PspB and PspC of Yersinia enterocolitica are dual function proteins: regulators and effectors of the phage-shock-protein response

The phage-shock-protein (Psp) stress-response system is conserved in many bacteria and has been linked to important phenotypes in Escherichia coli, Salmonella enterica and also Yersinia enterocolitica, where it is essential for virulence. It is activated by specific extracytoplasmic stress events such as the mislocalization of secretin proteins. From studies of the Psp system in E. coli, the cytoplasmic membrane proteins PspB and PspC have only been proposed to act as positive regulators of psp gene expression. However, in this study we show that PspB and PspC of Y. enterocolitica are dual function proteins, acting both as regulators and effectors of the Psp system. Consistent with the current model, they positively control psp gene expression in response to diverse inducing cues. PspB and PspC must work together to achieve this regulatory function, and bacterial two-hybrid (BACTH) analysis demonstrated a specific interaction between them, which was confirmed by in vivo cross-linking. We also show that PspB and PspC play a second role in supporting growth when a secretin protein is overexpressed. This function is independent from their role as regulators of psp gene expression. Furthermore, whereas PspB and PspC must work together for their regulatory function, they can apparently act independently to support growth during secretin production. This study expands the current understanding of the roles played by PspB and PspC, and demonstrates that they cannot be considered only as positive regulators of psp gene expression in Y. enterocolitica.     

Chemopreventive and renal protective effects for docosahexaenoic acid (DHA): implications of CRP and lipid peroxides

Background

The fish oil-derived ω-3 fatty acids, like docosahexanoic (DHA), claim a plethora of health benefits. We currently evaluated the antitumor effects of DHA, alone or in combination with cisplatin (CP) in the EAC solid tumor mice model, and monitored concomitant changes in serum levels of C-reactive protein (CRP), lipid peroxidation (measured as malondialdehyde; MDA) and leukocytic count (LC). Further, we verified the capacity of DHA to ameliorate the lethal, CP-induced nephrotoxicity in rats and the molecular mechanisms involved therein.

Results

EAC-bearing mice exhibited markedly elevated LC (2-fold), CRP (11-fold) and MDA levels (2.7-fold). DHA (125, 250 mg/kg) elicited significant, dose-dependent reductions in tumor size (38%, 79%; respectively), as well as in LC, CRP and MDA levels. These effects for CP were appreciably lower than those of DHA (250 mg/kg). Interestingly, DHA (125 mg/kg) markedly enhanced the chemopreventive effects of CP and boosted its ability to reduce serum CRP and MDA levels. Correlation studies revealed a high degree of positive association between tumor growth and each of CRP (r = 0.85) and leukocytosis (r = 0.89), thus attesting to a diagnostic/prognostic role for CRP. On the other hand, a single CP dose (10 mg/kg) induced nephrotoxicity in rats that was evidenced by proteinuria, deterioration of glomerular filtration rate (GFR, -4-fold), a rise in serum creatinine/urea levels (2–5-fold) after 4 days, and globally-induced animal fatalities after 7 days. Kidney-homogenates from CP-treated rats displayed significantly elevated MDA- and TNF-α-, but reduced GSH-, levels. Rats treated with DHA (250 mg/kg, but not 125 mg/kg) survived the lethal effects of CP, and showed a significant recovery of GFR; while their homogenates had markedly-reduced MDA- and TNF-α-, but -increased GSH-levels. Significant association was detected between creatinine level and those of MDA (r = 0.81), TNF-α ) r = 0.92) and GSH (r = -0.82); implying causal relationships.

Conclusion

DHA elicited prominent chemopreventive effects on its own, and appreciably augmented those of CP as well. The extent of tumor progression in various mouse groups was highly reflected by CRP levels (thus implying a diagnostic/prognostic role for CRP). Further, this study is the first to reveal that DHA can obliterate the lethal CP-induced nephrotoxicity and renal tissue injury. At the molecular level, DHA appears to act by reducing leukocytosis, systemic inflammation, and oxidative stress.     

