[Biomechanical study of different kinds of internal fixation for the typeâ Hangman fracture, type â ¡ odontoid fracture and the C(2/3) disc injury: a finite-element analysis].

Objectives: To analyze the biomechanical stability of four kinds of internal fixation for the type Ⅰ Hangman fracture, type Ⅱ odontoid fracture and the C(2/3) disc injury by finite element (FE) analysis. Methods: Thin-section spiral computed tomography (0.5 mm) was performed on C(1) to C(3) region of cervical vertebra in healthy male volunteers.A three-dimensional hexahedral FE model of upper cervical spine was established by software (Mimics, GEOMAGICS, Pro/E and Ansys). Then the weakening of the strength of grid was performed to simulate the FE model of the type Ⅰ Hangman fracture, type Ⅱ odontoid fracture and the C(2/3) disc injury (FE/Fracture), the four internal fixation models: anterior cervical plate+ odontoid screw+ cage (FE/ACP+ OS+ cage), affixing rods from pedicle screws in C(2) to lateral mass screws in C(3)+ odontoid screw + cage (FE/C(2)PS+ C(3)LMS+ OS+ cage), affixing rods from pedicle screws in C(1) to pedicle screws in C(2) and lateral mass screws in C(3) (FE/C(1)PS+ C(2)PS+ C(3)LMS), anterior odontoid screw plate fixation system (FE/AOSP) were simulated on the FE/Fracture model.Flexion, extension, lateral bending and axial rotation were imposed on the FE/Intact, FE/Fracture and the four fixation models respectively. Results: The intact model of upper cervical spine (C(1)-C(3)) was established successfully, consisting of 259 641 nodes and 403 674 units.There was no significant difference among the FE/ACP+ OS+ cage, the FE/ C(2)PS+ C(3)LMS+ OS+ cage and the FE/AOSP of ROMC(1/2).During flexion, extension, left axial rotation and right axial rotation of ROMC(2)-C(3), the FE/AOSP decreased 70.7%, 74.4%, 38.9%, 41.1% respectively compared with the FE/C(1)PS+ C(2)PS+ C(3)LMS.The ROMC(2)-C(3) during flexion, extension, left lateral bending, right lateral bending, left axial rotation and right axial rotation in the FE/AOSP decreased for 82.2%, 82.8%, 73.2%, 64.8%, 72.2%, 81.5% respectively when compared with those in FE/ACP+ OS+ cage.The ROMC(2)-C(3) during flexion, extension, left lateral bending, right lateral bending, left axial rotation and right axial rotation in the FE/AOSP decreased 88.2%, 81.2%, 47.6%, 41.2%, 38.9%, 39.0% respectively when compared with those in FE/C(2)PS+ C(3)LMS+ OS+ cage.The stress concentrated on the connection between plate and screw in the FE/ACP+ OS+ cage, the FE/C(2)PS+ C(3)LMS+ OS+ cage and the FE/C(1)PS+ C(2)PS+ C(3)LMS, while it distributed evenly in the FE/AOSP. Conclusion: Anterior odontoid screw plate fixation system can be used to treat the type Ⅰ Hangman fracture, type Ⅱ odontoid fracture, and the C(2/3) disc injury and can reserve the function of atlanto-axial joint.

Identification of aberrant promoter methylation of EDNRB gene in esophageal squamous cell carcinoma.

Epigenetic silencing of tumor suppressor genes is a major contributor to neoplastic transformation and is an area of intense research. The purpose of the present study was to identify the epigenetic changes in esophageal squamous cell carcinoma (ESCC). Methylation-sensitive arbitrarily primed polymerase chain reaction analysis was used on 21 matched ESCC tumors and adjacent normal tissues. Through this screen we identified a frequently methylated fragment that showed a high homology to the 5' CpG island of endothelin receptor type B (EDNRB) gene. The methylation status of the EDNRB gene was then detected by bisulfite sequencing and the levels of EDNRB mRNA were detected by quantitative real-time polymerase chain reaction (PCR). In addition, the effects of a methylation inhibitor 5-aza-2'-deoxycytidine on EDNRB mRNA expression was determined in cells of an ESCC cell lines. Hypermethylation of the 5' CpG island of EDNRB was found in 5 out of 21 (23.8%) primary tumors. Real-time PCR analysis demonstrated that EDNRB mRNA expression was significantly reduced in tumors showing high promoter methylation compared with paired normal tissues, whereas there is no significant difference between other paired samples. In addition, treatment of ESCC cell line with 5-aza-2'-deoxycytidine led to reexpression of the EDNRB transcript, which is correlated with the reversal of the methylation status of EDNRB promoter. In conclusion, promoter hypermethylation of EDNRB gene, which is associated with the loss of EDNRB mRNA expression, may play a role in the development of ESCC.

