| 1. |
- Rasanen, M., et al.
(författare)
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Intake of vitamin D by Finnish children aged 3 months to 3 years in relation to sociodemographic factors
- 2006
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Ingår i: European Journal of Clinical Nutrition. - Natl Publ Hlth Inst, Unit Nutr, Dept Hlth Promot & Chron Dis Prevent, Helsinki, Finland. Univ Tampere, Tampere Sch Publ Hlth, FIN-33101 Tampere, Finland. Natl Res & Dev Ctr Welf & Hlth, Helsinki, Finland. Univ Oulu, Dept Pediat, Oulu, Finland. Univ Helsinki, Hosp Children & Adolescents, Helsinki, Finland. Tampere Univ Hosp, Dept Pediat, Helsinki, Finland. Tampere Univ Hosp, Res Unit, Helsinki, Finland. : NATURE PUBLISHING GROUP. - 0954-3007 .- 1476-5640. ; 60:11, s. 1317-1322
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Tidskriftsartikel (refereegranskat)abstract
- Objective: To study the total daily intake of vitamin D from food and supplements among Finnish children aged 3 months to 3 years, the dietary sources of vitamin D and the association between vitamin D intake and sociodemographic factors. Subjects and methods: The subjects are participants in the Finnish Type I Diabetes Prediction and Prevention Nutrition Study born between October 1997 and October 1998. At the age of 3 and 6 months, 1, 2 and 3 years, 342 (72% of the invited families), 298 (63%), 267 (56%), 233 (49%) and 209 (44%) families, respectively, participated in the present study. Food consumption was assessed by a 3-day food record. A structured questionnaire was used to record the parents' socioeconomic status. Results: The mean dietary vitamin D intake exceeded the recommendation (10 mu g/day) at the age of 3 (11.0 mu g) and 6 months (12.0 mu g), but decreased thereafter being 9.8, 5.0 and 4.1 mu g at 1, 2 and 3 years of age, respectively. Among the children 91, 91, 81, 42 and 26% used vitamin D supplements at the age of 3 and 6 months, and 1, 2 and 3 years, respectively. In children not using vitamin D supplements, vitamin D intake was less than 10 mg/day at all ages. Vitamin D intake from food did not differ in children who used and did not use vitamin D supplements. Vitamin D supplements were the main source of vitamin D intake in all age groups studied, followed by vitamin D-fortified infant formula in 3-month-olds and infant formula and baby foods in 6-month-olds. After the age of 1 year, the most important food sources of vitamin D were margarine, fish, baby foods, low-fat milk and eggs. Sociodemographic factors, especially the number of children in the family and maternal age, were associated with the total vitamin D intake and vitamin D supplement use. Conclusion: Vitamin D supplements are not used according to the dietary recommendations in a substantial proportion of Finnish children.
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| 9. |
- Rajaei, Hossein, et al.
(författare)
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Catalogue of the lepidoptera of Iran
- 2023
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Ingår i: Integrative Systematics. - : Stuttgart State Museum of Natural History. - 2628-2380. ; 6:SP1, s. 121-459
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Tidskriftsartikel (refereegranskat)
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| 10. |
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| 11. |
- Schuller, Jan M., et al.
(författare)
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Redox-coupled proton pumping drives carbon concentration in the photosynthetic complex I
- 2020
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- Photosynthetic organisms capture light energy to drive their energy metabolism, and employ the chemical reducing power to convert carbon dioxide (CO2) into organic molecules. Photorespiration, however, significantly reduces the photosynthetic yields. To survive under low CO2 concentrations, cyanobacteria evolved unique carbon-concentration mechanisms that enhance the efficiency of photosynthetic CO2 fixation, for which the molecular principles have remained unknown. We show here how modular adaptations enabled the cyanobacterial photosynthetic complex I to concentrate CO2 using a redox-driven proton-pumping machinery. Our cryo-electron microscopy structure at 3.2 angstrom resolution shows a catalytic carbonic anhydrase module that harbours a Zn2+ active site, with connectivity to proton-pumping subunits that are activated by electron transfer from photosystem I. Our findings illustrate molecular principles in the photosynthetic complex I machinery that enabled cyanobacteria to survive in drastically changing CO2 conditions. Cyanobacteria evolved carbon-concentration mechanisms to enhance the efficiency of photosynthetic CO2 fixation, but the molecular principles have remained unknown. Here authors use cryo-EM to reveal how modular adaptations enabled the photosynthetic complex I from the cyanobacterium Thermosynechococcus elongatus to concentrate CO2.
