| 1. |
- Loth, Daan W, et al.
(författare)
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Genome-wide association analysis identifies six new loci associated with forced vital capacity
- 2014
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Ingår i: Nature Genetics. - : Springer Science and Business Media LLC. - 1061-4036 .- 1546-1718. ; 46, s. 669-677
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Tidskriftsartikel (refereegranskat)abstract
- Forced vital capacity (FVC), a spirometric measure of pulmonary function, reflects lung volume and is used to diagnose and monitor lung diseases. We performed genome-wide association study meta-analysis of FVC in 52,253 individuals from 26 studies and followed up the top associations in 32,917 additional individuals of European ancestry. We found six new regions associated at genome-wide significance (P < 5 × 10(-8)) with FVC in or near EFEMP1, BMP6, MIR129-2-HSD17B12, PRDM11, WWOX and KCNJ2. Two loci previously associated with spirometric measures (GSTCD and PTCH1) were related to FVC. Newly implicated regions were followed up in samples from African-American, Korean, Chinese and Hispanic individuals. We detected transcripts for all six newly implicated genes in human lung tissue. The new loci may inform mechanisms involved in lung development and the pathogenesis of restrictive lung disease.
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| 2. |
- Aoun, M., et al.
(författare)
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Antigen-presenting autoreactive B cells activate regulatory T cells and suppress autoimmune arthritis in mice
- 2023
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Ingår i: Journal of Experimental Medicine. - Stockholm : Karolinska Institutet, Dept of Medical Biochemistry and Biophysics. - 0022-1007 .- 1540-9538. ; 220:11
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Tidskriftsartikel (refereegranskat)abstract
- B cells undergo several rounds of selection to eliminate potentially pathogenic autoreactive clones, but in contrast to T cells, evidence of positive selection of autoreactive B cells remains moot. Using unique tetramers, we traced natural autoreactive B cells (C1-B) specific for a defined triple-helical epitope on collagen type-II (COL2), constituting a sizeable fraction of the physiological B cell repertoire in mice, rats, and humans. Adoptive transfer of C1-B suppressed arthritis independently of IL10, separating them from IL10-secreting regulatory B cells. Single-cell sequencing revealed an antigen processing and presentation signature, including induced expression of CD72 and CCR7 as surface markers. C1-B presented COL2 to T cells and induced the expansion of regulatory T cells in a contact-dependent manner. CD72 blockade impeded this effect suggesting a new downstream suppressor mechanism that regulates antigen-specific T cell tolerization. Thus, our results indicate that autoreactive antigen-specific naive B cells tolerize infiltrating T cells against self-antigens to impede the development of tissue-specific autoimmune inflammation.
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| 3. |
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| 4. |
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| 5. |
- Hagg, S, et al.
(författare)
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Short telomere length is associated with impaired cognitive performance in European ancestry cohorts
- 2017
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Ingår i: Translational psychiatry. - : Springer Science and Business Media LLC. - 2158-3188. ; 7:4, s. e1100-
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Tidskriftsartikel (refereegranskat)abstract
- The association between telomere length (TL) dynamics on cognitive performance over the life-course is not well understood. This study meta-analyses observational and causal associations between TL and six cognitive traits, with stratifications on APOE genotype, in a Mendelian Randomization (MR) framework. Twelve European cohorts (N=17 052; mean age=59.2±8.8 years) provided results for associations between qPCR-measured TL (T/S-ratio scale) and general cognitive function, mini-mental state exam (MMSE), processing speed by digit symbol substitution test (DSST), visuospatial functioning, memory and executive functioning (STROOP). In addition, a genetic risk score (GRS) for TL including seven known genetic variants for TL was calculated, and used in associations with cognitive traits as outcomes in all cohorts. Observational analyses showed that longer telomeres were associated with better scores on DSST (β=0.051 per s.d.-increase of TL; 95% confidence interval (CI): 0.024, 0.077; P=0.0002), and MMSE (β=0.025; 95% CI: 0.002, 0.047; P=0.03), and faster STROOP (β=−0.053; 95% CI: −0.087, −0.018; P=0.003). Effects for DSST were stronger in APOE ɛ4 non-carriers (β=0.081; 95% CI: 0.045, 0.117; P=1.0 × 10−5), whereas carriers performed better in STROOP (β=−0.074; 95% CI: −0.140, −0.009; P=0.03). Causal associations were found for STROOP only (β=−0.598 per s.d.-increase of TL; 95% CI: −1.125, −0.072; P=0.026), with a larger effect in ɛ4-carriers (β=−0.699; 95% CI: −1.330, −0.069; P=0.03). Two-sample replication analyses using CHARGE summary statistics showed causal effects between TL and general cognitive function and DSST, but not with STROOP. In conclusion, we suggest causal effects from longer TL on better cognitive performance, where APOE ɛ4-carriers might be at differential risk.
