Morphometric studies of axonal responses after traumatic axonal injury (TAI)

Sulaiman, Ahmed Mohammed (2005) Morphometric studies of axonal responses after traumatic axonal injury (TAI). PhD thesis, University of Glasgow.

Abstract

The optic nerve of adult guinea pigs contains 99,005 +/-9,199 (n=3) myelinated axons. Earlier studies have shown that axons of different diameters within 0.5?m wide numerical bins respond in different ways up to 7 days after traumatic axonal injury (TAI). The present study tested the hypothesis that such differential responses may continue over 3 weeks after TAI to result in a differential loss of intact or healthy axons. Stereological techniques were used to obtain estimates of the total number of intact axons, those lacking any morphological evidence of pathology. The number of intact axons fell from 99,005 to 74,845 at 1 week, to 66,744 at 2 weeks and to 55,696 at 3 weeks. However, statistically significant numerical differences and ultrastuctural evidence for loss of axons via Wallerian degeneration were obtained only at 3 weeks after TAI. A novel finding was that a few axons possessed intact cytoskeletal components within an electron dense axoplasm limited by an intact axolemma at 2 and 3 weeks after TAI. This finding was suggestive of a loss of axonal calibre. Estimates of the number of intact axons within different sizes of bin showed that the bin size containing the highest number of axons fell from a diameter of 1.5-2.0mum in controls to 1.0-1.5mum at 1 and 2 weeks, and to 0.5-1.0mum at 3 weeks after TAI. It is concluded there is both a loss of number and a previously unreported loss of calibre of axons after TAI in the CNS. Moreover, morphological evidence for Wallerian degeneration occurred only at 3 weeks after injury. As a result, the time course of loss of axons after TAI differs markedly from that described either in the PNS or after crush injury in the CNS.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Neurosciences.
• Colleges/Schools: College of Medical Veterinary and Life Sciences
• Supervisor's Name: Maxwell, Dr. William L.
• Date of Award: 2005
• Depositing User: Enlighten Team
• Unique ID: glathesis:2005-71458
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 17 May 2019 09:31
• Last Modified: 27 Aug 2021 15:22
• URI: https://theses.gla.ac.uk/id/eprint/71458