On high-cycle fatigue of 316L stents

This paper deals with fatigue life prediction of 316L stainless steel cardiac stents. Stents are biomedical devices used to reopen narrowed vessels. Fatigue life is dominated by the cyclic loading due to the systolic and diastolic pressure and the design against premature mechanical failure is of extreme importance. Here, a life assessment approach based on the Dang Van high cycle fatigue criterion and on finite element analysis is applied to explore the fatigue reliability of 316L stents subjected to multiaxial fatigue loading. A finite element analysis of the stent vessel subjected to cyclic pressure is performed to carry out fluctuating stresses and strain at some critical elements of the stent where cracks or complete fracture may occur. The obtained results show that the loading path of the analysed stent subjected to a pulsatile load pressure is located in the safe region concerning infinite lifetime.     

Characterization of Membrane Lipidome Changes in Pseudomonas aeruginosa during Biofilm Growth on Glass Wool

Bacteria cells within biofilms are physiologically distinct from their planktonic counterparts. In particular they are more resistant to detrimental environmental conditions. In this study, we monitored the evolution of the phospholipid composition of the inner and outer membranes of P. aeruginosa during the biofilm formation (i.e., from 1-, 2-, to 6-day-old biofilm). Lipidome analyses were performed by electrospray ionization mass spectrometry. In addition to the lipidomic analysis, the fatty acid composition was analysed by gas chromatography/mass spectrometry. We found that the lipidome alterations of the inner and the outer membranes varied with the biofilm age. These alterations in phospholipid compositions reflect a higher diversity in sessile organisms than in planktonic counterparts. The diversity is characterized by the presence of PE 30∶1, PE 31∶0 and PG 31∶0 for the lower masses as well as PE 38∶1, 38∶2, 39∶1, 39∶2 and PG 38∶0, 38∶1, 38∶2, 39∶1, 39∶2 for the higher masses. However, this lipidomic feature tends to disappear with the biofilm age, in particular the high mass phospholipids tend to disappear. The amount of branched chains phospholipids mainly located in the outer membrane decreased with the biofilm age, whereas the proportion of cyclopropylated phospholipids increased in both membranes. In bacteria present in oldest biofilms, i.e., 6-day-old, the phospholipid distribution moved closer to that of planktonic bacteria.     

Modeling Tuberculosis Dynamics,Detection and Control in Cattle Herds

Epidemiological models are key tools for designing and evaluating detection and control strategies against animal infectious diseases. In France, after decades of decrease of bovine tuberculosis (bTB) incidence, the disease keeps circulating. Increasing prevalence levels are observed in several areas, where the detection and control strategy could be adapted. The objective of this work was to design and calibrate a model of the within-herd transmission of bTB. The proposed model is a stochastic model operating in discrete-time. Three health states were distinguished: susceptible, latent and infected. Dairy and beef herd dynamics and bTB detection and control programs were explicitly represented. Approximate Bayesian computation was used to estimate three model parameters from field data: the transmission parameter when animals are inside (β_inside) and outside (β_outside) buildings, and the duration of the latent phase. An independent dataset was used for model validation. The estimated median was 0.43 [0.16–0.84] month⁻¹ for β_inside and 0.08 [0.01–0.32] month⁻¹ for β_outside. The median duration of the latent period was estimated 3.5 [2]–[8] months. The sensitivity analysis showed only minor influences of fixed parameter values on these posterior estimates. Validation based on an independent dataset showed that in more than 80% of herds, the observed proportion of animals with detected lesions was between the 2.5% and 97.5% percentiles of the simulated distribution. In the absence of control program and once bTB has become enzootic within a herd, the median effective reproductive ratio was estimated to be 2.2 in beef herds and 1.7 in dairy herds. These low estimates are consistent with field observations of a low prevalence level in French bTB-infected herds.     

