Objective To address the quality problems caused by high porosity in the preparation of dental cobalt-chrome alloy prosthetics based on selective laser melting(SLM)technology,we investigated the influence mechanism of different forming process parameters on the microstructure and properties of the materials.Moreover,the range of form-ing process parameters that can effectively reduce defects was precisely defined.Methods The effects of laser power,scanning speed,and scanning distance on the pore properties,surface roughness,and hardness of dental cobalt-chrome al-loy were investigated by adjusting the printing parame-ters in the process of SLM.Through metallographic anal-ysis,image analysis,and molten pool simulation,the pore formation mechanism was revealed,and the relation-ship between the porosity and energy density of SLM dental cobalt-chrome alloy was elucidated.Results When the linear energy density was higher than 0.18 J/mm,the po-rosity defect easily appeared at the bottom of the molten pool.When the laser energy density was lower than 0.13 J/mm,defects occurred in the gap of the molten pool due to insufficient melting of powder.In particular,when the linear energy density exceeded the threshold of 0.30 J/mm or was below 0.12 J/mm,the porosity increased significantly to more than 1%.In addition,we observed a negative correlation between free surface roughness and energy density and an inverse re-lationship between macroscopic hardness and porosity.Conclusion On the basis of the conditions of raw materials and molding equipment used in this study,the key process parameters of SLM of molding parts with porosity lower than 1%were successfully determined.Specifically,these key parameters included the line energy density,which ranged from 0.13 J/mm to 0.30 J/mm,and the scan spacing should be strictly controlled below 90 μm.

Objective:To explore the methods, complications and follow-up results of limb salvage for primary malignant tumors of the femoral shaft.Methods:From October 2006 to October 2019, 41 cases of primary malignant tumors of femoral shaft were analyzed retrospectively, 37 cases were followed up, including 22 males and 15 females, aged 8-46 years with an average age of 20.56±4.72 years old. All the lesions were located in the femoral shaft, and The Enneking stage was IIB. Tumor lesion ranged in the femur from 10 cm to 24 cm, and there was no pathological fracture. Pre-operative puncture biopsy was performed in all cases.22 cases were confirmed as osteosarcoma, 8 as chondrosarcoma, 5 as Ewing sarcoma, 2 as malignant fibrous histiocytoma. Neoadjuvant chemotherapy has been used to treat both osteosarcoma and Ewing sarcoma. Among the 37 patients, 8 cases of patients received total femoral prosthesis replacement, 14 cases of intramedullary nail fixation with allogenic bone graft, 8 cases of allograft-prosthetic composite (APC), and 7 cases of 3D printed prosthesis. The limb function was graded according to MSTS 93 system.Results:37 out of 41 patients were followed up, and the average follow-up time was 23.15±16.74 months (6-62 months). There were 9 patients with pulmonary metastases (26.47%), among which 6 patients passed away due to multiple metastases. 28 patients survived without tumor at last follow-up. The MSTS score was18-28 (average of 22.55±2.57). The average score of 3D printing prosthesis group was 27±1.74, allogeneic bone transplantation group was 22.85±2.59, total femoral prosthesis replacement group was 20.25±2.25, and the APC prosthesis group was 20.5±2.07. There was statistical difference between 3D printing group and other groups. The overall excellent and good rate of lower limb function was 79.41%, in which the 3D group was 100%, allogeneic bone group was 78.5%, APC prosthesis group was 87.5%, total femoral prosthesis replacement group was 62.5%. There was no statistical difference in the excellent and good rate of limb function among the groups. There weren't any cases of hip joint dislocation after total femoral prosthesis replacement. Delayed union of bone healing was seen in 3 cases of allogeneic bone transplantation and 2 cases APC patients. One patient suffered from the postoperative hemorrhage-related diseases-sciatic nerve compression, and the nerve recovered after emergency debridement. One patient suffered from poor wound healing. The overall complication rate was 24.32% (9/37).Conclusion:The patients with primary malignant tumors of the femoral shaft can effectively recover the lower extremity function by choosing the appropriate surgical scheme, in order to achieve the purpose of limb preservation and improve the quality of life of the patients. 3D printing prosthesis provides a new choice in the treatment of femoral shaft tumors.

