| 1. |
- Ahlqvist, Emma, et al.
(author)
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A link between GIP and osteopontin in adipose tissue and insulin resistance.
- 2013
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In: Diabetes. - : American Diabetes Association. - 1939-327X .- 0012-1797. ; 62:6, s. 2088-2094
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Journal article (peer-reviewed)abstract
- Low grade inflammation in obesity is associated with accumulation of the macrophagederived cytokine osteopontin in adipose tissue and induction of local as well as systemic insulin resistance. Since GIP (glucose-dependent insulinotropic polypeptide) is a strong stimulator of adipogenesis and may play a role in the development of obesity, we explored whether GIP directly would stimulate osteopontin (OPN) expression in adipose tissue and thereby induce insulin resistance. GIP stimulated OPN protein expression in a dose-dependent fashion in rat primary adipocytes. The level of OPN mRNA was higher in adipose tissue of obese individuals (0.13±}0.04 vs 0.04±}0.01, P<0.05) and correlated inversely with measures of insulin sensitivity (r=-0.24, P=0.001). A common variant of the GIP receptor (GIPR) (rs10423928) gene was associated with lower amount of the exon 9 containing isoform required for transmembrane activity. Carriers of the A-allele with a reduced receptor function showed lower adipose tissue OPN mRNA levels and better insulin sensitivity. Together, these data suggest a role for GIP not only as an incretin hormone, but also as a trigger of inflammation and insulin resistance in adipose tissue. Carriers of GIPR rs10423928 A-allele showed protective properties via reduced GIP effects. Identification of this unprecedented link between GIP and OPN in adipose tissue might open new avenues for therapeutic interventions.
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| 2. |
- Berglund, Lisa, et al.
(author)
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Glucose-Dependent Insulinotropic Polypeptide (GIP) Stimulates Osteopontin Expression in the Vasculature via Endothelin-1 and CREB.
- 2016
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In: Diabetes. - : American Diabetes Association. - 1939-327X .- 0012-1797. ; 65:1, s. 239-254
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Journal article (peer-reviewed)abstract
- Glucose-dependent insulinotropic polypeptide (GIP) is an incretin hormone with extrapancreatic effects beyond glycemic control. Here we demonstrate unexpected effects of GIP signaling in the vasculature. GIP induces the expression of the pro-atherogenic cytokine osteopontin (OPN) in mouse arteries, via local release of endothelin-1 (ET-1) and activation of cAMP response element binding protein (CREB). Infusion of GIP increases plasma OPN levels in healthy individuals. Plasma ET-1 and OPN levels are positively correlated in patients with critical limb ischemia. Fasting GIP levels are higher in individuals with a history of cardiovascular disease (myocardial infarction, stroke) when compared to controls. GIP receptor (GIPR) and OPN mRNA levels are higher in carotid endarterectomies from patients with symptoms (stroke, transient ischemic attacks, amaurosis fugax) than in asymptomatic patients; and expression associates to parameters characteristic of unstable and inflammatory plaques (increased lipid accumulation, macrophage infiltration and reduced smooth muscle cell content). While GIPR expression is predominantly endothelial in healthy arteries from human, mouse, rat and pig; remarkable up-regulation is observed in endothelial and smooth muscle cells upon culture conditions yielding a "vascular disease-like" phenotype. Moreover, a common variant rs10423928 in the GIPR gene associated with increased risk of stroke in type 2 diabetes patients.
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| 3. |
- Lyssenko, Valeriya, et al.
