Electric and electronic products are required to pass through the certification on electrical safety performance before entering into the market in order to reduce electrical shock and electrical fire so as to protect the safety of people and property. The leakage current is the most important factor in testing the electrical safety performance and the test theory is based on the perception current effect and threshold. The traditional method testing the current threshold for perception only depends on the sensing of the human body and is affected by psychological factors. Some authors filter the effect of subjective sensation by using physiological and psychological statistical algorithm in recent years and the reliability and consistency of the experiment data are improved. We established an experiment system of testing the human body's current threshold for perception based on EEG feature analysis, and obtained 967 groups of data. We used wavelet packet analysis to detect α wave from EEG, and used FFT to do spectral analysis on α wave before and after the current flew through the human body. The study has shown that about 97.72% α wave energy changes significantly when electrical stimulation occurs. It is well proved that when the EEG feature identification is applied to test the human body current threshold for perception, and meanwhile α wave energy change and human body sensing are used together to confirm if the current flowing through the human body reaches the perception threshold, the measurement of the human body current threshold for perception could be carried out objectively and accurately.
ObjectiveTo investigate the differentiation of rat adipose-derived stem cells (ADSCs) into neuronlike cells by indirect co-culture with Schwann cells (SCs) in vitro so as to look for the ideal seed cells for tissue engineering. MethodsSCs were isolated from sciatic nerves of 1-2 days old Sprague-Dawley rats with enzymatic digestion method. Immunofluorescence staining was used to identify SCs with the marker S-100. ADSCs were isolated from the epididymal fat pads of adult male Sprague-Dawley rats by means of differential attachment. And the cell phenotypes (CD29, CD34, CD45, CD73, CD90, and CD105) of ADSCs at passage 3 were determined by flow cytometry analysis. Primary SCs and ADSCs at passage 3 were co-cultured at a ratio of 2:1 in Transwell culture dishes (experimental group), and ADSCs cultured alone served as control group. Immunofluorescence and flow cytometry were adopted to investigate the neural differentiation of ADSCs at 14 days. The expression differences for neuron-specific enolase (NSE), microtubule-associated protein 2 (MAP2), neuronal nuclei protein (NeuN), and glial fibrillary acidic protein (GFAP) were detected, and the percentage of positive cells was calculated. ResultsADSCs were successfully extracted and can passage in a considerable large amount. Flow cytometry analysis showed that ADSCs at passage 3 were positive for CD29, CD90, CD73, and CD105 expression, but negative for CD34 and CD45 expression. The ADSCs of the experimental group showed contraction of nucleus, increasing of soma refraction, and several long and thick protrusions of cell body. The cell shape had no obvious change in the control group. Both immunofluorescence and flow cytometry analysis results showed the expressions of MAP2, NSE, NeuN, and GFAP at 14 days after co-cultured with SCs, and the positive cell ratios were significantly higher than those in the control group (P<0.01). ConclusionCo-culture with SCs not only can promote the survival regeneration of ADSCs, but also can induce the differentiation of ADSCs into neuron-like cells.
ObjectiveTo investigate the reasons and managements of implant-related complications after hinge knee replacement for tumors around the knee. MethodsA retrospective analysis was made on the clinical data of 96 patients undergoing hinge knee replacement between January 2000 and December 2012. There were 64 males and 32 females with the mean age of 31.0 years (range, 15-72 years). The most common tumor type was osteosarcoma (72 cases), and the second was giant cell tumor (15 cases). The tumor located at the distal femurs in 52 cases and at the proximal tibias in 44 cases. Fifteen hinge and 81 rotating hinge prostheses were used. The recurrence, metastasis, and survival were recorded. The implant-related complications were observed. ResultsThe median follow-up time was 43.5 months (range, 10-156 months). Complications were observed in 21 patients (25 implant-related complications);13 complications located at the femur and 12 complications at the tibia. The complications included aseptic loosening (8 cases), deep infection (7 cases), prosthetic breakage (4 cases), peri-prosthetic fracture (2 cases), and dislocation (4 cases). Most deep infection occurred within 12 months after operation (6/7), and most aseptic loosening after 40 months of operation (6/8). The rate of limb salvage was 90.6% (87/96) and the amputation rate was 9.4% (9/96). The overall survival rate of the prosthesis was 76.7% (5-year) and 47.2% (10-year). The 5-year survival rate was 82.9% for femoral prosthesis and 71.0% for tibial prosthesis, showing no significant difference (P=0.954). ConclusionHinge knee prosthesis still has a high rate of complications. Deep infection is main reason to decrease short-term prosthetic survival rate, and aseptic loosening shortens the long-short prosthetic survival time.
