527 research outputs found
Performance of LED fluorescence microscopy for the detection of acid-fast bacilli from respiratory samples in peripheral laboratories in Argentina
No full textIntroduction: Light-emitting diode fluorescence microscopy (LED-FM) has been endorsed by the World Health Organization (WHO) for tuberculosis diagnosis, but its accuracy in HIV-infected patients remains controversial, and only some few studies have explored procedural factors that may affect its performance.
Objective: To evaluate the performance of LED-FM for tuberculosis diagnosis in patients with and without HIV infection using a newer, less expensive LED lamp.
Materials and methods: We compared the performance of LED-FM and Ziehl-Neelsen (ZN) microscopy on respiratory specimen smears from tuberculosis (TB) suspects and patients on treatment examined by different technicians blinded for HIV-status and for the result of the comparative test. We analyzed the effect of concentrating specimens prior to microscopy using different examination schemes and user-appraisal of the LED device.
Results: Of the 6,968 diagnostic specimens collected, 869 (12.5%) had positive Mycobacterium tuberculosis cultures. LED-FM was 11.4% more sensitive than ZN (p<0.01). Among HIV-positive TB patients, sensitivity differences between LED-FM and ZN (20.6%) doubled the figure obtained in HIVnegative patients or in those with unknown HIV status (9.3%). After stratifying by direct and concentrated slides, the superiority of LED-FM remained. High specificity values were obtained both with LED-FM
(99.9%) and ZN (99.9%).The second reading of a sample of slides showed a significantly higher positive detection yield using 200x magnification (49.4 %) than 400x magnification (33.8%) (p<0.05). The LEDdevice had a very good acceptance among the technicians.
Conclusion: LED-FM better performance compared with ZN in HIV-infected patients and user-appraisal support the rapid roll-out of LED-FM. Screening at 200x magnification was essential to achieve LEDFM increased sensitivity
Advanced Fluorescence Microscopy Techniques-FRAP, FLIP, FLAP, FRET and FLIM
No full textFluorescence microscopy provides an efficient and unique approach to study fixed and living cells because of its versatility, specificity, and high sensitivity. Fluorescence microscopes can both detect the fluorescence emitted from labeled molecules in biological samples as images or photometric data from which intensities and emission spectra can be deduced. By exploiting the characteristics of fluorescence, various techniques have been developed that enable the visualization and analysis of complex dynamic events in cells, organelles, and sub-organelle components within the biological specimen. The techniques described here are fluorescence recovery after photobleaching (FRAP), the related fluorescence loss in photobleaching (FLIP), fluorescence localization after photobleaching (FLAP), Forster or fluorescence resonance energy transfer (FRET) and the different ways how to measure FRET, such as acceptor bleaching, sensitized emission, polarization anisotropy, and fluorescence lifetime imaging microscopy (FLIM). First, a brief introduction into the mechanisms underlying fluorescence as a physical phenomenon and fluorescence, confocal, and multiphoton microscopy is given. Subsequently, these advanced microscopy techniques are introduced in more detail, with a description of how these techniques are performed, what needs to be considered, and what practical advantages they can bring to cell biological research
Towards a Successful Clinical Implementation of Fluorescence-Guided Surgery
No full textDuring the European Molecular Imaging Meeting (EMIM) 2013, the fluorescence-guided surgery study group held its inaugural session to discuss the clinical implementation of fluorescence-guided surgery. The general aim of this study group is to discuss and identify the steps required to successfully and safely bring intraoperative fluorescence imaging to the clinics. The focus group intends to use synergies between interested groups as a tool to address regulatory and implementation hurdles in Europe and operates within the intraoperative focus group of the World Molecular Imaging Society (WMIS) that promotes the same interests at the WMIS level. The major topics on the critical path of implementation identified within the study group were quality controls and standards for ensuring accurate imaging and the ability to compare results from different studies, regulatory affairs, and strategies to increase awareness among physicians, regulators, insurance companies, and a broader audience. These hurdles, and the possible actions discussed to overcome them, are summarized in this report. Furthermore, a number of recommendations for the future shape of the fluorescence-guided study group are discussed. A main driving conclusion remains that intraoperative imaging has great clinical potential and that many of the solutions required are best addressed with the community working together to optimally promote and accelerate the clinical implementation of fluorescence imaging towards improving surgical procedures
Towards a successful clinical implementation of fluorescence-guided surgery.