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| 6. |
- Dimmock, Andrew P., et al.
(författare)
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Modeling the Geomagnetic Response to the September 2017 Space Weather Event Over Fennoscandia Using the Space Weather Modeling Framework : Studying the Impacts of Spatial Resolution
- 2021
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Ingår i: Space Weather. - : American Geophysical Union (AGU). - 1542-7390. ; 19:5
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Tidskriftsartikel (refereegranskat)abstract
- We must be able to predict and mitigate against geomagnetically induced current (GIC) effects to minimize socio-economic impacts. This study employs the space weather modeling framework (SWMF) to model the geomagnetic response over Fennoscandia to the September 7-8, 2017 event. Of key importance to this study is the effects of spatial resolution in terms of regional forecasts and improved GIC modeling results. Therefore, we ran the model at comparatively low, medium, and high spatial resolutions. The virtual magnetometers from each model run are compared with observations from the IMAGE magnetometer network across various latitudes and over regional-scales. The virtual magnetometer data from the SWMF are coupled with a local ground conductivity model which is used to calculate the geoelectric field and estimate GICs in a Finnish natural gas pipeline. This investigation has lead to several important results in which higher resolution yielded: (1) more realistic amplitudes and timings of GICs, (2) higher amplitude geomagnetic disturbances across latitudes, and (3) increased regional variations in terms of differences between stations. Despite this, substorms remain a significant challenge to surface magnetic field prediction from global magnetohydrodynamic modeling. For example, in the presence of multiple large substorms, the associated large-amplitude depressions were not captured, which caused the largest model-data deviations. The results from this work are of key importance to both modelers and space weather operators. Particularly when the goal is to obtain improved regional forecasts of geomagnetic disturbances and/or more realistic estimates of the geoelectric field.
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| 7. |
- Kaprio, J, et al.
(författare)
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The Older Finnish Twin Cohort - 45 Years of Follow-up
- 2019
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Ingår i: Twin research and human genetics : the official journal of the International Society for Twin Studies. - : Cambridge University Press (CUP). - 1832-4274. ; 22:4, s. 240-254
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Tidskriftsartikel (refereegranskat)abstract
- The older Finnish Twin Cohort (FTC) was established in 1974. The baseline survey was in 1975, with two follow-up health surveys in 1981 and 1990. The fourth wave of assessments was done in three parts, with a questionnaire study of twins born during 1945–1957 in 2011–2012, while older twins were interviewed and screened for dementia in two time periods, between 1999 and 2007 for twins born before 1938 and between 2013 and 2017 for twins born in 1938–1944. The content of these wave 4 assessments is described and some initial results are described. In addition, we have invited twin-pairs, based on response to the cohortwide surveys, to participate in detailed in-person studies; these are described briefly together with key results. We also review other projects based on the older FTC and provide information on the biobanking of biosamples and related phenotypes.
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| 8. |
- KAURISTIE, K, et al.
