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Distinguishing neuronal from astrocytic subcellular microstructures using in vivo Double Diffusion Encoded 1H MRS at 21.1 T.

Title: Distinguishing neuronal from astrocytic subcellular microstructures using in vivo Double Diffusion Encoded 1H MRS at 21.1 T.
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Name(s): Shemesh, Noam, author
Rosenberg, Jens T, author
Dumez, Jean-Nicolas, author
Grant, Samuel C, author
Frydman, Lucio, author
Type of Resource: text
Genre: Journal Article
Text
Date Issued: 2017-10-02
Physical Form: computer
online resource
Extent: 1 online resource
Language(s): English
Abstract/Description: Measuring cellular microstructures non-invasively and achieving specificity towards a cell-type population within an interrogated in vivo tissue, remains an outstanding challenge in brain research. Magnetic Resonance Spectroscopy (MRS) provides an opportunity to achieve cellular specificity via the spectral resolution of metabolites such as N-Acetylaspartate (NAA) and myo-Inositol (mI), which are considered neuronal and astrocytic markers, respectively. Yet the information typically obtained with MRS describes metabolic concentrations, diffusion coefficients or relaxation rates rather than microstructures. Understanding how these metabolites are compartmentalized is a challenging but important goal, which so far has been mainly addressed using diffusion models. Here, we present direct in vivo evidence for the confinement of NAA and mI within sub-cellular components, namely, the randomly oriented process of neurons and astrocytes, respectively. Our approach applied Relaxation Enhanced MRS at ultrahigh (21.1 T) field, and used its high 1H sensitivity to measure restricted diffusion correlations for NAA and mI using a Double Diffusion Encoding (DDE) filter. While very low macroscopic anisotropy was revealed by spatially localized Diffusion Tensor Spectroscopy, DDE displayed characteristic amplitude modulations reporting on confinements in otherwise randomly oriented anisotropic microstructures for both metabolites. This implies that for the chosen set of parameters, the DDE measurements had a biased sensitivity towards NAA and mI sited in the more confined environments of neurites and astrocytic branches, than in the cell somata. These measurements thus provide intrinsic diffusivities and compartment diameters, and revealed subcellular neuronal and astrocytic morphologies in normal in vivo rat brains. The relevance of these measurements towards human applications-which could in turn help understand CNS plasticity as well as diagnose brain diseases-is discussed.
Identifier: FSU_pmch_28968410 (IID), 10.1371/journal.pone.0185232 (DOI), PMC5624579 (PMCID), 28968410 (RID), 28968410 (EID), PONE-D-17-12913 (PII)
Publication Note: This NIH-funded author manuscript originally appeared in PubMed Central at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5624579.
Subject(s): Astrocytes/cytology
Diffusion
Humans
Magnetic Resonance Spectroscopy/methods
Neurons/cytology
Persistent Link to This Record: http://purl.flvc.org/fsu/fd/FSU_pmch_28968410
Host Institution: FSU
Is Part Of: PloS one.
1932-6203
Issue: iss. 10, vol. 12

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Shemesh, N., Rosenberg, J. T., Dumez, J. -N., Grant, S. C., & Frydman, L. (2017). Distinguishing neuronal from astrocytic subcellular microstructures using in vivo Double Diffusion Encoded 1H MRS at 21.1 T. Plos One. Retrieved from http://purl.flvc.org/fsu/fd/FSU_pmch_28968410