Prussian Blue based screen printed biosensors with improved characteristics of long-term lifetime and pH stability

The promising advantages of Prussian Blue (PB) as catalyst and of the thick film screen printing technology have been combined to assemble sensors with improved characteristics for the amperometric determination of H(2)O(2). PB-modified screen printed electrodes were applied to detect H(2)O(2) at an applied potential of -0.05 V versus the internal screen printed Ag pseudoreference electrode, showing a detection limit of 10(-7) mol l(-1), a linearity range from 10(-7) to 5x10(-5) mol l(-1), a sensitivity of 234 microA mmol l(-1) cm(-2), and a high selectivity. Improved stability at alkaline pH values was also observed, which made possible their use with enzymes having an optimum basic pH. Then, the immobilisation of a single enzyme (glucose oxidase (GOD) or choline oxidase (ChOX)) or of two enzymes, acetylcholinesterase (AchE) coimmobilised with ChOX, has been performed on the surface of PB modified screen-printed electrodes (SPEs) using glutaraldehyde and Nafion. ChOX has been selected as an example of enzyme working at alkaline pH. The choline biosensors showed a detection limit of 5x10(-7) mol l(-1), a wide linearity range (5x10(-7)-10(-4) mol l(-1)), a high selectivity and a remarkable long term stability of 9 months at 4 degrees C, and at least 4 weeks at room temperature. Similar analytical characteristics and stability were observed with the acetylcholine biosensors.     

Molecular characterization and in silico analysis of RNA polymerase alpha subunit gene (rpoA) in Date Palm (Phoenix dactylifera L.) cv. Deglet Nour

The rpoA gene coding for the ??-subunit of DNA-dependent RNA polymerase located in the chloroplastic genome of date palm has been characterized from the elite cultivar Deglet Nour by cloning and sequencing of the PCR amplification product. The full length of rpoA-Pd (Phoenix dactylifera) gene was 1014 bp. The comparison in Genbank showed that the rpoA gene has a 100% homology with the Khalas cultivar of date palm and a strong homology with Oil Palm (99%). The deduced protein full length is 337 amino acid corresponding to 38,692 Da polypeptide. It contained an Alpha N-terminal domain (alpha-NTD) between 1 to 233 (aa) and Alpha C-terminal domain (alpha-CTD) between 266 to 337 (aa). Initially, we have compared the sequences of the full-length DNA rpoA gene from Date Palm and Oil palm, 15 mutations have been detected, 4 do not affect amino acid sequences. A multiple alignment of protein sequences of Date Palm and other plants shows 6 mutations specific for palms family and one is specific to monocots species. A multiple alignment of 35 nucleotide sequences from different plant species shows 3 SNPs specific to Date Palm, 6 SNPs specific to Palms family and 6 other to monocot species. The phylogenetic analysis performed in this work shows a strong similarity between Pd-rpoA and rpoA genes from other plant species, but it shows a great divergence with the rpoA of E. coli. To explain whether the separation of the two clades was due to selection pressure. We calculate the ratio Ka/Ks for different species. A synteny analyses of rpoA genes was effected, a high genomic synteny is observed for the ropA in all the species included in this study.     

VEGF-C promotes immune tolerance in B16 melanomas and cross-presentation of tumor antigen by lymph node lymphatics

Tumor expression of the lymphangiogenic factor VEGF-C is correlated with metastasis and poor prognosis, and although VEGF-C enhances transport to the draining lymph node (dLN) and antigen exposure to the adaptive immune system, its role in tumor immunity remains unexplored. Here, we demonstrate that VEGF-C promotes immune tolerance in murine melanoma. In B16 F10 melanomas expressing a foreign antigen (OVA), VEGF-C protected tumors against preexisting antitumor immunity and promoted local deletion of OVA-specific CD8(+) T cells. Naive OVA-specific CD8(+) T cells, transferred into tumor-bearing mice, were dysfunctionally activated and apoptotic. Lymphatic endothelial cells (LECs) in dLNs cross-presented OVA, and naive LECs scavenge and cross-present OVA in vitro. Cross-presenting LECs drove the proliferation and apoptosis of OVA-specific CD8(+) T cells ex vivo. Our findings introduce a tumor-promoting role for lymphatics in the tumor and dLN and suggest that lymphatic endothelium in the local microenvironment may be a target for immunomodulation.     

