The Thai Journal of Veterinary Medicine


In comparative histochemical survey on the retinas of ten piscian species, paraffin sections were stained for cysteinyl thiol and cystinyl disulfide groups as well as for the basic groups on proteins. The routine hematoxylin-eosin staining was used for identification and orientation purposes. The piscian retinas were found for the first time to have the same pattern of thiol distribution reported in the literatues for other vertebrate classes. This is both very high density and relative concentration of protein thiol groups in the outer segments of the photoreceptors (rods and cones). The significant levels are found in the photoreceptor inner segments and their synaptic bodies, in the various cell types comprising the inner nuclear layer, and in the ganglion cells plus their axons making up the nerve fiber layer. It was also shown for the first time by histochemical means that the parts of the cephalopod retina which correspond to the vertebrate photoreceptor structure also are very rich in protein thiol groups. The results have led to the inference that the proteins of the visual pigments of all vertebrates and of the cephalopods probably have very similar thiol contents and that the thiol groups are necessary for the visual cycle.

First Page


Last Page