Pilot Study of Delayed ICOS/ICOS-L Blockade With alphaCD40 to Modulate Pathogenic Alloimmunity in a Primate Cardiac Allograft Model

Background: Inducible costimulator (ICOS) is rapidly upregulated with T-cell stimulation and may represent an escape pathway for T-cell costimulation in the setting of CD40/CD154 costimulation blockade. Induction treatment exhibited no efficacy in a primate renal allograft model, but rodent transplant models suggest that the addition of delayed ICOS/ICOS-L blockade may prolong allograft survival and prevent chronic rejection. Here, we ask whether ICOS-Ig treatment, timed to anticipate ICOS upregulation, prolongs NHP cardiac allograft survival or attenuates pathogenic alloimmunity. Methods: Cynomolgus monkey heterotopic cardiac allograft recipients were treated with alphaCD40 (2C10R4, d0-90) either alone or with the addition of delayed ICOS-Ig (d63-110). Results: Median allograft survival was similar between ICOS-Ig + alphaCD40 (120 days, 120-125 days) and alphaCD40 (124 days, 89-178 days) treated animals, and delayed ICOS-Ig treatment did not prevent allograft rejection in animals with complete CD40 receptor coverage. Although CD4(+) TEM cells were decreased in peripheral blood (115 +/- 24) and mLNs (49 +/- 1.9%) during ICOS-Ig treatment compared with monotherapy (214 +/- 27%, P = 0.01; 72 +/- 9.9%, P = 0.01, respectively), acute and chronic rejection scores and kinetics of alloAb elaboration were similar between groups. Conclusions: Delayed ICOS-Ig treatment with the reagent tested is probably ineffective in modulating pathogenic primate alloimmunity in this model

Evidence for enhanced dipolar interactions between Pt centers in binuclear phosphorescent complexes

a b s t r a c t Transient studies are used to examine the radiative decay dynamics in a series of phosphorescent platinum binuclear complexes. The complexes studied consist of square planar (2-(4 0 ,6 0 -difluorophenyl)pyridinato-N,C 2 0 )Pt units bridged by either pyrazole or thiopyridine ligands. We observe an increase in radiative lifetime as temperature is reduced from 300 K to 4 K when the binuclear complexes, named 1, 2 and 3 with Pt-Pt spacings 3.19 Å, 3.05 Å, and 2.83 Å, respectively, are doped into a p-bis(triphenylsilyly)benzene wide energy gap host. The lifetimes for 1, 2 and 3 are s = 6.3 ± 0.1 ls, s = 2.3 ± 0.1 ls, and s = 2.0 ± 0.1 ls at T = 295 K, respectively. At T = 4 K, those values increase to s = 8.6 ± 0.1 ls, s = 14.4 ± 0.1 ls, and s = 17.0 ± 0.1 ls, suggesting that the neighboring heavy metal centers in compounds 2 and 3 have significant orbital overlap. A three-level zero-field splitting model yields the lowest triplet energy splittings of 28 ± 3 cm À1 , 142 ± 9 cm À1 , and 113 ± 10 cm À1 for compounds 1, 2 and 3, respectively

Fretting wear behaviour of double-glow plasma Cr–Nb coating on γ-TiAl alloy

Double-glow plasma coatings are recommended for metallic components to mitigate the damage induced by complex loading conditions. In this paper, Cr–Nb alloyed layer was formed onto the TiAl substrate via a double-glow plasma process to enhance its anti-fretting wear performance. Nano-indentation and scratch tests were used to evaluate the mechanical properties of the coating. The fretting wear behaviour of the coating was investigated using a pin-on-plate fretting rig by rubbing against the Si3N4 ball. The 7 µm thick Cr–Nb coating was well bonded to the substrate with the 2 µm thick diffusion layer. The hardness of the coating was 9.5 GPa, which was 1.6 times greater than that of the uncoated TiAl substrate. Scratch tests showed that the critical load of Cr–Nb coating was 17.6 N. The fretting wear mechanism of the coatings was discussed in detail in this paper

A voxel-based finite element model for the prediction of bladder deformation.

