| 1. |
- Beal, Jacob, et al.
(författare)
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Robust estimation of bacterial cell count from optical density
- 2020
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Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data.
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| 2. |
- Botvinik-Nezer, Rotem, et al.
(författare)
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Variability in the analysis of a single neuroimaging dataset by many teams
- 2020
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 582, s. 84-88
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Tidskriftsartikel (refereegranskat)abstract
- Data analysis workflows in many scientific domains have become increasingly complex and flexible. Here we assess the effect of this flexibility on the results of functional magnetic resonance imaging by asking 70 independent teams to analyse the same dataset, testing the same 9 ex-ante hypotheses(1). The flexibility of analytical approaches is exemplified by the fact that no two teams chose identical workflows to analyse the data. This flexibility resulted in sizeable variation in the results of hypothesis tests, even for teams whose statistical maps were highly correlated at intermediate stages of the analysis pipeline. Variation in reported results was related to several aspects of analysis methodology. Notably, a meta-analytical approach that aggregated information across teams yielded a significant consensus in activated regions. Furthermore, prediction markets of researchers in the field revealed an overestimation of the likelihood of significant findings, even by researchers with direct knowledge of the dataset(2-5). Our findings show that analytical flexibility can have substantial effects on scientific conclusions, and identify factors that may be related to variability in the analysis of functional magnetic resonance imaging. The results emphasize the importance of validating and sharing complex analysis workflows, and demonstrate the need for performing and reporting multiple analyses of the same data. Potential approaches that could be used to mitigate issues related to analytical variability are discussed. The results obtained by seventy different teams analysing the same functional magnetic resonance imaging dataset show substantial variation, highlighting the influence of analytical choices and the importance of sharing workflows publicly and performing multiple analyses.
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| 3. |
- Aartsen, M. G., et al.
(författare)
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Very high-energy gamma-ray follow-up program using neutrino triggers from IceCube
- 2016
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Ingår i: Journal of Instrumentation. - 1748-0221. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- We describe and report the status of a neutrino-triggered program in IceCube that generates real-time alerts for gamma-ray follow-up observations by atmospheric-Cherenkov telescopes (MAGIC and VERITAS). While IceCube is capable of monitoring the whole sky continuously, high-energy gamma-ray telescopes have restricted fields of view and in general are unlikely to be observing a potential neutrino-flaring source at the time such neutrinos are recorded. The use of neutrino-triggered alerts thus aims at increasing the availability of simultaneous multi-messenger data during potential neutrino flaring activity, which can increase the discovery potential and constrain the phenomenological interpretation of the high-energy emission of selected source classes (e. g. blazars). The requirements of a fast and stable online analysis of potential neutrino signals and its operation are presented, along with first results of the program operating between 14 March 2012 and 31 December 2015.
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| 4. |
- Alkhori, Liza, et al.
(författare)
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Hh signalling regulates odorant receptor cilia localization in Drosophila
- 2014
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Hedgehog (Hh) signaling is a key regulatory pathway during development. Here, we show that in adult OSNs the Hh pathway regulate ?dorant receptor transport to cilia and put forward a novel non-developmental function of the pathway as a neuromodulator. We demonstrate that the level of Hh signal modulate the OSNs response to odors. We show that knock down of Hh and Smoothened (Smo), a transmembrane protein that transduce the signal, are required for receptor transport. We further show that the coreceptor, Orco, has an Hh independent transport path and that knock down of Smo segregate OR and Orco to different vesicular compartments. Last, we show that the odor response to the second receptor type in Drosophila olfaction, the ionotropic receptors (IRs), also require Hh signalling. Thus, Hh signalling is a general regulator of the odorant response that fulfils the criteria of being a potential player in Drosophila odorant adaptation.
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| 5. |
- Andersson, Arne, et al.
