| 1. |
- Alm, Kersti, et al.
(författare)
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Digital holography and cell studies
- 2011
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Ingår i: Holography, Research and Technologies. - : DKV - Deutscher Kälte- und Klimatechnischer Verein. - 9789533072272 ; , s. 237-252
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Digital holography microscopy (DHM) has developed into a broad field, and one of all the interesting applications is to study cells without staining, labeling or in any other way affecting them. Both fixed and living, dying or dead cells can be studied. The first DHM images showing living cells were published in 2004 and 2005 (Carl et al. 2004, Marquet et al. 2005), making this field of research rather new. Digital holography makes it possible to easily measure cell properties that previously have been very difficult to study, such as cell thickness and volume (Marquet et al. 2005, Mölder et al. 2008). Two of the major advantages of DHM is the 3-D imaging possibility and measurements over time. Digital holography has ben used to study several types of cells, such as nerve cells, red blood cells, stem cells and cancer cells (Emery et al. 2007, Kemper et al. 2006, Langehanenberg et al. 2009) . It has also been applied for studies of cell proliferation, cell movement, sub-cellular structures and cell morphology (Kemper et al. 2009, Yu et al. 2009). Both 2-D and 3-D cell movement can be determined ( Langehanenberg et al. 2009). Even cell viability status can be determined using DHM. Interestingly, it is possible to study both single cells and entire populations simultaneously, allowing for very nuanced studies. Older, well known techniques often require some degree of cell disturbance such as the fluorescent antibody labeling required for fluorescense or confocal microscopy studies. In this paper we will present some of the studies made possible by DHM. We will compare DHM with previously used techniques and discuss the benefits and drawbacks of digital holography cell measurements.
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| 2. |
- El-Schich, Zahra, et al.
(författare)
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Det digitala holografiska mikroskopet : innovativ teknik för analys av levande celler
- 2010
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Ingår i: Bioingenjøren. - : Norges Ingeniør- og Teknologorganisasjon. ; :9, s. 6-13
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Forskningsöversikt (övrigt vetenskapligt/konstnärligt)abstract
- Bakgrund: Digital holografi är en ny teknik som de senaste fem åren använts för att studera levande celler. Tekniken utgör en innovativ, icke-förstörande metod som möjliggör studier av levande celler över tid. Material och metoder: Litteraturen har valts ut genom att söka på redan kända forskargrupper och företag som arbetar både med digital holografi och cellstudier samt PubMed-sökningar. Resultat och sammanfattning: Digital holografi ger kunskap om cellernas brytningsindex, som kan ändras under olika förhållanden. De parametrar som kan mätas ger unik information om cellantal, cellernas area, tjocklek och volym, vilket kan omvandlas till proliferation, viabilitet och celldöd. Tekniken är relativt billig, snabb och enkel att använda.
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| 3. |
- El-Schich, Zahra, et al.
(författare)
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Digital holographic microscopy : innovative and non-destructive analysis of living cells
- 2010
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Ingår i: Microscopy: Science, Technology, Applications and Education. - : Formatex Research Center.
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Digital holography is a novel technique that has been developed recently to study living cells. The technique is an innovative, non-destructive method with possibilities to study living cells over time. We are investigating cell number, growth, viability and death of adherent cells using digital holography, which is a novel, label-free, imaging technique for biological applications. We have recently demonstrated that digital holography is highly comparable to the conventional manual cell counting method using a hemocytometer (Mölder et al., 2008). Digital holography is a method that gives us information about the refractive index of cells, which can change under different circumstances. The technique is cheap, fast and simple to use. The unique measurable parameters are the cell number, cell area, thickness and volume, which can be transformed to proliferation, migration, viability and cell death. The digital holographic images produced can provide both quantitative and qualitative phase information from a single hologram. Future applications can include real-time cell monitoring of various parameters of cells of different diseases in response to clinically relevant compounds.
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| 4. |
- El-Schich, Zahra, et al.