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| 12. |
- Auman, Dirk, et al.
(författare)
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Peroxy Intermediate Drives Carbon Bond Activation in the Dioxygenase AsqJ
- 2022
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 144:34, s. 15622-15632
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Tidskriftsartikel (refereegranskat)abstract
- Dioxygenases catalyze stereoselective oxygen atom transfer in metabolic pathways of biological, industrial, and pharmaceutical importance, but their precise chemical principles remain controversial. The α-ketoglutarate (αKG)-dependent dioxygenase AsqJ synthesizes biomedically active quinolone alkaloids via desaturation and subsequent epoxidation of a carbon–carbon bond in the cyclopeptin substrate. Here, we combine high-resolution X-ray crystallography with enzyme engineering, quantum-classical (QM/MM) simulations, and biochemical assays to describe a peroxidic intermediate that bridges the substrate and active site metal ion in AsqJ. Homolytic cleavage of this moiety during substrate epoxidation generates an activated high-valent ferryl (FeIV = O) species that mediates the next catalytic cycle, possibly without the consumption of the metabolically valuable αKG cosubstrate. Our combined findings provide an important understanding of chemical bond activation principles in complex enzymatic reaction networks and molecular mechanisms of dioxygenases.
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| 13. |
- Bridges, Hannah R., et al.
(författare)
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Structure of inhibitor-bound mammalian complex I
- 2020
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- Respiratory complex I (NADH:ubiquinone oxidoreductase) captures the free energy from oxidising NADH and reducing ubiquinone to drive protons across the mitochondrial inner membrane and power oxidative phosphorylation. Recent cryo-EM analyses have produced near-complete models of the mammalian complex, but leave the molecular principles of its long-range energy coupling mechanism open to debate. Here, we describe the 3.0-Ao resolution cryo-EM structure of complex I from mouse heart mitochondria with a substrate-like inhibitor, piericidin A, bound in the ubiquinone-binding active site. We combine our structural analyses with both functional and computational studies to demonstrate competitive inhibitor binding poses and provide evidence that two inhibitor molecules bind end-to-end in the long substrate binding channel. Our findings reveal information about the mechanisms of inhibition and substrate reduction that are central for understanding the principles of energy transduction in mammalian complex I. The respiratory complex I (NADH:ubiquinone oxidoreductase) is a large redox-driven proton pump that initiates respiration in mitochondria. Here, the authors present the 3.0 angstrom cryo-EM structure of complex I from mouse heart mitochondria with the ubiquinone-analogue inhibitor piericidin A bound in the active site and with kinetic measurements and MD simulations they further show that this inhibitor acts competitively against the native ubiquinone-10 substrate.
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| 14. |
- Di Trani, Justin M., et al.
(författare)
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Structural basis of mammalian complex IV inhibition by steroids
- 2022
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 119:30
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Tidskriftsartikel (refereegranskat)abstract
- The mitochondrial electron transport chain maintains the proton motive force that powers adenosine triphosphate (ATP) synthesis. The energy for this process comes from oxidation of reduced nicotinamide adenine dinucleotide (NADH) and succinate, with the electrons from this oxidation passed via intermediate carriers to oxygen. Complex IV (CIV), the terminal oxidase, transfers electrons from the intermediate electron carrier cytochrome c to oxygen, contributing to the proton motive force in the process. Within CIV, protons move through the K and D pathways during turnover. The former is responsible for transferring two protons to the enzyme’s catalytic site upon its reduction, where they eventually combine with oxygen and electrons to form water. CIV is the main site for respiratory regulation, and although previous studies showed that steroid binding can regulate CIV activity, little is known about how this regulation occurs. Here, we characterize the interaction between CIV and steroids using a combination of kinetic experiments, structure determination, and molecular simulations. We show that molecules with a sterol moiety, such as glyco-diosgenin and cholesteryl hemisuccinate, reversibly inhibit CIV. Flash photolysis experiments probing the rapid equilibration of electrons within CIV demonstrate that binding of these molecules inhibits proton uptake through the K pathway. Single particle cryogenic electron microscopy (cryo-EM) of CIV with glyco-diosgenin reveals a previously undescribed steroid binding site adjacent to the K pathway, and molecular simulations suggest that the steroid binding modulates the conformational dynamics of key residues and proton transfer kinetics within this pathway. The binding pose of the sterol group sheds light on possible structural gating mechanisms in the CIV catalytic cycle.
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| 15. |
- John, Juliane, et al.
(författare)
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Redox-controlled reorganization and flavin strain within the ribonucleotide reductase R2b–NrdI complex monitored by serial femtosecond crystallography
- 2022
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Ingår i: eLIFE. - 2050-084X. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- Redox reactions are central to biochemistry and are both controlled by and induce protein structural changes. Here, we describe structural rearrangements and crosstalk within the Bacillus cereus ribonucleotide reductase R2b–NrdI complex, a di-metal carboxylate-flavoprotein system, as part of the mechanism generating the essential catalytic free radical of the enzyme. Femtosecond crystallography at an X-ray free electron laser was utilized to obtain structures at room temperature in defined redox states without suffering photoreduction. Together with density functional theory calculations, we show that the flavin is under steric strain in the R2b–NrdI protein complex, likely tuning its redox properties to promote superoxide generation. Moreover, a binding site in close vicinity to the expected flavin O2 interaction site is observed to be controlled by the redox state of the flavin and linked to the channel proposed to funnel the produced superoxide species from NrdI to the di-manganese site in protein R2b. These specific features are coupled to further structural changes around the R2b–NrdI interaction surface. The mechanistic implications for the control of reactive oxygen species and radical generation in protein R2b are discussed.
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| 16. |
- John, Juliane, et al.
(författare)
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Redox-controlled reorganization and flavin strain within the ribonucleotide reductase R2b–NrdI complex monitored by serial femtosecond crystallography
- 2022
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Ingår i: eLIFE. - : eLife Sciences Publications Ltd. - 2050-084X. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- Redox reactions are central to biochemistry and are both controlled by and induce protein structural changes. Here, we describe structural rearrangements and crosstalk within the Bacillus cereus ribonucleotide reductase R2b–NrdI complex, a di-metal carboxylate-flavoprotein system, as part of the mechanism generating the essential catalytic free radical of the enzyme. Femtosecond crystallography at an X-ray free electron laser was utilized to obtain structures at room temperature in defined redox states without suffering photoreduction. Together with density functional theory calculations, we show that the flavin is under steric strain in the R2b–NrdI protein complex, likely tuning its redox properties to promote superoxide generation. Moreover, a binding site in close vicinity to the expected flavin O2 interaction site is observed to be controlled by the redox state of the flavin and linked to the channel proposed to funnel the produced superoxide species from NrdI to the di-manganese site in protein R2b. These specific features are coupled to further structural changes around the R2b–NrdI interaction surface. The mechanistic implications for the control of reactive oxygen species and radical generation in protein R2b are discussed.
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| 17. |
- Katsyv, Alexander., et al.
(författare)
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Molecular Basis of the Electron Bifurcation Mechanism in the [FeFe]- Hydrogenase Complex HydABC
- 2023
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 145:10, s. 5696-5709
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Tidskriftsartikel (refereegranskat)abstract
- Electron bifurcation is a fundamental energy coupling mechanism widespread in microorganisms that thrive under anoxic conditions. These organisms employ hydrogen to reduce CO2, but the molecular mechanisms have remained enigmatic. The key enzyme responsible for powering these thermodynamically challenging reactions is the electron-bifurcating [FeFe]-hydrogenase HydABC that reduces low-potential ferredoxins (Fd) by oxidizing hydrogen gas (H2). By combining single-particle cryo-electron microscopy (cryoEM) under catalytic turnover conditions with site-directed mutagenesis experiments, functional studies, infrared spectroscopy, and molecular simulations, we show that HydABC from the acetogenic bacteria Acetobacterium woodii and Thermoanaerobacter kivui employ a single flavin mononucleotide (FMN) cofactor to establish electron transfer pathways to the NAD(P)+ and Fd reduction sites by a mechanism that is fundamentally different from classical flavin-based electron bifurcation enzymes. By modulation of the NAD(P)+ binding affinity via reduction of a nearby iron–sulfur cluster, HydABC switches between the exergonic NAD(P)+ reduction and endergonic Fd reduction modes. Our combined findings suggest that the conformational dynamics establish a redox-driven kinetic gate that prevents the backflow of the electrons from the Fd reduction branch toward the FMN site, providing a basis for understanding general mechanistic principles of electron-bifurcating hydrogenases.
