| 1. |
- Andersson, Ann-Sofie, et al.
(författare)
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Cell adhesion on supported lipid bilayers
- 2003
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Ingår i: Journal of biomedical materials research. Part A. - : Wiley. - 1549-3296 .- 1552-4965. ; 64:4, s. 622-9
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Tidskriftsartikel (refereegranskat)abstract
- The cell and protein repellent properties of supported phospholipid bilayer (SPB) membranes were investigated. The SPBs were prepared by vesicle adsorption on SiO(2) surfaces. The vesicles of phosphatidylcholine fuse and rupture, and form a supported bilayer covering the surface. We carried out cell culture experiments on several surfaces, including SPBs, using two types of epithelial cells to address the cell adhesional properties. The Quartz Crystal Microbalance Dissipation (QCM-D) technique was used to monitor the SPB formation and subsequent protein adsorption. Neither cell type adhered or proliferated on SiO(2) surfaces coated with SPBs, whereas both cell types adhered and proliferated on the three control surfaces of SiO(2), tissue culture glass, and TiO(2). The QCM-D measurements showed that about two orders of magnitude less mass adsorbed on a SPB surface compared to a TiO(2) surface, from serum-containing media (10% fetal bovine serum). The reduced adsorption on the SPB is a likely explanation for the nondetectable epithelial cell adhesion on the SPB surface. Biomembranes are therefore attractive candidate systems to achieve alternating cell-resistant and cell-interacting regions on surfaces, by including specific cell-binding proteins in the latter regions.
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| 2. |
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| 3. |
- Kjellson, Fred, et al.
(författare)
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Water uptake and release from iodine-containing bone cement.
- 2004
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Ingår i: Journal of Biomedical Materials Research. Part A. - : Wiley. - 1552-4965 .- 0021-9304 .- 1097-4636. ; 71:2, s. 292-298
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Tidskriftsartikel (refereegranskat)abstract
- Water uptake and release characteristics of PMMA cement containing the water-soluble contrast media iohexol or iodixanol have been investigated. The water uptake study revealed that iohexol had the highest uptake of water (3.7%) and that iodixanol had an uptake close to that of Palacos(R) R (2.3% and 1.9%). The curves obtained showed the materials to follow classic diffusion theory, with an initial linearity with respect to t(1/2) making it possible to calculate the diffusion coefficients. This showed iohexol to have the lowest diffusion coefficient, Palacos(R) R the highest, and iodixanol close to that of Palacos(R) R. The release study showed that more iohexol than iodixanol was released from the bone cement; the long-term release was above 25 mug/ml, for iohexol compared to slightly above 10 mug/mL for iodixanol. A muCT investigation showed that the risk of developing an observable radiolucent zone is negligible. (C) 2004 Wiley Periodicals, Inc.
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| 4. |
- Larsson, Jenny, 1974-, et al.
(författare)
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Anti-inflammatory effects of a titanium-peroxy gel: role of oxygen metabolites and apoptosis.
- 2004
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Ingår i: Journal of biomedical materials research. Part A. - : Wiley. - 1549-3296 .- 0021-9304 .- 1097-4636. ; 68:3, s. 448-57
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Tidskriftsartikel (refereegranskat)abstract
- Polymorphonuclear neutrophils (PMN) are among the first inflammatory cells to arrive at an implant interface, where they encounter with the foreign material and may produce reactive oxygen species (ROS). During the interaction between titanium and ROS, titanium-peroxy (Ti-peroxy) compounds may be formed. We used a Ti-peroxy gel, made from titanium and hydrogen peroxide, to study the effects of Ti-peroxy compounds on PMN. In the absence of serum, the Ti-peroxy gel decreased the oxidative response of PMN to yeast and PMA and reduced PMN apoptosis without inducing necrosis. These effects could not be ascribed to the release of hydrogen peroxide from the Ti-peroxy gel, because a steady-state hydrogen peroxide producing system failed to mimic the effects of the gel. The effects were similarly unaffected when PMN were preincubated with beta(2)-integrin antibodies, questioning the involvement of adhesion molecules. Nevertheless, when a filter was used to separate the Ti-peroxy gel from the cells, the gel effect on PMN life span was abolished, pointing to a contact-dependent mechanism. In the presence of serum, the Ti-peroxy gel had no effect on the PMN oxidative response and life span, but appeared rather inert. In summary, this study demonstrates that the Ti-peroxy gel has potentially anti-inflammatory properties through a combined peroxide and physical contact effect, supporting the notion that interactions between titanium and inflammatory cells are responsible for the good performance of titanium in vivo.
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| 5. |
- Nimeri, G, et al.
