| 1. |
- Ahlberg, Per, et al.
(författare)
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Phosphatised olenid trilobites and associated fauna from the Upper Cambrian of Vastergotland, Sweden
- 2005
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Ingår i: Acta Palaeontologica Polonica. - 0567-7920. ; 50:3, s. 429-440
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Tidskriftsartikel (refereegranskat)abstract
- Secondarily phosphatised olenid trilobites from organic-rich limestones (orsten) in the Furongian (Upper Cambrian) of Vastergotland, south-central Sweden, are described and illustrated. All trilobites originate from the Peltura scarabaeoides Zone and were collected on the western slope of Kinnekulle. Only the dorsal exoskeletons have become secondarily phosphatised, and the ventral appendages are not preserved. Yet the material is otherwise remarkably well preserved and reveals the morphology of the olenid trilobites in greater detail than hitherto known. Species belonging to the genera Ctenopyge, Sphaerophthalmus, Parabolina, and Peltura are identified, and several juvenile specimens are present in the material. The material is disarticulated and fragmentary, and it has only been possible to identify a few specimens to species level. In addition to chaetognaths and conodonts, the trilobites are associated with pelmatozoan columnals, a possible camaroid, and fossils of uncertain affinities. These fossils, along with a probable conulariid fragment from the Peltura minor Zone, are also described and discussed. The presence of a benthic fauna of pelmatozoans, and possible conulariids and camaroids, indicates that at least parts of the Peltura zones were deposited during dysoxic rather than anoxic periods. Moreover, the sea floor must have been firm enough to allow colonisation by sessile organisms.
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| 2. |
- Bengtson, Per, et al.
(författare)
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Bacterial immobilization and remineralization of N at different growth rates and N concentrations
- 2005
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Ingår i: FEMS Microbiology Ecology. - : Oxford University Press (OUP). - 1574-6941 .- 0168-6496. ; 54:1, s. 13-19
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Tidskriftsartikel (refereegranskat)abstract
- An experiment was designed to resolve two largely unaddressed questions about the turnover of N in soils. One is the influence of microbial growth rate on mobilization and remineralization of cellular N. The other is to what extent heterotrophic immobilization of NO3- is controlled by the soil concentration of NH4+. Bacteria were extracted from a deciduous forest soil and inoculated into an aqueous medium. Various N pool dilution/enrichment experiments were carried out to: (1) calculate the gross N immobilization and remineralization rates; (2) investigate their dependence on NH4+ and NO3- concentrations; (3) establish the microbial preference for NH4+ and NO3- depending on the NH4+/NO3- concentration ratio. Remineralization of microbial N occurred mainly at high growth rates and NH4+ concentrations. There was a positive correlation between NH4+ immobilization and remineralization rates, and intracellular recycling of N seemed to be an efficient way for bacteria to withstand low inorganic N concentrations. Thus, extensive remineralization of microbial N is likely to occur only when environmental conditions promote high growth rates. The results support previous observations of high NO3- immobilization rates, especially at low NH4+ concentrations, but NO3- was also immobilized at high NH4 concentrations. The latter can be understood if part of the microbial community has a preference for NO3- over NH4+ (c) 2005 Federation of European Microbiological Societies. Published by Elsevier B.V. All rights reserved.
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| 3. |
- Bengtson, Per, 1971-, et al.
