Equilibrium freezing curve of Mg-2%Ga （mass fraction） alloy was calculated by CALPHALD method. Microstructures of the melted Mg-2%Ga alloys solidified by iron and copper moulds, respectively, were investigated using...Equilibrium freezing curve of Mg-2%Ga （mass fraction） alloy was calculated by CALPHALD method. Microstructures of the melted Mg-2%Ga alloys solidified by iron and copper moulds, respectively, were investigated using OM and SEM. Electrochemical properties of the Mg-2%Ga alloys with different freezing rates were measured by galvanostatic, potentiodynamic and electrochemical impedance spectroscopy tests. The results show that solidification by copper mould leads to intergranular MgsGa2 compounds with small size and large number density. Less adsorbent of Mg^＋ and oxide corrosion products occur on the surface of the Mg-2%Ga alloys solidified by copper mould, producing lower corrosion current density of 1.8×10^-5 mA/cm^2. In the galvanostatic tests with 100 mA/cm^2 current density, more negative stable potential of-1.604 V exists in the Mg-2%Ga alloys solidified by iron mould due to the lower freezing rate, which leads to smaller inductive and capacity time constants as well as shorter activity time and better electrochemical activity.展开更多
Mesenchymal stem cells （MSCs） have great potential for treating various diseases, especially those related to tissue damage involving immune reactions. Various studies have demonstrated that MSCs are strongly immuno...Mesenchymal stem cells （MSCs） have great potential for treating various diseases, especially those related to tissue damage involving immune reactions. Various studies have demonstrated that MSCs are strongly immunosuppressive in vitro and in vivo. Our recent studies have shown that un-stimulated MSCs are indeed incapable of immunosuppression; they become potently immunosuppressive upon stimulation with the supernatant of activated lymphocytes, or with combinations of IFN-γ, with TNF-α, IL-1α or IL-1β. This observation revealed that under certain circumstances, inflammatory cytokines can actually become immunosuppressive. We showed that there is a species variation in the mechanisms of MSC-mediated immunosuppression： immunosuppression by cytokine-primed mouse MSCs is mediated by nitric oxide （NO）, whereas immunosuppression by cytokine-primed human MSCs is executed through indoleamine 2, 3-dioxygenase （IDO）. Additionally, upon stimulation with the inflammatory cytokines, both mouse and human MSCs secrete several leukocyte chemokines that apparently serve to attract immune cells into the proximity with MSCs, where NO or IDO is predicted to be most active. Therefore, immunosuppression by inflammatory cytokine-stimulated MSCs occurs via the concerted action of chemokines and immune-inhibitory NO or IDO produced by MSCs. Thus, our results provide novel information about the mechanisms of MSC-mediated immunosuppression and for better application of MSCs in treating tissue injuries induced by immune responses.展开更多
Many identified and yet unknown factors contribute to the pathogenesis of inflammatory bowel disease(IBD).The genome-wide association studies clearly support the earlier developed concept that IBD occurs in geneticall...Many identified and yet unknown factors contribute to the pathogenesis of inflammatory bowel disease(IBD).The genome-wide association studies clearly support the earlier developed concept that IBD occurs in genetically predisposed individuals who are exposed to distinct environmental factors,which together result in dysregulation of the mucosal immune system.Thus,the majority of previous studies have focused on the immune response within the intestinal wall.The present review aims to emphasize the contribution of three extraluminal structures to this inflammatory process,namely the mesenteric fat tissue,the lymphatics and the microvasculature.Broadening our view across the intestinal wall will not only facilitate our understanding of the disease,but will also us to identify future therapeutic targets.展开更多
It is discovered a new three-, four-component Petasis, Passerini, Hantzsch, Kabachnic-Fields, Ugi reactions with of arsine, stibine and bismuthine in organometallic chemistry. Modifications were replaced to a nitrogen...It is discovered a new three-, four-component Petasis, Passerini, Hantzsch, Kabachnic-Fields, Ugi reactions with of arsine, stibine and bismuthine in organometallic chemistry. Modifications were replaced to a nitrogen atom of classical reactions of atoms of phosphorus, arsenic, antimony and bismuth. It has been proposed a new mechanism for possible reactions.展开更多
