Design of signal peptide bombyxin and its effect on secretory expression efficiency and levels of Helicobacter pylori urease subunit B in silkworm cells and larvae

This study employed a Bac-to-Bac/Bombyx mori bioreactor to mass-produce immunogenic urease subunit B (UreB) from Helicobacter pylori. The signal peptide bombyxin from B. mori was used to promote secretory expression to improve expression levels and was designed and integrated into the UreB gene to generate the Bacmid/BmNPV/(signal peptide)-UreB baculovirus expression system. To determine whether the bombyxin signal peptide resulted in secretory expression of recombinant UreB (rUreB) and to determine the secretory efficiency, we tested the secretory expression level of rUreB in Bm5 cells using ELISA. To further investigate whether secretory expression affected cell viability, cells were evaluated using 0.4% trypan blue staining, and Bacmid/BmNPV/UreB without the signal peptide served as a control. The above recombinant bacmid constructs were injected to silkworm larvae, and the secretory expression level of rUreB was detected using SDS-PAGE and semi-quantitative western blot analysis. The results indicated that the bombyxin signal peptide directed the secretory expression of rUreB and that this expression improved the viability of Bm5 cells. Moreover, the results showed that the expression level of rUreB was 1.5 times higher with the Bacmid/BmNPV constructs containing the bombyxin signal sequence than those without the signal sequence. These results demonstrate that secretory expression can enhance rUreB expression levels and is likely to aid in the large-scale expression and yield of rUreB in silkworm larvae.

The synthetic antimicrobial peptide pexiganan and its nanoparticles (PNPs) exhibit the anti-helicobacter pylori activity in vitro and in vivo.

The aim of this study was to probe the potential anti-H. pylori activity of the synthetic antimicrobial peptide pexiganan, which is an analog of the peptide magainin, and its nanoparticles (PNPs) that were prepared in our laboratory. To compare their antibacterial effects in vitro and in vivo, studies of H. pylori growth inhibition, kinetics and resistance assays were undertaken. The gastric mucoadhesive efficiency and H. pylori clearance efficiency of pexiganan and PNPs were evaluated in rats and mice infected with H. pylori. The eradication of H. pylori was determined using urease tests and a microbial culture method. We observed that PNPs adhered to gastric mucosa more effectively owing to a prolonged stay in the stomach, which resulted in a more effective H. pylori clearance. In addition, PNPs had greater anti-H. pylori effect than pexiganan in infected mice. The amount of pexiganan required to eradicate H. pylori was significantly less using PNPs than the corresponding pexiganan suspension. The results confirmed that PNPs improved peptide stability in the stomach and more effectively eradicated H. pylori from mice stomachs than pexiganan.

[Study on the extraction of mycelium polysaccharides from selenium-rich Morchella esculenta with neutral proteinase method].

OBJECTIVE: To study the extraction conditions of mycelium polysaccharides from selenium-rich Morchella esculenta with neutral proteinase for increasing of yield. METHODS: On the basis of single factor tests, orthogonal experiment design was applied to analyze the influence of factors including enzyme dosage, enzymolysis time, enzymolysis temperature and material/liquid ratio on the extraction rate of the polysaccharides. RESULTS: The optimal extraction conditions of mycelium polysaccharides from selenium-rich Morchella esculenta was as follows: enzyme dosage was 1.5%, enzymolysis time was 2 h, enzymolysis temperature was 40 degrees C, and material/liquid ratio was 1:15. The extraction rate of polysaccharide was 11.26% under the extraction conditions. CONCLUSION: The process is simple, stable and practicable, and can be used for the extraction of mycelium polysaccharides from selenium-rich Morchella esculenta.

[Comparison of genetic linkage maps based on F2F6 populations derived from rice subspecies cross].

A F2 population containing 180 lines, which was derived from the cross between the partially sequenced indica variety "Pei'ai 64S" and the completely sequenced japonica variety "Nipponbare" , was used to construct a genetic linkage framework map (referred to as F2 map), which included 138 microsatellite sites and covered 1737.81 cM of total genomic length, an average distance of 11.90 cM. Single seed descent F2:6 population with 330 lines was used to construct a genetic linkage map (known as F6 map) using 92 markers. The total genomic length and average distance were 2563.5 cM and 27.86 cM, respectively. The F2 and F6 maps differed in linkage groups, mapped markers, sequenced order of markers, ge-netic distance and average distance on the maps. Preliminary analysis about these difference was carried out.