17. A C T I O N S OF V I T A M I N S A A N D C
6 7 1
FIG. 12. Electron-micrograph of a basal cell in a similar explant to that in Fig. 10, after 7
days' growth in normal medium. The cytoplasm is packed with fine filamentous material.
X 25,000. (Fitton Jackson and Fell.)
vitamin A (2*5-10 i.u./ml), the epithelium acquires a pseudo
stratified or thin stratified structure, with high columnar ciliated and
mucous cells (Fig. 15); it presents a striking contrast to the thick,
stratified epithelium of the controls (Fig. 14). Although vitamin A
favours the development of glands in the lamina propria and causes
an increase in the numbers of superficial mucous cells, high concentrations partially inhibit the synthesis and secretion of mucus.
Lasnitzki (1963) studied the effect of vitamin A on the rat oesophagus
in culture; in vivo and when cultivated in normal medium the epithelium
keratinizes, but when exposed to excess of vitamin A, it undergoes a
complete mucous metaplasia with the formation of goblet cells.
4. Trachea
Explants of trachea from 13-day chick embryos were grown in the
presence of excess vitamin A (Aydelotte, 1963a). The main effects on
the epithelium were suppression of mucus-synthesis and improved
ciliation.
6 7 1
FIG. 12. Electron-micrograph of a basal cell in a similar explant to that in Fig. 10, after 7
days' growth in normal medium. The cytoplasm is packed with fine filamentous material.
X 25,000. (Fitton Jackson and Fell.)
vitamin A (2*5-10 i.u./ml), the epithelium acquires a pseudo
stratified or thin stratified structure, with high columnar ciliated and
mucous cells (Fig. 15); it presents a striking contrast to the thick,
stratified epithelium of the controls (Fig. 14). Although vitamin A
favours the development of glands in the lamina propria and causes
an increase in the numbers of superficial mucous cells, high concentrations partially inhibit the synthesis and secretion of mucus.
Lasnitzki (1963) studied the effect of vitamin A on the rat oesophagus
in culture; in vivo and when cultivated in normal medium the epithelium
keratinizes, but when exposed to excess of vitamin A, it undergoes a
complete mucous metaplasia with the formation of goblet cells.
4. Trachea
Explants of trachea from 13-day chick embryos were grown in the
presence of excess vitamin A (Aydelotte, 1963a). The main effects on
the epithelium were suppression of mucus-synthesis and improved
ciliation.