Copper ions inhibit Streptococcus mutans-Veillonella parvula dual biofilm by activating Streptococcus mutans reactive nitrogen species.

BACKGROUND: To investigate the inhibition mechanism of copper ions on Streptococcus mutans-Veillonella parvula dual biofilm. METHODS: S. mutans-V. parvula dual biofilm was constructed and copper ions were added at different concentrations. After the biofilm was collected, RNA-seq and qRT-PCR were then performed to get gene information. RESULTS: The coculture of S. mutans and V. parvula formed a significantly better dual biofilm of larger biomass than S. mutans mono biofilm. And copper ions showed a more significant inhibitory effect on S. mutans-V. parvula dual biofilm than on S. mutans mono biofilm when copper ions concentration reached 100 µM, and copper ions showed a decreased inhibitory effect on S. gordonii-V. parvula dual biofilm and S. sanguis-V.parvula dual biofilm than on the two mono biofilms as the concentration of copper ions increased. And common trace elements such as iron, magnesium, and zinc showed no inhibitory effect difference on S. mutans-V. parvula dual biofilm. The RNA-seq results showed a significant difference in the expression of a new ABC transporter SMU_651c, SMU_652c, SMU_653c, and S. mutans copper chaperone copYAZ. SMU_651c, SMU_652c, and SMU_653c were predicted to function as nitrite/nitrate transporter-related proteins, which suggested the specific inhibition of copper ions on S. mutans-V. parvula dual biofilm may be caused by the activation of S. mutans reactive nitrogen species. CONCLUSIONS: Streptococcus mutans and Veillonella parvula are symbiotic, forming a dual biofilm of larger biomass to better resist the external antibacterial substances, which may increase the virulence of S. mutans. While common trace elements such as iron, magnesium, and zinc showed no specific inhibitory effect on S. mutans-V. parvula dual biofilm, copper ion had a unique inhibitory effect on S. mutans-V. parvula dual biofilm which may be caused by activating S. mutans RNS when copper ions concentration reached 250 µM.

Validation of pentaacetylaldononitrile derivative for dual 2H gas chromatography/mass spectrometry and 13C gas chromatography/combustion/isotope ratio mass spectrometry analysis of glucose.

A reference method to accurately define kinetics in response to the ingestion of glucose in terms of total, exogenous and endogenous glucose is to use stable-isotope-labelled compounds such as 2H and 13C glucose followed by gas chromatography/mass spectrometry (GC/MS) and gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) analysis. The use of the usual pentaacetyl (5Ac) derivative generates difficulties in obtaining accurate and reproducible results due to the two chromatographic peaks for the syn and anti isomers, and to the isotopic effect occurring during acetylation. Therefore, the pentaacetylaldononitrile derivative (Aldo) was validated for both isotopes, and compared with the 5Ac derivative. A correction factor including carbon atom dilution (stoichiometric equation) and the kinetic isotopic effect (KIE) was determined. Analytical validation results for the 2H GC/MS and 13C GC/C/IRMS measurements produced acceptable results with both derivatives. When 2H enrichments of plasma samples were < or = 1 mol % excess (MPE), the repeatability (RSD(Aldo Intra assay and Intra day) <0.94%, RSD(5Ac Intra assay and Intra day) <3.29%), accuracy (Aldo <3.4%, 5Ac <29.0%), and stability of the derivatized samples were significantly better when the Aldo derivatives of the plasma samples were used (p < 0.05). When the glucose kinetics were assessed in nine human subjects, after glucose ingestion, the plasma glucose 2H enrichments were identical with both derivatives, whereas the 13C enrichments needed a correction factor to fit together. Due to KIE variation, this correction factor was not constant and had to be calculated for each batch of analyses, to obtain satisfactory results. Mean quantities of exogenous glucose exhibit marked difference (20.9 +/- 1.3g (5Ac) vs. 26.7 +/- 2.5g (Aldo)) when calculated with stoichiometric correction, but fit perfectly when calculated after application of the correction factor (22.1 +/- 1.3g (5Ac) vs. 22.9 +/- 1.9g (Aldo)). Finally, the pentaacetylaldononitrile derivative, used here in GC/C/IRMS for the first time, enables measurement of 2H and 13C enrichments in plasma glucose with a single sample preparation.

