We conducted electron microscopic observation of twenty diabetic preretinal membranes removed during vitrectomy. Membranes were composed of many different types of cells and vessels and intercellular substance. Vessels of develping stage had forming narrow lumen and endothelium showed pinocytic vesicles and apical microvilli, and surrounded with vascular pericytes and multilayed basement membrane. Vessels of mature stage had large lumen and endothelium was flat. In vessels of regressing stage, lumen was obstructed with plug of red blood cells and endothelial cells were degenerating with abundant residual bodies. Pericytes also showed degenerative change. Most of junctions between endothelial cells wer tight junciton in all stage of vessels, but incomplete form of tight junction with open intercellular cleft was found more frequently in vessels of immature stage. Cells found in membranes were fibroblast, macrophage, myofibroblast, fibrous astrocyte in frequency. Extravascular plasma cell and polymorphonuclear leukocytes were observed occasionally. Intercellular substance was lagely composed of mature collagen. These results suggest incomplete endothelial junctions may be partly responsible for permeability of diabetic new vessels, and degenerated endothelium and pericyte may contribute to vitreous hemorrhage.
Astrocytes ; Basement Membrane ; Collagen ; Endothelial Cells ; Endothelium ; Erythrocytes ; Fibroblasts ; Macrophages ; Membranes* ; Microvilli ; Myofibroblasts ; Neutrophils ; Pericytes ; Permeability ; Plasma Cells ; Tight Junctions ; Vitrectomy ; Vitreous Hemorrhage

Hyperosmotic agents such as mannitol are widely used in ophthalmology to lower intraocular pressure as a short-term or emergency method. The mechanism of action of these agents is not fully understood, but probably relates primarily to a reduction in vitreous volume. There are other theories of hypotensive meechanism such as hypothalamic-neural theory and altered epithelium theory. The author performed this animal experiment for the eletronmicroscopic study of ciliary epithelium after the intravenous mannitol injection. Five healthy adult male albino rabbits weighing 2.5 kg were used in this experiment. Four rabbits were administered 25 ml(2 gm/kg) of 20% mannitol and the other one was given 25 ml of normal saline as a control through ear vein within 5 minutes each. The mannitol group was enucleated 10, 20, 40 and 80 minutes after injection and the control one was enucleated 20 minutes after injection. The enucleated eyes were opened and fixed in mixed solution of 2% paraformaldehyde, 3% glutaraldehyde and 0.2M Milonig's buffer. Small pieces consisting of ciliary body were excised, postfixed in 1% osmium tetroxide, dehydrated in ethylalcohol and embedded in Epon 812. Thin section were stained with toluidine blue for general histologic study and ultrathin sections stained with 4% uranyl acetate and 0.4% lead citrate were examined with a Hitachi H-600 transmission electronmicroscopy. The results were as follow: 1. The ciliary epithelium showed normal appearence 20 minutes after injection of normal saline and was composed of double layered epithelial cells. The tight juctions(zonulae occludens) were present between nonpigmented epithelial cells. The active Golgi apparatus, numerous mitochondria, rough endoplasmic reticulum and smooth endoplasmic reticulum were visible in the nonpigmented epithelial cells. The intercellular spaces were not dilated. 2. In mannitol group, no cellular necrosis was observed and cells were invariably present and apparently unaltered. 3. The intercellular spaces of ciliary epithelium began to dilate 10 minutes after intravenous mannitol injection, maximally dilated after 40 minutes and recovered after 80 minutes. 4. In view of the morphological changes of cytoplasmic organelles such as Goigi apparatus, the secretory function of nonpigmented epithelial cells after intravenous mannitol seemed to be inhibited maximally at 20 minutes and then recovered after 80 minutes. 5. In conclusion, the hypotensive mechanism of the mannitol on the ciliary epithelium was considered of secretory inhibition of nonpigmented epithelial cells besides diffusion by the osmotic gradient.
Adult ; Animal Experimentation ; Ciliary Body ; Citric Acid ; Cytoplasm ; Diffusion ; Ear ; Emergencies ; Endoplasmic Reticulum, Rough ; Endoplasmic Reticulum, Smooth ; Epithelial Cells ; Epithelium* ; Extracellular Space ; Glutaral ; Golgi Apparatus ; Humans ; Intraocular Pressure ; Male ; Mannitol* ; Mitochondria ; Necrosis ; Ophthalmology ; Organelles ; Osmium Tetroxide ; Rabbits ; Tolonium Chloride ; Veins

A 11-days-old female was diagnosed as incontinentia pigmenti by skin biopsy was referred for ophthalmological examination.The fundus of the right eye showed vacularization only in the posteroir pole and neovascularization in the junctional area between vascular and avascula retina.Systemic evaluation revealed no associated abnormality.At 22 days of age, we ablated avascular retina with indirect diode laser photocoagulation under general anesthesia. Despite extensive 360 degree photocoagulation, fibrovascular proliferation was found to extend into vitreous cavity from optic disc 3 weeks after photocoagulation.
Anesthesia, General ; Biopsy ; Female ; Humans ; Incontinentia Pigmenti* ; Lasers, Semiconductor ; Light Coagulation* ; Retina ; Skin