Study of Grain Growth in a Ni-Based Superalloy by Experiments and Cellular Automaton Model.

The grain growth behavior in a typical Ni-based superalloy was investigated using isothermal heat treatment experiments over a holding temperature range of 1353-1473 K. The experimental results showed that the grain structure continuously coarsened as the holding time and holding temperature increased during heat treatment. A classical parabolic grain growth model was used to explore the mechanism of grain growth under experimental conditions. The grain growth exponent was found to be slightly above 2. This indicates that the current grain growth in the studied superalloy is mainly governed by grain boundary migration with a minor pinning effect from the precipitates. Then, the grain growth in the studied superalloy during isothermal heat treatment was modelled by a cellular automaton (CA) with deterministic state switch rules. The microscale kinetics of grain growth is described by the correlation between the moving velocity and curvature of the grain boundary. The local grain boundary curvature is well evaluated by a template disk method. The grain boundary mobility was found to increase with increasing temperature. The relationship between the grain boundary mobility and temperature has been established. The developed CA model is capable of capturing the dependence of the grain size on the holding time under different holding temperatures.

[Elemental Analysis of Alloys with Picosecond Dual-Pulse LA-LIBS under Low Sample Destruction].

A study on elemental analysis of alloy samples under low sample destruction with dual-pulse laser-ablation laser induced breakdown spectroscopy (LA-LIBS) based on one picosecond Nd : YAG laser is presented. In LA-LIBS, low pulse energy 532 nm laser was used for sample ablation and high pulse energy, time­delayed 1 064 nm laser was used for re-excitation of the ablated samples to enhance atomic emissions of the laser-induced plasma and signal detection sensitivity. The influence of pulse energies of the ablation laser and excitation laser to the signal intensities was studied experimentally. I was observed that Cu 324.75 nm line intensity in LA-LIBS was enhanced 86 times in comparison with that obtained in SP-LIBS under 10 µJ pulse energy of the ablation laser and 2.5 mJ pulse energy of the excitation laser. The diameter of the crater generated in LA-LIBS was less than 10 µm. It is demonstrated the possibility of using dual-pulse LA-LIBS to realize elemental analysis of solid sample under low sample destruction. This technique is valuable for elemental analysis of precious samples and 2D elements mapping under high spatial resolution.

[Research Advances on Gliding-associated Proteins of Toxoplasma gondii].

The ability to invade host cells is a key to the survival and pathogenicity of Apicomplexan parasites. Toxoplasma gondii is an obligatory intracellular parasite. Its motility, invasion into, and egression from host cells are powered by a machinery called acto-myosin motor （AMM）. The AMM is composed of myosin A, a myosin light chain （MLC1）, two essential light chains （ELC）1, 2 and gliding-associated protein （GAP）. The GAP family has been discovered to include GAP45, GAP50, GAP80, GAP70 and GAP40, which are the major components of glideosome that provides power for parasite motility. The glideosome of apicomplexan parasites is an actin- and myosin-based power machine located at the pellicle between the plasma membrane （PM） and inner membrane complex (IMC). This review outlines our current understanding of GAP function and architecture as well as the molecular basis for parasite motility. Meanwhile, the use of GAPs as the candidate toxoplasmosis vaccine is prospected.

[Research Advance on Toxoplasma gondii Rhoptry Protein 2 Family as Candidate Vaccine Molecules].

Toxoplasma gondii rhoptry protein 2 family (ROP2 family), secreted by the rhoptry, plays an important role in T. gondii invasion of host cells and its virulence. The ROP2 family members include ROP2, ROP4, ROP5, ROP8, ROP13, ROP16, ROP17, and ROP18. Recent studies have found that these members are potential vaccine candidates against toxoplasmosis, and can induce the protective immunity of the host. This paper reviews the research advance on the ROP2 family members as DNA or protein vaccines against toxoplasmosis.

