Chick embryonic pigmented retina is one of the group of epithelioid tissues that lack cytokeratins and desmosomes and have intermediate filaments composed of vimentin

Using sodium dodecyl sulphate/polyacrylamide gels to analyse detergent-insoluble residues, and indirect immunofluorescence, we have found that the major protein of intermediate filaments in cultures and freshly explanted fragments of chick embryonic retinal pigment epithelium (RPE) is vimentin. Moreover, these cells also fail to stain with antibodies against cytokeratins and most components of true desmosomes (maculae adhaerentes). Staining with anti-vinculin antibody suggests that the principal intercellular junction is the zonula adherens. Thus although RPE is an epithelium according to all other criteria, it belongs to a group of tissues (including vascular endothelium, iris and lens-forming epithelium) that have intermediate filaments composed of vimentin and possess neither cytokeratins nor desmosomes. That a tissue can be fully epithelial by other criteria, whilst lacking these components, is in agreement with other work, which has shown a lack of effect of micro-injection of antibodies to cytokeratin, and of the suppression of desmosome formation, on epithelial organization in culture. Although our observations were made solely on chick embryonic tissue, we suggest that published ultrastructural studies are consistent with the possibility that RPE of other species, including human, may lack true desmosomes.

Fibronectin, intercellular junctions and the sorting-out of chick embryonic tissue cells in monolayer

A hierarchy of relative cohesiveness in monolayer of four different embryonic chick tissues was determined in a previous study. The hierarchy is: corneal epithelium congruent to liver parenchyma greater than pigmented epithelium greater than limb bud mesenchyme. The purpose of this paper is to describe the correlation between these adhesive relationships and, firstly, the amount of the adhesive glycoprotein, fibronectin, associated with the cells and, secondly, the morphology of their intercellular contacts. Fluorescent antibody staining of the cells with anti-fibronectin antibody showed that limb bud mesenchyme cells, the most weakly cohesive, had much more fibronectin than the other cell types. Thus there was a negative correlation between the amount of fibronectin and cellular cohesiveness. Analysis of intercellular contacts by electron microscopy showed that the most strongly cohesive cell types, corneal epithelium and liver parenchyma, were also those that possessed desmosomes.

ÉTUDE DU VIRUS DE L'INFLUENZA: ANTIGÉNICITÉ DE SOUCHES GRIPPALES ADAPTÉES À DES CULTURES DE TISSUS

This paper deals with a study of the antigenic properties of influenza strains adapted to tissue cultures. When adapted to chick embryonic tissue, influenza strains lose most of their antigenicity; when adapted to monkey kidney cultures under the same conditions, influenza strains maintain their antigenic value to a high level.