Publications
550 results found
Kone M, Sun G, Ibberson M, et al., 2014, LKB1 and AMPK differentially regulate pancreatic beta-cell identity, Faseb Journal, Vol: 28, Pages: 4972-4985, ISSN: 1530-6860
Fully differentiated pancreatic b cellsare essential for normal glucose homeostasis in mammals.Dedifferentiation of these cells has been suggestedto occur in type 2 diabetes, impairing insulinproduction. Since chronic fuel excess (“glucotoxicity”)is implicated in this process, we sought here to identifythe potential roles in b-cell identity of the tumor suppressorliver kinase B1 (LKB1/STK11) and the downstreamfuel-sensitive kinase, AMP-activated proteinkinase (AMPK). Highly b-cell-restricted deletion ofeach kinase in mice, using an Ins1-controlled Cre, wastherefore followed by physiological, morphometric,and massive parallel sequencing analysis. Loss of LKB1strikingly (2.0–12-fold, E<0.01) increased the expressionof subsets of hepatic (Alb, Iyd, Elovl2) and neuronal(Nptx2, Dlgap2, Cartpt, Pdyn) genes, enhancing glutamatesignaling. These changes were partially recapitulatedby the loss of AMPK, which also up-regulated b-cell“disallowed” genes (Slc16a1, Ldha, Mgst1, Pdgfra) 1.8- to3.4-fold (E<0.01). Correspondingly, targeted promoterswere enriched for neuronal (Zfp206; P51.3310233)and hypoxia-regulated (HIF1; P52.5310216) transcriptionfactors. In summary, LKB1 and AMPK, through onlypartly overlapping mechanisms, maintain b-cell identityby suppressing alternate pathways leading to neuronal,hepatic, and other characteristics. Selective targetingof these enzymes may provide a new approach tomaintaining b-cell function in some forms of diabetes.—Kone,M., Pullen, T. J., Sun, G., Ibberson, M.,Martinez-Sanchez, A., Sayers, S., Nguyen-Tu, M.-S.,Kantor, C., Swisa, A., Dor, Y., Gorman, T., Ferrer, J.,Thorens, B., Reimann, F., Gribble, F., McGinty, J. A.,Chen, L., French, P. M., Birzele, F., Hildebrandt, T.,Uphues, I., Rutter, G. A. LKB1 and AMPK differentiallyregulate pancreatic b-cell identity.
Robinson T, Valluri P, Kennedy G, et al., 2014, Analysis of DNA Binding and Nucleotide Flipping Kinetics Using Two-Color Two-Photon Fluorescence Lifetime Imaging Microscopy, Analytical Chemistry, Vol: 86, Pages: 10732-10740, ISSN: 0003-2700
Uracil DNA glycosylase plays a key role in DNA maintenance via base excision repair. Its role is to bind to DNA, locate unwanted uracil, and remove it using a base flipping mechanism. To date, kinetic analysis of this complex process has been achieved using stopped-flow analysis but, due to limitations in instrumental dead-times, discrimination of the “binding” and “base flipping” steps is compromised. Herein we present a novel approach for analyzing base flipping using a microfluidic mixer and two-color two-photon (2c2p) fluorescence lifetime imaging microscopy (FLIM). We demonstrate that 2c2p FLIM can simultaneously monitor binding and base flipping kinetics within the continuous flow microfluidic mixer, with results showing good agreement with computational fluid dynamics simulations.
Chen L, Kumar S, Kelly D, et al., 2014, Remote focal scanning optical projection tomography with an electrically tunable lens, Biomedical Optics Express, Vol: 5, Pages: 3367-3375, ISSN: 2156-7085
We describe a remote focal scanning technique for optical projection tomography (OPT) implemented with an electrically tunable lens (ETL) that removes the need to scan the specimen or objective lens. Using a 4× objective lens the average spatial resolution is improved by ∼46% and the light collection efficiency by a factor of ∼6.76, thereby enabling increased acquisition speed and reduced light dose. This convenient implementation is particularly appropriate for lower magnifications and larger sample diameters where axial objective scanning would encounter problems with speed and stability.
