Recent progress in tissue optical clearing for spectroscopic application.

This paper aims to review recent progress in optical clearing of the skin and over naturally turbid biological tissues and blood using this technique in vivo and in vitro with multiphoton microscopy, confocal Raman microscopy, confocal microscopy, NIR spectroscopy, optical coherence tomography, and laser speckle contrast imaging. Basic principles of the technique, its safety, advantages and limitations are discussed. The application of optical clearing agent on a tissue allows for controlling the optical properties of tissue. Optical clearing-induced reduction of tissue scattering significantly facilitates the observation of deep-located tissue regions, at the same time improving the resolution and image contrast for a variety of optical imaging methods suitable for clinical applications, such as diagnostics and laser treatment of skin diseases, mucosal tumor imaging, laser disruption of pathological abnormalities, etc.

[Diffusion of methylene blue in the human maxillary sinus mucosa].

The coefficient of diffusion of methylene blue in pathologically changed human maxillary sinus mucosa in vitro has been estimated for the first time. The mean value of the diffusion coefficient is (4.8 +/- 2.9) x 10(-7) cm2/s. The method is based on the registration of the dynamics of reflectance of tissue samples under the action of the dye. The diffusion coefficient has been estimated by approximation of experimental data in the framework of the model presented.

[Determination of glucose diffusion coefficient in the human eye sclera]. / Opredelenie koéffitsienta diffuzii gliukozy v sklere glaza cheloveka.

The diffusion coefficients of aqueous glucose solutions in human sclera in vitro were estimated. The method is based on measurements of time-dependence of collimated transmittance of scleral samples under the action of biocompatible immersion liquids. It was shown that changes in collimated transmittance are connected with the matching between the indices of refraction of scleral scatterers and interstitial fluid. The dynamics of interstitial fluid replacement was registered by recording successively the collimated transmittance spectra in the range of 400-800 nm. For a quantitative description of the replacement process, a diffusion model was proposed, which assumes that the diffusion coefficient is constant throughout the volume of the scleral sample. Experimental results for glucose solutions of concentrations 0.18, 0.3, and 0.4 g/ml are presented. The diffusion coefficients were estimated by approximating the experimental data in the framework of the proposed model.

[Cholesterol uptake in the small intestine of the rat in experiments in vitro]. / Pogloshchenie kholesterina v tonkom kishechnike krys v opytakh in vitro.

The kinetic and thermodynamic parameters of cholesterol uptake in the small intestine of rats were determined in vitro under normal and hypercholesterolemic conditions. It is established that the cholesterol uptake by the small intestine mucosa is a process of the zero order and the rate of its uptake is constant during the whole period of studies. The cholesterol uptake by mucosa during hypercholesterolemia occurs at a higher rate than under normal conditions. Activation energy for the cholesterol uptake is 10.52 Cal/mol under normal conditions, while it is reduced to 7.9 Cal/mol under experimental hypercholesterolemia. The experimental data permit suggesting that the membrane of the mucous brush border possesses a rather high energy barrier for the cholesterol uptake indicating the active nature of its uptake in the small intestine.