Aberrant promoter methylation of the TPEF gene in esophageal squamous cell carcinoma.

Aberrant methylation of tumor suppressor genes plays an important role in the development of esophageal squamous cell carcinoma (ESCC). The purpose of the present study was to identify the epigenetic changes in ESCC. Methylation-sensitive arbitrarily primed polymerase chain reaction (MS AP-PCR) analysis was used on 22 matched ESCC tumors and adjacent normal tissues. Through this screen we identified a frequently methylated fragment that showed a high homology to the 5'-CpG island of the gene encoding a transmembrane protein containing epidermal growth factor and follistatin domains (TPEF). The methylation status of the TPEF gene was then detected by bisulfite sequencing and the levels of TPEF mRNA were detected by RT-PCR. In addition, the effects of a methylation inhibitor 5-aza-2'-deoxycytidine on TPEF mRNA expression was determined in cells of ESCC cell lines. Hypermethylation of the 5'-CpG island of TPEF was found in 12 of 22 (54.5%) primary tumors. Reverse transcription PCR analysis demonstrated that TPEF mRNA expression was significantly lower in tumors than in adjacent normal tissues, which is associated with promoter hypermethylation. In addition, treatment of ESCC cell lines with 5-aza-2'-deoxycytidine led to re-expression of the TPEF transcript. In conclusion, we observed promoter of TPEF gene is frequently hpermethylated, and is associated with the loss of TPEF mRNA expression in ESCC samples. Promoter hypermethylation of TPEF gene may play a role in the development of ESCC.

[Comparison of surface characteristics and cytocompatibility of Ti-6Al-4V alloy fabricated with select laser melting and electron beam melting].

Objective: To evaluate the surface characteristics and cytocompatibility of Ti-6Al-4V alloy fabricated using select laser melting (SLM) and electron beam melting (EBM) technique. Methods: Ti-6Al-4V alloy specimens were fabricated with SLM and EBM. A wrought form of Ti-6Al-4V alloy was used as a control. Its properties were evaluated using component analysis, contact angle test, surface roughness, surface topography, cell ultrastructure, cell attachment and proliferation observation, metal ion precipitation examination. Results: The roughness of SLM and EBM specimens was suitable for cell attachment but not the best. The character of SLM and EBM specimens was hydrophobic (>65°). The surface topography of EBM and SLM specimens were similar, but were not the best type for cell attachment. The components of Ti-alloy oxide film were detected in all the specimens. The content of Ti, Al, V ions of EBM, SLM and wrought specimens were very low and did not affect the cell attachment and proliferation. The ultrastructure of cell was normal, and the cytomembrane was intact. The number of cells was similar to each other among the three kinds of specimens and increased obviously with the culture time. Conclusions: The results of the study suggested that EBM and SLM Ti-6Al-4V specimens possessed good surface characteristics. However, the surface modification are needed further.

[Evaluation of biocompatibility of Ti-6Al-4V scaffolds fabricated by electron beam melting].

Objective: To investigate the biocompatibility of Ti-6Al-4V scaffolds fabricated by electron beam melting(EBM). Methods: Bone marrow mesenchymal stem cells(BMSC) co-cultured with Ti-6Al-4V specimens fabricated with EBM was prepared as experimental group and the regular cells culture was employed as control. The biocompatibility was detected using CCK-8 and cytoskeleton staining. The osteogenic differentiation ability was assessed using mineralization nodule formation. A 24 mm defect was created on the right mandibular body in 12 beagles. The mandibular defects were repaired with Ti-6Al-4V scaffolds mesh fabricated by EBM. General observation, CT and histology examination was carried out to evaluated the biocompatibility of Ti-6Al-4V scaffolds in vivo. Results: CCK-8 result showed the A values of the two groups had no significant difference(P >0.05). There was no significant difference between the two groups (P>0.05). Cytoskeletal staining showed that cells were fully stretched out and grew well on T-i6Al-4V specimen. The actin fibers were arranged in parallel and stained uniformly with fluorescent. After osteogenic culture, the quantity of the nodule formation of the experimental group and control group were 5.7±0.7 and 5.1 ± 0.6, respectively(P>0.05). All animals had tolerated the surgery and healed well. CT examination showed that Ti-6Al-4V scaffolds mesh had good retention with surrounding bone and the continuity of mandible was restored. Histological examination showed that no inflammation reaction or toxity was caused in the soft tissue surrounding the scaffolds and in the liver and kidney after implantation. Ti-6Al-4V scaffolds had good retention with surrounding bone. Conclusions: Ti-6Al-4V fabricated with electron beam melting has good biocompatibility.