(författare)
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ANALYSIS OF THE SUBSTORM TRIGGER PHASE USING MULTIPLE GROUND-BASED INSTRUMENTATION
- 1995
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Ingår i: GEOPHYSICAL RESEARCH LETTERS. - : AMER GEOPHYSICAL UNION. - 0094-8276. ; 22:15, s. 2065-2068
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- During the substorm trigger phase, i.e. during the last few minutes before the onset, the slowly and linearly developing growth phase features strengthen exponentially. Often the enhanced auroral activity fades abruptly during a couple of minutes just pri
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| 9. |
- Lanabere, Vanina, et al.
(författare)
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Analysis of the Geoelectric Field in Sweden Over Solar Cycles 23 and 24 : Spatial and Temporal Variability During Strong GIC Events
- 2023
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Ingår i: Space Weather. - : American Geophysical Union (AGU). - 1542-7390. ; 21:12
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Tidskriftsartikel (refereegranskat)abstract
- Geomagnetic storms can produce large perturbations on the Earth magnetic field. Through complex magnetosphere-ionosphere coupling, the geoelectric field (E) and geomagnetic field (B) are highly perturbed. The E is the physical driver of geomagnetically induced currents. However, a statistical study of the E in Sweden has never been done before. We combined geomagnetic data from the International Monitor for Auroral Geomagnetic Effects network in Northern Europe with a 3-D structure of Earth's electrical conductivity in Sweden as the input of a 1-D model to compute the E between 2000 and 2018. Northwestern Sweden presents statistically larger E magnitudes due to larger |dB/dt| variations in the north than in the south of Sweden and relative lower conductivity in the west compared to central and eastern Sweden. In contrast, the 15 strongest daily maximum |E| events present more frequently a maximum magnitude in central Sweden (62.25 degrees N) and their relative strengths are not the same for all latitudes. These results highlight the different regional response to geomagnetic storms, which can be related to ground conductivity variability and the complex magnetosphere-ionosphere coupling mechanisms. Solar storms represent a major threat to Earth's technology and therefore affect society and the economy. Historically, the main effects were related to electric power grid failures leaving many people without electricity for several hours. In order to prevent this from happening again, it is necessary to understand the temporal and spatial variability of the Earth's electric field in regions where electric power grids are placed. This study combines ground measurements of the magnetic fields in Finland and Estonia and ground conductivity maps in Sweden to estimate the ground electric fields in Sweden. A statistical analysis from 2000 to 2018 shows that the probability to find stronger daily maximum electric field magnitude (|E|) is higher in northwestern Sweden. However, the 15 strongest |E| events were found in the central region of Sweden. Furthermore, 80% of the electric power grid failure reports in Sweden during the period, correspond to events where the strongest daily maximum |E| were observed at 62.25 degrees N. This implies that a better understanding of the local geoelectric field and driving processes are required. The daily maximum geoelectric field magnitude is statistically larger in northwestern Sweden than in central and southern SwedenThe 15 strongest daily maximum geoelectric field events were more frequent in central Sweden than in northern SwedenThe 15 strongest events at each latitude are different, so the geoelectric field presents an important regional variability
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| 10. |
- Lonnblom, E, et al.