[Study of human leucine-rich amelogenin peptide and its regulation of mineralization by cryogenic transmission electron microscopy].

OBJECTIVE: Recombinant human leucine-rich amelogenin peptide (LRAP) was studied by cryogenic transmission electron microscopy (TEM); evaluation focused on its self-assembly and crystal growth in vitro. METHODS: Human LRAP was recombined through prokaryotic expression vector pCold-SUMO and transformed into Escherichia coli BL21plys to acquire purified proteins. Cryogen TEM recorded assembly and self-assembling of LRAP from pH 3.5 to pH 8.0, and the hydroxyapatite crystal growth in the mixture of LRAP protein solution and artificial saliva was observed using TEM and selected area electron diffraction. RESULTS: More than 90% purity LRAP was expressed, purified and identified as described in methods. LRAP linked into oligomers, nanospheres, nanochains, and microribbons, whereas pH value increased from 3.5 to 8.0. Mature hydroxyapatite crystal growth was guided in artificial saliva filled with calcium phosphate. CONCLUSIONS: LRAP is simplified amelogenin functional domain and conserved the basic characters of amelogenin such as self-assembling and inducing crystallization along c axis. In the area of acellular synthesis of hydroxyapatite using extracellular enamel matrix protein, LRAP is one of candidate repair materials for irregular hard tissue defection.
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[Effects of cotton straw returning on soil organic carbon, nitrogen, phosphorus and potas-sium contents in soil aggregates]. / 棉花秸秆还田对土壤团聚体有机碳及氮磷钾含量的影响.

To clarify the effects of cotton straw returning on the composition and contents of nu-trients in different particle sizes of aggregates, two treatments with or without cotton straw returning were tested in continuous three years. After three years straw treatments, we collected undisturbed soil within 0-5, 5-10, 10-20 and 20-30 cm soil layers, and to measure the composition, soil organic carbon, nitrogen, phosphorus and potassium contents in different particle sizes of aggregates classified using dry sieving. Returning cotton straw into the field significantly increased particle contents of 2-5 mm and >5 mm aggregates in 0-5 cm soil layer, while the content of <0.25 mm micro-aggregates was decreased. Cotton straw returning significantly improved soil organic carbon, nitrogen, and potassium contents by 19.2%, 14.2% and 17.3%, respectively, compared to no returning control. In 5-10 cm soil layer, cotton straw returning increased the contents of 2-5 mm and >5 mm aggregates, reduced the content of <0.25 mm micro-aggregate, but significantly increased contents of soil organic carbon, available nitrogen and potassium by 19.6%, 12.6% and 23.4%, compared to no straw returning control. In 10-20 cm soil layer, cotton straw returning significantly reduced the content of <0.25 mm micro-aggregates, and significantly enhanced soil organic carbon, nitrogen, and potassium contents by 8.4%, 10.9% and 11.5%, compared to the control. However, in 20-30 cm soil layer, cotton straw returning only increased soil available potassium content by 12.0%, while there were no significant changes in particle size, organic carbon, nitrogen and phosphorus contents. We concluded that cotton straw returning could significantly improve the structure of surface soil by increasing the number of macro-aggregates, contents of organic carbon, available nitrogen and potassium in aggregates, while decreasing micro-aggregate content. The enhancement of the contribution of macro-aggregates to soil fertility by returning cotton straw could improve soil physical structure, fertility and then increase cotton yield.

[Review of global activities and events for DNA 50 years].

