Ultrastructure and glycoconjugate histochemistry of the lens capsule during lens regeneration from the iris in the Newt.

The lens capsule of the regenerating lens develops from the basal lamina of the iris epithelium. As the lens differentiates and grows in size, the lens capsule increases in thickness by the formation of successive layers of basal laminar material resulting in a structure composed of increasing numbers of parallel lamellae. This initial arrangement may be lost and a more homogeneous composition of fine granules and filaments may characterize some parts of the capsule in older lenses.

Morphology and glycoconjugate histochemistry of the palpebral glands of the adult newt, Notophthalmus viridescens.

The eyelids of the newt were studied in 10 microns serial paraffin and 1-2 microns plastic sections using standard histological stains and special stains for glycoconjugates. The eyelids contain four different glands. Simple acinar serous and simple acinar mucous glands occur in the skin; unicellular mucous glands occur in the conjunctiva; and convoluted tubular seromucous glands are present in connective tissue beneath the conjunctiva.

Macrophage mobilization and morphology during lens regeneration from the iris epithelium in newts: studies with correlated scanning and transmission electron microscopy.

The lens was removed from both eyes of adult newts (Notophthalmus viridescens), and the eyes were fixed in Karnovsky's fixative every 2 days 0-20 days after operation. Anterior half-eyes were prepared by standard procedures for scanning electron microscopy of the surface. Before fixation, the posterior iris surface was cleaned of adhering vitreous mechanically with forceps or by treatment with bovine testicular hyaluronidase or with hyaluronidase and collagenase.

Macrophage invasion and phagocytic activity during lens regeneration from the iris epithelium in newts.

Following removal of the lens through the cornea, early stages of lens regeneration from the dorsal iris of the adult newt, Notophthalmus viridescens, were studied using light and electron microscopic observations on sectioned, plastic-embedded irises. Specimens were fixed in Karnovsky's fixative every 2 days from 0 to 12 and 15 days after lentectomy. Infiltration of the iris epithelium by macrophages and their phagocytosis of melanosomes and small fragments of iris epithelial cells were observed.

Availability time of tritium-labeled DNA precursors in newt eyes following intraperitoneal injection of 3H-thymidine.

Following intraperitoneal injection of 3H-thymidine into host newts, iris together with a regenerating lens was transplanted from a donor eye into a lentectomized host eye at frequent intervals for 20 hours and then every 1 or 2 days for 14 days. The eyes were fixed 2 hours and 1 or 2 days after implantation and autoradiographs prepared. Following fixation 2 hours after operation, incorporation of 3H-thymidine into DNA, as evidenced by grain counts over nuclei, fell rapidly for 3.

Lens regeneration from the pupillary margin of the eyecup in newt embryos.

Early stages in lens regeneration from the dorsal margin of the pupil, following removal of the young lens from the embryonic eyecup, were studied with transmission electron microscopy in Notophthalmus viridescens. At the stage of operation, the eyecup cells have an undifferentiated, embryonic appearance with numerous free ribosomes and scattered mitochondria. In normal embryonic eyes containing a lens, the iris epithelium differentiates from the edge of the optic cup by growth and flattening of the cells to form a two-layered cuboidal epithelium.

Dedifferentiation of iris epithelium during lens regeneration in newt larvae.

Early stages in lens regeneration from the pigmented epithelium of the dorsal iris were studied in larval Notophthalmus viridescens by means of transmission electron microscopy. Normal iris epithelium is composed of two layers of low cuboidal cells. packed with melanosomes and surrounded by a basal lamina.

Soluble protein synthesis in the neural retina during lens regeneration.

Lens regeneration in newts involves transformation of pigmented dorsal iris epithelial cells into lens cells. This process is somehow stimulated by the neural retina. In the present study, soluble proteins and their synthesis were analyzed in normal neural retina and in neural retina 12 days after lentectomy by means of disc and slab gel electrophoresis.

Role of neural retina and vitreous body during lens regeneration: transplantation and autoradiography.

The trophic influence of neural retina in regeneration of the lens from dorsal iris is well known. The first part of this study involved transplantation of dorsal iris pieces into various intra-ocular positions in order to determine the field of action of the neural retina. The most favorable location for lens regeneration was the pupillary space, closely followed by the vitreous chamber.

DNA synthesis during lens regeneration in larval Xenopus laevis.

Larvae of Xenopus laevis at stages 50-53 were lentectomized and then injected with tritiated thymidine at various times after lentectomy. In series I, the animals were injected 1,2,3,4,6,8,10,12,15, or 17 days after lens removal and fixed three hours after injection. Autoradiograpns of serial cross sections through the eyes were prepared.