Xavier GDS, Mondragon A, Mitchell R, et al., 2014, Defective glucose homeostasis in mice inactivated selectively for Tcf7l2 in the adult beta cell with an Ins1-controlled Cre, 50th EASD Annual Meeting, Publisher: Springer Verlag (Germany), Pages: S151-S151, ISSN: 1432-0428
Kelly DJ, Warren SC, Kumar S, et al., 2014, An automated multiwell plate reading film microscope for live cell autofluorescence lifetime assays, JOURNAL OF INNOVATIVE OPTICAL HEALTH SCIENCES, Vol: 7, ISSN: 1793-5458
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- Citations: 6
Sonnefraud Y, Sinclair HG, Sivan Y, et al., 2014, Experimental Proof of Concept of Nanoparticle-Assisted STED, NANO LETTERS, Vol: 14, Pages: 4449-4453, ISSN: 1530-6984
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- Citations: 26
Dunsby C, Mcginty J, French P, 2014, Multidimensional fluorescence imaging of biological tissue., Biomedical Photonics Handbook, Pages: 531-560, ISBN: 9781439804445
Marcu L, French PMW, Elson DS, 2014, Preface, Publisher: CRC Press
The text introduces these techniques within the wider context of fluorescence spectroscopy and describes basic principles underlying current instrumentation for fluorescence lifetime imaging and metrology (FLIM).
Marcu L, French P, Elson DS, 2014, Chapter 1: Introduction, Fluorescence Lifetime Spectroscopy and Imaging Principles and Applications in Biomedical Diagnostics, Publisher: CRC Press, ISBN: 9781439861677
The text introduces these techniques within the wider context of fluorescence spectroscopy and describes basic principles underlying current instrumentation for fluorescence lifetime imaging and metrology (FLIM).
Dyer B, Lagarto J, Sikkel M, et al., 2014, THE APPLICATION OF AUTOFLUORESCENCE LIFETIME METROLOGY AS A NOVEL LABEL-FREE TECHNIQUE FOR THE ASSESSMENT OF CARDIAC DISEASE, HEART, Vol: 100, Pages: A104-A104, ISSN: 1355-6037
Gore DM, Margineanu A, French P, et al., 2014, Two-Photon Fluorescence Microscopy of Corneal Riboflavin Absorption, INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE, Vol: 55, Pages: 2476-2481, ISSN: 0146-0404
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- Citations: 27
Gore DM, Margineanu A, French P, et al., 2014, Two-photon fluorescence (TPF) microscopy of corneal riboflavin absorption, Publisher: ASSOC RESEARCH VISION OPHTHALMOLOGY INC, ISSN: 0146-0404
sparks H, warren S, Guedes J, et al., 2014, A flexible wide-field FLIM endoscope utilising blue excitation light for label-free contrast of tissue., Journal of Biophotonics, Vol: 8, Pages: 168-178, ISSN: 1864-0648
Campagnola P, French PMW, Georgakoudi I, et al., 2014, Introduction: feature issue on optical molecular probes, imaging, and drug delivery, BIOMEDICAL OPTICS EXPRESS, Vol: 5, Pages: 643-644, ISSN: 2156-7085
Coda S, Thompson AJ, Kennedy GT, et al., 2014, Fluorescence lifetime spectroscopy of tissue autofluorescence in normal and diseased colon measured ex vivo using a fiber-optic probe, Biomedical Optics Express, Vol: 5, Pages: 515-538, ISSN: 2156-7085
We present an ex vivo study of temporally and spectrally resolved autofluorescence in a total of 47 endoscopic excision biopsy/resection specimens from colon, using pulsed excitation laser sources operating at wavelengths of 375 nm and 435 nm. A paired analysis of normal and neoplastic (adenomatous polyp) tissue specimens obtained from the same patient yielded a significant difference in the mean spectrally averaged autofluorescence lifetime −570 ± 740 ps (p = 0.021, n = 12). We also investigated the fluorescence signature of non-neoplastic polyps (n = 6) and inflammatory bowel disease (n = 4) compared to normal tissue in a small number of specimens.
Marcu L, French PMW, Elson DS, 2014, Preface, ISBN: 9781439861677
Wide-field time-gated fluorescence lifetime imaging (FLIM) essentially entails illuminating a sample with an ultrashort pulse of excitation radiation and sampling the resulting time varying fluorescence “image” following excitation by acquiring a series of gated fluorescence intensity images recorded at different relative delays with respect to the excitation pulse. This is represented schematically in Figure 8.1. In the simplest case, a map of the mean fluorescence decay times across the field of view is obtained. If the sampling of the fluorescence decay profiles is appropriately detailed, then the entire fluorescence decay profile for each image pixel can be acquired, and the resulting data set can be fitted to complex temporal decay models. For example, a double exponential decay model is frequently used to analyze data from Förster resonant energy transfer (FRET) experiments. The acquisition of time-gated fluorescence intensity images requires a 2-D detector, normally a charge-coupled device (CCD) camera, and some kind of fast “shutter” able to sample fluorescence decay profiles on subnanosecond timescales. Such a “shutter” function cannot be provided by mechanical means or yet by electronic circuitry and is typically provided by optical image intensifiers whose gain can be modulated by varying the applied voltage.
