title: Membrane fractions display different lipid and enzyme content in three cell types in 16-cell stage embryos of sea urchins.
abstract: Three cell types were isolated from dissociated 16-cell sea urchin embryos. Four membrane density fractions from discontinuous gradients have different proportions of lipids, surfacer markers and enzymes for the three cell types. Assays of lipid content, CH/PLIPID and SPH/PC ratios, acyl chain length, level of unsaturation by proton NMR and assays of enzyme activity revealed variation at the same density between the three cell types and among different densities from one cell type. There were also differences between whole embryos and dissociated embryo cells. There was no typical membrane domain at a particular density common to the cell types. Cell surface characteristics and polarity of adult cells rely on which lipid domains and enzymes are present, their association with cytoskeleton and how they are localized. At the 16-cell stage these characteristics are still very dynamic as revealed by cytochemical localization of Na+/K(+)-ATPase which varied with cell type and suggests endocytosis at set times in the division cycle. Polarity has not been permanently set for Na+/K(+)-ATPase yet. Membrane enzyme and lipid distributions unique to the three cell types seen in this study suggest parcelling out or insertion of new membrane domains occurs during early sea urchin cleavage. Perturbation of membrane density distribution and lipid content occurs after treatment of embryos with animalizing and vegetalizing teratogens which alter development.
authors.affiliation: Biology Department, California State University, Northridge 91330.
authors.forename: M L
authors.initials: ML
authors.lastname: Sparling
authors.forename: B
authors.initials: B
authors.lastname: Kruszewska
mesh_terms: D000818:Animals; D002455:Cell Division; D002462:Cell Membrane / Q000737:chemistry*; D002469:Cell Separation; D002855:Chromatography, Thin Layer; D004625:Embryo, Nonmammalian / Q000737:chemistry* / Q000166:cytology; D009682:Magnetic Resonance Spectroscopy; D008563:Membrane Lipids / Q000032:analysis*; D010042:Ouabain / Q000494:pharmacology; D012617:Sea Urchins / Q000196:embryology; D000254:Sodium-Potassium-Exchanging ATPase / Q000032:analysis
chemical_list: D008563:Membrane Lipids; D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase