Several Cell Responses to Insulin of Cultured Cells Derived from Micromeres, Isolated from Sea Urchin Embryos at the 16 Cell Stage: (Sea urchin/development/morphogenesis/insulin/micromere).

In micromere-derived cells of sea urchin embryos, treatment with insulin started for up to 24 h during culture at 20°C resulted in augmentation of P incorporation into protein (protein phosphorylation) followed by activation of P incorporation into RNA (RNA synthesis) and then induced pseudopodial cable growth, accompanied by considerable decreases in the rates of protein phosphorylation and RNA synthesis. This augmentation of RNA synthesis and cable growth induced by insulin were blocked by H-7, which inhibited protein phosphorylation, and were also inhibited by actinomycin D without any inhibition of protein phosphorylation. Similar results were obtained on treatment with horse serum, found to contain insulin-like compounds.

Changes in Insulin-Binding Capacity of the Plasma Membrane Fraction during Culture in vitro of Cells Derived from Micromeres of 16-Cell-Stage Sea Urchin Embryos: (sea urchin/development/micromere/insulin/insulin receptor).

In cultured cells derived from isolated micromeres of 16-cell stage sea urchin embryos, which undergo insulin-induced pseudopodial cable growth, specific and reversible insulin binding by a 52-kDa protein, probably an insulin receptor in the plasma membrane, is augmented during 5 h of culture without any change in the dissociation constant (Kuno et al : 1994). The increase in insulin-binding capacity in micromere-derived cells was only minimally blocked by actinomycin D and cycloheximide, which inhibited [U- H]uridine incorporation into RNA and [ S]methionine incorporation into protein, respectively. Insulin binding capacity was found in the plasma membrane fraction and the microsome fraction of isolated micromeres.

Insulin-Induced Outgrowth of Pseudopodial Cables from Cultured Micromere-Derived Cells Isolated from Sea Urchin Embryos at the 16 Cell Stage, with Special Reference to the Insulin-Receptor.: (sea urchin/micromere/insulin/psedopodial cable/receptor).

Cultured cells derived from micromeres isolated from sea urchin embryos at the 16 cell stage are known to show outgrowth of pseudopodial cables followed by spicule rod formation when cultured in the presence of horse serum. Micromere-derived cells cultured with bovine insulin showed pseudopodial cable growth but did not produce spicule rods. Micromere-derived cells reversibly bound to insulin through out the period between 3 and 20 hr of culture.