Objective To investigate the molecular epidemiology and antimicrobial resistance status of uropathogenic Escherichia coli (UPEC) in senior population in Putuo District ,Shanghai .Methods A total of 72 UPEC strains were isolated from elderly inpatients with urinary tract infections in Putuo Hospital ,Shanghai University of Traditional Chinese Medicine from January 2013 to March 2015 .The strains were characterized by multi‐locus sequence typing (MLST ) .The β‐lactamase gene and the plasmid mediated quinolone resistance (PMQR) gene were detected ,and the mutations of quinolone resistance‐determining regions (QRDR) in gyrA and parC genes were demonstrated .In vitro drug susceptibility test was performed .Continuous variables were compared using t test and categorical variables were compared using chi‐squared test or Fisher exact test .Results The UPEC strains showed different resistance rates to ciprofloxacin ,cefotaxime and trimethoprim‐sulfamethoxazole ,which were 76 .4% ,73 .6% and 65 .3% , respectively .UPEC still remained highly sensitive to imipenem ,meropenem ,amikacin and piperacillin‐tazobactam .Among 72 isolates ,55 (76 .4% ) of 49 (68 .1% ) extended‐spectrum β‐lactamase (ESBL )‐positive strains harbored blaCTX‐M genes .Among the 55 ciprofloxacin resistant strains ,51 (92 .7% ) had three or four mutations in QRDR of gyrA and parC genes .The “hot‐spot” mutations of QRDR were located at amino acid position 83 and 87 in gyrA gene and at positions 80 and 84 in parC gene .Forward analysis by MLST showed that the most frequent sequence types (ST ) were ST131 (18/72 ,25 .0% ) , ST1193(7/72 ,9 .7% ) ,ST405 (7/72 ,9 .7% ) ,ST38 (5/72 ,6 .9% ) and ST648 (3/72 ,4 .2% ) .ST131 isolates were predominant in ST which caused community‐onset urinary tract infections .Multiple drug‐resistance were detected in ST 131 ,ST405 ,ST38 and ST648 which were mainly producing blaCTX‐M ESBL .Conclusions Community‐acquired multiple drug‐resistant UPEC strains such as ST131 clone are prevalent in elderly patients .Thus ,monitoring of molecular epidemiology would be beneficial to prevent the prevalence of multiple drug‐resistant UPEC .

OBJECTIVEThe effect of sandblasting on the bond strength between 3mol% yttrium-stabilized tetragonal zirconium polycrystal (3Y-TZP) zirconia framework and veneering porcelain was evaluated.

METHODSA total of 21 specimens [(25 ± 1) mm x (3 ± 0.1) mmx (0.5 ± 0.05) mm] were prepared according to ISO 9693. The specimens were then randomly divided into 3 groups. Sandblasting was performed on 2 meshes of Al₂O₃ particles: group A with mesh 110 and group B with mesh 80. Group C, which was not sandblasted, was the control group. The surface roughness of the zirconia framework, as well as the bond strength between 3Y-TZP zirconia framework and veneering porcelain, was measured. The interface microstructure was observed by scanning electron microscope (SEM), and elemental distribution was detected by energy dispersive spectroscopy (EDS).

RESULTSSurface roughness values were (1.272 ± 0.149) μm for group A, (0.622 ± 0.113) μm for group B, and (0.221 ± 0.065) μm for group C. Statistical significance were found among groups (P < 0.05). The bond strength values were (28.21 ± 1.52) MPa for group A, (27.71 ± 1.27) MPa for group B, and (24.87 ± 3.84) MPa for group C. Statistical significance was found between group A and group C (P < 0.05), whereas the other groups had no statistical significance (P > 0.05). Interface adhesion failure was the primary performance. SEM images showed the close interface bonding, and EDS showed that the interface had no obvious element penetration.

CONCLUSIONAl₂O₃ sandblasting can slightly enhance the bond strength between zirconia framework and veneering porcelain.

Aluminum Oxide ; chemistry ; Dental Bonding ; Dental Porcelain ; chemistry ; Dental Stress Analysis ; Dental Veneers ; Materials Testing ; Microscopy, Electron, Scanning ; Shear Strength ; Surface Properties ; Yttrium ; chemistry ; Zirconium ; chemistry

OBJECTIVETo explore the differences in sensitivity to rapamycin of five esophageal squamous cell carcinoma cell lines with different differentiation and the changes of sensitivity of the cells after siRNA-interfered expression of p70S6K.

