| 1. |
- Anderson, Helén, et al.
(författare)
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Skapa kundnärvaro i innovationsprocessen
- 2008
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Ingår i: Innovationsförmåga. - Malmö : Holmbergs i Malmö AB. - 9789197785204 ; , s. 40-59
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Bokkapitel (populärvet., debatt m.m.)
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| 2. |
- Bergek, Sara, 1979-, et al.
(författare)
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Spatiotemporal analysis shows stable genetic differentiation and barriers to dispersal in the Eurasian perch (Perca fluviatilis L.)
- 2009
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Ingår i: Evolutionary Ecology Research. - Tucson : Evolutionary Ecology Ltd.. - 1522-0613 .- 1937-3791. ; 11:5, s. 827-840
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Tidskriftsartikel (refereegranskat)abstract
- Background: Recently, unexpected or cryptic barriers to gene flow causing genetic discontinuities have been found in a number of animal taxa, even in apparently highly connected areas such as aquatic environments. Goal: Investigate the temporal stability of previously documented microgeographic genetic structure in a fish. Organism: Eurasian perch (Perca fluviatilis L.) Method: We sampled four locations over a period of 2 years. We used six microsatellites to investigate population differentiation. We compared within-year to between-year differentiation. Results: The significant genetic differentiation found between locations in 2004 was still present in 2006. The strongest barriers to gene flow in the lake were consistent over both sampling periods. Furthermore, temporal differentiation existed within each site between the years. Populations of perch appear to cluster in different patches in the lake that harbour genetically differentiated groups of fish. Hence, limited migration and barriers to dispersal can persist over time, even at a very small geographical scale and in an open aquatic environment.
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| 3. |
- Bucin, Dragan, et al.
(författare)
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Heart transplantation across the antibodies against HLA and ABO
- 2006
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Ingår i: Transplant International. - : Frontiers Media SA. - 1432-2277 .- 0934-0874. ; 19:3, s. 239-244
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Tidskriftsartikel (refereegranskat)abstract
- We have intentionally performed heart transplantation in a 5-year-old child, despite the most unfavourable risk factors for patient survival; the presence of high level of antibodies against donor's human leucocyte antigen (HLA) class I/II and blood group antigens. Pretransplant treatment by mycophenolate mofetil, prednisolone, tacrolimus, intravenous immunoglobulin, rituximab, protein-A immunoadsorption (IA) and plasma exchange reduced antibody titres against the donor's lymphocytes from 128 to 16 and against the donor's blood group antigen from 256 to 0. The patient was urgently transplanted with a heart from an ABO incompatible donor (A(1) to O). A standard triple-drug immunosuppressive protocol was used. No hyperacute rejection was seen. Antibodies against the donor's HLA antigens remained at a low level despite three acute rejections. Rising anti-A(1) blood group antibodies preceded the second rejection and were reduced by two blood group-specific IAs and remained at a low level. The patient is doing well despite the persistence of donor-reactive antibodies.
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| 4. |
- de Jongh, Willem A., et al.
(författare)
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The Roles of Galactitol, Galactose-1-Phosphate, and Phosphoglucomutase in Galactose-Induced Toxicity in Saccharomyces cerevisiae
- 2008
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Ingår i: Biotechnology and Bioengineering. - 0006-3592 .- 1097-0290. ; 101:2, s. 317-326
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Tidskriftsartikel (refereegranskat)abstract
- The uptake and catabolism of galactose by the yeast Saccharomyces cerevisiae is much lower than for glucose and fructose, and in applications of this yeast for utilization of complex substrates that contain galactose, for example, lignocellulose and raffinose, this causes prolonged fermentations. Galactose is metabolized via the Leloir pathway, and besides the industrial interest in improving the flux through this pathway it is also of medical relevance to study the Leloir pathway. Thus, genetic disorders in the genes encoding galactose-1-phosphate uridylyltransferase or galactokinase result in galactose toxicity both in patients with galactosemia and in yeast. In order to elucidate galactose related toxicity, which may explain the low uptake and catabolic rates of S. cerevisiae, we have studied the physiological characteristics and intracellular metabolite profiles of recombinant S. cerevisiae strains with improved or impaired growth on galactose. Aerobic batch cultivations on galactose of strains with different combiantions of overexpression of the genes GAL1, GAL2, GAL7, and GAL10, which encode proteins that together convert extracellular galactose into glucose-1-phosphate, revealed a decrease in the maximum specific growth rate when compared to the reference strain. The hypothesized toxic intermediate galactose-1-phosphate cannot be the sole cause of galactose related toxicity, but indications were found that galactose-1-phosphate might cause a negative effect through inhibition of phosphoglucomutase. Furtermore, we show that galactitol is formed in S. cerevisiae, and that the combination of elevated intracellular galactitol concentration, and the ratio between galactose-1-phosphate concentration and phosphoglucomutase activity seems to be important for galactose related toxicity causing decreased growth rates.
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| 5. |
- Elg, Mattias, et al.
