The mechanism of micromere specification is one of the central issues in sea urchin development. In this study we have identified a sea urchin homologue of ets 1 + 2. HpEts, which is maternally expressed ubiquitously during the cleavage stage and which expression becomes restricted to the skeletogenic primary mesenchyme cells (PMC) after the hatching blastula stage. The overexpression of HpEts ...

Mesenchymal cells of the sea urchin embryo provide a valuable experimental model for the analysis of cell-cell fusion in vivo. The unsurpassed optical transparency of the sea urchin embryo facilitates analysis of cell fusion in vivo using fluorescent markers and time-lapse three-dimensional imaging. Two populations of mesodermal cells engage in homotypic cell-cell fusion during gastrulation: pr...

The trophic interactions of sea urchins are known to be the agents of phase shifts in benthic marine habitats such as tropical and temperate reefs. In temperate reefs, the grazing activity of sea urchins has been responsible for the destruction of kelp forests and the formation of 'urchin barrens', a rocky habitat dominated by crustose algae and encrusting invertebrates. Once formed, these urch...

The high frequency backscatter from cells with a nucleus to cell volume ratio of 0.50 cannot be adequately modeled as a homogeneous sphere. It was hypothesized that the cytoplasm of such cells is of fluid nature. This work attempts to model the ultrasound backscatter (10-62 MHz) from some non-nucleated biological specimens. This was done by measuring the backscatter response from individual sea...

Unexpected findings from the immune system of sea urchin larvae potentially provide insights into immune signaling in ancestral animals.

In the sea urchin embryo, the animal-vegetal axis is defined before fertilization and different embryonic territories are established along this axis by mechanisms which are largely unknown. Significantly, the boundaries of these territories can be shifted by treatment with various reagents including zinc and lithium. We have isolated and characterized a sea urchin homolog of GSK3β/shaggy, a li...

A Xenopus laevis DNA segment containing the structural gene for tRNA1Met and 22 base pairs at the 5' side of the gene is active in tRNA production. The DNA segment was ligated to sea urchin histone DNA and was also inserted into plasmid pCR1. Both recombinant DNAs were shown to produce mature tRNA1Met at a high rate when injected into centrifuged Xenopus oocytes.

Injury from sea urchin spines is not rare, especially during summer holidays in the sea side. Failure to remove these spines or inability to remove them completely can lead to long-term squeal of pain and impaired function. Treatment methods include alternative medicine, LASER and surgery. We describe the surgical removal of 102 sea urchin spines from the foot of a 36-year-old man. The wounds h...