[Quantitative Analysis of Copper Impurity in Silver Jewellery by Laser-Ablation Laser-Induced Breakdown Spectroscopy].

High spectral analysis sensitivity can be achieved with orthogonal dual-wavelength dual-pulse laser-ablation laser-induced breakdown spectroscopy under minimal sample ablation. Therefore, the contradiction between spatial resolution and analytical sensitivity existed in single-pulse laser-induced breakdown spectroscopy can be resolved fundamentally in this technique. In order to eliminate the influence of different experimental parameters to the signal intensities and final results of quantitative analysis, the correlation between copper atomic emission and silver atomic emission was studied experimentally in this technique for silver jewellery samples. It was demonstrated that the intensity of atomic emission of copper at 324.75 nm and that of silver at 328.07 nm was linearly correlated with high correlation coefficient. Therefore, it was possible to eliminate the influence of different experimental parameters, such as geometrical arrangement and pulse energy of the ablation laser to the signal of copper atomic emission by selecting 328.07 nm line of silver as internal standard. A quantitative analysis of copper impurity in silver jewellery can be realized by using orthogonal dual-wavelength dual-pulse laser-ablation laser-induced breakdown spectroscopy. A calibration curve of copper was successfully built based on internal standard method while selecting 328.07 nm line of silver as internal standard. The limit of detection of copper in silver matrix was determined to be 44 ppm in this technique when the crater's diameter was about 17 µm under current experimental condition.

Down-regulation of human enteric antimicrobial peptides by NOD2 during differentiation of the paneth cell lineage.

Ileal Crohn's disease (CD) arising from the alteration of intestinal homeostasis is characterized by two features, namely a decrease in Paneth cell-produced antimicrobial peptides that play a key role in maintaining this balance and an increase in NOD2, an intracellular sensor. Although mutations in NOD2 are highly correlated with the incidence of CD, the physiological role of NOD2 in intestinal immunity remains elusive. Here, we show that NOD2 can down-regulate the expression of human enteric antimicrobial peptides during differentiation of the Paneth cell lineage. This finding, which links the decrease of human enteric antimicrobial peptides to increased NOD2 in ileal CD patients, provides a new view into the pathogenesis of ileal CD.

Protective immunity induced by peptides of AMA1, RON2 and RON4 containing T-and B-cell epitopes via an intranasal route against toxoplasmosis in mice.

BACKGROUND: Toxoplasma gondii is a ubiquitous protozoan intracellular parasite, the causative agent of toxoplasmosis, and a worldwide zoonosis. Apical membrane antigen-1 (AMA1) and rhoptry neck protein (RON2, RON4) are involved in the invasion of T. gondii. METHODS: This study chemically synthesized peptides of TgAMA1, TgRON2 and TgRON4 that contained the T- and B-cell epitopes predicted by bioinformatics analysis. We evaluated the systemic response by proliferation, cytokine and antibody measurements as well as the mucosal response by examining the levels of antigen-specific secretory IgA (SIgA) in the nasal, vesical and intestinal washes obtained from mice after nasal immunization with single (AMA1, RON2, RON4) or mixtures of peptides (A1 + R2, A1 + R4, R2 + R4, A1 + R2 + R4). We also assessed the parasite burdens in the liver and brain as well as the survival of mice challenged with a virulent strain. RESULTS: The results showed that the mice immunized with single or mixed peptides produced effective mucosal and systemic immune responses with a high level of specific antibody responses, a strong lymphoproliferative response and significant levels of gamma interferon (IFN-γ), interleukin-2 (IL-2) and IL-4 production. These mice also elicited partial protection against acute and chronic T. gondii infection. Moreover, our study indicated that mixtures of peptides, especially the A1 + R2 mixture, were more powerful and efficient than any other single peptides. CONCLUSIONS: These results demonstrated that intranasal immunisation with peptides of AMA1, RON2 and RON4 containing T- and B-cell epitopes can partly protect mice against toxoplasmosis, and a combination of peptides as a mucosal vaccine strategy is essential for future Toxoplasma vaccine development.

