Neurofilaments in the chick embryo during early development. I. Immunofluorescent study with antisera to neurofilament protein.

The time of appearance of neurofilament protein was determined by indirect immunofluorescence in the chick. Immunofluorescence first appeared in 3-day embryos as a peripheral layer on the ventral and lateral surfaces of the spinal cord and hindbrain. Concomitant with a marked thickening of this layer on the ventrolateral surface of the neural tube, neurofibrils were seen emerging from the cord and the myelencephalon. The immunofluorescent layer could be followed rostrally on the surface of the brain up to the mesencephalic flexure. In this location a large bundle of fibrils was observed emerging from the ventral surface of the mesencephalon. The posterior root ganglia and inner layer of the retina were intensely immunofluorescent on day 4. In the following days of development the spinal cord and ganglia assumed a mature configuration. The appearance of the anterior horns on the 6th day was remarkably segmental, the anterior horns being detected in alternate sections in a series of transverse serial section.