Laser interference microscopy: a novel approach to the visualization of structural changes in myelin during the propagation of nerve impulses

Abstract

We used 3D phase images obtained by laser interference microscopy (LIM) for ex vivo evaluation of changes in the structure of myelin during repetitive stimulation. In this work we propose a simple model of myelinated nerve fiber (mNF), which describes phase images as a result of different geometry and membrane-to-cytoplasm ratio in various regions, particularly, the internode and paranodal–nodal–paranodal region, including the node of Ranvier. Application of this model provides clear interpretation of the phase images and also demonstrates that repetitive action potentials are accompanied by structural changes in myelin in the internode and cytoplasmic modification in the node of Ranvier. The first 20 min of stimulation did not induce significant changes in the measured parameters, but then the optical path difference at the periphery of mNF and at the node of Ranvier declined reversibly. We believe that our model is also applicable to other modifications of interference and non-interference imaging.

Heat damage of cytoskeleton in erythrocytes increases membrane roughness and cell rigidity

“…This type of a microscopic examination provides a quantitative evaluation of an optical path difference at each point of a phase image (PI) [14,15,[25][26][27][28]. Therefore, PI is a 2D projection of the OPD of a 3D object.…”

Acetylcholine as a trigger of the somatic exocytosis in Retzius neurons

“…In contrast to traditional optical microscopy, based on recording the distribution of light intensity, the DPM makes it possible to determine directly the optical phase difference (OPD) distribution in an interference image. The optical system of DPM consists of a modified Linnik interferometer with a coherent light source (helium -neon laser, λ=633.3nm, 1.5 mWt) and a dissector image tube acting as a coordinate-sensitive photo detector [17] The parameters of OPD measurements were: a size of the view field 128×128 p (20 × 20 μm), time of measurement t = 14.7 s. A line for scanning of length 40 p (6.1 microns) was chosen across a cell in its various areas and periodic measurements of OPD phase heights . CC-BY 4.0 International license bioRxiv a license to display the preprint in perpetuity.…”