(författare)
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Implementing statistical process control : An organizational perspective
- 2008
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Ingår i: International Journal of Quality & Reliability Management. - : Emerald. - 0265-671X .- 1758-6682. ; 25:6, s. 545-560
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Tidskriftsartikel (refereegranskat)abstract
- Purpose - The purpose of this paper is to contribute to the understanding of how statistical process control (SPC) methodology can be implemented and used in organizational settings. Design/methodology/approach - An action research model was used. Data were collected through formal meeting protocols, interviews and participant observation. Findings - Based on the results of an action research project, the paper emphasizes the need for: top management support with respect to roles such as infrastructural assistance, mentor, critic, financer, creating system validity through the involvement of people with experiential knowledge about the "world" in which SPC should be applied, keeping a small, highly knowledgeable development team with appropriate expertise together during the whole process from beginning to end, keeping the various end-users in focus but separate and prioritising between their different needs, and working with iterative design methodology. Research limitations/implications - The paper provides the research field with a unique case of implementing SPC using a computerized administrative data system. Practical implications - Organizations are given guidelines to use when implementing SPC. Originality/value - The paper contributes knowledge in an underdeveloped field of research. It may provide a basis for further research and scholarly analysis. © Emerald Group Publishing Limited.
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| 6. |
- Flodén, Liselott, 1967-, et al.
(författare)
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A myriad shades of green
- 2009
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Ingår i: Proceedings of Bridges 2009, Banff, Alberta, Canada.
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Konferensbidrag (refereegranskat)abstract
- We discuss the possible application of techniques inspired by the theories of G-convergence and homogenization to understand mixtures of colors and how they appear as observed by the human eye. The ideas are illustrated by pictures describing the equivalent of a convergence process for different kinds of mixtures of colors.
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| 7. |
- Flodén, Liselott, 1967-, et al.
(författare)
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On the determination of effective properties of certain structures with non-periodic temporal oscillations
- 2009
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Ingår i: MATHMOD 2009 - 6th Vienna International Conference on Mathematical Modelling. - Wien : Vienna University Press (WUV). - 9783901608353 ; , s. 2627-2630
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Konferensbidrag (refereegranskat)abstract
- We investigate the homogenization of an evolution problem modelled by a parabolic equation, where the coefficient describing the structure is periodic in space but may vary in time in a non-periodic way. This is performed applying a generalization of two-scale convergence called λ-scale convergence. We give a result on the characterization of the λ-scale limit of gradients under certain boundedness assumptions. This is then applied to perform the homogenization procedure. It turns out that, under a certain condition on the rate of change of the temporal variations, the effective property of the given structure can be determined the same way as in periodic cases.
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| 8. |
- Grotkjær, Thomas, et al.
(författare)
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Comparative metabolic network analysis of two xylose fermenting recombinant Saccharomyces cerevisiae strains
- 2005
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Ingår i: Metabolic engineering. - : Elsevier BV. - 1096-7176 .- 1096-7184. ; 7:5-6, s. 437-444
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Tidskriftsartikel (refereegranskat)abstract
- The recombinant xylose fermenting strain Saccharomyces cerevisiae TMB3001 can grow on xylose, but the xylose utilisation rate is low. One important reason for the inefficient fermentation of xylose to ethanol is believed to be the imbalance of redox co-factors. In the present study, a metabolic flux model was constructed for two recombinant S. cerevisiae strains: TMB3001 and CPB.CR4 which in addition to xylose metabolism have a modulated redox metabolism, i.e. ammonia assimilation was shifted from being NADPH to NADH dependent by deletion of gdh1 and over-expression of GDH2. The intracellular fluxes were estimated for both strains in anaerobic continuous cultivations when the growth limiting feed consisted of glucose (2.5 g L−1) and xylose (13 g L−1). The metabolic network analysis with 13C labelled glucose showed that there was a shift in the specific xylose reductase activity towards use of NADH as co-factor rather than NADPH. This shift is beneficial for solving the redox imbalance and it can therefore partly explain the 25% increase in the ethanol yield observed for CPB.CR4. Furthermore, the analysis indicated that the glyoxylate cycle was activated in CPB.CR4.
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| 9. |
- Hermann, Fredrik, et al.
(författare)
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Chemical analysis of combustion products from a high-pressure gas turbine combustor rig fueled by jet A1 fuel and a Fischer-Tropsch-based fuel
- 2006
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Ingår i: Proceedings of the ASME Turbo Expo. - 0791842363 ; 1, s. 523-532
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Konferensbidrag (refereegranskat)abstract
- A comparative experimental investigation has been performed, comparing the emissions from a synthetic jet fuel and from Jet AI. In the investigation, the unburned hydrocarbons were analyzed chemically and the regulated emissions of NOX, CO and HC were measured. All combustion tests were performed under elevated pressures in a gas turbine combustor rig. A Swedish company, Oroboros AB, has developed a novel clean synthetic jet fuel, LeanJet [registered trademark] . The fuel is produced synthetically from synthesis gas by a Fischer-Tropsch process. Except for the density, the fuel conforms to the Standard Specification for Aviation Turbine Fuels. The low density is due to the lack of aromatics and polyaromatics. Organic emissions from the gas turbine combustor rig were collected by adsorption sampling and analyzed chemically. Both the fuels and the organic emissions were analyzed by gas chromatography/flame ionization (GC/FlD) complemented with gas chromatography/mass spectrometry (GC/MS). Under the operating conditions investigated, no significant differences were found for the regulated emissions, except for emission of CO from the synthetic fuel, which, at leaner conditions, was one-quarter of that measured for Jet Al. Detailed analysis of the organic compounds showed that the emissions from both fuels were dominated by fuel alkanes and a significant amount of naphthalene. It was also found that Jet Al produced a much higher amount of benzene than the synthetic fuel. Copyright
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| 10. |
- Hermann, Fredrik, et al.