In 25, April, 1953, the paper discovering DNA double helix by Watson and Crick published in Nature, it is a great event for finding life secret in mankind history. This year is 50th anniversary of the event. Scientists in the world including in China have a lot of memorial activities to review research results obtained in past 50 years and to prospect developments in next 50 years. The paper reviews DNA 50 memorial activities and events in the world and predicts possible relation between DNA and Digital Human Project.

[Chitosan-collagen polymer induced remineralization of tooth hard tissue through self-growing methods].

OBJECTIVE: To modify biomacromolecules, such as chitosan and collagen, to synthesize a mineralized template that will induce self-growing remineralization of tooth enamel. METHODS: Natural polycation polysaccharide chitosan was modified through phosphorylation to synthesize the polyanion derivative ofphosphorylated chitosan. Parent hydrogels com- bined with chitosan and collagen I were built through peptide binding reaction using genipin as a crosslinker. The gels self- assembled on the tooth's inert surface, which was stimulated by ultraviolet radiation. The bionic saliva provided mineralized ion, and then the hydroxyapatite assembled and grew in situ on the tooth. RESULTS: The functional group P04(3-) (3,446 cm(-1)) was grafted on chitosan as confirmed by the Fourier transform infrared spectroscopy. The porous polyelectrolyte complex hydrogel formed by the interaction between the polycation chitosan and the polyanion phosphorylated chitosan could induce hydroxyapatite crystal nucleation and growth on the hydrogel fiber surfaces. The neonatal crystal was hydroxyapatite as confirmed by X-ray diffraction and was tightly connected to the tooth. A continuous structure of column crystals with sizes ranging from 30 nm to 60 nm was observed. The structure was in parallel direction similar to the direction of the enamel rod, and its hardness was close to dentin. CONCLUSION: The parent hydrogels that were easily obtained and controlled could mimic the template of the enamel mineralization and induce a self-growing hydroxyapatite, which is an important step in the structural bionics of enamel.

[Inhibitory effect of total flavonoids of Malus hupehensis on hepatic fibrosis induced by Schistosoma japonicum in mice].

OBJECTIVE: To investigate the effects of total flavonoids of Malus hupehensis on hepatic fibrosis in mice induced by Schistosoma japonicum. METHODS: The mice model of hepatic fibrosis which infected by cercariae of S. japonicum were randomly divided into 6 groups: Group A as a blank control, Group B as a model, Group C as a positive control by complex liver soften tablet of turtle, Group D, E, F treated with a high dose of 114 mg/(kg x d), middle dose of 57 mg/(kg d), and low dose of 28.5 mg/(kg x d) of total flavonoids of Malus hupehensis, respectively. Every group had 10 mice. Each group of C, D, E, F was orally given praziquantel at a dose of 500 mg/(kg x d) for 2 d, on 42 d after the infection, and then administered with total flavonoids of Malus hupehensis for 60 d. Group A and B were orally given with sodium chloride. All the mice were killed at the end of the administration. Serum hyaluronic acid (HA), alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were detected; hydroxyproline in liver tissues was detected; areas of egg granuloma and degrees of hepatic fibrosis were observed via HE and Masson staining. RESULTS: Compared with the blank control Group A, the egg granuloma appeared obviously, the collagen deposit and fibrosis occurred in liver tissues of Group B, C, D, E, F. The levels of ALT, AST, HA in sera and HYP in liver tissues were significantly higher (P < 0.05 or P < 0.01). However, the levels of ALT, AST, HA and HYP in the high, middle and low dose groups of total flavonoids were significantly lower than those in the model Group B (P < 0.05 or P < 0.01), the areas of egg granuloma, the collagen deposits and the degrees of hepatic fibrosis in Group C, D, E, F were significantly lower than those in the model Group B. CONCLUSION: The total flavonoids of Malus hupehensis have an obviously inhibitory effect on the hepatic fibrosis induced by Schistosomajaponicum infection.