Transcranical photobiomodulation (tPBM, 1267 nm, 32 J/cm2) is effective non-invasive method for clearance of beta-amyloid from the brain in mice with Alzheimer’s disease and for improvemen of their neurological status.
This review highlights two opposing concepts of lymphatics and glymphatics, which are used to explain the drainage and cleansing functions of the brain. "Stumbling blocks" in two concepts and ways of compromise between them are discussed.
Stroke and traumatic brain injury are often associated with formation of brain edema, which is a potentially fatal pathological state provoking extensive accumulation of fluid in the brain tissues resulting in elevation of intracranial pressure and leading to impaired nerve function. There is only symptomatic anti-edema therapy is currently available. Therefore, the development of novel strategies to remove edema fluid is required. The brain edema is classified as vasogenic or cytotoxic edema, which associated with excess accumulation of fluid (edema) around capillaries resulting from disruption of the blood-brain barrier (BBB) or intracellular spaces (cell swelling) of the brain, respectively. In this brief review, we discuss possible mechanisms underlying brain edema formation and new strategies in development of novel of anti-edema drugs.
Here we present preliminary experimental data suggesting about involvement of the meningeal and cervical lymphatics in neurorehabilitation. Using model of hemorrhagic stroke, immunohistochemical analysis and atomic absorption spectroscopy, we clearly demonstrate the lymphatic clearance from the blood after stroke via the meningeal lymphatic vessels with further accumulation of hemosiderin and iron (products of disaggregated hemoglobin) in the deep cervical node (dcLN). The optical coherent tomography (OCT) was used for in vivo monitoring of accumulation of gold nanorods (92 nm in diameter) in the dcLN after their injection into the cisterna magna with the aim of mimicking of the brain clearance from of blood. The both ex vivo and in vivo data show the lymphatic clearance from subjects (the blood/GNRs) injected into the subarachnoid space that might be an important mechanism of neurorehabilitation after the intracranial hemorrhages.
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.
Here we show the interaction between the meningeal lymphatic system and the blood-brain barrier (BBB) function. In normal state, the meningeal lymphatic vessels are invisible on optical coherent tomography (OCT), while during the opening of the BBB, meningeal lymphatic vessels are clearly visualized by OCT in the area of cerebral venous sinuses. These results give a significant impulse in the new application of OCT for the study of physiology of meningeal lymphatic system as well as sheds light on novel strategies in the prognosis of the opening of the BBB related with many central nervous system diseases, such as stroke, brain trauma, Alzheimers disease, etc.
The meningeal lymphatic vessels were discovered 2 years ago as the drainage system involved in the mechanisms underlying the clearance of waste products from the brain. The blood–brain barrier (BBB) is a gatekeeper that strongly controls the movement of different molecules from the blood into the brain. We know the scenarios during the opening of the BBB, but there is extremely limited information on how the brain clears the substances that cross the BBB. Here, using the model of sound-induced opening of the BBB, we clearly show how the brain clears dextran after it crosses the BBB via the meningeal lymphatic vessels. We first demonstrate successful application of optical coherence tomography (OCT) for imaging of the lymphatic vessels in the meninges after opening of the BBB, which might be a new useful strategy for noninvasive analysis of lymphatic drainage in daily clinical practice. Also, we give information about the depth and size of the meningeal lymphatic vessels in mice. These new fundamental data with the applied focus on the OCT shed light on the mechanisms of brain clearance and the role of lymphatic drainage in these processes that could serve as an informative platform for a development of therapy and diagnostics of diseases associated with injuries of the BBB such as stroke, brain trauma, glioma, depression, or Alzheimer disease.
Chronic hypertension itself does not cause stroke but significantly decreases the resistant to stroke induced by
stress due to exhausting of adaptive capacity of cerebral endothelium and decrease resistance of blood-brain
barrier to stress.
We study the noise activated dynamics of a model autapse neuron system that consists of a subcritical Hopf oscillator with
a time delayed nonlinear feedback. The coherence of the noise driven pulses of the neuron exhibits a novel double peaked
structure as a function of the noise amplitude. The two peaks correspond to separate optimal noise levels for excitation of
single spikes and multiple spikes (bursts) respectively. The relative magnitudes of these peaks are found to be a sensitive
function of time delay. The physical significance of our results and its practical implications in various real life systems
are discussed.
A noise-induced signal propagation is reported in oscillatory
media with FitzHugh-Nagumo dynamics which is based on a noise-induced phase transition to excitability. This transition occurs
via a noise-induced suppression of self-excited oscillations, while the overall phase-space structure of the system is maintained. The noise-induced excitability enables the information transport in the originally oscillatory media. We demonstrate this new feature by the propagation of a wave front and the formation of a spiral in a two dimensional lattice. These spatio-temporal structures transport information and can be observed only in the presence of suitable amount of noise and not in the deterministic self-sustained oscillatory system. Thus we extend classes of nonlinear systems with signal transmission properties also to oscillatory systems, which demonstrate a noise-induced phase transition to excitability. Further on, the mechanism of noise-induced excitability provides the opportunity to control the information transport by noise via a triggering mechanism, i.e. the information channel is switched on in the presence of noise and switched off in its absence.
KEYWORDS: Diffusion, Homogenization, Stochastic processes, Error control coding, Interference (communication), Chemical reactions, Wave propagation, Systems modeling, Control systems, Information operations
Constructive effects of noise have been well studied in spatially extended systems. In most of these studies, the media are static, reaction-diffusion type, and the constructive effects are a consequence of the interplay between local excitation due to noise perturbation and propagation of excitation due to diffusion. Many chemical or biological processes occur in a fluid environment with mixing. In this paper, we investigate the interplay among noise, excitability, diffusion and mixing in excitable media advected by a chaotic flow, in a 2D Fitz Hugh-Nagumo model described by a set of reaction-advection-diffusion equations. Without stirring, noise can only generate non-coherent excited patches of the static media. In the presence of stirring, we observe three dynamical and pattern formation regimes: (1) Non-coherent excitation, when mixing is not strong enough to achieve synchronization of independent excitations developed at different locations; (2) Coherent global excitation, when the noise-induced perturbation propagates by mixing and generates a synchronized excitation of the whole domain; and (3) Homogenization, when strong stirring dilutes quickly those noise-induced local excitations. In the presence of an external sub-threshold periodic forcing, the period of the noise-sustained oscillations can be locked by the forcing period with different ratios. Our results may be verified in experiments and find applications in population dynamics of oceanic ecological systems.
KEYWORDS: Stochastic processes, Oscillators, Signal to noise ratio, Complex systems, Interference (communication), Bistability, Solids, Statistical analysis, Neurons, Chemical elements
We study nonlinear systems under two noisy sources to demonstrate the concept of doubly stochastic effects. In such effects noise plays a twofold role: first it induces a special feature in the system, and second it interplays with this feature leading to noise-induced order. For this effect one needs to optimize both noisy sources, hence we call these phenomena doubly stochastic effects. To show the generality of this approach we apply this concept to several basic noise-induced phenomena: stochastic resonance, noise-induced propagation and coherence resonance. Additionally, we discuss an application of this concept to noise-induced transitions and ratchets. In all these noise-induced effects ordering occurs due to the joint action of two noisy sources.
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