Increased expression and possible role of chitinase 3-like-1 in a colitis-associated carcinoma model.

AIM: To investigate the possible role of chitinase 3-like-1 (CHI3L1) in the progression of colitis-associated carcinoma (CAC). METHODS: Thirty-four Balb/c mice were randomly assigned to five groups, including the control, CAC control, CAC + caffeine, colitis control and colitis + caffeine. Three animals were sacrificed every two weeks for blinded macroscopic inspection, histological analysis, and total RNA extraction. An immunofluorescent assay was performed using specimens from the colitis control and colitis + caffeine groups to investigate whether the protective effect of caffeine was associated with less oxidative DNA damage. In vitro, HT29 cells pre-stimulated with different concentrations of recombinant CHI3L1 protein and H2O2 were loaded with the DCFH-DA fluorescent probe to determine the effect of CHI3L1 on intracellular reactive oxygen species production. RESULTS: CHI3L1 mRNA was increased during the progression of colon carcinogenesis. Tumors were mostly located in the distal end of the colon where the expression of CHI3L1 was higher than in the proximal colon. Caffeine-treated mice developed fewer tumors and milder inflammation than untreated mice. CHI3L1 protein increased reactive oxygen species in HT29 cells when exposed to H2O2. CONCLUSION: Caffeine reduces tumor incidence by decreasing oxidative DNA damage. CHI3L1 may contribute to CAC by increasing reactive oxygen species production.

[Gene-cloning, expression and immunoreactivity detection of Toxoplasma gondii uridine phosphorylase].

OBJECTIVE: To predict the physicochemical properties and antigenic epitopes of Toxoplasma gondii uridine phosphorylase (TgUPase), clone, and express TgUPase gene, and analyze its immunoreactivity. METHODS: The physical and chemical characters and specific epitopes of TgUPase protein were predicted by bioinformatics software tools. Total RNA was extracted from RH strain T. gondii tachyzoites. A pair of specific primers was designed according to the open reading frame of TgUPase gene (GenBank Accession No. DQ385446.1). RT-PCR product was digested with restriction enzyme and ligated into a pET-30a(+) vector. The recombinant plasmid pET-30a(+)-TgUPase was transformed into E. coli DH5alpha and the positive clones were selected by colony PCR and confirmed by double restriction enzyme digestion and sequencing. The constructed pET-30a(+)-TgUPase was then transformed into E. coli BL21(DE3) and induced with IPTG for expression. The expression product was analyzed through SDS-PAGE followed by Coomassie blue staining. Western blotting assay with His primary antibody and human anti-T. gondii serum was used to confirm the expression of rTgU-Pase and detect its immunoreactivity. RESULTS: Bioinformatics prediction results showed that rTgUPase protein was 303 amino acids in length with a predicted molecular mass of M, 33 042.9, and this soluble protein had three potential T/B cell epitopes. The product of RT-PCR was 921 bp. Colony PCR, double restriction enzyme digestion and DNA sequencing confirmed that the recombinant plasmid pET-30a(+)-TgUPase was constructed. SDS-PAGE showed that bacteria containing recombinant plasmid pET-30a(+)-TgUPase expressed a soluble protein of His-TgUPase (about Mr 38,000) after being induced with IPTG. The recombinant protein reacted positively with His primary antibody and human anti-T. gondii serum by Western blotting analysis. CONCLUSION: The recombinant plasmid pET-30a (+)-TgUPase is constructed and the soluble rTgUPase shows immunoreactivity.

[Research progress on uridine phosphorylase in vertebrate and parasites].

