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Konopová B, Týč J. Minimal resin embedding of SBF-SEM samples reduces charging and facilitates finding a surface-linked region of interest. Front Zool 2023; 20:29. [PMID: 37641135 PMCID: PMC10463905 DOI: 10.1186/s12983-023-00507-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Accepted: 08/02/2023] [Indexed: 08/31/2023] Open
Abstract
BACKGROUND For decoding the mechanism of how cells and organs function information on their ultrastructure is essential. High-resolution 3D imaging has revolutionized morphology. Serial block face scanning electron microscopy (SBF-SEM) offers non-laborious, automated imaging in 3D of up to ~ 1 mm3 large biological objects at nanometer-scale resolution. For many samples there are obstacles. Quality imaging is often hampered by charging effects, which originate in the nonconductive resin used for embedding. Especially, if the imaged region of interest (ROI) includes the surface of the sample and neighbours the empty resin, which insulates the object. This extra resin also obscures the sample's morphology, thus making navigation to the ROI difficult. RESULTS Using the example of small arthropods and a fish roe we describe a workflow to prepare samples for SBF-SEM using the minimal resin (MR) embedding method. We show that for imaging of surface structures this simple approach conveniently tackles and solves both of the two major problems-charging and ROI localization-that complicate imaging of SBF-SEM samples embedded in an excess of overlying resin. As the surface ROI is not masked by the resin, samples can be precisely trimmed before they are placed into the imaging chamber. The initial approaching step is fast and easy. No extra trimming inside the microscope is necessary. Importantly, charging is absent or greatly reduced meaning that imaging can be accomplished under good vacuum conditions, typically at the optimal high vacuum. This leads to better resolution, better signal to noise ratio, and faster image acquisition. CONCLUSIONS In MR embedded samples charging is minimized and ROI easily targeted. MR embedding does not require any special equipment or skills. It saves effort, microscope time and eventually leads to high quality data. Studies on surface-linked ROIs, or any samples normally surrounded by the excess of resin, would benefit from adopting the technique.
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Affiliation(s)
- Barbora Konopová
- Institute of Entomology, Biology Centre CAS, České Budějovice, Czech Republic.
- Department of Zoology, Faculty of Science, University of South Bohemia, České Budějovice, Czech Republic.
| | - Jiří Týč
- Institute of Parasitology, Biology Centre CAS, České Budějovice, Czech Republic.
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Laurini E, Aulic S, Marson D, Fermeglia M, Pricl S. Cationic Dendrimers for siRNA Delivery: An Overview of Methods for In Vitro/In Vivo Characterization. Methods Mol Biol 2021; 2282:209-244. [PMID: 33928579 DOI: 10.1007/978-1-0716-1298-9_14] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
This chapter reviews the different techniques for analyzing the chemical-physical properties, transfection efficiency, cytotoxicity, and stability of covalent cationic dendrimers (CCDs) and self-assembled cationic dendrons (ACDs) for siRNA delivery in the presence and absence of their nucleic cargos. On the basis of the reported examples, a standard essential set of techniques is described for each step of a siRNA/nanovector (NV) complex characterization process: (1) analysis of the basic chemical-physical properties of the NV per se; (2) characterization of the morphology, size, strength, and stability of the siRNA/NV ensemble; (3) characterization and quantification of the cellular uptake and release of the siRNA fragment; (4) in vitro and (5) in vivo experiments for the evaluation of the corresponding gene silencing activity; and (6) assessment of the intrinsic toxicity of the NV and the siRNA/NV complex.
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Affiliation(s)
- Erik Laurini
- Molecular Biology and Nanotechnology Laboratory (MolBNL@UniTs), Department of Engineering and Architecture, University of Trieste, Trieste, Italy.