(författare)
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Oxygen radical production in neutrophils interacting with platelets and surface-immobilized plasma proteins : role of tyrosine phosphorylation
- 2003
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Ingår i: Journal of Biomedical Materials Research. - : Wiley. - 0021-9304 .- 1097-4636 .- 1549-3296. ; 67A:2, s. 439-447
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Tidskriftsartikel (refereegranskat)abstract
- The interaction between neutrophil granulocytes and platelets is considered to play an important role in the inflammatory process induced by an implanted foreign material. However, the cellular mechanisms involved remain incompletely understood. We used a luminol-dependent chemiluminescence (CL) technique to analyze the generation of reactive oxygen species (ROS) in human neutrophils interacting with different plasma protein-coated surfaces in the presence or absence of unstimulated or stimulated platelets. The role of tyrosine phosphorylation in the regulation of NADPH oxidase activity was evaluated with quantitative fluorescence microscopy and the specific tyrosine kinase inhibitor genistein. We found that the ROS-production is 2 to 3 times higher in neutrophils on immunoglobulin G (IgG)coated surfaces than in cells interacting with albumin- or fibrinogen-coated surfaces. Incubation with superoxide dismutase and catalase revealed that about 45% of the ROS was released extracellularly on IgG surfaces whereas corresponding values were 90% and 85% in neutrophils interacting with albumin and fibrinogen, respectively. The presence of platelets markedly increased the extracellular generation of ROS, mainly in neutrophils. interacting with IgG- or fibrinogen-coated surfaces whereas the intracellular production was only modestly affected. Quantitative fluorescence microscopy of neutrophils stained with FITC-conjugated anti-phosphotyrosine antibodies showed a correlation between tyrosine phosphorylation, cell spreading, and ROS production. Platelets markedly amplified the anti-phosphotyrosine staining on both fibrinogen- and IgG-coated surfaces whereas the low level of tyrosine phosphorylation in neutrophils on albumin-coated surfaces was not further elevated by platelets. Furthermore, the tyrosine kinase inhibitor genistein inhibited both extra- and intracellular ROS production in neutrophils regardless of the presence of platelets. We demonstrate that plasma protein coating and the presence of platelets are crucial for the inflammatory response of adhering neutrophils and that the oxidative response correlates with the extent of tyrosine phosphorylation of proteins in focal contacts. (C) 2003 Wiley Periodicals, Inc.
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| 6. |
- Söderholm, Patrik
(författare)
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Environmental policy in transition economies : will pollution charges work?
- 2001
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Ingår i: Journal of Environment and Development. - : SAGE Publications. - 1070-4965 .- 1552-5465. ; 10:4, s. 365-390
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Tidskriftsartikel (refereegranskat)abstract
- Many economists & analysts claim that extended use of pollution charges in environmental policy will have substantial efficiency advantages in transition economies. This article challenges this view & argues instead that the proposed policy presumes the existence of an already-functioning institutional framework. By focusing on the Russian case, the article discusses a number of reasons why it is difficult to implement pollution charges in an economic system in which Communist behavioral patterns & jurisdictions are still prevalent. The article identifies a number of institutional obstacles related both to enterprise behavior & to environmental regulation & enforcement. These obstacles suggest that it is appropriate to view environmental problems in transition economies primarily as the results of institutional inertia in the economic & political systems. The article ends by discussing alternative ways of controlling pollution in Russia & stresses the importance of improving the legitimacy & basic trust for environmental legislation.
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| 7. |
- Wetterö, Jonas, et al.
(författare)
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Interactions between surface-bound actin and complement, platelets, and neutrophils
- 2003
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Ingår i: Journal of Biomedical Materials Research. - : Wiley. - 0021-9304 .- 1097-4636 .- 1549-3296. ; 66A:1, s. 162-175
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Tidskriftsartikel (refereegranskat)abstract
- Actin exists as globular (G) monomers or polymeric filaments (F) in the cytoplasm of eukaryotic cells, mediating cell morphologic changes and motility. Large amounts of this protein may be released out to the extracellular compartment during tissue injury, but little is known about its role in biomaterial-related inflammation. We immobilized actin to methylated glass, methylated and aminated silicon, and gold model surfaces and studied the subsequent blood serum deposition and complement activation, generation of reactive oxygen species (ROS), and adhesion and aggregation of neutrophils and platelets. Null ellipsometry showed that approximately one monolayer of G-actin can be immobilized onto the model surfaces and that actin in buffer polymerized on top of this by the addition of K+ and Mg2+ ions to form a thicker layer of firmly bound F-actin. After serum incubation, F-actin bound low amounts of anti-complement factor 1q (anti-C1q). Cell responses upon contact with actin-coated surfaces were analyzed by luminol-amplified chemiluminescence, lumi-aggregometry, and fluorescence microscopy. It was shown that surface-triggered aggregation, spreading, and generation of ROS are down-regulated and comparable to the response by adsorbed albumin. However, F-actin on gold surfaces recruited platelets in a C1q-dependent manner. We conclude that in vitro adsorbed actin is a weak complement, platelet, and neutrophil activator, but that F-actin associates with both C1q and platelets. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 162–175, 2003
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