ULTRASTRUCTURE OF FIBER CELLS AND MULTILAMELLAR INCLUSIONS IN EXPERIMENTAL DIABETES

Purpose. The goal of this ultrastructural study was to examine fiber c ell shape and intercellular junctions during the early stages of fiber cell breakdown and edema in diabetic rabbit lenses. Methods. Lens abn ormalities were recorded with a slit lamp. Between 6-10 mo after drug treatment, diabetic lenses and untreated control lenses were freshly e nucleated and sectioned with a vibrating knife microtome. The thick ti ssue sections were chemically fixed and processed for thin-section ele ctron microscopy. Results. Alloxan-induced diabetes in albino rabbits produced clinically apparent cataracts as soon as 1 mo after the anima ls became hyperglycemic. The cataracts displayed cortical fluid-filled vacuoles in the equatorial region and at the cortex-nucleus interface , white specks scattered throughout the cortex, and posterior subcapsu lar cataracts. Fiber cells just deeper than the large cortical vacuole s had oval of spindle-shaped cross sections. Multilamellar inclusions, not reported previously for diabetic lenses, were observed at or near the fiber cell interfaces and were composed of concentric or spiral r ings of plasma membrane-bound cytoplasmic processes. Undulating membra nes were present throughout most of the multilamellar inclusions. Tran sparent lenses from untreated controls did not have such multilamellar bodies or extensive membrane undulations in cells at the same distanc e from the lens surface. Conclusions. Fiber cells respond to the diabe tic insult differently depending on their stage of differentiation and age. The observed changes are consistent with the hypothesis that hyp erglycemia accelerates the formation of age-related changes in fiber c ells.