(author)
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Pleiotropic Effects of GIP on Islet Function Involve Osteopontin
- 2011
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In: Diabetes. - : American Diabetes Association. - 1939-327X .- 0012-1797. ; 60:9, s. 2424-2433
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Journal article (peer-reviewed)abstract
- OBJECTIVE-The incretin hormone GIP (glucose-dependent insulinotropic polypeptide) promotes pancreatic beta-cell function by potentiating insulin secretion and beta-cell proliferation. Recently, a combined analysis of several genome-wide association studies (Meta-analysis of Glucose and Insulin-Related Traits Consortium [MAGIC]) showed association to postprandial insulin at the GIP receptor (GIPR) locus. Here we explored mechanisms that could explain the protective effects of GIP on islet function. RESEARCH DESIGN AND METHODS-Associations of GIPR rs10423928 with metabolic and anthropometric phenotypes in both nondiabetic (N = 53,730) and type 2 diabetic individuals (N = 2,731) were explored by combining data from 11 studies.Insulin secretion was measured both in vivo in nondiabetic subjects and in vitro in islets from cadaver donors. Insulin secretion was also measured in response to exogenous GIP. The in vitro measurements included protein and gene expression as well as measurements of beta-cell viability and proliferation. RESULTS-The A allele of GIPR rs10423928 was associated with impaired glucose- and GIP-stimulated insulin secretion and a decrease in BMI, lean body mass, and waist circumference. The decrease in BMI almost completely neutralized the effect of impaired insulin secretion on risk of type 2 diabetes. Expression of GIPR mRNA was decreased in human islets from carriers of the A allele or patients with type 2 diabetes. GIP stimulated osteopontin (OPN) mRNA and protein expression. OPN expression was lower in carriers of the A allele. Both GIP and OPN prevented cytokine-induced reduction in cell viability (apoptosis). In addition, OPN stimulated cell proliferation in insulin-secreting cells. CONCLUSIONS-These findings support beta-cell proliferative and antiapoptotic roles for GIP in addition to its action as an incretin hormone. Identification of a link between GIP and OPN may shed new light on the role of GIP in preservation of functional beta-cell mass in humans. Diabetes 60:2424-2433, 2011
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| 4. |
- Xie, Meng, et al.
(author)
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Secondary ossification center induces and protects growth plate structure
- 2020
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In: eLIFE. - : ELIFE SCIENCES PUBLICATIONS LTD. - 2050-084X. ; 9
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Journal article (peer-reviewed)abstract
- Growth plate and articular cartilage constitute a single anatomical entity early in development but later separate into two distinct structures by the secondary ossification center (SOC). The reason for such separation remains unknown. We found that evolutionarily SOC appears in animals conquering the land - amniotes. Analysis of the ossification pattern in mammals with specialized extremities (whales, bats, jerboa) revealed that SOC development correlates with the extent of mechanical loads. Mathematical modeling revealed that SOC reduces mechanical stress within the growth plate. Functional experiments revealed the high vulnerability of hypertrophic chondrocytes to mechanical stress and showed that SOC protects these cells from apoptosis caused by extensive loading. Atomic force microscopy showed that hypertrophic chondrocytes are the least mechanically stiff cells within the growth plate. Altogether, these findings suggest that SOC has evolved to protect the hypertrophic chondrocytes from the high mechanical stress encountered in the terrestrial environment.
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| 5. |
- Blanco, Fabiana, et al.
(author)
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In vivo inhibition of nuclear factor of activated T-cells leads to atherosclerotic plaque regression in IGF-II/LDLR -/-ApoB100/100 mice
- 2018
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In: Diabetes and Vascular Disease Research. - : SAGE Publications. - 1752-8984 .- 1479-1641. ; 15:4, s. 302-313
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Journal article (peer-reviewed)abstract
- AIMS: Despite vast clinical experience linking diabetes and atherosclerosis, the molecular mechanisms leading to accelerated vascular damage are still unclear. Here, we investigated the effects of nuclear factor of activated T-cells inhibition on plaque burden in a novel mouse model of type 2 diabetes that better replicates human disease.METHODS & RESULTS: IGF-II/LDLR-/-ApoB100/100mice were generated by crossbreeding low-density lipoprotein receptor-deficient mice that synthesize only apolipoprotein B100 (LDLR-/-ApoB100/100) with transgenic mice overexpressing insulin-like growth factor-II in pancreatic β cells. Mice have mild hyperglycaemia and hyperinsulinaemia and develop complex atherosclerotic lesions. In vivo treatment with the nuclear factor of activated T-cells blocker A-285222 for 4 weeks reduced atherosclerotic plaque area and degree of stenosis in the brachiocephalic artery of IGF-II/LDLR-/-ApoB100/100mice, as assessed non-invasively using ultrasound biomicroscopy prior and after treatment, and histologically after termination. Treatment had no impact on plaque composition (i.e. muscle, collagen, macrophages). The reduced plaque area could not be explained by effects of A-285222 on plasma glucose, insulin or lipids. Inhibition of nuclear factor of activated T-cells was associated with increased expression of atheroprotective NOX4 and of the anti-oxidant enzyme catalase in aortic vascular smooth muscle cells.CONCLUSION: Targeting the nuclear factor of activated T-cells signalling pathway may be an attractive approach for the treatment of diabetic macrovascular complications.
