Microtubules (“neurotubules”) appear as hollow, 25-nm-diameter tubes running longitudinally along dendrites and axons ( Prokop, 2020) in culture ( Fig.
This opened the golden era of thin-section EM of the nervous system, with the ultrastructural definition of the three main cytoskeleton components: microtubules, intermediate filaments, and actin.
2 A, from Horridge and Mackay, 1962) with a formaldehyde-fixed sample ( Fig. Inclusion in plastic resin, then aldehyde fixation ( Sabatini et al., 1963) greatly improved preservation of the neuronal cytoskeleton, allowing visualization of distinct microtubules compare a typical osmic-acid fixed sample ( Fig. The accuracy of EM observations goes hand in hand with the development of better fixation and sample processing techniques. Today's quantitative imaging has more rigorous and modern ways to refine and recapitulate information from a set of observations, but one may regret the artfulness and communication efficiency of these wonderful drawings, and hope for their renewed presence in scientific articles ( Chabrier and Janke, 2017).ĮM was instrumental in visualizing the details of cytoskeletal organization, with numerous ultrastructural studies in the 1940s and 1950s. The abstraction offered by drawings makes them a natural choice to recapitulate current knowledge in textbooks, such as the works of art by Radivoj V. 1 C, from Gray and Guillery, 1966) or the summary of Victoria Chan-Palay's observations on the submembrane organization of the axon initial segment ( Fig. Classic electron microscopy (EM) works from the 1950s to 1970s thus feature often beautiful, detailed drawings, such as the depiction of intermediate filament (“neurofilament”) loops within presynapses from George Gray and Ray Guillery ( Fig. The advent of microphotography allowed images to be captured directly from the microscope, but drawings were still used throughout the 20th century to summarize findings as platonic ideals from numerous observations. Staining techniques, such as the Golgi method and its refinements, revealed not only the morphology of isolated neurons, but also the details of intraneuronal fibers, which were termed “neurofibrils.” Beautiful drawings from light microscopy observations by Cajal and others depict these straight or wavy neurofibrils inside the cell body, dendrites, and axon of a variety of neurons ( Fig. This history of the cytoskeleton in pictures begins in the 19th century with the drawings of gifted scientists/artists. I will follow how preparation and culture procedures, staining methods, and microscopy techniques each brought new insight on key neuronal structures, such as microtubules, the axonal growth cone, and dendritic spines. The 40th anniversary of the Journal of Neuroscience first issue marks a great occasion to showcase how images have shaped our understanding of the neuronal cytoskeleton, from the early drawing of pioneers to the latest developments of microscope technology. Their cytoskeleton, the intricate array of microtubules, intermediate filaments, and actin filaments running throughout each neuron, allows them to build, maintain, and transform their fantastic architectures ( Leterrier et al., 2017 Tas and Kapitein, 2018). Neurons interconnect throughout the brain and body via the elaborate arborization of their dendrites and axon. Neurons are the “delicate and elegant…butterflies of the soul,” as Santiago Ramón y Cajal famously put it in his memoir ( Zwirn, 2015).
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