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Over the lifespan of an individual, brain function requires adjustments in response to environmental changes and learning experiences. During early development, neurons overproduce neurite branches, and neuronal pruning removes the unnecessary neurite branches to make a more accurate neural circuit. motoneurons prune their intermediate axon bundles rather than the terminal neuromuscular junction (NMJ) by degeneration, which provides a unique advantage for studying axon pruning. The pruning process of motor axon bundles can be directly analyzed by real-time imaging, and this protocol provides a straightforward method for monitoring the developmental process of motor neurons using live cell imaging. Key features • Long-range projecting axon bundles of motor neurons extending from soma on the ventral nerve cord (VNC) undergo degeneration rather than retraction during metamorphosis. • The pruning process of motor axon bundles can be directly observed by real-time live-cell imaging. • The complete clearance of axon bundles occurs approximately 22 h after pupal formation (22 h APF). • Mushroom body (MB) γ neuron axon pruning regulatory genes are conserved for motor neurons.
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http://dx.doi.org/10.21769/BioProtoc.5367 | DOI Listing |
Anat Sci Int
August 2025
Department of Anatomy and Neurobiology, National Defense Medical College, Tokorozawa, Saitama, 359-8513, Japan.
Numerous neuroanatomical tract-tracing techniques have been reported to demonstrate the origin, course, and termination of neural pathways. New techniques have been developed to achieve higher specificity and efficiency. Early tract-tracing studies at the microscopic level used non-specific staining, for example, by tracing fiber bundles of normal nervous tissue using myelin staining.
View Article and Find Full Text PDFImaging Neurosci (Camb)
March 2025
Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, United States.
Anatomic tracing is the gold standard tool for delineating brain connections and for validating more recently developed imaging approaches such as diffusion MRI tractography. A key step in the analysis of data from tracer experiments is the careful, manual charting of fiber trajectories on histological sections. This is a very time-consuming process, which limits the amount of annotated tracer data that are available for validation studies.
View Article and Find Full Text PDFImaging Neurosci (Camb)
June 2025
Department of Biomedical Engineering, McGill University, Montreal, QC, Canada.
The g-ratio of a myelinated axon is defined as the ratio of the inner-to-outer diameter of the myelin sheath and modulates conduction speed of action potentials along axons. This g-ratio can be mappedat the macroscopic scale across the entire human brain using multi-modal MRI and sampled along white matter streamlines reconstructed from diffusion-weighted images to derive the g-ratio of a white matter tract. This tractometry approach has shown spatiotemporal variations in g-ratio across white matter tracts and networks.
View Article and Find Full Text PDFImaging Neurosci (Camb)
November 2024
Department of Medical Biophysics, Schulich School of Medicine and Dentistry, Western University, London, ON, Canada.
Surgical resection is the method of choice for treating drug-resistant focal temporal lobe epilepsy (TLE). Postsurgical outcomes are better when magnetic resonance imaging (MRI) findings can localize the seizure focus for resection. However, many patients are MR-negative, meaning the focus cannot be differentiated from normal tissue in relaxation-weighted MRI.
View Article and Find Full Text PDFbioRxiv
July 2025
Laboratory of Sensory Neuroscience, The Rockefeller University, New York, NY 10065, USA.
Peripheral nerve regeneration requires precise selection of the appropriate targets of innervation, often in an environment that differs from that during the developmental wiring of the neural circuit. Severed axons of the zebrafish posterior lateral line nerve have the capacity to reinnervate mechanosensory hair cells clustered in neuromast organs. Regeneration represents a balance between fasciculated regrowth of the axonal bundle and defasciculation of individual axons into the epidermis where neuromasts reside.
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