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| 6. |
- Clemedson, Cecilia, et al.
(author)
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Development of an in vitro test battery for the estimation of acute human systemic toxicity : An outline of the EDIT project. Evaluation-guided Development of New In Vitro Test Batteries
- 2002
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In: ATLA (Alternatives to Laboratory Animals). - 0261-1929. ; 30:3, s. 313-321
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Journal article (peer-reviewed)abstract
- The aim of the Evaluation-guided Development of new In Vitro Test Batteries (EDIT) multicentre programme is to establish and validate in vitro tests relevant to toxicokinetics and for organ-specific toxicity, to be incorporated into optimal test batteries for the estimation of human acute systemic toxicity. The scientific basis of EDIT is the good prediction of human acute toxicity obtained with three human cell line tests (R(2) = 0.77), in the Multicentre Evaluation of In Vitro Cytotoxicity (MEIC) programme. However, the results from the MEIC study indicated that at least two other types of in vitro test ought to be added to the existing test battery to improve the prediction of human acute systemic toxicity - to determine key kinetic events (such as biotransformation and passage through biological barriers), and to predict crucial organ-specific mechanisms not covered by the tests in the MEIC battery. The EDIT programme will be a case-by-case project, but the establishment and validation of new tests will be carried through by a common, step-wise procedure. The Scientific Committee of the EDIT programme defines the need for a specific set of toxicity or toxicokinetic data. Laboratories are then invited to perform the defined tests in order to provide the "missing" data for the EDIT reference chemicals. The results obtained will be evaluated against the MEMO (the MEIC Monograph programme) database, i.e. against human acute systemic lethal and toxicity data. The aim of the round-table discussions at the 19th Scandinavian Society for Cell Toxicology (SSCT) workshop, held in Ringsted, Denmark on 6-9 September 2001, was to identify which tests are the most important for inclusion in the MEIC battery, i.e. which types of tests the EDIT programme should focus on. It was proposed that it is important to include in vitro methods for various kinetic events, such as biotransformation, absorption in the gut, passage across the blood-brain barrier, distribution volumes, protein binding, and renal clearance/accumulation. Models for target organ toxicity were also discussed. Because several of the outlier chemicals (paracetamol, digoxin, malathion, nicotine, paraquat, atropine and potassium cyanide) in the MEIC in vivo-in vitro evaluation have a neurotoxic potential, it was proposed that the development within the EDIT target organ programme should initially be focused on the nervous system.
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| 7. |
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| 8. |
- Kotova, Irina, et al.
(author)
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A mouse in vitro transcription system reconstituted from highly purified RNA polymerase II, TFIIH, and recombinant TBP, TFIIB, TFIIE and TFIIF.
- 2001
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In: European Journal of Biochemistry. - : Wiley. - 0014-2956 .- 1432-1033. ; 268:16, s. 4527-4536
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Journal article (peer-reviewed)abstract
- Unregulated transcription of protein-encoding genes in vitro is dependent on 12-subunit core RNA polymerase II and five general transcription factors; TATA binding protein (TBP), transcription factor (TF)IIB, TFIIE, TFIIF, and TFIIH. Here we describe cloning of the mouse cDNAs encoding TFIIB and the small and large TFIIE and TFIIF subunits. The cDNAs have been used to express the corresponding proteins in recombinant form in Escherichia coli and in Sf21 insect cells, and all proteins have been purified to > 90% homogeneity. We have also purified a recombinant His6-tagged mouse TBP to near homogeneity and show that it is active in both a reconstituted mouse in vitro transcription system and a TBP-dependent in vitro transcription system from Saccharomyces cerevisiae. The more complex general transcription factors, TFIIH and RNA polymerase II, were purified more than 1000-fold and to near homogeneity, respectively, from tissue cultured mouse cells. When combined, the purified factors were sufficient to initiate transcription from different promoters in vitro. Functional studies of the S-phase-specific mouse ribonucleotide reductase R2 promoter using both the highly purified system described here (a mouse cell nuclear extract in vitro transcription system) and in vivo R2-promoter reporter gene assays together identify an NF-Y interacting promoter proximal CCAAT-box as being essential for high-level expression from the R2 promoter.
