Temporal relationship between myelinogenesis and the appearance of a basic protein in the spinal cord of the white rat

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Abstract
In a previous study a low molecular weight basic protein, isolated from guinea pig brain, was shown to be localized in the myelin of adult nervous tissue. An antigenically similar protein was present in the central nervous system of a variety of mammals, the chicken and the frog. In the present study, the ability of the nervous system of the albino rat to react specifically with the fluorescent anti‐basic protein antibody was investigated during fetal and postnatal development. Although earlier stages were examined, the spinal cord of the rat was first observed to react with the antiserum in the twenty‐first day of gestation. Ultrastructural studies indicated that well formed myelin, and mature and immature synapses were present in the cervical cord at this time. A positive immune reaction was detected two days before a noticeable Weigert reaction was obtained; the sequence and spatial pattern of labeling with both techniques was similar, however. It was observed that the nucleolus and cytoplasmic web of dorsal root ganglion cells first reacted with the antiserum at a time immediately preceding the onset of rapid myelination of axonal fibers in the ganglion. The immune reaction in the cell body of the large ganglion cells diminished rapidly with the cessation of rapid myelination. The relationship of the findings to the present concept of myelinogenesis is discussed.