Expression of glial fibrillary acidic protein by immature oligodendroglia and its implications.

Correlative immunocytochemical and electron-microscopic studies of the subpial region of the human fetal spinal cord between 12-18 weeks of ovulation age revealed immature oligodendroglial cells showing immunoreactive GFAP within both the cytoplasm and its processes. By 17-18 weeks, however, GFAP immunoreactivity is no longer evident within such cells. The expression of GFAP by immature oligodendroglial cells in the developing human fetal spinal cord prior to the formation of compact myelin sheaths supports the hypothesis that oligodendrocytes, along with astrocytes, are ultimately derived from radial glial cells.

Computed tomography in migratory disorders of human brain development.

Computed tomographic findings in developmental brain anomalies are more easily classified when the system used is based on embryogenesis related to morphology. Analysis of computed tomographic findings in a series of 154 patients with brain anomalies (Chiari malformation not included) revealed that specific examples of abnormalities occurring in major stages of brain development may be recognized by computed tomography. This paper deals with a group of patients with abnormalities that reflect a disturbance in neuronal migration.

Myelination and cholinesterase activity of chick embryo spinal cord.

This work was undertaken to study the myelination and cholinesterase activity of the developing white matter of chick embryo spinal cord from the 6th day of incubation until hatching. Myelination of the white matter was always preceeded by the aggregation of neuroglial cells. The sequence of myelination in the cervical and thoracic segments was from before backwards, whereas in the lumbosacral segments it was from behind forewards. Myelination of the ventral column extended craniocaudally, whereas in the posterior column is extended caudocranially. True cholinesterase activity was encountered in the spinal white matter only before and during the process of myelination and was closely associated with the sites of neuroglial aggregations. No pseudocholinesterase activity could be seen in the white matter before myelination. However, during the period of active myelination, enzymatic activity was seen only at the sites of formed myelin and after myelination of all tracts; the whole white matter reacted positive for the enzyme. The significance of these findings is discussed.

Effects of the cholesterol biosynthesis inhibitor ay9944 on organotypic cultures ofmouse spinal cord. Retarded myelinogenesis and induction of cytoplasmic inclusions.

Young cultures of fetal mouse spinal cord were exposed to nutrient medium containingAY9944 [trans-1,4-bis(2-chlorobenzylaminomethyl)cyclohexane dihydrochloride], apotent cholesterol biosynthesis inhibitor, and their reactions were studied by light and electron microscopy. AY9944 treatment for 4 to 7 days retarded cultures revealed anaccumulation of numerous intracytoplasmic inclusions in perikarya of neurons, astrocytes,and oligodendrocytes. These inclusions were also found in dendritic processes, myelinated axons, and presynaptic terminals. These inclusions were composed of concentric lamellar structures or of reticular internal structures. Although considerable improvement of myelination and diminution of cytoplasmic inclusions were noted following the removal of the inhibitor and the restitution in normal nutrient medium, a complete recovery oflesions was not observed during the 3-week restitution period in vitro.