The fine structure of the developing retina in Xenopus laevis

Development ◽  
1972 ◽  
Vol 28 (3) ◽  
pp. 659-666
Author(s):  
J. S. Dixon ◽  
J. R. Cronly-Dillon
Keyword(s):  
Fine Structure ◽  
Xenopus Laevis ◽  
Retinal Cell ◽  
Optic Vesicle ◽  
Cell Specification ◽  
Ciliary Margin ◽  
Large Numbers ◽  
Outer Aspect ◽  
Cell To Cell Transfer ◽  
Pigment Epithelial Cells

The fine structure of the developing retinal cells in Xenopus laevis was studied from stages 26 to 36. At all stages examined the cells contained large numbers of free ribosomes, polysomes, small mitochondria, lipid and yolk droplets and scanty granular reticulum. A basal lamina covered the smooth internal margin of the optic vesicle and also the external aspect of the germinal pigment epithelial cells. At all stages examined zonulae adhaerentes occurred between adjacent cells at the outer aspect of the optic vesicle and maculae adhaerentes diminutae were occasionally observed. A third type of intercellular junction, characterized by a narrow gap of 3–9 nm, occurred throughout the retina up to stage 30 but only at the periphery beyond this stage. It is suggested that the disappearance of these junctions from the central portion of the retina may be correlated with retinal cell specification* which is known to occur at stage 30–31. These junctions may represent sites for the cell to cell transfer of small molecules which are required for cell differentiation. Since new cells are continually being added to the retina from the ciliary margin beyond stage 30 the persistence of junctions in this region may explain how these new cells also become specified.*

scholarly journals Evaluation of Effective and Practical Euthanasia Methods for Larval African Clawed Frogs (Xenopus laevis)

2020 ◽  
Vol 59 (3) ◽  
pp. 269-274
Author(s):  
Ilana A Galex ◽  
Cameron M Gallant ◽  
Nicole D'Avignon ◽  
Lauren M Kuchenbrod ◽  
Craig A Fletcher ◽  
...  
Keyword(s):  
Xenopus Laevis ◽  
Developmental Stages ◽  
Age Group ◽  
Research Model ◽  
Larval Stages ◽  
Large Numbers ◽  
Guidance Documents ◽  
Stock Solutions ◽  
Tricaine Methanesulfonate ◽  
Tank Water

Larval, or tadpole-stage Xenopus laevis frogs are a popular research model for developmental biology and disease studies. Existing euthanasia guidance documents offer recommendations for both eggs and adult stages, yet do not specifically address the larval stage. Data evaluating effective euthanasia methods for groups of X. laevis tadpoles would therefore be useful. The goal of the current study was to evaluate the efficacy of various immersion euthanasia procedures on tadpoles: tricaine methanesulfonate (MS222) at 6 g/L, eugenol at 800 μL/L and rapid chilling (2 to 4 °C). We also evaluated tadpoles at various developmental stages (NF stages 46, 47 and 49). Tadpoles (n = 70) were exposed to euthanasia solution for 15 min, and controls (n = 40) were placed in housing tank water for 15 min. All animals were then placed in recovery tanks containing housing tank water for 4 h to confirm irreversibility of each agent. Cessation of the heartbeat was assessed at the end of euthanasia solution exposure and at each hour thereafter. We found that immersion in a 6 g/L solution of MS222 resulted in 100% euthanasia of all larval stages tested. Conversely, eugenol produced variable euthanasia rates that were affected by both age group and batches of stock solutions. Rapid chilling was completely ineffective as a euthanasia method in our study. Based on our findings, we recommend MS222 as an effective and practical means of euthanizing large numbers of X. laevis tadpoles.

scholarly journals Islet-1 Immunoreactivity in the Developing Retina ofXenopus laevis

2013 ◽  
Vol 2013 ◽  
pp. 1-11 ◽  
Author(s):  
Guadalupe Álvarez-Hernán ◽  
Ruth Bejarano-Escobar ◽  
Ruth Morona ◽  
Agustín González ◽  
Gervasio Martín-Partido ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Ganglion Cells ◽  
Temporal Distribution ◽  
Cell Types ◽  
Horizontal Cells ◽  
Retinal Cell ◽  
Spatial And Temporal Distribution ◽  
Cell Nuclei ◽  
Cell Specification ◽  
Islet 1

The LIM-homeodomain transcription factor Islet1 (Isl1) has been widely used as a marker of neuronal differentiation in the developing visual system of different classes of vertebrates, including mammals, birds, reptiles, and fish. In the present study, we analyzed the spatial and temporal distribution of Isl1-immunoreactive cells duringXenopus laevisretinal development and its relation to the formation of the retinal layers, and in combination with different markers of cell differentiation. The earliest Isl1 expression appeared at St29-30 in the cell nuclei of sparse differentiating neuroblasts located in the vitreal surface of the undifferentiated retina. At St35-36, abundant Isl1-positive cells accumulated at the vitreal surface of the neuroepithelium. As development proceeded and through the postmetamorphic juveniles, Isl1 expression was identified in subpopulations of ganglion cells and in subsets of amacrine, bipolar, and horizontal cells. These data together suggest a possible role for Isl1 in the early differentiation and maintenance of different retinal cell types, and Isl1 can serve as a specific molecular marker for the study of retinal cell specification inX. laevis.

scholarly journals Studies on microperoxisomes. VII. Pigment epithelial cells and other cell types in the retina of rodents.

