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.

Specification of retinotectal connexions during development of the toad Xenopus laevis

Development ◽  
1980 ◽  
Vol 55 (1) ◽  
pp. 77-92
Author(s):  
S. C. Sharma ◽  
J. G. Hollyfield
Keyword(s):  
Xenopus Laevis ◽  
Ganglion Cell ◽  
Retinal Ganglion Cells ◽  
Optic Tectum ◽  
Ganglion Cells ◽  
The Other ◽  
Retinal Ganglion ◽  
Visual Projection ◽  
Series Of Experiments ◽  
The Right

The specification of central connexions of retinal ganglion cells was studied in Xenopus laevis. In one series of experiments, the right eye primordium was rotated 180° at embryonic stages 24–32. In the other series, the left eye was transplanted into the right orbit, and vice versa, with either 0° or 180° rotation. After metamorphosis the visual projections from the operated eye to the contralateral optic tectum were mapped electrophysiologically and compared with the normal retinotectal map. In all cases the visual projection map was rotated through the same angle as was indicated by the position of the choroidal fissure. The left eye exchanged into the right orbit retained its original axes and projected to the contralateral tectum. These results suggest that retinal ganglion cell connexions are specified before stage 24.

scholarly journals CTCF looping is established during gastrulation in medaka embryos

2018 ◽  
Author(s):  
Ryohei Nakamura ◽  
Yuichi Motai ◽  
Masahiko Kumagai ◽  
Haruyo Nishiyama ◽  
Neva C. Durand ◽  
...  
Keyword(s):  
Gene Regulation ◽  
Embryonic Development ◽  
Protein Binding ◽  
Early Development ◽  
Great Increase ◽  
Critical Role ◽  
Early Embryogenesis ◽  
Genome Architecture ◽  
Time Points ◽  
Genome Wide

Abstract:Genome architecture plays a critical role in gene regulation, but how the structures seen in mature cells emerge during embryonic development remains poorly understood. Here, we study early development in medaka (the Japanese killifish, Oryzias latipes) at 12 time points before, during, and after gastrulation which is the most dramatic event in early embryogenesis, and characterize transcription, protein binding, and genome architecture. We find that gastrulation is most associated with drastic changes in genome architecture, including the formation of the first loops between sites bound by the insulator protein CTCF and great increase in the size of contact domains. However, the position of CTCF is fixed throughout medaka embryogenesis. Interestingly, genome-wide transcription precedes the emergence of mature domains and CTCF-CTCF loops.

The role of water-regulating mechanisms in the development of the haploid syndrome in Xenopus laevis

Development ◽  
1972 ◽  
Vol 28 (2) ◽  
pp. 449-462
Author(s):  
Louie Hamilton ◽  
P. H. Tuft
Keyword(s):  
Xenopus Laevis ◽  
Cell Number ◽  
Gastrula Stage ◽  
Tail Bud ◽  
Volume Changes ◽  
Membrane Area ◽  
Flow Through ◽  
The Difference ◽  
Haploid Embryos

The uptake of water by haploid and diploid sibling embryos of Xenopus laevis has been investigated by measuring the density changes which occur during the development of intact embryos from the blastula to the late tail-bud stage, and of explants from which most of the presumptive endoderm has been removed. The results show that up to the mid-gastrula stage there is no difference between the haploid and diploid embryos; but from then on, whereas the diploid volume increases steadily, the haploid gastrulae undergo a series of cyclical volume changes due to loss of fluid through the blastopore. It is concluded that this is the result of an excessive inflow of water through the haploid ectoderm, because it was found that the volume of haploid ectodermal explants increased much more rapidly than the volume of similar diploid explants. Excess flow through the haploid ectoderm also accounts for other characteristics of the haploid syndrome – microcephaly and lordosis. It is suggested that it is the doubling of the cell number in haploid embryos with the consequent 25% increase in aggregate cell membrane area which accounts for the difference between the uptake of water by the two types of embryos. It is also suggested that changes in the rate of water flow through the ectoderm and endoderm which are thought to account for the accumulation of water in the blastocoel and archenteron in the normal diploid embryo arise in a similar way.