(författare)
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Characterization of EBV-transformed B-cells established from an individual homozygously mutated (G329A) in the FUT7 alpha1,3-fucosyltransferase gene
- 2005
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Ingår i: Scand J Immunol. - : Wiley. ; 62:3, s. 251-8
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Tidskriftsartikel (refereegranskat)abstract
- The alpha1,3-fucosyltransferase VII (Fuc-TVII) is involved in the biosynthesis of E- and P-selectin ligands such as sialyl Lewis x (SLe(x)) on human leukocytes. Recently, individuals were characterized carrying a missense mutation (G329A; Arg110-Gln) in the FUT7 gene encoding this enzyme. The mutated FUT7 construct produced a Fuc-TVII enzyme with impaired activity compared with the wildtype enzyme. Polymorphonuclear granulocytes from an individual carrying this mutation homozygously also showed a reduced expression of SLe(x). In the present study, we have established Epstein-Barr virus-transformed B-cell lines from this individual (SIGN) and from an individual not carrying the mutation (IWO). The cell lines were confirmed to be of B-cell origin by flow cytometry analysis. IWO cells interacted with E-selectin in an in vitro flow chamber analysis whereas SIGN cell did not. However, when SIGN cell was transiently transfected with wildtype FUT7 cDNA, interaction with E-selectin could be restored. Cell surface expression of the SLe(x)-related epitopes recognized by antibodies CSLEX-1, KM-93 and HECA-452 was elevated on IWO cells compared with that on SIGN cells, consistent with a role of these antigens in E-selectin recognition. These cell lines will be useful in further characterization of E-selectin ligands and encourage further studies on the consequences of the FUT7-G329A mutation in vivo.
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| 4. |
- Bengtson, Per, et al.
(författare)
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Links between methanotroph community composition and CH(4) oxidation in a pine forest soil
- 2009
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Ingår i: FEMS Microbiology Ecology. - : Oxford University Press (OUP). - 1574-6941 .- 0168-6496. ; 70:3, s. 356-366
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Tidskriftsartikel (refereegranskat)abstract
- The main gap in our knowledge about what determines the rate of CH(4) oxidation in forest soils is the biology of the microorganisms involved, the identity of which remains unclear. In this study, we used stable-isotope probing (SIP) following (13)CH(4) incorporation into phospholipid fatty acids (PLFAs) and DNA/RNA, and sequencing of methane mono-oxygenase (pmoA) genes, to identify the influence of variation in community composition on CH(4) oxidation rates. The rates of (13)C incorporation into PLFAs differed between horizons, with low (13)C incorporation in the organic soil and relatively high (13)C incorporation into the two mineral horizons. The microbial community composition of the methanotrophs incorporating the (13)C label also differed between horizons, and statistical analyses suggested that the methanotroph community composition was a major cause of variation in CH(4) oxidation rates. Both PLFA and pmoA-based data indicated that CH(4) oxidizers in this soil belong to the uncultivated 'upland soil cluster alpha'. CH(4) oxidation potential exhibited the opposite pattern to (13)C incorporation, suggesting that CH(4) oxidation potential assays may correlate poorly with in situ oxidation rates. The DNA/RNA-SIP assay was not successful, most likely due to insufficient (13)C-incorporation into DNA/RNA. The limitations of the technique are briefly discussed.
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| 5. |
- Bengtson, Per, et al.
(författare)
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Possible role of reactive chlorine in microbial antagonism and organic matter chlorination in terrestrial environments
- 2009
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Ingår i: Environmental Microbiology. - : Wiley. - 1462-2912 .- 1462-2920. ; 11:6, s. 1330-1339
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Forskningsöversikt (refereegranskat)abstract
- Several studies have demonstrated that extensive formation of organically bound chlorine occurs both in soil and in decaying plant material. Previous studies suggest that enzymatic formation of reactive chlorine outside cells is a major source. However, the ecological role of microbial-induced extracellular chlorination processes remains unclear. In the present paper, we assess whether or not the literature supports the hypothesis that extracellular chlorination is involved in direct antagonism against competitors for the same resources. Our review shows that it is by no means rare that biotic processes create conditions that render biocidal concentrations of reactive chlorine compounds, which suggest that extracellular production of reactive chlorine may have an important role in antagonistic microbial interactions. To test the validity, we searched the UniprotPK database for microorganisms that are known to produce haloperoxidases. It appeared that many of the identified haloperoxidases from terrestrial environments are originating from organisms that are associated with living plants or decomposing plant material. The results of the in silico screening were supported by various field and laboratory studies on natural chlorination. Hence, the ability to produce reactive chlorine seems to be especially common in environments that are known for antibiotic-mediated competition for resources (interference competition). Yet, the ability to produce haloperoxidases is also recorded, for example, for plant endosymbionts and parasites, and there is little or no empirical evidence that suggests that these organisms are antagonistic.
