Objective To observe the morphological change of retina and its affection on visual function after optic nerve crush in adult rat. Methods The models of optic nerve crush in rats were made. The change of retinas in different time (1,3 ,5 ,7,9,14,28,56,84d respectively) after injury were observed by light microscope, and the flash visual evoked potential (F-VEP) was recorded in normal and injured rats. Result The number of retinal ganglion cells (RGCs) was significantly reduced in the partial lesion of optic nerve crush compared with normal optic nerves without injury. The initial loss of RGCs was accelerated during 3-7days after nerve crush and then declined gradually by 14 days, and no change was observed after 28 days. The wave of F-VEP became lower and wider in one day after the crush, and the latency and amplitude of F-VEP declined gradually from one day to 14 days, and recovery response was observed by the time of 4 weeks after injury. Conclusion The secondary degeneration of RGCs following optic nerve crush is the important morphological foundation of fall of visual function, which have relativity with the regular decline of visual function.

Estimation the postmortem interval(PMI)is an important subject in forensic medicine practice.Recent research has found that the DNA molecular would degrade immediately following death,and the quantity of DNA in nuclear would be decreasing along with the elapse of the time since death.Seven parameter of cell nuclear,including the area and integral optical density,were chosen and the changes of DNA content in the brain cells of 15 rats were determined at every one hour during 48 horus after death by the auto TV imange analyses system.The results showed that the degradation rate of DNA in nuclear has a certainty relationship with early PMI in rats and indicated that the determination of the quantity of DNA in nuclear is the major method to estimate the PMI.