Screening for a Potent Antibacterial Peptide to Treat Mupirocin-Resistant MRSA Skin Infections

Mupirocin is the first-line topical antibacterial drug for treating skin infections caused primarily by meticillin-resistant Staphylococcus aureus (MRSA). Its widespread use since its introduction more than 30 years ago has resulted in the global emergence of mupirocin-resistant strains of MRSA. Antimicrobial peptides (AMPs) are a promising class of antibacterial compounds that can potentially be developed to replace mupirocin due to their rapid membrane-targeting bactericidal mode of action and predicted low propensity for resistance development. Herein, we conducted and compared the antibacterial activities of 61 AMPs between 3 and 11 residues in length reported in the literature over the past decade against mupirocin-resistant MRSA. The most potent AMP, 11-residue peptide 50, was selected and tested against a panel of clinical isolates followed by a time-kill and a human dermal keratinocyte cytotoxicity assay. Lastly, peptide 50 was formulated into a topical spray which showed strong in vitro bactericidal effects against mupirocin-resistant MRSA. Our results strongly suggest that peptide 50 has the potential to be further developed into a new class of topical antibacterial agent for treating drug-resistant MRSA skin infections.     

Use of enzyme penicillin acylase in selective amidation/amide hydrolysis to resolve ethyl 3-amino-4-pentynoate isomers

The beta-amino acid, (S)-ethyl-3-amino-4-pentynoate, is a chiral synthon used in the synthesis of xemilofiban hydrochloride, an anti-platelet agent. A biocatalytic approach was developed to resolve (R)- and (S)-enantiomers of ethyl 3-amino-4-pentynoate in enantiomerically pure form employing the enzyme Penicillin acylase. In the acylation, phenylacetic acid was used as an acylating agent. We have shown that both the acylation and deacylation can be employed and that the activity of the enzyme Penicillin acylase can be controlled by maintaining an appropriate pH of the reaction medium.     

A proteomic approach in investigating the hepatoprotective mechanism of Schisandrin B: role of raf kinase inhibitor protein

To identify key proteins involved in the hepatoprotection afforded by schisandrin B (Sch B), we used a proteomic approach to screen proteins that were specifically regulated by Sch B in mouse livers and to investigate the role of the proteins in hepatoprotection. Thirteen proteins were specifically activated or suppressed by Sch B treatment. Among the 13 proteins, Raf kinase inhibitor protein (RKIP) was postulated to be the key regulator involved in the development of hepatotoxin-induced cellular damage. The results indicated that the downregulation of RKIP by antisense RKIP vector transfection led to the activation of the Raf-1/MEK/ERK signaling pathway, as evidenced by increases in the level of MEK/ERK phosphorylation and the level of nuclear factor erythroid 2-related factor 2 in the nucleus. The signaling effect produced by RKIP downregulation resembled that triggered by Sch B, wherein both treatments resulted in a decrease in the extent of carbon tetrachloride-induced apoptotic cell death in AML12 hepatocytes. Overexpression of RKIP by the sense RKIP transfection vector or the inhibition of MEK kinase by PD98059 was able to abrogate the cytoprotective effect of Sch B in the hepatocytes. The results indicate that Sch B triggers the Raf/MEK/ERK signaling pathway, presumably by downregulating RKIP, thereby protecting against carbon tetrachloride-induced cytotoxicity.     

First report of a novel plant lysozyme with both antifungal and antibacterial activities

A novel lysozyme exhibiting antifungal activity and with a molecular mass of 14.4kDa in SDS-polyacrylamide gel electrophoresis was isolated from mung bean (Phaseolus mungo) seeds using a procedure that involved aqueous extraction, ammonium sulfate precipitation, ion exchange chromatography on CM-Sephadex, and high-performance liquid chromatography on POROS HS-20. Its N-terminal sequence was very different from that of hen egg white lysozyme. Its pI was estimated to be above 9.7. The specific activity of the lysozyme was 355U/mg at pH 5.5 and 30 degrees C. The lysozyme exhibited a pH optimum at pH 5.5 and a temperature optimum at 55 degrees C. It is reported herein, for the first time, that a novel plant lysozyme exerted an antifungal action toward Fusarium oxysporum, Fusarium solani, Pythium aphanidermatum, Sclerotium rolfsii, and Botrytis cinerea, in addition to an antibacterial action against Staphylococcus aureus.     