(författare)
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Chemical analysis of combustion products from a high-pressure gas turbine combustor rig fueled by jet A1 fuel and a flscher-tropsch-based fuel
- 2006
-
Ingår i: Proceedings of the ASME Turbo Expo 2006 - Power for Land, Sea, and Air. - 0791842363 - 9780791842362 - 0791837742 ; 1, s. 523-532
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Konferensbidrag (refereegranskat)abstract
- A comparative experimental investigation has been performed, comparing the emissions from a synthetic jet fuel and from Jet AI. In the investigation, the unburned hydrocarbons were analyzed chemically and the regulated emissions of NOX, CO and HC were measured. All combustion tests were performed under elevated pressures in a gas turbine combustor rig. A Swedish company, Oroboros AB, has developed a novel clean synthetic jet fuel, LeanJet®. The fuel is produced synthetically from synthesis gas by a Fischer-Tropsch process. Except for the density, the fuel conforms to the Standard Specification for Aviation Turbine Fuels. The low density is due to the lack of aromatics and polyaromatics. Organic emissions from the gas turbine combustor rig were collected by adsorption sampling and analyzed chemically. Both the fuels and the organic emissions were analyzed by gas chromatography/flame ionization (GC/FlD) complemented with gas chromatography/mass spectrometry (GC/MS). Under the operating conditions investigated, no significant differences were found for the regulated emissions, except for emission of CO from the synthetic fuel, which, at leaner conditions, was one-quarter of that measured for Jet Al. Detailed analysis of the organic compounds showed that the emissions from both fuels were dominated by fuel alkanes and a significant amount of naphthalene. It was also found that Jet Al produced a much higher amount of benzene than the synthetic fuel.
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| 11. |
- Kolm, Niclas, et al.
(författare)
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Group stability and homing behavior but no kin group sturcture in a coral reef fish
- 2005
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Ingår i: Behavioral Ecology. - : Oxford University Press (OUP). - 1045-2249 .- 1465-7279. ; 16:3, s. 521-527
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the reasons behind stable group formations has received considerable theoretical and empirical attention. Stable groups displaying homing behavior have been suggested to form as a result of, for instance, benefits from knowledge of the social or physical environment or through kin selection and the forming of kin groups. However, no one has disentangled preference for grouping in a familiar location from preference for grouping with familiar or related individuals. To investigate this, we conducted a series of field experiments and a group genetic analysis on the group-living Banggai cardinalfish (Pterapogon kauderni). We found homing behavior but no evidence for recognition of familiar group members. Instead, homing was based on the original location of their group rather than the individuals in that group. Moreover, we found no evidence for kin structures within these groups. We suggest that benefits from living in a known social environment drive homing behavior in this species and that homing behavior is not enough for the formation of kin group structures. Instead, our results suggest that kin recognition may be a prerequisite for the forming of kin groups.
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| 12. |
- Köhnke, Rickard, et al.
(författare)
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Thylakoids promote release of the satiety hormone cholecystokinin while reducing insulin in healthy humans.
- 2009
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Ingår i: Scandinavian Journal of Gastroenterology. - : Informa UK Limited. - 1502-7708 .- 0036-5521. ; 44:6, s. 712-719
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Tidskriftsartikel (refereegranskat)abstract
- Objective. The effects of a promising new appetite suppressor named "thylakoids" (membrane proteins derived from spinach leaves) were examined in a single meal in man. Thylakoids inhibit the lipase/colipase hydrolysis of triacylglycerols in vitro and suppress food intake, decrease body-weight gain and raise the satiety hormone cholecystokinin (CCK) in rats, but their effects in man remain unclear. The aim of this study was to investigate whether thylakoids, when added to a test meal, affect appetite regulation and blood parameters in healthy individuals. Material and methods. In an intervention crossover study, healthy individuals of normal weight (n=11) were offered a high-fat meal with and without the addition of thylakoids. Blood samples were taken 0 (prior to meal), 30, 60, 120, 180, 240, 300 and 360 min after the start of the meal. Blood samples were analysed for satiety and hunger hormones (CCK, leptin and ghrelin), insulin and blood metabolites (glucose and free fatty acids). Results. The CCK level increased, in particular between the 120 min time-point and onwards, the ghrelin level was reduced at 120 min and leptin level increased at 360 min after intake of the thylakoid-enriched meal. The insulin level was reduced, whereas glucose concentrations were unchanged. Free fatty acids were reduced between time-point 120 min and onwards after the thylakoid meal. Conclusions. The addition of thylakoids to energy-dense food promotes satiety signals and reduces insulin response during a single meal in man.
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| 13. |
- Liess, Antonia, et al.
