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  • 1
    Electronic Resource
    Electronic Resource
    Intermittent micromotion and polyethylene particles inhibit bone ingrowth into titanium chambers in rabbits (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 6 (1995), S. 161-165 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: We performed a histomorphological and morphometric analysis of the effects of short daily periods of micromotion and phagocytosable particles of high density polyethylene (PE) on bone ingrowth into a 1 × 1 × 5 mm canal within a titanium chamber in rabbits. The micromotion chamber (MC) was implanted in the tibia of nine mature New Zealand white rabbits. After osseointegration and first harvest of tissue, 40 micromotions (amplitude = 0.5 mm) were applied daily at a rate of 1 Hz for a 3-week period. The tissue within the chamber was then harvested. For the second treatment, PE particles (108/mL) were placed within the canal. The tissue in the chamber was harvested 3 weeks later. The next treatment was a 3-week rest period, in which neither micromotion nor particles were utilized; a harvest followed. The final treatment combined PE particles and micromotion, followed by a harvest 3 weeks later. Sections from control harvests contained extensive trabecular bone arranged longitudinally throughout the canal in a fibrovascular stroma. Micromotion produced longitudinally oriented fibrous tissue within the chamber. PE particles were associated with macrophages, surrounding and engulfing the birefringent particles. The combination of particles and micromotion produced a fibrous stroma laden with macrophages. PE particles and micromotion, alone or together, produced a similar effect in inhibiting bone ingrowth, compared to nonmoved chambers without particles. In this short-term experiment, no additive or potentiating effect of these two stimuli could be demonstrated. © 1995 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jab.770060303
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Histological, chemical, and crystallographic analysis of four calcium phosphate cements in different rabbit osseous sites (1998)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 43 (1998), S. 451-461 
    Details
    ISSN: 0021-9304
    Keywords: calcium phosphate(s) ; brushite ; hydroxyapatite ; calcite ; remodeling ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Four calcium phosphate cement formulations were implanted in the rabbit distal femoral metaphysis and middiaphysis. Chemical, crystallographic, and histological analyses were made at 2, 4, and 8 weeks after implantation. When implanted into the metaphysis, part of the brushite cement was converted into carbonated apatite by 2 weeks. Some of the brushite cement was removed by mononuclear macrophages prior to its conversion into apatite. Osteoclastlike cell mediated remodeling was predominant at 8 weeks after brushite had converted to apatite. The same histological results were seen for brushite plus calcite aggregate cement, except with calcite aggregates still present at 8 weeks. However, when implanted in the diaphysis, brushite and brushite plus calcite aggregate did not convert to another calcium phosphate phase by 4 weeks. Carbonated apatite cement implanted in the metaphysis did not transform to another calcium phosphate phase. There was no evidence of adverse foreign body reaction. Osteoclastlike cell mediated remodeling was predominant at 8 weeks. The apatite plus calcite aggregate cement implanted in the metaphysis that was not remodeled remained as poorly crystalline apatite. Calcite aggregates were still present at 8 weeks. There was no evidence of foreign body reaction. Osteoclastlike cell remodeling was predominant at 8 weeks. Response to brushite cements prior to conversion to apatite was macrophage dominated, and response to apatite cements was osteoclast dominated. Mineralogy, chemical composition, and osseous implantation site of these calcium phosphates significantly affected their in vivo host response. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 43: 451-461, 1998
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Effects of polyethylene particles on tissue surrounding knee arthroplasties in rabbits (1998)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 43 (1998), S. 123-130 
    Details
    ISSN: 0021-9304
