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Sökning: WFRF:(Kristjánsson G.)

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1.
  • Kulmala, M., et al. (författare)
  • General overview: European Integrated project on Aerosol Cloud Climate and Air Quality interactions (EUCAARI) - integrating aerosol research from nano to global scales
  • 2011
  • Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 11:24, s. 13061-13143
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper we describe and summarize the main achievements of the European Aerosol Cloud Climate and Air Quality Interactions project (EUCAARI). EUCAARI started on 1 January 2007 and ended on 31 December 2010 leaving a rich legacy including: (a) a comprehensive database with a year of observations of the physical, chemical and optical properties of aerosol particles over Europe, (b) comprehensive aerosol measurements in four developing countries, (c) a database of airborne measurements of aerosols and clouds over Europe during May 2008, (d) comprehensive modeling tools to study aerosol processes fron nano to global scale and their effects on climate and air quality. In addition a new Pan-European aerosol emissions inventory was developed and evaluated, a new cluster spectrometer was built and tested in the field and several new aerosol parameterizations and computations modules for chemical transport and global climate models were developed and evaluated. These achievements and related studies have substantially improved our understanding and reduced the uncertainties of aerosol radiative forcing and air quality-climate interactions. The EUCAARI results can be utilized in European and global environmental policy to assess the aerosol impacts and the corresponding abatement strategies.
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  • Abou-Hachem, Maher, et al. (författare)
  • The modular organisation and stability of a thermostable family 10 xylanase
  • 2003
  • Ingår i: Biocatalysis and Biotransformation. - : Informa UK Limited. - 1024-2422 .- 1029-2446. ; 21:5-6, s. 253-260
  • Tidskriftsartikel (refereegranskat)abstract
    • The thermophilic marine bacterium Rhodothermus marinus produces a modular family 10 xylanase (Xyn10A). It consists of two N-terminal family 4 carbohydrate binding modules (CBMs) followed by a domain of unknown function (D3), and a catalytic module (CM) flanked by a small fifth domain (D5) at its C-terminus. Several truncated mutants of the enzyme have been produced and characterised with respect to biochemical properties and stability. Multiple calcium binding sites are shown to be present in the two N-terminal CBMs and recent evidence suggests that the third domain of the enzyme also has the ability to bind the same metal ligand. The specific binding of Ca2+ was demonstrated to have a pronounced effect on thermostability as shown by differential scanning calorimetry and thermal inactivation studies. Furthermore, deletion mutants of the enzyme were less stable than the full-length enzyme suggesting that module interactions contributed to the stability of the enzyme. Finally, recent evidence indicates that the fifth domain of Xyn10A is a novel type of module mediating cell-attachment.
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11.
  • Birgisson, Hakon, et al. (författare)
  • A new thermostable alpha-L-arabinofuranosidase from a novel thermophilic bacterium
  • 2004
  • Ingår i: Biotechnology Letters. - 1573-6776. ; 26:17, s. 1347-1351
  • Tidskriftsartikel (refereegranskat)abstract
    • An alpha-L-arabinofuranosidase gene was identified in a sequenced genome of a novel thermophilic bacterium, which belongs to the recently described phylum of Thermomicrobia. Amino acid sequence comparison of the enzyme (designated AraF) revealed similarity to glycoside hydrolases of family 51. The gene was cloned into Escherichia coli and its recombinant product expressed and purified. The enzyme appeared to be a hexamer. AraF was optimally active at 70degreesC (over 10 min) and pH 6 having 92% residual activity after 1 h at 70degreesC. AraF had a K-m value of 0.6 rum and V-max value of 122 U mg(-1) on p-nitrophenyl-alpha-L-arabinofuranoside. AraF was almost equally active on branched arabinan and debranched arabinan, properties not previously found in alpha-L-arabinofuranosidases in GH family 51.
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  • Birgisson, Hakon, et al. (författare)
  • Two new thermostable alpha-L-rhamnosidases from a novel thermophilic bacterium
  • 2004
  • Ingår i: Enzyme and Microbial Technology. - : Elsevier BV. - 0141-0229. ; 34:6, s. 561-571
  • Tidskriftsartikel (refereegranskat)abstract
    • Two new thermostable alpha-L-rhamnosidases with novel substrate hydrolysis pattern were cloned and expressed from a new thermophilic bacterium. Fragments of the two alpha-L-rhamnosidase genes, rhmA and rhmB were identified in a partially sequenced genome of the bacterium. Whole genes were recovered by amplifying flanking sequences with single specific primers and nonspecific walking primers. The recovered Genes were then cloned into Escherichia coli and their enzymes produced and purified. Both enzymes were dimers and the MW of the monomers. were 104 and 107 kDa for RhmA and RhmB, respectively. Both rhamnosidases had a temperature optimum at 70degreesC. RhmA had pH optimum at 7.9 and RhmB had a broad pH optimum of 5.0 to 6.9 and RhmA had over 50% activity in the pH interval 5.0 to 8.7 and RhmB in the pH interval 4.0 to 7.9. Both enzymes had over 20% residual activity after 24-h incubation at 60degreesC. RhmA and RhmB had K values of 0.46 and 0.66 mM and V-max values of 134 and 352 U mg(-1) respectively, on p-nitrophenyl-alpha-L-rhamnopyrano side. Both rhamnosidases were active on both alpha-1,2- and alpha-1,6-linkages to beta-D-glucoside. (C) 2004 Elsevier Inc. All rights reserved.