感染球孢白僵菌后红火蚁体内蛋白质含量的变化

为了解球孢白僵菌Beauveria bassiana成功感染红火蚁Solenopsis invicta的生理生化机制, 本研究在室内条件下测定了经球孢白僵菌感染后红火蚁工蚁、蛹和幼蚁体内蛋白质含量的变化。结果表明: 红火蚁各虫态感染球孢白僵菌后体内蛋白质含量变化存在差异。在接种后12-72 h, 工蚁体内蛋白质含量在24 h时最高, 为47.12 mg/g, 显著低于对照的56.40 mg/g(P＜0.05), 此后呈下降趋势, 72 h时蛋白质含量下降至25.16 mg/g。幼蚁在接种36 h时体内蛋白质含量最高, 为24.13 mg/g, 此后呈下降趋势, 72 h时蛋白质含量为8.95 mg/g, 显著低于对照的24.80 mg/g。蛹感染球孢白僵菌后体内蛋白质含量一直呈下降趋势, 从12 h的36.57 mg/g降到72 h的10.42 mg/g, 与对照的38.61 mg/g相比差异显著(P＜0.05)。结果显示球孢白僵菌感染能显著降低红火蚁各虫态体内蛋白质含量。     

Cicada ear geometry: species and sex effects

Many insect species rely on their sense of audition to find a mate, to localize prey or to escape from a predator. Cicadas are particularly known for their loud call and the conspicuous tympanal hearing system located in their abdomen. The vibration pattern of the tympanal membrane (TM) has been investigated recently revealing mechanical properties specific to species and sex. Although TM size and shape is likely to affect these patterns, the geometry of the cicada ear has never been examined per se. Focusing on three Mediterranean cicada species, namely Cicadatra atra, Cicada orni and Lyristes plebejus, we investigated the structure of TM shape variation at two levels, within and across species. Applying an elliptic Fourier analysis to the outlines of both male and female TMs, we estimated sexual dimorphism and species effects. Cicadatra atra showed a large TM compared with its small size, probably as a result of selective constraints related to the role of the TM in sound production. Sexual dimorphism seemed to be greater than interspecific variation, indicating that constraints operating on sex might be more selective than those acting on species identification. In addition, C. orni appeared to be significantly different from the two other species. This morphological peculiarity could be related to the unique vibrational pattern of its membrane. This would establish for the first time a direct link between the shape and mechanism of a hearing organ. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101 , 922–934.     

Phylogeography of the mottled spinefoot Siganus fuscescens: Pleistocene divergence and limited genetic connectivity across the Philippine archipelago

Historical isolation during Pleistocene low sea level periods is thought to have contributed to divergence among marine basin populations across the Coral Triangle. In the Philippine archipelago, populations in the South China Sea, Sulu Sea–inland seas, and Philippine Sea‐Celebes Sea basins might have been partially isolated. Meanwhile, present‐day broadscale oceanographic circulation patterns suggest connectivity between these basins. To evaluate hypotheses regarding the influence of historical and contemporary factors on genetic structure, phylogeographic patterns based on mitochondrial control region sequences for a reef‐associated fish, Siganus fuscescens, were analysed. Three distinct lineages were recovered. One lineage was identified as the morphologically similar species Siganus canaliculatus, while two lineages are monophyletic with S. fuscescens. Clade divergence and demographic expansion in S. fuscescens occurred during the Pleistocene. A strong signal of latitudinal structure was detected (Φ_CT = 0.188), driven by marked differences in clade distribution: one clade is widely distributed (clade A), while a second clade (clade B) has a restricted northern distribution. Regional structure of clade A is consistent with the basin isolation hypothesis (Φ_CT = 0.040) and suggests isolation of the South China Sea (Φ_CT = 0.091). Fine‐scale structure was observed in the South China Sea and south Philippine Sea, while Sulu Sea and inland seas were unstructured. Genetic structure across multiple spatial scales (archipelagic, regional, and fine‐scale within basins) suggests the influence of vicariant barriers and contemporary limits to gene flow in S. fuscescens that may be influenced by oceanographic circulation, geographical distance between available habitats, and latitudinal temperature differences.     

<Emphasis Type="Italic">In vitro</Emphasis> and <Emphasis Type="Italic">ex vivo</Emphasis> effect of hyaluronic acid on erythrocyte flow properties

Background  

Hyaluronic acid (HA) is present in many tissues; its presence in serum may be related to certain inflammatory conditions, tissue damage, sepsis, liver malfunction and some malignancies. In the present work, our goal was to investigate the significance of hyaluronic acid effect on erythrocyte flow properties. Therefore we performed in vitro experiments incubating red blood cells (RBCs) with several HA concentrations. Afterwards, in order to corroborate the pathophysiological significance of the results obtained, we replicated the in vitro experiment with ex vivo RBCs from diagnosed rheumatoid arthritis (RA) patients, a serum HA-increasing pathology.     

