Electrokinetic properties of dissociated chick embryo cells. Calcium ion binding by neural retinal cells

Surface tensions of embryonic tissues predict their mutual envelopment behavior

During embryonic development, certain tissues stream to their destinations by liquidlike spreading movements. According to the ‘differential adhesion hypothesis’, these movements are guided by cell-adhesion-generated tissue surface tensions (sigmas), operating in the same manner as surface tensions do in the mutual spreading behavior of immiscible liquids, among which the liquid of lower surface tension is always the one that spreads over its partner. In order to conduct a direct physical test of the ‘differential adhesion hypothesis’, we have measured the sigmas of aggregates of five chick embryonic tissues, using a parallel plate compression apparatus specifically designed for this purpose, and compared the measured values with these tissues' mutual spreading behaviors. We show that aggregates of each of these tissues behave for a time as elasticoviscous liquids with characteristic surface tension values. Chick embryonic limb bud mesoderm (sigma = 20.1 dyne/cm) is enveloped by pigmented epithelium (sigma = 12.6 dyne/cm) which, in turn, is enveloped by heart (sigma = 8.5 dyne/cm) which, in turn, is enveloped by liver (sigma = 4.6 dyne/cm) which, in turn, is enveloped by neural retina (sigma = 1.6 dyne/cm). Thus, as predicted, the tissues' surface tension values fall in the precise sequence required to account for their mutual envelopment behavior.

Effects of copper on the sabellid polychaete, Eudistylia vancouveri. II. Copper accumulation and tissue injury in the branchial crown

Copper in seawater caused injury to the radioles (gills) of the sabellid polychaete, Eudistylia vancouveri. Light and electron microscopy showed the loss of cellular adhesion and the structural derangement that lead to cell necrosis and death. The progression of injury was related to the uptake of copper into the tissues. Copper was found by X-ray microanalysis to be localized subcellularly in membrane-bound vesicles that are similar to lysosomes. Cell breakdown may result from lysosomal labilization.

The binding of cations to the surfaces of cells from early chick blastoderms

Cells of the early chick blastoderms are either preparing for or undergoing regulated morphogenetic movements which culminate in the formation of a three-layered embryo. Information on the changes in the physical-chemical properties of cell surfaces may help in the understanding of this process. The binding of magnesium, manganese, strontium, barium and lanthanum to surfaces of early embryonic cells was estimated by the changes induced by these cations in the cells' electrophoretic mobilities (EPM). Cells show a positive EPM at concentrations of MgCl2 and MnCl2 at 3 X 10(-2) M while SrCl2 and BaCl2 were not able to reverse the cells' charge at concentrations up to 6 X 10(-2) M. CaCl3 reversed the cells' EPM at concentrations as low as 5 X 10(-3) M. Our results suggest that the surfaces of early embryonic cells have a high affinity for Mg and Mn. This is indicated by a reversal of polarity which cannot be detected in cells of differentiating or adult tissues at the cation concentrations used in these experiments.

Studies on intercellular adhesion. I. Adhesion of neural retina cells to isotypic aggregates in serum free medium

A quantitative assay for intercellular adhesion, which is a modification of the collecting aggregate assay (Roth et al., '71) is described. The use of mechanically dissociated single cells labeled with 3H-leucine, and of a gyratory shaker increased considerably the efficiency of cell collection. With chick embryo neural retina, it was shown that isotypic cell adhesion occurs in simple synthetic media and even in sodium chloride solution suggesting that divalent cations do not play a major role in adhesion of these cells. Cell collection in media without serum was not affected by metabolic or protein synthesis inhibitors. However, cell adhesion was temperature-dependent since no collection occurred at 4 degrees C but was maximal at 38 degrees C.

Influence of mono- and multivalent cations on the electrokinetic properties of Rana pipiens kidney cells

Changes in the cation composition of the ambient cell environment, at constant ionic strengths, altered the electrokinetic properties of the surface of normal adult Rana pipiens kidney cells in a manner which reflected its valence. the effect was expressed in the changes of the magnitude of the net surface charge, at any pH, and in the shift of the isoelectric point of the cell surface.