Salty Biofluidic Sample Clean-Up and Preconcentration with a Paper-Based Ion Concentration Polarization Interface.

Charged species from complex media could be separated and enriched taking advantage of ion concentration polarization (ICP) effect; thus, ICP can be used for sample purification and improvement of detection sensitivity. In this paper, a novel and reliable ICP interface was established on a paper-based analytical device (PAD) by using ion exchange membrane, and electrokinetic stacking of target analytes from salty media was successfully demonstrated. Steady ICP effect was well observed in aqueous solution with up to 400 mM NaCl as shown by a fluorescent probe, which makes it possible to directly process salty physiological samples such as blood and urine with this type of PAD. Application of this method was demonstrated by direct online stacking of total protein from urine samples and image-based colorimetric detection by a smartphone camera. The linear response was in the range of 50-350 mg/L (R2 = 0.99), with recovery rate in the range of 94.8-107.6% and relative standard deviation below 7.1%. The obtained results were consistent with that of the clinical method. As an off-line sample pretreatment method, the feasibility for rapid tandem mass spectrometry detection of amino acids from serum samples was also investigated, and promising results were obtained. This PAD method is of low cost, easy to operate, and reliable. As a disposable PAD, it is useful not only for sensitive point-of-care testing but also for direct purification and concentration of complex and highly conductive physiological samples for fast and accurate detection with advanced analytical instruments.

Ultra-high pressure treatment improve the content of characteristic aromatic components of melon juice from the view of physical changes.

Introduction: The effectiveness of ultra-high pressure (UHP) technology in retaining the flavor of fresh fruit and vegetable juices has been acknowledged in recent years. Along with previously hypothesized conclusions, the improvement in melon juice flavor may be linked to the reduction of its surface tension through UHP. Methods: In this paper, the particle size, free-water percentage, and related thermodynamic parameters of melon juice were evaluated in a physical point for a deeper insight. Results: The results showed that the UHP treatment of P2-2 (200 MPa for 20 min) raised the free water percentage by 7,000 times than the other treatments and both the melting enthalpy, binding constant and Gibbs free energy of P2-2 were minimized. This significantly increased the volatility of characteristic aromatic compounds in melon juice, resulting in a 1.2-5 times increase in the content of aromatic compounds in the gas phase of the P2-2 group compared to fresh melon juice.

Simultaneous enrichment and separation based on ion concentration polarization effect on a paper based analytical device.

In this paper, simultaneous enrichment and separation of ions and amphoteric components were successfully demonstrated by using electric field (E) and pH gradient (double gradient) in the ion depletion zone of anion concentration polarization interface established on a paper fluid channel. Experimental results were visualized with colored ions (bright blue and amaranth) and protein probes (phycocyanin and cytochrome C). With optimization, colored phycocyanin and bovine hemoglobin with similar pI as that of albumin and immunoglobulin respectively were well separated in 900 s with 10-fold enrichment effect. Based on the separation and enrichment function of this paper-based analytical device (PAD) and rapid selective staining of human serum albumin (HSA) with bromophenol blue, a rapid colorimetric detection of HSA was implemented with smartphone camera. A limit of detection (LOD) of 5.2 mg·L-1 was achieved in the clinically significant range of 10-300 mg·L-1 (R2 = 0.99). This method was applied to real human urine samples with good agreement (ɑ = 0.01) to clinical detection method (immunoturbidimetry). With the separation and enrichment functions of PAD, both the specificity and sensitivity were enhanced, which provides a solid basis for point-of-care test of microalbuminuria. Therefore, this PAD device is potential for sample pretreatment and detection of target components from complex physiological samples.

Unsupervised Hierarchical Dynamic Parsing and Encoding for Action Recognition.

