http://hdl.handle.net/1956/1016 Search the Channel search http://bora.uib.no/simple-search http://hdl.handle.net/1956/2356 Title: Meeting students’ and supervisors’ expectations : findings from a pilot study done at Centre for International Health, University of Bergen <br/> <br/>Authors: Costea, Daniela Elena http://hdl.handle.net/1956/2279 Title: Pathological mechanisms in oral lichen planus : a atudy of apoptosis - regulatory proteins and risk markers for malignant transformation <br/> <br/>Authors: Neppelberg, Evelyn <br/> <br/>Abstract: Oral lichen planus (OLP) is a chronic mucocutaneous disease characterized by basal cell destruction and a subepithelial band-like mononuclear inflammatory cell infiltrate predominated by T cells. Molecular biological changes in the basal cell compartment and keratinocyte cell death have been a matter of particular interest in later OLP research. The majority of OLP lesions run a benign course. However, OLP have been associated with an increased risk of malignant transformation. The aims of this study were to investigate apoptotic cell death and putative regulatory proteins in keratinocytes (Papers I-III), as well as potential risk markers for malignant transformation in OLP (Paper III). Biopsies from clinically and histologically verified OLP were investigated (Papers I-II), as well as a biopsy material from OLP patients where a certain amount of them had developed epithelial dysplasia and oral squamous cell carcinoma (OSCC) (Paper III). Tissues were evaluated by histomorphometry, imunnohistochemistry (Papers I-III), TUNEL method (Paper I), mRNA in situ hybridization (Paper II) and image cytometry for measurement of DNA content (Paper III). Our data show that apoptosis is increased within the epithelium of OLP compared with normal oral mucosa (OM), and that both Fas receptor (FasR) and Fas-ligand (FasL) apoptosis regulatory proteins are expressed within the epithelium and subepithelial cell infiltrate of OLP (Paper I). In actively diseased OLP lesions, basal keratinocytes are CD40 negative and epithelial (E)-cadherin negative in focal areas (Papers II-III). Cyclooxygenase-2 (Cox-2) is up-regulated within the epithelium of OLP lesions, compared with normal OM (Paper III). According to DNA content measurements, all biopsies were classified as diploid including OLP, epithelial dysplasia and OSCC, except for one biopsy from an OLP lesion with epithelial dysplasia which was tetraploid (Paper III). Based on these findings we conclude that basal keratinocytes in OLP die by apoptosis and regulation of apoptosis appears to involve following mechanisms; (1) dysfunction in FasR/FasL system; (2) by down-regulating CD40 in diseased areas, basal keratinocytes may escape CD40-CD40L mediated apoptosis; (3) an up-regulation of Cox-2 , which may inhibit apoptosis; (4) loss of E-cadherin in basal keratinocytes may promote apoptosis and contribute to reduced basal cell structural integrity in OLP, allowing T cells to enter the epithelial compartment. Our biopsy material indicates that neither DNA content, nor expression of Cox-2 and E-cadherin are reliable as prognostic markers to select the OLP patients at risk for development of OSCC. http://hdl.handle.net/1956/2189 Title: X-ray microanalytical studies of initial mineralization in induced heterotopic bone formation in guinea pigs <br/> <br/>Authors: Johannessen, Anne Christine; Nilsen, Rune; Bang, G. <br/> <br/>Abstract: Allogenic demineralized dentin implanted in the abdominal wall of guinea pigs induced heterotopic osteoid and bone formation. Samples of this tissue were frozen at -140° C, freeze-dried at -80° C, infiltrated with Spurr® epoxy resin and polymerized. The sections were studied in the scanning transmission electron microscope, and analytical studies were performed by means of energy dispersive microanalysis. Osteoblasts and young osteoid osteocytes contained much more calcium than undifferentiated cells and mature osteocytes. The Ca/P ratio in the cytoplasm of these young matrix-producing cells was high. Phosphorus was found in the nuclei of all cells and to a lesser degree also in the cytoplasm of cells rich in calcium. The initial extra-cellular mineral accumulation also showed a high Ca/P ratio. Small electron-dense areas in these regions exhibited both an amount of calcium and a Ca/P ratio resembling those of mature mineralized bone. The initial event of the mineralization process seemed to be an accumulation of calcium first in the young matrix-producing cells and then in the surrounding osteoid matrix. The results suggested that the matrix-producing cells are actively involved in the accumulation of calcium phosphorus both intra-and extra-cellularly. http://hdl.handle.net/1956/2188 Title: Microfilaments in cells associated with induced heterotpic bone formation in guinea pigs <br/> <br/>Authors: Nilsen, Rune <br/> <br/>Abstract: Sera from active chronic hepatitis were used to demonstrate actin microfilaments in cells of a bone-induced model. Demnineralized and freeze-dried allogenic dentine was implanted in the abdominal muscles of Guinea pigs. After 21 and 28 days the tissue was excised and showed: a) resorption areas of the dentine contained dentinoclasts and macrophages. B) osteoid and bone and c) areas of fibroblastic proliferation. Osteoblasts and young osteocytes showed the strongest fluorescent staining. Electron microscopy of these cells demonstrated abundant 5-7 nm microfilaments interpreted as actin in the outer parts and cell projections, in which some microtubules also were observed. Fewer microfilaments were present in mature osteocytes although the cell projections in mineralized bone also showed microfilaments. Microfilaments