| 1. |
- Speliotes, Elizabeth K., et al.
(författare)
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Association analyses of 249,796 individuals reveal 18 new loci associated with body mass index
- 2010
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Ingår i: Nature Genetics. - : Springer Science and Business Media LLC. - 1061-4036 .- 1546-1718. ; 42:11, s. 937-948
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Tidskriftsartikel (refereegranskat)abstract
- Obesity is globally prevalent and highly heritable, but its underlying genetic factors remain largely elusive. To identify genetic loci for obesity susceptibility, we examined associations between body mass index and ~2.8 million SNPs in up to 123,865 individuals with targeted follow up of 42 SNPs in up to 125,931 additional individuals. We confirmed 14 known obesity susceptibility loci and identified 18 new loci associated with body mass index (P < 5 × 10−8), one of which includes a copy number variant near GPRC5B. Some loci (at MC4R, POMC, SH2B1 and BDNF) map near key hypothalamic regulators of energy balance, and one of these loci is near GIPR, an incretin receptor. Furthermore, genes in other newly associated loci may provide new insights into human body weight regulation.
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| 2. |
- Kilpeläinen, Tuomas O, et al.
(författare)
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Genome-wide meta-analysis uncovers novel loci influencing circulating leptin levels
- 2016
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- Leptin is an adipocyte-secreted hormone, the circulating levels of which correlate closely with overall adiposity. Although rare mutations in the leptin (LEP) gene are well known to cause leptin deficiency and severe obesity, no common loci regulating circulating leptin levels have been uncovered. Therefore, we performed a genome-wide association study (GWAS) of circulating leptin levels from 32,161 individuals and followed up loci reaching P<10(-6) in 19,979 additional individuals. We identify five loci robustly associated (P<5 × 10(-8)) with leptin levels in/near LEP, SLC32A1, GCKR, CCNL1 and FTO. Although the association of the FTO obesity locus with leptin levels is abolished by adjustment for BMI, associations of the four other loci are independent of adiposity. The GCKR locus was found associated with multiple metabolic traits in previous GWAS and the CCNL1 locus with birth weight. Knockdown experiments in mouse adipose tissue explants show convincing evidence for adipogenin, a regulator of adipocyte differentiation, as the novel causal gene in the SLC32A1 locus influencing leptin levels. Our findings provide novel insights into the regulation of leptin production by adipose tissue and open new avenues for examining the influence of variation in leptin levels on adiposity and metabolic health.
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| 3. |
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| 4. |
- Ashar, Foram N., et al.
(författare)
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A comprehensive evaluation of the genetic architecture of sudden cardiac arrest
- 2018
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Ingår i: European Heart Journal. - : Oxford University Press. - 0195-668X .- 1522-9645. ; 39:44, s. 3961-
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Tidskriftsartikel (refereegranskat)abstract
- Aims: Sudden cardiac arrest (SCA) accounts for 10% of adult mortality in Western populations. We aim to identify potential loci associated with SCA and to identify risk factors causally associated with SCA.Methods and results: We carried out a large genome-wide association study (GWAS) for SCA (n = 3939 cases, 25 989 non-cases) to examine common variation genome-wide and in candidate arrhythmia genes. We also exploited Mendelian randomization (MR) methods using cross-trait multi-variant genetic risk score associations (GRSA) to assess causal relationships of 18 risk factors with SCA. No variants were associated with SCA at genome-wide significance, nor were common variants in candidate arrhythmia genes associated with SCA at nominal significance. Using cross-trait GRSA, we established genetic correlation between SCA and (i) coronary artery disease (CAD) and traditional CAD risk factors (blood pressure, lipids, and diabetes), (ii) height and BMI, and (iii) electrical instability traits (QT and atrial fibrillation), suggesting aetiologic roles for these traits in SCA risk.Conclusions: Our findings show that a comprehensive approach to the genetic architecture of SCA can shed light on the determinants of a complex life-threatening condition with multiple influencing factors in the general population. The results of this genetic analysis, both positive and negative findings, have implications for evaluating the genetic architecture of patients with a family history of SCA, and for efforts to prevent SCA in high-risk populations and the general community.
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| 5. |
- Berndt, Sonja I., et al.
(författare)
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Genome-wide meta-analysis identifies 11 new loci for anthropometric traits and provides insights into genetic architecture
- 2013
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Ingår i: Nature Genetics. - : Springer Science and Business Media LLC. - 1061-4036 .- 1546-1718. ; 45:5, s. 501-U69
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Tidskriftsartikel (refereegranskat)abstract
- Approaches exploiting trait distribution extremes may be used to identify loci associated with common traits, but it is unknown whether these loci are generalizable to the broader population. In a genome-wide search for loci associated with the upper versus the lower 5th percentiles of body mass index, height and waist-to-hip ratio, as well as clinical classes of obesity, including up to 263,407 individuals of European ancestry, we identified 4 new loci (IGFBP4, H6PD, RSRC1 and PPP2R2A) influencing height detected in the distribution tails and 7 new loci (HNF4G, RPTOR, GNAT2, MRPS33P4, ADCY9, HS6ST3 and ZZZ3) for clinical classes of obesity. Further, we find a large overlap in genetic structure and the distribution of variants between traits based on extremes and the general population and little etiological heterogeneity between obesity subgroups.
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| 6. |
- Erzurumluoglu, A. Mesut, et al.
(författare)
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Meta-analysis of up to 622,409 individuals identifies 40 novel smoking behaviour associated genetic loci
- 2020
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Ingår i: Molecular Psychiatry. - : Nature Publishing Group. - 1359-4184 .- 1476-5578. ; 25:10, s. 2392-2409
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Tidskriftsartikel (refereegranskat)abstract
- Smoking is a major heritable and modifiable risk factor for many diseases, including cancer, common respiratory disorders and cardiovascular diseases. Fourteen genetic loci have previously been associated with smoking behaviour-related traits. We tested up to 235,116 single nucleotide variants (SNVs) on the exome-array for association with smoking initiation, cigarettes per day, pack-years, and smoking cessation in a fixed effects meta-analysis of up to 61 studies (up to 346,813 participants). In a subset of 112,811 participants, a further one million SNVs were also genotyped and tested for association with the four smoking behaviour traits. SNV-trait associations with P < 5 × 10-8 in either analysis were taken forward for replication in up to 275,596 independent participants from UK Biobank. Lastly, a meta-analysis of the discovery and replication studies was performed. Sixteen SNVs were associated with at least one of the smoking behaviour traits (P < 5 × 10-8) in the discovery samples. Ten novel SNVs, including rs12616219 near TMEM182, were followed-up and five of them (rs462779 in REV3L, rs12780116 in CNNM2, rs1190736 in GPR101, rs11539157 in PJA1, and rs12616219 near TMEM182) replicated at a Bonferroni significance threshold (P < 4.5 × 10-3) with consistent direction of effect. A further 35 SNVs were associated with smoking behaviour traits in the discovery plus replication meta-analysis (up to 622,409 participants) including a rare SNV, rs150493199, in CCDC141 and two low-frequency SNVs in CEP350 and HDGFRP2. Functional follow-up implied that decreased expression of REV3L may lower the probability of smoking initiation. The novel loci will facilitate understanding the genetic aetiology of smoking behaviour and may lead to the identification of potential drug targets for smoking prevention and/or cessation.