(författare)
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AUTOANTIBODIES TO JOINT PROTEINS AS NOVEL BIOMARKERS FOR THE DIAGNOSIS OF UNTREATED EARLY RHEUMATOID ARTHRITIS
- 2022
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Ingår i: ANNALS OF THE RHEUMATIC DISEASES. - : BMJ. - 0003-4967 .- 1468-2060. ; 81, s. 546-546
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Autoantibodies to citrullinated protein (ACPA; measured as anti-CCP; aCCP) and rheumatoid factor (RF) appear years before clinical onset of RA and are essential tools in today’s classification criteria for RA. In animal models, antibodies to joint specific proteins (JP) can induce arthritis, and they are also present at onset of RA [1]. As there is a need for increased precision for early diagnosis of RA as well as identification of different subtypes of the disease, we aim to assess whether autoantibodies to native or modified JP can be used for early and precise diagnosis of RA.ObjectivesTo study whether antibodies to JP, alone or in combination with ACPA/RF, could increase the diagnostic sensitivity and specificity in untreated early (ue)RA patients.MethodsAntibodies to JP were analysed in serum from patients in three independent ueRA cohorts as well as from population controls without rheumatic diseases (WINGA, Gothenburg and MFM-ÅUS, Malmö n=1062). ERAp (n=66), the smallest and most recent cohort was chosen for screening, and BARFOT and TIRA-2 (n=1939) for validation. We have developed a bead-based multianalyte flow immunoassay [2] and screened approx. 350 peptides derived from JPs of interest. We included monoclonal antibodies as assay calibrators and determined limit of detection (LoD). To assess positivity for autoantibodies to JP of interest above LoD, we used 5MAD (median absolute deviation) of the control populations as the cut-off.ResultsIn the ERAp cohort, 5 autoantibodies discriminated RA patients from controls with 81% sensitivity and 100% specificity (Table 1). The same autoantibodies had 68% sensitivity and 98% specificity in the combined BARFOT and TIRA-2 cohorts. Together with RF and aCCP, only 2 of the 5 autoantibodies added statistically significant diagnostic value, increasing the sensitivity from 48% to 61% with 99% specificity. In aCCP- and RF-negative ueRA patients (n=536), the novel biomarkers identified 22.5% of the patients with 99% specificity compared to controls.Table 1.Diagnostic capacity of the joint-specific antibodiesTest panelPerformanceGroup of patientsaCCP+RF+JP+SensitivitySpecificityAUC(ROC)ERApAll patients (n=66)--X81%100%89%RF and aCCP-neg patients (n=7)1------BARFOT and TIRA-2, combined dataAll patients (N=1939)--X68%98%86%All patients (N=1939)X--58%99%78%All patients (N=1939)2XX-48%100%84%All patients (N=1939)2, 3XXX61%99%86%RF and/or aCCP-pos patients (N=1403)--X84%99%93%RF and aCCP-neg patients (N=536)--X22%99%67%RA, literature valuesAnti-CCP testXN/AN/A53–71%95–96%N/A1Not analysed due to lack of power2This patient population is both aCCP+ and RF+3Only 2 of the 5 autoantibodies added statistically significant to the diagnostic valueAUC, Area under the curve; ROC, receiver operating characteristic curve; N/A, not applicable. Controls without rheumatic diseases: N=935 for BARFOT / TIRA-2 and N=27 for ERAp.ConclusionAutoantibodies to JP discriminate ueRA patients better then aCCP and RF alone and add an increased diagnostic value in particular for seronegative patients.References[1]Holmdahl, R., V. Malmstrom, and H. Burkhardt, Autoimmune priming, tissue attack and chronic inflammation - the three stages of rheumatoid arthritis. Eur J Immunol, 2014. 44(6): p. 1593-9.[2]Viljanen, J., et al., Synthesis of an Array of Triple-Helical Peptides from Type II Collagen for Multiplex Analysis of Autoantibodies in Rheumatoid Arthritis. ACS Chem Biol, 2020. 15(9): p. 2605-2615. Correction: ACS Chem Biol, 2020. 15(11): p. 3072AcknowledgementsBARFOT study group.Disclosure of InterestsErik Lönnblom: None declared, Monica Leu Agelii: None declared, Outi Sareila Employee of: Part time employee in Vacara AB, Ingiäld Hafström: None declared, Maria Andersson: None declared, Lei Cheng: None declared, Göran Bergström: None declared, Anna-Karin H Ekwall: None declared, Anna Rudin: None declared, Alf Kastbom: None declared, Christopher Sjowall: None declared, Bingze Xu: None declared, Lennart T.H. Jacobsson: None declared, Johan Viljanen: None declared, Jan Kihlberg: None declared, Inger Gjertsson: None declared, Rikard Holmdahl Shareholder of: Rikard Holmdahl the founder of Vacara AB.
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| 11. |
- Nygård, K., et al.