Uridine phosphorylase (UPP) is a key enzyme of pyrimidine salvage pathways, catalyzing the reversible phosphorolysis of ribosides of uracil to nucleobases and ribose 1-phosphate. UPP plays an important role in the regulation of uridine homeostasis. Although UPP from a variety of organisms have many similarities in their functions, there are differences in many other aspects, such as physical and chemical properties, structure characteristics, active sites, and substrate binding sites. Therefore, UPP has broad application prospects in the design and development of antibacterial, antiparasitic drugs. This article summarizes the physico-chemical property and research progress of UPP from a variety of organisms, in order to integrate information of UPP, provide theoretic basis for further study of Toxoplasma gondii UPP protein as a feasible target antigen for toxoplasmosis vaccination.

[Laser ignition assisted spark-induced breakdown spectroscopy for element analysis of aluminum alloy with enhanced sensitivity].

The analytical performance of laser ignition assisted spark-induced breakdown spectroscopy (LI-SIBS) for the analysis of trace metal in aluminum alloy was reported in the present article. In order to improve the analytical performance of spark-induced breakdown spectroscopy, a low energy laser pulse was focused on the surface of the sample to produce plasma between discharge electrodes to trigger high voltage spark discharge. Under current geometrical arrangement, optimized discharge voltage and capacitance were determined, and copper in aluminum alloy was analyzed under optimized experimental condition. The limit of detection of copper in aluminum alloy was determined to be 0.7 ppm. Both signal stability and measurement accuracy for spark-induced breakdown spectroscopy were improved with the assistance of laser ignition. The discharge voltage could be reduced and the spatial resolution could be improved with the assistance of laser ignition at the same time. It was demonstrated that LI-SIBS has the characteristics of high sensitivity, good stability and better spatial resolution and is suitable for trace elements analysis in different alloys.

[Delivery of megawatts high energy laser pulse with large core diameter silica fiber and its application in dual-wavelength laser-ablation laser-induced breakdown spectroscopy].

To resolve the contradiction between spatial resolution and analysis sensitivity in single pulse laser-induced breakdown spectroscopy (LIBS), a study on dual-wavelength laser-ablation laser-induced breakdown spectroscopy (LA-LIBS) was carried out by using one Nd : YAG laser which was capable of two laser beam outputs with different wavelengths, where, the second harmonic output, 532 nm laser beam, was used as laser-ablation source, and the fundamental output, 1064 nm laser beam, was delivered with a large core diameter silica fiber to realize nanoseconds time-delay and then used to breakdown the ablated samples. Two laser beams were orthogonally arranged to realize element analysis with high spatial resolution and high sensitivity. Some key techniques on the coupling of 1064 nm laser beam into fiber, the collimation of laser at the fiber end and re-focusing of the laser beam were studied. The energy delivery capabilities of four fibers of different types were studied and the maximum values were determined experimentally. A Q-switched laser pulse with 15 mJ pulse energy was successfully delivered by selecting a 50 meter long silica fiber with 800 microm core diameter and 0. 39 numerical aperture. And 250 ns time-delay was realized. A copper alloy was analyzed by spectra with current established LA-LIBS system and the possibility of realizing dual-wavelength LA-LIBS analysis based on one Nd : YAG laser was demonstrated experimentally. In this technique, only one Nd: YAG laser was required to carry out spectral analysis. It has a few advantages, such as simple equipment structure, and being convenient to miniaturize the whole system etc. This dual-wavelength LA-LIBS technique was suitable for in-situ elements microanalysis for different samples with both high spatial resolution and high sensitivity.

[Cloning and expression of actin gene of Toxoplasma gondii].