| | - Suzana Aulic
- Molecular Biology and Nanotechnology Laboratory (MolBNL@UniTs), Department of Engineering and Architecture, University of Trieste, Trieste, Italy
| | - Domenico Marson
- Molecular Biology and Nanotechnology Laboratory (MolBNL@UniTs), Department of Engineering and Architecture, University of Trieste, Trieste, Italy
| | - Maurizio Fermeglia
- Molecular Biology and Nanotechnology Laboratory (MolBNL@UniTs), Department of Engineering and Architecture, University of Trieste, Trieste, Italy
| | - Sabrina Pricl
- Molecular Biology and Nanotechnology Laboratory (MolBNL@UniTs), Department of Engineering and Architecture, University of Trieste, Trieste, Italy
- Department of General Biophysics, Faculty of Biology and Environmental Protection, University of Lodz, Lodz, Poland
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Sodium-glucose co-transporter (SGLT) inhibitor restores lost axonal varicosities of the myenteric plexus in a mouse model of high-fat diet-induced obesity. Sci Rep 2020; 10:12372. [PMID: 32704004 PMCID: PMC7378553 DOI: 10.1038/s41598-020-69256-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Accepted: 07/08/2020] [Indexed: 01/19/2023] Open
Abstract
Diabetes impairs enteric nervous system functions; however, ultrastructural changes underlying the pathophysiology of the myenteric plexus and the effects of sodium-glucose co-transporter (SGLT) inhibitors are poorly understood. This study aimed to investigate three-dimensional ultrastructural changes in axonal varicosities in the myenteric plexus and the effect thereon of the SGLT inhibitor phlorizin in mice fed a high-fat diet (HFD). Three-dimensional ultrastructural analysis using serial block-face imaging revealed that non-treated HFD-fed mice had fewer axonal varicosities and synaptic vesicles in the myenteric plexus than did normal diet-fed control mice. Furthermore, mitochondrial volume was increased and lysosome number decreased in the axons of non-treated HFD-fed mice when compared to those of control mice. Phlorizin treatment restored the axonal varicosities and organelles in HFD-fed mice. Although HFD did not affect the immunolocalisation of PGP9.5, it reduced synaptophysin immunostaining in the myenteric plexus, which was restored by phlorizin treatment. These results suggest that impairment of the axonal varicosities and their synaptic vesicles underlies the damage to the enteric neurons caused by HFD feeding. SGLT inhibitor treatment could restore axonal varicosities and organelles, which may lead to improved gastrointestinal functions in HFD-induced obesity as well as diabetes.
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Riesterer JL, López CS, Stempinski ES, Williams M, Loftis K, Stoltz K, Thibault G, Lanicault C, Williams T, Gray JW. A workflow for visualizing human cancer biopsies using large-format electron microscopy. Methods Cell Biol 2020; 158:163-181. [PMID: 32423648 DOI: 10.1016/bs.mcb.2020.01.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Recent developments in large format electron microscopy have enabled generation of images that provide detailed ultrastructural information on normal and diseased cells and tissues. Analyses of these images increase our understanding of cellular organization and interactions and disease-related changes therein. In this manuscript, we describe a workflow for two-dimensional (2D) and three-dimensional (3D) imaging, including both optical and scanning electron microscopy (SEM) methods, that allow pathologists and cancer biology researchers to identify areas of interest from human cancer biopsies. The protocols and mounting strategies described in this workflow are compatible with 2D large format EM mapping, 3D focused ion beam-SEM and serial block face-SEM. The flexibility to use diverse imaging technologies available at most academic institutions makes this workflow useful and applicable for most life science samples. Volumetric analysis of the biopsies studied here revealed morphological, organizational and ultrastructural aspects of the tumor cells and surrounding environment that cannot be revealed by conventional 2D EM imaging. Our results indicate that although 2D EM is still an important tool in many areas of diagnostic pathology, 3D images of ultrastructural relationships between both normal and cancerous cells, in combination with their extracellular matrix, enables cancer researchers and pathologists to better understand the progression of the disease and identify potential therapeutic targets.
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Affiliation(s)
- Jessica L Riesterer
- OHSU Center for Spatial Systems Biomedicine, Oregon Health and Sciences University, Portland, OR, United States; Multiscale Microscopy Core, Oregon Health and Sciences University, Portland, OR, United States.
| | - Claudia S López
- OHSU Center for Spatial Systems Biomedicine, Oregon Health and Sciences University, Portland, OR, United States; Multiscale Microscopy Core, Oregon Health and Sciences University, Portland, OR, United States; Pacific Northwest Center for CryoEM, Oregon Health and Sciences University, Portland, OR, United States.
| | - Erin S Stempinski
- OHSU Center for Spatial Systems Biomedicine, Oregon Health and Sciences University, Portland, OR, United States; Multiscale Microscopy Core, Oregon Health and Sciences University, Portland, OR, United States
| | - Melissa Williams
- OHSU Center for Spatial Systems Biomedicine, Oregon Health and Sciences University, Portland, OR, United States; Multiscale Microscopy Core, Oregon Health and Sciences University, Portland, OR, United States
| | - Kevin Loftis
- OHSU Center for Spatial Systems Biomedicine, Oregon Health and Sciences University, Portland, OR, United States
| | - Kevin Stoltz
- OHSU Center for Spatial Systems Biomedicine, Oregon Health and Sciences University, Portland, OR, United States
| | - Guillaume Thibault
- OHSU Center for Spatial Systems Biomedicine, Oregon Health and Sciences University, Portland, OR, United States
| | - Christian Lanicault
- Department of Pathology, Oregon Health and Sciences University, Portland, OR, United States
| | - Todd Williams
- Department of Pathology, Oregon Health and Sciences University, Portland, OR, United States
| | - Joe W Gray
- OHSU Center for Spatial Systems Biomedicine, Oregon Health and Sciences University, Portland, OR, United States.
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