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Diffusion in the extracellular space (ECS) of the brain is constrained by the volume fraction and the tortuosity and a modified diffusion equation represents the transport behavior of many molecules in the brain. Deviations from the equation reveal loss of molecules across the blood-brain barrier, through cellular uptake, binding, or other mechanisms. Early(More)
The structure of brain extracellular space resembles foam. Diffusing molecules execute random movements that cause their collision with membranes and affect their concentration distribution. By measuring this distribution, the volume fraction (alpha) and the tortuosity (lambda) can be estimated. The volume fraction indicates the relative amount of(More)
Extracellular space volume fraction, tortuosity and nonspecific uptake of tetramethylammonium--three diffusion parameters of brain tissue--were measured in gray matter of the somatosensory neocortex and subcortical white matter of the rat during postnatal development. The three parameters were determined from concentration-time profiles of(More)
Extrasynaptic communication between neurons or neurons and glia is mediated by the diffusion of neuroactive substances in the volume of the extracellular space (ECS). The size and irregular geometry of the diffusion channels in the ECS substantially differ not only around individual cells but also in different CNS regions and thus affect and direct the(More)
We provide evidence for anisotropic diffusion in rat corpus callosum and hippocampus. The preferential diffusion pathway in corpus callosum is along the myelinated axon fibres; in the hippocampus diffusion is easier along the transversal axis (x) than along the sagittal (y) or vertical (z) axes. In all areas studied, i.e. in the cortex, corpus callosum and(More)
Changes in extracellular space (ECS) diffusion parameters in astrogliotic tissue around a unilateral cortical stab wound were determined from concentration-time profiles of tetramethylammonium (TMA(+)) using TMA(+)-selective microelectrodes. Three diffusion parameters-ECS volume fraction alpha (alpha = ECS volume/ total tissue volume), tortuosity lambda(More)
Emerging clinical studies of treating brain and spinal cord injury (SCI) with autologous adult stem cells led us to compare the effect of an intravenous injection of mesenchymal stem cells (MSCs), an injection of a freshly prepared mononuclear fraction of bone marrow cells (BMCs) or bone marrow cell mobilization induced by granulocyte colony stimulating(More)
Diffusion anisotropy was investigated in the developing rat brain [postnatal day (P)6-29] with the use of ion-selective microelectrodes to measure the three-dimensional distribution of tetramethylammonium (TMA+) iontophoresed into the extracellular space (ECS). The diffusion parameters, ECS volume fraction alpha (alpha = ECS volume/total tissue volume),(More)