Postnatal increase of unmyelinated axon profiles in the feline ventral root L7

Publisher Website
Google Scholar
Abstract
The proportion of unmyelinated axon profiles and possible agerelated, degenerative and regenerative alterations were studied ultrastructurally in the L7 ventral root of 25 cats ranging from 3 weeks to 11 years of age. For comparison, the ventral root C6 was examined in 5 of these animals. The sections were taken from a level midway between the proximal and distal ends of the roots. The proportion of unmyelinated axon profiles in the L7 ventral root increased from about 14% to around 31% between 4 and 7 months after birth. Simultaneously, the average number of unmyelinated axon profiles per Schwann cell was doubled from 2–3 to 4–5. Thereafter, these figures remained largely unchanged for at least a decade. The total number of myelinated axons was similar in kittens and in cats. In the C6 root the proportion of unmyelinated axon profiles was about 20%, both in kittens and in young or old adult cats. At both segmental levels in the oldest cats, some unmyelinated axons showed degenerative changes and medium‐sized and large axons had features characteristic of demyelination and remyelination.