A kinetic study of embryonic cell adhesion

A new assay is described for measuring the kinetics of adhesion of cells to collecting aggregates. The parameter measured is the percentage of cells in suspension adhering to a large number of collecting aggregates per unit time. Using this assay on trypsinized cells it is shown that several hours of recovery are required before the maximum adhesion rate is reached. The recovery period is sensitive to cycloheximide and to low temperature (4°C). As the cells approach the maximum adhesion rate, their collection to aggregates becomes increasingly insensitive to the addition of cycloheximide; this adhesion remains sensitive to low temperature. Specificity studies show that the rate of adhesion of embryonic cells to collecting aggregates is highest between cells and aggregates of the same histotype. This rate is affected by the embryonic age of the cells. Finally, when cells of a tissue are fractionated on Ficoll gradients, it is shown that subpopulations of cells adhere to collecting aggregates at different rates.