Magnetic resonance imaging study of the structure of the yolk in the developing avian egg

Abstract

Magnetic resonance imaging (MRI) techniques were used to study the morphology of the latebra and concentric rings seen in the yolk of White Leghorn eggs during development of the avian embryo. Previous studies of the macroscopic structure of avian yolk have revealed the latebra, a vase-shaped structure beneath the blastoderm composed of white yolk. The bulbous portion in the center of the yolk is termed the body of the latebra. The thinner portion extending toward the blastoderm is referred to as the neck of the latebra. As the neck of the latebra approaches the blastoderm, it flares out to become the nucleus of Pander. The remainder of the yolk often features alternating concentric layers of white and yellow yolk. These layers, which appear as rings in sections, are thought to represent the daily accumulation of yolk during oogenesis. In this study eggs were imaged with a single slice spin echo sequence using MRI parameters that maximized the visualization of the latebra and concentric rings in the egg yolk. Some experiments were conducted for 2 to 3 day periods with eggs kept in the bore of the magnet using a small incubator that was constructed using a temperature-controlled water pump. The concentric rings of the yolk and the body of the latebra flatten and become more elliptical during development. The neck of the latebra becomes shorter and disappears around the 7th day of incubation. The body of the latebra starts to become incorporated into the embryo at about the 7th day of incubation and usually disappears by the 13th day. The concentric rings are no longer visible as distinct entities at this time. Histochemical procedures carried out as a result of MRI findings indicate that the latebra is an iron-rich structure.

Influence of storage on the position of the germinal disc in the fertilized unincubated chicken egg

“…The strand which runs upwards from the latebra is called the neck of latebra. The neck of latebra connects the latebra to the nucleus of Pander; the nucleus of Pander contains a mass of cytoplasm, called the germinal disc, from which the embryo begins to develop (Falen et al, 1991). In Figure 2(b), a magnified part of this region is presented, showing the germinal disc, the nucleus of Pander, and the neck of latebra.…”

Origin, fate, and function of the components of the avian germ disc region and early blastoderm: Role of ooplasmic determinants

“…In the nucleus of Pander, I have observed the presence of some round Feulgen-positive spherules (Callebaut, 1994 H]tyrosine administration in ovo, before laying, an intense incorporation of these precursors was observed in and around the nucleus of Pander, which indicates DNA, RNA, and/or protein synthesis, perhaps in relation with the inductive influence emanating from the nucleus of Pander. The aspect and evolution of the nucleus of Pander during early incubation was studied by magnetic resonance imaging (Falen et al, 1991), however, without histological data.…”

Noninvasive monitoring of chick development in ovo using a 7T MRI system from day 12 of incubation through to hatching

“…Another advantage of MRI over other noninvasive technologies, such as ultrasound, is that the presence of the eggshell does not present a problem in terms of acquiring images of the interior of the egg. Nevertheless, there are only a few accounts of MRI being used to image fertile eggs, and most of these relate to the initial stages of incubation (3)(4)(5)(6). Chick movement in the later stages of incubation has made imaging much more problematic, particularly beyond the 10th day of incubation (2,7).…”