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| 9. |
- Kotova, Irina, et al.
(author)
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Sequences downstream of the transcription initiation site are important for proper initiation and regulation of mouse ribonucleotide reductase R2 gene transcription
- 2003
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In: European Journal of Biochemistry. - : Blackwell Publishing. - 0014-2956 .- 1432-1033. ; 270:8, s. 1791-1801
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Journal article (peer-reviewed)abstract
- Ribonucleotide reductase is essential for the synthesis of all four dNTPs required for DNA replication. The enzyme is composed of two proteins, R1 and R2, which are both needed for activity. Expression of the R1 and R2 mRNAs is restricted to the S-phase of the cell cycle, but the R1 and R2 promoters show no obvious sequence homologies that could indicate coordination of transcription. Here we study initiation of transcription at the natural mouse R2 promoter, which contains an atypical TATA-box with the sequence TTTAAA, using a combination of in vivo reporter gene assays and in vitro transcription. Our results indicate that in constructs where sequences from the R2 5'-UTR are present, the mouse R2 TATA-box is dispensable both for unregulated, basal transcription from the R2 promoter and for S-phase specific activity. Instead, initiation of R2 transcription is directed by sequences downstream from the transcription start. We report that this region contains a conserved palindrome sequence that interacts with TAF(II)s. This interaction down-regulates basal transcription from the R2 promoter, both in the absence and in the presence of the TATA-box.
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| 10. |
- Krus, Ulrika, et al.
(author)
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Pyruvate dehydrogenase kinase 1 controls mitochondrial metabolism and insulin secretion in INS-1 832/13 clonal beta-cells
- 2010
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In: Biochemical Journal. - 0264-6021 .- 1470-8728. ; 429, s. 205-213
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Journal article (peer-reviewed)abstract
- Tight coupling between cytosolic and mitochondrial metabolism is key for GSIS (glucose-stimulated insulin secretion). In the present study we examined the regulatory contribution of PDH (pyruvate dehydrogenase) kinase 1, a negative regulator of PDH, to metabolic coupling in 832/13 clonal beta-cells. Knockdown of PDH kinase 1 with siRNA (small interfering RNA) reduced its mRNA (>80 %) and protein level (>40 %) after 72 h. PDH activity, glucose-stimulated cellular oxygen consumption and pyruvate-stimulated mitochondrial oxygen consumption increased 1.7- (P < 0.05), 1.6- (P < 0.05) and 1.6-fold (P < 0.05) respectively. Gas chromatography/MS revealed an altered metabolite profile upon silencing of PDH kinase 1, determined by increased levels of the tricarboxylic acid cycle intermediates malate, fumarate and alpha-ketoglutarate. These metabolic alterations were associated with exaggerated GSIS (5-fold compared with 3.1-fold in control cells; P < 0.01). Insulin secretion, provoked by leucine and dimethylsuccinate, which feed into the tricarboxylic acid cycle bypassing PDH, was unaffected. The oxygen consumption and metabolic data strongly suggest that knockdown of PDH kinase 1 in beta-cells permits increased metabolic flux of glucose-derived carbons into the tricarboxylic acid cycle via PDH. Enhanced insulin secretion is probably caused by increased generation of tricarboxylic acid cycle-derived reducing equivalents for mitochondrial electron transport to generate ATP and/or stimulatory metabolic intermediates. On the basis of these findings, we suggest that PDH kinase 1 is an important regulator of PDH in clonal beta-cells and that PDH kinase 1 and PDH are important for efficient metabolic coupling. Maintaining low PDH kinase I expression/activity, keeping PDH in a dephosphorylated and active state, may be important for beta-cells to achieve the metabolic flux rates necessary for maximal GSIS.
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| 11. |
- Nalsen, C., et al.