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| 7. |
- Heid, Iris M, et al.
(författare)
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Meta-analysis identifies 13 new loci associated with waist-hip ratio and reveals sexual dimorphism in the genetic basis of fat distribution
- 2010
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Ingår i: Nature Genetics. - : Springer Science and Business Media LLC. - 1061-4036 .- 1546-1718. ; 42:11, s. 949-960
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Tidskriftsartikel (refereegranskat)abstract
- Waist-hip ratio (WHR) is a measure of body fat distribution and a predictor of metabolic consequences independent of overall adiposity. WHR is heritable, but few genetic variants influencing this trait have been identified. We conducted a meta-analysis of 32 genome-wide association studies for WHR adjusted for body mass index (comprising up to 77,167 participants), following up 16 loci in an additional 29 studies (comprising up to 113,636 subjects). We identified 13 new loci in or near RSPO3, VEGFA, TBX15-WARS2, NFE2L3, GRB14, DNM3-PIGC, ITPR2-SSPN, LY86, HOXC13, ADAMTS9, ZNRF3-KREMEN1, NISCH-STAB1 and CPEB4 (P = 1.9 × 10⁻⁹ to P = 1.8 × 10⁻⁴⁰) and the known signal at LYPLAL1. Seven of these loci exhibited marked sexual dimorphism, all with a stronger effect on WHR in women than men (P for sex difference = 1.9 × 10⁻³ to P = 1.2 × 10⁻¹³). These findings provide evidence for multiple loci that modulate body fat distribution independent of overall adiposity and reveal strong gene-by-sex interactions.
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| 8. |
- Hrastinski, Stefan, Professor, 1980-, et al.
(författare)
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Examining the Development of K-12 Students' Cognitive Presence over Time : The Case of Online Mathematics Tutoring
- 2023
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Ingår i: ONLINE LEARNING. - : The Online Learning Consortium. - 2472-5749. ; 27:3, s. 252-270
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Tidskriftsartikel (refereegranskat)abstract
- In this article, we focus on the cognitive presence element of the Community of Inquiry (CoI) framework. Cognitive presence consists of four categories: Triggering Event, Exploration, Integration, and Resolution. These categories have been described as phases following an idealized logical sequence, although the phases should not be seen as immutable. Few studies have empirically examined how the four categories develop over time during the inquiry process. This article uses learning analytics methods to study transitions between the categories in K-12 online mathematics tutoring. It was statistically most probable that the tutoring sessions started with Triggering Event (95%) and then transitioned to Exploration (51%). The transitions from Exploration to Integration (18%) and Integration to Resolution (21%) achieved statistical significance but were less likely. In fact, it was more likely that the tutoring sessions transitioned from Integration to Exploration (39%) and Resolution to Exploration (36%). In conclusion, the findings suggest that the idealized logical sequence is evident in the data but that other transitions occur as well; especially Exploration recurs throughout the sessions. It seems challenging for students to reach the Integration and Resolution categories. As the CoI framework is commonly adopted in practice, it is important that tutors and educators understand that the categories of cognitive presence will often not play out in idealized ways, underlining their role in supporting how the inquiry process unfolds. In order to gain an improved understanding of the inquiry process, future research is suggested to investigate how the presences and categories of the CoI framework develop over time in different educational settings.
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| 9. |
- Hrastinski, Stefan, 1980-, et al.
(författare)
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Identifying and exploring the effects of different types of tutor questions in individual online synchronous tutoring in mathematics
- 2019
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Ingår i: Interactive Learning Environments. - : Informa UK Limited. - 1049-4820 .- 1744-5191. ; , s. 1-13
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Tidskriftsartikel (refereegranskat)abstract
- Although we know that asking questions is an essential aspect of onlinetutoring, there is limited research on this topic. The aim of this paperwas to identify commonly used direct question types and explore theeffects of using these question types on conversation intensity, approachto tutoring, perceived satisfaction and perceived learning. The researchsetting was individual online synchronous tutoring in mathematics. Theempirical data was based on 13,317 logged conversations and aquestionnaire. The tutors used a mix of open, more student-centredquestions, and closed, more teacher-centred questions. In contrast toprevious research, this study provides a more positive account indicatingthat it is indeed possible to train tutors to focus on asking questions,rather than delivering content. Frequent use of many of the questiontypes contributed to increased conversation intensity. However, therewere few question types that were associated with statisticallysignificant effects on perceived satisfaction or learning. There are nosilver bullet question types that by themselves led to positive effects onperceived satisfaction and learning. The question types could be used byteachers and teacher students when reflecting on what types ofquestions they are asking, and what kind of questions they could be asking.
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| 10. |
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| 11. |
- Jansson, Malin, et al.
(författare)
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Online question and answer sessions : How students support their own and other students' processes of inquiry in a text-based learning environment
- 2021
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Ingår i: The Internet and higher education. - : Elsevier BV. - 1096-7516 .- 1873-5525. ; 51
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Tidskriftsartikel (refereegranskat)abstract
- Online tutoring has been found to have a positive impact on student learning in STEM education. The aim of this study was to explore how and to what extent students supported their own and other students' processes of inquiry during online tutoring. More specifically, question and answer sessions (Q&As) were studied, and online tutoring transcripts were analyzed using the Relationship of Inquiry coding scheme adapted from the Community of Inquiry framework. The students interacted voluntarily with each other and with the teachers. The results show that the students supported both their own process of inquiry as well as other students' process of inquiry. Furthermore, the results indicate that students acquired metacognitive development through self- and coregulation when they expressed teaching presence. Overall, we conclude that Q&As have the potential to support student learning when working on assignments in STEM education.
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| 12. |
- Jansson, Malin, 1988-
(författare)
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Spontaneous online tutoring : Students’ support of their own and other students’ process of inquiry in online text-based tutoring
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The use of online technologies has made education more accessible. In online education, there are increased expectations for students to be self-directed and take responsibility for their learning. Research has also shown that students can benefit from learning from each other. The purpose of this thesis is to explore how students support their own and other students’ process of inquiry in online text-based tutoring sessions. To enable the analysis of the conversations, a coding scheme for transcript analysis of online tutoring was introduced based on the Relationship of Inquiry framework, which is an adaptation of the Community of Inquiry framework.This thesis consists of four papers. The first paper focuses on the development of the RoI coding scheme, which is used in two of the following papers. In the second paper, the coding scheme is further revised regarding the aspect of students’ teaching presence and how it connects to students’ support of their own and other students’ inquiry process. In the third paper, students’ support of their own and other students’ process of inquiry in online text-based tutoring sessions is studied further, and their messages are analyzed with the revised coding scheme. The fourth paper adopts an inductive approach and analyzes how students take responsibility for their own and their peers’ problem-solving through thematic analysis. The findings show that in online tutoring sessions, students may spontaneously take on the role of a tutor. Through their expressions of teaching presence by, for example, explaining their issues and their previous steps, or answering other students’ questions and giving suggestions, students support their own as well as other students’ inquiry process. The findings indicate that students acquire metacognitive development, through self- and co-regulation, with their expressions of teaching and cognitive presence. Furthermore, the findings show that the coding scheme with fixed categories may not show the full picture of interactions in an online learning environment. Additional analysis reveals that students’ expressions focus on different levels of learning while supporting the problem-solving process. Lastly, this thesis offers guidance on how to create online tutoring sessions where students take responsibility for their learning and are encouraged to help one another.
