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Sökning: WFRF:(Jonsdottir I.)

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51.
  • D'Hertefeldt, Tina, et al. (författare)
  • Responses to mineral nutrient availability and heterogeneity in physiologically integrated sedges from contrasting habitats.
  • 2011
  • Ingår i: Plant Biology. - Chichester : Wiley. - 1438-8677 .- 1435-8603. ; 13:3, s. 483-492
  • Tidskriftsartikel (refereegranskat)abstract
    • Clonal plants from poor habitats benefit less from morphologically plastic responses to heterogeneity than plants from more productive sites. In addition, physiological integration has been suggested to either increase or decrease the foraging efficiency of clonal plants. We tested the capacity for biomass production and morphological response in two closely related, rhizomatous species from habitats that differ in resource availability, Carex arenaria (from poor sand dunes) and C. disticha (from nutrient-richer, moister habitats). We expected lower total biomass production and reduced morphological plasticity in C. arenaria, and that both species would produce more ramets in high nutrient patches, either in response to signals transported through physiological integration, or by locally determined responses to nutrient availability. To investigate mineral nutrient heterogeneity, plants were grown in boxes divided into two compartments with homogeneous or heterogeneous supply of high (H) or low (L) nutrient levels, resulting in four treatments, H-H, H-L, L-H and L-L. Both C. arenaria and C. disticha produced similar biomass in high nutrient treatments. C. disticha responded to high nutrients by increased biomass production and branching of the young parts and by altering root:shoot ratio and rhizome lengths, while C. arenaria showed localised responses to high nutrients in terms of local biomass and branch production in high nutrient patches. The results demonstrated that although it has a conservative morphology, C. arenaria responded to nutrient heterogeneity through morphological plasticity. An analysis of costs and benefits of integration on biomass production showed that young ramets of both species benefited significantly from physiological integration, but no corresponding costs were found. This suggests that plants from resource-poor but dynamic habitats like sand dunes respond morphologically to high nutrient patches. The two species responded to nutrient heterogeneity in different traits, and this is discussed in terms of local and distant signalling of plant status.
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52.
  • Ellbin, S., et al. (författare)
  • Assessment of cognitive function in patients with stress-related exhaustion using the Cognitive Assessment Battery (CAB)
  • 2018
  • Ingår i: Journal of Clinical and Experimental Neuropsychology. - : Informa UK Limited. - 1380-3395 .- 1744-411X. ; 40:6, s. 567-575
  • Tidskriftsartikel (refereegranskat)abstract
    • Introduction: The health care system is facing an increased number of patients seeking care for burnout/stress-related exhaustion. One of the core features of this condition is cognitive impairmenteffective and easy tools are needed to assess cognition in this patient group. Our objective was to determine whether the Cognitive Assessment Battery (CAB) could be used for this purpose. Method: Ninety-three patients diagnosed with exhaustion disorder (ED) and 111 controls were included in the study and tested with CAB. CAB consists of six short tests covering the cognitive domains speed and attention, episodic memory, visuospatial, language, and executive functions. The patients also completed questionnaires on subjective memory problems, degree of burnout, anxiety, and depression. Results: The patients performed worse than the controls on four tests of speed and attention, language, and executive function. Subjective memory problems, degree of burnout, and anxiety did not influence cognitive performance, only degree of depression influenced performance negatively on an executive test. Conclusion: CAB is a useful instrument for rapid, comprehensive screening of cognitive status in patients with stress-related exhaustion. Using it, we confirmed the most replicated findings regarding cognitive impairments in patients with stress-related exhaustion.
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53.
  • Elmendorf, Sarah C., et al. (författare)
  • Global assessment of experimental climate warming on tundra vegetation : heterogeneity over space and time
  • 2012
  • Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 15:2, s. 164-175
  • Forskningsöversikt (refereegranskat)abstract
    • Understanding the sensitivity of tundra vegetation to climate warming is critical to forecasting future biodiversity and vegetation feedbacks to climate. In situ warming experiments accelerate climate change on a small scale to forecast responses of local plant communities. Limitations of this approach include the apparent site-specificity of results and uncertainty about the power of short-term studies to anticipate longer term change. We address these issues with a synthesis of 61 experimental warming studies, of up to 20 years duration, in tundra sites worldwide. The response of plant groups to warming often differed with ambient summer temperature, soil moisture and experimental duration. Shrubs increased with warming only where ambient temperature was high, whereas graminoids increased primarily in the coldest study sites. Linear increases in effect size over time were frequently observed. There was little indication of saturating or accelerating effects, as would be predicted if negative or positive vegetation feedbacks were common. These results indicate that tundra vegetation exhibits strong regional variation in response to warming, and that in vulnerable regions, cumulative effects of long-term warming on tundra vegetation and associated ecosystem consequences have the potential to be much greater than we have observed to date.
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54.
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55.