(författare)
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Food web complexity affects stoichiometric and trophic interactions
- 2006
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Ingår i: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 114:1, s. 117-125
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Tidskriftsartikel (refereegranskat)abstract
- The stoichiometry of trophic interactions has mainly been studied in simple consumer–prey systems, whereas natural systems often harbour complex food webs with abundant indirect effects. We manipulated the complexity of trophic interactions by using simple laboratory food webs and complex field food webs in enclosures in Lake Erken. In the simple food web, one producer assemblage (periphyton) and its consumers (benthic snails) were amended by perch, which was externally fed by fish food. In the complex food web, two producer assemblages (periphyton and phytoplankton), their consumers (benthic invertebrates and zooplankton) and perch feeding on zooplankton were included. In the simple food web perch affected the stoichiometry of periphyton and increased periphyton biomass and the concentration of dissolved inorganic nitrogen. Grazers reduced periphyton biomass but increased its nutrient content. In the complex food web, in contrast to the simple food web, perch affected periphyton biomass negatively but increased phytoplankton abundance. Perch had no influence on benthic invertebrate density, zooplankton biomass or periphyton stoichiometry. Benthic grazers reduced periphyton biomass and nutrient content. The difference between the simple and the complex food web was presumably due to the increase of pelagic cyanobacteria (Gloeotrichia sp.) with fish presence in the complex food web, thus fish had indirect negative effects on periphyton biomass through nutrient competition and shading by cyanobacteria. We conclude that the higher food web complexity through the presence of pelagic primary producers (in this case Gloeotrichia sp.) influences the direction and strength of trophic and stoichiometric interactions.
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| 14. |
- Mapelli, Valeria, 1978, et al.
(författare)
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Metabolic footprinting in microbiology: methods and applications in functional genomics and biotechnology
- 2008
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Ingår i: Trends in Biotechnology. ; 26:9, s. 490-497
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Tidskriftsartikel (refereegranskat)abstract
- Metabolomics embraces several strategies that aim to quantify cell metabolites in order to increase our understanding of how metabolite levels and interactions influence phenotypes. Metabolic footprinting represents a niche within metabolomics, because it focuses on the analysis of extracellular metabolites. Although metabolic footprinting represents only a fraction of the entire metabolome, it provides important information for functional genomics and strain characterization, and it can also provide scientists with a key understanding of cell communication mechanisms, metabolic engineering and industrial biotechnological processes. Due to the tight and convoluted relationship between intracellular metabolism and metabolic footprinting, metabolic footprinting can provide precious information about the intracellular metabolic status. Hereby, we state that integrative information from metabolic footprinting can assist in further interpretation of metabolic networks.
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| 15. |
- Meijer, S. L., et al.
(författare)
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Gene deletion of cytosolic ATP: citrate lyase leads to altered organic acid production in Aspergillus niger
- 2009
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Ingår i: Journal of Industrial Microbiology and Biotechnology. - : Oxford University Press (OUP). - 1367-5435 .- 1476-5535. ; 36:10, s. 1275-1280
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Tidskriftsartikel (refereegranskat)abstract
- With the availability of the genome sequence of the filamentous fungus Aspergillus niger, the use of targeted genetic modifications has become feasible. This, together with the fact that A. niger is well established industrially, makes this fungus an attractive micro-organism for creating a cell factory platform for production of chemicals. Using molecular biology techniques, this study focused on metabolic engineering of A. niger to manipulate its organic acid production in the direction of succinic acid. The gene target for complete gene deletion was cytosolic ATP: citrate lyase (acl), which had previously been identified by using genome-scale stoichiometric metabolic model simulations. The acl gene was deleted using the bipartite gene-targeting method, and the mutant was characterized in batch cultivation. It was found that the succinic acid yield was increased threefold by deleting the acl gene. Additionally, the total amount of organic acids produced in the deletion strain was significantly increased. Genome-scale stoichiometric metabolic predictions can be used for identifying gene targets. Deletion of the acl led to increased succinic acid production by A. niger.
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| 16. |
- Meijer, S. L., et al.
(författare)
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Physiological characterisation of acuB deletion in Aspergillus niger
- 2009
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Ingår i: Applied Microbiology and Biotechnology. - : Springer Science and Business Media LLC. - 1432-0614 .- 0175-7598. ; 84:1, s. 157-167
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Tidskriftsartikel (refereegranskat)abstract
- The acuB gene of Aspergillus niger is an ortholog of facB in Aspergillus nidulans. Under carbon-repression conditions, facB is repressed, thereby preventing acetate metabolism when the repressing carbon source is present. Even though facB is reported to be repressed directly by CreA, it is believed that a basal level of FacB activity exists under glucose-repressive conditions. In the present study, the effect of deletion of acuB on the physiology of A. niger was assessed. Differences in organic acid and acetate production, enzyme activities and extracellular amino and non-amino organic acid production were determined under glucose-repressing and -derepressing conditions. Furthermore, consumption of alternative carbon sources (e.g. xylose, citrate, lactate and succinate) was investigated. It was shown that AcuB has pleiotropic effects on the physiology of A. niger. The results indicate that metabolic pathways that are not directly involved in acetate metabolism are influenced by acuB deletion. Clear differences in organic acid consumption and production were detected between the a dagger acuB and reference strain. However, the hypothesis that AcuB is responsible for basal AcuA activity necessary for activation of acetate metabolic pathways, even during growth on glucose, could not be confirmed. The experiments demonstrated that also when acuB was deleted, no acetate was formed. Therefore, AcuB cannot be the only activator of AcuA, and another control mechanism has to be available for activating AcuA.