No full textDuring the European Molecular Imaging Meeting (EMIM) 2013, the fluorescence-guided surgery study group held its inaugural session to discuss the clinical implementation of fluorescence-guided surgery. The general aim of this study group is to discuss and identify the steps required to successfully and safely bring intraoperative fluorescence imaging to the clinics. The focus group intends to use synergies between interested groups as a tool to address regulatory and implementation hurdles in Europe and operates within the intraoperative focus group of the World Molecular Imaging Society (WMIS) that promotes the same interests at the WMIS level. The major topics on the critical path of implementation identified within the study group were quality controls and standards for ensuring accurate imaging and the ability to compare results from different studies, regulatory affairs, and strategies to increase awareness among physicians, regulators, insurance companies, and a broader audience. These hurdles, and the possible actions discussed to overcome them, are summarized in this report. Furthermore, a number of recommendations for the future shape of the fluorescence-guided study group are discussed. A main driving conclusion remains that intraoperative imaging has great clinical potential and that many of the solutions required are best addressed with the community working together to optimally promote and accelerate the clinical implementation of fluorescence imaging towards improving surgical procedures
Solution and Fluorescence Properties of Symmetric Dipicolylamine-Containing Dichlorofluorescein-Based Zn[superscript 2+] Sensors
No full textThe mechanism by which dipicolylamine (DPA) chelate-appended fluorophores respond to zinc was investigated by the synthesis and study of five new analogues of the 2′,7′-dichlorofluorescein-based Zn[superscript 2+] sensor Zinpyr-1 (ZP1). With the use of absorption and emission spectroscopy in combination with potentiometric titrations, a detailed molecular picture has emerged of the Zn[superscript 2+] and H[superscript +] binding properties of the ZP1 family of sensors. The two separate N[subscript 3]O donor atom sets on ZP1 converge to form binding pockets in which all four heteroatoms participate in coordination to either Zn[superscript 2+] or protons. The position of the pyridyl group nitrogen atom, 2-pyridyl or 4-pyridyl, has a large impact on the fluorescence response of the dyes to protons despite relatively small changes in pK[subscript a] values. The fluorescence quenching effects of such multifunctional electron-donating units are often taken as a whole. Despite the structural complexity of ZP1, however, we provide evidence that the pyridyl arms of the DPA appendages participate in the quenching process, in addition to the contribution from the tertiary nitrogen amine atom. Potentiometric titrations reveal ZP1 dissociation constants (K[subscript d]) for Zn[superscript 2+] of 0.04 pM and 1.2 nM for binding to the first and second binding pockets of the ligand, respectively, the second of which correlates with the value observed by fluorescence titration. This result demonstrates that both binding pockets of this symmetric, ditopic sensor need to be occupied in order for full fluorescence turn-on to be achieved. These results have significant implications for the design and implementation of fluorescent sensors for studies of mobile zinc ions in biology.National Institute of General Medical Sciences (U.S.) (Grant GM065519)National Institutes of Health (U.S.) (Grant 1S10RR13886-01
A MIQE-Compliant Real-Time PCR Assay for Aspergillus Detection
No full textPMCID: PMC3393739This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
Electron Beam-Induced Fluorescence Localization : Implementation and Feasibility in Integrated Light-Electron Microscopy
No full textCorrelative light-electron microscopy (CLEM) combines the molecular specificity of fluorescence microscopy (FM) with the ultrastructural resolution of electron microscopy (EM) to provide functional information in the context of structural detail. However, the correlation between the two modalities is hindered by a 100-fold resolution gap. Superresolution fluorescence microscopy (SR-FM) has enabled more accurate correlation in CLEM, aided by advancements in sample preparation, bimodal registration, and optimized workflows. As the resolution of FM approaches that of EM, SR-FM becomes increasingly challenging due to the need for accurate registration and preservation of fluorophore properties during EM sample preparation. Integrated microscopes can remove the need for external alignment markers and achieve high registration accuracies, eliminating sample deformations and facilitating SR-CLEM. Yet, this necessitates samples that are simultaneously amenable to both FM and EM. While advancements are being made to engineer fixation-resistant fluorescent proteins and develop preparation protocols for preserving in-resin fluorescence, it is worth exploring the possibilities of the unified platform that integrated light-electron microscopy offers, especially for SR-FM. In caseswhere traditional SR-FM cannot be used due to vacuum or other limitations, the combination of both light and electron microscopy can provide valuable multi-modal information. It also enables central control of the experimental system, thereby offering new ways to manipulate, process, and interpret fluorescence data. This thesis aims to investigate and utilize luorescent response to electron irradiation using integrated light-electronmicroscopy....ImPhys/Hoogenboom grou
Dispensary level pilot implementation of rapid diagnostic tests: an evaluation of RDT acceptance and usage by providers and patients--Tanzania, 2005.