Generally, the evolution of an action is not uniform across the video, but exhibits quite complex rhythms and non-stationary dynamics. To model such non-uniform temporal dynamics, in this paper, we describe a novel hierarchical dynamic parsing and encoding method to capture both the locally smooth dynamics and globally drastic dynamic changes. It parses the dynamics of an action into different layers and encodes such multi-layer temporal information into a joint representation for action recognition. At the first layer, the action sequence is parsed in an unsupervised manner into several smooth-changing stages corresponding to different key poses or temporal structures by temporal clustering. The dynamics within each stage are encoded by mean-pooling or rank-pooling. At the second layer, the temporal information of the ordered dynamics extracted from the previous layer is encoded again by rank-pooling to form the overall representation. Extensive experiments on a gesture action data set (Chalearn Gesture) and three generic action data sets (Olympic Sports, Hollywood2, and UCF101) have demonstrated the effectiveness of the proposed method.

Discriminative Transformation for Multi-Dimensional Temporal Sequences.

Feature space transformation techniques have been widely studied for dimensionality reduction in vector-based feature space. However, these techniques are inapplicable to sequence data because the features in the same sequence are not independent. In this paper, we propose a method called max-min inter-sequence distance analysis (MMSDA) to transform features in sequences into a low-dimensional subspace such that different sequence classes are holistically separated. To utilize the temporal dependencies, MMSDA first aligns features in sequences from the same class to an adapted number of temporal states, and then, constructs the sequence class separability based on the statistics of these ordered states. To learn the transformation, MMSDA formulates the objective of maximizing the minimal pairwise separability in the latent subspace as a semi-definite programming problem and provides a new tractable and effective solution with theoretical proofs by constraints unfolding and pruning, convex relaxation, and within-class scatter compression. Extensive experiments on different tasks have demonstrated the effectiveness of MMSDA.

DNA Methylation and Transcription of HLA-F and Serum Cytokines Relate to Chinese Medicine Syndrome Classification in Patients with Chronic Hepatitis B / 中国结合医学杂志

OBJECTIVE@#To explore the molecular bases of Chinese medicine (CM) syndrome classification in chronic hepatitis B (CHB) patients in terms of DNA methylation, transcription and cytokines.@*METHODS@#Genome-wide DNA methylation and 48 serum cytokines were detected in CHB patients (DNA methylation: 15 cases; serum cytokines: 62 cases) with different CM syndromes, including dampness and heat of Gan (Liver) and gallbladder (CHB1, DNA methylation: 5 cases, serum cytokines: 15 cases), Gan stagnation and Pi (Spleen) deficiency (CHB2, DNA methylation: 5 cases, serum cytokines: 15 cases), Gan and Shen (Kidney) yin deficiency (CHB3, DNA methylation: 5 cases, serum cytokines: 16 cases), CHB with hidden symptoms (HS, serum cytokines:16 cases) and healthy controls (DNA methylation: 6 cases). DNA methylation of a critical gene was further validated and its mRNA expression was detected on enlarged samples. Genome-wide DNA methylation was detected using Human Methylation 450K Assay and furthered verified using pyrosequencing. Cytokines and mRNA expression of gene were evaluated using multiplex biometric enzyme-linked immunosorbent assay (ELISA)-based immunoassay and reverse transcription-quantitative polymerase chain reaction (RT-qPCR), respectively.@*RESULTS@#Totally 28,667 loci, covering 18,403 genes were differently methylated among CHB1, CHB2 and CHB3 (P<0.05 and |Δβ value| > 0.17). Further validation showed that compared with HS, the hg19 CHR6: 29691140 and its closely surrounded 2 CpG loci were demethylated and its mRNA expressions were significantly up-regulated in CHB1 (P<0.05). However, they remained unaltered in CHB2 (P>0.05). Levels of Interleukin (IL)-12 were higher in CHB3 and HS than that in CHB1 and CHB2 groups (P<0.05). Levels of macrophage inflammatory protein (MIP)-1α and MIP-1β were higher in CHB3 than other groups and leukemia inhibitory factor level was higher in CHB1 and HS than CHB2 and CHB3 groups (P<0.05). IL-12, MIP-1α and MIP-1β concentrations were positively correlated with human leukocyte antigen F (HLA-F) mRNA expression (R2=0.238, P<0.05; R2=0.224, P<0.05; R=0.447, P<0.01; respectively). Furthermore, combination of HLA-F mRNA and differential cytokines greatly improved the differentiating accuracy among CHB1, CHB2 and HS.@*CONCLUSIONS@#Demethylation of CpG loci in 5' UTR of HLA-F may up-regulate its mRNA expression and HLA-F expression was associated with IL-12, MIP-1α and MIP-1β levels, indicating that HLA-F and the differential cytokines might jointly involve in the classification of CM syndromes in CHB.@*REGISTRATION NO@#ChiCTR-RCS-13004001.

