[Establishment of PCR assays and genetic polymorphism analysis of genes encoding Clostridium perfringens β2 toxin from different sources]

Objective: To establish and optimize PCR methods for the gene encoding of Clostridium perfringens β₂ toxin (cpb₂) and atypical-cpb₂ (aty-cpb₂), analyze the epidemiological characteristics and genetic polymorphism of the cpb₂ of Clostridium perfringens in 9 Chinese areas from 2016 to 2021. Methods: The cpb₂ of 188 Clostridium perfringens strains were examined by PCR; the cpb₂ sequences were acquired by whole-genome sequencing to analyze the genetic polymorphism. Using Mega 11 and the Makeblastdb tool, a phylogenetic tree, and cpb₂-library based on 110 strains carrying the cpb₂ were produced. Using the Blastn technique, a comparison was made to discover sequence similarity between consensus-cpb₂ (con-cpb₂) and aty-cpb₂. Results: The specificity of PCR assay for the cpb₂ and aty-cpb₂ was verified. The PCR results for cpb₂ amplification were highly consistent with the whole-genome sequencing approach (Kappa=0.946, P<0.001). A total of 107 strains from nine regions in China carried cpb₂, 94 types A strains carried aty-cpb₂, 6 types A strains carried con-cpb₂, and 7 types F strains carried aty-cpb₂. The nucleotide sequence similarity between the two coding genes was 68.97%-70.97%, and the similarity between the same coding genes was 98.00%-100.00%. Conclusions: In this study, a specific PCR method for cpb₂ toxin was developed, and the previous PCR method for detecting aty-cpb₂ was improved. aty-cpb₂ is the primary gene encoding of β₂ toxin. There is a significant nucleotide sequence variance between the various cpb₂ genotypes.

[Progress in research of Clostridium perfringens toxin]

Clostridium perfringens can produce many kinds of toxins and hydrolase, causing gas gangrene, enteritis and enterotoxemia in both human and animals. It is known that C. perfringens can produce more than 20 toxins and hydrolases. The different toxin types are associated with specific disease types. At present, molecular toxin-typing method by PCR has replaced the traditional serological typing method. In this study, we systematically summarize the types, basic characteristics, pathogenic mechanism and the relationship with disease of C. perfringens toxins to provide evidence for the establishment of rapid detection method, immune antigen screening, antibody preparation and research of related pathogenic mechanism.

Magnetic field effect on topological properties of Dirac semimetals PdTe2/PtTe2/PtSe2

We investigated magnetic field effect on the topological properties of transition metal dichalcogenide Dirac semimetals (DSMs) PdTe₂/PtTe₂/PtSe₂based on Wannier-function-based tight-binding (WFTB) model obtained from first-principles calculations. The DSMs PdTe₂/PtTe₂/PtSe₂undergo a transition from DSMs into Weyl semimetals with four pairs of Weyl points (WPs) in the entire Brillouin zone by splitting Dirac points under external magnetic fieldB. The positions and energies of WPs vary linearly with the strength of theBfield under thec-axis magnetic fieldB. Under thea- andb-axisBfield, however, the positions of magnetic-field-inducing WPs deviate slightly from thecaxis, and theirk_zcoordinates and energies change in a parabolic-like curve with the increasingBfield. However, the system opens an axial gap on theA-Γ axis, and the gap changes with the direction of theBfield when the out ofc-axisBfield is applied. When we further apply the magnetic field in theac,bc, andabplanes, the results are more diverse compared to the axial magnetic field. Under theacandbcplaneBfield, thek_zand energies of WPs within angleθ= [0°, 90°] andθ= [90°, 180°] are mirror symmetrically distributed. The distribution of WPs shows broken rotational symmetry under theabplaneBfield due to the difference of non-diagonal part of Hamiltonian. Our theoretical findings can provide a useful guideline for the applications of DSM materials under external magnetic field in the future topological electronic devices.

Hetero-assembly of a Li4Ti5O12 nanosheet and multi-walled carbon nanotube nanocomposite for high-performance lithium and sodium ion batteries

Hetero-assembly of Li₄Ti₅O₁₂ nanosheets and multi-walled carbon nanotubes for superior Li/Na storage is demonstrated.

Late gestational liver dysfunction and its impact on pregnancy outcomes

OBJECTIVE

The aim of this study was to investigate the impacts of late gestational liver dysfunction and its impact on pregnancy outcomes.

MATERIALS AND METHODS

The patients hospitalized for liver dysfunction in their late pregnancy between 2010-2012 were set as the observation group, and the pregnant women with normal liver function at the same period were randomly selected and set as the control group. The impacts towards the pregnancy outcomes were compared between these two groups and the impacts of different-degree transaminase increasing towards the pregnancy outcome were analyzed.