No full textBACKGROUND\ud
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Malaria rapid diagnostic tests (RDTs) may assist in diagnosis, improve prescribing practices and reduce potential drug resistance development. Without understanding operational issues or acceptance and usage by providers and patients, the costs of these tests may not be justified.\ud
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OBJECTIVES\ud
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To evaluate the impact of RDTs on prescribing behaviours, assess prescribers' and patients' perceptions, and identify operational issues during implementation.\ud
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METHODS\ud
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Baseline data were collected at six Tanzanian public dispensaries. RDTs were implemented for eight weeks and data collected on frequency of RDT use, results, malaria diagnoses and the prescription of antimalarials. Patients referred for RDTs completed a standardised exit interview. Qualitative methods assessed attitudes toward and satisfaction with RDTs, perceptions about the test and operational issues related to implementation.\ud
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RESULTS\ud
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Of 595 patients at baseline, 200 (33%) were diagnosed clinically with malaria but had a negative RDT. Among the 2519 RDTs performed during implementation, 289 (11.5%) had a negative result and antimalarials prescribed. The proportion of "over-prescriptions" at baseline was 54.8% (198/365). At weeks four and eight this decreased to 16.1% (27/168) and 16.4% (42/256) respectively.A total of 355 patient or parent/caregiver and 21 prescriber individual interviews and 12 focus group discussions (FGDs) were conducted. Patients, caregivers and providers trusted RDT results, agreed that use of RDTs was feasible at dispensary level, and perceived that RDTs improved clinical diagnosis. Negative concerns included community suspicion and fear that RDTs were HIV tests, the need for additional supervision in interpreting the results, and increased work loads without added compensation.\ud
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CONCLUSION\ud
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Overprescriptions decreased over the study period. There was a high degree of patient/caregiver and provider acceptance of and satisfaction with RDTs. Implementation should include community education, sufficient levels of training and supervision and consideration of the need for additional staff
FPGA implementation of a 32x32 autocorrelator array for analysis of fast image series
No full textWith the evolving technology in CMOS integration, new classes of 2D-imaging detectors have recently become available. In particular, single photon avalanche diode (SPAD) arrays allow detection of single photons at high acquisition rates (? 100kfps), which is about two orders of magnitude higher than with currently available cameras. Here we demonstrate the use of a SPAD array for imaging fluorescence correlation spectroscopy (imFCS), a tool to create 2D maps of the dynamics of fluorescent molecules inside living cells. Time-dependent fluorescence fluctuations, due to fluorophores entering and leaving the observed pixels, are evaluated by means of autocorrelation analysis. The multi-? correlation algorithm is an appropriate choice, as it does not rely on the full data set to be held in memory. Thus, this algorithm can be efficiently implemented in custom logic. We describe a new implementation for massively parallel multi-? correlation hardware. Our current implementation can calculate 1024 correlation functions at a resolution of 10?s in real-time and therefore correlate real-time image streams from high speed single photon cameras with thousands of pixels.MicroelectronicsElectrical Engineering, Mathematics and Computer Scienc
Excitation-dependent fluorescence from atomic/molecular layer deposited sodium-uracil thin films
No full text| openaire: EC/FP7/339478/EU//LAYERENG-HYBMATAtomic/molecular layer deposition (ALD/MLD) offers unique possibilities in the fabrication of inorganic-organic thin films with novel functionalities. Especially, incorporating nucleobases in the thin-film structures could open new avenues in the development of bio-electronic and photonic devices. Here we report an intense blue and widely excitation-dependent fluorescence in the visible region for ALD/MLD fabricated sodium-uracil thin films, where the crystalline network is formed from hydrogen-bonded uracil molecules linked via Na atoms. The excitation-dependent fluorescence is caused by the red-edge excitation shift (REES) effect taking place in the red-edge of the absorption spectrum, where the spectral relaxation occurs in continuous manner as demonstrated by the time-resolved measurements.Peer reviewe
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