Effect of Shenqi Fuzheng Injection in Improving Sensitivity of Human Breast Cancer MDA-MB-231 Cells to Cisplatin Through Tumor Associated Macrophages / 中国实验方剂学杂志

Objective::To investigate the effect of Shenqi Fuzheng injection on the sensitivity of cisplatin through immunomodulation, in order to explore its mechanisms. Method::The cell survival was measured by thiazolyl blue tetrazolium bromide (MTT), the rate of apoptosis was detected by flow cytometry, the expressions of apoptosis-related proteins were detected by Western blot, and the expression level of cytokines was detected by enzyme linked immunosorbent assay (ELISA). Result::Shenqi Fuzheng injection 1, 10, 100 mL·L-1 significantly inhibited the growth of co-cultured cells, and the cell survival rate was 71.8%and 59.9%at the concentration of 10, 100 mL·L-1 respectively.Shenqi Fuzheng injection 10 mL·L-1 combined with cisplatin significantly increased the sensitivity of co-cultured cells to cisplatin.The half maximal inhibitory concentration (IC50) of cisplatin was reduced from 30 to 15 μmol·L-1.The rate of apoptosis induced by the combined treatment increased by 15.5%compared with that of cisplatin 15 μmol·L-1 (P<0.05). The expressions of B-cell lymphoma-2 (Bcl-2), B-cell lymphoma-w (Bcl-w) and B-cell lymphoma-extra large (Bcl-xl) were inhibited, and the expressions of Bcl-2-associated X protein (Bax) and protein induced by BH3 domain (Bid) apoptosis were increased (P<0.05). Shenqi Fuzheng injection reduced the release of interleukin-10 (IL-10) and prostaglandin E2 (PGE2) induced by cisplatin (P<0.05). Conclusion::Shenqi Fuzheng injection improves the sensitivity of MDA-MB-231 to cisplatin by regulating immune cells, and plays a synergistic role in inhibiting the proliferation of breast cancer cells.This study provides experimental basis for the prevention and treatment of tumors with Yiqi Fuzheng method, and experimental reference for the study of traditional Chinese medicine in alleviating drug resistance of tumors.

Clinical application of dynamic locking screw in treating humeral shaft fracture / 中国骨伤

OBJECTIVE@#To compare clinical effect of dynamic locking screws and common screws in treating humeral shaft fractures.@*METHODS@#From January 2016 to October 2018, clinical data of 46 patients with humeral shaft fracture were retrospectively analyzed, which were divided into dynamic locking screw internal fixation group (treatment group) and ordinary screw internal fixation group (control group). In treatment group, there were 14 males and 10 females, aged from 20 to 61 years old with an average of (36.8±10.9) years old;22 patients in control group, there were 13 males and 9 females, aged from 19 to 60 years old with an average of (35.9±12.8) years old. Length of incision, operation time, amount of bleeding, fracture healing time and complications were compared between two groups, Constant-Murley score of shoulder joint and Mayo score of elbow joint at 3 and 9 months after operation were compared to evaluate clinical effect.@*RESULTS@#Forty six patients were followed up from 9 to 43 months with an average of (18.6±7.9) months. There were no statistical differences in length of incision, operation time, amount of bleeding between two groups (>0.05);fracture healing time in treatment group was (12.2±3.2) weeks, and (15.6±4.7) weeks in control group;there was difference between two groups (0.05);One patient occurred neural paralysis in treatment group;1 patient occurred delayedunion, 2 patients occurred bone nonunion and 1 patient occurred broken nail in control group;while there was no statistical difference between two groups in complication.@*CONCLUSION@#Both of dynamic locking screws and ordinary screws could effectively treat humeral shaft fractures. dynamic locking screws has an advantage in fracture healing time, and recovery of early shoulder and elbow function. However, the active time of this technology is not too long in China, further study on long-term efficacy of large samples is needed.