1975 ◽  
Vol 65 (2) ◽  
pp. 324-334 ◽  
Author(s):  
P M Leuenberger ◽  
A B Novikoff
Keyword(s):  
Epithelial Cells ◽  
Vascular Endothelial Cells ◽  
Smooth Endoplasmic Reticulum ◽  
Photoreceptor Cells ◽  
Cell Types ◽  
Vascular Endothelial ◽  
Pigment Epithelial ◽  
Large Numbers ◽  
And Storage ◽  
Pigment Epithelial Cells

The pigment epithelial cell of the retina actively participates in two aspects of lipid metabolism: (a) the fatty acid esterification of vitamin A and its storage and transport to the photoreceptors, and (b) the phagocytosis and degradation of the lipoprotein membrane disks shed from the photoreceptor cells. Study of the pigment epithelial cells of adult albino and pigmented rodents has revealed the abundance of an organelle, microperoxisomes, not previously known to exist in this cell type. The metabolism, transport, and storage of lipids are major functions of other cell types which possess large numbers of microperoxisomes associated with a highly developed smooth endoplasmic reticulum. Microperoxisomes were encountered, but relatively rarely, in Müller cells and vascular endothelial cells. A tubular system in photoreceptor terminals is reactive in the cytochemical procedure used to visualize microperoxisomes.

scholarly journals The optic vesicle promotes cornea to lens transdifferentiation in larval Xenopus laevis

2008 ◽  
Vol 212 (5) ◽  
pp. 621-626 ◽  
Author(s):  
Stefano M. Cannata ◽  
Sergio Bernardini ◽  
Sergio Filoni ◽  
Cesare Gargioli
Keyword(s):  
Xenopus Laevis ◽  
Optic Vesicle

Organization of ampullary electric receptors in Gymnotidae (Pisces)

1968 ◽  
Vol 169 (1017) ◽  
pp. 345-378 ◽  
Keyword(s):  
Fine Structure ◽  
Evolutionary Relationships ◽  
Type I ◽  
Type Ii ◽  
Sense Organs ◽  
Large Numbers ◽  
Mode Of Operation ◽  
Points Of View ◽  
Eigenmannia Virescens ◽  
Electron Microscopes

Investigation of 14 species of gymnotid has established that large numbers of ampullary lateralis sense organs are present in each case. These organs have been examined with the light and electron microscopes. Two distinct types occur, and these are referred to as type I and type II; the latter is more common. The fine structure of the receptors in one species ( Eigenmannia virescens ) is described in detail, and is discussed from two points of view: (i) the function and mode of operation of the organs, and (ii) the evolutionary relationships to different receptors of the vertebrate acoustic-lateralis system.

Fine structure of psammoma bodies at the outer aspect of blood vessels in meningioma

1985 ◽  
Vol 66 (2) ◽  
pp. 163-166 ◽  
Author(s):  
T. Kubota ◽  
A. Hirano ◽  
K. Sato ◽  
S. Yamamoto
Keyword(s):  
Fine Structure ◽  
Blood Vessels ◽  
Psammoma Bodies ◽  
Outer Aspect

scholarly journals CHANGES IN CELL FINE STRUCTURE DURING LENS REGENERATION IN XENOPUS LAEVIS

1965 ◽  
Vol 24 (2) ◽  
pp. 211-222 ◽  
Author(s):  
Jane Overton
Keyword(s):  
Fine Structure ◽  
Xenopus Laevis ◽  
Normal Development ◽  
Low Density ◽  
Morphological Complexity ◽  
Lens Fibers ◽  
Lens Regeneration ◽  
Lens Vesicle ◽  
Rough Er ◽  
Two Phases

Changes at the level of cell fine structure have been studied during lens regeneration in the toad, Xenopus laevis, where cornea gives rise to the new lens. The transformation of these cells may be divided into three phases. (1) In the cornea, flattened cells become cuboidal and rough endoplasmic reticulum increases in amount. (2) In the new lens vesicle, cisternae of the rough ER break down into vesicles, smooth-walled vesicles and free ribosomes increase in number, and mitochondria can become enlarged and irregular, then centrally attenuated. Rudimentary cilia form. (3) As new lens fibers form, ribosomes become very numerous and low density fibrous elements and dense clumps appear in the cytoplasm. These phases are accompanied by marked nucleolar changes. The changes during the 3rd phase are similar to changes in the lens during normal development. The first two phases show an unexpected morphological complexity.

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