Potential immunosuppressive effects of Escherichia coli O157:H7 experimental infection on the bovine host

Background: Enterohaemorrhagic Escherichia coli (EHEC), like E. coli O157:H7 are frequently detected in bovine faecal samples at slaughter. Cattle do not show clinical symptoms upon infection, but for humans the consequences after consuming contaminated beef can be severe. The immune response against EHEC in cattle cannot always clear the infection as persistent colonization and shedding in infected animals over a period of months often occurs. In previous infection trials, we observed a primary immune response after infection which was unable to protect cattle from reinfection. These results may reflect a suppression of certain immune pathways, making cattle more prone to persistent colonization after re-infection. To test this, RNA-Seq was used for transcriptome analysis of recto-anal junction tissue and ileal Peyer's patches in nine Holstein-Friesian calves in response to a primary and secondary Escherichia coli O157: H7 infection with the Shiga toxin (Stx) negative NCTC12900 strain. Non-infected calves served as controls. Results: In tissue of the recto-anal junction, only 15 genes were found to be significantly affected by a first infection compared to 1159 genes in the ileal Peyer's patches. Whereas, re-infection significantly changed the expression of 10 and 17 genes in the recto-anal junction tissue and the Peyer's patches, respectively. A significant downregulation of 69 immunostimulatory genes and a significant upregulation of seven immune suppressing genes was observed. Conclusions: Although the recto-anal junction is a major site of colonization, this area does not seem to be modulated upon infection to the same extent as ileal Peyer's patches as the changes in gene expression were remarkably higher in the ileal Peyer's patches than in the recto-anal junction during a primary but not a secondary infection. We can conclude that the main effect on the transcriptome was immunosuppression by E. coli O157: H7 (Stx(-)) due to an upregulation of immune suppressive effects (7/12 genes) or a downregulation of immunostimulatory effects (69/94 genes) in the ileal Peyer's patches. These data might indicate that a primary infection promotes a re-infection with EHEC by suppressing the immune function

Compact, Low-Profile, Bandwidth-Enhanced Substrate Integrated Waveguide Filtenna

© 2011 IEEE. In this letter, a compact, low-profile, bandwidth-enhanced, dual-cavity substrate integrated waveguide (SIW) filtenna is demonstrated. Two SIW cavities are stacked vertically on top of each other. A complementary split-ring resonator slot is etched in the top surface of the uppermost cavity, causing the top surface to act as a patch antenna. The operational impedance bandwidth is significantly enhanced by merging the three resonances that arise from this configuration. One is introduced by the patch, and the other two are inherently generated by the two cavities. A metallized coupling post is introduced from the ground plane through both cavities to the upper surface to excite the fundamental resonant mode of the patch, as well as to electromagnetically couple the two cavities. The optimized filtenna was fabricated by a standard printed circuit board technology and tested. It has a low profile λ 0 and a compact size 0.62λ 0×0.62λ0 at its center frequency, f0=2.95GHz. The measured results agree well with their simulated values. They demonstrate a 6.3% fractional bandwidth, a maximum realized gain of 6.73 dBi, a flat gain profile within its passband, and an excellent out-of-band selectivity

Particle swarm optimized, 3-d-printed, wideband, compact hemispherical antenna

© 2002-2011 IEEE. A three-dimensional (3-D)-printed, wideband, compact hemispherical-shaped antenna is presented. It consists of a driven strip monopole and several parallel near-field resonant parasitic (NFRP) strips that reside on the surfaces of a hemispherical shell. The monopole strip lies on the interior surface; the NFRP strips lie on the exterior one. This arrangement facilitates the requisite stable near-field capacitive coupling between them over a wide frequency range. The particle swarm optimization algorithm is used to define the lengths and locations of these NFRP strips to achieve its optimized operational bandwidth around 700 MHz given its compact size. The hemispherical shell was 3-D printed with acrylonitrile butadiene styrene resin; the strips were applied to it with silver paste. This prototype was tested. The measured results, in agreement with their simulated values, demonstrate that it achieves a 17.97% -10 dB fractional impedance bandwidth over which stable realized gain values, near 3.5 dBi, are attained. With its low-cost fabrication and attractive performance characteristics, this 3-D printed antenna is suitable for indoor multipath wireless communication systems

A Bandwidth-Enhanced, Compact, Single-Feed, Low-Profile, Multilayered, Circularly Polarized Patch Antenna

© 2002-2011 IEEE. A bandwidth-enhanced, compact, single-feed, low-profile, multilayered, circularly polarized (CP) patch antenna is presented. A corner-truncated patch is introduced as a near-field resonant parasitic element directly beneath a specially engineered radiation patch. Without sacrificing the antenna's low profile and compact size, its presence not only introduces a new pair of orthogonal near-degenerate resonant modes, but also recovers a similar pair from the cross slot of the main patch. With the aid of both circular slots and meander-line slots on these patches, the resulting three pairs of adjacent near-degenerate modes have been successfully combined with the same clockwise polarization to enhance the CP bandwidth by more than a factor of two when compared to the same-height conventional single-layer patch antennas. Measured results are in good agreement with their simulated values and demonstrate that the reported antenna is low-profile: 0.016 λ achieves a -10-dB impedance bandwidth of ∼4.6%, and a 3-dB axial-ratio bandwidth of about 2.33% along with realized gains of 4.5 ± 0.15 dBi, throughout that bandwidth. Analyses of the current distributions are used to explain the contributions of the parasitic patch, and further simulation studies validate our design guidelines and show its advantages