OBJECTIVE: To clone and express the actin gene of Toxoplasma gondii, and analyze the immunoreactivity of the recombinant protein. METHODS: Total RNA was extracted from tachyzoites of RH strain of T. gondii. The open reading frame of TgACT gene was amplified with a pair of specific primers which were designed according to the coding sequence of TgACT gene (Accession No. XM_002369622.1). The RT-PCR product was cloned into the prokaryotic expression pET-30a (+) vector. The recombinant pET30a-TgACT plasmid was transformed into E. coli DH5alpha. The positive clones were selected through the colony-PCR and confirmed by the double restrict enzyme digestion and sequencing. The correct pET30a-TgACT plasmid was transformed into E. coli BL21(DE3) and induced by IPTG. The expressed proteins were analyzed by SDS-PAGE. Western blotting assay was performed with anti-poly-histidine tag (anti-His) antibody or rabbit anti-T. gondii serum. RESULTS: The product of RT-PCR was with 1 100 bp. The recombinant plasmid pET30a-TgACT was confirmed by colony-PCR, double restriction enzyme digestion and sequencing. SDS-PAGE results showed that the target protein was expressed in E. coli BL21(DE3) in the form of inclusion bodies with a rough molecular weight of 49 000. The purified soluble protein was obtained by using denaturation, renaturation and purification. Western blotting revealed that rTgACT can be recognized by anti-His antibody and rabbit anti-T. gondii serum. CONCLUSION: The recombinant plasmid pET30a-TgACT has been successfully constructed, and the recombinant protein TgACT is produced in E. coli and maintains specific immunoreactivity.

[Efficacy of albendazole orally administered at different dosages against Trichinella spiralis encapsulated larvae in mice].

OBJECTIVE: To evaluate the efficacy of albendazole (ABZ) orally administered at different dosages against Trichinella spiralis encapsulated larvae in striated muscle in mice. METHODS: A total of 72 BALB/c mice were divided equally into 9 groups. Each mouse was infected orally with 50 T. spiralis encapsulated larvae. At the 29th day after infection, albendazole was each orally administered to the mice of the 8 groups with doses of 50, 100, 150, 200, 250, 300, 350, and 400 mg/(kg x d), respectively, once a day at fixed time for 6 d. The control group was untreated. Mice were sacrificed at the 7th day post administration. The encapsulated larvae in diaphragmatic muscle, jugomaxillary muscle and gastrocnemius muscle were examined with pellet method. The encapsulated larva that the capsule was complete and the larva inside curled naturally with clear structure was considered survived. The therapeutic effect was estimated on the average quantity of total, survival and dead encapsulated larvae per gram muscle, total worm reduction and survival worm reduction. RESULTS: The total worm burden and survival worms showed a decreasing trend and the numbers of dead worms increased in diaphragmatic muscle, jugomaxillary muscle and gastrocnemius muscle when the dosage of albendazole were 50-250 mg/(kg x d), but the number of larvae in the muscles remained similar when the dosage of albendazole was greater than 250mg/kg x d. Compared with the control group, the total and survival worms in the muscles in 200 mg/(kg x d) and the greater dose groups decreased significantly (P<0.01). In 250 mg/(kg x d) group the total worm reduction in jugomaxillary muscle, diaphragmatic muscle and gastrocnemius muscle were 50.00%, 62.62% and 57.48%, and the survival worm reduction were 79.96%, 83.25% and 80.56%, respectively. CONCLUSION: Orally administered to mice for 6 d, albendazole at 250 mg/(kg x d) is a suitable dose against encapsulated larva stage of T. spiralis in muscle.

[Research progress in phosphoglycerate mutase].

Phosphoglycerate mutase (PGAM) is one of glycolytic enzymes, concerning with the transport of carbohydrates, metabolism, catalytic activity and growth development. PGAM was discovered in yeast firstly, and with its amino acid sequence and crystal structure determined, this protein was found in varies organism, such as human, Escherichia coli, Schistosoma japonicum and Toxoplasma gondii. This article reviews the physico-chemical property and research progress of PGAM of vertebrate, invertebrate and protozoa.

[Effect of oral administration of tribendimidine at different dosages against Trichinella spiralis encapsulated larvae in mice].