Identification and antibiotics sensitivity analysis of Herbaspirillum huttiense in catheter-related bloodstream infection / 中华检验医学杂志

Objective:To analyze the identification and antibiotics susceptibility of Herbaspirillum in catheter-related bloodstream infection, and improve the awareness and attention of the rare pathogenic microorganisms for clinicians and microbiologists. Methods:The bacterium was isolated from a positive blood culture of a hemodialysis patient with chronic renal failure. The smear of isolate was prepared, stained and observed by microscope. The single colonies were identified by mass spectrometry and VITEK 2 Compact identification and antibiotics sensitivity analysis system, respectively. Then, 16S ribosomal DNA (rDNA) was amplified and sequenced, and bacterial genome was sequenced.Results:The gram-negative bacilli was found in the positive blood culture bottle. After incubated on blood agar for 16 hours, milky white, bulging and non-haemolytic colonies were observed. The identification result was Burkholderia cepacian by VITEK 2_Compact and antimicrobial susceptibility testing showed resistance to aztreonam and polymyxin but sensitive to other drugs in N335 card. The isolate could not be identified by VITEK MS with clinical database. However, it was identified as Herbaspirillum huttiense/Herbaspirillum aquaticum with research database. The 16S rDNA of the strain was consistent with Herbaspirillum huttiense and Herbaspirillum aquaticum (more than 99%). High-throughput bacterial genome sequencing revealed that the isolate in this case shared 100% homology with Herbaspirillum huttiense subsp putei IAM 15032 in Genbank database, which confirmed that the isolate was Herbaspirillum huttiense. Conclusions:There are more and more environmental microorganisms evolved into human pathogenic bacteria. Herbaspirillum species are easy to be misidentified because its biochemical characteristics are similar to other strains.

The origin of Mosuo people as revealed by mtDNA and Y chromosome variation.

The Mosuo, living in the Lugu Lake area in northwest Yunnan Province, China, is the only matriarchal population in China. The Mosuo was officially identified as Naxi nationality although its relationship with Naxi remains controversial. We studied the genetic relationship between the Mosuo and five other ethnic groups currently residing in northwest Yunnan, i.e. Naxi, Tibetan, Bai, Yi and Pumi, by typing the genetic variations in mtDNA HVS1 and 21 Y chromosome markers (13 SNPs & 8 STR markers). We showed that the maternal lineages of the Mosuo bear the strongest resemblance with those found in Naxi while its paternal lineages are more similar to those that are prevalent in Yunnan Tibetan. The marked difference between paternal and maternal lineages may be attributable to the genetic history, matriarchal structure, and visiting marriage.

Research Methods of Compatibility of Traditional Chinese Medicine Formulas and Its Advances / 中国实验方剂学杂志

Traditional Chinese medicine formulas (TCMF) is composed of several Chinese herbal medicines based on the theory of TCM. It plays a synergistic role under the appropriate dosage ratio to achieve the overall adjustment and treatment of TCM. It is of great significance to study the compatibility of TCMF in promoting the modernization, development and clinical application of TCM. The compatibility law is the core of TCMF theory. In recent years, based on the seven compatible relations and monarch-minister-assistant-guide principles, the composition, pharmacological activity and pharmacokinetic properties of the TCMF and their compounds were studied by new techniques and new methods, and the scientific connotation of compatibility of TCMF was discussed from different perspectives. In addition, the establishment of a variety of mathematical methods and models, the development and application of network pharmacology and data mining methods also provide great help to the research on compatibility of TCMF. The development of research methods has promoted the scientific research on the compatibility of TCMF, but it is the main task of the research on the TCMF compatibility to establish the suitable research methods for the complex relationship of pharmacodynamic substances, to clarify the internal roles of TCMF and their compounds/components compatibility, and to construct a new modern TCMF.

Regulation of T cell immunity by cellular metabolism / 医学前沿

T cells are an important adaptive immune response arm that mediates cell-mediated immunity. T cell metabolism plays a central role in T cell activation, proliferation, differentiation, and effector function. Specific metabolic programs are tightly controlled to mediate T cell immune responses, and alterations in T cell metabolism may result in many immunological disorders. In this review, we will summarize the main T cell metabolic pathways and the important factors participating in T cell metabolic programming during T cell homeostasis, differentiation, and function.