Objective To investigate the feasibility of tendon engineering in vitro using tenocyws and polyglycolic acids （ PGA ）. Methods Tenocytes were isolated by tissue explant method and expanded in vitro. Cells of the sec...Objective To investigate the feasibility of tendon engineering in vitro using tenocyws and polyglycolic acids （ PGA ）. Methods Tenocytes were isolated by tissue explant method and expanded in vitro. Cells of the second passage were collected and seeded onto PGA scaffolds made from PGA unwoven fibers at the density of 20 × 10^6 cells/ml. At 1 week postseeding ,the constructs were divided into three groups as follows： cell-scaffold constructs under constant tension generated by a U-shaped spring as the experimental group （ n = 5 ）, cell-scaffold constructs under no tension as control group 1 （ n = 4 ）, cell-free scaffolds under constant tension as control group 2 （n =3）. Samples were harvested at 2, 4 and 6 weeks for histological and immunohistochemical （ IHC ） examinations. Transmission electron microscopy （TEM） and mechanical test were performed to evaluate the constructs of 6 weeks. Results At 2 weeks, the constructs were mainly composed of undegraded PGA fibers. Gross and histological examination revealed no difference between the groups. At 4 weeks, neo-tendon was visible through gross observation in experimental group and control group 1. Histology and immunohistochemistry revealed the formation of collagen fibers. While in control group 2, PGA fibers were mostly degraded. At 6 weeks, the constructs were much thinner in experimental group than those in control group 1 （ 1.44 ± 0.13mm vs 2.55 ± 0. 18mm in diameter ）. TEM showed periodical strata of collagen fibers in the constructs from experimental group and control group 1. However, histology in experimental group revealed longitudinal alignment of collagen fibers, which more resembled natural tendon than neotendon formed in control group 1. Besides, the maximum load to failure（ Newton/mm^2 ） was greater in experimental group than that in control group 1 （1. 107 ±0. 327 vs 0. 294 ± 0. 138, P 〈0.05）. Conclusion It＇ s possible to engineer tendon substitutes in vitro. Cyclic strain generated by a bioreactor may be the optimal mechanical stimulation and is currently under investigation.展开更多
Density functional theory(DFT)calculations are employed to disclose the detailed reaction mechanism of the synthesis of 3-phenyl-2,5-dihydro-lH-benzo[d]imidazo[5,1-b][1,3]oxazine-l-thione under unassisted,water-assist...Density functional theory(DFT)calculations are employed to disclose the detailed reaction mechanism of the synthesis of 3-phenyl-2,5-dihydro-lH-benzo[d]imidazo[5,1-b][1,3]oxazine-l-thione under unassisted,water-assisted,and trifluoroacetic acid(TFA)assisted conditions by 2,2-dihydroxy-1-phenylethanone(1),(2-aminophenyl)methanol(2),and KSCN(3).The computational results show that the title mechanism can be altered and accelerated by TFA,water,and substrate 2.Three types of mechanisms are reported by DFT calculations differing in the reaction sequence of substrates,such as M1:1+2 then 3;M2:1+3 then 2;M3:2+3 then 1.It is found that the nucleophilicity of substrate 2 is stronger than 3.The DFT calculations suggest that the TFA-water co-assisted pathway of M1 is the most favorable case,which proceeds the nucleophilic addition and H-shift,intramolecular cyclization and water elimination,second nucleophilic addition and H-shift,intramolecular cyclization[3+2]cyclo-addition,and C-C bond formation and water elimination.The rate-determining step is the process of[3+2]cycloaddition.More importantly,we found that TFA and water molecules play critical roles in the whole reaction,by acting as efficient catalysts,proton shuttle,and stabilizer to stabilize the structures of transition states and intermediates via O…H-N,O…H-O,and O…H-C interactions.And they also act as hydrogen bonds(HBs)donor and acceptor to improve the reactive activity of the substrates by changing the reaction form of glyoxal monohydrates and KSCN.Substrate 2 as HBs acceptor promotes the enol-ketone tautomerization and favors the proton transfer process.The origin of the different reactivity of M1,M2,and M3 is ascribed to the pivotal non-covalent interactions that exist between catalyst(water and TFA)and reactants.Interestingly,our computations revealed that the title reaction can be performed in water instead of CH_(3)CN,which paves the way to design a greener synthetic strategy for oxazine N-fused imidazole-2-thiones and their derivatives.展开更多