(författare)
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Amyloid Deposition in Transplanted Human Pancreatic Islets : A Conceivable Cause of Their Long-Term Failure
- 2008
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Ingår i: EXPERIMENTAL DIABETES RESEARCH. - : Hindawi Limited. - 1687-5214 .- 1687-5303. ; 2008:562985
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Tidskriftsartikel (refereegranskat)abstract
- Following the encouraging report of the Edmonton group, there was a rejuvenation of the islet transplantation field. After that, more pessimistic views spread when long-term results of the clinical outcome were published. A progressive loss of the beta-cell function meant that almost all patients were back on insulin therapy after 5 years. More than 10 years ago, we demonstrated that amyloid deposits rapidly formed in human islets and in mouse islets transgenic for human IAPP when grafted into nude mice. It is, therefore, conceivable to consider amyloid formation as one potential candidate for the long-term failure. The present paper reviews attempts in our laboratories to elucidate the dynamics of and mechanisms behind the formation of amyloid in transplanted islets with special emphasis on the impact of long-term hyperglycemia.
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| 6. |
- Carlsson, Jonas, et al.
(författare)
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A folding study on IAPP (Islet Amyloid Polypeptide) using molecular dynamics simulations
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Amyloidosis is the largest group among the protein misfolding diseases, and includes well known diseases such as Alzheimer’s disease and type 2 diabetes. In the latter, islet amyloid is present in the pancreas in almost all individuals. Today, more than 25 different proteins have been isolated from amyloid deposits in human. Even though these proteins differ in size, charge and sequence they all have the capacity to assemble in to fibrillar structures with inseparable morphological appearance. Therefore, it can be assumed that the fibril process is based upon principles that are general for all proteins and knowledge derived from one protein can be used for other amyloid proteins. In this paper, we study the process of amyloid formation in parts of islet amyloid polypeptide (residues 18-29 and 11-37) by analyzing mutations using three different in silico methods. Finally, we use the methods to predict the amyloidogenic properties of the native IAPP and 16 variants thereof and compare the result with in vitro measurements. Using a consensus prediction of the three methods we managed to correctly classify all but two peptides. We have also given further evidence to the importance of S28P for inhibiting amyloid fibre formation, found evidence for antiparallel stacking, and identified important regions for beta sheet stability.
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| 7. |
- Hermansson, Erik, et al.
(författare)
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The chaperone domain BRICHOS prevents CNS toxicity of amyloid-beta peptide in Drosophila melanogaster
- 2014
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Ingår i: Disease Models and Mechanisms. - : The Company of Biologists. - 1754-8411 .- 1754-8403. ; 7:6, s. 659-665
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Tidskriftsartikel (refereegranskat)abstract
- Aggregation of the amyloid-beta peptide (A beta) into toxic oligomers and amyloid fibrils is linked to the development of Alzheimer's disease (AD). Mutations of the BRICHOS chaperone domain are associated with amyloid disease and recent in vitro data show that BRICHOS efficiently delays A beta 42 oligomerization and fibril formation. We have generated transgenic Drosophila melanogaster flies that express the A beta 42 peptide and the BRICHOS domain in the central nervous system (CNS). Co-expression of A beta 42 and BRICHOS resulted in delayed A beta 42 aggregation and dramatic improvements of both lifespan and locomotor function compared with flies expressing A beta 42 alone. Moreover, BRICHOS increased the ratio of soluble: insoluble A beta 42 and bound to deposits of A beta 42 in the fly brain. Our results show that the BRICHOS domain efficiently reduces the neurotoxic effects of A beta 42, although significant A beta 42 aggregation is taking place. We propose that BRICHOS-based approaches should be explored with an aim towards the future prevention and treatment of AD.
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| 8. |
- Holland, Petter, et al.
(författare)
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HS1BP3 negatively regulates autophagy by modulation of phosphatidic acid levels
- 2016
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- A fundamental question is how autophagosome formation is regulated. Here we show that the PX domain protein HS1BP3 is a negative regulator of autophagosome formation. HS1BP3 depletion increased the formation of LC3-positive autophagosomes and degradation of cargo both in human cell culture and in zebrafish. HS1BP3 is localized to ATG16L1-and ATG9-positive autophagosome precursors and we show that HS1BP3 binds phosphatidic acid (PA) through its PX domain. Furthermore, we find the total PA content of cells to be significantly upregulated in the absence of HS1BP3, as a result of increased activity of the PA-producing enzyme phospholipase D (PLD) and increased localization of PLD1 to ATG16L1-positive membranes. We propose that HS1BP3 regulates autophagy by modulating the PA content of the ATG16L1-positive autophagosome precursor membranes through PLD1 activity and localization. Our findings provide key insights into how autophagosome formation is regulated by a novel negative-feedback mechanism on membrane lipids.
