Entamoeba histolytica, a pathogenic parasite, is the causative organism of amoebiasis and uses human colon to complete its life cycle. It destroys intestinal tissue leading to invasive disease. Since it does not form cyst in culture medium, a reptilian parasite Entamoeba invadens serves as the model system to study encystation. Detailed investigation on the mechanism of cyst formation, information on ultra-structural changes and cyst wall formation during encystation are still lacking in E. invadens. Here, we used electron microscopy to study the ultrastructural changes during cyst formation and showed that the increase in heterochromatin patches and deformation of nuclear shape were early events in encystation. These changes peaked at ∼20 h post induction, and normal nuclear morphology was restored by 72 h. Two types of cellular structures were visible by 16 h. One was densely stained and consisted of the cytoplasmic mass with clearly visible nucleus. The other consisted of membranous shells with large vacuoles and scant cytoplasm. The former structure developed into the mature cyst while the latter structure was lost after 20 h, This study of ultra-structural changes during encystation in E. invadens opens up the possibilities for further investigation into the mechanisms involved in this novel process.

溶组织内阿米巴是一种致病性寄生虫，是阿米巴病的病原体，利用人体结肠来完成其生命周期。它破坏肠道组织，导致侵袭性疾病。由于它不会在培养基中形成包囊，爬行动物寄生虫内阿米巴入侵作为研究包囊的模型系统。对包囊形成机制的详细研究，关于包囊形成过程中超微结构变化和包囊壁形成的信息仍然缺乏在入侵大肠杆菌中. 在这里，我们使用电子显微镜研究了囊肿形成过程中的超微结构变化，并表明异染色质斑块的增加和核形状的变形是囊肿形成的早期事件。这些变化在诱导后约 20 小时达到峰值，正常核形态在 72 小时后恢复。16 小时后可以看到两种类型的细胞结构。一个染色密集，由具有清晰可见细胞核的细胞质团组成。另一个由具有大液泡和缺乏细胞质的膜质壳组成。前者结构发育为成熟包囊，后者结构在 20 小时后消失，本研究对入侵E. 包囊形成过程中的超微结构变化进行了研究。 为进一步研究这一新过程所涉及的机制开辟了可能性。