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| 18. |
- Kriebisch, Brigitte A. K., et al.
(författare)
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Reciprocal Coupling in Chemically Fueled Assembly : A Reaction Cycle Regulates Self-Assembly and Vice Versa
- 2020
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 142:49, s. 20837-20844
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Tidskriftsartikel (refereegranskat)abstract
- In biology, self-assembly of proteins and energy-consuming reaction cycles are intricately coupled. For example, tubulin is activated and deactivated for assembly by a guanosine triphosphate (GTP)-driven reaction cycle, and the emerging microtubules catalyze this reaction cycle by changing the microenvironment of the activated tubulin. Recently, synthetic analogs of chemically fueled assemblies have emerged, but examples in which assembly and reaction cycles are reciprocally coupled remain rare. In this work, we report a peptide that can be activated and deactivated for self-assembly. The emerging assemblies change the microenvironment of their building blocks, which consequently accelerate the rates of building block deactivation and reactivation. We quantitatively understand the mechanisms at play, and we are thus able to tune the catalysis by molecular design of the peptide precursor.
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| 19. |
- Lebrette, Hugo, 1986-, et al.
(författare)
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Structure of a ribonucleotide reductase R2 protein radical
- 2023
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 382:6666, s. 109-113
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Tidskriftsartikel (refereegranskat)abstract
- Aerobic ribonucleotide reductases (RNRs) initiate synthesis of DNA building blocks by generating a free radical within the R2 subunit; the radical is subsequently shuttled to the catalytic R1 subunit through proton-coupled electron transfer (PCET). We present a high-resolution room temperature structure of the class Ie R2 protein radical captured by x-ray free electron laser serial femtosecond crystallography. The structure reveals conformational reorganization to shield the radical and connect it to the translocation path, with structural changes propagating to the surface where the protein interacts with the catalytic R1 subunit. Restructuring of the hydrogen bond network, including a notably short O-O interaction of 2.41 angstroms, likely tunes and gates the radical during PCET. These structural results help explain radical handling and mobilization in RNR and have general implications for radical transfer in proteins.
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| 20. |
- Lee, Kyung Min, et al.
(författare)
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Information Dropout Patterns in Restriction Site Associated DNA Phylogenomics and a Comparison with Multilocus Sanger Data in a Species-Rich Moth Genus
- 2018
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Ingår i: Systematic Biology. - : Oxford University Press (OUP). - 1063-5157 .- 1076-836X. ; 67:6, s. 925-939
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Tidskriftsartikel (refereegranskat)abstract
- A rapid shift from traditional Sanger sequencing-based molecular methods to the phylogenomic approach with large numbers of loci is underway. Among phylogenomic methods, restriction site associated DNA (RAD) sequencing approaches have gained much attention as they enable rapid generation of up to thousands of loci randomly scattered across the genome and are suitable for nonmodel species. RAD data sets however suffer from large amounts of missing data and rapid locus dropout along with decreasing relatedness among taxa. The relationship between locus dropout and the amount of phylogenetic information retained in the data has remained largely uninvestigated. Similarly, phylogenetic hypotheses based on RAD have rarely been compared with phylogenetic hypotheses based on multilocus Sanger sequencing, even less so using exactly the same species and specimens. We compared the Sanger-based phylogenetic hypothesis (8 loci; 6172 bp) of 32 species of the diverse moth genus Eupithecia (Lepidoptera, Geometridae) to that based on double-digest RAD sequencing (3256 loci; 726,658 bp). We observed that topologies were largely congruent, with some notable exceptions that we discuss. The locus dropout effect was strong. We demonstrate that number of loci is not a precise measure of phylogenetic information since the number of single-nucleotide polymorphisms (SNPs) may remain low at very shallow phylogenetic levels despite large numbers of loci. As we hypothesize, the number of SNPs and parsimony informative SNPs (PIS) is low at shallow phylogenetic levels, peaks at intermediate levels and, thereafter, declines again at the deepest levels as a result of decay of available loci. Similarly, we demonstrate with empirical data that the locus dropout affects the type of loci retained, the loci found in many species tending to show lower interspecific distances than those shared among fewer species. We also examine the effects of the numbers of loci, SNPs, and PIS on nodal bootstrap support, but could not demonstrate with our data our expectation of a positive correlation between them. We conclude that RAD methods provide a powerful tool for phylogenomics at an intermediate phylogenetic level as indicated by its broad congruence with an eight-gene Sanger data set in a genus of moths. When assessing the quality of the data for phylogenetic inference, the focus should be on the distribution and number of SNPs and PIS rather than on loci.
