| 1. |
- Widén, Anna, et al.
(författare)
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Nutrient balancing or spring flush – What determines spruce bark stripping level by red deer?
- 2022
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Ingår i: Forest Ecology and Management. - Amsterdam : Elsevier. - 0378-1127 .- 1872-7042. ; 520
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Tidskriftsartikel (refereegranskat)abstract
- The distribution and population density of red deer (Cervus elaphus) are increasing in several regions of Europe. The deer may cause severe damage in commercial forestry and agriculture. Bark stripping is the main problem in forests, especially on Norway spruce (Picea abies), and is thought to mostly occur during winter when other forage is scarce. It has been suggested that an imbalance in the nutrient intake, and especially a diet including high amounts of easily-digestible macronutrients, such as agricultural crops, can lead to an increased urge to consume bark. Feeding on brassicas, for example rapeseed (Brassica napus) might have this effect. The aim with this study was to investigate the relationship between intake of rapeseed and bark stripping on Norway spruce by red deer during early spring. We did this by a controlled feeding experiment with four groups of captive red deer in southern Sweden. All groups were given spruce logs every week, while only two groups had access to freshly harvested rapeseed plants. In addition, influence of air temperature and forage nutritional composition was taken into account. Our results show that red deer bark stripping can be considerable not only during winter but also during spring green-up. We found no significant influence of rapeseed on bark stripping performed by the deer. However, at a threshold temperature, deer suddenly started to ingest large amounts of bark biomass, coinciding with a significant change in the bark's concentration of starch. We suggest that the lack of effect of rapeseed feeding can partly be explained by overshadowing effects caused by such seasonal changes of bark characteristics, and partly by the fact that the rapeseed plants in our study contained lower than expected concentrations of easily-digestible macronutrients (apart from protein). We conclude that the risk of damage on spruce can be especially high during certain periods, something that is important to consider when mitigating bark stripping. However, several interactive effects are involved and must be considered in order to more efficiently mitigate damage. © 2022 The Author(s)
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| 2. |
- Leuzy, Antoine, et al.
(författare)
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Derivation and utility of an A beta-PET pathology accumulation index to estimate A beta load
- 2020
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Ingår i: Neurology. - : LIPPINCOTT WILLIAMS & WILKINS. - 0028-3878 .- 1526-632X. ; 95:21, s. E2834-E2844
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Tidskriftsartikel (refereegranskat)abstract
- Objective To evaluate a novel beta-amyloid (A beta)-PET-based quantitative measure (A beta accumulation index [A beta index]), including the assessment of its ability to discriminate between participants based on A beta status using visual read, CSF A beta(42)/A beta(40), and post-mortem neuritic plaque burden as standards of truth. Methods One thousand one hundred twenty-one participants (with and without cognitive impairment) were scanned with A beta-PET: Swedish BioFINDER, n = 392, [F-18]flutemetamol; Alzheimer's Disease Neuroimaging Initiative (ADNI), n = 692, [F-18]florbetapir; and a phase 3 end-of-life study, n = 100, [F-18] flutemetamol. The relationships between A beta index and standardized uptake values ratios (SUVR) from A beta-PET were assessed. The diagnostic performances of A beta index and SUVR were compared with visual reads, CSF A beta(42)/A beta(40), and A beta histopathology used as reference standards. Results Strong associations were observed between A beta index and SUVR (R-2: BioFINDER 0.951, ADNI 0.943, end-of-life, 0.916). Both measures performed equally well in differentiating A beta-positive from A beta-negative participants, with areas under the curve (AUCs) of 0.979 to 0.991 to detect abnormal visual reads, AUCs of 0.961 to 0.966 to detect abnormal CSF A beta(42)/A beta(40), and AUCs of 0.820 to 0.823 to detect abnormal A beta histopathology. Both measures also showed a similar distribution across postmortem-based A beta phases (based on anti-A beta 4G8 antibodies). Compared to models using visual read alone, the addition of the A beta index resulted in a significant increase in AUC and a decrease in Akaike information criterion to detect abnormal A beta histopathology. Conclusion The proposed A beta index showed a tight association to SUVR and carries an advantage over the latter in that it does not require the definition of regions of interest or the use of MRI. A beta index may thus prove simpler to implement in clinical settings and may also facilitate the comparison of findings using different A beta-PET tracers. Classification of evidence This study provides Class III evidence that the A beta accumulation index accurately differentiates A beta-positive from A beta-negative participants compared to A beta-PET visual reads, CSF A beta(42)/A beta(40), and A beta histopathology.