RESULTS

The incidence rates of cesarean section, post-partum hemorrhage, fetal distress, premature birth, premature rupture of membranes (PROM) of the observation group and the transaminase-severely-increased group (the severe group) were higher, and the differences were statistically significant (p < 0.01 or < 0.05); while only the cesarean rate of the mild and moderate group was significantly different from the control group (p < 0.01 or < 0.05). The ratios of intrahepatic cholestasis in pregnancy (ICP), gestational hypertension + HELLP syndrome, acute fatty liver in pregnancy (AFLP) of the severe group were higher than the mild and moderate group, and the differences were statistically significant; the non-alcoholic fatty liver disease (NAFLD) group and the unknown cause group mainly showed a mildly increased transaminase; the distributions of viral hepatitis in pregnancy (VHP), post-viral-hepatitis-B cirrhosis, biliary tract disease, and infected toxic liver dysfunction in different-degree increased transaminase groups had no significant difference.

CONCLUSIONS

Liver dysfunction in later pregnancy, especially with severe transaminase increase, might significantly increase the risk of adverse maternal events. The major causes of severe liver dysfunction in late pregnancy were ICP, gestational hypertensive disorders, and AFLP.

A new phase of phosphorus: the missed tricycle type red phosphorene

We predict a new two-dimensional allotrope of phosphorus, which we call red phosphorene, by restructuring the segments of the previously proposed blue and black phosphorenes. Its atomic and electronic structures as well as the thermodynamic and dynamic stabilities are systematically studied by first-principles calculations. The results indicate that the red phosphorene is dynamically stable and possesses remarkably thermodynamical stability comparable to that of the black one. Because of the sp(3)-hybridization and the formation of a localized lone pair, red phosphorene is a semiconductor with an indirect band gap of about 1.96 eV, which can be effectively modulated by in-plane strains due to its wave-like configuration. We find that the red, black and blue phosphorenes show evident distinction in their layer thicknesses, surface work functions, and possible colors, based on which one can distinguish them in future experiments.

Regulation of apoptosis in human gastric cancer cell line SGC-7901 by L-arginine

AIM

L-arginine (L-Arg) is an aminoacid that has immunomodulating and antitumor effects. It is possible that antitumor effects of L-Arg are due to induction of apoptosis in tumor cells. The present study assessed antiproliferating and proapoptotic effects of L-Arg in human gastric cancer cell line SGC-7901.

METHODS

Cell proliferation was quantified by MTT assay. Apoptosis was assessed using flow cytometry and FITC-Annexin-V/propidium iodide staining. Expression and activation of proteins pertinent to apoptosis (Bcl-2, surviving, p53, and XIAP) were studied using PCR, Western blot, and activity assays.

RESULTS

L-Arg significantly inhibited growth of SCG-7901 gastric cancer cells and downregulated expression of antiapoptotic gene Bcl-2 and survivin. By contrast, expression of p53 was upregulated by L-Arg.

CONCLUSION

Regulation of apoptosis by L-Arg via downregulation of antiapoptotic proteins Bcl-2 and surviving, and upregulation of proapoptotic protein p53 may represent the mechanism behind antitumor effects of L-Arg.

Regulation of apoptosis in human gastric cancer cell line SGC-7901 by L-arginine

Aim: L-arginine (LArg) is an amino acid that has immunomodulating and anti-tumor effects. It is possible that anti-tumor effects of L-Arg are due to induction of apoptosis in tumor cells. The present study assessed anti-proliferating and pro-apoptotic effects of L-Arg in human gastric cancer cell line SGC7901. Methods: Cell proliferation was quantified by MTT assay. Apoptosis was assessed using flow cytometry and FITCAnnexinV/ propidium iodide staining. Expression and activation of proteins pertinent to apoptosis (Bcl2, surviving, p53, and XIAP) were studied using PCR, Western blot, and activity assays. Results: L-Arg significantly inhibited growth of SCG-7901 gastric cancer cells and down-regulated expression of anti-apoptotic gene Bcl-2 and survivin. By contrast, expression of p53 was upregulated by L-Arg. Conclusion: Regulation of apoptosis by L-Arg via down-regulation of anti-apoptotic proteins Bcl-2 and surviving, and up-regulation of pro-apoptotic protein p53 may represent the mechanism behind antitumor effects of L-Arg.

L-arginine enhances arginine deiminase induced human lymphoma cell growth inhibition through NF-kBp65 and p53 expression in vitro

OBJECTIVE

Arginine deiminase (ADI) and L-arginine (L-Arg) can act as anti-tumor agents in-vitro and in-vivo. However, the mechanism of ADI and L-Arg as anti-tumor agents has not been clearly shown.

MATERIALS AND METHODS

With the goal of understanding the role of ADI and L-Arg in inhibition of cell growth, we used the Ramos human lymphoma cell line, which is known to be ADI-sensitive, and observed the p53 and NF-κBp65 protein expression after ADI and arginine treatment. After determining an optimal experimental ADI concentration (0.01 U/ml), we studied the effects of ADI treatment, when combined with different concentrations of L-arginine (control, ADI only, ADI with 10 mM/ml Arg, ADI with 30 mM/ml Arg, and ADI with 50 mM/ml Arg). An MTT assay was used to assess cell survival after treatment, Western blot analysis to determine the levels of the NF-κBp65, p53 and NO mediators and nitric oxide assays were used to determine nitrite levels.

