Silyl-heparin bonding improves the patency and in vivo thromboresistance of carbon-coated polytetrafluoroethylene vascular grafts

AbstractObjectivesOur purpose was to improve the performance of carbon-coated expanded polytetrafluoroethylene vascular grafts by bonding the grafts with silyl-heparin, a biologically active heparin analog, using polyethylene glycol as a cross-linking agent.Material and methodSilyl-heparin–bonded carbon-coated expanded polytetrafluoroethylene vascular grafts (Bard Peripheral Vascular, Tempe, Ariz), were evaluated for patency and platelet deposition 2 hours, 7 days, and 30 days after graft implantation in a canine bilateral aortoiliac artery model. Platelet deposition was determined by injection of autologous, 111Indium-radiolabeled platelets, followed by a 2-hour circulation period prior to graft explantation. Histologic studies were performed on a 2-mm longitudinal strip of each graft (7-day and 30-day groups). Heparin activity of the explanted silyl-heparin grafts was determined by using an antithrombin-III based thrombin binding assay.ResultsOverall chronic graft patency (7-day and 30-day groups) was 100% for the silyl-heparin bonded (16/16) grafts versus 68.75% for control (11/16) grafts (P = .043). Acute 2-hour graft patency was 100% for the silyl-heparin bonded (6/6) grafts versus 83.3% for control (5/6) grafts. Radiolabeled platelet deposition studies revealed a significantly lower amount of platelets deposited on the silyl-heparin grafts as compared with control grafts in the 30-day group (13.8 ± 7.18 vs 28.4 ± 9.73, CPM per cm2 per million platelets, mean ± SD, P = .0451, Wilcoxon rank sum test). In the 2-hour group of dogs, a trend towards a lower deposition of platelets on the silyl-heparin grafts was observed. There was no significant difference in platelet deposition between the two grafts in the 7-day group. Histologic studies revealed a significant reduction in intraluminal graft thrombus present on the silyl-heparin grafts as compared with control grafts in the 30-day group of animals. In contrast, there was no difference in amount of graft thrombus present on both graft types in the 7-day group of dogs. Pre-implant heparin activity on the silyl-heparin bonded grafts was 2.0 IU/cm2 (international units[IU]/cm2). Heparin activity remained present on the silyl-heparin grafts after explantation at all 3 time points (2 hours: above upper limit of assay, upper limit = 0.57, n = 6; 7 days: 0.106 ± 0.015, n = 5; 30 days: 0.007 ± 0.001, n = 5; mean ± SD, IU/cm2).ConclusionSilyl-heparin bonding onto carbon-coated expanded polytetrafluoroethylene vascular grafts resulted in (1) improved graft patency, (2) increased in vivo graft thromboresistance, and (3) a significant reduction in intraluminal graft thrombus. This graft may prove to be useful in the clinical setting.AbstractClinical relevanceExpanded polytetrafluoroethylene (ePTFE) remains the most commonly used prosthetic graft material in infrainguinal arterial reconstructions. Reported long-term patency rates of ePTFE bypass grafts are inferior to those observed with autogenous vein. Modification of the luminal surface of ePTFE bypass grafts may prevent early graft failure and ultimately improve long-term graft performance. Silyl-heparin is a biologically active heparin analog that is readily adsorbed onto hydrophobic surfaces while retaining its anticoagulant properties. Silyl-heparin bonding onto carbon-coated ePTFE grafts improves the patency and in vivo thromboresistance and results in a decrease in intraluminal graft thrombus. This graft may be useful in the clinical setting

Local Delivery of Basic Fibroblast Growth Factor (bFGF) Using Adsorbed Silyl-heparin, Benzyl-bis(dimethylsilylmethyl)oxycarbamoyl-heparin

A growth factor delivery system was developed that is based on the use of silyl-heparin, a chemically modified analogue of heparin. The silyl-heparin was adsorbed onto surfaces by hydrophobic interaction via the prosthetic unit and can then be used as a solid-phase adsorbent for bFGF. All the coating steps were performed by adsorption, a process that allowed preparation of surfaces by immersion or "dip-coating". In this study a series of silyl-heparins were synthesized and each of the analogues found to function similar to unmodified heparin relative to their binding of antithrombin III and also the binding of bFGF. The silyl-heparins were found to be adsorbed onto a wide variety of substrates including polystyrene and lactide:glycolide copolymer. Enzyme-linked immumosorbant assay (ELISA) was used to establish that bFGF was readily bound to surface adsorbed silyl-heparin, and that the amount bound was directly related to amount offered for binding. Once adsorbed the silyl-heparin/ FGF was able to induce capillary tube formation of endothelial cells and to increase the growth of endothelial cells. When coated onto suture material and implanted in muscle, the FGF/silyl-heparin coating caused an increased density of mesenchymal cells in the area of the implant. This coating method could prove to be useful in a number of tissue engineering applications for the local delivery of FGF and other growth factors

Plated Cambrian Bilaterians Reveal the Earliest Stages of Echinoderm Evolution

Echinoderms are unique in being pentaradiate, having diverged from the ancestral bilaterian body plan more radically than any other animal phylum. This transformation arises during ontogeny, as echinoderm larvae are initially bilateral, then pass through an asymmetric phase, before giving rise to the pentaradiate adult. Many fossil echinoderms are radial and a few are asymmetric, but until now none have been described that show the original bilaterian stage in echinoderm evolution. Here we report new fossils from the early middle Cambrian of southern Europe that are the first echinoderms with a fully bilaterian body plan as adults. Morphologically they are intermediate between two of the most basal classes, the Ctenocystoidea and Cincta. This provides a root for all echinoderms and confirms that the earliest members were deposit feeders not suspension feeders

Measurement of inclusive D*+- and associated dijet cross sections in photoproduction at HERA

Inclusive photoproduction of D*+- mesons has been measured for photon-proton centre-of-mass energies in the range 130 < W < 280 GeV and a photon virtuality Q^2 < 1 GeV^2. The data sample used corresponds to an integrated luminosity of 37 pb^-1. Total and differential cross sections as functions of the D* transverse momentum and pseudorapidity are presented in restricted kinematical regions and the data are compared with next-to-leading order (NLO) perturbative QCD calculations using the "massive charm" and "massless charm" schemes. The measured cross sections are generally above the NLO calculations, in particular in the forward (proton) direction. The large data sample also allows the study of dijet production associated with charm. A significant resolved as well as a direct photon component contribute to the cross section. Leading order QCD Monte Carlo calculations indicate that the resolved contribution arises from a significant charm component in the photon. A massive charm NLO parton level calculation yields lower cross sections compared to the measured results in a kinematic region where the resolved photon contribution is significant.Comment: 32 pages including 6 figure

The Fourteenth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the extended Baryon Oscillation Spectroscopic Survey and from the second phase of the Apache Point Observatory Galactic Evolution Experiment

The fourth generation of the Sloan Digital Sky Survey (SDSS-IV) has been in operation since July 2014. This paper describes the second data release from this phase, and the fourteenth from SDSS overall (making this, Data Release Fourteen or DR14). This release makes public data taken by SDSS-IV in its first two years of operation (July 2014-2016). Like all previous SDSS releases, DR14 is cumulative, including the most recent reductions and calibrations of all data taken by SDSS since the first phase began operations in 2000. New in DR14 is the first public release of data from the extended Baryon Oscillation Spectroscopic Survey (eBOSS); the first data from the second phase of the Apache Point Observatory (APO) Galactic Evolution Experiment (APOGEE-2), including stellar parameter estimates from an innovative data driven machine learning algorithm known as "The Cannon"; and almost twice as many data cubes from the Mapping Nearby Galaxies at APO (MaNGA) survey as were in the previous release (N = 2812 in total). This paper describes the location and format of the publicly available data from SDSS-IV surveys. We provide references to the important technical papers describing how these data have been taken (both targeting and observation details) and processed for scientific use. The SDSS website (www.sdss.org) has been updated for this release, and provides links to data downloads, as well as tutorials and examples of data use. SDSS-IV is planning to continue to collect astronomical data until 2020, and will be followed by SDSS-V.Comment: SDSS-IV collaboration alphabetical author data release paper. DR14 happened on 31st July 2017. 19 pages, 5 figures. Accepted by ApJS on 28th Nov 2017 (this is the "post-print" and "post-proofs" version; minor corrections only from v1, and most of errors found in proofs corrected

Plastisol Foaming Process. Decomposition of the Foaming Agent, Polymer Behavior in the Corresponding Temperature Range and Resulting Foam Properties

The decomposition of azodicarbonamide, used as foaming agent in PVC - plasticizer (1/1) plastisols was studied by DSC. Nineteen different plasticizers, all belonging to the ester family, two being polymeric (polyadipates), were compared. The temperature of maximum decomposition rate (in anisothermal regime at 5 K min-1 scanning rate), ranges between 434 and 452 K. The heat of decomposition ranges between 8.7 and 12.5 J g -1. Some trends of variation of these parameters appear significant and are discussed in terms of solvent (matrix) and viscosity effects on the decomposition reactions. The shear modulus at 1 Hz frequency was determined at the temperature of maximum rate of foaming agent decomposition, and differs significantly from a sample to another. The foam density was determined at ambient temperature and the volume fraction of bubbles was used as criterion to judge the efficiency of the foaming process. The results reveal the existence of an optimal shear modulus of the order of 2 kPa that corresponds roughly to plasticizer molar masses of the order of 450 ± 50 g mol-1. Heavier plasticizers, especially polymeric ones are too difficult to deform. Lighter plasticizers such as diethyl phthalate (DEP) deform too easily and presumably facilitate bubble collapse