Lenz MO, Sinclair HG, Savell A, et al., 2014, 3-D stimulated emission depletion microscopy with programmable aberration correction, Journal of Biophotonics, Vol: 7, Pages: 29-36, ISSN: 1864-063X
We present a stimulated emission depletion (STED) microscope that provides 3‐D super resolution by simultaneous depletion using beams with both a helical phase profile for enhanced lateral resolution and an annular phase profile to enhance axial resolution. The 3‐D depletion point spread function is realised using a single spatial light modulator that can also be programmed to compensate for aberrations in the microscope and the sample. We apply it to demonstrate the first 3‐D super‐resolved imaging of an immunological synapse between a Natural Killer cell and its target cell.
French PMW, 2014, Fluorescence lifetime imaging for biomedicine
I will review our development and application of fluorescence lifetime imaging implemented in microscopy, tomography and endoscopy to provide molecular readouts across the scales from super-resolved microscopy through imaging of disease models to clinical applications. © 2014 OSA.
Dunsby C, McGinty J, French P, 2014, Multidimensional fluorescence imaging of biological tissue, Biomedical Photonics Handbook, Second Edition: Fundamentals, Devices, and Techniques, Pages: 531-560, ISBN: 9781420085129
This chapter aims to review multidimensional fluorescence imaging (MDFI) technology and its application to biological tissue, with a particular emphasis on fluorescence lifetime imaging (FLIM) of biological tissue with examples from our work at Imperial College London. Fluorescence imaging is flourishing tremendously, partly driven by advances in laser and detector technology, partly by advances in labeling technologies such as genetically expressed fluorescent proteins, and partly by advances in computational analysis techniques. Increasingly, fluorescence instrumentation is developed to provide more information than just the localization or distribution of specific fluorescent molecules. Often, fluorescence signals are analyzed to provide information on the local fluorophore environment or to contrast different fluorophores in complex mixtures-as often occur in biological tissue. This trend to higher-content fluorescence imaging increasingly exploits MDFI and measurement capabilities with instrumentation that resolves fluorescence lifetime together with other spectroscopic parameters such as excitation and emission wavelength and polarization, providing image information in two or three spatial dimensions as well as with respect to elapsed time (Figure 18.1). However, caution should be exercised when acquiring such MDFI since photobleaching or experimental considerations usually impose a limited photon budget and/or a maximum image acquisition time and also present significant challenges with respect to data analysis and data management. These considerations are particularly important for real-time clinical diagnostic applications, for higher-throughput assays, and for the investigation of dynamic biological systems (Figure 18.1).
Coda S, French PMW, Dunsby C, 2014, Oncology applications: Gastrointestinal cancer, Fluorescence Lifetime Spectroscopy and Imaging: Principles and Applications in Biomedical Diagnostics, Pages: 379-386, ISBN: 9781439861677
Cancers of esophagus, stomach, and colon are among the most common cancers worldwide, accounting for a total of 2.2 million new cases each year (Boyle and Levin 2008). Prevention of these conditions is currently based on early detection of early-stage cancers or premalignant conditions during conventional white-light endoscopy (WLE). Today, there is a range of more sophisticated biophotonics techniques under development that aim to enhance the contrast of areas of concern beyond what is possible with conventional WLE. Commercially available techniques include high-definition endoscopy (HDE; Adler et al. 2009; Buchner 2010; Rex and Helbig 2007), narrow band imaging (NBI; Gono et al. 2004), magnifying chromoendoscopy (MCE; Kudo et al. 1996), autofluorescence (AF) imaging (AFI; Nakaniwa et al. 2005), and confocal laser endomicroscopy (CLE; Kiesslich et al. 2004; Wang et al. 2007).
Elson DS, Marcu L, French PMW, 2014, Overview of fluorescence lifetime imaging and metrology, ISBN: 9781439861677
This chapter aims to present an overview of fluorescence lifetime imaging (FLIM) and metrology in the context of their biomedical applications, introducing the main approaches that are discussed in detail in subsequent chapters of this book. Before discussing fluorescence lifetime measurements, however, it is important to understand the phenomenon of fluorescence, of which a brief discussion is provided here, and the reader is directed to the classic textbook by Lakowicz (1999) for further details.
