A molecular mechanism of symmetry breaking in the early chick embryo

It seems to be generally accepted that experimenting in ovo on the chick during the early stages of development (up to about 48 hours) is fraught with the greatest difficulty. After about this time no serious technical problems arise and a high proportion of successful results can be expected. It is natural to ask why there should be this change-over from extreme difficulty to reasonable simplicity. New (1955) attributed to this ‘inaccessibility of the chick embryo in the egg’ the invention of his own and many other in vitro methods during the last 30 years. There is no doubt that, when short-term experiments only are required, in vitro methods will probably always be preferred. But all in vitro methods suffer from the disadvantage that the embryo cannot be expected to survive for more than 48 hours or so after explantation.

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Segmental repetition of neuronal phenotype sets in the chick embryo hindbrain

Development ◽

10.1242/dev.118.1.151 ◽

1993 ◽

Vol 118 (1) ◽

pp. 151-162 ◽

Cited By ~ 25

Author(s):

J.D. Clarke ◽

A. Lumsden

Keyword(s):

Chick Embryo ◽

Cell Types ◽

Spatial Segregation ◽

Differential Migration ◽

Neuronal Phenotype ◽

Regional Diversity ◽

Early Chick Embryo ◽

Data Support ◽

Neuronal Types ◽

Neuronal Tracers

The neurons within the segmented hindbrain of the early chick embryo have been mapped with the neuronal tracers HRP and fluorescent lysinated dextran. We have categorised neurons according to their axonal pathways and have then compared rhombomeres with respect to the number and class of neurons present. The results indicate that most rhombomeres are similar in that they contain the same set of basic neuronal types but differ in that particular neuronal types are more abundant in some rhombomeres than others. The data support the concept that the hindbrain develops according to ‘variations on a segmental theme’ rather than ‘each segment is unique’. Many of the cell types occupy distinct mediolateral domains that are probably established by both the differential migration of some neuronal classes and the spatial segregation of distinct precursors. The caudal rhombomeres 7 and 8 are exceptional in that they do not have the full set of basic neuronal types and also contain two additional medial cell types that are not present rostrally. The mechanisms that may generate the regional diversity apparent in the more mature hindbrain are discussed.

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An electrosurgical technique for the production of localized tissue ablations in the early chick embryo

Development ◽

10.1242/dev.26.1.21 ◽

1971 ◽

Vol 26 (1) ◽

pp. 21-29

Author(s):

R. K. Jordan

Keyword(s):

Chick Embryo ◽

Low Frequency ◽

Alternating Current ◽

Chick Embryos ◽

Operating Microscope ◽

Young Chick ◽

Early Chick Embryo ◽

Electrolytic Corrosion ◽

Tungsten Metal

The passage of low-frequency alternating current was found superior to other methods considered for the production of small, discrete, electrolytic ablations in young chick embryos. Active electrodes of tungsten metal less than 5 µm in diameter were prepared by controlled electrolytic corrosion. These gave reproducible, discrete foci of destruction of the required size, with currents less than 2 mA. The identification of destroyed tissue areas was immediately apparent under the operating microscope and confirmed histologically. Preliminary studies on bilateral extirpation of the ultimobranchial primordia show the absence of the ultimobranchial bodies 6 days after destruction of the primordia at 96 h of incubation.

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