Observation of Scaling Violations in Scaled Momentum Distributions at HERA

Charged particle production has been measured in deep inelastic scattering (DIS) events over a large range of $x$ and $Q^2$ using the ZEUS detector. The evolution of the scaled momentum, $x_p$, with $Q^2,$ in the range 10 to 1280 $GeV^2$, has been investigated in the current fragmentation region of the Breit frame. The results show clear evidence, in a single experiment, for scaling violations in scaled momenta as a function of $Q^2$.Comment: 21 pages including 4 figures, to be published in Physics Letters B. Two references adde

D* Production in Deep Inelastic Scattering at HERA

This paper presents measurements of D^{*\pm} production in deep inelastic scattering from collisions between 27.5 GeV positrons and 820 GeV protons. The data have been taken with the ZEUS detector at HERA. The decay channel $D^{*+}\to (D^0 \to K^- \pi^+) \pi^+$ (+ c.c.) has been used in the study. The $e^+p$ cross section for inclusive D^{*\pm} production with $5<Q^2<100 GeV^2$ and $y<0.7$ is 5.3 \pms 1.0 \pms 0.8 nb in the kinematic region {$1.3<p_T(D^{*\pm})<9.0$ GeV and $| \eta(D^{*\pm}) |<1.5$}. Differential cross sections as functions of p_T(D^{*\pm}), $\eta(D^{*\pm}), W$ and $Q^2$ are compared with next-to-leading order QCD calculations based on the photon-gluon fusion production mechanism. After an extrapolation of the cross section to the full kinematic region in p_T(D^{*\pm}) and $\eta$(D^{*\pm}), the charm contribution $F_2^{c\bar{c}}(x,Q^2)$ to the proton structure function is determined for Bjorken $x$ between 2 $\cdot$ 10$^{-4}$ and 5 $\cdot$ 10$^{-3}$.Comment: 17 pages including 4 figure

Measurement of Jet Shapes in Photoproduction at HERA

The shape of jets produced in quasi-real photon-proton collisions at centre-of-mass energies in the range $134-277$ GeV has been measured using the hadronic energy flow. The measurement was done with the ZEUS detector at HERA. Jets are identified using a cone algorithm in the $\eta - \phi$ plane with a cone radius of one unit. Measured jet shapes both in inclusive jet and dijet production with transverse energies $E^{jet}_T>14$ GeV are presented. The jet shape broadens as the jet pseudorapidity ($\eta^{jet}$) increases and narrows as $E^{jet}_T$ increases. In dijet photoproduction, the jet shapes have been measured separately for samples dominated by resolved and by direct processes. Leading-logarithm parton-shower Monte Carlo calculations of resolved and direct processes describe well the measured jet shapes except for the inclusive production of jets with high $\eta^{jet}$ and low $E^{jet}_T$. The observed broadening of the jet shape as $\eta^{jet}$ increases is consistent with the predicted increase in the fraction of final state gluon jets.Comment: 29 pages including 9 figure

Measurement of the diffractive structure function in deep inelastic scattering at HERA

This paper presents an analysis of the inclusive properties of diffractive deep inelastic scattering events produced in $ep$ interactions at HERA. The events are characterised by a rapidity gap between the outgoing proton system and the remaining hadronic system. Inclusive distributions are presented and compared with Monte Carlo models for diffractive processes. The data are consistent with models where the pomeron structure function has a hard and a soft contribution. The diffractive structure function is measured as a function of \xpom, the momentum fraction lost by the proton, of $\beta$, the momentum fraction of the struck quark with respect to \xpom, and of $Q^2$. The \xpom dependence is consistent with the form \xpoma where $a~=~1.30~\pm~0.08~(stat)~^{+~0.08}_{-~0.14}~(sys)$ in all bins of $\beta$ and $Q^2$. In the measured $Q^2$ range, the diffractive structure function approximately scales with $Q^2$ at fixed $\beta$. In an Ingelman-Schlein type model, where commonly used pomeron flux factor normalisations are assumed, it is found that the quarks within the pomeron do not saturate the momentum sum rule.Comment: 36 pages, latex, 11 figures appended as uuencoded fil