Biomaterial Database

The relationship between retinal and tectal growth in larval Xenopus: implications for the development of the retino-tectal projection. 1979

R M Gaze, and M J Keating, and A Ostberg, and S H Chung

The modes of retinal and tectal histogenesis, as well as the patterns of terminal distribution of optic axons in larval Xenopus were studied, using anatomical techniques. We show that the retina grows by adding strips of cells at its ciliary margin. The pattern of retinal growth is asymmetrical along the dorso-ventral axis of the retina. On the other hand, the tectum grows by adding newly formed cells caudo-medially. The most rapid tectal growth takes place between stages 50 and 53, and thereafter only a small proportion of cells are added near the midline of the caudal tectum. Despite such incongruent modes of retinal and tectal growth, retinotopic order is maintained throughout larval life. We present here further evidence supporting the idea that connexions between the arrays of retinal and tectal cells shift progressively caudo-medially on the tectum during the period of growth. When the temporal pole of the retina is destroyed at various developmental stages, the density of degenerating synapses is always highest in the rostral pole of the tectum. Moreover, optic terminals stemming from the central retina spread caudally, invading newly maturing regions of the tectum. Quantitative analysis of the terminal distributions of optic axons suggest that orderly shifts in synaptic contacts between optic axons and tectal dendrites take place in the course of development. Ultrastructural observations on the maturing tectal neuropil are consistent with this view.

UI	MeSH Term	Description	Entries
D007814	Larva	Wormlike or grublike stage, following the egg in the life cycle of insects, worms, and other metamorphosing animals.	Maggots,Tadpoles,Larvae,Maggot,Tadpole
D008675	Metamorphosis, Biological	Profound physical changes during maturation of living organisms from the immature forms to the adult forms, such as from TADPOLES to frogs; caterpillars to BUTTERFLIES.	Biological Metamorphosis,Biological Metamorphoses,Metamorphoses, Biological
D009410	Nerve Degeneration	Loss of functional activity and trophic degeneration of nerve axons and their terminal arborizations following the destruction of their cells of origin or interruption of their continuity with these cells. The pathology is characteristic of neurodegenerative diseases. Often the process of nerve degeneration is studied in research on neuroanatomical localization and correlation of the neurophysiology of neural pathways.	Neuron Degeneration,Degeneration, Nerve,Degeneration, Neuron,Degenerations, Nerve,Degenerations, Neuron,Nerve Degenerations,Neuron Degenerations
D009900	Optic Nerve	The 2nd cranial nerve which conveys visual information from the RETINA to the brain. The nerve carries the axons of the RETINAL GANGLION CELLS which sort at the OPTIC CHIASM and continue via the OPTIC TRACTS to the brain. The largest projection is to the lateral geniculate nuclei; other targets include the SUPERIOR COLLICULI and the SUPRACHIASMATIC NUCLEI. Though known as the second cranial nerve, it is considered part of the CENTRAL NERVOUS SYSTEM.	Cranial Nerve II,Second Cranial Nerve,Nervus Opticus,Cranial Nerve, Second,Cranial Nerves, Second,Nerve, Optic,Nerve, Second Cranial,Nerves, Optic,Nerves, Second Cranial,Optic Nerves,Second Cranial Nerves
D012160	Retina	The ten-layered nervous tissue membrane of the eye. It is continuous with the OPTIC NERVE and receives images of external objects and transmits visual impulses to the brain. Its outer surface is in contact with the CHOROID and the inner surface with the VITREOUS BODY. The outer-most layer is pigmented, whereas the inner nine layers are transparent.	Ora Serrata
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D001369	Axons	Nerve fibers that are capable of rapidly conducting impulses away from the neuron cell body.	Axon
D013477	Superior Colliculi	The anterior pair of the quadrigeminal bodies which coordinate the general behavioral orienting responses to visual stimuli, such as whole-body turning, and reaching.	Colliculus, Superior,Optic Lobe, Human,Optic Lobe, Mammalian,Optic Tectum,Anterior Colliculus,Superior Colliculus,Tectum, Optic,Colliculi, Superior,Colliculus, Anterior,Human Optic Lobe,Human Optic Lobes,Mammalian Optic Lobe,Mammalian Optic Lobes,Optic Lobes, Human,Optic Lobes, Mammalian,Optic Tectums,Tectums, Optic
D013569	Synapses	Specialized junctions at which a neuron communicates with a target cell. At classical synapses, a neuron's presynaptic terminal releases a chemical transmitter stored in synaptic vesicles which diffuses across a narrow synaptic cleft and activates receptors on the postsynaptic membrane of the target cell. The target may be a dendrite, cell body, or axon of another neuron, or a specialized region of a muscle or secretory cell. Neurons may also communicate via direct electrical coupling with ELECTRICAL SYNAPSES. Several other non-synaptic chemical or electric signal transmitting processes occur via extracellular mediated interactions.	Synapse
D014795	Visual Pathways	Set of cell bodies and nerve fibers conducting impulses from the eyes to the cerebral cortex. It includes the RETINA; OPTIC NERVE; optic tract; and geniculocalcarine tract.	Pathway, Visual,Pathways, Visual,Visual Pathway