METHODSEffects of rapamycin on proliferation of ESCC cell lines with different differentiation, EC9706, TE-1, Eca109, KYSE790 and KYSE450 cells, were investigated using cell counting kit 8 (CCK-8) assay, and according to the above results, the EC9706 cells non-sensitive to rapamycin were chosen to be transfected with p70S6K-siRNA. The changes in sensitivity of cells to rapamycin were measured in vitro and in vivo using CCK-8 kit, flow cytometry and tumor formation in nude mice.

RESULTSCCK-8 results showed that all the five cell line cells were sensitive to low concentration of rapamycin (<100 nmol/L), but TE-1 and EC9706 cells, which were with poor differentiation, showed resistance to high concentration of rapamycin. After EC9706 cells were treated with 50, 100, 200, 500 and 1 000 nmol/L rapamycin and p70S6K-siRNA, the proliferation rates of EC9706 cells were (48.67 ± 1.68)%, (15.45 ± 1.54)%, (14.00 ± 0.91)%, (10.97 ± 0.72)% and (2.70 ± 0.32)%, respectively, and were significantly lower than that of cells treated with 50, 100, 200, 500 and 1 000 nmol/L rapamycin and control siRNA [(74.53 ± 1.71)%, (68.27 ± 1.35)%, (71.74 ± 2.44)%, (76.23 ± 1.02)% and (80.21 ± 2.77)%] (P<0.05 for all). The results of flow cytometry showed that the ratios of cells in G1 phase of the p70S6K-siRNA, rapamycin and p70S6K-siRNA+ rapamycin groups were (53.82 ± 1.78)%, (57.87 ± 4.01)% and (73.73 ± 3.68)%, respectively, significantly higher than that in the control group (46.09 ± 2.31)% (P<0.05 for all). The results of tumor formation test in vivo showed that the inhibitory effect of rapamycin on tumor growth was stronger after the cells were transfected with p70S6K-siRNA, and the inhibition rate was 96.5%.

CONCLUSIONESCC cells with different differentiation have different sensitivity to rapamycin, and p70S6K-siRNA can improve the sensitivity of cells to rapamycin in vitro and in vivo.

Animals ; Antibiotics, Antineoplastic ; pharmacology ; Carcinoma, Squamous Cell ; drug therapy ; metabolism ; pathology ; Cell Differentiation ; Cell Line, Tumor ; Cell Proliferation ; Esophageal Neoplasms ; drug therapy ; metabolism ; pathology ; Humans ; Mice ; Mice, Nude ; RNA, Small Interfering ; Ribosomal Protein S6 Kinases, 70-kDa ; genetics ; metabolism ; Signal Transduction ; Sirolimus ; pharmacology ; Transfection

In order to improve students' overall quality,Biomedical Engineering College of Chongqing Medical University has carried out quality development training in the 6 session of the 450 students.The content includes development projects,the queue training,humanities lectures,inspirational film etc.; the objective is to develop the students' mind,develop their team spirit and interpersonal communication skills.College has recruited and assisted professional instructors in the whole training.The centralized training in specific situations gives students a strong spiritual shock and strong positive energy.Before and after the training we use the same questionnaire to students,the results of which have shown that their comprehensive ability,EQ,and cohesion of the class have been improved.

Objective To explore the clinical efficacy and complications of the surgical treatment of sternal tumor resection and titanium mesh reconstruction.Methods From 2008 January to 2012 June,there were 8 cases of sternal tumor patients in our hospital,including 5 male and 3 female,with an average age of 50.4 (37-66) years old.The histological morphology included 2 cases of chondrosarcoma,1 case of osteosarcoma,2 cases of malignant fibrous histiocytoma,eosinophilic granuloma in 1 case,and 2 cases of sternal metastasis of breast cancer.Tumor invasion sites included the sternal manubrium in 3 cases,the body in 2 cases,and both in 3 cases.All patients had undergone preoperative puncture or incision biopsy.8 cases of sternal tumor patients were treated with sternal tumor resection and reconstruction of the thorax using titanium mesh.The clinical effect and complications were retrospectively analyzed.Results All patients were followed up for 9 months to 4 years.The operations went well in all cases,with no intraoperative crisis or operative death.Deep wound hematoma occurred in 1 patient 1 week postoperatively,who healed 2 weeks after drainage and debridement.There was no abnormal breathing,subcutaneous emphysema,pneumothorax,infection or other complications in other cases.1 case of malignant fibrous histiocytoma died of lung metastasis at 9 months follow-up,and 1 died of liver metastasis at 14 months,while other patients got no tumor recurrence,with good thoracic shape,free breathing,no titanium mesh loosening,dyspnea,chest tightness,pain,or abnormal respiratory discomfort during follow-up period.The chest radiograph showed no chest deformity,no loosening or fracture of the fixation device.Conclusion Sternal tumor resection and reconstruction with titanium mesh has the advantages of good shaping effect,fewer complications,and simple operation,showing that titanium mesh is an ideal material for the reconstruction of sternum.