1590名农村中老年人生存质量调查分析(英文)

目的:采用SF-36量表中文版评价农村中老年人生存质量,并为提高农村中老年人的生存质量和健康水平提供科学依据和建议。方法:采用随机抽样的方法,采用面对面访谈的形式,记分方法参照国际生存质量评价计划(IQOLA)的制定标准,评价其生理和心理健康状况。结果:1590名农村中老年人男性生存质量得分高于女性。经济水平对农村中老年人的生理健康的影响大于对其心理健康的影响。配偶健在的农村中老年人的各维度得分均高于无配偶者。农村中老年人的各维度得分随教育水平的升高呈升高趋势。结论:农村中老年人的生存质量与年龄成负相关,同时也受文化程度和经济水平等多个因素的影响。因而,对农村中老年人这一弱势群体应该给予更多关注。     

Identification of inducers of the Yersinia enterocolitica phage shock protein system and comparison to the regulation of the RpoE and Cpx extracytoplasmic stress responses

Known inducers of the phage shock protein (Psp) system suggest that it is an extracytoplasmic stress response, as are the well-studied RpoE and Cpx systems. However, a random approach to identify conditions and proteins that induce the Psp system has not been attempted. It is also unknown whether the proteins or mutations that induce Psp are specific or if they also activate the RpoE and Cpx systems. This study addressed these issues for the Yersinia enterocolitica Psp system. Random transposon mutagenesis identified null mutations and overexpression mutations that increase Phi(pspA-lacZ) operon fusion expression. The results suggest that Psp may respond exclusively to extracytoplasmic stress. Null mutations affected glucosamine-6-phosphate synthetase (glmS), which plays a role in cell envelope biosynthesis, and the F0F1 ATPase (atp operon). The screen also revealed that in addition to several secretins, the overexpression of three novel putative inner membrane proteins (IMPs) induced the Psp response. We also compared induction of the Y. enterocolitica Psp, RpoE, and Cpx responses. Overexpression of secretins or the three IMPs or the presence of an atpB null mutation only induced the Psp response. Similarly, known inducers of the RpoE and Cpx responses did not significantly induce the Psp response. Only the glmS null mutation induced all three responses. Therefore, Psp is induced distinctly from the RpoE and Cpx systems. The specific IMP inducers may be valuable tools to probe specific signal transduction events of the Psp response in future studies.     

'Cyclic alopecia' in Msx2 mutants: defects in hair cycling and hair shaft differentiation

Msx2-deficient mice exhibit progressive hair loss, starting at P14 and followed by successive cycles of wavelike regrowth and loss. During the hair cycle, Msx2 deficiency shortens anagen phase, but prolongs catagen and telogen. Msx2-deficient hair shafts are structurally abnormal. Molecular analyses suggest a Bmp4/Bmp2/Msx2/Foxn1 acidic hair keratin pathway is involved. These structurally abnormal hairs are easily dislodged in catagen implying a precocious exogen. Deficiency in Msx2 helps to reveal the distinctive skin domains on the same mouse. Each domain cycles asynchronously - although hairs within each skin domain cycle in synchronized waves. Thus, the combinatorial defects in hair cycling and differentiation, together with concealed skin domains, account for the cyclic alopecia phenotype.     

A solid-phase assay for identification of modulators of prion protein interactions

The progression of the transmissible spongiform encephalopathies (TSEs) is characterized in part by accumulation of a proteinase K-resistant form of the prion protein, which has been converted from the endogenous, proteinase K-sensitive form. This conversion reaction provides a target for possible anti-TSE strategies. We have adapted a cell-free conversion reaction to a high-throughput, solid-phase format that can be used to screen possible therapeutic compounds for inhibitory activity or to illuminate inhibition and conversion mechanisms. The solid-phase assay was compatible with reactions performed under a variety of conditions. Using this assay, we report that phthalocyanine tetrasulfonate, a known modulator of conversion, inhibited conversion by interfering with binding between the protease-sensitive and the protease-resistant forms of the prion protein. A biotinylated form of the protease-sensitive prion protein was successfully converted to the protease-resistant isoform in the solid-phase assay, indicating that biotinylation provides a nonisotopic labeling strategy for large-scale screens.