(författare)
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Induction of morphological changes in death-induced cancer cells monitored by holographic microscopy
- 2015
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Ingår i: Journal of Structural Biology. - : Elsevier. - 1047-8477 .- 1095-8657. ; 189:3, s. 207-212
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Tidskriftsartikel (refereegranskat)abstract
- We are using the label-free technique of holographic microscopy to analyze cellular parameters including cell number, confluence, cellular volume and area directly in the cell culture environment. We show that death-induced cells can be distinguished from untreated counterparts by the use of holographic microscopy, and we demonstrate its capability for cell death assessment. Morphological analysis of two representative cell lines (L929 and DU145) was performed in the culture flasks without any prior cell detachment. The two cell lines were treated with the anti-tumour agent etoposide for one to three days. Measurements by holographic microscopy showed significant differences in average cell number, confluence, volume and area when comparing etoposide-treated with untreated cells. The cell volume of the treated cell lines was initially increased at early time-points. By time, cells decreased in volume, especially when treated with high doses of etoposide. In conclusion, we have shown that holographic microscopy allows label-free and completely non-invasive morphological measurements of cell growth, viability and death. Future applications could include real-time monitoring of these holographic microscopy parameters in cells in response to clinically relevant compounds.
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| 5. |
- El-Schich, Zahra, et al.
(författare)
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Quantitative Phase Imaging for Label-Free Analysis of Cancer Cells-Focus on Digital Holographic Microscopy
- 2018
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Ingår i: Applied Sciences. - : MDPI. - 2076-3417. ; 8:7
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Forskningsöversikt (refereegranskat)abstract
- To understand complex biological processes, scientists must gain insight into the function of individual living cells. In contrast to the imaging of fixed cells, where a single snapshot of the cell’s life is retrieved, live-cell imaging allows investigation of the dynamic processes underlying the function and morphology of cells. Label-free imaging of living cells is advantageous since it is used without fluorescent probes and maintains an appropriate environment for cellular behavior, otherwise leading to phototoxicity and photo bleaching. Quantitative phase imaging (QPI) is an ideal method for studying live cell dynamics by providing data from noninvasive monitoring over arbitrary time scales. The effect of drugs on migration, proliferation, and apoptosis of cancer cells are emerging fields suitable for QPI analysis. In this review, we provide a current insight into QPI applied to cancer research.
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| 6. |
- Islam, Md Rafikul, et al.
(författare)
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Projected effects of climate change and forest management on carbon fluxes and biomass of a boreal forest
- 2024
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Ingår i: Agricultural and Forest Meteorology. - 0168-1923. ; 349
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Tidskriftsartikel (refereegranskat)abstract
- Boreal forests are key to global carbon (C) sequestration and storage. However, the potential impacts of climate change on these forests could be profound. Nearly 70 % of the European boreal forests are intensively managed, but our understanding of the combined effects of forest management and climate change on the forest's integral role as a C sink is still limited. In this study, we aim to fill this gap with simulations of the process-based dynamic global vegetation model LPJ-GUESS. We evaluated the effects of four forest management options under two different climate scenarios (RCP 4.5 and RCP 8.5), at a southern boreal forest stand in Sweden. These options were compared against a baseline without clear-cut or management interventions. We found that the projected increase in temperatures (+2 to +4 °C) during the latter part of the 21st century will reduce the net C sink strength, particularly in the unmanaged forest. The standing biomass C for reforestations was projected to be 57–67 % lower in 2100 than in the old forest in 2022. The study also revealed that the C sequestration potential of replanted pine forests may surpass that of 200-years old forests in the far future (2076–2100). The study did not detect statistically significant differences in overall net C exchange between the clear-cut with subsequent reforestation options and the baseline, even though specific reforestation strategies, such as pine plantations, enhanced the overall net C sink by 7–20 % relative to the baseline during 2022–2100. These findings underscore the profound influence of forest management on the net C budget, surpassing that of climate change scenarios alone. By adopting pertinent reforestation strategies, C uptake could be augmented, with concurrently improved forest productivity, resulting in favourable outcomes for the forest's critical role in C sequestration and storage amidst a changing climate.
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| 7. |
- Mölder, Anna Leida, et al.