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| 21. |
- Lumia, Mirka, et al.
(författare)
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Food consumption and risk of childhood asthma
- 2015
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Ingår i: Pediatric Allergy and Immunology. - : WILEY. - 0905-6157 .- 1399-3038. ; 26:8, s. 789-796
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundThe consumption of foods rich in n-3 polyunsaturated fatty acids has been proposed to protect against childhood asthma. This study explores the association of food consumption (including cow's milk (CM)-free diet) in early life and the risk of atopic and non-atopic asthma. MethodsFood intake of 182 children with asthma and 728 matched controls was measured using 3-day food records, within the Finnish Type 1 Diabetes Prediction and Prevention (DIPP) Nutrition Study cohort. The diagnoses of food allergies came both from the written questionnaire and from the registers of the Social Insurance Institution. Conditional logistic regression with generalized estimating equations framework was used in the analyses. ResultsThe diagnosis of cow's milk allergy (CMA) led to multiple dietary restrictions still evident at 4yr of age. Even after adjusting for CMA, higher consumption of CM products was inversely associated with the risk of atopic asthma and higher consumption of breast milk and oats inversely with the risk of non-atopic asthma. Early consumption of fish was associated with a decreased risk of all asthma. ConclusionsDietary intake in early life combined with atopy history has a clear impact on the risk of developing asthma. Our results indicate that CM restriction due to CMA significantly increases and mediates the association between food consumption and childhood asthma risk.
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| 22. |
- Ojwang', Vincent, et al.
(författare)
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Early exposure to cats, dogs and farm animals and the risk of childhood asthma and allergy.
- 2020
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Ingår i: Pediatric allergy and immunology : official publication of the European Society of Pediatric Allergy and Immunology. - : Wiley. - 1399-3038. ; 31:3, s. 265-272
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Tidskriftsartikel (refereegranskat)abstract
- Synergistic role of exposure to cats, dogs, and farm animals during infancy on the risk of childhood asthma and allergy remains unknown.To investigate independent and synergistic associations between exposure to indoor pets and farm animals during infancy and the risk of asthma and allergy by age 5.We studied 3781 children participating in the Finnish Type 1 Diabetes Prediction and Prevention (DIPP) nutrition study. At age 5, a validated version of the International Study of Asthma and Allergies in Childhood questionnaire was administered to collect information on asthma and allergic disease; and exposure to indoor pets and farm animals during the first year of life. Allergen-specific IgE antibodies were analyzed from serum samples. Statistical analyses employed Cox proportional hazards- and logistic regression.Having a dog in the house was inversely associated with the risk of asthma (HR 0.60; 95%CI, 0.38-0.96); allergic rhinitis (OR 0.72; 95%CI, 0.53-0.97); and atopic sensitization (OR 0.77; 95%CI, 0.63-0.96). Having a cat was associated with decreased risk of atopic eczema (OR 0.68; 95%CI, 0.51-0.92). Farm animals were neither independently nor in synergy with indoor pets associated with the outcomes.Having a dog or cat in the house during the first year of life may protect against childhood asthma and allergy. We did not find a synergistic association between cat, dog and farm animal exposure on the risk of childhood asthma and allergy. Future research should identify specific causative exposures conferred by indoor pets and whether they could be recommended for allergy prevention.
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| 23. |
- Parmesan, C, et al.
(författare)
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Poleward shifts in geographical ranges of butterfly species associated with regional warming
- 1999
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Ingår i: NATURE. - : MACMILLAN MAGAZINES LTD. - 0028-0836. ; 399:6736, s. 579-583
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Mean global temperatures have risen this century, and further warming is predicted to continue for the next 50-100 years(1-3) Some migratory species can respond rapidly to yearly climate variation by altering the timing or destination of migration(4), but
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| 24. |
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| 25. |
- Rivera, C, et al.
(författare)
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BDNF-induced TrkB activation down-regulates the K+-Cl- cotransporter KCC2 and impairs neuronal Cl- extrusion
- 2002
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Ingår i: Journal of Cell Biology. - : Rockefeller University Press. - 0021-9525 .- 1540-8140. ; 159:5, s. 747-752
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Tidskriftsartikel (refereegranskat)abstract
- Pathophysiological activity and various kinds of traumatic insults are known to have deleterious long-term effects on neuronal Cl- regulation, which can lead to a suppression of fast postsynaptic GABAergic responses. Brain-derived neurotrophic factor (BDNF) increases neuronal excitability through a conjunction of mechanisms that include regulation of the efficacy of GABAergic transmission. Here, we show that exposure of rat hippocampal slice cultures and acute slices to exogenous BDNF or neurotrophin-4 produces a TrkB-mediated fall in the neuron-specific K+-Cl- cotransporter KCC2 mRNA and protein, as well as a consequent impairment in neuronal Cl- extrusion capacity. After kindling-induced seizures in vivo, the expression of KCC2 is down-regulated in the mouse hippocampus with a spatio-temporal profile complementary to the up-regulation of TrkB and BDNF. The present data demonstrate a novel mechanism whereby BDNF/TrkB signaling suppresses chloride-dependent fast GABAergic inhibition, which most likely contributes to the well-known role of TrkB-activated signaling cascades in the induction and establishment of epileptic activity.
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| 26. |
- Roslin, Tomas, et al.
(författare)
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A molecular-based identification resource for the arthropods of Finland
- 2022
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Ingår i: Molecular Ecology Resources. - : Wiley. - 1755-098X .- 1755-0998. ; 22:2, s. 803-822
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Tidskriftsartikel (refereegranskat)abstract
- To associate specimens identified by molecular characters to other biological knowledge, we need reference sequences annotated by Linnaean taxonomy. In this study, we (1) report the creation of a comprehensive reference library of DNA barcodes for the arthropods of an entire country (Finland), (2) publish this library, and (3) deliver a new identification tool for insects and spiders, as based on this resource. The reference library contains mtDNA COI barcodes for 11,275 (43%) of 26,437 arthropod species known from Finland, including 10,811 (45%) of 23,956 insect species. To quantify the improvement in identification accuracy enabled by the current reference library, we ran 1000 Finnish insect and spider species through the Barcode of Life Data system (BOLD) identification engine. Of these, 91% were correctly assigned to a unique species when compared to the new reference library alone, 85% were correctly identified when compared to BOLD with the new material included, and 75% with the new material excluded. To capitalize on this resource, we used the new reference material to train a probabilistic taxonomic assignment tool, FinPROTAX, scoring high success. For the full-length barcode region, the accuracy of taxonomic assignments at the level of classes, orders, families, subfamilies, tribes, genera, and species reached 99.9%, 99.9%, 99.8%, 99.7%, 99.4%, 96.8%, and 88.5%, respectively. The FinBOL arthropod reference library and FinPROTAX are available through the Finnish Biodiversity Information Facility (www.laji.fi) at https://laji.fi/en/theme/protax. Overall, the FinBOL investment represents a massive capacity-transfer from the taxonomic community of Finland to all sectors of society.
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| 27. |
- Saura, Patricia, et al.
(författare)
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Electric fields control water-gated proton transfer in cytochrome c oxidase
- 2022
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 119:38
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Tidskriftsartikel (refereegranskat)abstract
- Aerobic life is powered by membrane-bound enzymes that catalyze the transfer of electrons to oxygen and protons across a biological membrane. Cytochrome c oxidase (CcO) functions as a terminal electron acceptor in mitochondrial and bacterial respiratory chains, driving cellular respiration and transducing the free energy from O2 reduction into proton pumping. Here we show that CcO creates orientated electric fields around a nonpolar cavity next to the active site, establishing a molecular switch that directs the protons along distinct pathways. By combining large-scale quantum chemical density functional theory (DFT) calculations with hybrid quantum mechanics/ molecular mechanics (QM/MM) simulations and atomistic molecular dynamics (MD) explorations, we find that reduction of the electron donor, heme a, leads to dissociation of an arginine (Arg438)–heme a3 D-propionate ion-pair. This ion-pair dissociation creates a strong electric field of up to 1 V Å-1 along a water-mediated proton array leading to a transient proton loading site (PLS) near the active site. Protonation of the PLS triggers the reduction of the active site, which in turn aligns the electric field vectors along a second, “chemical,” proton pathway. We find a linear energy relationship of the proton transfer barrier with the electric field strength that explains the effectivity of the gating process. Our mechanism shows distinct similarities to principles also found in other energy-converting enzymes, suggesting that orientated electric fields generally control enzyme catalysis.
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