Aikawa M, Hepler P K, Huff C G, Sprinz H
J Cell Biol. 1966 Feb;28(2):355-73. doi: 10.1083/jcb.28.2.355.
Electron microscope studies of the erythrocytic forms, including gametocytes and asexual schizonts, of the protozoa Plasmodium fallax, P. lophurae, and P. cathemerium, have revealed a "cytostome," a specialized organelle of the pellicular membrane which is active in the ingestion of host cell cytoplasm. In material fixed in glutaraldehyde and postfixed in OsO(4), the cytostome appears in face view as a pore limited by two dense circular membranes and having an inside diameter of approximately 190 mmicro. In cross-section, the cytostome is a cavity bounded on each side by two dense segments corresponding to the two dense circles observed in face view; its base consists of a single unit membrane. In the process of feeding, the cytostome cavity enlarges by expansion of its membrane, permitting a large quantity of red cell cytoplasm to come into contact with the cytostome wall. Subsequent digestion of erythrocyte cytoplasm occurs exclusively in food vacuoles which emanate from the cytostome invagination. As digestion progresses, the food vacuoles initially stain more densely and there is a marked build-up of hemozoin granules. In the final stage of digestion, a single membrane surrounds a cluster of residual pigment particles and very little of the original host cell cytoplasm remains. The cytostome in exoerythrocytic stages of P. fallax has been observed only in merozoites and does not seem to play the same role in the feeding mechanism.
对疟原虫伪疟原虫、洛氏疟原虫和昼夜疟原虫的红细胞内期形态，包括配子体和无性裂殖体进行的电子显微镜研究揭示了一种“胞口”，这是表膜上的一种特殊细胞器，在摄取宿主细胞质时起作用。在戊二醛固定并经四氧化锇后固定的材料中，胞口在正面观时表现为一个由两个致密的圆形膜界定的孔，内径约为190微米。在横切面上，胞口是一个腔，其两侧由对应于正面观中观察到的两个致密圆圈的两个致密部分界定；其底部由单层单位膜组成。在摄食过程中，胞口腔通过其膜的扩张而扩大，使大量红细胞质与胞口壁接触。随后红细胞质的消化仅发生在从胞口内陷产生的食物泡中。随着消化的进行，食物泡最初染色更深，疟色素颗粒明显积累。在消化的最后阶段，单个膜围绕着一簇残留色素颗粒，原始宿主细胞质几乎没有残留。伪疟原虫红细胞外期的胞口仅在裂殖子中观察到，似乎在摄食机制中不发挥相同的作用。