Liver Tissue-related Metabolic Mechanism of Different Infusion Volumes for Hemorrhagic Shock / 法医学杂志

Objective To investigate the curative effects of various infusion volumes on liver-related metabolic mechanism in the treatment of hemorrhagic shock.Methods A severe hemorrhagic shock rabbit model was established in 30 rabbits.The rabbits were randomly divided into three groups:non-infusion group (A), conventional infusion group (B), and excessive infusion group (C) (n=10 in each group).Taking group B as the control, groups A and C were observed for the damage of non-infusion and excessive infusion, respectively.The outcomes in the three groups and their relations with liver tissue metabolism changes were analyzed with gas chromatograph-mass spectrometer (GC-MS).Results The mortality in groups A, B, and C group were 80％, 0％, and 70％, respectively.The liver tissue metabolic profile in group B showed statistically significant difference compared with that in groups A and B.In group C, the levels of 21 metabolites were lower than those in group B, and the levels of8 metabolites were lower than those in group A.The relative contents of various metabolites were correlated with infusion volumes, and the succinic acid content was associated with death events (P＜0.05).Conclusion The conventional infusion has significant curative effect on hemorrhagic shock.The metabolites of liver tissues with excessive infusion are generally decompensated and have longer survival time than those in non-infusion group, which may caused by the excessive infusion-induced blood volume increase after hemorrhagic shock.Tissue fluid dilution is an important cause of death.

An overview of epigenetics in Chinese medicine researches / 中国结合医学杂志

Chinese medicine (CM) has contributed to human health care for several thousand years and is still popular in Asian countries. But the mechanisms underlying CM remain obscure, and need to be clarifified by modern biological subjects and methods. Recently, CM researches on epigenetics have gained obvious improvement following rapidly developed molecular technologies. In this review, we revealed mutual characteristics of epigenetics and CM, such as holism, yin-yang dynamic nature, reversibility and balance, and visceral manifestation. Moreover, epigenetic modifications, including DNA methylation, histone post-transcriptional modifications, micro RNA interference, etc. may help explore the molecular basis of CM syndrome classifification, and mechanisms of Chinese herbal medicine (CHM), CHM compounds and Chinese herbal formulae activities. Meanwhile, CM and epigenetics might promote each other and jointly develop following the continuous progress of epigenetics in CM researches.

Clinical observation of corneal collagen cross-linking and laser-assisted in situ keratomileusis for refractive error / 眼科新进展

Objective To observe the clinical outcomes of corneal collagen cross-linlIng (CLX) and laser-assisted in situ keratomileusis (LASIK) for refractive error.Methods Together 100 patients (200 eyes) with myopia and/or astigmatism who underwent LASIK were admitted from December 2015 to January 2016,and divided into treatment group (50 patients,100 eyes),in which patient received CXL-LASIK,and control group (50 patients,100 eyes),in which the controls were given LASIK alone.Then the optical variables,including visual acuity,diopter,cornea endothelium cell counting,corneal transparency,corneal collagen cross-linking line,were examined and analyzed before operation and 1 week,1 month,3 months,6 months and 12 months after opera tion.Results As for postoperative time points,the uncorrected visual acuity after operation was better than the best corrected visual acuity before surgery in the two groups,but the differences in diopter between the two groups were statistically significant (all P ＜ 0.05).There was no significant difference in diopter 1 month and 12 months postoperatively in the treatment group (t =0.021,P =0.070),while its difference in the control group 1 month and 12 months postoperatively(t =4.857,P =0.010).The differences of the cornea endothelium cell counting in the treatment group between before and after surgery were not statistically significant (F =1.163,P =0.327).Moreover,slightly opacification apPeared in anterior corneal stromal in the early stage after surgery in the treatment group,and the average thickness of corneal collagen cross-linking line was 210.00-340.00 (270.48 + 37.80) μm 1 month postoperatively,accounting for 63％ of the central cornea thickness.There were not flap-related complications in the treatment group,but the control group had corneal flap wrinkle in 3 eyes and displacement in 1 eye in the controls.Conclusion Corneal collagen cross-linlIng and laser-assisted in situ keratomileusis for refractive error can obtain better outcomes,including sound uncorrected visual acuity and stable diopter after surgery,without the loss of the corneal endothelial cells.