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| 3. |
- Lillja, Johan, et al.
(författare)
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Correlative image analysis for in-depth chemical analysis using multiple parallelized mass spectrometry imaging with high resolution and MSn
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Attaining specificity in mass spectrometry imaging (MSI) is challenging and often results in longer experimental runtime or lower spatial resolution. Herein we describe a novel method for acquisition of MS2 spectra in an ion trap parallel with high resolution accurate mass FTMS scans. Using the nanospray desorption electrospray ionization (nano-DESI) ion source for MSI, we were able to perform 28 MS2 events in an ion trap simultaneously to recording a transient for FTMS. This allowed for deep characterization of the targeted compounds and allowed for improved annotation by spatially correlating the FTMS and ITMS2 data. By combining the data streams from data with different specificities we were able to efficiently data mine the complex data set and could annotate several lipid species.
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| 4. |
- Lillja, Johan, et al.
(författare)
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Determination of Monounsaturated Fatty Acid Isomers in Biological Systems by Modeling MS3 Product Ion Patterns
- 2020
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Ingår i: Journal of the American Society for Mass Spectrometry. - WASHINGTON DC USA : American Chemical Society (ACS). - 1044-0305 .- 1879-1123. ; 31:12, s. 2479-2487
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Tidskriftsartikel (refereegranskat)abstract
- Unsaturated free fatty acids are natively present in biological samples as isomers, where double bonds can be situated on different carbons in the acyl chain. While these isomers can have different actions and impacts on biological systems, they are inherently difficult to identify and differentiate by mass spectrometry alone. To address this challenge, several techniques for derivatization of the double bond or metal cationization at the carboxylic group have yielded diagnostic product ions for the respective isomer in tandem mass spectrometry. However, diagnostic product ions do not necessarily reflect quantitative isomeric ratios since fatty acid isomers have different ionization and fragmentation efficiencies. Here, we introduce a simple and rapid approach to predict the quantitative ratio of isomeric monounsaturated fatty acids. Specifically, empirically derived MS3 product ion patterns from fatty acid silver adducts are modeled using a stepwise linear model. This model is then applied to predict the proportion oleic and vaccenic acid in chemically complex samples at individual concentrations between 0.45 and 5.25 mu M, with an average accuracy and precision below 2 and 5 mol %, respectively. We show that by simply including silver ions in the electrospray solvent, isomeric ratios are rapidly predicted in neat standards, rodent plasma, and tissue extract. Furthermore, we use the method to directly map isomeric ratios in tissue sections using nanospray desorption electrospray ionization MS3 imaging without any sample preparation or modification to the instrumental setup. Ultimately, this approach provides a simple and rapid solution to differentiate monounsaturated fatty acids using commonly available commercial mass spectrometers without any instrumental modifications.
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| 5. |
- Lillja, Johan, et al.
