Fig. 6

Double labeling of embryos with the antibody (α-Tb) for acetylated α-tubulin and in situ hybridization to zfIsl-2 or zfIsl-3 mRNA. Anterior, left; dorsal, up; S, spinal cord; N, notochord. The somite borders are indicated by broken lines. (A, B) Photomontaged lateral views of the spinal cord at the middle body trunk level of two 24-hr embryos double-stained by in situ hybridization to zfIsl-2 mRNA and by α-Tb, α-Tb stains alost all axons and some cell bodies of neurons in the spinal cord by brown reaction products. A single or a pair of ventral zfIsl-2-positive cells (open triangles) at each midsegment had thin purple precipitates around the contours of the cell bodies. Their cell bodies were connected with motor nerve roots (open stars) by the axons (arrows) which extended straight ventrally inside the spinal cord. Axons (arrowheads) were observed to extend longitudinally from the dorsal zfIsl-2-positive cells and ultimately became confluent with the dorsal longitudinal fascicle (DLF) (indicated by brackets). The commissural neurons (denoted as C) were all negative for the zfIsl-2 mRNA expression. (C) Photomontaged lateral views of the spinal cord at the middle body trunk level of a 24-hr embryo double-stained by in situ hybridization to zfIsl-3 mRNA and by α-Tb. The dorsal zfIsl-3-positive cells extended the axons (arrowheads) longitudinally which ultimately became confluent with DLF (bracket). Bars, 25 μm.