Clinical observation of corneal collagen cross-linking and laser-assisted in situ keratomileusis for refractive error / 眼科新进展

Objective To observe the clinical outcomes of corneal collagen cross-linlIng (CLX) and laser-assisted in situ keratomileusis (LASIK) for refractive error.Methods Together 100 patients (200 eyes) with myopia and/or astigmatism who underwent LASIK were admitted from December 2015 to January 2016,and divided into treatment group (50 patients,100 eyes),in which patient received CXL-LASIK,and control group (50 patients,100 eyes),in which the controls were given LASIK alone.Then the optical variables,including visual acuity,diopter,cornea endothelium cell counting,corneal transparency,corneal collagen cross-linking line,were examined and analyzed before operation and 1 week,1 month,3 months,6 months and 12 months after opera tion.Results As for postoperative time points,the uncorrected visual acuity after operation was better than the best corrected visual acuity before surgery in the two groups,but the differences in diopter between the two groups were statistically significant (all P ＜ 0.05).There was no significant difference in diopter 1 month and 12 months postoperatively in the treatment group (t =0.021,P =0.070),while its difference in the control group 1 month and 12 months postoperatively(t =4.857,P =0.010).The differences of the cornea endothelium cell counting in the treatment group between before and after surgery were not statistically significant (F =1.163,P =0.327).Moreover,slightly opacification apPeared in anterior corneal stromal in the early stage after surgery in the treatment group,and the average thickness of corneal collagen cross-linking line was 210.00-340.00 (270.48 + 37.80) μm 1 month postoperatively,accounting for 63％ of the central cornea thickness.There were not flap-related complications in the treatment group,but the control group had corneal flap wrinkle in 3 eyes and displacement in 1 eye in the controls.Conclusion Corneal collagen cross-linlIng and laser-assisted in situ keratomileusis for refractive error can obtain better outcomes,including sound uncorrected visual acuity and stable diopter after surgery,without the loss of the corneal endothelial cells.

Human remains from the Pleistocene-Holocene transition of southwest China suggest a complex evolutionary history for East Asians.

BACKGROUND: Later Pleistocene human evolution in East Asia remains poorly understood owing to a scarcity of well described, reliably classified and accurately dated fossils. Southwest China has been identified from genetic research as a hotspot of human diversity, containing ancient mtDNA and Y-DNA lineages, and has yielded a number of human remains thought to derive from Pleistocene deposits. We have prepared, reconstructed, described and dated a new partial skull from a consolidated sediment block collected in 1979 from the site of Longlin Cave (Guangxi Province). We also undertook new excavations at Maludong (Yunnan Province) to clarify the stratigraphy and dating of a large sample of mostly undescribed human remains from the site. METHODOLOGY/PRINCIPAL FINDINGS: We undertook a detailed comparison of cranial, including a virtual endocast for the Maludong calotte, mandibular and dental remains from these two localities. Both samples probably derive from the same population, exhibiting an unusual mixture of modern human traits, characters probably plesiomorphic for later Homo, and some unusual features. We dated charcoal with AMS radiocarbon dating and speleothem with the Uranium-series technique and the results show both samples to be from the Pleistocene-Holocene transition: ∼14.3-11.5 ka. CONCLUSIONS/SIGNIFICANCE: Our analysis suggests two plausible explanations for the morphology sampled at Longlin Cave and Maludong. First, it may represent a late-surviving archaic population, perhaps paralleling the situation seen in North Africa as indicated by remains from Dar-es-Soltane and Temara, and maybe also in southern China at Zhirendong. Alternatively, East Asia may have been colonised during multiple waves during the Pleistocene, with the Longlin-Maludong morphology possibly reflecting deep population substructure in Africa prior to modern humans dispersing into Eurasia.

Postmortem interval estimation by time-dependent changes of morphology and biomechanical properties in brain tissues / 医用生物力学

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.

Postmortem interval estimation by time-dependent changes of morphology and biomechanical properties in brain tissues / 医用生物力学

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.