| 41. |
- Rosengren, Anita, et al.
(författare)
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Reactive capsule formation around soft-tissue implants is related to cell necrosis
- 1999
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Ingår i: Journal of Biomedical Materials Research. - 0021-9304. ; 46:4, s. 458-464
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Tidskriftsartikel (refereegranskat)abstract
- Low-density polethylene disks with smooth or course surfaces were implanted in the abdominal wall of rats, and the tissue response was evaluated after 1, 6, or 12 weeks. Cell damage was detected by two different methods. Cells with increased membrane permeability could be identified using fluorescence microscopy by injection of propidium iodide prior to the killing of the rats. Second, cell death was verified by detection of DNA fragmentation. At 1 week a considerable number of the interfacial cells was stained with propidium iodide. Propidium-iodide-positive cells also were enriched at the edges of the disks irrespective of surface texture. The numbers of positive interfacial cells decreased markedly over time. Cells with DNA fragmentation initially displayed a scattered distribution; at later time points they appeared mainly in the outer portion of the enveloping capsule. The reactive capsule was thicker for the smooth surface, and there was a positive correlation between capsule thickness and propidium-iodide-positive cells at earlier implantation periods. The results suggest that the thickness of the reactive capsule is related to the extent of cell necrosis. It is suggested that the major initiator for this cell necrosis is mechanical shear since cell necrosis was found mainly in areas where mechanical shear could be expected.
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| 42. |
- Rosengren, Agneta, et al.
(författare)
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Tissue reactions to polyethylene implants with different surface topography
- 1999
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Ingår i: Journal of Materials Science: Materials in Medicine. - 1573-4838. ; 10:2, s. 75-82
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Tidskriftsartikel (refereegranskat)abstract
- This study investigates the importance of implant surface topography on soft tissue response. The tissue response in the rat abdominal wall to discs of low density polyethylene with smooth to coarse surfaces was evaluated after one, six or 12 weeks. Capsule thickness and immunohistochemical quantification of monocytes-macrophages were used as measures. The macrophage specific antibody ED1 was used for identification of newly recruited macrophages and the ED2 antibody for the mature tissue macrophages. The smoother surfaces gave a thicker capsule than the rougher surfaces, and at one week also larger total numbers of cells and ED1 positive macrophages at interface. The capsule thickness increased over time for the smooth and intermediate surface topographies. In contrast, the cell numbers generally decreased over time. In conclusion, a coarse surface elicited lesser tissue reaction compared with a smooth surface.
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| 43. |
- Sahlin, Herman, et al.
(författare)
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Anti-inflammatory properties of micropatterned titanium coatings
- 2006
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Ingår i: Journal of Biomedical Materials Research. Part A. - : Wiley. - 1552-4965 .- 1549-3296. ; 77A:1, s. 43-49
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Tidskriftsartikel (refereegranskat)abstract
- Prolonged inflammation and reactive oxygen species (ROS) generated around an implanted biosensor are the primary causes of the foreign body response, including encapsulation of biosensor membranes. We have previously demonstrated that TiO2 surfaces reduce ROS. Here we investigated the potential of using the anti-inflammatory properties of TiO2 in the design of biosensor membranes with improved long-term in vivo transport properties. Micropatterned Ti films were sputtered onto quartz surfaces in a series of hexagonally distributed dots with identical coverage area of 23% and dot size ranging from 5 to 100 microm. The antioxidant effect of the surfaces was investigated using a cell-free peroxynitrite donor assay and assays of superoxide released from stimulated surface-adhering neutrophils and macrophages. In all three assays, the amount of ROS was monitored using luminol-amplified chemiluminescence. Patterned surfaces in all experimental models significantly decreased ROS compared to the etched surfaces. In the cell-free experiment, the ROS reduction was only dependent on fractional surface coverage. In the cell experiments, however, a dot-size-dependent ROS reduction was seen, with the largest reduction at the smallest dot-size surfaces. These results indicate that micropatterned surfaces with small dots covering only 23% of the surface area exhibit similar antioxidative effect as fully covered surfaces.
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| 44. |
- Smith, Garrett, et al.
(författare)
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Soft tissue response to titanium dioxide nanotube modified implants.