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13.
  • Boy, M., et al. (författare)
  • Interactions between the atmosphere, cryosphere, and ecosystems at northern high latitudes
  • 2019
  • Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 19:3, s. 2015-2061
  • Tidskriftsartikel (refereegranskat)abstract
    • The Nordic Centre of Excellence CRAICC (Cryosphere-Atmosphere Interactions in a Changing Arctic Climate), funded by NordForsk in the years 2011-2016, is the largest joint Nordic research and innovation initiative to date, aiming to strengthen research and innovation regarding climate change issues in the Nordic region. CRAICC gathered more than 100 scientists from all Nordic countries in a virtual centre with the objectives of identifying and quantifying the major processes controlling Arctic warming and related feedback mechanisms, outlining strategies to mitigate Arctic warming, and developing Nordic Earth system modelling with a focus on short-lived climate forcers (SLCFs), including natural and anthropogenic aerosols. The outcome of CRAICC is reflected in more than 150 peer-reviewed scientific publications, most of which are in the CRAICC special issue of the journal Atmospheric Chemistry and Physics. This paper presents an overview of the main scientific topics investigated in the centre and provides the reader with a state-of-the-art comprehensive summary of what has been achieved in CRAICC with links to the particular publications for further detail. Faced with a vast amount of scientific discovery, we do not claim to completely summarize the results from CRAICC within this paper, but rather concentrate here on the main results which are related to feedback loops in climate change-cryosphere interactions that affect Arctic amplification.
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  • Kiemeney, Lambertus A, et al. (författare)
  • A sequence variant at 4p16.3 confers susceptibility to urinary bladder cancer.
  • 2010
  • Ingår i: Nature genetics. - : Springer Science and Business Media LLC. - 1546-1718 .- 1061-4036. ; 42:5, s. 415-9
  • Tidskriftsartikel (refereegranskat)abstract
    • Previously, we reported germline DNA variants associated with risk of urinary bladder cancer (UBC) in Dutch and Icelandic subjects. Here we expanded the Icelandic sample set and tested the top 20 markers from the combined analysis in several European case-control sample sets, with a total of 4,739 cases and 45,549 controls. The T allele of rs798766 on 4p16.3 was found to associate with UBC (odds ratio = 1.24, P = 9.9 x 10(-12)). rs798766 is located in an intron of TACC3, 70 kb from FGFR3, which often harbors activating somatic mutations in low-grade, noninvasive UBC. Notably, rs798766[T] shows stronger association with low-grade and low-stage UBC than with more aggressive forms of the disease and is associated with higher risk of recurrence in low-grade stage Ta tumors. The frequency of rs798766[T] is higher in Ta tumors that carry an activating mutation in FGFR3 than in Ta tumors with wild-type FGFR3. Our results show a link between germline variants, somatic mutations of FGFR3 and risk of UBC.
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  • Lampinen, M., et al. (författare)
  • Eosinophil granulocytes are activated during the remission phase of ulcerative colitis
  • 2005
  • Ingår i: Gut. ; 54:12, s. 1714-20
  • Tidskriftsartikel (refereegranskat)abstract
    • AIM: The aim of this study was to establish a method of investigating intestinal eosinophil and neutrophil granulocytes by flow cytometry, and to compare the distribution and activity of these cells in different stages of ulcerative colitis (UC). METHODS: Biopsy samples were taken from six locations of the entire colon and from the terminal ileum in 10 patients with active total UC, 10 patients with inactive total UC, eight patients with active distal UC, and 11 control subjects. Cell suspensions from biopsies and from peripheral blood were incubated with fluorophore conjugated monoclonal antibodies. The use of scatter plot-gating and specific antibodies was established in a flow cytometry assay. RESULTS: Eosinophils were more numerous and more active in patients with active UC than in controls. Interestingly, during inactive UC, the number of activated eosinophils was even larger. Eosinophil activity was high in the rectum of patients with distal colitis but was also slightly elevated in the proximal colon. Neutrophils were increased in number and activity during active but not inactive UC. In patients with distal colitis, activated neutrophils were only found in the sigmoid colon and rectum. CONCLUSION: With this method, we confirm that neutrophils participate in the inflammatory process during active UC, and that they express a resting phenotype during remission. The finding of activated eosinophils in inflamed intestine strengthens the view of these cells as proinflammatory and tissue damaging. Nevertheless, our new finding of high eosinophil activation during inactive UC suggests that eosinophils play a role in repair of injured epithelium.
