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.鸟类红细胞与多数脊椎动物的红细胞不同，其成熟后仍保留细胞核。在红细胞发育进程中，转录活动会逐步被抑制，细胞核也会逐渐浓缩并发生异染色质化。由于红细胞染色质仅由组蛋白与DNA构成，因此它是众多体内（in vivo）与体外（in vitro）研究的首选实验材料。本图像以胶片于100KV电压下拍摄，样品为经洗涤的血液制备的超薄切片：该样品先用戊二醛固定，再经四氧化锇（OsO4）后固定，随后进行塑料包埋，最终以铀盐与铅盐染色。图像中可见位于中央的深色细胞核十分醒目，染色质浓缩程度极高，以至于其纤维结构已无法分辨。