Trypsin treatment of cells dissociated from sea urchin embryos elicits DNA synthesis

Synthesis of heat shock proteins in dissociated sea urchin embryonic cells

Embryos dissociated into cells retain the stage-specific response to heat shock. The dissociated cells, irrespectively of whether they are reaggregated or not, undergo the developmental changes in their ability to respond to heat shock, at the same time as the entire embryos. The conclusion of the present experiments is that sea urchin embryonic cells become responsive to heat shock and produce heat shock proteins even in the absence of cell interactions.

Inverse affects on thymidine incorporation in dissociated blastula cells of the sea urchin Paracentrotus lividus induced by butanol treatment and fab addition

When dissociated blastula cells of the sea urchin Paracentrotus lividus were prevented from aggregating by extracting them with 2.5% n-butanol in sea water, they became unable to incorporate labelled thymidine, like over-diluted dissociated cells. If, however, cells were prevented from aggregating by the addition of Fab against plasma membranes, thymidine incorporation was not blocked, but increased compared to that of spontaneously aggregating cells. At the same time amino acid incorporation also increased.

Species-specific aggregation factor in sponges. V. Influence on programmed syntheses

Isolated cells from the siliceous sponge Geodia cydonium as well as small primary aggregates (diameter: 70 mum) consisting of them show no increase in rates of programmed syntheses and mitotic activity with time. After addition of a highly purified aggregation factor to a culture with primary aggregates which subsequently form secondary aggregates (diameter: larger than 1000 mum), a dramatic increase of DNA, RNA and protein synthesis occurs. Together with this increase, the cells show a high mitotic activity. The values for the mitotic coefficient reach a first maximum 8 h after the beginning of the secondary aggregation process. The stimulation of the mitotic activity of cells during the aggregation factor induced secondary aggregation process can be suppressed by inhibitors of RNA and protein synthesis as well as by a blocker of DNA synthesis. This finding may indicate that cells from the G0-population enter the proliferating cell pool via the G1-phase.

Isolation of the plasma membrane from sea urchin embryos

A method for isolation of sea urchin embryos plasma membranes is described. Purification of the obtained fraction was assayed by several enzymatic markers and electron microscopy. The isolated plasma membranes appear to be pure from contamination of other cell membranes (endoplasmic reticulum and mitochondria), and they can therefore be used for analytical studies on the composition and structure of plasma membrane.

Differential gene activity and segregation of cell lines: an attempt at a molecular interpretation of the primary events of embryonic development

The study of differentiation is concerned with the analysis of the processes responsible for ‘the cellular changes in macromolecular synthesis and composition, patterned in time and space and resulting in specialized functions, forms and organization’ (Moscona, 1973).