| 1. |
- Basnakova, G, et al.
(författare)
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Identification of Nickel Uranyl Phosphate Deposits on Citrobacter sp. Cells by Electron Microscopy with Electron Probe X-ray Microanalysis and by Proton-Induced X-ray Emission Analysis
- 1998
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 32:6, s. 760-765
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Tidskriftsartikel (refereegranskat)abstract
- Immobilized cells of a Citrobacter sp. can remove heavy metals from wastewaters by deposition ofmetals with enzymatically liberated phosphate. Nickel is not removed effectively by this technique, but Ni2+ can be intercalated into cell-bound, crystalline HUO2PO4 previously deposited enzymatically. This technique for efficient removal of Ni from solution has been generically termed microbially enhanced chemisorption of heavy metals(MECHM). The nickel uranyl phosphate deposits bound to Citrobactersp. cells immobilized in polyacrylamide gel (FAG) were analyzed using scanning transmission electronmicroscopy with electron probe X-ray microanalysis (EPXMA) and proton-induced X-ray emissionanalysis(PIXE). Both methods gave the molar ratios of nickel, uranium, and phosphorus in the depositsas close to 1:2:2 in all analyzed parts of the sample. EPXMA proved that the deposits were localized onthe surface of cells inside FAG particles as well as those immobilized on the edge. Small deposits ofnickel uranyl phosphate were also found in FAG between the cells, indicating the possible involvementof extracellular polymeric substances (EPS) in the creation of intercellular deposits. These findings confirm the mechanism of MECHM and show that this mechanism operates throughout the immobilized cell matrix. The use of two independent methods of solid-state analysis in a common sample provides validation of both techniques for the spatial and quantitative analysis of biomass-bound elements.
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| 2. |
- Briggs, Ewan P, et al.
(författare)
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Formation of highly adherent nano-porous alumina on Ti-based substrates : a novel bone implant coating
- 2004
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Ingår i: Journal of materials science. Materials in medicine. - 0957-4530 .- 1573-4838. ; 15:9, s. 1021-1029
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Tidskriftsartikel (refereegranskat)abstract
- Thin, nano-porous, highly adherent layers of anodised aluminium formed on the surface of titanium alloys are being developed as coatings for metallic surgical implants. The layers are formed by anodisation of a 1–5 m thick layer of aluminium which has been deposited on substrate material by electron beam evaporation. The surface ceramic layer so produced is alumina with 6–8 wt % phosphate ions and contains 5×108 cm–2 pores with a 160 nm average diameter, running perpendicular to the surface. Mechanical testing showed the coatings'' shear and tensile strength to be at least 20 and 10 MPa, respectively. Initial cell/material studies show promising cellular response to the nano-porous alumina. A normal osteoblastic growth pattern with cell number increasing from day 1 to 21 was shown, with slightly higher proliferative activity on the nano-porous alumina compared to the Thermanox control. Scanning electron microscopy (SEM) examination of the cells on the porous alumina membrane showed normal osteoblast morphology. Flattened cells with filopodia attaching to the pores and good coverage were also observed. In addition, the pore structure produced in these ceramic coatings is expected to be suitable for loading with bioactive material to enhance further their biological properties.
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| 3. |
- Karlsson, Marjam, et al.
(författare)
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Initial in vitro interaction of osteoblasts with nano-porous alumina
- 2003
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Ingår i: Biomaterials. - 0142-9612 .- 1878-5905. ; 24:18, s. 3039-3046
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Tidskriftsartikel (refereegranskat)abstract
- In the present study we have used a characterised primary human cell culture model to investigate cellular interactions with nano-porous alumina. This material, prepared by anodisation, is being developed as a coating on titanium alloy implants. The structure of the alumina, as determined by X-ray diffraction and transmission electron microscopy, was amorphous. When studying cell/material interactions we used both biochemical and morphological parameters. Cell viability, proliferation and phenotype were assessed by measurement of redox reactions in the cells, cellular DNA, tritiated thymidine ([H-3]-TdR) incorporation and alkaline phosphatase (ALP) production. Results showed a normal osteoblastic growth pattern with increasing cell numbers during the first 2 weeks. A peak in cell proliferation was seen on day 3, after which cell growth decreased, followed by an increase in ALP production, thus indicating that the osteoblastic phenotype was retained on the alumina. Cell adhesion was observed, the osteoblast-like cells having a flattened morphology with filipodia attached to the pores of the material. SDS-PAGE and western blot measurements showed that the nano-porous alumina was able to adsorb fibronectin. Trace amounts of aluminium ions were measured in the surrounding medium, but no adverse effect on cell activity was observed.