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| 17. |
- Meijer, S, et al.
(författare)
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Overexpression of isocitrate lyase-glyoxylate bypass influence on matabolism in Aspergillus niger
- 2009
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Ingår i: Metabolic Engineering. - : Elsevier BV. - 1096-7176 .- 1096-7184. ; :11, s. 107-116
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Tidskriftsartikel (refereegranskat)abstract
- In order to improve the production of succinate and malate by the filamentous fungus Aspergillus niger the activity of the glyoxylate bypass pathway was increased by over-expression of the isocitrate lyase (icl) gene. The hypothesis was that when isocitrate lyase was up-regulated the flux towards glyoxylate would increase, leading to excess formation of malate and succinate compared to the wild-type. However, metabolic network analysis showed that an increased icl expression did not result in an increased glyoxylate bypass flux. The analysis did show a global response with respect to gene expression, leading to an increased flux through the oxidative part of the TCA cycle. Instead of an increased production of succinate and malate, a major increase in fumarate production was observed. The effect of malonate, a competative inhibitor of succinate dehydrogenase (SDH), on the physiological behaviour of the cells was investigated. Inhibition of SDH was expected to lead to succinate production, but this was not observed. There was an increase in citrate and oxalate production in the wild-type strain. Furthermore, in the strain with over-expression of icl the organic acid production shifted from fumarate towards malate production when malonate was added to the cultivation medium. Overall, the icl over-expression and malonate addition had a significant impact on metabolism and on organic acid production profiles. Although the expected succiante and malate formation was not observed, a distinct and interesting production of fumarate and malate was found.
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| 18. |
- Olsson, Jens, et al.
(författare)
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Computer Forensic Timeline Visualization Tool
- 2009
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Ingår i: Digital Investigation. The International Journal of Digital Forensics and Incident Response. - : Elsevier. - 1742-2876 .- 1873-202X. ; 6:Supplement 1, s. 78-87
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Tidskriftsartikel (refereegranskat)abstract
- Computer Forensics is mainly about investigating crime where computers have been involved. There are many tools available to aid the investigator with this task. We have created a prototype of a new type of tool called CyberForensic TimeLab where all evidence is indexed by their time variables and plotted on a timeline. We believed that this way of visualizing the evidence allows the investigators to find coherent evidence faster and more intuitively. We have performed a user test where a group of people has evaluated our prototype tool against a modern commercial computer forensic tool and the results of this preliminary test are very promising. The results show that users completed the task in shorter time, with greater accuracy and with less errors using CyberForensic TimeLab. The subjects also experienced that the prototype were more intuitive to use and that it allowed them to easier locate evidence that was coherent in time.
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| 19. |
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| 20. |
- Olsson, Jens, et al.
(författare)
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Effects of resource level and habitat type on behavioural and morphological plasticity in Eurasian perch
- 2007
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Ingår i: Oecologia. - : Springer Science and Business Media LLC. - 0029-8549 .- 1432-1939. ; 152:1, s. 48-56
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Tidskriftsartikel (refereegranskat)abstract
- Spatial and temporal heterogeneity in the environment is a common feature affecting many natural populations. For example, both the resource levels and optimal habitat choices of individuals likely change over time. One way for organisms to cope with environmental variation is to display adaptive plasticity in traits such as behavior and morphology. Since trait plasticity is hypothesized to be a prerequisite for character divergence, studies of mechanisms behind such plasticity are warranted. In this study, we looked at the interaction of two potentially important environmental variables on behavioral and morphological plasticity in Eurasian perch (Perca fluviatilis L.). More specifically, the plastic responses in activity and morphology of perch exposed to different resource levels and simulated habitat types were studied in an aquarium experiment. The resource level experienced had a large influence on plasticity in both activity and morphology. Behavioral adaptations have been thought to mediate morphological transitions, and we suggest that the morphological response to the resource level was mediated by differences in activity and growth rates. The habitat type also affected morphological plasticity but to a lesser extent, and there was no effect on activity from habitat type. Based on these results, we suggest that it is essential to include several environmental factors acting in concert when studying mechanisms behind trait plasticity. We also propose that variation in resource levels might play a key role in fostering trait plasticity in at least fish populations, while other environmental variables such as divergent habitat complexities and prey types might be less influential. Dynamics in resource levels and optimal habitat choices might thus be important factors influencing character divergence in natural populations.
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| 21. |
- Olsson, Jens, et al.
