| 1. |
- Andersson, Björn, 1985, et al.
(författare)
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Cross-contamination risks in sediment-based resurrection studies of phytoplankton
- 2022
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Ingår i: Limnology and Oceanography Letters. - : Wiley. - 2378-2242. ; 8:2, s. 376-84
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Tidskriftsartikel (refereegranskat)abstract
- Resurrection studies can answer some fundamental questions in aquatic ecology and evolutionary biology. For phytoplankton resting stages, longevity of thousands to millions of years has recently been reported. However, contamination during sediment sampling could distort these estimates, and this risk has not been systematically evaluated. Here we used 4.5 mu m diameter microspheres to quantify contamination while reviving the resting stages of seven abundant estuarine diatom and cyanobacterial taxa. We observed a sharp decline in resting stages abundance from 10(6) (g wet sediment)(-1) at the surface to < 0.8 (g wet sediment)(-1) at 12.5 cm depth. Added microspheres (similar to 4.5 x 10(7) cm(-2)) were translocated even deeper down the sediment and could well explain the vertical distributions and abundances of revived cells. Without this control, we could have claimed to have revived seven multi-decades to centennial-old taxa. Our findings suggest that improved contamination controls are needed for sediment core sampling of rare cells, microfossils, or DNA molecules.
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| 2. |
- Andersson, Björn, 1985, et al.
(författare)
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Differences in metal tolerance among strains, populations, and species of marine diatoms – Importance of exponential growth for quantification
- 2020
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Ingår i: Aquatic Toxicology. - : Elsevier BV. - 0166-445X .- 1879-1514. ; 226
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Tidskriftsartikel (refereegranskat)abstract
- © 2020 The Author(s) Strains of microalgae vary in traits between species and populations due to adaptation or stochastic processes. Traits of individual strains may also vary depending on the acclimatization state and external forces, such as abiotic stress. In this study we tested how metal tolerance differs among marine diatoms at three organizational levels: species, populations, and strains. At the species level we compared two pelagic Baltic Sea diatoms (Skeletonema marinoi and Thalassiosira baltica). We found that the between-species differences in tolerance (EC50) to the biologically active metals (Cu, Co, Ni, and Zn) was similar to that within-species. In contrast, the two species differed significantly in tolerance towards the non-essential metals, Ag (three-fold higher in T. baltica), Pb and Cd (two and three-fold higher in S. marinoi). At the population level, we found evidence that increased tolerance against Cu and Co (17 and 41 % higher EC50 on average, respectively) had evolved in a S. marinoi population subjected to historical mining activity. On a strain level we demonstrate how the growth phase of cultures (i.e., cellular densities above exponential growth) modulated dose-response relationships to Ag, Cd, Co, Cu, and Zn. Specifically, the EC50's were reduced by 10–60 % in non-exponentially growing S. marinoi (strain RO5AC), depending on metal. For the essential metals these differences were often larger than the average differences between the two species and populations. Consequently, without careful experimental design, interactions between nutrient limitation and metal stress may interfere with detection of small, but evolutionary and ecologically important, differences in tolerance between microalgae. To avoid such artifacts, we outline a semi-continuous cultivation approach that maintains, and empirically tests, that exponential growth is achieved. We argue that such an approach is essential to enable comparison of population or strain differences in tolerance using dose-response tests on cultures of microalgae.
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| 3. |
- Andersson, Björn, 1985, et al.
(författare)
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Intraspecific variation in metal tolerance modulate competition between two marine diatoms
- 2022
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Ingår i: ISME Journal. - : Springer Science and Business Media LLC. - 1751-7362 .- 1751-7370. ; 16, s. 511-520
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Tidskriftsartikel (refereegranskat)abstract
- Despite widespread metal pollution of coastal ecosystems, little is known of its effect on marine phytoplankton. We designed a co-cultivation experiment to test if toxic dose–response relationships can be used to predict the competitive outcome of two species under metal stress. Specifically, we took into account intraspecific strain variation and selection. We used 72 h dose–response relationships to model how silver (Ag), cadmium (Cd), and copper (Cu) affect both intraspecific strain selection and competition between taxa in two marine diatoms (Skeletonema marinoi and Thalassiosira baltica). The models were validated against 10-day co-culture experiments, using four strains per species. In the control treatment, we could predict the outcome using strain-specific growth rates, suggesting low levels of competitive interactions between the species. Our models correctly predicted which species would gain a competitive advantage under toxic stress. However, the absolute inhibition levels were confounded by the development of chronic toxic stress, resulting in a higher long-term inhibition by Cd and Cu. We failed to detect species differences in average Cu tolerance, but the model accounting for strain selection accurately predicted a competitive advantage for T. baltica. Our findings demonstrate the importance of incorporating multiple strains when determining traits and when performing microbial competition experiments.
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| 4. |
- Andersson, Björn, et al.
(författare)
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Strain-specific metabarcoding reveals rapid evolution of copper tolerance in populations of the coastal diatom Skeletonema marinoi
- 2023
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Ingår i: Molecular Ecology. - 0962-1083 .- 1365-294X.
