||Fig. 5. Most neuronal precursor cells express XlHbox 6 in stage 24 spinal cord. Dorsal is uppermost in all panels.
(A) Section at high power magnification immunostained with anti-XlHbox 6 antibodies. (B) Same section counterstained
with Hoechst 33258 viewed under dark field illumination. Note that nearly all nuclei appear to be darkly stained in panel A
and that the Hoechst fluorescence in these nuclei is quenched by the immunostaining reaction product. (C) XlHbox 6
expression in lateral plate mesoderm. Transverse section of stage 25-26 tadpole decorated with XlHbox 6 antibodies and
overstained to show more clearly the less intense staining in the lateral plate mesoderm nuclei. Abbreviations:
ecto, ectoderm; ec, ependymal canal; sc, spinal cord; myo, myotome; LPM, lateral plate mesoderm; endo, endoderm;
arch, archenteron; no, notochord, remains of blastopore.
||Fig. 6. Distribution of XlHbox 6 antigens in the spinal cord
of stage 27 tadpole. A transverse section was (A)
immunostained with XlHbox 6 antibodies and (B)
counterstained with Hoechst 33258. At this stage of
development, the spinal cord starts to display a degree of
differentiation into defined layers. Now, not all of the spinal
cord nuclei express XlHbox 6 antigens. The more
peripheral nuclei which probably correspond to
differentiated primary neurons are no longer stained.
Immunostaining is confined to the entire inner layer
(ependymal layer) and a few cells that have migrated
laterally away from this mitotic zone. Note the nuclei that
are much less intensely immunostained in the lateral plate
mesoderm indicated by arrowheads. Abbreviations:
ec, ependymal canal; sc, spinal cord; no, notochord;
endo, endoderm; myo, myotome; ecto, ectoderm;
LPM, lateral plate mesoderm.
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||Fig. 4. Expression of XlHbox 6 antigens is limited to
posterior central nervous system. (A) A tailbud embryo
(stage 25) was paraffin sectioned and immunostained for
XlHbox 6 antigens. Black areas in the spinal cord represent
immunostaining. This embryo was curled so that an anterior
section through the brain is at left and a section through the
spinal cord is at right. (B) Expression of XlHbox 6 in a
stage 38 spinal cord. This is a slightly skewed, or oblique,
lateral section. The periodic row of black dots (arrowheads)
represents staining in a very few nuclei at the ependymal
surface of the spinal cord. Abbreviations: ec, ependymal
canal; sc, spinal cord; myo, myotomes; hb, hindbrain;
no, notochord; endo, endoderm; LPM, lateral plate
mesoderm; df, dorsal fin.