  • Gerber, M., et al. (författare)
  • Low leisure-time physical activity, but not shift-work, contributes to the development of sleep complaints in Swedish health care workers
  • 2017
  • Ingår i: Mental Health and Physical Activity. - : Elsevier BV. - 1755-2966. ; 13, s. 22-29
  • Tidskriftsartikel (refereegranskat)abstract
    • Problem Regular physical activity (PA) can prevent sleep complaints and improve sleep among people with sleep disorders, whereas nocturnal shift work is linked with a higher risk of sleep problems. The present study examines the prospective contribution of PA and nocturnal shift work to the development of subjective sleep complaints. Methods Data is based on 1406 health care workers (M = 45.67 years, 88% women). Physical activity and sleep complaints were assessed via self-reports twice across a 2-year period. To address the issue of reverse causation, only participants without initial sleep difficulties were included in the prospective analyses. Results Moderate-to-vigorous PA (MVPA) was associated with a lower risk of developing difficulties falling asleep at the 2-year follow-up. Both light PA and MVPA were associated with a lower risk of developing feeling of exhaustion upon waking. The prospective association between PA and these two sleep complaints persisted after controlling for covariates. No significant prospective association was found between PA and night time awakenings. Shift work was not related to any of the sleep complaints. Conclusions The findings suggest that regular PA contributes to the prevention of new sleep complaints, independent of whether participants engage in nocturnal shift work. Promoting PA can be a promising strategy to prevent sleep problems, both in shift-workers and non-shift-workers. © 2017 Elsevier Ltd
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62.
  • Gunnarsson, I, et al. (författare)
  • Rituximab treatment in lupus nephritis--where do we stand?
  • 2013
  • Ingår i: Lupus. - : SAGE Publications. - 1477-0962 .- 0961-2033. ; 22:4, s. 381-389
  • Tidskriftsartikel (refereegranskat)abstract
    • Renal involvement in systemic lupus erythematosus (SLE) is a severe disease manifestation in which novel therapeutic strategies are needed, especially in non-responding patients or patients who relapse after conventional treatment. Rituximab has been used as off-label treatment for lupus nephritis (LN) during the last decade, and to date reports on the clinical effects on more than 400 patients, including the randomized controlled LUNAR study population, have been published. Despite promising results obtained from observational studies and registries, with complete or partial renal response after 6–12 months in 67–77% of patients, the LUNAR trial failed to attain the primary endpoint and rituximab is today unlikely to be approved as treatment for LN. Rituximab has mainly been used as induction therapy in combination with standard of care but the optimal treatment protocol is still to be determined. From observational studies, rituximab has been shown to be efficient in both proliferative and membranous LN, and histopathological studies have demonstrated improvement in renal activity. Adverse events mainly include infusion reactions and infections. Although not approved for the treatment of LN, the currently available data support that rituximab may be used in severe, refractory cases of LN.
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63.
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64.
  • Helgadottir, Anna, et al. (författare)
  • The same sequence variant on 9p21 associates with myocardial infarction, abdominal aortic aneurysm and intracranial aneurysm
  • 2008
  • Ingår i: Nature Genetics. - : Springer Science and Business Media LLC. - 1546-1718 .- 1061-4036. ; 40:2, s. 217-224
  • Tidskriftsartikel (refereegranskat)abstract
    • Recently, two common sequence variants on 9p21, tagged by rs10757278-G and rs10811661-T, were reported to be associated with coronary artery disease (CAD)(1-4) and type 2 diabetes (T2D)(5-7), respectively. We proceeded to further investigate the contributions of these variants to arterial diseases and T2D. Here we report that rs10757278-G is associated with, in addition to CAD, abdominal aortic aneurysm (AAA; odds ratio (OR) 1.31, P = 1.2 x 10(-12)) and intracranial aneurysm (OR = 1.29, P = 2.5 x 10(-6)), but not with T2D. This variant is the first to be described that affects the risk of AAA and intracranial aneurysm in many populations. The association of rs10811661-T to T2D replicates in our samples, but the variant does not associate with any of the five arterial diseases examined. These findings extend our insight into the role of the sequence variant tagged by rs10757278-G and show that it is not confined to atherosclerotic diseases.
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71.
  • Jonsdottir, I.H. (författare)
  • Neuropeptides and their interaction with exercise and immune function
  • 2000
  • Ingår i: Immunology and Cell Biology. - Oxford : Blackwell Publishing. - 0818-9641 .- 1440-1711. ; 78:5, s. 562-570
  • Forskningsöversikt (refereegranskat)abstract
    • It is known today that the immune system is influenced by various types of psychological and physiological stressors, including physical activity. It is well known that physical activity can influence neuropeptide levels both in the central nervous system as well as in peripheral blood. The reported changes of immune function in response to exercise have been suggested to be partly regulated by the activation of different neuropeptides and the identification of receptors for neuropeptides and steroid hormones on cells of the immune system has created a new dimension in this endocrine-immune interaction. It has also been shown that immune cells are capable of producing neuropeptides, creating a bidirectional link between the nervous and immune systems. The most common neuropeptides mentioned in this context are the endogenous opioids. The activation of endogenous opioid peptides in response to physical exercise is well known in the literature, as well as the immunomodulation mediated by opioid peptides. The role of endogenous opioids in the exercise-induced modulation of immune function is less clear. The present paper will also discuss the role of other neuroendocrine factors, such as substance P, neuropeptide Y and vasoactive intestinal peptide, and pituitary hormones, including growth hormone, prolactin and adrenocorticotrophin, in exercise and their possible effects on immune function.
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72.
