Peridermal granules of the chick embryo: histochemical, ultrastructural and immuno-electron microscopical study

In the chick embryo, the periderm covering certain derivatives of the integumentum, such as the beak, the scale and the claw, grows thick and contains specific cytoplasmic granules. In this report, we present the histochemical properties and the fine structures of these peridermal granules especially over the egg tooth region of the upper beak. The granules were brilliantly stained with acid dyes. A positive reaction for tyrosine and arginine suggested that this acidophilia was due to a certain basic protein. Although the reaction of DDD to SH and SS groups was moderate, a presence of keratin was strongly suggested immunohistochemically by using the rabbit anti-keratin antiserum. There also existed a possibility of some compound lipids. Under an electron microscope, these granules were found to consist of anastomosing ribbons which were less than 60 nm in width and were stained with rabbit anti-keratin antiserum.