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Jacques Boutet de Monvel

Publications and source records attributed to Jacques Boutet de Monvel.

6 recordsLinked to original sources
PubMed2004

Measuring hearing organ vibration patterns with confocal microscopy and optical flow.

A new method for visualizing vibrating structures is described. The system provides a means to capture very fast repeating events by relatively minor modifications to a standard confocal microscope. An acousto-optic modulator was inserted in the beam path, generating brief pulses of laser light. Images were formed by summing consecutive frames until every pixel of the resulting image had been exposed to a laser pulse. Images were analyzed using a new method for optical flow computation; it was validated through introducing artificial displacements in confocal images. Displacements in the range of 0.8 to 4 pixels were measured with 5% error or better. The lower limit for reliable motion detection was 20% of the pixel size. These methods were used for investigating the motion pattern of the vibrating hearing organ. In contrast to standard theory, we show that the organ of Corti possesses several degrees of freedom during sound-evoked vibration. Outer hair cells showed motion indicative of deformation. After acoustic overstimulation, supporting cells contracted. This slowly developing structural change was visualized during simultaneous intense sound stimulation and its speed measured with the optical flow technique.

Acoustic Stimulation↗
PubMed2003

Image-adaptive deconvolution for three-dimensional deep biological imaging.

Deconvolution algorithms are widely used in conventional fluorescence microscopy, but they remain difficult to apply to deep imaging systems such as confocal and two-photon microscopy, due to the practical difficulty of measuring the system's point spread function (PSF), especially in biological experiments. Since a separate PSF measurement performed under the design optical conditions of the microscope cannot reproduce the true experimental conditions prevailing in situ, the most natural approach to solve the problem is to extract the PSF from the images themselves. We investigate here the approach of cropping an approximate PSF directly from the images, by exploiting the presence of small structures within the samples under study. This approach turns out to be practical in many cases, allowing significantly better restorations than with a design PSF obtained by imaging fluorescent beads in gel. We demonstrate the advantages of this approach with a number of deconvolution experiments performed both on artificially blurred and noisy test images, and on real confocal images taken within an in vitro preparation of the mouse hearing organ.

Algorithms↗
PubMed2003

On-line monitoring of apoptosis in insulin-secreting cells.

Apoptosis was monitored in intact insulin-producing cells both with microfluorometry and with two-photon laser scanning microscopy (TPLSM), using a fluorescent protein based on fluorescence resonance energy transfer (FRET). TPLSM offers three-dimensional spatial information that can be obtained relatively deep in tissues. This provides a potential for future in vivo studies of apoptosis. The cells expressed a fluorescent protein (C-DEVD-Y) consisting of two fluorophores, enhanced cyan fluorescent protein (ECFP) and enhanced yellow fluorescent protein (EYFP), linked by the amino acid sequence DEVD selectively cleaved by caspase-3-like proteases. FRET between ECFP and EYFP in C-DEVD-Y could therefore be monitored on-line as a sensor of caspase-3 activation. The relevance of using caspase-3 activation to indicate beta-cell apoptosis was demonstrated by inhibiting caspase-3-like proteases with Z-DEVD-fmk and thereby showing that caspase-3 activation was needed for high-glucose-and cytokine-induced apoptosis in the beta-cell and for staurosporine-induced apoptosis in RINm5F cells. In intact RINm5F cells expressing C-DEVD-Y and in MIN6 cells expressing the variant C-DEVD-Y2, FRET was lost at 155 +/- 23 min (n = 9) and 257 +/- 59 min (n = 4; mean +/- SE) after activation of apoptosis with staurosporine (6 micromol/l), showing that this method worked in insulin-producing cells.

Animals↗
PubMed2002

Internal shearing within the hearing organ evoked by basilar membrane motion.

The vibration of the hearing organ that occurs during sound stimulation is based on mechanical interactions between different cellular structures inside the organ of Corti. The exact nature of these interactions is unclear and subject to debate. In this study, dynamic structural changes were produced by stepwise alterations of scala tympani pressure in an in vitro preparation of the guinea pig temporal bone. Confocal images were acquired at each level of pressure. In this way, the motion of several structures could be observed simultaneously with high resolution in a nearly intact system. Images were analyzed using a novel wavelet-based optical flow estimation algorithm. Under these conditions, the reticular lamina moved as a stiff plate with a center of rotation in the region of the inner hair cells. Despite being enclosed in several types of supporting cells, the inner hair cells, together with the adjacent inner pillar cells, moved in a manner signifying high compliance. The outer hair cells displayed radial motion indicative of cellular bending. Together, these results show that shearing motion occurs between several parts of the organ, and that structural relationships within the organ change dynamically during displacement of the basilar membrane.

Animals↗
PubMedDate not supplied

Exploring the living cochlea using confocal microscopy.

To obtain a more integrated view of the cellular behaviour of the cochlea it is essential to observe not only wider regions of the exposed turns but also to visualize structures below the reticular lamina. Using confocal microscopy and in vitro preparations of guinea pig and mouse inner ears, cellular structures within the intact organ of Corti can be visualized at high resolution. The approach thus offers a means to investigate detailed cellular events, e.g. structural reorganization following acoustic overstimulation. Confocal microscope images, although sharper than images acquired using regular light microscopy, are still subject to problems related to light scattering within the optical system and low signal-to-noise ratio. Significant image restoration can, however, be obtained by applying a combination of wavelet denoising techniques and deconvolution algorithms. Future work will focus both on more dynamical cellular events and on new in vivo models where the inner ear is visualized at a better functional state.

Animals↗