  • Jonsdottir, I. H., et al. (författare)
  • Working memory and attention are still impaired after three years inpatients with stress-related exhaustion
  • 2017
  • Ingår i: Scandinavian Journal of Psychology. - : Wiley. - 0036-5564 .- 1467-9450. ; 58:6, s. 504-509
  • Tidskriftsartikel (refereegranskat)abstract
    • Cognitive impairment is one of the most pronounced symptoms reported by patients with stress-related mental health problems. Impairments related to executive function and to some extent speed and attention are therefore common in patients with stress-related burnout/exhaustion. In this paper we present a follow-up of cognitive performance in patients with stress-related exhaustion several years after they initially sought medical care. Thirty patients and 27 healthy controls, mean age 49 years (SD 6.5) and 55 years (SD 6.7) respectively, were included, all of whom had undergone baseline measurements of neuropsychological functioning. The mean follow-up time was three years. Half of the patients still reported mental health problems at follow-up and over time no major changes in cognitive performance were noted. The patients still performed significantly poorer than controls with regard to cognitive functions, mainly related to speed, attention and memory function. Long-lasting impairment of cognitive functions related to speed, attention and memory function noted in patients with stress-related exhaustion should be acknowledged and taken into consideration during treatment and when discussing a return to work. Follow-up periods longer than three years are needed to explore the persistence of the cognitive impairment. © 2017 Scandinavian Psychological Associations and John Wiley & Sons Ltd
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74.
  • Jonsdottir, I.S., et al. (författare)
  • Measuring growth rates in bryophytes and lichens
  • 1997
  • Ingår i: Summary document of 8th Annual ITEX Workshop. Royal Holloway Institute for Environmental Research, 19-22 April, 1997.
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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75.
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79.
  • Jonsson, B O, et al. (författare)
  • Clonal diversity and allozyme variation in populations of the arctic sedge Carex bigelowii (Cyperaceae).
  • 1996
  • Ingår i: Journal of Ecology. - 1365-2745. ; 84:3, s. 449-459
  • Tidskriftsartikel (refereegranskat)abstract
    • 1 A study of allozyme variation in vegetatively propagating populations of the rhizomatous sedge Carex bigelowii, revealed high levels of clonal diversity (genet diversity) within populations. The structure of allelic variation within the populations suggests that sexual reproduction has played a significant role in these C. bigelowii populations, despite present lack of seedling recruitment. The study was carried out in moss-heath communities on Icelandic lava-fields. Two adjacent populations were studied at one site, while a third population was studied at a second site, 35 km away from the first two populations. 2 The number of genets detected in each population, among 85-88 analysed ramets, ranged from 41 to 55 (minimum estimate). Samples were taken every 4 m along transects in the populations. Ramets with the same allozyme genotype were often spatially aggregated. No seedlings have been observed in the populations during five years of demographic studies. 3 All the populations studied showed a diploid expression of allozymes and high levels of allelic variation, with on average 491.77 alleles per locus (A) and an allelic diversity (HS) of 0.167. Similar levels of within-population variability are found in many wind-pollinated and outcrossing plant species. 4 The difference between observed and expected heterozygosity was small in all populations, suggesting high levels of outbreeding. 5 Comparisons with other Carex taxa show that the levels of and structuring of allozyme diversity in C. bigelowii is similar to that in other outbreeding species (usually rhizomatous), and much higher than in inbreeding species (which are usually caespitose). 6 Only 5the total allelic diversity was explained by differences between the two study sites (G ST = 0.055), suggesting extensive recent or historic gene-flow.
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80.
  • Krabbe, D., et al. (författare)
  • Executive function and attention in patients with stress-related exhaustion: perceived fatigue and effect of distraction
  • 2017
  • Ingår i: Stress-the International Journal on the Biology of Stress. - : Informa UK Limited. - 1025-3890. ; 20:4, s. 333-340
  • Tidskriftsartikel (refereegranskat)abstract
    • Cognitive impairment has frequently been shown in patients who seek medical care for stress-related mental health problems. This study aims to extend the current knowledge of cognitive impairments in these patients by focusing on perceived fatigue and effects of distraction during cognitive testing. Executive function and attention were tested in a group of patients with stress-related exhaustion (n=25) and compared with healthy controls (n=25). Perceived fatigue was measured before, during and after the test session, and some of the tests were administered with and without standardized auditory distraction. Executive function and complex attention performance were poorer among the patients compared to controls. Interestingly, their performance was not significantly affected by auditory distraction but, in contrast to the controls, they reported a clear-cut increase in mental tiredness, during and after the test session. Thus, patients with stress-related exhaustion manage to perform during distraction but this was achieved at a great cost. These findings are discussed in terms of a possible tendency to adopt a high-effort approach despite cognitive impairments and the likelihood that such an approach will require increased levels of effort, which can result in increased fatigue. We tentatively conclude that increased fatigue during cognitive tasks is a challenge for patients with stress-related exhaustion and plausibly of major importance when returning to work demanding high cognitive performance.
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81.