(författare)
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Growth rate constrain morphological divergence when driven by competition
- 2006
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Ingår i: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 115:1, s. 15-22
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Tidskriftsartikel (refereegranskat)abstract
- Resource competition has been hypothesized to be important in driving divergence by natural selection. The effect of competition on morphological divergence and plasticity has however rarely been investigated. Since low growth rates might constrain morphological modulation and individual growth rates usually are negatively related to the intensity of competition, there might be a connection between competition, growth rate and morphological divergence. We performed an aquarium experiment with young-of-the-year Eurasian perch (Perca fluviatilis L.) to investigate how individual growth rate affected morphological plasticity induced by contrasting habitat treatments. Furthermore, in a field study of 10 lakes we also related the degree of morphological differentiation between habitats to the intraspecific competitior biomass. In the aquarium experiment we found that morphological plasticity was growth rate dependent in that morphological differentiation between the habitat treatments was confined to high individual growth rates. In the field study we found that morphological differentiation between habitats decreased with increasing intraspecific competitior biomass. Since plasticity is hypothesized to be important in divergence and intraspecific biomass could serve as a proxy for the level of competition, we suggest that our results indicate that morphological divergence might be constrained during periods of intense intraspecific competition due to low growth rates. A possible scenario is that at low growth rates all energy available is used for metabolic maintenance and no surplus energy is therefore available for morphological modulation.
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| 22. |
- Olsson, Jens, et al.
(författare)
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Gut length plasticity in perch : Into the bowels of resource polymorphisms
- 2007
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Ingår i: Biological Journal of the Linnean Society. - : Oxford University Press (OUP). - 0024-4066 .- 1095-8312. ; 90:3, s. 517-523
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Tidskriftsartikel (refereegranskat)abstract
- Resource polymorphisms, intraspecific variation in morphology due to differential resource use, are common across a wide range of animal taxa. The focus in studies of such polymorphisms has been on external morphology, but the differential use of food resources could also influence other phenotypic traits such as the digestive performance. In the present study, we experimentally demonstrate that Eurasian perch (Perca fluviatilis L.) display adaptive plasticity in gut length when exposed to different food types. Perch fed a less digestible food type developed relatively longer guts compared to fish fed a more easily digested food type. This divergence in gut length was also apparent under natural conditions because perch inhabiting the littoral and pelagic habitats of a lake differed in resource use and relative gut length. Despite that the digestive system in perch is plastic, we found that individuals switching to a novel food type might experience an initial fitness cost of the diet switch in the form of a temporary reduction in body condition. These results show the importance of gut length plasticity for an ontogenetic omnivore but also a cost that might prevent diet switching in polymorphic populations.
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| 23. |
- Olsson, Jens, et al.
(författare)
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Habitat structure, feeding mode and morphological reversibility: factors influencing phenotypic plasticity in perch
- 2005
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Ingår i: Evolutionary Ecology Research. - 1522-0613 .- 1937-3791. ; 7:8, s. 1109-1123
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Tidskriftsartikel (refereegranskat)abstract
- Questions: Do both habitat structure and feeding mode contribute to morphological divergence within fish populations? To what extent may an induced morphology be reversed?Organism: Young-of-the-year Eurasian perch (Perca fluviatilis L.).Methods: An aquarium experiment with a 2 × 2 factorial design (two levels of habitat structure and two levels of feeding mode). The habitat structure and feeding mode were reversed for perch in two habitat treatments midway through the experiment.Results: Both habitat structure and feeding mode contributed to morphological divergence (40.7% and 4.9% of the total variation respectively), which suggests that both habitat complexity and prey type diversity influence morphological adaptations in this fish species. Perch morphology is highly plastic and can be reversed in as short a time as 4 weeks.
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| 24. |
- Olsson, Jens, 1976-
(författare)
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Interplay Between Environment and Genes on Morphological Variation in Perch – Implications for Resource Polymorphisms
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Recent research has suggested that individual specialization within populations could be substantial and more common than previously acknowledged. Eurasian perch is one of many species of fish in lakes of postglacial origin that displays a morphological and dietary variation tightly coupled to the littoral and pelagic habitats of the lake. The occurrence of such resource polymorphisms might have important consequences for local adaptation and might also be an important initial step in speciation. I have investigated the importance of a number of factors for the development of resource polymorphisms using perch as a study organism. I found a weak genetic basis for morphological differences, and the environmental influence on morphology was of such a magnitude that an induced morphology could be reversed. The results nevertheless suggested that genetic differentiation could be substantial at small spatial and temporal scales, even within habitats. Several environmental factors were shown to influence the morphological development, and the results also suggest that behavioral differences could mediate a morphological response. I also found evidence for that competition-driven divergence might only occur when divergence in resource use is favoured at the same time as growth rates are kept sufficiently high for character divergence to be effective. The results finally indicate that divergence in the gut length of individuals might co-vary with habitat and diet use in resource polymorphic populations. This might enhance habitat fidelity and possibly also facilitate the persistence of resource polymorphisms since individuals should experience a cost of switching diets due to a too specific digestive system. Based on these findings I conclude that small scaled genetic differentiation might be more common than currently acknowledged, that more multi-factorial studies are needed if we are to fully understand the mechanisms behind trait diversity, and that competition not always favors divergence.
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| 25. |
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| 26. |
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| 27. |
- Olsson, Åsa, et al.
(författare)
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Overweight in relation to tumour size and axillary lymph node involvement in postmenopausal breast cancer patients-differences between women invited to vs. not invited to mammography in a randomized screening trial.
