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  • 11
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Tissue reactions to rat lead samples, modelling for clinically used leads, were investigated in a late infection model, in which injection of bacteria was performed after a 3-week encapsulation process. At the site of injection, detachment of the original fibrous capsule, wound fluid infiltration, fibrin formation and granulocyte and macrophage infiltrations, occurred. Spreading of infection did not occur via the generally assumed direct bacterial adhesion to materials, but through blood vessels at the outside of capsules and through wound fluid passage at the interface and in the lumen of the lead sample. At day 5, infection had spread all over, but, apart from two small abscesses, seemed to be suppressed at day 10. However, probably due to luminal bacterial growth, at weeks 3 and 6 the reaction intensified showing larger abscesses with accumulations of lymphocytes. The results of this study represent a good basis for further studies aimed at developing infection-resistent lead material. Research efforts are first directed on modification of material surfaces to provide controlled release of antimicrobial agents.
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Applied Surface Science 70-71 (1993), S. 619-623 
    ISSN: 0169-4332
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 13
    ISSN: 1573-739X
    Keywords: Epoetin ; Injections, subcutaneous ; Pain ; Rating scales
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In this study, we examined the differences in pain score after subcutaneous injection of the epoetin preparations Eprex® and Recormon®. Patients (n=30) received 5 injections Eprex® and 5 injections Recormon® in a randomized double-blind sequence. 10 Min after receiving the injection the patient was asked to complete a visual and a verbal analogue scale and two descriptive scales. The results of 25 patients were used for statistical evaluation. The overall results indicate that there are significantly more patients reporting pain after subcutaneous injection of Eprex® than after Recormon® (11 versus 2 patients, p 〈0.05; McNemar test). 12 Patients reported no differences in pain. 43 Out of 123 injections Eprex® and 69 out of 125 injections Recormon® caused no pain (p 〈0.01; χ2 9.455). For 4 patients Recormon® was significantly (p 〈 0.05) less painful than Eprex®. It can be concluded that Recormon® may be a less painful alternative for individual patients reporting pain after subcutaneous injection of Eprex®.
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  • 14
    ISSN: 1573-739X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 15
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A surface modification technique was developed to achieve controlled release of gentamicin from implanted polyurethane (PU) rat lead samples. PU tubing first was provided with an acrylic acid/acrylamide copolymer surface graft and then loaded with gentamicin. This surface modification technique resulted in release of gentamicin base (GB) and was applied either to the inner luminal surface only (PU-GB-1x) or to both the inner and outer surfaces (PU-GB-2x). First we investigated whether the early tissue response was harmfully compromised when surface-modified rat lead samples were implanted without any infectious challenge. Additionally, the efficacy of this type of local gentamicin therapy was investigated by establishing its effect on tissue response and its ability to prevent lead-related infections after inoculation with Staphylococcus aureus. It was demonstrated that the applied surface modification(s) did not induce adverse effects although an increase in the infiltration of granulocytes and macrophages and an increase in the formation of wound fluid and fibrin were observed. This effect was stronger with PU-GB-2x than with PU-GB-1x. With bacterial inoculation the applied surface modification successfully suppressed the infectious challenge, PU-GB-2x more effectively than PU-GB-1x. PU-GB-2x also was more effective when compared to the gentamicin-delivery methods discussed in the first part of this two-part study, i.e., release through a vicinal gentamicin-containing collagen sponge and preoperative gentamicin solution-dipping of rat lead samples. © 1997 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
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  • 16
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 29 (1995), S. 1255-1266 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Polyacrylamide-grafted polyetherurethane sheets were modified by end-point and multipoint attachment of heparin. The surface-bound heparin was firmly attached. No release of heparin activity could be detected when the surface was rinsed at a wall shear rate of 2000 s-1. Uptake of antithrombin and thrombin inactivation were investigated under well-defined flow conditions by the use of a spinning device with an attached disk-shaped heparinized surface. It is demonstrated that the rate of thrombin inactivation at the antithrombin-heparin surface equals the maximal rate of transport of thrombin toward the surface when the surface coverage of antithrombin exceeds 10 pmol/cm2. This result indicates that a higher intrinsic catalytic efficiency of a surface does not necessarily result in a higher antithrombin activity. We varied the heparin content of the surfaces between 0 and 35 μg/cm2 by increasing the number of functional groups to which heparin could be covalently attached. The uptake of antithrombin increased with the heparin content of the surface, but the stoichiometry decreased from 2 to 0.5 pmol antithrombin/μg heparin. Apparently, antithrombin could not bind to heparins buried in the poly(acrylamide) layer. The rate of thrombin inactivation at surfaces with low heparin content (2 μg/cm2) fells below the transport limit of thrombin and became proportional with the heparin content of the surface. Although the contribution of surface-bound heparin to the neutralization of fluidphase thrombin was found to be negligible compared with the effect of fluid-phase antithrombin at physiologic relevant concentrations, these heparinized surfaces markedly delayed the onset of thrombin generation in platelet-rich plasma. It is concluded that the inhibition of locally produced thrombin might contribute to the thromboresistance of the heparinized surface. © 1995 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
