CIL:578, Gallus gallus gallus, erythrocyte. In Cell Image Library

Avian erythrocytes differ from most vertebrates in retaining the nucleus at maturity. During erythrocyte development, transcription is progressively shut down and nuclei become compact and heterochromatic. Since erythrocyte chromatin contains little other than histones and DNA, it is the material of choice for many in vivo and in vitro studies. This image, recorded on film at 100KV is a thin section, prepared from washed blood fixed with glutaraldehye, post-fixed with OsO4, embedded in plastic and stained with uranyl and lead salts. The dark, centrally located nucleus is prominent, and the chromatin so compact that the chromatin fiber organization is obscured.