were also found in some dentinoclasts where the actin was located in projections from the ruffles border protruding into the dentine. The localization in the ruffled border corresponded to the distribution of the fluorescent staining of actin. The high amount of actin in osteoblasts and osteocytes may be correlated to the synthesis and transport of the new matrix components. The microfilaments in the clear sealing zone of dentinoclasts were considered to have a function in the sealing of the ruffled border. http://hdl.handle.net/1956/2187 Title: Enzyme histochemical studies of induced heterotopic cartilage and bone formation in guinea pigs with special references to acid phosphatise. A light and enzyme electron microscopic study <br/> <br/>Authors: Nilsen, Rune; Magnusson, B. C. <br/> <br/>Abstract: Heterotopic bone and cartilage formation was studied in a bone induction model in abdominal muscles of guinea pigs using demineralized allogenic dentin as inductive material. The light microscopical study showed high activity of acid phosphatise (AcP) and leucine aminopeptidase (LAP) in young matrix-producing cells. The highest activity was seen in cells surrounded by inmineralized matrix. In the surrounding matrix there was strong staining of AcP, especially in matrix with high glycosaminoglycan content. Electron microscopical studies of AcP in unfixed frozen tissue showed intra-cellular activity mainly located in lysosomes. Extracellular AcP was found in matrix vescicles in the newly formed hard tissue. It was most pronounced in areas of cartilaginous differentiation. By means of energy dispersive x-ray microanalysis in a scanning transmission electron microscope, the deposits were confirmed to contain lead precipitates. With the exception of some lysosomal staining, prefixation with formaldehyde prevented demonstration of the enzyme activity. Both AcP and LAP may be involved in degradation of glycosaminoglycans or other organic components of the matrix which enable the matrix to mineralize. <br/> <br/>Description: Published as: Enzyme histochemical studies of induced heterotopic cartilage and bone formation in guinea pigs with special references to acid phosphatise http://hdl.handle.net/1956/2186 Title: Enzyme histochemical studies of acid phosphatise isoenzymes in induced heterotopic bone formation in guinea pigs <br/> <br/>Authors: Nilsen, Rune; Magnusson, B. C. <br/> <br/>Abstract: A bone induction model was used to study the effect of different pretreatments and inhibitors added to the substrate of acid phosphatise. Two different acid phosphatises (AcP) were demonstrated. The AcP of matrix-producing cells exhibited resistance to pre-treatment with EDTA while it was sensitive to tartrate added to the incubation medium. The AcP in dentin resorbing cells was EDTA sensitive but resistant to tartrate. Both resorbing and matrix-producing cells were generally sensitive to fluoride, copper and molybdate. In some of the dentionoclasts, fluoride resistant AcP was observed. The results support previous investigations on normal bone formation suggesting that two different isoenzymes of AcP exists. One of these seems to be related to matrix production and mineralization of the new heterotopic http://hdl.handle.net/1956/2181 Title: Enzyme histochemistry of induced heterotopic bone formation in guinea pigs <br/> <br/>Authors: Nilsen, Rune; Magnusson, B. C. <br/> <br/>Abstract: In an experimental bone induction model in guinea-pigs, large amounts of heterotopic osteiod and bone were found after 21 days. A semiquantiative intrasectional analysis of oxidative and hydrolytic enzyme activities in the reaction zones showed that matrix-producing cells as well as dentine-resorbing cells had acid phosphatise activity. Leucine aminopeptidase activity was lower in dentinoclasts and macrophages than in matrix-producing cells, which may indicate a function of this enzyme in the production of bone matrix. A substrate-specific ATPase, as well as non-specific alkaline phosphatise and acid phosphatise were active in matrix-producing cells. A close relationship between resorbing cells and matrix-producing cells suggested an inductive mechanism during heterotopic bone formation. http://hdl.handle.net/1956/2180 Title: Electronmicroscopic study of mineralization in induced heterotopic bone formation in guinea pigs <br/> <br/>Authors: Nilsen, Rune <br/> <br/>Abstract: Mineralization of heterotopic bone was studied in a bone induction model using allogenic demineralization dentin implanted in the abdominal wall of guinea pigs. There was a high yield of newly formed osteoid and bone as well as some cartilage together with areas of resorption of the dentin, and fibroblast proliferation. The osteoid contained many matrix vesicles II and less of lysosome-like type I vesicles. Early cartilage formation had more type I vesicles. The implanted dentin contained no matrix vesicles. The first sign of mineralization occurred mainly as irregular clusters of mineral crystals in the matrix close to the surface of collagen fibrils. Crystal-like figures were also found inside some type II matrix vesicles, although most of these vesciles in the mineralization zone had no crystals. The type I vesciles of both bone and cartilage exhibited often crystals near the outer membrane. The mineralizing bone showed a reduction in the size and number of proteoglycan particles. Remineralization of the implanted dentin was also often found and the mineralization pattern resembled the mineralization of bone except for the absence of matrix vesicles. Electron diffraction of selected areas showed that the crystals in the new bone and the mineralized dentin were hydroxyapatite.