Studies on the encystation of Entamoeba

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The encystation mechanism of Entamoeba spp. was investigated biochemically and morphologically. The results obtained are shown below.1. By epifluorometric assays of DNA contents in E. invadens cysts, it was revealed that total DNA per each cyst during nuclear divisions from uni- to tetra-nucleated cysts was constant to be 4C, which suggested the presence of meiosis in the cyst maturation.2. The numbers of chromosomes in E. invadens were counted to be 10-12 in uni-nucleated cysts, and 5-6 in matured tetra-nucleated cysts. These results also suggested the meiotic division in the encystation. However, synaptonemal complex could not be detected yet.3. Verrcarin A, one of the inhibitors of microtubule formation tested, strongly inhibited the nuclear division and encystation of Entamoeba Spp. Applications as a new amebicidal agent should be further investigated.4. The agents activating Ca^<2+>-dependent metabolic pathways such as Ca^<2+> ionophore (A23187) and TPA strongly inhibited the encystation of E. invadens, whereas those activating cAMP-dependent pathways had no significant effects.5. E. coli newly isolated from Japanese monkeys had encystation activity in the glucose-free medium as well as E. invadens. However, our attempts to induce the encystation of E. histolytica were unsuccessful.6. By hybridizing with H-ras probe, it was shown that E. invadens has a ras-related sequence.