- 2009
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Ingår i: Cancer Epidemiology. - : Elsevier BV. - 1877-7821. ; 33:1, s. 41532-41532
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: Overweight is associated with advanced stage at diagnosis in breast cancer patients. This could be explained by specific tumour characteristics or tumour promoting factors in the obese, but a diagnostic delay could also be of importance. Mammographic screening has caused a change towards diagnosis of less advanced tumours. This study investigates invitation to mammographic screening and the association between overweight and tumour size/axillary lymph node involvement at breast cancer diagnosis in postmenopausal women. METHODS: In 1976 a randomized mammographic screening trial, inviting 50% of all women aged 45-69 was set up in Malmö, Sweden. The present analysis examined overweight (body mass index >or=25) as a determinant for large tumours (>20mm) and axillary lymph node involvement in postmenopausal women. These associations were studied separately in patients diagnosed prior to the mammographic screening trial, in invited women and in non-invited subjects (controls). In all, 2478 postmenopausal women were diagnosed with invasive breast cancer in these groups between 1961 and 1991. Logistic regression analysis allowed adjustment for other potential determinants of tumours size and axillary lymph node involvement. RESULTS: In women diagnosed before the onset of the screening trial and in women not invited to mammography in the trial (controls), overweight was positively associated with large tumour size and axillary node involvement. There was no statistically significant association between overweight and these factors in women invited to mammographic screening. CONCLUSION: Invitation to mammographic screening may be particularly important for overweight postmenopausal women in order to detect breast tumours early.
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| 28. |
- Panagiotou, Gianni, et al.
(författare)
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Intracellular metabolite profiling of Fusarium oxysporum converting glucose to ethanol
- 2005
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Ingår i: Journal of Biotechnology. - : Elsevier BV. - 0168-1656 .- 1873-4863. ; 115:4, s. 425-434
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Tidskriftsartikel (refereegranskat)abstract
- The filamentous fungus Fusarium oxysporum is known for its ability to produce ethanol by simultaneous saccharification and fermentation (SSF) of cellulose. However, the conversion rate is low and significant amounts of acetic acid are produced as a by-product. In this study, the growth characteristics of F. oxysporum were evaluated in a minimal medium using glucose as the sole carbon source in aerobic, anaerobic and oxygen-limited batch cultivations. Under aerobic conditions the maximum specific growth rate was found to be 0.043 h−1, and the highest ethanol yield (1.66 mol/mol) was found under anaerobic conditions. During the different phases of the cultivations, the intracellular profiles were determined under aerobic and anaerobic conditions. The profiles of the phosphorylated intermediates indicated that there was a high glycolytic flux at anaerobic growth conditions, characterized by high efflux of glyceraldehyde-3-phosphate (G3P) and fructose-6-phosphate (F6P) from the pentose phosphate pathway (PPP) to the Embden–Meyerhof–Parnas (EMP) pathway, resulting in the highest ethanol production under these conditions. The amino acid profile clearly suggests that the TCA cycle was primarily active under aerobic cultivation. On the other hand, the presence of high levels of γ-amino-n-butyric acid (GABA) under anaerobic conditions suggests a functional GABA bypass and a possible block in the TCA cycle at these conditions.
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| 29. |
- Panagiotou, Gianni, 1974, et al.
(författare)
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Studies of the Production of Fungal Polyketides in Aspergillus nidulans by Using Systems Biology Tools
- 2009
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Ingår i: Applied and Environmental Microbiology. - 1098-5336 .- 0099-2240. ; 75:7, s. 2212-2220
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Tidskriftsartikel (refereegranskat)abstract
- Many filamentous fungi produce polyketide molecules with great significance as human pharmaceuticals; these molecules include the cholesterol-lowering compound lovastatin, which was originally isolated from Aspergillus terreus. The chemical diversity and potential uses of these compounds are virtually unlimited, and it is thus of great interest to develop a well-described microbial production platform for polyketides. Using genetic engineering tools available for the model organism Aspergillus nidulans, we constructed two recombinant strains, one expressing the Penicillium grisefulvum 6-methylsalicylic acid (6-MSA) synthase gene and one expressing the 6-MSA syntase gene and overexpressing the native xylulose-5-phosphate phosphoketolase gene (xpkA) for increasing the pool of polyketide precursor levels. The physiology of the recombinant strains and that of a reference wild-type strain were characterized on glucose, xylose, glycerol, and ethanol media in controlled bioreactors. Glucose was found to be the preferred carbon source for 6-MSA production, and 6-MSA concentrations up to 455 mg/liter were obtained for the recombinant strain harboring the 6-MSA gene. Our findings indicate that overexpression of xpkA does not directly improve 6-MSA production on glucose, but it is possible, if the metabolic flux through the lower part of glycolysis is reduced, to obtain quite high yields for conversion of sugar to 6-MSA. Systems biology tools were employed for in-depth analysis of the metabolic processes. Transcriptome analysis of 6-MSA-producing strains grown on glucose and xylose in the presence and absence of xpkA overexpression, combined with flux and phsyiology data, enabled us to propose an xpkA-msaS interaction model describing the competition between biomass formation and 6-MSA production for the available acetyl coenzyme A.
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| 30. |
- Panagiotou, Gianni, 1974, et al.
