and small round cavities were present which were filled with material having the same staining reactions as the epithelial border. Mitosis was common in all layers of the epidermis. The tissue below the epithelium (PL 1, fig. 2) had the same general structure as in the controls, i.e. it consisted of an outer dermal and an inner, compact fibrous zone; in the +A explants, however, the outer zone was much more oedematous, and in places the epidermis was sometimes detached from the dermis to form a blister filled with fluid. After 9 days in + A medium, the epithelium bore little resemblance to the keratinizing, squamous epidermis of the controls, but had assumed the charac¬ teristics of a secretory membrane. It had become thicker and the superficial flattened layer had disappeared and been replaced by cubical or, especially near the periphery of the explant, deep columnar ceils. In azan-stained preparations many small red granules were seen immediately within the free border of these cells, and below the granules were large vacuoles which stained blue with azan and bright red with PAS or mucicarmine. Many of the secretory cells protruded from the surface of the epithelium, and in places had escaped from their orderly arrangement to form irregular cords and clusters loosely adhering to the palisade of columnar cells repre¬ senting the original basal layer; it was this disorderly structure which caused the ‘fluffy’ appearance described in some of the living explants. The loss of cohesion between the epithelial cells was not associated with necrosis, and the papilliform masses thus produced were secreting actively and appeared healthy. This change in structure probably increased the permeability of the