    Keywords: total joint replacement ; animal model ; particles ; polyethylene ; interface ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Clinical studies suggest a role for polyethylene (PE) wear debris in the pathogenesis of osteolysis and loosening of total joint replacements. In this study, submicron particles of ultrahigh molecular weight PE (UHMWPE) were placed around pressfit tibial hemiarthroplasties in rabbits to determine the biological reaction. After 6 months the periprosthetic tissue was harvested and characterized biochemically by measuring the extracellular matrix macromolecules, collagen, and glycosaminoglycan (GAG) and quantifying the expression of inflammatory/osteolytic mediators [prostaglandin E2 (PGE2), hexosaminidase, transforming growth factor β (TGFβ), and interleukins-6 and -1 (IL-6, IL-1)]. Particle exposure resulted in a decrease in levels of total extracellular matrix molecules including a 53% decrease in total GAG (p 〈 0.05) and a 74% decrease in total collagen (p 〈 0.005). Collagen content remained significantly decreased when normalized for cellularity (DNA content). Total TGFβ release exhibited a downward trend (p = 0.06) in the particle exposed group. Hexosaminidase and PGE2 levels did not show a difference between groups; however, when normalized for cellularity, PGE2 values exhibited an upward trend in the particle exposed group (p = 0.1). IL-6 was undetected by bioassay and ELISA. Previous studies emphasized that PE debris enhances the degradation of bone. The data from this in vivo model suggest that submicron UHMWPE particles may also act to inhibit biosynthetic pathways of bone and mesenchymal tissue. Decreased levels of collagen, GAG, and TGFβ expression may indicate suppression of bone formation, possibly through a downregulation of osteoblast activity. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 43: 123-130, 1998
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 4
    Electronic Resource
    Electronic Resource
    Effect of size, concentration, surface area, and volume of polymethylmethacrylate particles on human macrophages in vitro (1996)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 30 (1996), S. 463-473 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: This study investigated effects of different sizes, concentrations, volumes, and surface areas of polymethylmethacrylate (PMMA) particles on human macrophages. Adherent peripheral blood monocytes isolated from five healthy individuals were exposed for 48 h to phagocytosable (0.325 μm and 5.5 μm) and nonphagocytosable (200 μm) spherical particles. Each particle size was tested over a range of concentrations (104-1011 particles per milliliter [0.325 μm], 102-107 particles per milliliter [5.5 μm], 101-104 particles per milliliter [200 μm]) to provide overlap in number, volume, and surface area. Primary human monocyte/macrophages were cultured in macrophage serum-free medium and 5% fetal calf serum. Macrophage viability was assessed by 3H-thymidine uptake and activation was quantified by release of interleukin-1β, interleukin-6, tumor necrosis factor-α, prostaglandin E2 (PGE2), and the lysosomal enzyme hexosaminidase. Medium alone served as a negative control; lipopolysaccharide (10 μg/mL) was also tested. PMMA particles were not toxic to human macrophages at any concentration tested. The smallest phagocytosable particles (0.325 μm) stimulated the release of interleukin-1β, interleukin-6, prostaglandin E2, and hexosaminidase at concentrations of 1010-1011 particles/mL. The release of cytokines, PGE2, and hexosaminidase depended on the size, concentration, surface area, and volume of the phagocytosable particles. This study demonstrates that PMMA particle load Mi.e., the concentration of phagocytosable particles per tissue volume, characterized by size, surface area, and volume, rather than simply particle number - determines the degree of macrophage activation. © 1996 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 5
    Electronic Resource
    Electronic Resource
    Inducible nitric oxide synthase messenger RNA levels in hip periprosthetic tissue: A preliminary study (1998)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 40 (1998), S. 419-424 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Nitric oxide (NO) is a ubiquitous molecule that has been associated with inflammation, arthritis, autoimmune disease, bone resorption, and other biological processes. Elucidating the role of NO at the bone-implant interface may further our understanding of the biological processes of osseointegration, loosening, and osteolysis. This study demonstrates the use of a molecular biological technique to investigate the possible role of NO in prosthetic loosening and periprosthetic bone resorption following total hip arthroplasty. Periprosthetic tissue from 12 patients undergoing revision hip arthroplasty was harvested and total ribonucleic acid (RNA) was extracted. In six of the 12 patients, multiple samples from different anatomic locations along the same interface were studied. To estimate the amount of NO present in the tissues in vivo, the level of inducible NO synthase (iNOS) messenger RNA (mRNA) was determined using a ribonuclease (RNase) protection assay. Inducible NOS mRNA was detected in every tissue sample; there was no correlation between iNOS mRNA levels and clinical loosening or osteolysis. Analysis of multiple tissue samples from the same prosthetic component revealed that the levels of iNOS mRNA vary greatly, confirming the heterogeneous nature of the interface. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 419-424, 1998.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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