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| 13. |
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| 14. |
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| 15. |
- King, Carina, et al.
(författare)
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COVID-19—a very visible pandemic
- 2020
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Ingår i: The Lancet. - : Elsevier. - 0140-6736 .- 1474-547X. ; 396:10248, s. 15-15
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Tidskriftsartikel (refereegranskat)
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| 16. |
- Luth, Stefan, et al.
(författare)
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Building 3D geomodels using XRF-XRT-generated drill core data : The Lovisa-Håkansboda base metal- and Strassa-Blanka iron deposits in Bergslagen, Sweden
- 2019
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Ingår i: LIFE WITH ORE DEPOSITS ON EARTH, PROCEEDINGS OF THE 15TH SGA BIENNIAL MEETING, 2019, VOLS 1-4. - : SOC GEOLOGY APPLIED MINERAL DEPOSITS-SGA. - 9780852619643 ; , s. 1282-1285
-
Konferensbidrag (refereegranskat)abstract
- 3D geological models based on data from geological field observations, magnetic airborne surveys and combined XRF-XRT scanning of drill core are presented for the Lovisa-Hakansboda and the Strassa-Blanka mineral systems (1.9 - 1.8 Ga). At first, the 3D architecture of several deposits was derived primarily from surface data and mine-level maps. Secondly, geochemical and structural constrains from drill core scanning (XRF-XRT) were used to refine the models locally to a detailed, in-mine scale. The constructed models were then placed in a regional context providing valuable insight on the area's local and regional deformation pattern. All modelled deposits are plunging 50-60 degrees towards the south-southeast reflecting D2 deformation (vertical shearing) during NW-SE-directed shortening and are locally overprinted by D3 (lateral shearing) during N-S-directed shortening.
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| 17. |
- Luth, Stefan, et al.
(författare)
-
Building 3D geomodels using XRF-XRT-generated drillcore data : The Lovisa-Håkansboda base metal- and Stråssa-Blanka iron deposits in Bergslagen, Sweden
- 2019
-
Ingår i: Life with Ore Deposits on Earth: Proceedings of the 15th SGA Biennial Meeting 2019, Glasgow, Scotland, 2019, Vol. 3, s. 1282-1485.
-
Konferensbidrag (refereegranskat)abstract
- 3D geological models based on data fromgeological field observations, magnetic airborne surveys and combined XRF-XRT scanning of drill core arepresented for the Lovisa-Håkansboda and the Stråssa-Blanka mineral systems (1.9 - 1.8 Ga). At first, the 3D architecture of several deposits was derived primarilyfrom surface data and mine-level maps. Secondly, geochemical and structural constrains from drill corescanning (XRF-XRT) were used to refine the modelslocally to a detailed, in-mine scale. The constructed models were then placed in a regional context providingvaluable insight on the area’s local and regional deformation pattern. All modelled deposits are plunging 50-60° towards the south-southeast reflecting D2 deformation (vertical shearing) during NW-SE-directed shortening and are locally overprinted by D3 (lateral shearing) during N-S-directed shortening.
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| 18. |
- Marouli, Eirini, et al.
(författare)
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Rare and low-frequency coding variants alter human adult height
- 2017
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 542:7640, s. 186-190
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Tidskriftsartikel (refereegranskat)abstract
- Height is a highly heritable, classic polygenic trait with approximately 700 common associated variants identified through genome-wide association studies so far. Here, we report 83 height-associated coding variants with lower minor-allele frequencies (in the range of 0.1-4.8%) and effects of up to 2 centimetres per allele (such as those in IHH, STC2, AR and CRISPLD2), greater than ten times the average effect of common variants. In functional follow-up studies, rare height increasing alleles of STC2 (giving an increase of 1-2 centimetres per allele) compromised proteolytic inhibition of PAPP-A and increased cleavage of IGFBP-4 in vitro, resulting in higher bioavailability of insulin-like growth factors. These 83 height-associated variants overlap genes that are mutated in monogenic growth disorders and highlight new biological candidates (such as ADAMTS3, IL11RA and NOX4) and pathways (such as proteoglycan and glycosaminoglycan synthesis) involved in growth. Our results demonstrate that sufficiently large sample sizes can uncover rare and low-frequency variants of moderate-to-large effect associated with polygenic human phenotypes, and that these variants implicate relevant genes and pathways.
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| 19. |
- Sundström, Johan, Professor, 1971-, et al.
(författare)
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A registry-based randomised trial comparing an SGLT2 inhibitor and metformin as standard treatment of early stage type 2 diabetes (SMARTEST): Rationale, design and protocol
- 2021
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Ingår i: Journal of Diabetes and Its Complications. - : Elsevier BV. - 1056-8727 .- 1873-460X. ; 35:10
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Tidskriftsartikel (refereegranskat)abstract
- Aim: SGLT2 inhibitors have been shown to reduce cardiovascular and renal complications in type 2 diabetes (T2D) patients at high cardiovascular risk. Metformin is currently widely used as initial monotherapy in T2D but lacks convincing data to show that it reduces risk of complications. We aim to compare the SGLT2 inhibitor dapagliflozin and metformin as first-line T2D medication with regard to development of complications in a registry-based randomised controlled trial. Methods: The SGLT2 inhibitor or metformin as standard treatment of early stage type 2 diabetes (SMARTEST) trial will enrol 4300 subjects at 30-40 study sites in Sweden who will be randomised 1:1 to either metformin or dapagliflozin. Participants must have T2D duration <4 years, no prior cardiovascular disease, and be either drug-naive or on monotherapy for T2D. Results: The primary endpoint is a composite of all-cause death, major adverse cardiovascular events and occurrence or progression of microvascular complications (retinopathy, nephropathy, diabetic foot lesions). Secondary endpoints include individual components of the primary endpoint, start of insulin therapy, risk factor biomarkers, patient-reported outcome measures, and cost-effectiveness analysis. Outcomes will primarily be assessed using nationwide healthcare registries. Conclusions: The SMARTEST trial will investigate whether dapagliflozin is superior to metformin in preventing complications in early stage T2D. (Clinicaltrials.gov identifier NCT03982381, EudraCT 2019-001046-17).
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| 20. |
- Thompson, Luke R., et al.
