The retinotectal projection from a double-ventral compound eye in Xenopus laevis

Development ◽  
1974 ◽  
Vol 31 (1) ◽  
pp. 123-137
Author(s):  
K. Straznicky ◽  
R. M. Gaze ◽  
M. J. Keating
Keyword(s):  
Xenopus Laevis ◽  
Compound Eye ◽  
Retinotectal Projection ◽  
Temporal Direction

The retinotectal projection was mapped in 22 post-metamorphic Xenopus in which the eye under investigation had been made double-ventral by operation at stage 32. The contralateral retinotectal projection from a double-ventral eye is neither normal nor does it show the type of abnormality predicted from previous work on double-nasal and double-temporal eyes. In the case of double-ventral eyes, the nasal part of the field projection tended to be reduplicated about the horizontal midline and those field positions corresponding to lateromedial rows of electrode positions on the tectum ran ventrodorsally in the field. As the electrode rows on the tectum progressed more caudally, so the corresponding rows of stimulus positions in the field tended to curl in a temporal direction. These observations have been interpreted as indicating that the nasotemporal and dorsoventral polarities of the eye are not irreversibly determined at stage 32 and that the mechanisms generating the nasotemporal and dorsoventral axes of the eye may interact with each other.

Retinal growth in double dorsal and double ventral eyes in Xenopus

Development ◽  
1977 ◽  
Vol 40 (1) ◽  
pp. 175-185
Author(s):  
K. Straznicky ◽  
D. Tay
Keyword(s):  
Xenopus Laevis ◽  
Compound Eye ◽  
Ganglion Cells ◽  
Cell Number ◽  
Early Embryogenesis ◽  
Time Points ◽  
Retinal Growth

The growth of normal and surgically produced compound dorsal and ventral retinae in Xenopus laevis has been studied autoradiographically following injections of [3H]thymidine at stages 50 and 58. The animals were sacrificed 3 weeks after metamorphosis. The histogenetic pattern of the dorsal and ventral retinal halves was different at the three time points investigated, i.e. up to stage 50, between stages 50 and 58 and between stage 58 and 3 weeks after metamorphosis. Asymmetrical dorsal retinal growth occurred up to stage 50. From stage 50 onwards the retinal growth tendency reversed so that more ganglion cells were produced along the ventral than the dorsal ciliary margins. The overall preponderance of ventral retinal growth was 32·4% in cell number and 12·4% in retinal length from early embryogenesis to 3 weeks after metamorphosis. The characteristic histogenetic pattern of the dorsal and ventral retinal halves was maintained in an ectopic position in the compound eye, indicating that this particular property of the retinal halves is intrinsically determined.

The development of the retinotectal projection in Xenopus with one compound eye

Development ◽  
1975 ◽  
Vol 33 (3) ◽  
pp. 775-787
Author(s):  
Joan D. Feldman ◽  
R. M. Gaze
Keyword(s):  
Compound Eye ◽  
Contralateral Side ◽  
Compound Eyes ◽  
Stages Of Development ◽  
Ipsilateral Side ◽  
Retinotectal Projection ◽  
Xenopus Embryos ◽  
Donor Embryo

Double-nasal and double-temporal compound eyes were constructed in Xenopus embryos at stages 32 and 37/38. A particular half was removed from the host eye anlage and replaced with the opposite half-eye from the contralateral side of a donor embryo. Control operations consisted of removing a half-eye and replacing it with a similar half from the ipsilateral side of the donor embryo. Whereas in control animals, each half-eye projected its fibres to the appropriate half-tectum, in operated animals each half of the compound eye spread its optic teiminals across the entire rostrocaudal extent of the dorsal tectal surface. The area of tectal surface covered by ganglion fibre terminals was similar in operated animals mapped at successive stages of development to that previously observed in normal animals at equivalent stages. Therefore the factors responsible for the extended distribution of fibre terminals from each half of a compound eye must exist at least from mid-tadpole life, and thereafter be continuously present throughout development.

Visual deprivation and the maturation of the retinotectal projection in Xenopus laevis

Development ◽  
1986 ◽  
Vol 91 (1) ◽  
pp. 101-115
Author(s):  
M. J. Keating ◽  
S. Grant ◽  
E. A. Dawes ◽  
K. Nanchahal
Keyword(s):  
Xenopus Laevis ◽  
Neural Activity ◽  
Ganglion Cells ◽  
Chronic Administration ◽  
Visual Deprivation ◽  
Lower Vertebrate ◽  
Initial Development ◽  
Retinotectal Projection ◽  
Spontaneous Neural Activity ◽  
Retinotectal System

There has been a resurgence of interest, recently, in the possible role of neural activity in the ordering of synaptic connections in the lower vertebrate retinotectal system. Blockade of all neural activity, by chronic administration of tetrodotoxin (TTX), during the regeneration of the optic nerve in goldfish has been found to prevent the re-emergence of a fully ordered retinotectal projection. We sought to determine the effects of visual deprivation, a less radical perturbation of neural activity than that produced by TTX, on the initial development of the retinotectal projection. The contralateral visuotectal projection was studied in Xenopus laevis which had been reared in darkness from before the onset of visual function. The projection mapped electrophysiologically at metamorphic climax, or in postmetamorphic juveniles, showed a normal retinotopic topography. The topographic precision of the projection, as revealed by the multiunit receptive field sizes, was the same in light- and dark-reared animals. The laminar distribution, in the superficial neuropil of the optic tectum, of terminals from different classes of retinal ganglion cells was also normal. It is concluded that the specific retinotectal connections underlying these features of the projection are generated by intrinsic developmental processes which do not require visual experience. Among these intrinsic processes might be ‘spontaneous’ neural activity.

