The influence of cell division order on the establishment of the embryonic-abembryonic axis (EA axis) of the mouse embryo was investigated. Aggregate embryos were constructed in which a labelled cell (or pair of cells) was combined with a group of unlabelled cells all of which were up to one cell cycle earlier or later in their progress through development to the blastocyst stage. The aggregate...

The dorsal blastopore lip (known as the Spemann organizer) is important for making the body plan in amphibian gastrulation. The organizer is believed to involute inward and migrate animally to make physical contact with the prospective head neuroectoderm at the blastocoel roof of mid- to late-gastrula. However, we found that this physical contact was already established at the equatorial region...

The cellular events that take place during reconstruction of larval forms from dissociated embryonic cells of the starfish are investigated by thick and thin sections. Dissociated cells reaggregate, form an external epithelium (ectoderm), internal epithelial vesicles (endoderm), the blastocoel and the mesenchyme. The internal vesicles continue to fuse until there is only one large one suspended...

During gastrulation of the nematode worm Caenorhabditis elegans, individual cells ingress into a solid ball of cells. Gastrulation in a basal nematode, in contrast, has now been found to occur by invagination into a blastocoel, revealing an unanticipated embryological affinity between nematodes and all other triploblastic metazoans.

rum, using two techniques. One lot of fragments was implanted into the blastocoel ; the second lot was cultured in vitro in association with undetermined epiblast excised from the ventral half of the blastocoel roof. All samples were cultured up to 3 days in Barth’s solution, optimized for the amphibian embryo and not permitting isolated mouse egg cylinder fragments to survive. Small grafts, co...

In mammals, female meiosis consists of two asymmetric cell divisions, which generate a large haploid oocyte and two small polar bodies. Asymmetric partitioning of the cytoplasm results from migration of the meiotic spindle toward the cortex and requires actin filaments. However, the subcellular localization and the role of the existing two cytoplasmic actin (CYA) isoforms, beta and gamma, have ...

In this paper, we study the mechanism by which a Xenopus cell line-derived mesoderm-inducing factor (MIF) might establish the spatial pattern of cellular differentiation in the mesoderm. The effects of the factor on competent animal pole tissue are consistent with it being identical to the natural mesoderm-inducing factor. The signal can only act on those membrane domains of the animal pole tha...

INTRODUCTION The earliest cell differentiation event in mammalian development occurs during preimplantation development when the outer blastomeres of the embryo form a monolayer of epithelial cells [trophectoderm (TE)] that envelops the remaining blastomeres [inner cell mass (ICM)]. In mice, TE specification occurs in the 8to 16-cell compacted morula. Developmental transition to blastocyst stag...

Sex determination of in-vitro matured/in-vitro fertilized ovine embryos cultured in synthetic oviduct fluid (SOF) medium was performed by the polymerase chain reaction amplification of specific Y DNA sequences so as to test the influence of sex on developmental growth during the preimplantation period. At 144 h post-insemination, embryos with a blastocoel were classified as the fast-developing ...