Doping effects on the phase separation in perovskite La0.67-xBixCa0.33MnO3

Effects of Bi, Cr, and Fe doping on phase separation of La0.67Ca0.33MnO3 have been experimentally studied. As proved by the electron-spin resonance and neutron-diffraction studies, partial replacement of La by Bi causes the simultaneous occurrence of ferromagnetic (FM) phase and charge-ordered antiferromagnetic phase. As a consequence, two subsequent magnetic transitions at ∼120 K and ∼230 K are resulted. A strong coupling between the coexisted phases is assumed, which is responsible for the insensitivity of Tc(L), the higher Curie temperature, to Bi doping after the appearance of phase separation, and consistent with the discontinuous variation of Tc(L) with Cr doping. As expected, the substitution of Cr for Mn in this case promotes the FM order, but its effects are significantly different for the two magnetic states. Each Cr drives ∼100 neighboring unit cells, for the high-moment state, and ∼60 unit cells, for the low-moment state, into the FM state. Two definite processes can be identified for the melting of the charge-ordered phase. The FM fraction increases rapidly in the initial stage of Cr doping, and then slowly when the FM population exceeds ∼90%. This could be a common feature of the phase-separated system suffering from random-phase fluctuation according to a theoretical analysis. Exactly opposite effects on phase constituent are produced by Cr doping and Bi doping, and 1% Cr are equivalent to ∼4.6% Bi. In contrast, both Cr doping and magnetic field promote the FM order. 1% Cr correspond to a field of ∼4.5 T for the low-moment state and 6 T for the high-moment state, reducing the energy difference between the charge ordering and the FM states by ∼0.96 meV/Mn and ∼1.3 meV/Mn, respectively.published_or_final_versio

Compact, Frequency-Reconfigurable Filtenna with Sharply Defined Wideband and Continuously Tunable Narrowband States

© 1963-2012 IEEE. A compact, frequency-reconfigurable filtenna with sharp out-of-band rejection in both its wideband and continuously tunable narrowband states is presented. It is intended for use in cognitive radio applications. The wideband state is the sensing state and operationally covers 2.35-4.98 GHz. The narrowband states are intended to cover communications within the 3.05-4.39 GHz range, which completely covers the Worldwide Interoperability for Microwave Access (WiMAX) band and the satellite communications C-band. A p-i-n diode is employed to switch between these wide and narrowband operational states. Two varactor diodes are used to shift the operational frequencies continuously among the narrowband states. The filtenna consists of a funnel-shaped monopole augmented with a reconfigurable filter; it has a compact electrical size: 0.235λLL × 0.392λL , where the wavelength λL corresponds to the lower bound of its operational frequencies. The measured reflection coefficients, radiation patterns, and realized gains for both operational states are in good agreement with their simulated values

Patent Human Infections with the Whipworm, Trichuris trichiura, Are Not Associated with Alterations in the Faecal Microbiota

Background: The soil-transmitted helminth (STH), Trichuris trichiura colonises the human large intestine where it may modify inflammatory responses, an effect possibly mediated through alterations in the intestinal microbiota. We hypothesised that patent T. trichiura infections would be associated with altered faecal microbiota and that anthelmintic treatment would induce a microbiota resembling more closely that observed in uninfected individuals. Materials and Methods: School children in Ecuador were screened for STH infections and allocated to 3 groups: uninfected, T. trichiura only, and mixed infections with T. trichiura and Ascaris lumbricoides. A sample of uninfected children and those with T. trichiura infections only were given anthelmintic treatment. Bacterial community profiles in faecal samples were studied by 454 pyrosequencing of 16 S rRNA genes. Results: Microbiota analyses of faeces were done for 97 children: 30 were uninfected, 17 were infected with T. trichiura, and 50 with T. trichiura and A. lumbricoides. Post-treatment samples were analyzed for 14 children initially infected with T. trichiura alone and for 21 uninfected children. Treatment resulted in 100% cure of STH infections. Comparisons of the microbiota at different taxonomic levels showed no statistically significant differences in composition between uninfected children and those with T. trichiura infections. We observed a decreased proportional abundance of a few bacterial genera from the Clostridia class of Firmicutes and a reduced bacterial diversity among children with mixed infections compared to the other two groups, indicating a possible specific effect of A. lumbricoides infection. Anthelmintic treatment of children with T. trichiura did not alter faecal microbiota composition. Discussion: Our data indicate that patent human infections with T. trichiura may have no effect on faecal microbiota but that A. lumbricoides colonisation might be associated with a disturbed microbiota. Our results also catalogue the microbiota of rural Ecuadorians and indicate differences with individuals from more urban industrialised societies

Possible mechanisms of host resistance to Haemonchus contortus infection in sheep breeds native to the Canary Islands

Haemonchus contortus appears to be the most economically important helminth parasite for small ruminant production in many regions of the world. The two sheep breeds native to the Canary Islands display distinctly different resistant phenotypes under both natural and experimental infections. Canaria Hair Breed (CHB) tends to have significantly lower worm burden and delayed and reduced egg production than the susceptible Canaria Sheep (CS). To understand molecular mechanisms underlying host resistance, we compared the abomasal mucosal transcriptome of the two breeds in response to Haemonchus infection using RNAseq technology. The transcript abundance of 711 and 50 genes were significantly impacted by infection in CHB and CS, respectively (false discovery rate <0.05) while 27 of these genes were significantly affected in both breeds. Likewise, 477 and 16 Gene Ontology (GO) terms were significantly enriched in CHB and CS, respectively (P < 1.0 × 10(−4)). A broad range of mechanisms have evolved in resistant CHB to provide protection against the parasite. Our findings suggest that readily inducible acute inflammatory responses, complement activation, accelerated cell proliferation and subsequent tissue repair, and immunity directed against parasite fecundity all contributed to the development of host resistance to parasitic infection in the resistant breed