Extrasynaptic volume transmission and diffusion parameters of the extracellular space

Neuroscience ◽  
2004 ◽  
Vol 129 (4) ◽  
pp. 861-876 ◽  
Author(s):  
E. Syková
Keyword(s):  
Extracellular Space ◽  
Volume Transmission ◽  
Diffusion Parameters ◽  
And Diffusion

scholarly journals Extracellular space diffusion and extrasynaptic transmission

2008 ◽  
pp. S89-S99
Author(s):  
L Vargová ◽  
E Syková
Keyword(s):  
Extracellular Matrix ◽  
Extracellular Space ◽  
Volume Fraction ◽  
Underlying Mechanism ◽  
Brain Regions ◽  
Diffusion Barriers ◽  
Cell Swelling ◽  
Long Distance ◽  
Diffusion Parameters ◽  
And Diffusion

The diffusion of neuroactive substances in the extracellular space (ECS) plays an important role in short- and long-distance communication between nerve cells and is the underlying mechanism of extrasynaptic (volume) transmission. The diffusion properties of the ECS are described by three parameters: 1. ECS volume fraction alpha (alpha=ECS volume/total tissue volume), 2. tortuosity lambda (lambda2=free/apparent diffusion coefficient), reflecting the presence of diffusion barriers represented by, e.g., fine neuronal and glial processes or extracellular matrix molecules and 3. nonspecific uptake k'. These diffusion parameters differ in various brain regions, and diffusion in the CNS is therefore inhomogeneous. Moreover, diffusion barriers may channel the migration of molecules in the ECS, so that diffusion is facilitated in a certain direction, i.e. diffusion in certain brain regions is anisotropic. Changes in the diffusion parameters have been found in many physiological and pathological states in which cell swelling, glial remodeling and extracellular matrix changes are key factors influencing diffusion. Changes in ECS volume, tortuosity and anisotropy significantly affect the accumulation and diffusion of neuroactive substances in the CNS and thus extrasynaptic transmission, neuron-glia communication, transmitter "spillover" and synaptic cross-talk as well as cell migration, drug delivery and treatment.

scholarly journals Glutamate, NMDA, and AMPA Induced Changes in Extracellular Space Volume and Tortuosity in the Rat Spinal Cord

2001 ◽  
Vol 21 (9) ◽  
pp. 1077-1089 ◽  
Author(s):  
Lýdia Vargová ◽  
Pavla Jendelová ◽  
Alexandr Chvátal ◽  
Eva Syková
Keyword(s):  
Spinal Cord ◽  
Glutamate Receptor ◽  
Extracellular Space ◽  
Volume Fraction ◽  
Glutamate Release ◽  
Extracellular Potassium ◽  
Receptor Agonists ◽  
Diffusion Parameters ◽  
Glutamate Receptor Agonists ◽  
Cellular Swelling

Glutamate release, particularly in pathologic conditions, may result in cellular swelling. The authors studied the effects of glutamate, N-methyl-d-aspartate (NMDA), and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) on extracellular pH (pHe), extracellular potassium concentration ([K+]e), and changes in extracellular space (ECS) diffusion parameters (volume fraction α, tortuosity λ) resulting from cellular swelling. In the isolated spinal cord of 4-to 12-day-old rats, the application of glutamate receptor agonists induced an increase in [K+]e, alkaline-acid shifts, a substantial decrease in α, and an increase in λ. After washout of the glutamate receptor agonists, α either returned to or overshot normal values, whereas λ remained elevated. Pretreatment with 20 mmol/L Mg++, MK801, or CNQX blocked the changes in diffusion parameters, [K+]e and pHe evoked by NMDA or AMPA. However, the changes in diffusion parameters also were blocked in Ca2+-free solution, which had no effect on the [K+]e increase or acid shift. The authors conclude that increased glutamate release may produce a large, sustained and [Ca2+]e-dependent decrease in α and increase in λ. Repetitive stimulation and pathologic states resulting in glutamate release therefore may lead to changes in ECS volume and tortuosity, affecting volume transmission and enhancing glutamate neurotoxicity and neuronal damage.

scholarly journals Regularity, Asymptotic Solutions and Travelling Waves analysis in a porous medium system to model the interaction between invasive and invaded species