(författare)
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ForMAX – a beamline for multiscale and multimodal structural characterization of hierarchical materials
- 2024
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Ingår i: Journal of Synchrotron Radiation. - : International Union of Crystallography (IUCr). - 0909-0495 .- 1600-5775. ; 31:Pt 2, s. 363-377
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Tidskriftsartikel (refereegranskat)abstract
- The ForMAX beamline at the MAX IV Laboratory provides multiscale and multimodal structural characterization of hierarchical materials in the nanometre to millimetre range by combining small- and wide-angle X-ray scattering with full-field microtomography. The modular design of the beamline is optimized for easy switching between different experimental modalities. The beamline has a special focus on the development of novel fibrous materials from forest resources, but it is also well suited for studies within, for example, food science and biomedical research.
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| 12. |
- Orava, J., et al.
(författare)
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Blunted Metabolic Responses to Cold and Insulin Stimulation in Brown Adipose Tissue of Obese Humans
- 2013
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Ingår i: Obesity. - : Wiley. - 1930-7381. ; 21:11, s. 2279-2287
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Tidskriftsartikel (refereegranskat)abstract
- Objective: Inactive brown adipose tissue (BAT) may predispose to weight gain. This study was designed to measure metabolism in the BAT of obese humans, and to compare it to that in lean subjects. The impact of weight loss on BAT and the association of detectable BAT with various metabolic characteristics were also assessed. Design and Methods: Using positron emission tomography (PET), cold-and insulin-stimulated glucose uptake and blood flow in the BAT of obese and lean humans were quantified. Further, cold-induced glucose uptake was measured in obese subjects before and after a 5-month conventional weight loss. Results: Mean responses in BAT glucose uptake rate to both cold and insulin stimulation were twice as large in lean as in obese subjects. Blood flow in BAT was also lower in obese subjects under cold conditions. The increase in cold-induced BAT glucose uptake rate after weight loss was not statistically significant. Subjects with cold-activated detectable BAT were leaner and had higher whole-body insulin sensitivity than BAT-negative subjects, irrespective of age and gender. Conclusions: The effects of cold and insulin on BAT activity are severely blunted in obesity, and the presence of detectable BAT may contribute to a metabolically healthy status.
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| 13. |
- Pulkkinen, A, et al.
(författare)
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Geomagnetic storm of 29-31 October 2003: Geomagnetically induced currents and their relation to problems in the Swedish high-voltage power transmission system
- 2005
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Ingår i: Space Weather: the International Journal of Research and Applications. - 1539-4956. ; 3:8
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Tidskriftsartikel (refereegranskat)abstract
- On 30 October 2003, an ongoing geomagnetic superstorm knocked down a part of the high- voltage power transmission system in southern Sweden. The blackout lasted for an hour and left about 50,000 customers without electricity. The incident was probably the most severe geomagnetically induced current ( GIC) failure observed since the well- known March 1989 Quebec blackout. The " three- phase'' storm produced exceptionally large geomagnetic activity at the Fennoscandian auroral region. Although the diversity of the GIC drivers is addressed in the study, the problems in operating the Swedish system during the storm are attributed geophysically to substorms, storm sudden commencement, and enhanced ionospheric convection, all of which created large and complex geoelectric fields capable of driving large GIC. On the basis of the basic twofold nature of the failure- related geoelectric field characteristics, a semideterministic approach for forecasting GIC- related geomagnetic activity in which average overall activity is supplemented with statistical estimations of the amplitudes of GIC fluctuations is suggested. The study revealed that the primary mode of GIC- related failures in the Swedish high- voltage power transmission system were via harmonic distortions produced by GIC combined with too sensitive operation of the protective relays. The outage in Malmo " on 30 October 2003 was caused by a combination of an abnormal switching state of the system and tripping of a low- set residual overcurrent relay that had a high sensitivity for the third harmonic of the fundamental frequency.
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| 14. |
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| 15. |
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| 16. |
- Tong, D. M., et al.