(författare)
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Systems Analysis Unfolds the Relationship between the Phosphoketolase Pathway and Growth in Aspergillus nidulans
- 2008
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203 .- 1932-6203. ; 3:12
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Tidskriftsartikel (refereegranskat)abstract
- Background: Aspergillus nidulans is an important model organism for studies on fundamental eukaryotic cell biology and on industrial processes due to its close relation to A. niger and A. oryzae. Here we identified the gene coding for a novel metabolic pathway in A. nidulans, namely the phosphoketolase pathway, and investigated the role of an increased phosphoketolase activity. Methodology/Principal findings: Over-expression of the phosphoketolase gene (phk) improved the specific growth rate on xylose, glycerol and ethanol. Transcriptome analysis showed that a total of 1,222 genes were significantly affected by over-expression of the phk, while more than half of the affected genes were carbon source specific. During growth on glucose medium, the transcriptome analysis showed that the response to phk over-expression is targeted to neutralize the effect of the over-expression by regulating the acetate metabolism and initiate a growth dampening response. Conclusions/Significance: Metabolic flux analysis using 13C-labelled glucose, showed that over-expression of phosphoketolase added flexibility to the central metabolism. Our findings further suggests that A. nidulans is not optimized for growth on xylose, glycerol or ethanol as the sole carbon sources.
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| 31. |
- Usaite, Renata, et al.
(författare)
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Characterization of Global Yeast Quantitative Proteome Data Generated from the Wild-Type and Glucose Repression Saccharomyces cerevisiae Strains: The comparison of two Quantitative Methods
- 2008
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Ingår i: Journal of Proteome Research. - 1535-3907 .- 1535-3893. ; 266:7, s. 266-275
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Tidskriftsartikel (refereegranskat)abstract
- The quantitative proteomic analysis of complex protein mixtures is emerging as a technically challenging but viable systems-level approach for studying cellular function. This study presents a large-scale comparative analysis of protein abundances from yeast protein lysates derived from both wild-type yeast and yeast strains lacking key components of the Snf1 kinase complex. Four different strains were grown under well-controlled chemostat conditions. Multidimensional protein identification technology followed by quantitation using either spectral counting or stable isotope labeling approaches was used to identify relative changes in the protein expression levels between the strains. A total of 2388 proteins were relatively quantified, and more than 350 proteins were found to have significantly different expression levels between the two strains of comparison when using the stable isotope labeling strategy. The stable isotope labeling based quantitative approach was found to be highly reproducible among biological replicates when complex protein mixtures containing small expression changes were analyzed. Where poor correlation between stable isotope labeling and spectral counting was found, the major reason behind the discrepancy was the lack of reproducible sampling for proteins with low spectral counts. The functional categorization of the relative protein expression differences that occur in Snf1-deficient strains uncovers a wide range of biological processes regulated by this important cellular kinase.
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| 32. |
- Usaite, Renata, et al.
(författare)
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Physiological characterization of glucose repression in the strains with SNF1 and SNF4 genes deleted
- 2008
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Ingår i: Journal of Biotechnology. - 1873-4863 .- 0168-1656. ; :133, s. 73-81
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Tidskriftsartikel (refereegranskat)abstract
- We investigated the effect of Snf1 kinase and its regulatory subunit Snf4 on the regulation of glucose and galactose metabolism in the yeast Saccharomyces cerevisiae by physiologically characterizing ∆snf1, ∆snf4 and ∆snf1∆snf4 in CEN.PK background in glucose and glucose-galactose-mixture batch cultivations. The main result of this study showed that delayed induction of galactose catabolism was SNF1 or SNF4 gene deletion specific. In comparison to the reference strain, growth delay on galactose was found to last 2.4 times (7 h), 3.1 times (10.5 h) and 9.6 times (43 h) longer for the ∆snf4, ∆snf1 and ∆snf1∆snf4 strains, respectively. The maximum specific growth rates on galactose were determined to be two to three times lower for the recombinant strains compared to the reference strain (0.13 h-1) and were found to be 0.07, 0.08 and 0.04 h-1 for the ∆snf1, ∆snf4 and ∆snf1∆snf4 strains, respectively. The study showed that Snf1 kinase was not solely responsible for the depression of galactose metabolism.
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| 33. |
- Usaite, Renata, et al.
(författare)
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Reconstruction of the yeast Snf1 kinase regulatory network reveals its role as a global energy regulator
- 2009
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Ingår i: Molecular Systems Biology. - : EMBO. - 1744-4292. ; 5:319, s. 1-12
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Tidskriftsartikel (refereegranskat)abstract
- Highly conserved among eukaryotic cells, ghe AMP-activated kinase (AMPK) is a central regulator of carbon metabolism. To map the complete network of interactions around AMPK in yeast (Snf1) and to evaluate the role of its regulatory subunit Snf4, we measured global mRNA, protein and metabolite levels in wild type, ∆snf1, ∆snf4, and ∆snf1∆snf4 knockout strains. Using four newly developed computional tools, including novel DOGMA sub-network analysis, we showed the benefits of three-level ome-data integration to uncover the global Snf1 kinase role in yeast. We for the first time identified Snf1's global regulation on gene and protein expression levels, and showed that yeast Snf1 has a far more extensive function in controlling energy metabolism that reported earlier. Additionally, we identified complementary roles of Snf1 and Snf4. Similar to the function of AMPK in humans, our findings showed that Snf1 is a low-energy checkpoint and that yeast can be used more extensively as a model system for studying the molecular mechanisms underlying the global regulation of AMPK in mammals, failure of which leads to metabolic diseases.
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