Morphological and immunocytochemical studies of fibronectin-coated, plasma membrane-limited vesicles in the early chicken embryo.
Vesticles with a mean outside diameter of 32.8 nm have been observed in the early chicken embryo after fixation with a mixture of glutaraldehyde and tannic acid. Densitometric tracing has revealed that the vesicles are limited by a unit membrane. The presence of complex carbohydrates is suggested by the increased electron density of the vesticles after addition of tannic acid to the fixative. Immunocytochemical staining with a monoclonal antibody directed against chicken cellular fibronectin demonstrated the presence of this glycoprotein along the surface of the vesicles. These results suggest a cellular origin of the vesicles, since their surface shares morphological and biochemical similarities with the cell surfaces of the embryonic tissue layers. Recycling of plasma-membrane vesicles may occur, as vesicles were found in the vicinity of coated vesicles. We postulate that extracellular materials of the cell surface, which may affect cell and tissue interactions, are shed in the environment together with plasma-membrane vesicles. The difficulties encountered in observing the vesicles stems from the facts that an adequate visualization method is necessary and that they are few in number. The latter reason suggests their transient nature. The vesicles probably rapidly disintegrate in the extracellular milieu or are recycled by the cell surface.
Harrisson
F
F
Department of Anatomy and Embryology, State University Center, Antwerp, Belgium.
Vanroelen
C
C
Vakaet
L
L
D000818:Animals; D001756:Blastoderm / Q000378:metabolism / Q000648:ultrastructure*; D002462:Cell Membrane / Q000502:physiology*; D002642:Chick Embryo; D003720:Densitometry; D005353:Fibronectins / Q000378:metabolism*; D007150:Immunohistochemistry
D005353:Fibronectins