  • Krebs, C. J., et al. (författare)
  • Terrestrial trophic dynamics in the Canadian Arctic
  • 2003
  • Ingår i: Canadian Journal of Zoology-Revue Canadienne De Zoologie. ; 81, s. 827-843
  • Tidskriftsartikel (refereegranskat)abstract
    • The Swedish Tundra Northwest Expedition of 1999 visited 17 sites throughout the Canadian Arctic. At 12 sites that were intensively sampled we estimated the standing crop of plants and the densities of herbivores and predators with an array of trapping, visual surveys, and faecal-pellet transects. We developed a trophic-balance model using ECOPATH to integrate these observations and determine the fate of primary and secondary production in these tundra ecosystems, which spanned an 8-fold range of standing crop of plants. We estimated that about 13% of net primary production was consumed by herbivores, while over 70% of small-herbivore production was estimated to flow to predators. Only 9% of large-herbivore production was consumed by predators. Organization of Canadian Arctic ecosystems appears to be more top-down than bottom-up. Net primary production does not seem to be herbivore-limited at any site. This is the first attempt to integrate trophic dynamics over the entire Canadian Arctic.
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83.
  • Kristjansson, S., et al. (författare)
  • Respiratory syncytial virus and other respiratory viruses during the first 3 months of life promote a local TH2-like response
  • 2005
  • Ingår i: J Allergy Clin Immunol. - : Elsevier BV. - 0091-6749. ; 116:4, s. 805-11
  • Tidskriftsartikel (refereegranskat)abstract
    • BACKGROUND: Respiratory syncytial virus (RSV) infections during infancy are considered to be a risk factor for developing asthma and possibly allergic sensitization. OBJECTIVE: The aim of this study was to investigate the cytokines, chemokines, and eosinophil cationic protein in the nasopharyngeal secretions of infants < or = 7 months of age with RSV infections or other respiratory viral infections and healthy infants as controls. Groups were also analyzed according to age, < or = 3 months and >3 months, and the levels were compared within and between groups. RESULTS: Thirty-nine infants with RSV, 9 with influenza or parainfluenza virus infections and 50 controls with no history of infections, were enrolled in the study. The RSV-infected infants had significantly higher levels of IL-4; macrophage inflammatory protein 1beta, a chemoattractant for T cells; and eosinophil cationic protein in nasopharyngeal secretions compared with the control group. The levels of the TH2 cytokine IL-4 were significantly higher in RSV-infected infants < or = months of age compared with RSV-infected infants >3 months of age. In infants < or = 3 months of age, infections with influenza or parainfluenza virus caused TH2-like responses similar to those produced by RSV. CONCLUSION: Infections with RSV as well as with influenza and parainfluenza virus during early infancy preferentially promote a TH2-like response in the nose with local production of IL-4, IL-5, and macrophage inflammatory protein 1beta and infiltration and activation of eosinophils.
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84.
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85.
  • Lett, Signe, et al. (författare)
  • Can bryophyte groups increase functional resolution in tundra ecosystems?
  • 2022
  • Ingår i: Arctic Science. - Ottawa : Canadian Science Publishing. - 2368-7460. ; 8:3, s. 609-637
  • Tidskriftsartikel (refereegranskat)abstract
    • The relative contribution of bryophytes to plant diversity, primary productivity, and ecosystem functioning increases towards colder climates. Bryophytes respond to environmental changes at the species level, but because bryophyte species are relatively difficult to identify, they are often lumped into one functional group. Consequently, bryophyte function remains poorly resolved. Here, we explore how higher resolution of bryophyte functional diversity can be encouraged and implemented in tundra ecological studies. We briefly review previous bryophyte functional classifications and the roles of bryophytes in tundra ecosystems and their susceptibility to environmental change. Based on shoot morphology and colony organization, we then propose twelve easily distinguishable bryophyte functional groups. To illustrate how bryophyte functional groups can help elucidate variation in bryophyte effects and responses, we compiled existing data on water holding capacity, a key bryophyte trait. Although plant functional groups can mask potentially high interspecific and intraspecific variability, we found better separation of bryophyte functional group means compared with previous grouping systems regarding water holding capacity. This suggests that our bryophyte functional groups truly represent variation in the functional roles of bryophytes in tundra ecosystems. Lastly, we provide recommendations to improve the monitoring of bryophyte community changes in tundra study sites.
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86.
  • Lindroth, Anders, et al. (författare)
  • CO2 and CH4 exchanges between moist moss tundra and atmosphere on Kapp Linne, Svalbard
  • 2022
  • Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 19:16, s. 3921-3934
  • Tidskriftsartikel (refereegranskat)abstract
    • We measured CO2 and CH4 fluxes using chambers and eddy covariance (only CO2) from a moist moss tundra in Svalbard. The average net ecosystem exchange (NEE) during the summer (9 June-31 August) was negative (sink), with -0.139 +/- 0.032 mu mol m(-2) s(-1) corresponding to -11.8 g C m(-2) for the whole summer. The cumulated NEE over the whole growing season (day no. 160 to 284) was -2.5 g C m(-2). The CH4 flux during the summer period showed a large spatial and temporal variability. The mean value of all 214 samples was 0.000511 +/- 0.000315 mu mol m(-2) s(-1), which corresponds to a growing season estimate of 0.04 to 0.16 g CH4 m(-2). Thus, we find that this moss tundra ecosystem is closely in balance with the atmosphere during the growing season when regarding exchanges of CO2 and CH4. The sink of CO2 and the source of CH4 are small in comparison with other tundra ecosystems in the high Arctic. Air temperature, soil moisture and the greenness index contributed significantly to explaining the variation in ecosystem respiration (R-eco), while active layer depth, soil moisture and the greenness index were the variables that best explained CH4 emissions. An estimate of temperature sensitivity of Reco and gross primary productivity (GPP) showed that the sensitivity is slightly higher for GPP than for R-eco in the interval 0-4.5 degrees C; thereafter, the difference is small up to about 6 degrees C and then begins to rise rapidly for R-eco. The consequence of this, for a small increase in air temperature of 1 degrees (all other variables assumed unchanged), was that the respiration increased more than photosynthesis turning the small sink into a small source (4.5 g C m(-2)) during the growing season. Thus, we cannot rule out that the reason why the moss tundra is close to balance today is an effect of the warming that has already taken place in Svalbard.
