Previous studies in sea urchin embryos have demonstrated that nuclearization of beta-catenin is essential for initial steps in the specification of endoderm and mesenchyme, which are derived from vegetal blastomeres. This process begins at the 4th and extends through the 9th cleavage stage, an interval in which the SpSoxB1 transcription regulator is downregulated by beta-catenin-dependent gene ...

Previous lineage tracing experiments have shown that the vegetal blastomers of cleavage stage embryos give rise to all the mesoderm and endoderm of the sea urchin larva. In these studies, vegetal blastomers were labeled no later than the sixth cleavage division (60-64 cell stage). In an earlier study we showed that single cells in the vegetal plate of the blastula stage Lytechinus variegatus em...

In Xenopus eggs, removal of small volumes of cytoplasm along with the surface (2-10% of the entire egg volume) causes very severe dorsal reduction (average DAI=1.4) when made at a site ventrally 30 degrees off the vegetal pole at 20% time of first cell cycle (0.2 NT). The greatest dorsal reduction (average DAI=1.1) occurs when removal is done at the vegetal pole at 0.3 NT, and intermediate redu...

Inverted amphibian embryos were employed for an analysis of pattern formation in early embryogenesis. Axolotl (Ambystoma) and Xenopus eggs were inverted prior to the first cleavage division and permitted to develop upside down to the early gastrulation stage. In both cases the cleavage patterns of the animal and vegetal hemispheres were reversed. By gastrulation, however, developmental arrest b...

Flow resistance due to vegetation may greatly affect the conveyance of a channel, and thus evaluating the resistance is a critical task in river engineering and restoration. Therefore, flow resistance of natural willows and sedges was studied in a laboratory flume. The aim was to investigate, how type, density and combination of vegetation, flow depth and velocity influence vegetal drag or fric...

Cell polarity is manifest along the animal/vegetal axis in eggs of the frog, Xenopus laevis. Along this axis, maternal cytoplasmic components are asymmetrically distributed and are thought to underlie specification of distinct cell fates. To ascertain the molecular identities of such cytoplasmic components, we have used a monoclonal antibody that specifically stains the vegetal hemisphere of Xe...

Pattern formation along the animal-vegetal (AV) axis in sea urchin embryos is initiated when canonical Wnt (cWnt) signaling is activated in vegetal blastomeres. The mechanisms that restrict cWnt signaling to vegetal blastomeres are not well understood, but there is increasing evidence that the egg's vegetal cortex plays a critical role in this process by mediating localized "activation" of Dish...

RNA localization is a widely conserved mechanism for generating cellular asymmetry. In Xenopus oocytes, microtubule-dependent transport of RNAs to the vegetal cortex underlies germ layer patterning. Although kinesin motors have been implicated in this process, the apparent polarity of the microtubule cytoskeleton has pointed instead to roles for minus-end-directed motors. To resolve this issue,...