| PrefaceInfective endophthalmistis is a potentially blinding condition and remains a serious postoperative complication of such frequently performed eye surgeries as cataract or ocular trauma. Vancomycin, an antibiotic effective against all Gram - positive bacteria that interferes with cell - wall synthesis, has been increasingly recommended for the diease of Staphylococcus epiderimidis and S. aureus. Endophthalmitis.However, the related reports were rare about its retinal toxicity mechanisms after different dose intravitreal injections. Oxygen - derived free radicals accelerate lipid peroxidation, cause degradation of function and structure in cell membrance, and induce oxidation of superoxide dismutase ( SOD ) and decrease its level. So the levels of SOD reflect the amount of oxygen - derived free radicals in tissues. Malondialdehyde ( MDA ) reflects the extend of lipid peroxidation in tissues.In our study, we established the animal model and selected biochemical assays , morphological observation and transmission electon microscopy to study the relationship between free radicals and vancomycin'retinal toxicity after intravitreal injections.Material and Methods 1. Animal grouping, administration and sample collection1. 1 Animal grouping: 96 healthy adult New Zealand albino rabbits of other sex ( body weight 2 -3.5Kg ) were randomly assigned into 4 groups after allowing free access to food and tap water for 7 days. The control group ( 24 rabbits, 48 eyes ) were injected intravitreally normal sodium 0. lml. Vancomycin 0. lml of 10, 20, 50mg/ml were injected intravitreally in48 eyes respectively as 3 experimental groups.1.2 Administration: Under general anesthetied, the needle was inserted carefully into rabbit eye approximately 2 -3 mm below the sclera - limbus junction through the pars plana into the mid vitreous and injected 0. lml various dose of drug.1. 3 Sample collection; The retina samples were collected at lth, 4th, 7th, 14th day and detected by SOD reagent box and MDA reagent box.2. Observation and determination2. 1 After intravitreal injections, all eyes were examined by ophthalmosco-py, light microscopy, and transmission electon microscopy on the lth, 4th, 7th, 14th day.2. 2 The activity of superoxide dismutas ( SOD ) and the levels of malondi-aldehyde ( MDA ) were determined with SOD reagent box and MDA reagent box.3. Reagent and ApparatusLeitzl 512 microtome, JEDL JEM - 1200EX transmission electron microscope , Bx60F/PM30 - 3 photomicroscope system, SOD reagent box. , MDA reagent box.4. Data statistical analysisAnalysis of variance were performed with SPSS packages.Results1. The histopatholigical changesBy light microscope , there was no toxic phenomenon in control group and experimental group 1. In experimental group 2 the structures of nerve fiber layer and ganglion cell layer disordering lightly were observed on day 7th after injec-tion, but recover on day 14th. In experimental group 3 the structures of retina were destroyed badly.In experimental group 2, the ultrastructural changes showed the ganglion cells twisted, mitochondria in the inner segment swollen. In experimental group 3, we found karyopyknosis in outer nuclear layer of the retina, edema of the inner plexiform layer and the nerve fiber layer, mitochondria in the ganlion cell layer swollen.2. The activities of SODThe SOD activities in the control group and experimental group 1 and at different time have no significant different. In experimental group 2 ( p <0. 05 ) and experimental group 3 ( p <0.01 ) the level of SOD in retina was significant lower than that in control group. Using square variance test, the SOD activities in the experimental group 2, experimental group 3 have significant different between different teams. The activities of SOD in retina was in a lowest level at 4th day after injection, and then increased along with time to the level in control group.3. The level of MDAThe level of MDA in the control group and experimental group 1 and at different time have no significant different ( p <0.05 ). In experimental group 2 ( p <0.05 ) and experimental group 3 ( p <0. 01 ) the level of MDA in retina was significant higher than that in control group. Using square variance test, the level of MDA in experimental group 2, experimental group 3 have significant different between different teams. The level of MDA in retina was in a highest level at 4th day after injection, and then decreased along with time to the level in control group.DiscussionFree radicals accelerate lipid peroxidation, cause degradation of function and structure in cell membrane, and induce cell toxicity. Extensive production of oxygen - derived free radicals induce oxidation of SOD and decrease its level. So the levels of SOD reflects the amount of oxygen - derived free radicals in tis-... |
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