The presence of multinucleated blastomeres (MNBs) in embryos is associated with poor developmental competence in assisted reproductive technologies. This phenomenon is observed not only in humans but also in other animal species. The purpose of the present study was to investigate the characteristics of embryos with MNBs (MNB embryos) that could be utilized in embryo transfer. The developmental...

The study of the sea urchin embryo has contributed importantly to our ideas about embryogenesis. This essay re-examines some issues where the concerns of classical experimental embryology and cell and molecular biology converge. The sea urchin egg has an inherent animal-vegetal polarity. An egg fragment that contains both animal and vegetal material will produce a fairly normal larva. However, ...

Domestic cat embryos of excellent quality appear to improve development of conspecific embryos when cultured together, providing an avenue for improving development of embryos from valuable species or individuals. To have relevance to rare species, it would be useful to understand if this advantage could be conferred by heterospecific companions because there usually are severely limited number...

Experimental analyses of decay in a tunicate deuterostome and three lophotrochozoans indicate that the controls on decay and preservation of embryos, identified previously based on echinoids, are more generally applicable. Four stages of decay are identified regardless of the environment of death and decay. Embryos decay rapidly in oxic and anoxic conditions, although the gross morphology of em...

On 30 November 2000, the Japanese Parliament enacted the Human Cloning Regulation Act.1 In its core, the Act prohibits transfer of human embryos and human-animal cloned embryos made by somatic nuclear transfer, as well as human-animal chimeric embryos, to a human or animal uterus. These provisions are more than mere lip service, as a breach of this prohibition of human cloning can be punished b...

The animal plate of the sea urchin embryo becomes the apical organ, a sensory structure of the larva. In the absence of vegetal signaling, an expanded and unpatterned apical organ forms. To investigate the signaling that restricts the size of the animal plate and patterns neurogenesis, we have expressed molecules that regulate specification of ectoderm in embryos and chimeras. Enhancing oral ec...

The rapid cell proliferation characteristic of early animal embryos is accomplished with an abbreviated cell cycle and no DNA replication checkpoint. Blythe and Wieschaus provide evidence that nascent zygotic transcription precedes—and may trigger—this checkpoint at the midblastula transition.

Par-1 encodes a serine/threonine kinase that is involved in asymmetric segregation of cell fate determinants in Caenorhabditis elegans and Drosophila embryos. Recent biochemical studies indicate an association of PAR-1 with the Dishevelled protein and suggest a role in so-called canonical Wnt signaling (Nat. Cell Biol. 3 (2001) 628). Here we describe two Xenopus laevis cDNAs, which encode PAR-1...

The temporal and spatial transcription patterns of the Xenopus laevis Bone morphogenetic protein 2 (BMP-2) gene have been investigated. Unlike the closely related BMP-4 gene, the BMP-2 gene is strongly transcribed during oogenesis. Besides some enrichment within the animal half, maternal BMP-2 transcripts are ubiquitously distributed in the early cleavage stage embryos but rapidly decline durin...