(författare)
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A communal catalogue reveals Earth's multiscale microbial diversity
- 2017
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 551:7681, s. 457-463
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Tidskriftsartikel (refereegranskat)abstract
- © 2017 Macmillan Publishers Limited, part of Springer Nature. All rights reserved. Our growing awareness of the microbial world's importance and diversity contrasts starkly with our limited understanding of its fundamental structure. Despite recent advances in DNA sequencing, a lack of standardized protocols and common analytical frameworks impedes comparisons among studies, hindering the development of global inferences about microbial life on Earth. Here we present a meta-analysis of microbial community samples collected by hundreds of researchers for the Earth Microbiome Project. Coordinated protocols and new analytical methods, particularly the use of exact sequences instead of clustered operational taxonomic units, enable bacterial and archaeal ribosomal RNA gene sequences to be followed across multiple studies and allow us to explore patterns of diversity at an unprecedented scale. The result is both a reference database giving global context to DNA sequence data and a framework for incorporating data from future studies, fostering increasingly complete characterization of Earth's microbial diversity.
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| 21. |
- Tunes, Matheus A., et al.
(författare)
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From high-entropy alloys to high-entropy ceramics : The radiation-resistant highly concentrated refractory carbide (CrNbTaTiW)C
- 2023
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Ingår i: Acta Materialia. - : Elsevier. - 1359-6454 .- 1873-2453. ; 250
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Tidskriftsartikel (refereegranskat)abstract
- High-entropy materials represent the state-of-the-art on the alloy design strategy for future applications in extreme environments. Recent data indicates that high-entropy alloys (HEAs) exhibit outstanding radiation resistance in face of existing diluted alloy counterparts due to suppressed damage formation and evolution. An extension of the HEA concept is presented in this paper towards the synthesis and characterization of novel high-entropy ceramics as emergent materials for application in environments where energetic particle irradiation is a major concern. A novel carbide within the quinary refractory system CrNbTaTiW has been synthesized using magnetron-sputtering. The material exhibited nanocrystalline grains, single-phase crystal structure and C content around 50 at.%. Heavy-ion irradiation with in-situ Transmission Electron Microscopy was used to assess the irradiation response of the new high-entropy carbide (HEC) at 573 K and a comparison with the HEA within the system is made. No displacement damage effects appear within the microstructures of both HEA and HEC up to a dose of 10 displacements-per-atom. Surprisingly, the HEC has not amorphized under the investigated conditions. Xe was implanted in both materials and bubbles nucleated, but smaller sizes compared with conventional nuclear materials shedding light they are potential candidates for use in nuclear energy.
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| 22. |
- Turcot, Valerie, et al.
(författare)
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Protein-altering variants associated with body mass index implicate pathways that control energy intake and expenditure in obesity
- 2018
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Ingår i: Nature Genetics. - : Nature Publishing Group. - 1061-4036 .- 1546-1718. ; 50:1, s. 26-41
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Tidskriftsartikel (refereegranskat)abstract
- Genome-wide association studies (GWAS) have identified >250 loci for body mass index (BMI), implicating pathways related to neuronal biology. Most GWAS loci represent clusters of common, noncoding variants from which pinpointing causal genes remains challenging. Here we combined data from 718,734 individuals to discover rare and low-frequency (minor allele frequency (MAF) < 5%) coding variants associated with BMI. We identified 14 coding variants in 13 genes, of which 8 variants were in genes (ZBTB7B, ACHE, RAPGEF3, RAB21, ZFHX3, ENTPD6, ZFR2 and ZNF169) newly implicated in human obesity, 2 variants were in genes (MC4R and KSR2) previously observed to be mutated in extreme obesity and 2 variants were in GIPR. The effect sizes of rare variants are similar to 10 times larger than those of common variants, with the largest effect observed in carriers of an MC4R mutation introducing a stop codon (p.Tyr35Ter, MAF = 0.01%), who weighed similar to 7 kg more than non-carriers. Pathway analyses based on the variants associated with BMI confirm enrichment of neuronal genes and provide new evidence for adipocyte and energy expenditure biology, widening the potential of genetically supported therapeutic targets in obesity.
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| 23. |
- Villarejo, Arsenio, et al.
(författare)
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Evidence for a protein transported through the secretory pathway en route to the higher plant chloroplast
- 2005
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Ingår i: Nature Cell Biology. - : Springer Nature. - 1465-7392 .- 1476-4679. ; 7:12, s. 1224-1231
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Tidskriftsartikel (refereegranskat)abstract
- In contrast to animal and fungal cells, green plant cells contain one or multiple chloroplasts, the organelle(s) in which photosynthetic reactions take place. Chloroplasts are believed to have originated from an endosymbiotic event and contain DNA that codes for some of their proteins. Most chloroplast proteins are encoded by the nuclear genome and imported with the help of sorting signals that are intrinsic parts of the polypeptides. Here, we show that a chloroplast-located protein in higher plants takes an alternative route through the secretory pathway, and becomes N-glycosylated before entering the chloroplast.
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| 24. |
- Wessel, Jennifer, et al.
(författare)
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Low-frequency and rare exome chip variants associate with fasting glucose and type 2 diabetes susceptibility
- 2015
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 6
-
Tidskriftsartikel (refereegranskat)abstract
- Fasting glucose and insulin are intermediate traits for type 2 diabetes. Here we explore the role of coding variation on these traits by analysis of variants on the HumanExome BeadChip in 60,564 non-diabetic individuals and in 16,491 T2D cases and 81,877 controls. We identify a novel association of a low-frequency nonsynonymous SNV in GLP1R (A316T; rs10305492; MAF = 1.4%) with lower FG (beta = -0.09 +/- 0.01 mmol l(-1), P = 3.4 x 10(-12)), T2D risk (OR[95% CI] = 0.86[0.76-0.96], P = 0.010), early insulin secretion (beta = -0.07 +/- 0.035 pmol(insulin) mmol(glucose)(-1), P = 0.048), but higher 2-h glucose (beta = 0.16 +/- 0.05 mmol l(-1), P = 4.3 x 10(-4)). We identify a gene-based association with FG at G6PC2 (p(SKAT) = 6.8 x 10(-6)) driven by four rare protein-coding SNVs (H177Y, Y207S, R283X and S324P). We identify rs651007 (MAF = 20%) in the first intron of ABO at the putative promoter of an antisense lncRNA, associating with higher FG (beta = 0.02 +/- 0.004 mmol l(-1), P = 1.3 x 10(-8)). Our approach identifies novel coding variant associations and extends the allelic spectrum of variation underlying diabetes-related quantitative traits and T2D susceptibility.
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| 25. |
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| 26. |
- Agardh, Carl-David, et al.
(författare)
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Varning för okritisk användning av överviktskirurgi vid typ 2-diabetes
- 2012
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Ingår i: Läkartidningen. - Stockholm : Läkartidningen förlag. - 0023-7205 .- 1652-7518. ; 109:25, s. 1208-1209
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Tidskriftsartikel (refereegranskat)abstract
- Överviktskirurgi diskuteras nu som ett behandlingsalternativ även för patienter med typ 2-diabetes där BMI inte överstiger nuvarande indikationsgräns 35 kg/m2. Artikelförfattarna vill varna för en sådan utveckling i avvaktan på kritisk värdering av denna typ av kirurgi.
