Age-Related Changes of Material Mechanics and Bone Material Parameters of Rat Skulls / 法医学杂志

Objective To study the relationship between material mechanics and bone material parameters of rat skulls and their correlation with age by examination of the parameters. Methods Forty-eight healthy male SD rats were divided into 2, 4, 6, 8, 17, 26, 52 and 104 week groups according to their age. Each group had six rats. The right cranium was compressed by KD Ⅱ-0.2 microcomputer controlled electronic universal testing machine, and material mechanics parameters （ultimate load, compression strength and compression modulus） were measured, then the skull slices were cut off and scanned by Micro-CT system to detect bone material parameters （skull thickness, bone mineral density, bone volume, and trabecular thickness）. Results The differences in ultimate load, compression strength and compression modulus among all groups had statistical significance （P<0.05）, and were positively correlated with age within 26 weeks （P<0.05）. The differences in skull thickness, bone mineral density, bone volume and trabecular thickness among all groups had statistical significance （P<0.05）, and were positively correlated with age within 52 weeks （P<0.05）. All material mechanics parameters were positively correlated with bone material parameters （P<0.05）. Conclusion There is a positive correlation between bone material parameters （skull thickness, bone mineral density, bone volume, trabecular thickness）, material mechanics parameter （skull ultimate load, compression strength, compression modulus） and age in a certain range, which can be used to infer age.

Application of Sequential Changes of Dural Thickness and Biomechanical Parameters in Postmortem Interval Estimation / 法医学杂志

Objective To study the relations of the dural thickness and the biomechanical parameters with postmortem interval （PMI） of human cadavers, and to explore the feasibility of the two indexes used for PMI estimation. Methods Dural samples were collected at different postmortem intervals of 6 h, 12 h, 18 h, 24 h, 30 h, 36 h, 48 h, 60 h, 72 h, 84 h and 96 h, then fabricated into 4.0 cm×1.0 cm A and B test specimens. The thickness of the A test specimen was measured, and the biomechanical parameters, such as ultimate load, maximum force deformation, tensile strength, elastic modulus and fracture force, were measured. The regression equations of thickness, biomechanical parameters and PMI were fitted respectively, and the difference between the predicted value and actual measured value of PMI was verified by the verification group. The B test specimen was fixed with 10% neutral formaldehyde solution, then tissue sections were prepared to observe its morphological changes. Results From 6 h to 96 h after death, the dural thickness decreased gradually, the collagen fibers gradually changed from clear arrangement to mutual fusion, and the number of nuclei decreased gradually. The dural thickness, ultimate load, tensile strength, elastic modulus and fracture force decreased sequentially, among which the dural thickness, ultimate load, elastic modulus and fracture force had a correlation with PMI （P<0.05）. In the return test, the difference between the predicted value and actual measured value of PMI in the verification group had no statistical significance （P>0.05）. Conclusion The dural thickness, ultimate load, elastic modulus and fracture force change sequentially from 6 h to 96 h after death. The regression equation established by the relationship between the changes and PMI can be used for PMI estimation.

Expression of PURA gene and its protein in nephridial tissue of rats with fluorosis of coal-burning / 中国地方病学杂志

Objective To investigate the meaning of PURA gene and its protein in nephridial tissue of the rats with endemic fluorosis of coal burning. Methods Thirty-six SD rats of 80 - 100 g, body weight were randomly divided into control group, low fluorosis group and high fluorosis group according to body weight, 12 in each group, the number of female and male in each group was the same respectively. The control group, Low fluorosis group and high fluorosis group rots were fed with 1.5,25.0,60.0 mg/kg fluoride content in feedstuff, to establish the animal model of fluorosis. Expressions of both mRNA and its protein of PURA gene in rat nephridium tissue, were determined by RT-PCR and immunohistochemistry after four-month experimental period. Results The expressions of PURA mRNA[(2.74± 1.06),(4.29 ± 2.11)] and its protein[ (28 827.91 ± 4801.94),(61 146.96 ± 4997.55)] in low fluorosis group and high fluorosis group was higher than that in the control group[ ( 1.13 ± 0.87), (7131.95 ± 1524.54), all P < 0.05]. And the expressions of PURA mRNA and protein in high fluorosis groups was higher than that in low fluorosis greup(all P < 0.05). Conclusion High fluoride can lead to the high expression of PURA gene mRNA and protein in the rat nephridium tissue exposed to sodium fluoride.