OBJECTIVE: To observe the efficacy of oral administration of tribendimidine (TBD) at different dosages against Trichinella spiralis encapsulated larvae in murine striated muscle. METHODS: A total of 88 BALB/c mice were divided equally into 11 groups. Each mouse was infected orally with 50 T spiralis encapsulated larvae. At day 29 after infection, TBD was each orally administered to mice of the 11 groups with doses of 0 (control group), 50, 100, 150, 200, 250, 300, 350, 400, 450, and 500 mg/(kg x d), respectively. All mice were administered once a day and lasted for 6d, and untoward drug reactions for mice were observed. Mice were sacrificed at the 7th day after administration of TBD, the encapsulated larvae in diaphragmatic muscle, jugomaxillary muscle, pectoral muscle and gastrocnemius muscle were examined by pellet method, and the total, survival and dead worms were counted. The therapeutic effect was estimated on the basis of average quantity of encapsulated larvae per gram muscle. RESULTS: During the administration period, no untoward reaction were observed in mice of 50-300 mg/(kg x d) groups. Mice in 350 and 400 mg/(kg x d) groups showed body hair dishevelment, emaciation and food-intake decrease, death rates were 25% and 50%, respectively. All mice in 450 and 500 mg/(kg x d) groups died on day 4 and 5 after TBD administration, respectively. In control group, the highest total burden (per gram) was found in diaphragmatic muscle, followed by jugomaxillary muscle, gastrocnemius muscles and pectoral muscles. TBD at dose of 50 mg/(kg x d) was unable to kill encapsulated larvae. In the rest groups, with the increase of drug dose, the total worm burden and the number of survival worms showed a decreasing trend in four kinds of muscles, and were significantly lower than that of the control group (P < 0.05 or P < 0.01). In 300 mg/(kg x d) group the number of survival worms in diaphragmatic muscle, jugomaxillary muscle, pectoral muscle and gastrocnemius muscle [8.6 +/- 1.7, 2.8 +/- 0.7, 3.9 +/- 0.8, and 0, respectively] were significantly lower than that of the control group [3648.1 +/- 989.2, 1266.4 +/- 812.3, 701.9 +/- 196.4, and 711.6 +/- 34.6] (P < 0.01). All encapsulated larvae in the four kinds of muscle died in 350 and 400 mg/(kg x d) groups. With the increase of TBD dosage, the mortality of encapsulated larvae increased in the muscles, reached up to 98.6%--100% in 300 m (kg x d) group (P < 0.01), and 100% in 350 and 400 mg/(kg x d) groups (P < .01). CONCLUSION: Oral tribendimidine administered at 50 mg/(kg x d) to mice for 6 d is unable to reduce worm burden in muscle. Tribendimidine 300 mg/(kg x d) effectively kill encapsulated larvae and is a suitable dose against encapsulated larva stage. However, tribendimidine at doses of 350 mg/(kg x d) and above for 6d is toxic to mice and even causing death.

[Rapid measurement of trace mercury in aqueous solutions with optical-electrical dual pulse LIBS technique].

A wood slice was used as absorber to transfer liquid sample to solid sample in order to solve the problems existing in directly analyzing aqueous solutions with laser-induced breakdown spectroscopy (LIBS). An optical-electrical dual pulse LIBS (OEDP-LIBS) technique was first used to enhance atomic emission of mercury in laser-induced plasma. The calibration curves of mercury were obtained by typical single pulse LIBS and OEDP-LIBS techniques. The limit of detection (LOD) of mercury in these two techniques reaches 2.4 and 0.3 mg x L(-1), respectively. Under current experimental conditions, the time-integrated a tomic emission of mercury at 253.65 nm was enhanced 50 times and the LOD of mercury was improved by one order, if comparing OEDP-LIBS to single pulse LIBS. The required time for a whole analysis process is less than 5 minutes. As the atomic emission of mercury decays slowly while increasing the delay time between electrical pulse and laser pulse, increasing the electrical pulse width can further enhance the time integrated intensity of mercury emission and improve the detection sensitivity of mercury by OEDP-LIBS technique.