(författare)
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Supervised classification of etoposide-treated in vitro adherent cells based on noninvasive imaging morphology
- 2017
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Ingår i: Journal of Medical Imaging. - : SPIE - International Society for Optical Engineering. ; 4:2
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Tidskriftsartikel (refereegranskat)abstract
- Single-cell studies using noninvasive imaging is a challenging, yet appealing way to study cellular characteristics over extended periods of time, for instance to follow cell interactions and the behavior of different cell types within the same sample. In some cases, e.g., transplantation culturing, real-time cellular monitoring, stem cell studies, in vivo studies, and embryo growth studies, it is also crucial to keep the sample intact and invasive imaging using fluorophores or dyes is not an option. Computerized methods are needed to improve throughput of image-based analysis and for use with noninvasive microscopy such methods are poorly developed. By combining a set of well-documented image analysis and classification tools with noninvasive microscopy, we demonstrate the ability for long-term image-based analysis of morphological changes in single cells as induced by a toxin, and show how these changes can be used to indicate changes in biological function. In this study, adherent cell cultures of DU-145 treated with low-concentration (LC) etoposide were imaged during 3 days. Single cells were identified by image segmentation and subsequently classified on image features, extracted for each cell. In parallel with image analysis, an MTS assay was performed to allow comparison between metabolic activity and morphological changes after long-term low-level drug response. Results show a decrease in proliferation rate for LC etoposide, accompanied by changes in cell morphology, primarily leading to an increase in cell area and textural changes. It is shown that changes detected by image analysis are already visible on day 1 for [Formula: see text] etoposide, whereas effects on MTS and viability are detected only on day 3 for [Formula: see text] etoposide concentration, leading to the conclusion that the morphological changes observed occur before and at lower concentrations than a reduction in cell metabolic activity or viability. Three classifiers are compared and we report a best case sensitivity of 88% and specificity of 94% for classification of cells as treated/untreated.
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| 8. |
- Mölder, Anna, et al.
(författare)
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Non-invasive, label-free cell counting and quantitative analysis of adherent cells using digital holography
- 2008
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Ingår i: Journal of Microscopy. - : Wiley. - 0022-2720 .- 1365-2818. ; 232:2, s. 240-247
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Tidskriftsartikel (refereegranskat)abstract
- Manual cell counting is time consuming and requires a high degree of skill on behalf of the person performing the count. Here we use a technique that utilizes digital holography, allowing label-free and completely non-invasive cell counting directly in cell culture vessels with adherent viable cells. The images produced can provide both quantitative and qualitative phase information from a single hologram. The recently constructed microscope HolomonitorTM (Phase Holographic Imaging AB, Lund, Sweden) combines the commonly used phase contrast microscope with digital holography, the latter giving us the possibility of achieving quantitative information on cellular shape, area, confluence and optical thickness. This project aimed at determining the accuracy and repeatability of cell counting measurements using digital holography compared to the conventional manual cell counting method using a haemocytometer. The collected datawere also used to determine cell size and cellular optical thickness.Theresults showthat digital holography can be used for non-invasive automatic cell counting as precisely as conventional manual cell counting
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| 9. |
- Tagesson, Torbern, et al.
(författare)
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Modelling of growing season methane fluxes in a high-Arctic wet tundra ecosystem 1997-2010 using in situ and high-resolution satellite data
- 2013
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Ingår i: Tellus. Series B: Chemical and Physical Meteorology. - : Stockholm University Press. - 0280-6509 .- 1600-0889. ; 65
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Tidskriftsartikel (refereegranskat)abstract
- Methane (CH4) fluxes 1997-2010 were studied by combining remotely sensed normalised difference water index (NDWI) with in situ CH4 fluxes from Rylekaerene, a high-Arctic wet tundra ecosystem in the Zackenberg valley, north-eastern Greenland. In situ CH4 fluxes were measured using the closed-chamber technique. Regression models between in situ CH4 fluxes and environmental variables [soil temperature (T-soil), water table depth (WtD) and active layer (AL) thickness] were established for different temporal and spatial scales. The relationship between in situ WtD and remotely sensed NDWI was also studied. The regression models were combined and evaluated against in situ CH4 fluxes. The models including NDWI as the input data performed on average slightly better [root mean square error (RMSE) = 1.56] than the models without NDWI (RMSE = 1.67), and they were better in reproducing CH4 flux variability. The CH4 flux model that performed the best included exponential relationships against temporal variation in T-soil and AL, an exponential relationship against spatial variation in WtD and a linear relationship between WtD and remotely sensed NDWI (RMSE = 1.50). There were no trends in modelled CH4 flux budgets between 1997 and 2010. Hence, during this period there were no trends in the soil temperature at 10 cm depth and NDWI.
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