(författare)
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A Shared Epitope of Collagen Type XI and Type II Is Recognized by Pathogenic Antibodies in Mice and Human with Arthritis
- 2018
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Ingår i: Frontiers in Immunology. - : Frontiers Media SA. - 1664-3224. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Background: Collagen XI (CXI) is a heterotrimeric molecule with triple helical structure in which the alpha 3(XI) chain is identical to the alpha 1(II) chain of collagen II (CII), but with extensive posttranslational modifications. CXI molecules are intermingled in the cartilage collagen fibers, which are mainly composed of CII. One of the alpha chains in CXI is shared with CII and contains the immunodominant T cell epitope, but it is unclear whether there are shared B cell epitopes as the antibodies tend to recognize the triple helical structures. Methods: Mice expressing the susceptible immune response gene A(q) were immunized with CII or CXI. Serum antibody responses were measured, monoclonal antibodies were isolated and analyzed for specificity to CII, CXI, and triple helical collagen peptides using bead-based multiplex immunoassays, enzyme-linked immunosorbent assays, and Western blots. Arthritogenicity of the antibodies was investigated by passive transfer experiments. Results: Immunization with CII or CXI leads to a strong T and B cell response, including a cross-reactive response to both collagen types. Immunization with CII leads to severe arthritis in mice, with a response toward CXI at the chronic stage, whereas CXI immunization induces very mild arthritis only. A series of monoclonal antibodies to CXI were isolated and of these, the L10D9 antibody bound to both CXI and CII equally strong, with a specific binding for the D3 epitope region of alpha 3(XI) or alpha 1(II) chain. The L10D9 antibody binds cartilage in vivo and induced severe arthritis. In contrast, the L5F3 antibody only showed weak binding and L7D8 antibody has no binding to cartilage and did not induce arthritis. The arthritogenic L10D9 antibody bound to an epitope shared with CII, the triple helical D3 epitope. Antibody levels to the shared D3 epitope were elevated in the sera from mice with arthritis as well as in rheumatoid arthritis. Conclusion: CXI is immunologically not exposed in healthy cartilage but contains T and B cell epitopes cross-reactive with CII, which could be activated in both mouse and human arthritis and could evoke an arthritogenic response.
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| 17. |
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| 18. |
- Wik, Magnus, et al.
(författare)
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Calculation of geomagnetically induced currents in the 400 kV power grid in southern Sweden
- 2008
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Ingår i: Space Weather: the International Journal of Research and Applications. - 1539-4956. ; 6:7
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Tidskriftsartikel (refereegranskat)abstract
- Sweden has experienced many geomagnetically induced current (GIC) events in the past, which is obviously due to the high-latitude location of the country. The largest GIC, almost 300 A, was measured in southern Sweden in the earthing lead of a 400 kV transformer neutral during the magnetic storm on 6 April 2000. On 30 October 2003, the city of Malmo at the southern coast suffered from a power blackout caused by GIC, leaving 50,000 customers without electricity for about 20-50 min. We have developed a model that enables calculation of GIC in the southern Swedish 400 kV power grid. This work constitutes the first modeling effort of GIC in Sweden. The model is divided into two parts. The electric field is first derived using a ground conductivity model and geomagnetic recordings from nearby stations. The conductivity model is determined from a least squares fit between measured and calculated GIC. GIC are calculated using a power grid model consisting of the topology of the system and of the transformer, transmission line, and station earthing resistances as well as of the coordinates of the stations. To validate the model, we have compared measured and calculated GIC from one site. In total, 24 events in 1998 to 2000 were used. In general the agreement is satisfactory as the correct GIC order of magnitude is obtained by the model, which is usually enough for engineering applications.
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| 19. |
- Wik, Magnus, et al.