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| 9. |
- Kuzhandaivel, Anujaianthi, et al.
(författare)
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Cilia-Mediated Hedgehog Signaling in Drosophila
- 2014
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Ingår i: Cell Reports. - : Elsevier. - 2211-1247. ; 7:3, s. 672-680
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Tidskriftsartikel (refereegranskat)abstract
- Cilia mediate Hedgehog (Hh) signaling in vertebrates and Hh deregulation results in several clinical manifestations, such as obesity, cognitive disabilities, developmental malformations, and various cancers. Drosophila cells are nonciliated during development, which has led to the assumption that cilia-mediated Hh signaling is restricted to vertebrates. Here, we identify and characterize a cilia-mediated Hh pathway in Drosophila olfactory sensory neurons. We demonstrate that several fundamental key aspects of the vertebrate cilia pathway, such as ciliary localization of Smoothened and the requirement of the intraflagellar transport system, are present in Drosophila. We show that Cos2 and Fused are required for the ciliary transport of Smoothened and that cilia mediate the expression of the Hh pathway target genes. Taken together, our data demonstrate that Hh signaling in Drosophila can be mediated by two pathways and that the ciliary Hh pathway is conserved from Drosophila to vertebrates.
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| 10. |
- Lozano, Rafael, et al.
(författare)
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Measuring progress from 1990 to 2017 and projecting attainment to 2030 of the health-related Sustainable Development Goals for 195 countries and territories: a systematic analysis for the Global Burden of Disease Study 2017
- 2018
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Ingår i: The Lancet. - : Elsevier. - 1474-547X .- 0140-6736. ; 392:10159, s. 2091-2138
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Tidskriftsartikel (refereegranskat)abstract
- Background: Efforts to establish the 2015 baseline and monitor early implementation of the UN Sustainable Development Goals (SDGs) highlight both great potential for and threats to improving health by 2030. To fully deliver on the SDG aim of “leaving no one behind”, it is increasingly important to examine the health-related SDGs beyond national-level estimates. As part of the Global Burden of Diseases, Injuries, and Risk Factors Study 2017 (GBD 2017), we measured progress on 41 of 52 health-related SDG indicators and estimated the health-related SDG index for 195 countries and territories for the period 1990–2017, projected indicators to 2030, and analysed global attainment. Methods: We measured progress on 41 health-related SDG indicators from 1990 to 2017, an increase of four indicators since GBD 2016 (new indicators were health worker density, sexual violence by non-intimate partners, population census status, and prevalence of physical and sexual violence [reported separately]). We also improved the measurement of several previously reported indicators. We constructed national-level estimates and, for a subset of health-related SDGs, examined indicator-level differences by sex and Socio-demographic Index (SDI) quintile. We also did subnational assessments of performance for selected countries. To construct the health-related SDG index, we transformed the value for each indicator on a scale of 0–100, with 0 as the 2·5th percentile and 100 as the 97·5th percentile of 1000 draws calculated from 1990 to 2030, and took the geometric mean of the scaled indicators by target. To generate projections through 2030, we used a forecasting framework that drew estimates from the broader GBD study and used weighted averages of indicator-specific and country-specific annualised rates of change from 1990 to 2017 to inform future estimates. We assessed attainment of indicators with defined targets in two ways: first, using mean values projected for 2030, and then using the probability of attainment in 2030 calculated from 1000 draws. We also did a global attainment analysis of the feasibility of attaining SDG targets on the basis of past trends. Using 2015 global averages of indicators with defined SDG targets, we calculated the global annualised rates of change required from 2015 to 2030 to meet these targets, and then identified in what percentiles the required global annualised rates of change fell in the distribution of country-level rates of change from 1990 to 2015. We took the mean of these global percentile values across indicators and applied the past rate of change at this mean global percentile to all health-related SDG indicators, irrespective of target definition, to estimate the equivalent 2030 global average value and percentage change from 2015 to 2030 for each indicator. Findings: The global median health-related SDG index in 2017 was 59·4 (IQR 35·4–67·3), ranging from a low of 11·6 (95% uncertainty interval 9·6–14·0) to a high of 84·9 (83·1–86·7). SDG index values in countries assessed at the subnational level varied substantially, particularly in China and India, although scores in Japan and the UK were more homogeneous. Indicators also varied by SDI quintile and sex, with males having worse outcomes than females for non-communicable disease (NCD) mortality, alcohol use, and smoking, among others. Most countries were projected to have a higher health-related SDG index in 2030 than in 2017, while country-level probabilities of attainment by 2030 varied widely by indicator. Under-5 mortality, neonatal mortality, maternal mortality ratio, and malaria indicators had the most countries with at least 95% probability of target attainment. Other indicators, including NCD mortality and suicide mortality, had no countries projected to meet corresponding SDG targets on the basis of projected mean values for 2030 but showed some probability of attainment by 2030. For some indicators, including child malnutrition, several infectious diseases, and most violence measures, the annualised rates of change required to meet SDG targets far exceeded the pace of progress achieved by any country in the recent past. We found that applying the mean global annualised rate of change to indicators without defined targets would equate to about 19% and 22% reductions in global smoking and alcohol consumption, respectively; a 47% decline in adolescent birth rates; and a more than 85% increase in health worker density per 1000 population by 2030. Interpretation: The GBD study offers a unique, robust platform for monitoring the health-related SDGs across demographic and geographic dimensions. Our findings underscore the importance of increased collection and analysis of disaggregated data and highlight where more deliberate design or targeting of interventions could accelerate progress in attaining the SDGs. Current projections show that many health-related SDG indicators, NCDs, NCD-related risks, and violence-related indicators will require a concerted shift away from what might have driven past gains—curative interventions in the case of NCDs—towards multisectoral, prevention-oriented policy action and investments to achieve SDG aims. Notably, several targets, if they are to be met by 2030, demand a pace of progress that no country has achieved in the recent past. The future is fundamentally uncertain, and no model can fully predict what breakthroughs or events might alter the course of the SDGs. What is clear is that our actions—or inaction—today will ultimately dictate how close the world, collectively, can get to leaving no one behind by 2030.
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| 11. |
- Migliano, Simona M., et al.
(författare)
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Removal of hypersignaling endosomes by simaphagy
- 2024
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Ingår i: Autophagy. - : Taylor & Francis. - 1554-8627 .- 1554-8635. ; 20:4, s. 769-791
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Tidskriftsartikel (refereegranskat)abstract
- Activated transmembrane receptors continue to signal following endocytosis and are only silenced upon ESCRT-mediated internalization of the receptors into intralumenal vesicles (ILVs) of the endosomes. Accordingly, endosomes with dysfunctional receptor internalization into ILVs can cause sustained receptor signaling which has been implicated in cancer progression. Here, we describe a surveillance mechanism that allows cells to detect and clear physically intact endosomes with aberrant receptor accumulation and elevated signaling. Proximity biotinylation and proteomics analyses of ESCRT-0 defective endosomes revealed a strong enrichment of the ubiquitin-binding macroautophagy/autophagy receptors SQSTM1 and NBR1, a phenotype that was confirmed in cell culture and fly tissue. Live cell microscopy demonstrated that loss of the ESCRT-0 subunit HGS/HRS or the ESCRT-I subunit VPS37 led to high levels of ubiquitinated and phosphorylated receptors on endosomes. This was accompanied by dynamic recruitment of NBR1 and SQSTM1 as well as proteins involved in autophagy initiation and autophagosome biogenesis. Light microscopy and electron tomography revealed that endosomes with intact limiting membrane, but aberrant receptor downregulation were engulfed by phagophores. Inhibition of autophagy caused increased intra- and intercellular signaling and directed cell migration. We conclude that dysfunctional endosomes are surveyed and cleared by an autophagic process, simaphagy, which serves as a failsafe mechanism in signal termination.
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| 12. |
- Oskarsson, Marie E., et al.