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| 4. |
- Pinheiro, Thomas Taro, et al.
(författare)
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Airborne Particulate Matter Localisation in the Human Respiratory System
- 1999
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Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - 0168-583X .- 1872-9584. ; 158:001-004, s. 499-504
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Tidskriftsartikel (refereegranskat)abstract
- Respired particles accumulated in the epithelial regions of trachea and bronchi were identified and characterised using micro-PIXE elemental mapping of thin frozen sections carried out at the Oxford Nuclear Microprobe facility. Isolated particles with diameters of 2-10 mu m could be detected, mainly atthe trachea epithelial surface. In bronchi respiratory mucosa, granular regions can also be observed that may correspond to particle agglomerations (2-4 mu m diameters) and/or inclusions inmacrophages. Particles, observed in the upper regions of the respiratory tract consist mainly of earth crust elements such as Al, Si, Ca and Fe. Occasionally, Ti and Zn are also present. Particles observedin the bronchi have a more varied chemical composition. Elements such as V, Cr, Mn, Fe, Cu, Zn were detected, mainly in association with S, K, Ca or Si.
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| 5. |
- Pålsgård, Eva, et al.
(författare)
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Bone growth and bone development in the presence of implants or after induced leg-lengthening is studied using the Oxford scanning proton microprobe
- 1997
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Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - 0168-583X .- 1872-9584. ; 130:1-4, s. 431-438
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Tidskriftsartikel (refereegranskat)abstract
- To respond to varying environmental demands the bone tissue in the body is under continual reconstruction throughout life. It is known that metallic elements are important for maintaining normal bone structure, bur their roles are not well understood. More information about the effects of metal excess or deficiency is needed to help in the development of metallic bone implants and to improve the treatment of bone fractures and defects. The Oxford Scanning Proton Microprobe (SPM) is being applied in two studies involving metal ions in bone: (1) bone regrowth and bonding to titanium bone implants may be influenced by diffusion of Ti ions into the bone. We are using microPIXE to determine the metal ion content of bone developing in contact with implants of pure Nb, Ti and Ti alloys. (2) Bone lengthening as a surgical procedure is induced by fracturing the bone and allowing it to heal with a small gap between the fractured ends created by the use of external fixators. The gap can be slowly increased during the healing process to stimulate the production of new bone. The enzymes and other constituents of the developing bone need certain metals for their function. Using experimental animals we have studied the concentrations of the metals and whether a deficiency of trace metals limits the optimum rate of bone lengthening.
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| 6. |
- Pålsgård, Eva, et al.
(författare)
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Direct measurement of elemental distributions in insulin-producing cells using nuclear microscopy
- 1996
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Ingår i: Cellular and Molecular Biology. - 0145-5680 .- 1165-158X. ; 42:1, s. 49-57
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Tidskriftsartikel (refereegranskat)abstract
- The nuclear microprobe was used to study elemental distributions in cultured insulin-producing cellsand in pancreatic tissue. To see whether insulin producing cells are polarized, the cells were stimulatedin the presence of Sr as a Ca analogue. The cells were stimulated to secrete insulin and Sr was detected in cells after momentary stimulation. We did not detect a polarized distribution of Sr in the RINm5F-cells. The distributions of Ca and Zn were affected when beta-cells (ob/ob) from a primary culture flattened out onto a substrate. In uprounded beta-cells (ob/ob) the distribution of Ca and Zn was polarized. Pancreatic tissue (ob/ob) was prepared for elemental analysis using freeze-substitution intetrahydrofurane (THF) followed by embedding in Araldite. The resulting samples can be sectioned at room temperature, easing physiological studies.