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| 27. |
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| 28. |
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| 29. |
- Albrectsen, Benedicte, et al.
(författare)
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From micro towards the macro scale
- 2006
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Ingår i: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; 172, s. 7-10
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Tidskriftsartikel (refereegranskat)
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| 30. |
- Albrectsen, Benedicte R., 1960-, et al.
(författare)
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Endophytic fungi in European aspen (Populus tremula) leaves - diversity, detection, and a suggested correlation with herbivory resistance
- 2010
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Ingår i: Fungal diversity. - : Springer Science and Business Media LLC. - 1560-2745 .- 1878-9129. ; 41:1, s. 17-28
-
Tidskriftsartikel (refereegranskat)abstract
- According to the geographic mosaic theory of coevolution (GMTC), clines of traits reflecting local co-adaptation (including resistance genes) should be common between a host and its parasite and should persist across time. To test the GMTC-assumption of persistent clinal patterns we compared the natural prevalence of two parasites on aspen Populus tremula trees: mining moths of the genus Phyllocnistis and leaf rust Melampsora spp. Damage data were collated from the Swedish National Forest Damage Inventory (2004–2006). In addition, occurrence of the parasites was scored in field conditions in two common gardens in the north and south of Sweden over five growing seasons (2004–2008), then related to biomass (stem height and diameter) and to concentrations of eleven leaf phenolics. Phyllocnistis mainly occurred in the northern garden, a distribution range which was confirmed by the countrywide inventory, although Phyllocnistis was more abundant on southern clones, providing evidence for possible local maladaptation. Melampsora occurred all over the country and in both gardens, but built up more quickly on northern clones, which suggests a centre of local clone maladaptation in the north. Stem growth also followed a clinal pattern as did the concentration of three phenolic compounds: benzoic acid, catechin and cinnamic acid. However, only benzoic acid was related to parasite presence: negatively to Phyllocnistis and positively to Melampsora and it could thus be a potential trait under selection. In conclusion, clines of Phyllocnistis were stronger and more persistent compared to Melampsora, which showed contrasting clines of varying strength. Our data thus support the assumption of the GMTC model that clines exist in the border between hot and cold spots and that they may be less persistent for parasites with an elevated gene flow, and/or for parasites which cover relatively larger hot spots surrounded by fewer cold spots.
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| 31. |
- Albrectsen, Benedicte R, 1960-, et al.
(författare)
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Large scale geographic clines of parasite damage to Populus tremula L
- 2010
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Ingår i: Ecography. - : Wiley. - 0906-7590 .- 1600-0587. ; 33:3, s. 483-493
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Tidskriftsartikel (refereegranskat)abstract
- In conclusion, clines of Phyllocnistis were stronger and more persistent compared to Melampsora, which showed contrasting clines of varying strength. Our data thus support the assumption of the GMTC model that clines exist in the border between hot and cold spots and that they may be less persistent for parasites with an elevated gene flow, and/or for parasites which cover relatively larger hot spots surrounded by fewer cold spots.
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| 32. |
- Algesten, Grete, et al.
(författare)
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Organic carbon budget for the Gulf of Bothnia
- 2006
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Ingår i: Journal of Marine Systems. - : Elsevier BV. - 0924-7963 .- 1879-1573. ; 63:3-4, s. 155-161
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Tidskriftsartikel (refereegranskat)abstract
- We calculated input of organic carbon to the unproductive, brackish water basin of the Gulf of Bothnia from rivers, point sources and the atmosphere. We also calculated the net exchange of organic carbon between the Gulf of Bothnia and the adjacent marine system, the Baltic Proper. We compared the input with sinks for organic carbon; permanent incorporation in sediments and mineralization and subsequent evasion of CO2 to the atmosphere. The major fluxes were riverine input (1500 Gg C year(-1)), exchange with the Baltic Proper (depending on which of several possible DOC concentration differences between the basins that was used in the calculation, the flux varied between an outflow of 466 and an input of 950 Gg C year(-1)), sediment burial (1100 Gg C year) and evasion to the atmosphere (3610 Gg C year(-1)). The largest single net flux was the emission of CO2 to the atmosphere, mainly caused by bacterial mineralization of organic carbon. Input and output did not match in our budget which we ascribe uncertainties in the calculation of the exchange of organic carbon between the Gulf of Bothnia and the Baltic Proper, and the fact that CO2 emission, which in our calculation represented 1 year (2002) may have been overestimated in comparison with long-term means. We conclude that net heterotrophy of the Gulf of Bothnia was due to input of organic carbon from both the catchment and from the Baltic Proper and that the future degree of net heterotrophy will be sensible to both catchment export of organic carbon and to the ongoing eutrophication of the Baltic Proper.
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| 33. |
- Andersson, Anders, et al.
(författare)
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A transcriptional timetable of autumn senescence
- 2004
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Ingår i: Genome Biology. - : Springer Science and Business Media LLC. - 1465-6906 .- 1474-760X. ; 5:4, s. R24-
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Tidskriftsartikel (refereegranskat)abstract
- Background We have developed genomic tools to allow the genus Populus (aspens and cottonwoods) to be exploited as a full-featured model for investigating fundamental aspects of tree biology. We have undertaken large-scale expressed sequence tag (EST) sequencing programs and created Populus microarrays with significant gene coverage. One of the important aspects of plant biology that cannot be studied in annual plants is the gene activity involved in the induction of autumn leaf senescence. Results On the basis of 36,354 Populus ESTs, obtained from seven cDNA libraries, we have created a DNA microarray consisting of 13,490 clones, spotted in duplicate. Of these clones, 12,376 (92%) were confirmed by resequencing and all sequences were annotated and functionally classified. Here we have used the microarray to study transcript abundance in leaves of a free-growing aspen tree (Populus tremula) in northern Sweden during natural autumn senescence. Of the 13,490 spotted clones, 3,792 represented genes with significant expression in all leaf samples from the seven studied dates. Conclusions We observed a major shift in gene expression, coinciding with massive chlorophyll degradation, that reflected a shift from photosynthetic competence to energy generation by mitochondrial respiration, oxidation of fatty acids and nutrient mobilization. Autumn senescence had much in common with senescence in annual plants; for example many proteases were induced. We also found evidence for increased transcriptional activity before the appearance of visible signs of senescence, presumably preparing the leaf for degradation of its components.
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| 34. |
- Andersson, Jenny, et al.