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| 6. |
- Bengtson, Per, et al.
(författare)
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Rapid turnover of DOC in temperate forests accounts for increased CO2 production at elevated temperatures
- 2007
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 10:9, s. 783-790
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The evidence for the contribution of soil warming to changes in atmospheric CO2 concentrations and carbon stocks of temperate forest ecosystems is equivocal. Here, we use data from a beech/oak forest on concentrations and stable isotope ratios of dissolved organic carbon (DOC), phosphate buffer-extractable organic carbon, soil organic carbon (SOC), respiration and microbial gross assimilation of N to show that respired soil carbon originated from DOC. However, the respiration was not dependent on the DOC concentration but exceeded the daily DOC pool three to four times, suggesting that DOC was turned over several times per day. A mass flow model helped to calculate that a maximum of 40% of the daily DOC production was derived from SOC and to demonstrate that degradation of SOC is limiting respiration of DOC. The carbon flow model on SOC, DOC, microbial C mobilization/immobilization and respiration is linked by temperature-dependent microbial and enzyme activity to global warming effects Of CO2 emitted to the atmosphere.
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| 7. |
- Bengtson, Per, et al.
(författare)
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Relieving substrate limitation-soil moisture and temperature determine gross N transformation rates
- 2005
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Ingår i: Oikos. - : Wiley. - 1600-0706 .- 0030-1299. ; 111:1, s. 81-90
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Tidskriftsartikel (refereegranskat)abstract
- A field experiment was designed with the objective to reveal the interactions between soil moisture, temperature, total, dissolved, and phosphate buffer extractable C and N, and microbial activity in the control of in situ gross N mineralization and immobilization rates in a deciduous forest. We had three alternative hypotheses to explain variations of the gross N transformations: 1) microorganisms are C limited, 2) microorganisms are N limited, or 3) neither C nor N limit the microorganisms but moisture and temperature conditions. Each hypothesis had specific criteria to be fulfilled for its acceptance. The results demonstrated that gross N transformation rates were more dependent on and variable with soil moisture and temperature than the size of the different C and N pools. The immobilization of N was dependent on the gross mineralization rate, suggesting that the production of enzymes for mineralization of organic N and the immobilization of N from the surrounding soil is disconfirmed when the intracellular N content of the microorganisms is sufficiently high. If the microorganisms are starved for N, enzyme systems involved in both the assimilation and mineralization of N are activated. The mean in situ gross N mineralization rate was two orders of magnitude higher than the natural N deposition in the area and the N addition in the NITREX experiments, meaning that a reduction in the gross N mineralization rate of about 1% would be enough to compensate for the addition of inorganic N. This decrease would hardly be detectable given the great spatial and temporal variability of N transformation rates.
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| 8. |
- Bengtson, Per, et al.
(författare)
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Spatial distributions of plants and gross N transformation rates in a forest soil
- 2006
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Ingår i: Journal of Ecology. - : Wiley. - 1365-2745 .- 0022-0477. ; 94:4, s. 754-764
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- 1 This work demonstrates that spatial distribution of understorey vegetation and gross N transformation rates in a mixed beach-oak forest is closely correlated within a distance of a few metres. The findings imply that plant diversity and productivity have a major influence on gross rates of N transformation and vice versa. 2 A geostatistical analysis was used to evaluate the spatial relationships between abundance and species composition of the understorey vegetation and in situ gross N mineralization, NH4+ immobolization and nitrification rates. 3 The gross N transformation rates and the plants spatial variation were correlated within the forest, but plant distribution was more dependent on the fraction of mineralized N that was nitrified than on individual N transformation rates. 4 The total cover of the understorey vegetation varied more in space than the species composition, and was higher in areas with high N transformation rates. 5 Plant species benefiting from high net nitrification rates were more common in areas with a low activity of mineralizing and nitrifying microorganisms, possibly because the net and gross rates were independent of each other. In fact, those species occurred most often in areas in which a large fraction of mineralized N was nitrified. 6 Beech and oak trees also had an effect on the spatial variation of the understorey vegetation. Beech trees provided conditions more suitable for plants benefiting from NO3-, whereas the vascular plant cover was greater under oak trees, probably in response to a higher light interception than under beech trees. 7 Oak generally had a positive impact on gross N transformation rates compared with beech, perhaps reflecting differences in litter quality and climate caused by the two species. 8 The influence of trees alone could not explain the full magnitude of the variation of N transformation rates or the presence of overlapping areas with high mineralization and immobilization rates. These were probably caused by other factors, such as soil moisture content. 9 This work sheds new light on the small-scale spatial links between above-ground plant diversity and abundance, and below-ground microbial N transformations.