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87.
  • Lundgren, Markus, et al. (författare)
  • Analgesic antipyretic use among young children in the TEDDY study : No association with islet autoimmunity
  • 2017
  • Ingår i: BMC Pediatrics. - : Springer Science and Business Media LLC. - 1471-2431. ; 17:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: The use of analgesic antipyretics (ANAP) in children have long been a matter of controversy. Data on their practical use on an individual level has, however, been scarce. There are indications of possible effects on glucose homeostasis and immune function related to the use of ANAP. The aim of this study was to analyze patterns of analgesic antipyretic use across the clinical centers of The Environmental Determinants of Diabetes in the Young (TEDDY) prospective cohort study and test if ANAP use was a risk factor for islet autoimmunity. Methods: Data were collected for 8542 children in the first 2.5 years of life. Incidence was analyzed using logistic regression with country and first child status as independent variables. Holm's procedure was used to adjust for multiplicity of intercountry comparisons. Time to autoantibody seroconversion was analyzed using a Cox proportional hazards model with cumulative analgesic use as primary time dependent covariate of interest. For each categorization, a generalized estimating equation (GEE) approach was used. Results: Higher prevalence of ANAP use was found in the U.S. (95.7%) and Sweden (94.8%) compared to Finland (78.1%) and Germany (80.2%). First-born children were more commonly given acetaminophen (OR 1.26; 95% CI 1.07, 1.49; p = 0.007) but less commonly Non-Steroidal Anti-inflammatory Drugs (NSAID) (OR 0.86; 95% CI 0.78, 0.95; p = 0.002). Acetaminophen and NSAID use in the absence of fever and infection was more prevalent in the U.S. (40.4%; 26.3% of doses) compared to Sweden, Finland and Germany (p < 0.001). Acetaminophen or NSAID use before age 2.5 years did not predict development of islet autoimmunity by age 6 years (HR 1.02, 95% CI 0.99-1.09; p = 0.27). In a sub-analysis, acetaminophen use in children with fever weakly predicted development of islet autoimmunity by age 3 years (HR 1.05; 95% CI 1.01-1.09; p = 0.024). Conclusions: ANAP use in young children is not a risk factor for seroconversion by age 6 years. Use of ANAP is widespread in young children, and significantly higher in the U.S. compared to other study sites, where use is common also in absence of fever and infection.
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88.
  • Magnusson, C., et al. (författare)
  • Designing motivating interactive balance and walking training for stroke survivors
  • 2019
  • Ingår i: Proceedings of the 13th EAI International Conference on Pervasive Computing Technologies for Healthcare, PervasiveHealth 2019. - New York, NY, USA : ACM. - 9781450361262 ; , s. 327-333
  • Konferensbidrag (refereegranskat)abstract
    • In the ActivAbles and STARR projects we are developing interactive training tools for stroke survivors. Our initial user studies pointed to balance being a key ability, therefore one of the developed tools is an interactive balance pad. Equipment exists for persons with good balance (eg. Wii), but most consumer games and exercises are less suited for many stroke survivors. The development process has been done in close collaboration with stroke survivors, and we have currently a prototype system that has been tested by 10 stroke survivors for a longer period in the home during a feasibility study. The system includes an interactive balance foam pad, feedback lamps and a step counting game app which all connect to a central server. The feedback is designed to be inclusive - designs are multimodal (visual and auditory), and the setup is flexible and can easily be adapted. In this paper we report and discuss the design of the system, pilot test results and the results from a feasibility study in the home.
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89.
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90.
  • Naylor, Andrew Stuart, 1977, et al. (författare)
  • Extended voluntary running inhibits exercise-induced adult hippocampal progenitor proliferation in the spontaneously hypertensive rat.
  • 2005
  • Ingår i: Journal of neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 93:5, s. 2406-14
  • Tidskriftsartikel (refereegranskat)abstract
    • Previous work has shown that voluntary running increases cell proliferation and neurogenesis in the dentate gyrus of the adult hippocampus. Here we report that long-term running for 24 days results in a down-regulation of hippocampal progenitor proliferation to one-half the level of nonrunning controls compared with a fivefold increase in progenitor proliferation seen after 9 days of voluntary running (short-term running). The negative effects seen on proliferation after 24 days of running were prevented by restricting daily running distances (by 30-50%) during 24 days. Long-term running for 24 days increases the response of the hypothalamic-pituitary-adrenal axis, with an increase in adrenal gland weight and increased plasma corticosterone levels, as well as decreased thymus weight, indicating a stress response as a possible mediator of decreased progenitor proliferation. Furthermore, the negative effects seen on the observed stress response after 24 days of running were prevented by restricting daily running distance. Short-term running did not alter these stress parameters compared with nonrunning controls. However, it increased phosphorylated cyclic AMP response element binding protein (pCREB) in the dentate gyrus, an increase that was not seen in nonrunning controls or after 24 days of running. Taken together, these data suggest that voluntary running does not always enhance proliferation and that the decrease in progenitor proliferation seen in long-term running is possibly mediated by mechanisms involving a stress response in the animal. However, a moderate level of long-term running was able to prevent the negative stress-related changes seen in unrestricted long-term running.
