Amata Hornbruch 1 Introduction

As the title indicates, this culture method was developed by Denis New and first described in 1955 (1). It enables the observer to study the events of gastrula-tion in the chick embryo in much greater detail than possible until then. It also opens the way to microsurgery without the problem that yolk and the vitelline membrane cause. Studying the effects of treatment with compound affecting morphogenesis and development became meaningful, because precise concentrations and volumes could be administered and successfully washed out again.

Most of the early work on the mechanics of gastrulation was performed on the egg of Xenopus laevis, because of its accessibility. New Culture offered a chance to emulate and refine some of those experiments in the chick embryo.

Several attempts have been made to culture blastoderms or fragments thereof in vitro, but none have been very successful. The chorioallantoic membrane (CAM grafts) has been used as a substratum to study self-differentiation, but fragments do not develop consistently true to origin. Spratt (2,3) grew blastoderms on a bed of a mixture of yolk and agar. Some of the observations from this culture method resulted in misleading conclusions being drawn because morphogenetic movements were inhibited in the layer that was in contact with the agar.

Gallera and Nicolet (4) tried a more fluid culture medium and were slightly more successful. They also tried a modification of New Culture with a doublering setup in which the vitelline membrane was sandwiched between the two rings, one of which was just small enough to fit into the larger one. This was to facilitate operations to the dorsal aspect of the embryo. The explanted embryo could be turned over without slipping off.

From: Methods in Molecular Biology, Vol. 97: Molecular Embryology: Methods and Protocols Edited by: P. T. Sharpe and I. Mason © Humana Press Inc., Totowa, NJ

The most successful method was pioneered by New (1). Blastoderms can be explanted unincubated or incubated for up to 30 h. This culture system not only allows observation of morphogenetic movements, which are so important for the normal development of the embryo, but also lends itself to a variety of minor and major transplantation experiments, ablations, treatment with compounds in solution or bound on beads, or other carriers and many other experiments. There are two main restrictions to the use of New Culture. First, only the ventral aspect of the blastoderm is accessible to immediate and direct manipulations, although there is no reason not to invade the epiblast as well. However, this can only be done by cutting through hypoblast and mesoderm, and causing perhaps unnecessary damage to these tissues. Second, the incubation time in culture is limited to about 48 h. Consequently, experiments have to be short term.

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