(author)
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Vitamin D status in children and adults in Sweden: dietary intake and 25-hydroxyvitamin D concentrations in children aged 10-12 years and adults aged 18-80 years
- 2020
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In: Journal of Nutritional Science. - : Cambridge University Press (CUP). - 2048-6790. ; 9
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Journal article (peer-reviewed)abstract
- The study aimed to estimate vitamin D intake and plasma/serum 25-hydroxyvitamin D (25(OH)D) concentrations, investigate determinants of 25(OH)D concentrations and compare two 25(OH)D assays. We conducted two nationwide cross-sectional studies in Sweden with 206 school children aged 10-12 years and 1797 adults aged 18-80 years (n 268 provided blood samples). A web-based dietary record was used to assess dietary intake. Plasma/serum 25 (OH)D was analysed by liquid chromatography-mass spectrometry (LC-MS) and immunoassay in adults and LC-MS/MS in children. Most participants reported a vitamin D intake below the average requirement (AR), 16 % of children and 33 % of adults met the AR (7.5 mu g). In adults, plasma 25 (OH)D below 30 and 50 nmol/l were found in 1 and 18 % of participants during the summer period and in 9 and 40 % of participants during the winter period, respectively. In children, serum 25(OH)D below 30 and 50 nmol/l were found in 5 and 42 % of participants (samples collected March-May), respectively. Higher 25(OH)D concentrations were associated with the summer season, vacations in sunny locations (adults), and dietary intake of vitamin D and use of vitamin D supplements, while lower concentrations were associated with a higher BMI and an origin outside of Europe. Concentrations of 25 (OH)D were lower using the immunoassay than with the LC-MS assay, but associations with dietary factors and seasonal variability were similar. In conclusion, vitamin D intake was lower than the AR, especially in children. The 25(OH)D concentrations were low in many participants, but few participants had a concentration below 30 nmol/l.
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| 12. |
- Palmroth, Minna, et al.
(author)
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Lower-thermosphere-ionosphere (LTI) quantities : current status of measuring techniques and models
- 2021
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In: Annales Geophysicae. - : Copernicus Publications. - 0992-7689 .- 1432-0576. ; 39:1, s. 189-237
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Journal article (peer-reviewed)abstract
- The lower-thermosphere-ionosphere (LTI) system consists of the upper atmosphere and the lower part of the ionosphere and as such comprises a complex system coupled to both the atmosphere below and space above. The atmospheric part of the LTI is dominated by laws of continuum fluid dynamics and chemistry, while the ionosphere is a plasma system controlled by electromagnetic forces driven by the magnetosphere, the solar wind, as well as the wind dynamo. The LTI is hence a domain controlled by many different physical processes. However, systematic in situ measurements within this region are severely lacking, although the LTI is located only 80 to 200 km above the surface of our planet. This paper reviews the current state of the art in measuring the LTI, either in situ or by several different remote-sensing methods. We begin by outlining the open questions within the LTI requiring high-quality in situ measurements, before reviewing directly observable parameters and their most important derivatives. The motivation for this review has arisen from the recent retention of the Daedalus mission as one among three competing mission candidates within the European Space Agency (ESA) Earth Explorer 10 Programme. However, this paper intends to cover the LTI parameters such that it can be used as a background scientific reference for any mission targeting in situ observations of the LTI.
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| 13. |
- Sarris, Theodore E., et al.