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Tidskriftsartikel (refereegranskat)abstract
- Phytoplankton have short generation times, flexible reproduction strategies, large population sizes and high standing genetic diversity, traits that should facilitate rapid evolution under directional selection. We quantified local adaptation of copper tolerance in a population of the diatom Skeletonema marinoi from a mining-exposed inlet in the Baltic Sea and in a non-exposed population 100 km away. We hypothesized that mining pollution has driven evolution of elevated copper tolerance in the impacted population of S. marinoi. Assays of 58 strains originating from sediment resting stages revealed no difference in the average tolerance to copper between the two populations. However, variation within populations was greater at the mining site, with three strains displaying hyper-tolerant phenotypes. In an artificial evolution experiment, we used a novel intraspecific metabarcoding locus to track selection and quantify fitness of all 58 strains during co-cultivation in one control and one toxic copper treatment. As expected, the hyper-tolerant strains enabled rapid evolution of copper tolerance in the mining-exposed population through selection on available strain diversity. Within 42 days, in each experimental replicate a single strain dominated (30%–99% abundance) but different strains dominated the different treatments. The reference population developed tolerance beyond expectations primarily due to slowly developing plastic response in one strain, suggesting that different modes of copper tolerance are present in the two populations. Our findings provide novel empirical evidence that standing genetic diversity of phytoplankton resting stage allows populations to evolve rapidly (20–50 generations) and flexibly on timescales relevant for seasonal bloom progressions.
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| 5. |
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| 6. |
- Falhammar, H, et al.
(författare)
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Fractures and Bone Mineral Density in Adult Women with 21-Hydroxylase Deficiency.
- 2007
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Ingår i: J Endocrinol Metab. - : The Endocrine Society. - 0021-972X .- 1945-7197.
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Tidskriftsartikel (refereegranskat)abstract
- Context: Patients with classic congenital adrenal hyperplasia (CAH) receive lifelong, often supraphysiological, glucocorticoid therapy. Pharmacologic doses of glucocorticoids are an established risk factor for osteoporosis. Objectives: To evaluate bone mineral density (BMD), fracture prevalence and markers of bone metabolism in adult females with CAH. Design: This was a cross-sectional observational study. Setting: Tertiary care referral centers. Participants: We studied 61 women, aged 18-63 years, with genetically verified CAH due to 21-hydroxylase deficiency. They were patients with salt-wasting (n = 27), simple virilising (n = 28) and non-classic 21-hydroxylase deficiency (n = 6). Sixty-one age-matched women were controls. Main outcome measures: History of fractures was recorded. Total body, lumbar spine and femoral neck BMD were measured by dual-energy X-ray absorptiometry. The WHO criteria for osteopenia and osteoporosis were used. Serum marker of bone resorption, beta-C telopeptide (CTX) was studied. Results: The mean glucocorticoid dose in hydrocortisone equivalents was 16.9 +/- 0.9 mg/m(2). Patients had lower BMD than controls at all measured sites (P < 0.001). In patients < 30 years old 48% were osteopenic vs 12% in controls (P < 0.009). In patients >/= 30 years old 73% were osteopenic or osteoporotic vs 21% in controls (P < 0.001). BMD was similar in the two classic forms and had no obvious relationship to genotypes. CTX was decreased in older patients. More fractures were reported in patients than controls (P < 0.001). The number of vertebrae and wrist fractures almost reached significance (P = 0.058). Conclusion: Women with CAH have low BMD and increased fracture risk. BMD should be monitored, adequate prophylaxis and treatment instituted, and glucocorticoid doses optimized from puberty.
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| 7. |
- Falhammar, Henrik, et al.
(författare)
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Increased liver enzymes in adult women with congenital adrenal hyperplasia due to 21-hydroxylase deficiency.
- 2009
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Ingår i: Endocrine journal. - 1348-4540. ; 56:4, s. 601-8
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Tidskriftsartikel (refereegranskat)abstract
- The aims were assessing liver function tests (LFT) in women with congenital adrenal hyperplasia (CAH) on glucocorticoids. Sixty-one women with genetically verified CAH due to 21-hydroxylase deficiency, aged 18-63 years were compared to 61 controls. Serum alkaline phosphatase (ALP), alanine aminotransferase (ALT), aspartate aminotransferase (AST) and gamma-glutamyl transpeptidase (GGT), anthropometry and fat mass (dual energy X-ray absorptiometry) were measured. ALT and GGT were higher in the entire patient group (p=0.01 and 0.002); AST, GGT and ALP in patients > or =30 years (p=0.007-0.045); all LFT in salt-wasting (p<0.001-0.042); GGT in simple virilizing (p=0.008); ALT, GGT and ALP in Null/Null genotype (p=0.018-0.040); ALT and GGT in I2splice genotype (p<0.001 and 0.011). Using a recently proposed cut-off level for ALT (>0.317 microkat/L), 54% of patients vs 23% of controls had elevated levels (p=0.028). In patients, GGT and ALP correlated with waist circumference and with total body and trunk fat (r=0.274-0.406, p=0.001-0.043). However, ALT, GGT and ALP were increased even in non-obese patients (waist circumference < or =88 cm and body mass index <30 kg/m(2)) (p=0.012-0.045) mainly attributed to the patients > or =30 years who also demonstrated elevated insulin levels and HOMA-indices. In conclusion, compared with controls, women with CAH have higher LFT, in particular patients > or =30 years and those with severe forms, probably reflecting a higher lifetime glucocorticoid exposure. LFT were positively correlated to measurements of body fat. These women might have increased frequency of NAFLD. The finding of higher LFT also in non-obese patients suggests that not only central obesity but also glucocorticoids per se may influence.
