dc.description.abstract |
This review summarizes our present state of knowledge about spectrally
different photoreceptor cell types in the Xenopus retina. The
classification of the photoreceptors was based on morphology, combined
with immunolabelling with various anti-visual pigment antibodies and
other molecular probes on semithin sections and retinal wholemounts.
The majority of photoreceptors is represented by rods. Altogether
97-98% of the total rod population consists of the principal ("red")
rods that are selectively labeled by N-terminal specific anti-bovine
rhodopsin monoclonal antibodies (mAbs) and are maximally sensitive to
green light. The other, rare, blue-sensitive rod type ("green rod") is
thinner, not stained by these antibodies but binds C-terminal specific
anti-rhodopsin mAbs. The major representatives of the cones are
red-sensitive and consist of a morphologically heterogeneous group
comprising both (principal and accessory) members of double cones, as
well as large single cones. Outer segments in this group are
selectively labeled by mAb COS-l, specific to the L/M group of cone
visual pigments. Another, relatively rare cone type is similar in size,
but slightly smaller than the large single cone and is not labeled by
mAb COS-1. This cone type is assumed to have a blue-sensitive cone
visual pigment. The third, least abundant, and immunocytochemically
distinct cone type is a small single (miniature) cone, which binds mAb
OS-2 relatively strongly, and anti-rhodopsin mAbs 4B4 and 1D4 weakly.
By exclusion, this small single cone may be identical with the
W-sensitive cone. Further studies are needed, however, to identify the
color sensitivity of the latter two cone types. (C) 2000 Wiley-Liss.
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