ObjectiveTo study the preparation and cytocompatibility of bone tissue engineering scaffolds by combining low temperature three dimensional (3D) printing and vacuum freeze-drying techniques. MethodsCollagen (COL)and silk fibroin (SF) were manufactured from fresh bovine tendon and silkworm silk. SolidWorks2014 was adopted to design bone tissue engineering scaffold models with the size of 9 mm×9 mm×3 mm and pore diameter of 500μm. According to the behavior of composite materials that low temperature 3D printing equipment required, COL, SF, and nano-hydroxyapatite (nHA)at a ratio of 9:3:2 and low temperature 3D printing in combination with vacuum freeze-drying techniques were accepted to build COL/SF/nHA composite scaffolds. Gross observation and scanning electron microscope (SEM) were applied to observe the morphology and surface structures of composite scaffolds. Meanwhile, compression displacement, compression stress, and elasticity modulus were measured by mechanics machine to analyze mechanical properties of composite scaffolds. The growth and proliferation of MC3T3-E1 cells were evaluated using SEM, inverted microscope, and MTT assay after cultured for 1, 7, 14, and 21 days on the composite scaffolds. The RT-PCR and Western blot techniques were adopted to detect the gene and protein expressions of COL I, alkaline phosphatase (ALP), and osteocalcin (OCN) in MC3T3-E1 cells after 21 days. ResultsCOL/SF/nHA composite scaffolds were successfully prepared by low temperature 3D printing technology and vacuum freeze-drying techniques; the SEM results showed that the bionic bone scaffolds were 3D polyporous structures with macropores and micropores. The mechanical performance showed that the elasticity modulus was (344.783 07±40.728 55) kPa; compression displacement was (0.958 41±0.000 84) mm; and compression stress was (0.062 15±0.007 15) MPa. The results of inverted microscope, SEM, and MTT method showed that a large number of cells adhered to the surface with full extension and good cells growth inside the macropores, which demonstrated a satisfactory proliferation rate of the MC3T3-E1 cells on the composite scaffolds. The RT-PCR and Western blot electrophoresis revealed gene expressions and protein synthesis of COL I, ALP, and OCN in MC3T3-E1 cells. ConclusionLow temperature 3D printing in combination with vacuum freeze-drying techniques could realize multi-aperture coexisted bionic bone tissue engineering scaffolds and control the microstructures of composite scaffolds precisely that possess good cytocompatibility. It was expected to be a bone defect repair material, which lays a foundation for further research of bone defect.
ObjectiveTo systematically review the association between LIG4 gene T9I polymorphism and cancer susceptibility. MethodsSuch databases as PubMed, EMbase, The Cochrane Library (Issue 10, 2013), CBM, CNKI, VIP and WanFang Data were electronically searched to collect case-control studies published up to Oct. 2013 on the association between LIG4 gene T9I polymorphism and cancer susceptibility. According to inclusion and exclusion criteria, two reviewers independently screened literature, extracted data, and assessed methodological quality of included studies. Then meta-analysis was performed using RevMan 5.0 software. ResultsA total of 11 case-control studies were included, which involved 5 016 cancer cases and 4 860 controls. The results of meta-analysis showed that, no significant association was found between LIG4 gene T9I polymorphism and the risk of cancer in the total analysis (TT+CT vs. CC:OR=0.96, 95%CI 0.80 to 1.15, P=0.63; TT vs. CT+CC:OR=1.10, 95%CI 0.78 to 1.56, P=0.59; TT vs. CC:OR=1.10, 95%CI 0.73 to 1.64, P=0.65; CT vs. CC:OR=0.94, 95%CI 0.80 to 1.11, P=0.48; T vs. C:OR=0.97, 95%CI 0.82 to 1.15, P=0.75). In the subgroup analysis, significant association was found in Caucasians (TT+CT vs. CC:OR=0.87, 95%CI 0.77 to 0.98, P=0.02) but not in Asians. ConclusionLIG4 gene T9I polymorphism could be associated with cancer susceptibility in Caucasians.
ObjectiveTo systematically review the association between the IL-6 gene -634G/C polymorphism and the risk of lung cancer. MethodsDatabases including the PubMed, EMbase, CNKI and WanFang Data were searched from inception to October 2015 to collect case-control studies about the correlation between the IL-6 gene -634G/C polymorphism and the risk of lung cancer. Two reviewers independently screened literature, extracted data and assessed the risk of bias of included studies. Then, meta-analysis was performed by using RevMan 5.3 software. ResultsA total of 12 case-control studies concerning 3 657 lung cancer cases and 4 100 controls from 11 articles were included. The results of meta-analysis showed that there was no significant association between the -634G/C polymorphism and the risk of lung cancer (GG+GC vs. CC: OR=1.11, 95%CI 0.89 to 1.39, P=0.37; GG vs. CC+GC: OR=1.17, 95%CI 0.88 to 1.55, P=0.27; GG vs. CC: OR=1.27, 95%CI 0.93 to 1.72, P=0.13; GC vs. CC: OR=1.12, 95%CI 0.89 to 1.40, P=0.33; G vs. C: OR=1.08, 95%CI 0.89 to 1.30, P=0.43). ConclusionIL-6 gene -634G/C polymorphism may not be a risk factor of lung cancer. Due to the limited quality and quantity of included studies, more high quality studies are needed to verify the above conclusion.