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J Comp Neurol
1998 Mar 02;3921:19-34. doi: 10.1002/(sici)1096-9861(19980302)392:1<19::aid-cne2>3.0.co;2-s.
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Floor plate and the subcommissural organ are the source of secretory compounds of related nature: comparative immunocytochemical study.
Yulis CR
,
Mota MD
,
Andrades JA
,
Rodríguez S
,
Peruzzo B
,
Mancera JM
,
Ramirez P
,
Garrido M
,
Pérez-Fígarez JM
,
Fernández-Llebrez P
,
Rodríguez EM
.
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The subcommissural organ of vertebrates secretes glycoproteins into the third ventricle that condense to form Reissner's fiber (RF). Antibodies raised against the bovine RF-glycoproteins reacted with the floor plate (FP) cells of two teleost (Oncorhynchus kisutch, Sparus aurata) and two amphibian (Xenopus laevis, Batrachyla taeniata) species. At the ultrastructural level, the immunoreactivity was confined to secretory granules, mainly concentrated at the apical cell pole. In the rostro-caudal axis, a clear zonation of the FP was distinguished, with the hindbrain FP being the most, or the only (Batrachyla taeniata), immunoreactive region of the FP. In all the species studied, the caudal FP lacked immunoreactivity. Both the chemical nature of the immunoreactive material and the rostro-caudal zonation of the FP appear to be conservative features. Evidence was obtained that the FP secretes into the cerebrospinal fluid a material chemically related to the RF-glycoproteins secreted by the subcommissural organ. Thus, in addition to being the source of contact-mediated and diffusible signals, the FP might also secrete compounds into the cerebrospinal fluid that may act on distant targets.
Fig. 6. Immunostaining of the CNS of Xenopus embryos using
AFRU. A: Midsagittal section of a 41-hour-old embryo. The immunocytochemical
reaction is confined to the SCO, FO, and FP. B: Higher
magnification of the SCO shown in a. C: Higher magnification of the
FO shown in a. AFRU-ir cells of the FO form a column closely apposed
to the notochord. The arrow indicates cephalic end of the immunoreactive
column of FP cells. D: Frontal section of a 33-hour-old embryo.
Moderate RF-immunoreactivity is seen in cells of the FO. E: Frontal
section of a 33-hour-old embryo. AFRU-ir material is present in the
lumen of the ampulla caudalis (arrowheads). Scale bar 5 30 μm. AC,
Ampulla caudalis; FO, flexural organ; FP, floor plate; N, notochord;
SCO, subcommissural organ. Scale bars5200 μm in A, 30 μm in B and
E, 50 μm in C and D.
Fig. 7. Light and transmission electron microscopy (TEM) of the
FP of 27-hour-old Xenopus embryos. A: Semi-thin section through the
FP. The black square frames an area similar to that shown in b. B: Low
magnification TEM of the FP showing accumulations of mitochondria
in the apical cytoplasm of the FP cells and abundant vitelline
inclusions and lipid droplets in the intermediate and basal cytoplasm.
C: Perinuclear region of FP cells with parallel arrays of flattened
cisternae of the rough endoplasmic reticulum. D: Apical protrusion of
a FP cell containing electron-lucent vesicles (arrowheads) and large
vacuoles. CC, Central canal; FP, floor plate; L, lipid droplets; M,
mitochondria; N, nuclei; NC, notochord; RER, rough endoplasmic
reticulum; V, vitelline inclusions. Scale bars 5 10 μm in A, 5 μm in B,
2 μm in C, 500 μm in D.
Fig. 8. TEM of the spinal cord of Xenopus embryos. A: Filamentous
material (arrow) on the free surface of FP cells of a 27-hour-old
embryo. Arrrowheads point to components of a junctional complex
between FP cells. B: RF (solid arrow) inside the central canal of a
60-hour-old embryo. Electron-dense floccular material appears attached
to RF and free surface of FP cells (open arrows). C: Detailed
magnification of RF of a 60-hour-old embryo. RF is formed by parallel
bundles of longitudinal filaments ranging in thickness between 3
(small arrowheads) and 14 nm (large arrowhead) bridged by short
perpendicular filaments ranging in thickness between 4 (small arrows)
and 14 nm (large arrows). Open arrows point to floccular
material attached to RF. CC, Central canal; V, vitelline inclusion.
Scale bars 5 500 μm inAand B, 200 μm in C.
sspo (SCO-spondin) gene expression IN Xenopus laevis embryo, assayed via immunostaining, NF stage 22/23, midsaggital section.anteriorleft, dorsal up.
Key: FO, flexural organ; FP, floor plate; SCO, subcommissural organ. Scale bars5200 μm in A
