title: Central projections of anuran optic nerves penetrating hindbrain or spinal cord regions of the neural tube.
abstract: To identify parameters of optic tract growth that may be independent of the region of the CNS in which the tract develops, eye primordia of embryonic Rana pipiens were transplanted to a variety of ectopic locations adjacent to the hindbrain and spinal cord. Longitudinal growth direction, cross-sectional growth position and possible termination sites of ectopic optic tracts from transplanted eyes were analyzed in serial section autoradiographs following intraocular injection of [3H]proline. Sixteen animals ranging in age from Taylor and Kollros Stage I32 to one month postmetamorphosis were used in this study. The analysis revealed that retinal ganglion cell axons are capable of growing in both rostral and caudal directions within all regions of the hindbrain and spinal cord. Within comparable regions of the hindbrain and spinal cord, all ectopic optic tracts were located in identical cross-sectional positions. The positions were always sub-adjacent to the pial surface of the CNS and contiguous to regions of the neural axis in which sensory fiber tracts are normally found. Possible termination sites of ascending ectopic optic tracts were detected within sensory regions of the hindbrain and posterior midbrain tegmentum. However, there was no consistent selection of particular regions of termination. No ectopic optic nerve fibers extended significantly beyond the hindbrain-midbrain junction and no fibers could be traced to the optic tecta.
authors.affiliation: Biology Department, Guyot Hall, Princeton University, Princeton, NJ 08540, USA.
authors.forename: M
authors.initials: M
authors.lastname: Constantine-Paton
mesh_terms: D000367:Age Factors; D000818:Animals; D001001:Anura; D001345:Autoradiography / Q000379:methods; D004625:Embryo, Nonmammalian; D005123:Eye / Q000166:cytology / Q000196:embryology / Q000637:transplantation; D007930:Leucine / Q000378:metabolism; D008526:Medulla Oblongata / Q000196:embryology / Q000502:physiology*; D054259:Neural Tube / Q000033:anatomy & histology* / Q000196:embryology; D009900:Optic Nerve / Q000201:enzymology / Q000502:physiology*; D013116:Spinal Cord / Q000196:embryology* / Q000502:physiology*; D014316:Tritium / Q000378:metabolism; D014795:Visual Pathways / Q000196:embryology / Q000502:physiology
chemical_list: D014316:Tritium; D007930:Leucine