(författare)
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In Vivo Seeding and Cross-Seeding of Localized Amyloidosis A Molecular Link between Type 2 Diabetes and Alzheimer Disease
- 2015
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Ingår i: American Journal of Pathology. - : Elsevier BV. - 0002-9440 .- 1525-2191. ; 185:3, s. 834-846
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Tidskriftsartikel (refereegranskat)abstract
- Several proteins have been identified as amyloid forming in humans, and independent of protein origin, the fibrils are morphologically similar. Therefore, there is a potential for structures with amyloid seeding ability to induce both homologous and heterologous fibril growth; thus, molecular interaction can constitute a Link between different amyloid forms. Intravenous injection with preformed fibrils from islet amyloid polypeptide (IAPP), proIAPP, or amyloid-beta (A beta) into human IAPP transgenic mice triggered IAPP amyloid formation in pancreas in 5 of 7 mice in each group, demonstrating that IAPP amyloid could be enhanced through homologous and heterologous seeding with higher efficiency for the former mechanism. Proximity Ligation assay was used for colocalization studies of IAPP and A beta in islet amyloid in type 2 diabetic patients and A beta deposits in brains of patients with Alzheimer disease. All reactivity was not detected in islet amyloid although islet beta cells express A beta PP and convertases necessary for A beta production. By contrast, IAPP and proIAPP were detected in cerebral and vascular A beta deposits, and presence of proximity Ligation signal at both locations showed that the peptides were <40 nm apart. It is not clear whether IAPP present in brain originates from pancreas or is Locally produced. Heterologous seeding between IAPP and All shown here may represent a molecular Link between type 2 diabetes and Alzheimer disease.
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| 13. |
- Paulsson, Johan F, et al.
(författare)
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Real-Time Monitoring of Apoptosis by Caspase-3-Like Protease Induced FRET Reduction Triggered by Amyloid Aggregation
- 2008
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Ingår i: Experimental Diabetes Research. - : Hindawi Limited. - 1687-5214 .- 1687-5303. ; 2008:865850
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Tidskriftsartikel (refereegranskat)abstract
- Amyloid formation is cytotoxic and can activate the caspase cascade. Here, we monitor caspase-3-like activity as reduction of fluorescence resonance energy transfer (FRET) using the contstruct pFRET2-DEVD containing enhanced cyan fluorescent protin (EYFP) linked by the caspase-3 specific cleavage site residues DEVD. Beta-TC-6 cells were transfected, and the fluoorescence was measured at 440 nm excitation and 535 nm (EYFP) and 480 nm (ECFP) emission wavelength. Cells were incubated with recombinant pro lset Amyloid Polypeptide (rec prolAPP) or the processing metabolites of prolAPP; the N-terminal flanking peptide withIAPP (recN+IAPP); IAPP with the C-terminal flanking peptied (recIAPP+C) and lslet Amyloid Polypeptide (recIAPP). Peptides were added in solubilized from (50 mu M) or as performed amyloid-like fibrils, or as a combination of these. FRET was measured and incubation with a mixture of solubilized peptide and performed fibrils resulted in loss of FRET and apoptosis was determined to occurein cells incubated with recproIAPP (49%), recN+IAPP (46%), recIAPP (72%) and recIAPP+C (59%). These results show that proIAPP and the processing intermediates reside the same cell toxic capacity as IAPP, and they can all have a central role in the reduction of beta-cell number in type 2 diabetes.
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| 14. |
- Paulsson, Johan F, et al.
(författare)
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There is a role for proIAPP in islet amyloid fibrillogenesis
- 2008
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Islet amyloid polypeptide (IAPP) can aggregate into amyloid, a common pathological finding present extracellularly in the islets of Langerhans in individuals with type 2 diabetes. IAPP arises from posttranslational processing of the precursor proIAPP. Accumulation of proIAPP in the secretory granules can result in proIAPP-amyloid formation. We raise the following hypothesis; proIAPP can under not yet defined circumstances aggregate into amyloid-like fibrils intracellularly and at this location act as template and cross-seed amyloid formation of IAPP. We have produced recombinant peptides corresponding to proIAPP and IAPP. These peptides aggregate readily into fibrils with typical amyloid characteristics. Sonicated recproIAPP- and recIAPP- preformed fibrillar aggregates were injected intravenously to +/hIAPP/-mIAPP transgenic mice. Male mice from this strain develop islet amyloid in response to high fat diet. Control animals received an injection of preformed amyloid fibrils from the proinsulin processing intermediate (C-peptide/A-chain) or sodium chloride. All animals were fed a diet high in fat over a ten month period. The presence of islet amyloid was studied after Congo red staining. We found amyloid in 20 % of the islets in animals injected with preformed recIAPP fibrils and in 10 % of the islets in animals injected with preformed recproIAPP fibrils. Control animals developed amyloid in 1-2% of the islets. Our results support the hypothesis that proIAPP-fibrils can act as template and induce conformational changes in soluble IAPP that results in propagation of the amyloid fibrils. This is the first report on in vivo seeding of a localized amyloid form and we present data that support transport of amyloid between islets as a putative route for the spreading of islet amyloid. Our finding suggests that therapies, which use capping of fibril endings, might be useless.