(författare)
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Space weather events in July 1982 and October 2003 and the effects of geomagnetically induced currents on Swedish technical systems
- 2009
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Ingår i: Annales Geophysicae. - 1432-0576. ; 27:4, s. 1775-1787
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we analyse in detail two famous space weather events; a railway problem on 13-14 July 1982 and a power blackout on 30 October 2003. Both occurred in Sweden during very intensive space weather storms and each of them a few years after the sunspot maximum. This paper provides a description of the conditions on the Sun and in the solar wind leading to the two GIC events on the ground. By applying modelling techniques introduced and developed in our previous paper, we also calculate the horizontal geoelectric field at the Earth's surface in southern Sweden during the two storms as well as GIC flowing in the southern Swedish 400 kV power grid during the event in October 2003. The results from the calculations agree with all measured data available. In the July-1982 storm, the geomagnetic field variation, Delta B-x, reached values up to similar to 2500 nT/min and the geoelectric field reached values in the order of several volts per kilometer. In the October-2003 storm, the geomagnetic field fluctuations were smaller. However, GIC of some hundreds of amperes flowed in the power grid during the October-2003 event. Technological issues related to the railway signalling in July 1982 and to the power network equipment in October 2003 are also discussed.
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| 20. |
- Amm, O., Janhunen, P., Kauristie, K., Opgenoorth, H.J., Pulkkinen, T.I. and Viljanen, A.
(författare)
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Mesoscale ionospheric electrodynamics observed with the MIRACLE network: 1. Analysis of a pseudobreakup spiral.
- 2001
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Ingår i: Journal of Geophysical Research. ; 106:111, s. 24675-24690
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Tidskriftsartikel (refereegranskat)abstract
- A short-lived auroral spiral is observed on February 3, 1999, around 2204 UT, using the Multi-Instrument Array for Ionosphere-Magnetosphere Coupling Studies (MIRACLE) network of ground-based instruments in Fennoscandia, which consists of magnetometers, co
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| 21. |
- Dimmock, Andrew P., et al.
(författare)
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On the Regional Variability ofdB/dtand Its Significance to GIC
- 2020
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Ingår i: Space Weather. - : AMER GEOPHYSICAL UNION. - 1542-7390. ; 18:8
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Tidskriftsartikel (refereegranskat)abstract
- Faraday's law of induction is responsible for setting up a geoelectric field due to the variations in the geomagnetic field caused by ionospheric currents. This drives geomagnetically induced currents (GICs) which flow in large ground-based technological infrastructure such as high-voltage power lines. The geoelectric field is often a localized phenomenon exhibiting significant variations over spatial scales of only hundreds of kilometers. This is due to the complex spatiotemporal behavior of electrical currents flowing in the ionosphere and/or large gradients in the ground conductivity due to highly structured local geological properties. Over some regions, and during large storms, both of these effects become significant. In this study, we quantify the regional variability ofdB/dtusing closely placed IMAGE stations in northern Fennoscandia. The dependency between regional variability, solar wind conditions, and geomagnetic indices are also investigated. Finally, we assess the significance of spatial geomagnetic variations to modeling GICs across a transmission line. Key results from this study are as follows: (1) Regional geomagnetic disturbances are important in modeling GIC during strong storms; (2)dB/dtcan vary by several times up to a factor of three compared to the spatial average; (3)dB/dtand its regional variation is coupled to the energy deposited into the magnetosphere; and (4) regional variability can be more accurately captured and predicted from a local index as opposed to a global one. These results demonstrate the need for denser magnetometer networks at high latitudes where transmission lines extending hundreds of kilometers are present.
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| 22. |
- Dimmock, Andrew P., et al.
