| 1. |
- Berclaz, Corinne, et al.
(författare)
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Label-free fast 3D coherent imaging reveals pancreatic islet micro-vascularization and dynamic blood flow
- 2016
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Ingår i: Biomedical Optics Express. - 2156-7085. ; 7:11, s. 4569-4580
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Tidskriftsartikel (refereegranskat)abstract
- In diabetes, pancreatic ß-cells play a key role. These cells are clustered within structures called islets of Langerhans inside the pancreas and produce insulin, which is directly secreted into the blood stream. The dense vascularization of islets of Langerhans is critical for maintaining a proper regulation of blood glucose homeostasis and is known to be affected from the early stage of diabetes. The deep localization of these islets inside the pancreas in the abdominal cavity renders their in vivo visualization a challenging task. A fast label-free imaging method with high spatial resolution is required to study the vascular network of islets of Langerhans. Based on these requirements, we developed a label-free and three-dimensional imaging method for observing islets of Langerhans using extended-focus Fourier domain Optical Coherence Microscopy (xfOCM). In addition to structural imaging, this system provides threedimensional vascular network imaging and dynamic blood flow information within islets of Langerhans. We propose our method to deepen the understanding of the interconnection between diabetes and the evolution of the islet vascular network.
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| 2. |
- Berclaz, Corinne, et al.
(författare)
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Longitudinal three-dimensional visualisation of autoimmune diabetes by functional optical coherence imaging.
- 2015
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Ingår i: Diabetologia. - : Springer Science and Business Media LLC. - 1432-0428 .- 0012-186X.
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Tidskriftsartikel (refereegranskat)abstract
- It is generally accepted that structural and functional quantitative imaging of individual islets would be beneficial to elucidate the pathogenesis of type 1 diabetes. We here introduce functional optical coherence imaging (FOCI) for fast, label-free monitoring of beta cell destruction and associated alterations of islet vascularisation.
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| 3. |
- Geissbuehler, Matthias, et al.
(författare)
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Triplet Imaging of Oxygen Consumption during the Contraction of a Single Smooth Muscle Cell (A7r5)
- 2010
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Ingår i: Biophysical Journal. - : Elsevier BV. - 0006-3495 .- 1542-0086. ; 98:2, s. 339-349
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Tidskriftsartikel (refereegranskat)abstract
- The measurement of tissue and cell oxygenation is important for understanding cell metabolism. We have addressed this problem with a novel optical technique, called triplet imaging, that exploits oxygen-induced triplet lifetime changes and is compatible with a variety of fluorophores. A modulated excitation of varying pulse widths allows the extraction of the lifetime of the essentially dark triplet state using a high-fluorescence signal intensity. This enables the monitoring of fast kinetics of oxygen concentration in living cells combined with high temporal and spatial resolution. First, the oxygen-dependent triplet-state quenching of tetramethylrhodamine is validated and then calibrated in an L-ascorbic acid titration experiment demonstrating the linear relation between triplet lifetime and oxygen concentration according to the Stern-Volmer equation. Second, the method is applied to a biological cell system, employing as reporter a cytosolic fusion protein of beta-galactosidase with SNAP-tag labeled with tetramethylrhodamine. Oxygen consumption in single smooth muscle cells A7r5 during an [Arg(8)]-vasopressin-induced contraction is measured. The results indicate a consumption leading to an intracellular oxygen concentration that decays monoexponentially with time. The proposed method has the potential to become a new tool for investigating oxygen metabolism at the single cell and the subcellular level.
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| 4. |
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| 5. |
- Harach, T., et al.
(författare)
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Reduction of Abeta amyloid pathology in APPPS1 transgenic mice in the absence of gut microbiota
- 2017
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- Alzheimer's disease is the most common form of dementia in the western world, however there is no cure available for this devastating neurodegenerative disorder. Despite clinical and experimental evidence implicating the intestinal microbiota in a number of brain disorders, its impact on Alzheimer's disease is not known. To this end we sequenced bacterial 16S rRNA from fecal samples of Aβ precursor protein (APP) transgenic mouse model and found a remarkable shift in the gut microbiota as compared to non-transgenic wild-type mice. Subsequently we generated germ-free APP transgenic mice and found a drastic reduction of cerebral Aβ amyloid pathology when compared to control mice with intestinal microbiota. Importantly, colonization of germ-free APP transgenic mice with microbiota from conventionally-raised APP transgenic mice increased cerebral Aβ pathology, while colonization with microbiota from wild-type mice was less effective in increasing cerebral Aβ levels. Our results indicate a microbial involvement in the development of Abeta amyloid pathology, and suggest that microbiota may contribute to the development of neurodegenerative diseases.
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| 6. |
- Hassler, Kai, et al.
(författare)
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Dynamic disorder in horseradish peroxidase observed with total internal reflection fluorescence correlation spectroscopy
- 2007
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Ingår i: Optics Express. - 1094-4087. ; 15:9, s. 5366-5375
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Tidskriftsartikel (refereegranskat)abstract
- This paper discusses the application of objective-type total internal reflection fluorescence correlation spectroscopy (TIR-FCS) to the study of the kinetics of immobilized horseradish peroxidase on a single molecule level. Objective-type TIR-FCS combines the advantages of FCS with TIRF microscopy in a way that allows for simultaneous ultra-sensitive spectroscopic measurements using a single-point detector and convenient localization of single molecules on a surface by means of parallel imaging.
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| 7. |
- Leutenegger, Marcel, et al.
(författare)
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Dual-color total internal reflection fluorescence cross-correlation spectroscopy
- 2006
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Ingår i: Journal of Biomedical Optics. - : SPIE-Intl Soc Optical Eng. - 1083-3668 .- 1560-2281. ; 11:4
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Tidskriftsartikel (refereegranskat)abstract
- We present the development and first application of a novel dual-color total internal reflection (TIR) fluorescence system for single-molecule coincidence analysis and fluorescence cross-correlation spectroscopy (FCCS). As a performance analysis, we measured a synthetic DNA-binding assay, demonstrating this dual-color TIR-FCCS approach to be a suitable method for measuring coincidence assays such as biochemical binding, fusion, or signal transduction at solid/liquid interfaces. Due to the very high numerical aperture of the epi-illumination configuration, our setup provides a very high fluorescence collection efficiency resulting in a two- to three- fold increase in molecular brightness compared to conventional confocal FCCS. Further improvements have been achieved through global analysis of the spectroscopic data.
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| 8. |
- Nguyen, David, et al.
(författare)
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Optical projection tomography for rapid whole mouse brain imaging
- 2017
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Ingår i: Biomedical Optics Express. - 2156-7085. ; 8:12, s. 5637-5650
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Tidskriftsartikel (refereegranskat)abstract
- In recent years, three-dimensional mesoscopic imaging has gained significant importance in life sciences for fundamental studies at the whole-organ level. In this manuscript, we present an optical projection tomography (OPT) method designed for imaging of the intact mouse brain. The system features an isotropic resolution of ~50 µm and an acquisition time of four to eight minutes, using a 3-day optimized clearing protocol. Imaging of the brain autofluorescence in 3D reveals details of the neuroanatomy, while the use of fluorescent labels displays the vascular network and amyloid deposition in 5xFAD mice, an important model of Alzheimer’s disease (AD). Finally, the OPT images are compared with histological slices.
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| 9. |
- Serov, Alexandre, et al.
(författare)
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Parallel Fluorescence Correlation Spectroscopy with a fully integratedsingle photon 2x2 detector array made with conventional CMOS technology
- 2003
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Ingår i: Optical Technologies in Biophysics and Medicine V. - : SPIE. - 0819453978 ; , s. 248-258
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Konferensbidrag (refereegranskat)abstract
- We present multipoint Fluorescence Correlation Spectroscopy (FCS) experiments with a fully integrated Complementary Metal Oxide Semiconductor (CMOS) single photon 2x2 detector array. Multifocal excitation was achieved with a diffractive optical element (DOE). Special emphasis was put on parallelization of the total system. In particular the performance of the single-photon CMOS detector was investigated and compared to a state-of-the art single-photon detecting module (actively quenched avalanche photo diode) by measurements on free difftising molecules at different concentrations. The potential of our new technique for high throughput FCS based systems is discussed.
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| 10. |
- Spielmann, Thiemo, et al.
(författare)
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Transient State Monitoring by Total Internal Reflection Fluorescence Microscopy
- 2010
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 114:11, s. 4035-4046
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Tidskriftsartikel (refereegranskat)abstract
- Triplet, photo-oxidized and other photoinduced, long-lived states Of fluorophores are sensitive to the local environment and thus attractive for microenvironmental imaging purposes. In this work, we introduce an approach where these states are monitored in a total internal reflection (TIR) fluorescence microscope, via the characteristic variations of the time-averaged fluorescence occuring ill response to different excitation modulation schemes. The surface-confined TIR excitation field generates a signal from the fluorescent molecules Close to the glass surface. Thereby, a high selectivity and low background noise is obtained, and in combination with IOW duty Cycles Of excitation, the overall photodegradation of the fluorescent molecules of the sample call be kept low, To verify the approach. the kinetics of the triplet and radical states of the dye Rhodamine 110 were imaged and analyzed in aqueous solutions at different concentrations of dissolved oxygen and of the reducing agent ascorbic acid. The experimental results Were compared to data from corresponding fluorescence correlation spectroscopy (FCS) measurements and simulations based oil finite element analysis. The approach was found to accurately determine relative populations and dynamics of triplet and photooxidized states, Overcoming passage time limitations seen ill FCS measurements. The method circumvents the need for time resolution ill the fluorescence detection, allowing simultaneous readout over the whole SLII-face area subject to excitation. It call be applied over a broad range of concentrations and does not require I strong fluorescence brightness of the sample molecules. Given the sensitivity of the triplet and photooxidized states to oxygen concentrations and not the least to local redox environments, we expect the approach to become an attractive tool for imaging cell metabolism.
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