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Kwon J, Kim M, Park H, Kang BM, Jo Y, Kim JH, James O, Yun SH, Kim SG, Suh M, Choi M. Label-free nanoscale optical metrology on myelinated axons in vivo. Nat Commun 2017; 8:1832. [PMID: 29184114 PMCID: PMC5705720 DOI: 10.1038/s41467-017-01979-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Accepted: 10/29/2017] [Indexed: 01/10/2023] Open
Abstract
In the mammalian nervous system, myelin provides electrical insulation for the neural circuit by forming a highly organized, multilayered thin film around the axon fibers. Here, we investigate the spectral reflectance from this subcellular nanostructure and devise a new label-free technique based on a spectroscopic analysis of reflected light, enabling nanoscale imaging of myelinated axons in their natural living state. Using this technique, we demonstrate three-dimensional mapping of the axon diameter and sensing of dynamic changes in the substructure of myelin at nanoscale. We further reveal the prevalence of axon bulging in the brain cortex in vivo after mild compressive trauma. Our novel tool opens new avenues of investigation by creating unprecedented access to the nanostructural dynamics of live myelinated axons in health and disease.
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Affiliation(s)
- Junhwan Kwon
- Center for Neuroscience Imaging Research (CNIR), Institute for Basic Science (IBS), Suwon, 16419, Republic of Korea
- Department of Biomedical Engineering, Sungkyunkwan University, Suwon, 16419, Republic of Korea
| | | | - Hyejin Park
- Center for Neuroscience Imaging Research (CNIR), Institute for Basic Science (IBS), Suwon, 16419, Republic of Korea
- Department of Biological Science, Sungkyunkwan University, Suwon, 16419, Republic of Korea
| | - Bok-Man Kang
- Center for Neuroscience Imaging Research (CNIR), Institute for Basic Science (IBS), Suwon, 16419, Republic of Korea
- Department of Biomedical Engineering, Sungkyunkwan University, Suwon, 16419, Republic of Korea
| | - Yongjae Jo
- Center for Neuroscience Imaging Research (CNIR), Institute for Basic Science (IBS), Suwon, 16419, Republic of Korea
- Department of Biomedical Engineering, Sungkyunkwan University, Suwon, 16419, Republic of Korea
| | - Jae-Hwan Kim
- Center for Neuroscience Imaging Research (CNIR), Institute for Basic Science (IBS), Suwon, 16419, Republic of Korea
- Department of Biomedical Engineering, Sungkyunkwan University, Suwon, 16419, Republic of Korea
| | - Oliver James
- Center for Neuroscience Imaging Research (CNIR), Institute for Basic Science (IBS), Suwon, 16419, Republic of Korea
| | | | - Seong-Gi Kim
- Center for Neuroscience Imaging Research (CNIR), Institute for Basic Science (IBS), Suwon, 16419, Republic of Korea
- Department of Biomedical Engineering, Sungkyunkwan University, Suwon, 16419, Republic of Korea
| | - Minah Suh
- Center for Neuroscience Imaging Research (CNIR), Institute for Basic Science (IBS), Suwon, 16419, Republic of Korea
- Department of Biomedical Engineering, Sungkyunkwan University, Suwon, 16419, Republic of Korea
| | - Myunghwan Choi
- Center for Neuroscience Imaging Research (CNIR), Institute for Basic Science (IBS), Suwon, 16419, Republic of Korea.
- Department of Biomedical Engineering, Sungkyunkwan University, Suwon, 16419, Republic of Korea.
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Krotov V, Tokhtamysh A, Kopach O, Dromaretsky A, Sheremet Y, Belan P, Voitenko N. Functional Characterization of Lamina X Neurons in ex-Vivo Spinal Cord Preparation. Front Cell Neurosci 2017; 11:342. [PMID: 29163053 PMCID: PMC5672841 DOI: 10.3389/fncel.2017.00342] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Accepted: 10/16/2017] [Indexed: 11/25/2022] Open
Abstract
Functional properties of lamina X neurons in the spinal cord remain unknown despite the established role of this area for somatosensory integration, visceral nociception, autonomic regulation and motoneuron output modulation. Investigations of neuronal functioning in the lamina X have been hampered by technical challenges. Here we introduce an ex-vivo spinal cord preparation with both dorsal and ventral roots still attached for functional studies of the lamina X neurons and their connectivity using an oblique LED illumination for resolved visualization of lamina X neurons in a thick tissue. With the elaborated approach, we demonstrate electrophysiological characteristics of lamina X neurons by their membrane properties, firing pattern discharge and fiber innervation (either afferent or efferent). The tissue preparation has been also probed using Ca2+ imaging with fluorescent Ca2+ dyes (membrane-impermeable or -permeable) to demonstrate the depolarization-induced changes in intracellular calcium concentration in lamina X neurons. Finally, we performed visualization of subpopulations of lamina X neurons stained by retrograde labeling with aminostilbamidine dye to identify sympathetic preganglionic and projection neurons in the lamina X. Thus, the elaborated approach provides a reliable tool for investigation of functional properties and connectivity in specific neuronal subpopulations, boosting research of lamina X of the spinal cord.