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| 9. |
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| 10. |
- Holmstedt, Göran, et al.
(författare)
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Determination of uncertainty of different CFD codes by means of comparison with experimental fire scenarios
- 2009
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Ingår i: Conference Proceedings - Fire and Materials 2009, 11th International Conference and Exhibition.
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Konferensbidrag (refereegranskat)abstract
- This article will summarise the evaluation of four CFD software codes (CFX, FDS4, SMAFS and SOFIE). Evaluation was performed by means of comparing the simulation data with experimental scenarios. The scenarios were chosen to represent scenarios frequently assessed using fire safety design based on performance. The greatest difficulty during validation of CFD-codes is to find well documented relevant experiments. It is true that many large scale experiments including smoke spread have been published but many of them are not described sufficiently and are therefore impossible to use for validation. It is very unusual that data on reproducibility and repeatability is available. After an extensive discussion between the participants in the project five scenarios were chosen. Scenarios 1A (large room with vents), and scenarios 1B1 and 1B2 (corridor with vents) were well documented experiments (repeatability) with ceiling vents and ceiling jets performed earlier at SP in Boras. Scenario 2 is a tunnel fire taken from an experimental study in Boston, US. Scenario 3 is an atrium fire taken from an experimental study in Japan. Lack of well documented fires in retail premises lead us to perform a series of tests in 1/2 scale, 4.1 and 4.2 at SP in Boras. Scenario 5 is an experimental study from Australia including smoke spread from a fire room to an adjacent corridor and a room. The conditions for the simulations included information about the scenarios given above. No information about experimental results was available until the results from the simulations had been sent in to the project manager. The intention was to imitate the working conditions for a consultant as far as possible when using a CFD-simulation to estimate fire safety. In this manner the simulations are dependent on many factors such as the CFD-code used, judgement of input data of the scenarios done by the operator, operator skill etc. The results from the evaluation of the CFD codes showed that the simulation results generally were a good description of the experimental fires studied, but that limitations and specific properties of the different codes, together with the operator factor, can strongly influence the results. The detailed results of all comparisons are given in the final report of the project. It was not possible to include these detailed evaluations in this conference paper but these results are available in the main report as well as in future scientific articles.
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| 11. |
- Holmstedt, Göran, et al.
(författare)
-
Validation of CFD codes
- 2008
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Use of CFD (computional fluid dynamics) softwarepackages within fire performance based engineeringand risk assessment is increasing substantially.An important part in the process is thequality assurance. For this reason the SwedishRescue Services Agency (SRV) sponsored aunique research project. Within the project differentcodes for smoke spread and evacuationhave been evaluated. This poster will focus onthe evaluation of four CFD software codes.
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| 12. |
- Månsson, Katarina, et al.