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  • Lidén, Maria, et al. (författare)
  • Cow's milk protein sensitivity assessed by the mucosal patch technique is related to irritable bowel syndrome in patients with primary Sjögren's syndrome
  • 2008
  • Ingår i: Clinical and Experimental Allergy. - : Wiley. - 0954-7894 .- 1365-2222. ; 38:6, s. 929-935
  • Tidskriftsartikel (refereegranskat)abstract
    • INTRODUCTION: Patients with primary Sjögren's syndrome (pSS) are reported to have a variety of gastrointestinal symptoms partly attributed to an overrepresentation of celiac disease. We have observed that irritable bowel syndrome (IBS)-like symptoms are frequent complaints in this patient group. Allergic manifestations to various drugs are also common in pSS. A role of food allergy in IBS has been proposed. OBJECTIVE: This study is aimed at evaluating the mucosal response to rectal challenge with cow's milk protein (CM) in patients with pSS and relates possible CM reactivity to their intestinal symptoms. Methods: A rectal challenge with CM was performed in 21 patients with pSS and 18 healthy controls. Fifteen hours after challenge the mucosal production of nitric oxide (NO) and the release of myeloperoxidase (MPO) as signs of mucosal inflammatory reaction were measured using the mucosal patch technique. RESULTS: Eight out of 21 patients with pSS had a definite increase of mucosal NO synthesis and the luminal release of MPO after rectal CM challenge. This sign of milk sensitivity was not linked to IgG/IgA antibodies to milk proteins. The symptoms for IBS according to Rome III criteria were fulfilled in 13 patients. All patients who were CM sensitive suffered from IBS. In a small open study, patients reactive to CM reported an improvement of intestinal symptoms on a CM-free diet. CONCLUSION: A rectal mucosal inflammatory response after CM challenge is seen in 38% of patients with pSS as a sign of CM sensitivity. IBS-like symptoms were common in pSS, linked to CM sensitivity.
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  • Love, G, et al. (författare)
  • A single-item measure of childhood relationship quality and association with adult health and health behaviours
  • 2023
  • Ingår i: Scandinavian journal of public health. - : SAGE Publications. - 1651-1905 .- 1403-4948. ; 51:2, s. 233-240
  • Tidskriftsartikel (refereegranskat)abstract
    • Adverse childhood experiences are known to relate positively to various health risks and adverse health behaviour in adult life, although the precise mechanisms are still debated. The aim of this study was to investigate whether a single-item measure of the quality of childhood relationships with family and household members might show a similar association. Methods: We measured the overall quality of relationships with family and household members during the first 18 years of life. A one-dimensional question scored 0–10 ( N=4983) was included in the ongoing SIBS Iceland Patient Association’s national ‘Life and Health’ public health prevention project among adults. Relationship quality was then assessed against measures of health and health behaviour using 21 validated scales. Results: A lower childhood relationships score was associated with a higher risk of all 21 suboptimal health and health behaviour outcomes in adulthood, with adjusted effect sizes measured by standardised betas (magnitude 0.111–0.284), variance explained (1.3–8.5%) and per-point adjusted odds ratios (1.10–1.30). The strongest associations were found with measures of social and mental health, followed by physical health, alcohol and tobacco use, sleeping problems, financial sustenance, physical pain and aerobic fitness. Conclusions: Odds were found to match well with pooled odds ratios presented in a systematic review of 37 adverse childhood experiences studies. This may indicate that a one-dimensional relationships question is a useful substitute in surveys in which a traditional multi-question adverse childhood experiences scale cannot be accommodated. Further investigations are recommended to investigate the applicability of a single adverse childhood experiences question.
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20.
  • Malavelle, Florent F., et al. (författare)
  • Strong constraints on aerosol-cloud interactions from volcanic eruptions
  • 2017
  • Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 546:7659, s. 485-491
  • Tidskriftsartikel (refereegranskat)abstract
    • Aerosols have a potentially large effect on climate, particularly through their interactions with clouds, but the magnitude of this effect is highly uncertain. Large volcanic eruptions produce sulfur dioxide, which in turn produces aerosols; these eruptions thus represent a natural experiment through which to quantify aerosol-cloud interactions. Here we show that the massive 2014-2015 fissure eruption in Holuhraun, Iceland, reduced the size of liquid cloud droplets-consistent with expectations-but had no discernible effect on other cloud properties. The reduction in droplet size led to cloud brightening and global-mean radiative forcing of around -0.2 watts per square metre for September to October 2014. Changes in cloud amount or cloud liquid water path, however, were undetectable, indicating that these indirect effects, and cloud systems in general, are well buffered against aerosol changes. This result will reduce uncertainties in future climate projections, because we are now able to reject results from climate models with an excessive liquid-water-path response.