RESULTS AND CONCLUSIONS

L-arginine enhanced ADI-induced inhibited cell growth through expression of NF-κBp65 and p53 in a dose-dependent manner.

Fabrication of ordered NiO coated Si nanowire array films as electrodes for a high performance lithium ion battery

Highly ordered NiO coated Si nanowire array films are fabricated as electrodes for a high performance lithium ion battery via depositing Ni on electroless-etched Si nanowires and subsequently annealing. The structures and morphologies of as-prepared films are characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. When the potential window versus lithium was controlled, the coated NiO can be selected to be electrochemically active to store and release Li+ ions, while highly conductive crystalline Si cores function as nothing more than a stable mechanical support and an efficient electrical conducting pathway. The hybrid nanowire array films exhibit superior cyclic stability and reversible capacity compared to that of NiO nanostructured films. Owing to the ease of large-scale fabrication and superior electrochemical performance, these hybrid nanowire array films will be promising anode materials for high performance lithium-ion batteries.

Magnetic and upconverted luminescent properties of multifunctional lanthanide doped cubic KGdF4 nanocrystals

Lanthanide (Ln3+) doped KGdF4 (Ln=Yb3+, Er3+, Ho3+, Tm3+) nanocrystals with a mean diameter of approximately 12 nm were synthesized by a hydrothermal method using oleic acid as a stabilizing agent at 180 °C. The nanocrystals crystallize in the cubic phase as α-NaGdF4. When excited by a 980 nm laser, these Ln3+ doped nanocrystals exhibit multicolor up-conversion (UC) emissions in red, yellow, blue and white. The calculated color coordinates demonstrate that white UC emission (CIE-X=0.352, CIE-Y=0.347) can be obtained by varying the dopant concentrations in the Yb3+/Ho3+/Tm3+ triply-doped nanocrystals to yield different RGB emission intensities. The measured field dependence of magnetization (M-H curves) of the KGdF4 nanocrystals shows their paramagnetic characteristics that can be ascribed to the non-interacting localized nature of the magnetic moment of Gd3+ ions. Moreover, low temperature thermal treatment can enhance UC properties, magnetization and magnetic mass susceptibility of Ln3+ doped KGdF4 nanocrystals. The multifunctional Ln3+ doped KGdF4 nanocrystals have potential applications in color displays, bioseparation, and optical-magnetic dual modal nanoprobes in biomedical imaging.

Sharp corners in the cross section of ultrathin Si nanowires

We have determined stable geometries for pristine Si nanowires grown along their 100 axis through systematic density functional studies. Strikingly, Si nanowires with diameters smaller than 1.7 nm prefer a shape that has a square cross section. This stems from dimerization between corner atoms and also from benign reconstruction patterns that maximally saturate Si dangling bonds.

[Synthesis and antimalarial activities of fluorenemethanols]

For the purpose of improving the oral antimalarial activities of the fluorenemethanols (reported by us in previous articles) which were less effective by oral than by subcutaneous administration, 24 alpha-(alkylaminomethyl)-2, 7-dichloro-9-substituted benzylidene-4-fluorenemethanols (III) were synthesized. The results of preliminary screenings demonstrated that five compounds (No. 1-4, 8) exhibited significant antimalarial activities against Plasmodium berghei NK65 strain in mice by oral administration, at dose of 6.25 mg.kg-1.d-1 x 3 with suppressive rate of 100%. Further evaluation of these 5 compounds showed that 4 of them (No. 1-4) were superior to chloroquine in parallel tests, their ED50 and ED90 were 1.0, 1.6; 0.6, 0.9; 0.7, 1.5 and 0.8, 1.6 mg.kg-1.d-1 x 3 respectively, while the ED50 and ED90 of chloroquine were 1.9 and 2.9 mg.kg-1. d-1 x 3 respectively; one compound (No 8) was equal to chloroquine, its ED50 and ED90 were 1.5 and 3.2 mg.kg-1.d-1 x 3 respectively. Further assessment of these 4 compounds are in progress.

[Crystal and molecular structure of the antimalarial agent alpha-(dibutylaminomethyl)-2, 7-dichloro-9-(p-chlorobenzylidene)-4- fluorenemethanol(benflumetol)]

The three-dimensional crystal and molecular structure of benflumetol(I), alpha-(dibutylaminomethyl)-2, 7-dichloro-9-(p-chlorobenzylidene)-4-fluorenemethanol, was determined by X-ray crystallography and compared with the crystal structures of the cinchona alkaloids. The aromatic rings of fluorene-phenyl system of benflumetol are twisted from each other by 52.8 degrees. The torsion angle of N-C-C-O of benflumetol is 47.6 degrees. The intramolecular aliphatic N-O distance in benflumetol is 2.709A, which is close to the N-O distance found in antimalarial cinchona alkaloids. Benflumetol contains an intramolecular hydrogen bond between the aliphatic nitrogen and oxygen atoms, no intermolecular hydrogen bond was found, which is different from the known amino alcohol antimalarials.