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91.
  • Oberbauer, S F, et al. (författare)
  • Phenological response of tundra plants to background climate variation tested using the International Tundra Experiment.
  • 2013
  • Ingår i: Philosophical transactions of the Royal Society of London. Series B, Biological sciences. - : The Royal Society. - 1471-2970. ; 368:1624
  • Tidskriftsartikel (refereegranskat)abstract
    • The rapidly warming temperatures in high-latitude and alpine regions have the potential to alter the phenology of Arctic and alpine plants, affecting processes ranging from food webs to ecosystem trace gas fluxes. The International Tundra Experiment (ITEX) was initiated in 1990 to evaluate the effects of expected rapid changes in temperature on tundra plant phenology, growth and community changes using experimental warming. Here, we used the ITEX control data to test the phenological responses to background temperature variation across sites spanning latitudinal and moisture gradients. The dataset overall did not show an advance in phenology; instead, temperature variability during the years sampled and an absence of warming at some sites resulted in mixed responses. Phenological transitions of high Arctic plants clearly occurred at lower heat sum thresholds than those of low Arctic and alpine plants. However, sensitivity to temperature change was similar among plants from the different climate zones. Plants of different communities and growth forms differed for some phenological responses. Heat sums associated with flowering and greening appear to have increased over time. These results point to a complex suite of changes in plant communities and ecosystem function in high latitudes and elevations as the climate warms.
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92.
  • Olafsson, S, et al. (författare)
  • Fourteen sequence variants that associate with multiple sclerosis discovered by meta-analysis informed by genetic correlations
  • 2017
  • Ingår i: NPJ genomic medicine. - : Springer Science and Business Media LLC. - 2056-7944. ; 2, s. 24-
  • Tidskriftsartikel (refereegranskat)abstract
    • A meta-analysis of publicly available summary statistics on multiple sclerosis combined with three Nordic multiple sclerosis cohorts (21,079 cases, 371,198 controls) revealed seven sequence variants associating with multiple sclerosis, not reported previously. Using polygenic risk scores based on public summary statistics of variants outside the major histocompatibility complex region we quantified genetic overlap between common autoimmune diseases in Icelanders and identified disease clusters characterized by autoantibody presence/absence. As multiple sclerosis-polygenic risk scores captures the risk of primary biliary cirrhosis and vice versa (P = 1.6 × 10−7, 4.3 × 10−9) we used primary biliary cirrhosis as a proxy-phenotype for multiple sclerosis, the idea being that variants conferring risk of primary biliary cirrhosis have a prior probability of conferring risk of multiple sclerosis. We tested 255 variants forming the primary biliary cirrhosis-polygenic risk score and found seven multiple sclerosis-associating variants not correlated with any previously established multiple sclerosis variants. Most of the variants discovered are close to or within immune-related genes. One is a low-frequency missense variant in TYK2, another is a missense variant in MTHFR that reduces the function of the encoded enzyme affecting methionine metabolism, reported to be dysregulated in multiple sclerosis brain.
  •  
93.
  • Palsdottir, A, et al. (författare)
  • Study of restriction fragment length polymorphism in the cystatin C gene of elderly patients with dementia and aged Down's syndrome patients
  • 1989
  • Ingår i: Progress in Clinical and Biological Research. - 0361-7742. ; 317, s. 235-239
  • Tidskriftsartikel (refereegranskat)abstract
    • Using a full length cystatin C cDNA probe and the Alu I restriction enzyme a total of 33 patients with senile dementia, Alzheimer type and 31 Down's syndrome patients have been investigated for the presence of the 630 bp Alu I restriction fragment length polymorphism in the cystatin C gene detected in Icelandic patients with hereditary cystatin C amyloid angiopathy. Results showed that all the patients had normal cystatin C fragment length of 600 bp.
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94.
  • Persson, Anders I., 1973, et al. (författare)
  • Differential regulation of hippocampal progenitor proliferation by opioid receptor antagonists in running and non-running spontaneously hypertensive rats.