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| 7. |
- Pålsgård, Eva, et al.
(författare)
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Effects of K+-induced depolarization and purinergic receptor activation on elemental content in insulin-producing RINm5F-cells
- 1995
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Ingår i: Cell Biology International. - : Wiley. - 1065-6995 .- 1095-8355. ; 19:1, s. 25-34
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Tidskriftsartikel (refereegranskat)abstract
- X-ray microanalysis was used to detect elemental changes in the insulin-producing tumor cell-lineRINm5F. To improve discrimination between mobile ions and ions bound to macromolecules a new approach was employed, consisting of multivariate statistical analysis of correlations between the concentrations of Na, Mg, P, S, CI, K, and Ca. RINm5F cells, cultured an Formvar-coated titanium grids, were stimulated with high K+ or ATP, that are both known to stimulate insulin release. The buffers used contained Ca2+ or one of the Ca2+-analogues Sr2+ and Ba2+, to represent Ca2+ uptake inresponse to stimulation. After stimulation the cells were shock-frozen and freeze-dried overnight. Incubation for 10-20 seconds in a Ca2+-containing buffer did not significantly affect elementalcomposition, whereas cellular Mg, P and K decreased in a Sr2+-containing buffer. Depolarization with high K+ concentration caused an increase in the cellular Na content, both in Ca2+- and Sr2+-containing buffers, but not in the buffer where Ca2+ had been replaced by Ba2+. X-ray microanalysis is useful for detection of elemental changes subsequent to stimulation of cultured cells. Moreover, multivariate statistical analysis strengthens the idea that stimulation of RINm5F cells causes redistribution of ions possibly due to changes in the state of binding of some elements to cellular proteins.
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| 8. |
- Pålsgård, Eva, et al.
(författare)
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Ion dynamics in cells-preparation for studies of intracellular processes
- 1995
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Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - 0168-583X .- 1872-9584. ; 104:1-4, s. 324-327
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Tidskriftsartikel (refereegranskat)abstract
- A proton beam of about 1 mu m allows the study of inner structures of cells. These studies demand sophisticated preparation methods, not to destroy the morphology or the elemental distribution. Analysing a well-preserved cell may lead to important knowledge about basic regulatory processes at the cellular level. Freezing followed by removal of water by drying or by substitution with an organic solvent will be exemplified. Insulin-producing cells were studied to reach a further understanding of the signal transduction between stimulation to secrete insulin and the secretion.
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| 9. |
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| 10. |
- Pålsgård, Eva, et al.
(författare)
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Proton-induced and electron-induced X-ray microanalysis of insulin-secreting cells
- 1994
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Ingår i: Scanning Microscopy Suppl.. ; 8, s. 325-333
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Tidskriftsartikel (refereegranskat)abstract
- Elemental redistribution induced by insulin secretion, was investigated by electron and proton probe X-ray microanalysis. In particular, ion fluxes following immediately upon stimulation were studied. As the sensitivity of the electron probe was insufficient, the proton microprobe was employed. In order to see whether the cell is asymmetric with respect to Ca2+ influx, the cells were stimulated in the presence of Sr2+ (as a Ca2+ analog). Insulin-secreting cells (RINm5F cells and isolated mouse beta-cells) were cultured on grids and shock-frozen at 2-30 seconds after stimulation. In a large number of cells, the major elements and and large fluxes were analyzed by the electron microprobe. In the proton microprobe, selected cells were analyzed and elemental maps were compared with electron micrographs of the same cells. The proton microprobe, but not the electron microprobe, could detect an influx of Sr in response to K+-stimulation for 2 seconds, in RINm5F cells. No polarization of Sr2+ uptake in RINm5F-cells could be detected, and the beta-cells did not respond to high K+ by uptake of Sr. Momentary stimulation of beta-cells also resulted in a significant increase in Na, detected by the electron probe. Spreading of the beta-cells on the substrate appears to influence the subcellular elemental distribution. Thus, the proton probe has potential to detect small changes in elements such as those occurring after short-time stimulation.
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