| ABSTRACT.
Purpose: To investigate the doses of the plasmin to induce posterior vitreous detachment (PVD) and the effect of plasmin on the collagen fibril organization in human vitreous gel.
Methods: Plasmin (2u or 3u/0.1ml) was injected into vitreous cavity of enucleated fresh human eyes. After incubation at 37°C for 30-120 minutes, the globes were hemisected and the extent of PVD was graded as complete, partial, or no. Scanning electron microscopy was performed to examine the ultrastructure of the vitreoretinal interface. Intact vitreous gels from young donor¢s eyes were incubated with 3 units plasmin at 37°C for 24 hours, specimens from central, cortical and basal vitreous were obtained with microscissors. Freeze etching electron microscopy was performed to study the collagen fibril organization.
Results: After 30 minutes, in eyes incubated with 2 U plasmin, 8/10 had partial PVD and 2/10 had complete PVD, while in eyes incubated with 3 U plasmin , 10/10 eyes had complete PVD. In control eyes, only 2 eyes were observed to be partial PVD. After 120 minutes, 2 unites plasmin induced all eyes complete PVD. In control eyes, complete, partial and no PVD was 2/10, 7/10 and 1/10 respectively. Eyes with complete PVD induced by plasmin had a smooth retinal surface. After incubation with 3 units plasmin, the vitreous collagen fibril network was destroyed. In all controls, the collagen fibrils were linked into network, its fine three-dimensional structure is normal.
Conclusions: The degree of PVD induced by plasmin was related with the concentration and exposure times of plasmin. Meanwhile, plasmin can also destruct the collagen fibril network. It may be used not only as a viable biochemical adjunct to vitrectomy but also as a drug to prevent the occurrence of proliferation in some disease.
Key words: Plasmin - posterior vitreous detachment - freeze-fracture - Deep-etching and Replication - Collagen fibrillar organization
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