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Biomedical subjects

L Moreaux

Publications and source records attributed to L Moreaux.

7 recordsLinked to original sources
PubMed2003

Electro-optic response of second-harmonic generation membrane potential sensors.

We quantify and ascertain the nature of the second-harmonic generation (SHG) response of amphiphilic push-pull chromophores to a transmembrane electric field. Our technique is based on the application of an alternating field across labeled giant unilamelar vesicles. For chromophore responses that are purely electro-optic, our technique provides an estimate of photoinduced charge shifts based on the observed dispersion of the field response, in accord with a two-level perturbation theory. These results are applicable to the optimization of membrane potential sensors for SHG microscopy.

Cell Physiological Phenomena↗
PubMed2001

Odor-evoked calcium signals in dendrites of rat mitral cells.

Mitral cell dendrites do more than passively integrate and convey synaptic potentials to the soma, they release transmitter onto local interneurones to mediate recurrent and lateral inhibition. Several mechanisms may control the level of dendritic intracellular calcium ([Ca(2+)]) and define timing for dendritic release. Here we investigated in vivo, how odor controls calcium dynamics in mitral cell dendrites by combining intracellular recording and two-photon microscopy imaging of [Ca(2+)]. During odor stimulation, two types of [Ca(2+)] changes accompany membrane potential oscillations that are phase-locked with the respiratory cycle: (i) one is graded and parallels the membrane potential, even below the threshold for action potential firing; (ii) a second is transient, triggered by sodium action potentials that invade the entire dendritic tree. These results indicate that mitral cell dendritic compartments are synchronized by action potentials and suggest that the efficacy of dendritic synapses is finely tuned by odor-evoked graded changes in [Ca(2+)].

Action Potentials↗
PubMed2001

Coherent scattering in multi-harmonic light microscopy.

By focusing a pulsed laser beam into a sample, harmonic up-conversion can be generated as well as multi-photon excited fluorescence. Whereas multi-photon excited fluorescence microscopy is well established, the use of multi-harmonic generation for three-dimensional image contrast is very recent. Both techniques can provide similar resolution and, for adequate radiating source density, comparable signal levels, allowing them to be combined in a single versatile instrument. However, harmonic generation differs fundamentally from fluorescence generation in that it is coherent and produces radiation patterns that are highly sensitive to phase. As such, multi-harmonic generation microscopy provides a unique window into molecular spatial organization that is inaccessible to fluorescence.

Animals↗
PubMed1999

Dynamics of transient pores in stretched vesicles.

We image macroscopic transient pores in mechanically stretched giant vesicles. Holes open above a critical radius r(c1), grow up to a radius r(c2), and close. We interpret the upper limit r(c2) by a relaxation of the membrane tension as the holes expand. The closing of the holes is caused by a further relaxation of the surface tension when the internal liquid leaks out. A dynamic model fits our data for the growth and closure of pores.

Cell Membrane Permeability↗