基金Project (JPPT-115-4-1682) supported by the National Defense Science and Technology Industry Committee of China
文摘Equilibrium freezing curve of Mg-2%Ga （mass fraction） alloy was calculated by CALPHALD method. Microstructures of the melted Mg-2%Ga alloys solidified by iron and copper moulds, respectively, were investigated using OM and SEM. Electrochemical properties of the Mg-2%Ga alloys with different freezing rates were measured by galvanostatic, potentiodynamic and electrochemical impedance spectroscopy tests. The results show that solidification by copper mould leads to intergranular MgsGa2 compounds with small size and large number density. Less adsorbent of Mg^＋ and oxide corrosion products occur on the surface of the Mg-2%Ga alloys solidified by copper mould, producing lower corrosion current density of 1.8×10^-5 mA/cm^2. In the galvanostatic tests with 100 mA/cm^2 current density, more negative stable potential of-1.604 V exists in the Mg-2%Ga alloys solidified by iron mould due to the lower freezing rate, which leads to smaller inductive and capacity time constants as well as shorter activity time and better electrochemical activity.
文摘Mesenchymal stem cells （MSCs） have great potential for treating various diseases, especially those related to tissue damage involving immune reactions. Various studies have demonstrated that MSCs are strongly immunosuppressive in vitro and in vivo. Our recent studies have shown that un-stimulated MSCs are indeed incapable of immunosuppression; they become potently immunosuppressive upon stimulation with the supernatant of activated lymphocytes, or with combinations of IFN-γ, with TNF-α, IL-1α or IL-1β. This observation revealed that under certain circumstances, inflammatory cytokines can actually become immunosuppressive. We showed that there is a species variation in the mechanisms of MSC-mediated immunosuppression： immunosuppression by cytokine-primed mouse MSCs is mediated by nitric oxide （NO）, whereas immunosuppression by cytokine-primed human MSCs is executed through indoleamine 2, 3-dioxygenase （IDO）. Additionally, upon stimulation with the inflammatory cytokines, both mouse and human MSCs secrete several leukocyte chemokines that apparently serve to attract immune cells into the proximity with MSCs, where NO or IDO is predicted to be most active. Therefore, immunosuppression by inflammatory cytokine-stimulated MSCs occurs via the concerted action of chemokines and immune-inhibitory NO or IDO produced by MSCs. Thus, our results provide novel information about the mechanisms of MSC-mediated immunosuppression and for better application of MSCs in treating tissue injuries induced by immune responses.
基金Supported by SFB 633 of the Deutsche Forschungsgemeinschaft
文摘Many identified and yet unknown factors contribute to the pathogenesis of inflammatory bowel disease(IBD).The genome-wide association studies clearly support the earlier developed concept that IBD occurs in genetically predisposed individuals who are exposed to distinct environmental factors,which together result in dysregulation of the mucosal immune system.Thus,the majority of previous studies have focused on the immune response within the intestinal wall.The present review aims to emphasize the contribution of three extraluminal structures to this inflammatory process,namely the mesenteric fat tissue,the lymphatics and the microvasculature.Broadening our view across the intestinal wall will not only facilitate our understanding of the disease,but will also us to identify future therapeutic targets.
文摘It is discovered a new three-, four-component Petasis, Passerini, Hantzsch, Kabachnic-Fields, Ugi reactions with of arsine, stibine and bismuthine in organometallic chemistry. Modifications were replaced to a nitrogen atom of classical reactions of atoms of phosphorus, arsenic, antimony and bismuth. It has been proposed a new mechanism for possible reactions.