(författare)
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Plant-microbial competition for nitrogen uncoupled from soil C:N ratios
- 2009
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Ingår i: Oikos. - : Wiley. - 1600-0706 .- 0030-1299. ; 118:12, s. 1908-1916
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Tidskriftsartikel (refereegranskat)abstract
- A green house experiment was designed to test the idea that competition for inorganic nitrogen (N) between plants and heterotrophic microorganisms occurs in soils with high C:N ratios, qualifying for N limited microbial activity, but not at low C:N ratios. The short- term (24 h) N-15 uptake by the grass Festuca gigantea and microorganisms in planted and unplanted soils was determined, and the bacterial activity was measured by the H-3-thymidine incorporation technique. Two deciduous forest soils, with C:N-ratios of 20 and 31, and the 20 soil amended with litter to a C:N ratio of 34, were used. A novel and important part of the experimental design was the preparation of the unplanted reference soil with plants present until the competition assay started by the addition of N-15 labelled ammonium (NH4+) or nitrate (NO3-). The results suggested that plants and soil microorganisms competed for mineral N but under influence of other factors than the soil C:N ratio. The plants reduced the microbial uptake of NH4+ and NO3- in the soil with low C:N ratio, which also had the lowest bacterial activity. The plants had a larger N uptake than microorganisms in the two natural soils but smaller in the litter-amended, and their presence enhanced the bacterial activity, especially in the latter soil. The litter-amended soil with its high C:N ratio and easily decomposable C was the soil that best fulfilled the criteria for competition, including a net consumption of mineral N during the assay, the lowest plant uptake of mineral N due to the high N immobilization by microorganisms, and a reduced microbial N-15 uptake-to-bacterial activity in the presence of plants. Thus, other factors, such as the decomposability of the soil C and the bacterial activity, were more important than the soil C:N ratio to the outcome of plant-microbial competition for N.
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| 13. |
- Olsson, Pål Axel, et al.
(författare)
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C-13 incorporation into signature fatty acids as an assay for carbon allocation in arbuscular mycorrhiza
- 2005
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Ingår i: Applied and Environmental Microbiology. - 0099-2240. ; 71:5, s. 2592-2599
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Tidskriftsartikel (refereegranskat)abstract
- The ubiquitous arbuscular mycorrhizal fungi consume significant amounts of plant assimilated C, but this C flow has been difficult to quantify. The neutral lipid fatty acid 16:1ω 5 is a quantitative signature for most arbuscular mycorrhizal fungi in roots and soil. We measured carbon transfer from four plant species to the arbuscular mycorrhizal fungus Glomus intraradices by estimating C-13 enrichment of 16:1ω 5 and compared it with C-13 enrichment of total root and mycelial C. Carbon allocation to mycelia was detected within 1 day in monoxenic arbuscular mycorrhizal root cultures labeled with [C-13] glucose. The 13 C enrichment of neutral lipid fatty acid 16:1ω 5 extracted from roots increased from 0.14% 1 day after labeling to 2.2% 7 days after labeling. The colonized roots usually were more enriched for C-13 in the arbuscular mycorrhizal fungal neutral lipid fatty acid 16:1w5 than for the root specific neutral lipid fatty acid 18:2ω 6,9. We labeled plant assimilates by using (CO2)-C-13 in whole-plant experiments. The extraradical mycelium often was more enriched for C-13 than was the intraradical mycelium, suggesting rapid translocation of carbon to and more active growth by the extraradical mycelium. Since there was a good correlation between 13C enrichment in neutral lipid fatty acid 16:1ω 5 and total C-13 in extraradical mycelia in different systems (r(2) = 0.94), we propose that the total amount of labeled C in intraradical and extraradical mycelium can be calculated from the C-13 enrichment of 16:1ω 5. The method described enables evaluation of C flow from plants to arbuscular mycorrhizal fungi to be made without extraction, purification and identification of fungal mycelia.
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| 14. |
- Svensson, Katrin, et al.
(författare)
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Hypoxia-mediated induction of the polyamine system provides opportunities for tumor growth inhibition by combined targeting of vascular endothelial growth factor and ornithine decarboxylase.
