Time-Dependent Diffusion of Water in a Biological Model System

Packed erythrocytes are ideally suited as a model system for the study of water diffusion in biological tissue, because cell size, membrane permeability, and extracellular volume fraction can be varied independently. We used a pulsed-field-gradient spin echo NMR technique to measure the time-depende...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 1994-02, Vol.91 (4), p.1229-1233
Main Authors: Latour, Lawrence L., Svoboda, Karel, Mitra, Partha P., Sotak, Christopher H.
Format: Article
Language:English
Subjects:
Animals
Biological and medical sciences
Biological Transport
Brain Ischemia
Cattle
Cell Membrane Permeability
Cell membranes
Cell Size
Cellular biology
Diffusion
Diffusion coefficient
Erythrocyte membrane
Erythrocyte Membrane - metabolism
Erythrocytes
Extracellular fluid
Fluid permeability
Fundamental and applied biological sciences. Psychology
General aspects, investigation technics, apparatus
Humans
Magnetic Resonance Spectroscopy - methods
Material concentration
Models, Biological
Models, Theoretical
Physics
Porous materials
Surface Properties
Time dependence
Time Factors
Tissues, organs and organisms biophysics
Ungulates
Water - metabolism
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Summary:Packed erythrocytes are ideally suited as a model system for the study of water diffusion in biological tissue, because cell size, membrane permeability, and extracellular volume fraction can be varied independently. We used a pulsed-field-gradient spin echo NMR technique to measure the time-dependent diffusion coefficient D(t) in packed erythrocytes. The long-time diffusion constant, Deff, depends sensitively on the extracellular volume fraction. This may explain the drop in Deffduring the early stages of brain ischemia, where just minutes after an ischemic insult the extra-cellular volume in the affected region of the brain is significantly reduced. Using an effective medium formula, we estimate the erythrocyte membrane permeability, in good agreement with measurements on isolated cells. From the short-time behavior of D(t), we determine the surface-to-volume ratio of the cells,$\thickapprox$(0.72 μm)-1.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.91.4.1229