Control of mitotic activity in Wolffian lens regenerration.

Abstract

AbstractThe total numbers of mitotic cells in the iris epithelium, ciliary epithelium, and ora serrata were counted at various time intervals after lentectomy of adult newts, Notophthalmus (Triturus) viridescens, in bleached serial sections. In some cases colchicine was injected for the purpose of accumulating mitotic figures.In the iris epithelium, which normally shows no mitotic cells, a wave of mitoses is induced by lentectomy. The wave starts on day 4 and has its peak period during days 7 to 15, when a portion of the iris epithelial cells depigment and form the lens vesicle. In the iris epithelium the wave subsides after formation of the regenerated lens and is gone by day 30. On the other hand, in the regenerated lens the mitotic activity is retained in the lens epithelium. The colchicine treatment has revealed an extremely small number of iris epithelial cells going into mitoses within one day after lentectomy. However, the same treatment failed to demonstrate any mitotic cells on days 0, 2, and 3.Mitotic activity is also induced in the ciliary epithelium, which does not take part in formation of the lens regenerate. This induction is much lower in intensity than that in the iris epithelium.The ora serrata area has a low level of mitotic activity in the normal condition, which is elevated to a high level after day 20. Significance of these observations for the mechanism of lens regeneration is discussed.Estimation of the total cell number of iris and ciliary epithelia during the first 15 days after lentectomy indicated an increase in the iris epithelium, which can be accounted for by the number of mitoses counted during the corresponding period in the same tissue.Some data on mitosis in the normal and regenerated lenses are also presented.