The Experimental Research Of Different Dosage Of KI On The Morphological Changes Of Cerebellum In Balb/c Mice

Objectives:To study the effect of different dosage of KI upon the morphological changes incerebellum in adult Balb/c mice and in their filial generations of 20-day and 40-day.Methods:Balb/c mice weighted 16-20 gram at the age of one month, half of male and halfof female, were divided into five groups randomly and given by different dosage ofKI, which were low iodine(M), normal iodine(NI), 5high-iodine(5HI), 10high-iodine(10HI), 50 high-iodine(50HI). The mice of the LI group were fed with thediet derived from endemic goiter area containing iodine concentration is less than50μg/kg, The mice of the other four groups were fed with standard diet containingiodine of 300μg/kg. The mice of the LI and NI group drank deironized water, themice of the other three groups drank different iodine concentration deironized waterrespectively. According to intake of the 5ml water and the 5g diet everyday, the iodineintake of the whole day of the five groups are estimated as follows:＜0.25μg/d(LI),1.5μg/d(NI), 7.5μg/d(5HI), 15μg/d(10HI), 75μg/d(50HI). After three months, somemice mated and their filial generations of 20-day and 40-day were observed. Theothers mice were sacrificed at the end of the third . 10 mice from each group wereselected randomly to observe the morphological changes of Cerebellum. The wholebrains were weighed. The expressions of NSE in the neurons of the Purkinje layer, theexpressions of GFAP and MBP in the glial cell in the medulla were examined byimmunohistochemistry, and volume density (Vv), numerical density on area (N_A) andaverage optical density were measured. After strained by the special purple dye, thethickness of the molecular layer and granular layer were measured respectively. The area percentages of the Nissl bodies in the soma of the Purkinje cells in the Purkinjelayer were also measured.Results:1. The three-month adult mice: Serum TT₄ and FT₄ levels in the LI groupwere lower than those in the NI group(P＜0.01). Compared with the NI group, serumTT₃and FT₃ levels in the 10HI ,50HI group were lower(P＜0.01).The urinary iodinewas significantly lower in the LI group than in the NI group ,and the urinary iodine inthe 5HI, 10HI and 50HI increased in folds compared with the NI group. The changesin brain weights were insignificant in all iodine excess groups and LI group. Thebody weights in the LI group decreased(P＜0.01). There were no significant changesin the thickness of the molecular layer ,the thickness of the granular layer, the areapercentages of the Nissl bodies in the soma of the Purkinje cells in the Purkinje layerin all groups(P＞0.05). In contrast to the NI group, the average optical density in thecytoplasm of the NSE positive Purkinje cell were lower in the LI and 50HIgroup(P＜0.05). But there were no significant changes in the 5HI and 10HI group. Thechanges of N_A and V_v of the NSE positive Purkinje cells in the Purkinje layer wereinsignificant in all groups(P＞0.05). There were no significant changes in theexpressions of GFAP and MBP in the glial cell in the medulla in all groups.2. The 20-day and 40-day filial generations: a. There were no significantchanges in the relative weight of brain in all groups, the body weight and the absoluteweight of brain were significantly lower in the LI and 50HI group than those of in theNI group(P＜0.01), b. Compared with the NI group, the thickness of the molecularlayer decreased and the thickness of the granular layer increased in the LI and 50HIgroup(P＜0.05), the area percentages of the Nissl bodies in the soma of the Purkinjecells in the Purkinje layer remarkably decreased in the LI group(P＜0.05), c. Theaverage optical density in the cytoplasm of the NSE positive Purkinje cell were lowerin the LI and 50HI group(P＜0.01).and there were no significant changes in otheriodine excess groups. The V_v of the NSE positive Purkinje cells in the Purkinje layer decreased in the LI group in 20-day Balb/c mice(P＜0.01), and the NA and Vvdecreased in the LI group in 40-day Balb/c mice(P＜0.05).The NA, Vv and AO of theGFAP positive glial cell in the medulla were lower in the LI group than in the NIgroup(P＜0.01), the NA and AO also decreased in the 50HI group(P＜0.05), but thechanges of the Vv were insignificant(P＞0.05), and there were no significant changesin other iodine excess groups. The AO of MBP positive nerve fiber in the medullawere lower in the LI and 50HI group than in the NI group(P＜0.01),but the changes inother excess iodine groups were insignificant.Conclusions:1. Iodine deficiency or iodine excess can not make significant morphologicalchange of the cortex and medulla of Cerebellum in adult Balb/c mice. But iodinedeficiency or chronic long-term iodine excess intake can weaken the function of thethyroid, which result to decreasing of the concentrations of T4 and T3, Due to thedecreasing of the concentration of T4 ,the energy metabolism of the Purkinje cells inthe Purkinje layer will be lower.2. Iodine deficiency or chronic long-term iodine excess intake would affect thedevelopment of the cerebellum in the filial generations, Balb/c mice have highendurance to high doses of iodine, so iodine intake within 50HI has no effect on theirdevelopment of the Cerebellum in the filial generations.