Differentiation of the blastocyst of the rhesus monkey

Abstract

A method of flushing the oviduct and/or uterus of rhesus monkeys was used to obtain a number of preimplantation stages, of which four cleavage stages and seven blastocysts that were judged to be normal were studied cytologically using transmission electron microscopy. In addition to the usual changes in mitochondria and endoplasmic reticulum that accompany differentiation of the blastomeres, the blastocysts with zonae showed sequestration of areas of cytoplasm. The first indications of junctional complexes were short stretches of parallel membrane with a slightly increased density found in the morula stage. Blastocysts developed typical apical junctional complexes, but in addition showed extensive gap junctions linking trophoblast and inner cell mass, and epiblast and differentiating endoderm. Endodermal differentiation occurred at about the same time that a basal lamina was found under mural trophoblast and epiblast (but not polar trophoblast or endoderm). Enlarged torn zonae were found in association with one blastocyst and unaccompanied by blastocysts, including a case in which the animal subsequently prove to be pregnant. This observation suggests that hatching is a normal feature of zonal escape in this species. The trophoblast of blastocysts without zonae had well-formed apical absorptive areas and, in some instances, long irregular microvilli in the area near the inner cell mass. Cell debris, vacuoles containing debris and isolated cells, although variable, were common features of the preimplantation stage in the rhesus monkey.

Regulation of human embryonic stem cell differentiation by BMP-2 and its antagonist noggin

“…This cell was known classically in the human embryology literature as a mesoblast, but on comparative anatomical grounds Luckett (Luckett, 1978) argued that these cells were more likely to represent extra-embryonic endoderm. Several further morphological studies of the primate embryo have documented the development of cells resembling parietal endoderm and visceral endoderm from flattened cells formed below the epiblast (Enders et al, 1990;Enders and Schlafke, 1981;Enders et al, 1986). Although detailed studies of marker expression in these cells in the primate embryo have not been carried out, the properties of the BMP-induced cell are consistent with their identification as extra-embryonic endoderm.…”

Differentiation of the embryonic disc, amnion, and yolk sac in the rhesus monkey

“…The methods used for collection, dissection, and fixation of the blastocyst and implantation sites have been described previously (Enders and Schlafke, 1981; Enders et al, 1983Enders et al, , 1985. Briefly, while animals were under deep Ketamine anesthesia, the abdominal aorta was infused with Earle's basic salt solution and then with 2% formaldehyde-2% glutaraldehyde fixative.…”

Human embryonic stem cells: prospects for development

“…1). It is important to remember that the primate embryo devotes its first two weeks almost exclusively to the formation of extraembryonic membranes (Enders and Schlafke, 1981;Enders et al, 1986;Luckett, 1978). Thus, in the time it takes the mouse embryo to develop past midgestation, the primate embryo has just begun germ layer formation.…”