Effects of nasal continuous positive-airway pressure on nutritive swallowing in lambs

Current knowledge suggests that, to be successful, oral feeding in preterm infants should be initiated as soon as possible, often at an age where immature respiration still requires ventilatory support in the form of nasal continuous positive airway pressure (nCPAP). While some neonatologist teams claim great success with initiation of oral feeding in immature infants with nCPAP, others strictly wait for this ventilatory support to be no longer necessary before any attempt at oral feeding, fearing laryngeal penetration and tracheal aspiration. Therefore, the aim of the present study was to provide a first assessment of the effect of various levels of nCPAP on bottle-feeding in a neonatal ovine model, including feeding safety, feeding efficiency, and nutritive swallowing-breathing coordination. Eight lambs born at term were surgically instrumented 48 h after birth to collect recordings of electrical activity of laryngeal constrictor muscle, electrocardiography, and arterial blood gases. Two days after surgery, lambs were bottle-fed under five randomized nCPAP conditions, including without any nCPAP or nasal mask and nCPAP of 0, 4, 7, and 10 cmH(2)O. Results revealed that application of nCPAP in the full-term lamb had no deleterious effect on feeding safety and efficiency or on nutritive swallowing-breathing coordination. The present study provides a first and unique insight on the effect of nCPAP on oral feeding, demonstrating its safety in newborn lambs born at term. These results open the way for further research in preterm lambs to better mimic the problems encountered in neonatology.     

Transparent mediation-based access to multiple yeast data sources using an ontology driven interface

BACKGROUND: Saccharomyces cerevisiae is recognized as a model system representing a simple eukaryote whose genome can be easily manipulated. Information solicited by scientists on its biological entities (Proteins, Genes, RNAs...) is scattered within several data sources like SGD, Yeastract, CYGD-MIPS, BioGrid, PhosphoGrid, etc. Because of the heterogeneity of these sources, querying them separately and then manually combining the returned results is a complex and time-consuming task for biologists most of whom are not bioinformatics expert. It also reduces and limits the use that can be made on the available data. RESULTS: To provide transparent and simultaneous access to yeast sources, we have developed YeastMed: an XML and mediator-based system. In this paper, we present our approach in developing this system which takes advantage of SB-KOM to perform the query transformation needed and a set of Data Services to reach the integrated data sources. The system is composed of a set of modules that depend heavily on XML and Semantic Web technologies. User queries are expressed in terms of a domain ontology through a simple form-based web interface. CONCLUSIONS: YeastMed is the first mediation-based system specific for integrating yeast data sources. It was conceived mainly to help biologists to find simultaneously relevant data from multiple data sources. It has a biologist-friendly interface easy to use. The system is available at http://www.khaos.uma.es/yeastmed/.     

HCV NS5B蛋白对HCV RNA的模板特异性研究

在大肠杆菌菌株BL21(DE3)中表达并纯化HCV的依赖于RNA的RNA多聚酶(RNA-dependent RNA polymerase,RdRp,NS5B蛋白).以HCV正、负链RNA 3′末端的序列为模板,体外研究NS5B蛋白催化的RNA合成.结果显示,正链RNA在体外不能指导RNA合成,而负链RNA模板可以产生一条全长的正链RNA产物,表明NS5B对负链RNA具有模板特异性.NS5B对负链RNA的特异性在模板竞争性实验中得到进一步证实,正链RNA的存在和竞争对以负链为模板的RNA合成没有影响.这样,就合理解释了在HCV RNA复制时正链RNA的数量远比负链RNA多这一问题.同时,本实验的结果也为进一步研究病毒或其它细胞因子参与以正链RNA为模板进行的RNA合成,以及有关负链RNA模板特性的研究奠定了基础.