In situ magnetic resonance imaging of plant roots

Visualization of the root system architecture of plants is possible using a combination of magnetic resonance imaging of water mobility and trac-tography. Diffusion tensor imaging (DTI), a magnetic resonance application, was used to provide a three-dimensional map of water mobility inside a pot containing soil and roots. Tractography generates channels that constitute pathways of facilitated water movement, representing the roots, calculated from water diffusion properties obtained from DTI experiments. Examples of pea (Pisum sativum L.) and corn [Zea mays L. var. indentata (Sturtev.) L.H. Bailey] root growth are provided.Peer reviewed: YesNRC publication: Ye

Improvements in MR imaging of solids through gradient waveform optimization

Magnetic resonance imaging (MRI) is known to provide a useful approach for the exploration of the chemistry and dynamics of a wide range of soft condensed materials. However, its application to solids has been limited to those materials with relatively narrow resonances. The time needed to obtain an image of a solid with a given resolution and signal-to-noise ratio (SNR) is directly proportional to the line width of the resonance. For MRI to become practical for the imaging of solids it will have to rely on the development and use of MR sequences that avoid the issues raised by line broadening of the resonance. In this paper we review the latest contributions towards MR imaging of solids from our laboratory, in particular, applications using optimized gradient waveforms. Acoustic noise reduction and SNR improvement obtained with modifications of the standard single-point imaging sequence are presented and discussed using examples.Peer reviewed: YesNRC publication: Ye

Effects of sodium chloride on plant cells; a 31P and 23Na NMR system to study salt tolerance

Peer reviewed: YesNRC publication: Ye

Characterization of food stuffs using magnetic resonance elastography

Viscoelastic properties of formulated food products are often associated with the textural properties of the material. Plasticity provides an important food quality factor. Unfortunately, viscoelastic properties of food stuffs are normally measured in the bulk phase, prior to packaging. Here we describe the application of a Magnetic Resonance Elastography (MRE) method using a specially designed sample holder for fast, reproducible and non-invasive measurement of spatially averaged viscoelastic constants of packaged samples. MRE experiments provide viscoelastic data as a function of position within samples and can be performed prior and post packaging, on samples including those with an optically opaque container or wrapper.Peer reviewed: YesNRC publication: Ye

A 133Cs Nuclear magnetic resonance study of endothelial Na(+)-K(+)-ATPase activity: can actin regulate its activity?

Using (133)Cs+ NMR, we developed a technique to repetitively measure, in vivo, Na(+)-K(+)-ATPase activity in endothelial cells. The measurements were made without the use of an exogenous shift reagent, because of the large chemical shift of 1.36 +/- 0.13 ppm between intra- and extracellular Cs+. Intracellularly we obtained a spin lattice relaxation time (T1) of 2.0 +/- 0.3 s, and extracellular T1 was 7.9 +/- 0.4 s. Na(+)-K+ pump activity in endothelial cells was determined at 12 +/- 3 nmol Cs+ x min(-1) x (mg Prot)[-1] under control conditions. When intracellular ATP was depleted by the addition of 5 mM 2-deoxy-D-glucose (DOG) and NaCN to about 5% of control, the pump rate decreased by 33%. After 80 min of perfusion with 5 mM DOG and NaCN, reperfusion with control medium rapidly reestablished the endothelial membrane Cs+ gradient. Using (133)Cs+ NMR as a convenient tool, we further addressed the proposed role of actin as a regulator of Na(+)-K+ pump activity in intact cells. Two models of actin rearrangement were tested. DOG caused a rearrangement of F-actin and an increase in G-actin, with a simultaneous decrease in ATP concentration. Cytochalasin D, however, caused an F-actin rearrangement different from that observed for DOG and an increase in G-actin, and cellular ATP levels remained unchanged. In both models, the Na(+)-K(+)-pump activity remained unchanged, as measured with (133)Cs NMR. Our results demonstrate that (133)Cs NMR can be used to repetitively measure Na(+)-K(+)-ATPase activity in endothelial cells. No evidence for a regulatory role of actin on Na(+)-K(+)-ATPase was found.NRC publication: Ye

Bloch simulations with intra-voxel spin dephasing

A common problem in simulations of MRI-experiments based on the numerical solution of the Bloch equations is the finite number of isochromats used in the calculations. This usually results in false or spurious signals and is a source of various differences between calculated and experimentally obtained data. In this paper, we are proposing a technique representing each sample voxel by a central and three additional isochromats, slightly shifted in orthogonal directions from center, thus providing a linear approximation of intra-voxel dephasing. This approach allows for further improvement and precision of the calculated NMR signal and virtually avoids the problem related to an finite set of isochromats. Here we provide details of the algorithm together with examples of simulations which prove the efficiency of this approach.Peer reviewed: YesNRC publication: Ye

Measurement of Water Diffusivities in Barley Components Using Diffusion Weighted Imaging and Validation with a Drying Model

Diffusion-weighted magnetic resonance imaging was used to determine water diffusion coefficients (D) in hull-less barley kernel components (endosperm and embryo) at 20.5\ub10.5\ub0C. The D values in barley components were time-dependent and restricted in nature as indicated by the decrease in the apparent diffusion coefficient with increasing diffusion time (from 3 to 25 ms). A four-parameter Pad\ue9 approximation model was used to estimate D and pore geometry (pore surface area\u2013to-volume ratio, pore size, porosity, electrical conductivity and permeability of water) of the barley components after long diffusion time (t \u2192 1e) using data obtained during a relatively short period of diffusion. The D of embryo and endosperm were 2.2\ub10.07 7 10 125 mm 2 2. Czuchajowska , Z. ; Klamczynski , A. ; Paszczynska , B. ; Baik , B.-K. Structure and functionality of barley starches . Cereal Chemistry 1998 , 75 ( 5 ), 747 \u2013 754 . [CrossRef], [Web of Science \uae] View all references/s and 1.0\ub10.10 7 10 125 mm 2 2. Czuchajowska , Z. ; Klamczynski , A. ; Paszczynska , B. ; Baik , B.-K. Structure and functionality of barley starches . Cereal Chemistry 1998 , 75 ( 5 ), 747 \u2013 754 . [CrossRef], [Web of Science \uae] View all references/s, respectively. These D values were used to simulate moisture and temperature patterns during the drying of a barley kernel using a two-dimensional simultaneous heat and moisture transfer model and compared with literature D values for validation purposes. Based on the comparison, the D values of barley components obtained from our study can be used to develop realistic models of water transport in barley during different postharvest processing operations (e.g., drying, kilning, steeping).Peer reviewed: YesNRC publication: Ye

Measurements of mitochondrial K+ fluxes in whole rat hearts using 87Rb-NMR

NRC publication: Ye

Diagnosing liver cancer : a multi-modal approach

Peer reviewed: YesNRC publication: Ye