The processing conditions, microstructure, and dielectric properties of strontium bismuth niobate vanadate ceramics, SrBi2(VxNb1−x)2O9 (SBVN, with 0 ≤x≤ 0.3), were systematically studied. A relative ...density of >90% was obtained for all the samples using a two‐step sintering process. XRD showed that a single phase with the layered perovskite structure of SrBi2Nb2O9 (SBN) was formed with a vanadium content of up to 30 at.%. SEM revealed that the average grain size decreased gradually with an increase in vanadium content. The Curie point was found to gradually increase from ∼418°C for SBN to ∼459°C for SBVN with 30 at.% vanadium. Dielectric constants at room temperature and their respective Curie points were found to peak at a composition with 10–15 at.%; vanadium. Moreover, a high concentration of vanadium (>5 at.%) resulted in a significant increase in tangent loss at low frequencies (<1000 Hz). The relationships between chemical composition, processing condition, microstructure, and dielectric properties of SBVN ferroelectric ceramics are discussed.
Non-enveloped viruses must deliver their viral genome across a cell membrane without the advantage of membrane fusion. The mechanisms used to achieve this remain poorly understood. Human rhinovirus, ...a frequent cause of the common cold, is a non-enveloped virus of the picornavirus family, which includes other significant pathogens such as poliovirus and foot-and-mouth disease virus. During picornavirus cell entry, the small myristoylated capsid protein VP4 is released from the virus, interacts with the cell membrane and is implicated in the delivery of the viral RNA genome into the cytoplasm to initiate replication. In this study, we have produced recombinant C-terminal histidine-tagged human rhinovirus VP4 and shown it can induce membrane permeability in liposome model membranes. Dextran size-exclusion studies, chemical crosslinking and electron microscopy demonstrated that VP4 forms a multimeric membrane pore, with a channel size consistent with transfer of the single-stranded RNA genome. The membrane permeability induced by recombinant VP4 was influenced by pH and was comparable to permeability induced by infectious virions. These findings present a molecular mechanism for the involvement of VP4 in cell entry and provide a model system which will facilitate exploration of VP4 as a novel antiviral target for the picornavirus family.
Mutations in Sp110 are the underlying cause of veno-occlusive disease with immunodeficiency (VODI), a combined immunodeficiency that is difficult to treat and often fatal. Because early treatment is ...critically important for patients with VODI, broadly usable diagnostic tools are needed to detect Sp110 protein deficiency. Several factors make establishing the diagnosis of VODI challenging: (1) Current screening strategies to identify severe combined immunodeficiency are based on measuring T cell receptor excision circles (TREC). This approach will fail to identify VODI patients because the disease is not associated with severe T cell lymphopenia at birth; (2) the
SP110
gene contains 17 exons, making it a challenge for Sanger sequencing. The recently developed next-generation sequencing (NGS) platforms that can rapidly determine the sequence of all 17 exons are available in only a few laboratories; (3) there is no standard functional assay to test for the effects of novel mutations in Sp110; and (4) it has been difficult to use flow cytometry to identify patients who lack Sp110 because of the low level of Sp110 protein in peripheral blood lymphocytes. We report here a novel flow cytometric assay that is easily performed in diagnostic laboratories and might thus become a standard assay for the evaluation of patients who may have VODI. In addition, the assay will facilitate investigations directed at understanding the function of Sp110.
Abstract only
The type VI secretion system (T6SS) has emerged as an important mediator of interbacterial interactions. A T6SS from
Pseudomonas aeruginosa
targets at least three toxic effectors,
t
ype ...VI
s
ecretion
e
xported 1–3 (Tse1‐3), to recipient Gram‐negative bacterial cells. Tse2 is a potent cytoplasmic toxin that inhibits target cell proliferation through an unknown mechanism. When translocated into other bacterial cells, the protein provides a fitness advantage for
P. aeruginosa
. The
t
ype VI
s
ecretion
i
mmunity protein 2 (Tsi2) was found to protect against endogenous and intercellularly‐transferred Tse2. Here we showed that Tse2 delivered by the T6SS efficiently induces stasis, not death of recipient cells. Despite direct interaction of Tsi2 and Tse2 in the cytoplasm, we found Tsi2 is dispensable for targeting the toxin to the secretory apparatus. By mapping the results of genetic screening data onto our 1.0 Å X‐ray crystal structure of Tsi2, we discovered an acidic patch on the Tsi2 surface that mediates Tse2 interaction and immunity. Interestingly, our results indicated that Tsi2 shares structural similarity to the N‐terminal domain of the Vti1p SNARE protein and that these proteins interact with binding partners in a chemically and spatially overlapping motif. Our findings provided the first molecular insights into T6 effector secretion and immunity that distinguish the system from analogous cellular pathways.
Topical hemostatic agents have been particularly useful for preventing bleeding in tubeless percutaneous nephrolithotomy. In the present study, we investigated the effect of gelatin matrix hemostatic ...sealant (FloSeal), fibrin glue (Tisseel,), polyethylene glycol polymers (CoSeal), and bovine serum albumin/ glutaraldehyde (BioGlue) in the pig urinary collecting system after injection through a percutaneous nephrostomy (PCN) tract.
Percutaneous nephrostomy was performed in 40 kidneys in 24 domestic pigs. Animals were divided into four groups of six each: (1) FloSeal; (2) Tisseel; (3) CoSeal; and (4) BioGlue. In 16 animals that tolerated the procedure, the contralateral kidney was used as a control for PCN only. All tracts were dilated to 30F with the Amplatz dilator, and 2 mL of the hemostatic agent was injected into the collecting system before pulling back to seal the puncture.
Among the control PCN kidneys, no obstruction was detected at the end of a 5-day period. However, three of six kidneys injected with FloSeal, Tisseel, or CoSeal and four of six kidneys injected with BioGlue were obstructed. In each of these cases, there was an associated retroperitoneal urinoma.
FloSeal, Tisseel, CoSeal, and BioGlue, if injected directly into the porcine collecting system, can result in significant obstruction that does not resolve over a 5-day period. Until there are clinical data to the contrary, we believe that when using one of these hemostatic agents in association with a tubeless percutaneous procedure, a retrograde occlusion balloon catheter should be considered to prevent inadvertent injection of these materials into the collecting system.
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