文摘Objective To investigate the feasibility of tendon engineering in vitro using tenocyws and polyglycolic acids （ PGA ）. Methods Tenocytes were isolated by tissue explant method and expanded in vitro. Cells of the second passage were collected and seeded onto PGA scaffolds made from PGA unwoven fibers at the density of 20 × 10^6 cells/ml. At 1 week postseeding ,the constructs were divided into three groups as follows： cell-scaffold constructs under constant tension generated by a U-shaped spring as the experimental group （ n = 5 ）, cell-scaffold constructs under no tension as control group 1 （ n = 4 ）, cell-free scaffolds under constant tension as control group 2 （n =3）. Samples were harvested at 2, 4 and 6 weeks for histological and immunohistochemical （ IHC ） examinations. Transmission electron microscopy （TEM） and mechanical test were performed to evaluate the constructs of 6 weeks. Results At 2 weeks, the constructs were mainly composed of undegraded PGA fibers. Gross and histological examination revealed no difference between the groups. At 4 weeks, neo-tendon was visible through gross observation in experimental group and control group 1. Histology and immunohistochemistry revealed the formation of collagen fibers. While in control group 2, PGA fibers were mostly degraded. At 6 weeks, the constructs were much thinner in experimental group than those in control group 1 （ 1.44 ± 0.13mm vs 2.55 ± 0. 18mm in diameter ）. TEM showed periodical strata of collagen fibers in the constructs from experimental group and control group 1. However, histology in experimental group revealed longitudinal alignment of collagen fibers, which more resembled natural tendon than neotendon formed in control group 1. Besides, the maximum load to failure（ Newton/mm^2 ） was greater in experimental group than that in control group 1 （1. 107 ±0. 327 vs 0. 294 ± 0. 138, P 〈0.05）. Conclusion It＇ s possible to engineer tendon substitutes in vitro. Cyclic strain generated by a bioreactor may be the optimal mechanical stimulation and is currently under investigation.
基金Financial support by the National Natural Science Foundation of China(21873018,21573036,and 21603028)the Fundamental Research Funds for the Central Universities(2412019FZ010)the open project of the Jilin Province Key Laboratory of Organic Functional Molecular Design and Synthesis(130028655)are greatly acknowledged
文摘Density functional theory(DFT)calculations are employed to disclose the detailed reaction mechanism of the synthesis of 3-phenyl-2,5-dihydro-lH-benzo[d]imidazo[5,1-b][1,3]oxazine-l-thione under unassisted,water-assisted,and trifluoroacetic acid(TFA)assisted conditions by 2,2-dihydroxy-1-phenylethanone(1),(2-aminophenyl)methanol(2),and KSCN(3).The computational results show that the title mechanism can be altered and accelerated by TFA,water,and substrate 2.Three types of mechanisms are reported by DFT calculations differing in the reaction sequence of substrates,such as M1:1+2 then 3;M2:1+3 then 2;M3:2+3 then 1.It is found that the nucleophilicity of substrate 2 is stronger than 3.The DFT calculations suggest that the TFA-water co-assisted pathway of M1 is the most favorable case,which proceeds the nucleophilic addition and H-shift,intramolecular cyclization and water elimination,second nucleophilic addition and H-shift,intramolecular cyclization[3+2]cyclo-addition,and C-C bond formation and water elimination.The rate-determining step is the process of[3+2]cycloaddition.More importantly,we found that TFA and water molecules play critical roles in the whole reaction,by acting as efficient catalysts,proton shuttle,and stabilizer to stabilize the structures of transition states and intermediates via O…H-N,O…H-O,and O…H-C interactions.And they also act as hydrogen bonds(HBs)donor and acceptor to improve the reactive activity of the substrates by changing the reaction form of glyoxal monohydrates and KSCN.Substrate 2 as HBs acceptor promotes the enol-ketone tautomerization and favors the proton transfer process.The origin of the different reactivity of M1,M2,and M3 is ascribed to the pivotal non-covalent interactions that exist between catalyst(water and TFA)and reactants.Interestingly,our computations revealed that the title reaction can be performed in water instead of CH_(3)CN,which paves the way to design a greener synthetic strategy for oxazine N-fused imidazole-2-thiones and their derivatives.