Gene expression in Xenopus embryogenesis

Development ◽  
1985 ◽  
Vol 89 (Supplement) ◽  
pp. 113-124
Author(s):  
Igor B. Dawid ◽  
Susan R. Haynes ◽  
Milan Jamrich ◽  
Erzsebet Jonas ◽  
Seiji Miyatani ◽  
...  
Keyword(s):  
Gene Expression ◽  
Protein Synthesis ◽  
Xenopus Laevis ◽  
Cdna Cloning ◽  
Early Embryogenesis ◽  
Gene Activity ◽  
Complex Nature ◽  
Cdna Clones ◽  
Midblastula Transition ◽  
First Time

This article considers some aspects of the storage of macromolecules in the oocyte of Xenopus laevis and the activation of previously unexpressed genes during early embryogenesis. The large quantity and complex nature of poly(A)+ RNA accumulated in the egg provides the cleavage embryo with a supply of mRNA sufficient to sustain protein synthesis for several hours of development. Onset of gene activity at the midblastula transition (MBT) leads to the synthesis and accumulation of molecules of various RNA classes, including tRNAs, rRNAs, mRNAs and mitochondrial RNAs. At gastrulation the poly(A)+ RNA population is still qualitatively similar to that of the egg but some sequences not present in egg RNA have accumulated by this time. Through the use of a subtractive cDNA cloning procedure we have prepared a library of sequences that represent genes activated for the first time between MBT and gastrula. A study of several of these cDNA clones suggests that genes in this class are restricted in their activity to embryonic and tadpole stages.

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.

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.

The effect of retinal growth on the postnatal development and distribution of displaced retinal ganglion cells in the retina of the chameleon (squamata)

2003 ◽  
Vol 20 (3) ◽  
pp. 273-283 ◽  
Author(s):  
MATTHIAS OTT ◽  
BRENO BELLINTANI-GUARDIA
Keyword(s):  
Retinal Ganglion Cells ◽  
Ganglion Cells ◽  
Retrograde Transport ◽  
Dendritic Arbor ◽  
Adult Size ◽  
Retinal Ganglion ◽  
Accessory Optic System ◽  
Dendritic Field ◽  
Eye Size ◽  
Retinal Growth

Retinal ganglion cells (RGCs) usually increase their dendritic field area with postnatal retinal growth. The mechanisms that regulate the postnatal shape of dendritic arbors in the growing retina are not well understood. Quantitative studies suffer from the difficulty of labeling specific subpopulations of RGCs selectively including their dendritic processes. In this study, we labeled displaced retinal ganglion cells (DGC) that are known to project to the accessory optic system (AOS) in juvenile and adult chameleons by retrograde transport of dextran amines. The complete population of DGCs was quantitatively screened for the effects of postnatal retinal growth on cell morphology, dendritic field coverage, and dendritic arbor size. The adult eye contained 2000 DGCs/retina. This number was already present at birth. The smaller size of the hatchling eye (approximately 1/3 of the adult size) led to higher densities of DGCs. The greatest accumulation of juvenile DGCs (two-fold higher compared to the adult) was found in the periphery of the retina where the greatest surface expansion was observed. DGC dendritic field areas were adjusted proportionally to this expansion in order to maintain a constant dendritic coverage. The increase of dendritic fields was mediated by two putative passive mechanisms: First, an elongation of individual dendrites similar to previous reports of postnatal RGC development in the retina of goldfish and chicks. Second, and more prominent, we observed that neighboring dendrites were pulled apart from each other. This resulted in a looser spacing of the initially tightly packed dendrites of each dendritic arbor. This dispersal of dendrites over a larger area was, due to its passive nature, proportional to the increase of the retinal surface and preserved a constant dendritic coverage irrespective of the animal's age and eye size.

Sign in / Sign up

Export Citation Format

Share Document