(författare)
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Absence of the Lhcb1 and Lhcb2 proteins of the light-harvesting complex of photosystem II - effects on photosynthesis, grana stacking and fitness
- 2003
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Ingår i: The Plant Journal. - : Wiley. - 0960-7412 .- 1365-313X. ; 35:3, s. 350-361
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Tidskriftsartikel (refereegranskat)abstract
- We have constructed Arabidopsis thaliana plants that are virtually devoid of the major light-harvesting complex, LHC II. This was accomplished by introducing the Lhcb2.1 coding region in the antisense orientation into the genome by Agrobacterium-mediated transformation. Lhcb1 and Lhcb2 were absent, while Lhcb3, a protein present in LHC II associated with photosystem (PS) II, was retained. Plants had a pale green appearance and showed reduced chlorophyll content and an elevated chlorophyll a/b ratio. The content of PS II reaction centres was unchanged on a leaf area basis, but there was evidence for increases in the relative levels of other light harvesting proteins, notably CP26, associated with PS II, and Lhca4, associated with PS I. Electron microscopy showed the presence of grana. Photosynthetic rates at saturating irradiance were the same in wild-type and antisense plants, but there was a 10-15% reduction in quantum yield that reflected the decrease in light absorption by the leaf. The antisense plants were not able to perform state transitions, and their capacity for non-photochemical quenching was reduced. There was no difference in growth between wild-type and antisense plants under controlled climate conditions, but the antisense plants performed worse compared to the wild type in the field, with decreases in seed production of up to 70%.
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| 35. |
- Andersson, Jenny, et al.
(författare)
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Antisense inhibition of the photosynthetic antenna proteins CP29 and CP26 : implications for the mechanism of protective energy dissipation
- 2001
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Ingår i: The Plant Cell. - : American Society of Plant Biologists. - 1040-4651 .- 1532-298X. ; 13:5, s. 1193-1204
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Tidskriftsartikel (refereegranskat)abstract
- The specific roles of the chlorophyll a/b binding proteins CP29 and CP26 in light harvesting and energy dissipation within the photosynthetic apparatus have been investigated. Arabidopsis was transformed with antisense constructs against the genes encoding the CP29 or CP26 apoprotein, which gave rise to several transgenic lines with remarkably low amounts of the antisense target proteins. The decrease in the level of CP24 protein in the CP29 antisense lines indicates a physical interaction between these complexes. Analysis of chlorophyll fluorescence showed that removal of the proteins affected photosystem II function, probably as a result of changes in the organization of the light-harvesting antenna. However, whole plant measurements showed that overall photosynthetic rates were similar to those in the wild type. Both antisense lines were capable of the qE type of nonphotochemical fluorescence quenching, although there were minor changes in the capacity for quenching and in its induction kinetics. High-light-induced violaxanthin deepoxidation to zeaxanthin was not affected, although the pool size of these pigments was decreased slightly. We conclude that CP29 and CP26 are unlikely to be sites for nonphotochemical quenching.
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| 36. |
- Andersson, Jonas, et al.
(författare)
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Diabetes mellitus, high BMI and low education level predict sudden cardiac death within 24 hours of incident myocardial infarction
- 2016
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Ingår i: European Journal of Preventive Cardiology. - : Oxford University Press (OUP). - 2047-4873 .- 2047-4881. ; 23:17, s. 1814-1820
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: More than half of cardiovascular mortality occurs outside the hospital, mainly due to consistently low survival rates from out-of-hospital cardiac arrest.METHODS: This is a prospective, nested, case-control study derived from the Västerbotten Intervention Programme and the World Health Organization's Multinational Monitoring of Trends and Determinants in Cardiovascular Disease study in northern Sweden (1986-2006). To determine predictors for sudden cardiac death risk factors for cardiovascular disease were compared between incident myocardial infarction with sudden cardiac death (n = 363) and survivors of incident myocardial infarction (n = 1998) using multivariate logistic regression analysis.RESULTS: Diabetes had the strongest association with sudden cardiac death out of all evaluated risk factors (odds ratio (OR) 1.83, 95% confidence interval (CI) 1.30-2.59), followed by low education (OR 1.55, 95% CI 1.19-2.01), high body mass index (OR 1.05, 95% CI 1.02-1.08) and male sex (OR 1.42, 95% CI 1.001-2.01).CONCLUSIONS: The pattern of risk factors for incident myocardial infarction is different among survivors and those who die within 24 hours. The risk factors that contribute the most to death within 24 hours are diabetes mellitus, high body mass index and low education level, and can be addressed at both the public health level and by general practitioners.
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| 37. |
- Andersson, Maria L.E. 1968-, et al.
(författare)
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Baseline levels of circulating galectin-1 associated with radiographic hand but not radiographic knee osteoarthritis at a two-year follow-up
- 2024
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Ingår i: OSTEOARTHRITIS AND CARTILAGE OPEN. - Oxford : Elsevier. - 2665-9131. ; 6:2
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Tidskriftsartikel (refereegranskat)abstract
- Objective: We tested the potential of circulating galectin-1, interleukin (IL)-1 beta, IL-6, and tumour necrosis factor alpha (TNF alpha) levels at baseline in individuals with knee pain as biomarkers for development of radiographic knee and/or hand osteoarthritis (OA). Design:This study comprised 212 individuals with knee pain from the Halland osteoarthritis cohort (HALLOA). Clinical characteristics and serum/plasma levels of galectin-1, IL-1 beta, IL-6, and TNF alpha were measured at baseline, and knee and hand radiographs were obtained at a two-year follow-up. The predictive value of circulating inflammatory markers and clinical variables at baseline was assessed using multinominal logistic regression for those who developed radiographic OA in knees only (n = 25), in hands only (n = 40), and in both knees and hands (n = 43); the group who did not develop OA (n = 104) was used as reference. Correlations were assessed using Spearman's correlation coefficients. Results: As expected, age was identified as a risk factor for having radiographic knee and/or hand OA at the twoyear follow-up. Baseline circulating galectin-1 levels did not associate with developing radiographic knee OA but associated with developing radiographic hand OA (odds ratio (OR) for a 20% increased risk: 1.14, 95% confidence interval (CI) 1.01-1.29) and both radiographic knee and hand OA (OR for a 20% increased risk: 1.18, 95% CI 1.05-1.30). However, baseline IL-1 beta, IL-6, and TNF alpha did not associate with developing radiographic knee and/or hand OA. Conclusion: Non-age adjusted circulating galectin-1 is superior to IL-6, IL-1 beta, and TNF alpha in predicting radiographic hand but not knee OA.
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| 38. |
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| 39. |
- Andersson, Ulf Bertil, et al.
(författare)
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Emendment to the term complex in: “Guide for geological nomenclature in Sweden” (Kumpulainen 2016)
- 2022
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Ingår i: GFF. - : Taylor & Francis. - 1103-5897 .- 2000-0863. ; 144:3-4, s. 151-151
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Since the publication of Kumpulainen (2016), the Committeehave been alerted by the investigation and subsequent changesto the North American Stratigraphic Code concerning thelithodemic unit“complex”(Easton et al.2016; North Ameri-can Commission on Stratigraphic Nomenclature (NACSN)2017). These changes concern the introduction of the nomen-clature unit“Intrusive Complex”. In the original version(NACSN1983), as well as in the Swedish Guide for nomencla-ture (Kumpulainen2016), the unit“complex”is defined ascontaining at least two genetic classes of rocks, i.e., igneous,sedimentary, or metamorphic.
