The transplantation of eyes to genetically eyeless salamanders: visual projections and somatosensory interactions

Abstract

Eyes were transplanted from normal axolotls to eyeless mutants, and several anatomical and physiological observations were made on the central visual centers in these animals. Some central projections were bilateral to the optic centers of the thalamus and midbrain, some traveled ipsilaterally to the same centers, and the rest grew down the spinal cord. This is similar to what has been found in eyes transplanted to normal hosts. The type of projection made in eyeless hosts correlated with the site of nerve entry into the CNS as in control hosts. Thus, the transplanted projection did not appear to be influenced by the host's optic nerves and tracts or lack of them. In spite of the transplanted optic fibers' taking abnormal paths, they made normally organized topographic maps on the host tecta. The visual and somatosensory topographic projections to the tectum were found to be in near perfect register normally, but in eyeless mutants to which rotated eyes had been transplanted, they were not. Acetylcholinesterase activity, found in the primary optic neuropil in normal animals, was greatly diminished in eyeless mutants, yet normal mutants with grafted eyes. Finally, transplantation of an eye to an eyeless mutant corrected the abnormally dark pigmentation caused by eyelessness but only in those cases of bilateral central innervation.

Position, guidance, and mapping in the developing visual system

“…Since these fibers almost certainly entered the tectum from a disorganized pathway as commonly occurs during regeneration, we must conclude that original growth of retinal fibers onto the tectum does not give it its polarity, but rather the tectum has its own intrinsic polarity. Ectopic eyes with abnormal and probably scrambled pathways, also make retinotopically appropriate connections on embryonic virgin tecta (Harris, 1982;Harris, 1984), reinforcing the above conclusion.…”

Organization of the Caudal Rhombencephalic Alar Plate of the Ribbed Newt <i>Pleurodeles waltl: </i>Evidence for the Presence of Dorsal Column and Lateral Cervical Nuclei

“…Various studies have dealt with somatosensory processing in the deep neuropil and the gray of the optic tectum of different urodele species [Grüsser-Cornehls and Himstedt, 1973;Gruberg and Solish, 1978;Gruberg and Harris, 1981;Harris, 1982Harris, , 1989Stirling and Brändle, 1982]. Roth et al [1990] described the tectum as a polysensory integrative center of retinal and non-retinal input.…”

Alteration of the retinotectal map in Xenopus by antibodies to neural cell adhesion molecules.

“…While some evidence now indicates that an activity-dependent process is involved in refining the order of the projection, its overall topography can be formed in the absence of visual experience or nerve activity (3,4). Furthermore, experiments on the development of the projection pattern have indicated that a normally oriented projection can form in the absence of the optic tract or nerve activity (5,6). The overall picture that emerges is that the retinotectal projection is initially patterned by cell interactions independent of the path of arrival of nerve fibers or their neuronal activity; the later refinement of the projection appears, however, to be an activity-dependent process.…”

“…Antibodies against the chicken liver cell adhesion molecule, L-CAM, have been described (10). The (3)(4)(5)(6) mg/ml) was added. The plate was sealed and refrigerated for 24 hr; internal humidity was regulated by a 1 M salt solution placed inside the multiwell plate.…”