NMR “diffusion‐diffraction” of water revealing alignment of erythrocytes in a magnetic field and their dimensions and membrane transport characteristics

Abstract

"Diffusion-diffraction" experiments on water, yielding "q-space" plots, were conducted on suspensions of oxygenated (diamagnetic) human erythrocytes. (i) These suspensions displayed diffusion-diffraction of water; (ii) the shape of the q-space plots depended on the direction along which the diffusion was measured, thus implying alignment of the cells in the magnetic field of the NMR spectrometer; (iii) the diffusion anisotropy was altered in a predictable way by converting the hemoglobin to a paramagnetic form; (iv) the shapes of the q-space plots were altered in a predictable way by inhibiting water transport; (v) the pseudo-first order rate constant characterizing the covalent inhibition of water transport, by p-chloromercuribenzenesulfonate (p-CMBS), was measured; and (vi) the cell diameter and intercellular spacing were measured from the positions of the interference minima and maxima in the q-space plots. The relevance of these findings to NMR-based histological characterization of tissues, and the implications, for magnetic resonance imaging (MRI), of erythrocyte alignment in the small vessels of the brain in particular, are noted.

Erythrocyte‐shape evolution recorded with fast‐measurement NMR diffusion–diffraction

“…From conventional PFGSTE experiments, the minima were at q min1 ϭ 1.9 ϫ 10 5 m Ϫ1 and q min2 ϭ 3.7 ϫ 10 5 m Ϫ1 , whereas for the fast-measurement methods, these minima were at q min1 ϭ 2.0 ϫ 10 5 m Ϫ1 and q min2 ϭ 4.2 ϫ 10 5 m Ϫ1 . These values are related in a simple way to the mean diameter of the cells (8,12) and correspond to an apparent diameter of 6.4 m and 6.9 m, and 6.1 m and 5.8 m, respectively, for classical and fast-measurement experiments. The water restriction effect occurs for low residual water signal, that is, around 0.2% and 0.02% for the first and second minimum, respectively.…”

“…Pulsed-field gradient-stimulated echo (PFGSTE) NMR experiments are able to estimate RBC dimensions and intercellular separation from the "diffusion-diffraction" pattern of water (8). This is achieved from the data representing the NMR signal decay vs. the "spatial wave-number vector" q ϭ (2 ) Ϫ1 ␥ ␦ g, where ␥ is the magnetogyric ratio of the nuclei, ␦ is the duration of the magnetic field gradient pulses used in the experiment, and g is the magnetic field gradient vector of magnitude g. Such a "q-space plot" (9) displays a minimum, then a maximum, and then subsequent minima and maxima (10 -12).…”

Efficient and robust computation of PDF features from diffusion MR signal

“…The hematocrit values are in decreasing order from the top of the figure, starting from a value of 93%, followed by 83,73,63,47,42 and ending at 25% at the bottom of the figure (from Kuchel et al [14]) (b) First basis functions of the radial orthonormal basis R n with scaling factor ζ = 100. Low order n functions exhibits Gaussian attenuation behavior whereas higher order n are helpful to capture oscillating components of the MR signal.…”

“…(1) with the main difference that the latter allows to measure the signal along multiple b values. q-space NMR experiments provides clues of the radial diffusion behavior of solvents and solutes in heterogeneous systems, including yeast cells, human erythrocytes and tissues [9,14,15]. Additionally, q-space NMR enables to validate complex diffusion models such as the impermeable parallel planes method [16,17].…”

Use, misuse, and abuse of apparent diffusion coefficients

“…Balinov and coworkers observed diffraction-like effects in the PGSE experiment when applied to a highly concentrated water-oil emulsion (35). Kuchel et al presented data showing the diffusion-diffraction effect of water in cell suspensions and the ability to determine cell dimension(s) from these data (36). In all these cases, the macroscopic signal as a function of gradient intensity is used to characterize restricted diffusion and a porous medium, without appealing to ADC [see reviews (13)(14)(15) for further details].…”