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  • Polymer and Materials Science  (7)
  • Freeze-fracture  (2)
  • Life and Medical Sciences  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Biochimica et Biophysica Acta (BBA)/Biomembranes 777 (1984), S. 41-55 
    ISSN: 0005-2736
    Keywords: (R. sphaeroides) ; Cell cycle ; Chromatophore ; Electron microscopy ; Freeze-fracture ; Photosynthetic membrane
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Medicine , Physics
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Biochimica et Biophysica Acta (BBA)/Biomembranes 688 (1982), S. 605-621 
    ISSN: 0005-2736
    Keywords: (Rps. sphaeroides) ; Chromatophore fusion ; Freeze-fracture ; Membrane fragment ; Membrane orientation
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Medicine , Physics
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 24 (1986), S. 1173-1183 
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mass spectral analysis of the gas-chromatography-separated pyrolysis products of the solid polymer formed in a toluene plasma has shown the presence of a number of phenyl-containing structures. Of particular interest is the biphenyl product, whose isotopic distribution patterns are very different for the polymers prepared from natural 13C abundance and 13CH3-labeled toluene. This result is interpreted in terms of carbon atom scrambling via seven-membered-ring intermediates in the gas phase during plasma polymerization. A comparison of measured isotopic patterns with calculated patterns reveals that 34 ± 10% of the toluene molecules scramble prior to polymer formation. This value is similar to an upper bound on scrambling determined here but based on earlier NMR results1 and reinforces a model for the structure of plasma-polymerized toluene established in that work.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 4
    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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  • 5
    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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  • 6
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Biomaterial-associated infection results in increased morbidity and mortality, and may occur because of nonproductive premature activation of neutrophils resulting in impaired phagocyte function at the biomaterial surface in the event of bacterial challenge. To further explore the effects of this premature activation, we evaluated the supernatants of biomaterial associated neutrophils to determine whether soluble mediators were released, and the likely role of these mediators. We show that these supernatants contain a chemoattractant and thereby induce chemotaxis by fresh neutrophils. No evidence of enhanced oxidative free radical production by either unstimulated neutrophils or a primed response to other mediators occurs when neutrophils were incubated with these supernatants. We also examined the effect of adding fresh neutrophils to a biomaterial surface containing a previous inoculum of neutrophils, and observed that the fresh cells did not become stimulated to release reactive oxygen intermediates (ROI) and also exhibited impaired killing of staphylococci. These studies suggest that not only does the biomaterial surface activate the initial wave of neutrophils but that subsequent waves of neutrophils exhibit an impaired host-defense function. These results are consistent with the known impairment of host defense in the presence of biomaterials, and provide evidence for a long-term down-regulation of neutrophil function at biomaterial surfaces. © 1995 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 224 (1989), S. 426-430 
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The pectoralis (pars thoracicus) of the domestic pigeon (Columba livia) is divisible into two anatomical parts, the pars sternobrachialis (SB) and the pars thoracobrachialis (TB). Innervation to this complex is from rostral and caudal branches of the brachial ventral cord. In four anesthetized pigeons, the distribution of muscle units associated with each nerve branch was mapped after prolonged stimulation of each nerve and subsequent analysis for muscle fiber glycogen. An additional three animals were used to analyze the morphology, distribution, and histochemical profiles of the muscle fibers in the SB and TB subregions. Fibers were characterized on the basis of their reactions for myofibrillar adenosine triphosphates (alkaline and acid preincubation) and reduced nicotinamide adenine dinucleotide diaphorase (NADH-D). The SB is primarily innervated by the rostral nerve branch and the TB by the caudal nerve branch. For two-thirds of the muscle's length, the SB is separated from the TB by an aponeurosis, the membrana intermuscularis (MI). SB and TB fibers located posteroventral to the caudal margin of the MI are innervated variously by both nerves. Two populations of fibers were recognized, distinguishable primarily by (1) fiber diameter and (2) density of the NADH-D reaction product. Compared to the TB, the SB possesses a higher average percentage of large fibers. Within the SB but not the TB the percentage of large fibers increases from deep to superficial. These data support our previous findings that the pars thoracicus of the pigeon is partitioned into at least two functional subunits, each with a potential for independent action on the wing during flight.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 8
    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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  • 9
    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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  • 10
    Electronic Resource
    Electronic Resource
    Hoboken, NJ [u.a.] : Wiley-Blackwell
    Journal of Orthopaedic Research 3 (1985), S. 325-330 
    ISSN: 0736-0266
    Keywords: Fracture healing ; Biomechanics ; External fixation ; Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Fercture site axial rigidity was monitored nonestructively at weekly intervals during healing of tibial osteotomies in adult rabbits. Two groups of 20 rabbits each were treated with external fixators of two different rigidities. Four animals from each group were killed at 3,5,6,7, and 8 weeks to determine the bending moments at failure of the healing fractures. Normal fracture healing was accompanied by characteristic phases in the development of fracture site axial rigidity. From 0 to 3 weeks there was a period of low and approximately constant rigidity, followed by a linear increase during 3 to 5 weeks to an approximately three to four times greater rigidity. The maximum average normalized axial rigidities were reached at 6 weeks and were 57% (high rigidity group) and 77% (low rigidity group) of the untreated contralatreal controls. The Maximum average normalized failure moments occurred at 8 weeks and were 48% (high rigidity) and 44% (low rigidity) of controls. The differences due to fixator rigidity were not statistically significant except for a large increse in failure moments at 3 weeks for the low rigidity group. Axial rigidities were correlated (r2 = 0.74 and 0.53, respectively) with failure moments, but only during the first 6 weeks. The monitoring technique provides a nondestructive means for following the biomechanical progress of fracture healing in in an animal model. The occurrence of the characteristic increase in fracture site axial rigidity at 3 to 5 weeks can also be used to distinguish between normal and abnormal healing.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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