APPEARANCE OF IRIS MUSCLE-LIKE CELLS IN THE PIGMENTED IRIS EPITHELIUMAFTER DISAPPEARANCE OF INTACT IRIS MUSCLE-CELLS IN THE LENTECTOMIZED NEWT EYE

The behavior of the iris muscle in the dorsal marginal iris in the Jap anese common newt Cynops pyrrhogaster was examined by electron microsc opy over one year after lens removal. Within 1 week after lentectomy, the myofilaments of the iris muscle gradually diminished and the forma tion of polyribosomes was activated. This was the same reaction shown by pigmented iris epithelial cells that transdifferentiate into lens c ells. The iris muscle and associated nerve fibers were then separated from lens forming cells and finally disappeared after about 2-3 weeks. Myofilament-containing iris muscle-like cells appeared in the anterio r pigmented iris epithelium at about one-and-one-half years after lens removal. These cells were connected to each other by a gap junction t hat is not found in mature iris muscle. The possibility of the regener ation of the iris muscle from pigmented iris epithelial cells was disc ussed.