(författare)
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The GIC and Geomagnetic Response Over Fennoscandia to the 7-8 September 2017 Geomagnetic Storm
- 2019
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Ingår i: Space Weather. - 1542-7390. ; 17:7, s. 989-1010
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Tidskriftsartikel (refereegranskat)abstract
- Between 7 and 8 September 2017, Earth experienced extreme space weather events. We have combined measurements made by the IMAGE magnetometer array, ionospheric equivalent currents, geomagnetically induced current (GIC) recordings in the Finnish natural gas pipeline, and multiple ground conductivity models to study the Fennoscandia ground effects. This unique analysis has revealed multiple interesting physical and technical insights. We show that although the 7-8 September event was significant by global indices (Dst similar to 150 nT), it produced an unexpectedly large peak GIC. It is intriguing that our peak GIC did not occur during the intervals of largest geomagnetic depressions, nor was there any clear upstream trigger. Another important insight into this event is that unusually large and rare GIC amplitudes (>10 A) occurred in multiple Magnetic Local Time (MLT) sectors and could be associated with westward and eastward electrojets. We were also successfully able to model the geoelectric field and GIC using multiple models, thus providing a further important validation of these models for an extreme event. A key result from our multiple conductivity model comparison was the good agreement between the temporal features of 1-D and 3-D model results. This provides an important justification for past and future uses of 1-D models at Mantsala which is highly relevant to additional uses of this data set. Although the temporal agreement (after scaling) was good, we found a large (factor of 4) difference in the amplitudes between local and global ground models due to the difference in model conductivities. Thus, going forward, obtaining accurate ground conductivity values are key for GIC modeling.
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| 23. |
- Hallsten, K, et al.
(författare)
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Rosiglitazone but not metformin enhances insulin- and exercise-stimulated skeletal muscle glucose uptake in patients with newly diagnosed type 2 diabetes
- 2002
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Ingår i: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 51:12, s. 3479-3485
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Tidskriftsartikel (refereegranskat)abstract
- Rosiglitazone, a thiazolidinedione, enhances peripheral insulin sensitivity in patients with type 2 diabetes. Because the synergic action of insulin and exercise has been shown to be decreased in insulin resistance, the aim of this study was to compare the effects of rosiglitazone and metformin on muscle insulin responsiveness at rest and during exercise in patients with type 2 diabetes. Therefore, 45 patients with newly diagnosed or diet-treated type 2 diabetes were randomized for treatment with rosiglitazone (4 mg b.i.d.), metformin (1 g b.i.d.), or placebo in a 26-week double-blind trial. Skeletal muscle glucose uptake was measured using fluorine-18-labeled fluoro-deoxy-glucose and positron emission tomography (PET) during euglycemic-hyperinsulinemic clamp and one-legged exercise before and after the treatment period. Rosiglitazone (P < 0.05) and metformin (P < 0.0001) treatment lowered the mean glycosylated hemoglobin. The skeletal muscle glucose uptake was increased by 38% (P < 0.01) and whole-body glucose uptake by 44% in the rosiglitazone group. Furthermore, the exercise-induced increment during insulin stimulation was enhanced by 99% (P < 0.0001). No changes were observed in skeletal muscle or whole-body insulin sensitivity in the metformin group. In conclusion, rosiglitazone but not metformin 1) improves insulin responsiveness in resting skeletal muscle and 2) doubles the insulin-stimulated glucose uptake rate during physical exercise in patients with type 2 diabetes. Our results suggest that rosiglitazone improves synergic action of insulin and exercise.
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| 24. |
- Jackel, B., Eglitis, P., Donovan, E., Viljanen, A., Wallis, D., Cogger, L. and Opgenoorth, H.
(författare)
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Observations of highly correlated near-simultaneous magnetic field perturbations at contraposed ground stations.
- 2001
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Ingår i: Journal of Geophysical Research. ; 106, s. 25857-
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Tidskriftsartikel (refereegranskat)abstract
- A merged data set from Canadian Auroral Network for the OPEN Program Unified Study (CANOPUS) and Magnetometers-Ionospheric Radars-All-Sky Cameras Large Experiment (MIRACLE) magnetometer stations is used to study variations observed at widely separated loc
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| 25. |
- Kaurisitie, K., Syrjsuo, M., Amm, O., Viljanen, A., Pulkkinen, T.I. and Opgenoorth, H.J.
(författare)
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A statistical study of evening sectorarcs and electrojets.
- 2001
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Ingår i: Advances in Space Research. ; 28, s. 16045-1610
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Tidskriftsartikel (refereegranskat)abstract
- We present results of a statistical study of evening sector auroral arcs associated with electrojets. The study (including similar to 1000 all-sky camera (ASC) frames) is based on data of the MIRACLE instrument network. An automatic search engine is used
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