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| 40. |
- Antonson, Hans, 1963-
(författare)
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Landskap och ödesbölen : Jämtland före, under och efter den medeltida agrarkrisen
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This study examines landscape change in the Province of Jämtland during c. 1000–1750 AD. Settlement and arable cultivation are two of the most important sources in this study. They are therefore treated in depth, particularly farmsteads that were deserted during the late medieval agrarian crisis, so-called ödesbölen, and their fossil field-traces. The dissertation contains four major investigations. In the first investigation 610 possible ödesbölen were identified. The desertion was estimated at 50 per cent. The second investigation had its focus on the geographic location, and the conclusion was that the ödesbölen may have been deserted when the climate turned colder in the 14th century. The third investigation concerned medieval agriculture. Using historical maps and detailed mapping of fossil field traces it was established that the annually cultivated acreage decreased from the High Middle Ages until early modern times. This probably means that the agrarian crisis caused a change in the agrarian regime, from predominant arable farming to predominant stock-raising. The fourth investigation was whether the ownership or the use of the ödesbölen created obstacles to recolonization when the crisis subsided. This turned out not to be so in the case of ownership, but may have been so with regard to communal forest grazing. According to historical maps the ödesbölen in Jämtland were finally recolonized about 200 years later than for example in southern Sweden. The reasons probably were wars and a worse climate. The dissertation is capped off with both a model and a description of landscape change in Jämtland. Characteristic for the development of the landscape has been fluctuations in settlement. The ödesbölen are part of a pattern in which they are colonized, deserted, recolonized and again deserted in a cyclical course of events. The openness of the landscape is not part of this course of events.
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| 41. |
- Apuli, Rami-Petteri, et al.
(författare)
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Inferring the Genomic Landscape of Recombination Rate Variation in European Aspen (Populus tremula)
- 2020
-
Ingår i: G3. - : GENETICS SOCIETY AMERICA. - 2160-1836. ; 10:1, s. 299-309
-
Tidskriftsartikel (refereegranskat)abstract
- The rate of meiotic recombination is one of the central factors determining genome-wide levels of linkage disequilibrium which has important consequences for the efficiency of natural selection and for the dissection of quantitative traits. Here we present a new, high-resolution linkage map for Populus tremula that we use to anchor approximately two thirds of the P. tremula draft genome assembly on to the expected 19 chromosomes, providing us with the first chromosome-scale assembly for P. tremula (Table 2). We then use this resource to estimate variation in recombination rates across the P. tremula genome and compare these results to recombination rates based on linkage disequilibrium in a large number of unrelated individuals. We also assess how variation in recombination rates is associated with a number of genomic features, such as gene density, repeat density and methylation levels. We find that recombination rates obtained from the two methods largely agree, although the LD-based method identifies a number of genomic regions with very high recombination rates that the map-based method fails to detect. Linkage map and LD-based estimates of recombination rates are positively correlated and show similar correlations with other genomic features, showing that both methods can accurately infer recombination rate variation across the genome. Recombination rates are positively correlated with gene density and negatively correlated with repeat density and methylation levels, suggesting that recombination is largely directed toward gene regions in P. tremula.
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| 42. |
- Arshad, Rameez, et al.
(författare)
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A kaleidoscope of photosynthetic antenna proteins and their emerging roles
- 2022
-
Ingår i: Plant Physiology. - : Oxford University Press. - 0032-0889 .- 1532-2548. ; 189:3, s. 1204-1219
-
Tidskriftsartikel (refereegranskat)abstract
- Photosynthetic light-harvesting antennae are pigment-binding proteins that perform one of the most fundamental tasks on Earth, capturing light and transferring energy that enables life in our biosphere. Adaptation to different light environments led to the evolution of an astonishing diversity of light-harvesting systems. At the same time, several strategies have been developed to optimize the light energy input into photosynthetic membranes in response to fluctuating conditions. The basic feature of these prompt responses is the dynamic nature of antenna complexes, whose function readily adapts to the light available. High-resolution microscopy and spectroscopic studies on membrane dynamics demonstrate the crosstalk between antennae and other thylakoid membrane components. With the increased understanding of light-harvesting mechanisms and their regulation, efforts are focusing on the development of sustainable processes for effective conversion of sunlight into functional bio-products. The major challenge in this approach lies in the application of fundamental discoveries in light-harvesting systems for the improvement of plant or algal photosynthesis. Here, we underline some of the latest fundamental discoveries on the molecular mechanisms and regulation of light harvesting that can potentially be exploited for the optimization of photosynthesis.
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| 43. |
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| 44. |
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| 45. |
- Babst, Benjamin A, et al.
(författare)
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Local and systemic transcriptome responses to herbivory and jasmonic acid in Populus
- 2009
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Ingår i: The Genetics & Genomes. - : Springer Science and Business Media LLC. - 1614-2942 .- 1614-2950. ; 5:3, s. 459-474
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Tidskriftsartikel (refereegranskat)abstract
- We used DNA microarrays to examine local and systemic transcriptional responses to herbivory by gypsy moth larvae (GM) and exogenous jasmonic acid (JAtrt) in leaves of Populus nigra L. to identify candidate signaling and defense genes and also to examine primary metabolism, as might relate to tolerance of damage. GM and JAtrt altered expression of over 800 genes, most of which have putative roles in defense signaling, secondary metabolism, and primary metabolism. Additionally, numerous uncharacterized genes responded to herbivory, providing a rich resource for future studies. There was limited overlap (14%) between the responses to GM and JAtrt. GM did, however, result in strong upregulation of genes involved not only in JA biosynthesis but also abscisic acid biosynthesis and other signaling pathways. GM induced known resistance transcripts, including polyphenolic biosynthetic genes, proteinase inhibitors, and amino acid deaminases. According to GOStats pathway level analysis, GM altered primary metabolism, including aromatic amino acid biosynthesis, fatty acid β-oxidation, and carbohydrate and organic acid metabolism. These alterations may be related to increased demands for substrate for secondary metabolites or may serve a tolerance-related role. Responses were more intense locally in treated leaves than in untreated (systemic) leaves and systemic responses were mostly a subset of the genes induced locally. A stronger local response might be needed to cope with localized stresses and wound healing. Since Populus in general and this clone in particular are known for their systemic induced resistance, genes induced both locally and systemically may be the highest quality candidates for resistance.
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| 46. |
- BADER, P, et al.
(författare)
-
WOOD-INHABITING FUNGI AND SUBSTRATUM DECLINE IN SELECTIVELY LOGGED BOREAL SPRUCE FORESTS
- 1995
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Ingår i: Biological Conservation. - 0006-3207 .- 1873-2917. ; 72:3, s. 355-362
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Tidskriftsartikel (refereegranskat)abstract
- Eleven Norway spruce Picea abies (L.) Karst. forests in the boreal zone of Sweden were studied to investigate the effects of selective cuttings on wood-inhabiting fungi from the families Polyporaceae, Hymenochaetaceae and Corticiaceae (Basidiomycota). The II sites constitute a gradient from extensively logged to semi-natural forests. Old selective leggings that occurred about 100 years ago have significantly decreased the availability of large and highly decayed logs. Based on fruit bodies, both the total species number as well as the number of threatened species decreased with increasing degree of cutting. Some of the occurring wood-inhabiting fungi are commonly accepted as indicator species of forests with old-growth conditions. These species showed pronounced preferences for well decayed and large logs. They were also more frequent in the less affected sites and became rarer with increasing degree of cutting; they therefore seem to be good indicators of forests less affected by logging.
