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- Articus, Kristina, et al.
(författare)
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Phylogenetic studies in Usnea.
- 2000
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Ingår i: The Fourth IAL Symposium Progress and Problems in Lichenology at the Turn of the Millenium, Abstracts: 100. Barcelona..
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 4. |
- Articus, Kristina, 1971-
(författare)
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Phylogenetic Studies in Usnea (Parmeliaceae) and Allied Genera
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis deals with the phylogeny of the lichen genus Usnea (Parmeliaceae, Ascomycetes). The relationships and the morphological variation among Usnea species has been studied, as well as the relationship of Usnea to allied genera. Two species, U. florida and U. subfloridana, which earlier were regarded to form two separate species have been synonymized. In an analysis based on sequence data these two taxa formed a monophyletic group of intermixed specimens. Usnea florida and U. subfloridana have earlier been regarded to form a species pair, but the species pairs concept cannot be applied in this case. The morphological characters traditionally used for species recognition of a number of European Usnea species have been analyzed regarding their reliability. The evolution and distribution of the morphological characters was studied in relation to a phylogeny based on sequence data. Most characters proved to be homoplastic in relation to the phylogeny. Few characters were consistent in a clade, and the same character could be inconsistent in another clade. Therefore a combination of several characters is recommended for species recognition. The relationship of Neuropogon to Usnea was investigated based on sequence data. Neuropogon showed to be closely related to Usnea subg. Usnea. The subgenera Eumitria and Dolichousnea formed the sister group to the clade comprising subg. Usnea and Neuropogon. Usnea is paraphyletic in this investigation. Eumitria is treated as a genus and the subgenus Dolichousnea is elevated to generic rank. The position of Usnea, Neuropogon, Eumitria, and Dolichousnea in the family Parmeliaceae was investigated based on a phylogeny obtained by sequence data. Protousnea probably forms the sister group to the clade of Usnea, Neuropogon, Eumitria, and Dolichousnea. Several monophyletic groups in the family Parmeliaceae were identified.
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- Articus, Kristina, et al.
(författare)
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Ribosomal DNA and beta-tubulin data do not support the separation of the lichens Usnea florida and U-subfloridana as distinct species
- 2002
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Ingår i: Mycological Research. - 0953-7562 .- 1469-8102. ; 106, s. 412-418
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Tidskriftsartikel (refereegranskat)abstract
- The lichens Usnea florida and U. subfloridana have since long been recognised as distinct species. They show many similarities in morphology, but have different reproductive strategies. Usnea florida is always provided with many apothecia and produces no specialised asexual propagules. Usnea subfloridana has soralia, isidiomorphs and occasionally apothecia. Phylogenetic analyses based on continuous sequences of the ITS and LSU regions of the nuclear ribosomal DNA and the gene coding for beta-tubulin, show that specimens of the two species form one monophyletic group of intermixed specimens, and not two groups corresponding to morphology, which Would have been expected if two species were at hand. The 'species pair' concept in lichenology is discussed. Other Usnea species included in the study are: U. articulata, U. barbata, U. ceratina, U. filipendula. U. hirta, U. rigida and U. wasmuthii.
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- Edgren, FRedrik, et al.
(författare)
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Formation of damage and its effects on non-crimp fabric reinforced composites loaded in tension
- 2004
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Ingår i: Composites Science And Technology. - 0266-3538 .- 1879-1050. ; 64:5, s. 675-692
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Tidskriftsartikel (refereegranskat)abstract
- Non-crimp fabric (NCF) composites, manufactured by resin infusion techniques are one of the most promising next generation composite materials. They offer large potential for application in primary structures as they give excellent performance at low production costs. However, before NCF composites will be efficiently used in design, detailed understanding of governing micro mechanisms must be accumulated and described by predictive models. In the present study, NCF cross-ply laminates have been tested in tension. Intralaminar cracks caused in the 90° fibre bundle layers and their effect on laminate mechanical properties have been monitored. Occurrence of 'novel' type of cracks propagating in the load direction (longitudinal cracks) is explained by a thorough FE analysis using an Representative Volume Element (RVE) approach, revealing stress concentrations caused by 0° fibre bundle waviness. Effects of damage on mechanical properties are modelled using modified micro mechanical models developed for analysis of conventional laminated composites. The analysis reveals mechanical degradation to be ruled by the crack opening displacement (COD). However, unlike traditional composites, transverse cracks do not generally extend through the entire thickness of the 90° layer, but are rather contained in single fibre bundles, limiting the COD. © 2003 Elsevier Ltd. All rights reserved.
