Sheath lengths of large motor axons in the ventral root L5 of neonatal and adult rats.
This study examines the developmental sheath elongation in the rat ventral root L5. Electron microscopic analysis of serial transverse sections through roots from newborn rats shows an average internuclear distance (IND) of 66 microns (calculated fresh length 73 microns). Light microscopic analysis of teased adult roots shows that the largest fibers have an average internodal length of some 1250 microns at 5 months. Hence, large fibers exhibit a developmental sheath elongation of 17 times. The ventral root L5 elongates 11 times only. This mismatch necessitates a myelin sheath remodelling.
Hildebrand
C
C
Department of Cell Biology, University of Linköping, Sweden.
Loeliger
S
S
Bjartmar
C
C
Karlsson
M
M
D000375:Aging / Q000502:physiology; D000818:Animals; D000831:Animals, Newborn / Q000502:physiology*; D001369:Axons / Q000502:physiology* / Q000648:ultrastructure; D005260:Female; D008297:Male; D008854:Microscopy, Electron; D009046:Motor Neurons / Q000502:physiology* / Q000648:ultrastructure; D009186:Myelin Sheath / Q000502:physiology* / Q000648:ultrastructure; D051381:Rats; D013126:Spinal Nerve Roots / Q000254:growth & development* / Q000648:ultrastructure