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| 47. |
- Bag, Pushan, 1993-, et al.
(författare)
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An atlas of the Norway spruce needle seasonal transcriptome
- 2021
-
Ingår i: The Plant Journal. - : John Wiley & Sons. - 0960-7412 .- 1365-313X. ; 108:6, s. 1815-1829
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Tidskriftsartikel (refereegranskat)abstract
- Boreal conifers possess a tremendous ability to survive and remain evergreen during harsh winter conditions and resume growth during summer. This is enabled by coordinated regulation of major cellular functions at the level of gene expression, metabolism, and physiology. Here we present a comprehensive characterization of the annual changes in the global transcriptome of Norway spruce (Picea abies) needles as a resource to understand needle development and acclimation processes throughout the year. In young, growing needles (May 15 until June 30), cell walls, organelles, etc., were formed, and this developmental program heavily influenced the transcriptome, explained by over-represented Gene Ontology (GO) categories. Later changes in gene expression were smaller but four phases were recognized: summer (July–August), autumn (September–October), winter (November–February), and spring (March–April), where over-represented GO categories demonstrated how the needles acclimated to the various seasons. Changes in the seasonal global transcriptome profile were accompanied by differential expression of members of the major transcription factor families. We present a tentative model of how cellular activities are regulated over the year in needles of Norway spruce, which demonstrates the value of mining this dataset, accessible in ConGenIE together with advanced visualization tools.
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| 48. |
- Bag, Pushan, 1993-, et al.
(författare)
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Direct energy transfer from photosystem II to photosystem I confers winter sustainability in Scots Pine
- 2020
-
Ingår i: Nature Communications. - : Nature Publishing Group. - 2041-1723. ; 11:1
-
Tidskriftsartikel (refereegranskat)abstract
- Evergreen conifers in boreal forests can survive extremely cold (freezing) temperatures during long dark winter and fully recover during summer. A phenomenon called "sustained quenching" putatively provides photoprotection and enables their survival, but its precise molecular and physiological mechanisms are not understood. To unveil them, here we have analyzed seasonal adjustment of the photosynthetic machinery of Scots pine (Pinus sylvestris) trees by monitoring multi-year changes in weather, chlorophyll fluorescence, chloroplast ultrastructure, and changes in pigment-protein composition. Analysis of Photosystem II and Photosystem I performance parameters indicate that highly dynamic structural and functional seasonal rearrangements of the photosynthetic apparatus occur. Although several mechanisms might contribute to 'sustained quenching' of winter/early spring pine needles, time-resolved fluorescence analysis shows that extreme down-regulation of photosystem II activity along with direct energy transfer from photosystem II to photosystem I play a major role. This mechanism is enabled by extensive thylakoid destacking allowing for the mixing of PSII with PSI complexes. These two linked phenomena play crucial roles in winter acclimation and protection. Evergreen conifers rely on 'sustained quenching' to protect their photosynthetic machinery during long, cold winters. Here, Bag et al. show that direct energy transfer (spillover) from photosystem II to photosystem I triggered by loss of grana stacking in chloroplast is the major component of sustained quenching in Scots pine.
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| 49. |
- Bag, Pushan, 1993-, et al.
(författare)
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Flavodiiron-mediated O2 photoreduction at photosystem I acceptor-side provides photoprotection to conifer thylakoids in early spring
- 2023
-
Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 14:1
-
Tidskriftsartikel (refereegranskat)abstract
- Green organisms evolve oxygen (O2) via photosynthesis and consume it by respiration. Generally, net O2 consumption only becomes dominant when photosynthesis is suppressed at night. Here, we show that green thylakoid membranes of Scots pine (Pinus sylvestris L) and Norway spruce (Picea abies) needles display strong O2 consumption even in the presence of light when extremely low temperatures coincide with high solar irradiation during early spring (ES). By employing different electron transport chain inhibitors, we show that this unusual light-induced O2 consumption occurs around photosystem (PS) I and correlates with higher abundance of flavodiiron (Flv) A protein in ES thylakoids. With P700 absorption changes, we demonstrate that electron scavenging from the acceptor-side of PSI via O2 photoreduction is a major alternative pathway in ES. This photoprotection mechanism in vascular plants indicates that conifers have developed an adaptative evolution trajectory for growing in harsh environments.
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| 50. |
- Bag, Pushan, 1993-
(författare)
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How could Christmas trees remain evergreen? : photosynthetic acclimation of Scots pine and Norway spruce needles during winter
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Plants and other green organisms harvest sunlight by green chlorophyll pigments and covertit to chemical energy (sugars) and oxygen in a process called photosynthesis providing the foundation for life on Earth. Although it is unanimously believed that oceanic phytoplanktons are the main contributors to the global photosynthesis, the contribution of coniferous boreal forests distributed across vast regions of the northern hemisphere cannot be undermined. Hence boreal forests account signifificantly for social, economical and environmental sustainability. Not only do conifers thrive in the tundra regions with extreme climate, but they also maintain their needles green over the boreal winter. A question remains; what makes them so resilient? In this respect, we aimed to understand the remarkable winter adaptation strategies in two dominant boreal coniferous species,i.e., Pinus sylvestris and Picea abies. First, we mapped the transcriptional landscape in Norway spruce (Picea abies) needles over the annual cycle. Transcriptional changes in the nascent needles reflflected a sequence of developmental processes and active vegetative growth during early summer and summer. Later after maturation, transcriptome reflflected activated defense against biotic factors and acclimationin response to abiotic environmental cues such as freezing temperatures during winter. Secondly, by monitoring the photosynthetic performance of Scot pine needles, we found that the trees face extreme stress during the early spring (Feb-Mar) when sub-zero temperatures are accompanied by high solar radiation. At this time, drastic changes occur in the thylakoid membranes of the chloroplast that allows the mixing of photosystem I and photosystem II that typically remain laterally segregated. This triggers direct energy transfer from PSII to PSI and thus protects PSII from damage. Furthermore, we found that this loss of lateral segregation may be a consequence of triple phosphorylationof Lhcb1 (Light harvesting complex1 of photosystem II). The structural changes in thylakoid membranes also lead to changes inthe thylakoid macro domain organisationand pigment protein composition. Furthermore, we discovered that while PSII is protected by direct energy transfer, the protection of PSI is provided through photoreduction of oxygen by flavodiiron proteins, which in turn allows P700 to stay in an oxidised state necessary for direct energy transfer. These coordinated cascades of changes concomitantly protect both PSI and PSII to maintain the needles green over the winter.
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