French PMW, 2014, Fluorescence lifetime imaging for biomedicine
I will review our development and application of fluorescence lifetime imaging implemented in microscopy, tomography and endoscopy to provide molecular readouts across the scales from super-resolved microscopy through imaging of disease models to clinical applications. © 2014 OSA.
French PMW, 2014, Fluorescence Lifetime Imaging for Biomedicine, 2014 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO), ISSN: 2160-9020
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- Citations: 1
French PMW, 2014, Overview of fluorescence imaging for biophotonics, 181st International School of Physics Enrico Fermi on Microscopy Applied to Biophotonics, Publisher: IOS PRESS, Pages: 1-27, ISSN: 0074-784X
Nickdel MB, Lagarto JL, Kelly DJ, et al., 2014, Autofluorescence lifetime metrology for label-free detection of cartilage matrix degradation, Conference on Optical Biopsy XII, Publisher: SPIE-INT SOC OPTICAL ENGINEERING, ISSN: 0277-786X
Sonnefraud Y, Sivan Y, Sinclair HG, et al., 2014, Nanoparticle-assisted STED, theory, and experimental demonstration, Conference on Nanoimaging and Nanospectroscopy II, Publisher: SPIE-INT SOC OPTICAL ENGINEERING, ISSN: 0277-786X
Xavier GDS, Bellomo EA, McGinty JA, et al., 2013, Animal Models of GWAS-Identified Type 2 Diabetes Genes, Journal of Diabetes Research, Vol: 2013, ISSN: 2314-6753
More than 65 loci, encoding up to 500 different genes, have been implicated by genome-wide association studies (GWAS) as conferring an increased risk of developing type 2 diabetes (T2D). Whilst mouse models have in the past been central to understanding the mechanisms through which more penetrant risk genes for T2D, for example, those responsible for neonatal or maturity-onset diabetes of the young, only a few of those identified by GWAS, notably TCF7L2 and ZnT8/SLC30A8, have to date been examined in mouse models. We discuss here the animal models available for the latter genes and provide perspectives for future, higher throughput approaches towards efficiently mining the information provided by human genetics.
Myatt SS, Kongsema M, Man CW-Y, et al., 2013, SUMOylation inhibits FOXM1 activity and delays mitotic transition, Oncogene, Vol: 33, Pages: 4316-4329, ISSN: 1476-5594
The forkhead box transcription factor FOXM1 is an essential effector of G2/M-phase transition, mitosis and the DNA damage response. As such, it is frequently deregulated during tumorigenesis. Here we report that FOXM1 is dynamically modified by SUMO1 but not by SUMO2/3 at multiple sites. We show that FOXM1 SUMOylation is enhanced in MCF-7 breast cancer cells in response to treatment with epirubicin and mitotic inhibitors. Mutation of five consensus conjugation motifs yielded a SUMOylation-deficient mutant FOXM1. Conversely, fusion of the E2 ligase Ubc9 to FOXM1 generated an auto-SUMOylating mutant (FOXM1-Ubc9). Analysis of wild-type FOXM1 and mutants revealed that SUMOylation inhibits FOXM1 activity, promotes translocation to the cytoplasm and enhances APC/Cdh1-mediated ubiquitination and degradation. Further, expression of the SUMOylation-deficient mutant enhanced cell proliferation compared with wild-type FOXM1, whereas the FOXM1-Ubc9 fusion protein resulted in persistent cyclin B1 expression and slowed the time from mitotic entry to exit. In summary, our findings suggest that SUMOylation attenuates FOXM1 activity and causes mitotic delay in cytotoxic drug response.
Roper JC, Yerolatsitis S, Birks TA, et al., 2013, Minimising group index variations in a multicore endoscope fibre
We describe a multicore endoscope fibre with minimised group index variation between cores that is obtained at a V parameter of 3. Tapering the fibre input enables us to achieve single-mode propagation. © OSA 2013.
Nickdel MB, Lagarto JL, Kelly DJ, et al., 2013, Detection of cartilage matrix degradation by autofluorescence lifetime, Spring Meeting of the British-Society-for-Matrix-Biology, Publisher: WILEY-BLACKWELL, Pages: A12-A13, ISSN: 0959-9673
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