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In JoVE (1)
Other Publications (4)
Articles by Lindsay S. Cahill in JoVE
JoVE Neuroscience
Multiple-mouse Neuroanatomical Magnetic Resonance Imaging
1Mouse Imaging Centre, Hospital for Sick Children, 2Department of Medical Biophysics and Medical Imaging, University of Toronto
Magnetic resonance imaging (MRI) has become an increasingly popular tool for examining the phenotype of genetically altered mice. This article illustrates the methods necessary to achieve high-throughput phenotyping of genetically altered mice using multiple-mouse MRI.
Other articles by Lindsay S. Cahill on PubMed
Natural Abundance (25)Mg Solid-state NMR of Mg Oxyanion Systems: a Combined Experimental and Computational Study
Solid-state (25)Mg magic angle spinning nuclear magnetic resonance (MAS NMR) data are reported from a range of organic and inorganic magnesium-oxyanion compounds at natural abundance. To constrain the determination of the NMR interaction parameters (delta(iso), chi(Q), eta(Q)) data have been collected at three external magnetic fields (11.7, 14.1 and 18.8 T). Corresponding NMR parameters have also been calculated by using density functional theory (DFT) methods using the GIPAW approach, with good correlations being established between experimental and calculated values of both chi(Q) and delta(iso). These correlations demonstrate that the (25)Mg NMR parameters are very sensitive to the structure, with small changes in the local Mg(2+) environment and the overall hydration state profoundly affecting the observed spectra. The observations suggest that (25)Mg NMR spectroscopy is a potentially potent probe for addressing some key problems in inorganic materials and of metal centres in biologically relevant molecules.
A 93Nb Solid-state NMR and Density Functional Theory Study of Four- and Six-coordinate Niobate Systems
A variable B(0) field static (broadline) NMR study of a large suite of niobate materials has enabled the elucidation of high-precision measurement of (93)Nb NMR interaction parameters such as the isotropic chemical shift (delta(iso)), quadrupole coupling constant and asymmetry parameter (C(Q) and eta(Q)), chemical shift span/anisotropy and skew/asymmetry (Omega/Deltadelta and kappa/eta(delta)) and Euler angles (alpha, beta, gamma) describing the relative orientation of the quadrupolar and chemical shift tensorial frames. These measurements have been augmented with ab initio DFT calculations by using WIEN2k and NMR-CASTEP codes, which corroborate these reported values. Unlike previous assertions made about the inability to detect CSA (chemical shift anisotropy) contributions from Nb(V) in most oxo environments, this study emphasises that a thorough variable B(0) approach coupled with the VOCS (variable offset cumulative spectroscopy) technique for the acquisition of undistorted broad (-1/2<-->+1/2) central transition resonances facilitates the unambiguous observation of both quadrupolar and CSA contributions within these (93)Nb broadline data. These measurements reveal that the (93)Nb electric field gradient tensor is a particularly sensitive measure of the immediate and extended environments of the Nb(V) positions, with C(Q) values in the 0 to >80 MHz range being measured; similarly, the delta(iso) (covering an approximately 250 ppm range) and Omega values (covering a 0 to approximately 800 ppm range) characteristic of these niobate systems are also sensitive to structural disposition. However, their systematic rationalisation in terms of the Nb-O bond angles and distances defining the immediate Nb(V) oxo environment is complicated by longer-range influences that usually involve other heavy elements comprising the structure. It has also been established in this study that the best computational method(s) of analysis for the (93)Nb NMR interaction parameters generated here are the all-electron WIEN2k and the gauge included projector augmented wave (GIPAW) NMR-CASTEP DFT approaches, which account for the short- and long-range symmetries, periodicities and interaction-potential characteristics for all elements (and particularly the heavy elements) in comparison with Gaussian 03 methods, which focus on terminated portions of the total structure.
Investigation of Proton Dynamics and the Proton Transport Pathway in Choline Dihydrogen Phosphate Using Solid-state NMR
Choline dihydrogen phosphate has previously been shown to be a good ionic conductor as well as an excellent host for acid doping, leading to high proton conductivities required for e.g., electrochemical devices including proton membrane fuel cells and sensors. A combination of variable-temperature (1)H solid-state NMR and 2D NMR pulse sequences, including (31)P and (13)C CODEX and (1)H BaBa, show that the proton conduction mechanism primarily involves assisted transport via a restricted three-site motion of the phosphate unit around the P-O bond that is hydrogen bonded to the choline and exchange of protons between these anions. In other words, proton transport at ambient temperatures appears to occur most favorably along the crystallographic b axis, from phosphate dimer to dimer. At elevated temperatures exchange between the protons of the hydroxyl group on the choline cation and the hydrogen-bonded dihydrogen phosphate groups also contributes to the structural diffusion of the protons in this solid state conductor.
Preparation of Fixed Mouse Brains for MRI
In fixed mouse brain magnetic resonance images, a high prevalence of fixation artifacts have been observed. Of more than 1700 images of fixed brains acquired at our laboratory, fixation artifacts were present in approximately 30%. In this study, two of these artifacts are described and their causes are identified. A hyperintense rim around the brain is observed when using perfusates reconstituted from powder and delivered at a high flow rate. It is proposed that these perfusion conditions cause blockage of the capillary beds and an increase in pressure that ruptures the vessels, resulting in a blister of liquid below the dura mater. Secondly, gray-white matter contrast inversion is observed when too short a fixation time or too low a concentration of fixative is used, resulting in inadequate fixation. The deleterious consequences of these artifacts for quantitative data analysis are discussed, and precautions for their prevention are provided.
