Internodal Schwann cell fingers in the ventral spinal roots in mice: incidence and relationship to the diameter of myelinated fibers.
Internodal Schwann cell fingers were present in the lumbar, cervical, and thoracic spinal roots of adult mice at the age of 3 months, but they were not recognized in five mice examined at the age of 3 weeks. In the L4 ventral roots of ICR mice aged 3 months, the incidence of internodal Schwann cell fingers was 0.79% at the central-peripheral transitional zone and 2.43% at the distal regions, respectively. The ratio of axon diameter to total fiber diameter of myelinated fibers with internodal Schwann cell fingers was lower than that of fibers without them. Therefore, we conclude that internodal Schwann cell fingers are probably related to the developmental increase in the thickness of the myelin sheaths in the ventral spinal roots at all levels of the spinal cord.
Ishii
H
H
Division of Ultrastructural Research, National Institute of Neuroscience, NCNP, Tokyo, Japan.
Suzuki
K
K
Nonaka
I
I
D000818:Animals; D051379:Mice; D009413:Nerve Fibers, Myelinated / Q000648:ultrastructure*; D012583:Schwann Cells / Q000648:ultrastructure*; D013126:Spinal Nerve Roots / Q000648:ultrastructure*