  • 2004
  • Ingår i: The European journal of neuroscience. - : Wiley. - 0953-816X .- 1460-9568. ; 19:7, s. 1847-55
  • Tidskriftsartikel (refereegranskat)abstract
    • Voluntary running in mice and forced treadmill running in rats have been shown to increase the amount of proliferating cells in the hippocampus. Little is known as yet about the mechanisms involved in these processes. It is well known that the endogenous opioid system is affected during running and other forms of physical exercise. In this study, we evaluated the involvement of the endogenous opioids in the regulation of hippocampal proliferation in non-running and voluntary running rats. Nine days of wheel running was compared with non-running in spontaneously hypertensive rats (SHR), a rat strain known to run voluntarily. On the last 2 days of the experimental period all rats received two daily injections of the opioid receptor antagonists naltrexone or naltrindole together with injections of bromodeoxyuridine to label dividing cells. Brain sections from the running rats showed approximately a five-fold increase in newly generated cells in the hippocampus, and this increase was partly reduced by naltrexone but not by naltrindole. By contrast, both naltrexone and naltrindole increased hippocampal proliferation in non-running rats. In non-running rats the administration of naltrexone decreased corticosterone levels and adrenal gland weights, whereas no significant effects on these parameters could be detected for naltrindole. However, adrenal gland weights were increased in naltrexone- but not in naltrindole-administered running rats. In addition, in voluntary running rats there was a three-fold increase in the hippocampal levels of Met-enkephalin-Arg-Phe compared with non-runners, indicating an increase in opioid activity in the hippocampus during running. These data suggest an involvement of endogenous opioids in the regulation of hippocampal proliferation in non-running rats, probably through hypothalamic-pituitary-adrenal axis modulation. During voluntary running in SHR naltrexone altered hippocampal proliferation via as yet unknown mechanisms.
  •  
95.
  • Pind, A. A. A., et al. (författare)
  • Adjuvants Enhance the Induction of Germinal Center and Antibody Secreting Cells in Spleen and Their Persistence in Bone Marrow of Neonatal Mice
  • 2019
  • Ingår i: Frontiers in Immunology. - : Frontiers Media SA. - 1664-3224. ; 10
  • Tidskriftsartikel (refereegranskat)abstract
    • Immaturity of the immune system contributes to poor vaccine responses in early life. Germinal center (GC) activation is limited due to poorly developed follicular dendritic cells (FDC), causing generation of few antibody-secreting cells (ASCs) with limited survival and transient antibody responses. Herein, we compared the potential of five adjuvants, namely LT-K63, mmCT, MF59, IC31, and alum to overcome limitations of the neonatal immune system and to enhance and prolong responses of neonatal mice to a pneumococcal conjugate vaccine Pnc1-TT. The adjuvants LT-K63, mmCT, MF59, and IC31 significantly enhanced GC formation and FDC maturation in neonatal mice when co-administered with Pnc1-TT. This enhanced GC induction correlated with significantly enhanced vaccine-specific ASCs by LT-K63, mmCT, and MF59 in spleen 14 days after immunization. Furthermore, mmCT, MF59, and IC31 prolonged the induction of vaccine-specific ASCs in spleen and increased their persistence in bone marrow up to 9 weeks after immunization, as previously shown for LT-K63. Accordingly, serum Abs persisted above protective levels against pneumococcal bacteremia and pneumonia. In contrast, alum only enhanced the primary induction of vaccine-specific IgG Abs, which was transient. Our comparative study demonstrated that, in contrast to alum, LT-K63, mmCT, MF59, and IC31 can overcome limitations of the neonatal immune system and enhance both induction and persistence of protective immune response when administered with Pnc1-TT. These adjuvants are promising candidates for early life vaccination.
  •  
96.
  • Rheubottom, Sarah, I, et al. (författare)
  • Hiding in the background : community-level patterns in invertebrate herbivory across the tundra biome
  • 2019
  • Ingår i: Polar Biology. - : Springer. - 0722-4060 .- 1432-2056. ; 42:10, s. 1881-1897
  • Tidskriftsartikel (refereegranskat)abstract
    • Invertebrate herbivores depend on external temperature for growth and metabolism. Continued warming in tundra ecosystems is proposed to result in increased invertebrate herbivory. However, empirical data about how current levels of invertebrate herbivory vary across the Arctic is limited and generally restricted to a single host plant or a small group of species, so predicting future change remains challenging. We investigated large-scale patterns of invertebrate herbivory across the tundra biome at the community level and explored how these patterns are related to long-term climatic conditions and year-of-sampling weather, habitat characteristics, and aboveground biomass production. Utilizing a standardized protocol, we collected samples from 92 plots nested within 20 tundra sites during summer 2015. We estimated the community-weighted biomass lost based on the total leaf area consumed by invertebrates for the most common plant species within each plot. Overall, invertebrate herbivory was prevalent at low intensities across the tundra, with estimates averaging 0.94% and ranging between 0.02 and 5.69% of plant biomass. Our results suggest that mid-summer temperature influences the intensity of invertebrate herbivory at the community level, consistent with the hypothesis that climate warming should increase plant losses to invertebrates in the tundra. However, most of the observed variation in herbivory was associated with other site level characteristics, indicating that other local ecological factors also play an important role. More details about the local drivers of invertebrate herbivory are necessary to predict the consequences for rapidly changing tundra ecosystems.
  •  
97.
  • Rivas, Manuel A., et al. (författare)
  • A protein-truncating R179X variant in RNF186 confers protection against ulcerative colitis
  • 2016
  • Ingår i: Nature Communications. - London, United Kingdom : Nature Publishing Group. - 2041-1723. ; 7
  • Tidskriftsartikel (refereegranskat)abstract
    • Protein-truncating variants protective against human disease provide in vivo validation of therapeutic targets. Here we used targeted sequencing to conduct a search for protein-truncating variants conferring protection against inflammatory bowel disease exploiting knowledge of common variants associated with the same disease. Through replication genotyping and imputation we found that a predicted protein-truncating variant (rs36095412, p.R179X, genotyped in 11,148 ulcerative colitis patients and 295,446 controls, MAF=up to 0.78%) in RNF186, a single-exon ring finger E3 ligase with strong colonic expression, protects against ulcerative colitis (overall P=6.89 × 10(-7), odds ratio=0.30). We further demonstrate that the truncated protein exhibits reduced expression and altered subcellular localization, suggesting the protective mechanism may reside in the loss of an interaction or function via mislocalization and/or loss of an essential transmembrane domain.
