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Development of the corticospinal tract in the mouse spinal cord: a quantitative ultrastructural analysis
- Source :
- Brain research. 1084(1)
- Publication Year :
- 2005
-
Abstract
- The growth of corticospinal tract (CST) axons was studied quantitatively at the 7th cervical (C7) and the 4th lumbar (L4) spinal segments in the balb/cByJ mice at the ages of postnatal day (P) 0, 2, 4, 6, 8, 10, 14, and 28. The cross-sectional area of the CST increased progressively with time. Unmyelinated axons, the most prominent CST element during early development, reached maximum at C7 and L4 on P14. Two phases of increase in the number of unmyelinated axons were observed at C7, while only one surge of axonal outgrowth was found at the L4 level. Pro-myelinated axons, defined as axons surrounded by only one layer of oligodendrocytic process, were first seen at P2 and P4 in the C7 and the L4 level, respectively, followed by a dramatic increase in the number of myelinated axons from P14 onwards at both spinal levels. Myelination of the CST axons occurred topographically in a dorsal-to-ventral pattern. The number of growth cones increased rapidly at the C7 level to reach its maximum at P4, while those at L4 increased steadily to the peak at P10. Growth cones with synapse-like junctions were occasionally observed in the growing CST. Degenerating axons and growth cones partly accounted for the massive axon loss at both spinal segments during CST development. Overall, the mouse CST elements changed dynamically in numbers during postnatal development, suggesting a vigorous growing and pruning activity in the tract. The mouse CST also showed a similar growth pattern to that of the rat CST.
- Subjects :
- Central nervous system
Growth Cones
Pyramidal Tracts
Biology
Nerve Fibers, Myelinated
Functional Laterality
Mice
Mouse Spinal Cord
Lumbar
Nerve Fibers
Microscopy, Electron, Transmission
medicine
Animals
Axon
Growth cone
Molecular Biology
Spinal Cord Injuries
Nerve Fibers, Unmyelinated
General Neuroscience
Age Factors
Anatomy
Spinal cord
Nerve Regeneration
Mice, Inbred C57BL
medicine.anatomical_structure
nervous system
Animals, Newborn
Spinal Cord
Corticospinal tract
Ultrastructure
Neurology (clinical)
human activities
Developmental Biology
Subjects
Details
- ISSN :
- 00068993
- Volume :
- 1084
- Issue :
- 1
- Database :
- OpenAIRE
- Journal :
- Brain research
- Accession number :
- edsair.doi.dedup.....cc17663fa829c1fc37c37e327d041c65