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| 8. |
- Falhammar, Henrik, et al.
(författare)
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Metabolic profile and body composition in adult women with congenital adrenal hyperplasia due to 21-hydroxylase deficiency.
- 2007
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Ingår i: The Journal of clinical endocrinology and metabolism. - : The Endocrine Society. - 0021-972X .- 1945-7197. ; 92:1, s. 110-6
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Tidskriftsartikel (refereegranskat)abstract
- CONTEXT: The chronic, often supraphysiological glucocorticoid doses used in congenital adrenal hyperplasia (CAH) might increase morbidity in cardiovascular disease and diabetes. OBJECTIVE: Our aim was to assess risk factors for cardiovascular disease and diabetes in CAH women. SUBJECTS, METHODS, AND DESIGN: We compared 61 women, 18-63 yr, with CAH due to 21-hydroxylase deficiency with 61 age- and sex- matched controls. Twenty-seven were younger than 30 yr, and 34 were 30 yr or older. Anthropometry, fat and lean mass measured by dual-energy x-ray absorptiometry, serum lipids, insulin, and adrenocortical steroids were studied. MAIN OUTCOME MEASURE: Body composition and cardiovascular risk factors were the main outcome measures. RESULTS: Younger patients and controls had similar waist to hip ratio, lean and fat mass, and insulin. Older patients had higher waist to hip ratio, lean mass, and insulin than controls. Fat mass was similar to controls but higher than in younger patients. Lipid profiles were slightly more favorable in older patients than controls. Gestational diabetes was more common in patients (21% of pregnancies vs. 0, P < 0.026). Few older patients had hypertension, cardiovascular disease, or diabetes. Despite moderate glucocorticoid doses, most patients had suppressed androgens. CONCLUSIONS: No clear evidence of unfavorable cardiovascular risk factors were found. Increased fat mass and higher insulin levels were, however, found in patients older than 30 yr. High frequency of gestational diabetes is a risk marker for future diabetes. Lifelong follow-up, lifestyle modifications, and attempts to adjust and reduce the glucocorticoid doses seem important.
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| 9. |
- Filipsson, Peter J, 1985, et al.
(författare)
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A thermal model of an active chilled beam
- 2017
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Ingår i: Energy and Buildings. - : Elsevier BV. - 0378-7788. ; 149, s. 83-90
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Tidskriftsartikel (refereegranskat)abstract
- Active chilled beams (ACBs) have gained increased recognition as a feasible technology for comfort cooling during the last decades. One of the advantages with such systems is utilization of high temperature cooling. This provides exergetic benefits and also reduces the need for individual room control. However, individual room control normally serves as compensation for the safety margin applied when dimensioning the cooling systems. Therefore, the absence of individual room controls calls for accurate dimensioning tools. This paper presents a model to be used to calculate cooling capacities of ACBs. The model is based on NTU analysis and is a hybrid of first principles and empirical data in order to ensure high accuracy without requiring extensive measurements for model calibration. The model explicitly captures the influence of buoyant forces acting on the air passing the chilled coil in the beam. Output from the model also includes temperature and flow of supply air. The model shows good compliance with measured data in a wide range of operating conditions (average error of 1.7% if six cases is used for model calibration). The model can be appropriately implemented in building performance simulation tools, thus improving the design of ACB systems.
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| 10. |
- Filipsson, Peter J, 1985, et al.
(författare)
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Chilled water temperature control of self-regulating active chilled beams
- 2020
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Ingår i: SINTEF Proceedings. - 2387-4295. - 9788253616797 ; 5, s. 230-237
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Konferensbidrag (refereegranskat)abstract
- The flow rate of chilled water in a self-regulating active chilled beam is constant without respect to the actual cooling load. The cooling capacity is instead determined by the room temperature, which gives rise to the self-regulating effect, and also by the centrally controlled chilled water temperature, which is the focus of this paper . Previous studies have emphasized the benefit of avoiding room-level control equipment, but also highlighted the risk of overcooling with detrimental effects on thermal climate and energy demand. Overcooling may be avoided by supply temperature control, but strategies have not yet been studied in systems operating in cooling mode only. Simulations are carried out with IDA ICE. The results show that overcooling is effectively avoided by proper control of the chilled water temperature. Desired thermal climate is achieved and the energy demand is in the same order of magnitude as in a system with individually and ideally PI-controlled active chilled beams.
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