Unexpected survival of neurons of origin of the pyramidal tract after spinal cord injury. 2010

Jessica L Nielson, and Ilse Sears-Kraxberger, and Melissa K Strong, and Jamie K Wong, and Rafer Willenberg, and Oswald Steward
Department of Anatomy and Neurobiology, Reeve-Irvine Research Center, University of California, Irvine, California 92697, USA.

There is continuing controversy about whether the cells of origin of the corticospinal tract (CST) undergo retrograde cell death after spinal cord injury (SCI). All previous attempts to assess this have used imaging and/or histological techniques to assess upper motoneurons in the cerebral cortex. Here, we address the question in a novel way by assessing Wallerian degeneration and axon numbers in the medullary pyramid of Sprague Dawley rats after both acute SCI, either at cervical level 5 (C5) or thoracic level 9 (T9), and chronic SCI at T9. Our findings demonstrate that only a fraction of a percentage of the total axons in the medullary pyramid exhibit any sign of degeneration at any time after SCI--no more so than in uninjured control rats. Moreover, design-based counts of myelinated axons revealed no decrease in axon number in the medullary pyramid after SCI, regardless of injury level, severity, or time after injury. Spinal cord-injured rats had fewer myelinated axons in the medullary pyramid at 1 year after injury than aged matched controls, suggesting that injury may affect ongoing myelination of axons during aging. We conclude that SCI does not cause death of the CST cell bodies in the cortex; therefore, therapeutic strategies aimed at promoting axon regeneration of the CST in the spinal cord do not require a separate intervention to prevent retrograde degeneration of upper motoneurons in the cortex.

UI MeSH Term Description Entries
D008297 Male Males
D009474 Neurons The basic cellular units of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the NERVOUS SYSTEM. Nerve Cells,Cell, Nerve,Cells, Nerve,Nerve Cell,Neuron
D011712 Pyramidal Tracts Fibers that arise from cells within the cerebral cortex, pass through the medullary pyramid, and descend in the spinal cord. Many authorities say the pyramidal tracts include both the corticospinal and corticobulbar tracts. Corticobulbar Tracts,Corticospinal Tracts,Decussation, Pyramidal,Corticobulbar Tract,Corticospinal Tract,Pyramidal Decussation,Pyramidal Tract,Tract, Corticobulbar,Tract, Corticospinal,Tract, Pyramidal,Tracts, Corticobulbar,Tracts, Corticospinal,Tracts, Pyramidal
D002470 Cell Survival The span of viability of a cell characterized by the capacity to perform certain functions such as metabolism, growth, reproduction, some form of responsiveness, and adaptability. Cell Viability,Cell Viabilities,Survival, Cell,Viabilities, Cell,Viability, Cell
D002574 Cervical Vertebrae The first seven VERTEBRAE of the SPINAL COLUMN, which correspond to the VERTEBRAE of the NECK. Cervical Spine,Cervical Spines,Spine, Cervical,Vertebrae, Cervical
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D013119 Spinal Cord Injuries Penetrating and non-penetrating injuries to the spinal cord resulting from traumatic external forces (e.g., WOUNDS, GUNSHOT; WHIPLASH INJURIES; etc.). Myelopathy, Traumatic,Injuries, Spinal Cord,Post-Traumatic Myelopathy,Spinal Cord Contusion,Spinal Cord Laceration,Spinal Cord Transection,Spinal Cord Trauma,Contusion, Spinal Cord,Contusions, Spinal Cord,Cord Contusion, Spinal,Cord Contusions, Spinal,Cord Injuries, Spinal,Cord Injury, Spinal,Cord Laceration, Spinal,Cord Lacerations, Spinal,Cord Transection, Spinal,Cord Transections, Spinal,Cord Trauma, Spinal,Cord Traumas, Spinal,Injury, Spinal Cord,Laceration, Spinal Cord,Lacerations, Spinal Cord,Myelopathies, Post-Traumatic,Myelopathies, Traumatic,Myelopathy, Post-Traumatic,Post Traumatic Myelopathy,Post-Traumatic Myelopathies,Spinal Cord Contusions,Spinal Cord Injury,Spinal Cord Lacerations,Spinal Cord Transections,Spinal Cord Traumas,Transection, Spinal Cord,Transections, Spinal Cord,Trauma, Spinal Cord,Traumas, Spinal Cord,Traumatic Myelopathies,Traumatic Myelopathy
D013904 Thoracic Vertebrae A group of twelve VERTEBRAE connected to the ribs that support the upper trunk region. Vertebrae, Thoracic
D014855 Wallerian Degeneration Degeneration of distal aspects of a nerve axon following injury to the cell body or proximal portion of the axon. The process is characterized by fragmentation of the axon and its MYELIN SHEATH. Degeneration, Wallerian
D017207 Rats, Sprague-Dawley A strain of albino rat used widely for experimental purposes because of its calmness and ease of handling. It was developed by the Sprague-Dawley Animal Company. Holtzman Rat,Rats, Holtzman,Sprague-Dawley Rat,Rats, Sprague Dawley,Holtzman Rats,Rat, Holtzman,Rat, Sprague-Dawley,Sprague Dawley Rat,Sprague Dawley Rats,Sprague-Dawley Rats

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