(författare)
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Ion-to-Image, i2i, a Mass Spectrometry Imaging Data Analysis Platform for Continuous Ionization Techniques
- 2023
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 95:31, s. 11589-11595
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Tidskriftsartikel (refereegranskat)abstract
- Mass spectrometry imaging (MSI) techniques generate data that reveal spatial distributions of molecules on a surface with high sensitivity and selectivity. However, processing large volumes of mass spectrometry data into useful ion images is not trivial. Furthermore, data from MSI techniques using continuous ionization sources where data are acquired in line scans require different data handling strategies compared to data collected from pulsed ionization sources where data are acquired in grids. In addition, for continuous ionization sources, the pixel dimensions are influenced by the mass spectrometer duty cycle, which, in turn, can be controlled by the automatic gain control (AGC) for each spectrum (pixel). Currently, there is a lack of data-handling software for MSI data generated with continuous ionization sources and AGC. Here, we present ion-to-image (i2i), which is a MATLAB-based application for MSI data acquired with continuous ionization sources, AGC, high resolution, and one or several scan filters. The source code and a compiled installer are available at https://github.com/LanekoffLab/i2i. The application includes both quantitative, targeted, and nontargeted data processing strategies and enables complex data sets to be processed in minutes. The i2i application has high flexibility for generating, processing, and exporting MSI data both from simple full scans and more complex scan functions interlacing MSn and SIM scan data sets, and we anticipate that it will become a valuable addition to the existing MSI software toolbox.
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| 6. |
- Lillja, Johan
(författare)
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Novel strategies to increase throughput and differentiate lipid isomers in mass spectrometry imaging : Development of computational tools and complex mass spectrometric methods for nanospray desorption electrospray ionization
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis, method development for improved analyte identification and throughput in mass spectrometry imaging (MSI) is discussed. In MSI, the spatial distribution of analytes from a sample is determined and visualized, information about the detected molecules interaction within the sample can thereby the deduced. Most MSI methods utilize high resolution accurate mass (HRAM) to assign an identity to a feature by its mass-to-charge (m/z) value. However, HRAM cannot distinguish isomeric species. I have therefore developed novel tools for annotation and separation of lipid isomer for MSI with nanospray desorption electrospray ionization (nano-DESI). Specifically, I show that tandem mass spectrometry (MSn) of silver ion species of lipids can be used for the separation of both fatty acid and phospholipid isomers. Additionally, I developed a method for parallelized MSn experiments, by performing multiple ion trap MSn in parallel to a fourier transform mass spectrometry (FTMS) transient. The ion trap MSn, albeit with lower resolution, has orthogonal specificity to FTMS and therefore generates a data set where the analytes identity can be deduced. Because the ITMS is executed in parallel to the typically used FTMS scan the imaging parameters are kept constant, thus generating a richer data set without increasing spatial resolution or experimental runtime.Lastly, data sets generated with nano-DESI MSI are complex and require specialized software tools for processing. I also discuss an open-source tool for data processing with high flexibility and fast processing speeds. With the newly developed tool we were able to process and interrogate data sets, thereby making better use of the acquired data.
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| 7. |
- Lillja, Johan, et al.
(författare)
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Quantitative determination of sn-positional phospholipid isomers in MSn using silver cationization
- 2022
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Ingår i: Analytical and Bioanalytical Chemistry. - : Springer. - 1618-2642 .- 1618-2650. ; 414:25, s. 7473-7482
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Tidskriftsartikel (refereegranskat)abstract
- Glycerophospholipids are one of the fundamental building blocks for life. The acyl chain connectivity to the glycerol backbone constitutes different sn-positional isomers, which have great diversity and importance for biological function. However, to fully realize their impact on function, analytical techniques that can identify and quantify sn-positional isomers in chemically complex biological samples are needed. Here, we utilize silver ion cationization in combination with tandem mass spectrometry (MSn) to identify sn-positional isomers of phosphatidylcholine (PC) species. In particular, a labile carbocation is generated through a neutral loss (NL) of AgH, the dissociation of which provides diagnostic product ions that correspond to acyl chains at the sn-1 or sn-2 position. The method is comparable to currently available methods, has a sensitivity in the nM-mu M range, and is compatible with quantitative imaging using mass spectrometry in MS4. The results reveal a large difference in isomer concentrations and the ion images show that the sn-positional isomers PC 18:1_18:0 are homogeneously distributed, whereas PC 18:1_16:0 and PC 20:1_16:0 show distinct localizations to sub-hippocampal structures.
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