In our experiments on rats we performed visualization of brain clearing from substances injected into the brain parenchyma using optical coherent tomography and fluorescence microscopy. Our results uncovered that the meningeal lymphatic system play an important role in the brain clearing processes, where the deep cervical lymph node is the first anatomical station of cerebral fluid exist from the brain. These data shed light on the novel mechanisms underlying drainage and clearing function of the brain.
Fluorescent methods are widely used in studies of the physiology of the brain in general, and in the analysis of the degree of permeability of the blood-brain barrier (BBB) in particular. As recent experimental data show, the spatial patterns of the BBB opening, on the one hand, observed for the whole brain, and on the other, they can be highly localized if one track their from the very beginning. We consider the issues related to image analysis from the point of view of the classification of flowrescent objects, and also propose a technology for simulating BBB leakage based on layer-by-layer modeling of the diffusion process in a heterogeneous spatial template created directly from experimental data.
The development of novel technologies for the imaging of meningeal lymphatic vessels is one of the amazing trends of biophotonics thanks to discovery of brain lymphatics over several years ago. However, there is the limited technologies exist for the study of lymphatics in vivo because lymphatic vessels are transparent with a low speed flow of lymph. Here we demonstrate the successful application of fluorescent microscopy for the imaging of lymphatic system in the mouse brain in vivo.
Here we studied the role of cerebral lymphatic system in the brain clearing using intraparenchymal injection of Evans Blue and gold nanorods assessed by optical coherent tomography and fluorescence microscopy. Our data clearly show that the cerebral lymphatic system plays an important role in the brain cleaning via meningeal lymphatic vessels but not cerebral veins. Meningeal lymphatic vessels transport fluid from the brain into the deep cervical node, which is the first anatomical “station” for lymph outflow from the brain. The lymphatic processes underlying brain clearing are more slowly vs. peripheral lymphatics. These results shed light on the lymphatic mechanisms responsible for brain clearing as well as interaction between the intra- and extracranial lymphatic compartment.
The main research objective is the development of innovative optical technologies for sensitive diagnosis of early stages of development of stomach cancer and monitoring of stress-induced appearance and development of tumors of the gastrointestinal tract by applying endogenous and exogenous fluorescence spectroscopy modalities.
Different mechanisms solely and in combination for evaluation of the joint impact of bioenvironmental factors (stress, Helicobacter pillory, exo-toxins in the food, water, soil and air) were applied to induce gastrointestinal tract (GIT) neoplasia in rats. The transformation of damaged areas of the stomach mucosa into malignancies in all parts of gastrointestinal tract were detected using exogenous fluorescence of photosensitizers - 5-aminolevulinic acid (5-ALA) and aluminum phthalocyanine (Al-Pc). Fluorescent mapping of different organs (liver, spleen, lungs, brain) also was developed – to evaluate the distribution of the photosensitizers in the whole body on the second hour after photosensitizer application by intravenous injection. Fiber-optic probe was used to measure the organs investigated. Fluorescence spectra were detected by microspectrometer USB4000 (OceanOptics Inc., USA), and FS405 LED source on 405 nm was used as excitation source for both types of photosensitizers applied.
Diagnostically-important parameters of oximetry, optical coherence tomography and speckle-imaging of the microcirculation of the stomach were also evaluated, to evaluate changes in the blood flow and vascular architecture, during the formation of the initial phases of the neoplasm development.
Fluorescent angiography approach in application to a living chicken embryo is discussed. It provides precise vessel wall detection and demonstrates usefulness for real time monitoring of vasoconstriction and vasodilatation related to self regulation of vascular network as well as to response to external factors. On the other hand, high stability of fluorescence and long period of dye elimination makes variations of fluorescent intensity practically independent from fast variations of blood flow rate. Therefore, we proposed the improvement of fluorescent angiography technique by introduction of photobleaching fluorescent velocimetry approach. We have developed the imaging system for intravital microscopic photobleaching velocimetry and tested it by using a glass capillary tube as a model of blood vessel. We demonstrated high potential of the technique for instant flow velocity distribution profile measurement with high spatial and temporal resolution up to 2 μm and 60 ms, respectively.
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