Objective To investigate the growth inhibition of human osteosareoma cell line(MG-63) intervened by Hydralazine and 5'-aza-2'-deoxycytidine (5-Aza-CdR),and the effect on the mRNA expression of gene WW domain-containing oxidoreductase (WWOX).Methods Certain volume of 5 × 104/ml of human osteosarcoma cell line MG-63 in logarithmic growth phase were added into 96-well plate.There were Hydralazine group (drug concentration,0.1,1.0,10 μmol/L),5-Aza-CdR group (drug concentration,5,10,20 μmol/L),Hydralazine combined with 5-Aza-CdR group (drug concentration,0.1 μmo/L + 5 μmol/L,1.0 μmol/L + 10 μmol/L,10 μmol/L + 20 μmol/L) and control group (culture medium).Methyl thiazol tetrazolium(MTT) colorimetric methods were used to test the growth inhibition of MG-63 cells intervened by different concentrations of Hydralazine and 5'-aza -2'-deoxycytidine (5-Aza-CdR).Flow cytometry AnnexinV-FITC/PI methods were used to assay the effects of Hydralazine and 5-Aza-CdR inducing apoptosis in osteosarcoma cells in vitro.Real-time polymerase chain reaction (Real-Time PCR)methods were used to detect amplification of WWOX mRNA induced by Hydralazine combined with 5-Aza-CdR or alone.Western-blotting methods were used to examine the expression of WWOX in MG-63 cells.Results Hydralazine and 5-Aza-CdR effectively inhibited the growth of MG-63 cells in a concentration and time-dependent manner.Combined effect was more obvious.Further more the expression levels of WWOX mRNA and protein were increased significantly in combined groups as compared with other groups.Conclusion Hydralazine and 5-Aza-CdR could effectively inhibit the proliferation of MG-63 cells and induce apoptosis which is concurrent with the promotion of the expression of WWOX.The mechanism may be that Hydralazine/5-Aza-CdR effectively cause the demethylated of WWOX gene CpG-rich promoter regions,leading to the high expression of WWOX and inhibit the growth of MG-63 cells.The use of hydralazine in the treatment of osteosarcoma is worthy of further investigation.

Objective:To construct a fusion protein of extracellular domain peptide fragment of muscle specific kinase ( MuSK) and fluorescent protein mCherry ,and used as antigen in the detection of antibodies against MuSK ( MuSKAb ) in the sera of patients with myasthenia gravis ( MG).Methods:The mCherry gene was amplified by PCR from vector pRSET-B and cloned into pGEM-T Easy Vector,and furthermore, cloned into Eukaryotic expression vector pMT /BiP/V5-His ( MuSK), which contains MuSK extracellular domain 22-452 amino acid peptide fragment gene to construct the fluorescent fusion protein gene MuSK -mCherry.The recombinant vector was subsequently transfected into drosophila S 2 cells for expression.The expressed fusion proteins were verified in confocal mi-croscope ,and used as antigen in the detection of MuSKAb in sera of MG patents in fluorescence immunoprecipitation test .Results:The fluorescent fusion protein MuSK-mCherry was successfully constructed and expressed.The MuSKAb in sera of patents with MG could be detected in fluorescence immunoprecipitation test using the constructed MuSK-mCherry fusion protein as antigen.Conclusion: It is available to use the constructed fluorescent fusion protein MuSK-mCherry as antigen in fluorescence immunoprecipitation test for the detection of MuSKAb in sera of patents with MG.

This paper discussed on the innovative efforts of establishing production-teaching-research platform and multi-channel international cooperation model by Chongqing Medical University. Measures taken included offering theoretical courses across the first-level disciplines of medicine and engineering and encouraging research tasks that involve the cooperation among hospitals , businesses and universities, creating education environment for postgraduates combing medicine and engineering and launching the cultivation of biomedical engineering postgraduates. The aim of these measures was to incorporate the achievements of scientific research innovation into postgraduate education and to improve its quality.