ABSTRACT
Objective To study the effect of 125Iodine seed on the rabbit ischiadic nerve at different time point after implantation. Methods Thirty healthy New-Zealand rabbits were randomly assigned into 3 groups( 2-week group, 2-month group and 4-month group) using envelope method. During operation, 10 radioactive 125I seeds were implanted randomly near one of the ischiadic nerve, while 10 non-radioactive seeds were implanted into the contralateral ischiadie nerve. According to treatment plan system(TPS),90% of the prescription dose (PD)was centered in the specific place, where the nerves were chosen to be studied. After 2 weeks, 2 months and 4 months respectively, nerve electro-physiolngy experiment was used to evaluate the bilateral ischiadic nerves, at the same time the morphology of the ischiadic nerve was examined by general observation, light microscope and electron microscope. The electron microscope photo with the same ×4000 amplification was divided into 100( 10 × 10) cages and non-specific changes in one cage account for 1%. The t test and sum rank test were used for statistics. Results Potential leaking point of experimental ischiadic nerves near heart in 2-week group ,2-month group and 4-month group were (0.52± 0.26), (0.60±0.19), (0.48±0.17)V, while that of the control sides were (0.59±0.19), (0.60± 0.15), (0.53±0.13 ) V, there was no statistical significance in the same group respectively (t=0.91, 0.03,0.67,P>0.05). Potential leak point of experimental ischiadic nerves far from heart in 2-week group, 2-month group and 4-month group were (0.51±0.15), (0.52 s0. 11 ), (0. 53±0.15) V,the control sides were (0.52±0.10), (0.56±0.12), (0.54±0.10)V, there was no statistical significance in the same group respectively (t= 0.25,0.74,0.17, P > 0.05 ). Action potential amplitude of experimental ischiadic nerves near heart in 2-week group,2-menth group and 4-month group were (13.18±4.09), (12.78± 4.42), (12.09±1.20) mV, while that of the control sides were (10.55± 4.21 ), ( 10.31±4.22), (12.88±3.54) mV, there was no statistical significance in the same group respectively (t=1.57,1.36, 0.50,P>0.05). Action potential amplitude of experimental ischiadic nerves far from heart in 2-week group,2-month group and 4-month group were (11.18±3.38), (11.68±3.21), ( 12.52±3.09) mV, while that of the control sides were (11.56±4.80), (10.71±3.40), (11.67±2.48) mV ,there was no statistical significance in the same group respectively(t=0.29,1.01,0.55, P>0.05 ). Nerve conduction velocity of experimental ischiadic nerves in 2-week group,2-month group and 4-month group were (40.56± 9.46), (38.79±5.78), (39.44±8.64) m/V, the control sides were (42.56±6.59), (44.64±7.53), (43.33±6.05)m/V, there was no statistical significance in the same group respectively( t = 0.57,1.94, 0.01,P>0.05). There were some changes in general observation and light microscope, in electron microscope, many non-specificity changes were observed. All of these changes included delamination, collapse, disaggregation of the myelinated nerve, mitochondria swelling and vacuolization of neurilemma cell and axon. The ratio of degenerative alterations in nerves was 60% --70% in 2-week group, 50% in 2-month group and 30% in 4-month group, and there was statistical significance among three groups (P<0.05). Conclusion 125I permanent plantation in our test dose has little effect on ischiadic nerve, all these non-specificity changes were observed in electron microscope, and it has no evident impacts on physiological functions.