Cytochalasin B-induced structural changes in the anterior ocular segment of the cynomolgus monkey.

Abstract

Three cynomolgus monkeys had 5jxg of cytochalasin B (CYTO) infused intracamerally in one eye and the dimethylsulfoxide vehicle (DMSO) toithout CYTO infused into the other. Thirty minutes later, when the CYTO eyes demonstrated the expected large increase in gross outflow facility, the anterior segments were fixed at physiologic 1OP. Four other monkeys received intracameral injection of CYTO in one eye and DMSO vehicle in the other eye 5 hr, 24 hr, 6 days, or 7 days prior to facility measurement. No CYTO-induced facility increase persisted, but the 5 hr and 6-day eyes were nonetheless fixed. The fixed eyes were studied by light microscopy and scanning and transmission electron microscopy. The acute DMSO eyes demonstrated no structural abnormalities in the chamber angle, ciliary body, iris, or cornea; the 5 hr and 6-day post-DMSO eyes showed structural alterations in the ciliary processes similar to those in their fellow CYTO eyes. The acute CYTO eyes demonstrated the following structural abnormalities: (1) uveal and corneoscleral meshwork: separation, degeneration, and disappearance of endothelial cells; (2) cribriform meshwork: distention, with separation of cells and loss of extracellular material; (3) inner wall of Schlemm's canal: separation from the underlying tissue, abnormally large invaginations, frank ruptures, and increased frequency of normal appearing pores; (4) anterior ciliary processes: large plasma-filled spaces in the stroma and between the epithelial layers; (5) iris pigmented epitheliwn: empty intracellular vacuoles sometimes compressing the cell nucleus; (6) corneal endothelial cells: blebbing, loss of the terminal web of microfilaments, empty intracellular vacuoles sometimes compressing the nucleus, large central craters, and widened intercellular spaces. Repair and recovery began very quickly, with degranulated platelets plugging the inner wall ruptures in the acute eyes. By 5 hr, the meshwork, inner wall, and ciliary process abnormalities were much less striking, and the iris and cornea appeared entirely normal. By 6 days, the meshwork and inner wall appeared normal, but structural alterations were still present in the ciliary processes.