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Affiliation(s)
- Volodymyr Krotov
- Department of Sensory Signalling, Bogomoletz Institute of Physiology, Kyiv, Ukraine.,Department of Molecular Biophysics, Bogomoletz Institute of Physiology, Kyiv, Ukraine
| | - Anastasia Tokhtamysh
- Department of Sensory Signalling, Bogomoletz Institute of Physiology, Kyiv, Ukraine
| | - Olga Kopach
- Department of Sensory Signalling, Bogomoletz Institute of Physiology, Kyiv, Ukraine
| | - Andrew Dromaretsky
- Department of Molecular Biophysics, Bogomoletz Institute of Physiology, Kyiv, Ukraine
| | - Yevhenii Sheremet
- Department of Molecular Biophysics, Bogomoletz Institute of Physiology, Kyiv, Ukraine
| | - Pavel Belan
- Department of Molecular Biophysics, Bogomoletz Institute of Physiology, Kyiv, Ukraine.,Chair of Biophysics and Molecular Physiology, Kyiv Academic University, Kyiv, Ukraine
| | - Nana Voitenko
- Department of Sensory Signalling, Bogomoletz Institute of Physiology, Kyiv, Ukraine.,Chair of Biophysics and Molecular Physiology, Kyiv Academic University, Kyiv, Ukraine
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Richner M, Jager SB, Siupka P, Vaegter CB. Hydraulic Extrusion of the Spinal Cord and Isolation of Dorsal Root Ganglia in Rodents. J Vis Exp 2017. [PMID: 28190031 PMCID: PMC5352284 DOI: 10.3791/55226] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Traditionally, the spinal cord is isolated by laminectomy, i.e. by breaking open the spinal vertebrae one at a time. This is both time consuming and may result in damage to the spinal cord caused by the dissection process. Here, we show how the spinal cord can be extruded using hydraulic pressure. Handling time is significantly reduced to only a few minutes, likely decreasing protein damage. The low risk of damage to the spinal cord tissue improves subsequent immunohistochemical analysis. By performing hydraulic spinal cord extrusion instead of traditional laminectomy, the rodents can further be used for DRG isolation, thereby lowering the number of animals and allowing analysis across tissues from the same rodent. We demonstrate a consistent method to identify and isolate the DRGs according to their localization relative to the costae. It is, however, important to adjust this method to the particular animal used, as the number of spinal cord segments, both thoracic and lumbar, may vary according to animal type and strain. In addition, we illustrate further processing examples of the isolated tissues.
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Blivis D, O'Donovan MJ. Retrograde loading of nerves, tracts, and spinal roots with fluorescent dyes. J Vis Exp 2012:4008. [PMID: 22547001 DOI: 10.3791/4008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Retrograde labeling of neurons is a standard anatomical method(1,2) that has also been used to load calcium and voltage-sensitive dyes into neurons(3-6). Generally, the dyes are applied as solid crystals or by local pressure injection using glass pipettes. However, this can result in dilution of the dye and reduced labeling intensity, particularly when several hours are required for dye diffusion. Here we demonstrate a simple and low-cost technique for introducing fluorescent and ion-sensitive dyes into neurons using a polyethylene suction pipette filled with the dye solution. This method offers a reliable way for maintaining a high concentration of the dye in contact with axons throughout the loading procedure.
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Affiliation(s)
- Dvir Blivis
- Developmental Neurobiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA.
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Garudadri S, Gallarda B, Pfaff S, Alaynick W. Spinal cord electrophysiology II: extracellular suction electrode fabrication. J Vis Exp 2011:2580. [PMID: 21372792 DOI: 10.3791/2580] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Development of neural circuitries and locomotion can be studied using neonatal rodent spinal cord central pattern generator (CPG) behavior. We demonstrate a method to fabricate suction electrodes that are used to examine CPG activity, or fictive locomotion, in dissected rodent spinal cords. The rodent spinal cords are placed in artificial cerebrospinal fluid and the ventral roots are drawn into the suction electrode. The electrode is constructed by modifying a commercially available suction electrode. A heavier silver wire is used instead of the standard wire given by the commercially available electrode. The glass tip on the commercial electrode is replaced with a plastic tip for increased durability. We prepare hand drawn electrodes and electrodes made from specific sizes of tubing, allowing consistency and reproducibility. Data is collected using an amplifier and neurogram acquisition software. Recordings are performed on an air table within a Faraday cage to prevent mechanical and electrical interference, respectively.
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Affiliation(s)
- Suresh Garudadri
- Howard Hughes Medical Institute and Gene Expression Laboratory, The Salk Institute for Biological Studies, USA
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