Purpose: A finite element (FE) bladder model was previously developed to predict bladder deformation caused by bladder filling change. However, two factors prevent a wide application of FE models: (1) the labor required to construct a FE model with high quality mesh and (2) long computation time needed to construct the FE model and solve the FE equations. In this work, we address these issues by constructing a low-resolution voxel-based FE bladder model directly from the binary segmentation images and compare the accuracy and computational efficiency of the voxel-based model used to simulate bladder deformation with those of a classical FE model with a tetrahedral mesh. Methods: For ten healthy volunteers, a series of MRI scans of the pelvic region was recorded at regular intervals of 10 min over 1 h. For this series of scans, the bladder volume gradually increased while rectal volume remained constant. All pelvic structures were defined from a reference image for each volunteer, including bladder wall, small bowel, prostate (male), uterus (female), rectum, pelvic bone, spine, and the rest of the body. Four separate FE models were constructed from these structures: one with a tetrahedral mesh (used in previous study), one with a uniform hexahedral mesh, one with a nonuniform hexahedral mesh, and one with a low-resolution nonuniform hexahedral mesh. Appropriate material properties were assigned to all structures and uniform pressure was applied to the inner bladder wall to simulate bladder deformation from urine inflow. Performance of the hexahedral meshes was evaluated against the performance of the standard tetrahedral mesh by comparing the accuracy of bladder shape prediction and computational efficiency. Results: FE model with a hexahedral mesh can be quickly and automatically constructed. No substantial differences were observed between the simulation results of the tetrahedral mesh and hexahedral meshes ( <1% difference in mean dice similarity coefficient to manual contours and <0.02 cm difference in mean standard deviation of residual errors). The average equation solving time (without manual intervention) for the first two types of hexahedral meshes increased to 2.3 h and 2.6 h compared to the 1.1 h needed for the tetrahedral mesh, however, the low-resolution nonuniform hexahedral mesh dramatically decreased the equation solving time to 3 min without reducing accuracy. Conclusions: Voxel-based mesh generation allows fast, automatic, and robust creation of finite element bladder models directly from binary segmentation images without user intervention. Even the low-resolution voxel-based hexahedral mesh yields comparable accuracy in bladder shape prediction and more than 20 times faster in computational speed compared to the tetrahedral mesh. This approach makes it more feasible and accessible to apply FE method to model bladder deformation in adaptive radiotherapy. (C) 2012 American Association of Physicists in Medicine. [DOI: 10.1118/1.3668060

Four-Dimensional Characterization of Thrombosis in a Live-Cell, Shear-Flow Assay: Development and Application to Xenotransplantation

<div><p>Background</p><p>Porcine xenografts are a promising source of scarce transplantable organs, but stimulate intense thrombosis of human blood despite targeted genetic and pharmacologic interventions. Current experimental models do not enable study of the blood/endothelial interface to investigate adhesive interactions and thrombosis at the cellular level under physiologic conditions. The purpose of this study was to develop and validate a live-cell, shear-flow based thrombosis assay relevant to general thrombosis research, and demonstrate its potential in xenotransplantation applications.</p><p>Methodology/Principal Findings</p><p>Confluent wild-type (WT, n = 48) and Gal transferase knock-out (GalTKO, which resist hyperacute rejection; n = 11) porcine endothelia were cultured in microfluidic channels. To mimic microcirculatory flow, channels were perfused at 5 dynes/cm² and 37°C with human blood stained to fluorescently label platelets. Serial fluorescent imaging visualized percent surface area coverage (SA, for adhesion of labeled cells) and total fluorescence (a metric of clot volume). Aggregation was calculated by the fluorescence/SA ratio (FR). WT endothelia stimulated diffuse platelet adhesion (SA 65 ± 2%) and aggregation (FR 120 ± 1 a.u.), indicating high-grade thrombosis consistent with the rapid platelet activation and consumption seen in whole-organ lung xenotransplantation models. Experiments with antibody blockade of platelet aggregation, and perfusion of syngeneic and allo-incompatible endothelium was used to verify the biologic specificity and validity of the assay. Finally, with GalTKO endothelia thrombus volume decreased by 60%, due primarily to a 58% reduction in adhesion (P < 0.0001 each); importantly, aggregation was only marginally affected (11% reduction, P < 0.0001).</p><p>Conclusions/Significance</p><p>This novel, high-throughput assay enabled dynamic modeling of whole-blood thrombosis on intact endothelium under physiologic conditions, and allowed mechanistic characterization of endothelial and platelet interactions. Applied to xenogeneic thrombosis, it enables future studies regarding the effect of modifying the porcine genotype on sheer-stress-dependent events that characterize xenograft injury. This in-vitro platform is likely to prove broadly useful to study thrombosis and endothelial interactions under dynamic physiologic conditions.</p></div

A—C. Representative volumetric thrombus models.

<p>3D surface renderings of end-perfusion images (<i>t</i> = 50 minutes) for WT and GalTKO endothelia perfused with heparinized human blood (A & B, respectively) and WT endothelium perfused with heparinized human blood treated with 0.5 μg/mL abciximab (C). Panel A demonstrates significant adhesion and aggregation. In Panel B adhesion is reduced but aggregation is mostly intact, while in Panel C aggregation is ablated. Source images were taken at 100x magnification using a 100-millisecond exposure and rendered using ImageJ.</p

Thrombus generation curves for primary wild type and GalTKO endothelia.

<p>Summary of thrombus volume for primary WT versus GalTKO.hCD46 endothelia perfused with heparinized human blood. a.u., arbitrary units. Values are corrected for streak artifact (presumed embolization events) and photo-bleaching, and are expressed as mean ± SEM.</p

Results from xenoperfusion of porcine endothelia with human blood.

<p>*All experiments were performed with heparinized blood. a.u., arbitrary units; TV, thrombus volume; Δ, relative change; SA, percent surface area coverage; FR, fluorescence ratio; T₅₀, time to 50% maximal surface area coverage. All Δ & <i>P</i> values are versus WT controls, and are expressed as mean ± SEM.</p><p>Results from xenoperfusion of porcine endothelia with human blood.</p