2021 ◽  
Author(s):  
José Díaz ◽  
Antonio Naranjo
Keyword(s):  
Porous Medium ◽  
Travelling Waves ◽  
Stationary Solutions ◽  
Uniqueness Of Solutions ◽  
Linear Diffusion ◽  
Diffusion Parameters ◽  
Medium System ◽  
Topological Argument ◽  
And Diffusion ◽  
Stable Connection

This work provides an analytical approach to characterize and determine solutions to a porous medium system of equations with views in applications to invasive-invaded biological dynamics. Firstly, the existence and uniqueness of solutions are proved. Afterwards, profiles of solutions are obtained making use of the selfsimilar structure that permits to show the existence of a diffusive front. The solutions are then studied within the Travelling Waves (TW) domain showing the existence of potential and exponential profiles in the stable connection that converges to the stationary solutions in which the invasive specie predominates. The TW profiles are shown to exist based on the geometry perturbation theory together with an analytical-topological argument in the phase plane. The finding of an exponential decaying rate (related with the advection and diffusion parameters) in the invaded specie TW is not trivial in the non-linear diffusion case and reflects the existence of a TW trajectory governed by the invaded specie runaway (in the direction of the advection) and the diffusion (acting along a finite speed front or support).

scholarly journals On FTCS Approach for Box Model of Three-Dimension Advection-Diffusion Equation

2018 ◽  
Vol 2018 ◽  
pp. 1-9
Author(s):  
Jeffry Kusuma ◽  
Agustinus Ribal ◽  
Andi Galsan Mahie
Keyword(s):  
Mathematical Model ◽  
Three Dimension ◽  
Sand Mining ◽  
Mining Pollution ◽  
Advection Diffusion Equation ◽  
Advection Diffusion ◽  
Diffusion Parameters ◽  
Sea Sand ◽  
And Diffusion ◽  
Pollution Distribution

This paper describes a numerical solution for mathematical model of the transport equation in a simple rectangular box domain. The model of street tunnel pollution distribution using two-dimension advection and three-dimension diffusion is solved numerically. Because of the nature of the problem, the model is extended to become three-dimension advection and three-dimension diffusion to study the sea-sand mining pollution distribution. This model with various advection and diffusion parameters and the boundaries conditions is also solved numerically using a finite difference (FTCS) method.

Determination of sorption and diffusion parameters of 99Tc in crushed granite using through-diffusion experiments

2016 ◽  
Vol 311 (2) ◽  
pp. 1111-1116 ◽  
Author(s):  
Yu-Hung Shih ◽  
Tsuey-Lin Tsai ◽  
Liang-Cheng Chen ◽  
Te-Yen Su ◽  
Chuan-Pin Lee ◽  
...  
Keyword(s):  
Diffusion Parameters ◽  
Crushed Granite ◽  
Through Diffusion ◽  
And Diffusion

scholarly journals A Framework for Evaluating Variation in (U-Th)/He Datasets

Minerals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1111
Author(s):  
Francis J. Sousa ◽  
Kenneth A. Farley
Keyword(s):  
Thermal History ◽  
Synthetic Data ◽  
Diffusion Parameters ◽  
Modeling Software ◽  
History Of ◽  
Single Grain ◽  
Thermal Histories ◽  
The Impact ◽  
And Diffusion ◽  
New Framework

This paper presents a framework for evaluating variation in (U-Th)/He datasets. The framework is objective, repeatable, and based on compatibility of thermal histories derived from individual (U-Th)/He dates. The structure of this new method includes three fundamental steps. First, the allowable thermal history of each individual grain is quantitatively constrained with a model. Second, the thermal histories of all grains from a sample are visualized on the same axes. Third, the compatibility of the allowable thermal histories of each individual grain is evaluated. This allows a user to assess whether variation among single grain dates can plausibly be explained (referred to here as legitimate) or not (illegitimate). Additionally, this methodology allows for accurate representation of the impact that illegitimate variation has on the thermal history constraints of a sample. We demonstrate the application of this new framework using a variety of examples from the literature, as well as with synthetic data. Modeling presented here is executed using the modeling software QTQt (version 5.6.0) and the He diffusion kinetics based on the radiation damage accumulation and annealing model, but the framework is designed to be easily adaptable to any modeling software and diffusion parameters.

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