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  • 1990-1994  (4)
  • 1980-1984  (2)
  • 1970-1974
  • Polymer and Materials Science  (5)
  • revascularization  (1)
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  • 1
    ISSN: 1435-1803
    Keywords: myocardial ischemia ; revascularization ; laser ; systolicperfusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Laser-induced intramyocardial revascularization (LIR) has been used to promote direct communications between blood within the ventricular cavity and that of the existing myocardial vasculature in an attempt to increase perfusion in patients with ischemic heart discase. This study was conducted to measure the effects of LIR channels on regional myocardial flood flow (microspheres), cardiac mechanics (sonomicrometers), and myocardial tissue pressures in 18 dogs. Under baseline hemodynamic conditions (mean HR=165.2±11.4 bpm, LVP=123.6±22.9/4.0±1.8 mmHg, AoP=112.8±27.1/77.0±22.5 mmHg), myocardial blood flow in laser-treated tissue (mean =1.11±.10 cc/min/gm before laser; .71±.19 cc/min/gm after laser) was reduced as compared to blood flow in control tissue (mean=1.12±.15 cc/min/gm before laser; 1.25±.22 cc/min/gm after laser). Regional myocardial systolic shortening (11.32%±3.82% before laser; 7.49%±2.86% after laser) was decreased by 33%. During simultaneous reversible ligation of the LAD and LCCA for 2 min, when intramyocardial channels represented the only tissue access for the injected microspheres, blood flow in laser-treated tissue was not increased above that of the control non-lasered tissue. However, regional blood flow was greater in laser-treated ischemic tissue (mean=.61±.12 cc/min/gm) than in untreated ischemic areas (mean=.04±.03 cc/min/gm) when left ventricular pressure (LVP) was acutely elevated (mean SLVP=207.0±16.1 mmHg). Using these measurements, a model is proposed to predict regional systolic pressure gradients between the left ventricular cavity and coronary intramyocardial vasculature required to permit restoration of blood flow to ischemic myocardium. We conclude that improved perfusion via laser-induced intramyocardial channels does not occur in otherwise normal myocardium exposed to acute coronary ligation and only small improvements in perfusion are noted when LVP is significantly elevated. Consideration of further clinical application of this approach is seriously cautioned awaiting additional experimental studies.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 28 (1994), S. 377-386 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Biomaterial-centered infection is an important cause of the failure of prosthetic implants and organs. Because neutrophils mediate host defense against infection, the effect of biomaterials on neutrophil superoxide release and the mechanism of that effect were investigated using three materials commonly employed in surgical practice. The graft materials were expanded polytetrafluorethylene (PTFE), polyurethane and woven dacron. Polystyrene, a commonly used laboratory support vessel, was also studied. Both polystyrene and polyurethane were activating, but serum inhibitable, whereas PTFE was nonactivating, and woven dacron was not activating unless serum was present. The signaling mechanisms used by these materials demonstrated time and material dependency. Pertussis toxin inhibition of G proteindependent activation had little or no effect on biomaterial induced activation, whereas FMLP-induced activation of the same biomaterial-associated cells was inhibited. Protein kinase C inhibition with staurosporine greatly inhibited polystyrene-induced activation, but had only a partial effect with polyurethane and even less effect with the activation associated with serum-treated woven dacron. These studies demonstrated that biomaterial contact-induced neutrophil activation differed from that described for cells in suspension, and showed that activation mechanisms on one material cannot be extrapolated to mechanisms on other materials. © 1994 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 26 (1992), S. 1039-1051 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Because periprosthetic infection remains a vexing problem for patients receiving implanted devices, we evaluated the effect of several materials on neutrophil free radical production. Human peripheral blood neutrophils were incubated with several sterile, lipopolysaccharide (LPS)- free biomaterials used in surgically implantable prosthetic devices: polyurethane, woven dacron, and Velcro. Free radical formation as the superoxide (O2-) anion was evaluated by cytochrome c reduction in neutrophils that were exposed to the materials and then removed and in neutrophils allowed to remain in association with the materials. Neutrophils exposed to polyurethane or woven dacron for 30 or 60 min and then removed consistently exhibited an enhanced release of O2- after simulation via receptor engagement with formyl methionyl-leucyl- phenylalanine. Enhanced reactivity to stimulation via protein kinase C with phorbol myristate acetate, however, was not consistently observed. The cells evalu- ated for O2- release during continuous association with the biomaterials showed enhanced metabolic activity during short periods of association (especially with polyurethane and woven dacron). Although O2- release by neutrophils in association with these materials decreased with longer periods of incubation, it was not obliterated. These studies, therefore, show that several commonly used biomaterials activate neutrophils soon after exposure and that this activated state diminishes with prolonged exposure but nevertheless remains measurable. The diminishing level of activity with prolonged exposure, however, suggests that ultimately a depletion of reactivity may occur and may result in increased susceptibility to periprosthetic infection.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 20 (1993), S. 331-336 
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The virtues of chemical inertness and low surface energy which make polytetrafluoroethylene (PTFE) a valuable engineering polymer also account for the difficulty in achieving structural adhesive bonds. While plasma surface treatment has proven to be the most effective means of maximizing strength and permanence of adhesive bonds with the most inert of engineering polymers, a simple plasma treatment has proven elusive for PTFE. The following studies evaluate two very different plasma processes, activation and deposition, as a means to achieve reliable and high-strength structural adhesive bonds. Sodium naphthalene-etched PTFE is used as a control. Presented are ESCA data which support a theory that improvement is limited by a weakened boundary layer of the PTFE.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 19 (1981), S. 2987-2996 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Solid-state 13C-NMR spectra were obtained by cross-polarization and magic angle spinning of polymers prepared by injecting ethane, ethylene, and acetylene into a radiofrequency plasma. By use of the delayed decoupling technique to suppress protonated carbon peaks and difference spectroscopy five resolved spectral bands can be distinguished. These bands are assigned to (I) unsaturated nonprotonated, (II) unsaturated CH and CH2, (III) quaternary, (IV) methine and methylene, and (V) methyl carbons by comparison with standard 13C shifts compiled for organic materials. The relative amounts of these structural features in the polymers were determined quantitatively and the possible sources of errors considered.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 21 (1983), S. 1819-1829 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A detailed magic angle spinning 13C-NMR investigation of the intractable polymer prepared by plasma polymerization of toluene and isotopically labeled toluene led to a proposed model for the structure of the polymer and suggested some of the likely processes that occur in the gas phase leading to film formation. From the 13C spectra four resolved resonances permitted the determination of the contribution of nonprotonated and protonated unsaturated as well as methyl and other aliphatic carbons to the polymer structure. Specific 13C isotopic labeling of the methyl and phenyl C-1 toluene carbons in the injected liquid vapor allowed the destination of these carbons in the deposited polymer to be traced. The dominant structure is derived primarily from two precursors: benzyl radical and toluene itself. The 13C data further requires a net saturation of ca. 30% of the toluene double bonds and a net displacement of hydrogen by carbon on ca. 20% of the toluene ring carbons.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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