Localization of lysosomal enzymes in the retina and retinal pigment epithelium of RCS rats.

Using ultrahistochemical and immunohistochemical techniques, localization of acid phosphatase and cathepsin D was demonstrated in the retina and pigment epithelium of 1 to 42 day old RCS rats and its nonaffected congenic rat strain. Both enzymes are present in the pigment epithelium of the normal and dystrophic rat eye. As early as the age of 1 week, it was found that the lysosomes in the dystrophic rat retina are less stable in releasing acid phosphatase than those of control animals. Infiltration of cathepsin D into the subretinal space could first be detected with certainty in 2-week-old animals. The fragility of the lysosomal membrane and, therefore, the release of both enzymes became more pronounced as the animals aged. The findings of this study indicate that the instability of the lysosomal membrane in the RCS rat pigment epithelium may initiate degeneration of photoreceptors and pigment epithelium. The demonstration of cathepsin D activity has proved very helpful in revealing the physiological or pathophysiological condition of retinal pigment epithelium.

Ultrastructure and regression of the tunica vasculosa lentis in newborn Wistar rats.

In this study, regression of the hyaloid vessels has been followed in the tunica vasculosa lentis (TVL) of the Wistar rat using light, transmission and scanning electron microscopy. The investigation extended from the 1st to the 32nd postnatal day. On day one, the posterior tunica vasculosa lentis is made up of radiating capillaries connected by side-arm branches, the vascular walls of which possess a continuous endothelium, a basement membrane and an incomplete pericyte covering. Endothelial cell specialization is apparent in the form of extreme thinning and fenestration in capillary regions lying opposite the lenticular capsule. The earliest detectable regressive changes become apparent on approximately day 3 and initially involve the short connecting capillaries surrounding the posterior pole of the lens and proceed from there. Regression takes place in the presence of rarefaction of vessel wall cells and the accumulation of endothelial cells in the adjacent capillaries. This leads to the formation of acellular channels which are made up of only basement membrane tubes. After the complete disappearance of these transitional acellular channels, the capillary meshwork coarsens. Remnants of these capillaries are detectable until the 30th postnatal day.