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| 13. |
- Mattsson, Göran, et al.
(författare)
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Evidence of Functional Impairment of Syngeneically Transplanted Mouse Pancreatic Islets Retrieved from the Liver
- 2004
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Ingår i: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 53:4, s. 948-954
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Tidskriftsartikel (refereegranskat)abstract
- A drawback in pancreatic islet transplantation is the large number of islets needed to obtain insulin independence in patients with diabetes. This most likely reflects extensive posttransplantation islet cell death and functional impairment of the remaining endocrine cells. We aimed to develop an experimental method to retrieve transplanted islets from the mouse liver, which would enable comparisons of transplanted and endogenous islets and provide valuable information on functional changes induced by intraportal transplantation. Transplanted islets were obtained by retrograde perfusion of the liver with collagenase. The identity of retrieved tissue as transplanted islets was confirmed by intravital staining, immunohistochemistry, and electron microscopy. The retrieved islets, irrespective of whether they had resided in diabetic or nondiabetic recipients, had a markedly lower insulin content and glucose-stimulated insulin release when compared with isolated endogenous islets. The glucose oxidation rate was also markedly lower in the retrieved islets, suggesting mitochondrial dysfunction. These disturbances in insulin content, insulin release, and glucose oxidation rate were not reversed by a few days of culture after retrieval. The results implicate changes in islet function after intraportal transplantation. Such dysfunction may contribute to the high number of islets needed for successful transplantation in diabetic individuals.
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| 14. |
- Mattsson, Göran, 1967-
(författare)
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Experimental Studies on the Vasculature of Endogenous and Transplanted Islets of Langerhans
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The blood vessels of the pancreatic islets are of crucial importance for oxygen and metabolite supply as well as dispersal of secreted hormones. In addition to this, endothelial cells have an important role in the revascularization process after islet transplantation. Previous studies have reported signs of poor engraftment of transplanted islets, presumably due to impaired revascularization. The aims of this thesis were to investigate the revascularization process of transplanted islets and to examine the role of islet endothelial cells. In this context, the lectin Bandeiraea simplicifolia was found to stain endothelium of both endogenous and transplanted pancreatic islets. By using this lectin we investigated the vascular density of both endogenous and islets transplanted syngeneically beneath the renal capsule, into the spleen or intraportally into the liver of normoglycemic C57BL/6 mice. One month post-transplantation, a time point when the grafts are assumed to be completely revascularized, the vascular density was decreased at all three implantation sites when compared to endogenous islets. Furthermore, most of the blood vessels were located in the graft connective tissue stroma. Similar results were obtained when islet transplant vascular density was determined six months post-transplantation and in cured diabetic animals after one month. In order to evaluate the function of intraportally transplanted islets, we developed a method to retrieve such islets. We treated the implantation organ (liver) first enzymatically (collagenase) and then mechanically, thereafter we could re-isolate the transplanted islets for further in vitro studies. The retrieved islets had a decreased insulin relase, insulin content and glucose oxidation rate when compared to non-transplanted control islets. To understand the role of islet endothelium in the revascularization of transplanted islets we performed angiogenesis GEArray studies on islet endothelial cells, from non-cultured, cultured and transplanted islets. We found that the islet endothelium expressed mRNA for both inhibitors and inducers of angiogenesis, and that this expression differed with time. The functional consequences of this remain to be determined. In summary, the results presented above provide a useful platform for future studies of the morphology and function of islet endothelial cells, especially with a view for elucidating changes induced by islet transplantation.
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- Mattsson, Magnus, et al.
(författare)
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Mixing and displacement ventilation compared in classrooms; distribution of particles, cat allergen and CO2
- 2003
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Ingår i: Proceedings from Healthy Buildings 2003. ; , s. 458-464
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Konferensbidrag (refereegranskat)abstract
- Mixing ventilation and displacement ventilation were compared in an intervention study in classrooms. Particles, cat allergen and CO2, were measured in classroom air at different levels above the floor, during regular lessons. With mixing ventilation, the particle concentration tended to decrease with height, with a stronger gradient occurring for larger particles. With displacement ventilation, the particle concentration increased with height, except for particles >25 µm. The displacement system thus tended to have a slight upward displacement effect on most of the particles. Significant correlations were found between concentrations of cat allergen and particles in the size fraction 1–10 µm. The particle and cat allergen concentration at breathing height did not, however, differ significantly between the two ventilation systems. CO2 was about 10% lower with displacement ventilation. A fairly high level of physical activity of the pupils is believed to have had significant dispersing effect on the airborne contaminants.
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