Cryoultramicroscopy of the retina and choroid in rat.

Preparations of ultrathin frozen sections of the retina and choroid in rat were studied by the new technique of Tokuyasu (1973). All membrane structures were observable in ultrathin frozen sections, so that this method is likely to be most valuable for the morphologic study of membranes. However, there are some disadvantages to the use of this technique in that identification of some intracellular organelles such as ribosomes and glycogen is difficult. A fibrous dense network was observed in the interphotoreceptor spaces, the intermicrovilli spaces of the pigment epithelium, and it appeared in the space between the photoreceptor and the microvilli. The network almost disappeared after treatment with hyaluronidase for 30 min, suggesting that it may consist of aid mucopolysaccharide.