(author)
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Daedalus MASE (mission assessment through simulation exercise): A toolset for analysis of in situ missions and for processing global circulation model outputs in the lower thermosphere-ionosphere
- 2023
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In: Frontiers in Astronomy and Space Sciences. - : Frontiers Media SA. - 2296-987X. ; 9
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Journal article (peer-reviewed)abstract
- Daedalus MASE (Mission Assessment through Simulation Exercise) is an open-source package of scientific analysis tools aimed at research in the Lower Thermosphere-Ionosphere (LTI). It was created with the purpose to assess the performance and demonstrate closure of the mission objectives of Daedalus, a mission concept targeting to perform in-situ measurements in the LTI. However, through its successful usage as a mission-simulator toolset, Daedalus MASE has evolved to encompass numerous capabilities related to LTI science and modeling. Inputs are geophysical observables in the LTI, which can be obtained either through in-situ measurements from spacecraft and rockets, or through Global Circulation Models (GCM). These include ion, neutral and electron densities, ion and neutral composition, ion, electron and neutral temperatures, ion drifts, neutral winds, electric field, and magnetic field. In the examples presented, these geophysical observables are obtained through NCAR’s Thermosphere-Ionosphere-Electrodynamics General Circulation Model. Capabilities of Daedalus MASE include: 1) Calculations of products that are derived from the above geophysical observables, such as Joule heating, energy transfer rates between species, electrical currents, electrical conductivity, ion-neutral collision frequencies between all combinations of species, as well as height-integrations of derived products. 2) Calculation and cross-comparison of collision frequencies and estimates of the effect of using different models of collision frequencies into derived products. 3) Calculation of the uncertainties of derived products based on the uncertainties of the geophysical observables, due to instrument errors or to uncertainties in measurement techniques. 4) Routines for the along-orbit interpolation within gridded datasets of GCMs. 5) Routines for the calculation of the global coverage of an in situ mission in regions of interest and for various conditions of solar and geomagnetic activity. 6) Calculations of the statistical significance of obtaining the primary and derived products throughout an in situ mission’s lifetime. 7) Routines for the visualization of 3D datasets of GCMs and of measurements along orbit. Daedalus MASE code is accompanied by a set of Jupyter Notebooks, incorporating all required theory, references, codes and plotting in a user-friendly environment. Daedalus MASE is developed and maintained at the Department for Electrical and Computer Engineering of the Democritus University of Thrace, with key contributions from several partner institutions.
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| 14. |
- Xie, Meng, et al.
(author)
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Secondary ossification center induces and protects growth plate structure
-
In: eLIFE. - 2050-084X.
-
Journal article (peer-reviewed)abstract
- Growth plate and articular cartilage constitute a single anatomical entity, but later separate into two distinct structures by the formation of secondary ossification center (SOC). The reason for such spatial separation remains unknown. Here, we demonstrate that evolutionarily SOC first appears in amniotes. Mathematical modelling reveals that SOC reduces mechanical stress within the growth plate. Analysis of mammals with specialized extremities reveals that SOC size correlates with the extent of mechanical demands. Ex and in vivo experiments demonstrate that SOC allows epiphyseal chondrocytes to withstand a several-fold higher load before activation of the YAP-p73 signalling pathway and caspase-dependent apoptosis, with hypertrophic chondrocytes being the most load-sensitive cells. Atomic force microscopy shows that hypertrophic chondrocytes are the least mechanically stiff cells within the growth plate. Altogether, these findings suggest that SOC is evolved to protect epiphyseal chondrocytes, especially the hypertrophic chondrocytes, from the high mechanical stress encountered in the terrestrial environment.
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| 15. |
- Zetterqvist, Anna, et al.
(author)
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Nuclear Factor of Activated T Cells Is Activated in the Endothelium of Retinal Microvessels in Diabetic Mice.
- 2015
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In: Journal of Diabetes Research. - : Hindawi Limited. - 2314-6753 .- 2314-6745. ; 2015
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Journal article (peer-reviewed)abstract
- The pathogenesis of diabetic retinopathy (DR) remains unclear but hyperglycemia is an established risk factor. Endothelial dysfunction and changes in Ca(2+) signaling have been shown to precede the onset of DR. We recently demonstrated that high extracellular glucose activates the Ca(2+)/calcineurin-dependent transcription factor NFAT in cerebral arteries and aorta, promoting the expression of inflammatory markers. Here we show, using confocal immunofluorescence, that NFAT is expressed in the endothelium of retinal microvessels and is readily activated by high glucose. This was inhibited by the NFAT blocker A-285222 as well as by the ectonucleotidase apyrase, suggesting a mechanism involving the release of extracellular nucleotides. Acute hyperglycemia induced by an IP-GTT (intraperitoneal glucose tolerance test) resulted in increased NFATc3 nuclear accumulation and NFAT-dependent transcriptional activity in retinal vessels of NFAT-luciferase reporter mice. In both Akita (Ins2(+/-) ) and streptozotocin- (STZ-) induced diabetic mice, NFAT transcriptional activity was elevated in retinal vessels. In vivo inhibition of NFAT with A-285222 decreased the expression of OPN and ICAM-1 mRNA in retinal vessels, prevented a diabetes driven downregulation of anti-inflammatory IL-10 in retina, and abrogated the increased vascular permeability observed in diabetic mice. Results identify NFAT signaling as a putative target for treatment of microvascular complications in diabetes.
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