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.

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    epidermis, particularly of the stratum granulosum, and a decreased rate of keratin-formation with an increased production of kerato-hyalin. They remark that both their own experiments and those of Studer & Frey suggest, but do not establish, the ability of vitamin A in high concentrations to counteract keratin-formation in the skin epidermis. It is evident from these experiments that increased concentrations of vitamin A, whether systemically given or locally applied, have a definite effect on skin epidermis. The ectoderm of the embryonic chick is known to develop normally though precociously in tissue culture (Miszurski, 1937) and to produce large quantities of keratin. The following experiments were undertaken to see what effect the addition of excess vitamin A to the medium would have on keratinization in such cultures. The results to be described showed that cornification was com¬ pletely suppressed by the high vitamin A, but a quite unexpected effect was also produced. In the high A medium, the ectoderm differentiated into a mucus-secreting sometimes ciliated membrane resembling that of the normal nasal mucosa, and when the explants were transferred to normal medium, this metaplastic change was reversed, and the natural keratinizing epithelium of the skin was produced. Two main groups of experiments were made. In the first (described in section I) the effect of excess vitamin A on the differentiation of the ectoderm was studied; the explants derived from one side of each embryo were grown in medium to which vitamin A had been added (+ A medium) and those from the opposite side in normal (control) medium. The second group of experiments (see section II) were undertaken to find whether the effect of the vitamin was reversible; the explants from both sides of each chick were grown in +A medium for periods ranging from 7 to 14 days; the explants from one side were then transferred to normal medium and those from the other were either fixed to show the histology of the tissue at the time of transfer to normal medium, or were cultivated in + A medium until the sister cultures in normal medium were fixed. MATERIAL AND METHODS Material The explants were obtained from the trunk and limbs of 6- to 7-day chick embryos. The head, viscera and distal part of the limbs were removed; the body was then laid with the epidermal surface upwards and the spinal region with its associated ectoderm and the thin ventral body wall were cut away and rejected. Each half of the trunk and the attached portions of the limbs were cut into large fragments from which as much as possible of the skeletal tissue was dissected; the surface fragments were then cut into smaller pieces suitable for explantation. The explants from one half embryo were kept separate from those of the other half. Vitamin A In all the experiments in the present work, the vitamin A was added to the plasma either in the form of the alcohol or acetate, to produce what in our previous work we have described as artificial hypervitaminotic (AH) plasma. The vitamin A alcohol solution was prepared from a sample of