The anionic binding-sites at the cell surface after tissue dissociation and during the early phases of cell reaggregation

Abstract

ABSTRACT The fixation of dissociated chick embryonic cells in the presence of ruthenium red or alcian blue revealed a remarkable reduction in the binding of these cations to cell surfaces following tryptic digestion at 37 °C, but not after trypsin used at 4 °C or EDTA. The reconstitution of anionic sites present over the cell plasma membrane was studied in retina, liver and heart cells from embryos of different ages, cultivated according to a method which promotes cell reaggregation. All these cells regenerated ruthenium red-stainability within the first hour of culture. Culturing at 15 °C, substitution of saline for the culture medium or addition of puromycin or of neuraminidase to the culture media did not affect this restitutive process. Neuraminidase and hyaluronidase digestion were not able to alter the ruthenium red-binding, once it was present. From these data and from the reports available in the literature it has been concluded that the anionic binding-sites cannot be identified with the cell surface coat, and probably not with sialic acids, which require active metabolic processes and a much longer time interval for regeneration. The presence of these sites probably favours the formation of initial cell contacts but is not sufficient for cell reaggregation.