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  • 17
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The effect of local gentamicin release through a vicinal collagen sponge or through preoperative solution-dipping of rat lead samples was investigated in an early-infection model. The efficacy of these methods and their effect on tissue response were determined. It was demonstrated that both methods of local gentamicin release suppress lead-related infectious complications as compared to the control lead, which showed a high presence of inflamed/infected tissues and bacterial growth at each explantation time point. The first day the vicinal collagen sponge was more effective in suppressing the infection than was the solution-dipped lead, probably because there is a faster and higher dose release of gentamicin from the sponge. However, continued implantation time revealed that gentamicin release from the solution-dipped lead was more effective than the sponge. This supports our hypothesis that the presence of lumina are decisive for bacterial growth and persistence of implant-related infections. © 1997 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
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  • 18
    ISSN: 0021-9304
    Keywords: biomaterials ; polyurethanes ; infection ; infection resistance ; surface modification ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Tissue reactions to implantable pacemaker leads were investigated in an early infection model in rabbits. Both standard leads and surface-modified leads were used. The surface modification technique was applied to achieve controlled release of the antibiotic gentamicin. The insulating polyurethane tubing material of the leads was provided with an acrylic acid/acrylamide copolymer surface graft and then loaded with gentamicin. Implantation periods varied from day 4, to week 3½, to week 10. We investigated tissue reactions in the absence of an infectious challenge and also the efficacy of surface-modified leads in preventing infection after challenge with Staphylococcus aureus was evaluated. It was demonstrated that the applied surface modification did not induce adverse effects although during early postimplantation an increase in infiltration of granulocytes and macrophages and wound fluid and fibrin deposition were observed. After bacterial challenge, standard leads were heavily infected at each explantation period, denoted by abscesses, cellular debris, and bacterial colonies. In contrast, little or no infection was observed, either macroscopically or by bacterial cultures, with the surface-modified leads. Microscopy showed little evidence of the bacterial challenge, and that primarily at day 4. It was concluded that the applied surface modification demonstrated enhanced infection resistance and thus represents a sound approach to the battle against infectious complications with biomaterials. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 41, 142-153, 1998.
    Additional Material: 12 Ill.
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  • 19
    Publication Date: 2003-01-01
    Description: Current advances in finite element computer codes and increase in computer power theoretically allow quantitative modelling of the geomechanical effects of hydrocarbon depletion from reservoirs. Here we show that it is technically possible to incorporate the full complexity of the 3D geological structure of a reservoir including faults into geomechanical models. In the workflow GOCAD is used for the structural modelling, integrated with DIANA for the geomechanical calculations. A case study on the Roswinkel gas field in the eastern Netherlands illustrates the working methodology. The case study clearly shows the strong dependency of gas depletion deformation effects on the prevailing tectonic stress field. Our models for gas depletion predict a stabilization of the stress field (further away from failure) for reservoirs in compressive and strike-slip regimes. On the other hand extensional stress regimes will result in failure of the reservoir, in agreement with observed earthquakes, provided that (a) the reservoir material or existing faults are weak and (b) the state of stress is close to failure of the material. The Roswinkel field, which is marked by a high abundance of earthquakes occurring after gas depletion started, is therefore most likely marked by an extensional tectonic regime and by geomechanically weak rock or pre-existing faults. According to base Tertiary fault displacements and the World Stress Map, the extension (minimum horizontal principal stress) is most likely NE-SW oriented.
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  • 20
    Publication Date: 1990-12-17
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
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