Mechanisms of the oxidations of NAD(P)H model Hantzsch 1,4-dihydropyridines by nitric oxide and its donor N-methyl-N-nitrosotoluene-p-sulfonamide.

4-Substituted derivatives of Hantzsch 1,4-dihydropyridine were treated by nitric oxide (NO) or its donor N-methyl-N-nitrosotoluene-p-sulfonamide (MNTS) to give the corresponding pyridine derivatives. When the 4-substituted group was methyl, ethyl, n-propyl, and aryl groups, it was preserved, but when the group was isopropyl or benzyl one, it was lost. 2,3-Dichloro-5, 6-dicyano-1,4-benzoquinone (DDQ) was used in place of NO and MNTS to react with the 4-substituted Hantzsch 1,4-dihydropyridines, no the corresponding 4-dealkyl Hantzsch pyridines were obtained from all the reactions. 1-Benzyl-1,4-dihydronicotinamide (BNAH), a close analogue of Hantzsch 1,4-dihydropyridine (HEH), was used instead of HEH to react with either of NO and MNTS, no reactions were observed for 3 days. Replacement of HEH by N-d-HEH and HEH-4,4-d(2) to react with NO, MNTS and DDQ gave the observed kinetic isotope effects of 3.1 and 1.4 for NO, 1.1 and 1.3 for MNTS, and 1.1 and 2.1 for DDQ, respectively. When p-dinitrobenzene, an electron-transfer inhibitor, was added into the title reaction systems, no remarkable inhibitory effect was observed. These results indicated that the oxidation of HEH by NO was initiated by hydrogen transfer from the N(1)-position to give the corresponding aminyl radical, which then underwent homolytic cleavage to become the final aromatized product (A). But the reaction of HEH with MNTS was initiated by nitrosation to give the corresponding N-nitroso compound, which was subsequently subjected to two steps of homolytic cleavage to afford the aromatized Hantzsch pyridine A.

An old but simple and efficient method to elucidate the oxidation mechanism of NAD(P)H model 1-Aryl-1,4-dihydronicotinamides by cations 2-methyl-5-nitroisoquinolium, tropylium, and xanthylium in aqueous solution.

Cations 2-methyl-5-nitroisoquinolinium (IQ+), tropylium (T+), and xanthylium (Xn+) were treated by an NAD(P)H model 1-(p-substituted phenyl)-1.4-dihydronicotinamide series (1) in buffered aqueous solution to give the corresponding reduced products by accepting hydride. Effects of the 4-substituents of 1 on the reaction rates were investigated. Hammett's linear free energy relationship analysis on the three reactions of 1 provides the reaction constants of -0.48, -2.2, and -1.4 with IQ+, T+, and Xn+ as the hydride acceptors, respectively. Comparison of the present reactions with the reaction examples whose mechanisms are well-known, such as the reaction of 1 with a one-electron oxidant Fe(CN)6(-3), shows that the active site of 1 in the oxidation with IQ+ is at the 4-position on the dihydropyridine ring but that the active site of 1 in the oxidations with T+ and Xn+ is at the 1-position, which is in agreement with the results from the Brønsted-type linear analysis and the relation studies of the logarithm of the second-order rate constants with the oxidation potentials of the hydride donors. According to the dependence of the reaction mechanism on the active site of 1, a conclusion can be made that the reaction of 1 with IQ+ proceeds by direct one-step hydride transfer mechanism, but the reactions of 1 with T+ and Xn+ would take place via multistep hydride transfer mechanism initiated by one-electron transfer.