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  • Skulason, Skuli, et al. (författare)
  • A way forward with eco evo devo : an extended theory of resource polymorphism with postglacial fishes as model systems
  • 2019
  • Ingår i: Biological Reviews. - : John Wiley & Sons. - 1464-7931 .- 1469-185X. ; 94:5, s. 1786-1808
  • Forskningsöversikt (refereegranskat)abstract
    • A major goal of evolutionary science is to understand how biological diversity is generated and altered. Despite considerable advances, we still have limited insight into how phenotypic variation arises and is sorted by natural selection. Here we argue that an integrated view, which merges ecology, evolution and developmental biology (eco evo devo) on an equal footing, is needed to understand the multifaceted role of the environment in simultaneously determining the development of the phenotype and the nature of the selective environment, and how organisms in turn affect the environment through eco evo and eco devo feedbacks. To illustrate the usefulness of an integrated eco evo devo perspective, we connect it with the theory of resource polymorphism (i.e. the phenotypic and genetic diversification that occurs in response to variation in available resources). In so doing, we highlight fishes from recently glaciated freshwater systems as exceptionally well‐suited model systems for testing predictions of an eco evo devo framework in studies of diversification. Studies on these fishes show that intraspecific diversity can evolve rapidly, and that this process is jointly facilitated by (i) the availability of diverse environments promoting divergent natural selection; (ii) dynamic developmental processes sensitive to environmental and genetic signals; and (iii) eco evo and eco devo feedbacks influencing the selective and developmental environments of the phenotype. We highlight empirical examples and present a conceptual model for the generation of resource polymorphism – emphasizing eco evo devo, and identify current gaps in knowledge.
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  • Thompson, Deborah J, et al. (författare)
  • Genetic predisposition to mosaic Y chromosome loss in blood
  • 2019
  • Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 575, s. 652-657
  • Tidskriftsartikel (refereegranskat)abstract
    • Mosaic loss of chromosome Y (LOY) in circulating white blood cells is the most common form of clonal mosaicism1-5, yet our knowledge of the causes and consequences of this is limited. Here, using a computational approach, we estimate that 20% of the male population represented in the UK Biobank study (n = 205,011) has detectable LOY. We identify 156 autosomal genetic determinants of LOY, which we replicate in 757,114 men of European and Japanese ancestry. These loci highlight genes that are involved in cell-cycle regulation and cancer susceptibility, as well as somatic drivers of tumour growth and targets of cancer therapy. We demonstrate that genetic susceptibility to LOY is associated with non-haematological effects on health in both men and women, which supports the hypothesis that clonal haematopoiesis is a biomarker of genomic instability in other tissues. Single-cell RNA sequencing identifies dysregulated expression of autosomal genes in leukocytes with LOY and provides insights into why clonal expansion of these cells may occur. Collectively, these data highlight the value of studying clonal mosaicism to uncover fundamental mechanisms that underlie cancer and other ageing-related diseases.
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  • Thorgeirsson, Thorgeir E, et al. (författare)
  • A variant associated with nicotine dependence, lung cancer and peripheral arterial disease
  • 2008
  • Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 452:7187, s. 9-638
  • Tidskriftsartikel (refereegranskat)abstract
    • Smoking is a leading cause of preventable death, causing about 5 million premature deaths worldwide each year(1,2). Evidence for genetic influence on smoking behaviour and nicotine dependence (ND)(3-8) has prompted a search for susceptibility genes. Furthermore, assessing the impact of sequence variants on smoking-related diseases is important to public health(9,10). Smoking is the major risk factor for lung cancer (LC)(11-14) and is one of the main risk factors for peripheral arterial disease (PAD)(15-17). Here we identify a common variant in the nicotinic acetylcholine receptor gene cluster on chromosome 15q24 with an effect on smoking quantity, ND and the risk of two smoking- related diseases in populations of European descent. The variant has an effect on the number of cigarettes smoked per day in our sample of smokers. The same variant was associated with ND in a previous genomewide association study that used low- quantity smokers as controls(18,19), and with a similar approach we observe a highly significant association with ND. A comparison of cases of LC and PAD with population controls each showed that the variant confers risk of LC and PAD. The findings provide a case study of a gene - environment interaction(20), highlighting the role of nicotine addiction in the pathology of other serious diseases.
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