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| 15. |
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| 16. |
- Reichel, Ludwig, et al.
(författare)
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On the origin of perpendicular magnetic anisotropy in strained Fe-Co(-X) films
- 2017
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Ingår i: Journal of Physics D. - : IOP Publishing. - 0022-3727 .- 1361-6463. ; 50:4
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Tidskriftsartikel (refereegranskat)abstract
- Very high magnetic anisotropies have been theoretically predicted for strained Fe-Co(-X) and indeed several experiments on epitaxial thin films seemed to confirm strain induced anisotropy enhancement. This study presents a critical analysis of the different contributions to perpendicular anisotropy: volume, interface and surface anisotropies. Tracing these contributions, thickness series of single layer films as well as multilayers with Au-Cu buffers/interlayers of different lattice parameters have been prepared. The analysis of their magnetic anisotropy reveals a negligible influence of the lattice parameter of the buffer. Electronic effects, originating from both, the Au-Cu interface and the film surface, outrange the elastic effects. Surface anisotropy, however, exceeds the interface anisotropy by more than a factor of three. A comparison with results from Density Functional Theory suggests, that the experimentally observed strong perpendicular surface anisotropy originates from a deviation from an ideal oxide-free surface. Accordingly, tailored Fe-Co-X/oxideinterfaces may open a route towards high anisotropy in rare-earth free materials.
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| 17. |
- Sanchez, Gonzalo Manuel, et al.
(författare)
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Hedgehog Signaling Regulates the Ciliary Transport of Odorant Receptors in Drosophila
- 2016
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Ingår i: Cell Reports. - : CELL PRESS. - 2211-1247. ; 14:3, s. 464-470
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Tidskriftsartikel (refereegranskat)abstract
- Hedgehog (Hh) signaling is a key regulatory pathway during development and also has a functional role in mature neurons. Here, we show that Hh signaling regulates the odor response in adult Drosophila olfactory sensory neurons (OSNs). We demonstrate that this is achieved by regulating odorant receptor (OR) transport to and within the primary cilium in OSN neurons. Regulation relies on ciliary localization of the Hh signal transducer Smoothened (Smo). We further demonstrate that the Hh- and Smo-dependent regulation of the kinesin-like protein Cos2 acts in parallel to the intraflagellar transport system (IFT) to localize ORs within the cilium compartment. These findings expand our knowledge of Hh signaling to encompass chemosensory modulation and receptor trafficking.
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| 18. |
- Schneider, Sebastian, et al.
(författare)
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Magnetic properties of single nanomagnets : Electron energy-loss magnetic chiral dichroism on FePt nanoparticles
- 2016
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Ingår i: Ultramicroscopy. - : Elsevier BV. - 0304-3991 .- 1879-2723. ; 171, s. 186-194
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Tidskriftsartikel (refereegranskat)abstract
- Electron energy-loss magnetic chiral dichroism (EMCD) allows for the quantification of magnetic properties of materials at the nanometer scale. It is shown that with the support of simulations that help to identify the optimal conditions for a successful experiment and upon implementing measurement routines that effectively reduce the noise floor, EMCD measurements can be pushed towards quantitative magnetic measurements even on individual nanoparticles. With this approach, the ratio of orbital to spin magnetic moments for the Fe atoms in a single Ll(0) ordered FePt nanoparticle is determined to be m(l)/m(s) = 0.08 +/- 0.02. This finding is in good quantitative agreement with the results of XMCD ensemble measurements. (C) 2016 Elsevier B.V. All rights reserved.
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| 19. |
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| 20. |
- Schultz, Sebastian, et al.