- 2011
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Ingår i: Acta Biomaterialia. - : Elsevier BV. - 1878-7568 .- 1742-7061. ; 7, s. 3209-3215
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Tidskriftsartikel (refereegranskat)abstract
- Titanium is widely used clinically, yet little is known regarding the effects of modifying its three-dimensional surface geometry at the nanoscale level. In this project we have explored the in vivo response in terms of nitric oxide scavenging and fibrotic capsule formation to nano-modified titanium implant surfaces. We compared titanium dioxide (TiO(2)) nanotubes with 100nm diameters fabricated by electrochemical anodization with TiO(2) control surfaces. Significantly lower nitric oxide was observed for the nanostructured surface in solution, suggesting that nanotubes break down nitric oxide. To evaluate the soft tissue response in vivo TiO(2) nanotube and TiO(2) control implants were placed in the rat abdominal wall for 1 and 6weeks. A reduced fibrotic capsule thickness was observed for the nanotube surfaces for both time points. Significantly lower nitric oxide activity, measured as the presence of nitrotyrosine (P<0.05), was observed on the nanotube surface after 1week, indicating that the reactive nitrogen species interaction is of importance. The differences observed between the titanium surfaces may be due to the catalytic properties of TiO(2), which are increased by the nanotube structure. These findings may be significant for the interaction between titanium implants in soft tissue as well as bone tissue and provide a mechanism by which to improve future clinical implants.
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| 45. |
- Stevens, H Y, et al.
(författare)
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COX-2 is necessary for venous ligation-mediated bone adaptation in mice
- 2006
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Ingår i: Bone. - : Elsevier BV. - 1873-2763 .- 8756-3282. ; 38:1, s. 93-104
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Tidskriftsartikel (refereegranskat)abstract
- In osteoblasts, cyclooxygenase 2 (COX-2) is the major isozyme responsible for production of prostaglandins. Prostaglandins are local mediators of bone resorption and formation and are known to be involved in bone's adaptive response to fluid shear stress (FSS). We have previously described a model of trabecular bone loss in hindlimb-suspended mice and rats and demonstrated partial protection from osteopenia by ligation of the femoral vein. The increased FSS resulting from this ligation drove bone adaptation in the absence of mechanical loading. In this study, we investigated the role of COX-2 in this adaptive response to FSS by use of COX-2 knockout mice. COX-2 knockout ("KO"), COX-2 heterozygote ("HET"), and COX-2 wild-type ("WT") animals all lost comparable amounts of trabecular bone from sham-operated limbs as a result of suspension. In WT mice, loss of trabecular BMD in the venous-ligated limb was significantly less than that of the sham-operated limb; this effect, however, was not seen in KO or HET mice. Percentage gain in femoral periosteal circumference was greater in the ligated limb than the sham-operated limb for WT mice. KO and HET mice already possess femora of larger periosteal circumference than their WT littermates and ligation in these bones did not result in an increase in perimeter relative to sham. Histomorphometry on embedded bones revealed thinner cortices and less mineralizing perimeter in KO femora than controls. In conclusion, this is the first in vivo study to show that fluid-flow-mediated bone adaptation, independent of mechanical strain, is COX-2 dependent.
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| 46. |
- Svanborg Eden, C, et al.
(författare)
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Influence of adhesins on the interaction of Escherichia coli with human phagocytes
- 1984
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Ingår i: Infection and Immunity. - 1098-5522. ; 44:3, s. 672-680
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Tidskriftsartikel (refereegranskat)abstract
- The fitness between bacterial adhesins and target cell receptors, determining bacterial adherence to epithelial cells in urinary tract infections, was shown to influence also the interaction with human polymorphonuclear leukocytes (PMNL). Two sets of homogenic strains, constructed to express either, both, or none of the globotetraosylceramide-sensitive (GS) adhesins specific for globoseries glycolipid receptors or the mannose-sensitive (MS) adhesins inhibited by alpha-methyl mannoside were compared regarding charge, hydrophobicity, and binding to PMNL. The mutants of a hydrophilic pyelonephritis strain required MS adhesins for binding to and activation of the PMNL. Removal of the MS adhesins from the mutant carrying both MS and GS adhesins abolished chemiluminescence and binding. A pronounced chemiluminescence reaction was induced by the hydrophobic strain without GS or MS adhesins . Transformants of this strain expressing the MS adhesin bound to and activated the PMNL. Poor binding and activation were found with mutants and transformants carrying only the GS adhesins . The improved reactivity after coating of the PMNL with the appropriate receptor glycolipid supported the previously reported absence of globoseries glycolipids in those cells as the reason for the refractoriness to bacteria with GS adhesins . The mechanism of binding, which improves epithelial cell adhesion, may prevent binding to PMNL, thus improving the survival of Escherichia coli in the kidney.
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| 47. |
- Terada, Nobuki, et al.