Protein kinase C delta null mice exhibit structural alterations in articular surface,intra-articular and subchondral compartments

IntroductionStructural alterations in intra-articular and subchondral compartments are hallmarks of osteoarthritis, a degenerative disease that causes pain and disability in the aging population. Protein kinase C delta (PKC-δ) plays versatile functions in cell growth and differentiation, but its role in the articular cartilage and subchondral bone is not known.MethodsHistological analysis including alcian blue, safranin O staining and fluorochrome labeling were used to reveal structural alterations at the articular cartilage surface and bone–cartilage interface in PKC-δ knockout (KO) mice. The morphology and organization of chondrocytes were studied using confocal microscopy. Glycosaminoglycan content was studied by micromass culture of chondrocytes of PKC-δ KO mice.ResultsWe uncovered atypical structural demarcation between articular cartilage and subchondral bone of PKC-δ KO mice. Histology analyses revealed a thickening of the articular cartilage and calcified bone–cartilage interface, and decreased safranin O staining accompanied by an increase in the number of hypertrophic chondrocytes in the articular cartilage of PKC-δ KO mice. Interestingly, loss of demarcation between articular cartilage and bone was concomitant with irregular chondrocyte morphology and arrangement. Consistently, in vivo calcein labeling assay showed an increased intensity of calcein labeling in the interface of the growth plate and metaphysis in PKC-δ KO mice. Furthermore, in vitro culture of chondrocyte micromass showed a decreased alcian blue staining of chondrocyte micromass in the PKC-δ KO mice, indicative of a reduced level of glycosaminoglycan production.ConclusionsOur data imply a role for PKC-δ in the osteochondral plasticity of the interface between articular cartilage and the osteochondral junction.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-015-0720-4) contains supplementary material, which is available to authorized users.     

不受欢迎的生物多样性：香港的外来植物物种

香港早在19世纪中叶开始就有外来植物入侵的记录,迄今为止,已发现多达238种已归化的外来或怀疑为外来的植物,其中又以薇甘菊（Mikania micrantha)、五爪金龙（Ipomoea cairica)、假臭草（Eupatorium catarium)、大黍（Panicum maximum)等最常见,外来植物最常见于受人为干扰的生境,例如荒废农田及路旁等,而较少在天然林地生境及贫瘠的灌草丛中发现,外来植物的对本地生态系统的影响主要局限于低地生境,它们常形成单优种群,减少了生境及贫瘠的灌草丛中发现,外来植物对本地生态系统的影响主要局限于低地生境,它们常形成单优种群,减少少了生境及动植物的多样性,外来动物对香港原生植物影响最大的是于20世纪70年代入侵的松树线虫（Bur-saphelenchus xylophilus)。外来的脊椎动物也有可能对香港的植物被演替产生影响,目前香港的外来植物当中,有些在大陆较少分布或没有记录,作为华南最大的港口,香港对外来物种的引入扮演着重要的角色,因此制定控制外来种在香港及华南地区的引入及传播的政策及措施非常重要。     

Linkage studies with chromosome 17 DNA markers in 45 neurofibromatosis 1 families

A locus for von Recklinghausen neurofibromatosis (NF1) has recently been mapped near the chromosome 17 centromere. We have extended these linkage studies by genotyping 45 NF1 families with three DNA probes known to be linked to the chromosome 17 centromeric region. Of 34 families informative for NF1 and at least one of the three probes, 28 families show no recombinants with the disease gene. These data provide additional support for genetic homogeneity of NF1 and for a primary NF1 locus linked to the chromosome 17 centromere. Among the informative families were 7 families with apparent new NF1 mutations. Our data suggest that these mutations are probably at the chromosome 17 NF1 locus.