Until the advent of MR imaging, knowledge of the structure of myelin and the process of myelination were of little importance to the neuroradiologist. Other than some mild changes in the attenuation of white matter, myelination resulted in no significant alterations of CT (1) or sonographic studies. MR studies, on the other hand, have been increasingly used for pediatric brain imaging. MR imagi...

Schwann cells in the peripheral nervous systems extend their membranes to wrap axons concentrically and form the insulating sheath, called myelin. The spaces between layers of myelin are sealed by myelin junctions. This tight insulation enables rapid conduction of electric impulses (action potentials) through axons. Demyelination (stripping off the insulating sheath) has been widely regarded as...

The effect of aging on myelin sheaths in the rhesus monkey was studied in the vertical bundles of nerve fibers that traverse monkey cerebral cortex in primary visual area 17 and prefrontal area 46. As shown previously, with age the internodes of many of these myelin sheaths show structural changes, the most common of which is an accumulation of electron-dense cytoplasm within some sheaths, a ch...

A time-sequence study of the incorporation and distribution of cholesterol in peripheral nerve myelin was carried out by electron microscope autoradiography. [1,2-(3)H]Cholesterol was injected into 10-day old mice and the sciatic nerves were dissected out at 10, 20, 40, 60, 90, 120, and 180 min after the injection. 20 min after injection the higher densities of grains due to the presence of [(3...

Peculiar myelin figures were abundantly found in some basal-granulated cells including S, D1 and I cells in human Brunner's glands. Intense acid phosphatase activity was found in the periphery of the myelin figures, indicating that they were secondary lysosomes or residual bodies. The acid phosphatase activity was also found in some secretory granules. There were some secretory granules which w...

The response of neonatal rat locus coeruleus neurons to contact with myelin extracts prepared from the CNS and PNS was examined. The growth cones of these neurons collapsed following contact with central myelin, but continued to elongate on contact with peripheral myelin. Central myelin elicited an increase in the intracellular free calcium concentration in these growth cones, while peripheral ...

Before the advent of critical isotope-labelling experiments (Eichberg & Dawson, 1965), myelin was believed to be metabolically inert. Evidence soon accumulated which indicated that not only did an active myelin metabolism persist in young adult animals, but was accompanied by a progressive change in chemical composition of the sheath. Typically the myelin isolated by centrifugation from develop...

In vitro assays reveal that myelin and oligodendrocytes of the Xenopus spinal cord (SC) are--unlike corresponding components of the optic nerve/tectum (OT)--nonpermissive substrates for regenerating retinal axons. The number of growth cones that crossed SC oligodendrocytes is low but increases significantly (four- to fivefold) in the presence of the antibody IN-1, in which case their numbers ar...

The old concept of myelin as a metabolically inert membrane has been considerably revised as a result of the discovery of numerous enzyme activities in the isolated membrane. The high degree of purification and low levels of contamination markers leave little doubt that the measured activities are intrinsic to myelin itself. Slightly more than half of the discovered activities involve lipid met...

Introduction Myelin water imaging has been successfully used to assess myelin content in human and animal CNS tissue [1,2]. It has been shown that myelin water fraction (MWF) [3] correlates well with the amount of myelin in a rat model of spinal cord injury (SCI) [2] and can therefore be an important marker of the cord pathology. Quantitative T2 measurements used in myelin water imaging require...