[Morphology and histochemistry of regenerating corneal epithelium in Triturus cristatus. 1. Preliminary observations].

The corneal epithelium of Triturus cristatus was studied by light and electron microscopy. It consists of three cellular layers; the superficial cells, which show numerous short microvilli, are held together by typical junctional complexes. The basal cells adhere to the basal lamina by hemidesmosomes. Furthermore all cells form with the neighboring ones interdigitations and establish with them desmosomal contacts. Secretion granules and vesicles are present throughout the epithelium, mainly in the upper layer; they are filled with an electron dense material, containing glycoproteins as suggested by the histochemical analysis. Mitoses are very frequent in the basal layer. Occasionally exfoliating cells showing signs of degeneration were observed in the superficial layer. The morphological changes occurring during epithelization of wound linearly incised, were studied by light microscopy at several time intervals and the detachement and migration of the cells was particularly investigated. Very early after wounding (5') necrotic cells and cell debris are present at the wound edges. Soon after, thin protrusions originate from surrounding undamaged cells and push through the cellular fragments sliding on the underlining connective tissue. After 2 h, the wound is completely closed by such flattened protrusions. The newly formed epithelium becomes gradually thicker (3-7 h) and the mitotic activity till now suppressed, is resumed (24 h). Studies are in progress on the modifications of the junctional complexes and on the enzymatic mechanism possibly involved in cell mobilization.