This event takes place in a space lacking organized ECM4 and delimited by the squamous epithelial enveloping cell layer (EVL) and the yolk syncytial layer (YSL; Fig. 1 2.
Using in vivo experimentation and physical modelling we reveal that the extra-embryonic epithelial enveloping cell layer, thought mainly to provide protection to the embryo, directs cell migration and the spreading of embryonic tissue during early development.
Representative high-resolution spinning disk microscope z stacks of A. nigripinnis embryos expressing GAP43-EGFP or lifeact-GFP, taken parallel to the embryo surface at 0.5 μm interval, were chosen to quantify the contact area between the membrane of individual cells of the deep cell layer (DCL) and enveloping cell layer (EVL).
Smoothing of the enveloping cell layer at the midblastula transition occurred normally and expression of bon/mixer and mezzo, zygotic transcription factors indicated that activation of the zygotic genome did occur.
Transgene expression can be induced in additional regions of the neural tube and retina as well as the immature notochord, hatching gland, enveloping cell layer, and fin by exposing embryos to retinoic acid.
These embryos were fixed, dechorionated and imaged focusing on enveloping cell layer at the embryo margin.
Recent studies of epiboly [ 7], a movement that stretches an epithelial sheet to completely enclose the embryo early during gastrulation, showed that significant tension exists within the cortex of the yolk cell perpendicular to the supracellular actin bundles at the leading edge of the enveloping cell layer.
Dr. Skou recalled that critics scoffed at his claims that an enzyme could move ions across the membranes enveloping cells.
Three basic types of Drosophila blood cell (known as hemocytes) perform these functions: plasmatocytes, which are professional phagocytic cells akin to mammalian macrophages; lamellocytes, which wrap themselves around invading microorganisms to form an enveloping capsule; and crystal cells, which contain the enzymes that catalyze melanization (Meister, 2004) (Fig. 1B).
When one cell type was differentiated, the most consistent and striking observation was that differentiated cells sort to the surface and form an enveloping layer regardless the relative cell adhesive affinity of any combination in the chimeric embryoid bodies, further substantiating our previous finding (Moore et al., 2009).
A heating/cooling system enveloping the cell, used together with a Neslab ULT-80 thermal bath, allows spectroscopic studies of gas samples at temperatures ranging from 205 to 350 K and at pressures up to 1 atm.