  •  
98.
  • Saevarsdottir, KS, et al. (författare)
  • Illness severity and risk of mental morbidities among patients recovering from COVID-19: a cross-sectional study in the Icelandic population
  • 2021
  • Ingår i: BMJ open. - : BMJ. - 2044-6055. ; 11:7, s. e049967-
  • Tidskriftsartikel (refereegranskat)abstract
    • To test if patients recovering from COVID-19 are at increased risk of mental morbidities and to what extent such risk is exacerbated by illness severity.DesignPopulation-based cross-sectional study.SettingIceland.ParticipantsA total of 22 861 individuals were recruited through invitations to existing nationwide cohorts and a social media campaign from 24 April to 22 July 2020, of which 373 were patients recovering from COVID-19.Main outcome measuresSymptoms of depression (Patient Health Questionnaire), anxiety (General Anxiety Disorder Scale) and posttraumatic stress disorder (PTSD; modified Primary Care PTSD Screen for DSM-5) above screening thresholds. Adjusting for multiple covariates and comorbidities, multivariable Poisson regression was used to assess the association between COVID-19 severity and mental morbidities.ResultsCompared with individuals without a diagnosis of COVID-19, patients recovering from COVID-19 had increased risk of depression (22.1% vs 16.2%; adjusted relative risk (aRR) 1.48, 95% CI 1.20 to 1.82) and PTSD (19.5% vs 15.6%; aRR 1.38, 95% CI 1.09 to 1.75) but not anxiety (13.1% vs 11.3%; aRR 1.24, 95% CI 0.93 to 1.64). Elevated relative risks were limited to patients recovering from COVID-19 that were 40 years or older and were particularly high among individuals with university education. Among patients recovering from COVID-19, symptoms of depression were particularly common among those in the highest, compared with the lowest tertile of influenza-like symptom burden (47.1% vs 5.8%; aRR 6.42, 95% CI 2.77 to 14.87), among patients confined to bed for 7 days or longer compared with those never confined to bed (33.3% vs 10.9%; aRR 3.67, 95% CI 1.97 to 6.86) and among patients hospitalised for COVID-19 compared with those never admitted to hospital (48.1% vs 19.9%; aRR 2.72, 95% CI 1.67 to 4.44).ConclusionsSevere disease course is associated with increased risk of depression and PTSD among patients recovering from COVID-19.
  •  
99.
  • Sarneel, Judith M., et al. (författare)
  • Reading tea leaves worldwide : decoupled drivers of initial litter decomposition mass-loss rate and stabilization
  • 2024
  • Ingår i: Ecology Letters. - : John Wiley & Sons. - 1461-023X .- 1461-0248. ; 27:5
  • Tidskriftsartikel (refereegranskat)abstract
    • The breakdown of plant material fuels soil functioning and biodiversity. Currently, process understanding of global decomposition patterns and the drivers of such patterns are hampered by the lack of coherent large-scale datasets. We buried 36,000 individual litterbags (tea bags) worldwide and found an overall negative correlation between initial mass-loss rates and stabilization factors of plant-derived carbon, using the Tea Bag Index (TBI). The stabilization factor quantifies the degree to which easy-to-degrade components accumulate during early-stage decomposition (e.g. by environmental limitations). However, agriculture and an interaction between moisture and temperature led to a decoupling between initial mass-loss rates and stabilization, notably in colder locations. Using TBI improved mass-loss estimates of natural litter compared to models that ignored stabilization. Ignoring the transformation of dead plant material to more recalcitrant substances during early-stage decomposition, and the environmental control of this transformation, could overestimate carbon losses during early decomposition in carbon cycle models.
  •  
100.
  • Skuladottir, AT, et al. (författare)
  • A genome-wide meta-analysis identifies 50 genetic loci associated with carpal tunnel syndrome
  • 2022
  • Ingår i: Nature communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 13:1, s. 1598-
  • Tidskriftsartikel (refereegranskat)abstract
    • Carpal tunnel syndrome (CTS) is the most common entrapment neuropathy and has a largely unknown underlying biology. In a genome-wide association study of CTS (48,843 cases and 1,190,837 controls), we found 53 sequence variants at 50 loci associated with the syndrome. The most significant association is with a missense variant (p.Glu366Lys) in SERPINA1 that protects against CTS (P = 2.9 × 10−24, OR = 0.76). Through various functional analyses, we conclude that at least 22 genes mediate CTS risk and highlight the role of 19 CTS variants in the biology of the extracellular matrix. We show that the genetic component to the risk is higher in bilateral/recurrent/persistent cases than nonrecurrent/nonpersistent cases. Anthropometric traits including height and BMI are genetically correlated with CTS, in addition to early hormonal-replacement therapy, osteoarthritis, and restlessness. Our findings suggest that the components of the extracellular matrix play a key role in the pathogenesis of CTS.
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