- 2008
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Ingår i: Cancer Research. - 1538-7445. ; 68:22, s. 9291-9301
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Tidskriftsartikel (refereegranskat)abstract
- Hypoxia is a hallmark of solid tumors, which may offer opportunities for targeted therapies of cancer; however, the mechanisms that link hypoxia to malignant transformation and tumor progression are not fully understood. Here, we show that up-regulation of the polyamine system promotes cancer cell survival during hypoxic stress. Hypoxia was found to induce polyamine transport and the key enzyme of polyamine biosynthesis, ornithine decarboxylase (ODC), in a variety of cancer cell lines. Increased ODC protein expression was shown in hypoxic, GLUT-1-expressing regions of tumor spheroids and experimental tumors, as well as in clinical tumor specimens. Hypoxic induction of the polyamine system was dependent on antizyme inhibitor (i.e., a key positive regulator of ODC and polyamine transport), as shown by RNA interference experiments. Interestingly, depletion of the polyamines during hypoxia resulted in increased apoptosis, which indicates an essential role of the polyamines in cancer cell adaptation to hypoxic stress. These results were supported by experiments in an in vivo glioma tumor model, showing significantly enhanced antitumor effects of the antiangiogenic, humanized anti-vascular endothelial growth factor (VEGF) antibody bevacizumab when used in combination with the well-established, irreversible inhibitor of ODC, alpha-difluoromethylornithine. Our results provide important insights into the hypoxic stress response in malignant cells and implicate combined targeting of VEGF and ODC as an alternative strategy to treat cancer disease.
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| 15. |
- Welch, Johanna E, et al.
(författare)
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Single chain fragment anti-heparan sulfate antibody targets the polyamine transport system and attenuates polyamine-dependent cell proliferation.
- 2008
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Ingår i: International Journal of Oncology. - 1019-6439. ; 32:4, s. 749-756
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Tidskriftsartikel (refereegranskat)abstract
- The growth-promoting polyamines are polybasic compounds that efficiently enter cancer cells by as yet incompletely defined mechanisms. Strategies to inhibit their internalization may have important implications in the management of tumor disease. Here, we show that cellular binding and uptake of polyamines are inhibited by a single chain variable fragment anti-heparan sulfate (HS) antibody. Polyamine uptake was inhibited in a dose-dependent manner, and was associated with compensatory up-regulation of ornithine decarboxylase (ODC), i.e. the key enzyme of the polyamine biosynthesis pathway. Conversely, depletion of intracellular polyamines by the specific ODC-inhibitor alpha-difluoromethylornithine (DFMO) resulted in increased cellular binding of polyamine and anti-HS antibody. Importantly, anti-HS antibody also efficiently targeted DFMO-induced polyamine uptake, and combined polyamine biosynthesis inhibition by DFMO, and uptake inhibition by anti-HS antibody attenuated tumor cell proliferation in vitro. In conclusion, cell-surface HS proteoglycan is a relevant target for antibody-mediated inhibition of the uptake of polyamines, and polyamine-dependent cell proliferation.
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| 16. |
- Wittrup, Anders, et al.
(författare)
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ScFv antibody-induced translocation of cell-surface heparan sulfate proteoglycan to endocytic vesicles: Evidence for heparan sulfate epitope specificity and role of both syndecan and glypican.
- 2009
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Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 284:47, s. 32959-32967
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Tidskriftsartikel (refereegranskat)abstract
- Cellular uptake of several viruses and polybasic macromolecules requires the expression of cell-surface heparan sulfate proteoglycan (HSPG) through as yet ill-defined mechanisms. We unexpectedly found that among several cell-surface binding scFv anti-HS antibody (alphaHS) clones only one, AO4B08, efficiently translocated macromolecular cargo to intracellular vesicles through induction of HSPG endocytosis. Interestingly, AO4B08-induced PG internalization was strictly dependent on HS 2-O-sulfation and appeared independent on intact N-sulfation. AO4B08 and HIV-tat, i.e. a well-known cell penetrating peptide, were shown to compete for the internalizing PG population. To obtain a more detailed characterization of this pathway, we have developed a procedure for the isolation of endocytic vesicles by conjugating AO4B08 with superparamagnetic nano-particles. [35S]sulfate-labelled HSPG was found to accumulate in isolated, AO4B08-containing vesicles, providing first biochemical evidence for intact HSPG co-internalization with its ligand. Further analysis revealed the existence of both syndecan, i.e. a transmembrane HSPG, and glycosylphosphatidyl- inositol anchored glypican in purified vesicles. Importantly, internalized syndecan and glypican were found to colocalize in AO4B08-containing vesicles. Our data establish HSPGs as true internalizing receptors of macromolecular cargo, and indicate that the sorting of cell-surface HSPG to endocytic vesicles is determined by a specific HS epitope that can be carried by both syndecan and glypican core protein.
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