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255 results on '"Marcel Ameloot"'

251. Fast fourier-transform second-harmonic generation (FFT-SHG) provides a solution for measuring nonlinear effects on fragile structures

Author

Dirk De Vos, Inge Asselberghs, Karen Markey, Ventsislav K. Valev, Maarten Vanbel, M. A. van der Veen, Pieterjan Valvekens, Stefaan Vandendriessche, Thierry Verbiest, R. Paesen, Jean-Pierre Locquet, Marcel Ameloot, Ward Brullot, Kang, I, Reitze, D, Alic, N, Hagan, D, and Kang, I.

Subjects
Point spread function, Nonlinear system, Optics, Materials science, business.industry, Fast Fourier transform, Nonlinear optics, Second-harmonic generation, Laser power scaling, business, Polarization (waves), Photon counting
Abstract

The intense laser power required to measure nonlinear effects can damage the structures upon measuring. We demonstrate that fast Fourier-transform second-harmonic generation (FFT-SHG) technique provides an elegant solution to obtain polarization patterns of degrading structures. ispartof: Frontiers in optics ispartof: Frontiers in optics date:6 Oct - 10 Oct 2013 status: published

253. Raster Image Correlation Spectroscopy (RICS) with One Photon Excitation and Analog Detection: Some Practical Considerations for GUVs and Cell Membranes

Author

Martin vandeVen, E. Gielen, B. De Clercq, Marcel Ameloot, and Nick Smisdom

Subjects
Photon, Microscope, Laser scanning, business.industry, Chemistry, Biophysics, computer.file_format, Laser, Noise (electronics), law.invention, Optics, law, Microscopy, Raster graphics, Diffusion (business), business, computer
Abstract

Raster Image Correlation Spectroscopy (RICS) allows for mapping the local translational diffusion coefficient(s). The applicability of the technique has recently been extended by implementation on confocal laser scanning microscopes (CLSM) having one-photon laser excitation and analog detection [1-4]. To better understand the reproducibility and accuracy of RICS analysis of cellular membranes and the top membranes of Giant Unilamellar Vesicles (GUVs) [4], the influence and the constraints imposed by instrumentation characteristics and by sample properties on the retrieved diffusion values have been simulated. Similarly to Brown et al [1], particle numbers in the observation volume and analysis brick size were varied. In addition the workable scan speed range was explored as well as the amount of allowed detection noise. We present evidence for a drop in D values when mapping towards the GUV perimeter and corroborate results when both the total number of particles and the mapping brick size get small. Experimental results show that the magnitude of correlated detection noise in our Zeiss LSM 510 META confocal system (build 2002) along the fast x-scan axis (ψ= 0) is considerably larger than reported by others [1-3]. The effect of omitting the ψ= 0 line in the analysis was investigated. Both the LFD, UCI RICS package as well as our Matlab software based on routines supplied by D. Kolin (McGill University) gave similar simulation and translational diffusion mapping results.[1] Brown 2008, J. Microsc. 229, 78-91.[2] Dalal 2008, Microscopy Research and Technique 71, 69-81.[3] Sanabria 2008, Biophys J doi:10.1529/biophysj.108.138974.[4] Gielen 2008, J. Fluoresc. 18, 813-819.

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254. Fluorescence recovery after photobleaching on the confocal laser-scanning microscope: generalized model without restriction on the size of the photobleached disk.

Author

Nick Smisdom, Kevin Braeckmans, Hendrik Deschout, Martin vandeVen, Jean-Michel Rigo, Stefaan C. De Smedt, and Marcel Ameloot

Subjects
MICROSCOPICAL technique, FLUORESCENCE, BLEACHING (Chemistry), SOLUTION (Chemistry), LEAST squares, CALIBRATION
Abstract

Fluorescence recovery after photobleaching (FRAP) carried out on a confocal laser-scanning microscope (CLSM) performs well for photobleached disks that are large compared to the resolution of the bleaching beam. For smaller disks approaching this resolution, current FRAP models providing a closed-form solution do not allow one to extract the diffusion coefficient accurately. The new generalized disk model we present addresses this shortcoming by bringing into account the bleaching resolution and the total confocal imaging resolution. A closed-form solution is obtained under the assumption of linear photobleaching. Furthermore, simultaneous analysis of FRAP data collected at various disk sizes allows for the intrinsic determination of the instrumental resolution parameters, thereby obviating the need for an extrinsic calibration. A new method to estimate the variance of FRAP data is introduced to allow for proper weighting in this global analysis approach by nonlinear least squares. Experiments are performed on two independent CLSMs on homogeneous samples providing validation over a large range of diffusion coefficients. [ABSTRACT FROM AUTHOR]

Published
2011
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255. Ca2+ uptake in mitochondria occurs via the reverse action of the Na+/Ca2+ exchanger in metabolically inhibited MDCK cells.

Author

Ilse, Smets, Adrian, Caplanusi, Sanda, Despa, Zsolt, Molnar, Mihai, Radu, Martin, VandeVen, Marcel, Ameloot, and Paul, Steels

Abstract

In ischemic o hypoxic tissues, elevated Ca(2+) levels have eme ged as one of the main damaging agents among othe Ca(2+)-independent mechanisms of cellula inju y. Because mitochond ia, besides the endoplasmic eticulum, play a key ole in the maintainance of cellula Ca(2+) homeostasis, alte ations in the mitochond ial Ca(2+) content ([Ca(2+)](m)) we e monito ed in addition to changes in cytosolic Ca(2+) concent ation ([Ca(2+)](i)) du ing metabolic inhibition (MI) in enal epithelial Madin-Da by canine kidney (MDCK) cells. [Ca(2+)](i) and [Ca(2+)](m) we e monito ed via, espectively, fu a 2 and hod 2 measu ements. MI induced an inc ease in [Ca(2+)](i) eaching 631 +/- 78 nM in approximately 20 min, followed by a dec ease to 118 +/- 9 nM in the next approximately 25 min. A p onounced d op in cellula ATP levels and a apid inc ease in int acellula Na(+) concent ations in the fi st 20 min of MI excluded Ca(2+) efflux in the second phase via plasma memb ane ATPases o Na(+)/Ca(2+) exchange s (NCE). Mitochond ial hod 2 intensities inc eased to 434 +/- 46% of the cont ol value du ing MI, indicating that mitochond ia sequeste Ca(2+) du ing MI. The mitochond ial potential (DeltaPsi(m)) was lost in 20 min of MI, excluding mitochond ial Ca(2+) uptake via the DeltaPsi(m)-dependent mitochond ial Ca(2+) unipo te afte 20 min of MI. Unde Na(+)-f ee conditions, o when CGP-37157, a specific inhibito of the mitochond ial NCE, was used, no d op in [Ca(2+)](i) was seen du ing MI, whe eas the MI-induced inc ease in mitochond ial hod 2 fluo escence was st ongly educed. To ou knowledge, this study is the fi st to epo t that in metabolically inhibited enal epithelial cells mitochond ia take up Ca(2+) via the NCE acting in the eve se mode.

Published
2004

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