Gradual appearance of a regulated retinotectal projection pattern in Xenopus laevis

1989 ◽  
Vol 132 (1) ◽  
pp. 251-265 ◽  
Author(s):  
Nancy A. O'Rourke ◽  
Scott E. Fraser
Keyword(s):  
Xenopus Laevis ◽  
Retinotectal Projection ◽  
Projection Pattern

The retinotectal projection of quarter eyes in Xenopus laevis

1986 ◽  
Vol 29 (1) ◽  
pp. 141-143 ◽  
Author(s):  
Norbert Degen ◽  
Kurt Brändle
Keyword(s):  
Xenopus Laevis ◽  
Retinotectal Projection

The growth of the retina in Xenopus laevis, an autoradiographic study

Development ◽  
1972 ◽  
Vol 27 (2) ◽  
pp. 381-387
Author(s):  
Joan D. Feldman ◽  
R. M. Gaze
Keyword(s):  
Cell Division ◽  
Xenopus Laevis ◽  
Compound Eye ◽  
Normal Animal ◽  
Autoradiographic Study ◽  
Compound Eyes ◽  
Dorsoventral Axis ◽  
Experimental Animals ◽  
Cut Edge ◽  
Ciliary Margin

The retina of Xenopus laevis has previously been shown, using autoradiographic methods, to develop in the normal animal by the annular addition of cells at the ciliary margin. The development of the retina in animals with surgically produced “compound eyes” was subsequently studied. In these animals the eye cup was split along the dorsoventral axis and the resulting half-eyes were recombined so as to form animals with a double-nasal eye. The retina in experimental animals was found to develop as in the normal animal. No labelling of cells with radioactive thymidine was seen along the cut edge of each half-eye; thus in terms of cell division each half of the compound eye remains a half.

Computer Reconstruction of the Cellular Architecture of the Daphnia Magna Optic Ganglion

1975 ◽  
Vol 33 ◽  
pp. 284-285
Author(s):  
E. R. Macagno ◽  
C. Levinthal
Keyword(s):  
Daphnia Magna ◽  
Genetic Background ◽  
Compound Eye ◽  
Synaptic Connectivity ◽  
Serial Sections ◽  
Cross Sectional ◽  
Small Crustacean ◽  
Optic Ganglion ◽  
Structural Invariance ◽  
High Degree

The optic ganglion of Daphnia Magna, a small crustacean that reproduces parthenogenetically contains about three hundred neurons: 110 neurons in the Lamina or anterior region and about 190 neurons in the Medulla or posterior region. The ganglion lies in the midplane of the organism and shows a high degree of left-right symmetry in its structures. The Lamina neurons form the first projection of the visual output from 176 retinula cells in the compound eye. In order to answer questions about structural invariance under constant genetic background, we have begun to reconstruct in detail the morphology and synaptic connectivity of various neurons in this ganglion from electron micrographs of serial sections (1). The ganglion is sectioned in a dorso-ventra1 direction so as to minimize the cross-sectional area photographed in each section. This area is about 60 μm x 120 μm, and hence most of the ganglion fit in a single 70 mm micrograph at the lowest magnification (685x) available on our Zeiss EM9-S.

Androgen-induced plasticity at a “vocal” neuromuscular synapse

1994 ◽  
Vol 52 ◽  
pp. 32-33
Author(s):  
Darcy B. Kelley ◽  
Martha L. Tobias ◽  
Mark Ellisman
Keyword(s):  
Xenopus Laevis ◽  
Motor Neurons ◽  
Sexual Differentiation ◽  
Molecular Basis ◽  
Neuromuscular Synapse ◽  
Sexually Dimorphic ◽  
Intracellular Protein ◽  
Developmental Program ◽  
Androgen Action ◽  
Clawed Frog

Brain and muscle are sexually differentiated tissues in which masculinization is controlled by the secretion of androgens from the testes. Sensitivity to androgen is conferred by the expression of an intracellular protein, the androgen receptor. A central problem of sexual differentiation is thus to understand the cellular and molecular basis of androgen action. We do not understand how hormone occupancy of a receptor translates into an alteration in the developmental program of the target cell. Our studies on sexual differentiation of brain and muscle in Xenopus laevis are designed to explore the molecular basis of androgen induced sexual differentiation by examining how this hormone controls the masculinization of brain and muscle targets.Our approach to this problem has focused on a highly androgen sensitive, sexually dimorphic neuromuscular system: laryngeal muscles and motor neurons of the clawed frog, Xenopus laevis. We have been studying sex differences at a synapse, the laryngeal neuromuscular junction, which mediates sexually dimorphic vocal behavior in Xenopus laevis frogs.

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