Intracellular and Extracellular Changes During Early Ocular Development in the Chick Embryo

Hilfer, S. Robert; Brady, Richard C.; Yang, Jyh-Jia W.

doi:10.1007/978-1-4612-5964-0_3

Cited by 23 publications

(28 citation statements)

References 25 publications

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“…Comparing the predicted shapes of the OV at various stages with corresponding sketches provided in Hilfer et al (1981) reveals reasonably good agreement (Fig. 9).…”

Section: Resultssupporting

confidence: 60%

“…In the transverse-plane model, the brain tube and OV are divided into sections with tangential growth specified separately in each section according to the measurements of Hilfer et al (1981) (see Methods section). Comparing the predicted shapes of the OV at various stages with corresponding sketches provided in Hilfer et al (1981) reveals reasonably good agreement (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…The transverse-plane model includes 5540 elements, and we used the measurements of Hilfer et al (1981) to define the growth in different regions of the OV (Fig. 2D).…”

Section: Methodsmentioning

confidence: 99%

“…Regardless of the specific mechanism, it appears that addition of new cells to the OVs drives evagination, rather than, for example, active changes in cell shape. In addition, Hilfer et al (1981) speculated that OV shape is influenced by external constraints on its expansion, but this idea apparently has heretofore not been confirmed.…”

Section: Introductionmentioning

confidence: 99%

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Mechanical effects of the surface ectoderm on optic vesicle morphogenesis in the chick embryo

Hosseini

Beebe

Taber

2014

Journal of Biomechanics

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Precise shaping of the eye is crucial for proper vision. Here, we use experiments on chick embryos along with computational models to examine the mechanical factors involved in the formation of the optic vesicles (OVs), which grow outward from the forebrain of the early embryo. First, mechanical dissections were used to remove the surface ectoderm (SE), a membrane that contacts the outer surfaces of the OVs. Principal components analysis of OV shapes suggests that the SE exerts asymmetric loads that cause the OVs to flatten and shear caudally during the earliest stages of eye development and later to bend in the caudal and dorsal directions. These deformations cause the initially spherical OVs to become pear-shaped. Exposure to the myosin II inhibitor blebbistatin reduced these effects, suggesting that cytoskeletal contraction controls OV shape by regulating tension in the SE. To test the physical plausibility of these interpretations, we developed 2-D finite-element models for frontal and transverse cross-sections of the forebrain, including frictionless contact between the SE and OVs. With geometric data used to specify differential growth in the OVs, these models were used to simulate each experiment (control, SE removed, no contraction). For each case, the predicted shape of the OV agrees reasonably well with experiments. The results of this study indicate that differential growth in the OV and external pressure exerted by the SE are suffcient to cause the global changes in OV shape observed during the earliest stages of eye development.

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“…Comparing the predicted shapes of the OV at various stages with corresponding sketches provided in Hilfer et al (1981) reveals reasonably good agreement (Fig. 9).…”

Section: Resultssupporting

confidence: 60%

Section: Resultsmentioning

confidence: 99%

“…The transverse-plane model includes 5540 elements, and we used the measurements of Hilfer et al (1981) to define the growth in different regions of the OV (Fig. 2D).…”

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Mechanical effects of the surface ectoderm on optic vesicle morphogenesis in the chick embryo

Hosseini

Beebe

Taber

2014

Journal of Biomechanics

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“…This asymmetric growth is accompanied by numerous mitotic figures within the posterior region of the primordia. A similar elongation of the optic vesicles has been described in amphibians, birds and mammals (Mann, 1964;Grant et al, 1980;Schook, 1980a,b) and has also been attributed to differential prolif-eration (Hilfer et al, 1981). Also, prior to invagination in the zebrafish, cells within the dorsal half of the optic primordia, destined to become the neural retina, elongate between the 10 and 14 somite stages.…”

Section: Discussionmentioning

confidence: 80%

Early‐eye morphogenesis in the zebrafish, Brachydanio rerio

Schmitt¹,

Dowling²

1994

J of Comparative Neurology

250

241

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Early eye morphogenesis in the zebrafish between 12 and 36 hours postfertilization was studied by light- and scanning electron microscopy. Overall, early eye morphogenesis in the zebrafish is similar to that of other vertebrates even though the optic primordia evaginate from the forebrain as solid masses of cells. After initial evagination (6-7 somite stage [SS]), the optic primordia take on a wing-like shape (8-9 SS). Subsequently, they bend ventrally and rotate slightly in an anterior direction (10-12 SS). These changes serve to bring the primordia from a horizontal to a more vertical orientation in relation to the embryonic neural axis. Invagination commences from the center of each primordium (14 SS) and progresses symmetrically out towards the periphery (14-20 SS). The choroid fissure forms by an involution along the anterior region of the eyecup (18-20 SS). By 24 hours postfertilization (pf), the eyecups are well formed. Between 24 and 36 hours pf, the eyes rotate further in relation to the axis of the embryo, and this repositions the choroid fissue to a typical ventral location by 36 hours pf. Because of the two rotations of the eye during early morphogenesis, particularly the later one, the anterior-posterior orientation of the emerging optic primordium ultimately becomes the ventral-dorsal axis of the completed eyecup.

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Retinal cell death occurs in the absence of retinal disc invagination: Experimental evidence in papaverine‐treated chicken embryos

1987

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In an attempt to clarify the relationship between the presence of retinal cell death and the invagination of the optic vesicle, we have tested the occurrence and cytological characteristics of the retinal necrotic areas in the embryonic chicken after the administration in ovo of papaverine. Papaverine, a Ca2+ antagonist, was found to prevent the invagination of the optic vesicle. All embryonic retinae presented two distinct necrotic areas. However, these areas of cell death appeared abnormally located in the experimental, uninvaginated retina. One area was located at the transition between the retinal disc and the ventral wall of the optic vesicle; a second area was located in the dorsal wall of the optic vesicle, close to the optic stalk. We suggest that these necrotic areas represent the normal necrotic areas, should the invagination of the retinal disc have taken place. Retinal cell death appears to be programmed; it occurs whether the retinal disc invaginates or not. Cell death appears, in this experimental model, as a natural marker giving evidence that the embryonic retinal cells move from the optic stalk into the invagination retinal disc during normal eye cup formation. In addition to the uninvaginated optic vesicle the lens placode failed to invaginate in 45% of the cases, forming a lens vesicle in 55% of the remaining cases. This suggests that the two processes of invagination are governed by a different set of factors.

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Intracellular and Extracellular Changes During Early Ocular Development in the Chick Embryo

Cited by 23 publications

References 25 publications

Mechanical effects of the surface ectoderm on optic vesicle morphogenesis in the chick embryo

Mechanical effects of the surface ectoderm on optic vesicle morphogenesis in the chick embryo

Early‐eye morphogenesis in the zebrafish, Brachydanio rerio

Retinal cell death occurs in the absence of retinal disc invagination: Experimental evidence in papaverine‐treated chicken embryos

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