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San Martín Molina I, Fratini M, Campi G, Burghammer M, Grünewald TA, Salo RA, Narvaez O, Aggarwal M, Tohka J, Sierra A. A multiscale tissue assessment in a rat model of mild traumatic brain injury. J Neuropathol Exp Neurol 2022; 82:71-83. [PMID: 36331507 PMCID: PMC9764078 DOI: 10.1093/jnen/nlac100] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Diffusion tensor imaging (DTI) has demonstrated the potential to assess the pathophysiology of mild traumatic brain injury (mTBI) but correlations of DTI findings and pathological changes in mTBI are unclear. We evaluated the potential of ex vivo DTI to detect tissue damage in a mild mTBI rat model by exploiting multiscale imaging methods, histology and scanning micro-X-ray diffraction (SμXRD) 35 days after sham-operation (n = 2) or mTBI (n = 3). There were changes in DTI parameters rostral to the injury site. When examined by histology and SμXRD, there was evidence of axonal damage, reduced myelin density, gliosis, and ultrastructural alterations in myelin that were ongoing at the experimental time point of 35 days postinjury. We assessed the relationship between the 3 imaging modalities by multiple linear regression analysis. In this analysis, DTI and histological parameters were moderately related, whereas SμXRD parameters correlated weakly with DTI and histology. These findings suggest that while DTI appears to distinguish tissue changes at the microstructural level related to the loss of myelinated axons and gliosis, its ability to visualize alterations in myelin ultrastructure is limited. The use of several imaging techniques represents a novel approach to reveal tissue damage and provides new insights into mTBI detection.
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Affiliation(s)
| | - Michela Fratini
- Institute of Nanotechnology-CNR c/o Physics Department, Sapienza University of Rome, Rome, Italy,IRCCS Fondazione Santa Lucia, Rome, Italy
| | | | | | - Tilman A Grünewald
- European Synchrotron Radiation Facility, Grenoble Cedex, France,Aix-Marseille Université, CNRS, Centrale Marseille, Institut Fresnel, Marseille, France
| | - Raimo A Salo
- A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland
| | - Omar Narvaez
- A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland
| | - Manisha Aggarwal
- Russell H. Morgan Department of Radiology and Radiological Science, John Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Jussi Tohka
- A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland
| | - Alejandra Sierra
- Send correspondence to: Alejandra Sierra, PhD, A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland (Kuopio Campus), PO Box 1627, Neulaniementie 2, FI-70211 Kuopio, Finland; E-mail:
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Pusterla JM, Cannas SA, Schneck E, Oliveira RG. Purified myelin lipids display a critical mixing point at low surface pressure. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2022; 1864:183874. [PMID: 35120896 DOI: 10.1016/j.bbamem.2022.183874] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Revised: 01/26/2022] [Accepted: 01/27/2022] [Indexed: 06/14/2023]
Abstract
Lipids extracted from Purified Myelin Membranes (LPMM) were spread as monomolecular films at the air/aqueous interface. The films were visualized by Brewster Angle Microscopy (BAM) at different lateral pressures (π) and ionic environments. Coexistence of Liquid-Expanded (LE) and cholesterol-enriched (CE) rounded domains persisted up to π ≈ 5 mN/m but the monolayers became homogeneous at higher surface pressures. Before mixing, the domains distorted to non-rounded domains. We experimentally measured the line tension (λ) for the lipid monolayers at the domain borders by a shape relaxation technique using non-homogeneous electric fields. Regardless of the subphase conditions, the obtained line tensions are of the order of pN and tended to decrease as lateral pressure increased toward the mixing point. From the mean square displacement of nested trapped domains, we also calculated the dipole density difference between phases (μ). A non-linear drop was detected in this parameter as the mixing point is approached. Here we quantitively evaluated the π-dependance of both parameters with proper power laws in the vicinity of the critical mixing surface pressure, and the exponents showed to be consistent with a critical phenomenon in the two-dimensional Ising universality class. This idea of bidimensionality was found to be compatible only for simplified lipidic systems, while for whole myelin monolayers, that means including proteins, no critical mixing point was detected. Finally, the line tension values were related with the thickness differences between phases (Δt) near the critical point.
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Affiliation(s)
- Julio M Pusterla
- Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC)-Departamento de Química Biológica Ranwel Caputto, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Haya de la Torre y Medina Allende, Ciudad Universitaria, X5000HUA Córdoba, Argentina; Institut für Physik Kondensierter Materie, Technische Universität Darmstadt, Hochschulstrasse 8, 64289 Darmstadt, Germany.
| | - Sergio A Cannas
- Instituto de Física Enrique Gaviola (IFEG-CONICET), Facultad de Matemática Astronomía Física y Computación, Universidad Nacional de Córdoba, 5000 Córdoba, Argentina.
| | - Emanuel Schneck
- Institut für Physik Kondensierter Materie, Technische Universität Darmstadt, Hochschulstrasse 8, 64289 Darmstadt, Germany.
| | - Rafael G Oliveira
- Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC)-Departamento de Química Biológica Ranwel Caputto, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Haya de la Torre y Medina Allende, Ciudad Universitaria, X5000HUA Córdoba, Argentina.
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Ionic environment, thickness and line tension as determinants of phase separation in whole Purified Myelin Membranes monolayers. Colloids Surf B Biointerfaces 2021; 207:112027. [PMID: 34388613 DOI: 10.1016/j.colsurfb.2021.112027] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Revised: 06/14/2021] [Accepted: 08/03/2021] [Indexed: 11/24/2022]
Abstract
Purified myelin membranes (PMM) were spread as monomolecular films at the air/aqueous solution interface, and visualized by Brewster Angle Microscopy (BAM) at different lateral pressures (π) on three specific aqueous solutions: absence of salts, physiological conditions and presence of calcium. Coexistence of Liquid-Expanded (LE) and Liquid Ordered (LO) phases persisted up to collapse in the presence of salts, whereas monolayers became homogeneous at π ≥ 35-40 mN/m when salts are absent. This PMM phase-mixing behavior in monolayers is similar to the previously reported behavior of PMM multilamellar vesicles. Reflectivities (Rp) of p-polarized light from both phases were assessed throughout the whole π -range, and film thicknesses (t) were calculated from the Rp values and measured film refractive indices (n). The LO phase was found to be more reflective and thicker than the LE phase at π ≤ 15 mN/m, but less reflective and thinner at higher π. We also determined the line tension (λ) of PMM monolayers at the domain boundaries from the rate of domain shape relaxation, which turned out to be of the order of picoNewtons (pN) and decreased as π increased. A correlation between λ and thickness differences (Δt) was found, suggesting that Δt is a molecular determinant for λ in PMM monolayers. Both λ and Δt were found to increase markedly when calcium was present in the subphase. This result corroborates the concept of divalent cations as a stabilizing factor for phase separation, in line with earlier studies on this mixture forming multilamellar membrane arrangements.
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