(författare)
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Drosophila Melanogaster as a Model System for Studies of Islet Amyloid Polypeptide Aggregation
- 2011
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 6:6
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Tidskriftsartikel (refereegranskat)abstract
- Background: Recent research supports that aggregation of islet amyloid polypeptide (IAPP) leads to cell death and this makes islet amyloid a plausible cause for the reduction of beta cell mass, demonstrated in patients with type 2 diabetes. IAPP is produced by the beta cells as a prohormone, and proIAPP is processed into IAPP by the prohormone convertases PC1/3 and PC2 in the secretory granules. Little is known about the pathogenesis for islet amyloid and which intracellular mechanisms are involved in amyloidogenesis and induction of cell death.Methodology/Principal Findings: We have established expression of human proIAPP (hproIAPP), human IAPP (hIAPP) and the non-amyloidogenic mouse IAPP (mIAPP) in Drosophila melanogaster, and compared survival of flies with the expression driven to different cell populations. Only flies expressing hproIAPP in neurons driven by the Gal4 driver elavC(155,Gal4) showed a reduction in lifespan whereas neither expression of hIAPP or mIAPP influenced survival. Both hIAPP and hproIAPP expression caused formation of aggregates in CNS and fat body region, and these aggregates were both stained by the dyes Congo red and pFTAA, both known to detect amyloid. Also, the morphology of the highly organized protein granules that developed in the fat body of the head in hIAPP and hproIAPP expressing flies was characterized, and determined to consist of 15.8 nm thick pentagonal rod-like structures.Conclusions/Significance: These findings point to a potential for Drosophila melanogaster to serve as a model system for studies of hproIAPP and hIAPP expression with subsequent aggregation and developed pathology.
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| 21. |
- Schultz, Sebastian, et al.
(författare)
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Fly model of type 2 diabetes: processing of proIAPP makes a difference
- 2010
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Ingår i: Amyloid. - : Informa Healthcare. - 1350-6129 .- 1744-2818. ; 17:S1, s. 44-45
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Patients with type 2 diabetes have a marked reducedbeta cell mass and fail to produce sufficient amounts of insulin required for regulation of glucose home- ostasis. Recent research supports that intracellular aggregation of islet amyloid polypeptide (IAPP) leads to cell death and therefore makes IAPP aggregation a plausible cause for the beta cell reduction. Little is known about the mechanisms that precede amyloid formation or which cellular pathways are involved in this process. To gain better understanding we haveestablished a Drosophila melanogaster model, where GAL4 drives expression of UAS-targeted transgenes in a cell or tissue specific pattern. The fruit fly offers a unique option to manipulate any cellular pathway with different genetic tools. The knowledge that*70% of all Drosophila melanogaster genes have anorthologue in humans stress the potential for path- ways found in D. melanogaster to be of importance in humans as well. Transgenic flies expressing human proIAPP (the precursor of IAPP) and IAPP and the non-amyloidogenic mouse IAPP (mIAPP) have been generated. Expression of proIAPP in the brain reduced the lifespan of the fly whereas neither IAPP nor mIAPP expression influenced survival. Immu- nolabelling with an antibody raised against human IAPP and that cross-reacts with murine IAPP labelled neurons in all three strains, whereas a concomitant loss of cell nuclei only appeared during proIAPP and IAPP expression. Furthermore, we detected an early potentiated activation of the autophagy pathway in proIAPP flies. Interestingly, even though IAPP expression was not related to a shorter lifespan, both IAPP and proIAPP expression in the central nervous system led to amyloid deposition in the fat body of the head as shown with Congo red and pFTAA, a newly synthesised luminescent conjugated polymer. Our results de- monstrate that D. melanogaster has a great potential as a model for studies of proIAPP and IAPP expression with subsequent amyloid formation and connected cellular response mechanisms. The find- ing that proIAPP aggregation seems to exert a more toxic impact at a cellular level is in line with ourresults from mammalian cell lines.
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| 22. |
- Schultz, Sebastian, et al.