(författare)
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Bioartificial nerve grafts based on absorbable guiding filament structures--early observations
- 1997
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Ingår i: Scandinavian Journal of Plastic and Reconstructive Surgery and Hand Surgery. - : Informa UK Limited. - 1651-2073 .- 0284-4311. ; 31:1, s. 1-6
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Tidskriftsartikel (refereegranskat)abstract
- Gaps 10 mm wide in the sciatic nerves of 64 rats were bridged by bioartificial nerve grafts consisting of a silicone tube containing seven longitudinally placed filaments made of non-absorbable, (polyamide [Ethilon]) or absorbable, material (polydioxanone [PDS], polyglactin [Vicryl], and catgut). The purpose was to study the organisation of axonal growth inside the tube along such filaments. After two and four weeks histological techniques were used to study the contents of the tube and at four weeks immunohistological techniques were used to confirm the presence of axons distal to the tube. In all experimental groups axons had traversed the tube and reached the distal segment after four weeks. Inside the tube axons were organised in multiple minifascicles in all groups, but there were no axons growing in direct contact with the filaments. We conclude that resorbable filaments placed inside a silicone tube do not disturb axonal growth across the tube.
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| 48. |
- Terada, N, et al.
(författare)
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The role of macrophages in bioartificial nerve grafts based on resorbable guiding filament structures
- 1997
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Ingår i: Journal of Materials Science: Materials in Medicine. - 1573-4838. ; 8:6, s. 391-394
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Tidskriftsartikel (refereegranskat)abstract
- A 10 mm gap in a rat sciatic nerve was bridged by a bioartificial nerve graft consisting of a silicone tube containing seven longitudinally placed filaments made of non-resorbable material (polyamide [Ethilon]) or resorbable materials (polydioxanon [PDS], polyglactin [Vicryl] or catgut). The purpose was to study the tissue reaction induced by the four different types of materials. At 4 weeks an immunocytochemical technique, using ED1 and ED2 monoclonal antibodies, was used to study the presence and location of macrophages. A large number of macrophages were found accumulating on the surface of catgut and polyglactin, while few were found on the surface of polyamide and polydioxanon filaments. It is concluded that the cell layers on the filament surface mainly consisted of ED1 positive cells and their thickness depends on the filament materials.
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| 49. |
- Thomsen, P, et al.
(författare)
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Acute synovitis induced by preformed immune complexes
- 1986
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Ingår i: Scandinavian Journal of Rheumatology. - : Informa UK Limited. - 1502-7732 .- 0300-9742. ; 15:2, s. 134-142
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Tidskriftsartikel (refereegranskat)abstract
- The morphology of acute immune complex (IC) elicited synovitis in rabbit knee joints was studied, as well as IC-induced leukocyte activation in vivo and in vitro. Acute synovitis was induced by intra-articular injection of in vitro preformed, complement activating bovine serum albumin (BSA)-anti-BSA IC. Within 30 min, migration of polymorphonuclear granulocytes (PMNGs) was observed. Scanning electron microscopy showed that adhering, apparently activated leukocytes were attached to the synovial lining, often forming clusters. Phagocytosis of IC was evident, as immunoglobulins were detected within the leukocyte cytoplasm by the direct immunofluorescence technique. At the peak accumulation of PMNGs, focal erosions of the synovial lining were observed. Later, monocytes and macrophages appeared and degenerated PMNGs were found, sometimes within the cytoplasm of large macrophages. Chemiluminescence experiments showed a maximum in vitro activation of leukocytes by complement activating IC formed near optimal precipitation proportions and in slight antigen excess, whereas IC in large antigen excess gave a smaller and later response.
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| 50. |
- Thomsen, P, et al.
(författare)
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Inhibitory effect of honey bee venom on immune complex mediated leukocyte migration into rabbit knee-joints
- 1984
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Ingår i: Agents and Actions. - 0065-4299. ; 14:5-6, s. 662-666
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Tidskriftsartikel (refereegranskat)abstract
- The anti-inflammatory effect of purified honey bee venom (HBV) was studied using a recently described animal model in which preformed immune complexes were injected into rabbit knee-joints. As little as a single injection of 1.2 micrograms HBV/kg body weight subcutaneously significantly reduced the immune complex induced joint inflammation as measured by reduction in leukocyte counts in the joint fluid. This decrease was obvious 3 and 6 but not 9 hours after induction of the inflammation. There was no significant effect on leukocyte random migration, chemotactic responsiveness or phagocytosis, indicating that HBV did not interfere with normal phagocyte motility and ingestion. The modifying effects by HBV on the inflammatory response to immune complexes in vivo is most likely due to interference with other components of the inflammatory response.
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