ABSTRACT
Objective To explore the regularity of time-dependent changes in morphology and biomechanical properties of brain tissues in pigs, and value the feasibility of deducing the postmortem interval (PMI). Methods Brain tissues were taken from 42 pigs and kept in an artificial climate chamber with the temperature of 25 ℃ and humidity of 75%. The samples were collected from telencephalon at sequential time intervals (0, 12, 24, 36, 48, 60 h；n=6) according to the principle of predefined time, position, direction, ratio, quantity and shape. The samples fixed with formaldehyde were then immediately tested by mechanical testing machine to obtain their biomechanical parameters and the histological sections were prepared. Results With the extension of PMI (0-60 h), brain tissues gradually became discolored, weak, mudding and liquefied under the influence of autolysis and putrefaction. Both clearance area of the white matter and its integrated optical density (IOD) significantly increased during 0-48 h. Biomechanical properties of brain tissues including the limit load, average force, elastic modulus and fracture energy all presented a declining tendency at the interval of 12-60 h. The limit load was considered highly statistically significant, and statistical differences were found in average force, elastic modulus and fracture energy. Conclusions There exists a significantly negative structure-activity relationship between the morphology of brain tissues and biomechanical properties. The limit load of postmortem brain tissues in 60 h is the optimum in the window period, which can be used as a new method for estimating PMI.
ABSTRACT
Objective To explore the regularity of time-dependent changes in morphology and biomechanical properties of brain tissues in pigs,and value the feasibility of deducing the postmortem interval (PMI).Methods Brain tissues were taken from 42 pigs and kept in an artificial climate chamber with the temperature of 25 ℃ and humidity of 75％.The samples were collected from telencephalon at sequential time intervals (0,12,24,36,48,60 h;n =6) according to the principle of predefined time,position,direction,ratio,quantity and shape.The samples fixed with formaldehyde were then immediately tested by mechanical testing machine to obtain their biomechanical parameters and the histological sections were prepared.Results With the extension of PMI (0-60 h),brain tissues gradually became discolored,weak,mudding and liquefied under the influence of autolysis and putrefaction.Both clearance area of the white matter and its integrated optical density (IOD) significantly increased during 0-48 h.Biomechanical properties of brain tissues including the limit load,average force,elastic modulus and fracture energy all presented a declining tendency at the interval of 12-60 h.The limit load was considered highly statistically significant,and statistical differences were found in average force,elastic modulus and fracture energy.Conclusions There exists a significantly negative structure-activity relationship between the morphology of brain tissues and biomechanical properties.The limit load of postmortem brain tissues in 60 h is the optimum in the window period,which can be used as a new method for estimating PMI.
ABSTRACT
Objective To detect nuclear DNA degradation of bone marrows and brains in rat cadavers at different temperatures,and develop a new parameter for estimating early postmortem interval(PMI).Methods The brain and bone marrow were taken out for every 4h,during 0~40h after death at 10℃ and 20℃,respectively.And the single cell gel electrophoresis(SCGE) was carried out to detect the nuclear DNA degradation.Linear regression analysis was used to assay the relationship of the comet parameter HeadDNA%,Tail Length(TL) and Olive TailMoment(TM) with PMI.Results Different decline degrees of comet HeadDNA% were found in both brain cells and bone marrow cells after death,the decline of HeadDNA% in brain cells at 20℃ was faster.Compared with degradation in marrow cells,the linear relation between degradation of brain cells and PMI was better.Conclusion with that of comet parameters TL and TM,the perfect linear relationship between HeadDNA% and PMI was also observed.Conclusion Brain tissues are more suitable for PMI estimation by detecting degradation of DNA with SCGE.The HeadDNA% is more valuable for PMI estimation than TL and TM.
ABSTRACT
Objective To observe the degradation pattern of tubulin in the cardiac muscle and lung tissue of rats after death.Methods 24 young male Sprague-Dawley rats were divided into 6 groups averagely.After being killed by bleeding,the rats were kept in an artificial climate incubator;the experimental temperature was kept at 20℃ and humidity at 50%.Proteins in cardiac muscle and lung tissue were extracted and tubulin was then examined by Western blot.Thereafter,the semi-quantitative analysis of the Western blot images was performed.Results Tubulin can be detected in the normal cardiac muscle and lung tissue of rats.After 1d postmortem,the tubulin content in these tissues began to decline,and it might still be detected at 7d postmortem,but the tubulin content in lung decreased faster than that in cardiac muscle.A linear relationship between tubulin content in cardiac muscle and lung of rats and the postmortem interval was determined.The linear regression equations and coefficients for integral optic density in relation to PMI were y=-1726.1x+14083 with correlative coefficient r=0.9684 for cardiac muscle and y=-1439.89x+12041 with correlative coefficient r=0.9808 for lung,respectively.Conclusion The level of tubulin in cardiac muscle and lung tissue of rats varied with PMI and the time dependent degradation of this protein was potentially useful for the PMI estimation.