(författare)
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HIAPP and hproIAPP triggers elective autophagy and inhibit the neuro-protective effect of autophagy
- 2010
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Introduction: Amyloid formation is associated with cell death and islet amyloid is thought to participate in the 50-60% β-cell reduction detected in patients with type 2 diabetes. Islet amyloid polypeptide (IAPP) is the main amyloid protein in the islets of Langerhans. Initial IAPP-amyloid formation is intracellular and part of this amyloid constitutes of proIAPP. Material & methods: We have established a new model in Drosophila melanogaster where expression of hproIAPP and IAPP results in the formation of amyloid. With this model, we have investigated the effect of protein aggregation on pathways such as ER-stress, unfolded protein response (UPR), apoptosis and autophagy. Important steps in the different pathways were manipulated by RNAi-technique or over- expression of endogenous Drosophila proteins. Results: Expression of hproIAPP and hIAPP driven to the pdf-neurons led to cell death, but this was without activation of ER-stress, UPR or apoptosis. Aggregated hproIAPP and IAPP, labeled with antibodies against ubiquitin and p62 were accumulated intracellular, a finding that points to an involvement of autophagy. HproIAPP and hIAPP were shown to exert their toxic activity by an intracellular mechanism in contrary to Aβ42 and Aβ42 E22G that exhibit an extracellular toxic activity. Conclusion: Studies on toxicity suggest that hproIAPP and hIAPP aggregates can occupy the autophagy pathway and prevent maintenance of basal cellular homeostasis. Comparison of proIAPP/IAPP and Aβ42 toxicity shows that amyloid proteins of separate origin can exhibit different toxicity.
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| 23. |
- Schultz, Sebastian
(författare)
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Studies on Islet Amyloid Polypeptide Aggregation : From Model Organism to Molecular Mechanisms
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The proper folding of a protein into its defined three--‐dimensional structure is one of the many fundamental challenges a cell encounters. A number of tightly controlled pathways have evolved to assist in the proper folding of a protein, but also to aid in the removal of misfolded proteins. Despite the presence of these pathways accumulation of misfolded proteins can still occur. Amyloid deposits consist of misfolded proteins with a characteristic highly ordered fibrillar structure that will exert affinity for the amyloid dye Congo red and has a unique X-ray diffraction pattern. Currently 27 different proteins have been identified as amyloid forming proteins in human, however the exact role of amyloid in the pathogenesis of the connected disease is most often unclear.Islet amyloid is made up of the beta cell derived hormone islet amyloid polypeptide (IAPP) and is associated with the development of type 2 diabetes. Propagation of IAPP-fibrils is believed to be one important cause of the pancreatic beta cell death detected in patients with type 2 diabetes. IAPP is a naturally occurring polypeptide hormone stored and secreted together with insulin. IAPP and insulin arise from posttranslational processing of their biological inactive precursors proIAPP and proinsulin. In addition to human, cat and monkey IAPP will form amyloid deposits in conditions resembling human type 2 diabetes. However, IAPP from mouse and rat do not form amyloid as a result of the differences in amino acid sequence.My main research goal was to establish a unique model system suitable to study the effects of proIAPP and IAPP aggregation. I selected Drosophila melanogaster due to its many suitable characteristics as a model organism and its superior genetic toolbox. I have demonstrated that over--‐expression of hproIAPP and hIAPP in the central nervous system (CNS) results in aggregate formation in the brain and neighbouring fat body. Consistent with previous studies, expression of mIAPP does not result in the formation of aggregates. To investigate the intracellular effects of hproIAPP and hIAPP aggregation on a specific population of neurons, we targeted the expression of these peptides specifically to 16 neurons in the brain, the pdf- neurons. These pdf-neurons are divided into 2 clusters of 8 cells per brain hemisphere. First I showed that expression of aggregation prone hIAPP and hproIAPP resulted in significant death of the 8 cells, whereas expression of mIAPP had no such effect. In efforts to pinpoint the mechanisms behind the observed cell death I demonstrated that hproIAPP and hIAPP both pass the ERs quality control for protein folding and that the initiated cell death does not occur through classical apoptosis. Instead, selective autophagy is activated by hIAPP and hproIAPP. This activation counteracts the usually neuro-protective effects of autophagy and contributes to cell death. Strikingly, I also showed that Aâ, the amyloid protein implicated in Alzheimer’s disease, does not exhibit any intracellular toxicity when expressed in pdf-cells. This supports the existence of separate toxic pathways for different amyloid proteins.
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